CCSP 4.1 January 15, 2009

1 of 784 Final Report 

U.S. Climate Change Science Program 

Synthesis and Assessment Product 4.1 

Coastal Sensitivity to Sea Level Rise: 

A Focus on the Mid-Atlantic Region 

Lead Agency: 

U.S. Environmental Protection Agency 

Other Key Participating Agencies: 

U.S. Geological Survey 

National Oceanic and Atmospheric Administration 

Contributing Agencies: 

Department of Transportation 
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P.1 SCOPE AND APPROACH OF THIS PRODUCT ....................................................................... 11

P.2 FUTURE SEA-LEVEL SCENARIOS ADDRESSED IN THIS PRODUCT ............................. 14

P.3 PRODUCT ORGANIZATION ...................................................................................................... 16

EXECUTIVE SUMMARY ........................................................................................................................ 19

ES.1 WHY IS SEA LEVEL RISING? HOW MUCH WILL IT RISE? ........................................... 20

ES.2 WHAT ARE THE EFFECTS OF SEA-LEVEL RISE? ............................................................ 21

ES.2.1 Sea-Level Rise and the Physical Environment ...................................................................... 22

ES.2.2 Societal Impacts and Implications ......................................................................................... 27

ES.3 HOW CAN PEOPLE PREPARE FOR SEA-LEVEL RISE? ................................................... 28

ES.3.1 Options for Adapting to Sea-level Rise .................................................................................... 28

ES.3.2 Adapting to Sea-level Rise ....................................................................................................... 28

ES.4 HOW CAN SCIENCE IMPROVE UNDERSTANDING AND PREPAREDNESS FOR 

FUTURE SEA-LEVEL RISE? ............................................................................................................. 30

ES.4.1 Enhance Understanding .......................................................................................................... 32

ES.4.2 Enhance Decision Support ...................................................................................................... 33

PART I OVERVIEW. THE PHYSICAL ENVIRONMENT ................................................................. 34

CHAPTER 1: SEA-LEVEL RISE AND ITS EFFECTS ON THE COAST .......................................... 38

KEY POINTS ......................................................................................................................................... 38

1.1 INTRODUCTION ............................................................................................................................ 40

1.1.1 Climate Change Basis for this Product .................................................................................... 45

1.2 WHY IS GLOBAL SEA LEVEL RISING? ................................................................................... 47

1.3 RELATIVE SEA-LEVEL RISE AROUND THE UNITED STATES ........................................ 52

1.4 IMPACTS OF SEA-LEVEL RISE FOR THE UNITED STATES ............................................. 59

1.4.1 Coastal Vulnerability for the United States .............................................................................. 59

1.4.2 Climate Change, Sea-Level Rise and Storms ........................................................................... 61

1.4.3 Shoreline Change and Coastal Erosion ................................................................................... 62

1.4.4 Managing the Coastal Zone as Sea Level Rises ....................................................................... 64

CHAPTER 1 REFERENCES ............................................................................................................... 67

CHAPTER 2. COASTAL ELEVATIONS ............................................................................................... 77

KEY FINDINGS .................................................................................................................................... 77

2.1 INTRODUCTION ............................................................................................................................ 79

2.2 ELEVATION DATA ....................................................................................................................... 86

2.2.1 Topographic Maps, Digital Elevation Models, and Accuracy Standards ............................... 86

2.2.2 Lidar Elevation Data ................................................................................................................. 89

2.2.3 Tides, Sea Level, and Reference Datums ................................................................................. 91

2.2.4 Topographic/Bathymetric/Water Level Data Integration ........................................................ 95

2.3 VULNERABILTY MAPS AND ASSESSMENTS ......................................................................... 96

2.3.1 Large-Area Studies (Global and United States) ....................................................................... 98

2.3.2 Mid-Atlantic Region, States, and Localities ............................................................................101

2.3.3 Other Reports ...........................................................................................................................103

2.3.4 Limitations of Previous Studies ...............................................................................................104

2.4 FUTURE VULNERABILITY ASSESSMENTS ..........................................................................112

2.5 SUMMARY, CONCLUSIONS, AND FUTURE DIRECTIONS .................................................121

CHAPTER 2 REFERENCES ..............................................................................................................127

CHAPTER 3. OCEAN COASTS .............................................................................................................141

KEY FINDINGS ...................................................................................................................................141

3.1 INTRODUCTION ...........................................................................................................................141

3.2 ASSESSING THE POTENTIAL IMPACT OF SEA-LEVEL RISE ON THE OCEAN COASTS

OF THE MID-ATLANTIC ..................................................................................................................145
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3.3 GEOLOGICAL CHARACTER OF THE MID-ATLANTIC COAST .......................................148

3.4 IMPORTANT FACTORS FOR MID-ATLANTIC SHORELINE CHANGE ...........................149

3.4.1 Geologic Framework ................................................................................................................150

3.4.2 Physical Processes ....................................................................................................................152

3.4.3 Sediment Supply .......................................................................................................................154

3.4.4 Human Impacts ........................................................................................................................156

3.5 COASTAL LANDFORMS OF THE MID-ATLANTIC ..............................................................157

3.5.1 Spits ..........................................................................................................................................158

3.5.2 Headlands .................................................................................................................................159

3.5.3 Wave-Dominated Barrier Islands ............................................................................................159

3.5.4 Mixed-Energy Barrier Islands .................................................................................................161

3.6 POTENTIAL RESPONSES TO FUTURE SEA-LEVEL RISE ..................................................162

3.6.1 Bluff and Upland Erosion .......................................................................................................162

3.6.2 Overwash, Inlet Processes, and Barrier Island Morphologic Changes .................................162

3.6.3 Threshold Behavior ..................................................................................................................164

3.7 POTENTIAL CHANGES TO THE MID-ATLANTIC OCEAN COAST DUE TO SEA-LEVEL

RISE .......................................................................................................................................................170

3.7.1 Spits ..........................................................................................................................................171

3.7.2 Headlands .................................................................................................................................171

3.7.3 Wave-Dominated Barrier Islands ............................................................................................171

3.7.4 Mixed-Energy Barrier Islands .................................................................................................174

CHAPTER 3 REFERENCES ..............................................................................................................176

CHAPTER 4. COASTAL WETLAND SUSTAINABILITY .................................................................189

KEY FINDINGS ...................................................................................................................................189

4.1 INTRODUCTION ...........................................................................................................................191

4.2 WETLAND SETTINGS OF THE MID-ATLANTIC REGION..................................................193

4.3 VERTICAL DEVELOPMENT AND ELEVATION CHANGE .................................................194

4.3.1 Wetland Vertical Development ................................................................................................195

4.3.2 Influence of Climate Change on Wetland Vertical Development ..........................................200

4.4 HORIZONTAL MIGRATION ......................................................................................................202

4.5 VULNERABILITY OF WETLANDS TO TWENTIETH CENTURY SEA-LEVEL RISE .....204

4.5.1 Sudden Marsh Dieback ............................................................................................................205

4.6 PREDICTING FUTURE WETLAND SUSTAINABILITY ........................................................206

4.6.1 Case Study: Mid-Atlantic Regional Assessment, New York to Virginia ................................210

4.6.2 Case Study: Albemarle–Pamlico Sound Wetlands and Sea-Level Rise .................................221

4.7 DATA NEEDS .................................................................................................................................228

CHAPTER 4 REFERENCES ..............................................................................................................230

CHAPTER 5. VULNERABLE SPECIES: THE EFFECTS OF SEA-LEVEL RISE ON COASTAL 

HABITATS ................................................................................................................................................238

KEY FINDINGS ...................................................................................................................................238

5.1 INTRODUCTION ...........................................................................................................................239

5.2 TIDAL MARSHES .........................................................................................................................243

5.3 FRESHWATER FORESTED WETLANDS ................................................................................252

5.4 SEA-LEVEL FENS .........................................................................................................................254

5.5 SUBMERGED AQUATIC VEGETATION .................................................................................254

5.6 TIDAL FLATS ................................................................................................................................257

5.7 ESTUARINE BEACHES ...............................................................................................................259

5.8 CLIFFS ............................................................................................................................................262

5.9 SUMMARY OF IMPACTS TO WETLAND-DEPENDENT SPECIES .....................................264

CHAPTER 5 REFERENCES ..............................................................................................................266

ZEDLER, J.B. AND J.C. CALLAWAY, 1999: TRACKING WETLAND RESTORATION: DO 

MITIGATION SITES FOLLOW DESIRED TRAJECTORIES? RESTORATION ECOLOGY, 7(1), 

69-73. ...........................................................................................................................................................275
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PART II OVERVIEW. SOCIETAL IMPACTS AND IMPLICATIONS ............................................276

CHAPTER 6. SHORE PROTECTION AND RETREAT .....................................................................281

KEY FINDINGS ...................................................................................................................................281

6.1 TECHNIQUES FOR SHORE PROTECTION AND RETREAT ..............................................282

6.1.1 Shore Protection .......................................................................................................................282

6.1.2 Retreat ......................................................................................................................................295

6.1.3 Combinations of Shore Protection and Retreat ......................................................................301

6.2 WHAT FACTORS INFLUENCE THE DECISION WHETHER TO PROTECT OR RETEAT?

 ................................................................................................................................................................303

6.2.1 Site-Specific Factors ................................................................................................................303

6.2.2 Regional Scale Factors ............................................................................................................305

6.2.3 Mutual Reinforcement Between Coastal Development and Shore Protection .......................307

6.3 WHAT ARE THE ENVIRONMENTAL CONSEQUENCES OF RETREAT AND SHORE

PROTECTION? ...................................................................................................................................308

6.4 WHAT ARE THE SOCIETAL CONSEQUENCES OF SHORE PROTECTION AND 

RETREAT AS SEA LEVEL RISES? .................................................................................................313

6.4.1 Short-Term Consequences .......................................................................................................313

6.4.2 Long-Term Consequences .......................................................................................................314

6.5 HOW SUSTAINABLE ARE SHORE PROTECTION AND RETREAT? ...............................315

6.5.1 Is “Business as Usual” Shore Protection Sustainable? ............................................................317

6.5.2 Sustainable Shore Protection May Require Regional Coordination ......................................318

6.5.3 Either Shore Protection or a Failure to Plan can Limit the Flexibility of Future Generations

 ...........................................................................................................................................................320

CHAPTER 6 REFERENCES ..............................................................................................................321

CHAPTER 7. POPULATION, LAND USE, AND INFRASTRUCTURE ...........................................332

KEY FINDINGS ...................................................................................................................................332

7.1 INTRODUCTION ...........................................................................................................................333

7.2 POPULATION STUDY ASSESSMENT .......................................................................................333

7.3 MID-ATLANTIC POPULATION ANALYSIS ............................................................................338

7.3.1 Example Population Analysis Results .....................................................................................346

7.4 LAND USE .......................................................................................................................................352

7.5 TRANSPORTATION INFRASTRUCTURE ...............................................................................355

7.5.1 General Considerations ...........................................................................................................355

7.5.2 Recent U.S. Department of Transportation Studies ................................................................357

CHAPTER 7 REFERENCES ..............................................................................................................364

CHAPTER 8. PUBLIC ACCESS .............................................................................................................368

KEY FINDINGS ...................................................................................................................................368

8.1 INTRODUCTION ...........................................................................................................................369

8.2 EXISTING PUBLIC ACCESS AND THE PUBLIC TRUST DOCTRINE ................................369

8.3 IMPACT OF SHORE EROSION ON PUBLIC ACCESS ...........................................................375

8.4 IMPACT OF RESPONSES TO SEA-LEVEL RISE ON PUBLIC ACCESS .............................379

CHAPTER 8 REFERENCES ..............................................................................................................383

CHAPTER 9. COASTAL FLOODING, FLOODPLAINS AND COASTAL ZONE MANAGEMENT 

ISSUES .......................................................................................................................................................386

KEY FINDINGS ...................................................................................................................................386

9.1 INTRODUCTION ...........................................................................................................................387

9.2 PHYSICAL CHARACTERISTICS ..............................................................................................388

9.2.1 Floodplain ................................................................................................................................388

9.3 POTENTIAL IMPACTS OF SEA-LEVEL RISE ON COASTAL FLOODPLAINS ................390

9.4 POTENTIAL EFFECTS OF SEA-LEVEL RISE ON THE IMPACTS OF COASTAL STORMS

 ................................................................................................................................................................392

9.4.1 Historical Comparison at Tide Stations ..................................................................................393
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9.4.2 Typical 100-Year Storm Surge Elevations Relative to Mean Higher High Water within the 

Mid-Atlantic Region ..........................................................................................................................397

9.5 FLOODPLAIN MAPPING AND SEA-LEVEL RISE .................................................................400

9.6 STUDIES OF FUTURE COASTAL CONDITIONS AND FLOODPLAIN MAPPING ..........402

9.6.1 FEMA Coastal Studies .............................................................................................................402

9.6.2 Mapping Potential Impacts of Sea-Level Rise on Coastal Floodplains .................................405

9.7 HOW COASTAL RESOURCE MANAGERS COPE WITH SEA-LEVEL RISE AND ISSUES

THEY FACE .........................................................................................................................................406

9.7.1 Studies by the Association of State Floodplain Managers ......................................................406

9.7.2 The Response through Floodproofing.....................................................................................407

9.7.3 Coastal Zone Management Act ................................................................................................409

9.7.4 The Coastal Zone Management Act and Sea-Level Rise Issues .............................................410

9.7.5 The Coastal Zone Enhancement Program ..............................................................................411

9.7.6 Coastal States Strategies ..........................................................................................................413

PART III OVERVIEW. PREPARING FOR SEA-LEVEL RISE ........................................................423

CHAPTER 10. IMPLICATIONS FOR DECISIONS ............................................................................427

KEY FINDINGS ...................................................................................................................................427

10.1 INTRODUCTION .........................................................................................................................428

10.2 DECISIONS WHERE PREPARING FOR SEA-LEVEL RISE IS WORTHWHILE .............431

10.2.1 Decisions that Address Large Near-Term Impacts ...............................................................434

10.2.2 Decisions Where Preparing Now Costs Little .......................................................................435

10.2.3 Options That Reallocate or Clarify Risks from Sea-Level Rise ............................................437

10.3 PROTECTING COASTAL WETLANDS ..................................................................................441

10.4 SHORE PROTECTION ...............................................................................................................447

10.5 LONG-LIVED STRUCTURES: SHOULD WE PLAN NOW OR LATER? ...........................448

10.6 DECISIONS BY COASTAL PROPERTY OWNERS ON ELEVATING HOMES ................452

10.7 FLOODPLAIN MANAGEMENT ...............................................................................................453

10.7.1 Floodplain Regulations ..........................................................................................................454

10.7.2 Floodplain Mapping ...............................................................................................................454

10.7.3 Federal Flood Insurance Rates .............................................................................................455

10.7.4 Post-Disaster Hazard Mitigation ...........................................................................................466

10.8 CONCLUSIONS ...........................................................................................................................466

CHAPTER 10 REFERENCES ............................................................................................................470

CHAPTER 11. ONGOING ADAPTATION ...........................................................................................480

KEY FINDINGS ...................................................................................................................................480

11.1 INTRODUCTION .........................................................................................................................480

11.2 ADAPTATION FOR ENVIRONMENTAL PURPOSES ..........................................................481

11.2.1 Environmental Regulators .....................................................................................................481

11.2.2 Environmental Land Managers .............................................................................................482

11.3 OTHER ADAPTATION OPTIONS BEING CONSIDERED BY FEDERAL, STATE, AND

LOCAL GOVERNMENTS ..................................................................................................................485

11.3.1 Federal Government ..............................................................................................................485

11.3.2 State Government ...................................................................................................................487

11.3.3 Local Government ..................................................................................................................488

CHAPTER 11 REFERENCES ............................................................................................................491

CHAPTER 12. INSTITUTIONAL BARRIERS .....................................................................................495

KEY FINDINGS ...................................................................................................................................495

12.1 INTRODUCTION .........................................................................................................................495

12.2 SOME SPECIFIC INSTITUTIONAL BARRIERS AND BIASES ...........................................499

12.2.1 Shore Protection versus Retreat ............................................................................................499

12.2.2 Shoreline Armoring versus Living Shorelines ......................................................................508

12.2.3 Coastal Development ..............................................................................................................511
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12.3 INTERDEPENDENCE: A BARRIER OR A SUPPORT NETWORK? ...................................515

12.3.1 Three Fundamental Pathways: Armor, Elevate, or Retreat .................................................516

12.3.2 Decisions That Cannot Be Made Until the Pathway Is Chosen ...........................................519

12.3.3 Opportunities for Deciding on the Pathway ..........................................................................525

CHAPTER 12 REFERENCES ............................................................................................................526

PART IV OVERVIEW. NATIONAL IMPLICATIONS AND A SCIENCE STRATEGY FOR THE 

WAY FORWARD .....................................................................................................................................534

CHAPTER 13. IMPLICATIONS OF SEA-LEVEL RISE TO THE NATION ...................................536

KEY FINDINGS ...................................................................................................................................536

13.1 INTRODUCTION .........................................................................................................................538

13.2 TYPES OF COASTS ....................................................................................................................540

13.2.1 Cliff and Bluff Shorelines ......................................................................................................540

13.2.2 Sandy Shores, Pocket Beaches, Barrier Beaches, Spits, and Dunes ....................................541

13.2.3 Coastal Marshes, Mangroves, and Mud Flat Shorelines......................................................542

13.2.4 Tropical Coral Reef Coasts ....................................................................................................543

13.3 POTENTIAL FOR FUTURE SHORELINE CHANGE ............................................................................544

13.4 CONCLUSIONS ...........................................................................................................................548

CHAPTER 13 REFERENCES ............................................................................................................549

CHAPTER 14. A SCIENCE STRATEGY FOR IMPROVING THE UNDERSTANDING OF SEALEVEL RISE AND ITS IMPACTS ON U.S. COASTS .........................................................................556

KEY FINDINGS ...................................................................................................................................556

14.1 INTRODUCTION .........................................................................................................................557

14.2 A SCIENCE STRATEGY TO ADDRESS SEA-LEVEL RISE .................................................558

14.2.1 Learn From the Historic and Recent Geologic Past .............................................................560

14.2.2 Monitor Modern Coastal Conditions .....................................................................................563

14.2.3 Predict Future Coastal Conditions ........................................................................................570

14.2.4 Improve Understanding of Societal Impacts .........................................................................572

14.2.5 Develop Coastal Decision Support Systems for Planning and Policy Making ....................573

CHAPTER 14 REFERENCES ............................................................................................................577

APPENDIX 1. STATE AND LOCAL INFORMATION ON VULNERABLE SPECIES AND 

COASTAL POLICIES IN THE MID-ATLANTIC ...............................................................................584

OVERVIEW ...........................................................................................................................................584

A1.A. LONG ISLAND ...............................................................................................................................586

A1.A.1 Environmental Implications .................................................................................................587

A1.A.2 Development, Shore Protection, and Coastal Policies .........................................................592

A1.B. NEW YORK METROPOLITAN AREA ............................................................................................598

A1.C. NEW JERSEY SHORE ......................................................................................................................605

A1.C.1 Environmental Implications .................................................................................................606

A1.C.2 Development, Shore Protection, and Coastal Policies .........................................................614

A1.D. DELAWARE ESTUARY ..................................................................................................................619

A1.D.1 Environmenal Implications ..................................................................................................619

A1.D.2 Development, Shore Protection, and Coastal Policies .........................................................624

A1.E. THE ATLANTIC COAST OF VIRGINIA, MARYLAND, AND DELAWARE (INCLUDING COASTAL 

BAYS) ......................................................................................................................................................634

A1.E.1 Environmental Implications .................................................................................................635

A1.E.2 Development, Shore Protection, and Coastal Policies .........................................................640

A1.F CHESAPEAKE BAY.........................................................................................................................645

A1.F.1 Inundation, Development and Shore Protection, and Vulnerable Habitat .........................646

A1.F.2 Baywide Policy Context ........................................................................................................674

A1.G NORTH CAROINA ...........................................................................................................................686

A1.G.1 Introduction ..........................................................................................................................686

A1.G.2 Shore Processes ....................................................................................................................691
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A1.G.3 Vulnerable Habitats and Species .........................................................................................694

A1.G.4 Development, Shore Protection, and Coastal Policies .........................................................700

APPENDIX 1 REFERENCES .............................................................................................................710

APPENDIX 2. BASIC APPROACHES FOR SHORELINE CHANGE PROJECTIONS .................749

APPENDIX 2 REFERENCES .............................................................................................................759

GLOSSARY ...............................................................................................................................................766

SCIENTIFIC NAMES—CHAPTER 5 SPECIES ..................................................................................781

ACRONYMS AND ABBREVIATIONS ..................................................................................................783
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ACKNOWLEDGEMENTS 

Throughout the process of preparing SAP 4.1, the authors were advised by a Federal 

Advisory Committee chosen for their diverse perspectives and technical expertise. The 

Coastal Elevations and Sea-Level Rise Advisory Committee (CESLAC) consisted of: 

Margaret Davidson (Chairperson), NOAA ; Rebecca Beavers, National Park Service; 

Alan Belensz, New York State Office of the Attorney General; Mark Crowell, Federal 

Emergency Management Agency; Andrew Garcia, U.S. Army Corps of Engineers; Carl 

Hershner, Virginia Institute of Marine Science; Julie Hunkins, North Carolina 

Department of Transportation; Mark Mauriello, New Jersey Department of 

Environmental Protection; Mark Monmonier, Syracuse University; William S. 

Nechamen, Association of State Floodplain Managers; Sam Pearsall, Environmental 

Defense Fund; Anthony Pratt, Coastal States Organization; Greg Rudolph, American 

Shore and Beach Preservation Association; Harvey Ryland, Institute for Business and 

Home Safety; Gwynne Schultz, Maryland Department of Natural Resources. Jack 

Fitzgerald of EPA was the Designated Federal Official for the CESLAC, with support 

provided by Stratus Consulting. 

Technical expert review was provided by: Fred Anders, New York Department of State; 

Mark Davis, Tulane University; Lesley Ewing, California Coastal Commission; Janet 

Freedman, Rhode Island Coastal Resources Council; Vivien Gornitz, NASA; Ellen 

Hartig, New York City Department of Parks & Recreation; Maria Honeycutt, AGI 

Congressional Fellow; Kurt Kalb, New Jersey Department of Environmental Protection; 

Stephen Leatherman, Florida International University; Ken Miller, Maryland Department 

of Natural Resources; Jim O’Connell, University of Hawaii, Sea Grant; Richard Osman, 

Smithsonian Institution; Marc Perry, U.S. Census Bureau; Chris Spaur, U.S. Army Corps 

of Engineers; John Teal, Teal Partners; John Thayer, North Carolina Department of 

Environment and Natural Resources; Dan Trescott, Southwest Florida Regional Planning 

Council; John Whitehead, Appalachian State University; Rob Young, Western Carolina 

University. An expert review of an early draft of Chapter 2 was also provided by an 

interagency geospatial team consisting of Eric Constance, USGS; Todd Davison, NOAA; 

Dean Gesch, USGS; and Jerry Johnston, EPA. 

This report relied heavily on stakeholder involvement that was implemented through a 

series of three meetings held in the Mid-Atlantic Region (Easton, Maryland; Red Bank, 

New Jersey; and Plymouth, North Carolina). Many of the comments received and 

discussion initiated at these meetings helped to define some of the issues addressed in this 

report. Linda Hamalak of NOAA organized these public meetings and the subsequent 

author meetings. The author meetings were hosted by the Blackwater National Wildlife 

Refuge in Maryland; the NOAA National Marine Fisheries Service in Sandy Hook, New 

Jersey; and the Partnership for the Sounds in Columbia, North Carolina 

The authors were also assisted by several of their colleagues at EPA, NOAA, and USGS. 

The interagency management team of Rona Birnbaum, EPA; Patricia Jellison, USGS; 

and Michael Szabados, NOAA, were instrumental in advising the authors during the final 

stages of the report. Rebecca Feldman of NOAA provided key logistical support in 
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addition to her contributions as an author. Karen Scott of EPA managed the expert review 

process, supported by Perrin Quarles Associates. 

The USGS authors thank several colleagues for their reviews, discussions, and 

contributions to Chapters 1, 3, 4, 13, and 14, as well as other portions of the report. These 

include: Mark Brinson, East Carolina University; Tom Cronin, USGS; Duncan 

FitzGerald, Boston University; Virginia Burkett, USGS; Curt Larsen, USGS, (retired); 

Laura Moore, University of Virginia; Elizabeth Pendleton, USGS; Shea Penland 

(deceased), University of New Orleans; and Asbury Sallenger, USGS. 

Russ Jones of Stratus Consulting coordinated technical and GIS support for several 

chapters in this report, with support from Jue Wang, Pyramid Systems Inc.; Richard 

Streeter and Tom Hodgson, Stratus Consulting; and John Herter and Gaurav Sinha, 

Industrial Economics. Christina Thomas (contractor to Stratus Consulting) edited the 

expert review draft. 

Chapter 3 includes results of a panel assessment. The authors of Chapter 3 thank the 

panelists for their contributions: Fred Anders, New York State, Dept. of State; K. Eric 

Anderson, USGS; Mark Byrnes, Applied Coastal Research and Engineering; Donald R. 

Cahoon, USGS; Stewart Farrell, Richard Stockton College; Duncan FitzGerald, Boston 

University, Massachusetts; Paul Gayes, Coastal Carolina University; Carl Hobbs, 

Virginia Institute of Marine Science; Randy McBride, George Mason University; Jesse 

McNinch, Virginia Institute of Marine Science; Stan Riggs, East Carolina University; 

Antonio Rodriguez, University North Carolina; Jay Tanski, New York Sea Grant; Art 

Trembanis, University of Delaware. 

Chapter 4 includes results based on a panel assessment. The panel consisted of: Denise 

Reed, University of New Orleans; Dana Bishara, USGS; Jeffrey Donnelly, Woods Hole 

Oceanographic Institution; Michael Kearney, University of Maryland; Alexander Kolker, 

Louisiana Universities Marine Consortium; Lynn Leonard, University of North CarolinaWilmington; Richard Orson, Orson Environmental Consulting, J. Court Stevenson, 

University of Maryland. The panel was conducted under contract to EPA, with James G. 

Titus as the project officer. Jeff DeBlieux of The Nature Conservancy also contributed to 

portions of Chapter 4. 

The review process for SAP 4.1 included a public review of the Second draft. We thank 

the individuals who commented on this draft. The author team carefully considered all 

comments submitted, and many resulted in improvements to this Product. 

We also thank the team of editors that worked closely with authors to produce this 

product. This includes Anne Waple, CCSP/STG Inc., and the graphics team at the 

National Climatic Data Center. 

Finally, we are especially grateful to Alan Cohn of EPA for his management of the dayto-day process of developing and producing this report, and providing overall 

coordination for this effort.
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Preface

The U.S. Climate Change Science Program (CCSP) was launched in February 2002 as a 

collaborative federal interagency program, under a new cabinet-level organization 

designed to improve the government-wide management and dissemination of climate 

change science and related technology development. The mission of the CCSP is to 

“facilitate the creation and application of knowledge of the Earth’s global environment 

through research, observations, decision support, and communication”. This Product is 

one of 21 synthesis and assessment products (SAPs) identified in the 2003 Strategic Plan 

for the U.S. Climate Change Science Program, written to help achieve this mission. The 

SAPs are intended to support informed discussion and decisions by policymakers, 

resource managers, stakeholders, the media, and the general public. The products help 

meet the requirements of the Global Change Research Act of 1990, which directs 

agencies to “produce information readily usable by policymakers attempting to formulate 

effective strategies for preventing, mitigating, and adapting to the effects of global 

change” and to undertake periodic scientific assessments. 

One of the major goals within the mission is to understand the sensitivity and adaptability 

of different natural and managed ecosystems and human systems to climate and related 

global changes. This SAP (4.1), Coastal Sensitivity to Sea-Level Rise: A Focus on the 

Mid-Atlantic Region, addresses this goal by providing a detailed assessment of the effects 

of sea-level rise on coastal environments and presenting some of the challenges that need 

to be addressed in order to adapt to sea-level rise while protecting environmental 

resources and sustaining economic growth. It is intended to provide the most current 
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knowledge regarding the implications of rising sea level and possible adaptive responses, 

particularly in the mid-Atlantic region of the United States. 

P.1 SCOPE AND APPROACH OF THIS PRODUCT 

The focus of this Product is to identify and review the potential impacts of future sealevel rise based on present scientific understanding. To do so, this Product evaluates 

several aspects of sea-level rise impacts to the natural environment and examines the 

impact to human land development along the coast. In addition, the Product addresses the 

connection between sea-level rise impacts and current adaptation strategies, and assesses 

the role of the existing coastal management policies in identifying and responding to 

potential challenges. 

As with other SAPs, the first step in the process of preparing this Product was to publish 

a draft prospectus listing the questions that the product would seek to answer at the local 

and mid-Atlantic scale. After public comment, the final prospectus listed ten questions. 

This Product addresses those ten questions, and answers most of them with specificity. 

Nevertheless, development of this Product has also highlighted current data and 

analytical capacity limitations. The analytical presentation in this Product focuses on 

what characterizations can be provided with sufficient accuracy to be meaningful. For a 

few questions, the published literature was insufficient to answer the question with great 

specificity. Nevertheless, the effort to answer the question has identified what 

information is needed or desirable, and current limitations with regard to available data 

and tools. 
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This Product focuses on the U.S. mid-Atlantic coast, which includes the eight states from 

New York to North Carolina. The Mid-Atlantic is a region where high population density 

and extensive coastal development is likely to be at increased risk due to sea-level rise. 

Other coastal regions in the United States, such as the Gulf of Mexico and the Florida 

coast, are potentially more vulnerable to sea-level rise and have been the focus of other 

research and assessments, but are outside the scope of this Product. 

During the preparation of this Product, three regional meetings were held between the 

author team and representatives from relevant local, county, state, and federal agencies, 

as well non-governmental organizations. Many of the questions posed in the prospectus 

for SAP 4.1 were discussed in detail and the feedback has been incorporated into the 

Product. However, the available data are insufficient to answer all of the questions at both 

the local and regional scale. Therefore, the results of this Product are best used as a 

“starting point” for audiences seeking information about sensitivity to and implications of 

sea-level rise. 

 

Many of the findings included in this Product are expressed using common terms of 

likelihood (e.g., very likely, unlikely), similar to those used in the 2007 

Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, Climate 

Change 2007: The Physical Science Basis. The likelihood determinations used in this 

Product were established by the authors and modeled after other CCSP SAPs such as 

CCSP SAP 1.1, Temperature Trends in the Lower Atmosphere: Steps for Understanding 
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and Reconciling Differences. However, characterizations of likelihood in this Product are 

largely based on the judgment of the authors and uncertainties from published peerreviewed literature (Figure P.1). Data on how coastal ecosystems and specific species 

may respond to climate change is limited to a small number of site-specific studies, often 

carried out for purposes unrelated to efforts to evaluate the potential impact of sea-level 

rise. Nevertheless, being able to characterize current understanding―and the uncertainty 

associated with that information―is important. In the main body of this Product, any use 

of the terms in Figure P.1 reflect qualitative assessment of potential changes based on the 

authors’ review and understanding of available published coastal science literature and of 

governmental policies (the appendices do not contain findings). Statements that do not 

use these likelihood terms either have an insufficient basis for assessing likelihood or 

present information provided in the referenced literature which was not accompanied by 

assessments of likelihood. 

Figure P.1 Likelihood terms and related probabilities used for this Product (with the exception of 

Appendix 1). 

The International System of Units (SI) have been used in this Product; with English units 

often provided in parentheses. Where conversions are not provided, some readers may 

wish to convert from SI to English units using the following table: 
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Table P.1 Conversion from the International System of Units (SI) to English units

Multiply By To obtain 

Length 

centimeter (cm) 0.3937 inch (in) 

millimeter (mm) 0.0394 inch (in) 

meter (m) 3.2808 foot (ft) 

kilometer (km) 0.6214 mile (mi) 

meter (m) 1.0936 yard (yd) 

Area 

square meter (sq m) 0.000247 acres 

hectare (ha) 2.47 acres 

square kilometer (sq km) 247 acres 

square meter (sq m) 10.7639 square foot (sq ft) 

hectare (ha) 0.00386 square mile (sq mi) 

square kilometer (sq km) 0.3861 square mile (sq mi) 

Rate of Change 

meters per year (m per year) 3.28084 foot per year (ft per year) 

millimeters per year (mm per year) 0.03937 inch per year (in per year) 

meters per second (m per sec) 1.943 knots 

P.2 FUTURE SEA-LEVEL SCENARIOS ADDRESSED IN THIS PRODUCT 

In this Product, the term “sea level” refers to mean sea level or the average level of tidal 

waters, generally measured over a 20-year period. These measurements generally indicate 

the water level relative to the land, and thus incorporate changes in the elevation of the 

land (i.e., subsidence or uplift) as well as absolute changes in sea level (i.e., rise in sea 

level caused by increasing its volume or adding water). For clarity, scientists often use 

two different terms: 

 “Global sea-level rise” is the average increase in the level of the world’s oceans 

that occurs due to a variety of factors, the most significant being thermal 
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expansion of the oceans and the addition of water by melting of land-based ice 

sheets, ice caps, and glaciers. 

 “Relative sea-level rise” refers to the change in sea level relative to the elevation 

of the adjacent land, which can also subside or rise due to natural and humaninduced factors. Relative sea-level changes include both global sea-level rise and 

changes in the vertical elevation of the land surface. 

In this Product, both terms are used. Global sea-level rise is used when referring to the 

worldwide average increase in sea level. Relative sea-level rise, or simply sea-level rise, 

is used when referring to the scenarios used in this Product and effects on the coast. 

This Product does not provide a forecast of future rates of sea-level rise. Rather, it 

evaluates the implications of three relative sea-level rise scenarios over the next century 

developed from a combination of the twentieth century relative sea-level rise rate and 

either a 2 or 7 millimeter per year increase in global sea level: 

 Scenario 1: the twentieth century rate, which is generally 3 to 4 millimeters per 

year in the mid-Atlantic region (30 to 40 centimeters total by the year 2100); 

 Scenario 2: the twentieth century rate plus 2 millimeters per year acceleration (up 

to 50 centimeters total by 2100); 

 Scenario 3: the twentieth century rate plus 7 millimeters per year acceleration (up 

to 100 centimeters total by 2100). 
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The twentieth century rate of sea-level rise refers to the local long-term rate of relative 

sea-level rise that has been observed at NOAA National Ocean Service (NOS) tide 

gauges in the mid-Atlantic study region. Scenario 1 assesses the impacts if future sealevel rise occurs at the same rate as was observed over the twentieth century at a 

particular location. Scenarios 1 and 2 are within the range of those reported in the recent 

IPCC Report Climate Change 2007: The Physical Science Basis, specifically in the 

chapter Observations: Oceanic Climate Change and Sea Level, while Scenario 3 exceeds 

the IPCC scenario range by up to 40 centimeters by 2100. Higher estimates, as suggested 

by some recent publications, are the basis for Scenario 3. In addition to these three 

scenarios, some chapters refer to even higher sea-level rise scenarios, such as a 200 

centimeter rise over the next few hundred years (a high but plausible estimate if ice sheet 

melting on Greenland and West Antarctica exceeds IPCC model estimates). 

P.3 PRODUCT ORGANIZATION 

This Product is divided into four parts: 

Part I first provides context and addresses the effects of sea-level rise on the physical 

environment. Chapter 1 provides the context for sea-level rise and its effects. Chapter 2 

discusses the current knowledge and limitations in coastal elevation mapping. Chapter 3 

describes the physical changes at the coast that will result in changes to coastal landforms 

(e.g., barrier islands) and shoreline position in response to sea-level rise. Chapter 4 

considers the ability of wetlands to accumulate sediments and survive in response to 
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rising sea level. Chapter 5 examines the habitats and species that will be vulnerable to 

sea-level rise related impacts. 

Part II describes the societal impacts and implications of sea-level rise. Chapter 6 

provides a framework for assessing shoreline protection options in response to sea-level 

rise. Chapter 7 discusses the extent of vulnerable population and infrastructure, and 

Chapter 8 addresses the implications for public access to the shore. Chapter 9 reviews the 

impact of sea-level rise to flood hazards. 

Part III examines strategies for coping with sea-level rise. Chapter 10 outlines key 

considerations when making decisions to reduce vulnerability. Chapter 11 discusses what 

organizations are currently doing to adapt to sea-level rise, and Chapter 12 examines 

possible institutional barriers to adaptation. 

Part IV examines national implications and a science strategy for moving forward. 

Chapter 13 discusses sea-level rise impacts and implications at a national scale and 

highlights how coasts in other parts of the United States are vulnerable to sea-level rise. 

Chapter 14 presents opportunities for future efforts to reduce uncertainty and close gaps 

in scientific knowledge and understanding. 

Finally, this Product also includes two appendices: Appendix 1 discusses many of the 

species that depend on potentially vulnerable habitat in specific estuaries, providing local 

elaboration of the general issues examined in Chapter 5. The Appendix also describe key 
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statutes, regulations, and other policies that currently define how state and local 

governments are responding to sea-level rise, providing support for some of the 

observations made in Part III. This Appendix is provided as background information and 

does not include findings or an independent assessment of likelihood. 

 

Appendix 2 reviews some of the basic approaches that have been used to conduct 

shoreline change or land loss assessments in the context of sea-level rise and some of the 

difficulties that arise in using these methods. 

Technical and scientific terms are used throughout this Product. To aid readers with these 

terms, a Glossary and a list of Acronyms and Abbreviations are included at the end of the 

Product. 
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Executive Summary 

Authors: K. Eric Anderson, USGS; Donald R. Cahoon, USGS; Stephen K. Gill, NOAA; 

Benjamin T. Gutierrez, USGS; E. Robert Thieler, USGS; James G. Titus, U.S. EPA; S. 

Jeffress Williams, USGS (lead authors arranged in alphabetical order). 

Global sea level is rising, and there is evidence that the rate is accelerating. Increasing 

atmospheric concentrations of greenhouse gases, primarily from human contributions, are 

very likely warming the atmosphere and oceans. The warmer temperatures raise sea level 

by expanding ocean water, melting glaciers, and possibly increasing the rate at which ice 

sheets discharge ice and water into the oceans. Rising sea level and the potential for 

stronger storms pose an increasing threat to coastal cities, residential communities, 

infrastructure, beaches, wetlands, and ecosystems. The potential impacts to the United 

States extend across the entire country: ports provide gateways for transport of goods 

domestically and abroad; coastal resorts and beaches are central to the U.S. economy; 

wetlands provide valuable ecosystem services such as water filtering and spawning 

grounds for commercially important fisheries. How people respond to sea-level rise in the 

coastal zone will have potentially large economic and environmental costs. 

This Synthesis and Assessment Product examines the implications of rising sea level, 

with a focus on the mid-Atlantic region of the United States, where rates of sea-level rise 

are moderately high, storm impacts occur, and there is a large extent of critical habitat 
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(marshes), high population densities, and infrastructure in low-lying areas. Although 

these issues apply to coastal regions across the country, the mid-Atlantic region was 

selected as a focus area to explore how addressing both sensitive ecosystems and impacts 

to humans will be a challenge. Using current scientific literature and expert panel 

assessments, this Product examines potential risks, possible responses, and decisions that 

may be sensitive to sea-level rise. 

The information, data, and tools needed to inform decision-making with regard to sealevel rise are evolving, but insufficient to assess the implications at scales of interest to all 

stakeholders. Accordingly, this Product can only provide a starting point to discuss 

impacts and examine possible responses at the regional scale. The Product briefly 

summarizes national scale implications and outlines the steps involved in providing 

information at multiple scales (e.g., local).

ES.1 WHY IS SEA LEVEL RISING? HOW MUCH WILL IT RISE? 

During periods of climate warming, two major processes cause global mean sea-level 

rise: (1) as the ocean warms, the water expands and increases its volume and (2) land 

reservoirs of ice and water, including glaciers and ice sheets, contribute water to the 

oceans. In addition, the land in many coastal regions is subsiding, adding to the 

vulnerability to the effects of sea-level rise. 

Recent U.S. and international assessments of climate change show that global average sea 

level rose approximately 1.7 millimeters per year through the twentieth century, after a 
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period of little change during the previous two thousand years. Observations suggest that 

the rate of global sea-level rise may be accelerating. In 2007, the Intergovernmental Panel 

on Climate Change (IPCC) projected that global sea level will likely rise between 19 and 

59 centimeters (7 and 23 inches) by the end of the century (2090 to 2099), relative to the 

base period (1980 to 1999), excluding any rapid changes in ice flow from Greenland and 

Antarctica. According to the IPCC, the average rate of global sea-level rise during the 

twenty-first century is very likely to exceed the average rate over the last four decades. 

Recently observed accelerated ice flow and melting in some Greenland outlet glaciers 

and West Antarctic ice streams could substantially increase the contribution from the ice 

sheets to rates of global sea-level rise. Understanding of the magnitude and timing of 

these processes is limited and, thus, there is currently no consensus on the upper bound of 

global sea-level rise. Recent studies suggest the potential for a meter or more of global 

sea-level rise by the year 2100, and possibly several meters within the next several 

centuries. 

In the mid-Atlantic region from New York to North Carolina, tide-gauge observations 

indicate that relative sea-level rise (the combination of global sea-level rise and land 

subsidence) rates were higher than the global mean and generally ranged between 2.4 and 

4.4 millimeters per year, or about 0.3 meters (1 foot) over the twentieth century. 

ES.2 WHAT ARE THE EFFECTS OF SEA-LEVEL RISE? 

Coastal environments such as beaches, barrier islands, wetlands, and estuarine systems 

are closely linked to sea level. Many of these environments adjust to increasing water 
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level by growing vertically, migrating inland, or expanding laterally. If the rate of sealevel rise accelerates significantly, coastal environments and human populations will be 

affected. In some cases, the effects will be limited in scope and similar to those observed 

during the last century. In other cases, thresholds may be crossed, beyond which the 

impacts would be much greater. If the sea rises more rapidly than the rate with which a 

particular coastal system can keep pace, it could fundamentally change the state of the 

coast. For example, rapid sea-level rise can cause rapid landward migration or 

segmentation of some barrier islands, or disintegration of wetlands. 

Today, rising sea levels are submerging low-lying lands, eroding beaches, converting 

wetlands to open water, exacerbating coastal flooding, and increasing the salinity of 

estuaries and freshwater aquifers. Other impacts of climate change, coastal development, 

and natural coastal processes also contribute to these impacts. In undeveloped or lessdeveloped coastal areas where human influence is minimal, ecosystems and geological 

systems can sometimes shift upward and landward with the rising water levels. Coastal 

development, including buildings, roads, and other infrastructure, are less mobile and 

more vulnerable. Vulnerability to an accelerating rate of sea-level rise is compounded by 

the high population density along the coast, the possibility of other effects of climate 

change, and the susceptibility of coastal regions to storms and environmental stressors, 

such as drought or invasive species. 

ES.2.1 Sea-Level Rise and the Physical Environment 
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The coastal zone is dynamic and the response of coastal areas to sea-level rise is more 

complex than simple inundation. Erosion is a natural process from waves and currents 

and can cause land to be lost even with a stable sea level. Sea-level rise can exacerbate 

coastal change due to erosion and accretion. While some wetlands can keep pace with 

sea-level rise due to sediment inputs, those that cannot keep pace will gradually degrade 

and become submerged. Shore protection and engineering efforts also affect how coasts 

are able to respond to sea-level rise. 

For coastal areas that are vulnerable to inundation by sea-level rise, elevation is generally 

the most critical factor in assessing potential impacts. The extent of inundation is 

controlled largely by the slope of the land, with a greater area of inundation occurring in 

locations with more gentle gradients. Most of the currently available elevation data do not 

provide the degree of confidence that is needed for making quantitative assessments of 

the effects of sea-level rise for local planning and decision making. However, systematic 

collection of high-quality elevation data (i.e., lidar) will improve the ability to conduct 

detailed assessments (Chapter 2). 

Nationally, coastal erosion will probably increase as sea-level rises at rates higher than 

those that have been observed over the past century. The exact manner and rates at which 

these changes are likely to occur will depend on the character of coastal landforms (e.g., 

barrier islands, cliffs) and physical processes (Part I). Particularly in sandy shore 

environments which comprise the entire mid-Atlantic ocean coast (Figure ES.1), it is 

virtually certain that coastal headlands, spits, and barrier islands will erode at a faster 
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pace in response to future sea-level rise. For sea-level rise scenarios greater than 7 

millimeters per year, it is likely that some barrier islands in this region will cross a 

threshold where rapid barrier island migration or segmentation will occur (Chapter 3). 

Figure ES.1 Potential mid-Atlantic coastal landform responses to three sea-level rise scenarios. Most 

coastal areas are currently experiencing erosion, which is expected to increase with future sea-level rise. In 

addition to undergoing erosion, coastal segments denoted with a “T” may also cross a threshold where 

rapid barrier island migration or segmentation will occur. 

Tidal wetlands in the United States, such as the Mississippi River Delta in Louisiana and 

Blackwater River marshes in Maryland, are already experiencing submergence by 

relative sea-level rise and associated high rates of wetland loss. 
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For the mid-Atlantic region (Figure ES.2), acceleration in sea-level rise by 2 millimeters 

per year will cause many wetlands to become stressed; it is likely that most wetlands will 

not survive acceleration in sea-level rise by 7 millimeters per year. Wetlands may expand 

inland where low-lying land is available but, if existing wetlands cannot keep pace with 

sea-level rise, the result will be an overall loss of wetland area in the Mid-Atlantic. The 

loss of associated wetland ecosystem functions (e.g., providing flood control, acting as a 

storm surge buffer, protecting water quality buffer, and serving as a nursery area) can 

have important societal consequences, such as was seen with the storm surge impacts 

associated with Hurricanes Katrina and Rita in southern Louisiana, including New 

Orleans, in 2005. Nationally, tidal wetlands already experiencing submergence by sealevel rise and associated land loss (e.g., Mississippi River delta in Louisiana, and 

Blackwater River marshes in Maryland) will continue to lose area in response to future 

accelerated rates of sea-level rise and changes in other climate and environmental drivers. 
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Figure ES.2 Areas where wetlands would be marginal or lost (i.e., converted to open water) under three 

sea-level rise scenarios. 

Terrestrial and aquatic plants and animals that rely on coastal habitat are likely to be 

stressed and adversely affected as sea level rises. The quality, quantity, and spatial 

distribution of coastal habitats will change as a result of erosion, salinity changes, and 

wetland loss. Depending on local conditions, habitat may be lost or migrate inland in 

response to sea-level rise. Loss of tidal marshes would seriously threaten coastal 

ecosystems, causing fish and birds to move or produce fewer offspring. Many estuarine 

beaches may also be lost, threatening numerous species (Chapter 5). 
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Sea-level rise is just one of many factors affecting coastal habitats: sediment input, 

nutrient runoff, fisheries management, and other factors are also important. Under natural 

conditions, habitats are continually shifting, and species generally have some flexibility 

to adapt to varied geography and/or habitat type. Future habitat and species loss will be 

determined by factors that include rates of wetland submergence, coastal erosion, and 

whether coastal landforms and present-day habitats have space to migrate inland. As 

coastal development continues, the ability for habitats to change and migrate inland along 

the rest of the coast will not only be a function of the attributes of the natural system, but 

also of the coastal management policies for developed and undeveloped areas. 

ES.2.2 Societal Impacts and Implications 

Increasing population, development, and supporting infrastructure in the coastal zone 

often compete with the desire to maintain the benefits that natural ecosystems (e.g., 

beaches, barrier islands, and wetlands) provide to humans. Increasing sea level will put 

additional stress on the ability to manage these competing interests effectively (Chapter 

7). In the Mid-Atlantic, for example, movement to the coast and development continues, 

despite the growing vulnerability to coastal hazards. 

Rising sea level increases the vulnerability of development on coastal floodplains. Higher 

sea level provides an elevated base for storm surges to build upon and diminishes the rate 

at which low-lying areas drain, thereby increasing the risk of flooding from rainstorms. 

Increases in shore erosion also contribute to greater flood damages by removing 
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protective dunes, beaches, and wetlands and by leaving some properties closer to the 

water's edge (Chapter 9). 

ES.3 HOW CAN PEOPLE PREPARE FOR SEA-LEVEL RISE? 

ES.3.1 Options for Adapting to Sea-level Rise 

At the current rate of sea-level rise, coastal residents and businesses have been 

responding by rebuilding at the same location, relocating, holding back the sea by coastal 

engineering, or some combination of these approaches. With a substantial acceleration of 

sea-level rise, traditional coastal engineering may not be economically or 

environmentally sustainable in some areas (Chapter 6). 

Nationally, most current coastal policies do not accommodate accelerations in sea-level 

rise. Floodplain maps, which are used to guide development and building practices in 

hazardous areas, are generally based upon recent observations of topographic elevation 

and local mean sea-level. However, these maps often do not take into account accelerated 

sea-level rise or possible changes in storm intensity (Chapter 9). As a result, most shore 

protection structures are designed for current sea level, and development policies that rely 

on setting development back from the coast are designed for current rates of coastal 

erosion, not taking into account sea level rise. 

ES.3.2 Adapting to Sea-level Rise 

The prospect of accelerated sea-level rise underscores the need to rigorously assess 

vulnerability and examine the costs and benefits of taking adaptive actions. Determining 
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whether, what, and when specific actions are justified is not simple, due to uncertainty in 

the timing and magnitude of impacts, and difficulties in quantifying projected costs and 

benefits. Key opportunities for preparing for sea-level rise include: provisions for 

preserving public access along the shore (Chapter 8); land-use planning to ensure that 

wetlands, beaches, and associated coastal ecosystem services are preserved (Chapter 10); 

siting and design decisions such as retrofitting (e.g., elevating buildings and homes) 

(Chapter 10); and examining whether and how changing risk due to sea-level rise is 

reflected in flood insurance rates (Chapter 10). 

However, the time, and often cultural shift, required to make change in federal, state, and 

local policies is sometimes a barrier to change. In the mid-Atlantic coastal zone, for 

example, although the management community recognizes sea-level rise as a coastal 

flooding hazard and state governments are starting to face the issue of sea-level rise, only 

a limited number of analyses and resulting statewide policy revisions to address rising sea 

level have been undertaken (Chapters 9, 11). Current policies in some areas are now 

being adapted to include the effects of sea-level rise on coastal environments and 

infrastructure. Responding to sea-level rise requires careful consideration regarding 

whether and how particular areas will be protected with structures, elevated above the 

tides, relocated landward, or left alone and potentially given up to the rising sea (Chapter 

12). 

Many coastal management decisions made today have implications for sea-level rise 

adaptation. Existing state policies that restrict development along the shore to mitigate 
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hazards or protect water quality (Appendix 1) could preserve open space that may also 

help coastal ecosystems adapt to rising sea level. On the other hand, efforts to fortify 

coastal development can make it less likely that such an area would be abandoned as sea 

level rises (Chapter 6). A prime opportunity for adapting to sea-level rise in developed 

areas may be in the aftermath of a severe storm (Chapter 9). 

ES.4 HOW CAN SCIENCE IMPROVE UNDERSTANDING AND 

PREPAREDNESS FOR FUTURE SEA-LEVEL RISE? 

This Product broadly synthesizes physical, biological, social, and institutional topics 

involved in assessing the potential vulnerability of the mid-Atlantic United States to sealevel rise. This includes the potential for landscape changes and associated geological and 

biological processes; and the ability of society and its institutions to adapt to change. 

Current limitations in the ability to quantitatively assess these topics at local, regional, 

and national scales may affect whether, when, and how some decisions will be made. 

Scientific syntheses and assessments such as this have different types and levels of 

uncertainty. Part I of this Product describes the physical settings and processes in the 

Mid-Atlantic and how they may be impacted by sea-level rise. There is uncertainty 

regarding coastal elevations and the extent to which some areas will be inundated. In 

some areas, coastal elevations have been mapped with great detail and accuracy, and thus 

the data have the requisite high degree of certainty for local decision making by coastal 

managers. In many other areas, the coarser resolution and limited vertical accuracy of the 

available elevation data preclude their use in detailed assessments, but the uncertainty can 
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be explicitly quantified (Chapter 2). The range of physical and biological processes 

associated with coastal change is poorly understood at some of the time and space scales 

required for decision making. For example, although the scope and general nature of the 

changes that can occur on ocean coasts in response to sea-level rise are widely 

recognized, how these changes occur in response to a specific rise in sea level is difficult 

to predict (Chapter 3). Similarly, current model projections of wetland vulnerability on 

regional and national scales are uncertain due to the coarse level of resolution of 

landscape-scale models. While site-specific model projections are quite good where local 

information has been acquired on factors that control local accretionary processes in 

specific wetland settings, such projections cannot presently be generalized so as to apply 

to larger regional or national scales with high confidence (Chapter 4). The cumulative 

impacts of physical and biological change due to sea-level rise on the quality and quantity 

of coastal habitats are not well understood. 

Like the uncertainties associated with the physical settings, the potential human responses 

to future sea-level rise described in Part II of this Product are also uncertain. Society 

generally responds to changes as they emerge. The decisions that people make to respond 

to sea-level rise could be influenced by the physical setting, the properties of the built 

environment, social values, the constraints of regulations and economics, as well as the 

level of uncertainty in the form and magnitude of future coastal change. This Product 

examines some of the available options and assesses actions that federal and state 

governments and coastal communities could take in response to sea-level rise. For 

example, as rising sea level impacts coastal lands, a fundamental choice is whether to 
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attempt to hold back the sea or allow nature to takes its course. Both choices have 

important costs and uncertainties (Chapter 6). 

 

Part III of this Product focuses on what might be done to prepare for sea-level rise. As 

discussed above, the rate, timing, and impacts of future sea-level rise are uncertain, with 

important implications for decision-making. For example, planning for sea-level rise 

requires examining the benefits and costs of such issues as coastal wetland protection, 

existing and planned coastal infrastructure, and management of floodplains in the context 

of temporal and spatial uncertainty (Chapter 10). In addition, institutional barriers can 

make it difficult to incorporate the potential impacts of future sea-level rise into coastal 

planning (Chapter 12). 

ES.4.1 Enhance Understanding 

An integrated scientific program of sea-level studies would reduce gaps in current 

knowledge and the uncertainty about the potential responses of coasts, estuaries, 

wetlands, and human populations to sea-level rise. This program should focus on 

expanded efforts to monitor ongoing physical and environmental changes, using new 

technologies and higher resolution elevation data as available. Insights from the historic 

and geologic past also provide important perspectives. A key area of uncertainty is the 

vulnerability of coastal landforms and wetlands to sea-level rise; therefore, it is important 

to understand the dynamics of barrier island processes and wetland accretion, wetland 

migration, and the effects of land-use change as sea-level rise continues. Understanding, 

predicting, and responding to the environmental and societal effects of sea-level rise 
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would require an integrated program of research that includes both natural and social 

sciences. Social science research is a necessary component as sea-level rise vulnerability, 

sea-level rise impacts, and the success of many adaptation strategies will depend on 

characterizing the social, economic, and political contexts in which management 

decisions are made (Chapter 14). 

ES.4.2 Enhance Decision Support 

Decision making on regional and local levels in the coastal zone can be supported by 

improved understanding of vulnerabilities and risks of sea-level rise impacts. Developing 

tools, datasets, and other coastal management information is key to supporting and 

promoting sound coastal planning, policy making, and decisions. This includes providing 

easy access to data and information resources and applying this information in an 

integrated framework using such tools as geographic information systems. Integrated 

assessments linking physical vulnerability with economic analyses and planning options 

will be valuable, as will efforts to assemble and assess coastal zone planning adaptation 

options for federal, state, and local decision makers. Stakeholder participation in every 

phase of this process is important, so that decision makers and the public have access to 

the information that they need and can make well-informed choices regarding sea-level 

rise and the consequences of different management decisions. Coastal planning and 

policies that are consistent with the reality of a rising sea could enable U.S. coastal 

communities to avoid or adapt to its potential environmental, societal, and economic 

impacts. 
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Part I Overview. The Physical Environment 

Authors: Donald R. Cahoon, USGS; S. Jeffress Williams, USGS; Benjamin T. 

Gutierrez, USGS; K. Eric Anderson, USGS; E. Robert Thieler, USGS; Dean B. Gesch; 

USGS 

The first part of this Product examines the potential physical and environmental impacts 

of sea-level rise on the coastal environments of the mid-Atlantic region. Rising sea level 

over the next century will have a range of effects on coastal regions, including land loss 

and shoreline retreat from erosion and inundation, an increase in the frequency of stormrelated flooding, and intrusion of salt water into coastal freshwater aquifers. The 

sensitivity of a coastal region to sea-level rise depends both on the physical aspects 

(shape and composition) of a coastal landscape and its ecological setting. One of the most 

obvious impacts is that there will be land loss as coastal areas are inundated and eroded. 

Rising sea level will not only inundate the landscape but will also be a driver of change 

for the coastal landscape. These impacts will have large effects on natural environments 

such as coastal wetland ecosystems, as well as effects on human development in coastal 

regions (see Part II of this Product). Making long-term projections of coastal change is 

difficult because of the multiple, interacting factors that contribute to that change. Given 

the large potential impacts to human and natural environments, there is a need to improve 

our ability to conduct long-term projections. 
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Part I describes the physical settings of the mid-Atlantic coast as well as the processes 

that influence shoreline change and land loss in response to sea-level rise. Part I also 

provides an assessment of coastal changes that may occur over the twenty-first century, 

as well as the consequences of those changes for coastal habitats and the flora and fauna 

they support. 

Chapter 1 provides an overview of the current understanding of climate change and sealevel rise and their potential effects on both natural environments and society, and 

summarizes the background information that was used to develop this Product. Sea-level 

rise will have a range of impacts to both natural systems and human development and 

infrastructure in coastal regions. A major challenge is to understand the extent of these 

impacts and how to develop planning and adaption strategies that address both the quality 

of the natural environment and human interests. 

Chapter 2 highlights the important issues in analysis of sea-level rise vulnerability based 

on coastal elevation data. Elevation is a critical factor in determining vulnerability to 

inundation, which will be the primary response to sea-level rise for only some locations 

in the mid-Atlantic region. Because sea-level rise impact assessments often rely on 

elevation data, it is important to understand the inherent accuracy of the underlying data 

and its effects on the uncertainty of any resulting vulnerability maps and statistical 

summaries. The existing studies of sea-level rise vulnerability in the Mid-Atlantic based 

on currently available elevation data do not provide the level of confidence that is optimal 

for local decision making. However, recent research using newer high-resolution, high 
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accuracy elevation data is leading toward development of improved capabilities for 

vulnerability assessments. 

Chapter 3 summarizes the factors and processes controlling the dynamics of ocean coasts. 

The major factor affecting the location and shape of coasts at centennial and longer time 

scales is global sea-level change, which is linked to the Earth’s climate. These close 

linkages are well documented in the scientific literature from field studies conducted over 

the past few decades. The details of the process-response relationships, however, are the 

subject of active, ongoing research. The general characteristics and shape of the coast 

(coastal morphology) reflects complex and ongoing interactions between changes in sea 

level, the physical processes that act on the coast (hydrodynamic regime, e.g., waves and 

tidal characteristics), the availability of sediment (sediment supply) transported by waves 

and tidal currents at the shore, and underlying geology (the structure and composition of 

the landscape which is often referred to as the geologic framework). Variations in these 

three factors are responsible for the different coastal landforms and environments 

occurring in the coastal regions of the United States. Chapter 2 presents a synthesis and 

assessment of the potential changes that can be expected for the mid-Atlantic shores of 

the United States which are primarily comprised of beaches and barrier islands. 

Chapter 4 describes the vulnerability of coastal wetlands in the mid-Atlantic region to 

current and future sea-level rise. The fate of coastal wetlands is determined in large part 

by the way in which wetland vertical development processes change with climate drivers. 

In addition, the processes by which wetlands build vertically vary by geomorphic setting. 
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Chapter 3 identifies those important climate drivers affecting wetland vertical 

development in the geomorphic settings of the mid-Atlantic region. The information on 

climate drivers, wetland vertical development, geomorphic settings, and local sea-level 

rise trends was synthesized and assessed using an expert decision process to determine 

wetland vulnerability for each geomorphic setting in each subregion of the mid-Atlantic 

region. 

Chapter 5 summarizes the potential impacts to biota as a result of habitat change or loss 

driven by sea-level rise. Habitat quality, extent, and spatial distribution will change as a 

result of shore erosion, wetland loss, and shifts in estuarine salinity gradients. Of 

particular concern is the loss of wetland habitats and the important ecosystem functions 

they provide, which include critical habitat for wildlife, the trapping of sediments, 

nutrients, and pollutants, the cycling of nutrients and minerals, the buffering of storm 

impacts on coastal environments, and the exchange of materials with adjacent 

ecosystems. 

 
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Chapter 1: Sea-Level Rise and its Effects on the Coast 

Lead Authors: S. Jeffress Williams, USGS; Benjamin T. Gutierrez, USGS; James G. 

Titus, U.S. EPA; Stephen K. Gill, NOAA; Donald R. Cahoon, USGS; E. Robert Thieler, 

USGS; K. Eric Anderson, USGS (retired) 

Contributing Authors: Duncan FitzGerald, Boston University; Virginia Burkett, 

USGS; Jason Samenow, U.S. EPA 

KEY POINTS 

 Consensus in the climate science community is that the global climate is 

changing, mostly due to mankind’s increased emissions of greenhouse gases (25 

percent increase in the last century), such as carbon dioxide, methane, and nitrous 

oxide from burning of fossil fuels and land-use change. Warming of the climate 

system is unequivocal, but the effects of climate change are highly variable across 

regions and difficult to predict with high confidence based on limited 

observations over time and space. Two effects of atmospheric warming on coasts 

on regional, national, and global scales are sea-level rise and increase in major 

cyclone intensity. 

 Global sea level has risen about 120 meters at highly variable rates due to natural 

processes since the end of the Last Glacial Maximum (i.e., last Ice Age). More 

recently, the sea-level rise rate has increased over natural rise due to increase in 

the burning of fossil fuels. In some regions, such as the mid-Atlantic region and 
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much of the Gulf of Mexico, sea-level rise is significantly greater than the 

observed global sea-level rise due to sinking of the land as a result of sediment 

compaction processes. 

 Instrumental observations over the past 15 years show that global mean sea level 

has been highly variable at regional scales around the world and, on average, the 

rate of rise appears to have accelerated over twentieth century rates, possibly due 

to atmospheric warming causing expansion of ocean water and ice-sheet melting. 

 Results of climate model studies suggest sea-level rise in the twenty-first century 

will significantly exceed rates over the past century. Rates and the magnitude of 

rise could be much greater if warming affects dynamical processes that determine 

ice flow and losses in Greenland and Antarctica. 

 Beyond the scope of this Product but important to consider, global sea-level 

elevations at the peak of the last interglacial warm cycle were 4 to 6 meters (13 to 

20 feet) above present, and could be realized within the next several hundred 

years if warming and glacier and ice-sheet melting continue. 

 Coastal regions are characterized by dynamic landforms and processes because 

they are the juncture between the land, oceans, and atmosphere. Features such as 

barrier islands, bluffs, dunes, and wetlands constantly undergo change due to 

driving processes such as storms, sediment supply, and sea-level change. Based 

on surveys over the past century, all U.S. coastal states are experiencing overall 

erosion at highly variable rates. Sea-level rise will have profound effects by 

increasing flooding frequency and inundating low-lying coastal areas, but other 
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processes such as erosion and accretion will have cumulative effects that are 

profound but not yet predictable with high reliability. There is some recent 

scientific opinion that coastal landforms such as barrier islands and wetlands may 

have thresholds or tipping points with sea-level rise and storms, leading to rapid 

and irreversible change. 

 Nearly one-half of the 6.7 billion people around the world live near the coast and 

are highly vulnerable to storms and sea-level rise. In the United States, coastal 

populations have doubled over the past 50 years, greatly increasing exposure to 

risk from storms and sea-level rise. Continued population growth in low-lying 

coastal regions worldwide and in the United States will increase vulnerability to 

these hazards as the effects of climate change become more pronounced. 

 Most coastal regions are currently managed under the premise that sea-level rise 

is not significant and that shorelines are static or can be fixed in place by 

engineering structures. The new reality of sea-level rise due to climate change 

requires new considerations in managing areas to protect resources and reduce 

risk to humans. Long-term climate change impact data are essential for adaptation 

plans to climate change and coastal zone plans are most useful if they have the 

premise that coasts are dynamic and highly variable.

1.1 INTRODUCTION 

The main objective of this Product is to review and assess the potential impacts of sealevel rise on U.S.coastal regions. Careful review and critique of sea-level and climate 

change science is beyond the scope of this Product; however, that information is central 
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in assessing coastal impacts. Climate and coastal scientific disciplines are relatively 

recent, and while uncertainty exists in predicting quantitatively the magnitude and rates 

of change in sea level, a solid body of scientific evidence exists that sea level has risen 

over the recent geologic past, is currently rising and contributing to various effects such 

as coastal erosion, and has the potential to rise at an accelerated rate this century and 

beyond. Worldwide data also show that rates of global sea-level rise are consistent with 

increasing greenhouse gas concentrations and global warming (IPCC, 2001, 2007; 

Hansen et al., 2007; Broecker and Kunzig, 2008). Global climate change is already 

having significant and wide ranging effects on the Earth’s ecosystems and human 

populations (Nicholls et al., 2007). 

In recognition of the influence of humans on the Earth, including the global climate, the 

time period since the nineteenth century is being referred to by scientists as the 

Anthropocene Era (Pearce, 2007; Zalasiewicz, 2008). Changes to the global climate have 

been dramatic and the rapid rate of climate change observed over the past two decades is 

an increasing challenge for adaptation, by humans and animals and plants alike. 

Effects from climate change are not uniform, but vary considerably from region to region 

and over a range of time scales (Nicholls et al., 2007). These variations occur due to 

regional and local differences in atmospheric, terrestrial, and oceanographic processes. 

The processes driving climate change are complex and so-called feedback interactions 

between the processes can both enhance and diminish sea-level rise impacts, making 

prediction of long-term effects difficult. Accelerated global sea-level rise, a likely major 
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long-term outcome of climate change, will have increasingly far-reaching impacts on 

coastal regions of the United States and around the world (Nicholls et al., 2007). Relative 

sea-level rise impacts are already evident for many coastal regions and will increase 

significantly during this century and beyond (FitzGerald et al, 2008; IPCC, 2007; 

Nicholls et al., 2007). Sea-level rise will cause significant and often dramatic changes to 

coastal landforms (e.g., barrier islands, beaches, dunes, marshes), as well as ecosystems, 

estuaries, waterways, and human populations and development in the coastal zone 

(Nicholls et al., 2007; Rosenzweig et al., 2008; FitzGerald et al., 2008). Low-lying 

coastal plain regions, particularly those that are densely populated (e.g.,the Mid-Atlantic, 

the north central Gulf of Mexico), are especially vulnerable to sea-level rise and land 

subsidence and their combined impacts to the coast and to development in the coastal 

zone (e.g., McGranahan et al., 2007; Day et al., 2007a). 

The effects of sea-level rise are not necessarily obvious in the short term, but are evident 

over the longer term in many ways. Arguably, the most visible effect is seen in changing 

coastal landscapes, which are altered through more frequent flooding, inundation, and 

coastal erosion as barrier islands, beaches, and sand dunes change shape and move 

landward in concert with sea-level rise and storm effects. In addition, the alteration or 

loss of coastal habitats such as wetlands, bays, and estuaries has negative impacts on 

many animal and plant species that depend on these coastal ecosystems. 

Understanding how sea-level rise is likely to affect coastal regions and, consequently, 

how society will choose to address this issue in the short term in ways that are sustainable 
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for the long term, is a major challenge for both scientists and coastal policy makers and 

managers. While human populations in high-risk coastal areas continue to expand 

rapidly, the analyses of long-term sea-level measurements show that sea level rose on 

average 19 centimeters (cm) (7.5 inches [in]) globally during the twentieth century 

(Jevrejeva et al., 2008). In addition, satellite data show global sea-level rise has 

accelerated over the past 15 years, but at highly variable rates on regional scales. 

Analyses indicate that the magnitude and rate of sea-level rise for this century and 

beyond is likely to exceed that of the past century (Meehl et al., 2007; Rahmstorf, 2007; 

Jevrejeva et al., 2008). 

Over the last century, humans have generally responded to eroding shorelines and 

flooding landscapes by using engineering measures to protect threatened property or by 

relocating development inland to higher ground. In the future, these responses will 

become more widespread and more expensive for society as sea-level rise accelerates 

(Nicholls et al., 2007). Currently the world population is 6.7 billion people and is 

predicted to expand to 9.1 billion by the year 2042 (UN, 2005). Globally, 44 percent of 

the world’s population lives within 150 kilometers (km) (93 miles [mi]) of the ocean 

(<http://www.oceansatlas.org/index.jsp>) and more than 600 million people live in low 

elevation coastal zone areas that are less than 10 meters (m) (33 feet [ft]) above sea level 

(McGranahan et al., 2007), putting them at significant risk to the effects of sea-level rise. 

The 10 m elevation was chosen as a benchmark for providing population statistics to 

meet data resolution and quality needs because that elevation is a commonly used 

reference elevation for coastal plain regions vulnerable to coastal hazards such as storm-
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surge flooding and sea-level rise. Eight of the 10 largest cities in the world are sited on 

the ocean coast. In the United States, 14 of the 20 largest urban centers are located within 

100 km of the coast and less than 10 m above sea level. Using the year 2000 census data 

for U.S. coastal counties as defined by the National Oceanic and Atmospheric 

Administration (NOAA) and excluding the Great Lakes states, approximately 126 million 

people resided in coastal areas (Crossett et al., 2004). The Federal Emergency 

Management Agency (FEMA), using the same 2000 census data but different criteria for 

defining coastal counties, estimated the coastal population to be 86 million people 

(Crowell, et al., 2007). Regardless, U.S. coastal populations have expanded greatly over 

the past 50 years, increasing exposure to risk from storms and sea-level rise. Continued 

population growth in low-lying coastal regions worldwide and in the United States will 

increase vulnerability to these hazards. 

Modern societies around the world have developed and populations have expanded over 

the past several thousand years under a relatively mild and stable world climate and 

relatively stable sea level (Stanley and Warne, 2003; Day et al., 2007b). However, with 

continued population growth, particularly in coastal areas, and the probability of 

accelerated sea-level rise and increased storminess, adaptation to expected changes will 

become increasingly challenging. 

This Product reviews available scientific literature through late 2008 and assesses the 

likely effects of sea-level rise on the coast of the United States, with a focus on the midAtlantic region. An important point to emphasize is that sea-level rise impacts will be far-
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reaching. Coastal lands will not simply be flooded by rising seas, but will be modified by 

a variety of processes (e.g., erosion, accretion) whose impacts will vary greatly by 

location and geologic setting. For example, the frequency and magnitude of flooding may 

change and sea-level rise can alsoaffect water table elevations, impacting fresh water 

supplies. These changes will have a broad range of human and environmental impacts. 

To effectively cope with sea-level rise and its impacts, current policies and economic 

considerations should be examined, and possible options for changing planning and 

management activities are warranted so that society and the environment are better able 

to adapt to potential accelerated rise in sea level. This Product examines the potential 

coastal impacts for three different plausible scenarios of future sea-level rise, and focuses 

on the potential effects to the year 2100. The effects, of course, will extend well beyond 

2100, but detailed discussion of effects farther into the future is outside the scope of this 

Product. 

1.1.1 Climate Change Basis for this Product 

The scientific study of climate change and associated global sea-level rise is complicated 

due to differences in observations, data quality, cumulative effects, and many other 

factors. Both direct and indirect methods are useful for studying past climate change. 

Instrument records and historical documents are most accurate, but are limited to the past 

100 to 150 years in the United States. Geological information from analyses of 

continuous cores sampled from ice sheets and glaciers, sea and lake sediments, and sea 

corals provide useful proxies that have allowed researchers to decipher past climate 

conditions and a record of climate and sea-level changes stretching back millions of years 
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before recorded history (Miller et al., 2005; Jansen et al., 2007). The most precise 

methods have provided accurate high-resolution data on the climate (e.g., global 

temperature, atmospheric composition) dating back more than 400,000 years. 

The Intergovernmental Panel on Climate Change (IPCC) 2007 Fourth Assessment Report 

provides a comprehensive review and assessment of global climate change trends, 

expected changes over the next century, and the impacts and challenges that both humans 

and the natural world are likely to be confronted with during the next century (IPCC, 

2007). Some key findings from this report are summarized in Box 1.1. A 2008 U.S. 

Climate Change Science Program (CCSP) report provides a general assessment of current 

scientific understanding of climate change impacts to the United States (CENR, 2008) 

and the recent CCSP Synthesis and Assessment (SAP) 3.4 report on Abrupt Climate 

Change discusses the effects of complex changes in ice sheets and glaciers on sea level 

(Steffen et al., 2008). CCSP SAP 4.1 provides more specific information and scientific 

consensus on the likely effects and implications of future sea-level rise on coasts and 

wetlands of the United States and also includes a science strategy for improving the 

understanding of sea-level rise, documenting its effects, and devising robust models and 

methods for reliably predicting future changes and impacts to coastal regions. 

BOX 1.1 SELECTED FINDINGS OF THE INTERGOVERNMENTAL PANEL ON CLIMATE 

CHANGE (IPCC) (2007A AND B) ON CLIMATE AND GLOBAL SEA-LEVEL RISE 

Recent Global Climate Change: 

Note: The likelihood scale, established by the IPCC and used throughout SAP 4.1, is described in the 

Preface. The terms used in that scale will be italicized when used as such in this Product 

Warming of the climate system is unequivocal, as is now evident from observations of increases in global 

average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea 

level. 
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Human-induced increase in atmospheric carbon dioxide is the most important factor affecting the warming 

of the Earth’s climate since the start of the Industrial Era. The atmospheric concentration of carbon dioxide 

in 2005 exceeds by far the natural range over the last 650,000 years.

Most of the observed increase in global average temperatures since the mid-twentieth century is very likely 

due to the observed increase in human-caused greenhouse gas concentrations. Discernible human 

influences now extend to other aspects of climate, including ocean warming, continental-average 

temperatures, temperature extremes, and wind patterns. 

Recent Global Sea-Level Rise 

Observations since 1961 show that the average temperature of the global ocean has increased to depths of 

at least 3,000 meters (m) and that the ocean has been absorbing more than 80 percent of the heat added to 

the climate system. Such warming causes seawater to expand, contributing to global sea-level rise. 

Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in 

glaciers and ice caps have contributed to global sea-level rise. 

New data show that losses from the ice sheets of Greenland and Antarctica have very likely contributed to 

global sea-level rise between 1993 and 2003. 

Global average sea level rose at an average rate of 1.8 (1.3 to 2.3) millimeters (mm) per year between 1961 

and 2003. The rate was faster between 1993 and 2003: about 3.1 (2.4 to 3.8) mm per year. Whether the 

faster rate for 1993 to 2003 reflects decadal variability or an increase in the longer term trend is unclear 

(see Figure 1.3). 

Global average sea level in the last interglacial period (about 125,000 years ago) was likely 4 to 6 m higher 

than during the twentieth century, mainly due to the retreat of polar ice. Ice core data indicate that average 

polar temperatures at that time were 3 to 5°C higher than present, because of differences in the Earth’s 

orbit. The Greenland ice sheet and other arctic ice fields likely contributed no more than 4 m of the 

observed global sea-level rise. There may also have been contributions from Antarctica ice sheet melting. 

Projections of the Future: 

Continued greenhouse gas emissions at or above current rates would cause further warming and induce 

many changes in the global climate system during the twenty-first century that would very likely be larger 

than those observed during the twentieth century. 

Based on a range of possible greenhouse gas emission scenarios for the next century, the IPCC estimates 

the global increase in temperature will likely be between 1.1 and 6.4oC. Estimates of sea-level rise for the 

same scenarios are 0.18 m to 0.59 m, excluding the contribution from accelerated ice discharges from the 

Greenland and Antarctica ice sheets. 

Extrapolating the recent acceleration of ice discharges from the polar ice sheets would imply an additional 

contribution up to 0.20 m. If melting of these ice caps increases, larger values of sea-level rise cannot be 

excluded. 

In addition to global sea-level rise, the storms that lead to coastal storm surges could become more intense. 

The IPCC indicates that, based on a range of computer models, it is likely that hurricanes will become more 

intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of 

tropical sea surface temperatures, while the tracks of “winter” or extratropical cyclones are projected to 

shift towards the poles along with some indications of an increase in intensity in the North Atlantic. 

-end-text box1.2 WHY IS GLOBAL SEA LEVEL RISING? 
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The elevation of global sea level is determined by the dynamic balance between the mass 

of ice on land (in glaciers and ice sheets) and the mass of water in ocean basins. Both of 

these factors are highly influenced by the Earth’s atmospheric temperature. During the 

last 800,000 years, global sea level has risen and fallen about 120 m (400 ft) in response 

to the alternating accumulation and decline of large continental ice sheets about 2 to 3 km 

(1 to 2 mi) thick as climate warmed and cooled in naturally occurring 100,000 year 

astronomical cycles (Imbrie and Imbrie, 1986; Lambeck et al., 2002). Figure 1.1 shows a 

record of large global sea-level change over the past 400,000 years during the last four 

cycles, consisting of glacial maximums with low sea levels and interglacial warm periods 

with high sea levels. The last interglacial period, about 125,000 years ago, lasted about 

10,000 to 12,000 years, with average temperatures warmer than today but close to those 

predicted for the next century, and global sea level was 4 to 6 m (13 to 20 ft) higher than 

present (Imbrie and Imbrie, 1986). Following the peak of the last Ice Age about 21,000 

years ago, the Earth entered the present interglacial warm period. Global sea level rose 

very rapidly at average rates of 10 to 20 mm per year punctuated with periodic large 

“meltwater pulses” with rates of more than 50 mm per year from about 21,000 to 6,000 

years ago. Sea-level rise then slowed to a rate of about 0.5 mm per year from 6,000 to 

3,000 years ago (Fairbanks, 1989; Rohling et al., 2008). During the past 2,000 to 3,000 

years the rate slowed to approximately 0.2 mm per year until an acceleration occurred in 

the late nineteenth century (IPCC 2001). 

There is growing scientific evidence that, at the onset of the present interglacial warm 

period, the Earth underwent abrupt changes when the climate system crossed several 
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thresholds or tipping points (points or levels in the evolution of the Earth's climate 

leading to irreversible change) that triggered dramatic changes in temperature, 

precipitation, ice cover, and sea level. These changes are thought to have occurred over a 

few decades to a century and the causes are not well understood (NRC, 2002; Alley et al., 

2003). One cause is thought to be disruption of major ocean currents by influxes of fresh 

water from glacial melt. It is not known with any confidence how anthropogenic climate 

change might alter the natural glacial-interglacial cycle or the forcings that drive abrupt 

change in the Earth’s climate system. Imbrie and Imbrie (1986) surmise that the world 

might experience a “super-interglacial” period with mean temperatures higher than past 

warm periods. 

Figure 1.1 Plot of large variations in global sea level elevation over the last 400,000 years resulting from 

four natural glacial and interglacial cycles. Evidence suggests that sea level was about 4 to 6 meters (m) 

higher than present during the last interglacial warm period 125,000 years ago and 120 m lower during the 

last Ice Age, about 21,000 years ago (see reviews in Muhs et al., 2004 and Overpeck et al., 2006). 

(Reprinted from Quaternary Science Reviews, 21/1-3, Phillippe Huybrechts, Sea-level changes at the LGM 

from ice-dynamic reconstructions of the Greenland and Antarctic ice sheets during the glacial cycles, 203-

231, Copyright [2002], with permission from Elsevier.) 
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At the peak of the last Ice Age, sea level was approximately 120 m lower than today and 

the shoreline was far seaward of its present location, at the margins of the continental 

shelf (Figure 1.2). As the climate warmed and ice sheets melted, sea level rose rapidly but 

at highly variable rates, eroding and submerging the coastal plain to create the continental 

shelves, drowning ancestral river valleys, and creating major estuaries such as Long 

Island Sound, Delaware Bay, Chesapeake Bay, Tampa Bay, Galveston Bay, and San 

Francisco Bay. 

Figure 1.2 Generalized plot of the rise in global sea level at variable rates over the last 18,000 years as the 

Earth moved from a glacial period to the present interglacial warm period. This curve is reconstructed from 

geologic samples, shown as data points. Rise was rapid but highly variable for much of the time and slowed 

about 3,000 years ago. Recent acceleration is not shown at this scale. Reprinted by permission from 

Macmillan Publishers Ltd: Nature (Fairbanks, R.G., A 17,000-year glacio-eustatic sea level 
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record―influence of glacial melting rates on the Younger Dryas event and deep-sea circulation, 349[6250], 

637-642), ©1989.

Global sea level was relatively stable with rates of rise averaging 0 to 0.2 mm per year 

until rates increased in the late nineteenth and early twentieth centuries (Bindoff et al.,

2007; Lambeck et al., 2004; Gehrels et al., 2008). Some studies indicate that acceleration 

in sea-level rise may have begun earlier, in the late eighteenth century (Jevrejeva et al., 

2008). Analyses of tide-gauge data indicate that the twentieth century rate of sea-level 

rise averaged 1.7 mm per year on a global scale (Figure 1.3) (Bindoff et al., 2007), but 

that the rate fluctuated over decadal periods throughout the century (Church and White, 

2006; Jevrejeva et al., 2006, 2008). Between 1993 and 2003, both satellite altimeter and 

tide-gauge observations indicate that the rate of sea-level rise increased to 3.1 mm per 

year (Bindoff et al., 2007); however, with such a short record, it is not yet possible to 

determine with certainty whether this is a natural decadal variation or due to humaninduced climate warming (Bindoff et al., 2007). 
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Figure 1.3 Annual averages of global mean sea level in millimeters from IPCC (2007). The red curve 

shows sea-level fields since 1870 (updated from Church and White, 2006); the blue curve displays tide 

gauge data from Holgate and Woodworth (2004), and the black curve is based on satellite observations 

from Leuliette et al. (2004). The red and blue curves are deviations from their averages for 1961 to 1990, 

and the black curve is the deviation from the average of the red curve for the period 1993 to 2001. Vertical 

error bars show 90 percent confidence intervals for the data points. Adapted from Climate Change 2007: 

The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. Figure 5.13. Cambridge University Press.

Box 1.2 Relative Sea Level 

“Global sea-level rise” results mainly from the worldwide increase in the volume of the world’s oceans that 

occurs as a result of thermal expansion of warming ocean water and the addition of water to the ocean from 

melting ice sheets and glaciers (ice masses on land). “Relative sea-level rise” is measured directly by 

coastal tide gauges, which record both the movement of the land to which they are attached and changes in 

global sea level. Global sea-level rise can be estimated from tide gauge data by subtracting the land 

elevation change component. Thus, tide gauges are important observation instruments for measuring sealevel change trends. However, because variations in climate and ocean circulation can cause fluctuations 

over 10-year time periods, the most reliable sea level data are from tide gauges having records 50 years or 

longer and for which the rates have been adjusted using a global isostatic adjustment model (Douglas et al., 

2001) 

At regional and local scales along the coast, vertical movements of the land surface can also contribute 

significantly to sea-level change and the combination of global sea-level and land-level change is referred 

to as “relative sea level” (Douglas, 2001).Thus, “relative sea-level rise” refers to the change in sea level 

relative to the elevation of the land, which includes both global sea-level rise and vertical movements of the 

land. Both terms, global sea level and relative sea level, are used throughout this Product. 

Vertical changes of the land surface result from many factors including tectonic processes and subsidence 

(sinking of the land) due to compaction of sediments and extraction of subsurface fluids such as oil, gas, 

and water. A principal contributor to this change along the Atlantic Coast of North America is the vertical 

relaxation adjustments of the Earth’s crust to reduced ice loading due to climate warming since the last Ice 

Age. In addition to glacial adjustments, sediment loading also contributes to regional subsidence of the land 

surface. Subsidence contributes to high rates of relative sea-level rise (9.9 millimeters per year) in the 

Mississippi River delta where thick sediments have accumulated and are compacting. Likewise, fluid 

withdrawal from coastal aquifers causes the sediments to compact locally as the water is extracted. In 

Louisiana, Texas, and Southern California, oil, gas and ground-water extraction have contributed markedly 

to subsidence and relative sea-level rise (Gornitz and Lebedeff, 1987; Emery and Aubrey, 1991; Nicholls 

and Leatherman, 1996; Galloway et al., 1999; Morton et al., 2004). In locations where the land surface is 

subsiding, rates of relative sea-level rise exceed the average rate of global rise (e.g., the north central Gulf 

of Mexico Coast and mid-Atlantic coast). 

--End Text Box— 

1.3 RELATIVE SEA-LEVEL RISE AROUND THE UNITED STATES 

Geologic data from radiocarbon age-dating organic sediments in cores and coral reefs are 

indirect methods used for determining sea-level elevations over the past 40,000 years, but 
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the records from long-term (more than 50 years) tide-gauge stations have been the 

primary direct measurements of relative sea-level trends over the past century (Douglas, 

2001). Figure 1.4 shows the large variations in relative sea level for U.S. coastal regions. 

The majority of the Atlantic Coast and Gulf of Mexico Coast experience higher rates of 

sea-level rise (2 to 4 mm per year and 2 to 10 mm per year, respectively) than the current 

global average (1.7 mm per year). 

Figure 1.4 Map of twentieth century annual relative sea-level rise rates around the U.S. coast. The higher 

rates for Louisiana (9.85 millimeters [mm] per year) and the mid-Atlantic region (1.75 to 4.42 mm per 

year) are due to land subsidence. Sea level is stable or dropping relative to the land in the Pacific 

Northwest, as indicated by the negative values, where the land is tectonically active or rebounding upward 

in response to the melting of ice sheets since the last Ice Age (data from Zervas, 2001).

There are large variations for relative sea-level rise (and fall) around the United States, 

ranging from a fall of 16.68 mm per year at Skagway in southeast Alaska due to tectonic 
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processes and land rebound upward as a result of glacier melting (Zervas, 2001), to a rise 

of 9.85 mm per year at Grand Isle, Louisiana, due to land subsidence downward from 

natural causes and possibly oil and gas extraction. 

The rate of relative sea-level rise (see Box 1.2 for definition) measured by tide gauges at 

specific locations along the Atlantic coast of the United States varies from 1.75 mm to as 

much as 4.42 mm per year (Table 1.1; Figure 1.4; Zervas, 2001). The lower rates, which 

occur along New England and from Georgia to northern Florida, are close to the global 

rate of 1.7 ±0.5 mm per year (Bindoff et al., 2007). The highest rates are in the midAtlantic region between northern New Jersey and southern Virginia. Figure 1.5 is an 

example of the monthly average (mean) sea-level record and the observed relative sealevel rise trend at Baltimore, Maryland. At this location, the relative sea-level trend is 

3.12 (±0.08) mm per year, almost twice the present rate of global sea-level rise. 

Subsidence of the land surface, attributed mainly to adjustments of the Earth’s crust in 

response to the melting of the Laurentide ice sheet and to the compaction of sediments 

due to freshwater withdrawal from coastal aquifers, contributes to the high rates of 

relative sea-level rise observed in this region (Gornitz and Lebedeff, 1987; Emery and 

Aubrey, 1991; Kearney and Stevenson, 1991; Douglas, 2001; Peltier, 2001). 
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Figure 1.5 The monthly computed average sea-level record (black line) from 1900 to 2000 from the 

Baltimore, Maryland tide gauge. Blue line is the observed data. The zero line is the latest 19-year National 

Tidal Datum Epoch mean value. The rate, 3.12 millimeters (mm) per year, is nearly double the present rate 

(1.7 mm per year) of global sea-level rise due to land subsidence (based on Zervas, 2001). 

Table 1.1 Rates of relative sea-level rise for selected long-term tide gauges on the Atlantic coast of 

the United States (Zervas, 2001). For comparison, the global average rate is 1.7 millimeters per year. 

Station 

Rate of Sealevel rise 

(mm per 

year) 

Time Span of 

Record 

Eastport, Maine 2.12 ±0.13 1929-1999 

Portland, Maine 1.91 ±0.09 1912-1999 

Seavey Island, Maine 1.75 ±0.17 1926-1999 

Boston, Massachusetts 2.65 ±0.10 1921-1999 

Woods Hole, Massachusetts 2.59 ±0.12 1932-1999 

Providence, Rhode Island 1.88 ±0.17 1938-1999 

Newport, Rhode Island 2.57 ±0.11 1930-1999 

New London, Connecticut 2.13 ±0.15 1938-1999 

Montauk, New York 2.58 ±0.19 1947-1999 

Willets Point, New York 2.41 ±0.15 1931-1999 

The Battery, New York 2.77 ±0.05 1905-1999 

Sandy Hook, New Jersey 3.88 ±0.15 1932-1999 

Atlantic City, New Jersey 3.98 ±0.11 1911-1999 

Philadelphia, Pennsylvania 2.75 ±0.12 1900-1999 

Lewes, Delaware 3.16 ±0.16 1919-1999 

Baltimore, Maryland 3.12 ±0.08 1902-1999 

Annapolis, Maryland 3.53 ±0.13 1928-1999 
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Solomons Island, Maryland 3.29 ±0.17 1937-1999 

Washington, D.C. 3.13 ±0.21 1931-1999 

Hampton Roads, Virginia 4.42 ±0.16 1927-1999 

Portsmouth, Virginia 3.76 ±0.23 1935-1999 

Wilmington, North Carolina 2.22 ±0.25 1935-1999 

Charleston, South Carolina 3.28 ±0.14 1921-1999 

Fort Pulaski, Georgia 3.05 ±0.20 1935-1999 

Fernandina Beach, Florida 2.04 ±0.12 1897-1999 

Mayport, Florida 2.43 ±0.18 1928-1999 

Miami, Florida 2.39 ±0.22 1931-1999 

Key West, Florida 2.27 ±0.09 1913-1999 

While measuring and dealing with longer term global averages of sea-level change is 

useful in understanding effects on coasts, shorter term and regional-scale variations due 

primarily to warming and oceanographic processes can be quite different from long term 

averages, and equally important for management and planning. As shown in Figure 1.6 

from Bindoff et al. (2007) based on a decade of data, some of the highest rates of rise are 

off the U.S. Mid-Atlantic and the western Pacific, while an apparent drop occurred off 

the North and South American Pacific Coast. 
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Fi gur e 5. 15

Figure 1.6 (Top) Geographic distribution of short-term linear trends in mean sea level (millimeters [mm] 

per year) for 1993 to 2003 based on TOPEX/Poseidon satellite altimetry (updated from Cazenave and 

Nerem, 2004) and (bottom) geographic distribution of linear trends in thermal expansion (mm per year) for 

1993 to 2003 (based on temperature data down to 700 meters [from Ishii et al., 2006]). Adapted from 

Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change. Figure 5.15. Cambridge University 

Press.

Recently, the IPCC Fourth Assessment Report (IPCC, 2007) estimated that global sea 

level is likely to rise 18 to 59 cm (7 to 23 in) over the next century; however, possible 

increased melt water contributions from Greenland and Antarctic have been excluded 

(Meehl et al., 2007; IPCC, 2007). The IPCC projections (Figure 1.7) represent a “likely 

range” which inherently allows for the possibility that the actual rise may be higher or 

lower. Recent observations suggest that sea-level rise rates may already be approaching 

the higher end of the IPCC estimates (Rahmstorf et al., 2007; Jevrejeva et al., 2008). This 

is because potentially important meltwater contributions from Greenland and Antarctica 

were excluded due to limited data and an inability at that time to adequately model ice 
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flow processes. It has been suggested by Rahmstorf (2007) and other climate scientists 

that a global sea-level rise of 1 m (3 ft) is plausible within this century if increased 

melting of ice sheets in Greenland and Antarctica is added to the factors included in the 

IPCC estimates. Therefore, thoughtful precaution suggests that a global sea-level rise of 1 

m to the year 2100 should be considered for future planning and policy discussions 

Figure 1.7 Plot in centimeters rise over time of past sea-level observations and several future sea-level 

projections to the year 2100 based on various computer models. The blue shaded area is the projection by 

Bindoff et al. (2007) and the basis for the IPCC (2007) estimates. The higher gray and dash line projections 

are from Rahmstorf (2007) considering the factors used in the IPCC estimates, and also potentially 

increased melting of ice sheets in Greenland and Antarctica. From: Rahmstorf, S., 2007: A semi-empirical 

approach to projecting future sea-level rise. Science, 315(5810), 368-370.Reprinted with permission from 

AAAS. 

This Product focuses on the effects of sea-level rise on U.S. coasts over the next century, 

but climate warming and its effects are likely to continue well beyond that due to the 

amount of greenhouse gases already in the atmosphere. Currently, the amount of potential 

melting from land-based ice masses (primarily Greenland and West Antarctica) is 

uncertain and is therefore not fully incorporated into all sea-level rise model projections. 
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Recent observations of changes in ice cover and glacial melting on Greenland, West 

Antarctica, and smaller glaciers and ice caps around the world indicate that ice loss could 

be more rapid than the trends evaluated for the IPCC (2007) report (Chen et al., 2006; 

Shepherd and Wingham, 2007; Meier et al., 2007; Fettweis et al., 2007). The science 

needed to assign probability to these high scenarios is not yet well established, but 

scientists agree that this topic is worthy of continued study because of the grave

implications for coastal areas in the United States and around the world. 

1.4 IMPACTS OF SEA-LEVEL RISE FOR THE UNITED STATES

1.4.1 Coastal Vulnerability for the United States 

Coastal communities and habitats will be increasingly stressed by climate change impacts 

due to sea-level rise and storms (Field et al., 2007). To varying degrees over decades, 

rising sea level will affect entire coastal systems from the ocean shoreline well landward. 

The physical and ecological changes that occur in the near future will impact people and 

coastal development. Impacts from sea-level rise include: land loss through submergence 

and erosion of lands in coastal areas; migration of coastal landforms and habitats; 

increased frequency and extent of storm-related flooding; wetland losses; and increased 

salinity in estuaries and coastal freshwater aquifers. Each of these effects can have 

impacts on both natural ecosystems and human developments. Often the impacts act 

together and the effects are cumulative. Other impacts of climate change, such as 

increasingly severe droughts and storm intensity—combined with continued rapid coastal 

development—could increase the magnitude and extent of sea-level rise impacts 

(Nicholls, et al., 2007). To deal with these impacts, new practices in managing coasts and 
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the combined impacts of mitigating changes to the physical system (e.g., coastal erosion 

or migration, wetland losses) and impacts to human populations (e.g., property losses, 

more frequent flood damage) should be considered. 

Global sea-level rise, in combination with the factors above, is already having significant 

effects on many U.S. coastal areas. Flooding of low-lying regions by storm surges and 

spring tides is becoming more frequent. In certain areas, wetland losses are occurring, 

fringe forests are dying and being converted to marsh, farmland and lawns are being 

converted to marsh (e.g., see Riggs and Ames, 2003; 2007), and some roads and urban 

centers in low elevation areas are more frequently flooded during spring high tides 

(Douglas, 2001). In addition, “ghost forests” of standing dead trees killed by salt water 

intrusion are becoming increasingly common in southern New Jersey, Maryland, 

Virginia, Louisiana, and North Carolina (Riggs and Ames, 2003). Relative sea level rise 

is causing salt water intrusion into estuaries and threatening freshwater resources in some 

parts of the mid-Atlantic region (Barlow, 2003). 

Continued rapid coastal development exacerbates both the environmental and the human 

impact of rising sea level. Due to the increased human population in coastal areas, once 

sparsely developed coastal areas have been transformed into high-density year-round 

urban complexes (e.g., Ocean City, Maryland; Virginia Beach, Virginia; Myrtle Beach, 

South Carolina). With accelerated rise in sea level and increased intensity of storms, the 

vulnerability of development at the coast and risks to people will increase dramatically 
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unless new and innovative coastal zone management and planning approaches are 

employed. 

1.4.2 Climate Change, Sea-Level Rise and Storms 

Although storms occur episodically, they can have long-term impacts to the physical 

environment and human populations. Coupled with rise in sea level, the effects of storms 

could be more extensive in the future due to changes in storm character, such as intensity, 

frequency, and storm tracking. In addition to higher sea level, coastal storm surge from 

hurricanes could become higher and more intense rainfall could raise the potential for 

flooding from land runoff. Recent studies (e.g., Emanuel, et al., 2004, 2008; Emanuel, 

2005; Komar and Allen, 2008; Elsner et al., 2008) have concluded that there is evidence 

that hurricane intensity has increased during the past 30 years over the Atlantic Ocean; 

however, it is unknown whether these trends will continue. There is currently no 

scientific consensus on changes in the frequency of major storms. Emanuel et al. (2008) 

suggest that increased wind shear from global warming, which weakens hurricanes, may 

reduce the global frequency of hurricanes. This is in agreement with Gutowski et al. 

(2008). 

Land-falling Atlantic coast hurricanes can produce storm surges of 5 m (16 ft) or more 

(Karl et al., 2008). The power and frequency of Atlantic hurricanes has increased 

substantially in recent decades, though North American mainland land-falling hurricanes 

do not appear to have increased over the past century (Karl et al., 2008). The IPCC 

(2007) and Karl et al. (2008) indicate that, based on computer models, it is likely that 

hurricanes will become more intense, with increases in tropical sea surface temperatures. 
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Although hurricane intensity is expected to increase on average, the effects on hurricane 

frequency in the Atlantic are still not certain and are the topic of considerable scientific 

study (Elsner et al., 2008; Emanuel et al., 2008; see also review in Karl et al., 2008). 

Extratropical cyclones can also produce significant storm surges. These storms have 

undergone a northward shift in track over the last 50 years (Karl et al., 2008). This has 

reduced storm frequencies and intensities in the mid-latitudes and increased storm 

frequencies and intensities at high latitudes (Gutowski et al., 2008). Karl et al. (2008) 

conclude that future intense extratropical cyclones will become more frequent with 

stronger winds and more extreme wave heights though the overall number of storms may 

decrease. So, while general storm projections are possible, specific projections for 

regional changes in extratropical cyclone activity, such as for the mid-Atlantic coast, are 

not yet available. Thus, while increased storm intensity is a serious risk in concert with 

sea-level rise, specific storm predictions are not so well established that planners can yet 

rely on them. 

1.4.3 Shoreline Change and Coastal Erosion 

The diverse landforms comprising more than 152,750 km (95,471 mi) of U.S. tidal 

coastline (<http://shoreline.noaa.gov/faqs.html>) reflect a dynamic interaction between: 

(1) natural factors and physical processes that act on the coast (e.g., storms, waves, 

currents, sand sources and sinks, relative sea level), (2) human activity (e.g., dredging, 

dams, coastal engineering), and (3) the geological character of the coast and nearshore. 

Variations of these physical processes in both location and time, and the local geology 
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along the coast, result in the majority of the U.S. coastlines undergoing overall long-term 

erosion at highly varying rates, as shown in Figure 1.7. 

Figure 1.8 Shoreline change around the United States based on surveys over the past century. All 30 

coastal states are experiencing overall erosion at highly variable rates due to natural processes (e.g., storms, 

sea-level rise) and human activity (From USGS, 1985). 

The complex interactions between these factors make it difficult to relate sea-level rise 

and shoreline change and to reach agreement among coastal scientists on approaches to 

predict how shorelines will change in response to sea-level rise. The difficulty in linking 

sea-level rise to coastal change stems from the fact that shoreline change is not driven 

solely by sea-level rise. Instead, coasts are in dynamic flux, responding to many driving 

forces, such as the underlying geological character, changes in tidal flow, and volume of 

sediment in the coastal system. For example, FitzGerald et al. (2008) discuss the dramatic 

effects that changes in tidal wetland area can have on entire coastal systems by altering 
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tidal flow, which in turn affects the size and shape of tidal inlets, ebb and flood tide 

deltas, and barrier islands. Consequently, while there is strong scientific consensus that 

climate change is accelerating sea-level rise and affecting coastal regions, there are still 

considerable uncertainties predicting in any detail how the coast will respond to future 

sea-level rise in concert with other driving processes. 

There is some scientific opinion that barrier islands, wetlands, and other parts of coastal 

systems might have tipping points or thresholds, such that when limits are exceeded the 

landforms become unstable and undergo large irreversible changes (NRC, 2002; Riggs 

and Ames, 2003; Nicholls et al., 2007). These changes are thought to occur rapidly and 

are thus far unpredictable. It is possible that this is happening to barrier islands along the 

Louisiana coast that are subject to high rates of sea-level rise, frequent major storms over 

the past decade, and limited sediment supply (Sallenger et al., 2007). Further 

deterioration of the barrier islands and wetlands may also occur in the near future along 

the North Carolina Outer Banks coast as a result of increased sea-level rise and storm 

activity (Culver et al., 2007, 2008; Riggs and Ames, 2003). 

1.4.4 Managing the Coastal Zone as Sea Level Rises

A key issue for coastal zone management is how and where to adapt to the changes that 

will result from sea-level rise in ways that benefit or minimize impacts to both the natural 

environment and human populations. Shore protection policies have been developed in 

response to shoreline retreat problems that affect property or coastal wetland losses. 

While it is widely recognized that sea-level rise is an underlying cause of these changes, 
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there are few existing policies that explicitly address or incorporate sea-level rise into 

decision making. Many property owners and government programs engage in coastal 

engineering activities designed to protect property and beaches such as beach 

nourishment or seawall or breakwater construction. Some of the current practices affect 

the natural behavior of coastal landforms and disrupt coastal ecosystems. In the short 

term, an acceleration of sea-level rise may simply increase the cost of current shore 

protection practices (Nordstrom, 2000). In the long term, policy makers might evaluate 

whether current approaches and justifications for coastal development and protection 

need to be modified to reflect the increasing vulnerability to accelerating rates of sealevel rise. 

To facilitate these decisions, policy makers require credible scientific data and 

information. Predicting sea-level rise impacts such as shoreline changes or wetland losses 

with quantitative precision and certainty is often not possible. Related effects of climate 

change, including increased storms, precipitation, runoff, drought, and sediment supply 

add to the difficulty of providing accurate reliable information. Predicting future effects 

is challenging because the ability to accurately map and quantify the physical response of 

the coast to sea-level rise, in combination with the wide variety of other processes and 

human engineering activities along the shoreline, has not yet been well developed. 

United States coastal regions are generally managed under the premise that sea level is 

stable, shorelines are static, and storms are regular and predictable. This Product 

examines how sea-level rise and changes in storm intensity and frequency due to climate 
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change call for new considerations in managing areas to protect resources and reduce 

risk. This SAP 4.1 also examines possible strategies for coastal planning and 

management that will be effective as sea-level rise accelerates. For instance, broader 

recognition is needed that coastal sediments are a valuable resource, best conserved by 

implementing Best Coastal Sediment Management practices (see 

<http://www.wes.army.mil/rsm/>) on local, regional, and national levels in order to 

conserve sediment resources and maintain natural sediment transport processes. 

This Product assesses the current scientific understanding of how sea-level rise can 

impact the tidal inundation of low-lying lands, ocean shoreline processes, and the vertical 

accretion of tidal wetlands. It also discusses the challenges that will be present in 

planning for future sea-level rise and adapting to these impacts. The SAP 4.1 is intended 

to provide information for coastal decision makers at all levels of government and society 

so they can better understand this topic and incorporate the effects of accelerating rates of 

sea-level rise into long-term management and planning. 
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 Chapter 2. Coastal Elevations 

Lead Author: Dean B. Gesch, USGS 

Contributing Authors: Benjamin T. Gutierrez, USGS; Stephen K. Gill, NOAA 

KEY FINDINGS 

 Coastal changes are driven by complex and interrelated processes. Inundation will be 

the primary response to sea-level rise in some coastal locations; yet there has been 

little recognition in previous studies that inundation is just one response out of a 

number of possible responses to sea-level rise. A challenge remains to quantify the 

various effects of sea-level rise and to identify the areas and settings along the coast 

where inundation will be the dominant coastal change process in response to rising 

seas. 

 Sheltered, low-energy coastal areas, where sediment influx is minimal and wetlands 

are absent or are unable to build vertically in response to rising water levels, may be 

submerged. In these cases, the extent of inundation is controlled largely by the slope 

of the land, with a greater degree of inundation occurring in areas with more gentle 

gradients. In areas that are vulnerable to a simple inundation response to rising seas, 

elevation is a critical factor in assessing potential impacts. 

 Accurate delineations of potential inundation zones are critical for meeting the 

challenge of fully determining the potential socioeconomic and environmental 

impacts of predicted sea-level rise. 
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 Coastal elevation data have been widely used to quantify the potential effects of 

predicted sea-level rise, especially the area of land that could be inundated and the 

affected population. Because sea-level rise impact assessments often rely on elevation 

data, it is critical to understand the inherent accuracy of the underlying data and its 

effects on the uncertainty of any resulting vulnerability maps and statistical 

summaries. 

 The accuracy with which coastal elevations have been mapped directly affects the 

reliability and usefulness of sea-level rise impact assessments. Although previous 

studies have raised awareness of the problem of mapping and quantifying sea-level 

rise impacts, the usefulness and applicability of many results are hindered by the 

coarse resolution of available input data. In addition, the uncertainty of elevation data 

is often neglected. 

 Existing studies of sea-level rise vulnerability based on currently available elevation 

data do not provide the degree of confidence that is optimal for local decision 

making. 

 There are important technical considerations that need to be incorporated to improve 

future sea-level rise impact assessments, especially those with a goal of producing 

vulnerability maps and statistical summaries that rely on the analysis of elevation 

data. The primary aspect of these improvements focuses on using high-resolution, 

high-accuracy elevation data, and consideration and application of elevation 

uncertainty information in development of vulnerability maps and area statistics. 
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 Studies that use elevation data as an input for vulnerability maps and/or statistics need 

to have a clear statement of the absolute vertical accuracy. There are existing national 

standards for quantifying and reporting elevation data accuracy. 

 Currently best available elevation data for the entire mid-Atlantic region do not 

support an assessment using a sea-level rise increment of 1 meter or less, using 

national geospatial standards for accuracy assessment and reporting. This is 

particularly important because the 1-meter scenario is slightly above the range of 

current sea-level rise estimates for the remainder of this century and slightly above 

the highest scenario used in this report. 

 High-quality lidar elevation data, such as that which could be obtained from a 

national lidar data collection program, would be necessary for the entire coastal zone 

to complete a comprehensive assessment of sea-level rise vulnerability in the midAtlantic region. The availability of such elevation data will narrow the uncertainty 

range of elevation datasets, thus improving the ability to conduct detailed assessments 

that can be used in local decision making. 

2.1 INTRODUCTION

Sea-level rise is a coastal hazard that can exacerbate the problems posed by waves, storm 

surges, shoreline erosion, wetland loss, and saltwater intrusion (NRC, 2004). The ability 

to identify low-lying lands is one of the key elements needed to assess the vulnerability 

of coastal regions to these impacts. For nearly three decades, a number of large area sealevel rise vulnerability assessments have focused mainly on identifying land located 

below elevations that would be affected by a given sea-level rise scenario (Schneider and 
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Chen, 1980; U.S. EPA, 1989; Najjar et al., 2000; Titus and Richman, 2001; Ericson et 

al., 2006; Rowley et al., 2007). These analyses require use of elevation data from 

topographic maps or digital elevation models (DEMs) to identify low-lying land in 

coastal regions. Recent reports have stressed that sea-level rise impact assessments need 

to continue to include maps of these areas subject to inundation based on measurements 

of coastal elevations (Coastal States Organization, 2007; Seiden, 2008). Accurate 

mapping of the zones of potential inundation is critical for meeting the challenge of 

determining the potential socioeconomic and environmental impacts of predicted sealevel rise (FitzGerald et al., 2008). 

Identification of the socioeconomic impacts of projected sea-level rise on vulnerable 

lands and populations is an important initial step for the nation in meeting the challenge 

of reducing the effects of natural disasters in the coastal zone (Subcommittee on Disaster 

Reduction, 2008). A number of state coastal programs are using sea-level rise inundation 

models (including linked storm surge/sea-level rise models) to provide a basis for coastal 

vulnerability and socioeconomic analyses (Coastal States Organization, 2007). State 

coastal managers are concerned that these research efforts and those of the federal 

government should be well coordinated, complementary, and not redundant. Despite the 

common usage of elevation datasets to investigate sea-level rise vulnerability, there are 

limitations to elevation-based analyses. These limitations are related to the relevance of 

this approach in a variety of settings and to the data sources and methodologies used to 

conduct these analyses. Thus, an important objective of this Chapter is to review the 

available data and techniques, as well as the suitability of elevation-based analyses for 
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informing sea-level rise assessments, to provide guidance for both scientists and coastal 

managers. 

While elevation-based analyses are a critical component of sea-level rise assessments, 

this approach only addresses a portion of the vulnerability in coastal regions. Coastal 

changes are driven by complex and interrelated processes such as storms, biological 

processes, sea-level rise, and sediment transport, which operate over a range of time 

scales (Carter and Woodroffe, 1994; Brinson et al., 1995; Eisma, 1995; Pilkey and 

Cooper, 2004; FitzGerald et al., 2008). The response of a coastal region to sea-level rise 

can be characterized by one or more of the processes in the following broad categories 

(Leatherman, 2001; Valiela, 2006; FitzGerald et al., 2008): 

 land loss by inundation of low-lying lands; 

 land loss due to erosion (removal of material from beaches, dunes, and cliffs); 

 barrier island migration, breaching, and segmentation; 

 wetland accretion and migration; 

 wetland drowning (deterioration and conversion to open water); 

 expansion of estuaries; 

 salt water intrusion (into freshwater aquifers and surface waters); and 

 increased frequency of storm flooding (especially of uplands and developed 

coastal lands). 

Because large portions of the population (both in the United States and worldwide) are 

located in coastal regions, each of these impacts has consequences for the natural 

environment as well as human populations. Using elevation datasets to identify and 
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quantify low-lying lands is only one of many aspects that need to be considered in these 

assessments. Nonetheless, analyses based on using elevation data to identify low-lying 

lands provide an important foundation for sea-level rise impact studies. 

There is a large body of literature on coastal processes and their role in both shoreline and 

environmental change in coastal regions (Johnson, 1919; Curray, 1964; Komar, 1983; 

Swift et al., 1985; Leatherman, 1990; Carter and Woodroffe, 1994; Brinson, 1995; 

Eisma, 1995; Wright, 1995; Komar, 1998; Dean and Dalrymple, 2002; FitzGerald et al., 

2008). However, there is generally little discussion of the suitability of using elevation 

data to identify the vulnerability of coastal regions to sea-level rise. While it is 

straightforward to reason that low-lying lands occurring below a future sea-level rise 

scenario are vulnerable, it is often generally assumed that these lands will be inundated. 

Instead, inundation is likely only one part of the response out of a number of possible 

sea-level rise impacts. Despite this, some assessments have opted for inundation-based 

assessments due to the lack of any clear alternatives and the difficulty in accounting for 

complex processes such as sedimentation (Najjar et al., 2000). It is plausible that extreme 

rates of sea-level rise (e.g., 1 meter or more in a single year) could result in widespread 

simple coastal inundation. However, in the more common and likely case of much lower 

sea-level rise rates, the physical processes are more complex and rising seas do not 

simply flood the coastal landscape below a given elevation contour (Pilkey and Thieler, 

1992). Instead, waves and currents will modify the landscape as sea level rises (Bird, 

1995; Wells, 1995). Still, inundation is an important component of coastal change 

(Leatherman, 2001), especially in very low gradient regions such as North Carolina. 
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However, due to the complexity of the interrelated processes of erosion and sediment 

redistribution, it is difficult to distinguish and quantify the individual contributions from 

inundation and erosion (Pilkey and Cooper, 2004). 

Inundation will be the primary response to sea-level rise only in some coastal locations. 

In many other coastal settings, long-term erosion of beaches and cliffs or wetland 

deterioration will alter the coastal landscape leading to land loss. To distinguish the term 

inundation from other processes, especially erosion, Leatherman (2001) offered the 

following important distinction: 

 erosion involves the physical removal of sedimentary material 

 inundation involves the permanent submergence of land. 

Another term that can confuse the discussion of sea-level rise and submergence is the 

term flooding (Wells, 1995; Najjar et al., 2000), which in some cases has been used 

interchangeably with inundation. Flooding often connotes temporary, irregular highwater conditions. The term inundation is used in this Chapter (but not throughout the 

entire Product) to refer to the permanent submergence of land by rising seas. 

It is unclear whether simply modeling the inundation of the land surface provides a useful 

approximation of potential land areas at risk from sea-level rise. In many settings, the 

presence of beaches, barrier islands, or wetlands indicates that sedimentary processes 

(erosion, transport, or accumulation of material) are active in both the formation of and/or 

retreat of the coastal landscape. Sheltered, low-energy coastal areas, where sediment 

influx is minimal and wetlands are absent or are unable to build vertically in response to 
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rising water levels, may be submerged. In these cases, the extent of inundation is 

controlled by the slope of the land, with a greater degree of inundation occurring in the 

areas with more gentle gradients (Leatherman, 2001). In addition, inundation is a likely 

response in heavily developed regions with hardened shores. The construction of 

extensive seawalls, bulkheads, and revetments to armor the shores of developed coasts 

and waterways have formed nearly immovable shorelines that may become submerged. 

However, the challenge remains to quantify the various effects of sea-level rise and to 

identify the areas and settings along the coast where inundation will be the dominant 

coastal change process from sea-level rise. 

Despite several decades of research, previous studies do not provide the full answers 

about sea-level rise impacts for the mid-Atlantic region with the degree of confidence 

that is optimal for local decision making. Although these studies have illuminated the 

challenges of mapping and quantifying sea-level rise impacts, the usefulness and 

applicability of many results are hindered by the quality of the available input data. In 

addition, many of these studies have not adequately reported the uncertainty in the 

underlying elevation data and how that uncertainty affects the derived vulnerability maps 

and statistics. The accuracy with which coastal elevations have been mapped directly 

affects the reliability and usefulness of sea-level rise impact assessments. Elevation 

datasets often incorporate a range of data sources, and some studies have had to rely on 

elevation datasets that are poorly suited for detailed inundation mapping in coastal 

regions, many of which are gently sloping landscapes (Ericson et al., 2006; Rowley et al., 

2007; McGranahan et al., 2007). In addition to the limited spatial detail, these datasets 
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have elevation values quantized only to whole meter intervals, and their overall vertical 

accuracy is poor when compared to the intervals of predicted sea-level rise over the next 

century. These limitations can undermine attempts to achieve high-quality assessments of 

land areas below a given sea-level rise scenario and, consequently, all subsequent 

analyses that rely on this foundation. 

Due to numerous studies that used elevation data, but have lacked general recognition of 

data and methodology constraints, this Chapter provides a review of data sources and 

methodologies that have been used to conduct sea-level rise vulnerability assessments. 

New high-resolution, high-accuracy elevation data, especially lidar (light detection and 

ranging) data, are becoming more readily available and are being integrated into national 

datasets (Gesch, 2007) as well as being used in sea-level rise applications (Coastal States 

Organization, 2007). Research is also progressing on how to take advantage of the 

increased spatial resolution and vertical accuracy of the new data (Poulter and Halpin, 

2007; Gesch, 2009). Still, there is a critical need to thoroughly evaluate the elevation 

data, determine how to appropriately utilize the data to deliver well-founded results, and 

accurately communicate the associated uncertainty. 

The widespread use of vulnerability assessments, and the attention they receive, is likely 

an indication of the broad public interest in sea-level rise issues. Because of this 

extensive exposure, it is important for the coastal science community to be fully engaged 

in the technical development of elevation-based analyses. Many recent reports have been 

motivated and pursued from an economic or public policy context rather than a 
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geosciences perspective. It is important for scientists to communicate and collaborate 

with coastal managers to actively identify and explain the applications and limitations of 

sea-level rise impact assessments. Arguably, sea-level rise is one of the most visible and 

understandable consequences of climate change for the general public, and the coastal 

science community needs to ensure that appropriate methodologies are developed to meet 

the needs for reliable information. This Chapter reviews the various data sources that are 

available to support inundation vulnerability assessments. In addition, it outlines what is 

needed to conduct and appropriately report results from elevation-based sea-level rise 

vulnerability analyses and discusses the context in which these analyses need to be 

applied. 

2.2 ELEVATION DATA 

Measurement and representation of coastal topography in the form of elevation data 

provide critical information for research on sea-level rise impacts. Elevation data in its 

various forms have been used extensively for sea-level rise studies. This section reviews 

elevation data sources in order to provide a technical basis for understanding the 

limitations of past sea-level rise impact analyses that have relied on elevation data. While 

use of coastal elevation data is relatively straightforward, there are technical aspects that 

are important considerations for conducting valid quantitative analyses. 

2.2.1 Topographic Maps, Digital Elevation Models, and Accuracy Standards

Topographic maps with elevation contours are perhaps the most recognized form of 

elevation information. The U.S. Geological Survey (USGS) has been a primary source of 
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topographic maps for well over a century. The base topographic map series for the United 

States (except Alaska) is published at a scale of 1:24,000, and the elevation information 

on the maps is available in digital form as digital elevation models. The USGS began 

production of DEMs matching the 1:24,000-scale quadrangle maps in the mid-1970s 

using a variety of image-based (photogrammetric) and cartographic techniques (Osborn 

et al., 2001). Coverage of the conterminous United States with 30-meter (m) (98-foot [ft]) 

horizontal resolution DEMs was completed in 1999, with most of the individual elevation 

models being derived from the elevation contours and spot heights on the corresponding 

topographic maps. Most of these maps have a 5-ft, 10-ft, 20-ft, or 40-ft contour interval, 

with 5-ft being the contour interval used in many low relief areas along the coast. About 

the time 30-m DEM coverage was completed, the USGS began development of a new 

seamless raster (gridded) elevation database known as the National Elevation Dataset 

(NED) (Gesch et al., 2002). As the primary elevation data product produced and 

distributed by the USGS, the NED includes many USGS DEMs as well as other sources 

of elevation data. The diverse source datasets are processed to a specification with a 

consistent resolution, coordinate system, elevation units, and horizontal and vertical 

datums to provide the user with an elevation product that represents the best publicly 

available data (Gesch, 2007). DEMs are also produced and distributed in various formats 

by many other organizations, and they are used extensively for mapping, engineering, 

and earth science applications (Maune, 2007; Maune et al., 2007a). 

Because sea-level rise impact assessments often rely on elevation data, it is important to 

understand the inherent accuracy of the underlying data and its effects on the uncertainty 
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of any resulting maps and statistical summaries from the assessments. For proper 

quantitative use of elevation data, it is important to identify and understand the vertical 

accuracy of the data. Vertical accuracy is an expression of the overall quality of the 

elevations contained in the dataset in comparison to the true ground elevations at 

corresponding locations. Accuracy standards and guidelines exist, in general for 

geospatial data, and specifically for elevation data. For topographic maps, the National 

Map Accuracy Standards (NMAS) issued in 1947 are the most commonly used; they 

state that “vertical accuracy, as applied to contour maps on all publication scales, shall be 

such that not more than 10 percent of the elevations tested shall be in error by more than 

one-half the contour interval” (USGS, 1999). An alternative way to state the NMAS 

vertical accuracy standard is that an elevation obtained from the topographic map will be 

accurate to within one-half of the contour interval 90 percent of the time. This has also 

been referred to as “linear error at 90 percent confidence” (LE90) (Greenwalt and Shultz, 

1962). For example, on a topographic map with a 10-ft contour interval that meets 

NMAS, 90 percent of the elevations will be accurate to within 5 ft, or stated alternatively, 

any elevation taken from the map will be within 5 ft of the actual elevation with a 90-

percent confidence level. Even though the NMAS was developed for printed topographic 

maps and it predates the existence of DEMs, it is important to understand its application 

because many DEMs are derived from topographic maps. 

As the production and use of digital geospatial data became commonplace in the 1990s, 

the Federal Geographic Data Committee (FGDC) developed and published geospatial 

positioning accuracy standards in support of the National Spatial Data Infrastructure 
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(Maune et al., 2007b). The FGDC standard for testing and reporting the vertical accuracy 

of elevation data, termed the National Standard for Spatial Data Accuracy (NSSDA), 

states that the “reporting standard in the vertical component is a linear uncertainty value, 

such that the true or theoretical location of the point falls within +/- of that linear 

uncertainty value 95 percent of the time” (Federal Geographic Data Committee, 1998). In 

practice, the vertical accuracy of DEMs is often reported as the root mean square error 

(RMSE). The NSSDA provides the method for translating a reported RMSE to a linear 

error at the 95-percent confidence level. Maune et al. (2007b) provide a useful 

comparison of NMAS and NSSDA vertical accuracy measures for common contour 

intervals (Table 2.1) and methods to convert between the reporting standards. The 

NSSDA, and in some cases even the older NMAS, provides a useful approach for testing 

and reporting the important vertical accuracy information for elevation data used in sealevel rise assessments. 

Table 2.1 Comparison of National Map Accuracy Standards and National Standard for Spatial Data 

Accuracy vertical accuracy values with the equivalent common contour intervals (Maune et al., 

2007b).

NMAS 

Equivalent contour 

interval 

NMAS 

90-percent confidence 

level (LE90) 

NSSDA 

RMSE 

NSSDA 

95-percent confidence 

level 

1 ft 0.5 ft 0.30 ft (9.25 cm) 0.60 ft (18.2 cm) 

2 ft 1 ft 0.61 ft (18.5 cm) 1.19 ft (36.3 cm) 

5 ft 2.5 ft 1.52 ft (46.3 cm) 2.98 ft (90.8 cm) 

10 ft 5 ft 3.04 ft (92.7 cm) 5.96 ft (1.816 m) 

20 ft 10 ft 6.08 ft (1.853 m) 11.92 ft (3.632 m) 

2.2.2 Lidar Elevation Data 

Currently, the highest resolution elevation datasets are those derived from lidar surveys. 

Collected and post-processed under industry-standard best practices, lidar elevation data 

routinely achieve vertical accuracies on the order of 15 centimeters (cm) (RMSE). Such 
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accuracies are well suited for analyses of impacts of sea-level rise in sub-meter 

increments (Leatherman, 2001). Using the conversion methods between accuracy 

standards documented by Maune et al. (2007b), it can be shown that lidar elevation data 

with an accuracy of equal to or better than 18.5 cm (RMSE) is equivalent to a 2-ft 

contour interval map meeting NMAS. 

Lidar is a relatively recent remote sensing technology that has advanced significantly 

over the last 10 years to the point where it is now a standard survey tool used by 

government agencies and the mapping industry to collect very detailed, high-accuracy 

elevation measurements, both on land and in shallow water coastal areas. The discussion 

of lidar in this Chapter is limited to topographic lidar used to map land areas. Lidar 

measurements are acquired using laser technology to precisely measure distances, most 

often from an aircraft, that are then converted to elevation data and integrated with 

Global Positioning System (GPS) information (Fowler et al., 2007). Because of their high 

vertical accuracy and spatial resolution, elevation data derived from lidar surveys are 

especially useful for applications in low relief coastal environments. The technical 

advantages of lidar in dynamic coastal settings, including the ability to perform repeat 

high-precision surveys, have facilitated successful use of the data in studies of coastal 

changes due to storm impacts (Brock et al., 2002; Sallenger et al., 2003; Stockdon et al., 

2007). Numerous organizations, including many state programs, have recognized the 

advantages of lidar for use in mapping the coastal zone. As an example, the Atlantic 

states of Maine, Connecticut, New Jersey, Delaware, Maryland, North Carolina, and 
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Florida have invested in lidar surveys for use in their coastal programs (Coastal States 

Organization, 2007; Rubinoff, et al., 2008). 

2.2.3 Tides, Sea Level, and Reference Datums 

Sea-level rise assessments typically focus on understanding potential changes in sea 

level, but elevation datasets are often referenced to a “vertical datum,” or reference point, 

that may differ from sea level at any specific location. In any work dealing with coastal 

elevations, water depths, or water levels, the reference to which measurements are made 

must be carefully addressed and thoroughly documented. All elevations, water depths, 

and sea-level data are referenced to a defined vertical datum, but different datums are 

used depending on the data types and the original purpose of the measurements. A 

detailed treatment of the theory behind the development of vertical reference systems is 

beyond the scope of this Product. However, a basic understanding of vertical datums is 

necessary for fully appreciating the important issues in using coastal elevation data to 

assess sea-level rise vulnerability. Zilkoski (2007), Maune et al. (2007a), and NOAA 

(2001) provide detailed explanations of vertical datums and tides, and the brief 

introduction here is based largely on those sources. 

Land elevations are most often referenced to an orthometric (sea-level referenced) datum, 

which is based on a network of surveyed (or “leveled”) vertical control benchmarks. 

These benchmarks are related to local mean sea level at specific tide stations along the 

coast. The elevations on many topographic maps, and thus DEMs derived from those 

maps, are referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29), 
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which uses mean sea level at 26 tide gauge sites (21 in the United States and 5 in 

Canada). Advances in surveying techniques and the advent of computers for performing 

complex calculations allowed the development of a new vertical datum, the North 

American Vertical Datum of 1988 (NAVD 88). Development of NAVD 88 provided an 

improved datum that allowed for the correction of errors that had been introduced into the 

national vertical control network because of crustal motion and ground subsidence. In 

contrast to NGVD 29, NAVD 88 is tied to mean sea level at only one tide station, located 

at Father Point/Rimouski, Quebec, Canada. Orthometric datums such as NGVD 29 and 

NAVD 88 are referenced to tide gauges, so they are sometimes informally referred to as 

“sea level” datums because they are inherently tied to some form of mean sea level. 

NAVD 88 is the official vertical datum of the United States, as stated in the Federal 

Register in 1993, and as such, it should serve as the reference for all products using land 

elevation data. 

Water depths (bathymetry data) are usually referenced vertically to a tidal datum, which 

is defined by a specific phase of the tides. Unlike orthometric datums such as NGVD 29 

and NAVD 88, which have national or international coverage, tidally referenced datums 

are local datums because they are relative to nearby tide stations. Determination of tidal 

datums in the United States is based on observations of water levels over a 19-year 

period, or tidal epoch. The current official tidal epoch in use is the 1983-2001 National 

Tidal Datum Epoch (NTDE). Averaging over this period is necessary to remove random 

and periodic variations caused by seasonal differences and the nearly 19-year cycle of the 
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lunar orbit. NTDEs are updated approximately every 25 years to account for relative sealevel change (NOAA, 2001). The following are the most commonly used tidal datums: 

 Mean higher high water (MHHW): the average of the higher high water levels 

observed over a 19-year tidal epoch (only the higher water level of the pair of 

high waters in a tidal day is used); 

 Mean high water (MHW): the average of the high water levels observed over a 

19-year tidal epoch; 

 Local mean sea level (LMSL): the average of hourly water levels observed over a 

19-year tidal epoch; 

 Mean low water (MLW): the average of the low water levels observed over a 19-

year tidal epoch; and 

 Mean lower low water (MLLW): the average of the lower low water levels 

observed over a 19-year tidal epoch (only the lower water level of the pair of low 

waters in a tidal day is used). MLLW is the reference chart datum used for NOAA 

nautical chart products. 

As an illustration, Figure 2.1 depicts the relationship among vertical datums for a point 

located on the shore at Gibson Island, Chesapeake Bay. These elevations were calculated 

with use of the “VDatum” vertical datum transformation tool (Parker et al., 2003; Myers, 

2005), described in the following section. Sea-level rise trends at specific tide stations are 

generally calculated based on observed monthly mean sea level values to filter out the 

high frequency fluctuations in tide levels. 
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Figure 2.1 Diagram of the VDatum derived relationship among vertical datums for a point on the shore at 

Gibson Island, Chesapeake Bay. The point is located between the tide stations at Baltimore and Annapolis, 

Maryland where datum relationships are based on observations. The numbers represent the vertical 

difference above or below NAVD 88. For instance, at this location in the Chesapeake Bay the estimated 

MLLW reference is more than 20 centimeters below the NAVD 88 zero reference, whereas local mean sea 

level is only about 1 centimeter below NAVD zero. 

Based on surveys at tide stations, NAVD 88 ranges from 15 cm below to 15 cm above 

LMSL in the mid-Atlantic region. Due to slopes in the local sea surface from changes in 

tidal hydrodynamics, LMSL generally increases in elevation relative to NAVD 88 for 

locations increasingly farther up estuaries and tidal rivers. For smaller scale topographic 

maps and coarser resolution DEMs, the two datums are often reported as being 

equivalent, when in reality they are not. The differences should be reported as part of the 

uncertainty analyses. Differences between NAVD 88 and LMSL on the U.S. West Coast 

often exceed 100 cm and must be taken into account in any inundation mapping 

application. Similarly, but more importantly, many coastal projects still inappropriately 

use NGVD 29 as a proxy for local mean sea level in planning, designing, and reference 

mapping. In the Mid-Atlantic, due to relative sea level change since 1929, the elevation 

of NGVD 29 ranges from 15 cm to more than 50 cm below the elevation of LMSL 

Relationship of vertical datums for Gibson Island, Chesapeake Bay

 MLLW 

 MLW 

 LMSL 

 NAVD 88 

 MHW 

 MHHW 

 -0.80 ft 

 -0.75 ft 

 -0.53 ft 

 -0.04 ft 

 0.00 ft 

 0.44 ft 

 0.72 ft 

 0.000 m 

 -0.012 m 

 -0.163 m 

 -0.229 m 

 -0.244 m 

 0.219 m 

 0.134 m 

 NGVD 29 
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(1983-2001 NTDE). This elevation difference must be taken into account in any type of 

inundation mapping. Again, because LMSL is a sloped surface relative to orthometric 

datums due to the complexity of tides in estuaries and inland waterways, the elevation 

separation between LMSL and NGVD 29 increases for locations farther up estuaries and 

tidal rivers. 

2.2.4 Topographic/Bathymetric/Water Level Data Integration 

High-resolution datasets that effectively depict elevations across the land-sea boundary 

from land into shallow water are useful for many coastal applications (NRC, 2004), 

although they are not readily available for many areas. Sea-level rise studies can benefit 

from the use of integrated topographic/bathymetric models because the dynamic 

land/water interface area, including the intertidal zone, is properly treated as one seamless 

entity. In addition, other coastal research topics rely on elevation data that represent nearshore topography and bathymetry (water depths), but because existing topographic, 

bathymetric, and water level data have been collected independently for different 

purposes, they are difficult to use together. The USGS and the National Oceanic and 

Atmospheric Administration (NOAA) have worked collaboratively to address the 

difficulties in using disparate elevation and depth information, initially in the Tampa Bay 

region in Florida (Gesch and Wilson, 2002). The key to successful integration of 

topographic, bathymetric, and water level data is to place them in a consistent vertical 

reference frame, which is generally not the case with terrestrial and marine data. A 

vertical datum transformation tool called VDatum developed by NOAA’s National Ocean 

Service provides the capability to convert topographic, bathymetric and water level data 
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to a common vertical datum (Parker et al., 2003; Myers, 2005). Work was completed in 

mid-2008 on providing VDatum coverage for the mid-Atlantic region. VDatum uses tidal 

datum surfaces, derived from hydrodynamic models corrected to match observations at 

tide stations, to interpolate the elevation differences between LMSL and NAVD 88. An 

integrated uncertainty analysis for VDatum is currently underway by NOAA. 

The National Research Council (NRC, 2004) has recognized the advantages of seamless 

data across the land/water interface and has recommended a national implementation of 

VDatum and establishment of protocols for merged topographic/bathymetric datasets 

(NOAA, 2008a). Work has continued on production of other such merged datasets for 

coastal locations, including North Carolina and the Florida panhandle (Feyen et al., 2005, 

2008). Integrated topographic/bathymetric lidar (Nayegandhi et al., 2006; Guenther, 

2007) has been identified as a valuable technology for filling critical data gaps at the 

land/water interface, which would facilitate development of more high quality datasets 

(NRC, 2004). 

2.3 VULNERABILTY MAPS AND ASSESSMENTS 

Maps that depict coastal areas at risk of potential inundation or other adverse effects of 

sea-level rise are appealing to planners and land managers that are charged with 

communicating, adapting to, and reducing the risks (Coastal States Organization, 2007). 

Likewise, map-based analyses of sea-level rise vulnerability often include statistical 

summaries of population, infrastructure, and economic activity in the mapped impact 

zone, as this information is critical for risk management and mitigation efforts. Many 
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studies have relied on elevation data to delineate potential impact zones and quantify 

effects. During the last 15 years, this approach has also been facilitated by the increasing 

availability of spatially extensive elevation, demographic, land use/land cover, and 

economic data and advanced geographic information system (GIS) tools. These tools 

have improved access to data and have provided the analytical software capability for 

producing map-based analyses and statistical summaries. The body of peer reviewed 

scientific literature cited in this Chapter includes numerous studies that have focused on 

mapping and quantifying potential sea-level rise impacts. 

A number of terms are used in the literature to describe the adverse effects of sea-level 

rise, including inundation, flooding, submergence, and land loss. Likewise, multiple 

terms are used to refer to what this Chapter has called vulnerability, including at risk, 

subject to, impacted by, and affected by. Many reports do not distinguish among the range 

of responses to sea-level rise, as described in Section 2.1. Instead, simple inundation, as a 

function of increased water levels projected onto the land surface, is assumed to reflect 

the vulnerability. 

Monmonier (2008) has recognized the dual nature of sea-level rise vulnerability maps as 

both tools for planning and as cartographic instruments to illustrate the potential 

catastrophic impacts of climate change. Monmonier cites reports that depict inundation 

areas due to very large increases in global sea-level. Frequently, however, the sea-level 

rise map depictions have no time scales and no indication of uncertainty or data 

limitations. Presumably, these broad-scale maps are in the illustration category, and only 
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site-specific, local scale products are true planning tools, but therein is the difficulty. 

With many studies it is not clear if the maps (and associated statistical summaries) are 

intended simply to raise awareness of potential broad impacts or if they are intended to be 

used in decision making for specific locations. 

2.3.1 Large-Area Studies (Global and United States) 

Sea-level rise as a consequence of climate change is a global concern, and this is reflected 

in the variety of studies conducted for locations around the world as well as within the 

United States. Table 2.2 summarizes the characteristics of a number of the sea-level rise 

assessments conducted over broad areas, with some of the studies discussed in more 

detail below. 

Table 2.2 Characteristics of some sea-level rise assessments conducted over broad areas. GTOPO30 

is a global raster DEM with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). 

SRTM is the Shuttle Radar Topography Mission data. NED is the National Elevation Dataset. 

Study Study area Elevation data Sea-level rise 

scenario 

Elevation 

accuracy 

reported? 

Maps 

published? 

Schneider and 

Chen (1980) 

Conterminous 

United States 

15- and 25-

foot contours 

from USGS 

1:24,000-scale 

maps 

4.6 and 7.6 m No Yes 

U.S. EPA 

(1989) 

Conterminous 

United States 

Contours from 

USGS maps 0.5, 1, and 2 m No No 

Titus et al. 

(1991) 

Conterminous 

United States 

Contours from 

USGS maps, 

wetland 

delineations, 

and tide data 

0.5, 1, and 2 m No No 

FEMA (1991) United States 

Coastal 

floodplain 

maps 

1 ft and 3 ft No No 

Small and 

Nicholls 

(2003) 

Global GTOPO30 

5-m land 

elevation 

increments 

Estimated a 5-

meter 

uncertainty for 

elevation data 

(no error 

metric 

specified) 

No 
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Ericson et al. 

(2006) 

40 deltas 

distributed 

worldwide 

GTOPO30 

0.5-12.5 mm 

per year for 

years 2000-

2050 

No No 

Rowley et al. 

(2007) Global GLOBE (GTOPO30) 

1, 2, 3, 4, 5, 

and 6 m No Yes 

McGranahan 

et al. (2007) Global SRTM 

Land 

elevations 0 to 

10 m (to 

define the 

“low elevation 

coastal zone”) 

No, although 

10-meter 

elevation 

increment was 

used in 

recognition of 

data 

limitations 

Yes 

Demirkesen et 

al. (2007) Izmir, Turkey SRTM 2 and 5 m 

Yes, but no 

error metric 

specified 

Yes 

Demirkesen et 

al. (2008) Turkey SRTM 1, 2, and 3 m 

Yes, but no 

error metric 

specified 

Yes 

Marfai and 

King (2008) 

Semarang, 

Indonesia 

Local survey 

data 1.2 and 1.8 m No Yes 

Kafalenos et 

al. (2008) 

U.S. Gulf 

Coast NED 2 and 4 ft No Yes 

Schneider and Chen (1980) presented one of the early reports on potential sea-level rise 

impacts along U.S. coastlines. They used the 15-ft and 25-ft contours from USGS 

1:24,000-scale maps to “derive approximate areas flooded within individual counties” 

along the coast. As with many of the vulnerability studies, Schneider and Chen also 

combined their estimates of submerged areas with population and property value data to 

estimate socioeconomic impacts, in this case on a state-by-state basis. 

Reports to Congress by the U.S. Environmental Protection Agency (EPA) and the Federal 

Emergency Management Agency (FEMA) contributed to the collection of broad area 

assessments for the United States. The EPA report (U.S. EPA, 1989; Titus et al., 1991) 

examined several different global sea-level rise scenarios in the range of 0.5 to 2 m (1.6 

to 6.6 ft), and also discussed impacts on wetlands under varying shoreline protection 
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scenarios. For elevation information, the study used contours from USGS topographic 

maps supplemented with wetland delineations from Landsat satellite imagery and tide 

gauge data. The study found that the available data were inadequate for production of 

detailed maps. The FEMA (1991) report estimated the increase of land in the 100-year 

floodplain from sea-level rises of 1 ft (0.3 m) and 3 ft (0.9 m). FEMA also estimated the 

increase in annual flood damages to insured properties by the year 2100, given the 

assumption that the trends of development would continue. 

Elevation datasets with global or near-global extent have been used for vulnerability 

studies across broad areas. For their studies of the global population at risk from coastal 

hazards, Small and Nicholls (2003) and Ericson et al. (2006) used GTOPO30, a global 

30-arc-second (about 1-kilometer [km]) elevation dataset produced by the USGS (Gesch 

et al., 1999). Rowley et al. (2007) used the GLOBE 30-arc-second DEM (Hastings and 

Dunbar, 1998), which is derived mostly from GTOPO30. As with many vulnerability 

studies, these investigations used the delineations of low-lying lands from the elevation 

model to quantify the population at risk from sea-level rise, in one instance using 

increments as small as 1 m (Rowley et al., 2007). 

Elevation data from the Shuttle Radar Topography Mission (SRTM) (Farr et al., 2007) 

are available at a 3-arc-second (about 90-m) resolution with near-global coverage. 

Because of their broad area coverage and improved resolution over GTOPO30, SRTM 

data have been used in several studies of the land area and population potentially at risk 

from sea-level rise (McGranahan et al., 2007; Demirkesen et al., 2007, 2008). Similar to 
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other studies, McGranahan et al. (2007) present estimates of the population at risk, while 

Demirkesen et al. (2007) document the dominant land use/land cover classes in the 

delineated vulnerable areas. 

2.3.2 Mid-Atlantic Region, States, and Localities 

A number of sea-level rise vulnerability studies have been published for sites in the midAtlantic region, the focus area for this Product. Table 2.3 summarizes the characteristics 

for these reports, and important information from some of the studies is highlighted. 

Table 2.3 Characteristics of some sea-level rise vulnerability studies conducted over mid-Atlantic 

locations. GTOPO30 is a global raster DEM with a horizontal grid spacing of 30 arc seconds 

(approximately 1 kilometer). SRTM is the Shuttle Radar Topography Mission data. NED is the 

National Elevation Dataset.

Study Study area Elevation data Sea-level rise 

scenarios 

Elevation 

accuracy 

reported? 

Maps 

published? 

Titus and 

Richman 

(2001) 

U.S. Atlantic 

and Gulf 

coasts 

USGS DEMs 

derived from 

1:250,000-

scale maps 

1.5- and 3.5-m 

land elevation 

increments 

No Yes 

Najjar et al. 

(2000) Delaware 30-meter USGS DEMs 2 ft No Yes 

Kleinosky et 

al. (2007) 

Hampton 

Roads, 

Virginia 

10-meter and 

30-meter 

USGS DEMs 

30, 60, and 90 

cm 

No Yes 

Wu et al. 

(2002) 

Cape May 

County, New 

Jersey 

30-meter 

USGS DEMs 60 cm No Yes 

Gornitz et al. 

(2002) 

New York 

City area 

30-meter 

USGS DEMs 

5-ft land 

elevation 

increments 

No, although 

only 

qualitative 

results were 

reported 

Yes 

Titus and 

Wang (2008) 

Mid-Atlantic 

states 

Contours from 

USGS 

1:24,000-scale 

maps, lidar, 

local data 

0.5-m land 

elevation 

increments 

Yes, RMSE 

vs. lidar for a 

portion of the 

study area 

Yes 

Larsen et al. 

(2004) 

Blackwater 

National 

Wildlife 

Refuge, 

Maryland 

Lidar 

30-cm land 

elevation 

increments 

No Yes 
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Gesch, (2009) North Carolina 

GTOPO30, 

SRTM, NED, 

lidar 

1 m 

Yes, with 

NSSDA error 

metric (95% 

confidence) 

Yes 

A study by Titus and Richman (2001) is often referred to in discussions of the land in the 

United States that is subject to the effects of sea-level rise. The methods used to produce 

the maps in that report are clearly documented. However, because they used very coarse 

elevation data (derived from USGS 1:250,000-scale topographic maps), the resulting 

products are general and limited in their applicability. The authors acknowledge the 

limitations of their results because of the source data they used, and clearly list the 

caveats for proper use of the maps. As such, these maps are useful in depicting broad 

implications of sea-level rise, but are not appropriate for site-specific decision making. 

Numerous studies have used the NED, or the underlying USGS DEMs from which much 

of the NED is derived, as the input elevation information. Najjar et al. (2000) show an 

example of using USGS 30-m DEMs for a simple inundation model of Delaware for a 2-

ft (0.6-m) sea-level rise. In another study, Kleinosky et al. (2007) used elevation 

information from USGS 10-m and 30-m DEMs to depict vulnerability of the Hampton 

Roads, Virginia area to storm surge flooding in addition to sea-level rise. Storm surge 

heights were first determined by modeling, then 30-, 60-, and 90-cm increments of sealevel rise were added to project the expansion of flood risk zones onto the land surface. In 

addition, Wu et al. (2002) conducted a study for Cape May County, New Jersey using an 

approach similar to Kleinosky et al. (2007), where they added 60 cm to modeled storm 

surge heights to account for sea-level rise. 
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More recently, Titus and Wang (2008) conducted a study of the mid-Atlantic states (New 

York to North Carolina) using a variety of elevation data sources including USGS 

1:24,000-scale topographic maps (mostly with 5- or 10-ft contour intervals), lidar data, 

and some local data provided by state agencies, counties, and municipalities. They used 

an approach similar to that described in Titus and Richman (2001) in which tidal wetland 

delineations are employed in an effort to estimate additional elevation information below 

the first topographic map contour. 

2.3.3 Other Reports 

In addition to reports by federal government agencies and studies published in the peerreviewed scientific literature, there have been numerous assessment reports issued by 

various non-governmental organizations, universities, state and local agencies, and other 

private groups (e.g., Anthoff et al., 2006; Dasgupta et al., 2007; Stanton and Ackerman, 

2007; US DOT, 2008; Mazria and Kershner, 2007; Glick et al., 2008; Cooper et al., 

2005; Lathrop and Love, 2007; Johnson et al., 2006; Bin et al., 2007; Slovinsky and 

Dickson, 2006). While it may be difficult to judge the technical veracity of the results in 

these reports, they do share common characteristics with the studies reviewed in Sections 

2.3.1 and 2.3.2. Namely, they make use of the same elevation datasets (GTOPO30, 

SRTM, NED, and lidar) to project inundation from sea-level rise onto the land surface to 

quantify vulnerable areas, and they present statistical summaries of impacted population 

and other socioeconomic variables. Many of these reports include detailed maps and 

graphics of areas at risk. Although some are also available in printed formats, all of the 
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reports listed above are available online (see Chapter 2 References for website 

information). 

This category of reports is highlighted because some of the reports have gained wide 

public exposure through press releases and subsequent coverage in the popular press and 

on Internet news sites. For example, the report by Stanton and Ackerman (2007) has been 

cited at least eight times by the mainstream media (see: 

<http://ase.tufts.edu/gdae/Pubs/rp/FloridaClimate.html>). The existence of this type of 

report, and the attention it has received, is likely an indication of the broad public interest 

in sea-level rise issues. These reports are often written from an economic or public policy 

context rather than from a geosciences perspective. Nevertheless, it is important for the 

coastal science community to be cognizant of them because the reports often cite journal 

papers and they serve as a conduit for communicating recent sea-level rise research 

results to less technical audiences. It is interesting to note that all of the reports listed here 

were produced over the last three years, thus, it is likely that that this type of outlet will 

continue to be used to discuss sea-level rise issues as global climate change continues to 

garner more public attention. Arguably, sea-level rise is among the most visible and 

understandable consequences of climate change for the general public, and they will 

continue to seek information about it from the popular press, Internet sites, and reports 

such as those described here. 

2.3.4 Limitations of Previous Studies 
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It is clear from the literature reviewed in Sections 2.3.1, 2.3.2, and 2.3.3 that the 

development of sea-level rise impact assessments has been an active research topic for 

the past 25 years. However, there is still significant progress to be made in improving the 

physical science-based information needed for decision making by planners and land and 

resource managers in the coastal zone. Although previous studies have brought ample 

attention to the problem of mapping and quantifying sea-level rise impacts, the quality of 

the available input data and the common tendency to overlook the consequences of 

coarse data resolution and large uncertainty ranges hinder the usefulness and applicability 

of many results. Specifically, for this Product, none of the previous studies covering the 

mid-Atlantic region can be used to fully answer with high confidence the Synthesis and 

Assessment Product (SAP) 4.1 prospectus question (CCSP, 2006) that relates directly to 

coastal elevations: “Which lands are currently at an elevation that could lead them to be 

inundated by the tides without shore protection measures?” The collective limitations of 

previous studies are described in this Section, while the “lessons learned”, or 

recommendations for required qualities of future vulnerability assessments, are discussed 

in Section 2.4. 

Overall, there has been little recognition in previous studies that inundation is only one 

response out of a number of possible responses to sea-level rise (see Section 2.1). Some 

studies do mention the various types of coastal impacts (erosion, saltwater intrusion, 

more extreme storm surge flooding) (Najjar et al., 2000; Gornitz et al., 2002), and some 

studies that focus on wetland impacts do consider more than just inundation (U.S.EPA, 

1989; Larsen et al., 2004). However, in general, many vulnerability maps (and 
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corresponding statistical summaries) imply that a simple inundation scenario is an 

adequate representation of the impacts of rising seas (Schneider and Chen, 1980; Rowley 

et al., 2007; Demirkesen et al., 2008; Najjar et al., 2000). 

Based on the review of the studies cited in Sections 2.3.1, 2.3.2, and 2.3.3, these general 

limitations have been identified: 

1. Use of lower resolution elevation data with poor vertical accuracy. Some studies 

have had to rely on elevation datasets that are poorly suited for detailed inundation 

mapping (e.g., GTOPO30 and SRTM). While these global datasets may be useful for 

general depictions of low elevation zones, their relatively coarse spatial detail 

precludes their use for production of detailed vulnerability maps. In addition to the 

limited spatial detail, these datasets have elevation values quantized only to whole 

meter intervals, and their overall vertical accuracy is poor when compared to the 

intervals of predicted sea-level rise over the next century. The need for better 

elevation information in sea-level rise assessments has been broadly recognized 

(Leatherman, 2001; Marbaix, and Nicholls, 2007; Jacob et al., 2007), especially for 

large-scale planning maps (Monmonier, 2008) and detailed quantitative assessments 

(Gornitz et al., 2002). 

2. Lack of consideration of uncertainty of input elevation data. A few studies 

generally discuss the limitations of the elevation data used in terms of accuracy 

(Small and Nicholls, 2003; McGranahan et al., 2007; Titus and Wang, 2008). 

However, none of these studies exhibit rigorous accuracy testing and reporting 
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according to accepted national standards (NSSDA and NMAS). Every elevation 

dataset has some vertical error, which can be tested and measured, and described by 

accuracy statements. The overall vertical error is a measure of the uncertainty of the 

elevation information, and that uncertainty is propagated to any derived maps and 

statistical summaries. Gesch (2009) demonstrates why it is important to account for 

vertical uncertainty in sea-level rise vulnerability maps and area statistics derived 

from elevation data (see Box 2.1). 

3. Elevation intervals or sea-level rise increments not supported by vertical accuracy 

of input elevation data. Most elevation datasets, with the exception of lidar, have 

vertical accuracies of several meters or even tens of meters (at the 95 percent 

confidence level). Figure 2.2 shows a graphical representation of DEM vertical 

accuracy using error bars around a specified elevation. In this case, a lidar-derived 

DEM locates the 1-meter elevation to within ±0.3 m at 95-percent confidence. (In 

other words, the true elevation at that location falls within a range of 0.7 to 1.3 m.) A 

less accurate topographic map-derived DEM locates the 1-m elevation to within ±2.2 

m at 95-percent confidence, which means the true land elevation at that location falls 

within a range of 0 (assuming sea level was delineated accurately on the original 

topographic map) to 3.2 m. Many of the studies reviewed in this Chapter use land 

elevation intervals or sea-level rise increments that are 1 m or less. Mapping of submeter increments of sea-level rise is highly questionable if the elevation data used 

have a vertical accuracy of a meter or more (at the 95-percent confidence level) 

(Gesch, 2009). For example, by definition a topographic map with a 5-ft contour 
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interval that meets NMAS has an absolute vertical accuracy (which accounts for all 

effects of systematic and random errors) of 90.8 cm at the 95-percent confidence level 

(Maune, et al., 2007b). Likewise, a 10-ft contour interval map has an absolute vertical 

accuracy of 181.6 cm (1.816 m) at the 95-percent confidence level. If such maps were 

used to delineate the inundation zone from a 50-cm sea-level rise, the results would 

be uncertain because the vertical increment of rise is well within the bounds of 

statistical uncertainty of the elevation data. 

Figure 2.2 Diagram of how a sea-level rise of 1 meter is mapped onto the land surface using two 

digital elevation models with differing vertical accuracies. The more accurate lidar-derived DEM (±0.3 

m at 95-percent confidence) results in a delineation of the inundation zone with much less uncertainty 

than when the less accurate topographic map-derived DEM (±2.2 m at 95-percent confidence) is used 

(Gesch, 2009). 

4. Maps without symbology or caveats concerning the inherent vertical uncertainty of 

input elevation data. Some studies have addressed limitations of their maps and 

statistics (Titus and Richman, 2001; Najjar et al., 2000), but most reports present 
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maps without any indication of the error associated with the underlying elevation data 

(see number 3 above). Gesch (2009) presents one method of spatially portraying the 

inherent uncertainty of a mapped sea-level rise inundation zone (see Box 2.1). 

5. Inundated area and impacted population estimates reported without a range of 

values that reflect the inherent vertical uncertainty of input elevation data. Many 

studies use the mapped inundation zone to calculate the at-risk area, and then overlay 

that delineation with spatially distributed population data or other socioeconomic 

variables to estimate impacts. If a spatial expression of the uncertainty of the 

inundation zone (due to the vertical error in the elevation data) is not included, then 

only one total can be reported. More complete and credible information would be 

provided if a second total was calculated by including the variable (area, population, 

or economic parameter) that falls within an additional delineation that accounts for 

elevation uncertainty. A range of values can then be reported, which reflects the 

uncertainty of the mapped inundation zone. 

6. Lack of recognition of differences among reference orthometric datums, tidal 

datums, and spatial variations in sea-level datums. The vertical reference frame of 

the data used in a particular study needs to be specified, especially for local studies 

that produce detailed maps, since there can be significant differences between an 

orthometric datum zero reference and mean sea level (Figure 2.1; see also Section 

2.2.3). As described earlier, there are important distinctions between vertical 

reference systems that are used for land elevation datasets and those that are used to 
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establish the elevations of sea level. Most of the reviewed studies did not specify 

which vertical reference frame was used. Often, it was probably an orthometric datum 

because most elevation datasets are in reference to such datums. Ideally, a tool such 

as VDatum will be available so that data may be easily transformed into a number 

vertical reference frames at the discretion of the user. 

Start box*****

Text Box 2.1: A Case Study Using Lidar Elevation Data 

To illustrate the application of elevation uncertainty information and the advantages of lidar elevation data 

for sea-level rise assessment, a case study for North Carolina (Gesch, 2009) is presented and summarized 

here. North Carolina has a broad expanse of low-lying land (Titus and Richman, 2001), and as such is a 

good site for a mapping comparison. Lidar data at 1/9-arc-second (about 3 meters [m]) grid spacing were 

analyzed and compared to 1-arc-second (about 30 m) DEMs derived from 1:24,000-scale topographic 

maps. The potential inundation zone from a 1-m sea-level rise was mapped from both elevation datasets, 

and the corresponding areas were compared. The analysis produced maps and statistics in which the 

elevation uncertainty was considered. Each elevation dataset was “flooded” by identifying the grid cells 

that have an elevation at or below 1 m and are connected hydrologically to the ocean through a continuous 

path of adjacent inundated grid cells. For each dataset, additional areas were delineated to show a spatial 

representation of the uncertainty of the projected inundation area. This was accomplished by adding the 

linear error at 95-percent confidence to the 1-m sea-level increase and extracting the area at or below that 

elevation using the same flooding algorithm. The lidar data exhibited ±0.27 m error at 95-percent 

confidence based on accuracy reports from the data producer, while the topographic map-derived DEMs 

had ±2.21 m error at 95-percent confidence based on an accuracy assessment with high-quality surveyed 

control points. 

Box Figure 2.1 and Box Table 2.1 show the results of the North Carolina mapping comparison. In Box 

Figure 2.1 the darker blue tint represents the area at or below 1-m in elevation, and the lighter blue tint 

represents the additional area in the vulnerable zone given the vertical uncertainty of the input elevation 

datasets. The more accurate lidar data for delineation of the vulnerable zone results in a more certain 

delineation (Box Figure 2.1B), or in other words the zone of uncertainty is small. Box Table 2.1 compares 

the vulnerable areas as delineated from the two elevation datasets. The delineation of the 1-m zone from the 

topographic map-derived DEMs more than doubles when the elevation uncertainty is considered, which 

calls into question the reliability of any conclusions drawn from the delineation. It is apparent that for this 

site the map-derived DEMs do not have the vertical accuracy required to reliably delineate a 1-m sea-level 

rise inundation zone. Lidar is the appropriate elevation dataset for answering the question about how much 

land in the study site is vulnerable to a 1-m sea-level rise, for which the answer is: “4,195 to 4,783 square 

kilometers (sq km) at a 95-percent confidence level”. This case study emphasizes why a range of values 

should be given when reporting the size of the inundation area for a given sea-level rise scenario, especially 

for sites where high-accuracy lidar data are not available Without such a range being reported, users of an 

assessment report may not understand the amount of uncertainty associated with area delineations from less 

accurate data and the implications for any subsequent decisions based on the reported statistics. 

Box Table 2.1 The area of land vulnerable to a 1-meter sea-level rise as calculated from two 

elevation datasets (see Box Figure 2.1), as well as the area of vulnerability when the uncertainty of 

the elevation data is considered (Gesch, 2009).
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Elevation dataset 

Area less than or equal 

to 1 meter in elevation 

(sq km) 

Area less than or equal 

to 1 meter in elevation 

at 95 percent 

confidence 

(sq km) 

Percent increase in 

vulnerable area when 

elevation uncertainty is 

included 

1-arc-second 

(30-m) DEMs derived 

from 1:24,000-scale 

topographic maps 

4,014 8,578 114% 

1/9-arc-second 

(3-m) lidar elevation 

grid 

4,195 4,783 14% 
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Box Figure 2.1 Lands vulnerable to a 1-meter sea-level rise, developed from topographic map-derived 

DEMs (A), and lidar elevation data (B) (Gesch, 2009). The background is a recent true color orthoimage. 

End Box 2.1**** 

2.4 FUTURE VULNERABILITY ASSESSMENTS 
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To fully answer the relevant elevation question from the prospectus for this SAP 4.1 (see 

Section 2.3.4), there are important technical considerations that need to be incorporated 

to improve future sea-level rise impact assessments, especially those with a goal of 

producing vulnerability maps and statistical summaries of impacts. These considerations 

are important for both the researchers who develop impact assessments, as well as the 

users of those assessments who must understand the technical issues to properly apply the 

information. The recommendations for improvements described below are based on the 

review of the previous studies cited in Sections 2.3.1, 2.3.2, 2.3.3, and other recent 

research: 

1. Determine where inundation will be the primary response to sea-level rise.

Inundation (submergence of the uplands) is only one of a number of possible 

responses to sea-level rise (Leatherman, 2001; Valiela, 2006; FitzGerald et al., 2008). 

If the complex nature of coastal change is not recognized up front in sea-level rise 

assessment reports, a reader may mistakenly assume that all stretches of the coast that 

are deemed vulnerable will experience the same “flooding” impact, as numerous 

reports have called it. For the coastal settings in which inundation is the primary 

vulnerability, elevation datasets should be analyzed as detailed below to produce 

comprehensive maps and statistics. 

2. Use lidar elevation data (or other high-resolution, high-accuracy elevation 

source). To meet the need for more accurate, detailed, and up-to-date sea-level rise 

vulnerability assessments, new studies should be based on recently collected high-
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resolution, high-accuracy, lidar elevation data. Other mapping approaches, including 

photogrammetry and ground surveys, can produce high-quality elevation data suitable 

for detailed assessments, but lidar is the preferred approach for cost-effective data 

collection over broad coastal areas. Lidar has the added advantage that, in addition to 

high-accuracy measurements of ground elevation, it also can be used to produce 

information on buildings, infrastructure, and vegetation, which may be important for 

sea-level rise impact assessments. As Leatherman (2001) points out, inundation is a 

function of slope. The ability of lidar to measure elevations very precisely facilitates 

the accurate determination of even small slopes, thus it is quite useful for mapping 

low relief coastal landforms. The numerous advantages of lidar elevation mapping in 

the coastal zone have been widely recognized (Leatherman, 2001; Coastal States 

Organization, 2007; Monmonier, 2008; Subcommittee on Disaster Reduction, 2008; 

Feyen et al., 2008; Gesch, 2009). A recent study by the National Research Council 

(NRC, 2007) concluded that FEMA’s requirements for floodplain mapping would be 

met in all areas by elevation data with 1-ft to 2-ft equivalent contour accuracy, and 

that a national lidar program called “Elevation for the Nation” should be carried out 

to create a new national DEM. Elevation data meeting 1-ft contour interval accuracy 

(NMAS) would allow effective sea-level rise inundation modeling for increments in 

the 0.35 m range, while data with 2-ft contour interval accuracy would be suitable for 

increments of about 0.7 m. 

3. Test and report absolute vertical accuracy as a measure of elevation uncertainty.

Any studies that use elevation data as an input for vulnerability maps and/or statistics 
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need to have a clear statement of the absolute vertical accuracy (in reference to true 

ground elevations). The NSSDA vertical accuracy testing and reporting methodology 

(Federal Geographic Data Committee, 1998), which uses a metric of linear error at 

95-percent confidence, is the preferred approach. Vertical accuracy may be reported 

with other metrics including RMSE, standard deviation (one sigma error), LE90, or 

three sigma error. Maune et al. (2007b) and Greenwalt and Shultz (1962) provide 

methods to translate among the different error metrics. In any case, the error metric 

must be identified because quoting an accuracy figure without specifying the metric is 

meaningless. For lidar elevation data, a specific testing and reporting procedure that 

conforms to the NSSDA has been developed by the National Digital Elevation 

Program (NDEP) (2004). The NDEP guidelines are useful because they provide 

methods for accuracy assessment in “open terrain” versus other land cover categories 

such as forest or urban areas where the lidar sensor may not have detected ground 

level. NDEP also provides guidance on accuracy testing and reporting when the 

measured elevation model errors are from a non-Gaussian (non-normal) distribution. 

4. Apply elevation uncertainty information in development of vulnerability maps and 

area statistics. Knowledge of the uncertainty of input elevation data should be 

incorporated into the development of sea-level rise impact assessment products. In 

this case, the uncertainty is expressed in the vertical error determined through 

accuracy testing, as described above. Other hydrologic applications of elevation data, 

including rainfall runoff modeling (Wu et al., 2008) and riverine flood inundation 

modeling (Yilmaz et al., 2004, 2005), have benefitted from the incorporation of 
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elevation uncertainty. For sea-level rise inundation modeling, the error associated 

with the input elevation dataset is used to include a zone of uncertainty in the 

delineation of vulnerable land at or below a specific elevation. For example, assume a 

map of lands vulnerable to a 1-m sea-level rise is to be developed using a DEM. That 

DEM, similar to all elevation datasets, has an overall vertical error. The challenge, 

then, is how to account for the elevation uncertainty (vertical error) in the mapping of 

the vulnerable area. Figure 2.2 (Gesch, 2009) shows how the elevation uncertainty 

associated with the 1-m level, as expressed by the absolute vertical accuracy, is 

projected onto the land surface. The topographic profile diagram shows two different 

elevation datasets with differing vertical accuracies depicted as error bars around the 

1-m elevation. One dataset has a vertical accuracy of ±0.3 m at the 95-percent 

confidence level, while the other has an accuracy of ±2.2 m at the 95-percent 

confidence level. By adding the error to the projected 1-m sea-level rise, more area is 

added to the inundation zone delineation, and this additional area is a spatial 

representation of the uncertainty. The additional area is interpreted as the region in 

which the 1-m elevation may actually fall, given the statistical uncertainty of the 

DEMs. 

Recognizing that elevation data inherently have vertical uncertainty, vulnerability 

maps derived from them should include some type of indication of the area of 

uncertainty. This could be provided as a caveat in the map legend or margin, but a 

spatial portrayal with map symbology may be more effective. Merwade et al. (2008) 

have demonstrated this approach for floodplain mapping where the modeled 
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inundation area has a surrounding uncertainty zone depicted as a buffer around the 

flood boundary. Gesch (2009) used a similar approach to show a spatial 

representation of the uncertainty of the projected inundation area from a 1-m sea-level 

rise, with one color for the area below 1-m in elevation and another color for the 

adjacent uncertainty zone (see Box 2.1). 

As with vulnerability maps derived from elevation data, statistical summaries of 

affected land area, population, land use/land cover types, number of buildings, 

infrastructure extent, and other socioeconomic variables should include recognition of 

the vertical uncertainty of the underlying data. In many studies, the delineated 

inundation zone is intersected with geospatial representations of demographic or 

economic variables in order to summarize the quantity of those variables within the 

potential impact zone. Such overlay and summarizing operations should also include 

the area of uncertainty associated with the inundation zone, and thus ranges of the 

variables should be reported. The range for a particular variable would increase from 

the total for just the projected inundation zone up to the combined total for the 

inundation zone plus the adjacent uncertainty zone. Additionally, because the 

combined area of the inundation zone and its adjacent uncertainty zone has a known 

confidence level, the range can be reported with that same confidence level. Merwade 

et al. (2008) have recommended such an approach for floodplain mapping when they 

state that the flood inundation extent should be reported as being “in the range from x

units to y units with a z-% confidence level”. 
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An important use of elevation data accuracy information in an assessment study is to 

guide the selection of land elevation intervals or sea-level rise increments that are 

appropriate for the available data. Inundation modeling is usually a simple process 

wherein sea level is effectively raised by delineating the area at and below a specified 

land elevation to create the inundation zone. This procedure is effectively a 

contouring process, so the vertical accuracy of a DEM must be known to determine 

the contour interval that is supported. DEMs can be contoured at any interval, but, 

just by doing so, it does not mean that the contours meet published accuracy 

standards. Likewise, studies can use small intervals of sea-level rise, but the 

underlying elevation data must have the vertical accuracy to support those intervals. 

The intervals must not be so small that they are within the bounds of the statistical 

uncertainty of the elevation data. 

5. Produce spatially explicit maps and detailed statistics that can be used in local 

decision making. The ultimate use of a sea-level rise assessment is as a planning and 

decision-making tool. Some assessments cover broad areas and are useful for scoping 

the general extent of the area of concern for sea-level rise impacts. However, the 

smaller-scale maps and corresponding statistics from these broad area assessments 

cannot be used for local decision making, which require large-scale map products and 

site specific information. Such spatially explicit planning maps require highresolution, high-accuracy input data as source information. Monmonier (2008) 

emphasizes that “reliable large-scale planning maps call for markedly better elevation 

data than found on conventional topographic maps”. Even with source data that 
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supports local mapping, it is important to remember, as Frumhoff et al. (2007) point 

out, due to the complex nature of coastal dynamics that “projecting the impacts of 

rising sea level on specific locations is not as simple as mapping which low-lying 

areas will eventually be inundated”. 

Proper treatment of elevation uncertainty is especially important for development of 

large-scale maps that will be used for planning and resource management decisions. 

Several states have realized the advantages of using high-accuracy lidar data to reduce 

uncertainty in sea-level rise studies and development of local map products (Rubinoff, et 

al., 2008). Accurate local-scale maps can also be generalized to smaller-scale maps for 

assessments over larger areas. Such aggregation of detailed information benefits broad 

area studies by incorporating the best available, most detailed information. 

Development of large-scale spatially explicit maps presents a new set of challenges. At 

scales useful for local decision making, the hydrological connectivity of the ocean to 

vulnerable lands must be mapped and considered. In some vulnerable areas, the drainage 

network has been artificially modified with ditches, canals, dikes, levees, and seawalls 

that affect the hydrologic paths rising water can traverse (Poulter and Halpin, 2007; 

Poulter et al., 2008). Fortunately, lidar data often include these important features, which 

are important for improving large-scale inundation modeling (Coastal States 

Organization, 2007). Older, lower resolution elevation data often do not include these 

fine-scale manmade features, which is another limitation of these data for large-scale 

maps. 
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Other site-specific data should be included in impact assessments for local decision 

making, including knowledge of local sea-level rise trends and the differences among the 

zero reference for elevation data (often an orthometric datum), local mean sea level, and 

high water (Marbaix, and Nicholls, 2007; Poulter and Halpin, 2007). The high water level 

is useful for inundation mapping because it distinguishes the area of periodic 

submergence by tides from those areas that may become inundated as sea-level rises 

(Leatherman, 2001). The importance of knowing the local relationships of water level 

and land vertical reference systems emphasizes the need for a national implementation of 

VDatum (Parker et al., 2003; Myers, 2005) so that accurate information on tidal 

dynamics can be incorporated into local sea-level rise assessments. 

Another useful advance for detailed sea-level rise assessments can be realized by better 

overlay analysis of a delineated vulnerability zone and local population data. Population 

data are aggregated and reported in census blocks and tracts, and are often represented in 

area-based statistical thematic maps, also known as choropleth maps. However, such 

maps usually do not represent actual population density and distribution across the 

landscape because census units include both inhabited and uninhabited land. Dasymetric 

mapping (Mennis, 2003) is a technique that is used to disaggregate population density 

data into a more realistic spatial distribution based on ancillary land use/land cover 

information or remote sensing images (Sleeter and Gould, 2008; Chen, 2002). This 

technique holds promise for better analysis of population, or other socioeconomic data, to 

report statistical summaries of sea-level rise impacts within vulnerable zones. 
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2.5 SUMMARY, CONCLUSIONS, AND FUTURE DIRECTIONS 

The topic of coastal elevations is most relevant to the first SAP 4.1 prospectus question 

(CCSP, 2006): “Which lands are currently at an elevation that could lead them to be 

inundated by the tides without shore protection measures?” The difficulty in directly 

answering this question for the mid-Atlantic region with a high degree of confidence was 

recognized. Collectively, the available previous studies do not provide the full answer for 

this region with the degree of confidence that is optimal for local decision making. 

Fortunately, new elevation data, especially lidar, are becoming available and are being 

integrated into the USGS NED (Gesch, 2007) as well as being used in sea-level rise 

applications (Coastal States Organization, 2007). Also, research is progressing on how to 

take advantage of the increased spatial resolution and vertical accuracy of new data 

(Poulter and Halpin, 2007; Gesch, 2009). 

Using national geospatial standards for accuracy assessment and reporting, the currently 

best available elevation data for the entire mid-Atlantic region do not support an 

assessment using a sea-level rise increment of 1-m or less, which is slightly above the 

range of current estimates for the remainder of this century and the high scenario used in 

this Product. Where lidar data meeting current industry standards for accuracy are 

available, the land area below the 1-m contour (simulating a 1-m sea-level rise) can be 

estimated for those sites along the coast at which inundation will be the primary response. 

The current USGS holdings of the best available elevation data include lidar for North 

Carolina, parts of Maryland, and parts of New Jersey (Figure 2.3). Lidar data for portions 
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of Delaware and more of New Jersey and Maryland will be integrated into the NED in 

2009. However, it may be some time before the full extent of the mid-Atlantic region has 

sufficient coverage of elevation data that are suitable for detailed assessments of submeter increments of sea-level rise and development of spatially explicit local planning 

maps. 

Figure 2.3 The current best available elevation source data (as of August 2008) for the National Elevation 

Dataset over the mid-Atlantic region. 

Given the current status of the NED for the mid-Atlantic region (Figure 2.3), the finest 

increment of sea-level rise that is supported by the underlying elevation data varies across 

the area (Table 2.4 and Figure 2.4). At a minimum, a sea-level rise increment used for 

inundation modeling should not be smaller than the range of statistical uncertainty of the 

elevation data. For instance, if an elevation dataset has a vertical accuracy of ±1 m at 95-

percent confidence, the smallest sea-level rise increment that should be considered is 1 m. 
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Even then, the reliability of the vulnerable area delineation would not be high because the 

modeled sea-level rise increment is the same as the inherent vertical uncertainty of the 

elevation data. Thus, the reliability of a delineation of a given sea-level rise scenario will 

be better if the inherent vertical uncertainty of the elevation data is much less than the 

modeled water level rise For example, a sea-level rise of 0.5 m is reliably modeled with 

elevation data having a vertical accuracy of ±0.25 m at 95-percent confidence. This 

guideline, with the elevation data being at least twice as accurate as the modeled sea-level 

rise, was applied to derive the numbers in Table 2.4. 

Table 2.4 Minimum sea-level rise scenarios for vulnerability assessments supported by elevation 

datasets of varying vertical accuracy.

Elevation data source Vertical accuracy: 

RMSE 

Vertical accuracy: linear 

error at 95-percent 

confidence 

Minimum sea-level rise 

increment for inundation 

modeling 

1-foot contour interval 

map 

9.3 cm 18.2 cm 36.4 cm 

Lidar 15.0 cm 29.4 cm 58.8 cm 

2-foot contour interval 

map 

18.5 cm 36.3 cm 72.6 cm 

1-meter contour interval 

map 

30.4 cm 59.6 cm 1.19 m 

5-foot contour interval 

map 

46.3 cm 90.7 cm 1.82 m 

10-foot contour interval 

map 

92.7 cm 1.82 m 3.64 m 

20-foot contour interval 

map 

1.85 m 3.63 m 7.26 m 
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Figure 2.4 The estimated minimum sea-level rise scenarios for inundation modeling in the mid-Atlantic 

region given the current best available elevation data. 

High-quality lidar elevation data, such as that which could be collected in a national lidar 

survey, would be necessary for the entire coastal zone to complete a comprehensive 

assessment of sea-level rise vulnerability in the mid-Atlantic region. Lidar remote sensing 

has been recognized as a means to provide highly detailed and accurate data for 

numerous applications, and there is significant interest from the geospatial community in 

developing an initiative for a national lidar collection for the United States (Stoker et al., 

2007, 2008). If such an initiative is successful, then a truly national assessment of 

potential sea-level rise impacts could be realized. A U.S. national lidar dataset would 

facilitate consistent assessment of vulnerability across state or jurisdictional boundaries, 

an approach for which coastal states have voiced strong advocacy (Coastal States 
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Organization, 2007). Even with the current investment in lidar by several states, there is a 

clear federal role in the development of a national lidar program (NRC, 2007; 

Monmonier, 2008; Stoker et al., 2008). 

Use of recent, high-accuracy lidar elevation data, especially with full consideration of 

elevation uncertainty as described in Section 2.4, will result in a new class of 

vulnerability maps and statistical summaries of impacts. These new assessment products 

will include a specific level of confidence, with ranges of variables reported. The level of 

statistical confidence could even be user selectable if assessment reports publish results at 

several confidence levels. 

It is clear that improved elevation data and analysis techniques will lead to better sealevel rise impact assessments. However, new assessments must include recognition that 

inundation, defined as submergence of the uplands, is the primary response to rising seas 

in only some areas. In other areas, the response may be dominated by more complex 

responses such as those involving shoreline erosion, wetland accretion, or barrier island 

migration. These assessments should first consider the geological setting and the 

dominant local physical processes at work to determine where inundation might be the 

primary response. Analysis of lidar elevation data, as outlined above, should then be 

conducted in those areas. 

Investigators conducting sea-level rise impact studies should strive to use approaches that 

generally follow the guidelines above so that results can be consistent across larger areas 
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and subsequent use of the maps and data can reference a common baseline. Assessment 

results, ideally with spatially explicit vulnerability maps and summary statistics having 

all the qualities described in Section 2.4, should be published in peer-reviewed journals 

so that decision makers can be confident of a sound scientific base for their decisions 

made on the basis of the findings. If necessary, assessment results can be reformatted into 

products that are more easily used by local planners and decision makers, but the 

scientific validity of the information remains. 
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CHAPTER 2 REFERENCES

* Indicates non-peer reviewed literature; available upon request

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Exposure to Large Rises in Sea-level: A Sensitivity Analysis. Working paper 96. 

Tyndall Centre for Climate Change Research, Southampton, UK, 31 pp. 

<http://www.tyndall.ac.uk/publications/working_papers/twp96.pdf> 

* Bin, O., C. Dumas, B. Poulter, and J. Whitehead, 2007: Measuring the Impacts of 

Climate Change on North Carolina Coastal Resources. Department of 

Economics, Appalachian State University, Boone, NC, 91 pp. 

<http://econ.appstate.edu/climate/> 

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Chapter 3. Ocean Coasts 

Authors: Benjamin T. Gutierrez, USGS; S. Jeffress Williams, USGS; E. Robert Thieler, 

USGS 

KEY FINDINGS 

 Along the ocean shores of the Mid-Atlantic, which are comprised of headlands, 

barrier islands, and spits, it is virtually certain that erosion will dominate changes 

in shoreline position in response to sea-level rise and storms over the next 

century. 

 It is very likely that landforms along the mid-Atlantic coast of the United States 

will undergo large changes if the higher sea-level rise scenarios occur. The 

response will vary depending on the type of coastal landforms and the local 

geologic and oceanographic conditions, and could be more variable than the 

changes observed over the last century. 

 For higher sea-level rise scenarios, it is very likely that some barrier island coasts 

will cross a threshold and undergo significant changes. These changes include 

more rapid landward migration or segmentation of some barrier islands. 

3.1 INTRODUCTION 

The general characteristics of the coast, such as the presence of beaches versus cliffs, 

reflects a complex and dynamic interaction between physical processes (e.g., waves and 

tidal currents) that act on the coast, availability of sediment transported by waves and 
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tidal currents, underlying geology, and changes in sea level (see review in Carter and 

Woodroffe, 1994a). Variations in these factors from one region to the next are 

responsible for the different coastal landforms, such as beaches, barrier islands, and cliffs 

that are observed along the coast today. Based on studies of the geologic record, the 

scope and general nature of the changes that can occur in response to sea-level rise are 

widely recognized (Curray, 1964; Carter and Woodroffe, 1994a; FitzGerald et al., 2008). 

On the other hand, determining precisely how these changes occur in response to a 

specific rise in sea level has been difficult. Part of the complication arises due to the 

range of physical processes and factors that modify the coast and operate over a range of 

time periods (e.g., from weeks to centuries to thousands of years) (Cowell and Thom, 

1994; Stive et al., 2002; Nicholls et al., 2007). Because of the complex interactions 

between these factors and the difficulty in determining their exact influence, it has been 

difficult to resolve a quantitative relationship between sea-level rise and shoreline change 

(e.g., Zhang et al., 2004; Stive, 2004). Consequently, it has been difficult to reach a 

consensus among coastal scientists as to whether or not sea-level rise can be 

quantitatively related to observed shoreline changes and determined using quantitative 

models (Dubois, 2002; Stive, 2004; Pilkey and Cooper, 2004; Cowell et al., 2006). 

Along many U.S. shores, shoreline changes are related to changes in the shape of the 

landscape at the water’s edge (e.g., the shape of the beach). Changes in beach 

dimensions, and the resulting shoreline changes, do not occur directly as the result of sealevel rise but are in an almost continual state of change in response to waves and currents 

as well as the availability of sediment to the coastal system (see overviews in Carter and 
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Woodroffe, 1994b; Stive et al., 2002; Nicholls et al., 2007). This is especially true for 

shoreline changes observed over the past century, when the increase in sea level has been 

relatively small (about 30 to 40 centimeters, or 12 to16 inches, along the mid-Atlantic 

coast). During this time, large storms, variations in sediment supply to the coast, and 

human activity have had a more obvious influence on shoreline changes. Large storms 

can cause changes in shoreline position that persist for weeks to a decade or more 

(Morton et al., 1994; Zhang et al., 2002, 2004; List et al., 2006; Riggs and Ames, 2007). 

Complex interactions with nearshore sand bodies and/or underlying geology (the 

geologic framework), the mechanics of which are not yet clearly understood, also 

influence the behavior of beach morphology over a range of time periods (Riggs et al., 

1995; Honeycutt and Krantz, 2003; Schupp et al., 2006; Miselis and McNinch, 2006). In 

addition, human actions to control changes to the shore and coastal waterways have 

altered the behavior of some portions of the coast considerably (e.g., Assateague Island, 

Maryland, Dean and Perlin, 1977; Leatherman, 1984; also see reviews in Nordstrom, 

1994, 2000; Nicholls et al., 2007). 

It is even more difficult to develop quantitative predictions of how shorelines may change 

in the future (Stive, 2004; Pilkey and Cooper, 2004; Cowell et al., 2006). The most easily 

applied models incorporate relatively few processes and rely on assumptions that do not 

always apply to real-world settings (Thieler et al., 2000; Cooper and Pilkey, 2004). In 

addition, model assumptions often apply best to present conditions, but not necessarily to 

future conditions. Models that incorporate more factors are applied at specific locations 

and require precise knowledge regarding the underlying geology or sediment budget 
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(e.g., GEOMBEST, Stolper et al., 2005), and it is therefore difficult to apply these 

models over larger coastal regions. Appendix 2 presents brief summaries of a few basic 

methods that have been used to predict the potential for shoreline changes in response to 

sea-level rise. 

As discussed in Chapter 2, recent and ongoing assessments of sea-level rise impacts 

commonly examine the vulnerability of coastal lands to inundation by specific sea-level 

rise scenarios (e.g., Najjar et al., 2000; Titus and Richman, 2001; Rowley et al., 2007). 

This approach provides an estimate of the land area that may be vulnerable, but it does 

not incorporate the processes (e.g., barrier island migration) nor the environmental 

changes (e.g., salt marsh deterioration) that may occur as sea level rises. Because of these 

complexities, inundation can be used as a basic approach to approximate the extent of 

land areas that could be affected by changing sea level. Because the majority of the U.S. 

coasts, including those along the Mid-Atlantic, consist of sandy shores, inundation alone 

is unlikely to reflect the potential consequences of sea-level rise. Instead, long-term 

shoreline changes will involve contributions from both inundation and erosion 

(Leatherman, 1990, 2001) as well as changes to other coastal environments such as 

wetland losses. 

Most portions of the open coast of the United States will be subject to significant physical 

changes and erosion over the next century because the majority of coastlines consist of 

sandy beaches which are highly mobile and in a continual state of change. This Chapter 

presents an overview and assessment of the important factors and processes that influence 
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potential changes to the mid-Atlantic ocean coast due to sea-level rise expected by the 

end of this century. This overview is based in part on a panel assessment (i.e., expert 

judgement) that was undertaken to address this topic for this Product (Gutierrez et al., 

2007). The panel assessment process is described in Section 3.2 and Box 3.1. Section 3.3 

reviews the geological characteristics of the mid-Atlanic coast. Section 3.4 provides an 

overview of the basic factors that influence sea-level rise-driven shoreline changes. 

Sections 3.5 and 3.6 describe the coastal landforms of the mid-Atlantic coast of the 

United States and what is known regarding how these landforms respond to changes in 

sea-level based on a literature review included as part of the panel assessment (Gutierrez 

et al., 2007). The potential responses of mid-Atlantic coastal landforms to sea-level rise, 

which were defined in the panel assessment, are presented in Section 3.7 and 

communicated using the likelihood terms specified in the Preface (see Figure P.1). 

3.2 ASSESSING THE POTENTIAL IMPACT OF SEA-LEVEL RISE ON THE 

OCEAN COASTS OF THE MID-ATLANTIC 

Lacking a single agreed-upon method or scientific consensus view about shoreline 

changes in response to sea-level rise at a regional scale, a panel was consulted to address 

the key question that guided this Chapter (Gutierrez et al., 2007). The panel consisted of 

coastal scientists whose research experiences have focused on the mid-Atlantic region 

and have been involved with coastal management in the mid-Atlantic region1

. The panel 

 

1

 Fred Anders (New York State, Dept. of State, Albany, NY), Eric Anderson (USGS, NOAA Coastal 

Services Center, Charleston, SC), Mark Byrnes (Applied Coastal Research and Engineering, Mashpee, 

MA), Donald Cahoon (USGS, Beltsville, MD), Stewart Farrell (Richard Stockton College, Pomona, NJ), 

Duncan FitzGerald (Boston University, Boston, MA), Paul Gayes (Coastal Carolina University, Conway, 

SC), Benjamin Gutierrez (USGS, Woods Hole, MA), Carl Hobbs (Virginia Institute of Marine Science, 

Gloucester Pt., VA), Randy McBride (George Mason University, Fairfax, VA), Jesse McNinch (Virginia 

Institute of Marine Science, Gloucester Pt., VA), Stan Riggs (East Carolina University, Greenville, NC), 
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discussed the changes that might be expected to occur to the ocean shores of the U.S. 

mid-Atlantic coast in response to predicted accelerations in sea-level rise over the next 

century, and considered the important geologic, oceanographic, and anthropogenic 

factors that contribute to shoreline changes in this region. The assessment presented here 

is based on the professional judgment of the panel. This qualitative assessment of 

potential changes that was developed by the panel is based on an understanding of both 

coastal science literature and their personal field observations. 

This assessment focuses on four sea-level rise scenarios. As defined in the Preface and 

Chapter 1, the first three sea-level rise scenarios (Scenarios 1 through 3) assume that: (1) 

the sea-level rise rate observed during the twentieth century will persist through the 

twenty-first century; (2) the twentieth century rate will increase by 2 millimeters (mm) 

per year, and (3) the twentieth century rate will increase by 7 mm per year. Lastly, a 

fourth scenario is discussed, which considers a 2-meter (6.6-foot) rise over the next few 

hundred years. In the following discussions, sea-level change refers to the relative sealevel change, which is the combination of global sea-level change and local change in 

land elevation. Using these scenarios, this assessment focuses on: 

 Identifying important factors and processes contributing to shoreline change over 

the next century; 

 Identifying key geomorphic settings along the coast of the mid-Atlantic region; 

 Defining potential responses of shorelines to sea-level rise; and 

 Antonio Rodriguez (University of North Carolina, Morehead City, NC), Jay Tanski (New York Sea Grant, 

Stony Brook, NY), E. Robert Thieler (USGS, Woods Hole, MA), Art Trembanis (University of Delaware, 

Newark, DE), S. Jeffress Williams (USGS, Woods Hole, MA).
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 Assessing the likelihood of these responses. 

Box 3.1: The Panel Assessment Process Used in SAP 4.1, Chapter 3 

As described in this Product, there is currently a lack of scientific consensus regarding local-, regional-, and 

national-scale coastal changes in response to sea-level rise, due to limited elevation and observational data 

and lack of adequate scientific understanding of the complex processes that contribute to coastal change. To 

address the question of potential future changes to the mid-Atlantic coast posed in the SAP 4.1 Prospectus, 

the authors assembled 13 coastal scientists for a meeting to evaluate the potential outcomes of the sea-level 

rise scenarios used in this Product. These scientists were chosen on the basis of their technical expertise and 

experience in the coastal research community, and also their involvement with coastal management issues in 

the mid-Atlantic region. Prior to the meeting, the scientists were provided with documents describing the 

Climate Change Science Program, and the Prospectus for this Product. The Prospectus included key 

questions and topics that the panel was charged to address. The panel was also provided a draft version of 

the report by Reed et al. (2008), which documented a similar panel-assessment approach used in developing 

Chapter 4 of this Product. 

The sea-level rise impact assessment effort was conducted as an open discussion facilitated by the USGS 

authors over a two-day period. The main topics that the panel discussed were: 

1) approaches that can be used to conduct long-term assessments of coastal change; 

2) key geomorphic environments in the mid-Atlantic region from Long Island, NY to North Carolina; 

3) potential responses of these environments to sea-level rise based on an understanding of important 

factors and processes contributing to coastal change; and 

4) the likelihood of these responses to the sea-level rise scenarios used in this Product (see Section 3.7). 

The qualitative, consensus-based assessment of potential changes and their likelihood developed by the 

panel was based on their review and understanding of peer reviewed published coastal science literature, as 

well as field observations drawn from other studies conducted in the mid-Atlantic region. The likelihood 

statements reported in Section 3.7 were determined based on the results of the discussion during the two-day 

meeting and revised according comments from panelists during the drafting of a summary report. The 

USGS report (Gutierrez et al., 2007) summarizing the process used, the basis in the published literature, and 

a synthesis of the resulting assessment was produced based on results of the meeting, reviewed as part of the 

USGS peer review process, and approved by members of the panel. 
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3.3 GEOLOGICAL CHARACTER OF THE MID-ATLANTIC COAST 

The mid-Atlantic margin of the United States is a gently sloping coastal plain that has 

accumulated over millions of years in response to the gradual erosion of the Appalachian 

mountain chain. The resulting sedimentation has constructed a broad coastal plain and a 

continental shelf that extends almost 300 kilometers (approximately 185 miles) seaward 

of the present coast (Colquhoun et al., 1991). The current morphology of this coastal 

plain has resulted from the incision of rivers that drain the region and the construction of 

barrier islands along the mainland occurring between the river systems. Repeated ice 

ages, which have resulted in sea-level fluctuations up to 140 meters (460 feet) (Muhs et 

al., 2004), caused these rivers to erode large valleys during periods of low sea level that 

then flooded and filled with sediments when sea levels rose. The northern extent of the 

mid-Atlantic region considered in this Product, Long Island, New York, was also shaped 

by the deposition of glacial outwash plains and moraines that accumulated from the 

retreat of the Laurentide ice sheet, which reached its maximum extent approximately 

21,000 years ago. This sloping landscape that characterizes entire mid-Atlantic margin, in 

combination with slow rates of sea-level rise over the past 5,000 years and sufficient sand 

supply, is also thought to have enabled the formation of the barrier islands that comprise 

the majority of the Atlantic Coast (Walker and Coleman, 1987; Psuty and Ofiara, 2002). 

The mid-Atlantic coast is generally described as a sediment-starved coast (Wright, 1995). 

Presently, sediments from the river systems of the region are trapped in estuaries and 

only minor amounts of sediment are delivered to the open ocean coast (Meade, 1969, 

1972). In addition, these estuaries trap sandy sediment from the continental shelf (Meade, 
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1969). Consequently, the sediments that form the mainland beach and barrier beach 

environments are thought to be derived mainly from the wave-driven erosion of the 

mainland substrate and sediments from the seafloor of the continental shelf (Niedoroda et 

al., 1985; Swift et al., 1985; Wright, 1995). Since the largest waves and associated 

currents occur during storms along the Atlantic Coast, storms are often thought to be 

significant contributors to coastal changes (Niedoroda et al., 1985; Swift et al., 1985; 

Morton and Sallenger, 2003). 

The majority of the open coasts along the mid-Atlantic region are sandy shores that 

include the beach and barrier environments. Although barriers comprise only 15 percent 

of the world coastline (Glaeser, 1978), they are the dominant shoreline type along the 

Atlantic Coast. Along the portion of the mid-Atlantic coast examined here, which ranges 

between Montauk, New York and Cape Lookout, North Carolina, barriers line the 

majority of the open coast. Consequently, scientific investigations exploring coastal 

geology of this portion of North America have focused on understanding barrier island 

systems (Fisher, 1962, 1968; Pierce and Colquhoun, 1970; Kraft, 1971; Leatherman, 

1979; Moslow and Heron, 1979, 1994; Swift, 1975; Nummedal, 1983; Oertel, 1985; 

Belknap and Kraft, 1985; Hine and Snyder, 1985; Davis, 1994). 

3.4 IMPORTANT FACTORS FOR MID-ATLANTIC SHORELINE CHANGE 

Several important factors influence the evolution of the mid-Atlantic coast in response to 

sea-level rise including: (1) the geologic framework, (2) physical processes, (3) the 

sediment supply, and (4) human activity. Each of these factors influences the response of 
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coastal landforms to changes in sea level. In addition, these factors contribute to the local 

and regional variations of sea-level rise impacts that are difficult to capture using 

quantitative prediction methods. 

3.4.1 Geologic Framework 

An important factor influencing coastal morphology and behavior is the underlying 

geology of a setting, which is also referred to as the geological framework (Belknap and 

Kraft, 1985; Demarest and Leatherman, 1985; Schwab et al., 2000). On a large scale, an 

example of this is the contrast in the characteristics of the Pacific Coast versus the 

Atlantic Coast of the United States. The collision of tectonic plates along the Pacific 

margin has contributed to the development of a steep coast where cliffs line much of the 

shoreline (Inman and Nordstrom, 1971; Muhs et al., 1987; Dingler and Clifton, 1994; 

Griggs and Patsch, 2004; Hapke et al., 2006; Hapke and Reid, 2007). While common, 

sandy barriers and beaches along the Pacific margin are confined to river mouths and 

low-lying coastal plains that stretch between rock outcrops and coastal headlands. On the 

other hand, the Gulf of Mexico and Atlantic coasts of the United States are situated on a 

passive margin where tectonic activity is minor (Walker and Coleman, 1987). As a result, 

these coasts are composed of wide coastal plains and wide continental shelves extending 

far offshore. The majority of these coasts are lined with barrier beaches and lagoons, 

large estuaries, isolated coastal capes, and mainland beaches that abut high grounds in the 

surrounding landscape. 
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From a smaller-scale perspective focused on the mid-Atlantic region, the influence of the 

geological framework involves more subtle details of the regional geology. More 

specifically, the distribution, structure, and orientation of different rock and sediment 

units, as well as the presence of features such as river and creek valleys eroded into these 

units, provides a structural control on a coastal environment (e.g., Kraft, 1971; Belknap 

and Kraft, 1985; Demarest and Leatherman, 1985; Fletcher et al., 1990; Riggs et al., 

1995; Schwab et al., 2000; Honeycutt and Krantz, 2003). Moreover, the framework 

geology can control (1) the location of features, such as inlets, capes, or sand-ridges, (2) 

the erodibility of sediments, and (3) the type and abundance of sediment available to 

beach and barrier island settings. In the mid-Atlantic region, the position of tidal inlets, 

estuaries, and shallow water embayments can be related to the existence of river and 

creek valleys that were present in the landscape during periods of lower sea level in a 

number of cases (e.g., Kraft, 1971; Belknap and Kraft, 1985; Fletcher et al., 1990). 

Elevated regions of the landscape, which can often be identified by areas where the 

mainland borders the ocean coast, form coastal headlands. The erosion of these features 

supplies sand to the nearshore system. Differences in sediment composition (e.g., 

sediment size or density), can sometimes be related to differences in shoreline retreat 

rates (e.g., Honeycutt and Krantz, 2003). In addition, the distribution of underlying 

geological units (rock outcrops, hard-grounds, or sedimentary strata) in shallow regions 

offshore of the coast can modify waves and currents and influencing patterns of sediment 

erosion, transport, and deposition on the adjacent shores (Riggs et al., 1995; Schwab et 

al., 2000). These complex interactions with nearshore sand bodies and/or underlying 

geology can also influence the behavior of beach morphology over a range of time scales 
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(Riggs et al., 1995; Honeycutt and Krantz, 2003; Schupp et al., 2006; Miselis and 

McNinch, 2006). 

3.4.2 Physical Processes 

The physical processes acting on the coast are a principal factor shaping coastal 

landforms and consequently changes in shoreline position (see reviews in Davis, 1987; 

Komar, 1998). Winds, waves, and tidal currents continually erode, rework, winnow, 

redistribute, and shape the sediments that make up these landforms. As a result, these 

forces also have a controlling influence on the composition and morphology of coastal 

landforms such as beaches and barrier islands. 

Winds have a range of effects on coastal areas. They are the main cause of waves and 

also generate currents that transport sediments in shallow waters. In addition, winds are a 

significant mechanism transporting sand along beaches and barrier islands that generate 

and sustain coastal dunes. 

Waves are either generated by local winds or result from far-away disturbances such as 

large storms out at sea. As waves propagate into shallow water, their energy decreases 

but they are also increasingly capable of moving the sediment on the seabed. Close to 

shore each passing wave or breaking wave suspends sediments off the seabed. Once 

suspended above the bottom, these sediments can be carried by wave- or tide-generated 

currents. 
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Wave-generated currents are important agents of change on sandy shores. The main 

currents that waves generate are longshore currents, rip currents, and onshore and 

offshore directed currents that accompany the surge and retreat of breaking waves. 

Longshore currents are typically the most important for sediment transport that influences 

changes in shoreline position. Where waves approach the coast at an angle, longshore 

currents are generated. The speed of these currents varies, depending on the wave climate 

(e.g., average wave height and direction) and more specifically, on the power and angle 

of approach of the waves (e.g., high waves during storms, low waves during fair 

weather). These currents provide a mechanism for sand transport along the coast, referred 

to as littoral transport, longshore drift, or longshore transport. During storms, high 

incoming waves can generate longshore currents exceeding 1 meter (3 feet) per second 

and storm waves can transport thousands of cubic meters of sand in a relatively short 

time period, from hours to days. During calm conditions, waves are weaker but can still 

gradually transport large volumes of sand over longer time periods, ranging from weeks 

to months. Where there are changes in coastal orientation, the angle at which waves 

approach the coast changes and can lead to local reversals in longshore sediment 

transport. These variations can result in the creation of abundances or deficits of 

longshore sediment transport and contribute to the seaward growth or landward retreat of 

the shoreline at a particular location (e.g., Cape Lookout, North Carolina, McNinch and 

Wells [1999]). 

The effect of tidal currents on shores is more subtle except for regions near the mouths of 

inlets, bays, or areas where there is a change in the orientation of the shore. The rise and 
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fall of the water level caused by tides moves the boundary between the land and sea (the 

shoreline), causing the level that waves act on a shore to move as well. In addition, this 

controls the depth of water which influences the strength of breaking waves. In regions 

where there is a large tidal range, there is a greater area over which waves can act on a 

shore. The rise and fall of the water level also generates tidal currents. Near the shore, 

tidal currents are small in comparison to wave-driven currents. Near tidal inlets and the 

mouths of bays or estuaries, tidal currents are strong due to the large volumes of water 

that are transported through these conduits in response to changing water levels. In these 

settings, tidal currents transport sediment from ocean shores to back-barrier wetlands, 

inland waterways on flood tides and vice versa on ebb tides. Aside from these settings, 

tidal currents are generally small along the mid-Atlantic region except near changes in 

shoreline orientation or sand banks (e.g., North Carolina Capes, Cape Henlopen, 

Delaware). In these settings, the strong currents generated can significantly influence 

sediment transport pathways and the behavior of adjacent shores. 

3.4.3 Sediment Supply 

The availability of sediments to a coastal region also has important effects on coastal 

landforms and their behavior (Curray, 1964). In general, assuming a relatively stable sea 

level, an abundance of sediment along the coast can cause the coast to build seaward over 

the long term if the rate of supply exceeds the rate at which sediments are eroded and 

transported by nearshore currents. Conversely, the coast can retreat landward if the rate 

of erosion exceeds the rate at which sediment is supplied to a coastal region. One way to 

evaluate the role of sediment supply in a region or specific location is to examine the 
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amount of sediment being gained or lost along the shore. This is often referred to as the 

sediment budget (Komar, 1996; List, 2005; Rosati, 2005). Whether or not there is an 

overall sediment gain or loss from a coastal setting is a critical determinant of the 

potential response to changes in sea level; however, it is difficult if to quantify with high 

confidence the sediment budget over time periods as long as a century or its precise role 

in influencing shoreline changes. 

The recent Intergovernmental Panel on Climate Change (IPCC) chapter on coastal 

systems and low-lying regions noted that the availability of sediment to coastal regions 

will be a key factor in future shoreline changes (Nicholls et al., 2007). In particular, the 

deposition of sediments in coastal embayments (e.g., estuaries and lagoons) may be a 

significant sink for sediments as they deepen in response to sea-level rise and are able to 

accommodate sediments from coastal river systems and adjacent open ocean coasts. For 

this reason, it is expected that the potential for erosion and shoreline retreat will increase, 

especially in the vicinity of tidal inlets (see Nicholls et al., 2007). In addition, others have 

noted an important link between changes in the dimension of coastal embayments, the 

sediment budget, and the potential for shoreline changes (FitzGerald et al., 2006, 2008). 

In the mid-Atlantic region, coastal sediments generally come from erosion of both the 

underlying coastal landscape and the continental shelf (Swift et al., 1985; Niedoroda et 

al., 1985). Sediments delivered through coastal rivers in the mid-Atlantic region, are 

generally captured in estuaries contributing minor amounts of sediments to the openocean coast (Meade, 1969). 
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3.4.4 Human Impacts 

The human impact on the coast is another important factor affecting shoreline changes. A 

variety of erosion control practices have been undertaken over the last century along 

much of the mid-Atlantic region, particularly during the latter half of the twentieth 

century (see reviews in Nordstrom, 1994; 2000). As discussed later in Chapter 6, 

shoreline engineering structures such as seawalls, revetments, groins, and jetties have 

significantly altered sediment transport processes, and consequently affect the availability 

of sediment (e.g., sediment budget) to sustain beaches and barriers and the potential to 

exacerbate erosion on a local level (see discussion on Assateague Island in Box 3.2). 

Beach nourishment, a commonly used approach, has been used on many beaches to 

temporarily mitigate erosion and provide storm protection by adding to the sediment 

budget. 

The management of tidal inlets by dredging has had a large impact to the sediment 

budget particularly at local levels (see review in Nordstrom, 1994; 2000). In the past, 

sand removed from inlet shoals has been transferred out to sea, thereby depleting the 

amount of sand available to sustain portions of the longshore transport system and, 

consequently, adjacent shores (Marino and Mehta, 1988; Dean, 1988). More recently, 

inlet management efforts have attempted to retain this material by returning it to adjacent 

shores or other shores where sand is needed. 

A major concern to coastal scientists and managers is whether or not erosion 

management practices are sustainable for the long term, and whether or how these 
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shoreline protection measures might impede the ability of natural processes to respond to 

future sea-level rise, especially at accelerated rates. It is also uncertain whether beach 

nourishment will be continued into the future due to economic constraints and often 

limited supplies of suitable sand resources. Chapter 6 describes some of these erosion 

control practices and their management and policy implications further. In addition, 

Chapter 6 also describes the important concept of “Regional Sediment Management” 

which is used to guide the management of sediment in inlet dredging, beach nourishment, 

or other erosion control activities. 

3.5 COASTAL LANDFORMS OF THE MID-ATLANTIC 

For this assessment, the coastal landforms along the shores of the mid-Atlantic region are 

classified using the criteria developed by Fisher (1967; 1982), Hayes (1979), and Davis 

and Hayes (1984). Four distinct geomorphic settings, including spits, headlands, and 

wave-dominated and mixed-energy barrier islands, occur in the mid-Atlantic region, as 

shown in Figure 3.1 and described below. 
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Figure 3.1 Map of the mid-Atlantic coast of the United States showing the occurrence of the four coastal 

landform types (geomorphic settings). Numbers on the map designate distinct portions of the coast divided 

by landform type and refer to the discussions in Sections 3.5 and 3.7. Numbers on the photographs refer to 

specific sections of the coast that are depicted on the map. Images from Google Earth. (Gutierrez et. al., 

2007). 

3.5.1 Spits 

The accumulation of sand from longshore transport has formed large spits that extend 

from adjacent headlands into the mouths of large coastal embayments (Figure 3.1, 

Sections 4, 9, and 15). Outstanding examples of these occur at the entrances of Raritan 

Bay (Sandy Hook, New Jersey) and Delaware Bay (Cape Henlopen, Delaware). The 

evolution and existence of these spits results from the interaction between alongshore 

transport driven by incoming waves and the tidal flow through the large embayments. 

Morphologically, these areas can evolve rapidly. For example, since 1842 Cape Henlopen 

(Figure 3.1, Section 9) has extended almost 1.5 kilometers (0.9 miles) to the north into 
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the mouth of Delaware Bay as the northern Delaware shoreline has retreated and 

sediment has been transported north by longshore currents (Kraft, 1971; Kraft et al., 

1978; Ramsey et al., 2001). 

3.5.2 Headlands 

Along the shores of the mid-Atlantic region, coastal headlands typically occur where 

elevated regions of the landscape intersect the coast. These regions are often formed 

where drainage divides that separate creeks and rivers from one another occur in the 

landscape, or where glacial deposits create high grounds (Taney, 1961; Kraft, 1971; 

Nordstrom et al., 1977). The erosion of headlands provides a source of sediment that is 

incorporated into the longshore transport system that supplies and maintains adjacent 

beaches and barriers. Coastal headlands are present on Long Island, New York (see 

Figure 3.1), from Southampton to Montauk (Section 1), in northern New Jersey from 

Monmouth to Point Pleasant (Section 5; Oertel and Kraft, 1994), in southern New Jersey 

at Cape May (Section 8), on Delaware north and south of Indian River and Rehoboth 

Bays (Sections 10 and 12; Kraft, 1971; Oertel and Kraft, 1994; Ramsey et al., 2001), and 

on the Virginia Coast, from Cape Henry to Sandbridge (Section 16). 

3.5.3 Wave-Dominated Barrier Islands 

Wave-dominated barrier islands occur as relatively long and thin stretches of sand 

fronting shallow estuaries, lagoons, or embayments that are bisected by widely-spaced 

tidal inlets (Figure 3.1, Sections 2, 6, 10, 13, and 17). These barriers are present in 

regions where wave energy is large relative to tidal energy, such as in the mid-Atlantic 
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region (Hayes, 1979; Davis and Hayes, 1984). Limited tidal ranges result in flow-through 

tidal inlets that are marginally sufficient to flush the sediments that accumulate from 

longshore sediment transport. In some cases, this causes the inlet to migrate over time in 

response to a changing balance between tidal flow through the inlet and wave-driven 

longshore transport. Inlets on wave-dominated coasts often exhibit large flood-tidal deltas 

and small ebb-tidal deltas as tidal currents are often stronger during the flooding stage of 

the tide. 

In addition, inlets on wave-dominated barriers are often temporary features. They open 

intermittently in response to storm-generated overwash and migrate laterally in the 

overall direction of longshore transport. In many cases, these inlets are prone to filling 

with sands from alongshore sediment transport (e.g., McBride, 1999). 

Overwash produced by storms is common on wave-dominated barriers (e.g., Morton and 

Sallenger, 2003; Riggs and Ames, 2007). Overwash erodes low-lying dunes into the 

island interior. Sediment deposition from overwash adds to the island’s elevation. 

Overwash deposits (washover fans) that extend into the back-barrier waterways form 

substrates for back-barrier marshes and submerged aquatic vegetation. 

The process of overwash is an important mechanism by which some types of barriers 

migrate landward and upward over time. This process of landward migration has been 

referred to as “roll-over” (Dillon, 1970; Godfrey and Godfrey, 1976; Fisher, 1982; Riggs 

and Ames, 2007). Over decades to centuries, the intermittent processes of overwash and 
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inlet formation enable the barrier to migrate over and erode into back-barrier 

environments such as marshes as relative sea-level rise occurs over time. As this occurs, 

back-barrier environments such as marshes are eroded and buried by barrier beach and 

dune sands. 

3.5.4 Mixed-Energy Barrier Islands 

The other types of barrier islands present along the U.S. Atlantic coast are mixed-energy 

barrier islands, which are shorter and wider than their wave-dominated counterparts 

(Hayes, 1979; Figure 3.1, Sections 3, 4, 7, and 14). The term “mixed-energy” refers to the 

fact that both waves and tidal currents are important factors influencing the morphology 

of these systems. Due to the larger tidal range and consequently stronger tidal currents, 

mixed energy barriers are shorter in length and well-developed tidal inlets are more 

abundant than for wave-dominated barriers. Some authors have referred to the mixedenergy barriers as tide-dominated barriers along the New Jersey and Virginia coasts (e.g., 

Oertel and Kraft, 1994). 

The large sediment transport capacity of the tidal currents within the inlets of these 

systems maintains large ebb-tidal deltas seaward of the inlet mouth. The shoals that 

comprise ebb-tidal deltas cause incoming waves to refract around the large sand body 

that forms the delta such that local reversals of alongshore currents and sediment 

transport occur downdrift of the inlet. As a result, portions of the barrier downdrift of 

inlets accumulate sediment which form recurved sand ridges and give the barrier islands 

a ‘drumstick’-like shape (Hayes 1979; Davis, 1994). 
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3.6 POTENTIAL RESPONSES TO FUTURE SEA-LEVEL RISE 

Based on current understanding of the four landforms discussed in the previous section, 

three potential responses could occur along the mid-Atlantic coast in response to sealevel rise over the next century. 

3.6.1 Bluff and Upland Erosion 

Shorelines along headland regions of the coast will retreat landward with rising sea level. 

As sea level rises over time, uplands will be eroded and the sediments incorporated into 

the beach and dune systems along these shores. Along coastal headlands, bluff and 

upland erosion will persist under all four of the sea-level rise scenarios considered in this 

Product. A possible management reaction to bluff erosion is shore armoring (e.g.

Nordstrom, 2000; Psuty and Ofiara, 2002; see Chapter 6). This may reduce bluff erosion 

in the short term but could increase long-term erosion of the adjacent coast by reducing 

sediment supplies to the littoral system. 

3.6.2 Overwash, Inlet Processes, and Barrier Island Morphologic Changes 

For barrier islands, three main processes are agents of change as sea level rises. First, 

with higher sea level, storm overwash may occur more frequently. This is especially 

critical if the sand available to the barrier, such as from longshore transport, is 

insufficient to allow the barrier to maintain its width and/or build vertically over time in 

response to rising water levels. If sediment supplies or the timing of the barrier recovery 

are insufficient, storm surges coupled with breaking waves will affect increasingly higher 
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elevations of the barrier systems as mean sea level increases, possibly causing more 

extensive erosion and overwash. In addition, it is possible that future hurricanes may 

become more intense, possibly increasing the potential for episodic overwash, inlet 

formation, and shoreline retreat. The topic of recent and future storm trends has been 

debated in the scientific community, with some researchers suggesting that other climate 

change impacts such as strengthening wind shear may lead to a decrease in future 

hurricane frequency (see Chapter 1 and reviews in Meehl et al., 2007; Karl et al., 2008; 

Gutowski et al., 2008). It is also expected that extratropical storms will be more frequent 

and intense in the future, but these effects will be more pronounced at high latitudes (60° 

to 90°N) and possibly decreased at midlatitudes (30° to 60°N) (Meehl et al., 2007; Karl et 

al., 2008; and Gutowski et al., 2008). 

Second, tidal inlet formation and migration will contribute to important changes in future 

shoreline positions. Storm surges coupled with high waves can cause not only barrier 

island overwash but also breach the barriers and create new inlets. In some cases, 

breaches can be large enough to form inlets that persist for some time until the inlet 

channels fill with sediments accumulated from longshore transport. Numerous deposits 

have been found along the shores of the mid-Atlantic region, indicating former inlet 

positions (North Carolina: Moslow and Heron, 1979 and Everts et al., 1983; Fire Island, 

New York: Leatherman, 1985). Several inlets along the mid-Atlantic coast were formed 

by the storm surges and breaches from an unnamed 1933 hurricane, including 

Shackleford Inlet in North Carolina; Ocean City inlet in Maryland; Indian River Inlet in 

Delaware; and Moriches Inlet in New York. Recently, tidal inlets were formed in the 
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North Carolina Outer Banks in response to Hurricane Isabel in 2003. While episodic inlet 

formation and migration are natural processes and can occur independently of long-term 

sea-level rise, a long-term increase in sea level coupled with limited sediment supply and 

increases in storm frequency and/or intensity could increase the likelihood for future inlet 

breaching. 

Third, the combined effect of rising sea level and stronger storms could accelerate barrier 

island shoreline changes. These will involve both changes to the seaward facing and 

landward facing shores of some barrier islands. Assessments of shoreline change on 

barrier islands indicate that barriers have thinned in some areas over the last century 

(Leatherman, 1979; Jarrett, 1983; Everts et al., 1983; Penland et al., 2005). Evidence of 

barrier migration is not widespread on the mid-Atlantic coast (Morton et al., 2003), but is 

documented at northern Assateague Island in Maryland (Leatherman, 1979) and Core 

Banks, North Carolina (Riggs and Ames, 2007). 

3.6.3 Threshold Behavior 

Barrier islands are dynamic environments that are sensitive to a range of physical and 

environmental factors. Some evidence suggests that changes in some or all of these 

factors can lead to conditions where a barrier system becomes less stable and crosses a 

geomorphic threshold. Once a threshold is crossed, the potential for significant and 

irreversible changes to the barrier island is high. These changes can involve landward 

migration or changes to the barrier island dimensions such as reduction in size or an 
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increased presence of tidal inlets. Although it is difficult to precisely define an unstable 

barrier, indications include: 

 Rapid landward migration of the barrier; 

 Decreased barrier width and height, due to a loss of sand eroded from beaches and 

dunes; 

 Increased frequency of overwash during storms; 

 Increased frequency of barrier breaching and inlet formation; and 

 Segmentation of the barrier. 

Given the unstable state of some barrier islands under current rates of sea-level rise and 

climate trends, it is very likely that conditions will worsen under accelerated sea-level 

rise rates. The unfavorable conditions for barrier maintenance could result in significant 

changes, for example, to barrier islands as observed in coastal Louisiana (further 

discussed in Box 3.2; McBride et al., 1995; McBride and Byrnes, 1997; Penland et al., 

2005; Day et al., 2007; Sallenger et al., 2007; FitzGerald et al., 2008). In one case, recent 

observations indicate that the Chandeleur Islands are undergoing a significant land loss 

due to several factors which include: (1) limited sediment supply by longshore or crossshore transport, (2) accelerated rates of sea-level rise, and (3) permanent sand removal 

from the barrier system by storms such as Hurricanes Camille, Georges, and Katrina. 

Likewise, a similar trend has been observed for Isle Dernieres, also on the Louisiana 

coast (see review in FitzGerald et al., 2008). In addition, recent studies from the North 

Carolina Outer Banks indicate that there have been at least two periods during the past 

several thousand years where fully open-ocean conditions have occurred in Albemarle 
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and Pamlico Sounds, which are estuaries fronted by barrier islands at the present time 

(Mallinson et al., 2005; Culver et al., 2008). This indicates that portions of the North 

Carolina barrier island system may have segmented or become less continuous than the 

present time for periods of a few hundred years, and later reformed. Given future 

increases in sea level and/or storm activity, the potential for a threshold crossing exists, 

and portions of these barrier islands could once again become segmented. 

Changes in sea level coupled with changes in the hydrodynamic climate and sediment 

supply in the broader coastal environment contribute to the development of unstable 

barrier island behavior. The threshold behavior of unstable barriers could result in: barrier 

segmentation, barrier disintegration, or landward migration and roll-over. If the barrier 

were to disintegrate, portions of the ocean shoreline could migrate or back-step toward 

and/or merge with the mainland. 

The mid-Atlantic coastal regions most vulnerable to threshold behavior can be estimated 

based on their physical dimensions. During storms, large portions of low-elevation, 

narrow barriers can be inundated under high waves and storm surge. Narrow, lowelevation barrier islands, such as the northern portion of Assateague Island, Maryland are 

most susceptible to storm overwash, which can lead to landward migration and the 

formation of new tidal inlets (e.g., Leatherman, 1979; see also Box 3.2). 

The future evolution of some low-elevation, narrow barriers could depend in part on the 

ability of salt marshes in back-barrier lagoons and estuaries to keep pace with sea-level 
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rise (FitzGerald et al., 2006, 2008; Reed et al., 2008). A reduction of salt marsh in backbarrier regions could increase the volume of water exchanged with the tides (e.g., the 

tidal prism) of back-barrier systems, altering local sediment budgets and leading to a 

reduction in sandy materials available to sustain barrier systems (FitzGerald et al., 2006, 

2008). 

BOX 3.2: Evidence for Threshold Crossing of Coastal Barrier Landforms 

Barrier islands change and evolve in subtle and somewhat predictable ways over time in response to 

storms, changing sediment supply, and changes in sea level. Recent field observations suggest that some 

barrier islands can reach a “threshold” condition: that is, a point where they become unstable and 

disintegrate. Two sites where barrier island disintegration is occurring and may continue to occur are along 

the 72 kilometers (about 45 miles) long Chandeleur Islands in Louisiana, east of the Mississippi River 

Delta, due to impacts of Hurricane Katrina in September 2005; and the northern 10 kilometers (6 miles) of 

Assateague Island National Seashore, Maryland due to 70 years of sediment starvation caused by the 

construction of jetties to maintain Ocean City Inlet. 

Chandeleur Islands, Louisiana

In the Chandeleur Islands, the high storm surge (about 4 meters or 13 feet) and waves associated with 

Hurricane Katrina in 2005 completely submerged the islands and eroded about 85 percent of the sand from 

the beaches and dunes (Sallenger et al., 2007). Box Figure 3.2a (UTM Northing) shows the configuration 

of the barriers in 2002, and in 2005 after Katrina’s passage. Follow-up aerial surveys by the U.S. 

Geological Survey indicate that erosion has continued since that time. When the Chandeleur Islands were 

last mapped in the late 1980s and erosion rates were calculated from the 1850s, it was estimated that the 

Chandeleurs would last approximately 250 to 300 years (Williams et al., 1992). The results from postKatrina studies suggest that a threshold has been crossed such that conditions have changed and natural 

processes may not contribute to the rebuilding of the barrier in the future. 

Assateague Island National Seashore, Maryland 

An example of one shoreline setting where human activity has increased the vulnerability of the shore to 

sea-level rise is Assateague Island, Maryland. Prior to a hurricane in 1933, Assateague Island was a 

continuous, straight barrier connected to Fenwick Island (Dolan et al., 1980). An inlet that formed during 

the storm separated the island into two sections at the southern end of Ocean City, Maryland. Subsequent 

construction of two stone jetties to maintain the inlet for navigation interrupted the longshore transport of 

sand to the south. Since then, the jetties have trapped sand, building the Ocean City shores seaward by 250 

meters (820 feet) by the mid-1970s (Dean and Perlin, 1977). In addition, the development of sand shoals 

(ebb tidal deltas) around the inlet mouth has sequestered large volumes of sand from the longshore 

transport system (Dean and Perlin, 1977; FitzGerald, 1988). South of the inlet, the opposite has occurred. 

The sand starvation on the northern portion of Assateague Island has caused the shore to migrate almost 

700 meters (2,300 feet) landward and transformed the barrier into a low-relief, overwash-dominated barrier 

(Leatherman, 1979; 1984). This extreme change in barrier island sediment supply has caused a previously 

stable segment of the barrier island to migrate. To mitigate the effects of the jetties, and to restore the 

southward sediment transport that was present prior to the existence of Ocean City inlet, the U.S. Army 

Corps of Engineers and National Park Service mechanically transfer sand from the inlet and the ebb and 

flood tidal deltas, where the sand is now trapped, to the shallow nearshore regions along the north end of 

the island. Annual surveys indicate that waves successfully transport the sediment alongshore and have 

slowed the high shoreline retreat rates present before the project began (Schupp et al., 2007). Current plans 

call for continued biannual transfer of sand from the tidal deltas to Assateague Island to mitigate the 

continued sediment starvation by the Ocean City inlet jetties. 
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Box Figure 3.2a Maps showing the extent of the Chandeleur Islands in 2002, three years before Hurricane 

Katrina and in 2005, after Hurricane Katrina. Land area above mean high water. Source: A. Sallenger, 

USGS. 

Box Figure 3.2b Aerial Photo of northern Assateague Island and Ocean City, Maryland showing former 

barrier positions. Note that in 1850, a single barrier island, shown in outlined in yellow, occupied this 

stretch of coast. In 1933, Ocean City inlet was created by a hurricane. The inlet improved accessibility to 

the ocean and was stabilized by jetties soon after. By 1942, the barrier south of the inlet had migrated 
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landward (shown as a green shaded region). Shorelines acquired from the State of Maryland Geological 

Survey. Photo source: NPS. 

Box Figure 3.2c North oblique photographs of northern Assateague Island in 1998 after a severe winter 

storm. The left photo of Assateague Island barrier shows clear evidence of overwash. The right 2006 photo 

shows a more robust barrier that had been augmented by recent beach nourishment. The white circles in the 

photos specify identical locations on the barrier. The offset between Fenwick Island (north) and Assateague 

Island due to Ocean City inlet and jetties can be seen at the top of the photo. Sources: a) National Park 

Service, b) Jane Thomas, IAN Photo and Video Library. 

END BOX**** 
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388 3.7 POTENTIAL CHANGES TO THE MID-ATLANTIC OCEAN COAST DUE 

389 TO SEA-LEVEL RISE 

390 In this Section, the responses to the four sea-level rise scenarios considered in this 

391 Chapter are described according to coastal landform types (Figure 3.2). The first three 

392 sea-level rise scenarios (Scenarios 1 through 3) are: (1) a continuation of the twentieth 

393 century rate, (2) the twentieth century rate plus 2 mm per year, and (3) the twentieth 

394 century rate plus 7 mm per year. Scenario 4 specifies a 2-meter rise (6.6-foot) over the 

395 next few hundred years. Because humans have a significant impact on portions of the 

396 mid-Atlantic coast, this assessment focuses on assessing the vulnerability of the coastal 

397 system as it currently exists (see discussion in Section 3.4). However, there are a few 

398 caveats to this approach: 

399  This is a regional-scale assessment and there are local exceptions to these 

400 geomorphic classifications and potential outcomes; 

401  Given that some portions of the mid-Atlantic coast are heavily influenced by 

402 development and erosion mitigation practices, it cannot be assumed that current 

403 practices will continue into the future given uncertainties regarding the decision404 making process that occurs when these practices are pursued; but, 

405  At the same time, there are locations where some members of the panel believe 

406 that erosion mitigation will be implemented regardless of cost. 

407 To express the likelihood of a given outcome for a particular sea-level rise scenario, the 

408 terminology advocated by ongoing CCSP assessments was used (see Preface, Figure P.1; 

409 CCSP, 2006). This terminology is used to quantify and communicate the degree of 

410 likelihood of a given outcome specified by the assessment. These terms should not be 
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411 construed to represent a quantitative relationship between a specific sea-level rise 

412 scenario and a specific dimension of coastal change, or rate at which a specific process 

413 operates on a coastal geomorphic compartment. The potential coastal responses to the 

414 sea-level rise scenarios are described below according to the coastal landforms defined in 

415 Section 3.5. 

 416 

417 3.7.1 Spits 

418 

419 For sea-level rise Scenarios 1 through 3, it is virtually certain that the coastal spits along 

420 the mid-Atlantic coast will be subject to increased storm overwash, erosion, and 

421 deposition over the next century (see Figure 3.2, Sections 4, 9, 15). It is virtually certain

422 that some of these coastal spits will continue to grow though the accumulation of 

423 sediments from longshore transport as the erosion of updrift coastal compartments 

424 occurs. For Scenario 4, it is likely that threshold behavior could occur for this type of 

425 coastal landform (rapid landward and/or alongshore migration). 

 426 

427 3.7.2 Headlands 

428 Over the next century, it is virtually certain that these headlands along the mid-Atlantic 

429 coast will be subject to increased erosion for all four sea-level rise scenarios (see Figure 

430 3.2, Sections 1, 5, 8, 10, 12, and 16). It is very likely that shoreline and upland (bluff) 

431 erosion will accelerate in response to projected increases in sea level. 

 432 

433 3.7.3 Wave-Dominated Barrier Islands 

434 Potential sea-level rise impacts on wave-dominated barriers in the Mid-Atlantic vary by 

435 location and depend on the sea-level rise scenario (see Figure 3.2, Sections 2, 6, 11, 13, 
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436 17). For Scenario 1, it is virtually certain that the majority of the wave-dominated barrier 

437 islands along the mid-Atlantic coast will continue to experience morphological changes 

438 through erosion, overwash, and inlet formation as they have over the last several 

439 centuries, except for the northern portion of Assateague Island (Section 13). In this area, 

440 the shoreline exhibits high rates of erosion and large portions of this barrier are 

441 submerged during moderate storms. In the past, large storms have breached and 

442 segmented portions of northern Assateague Island (Morton et al., 2003). Therefore, it is 

443 possible that these portions of the coast are already at a geomorphic threshold. With any 

444 increase in the rate of sea-level rise, it is virtually certain that this barrier island will 

445 exhibit large changes in morphology, ultimately leading to the degradation of the island. 

446 At this site, however, periodic transfer of sand from the shoals of Ocean City Inlet appear 

447 to be reducing erosion and shoreline retreat in Section13 (see Box 3.2). Portions of the 

448 North Carolina Outer Banks (Figure 3.2) may similarly be nearing a geomorphic 

449 threshold.

 450 

451 For Scenario 2, it is virtually certain that the majority of the wave-dominated barrier 

452 islands in the mid-Atlantic region will continue to experience morphological changes 

453 through overwash, erosion, and inlet formation as they have over the last several 

454 centuries. It is also about as likely as not that a geomorphic threshold will be reached in a 

455 few locations, resulting in rapid morphological changes in these barrier systems. Along 

456 the shores of northern Assateague Island (Section 13) and a substantial portion of Section 

457 17 it is very likely that the barrier islands could exhibit threshold behavior (barrier 

458 segmentation). For this scenario, the ability of wetlands to maintain their elevation 

459 through accretion at higher rates of sea-level rise may be reduced (Reed et al., 2008). It is 
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460 about as likely as not that the loss of back-barrier marshes will lead to changes in 

461 hydrodynamic conditions between tidal inlets and back-barrier lagoons, thus affecting the 

462 evolution of barrier islands (e.g., FitzGerald et al., 2006; FitzGerald et al., 2008). 

 463 

464 For Scenario 3, it is very likely that the potential for threshold behavior will increase 

465 along many of the mid-Atlantic barrier islands. It is virtually certain that a 2-meter (6.6-

466 foot) sea-level rise will lead to threshold behavior (segmentation or disintegration) for 

467 this landform type. 

468 
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469 

470 Figure 3.2 Map showing the potential sea-level rise responses for each coastal compartment. Colored 

471 portions of the coastline indicates the potential response for a given sea-level rise scenario according to the 

472 inset table (Gutierrez et. al., 2007). The color scheme was created using ColorBrewer by Cindy Brewer and 

473 Mark Harrower. 

 474 

475 3.7.4 Mixed-Energy Barrier Islands 

476 

477 The response of mixed-energy barrier islands will vary (see Figure 3.2, Sections 3, 7, 14). 

478 For Scenarios 1 and 2, the mixed-energy barrier islands along the mid-Atlantic will be 

479 subject to processes much as have occurred over the last century such as storm overwash 

480 and shoreline erosion. Given the degree to which these barriers have been developed, it is 

481 difficult to determine the likelihood of future inlet breaches, or whether these would be 
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482 allowed to persist due to common management decisions to repair breaches when they 

483 occur. In addition, changes to the back-barrier shores are uncertain due to the extent of 

484 coastal development. 

 485 

486 It is about as likely as not that four of the barrier islands along the Virginia Coast 

487 (Wallops, Assawoman, Metompkin, and Cedar Islands) are presently at a geomorphic 

488 threshold. Thus, it, it is very likely that further sea-level rise will contribute to significant 

489 changes resulting in the segmentation, disintegration and/or more rapid landward 

490 migration of these barrier islands. 

 491 

492 For the higher sea-level rise scenarios (Scenarios 3 and 4), it is about as likely as not that 

493 these barriers could reach a geomorphic threshold. This threshold is dependent on the 

494 availability of sand from the longshore transport system to supply the barrier. It is 

495 virtually certain that a 2-meter (6.6-foot) sea-level rise will have severe consequences 

496 along the shores of this portion of the coast, including one or more of the extreme 

497 responses described above. For Scenario 4, the ability of wetlands to maintain their 

498 elevation through accretion at higher rates of sea-level rise may be reduced (Reed et al., 

499 2008). It is about as likely as not that the loss of back-barrier marshes could lead to 

500 changes in the hydrodynamic conditions between tidal inlets and back-barrier lagoons, 

501 affecting the evolution of barrier islands (FitzGerald et al., 2006, 2008). 

502 
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503 CHAPTER 3 REFERENCES

504 * Indicates non-peer reviewed literature; available upon request

505 

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510 Shoreline Morphodynamics. Cambridge University Press, Cambridge, UK, 517 

511 pp. 

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519 Colquhoun, D.J., G.H. Johnson, P.C. Peebles, P.F. Huddleston, and T. Scott, 1991: 

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531 Culver, S.J., K.M. Farrell, D.J. Mallinson, B.P. Horton, D.A. Willard, E.R. Thieler, S.R. 

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556 Dillon, W.P., 1970: Submergence effects on Rhode Island barrier and lagoon and 

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567 Everts, C.H., J.P. Battley Jr., and P.N. Gibson, 1983: Shoreline Movements:Report 1, 

568 Cape Henry, Virginia to Cape Hatteras, North Carolina, 1849-1980. Technical 

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570 National Oceanic and Atmospheric Administration, Rockville, MD, 111 pp. 

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573 of North Carolina, Chapel Hill, 120 pp. 

574 * Fisher, J.J., 1967: Origin of barrier island chain shoreline, Middle Atlantic states. In: 

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577 Fisher, J.J., 1968: Barrier island formation: discussion. Geological Society of America 

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579 Fisher, J.J., 1982: Barrier islands. In: The Encyclopedia of Beaches and Coastal 

580 Environments [Schwartz, M.L. (ed.)]. Hutchinson Ross Publishing Company, 

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837 
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838 Chapter 4. Coastal Wetland Sustainability 

839 

840 Lead Authors: Donald R. Cahoon, USGS; Denise J. Reed, University of New Orleans; 

841 Alexander S. Kolker, Louisiana Universities Marine Consortium; Mark M. Brinson, East 

842 Carolina University 

843 

844 Contributing Authors: J. Court Stevenson, University of Maryland; Stanley Riggs, East 

845 Carolina University; Robert Christian, East Carolina University; Enrique Reyes, East 

846 Carolina University; Christine Voss, East Carolina University; David Kunz, East 

847 Carolina University 

 848 

849 KEY FINDINGS 

850  It is virtually certain that tidal wetlands already experiencing submergence by sea851 level rise and associated high rates of loss (e.g., Mississippi River Delta in 

852 Louisiana, Blackwater River marshes in Maryland) will continue to lose area in 

853 response to future accelerated rates of sea-level rise and changes in other climate 

854 and environmental drivers (factors that cause measurable changes). 

855  It is very unlikely that there will be an overall increase in tidal wetland area in the 

856 United States over the next 100 years, given current wetland loss rates and the 

857 relatively minor accounts of new tidal wetland development (e.g., Atchafalaya Delta 

858 in Louisiana). 

859  Current model projections of wetland vulnerability on regional and national scales 

860 are uncertain due to the coarse level of resolution of landscape-scale models. In 
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861 contrast, site-specific model projections are quite good where local information has 

862 been acquired on factors that control local accretionary processes in specific wetland 

863 settings. However, the authors have low confidence that site-specific model 

864 simulations can be successfully generalized so as to apply to larger regional or 

865 national scales. 

866  An assessment of the mid-Atlantic region based on an opinion approach by scientists 

867 with expert knowledge of wetland accretionary dynamics projects with a moderate 

868 level of confidence that those wetlands keeping pace with twentieth century rates of 

869 sea-level rise (Scenario 1) would survive a 2 millimeter per year acceleration of sea870 level rise (Scenario 2) only under optimal hydrology and sediment supply 

871 conditions, and would not survive a 7 millimeter per year acceleration of sea-level 

872 rise (Scenario 3). There may be localized exceptions in regions where sediment 

873 supplies are abundant, such as at river mouths and in areas where storm overwash 

874 events are frequent. 

875  The mid-Atlantic regional assessment revealed a wide variability in wetland 

876 responses to sea-level rise, both within and among subregions and for a variety of 

877 wetland geomorphic settings. This underscores both the influence of local processes 

878 on wetland elevation and the difficulty of generalizing from regional/national scale 

879 projections of wetland sustainability to the local scale in the absence of local 

880 accretionary data. Thus, regional or national scale assessments should not be used to 

881 develop local management plans where local accretionary dynamics may override 

882 regional controls on wetland vertical development. 
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883  Several key uncertainties need to be addressed in order to improve confidence in 

884 projecting wetland vulnerability to sea-level rise, including: a better understanding 

885 of maximum rates at which wetland vertical accretion can be sustained; interactions 

886 and feedbacks among wetland elevation, flooding, and soil organic matter accretion; 

887 broad-scale, spatial variability in accretionary dynamics; land use change effects 

888 (e.g., freshwater runoff, sediment supply, barriers to wetland migration) on tidal 

889 wetland accretionary processes; and local and regional sediment supplies, 

890 particularly fine-grain cohesive sediments needed for wetland formation. 

 891 

892 4.1 INTRODUCTION

893 Given an expected increase in the rate of sea-level rise in the next century, effective 

894 management of highly valuable coastal wetland habitats and resources in the United 

895 States will be improved by an in-depth assessment of the effects of accelerated sea-level 

896 rise on wetland vertical development (i.e., vertical accretion), the horizontal processes of 

897 shore erosion and landward migration affecting wetland area, and the expected changes 

898 in species composition of plant and animal communities (Nicholls et al., 2007). This 

899 Chapter assesses current and projected future rates of vertical buildup of coastal wetland 

900 surfaces and wetland sustainability during the next century under the three sea-level rise 

901 scenarios, as described briefly above, and in greater detail in Chapter 1. 

 902 

903 Many factors must be considered in such an assessment, including: the interactive effects 

904 of sea-level rise and other environmental drivers, (e.g., changes in sediment supplies 

905 related to altered river flows and storms); local processes controlling wetland vertical and 
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906 horizontal development and the interaction of these processes with the array of 

907 environmental drivers; geomorphic setting; and limited opportunities for landward 

908 migration (e.g., human development on the coast, or steep slopes) (Figures 4.1 and 4.2). 

909 Consequently, there is no simple, direct answer on national or regional scales to the key 

910 question facing coastal wetland managers today, namely, “Are wetlands building 

911 vertically at a pace equal to current sea-level rise, and will they build vertically at a pace 

912 equal to future sea-level rise?” This is a difficult question to answer because of the 

913 various combinations of local drivers and processes controlling wetland elevation across 

914 the many tidal wetland settings found in North America, and also due to the lack of 

915 available data on the critical drivers and local processes across these larger landscape 

916 scales. 

917 

918 Figure 4.1 Climate and environmental drivers influencing vertical and horizontal wetland development. 

 919 
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920 The capacity of wetlands to keep pace with sea-level rise can be more confidently 

921 addressed at the scale of individual sites where data are available on the critical drivers 

922 and local processes. However, scaling up from the local to the national perspective is 

923 difficult, and is rarely done, because of data constraints and because of variations in 

924 climate, geology, species composition, and human-induced stressors that become 

925 influential at larger scales. Better estimates of coastal wetland sustainability under rising 

926 sea levels and the factors influencing future sustainability are needed to inform coastal 

927 management decision making. This Chapter provides an overview of the factors 

928 influencing wetland sustainability (e.g., environmental drivers, accretionary processes, 

929 and geomorphic settings), the state of knowledge of current and future wetland 

930 sustainability, including a regional case study analysis of the mid-Atlantic coast of the 

931 United States, and information needed to improve projections of future wetland 

932 sustainability at continental, regional, and local scales. 

 933 

934 4.2 WETLAND SETTINGS OF THE MID-ATLANTIC REGION 

935 Coastal wetlands in the continental United States occur in a variety of physical settings 

936 (Table 4.1). The geomorphic classification scheme presented in Table 4.1, developed by 

937 Reed et al. (2008) (based on Woodroffe, 2002 and Cahoon et al., 2006), provides a useful 

938 way of examining and comparing coastal wetlands on a regional scale. Of the 

939 geomorphic settings described in Table 4.1, saline fringe marsh, back-barrier lagoon 

940 marsh, estuarine brackish marsh, tidal fresh marsh, and tidal fresh forest are found in the 

941 mid-Atlantic region of the United States. Back-barrier lagoon salt marshes are either 

942 attached to the backside of the barrier island, or are islands either landward of a tidal inlet 

943 or behind the barrier island. Saline fringe marshes are located on the landward side of 
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944 lagoons where they may be able to migrate upslope in response to sea-level rise (see 

945 Section 4.3 for a description of the wetland migration process). Estuarine marshes are 

946 brackish (a mixture of fresh and salt water) and occur along channels rather than open 

947 coasts, either bordering tidal rivers or embayments; or as islands within tidal channels. 

948 Tidal fresh marshes and tidal fresh forests occur along river channels, usually above the 

949 influence of salinity but not of tides. These wetlands can be distinguished based on 

950 vegetative type (species composition; herbaceous versus forested) and the salinity of the 

951 area. Given the differing hydrodynamics, sediment sources, and vegetative community 

952 characteristics of these geomorphic settings, the relationship between sea-level rise and 

953 wetland response will also differ. 

954 

955 4.3 VERTICAL DEVELOPMENT AND ELEVATION CHANGE 

956 A coastal marsh will survive if it builds vertically at a rate equal to the rise in sea level; 

957 that is, if it maintains its elevation relative to sea level. It is well established that marsh 

958 surface elevation changes in response to sea-level rise. Tidal wetland surfaces are 

959 frequently considered to be closely coupled with local mean sea level (e.g., Pethick, 

960 1981; Allen, 1990). If a marsh builds vertically at a slower rate than the sea rises, 

961 however, then a marsh area cannot maintain its elevation relative to sea level. In such a 

962 case, a marsh will gradually become submerged and convert to an intertidal mudflat or to 

963 open water over a period of many decades (Morris et al., 2002). 

 964 

965 The processes contributing to the capacity of a coastal wetland to maintain a stable 

966 relationship with changing sea levels are complex and often nonlinear (Cahoon et al., 
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967 2006). For example, the response of tidal wetlands to future sea-level rise will be 

968 influenced not only by local site characteristics, such as slope and soil erodibility 

969 influences on sediment flux, but also by changes in drivers of vertical accretion, some of 

970 which are themselves influenced by climate change (Figure 4.1). In addition to the rate of 

971 sea-level rise, vertical accretion dynamics are sensitive to changes in a suite of human 

972 and climate-related drivers, including alterations in river and sediment discharge from 

973 changes in precipitation patterns and in discharge and runoff related to dams and 

974 increases in impervious surfaces, increased frequency and intensity of hurricanes, and 

975 increased atmospheric temperatures and carbon dioxide concentrations. Vertical accretion 

976 is also affected by local environmental drivers such as shallow (local) and deep (regional) 

977 subsidence and direct alterations by human activities (e.g., dredging, diking). The relative 

978 roles of these drivers of wetland vertical development vary with geomorphic setting. 

 979 

980 4.3.1 Wetland Vertical Development 

981 Projecting future wetland sustainability is made more difficult by the complex interaction 

982 of processes by which wetlands build vertically (Figure 4.2) and vary across geomorphic 

983 settings (Table 4.1). Figure 4.2 shows how environmental drivers, mineral and organic 

984 soil development processes, and wetland elevation interact. Tidal wetlands build 

985 vertically through the accumulation of mineral sediments and plant organic matter 

986 (primarily plant roots). The suite of processes shown in Figure 4.2 controls the rates of 

987 mineral sediment deposition and accumulation of plant organic matter in the soil, and 

988 ultimately elevation change. Overall mineral sedimentation represents the balance 

989 between sediment import and export, which is influenced by sediment supply and the 
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990 relative abundance of various particle sizes, and varies among geomorphic settings and 

991 different tidal and wave energy regimes. Sediment deposition occurs when the surface of 

992 a tidal wetland is flooded. Thus, flooding depth and duration are important controls on 

993 deposition. The source of sediment may be supplied from within the local estuary (Reed, 

994 1989), and by transport from riverine and oceanic sources. Sediments are remobilized by 

995 storms, tides, and, in higher latitudes, ice rafting. 

 996 

997 

998 Figure 4.2 A conceptual diagram illustrating how environmental drivers (white boxes) and accretionary 

999 processes (grey boxes) influence vertical wetland development. 

 1000 

1001 The formation of organic-rich wetland soils is an important contributor to elevation in 

1002 both mineral sediment rich and mineral sediment poor wetlands (see review by Nyman et 

1003 al., 2006). Organic matter accumulation represents the balance between plant production 
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1004 (especially by roots and rhizomes) and decomposition and export of plant organic matter 

1005 (Figure 4.2). Accumulation comes from root and rhizome growth, which contributes 

1006 mass, volume, and structure to the sediments. The relative importance of mineral and 

1007 organic matter accumulation can vary depending on local factors such as rates of 

1008 subsidence and salinity regimes. 

1009 Table 4.1 Wetland types and their characteristics as they are distributed within geomorphic settings 

1010 in the continental United States. 

 1011 

Geomorphic 

Setting Description Subsettings 

Dominant accretion 

processes 

Example 

Site 

Dominant 

vegetation 

Open Coast Areas sheltered 

from waves and 

currents due to 

coastal 

topography or 

bathymetry 

 Storm sedimentation 

Peat accumulation 

Appalachee 

Bay, Florida 

smooth cordgrass

(Spartina 

alterniflora) 

black needlerush

(Juncus 

roemerianus) 

spike grass

(Distichlis spicata) 

salt hay (Spartina 

patens) 

glasswort

(Salicornia spp.) 

saltwort 

(Batis maritima)

Back-Barrier 

Lagoon 

Marsh (BB) 

Occupies fill 

within 

transgressive 

back-barrier 

lagoons 

Back-barrier 

Active flood 

tide delta 

Lagoonal fill 

Storm sedimentation 

(including barrier 

overwash) 

Peat accumulation 

Oceanic inputs via 

inlets 

Great South 

Bay, New 

York; 

Chincoteague 

Bay, 

Maryland, 

Virginia 

smooth cordgrass

(Spartina 

alterniflora) 

black needlerush

(Juncus 

roemerianus) 

spike grass

(Distichlis spicata) 

salt hay 

(Spartina patens) 

glasswort

(Salicornia spp.) 

saltwort 

(Batis maritima)

Estuarine 

Embayment 

Shallow coastal 

embayments with 

some river 

discharge, 

frequently 

drowned river 

valleys 

 Chesapeake 

Bay,Maryland, 

Virginia; 

Delaware Bay, 

New Jersey, 

Pennsylvania, 

Delaware, 

Estuarine 

Embayment 

a. Saline 

Fringe 

Marsh (SF) 

Transgressive 

marshes 

bordering uplands 

at the lower end 

of estuaries (can 

also be found in 

back-barrier 

 Storm sedimentation 

Peat accumulation 

Peconic Bay, 

New York; 

Western 

Pamlico 

Sound, North 

Carolina 

smooth cordgrass 

(Spartina 

alterniflora) 

black needlerush 

(Juncus 

roemerianus) 

spike grass
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Geomorphic 

Setting Description Subsettings 

Dominant accretion 

processes 

Example 

Site 

Dominant 

vegetation 

lagoons) (Distichlis spicata) 

salt hay 

(Spartina patens) 

glasswort 

(Salicornia spp.) 

saltwort 

(Batis maritima)

Estuarine 

Embayment 

b. Stream 

Channel 

Wetlands 

Occupy 

estuarine/alluvial 

channels rather 

than open coast 

 Dennis Creek, 

New Jersey; 

Lower 

Nanticoke 

River, 

Maryland 

Estuarine 

Brackish 

Marshes (ES) 

Located in 

vicinity of 

turbidity maxima 

zone 

Meander 

Fringing 

Island 

Alluvial and tidal inputs 

Peat accumulation 

Lower James 

River, 

Virginia; 

Lower 

Nanticoke 

River, 

Maryland; 

Neuse River 

Estuary, North 

Carolina 

smooth cordgrass

(Spartina 

alterniflora) 

salt hay 

(Spartina patens) 

spike grass 

(Distichlis spicata) 

black grass

(Juncus gerardi) 

black needlerush

(Juncus 

roemerianus) 

sedges 

(Scirpus olneyi) 

cattails 

(Typha spp.) 

big cordgrass

(Spartina 

cynosuroides) 

pickerelweed

(Pontederis 

cordata) 

Tidal Fresh 

Marsh (FM) 

Located above 

turbidity maxima 

zone; develop in 

drowned river 

valleys as filled 

with sediment

Alluvial and tidal inputs 

Peat accumulation

Upper 

Nanticoke 

River, 

Maryland; 

Anacostia 

River, 

Washington, 

DC

arrow arum

(Peltandra 

virginica) 

pickerelweed

(Pontederis 

cordata) 

arrowhead

(Sagitarria spp.) 

bur-marigold

(Bidens laevis) 

halberdleaf 

tearthumb

(Polygonum 

arifolium) 

scarlet rosemallow 

(Hibiscus 

coccineus) 

wild-rice 

(Zizannia 

aquatica) 

cattails 

(Typha spp.) 
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Geomorphic 

Setting Description Subsettings 

Dominant accretion 

processes 

Example 

Site 

Dominant 

vegetation 

giant cut grass

(Zizaniopsis 

miliacea) 

big cordgrass 

(Spartina 

cynosuroides) 

Tidal Fresh 

Forests (FF) 

Develop in 

riparian zone 

along rivers and 

backwater areas 

beyond direct 

influence of 

seawater 

Deepwater 

Swamps 

(permanently 

flooded) 

Bottomland 

Hardwood 

Forests 

(seasonally 

flooded)

Alluvial input 

Peat accumulation 

Upper Raritan 

Bay, New 

Jersey; 

Upper Hudson 

River, New 

York 

bald cypress 

(Taxodium 

distichum) 

blackgum

(Nyssa sylvatica) 

oak

(Quercus spp.) 

green ash

(Fraxinus 

pennsylvanica)

(var. lanceolata)

Nontidal 

Brackish 

Marsh 

Transgressive 

marshes 

bordering uplands 

in estuaries with 

restricted tidal 

signal 

Alluvial input 

Peat accumulation 

Pamlico 

Sound, North 

Carolina 

black needlerush

(Juncus 

roemerianus) 

smooth cordgrass

(Spartina 

alterniflora) 

spike grass 

(Distichlis spicata) 

salt hay 

(Spartina patens) 

big cordgrass 

(Spartina 

cynosuroides)

Nontidal 

Forests 

Develop in 

riparian zone 

along rivers and 

backwater areas 

beyond direct 

influence of 

seawater in 

estuaries with 

restricted tidal 

signal 

Bottomland 

Hardwood 

Forests 

(seasonally 

flooded)

Alluvial input 

Peat accumulation 

Roanoke 

River, North 

Carolina; 

Albemarle 

Sound, North 

Carolina 

bald cypress 

(Taxodium 

distichum) 

blackgum 

(Nyssa sylvatica) 

oak

(Quercus spp.) 

Green ash, 

Fraxinus 

pennsylvanica

4. Delta Develop on 

riverine sediments 

in shallow open 

water during 

active deposition; 

reworked by 

marine processes 

after 

abandonment 

Alluvial input 

Peat accumulation 

Compaction/Subsidence 

Storm sedimentation 

Marine Processes 

Mississippi 

Delta, 

Louisiana 

smooth cordgrass

(Spartina 

alterniflora) 

black needlerush

(Juncus 

roemerianus) 

spike grass 

(Distichlis spicata) 

salt hay 

(Spartina patens) 

glasswort

(Salicornia spp.) 

saltwort 

(Batis maritima) 

maidencane 

(Panicum 

haemitomon) 

arrowhead

(Sagitarria spp.) 
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1012 4.3.2 Influence of Climate Change on Wetland Vertical Development 

1013 Projections of wetland sustainability are further complicated by the fact that sea-level rise 

1014 is not the only factor influencing accretionary dynamics and sustainability (Figure 4.1). 

1015 The influence of sea-level rise and other human- and climate-related environmental 

1016 drivers on mineral sediment delivery systems is complex. For example, the timing and 

1017 amount of river flows are altered by changes in discharge related to both the effects of 

1018 dams and impervious surfaces built by humans and to changes in precipitation patterns 

1019 from changing climate. This results in a change in the balance of forces between river 

1020 discharge and the tides that control the physical processes of water circulation and 

1021 mixing, which in turn determines the fate of sediment within an estuary. Where river 

1022 discharge dominates, highly stratified estuaries prevail, and where tidal motion 

1023 dominates, well-mixed estuaries tend to develop (Dyer, 1995). Many mid-Atlantic 

1024 estuaries are partially mixed systems because the influence of river discharge and tides 

1025 are more balanced. 

 1026 

1027 River discharge is affected by interannual and interseasonal variations and intensities of 

1028 precipitation and evapotranspiration patterns, and by alterations in land use (e.g., 

1029 impervious surfaces and land cover types) and control over river flows (e.g., 

1030 impoundments and withdrawals). Sea-level rise can further change the balance between 

1031 river discharge and tides by its effect on tidal range (Dyer, 1995). An increase in tidal 

1032 range would increase tidal velocities and, consequently, tidal mixing and sediment 

1033 transport, as well as extend the reach of the tide landward. In addition, sea-level rise can 

1034 affect the degree of tidal asymmetry in an estuary (i.e., ebb versus flood dominance). In 
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1035 flood dominant estuaries, marine sediments are more likely to be imported to the estuary. 

1036 However, an increase in sea level without a change in tidal range may cause a shift 

1037 toward ebb dominance, thereby reducing the input of marine sediments that might 

1038 otherwise be deposited on intertidal flats and marshes (Dyer, 1995). Estuaries with 

1039 relatively small intertidal areas and small tidal amplitudes would be particularly 

1040 susceptible to such changes. The current hydrodynamic status of estuaries today is the 

1041 result of thousands of years of interaction between rising sea level and coastal landforms. 

 1042 

1043 The degree of influence of sea-level rise on wetland flooding, sedimentation, erosion, and 

1044 salinity is directly linked with the influence of altered river flows and storm impacts 

1045 (Figure 4.2). Changes in freshwater inputs to the coast can affect coastal wetland 

1046 community structure and function (Sklar and Browder, 1998) through fluctuations in the 

1047 salt balance up and down the estuary. Low-salinity and freshwater wetlands are 

1048 particularly affected by increases in salinity. In addition, the location of the turbidity 

1049 maximum zone (the region in many estuaries where suspended sediment concentrations 

1050 are higher than in either the river or sea) can shift seaward with increases in river 

1051 discharge, and the size of this zone will increase with increasing tidal ranges (Dyer, 

1052 1995). Heavy rains (freshwater) and tidal surges (salty water) from storms occur over 

1053 shorter time periods than interannual and interseasonal variation. This can exacerbate or 

1054 alleviate (at least temporarily) salinity and inundation effects of altered freshwater input 

1055 and sea-level rise in all wetland types. The direction of elevation change depends on the 

1056 storm characteristics, wetland type, and local conditions at the area of storm landfall 

1057 (Cahoon, 2006). Predicted increases in the magnitude of coastal storms from higher sea 
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1058 surface temperatures (Webster et al., 2005) will likely increase storm-induced wetland 

1059 sedimentation in the mid-Atlantic regional wetlands. Increased storm intensity could 

1060 increase the resuspension of nearshore sediments and the storm-related import of oceanic 

1061 sediments into tidal marshes. 

 1062 

1063 In addition to sediment supplies, accumulation of plant organic matter is a primary 

1064 process controlling wetland vertical development of soil. The production of organic 

1065 matter is influenced by factors associated with climate change, including increases in 

1066 atmospheric carbon dioxide concentrations, rising temperatures, more frequent and 

1067 extensive droughts, higher nutrient loading from floodwaters and ground waters, and 

1068 increases in salinity of flood waters. Therefore, a critical question that scientists must 

1069 address is: “How will these potential changes in plant growth affect wetland elevations 

1070 and the capacity of the marsh to keep pace with sea-level rise?” Some sites depend 

1071 primarily on plant matter accumulation to build vertically. For example, many brackish 

1072 marshes dominated by salt hay (Spartina patens) (McCaffrey and Thomson, 1980) and 

1073 mangroves on oceanic islands with low mineral sediment inputs (McKee et al., 2007), 

1074 changes in root production (Cahoon et al., 2003, 2006) and nutrient additions (McKee et 

1075 al., 2007) can significantly change root growth and wetland elevation trajectories. These 

1076 changes and their interactions warrant further study. 

 1077 

1078 4.4 HORIZONTAL MIGRATION

1079 Wetland vertical development can lead to horizontal expansion of wetland area (both 

1080 landward and seaward; Redfield, 1972), depending on factors such as slope, sediment 

1081 supply, shoreline erosion rate, and rate of sea-level rise. As marshes build vertically, they 
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1082 can migrate inland onto dry uplands, given that the slope is not too steep and there is no 

1083 human-made barrier to migration (Figure 4.1). Some of the best examples of submerged 

1084 upland types of wetlands in the mid-Atlantic region are found on the Eastern Shore of 

1085 Chesapeake Bay, a drowned river valley estuary (Darmody and Foss, 1979). Given a 

1086 setting with a low gradient slope, low wave energy, and high sediment supply (e.g., 

1087 Barnstable Marsh on Cape Cod, Massachusetts), a marsh can migrate both inland onto 

1088 uplands and seaward onto sand flats as the shallow lagoon fills with sediment (Redfield, 

1089 1972). Most coasts, however, have enough wave energy to prevent seaward expansion of 

1090 the wetlands. The more common alternative is erosion of the seaward boundary of the 

1091 marsh and retreat. In these settings, as long as wetland vertical development keeps pace 

1092 with sea-level rise, wetland area will expand where inland migration is greater than 

1093 erosion of the seaward boundary, remain unchanged where inland migration and erosion 

1094 of the seaward boundary are equal, or decline where erosion of the seaward boundary is 

1095 greater than inland migration (e.g., Brinson et al., 1995). If wetland vertical development 

1096 lags behind sea-level rise (i.e., wetlands do not keep pace), the wetlands will eventually 

1097 become submerged and deteriorate even as they migrate, resulting in an overall loss of 

1098 wetland area, as is occurring at Blackwater National Wildlife Refuge in Dorchester 

1099 County, Maryland (Stevenson et al., 1985). Thus, wetland migration is dependent on 

1100 vertical accretion, which is the key process for both wetland survival and expansion. If 

1101 there is a physical obstruction preventing inland wetland migration, such as a road or a 

1102 bulkhead, and the marsh is keeping pace with sea-level rise, then the marsh will not 

1103 expand but will survive in place as long as there is no lateral erosion at its seaward edge. 

1104 Otherwise, the wetland will become narrower as waves erode the shoreline. Thus, having 
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1105 space available with a low gradient slope for inland expansion is critical for maintaining 

1106 wetland area in a setting where seaward erosion of the marsh occurs. 

1107 

1108 4.5 VULNERABILITY OF WETLANDS TO TWENTIETH CENTURY SEA1109 LEVEL RISE 

1110 A recent evaluation of accretion and elevation trends from 49 salt marshes located around 

1111 the world, including sites from the Atlantic, Gulf of Mexico, and Pacific coasts of the 

1112 United States, provides insights into the mechanisms and variability of wetland responses 

1113 to twentieth century trends of local sea-level rise (Cahoon et al., 2006). Globally, average 

1114 wetland surface accretion rates were greater than and positively related to local relative 

1115 sea-level rise, suggesting that the marsh surface level was being maintained by surface 

1116 accretion within the tidal range as sea level rose. In contrast, average rates of elevation 

1117 rise were not significantly related to sea-level rise and were significantly lower than 

1118 average surface accretion rates, indicating that shallow soil subsidence occurs at many 

1119 sites. Regardless, elevation changes at many sites were greater than local sea-level rise 

1120 (Cahoon et al., 2006). Hence, understanding elevation change, in addition to surface 

1121 accretion, is important when determining wetland sustainability. Secondly, accretionary 

1122 dynamics differed strongly among geomorphic settings, with deltas and embayments 

1123 exhibiting high accretion and high shallow subsidence compared to back-barrier and 

1124 estuarine settings (see Cahoon et al., 2006). Thirdly, strong regional differences in 

1125 accretion dynamics were observed for the North American salt marshes evaluated, with 

1126 northeastern U.S. marshes exhibiting high rates of both accretion and elevation change, 

1127 southeastern Atlantic and Gulf of Mexico salt marshes exhibiting high rates of accretion 
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1128 and low rates of elevation change, and Pacific salt marshes exhibiting low rates of both 

1129 accretion and elevation change (see Cahoon et al., 2006). The marshes with low elevation 

1130 change rates are likely vulnerable to current and future sea-level rise, with the exception 

1131 of those in areas where the land surface is rising, such as on the Pacific Northwest Coast 

1132 of the United States. 

 1133 

1134 4.5.1 Sudden Marsh Dieback 

1135 An increasing number of reports available online (see e.g., <http://wetlands.neers.org/>, 

1136 <www.inlandbays.org>, <www.brownmarsh.net>, <www.lacoast.gov/watermarks/2004-

1137 04/3crms/index.htm>) of widespread “sudden marsh dieback” and “brown marsh 

1138 dieback” from Maine to Louisiana, along with published studies documenting losses of 

1139 marshes dominated by saltmarsh cordgrass (Spartina alterniflora) and other halophytes 

1140 (plants that naturally grow in salty soils), suggest that a wide variety of marshes may be 

1141 approaching or have actually gone beyond their tipping point where they can continue to 

1142 accrete enough inorganic material to survive (Delaune et al., 1983; Stevenson et al.,

1143 1985; Kearney et al., 1988, 1994; Mendelssohn and McKee, 1988; Hartig et al., 2002; 

1144 McKee et al., 2004; Turner et al., 2004). Sudden dieback was documented over 40 years 

1145 ago by marsh ecologists (Goodman and Williams, 1961). However, it is not known 

1146 whether all recently identified events are the same phenomenon and caused by the same 

1147 factors. There are biotic factors, in addition to insufficient accretion, that have been 

1148 suggested to contribute to sudden marsh dieback, including fungal diseases and 

1149 overgrazing by animals such as waterfowl, nutria, and snails. Interacting factors may 

1150 cause marshes to decline even more rapidly than scientists would predict from one driver, 
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1151 such as sea-level rise. There are few details about the onset of sudden dieback because 

1152 most studies are done after it has already occurred (Ogburn and Alber, 2006). Thus, more 

1153 research is needed to understand sudden marsh dieback. The apparent increased 

1154 frequency of this phenomenon over the last several years suggests an additional risk 

1155 factor for marsh survival over the next century (Stevenson and Kearney, in press). 

 1156 

1157 4.6 PREDICTING FUTURE WETLAND SUSTAINABILITY 

1158 Projections of future wetland sustainability on regional to national scales are constrained 

1159 by the limitations of the two modeling approaches used to evaluate the relationship 

1160 between future sea-level rise and coastal wetland elevation: landscape scale models and 

1161 site-specific models. Large scale landscape models, such as the Sea Level Affecting 

1162 Marshes Model (SLAMM) (Park et al., 1989), simulate general trends over large areas, 

1163 but typically at a very coarse resolution. These landscape models do not mechanistically 

1164 simulate the processes that contribute to wetland elevation; the processes are input as 

1165 forcing functions and are not simulated within the model. Thus, this modeling approach 

1166 does not account for infrequent events that influence wetland vertical development, such 

1167 as storms and floods, or for frequent elevation feedback mechanisms affecting processes 

1168 (for example, elevation change alters flooding patterns that in turn affect sediment 

1169 deposition, decomposition, and plant production). In addition, these models are not 

1170 suitable for site-specific research and management problems because scaling down of 

1171 results to the local level is not feasible. Therefore, although landscape models can 

1172 simulate wetland sustainability on broad spatial scales, their coarse resolution limits their 

1173 accuracy and usefulness to the local manager. 
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 1174 

1175 On the other hand, process oriented site-specific models (e.g., Morris et al., 2002; 

1176 Rybczyk and Cahoon, 2002) are more mechanistic than landscape models and are used to 

1177 simulate responses for a specific site with a narrow range of conditions and settings. 

1178 These site-specific models can account for accretion events that occur infrequently, such 

1179 as hurricanes and major river floods, and the feedback effects of elevation on inundation 

1180 and sedimentation that influence accretionary processes over timeframes of a century. 

1181 The use of site-specific conditions in a model makes it possible to predict long-term 

1182 sustainability of an individual wetland in a particular geomorphic setting. However, like 

1183 the landscape models, site-specific models also have a scaling problem. Using results 

1184 from an individual site to make long-term projections at larger spatial scales is 

1185 problematic because accretionary and process data are not available for the variety of 

1186 geomorphic settings across these larger-scale landscapes for calibrating and verifying 

1187 models. Thus, although site-specific models provide high resolution simulations for a 

1188 local site, at the present time future coastal wetland response to sea-level rise over large 

1189 areas can be predicted with only low confidence. 

 1190 

1191 Recently, two different modeling approaches have been used to provide regional scale 

1192 assessments of wetland response to climate change. In a hierarchical approach, detailed 

1193 site-specific models were parameterized with long-term data to generalize landscape1194 level trends with moderate confidence for inland wetland sites in the Prairie Pothole 

1195 Region of the Upper Midwest of the United States (Carroll et al., 2005; Voldseth et al., 

1196 2007; Johnson et al., 2005). The utility of this approach for coastal wetlands has not yet 
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1197 been evaluated. Alternatively, an approach was used to assess coastal wetland 

1198 vulnerability at regional-to-global scales from three broad environmental drivers: (1) ratio 

1199 of relative sea-level rise to tidal range, (2) sediment supply, and (3) lateral 

1200 accommodation space (i.e., barriers to wetland migration) (McFadden et al., 2007). This 

1201 model suggests that, from 2000 to 2080, there will be global wetland area losses of 33 

1202 percent for a 36 centimeter (cm) rise in sea level and 44 percent for a 72 cm rise; and that 

1203 regionally, losses on the Atlantic and Gulf of Mexico coasts of the United States will be 

1204 among the most severe (Nicholls et al., 2007). However, this model, called the Wetland 

1205 Change Model, remains to be validated and faces similar challenges when downscaling, 

1206 as does the previously described model when scaling up. 

 1207 

1208 Taking into account the limitations of current predictive modeling approaches, the 

1209 following assessments can be made about future wetland sustainability at the national 

1210 scale: 

1211  It is virtually certain that tidal wetlands already experiencing submergence by sea1212 level rise and associated high rates of loss (e.g., Mississippi River Delta in 

1213 Louisiana, Blackwater National Wildlife Refuge marshes in Maryland) will continue 

1214 to lose area under the influence of future accelerated rates of sea-level rise and 

1215 changes in other climate and environmental drivers. 

1216  It is very unlikely that there will be an overall increase in tidal wetland area on a 

1217 national scale over the next 100 years, given current wetland loss rates and the 

1218 relatively minor accounts of new tidal wetland development (e.g., Atchafalaya Delta 

1219 in Louisiana). 
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1220  Current model projections of wetland vulnerability on regional and national scales 

1221 are uncertain because of the coarse level of resolution of landscape scale models. In 

1222 contrast, site-specific model projections are quite good where local information has 

1223 been acquired on factors that control local accretionary processes in specific wetland 

1224 settings. However, the authors have low confidence that site-specific model 

1225 simulations, as currently portrayed, can be successfully scaled up to provide realistic 

1226 projections at regional or national scales. 

 1227 

1228 The following information is needed to improve the confidence in projections of future 

1229 coastal wetland sustainability on regional and continental scales: 

1230  Models and validation data. To scale up site-specific model outputs to regional 

1231 and continental scales with high confidence, detailed data are needed on the 

1232 various local drivers and processes controlling wetland elevation across all tidal 

1233 geomorphic settings of the United States. Obtaining and evaluating the necessary 

1234 data will be an enormous and expensive task, but not an impractical one. It will 

1235 require substantial coordination with various private and government 

1236 organizations in order to develop a large, searchable database. Until this type of 

1237 database becomes a reality, current modeling approaches need to improve or 

1238 adapt such that they can be applied across a broad spatial scale with better 

1239 confidence. For example, evaluating the utility of applying the multi-tiered 

1240 modeling approach used in the Prairie Pothole Region to coastal wetland systems 

1241 and validating the broad scale Wetland Change Model for North American coastal 

1242 wetlands will be important first steps. Scientists’ ability to predict coastal wetland 
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1243 sustainability will improve as specific ecological and geological processes 

1244 controlling accretion and their interactions on local and regional scales are better 

1245 understood. 

1246  Expert opinion. Although models driven by empirical data are preferable, given 

1247 the modeling limitations described, an expert opinion (i.e., subjective) approach 

1248 can be used to develop spatially explicit landscape-scale predictions of coastal 

1249 wetland responses to future sea-level rise with a low-to-moderate level of 

1250 confidence. This approach requires convening a group of scientists with expert 

1251 knowledge of coastal wetland geomorphic processes, with conclusions based on 

1252 an understanding of the processes driving marsh survival during sea-level rise and 

1253 of how the magnitude and nature of these processes might change due to the 

1254 effects of climate change and other factors. Because of the enormous complexity 

1255 of these issues at the continental scale, the expert opinion approach would be 

1256 applied with greater confidence at the regional scale. Two case studies are 

1257 presented in Sections 4.6.1 and 4.6.2; the first, using the expert opinion approach 

1258 applied to the mid-Atlantic region from New York to Virginia, the second, using a 

1259 description of North Carolina wetlands from the Albemarle–Pamlico Region and 

1260 an evaluation of their potential response to sea-level rise, based on a review of the 

1261 literature. 

1262 

1263 

1264 4.6.1 Case Study: Mid-Atlantic Regional Assessment, New York to Virginia 

1265 

1266 A panel of scientists with diverse and expert knowledge of wetland accretionary 

1267 processes was convened to develop spatially explicit landscape-scale predictions of 
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1268 coastal wetland response to the three scenarios of sea-level rise assessed in this Product 

1269 (see Chapter 1) for the mid-Atlantic region from New York to Virginia (see Text Box 

1270 4.1). The results of the panel’s effort (Reed et al., 2008) inform this Product assessment 

1271 of coastal elevations and sea-level rise. 

1272 Begin text box 

1273 

1274 Text Box 4.1: The Wetland Assessment Process Used by a Panel of Scientists 

1275 

1276 As described in this Product, scientific consensus regarding regional-scale coastal changes in response to 

1277 sea-level rise is currently lacking. To address the issue of future changes to mid-Atlantic coastal wetlands, 

1278 Denise Reed, a wetlands specialist at the University of New Orleans, was contracted by the U.S.EPA to 

1279 assemble a panel of coastal wetland scientists to evaluate the potential outcomes of the sea-level rise 

1280 scenarios used in this Product. Denise Reed chose the 8 members of this panel on the basis of their 

1281 technical expertise and experience in the coastal wetland research community, particularly with coastal 

1282 wetland geomorphic processes, and also their involvement with coastal management issues in the mid1283 Atlantic region. The panel was charged to address the question, “To what extent can wetlands vertically 

1284 accrete and thus keep pace with rising sea level, that is, will sea-level rise cause the area of wetlands to 

1285 increase or decrease?”. 

1286 

1287 The sea-level rise impact assessment effort was conducted as an open discussion facilitated by Denise Reed 

1288 over a two-day period. Deliberations were designed to ensure that conclusions were based on an 

1289 understanding of the processes driving marsh survival as sea level rises and how the magnitude and nature 

1290 of these processes might change in the future in response to climate change and other factors. To ensure a 

1291 systematic approach across regions within the mid-Atlantic region, the panel: 

1292 

1293 1) identified a range of geomorphic settings to assist in distinguishing among the different process 

1294 regimes controlling coastal wetland accretion (see Figure 4.3 and Table 4.1); 

1295 2) identified a suite of processes that contribute to marsh accretion (see Table 4.1) and outlined 

1296 potential future changes in current process regimes caused by climate change; 

1297 3) divided the mid-Atlantic into a series of regions based on similarity of process regime and current 

1298 sea-level rise rates; and 

1299 4) delineated geomorphic settings within each region on 1:250,000 scale maps, and agreed upon the 

1300 fate of the wetlands within these settings under the three sea-level rise scenarios, with three 

1301 potential outcomes: keeping pace, marginal, and loss (see Figure 4.4). 

1302 

1303 The qualitative, consensus-based assessment of potential changes and their likelihood developed by the 

1304 panel is based on their review and understanding of published coastal science literature (e.g., 88 published 

1305 rates of wetland accretion from the mid-Atlantic region, and sea-level rise rates based on NOAA tide gauge 

1306 data), as well as field observations drawn from other studies conducted in the mid-Atlantic region. A report 

1307 (Reed et al., 2008) summarizing the process used, basis in the published literature, and a synthesis of the 

1308 resulting assessment was produced and approved by all members of the panel. 

1309 

1310 The report was peer reviewed by external subject-matter experts in accordance with U.S. EPA peer review 

1311 policies. Reviewers were asked to examine locality-specific maps for localities with which they were 

1312 familiar, and the documentation for how the maps were created. They were then asked to evaluate the 

1313 assumptions and accuracy of the maps, and errors or omissions in the text. The comments of all reviewers 

1314 were carefully considered and incorporated, wherever possible, throughout the report. The final report was 

1315 published and made available online in February 2008 as a U.S. Environmental Protection Agency report: 

1316 <http://epa.gov/climatechange/effects/downloads/section2_1.pdf>. 

1317 
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1318 End text box 

 1319 

1320 4.6.1.1 Panel Assessment Methods. 

1321 The general approach used by the panel is summarized in Box 4.1. The panel recognized 

1322 that accretionary processes differ among settings and that these processes will change in 

1323 magnitude and direction with future climate change. For example, it is expected that the 

1324 magnitude of coastal storms will increase as sea-surface temperatures increase (Webster 

1325 et al., 2005), likely resulting in an increase in storm sedimentation and oceanic sediment 

1326 inputs. Also, the importance of peat accumulation to vertical accretion in freshwater 

1327 systems (Neubauer 2008) is expected to increase in response to sea-level rise up to a 

1328 threshold capacity, beyond which peat accumulation can no longer increase. However, if 

1329 salinities also increase in freshwater systems, elevation gains from increased peat 

1330 accumulation could be offset by increased decomposition from sulfate reduction. 

1331 Enhanced microbial breakdown of organic-rich soils is likely to be most important in 

1332 formerly fresh and brackish environments where the availability of sulfate, and not 

1333 organic matter, generally limits sulfate-reduction rates (Goldhaber and Kaplan, 1974). 

1334 Increases in air and soil temperatures are expected to diminish the importance of ice 

1335 effects. Changes in precipitation and human land-use patterns will alter fluvial sediment 

1336 inputs. 

 1337 

1338 The fate of mid-Atlantic wetlands for the three sea-level rise scenarios evaluated in this 

1339 Product was determined by the panel through a consensus opinion after all information 

1340 was considered (see Figure 4.4). The wetlands were classified as keeping pace, marginal, 

1341 or loss (Reed et al., 2008): 
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1342 1. Keeping pace: Wetlands will not be submerged by rising sea levels and will be 

1343 able to maintain their relative elevation. 

1344 2. Marginal: Wetlands will be able to maintain their elevation only under optimal 

1345 conditions. Depending on the dominant accretionary processes, this could include 

1346 inputs of sediments from storms or floods, or the maintenance of hydrologic 

1347 conditions conducive for optimal plant growth. Given the complexity and inherent 

1348 variability of climatic and other factors influencing wetland accretion, the panel 

1349 cannot predict the fate of these wetlands. Under optimal conditions they are 

1350 expected to survive. 

1351 3. Loss: Wetlands will be subject to increased flooding beyond that normally 

1352 tolerated by vegetative communities, leading to deterioration and conversion to 

1353 open water habitat. 

 1354 

 1355 

 1356 

 1357 

 1358 

 1359 

 1360 

 1361 
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1362 

1363 Figure 4.3 Geomorphic settings of mid-Atlantic tidal wetlands (data source: Reed et al., 2008; map 

1364 source: Titus et al., 2008). 

1365 

1366 The panel recognized that wetlands identified as marginal or loss will become so at an 

1367 uneven rate and that the rate and spatial distribution of change will vary within and 

1368 among similarly designated areas. The panel further recognized that wetland response to 

1369 sea-level rise over the next century will depend upon the rate of sea-level rise, existing 

1370 wetland condition (e.g., elevation relative to sea level), and local controls of accretion 

1371 processes. In addition, changes in flooding and salinity patterns may result in a change of 

1372 dominant species (i.e., less flood-tolerant high marsh species replaced by more flood1373 tolerant low marsh species), which could affect wetland sediment trapping and organic 
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1374 matter accumulation rates. A wetland is considered marginal when it becomes severely 

1375 degraded (greater than 50 percent of vegetated area is converted to open water) but still 

1376 supports ecosystem functions associated with that wetland type. A wetland is considered 

1377 lost when its function shifts primarily to that of shallow open water habitat. 

 1378 

1379 There are several caveats to the expert panel approach, interpretations, and application of 

1380 findings. First, regional scale assessments are intended to provide a landscape-scale 

1381 projection of wetland vulnerability to sea-level rise (e.g., likely trends, areas of major 

1382 vulnerability) and not to replace assessments based on local process data. The authors 

1383 recognize that local exceptions to the panel’s regional scale assessment likely exist for 

1384 some specific sites where detailed accretionary data are available. Second, the panel’s 

1385 projections of back-barrier wetland sustainability assume that protective barrier islands 

1386 retain their integrity. Should barrier islands collapse (see Section 3.7.3), the lagoonal 

1387 marshes would be exposed to an increased wave energy environment and erosive 

1388 processes, with massive marsh loss likely over a relatively short period of time. (In such a 

1389 case, vulnerability to marsh loss would be only one of a host of environmental problems.) 

1390 Third, the regional projections of wetland sustainability assume that the health of marsh 

1391 vegetation is not adversely affected by local outbreaks of disease or other biotic factors 

1392 (e.g., sudden marsh dieback). Fourth, the panel considered the effects of a rate 

1393 acceleration above current of 2 mm per year (Scenario 2) and 7 mm per year (Scenario 

1394 3), but not rates in between. Determining wetland sustainability at sea-level rise rates 

1395 between Scenarios 2 and 3 requires greater understanding of the variations in the 

1396 maximum accretion rate regionally and among vegetative communities (Reed et al.,
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1397 2008). Currently, there are few estimates of the maximum rate at which marsh vertical 

1398 accretion can occur (Bricker-Urso et al., 1989; Morris et al., 2002) and no studies 

1399 addressing the thresholds for organic matter accumulation in the marshes considered by 

1400 the panel. Lastly, the panel recognized the serious limitations of scaling down their 

1401 projections from the regional to local level and would place a low level of confidence on 

1402 such projections in the absence of local accretionary and process data. Thus, findings 

1403 from this regional scale approach should not be used for local planning activities where 

1404 local effects on accretionary dynamics may override regional controls on accretionary 

1405 dynamics. 

 1406 

1407 4.6.1.2 Panel Findings.

1408 The panel developed an approach for predicting wetland response to sea-level rise that 

1409 was more constrained by available studies of accretion and accretionary processes in 

1410 some areas of the mid-Atlantic region (e.g., Lower Maryland Eastern Shore) than in other 

1411 areas (e.g., Virginia Beach/Currituck Sound). Given these inherent data and knowledge 

1412 constraints, the authors classified the confidence level for all findings in Reed et al.

1413 (2008) as likely (i.e., greater than 0.66 but less than 0.90). 

 1414 

1415 Figure 4.4 and Table 4.2 present the panel’s consensus findings on wetland vulnerability 

1416 of the mid-Atlantic region. The panel determined that a majority of tidal wetlands settings 

1417 in the mid-Atlantic region (with some local exceptions) are likely keeping pace with 

1418 Scenario 1, that is, continued sea-level rise at the twentieth century rate, 3 to 4 mm per 

1419 year (Table 4.2, and areas depicted in brown, beige, yellow, and green in Figure 4.4) 
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1420 through either mineral sediment deposition, organic matter accumulation, or both. 

1421 However, under this scenario, extensive areas of estuarine marsh in Delaware Bay and 

1422 Chesapeake Bay are marginal (areas depicted in red in Figure 4.4), with some areas 

1423 currently being converted to subtidal habitat (areas depicted in blue in Figure 4.4). It is 

1424 virtually certain that estuarine marshes currently so converted will not be rebuilt or 

1425 replaced by natural processes. Human manipulation of hydrologic and sedimentary 

1426 processes and the elimination of barriers to onshore wetland migration would be required 

1427 to restore and sustain these degrading marsh systems. The removal of barriers to onshore 

1428 migration invariably would result in land use changes that have other societal 

1429 consequences such as property loss. 

 1430 

1431 Under accelerated rates of sea-level rise (Scenarios 2 and 3), the panel agreed that 

1432 wetland survival would very likely depend on optimal hydrology and sediment supply 

1433 conditions. Wetlands primarily dependent on mineral sediment accumulation for 

1434 maintaining elevation would be very unlikely to survive Scenario 3, (i.e., at least 10 mm 

1435 per year rate of sea-level rise when added to the twentieth century rate). Exceptions may 

1436 occur locally where sediment inputs from inlets, overwash events, or rivers are 

1437 substantial (e.g., back-barrier lagoon and lagoonal fill marshes depicted in green on 

1438 western Long Island, Figure 4.4). 

 1439 

1440 Wetland responses to sea-level rise are typically complex. A close comparison of Figure 

1441 4.3 and Figure 4.4 reveals that marshes from all geomorphic settings, except estuarine 

1442 meander (which occurs in only one subregion), responded differently to sea-level rise 
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slr +2 +7 slr +2 +7 slr +2 +7 slr +2 +7 slr +2 +7 slr +2 +7 slr +2 +7 slr +2 +7

Back barrier 

lagoon, other K K,M K,L K M L K M L M M-L L

Back barrier 

lagoon, flood 

tide delta

KKM KML K M L

Back barrier 

lagoon, 

lagoonal fill

K,L M,L L K M L K M L

Estuarine 

marsh K M L K M L K,M M,L L K,M,L M-L L L,M L L K M L

Estuarine 

fringe K M L KML M M-L L

Estuarine 

meander K M L KML

Saline fringe K K,L M K M L K M L K M L K,L M,L L

Tidal fresh 

forest K K K M M-L

Tidal fresh 

marsh K K K KML K K K K K K K K K K K K

K = keeping pace, M = marginal, L = loss; multiple letters under a single slr scenario (e.g., K,M or K,M,L) indicate more than one response for 

that geomorphic setting; M-L indicates that the wetland would be either marginal or lost.

Virginia Beach 

– Currituck 

Sound

Table 3.2 The range of wetland responses to three sea level rise (slr) scenarios (20th Century rate, 20th Century rate + 2 mm/yr, and 

20th Century rate + 7 mm/y) within and among geomorphic settings and subregions of the Mid-Atlantic Region from New York to 

Virginia

Region

Delaware Bay

Maryland -

Virginia Chesapeake Bay

Lower 

Maryland 

Eastern Shore

Geomorphic 

Setting

Long Island, 

NY

Raritan 

Bay, NY

New 

Jersey

1443 within and/or among subregions, underscoring why local processes and drivers must be 

1444 taken into account. Given the variety of marsh responses to sea-level rise among and 

1445 within subregions (Table 4.2), assessing the likelihood of survival for each wetland 

1446 setting is best done by subregion, and within subregion, by geomorphic setting. 

1447 
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1448 The scientific panel determined that tidal fresh marshes and forests in the upper reaches 

1449 of rivers are likely to be sustainable (i.e., less vulnerable to future sea-level rise than most 

1450 other wetland types) (Table 4.2), because they have higher accretion rates and accumulate 

1451 more organic carbon than saline marshes (Craft, 2007). Tidal fresh marshes have access 

1452 to reliable and often abundant sources of mineral sediments, and their sediments typically 

1453 have 20 to 50 percent organic matter content, indicating that large quantities of plant 

1454 organic matter are also available. Assuming that salinities do not increase, a condition 

1455 that may reduce soil organic matter accumulation rates, and current mineral sediment 

1456 supplies are maintained, the panel considered it likely that tidal fresh marshes and forests 

1457 would survive under Scenario 3. Vertical development, response to accelerated sea-level 

1458 rise, and movement into newly submerged areas are rapid for tidal fresh marshes (Orson, 

1459 1996). For several tidal fresh marshes in the high sediment-load Delaware River Estuary 

1460 vertical accretion through the accumulation of both mineral and plant matter ranged from 

1461 7 mm per year to 17.4 mm per year from the 1930s to the 1980s as tidal influences 

1462 became more dominant (Orson et al., 1992). Exceptions to the finding that fresh marshes 

1463 and forests would survive under Scenario 3 are the New Jersey shore, where tidal fresh 

1464 marsh is considered marginal under Scenario 2 and lost under Scenario 3, and Virginia 

1465 Beach–Currituck Sound where fresh forest is marginal under Scenario 1, marginal or lost 

1466 under Scenario 2, and lost under Scenario 3. 

 1467 

1468 Different marshes from the geomorphic settings back-barrier other, back-barrier lagoonal 

1469 fill, estuarine marsh, and saline fringe settings responded differently to sea-level rise 

1470 within at least one subregion as well as among subregions (Table 4.2). For example, 
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1471 back-barrier lagoonal fill marshes on Long Island, New York were classified as either 

1472 keeping pace or lost at the current rate of sea-level rise. Those marshes surviving under 

1473 Scenario 1 were classified as either marginal (brown) or keeping up (beige and green) 

1474 under Scenario 2 (Figure 4.4). Under Scenario 3, only the lagoonal fill marshes depicted 

1475 in green in Figure 4.4 are expected to survive. 

 1476 

1477 The management implications of these findings are important on several levels. The 

1478 expert panel approach provides a regional assessment of future wetland resource 

1479 conditions, defines likely trends in wetland change, and identifies areas of major 

1480 vulnerability. However, the wide variability of wetland responses to sea-level rise within 

1481 and among subregions for a variety of geomorphic settings underscores not only the 

1482 influence of local processes on wetland elevation but also the difficulty of scaling down 

1483 predictions of wetland sustainability from the regional to the local scale in the absence of 

1484 local accretion data. Most importantly for managers, regional scale assessments such as 

1485 this should not be used to develop local management plans because local accretionary 

1486 effects may override regional controls on wetland vertical development (McFadden et al.,

1487 2007). Instead, local managers are encouraged to acquire data on the factors influencing 

1488 the sustainability of their local wetland site, including environmental stressors, 

1489 accretionary processes, and geomorphic settings, as a basis for developing local 

1490 management plans. 

 1491 
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1492 

1493 Figure 4.4 Wetland survival in response to three sea-level rise scenarios (data source: Reed et al., 2008; 

1494 map source: Titus et al., 2008). 

1495 

1496 4.6.2 Case Study: Albemarle–Pamlico Sound Wetlands and Sea-Level Rise 

1497 The Albemarle–Pamlico (A–P) region of North Carolina is distinct in the manner and the 

1498 extent to which rising sea level is expected to affect coastal wetlands. Regional wetlands 

1499 influenced by sea level are among the most extensive on the U.S. East Coast because of 
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1500 large regions that are less than 3 meters (m) above sea level, as well as the flatness of the 

1501 underlying surface. Further, the wetlands lack astronomic tides as a source of estuarine 

1502 water to wetland surfaces in most of the A–P region. Instead, wind-generated water level 

1503 fluctuations in the sounds and precipitation are the principal sources of water. This 

1504 “irregular flooding” is the hallmark of the hydrology of these wetlands. Both forested 

1505 wetlands and marshes can be found; variations in salinity of floodwater determine 

1506 ecosystem type. This is in striking contrast to most other fringe wetlands on the East 

1507 Coast. 

 1508 

1509 4.6.2.1 Distribution of Wetland Types 

1510 Principal flows to Albemarle Sound are from the Chowan and Roanoke Rivers, and to 

1511 Pamlico Sound from the Tar and Neuse Rivers. Hardwood forests occupy the floodplains 

1512 of these major rivers. Only the lower reaches of these rivers are affected by rising sea 

1513 level. Deposition of riverine sediments in the estuaries approximates the current rate of 

1514 rising sea level (2 to 3 mm per year) (Benninger and Wells, 1993). These sediments 

1515 generally do not reach coastal marshes, in part because they are deposited in subtidal 

1516 areas and in part because astronomic tides are lacking to carry them to wetland surfaces. 

1517 Storms, which generate high water levels (especially nor’easters and tropical cyclones), 

1518 deposit sediments on shoreline storm levees and to a lesser extent onto the surfaces of 

1519 marshes and wetland forests. Blackwater streams that drain pocosins (peaty, evergreen 

1520 shrub and forested wetlands), as well as other tributaries that drain the coastal plain, are a 

1521 minor supply of suspended sediment to the estuaries. 

 1522 
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1523 Most wetlands in the A–P region were formed upon Pleistocene sediments deposited 

1524 during multiple high stands of sea level. Inter-stream divides, typified by the Albemarle–

1525 Pamlico Peninsula, are flat and poorly drained, resulting in extensive developments of 

1526 pocosin swamp forest habitats. The original accumulation of peat was not due to rising 

1527 sea level but to poor drainage and climatic controls. Basal peat ages of even the deepest 

1528 deposits correspond to the last glacial period when sea level was over 100 m below its 

1529 current position. Rising sea level has now intercepted some of these peatlands, 

1530 particularly those at lower elevations on the extreme eastern end of the A–P Peninsula. 

1531 As a result, eroding peat shorelines are extensive, with large volumes of peat occurring 

1532 below sea level (Riggs and Ames, 2003). 

 1533 

1534 Large areas of nontidal marshes and forested wetlands in this area are exposed to the 

1535 influence of sea level. They can be classified as fringe wetlands because they occur along 

1536 the periphery of estuaries that flood them irregularly. Salinity, however, is the major 

1537 control that determines the dominant vegetation type. In the fresh-to-oligohaline (slightly 

1538 brackish) Albemarle Sound region, forested and shrub-scrub wetlands dominate. As the 

1539 shoreline erodes into the forested wetlands, bald cypress trees become stranded in the 

1540 permanently flooded zone and eventually die and fall down. This creates a zone of 

1541 complex habitat structure of fallen trees and relic cypress knees in shallow water. 

1542 Landward, a storm levee of coarse sand borders the swamp forest in areas exposed to 

1543 waves (Riggs and Ames, 2003). 

 1544 
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1545 Trees are killed by exposure to extended periods of salinity above approximately one1546 quarter to one-third sea water, and most trees and shrubs have restricted growth and 

1547 reproduction at much lower salinities (Conner et al., 1997). In brackish water areas, 

1548 marshes consisting of halophytes replace forested wetlands. Marshes are largely absent 

1549 from the shore of Albemarle Sound and mouths of the Tar and Neuse Rivers where 

1550 salinities are too low to affect vegetation. In Pamlico Sound, however, large areas consist 

1551 of brackish marshes with few tidal creeks. Small tributaries of the Neuse and Pamlico 

1552 River estuaries grade from brackish marsh at estuary mouths to forested wetlands in 

1553 oligohaline regions further upstream (Brinson et al., 1985). 

 1554 

1555 4.6.2.2 Future Sea-Level Rise Scenarios 

1556 Three scenarios were used to frame projections of the effects of rising sea level over the 

1557 next few decades in the North Carolina non-tidal coastal wetlands. The first is a non1558 drowning scenario that assumes rising sea level will maintain its twentieth century, 

1559 constant rate of 2 to 4 mm per year (Scenario 1). Predictions in this case can be inferred 

1560 from wetland response to sea-level changes in the recent past (Spaur and Snyder, 1999; 

1561 Horton et al., 2006). Accelerated rates of sea-level rise (Scenarios 2 and 3), however, 

1562 may lead to a drowning scenario. This is more realistic if IPCC predictions and other 

1563 climate change models prove to be correct (Church and White, 2006), and the Scenario 1 

1564 rates double or triple. An additional scenario possible in North Carolina involves the 

1565 collapse of barrier islands, as hypothesized by Riggs and Ames (2003). This scenario is 

1566 more daunting because it anticipates a shift from the current non-tidal regime to one in 

1567 which tides would be present to initiate currents capable of transporting sediments 
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1568 without the need of storms and frequently possibly flooding wetland surfaces now only 

1569 flooded irregularly. The underlying effects of these three scenarios and effects on coastal 

1570 wetlands are summarized in Table 4.3. 

 1571 

Table 4.3 Comparison of three scenarios of rising sea level and their effects on coastal processes. 

Scenario 

Vertical accretion 

of wetland surface 

Shoreline 

erosion rate Sediment supply 

Non-drowning: historical 

exposure of wetlands (past 

hundreds to several thousand yrs) 

is predictive of future behavior. 

Vertical accretion will keep pace 

with rising sea level (~2-4 mm/yr) 

Keeps pace with 

rising sea level 

Recent historical 

patterns are 

maintained 

Low due to a lack of sources; 

vertical accretion mostly 

biogenic 

Drowning: vertical accretion rates 

cannot accelerate to match rates of 

rising sea level; barrier islands 

remain intact 

Wetlands undergo 

collapse and 

marshes break up 

from within 

Rapid 

acceleration when 

erosion reaches 

collapsed regions 

Local increases of organic 

and inorganic suspended 

sediments as wetlands erode 

Barrier islands breached:

change to tidal regime throughout 

Pamlico Sound 

Biogenic accretion 

replaced by 

inorganic sediment 

supply 

Rapid erosion 

where high tides 

overtop wetland 

shorelines 

Major increase in sediments 

and their redistribution; tidal 

creeks develop along 

antecedent drainages mostly 

in former upland regions 

 1572 

1573 Under the non-drowning scenario, vertical accretion would keep pace with rising sea 

1574 level as it has for millennia. Current rates (Cahoon, 2003) and those based on basal peats 

1575 suggest that vertical accretion roughly matches the rate of rising sea level (Riggs et al.,

1576 2000; Erlich, 1980; Whitehead and Oakes, 1979). Sources of inorganic sediment to 

1577 supplement vertical marsh accretion are negligible due to both the large distance between 

1578 the mouths of piedmont-draining Neuse, Tar, Roanoke and Chowan Rivers and the 

1579 absence of tidal currents and tidal creeks to transport sediments to marsh surfaces. 

 1580 

1581 Under the drowning scenario, the uncertainty of the effects of accelerated rates lies in the 

1582 untested capacity of marshes and swamp forests to biogenically accrete organic matter at 

1583 sea-level rise rates more rapid than experienced currently. It has been suggested that 

1584 brackish marshes of the Mississippi Delta cannot survive when subjected to relative rates 
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1585 of sea-level rise of 10 mm per year (Day et al., 2005), well over twice the rate currently 

1586 experienced in Albemarle and Pamlico Sounds. As is the case for the Mississippi Delta 

1587 (Reed et al., 2006), external sources of mineral sediments would be required to 

1588 supplement or replace the process of organic accumulation that now dominates wetlands 

1589 of the A–P region. Where abundant supplies of sediment are available and tidal currents 

1590 strong enough to transport them, as in North Inlet, South Carolina, Morris et al. (2002) 

1591 reported that the high salt marsh (dwarf Spartina) could withstand a 12 mm per year rate. 

1592 In contrast to fringe wetlands, swamp forests along the piedmont-draining rivers above 

1593 the freshwater–seawater interface are likely to sustain themselves under drowning 

1594 scenario conditions because there is a general abundance of mineral sediments during 

1595 flood stage. This applies to regions within the floodplain but not at river mouths where 

1596 shoreline recession occurs in response to more localized drowning. 

 1597 

1598 Pocosin peatlands and swamp forest at higher elevations of the coastal plain will continue 

1599 to grow vertically since they are both independent of sea-level rise. Under the drowning 

1600 scenario, however, sea-level influenced wetlands of the lower coastal plain would convert 

1601 to aquatic ecosystems, and the large, low, and flat pocosin areas identified by Poulter 

1602 (2005) would transform to aquatic habitat. In areas of pocosin peatland, shrub and forest 

1603 vegetation first would be killed by brackish water. It is unlikely that pocosins would 

1604 undergo a transition to marsh for two reasons: (1) the pocosin root mat would collapse 

1605 due to plant mortality and decomposition, causing a rapid subsidence of several 

1606 centimeters, and resulting in a transition to ponds rather than marshes and (2) brackish 

1607 water may accelerate decomposition of peat due to availability of sulfate to drive 
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1608 anaerobic decomposition. With the simultaneous death of woody vegetation and 

1609 elimination of potential marsh plant establishment, organic-rich soils would be exposed 

1610 directly to the effects of decomposition, erosion, suspension, and transport without the 

1611 stabilizing properties of vegetation. 

 1612 

1613 Under the collapsed barrier island scenario (see Section 3.7.3), the A–P regions would 

1614 undergo a change from a non-tidal estuary to one dominated by astronomic tides due to 

1615 the collapse of some portions of the barrier islands. A transition of this magnitude is 

1616 difficult to predict in detail. However, Poulter (2005), using the ADCIRC-2DDI model of 

1617 Luettich et al. (1992), estimated that conversion from a non-tidal to tidal estuary might 

1618 flood hundreds of square kilometers. The effect is largely due to an increase in tidal 

1619 amplitude that produces the flooding rather than a mean rise in sea level itself. While the 

1620 mechanisms of change are speculative, it is doubtful that an intermediate stage of marsh 

1621 colonization would occur on former pocosin and swamp forest areas because of the 

1622 abruptness of change. Collapse of the barrier islands in this scenario would be so severe 

1623 due to the sediment-poor condition of many barrier segments that attempts to maintain 

1624 and/or repair them would be extremely difficult, or even futile. 

 1625 

1626 The conversion of Pamlico Sound to a tidal system would likely re-establish tidal 

1627 channels where ancestral streams are located, as projected by Riggs and Ames (2003). 

1628 The remobilization of sediments could then supply existing marshes with inorganic 

1629 sediments. It is more likely, however, that marshes would become established landward 

1630 on newly inundated mineral soils of low-lying uplands. Such a state change has not been 
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1631 observed elsewhere, and computer models are seldom robust enough to encompass such 

1632 extreme hydrodynamic transitions. 

1633 

1634 4.7 DATA NEEDS 

1635 A few key uncertainties must be addressed in order to increase confidence in the authors’ 

1636 predictions of wetland vulnerability to sea-level rise. First, determining the fate of coastal 

1637 wetlands over a range of accelerated sea-level rise rates requires more information on 

1638 variations in the maximum accretion rate regionally, within geomorphic settings, and 

1639 among vegetative communities. To date, few studies have specifically addressed the 

1640 maximum rates at which marsh vertical accretion can occur, particularly the thresholds 

1641 for organic accumulation. Second, although the interactions among changes in wetland 

1642 elevation, sea level, and wetland flooding patterns are becoming better understood, the 

1643 interaction of these feedback controls between flooding and changes in other accretion 

1644 drivers, such as nutrient supply, sulfate respiration, and soil organic matter accumulation 

1645 is less well understood. Third, scaling up from numerical model predictions of local 

1646 wetland responses to sea-level rise to long-term projections at regional or continental 

1647 scales is severely constrained by a lack of available accretionary and process data at these 

1648 larger landscape scales. Newly emerging numerical models used to predict wetland 

1649 response to sea-level rise need to be applied across the range of wetland settings. Fourth, 

1650 scientists need to better understand the role of changing land use on tidal wetland 

1651 processes, including space available for wetlands to migrate landward and alteration in 

1652 the amount and timing of freshwater runoff and sediment supply. Finally, sediment 

1653 supply is a critical factor influencing wetland vulnerability, but the amount and source of 
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1654 sediments available for wetland formation and development is often poorly understood. 

1655 Coastal sediment budgets typically evaluate coarse-grain sediments needed for beach and 

1656 barrier development. In contrast, fine-grain cohesive sediments needed for wetland 

1657 formation and development are typically not evaluated. Improving our understanding of 

1658 each of these factors is critical for predicting the fate of tidal marshes. 

 1659 

1660 
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1661 CHAPTER 4 REFERENCES

1662 * Indicates non-peer reviewed literature; available upon request

1663 

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1715 Dyer, K., 1995: Response of estuaries to climate change. In: Climate Change: Impact on 

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1718 * Erlich, R.N., 1980: Early Holocene to Recent Development and Sedimentation of the 

1719 Roanoke River Area, North Carolina. M.S. thesis, Department of Geology. 

1720 University of North Carolina, Chapel Hill, 83 pp. 

1721 Goldhaber, M.B. and I.R. Kaplan, 1974: The sulfur cycle. In: Marine Chemistry. 

1722 [Goldberg, E.D. (ed.)]. Wiley, New York, pp. 569-655. 

1723 Goodman, P.J. and W.T. Williams, 1961: Investigations into ‘die-back’ of Spartina 

1724 townsendii agg.: III. Physical correlates of ‘die-back’. Journal of Ecology, 49(2), 

1725 391-398. 

1726 Hartig, E.K., V. Gornitz, A. Kolker, F. Muschacke, and D. Fallon, 2002: Anthropogenic 

1727 and climate-change impacts on salt marshes of Jamaica Bay, New York City. 

1728 Wetlands, 22(1), 71-89. 

1729 Horton, B.P., R. Corbett, S. J. Culver, R. J. Edwards, C. Hillier, 2006: Modern salt 

1730 marsh diatom distributions of the Outer Banks, North Carolina, and the 

1731 development of a transfer function for high resolution reconstructions of sea level. 

1732 Estuarine, Coastal and Shelf Science, 69(3-4), 381-394. 

1733 Johnson, W.C., B.V. Millett, T. Gilmanov, R.A. Voldseth, G.R. Guntenspergen, and 

1734 D.E. Naugle, 2005: Vulnerability of northern prairie wetlands to climate change. 

1735 Bioscience, 55(10), 863-872. 

1736 Kearney, M.S., R.E. Grace, and J.C. Stevenson, 1988: Marsh loss in the Nanticoke 

1737 Estuary, Chesapeake Bay. Geographical Review, 78, 205-220. 
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1738 Kearney, M.S., J.C. Stevenson, and L.G. Ward, 1994: Spatial and temporal changes in 

1739 marsh vertical accretion rates at Monie Bay: implications for sea level rise. 

1740 Journal of Coastal Research, 10(4), 1010-1020. 

1741 Luettich, R.A., Jr., J.J. Westerink, and N.W. Scheffener, 1992: ADCIRC: An Advanced 

1742 Three-dimensional Circulation Model for Shelves, Coasts, and Estuaries. Report 

1743 1: Theory and Methodology of ADCIRC-2DDI and ADCIRC-3DL. Technical 

1744 report DRP-92-6. U.S. Army Engineers Waterways Experiment Station, 

1745 Vicksburg, MS, 141 pp. 

1746 McCaffrey, R.J. and J. Thomson, 1980: A record of the accumulation of sediment and 

1747 trace metals in a Connecticut salt marsh. In: Estuarine Physics and Chemistry: 

1748 Studies in Long Island Sound. [Saltzman, B. and R.C. Aller (eds.)]. Advances in 

1749 geophysics volume 22. Academic Press, New York, 424 pp. 

1750 McFadden, L., T. Spencer, and R.J. Nicholls, 2007: Broad-scale modelling of coastal 

1751 wetlands: what is required? Hydrobiologia, 577, 5-15. 

1752 McKee, K.L., I.A. Mendelssohn, and M.D. Materne, 2004: Acute salt marsh dieback in 

1753 the Mississippi deltaic plain: a drought induced phenomenon? Global Ecology 

1754 and Biogeography, 13(1), 65-73. 

1755 McKee, K.L., D.R. Cahoon, and I.C. Feller, 2007: Caribbean mangroves adjust to rising 

1756 sea level through biotic controls on change in soil elevation. Global Ecology and 

1757 Biogeography, 16(5), 545-556. 

1758 Mendelssohn, I.A. and K.L. McKee, 1988: Spartina alterniflora die-back in Louisiana: 

1759 time-course investigation of soil waterlogging effects. Journal of Ecology, 76(2), 

1760 509-521. 

1761 Morris, J.T., P.V. Sundareshwar, C.T. Nietch, B. Kjerfve, and D.R. Cahoon, 2002: 

1762 Responses of coastal wetlands to rising sea level. Ecology, 83(10), 2869-2877. 

1763 Neubauer, S.C. 2008: Contributions of mineral and organic components to tidal 

1764 freshwater marsh accretion. Estuarine Coastal and Shelf Science, 78(1), 78-88. 
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1765 Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. 

1766 Ragoonaden, and C.D. Woodroffe, 2007. Coastal systems and low-lying areas. 

1767 Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of 

1768 Working Group II to the Fourth Assessment Report of the Intergovernmental 

1769 Panel on Climate Change [Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. vaan der 

1770 Linden, and C.E. Hanson (eds.)]. Cambridge University Press, Cambridge, UK, 

1771 and New York, pp. 315-356. 

1772 Nyman, J.A., R.J. Walters, R.D. Delaune, and W.H. Patrick, Jr., 2006: Marsh vertical 

1773 accretion via vegetative growth. Estuarine Coastal and Shelf Science, 69(3-4), 

1774 370-380. 

1775 Ogburn, M.B. and M. Alber, 2006: An investigation of salt marsh dieback in Georgia 

1776 using field transplants. Estuaries and Coasts, 29(1), 54-62. 

1777 Orson, R.A., 1996: Some applications of paleoecology to the management of tidal 

1778 marshes. Estuaries, 19(2A), 238-246. 

1779 Orson, R.A., R.L. Simpson, and R.E. Good, 1992: A mechanism for the accumulation 

1780 and retention of heavy metals in tidal freshwater marshes of the upper Delaware 

1781 River estuary. Estuarine, Coastal and Shelf Science, 34(2), 171-186. 

1782 Park, R.A., M.S. Trehan, P.W. Mausel, and R.C. Howe, 1989: The effects of sea level 

1783 rise on U.S. coastal wetlands. In: The Potential Effects of Global Climate Change 

1784 on the United States. Appendix: B, Sea Level Rise. EPA 230-05-89-052. U.S. 

1785 Environmental Protection Agency, Washington, DC, 1-1 to1-55. 

1786 <http://epa.gov/climatechange/effects/coastal/appB.html> 

1787 Pethick, J., 1981: Long-term accretion rates on tidal salt marshes. Journal of 

1788 Sedimentary Petrology, 51, 571-577. 

1789 * Poulter, B., 2005: Interactions Between Landscape Disturbance and Gradual 

1790 Environmental Change: Plant Community Migration in Response to Fire and Sea 
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1791 Level Rise. Ph.D. dissertation, Nicholas School of the Environment and Earth 

1792 Sciences. Duke University, Durham, NC, 216 pp. 

1793 Redfield, A.C., 1972: Development of a New England salt marsh. Ecological 

1794 Monographs, 42, 201-237. 

1795 Reed, D.J., 1989: Patterns of sediment deposition in subsiding coastal salt marshes, 

1796 Terrebonne Bay, Louisiana: the role of winter storms. Estuaries, 12(4), 222-227. 

1797 Reed, D.J., M.S. Peterson, and B.J. Lezina, 2006: Reducing the effects of dredged 

1798 material levees on coastal marsh function: Sediment deposition and nekton 

1799 utilization. Environmental Management, 37(5), 671-685. 

1800 Reed, D.J., D. Bishara, D. Cahoon, J. Donnelly, M. Kearney, A. Kolker, L. Leonard, 

1801 R.A. Orson, and J.C. Stevenson, 2008: Site-specific scenarios for wetlands 

1802 accretion as sea level rises in the mid-Atlantic region. Section 2.1 in: Background 

1803 Documents Supporting Climate Change Science Program Synthesis and 

1804 Assessment Product 4.1, J.G. Titus and E.M. Strange (eds.). EPA 430R07004. 

1805 U.S. Environmental Protection Agency, Washington, DC. 

1806 Riggs, S.R. and D.V. Ames, 2003: Drowning the North Carolina Coast: Sea-level Rise 

1807 and Estuarine Dynamics. Publication no. UNC-SG-03-04, North Carolina Sea 

1808 Grant, Raleigh, NC, 152 pp. 

1809 Riggs, S.R., G.L. Rudolph, and D.V. Ames, 2000: Erosional Scour and Geologic 

1810 Evolution of Croatan Sound, Northeastern North Carolina. Report nNo. 

1811 FHWA/NC/2000-002. North Carolina Department of Transportation, Raleigh, 

1812 NC, 115 pp. 

1813 Rybczyk, J.M. and D.R. Cahoon, 2002: Estimating the potential for submergence for two 

1814 subsiding wetlands in the Mississippi River delta. Estuaries, 25(5), 985-998. 

1815 Sklar, F.H. and J.A. Browder, 1998: Coastal environmental impacts brought about by 

1816 alterations to freshwater flow in the Gulf of Mexico. Environmental Management, 

1817 22(4), 547-562. 
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1818 Spaur, C.C. and S.W. Snyder, 1999: Coastal wetlands evolution at the leading edge of 

1819 the marine transgression: Jarrett Bay, North Carolina. Journal of the Elisha 

1820 Mitchell Scientific Society, 115, 20-46. 

1821 Stevenson, J.C. and M.S. Kearney, In press: Impacts of global change and sea level rise 

1822 on tidal wetlands. In: Human Impacts on Marshes: A Global Perspective

1823 [Silliman. B.R., M.D. Bertness, and E. Grosholz (eds.)]. University of California 

1824 Press, Berkeley, 49 pp. (expected June 2009). 

1825 Stevenson, J.C., M.S. Kearney, and E. C. Pendleton, 1985: Sedimentation and erosion in 

1826 a Chesapeake Bay brackish marsh system. Marine Geology, 67(3-4), 213-235. 

1827 Titus, J. G., R. Jones, and R. Streeter, 2008: Maps depicting site-specific scenarios for 

1828 wetlands accretion as sea level rises in the Mid-Atlantic region. Section 2.2 in: 

1829 Background Documents Supporting Climate Change Science Program Synthesis 

1830 and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise

1831 [Titus, J.G. and E.M. Strange (eds.)]. EPA 430R07004. U.S. Environmental 

1832 Protection Agency, Washington, DC, pp. 176-186. 

1833 <http://epa.gov/climatechange/effects/coastal/background.html> 

1834 Turner, R.E., E.M. Swenson, C.S. Milan, J.M. Lee, and T.A. Oswald, 2004: Below1835 ground biomass in healthy and impaired salt marshes. Ecological Research, 19(1), 

1836 29-35. 

1837 Voldseth, R.A., W.C. Johnson, T. Gilmanov, G. R. Guntenspergen, and B.V. Millet, 

1838 2007: Model estimation of land use effects on water levels of northern prairie 

1839 wetlands. Ecological Applications, 17(2), 527-540. 

1840 Webster, P.J., G.J. Holland, J.A. Curry, and H.R. Chang, 2005: Changes in tropical 

1841 cyclone number, duration, and intensity in a warming environment. Science, 

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1843 Whitehead, D.R. and R.Q. Oaks, 1979: Developmental history of the Dismal Swamp. In: 

1844 The Great Dismal Swamp [Kirk, P.W. (ed.)]. University Press of Virginia, 

1845 Charlottesville, VA, pp. 25-43. 

1846 Woodroffe, C.I., 2002: Coasts: Form, Process and Evolution. Cambridge University 

1847 Press, Cambridge, UK, and New York, 623 pp. 

1848 
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1849 Chapter 5. Vulnerable Species: the Effects of Sea-Level 

1850 Rise on Coastal Habitats 

1851 

1852 Authors: Ann Shellenbarger Jones, Industrial Economics, Inc.; Christina Bosch, 

1853 Industrial Economics, Inc.; Elizabeth Strange, Stratus Consulting, Inc. 

 1854 

1855 KEY FINDINGS 

1856  The quality, quantity, and spatial distribution of coastal habitats continuously change 

1857 as a result of shore erosion, salinity changes, and wetland dynamics; however, 

1858 accelerated rates of sea-level rise will change some of the major controls of coastal 

1859 wetland maintenance. Shore protection and development now prevents migration of 

1860 coastal habitats in many areas. Vulnerable species that rely on these habitats include 

1861 an array of biota ranging from endangered beetles to commercially important fish and 

1862 shellfish; and from migratory birds to marsh plants and aquatic vegetation. 

1863  Three key determinants of future tidal marsh acreage are: (1) the capacity of the 

1864 marsh to raise its surface to match the rate of rising sea level, (2) the rate of erosion of 

1865 the seaward boundary of the marsh, and (3) the availability of space for the marsh to 

1866 migrate inland. Depending on local conditions, a tidal marsh may be lost or migrate 

1867 landward in response to sea-level rise. 

1868  Where tidal marshes become submerged or are eroded, the expected overall loss of 

1869 wetlands would cause wetland-dependent species of fish and birds to have reduced 

1870 population sizes. Tidal marshes and associated submerged aquatic plant beds are 
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1871 important spawning, nursery, and shelter areas for fish and shellfish, including 

1872 commercially important species like the blue crab. 

1873  Many estuarine beaches may also be lost in areas with vertical shore protection and 

1874 insufficient sediment supply. Endangered beetles, horseshoe crabs, the red knot 

1875 shorebird, and diamondback terrapins are among many species that rely on sandy 

1876 beach areas. 

1877  Loss of isolated marsh islands already undergoing submersion will reduce available 

1878 nesting for bird species, especially those that rely on island habitat for protection from 

1879 predators. Additional temporary islands may be formed as tidal marshes are 

1880 inundated, although research on this possibility is limited. 

1881  Many of the freshwater tidal forest systems such as those found in the Mid-Atlantic 

1882 are considered globally imperiled, and are at risk from sea-level rise among other 

1883 threats. 

1884  Tidal flats, a rich source of invertebrate food for shorebirds, may be inundated, 

1885 though new areas may be created as other shoreline habitats are submerged. 

 1886 

1887 5.1 INTRODUCTION 

1888 Coastal ecosystems consist of a variety of environments, including tidal marshes, tidal 

1889 forests, aquatic vegetation beds, tidal flats, beaches, and cliffs. For tidal marshes, Table 

1890 4.1 outlines the major marsh types, relevant accretionary processes, and the primary 

1891 vegetation. These environments provide important ecological and human use services, 

1892 including habitat for endangered and threatened species. The ecosystem services, 

1893 described in detail within this Chapter, include not only those processes that support the 
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1894 ecosystem itself, such as nutrient cycling, but also the human benefits derived from those 

1895 processes, including fish production, water purification, water storage and delivery, and 

1896 the provision of recreational opportunities that help promote human well-being. The high 

1897 value that humans place on these services has been demonstrated in a number of studies, 

1898 particularly of coastal wetlands (NRC, 2005).

 1899 

1900 The services provided by coastal ecosystems could be affected in a number of ways by 

1901 sea-level rise and coastal engineering projects designed to protect coastal properties from 

1902 erosion and inundation. As seas rise, coastal habitats are subject to inundation, storm 

1903 surges, salt water intrusion, and erosion. In many cases, the placement of hard structures 

1904 along the shore will reduce sediment inputs from upland sources and increase erosion 

1905 rates in front of the structures (USGS, 2003). If less sediment is available, marshes that 

1906 are seaward of such structures may have difficulty maintaining appropriate elevations in 

1907 the face of rising seas. Wetlands that are unable to accrete sufficient substrate as sea level 

1908 rises will gradually convert to open water, even if there is space available for them to 

1909 migrate inland, thereby eliminating critical habitat for many coastal species. In addition, 

1910 landward migration of wetlands may replace current upland habitats that are blocked 

1911 from migration (NRC, 2007; MEA, 2005). Shallow water and shore habitats are also 

1912 affected by shore responses. Table 6.1 provides a preliminary overview of the expected 

1913 environmental effects of human responses to sea-level rise. 

 1914 

1915 Habitat changes in response to sea-level rise and related processes may include structural 

1916 changes (such as shifts in vegetation zones or loss of vegetated area) and functional 
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1917 changes (such as altered nutrient cycling). In turn, degraded ecosystem processes and 

1918 habitat fragmentation and loss may not only alter species distributions and relative 

1919 abundances, but may ultimately reduce local populations of the species that depend on 

1920 coastal habitats for feeding, nesting, spawning, nursery areas, protection from predators, 

1921 and other activities that affect growth, survival, and reproductive success. 

 1922 

1923 Habitat interactions are extremely complex. Each habitat supports adjacent systems—for 

1924 example, the denitrifying effects of wetlands aid adjacent submerged vegetation beds by 

1925 reducing algal growth; the presence of nearshore oyster or mussel beds reduces wave 

1926 energy which decreases erosion of marsh edges; and primary productivity is exported 

1927 from marsh to open waters (see Box 5.1). This Chapter presents simplifications of these 

1928 interactions in order to identify primary potential effects of both increased rates of sea1929 level rise and likely shore protections on vulnerable species. In particular, sea-level rise is 

1930 just one factor among many affecting coastal areas; sediment input, nutrient runoff, fish 

1931 and shellfish management, and other factors all contribute to the ecological condition of 

1932 the various habitats discussed in this Section. Sea-level rise may also exacerbate pollution 

1933 through inundation of upland sources of contamination such as landfills, industrial 

1934 storage areas, or agricultural waste retention ponds. Under natural conditions, habitats are 

1935 also continually shifting; the focus of this Chapter is the effect that shoreline management 

1936 will have on the ability for those shifts to occur (e.g., for marshes or barrier islands to 

1937 migrate, for marsh to convert to tidal flat or vice versa) and any interruption to the natural 

1938 shift. 

1939 BOX 5.1: Finfish, Tidal Salt Marshes, and Habitat Interconnectedness 

1940 
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1941 Tidal salt marshes are among the most productive habitats in the world (Teal, 1986). While this 

1942 productivity is used within the marshes, marsh-associated organic matter is also exported to food webs 

1943 supporting marine transient fish production in open waters. Marine transients are adapted to life on a 

1944 “coastal conveyor belt”, often spawning far out on the continental shelf and producing estuarine-dependent 

1945 young that are recruited into coastal embayments year-round (Deegan et al., 2000). These fish comprise 

1946 more than 80 percent of species of commercial and recreational value that occupy inshore waters. 

1947 

1948 Tidal salt marshes serve two critical functions for young finfish (Boesch and Turner, 1984). First, abundant 

1949 food and the warm shallow waters of the marsh are conducive to rapid growth of both resident and 

1950 temporary inhabitants. Second, large predators are generally less abundant in subtidal marsh creeks; 

1951 consequently marshes and their drainage systems may serve as a shelter from predators for the young fish. 

1952 Protection, rapid growth, and the ability to deposit energy reserves from the rich marsh diet prepare young 

1953 fish for the rigors of migration and/or overwintering (Weinstein et al., 2005; Litvin and Weinstein, in 

1954 press). 

1955 

1956 Effects of Sea-Level Rise 

1957 Intertidal and shallow subtidal waters of estuarine wetlands are “epicenters” of material exchange, primary 

1958 (plant) and secondary (animal) production, and are primary nurseries for the young of many fish and 

1959 shellfish species (Childers et al., 2000; Weinstein, 1979; Deegan et al., 2000). The prospect of sea-level 

1960 rise, sometimes concomitant with land subsidence, human habitation of the shore zone, and shore 

1961 stabilization place these critical resources at risk. Such ecological hotspots could be lost as a result of sea1962 level rise because human presence in the landscape leaves tidal wetlands little or no room to migrate inland. 

1963 Because of lack of a well-defined drainage system, small bands of intertidal marsh located seaward of 

1964 armored shorelines have little ecological value in the production of these finfish (Weinstein et al., 2005; 

1965 Weinstein, 1983). Due to its interconnectedness with adjacent habitats, loss of tidal salt marshes would 

1966 significantly affect fish populations, both estuarine and marine, throughout the mid-Atlantic region. 

 1967 

1968 While habitat migration, loss, and gain have all occurred throughout geological history, 

1969 the presence of developed shorelines introduces a new barrier. Although the potential 

1970 ecological effects are understood in general terms, few studies have sought to 

1971 demonstrate or quantify how the interactions of sea-level rise and different types of shore 

1972 protections may affect the ecosystem services provided by coastal habitats, and in 

1973 particular the abundance and distribution of animal species (see Chapter 6 for discussion 

1974 of shore protections). While some studies have examined impacts of either sea-level rise 

1975 (e.g., Erwin et al., 2006; Galbraith et al., 2002) or shore protections (e.g., Seitz et al., 

1976 2006) on coastal fauna, minimal literature is available on the combined effects of rising 

1977 seas and shore protections. Nonetheless, it is possible in some cases to identify species 

1978 most likely to be affected based on knowledge of species-habitat associations. Therefore, 
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1979 this Chapter draws upon the ecological literature to describe the primary coastal habitats 

1980 and species that are vulnerable to the interactive effects of sea-level rise and shore 

1981 protection activities, and highlights those species that are of particular concern. While 

1982 this Chapter provides a detailed discussion on a region-wide scale, Appendix 1 of this 

1983 Product provides much more detailed discussions of specific local habitats and animal 

1984 populations that may be at risk on a local scale along the mid-Atlantic coast. 

 1985 

1986 5.2 TIDAL MARSHES 

1987 In addition to their dependence on tidal influence, tidal marshes are defined primarily in 

1988 terms of their salinity: salt, brackish, and freshwater. Chapter 4 describes the structure 

1989 and flora of these marshes as well as their likely responses to sea-level rise. Table 5.1 

1990 presents a general overview of the habitat types, fauna, and vulnerability discussed in this 

1991 Chapter. Localized information on endangered or threatened species is available through 

1992 the state natural heritage programs (see Box 5.2). 

1993 Box 5.2 Identifying Local Ecological Communities and Species at Risk 

1994 

1995 Every state and Washington, D.C. has Natural Heritage Programs (NHPs) that inventory and track the 

1996 natural diversity of the state, including rare or endangered species. These programs provide an excellent 

1997 resource for identifying local ecological communities and species at risk. Contact information for NHPs 

1998 throughout the mid-Atlantic region is provided in Box Table 5.1. 

1999 

Box Table 5.1 State Natural Heritage Program Contact Information 

Office Website Phone 

New York State Department of 

Environmental Conservation, Division of 

Fish, Wildlife and Marine Resources 

<http://www.nynhp.org/> (518) 402-

8935 

New Jersey Department of Environmental 

Protection, Division of Parks and Forestry, 

Office of Natural Lands Management 

<http://www.state.nj.us/dep/parksandfore

sts/natural/heritage/index.html> 

(609) 984-

1339 

Pennsylvania Department of Conservation 

and Natural Resources, Office of 

Conservation Science 

<http://www.naturalheritage.state.pa.us/> (717) 783-

1639 

Delaware Department of Natural Resources 

and Environmental Control, Division of Fish <http://www.dnrec.state.de.us/nhp/> (302) 653-

2880 
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and Wildlife 

Maryland Department of Natural Resources, 

Wildlife and Heritage Service <http://www.dnr.state.md.us/wildlife/> (410) 260-8DNR 

The District of Columbia's Department of 

Health, Fisheries and Wildlife Division 

<http://doh.dc.gov/doh/cwp/view,a,1374,

Q,584468,dohNav_GID,1810,.asp> 

(202) 671-

5000 

Virginia Department of Conservation and 

Recreation 

<http://www.dcr.virginia.gov/natural_her

itage/index.shtml> 

(804) 786-

7951 

North Carolina Department of Environment 

and Natural Resources, Office of 

Conservation and Community Affairs 

<http://www.ncnhp.org/index.html> (919) 715-

4195 

2000 

2001 A useful resource for species data outside of each state’s own NHP is NatureServe Explorer. NatureServe 

2002 (<http://www.natureserve.org/>) is a non-profit conservation organization which represents the state 

2003 Natural Heritage Programs and other conservation data centers. NatureServe Explorer allows users to 

2004 search for data on the geographic incidence of plant and animal species in the United States and Canada. 

2005 The program provides an extensive array of search criteria, including species’ taxonomies, classification 

2006 status, ecological communities, or their national and sub-national distribution. For example, one could 

2007 search for all vertebrate species federally listed as threatened that live in Delaware’s section of the 

2008 Chesapeake Bay. For identifying threatened and endangered species extant in vulnerable areas, the smallest 

2009 geographic unit of analysis is county-level. 

 2010 

Table 5.1 Key Fauna/Habitat Associations and Degree of Dependence 

Habitat Type

Fauna 

Tidal Marsh 

Forested 

Wetland 

Sea-Level Fens 

SAV 

Tidal Flats 

Estuarine 

Beaches 

Unvegetated 

Cliffs 

Fish (Juvenile)  - -    - 

Fish (Adult)  - -    - 

Crustaceans/ 

Mollusks  - -    - 

Other 

invertebrates       

Turtles/ Terrapins     -  - 

Other reptiles/ 

amphibians     - - - 

Wading Birds  - - -   - 

Shorebirds  - - -   - 

Waterbirds  - -    - 

Songbirds   - - - - 

Mammals   - - -  

Notes: Symbols represent the degree of dependence that particular fauna have on habitat types, as 

described in the sections below.  indicates that multiple species, or certain rare or endangered species, 

depend heavily on that habitat.  indicates that the habitat provides substantial benefits to the fauna. 

indicates that some species of that fauna type may rely on the habitat, or that portions of their lifecycle 

may be carried out there. – indicates that negligible activity by a type of fauna occurs in the habitat. 

Further details on these interactions, including relevant references, are in the sections by habitat below. 

SAV is submerged aquatic vegetation, discussed later in this Chapter (Section 5.5). 

 2011 
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2012 Salt marshes (back-barrier lagoon marsh or saline fringe marsh, described in Table 4.1) 

2013 are among the most productive systems in the world because of the extraordinarily high 

2014 amount of above- and below-ground plant matter that many of them produce, up to 25 

2015 metric tons per hectare (ha) aboveground alone (Mitsch and Gosselink, 1993). In turn, 

2016 this large reservoir of primary production supports a wide variety of invertebrates, fish, 

2017 birds, and other animals that make up the estuarine food web (Teal, 1986). Insects and 

2018 other small invertebrates feed on this organic material of the marsh as well as detritus and 

2019 algae on the marsh surface. These in turn provide food for larger organisms, including 

2020 crabs, shrimp, and small fishes, which then provide food for larger consumers such as 

2021 birds and estuarine fishes that move into the marsh to forage (Mitsch and Gosselink, 

2022 1993). 

 2023 

2024 Although much of the primary production in a marsh is used within the marsh itself, 

2025 some is exported to adjacent estuaries and marine waters. In addition, some of the 

2026 secondary production of marsh resident fishes, particularly mummichog, and of juveniles, 

2027 such as blue crab, is exported out of the marsh to support both nearshore estuarine food 

2028 webs as well as fisheries in coastal areas (Boesch and Turner, 1984; Kneib, 1997, 2000; 

Deegan et al., 2000; Beck et al., 2003; Dittel et al., 2006; Stevens et al., 2006)2 2029 . As 

2030 studies of flood pulses have shown, the extent of the benefits provided by wetlands may 

2031 be greater in regularly flooded tidal wetlands than in irregularly flooded areas (Bayley, 

2032 1991; Zedler and Calloway, 1999). 

 2033 

 

2

 See Glossary for a list of correspondence between common and scientific names. 
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2034 

2035 Figure 5.1 Marsh and tidal creek, Bethels Beach (Mathews County) Virginia. June 2002. 

 2036 

2037 Tidal creeks and channels (Figure 5.1) frequently cut through low marsh areas, draining 

2038 the marsh surface and serving as routes for nutrient-rich plant detritus (dead, decaying 

2039 organic material) to be flushed out into deeper water as tides recede and for small fish, 

2040 shrimp, and crabs to move into the marsh during high tides (Mitsch and Gosselink, 1993; 

2041 Lippson and Lippson, 2006). In addition to mummichog, fish species found in tidal 

2042 creeks at low tide include Atlantic silverside, striped killifish, and sheepshead minnow 

2043 (Rountree and Able, 1992). Waterbirds such as great blue herons and egrets are attracted 

2044 to marshes to feed on the abundant small fish, snails, shrimp, clams, and crabs found in 

2045 tidal creeks and marsh ponds. 

 2046 

2047 Brackish marshes support many of the same wildlife species as salt marshes, with some 

2048 notable exceptions. Bald eagles forage in brackish marshes and nest in nearby wooded 

2049 areas. Because there are few resident mammalian predators (such as red fox and 

2050 raccoons), small herbivores such as meadow voles thrive in these marshes. Fish species 

2051 common in the brackish waters of the Mid-Atlantic include striped bass and white perch, 

2052 which move in and out of brackish waters year-round. Anadromous fish found in the 
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2053 Mid-Atlantic (those that live primarily in salt water but return to freshwater to spawn) 

2054 include herring and shad, while marine transients such as Atlantic menhaden and drum 

2055 species are present in summer and fall (White, 1989). 

 2056 

2057 Tidal fresh marshes are characteristic of the upper reaches of estuarine tributaries. In 

2058 general, the plant species composition of freshwater marshes depends on the degree of 

2059 flooding, with some species germinating well when completely submerged, while others 

2060 are relatively intolerant of flooding (Mitsch and Gosselink, 2000). Some tidal fresh 

2061 marshes possess higher plant diversity than other tidal marsh types (Perry and Atkinson, 

2062 1997). 

2063 

2064 Tidal fresh marshes provide shelter, forage, and spawning habitat for numerous fish 

2065 species, primarily cyprinids (minnows, shiners, carp), centrarchids (sunfish, crappie, 

2066 bass), and ictalurids (catfish). In addition, some estuarine fish and shellfish species 

2067 complete their life cycles in freshwater marshes. Tidal fresh marshes are also important 

2068 for a wide range of bird species. Some ecologists suggest that freshwater tidal marshes 

2069 support the greatest diversity of bird species of any marsh type (Mitsch and Gosselink, 

2070 2000). The avifauna of these marshes includes waterfowl; wading birds; rails and 

2071 shorebirds; birds of prey; gulls, terns, kingfishers, and crows; arboreal birds; and ground 

2072 and shrub species. Perching birds such as red-winged blackbirds are common in stands of 

2073 cattail. Tidal freshwater marshes support additional species that are rare in saline and 

2074 brackish environments, such as frogs, turtles, and snakes (White, 1989). 

 2075 
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2076 Marsh islands are a critical subdivision of the tidal marshes. These islands are found 

2077 throughout the mid-Atlantic study region, and are particularly vulnerable to sea-level rise 

2078 (Kearney and Stevenson, 1991). Islands are common features of salt marshes, and some 

2079 estuaries and back-barrier bays have islands formed by deposits of dredge spoil. Many 

2080 islands are a mixture of habitat types, with vegetated and unvegetated wetlands in 

combination with upland areas3 2081 . These isolated areas provide nesting sites for various 

2082 bird species, particularly colonial nesting waterbirds, where they are protected from 

2083 terrestrial predators such as red fox. Gull-billed terns, common terns, black skimmers, 

2084 and American oystercatchers all nest on marsh islands (Rounds et al., 2004; Eyler et al., 

2085 1999; McGowan et al., 2005). 

 2086 

2087 As discussed in Chapter 4, tidal marshes can keep pace with sea-level rise through 

2088 vertical accretion (i.e., soil build up through sediment deposition and organic matter 

2089 accumulation) as long as a sufficient sediment supply exists. Where inland movement is 

2090 not impeded by artificial shore structures (Figure 5.2) or by geology (e.g., steeply sloping 

2091 areas between geologic terraces, as found around Chesapeake Bay) (Ward et al., 1998; 

2092 Phillips, 1986), tidal marshes can expand inland, which would increase wetland area if 

2093 the rate of migration exceeds that of erosion of the marsh’s seaward boundary. However, 

2094 wetland area would decrease even when a marsh migrates inland if the rate of erosion of 

2095 the seaward boundary exceeds the rate of migration. Further, in areas where sufficient 

2096 accretion does not occur, increased tidal flooding will stress marsh plants through 

 

3

 Thompson’s Island in Rehoboth Bay, Delaware, is a good example of a mature forested upland with 

substantial marsh and beach area. The island hosts a large population of migratory birds. See Maryland and 

Delaware Coastal Bays in Strange et al. (2008). 
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2097 waterlogging and changes in soil chemistry, leading to a change in plant species 

2098 composition and vegetation zones. If marsh plants become too stressed and die, the marsh 

2099 will eventually convert to open water or tidal flat (Callaway et al., 1996; Morris et al., 

2002)4 2100 . 

 2101 

2102 

2103 Figure 5.2 Fringing marsh and bulkhead, Monmouth County, New Jersey. 

 2104 

2105 Sea-level rise is also increasing salinity upstream in some rivers, leading to shifts in 

2106 vegetation composition and the conversion of some tidal fresh marshes into brackish 

2107 marshes (MD DNR, 2005). At the same time, brackish marshes can deteriorate as a result 

2108 of ponding and smothering of marsh plants by beach wrack (seaweed and other marine 

2109 detritus left on the shore by the tide) as salinity increases and storms accentuate marsh 

fragmentation5 2110 (Strange et al., 2008). While this process may allow colonization by 

2111 lower-elevation marsh species, that outcome is not certain (Stevenson and Kearney, 

 

4

 The Plum Tree Island National Wildlife Refuge is an example of a marsh deteriorating through lack of 

sediment input. Extensive mudflats front the marsh (see Appendix 1.F for additional details). 5

 Along the Patuxent River, Maryland, refuge managers have noted marsh deterioration and ponding with 

sea-level rise. See Appendix 1.F for additional details. 
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2112 1996). Low brackish marshes can change dynamically in area and composition as sea 

2113 level rises. If they are lost, forage fish and invertebrates of the low marsh, such as fiddler 

2114 crabs, grass shrimp, and ribbed mussels, may also be lost, which would affect fauna 

2115 further up the food chain (Strange et al., 2008). Though more ponding may provide some 

2116 additional foraging areas as marshes deteriorate, the associated increase in salinity due to 

2117 evaporative loss can also inhibit the growth of marsh plants (MD DNR, 2005). Many 

2118 current marsh islands will be inundated; however, in areas with sufficient sediment, new 

2119 islands may form, although research on this possibility is limited (Cleary and Hosler, 

1979). New or expanded marsh islands are also formed through dredge spoil projects6 2120 . 

 2121 

2122 Effects of marsh inundation on fish and shellfish species are likely to be complex. In the 

2123 short term, inundation may make the marsh surface more accessible, increasing 

2124 production. However, benefits will decrease as submergence decreases total marsh 

2125 habitat (Rozas and Reed, 1993). For example, increased deterioration and mobilization of 

2126 marsh peat sediments increases the immediate biological oxygen demand and may 

2127 deplete oxygen in marsh creeks and channels below levels needed to sustain fish. In these 

2128 oxygen-deficient conditions, mummichogs and other killifish may be among the few 

2129 species able to persist (Stevenson et al., 2002). 

 2130 

2131 In areas where marshes are reduced, remnant marshes may provide lower quality habitat, 

2132 fewer nesting sites, and greater predation risk for a number of bird species that are marsh 

2133 specialists and are also important components of marsh food webs, including the clapper 

 

6

 For example, see discussions of Hart-Miller and Poplar Islands in Chesapeake Bay in Appendix 1.F. 
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2134 rail, black rail, least bittern, Forster’s tern, willet, and laughing gull (Figure 5.3) (Erwin et 

2135 al., 2006). The majority of the Atlantic Coast breeding populations of Forster’s tern and 

2136 laughing gull are considered to be at risk because of loss of lagoonal marsh habitat due to 

2137 sea-level rise (Erwin et al., 2006). In a Virginia study, scientists found that the minimum 

2138 marsh size to support significant marsh bird communities was 4.1 to 6.7 hectares (ha) 

2139 (10.1 to 16.6 acres [ac]) (Watts, 1993). Some species may require even larger marsh 

2140 sizes; minimum marsh size for successful communities of the saltmarsh sharp-tailed 

2141 sparrow and the seaside sparrow, both on the Partners in Flight Watch List, are estimated 

2142 at 10 and 67 ha (25 and 166 ac), respectively (Benoit and Askins, 2002). 

 2143 

2144 

2145 Figure 5.3 Marsh drowning and hummock in Blackwater Wildlife Refuge, Maryland. November, 2002. 

 2146 
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2147 

2148 Figure 5.4 Pocosin in Green Swamp, North Carolina 

 2149 

2150 5.3 FRESHWATER FORESTED WETLANDS 

2151 Forested wetlands influenced by sea level line the mid-Atlantic coast. Limited primarily 

2152 by their requirements for low-salinity water in a tidal regime, tidal fresh forests occur 

2153 primarily in upper regions of tidal tributaries in Virginia, Maryland, Delaware, New 

2154 Jersey, and New York (NatureServe, 2006). The low-lying shorelines of North Carolina 

2155 also contain large stands of forested wetlands, including cypress swamps and pocosins 

2156 (Figure 5.4). Also in the mid-Atlantic coastal plains (e.g., around Barnegat Bay, New 

2157 Jersey) are Atlantic white cedar swamps, found in areas where a saturated layer of peat 

2158 overlays a sandy substrate (NatureServe, 2006). Forested wetlands support a variety of 

2159 wildlife, including the prothonotary warbler, the two-toed amphiuma salamander, and the 

2160 bald eagle. Forested wetlands with thick understories provide shelter and food for an 

2161 abundance of breeding songbirds (Lippson and Lippson, 2006).Various rare and greatest 

2162 conservation need (GCN) species reside in mid-Atlantic tidal swamps, including the 

2163 Delmarva fox squirrel (federally listed as endangered), the eastern red bat, bobcats, bog 

2164 turtles, and the redbellied watersnake (MD DNR, 2005). 
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 2165 

2166 Tidal fresh forests, such as those found in the Mid-Atlantic, face a variety of threats, 

including sea-level rise, and are currently considered globally imperiled7 2167 . The responses 

2168 of these forests to sea-level rise may include retreat at the open-water boundary, 

2169 drowning in place, or expansion inland. Fleming et al. (2006) noted that, “Crown dieback 

2170 and tree mortality are visible and nearly ubiquitous phenomena in these communities and 

2171 are generally attributed to sea-level rise and an upstream shift in the salinity gradient in 

2172 estuarine rivers”. Figure 5.5 presents an example of inundation and tree mortality. In 

2173 Virginia, tidal forest research has indicated that where tree death is present, the 

2174 topography is limiting inland migration of the hardwood swamp and the understory is 

2175 converting to tidal marsh (Rheinhardt, 2007). 

 2176 

2177 

2178 Figure 5.5 Inundation and tree mortality in forested wetlands at Swan’s Point, Lower Potomac River. 

2179 These wetlands are irregularly flooded by wind-generated tides, unaffected by astronomic tides; their 

2180 frequency of inundation is controlled directly by sea level. 

 2181 

 

7

 As presented in NatureServe (<http://www.natureserve.org/>), the prevalent tidal forest associations such 

as freshwater tidal woodlands and tidal freshwater cypress swamps are considered globally imperiled. 
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2182 5.4 SEA-LEVEL FENS 

2183 Sea-level fens are a rare type of coastal wetland with a mix of freshwater tidal and 

2184 northern bog vegetation, resulting in a unique assemblage that includes carnivorous 

2185 plants such as sundew and bladderworts (Fleming et al., 2006; VNHP, 2006). Their 

2186 geographic distribution includes isolated locations on Long Island's South Shore; coastal 

2187 New Jersey; Sussex County, Delaware; and Accomack County, Virginia. The eastern 

2188 mud turtle and the rare elfin skimmer dragonfly are among the animal species found in 

2189 sea-level fens. Fens may occur in areas where soils are acidic and a natural seep from a 

2190 nearby slope provides nutrient-poor groundwater (VNHP, 2006). Little research has been 

2191 conducted on the effects of sea-level rise on groundwater fens; however, the Virginia 

2192 Natural Heritage Program has concluded that sea-level rise is a primary threat to the fens 

2193 (VNHP, 2006). 

 2194 

2195 5.5 SUBMERGED AQUATIC VEGETATION 

2196 Submerged aquatic vegetation (SAV) is distributed throughout the mid-Atlantic region, 

2197 dominated by eelgrass in the higher-salinity areas and a large number of brackish and 

2198 freshwater species elsewhere (e.g., widgeon grass, wild celery) (Hurley, 1990). SAV 

2199 plays a key role in estuarine ecology, helping to regulate the oxygen content of nearshore 

2200 waters, trapping sediments and nutrients, stabilizing bottom sediments, and reducing 

2201 wave energy (Short and Neckles, 1999). SAV also provides food and shelter for a variety 

2202 of fish and shellfish and the species that prey on them. Organisms that forage in SAV 

2203 beds feed on the plants themselves, the detritus and the epiphytes on plant leaves, and the 

2204 small organisms found within the SAV bed (e.g., Stockhausen and Lipcius [2003] for 
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2205 blue crabs; Wyda et al. [2002] for fish). The commercially valuable blue crab hides in 

2206 eelgrass during its molting periods, when it is otherwise vulnerable to predation. In 

2207 Chesapeake Bay, summering sea turtles frequent eelgrass beds. The Kemp’s ridley sea 

2208 turtle, federally listed as endangered, forages in eelgrass beds and flats, feeding on blue 

2209 crabs in particular (Chesapeake Bay Program, 2007). Various waterbirds feed on SAV, 

2210 including brant, canvasback, and American black duck (Perry and Deller, 1996). 

 2211 

2212 Forage for piscivorous birds and fish is also provided by residents of nearby marshes that 

2213 move in and out of SAV beds with the tides, including mummichog, Atlantic silverside, 

2214 naked goby, northern pipefish, fourspine stickleback, and threespine stickleback (Strange 

2215 et al., 2008). Juveniles of many commercially and recreationally important estuarine and 

2216 marine fishes (such as menhaden, herring, shad, spot, croaker, weakfish, red drum, 

2217 striped bass, and white perch) and smaller adult fish (such as bay and striped anchovies) 

2218 use SAV beds as nurseries (NOAA Chesapeake Bay Office, 2007; Wyda et al., 2002). 

2219 Adults of estuarine and marine species such as sea trout, bluefish, perch, and drum search 

2220 for prey in SAV beds (Strange et al., 2008). 

 2221 

2222 Effects of sea-level rise on SAV beds are uncertain because fluctuations in SAV occur on 

2223 a year-to-year basis, a significantly shorter timescale than can be attributed to sea-level 

rise8 2224 . However, Short and Neckles (1999) estimate that a 50 centimeter (cm) increase in 

2225 water depth as a result of sea-level rise could reduce light penetration to current seagrass 

2226 beds in coastal areas by 50 percent. This would result in a 30 to 40 percent reduction in 

 

8 For example, nutrient enrichment and resultant eutrophication are a common problem for SAV beds 

(USFWS, undated)
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2227 seagrass growth in those areas due to decreased photosynthesis (Short and Neckles, 

2228 1999). Increased erosion, with concomitant increased transport and delivery of sediment, 

2229 would also reduce available light (MD DNR, 2000). 

 2230 

2231 Although plants in some portion of an SAV bed may decline as a result of such factors, 

2232 landward edges may migrate inland depending on shore slope and substrate suitability. 

2233 SAV growth is significantly better in areas where erosion provides sandy substrate, rather 

2234 than fine-grained or high organic matter substrates (Stevenson et al., 2002). 

 2235 

2236 Sea-level rise effects on the tidal range could also impact SAV, and the effect could be 

2237 either detrimental or beneficial. In areas where the tidal range increases, plants at the 

2238 lower edge of the bed will receive less light at high tide, increasing plant stress (Koch and 

2239 Beer, 1996). In areas where the tidal range decreases, the decrease in intertidal exposure 

2240 at low tide on the upper edge of the bed will reduce plant stress (Short and Neckles, 

2241 1999). 

 2242 

2243 Shore construction and armoring will impede shoreward movement of SAV beds (Short 

2244 and Neckles, 1999) (see Chapter 6 for additional information on shore protections). First, 

2245 hard structures tend to affect the immediate geomorphology as well as any adjacent 

2246 seagrass habitats (Strange et al., 2008). Particularly during storm events, wave reflection 

2247 off of bulkheads or seawalls can increase water depth and magnify the inland reach of 

2248 waves on downcoast beaches (Plant and Griggs, 1992; USGS, 2003; Small and Carman, 

2249 2005). Second, as sea level rises in armored areas, the nearshore area deepens and light 
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2250 attenuation increases, restricting and finally eliminating seagrass growth (Strange et al., 

2251 2008). Finally, high nutrient levels in the water limit vegetation growth. Sediment 

2252 trapping behind breakwaters, which increases the organic content, may limit eelgrass 

2253 success (Strange et al., 2008). Low-profile armoring, including stone sills and other 

2254 “living shorelines” projects, may be beneficial to SAV growth (NRC, 2007). Projects to 

2255 protect wetlands and restore adjacent SAV beds are taking place and represent a potential 

2256 protection against SAV loss (e.g., U.S. Army Corps of Engineers restoration for Smith 

2257 Island in Chesapeake Bay) (USACE, 2004). 

 2258 

2259 Loss of SAV affects numerous animals that depend on the vegetation beds for protection 

2260 and food. By one estimate, a 50-percent reduction in SAV results in a roughly 25-percent 

2261 reduction in Maryland striped bass production (Kahn and Kemp, 1985). For diving and 

2262 dabbling ducks, a decrease in SAV in their diets since the 1960s has been noted (Perry 

2263 and Deller, 1996). The decreased SAV in Chesapeake Bay is cited as a major factor in the 

2264 substantial reduction in wintering waterfowl (Perry and Deller, 1996). 

2265 

2266 5.6 TIDAL FLATS 

2267 Tidal flats are composed of mud or sand and provide habitat for a rich abundance of 

2268 invertebrates. Tidal flats are critical foraging areas for numerous birds, including wading 

2269 birds, migrating shorebirds, and dabbling ducks (Strange et al., 2008). 

 2270 

2271 In marsh areas where accretion rates lag behind sea-level rise, marsh will eventually 

2272 revert to unvegetated flats and eventually open water as seas rise (Brinson et al., 1995). 
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2273 For example, in New York’s Jamaica Bay, several hundred acres of low salt marsh have 

2274 converted to open shoals (see Appendix 1.B for additional details). In a modeling study, 

2275 Galbraith et al. (2002) predicted that under a 2°C global warming scenario, sea-level rise 

2276 could inundate significant areas of intertidal flats in some regions. In some cases where 

2277 tidal range increases with increased rates of sea-level rise; however, there may be an 

2278 overall increase in the acreage of tidal flats (Field et al., 1991). 

 2279 

2280 In low energy shores with high sediment supplies, where sediments accumulate in 

2281 shallow waters, flats may become vegetated as low marsh encroaches waterward, which 

2282 will increase low marsh at the expense of tidal flats (Redfield, 1972). If sediment inputs 

2283 are not sufficient, tidal flats will convert to subtidal habitats, which may or may not be 

2284 vegetated depending on substrate composition and water transparency (Strange et al., 

2285 2008). 

 2286 

2287 Loss of tidal flats would eliminate a rich invertebrate food source for migrating birds, 

2288 including insects, small crabs, and other shellfish (Strange et al., 2008). As tidal flat area 

2289 declines, increased crowding in remaining areas could lead to exclusion and reductions in 

2290 local shorebird populations (Galbraith et al., 2002). At the same time, ponds within 

2291 marshes may become more important foraging sites for the birds if flats are inundated by 

2292 sea-level rise (Erwin et al., 2004). 

 2293 
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2294 

2295 Figure 5.6 Estuarine beach and bulkhead along Arthur Kills, Woodbridge Township, New Jersey (August 

2296 2003).

 2297 

2298 5.7 ESTUARINE BEACHES 

2299 Throughout most of the mid-Atlantic region and its tributaries, estuarine beaches front 

2300 the base of low bluffs and high cliffs as well as bulkheads and revetments (see Figure 

2301 5.6) (Jackson et al., 2002). Estuarine beaches can also occur in front of marshes and on 

2302 the mainland side of barrier islands (Jackson et al., 2002). 

2303 

2304 Figure 5.7 Peconic Estuary Beach, Riverhead, New York (September 2006). 
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2305 The most abundant beach organisms are microscopic invertebrates that live between sand 

2306 grains, feeding on bacteria and single-celled protozoa. It is estimated that there are over 

2307 two billion of these organisms in a single square meter of sand (Bertness, 1999). They 

2308 play a critical role in beach food webs as a link between bacteria and larger consumers 

2309 such as sand diggers, fleas, crabs, and other macroinvertebrates that burrow in sediments 

2310 or hide under rocks (Strange et al., 2008). Various rare and endangered beetles also live 

2311 on sandy shores. Diamondback terrapin and horseshoe crabs bury their eggs in beach 

2312 sands. In turn, shorebirds such as the piping plover, American oystercatcher, and 

2313 sandpipers feed on these resources (USFWS, 1988). The insects and crustaceans found in 

2314 deposits of wrack on estuarine beaches are also an important source of forage for birds 

2315 (Figure 5.7) (Dugan et al., 2003). 

 2316 

2317 As sea level rises, the fate of estuarine beaches depends on their ability to migrate and the 

2318 availability of sediment to replenish eroded sands (Figure 5.8) (Jackson et al., 2002). 

2319 Estuarine beaches continually erode, but under natural conditions the landward and 

2320 waterward boundaries usually retreat by about the same distance. Shoreline protection 

2321 structures may prevent migration, effectively squeezing beaches between development 

2322 and the water. Armoring that traps sand in one area can limit or eliminate longshore 

2323 transport, and, as a result, diminish the constant replenishment of sand necessary for 

2324 beach retention in nearby locations (Jackson et al., 2002). Waterward of bulkheads, the 

2325 foreshore habitat will likely be lost through erosion, frequently even without sea-level 

2326 rise. Only in areas with sufficient sediment input relative to sea-level rise (e.g., upper 
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2327 tributaries and upper Chesapeake Bay) are beaches likely to remain in place in front of 

2328 bulkheads. 

 2329 

2330 

2331 Figure 5.8 Beach with beach wrack and marsh in Bethel Beach (Mathews County), Virginia. 

 2332 

2333 In many developed areas, estuarine beaches may be maintained with beach nourishment 

2334 if there are sufficient sources and the public pressure and economic ability to do so. 

2335 However, the ecological effects of beach nourishment remain uncertain. Beach 

2336 nourishment will allow retention in areas with a sediment deficit, but may reduce habitat 

2337 value through effects on sediment characteristics and beach slope (Peterson and Bishop, 

2338 2005). 

 2339 

2340 Beach loss will cause declines in local populations of rare beetles found in Calvert 

2341 County, Maryland. While the Northeastern beach tiger beetle is able to migrate in 

2342 response to changing conditions, suitable beach habitat must be available nearby 

2343 (USFWS, 1994). 

 2344 
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2345 At present, the degree to which horseshoe crab populations will decline as beaches are 

2346 lost remains unclear. Early research results indicate that horseshoe crabs may lay eggs in 

2347 intertidal habitats other than estuarine beaches, such as sandbars and the sandy banks of 

2348 tidal creeks (Loveland and Botton, 2007). Nonetheless, these habitats may only provide a 

2349 temporary refuge for horseshoe crabs if they are inundated as well (Strange et al., 2008). 

 2350 

2351 Where horseshoe crabs decline because of loss of suitable habitat for egg deposition, 

2352 there can be significant implications for migrating shorebirds, particularly the red knot, a 

2353 candidate for protection under the federal Endangered Species Act, which feeds almost 

2354 exclusively on horseshoe crab eggs during stopovers in the Delaware Estuary (Karpanty 

2355 et al., 2006). 

 2356 

2357 In addition, using high-precision elevation data from nest sites, researchers are beginning 

2358 to examine the effects that sea-level rise will have on oystercatchers and other shore birds 

2359 (Rounds and Erwin, 2002). To the extent that estuarine and riverine beaches, particularly 

2360 on islands, survive better than barrier islands, shorebirds like oystercatchers might be able 

2361 to migrate to these shores (McGowan et al., 2005). 

 2362 

2363 5.8 CLIFFS 

2364 Unvegetated cliffs and the sandy beaches sometimes present at their bases are constantly 

2365 reworked by wave action, providing a dynamic habitat for cliff beetles and birds. Little 

2366 vegetation exists on the cliff face due to constant erosion, and the eroding sediment 

2367 augments nearby beaches. Cliffs are present on Chesapeake Bay’s western shore and 
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2368 tributaries and its northern tributaries (see Figure 5.9), as well as in Hempstead Harbor on 

2369 Long Island’s North Shore and other areas where high energy shorelines intersect steep 

2370 slopes (Strange et al., 2008). 

 2371 

2372 

2373 Figure 5.9 Crystal Beach, along the Elk River, Maryland (May 2005). 

 2374 

2375 If the cliff base is armored to protect against rising seas, erosion rates may decrease, 

2376 eliminating the unvegetated cliff faces that are sustained by continuous erosion and 

2377 provide habitat for species such as the Puritan tiger beetle and bank swallow. Cliff 

2378 erosion also provides a sediment source to sustain the adjacent beach and littoral zone 

2379 (the shore zone between high and low water marks) (Strange et al., 2008). Naturally 

2380 eroding cliffs are “severely threatened by shoreline erosion control practices” according 

2381 to the Maryland Department of Natural Resource’s Wildlife Diversity Conservation Plan 

2382 (MD DNR, 2005). Shoreline protections may also subject adjacent cliff areas to wave 

2383 undercutting and higher recession rates as well as reduction in beach sediment (Wilcock 
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2384 et al., 1998). Development and shoreline stabilization structures that interfere with 

2385 natural erosional processes are cited as threats to bank-nesting birds as well as two 

2386 species of tiger beetles (federally listed as threatened) at Maryland’s Calvert Cliffs 

2387 (USFWS, 1993, 1994; CCB, 1996). 

 2388 

2389 5.9 SUMMARY OF IMPACTS TO WETLAND-DEPENDENT SPECIES 

2390 Based on currently available information, it is possible to identify particular taxa and 

2391 even some individual species that appear to be at greatest risk if coastal habitats are 

2392 degraded or diminished in response to sea-level rise and shoreline hardening: 

2393  Degradation and loss of tidal marshes will affect fish and shellfish production in both 

2394 the marshes themselves and adjacent estuaries. 

2395  Bird species that are marsh specialists, including the clapper rail, black rail, least 

2396 bittern, Forster’s tern, willet, and laughing gull, are particularly at risk. At present, the 

2397 majority of the Atlantic Coast breeding populations of Forster’s tern and laughing 

2398 gull are considered to be at risk from loss of lagoonal marshes. 

2399  Increased turbidity and eutrophication in nearshore areas and increased water depths 

2400 may reduce light penetration to SAV beds, reducing photosynthesis, and therefore the 

2401 growth and survival of the vegetation. Degradation and loss of SAV beds will affect 

2402 the numerous organisms that feed, carry on reproductive activities, and seek shelter in 

2403 seagrass beds. 

2404  Diamondback terrapin are at risk of losing both marsh habitat that supports growth 

2405 and adjoining beaches where eggs are buried. 
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2406  Many marsh islands along the Mid-Atlantic, and particularly in Chesapeake Bay, 

2407 have already been lost or severely reduced as a result of lateral erosion and flooding 

2408 related to sea-level rise. Loss of such islands poses a serious, near-term threat for 

2409 island-nesting bird species such as gull-billed terns, common terns, black skimmers, 

2410 and American oystercatchers. 

2411  Many mid-Atlantic tidal forest associations may be at risk from sea-level rise and a 

2412 variety of other threats, and are now considered globally imperiled. 

2413  Shoreline stabilization structures interfere with natural erosional processes that 

2414 maintain unvegetated cliff faces that provide habitat for bank-nesting birds and tiger 

2415 beetles. 

2416  Loss of tidal flats could lead to increased crowding of foraging birds in remaining 

2417 areas, resulting in exclusion of many individuals; if alternate foraging areas are 

2418 unavailable, starvation of excluded individuals may result, ultimately leading to 

2419 reductions in local bird populations. 

2420  Where horseshoe crabs decline because of loss of suitable beach substrate for egg 

2421 deposition, there could be significant implications for migrating shorebirds, 

2422 particularly the red knot, a candidate for protection under the federal Endangered 

2423 Species Act. Red knot feed almost exclusively on horseshoe crab eggs during 

2424 stopovers in the Delaware Estuary. 

2425 
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2426 CHAPTER 5 REFERENCES

2427 * Indicates non-peer reviewed literature; available upon request

2428 

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2434 nurseries. Issues in Ecology, 11, 1-12. 

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2452 Childers, D.L., J.W. Day Jr., and H.N. Kellar Jr., 2000: Twenty more years of marsh and 

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2658 Wilcock, P.R., D.S. Miller, R.H. Shea, and R.T. Kerhin, 1998: Frequency of effective 

2659 wave activity and the recession of coastal bluffs: Calvert Cliffs, Maryland. 

2660 Journal of Coastal Research, 14(1), 256-268. 

2661 Wyda, J.C., L.A. Deegan, J.E. Hughes, and M.J. Weaver, 2002: The response of fishes to 

2662 submerged aquatic vegetation complexity in two ecoregions of the mid-Atlantic 

2663 bight: Buzzards Bay and Chesapeake Bay. Estuaries, 25(1), 86-100. 

2664 Zedler, J.B. and J.C. Callaway, 1999: Tracking wetland restoration: do mitigation sites 

2665 follow desired trajectories? Restoration Ecology, 7(1), 69-73. 

2666 
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2667 Part II Overview. Societal Impacts and Implications 

2668 

2669 Authors: James G. Titus, U.S. EPA; Stephen K. Gill, NOAA 

 2670 

2671 The previous chapters in Part I examined some of the impacts of sea-level rise on the 

2672 Mid-Atlantic, with a focus on the natural environment. Part II examines the implications 

2673 of sea-level rise for developed lands. Although the direct effects of sea-level rise would 

2674 be similar to those on the natural environment, people are part of this “built 

2675 environment”; and people will generally respond to changes as they emerge, especially if 

2676 important assets are threatened. The choices that people make could be influenced by the 

2677 physical setting, the properties of the built environment, human aspirations, and the 

2678 constraints of laws and economics. 

 2679 

2680 The chapters in Part II examine the impacts on four human activities: shore 

2681 protection/retreat, human habitation, public access, and flood hazard mitigation. This 

2682 assessment does not predict the choices that people will make; instead it examines some 

2683 of the available options and assesses actions that federal and state governments and 

2684 coastal communities can take in response to sea-level rise. 

2685 

2686 As rising sea level threatens coastal lands, the most fundamental choice that people face 

2687 is whether to attempt to hold back the sea or allow nature to takes its course. Both choices 

2688 have important costs and uncertainties. “Shore protection” allows homes and businesses 

2689 to remain in their current locations, but often damages coastal habitat and requires 
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2690 substantial expenditure. “Retreat” can avoid the costs and environmental impacts of shore 

2691 protection, but often at the expense of lost land and—in the case of developed areas—the 

2692 loss of homes and possibly entire communities. In nature reserves and major cities, the 

2693 preferred option may be obvious. Yet because each choice has some unwelcome 

2694 consequences, the decision may be more difficult in areas that are developing or only 

2695 lightly developed. Until this choice is made, however, preparing for long-term sea-level 

2696 rise in a particular location may be impossible. 

 2697 

2698 Chapter 6 outlines some of the key factors likely to be a part of any dialogue on whether 

2699 to protect or retreat in a given area: 

2700  What are the technologies available for shore protection and the institutional 

2701 measures that might help foster a retreat? 

2702  What is the relationship between land use and shore protection? 

2703  What are the environmental and social consequences of shore protection and 

2704 retreat? 

2705  Is shore protection sustainable? 

2706 Most areas lack a plan that specifically addresses whether the shore will retreat or be 

2707 protected. Even in those areas where a state plans to hold the line or a park plans to allow 

2708 the shore to retreat, the plan is based on existing conditions. Current plans do not 

2709 consider the costs or environmental consequences of sustaining shore protection for the 

2710 next century and beyond. 

 2711 
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2712 One of the most important decisions that people make related to sea-level rise is the 

2713 decision to live or build in a low-lying area. Chapter 7 provides an uncertainty range of 

2714 the population and number of households with a direct stake in possible inundation as sea 

2715 level rises. The results are based on census data for the year 2000, and thus are not 

2716 estimates the number of people or value of structures that will be affected, but rather 

2717 estimate the number of people who have a stake today in the possible future 

2718 consequences of rising sea level. Because census data estimates the total population of a 

2719 given census block, but does not indicate where in that block the people live or the 

2720 elevation of their homes, the estimates in Chapter 7 should not be viewed as the number 

2721 of people whose homes would be lost. Rather, it estimates the number of people who 

2722 inhabit a parcel of land with at least some land within a given elevation above the sea. 

2723 The calculations in this Chapter build quantitatively on some of the elevation studies 

2724 discussed in Chapter 2, and consider uncertainties in both the elevation data and the 

2725 location of homes within a given census block. Chapter 7 also summarizes a study 

2726 sponsored by the U.S Department of Transportation on the potential impacts of global 

2727 sea-level rise on the transportation infrastructure. 

 2728 

2729 Chapter 8 looks at the implications of sea-level rise for public access to the shore. The 

2730 published literature suggests that the direct impact of sea level rise on public access 

2731 would be minor because the boundary between public and private lands moves inland as 

2732 the shore retreats. But responses to sea-level rise could have a substantial impact. One 

2733 common response (publicly funded beach nourishment) sometimes increases public 

2734 access to the shore; but another class of responses (privately funded shoreline armoring) 
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2735 can eliminate public access along the shore if the land seaward of the shore protection 

2736 structure erodes. In parts of New Jersey, regulations governing permits for shoreline 

2737 armoring avoid this impact by requiring property owners to provide access along the 

2738 shore inland of the new shore protection structures. 

 2739 

2740 Finally, Chapter 9 examines the implications of rising sea level for flood hazard 

2741 mitigation, with a particular focus on the implications for the Federal Emergency 

2742 Management Agency (FEMA) and other coastal floodplain managers. Rising sea level 

2743 increases the vulnerability of coastal areas to flooding because higher sea level increases 

2744 the frequency of floods by providing a higher base for flooding to build upon. Erosion of 

2745 the shoreline could also make flooding more likely because erosion removes dunes and 

2746 other natural protections against storm waves. Higher sea level also raises groundwater 

2747 levels, which can increase basement flooding and increase standing water. Both the 

2748 higher groundwater tables and higher surface water levels can slow the rate at which 

2749 areas drain, and thereby increase the flooding from rainstorms. 

 2750 

2751 Chapter 9 opens with results of studies on the relationship of coastal storm tide elevations 

2752 and sea-level rise in the Mid-Atlantic. It then provides background on government 

2753 agency floodplain management and on state activities related to flooding and sea-level 

2754 rise under the Coastal Zone Management Act. Federal agencies, such as FEMA, are 

2755 beginning to specifically plan for future climate change in their strategic planning. Some 

2756 coastal states, such as Maryland, have conducted state-wide assessments and studies of 
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2757 the impacts of sea-level rise and have taken steps to integrate this knowledge with local 

2758 policy decisions. 

 2759 

2760 The chapters in Part II incorporate the underlying sea-level rise scenarios of this Product 

2761 differently, because of the differences in the underlying analytical approaches. Chapter 6 

2762 evaluates the population and property vulnerable to a 100-centimeter rise in sea level, and 

2763 summarizes a study by the U.S. Department of Transportation concerning the impact of a 

2764 59-centimeter rise. Chapters 6, 8 and 9 provide qualitative analyses that are generally 

2765 valid for the entire uncertainty range of future sea level rise. 

 2766 

2767 
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2768 Chapter 6. Shore Protection and Retreat 

2769 

2770 Lead Authors: James G. Titus, U.S. EPA; Michael Craghan, Middle Atlantic Center for 

2771 Geography and Environmental Studies 

2772 

2773 Contributing Authors: Stephen K. Gill, NOAA; S. Jeffress Williams, USGS 

 2774 

 2775 

2776 KEY FINDINGS 

2777  Many options are available for protecting land from inundation, erosion, and flooding 

2778 (“shore protection”), or for minimizing hazards and environmental impacts by 

2779 removing development from the most vulnerable areas (“retreat”). 

2780  Coastal development and shore protection can be mutually reinforcing. Coastal 

2781 development often encourages shore protection because shore protection costs more 

2782 than the market value of undeveloped land, but less than the value of land and 

2783 structures. Shore protection sometimes encourages coastal development by making a 

2784 previously unsafe area safe for development. Under current policies, shore protection 

2785 is common along developed shores and rare along shores managed for conservation, 

2786 agriculture, and forestry. Policymakers have not decided whether the practice of 

2787 protecting development should continue as sea level rises, or be modified to avoid 

2788 adverse environmental consequences and increased costs of shore protection. 

2789  Most shore protection structures are designed for the current sea level, and retreat 

2790 policies that rely on setting development back from the coast are designed for the 

2791 current rate of sea-level rise. Those structures and policies would not necessarily 

2792 accommodate a significant acceleration in the rate of sea-level rise. 
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2793  Although shore protection and retreat both have environmental impacts, the long-term 

2794 impacts of shore protection are likely to be greater. 

2795  In the short-term, retreat is more socially disruptive than shore protection. In the long2796 term, however, shore protection may be more disruptive—especially if it fails or 

2797 proves to be unsustainable. 

2798  We do not know whether “business as usual” shore protection is sustainable.

2799  A failure to plan now could limit the flexibility of future generations to implement 

2800 preferred adaptation strategies. Short-term shore protection projects can impair the 

2801 flexibility to later adopt a retreat strategy. By contrast, short-term retreat does not 

2802 significantly impair the ability to later erect shore protection structures inland from 

2803 the present shore. 

2804 

2805 6.1 TECHNIQUES FOR SHORE PROTECTION AND RETREAT 

2806 Most of the chapters in this Product discuss some aspect of shore protection and retreat. 

2807 This Section provides an overview of the key concepts and common measures for 

2808 holding back the sea or facilitating a landward migration of people, property, wetlands, 

2809 and beaches. Chapter 9 discusses floodproofing and other measures that accommodate 

2810 rising sea level without necessarily involving choosing between shore protection and 

2811 retreat. 

 2812 

2813 6.1.1 Shore Protection 

2814 The term “shore protection” generally refers to a class of coastal engineering activities 

2815 that reduce the risk of flooding, erosion, or inundation of land and structures (USACE, 
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2816 2002). The term is somewhat of a misnomer because shore-protection measures protect 

land and structures immediately inland of the shore rather than the shore itself9 2817 . Shore2818 protection structures sometimes eliminate the existing shore, and shore protection does 

2819 not necessarily mean environmental preservation. This Product focuses on shore2820 protection measures that prevent dry land from being flooded, or converted to wetlands or 

2821 open water. 

 2822 

2823 Shore-protection measures can be divided into two categories: shoreline armoring and 

2824 elevating land surfaces. Shoreline armoring replaces the natural shoreline with an 

2825 artificial surface, but areas inland of the shore are generally untouched. Elevating land 

2826 surfaces, by contrast, can maintain the natural character of the shore, but requires 

2827 rebuilding all vulnerable land. Some methods are hybrids of both approaches. For 

2828 centuries, people have used both shoreline armoring (Box 6.1) and elevating land 

2829 surfaces (Box 6.2) to reclaim dry land from the sea. This Section discusses how those 

2830 approaches might be used to prevent a rising sea level from converting dry land to open 

2831 water. For a comprehensive discussion, see the Coastal Engineering Manual (USACE, 

2832 2002). 

2833 

 

9

 The shore is the land immediately in contact with the water. 
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2834 Strat box*** 

2835 BOX 6.1 Historic use of Dikes to Reclaim Land in the Delaware Estuary 

2836 Until the twentieth century, tidal wetlands were often converted to dry land through the use of dikes and 

2837 drainage systems very similar to the systems that might be used to prevent land from being inundated as sea 

2838 level rises. Nowhere in the United States was more marsh converted to dry land than along the Delaware 

2839 River and Delaware Bay. A Dutch governor of New Jersey diked the marsh on Burlington Island, New 

2840 Jersey. In 1680, after the English governor took possession of the island, observers commented that the 

2841 marsh farm had achieved greater yields of grain than nearby farms created by clearing woodland 

2842 (Danckaerts, 1913). In 1675, an English governor ordered the construction of dikes to facilitate 

2843 construction of a highway through the marsh in New Castle County, Delaware (Sebold, 1992). 

2844 

2845 Colonial (and later state) governments in New Jersey chartered and authorized “meadow companies” to 

2846 build dikes and take ownership of the reclaimed lands. During the middle of the nineteenth century, the 

2847 state agriculture department extolled the virtues of reclaimed land for growing salt hay. By 1866, 20,000 

2848 acres of New Jersey’s marshes had been reclaimed from Delaware Bay, mostly in Salem and Cumberland 

2849 counties (Sebold, 1992). In 1885, the U.S. Department of Agriculture cited land reclamation in Cumberland 

2850 County, New Jersey, as among the most impressive in the nation (Nesbit, 1885, as quoted in Sebold, 1992).

2851 By 1885, land reclamation had converted 10,000 out of 15,000 acres of the marsh in New Castle County to 

2852 agricultural lands, as well as 8,000 acres in Delaware’s other two counties (Nesbit, 1885). In Pennsylvania, 

2853 most of the reclaimed land was just south of the mouth of the Schuylkill along the Delaware River, near the 

2854 present location of Philadelphia International Airport. 

2855 

2856 During the twentieth century, these land reclamation efforts were reversed. In many cases, lower prices for 

2857 salt hay led farmers to abandon the dikes (DDFW, 2007). In some cases, where dikes remain, rising sea 

2858 level has limited the ability of dikes to drain the land, and the land behind the dike has converted to marsh, 

2859 such as the land along the Gibbstown Levee (See Box A1.4 in Appendix 1and Figure 11.4 c and d). Efforts 

2860 are under way to restore the hydrology of many lands that were formerly diked (DDFW, 2007). In areas 

2861 where dikes protect communities from flooding, however, public officials area also considering the 

2862 possibility of upgrading the dikes and drainage systems. 

2863 

2864 End box*** 

2865 Start box*** 

2866 Box 6.2 Creation of the National Monument Area in Washington D.C. through Nineteenth Century 

2867 Dredge and Fill

2868 Like many coastal cities, important parts of Washington, D.C. are on land that was previously created by 

2869 filling wetlands and navigable waterways. When the city of Washington was originally planned, the 

2870 Potomac River was several times as wide immediately south of Georgetown as above Georgetown (see Box 

2871 Figure 6.2). L’Enfant’s plan put the President’s residence just northeast of the mouth of Tiber Creek. Thus, 

2872 the White House grounds originally had a tidal shoreline. To improve navigation, canals connected Tiber 

2873 Creek to the Anacostia River (Bryan, 1914). The White House and especially the Capitol were built on high 

2874 ground immune from flooding, but much of the land between the two was quite low. 

2875 

2876 During the nineteenth century, soil eroded from upstream farming was deposited in the wide part of the 

2877 river where the current slowed, which created wide mudflats below Georgetown. The success of railroads 

2878 made canals less important, while the increasing population converted the canals into open sewers. During 

2879 the early 1870s, Governor Boss Shephard had the canals filled and replaced with drain pipes. A large 

2880 dredge-and-fill operation excavated Washington Channel from the mudflats, and used the material to create 

2881 the shores of the Tidal Basin and the dry land on which the Lincoln Memorial, Jefferson Memorial, 

2882 Reflecting Pool, East Potomac Park, and Hains Point sit today (Bryan, 1914). Similarly, about half of the 
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2883 width of the Anacostia River was filled downstream from Poplar Point, creating what later became the U.S. 

2884 Naval Air Station (now part of Bolling Air Force Base). 

2885 

2886 2887 

2888 Figure Box 6.2 L’Enfant’s Plan for the City of Washington 

2889 Source: Library of Congress (Labels for White House, Georgetown, and Tiber Creek added). 

2890 End box*** 

2891 6.1.1.1 Shoreline Armoring 

2892 Shoreline armoring involves the use of structures to keep the shoreline in a fixed position 

2893 or to prevent flooding when water levels are higher than the land. Although the term is 

2894 often synonymous with “shoreline hardening”, some structures are comprised of 

2895 relatively soft material, such as earth and sand. 

 2896 

2897 Keeping the shoreline in a fixed position 

2898 Seawalls are impermeable barriers designed to withstand the strongest storm waves and 

2899 to prevent overtopping during a storm. During calm periods, their seaward side may 

2900 either be landward of a beach or in the water. Seawalls are often used along important 

2901 transportation routes such as highways or railroads (Figure 6.1a). 
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2902 

2903 Figure 6.1 Seawalls and Bulkheads (a) Galveston Seawall in Texas (May 2003) and (b) Bulkheads with 

2904 intervening beach along Magothy River in Anne Arundel County, Maryland (August 2005). 

 2905 

2906 Bulkheads are vertical walls designed to prevent the land from slumping toward the water 

2907 (Figure 6.1b). They must resist waves and currents to accomplish their design intent, but 

2908 unlike seawalls, they are not designed to withstand severe storms. They are usually found 

2909 along estuarine shores where waves have less energy, particularly in marinas and other 

2910 places where boats are docked, and residential areas where homeowners prefer a tidy 

2911 shoreline. Bulkheads hold soils in place, but they do not normally extend high enough to 

2912 keep out foreseeable floods. Like seawalls, their seaward sides may be inland of a beach 

2913 (or marsh) or in the water. 

 2914 

2915 Retaining structures include several types of structures that serve as a compromise 

2916 between a seawall and a bulkhead. They are often placed at the rear of beaches and are 

2917 unseen. Sometimes they are sheet piles driven downward into the sand; sometimes they 

2918 are long, cylindrical, sand-filled “geo-tubes” (Figure 6.2). Retaining structures are often 

2919 concealed as the buried core of an artificial sand dune. Like seawalls, they are intended to 

2920 be a final line of defense against waves after a beach erodes during a storm; but they can 

2921 not survive wave attack for long. 
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2922 

2923 Figure 6.2 Geotube (a) before and (b) after being buried by beach sand at Bolivar Peninsula, Texas (May 

2924 2003). 

2925 

2926 Revetments are walls whose sea side follows a slope. Like the beach they replace, their 

2927 slope makes them more effective at dissipating the energy of storm waves than bulkheads 

2928 and seawalls. As a result, revetments are less likely than bulkheads and seawalls to cause 

2929 the beach immediately seaward to erode (USACE, 1995), which makes them less likely 

2930 to fail during a storm (Basco, 2003; USACE, 1995). Some revetments are smooth walls, 

2931 while others have a very rough appearance (Figure 6.3). 

2932 

2933 Figure 6.3 Two types of stone revetments (a) near Surfside, Texas and (b) at Jamestown, Virginia.

 2934 

2935 Protecting Against Flooding or Permanent Inundation 
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2936 Dikes are high, impermeable earthen walls designed to keep the area behind them dry. 

2937 They can be set back from the shoreline if the area to be protected is a distance inland and 

2938 usually require an interior drainage system. Land below mean low water requires a 

2939 pumping system to remove rainwater and any water that seeps through the ground below 

2940 the dike. Land whose elevation is between low and high tide can be drained at low tide, 

2941 except during storms (Figure 6.4a). 

2942 

2943 Dunes are accumulations of windblown sand and other materials which function as a 

2944 temporary barrier against wave runup and overwash (Figure 6.4b, see also Section 

2945 6.1.1.2). 

2946 

2947 Figure 6.4 (a) A dike in Miami-Dade County, Florida, and (b) a newly-created dune in Surf City, New 

2948 Jersey. 

2949 

2950 Tide gates are barriers across small creeks or drainage ditches. By opening during low 

2951 tides and closing during high tides, they enable a low-lying area above mean low water to 

2952 drain without the use of pumps (Figure 6.5). 
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2953 

2954 Figure 6.5: The tide gate at the mouth of Army Creek on the Delaware side of the Delaware River. The 

2955 tide gate drains flood and rain water out of the creek to prevent flooding. The five circular mechanisms on 

2956 the gate open and close to control water flow (courtesy NOAA Photo Library). 

2957 

2958 

2959 Storm surge barriers are similar to tide gates, except that they close only during storms 

2960 rather than during high tides, and they are usually much larger, closing off an entire river 

2961 or inlet. The barrier in Providence, Rhode Island (Figure 6.6) has gates that are lowered 

2962 during a storm; the Thames River Barrier in London, by contrast, has a submerged 

2963 barrier, which allows tall ships to pass. As sea level rises and storm surges become higher 

2964 (see Chapter 9), these barriers must be closed more frequently. The gates in Providence, 

2965 Rhode Island (Figure 6.6), for example, are currently closed an average of 19 days per 

2966 year (NOAA Coastal Services Center, 2008). 

2967 

2968 Figure 6.6 Storm surge barriers. (a) Fox Point Hurricane Barrier, Providence, Rhode Island (March 1966) 

2969 and (b) Moses Lake Floodgate, Texas City, Texas (March 2006).

2970 

2971 6.1.1.2 Elevating Land Surfaces 
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2972 A second general approach to shore protection is to elevate land and structures. Tidal 

2973 marshes have long adapted to sea-level rise by elevating their land surfaces to keep pace 

2974 with the rising sea (Chapter 4). Elevating land and structures by the amount of sea-level 

2975 rise can keep a community’s assets at the same elevation relative to the sea and thereby 

2976 prevent them from becoming more vulnerable as sea level rises. These measures are 

2977 sometimes collectively known as “soft” shore protection. 

 2978 

2979 Beachfill, also known as beach nourishment or sand replenishment, involves the 

2980 purposeful addition of the native beach material (usually sand but possibly gravel) to a 

2981 beach to make it higher and wider. Sand from an offshore or inland source is added to a 

2982 beach to provide a buffer against wave action and flooding (USACE, 2002; Dean and 

2983 Dalrymple, 2002). Placing sand onto an eroding beach can offset the erosion that would 

2984 otherwise occur over a limited time; but erosion processes continue, necessitating 

2985 periodic re-nourishment. 

 2986 

2987 Dunes are often part of a beach nourishment program. Although they also occur 

2988 naturally, engineered dunes are designed to intercept wind-transported sand and keep it 

2989 from being blown inland and off the beach. Planting dune grass and installing sand 

2990 fencing increases the effectiveness and stability of dunes. 

 2991 

2992 Elevating land and structures is the equivalent of a beachfill operation in the area 

2993 landward of the beach. In most cases, existing structures are temporarily elevated with 

2994 hydraulic jacks and a new masonry wall is built up to the desired elevation, after which 
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2995 the house is lowered onto the wall (See Figure 12.5). In some cases the house is moved to 

2996 the side, pilings are drilled, and the house is moved onto the pilings. Finally, sand, soil, or 

2997 gravel are brought to the property to elevate the land surface. After a severe hurricane in 

2998 1900, most of Galveston, Texas was elevated by more than one meter (NRC, 1987). This 

2999 form of shore protection can be implemented by individual property owners as needed, or 

3000 as part of a comprehensive program. Several federal and state programs exist for 

3001 elevating homes, which has become commonplace in some coastal areas, especially after 

3002 a major flood (see also Chapters 9 and 10). 

 3003 

3004 Dredge and fill was a very common approach until the 1970s, but it is rarely used today 

3005 because of the resulting loss of tidal wetlands. Channels were dredged through the marsh, 

3006 and the dredge material was used to elevate the remaining marsh to create dry land (e.g., 

3007 Nordstrom, 1994). The overall effect was that tidal wetlands were converted to a 

3008 combination of dry land suitable for home construction and navigable waterways to 

3009 provide boat access to the new homes. The legacy of previous dredge-and-fill projects 

3010 includes a large number of very low-lying communities along estuaries, including the bay 

3011 sides of many developed barrier islands. Recently, some wetland restoration projects 

3012 have used a similar approach to create wetlands, by using material from dredged 

3013 navigation channels to elevate shallow water up to an elevation that sustains wetlands. 

3014 (USFWS, 2008; see Section 11.2.2 in Chapter 11). 

3015 

3016 6.1.1.3 Hybrid Approaches to Shore Protection 
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3017 Several techniques are hybrids of shoreline armoring and the softer approaches to shore 

3018 protection. Often, the goal of these approaches is to retain some of the storm-resistance of 

3019 a hard structure, while also maintaining some of the features of natural shorelines. Groins 

3020 are hard structures perpendicular to the shore extending from the beach into the water, 

3021 usually made of large rocks, wood, or concrete (see Figure 6.7b.). Their primary effect is 

3022 to diminish forces that transport sand along the shore. Their protective effect is often at 

3023 the expense of increased erosion farther down along the shore; so they are most useful 

3024 where an area requiring protection is updrift from an area where shore erosion is more 

3025 acceptable. Jetties are similar structures intended to guard a harbor entrance, but they 

3026 often act as a groin, causing large erosion on one side of the inlet and accretion on the 

3027 other side. 

 3028 

3029 Breakwaters are hard structures placed offshore, generally parallel to the shore (see 

3030 Figure 6.7a). They can mitigate shore erosion by preventing large waves from striking the 

3031 shore. Like groins, breakwaters often slow the transport of sand along the shore, and 

3032 thereby increase erosion of shores adjacent to the area protected by the breakwaters. 

 3033 

3034 Dynamic revetments (also known as cobble beaches) are a hybrid of beach nourishment 

3035 and hard structures, in which an eroding mud or sand beach in an area with a light wave 

3036 climate is converted to a cobble or pebble beach (see Figure 6.7d). The cobbles are heavy 

3037 enough to resist erosion, yet small enough to create a type of beach environment 

3038 (USACE, 1998; Komar, 2007; Allan et al., 2005). 

 3039 
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3040 Recently, several state agencies, scientists, environmental organizations, and property 

3041 owners have become interested in measures designed to reduce erosion along estuarine 

3042 shores, while preserving more habitat than bulkheads and revetments (see Box 6.3). 

3043 “Living Shorelines” are shoreline management options that allow for natural coastal 

3044 processes to remain through the strategic placement of plants, stone, sand fill, and other 

3045 structural and organic materials. They often rely on native plants, sometimes 

supplemented with groins, breakwaters, stone sills, or biologs10 3046 to reduce wave energy, 

3047 trap sediment, and filter runoff, while maintaining (or increasing) beach or wetland 

3048 habitat (NRC, 2007). 

3049 Start box******** 

3050 Box 6.3 Shore Protection Alternatives in Maryland: Living Shorelines

3051 

3052 Shore erosion and methods for its control are a major concern in estuarine and marine ecosystems. 3053 However, awareness of the negative impacts that many traditional shoreline protection methods have, 

3054 including loss of wetlands and their buffering capacities, impacts on nearshore biota, and ability to 

3055 withstand storm events, has grown in recent years. Non-structural approaches, or hybrid-type projects that 

3056 combine a marsh fringe with groins or breakwaters, are being considered along all shorelines except for 

3057 those with large waves (from either boat traffic or a long fetch). The initial cost for these projects is often 

3058 significantly less than for bulkheads or revetments; the long-run cost can be greater or less depending on 

3059 how frequently the living shoreline must be rebuilt. 3060 

3061 These projects typically combine marsh replanting (generally Spartina patens and Spartina alterniflora) 

3062 and stabilization through sills, groins, or breakwaters. A survey of projects on the eastern and western sides 

3063 of Chesapeake Bay (including Wye Island, Epping Forest near Annapolis, and the Jefferson Patterson Park 

3064 and Museum on the Patuxent) found that the sill structures or breakwaters were most successful in 

3065 attenuating wave energy and allowing the development of a stable marsh environment. 

 

10 Biologs are assemblages of woody, organic, and biodegradable material in a log-shaped form. 
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3066 

3067 Box Figure 6.1 Depiction of Living Shoreline Treatments from the Jefferson Patterson Park and Museum, 

3068 Patuxent River. 

3069 

3070 Sources: Content developed by David G. Burke for Jefferson Patterson Park and Museum, <www.jefpat.org>. 

3071 End box*************** 

 3072 

3073 In addition to the hybrid techniques, communities often use a combination of shoreline 

3074 armoring and elevation. Many barrier island communities apply beach nourishment on 

3075 the ocean side, while armoring the bay side. Ocean shore protection projects in urban 

3076 areas sometimes include both beach nourishment and a seawall to provide a final line of 

3077 defense if the beach erodes during a storm. Beach nourishment projects along estuaries 

3078 often include breakwaters to reduce wave erosion (Figure 6.7a), or a terminal groin to 

3079 keep the sand within the area meant to be nourished (see Figure 6.7 c). 

 3080 
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3081 

 3082 

3083 3084 

3085 Figure 6.7 Hybrid approaches to shore protection. (a) Breakwaters and groins along Chesapeake Bay in 

3086 Bay Ridge (near Annapolis) Maryland (July 2008). The rock structures parallel to the shore in the bay are 

3087 breakwaters; the structures perpendicular to the shore are groins; (b) wooden groins and bulkhead along the 

3088 Peconic Estuary on Long Island, New York (September 2006). The beach is wider near the groin and 

3089 narrower between groins; (c) a nourished beach with a terminal groin at North Beach (Maryland) 

3090 (September 2008); (d) a dynamic revetment placed over the mud shore across Swan Creek from the Fort 

3091 Washington (Maryland) unit of National Capital Parks East. Logs have washed onto the shore since the 

3092 project was completed (July 2008). 

 3093 

3094 6.1.2 Retreat 

3095 The primary alternative to “shore protection” is commonly known as retreat (or 

3096 relocation). Shore protection generally involves coastal engineering to manage the forces 

3097 of nature and environmental engineering to manage environmental consequences. By 

3098 contrast, retreat often emphasizes the management of human expectations, so that people 

3099 do not make investments inconsistent with the eventual retreat. 
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 3100 

3101 A retreat can either occur as an unplanned response in the aftermath of a severe storm or 

3102 as a planned response to avoid the costs or other adverse effects of shore protection. In 

3103 Great Britain, an ongoing planned retreat is known as “managed realignment” (Rupp3104 Armstrong and Nicholls, 2007; Shih and Nicholls, 2007; UK Environment Agency, 2007; 

3105 Midgley and McGlashan, 2004). An optimal retreat generally requires a longer lead time 

3106 than shore protection (e.g., Yohe and Neumann, 1997; Titus, 1998; IPCC CZMS, 1992) 

3107 because the economic investments in buildings and infrastructure, and human investment 

3108 in businesses and communities, can have useful lifetimes of many decades or longer. 

3109 Therefore, planning, regulatory, and legal mechanisms usually play a more important role 

3110 in facilitating a planned retreat than for shore protection, which for most projects can be 

3111 undertaken in a matter of months or years. Some retreat measures are designed to ensure 

3112 that a retreat occurs in areas where shores would otherwise be protected; other measures 

3113 are designed to decrease the costs of a retreat but not necessarily change the likelihood of 

3114 a retreat occurring. For a comprehensive review, see Shoreline Management Technical 

3115 Assistance Toolbox (NOAA, 2006). The most widely assessed and implemented 

3116 measures are discussed below. 

3117 

3118 Relocating structures is possibly the most engineering-related activity involved in a 

3119 retreat. The most ambitious relocation in the Mid-Atlantic during the last decade has been 

3120 the landward relocation of the Cape Hatteras Lighthouse (Figure 6.8a; see also Section 

3121 A1.G.4.2 in Appendix 1). More commonplace are the routine “structural moving” 
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3122 activities involved in relocating a house back several tens of meters within a given 

3123 shorefront lot, and the removal of structures threatened by shore erosion (Figure 6.8b). 

3124 

3125 Figure 6.8 Relocating structures along the Outer Banks (a) Cape Hatteras Lighthouse after relocation at 

3126 the Cape Hatteras National Seashore, Buxton, North Carolina (June 2002); the original location is outlined 

3127 in the foreground, and.(b) a home threatened by shore erosion in Kitty Hawk, North Carolina (June 2002). 

3128 The geotextile sand bags are used to protect the septic system. 

 3129 

3130 Buyout programs provide funding to compensate landowners for losses from coastal 

3131 hazards by purchasing vulnerable property. In effect, these programs transfer some of the 

3132 risk of sea-level rise from the property owner to the public, which pays the cost (see 

3133 Chapter 12). 

 3134 

3135 Conservation easements are an interest in land that allows the owner of the easement to 

3136 prevent the owner of the land from developing it. Land conservation organizations have 

3137 purchased non-development easements along coastal bays and Chesapeake Bay in 

3138 Maryland (MALPF, 2003). In most cases, the original motivation for these purchases has 

3139 been the creation of a buffer zone to protect the intertidal ecology (MDCPB, 1999; 

3140 MALPF, 2003). These vacant lands also leave room for landward migration of wetlands 

3141 and beaches (a concept also recognized in New Jersey Coastal Management Program 
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3142 2006). Organizations can also create buffers specifically for the purpose of 

3143 accommodating rising sea level. Blackwater Wildlife Refuge in Maryland and Gateway 

3144 National Recreation Area in New York both own considerable amounts of land along the 

3145 water onto which wetlands and beaches, respectively, could migrate inland. 

 3146 

3147 Acquisition programs involve efforts by government or a conservation entity to obtain 

3148 title to the land closest to the sea. Titles may be obtained by voluntary transactions, 

3149 eminent domain, or dedication of flood-prone lands as part of a permitting process. In 

3150 Barnegat Light, New Jersey and Virginia Beach, Virginia, for example, governments own 

3151 substantial land along the shore between the Atlantic Ocean and the oceanside 

3152 development. 

 3153 

3154 Setbacks are the regulatory equivalent to conservation easements and purchase programs. 

3155 The most common type of setback used to prepare for sea-level rise is the erosion-based 

3156 setback, which prohibits development on land that is expected to erode within a given 

3157 period of time. North Carolina requires new structures to be set back from the primary 

3158 dune based on the current erosion rate times 30 years for easily moveable homes, or 60 

3159 years for large immoveable structures (see Section A1.G.4.1 in Appendix 1). Maine’s 

setback rule assumes a 60 centimeter (cm) rise in sea level during the next 100 years11,12 3160 . 

 3161 

 

11 06-096 Code of Maine Rules §355.5(C), (2007). 

12 06-096 Code of Maine Rules §355.5(C), (2007). 
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3162 Flood hazard regulations sometimes prohibit development based on elevation, rather 

3163 than proximity to the shore. Aside from preventing flood damages, these elevation-based 

3164 setbacks can ensure that there is room for wetlands or other intertidal habitat to migrate 

3165 inland as sea level rises in areas that are vulnerable to inundation rather than wave3166 generated erosion. Two counties in Delaware prohibit development in the 100-year 

3167 floodplain along the Delaware River and Delaware Bay (Section A1.D.2.2 in Appendix 

3168 1). 

 3169 

3170 Rolling easements are regulatory mechanisms (Burka, 1974) or interests in land (Titus, 

3171 1998) that prohibit shore protection and instead allow wetlands or beaches to migrate 

3172 inland as sea level rises. Rolling easements transfer some of the risk of sea-level rise from 

3173 the environment or the public to the property owner (Titus, 1998). When implemented as 

3174 a regulation, they are an alternative to prohibiting all development in the area at risk, 

3175 which may be politically infeasible, inequitable, or a violation of the “takings clause” of 

3176 the U.S. Constitution (Titus, 1998; Caldwell and Segall, 2007). When implemented as an 

3177 interest in land, they are an alternative to outright purchases or conservation easements 

3178 (Titus, 1998). 

 3179 

3180 The purpose of a rolling easement is to align the property owner’s expectations with the 

3181 dynamic nature of the shore (Titus, 1998). If retreat is the eventual objective, property 

3182 owners can more efficiently prepare for that eventuality if they expect it than if it takes 

3183 them by surprise (Yohe et al., 1996; Yohe and Neumann, 1997). Preventing development 

3184 in the area at risk through setbacks, conservations easements, and land purchases can also 
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3185 be effective—but such restrictions could be costly if applied to thousands of square 

3186 kilometers of valuable coastal lands (Titus, 1991). Because rolling easements allow 

3187 development but preclude shore protection, they are most appropriate for areas where 

3188 preventing development is not feasible and shore protection is unsustainable. Conversely, 

3189 rolling easements are not useful in areas where shore protection or preventing 

3190 development are preferred outcomes. 

 3191 

3192 Rolling easements were recognized by the common law along portions of the Texas Gulf 

3193 Coast (Feinman v. State; Matcha v. Mattox) and reaffirmed by the Texas Open Beaches 

Act13 3194 , with the key purpose being to preserve the public right to traverse the shore. 

3195 Massachusetts and Rhode Island prohibit shoreline armoring along some estuarine shores 

3196 so that ecosystems can migrate inland, and several states limit armoring along ocean 

3197 shores (see Chapter 11). Rolling easements can also be implemented as a type of 

3198 conservation easement, purchased by government agencies or conservancies from willing 

3199 sellers, or dedicated as part of a planning review process (Titus, 1998); but to date, rolling 

3200 easements have only been implemented by regulation. 

3201 

3202 Density restrictions allow some development but limit densities near the shore. In most 

3203 cases, the primary motivation has been to reduce pollution runoff into estuaries; but they 

3204 also can facilitate a retreat by decreasing the number of structures potentially lost if 

3205 shores retreat. Maryland limits development to one home per 8.1 hectares (20 acres) 

 

13 TEX. NAT. RES. CODE ANN. §§ 61.001-.178 (West 1978 & Supp. 1998). 
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3206 within 305 meters (m) (1000 feet [ft]) of the shore in most coastal areas (see Section 

3207 A1.F.2.1 in Appendix 1). In areas without public sewer systems, zoning regulations often 

3208 restrict densities (e.g., Accomack County, 2008; U.S. EPA, 1989). 

 3209 

3210 Size limitations also allow development but limit the intensity of the development placed 

3211 at risk. Moreover, small structures are relocated more easily than a large structure. North 

3212 Carolina limits the size of new commercial or multi-family residential buildings to 464 

3213 square meters (sq m) (5000 square feet [sq ft]) in the area that would be subject to shore 

3214 erosion during the next 60 years given the current rate of shore erosion, or within 36 m 

(120 ft) of the shore, whichever is farther inland14 3215 . Maine’s Sand Dune Rules prohibit 

3216 structures taller than 10.7 m (35 ft) or with a “footprint” greater than 232 sq m (2500 sq 

ft) in all areas that are potentially vulnerable to a 60 cm rise in sea level15 3217 . 

 3218 

3219 6.1.3 Combinations of Shore Protection and Retreat 

3220 Although shore protection and retreat are fundamentally different responses to sea-level 

3221 rise, strategies with elements of both approaches are possible. In most cases, a given 

3222 parcel of land at a particular time is either being protected or not—but a strategy can vary 

3223 with both time and place, or hedge against uncertainty about the eventual course of 

3224 action. 

 3225 

 

14 15A NCAC 07H. 0305-0306. The required setback for single-family homes and smaller commercial 

structures is half as great (see Section A1.G.4 in Appendix 1 for details). 

15 06-096 Code of Maine Rules §355 (5) (D). (2007).
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3226 Time. Sometimes a community switches from retreat to protection. It is common to allow 

3227 shores to retreat as long as only vacant land is lost, but to erect shore protection structures 

3228 once homes or other buildings are threatened. Setbacks make it more likely that an 

3229 eroding shore will be allowed to retreat (Beatley et al., 2002; NRC, 1987; NOAA, 2007); 

3230 once the erosion reaches the setback line, the economics of shore protection are similar 

3231 to what they would have been without the setback. Conversely, protection can switch to 

3232 retreat. Property owners sometimes erect low-cost shore protection (e.g., geotextile 

3233 sandbags, shown in Figure 6.7b) that extends the lifetimes of their property, but 

3234 ultimately fails in a storm. Increasing environmental implications or costs of shore 

3235 protection may also motivate a switch from protection to retreat (see Section 6.5). To 

3236 minimize economic and human impacts, retreat policies based on rolling easements can 

3237 be designed to take effect 50 to 100 years hence, until which time protection might be 

3238 allowed (Titus, 1998). 

 3239 

3240 Place. Different responses operate on different scales. In general, a project to retreat or 

3241 protect a given parcel will usually have effects on other parcels. For example, sand 

3242 provided to an open stretch of ocean beach will be transported along the shore a 

3243 significant distance by waves and currents; hence, beach nourishment along the ocean 

3244 coast generally involves at least a few kilometers of shoreline or an entire island. Along 

3245 estuaries, however, sands are not transported as far—especially when the shoreline has an 

3246 indentation—so estuarine shore protection can operate on a smaller scale. Shoreline 

3247 armoring that protects one parcel may cause adjacent shores to erode or accrete. 

3248 Nevertheless, along tidal creeks and other areas with small waves, it is often feasible to 
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3249 protect one home with a hard structure, while allowing an adjacent vacant lot to erode. In 

3250 areas with low density zoning, it may be possible to protect the land immediately 

3251 surrounding a home while the rest of the lot converts to marsh, mudflat, or shallow water 

3252 habitat. 

 3253 

3254 Uncertainty. Some responses to sea-level rise may be appropriate in communities whose 

3255 eventual status is unknown. Floodproofing homes (see Chapter 9), elevating evacuation 

3256 routes, and improving drainage systems can provide cost-effective protection from 

3257 flooding in the short term, whether or not a given neighborhood will eventually be 

3258 protected or become subjected to tidal inundation. A setback can reduce hazards whether 

3259 or not a shore protection project will eventually be implemented. 

 3260 

3261 6.2 WHAT FACTORS INFLUENCE THE DECISION WHETHER TO PROTECT 

3262 OR RETEAT? 

3263 6.2.1 Site-Specific Factors 

3264 Private landowners and government agencies who contemplate possible shore protection 

3265 are usually motivated by either storm damages or the loss of land (NRC, 2007). They 

3266 inquire about possible shore protection measures, investigate the costs and consequences 

3267 of one or more measures, and consider whether undertaking the costs of shore protection 

3268 is preferable to the consequences of not doing so. For most homeowners, the costs of 

3269 shore protection include the costs of both construction and necessary government 

3270 permits; the benefits include the avoided damages or loss of land and structures. 

3271 Businesses might also consider avoided disruptions in business operations. Regulatory 
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3272 authorities that issue or deny permits for private shore protection consider possible 

3273 impacts of shore protection on the environment, public access along ocean shores, and 

3274 whether the design minimizes those impacts (NRC, 2007). Government agencies consider 

3275 the same factors as private owners as well as public benefits of shore protection, such as 

3276 greater recreational opportunities from wider beaches, increased development made 

3277 possible by the shore protection (where applicable), and public safety. 

 3278 

3279 Accelerated sea-level rise does not change the character of those considerations, but it 

3280 would increase the magnitude of both the benefits and the consequences (monetary and 

3281 otherwise) of shore protection. In some areas, accelerated sea-level rise would lead 

3282 communities that are unprotected today to adopt shore protection; in other areas, the 

3283 increased costs of shore protection may begin to outweigh the benefits. No published 

3284 study provides a comprehensive assessment of how sea-level rise changes the costs and 

3285 benefits of shore protection. However, the available evidence suggests that the 

3286 environmental and social impacts could increase more than proportionately with the rate 

3287 of sea-level rise (see Section 6.3 and 6.4). A case study of Long Beach Island, New 

3288 Jersey (a densely developed barrier island with no high-rise buildings) concluded that 

3289 shore protection is more cost-effective than retreat for the first 50 to 100 cm of sea-level 

3290 rise (Titus, 1990). If the rise continues to accelerate, however, then eventually the costs of 

3291 protection would rise more rapidly than the benefits, and a strategic retreat would then 

3292 become the more cost-effective response, assuming that the island could be sustained by 

3293 a landward migration. An economic analysis by Yohe et al. (1996) found that higher rates 

3294 of sea-level rise make shore protection less cost-effective in marginal cases. 
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 3295 

3296 6.2.2 Regional Scale Factors 

3297 Potential benefits and consequences are usually the key to understanding whether a 

3298 particular project will be adopted. At a broader scale, however, land use and shoreline 

3299 environment are often indicators of the likelihood of shore protection. Land use provides 

3300 an indicator of the resources being protected, and the shoreline environment provides an 

3301 indicator of the type of shore protection that would be needed. 

 3302 

3303 Most land along the mid-Atlantic ocean coast is either developed or part of a park or 

3304 conservation area. This region has approximately 1,100 kilometers (almost 700 miles) of 

3305 shoreline along the Atlantic Ocean. Almost half of this coastline consists of ocean beach 

3306 resorts with dense development and high property values. Federal shore protection has 

3307 been authorized along most of these developed shores. These lands are fairly evenly 

3308 spread throughout the mid-Atlantic states, except Virginia (see Section A1.E.2.1 in 

3309 Appendix 1). However, a large part of the coast is owned by landowners who are 

3310 committed to allowing natural shoreline processes to operate, such as The Nature 

3311 Conservancy, National Park Service (see Section 11.2.1), and U.S. Fish and Wildlife 

3312 Service. These shores include most of North Carolina’s Outer Banks, all of Virginia’s 

3313 Atlantic coast except for part of Virginia Beach and a NASA installation, more than two3314 thirds of the Maryland coast and New York’s Fire Island. The rest of the ocean coast in 

3315 this region is lightly developed, yet shore protection is possible for these coasts as well 

3316 due to the presence of important coastal highways. 

 3317 
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3318 Development is less extensive along many estuaries than along the ocean coast. The 

3319 greatest concentrations of low-lying undeveloped lands along estuaries are in North 

3320 Carolina, the Eastern Shore of Chesapeake Bay, and portions of Delaware Bay. 

3321 Development has come more slowly to the lands along the Albemarle and Pamlico 

3322 Sounds in North Carolina than to other parts of the mid-Atlantic coast (Hartgen, 2003.) 

3323 Maryland law prevents development along much of the Chesapeake Bay shore (Section 

3324 A1.F.2.1 in Appendix 1), and a combination of floodplain regulations and aggressive 

3325 agricultural preservation programs limit development along the Delaware Bay shore in 

3326 Delaware (Section A1.D.2.2 in Appendix 1). Yet there is increasing pressure to develop 

3327 land along tidal creeks, rivers, and bays (USCOP, 2004; DNREC, 2000; Titus, 1998), and 

3328 barrier islands are in a continual state of redevelopment in which seasonal cottages are 

3329 replaced with larger homes and high-rises (e.g., Randall, 2003). 

 3330 

3331 If threatened by rising sea level, these developed lands (e.g., urban, residential, 

3332 commercial, industrial, transportation) would require shore protection for current land 

3333 uses to continue. Along estuaries, the costs of armoring, elevating, or nourishing 

3334 shorelines are generally less than the value of the land to the landowner, suggesting that 

3335 under existing trends shore protection would continue in most of these areas. But there 

3336 are also some land uses for which the cost and effort of shore protection may be less 

3337 attractive than allowing the land to convert to wetland, beach, or shallow water. Those 

3338 land uses might include marginal farmland, conservations lands, portions of some 

3339 recreational parks, and even portions of back yards where lot sizes are large. Along the 

3340 ocean, shore protection costs are greater—but so are land values. 
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 3341 

3342 Shore protection is likely along much of the coastal zone, but substantial areas of 

3343 undeveloped (but developable) lands remain along the mid-Atlantic estuaries, where 

3344 either shore protection or wetland migration could reasonably be expected to occur 

3345 (NRC, 2007; Yohe et al., 1996; Titus et al., 1991). Plans and designs for the development 

3346 of those lands generally do not consider implications of future sea-level rise (see Chapter 

3347 11). A series of studies have been undertaken that map the likelihood of shore protection 

3348 along the entirety of the U.S. Atlantic Coast as a function of land use (Nicholls et al., 

3349 2007; Titus, 2004, 2005; Clark, 2001; Nuckols, 2001). 

 3350 

3351 6.2.3 Mutual Reinforcement Between Coastal Development and Shore Protection 

3352 Lands with substantial shore protection are more extensively developed than similar 

3353 lands without shore protection, both because shore protection encourages development 

3354 and development encourages shore protection. People develop floodplains, which leads to 

3355 public funding for flood control structures, which in turn leads to additional development 

3356 in the area protected (e.g., Burby, 2006). Few studies have measured this effect, but 

3357 possible mechanisms include: 

3358  Flood insurance rates that are lower in protected areas (see Chapter 10); 

3359  Development that may be allowed in locations that might otherwise be off limits; 

3360  Erosion-based setbacks that require less of a setback if shore protection slows or 

3361 halts erosion (see Section 6.1); and 

3362  Fewer buildings that are destroyed by storms, so fewer post-disaster decisions to 

3363 abandon previously developed land (e.g., Weiss, 2006) would be expected. 
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 3364 

3365 The impact of coastal development on shore protection is more firmly established. 

3366 Governments and private landowners generally implement a shore protection project only 

3367 when the value of land and structures protected is greater than the cost of the project (see 

3368 Sections 6.1 and 12.2.3). 

 3369 

3370 6.3 WHAT ARE THE ENVIRONMENTAL CONSEQUENCES OF RETREAT 

3371 AND SHORE PROTECTION?

3372 In the natural setting, sea-level rise can significantly alter barrier islands and estuarine 

3373 environments (Chapters 3, 4, and 5). Because a policy of retreat allows natural processes 

3374 to work, the environmental impacts of retreat in a developed area can be similar to the 

3375 impacts of sea-level rise in the natural setting, provided that management practices are 

3376 adopted to restore lands to approximately their natural condition before they are 

3377 inundated, eroded, or flooded. In the absence of management practices, possible 

3378 environmental implications of retreat include: 

3379  Contamination of estuarine waters from flooding of hazardous waste sites (Flynn et 

3380 al., 1984) or areas where homes and businesses store toxic chemicals; 

3381  Increased flooding (Wilcoxen, 1986; Titus et al., 1987) or infiltration into public 

3382 sewer systems (Zimmerman and Cusker, 2001); 

3383  Groundwater contamination as septic tanks and their drain fields become submerged; 

3384  Debris from abandoned structures; and 
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3385  Interference with the ability of wetlands to keep pace or migrate inland due to 

3386 features of the built landscape (e.g., elevated roadbeds, drainage ditches, and 

3387 impermeable surfaces). 

 3388 

3389 Shore protection generally has a greater environmental impact than retreat (see Table 

3390 6.1). The impacts of beach nourishment and other soft approaches are different than the 

3391 impacts of shoreline armoring. 

 3392 

3393 Beach nourishment affects the environment of both the beach being filled and the nearby 

3394 seafloor “borrow areas” that are dredged to provide the sand. Adding large quantities of 

3395 sand to a beach is potentially disruptive to turtles and birds that nest on dunes and to the 

3396 burrowing species that inhabit the beach (NRC, 1995), though less disruptive in the long 

3397 term than replacing the beach and dunes with a hard structure. The impact on the borrow 

3398 areas is a greater concern: The highest quality sand for nourishment is often contained in 

3399 a variety of shoals which are essential habitat for shellfish and related organisms 

3400 (USACE, 2002). For this reason, the U.S. Army Corps of Engineers has denied permits to 

3401 dredge sand for beach nourishment in New England (e.g., NOAA Fisheries Service, 

3402 2008; USACE, 2008a). As technology improves to recover smaller, thinner deposits of 

3403 sand offshore, a greater area of ocean floor must be disrupted to provide a given volume 

3404 of sand. Moreover, as sea level rises, the required volume is likely to increase, further 

3405 expanding the disruption to the ocean floor. 

3406 
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3407 As sea level rises, shoreline armoring eventually eliminates ocean beaches (IPCC, 1990); 

3408 estuarine beaches (Titus, 1998), wetlands (IPCC, 1990), mudflats (Galbraith et al., 2002), 

3409 and very shallow open water areas by blocking their landward migration. By redirecting 

3410 wave energy, these structures can increase estuarine water depths and turbidity nearby, 

3411 and thereby decrease intertidal habitat and submerged aquatic vegetation. The more 

3412 environmentally sensitive “living shoreline” approaches to shore protection preserve a 

3413 narrow strip of habitat along the shore (NRC, 2007); however, they do not allow large3414 scale wetland migration. To the extent that these approaches create or preserve beach and 

3415 marsh habitat, it is at the expense of the shallow water habitat that would otherwise 

3416 develop at the same location. 

3417 

3418 The issue of wetland and beach migration has received considerable attention in the 

3419 scientific, planning, and legal literature for the last few decades (NRC, 1987; Barth and 

3420 Titus, 1984; IPCC, 1990). Wetlands and beaches provide important natural resources, 

3421 wildlife habitat, and storm protection (see Chapter 5). As sea level rises, wetlands and 

3422 beaches can potentially migrate inland as new areas become subjected to waves and tidal 

3423 inundation—but not if human activities prevent such a migration. For example, early 

3424 estimates (e.g., U.S. EPA, 1989) suggested that a 70 cm rise in sea level over the course 

3425 of a century would convert 65 percent of the existing mid-Atlantic wetlands to open 

3426 water, and that this region would experience a 65 percent overall loss if all shores were 

3427 protected so that no new wetlands could form inland. The results in Chapter 4 are broadly 

3428 consistent with the 1989 study. That loss would only be 27 percent, however, if new 
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3429 wetlands were able to form on undeveloped lands, and 16 percent if existing developed 

3430 areas converted to marsh as well. 

 3431 

3432 Very little land has been set aside for the express purpose of ensuring that wetlands and 

3433 other tidal habitat can migrate inland as sea level rises (see Chapter 11 of this Product; 

3434 Titus, 2000), but those who own and manage estuarine conservation lands do allow 

wetlands to migrate onto adjacent dry land. With a few notable exceptions16 3435 , the 

3436 managers of most conservation lands along the ocean and large bays allow beaches to 

3437 erode as well (see Chapter 11) The potential for landward migration of coastal wetlands 

3438 is limited by the likelihood that many shorelines will be preserved for existing land uses 

3439 (e.g., U.S. EPA, 1989; IPCC, 1990; Nicholls et al., 1999). Some preliminary studies (e.g., 

3440 Titus, 2004) indicate that in the mid-Atlantic region, the land potentially available for 

3441 new wetland formation would be almost twice as great if future shore protection is 

3442 limited to lands that are already developed, than if both developed and legally 

3443 developable lands are protected. 

3444 

 

16 Exceptions include Cape May Meadows in New Jersey (protecting freshwater wetlands near the ocean), 

beaches along both sides of Delaware Bay (horseshoe crab habitat) and Assateague Island, Maryland (to 

prevent the northern part of the island from disintegrating). 
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3445 Table 6.1 Selected Measures for Responding to Sea-Level Rise: Objective and Environmental Effects 

 3446 

Response 

Measure 

Method for Protection or Retreat Key Environmental effects 

 Shoreline armoring that interferes with waves and currents

Breakwater Reduce erosion May attract marine life; downdrift erosion 

Groin Reduce erosion May attract marine life; downdrift erosion 

 Shoreline armoring used s to define a shoreline

Seawall Reduce erosion, protect against flood and wave 

overtopping 

Elimination of beach; scour and deepening in 

front of wall; erosion exacerbated at terminus 

Bulkhead Reduce erosion, protect new land fill Prevents inland migration of wetlands and 

beaches. Wave reflection erodes bay bottom, 

preventing SAV. Prevents amphibious 

movement from water to land. 

Revetment Reduce erosion, protect land from storm waves, 

protect new land fill 

Prevents inland migration of wetlands and 

beaches. Traps horseshoe crabs and prevents 

amphibious movement. May create habitat 

for oysters and refuge for some species. 

 Shoreline armoring used protect against floods and/ or permanent inundation

Dike Prevents flooding and permanent inundation 

(when combined with a drainage system). 

Prevents wetlands from migrating inland. 

Thwarts ecological benefits of floods (e.g., 

annual sedimentation, higher water tables, 

habitat during migrations, productivity 

transfers) 

Tide gate Reduces tidal range by draining water at low tide 

and closing at high tide. 

Restricts fish movement. Reduced tidal range 

reduces intertidal habitat. May convert saline 

habitat to freshwater habitat. 

Storm 

surge 

barrier 

Eliminates storm surge flooding; could protect 

against all floods if operated on a tidal schedule 

Necessary storm surge flooding in salt 

marshes is eliminated. 

 Elevating land 

Dune Protect inland areas from storm waves, provide a 

source of sand during storms to offset erosion. 

Can provide habitat; can set up habitat for 

secondary dune colonization behind it 

Beachfill Reverses shore erosion, and provide some 

protection from storm waves. 

Short-term loss of shallow marine habitat; 

could provide beach and dune habitat 

Elevate 

land and 

structures 

Avoid flooding and inundation from sea-level rise 

by elevating everything as much as sea rises. 

Deepening of estuary unless bay bottoms are 

elevated as well. 

 Retreat

Setback Delay the need for shore protection by keeping 

development out of the most vulnerable lands. 

Impacts of shore protection delayed until 

shore erodes up to the setback line. Impacts 

of development also reduced. 

Rolling 

easement 

Prohibit shore protection structures. Impacts of shore protection structures 

avoided. 

Density or 

size 

restriction 

Reduce the benefits of shore protection and 

thereby make it less likely. 

Depends on whether owners of large lots 

decide to protect shore. Impacts of intense 

development reduced. 

 3447 

3448 
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3449 6.4 WHAT ARE THE SOCIETAL CONSEQUENCES OF SHORE PROTECTION 

3450 AND RETREAT AS SEA LEVEL RISES?

 3451 

3452 6.4.1 Short-Term Consequences 

3453 Shore protection generally is designed to enable existing land uses to continue. By 

3454 insulating a community from erosion, storms, and other hazards, the social consequences 

3455 of sea-level rise can be minimal, at least for the short term. In the Netherlands, shore 

3456 protection helped to foster a sense of community as residents battled a common enemy 

3457 (Disco, 2006). In other cases, the interests of some shorefront property owners may 

3458 diverge from the interests of other residents (NRC, 2007). For example, many property 

3459 owners in parts of Long Beach Island, New Jersey strongly supported beach 

3460 nourishment—but some shorefront owners in areas with wide beaches and dunes have 

3461 been reluctant to provide the state with the necessary easements (NJDEP, 2006; see 

3462 Section A1.C.2 in Appendix 1). 

 3463 

3464 Allowing shores to retreat can be disruptive. If coastal erosion is gradual, one often sees a 

3465 type of coastal blight in what would otherwise be a desirable community, with exposed 

3466 septic tanks and abandoned homes standing on the beach, and piles of rocks or geotextile 

3467 sand bags in front of homes that remain occupied (Figures 6.8b and 6.9). If the loss of 

3468 homes is episodic, communities can be severely disrupted by the sudden absence of 

3469 neighbors who previously contributed to the local economy and sense of community 

3470 (IPCC, 1990; Perrin et al., 2008; Birsch and Wachter, 2006). People forced to relocate 

3471 after disasters are often at increased risk to both health problems (Yzermans et al., 2005) 

3472 and depression (Najarian et al., 2001). 

3473 
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3474 

3475 Figure 6.9 The adverse impacts of retreat on safety and aesthetic appeal of recreational beaches (a) 

3476 Exposed septic tank and condemned houses at Kitty Hawk, North Carolina (June 2002); (b) Beach 

3477 unavailable for recreation where homes were built to withstand shore erosion and storms, at Nags Head, 

3478 North Carolina (June 2007). 

3479 

3480 6.4.2 Long-Term Consequences 

3481 The long-term consequences of a retreat can be similar to the short-term consequences. In 

3482 some areas, however, the consequences may become more severe over time. For 

3483 example, a key roadway originally set far back from the shore may become threatened 

3484 and have to be relocated. In the case of barrier islands, the long-term implications of 

3485 retreat depend greatly on whether new land is created on the bay side to offset oceanfront 

3486 erosion. If so, communities can be sustained as lost oceanfront homes are rebuilt on the 

3487 bay side; if not, the entire community could be eventually lost. 

 3488 

3489 The long-term consequences of shore protection could be very different from the short3490 term consequences. As discussed below, shore protection costs could escalate. The 

3491 history of shore protection in the United States suggests that some communities would 

3492 respond to the increased costs by tolerating a lower level of shore protection, which could 

3493 lead eventually to dike failures (Seed et al., 2005; Collins, 2006) and resulting unplanned 

3494 retreat. In other cases, communities would not voluntarily accept a lower level of 
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3495 protection, but the reliance on state or federal funding can lead to a lower level while 

3496 awaiting funds (a common situation for communities awaiting beach nourishment). For 

3497 communities that are able to keep up with the escalated costs, tax burdens would 

3498 increase, possibly leading to divisive debates over a reconsideration of the shore 

3499 protection strategy. 

3500 

3501 6.5 HOW SUSTAINABLE ARE SHORE PROTECTION AND RETREAT? 

3502 Coastal communities were designed and built without recognition of rising sea level. 

3503 Thus, people in areas without shore protection will have to flood-proof structures (see 

3504 Chapter 9), implement shore protection, (Section 6.1.1) or plan a retreat (Section 6.1.2). 

3505 Those who inhabit areas with shore protection are potentially vulnerable as well. Are the 

3506 known approaches to shore protection and retreat sustainable, that is, can they be 

3507 maintained for the foreseeable future? 

 3508 

3509 Most shore protection structures are designed for current sea level and may not 

3510 accommodate a significant rise. Seawalls (Kyper and Sorenson, 1985; NRC, 1987), 

3511 bulkheads (Sorenson et al., 1984.), dikes, (NRC, 1987), sewers (Wilcoxen, 1986) and 

3512 drainage systems (Titus et al., 1987) are designed based on the waves, water levels, and 

3513 rainfall experienced in the past. If conditions exceed what the designers expect, disaster 

3514 can result—especially when sea level rises above the level of the land surface. The failure 

3515 of dikes protecting land below sea level resulted in the deaths of approximately 1800 

3516 people in the Netherlands in a 1953 storm (Roos and Jonkman, 2006), and more than 

3517 1000 people in the New Orleans area from Hurricane Katrina in 2005 (Knabb et al., 
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3518 2005). A dike along the Industrial Canal in New Orleans which failed during Katrina had 

3519 been designed for sea level approximately 60 cm lower than today, because designers did 

3520 not account for the land subsidence during the previous 50 years (Interagency 

3521 Performance Evaluation Taskforce, 2006). 

 3522 

3523 One option is to design structures for future conditions. Depending on the incremental 

3524 cost of designing for higher sea level compared with the cost of rebuilding later, it may 

3525 be economically rational to build in a safety factor today to account for future conditions, 

3526 such as higher and wider shore protection structures (see Chapter 10). But doing so is not 

3527 always practical. Costs generally rise more than proportionately with higher water 

levels17 3528 . Project managers would generally be reluctant to overdesign a structure for 

3529 today’s conditions (Schmeltz, 1984). Moreover, aesthetic factors such as loss of 

3530 waterfront views or preservation of historic structures (e.g., Charleston Battery in South 

3531 Carolina; see Figure 6.10) can also make people reluctant to build a dike or seawall 

3532 higher than what is needed today. 

3533 

 

17 Weggel et al., (1989) estimate that costs are proportional to the height of the design water level raised to 

the 1.5 power. 
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3534 Figure 6.10. Historic homes along the Charleston Battery. Charleston, South Carolina. (April 2004).

3535 

3536 6.5.1 Is “Business as Usual” Shore Protection Sustainable? 

3537 Public officials and property owners in densely developed recreational communities 

3538 along the mid-Atlantic coast generally expect governmental actions to stabilize shores. 

3539 But no one has assessed the cost and availability of sand required to keep the shorelines 

3540 in their current locations through beach nourishment even if required sand is proportional 

3541 to sea-level rise, which previous assessments of the cost of sea level rise have assumed 

3542 (e.g., U.S. EPA, 1989; Leatherman, 1989; Titus et al., 1991). The prospects of barrier 

3543 island disintegration and segmentation examined in Chapter 3 would require much more 

3544 sand to stabilize the shore. Maintaining the shore may at first seem to require only the 

3545 simple augmentation of sand along a visible beach, but over a century or so other parts of 

3546 the coastal environment would capture increasing amounts of sand to maintain elevation 

3547 relative to the sea. In effect, beach nourishment would indirectly elevate those areas as 

3548 well (by replacing sand from the beach that is transported to raise those areas), including 

3549 the ocean floor immediately offshore, tidal deltas, and eventually back-barrier bay 

3550 bottoms and the bay sides of barrier islands. Similarly, along armored shores in urban 

3551 areas, land that is above sea level today would become farther and farther below sea 

3552 level, increasing the costs of shore protection and setting up greater potential disasters in 

3553 the event of a dike failure. It is not possible to forecast whether these costs will be greater 

3554 than what future generations will choose to bear. But in those few cases where previous 

3555 generations have bequeathed this generation with substantial communities below sea 

3556 level, a painful involuntary relocation sometimes occurs after severe storms (e.g., New 

3557 Orleans after Katrina). 
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 3558 

3559 Most retreat policies are designed for current rates of sea-level rise and would not 

3560 necessarily accommodate a significant acceleration in the rate of sea-level rise. Erosion3561 based setbacks along ocean shores generally require homes to be set back from the 

3562 primary dune by a distance equal to the annual erosion rate times a number years 

3563 intended to represent the economic lifetime of the structure (e.g., in North Carolina, 60 

3564 years times the erosion rate for large buildings [see Section A1.G.1 in Appendix 1). If 

3565 sea-level rise accelerates and increases the erosion rate, then the buildings will not have 

3566 been protected for the presumed economic lifetimes. Yet larger setback distances may not 

3567 be practicable if they exceed the depth of buildable lots. Moreover, erosion-based setback 

3568 policies generally do not articulate what will happen once shore erosion consumes the 

3569 setback. The retreat policies followed by organizations that manage undeveloped land for 

3570 conservation purposes may account for foreseeable erosion, but not for the consequences 

3571 of an accelerated erosion that consumes the entire coastal unit. 

 3572 

3573 6.5.2 Sustainable Shore Protection May Require Regional Coordination 

3574 Regional Sediment Management is a relatively new strategy or planning tool for 

3575 managing sand as a resource (NRC, 2007). The strategy recognizes that coastal 

3576 engineering projects have regional impacts on sediment transport processes and 

3577 availability. This approach includes: 

3578 • Conservation and management of sediments in along the shore and immediate 

3579 offshore areas, viewing sand as a resource; 
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3580 • Attempt to design with nature, understanding sediment movement in a region and 

3581 the interrelationships of projects and management actions; 

3582 • Conceptual and programmatic connections among all activities that involve 

3583 sediment in a region (e.g., navigation channel maintenance, flood and storm damage 

3584 reduction, ecosystem restoration and protection, beneficial uses of dredged 

3585 material); 

3586 • Connections between existing and new projects to use sediment more efficiently; 

3587 • Improved program effectiveness through collaborative partnerships between 

3588 agencies; and 

3589 • Overcoming institutional barriers to efficient management (Martin, 2002). 

 3590 

3591 The Philadelphia and New York Districts of the U.S. Army Corps of Engineers have a 

3592 joint effort at regional sediment management for the Atlantic coast of New Jersey 

3593 (USACE, 2008b). By understanding sediment sources, losses, and transport; how people 

3594 have altered the natural flow; and ways to work with natural dynamics, more effective 

3595 responses to rising sea level are possible. 

 3596 

3597 One possible way to promote better regional sediment management would be the 

3598 development of a set of “best sediment management practices”. Previously, standard 

3599 practices have been identified to minimize the runoff of harmful sediment into estuaries 

3600 (NJDEP, 2004; City of Santa Cruz, 2007). A similar set of practices for managing 

3601 sediments along shores could help reduce the environmental and economic costs of shore 

3602 protection, without requiring each project to conduct a regional sediment management 

3603 study. 
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 3604 

3605 6.5.3 Either Shore Protection or a Failure to Plan can Limit the Flexibility of Future 

3606 Generations 

3607 The economic feasibility of sustained shore protection as sea level rises is unknown, as is 

3608 the political and social feasibility of a planned retreat away from the shore. The absence 

3609 of a comprehensive long-term shoreline plan often leaves property owners with the 

3610 assumption that the existing development can and should be maintained. Property3611 specific shoreline armoring and small beach nourishment projects further reinforce the 

3612 expectation that the existing shoreline will be maintained indefinitely, often seeming to 

3613 justify additional investments by property owners in more expensive dwellings 

3614 (especially if there is a through-road parallel to the shore). 

 3615 

3616 Shore protection generally limits flexibility more than retreat. Once shore protection 

3617 starts, retreat can be very difficult to enact because investments and expectations are 

3618 based on the protection, which in turn increases the economic justification for continued 

3619 shore protection. A policy of retreat can be more easily replaced with a policy of shore 

3620 protection, because people do not make substantial investments on the assumption that 

3621 the shore will retreat. This is not to say that all dikes and seawalls would be maintained 

3622 and enlarged indefinitely if sea level continues to rise. Nevertheless, the abandonment of 

3623 floodprone communities rarely (if ever) occurs because of the potential vulnerability or 

3624 cost of flood protection, but rather in the aftermath of a flood disaster (e.g., Missouri 

3625 State Emergency Management Agency, 1995). 

3626 
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3627 CHAPTER 6 REFERENCES

3628 * Indicates non-peer reviewed literature; available upon request

3629 

3630 Accomack County, 2008: Respecting the Past, Creating the Future: The Accomack 

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3632 Department, Accomack County. [Note: The town and county are spelled 

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3641 Barth, M.C. and J.G. Titus (eds.), 1984: Greenhouse Effect and Sea Level Rise: A 

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3643 Beatley, T., D.J Brower, and A.K. Schwab, 2002: An Introduction to Coastal Zone 

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3645 Birch, E.L. and S.M. Wachter (eds.), 2006: Rebuilding Urban Places after Disaster: 

3646 Lessons from Katrina. University of Pennsylvania Press, Philadephia, 375 pp. 

3647 Bryan, W.B, 1914: A Hisory of the National Capital from its Foundation Through the 

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3650 Burka, P., 1974: Shoreline erosion: implications for public rights and private ownership. 

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3652 Burby, R.J., 2006: Hurricane Katrina and the paradoxes of government disaster policy: 

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3676 * DDFW (Delaware Division of Fish and Wildlife), 2007: Northern Delaware Wetlands 

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3679 Dean, R.G. and R.A. Dalrymple, 2002: Coastal Processes with Engineering 

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3834 restructure federal programs so that wetlands and beaches survive. Golden Gate 

3835 University Law Review, 30(4), 717-778. 

3836 * Titus, J.G., 2004: Maps that depict the business-as-usual response to sea level rise in 

3837 the decentralized United States of America. Presented at: Global Forum on 
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3838 Sustainable Development, Paris, 11-12 November 2004. Organization of 

3839 Economic Cooperation and Development, Paris. 

3840 Titus, J.G., 2005: Does shoreline armoring violate the Clean Water Act? Rolling 

3841 easements, shoreline planning, and other responses to sea level rise. In: America's 

3842 Changing Coasts: Private Rights and Public Trust. [Whitelaw D.M. and G.R. 

3843 Visgilio (eds.)]. Edward Elgar Publishing, Cheltenham, UK, Northampton, MA, 

3844 248 pp. 

3845 Titus, J.G., C.Y. Kuo, M.J. Gibbs, T.B. LaRoche, M.K. Webb, and J.O. Waddell, 1987:

3846 Greenhouse effect, sea level rise, and coastal drainage systems. Journal of Water 

3847 Resources Planning and Management, 113(2), 216-227. 

3848 Titus, J.G., R.A. Park, S.P. Leatherman, J.R. Weggel, M.S. Greene, P.W. Mansel, S. 

3849 Brown, G. Gaunt, M. Treehan, and G. Yohe. 1991: Greenhouse effect and sea 

3850 level rise: the cost of holding back the sea. Coastal Management, 19(2), 171-204. 

3851 UK Environment Agency, 2007: Managed Realignment Electronic Platform. Version 

3852 1.0. <http://www.intertidalmanagement.co.uk/> 

3853 USACE (U.S. Army Corps of Engineers), 1995: Engineering and Design: Design of 

3854 Coastal Revetments, Seawalls, and Bulkheads. Engineer manual no. 1110-2-1614. 

3855 U.S. Army Corps of Engineers, Washington, DC. 

3856 USACE (U.S. Army Corps of Engineers), 1998. Shoreline and Channel Erosion 

3857 Protection: Overview of Alternatives. WRP technical note HS-RS-4.1. U.S. Army 

3858 Corps of Engineers Wetlands Research Program, [Vicksburg, MS], 8 pp. 

3859 http://el.erdc.usace.army.mil/elpubs/pdf/hsrs4-1.pdf

3860 USACE (U.S. Army Corps of Engineers), 2002: Coastal Engineering Manual. Engineer 

3861 manual 1110-2-1100. U.S. Army Corps of Engineers, Washington, DC, (in 

3862 6volumes issued between 2002 and 2006). 

3863 * USACE (U.S. Army Corps of Engineers), 2008a: Corps of Engineers Public Interest 

3864 Review Results in Permit Denial for Winthrop Beach. News Release April 23, 
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3865 2008. <http://www.nae.usace.army.mil/news/2008-041.htm> 

3866 USACE (U.S. Army Corps of Engineers), 2008b: Project Factsheet: New Jersey 

3867 Alternative Long-Term Nourishment RSM (Regional Sediment Management) 

3868 Study. USACE Philadelphia District, 2 pp. 

3869 <http://www.nap.usace.army.mil/cenap3870 dp/projects/factsheets/NJ/NJ%20Alt%20LT%20Nourishment.pdf> 

3871 USCOP (U.S. Commission on Ocean Policy), 2004: An Ocean Blueprint for the 21st 

3872 Century. U.S. Commission on Ocean Policy, Washington DC. 

3873 <http://www.oceancommission.gov> 

3874 U.S. EPA (Environmental Protection Agency), 1989: The Potential Effects of Global 

3875 Climate Change on the United States. Appendix: B, Sea Level Rise. EPA 230-05-

3876 89-052. U.S. Environmental Protection Agency, Washington, DC. 

3877 <http://epa.gov/climatechange/effects/coastal/appB.html> 

3878 * USFWS (United States Fish and Wildlife Service), 2008: Blackwater National Wildlife 

3879 Refuge: Wetland Restoration. [web site] 

3880 <http://www.fws.gov/blackwater/restore.html> 

3881 Weggel, J.R., S. Brown, J.C. Escajadillo, P. Breen, and E.L. Doheny, 1989: The cost of 

3882 defending developed shorelines along sheltered waters of the United States from a 

3883 two meter rise in mean sea level. In: The Potential Effects of Global Climate 

3884 Change on the United States. Appendix: B, Sea Level Rise. EPA 230-05-89-052. 

3885 U.S. Environmental Protection Agency, Washington, DC, pp. 3-1 to 3-90. 

3886 <http://epa.gov/climatechange/effects/coastal/appB.html> 

3887 Weiss, N.E., 2006: Rebuilding Housing after Hurricane Katrina: Lessons Learned and 

3888 Unresolved Issues. Congressional Research Service, Washington, DC, 13 pp. 

3889 <http://assets.opencrs.com/rpts/RL33761_20061219.pdf> 

3890 Wilcoxen, P.J., 1986: Coastal erosion and sea level rise: implications for Ocean Beach 

3891 and San Francisco’s Westside Transport Project. Coastal Zone Management 
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3892 Journal, 14(3), 173-192. 

3893 Yohe, G. and J.E. Neumann, 1997: Planning for sea level rise and shore protection under 

3894 climate uncertainty. Climatic Change, 37(1), 243-270.

3895 Yohe, G., J.E. Neumann, P. Marshall, and H. Ameden, 1996: The economic cost of 

3896 greenhouse induced sea level rise in the United States. Climatic Change, 32(4), 

3897 387-410. 

3898 Yzermans, C.J., G.A. Donker, J.J. Kerssens, A.J.E Dirkzwager, R.J.H. Soeteman, and 

3899 P.M.H. ten Veen, 2005: Health problems of victims before and after disaster: a 

3900 longitudinal study in general practice. International Journal of Epidemiology, 

3901 34(4), 820-826. 

3902 Zimmerman, R. and M. Cusker, 2001: Institutional decision-making. In: Climate 

3903 Change and a Global City: The Potential Consequences of Climate Variability 

3904 and Change. Metro East Coast [Rosenzweig, C. and W.D. Solecki (eds.)]. 

3905 Columbia Earth Institute and Goddard Institute of Space Studies, New York, pp. 

3906 9-1 to 9-25; A11-A17. 

3907 
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3908 Chapter 7. Population, Land Use, and Infrastructure 

3909 

3910 Lead Authors: Stephen K. Gill, NOAA; Robb Wright, NOAA; James G. Titus, U.S. 

3911 EPA 

3912 Contributing Authors: Robert Kafalenos, DOT; Kevin Wright, ICFI, Inc. 

3913 

 3914 

3915 KEY FINDINGS 

3916  The comprehensive high-resolution and precise analyses of the spatial 

3917 distributions of population and infrastructure vulnerable to sea-level rise in the 

3918 Mid-Atlantic required for planning and response do not exist at the present time. 

3919 Existing studies do not have the required underlying land elevation data with the 

3920 degree of confidence necessary for local and regional decision-making (see 

3921 Chapter 2 of this Product).

3922  Existing generalized data can only support a range of estimates. For instance, in 

3923 the Mid-Atlantic, between approximately 900,000 and 3,400,000 people (between 

3924 3 and 10 percent of the total population in the mid-Atlantic coastal region) live on 

3925 parcels of land or city blocks with at least some land less than 1 meter above 

3926 monthly highest tides. Approximately 40 percent of this population is located 

3927 along the Atlantic Ocean shoreline or small adjacent inlets and coastal bays (as 

3928 opposed to along the interior shorelines of the large estuaries, such as Delaware 

3929 Bay and Chesapeake Bay). 
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3930  Agriculture lands, forests, wetlands, and developed lands in lower elevation areas 

3931 are likely to be most impacted by a 1-meter sea-level rise for the Mid-Atlantic. 

3932  The coupling of sea-level rise with storm surge is one of the most important 

3933 considerations for assessing impacts of sea-level rise on infrastructure. Sea-level 

3934 rise poses a risk to transportation in ensuring reliable and sustained transportation 

3935 services. 

3936 

3937 7.1 INTRODUCTION 

3938 Coastal areas in the United States have competing interests of population growth 

3939 (accompanied by building of the necessary supporting infrastructure), the preservation of 

3940 natural coastal wetlands and creation of buffer zones. Increasing sea level will put 

3941 increasing stress on the ability to manage these competing interests effectively and in a 

3942 sustained manner. This Chapter examines the current population, infrastructure, and 

3943 socioeconomic activity that may potentially be affected by sea-level rise. 

 3944 

3945 7.2 POPULATION STUDY ASSESSMENT 

3946 The population assessment for the Mid-Atlantic can be put into a regional perspective by 

3947 first examining some recent national statistics and trends that illustrate the relative 

3948 socioeconomic stress on our coasts: 

 3949 

3950  Using an analysis of coastal counties defined to have a coastline bordering the 

3951 ocean or associated water bodies, or those containing special velocity zones (V 

3952 Zones) defined by the Federal Emergency Management Administration (FEMA), 
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3953 Crowell et al. (2007) estimate that 37 percent of the total U.S. population is found 

3954 in 364 coastal counties, including the Great Lakes. Excluding the Great Lakes 

3955 counties, 30 percent of the total U.S. population is found in 281 coastal counties.

3956  Using an analysis with a broader definition of a coastal county to include those 

3957 found in coastal watersheds in addition to those bordering the ocean and 

3958 associated water bodies, the National Oceanic and Atmospheric Administration 

3959 (NOAA) estimates that U.S. coastal counties, including the Great Lakes and 

3960 excluding Alaska, contain 53 percent of the nation’s population, yet account for 

3961 only 17 percent of the total U.S. land area (Crossett et al., 2004)

3962  Twenty-three of the 25 most densely populated U.S. counties are coastal counties. 

3963 From 1980 to 2003, population density (defined as persons per unit area) 

3964 increased in coastal counties by 28 percent and was expected to increase another 4 

3965 percent by 2008 (Crossett et al., 2004). 

3966  Construction permits can be used to indicate economic growth and urban sprawl. 

3967 More than 1,540 single family housing units are permitted for construction every 

3968 day in coastal counties across the United States. From 1999 to 2003, 2.8 million 

3969 building permits were issued for single family housing units (43 percent of U.S. 

3970 total) and 1.0 million building permits were issued for multi-family housing units 

3971 (51 percent of the U.S. total) (Crossett et al., 2004). 

3972  In 2000, there were approximately 2.1 million seasonal or vacation homes in 

3973 coastal counties (54 percent of the U.S. total) (Crossett et al., 2004). 

 3974 
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3975 Regional trends for the Mid-Atlantic can also be summarized, based on Crossett et al.

3976 (2004). This Product includes the mid-Atlantic states, defined in the Product to include 

3977 the area from New York to Virginia, as part of their defined Northeast region, with North 

3978 Carolina included in the Southeast region. The statistics serve to illustrate the relative 

3979 vulnerability of the coastal socioeconomic infrastructure, either directly or indirectly, to 

3980 sea-level rise. 

3981  Of the 10 largest metropolitan areas in the United States, three (New York, 

3982 Washington, D.C., and Philadelphia) are located in the coastal zone of the mid3983 Atlantic region. 

3984  The coastal population in the Northeast (Maine to Virginia) is expected to 

3985 increase by 1.7 million people from 2003 to 2008, and this increase will occur 

3986 mostly in counties near or in major metropolitan centers. Six of the counties near 

3987 metropolitan areas with the largest expected population increases are in the New 

3988 York City area and four are in the Washington, D.C. area. 

3989  The greatest percent population changes from 2003 to 2008 in the U.S. Northeast 

3990 are expected to occur in Maryland and Virginia. Eight of the 10 coastal counties 

3991 with the greatest expected percent population increases are located in Virginia and 

3992 two are located in Maryland. 

3993  North Carolina coastal counties rank among the highest in the U.S. Southeast for 

3994 expected percent population change from 2003 to 2008. For instance, Brunswick 

3995 County is expected to have the greatest percent increase, at 17 percent. 

 3996 
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3997 Crossett et al. (2004), show the mid-Atlantic states in context with the larger Atlantic 

3998 Coast region. By presenting total land area and coastal land area, as well as total and 

3999 coastal county population statistics, both in absolute numbers and in population density, 

4000 the NOAA report quantifies the socioeconomic stressor of population change on the 

4001 coastal region. As pointed out by Crowell et al. (2007), the coastal counties used in the 

4002 NOAA study represent counties in a broader watershed area that include more than those 

4003 counties that border the land-water interface and that detailed analyses and summary 

4004 statistics for populations at direct risk for inundation due to sea-level rise must use only 

4005 that subset of coastal counties subject to potential inundation. The analyses and statistics 

4006 discussed in subsequent sections of this Product use those subsets. Crossett et al. (2004) 

4007 is used simply to illustrate the increasing stress on coastal areas in general. The mid4008 Atlantic coastal counties are among the most developed and densely populated coastal 

4009 areas in the nation. It is this environment that coastal managers must plan strategies for 

4010 addressing impacts of climate change, including global sea-level rise.

4011 

4012 Several regionally focused reports on examining populations at risk to sea-level rise in 

4013 the Mid-Atlantic are found in the literature. For example Gornitz et al. (2001) includes a 

4014 general discussion of population densities and flood risk zones in the New York 

4015 metropolitan region and examines impacts of sea-level rise on this area. In this report, the 

4016 authors also consider that low-lying areas will be more at risk to episodic flooding from 

4017 storm events because storm tide elevations for a given storm will be higher with sea-level 

4018 rise than without. They suggest that the overall effect for any given location will be a 

4019 reduction in the return period of the 100-year storm flooding event. A similar analysis 
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4020 was performed for the Hampton Roads, Virginia area by Kleinosky et al. (2006) that 

4021 attempts to take into account increased population scenarios by 2100. 

 4022 

4023 Bin et al. (2007) studied the socioeconomic impacts of sea-level rise in coastal North 

4024 Carolina, focusing on four representative coastal counties (New Hanover, Dare, Carteret, 

4025 and Bertie) that range from high-development to rural, and from marine to estuarine 

4026 shoreline. Their socioeconomic analyses studied impacts of sea-level rise on the coastal 

4027 real estate market, on coastal recreation and tourism, and the impacts of tropical storms 

4028 and hurricanes on business activity using a baseline year of 2004. 

 4029 

4030 Comprehensive assessments of impacts of sea-level rise on transportation and 

4031 infrastructure are found in the CCSP Synthesis and Assessment Product (SAP) 4.7 

4032 (CCSP, 2008), which focuses on the Gulf of Mexico, but provides a general overview of 

4033 the scope of the impacts on transportation and infrastructure. In the Mid-Atlantic, focused 

4034 assessments on the effects of sea-level rise to infrastructure in the New York City area 

4035 are available in Jacob et al. (2007). 

 4036 

4037 Some of the recent regional population and infrastructure assessments typically use the 

4038 best available information layers (described in the following section), gridded elevation 

4039 data, gridded or mapped population distributions, and transportation infrastructure maps 

4040 to qualitatively depict areas at risk and vulnerability (Gornitz et al., 2001). The 

4041 interpretation of the results from these assessments is limited by the vertical and 

4042 horizontal resolution of the various data layers, the difference in resolution and matching 
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4043 of the fundamental digital-layer data cells, and the lack of spatial resolution of the 

4044 population density and other data layers within the fundamental area blocks used (see 

4045 Chapter 2 for further discussion). As discussed in Chapter 2, the available elevation data 

4046 for the entire mid-Atlantic region do not support inundation modeling for sea-level rise 

4047 scenarios of 1 meter or less. Therefore, the results reported in this Chapter should not be 

4048 considered as reliable quantitative findings, and they serve only as demonstrations of the 

4049 types of analyses that should be done when high-accuracy elevation data become 

4050 available. 

 4051 

4052 7.3 MID-ATLANTIC POPULATION ANALYSIS

4053 In this Chapter, the methodology for addressing population and land use utilizes a 

4054 Geographic Information Systems (GIS) analysis approach, creating data layer overlays 

4055 and joining of data tables to provide useful summary information. GIS data are typically 

4056 organized in themes as data layers. Data can then be input as separate themes and 

4057 overlaid based on user requirements. Essentially, the GIS analysis is a vertical layering of 

4058 the characteristics of the Earth's surface and is used to logically order and analyze data in 

4059 most GIS software. Data layers can be expressed visually as map layers with underlying 

4060 tabular information of the data being depicted. The analysis uses data layers of 

4061 information and integrates them to obtain the desired output and estimated uncertainties 

4062 in the results. The GIS layers used here are population statistics, land use information, 

4063 and land elevation data. 

 4064 
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4065 The population and land use statistics tabulated in the regional summary tables (Tables 

4066 7.1 through 7.6) use an area-adjusted system that defines regions and subregions for 

4067 analysis such that they are (1) higher than the zero reference contour (Spring High Water) 

4068 used in a vertical datum-adjusted elevation model, and (2) not considered a wetland or 

4069 open water, according to the state and National Wetlands Inventory wetlands data 

4070 compiled by the U.S. Fish and Wildlife Service (USFWS, 2007). Uncertainties are 

4071 expressed in the tables in terms of low and high statistical estimates (a range of values) in 

4072 each case to account for the varying quality of topographic information and the varying 

4073 spatial resolution of the other data layers. The estimated elevation of spring high water is 

4074 used as a boundary that distinguishes between normal inundation that would occur due to 

4075 the normal monthly highest tides and the added inundation due to a 1-meter (m) rise in 

4076 sea level (Titus and Cacela, 2008) . 

 4077 

4078 Census block statistics determined for the estimated area and the percent of a block 

4079 affected by sea-level rise and the estimated number of people and households affected by 

4080 sea-level rise are based on two methods: (1) a uniform distribution throughout the block 

4081 and (2) a best estimate based on assumptions concerning elevation and population 

4082 density. For instance, there is an uncertainty regarding where the population resides 

4083 within the census block, and the relationship between the portion of a block’s area that is 

4084 lost to sea-level rise and the portion of the population residing in the vulnerable area is 

4085 also uncertain. Analysis estimates of vulnerable population are based on the percentage 

4086 of a census block that is inundated. Homes are not necessarily distributed uniformly 

4087 throughout a census block. In addition, the differences in grid sizes between the census 
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4088 blocks and the elevation layers results in various blocks straddling differing elevation 

4089 grids and adds to the uncertainty of the process. 

 4090 

4091 Discussion on coastal elevations and mapping limitations and uncertainties as applied for 

4092 inundation purposes is provided in Chapter 2. Given these limitations and uncertainties, 

4093 the population and land use analyses presented here are only demonstrations of 

4094 techniques using a 1-meter (m) sea-level rise scenario. More precise quantitative 

4095 estimates require high-resolution elevation data and population data with better horizontal 

4096 resolution. 

 4097 

4098 Figure 7.1 illustrates the three GIS data layers used in the population and land use 

4099 analysis: the elevation layer (Titus and Wang, 2008), a census layer (GeoLytics, 2001), 

4100 and a land-use layer (USGS, 2001). 

 4101 

4102 Figures 7.2, 7.3, and 7.4 show the fundamental underlying layers used in this study, using 

4103 Delaware Bay as an example. The GIS layers used here are: 

4104  Elevation data: The elevation data is the driving parameter in the population 

4105 analysis. The elevation data is gridded into 30-m pixels throughout the region. All 

4106 other input datasets are gridded to this system from their source format (Titus and 

4107 Wang, 2008). The elevations are adjusted such that the zero-contour line is set 

4108 relative to the Spring High Water vertical datum, which is interpolated from point 

4109 sources derived from NOAA tide station data (Titus and Cacela, 2008). 
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4110  Census data: Census 2000 dataset (GeoLytics, 2001) is used in the analysis. Block 

4111 boundaries are the finest-scale data available, and are the fundamental units of area 

4112 of the census analysis. Tract, county, and state boundaries are derived from 

4113 appropriate aggregations from their defining blocks. The census tract boundaries are 

4114 the smallest census unit that contains property and tax values. Tract and county 

4115 boundaries also extend fully into water bodies. For this analysis, these boundaries 

4116 are cropped back to the sea-level boundary, but source census data remain intact. 

4117  Land use data: The National Land Cover Data (NLCD) (USGS, 2001) dataset is 

4118 used in this analysis. It consists of a 30-m pixel classification from circa 2001 

4119 satellite imagery and is consistently derived across the region. The caveat with the 

4120 product is that pixels are classified as “wetland” and “open water” in places that are 

4121 not classified as such by the wetland layer. Wetland layers are derived from state 

4122 wetlands data (Titus and Wang, 2008). Usually, the NLCD Wetland class turns out 

4123 to be forested land and the water tends to be edge effects (or uncertainty due to lack 

4124 of resolution) along the shore or near farm ponds. This analysis folds the NLCD 

4125 wetland pixels into forested land. 

 4126 

4127 Figure 7.2 is an example of the county overlay, and Figure 7.3 is an example of the 

4128 census tract overlay. A census tract is a small, relatively permanent statistical subdivision 

4129 of a county used for presenting census data. Census tract boundaries normally follow 

4130 visible features such as roads and rivers, but may follow governmental unit boundaries 

4131 and other non-visible features in some instances; they are always contained within 

4132 counties. Census tracts are designed to be relatively homogeneous units with respect to 
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4133 population characteristics, economic status, and living conditions at the time of 

4134 establishment, and they average about 4,000 inhabitants. The tracts may be split by any 

4135 sub-county geographic entity. 

 4136 

4137 Figure 7.4 provides an example of the census block overlay. A census block is a 

4138 subdivision of a census tract (or, prior to 2000, a block numbering area). A block is the 

4139 smallest geographic unit for which the Census Bureau tabulates data. Many blocks 

4140 correspond to individual city blocks bounded by streets; however, blocks–especially in 

4141 rural areas—may include many square kilometers and due to lack of roads, may have 

4142 some boundaries that are other features such as rivers and streams. The Census Bureau 

4143 established blocks covering the entire nation for the first time in 1990. Previous censuses 

4144 back to 1940 had blocks established only for part of the United States. More than 8 

4145 million blocks were identified for Census 2000 (U.S. Census Bureau, 2007). 

 4146 

4147 The Digital Elevation Model (DEM) (Titus and Wang, 2008) was the base for this 

4148 analysis. The areas of various land use, counties, tracts, and blocks are rasterized

4149 (converted in a vector graphics format [shapes]) into a gridded raster image (pixels or 

4150 dots) to the DEM base. This ensures a standard projection (an equal-area projection), 

4151 pixel size (30 m), grid system (so pixels overlay exactly), and geographic extent. A GIS 

4152 data layer intersection was completed for each of the geographic reporting units (land 

4153 use, county, tract, and block) with elevation ranges to produce a table of unique 

4154 combinations. 

 4155 
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4156 

4157 Figure 7.1 The three input data layers to the GIS analysis.

4158 

4159 Figure 7.2 The county overlay example for Delaware Bay with each colored area depicting a county. 

4160 
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4161 

4162 

4163 Figure 7.3 The census tract overlay example for Delaware Bay with each colored area depicting a census 

4164 tract. 

4165 

4166 

4167 

4168 Figure 7.4 The census block overlay example for Delaware Bay with gray lines outlining individual areas 

4169 of a census block.

4170 
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4171 This Chapter examines the mid-Atlantic region and makes some inferences on the 

4172 populations that may be affected by sea-level rise. This assessment divides the mid4173 Atlantic region into sub-regions defined by watersheds (Crossett et al., 2004), as shown 

4174 in Figure 7.5. The general populations within the various watersheds, although sometimes 

4175 in more than one state, have to address common problems driven by common 

4176 topographies, and natural hydrological regimes. Most of the watershed boundaries are 

4177 clear, for instance the Potomac River and Chesapeake Bay. The watershed boundaries 

4178 used do not include the upland portions of the watershed located in upland mountains and 

4179 hills; those portions are not required for the analyses of the low-lying areas. The Atlantic 

4180 Ocean watershed is the most complex because it is not defined by a discrete estuarine 

4181 river watershed boundary, but by exposure to the outer coastline, and it has components 

4182 in several states. 
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4183 

 4184 

4185 Figure 7.5 The mid-Atlantic region generalized watersheds. 

4186 

4187 7.3.1 Example Population Analysis Results 

4188 Not everyone who resides in a watershed lives in a low-lying area that may be at risk to 

4189 the effects of sea-level rise. Table 7.1 provides a summary analysis of those populations 

4190 in each watershed at potential risk for a 1-m sea-level rise. The low and high estimates in 

4191 Table 7.1 provide the range of uncertainty by using the low and high DEMs (Titus and 

4192 Wang, 2008; Titus and Cacela, 2008). The high elevation is equal to the best estimate 

4193 plus the vertical error of the elevation data; the low elevation estimate is equal to the best 

4194 estimate minus the vertical error. The high vulnerability estimate uses the low elevation 

4195 estimate because if elevations are lower than expected a greater population is vulnerable. 

4196 Similarly, the low vulnerability estimate uses the high end of the uncertainty range of 
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4197 elevation estimates. These DEMs are required to express the uncertainty in the numerical 

4198 results because of the varying scales and resolutions of the data in the various overlays 

4199 (for instance, the census block boundaries may not line up with specific elevation 

4200 contours being used and interpolation algorithms must be used to derive population 

4201 statistics within certain contour intervals. As previously mentioned, this analysis is also 

4202 limited by the assumption that population has uniform density within the inhabited 

4203 portion of particular census block. The census data provide no information where the 

4204 population resides within a particular block. 

4205 

4206 The uncertainty in how much of a particular census tract or block may be inundated must 

4207 also be addressed by listing high and low estimates. Table 7.1 is a maximum estimate of 

4208 the potential populations because it is for census blocks that could have any inundation at 

4209 all and thus includes a maximum count. Similarly, it should be noted that Table 7.3 also 

4210 provides maximum estimates for the Chesapeake Bay and the Atlantic Ocean. 

4211 

4212 Table 7.1 Estimated mid-Atlantic low and high population estimates by watershed for a 1-meter sea4213 level rise (population is based on Census [2000] data). The reported numbers are subject to the 

4214 caveat given at the end of Section 7.2.

 4215 

Population 

count 

 1m Sea level Rise 

Watershed 

Low 

Estimate 

High 

Estimate 

 

Long Island Sound 1,640 191,210 

Peconic Bay 7,870 29,140 

NHY-Raritan Bay 35,960 678,670 

Delaware Bay 22,660 62,770 

Delaware River 19,380 239,480 

Chesapeake Bay 326,830 807,720 

Potomac River 0 124,510 
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Albemarle Sound 61,140 75,830 

Pamlico Sound 69,720 147,290 

Atlantic Ocean 362,800 1,109,280 

 

All Watersheds 908,020 3,465,940 

 4216 

 4217 

4218 To illustrate the nature of using the various sets of data and layers for analyses, and the 

4219 uncertainty in the population distributions within a census block, a second type of 

4220 analysis is useful. Because there is an uncertainty regarding where the population resides 

4221 within the census block, the relationship between the portion of a block’s area that is lost 

4222 to sea-level rise and the portion of the population residing in the vulnerable area is also 

4223 uncertain. Analysis estimates of vulnerable population are based on the percentage of a 

4224 census block that is inundated. For instance, the total 2000 population low and high 

4225 estimated counts for a 1-m sea-level rise for all watersheds are 908,020 and 3,465,940 for 

4226 “any inundation” of census block (see Table 7.1). However, homes are not necessarily 

4227 distributed uniformly throughout a census block. If 10 percent of a block is very low, for 

4228 example, that land may be part of a ravine, or below a bluff, or simply the low part of a 

4229 large parcel of land. Therefore, the assumption of uniform density would often overstate 

4230 the vulnerable population. Table 7.2 provides estimates that assume distributions other 

4231 than uniform density regarding the percentage of a block that must be vulnerable before 

4232 one assumes that homes are at risk. (This table presents the results by state rather than by 

4233 subregion.) If it is assumed that 90 percent of a block must be lost before homes are at 

4234 risk, and that the population is uniformly distributed across the highest 10 percent of the 

4235 block, then between 26,000 and 959,000 people live less than one meter above the 

4236 elevation spring high water (see NOAA, 2000 and Titus and Wang, 2008), allowing for 
CCSP 4.1 January 15, 2009

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4237 low and high elevation estimates. The estimated elevation of spring high water is used as 

4238 a boundary that distinguishes between normal inundation that would occur due to the 

4239 normal monthly highest tides and the added inundation due to a 1-m rise in sea level. The 

4240 spread of these estimated numbers depending upon the underlying assumptions listed at 

4241 the end of Table 7.2 underscore the uncertainty inherent in making population 

4242 assessments based in limited elevation data. As reported in Chapter 2, the disaggregation 

4243 of population density data into a more realistic spatial distribution would be to use a 

4244 Dasymetric mapping technique (Mennis, 2003) which holds promise for better analysis of 

4245 population, or other socioeconomic data, and to report statistical summaries of sea-level 

4246 rise impacts within vulnerable zones. 

 4247 

4248 The census information also allows further analysis of the population, broken down by 

4249 owner and renter-occupied residences. This information gives a sense of the 

4250 characterization of permanent home owners versus the more transient rental properties 

4251 that could translate to infrastructure and local economy at risk as well. The estimated 

4252 number of owner- and renter-occupied housing units in each watershed are shown in 

4253 Tables 7.3 and 7.4. Similar to the estimates in Table 7.1, these are high estimates for 

4254 which any portion of a particular census block is inundated. 

4255 Table 7.2 Low and High estimates of population living on land within one meter above spring high 

4256 water (Using assumptions other than uniform population density about how much of the land must 

4257 be lost before homes are lost). The reported numbers are subject to the caveat given at the end of 

4258 Section 7.2. 

4259 

 Percentage of census block within 1 m above spring high water 

991

 902 503 04

State Low High Low High Low High Low High 
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NY 780 421,900 780 470,900 2,610 685,500 42,320 1,126,290 

NJ 12,540 302,800 15,770 352,510 41,260 498,650 177,500 834,440 

DE 480 7,200 810 9,230 2,040 16,650 44,290 85,480 

PA 640 7,830 640 8,940 1,530 15,090 10,360 43,450 

VA 950 59,310 1,020 84,360 5,190 173,950 232,120 662,400 

MD 610 4,840 1,890 8,040 4,380 17,710 46,890 137,490 

DC 0 0 0 0 0 40 0 9,590 

NC 1,920 14,140 5,320 25,090 17,450 60,090 283,590 345,530 

Total 17,920 818,020 26,230 959,070 74,460 1,467,680 837,070 3,244,670 

1 Population estimates in this column assume that no homes are vulnerable unless 99 percent of the dry 

land in census block is within 1 m above spring high water. 

2 Population estimates in this column assume that no homes are vulnerable unless 90 percent of the dry 

land in census block is within 1 m above spring high water. 

3

 Population estimates in this column assume that no homes are vulnerable unless 50 percent of the dry 

land in census block is within 1 m above spring high water. 

4 Assumes uniform population distribution. 

 4260 

 4261 

4262 The actual coastal population potentially affected by sea-level rise also includes hotel 

4263 guests and those temporarily staying at vacation properties. Population census data on 

4264 coastal areas are rarely able to fully reflect the population and resultant economic 

4265 activity. The analysis presented in this Product does not include vacant properties used 

4266 for seasonal, recreational, or occasional use nor does it characterize the “transient” 

4267 population, who make up a large portion of the people found in areas close to sea level in 

4268 the Mid-Atlantic during at least part of the year. These temporary residents include the 

4269 owners of second homes. A significant portion of coastal homes are likely to be second 

4270 homes occupied for part of the year by owners or renters who list an inland location as 

4271 their permanent residence for purposes of census data. In many areas, permanent 
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4272 populations are expected to increase as retirees occupy their seasonal homes for longer 

4273 portions of the year. 

4274 Table 7.3 Low and high estimates of number of owner occupied residences in each watershed region 

4275 for a 1- meter sea-level rise scenario. The reported numbers are subject to the caveat given at the end 

4276 of Section 7.2.

 4277 

 4278 

Number of owner 

occupied residences

1- meter rise in sea level

Watershed 

Low 

Estimate 

High 

Estimate 

Long Island Sound 0 0

Peconic Bay 3,400 11,650

NYH-Raritan Bay 13,440 269,420

Delaware Bay 8,720 23,610

Delaware River 6,010 89,710

Chesapeake Bay 120,790 299,550

Potomac River 0 46,070

Albemarle Sound 22,760 28,720

Pamlico Sound 26,730 52,450

Atlantic Ocean 140,670 423,540

All Watersheds 342,520 1,244,720

 4279 

 4280 

4281 Table 7.4 Low and high estimates of the number of renter occupied housing units by watershed for a 

4282 1-meter sea-level rise scenario. The reported numbers are subject to the caveat given at the end of 

4283 Section 7.2. 

 4284 

 4285 

Number of renter occupied 

residences 

 1- meter rise in sea level 

Watershed Low Estimate High Estimate 

Long Island Sound 70 31,010 

Peconic Bay 520 2,460 

NYH-Raritan Bay 4,270 178,790 

Delaware Bay 2,630 5,880 

Delaware River 2,110 32,760 

Chesapeake Bay 35,880 84,630 

Potomac River 0 17,470 

Albemarle Sound 5,260 6,830 

Pamlico Sound 6,000 10,660 

Atlantic Ocean 40,220 154,500 
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All Watersheds 96,960 524,990 

 4286 

4287 7.4 LAND USE 

4288 The National Land Cover Database (USGS, 2001) is used to overlay land use onto the 

4289 DEMs for a 1-m scenario of sea-level rise. Major land-use categories used for this 

4290 analysis include: agriculture, barren land, developed land, forest, grassland, shrub-scrub, 

4291 water, and wetland. An estimate of the area of land categorized by land use for all 

4292 watersheds for the Mid-Atlantic is listed in Table 7.5. In the land-use tables, ranges of 

4293 uncertainty are provided by showing the low and high estimated size of the areas for the 

4294 1-m sea-level rise scenario. The high and low estimates show significant differences in 

4295 area and express the uncertainty in using this type of data layer integration. 

4296 Table 7.5 Mid-Atlantic All Watersheds Summary by Land Use category, depicting low and high 

4297 estimates of areas affected by a 1-meter sea-level rise (in hectares; 1 hectare is equal to 2.47 acres). 

4298 The reported numbers are subject to the caveat given at the end of Section 7.2. 

4299 

Area (in 

hectares) 1-meter rise in sea level 

Land Use 

Category Low Estimate High estimate 

Agriculture 43,180 141,800 

Barren Land 5,040 14,750 

Developed 11,970 92,950 

Forest 27,050 94,280 

Grassland 7,640 14,200 

Shrub-scrub 3,790 7,720 

Water 1,960 4,110 

Wetland 34,720 66,590 

 4300 

4301 The developed land-use acreage dominates northeast watersheds such as Long Island 

4302 Sound and New York Harbor, as well as the Atlantic Coast watershed. This is in contrast 

4303 to the Chesapeake Bay watershed that is dominated by agriculture and forest. 

4304 
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4305 Table 7.6 Low and high area estimates by land use category for the mid-Atlantic for a 1-meter sea4306 level rise scenario (in hectares). The reported numbers are subject to the caveat given at the end of 

4307 Section 7.2. 

 4308 

Area (in hectares) For a 1-meter rise in sea level 

Watershed Land Use 

Category 

Low Estimate High Estimate 

Long Island Sound Agriculture 0 20 

 Barren Land 0 180 

 Developed 90 3,280 

 Forest 0 210 

 Grassland 0 100 

 Shrub-scrub 0 60 

 Water 0 90 

 Wetland 0 530 

Peconic Bay Agriculture 20 360 

 Barren Land 20 340 

 Developed 100 1,580 

 Forest 50 760 

 Grassland 0 170 

 Shrub-scrub 0 70 

 Water 10 150 

 Wetland 70 770 

NYH-Raritan Bay Agriculture 30 870 

 Barren Land 40 340 

 Developed 330 21,090 

 Forest 40 720 

 Grassland 0 10 

 Shrub-scrub 0 10 

 Water 9 230 

 Wetland 140 2,600 

Delaware Bay Agriculture 950 9,590 

 Barren Land 280 1,040 

 Developed 210 1,760 

 Forest 590 4,280 

 Water 80 130 

 Wetland 900 2,420 

Delaware River Agriculture 310 8,190 

 Barren Land 20 560 

 Developed 430 10,960 

 Forest 90 2,130 

 Water 20 200 

 Wetland 330 3,010 

4309 

4310 
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4311 Table 7.6 (continued) Low and high area estimates by land use category for the mid-Atlantic for a 1-

4312 meter sea-level rise scenario (in hectares). The reported numbers are subject to the caveat given at 

4313 the end of Section 7.2. 

 4314 

Area (in hectares) For a 1- meter rise in sea level 

Watershed Land Use 

Category 

Low Estimate High Estimate 

Chesapeake Bay Agriculture 11,180 40,460 

 Barren Land 2,070 4,650 

 Developed 2,220 13,180 

 Forest 9,100 38,370 

 Water 160 660 

 Wetland 5,010 14,280 

 

Potomac River Agriculture 0 490 

 Barren Land 0 460 

 Developed 0 1,830 

 Forest 0 4,630 

 Water 0 130 

 Wetland 0 1,120 

 

Albemarle Sound Agriculture 16,440 12,810 

 Barren Land 320 5,900 

 Developed 2,460 8,270 

 Forest 8,680 4,950 

 Grassland 4,790 44,720 

 Shrub-scrub 2,720 10 

 Water 750 8,440 

 Wetland 14,480 920 

 

Pamlico Sound Agriculture 1,3130 3,9670 

 Barren Land 470 1,327 

 Developed 1,620 4,583 

 Forest 5,490 1,380 

 Grassland 2,010 3,570 

 Shrub-scrub 670 1,430 

 Water 210 290 

 Wetland 8,500 12,070 

 

Atlantic Ocean Agriculture 1,090 8,220 

 Barren Land 1,800 5,410 

 Developed 4,470 29,210 

 Forest 2,980 11,540 

 Grassland 820 2,010 

 Shrub-scrub 380 1,360 

 Water 690 1,210 

 Wetland 5,260 10,870 

 4315 

4316 
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4317 7.5 TRANSPORTATION INFRASTRUCTURE 

4318 7.5.1 General Considerations 

4319 The coupling of sea-level rise with storm surge is one of the most important 

4320 considerations for assessing impacts of sea-level rise on infrastructure. Sea-level rise 

4321 poses a risk to transportation in ensuring reliable and sustained transportation services. 

4322 Transportation facilities serve as the life-line to communities, and inundation of even the 

4323 smallest component of an intermodal system can result in a much larger system shut4324 down. For instance, even though a port facility or a railway terminal may not be affected, 

4325 the access roads to the port and railways could be, thus forcing the terminal to cease or 

4326 curtail operation. 

 4327 

4328 Sea-level rise will reduce the 100-year flood return periods and will lower the current 

4329 minimum critical elevations of infrastructure such as airports, tunnels, and ship terminals 

4330 (Jacob et al., 2007). Some low-lying railroads, tunnels, ports, runways, and roads are 

4331 already vulnerable to flooding and a rising sea level will only exacerbate the situation by 

4332 causing more frequent and more serious disruption of transportation services. It will also 

4333 introduce problems to infrastructure not previously affected by these factors. 

 4334 

4335 The CCSP SAP 4.7 (Kafalenos et al., 2008) discusses impacts of sea-level rise on 

4336 transportation infrastructure by addressing the impacts generally on highways, transit 

4337 systems, freight and passenger rail, marine facilities and waterways, aviation, pipelines, 

4338 and implications for transportation emergency management and also specifically for the 
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4339 U.S. Gulf Coast region. Each of these transportation modes also apply to the mid-Atlantic 

4340 region. 

 4341 

4342 One impact of sea-level rise not generally mentioned is the decreased clearance under 

4343 bridges. Even with precise timing of the stage of tide and passage under fixed bridges, 

4344 sea-level rise will affect the number of low water windows available for the large vessels 

4345 now being built. Bridge clearance has already become an operational issue for major 

4346 ports, as evidenced by the installation of real-time reporting air gap/bridge clearance 

4347 sensors in the NOAA Physical Oceanographic Real-Time System (PORTS) (NOAA, 

4348 2005). Clearance under bridges has become important because the largest vessels need to 

4349 synchronize passage with the stage of tide and with high waters due to weather effects 

4350 and high river flows. To provide pilots with this critical information, air gap sensors in 

4351 the Mid-Atlantic have been deployed at the Verrazano Narrows Bridge at the entrance to 

4352 New York Harbor, the Chesapeake Bay Bridge located in mid-Chesapeake Bay, and on 

4353 bridges at both ends of the Chesapeake and Delaware Canal connecting the upper 

4354 Chesapeake Bay with mid-Delaware Bay (NOAA, 2008). 

 4355 

4356 There are other potential navigation system effects as well because of sea-level rise. 

4357 Estuarine navigation channels may need to be extended landward from where they 

4358 terminate now to provide access to a retreating shoreline. The corollary benefit is that less 

4359 dredging will be required in deeper water because a rising water elevation will provide 

4360 extra clearance. 

 4361 
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4362 This discussion is limited in scope to transportation infrastructure. Complete 

4363 infrastructure assessments need to include other at-risk engineering and water control 

4364 structures such as spillways, dams, levees and locks, with assessments of their locations 

4365 and design capacities. 

4366 

4367 7.5.2 Recent U.S. Department of Transportation Studies 

4368 The U.S. Department of Transportation (US DOT) studied the impacts of sea-level rise 

4369 on transportation, as discussed in US DOT (2002). The study addresses the impacts of 

4370 sea-level rise on navigation, aviation, railways and tunnels, and roads, and describes 

4371 various options to address those impacts, such as elevating land and structures, protecting 

4372 low-lying infrastructure with dikes, and applying retreat and accommodation strategies. 

4373 

4374 The US DOT has recently completed an update of the first phase of a study, “The 

4375 Potential Impacts of Global Sea Level Rise on Transportation Infrastructure” (US DOT, 

4376 2008). The study covers the mid-Atlantic region and is being implemented in two phases: 

4377 Phase 1 focuses on North Carolina, Virginia, Washington, D.C., and Maryland. Phase 2 

4378 focuses on New York, New Jersey, Pennsylvania, Delaware, South Carolina, Georgia, 

4379 and the Atlantic Coast of Florida. This second phase is expected to be completed by the 

4380 end of 2008. This study was designed to produce rough quantitative estimates of how 

4381 future climate change, specifically sea-level rise and storm surge, might affect 

4382 transportation infrastructure on a portion of the East Coast of the United States. The 

4383 major purpose of the study is to aid policy makers responsible for transportation 

4384 infrastructure including roads, rails, airports, and ports in incorporating potential impacts 
CCSP 4.1 January 15, 2009

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4385 of sea-level rise in planning and design of new infrastructure and in maintenance and 

4386 upgrade of existing infrastructure. 

 4387 

4388 The report considers that the rising sea level, combined with the possibility of an increase 

4389 in the number of hurricanes and other severe weather related incidents, could cause 

4390 increased inundation and more frequent flooding of roads, railroads, and airports, and 

4391 could have major consequences for port facilities and coastal shipping. 

4392 

4393 The GIS approach (US DOT, 2008) produces maps and statistics that demonstrate the 

4394 location and quantity of transportation infrastructure that could be regularly inundated by 

4395 sea-level rise and at risk to storm surge under a range of potential sea-level rise scenarios. 

4396 The elevation data for the transportation facilities is the estimated elevation of the land 

4397 upon which the highway or rail line is built.) 

 4398 

4399 The three basic steps involved in the US DOT analysis help identify areas expected to be 

4400 regularly inundated or that are at-risk of periodic flooding due to storm surge: 

4401  Digital Elevation Models were used to evaluate the elevation in the coastal areas 

4402 and to create tidal surfaces in order to describe the current and future predicted 

4403 sea water levels. 

4404  Land was identified that, without protection, will regularly be inundated by the 

4405 ocean or is at risk of inundation due to storm surge under each sea-level rise 

4406 scenario. 
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4407  Transportation infrastructure was identified that, without protection, will regularly 

4408 be inundated by the ocean or be at risk of inundation due to storm surge under the 

4409 given sea-level rise scenario. 

4410 

4411 The US DOT study compares current conditions (for 2000) to estimates of future 

4412 conditions resulting from increases in sea level. The study examines the effects of a range 

4413 of potential increases in sea level up to 59 centimeters (cm). The estimates of increases in 

4414 sea level are based upon two sources: (1) the range of averages of the Atmosphere-Ocean 

4415 General Circulation Models for all 35 SRES (Special Report on Emission Scenarios), as 

reported in Figure 11.1218 4416 from the IPCC Third Assessment Report and (2) the highest 

4417 scenario (59 cm) that corresponds with the highest emission scenario modeled by the 

4418 IPCC Fourth Assessment Report (Meehl et al., 2007). 

 4419 

4420 As noted above, the US DOT study was not intended to create a new estimate of future 

4421 sea levels or to provide a detailed view of a particular area under a given scenario; 

4422 similarly, the results should not be viewed as predicting the specific timing of any 

4423 changes in sea levels. The inherent value of this study is the broad view of the subject and 

4424 the overall estimates identified. Due to the overview aspect of the US DOT study, and 

4425 systematic and value uncertainties in the involved models, this US DOT analysis 

4426 appropriately considered sea-level rise estimates from the IPCC reports as uniform sea4427 level rise estimates, rather than estimates for a particular geographic location. The 

4428 confidence stated by IPCC in the regional distribution of sea-level change is low, due to 

 

18 IPCC3, WG1, c.11, page 671. <http://www.grida.no/climate/ipcc_tar/wg1/pdf/TAR-11.PDF> 
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4429 significant variations in the included models; thus, it would be inappropriate to use the 

4430 IPCC model series to estimate local changes. Local variations, whether caused by 

4431 erosion, subsidence (sinking of land) or uplift, local steric (volumetric increase in water 

4432 due to thermal expansion) factors or even coastline protection, were not considered in this 

study19 4433 . Given the analysis and cautionary statements presented in Chapter 2 regarding 

4434 using the USGS National Elevation Data (NED) with small increments of sea-level rise 

4435 as used in this US DOT study, only representative statistical estimations are presented 

4436 here for just the largest 59-cm scenario. Because the 59-cm sea-level rise scenario is 

4437 within the statistical uncertainty of the elevation data, the statistics are representative of 

4438 the types of analyses that could be done if accurate elevation data were available. 

 4439 

4440 The study first estimates the areas that would be regularly inundated or at risk during 

4441 storm conditions, given nine potential scenarios of sea-level rise. It defines regularly 

4442 inundated areas or base sea level as NOAA’s mean higher high water (MHHW) for 2000. 

4443 The regularly inundated areas examined are the regions of the coast that fall between 

4444 MHHW in 2000 and the adjusted MHHW levels (MHHW in 2000 plus for several 

4445 scenarios up to 59 cm). For at-risk areas or areas that could be affected by storm 

4446 conditions, the study uses a base level of NOAA’s highest observed water levels 

4447 (HOWL) for 2000, and adjusts this upwards based on the nine sea-level rise scenarios. 

4448 The at-risk areas examined are those areas falling between the adjusted MHHW levels 

4449 and the adjusted HOWL levels. 

 

19 It is recognized that protection such as bulkheads, seawalls or other protective measures may exist or be 

built that could protect specific land areas but, due to the overview nature of this study, they were not 

included in the analysis. 
CCSP 4.1 January 15, 2009

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 4450 

4451 A sample of output tables from the US DOT study are shown in Table 7.7, which covers 

4452 the state of Virginia. The numerical values for length and area in Tables 7.7 and 7.8 have 

4453 been rounded down to the nearest whole number to be conservative in the estimates for 

4454 lengths and areas at risk. This was done to avoid overstating the estimates as there are no 

4455 estimates of uncertainty or error in the numbers presented. 

 4456 

4457 Table 7.7 A representative output table for Virginia showing estimates of regularly inundated and 

4458 at-risk areas and lengths under the 59 centimeter (cm) scenario, the highest level examined in the 

4459 U.S. Department of Transportation (US DOT) study. The percent affected represent the proportion 

4460 for the entire state, not only coastal areas (From US DOT, 2008). The reported numbers are subject 

4461 to the caveat given at the end of Section 7.2.

4462 

 4463 

4464 Table 7.7 indicates there is some transportation infrastructure at risk under the 59-cm sea 

4465 level rise scenario. Less than 1 percent (7 kilometers [km] of interstates, 12 km of non4466 interstate principal arterials) of the Virginia highways examined in the US DOT study 

4467 would be regularly inundated, while an additional 1 percent (16 km of interstates, 62 km 

State of Virginia Statistics 

 For a 59-cm rise in sea level 

Regularly 

Inundated 

At-Risk to Storm 

Surge Total 

 By Length in Kilometers 

(km) 

Length 

(km) 

 Percent 

Affected 

Length 

(km) 

 Percent 

Affected 

Length 

(km) 

 Percent 

Affected 

Interstates 7 0% 16 1% 23 1%

Non-Interstate Principal 

Arterials 12 0% 62 1% 74 2%

NHS Minor Arterials 2 0% 9 0% 11 0%

National Highway System 

(NHS) 22 0% 64 1% 86 2%

Rails 19 0% 64 1% 83 1%

 By Area in Hectares 

Area 

(Hectares) 

 Percent 

Affected 

Area 

(Hectares) 

 Percent 

Affected 

Area 

(Hectares) 

 Percent 

Affected 

Ports 60 11% 132 24% 192 35%

Airport Property 277 2% 365 3% 642 4%

Airport Runways 29 2% 37 3% 66 5%

Total Land Area Affected 68,632 1% 120,996 1% 189,628 2%
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4468 of non-interstate principal arterials) could be affected by storm conditions. It should be 

4469 noted that these percentages are given as a percentage of the total for each state, not only 

4470 for coastal counties. 

 4471 

4472 Table 7.8 provides the areas and percent of total areas affected of the various regularly 

4473 inundated and at-risk transportation categories for the US DOT (2008) 59-cm sea-level 

4474 rise scenario for Washington, D.C., Virginia, Maryland, and North Carolina. 

 4475 

4476 Table 7.8 Summary of estimated areas and lengths for the total of regularly inundated and at risk 

4477 infrastructure combined for a 59 centimeters (cm) increase in sea-level rise (based on US DOT, 

4478 2008). The reported numbers are subject to the caveat given at the end of Section 7.2.

4479 

Total, Regularly 

Inundated and At Risk 

For a 59-cm increase in 

sea level Washington, D.C. Virginia Maryland North Carolina 

By Length in 

Kilometers(km) 

Length 

(km) 

 % 

Affected 

Length 

(km) 

% 

Affected 

Length 

(km) 

 % 

Affected 

Length 

(km) 

 % 

Affected 

Interstates 1 5% 25 1% 2 0% 1 0% 

Non-Interstate Principal 

Arterials 7 4% 75 2% 21 1% 130 2% 

Minor Arterials 0 0% 11 0% 66 4% 209 4% 

National Highway System 

(NHS) 7 5% 87 2% 19 1% 305 4% 

Rails 3 5% 84 1% 44 2% 105 1% 

By Area in hectares Hectares 

 % 

Affected Hectares 

 % 

Affected Hectares 

 % 

Affected Hectares 

 % 

Affected 

Ports n/a n/a 192 35% 120 32% 88 47% 

Airport Property n/a n/a 642 4% 59 1% 434 3% 

Airport Runways n/a n/a 66 5% 1 0% 27 2% 

Total Land Area Affected 968 6% 189,628 2% 192,044 8% 743,029 6% 

 4480 

 4481 

4482 Based on the small percentage (1 to 5 percent) statistics in Table 6.8, the combination of 

4483 rising sea level and storm surge appears to have the potential to affect only a small 
CCSP 4.1 January 15, 2009

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4484 portion of highways and roads across the region. However, because these transportation 

4485 systems are basically networks, just a small disruption in one portion could often be 

4486 sufficient to have far-reaching effects, analogous to when a storm causes local closure of 

4487 a major airport, producing ripple effects nation-wide due to scheduling and flight 

4488 connections and delays. Local flooding could have similar ripple effects in a specific 

4489 transportation sector. 

 4490 

4491 North Carolina appears slightly more vulnerable to regular inundation due to sea-level 

4492 rise, both in absolute terms and as a percentage of the state highways: less than 1 percent 

4493 of interstates (0.3 km), 1 percent of non-interstate principal arterials (59 km) and 2 

4494 percent of National Highway System (NHS) minor arterials (93 km) in the state would be 

4495 regularly inundated given a sea-level rise of 59 cm. This US DOT study focuses on larger 

4496 roads but there are many miles of local roads and collectors that could also be affected. In 

4497 general, areas at risk to storm surge are limited. Washington, D.C. shows the greatest 

4498 vulnerability on a percentage basis for both interstates and NHS roads for all sea-level 

4499 rise scenarios examined. 

 4500 

4501 Please refer to the US DOT study for complete results, at: 

4502 <http://climate.dot.gov/publications/potential_impacts_of_global_sea_level_rise/index.ht

4503 ml> 

4504 

4505 
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4506 CHAPTER 7 REFERENCES 

4507 Bin, P., C. Dumas, B. Poulter, and J. Whitehead, 2007: Measuring the Impacts of Climate 

4508 Change on North Carolina Coastal Resources. Department of Economics, 

4509 Appalachian State University, Boone, NC, 91 pp. 

4510 <http://econ.appstate.edu/climate/ >

4511 CCSP (Climate Change Science Program), 2008: Impacts of Climate Change and 

4512 Variability on Transportation Systems and Infrastructure: Gulf Coast Study, 

4513 Phase I. [Savonis, M.J., V.R. Burkett and J.R. Potter (eds.)]. Climate Change 

4514 Science Program Synthesis and Assessment Product 4.7. U.S. Department of 

4515 Transportation, Washington DC, 445 pp. 

4516 Crossett, K.M., T.J. Culliton, P.C. Wiley, and T.R. Goodspeed, 2004: Population Trends 

4517 along the Coastal United States 1980-2008. NOAA National Ocean Service, 

4518 Special Projects Office, [Silver Spring, MD], 47 pp. 

4519 Crowell, M., S. Edelman, K. Coulton, and S. McAfee, 2007: How many people live in 

4520 coastal areas? Journal of Coastal Research, 23(5), iii-vi. 

4521 GeoLytics, 2001: CensusCD 2000. Version 1.1. GeoLytics, Inc., East Brunswick, NJ.

4522 Gornitz, V., S. Couch, and E.K. Hartig, 2001: Impacts of sea level rise in the New York 

4523 City metropolitan area. Global and Planetary Change, 32(1), 61-88. 

4524 Jacob, K., V. Gornitz, and C. Rosenzweig, 2007: Vulnerability of the New York City 

4525 metropolitan area to coastal hazards, including sea-level rise: Inferences for urban 

4526 coastal risk management and adaptation policies. In: Managing Coastal 

4527 Vulnerability. [McFadden, L., R.J. Nicholls, and E.C. Penning-Rowsell (eds.)]. 

4528 Elsevier, Amsterdam and Oxford, pp. 139-156. 

4529 Kafalenos, R.S., K.J. Leonard, D.M. Beagan, V.R. Burkett, B.D. Keim, A. Meyers, D.T. 

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4532 change and variability for Gulf Coast transportation? In: Impacts of Climate 
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4533 Change and Variability on Transportation Systems and Infrastructure: Gulf Coast 

4534 Study, Phase I. [Savonis, M.J., V.R. Burkett, and J.R. Potter (eds.)]. Climate 

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4537 Kleinosky, L.R., B. Yarnal, and A. Fisher, 2006: Vulnerability of Hampton Roads, 

4538 Virginia to storm-surge flooding and sea level rise. Natural Hazards,40(1), 43-70. 

4539 Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. 

4540 Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. 

4541 Weaver, and Z.-C. Zhao, 2007: Global climate projections. In: Climate Change 

4542 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth 

4543 Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, 

4544 S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. 

4545 Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, pp. 

4546 747-845. 

4547 Mennis, J., 2003: Generating surface models of population using dasymetric mapping. 

4548 Professional Geographer, 55(1), 31-42. 

4549 NOAA (National Oceanic and Atmospheric Administration), 2000: Tide and Current 

4550 Glossary. NOAA National Ocean Service, Silver Spring, MD, 29 pp. 

4551 <http://tidesandcurrents.noaa.gov/publications/glossary2.pdf> 

4552 NOAA (National Oceanic and Atmospheric Administration), 2005: Microwave Air Gap4553 Bridge Clearance Sensor Test, Evaluation, and Implementation Report. NOAA 

4554 technical report NOS CO-OPS 042. NOAA National Ocean Service Ocean 

4555 Systems Test and Evaluation Program, Silver Spring, MD, 111 pp. 

4556 NOAA (National Oceanic and Atmospheric Administration), 2008: The Physical 

4557 Oceanographic Real-Time System (PORTS). [Website] 

4558 <http://tidesandcurrents.noaa.gov/ports.html> 
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4559 Titus, J.G. and P. Cacela, 2008: Uncertainty ranges associated with EPA’s estimates of 

4560 the area of land close to sea level. Section 1.3b in: Background Documents 

4561 Supporting Climate Change Science Program Synthesis and Assessment Product 

4562 4.1: Coastal Elevations and Sensitivity to Sea Level Rise [Titus, J.G. and E.M. 

4563 Strange (eds.)]. EPA 430R07004. U.S. Environmental Protection Agency, 

4564 Washington, DC, pp. 69-133. 

4565 <http://epa.gov/climatechange/effects/coastal/background.html>

4566 Titus, J.G. and J. Wang, 2008: Maps of lands close to sea level along the middle Atlantic 

4567 coast of the United States: an elevation data set to use while waiting for LIDAR. 

4568 Section 1.1 in: Background Documents Supporting Climate Change Science 

4569 Program Synthesis and Assessment Product 4.1: Coastal Elevations and 

4570 Sensitivity to Sea Level Rise [Titus, J.G. and E.M. Strange (eds.)]. EPA 

4571 430R07004. U.S. Environmental Protection Agency, Washington, DC, pp. 2-44.

4572 U.S. Census Bureau, 2000: United States Census 2000. [Website] U.S. Census Bureau, 

4573 Washington, DC. <http://www.census.gov/main/www/cen2000.html> 

4574 U.S. Census Bureau, 2007: American FactFinder Glossary. [U.S. Census Bureau, 

4575 Washington, DC.] <http://factfinder.census.gov/home/en/epss/glossary_a.html> 

4576 US DOT (Department of Transportation), 2002: The Potential Impacts of Climate 

4577 Change on Transportation, Workshop Proceedings; J. Titus: Does Sea Level Rise 

4578 matter to Transportation along the Atlantic Coast? October 1-2, 2002, Summary 

4579 and Discussion Papers. 

4580 <http://www.epa.gov/climatechange/effects/downloads/Transportation_Paper.pdf

4581 > 

4582 US DOT, 2008: The Potential Impacts of Global Sea Level Rise on Transportation 

4583 Infrastructure, Phase 1 - Final Report: the District of Columbia, Maryland, North 

4584 Carolina and Virginia. Center for Climate Change and Environmental 

4585 Forecasting, U.S. Department of Transportation, Washington DC. 
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4586 USGS (U.S. Geological Survey), 2001: National Land Cover Database 2001. U.S. 

4587 Geological Survey, Sioux Falls, SD. <http://www.mrlc.gov/mrlc2k_nlcd.asp> 

4588 
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4589 Chapter 8. Public Access 

4590 

4591 Author: James G. Titus, U.S. EPA 

 4592 

 4593 

4594 KEY FINDINGS 

4595  The Public Trust Doctrine provides access along the shore below mean high 

4596 water, but it does not include the right to cross private property to reach the shore. 

4597 Therefore, access to the shore varies greatly, depending on the availability of 

4598 roads and public paths to the shore. 

4599  Rising sea level alone does not have a significant impact on either access to the 

4600 shore or access along the shore; however, responses to sea-level rise can decrease 

4601 or increase access. 

4602  Shoreline armoring generally eliminates access along estuarine shores, by 

4603 eliminating the intertidal zone along which the public has access. New Jersey has 

4604 regulatory provisions requiring shorefront property owners in some urban areas to 

4605 provide alternative access inland of new shore protection structures. Other mid4606 Atlantic states lack similar provisions to preserve public access. 

4607  Beach nourishment has minimal impact in areas with ample access; however, it 

4608 can increase access in areas where public access is restricted. Federal and state 

4609 policies generally require public access to and along a shore before providing 

4610 subsidized beach nourishment. In several communities, property owners have 

4611 assigned public access easements in return for beach nourishment. 
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4612 Responses based on allowing shores to retreat generally have minimal impact on public 

4613 access to and along the shore. 

 4614 

4615 8.1 INTRODUCTION 

4616 Rising sea level does not inherently increase or decrease public access to the shore, but 

4617 the response to sea-level rise can. Beach nourishment tends to increase public access 

4618 along the shore because federal (and some state) laws preclude beach nourishment 

4619 funding unless the public has access to the beach that is being restored. Shoreline 

4620 armoring, by contrast, can decrease public access along the shore, because the intertidal 

4621 zone along which the public has access is eliminated. 

 4622 

4623 This Chapter examines the impacts of sea-level rise on public access to the shore and 

4624 describes existing public access to the shore (Section 8.2), the likely impacts of shoreline 

4625 changes (Section 8.3), and how responses to sea-level rise might change public access 

4626 (Section 8.4) The focus of this Chapter is on the public’s legal right to access the shore, 

not on the transportation and other infrastructure that facilitates such access20 4627 . 

4628 

4629 8.2 EXISTING PUBLIC ACCESS AND THE PUBLIC TRUST DOCTRINE 

4630 The right to access tidal waters and shores is well established. Both access to and 

4631 ownership of tidal wetlands and beaches is defined by the “Public Trust Doctrine”, which 

4632 is part of the common law of all the mid-Atlantic states. According to the Public Trust 

 

20 Chapter 7 discusses impacts on transportation infrastructure. 
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4633 Doctrine, navigable waters and the underlying lands were publicly owned at the time of 

4634 statehood and remain so today. 

 4635 

4636 The Public Trust Doctrine is so well established that it often overrides specific 

4637 governmental actions that seem to transfer ownership to private parties (Lazarus, 1986; 

4638 Rose, 1986). Many courts have invalidated state actions that extinguished public 

4639 ownership or access to the shore (Illinois Central R.R. v. Illinois; Arnold v. Mundy; see 

4640 also Slade, 1990). Even if a land deed states that someone’s property extends into the 

4641 water, the Public Trust Doctrine usually overrides that language and the public still owns 

the shore21 4642 . In those cases when government agencies do transfer ownership of coastal 

4643 land to private owners, the public still has the right to access along the shore for fishing, 

4644 hunting, and navigation, unless the state explicitly indicates an intent to extinguish the 

4645 public trust (Lazarus, 1986; Slade, 1990). 

 4646 

4647 Figure 8.1 illustrates some key terminology used in this Chapter. Along sandy shores 

4648 with few waves, the wet beach lies between mean high water and mean low water. 

4649 (Along shores with substantial waves, the beach at high tide is wet inland from the mean 

4650 high water mark, as waves run up the beach.) The dry beach extends from approximately 

4651 mean high water inland to the seaward edge of the dune grass or other terrestrial plant 

4652 life, sometimes called the vegetation line (Slade, 1990). The dune grass generally extends 

4653 inland from the point where a storm in the previous year struck with sufficient force to 

4654 erode the vegetation (Pilkey, 1984), which is well above mean high water. Along marshy 

 

21 The “mean low water states” (i.e., Virginia, Delaware, and Pennsylvania), are an exception. See Figure 

8.2. 
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4655 shores, mudflats are found between mean low water and mean sea level, low marsh is 

4656 found between mean sea level and mean high water, and high marsh extends from mean 

4657 high water to spring high water. Collectively, the lands between mean high water and 

4658 mean low water (mudflats, low marsh, and wet beaches) are commonly known as 

4659 tidelands. 

4660 

4661 MSL = Mean Sea level 

4662 MLW = Mean Low Level 

4663 MHW = Mean High Water 

4664 SHW = Spring High Water 

4665 Storm = Average Annual Storm Tide 

4666 

4667 Figure 8.1 Legal and geological tideland zonation. The area below mean high water is usually publicly 

4668 owned, and in all cases is subject to public access for fishing and navigation. Along the ocean, the dry 

4669 beach above mean high water may be privately owned; however, in several states the public has an 

4670 easement. Along the bay, the high marsh above mean high water is also privately owned, but wetland 

4671 protection laws generally prohibit or discourage development. 

 4672 

4673 The Public Trust Doctrine includes these wetlands and beaches because of the needs 

4674 associated with hunting, fishing, transportation along the shore, and landing boats for rest 

4675 or repairs (Figure 8.2). In most states, the public owns all land below the high water mark 

4676 (Slade, 1990) which is generally construed as mean high water. The precise boundary 
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4677 varies in subtle ways from state to state. The portion of the wet beach inland of mean 

4678 high water resulting from wave runup has also been part of the public trust lands in some 

4679 cases (see e.g., State v. Ibbison and Freedman and Higgins [undated]). Thus, in general, 

4680 the public trust includes mudflats, low marsh, and wet beach, while private parties own 

4681 the high marsh and dry beach (Figure 8.3). Nevertheless, Figure 8.4.shows that there are 

4682 some exceptions. In Pennsylvania, Delaware, and Virginia, the publicly owned land 

4683 extends only up to the low water mark (Slade, 1990). In New York, by contrast, the 

4684 inland extent of the public trust varies; in some areas the public owns the dry beach as 

well22 4685 . The public has also obtained ownership to some beaches through government 

4686 purchase, land dedication by a developer, or other means (see Slade 1990; Figure 8.5). 

4687 

4688 Figure 8.2. Traditional purposes of the Public Trust Doctrine include fishing and transportation along the 

4689 shore. (a) New Jersey side of Delaware River, below Delaware Memorial Bridge (March 2003). (b) Beach 

4690 provided primary access to homes along the beach at Surfside, Texas (May 2003). 

 4691 

 

22 e.g. Dolphin Lane Assocs. v. Town of Southampton, 333 N.E.2d 358, 360 (N.Y. 1975) 
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4692 

4693 Figure 8.3. Privately owned dunes adjacent to publicly owned intertidal beach. Southold, New York. 

4694 (September 2006). 

4695 

4696 

Below mean low water; access to wet 

beach for hunting, fishing, navigation 

Wet beach below high water

Wet and dry beach

Wet beach; access along dry

The Public Owns: 

4697 

4698 Figure 8.4 The public’s common law interest in the shores of various coastal states. Source: Titus (1998) 

 4699 

 4700 
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4701 

4702 Figure 8.5 Public beach owned by local government. Beaches that are owned by local governments 

4703 sometimes have access restrictions for nonresidents. Atlantic Beach, New York (September, 2006). 

4704 

4705 Ownership, however, is only part of the picture. In Pennsylvania, Delaware, and Virginia, 

4706 the Public Trust Doctrine provides an easement along the tidelands for hunting, fishing, 

4707 and navigation. In New Jersey, the Public Trust Doctrine includes access along the dry

4708 part of the beach for recreation, as well as the traditional public trust purposes (Matthews 

4709 v. Bay Head). Other states have gradually obtained easements for access along some dry 

4710 beaches either through purchases or voluntary assignment by the property owners in 

4711 return for proposed beach nourishment. The federal policy precludes funding for beach 

4712 nourishment unless the public has access (USACE, 1996). Some state laws specify that 

4713 any land created with beach nourishment belong to the state (e.g., MD. CODE ANN., NAT.

4714 RES. II 8-1103 [1990]). 

 4715 

4716 The right to access along the shore does not mean that the public has a right to cross 

4717 private land to get to the shore. Unless there is a public road or path to the shore, access 

4718 along the shore is thus only useful to those who either reach the shore from the water or 

4719 have permission to cross private land. Although the public has easy access to most ocean 

4720 beaches and large embayments like Long Island Sound and Delaware Bay, the access 
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4721 points to the shores along most small estuaries are widely dispersed (e.g., Titus, 1998). 

4722 However, New Jersey is an exception: its Public Trust Doctrine recognizes access to the 

4723 shore in some cases (Matthews v. Bay Head); and state regulations require new 

4724 developments with more than three units along all tidal waters to include public access to 

4725 the shore (NJAC 7:7E-8.11 [d-f]). Given the federal policy promoting access, the lack of 

4726 access to the shore has delayed several beach nourishment projects. To secure the 

4727 funding, many communities have improved public access to the shore, not only with 

4728 more access ways to the beach, but also by upgrading availability of parking, restrooms, 

4729 and other amenities (e.g., New Jersey, 2006). 

 4730 

4731 8.3 IMPACT OF SHORE EROSION ON PUBLIC ACCESS 

4732 The rule that property lines retreat whenever shores erode gradually has been part of the 

4733 common law for over one thousand years (County of St. Clair v. Lovingston; DNR v. 

4734 Ocean City), assuming that the shoreline change is natural. Therefore, as beaches migrate 

4735 landward, the public’s access rights to tidal wetlands and beaches do not change, they 

4736 simply migrate landward along with the wetlands and beaches. Nevertheless, the area to 

4737 which the public has access may increase or decrease, if sea-level rise changes the area of 

4738 wetlands or beaches. 

 4739 

4740 When riparian landowners caused the shorelines to advance seaward, the common law 

4741 did not vest owners with title to land reclaimed from the sea, although legislatures 

4742 sometimes have (ALR, 1941). If beach nourishment or a federal navigation jetty 

4743 artificially creates new land, a majority of states (e.g., MD. CODE ANN., ENVIR. 16-201) 
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4744 award the new land to the riparian owner if he or she is not responsible for creating the 

4745 land (Slade, 1990); a minority of states (e.g., Garrett v. State of New Jersey; N.C. Gen 

4746 Stat §146-6[f]) vest the state public trust with the new land. Although these two 

4747 approaches were established before sea-level rise was widely recognized, legal scholars 

4748 have evaluated the existing rules in the analogous context of shore erosion (e.g., Slade, 

4749 1990). Awarding artificially created land to the riparian owner has two practical 

4750 advantages over awarding it to the state. First, determining what portion of a shoreline 

4751 change resulted from some artificial causes, (e.g., sedimentation from a jetty or a river 

4752 diversion) is much more difficult than determining how much the shoreline changed 

4753 when the owner filled some wetlands. Second, this approach prevents the state from 

4754 depriving shorefront owners of their riparian access by pumping sand onto the beach and 

4755 creating new land (e.g., Board of Public Works v. Larmar Corp). A key disadvantage is 

4756 that federal and state laws generally prevent the use of public funds to create land that 

4757 accrues to private parties. Therefore, part of the administrative requirements of a beach 

4758 nourishment project is to obtain easements or title to the newly created land. Obtaining 

4759 those rights can take time, and significantly delayed a beach nourishment project at 

4760 Ocean City, Maryland (Titus, 1998). 

 4761 

4762 Sea-level rise causes shores to retreat both through inundation and erosion. Although the 

4763 case law generally assumes that the shore is moving as a result of sediment being 

4764 transported, inundation and shore erosion are legally indistinguishable. Among the causes 

4765 of natural shoreline change, the major legal distinction has been between gradual and 

4766 imperceptible shifts, and sudden shifts that leave land intact but on the other side of a 
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4767 body of water, often known as “avulsion”. Shoreline erosion changes ownership; avulsion 

4768 does not. If an inlet formed 200 meters (m) west of one’s home during a storm after 

4769 which an existing inlet 200 m east of the home closed, an owner would still own her 

4770 home because this shoreline change is considered to be avulsion. But if the inlet 

4771 gradually migrated 400 m west, entirely eroding the property but later creating land in the 

4772 same location, all of the newly created land will belong to the owner to the east (see 

4773 Figure 8.6). The public trust has the same rights of access to beaches created through 

4774 avulsion as to beaches migrating by gradual erosion in New York (People v. Steeplechase 

4775 Park Co.) and North Carolina (Kalo, 2005). In other states, the law is less clear (Slade, 

4776 1990). 

 4777 
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4778 

4779 Figure 8.6 Impact of inlet migration and inlet breech on land ownership. In this example, the island to the 

4780 west is privately owned while the island to the east is a county park. 

 4781 

4782 Because the public has access to the intertidal zone as long as it exists, the direct effect of 

4783 sea-level rise on public access depends on how the intertidal zone changes. Along an 

4784 undeveloped or lightly developed ocean beach, public access is essentially unchanged as 

4785 the beach migrates inland (except perhaps where a beach is in front of a rocky cliff, 

4786 which is rare in the Mid-Atlantic). If privately owned high marsh becomes low marsh, 

4787 then the public will have additional lands on which they may be allowed to walk 

private 

private 

private 

private 

privately

private 

privately

county

county

county

county

county

county

Initial Condition 

10 years later 

20 years later 

30 years later 

After storm creates new inlet 

Initial Condition 

Gradual inlet migration 

privatel privatel county

county private privatel

After old inlet closes 

Inlet breech followed by inlet closing 
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4788 (provided that environmental regulations to protect the marsh do not prohibit it). 

4789 Conversely, if sea-level rise reduces the area of low marsh, then pedestrian access may be 

4790 less, although areas that convert to open water remain in the public trust. 

 4791 

4792 8.4 IMPACT OF RESPONSES TO SEA-LEVEL RISE ON PUBLIC ACCESS 

4793 Although sea-level rise appears to have a small direct effect on public access to the shore, 

4794 responses to sea-level rise can have a significant impact, especially in developed areas. 

4795 Along developed bay beaches, by contrast, public access along the shore can be 

4796 eliminated if the shorefront property owner erects a bulkhead, because the beach is 

4797 eventually eliminated. A number of options are available for state governments that wish 

4798 to preserve public access along armored shores, such as public purchases of the 

4799 shorefront (Figure 8.7) and protecting public access in permits for shore protection 

4800 structures. New Jersey requires pathways to be at least 5 m (16 feet [ft]) wide between 

4801 the shore and new developments with more than three units along urban tidal rivers 

4802 (NJAC 7.7E-8.11[e]; see also Section A1.D.2 in Appendix 1) and some other areas, and 

4803 has a more general requirement to preserve public access elsewhere. (NJAC 7.7E-8.11 [d] 

4804 [1]). However, single-family homes are generally exempt (NJAC 7.7E-8.11[f] [7])—and 

4805 other mid-Atlantic states have no such requirements. Therefore, sea-level rise has reduced 

4806 public access along many estuarine shores and is likely to do so in the future as well. 

4807 
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4808 

4809 Figure 8.7 Public access along a bulkheaded shore. In North Beach, Maryland, one block of Atlantic 

4810 Avenue is a walkway along Chesapeake Bay (May,2006). 

 4811 

4812 Government policies related to beach nourishment, by contrast, set a minimum standard 

4813 for public access (USACE, 1996), which often increases public access along the shore. 

4814 Along the ocean shore from New York to North Carolina, the public does not have access 

along the dry beach under the Public Trust Doctrine (except in New Jersey)23 4815 . However, 

4816 once a federal beach nourishment project takes place, the public gains access. Beach 

4817 nourishment projects have increased public access along the shore in Ocean City, 

4818 Maryland and Sandbridge (Virginia Beach), Virginia, where property owners had to 

4819 provide easements to the newly created beach before the projects began (Titus, 1998; 

4820 Virginia Marine Resources Commission, 1988). 

 4821 

4822 Areas where public access to the beach is currently limited by a small number of access 

4823 points include the area along the Outer Banks from Southern Shores to Corolla, North 

4824 Carolina (NC DENR, 2008); northern Long Beach Township, New Jersey (USACE, 

 

23 In some places, the public has obtained access through government purchase, land dedication by a 

developer, or other means. See Slade (1990). 
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4825 1999); and portions of East Hampton, South Hampton, Brookhaven, and Islip along the 

4826 South Shore of Long Island, New York (Section A1.A.2 in Appendix 1). In West 

4827 Hampton, landowners had to provide six easements for perpendicular access from the 

4828 street to the beach in order to meet the New York state requirement of public access 

4829 every one-half mile (see Section A1.A.2 in Appendix 1). A planned $71 million beach 

4830 restoration project for Long Beach Island has been stalled (Urgo, 2006), pending 

4831 compliance with the New Jersey state requirement of perpendicular access every one4832 quarter mile (USACE, 1999). An additional 200 parking spaces for beachgoers must also 

4833 be created in Northern Long Beach Township (USACE, 1999). Private communities 

4834 along Delaware Bay have granted public access to the beaches in return for state 

4835 assistance for beach protection (Beaches 2000 Planning Group, 1988). 

 4836 

4837 If other communities with limited access seek federal beach nourishment in the future, 

4838 public access would similarly increase. Improved access to the beach for the disabled 

4839 may also become a requirement for future beach nourishment activities (e.g., Rhode 

4840 Island CRMC, 2007). This is not to say that all coastal communities would provide public 

4841 access in return for federal funds. But aside from the portion of North Carolina southwest 

4842 of Cape Lookout, the Mid-Atlantic has no privately owned gated barrier islands, unlike 

4843 the Southeast, where several communities have chosen to expend their own funds on 

4844 beach nourishment rather than give up their exclusivity. 

 4845 

4846 Ultimately, the impact of sea-level rise on public access will depend on the policies and 

4847 preferences that prevail over the coming decades. Sometimes the desire to protect 
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4848 property as shores erode will come at the expense of public access. Sometimes it will 

4849 promote an entire re-engineering of the coast, which under today’s policies generally 

4850 favors public access. It is possible that rising sea level is already starting to cause people 

4851 to rethink the best way to protect property along estuarine shores (NRC, 2007) to protect 

4852 the environmental benefits of natural shores. If access along estuarine shores becomes a 

4853 policy goal, techniques are available for preserving public access as sea level rises. 

 4854 

4855 
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4856 CHAPTER 8 REFERENCES

4857 * Indicates non-peer reviewed literature; available upon request

4858 

4859 ALR, 1941: Annotation: Waters: rights in respect of changes by accretion or reliction due 

4860 to artificial conditions. American Law Review, 134, 467-472. 

4861 Arnold v. Mundy, 6 N.J.L. 1 (1821) 

4862 Beaches 2000 Planning Group, 1988: Beaches 2000: Report to the Governor 

4863 [Delaware], June 21, 1988. 

4864 Board of Pub. Works v. Larmar Corp., 277 A.2d 427, 436 (Md. 1971) 

4865 County of St. Clair v. Lovingston, 90 U.S. (23 Wall.) 46, 66-69 (1874) (quoting the 

4866 Institutes of Justinian, Code Napoleon, and Blackstone for the universal rule that a 

4867 boundary shifts with the shore) 

4868 DNR (Department of Natural Resources) v. Ocean City, 332 A.2d 630-638 (Md. 1975) 

4869 Freedman, J. and M. Higgins, Undated: What Do You Mean by High Tide? The Public 

4870 Trust Doctrine in Rhode Island. Rhode Island Coastal Resources Management 

4871 Council, Wakefield, 5 pp. 

4872 <http://www.crmc.state.ri.us/presentations/presentations/wdymbht.pdf> 

4873 Garrett v. State [of New Jersey]. 118 N.J. Super. 594 (Ch. Div. 1972), 289 A.2d 542 

4874 (N.J. Super 1972). 

4875 Illinois Central R.R. v. Illinois, 146 U.S. 387 (1982) 

4876 Kalo, J.J., 2005: North Carolina oceanfront property and public waters and beaches: the 

4877 rights of littoral owners in the twenty-first century. North Carolina Law Review, 

4878 83, 1427-1506. 

4879 Lazarus, R.J., 1986: Changing conceptions of property and sovereignty in natural 

4880 resources: questioning the Public Trust Doctrine. Iowa Law Review, 71, 631. 
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4881 Matthews v. Bay Head Improvement Association, 471 A.2d 355-358 (N.J. 1984) 

4882 New Jersey, 2006: Highlights of the Public Access Proposal. New Jersey Department of 

4883 Environmental Protection Coastal Management Program, 4 pp. 

4884 <http://www.nj.gov/dep/cmp/access/pa_rule_highlights.pdf> 

4885 NC DENR (North Carolina Department of Environment and Natural Resources), 2008: 

4886 Public Beach & Waterfront Access Interactive Mapping.

4887 <http://dcm2.enr.state.nc.us/Access/sites.htm> 

4888 NRC (National Research Council), 2007: Mitigating Shore Erosion Along Sheltered 

4889 Coasts. National Academies Press, Washington DC, 188 pp. 

4890 People v. Steeplechase Park Co., 82 Misc 247, 255-256; 143, N.Y.S. 503, 509 

4891 Pilkey, O.H., Jr. (ed.), 1984: Living with the East Florida Shore. Duke University Press, 

4892 Durham, NC, 259 pp. 

4893 Rhode Island CRMC (Coastal Resources Management Council), 2007: Coastal 

4894 Resources Management Program, as Amended (a.k.a. the “Red Book”). State of 

4895 Rhode Island Coastal Resources Management Council, Providence, RI. 

4896 <http://www.crmc.state.ri.us/regulations/programs/redbook.html> 

4897 Rose, C., 1986: The comedy of the commons: custom, commerce, and inherently public 

4898 property. University of Chicago Law Review, 53, 711, 715-723. 

4899 Slade, D.C., 1990: Lands, waters and living resources subject to the Public Trust 

4900 Doctrine. In: Putting the Public Trust Doctrine to Work. Coastal States 

4901 Organization, Washington, DC, pp. 13, 59. 

4902 State v. Ibbison. 448 A.2d 728 (Rhode Island, 1982).Titus, J.G., 1998: Rising seas, 

4903 coastal erosion, and the takings clause: how to save wetlands and beaches without 

4904 hurting property owners. Maryland Law Review, 57(4), 1277-1399. 
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4905 Titus, J.G., 1998: Rising seas, coastal erosion and the taking clause: how to save 

4906 wetlands and beaches without hurting property owners. Maryland Law Review, 

4907 57(4), 1277-1399. 

4908 * Urgo, J.L., 2006: A standoff over sand: A state beach project requires more public 

4909 access, but in Loveladies and North Beach, it’s meeting some resistance. 

4910 Philadelphia Inquirer, June 11, 2006. 

4911 USACE (U.S. Army Corps of Engineers), 1996: Digest of Water Resources Policies and 

4912 Authorities 14-1: Shore Protection. EP 1165-2-1, U.S. Army Corps of Engineers, 

4913 Washington, DC. 

4914 USACE (U.S. Army Corps of Engineers), 1999: Barnegat Inlet to Little Egg Inlet. Final 

4915 Feasibility Report and Integrated Final Environmental Impact Statement. 

4916 USACE (U.S. Army Corps of Engineers), and New Jersey Department of Environmental 

4917 Protection, 1999: Barnegat Inlet to Little Egg Inlet, Final Feasibility and 

4918 Integrated Final Environmental Impact Statement. 

4919 Virginia Marine Resources Commission, 1988: Criteria for the Placement of Sandy 

4920 Dredged Material along Beaches in the Commonwealth. Regulation VAC 20-

4921 400-10 et seq. <http://www.mrc.virginia.gov/regulations/fr400.shtm> 

 4922 

4923 
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4924 Chapter 9. Coastal Flooding, Floodplains and Coastal 

4925 Zone Management Issues 

4926 

4927 Lead Authors: Stephen K. Gill, NOAA; Doug Marcy, NOAA 

4928 

4929 Contributing Author: Zoe Johnson, Maryland Department of Natural Resources 

4930 

4931 KEY FINDINGS 

4932  Rising sea level increases the vulnerability of coastal areas to flooding. The 

4933 higher sea level provides a higher base for storm surges to build upon. It also 

4934 diminishes the rate at which low-lying areas drain, thereby increasing the risk of 

4935 flooding from rainstorms. Increased shore erosion can further increase flood 

4936 damages by removing protective dunes, beaches, and wetlands, thus leaving 

4937 previously protected properties closer to the water's edge. In addition to flood 

4938 damages, many other effects, responses, and decisions are likely to occur during 

4939 or in the immediate aftermath of severe storms. Beach erosion and wetlands loss 

4940 often occur during storms, and the rebuilding phase after a severe storm often 

4941 presents the best opportunity for developed areas to adapt to future sea-level rise. 

4942  Coastal storms could have higher flooding potential in the future due to higher sea 

4943 levels relative to the land. 

4944  The most recent Federal Emergency Management Agency (FEMA) study on the 

4945 potential effects of sea-level rise on the Nation’s flood insurance program was 
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4946 published in 1991. Because of the uncertainties in the projections of potential 

4947 changes in sea level at the time and the ability of the rating system to respond 

4948 easily to a 0.3 meter rise in sea level, the 1991 FEMA study (FEMA, 1991) 

4949 concluded that no immediate program changes were needed. 

4950  The mid-Atlantic coastal zone management community is increasingly 

4951 recognizing that sea-level rise is a high-risk coastal hazard as evidenced by the 

4952 recent comprehensive analyses and studies needed to make recommendations for 

4953 state policy formulation performed by Maryland. 

 4954 

4955 9.1 INTRODUCTION 

4956 This Chapter examines the effects of sea-level rise on coastal floodplains and on coastal 

4957 flooding management issues confronting the U.S. Federal Emergency Management 

4958 Agency (FEMA), the floodplain management community, the coastal zone management 

4959 community, coastal resource managers, and the public, including private industry. Sea4960 level rise is just one of numerous complex scientific and societal issues these groups face. 

4961 There is also uncertainty in the local rate of sea-level change, which needs to be taken 

4962 into account along with the interplay with extreme storm events (see Chapter 1). In 

4963 addition, impacts of increased flooding frequency and extent on coastal areas can be 

4964 significant for marine ecosystem health and human health in those areas (Boesch et al., 

4965 2000). This Chapter provides a discussion of the current state of knowledge and provides 

4966 assessments for a range of actions being taken by many state and federal agencies and 

4967 other groups related to coastal flooding. 

4968 
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4969 9.2 PHYSICAL CHARACTERISTICS 

4970 9.2.1 Floodplain 

4971 In general, a floodplain is any normally dry land surrounding a natural water body that 

4972 holds the overflow of water during a flood. Because they border water bodies, floodplains 

4973 have been popular sites to establish settlements, which subsequently become susceptible 

4974 to flood-related disasters. Most management and regulatory definitions of floodplains 

4975 apply to rivers; however, open-coast floodplains characterized by beach, dunes, and 

4976 shrub-forest are also important since much of the problematic development and 

4977 infrastructure is concentrated in these areas (see Chapter 3 for a detailed description of 

4978 this environment). 

 4979 

4980 The federal regulations governing FEMA (2008) via Title 44 of the Code of Federal 

4981 Regulations defines floodplains as “any land area susceptible to being inundated by flood 

4982 waters from any source”. The FEMA (2002) Guidelines and Specifications for Flood 

4983 Hazard Mapping Partners Glossary of Terms defines floodplains as: 

4984 1. A flat tract of land bordering a river, mainly in its lower reaches, and consisting of 

4985 alluvium deposited by the river. It is formed by the sweeping of the meander belts 

4986 downstream, thus widening the valley, the sides of which may become some 

4987 kilometers apart. In time of flood, when the river overflows its banks, sediment is 

4988 deposited along the valley banks and plains. 

4989 2. Synonymous with the 100-year floodplain, which is defined as the land area 

4990 susceptible to being inundated by stream derived waters with a 1-percent-annual4991 chance of being equaled or exceeded in a given year. 
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4992 The National Oceanic and Atmospheric Administration (NOAA) National Weather 

4993 Service (NWS) defines a floodplain as the portion of a river valley that has been 

4994 inundated by the river during historic floods. None of these formal definitions of 

4995 floodplains include the word “coastal”. However, as river systems approach coastal 

4996 regions, river base levels approach sea level, and the rivers become influenced not only 

4997 by stream flow, but also by coastal processes such as tides, waves, and storm surges. In 

4998 the United States, this complex interaction takes place near the governing water body, 

4999 either open ocean, estuaries, or the Great Lakes. 

 5000 

5001 The slope and width of the coastal plain determines the size and inland extent of coastal 

5002 influences on river systems. Coastal regions are periodically inundated by tides, and 

5003 frequently inundated by high waves and storm surges. Therefore, a good working 

5004 definition of a coastal floodplain, borrowing from the general river floodplain definition, 

5005 is any normally dry land area in coastal regions that is susceptible to being inundated by 

5006 water from any natural source, including oceans (e.g., tsunami runup, coastal storm surge, 

5007 relative sea-level rise), rivers, streams, and lakes. 

 5008 

5009 Floodplains generally contain unconsolidated sediments, often extending below the bed 

5010 of the stream or river. These accumulations of sand, gravel, loam, silt, or clay are often 

5011 important aquifers; the water drawn from them is prefiltered compared to the water in the 

5012 river or stream. Geologically ancient floodplains are often revealed in the landscape by 

5013 terrace deposits, which are old floodplain deposits that remain relatively high above the 

5014 current floodplain and often indicate former courses of rivers and streams. 
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 5015 

5016 Floodplains can support particularly rich ecosystems, both in quantity and diversity. 

5017 These regions are called riparian zones or systems. Wetting of the floodplain soil releases 

5018 an immediate surge of nutrients, both those left over from the last flood and those from 

5019 the rapid decomposition of organic matter that accumulated since the last flood. 

5020 Microscopic organisms thrive and larger species enter a rapid breeding cycle. 

5021 Opportunistic feeders (particularly birds) move in to take advantage of these abundant 

5022 populations. The production of nutrients peaks and then declines quickly; however, the 

5023 surge of new growth endures for some time, thus making floodplains particularly 

5024 valuable for agriculture. Markedly different species grow within floodplains compared to 

5025 surrounding regions. For instance, certain riparian trees species (that grow in floodplains 

5026 near river banks) tend to be very tolerant of root disturbance and thus tend to grow 

5027 quickly, compared to different tree species growing in a floodplain some distance from a 

5028 river. 

5029 

5030 9.3 POTENTIAL IMPACTS OF SEA-LEVEL RISE ON COASTAL 

5031 FLOODPLAINS 

5032 Assessing the impacts of sea-level rise on coastal floodplains is a complicated task, 

5033 because those impacts are coupled with impacts of climate change on other coastal and 

5034 riverine processes and can be offset by human actions to protect life and property. 

5035 Impacts may range from extended periods of drought and lack of sediments to extended 

5036 periods of above-normal freshwater runoff and associated sediment loading. Some 

5037 seasons may have higher than normal frequency and intensity of coastal storms and 
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5038 flooding events. Impacts will also depend on construction and maintenance of dikes, 

5039 levees, waterways, and diversions for flood management. 

 5040 

5041 With no human intervention, the hydrologic and hydraulic characteristics of coastal and 

5042 river floodplain interactions will change with sea-level rise. Fundamentally, the 

5043 floodplains will become increasingly vulnerable to inundation. In tidal areas, the tidal 

5044 inundation characteristics of the floodplain may change with the range of tide and 

5045 associated tidal currents increasing with sea-level rise. With this inundation, floodplains 

5046 will be vulnerable to increased coastal erosion from waves, river and tidal currents, 

5047 storm-induced flooding, and tidal flooding. Upland floodplain boundaries will be 

5048 vulnerable to horizontal movement. Coastal marshes could be vulnerable to vertical 

5049 buildup or inundation (see Chapter 4 for further discussion). 

 5050 

5051 In a study for the state of Maine (Slovinsky and Dickson, 2006), the impacts of sea-level 

5052 rise on coastal floodplains were characterized by marsh habitat changes and flooding 

5053 implications. The coast of Maine has a significant spring tidal range of 2.6 to 6.7 meters 

5054 (m) (8.6 to 22.0 feet [ft]), such that impacts of flooding are coupled with the timing of 

5055 storms and the highest astronomical tides on top of sea-level rise. The study found that 

5056 there was increasing susceptibility to inlet and barrier island breaches where existing 

5057 breach areas were historically found, increased stress on existing flood-prevention 

5058 infrastructure (levees, dikes, roads), and a gradual incursion of low marsh into high marsh 

5059 with development of a steeper bank topography. On the outer coast, impacts included 

5060 increased overwash and erosion. 
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 5061 

5062 In addition, the effects of significant local or regional subsidence of the land will add to 

5063 the effects of sea-level rise on coastal floodplains. Regional areas with significant 

5064 subsidence include the Mississippi River Delta region (AGU, 2006), the area around the 

5065 entrance to the Chesapeake Bay (Poag, 1997), and local areas such as the Blackwater 

5066 National Wildlife Refuge on the Eastern Shore of Maryland (Larsen et al., 2004). 

 5067 

5068 9.4 POTENTIAL EFFECTS OF SEA-LEVEL RISE ON THE IMPACTS OF 

5069 COASTAL STORMS 

5070 The potential interaction among increased sea levels, storm surges, and upstream rivers is 

5071 complex. The storm surge of any individual storm is a function of storm intensity defined 

5072 by storm strength and structure, forward speed, landfall location, angle of approach, and 

5073 local bathymetry and topography. However, the absolute elevation of the maximum water 

5074 levels observed relative to the land during a storm (operationally defined as storm tides) 

5075 are a combination of the storm surge defined above, plus the non-storm-related 

5076 background water level elevations due to the stage of tide, the time of year (sea level 

5077 varies seasonally), river flow, local shelf circulation patterns (such as the Gulf Loop 

5078 Current/eddies and the El Niño-Southern Oscillation [especially on the west coast]). 

5079 Storm surge "rides” on top of these other variations, including sea level rise (NOAA, 

5080 2008). Storm surge can travel several hundred kilometers up rivers at more than 40 

5081 kilometers (km) (25 miles [mi]) per hour, as on the Mississippi River, where storm surge 

5082 generated by land-falling hurricanes in the Gulf of Mexico can be detected on stream 
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5083 gauges upstream of Baton Rouge, Louisiana, more than 480 km (300 mi) from the mouth 

5084 of the river (Reed and Stucky, 2005). 

5085 

5086 Both NWS (for flood forecasting) and FEMA (for insurance purposes and land use 

5087 planning) recognize the complexity of the interactions among sea-level rise, storm surge, 

5088 and river flooding. For instance, NWS uses both a hurricane storm surge model (the Sea, 

5089 Lakes, and Overland Surge from Hurricanes [SLOSH] model, Jelesnianski et al., 1992) 

5090 and a riverine hydraulic model (the Operational Dynamic Wave Model) to forecast 

5091 effects of storm surge on river stages on the Mississippi River. The two models are 

5092 coupled such that the output of the storm surge model is used as the downstream 

5093 boundary of the river model. This type of model coupling is needed to determine the 

5094 effects of sea-level rise and storm surge on riverine systems. Other modeling efforts are 

5095 starting to take into account river and coastal physical process interactions, such as use of 

5096 the two-dimensional hydrodynamic model (the Advanced Circulation Model or 

5097 ADCIRC; Luettich et al., 1992) on the Wacammaw River in South Carolina to predict 

5098 effects of storm surge on river stages as far inland as Conway, 80 km (50 mi) from the 

5099 Atlantic Ocean (Hagen et al., 2004). These model coupling routines are becoming 

5100 increasingly more common and have been identified as future research needs by such 

5101 agencies as NOAA and the U.S. Geological Survey (USGS), as scientists strive to model 

5102 the complex interactions between coastal and riverine processes. As sea level rises, these 

5103 interactions will become ever more important to the way the coastal and riverine 

5104 floodplains respond (Pietrafesa et al., 2006). 

 5105 

5106 9.4.1 Historical Comparison at Tide Stations 
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5107 There is the potential for higher elevations of coastal flooding from coastal storms over 

5108 time as sea level rises relative to the land. Looking at storms in historical context and 

5109 accounting for sea level change is one way to estimate maximum potential storm water 

5110 levels. For example, this assessment can be made by analyzing the historical record of 

5111 flooding elevations observed at NOAA tide stations in the Chesapeake Bay. The 

5112 following analysis compares the elevation of the storm tides for a particular storm at a 

5113 particular tide station; that is from when it occurred historically to as if the same exact 

5114 storm occurred today under the exact same conditions, but adjusted for relative sea level 

5115 rise at that station. These comparisons are enabled because NOAA carefully tabulates 

5116 water level elevations over time relative to a common reference datum that is connected 

5117 to the local land elevations at each tide station. From this, relative sea level trends can be 

5118 determined and maximum water level elevations recorded during coastal storms can be 

5119 directly compared over the time period of record (Zervas, 2001). The relative sea level 

5120 trend provides the numerical adjustment needed depending on the date of each storm. 

 5121 

5122 The NOAA post-hurricane report (Hovis, 2004) on the observed storm tides of Hurricane 

5123 Isabel assessed the potential effects of sea-level rise on maximum observed storm tides 

5124 for four long-term tide stations in the Chesapeake Bay. Prior to Hurricane Isabel, the 

5125 highest water levels reached at the NOAA tide stations at Baltimore, Maryland; 

5126 Annapolis, Maryland; Washington, D.C.; and Sewells Point, Virginia occurred during the 

5127 passage of an unnamed hurricane in August, 1933. At the Washington, D.C. station, the 

5128 1933 hurricane caused the third highest recorded water level, surpassed only by river 

5129 floods in October 1942 and March 1936. Hurricane Isabel caused water levels to exceed 
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5130 the August 1933 levels at Baltimore, Annapolis and Washington, D.C. by 0.14, 0.31, and 

5131 0.06 meters (m), respectively. At Sewells Point, the highest water level from Hurricane 

5132 Isabel was only 0.04 m below the level reached in August 1933. Zervas (2001) calculated 

5133 sea-level rise trends for Baltimore, Annapolis, Washington, and Sewells Point of 3.12, 

5134 3.53, 3.13, and 4.42 millimeters (mm) per year, respectively. Using these rates, the time 

5135 series of monthly highest water level were adjusted for the subsequent sea-level rise up to 

5136 the year 2003. The resulting time series, summarized in Tables 9.1, 9.2, 9.3, and 9.4, 

5137 indicate the highest level reached by each storm as if it had taken place in 2003 under the 

5138 same conditions, thus allowing an unbiased comparison of storms. The purpose of Tables 

5139 9.1 through 9.4 is to show that the relative ranking of the flooding elevations from 

5140 particular storm events changes at any given station once the adjustment for sea level 

5141 trend is taken into account. The 1933 hurricane, especially, moves up in ranking at 

5142 Baltimore and Washington, DC once adjusted for the local sea level trend. Hurricane 

5143 Hazel moved up in ranking at Annapolis. If the 1933 hurricane occurred today under the 

5144 same conditions, it would have had the highest water level of record at Baltimore, not 

5145 Hurricane Isabel. Elevations are relative to the tidal datum of mean higher high water 

5146 (MHHW). Noting the earlier discussion in this section on the operational difference 

5147 between storm surge and the actual observed storm tide elevation, the tables suggest that, 

5148 while not affecting intensity of storms and the resulting amplitude of storm surges, sea5149 level rise could increasingly add to the potential maximum water level elevations 

5150 observed relative to the land during coastal storms. 

 5151 

5152 Table 9.1 Five highest water levels for Baltimore, Maryland in meters above mean higher high 

5153 water. Ranked first by absolute elevation and then ranked again after adjustment for sea level rise.

5154 
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5155 Absolute water level Corrected for sea-level rise to 2003 

5156 Event Date Elevation (m) Event Date Elevation (m) 

Hurricane 

Isabel 

Sep 2003 1.98 Hurricane Aug 1933 2.06 

Hurricane Aug 1933 1.84 Hurricane 

Isabel 

Sep 2003 1.98 

Hurricane 

Connie 

Aug 1955 1.44 Hurricane 

Connie 

Aug 1955 1.59 

Hurricane 

Hazel 

Oct 1954 1.17 Hurricane Aug 1915 1.38 

Hurricane Aug 1915 1.11 Hur. Hazel Oct 1954 1.32 

5157 

5158 

5159 Table 9.2 Five highest water levels for Annapolis, Maryland in meters above mean higher high 

5160 water. Ranked first by absolute elevation and then ranked again after adjustment for sea level rise. 

5161 

5162 Absolute water level. Corrected for sea-level rise to 2003 

5163 Event Date Elevation (m) Event Date Elevation (m) 

Hurricane 

Isabel 

Sep 2003 1.76 Hurricane 

Isabel 

Sep 2003 1.76 

Hurricane Aug 1933 1.45 Hurricane Aug 1933 1.69 

Hurricane 

Connie 

Aug 1955 1.08 Hurricane 

Connie 

Aug 1955 1.25 

Hurricane Fran Sep 1996 1.04 Hurricane 

Hazel 

Oct 1954 1.19 

Hurricane 

Hazel 

Oct 1954 1.02 Hurricane Fran Sep 1996 1.06 

5164 

5165 

5166 Table 9.3 Five highest water levels for Washington, D.C. in meters above mean higher high water.

5167 Ranked first by absolute elevation and then ranked again after adjustment for sea level rise.

5168 

5169 Absolute water level Corrected for sea-level rise to 2003 

5170 Event Date Elevation (m) Event Date Elevation (m) 

Flood Oct 1942 2.40 Flood Oct 1942 2.59 

Flood Mar 1936 2.25 Flood Mar 1936 2.46 

Hurricane 

Isabel 

Sep 2003 2.19 Hurricane Aug 1933 2.35 

Hurricane Aug 1933 2.13 Hurricane 

Isabel 

Sep 2003 2.19 

Flood Apr 1937 1.70 Flood Apr 1937 1.91 

5171 

5172 

5173 Table 9.4 Five highest water levels for Sewells Point, Virginia in meters above mean higher high 

5174 water. Ranked first by absolute elevation and then ranked again after adjustment for sea level rise.

5175 

5176 Absolute water level Corrected for sea-level rise to 2003 

5177 Event Date Elevation (m) Event Date Elevation (m) 

Hurricane Aug 1933 1.60 Hurricane Aug 1933 1.91 
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Hurricane 

Isabel 

Sep 2003 1.56 Hurricane 

Isabel 

Sep 2003 1.56 

Winter Storm Mar 1962 1.36 Winter Storm Mar 1962 1.54 

Hurricane Sep 1936 1.21 Hurricane Sep 1936 1.50 

Winter Storm Feb 1998 1.16 Hurricane Sep 1933 1.33 

5178 

5179 

5180 9.4.2 Typical 100-Year Storm Surge Elevations Relative to Mean Higher High 

5181 Water within the Mid-Atlantic Region 

5182 A useful application of long-term tide gauge data is a return frequency analysis of the 

5183 monthly and annual highest and lowest observed water levels. This type of analysis 

5184 provides information on how often extreme water levels can be expected to occur (e.g., 

5185 once every 100 years, once every 50 years, once every 10 years?) On the East Coast and 

5186 in the Gulf of Mexico, hurricanes and winter storms interact with the wide, shallow, 

5187 continental shelf to produce large extreme storm tides. A generalized extreme value 

5188 distribution can be derived for each station after correcting the values for the long-term 

5189 sea-level trend (Zervas, 2005). Theoretical exceedance probability statistics give the 99-

5190 percent, 50-percent, 10-percent, and 1-percent annual exceedance probability levels. 

5191 These levels correspond to average storm tide return periods of 1, 2, 10, and 100 years. 

5192 The generalized extreme value analyses are run on the historical data from each tide 

5193 station. Interpolating exceedance probability results away from the tide station location is 

5194 not recommended as elevations of tidal datums and the extremes are highly localized. 

5195 Figures 9.1 and 9.2 show the variations in these statistics along the mid-Atlantic coast. 

5196 Figure 9.1 shows exceedance elevations above local mean sea level (LMSL) at mid5197 Atlantic stations relative to the 1983 to 2001 National Tidal Datum Epoch (NTDE). 
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5198 Figure 9.2 shows the same exceedance elevations, except the elevations are relative to 

5199 mean higher high water (MHHW) computed for the same 1983 to 2001 NTDE. 

 5200 

5201 In Figure 9.1, the elevations relative to LMSL are highly correlated with the range of tide 

5202 at each station (Willets Point, New York has a very high range of tide, 2.2 m), except for 

5203 the 1-percent level at Washington D.C., which is susceptible to high flows of the 

5204 Potomac River. Due to their varying locations, the 1-percent elevation level varies the 

5205 most among the stations. Figure 9.2 shows a slightly geographically decreasing trend in 

5206 the elevations from north to south. 

 5207 

Exceedance Probability Elevations: Mid-Atlantic Tide 

Stations - Relative to Local Mean Sea Level

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

New London,CT Bridgeport, CT

New Rochelle, NY

Port Jefferson, NY

Willets Point, NY

Sandy Hook, NJ

The Battery, NYC

Atlantic City, NJ

Cape May, NJ Lewes, DE

Philadelphia,PA

CBBT, VA

Sewells Point,VA Portsmouth, VA Gloucester Point, VA

Kiptopeake, VA

Cambridge, MD

Solomons Island, MD Annapolis, MD Baltimore, MD Lewisetta, VA

Colonial Beach, VA

Washington, DC

Beaufort, NC Wilmington, NC

Elevation Relative to Local MSL (meters)

1%

10%

50%

99%

MHHW

NAVD88

5208 

5209 Figure 9.1 Exceedance probabilities for mid-Atlantic tide stations relative to local mean sea level. 
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5210 

Exceedance Probability Elevations: Mid-Atlantic Tide 

Stations Relative to MHHW

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

New London,CT

Bridgeport, CT

New Rochelle, NY

Port Jefferson, NY

Willets Point, NY

Sandy Hook, NJ

The Battery, NYC

Atlantic City, NJ

Cape May, NJ

Lewes, DE

Philadelphia,PA

CBBT, VA

Sewells Point,VA

Portsmouth, VA

Gloucester Point, VA

Kiptopeake, VA

Cambridge, MD

Solomons Island, MD

Annapolis, MD

Baltimore, MD

Lewisetta, VA

Colonial Beach, VA

Washington, DC

Beaufort, NC

Wilmington, NC

Elevation Above MHHW (meters)

1%

10%

50%

99%

5211 

5212 Figure 9.2 Exceedance probabilities at mid-Atlantic tide stations relative to mean higher high water. 

 5213 

5214 Examining the effects of sea-level rise on the highest water level during a hurricane or 

5215 coastal storm does not provide a complete picture because the impacts of sea-level rise on 

5216 the duration of the inundation can be as important as the maximum height. Sea-level rise, 

5217 coupled with any increased frequency of extra-tropical storms (nor’easters), may also 

5218 increase the durations of inundation from extra-tropical storms (NOAA, 1992). For 

5219 instance, some of the most severe impacts of nor’easters are generally felt in bays where 

5220 water can get in but not out for several days as the storms slowly transit parallel to the 

5221 coast. 

 5222 
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5223 Other federal agencies, such as NOAA, have been sponsoring applied research programs 

5224 to bring an integrated approach to understanding the effects of sea-level rise into 

5225 operations. One such study on the ecological effects of sea-level rise is discussed in Box 

5226 9.1 (NOAA, 2007), which is due to come out with a final report in 2009. 

5227 

5228 9.5 FLOODPLAIN MAPPING AND SEA-LEVEL RISE 

5229 A nationwide study was performed by FEMA (1991) (see Box 9.2) in which costs for 

5230 remapping floodplains were estimated at $150,000 per county (in 1991 dollars) or $1,500 

5231 per map panel (the standard map presentation used by FEMA). With an estimated 283 

5232 counties (5,050 map panels) potentially in need of remapping, the total cost of restudies 

5233 and remapping was estimated at $30 million (in 1991). Based on this study and assuming 

5234 that the maps are revised on a regular basis, such an undertaking today would cost about 

5235 $46.5 million. The 1991 study concluded that “there are no immediate program changes 

5236 needed” (FEMA, 1991). 

 5237 

5238 At present, FEMA periodically revises Flood Insurance Rate Maps (FIRMs) to reflect 

5239 new engineering, scientific, and imagery data. In addition, under their Map 

5240 Modernization and post-Map Modernization Programs, FEMA intends to assess the 

5241 integrity of the flood hazard data by reviewing the flood map inventory every five years. 

5242 Where the review indicates the flood data integrity has degraded the flood maps (due to 

5243 outdated data and known changes in hydrology and floodplain elevation since the last 

5244 maps were issued), updates will be provided or new studies will be performed. Whenever 

5245 an update or remap of coastal areas is made, changes that had occurred in the interim due 
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5246 to sea-level rise will be accounted for. An upcoming Impact of Climate Change on the 

5247 National Flood Insurance Program study (scheduled to begin at the end of fiscal year 

5248 2008 and last 1.5 years) may come up with different conclusions than the 1991 study and 

5249 cause FEMA to rethink the issue. 

 5250 

5251 The primary floodplain management adjustment for sea-level rise is the local increase in 

5252 required base flood elevation (BFE) for new construction. Elevating a building’s lowest 

5253 floor above predicted flood elevations by a small additional height, generally 0.3 to 0.9 

5254 meters above National Flood Insurance Program (NFIP) minimum height requirements, 

5255 is termed a freeboard addition. Freeboard additions are generally justified for other more 

5256 immediate purposes including the lack of safety factor in the 1-percent flood and 

5257 uncertainties in prediction and modeling. FEMA encourages freeboard adoptions through 

5258 the Community Rating System, which offers community-wide flood insurance premium 

5259 discounts for higher local standards and for individuals through premium discounts for 

5260 higher than minimum elevation on higher risk buildings. Velocity flood zones, known as 

5261 V Zones or coastal high hazard areas, have been identified by FEMA as areas "where 

5262 wave action and/or high velocity water can cause structural damage in the 100-year 

5263 flood", a flood with a 1 percent chance of occurring or being exceeded in a given year. 

5264 FEMA also defines A Zones as areas inundated in a 100-year storm event that experience 

5265 conditions of less severity, for example, wave heights less than 1 m, than conditions 

5266 experienced in V Zones. Accurate determination of the spatial extent of these zones is 

5267 vital to understanding the level of risk for a particular property or activity. 

 5268 
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5269 A recent historical overview of FEMA’s Coastal Risk Assessment process is found in 

5270 Crowell et al. (2007), and includes overviews of the FEMA Map Modernization 

5271 Program, revised coastal guidelines, and FEMA’s response to recommendations of a 

5272 Heinz Center report, Evaluation of Erosion Hazards (Heinz Center, 2000). 

 5273 

5274 9.6 STUDIES OF FUTURE COASTAL CONDITIONS AND FLOODPLAIN 

5275 MAPPING 

5276 9.6.1 FEMA Coastal Studies 

5277 Currently, communities can opt to use future conditions (projected) hydrology for 

mapping according to FEMA rules established in December 200124 5278 . Showing future 

5279 conditions flood boundaries has been provided at the request of some communities in 

5280 Flood Map Modernization, but it is not a routine product. As outlined in those rules, 

5281 showing a future condition boundary in addition to the other boundaries normally shown 

5282 on a FIRM is acceptable. FEMA shows future condition boundaries for informational 

5283 purposes only and carries with it no additional requirements for floodplain management. 

5284 Insurance would not be rated using a future condition boundary. The benefits showing 

5285 future condition flood boundaries relate to the fact that future increases in flood risk can 

5286 lead to significant increases in both calculated and experienced flood heights, resulting in 

5287 serious flood losses (structural damage and economic) as well as loss of levee 

5288 certification and loss of flood protection for compliant post-FIRM structures. Providing 

5289 this information to communities may lead to coordinated watershed-wide actions to 

5290 manage for, or otherwise mitigate, these future risks. 

 

24 Input to author team during CCSP SAP 4.1 Federal Advisory Committee review, Mark Crowell, FEMA.
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 5291 

5292 A recent increase in losses from coastal storms has been recognized by FEMA (Crowell, 

5293 2008). In 2005, Hurricane Katrina clearly illustrated this, reporting the most losses of any 

5294 U.S. natural disaster to date. This fact, coupled with the facts that new developments in 

5295 modeling and mapping technology have allowed for more accurate flood hazard 

5296 assessment over the past few years and that populations at risk are growing in coastal 

5297 areas, has caused FEMA to develop a new national coastal strategy. This strategy consists 

5298 of assessing coastal Flood Insurance Studies on a national scale and developing a 

5299 nationwide plan for improved coastal flood hazard identification. The assessment will 

5300 prioritize regional studies, look at funding allocations, and develop timelines for coastal 

5301 study updates. 

 5302 

5303 River models that are affected by tides and storm surge require the downstream boundary 

5304 starting water surface elevation to be the “1-percent-annual-chance” base flood elevation 

5305 (BFE) from an adjacent coastal study. If the coastal study BFE is raised by 0.3 m or even 

5306 0.9 m because of sea-level rise, the river study flood profile will be changed as well and 

5307 this will ultimately affect the resulting FIRMs that are published. This is a complicated 

5308 issue and points out the fact that simply raising the coastal BFEs to estimate a new 1-

5309 percent-annual-chance floodplain is not taking into account the more complex hydraulics 

5310 that will have undetermined effects on the upstream 1-percent-annual-chance floodplains 

5311 as well. The 1991 study does not factor in the complexity of different tidal regimes that 

5312 would be occurring because of an increased sea level and how those regimes would affect 
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5313 the geomorphology of the floodplains. This is because FEMA is restricted in what it can 

5314 and cannot do in the regulated NFIP process (Crowell, 2008). 

 5315 

5316 Maryland has completed a comprehensive state strategy document in response to sea5317 level rise (MD DNR, 2000). The Maryland Department of Natural Resources (MD DNR, 

5318 2000) requires all communities to adopt standards that call for all structures in the non5319 tidal floodplain to be elevated 0.3 m (1 ft) above the 100-year floodplain elevation, and 

5320 all coastal counties except Worcester, Somerset, and Dorchester (the three most 

5321 vulnerable to exacerbated flooding due to sea-level rise) have adopted the 1-ft freeboard 

5322 standard. Although 1 foot of freeboard provides an added cushion of protection to guard 

5323 against uncertainty in floodplain projections, it may not be enough in the event of 0.6 to 

5324 0.9 m (2 to 3 ft) of sea-level rise, as MD DNR (2000) points out. 

 5325 

5326 Crowell et al. (2007) identified a need for a tide-gauge analysis for FEMA Region III, 

5327 which encompasses the mid-Atlantic states, similar to new studies being done currently 

5328 on Chesapeake Bay by the state of Maryland. Each coastal FEMA region has been 

5329 evaluated and new guidelines and specifications have been developed by FEMA for 

5330 future coastal restudies, the first of which was for the Pacific Coast region. These 

5331 guidelines outline new coastal storm surge modeling and mapping procedures and allow 

5332 for new flooding and wave models to be used for generating coastal BFEs. 

 5333 

5334 To aid in ongoing recovery and rebuilding efforts, FEMA initiated short-term projects in 

5335 2004 and 2005 to produce coastal flood recovery maps for areas that were most severely 
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5336 affected by Hurricanes Ivan, Katrina, and Rita. The Katrina maps, for example, show 

5337 high water marks surveyed after the storm, an inundation limit developed from these 

5338 surveyed points, and FEMA’s Advisory Base Flood Elevations (ABFEs) and estimated 

5339 zone of wave impacts. 

 5340 

5341 These maps and associated ABFEs (generated for Katrina and Rita only) were based on 

5342 new flood risk assessments that were done immediately following the storms to assist 

5343 communities with rebuilding. The recovery maps provide a graphical depiction of ABFEs 

5344 and coastal inundation associated with the observed storm surge high water mark values, 

5345 in effect documenting the flood imprint of the event to be used in future studies and 

5346 policy decisions. Adherence to the ABFEs following Katrina affected eligibility for 

5347 certain FEMA-funded mitigation and recovery projects. They were used until the Flood 

5348 Insurance Studies (FIS) were updated for the Gulf region and are available as advisory 

5349 information to assist communities in rebuilding efforts. 

 5350 

5351 FEMA cannot require the use of future conditions data based on planned land-use 

5352 changes or proposed development for floodplain management or insurance rating 

5353 purposes unless statutory and regulatory changes to the NFIP are made. In addition, using 

5354 projected coastal erosion information for land-use management and insurance rating 

5355 purposes through the NFIP would require a legislative mandate and regulatory changes. 

 5356 

5357 9.6.2 Mapping Potential Impacts of Sea-Level Rise on Coastal Floodplains 
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5358 Floodplain management regulations are intended to minimize damage as a result of 

5359 flooding disasters, in conjunction with other local land-use requirements and building 

5360 codes. Meeting only these minimum requirements will not guarantee protection from 

5361 storm damages. Management activities that focus on mitigating a single, short-term 

5362 hazard can result in structures that are built only to withstand the hazards as they are 

5363 identified today, with no easy way to accommodate an increased risk of damage in the 

5364 coming decades (Honeycutt and Mauriello, 2005). The concept of going above and 

5365 beyond current regulations to provide additional hazards information other than BFEs 

5366 and the 1-percent-annual-chance flood (coastal erosion and storm surge inundation 

5367 potential) has been advocated in some quarters with a No Adverse Impact (NAI) program 

5368 (Larson and Plasencia, 2002). A NAI toolkit was developed that outlines a strategy for 

5369 communities to implement a NAI approach to floodplain management (ASFPM, 2003, 

5370 2008). 

 5371 

5372 The International Codes (FEMA, 2005) include freeboard (elevations above the BFE) and 

5373 standards for coastal A Zones that are more stringent than the NFIP criteria. The 

5374 International Codes also incorporate criteria from the national consensus document 

5375 ASCE 24-05 Flood Resistant Design and Construction Standard (ASCE, 2006). 

5376 

5377 9.7 HOW COASTAL RESOURCE MANAGERS COPE WITH SEA-LEVEL RISE 

5378 AND ISSUES THEY FACE 

5379 9.7.1 Studies by the Association of State Floodplain Managers 

5380 The Association of State Floodplain Mangers (ASFPM) recently completed a study that 

5381 contains a broad spectrum of recommendations for improving the management of U.S. 
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5382 floodplains (ASFPM, 2007). In their study, ASFPM noted that changing climate was one 

5383 of the major challenges for the significant changes in social, environmental, and political 

5384 realities and their impact on floodplain management, and highlights the wide spread 

5385 implications for flood protection. 

 5386 

5387 9.7.2 The Response through Floodproofing

5388 The U.S. Army Corps of Engineers heads the national floodproofing committee, 

5389 established through the USACE’s floodplain management services program, to promote 

5390 the development and use of proper floodproofing techniques throughout the United States 

5391 (USACE, 1996). The USACE publication on floodproofing techniques, programs, and 

5392 references gives an excellent overview of currently accepted flood mitigation practices 

5393 from an individual structure perspective. 

 5394 

5395 Mitigating flooding or “floodproofing” is a process for preventing or reducing flood 

5396 damages to structures and/or to the contents of buildings located in flood hazard areas. It 

5397 mainly involves altering or changing existing properties; however, it can also be 

5398 incorporated into the design and construction of new buildings. There are three general 

5399 approaches to floodproofing: 

5400 1. Raising or moving the structure. Raising or moving the structure such that 

5401 floodwaters cannot reach damageable portions of it is an effective floodproofing 

5402 approach. 

5403 2. Constructing barriers to stop floodwater from entering the building. Constructing 

5404 barriers can be an effective approach used to stop floodwaters from reaching the 
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5405 damageable portions of structures. There are two techniques employed in 

5406 constructing barriers. The first technique involves constructing free-standing 

5407 barriers that are not attached to the structure. The three primary types of free5408 standing barriers used to reduce flood damages are berms, levees, or floodwalls. 

5409 The second technique that can be used to construct a barrier against floodwaters is 

5410 known as “dry floodproofing”. With this technique, a building is sealed such that 

5411 floodwaters cannot get inside. 

5412 3. Wet Floodproofing. This approach to floodproofing involves modifying a 

5413 structure to allow floodwaters inside, but ensuring that there is minimal damage to 

5414 the building's structure and to its contents. Wet floodproofing is often used when 

5415 dry floodproofing is not possible or is too costly. Wet floodproofing is generally 

5416 appropriate in cases where an area is available above flood levels to which 

5417 damageable items can be relocated or temporarily stored. 

5418 The recommended techniques of levees, berms, floodwalls and wet floodproofing are not 

5419 allowed under the NFIP to protect new individual structures. These techniques may also 

5420 have limited use in protecting older existing structures in coastal areas. Although dry 

5421 floodproofing is allowed in A Zones (not V Zones), FEMA does not generally 

5422 recommend its use for new non-residential structures in the coastal A Zones due to the 

5423 potential flood forces. Under the NFIP, all new construction and substantial 

5424 improvements of residential buildings in A Zones must have the lowest floor elevated to 

5425 or above the BFE. All new construction and substantial improvement of non-residential 

5426 buildings in A Zones must have either the lowest floor elevated to or above the BFE or 

5427 the building must be dry floodproofed to the BFE. In V Zones, all new construction and 
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5428 substantial improvements must have the bottom of the lowest horizontal structural 

5429 member of the lowest floor elevated to or above the BFE on a pile or column foundation. 

5430 Although the NFIP allows dry floodproofing in coastal A Zone areas, FEMA does not 

5431 recommend its use in the coastal A Zone because of the potential for severe flood 

5432 hazards. While Base Flood Elevations in coastal A Zones contain a wave height of less 

5433 than 3 feet, the severity of the hazard in coastal A Zones is often much greater than in 

5434 non-coastal A Zones due to the combination of water velocity, wave action, and debris 

5435 impacts that can occur in these areas. For existing, older structures in the coastal area, the 

5436 best way to protect the structure is elevating or relocating the structure. 

 5437 

5438 9.7.3 Coastal Zone Management Act 

5439 Dramatic population growth along the coast brings new challenges to managing national 

5440 coastal resources. Coastal and floodplain managers are challenged to strike the right 

5441 balance between a naturally changing shoreline and the growing population’s desire to 

5442 use and develop coastal areas. Challenges include protecting life and property from 

5443 coastal hazards; protecting coastal wetlands and habitats while accommodating needed 

5444 economic growth; and settling conflicts between competing needs such as dredged 

5445 material disposal, commercial development, recreational use, national defense, and port 

5446 development. Coastal land loss caused by chronic erosion has been an ongoing 

5447 management issue in many coastal states that have Coastal Zone Management (CZM) 

5448 programs and legislation to mitigate erosion using a basic retreat policy. With the 

5449 potential impacts of sea-level rise, managers and lawmakers must now decide how or 
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5450 whether to adapt their current suite of tools and regulations to face the prospect of an 

5451 even greater amount of land loss in the decades to come. 

 5452 

5453 The U.S. Congress recognized the importance of meeting the challenge of continued 

5454 growth in the coastal zone and responded by passing the Coastal Zone Management Act 

5455 in 1972. The amended act (CZMA, 1996), administered by NOAA, provides for 

5456 management of U.S. coastal resources, including the Great Lakes, and balances economic 

5457 development with environmental conservation. 

 5458 

5459 As a voluntary federal–state partnership, the CZMA is designed to encourage state5460 tailored coastal management programs. It outlines two national programs, the National 

5461 Coastal Zone Management Program and the National Estuarine Research Reserve 

5462 System, and aims to balance competing land and water issues in the coastal zone, while 

5463 estuarine reserves serve as field laboratories to provide a greater understanding of 

5464 estuaries and how humans impact them. The overall program objectives of CZMA 

5465 remain balanced to “preserve, protect, develop, and where possible, to restore or enhance 

5466 the resources of the nation’s coastal zone” (CZMA, 1996). 

 5467 

5468 9.7.4 The Coastal Zone Management Act and Sea-Level Rise Issues 

5469 The CZMA language (CZMA, 1996) refers specifically to sea-level rise issues (16 U.S.C. 

5470 § 1451). Congressional findings (§ 302) calls for coastal states to anticipate and plan for 

5471 sea-level rise and climate change impacts. 

 5472 
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5473 In 16 U.S.C. § 1452, Congressional declaration of policy (§ 303), the Congress finds and 

5474 declares that it is the national policy to manage coastal development to minimize the loss 

5475 of life and property caused by improper development in flood-prone, storm surge, 

5476 geological hazard, and erosion-prone areas, and in areas likely to be affected by or 

5477 vulnerable to sea-level rise, land subsidence, and saltwater intrusion, and by the 

5478 destruction of natural protective features such as beaches, dunes, wetlands, and barrier 

5479 islands; to study and develop plans for addressing the adverse effects upon the coastal 

5480 zone of land subsidence and of sea-level rise; and to encourage the preparation of special 

5481 area management plans which provide increased specificity in protecting significant 

5482 natural resources, reasonable coastal-dependent economic growth, improved protection 

5483 of life and property in hazardous areas, including those areas likely to be affected by land 

5484 subsidence, sea-level rise, or fluctuating water levels of the Great Lakes, and improved 

5485 predictability in governmental decision-making. 

5486 

5487 9.7.5 The Coastal Zone Enhancement Program 

5488 The reauthorization of CZMA in 1996 by the U.S. Congress led to the establishment of 

5489 the Coastal Zone Enhancement Program (CZMA §309), which allows states to request 

5490 additional funding to amend their coastal programs in order to support attainment of one 

5491 or more coastal zone enhancement objectives. The program is designed to encourage 

5492 states and territories to develop program changes in one or more of the following nine 

5493 coastal zone enhancement areas of national significance: wetlands, coastal hazards, 

5494 public access, marine debris, cumulative and secondary impacts, special area 

5495 management plans, ocean/Great Lakes resources, energy and government facility citing, 
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5496 and aquaculture. The Coastal Zone Enhancement Grants (§ 309) defines a “Coastal zone 

5497 enhancement objective” as “preventing or significantly reducing threats to life and 

5498 destruction of property by eliminating development and redevelopment in high-hazard 

5499 areas, managing development in other hazard areas, and anticipating and managing the 

5500 effects of potential sea-level rise and Great Lakes level rise”. 

 5501 

5502 Through a self-assessment process, state coastal programs identify high-priority 

5503 enhancement areas. In consultation with NOAA, state coastal programs then develop 

5504 five-year strategies to achieve changes (enhancements) to their coastal management 

5505 programs within these high-priority areas. Program changes often include developing or 

5506 revising a law, regulation or administrative guideline, developing or revising a special 

5507 area management plan, or creating a new program such as a coastal land acquisition or 

5508 restoration program. 

 5509 

5510 For coastal hazards, states base their evaluation on the following criteria: 

5511 1. What is the general level or risk from specific coastal hazards (i.e., hurricanes, 

5512 storm surge, flooding, shoreline erosion, sea-level rise, Great Lakes level 

5513 fluctuations, subsidence, and geological hazards) and risk to life and property due 

5514 to inappropriate development in the state? 

5515 2. Have there been significant changes to the state’s hazards protection programs 

5516 (e.g., changes to building setbacks/restrictions, methodologies for determining 

5517 building setbacks, restriction of hard shoreline protection structures, beach/dune 
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5518 protection, inlet management plans, local hazard mitigation planning, or local 

5519 post-disaster redevelopment plans, mapping/GIS/tracking of hazard areas)? 

5520 3. Does the state need to direct future public and private development and 

5521 redevelopment away from hazardous areas, including the high hazard areas 

5522 delineated as FEMA V Zones and areas vulnerable to inundation from sea- and 

5523 Great Lakes level rise? 

5524 4. Does the state need to preserve and restore the protective functions of natural 

5525 shoreline features such as beaches, dunes, and wetlands? 

5526 5. Does the state need to prevent or minimize threats to existing populations and 

5527 property from both episodic and chronic coastal hazards? 

5528 Section 309 grants have benefited states such as Virginia in developing local 

5529 conservation corridors that identify and prioritize habitat areas for conservation and 

5530 restoration; and New Jersey for supporting new requirements for permittees to submit 

5531 easements for land dedicated to public access, when such access is required as a 

5532 development permit condition and is supporting a series of workshops on the Public Trust 

5533 Doctrine and ways to enhance public access (see 

5534 <http://coastalmanagement.noaa.gov/nationalsummary.html>). 

 5535 

5536 9.7.6 Coastal States Strategies 

5537 Organizations such as the Coastal States Organization have recently become more 

5538 proactive in how coastal zone management programs consider adaptation to climate 

5539 change, including sea-level rise (Coastal States Organization, 2007) and are actively 

5540 leveraging each other’s experiences and approaches as to how best obtain baseline 
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5541 elevation information and inundation maps, how to assess impacts of sea-level rise on 

5542 social and economic resources and coastal habitats, and how to develop public policy. 

5543 There have also been several individual state-wide studies on the impact of sea-level rise 

5544 on local state coastal zones (e.g., Johnson [2000] for Maryland; Cooper et al. [2005] for 

5545 New Jersey). Many state coastal management websites show an active public education 

5546 program with regards to providing information on impacts of sea-level rise: 

5547 New Jersey: <http://www.nj.gov/dep/njgs/enviroed/infocirc/sealevel.pdf> 

5548 Delaware: 

5549 <http://www.dnrec.delaware.gov/Climate+change+shoreline+erosion.htm> 

5550 Maryland: <http://www.dnr.state.md.us/Bay/czm/sea_level_rise.html> 

 5551 

5552 9.7.6.1 Maryland’s Strategy 

5553 The evaluation of sea-level rise response planning in Maryland and the resulting strategy 

5554 document constituted the bulk of the state’s CZMA §309 Coastal Hazard Assessment and 

5555 Strategy for 2000–2005 and in the 2006-2010 Assessment and Strategy (MD DNR, 

5556 2006). Other mid-Atlantic states mention sea-level rise as a concern in their assessments, 

5557 but have not yet developed a comprehensive strategy. 

 5558 

5559 The sea-level rise strategy is designed to achieve the desired outcome within a five-year 

5560 time horizon. Implementation of the strategy is evolving over time and is crucial to 

5561 Maryland’s ability to achieve sustainable management of its coastal zone. The strategy 

5562 states that planners and legislators should realize that the implementation of measures to 

5563 mitigate impacts associated with erosion, flooding, and wetland inundation will also 
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5564 enhance Maryland’s ability to protect coastal resources and communities whether sea 

5565 level rises significantly or not. 

 5566 

5567 Maryland has taken a proactive step towards addressing a growing problem by 

5568 committing to implementation of this strategy and increasing awareness and 

5569 consideration of sea-level rise issues in both public and governmental arenas. The 

5570 strategy suggests that Maryland will achieve success in planning for sea-level rise by 

5571 establishing effective response mechanisms at both the state and local levels. Sea-level 

5572 rise response planning is crucial in order to ensure future survival of Maryland’s diverse 

5573 and invaluable coastal resources. 

 5574 

5575 Since the release of Maryland’s sea-level rise response strategy (Johnson, 2000), the state 

5576 has continued to progressively plan for sea-level rise. The strategy is being used to guide 

5577 Maryland’s current sea-level rise research, data acquisition, and planning and policy 

5578 development efforts at both the state and local level. Maryland set forth a design vision 

5579 for “resilient coastal communities” in its CZMA §309 Coastal Hazard Strategy for 2006–

5580 2010 (MD DNR, 2006). The focus of the approach is to integrate the use of recently 

5581 acquired sea-level rise data- and technology-based products into both state and local 

5582 decision-making and planning processes. Maryland’s coastal program is currently 

5583 working with local governments and other state agencies to: (1) build the capacity to 

5584 integrate data and mapping efforts into land-use and comprehensive planning efforts; (2) 

5585 identify specific opportunities (i.e., statutory changes, code changes, comprehensive plan 

5586 amendments) for advancing sea-level rise at the local level; and (3) improve state and 
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5587 local agency coordination of sea-level rise planning and response activities (MD DNR, 

5588 2006). 

 5589 

5590 In April 2007, Maryland’s Governor, Martin O’Malley, signed an Executive Order 

5591 establishing a Commission on Climate Change (Maryland, 2007) that is charged with 

5592 advising both the Governor and Maryland’s General Assembly on matters related to 

5593 climate change and is charged with developing a Plan of Action that will address climate 

5594 change on all fronts, including both the drivers and the consequences. The Maryland 

5595 Commission on Climate Change released its Climate Action Plan in August 2008 

5596 (Maryland, 2008). A key component of the Action Plan is The Comprehensive Strategy 

5597 to Reduce Maryland’s Vulnerability to Climate Change. The Strategy, which builds upon 

5598 Maryland’s sea-level rise response strategy (Johnson, 2000), sets forth specific actions 

5599 necessary to protect Maryland’s people, property, natural resources, and public 

5600 investments from the impacts of climate change, sea-level rise, and coastal storms. A 

5601 comprehensive strategy and plan of action were presented to the Maryland’s Governor 

5602 and General Assembly in April 2008. 

 5603 

5604 The Maryland Department of Natural Resources has been active in developing an online 

5605 mapping tool for general information and educational purposes that provides user-driven 

5606 maps for shoreline erosion and for various sea-level rise scenarios (see 

5607 <http://shorelines.dnr.state.md.us/coastal_hazards.asp#slr>) and has completed case 

5608 studies with other agencies (see Box 9.3) for studying implication of sea-level rise for 

5609 county level planning. Although this particular case study did not base results on a 
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5610 numerical storm surge model, it represents the type of initial analyses that local planners 

5611 need to undertake. 

5612 
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5613 CHAPTER 9 REFERENCES

5614 AGU (American Geophysical Union), 2006: Hurricanes and the U.S. Gulf Coast: 

5615 Science and Sustainable Rebuilding. American Geophysical Union, [Washington, 

5616 DC], 29 pp. <http://www.agu.org/report/hurricanes> 

5617 ASCE (American Society of Civil Engineers), 2006: Flood Resistant Design and 

5618 Construction. ASCE/SEI 24-05. American Society of Civil Engineers, Reston, 

5619 VA, 61 pp. 

5620 ASFPM (Association of State Floodplain Managers), 2003: No Adverse Impact. A 

5621 Toolkit for Common Sense Floodplain Management. [Larson, L.A., M.J. Klitzke, 

5622 and D.A Brown eds.]. Association of State Floodplain Managers, Madison, WI, 

5623 108 pp. 

5624 ASFPM (Association of State Floodplain Managers), 2007: National Flood Programs 

5625 and Policies in Review – 2007. Association of State Floodplain Managers, 

5626 Madison, WI, 92 pp. 

5627 ASFPM (Association of State Floodplain Managers), 2008: Coastal No Adverse Impact 

5628 Handbook. Association of State Floodplain Managers, Madison, WI, 165 pp. 

5629 <http://www.floods.org/CNAI/CNAI_Handbook.asp> 

5630 Boesch, D.F., J.C. Field, and D. Scavia, (eds.): 2000. The Potential Consequences of 

5631 Climate Variability and Change on Coastal Areas and Marine Resources: Report 

5632 of the Coastal Areas and Marine Resources Sector Team, U.S. National 

5633 Assessment of the Potential Consequences of Climate Variability and Change, 

5634 U.S. Global Change Research Program. NOAA Coastal Ocean Program decision 

5635 analysis series no. 21. NOAA Coastal Ocean Program, Silver Spring, MD, 163 

5636 pp. 

5637 Coastal States Organization, 2007: The Role of Coastal Zone Management Programs in 

5638 Adaptation to Climate Change. CSO Climate Change Work Group, Washington, 

5639 DC, 27 pp. 
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5640 <http://www.coastalstates.org/uploads/PDFs/CSO%20Climate%20Change%20Re

5641 port%20-%20Final%2010-1-07.pdf> 

5642 Cooper, M.J.P., M.D. Beevers, and M. Oppenheimer, 2005: Future Sea Level Rise And 

5643 The New Jersey Coast: Assessing Potential Impacts and Opportunities. Science, 

5644 Technology and Environmental Policy Program, Woodrow Wilson School of 

5645 Public and International Affairs, Princeton University, Princeton, NJ, 36 pp. 

5646 <http://www.princeton.edu/~cmi/news/Future%20of%20Sea%20Level%20Rise%

5647 20and%20the%20New%20Jersey%20Coast.pdf> Crowell, M., E. Hirsch, and 

5648 T.L. Hayes, 2007: Improving FEMA’s coastal risk assessment through the 

5649 National Flood Insurance Program: an historical overview. Marine Technology 

5650 Science, 41(1), 18-27. 

5651 CZMA (Coastal Zone Management Act), 1996: The Coastal Zone Management Act of 

5652 1972, as amended through P.L. 104-150, The Coastal Zone Protection Act of 

5653 1996, 16 U.S.C. § 1451 through 16 U.S.C. § 1465. 

5654 FEMA (Federal Emergency Management Agency), 1991: Projected Impact of Relative 

5655 Sea-level Rise on the National Flood Insurance Program. Federal Emergency 

5656 Management Agency, Washington, DC, 61 pp. 

5657 FEMA (Federal Emergency Management Agency), 2002: Guidelines and Specifications 

5658 for Flood Hazard Mapping Partners Archive. [web site] Federal Emergency 

5659 Management Agency. <http://www.fema.gov/plan/prevent/fhm/gs_arch.shtm> 

5660 FEMA (Federal Emergency Management Agency), 2005: Reducing Flood Losses 

5661 Through the International Codes, Meeting the Requirements of the National 

5662 Flood Insurance Program. Federal Emergency Management Agency and 

International Code Council, [Washington, DC], 2nd 5663 edition, 156 pp. 

5664 FEMA (Federal Emergency Management Agency), 2008: National Flood Insurance 

5665 Program Definitions [web page] 

5666 <http://www.fema.gov/business/nfip/19def2.shtm> 
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5667 Hagen, S.C., W. Quillian, and R. Garza, 2004: A Demonstration of Real-time Tide and 

5668 Hurricane Storm Surge Predictions for the National Weather Service River 

5669 Forecast System. Technical report, UCAR Contract No. S01-32794. CHAMPS 

5670 Laboratory, University of Central Florida, Orlando. 

5671 Heinz Center, 2000: Evaluation of Erosion Hazards. The H. John Heinz III Center for 

5672 Science, Economics and the Environment, Washington, DC, 203 pp. 

5673 Honeycutt, M.G. and M.N. Mauriello, 2005: Multi-hazard mitigation in the coastal zone: 

5674 when meeting the minimum regulatory requirements isn’t enough: In: Solutions to 

5675 Coastal Disasters 2005, Proceedings of the conference, May 8-11, Charleston, 

5676 SC. American Society of Civil Engineers, Reston VA, pp. 713-722. 

5677 Hovis, J., W. Popovich, C. Zervas, J. Hubbard, H.H. Shih, and P. Stone, 2004: Effect of 

5678 Hurricane Isabel on Water Levels: Data Report. NOAA technical Report NOS 

5679 CO-OPS 040. NOAA, Silver Spring, MD, 120 pp. 

5680 Jelesnianski, C.P., J. Chen, and W.A. Shaffer, 1992: SLOSH: Sea, Lake, and Overland 

5681 Surges from Hurricanes. NOAA technical report NWS 48. National Weather 

5682 Service, Silver Spring, MD, 71 pp. 

5683 Johnson, Z.P., 2000: A Sea Level Response Strategy for the State of Maryland. Maryland 

5684 Department of Natural Resources, Coastal Zone Management Division, 

5685 Annapolis, 49 pp. 

5686 Larsen, C., I. Clark, G.R. Guntenspergen, D.R. Cahoon, V. Caruso, C. Hupp, and T. 

5687 Yanosky, 2004: The Blackwater NWR Inundation Model. Rising Sea Level on a 

5688 Low-lying Coast: Land Use Planning for Wetlands. U.S. Geological Survey open 

5689 file report 04-1302. U.S. Geological Survey, Reston, VA. 

5690 <http://pubs.usgs.gov/of/2004/1302/> 

5691 Luettich, R.A., Jr., J.J. Westerink, and N.W. Scheffner, 1992: ADCIRC: An Advanced 

5692 Three-dimensional Circulation Model of Shelves, Coasts and Estuaries, Report 1: 

5693 Theory and Methodology of ADCIRC-2DD1 and ADCIRC-3DL. Technical report 
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5694 DRP-92-6. U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 

5695 141 pp. 

5696 Maryland, 2007: Maryland Executive Order 01.01.2007.07, Commission on Climate 

5697 Change. State of Maryland, Executive Department, [Annapolis]. 

5698 Maryland, 2008: Climate Action Plan. Maryland Commission on Climate Change and 

5699 Maryland Department of Environment, Baltimore, 356 pp. 

5700 <http://www.mdclimatechange.us/> 

5701 MD DNR (Maryland Department of Natural Resources), Coastal Zone Management 

5702 Program, 2006: Coastal Zone Management Assessment, Section 309, Assessment 

5703 and Strategy. 

5704 NOAA (National Oceanic and Atmospheric Administration), 1992: Effects of the Late 

5705 October 1991 North Atlantic Extra-Tropical Storm on Water Levels: Data 

5706 Report. NOAA National Ocean Service, Rockville, MD, 46 pp. 

5707 NOAA (National Oceanic and Atmospheric Administration), 2007: NOAA’s Sea level 

5708 Rise Research Program: North Carolina Managers Meetings Fact Sheet. NOAA 

5709 National Centers for Coastal Ocean Science, Silver Spring, MD, 2 pp. 

5710 http://www.cop.noaa.gov/stressors/climatechange/current/slr/SLR_manager_hand

5711 out.pdf 

5712 NOAA (National Oceanic and Atmospheric Administration), 2008: Glossary of NHC 

5713 Terms. NOAA National Weather Service, National Hurricane Center, Miami, FL. 

5714 See defintions for Storm Surge and for Storm Tide. 

5715 <http://www.nhc.noaa.gov/aboutgloss.shtml> 

5716 Pietrafesa, L.J., E.B. Buckley, M. Peng, S. Bao, H. Liu, S. Peng, L. Xie, and D.A. 

5717 Dickey, 2007: On coastal ocean systems, coupled model architectures, products 

5718 and services: morphing from observations to operations and applications. Marine 

5719 Technology Societyl, 41(1), 44-52. 
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5720 Poag, C.W., 1997: Chesapeake Bay bolide impact: a convulsive event in Atlantic Coastal 

5721 Plain evolution. Sedimentary Geology, 108(1-4), 45-90. 

5722 Reed, D.B. and B.E. Stucky, 2005: Forecasting storm surge on the Mississippi River. In: 

5723 Solutions to Coastal Disasters, Proceedings of the conference, May 8-11, 

5724 Charleston, SC. American Society of Civil Engineers, Reston, VA, pp. 52-60. 

5725 Slovinsky, P.A. and S.M. Dickson, 2006: Impacts of Future Sea Level Rise on the 

5726 Coastal Floodplain. MGS open-file 06-14. Maine Geological Survey, Augusta, 

5727 ME, [26 pp.] <http://www.maine.gov/doc/nrimc/mgs/explore/marine/sea5728 level/contents.htm>

5729 USACE (U.S. Army Corps of Engineers), 1996: Flood Proofing Techniques, Programs 

5730 and References. U.S. Army Corps of Engineers, Washington, DC, 25 pp. 

5731 Worcester County Planning Commission, 2006: Comprehensive Plan, Worcester 

5732 County Maryland. Worcester County Commissioners, Snow Hill, MD, 96 pp. 

5733 <http://www.co.worcester.md.us/cp/finalcomp31406.pdf> 

5734 Zervas, C.E., 2001: Sea Level Variations for the Unites States 1854-1999. NOAA 

5735 technical report NOS CO-OPS 36. NOAA National Ocean Service, Silver Spring, 

5736 MD, 186 pp. <http://tidesandcurrents.noaa.gov/publications/techrpt36doc.pdf> 

5737 Zervas, C.E., 2005: Extreme Storm Tide Levels of the United States 1897-2004. Poster 

5738 paper presented at NOAA Climate Program Office, Office of Climate 

5739 Observations Annual Meeting, Silver Spring, MD. 

5740 
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5741 Part III Overview. Preparing for Sea-Level Rise 

5742 

5743 Author: James G. Titus, U.S. EPA

5744 

5745 For at least the last four centuries, people have been erecting permanent settlements in the 

5746 coastal zone of the Mid-Atlantic without regard to the fact that the sea is rising. Because 

5747 the sea has been rising slowly and only a small part of the coast was developed, the 

5748 consequences have been relatively isolated and manageable. Part I of this Product 

5749 suggests, however, that a 2 millimeter per year acceleration of sea-level rise could

5750 transform the character of the mid-Atlantic coast, with a large scale loss of tidal wetlands 

5751 and possible disintegration of barrier islands. A 7 millimeter per year acceleration is 

5752 likely to cause such a transformation, although shore protection may prevent some 

5753 developed barrier islands from disintegrating and low-lying communities from being 

5754 taken over by wetlands. 

 5755 

5756 For the last quarter century, scientific assessments have concluded that regardless of 

5757 possible policies to reduce emissions of greenhouse gases, people will have to adapt to a 

5758 changing climate and rising sea level. Adaptation assessments differentiate “reactive 

5759 adaptation” from “anticipatory adaptation”. 

 5760 

5761 Part III focuses on what might be done to prepare for sea-level rise. Chapter 10 starts by 

5762 asking whether preparing for sea-level rise is even necessary. In many cases, reacting 

5763 later is more justifiable than preparing now, both because the rate and timing of future 
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5764 sea-level rise is uncertain and the additional cost of acting now can be high when the 

5765 impacts are at least several decades in the future. Nevertheless, for several types of 

5766 impacts, the cost of preparing now is very small compared to the cost of reacting later. 

5767 Examples where preparing can be justified include: 

5768  Coastal wetland protection. It may be possible to reserve undeveloped lands for 

5769 wetland migration, but once developed, it is very difficult to make land available for 

5770 wetland migration. Therefore, it is far more feasible to aid wetland migration by 

5771 setting aside land before it is developed, than to require development to be removed 

5772 as sea level rises. 

5773  Some long-lived infrastructure. Whether it is beneficial to design coastal 

5774 infrastructure to anticipate rising sea level depends on economic analysis of the 

5775 incremental cost of designing for a higher sea level now, and the retrofit cost of 

5776 modifying the structure at some point in the future. Most long-lived infrastructure in 

5777 the threatened areas is sufficiently sensitive to rising sea level to warrant at least an 

5778 assessment of the costs and benefits of preparing for rising sea level. 

5779  Floodplain management. Rising sea level increases the potential disparity between 

5780 rates and risk. Even without considering the possibility of accelerated sea-level rise, 

5781 the National Academy of Sciences and a Federal Emergency Management Agency 

5782 (FEMA)-supported study by the Heinz Center recommended to Congress that 

5783 insurance rates should reflect the changing risks resulting from coastal erosion. 

 5784 

5785 Chapter 11 discusses organizations that are preparing for a possible acceleration of sea5786 level rise. Few organizations responsible for managing coastal resources vulnerable to 
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5787 sea-level rise have modified their activities. Most of the best examples of preparing for 

5788 the environmental impacts of sea-level rise are in New England, where several states 

5789 have enacted policies to enable wetlands to migrate inland as sea-level rise. Ocean City, 

5790 Maryland is an example of a town considering future sea-level rise in its infrastructure 

5791 planning. 

 5792 

5793 Chapter 12 examines the institutional barriers that make it difficult to take the potential 

5794 impacts of future sea-level rise into account for coastal planning. Although few studies 

5795 have discussed the challenge of institutional barriers and biases in coastal decision 

5796 making, their implications for sea-level rise are relatively straightforward: 

5797  Inertia and short-term thinking. Most institutions are slow to take on new 

5798 challenges, especially those that require preparing for the future rather than fixing a 

5799 current problem. 

5800  The interdependence of decisions reinforces institutional inertia. In many cases, 

5801 preparing for sea-level rise requires a decision as to whether a given area will 

5802 ultimately be given up to the sea, protected with structures and drainage systems, or 

5803 elevated as the sea rises. Until communities decide which of those three pathways 

5804 they will follow in a given area, it is difficult to determine which anticipatory or 

5805 initial response measures should be taken. 

5806  Policies favoring protection of what is currently there. In some cases, longstanding 

5807 preferences for shore protection (as discussed in Chapter 6) discourage planning 

5808 measures that foster retreat. Because retreat may require a greater lead time than 

5809 shore protection, the presumption that an area will be protected may imply that 
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5810 planning in unnecessary. On the other hand, these preferences may help accelerate 

5811 the response to sea-level rise in areas where shore protection is needed. 

5812  Policies Favoring Coastal Development. One possible response to sea-level rise is to 

5813 invest less in the lands likely to be threatened. However, longstanding policies that 

5814 encourage coastal development can discourage such a response. On the other hand, 

5815 increasingly dense coastal development improves the ability to raise funds required 

5816 for shore protection. Therefore, policies that encourage coastal development may be 

5817 part of an institutional bias favoring shore protection, but they are not necessarily a 

5818 barrier to responding to sea-level rise. 

 5819 

5820 Although most institutions have not been preparing for a rising sea, (Chapter 11) , that 

5821 may be changing. As these chapters were drafted, several states have started to seriously 

5822 examine possible responses. For example, Maryland enacted a statute to limit the adverse 

5823 environmental impact of shore protection structures as sea level rises; and FEMA is 

5824 beginning to assess possible changes to the National Flood Insurance Program. It is too 

5825 soon to tell whether the increased interest in the consequences of climate change will 

5826 overtake—or be thwarted by—the institutional barriers that have discouraged actionuntil 

5827 now. 

 5828 

5829 
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5830 Chapter 10. Implications for Decisions 

5831 

5832 Lead Author: James G. Titus, U.S. EPA 

5833 

5834 Contributing Author: James E. Neumann, Industrial Economics, Inc. 

5835 

5836 KEY FINDINGS 

5837  In many cases, it is difficult to determine whether taking a specific action to 

5838 prepare for sea-level rise is justified, due to uncertainty in the timing and 

5839 magnitude of impacts, and difficulties in quantifying projected benefits and costs. 

5840 Nevertheless, published literature has identified some cases where acting now can 

5841 be justified. 

5842  Key opportunities for preparing for sea-level rise concern coastal wetland 

5843 protection, flood insurance rates, and the location and elevation of coastal homes, 

5844 buildings, and infrastructure. 

5845  Incorporating sea-level rise into coastal wetlands programs can be justified 

5846 because the Mid-Atlantic still has substantial vacant land onto which coastal 

5847 wetlands could migrate as sea level rises. Policies to ensure that wetlands are able 

5848 to migrate inland are likely to be less expensive and more likely to succeed if the 

5849 planning takes place before people develop these dry lands than after the land 

5850 becomes developed. Possible tools include rolling easements, density restrictions, 

5851 coastal setbacks, and vegetative buffers. 
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5852  Sea-level rise does not threaten the financial integrity of the National Flood 

5853 Insurance Program. Incorporating sea-level rise into the program, however, could 

5854 allow flood insurance rates to more closely reflect changing risk and enable 

5855 participating local governments to more effectively manage coastal floodplains. 

5856  Long-term shoreline planning is likely to yield benefits greater than the costs; the 

5857 more sea level rises, the greater the value of that planning. 

 5858 

5859 10.1 INTRODUCTION 

5860 Most decisions of everyday life in the coastal zone have little to do with the fact that the 

5861 sea is rising. Some day-to-day decisions depend on today’s water levels. For example, 

5862 sailors, surfers, and fishermen all consult tide tables before deciding when to go out. 

5863 People deciding whether to evacuate during a storm consider how high the water is 

5864 expected to rise above the normal level of the sea. Yet the fact that the normal sea level is 

5865 rising about 0.01 millimeters (mm) per day does not affect such decisions. 

 5866 

5867 Sea-level rise can have greater impacts on the outcomes of decisions with long-term 

5868 consequences. Those impacts do not all warrant doing things differently today. In some 

5869 cases, the expected impacts are far enough in the future that people will have ample time 

5870 to respond. For example, there is little need to anticipate sea-level rise in the construction 

5871 of docks, which are generally rebuilt every few decades, because the rise can be 

5872 considered when they are rebuilt (NRC, 1987). In other cases, the adverse impacts of sea5873 level rise can be more effectively addressed by preparing now than by reacting later. If a 

5874 dike will eventually be required to protect a community, for example, it can be more cost-
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5875 effective to leave a vacant right-of-way when an area is developed or redeveloped, rather 

5876 than tear buildings down later. 

5877 

5878 People will have to adapt to a changing climate and rising sea level (NRC, 1983; 

5879 Hoffman et al., 1983; IPCC 1990, 1996, 2001, 2007). The previous chapters (as well as 

5880 Appendix 1) discuss vulnerable private property and public resources, including 

5881 ecosystems, real estate, infrastructure (e.g., roads, bridges, parks, playgrounds, 

5882 government buildings), and commercial buildings (e.g., hotels, office buildings, industrial 

5883 facilities). Those responsible for managing those assets will have to adapt to changing 

5884 climate and rising sea level regardless of possible efforts to reduce greenhouse gases, 

5885 because society has already changed the atmosphere and will continue to do so for at 

5886 least the next few decades (NRC, 1983; Hoffman et al., 1983; IPCC 1990, 1996, 2001, 

5887 2007). Some of these assets will be protected or preserved in their current locations, 

5888 while others must be moved inland or be lost. Chapters 6, 8, and 9 examine government 

5889 policies that are, in effect, the current response to sea-level rise. Previous assessments 

5890 have emphasized the need to distinguish the problems that can be solved by future 

5891 generations reacting to changing climate from problems that could be more effectively 

5892 solved by preparing today (Titus, 1990; Scheraga and Grambsch, 1998; Klein et al., 

5893 1999; Frankhauser et al., 1999; OTA 1993). Part III (i.e., this Chapter and the next two 

5894 chapters) makes that distinction. 

 5895 

5896 This Chapter addresses the question: “Which decisions and activities (if any) have 

5897 outcomes sufficiently sensitive to sea-level rise so as to justify doing things differently, 

5898 depending on how much the sea is expected to rise?” (CCSP, 2006). Doing things 
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5899 differently does not always require novel technologies or land-use mechanisms; most 

5900 measures for responding to erosion or flooding from sea-level rise have already been 

5901 used to address erosion or flooding caused by other factors (see Section 6.1 in Chapter 6). 

5902 Section 10.2 describes some categories of decisions that may be sensitive to sea-level 

5903 rise, focusing on the idea that preparing now is not worthwhile unless the expected 

5904 present value of the benefits of preparing is greater than the cost. Sections 10.3 to 10.7 

5905 examine five issues related to rising sea level: wetland protection, shore protection, long5906 lived structures, elevating homes, and floodplain management. 

 5907 

5908 The examples discussed in this Chapter focus on activities by governments and 

5909 homeowners, not by corporations. Most published studies about responses to sea-level 

5910 rise have been funded by governments, with a goal to improve government programs, 

5911 communicate risk, or provide technical support to homeowners and small businesses. 

5912 Corporations also engage in many of the activities discussed in this Chapter. It is possible 

5913 that privately funded (and unpublished) strategic assessments have identified other near5914 term decisions that are sensitive to sea-level rise. 

 5915 

5916 A central premise of this Chapter is that the principles of economics and risk 

5917 management provide a useful paradigm for thinking about the implications of sea-level 

5918 rise for decision making. In this paradigm, decision makers have a well-defined objective 

5919 concerning potentially vulnerable coastal resources, such as maximizing return on an 

5920 investment (for a homeowner or investor) or maximizing overall social welfare (for a 

5921 government). Box 10.1 elaborates on this analytical framework. Although economic 
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5922 analysis is not the only method for evaluating a decision, emotions, perceptions, 

5923 ideology, cultural values,family ties, and other non-economic factors are beyond the 

5924 scope of this Chapter. 

 5925 

5926 This Chapter is not directly tied to specific sea-level rise scenarios. Instead, it considers a 

5927 wide range of plausible sea-level rise over periods of time ranging from decades to 

5928 centuries, depending on the decision being examined. The Chapter does not quantify the 

5929 extent to which decisions might be affected by sea-level rise. All discussions of costs 

5930 assume constant (inflation-adjusted) dollars. 

 5931 

5932 BOX 10.1: Conceptual Framework for Decision Making with Sea-Level Rise 

5933 

5934 This Chapter’s conceptual framework for decision making starts with the basic assumption that 

5935 homeowners or governments with an interest in coastal resources seek to maximize the value of those 

5936 resources to themselves (homeowners) or to the public as a whole (governments), over a period of time 

5937 (planning horizon). Each year, coastal resources provide some value to its owner. In the case of the 

5938 homeowner, a coastal property might provide rental income, or it might provide "imputed rent" that the 

5939 owner derives from owning the home rather than renting a similar home. The market value of a property 

5940 reflects an expectation that property will generate similar income over many years. Because a dollar of 

5941 income today is worth more than a dollar in the future, however, the timing of the income stream associated 

5942 with a property also affects the value (see explanation of "discounting" in Section 10.2). 

5943 

5944 Natural hazards and other risks can also affect the income a property provides over time. Erosion, hurricane 

5945 winds, episodic flooding, and other natural hazards can cause damages that reduce the income from the 

5946 property or increase the costs of maintaining it, even without sea-level rise,. These risks are taken into 

5947 account by owners, buyers, and sellers of property to the extent that they are known and understood. 

5948 

5949 Sea-level rise changes the risks to coastal resources, generally by increasing existing risks. This Chapter 

5950 focuses on investments to mitigate those additional risks. 

5951 

5952 In an economic framework, investing to mitigate coastal hazards will only be worthwhile if the cost of the 

5953 investment (incurred in the short term) is less than net expected returns (which accrue over the long-term). 

5954 Therefore, these investments are more likely to be judged worthwhile when: (1) there is a large risk of near5955 term damage (and it can be effectively reduced); (2) there is a small cost to effectively reduce the risk; or 

5956 (3) the investment shifts the risk to future years. 

 5957 

5958 10.2 DECISIONS WHERE PREPARING FOR SEA-LEVEL RISE IS 

5959 WORTHWHILE 
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5960 Sea-level rise justifies changing what people do today if the outcome from considering 

5961 sea-level rise has an expected net benefit, that is, the benefit is greater than the cost. Thus, 

5962 when considering decisions where sea-level rise justifies doing things differently, one can 

5963 exclude from further consideration those decisions where either (1) the administrative 

5964 costs of preparing are large compared to the impacts, or (2) the net benefits are likely to 

5965 be small or negative. Few, if any, studies have analyzed the administrative costs of 

5966 preparing for sea-level rise. Nevertheless, one can infer that administrative costs exceed 

any benefits from preparing for a very small rise in sea level.25 5967 Most published studies 

5968 that investigate which decisions are sensitive to sea-level rise (IPCC, 1990; NRC 1987; 

5969 Titus and Narayanan, 1996) concern decisions whose consequences last decades or 

5970 longer, during which time a significant rise in sea level might occur. Those decisions 

5971 mostly involve long-lived structures, land-use planning, or infrastructure, which can 

5972 influence the location of development for centuries, even if the structures themselves do 

5973 not remain that long. 

 5974 

5975 For what type of decision is a net benefit likely from considering sea-level rise? Most 

5976 analyses of this question have focused on cases where (1) the more sea level rises, the 

5977 greater the impact; (2) the impacts will mostly occur in the future and are uncertain 

5978 because the precise impact of sea-level rise is uncertain; and (3) preparing now will 

5979 reduce the eventual adverse consequences (see Figure 10.1). 

 5980 

 

25 Administrative costs (e.g., studies, regulations, compliance, training) of addressing a new issue are 

roughly fixed regardless of how small the impact may be, while the benefits of addressing the issue depend 

on the magnitude of sea-level rise. Therefore, there would be a point below which the administrative costs 

would be greater than any benefits from addressing the issue. 
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5981 In evaluating a specific activity, the first question is whether preparing now would be 

5982 better than never preparing. If so, a second question is whether preparing now is also 

5983 better than preparing during some future year. Preparing now to avoid possible effects in 

5984 the future involves two key economic principles: uncertainty and discounting. 

 5985 

5986 Uncertainty. Because projections of sea-level rise and its precise effects are uncertain, 

5987 preparing now involves spending today for the sake of uncertain benefits. If sea level 

5988 rises less than expected, then preparing now may prove, in retrospect, to have been 

5989 unnecessary. Yet if sea level rises more than expected, whatever one does today may 

5990 prove to be insufficient. That possibility tends to justify waiting to prepare later, if people 

5991 expect that a few years later (1) they will know more about the threat and (2) the 

opportunity to prepare will still be available26 5992 . Given these reasons to delay, responding 

5993 now may be difficult to justify, unless preparing now is either fairly inexpensive, or part 

5994 of a “robust” strategy (i.e., it works for a wide range of possible outcomes). For example, 

5995 if protecting existing development is important, beach nourishment is a robust way to 

5996 prepare, because the sand will offset some shore erosion no matter how fast or slow the 

5997 sea rises. 

 5998 

 

26 There is an extensive economic literature on decision-making and planning under uncertainty, 

particularly where some effects are irreversible. A review of this literature on the topic of "quasi-option 

value" can be found in Freeman (2003),. Quasi-option value arises from the value of information gained by 

delaying an irreversible decision (e.g., to rebuild a structure to withstand higher water levels). In the sealevel rise context, it applies because the costs and benefits of choosing to retreat or protect are uncertain, 

and it is reasonable to expect that uncertainty will narrow over time concerning rates of sea level rise, the 

effects, how best to respond, and the costs of each response option. Two influential works in this area 

include Arrow and Fisher (1974) and Fisher and Hanemann (1987); an application to climate policy 

decisions can be found in Ha-Duong (1998). 
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5999 Discounting. Discounting is a procedure by which economists determine the “present 

6000 value” of something given or received at a future date (U.S. EPA, 2000). A dollar today 

6001 is preferred over a dollar in the future, even without inflation (Samuelson and Nordhaus, 

6002 1989); therefore, a future dollar must be discounted to make costs and benefits received 

6003 in different years comparable. Economists generally agree that the appropriate way to 

6004 discount is to choose an assumed annual interest rate and compound it year-by-year (just 

6005 as interest compounds) and use the result to discount future dollars (U.S. EPA, 2000; 

6006 Congressional Research Service, 2003; OMB, 1992; Nordhaus, 2007a b; Dasgupta, 

6007 2007). 

 6008 

6009 Most of the decisions where preparing now has a positive net benefit fall into at least one 

6010 of three categories: (1) the near-term impact may be large; (2) preparing now costs little 

6011 compared to the cost of the possible impact; or (3) preparing now involves options that 

6012 reallocate (or clarify) risk. 

 6013 

6014 10.2.1 Decisions that Address Large Near-Term Impacts 

6015 If the near-term impact of sea-level rise is large, preparing now may be worthwhile. Such 

6016 decisions might include: 

6017  Beach nourishment to protect homes that are in imminent danger of being lost. 

6018 The cost of beach nourishment is often less than the value of the threatened 

6019 structures (USACE, 2000a). 
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6020  Enhancing vertical accretion (build-up) of wetlands that are otherwise in danger 

6021 of being lost in the near term (Kentula, 1999; Kussler, 2006). Once wetlands are 

6022 lost, it can be costly (or infeasible) to bring them back. 

6023  Elevating homes that are clearly below the expected flood level due to historic 

6024 sea-level rise (see Sections 10.6 and 10.7). If elevating the home is infeasible 

6025 (e.g., historic row houses), flood-proofing walls, doors, and windows may provide 

6026 a temporary solution (see Chapter 9). 

6027  Fortifying dikes to the elevation necessary to protect from current floods. Because 

6028 sea level is rising, dikes that once protected against a 100-year storm would be 

6029 overtopped by a similar flood on top of today’s higher sea level (see e.g., IPET, 

6030 2006). 

6031 

6032 10.2.2 Decisions Where Preparing Now Costs Little 

6033 These response options can be referred to as “low regrets” and “no regrets”, depending 

6034 on whether the cost is little or nothing. The measures are justifiable, in spite of the 

6035 uncertainty about future sea-level rise, because little or nothing is invested today, in 

6036 return for possibly averting or delaying a serious impact. Examples include: 

6037  Setting a new home back from the sea within a given lot. Setting a home back 

6038 from the water can push the eventual damages from sea-level rise farther into the 

future, lowering their expected present value27 6039 . Unlike the option of not building, 

6040 this approach retains almost the entire value of using the property—especially if 

6041 nearby homes are also set back so that all properties retain the complete panorama 

 

27 The present value of a dollar T years in the future is 1/(1+i)T

 , where i is the interest rate (discount rate) 

used for the calculations (see Samuelson and Nordhaus, 1989). 
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6042 view of the waterfront—provided that the lot is large enough to build the same 

6043 house as would have been built without the setback requirement. 

6044  Building a new house with a higher floor elevation. While elevating an existing 

6045 house can be costly, building a new house on pilings one meter (a few feet) higher 

6046 only increases the construction cost by about 1 percent (Jones et al., 2006). 

6047  Designing new coastal drainage systems with larger pipes to incorporate future 

6048 sea-level rise. Retrofitting or rebuilding a drainage system can cost 10 to 20 times 

6049 as much as including larger pipes in the initial construction (Titus et al., 1987). 

6050  Rebuilding roads to a higher elevation during routine reconstruction. If a road 

6051 will eventually be elevated, it is least expensive to do so when it is rebuilt for 

6052 other purposes. 

6053  Designing bridges and other major facilities. As sea level rises, clearance under 

6054 bridges declines, impairing navigation (TRB, 2008). Building the bridge higher in 

6055 the first place can be less expensive than rebuilding it later. 

 6056 

6057 

6058 Figure 10.1 Homes set back from the shore. Myrtle Beach, South Carolina. (April, 2004) 
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6059 

6060 10.2.3 Options That Reallocate or Clarify Risks from Sea-Level Rise 

6061 Instead of imposing an immediate cost to avoid problems that may or may not occur, 

6062 these approaches impose a future cost, but only if and when the problem emerges. The 

6063 premise for these measures is that current rules or expectations can encourage people to 

6064 behave in a fashion that increases costs more than necessary. People make better 

6065 decisions when all of the costs of a decision are internalized (Samuelson and Nordhaus, 

6066 1989). Changing rules and expectations can avoid some costs, for example, by 

6067 establishing today that the eventual costs of sea-level rise will be borne by a property 

6068 owner making a decision sensitive to sea-level rise, rather than by third parties (e.g., 

6069 governments) not involved in the decision. Long-term shoreline planning and rolling 

6070 easements are two example approaches. 

 6071 

6072 Long-term shoreline planning can reduce economic or environmental costs by 

6073 concentrating development in areas that will not eventually have to be abandoned to the 

6074 rising sea. People logically invest more along eroding shores if they assume that the 

6075 government will provide subsidized shore protection (see Box 10.2) than in areas where 

6076 owners must pay for the shore protection or where government rules require an eventual 

6077 abandonment. The value to a buyer of that government subsidy is capitalized into higher 

6078 land prices, which can further encourage increased construction. Identifying areas that 

6079 will not be protected can avoid misallocation of both financial and human resources. If 

6080 residents wrongly assume that they can expect shore protection and the government does 

6081 not provide it, then real estate prices can decline; in extreme cases, people can lose their 
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6082 homes unexpectedly. People’s lives and economic investments can be disrupted if dunes 

6083 or dikes fail and a community is destroyed. A policy that clearly warns that such an area 

6084 will not be protected (see Section 12.3 in Chapter 12) could lead owners to strategically 

depreciate the physical property28 6085 and avoid some of the noneconomic impacts that can 

6086 occur after an unexpected relocation (see Section 6.4.1). (see Section 12.3 for further 

6087 discussion). 

 6088 

6089 START BOX HERE 

6090 BOX 10.2: Erosion, Coastal Programs, and Property Values 

6091 

6092 Do government shore protection and flood insurance programs increase property values and encourage 

6093 coastal development? Economic theory would lead one to expect that in areas with high land values, the 

6094 benefits of coastal development are already high compared to the cost of development, and thus most of 

6095 these areas will become developed unless the land is acquired for other purposes. In these areas, 

6096 government programs that reduce the cost of maintaining a home should generally be reflected in higher 

6097 land values; yet they would not significantly increase development because development would occur 

6098 without the programs. By contrast, in marginal areas with low land prices, coastal programs have the 

6099 potential to reduce costs enough to make a marginal investment profitable. 

6100 

6101 Several studies have investigated the impact of flood insurance on development, with mixed results. 

6102 Leatherman (1997) examined North Bethany Beach, Delaware, a community with a checkerboard pattern 

6103 of lands that were eligible and ineligible for federal flood insurance due to the Coastal Barrier Resources 

6104 Act. He found that ocean-front lots generally sold for $750,000, with homes worth about $250,000. 

6105 Development was indistinguishable between areas eligible and ineligible for flood insurance. In the less 

6106 affluent areas along the back bays, however, the absence of federal flood insurance was a deterrent to 

6107 developing some of the lower priced lots. Most other studies have not explicitly attempted to distinguish 

6108 the impact of flood insurance on low- and high-value lands. Some studies (e.g., Cordes and Yezer, 1998; 

6109 Shilling et al., 1989) have concluded that the highly subsidized flood insurance policies during the 1970s 

6110 increased development, but the actuarial policies since the early 1980s have had no detectable impact on 

6111 development. Others have concluded that flood insurance has a minimal impact on development (e.g., 

6112 GAO 1982; Miller, 1981). The Heinz Center (2000) examined the impacts of the National Flood Insurance 

6113 Program (NFIP) and estimated that “the density of structures built within the V Zone after 1981 may be 15 

6114 percent higher than it would have been if the NFIP had not been adopted. However, the expected average 

6115 annual flood and erosion damage to these structures dropped close to 35 percent. Thus, overall, the damage 

6116 to V Zone structures built after 1981 is between 25 and 30 percent lower than it would have been if 

6117 development had occurred at the lower densities, but higher expected damage that would have occurred 

6118 absent the NFIP”. A report to the Federal Emergency Management Agency (FEMA) reviewed 36 published 

6119 studies and commentaries concerning the impacts of flood insurance on development and concluded that 

6120 none of the studies offer irrefutable evidence that the availability, or the lack of availability, of flood 

6121 insurance is a primary factor in floodplain development today (Evatt, 1999, 2000). 

6122 

6123 Considering shore protection and flood insurance together, The Heinz Center (2000) estimated that “in the 

6124 absence of insurance and other programs to reduce flood risk, development density would be about 25 

 

28 Yohe et al. (1996) estimated that the nationwide value of “foresight” regarding response to sea-level rise 

is $20 billion, based largely on the strategic depreciation that foresight makes possible. 
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6125 percent lower in areas vulnerable to storm wavers ( i.e., V Zones ) than in areas less susceptible to damage 

6126 from coastal flooding”. Cordes and Yezer (1998) modeled the impact on new building permit activity in 

6127 coastal areas of shore protection activity in 42 coastal counties, including all of the counties with developed 

6128 ocean coasts in New York, New Jersey, Maryland, and Virginia. They did not find a statistically significant 

6129 relationship between shore protection and building permits. 

6130 

6131 The impact of federal programs on property values has not been assessed to the same extent. The Heinz 

6132 Center (2000) reported that along the Atlantic coast, a house with a remaining lifetime of 10 to 20 years 

6133 before succumbing to erosion is worth 20 percent less than a home expected to survive 200 years. Landry et 

6134 al. (2003) found that property values tend to be higher with wide beaches and low erosion risk. It would 

6135 therefore follow that shore protection programs that widen beaches, decrease erosion risk, and lengthen a 

6136 home’s expected lifetime would increase property values. Nevertheless, estimates of the impact on property 

6137 values are complicated by the fact that proximity to the shore increases the risk of erosion but also 

6138 improves access to the beach and views of the water (Bin et al., 2008). 

6139 END BOX 

 6140 

6141 Rolling easements can also reallocate or clarify the risks of sea-level rise, depending on 

6142 the pre-existing property rights of a given jurisdiction (Titus, 1998). A rolling easement is 

6143 an arrangement under which property owners have no right or expectation of holding 

6144 back the sea if their property is threatened. Rolling easements have been implemented by 

6145 regulation along ocean and sheltered shores in three New England states (see Section 

6146 11.2 in Chapter 11 and along ocean shores in Texas and South Carolina. Rolling 

6147 easements can also be implemented as a type of conservation easement, with the 

6148 easement donated, purchased at fair market value, or exacted as a permit condition for 

6149 some type of coastal development (Titus, 1998). In either case, they prevent property 

6150 owners from holding back the sea but otherwise do not alter what an owner can do with 

6151 the property. As the sea advances, the easement automatically moves or “rolls” landward. 

6152 Without shoreline armoring, sediment transport remains undisturbed and wetlands and 

6153 other tidal habitat can migrate naturally. Because the dry beach and intertidal land 
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6154 continues to exist, the rolling easement also preserves the public’s lateral access right to 

walk along the shore29 6155 (Matcha versus Mattox, 1986). 

 6156 

6157 Under a rolling easement, the property owner bears all of the risk of sea-level rise. 

6158 Without a rolling easement, property owners along most shores invest as if their real 

6159 estate is sustainable, and then expend resources—or persuade governments to expend 

6160 resources—to sustain the property. The overall effect of the rolling easement is that a 

6161 community clearly decides to pursue retreat instead of shore protection in the future. The 

6162 same result could also be accomplished by purchasing (or prohibiting development on) 

6163 the land that would potentially be eroded or submerged as sea level rises. That approach, 

6164 however, would have a large near-term social cost because the coastal land would then be 

6165 unavailable for valuable uses. By contrast, rolling easements do not prevent the property 

6166 from being used for the next several decades while the land remains dry. (Even if the 

6167 government purchases the rolling easement, the purchase price is a transfer of wealth, not 

a cost to society30 6168 .) The landward migration from the rolling easement should also have 

6169 lower eventual costs than having the government purchase property at fair market value 

6170 as it becomes threatened (Titus, 1991). Property owners can strategically depreciate their 

6171 property and make other decisions that are consistent with the eventual abandonment of 

6172 the property (Yohe et al., 1996; Titus, 1998), efficiently responding to information on 

 

29Another mechanism for allowing wetlands and beaches to migrate inland are setbacks, which prohibit 

development near the shore. Setbacks can often result in successful “takings” claims if a property is 

deemed undevelopable due to the setback line. By contrast, rolling easements place no restrictions on 

development and hence are not constitutional takings (see, e.g., Titus [1998]). 30A social cost involves someone losing something of value (e.g,. the right to develop coastal property) 

without a corresponding gain by someone else. A wealth transfer involves one party losing something of 

value with another party gaining something of equal value (e.g., the cost of a rolling easement being 

transferred from the government to a land owner). For additional details, see Samuelson and Nordhaus 

(1989). 
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6173 sea-level rise as it becomes available. Figure 9.1 shows how a rolling easement might 

6174 work over time in an area already developed when rolling easements are obtained. 

6175 

6176 Figure 10.2 The landward migration of wetlands onto property subject to a rolling easement. A rolling 

6177 easement allows construction near the shore, but requires the property owner to recognize nature’s right-of6178 way to advance inland as sea level rises. In the case depicted, the high marsh reaches the footprint of the 

6179 house 40 years later. Because the house is on pilings, it can still be occupied (assuming that it is hooked to 

6180 a sewerage treatment plant. A flooded septic system would probably fail, because the drainfield must be a 

6181 minimum distance above the water table). After 60 years, the marsh has advanced enough to require the 

6182 owner to park their car along the street and construct a catwalk across the front yard. After 80 years, the 

6183 marsh has taken over the entire yard; moreover, the footprint of the house is now seaward of mean high 

6184 water and hence, on public property. At this point, additional reinvestment in the property is unlikely. 

6185 Twenty years later, the particular house has been removed, although other houses on the same street may 

6186 still be occupied. Eventually, the entire area returns to nature. A home with a rolling easement would 

6187 depreciate in value rather than appreciate like other coastal real estate. But if the loss is expected to occur 

6188 100 years from today, it would only offset the current property value by 1 to 5 percent, which could be 

6189 compensated or offset by other permit considerations (Titus, 1998). 

6190 

 6191 

6192 10.3 PROTECTING COASTAL WETLANDS 

6193 The nation’s wetland programs generally protect wetlands in their current locations, but 

6194 they do not explicitly consider retreating shorelines. As sea level rises, wetlands can 
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6195 adapt by accreting vertically (Chapter 4) and migrating inland. Most tidal wetlands are 

6196 likely to keep pace with the current rate of sea-level rise but could become marginal with 

6197 an acceleration of 2 millimeters (mm) per year, and are likely to be lost if sea-level rise 

6198 accelerates by 7 mm per year (see Chapter 4). Although the dry land available for 

6199 potential wetland migration or formation is estimated to be less than 20 percent of the 

6200 current area of wetlands (see Titus and Wang 2008), these lands could potentially become 

6201 important wetland areas in the future. However, given current policies and land-use 

6202 trends, they may not be available for wetland migration and formation (Titus 1998, 

6203 2001). Much of the coast is developed or being developed, and those who own developed 

6204 dry land adjacent to the wetlands increasingly take measures to prevent the wetlands from 

6205 migrating onto their property (see Figure 10.4 and Chapter 6). 

 6206 

6207 

6208 Figure 10.3 Coastal Wetlands migrating onto previously dry lowland. Webbs Island, just east of 

6209 Machipongo, in Northampton County, Virginia (June, 2007). 

6210 

6211 

 6212 
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6213 

6214 Figure 10.4 Wetland Migration thwarted by development and shore protection. Elevating the land surface 

6215 with fill prevents wetlands from migrating into the back yard with a small or modest rise in sea level. The 

6216 bulkhead prevents waves from eroding the land, which would otherwise provide sand and other soil 

6217 materials to help enable the wetlands to accrete with rising sea level (Monmouth New Jersey, August, 

6218 2003). 

 6219 

6220 Continuing the current practice of protecting almost all developed estuarine shores could 

6221 reverse the accomplishments of important environmental programs (e.g., Titus 1991, 

6222 2001, 2005). Until the mid-twentieth century, tidal wetlands were often converted to 

6223 dredge-and-fill developments (see Section 6.1.1.2 in Chapter 6 for an explanation of 

6224 these developments and their vulnerability to sea-level rise). By the 1970s, the aggregate 

6225 result of the combination of federal and state regulations had, for all practical purposes, 

6226 halted that practice. Today, most tidal wetlands in the Mid-Atlantic are off-limits to 

6227 development. Coastal states generally prohibit the filling of low marsh, which is publicly 

6228 owned in most states under the Public Trust Doctrine (see Section 8.2). 

 6229 

6230 A landowner who wants to fill tidal wetlands on private property must usually obtain a 

permit from the U.S. Army Corps of Engineers (USACE)31 6231 . These permits are generally 

not issued unless the facility is inherently water-related, such as a marina32 6232 . Even then, 

 

31 33 U.S.C. §§ 403, 409, 1344(a) 

32 40 C.F.R. § 230.10(a)(3)
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6233 the owners usually must mitigate the loss of wetlands by creating or enhancing wetlands 

6234 elsewhere (U.S. EPA and USACE, 1990). (Activities with small impacts on wetlands, 

6235 however, are often covered by a nationwide permit, which exempts the owner from 

6236 having to obtain a permit [see Section 12.2]). The overall effect of wetland programs has 

6237 been to sharply reduce the rate of coastal wetland loss (e.g., Stockton and Richardson, 

6238 1987; Hardisky and Klemas, 1983) and to preserve an almost continuous strip of 

6239 marshes, beaches, swamps, and mudflats along the U.S. coast. If sea-level rise 

6240 accelerates, these coastal habitats could be lost by submergence and—in developed areas 

6241 where shores are protected—by prevention of their natural inland migration (Reed et al., 

6242 2008), unless future generations use technology to ensure that wetland surfaces rise as 

6243 rapidly as the sea (NRC, 2007). 

 6244 

6245 Current approaches would not protect wetlands for future generations if sea level rises 

6246 beyond the ability of wetlands to accrete, which is likely for most of Chesapeake Bay’s 

6247 wetlands if sea level rises 50 centimeters (cm) in the next century, and for most of the 

6248 Mid-Atlantic if sea level rises 100 cm (see Figure 4.4). 

 6249 

6250 Current federal statutes are designed to protect existing wetlands, but the totality of the 

6251 nation’s wetland protection program is the end result of decisions made by many actors. 

6252 Federal programs discourage destruction of most existing coastal wetlands, but the 

6253 federal government does little to allow tidal wetlands to migrate inland (Titus, 2000). 

6254 North Carolina, Maryland, New Jersey, and New York own the tidal wetlands below 

6255 Mean High Water; and Virginia, Delaware, and Pennsylvania have enough ownership 
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6256 interest under the Public Trust Doctrine to preserve them (Titus, 1998). However, most 

6257 states give property owners a near-universal permit to protect property by preventing 

6258 wetlands from migrating onto dry land. Farmers rarely erect shore protection structures, 

6259 but homeowners usually do (Titus, 1998; NRC, 2006). Only a few coastal counties and 

6260 states have decided to keep shorefront farms and forests undeveloped, (see Sections 

6261 A1.D, A1.E, and A1.F in Appendix 1). Government agencies that hold land for 

6262 conservation purposes are not purchasing the land or easements necessary to enable 

6263 wetlands to migrate inland (Section 11.2.1 discusses private conservancies). In effect, the 

6264 nation has decided to save its existing wetlands. Yet the overall impact of the decisions 

6265 made by many different agencies is very likely to eliminate wetlands by blocking their 

6266 landward migration as a rising sea erodes their outer boundaries. 

 6267 

6268 Not only is the long-term success of wetland protection sensitive to sea-level rise, it is 

6269 also sensitive to when people decide to prepare. The political and economic feasibility of 

6270 allowing wetlands to take over a given parcel as sea level rises is much greater if 

6271 appropriate policies are in place before that property is intensely developed. Many coastal 

6272 lands are undeveloped today, but development continues. Deciding now that wetlands 

6273 will have land available to migrate inland could protect more wetlands at a lower cost 

6274 than deciding later (Titus, 1991). In some places, such policies might discourage 

6275 development in areas onto which wetlands may be able to migrate. In other areas, 

6276 development could occur with the understanding that eventually land will revert to nature 

6277 if sea level rises enough to submerge it. As with beach nourishment, artificially elevating 

6278 the surfaces of tidal wetlands would not always require a lead-time of several decades; 
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6279 but developing technologies to elevate the wetlands, and determining whether and where 

6280 they are appropriate, could take decades. Finally, in some areas, the natural vertical 

6281 accretion (build-up) of tidal wetlands is impaired by human activities, such as water flow 

6282 management, development that alters drainage patterns, and beach nourishment and inlet 

6283 modification, which thwarts barrier island overwash. In those areas, restoring natural 

6284 processes before the wetlands are lost is more effective than artificially re-creating them 

6285 (U.S. EPA, 1995; U.S. EPA and USACE, 1990; Kruczynski, 1990). 

 6286 

6287 Although the long-term success of the nation’s efforts to protect wetlands is sensitive to 

6288 sea-level rise, most of the individual decisions that ultimately determine whether 

6289 wetlands can migrate inland depend on factors that are not sensitive to sea-level rise. The 

6290 desire of bay-front homeowners to keep their homes is strong, and unlikely to diminish 

even with a significant acceleration of sea-level rise33 6291 . State governments must balance 

6292 the public interest in tidal wetlands against the well-founded expectations of coastal 

6293 property owners that they will not have to yield their property. Only a few states (none in 

6294 the Mid-Atlantic) have decided in favor of the wetlands (see Section 11.2.1). Local 

6295 government decisions regarding land use reflect many interests. Objectives such as near6296 term tax revenues (often by seasonal residents who make relatively few demands for 

6297 services) and a reluctance to undermine the economic interests of landowners and 

6298 commercial establishments are not especially sensitive to rising sea level. 

 6299 

 

33 See Weggel et al. (1989), Titus et al. (1991), and NRC (2007) for an examination of costs and options for 

estuarine shore protection. 
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6300 Today’s decentralized decision-making process seems to protect existing coastal 

6301 wetlands reasonably well at the current rate of sea-level rise; however, it will not enable 

6302 wetlands to migrate inland as sea-level rise continues or accelerates. A large-scale 

6303 landward migration of coastal wetlands is very unlikely to occur in most of the Mid6304 Atlantic unless a conscious decision is made for such a migration by a level of 

6305 government with authority to do so. Tools for facilitating a landward migration include 

6306 coastal setbacks, density restrictions, rolling easements, vegetation buffers, and building 

6307 design standards (see Sections 6.1.2 and A1.D, and A1.F in Appendix 1 for further 

6308 details). 

 6309 

6310 10.4 SHORE PROTECTION 

6311 The case for anticipating sea-level rise as part of efforts to prevent erosion and flooding 

6312 has not been as strong as the case for wetland protection. Less lead time is required for 

6313 shore protection than for a planned retreat and wetland migration (NRC, 1987). Dikes, 

6314 seawalls, bulkheads, and revetments can each be built within a few years. Beach 

6315 nourishment is an incremental periodic activity; if the sea rises more than expected, 

6316 communities can add more sand. 

 6317 

6318 The U.S. Army Corps of Engineers (USACE) has not evaluated whether sea-level rise 

6319 will ultimately require fundamental changes in shore protection; such changes do not 

6320 appear to be urgent. Since the early 1990s, USACE has recommended robust strategies: 

6321 “Feasibility studies should consider which designs are most appropriate for a range of 

6322 possible future rates of rise. Strategies that would be appropriate for the entire range of 
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6323 uncertainty should receive preference over those that would be optimal for a particular 

6324 rate of rise but unsuccessful for other possible outcomes” (USACE, 2000a). To date, this 

6325 guidance has not significantly altered USACE’s approach to shore protection. 

6326 Nevertheless, there is some question as to whether continued beach nourishment would 

6327 be sustainable in the future if the rate of sea-level rise accelerates. It may be possible to 

6328 double or triple the rate at which USACE nourishes beaches and to elevate the land 

6329 surfaces of barrier islands 50 to 100 cm, and thereby enable land surfaces to keep pace 

6330 with rising sea level in the next century. Yet continuing such a practice indefinitely 

6331 would eventually leave back-barrier bays much deeper than today (see Chapter 5), with 

6332 unknown consequences for the environment and the barrier islands themselves. Similarly, 

6333 it may be possible to build a low bulkhead along mainland shores as sea level rises 50 to 

6334 100 cm; however, it could be more challenging to build a tall dike along the same shore 

6335 because it would block waterfront views, require continual pumping, and expose people 

6336 behind the dike to the risk of flooding should that dike fail (Titus, 1990). 

 6337 

6338 10.5 LONG-LIVED STRUCTURES: SHOULD WE PLAN NOW OR LATER? 

6339 The fact that eventually a landowner will either hold back the sea or allow it to inundate a 

6340 particular parcel of land does not, by itself, imply that the owner must respond today. A 

6341 community that will not need a dike until the sea rises 50 to 100 cm has little reason to 

6342 build that dike today. Nevertheless, if the land where the dike would eventually be 

6343 constructed is vacant now, the prospect of future sea-level rise might be a good reason to 

6344 leave that land vacant. A homeowner whose house will be inundated (or eroded) in 30 to 

6345 50 years has little reason to move the house back today, but if it is damaged by fire or 
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6346 storms, it might be advisable to rebuild the house on a higher (or more inland) part of the 

6347 lot to provide the rebuilt structure a longer lifetime. 

 6348 

6349 Whether one must be concerned about long-term sea-level rise ultimately depends on the 

6350 lead time of the response options and on the costs and benefits of acting now versus

6351 acting later. A fundamental premise of cost-benefit analysis is that resources not yet 

6352 deployed can be invested profitably in another activity and yield a return on investment. 

6353 Delaying the response is economically efficient if the most effective response can be 

6354 delayed with little or no additional cost, which is the case with most engineering 

6355 responses to sea-level rise. For a given level of protection, dikes, seawalls, beach 

6356 nourishment, and elevating structures and roadways are unlikely to cost more in the 

6357 future than they cost today (USACE, 2000b, 2007). Moreover, these approaches can be 

6358 implemented within the course of a few years. If shore protection is the primary approach 

6359 to sea-level rise, responding now may not be necessary, with two exceptions. 

 6360 

6361 The first exception could be called the “retrofit penalty” for failure to think long-term. It 

6362 may be far cheaper to design for rising sea level in the initial design of a new (or rebuilt) 

6363 road or drainage system than to modify it later because modifying it later requires the 

6364 facility, in effect, to be built twice. For example, in a particular watershed in Charleston, 

6365 South Carolina, if sea level rises 30 cm (1 ft), the planned drainage system would fail and 

6366 need to be rebuilt, but it would only cost an extra 5 percent to initially design the system 

6367 for a 30-cm rise (Titus et al., 1987). Similarly, bridges are often designed to last for 100 

6368 years, and although roads are paved every 10 to 20 years, the location of a road may stay 
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6369 the same for centuries. Thus, choices made today about the location and design of 

6370 transportation infrastructures can have a large impact on the feasibility and cost of 

6371 accommodating rising sea level in the future (TRB, 2008). The design and location of a 

6372 house is yet another example. If a house is designed to be movable, it can be relocated 

6373 away from the shore; but non-moveable houses, such as a brick house on a slab 

6374 foundation, could be more problematic. Similarly, the cost of building a house 10 meters 

6375 (m) farther from the shore may be minor if the lot is large enough, whereas the cost of 

6376 moving it back 10 m could be substantial (U.S. EPA, 1989). 

 6377 

6378 The second exception concerns the incidental benefits of acting sooner. If a dike is not 

6379 needed until the sea rises 0.5 m, because at that point a 100-year storm would flood the 

6380 streets with 1 m of water, the decision to not build the dike today implicitly accepts the 

6381 0.5 m of water that such a storm would provide today. If a dike is built now, it would stop 

6382 this smaller flood as well as protect from the larger flood that will eventually occur. This 

6383 reasoning was instrumental in leading the British to build the Thames River Barrier, 

6384 which protects London. Some people argued that this expensive structure was too costly 

6385 given the small risk of London flooding, but rising sea level implied that such a structure 

6386 would eventually have to be built. Hence, the Greater London Council decided to build it 

6387 during the 1970s (Gilbert and Horner, 1984). As expected, the barrier closed 88 times to 

6388 prevent flooding between 1983 and 2005 (Lavery and Donovan 2005). 

 6389 

6390 While most engineering responses can be delayed with little penalty, failure to consider 

6391 sea-level rise when making land-use decisions could be costly. Once an area is 
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6392 developed, the cost of vacating it as the sea rises is much greater than that cost would 

6393 have been if the area was not developed. This does not mean that eventual inundation 

6394 should automatically result in placing land off-limits to development. Even if a home has 

6395 to be torn down 30 to 50 years hence, it might still be worth building. In some coastal 

6396 areas where demand for beach access is great and land values are higher than the value of 

6397 the structures, rentals may recover the cost of home construction in less than a decade. 

6398 However, once an area is developed, it is unlikely to be abandoned unless either the 

6399 eventual abandonment was part of the original construction plan, or the owners can not 

6400 afford to hold back the sea. Therefore, the most effective way to preserve natural shores 

6401 is to make such a decision before an area is developed. Because the coast is being 

6402 developed today, a failure to deal with this issue now is, in effect, a decision to allow the 

6403 loss of wetlands and bay beaches along most areas where development takes place. 

 6404 

6405 Many options can be delayed, because the benefits of preparing for sea-level rise would 

6406 still accrue later. Delaying action decreases the present value of the cost of acting and 

6407 may make it easier to tailor the response to what is actually necessary. Yet delay can also 

6408 increase the likelihood that people do not prepare until it is too late. One way to address 

6409 this dilemma is to consider the lead times associated with particular types of adaptation 

6410 (IPCC CZMG, 1992; O’Callahan, 1994). Emergency beach nourishment and bulkheads 

6411 along estuarine shores can be implemented in less than a year. Large-scale beach 

6412 nourishment generally takes a few years. Major engineering projects to protect London 

6413 and the Netherlands took a few decades to plan, gain consensus, and construct (e.g., 
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6414 Gilbert and Horner, 1984). To minimize the cost of abandoning an area, land use 

6415 planning requires a lead time of 50 to 100 years (Titus, 1991, 1998). 

 6416 

6417 10.6 DECISIONS BY COASTAL PROPERTY OWNERS ON ELEVATING 

6418 HOMES 

6419 People are increasingly elevating homes to reduce the risk of flooding during severe 

6420 storms and, in very low-lying areas, people are also elevating their yards. The cost of 

6421 elevating even a small wood-frame cottage on a block foundation is likely to be $15,000 

6422 to $20,000; larger houses cost proportionately more (Jones et al., 2006; FEMA, 1998). If 

6423 it is necessary to drill pilings, the cost is higher because the house must be moved to the 

6424 side and then moved back onto the pilings. If elevating the home prevents its subsequent 

6425 destruction within a few decades, it will have been worthwhile. At a 5 percent discount 

6426 rate, for example, it is worth investing 25 percent of the value of a structure to avoid a 

guaranteed loss 28 years later34 6427 . In areas where complete destruction is unlikely, people 

6428 sometimes elevate homes to obtain lower insurance rates and to avoid the risk of water 

6429 damages to walls and furniture. The decision to elevate involves other factors, both 

6430 positive and negative, including better views of the water, increased storage and/or 

6431 parking spaces, and greater difficulty for the elderly or disabled to enter their homes. 

6432 Rising sea level can also be a motivating factor when an owner is uncertain about 

6433 whether the current risks justify elevating the house, because rising water levels would 

 

34 i.e., $25 invested today would be worth $25 x (1.05)28 = $98 twenty eight years hence. Therefore, it is 

better to invest $25 today than to face a certain loss of $100 28 years hence (see glossary for definition of 

discount rate). 
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6434 eventually make it necessary to elevate it (unless there is a good chance that the home 

6435 will be rebuilt or replaced before it is flooded). 

 6436 

6437 In cases where a new home is being constructed, or an existing home is elevated for 

6438 reasons unrelated to sea-level rise (such as a realization of the risk of flooding), rising sea 

6439 level would justify a higher floor elevation that would otherwise be the case. For 

6440 example, elevating a $200,000 home on pilings to 30cm above the base flood elevation 

6441 when the home is built would increase the construction cost by approximately $500-1000 

6442 more than building the home at the base flood elevation (Jones et al., 2006). Yet a 30 cm 

6443 rise in sea level would increase the actuarial annual flood insurance premium by more 

6444 than $2000 if the home was not elevated the extra 30 cm (NFIP, 2008). 

 6445 

6446 10.7 FLOODPLAIN MANAGEMENT 

6447 The Federal Emergency Management Agency (FEMA) works with state and local 

6448 governments on a wide array of activities that are potentially sensitive to rising sea level, 

6449 including floodplain mapping, floodplain regulations, flood insurance rates, and the 

6450 various hazard mitigation activities that often take place in the aftermath of a serious 

6451 storm. Although the outcomes of these activities are clearly sensitive to sea-level rise, 

6452 previous assessments have focused on coastal erosion rather than on sea-level rise. 

6453 Because implications of sea-level rise and long-term erosion overlap in many cases, 

6454 previous efforts provide insights on cases where the risks of future sea-level rise may 

6455 warrant changing the way things are done today. 

 6456 
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6457 10.7.1 Floodplain Regulations 

6458 The flood insurance program requires new or substantially rebuilt structures in the coastal 

6459 floodplain to have the first floor above the base flood elevation, i.e., 100-year flood level. 

6460 (see Chapter 9). The program vests considerable discretion in local officials to tailor 

6461 specific requirements to local conditions, or to enact regulations that are more stringent 

6462 than FEMA’s minimum requirements. Several communities have decided to require floor 

6463 levels to be 30 cm (or more) above the base flood elevation (e.g., Township of Long 

6464 Beach, 2008; Town of Ocean City, 1999; see also Box A1.5 in Appendix 1). In some 

6465 cases, past or future sea-level rise has been cited as one of the justifications for doing so 

6466 (Cape Cod Commission, 2002). There is considerable variation in both the costs and 

6467 benefits of designing buildings to accommodate future sea-level rise. If local 

6468 governments believe that property owners need an incentive to optimally address sea6469 level rise, they can require more stringent (i.e., higher) floor elevations. A possible reason 

6470 for requiring higher floor elevations in anticipation of sea-level rise (rather than allowing 

6471 the owner to decide) is that, under the current structure of the program, the increased risk 

6472 from sea-level rise does not lead to proportionately higher insurance rates (see Section 

6473 10.7.3.1) (although rates can rise for other reasons). 

 6474 

6475 10.7.2 Floodplain Mapping 

6476 Local jurisdictions have pointed out (see Box A1.6 in Appendix 1) that requiring floor 

6477 elevations above the base flood elevation to prepare for sea level rise can create a 

6478 disparity between property inside and outside the existing 100-year floodplain. 

 6479 
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6480 Unless floodplain mapping also takes sea-level rise into account, a building in the current 

6481 floodplain would have to be higher than adjacent buildings on higher ground just outside 

6482 the floodplain (see Figure 10.5). Thus, the ability of local officials to voluntarily prepare 

6483 for rising sea level is somewhat constrained by the lack of floodplain mapping that takes 

6484 sea-level rise into account. Incorporating sea-level rise into floodplain maps would be a 

6485 low-regrets activity, because it is relatively inexpensive and would enable local officials 

6486 to modify requirements where appropriate. 

 6487 

6488 

6489 Figure 10.5 Rationale for incorporating sea-level rise into floodplain mapping. In this figure, the (left) 

6490 three houses in the existing floodplain have first floor elevations about 80 centimeters (cm) above the level 

6491 of the 100-year storm, to account for a projected 50-cm rise in sea level and the standard requirement for 

6492 floors to be 30 cm above the base flood elevation. The (right) three homes outside of the regulated 

6493 floodplain are exempt from the requirement. Actual floods, however, do not comply with floodplain 

6494 regulations. A 100-year storm on top of the higher sea level would thus flood the buildings to the right 

6495 which are outside of today’s floodplain, while the regulated buildings would escape the flooding. This 

6496 potential disparity led the city of Baltimore to suggest that floodplain mapping should account for sea level 

6497 rise as part of any process to increase the freeboard requirement (see Box A1.7, Section A1.F in Appendix 

1). 6498 

 6499 

6500 10.7.3 Federal Flood Insurance Rates 

6501 The available reports on the impacts of rising sea level or shoreline retreat on federal 

6502 flood insurance have generally examined one of two questions: 

6503  What is the risk to the financial integrity of the flood insurance program? 

6504  Does the program discourage policyholders from preparing for sea-level rise by 

6505 shielding them from the consequences of increased risk? 
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6506 No assessment has found that sea-level rise threatens the federal program’s financial 

6507 integrity. A 1991 report to Congress by FEMA, for example, concluded that there was 

6508 little need to change the Flood Insurance Program because rates would be adjusted as sea 

6509 level rises and flood maps are revised (FEMA, 1991). Nevertheless, the current rate 

6510 structure can discourage some policyholders from preparing for increases in flood risks 

6511 caused by sea-level rise, shore erosion, and other environmental changes. For new and 

6512 rebuilt homes, the greater risks from sea-level rise cause a roughly proportionate increase 

6513 in flood insurance premiums. For existing homes, however, the greater risks from sea6514 level rise cause premiums to rise much less than proportionately, and measures taken to 

6515 reduce vulnerability to sea-level rise do not necessarily cause rates to decline. 

 6516 

6517 Flood insurance policies can be broadly divided into actuarial and subsidized. “Actuarial” 

6518 means that the rates are designed to cover the expected costs; “subsidized” means that the 

6519 rates are designed to be less than the cost, with the government making up the difference. 

6520 Most of the subsidized policies apply to “pre-FIRM” construction, that is, homes that 

6521 were built before the Flood Insurance Rate Map (FIRM) was adopted for a given 

locality35 6522 ; and most actuarial policies are for post-FIRM construction. Nevertheless, there 

6523 are also a few small classes of subsidized policies for post-FIRM construction; and some 

6524 owners of pre-FIRM homes pay actuarial rates. The following subsections discuss these 

6525 two broad categories in turn. 

 6526 

6527 10.7.3.1 Actuarial (Post-FIRM) Policies 

 

35 Flood Insurance Rate Maps display the flood hazards of particular locations for purposes of setting flood 

insurance rates. The maps do not show flood insurance rates (see Chapter 9 for additional details). 
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6528 Flood Insurance Rate Maps show various hazard zones, such as V (wave velocity) Zone, 

A (stillwater flooding during a 100-year storm) Zone and the “shaded X Zone”36 6529 

6530 (stillwater flooding during a 500-year storm) (see Chapter 9). These zones are used as 

6531 classes for setting rates. The post-FIRM classes pay actuarial rates. For example, the total 

6532 premiums by all post-FIRM policyholders in the A Zone equals FEMA’s estimate of the 

claims and administrative costs for the A Zone37 6533 . Hypothetically, if sea-level rise were to 

6534 double flood damage claims in the A Zone, then flood insurance premiums would double 

(ignoring administrative costs)38 6535 . Therefore, the impact of sea-level rise on post-FIRM 

6536 policy holders would not threaten the program’s financial integrity under the current rate 

6537 structure. 

 6538 

6539 The rate structure can, however, insulate property owners from the effects of sea-level 

rise, removing the market signal39 6540 that might otherwise induce a homeowner to prepare or 

6541 respond to sea-level rise. Although shoreline erosion and rising sea level increase the 

6542 expected flood damages of a given home, the increased risk to a specific property does 

6543 not cause the rate on that specific property to rise. Unless a home is substantially 

 

36 The shaded X Zone was formerly known as the B Zone. 

37 Owners of pre-FIRM homes can also pay the actuarial rate, if it is less than the subsidized rate. 38 The National Flood Insurance Program (NFIP) modifies flood insurance rates every year based on the 

annual “Actuarial Rate Review”. Rates can either be increased, decreased, or stay the same, for any given 

flood insurance class. The rates for post-FIRM policies are adjusted based on the risk involved and 

accepted actuarial principals. As part of this rate adjustment, hydrologic models are used to estimate loss 

exposure in flood-prone areas. These models are rerun every year using the latest hydrologic data available. 

As such, the models incorporate the retrospective effects of sea level rise. The rates for pre-FIRM 

(subsidized) structures are also modified every year based in part on a determination of what is known as 

the “Historical Average Loss Year”. The goal of the NFIP is for subsidized policyholders to pay premiums 

that are sufficient, when combined with the premium paid by actuarially priced (post-FIRM) policyholders, 

to provide the NFIP sufficient revenue to pay losses associated with the historical average loss year. 

39 In economics, “market signal” refers to information passes indirectly or unintentionally between 

participants in a market. For example, higher flood insurance rates convey the information that a property is 

viewed as being riskier than previously thought. 
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changed, its assumed risk is grandfathered40 6544 , that is, FEMA assumes that the risk has not 

6545 increased when calculating the flood insurance rate (e.g., NFIP, 2007; Heinz Center, 

2000)41 6546 . Because the entire class pays an actuarial rate, the grandfathering causes a 

6547 “cross-subsidy” between new or rebuilt homes and the older grandfathered homes. 

 6548 

6549 Grandfathering can discourage property owners from either anticipating or responding to 

6550 sea-level rise. If anticipated risk is likely to increase, for example, by about a factor of 10 

6551 and a total loss would occur eventually (e.g., a home on an eroding shore), grandfathering 

6552 the assumed risk may allow the policy holder to secure compensation for a total loss at a 

6553 small fraction of the cost of that loss. For instance, a $250,000 home built to base flood 

6554 elevation in the A Zone would typically pay about $900 per year (NFIP, 2008); but if 

6555 shore erosion left the property in the V Zone, the annual rate would rise to more than 

$10,000 (NFIP, 2008)42 6556 , if the property was not grandfathered. Under such 

6557 circumstances, the $9,000 difference in eventual insurance premiums might be enough of 

6558 a subsidy to encourage owners to build in locations more hazardous than where they 

6559 might have otherwise built had they anticipated that they would bear the entire risk (cf.

 

40 Under the NFIP grandfathering policy, whenever FEMA revises the flood risk maps used to calculate the 

premium for specific homes, a policy holder can choose between the new map and the old map, whichever 

results in the lower rate (NFIP, 2007). 

41 Although rates for individual policies may be grandfathered, rates for the entire A or V Zone (or any 

flood zone) can still increase each year up to a maximum of 10 percent; therefore a grandfathered policy 

may still see annual rate increases. For example, a post-FIRM structure might be originally constructed in 

an A Zone at 30 cm (1 ft) above base flood elevation. If shore erosion, sea-level rise, or a revised mapping 

procedure leads to a new map that shows the same property to be in the V Zone and 60 cm (2 ft) below 

base flood elevation, the policy holder can continue to pay as if the home was 30 cm above base flood 

elevation in the A Zone. However, the entire class of A Zone rates could still increase as a result of annual 

class-wide rate adjustments based on the annual “Actuarial Rate Review”. Those class-wide increases 

could be caused by long-term erosion, greater flooding from sea-level rise, increased storm severity, higher 

reconstruction or administrative costs, or any other factors that increase the cost of paying claims by 

policyholders. 

42 This calculation assumes a storm-wave height adjustment of 90 cm and no sea-level rise (see NFIP, 

2008). 
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6560 Heinz Center, 2000). For homes built in the A Zone, the effect of grandfathering is less, 

6561 but still potentially significant (see Figure 10.6). 

 6562 

6563 Grandfathering can also remove the incentive to respond as sea level rises. Consider a 

6564 home in the A Zone that is originally 30 cm (about 1 ft) above the base flood elevation. If 

6565 sea level rises 30 to 90 cm (almost 1 to 3 ft), then the actuarial rates would typically rise 

6566 by approximately two to ten times the original amount (NFIP, 2008), but because of 

6567 grandfathering, the owners would continue to pay the same premium. Therefore, if the 

6568 owner were to elevate the home 30 to 90 cm, the insurance premium would not decline 

6569 because the rate already assumes that the home is 30 cm above the flood level (see the 

6570 bottom four panels of Figure 10.6). 

 6571 
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6572 

6573 

6574 Figure 10.6 Impact of grandfathering and floor elevation on flood insurance rates in the A Zone as sea 

6575 level rises. Without grandfathering, a 90-centimeter (cm) rise in sea level would increase the flood 

6576 insurance rate from $355 to $4720, for a home built 60 cm above today’s 100-year flood elevation (left 

6577 column); if the home is built 150 cm above the 100-year flood, sea level rise increases the rate from $280 to 

6578 $355. Elevating the house 90 cm after sea level rise lowers the rate to what it had been originally, Thus, if 

6579 the 90 cm rise is expected during the owner’s planning horizon, there would be a significant incentive to 

6580 either build the house higher or elevate it later. With grandfathering, however, sea-level rise does not 

6581 increase the rate and elevating the home later does not reduce the rate. Thus, grandfathering reduces the 

6582 incentive to anticipate sea level rise or react to it after the fact. 

6583 Caveat: The numerical example is based on rates published in NFIP (2008), Table 3B, and does not include 

6584 the impact of the annual changes in the rate structure. Such rate changes would complicate the numerical 

6585 illustration, but would not fundamentally alter the incentives illustrated, because the annual rate changes 

6586 are across-the-board within a given class. For example, if rates increased by 50 percent by the time sea 

6587 level rises 90 cm, then all of the premiums shown in the bottom four boxes would rise 50 percent. 

6588 
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 6589 

6590 The importance of grandfathering is sensitive to the rate of sea-level rise. At the current 

6591 rate of sea-level rise (3 mm per year), most homes would be rebuilt (and thus lose the 

6592 grandfathering benefit) before the 100 to 300 years it takes for the sea to rise 30 to 90 cm. 

6593 By contrast, if sea level rises 1 cm per year, this effect would only take 30 to 90 years—

6594 and many coastal homes survive that long. 

 6595 

6596 Previous assessments have examined this issue (although they were focused on shoreline 

6597 erosion from all causes, rather than from sea-level rise). The National Academy of 

6598 Sciences (NAS) has recommended that the Flood Insurance Program create mechanisms 

6599 to ensure that insurance rates reflect the increased risks caused by long-term coastal 

6600 erosion (NAS, 1990). NAS pointed out that Congress has explicitly included storm6601 related erosion as part of the damages covered by flood insurance (42 U.S.C. §4121), and 

6602 that FEMA’s regulations (44 CFR Part 65.1) have already defined special “erosion 

zones”, which consider storm-related erosion (NAS, 1990)43 6603 . A FEMA-supported report 

6604 to Congress by The Heinz Center (2000) and a theme issue in the Journal of Coastal 

6605 Research (Crowell and Leatherman, 1999) also concluded that, because of existing long6606 term shore erosion, there can be a substantial disparity between actual risk and insurance 

6607 rates. 

 6608 

 

43 Note that: (1) the NFIP insures against damages caused by flood-related-erosion; (2) the probability of 

flood-related erosion is considered in defining the landward limit of V Zones; and (3) flood insurance rates 

in the V Zone are generally much higher than A Zone rates. Part of the reason for this is consideration of 

the potential for flood-related erosion. 
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6609 Would sea-level rise justify changing the current approach? Two possible alternatives 

6610 would be to (1) shorten the period during which the assumed risk is kept fixed so that 

6611 rates can respond to risk and property owners can respond, or (2) lengthen the duration of 

6612 the insurance policy to the period of time between risk calculations, that is, instead of 

6613 basing rates on the risk when the house is built, which tends to increasingly 

6614 underestimate the risk, base the rate on an estimate of the average risk over the lifetime of 

6615 the structure, using “erosion-hazard mapping” with assumed rates of sea-level rise, shore 

6616 erosion, and structure lifetime. Both of these alternatives address changing risk by 

6617 estimating risk over a time horizon equal to the period of time between risk recalculation. 

6618 The erosion-hazard mapping approach has received considerable attention; the Heinz 

6619 Center study also recommended that Congress authorize erosion-hazard mapping. 

6620 Although Congress has not provided FEMA with authority to base rates on erosion 

6621 hazard mapping, FEMA has raised rates in the V Zone by 10 percent per year (during 

6622 most years) as a way of anticipating the increased flood damages resulting from the long6623 term erosion that The Heinz Center evaluated (Crowell et al., 2007). 

 6624 

6625 The Heinz Center study and recent FEMA efforts have assumed current rates of sea-level 

6626 rise. FEMA has not investigated whether accelerated sea-level rise would increase the 

6627 disparity between risks and insurance rates enough to institute additional changes in rates; 

6628 nor has it investigated the option of relaxing the grandfathering policy so that premiums 

6629 on existing homes rise in proportion to the increasing risk. Nevertheless, the Government 

6630 Accountability Office (2007) recently recommended that FEMA analyze the potential 

6631 long-term implications of climate change for the National Flood Insurance Program 
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6632 (NFIP). FEMA agreed to undertake such a study (Buckley, 2007) and initiated it in 

6633 September 2008 (Department of Homeland Security, 2008). 

 6634 

6635 10.7.3.2 Pre-FIRM and other Subsidized Policies 

6636 Since the 1970s, the flood insurance program has provided a subsidized rate for homes 

6637 built before the program was implemented, that is, before the release of the first flood 

6638 insurance rate map for a given location (Hayes et al., 2006). The premium on a $100,000 

6639 home, for example, is generally $650 and $1170 for the A and V Zones, respectively—

6640 regardless of how far above or below the base flood elevation the structure may be 

6641 (NFIP, 2008). Not all pre-FIRM homes obtain the subsidized policy. The subsidized rate 

6642 is currently greater than the actuarial rate in the A and V Zones for homes that are at least 

6643 30 cm and 60 cm, respectively, above the base flood elevation (NFIP, 2008). But the 

6644 subsidy is substantial for homes that are below the base flood elevation. Homes built in 

6645 the V Zone between 1975 and 1981 also receive a subsidized rate; which is about $1500 

6646 for a $100,000 home built at the base flood elevation (NFIP, 2008). 

 6647 

6648 Does sea-level rise justify changing the rate structure for subsidized policies? Economics 

6649 alone can not answer that question because the subsidies are part of the program for 

6650 reasons other than risk management and economic efficiency, such as the original 

6651 objective of providing communities with an incentive to join the NFIP and the policy 

6652 goal of not pricing people out of their homes (Hayes et al., 2006). Moreover, the 

6653 implications depend in large measure on whether the NFIP responds to increased 

6654 damages from sea-level rise by increasing premiums or the subsidy, a question that rests 
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6655 on decisions that have not yet been made. Sea-level rise elevates the base flood elevation; 

6656 and the subsidized rate is the same regardless of how far below the base flood elevation a 

6657 home is built. Considering those factors alone, sea-level rise increases expected damages, 

6658 but not the subsidized rate. However, the NFIP sets the subsidized rates to ensure that the 

entire program covers its costs during the average non-catastrophic year44 6659 . Therefore, if 

6660 total damages (which include inland flooding) rise by the same proportion as damages to 

6661 subsidized policies, the subsidized portion would stay the same as sea level rises. 

 6662 

6663 FEMA has not yet quantified whether climate change is likely to increase total damages 

6664 by a greater or smaller proportion than the increase due to sea-level rise. Without an 

6665 assessment of whether the subsidy would increase or decrease, it would be premature to 

6666 conclude that sea-level rise warrants a change in FEMA’s rate structure. Nevertheless, 

6667 sea-level rise is unlikely to threaten the financial integrity of the flood insurance program 

6668 as long as subsidized rates are set high enough to cover claims during all but the 

6669 catastrophic loss years, and Congress continues to provide the program with the 

6670 necessary funds during the catastrophic years. Because the pre-FIRM subsidies only 

6671 apply to homes that are several decades old, they do not encourage hazardous 

6672 construction. As with grandfathering, the subsidized rate discourages owners of homes 

6673 below the base flood elevation from elevating or otherwise reducing the risk to their 

6674 homes as sea level rises, because the premium is already as low as it would be from 

elevating the home to the base flood elevation45 6675 . 

 

44 The year 2005 (Hurricanes Katrina, Rita, and Wilma) is excluded from such calculations. 

45 Pre-FIRM owners of homes a few feet below the base flood elevation could achieve modest saving by 

elevating homes a few feet above the base flood elevation; but those savings are small compared to the 

savings available to the owner of a post-FIRM home at the same elevation relative to base flood elevation. 
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 6676 

6677 The practical importance of the pre-FIRM subsidy is sensitive to the future rate of sea6678 level rise. Today, pre-FIRM policies account for 24 percent of all policies (Hayes et al., 

6679 2006). However, that fraction is declining (Crowell et al., 2007) because development 

6680 continues in coastal floodplains, and because the total number of homes eligible for pre6681 FIRM rates is declining, as homes built before the 1970s are lost to fire and storms, 

6682 enlarged, or replaced with larger homes. A substantial rise in sea level over the next few 

6683 decades would affect a large class of subsidized policy holders by the year 2100. 

6684 Nevertheless, the portion of pre-FIRM houses is likely to be very small, unless there is a 

6685 shift in the factors that have caused people to replace small cottages with larger houses 

6686 and higher-density development (see Section 12.2.3). 

 6687 

6688 Two other classes, which together account for 2 percent of policies, also provide 

6689 subsidized rates. The A99 Zone consists of areas that are currently in the A Zone, but for 

6690 which structural flood protection such as dikes are at least 50 percent complete. 

6691 Policyholders in such areas pay a rate as if the structural protection was already complete 

6692 (and successful). The AR Zone presents the opposite situation: locations where structural 

6693 protection has been decertified. Provided that the structures are on a schedule for being 

6694 rebuilt, the rates are set to the rate that applies to the X Zone or the pre-FIRM subsidized 

6695 rate, whichever is less. As sea level rises, the magnitude of these subsidies may increase, 

6696 both because the base flood elevations (without the protection) will be higher, and 

6697 because more coastal lands may be protected with dikes and other structural measures. 

6698 Unlike the pre-FIRM subsidies, the A99 and AR Zone subsidies may encourage 
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6699 construction in hazardous areas; but unlike other subsidies, the A99 and AR Zone 

6700 subsidies encourage protection measures that reduce hazards. 

 6701 

6702 10.7.4 Post-Disaster Hazard Mitigation 

6703 If a coastal community is ultimately going to be abandoned to the rising sea, a major 

6704 rebuilding effort in the current location may be less useful than expending the same 

6705 resources to rebuild the community on higher ground. On the other hand, if the 

6706 community plans to remain in its current location despite the increasing costs of shore 

6707 protection, then it is important for people to understand that commitment. Unless 

6708 property owners know which path the community is following, they do not know whether 

6709 to reinvest. Moreover, if the community is going to stay in its current location, owners 

6710 need to know whether their land will be protected with a dike or if land surfaces are 

6711 likely to be elevated over time (see Section 12.3). 

 6712 

6713 10.8 CONCLUSIONS 

6714 The need to prepare for rising sea level depends on the length of time over which the 

6715 decision will continue to have consequences; how sensitive those consequences are to sea 

6716 level; how rapidly the sea is expected to rise and the magnitude of uncertainty over that 

6717 expectation; the decision maker’s risk tolerance; and the implications of deferring a 

6718 decision to prepare. Considering sea-level rise may be important if the decision has 

6719 outcomes over a long period of time and concerns an activity that is sensitive to sea level, 

6720 especially if what can be done to prepare today would not be feasible later. Those making 

6721 decisions with outcomes over a short period of time concerning activities that are not 
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6722 sensitive to sea level probably need not consider sea-level rise, especially if preparing 

6723 later is as effective as preparing today. 

 6724 

6725 Instances where the existing literature provides an economic rationale for preparing for 

6726 accelerated sea-level rise include: 

6727  Coastal wetland protection. Wetlands and the success of wetland-protection 

6728 efforts are almost certainly sensitive enough to sea-level rise to warrant 

6729 examination of some changes in coastal wetland protection efforts, assuming that 

6730 the objective is to ensure that most estuaries that have extensive wetlands today 

6731 will continue to have tidal wetlands in the future. Coastal wetlands are sensitive to 

6732 rising sea level, and many of the possible measures needed to ensure their survival 

6733 as sea level rises are least disruptive with a lead time of several decades. Changes 

6734 in management approaches would likely involve consideration of options at 

6735 various levels of authority. 

6736  Coastal infrastructure. Whether it is beneficial to design coastal infrastructure to 

6737 anticipate rising sea level depends on the ratio of the incremental cost of 

6738 designing for a higher sea level now, compared with the retrofit cost of modifying 

6739 the structure later. No general statement is possible because this ratio varies and 

6740 relatively few engineering assessments of the question have been published. 

6741 However, because the cost of analyzing this question is very small compared with 

6742 the retrofit cost, it is likely that most long-lived infrastructure in the coastal zone 

6743 is sufficiently sensitive to rising sea level to warrant an analysis of the 

6744 comparative cost of designing for higher water levels now and retrofitting later. 
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6745  Building along the coast. In general, the economics of coastal development alone 

6746 does not currently appear to be sufficiently sensitive to sea-level rise to avoid 

6747 construction in coastal areas. Land values are so high that development is often 

6748 economic even if a home is certain to be lost within a few decades. The optimal 

6749 location and elevation of new homes may be sensitive to how rapidly sea level is 

6750 expected to rise. 

6751  Shoreline planning. A wide array of measures for adapting to rising sea level 

6752 depend on whether a given area will be elevated, protected with structures, or 

6753 abandoned to the rising sea. Several studies have shown that in those cases where 

6754 the shores will retreat and structures will be removed, the economic cost will be 

6755 much less if people plan for that retreat. The human toll of an unplanned 

6756 abandonment may be much greater than if people gradually relocate when it is 

6757 convenient to do so. Conversely, people may be reluctant to invest in an area 

6758 without some assurance that lands will not be lost to the sea. Therefore, long-term 

6759 shoreline planning is generally justified and will save more than it costs; the more 

6760 the sea ultimately rises, the greater the value of that planning. 

6761  Rolling easements, density restrictions, and coastal setbacks. Several studies have 

6762 shown that, in those cases where the shores will retreat and structures will be 

6763 removed, the economic cost will be much less if people plan for that retreat. 

6764 Along estuaries, a retreat in developed areas rarely occurs and thus is likely to 

6765 only occur if land remains lightly developed. It is very likely that options such as 

6766 rolling easements, density restrictions, coastal setbacks, and vegetative buffers, 

6767 would increase the ability of wetlands and beaches to migrate inland. 
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6768  Floodplain management: Consideration of reflecting actual risk in flood 

6769 insurance rates. Economists and other commentators generally agree that 

6770 insurance works best when the premiums reflect the actual risk. Even without 

6771 considering the possibility of accelerated sea-level rise, the National Academy of 

6772 Sciences (NAS, 1990) and a FEMA-supported study by The Heinz Center (2000) 

6773 concluded and recommended to Congress that insurance rates should reflect the 

6774 changing risks resulting from coastal erosion. Rising sea level increases the 

6775 potential disparity between rates and risks of storm-related flooding. 

6776 
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6777 CHAPTER 10 REFERENCES

6778 * Indicates non-peer reviewed literature; available upon request

6779 

6780 Arrow, K.J. and A.C. Fisher, 1974: Environmental preservation, uncertainty, and 

6781 irreversibility. Quarterly Journal of Economics, 88(1), 312-319. 

6782 Bin, O., T. Crawford, J.B. Kruse, and C.E. Landry, 2008: Viewscapes and flood hazard: 

6783 coastal housing market response to amenities and risk. Land Economics, 84(3), 

6784 434-448. 

6785 Buckley, M., 2007: Testimony of Michael Buckley, U.S. Senate Committee on 

6786 Homeland Security and Government Affairs, April 19, 2007. 

6787 Cape Cod Commission, 2002: Model Floodplain District Bylaw. Cape Cod 

6788 Commission, Barnstable, MA, section 06.1. 

6789 <http://www.capecodcommission.org/bylaws/floodplain.html> 

6790 CCSP (Climate Change Science Program), 2006: Coastal Elevations and Sensitivity to 

6791 Sea level Rise Final Prospectus for Synthesis and Assessment Product 4.1. United 

6792 States Climate Change Science Program, Washington, DC, 19 pp.

6793 Congressional Research Service, 2003: Benefit-Cost Analysis and the Discount Rate for 

6794 the Corps of Engineers’ Water Resource Projects: Theory and Practice. [Power, 

6795 K. (analyst)]. RL31976. Congressional Research Service, Washington, DC, 26 pp. 

6796 Cordes, J.J. and A.M.J. Yezer, 1998: In harm's way: does federal spending on beach 

6797 enhancement and protection induce excessive development in coastal areas? Land 

6798 Economics, 74(1), 128-145. 

6799 Crowell, M. and S.P. Leatherman (eds.), 1999: Coastal erosion mapping and 

6800 management. Journal of Coastal Research, Special Issue 28, 196 pp. 

6801 Crowell, M., E. Hirsch, and T.L. Hayes, 2007: Improving FEMA’s coastal risk 

6802 assessment through the National Flood Insurance Program: an historical 

6803 overview. Marine Technology Society Journal, 41(1), 18-27. 
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6804 Dasgupta, P., 2007: Commentary: The Stern Review’s economics of climate change.

6805 National Institute Economic Review, 199, 4-7. 

6806 Department of Homeland Security, 2008: Impact of Climate Change on the National 

6807 Flood Insurance Program. Solicitation number HSFEHQ-08-R-0082. 

6808 <http://www.FedBizOpps.gov> 

6809 Evatt, D.S., 1999: National Flood Insurance Program: Issues Assessment. Federal 

6810 Emergency Management Agency, Washington, DC, 123 pp. 

6811 Evatt, D.S., 2000: Does the national flood insurance program drive floodplain 

6812 development? Journal of Insurance Regulation, 18(4), 497-523. 

6813 FEMA (Federal Emergency Management Agency), 1991: Projected Impact of Relative 

6814 Sea Level Rise on the National Flood Insurance Program. FEMA Flood 

6815 Insurance Administration, Washington DC, 72 pp.

6816 Fisher, A.C. and W.M. Hanemann, 1987: Quasi-option value: some misconceptions 

6817 dispelled. Journal of Environmental Economics and Management, 14(2), 183-

6818 190. 

6819 Frankhauser, S., J.B. Smith, and R.S.J. Tol, 1999: Weathering climate change: Some 

6820 simple rules to guide adaptation decisions. Ecological Economics, 30(1), 67-78. 

6821 Freeman, A.M., 2003: The Measurement of Environmental and Resource Values: Theory 

6822 and Methods. Resources for the Future, Washington, DC, 2nd ed., 491 pp. 

6823 Gilbert, S. and R. Horner, 1984: The Thames Barrier. Thomas Telford, London, 182 pp. 

6824 GAO (General Accounting Office), 1982: National Flood Insurance: Marginal Impact 

6825 on Floodplain Development, Administrative Improvements Needed. Report to the 

6826 Subcommittee on Consumer Affairs, Committee on Banking, Housing, and Urban 

6827 Affairs, U.S. Senate. General Accounting Office, Washington, DC, 59 pp. 
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6828 GAO (Government Accountability Office), 2007: Climate Change: Financial Risks to 

6829 Federal and Private Insurers in Coming Decades are Potentially Significant. 

6830 GAO-07-285. Government Accountability Office, Washington DC, 68 pp. 

6831 <http://www.gao.gov/new.items/d07285.pdf> 

6832 Ha-Duong, M., 1998: Quasi-option value and climate policy choices. Energy Economics, 

6833 20(5/6), 599-620. 

6834 Hardisky, M.A. and V. Klemas, 1983: Tidal wetlands natural and human-made change 

6835 from 1973 to 1979 in Delaware: mapping techniques and results. Environmental 

6836 Management, 7(4), 339-344. 

6837 Hayes, T.L., D.R. Spafford, and J.P. Boone, 2006: Actuarial Rate Review. National 

6838 Flood Insurance Program, Washington DC, 34 pp. 

6839 <http://www.fema.gov/library/viewRecord.do?id=2363> 

6840 Heinz Center, 2000: Evaluation of Erosion Hazards. The H. John Heinz III Center for 

6841 Science, Economics, and the Environment, Washington, DC, 252 pp. 

6842 <http://www.heinzctr.org/publications.shtml#erosionhazards> 

6843 Hoffman, J.S., D. Keyes, and J.G. Titus, 1983: Projecting Future Sea Level Rise; 

6844 Methodology, Estimates to the Year 2100, and Research Needs. U.S. 

6845 Environmental Protection Agency, Washington DC, 121 pp. 

6846 IPCC (Intergovernmental Panel on Climate Change), 1990: Strategies for Adaptation to 

6847 Sea Level Rise. Report of the Coastal Zone Management Subgroup, IPCC 

6848 Response Strategies Working Group. Ministry of Transport and Public Works, 

6849 The Hague, the Netherlands, 131 pp. 

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6853 Science of Climate Change. Contribution of Working Group I to the Second 

6854 Assessment Report of the Intergovernmental Panel on Climate Change. 
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6855 [Houghton, J.J., L.G. Meiro Filho, B.A. Callander, N. Harris, A. Kattenberg, and 

6856 K. Maskell (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 

6857 572 pp. 

6858 IPCC (Intergovernmental Panel on Climate Change), 2001: Climate Change 2001: The 

6859 Scientific Basis. Contribution of Working Group I to the Third Assessment Report 

6860 of the Intergovernmental Panel on Climate Change [Houghton, J.T., Y. Ding, D.J. 

6861 Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnston 

6862 (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 881 pp. 

6863 IPCC (Intergovernmental Panel on Climate Change), 2007: Climate Change 2007: The 

6864 Physical Science Basis. Contribution of Working Group I to the Fourth 

6865 Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, 

6866 S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. 

6867 Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 996 

6868 pp. 

6869 IPCC CZMS (Intergovernmental Panel on Climate Change Coastal Zone Management 

6870 Subgroup), 1992: Global Climate Change and the Rising Challenge of the Sea.

6871 IPCC Response Strategies Working Group, Rijkswaterstaat, The Hague, the 

6872 Netherlands. 

6873 IPET (Interagency Performance Evaluation Task Force), 2006: Performance Evaluation 

6874 of the New Orleans and Southeast Louisiana Hurricane Protection System. U.S. 

6875 Army Corps of Engineers, Washington, DC. <https://ipet.wes.army.mil/> 

6876 Jones, C.P., W.L. Coulbourne, J. Marshall, and S.M. Roger Jr, 2006: Evaluation of the 

6877 National Flood Insurance Program’s Building Standards. American Institutes for 

6878 Research, Washington, DC. 

6879 Kentula, M., 1999: Restoration, creation, and recovery of wetlands: wetland restoration 

6880 and creation. In: National Water Summary on Wetland Resources. [Fretwell, 

6881 J.D., R.J. Redman, and J.S. Williams (eds.)]. United States Geological Survey 
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6882 water supply paper 2425. U.S. Geological Survey, [Reston, VA]. 

6883 <http://water.usgs.gov/nwsum/WSP2425/restoration.html> 

6884 Klein, R.J.T., R.J. Nicholls, and N. Mimura, 1999: Coastal adaptation to climate change: 

6885 Can the IPCC technical guidelines be applied? Mitigation and Adaptation 

6886 Strategies for Global Change, 4(3-4), 239-252. 

6887 Kruczynski, W.L., 1990: Options to be considered in preparation and evaluation of 

6888 mitigation plans. In: Wetland Creation and Restoration: The Status of the Science

6889 [Kusler, J.A. and M.E. Kentula (eds.)]. Island Press, Washington, DC, 594 pp. 

6890 Kussler, J., 1999: Common Questions: Wetland Restoration, Creation, and 

6891 Enhancement. Association of State Wetland Managerss, Berne, NY, 15 pp. 

6892 <http://www.aswm.org/propub/20_restoration_6_26_06.pdf> 

6893 Lavery, S. and B. Donovan, 2005: Flood risk management in the Thames Estuary 

6894 looking ahead 100 years. Philosophical Transactions of the Royal Society A, 363, 

6895 1455-1474. 

6896 Landry, C.E., A.G. Keeler, and W. Kriesel, 2003: An economic evaluation of beach 

6897 erosion management alternatives. Marine Resource Economics, 18(2), 105-127. 

6898 Leatherman, S., 1997: Flood Insurance Availability in Coastal Areas: The Role It Plays in 

6899 Encouraging Development Decisions. Federal Emergency Management Agency, 

6900 Washington, DC.

6901 Matcha vs Maddox, 711 S.W.2d 95, 100 (Tex. App. 1986). 

6902 Miller, H.C., 1981: Coastal Flood Hazards and the National Flood Insurance Program. 

6903 Federal Emergency Management Agency, Washington, DC, 50 pp. 

6904 NAS (National Academy of Sciences), 1990: Managing Coastal Erosion. National 

6905 Academy Press, Washington, DC, 182 pp. 
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6906 NFIP (National Flood Insurance Program), 2007: Fact Sheet: Saving on Flood Insurance 

6907 Information about the NFIP’s Grandfathering Rule. FEMA, [Washington DC], 2 

6908 pp. <http://www.fema.gov/library/viewRecord.do?id=2497> 

6909 NFIP (National Flood Insurance Program), 2008: Flood Insurance Manual. Federal 

6910 Emergency Management Agency, Washington DC. 

6911 Nordhaus, W.D., 2007a: Critical assumptions in the Stern Review on Climate Change. 

6912 Science, 317(5835), 201-202. 

6913 Nordhaus, W.D., 2007b: A review of the Stern Review on The Economics of Climate 

6914 Change. Journal of Economic Literature, 45, 686-702. 

6915 NRC (National Research Council), 1983: Changing Climate. National Academy Press, 

6916 Washington, DC, 496 pp. 

6917 NRC (National Research Council), 1987: Responding to Changes in Sea Level: 

6918 Engineering Implications. National Academy Press, Washington, DC, 148 pp. 

6919 NRC (National Research Council), 2007: Mitigating Shore Erosion Along Sheltered 

6920 Coasts. National Academies Press, Washington, DC, 174 pp. 

6921 O’Callahan, J. (ed.), 1994: Global Climate Change and the Rising Challenge of the Sea. 

6922 Proceedings of the third IPCC CZMS workshop, Isla de Margarita, Venezuela, 9–

6923 13 March 1992. National Oceanic and Atmospheric Administration, Silver 

6924 Spring, MD, 691 pp. 

6925 OMB (Office of Management and Budget), 1992: Guidelines and Discount Rates for 

6926 Benefit-Cost Analysis of Federal Programs. OMB Circular A-94, Office of 

6927 Management and Budget, Washington, DC. 

6928 <http://www.whitehouse.gov/omb/circulars/a094/a094.html> 

6929 OTA (Office of Technology Assessment), 1993: Preparing for an Uncertain Climate – 

6930 Volume I. OTA-O-567. U.S. Government Printing Office, Washington, DC, 359 

6931 pp. 
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6932 Reed, D.J., D. Bishara, D. Cahoon, J. Donnelly, M. Kearney, A. Kolker, L. Leonard, 

6933 R.A. Orson, and J.C. Stevenson, 2008: Site-specific scenarios for wetlands 

6934 accretion as sea level rises in the mid-Atlantic region. Section 2.1 in: Background 

6935 Documents Supporting Climate Change Science Program Synthesis and 

6936 Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise

6937 [Titus, J.G. and E.M. Strange (eds.)]. EPA 430R07004. U.S. Environmental 

6938 Protection Agency, Washington, DC, pp. 134-174.

6939 <http://epa.gov/climatechange/effects/coastal/background.html>

6940 Samuelson, P.A. and W.D. Nordhaus, 1989: Economics. McGraw-Hill, New York, 13th 

6941 ed., 1013 pp. 

6942 Scheraga, J.D. and A.E. Grambsch, 1998: Risks, opportunities, and adaptation to climate 

6943 change. Climate Research, 11(1), 85-95. 

6944 Shilling, J.D., C.E. Sirmans, and J.D. Benjamin, 1989: Flood insurance, wealth 

6945 redistribution, and urban property values. Journal of Urban Economics, 26(1), 43-

6946 53. 

6947 Stockton, M.B. and C.J. Richardson, 1987: Wetland development trends in coastal North 

6948 Carolina, USA, from 1970 to 1984. Environmental Management, 11(5), 649-657. 

6949 Titus, J.G., 1990: Greenhouse effect, sea level rise, and barrier islands: case study of 

6950 Long Beach Island, New Jersey. Coastal Management, 18(1), 65-90. 

6951 Titus, J.G., 1991: Greenhouse effect and coastal wetland policy: how Americans could 

6952 abandon an area the size of Massachusetts at minimum cost. Environmental 

6953 Management, 15(1), 39-58. 

6954 Titus, J.G., 1998: Rising seas, coastal erosion and the takings clause: how to save 

6955 wetlands and beaches without hurting property owners. Maryland Law Review, 

6956 57(4), 1279-1299. 
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6957 Titus, J.G., 2000: Does the U.S. government realize that the sea is rising? How to 

6958 restructure federal programs so that wetlands and beaches survive. Golden Gate 

6959 Law Review, 30(4), 717–786. 

6960 Titus, J.G., 2005: Does shoreline armoring violate the Clean Water Act? Rolling 

6961 easements, shoreline planning, and other responses to sea level rise. In: America’s 

6962 Changing Coasts: Private Rights and Public Trust [Whitelaw, D.M. and G.R. 

6963 Visgilio (eds.)]. Edward Elgar Publishing, Cheltenham, UK, and Northampton, 

6964 MA, 248 pp. 

6965 Titus, J.G. and V. Narayanan, 1996: The risk of sea level rise. Climatic Change, 33(2),

6966 151-212. 

6967 Titus, J.G. and J. Wang, 2008: Maps of lands close to sea level along the middle Atlantic 

6968 coast of the United States: an elevation data set to use while waiting for LIDAR. 

6969 Section 1.1 in: Background Documents Supporting Climate Change Science 

6970 Program Synthesis and Assessment Product 4.1: Coastal Elevations and 

6971 Sensitivity to Sea Level Rise [Titus, J.G. and E.M. Strange (eds.)]. EPA 

6972 430R07004. U.S. Environmental Protection Agency, Washington, DC, pp. 2-44.

6973 Titus, J.G., C.Y. Kuo, M.J. Gibbs, T.B. LaRoche, M.K. Webb, and J.O. Waddell, 1987: 

6974 Greenhouse effect, sea level rise, and coastal drainage systems. Journal of Water 

6975 Resources Planning and Management, 113(2), 216-227. 

6976 Titus, J.G., R.A. Park, S.P. Leatherman, J.R. Weggel, M.S. Greene, P.W. Mansel, S. 

6977 Brown, G. Gaunt, M. Treehan, and G. Yohe, 1991: Greenhouse effect and sea 

6978 level rise: the cost of holding back the sea. Coastal Management, 19(2), 171-204. 

6979 Township of Long Beach (New Jersey), 2008: Important Flood Information.

6980 <http://longbeachtownship.com/importantfloofing information.html> 

6981 Town of Ocean City, Maryland, 1999: City Code § 38-71. 

6982 TRB (Transportation Research Board), 2008: Potential Impacts of Climate Change on 

6983 U.S. Transportation. National Academies Press, Washington, DC, 234 pp. 
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6984 USACE (U.S. Army Corps of Engineers), 2000a: Planning Guidance Notebook: 

6985 Appendix E: Civil Works Missions and Evaluation Procedures. ER 1105-2-100. 

6986 U. S. Army Corps of Engineers, Washington, DC, 310 pp. 

6987 <http://www.usace.army.mil/publications/eng-regs/er1105-2-100/toc.htm> 

6988 USACE (U.S. Army Corps of Engineers), 2000b: Civil Works Construction Cost Index 

6989 System (CWCCIS). EM 1110-2-1304. U.S. Army Corps of Engineers, 

6990 Washington, DC. For updated CWCCIS data tables, see: 

6991 <http://www.usace.army.mil/publications/eng-manuals/em1110-2-1304/toc.htm> 

6992 USACE (U.S. Army Corps of Engineers), 2007: Civil Works Construction Cost Index 

6993 System (CWCCIS): Revised Tables. EM 1110-2-1304. U.S. Army Corps of 

6994 Engineers, Washington, DC. Tables revised 30 September 2007. 

6995 <http://www.usace.army.mil/publications/eng-manuals/em1110-2-1304/toc.htm> 

6996 U.S. EPA (Environmental Protection Agency), 1989: Potential Effects of Global Climate 

6997 Change on the United States: Report to Congress. EPA 230-05-89-050. U.S. 

6998 Environmental Protection Agency, Washington, DC. 

6999 U.S. EPA (Environmental Protection Agency), 1995: Federal guidance for the 

7000 establishment, use and operation of mitigation banks. Federal Register, 60(228), 

7001 58605-58614. 

7002 U.S. EPA (Environmental Protection Agency), 2000: Guidelines for Preparing Economic 

7003 Analyses. EPA 240-R-00-003. EPA Office of the Administrator, [Washington 

7004 DC]. <http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html> 

7005 U.S. EPA (Environmental Protection Agency) & USACE (U.S. Army Corps of 

7006 Engineers), 1990: Mitigation Memorandum of Agreement 4 (Feb. 6, 1990). 

7007 Weggel, J.R., S. Brown, J.C. Escajadillo, P. Breen, and E. Doheyn, 1989: The cost of 

7008 defending developed shorelines along sheltered waters of the United States from a 

7009 two meter rise in mean sea level. In: Potential Effects of Global Climate Change 

7010 on the United States. Appendix: B, Sea Level Rise. U.S. Environmental Protection 
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7011 Agency, Washington, DC, pp. 3-1 to 3-90. 

7012 <http://epa.gov/climatechange/effects/coastal/appB.html> 

7013 Yohe, G., J.E. Neumann, P. Marshall, and H. Ameden, 1996: The economic cost of 

7014 greenhouse-induced sea-level rise for developed property in the United States. 

7015 Climatic Change, 32(4), 387-410. 

7016 
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7017 Chapter 11. Ongoing Adaptation 

7018 

7019 Author: James G. Titus, EPA

 7020 

7021 KEY FINDINGS 

7022  Most organizations are not yet taking specific measures to prepare for rising sea 

7023 level. Recently, however, many public and private organizations have begun to 

7024 assess possible response options. 

7025  Most of the specific measures that have been taken to prepare for accelerated sea7026 level rise have had the purpose of reducing the long-term adverse environmental 

7027 impacts. 

 7028 

7029 11.1 INTRODUCTION 

7030 Preparing for the consequences of rising sea level has been the exception rather than the 

7031 rule in the Mid-Atlantic. Nevertheless, many coastal decision makers are now starting to 

7032 consider how to prepare. 

 7033 

7034 This Chapter examines those cases in which organizations are taking specific measures to 

7035 consciously anticipate the effects of sea-level rise. It does not include most cases in 

7036 which an organization has authorized a study but not yet acted upon the study. Nor does 

7037 it catalogue the activities undertaken for other reasons that might also help to prepare for 

accelerated sea-level rise46 7038 , or cases where people responded to sea level rise after the 

7039 fact (see Box 11.1). Finally, it only considers measures that had been taken by March 

 

46 Appendix 1, however, does examine such policies. 
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7040 2008. Important measures may have been adopted between the time this Product was 

7041 drafted and its final publication. 

 7042 

7043 11.2 ADAPTATION FOR ENVIRONMENTAL PURPOSES 

7044 Many organizations that manage land for environmental purposes are starting to 

7045 anticipate the effects of sea-level rise. Outside the Mid-Atlantic, some environmental 

7046 regulators have also begun to address this issue. 

 7047 

7048 11.2.1 Environmental Regulators 

7049 Organizations that regulate land use for environmental purposes generally have not 

7050 implemented adaptation options to address the prospects of accelerated sea-level rise. 

7051 Congress has given neither the U.S. Army Corps of Engineers (USACE) nor the U.S. 

7052 Environmental Protection Agency (EPA) a mandate to modify existing wetland 

7053 regulations to address rising sea level; nor have those agencies developed approaches for 

7054 moving ahead without such a mandate (see Chapter 12). For more than a decade, 

Maine47, Massachusetts48, and Rhode Island49 7055 have had statutes or regulations that restrict 

7056 shoreline armoring to enable dunes or wetlands to migrate inland with an explicit 

7057 recognition of rising sea level (Titus, 1998). 

 7058 

7059 None of the eight mid-Atlantic states require landowners to allow wetlands to migrate 

7060 inland as sea level rises (NOAA, 2006). During 2008, however, the prospect of losing 

7061 ecosystems to a rising sea prompted Maryland to enact the “Living Shoreline Protection 

 

47 06-096 Code of Maine Rules §355(3)(B)(1) (2007). 

48 310 Code Mass Regulations §10.30 (2005). 

49 Rhode Island Coastal Resource Management Program §210.3(B)(4) and §300.7(D) (2007). 
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Act”50 7062 . Under the Act, the Department of Environment will designate certain areas as 

7063 appropriate for structural shoreline measures (e.g., bulkheads and revetments). Outside of 

7064 those areas, only nonstructural measures (e.g., marsh creation, beach nourishment) will 

7065 be allowed unless the property owner can demonstrate that nonstructural measures are 

infeasible51 7066 . The new statute does not ensure that wetlands are able to migrate inland; but 

7067 Maryland’s coastal land use statute limits development to one home per 8.09 hectares 

7068 (ha) (20 acres [ac]) in most rural areas within 305 meters (m) (1000 feet [ft]) of the shore 

7069 (see Section A1.F.2.1 in Appendix 1). Although that statute was enacted in the 1980s to 

7070 prevent deterioration of water quality, the state now considers it to be part of its sea-level 

rise adaptation strategy.52 7071 

 7072 

7073 11.2.2 Environmental Land Managers

7074 Those who manage land for environmental purposes have taken some initial steps to 

7075 address rising sea level. 

7076 Federal Land Managers 

7077 The Department of Interior (Secretarial Order 3226, 2001) requires climate change 

7078 impacts be taken into account in planning and decision making (Scarlett, 2007). The 

7079 National Park Service has worked with the United States Geological Survey (USGS) to 

7080 examine coastal vulnerability on 25 of its coastal parks (Pendleton et al., 2004). The U.S. 

7081 Fish and Wildlife Service is incorporating studies of climate change impacts, including 

7082 sea-level rise, in their Comprehensive Conservation Plans where relevant. 

 7083 

 

50 Maryland House Bill 273-2008. 

51MD Code Environment §16-201(c)

52 Maryland House Bill 273-2008. 
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7084 The National Park Service and the U.S. Fish and Wildlife Service each have large coastal 

7085 landholdings that could erode or become submerged as sea level rises (Thieler et al., 

7086 2002; Pendleton et al., 2004). Neither organization has an explicit policy concerning sea7087 level rise, but both are starting to consider their options. The National Park Service 

7088 generally favors allowing natural shoreline processes to continue (NPS Management 

7089 Policies §4.8.1), which allows ecosystems to migrate inland as sea level rises (see Figure 

7090 11.1). In 1999, this policy led the Park Service to move the Cape Hatteras Lighthouse 

7091 inland 900 m (2900 ft) at a cost of $12 million. The U.S. Fish and Wildlife Service 

7092 generally allows dry land to convert to wetlands, but it is not necessarily passive as rising 

7093 sea level erodes the seaward boundary of tidal wetlands. Blackwater National Wildlife 

7094 Refuge, for example, has used dredge material to rebuild wetlands on a pilot basis, and is 

7095 exploring options to recreate about 3000 ha (7000 ac) of marsh (see Figure 11.2). Neither 

7096 agency has made land purchases or easements to enable parks and refuges to migrate 

7097 inland. 

7098 

7099 Figure 11.1 Allowing beaches and wetlands to migrate inland in the national parks (a) Cape Hatteras 

7100 National Seashore. (June 2002) Until it was relocated inland in 1999, the lighthouse was just to the right of 

7101 the stone groin in the foreground. (b) Jamestown Island ,Virginia (September 2004). As sea level rises, 

7102 marshes have taken over land that was cultivated during colonial times. 

 7103 
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7104 

 7105 

7106 Figure 11.2 Responding to sea-level rise at Blackwater National Wildlife Refuge, Maryland (October 

7107 2002). (a) Marsh Deterioration. (b) Marsh Creation. The dredge fills the area between the stakes to create 

7108 land at an elevation flooded by the tides, after which marsh grasses are planted 

7109 

7110 The Nature Conservancy 

7111 The Nature Conservancy (TNC) is the largest private holder of conservation lands in the 

7112 Mid-Atlantic. It has declared as a matter of policy that it is trying to anticipate rising sea 

7113 level and climate change. Its initial focus has been to preserve ecosystems on the 

7114 Pamlico-Albemarle Peninsula, such as those shown in Figure 11.3 (Pearsall and Poulter, 

7115 2005; TNC, 2007). Options under consideration include: plugging canals to prevent 

7116 subsidence-inducing saltwater intrusion, planting cypress trees where pocosins have been 

7117 converted to dry land, and planting brackish marsh grasses in areas likely to be inundated. 

7118 As part of that project, TNC undertook the first attempt by a private conservancy to 

7119 purchase rolling easements (although none were purchased). TNC owns the majority of 

7120 barrier islands along the Delmarva Peninsula, but none of the mainland shore. TNC is 

7121 starting to examine whether preserving the ecosystems as sea level rises would be best 

7122 facilitated by purchasing land on the mainland side as well, to ensure sediment sources 

7123 for the extensive mudflats so that they might keep pace with rising sea level. 
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 7124 

7125 State conservation managers have not yet started to prepare for rising sea level (NOAA, 

7126 2006). But at least one state (Maryland) is starting to refine a plan for conservation that 

7127 would consider the impact of rising sea level. 

7128 

7129 

7130 Figure 11.3 The Albemarle Sound environment that the Nature Conservancy seeks to preserve as sea level 

7131 rises (June 2002). (a) Nature Conservancy lands on Roanoke Island depict effects of rising sea level. Tidal 

7132 wetlands (juncas and spartina patens) have taken over most of the area depicted as sea level rises, but a 

7133 stand of trees remains in a small area of higher ground. (b) Mouth of the Roanoke River, North Carolina. 

7134 Cypress trees germinate on dry land; but continue to grow in the water after the land is eroded or 

7135 submerged by rising sea level.

7136 

7137 

7138 11.3 OTHER ADAPTATION OPTIONS BEING CONSIDERED BY FEDERAL, 

7139 STATE, AND LOCAL GOVERNMENTS 

7140 11.3.1 Federal Government 
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7141 Federal researchers have been examining how best to adapt to sea-level rise for the last 

7142 few decades, and those charged with implementing programs are also now beginning to 

7143 consider implications and options. The longstanding assessment programs will enable 

7144 federal agencies to respond more rapidly and reasonably if and when policy decisions are 

7145 made to begin preparing for the consequences of rising sea level. 

 7146 

7147 The Coastal Zone Management Act is a typical example. The Act encourages states to 

7148 protect wetlands, minimize vulnerability to flood and erosion hazards, and improve 

7149 public access to the coast. Since 1990, the Act has included sea-level rise in the list of 

7150 hazards that states should address. This congressional mandate has induced NOAA to 

7151 fund state-specific studies of the implications of sea-level rise, and encouraged states to 

7152 periodically designate specific staff to keep track of the issue. But it has not yet altered 

7153 what people actually do along the coast (New York, 2006; New Jersey, 2006; 

7154 Pennsylvania, 2006; Delaware, 2005; Maryland, 2006; Virginia, 2006; North Carolina, 

7155 2006). Titus (2000) and CSO (2007) have examined ways to facilitate implementation of 

7156 this statutory provision, such as federal guidance and/or additional interagency 

7157 coordination. Similarly, the U.S. Army Corps of Engineers (USACE) has formally 

7158 included the prospect of rising sea level for at least a decade in its planning guidance for 

7159 the last decade (USACE, 2000), and staff have sometimes evaluated the implications for 

7160 specific decisions (e.g., Knuuti, 2002). But the prospect of accelerated sea-level rise has 

7161 not caused a major change in the agency’s overall approach to wetland permits and shore 

7162 protection (see Chapter 12). 

 7163 
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7164 11.3.2 State Government 

7165 Maryland has considered the implications of sea-level rise in some decisions over the last 

7166 few decades. Rising sea level was one reason that the state gave for changing its shore 

7167 protection strategy at Ocean City from groins to beach nourishment (see Section A1.F in 

7168 Appendix 1). Using NOAA funds, the state later developed a preliminary strategy for 

7169 dealing with sea-level rise. As part of that strategy, the state also recently obtained a 

7170 complete lidar dataset of coastal elevations. 

 7171 

7172 Delaware officials have long considered how best to modify infrastructure as sea level 

7173 rises along Delaware Bay, although they have not put together a comprehensive strategy 

7174 (CCSP, 2007). 

 7175 

7176 Because of the vulnerability of the New Jersey coast to flooding, shoreline erosion, and 

7177 wetland loss (see Figure 11.4), the coastal management staff of the New Jersey 

7178 Department of Environmental Protection have been guided by a long-term perspective on 

7179 coastal processes, including the impacts of sea-level rise. So far, neither Delaware nor 

7180 New Jersey has specifically altered their activities because of projected sea-level rise. 

7181 Nevertheless, New Jersey is currently undertaking an assessment that may enable it to 

7182 factor rising sea level into its strategy for preserving the Delaware Estuary (CCSP, 2007). 

 7183 

7184 In the last two years, states have become increasingly interested in addressing the 

7185 implications of rising sea level. A bill in the New York General Assembly would create a 

7186 sea-level rise task force (Bill AO9002 2007-2008 Regular Session). Maryland and 
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7187 Virginia have climate change task forces that have focused on adapting to rising sea 

7188 level. (For a comprehensive survey of what state governments are doing in response to 

7189 rising sea level, see Coastal States Organization, 2007.) 

 7190 

7191 

7192 

7193 Figure 11.4 Vulnerability of New Jersey’s coastal zone (a) Wetland fringe lacks room for wetland 

7194 migration (Monmouth August 2003). (b) Low bay sides of barrier islands are vulnerable to even a modest 

7195 storm surge. (Ship Bottom, September 2, 2006). (c) Gibbstown Levee and (d) associated tide gate protect 

7196 lowlying areas of Greenwich Township (March 2003). 

7197 

7198 11.3.3 Local Government 

7199 A few local governments have considered the implications of rising sea level for roads, 

7200 infrastructure, and floodplain management (see Boxes A1.4 and A1.6 in Appendix 1). 

7201 New York City’s plan for the year 2030 includes adapting to climate change (City of 

7202 New York, 2008). The New York City Department of Environmental Protection is 
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7203 looking at ways to decrease the impacts of storm surge by building flood walls to protect 

7204 critical infrastructure such as waste plants, and is also examining ways to prevent the 

7205 sewer system from backing up more frequently as sea level rises (Rosenzweig et al., 

7206 2006). The city has also been investigating the possible construction of a major tidal 

7207 flood gate across the Verizano Narrows to protect Manhattan (Velasquez-Manoff, 

7208 2006). 

 7209 

7210 Outside of the Mid-Atlantic, Miami-Dade County in Florida has been studying its 

7211 vulnerability to sea-level rise, including developing maps to indicate which areas are at 

7212 greatest risk of inundation. The county is hardening facilities to better withstand 

7213 hurricanes, monitoring the salt front, examining membrane technology for desalinating 

7214 seawater, and creating a climate advisory task force to advise the county commission 

7215 (Yoder, 2007). 

7216 Begin box********* 

7217 Box 11.1. Jamestown: An Historic Example of Retreat in Response to Sea Level Rise 

7218 Established in 1607 along the James River, Jamestown was the capital of Virginia until 1699, when a fire 

7219 destroyed the statehouse. Nevertheless, rising sea level was probably a contributing factor in the decision to 

7220 move the capital to Williamsburg, because it was making the Jamestown peninsula less habitable than it 

7221 had been during the previous century. Fresh water was scarce, especially during droughts (Blanton, 2000). 

7222 The James River was brackish, so groundwater was the only reliable source of freshwater. But the low 

7223 elevations on Jamestown limited the thickness of the freshwater table—especially during droughts. As Box 

7224 Figure 11.1 shows, a 10 centimeter (cm) rise in sea level can reduce the thickness of the freshwater table by 

7225 four meters on a low-lying island where the freshwater lens floats atop the salt water. 

7226 

7227 Rising sea level has continued to alter Jamestown. Two hundred years ago, the isthmus that connected the 

7228 peninsula to the mainland eroded, creating Jamestown Island (Johnson and Hobbs, 1994). Shore erosion 

7229 also threatened the location of the historic town itself, until a stone revetment was constructed (Johnson and 

7230 Hobbs, 1994). As the sea rose, the shallow valleys between the ridges on the island became freshwater 

7231 marsh, and then tidal marsh (Johnson and Hobbs, 1994). Maps from the seventeenth century show 

7232 agriculture on lands that today are salt marsh. Having converted mainland to island, the rising sea will 

7233 eventually convert the island to open water, unless the National Park Service continues to protect it from 

7234 the rising water. 

7235 

7236 Other shorelines along Chesapeake Bay have also been retreating over the last four centuries. Several bay 

7237 island fishing villages have had to relocate to the mainland as the islands on which they were located 
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7238 eroded away (Leatherman et al., 1995). Today, low-lying farms on the Eastern Shore are converting to 

7239 marsh, while the marshes in wildlife refuges convert to open water. 

7240 

7241 Box Figure 11.1 Impact of sea-level rise on an island freshwater table. (a) According to the Ghyben7242 Herzberg relation, the freshwater table extends below sea level 40 cm for every 1 cm by which it extends 

7243 above sea level (Ghyve [1889] and Herzberg [1901], as cited by Freeze and Cherry [1979]). (b) For islands 

7244 with substantial elevation, a 1-m rise in sea level simply shifts the entire water table up 1 meter, and the 

7245 only problem is that a few wells will have to be replaced with shallower wells. (c) However, for very low 

7246 islands the water table cannot rise because of runoff, evaporation, and transpiration. A rise in sea level 

7247 would thus narrow the water table by 40 cm for every 1 cm that the sea level rises, effectively eliminating 

7248 groundwater supplies for the lowest islands. 

7249 End Box 

7250 

7251 
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7252 CHAPTER 11 REFERENCES

7253 * Indicates non-peer reviewed literature; available upon request

7254 

7255 Blanton, D.B., 2000: Drought as a factor in the Jamestown colony, 1607-1612. 

7256 Historical Archaeology, 34(4), 74-81.

7257 CCSP (Climate Change Science Program), 2007: Stakeholder Meetings Final Report: 

7258 Climate Change Science Program Synthesis and Assessment Product 4.1. 

7259 [National Oceanic and Atmospheric Administration, Silver Spring, MD], 81 pp. 

7260 <http://www.climatescience.gov/Library/sap/sap4-

7261 1/stakeholdermeetingfinalreport.pdf> 

7262 City of New York, 2008: PlaNYC: A Greater, Greener New York. City of New York, 

7263 New York, 155 pp. 

7264 <http://home2.nyc.gov/html/planyc2030/downloads/pdf/full_report.pdf> 

7265 (CSO) Coastal States Organization, 2007: The Role of Coastal Zone Management 

7266 Programs in Adaptation to Climate Change. Coastal States Organization, 

7267 Washington, DC, 27 pp. 

7268 <http://www.coastalstates.org/documents/CSO%20Climate%20Change%20Final

7269 %20Report.pdf> 

7270 Delaware (Delaware Coastal Programs), 2005: Delaware Coastal Programs: Section 309 

7271 Enhancement Assessment. Department of Natural Resources and Environmental 

7272 Control, Dover, DE, 46 pp. 

7273 Freeze, R.A. and J.A. Cherry, 1979: Groundwater. Prentice-Hall, Englewood Cliffs, NJ, 

7274 604 pp. 

7275 Johnson, G.H. and C.H. Hobbs, 1994: The geological history of Jamestown Island. 

7276 Jamestown Archaeological Assessment Newsletter, 1(2/3), 9-11. 

7277 Knuuti, K., 2002: Planning for sea level rise: U.S. Army Corps of Engineers policy. In: 

7278 Solutions to Coastal Disasters '02 [Ewing, L. and L. Wallendorf (eds.)]. 

7279 American Society of Civil Engineers, Reston, VA, pp. 549-560. 
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7280 * Leatherman, S.P., R. Chalfont, E.C. Pendleton, and T.L. McCandless, 1995: 

7281 Vanishing Lands: Sea Level, Society, and Chesapeake Bay. Laboratory of Coastal 

7282 Research, University of Maryland, College Park, and Department of the Interior, 

7283 [Washington, DC], 47 pp. 

7284 Maryland, 2006: CZMA, Secton 309 Assessment and Strategy. Maryland Department of 

7285 Natural Resources, Coastal Zone Management Division, Watershed Services 

7286 Center, Annapolis, 70 pp. 

7287 <http://www.dnr.state.md.us/bay/czm/assessment.html> 

7288 New Jersey, 2006: New Jersey Coastal Management Program: Assessment and 

7289 Enhancement Strategy, FY2006-2010. New Jersey Department of Environmental 

7290 Protection Coastal Management Office, Trenton, 84 pp. 

7291 <http://www.state.nj.us/dep/cmp/czm_309.html> 

7292 New York, 2006: New York State Coastal Management Program: 309 Assessment and 

7293 Strategies, July 1, 2006 through June 30, 2010. Department of State, New York 

7294 State, Albany, 98 pp.

7295 North Carolina, 2006: Assessment and Strategy of the North Carolina Coastal 

7296 Management Program. North Carolina Department of Environment and Natural 

7297 Resources, Raleigh, 90pp. 

7298 NOAA (National Oceanic and Atmospheric Administration), 2006: Responses to Section 

7299 309 of the Coastal Zone Management Act. Coastal Zone Enhancement Program 

7300 compiled by NOAA Office of Ocean and Coastal Resource Management, Silver 

7301 Spring, MD. <http://coastalmanagement.noaa.gov/enhanc.html> 

7302 Pearsall, S.H., III, and B. Poulter, 2005: Adapting coastal lowlands to rising seas: a case 

7303 study. In: Principles of Conservation Biology [Groom, M.J., G.K. Meffe, and 

7304 C.R. Carroll (eds.)]. Sinauer Associates, Sunderland, MA, 3rd edition, pp. 366-

7305 370. 
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7306 Pendleton, E.A., S.J. Williams, and E.R. Thieler, 2004: Coastal Vulnerability 

7307 Assessment of Assateague Island National Seashore (ASIS) to Sea-level Rise. U.S. 

7308 Geological Survey open-file report 2004-1020. U.S. Geological Survey, Reston, 

7309 VA, 20 pp. <http://pubs.usgs.gov/of/2004/1020/> 

7310 Pennsylvania, 2006: Section 309 Assessment and Strategy: Pennsylvania’s Coastal 

7311 Resources Management Program. Pennsylvania Department of Environmental 

7312 ProtectionWater Planning Office, Harrisburg, 69 pp. 

7313 <http://www.dep.state.pa.us/river/docs/309_FINAL_June30_06.pdf> 

7314 Rosenzweig, C., D. Majors, M. Tults, and K. Demong, 2006: New York City Climate 

7315 Change Task Force. In: Adapting to Climate Change: Lessons for London.

7316 Greater London Authority, London, pp. 150-153. 

7317 <http://www.london.gov.uk/climatechangepartnership/> 

7318 * Scarlett, L., 2007: Testimony of P. Lynn Scarlett, Deputy Secretary Department of the 

7319 Interior, before the House Appropriations Subcommittee on Interior, Environment 

7320 and Related Agencies Regarding Climate Change. April 26, 2007. 

7321 Thieler, E.R., S.J. Williams, and R. Beavers, 2002: Vulnerability of U.S. National Parks 

7322 to Sea-Level Rise and Coastal Change. U.S. Geological Survey fact sheet FS 095-

7323 02. [U.S. Geological Survey, Reston, VA], 2 pp. <http://pubs.usgs.gov/fs/fs095-

7324 02/> 

7325 Titus, J.G., 1998: Rising seas, coastal erosion, and the takings clause: how to save 

7326 wetlands and beaches without hurting property owners. Maryland Law Review,

7327 57(4), 1376-1378. 

7328 Titus, J.G., 2000: Does the US government realize that the sea is rising? How to 

7329 restructure federal programs so that wetlands and beaches survive. Golden Gate 

7330 University Law Review, 30(4), 717-778. 
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7331 * TNC (The Nature Conservancy), 2007: Save of the Week: Climate Change Action on 

7332 North Carolina’s Albemarle Peninsula. The Nature Conservancy, Arlington, VA. 

7333 <http://www.nature.org/success/art14181.html> 

7334 USACE (U.S. Army Corps of Engineers), 2000: Planning Guidance Notebook Appendix 

7335 E: Civil Works Missions and Evaluation Procedures. Army Corps of Engineers 

7336 document # ER 1105-2-100. Department of the Army, U. S. Army Corps of 

7337 Engineers, Washington, DC, 310 pp. 

7338 <http://www.usace.army.mil/publications/eng-regs/er1105-2-100/toc.htm> 

7339 * Velasquez-Manoff, M., 2006: How to keep New York afloat. The Christian Science 

7340 Monitor, November 9, 2006, p. 13. 

7341 Virginia, 2006: Virginia Coastal Zone Management Program: Section 309 Needs 

7342 Assessment and Strategy. Virginia Coastal Zone Management Program, 

7343 Richmond, 104 pp. <http://www.deq.state.va.us/coastal/assess.html> 

7344 * Yoder, D., 2007: Miami Dade Water and Sewer Department presentation to American 

7345 Water Works Association webcast, Global Climate Impacts, March 14, 2006. 

7346 
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7347 Chapter 12. Institutional Barriers 

7348 

7349 Author: James G. Titus, U.S. EPA 

7350 

7351 KEY FINDINGS 

7352  Most coastal institutions were designed without considering sea-level rise. 

7353  Some regulatory programs were created in order to respond to a demand for 

7354 hard shoreline structures (e.g., bulkheads) to hold the coast in a fixed location, 

7355 and have generally not shifted to retreat or soft shore protection (e.g., beach 

7356 nourishment). 

7357  The interdependence of decisions made by property owners and federal, state, 

7358 and local governments creates an institutional inertia that currently impedes 

7359 preparing for sea-level rise, as long as no decision has been made regarding 

7360 whether particular locations will be protected or yielded to the rising sea. 

 7361 

7362 12.1 INTRODUCTION

7363 Chapter 10 described several categories of decisions where the risk of sea-level rise can 

7364 justify doing things differently today. Chapter 11, however, suggested that only a few 

7365 organizations have started to prepare for rising sea level since the 1980s when projections 

7366 of accelerated sea-level rise first became widely available. 

 7367 

7368 It takes time to respond to new problems. Most coastal institutions were designed before 

7369 the 1980s. Therefore, land-use planning, infrastructure, home building, property lines, 

7370 wetland protection, and flood insurance all were designed without considering the 
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7371 dynamic nature of the coast (see Chapters 6, 8, 9, 10). A common mindset is that sea 

7372 level and shores are stable, or that if they are not then shores should be stabilized (NRC, 

7373 2007). Even when a particular institution has been designed to account for shifting 

7374 shores, people are reluctant to give up real estate to the sea. Although scientific 

7375 information can quickly change what people expect, it takes longer to change what 

7376 people want. 

 7377 

7378 Short-term thinking often prevails. The costs of planning for hazards like sea-level rise 

7379 are apparent today, while the benefits may not occur during the tenure of current elected 

7380 officials (Mileti, 1999). Local officials tend to be responsive to citizen concerns, and the 

7381 public is generally less concerned about hazards and other long-term or low-probability 

7382 events than about crime, housing, education, traffic, and other issues of day-to-day life 

7383 (Mileti, 1999; Depoorter, 2006). Land-use and transportation planners generally have 

7384 horizons of 20 to 25 years (TRB, 2008), while the effects of sea-level rise may emerge 

7385 over a period of several decades. Although federal law requires transportation plans to 

have a time horizon of at least 20 years53 7386 , some officials view that time horizon as the 

7387 maximum (TRB, 2008). Uncertainty about future climate change is a logical reason to 

prepare for the range of uncertainty (see Chapter 10) but cognitive dissonance54 7388 can lead 

7389 people to disregard the new information instead (Kunreuther et al., 2004; Bradshaw and 

 

53 23 U.S.C. §135(f)(1) (2008). 

54 Cognitive dissonance is a feeling of conflict or anxiety caused by holding two contradictory ideas 

simultaneously, especially when there is a discrepancy between one’s beliefs or actions and information 

that contradicts those beliefs or actions. When confronted with information (e.g., about risk) that 

contradicts one’s pre-existing beliefs or self-image (e.g., that they are acting reasonably), people often 

respond by discounting, denying, or ignoring the information (e.g., Festinger [1957], Harmon-Jones and 

Mills, [1999]).
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7390 Borchers, 2000; Akerlof and Dickens, 1982). Some officials resist changing procedures 

7391 unless they are provided guidance (TRB, 2008). 

 7392 

7393 Finally, a phenomenon known as “moral hazard” can discourage people from preparing 

7394 for long-term consequences. Moral hazard refers to a situation in which insurance or the 

7395 expectation of a government bailout reduces someone’s incentive to prevent or decrease 

7396 the risk of a disaster (Pauly, 1974). The political process tends to sympathize with those 

7397 whose property is threatened, rather than allowing them to suffer the consequences of the 

7398 risk they assumed when they bought the property (Burby, 2006). It can be hard to say 

7399 “no” to someone whose home is threatened (Viscusi and Zeckhauser, 2006). 

 7400 

7401 This Chapter explores some of the institutional barriers that discourage people and 

7402 organizations from preparing for the consequences of rising sea level. “Institution” refers 

7403 to governmental and nongovernmental organizations and the programs that they 

7404 administer. “Institutional barriers” refer to characteristics of an institution that prevent 

7405 actions from being taken. This discussion has two general themes. First, institutional 

7406 biases are more common than actual barriers. For example, policies that encourage 

7407 higher densities in the coastal zone may be barriers to wetland migration, but they 

7408 improve the economics of shore protection. Such a policy might be viewed as creating a 

7409 bias in favor of shore protection over wetland migration, but it is not really a barrier to 

7410 adaptation from the perspective of a community that prefers protection anyway. A bias 

7411 encourages one path over another; a barrier can block a particular path entirely. 

 7412 
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7413 Second, interrelationships between various decisions tend to reinforce institutional inertia 

7414 For instance, omission of sea-level rise from a land-use plan may discourage 

7415 infrastructure designers from preparing for the rise, and a federal regulatory preference 

7416 for hard structures may prevent state officials from encouraging soft structures. Although 

7417 inertia has slowed current acts to respond to the risk of sea-level rise, it could just as 

7418 easily help to sustain momentum toward a response once key decision makers decide 

7419 which path to follow. 

 7420 

7421 The barriers and biases examined in this Chapter mostly concern governmental rather 

7422 than private sector institutions. Private institutions do not always exhibit foresight. In 

7423 fact, their limitations have helped motivate the creation of government flood insurance 

7424 (Kunreuther, 1978), wetland protection (Scodari, 1997), shore protection, and other 

7425 government programs (Bator, 1958; Arrow, 1970). This Chapter omits an analysis of 

7426 private institutions for two reasons. First, there is little literature available on private 

7427 institutional barriers to preparing for sea-level rise. It is unclear whether this absence 

7428 implies that the private barriers are less important, or simply that private organizations 

7429 keep their affairs private. Second, the published literature provides no reason to expect 

7430 that private institutions have important barriers different from those of public institutions. 

7431 The duty of for-profit corporations to maximize shareholder wealth, for example, may 

7432 prevent a business from giving up property to facilitate future environmental preservation 

7433 as sea level rises. At first glance, this duty might appear to be a barrier to responding to 

7434 sea-level rise, or at least a bias in favor of shore protection over retreat. Yet that same 

7435 duty would lead a corporation to sell the property to an organization willing to offer a 
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7436 profitable price, or invest money for shore protection. Thus, the duty to maximize 

7437 shareholder wealth is a bias in favor of profitable responses over money-losing responses, 

7438 but not a barrier to preparing for sea level rise. 

7439 12.2 SOME SPECIFIC INSTITUTIONAL BARRIERS AND BIASES 

7440 Productive institutions are designed to accomplish a mission, and rules and procedures 

7441 are designed to help accomplish those objectives. These rules and procedures are 

7442 inherently biased toward achieving the mission, and against anything that thwarts the 

7443 mission. By coincidence more than design, the rules and procedures may facilitate or 

7444 thwart the ability of others to achieve other missions. 

 7445 

7446 No catalogue of institutional biases in the coastal zone is available; but three biases have 

7447 been the subject of substantial commentary: (1) shore protection versus retreat; (2) hard 

7448 structures versus soft engineering solutions; and (3) coastal development versus

7449 preservation. 

 7450 

7451 12.2.1 Shore Protection versus Retreat 

7452 Federal, state, local, and private institutions generally have a strong bias favoring shore 

7453 protection over retreat in developed areas. Many institutions also have a bias against 

7454 shore protection in undeveloped areas. 

7455 

7456 U.S. Army Corps of Engineers (USACE) Civil Works. Congressional appropriations for 

7457 shore protection in coastal communities generally provide funds for various engineering 

7458 projects to limit erosion and flooding (see Figure 12.1). The planning guidance 
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7459 documents for USACE appear to provide the discretion to relocate or purchase homes if a 

7460 policy of retreat is the locally preferred approach and is more cost-effective than shore 

7461 protection (USACE, 2000). In part because the federal government generally pays for 65 

percent of the initial cost55 7462 , retreat is rarely the locally preferred option (Lead and 

7463 Meiners, 2002; NRC, 2004). USACE’s environmental policies discourage its Civil 

7464 Works program from seriously considering projects to foster the landward migration of 

7465 developed barrier islands (see Wetland Protection discussed further below). Finally, the 

7466 general mission of this agency, its history (Lockhart and Morang, 2002), staff expertise, 

7467 and funding preferences combine to make shore protection far more common than a 

7468 retreat from the shore. 

 7469 

7470 State Shore Protection. North Carolina, Virginia, Maryland, Delaware, and New Jersey 

7471 all have significant state programs to support beach nourishment along the Atlantic 

7472 Ocean (see Figure 12.1 and Sections A1.C.2, A1.E.2, and A1.G.4 in Appendix 1). 

7473 Virginia, Maryland, Delaware, and New Jersey have also supported beach nourishment in 

7474 residential areas along estuaries (see Figure 12.2). Some agencies in Maryland encourage 

7475 private shore protection to avoid the environmental effects of shore erosion (see Section 

7476 A1.F.2 in Appendix 1), and the state provides interest-free loans for up to 75 percent of 

7477 the cost of nonstructural erosion control projects on private property (MD DNR, 2008). 

7478 Although a Maryland guidance document for property owners favors retreat over shore 

7479 protection structures (MD DNR, 2006), none of these states has a program to support a 

7480 retreat in developed areas. 

 

55 33 USC §2213. 
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 7481 

7482 

7483 Figure 12.1 Recently nourished beach and artificially created dune in Surf City, New Jersey, with recent 

7484 plantings of dune grass. (June 2007). 

7485 

7486 

7487 Figure 12.2 Beach nourishment along estuaries. (a) The Department of Natural Resources provided an 

7488 interest-free loan to private landowners for a combined breakwater and beach nourishment project to 

7489 preserve the recreational beach and protect homes in Bay Ridge, Maryland (July 2008). (b) The Virginia 

7490 Beach Board and Town of Colonial Beach nourished the public beach along the Potomac River for 

7491 recreation and to protect the road and homes to the left (October 2002). 

7492 
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 7493 

7494 FEMA Programs. Some aspects of the National Flood Insurance Program (NFIP) 

7495 encourage shore protection, while others encourage retreat. The Federal Emergency 

7496 Management Agency (FEMA) requires local governments to ensure that new homes 

7497 along the ocean are built on pilings sunk far enough into the ground so that the homes 

7498 will remain standing even if the dunes and beach are largely washed out from under the 

house during a storm56 7499 . The requirement for construction on pilings can encourage larger 

7500 homes; after a significant expense for pilings, people rarely build a small, inexpensive 

7501 cottage. These larger homes provide a better economic justification for government7502 funded shore protection than the smaller homes. 

 7503 

7504 Beaches recover to some extent after storms, but they frequently do not entirely recover. 

7505 In the past, before homes were regularly built to withstand the 100-year storm, retreat 

7506 from the shore often occurred after major storms (i.e., people did not rebuild as far 

7507 seaward as homes had been before the storm). Now, many homes can withstand storms, 

7508 and the tendency is for emergency beach nourishment operations to protect oceanfront 

7509 homes. A FEMA emergency assistance program often funds such nourishment in areas 

where the beach was nourished before the storm57 7510 (FEMA, 2007a). For example, Topsail 

7511 Beach, North Carolina received over $1 million for emergency beach nourishment after 

7512 Hurricane Ophelia in 2005, even though it is ineligible for USACE shore protection 

7513 projects and flood insurance under the Coastal Barrier Resources Act (GAO, 2007a). In 

7514 portions of Florida that receive frequent hurricanes, these projects are a significant 

 

5644 Code of Federal Regiulations §60.3(e)(4) 

5744 CFR §206.226(j)
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7515 portion of total beach nourishment (see Table 12.1). They have not yet been a major 

7516 source of funding for beach nourishment in the Mid-Atlantic. 

 7517 

7518 Several FEMA programs are either neutral or promote retreat. In the wake of Hurricane 

7519 Floyd in 1999, one county in North Carolina used FEMA disaster funds to elevate 

7520 structures, while an adjacent county used those funds to help people relocate rather than 

7521 rebuild (see Section A1.G in Appendix 1.). Repetitively flooded homes have been 

7522 eligible for relocation assistance under a number of programs. Because of FEMA’s rate 

7523 map grandfathering policy (see Section 10.7.3.1 in Chapter 10), a statutory cap on annual 

7524 flood insurance rate increases, and limitations of the hazard mapping used to set rates, 

7525 some properties have rates that are substantially less than the actuarial rate justified by 

7526 the risk. As a result, relocation programs assist property owners and save the flood 

7527 insurance program money by decreasing claims. From 1985 to 1995, the Upton-Jones 

7528 Amendment to the National Flood Insurance Act helped fund the relocation of homes in 

7529 imminent danger from erosion (Crowell et al., 2007). FEMA’s Severe Repetitive Loss 

7530 Program is authorized to spend $80 million to purchase or elevate homes that have made 

7531 either four separate claims or at least two claims totaling more than the value of the 

7532 structure (FEMA, 2008a). Several other FEMA programs provide grants for reducing 

7533 flood damages, which states and communities can use for relocating residents out of the 

7534 flood plain, erecting flood protection structures, or flood-proofing homes (FEMA, 2008b, 

7535 c, d, e). 

7536 
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 7537 

Table 12.1 Selected Beach Nourishment Projects in Florida Authorized by FEMA’s Public Assistance Grant 

Program

Year Location Hurricane Authorized Volume 

of Sand

(cubic meters d) 

Obligated Funds a

(dollars) 

1987 Jupiter Island Floyd 90,000 637,670 

1999 Jupiter Island Irene 48,500 343,101 

 0 

2001 Longboat Key Gabrielle 48,253 596,150 

2001 Collier County Gabrielle 37,800 452,881 

2001 Vanderbilt Beach Gabrielle 61,534 1,592,582 

2001 Vanderbilt Beach Gabrielle b 738,821 

2004 Manasota Key/Knights 

Island 

Charley et al.

c

115,700 

2,272,521 

2004 Bonita Beach Charley et al.

c

21,652 1,678,221 

2004 Lovers Key Charley et al.

c

13,300 102,709 

2004 Lido Key Charley et al.

c

67,600 2,319,322 

2004 Boca Raton Frances 297,572 3,313,688 

2004 Sabastian Inlet Recreation 

Area 

Frances 

184,755 10,097,507 

2004 Hillsboro Beach Frances 83,444 1,947,228 

2004 Jupiter Island Frances 871,187 8,317,345 

2004 Pensacola Beach Ivan 2,500,000 11,069,943 

2004 Bay County Ivan 56,520 1,883,850 

2005 Pensacola Beach Dennis 400,000 2,338,248 

2005 Naples Beach Katrina 34,988 1,221,038 

2005 Pensacola Beach Katrina 482,000 4,141,019 

2005 Naples Beach Wilma 44,834 3,415,844 

2005 Longboat Key Wilma 66,272 1,093,011 

Source: Federal Emergency Management Agency. 2008. “Project Worksheets Involving ‘Beach Nourishment’ Obligated 

Under FEMA’s Public Assistance Grant Program: As of June 19, 2008.” a For some projects, the figure may include costs other than placing sand into the beach system, such as reconstructing dunes 

and planting dune vegetation, as well as associated planning and engineering costs. b

 Supplemental grant. Applicant lost original sand source and had to go 50 kilometers offshore to collect the sand being used. 

This increased the cost to $30.82 per cubic meter ($23.57 per cubic yard), compared with originally assumed cost of $10.80 

per cubic meter ($8.25 per cubic yard). 

c

 Cumulative impact of the 2004 hurricanes Charley Frances, Ivan Jeanne. 

d. Converted from cubic yards, preserving significant digits from the original source, which varies by project. 

7538 
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 7539 

7540 Flood insurance rates are adjusted downward to reflect the reduced risk of flood damages 

7541 if a dike or seawall decreases flood risks during a 100-year storm. Because rates are 

7542 based on risk, this adjustment is not a bias toward shore protection, but rather a neutral 

7543 reflection of actual risk. 

 7544 

7545 Wetland Protection. The combination of federal and state regulatory programs to protect 

7546 wetlands in the Mid-Atlantic strongly discourages development from advancing into the 

7547 sea, by prohibiting or strongly discouraging the filling or diking of tidal wetlands for 

7548 most purposes (see Chapter 9). Within the Mid-Atlantic, New York promotes the 

7549 landward migration of tidal wetlands in some cases (see Section A1.A.2 in Appendix 1), 

7550 and Maryland favors shore protection in some cases. The federal wetlands regulatory 

7551 program has no policy on the question of retreat versus shore protection. Because the 

7552 most compelling argument against estuarine shore protection is often the preservation of 

7553 tidal ecosystems (e.g., NRC, 2007), a neutral regulatory approach has left the strong 

7554 demand for shore protection from property owners without an effective countervailing 

7555 force for allowing wetlands to migrate (Titus 1998, 2000). Wetlands continue to migrate 

7556 inland in many undeveloped areas (see Figure 12.3) but not in developed areas, which 

7557 account for an increasing portion of the coast. 

 7558 

7559 Neither federal nor most state regulations encourage developers to create buffers that 

7560 might enable wetlands to migrate inland, nor do they encourage landward migration in 

7561 developed areas (Titus, 2000). In fact, USACE has issued a nationwide permit for 
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bulkheads and other erosion-control structures58 7562 . Titus (2000) concluded that this permit 

7563 often ensures that wetlands will not be able to migrate inland unless the property owner 

7564 does not want to control the erosion. For this and other reasons, the State of New York 

7565 has decided that bulkheads and erosion structures otherwise authorized under the 

7566 nationwide permit will not be allowed without state concurrence (NYDOS 2006; see 

7567 Section A1.A.2 in Appendix 1). 

 7568 

7569 Federal statutes appear to discourage regulatory efforts to promote landward migration of 

7570 wetlands. Section 10 of the Rivers and Harbors Act of 1899 and Section 404 of the Clean 

7571 Water Act require a permit to dredge or fill any portion of the navigable waters of the 

United States59 7572 . Courts have long construed this jurisdiction to include lands within the 

7573 “ebb and flow of the tides”, (e.g., Gibbons v. Ogden; Zabel v. Tabb; 40 C.F.R. § 

7574 230.3[s][1], 2004), but it does not extend inland to lands that are dry today but would 

7575 become wet if the sea were to rise one meter (Titus, 2000). The absence of federal 

7576 jurisdiction over the dry land immediately inland of the wetlands can limit the ability of 

7577 federal wetlands programs to anticipate sea-level rise. 

 7578 

7579 Although the federal wetlands regulatory program generally has a neutral effect on the 

7580 ability of wetlands to migrate as sea level rises, along the bay sides of barrier islands, 

7581 regulatory programs, discourage or prevent wetland migration. Under natural conditions, 

 

58 See 61 Federal Register 65,873, 65,915 (December 13, 1996) (reissuing Nationwide Wetland Permit 13, 

Bank Stabilization activities necessary for erosion prevention). See also Reissuance of Nationwide Permits, 

72 Fed. Reg. 11,1108-09, 11183 (March 12, 2007) (reissuing Nationwide Wetland Permit 13 and 

explaining that construction of erosion control structures along coastal shores is authorized). 

59 See The Clean Water Act of 1977, § 404, 33 U.S.C. § 1344; The Rivers and Harbors Act of 1899, § 10, 

33 U.S.C. §§ 403, 409 (1994).
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7582 barrier islands often migrate inland as sea level rises (see Chapter 3). Winds and waves 

7583 tend to fill the shallow water immediately inland of the islands, allowing bayside beaches 

7584 and marshes to slowly advance into the bay toward the mainland (Dean and Dalrymple, 

7585 2002; Wolf 1989). Human activities on developed islands, however, limit or prevent 

7586 wetland migration (Wolf, 1989). Artificial dunes limit the overwash (see Section 6.2 in 

7587 Chapter 6). Moreover, when a storm does wash sand from the beach onto other parts of 

7588 the island, local governments bulldoze the sand back onto the beach; wetland rules 

7589 against filling tidal waters prevent people from artificially imitating the overwash process 

7590 by transporting sand directly to the bay side (see Section 10.3). Although leaving the 

7591 sand in place would enable some of it to wash or blow into the bay and thereby accrete 

7592 (build land) toward the mainland, doing so is generally impractical. If regulatory agencies 

7593 decided to make wetland migration a priority, they would have more authority to 

7594 encourage migration along the bay sides of barrier islands than elsewhere, because the 

7595 federal government has jurisidiction over the waters onto which those wetlands would 

7596 migrate. 

 7597 

7598 In addition to the regulatory programs, the federal government preserves wetlands 

7599 directly through acquisition and land management. Existing statutes give the U.S. Fish 

7600 and Wildlife Service and other coastal land management agencies the authority to foster 

7601 the landward migration of wetlands (Titus, 2000). A 2001 Department of Interior (DOI) 

7602 order directed the Fish and Wildlife Service and the National Park Service to address 

climate change60 7603 . However, resource managers have been unable to implement the order 

 

60 Department of Interior Secretarial Order 3226 
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7604 because (1) they have been given no guidance on how to address climate change and (2) 

7605 preparing for climate change has not been a priority within their agencies (GAO, 2007b). 

 7606 

7607 

7608 Figure 12.3 Tidal Wetland Migration. (a) Marshes taking over land on Hooper Island (Maryland) that had 

7609 been pine forest until recently, with some dead trees standing in the foreground and a stand of trees on 

7610 slightly higher ground visible in the rear [October 2004]. (b) Marshes on the mainland opposite 

7611 Chintoteague Island, Virginia (June 2007).

7612 

7613 Relationship to Coastal Development. Many policies encourage or discourage coastal 

7614 development, as discussed in Section 12.2.3. Even policies that subsidize relocation may 

7615 have the effect of encouraging development, by reducing the risk of an uncompensated 

7616 loss of one’s investment. 

 7617 

7618 12.2.2 Shoreline Armoring versus Living Shorelines 

7619 The combined effect of federal and state wetland protection programs is a general 

7620 preference for hard shoreline structures over soft engineering approaches to stop erosion 

7621 along estuarine shores (see Box 12.1). USACE has issued nationwide permits to expedite 

the ability of property owners to erect bulkheads and revetments61 7622 , but there are no such 

 

61 Reissuance of Nationwide Permits, 72 Federal Register 11,1108-09, 11183 ((March 12, 2007) (reissuing 

Nationwide Wetland Permit 13 and explaining that construction of erosion control structures along coastal 
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permits for soft solutions such as rebuilding an eroded marsh or bay beach62 7623 . The bias in 

7624 favor of shoreline armoring results indirectly because the statute focuses on filling 

7625 navigable waterways, not on the environmental impact of the shore protection. 

7626 Rebuilding a beach or marsh requires more of the land below high water to be filled than 

7627 building a bulkhead. 

 7628 

7629 Until recently, state regulatory programs shared the preference for hard structures, but 

7630 Maryland now favors “living shorelines” (see Chapter 11), a soft engineering approach 

7631 that mitigates coastal erosion while preserving at least some of the features of a natural 

7632 shoreline (compare Figure 12.4a with 12.4b). Nevertheless, federal rules can be a barrier 

7633 to these state efforts (see e.g., Section A1.F.2.2 in Appendix 1), because the living 

7634 shoreline approaches generally include some filling of tidal waters or wetlands, which 

7635 requires a federal permit (see Section 10.3). 

 7636 

7637 The regulatory barrier to soft solutions appears to result more from institutional inertia 

7638 than from a conscious bias in favor of hard structures. The nationwide permit program is 

7639 designed to avoid the administrative burden of issuing a large number of specific but 

7640 nearly-identical permits (Copeland, 2007). For decades, many people have bulkheaded 

7641 their shores, so in the 1970s USACE issued Nationwide Permit 13 to cover bulkheads 

7642 and similar structures. Because few people were rebuilding their eroding tidal wetlands, 

 shores is authorized). See also Nationwide Permits 3 (Maintenance), 31 (Maintenance of Existing Flood 

Control Facilities) and 45 (Repair of Uplands Damaged by Discrete Events). 72 Federal Register 11092-

11198 (March 12, 2007).

62 Reissuance of Nationwide Permits, 72 Federal Register 11, 11183, 11185 ((March 12, 2007) (explaining 

that permit 13 requires fill to be minimized and that permit 27 does not allow conversion of open to water 

to another habitat such as beach or tidal wetlands) 
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7643 no nationwide permit was issued for this activity. Today, as people become increasingly 

7644 interested in more environmentally sensitive shore protection, they must obtain permits 

7645 from institutions that were created to respond to requests for hard shoreline structures. 

7646 During the last few years however, those institutions have started to investigate policies 

7647 for soft shore protection measures along estuarine shores. 

 7648 

7649 

7650 Figure 12.4 Hard and Soft Shore Protection. (a) Stone Revetment along Elk River at Port Herman, 

7651 Maryland, May 2005 (b) Dynamic Revetment along Swan Creek, at Fort Washington, Maryland, 

7652 September 2008. 

7653 
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7654 BEGIN BOX: 

7655 Box 12.1 The Existing Decision-Making Process for Shoreline Protection on Sheltered Coasts 

7656 

7657  There is an incentive to install seawalls, bulkheads, and revetments on sheltered coastlines because 

7658 these structures can be built landward of the federal jurisdiction and thus avoid the need for federal 

7659 permits. 

7660 

7661  Existing biases of many decision makers in favor of bulkheads and revetments with limited 

7662 footprints limit options that may provide more ecological benefits. 

7663 

7664  The regulatory framework affects choices and outcomes. Regulatory factors include the length of 

7665 time required for permit approval, incentives that the regulatory system creates, [and] general 

7666 knowledge of available options and their consequences. 

7667 

7668  Traditional structural erosion control techniques may appear to be the most cost-effective. 

7669 However, they do not account for the cumulative impacts that result in environmental costs nor the 

7670 undervaluation of the environmental benefits of the nonstructural approaches. 

7671 

7672  There is a general lack of knowledge and experience among decision makers regarding options for 

7673 shoreline erosion mitigation on sheltered coasts, especially options that retain more of the 

7674 shorelines’ natural features. 

7675 

7676  The regulatory response to shoreline erosion on sheltered coasts is generally reactive rather than 

7677 proactive. Most states have not developed plans for responding to erosion on sheltered shores. 

7678 

7679 Source: NRC (2007) 

7680 

7681 END BOX 

 7682 

7683 12.2.3 Coastal Development 

7684 Federal, state, local, and private institutions all have a modest bias favoring increased 

7685 coastal development in developed areas. The federal government usually discourages 

7686 development in undeveloped areas, while state and local governments have a more 

7687 neutral effect. 

 7688 

7689 Coastal counties often favor coastal development because expensive homes with seasonal 

7690 residents can substantially increase property taxes without much demand for government 

7691 services (GAO, 2007a). Thus, local governments provide services (e.g., police, fire, trash 

7692 removal) to areas in Delaware and North Carolina that are ineligible for federal funding 
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under the Coastal Barrier Resources Act63 7693 . The property tax system often encourages 

7694 coastal development. A small cottage on a lot that has appreciated to $1 million can have 

7695 an annual property tax bill greater than the annual rental value of the cottage. 

 7696 

7697 Governments at all levels facilitate the continued human occupation of low-lying lands 

7698 by providing roads, bridges, and other infrastructure. As coastal farms are replaced with 

7699 development, sewer service is often extended to the new communities—helping to 

7700 protect water quality but also making it possible to develop these lands at higher densities 

7701 than would be permitted by septic tank regulations. 

 7702 

7703 Congressional appropriations for shore protection can encourage coastal development 

7704 along shores that are protected by reducing the risk that the sea will reclaim the land and 

7705 structures (NRC, 1995; Wiegel, 1992). This reduced risk increases land values and 

7706 property taxes, which may encourage further development In some cases, the induced 

7707 development has been a key justification for the shore protection (GAO, 1976; Burby, 

7708 2006). Shore protection policies may also encourage increased densities in lightly 

7709 developed areas. The benefit-cost formulas used to determine eligibility (USACE, 2000) 

7710 find greater benefits in the most densely developed areas, making increased density a 

7711 possible path toward federal funding for shore protection. Keeping hazardous areas 

7712 lightly developed, by contrast, is not a path for federal funding (USACE, 1998; cf. 

7713 Cooper and McKenna, 2008). 

 7714 

 

63 16 U.S.Code. §3501 et seq. 
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7715 Several authors have argued that the National Flood Insurance Program (NFIP) 

7716 encourages coastal development (e.g., Tibbetts, 2006; Suffin, 1981; Simmons, 1988; 

7717 USFWS, 1997). Insurance converts a large risk into a modest annual payment that people 

are willing to pay. Without insurance, some people would be reluctant to risk $250,00064 7718 

7719 on a home that could be destroyed in a storm. However, empirical studies suggest that the 

7720 NFIP no longer has a substantial impact on the intensity of coastal development (Evatt, 

7721 2000; see Chapter 10). The program provided a significant incentive for construction in 

7722 undeveloped areas during the 1970s, when rates received a substantial subsidy (Cordes 

7723 and Yezer, 1998; Shilling et al., 1989; Evatt, 1999). During the last few decades, 

7724 however, premiums on new construction have not been subsidized and hence, the 

7725 program has had a marginal impact on construction in undeveloped areas (Evatt, 2000; 

7726 Leatherman, 1997; Cordes and Yezer, 1998; see Chapter 10). Nevertheless, in the 

7727 aftermath of severe storms, the program provides a source of funds for reconstruction—

7728 and subsidized insurance while shore protection structures are being repaired (see 

7729 Chapter 10). Thus, in developed areas the program helps rebuild communities that might 

7730 be slower to rebuild (or be abandoned) if flood insurance and federal disaster assistance 

7731 were unavailable. More broadly, the combination of flood insurance and the various post7732 disaster and emergency programs providing relocation assistance, mitigation (e.g., home 

7733 elevation), reconstruction of infrastructure, and emergency beach nourishment provide 

7734 coastal construction with a federal safety net that makes coastal construction a safe 

7735 investment. 

 7736 

 

64 NFIP only covers the first $250,000 in flood losses (44 CFR 61.6) For homes with a construction cost 

greater than $250,000, federal insurance reduces a property owner’s risk, but to a lesser extent. 
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7737 Flood ordinances have also played a role in the creation of three-story homes where local 

7738 ordinances once limited homes to two stories. Flood regulations have induced some 

7739 people to build their first floor more than 2.5 meters (8 feet) above the ground (FEMA, 

7740 1984, 1994, 2000, 2007b). Local governments have continued to allow a second floor no 

7741 matter the elevation of the first floor. Property owners often enclose the area below the 

first floor (e.g., FEMA, 2002), creating ground-level (albeit illegal65 and uninsurable66 7742 ) 

7743 living space. 

 7744 

7745 The totality of federal programs, in conjunction with sea-level rise, creates moral hazard. 

7746 Coastal investment is profitable but risky. If government assumes much of this risk, then 

7747 the investment can be profitable without being risky—an ideal situation for investors 

7748 (Loucks et al., 2006). The “moral hazard” concern is that when investors make risky 

7749 decisions whose risk is partly borne by someone else, there is a chance that they will 

7750 create a dangerous situation by taking on too much risk (Pauly, 1974). The government 

7751 may then be called upon to take on even the risks that the private investors had 

7752 supposedly assumed because the risk of cascading losses could harm the larger economy 

7753 (Kunreuther and Michel-Kerjant, 2007). Investors assume that shore protection is cost7754 effective and governments assume that flood insurance rates reflect the risk in most 

7755 cases; however, if sea-level rise accelerates, will taxpayers, coastal property owners, or 

7756 inland flood insurance policyholders have to pay the increased costs? 

 7757 

 

65 44 CFR §60.3(c)(2) 

66 44 CFR §61.5(a) 
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7758 The Coastal Barrier Resources Act (16 U.S.C. U.S.C. §3501 et seq.) discourages the 

7759 development of designated undeveloped barrier islands and spits, by denying them shore 

7760 protection, federal highway funding, mortgage funding, flood insurance on new 

construction, some forms of federal disaster assistance67 7761 , and most other forms of federal 

7762 spending. Within the Mid-Atlantic, this statute applies to approximately 90 square 

kilometers of land, most of which is in New York or North Carolina (USFWS, 2002)68 7763 . 

7764 The increased demand for coastal property has led the most developable of these areas to 

7765 become developed anyway (GAO, 1992; 2007a). “Where the economic incentive for 

7766 development is extremely high, the Act’s funding limitations can become irrelevant” 

7767 (USFWS, 2002). 

 7768 

7769 12.3 INTERDEPENDENCE: A BARRIER OR A SUPPORT NETWORK? 

7770 Uncertainty can be a hurdle to preparing for sea-level rise. Uncertainty about sea-level 

7771 rise and its precise effects is one problem, but uncertainty about how others will react can 

7772 also be a barrier. For environmental stresses such as air pollution, a single federal agency 

7773 (U.S. EPA) is charged with developing and coordinating the nation’s response. By 

7774 contrast, the response to sea-level rise would require coordination among several 

7775 agencies, including U.S. EPA (protecting the environment), USACE (shore protection), 

7776 Department of Interior (managing conservation lands), FEMA (flood hazard 

7777 management), and NOAA (coastal zone management). State and local governments 

7778 generally have comparable agencies that work with their federal counterparts. No single 

 

67 Communities are eligible for emergency beach nourishment after a storm, provided that the beach had 

been previously nourished (GAO, 2007). 

68 The other mid-Atlantic states each have less than 6 square kilometers within the CBRA system. A small 

area within the system in Delaware is intensely developed (see Box 9.2).
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7779 agency is in charge of developing a response to sea-level rise, which affects the missions 

7780 of many agencies. 

 7781 

7782 The decisions that these agencies and the private sector make regarding how to respond 

7783 to sea-level rise are interdependent. From the perspective of one decision maker, the fact 

7784 that others have not decided on their response can be a barrier to preparing his or her own 

7785 response. One of the barriers of this type is the uncertainty whether the response to sea7786 level rise in a particular area will involve shoreline armoring, elevating the land, or retreat 

7787 (see Chapter 6 for a discussion of specific mechanisms for each of these pathways). 

 7788 

7789 12.3.1 Three Fundamental Pathways: Armor, Elevate, or Retreat 

7790 Long-term approaches for managing low coastal lands as the sea rises can be broadly 

7791 divided into three pathways: 

7792  Protect the dry land with seawalls, dikes, and other structures, eliminating wetlands 

7793 and beaches (also known as “shoreline armoring”) (see Figure 12.4a and Section 

7794 6.1.1). 

7795  Elevate the land, and perhaps the wetlands and beaches as well, enabling them to 

7796 survive (see Figures 12.1 and 12.5) 

7797  Retreat by allowing the wetlands and beaches to take over land that is dry today (see 

7798 Figure 12.6). 

7799 Combinations of these three approaches are also possible. Each approach will be 

7800 appropriate in some locations and inappropriate in others. Shore protection costs, 

7801 property values, the environmental importance of habitat, and the feasibility of protecting 
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7802 shores without harming the habitat all vary by location. Deciding how much of the coast 

7803 should be protected may require people to consider social priorities not easily included in 

7804 a cost-benefit analysis of shore protection. 

 7805 

7806 Like land use planning, the purpose of selecting a pathway would be to foster a 

7807 coordinated response to sea-level rise, not to lock future generations into a particular 

7808 approach. Shoreline armoring may be appropriate over the next few decades to halt 

7809 shoreline erosion along neighborhoods that are about one meter above high water; but as 

7810 sea level continues to rise, the strategy may switch to elevating land surfaces and homes 

7811 rather than erecting dikes, which eventually leads to land becoming below sea level. 

7812 Some towns may be protected by dikes at first, but eventually have to retreat as shore 

7813 protection costs increase beyond the value of the assets protected. In other cases, retreat 

7814 may be viable up to a point, past which the need to protect critical infrastructure and 

7815 higher density development may justify shore protection. 

 7816 

7817 
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7818 

7819 Figure 12.5 Elevating land and house. (a) Initial elevation of house in Brant Beach (New Jersey). (b) 

7820 Structural beams placed under house, which is lifted approximately 1.5 meters by hydraulic jack in blue 

7821 truck. (c) Three course of cinder blocks added then house set down onto the blocks. (d) Soil and gravel 

7822 brought in to elevate land surface. (January through June 2005) 

7823 

7824 . 

7825 7826 Figure 12.6 Retreat. (a) Houses along the shore in Kitty Hawk, North Carolina (June 2002). Geotextile 

7827 sand bags protect the septic tank buried in the dunes. (b) October 2002. (c) June 2003 

 7828 

7829 
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7830 12.3.2 Decisions That Cannot Be Made Until the Pathway Is Chosen 

7831 Rising sea level has numerous implications for current activities. In most cases, the 

7832 appropriate response depends on which of the three pathways a particular community 

7833 intends to follow. This subsection examines the relationship between the three pathways 

7834 and six example activities, summarized in Table 12.2. 

 7835 

Table 12.2 The best way to prepare for sea-level rise depends on whether (and how) a community intends 

to hold back the sea. 

 Pathways for responding to sea-level rise 

Activity 

Shoreline armoring 

(e.g., dike or seawall) Elevate land Retreat/wetland migration 

Rebuild drainage 

systems 

Check valves, holding tanks; 

room for pumps 

No change needed Install larger pipes, larger 

rights of way for ditches 

Replace septics with 

public sewer 

Extending sewer helps 

improve drainage 

Mounds systems; elevate 

septic system; extending 

sewer also acceptable 

Extending sewer 

undermines policy; 

mounds system acceptable 

Rebuild roads Keep roads at same 

elevation; owners will not 

have to elevate lots 

Rebuild road higher; 

motivates property 

owners to elevate lots 

Elevate roads to facilitate 

evacuation 

Location of roads Shore-parallel road needed 

for dike maintenance 

No change needed Shore parallel road will be 

lost; all must have access 

to shore-perpendicular 

road 

Setbacks/subdivisions Setback from shore to leave 

room for dike 

No change needed Erosion-based setbacks 

Easements Easement or option to 

purchase land for dike 

No change needed Rolling easements to 

ensure that wetlands and 

beaches migrate 

 7836 

7837 Coastal Drainage Systems in Urban Areas. Sea-level rise slows natural drainage and the 

7838 flow of water through drain pipes that rely on gravity. If an area will not be protected 

7839 from increased inundation, then larger pipes or wider ditches (see Figure 12.7) may be 

7840 necessary to increase the speed at which gravity drains the area. If an area will be 

7841 protected with a dike, then it will be more important to pump the water out and to ensure 

7842 that seawater does not back up into the streets through the drainage system; so then larger 

7843 pipes will be less important than underground storage, check valves, and ensuring that the 
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7844 system can be retrofitted to allow for pumping (Titus et al., 1987). If land surfaces will be 

7845 elevated, then sea-level rise will not impair drainage. 

 7846 

7847 In many newly developed areas, low-impact development attempts to minimize runoff 

7848 into the drainage system in favor of on-site recharge. In areas where land surfaces will be 

7849 elevated over time, the potential for recharge would remain roughly constant as land 

7850 surfaces generally rise as much as the water table (i.e., groundwater level). In areas that 

7851 will ultimately be protected with dikes, by contrast, centralized drainage would 

7852 eventually be required because land below sea level can not drain unless artificial 

7853 measures keep the water table even father below sea level. 

 7854 

7855 

7856 
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7857 Figure 12.7 Tidal Ditches in the Mid-Atlantic. (a) Hoopers Island, Maryland (October 2004). (b) 

7858 Poquoson, Virginia (June 2002). (c) Swan Quarter, North Carolina (October 2002). (d) Sea Level, North 

7859 Carolina. (October 2002). The water rises and falls with the tides in all of these ditches, although the 

7860 astronomic tide is negligible in (c) Swan Quarter. Wetland vegetation is often found in these ditches. 

7861 Bulkheads are necessary to prevent the ditch from caving in and blocking the flow of water in (b). 

 7862 

7863 Septics and Sewer. Rising sea level can elevate the water table (ground water) to the point 

where septic systems no longer function properly (U.S. EPA, 2002)69 7864 . If areas will be 

7865 protected with a dike, then all of the land protected must eventually be artificially drained 

7866 and sewer lines further extended to facilitate drainage. On the other hand, extending 

7867 sewer lines would be entirely incompatible with allowing wetlands to migrate inland, 

7868 because the high capital investment tends to encourage coastal protection; a mounds7869 based septic system (see Figure 12.8) is more compatible. If a community’s long-term 

7870 plan is to elevate the area, then either a mounds-based system or extended public sewage 

7871 will be compatible. 

 7872 

7873 Road Maintenance. As the sea rises, roads flood more frequently. If a community expects 

7874 to elevate the land with the sea, then routine repaving projects would be a cost-effective 

7875 time to elevate the streets. If a dike is expected, then repaving projects would consciously 

7876 avoid elevating the street above people’s yards, lest the projects cause those yards to 

7877 flood or prompt people to spend excess resources on elevating them, when doing so is not 

7878 necessary in the long run. 

7879 

 

69 “Most current onsite wastewater system codes require minimum separation distances of at least 18 inches 

from the seasonally high water table or saturated zone irrespective of soil characteristics. Generally, 2- to 4-

foot separation distances have proven to be adequate in removing most fecal coliforms in septic tank 

effluent” U.S. EPA (2002). 
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 7880 

7881 

 7882 

7883 Figure 12.8 Mounds-based septic system for areas with high water tables. For areas with high water 

7884 tables, where traditional septic/drainfield systems do not work, sand mounds are often used. In this system, 

7885 a sand mound is contructed on the order of 50 to 100 cm above the ground level, with perforated drainage 

7886 pipes in the mound above the level of adjacent ground, on top of a bed of gravel to ensure proper drainage. 

7887 Effluent is pumped from the septic tank up to the perforated pipe drainage pipe. Source: Converse and 

7888 Tyler (1998). 

 7889 

 7890 

7891 The Town of Ocean City, Maryland, currently has policies in place that could be 

7892 appropriate if the long-term plan was to build a dike and pumping system, but not 

7893 necessarily cost-effective if land surfaces are elevated as currently expected.the town 

7894 expects to elevate instead. Currently, the town has an ordinance that requires property 

7895 owners to maintain a 2 percent grade so that rainwater drains into the street. The town has 

7896 interpreted this rule as imposing a reciprocal responsibility on the town itself to not 

7897 elevate roadways above the level where yards can drain, even if the road is low enough to 

7898 flood during minor tidal surges. Thus, the lowest lot in a given area dictates how high the 

7899 street can be. As sea level rises, the town will be unable to elevate its streets, unless it 

7900 changes this rule. Yet public health reasons require drainage to prevent standing water in 

7901 which mosquitoes breed. Therefore, Ocean City has an interest in ensuring that all 
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7902 property owners gradually elevate their yards so that the streets can be elevated as the sea 

7903 rises without causing public health problems. The town has developed draft rules that 

7904 would require that, during any significant construction, yards be elevated enough to drain 

7905 during a 10-year storm surge for the life of the project, considering projections of future 

7906 sea-level rise. The draft rules also state that Ocean City’s policy is for all lands to 

7907 gradually be elevated as the sea rises (see Box A1.5 in Appendix 1). 

 7908 

7909 Locations of Roads. As the shore erodes, any home that is accessed only by a road 

7910 seaward of the house could lose access before the home itself is threatened. Homes 

7911 seaward of the road might also lose access if that road were washed out elsewhere. 

7912 Therefore, if the shore is expected to erode, it is important to ensure that all homes are 

7913 accessible by shore-perpendicular roads, a fact that was recognized in the layout of early 

7914 beach resorts along the New Jersey and other shores. If a dike is expected, then a road 

7915 along the shore would be useful for dike construction and maintenance. Finally, if all land 

7916 is likely to be elevated, then sea-level rise may not have a significant impact on the best 

7917 location for new roads. 

 7918 

7919 Subdivision and Setbacks. If a dike is expected, then houses need to be set back enough 

7920 from the shore to allow room for the dike and associated drainage systems. Setbacks and 

7921 larger coastal lot sizes are also desirable in areas where a retreat policy is preferred for 

7922 two reasons. First, the setback provides open lands onto which wetlands and beaches can 

7923 migrate inland without immediately threatening property. Second, larger lots mean lower 

7924 density and hence fewer structures that would need to be moved, and less justification for 
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7925 investments in central water and sewer. By contrast, in areas where the plan is to elevate 

7926 the land, sea-level rise does not alter the property available to the homeowner, and hence 

7927 would have minor implication for setbacks and lot sizes. 

 7928 

7929 Covenants and Easements Accompanying Subdivision. Although setbacks are the most 

7930 common way to anticipate eventual dike construction and the landward migration of 

7931 wetlands and beaches, a less expensive method would often be the purchase of (or 

7932 regulatory conditions requiring) rolling easements, which allow development but prohibit 

7933 hard structures that stop the landward migration of ecosystems. The primary advantage of 

7934 a rolling easement is that society makes the decision to allow wetlands to migrate inland 

7935 long before the property is threatened, so owners can plan around the assumption of 

7936 migrating wetlands, whether that means leaving an area undeveloped or building 

7937 structures that can be moved. 

 7938 

7939 Local governments can also obtain easements for future dike construction. This type of 

7940 easement, as well as rolling easements, would each have very low market prices in most 

7941 areas, because the fair market value is equal to today’s land value discounted by the rate 

7942 of interest compounded over the many decades that will pass before the easement would 

7943 have any effect (Titus, 1998). As with setbacks, a large area would have to be covered by 

7944 the easements if wetlands are going to migrate inland; a narrow area would be required 

7945 along the shore for a dike; and no easements are needed if the land will be elevated in 

7946 place. 

7947 
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7948 12.3.3 Opportunities for Deciding on the Pathway 

7949 At the local level, officials make assumptions about which land will be protected in order 

7950 to understand which lands will truly become inundated (see Chapter 2) and how 

7951 shorelines will actually change (see Chapter 3), which existing wetlands will be lost (see 

7952 Chapter 4), whether wetlands will be able to migrate inland (see Chapter 6), and the 

7953 potential environmental consequences (see Chapter 5); the population whose homes 

7954 would be threatened (see Chapter 7) and the implications of sea-level rise for public 

7955 access (see Chapter 8) and floodplain management (see Chapter 9). Assumptions about 

7956 which shores will be protected are also necessary in order to estimate the level of 

7957 resources that would be needed to fulfill property owners’ current expectations for shore 

7958 protection (e.g., Titus, 2004). 

 7959 

7960 Improving the ability to project the impacts of sea-level rise is not the only for such 

7961 analyses utility of data regarding shore protection. Another use of such studies has been 

7962 to initiate a dialogue about what should be protected, so that state and local governments 

7963 can decide upon a plan of what will actually be protected. Just as the lack of a plan can 

7964 be a barrier to preparing for sea-level rise, the adoption of a plan could remove an 

7965 important barrier and signal to decision makers that it may be possible for them to plan 

7966 for sea-level rise as well. 

 7967 

7968 
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7969 CHAPTER 12 REFERENCES

7970 * Indicates non-peer reviewed literature; available upon request

7971 

7972 

7973 Akerlof, G.A. and W.T. Dickens, 1982: The economic consequences of cognitive 

7974 dissonance. American Economic Review, 72, 307, 309. 

7975 Arrow, K.J., 1970: The organization of economic activity: issues pertinent to the choice 

7976 of market versus nonmarket allocation. In: Public Expenditures and Policy 

7977 Analysis [Margolis, J. (ed.)]. Markham Publishing Company, Chicago, pp. 59-73. 

7978 Bator, F.M., 1958: The anatomy of market failure. The Quarterly Journal of 

7979 Economics,72(3), 351-79. 

7980 Bradshaw, G.A. and J.G. Borchers, 2000: Uncertainty as information: narrowing the 

7981 science-policy gap. Conservation Ecology, 4(1), 7.

7982 Burby, R.J., 2006: Hurricane Katrina and the Paradoxes of Government Disaster Policy: 

7983 Bringing About Wise Governmental Decisions for Hazardous Areas. The Annals 

7984 of the American Academy of Political and Social Science, 604(1), 171-191. 

7985 Converse, J.C. and E.J. Tyler, 1998: Soil treatment of aerobically treated domestic 

7986 wastewater with emphasis on modified mounds. In: On-Site Wastewater 

7987 Treatment: Proceedings of the Eighth National Symposium on Individual and 

7988 Small Community Sewage Systems [Sievers, D.M. (ed.)]. American Society of 

7989 Agricultural Engineers, St. Joseph, MI. 

7990 Cooper, J.A.G. and J. McKenna, 2008: Social justice in coastal erosion management: the 

7991 temporal and spatial dimensions. Geoforum, 39(1), 294-306. 

7992 Copeland, C., 2007: The Army Corps of Engineers’ Nationwide Permits Program: Issues 

7993 and Regulatory Developments. Congressional Research Service, Washington, DC, 

7994 [30 pp.]
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7995 Cordes, J.J. and A.M.J. Yezer, 1998: In harm's way: does federal spending on beach 

7996 enhancement and protection induce excessive development in coastal areas? Land 

7997 Economics, 74(1), 128-145. 

7998 Crowell, M., E. Hirsch, and T.L. Hayes, 2007: Marine Technology Society Journal, 

7999 41(1), 18-27. 

8000 Dean, R.G. and R.A. Dalrymple, 2002: Coastal Processes with Engineering 

8001 Applications. Cambridge University Press, Cambridge, UK, and New York, 475 

8002 pp. 

8003 Depoorter, B., 2006: Horizontal political externalities: the supply and demand of disaster 

8004 management. Duke Law Journal, 56(1), 101-125. 

8005 Evatt, D.S., 1999: National Flood Insurance Program: Issues Assessment. Federal 

8006 Emergency Management Agency, Washington, DC, 123 pp. 

8007 Evatt, D.S., 2000: Does the national flood insurance program drive floodplain 

8008 development? Journal of Insurance Regulation, 18(4), 497-523. 

8009 FEMA (Federal Emergency Management Agency), 1984: Elevated Residential 

8010 Structures. FEMA 54. Federal Emergency Management Agency, Washington, 

8011 DC, 144 pp. 

8012 FEMA (Federal Emergency Management Agency), 1994: Mitigation of Flood and 

8013 Erosion Damage to Residential Buildings in Coastal Areas. FEMA 257. Federal 

8014 Emergency Management Agency, Washington, DC, 40 pp. 

8015 FEMA (Federal Emergency Management Agency), 2000: Above the Flood: Elevating 

8016 Your Floodprone House. FEMA 347. Federal Emergency Management Agency, 

8017 Washington, DC, 69 pp. 

8018 FEMA (Federal Emergency Management Agency), 2002: FEMA Notifies Monroe 

8019 County, Florida, of Impending Flood Insurance Probation. Region IV News 
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8020 Release Number: R4-02-15. 

8021 <http://www.fema.gov/news/newsrelease.fema?id=4528> 

8022 FEMA (Federal Emergency Management Agency), 2007a: Public Assistance Guide. 

8023 FEMA 322. Federal Emergency Management Agency, Washington, DC. 

8024 <http://www.fema.gov/government/grant/pa/policy.shtm> 

8025 FEMA (Federal Emergency Management Agency), 2007b: Coastal Construction 

8026 Manual. Federal Emergency Management Agency, Washington, DC. 

8027 <http://www.fema.gov/rebuild/mat/fema55.shtm> 

8028 FEMA (Federal Emergency Management Agency), 2008a: Severe Repetitive Loss 

8029 Program. [Web site] Federal Emergency Management Agency, Washington, DC. 

8030 <http://www.fema.gov/government/grant/srl/index.shtm> 

8031 FEMA (Federal Emergency Management Agency), 2008b: Repetitive Flood Claims 

8032 Program: Program Overview. [Web site] Federal Emergency Management 

8033 Agency, Washington, DC. 

8034 <http://www.fema.gov/government/grant/rfc/index.shtm> 

8035 FEMA (Federal Emergency Management Agency), 2008c: Hazard Mitigation Grant 

8036 Program. [Web site] Federal Emergency Management Agency, Washington, DC. 

8037 <http://www.fema.gov/government/grant/hmgp/> 

8038 FEMA (Federal Emergency Management Agency), 2008d: Flood Mitigation Assistance 

8039 Program [Web site] Federal Emergency Management Agency, Washington, DC. 

8040 <http://www.fema.gov/government/grant/fma/index.shtm> 

8041 FEMA (Federal Emergency Management Agency), 2008e: Pre-Disaster Mitigation 

8042 Program. [Web site] Federal Emergency Management Agency, Washington, DC. 

8043 <http://www.fema.gov/government/grant/pdm/index.shtm> 

8044 Festinger, L., 1957: A Theory of Cognitive Dissonance. Stanford University Press, 

8045 Stanford, CA, 291 pp. 
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8046 GAO (General Accounting Office), 1976: Cost, Schedule, and Performance Problems of 

8047 the Lake Pontchartrain and Vicinity, Louisiana, Hurricane Protection Project. 

8048 PSAD-76-161. General Accounting Office, Washington, DC, 25 pp. 

8049 GAO (General Accounting Office), 1992: Coastal Barriers: Development Occurring 

8050 Despite Prohibitions Against Federal Assistance. GAO/RCED-92-115. General 

8051 Accounting Office, Washington, DC, 71 pp. 

8052 GAO (Government Accountability Office), 2007a: Coastal Barriers Resources System: 

8053 Status of Development that Has Occurred and Financial Assistance Provided by 

8054 Federal Agencies: Development Occurring Despite Prohibitions Against Federal 

8055 Assistance. GAO/07-356. Government Accountability Office, Washington, DC, 

8056 66 pp. 

8057 GAO (Government Accountability Office), 2007b. Climate Change: Agencies Should 

8058 Develop Guidance for Addressing the Effects on Federal Land and Water 

8059 Resources. GAO-07-863. Government Accountability Office, Washington, DC, 

8060 179 pp. 

8061 Gibbons v. Ogden, 22 U.S. 1, 217-18 (9 Wheat. 1824) 

8062 Harmon-Jones, E. and J. Mills, 1999: Cognitive Dissonance: Progress on a Pivotal 

8063 Theory in Social Psychology. American Psychological Association, Washington, 

8064 DC, 411 pp. 

8065 Kunreuther, H., R. Ginsberg, L. Miller, P. Sagi, P. Slovic, B. Borkan, and N. Katz, 

8066 1978: Disaster Insurance Protection. John Wiley and Sons, New York, 400 pp. 

8067 Kunreuther, H.C. and E.O. Michel-Kerjant, 2007: Climate change, insurability of large8068 scale disasters, and the emerging liability challenge. University of Pennsylvania 

8069 Law Review, 155(6), 1795-1842. 

8070 Kunreuther, H., R. Meyer, and C. Van den Bulte, 2004: Risk Analysis for Extreme 

8071 Events: Economic Incentives for Reducing Future Losses. National Institute of 

8072 Standards and Technology, Gaithersburg, MD, 93 pp. 
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8073 Lead, D. and R.E. Meiners, 2002: Government vs. Environment. Rowan and Littlefield, 

8074 Lanham, MD, 207 pp. 

8075 Leatherman, S.P., 1997: Flood Insurance Availability in Coastal Areas: The Role It 

8076 Plays in Encouraging Development Decisions. Federal Emergency Management 

8077 Agency,Washington, DC. 

8078 Lockhart, J. and A. Morang, 2002: History of coastal engineering. In: Coastal 

8079 Engineering Manual, Part I [Morang, A. (ed.)]. Engineer manual 1110-2-1100. 

8080 U.S. Army Corps of Engineers, Washington, DC, [39 pp.] 

8081 <http://chl.erdc.usace.army.mil/cemtoc> 

8082 Loucks, D.P., J.R. Stedinger, and E.Z. Stakhiv, 2006: Individual and societal responses 

8083 to natural hazards. Journal of Water Resources Planning & Management, 132(5), 

8084 315-319. 

8085 MD DNR (Maryland Department of Natural Resources), 2006: Shore Erosion Control 

8086 Guidelines for Waterfront Property Owners. Maryland Department of Natural 

8087 Resources, Annapolis, 30 pp. 

8088 <http://www.dnr.state.md.us/ccws/sec/download/waterfrontpropertyownersguide.

8089 pdf >

8090 MD DNR (Maryland Department of Natural Resources), 2008: Grants and Loans: Shore 

8091 Erosion Control. [web site] Maryland Department of Natural Resources, 

8092 Annapolis. <http://www.dnr.state.md.us/land/sec/> 

8093 Mileti, D.S., 1999: Disasters by Design: A Reassessment of Natural Hazards in the 

8094 United States. Joseph Henry Press, Washington, DC, 351 pp. 

8095 NRC (National Research Council), 1995: Beach Nourishment and Protection. National 

8096 Academy Press, Washington, DC, 334 pp. 

8097 NRC (National Research Council), 2004: River Basins and Coastal Systems Planning 

8098 Within the U.S. Army Corps of Engineers. National Academies Press, 

8099 Washington, DC, 167 pp. 
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8100 NRC (National Research Council), 2007: Mitigating Shore Erosion along Sheltered 

8101 Coasts. National Academies Press, Washington, DC, 174 pp. 

8102 NYDOS (New York Department of State), 2006: Department of State review of US 

8103 Army Corps of Engineers consistency determination for reissuance, modification, 

8104 and issuance of new nationwide permits and conditions. Letter to USACE Buffalo 

8105 and New New York districts, December 8, 2006. New York Division of Coastal 

8106 Resources, Albany, 5 pp. 

8107 Pauly, M.V., 1974: Overinsurance and public provision of insurance: the roles of moral 

8108 hazard and adverse selection. Quarterly Journal of Economics, 88(1), 44-62. 

8109 Scodary, P., 1997: Measuring the Benefits of Federal Wetland Protection Programs. 

8110 Environmental Law Institute, Washington, DC, 103 pp. 

8111 Simmons, M., 1988: The Evolving National Flood Insurance Program. 86-641 ENR. 

8112 Congressional Research Service Washington, DC. 

8113 Shilling, J.D., C.E. Sirmans, and J.D. Benjamin, 1989: Flood insurance, wealth 

8114 redistribution, and urban property values. Journal of Urban Economics, 26(1), 43-

8115 53. 

8116 Suffin, W.J., 1981: Bureaucracy, entrepreneurship, and natural resources: witless policy 

8117 and barrier islands. Cato Journal, 1(1), 293-311.

8118 Tibbetts, J.H., 2006: After the storm. Coastal Heritage, 20(4), 3-11. 

8119 Titus, J.G., 1998: Rising seas, coastal erosion and the taking clause: how to save 

8120 wetlands and beaches without hurting property owners. Maryland Law Review,

8121 57(4), 1277-1399. 

8122 Titus, J.G., 2000: Does the U.S. government realize that the sea is rising? How to 

8123 restructure federal programs so that wetlands and beaches survive. Golden Gate 

8124 University Law Review, 30(4), 717-778. 
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8125 * Titus, J.G., 2004: Maps that depict the business-as-usual response to sea level rise in 

8126 the decentralized United States of America. Presented at: Global Forum on 

8127 Sustainable Development, Paris, 11-12, November 2004. Organization of 

8128 Economic Cooperation and Development, Paris. 

8129 Titus, J.G., C.Y. Kuo, M.J. Gibbs, T.B. LaRoche, M.K. Webb, and J.O. Waddell, 1987: 

8130 Greenhouse effect, sea level rise, and coastal drainage systems. Journal of Water 

8131 Resources Planning and Management, 113(2), 216-227. 

8132 TRB (Transportation Research Board), 2008: Potential Impacts of Climate Change on 

8133 U.S. Transportation. National Academies Press, Washington, DC, 234 pp. 

8134 USACE (U.S. Army Corps of Engineers), 1998: Atlantic Coast of Long Island, Fire 

8135 Island Inlet to Montauk Point: Alternative Screening Report. Draft report. U.S. 

8136 Army Corps of Engineers New York District, New York, 118 pp. 

8137 <http://www.nan.usace.army.mil/fimp/pdf/montauk/screening.pdf> 

8138 USACE (U.S. Army Corps of Engineers), 2000: Planning Guidance Notebook. 

8139 Document ER 1105-2-100. U.S. Army Corps of Engineers, Washington, DC. 

8140 <http://www.usace.army.mil/publications/eng-regs/er1105-2-100/> 

8141 U.S. EPA (Environmental Protection Agency), 2002: Onsite Wastewater Treatment 

8142 Systems Manual. EPA/625/R-00/008. EPA Office of Water and Office of 

8143 Research and Development, Washington, DC, [367 pp.] 

8144 <http://purl.access.gpo.gov/GPO/LPS21380> 

8145 USFWS (U.S. Fish and Wildlife Service), 1997: Biological Opinion: Administration of 

8146 the National Flood Insurance Program in Monroe County, Florida, by the 

8147 Federal Emergency Management Agency. U.S. Fish and Wildlife Service, 

8148 Atlanta, GA. 

8149 USFWS (U.S. Fish and Wildlife Service), 2002: The Coastal Barrier Resources Act: 

8150 Harnessing the Power of Market Forces to Conserve America’s Coasts and Save 
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8151 Taxpayers’ Money. U.S. Fish and Wildlife Service, Arlington, VA, 34 pp. 

8152 <http://www.fws.gov/habitatconservation/TaxpayerSavingsfromCBRA.pdf> 

8153 Viscusi, W.K. and R.J. Zeckhauser, 2006: National survey evidence on disasters and 

8154 relief: risk beliefs, self-interest, and compassion. Journal of Risk & Uncertainty, 

8155 33(1/2), 13-36. 

8156 Wolff, F., 1989: Environmental assessment of human interference on the natural 

8157 processes affecting the barrier beaches of Long Island, New York. Northeastern 

8158 Environmental Science, 8(2), 119-134. 

8159 Wiegel, R.L., 1992: Dade County, Florida beach nourishment and hurricane surge 

8160 protection. Shore and Beach, 60(4), 2-28. 

8161 Zabel v. Tabb, 430 F.2d 199, 215 (5th Cir. 1970) 

8162 
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8163 Part IV Overview. National implications and a science 

8164 strategy for the way forward 

 8165 

8166 Authors: S. Jeffress Williams, USGS; E. Robert Thieler, USGS; Benjamin T. Gutierrez, 

8167 USGS; Dean B. Gesch; USGS; Donald R. Cahoon, USGS; K. Eric Anderson, USGS 

8168 

8169 Climate change and effects such as sea-level rise have global implications and will 

8170 increasingly affect the entire nation. While this Product focuses primarily on the mid8171 Atlantic region of the United States, many of the issues discussed in earlier chapters are 

8172 relevant at the national scale. 

 8173 

8174 Chapter 13 draws on findings from the mid-Atlantic focus area that have relevance to 

8175 other parts of the United States, provides an overview of coastal environments and 

8176 landforms in the United States, and describes the issues faced in understanding how these 

8177 environments may be impacted and respond to sea-level rise. The diversity of U.S. 

8178 coastal settings includes bedrock coasts in Maine, glacial bluffs in New York, barrier 

8179 islands in the mid-Atlantic and Gulf of Mexico, coral reefs in Florida, the Caribbean, and 

8180 Hawaii, one of the world’s major delta systems in Louisiana, a wide variety of pocket 

8181 beaches and cliffed coasts along the Pacific coast, Pacific atolls, and a number of arctic 

8182 coastline types in Alaska. In addition, the large bays and estuaries around the country also 

8183 exhibit a diverse range of shoreline types, large wetland systems, and extensive coastal 

8184 habitats. 
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 8185 

8186 Understanding how the different coastal environments of the United States will respond 

8187 to future climate and sea-level change is a major challenge. In addition, as highlighted in 

8188 earlier Parts of this Product, human actions and policy decisions also substantially 

8189 influence the evolution of the coast. The knowledge gaps and data limitations identified 

8190 in this Product focusing on the mid-Atlantic have broad relevance to the rest of the U.S. 

8191 Chapter 14 identifies opportunities for increasing the scientific understanding of future 

8192 sea-level rise impacts. This includes basic and applied research in the natural and the 

8193 social sciences. A significant emphasis is placed on developing linkages between 

8194 scientists, policy makers, and stakeholders at all levels, so that information can be shared 

8195 and utilized efficiently and effectively as sea-level rise mitigation and adaptation plans 

8196 evolve. 

8197 
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8198 Chapter 13. Implications of Sea-Level Rise to the 

8199 Nation 

8200 

8201 Authors: S. Jeffress Williams, USGS; Benjamin T. Gutierrez, USGS; James G. Titus, 

8202 USEPA; Eric Anderson, USGS (retired); Stephen K. Gill, NOAA; Donald R. Cahoon, 

8203 USGS; E. Robert Thieler, USGS; and Dean B. Gesch, USGS 

8204 

8205 KEY FINDINGS

8206  Nationwide, more than one-third of the United States population currently lives in 

8207 the coastal zone and movement to the coast and development continues, along 

8208 with the current and growing vulnerability to coastal hazards such as storms and 

8209 sea-level rise. Fourteen of the 20 largest U.S. urban centers are located along the 

8210 coast. With the very likely accelerated rise in sea level and increased storm 

8211 intensity, the conflicts between people and development at the coast and the 

8212 natural processes will increase, causing economic and societal impacts. 

8213  For much of the U.S., shores comprised of barrier islands, dunes, spits, and sandy 

8214 bluffs, erosion processes will dominate at highly variable rates in response to sea8215 level rise and storms over the next century and beyond. Some coastal landforms in 

8216 the U.S. may undergo large changes in shape and location if the rate of sea-level 

8217 rise increases as predicted. Increased inundation and more frequent flooding will 

8218 affect estuaries and low-lying coastal areas. The response to these driving forces 

8219 will vary depending on the type of coastal landform and local conditions, but will 
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8220 be more extreme, more variable and less predictable than the changes observed 

8221 over the last century. 

8222  For higher sea-level rise scenarios, some barrier island coasts and wetlands may 

8223 cross thresholds and undergo significant and irreversible changes. These changes 

8224 include rapid landward migration and segmentation of some barrier islands and 

8225 disintegration and drowning of wetlands. 

8226  Nationally, tidal wetlands already experiencing submergence by sea-level rise and 

8227 associated land loss, in concert with other factors, will continue to deteriorate in 

8228 response to changing climate. 

8229  Coastal change is driven by complex and interrelated processes. Over the next 

8230 century and beyond, with an expected acceleration in sea-level rise, the potential 

8231 for coastal change is likely to be greater than has been observed in historic past. 

8232 These changes to coastal regions will have especially large impacts on urban 

8233 centers and developed areas. Some portions of the U.S. coast, however, will be 

8234 subject primarily to inundation from sea-level rise over the next century. A 

8235 substantial challenge remains to quantify the various effects of sea-level rise and 

8236 to identify the dominant coastal change processes for each region of the U.S. 

8237 coast. 

8238  Many coastal areas in the United States will likely experience an increased 

8239 frequency and magnitude of storm-surge flooding and coastal erosion due to 

8240 storms over the next century, in response to sea-level rise. The impacts from these 

8241 storm events are likely to extend farther inland from the coast than those that 

8242 would be affected by sea-level rise alone. 
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8243  Understanding, predicting, and responding to the environmental and societal 

8244 effects of sea-level rise would benefit from a national program of integrated 

8245 research that includes the natural and social sciences. Research on adaptation, 

8246 mitigation, and avoidance-of-risk measures would enable improved understanding 

8247 of the many and varied potential societal impacts of sea-level rise that would 

8248 benefit the U.S as well as coastal nations around the world. 

 8249 

8250 13.1 INTRODUCTION 

8251 As defined in the SAP 4.1 Prospectus and discussed in earlier chapters, this Product 

8252 focuses on assessing potential impacts to the mid-Atlantic region; however, some 

8253 discussion of impacts to other regions and the nation as a whole is warranted. The mid8254 Atlantic region is highly vulnerable to sea-level rise, but regions like the central Gulf 

8255 Coast (Louisiana, Texas) are just as vulnerable or more so. The challenge in carrying out 

8256 a national assessment is that nationwide data bases and scientific publications of national 

8257 scale and scope are limited. Modest efforts at monitoring and observations for national8258 scale assessments of coastal change and hazards are underway by various organizations, 

8259 but more effort is needed. The discussion in ection 13.3 is largely the expert opinions of 

8260 the lead authors, informed by results of the two expert science panel reports (Reed et al., 

8261 2008, Gutierrez, et al., 2007) and available scientific literature. Because of the relative 

8262 lack of adequate background literature and high reliance on expert opinion, the likehood 

8263 statements as used in other chapters are not included in this discussion of potential 

8264 impacts to the nation. 

8265 
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8266 A large and expanding proportion of the U.S. population and related urban development 

8267 is located along the Atlantic, Gulf of Mexico, and Pacific coasts and increasingly 

8268 conflicts with the natural processes associated with coastal change from storms and sea8269 level rise (see a review in Williams et al., 1991). Development in low-lying regions (i.e., 

8270 New Orleans) and islands (e.g., in the Chesapeake Bay, Caribbean, Pacific Ocean) are 

8271 particularly at risk (see Gibbons and Nicholls, 2006) In the future, as the effects of 

8272 climate change intensify, these interactions will become more frequent and more 

8273 challenging to society. Currently, more than one-third of the population lives in the 

8274 coastal zone and movement to the coast and development continues, along with the 

8275 growing vulnerability to coastal hazards. Fourteen of the 20 largest U.S. urban centers are 

8276 located along the coast (Crossett et al., 2004; Crowell et al., 2007). With the likely 

8277 accelerated rise in sea level and increased storm intensity, the conflicts between people 

8278 and development at the coast and the natural processes will increase, affecting all parts of 

8279 society (Leatherman, 2001; FitzGerald et al., 2008). 

8280 

8281 Global sea-level rise associated with climate change is likely to be in the range of 19 cm 

8282 to as much as 1 m over the next century and possibly as much as 4 to 6 m over the next 

8283 several centuries (IPCC, 2007; Rahmstorf, 2007; Rahmstorf, et al., 2007; Overpeck et al., 

8284 2006). The expected rise will increase erosion and the frequency of flooding and coastal 

8285 areas will be at increasing risk. For some regions, adaptation using engineering means 

8286 may be effective; for other coastal areas, however, adaption by relocation landward to 

8287 higher elevated ground may be appropriate for longer-term sustainability (NRC, 1987). 

8288 
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8289 Coastal landforms reflect the complex interaction between the natural physical processes 

8290 that act on the coast, the geologic characteristics of the coast, and human activities. 

8291 Spatial and temporal variations in these physical processes and the geology along the 

8292 coast are responsible for the wide variety of landforms around the United States 

8293 (Williams, 2003). With future sea-level rise, portions of the U.S. ocean coast are likely to 

8294 undergo long-term net erosion, at rates higher than those that have been observed over 

8295 the past century (see Chapter 3). The exact manner and rates at which these changes are 

8296 likely to occur depend on the character of coastal landforms (e.g., barrier islands, cliffs) 

8297 and the physical processes (e.g., waves and winds) that shape these landforms (see 

8298 Chapters 3 and 4). Low-relief coastal regions, areas undergoing land subsidence and land 

8299 subject to frequent storm landfalls, such as the northern Gulf of Mexico, Florida, Hawaii, 

8300 Puerto Rico, the San Francisco-Sacramento Delta region, and the Mid-Atlantic region, 

8301 are particularly vulnerable. 

8302 

8303 13.2 TYPES OF COASTS 

8304 Coasts are dynamic junctions of the oceans, atmosphere, and land and differ greatly in 

8305 physical character and vulnerability to erosion, storms, and sea-level rise (NRC, 1990). 

8306 The principal coastal types are described in Chapters 3 and 4, and summarized below. 

8307 With future sea-level rise, all of these landforms will become more dynamic (Nicholls et 

8308 al., 2007), but predicting and quantifying changes that are likely to occur with high 

8309 confidence is currently scientifically challenging. 

 8310 

8311 13.2.1 Cliff and Bluff Shorelines 
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8312 Substantial portions of the U.S. coast are comprised of coastal cliffs and bluffs that vary 

8313 greatly in height, morphology, and sedimentary composition. These occur predominantly 

8314 along the New England and Pacific coasts, Hawaii, and Alaska. Coastal cliff is a general 

8315 term that refers to steep slopes along the shoreline that commonly form in response to 

8316 long-term rise in sea-level. The term “bluff” also can refer to escarpments eroded into 

8317 unlithified material, such as glacial till, along the shore (Hampton and Griggs, 2004). The 

8318 terms “cliff” and “bluff” are often used interchangeably. Coastal cliffs erode in response 

8319 to a variety of both marine and terrestrial processes. Cliff retreat can be fairly constant, 

8320 but can also be episodic. In contrast to sandy coasts, which may erode landward or 

8321 accrete seaward, cliffs retreat only in a landward direction. Because rocky cliff coasts are 

8322 composed of resistant materials, erosion can can occur more slowly than for those 

8323 comprised of unconsolidated sediments and response times to sea-level rise much longer 

8324 than for sandy coasts (NRC, 1987), but land slumping due to wave action or land surface 

8325 water runoff can result in rapid retreat. Hampton and Griggs (2004) provide a review of 

8326 the origin, U.S. distribution, evolution, and regional issues associated with coastal cliffs. 

8327 Predicting the response of coastal cliffs to future sea-level rise is a topic of active 

8328 research (Trenhaile, 2001; Walkden and Hall, 2005; Dickson et al., 2007; Walkden and 

8329 Dickson, 2008) 

8330 

8331 13.2.2 Sandy Shores, Pocket Beaches, Barrier Beaches, Spits, and Dunes 

8332 Sandy beaches are often categorized into a few basic types which commonly include 

8333 mainland, pocket, and barrier beaches (Wells, 1995; Davis and FitzGerald, 2004). The 

8334 sediments that comprise beaches are derived mainly from the erosion of the adjacent 
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8335 mainland and continental shelf, and sometimes from sediments supplied from coastal 

8336 rivers. Mainland beaches occur where the land intersects the shore. Some mainland 

8337 beaches occur in low-relief settings and are surrounded by coastal dunes, while others 

8338 occur along steep portions of the coast and are backed by bluffs. Examples of mainland 

8339 beaches include the shores of eastern Long Island, northern New Jersey (Oertel and 

8340 Kraft, 1994), and parts of Delaware, (Kraft, 1971). Pocket beaches form in small bays, 

8341 often occurring between rocky headlands and are common along parts of the southern 

8342 New England coast, portions of California and Oregon (Hapke et al., 2006), and in parts 

8343 of the Hawaiian Islands. Barrier beaches and spits are the most abundant coastal 

8344 landforms along the Atlantic and Gulf of Mexico coasts. In general, it is expected that 

8345 accelerations in sea-level rise will enhance beach erosion globally, but on a local scale 

8346 this response will depend on the sediment budget (Nicholls et al., 2007). 

 8347 

8348 13.2.3 Coastal Marshes, Mangroves, and Mud Flat Shorelines 

8349 Coastal wetlands include swamps and tidal flats, salt and brackish marshes, mangroves, 

8350 and bayous. They form in low-relief, low-energy sheltered coastal environments, often in 

8351 conjunction with river deltas, landward of barrier islands, and along the flanks of 

8352 estuaries (e.g., Delaware Bay, Chesapeake Bay, Everglades, Lake Pontchatrain, 

8353 Galveston Bay, San Francisco Bay, and Puget Sound). Most coastal wetlands are in 

8354 Louisiana, North and South Carolina, south Florida, and Alaska (Dahl, 1990; NRC, 

8355 1995a). Wetlands are extremely vulnerable to sea-level rise and can maintain their 

8356 elevation and viability only if sediment accumulation (both mineral and organic matter) 

8357 keeps pace with sea-level rise (Cahoon et al., 2006; Nyman et al., 2006; Morris et al.,
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8358 2002; Rybczyk and Cahoon, 2002). Future wetland area will also be determined, in part, 

8359 by the amount of space (e.g., mud flat or tidal flat area) available for landward migration 

8360 and the rates of lateral erosion of the seaward edge of the marsh (see Chapter 4; Poulter, 

8361 2005). Wetlands will be especially vulnerable to the higher projected rates of future sea8362 level rise (e.g., greater than 70 cm by the year 2100), but some will survive a 1 meter rise 

8363 (Morris et al., 2002). Even under lower accelerated sea-level rise rates, wetlands may be 

8364 sustained only where conditions are optimal for vertical wetland development (e.g., 

8365 abundant sediment supply and low regional subsidence rate) (Rybczyk and Cahoon, 

8366 2002). 

 8367 

8368 Mud flat shorelines represent a relatively small portion of U.S. coasts, but are important 

8369 in providing the foundation for wetlands and marshes (Mitsch and Gosselink, 1986). 

8370 They are frequently associated with wetlands, and occur predominately in low-energy, 

8371 low-relief regions with high inputs of fine-grained river-born sediments and organic 

8372 materials and large tidal ranges. These shoreline types are common in western Louisiana 

8373 (i.e., Chenier Plain) and along northeastern parts of the Gulf Coast of Florida. Muddy 

8374 coasts may be drowned with sea-level rise unless sediment inputs are sufficiently large, 

8375 such as the Atchafalaya River delta region of southwestern Louisiana, and the flats are 

8376 able to be colonized by plants. 

 8377 

8378 13.2.4 Tropical Coral Reef Coasts 

8379 Tropical coral reefs, made up of living organisms very sensitive to ocean temperature and 

8380 chemistry, are found in the U.S. along the south coast of Florida; around the Hawaiian 
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8381 Islands, Puerto Rico, the Virgin Islands, and many of the U.S. territories in the Pacific 

8382 (Riegl and Dodge, 2008). In tropical environments, living coral organisms build reefs that 

8383 are important ecological resources (Smith and Buddemeier, 1992; Boesch et al., 2000). 

8384 Most corals are able to tolerate rates of sea-level rise of 10 to 20 mm per year or more 

8385 (Smith and Buddemeier, 1992; Bird, 1995; Wells, 1995; Hallock, 2005). Nonetheless, 

8386 the ability of coral reef systems to survive future sea-level rise will depend heavily on 

8387 other climate change impacts such as increase in ocean temperature and or acidity, 

8388 sediment runoff from the land, as well as episodic storm erosion (Hallock, 2005; Nicholls 

8389 et al., 2007). In addition, human caused stresses such as over-fishing or pollution can 

8390 contribute to the vulnerability of these systems to climate change (Buddemeier et al., 

8391 2004; Mimura et al., 2007). 

 8392 

8393 13.3 Potential for Future Shoreline Change 

8394 Over the next century and beyond, with an expected acceleration in sea-level rise, the 

8395 potential for coastal change will increase and coastal change is likely to be more 

8396 widespread and variable than has been observed in historic past (NRC, 1987; Brown and 

8397 McLachlan, 2002; Nicholls et al., 2007). However, it is difficult at present to 

8398 quantitatively attribute shoreline changes directly to sea-level rise (Rosenzweig et al., 

8399 2007). The potential changes include increased coastal erosion, more frequent tidal and 

8400 storm-surge flooding of low-relief areas, and wetland deterioration and losses. Many of 

8401 these changes will occur in all coastal states. These changes to the coastal zone can be 

8402 expected to have especially large impacts to developed areas (Nicholls et al., 2007). 

8403 Some portions of the U.S. coast will be subject principally to inundation from sea-level 
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8404 rise over the next century, including upper reaches of bays and estuaries (e.g., 

8405 Chesapeake and Delaware Bays, Tampa Bay, Lake Pontchartrain, San Francisco Bay), 

8406 and hardened urban shorelines. Erosion, sediment transport, and sediment deposition in 

8407 coastal environments are active processes and will drive coastal change in concert with 

8408 the combined effects of future sea-level rise and storms (Stive, 2004). 

 8409 

8410 Coastal landforms may become even more dynamic and that erosion will dominate 

8411 changes in shoreline position over the next century and beyond (Nicholls et al., 2007). 

8412 Wetlands with sufficient sediment supply and available land for inland migration may be 

8413 able to maintain elevation, keeping pace with sea-level rise, but sediment starved 

8414 wetlands and those constrained by engineering structures (e.g., seawalls, revetments) or 

8415 steep uplands are likely to deteriorate and convert to open water through vertical 

8416 accretion deficits and lateral erosion (see Chapter 4). On barrier island shores, erosion is 

8417 likely to occur on both the ocean front and the landward side of the island due to a 

8418 combination of storm activity, changes in sediment budget, more frequent tidal flooding, 

8419 and rising water levels (Nicholls et al., 2007). 

 8420 

8421 Sea-level rise is a particular concern for islands (Mimura et al., 2007). Of particular 

8422 concern are islands comprised of coral atolls (e.g., Midway Atoll), which are typically 

8423 low-lying and dependent on the health of coral reefs that fringe the atolls. Populated 

8424 islands with higher elevations (e.g., the Northern Mariana Islands) are also frequently at 

8425 risk as the infrastructure is frequently located in low-lying coastal regions along the 

8426 periphery of the islands. 
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 8427 

8428 Many coastal areas in the United States will likely experience an increased frequency and 

8429 magnitude of storm-surge flooding, greater wave heights, and more erosion due to storms 

8430 as part of the response to sea-level rise (NRC, 1987; Woodworth and Blackman, 2004; 

8431 Nicholls et al., 2007; Gutowski et al., 2008). Impacts from these storm events may 

8432 extend farther inland than those that would be affected by sea-level rise alone. Many 

8433 regions may also experience large changes to coastal systems, such as increased rates of 

8434 erosion, barrier island and dune landward migration, and potential barrier island collapse 

8435 (Nicholls et al., 2007; see also Chapters 1, 3, and 14 for discussion of geomorphic 

8436 thresholds). The potential of crossing thresholds, potentially leading to barrier and 

8437 wetland collapse, may increase with higher rates of sea-level rise. 

 8438 

8439 The use of so called “soft” coastal engineering mitigation measures, such as beach 

8440 nourishment, usually using sand dredged from offshore Holocene-age sand bodies, may 

8441 reduce the risk of storm flooding and coastal erosion temporarily (NRC, 1987, 1995b). 

8442 However, an important issue is whether or not these practices are able to be maintained 

8443 into the future to provide sustainable and economical shoreline protection in the face of 

8444 high cost, need for periodic re-nourishment, and limited sand resources of suitable quality 

8445 for nourishment for many regions of the country (NRC, 1995b; Magoon et al., 2004). 

8446 Results from offshore geologic mapping studies indicate that most continental shelf 

8447 regions of the U.S. have relatively limited Holocene-age sediment that can be deemed 

8448 available and suitable for uses such as beach nourishment (Schwab et al., 2000; Gayes et 

8449 al., 2003; Pilkey et al., 1981; Kraft, 1971). In some cases, potential sand volumes are 
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8450 reduced because of economic and environmental factors such as water depth, benthic 

8451 environmrntal concerns, and concerns that sand removal may alter sediment exchange 

8452 with the adjacent coast (Bliss et al., 2009). The result is limited volumes of high-quality 

8453 offshore sand resources readily available for beach nourishment. The issue of relying 

8454 long term on using offshore sand for beach nourishment to mitigate erosion is important 

8455 and needs to be addressed. 

 8456 

8457 More widespread implementation of regional sediment or best sediment management 

8458 practices to conserve valuable coastal sediments from offshore disposal of clean sandy 

8459 dredged spoils will enhance the long term sustainability of sandy coastal landforms 

8460 (NRC, 2007). The use of so called “hard” engineering structures (e.g., seawalls, 

8461 breakwaters) to protect property from erosion and flooding may be justified for urban 

8462 coasts, but their use on sandy shores can further exacerbate erosion over time due to 

8463 disruption of sediment transport processes. Alternatives, such as relocation landward, 

8464 strategic removal of development or limiting redevelopment following storm disasters 

8465 from highly vulnerable parts of the coast, may provide longer term sustainability of both 

8466 coastal landforms and development, especially if the higher rates of sea-level rise are 

8467 realized (NRC, 1987). An example of abandonment of an island in Chesapeake Bay due 

8468 to sea-level rise is detailed in Gibbons and Nicholls (2006). If coastal development is 

8469 relocated, those areas could be converted to marine protected areas, public open-space 

8470 lands that would serve to buffer sea-level rise effects landward and also provide 

8471 recreation benefits and wildlife habitat values (see Salm and Clark, 2000). 

 8472 
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8473 13.4 CONCLUSIONS 

8474 Global climate is changing, largely due to carbon emissions from human activities (IPCC, 

8475 2001; 2007). Sea-level rise is one of the impacts of climate change that will affect all 

8476 coastal regions of the United States over the next century and beyond (NRC, 1987; 

8477 Nicholls et al., 2007). The scientific tools and techniques for assessing the effects of 

8478 future sea-level rise on coastal systems are improving, but much remains to be done in 

8479 order to develop useful forecasts of potential effects. Chapter 14 of this Product identifies 

8480 research opportunities that, if implemented, would lead to better understanding and 

8481 prediction of sea-level rise effects that are likely to further impact the United States in the 

8482 near future. Planning for accelerating sea-level rise should include thorough evaluation of 

8483 a number of alternatives, such as cost-effective and sustainable shore protection and 

8484 strategic relocation of development within urban centers. Important decisions like these 

8485 should ideally be based on the best available science and careful consideration of long8486 term benefits for a sustainable future, and the total economic, social, and environmental 

8487 costs of various methods of shore protection, relocation, and adaptation. 

8488 
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8565 Leatherman, S.P., 2001: Social and economic costs of sea level rise. In: Sea Level Rise: 

8566 History and Consequences [Douglas, B.C., M.S. Kearney, and S.P. Leatherman 

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8568 Magoon, O.T., S.J. Williams, L.K. Lent, S.L. Douglass, B.L. Edge, J.A. Richmond, D.D 

8569 Treadwell, L.C. Ewing, and A.P. Pratt, 2004: Economic impacts of anthropogenic 

8570 activities on coastlines of the U.S., In: Coastal Engineering 2004, Proceedings of 

8571 the 29th International Conference, Lisbon, Portugal. World Scientific Publishing, 

8572 New Jersey and London, pp. 3022-3035. 

8573 Mimura, N.L., L. Nurse, R.F. McLean, J. Agard, L. Briguglio, P. Lefale, R. Payet, and 

8574 G. Sem, 2007: Small islands. In: Climate Change 2007: Impacts, Adaptation and 

8575 Vulnerability. Contribution of Working Group II to the Fourth Assessment Report 

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8577 J.P., Palutikof, P.J. van der Linden, and C.E. Hanson (eds.)]. Cambridge 

8578 University Press, Cambridge, UK, and New York, pp. 688-716. 

8579 Mitsch, W.J. and J.G. Gosselink, 1986: Wetlands. Van Nostrand, New York, 537 pp. 

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8581 Responses of coastal wetlands to rising sea level. Ecology, 83(10), 2869-2877. 

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8586 NRC (National Research Council), 1995a: Wetlands: Characteristics and Boundaries. 

8587 National Academy Press, Washington, DC, 306 pp. 

8588 NRC (National Research Council), 1995b: Beach Nourishment and Protection. National 

8589 Academy Press, Washington, DC, 334 pp. 

8590 NRC (National Research Council), 2007: Mitigating Shore Erosion Along Sheltered 

8591 Coasts. National Academies Press, Washington, DC, 174 pp. 

8592 Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. 

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8599 Nyman, J.A., R.J. Walters, R.D. Delaune, and W.H. Patrick Jr., 2006: Marsh vertical 

8600 accretion via vegetative growth. Estuarine Coastal and Shelf Science, 69(3-4), 

8601 370-380. 

8602 Oertel, G.F. and J.C. Kraft, 1994: New Jersey and Delmarva barrier islands. In: Geology 

8603 of Holocene Barrier Island Systems [Davis, R.A. (ed.)]. Springer-Verlag, New 

8604 York, pp. 207-232. 

8605 Overpeck, J.T., B.L. Otto-Bliesner, G.H. Miller, D.R. Muhs, R.B. Alley, and J.T. Keihl, 

8606 2006: Paleo-climatic evidence for the future ice-sheet instability and rapid sea 

8607 level rise. Science, 311(5768), 1747-1750. 

8608 Pilkey, O.H., B.W. Blackwekder, H.J. Knebel, and M.W. Ayers, 1981: The Georgia 

8609 Embayment continental shelf: Stratigraphy of a submergence. Geological Society 

8610 of America Bulletin, 92(1), 52-63. 

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8612 Science, 315(5810), 368-370. 

8613 Rahmstorf, S., A. Cazenave, J.A. Church, J.E. Hansen, R.F. Keeling, D.E. Parker, and 

8614 R.C.J. Somerville, 2007: Recent climate observations compared to projections. 

8615 Science, 316(5825), 709. 

8616 Reed, D.J., D. Bishara, D. Cahoon, J. Donnelly, M. Kearney, A. Kolker, L. Leonard, 

8617 R.A. Orson, and J.C. Stevenson, 2008: Site-specific scenarios for wetlands 

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8622 Protection Agency, Washington, DC, pp. 134-174.

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8639 behavior of the barrier island system between Fire Island inlet and Shinnecock 

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8643 Stive, M.J.F., 2004: How important is global warming for coastal erosion? An editorial 

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8664 
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8665 Chapter 14. A Science Strategy for Improving the 

8666 Understanding of Sea-Level Rise and its Impacts on 

8667 U.S. Coasts 

8668 

8669 Authors: E. Robert. Thieler, USGS; K. Eric Anderson, USGS; Donald R. Cahoon, 

8670 USGS; S. Jeffress Williams, USGS; Benjamin T. Gutierrez, USGS

8671 

8672 KEY FINDINGS 

8673  Understanding, predicting, and responding to the environmental and human 

8674 effects of sea-level rise requires an integrated program of research that includes 

8675 natural and social sciences. 

8676  Monitoring of modern processes and environments could be improved by 

8677 expanding the network of basic observations and observing systems, developing 

8678 time series data on environmental and landscape changes, and assembling 

8679 baseline data for the coastal zone. 

8680  The historic and geologic record of coastal change should be used to improve the 

8681 understanding of natural and human-influenced coastal systems, increase 

8682 knowledge of sea-level rise and coastal change over the past few millennia, 

8683 identify thresholds or tipping points in coastal systems, and more closely relate 

8684 past changes in climate to coastal change. 
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8685  Increases in predictive capabilities can be achieved by improving quantitative 

8686 assessment methods and integrating studies of the past and present into predictive 

8687 models. 

8688  Research on adaptation, mitigation, and avoidance measures will enable better 

8689 understanding of the societal impacts of sea-level rise. 

8690  Decision making in the coastal zone can be supported by providing easy access to 

8691 data and resources, transferring knowledge of vulnerability and risk that affect 

8692 decision making, and educating the public about consequences and alternatives. 

 8693 

8694 14.1 INTRODUCTION 

8695 Chapter 14 identifies several major themes that present opportunities to improve the 

8696 scientific understanding of future sea-level rise and its impacts on U.S. coastal regions. 

8697 Advances in scientific understanding will enable the development of higher quality and 

8698 more reliable information for planners and decision makers at all levels of government, as 

8699 well as the public. 

 8700 

8701 A number of recent studies have focused specifically on research needs in coastal areas. 

8702 Two National Research Council (NRC) studies, Science for Decision-making (NRC, 

8703 1999) and A Geospatial Framework for the Coastal Zone (NRC, 2004) contain 

8704 recommendations for science activities that can be applied to sea-level rise studies. Other 

8705 relevant NRC reports include Responding to Changes in Sea Level (NRC, 1987), Sea 

8706 Level Change (NRC, 1990b) and Abrupt Climate Change (NRC, 2002). The Marine 

8707 Board of the European Science Foundation’s Impacts of Climate Change on the European 
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8708 Marine and Coastal Environment (Philippart et al., 2007) identified numerous research 

8709 needs, many of which have application to the United States. Recent studies on global 

8710 climate change by the Pew Charitable Trusts also included the coastal zone (e.g., 

8711 Neumann et al., 2000, Panetta, 2003; Kennedy et al., 2002). Other studies by the NRC 

8712 (1990a, 1990b, 1990c, 2001, 2006a, 2007) and the Heinz Center (2000, 2002a, 2002b, 

8713 2006) have addressed issues relevant to the impacts of sea-level rise on the coastal zone. 

8714 These reports and related publications have helped guide the development of the potential 

8715 research and decision-support activities described in the following sections. 

 8716 

8717 14.2 A SCIENCE STRATEGY TO ADDRESS SEA-LEVEL RISE 

8718 An integrated scientific program of sea level studies that seeks to learn from the historic 

8719 and geologic past, and monitors ongoing physical and environmental changes, will 

8720 improve the level of knowledge and reduce the uncertainty about potential responses of 

8721 coasts, estuaries, and wetlands to sea-level rise. Outcomes of both natural and social 

8722 scientific research will support decision making and adaptive management in the coastal 

8723 zone. The main elements of a potential science strategy and their interrelationships are 

8724 shown in Figure14.1. 
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8725 

8726 Figure 14.1 Schematic flow diagram summarizing a science strategy for improvement of scientific 

8727 knowledge and decision-making capability needed to address the impacts of future sea-level rise. 

 8728 

8729 Building on and complementing ongoing efforts at federal agencies and universities, a 

8730 research and observation program could incorporate new technologies to address the 

8731 complex scientific and societal issues highlighted in this Product. These studies could 

8732 include further development of a robust monitoring program for all coastal regions, 

8733 leveraging the existing network of site observations, as well as the growing array of 

8734 coastal observing systems. Research should also include studies of the historic and recent 
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8735 geologic past to understand how coastal systems evolved in response to past changes in 

8736 sea level. The availability of higher resolution data collected over appropriate time spans, 

8737 coupled with conceptual and numerical models of coastal evolution, will provide the 

8738 basis for improved quantitative assessments and the development of predictive models 

8739 useful for decision making. Providing ready access to interpretations from scientific 

8740 research—as well as the underlying data—by means of publications, data portals, and 

8741 decision-support systems will allow coastal managers to evaluate alternative strategies for 

8742 mitigation, develop appropriate responses to sea-level rise, and practice adaptive 

8743 management as new information becomes available. 

 8744 

8745 14.2.1 Learn From the Historic and Recent Geologic Past 

8746 Studies of the recent geologic and historical record of sea-level rise and coastal and 

8747 environmental change are needed to improve the state of knowledge of the key physical 

8748 and biological processes involved in coastal change. As described throughout this 

8749 Product, particularly in Chapters 1 through 5, significant knowledge gaps exist that 

8750 inhibit useful prediction of future changes. The following research activities will help 

8751 refine our knowledge of past changes and their causes. 

8752 

8753 Improve understanding of natural and human-influenced coastal systems 

8754 Significant opportunities exist to improve predictions of coastal response to sea-level rise. 

8755 For example, scientists’ understanding of the processes controlling rates of sediment flux 

8756 in both natural and especially in human-modified coastal systems is still evolving. This is 

8757 particularly true at the regional (littoral cell) scale, which is often the same scale at which 
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8758 management decisions are made. As described in Chapters 3 and 6, the human impact on 

8759 coastal processes at management scales is not well understood. Shoreline engineering 

8760 such as bulkheads, revetments, seawalls, groins, jetties, and beach nourishment can 

8761 fundamentally alter the way a coastal system behaves by changing the transport, storage, 

8762 and dispersal of sediment. The same is true of development and infrastructure on mobile 

8763 landforms such as the barrier islands that comprise much of the mid-Atlantic coast. 

 8764 

8765 Develop better information on the effects of sea-level rise over the past 5,000 years 

8766 The foundation of modern coastal barrier island and wetland systems has evolved over 

8767 the past 5,000 years as the rate of sea-level rise slowed significantly (see Chapters 1, 3, 

8768 and 4). More detailed investigation of coastal sedimentary deposits is needed to 

8769 understand the rates and patterns of change during this part of the recent geologic past. 

8770 Advances in methods to obtain samples of the geologic record, along with improvements 

8771 in analytical laboratory techniques since the early 1990s, have significantly increased the 

8772 resolution of the centennial-to-millennial scale record of sea-level rise and coastal 

8773 environmental change (e.g., Gehrels, 1994; Gehrels et al., 1996; van de Plassche et al.,

8774 1998; Donnelly et al., 2001; Horton et al., 2006) and provide a basis for future work. 

8775 Archaeological records of past sea-level change also exist in many locales, and provide 

8776 additional opportunities to understand coastal change and impacts on human activity. 

8777 

8778 Understand thresholds in coastal systems that, if crossed, could lead to rapid changes to 

8779 coastal and wetland systems 
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8780 Several aspects of climate change studies, such as atmosphere-ocean interactions, 

8781 vegetation change, sea ice extent, and glacier and ice cap responses to temperature and 

8782 precipitation, involve understanding the potential for abrupt climate change or “climate 

8783 surprises” (NRC, 2002; Meehl et al., 2007). Coastal systems may also respond abruptly 

8784 to changes in sea-level rise or other physical and biological processes (see Chapter 3, Box 

8785 3.1). Coastal regions that may respond rapidly to even modest changes in future external 

8786 forcing need to be identified, as well as the important variables driving the changes. For 

8787 example, limited sediment supply, and/or permanent sand removal from the barrier 

8788 system, in combination with an acceleration in the rate of sea-level rise, could result in 

8789 the development of an unstable state for some barrier island systems (i.e., a behavioral 

8790 threshold or tipping point, as described in Chapters 1 and 3). Coastal responses could 

8791 result in landward migration or roll-over, or barrier segmentation. Understanding and 

8792 communicating the potential for such dramatic changes in the form and rate of coastal 

8793 change will be crucial for the development of adaptation, mitigation, and other strategies 

8794 for addressing sea-level rise. 

 8795 

8796 The future evolution of low-elevation, narrow barriers will likely depend in part on the 

8797 ability of salt marshes in back-barrier lagoons and estuaries to keep pace with sea-level 

8798 rise (FitzGerald et al., 2004, 2008; Reed et al., 2008). It has been suggested that a 

8799 reduction of salt marsh in back-barrier regions could change the hydrodynamics of back8800 barrier systems, altering local sediment budgets and leading to a reduction in sandy 

8801 materials available to sustain barrier systems (FitzGerald et al., 2004, 2008). 

8802 
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8803 Relate climate proxies to coastal change

8804 Links between paleoclimate proxies (e.g., atmospheric gases in ice cores, isotopic 

8805 composition of marine microfossils, tree rings), sea-level rise, and coastal change should 

8806 be explored. Previous periods of high sea level, such as those during the last several 

8807 interglacial periods, provide tangible evidence of higher-than-present sea levels that are 

8808 broadly illustrative of the potential for future shoreline changes. For example, high stands 

8809 of sea level approximately 420,000 and 125,000 years ago left distinct shoreline and 

8810 other coastal features on the U.S. Atlantic coastal plain (Colquhoun et al., 1991; Baldwin 

8811 et al., 2006). While the sedimentary record of these high stands is fragmentary, 

8812 opportunities exist to relate past shoreline positions with climate proxies to improve the 

8813 state of knowledge of the relationships between the atmosphere, sea level, and coastal 

8814 evolution. Future studies may also provide insight into how coastal systems respond to 

8815 prolonged periods of high sea level and rapid sea-level fluctuations during a high stand. 

8816 Examples of both exist in the geologic record and have potential application to 

8817 understanding and forecasting future coastal evolution. 

 8818 

8819 14.2.2 Monitor Modern Coastal Conditions 

8820 The status and trends of sea-level change, and changes in the coastal environment, are 

8821 monitored through a network of observation sites, as well as through coastal and ocean 

8822 observing systems. Monitoring of modern processes and environments could be 

8823 improved by expanding the network of basic observations, as well as the continued 

8824 development of coastal and ocean observing systems. There are numerous ongoing 
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8825 efforts that could be leveraged to contribute to understanding patterns of sea-level rise 

8826 over space and time and the response of coastal environments. 

 8827 

8828 Expand the network of basic observations

8829 An improvement in the coverage and quality of the U.S. network of basic sea-level 

8830 observations could better inform researchers about the rate of sea-level rise in various 

8831 geographic areas. Tide gauges are a primary source of information for sea-level rise data 

8832 at a wide range of time scales, from minutes to centuries. These data contribute to a 

8833 multitude of studies on local to global sea-level trends. Tide gauge data from the United 

8834 States include some of the longest such datasets in the world and have been especially 

8835 valuable for monitoring long-term trends. A denser network of high-resolution gauges 

8836 would more rigorously assess regional trends and effects. The addition of tide gauges 

8837 along the open ocean coast of the United States would be valuable in some regions. These 

8838 data can be used in concert with satellite altimetry observations. 

 8839 

8840 Tide-gauge observations also provide records of terrestrial elevation change that 

8841 contributes to relative sea-level change, and can be coupled with field- or model-based 

8842 measurements or estimates of land elevation changes. Existing and new gauges should be 

8843 co-located with continuously operating Global Positioning System (GPS) reference 

8844 stations (CORS) or surveyed periodically using GPS and other Global Navigation 

8845 Satellite System technology. This will enable the coupling of the geodetic (earth-based) 

8846 reference frame and the oceanographic reference frame at the land-sea interface. Long 

8847 time series from CORS can provide precise local vertical land movement information in 
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8848 the ellipsoidal frame (e.g., Snay et al., 2007; Woppelmann et al., 2007). Through a 

8849 combined effort of monitoring ellipsoid heights and the geoid, as well as through gravity 

8850 field monitoring, changes to coastal elevations can be adequately tracked. 

 8851 

8852 Develop and maintain coastal observing systems 

8853 Observing systems have become an important tool for examining environmental change. 

8854 They can be place-based (e.g., specific estuaries or ocean locations) or consist of regional 

8855 aggregations of data and scientific resources (e.g., the developing network of coastal 

8856 observing systems) that cover an entire region. Oceanographic observations also need to 

8857 be integrated with observations of the physical environment, as well as habitats and 

8858 biological processes. 

 8859 

8860 An example of place-based observing systems is the National Estuarine Research 

8861 Reserve System (NERRS: <http://www.nerrs.noaa.gov>), a network of 27 reserves for 

8862 long-term research, monitoring, education, and resource stewardship. Targeted 

8863 experiments in such settings can potentially elucidate impacts of sea-level rise on the 

8864 physical environment, such as shoreline change or impacts to groundwater systems, or on 

8865 biological processes, such as species changes or ecosystem impacts. Important 

8866 contributions can also be made by the Long Term Ecological Research sites 

8867 (<http://www.lternet.edu>) such as the Virginia Coast Reserve in the mid-Atlantic area 

8868 (part of the focus of this Product). The sites combine long-term data with current research 

8869 to examine ecosystem change over time. Integration of these ecological monitoring 
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8870 networks with the geodetic and tide gauge networks mentioned previously would also be 

8871 an important enhancement. 

 8872 

8873 The Integrated Ocean Observing System (IOOS) (<http://www.ocean.us>) will bring 

8874 together observing systems and data collection efforts to understand and predict changes 

8875 in the marine environment. Many of these efforts can contribute to understanding 

8876 changes in sea-level rise over space and time. These observing systems incorporate a 

8877 wide range of data types and sources, and provide an integrated approach to ocean 

8878 studies. Such an approach should enable sea-level rise-induced changes to be 

8879 distinguished from the diverse processes that drive changes in the coastal and marine 

8880 environment. 

 8881 

8882 A new initiative began in 2005 with a worldwide effort to build a Global Earth 

8883 Observation System of Systems (GEOSS) (<http://www.earthobservations.org>) over the 

8884 next 10 years. GEOSS builds upon existing national, regional, and international systems 

8885 to provide comprehensive, coordinated Earth observations from thousands of instruments 

8886 worldwide, which have broad application to sea-level rise studies. 

 8887 

8888 Develop time series data to monitor environmental and landscape changes 

8889 Observations of sea level using satellite altimetry (e.g., TOPEX/Poseidon and Jason-1) 

8890 have provided new and important insights into the patterns of sea-level change across 

8891 space and time. Such observations have allowed scientists to examine sea-level trends 

8892 and compare them to the instrumental record (Church et al., 2001, 2004), as well as 
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8893 predictions made by previous climate change assessments (Rahmstorf, 2007). The 

8894 satellite data provide spatial coverage not available with ground-based methods such as 

8895 tide gauges, and provide an efficient means for making global observations. Plans for 

8896 future research could include a robust satellite observation program to ensure 

8897 comprehensive coverage. 

 8898 

8899 Studies of environmental and landscape change can also be expanded across larger spatial 

8900 scales and longer time scales. Examples include systematic mapping of shoreline changes 

8901 and coastal barriers and dunes around the United States (e.g., Morton and Miller, 2005), 

8902 and other national mapping efforts to document land-use and land-cover changes (e.g., 

8903 the NOAA Coastal Change Analysis Program: 

8904 <http://www.csc.noaa.gov/crs/lca/ccap.html>). It is also important to undertake a 

8905 rigorous study of land movements beyond the point scale of tide gauges and GPS 

8906 networks. For example, the application of an emerging technology—Interferometric 

8907 Synthetic Aperture Radar (InSAR)—enables the development of spatially-detailed maps 

8908 of land-surface displacement over broad areas (Brooks et al., 2007). 

 8909 

8910 Determining wetland sustainability to current and future sea-level rise requires a broader 

8911 foundation of observations if they are to be applied with high confidence at regional and 

8912 national scales. In addition, there is a significant knowledge gap concerning the viability 

8913 or sustainability of human-impacted and restored wetlands in a time of accelerating sea8914 level rise. The maintenance of a network of sites that utilize surface elevation tables and 

8915 soil marker horizons for measuring marsh accretion or loss will be essential in 
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8916 understanding the impacts on areas of critical wetland habitat. The addition of sites to the 

8917 network would aid in delineating regional variations (Cahoon et al., 2006). Similar long8918 term studies for coastal erosion, habitat change, and water quality are also essential. 

 8919 

8920 Coastal process studies require data to be collected over a long period of time in order to 

8921 evaluate changes in beach and barrier profiles and track morphological changes over a 

8922 time interval where there has been a significant rise in sea level. These data will also 

8923 reflect the effects of storms and the sediment budget that frequently make it difficult to 

8924 extract the coastal response to sea-level change. For example, routine lidar mapping 

8925 updates to track morphological changes and changes in barrier island area above mean 

8926 high water (e.g., Morton and Sallenger, 2003), as well as dune degradation and recovery, 

8927 and shore-face profile and near-shore bathymetric evolution may provide insight into 

8928 how to distinguish various time and space scales of coastal change and their relationship 

8929 to sea-level rise. 

 8930 

8931 Time series observations can also be distributed across the landscape and need not be tied 

8932 to specific observing systems or data networks. They do, however, need a means to have 

8933 their data assimilated into a larger context. For example, development of new remote 

8934 sensing and in-situ technologies and techniques would help fill critical data gaps at the 

8935 land-water interface. 

 8936 

8937 Assemble and update baseline data for the coastal zone
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8938 Baseline data for the coastal zone, including elevation, bathymetry, shoreline position, 

8939 and geologic composition of the coast, as well as biologic and ecologic parameters such 

8940 as vegetation and species distribution, and ecosystem and habitat boundaries, should be 

8941 collected at high spatial resolution. As described in Chapter 2, existing 30-m (100-ft) 

8942 digital elevation models are generally inadequate for meaningful mapping and analyses in 

8943 the coastal zone. The use of lidar data, with much better horizontal and vertical accuracy, 

8944 is essential. While some of these mapping data are being collected now, there are 

8945 substantial areas around the United States that would benefit from higher quality data. 

8946 More accurate bathymetric data, especially in the near-shore, is needed for site-specific 

8947 analyses and to develop a complete topographic-bathymetric model of the coastal zone to 

8948 be able to predict with greater confidence wave and current actions, inundation, coastal 

8949 erosion, sediment transport, and storm effects. 

 8950 

8951 To improve confidence in model predictions of wetland vulnerability to sea-level rise, 

8952 more information is needed on: (1) maximum accretion rates (i.e., thresholds) regionally 

8953 and among vegetative communities; (2) wetland dynamics across larger landscape scales; 

8954 (3) the interaction of feedback controls on flooding with other accretion drivers (e.g., 

8955 nutrient supply and soil organic matter accumulation); (4) fine-grained, cohesive 

8956 sediment supplies; and (5) changing land use in the watershed (i.e., altered river flows 

8957 and accommodation space for landward migration of wetlands). In addition, population 

8958 data on different species in near shore areas are needed to accurately judge the effects of 

8959 habitat loss or transformation. More extensive and detailed areas of habitat mapping will 

8960 enable preservation efforts to be focused on the most important areas. 
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8961 

8962 14.2.3 Predict Future Coastal Conditions

8963 Studies of the past history of sea-level rise and coastal response, combined with extensive 

8964 monitoring of present conditions, will enable more robust predictions of future sea-level 

8965 rise impacts. Substantial opportunities exist to improve methods of coastal impact 

8966 assessment and prediction of future changes. 

 8967 

8968 Develop quantitative assessment methods that identify high-priority areas needing useful 

8969 predictions 

8970 Assessment methods are needed to identify both geographic and topical areas most in 

8971 need of useful predictions of sea-level rise impacts. For example, an assessment 

8972 technique for objectively assessing potential effects of sea-level rise on open coasts, the 

8973 Coastal Vulnerability Index (CVI), has been employed in the United States and elsewhere 

8974 (e.g., Gornitz et al., 1997; Shaw et al., 1998; Thieler and Hammar-Klose, 1999, 2000a, 

8975 2000b). Although the CVI is a fairly simplistic technique, it can provide useful insights 

8976 and has found application as a coastal planning and management tool (Thieler et al., 

8977 2002). Such assessments have also been integrated with socioeconomic vulnerability 

8978 criteria to yield a more integrative measure of community vulnerability (Boruff et al., 

8979 2005). 

 8980 

8981 Projecting long-term wetland sustainability to future sea-level rise requires data on 

8982 accretionary events over sufficiently long time scales that include the return periods of 

8983 major storms, floods, and droughts, as well as information on the effects of wetland 
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8984 elevation feedback on inundation and sedimentation processes that affect wetland vertical 

8985 accretion. Numerical models can be applied to predict wetland sustainability at the local 

8986 scale, but there is not sufficient data to populate these models at the regional or national 

8987 scale (see Chapter 4). Given this data constraint, current numerical modeling approaches 

8988 will need to improve or adapt such that they can be applied at broader spatial scales with 

8989 more confidence. 

 8990 

8991 Integrate studies of past and present coastal behavior into predictive models 

8992 Existing shoreline-change prediction techniques are typically based on assumptions that 

8993 are either difficult to validate or too simplistic to be reliable for many real-world 

8994 applications (see Appendix 2). As a result, the usefulness of these modeling approaches 

8995 has been debated in the coastal science community (see Chapter 3). Newer models that 

8996 include better representations of real-world settings and processes (e.g., Cowell et al.,

8997 1992; Stolper et al., 2005; Pietrafesa et al., 2007) have shown promise in predicting 

8998 coastal evolution. Informing these models with improved data on past coastal changes 

8999 should result in better predictions of future changes. 

 9000 

9001 The process of marine transgression across the continental shelf has left an incomplete 

9002 record of sea-level and environmental change. An improved understanding of the rate and 

9003 timing of coastal evolution will need to draw on this incomplete record, however, in order 

9004 to improve models of coastal change. Using a range of techniques, such as high9005 resolution seafloor and geologic framework mapping coupled with geochronologic and 

9006 paleoenvironmental studies, the record of coastal evolution during the Pleistocene (1.8 
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9007 million to 11,500 years ago) and the Holocene (the last 11,500 years) can be explored to 

9008 identify the position and timing of former shorelines and coastal environments. 

9009 

9010 14.2.4 Improve Understanding of Societal Impacts 

9011 Research in the social sciences will be critical to understanding the potential effects on 

9012 society and social systems resulting from sea-level rise. 

 9013 

9014 Increase research on adaptation, mitigation, and avoidance measures 

9015 This Product describes a wide variety of potential impacts of sea-level rise, including the 

9016 effects on the physical environment, biological systems, and coastal development and 

9017 infrastructure. While the ability to predict future changes is currently inadequate for 

9018 many decisions, adaptation, mitigation, and avoidance strategies must evolve as scientific 

9019 knowledge and predictive ability increase. For example, expanded research and 

9020 assessments of the economic and environmental costs of present and future actions are 

9021 needed to allow a more complete analysis of the tradeoffs involved in sea-level rise 

9022 decision making. In addition, opportunities to engage stakeholders such as federal 

9023 agencies, states, counties, towns, non-government organizations, and private landowners 

9024 in the design and implementation of sea-level rise impact and response planning should 

9025 be created. 

 9026 

9027 Develop multi-disciplinary groups that integrate natural and social sciences 

9028 Interdisciplinary research that combines natural and social sciences will be crucial to 

9029 understanding the interplay of the physical, environmental, and societal impacts of sea-
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9030 level rise. Development of programs that facilitate such collaborations should be 

9031 encouraged. 

 9032 

9033 Expand institutional capacity and overcome barriers 

9034 Substantial opportunities exist to expand and improve upon the ability of institutions to 

9035 respond to sea-level rise (see Chapter 10, 11, and 12). Research is needed to define the 

9036 capacity needed for decision making, as well as the methods that can be best employed 

9037 (e.g., command and control, economic incentive) to achieve management goals. 

9038 Overcoming the institutional barriers described in Chapter 12 is also necessary for 

9039 effective response to the management challenges presented by sea-level rise. 

9040 

9041 14.2.5 Develop Coastal Decision Support Systems for Planning and Policy Making 

9042 For coastal zone managers in all levels of government, there is a pressing need for more 

9043 scientific information, a reduction in the ranges of uncertainty for processes and impacts, 

9044 and new methods for assessing options and alternatives for management strategies. 

9045 Geospatial information on a wide range of themes such as topography, bathymetry, land 

9046 cover, population, and infrastructure, that is maintained on regular cycle will be a key 

9047 component of planning for mitigation and adaptation strategies. For example, specialized 

9048 themes of data such as hydric (abundantly moist) soils may be critical to understanding 

9049 the potential for wetland survival in specific areas. Developing and maintaining high9050 resolution maps that incorporate changes in hazard type and distribution, coastal 

9051 development, and societal risk will be critical. Regularly conducting vulnerability 

9052 assessments and reviews will be necessary in order to adapt to changing conditions. 
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 9053 

9054 Provide easy access to data and information resources for federal, state, local, academic, 

9055 and public users 

9056 Understanding and acting on scientific information about sea-level rise and its impacts 

9057 will depend upon common, consistent, shared databases for integrating knowledge and 

9058 providing a basis for decision making. Thematic data and other value-added products 

9059 should adhere to predetermined standards to make them universally accessible and 

9060 transferable through internet portals. All data should be accompanied by appropriate 

9061 metadata describing its method of production, extent, quality, spatial reference, 

9062 limitations of use, and other characteristics (NRC, 2004). 

 9063 

9064 An opportunity exists to develop a national effort to develop and apply data integration 

9065 tools to combine terrestrial and marine data into a seamless geospatial framework. This 

9066 would involve the collection of real-time tide data and the development of more 

9067 sophisticated hydrodynamic models for the entire U.S. coastline, as well as the 

9068 establishment of protocols and tools for merging bathymetric and topographic datasets 

9069 (NRC, 2004). Modern and updated digital flood insurance rate maps (DFIRM) that 

9070 incorporate future sea-level rise are needed in the coastal zone (see Chapter 9). 

 9071 

9072 Transfer scientific knowledge to studies of vulnerability, risk, and societal impacts 

9073 In addition to basic scientific research and environmental monitoring, a significant need 

9074 exists to integrate the results of these efforts into comprehensive vulnerability and risk 

9075 assessments. Tools are needed for mapping, modeling, and communicating risk to help 
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9076 public agencies and communities understand and reduce their vulnerability to, and risk 

9077 of, sea-level rise hazards. Social science research activities are also needed that examine 

9078 societal consequences and economic impacts of sea-level rise, as well as identify 

9079 institutional frameworks needed to adapt to changes in the coastal zone. For example, 

9080 analyses of the economic costs of armoring shores at risk of erosion and the expected 

9081 lifespan of such efforts will be required, as will studies on the durability of armored 

9082 shorefronts under different sea-level rise scenarios. The physical and biological 

9083 consequences of armoring shores will need to be quantified and the tradeoffs 

9084 communicated. Effective planning for sea-level rise will also require integrated economic 

9085 assessments on the impact to fisheries, tourism, and commerce. 

 9086 

9087 Applied research in the development of coastal flooding models for the subsequent study 

9088 of ecosystem response to sea-level rise is underway in coastal states such as North 

9089 Carolina (Feyen et al., 2006). There is also a need for focused study on the ecological 

9090 impacts of sea-level rise and in how the transfer of this knowledge can be made to coastal 

9091 managers for decision-making. 

 9092 

9093 Develop decision support systems 

9094 County and state planners need tools to analyze vulnerabilities, explore the implications 

9095 of alternative response measures, assess the costs and benefits of options, and provide 

9096 decision-making support. These might take the form of guidelines, checklists, or software 

9097 tools. In addition, there is a need to examine issues in a landscape or ecosystem context 

9098 rather than only administrative boundaries. 
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 9099 

9100 In addition to new and maintained data, models, and research, detailed site studies are 

9101 needed to assess potential impacts on a site-specific basis and provide information that 

9102 allows informed decision making. Appropriate methodologies need to be developed and 

9103 made available. These will have to look at a full range of possible impacts including 

9104 aquifer loss by saltwater intrusion, wetland loss, coastal erosion, and infrastructure 

9105 implications, as well as the impact of adaptation measures themselves. Alternative 

9106 strategies of adaptive management will be required. Each locality may need a slightly 

9107 different set of responses to provide a balanced policy of preserving ecosystems, 

9108 protecting critical infrastructure, and adjusting to property loss or protection. Providing a 

9109 science-based set of decision support tools will provide a sound basis for making these 

9110 important decisions. 

 9111 

9112 Educate the public on consequences and alternatives 

9113 Relative to other natural hazards such as earthquakes, volcanic eruptions, and severe 

9114 weather (e.g., hurricanes, tornadoes) that typically occur in minutes to days, sea-level rise 

9115 has a long time horizon over which effects become clear. Thus, it is often difficult to 

9116 communicate the consequences of this sometimes slow process that occurs over many 

9117 years. The impacts of sea-level rise, however, are already being felt across the United 

9118 States (see Chapter 13). Public education will be crucial for adapting to physical, 

9119 environmental, economic, and social changes resulting from sea-level rise. Research 

9120 activities that result in effective means to conduct public education and outreach 

9121 concerning sea-level rise consequence and alternatives should be encouraged.

9122 
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9123 CHAPTER 14 REFERENCES

9124 * Indicates non-peer reviewed literature; available upon request

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9126 Driscoll, J.F. Denny, and W.C. Schwab, 2006: Migration of the Pee Dee River 

9127 system inferred from ancestral paleochannels underlying the South Carolina 

9128 Grand Strand and Long Bay inner shelf. Geological Society of America Bulletin, 

9129 118(5/6), 533-549. 

9130 Boruff, B.J., C. Emrich, and S.L. Cutter, 2005: Erosion hazard vulnerability of US 

9131 coastal counties. Journal of Coastal Research, 21(5), 932-942. 

9132 Brooks, B.A., M.A. Merrifield, J. Foster, C.L. Werner, F. Gomez, M. Bevis, and S. Gill, 

9133 2007: Space geodetic determination of spatial variability in relative sea level 

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9136 Cahoon, D.R., P.F. Hensel, T. Spencer, D.J. Reed, K.L., McKee, and N. Saintilan, 2006: 

9137 Coastal wetland vulnerability to relative sea-level rise: wetland elevation trends 

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9141 Church, J.A., J.M. Gregory, P. Huybrechts, M. Kuhn, K. Lambeck, M.T. Nhuan, D. Qin, 

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9145 Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. 

9146 Johnson (eds.)]. Cambridge University Press, Cambridge UK, and New York, pp. 

9147 639-693. 

9148 Church, J.A., N.J. White, R. Coleman, K. Lambeck, and J.X. Mitrovica, 2004: Estimates 

9149 of the regional distribution of sea-level rise over the 1950-2000 period. Journal of 

9150 Climate, 17(13), 2609-2625. 
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9151 Colquhoun, D.J., G.H. Johnson, P.C. Peebles, P.F. Huddlestun, and T. Scott, 1991: 

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9155 Cowell, P.J., P.S. Roy, and R.A. Jones, 1992: Shoreface translation model: computer 

9156 simulation of coastal-sand-body response to sea-level rise. Mathematics and 

9157 Computers in Simulation, 33(5-6), 603-608. 

9158 Donnelly, J.P., S.S. Bryant, J. Butler, J. Dowling, L. Fan, N. Hausmann, P. Newby, B. 

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9160 record of intense hurricane landfalls in southern New England. Geological Society 

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9164 flooding model to study sea-level rise in North Carolina. In: Proceedings of the 

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9175 and plant zones on the coast of Maine, U.S.A. Journal of Coastal Research, 

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9177 Gehrels, W.R., D.F. Belknap, and J.T. Kelley, 1996: Integrated high-precision analyses 

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9179 Geological Society of America Bulletin, 108(9), 1073-1088. 

9180 * Gornitz, V. T.W. Beaty, and R.C. Daniels, 1997: A Coastal Hazards Database for the 

9181 U.S. West Coast. ORNL/CDIAC-81, NDP-043C. Oak Ridge National Laboratory, 

9182 Oak Ridge, TN, 162 pp. <http://cdiac.ornl.gov/ndps/ndp043c.html> 

9183 * Heinz Center, 2000: Evaluation of Erosion Hazards. The H. John Heinz III Center for 

9184 Science, Economics, and the Environment, Washington, DC, 203 pp. 

9185 * Heinz Center, 2002a: Human Links to Coastal Disasters. The H. John Heinz III Center 

9186 for Science, Economics, and the Environment, Washington, DC, 139 pp. 

9187 * Heinz Center, 2002b: The State of the Nation’s Ecosystems: Measuring the Lands, 

9188 Waters, and Living Resources of the United States. Cambridge University Press, 

9189 New York, 270 pp. 

9190 * Heinz Center, 2006: Filling the Gap--Priority Data Needs and Key Management 

9191 Challenges for National Reporting on Ecosystem Condition. The H. John Heinz 

9192 III Center for Science, Economics, and the Environment, Washington, DC, 110 

9193 pp. 

9194 Horton, B.P., R. Corbett, S.J. Culver, R.J. Edwards, and C. Hillier, 2006: Modern salt 

9195 marsh diatom distributions of the Outer Banks, North Carolina, and the 

9196 development of a transfer function for high resolution reconstructions of sea level. 

9197 Estuarine, Coastal, and Shelf Science, 69(3-4), 381-394. 

9198 * Kennedy, V.S., R.R. Twilley, J.A. Kleypas, J.H. Cowan, and S.R. Hare, 2002: Coastal 

9199 and Marine Ecosystems & Global Climate Change: Potential Effects on U.S. 

9200 Resources. Pew Center on Global Climate Change, Arlington, VA, 52 pp. 

9201 Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. 

9202 Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. 

9203 Weaver, and Z.-C. Zhao, 2007: Global climate projections. In: Climate Change 
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9205 Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, 

9206 S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. 

9207 Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, pp. 

9208 747-845. 

9209 Morton, R.A. and T.L. Miller, 2005: National Assessment of Shoreline Change: Part 2, 

9210 Historical Shoreline Changes and Associated Coastal Land Loss Along the U.S. 

9211 Southeast Atlantic Coast. U.S. Geological Survey open-file report 2005-1401, 

9212 U.S. Geological Survey, [St. Petersburg, FL], 35 pp. 

9213 <http://pubs.usgs.gov/of/2005/1401> 

9214 Morton, R.A. and A.H. Sallenger Jr., 2003: Morphological impacts of extreme storms on 

9215 sandy beaches and barriers. Journal of Coastal Research, 19(3), 560-573. 

9216 * Neumann, J.E., G. Yohe, R. Nicholls, and M. Manion, 2000: Sea-level Rise and Global 

9217 Climate Change: A Review of Impacts to U.S. Coasts. Pew Center on Global 

9218 Climate Change, Arlington, VA, 38 pp. <http://www.pewclimate.org/global9219 warming-in-depth/all_reports/sea_level_rise> 

9220 NRC (National Research Council), 1987: Responding to Changes in Sea Level: 

9221 Engineering Implications. National Academy Press, Washington, DC, 148 pp. 

9222 NRC (National Research Council), 1990a: Managing Coastal Erosion. National 

9223 Academy Press, Washington, DC, 182 pp. 

9224 NRC (National Research Council), 1990b: Sea Level Change. National Academy Press, 

9225 Washington, DC, 256 pp. 

9226 NRC (National Research Council), 1990c: Spatial Data Needs: The Future of the 

9227 National Mapping Program. National Academy Press, Washington, DC, 78 pp. 

9228 NRC (National Research Council), 1999: Science for Decisionmaking: Coastal and 

9229 Marine Geology at the U.S. Geological Survey. National Academy Press, 

9230 Washington, DC, 113 pp. 
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9231 NRC (National Research Council), 2001: Sea Level Rise and Coastal Disasters: 

9232 Summary of a Forum. National Academies Press, Washington, DC, 24 pp. 

9233 NRC (National Research Council), 2002: Abrupt Climate Change: Inevitable Surprises. 

9234 National Academy Press, Washington, DC, 230 pp. 

9235 NRC (National Research Council), 2004: A Geospatial Framework for the Coastal Zone: 

9236 National Needs for Coastal Mapping and Charting. National Academies Press, 

9237 Washington, DC, 149 pp. 

9238 NRC (National Research Council), 2006: Beyond Mapping: Meeting National Needs 

9239 Through Enhanced Geographic Information Science. National Academies Press, 

9240 Washington, DC, 100 pp. 

9241 NRC (National Research Council), 2007: Mitigating Shore Erosion on Sheltered Coasts.

9242 National Academies Press, Washington, DC, 174 pp. 

9243 * Panetta, L.E., 2003: America’s Living Oceans: Charting a Course for Sea Change: A 

9244 Report to the Nation: Recommendations for a New Ocean Policy. Pew Oceans 

9245 Commission, Arlington, VA, 145 pp. 

9246 <http://www.pewtrusts.org/pdf/env_pew_oceans_final_report.pdf> 

9247 Philippart, C.J.M., R. Anadón, R. Danovaro, J.W. Dippner, K.F. Drinkwater, S.J. 

9248 Hawkins, G. O’Sullivan, T. Oguz, and P.C. Reid, 2007: Impacts of Climate 

9249 Change on the European Marine and Coastal Environment. Marine Board 

9250 position paper 9, European Science Foundation, Strasbourg, France, 84 pp. 

9251 <http://www.sesame-ip.eu/doc/MB_Climate_Change_VLIZ_05031.pdf> 

9252 Pietrafesa, L.J., K. Kelleher, T. Karl, M. Davidson, M. Peng, S. Bao, D. Dickey, L. Xie, 

9253 H. Liu, and M. Xia, 2007: A new architecture for coastal inundation and flood 

9254 warning prediction. Marine Technology Society Journal, 40(4), 71-77. 

9255 Rahmstorf, S., 2007: A semi-empirical approach to projecting future sea-level rise. 

9256 Science, 315(5810), 368-370. 
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9257 Reed, D.J., D. Bishara, D. Cahoon, J. Donnelly, M. Kearney, A. Kolker, L. Leonard, 

9258 R.A. Orson, and J.C. Stevenson, 2008: Site-specific scenarios for wetlands 

9259 accretion as sea level rises in the mid-Atlantic region. Section 2.1 in: Background 

9260 Documents Supporting Climate Change Science Program Synthesis and 

9261 Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise

9262 [Titus, J.G. and E.M. Strange (eds.)]. EPA 430R07004. U.S. Environmental 

9263 Protection Agency, Washington, DC, pp. 134-174. 

9264 <http://epa.gov/climatechange/effects/coastal/background.html>

9265 Shaw, J., R.B. Taylor, S. Solomon, H.A. Christian, and D.L. Forbes, 1998: Potential 

9266 impacts of global sea-level rise on Canadian coasts. The Canadian Geographer, 

9267 42(4), 365-379. 

9268 Snay, R., M. Cline, W. Dillinger, R. Foote, S. Hilla, W. Kass, J. Ray, J. Rohde, G. Sella, 

9269 and T. Soler, 2007: Using global positioning system-derived crustal velocities to 

9270 estimate rates of absolute sea level change form North American ride gauge 

9271 records. Journal of Geophysical Research, 112, B04409, 

9272 doi:10.1029/2006JB004606. 

9273 Stolper, D., J.H. List, and E.R. Thieler, 2005: Simulating the evolution of coastal 

9274 morphology and stratigraphy with a new morphological-behavior model 

9275 (GEOMBEST). Marine Geology, 218(1-4), 17-36. 

9276 Thieler, E.R. and E.S. Hammar-Klose, 1999: National Assessment of Coastal 

9277 Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Atlantic Coast. 

9278 U.S. Geological Survey open-file report 99-593. U.S. Geological Survey, Reston, 

9279 VA, 1 sheet. <http://pubs.usgs.gov/of/of99-593/> 

9280 Thieler, E.R. and E.S. Hammar-Klose, 2000a: National Assessment of Coastal 

9281 Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Pacific Coast. 

9282 U.S. Geological Survey open-file report 00-178. U.S. Geological Survey, Reston, 

9283 VA, 1 sheet. <http://pubs.usgs.gov/of/2000/of00-178/> 
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9284 Thieler, E.R. and E.S. Hammar-Klose, 2000b: National Assessment of Coastal 

9285 Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico 

9286 Coast. U.S. Geological Survey open-file report 00-179. U.S. Geological Survey, 

9287 Reston, VA, 1 sheet. <http://pubs.usgs.gov/of/2000/of00-179/> 

9288 Thieler, E.R., S.J. Williams, and R. Beavers, 2002: Vulnerability of U.S. National Parks 

9289 to Sea-Level Rise and Coastal Change. U.S. Geological Survey fact sheet FS 095-

9290 02. [U.S. Geological Survey, Reston, VA], 2 pp. <http://pubs.usgs.gov/fs/fs095-

9291 02/> 

9292 van de Plassche, O., K. van der Borg, and A.F.M. de Jong, 1998: Sea level-climate 

9293 correlation during the past 1400 years. Geology, 26(4), 319-322. 

9294 Woppelmann, G., B.M. Miguez, M.-N. Bouin, and Z. Altamimi, 2007: Geocentric sea9295 level trend estimates from GPS analyses at relevant tide gauges world wide, 

9296 Global and Planetary Change, 57(3-4), 396-406. 

9297 
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9298 Appendix 1. State and Local Information on Vulnerable 

9299 Species and Coastal Policies in the Mid-Atlantic 

9300 

9301 

9302 OVERVIEW

9303 Appendix 1 discusses many of the species that depend on potentially vulnerable habitat in 

9304 specific estuaries, providing local elaboration of the general issues examined in Chapter 

9305 5. It also describes key statutes, regulations, and other policies that currently define how 

9306 state and local governments are responding to sea level rise, providing support for some 

9307 of the observations made in Part III. This set of information was not developed as a 

9308 quantitative nor analytical assessment and therefore is not intended as a complete or 

9309 authoritative basis for decision-making; rather, it is a starting point for those seeking to 

9310 discuss local impacts and to examine the types of decisions and potential policy 

9311 responses related to sea-level rise. 

 9312 

9313 The sections concerning species and habitat are largely derived from a U.S. EPA report 

9314 developed in support of this Synthesis and Assessment Product (U.S. EPA, 2008), with 

9315 additional input from stakeholders as well as expert and public reviewers. That report 

9316 synthesized what peer-reviewed literature was available, and augmented that information 

9317 with reports by organizations that manage the habitats under discussion, databases, and 

9318 direct observations by experts in the field. The sections that concern state and local 

9319 policies are based on statutes, regulations, and other official documents published by state 

9320 and local governments. 

 9321 
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9322 Characterizations of likelihood in this Product are largely based on the judgment of the 

9323 authors and on published peer-reviewed literature and existing policies, rather than a 

9324 formal quantification of uncertainty. Data on how coastal ecosystems and specific 

9325 species may respond to climate change is limited to a small number of site-specific 

9326 studies, often carried out for purposes unrelated to efforts to evaluate the potential impact 

9327 of sea level rise. Although being able to characterize current understanding―and the 

9328 uncertainty associated with that information―is important, quantitative and qualitative 

9329 assessments of likelihood are not unavailable for the site-specific issues discussed in this 

9330 Appendix. Unlike the main body of the Product, any likelihood statements in this 

9331 Appendix regarding specific habitat or species reflect likelihood as expressed in 

9332 particular reports being cited. Statements about the implications of coastal policies in this 

9333 Appendix are based on the authors qualitative assessment of available published literature 

9334 and of the governmental policies. Published information, data, and tools are evolving to 

9335 further examine sea-level rise at this scale. 

 9336 

9337 The synthesis was compiled by the following authors for the specific areas of focus and 

9338 edited by K. Eric Anderson, USGS; Stephen K. Gill, NOAA; Daniel Hudgens, Industrial 

9339 Economics, Inc.; and James G. Titus, U.S. EPA: 

 9340 

9341 A. Long Island page 586 

9342 Lead Authors: Daniel Hudgens, Industrial Economics Inc.; Ann 

9343 Shellenbarger Jones, Industrial Economics Inc.; James G. Titus, EPA. 

9344 Contributing Authors: Elizabeth M. Strange, Stratus Consulting Inc.; J. 

9345 Tanski, New York Sea Grant; G. Sinha, University of Ohio; 

9346 

9347 B. New York Metropolitan Area page 598 

9348 Lead Author: Elizabeth M. Strange, Stratus Consulting Inc; 
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9349 Contributing Authors: Daniel Hudgens, Industrial Economics Inc.; Ann 

9350 Shellenbarger Jones, Industrial Economics Inc. 

9351 

9352 C. New Jersey Shore page 605 

9353 Lead Author: James G. Titus, U.S. EPA 

9354 Contributing Author: Elizabeth M. Strange, Stratus Consulting Inc. 

9355 

9356 D. Delaware Estuary page 619 

9357 Lead Author: James G. Titus, U.S. EPA 

9358 Contributing Authors: Chris Linn, Delaware Valley Regional Planning 

9359 Commission; Danielle Kreeger, Partnership for the Delaware Estuary, Inc.; 

9360 Michael Craghan, Middle Atlantic Center for Geography & Environmental 

9361 Studies; Michael Weinstein, New Jersey Marine Sciences Consortium 

9362 (NJMSC) and Director, New Jersey Sea Grant College Program 

9363 

9364 E. The Atlantic Coast of Virginia, Maryland, and Delaware page 634 

9365 Lead Author: James G. Titus, U.S. EPA 

9366 Contributing Author: Elizabeth M. Strange, Stratus Consulting Inc. 

9367 

9368 F. Chesapeake Bay page 645 

9369 Lead Author: James G. Titus, U.S. EPA 

9370 Contributing Authors: Ann Shellenbarger Jones, Industrial Economics Inc.; 

9371 Peter Conrad, City of Baltimore; Elizabeth M. Strange, Stratus Consulting; 

9372 Zoe Johnson, Maryland Department of Natural Resources; Michael Weinstein, 

9373 New Jersey Sea Grant 

9374 

9375 G. North Carolina page 686 

9376 Lead Authors: James G. Titus, U.S. EPA; Rebecca L. Feldman, NOAA; Ben 

9377 Poulter, Potsdam Institute for Climate Impact Research 

9378 Contributing Authors: Jeff DeBlieu, The Nature Conservancy; Ann 

9379 Shellenbarger Jones, Industrial Economics Inc. 

 9380 

9381 A1.A. Long Island

9382 The North Shore of Long Island is generally characterized by high bluffs of glacial 

9383 origin, making this area less susceptible to problems associated with increased sea level. 

9384 The South Shore, by contrast, is generally low lying and fronted by barrier islands, except 

9385 for the easternmost portion. As a result, there are already major planning efforts 

9386 underway in the region to preserve the dry lands under threat of inundation. A brief 
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9387 discussion of these efforts, especially on the South Shore, is provided in Section A1.A.2 

9388 of this Appendix. Maps and estimates of the area of land close to sea level are provided in 

9389 Titus and Richman (2001). Further information on portions of the South Shore can be 

9390 found in Gornitz et al. (2002). 

 9391 

9392 A1.A.1 Environmental Implications 

9393 North Shore and Peconic Bay. 

9394 Of the 8,426 hectares (ha) (20,820 acres [ac]) of tidal wetlands in Long Island Sound, 

9395 about 15 percent are in New York, primarily along the shores of Westchester and Bronx 

9396 counties (Holst et al., 2003). Notable areas of marsh are in and around Stony Brook 

9397 Harbor and West Meadow, bordering the Nissequogue River and along the Peconic 

9398 Estuary (NYS DOS, 2004). In general, tidal wetlands along the North Shore are limited; 

the glacial terminal moraine70 resulted in steep uplands and bluffs and more kettle-hole71 9399 

9400 wetlands along the eastern portion (LISHRI, 2003). In the eastern portion, there has 

9401 already been a significant loss of the historical area of vegetated tidal wetlands (Holst et 

9402 al., 2003; Hartig and Gornitz, 2004), which some scientists partially attribute to sea-level 

9403 rise (Mushacke, 2003). 

 9404 

9405 The loss of vegetated low marsh reduces habitat for several rare bird species (e.g., seaside 

9406 sparrow) that nest only or primarily in low marsh (see Section 5.2). Low marsh also 

9407 provides safe foraging areas for small resident and transient fishes (e.g., weakfish, winter 

9408 flounder). Diamondback terrapin live in the creeks of the low marsh, where they feed on 

 

70 A glacial terminal moraine is a glacial deposit landform that marks the limit of glacial advance. 71 A kettle hole is a depression landform formed in glacial deposit sediments from a time when a large 

block of glacial ice remained and melted after a glacial retreat.
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9409 plants, mollusks, and crustaceans (LISF, 2008). Some wetlands along Long Island Sound 

9410 may be allowed to respond naturally to sea-level rise, including some in the Peconic 

9411 Estuary. Where migration is possible, preservation of local biodiversity as well as some 

9412 regionally rare species is possible (Strange et al., 2008). 

 9413 

9414 Beaches are far more common than tidal wetlands in the Long Island Sound study area. 

9415 Several notable barrier beaches exist. For example, the sandy barrier-beach system 

9416 fronting Hempstead Harbor supports a typical community progression from the foreshore 

9417 to the bay side, or backshore (LISHRI, 2003). The abundant invertebrate fauna provide 

9418 forage for sanderling, semipalmated plovers, and other migrating shorebirds (LISHRI, 

9419 2003). The maritime beach community between the mean high tide and the primary dune 

9420 provides nesting sites for several rare bird species, including piping plover, American 

9421 oystercatcher, black skimmer, least tern, common tern, roseate tern, the Northeastern 

9422 beach tiger beetle, and horseshoe crab (LISHRI, 2003) (see Box A1.1). Diamondback 

9423 terrapin use dunes and the upper limit of the backshore beach for nesting (LISHRI, 2003). 

 9424 

9425 Since nearly all of the Long Island Sound shoreline is densely populated and highly 

9426 developed, the land may be armored in response to sea-level rise, raising the potential for 

9427 beach loss. The Long Island Sound Habitat Restoration Initiative cautions: “Attempts to 

9428 alter the natural cycle of deposition and erosion of sand by construction of bulkheads, 

9429 seawalls, groins, and jetties interrupt the formation of new beaches” (LISHRI, 2003). 

9430 
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9431 Shallow water habitats are a major ecological feature in and around the Peconic Estuary. 

9432 Eelgrass beds provide food, shelter, and nursery habitats to diverse species, including 

9433 worms, shrimp, scallops and other bivalves, crabs, and fish (PEP, 2001). Horseshoe crabs 

9434 forage in the eelgrass beds of Cedar Point/Hedges Bank, where they are prey for 

9435 loggerhead turtles (federally listed as threatened), crabs, whelks, and sharks (NYS DOS, 

9436 2004). Atlantic silverside spawn here; silverside eggs provide an important food source 

9437 for seabirds, waterfowl, and blue crab, while adults are prey for bluefish, summer 

9438 flounder, rainbow smelt, white perch, Atlantic bonito, and striped bass (NYS DOS, 

9439 2004). The Cedar Point/Hedges Bank Shallows eelgrass beds are known for supporting a 

9440 bay scallop fishery of statewide importance (NYS DOS, 2004). 

 9441 

9442 Other noteworthy habitats that could be affected by sea-level rise include the sea-level 

9443 fen vegetation community that grows along Flanders Bay (NYS DOS, 2004), and the 

9444 Long Island’s north shore tidal flats, where longshore drift carries material that erodes 

9445 from bluffs and later deposits it to form flats and barrier spits or shoals (LISHRI, 2003). 

9446 One of the largest areas of tidal mudflats on the North Shore is near Conscience Bay, 

9447 Little Bay, and Setauket Harbor west of Port Jefferson (NYS DOS, 2004). Large beds of 

9448 hard clams, soft clams, American oysters, and ribbed mussels are found in this area (NYS 

9449 DOS, 2004). 

 9450 

9451 South Shore. 

9452 Extensive back-barrier salt marshes exist to the west of Great South Bay in southern 

9453 Nassau County (USFWS, 1997). These marshes are particularly notable given 
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9454 widespread marsh loss on the mainland shoreline of southern Nassau County (NYS DOS 

9455 and USFWS, 1998; USFWS, 1997). To the east of Jones Inlet, the extensive back-barrier 

9456 and fringing salt marshes are keeping pace with current rates of sea-level rise, but experts 

9457 predict that the marshes’ ability to keep pace is likely to be marginal if the rate of sea9458 level rise increases moderately, and that the marshes are likely to be lost under higher 

9459 sea-level rise scenarios (Strange et al., 2008, interpreting the findings of Reed et al., 

9460 2008). Opportunities for marsh migration along Long Island’s South Shore would be 

9461 limited if the mainland shores continue to be bulkheaded. Outside of New York City, the 

9462 state requires a minimum 22.9-meter (m) (75-foot [ft]) buffer around tidal wetlands to 

9463 allow marsh migration, but outside of this buffer, additional development and shoreline 

protection are permitted72 9464 (NYS DEC, 2006). Numerous wildlife species could be 

9465 affected by salt marsh loss. For example, the Dune Road Marsh west of Shinnecock Inlet 

9466 provides nesting sites for several species that are already showing significant declines, 

9467 including clapper rail, sharp-tailed sparrow, seaside sparrow, willet, and marsh wren 

9468 (USFWS, 1997). The salt marshes of Gilgo State Park provide nesting sites for northern 

9469 harrier, a species listed by the state as threatened (NYS DOS, 2004). 

 9470 

9471 Of the extensive tidal flats along Long Island’s southern shoreline, most are found west 

9472 of Great South Bay and east of Fire Island Inlet, along the bay side of the barrier islands, 

9473 (USFWS, 1997) in the Hempstead Bay–South Oyster Bay complex, (USFWS, 1997) and 

9474 around Moriches and Shinnecock Inlets (NYS DOS and USFWS, 1998). These flats 

9475 provide habitat for several edible shellfish species, including soft clam, hard clam, bay 

 

72 The state has jurisdiction up to 300 feet beyond the tidal wetland boundary in most areas (but only 150 

feet in New York City). 
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9476 scallop, and blue mussel. The tidal flats around Moriches and Shinnecock Inlets are 

9477 particularly important foraging areas for migrating shorebirds. The South Shore Estuary 

9478 Reserve Council asserts that “because shorebirds concentrate in just a few areas during 

9479 migration, loss or degradation of key sites could devastate these populations” (NYS DOS 

9480 and USFWS, 1998). 

 9481 

9482 The back-barrier beaches of the South Shore also provide nesting sites for the endangered 

9483 roseate tern and horseshoe crabs (USFWS, 1997). Shorebirds, such as the red knot, feed 

9484 preferentially on horseshoe crab eggs during their spring migrations. 

 9485 

9486 Increased flooding and erosion of marsh and dredge spoil islands will reduce habitat for 

9487 many bird species that forage and nest there, including breeding colonial waterbirds, 

9488 migratory shorebirds, and wintering waterfowl. For example, erosion on Warner Island is 

9489 reducing nesting habitat for the federally endangered roseate tern and increasing flooding 

9490 risk during nesting (NYS DOS and USFWS, 1998). The Hempstead Bay–South Oyster 

9491 Bay complex includes a network of salt marsh and dredge spoil islands that are important 

9492 for nesting by herons, egrets, and ibises. Likewise, Lanes Island and Warner Island in 

9493 Shinnecock Bay support colonies of the state-listed common tern and the roseate tern 

9494 (USFWS, 1997). 

9495 --START TEXT BOX-- 

9496 BOX A1.1: Effects on the Piping Plover 

9497 Piping Plover Charadrius melodus

9498 Habitat: The piping plover, federally listed as threatened, is a small migratory shorebird that primarily 

9499 inhabits open sandy barrier island beaches on Atlantic coasts (USFWS, 1996). Major contributing factors to 

9500 the plover’s status as threatened are beach recreation by pedestrians and vehicles that disturb or destroy 

9501 plover nests and habitat, predation by mammals and other birds, and shoreline development that inhibit the 

9502 natural renewal of barrier beach and overwash habitats (USFWS, 1996). In some locations, dune 
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9503 maintenance for protection of access roads associated with development appears to be correlated with 

9504 absence of piping plover nests from former nesting sites (USFWS, 1996). 

9505 

9506 Locations: The Atlantic population of piping plovers winters on beaches from the Yucatan Peninsula to 

9507 North Carolina. In the summer, they migrate north and breed on beaches from North Carolina to 

9508 Newfoundland (CLO, 2004). In the mid-Atlantic region, breeding pairs of plovers can be observed on 

9509 coastal beaches and barrier islands, although suitable habitat is limited in some areas. In New York, piping 

9510 plovers breed more frequently on Long Island’s sandy beaches, from Queens to the Hamptons, in the 

9511 eastern bays and in the harbors of northern Suffolk County. New York’s Breezy Point barrier beach, at the 

9512 mouth of Jamaica Bay, consistently supports one of the largest piping plover nesting sites in the entire New 

9513 York Bight coastal region (USFWS, 1997). New York has seen an increase in piping plover breeding pairs 

9514 in the last decade from less than 200 in 1989 to near 375 in recent years (2003 to 2005), representing nearly 

9515 a quarter of the Atlantic coast’s total breeding population (USFWS, 2004a). Despite this improvement, 

9516 piping plovers remain state listed as endangered in New York (NYS DEC, 2007). 

9517 

9518 Impact of Sea-Level Rise: Where beaches are prevented from migrating inland by shoreline armoring, 

9519 sea-level rise will negatively impact Atlantic coast piping plover populations. To the degree that developed 

9520 shorelines result in erosion of ocean beaches, and to the degree that stabilization is undertaken as a 

9521 response to sea-level rise, piping plover habitat will be lost. In contrast, where beaches are able to migrate 

9522 landward, plovers may find newly available habitat. For example, on Assateague Island, piping plover 

9523 populations increased after a storm event that created an overwash area on the north of the island (Kumer, 

9524 2004). This suggests that if barrier beaches are allowed to migrate in response to sea-level rise, piping 

9525 plovers might adapt to occupy new inlets and beaches created by overwash events. 

9526 

9527 Beach nourishment, the anticipated protection response for much of New York’s barrier beaches such as 

9528 Breezy Point, can benefit piping plovers and other shorebirds by increasing available nesting habitat in the 

9529 short term, offsetting losses at eroded beaches, but may also be detrimental, depending on timing and 

9530 implementation (USFWS, 1996). For instance, a study in Massachusetts found that plovers foraged on 

9531 sandflats created by beach nourishment (Cohen et al,, 2005). However, once a beach is built and people 

9532 spread out to enjoy it, many areas become restricted during nesting season. Overall, throughout the Mid9533 Atlantic, coastal development and shoreline stabilization projects constitute the most serious threats to the 

9534 continuing viability of storm-maintained beach habitats and their dependent species, including the piping 

9535 plover (USFWS, 1996). 

9536 

9537 Photograph credit: USFWS, New Jersey Field Office /Gene Nieminen, 2006. 

9538 

9539 -- END TEXT BOX – 

9540 

9541 A1.A.2 Development, Shore Protection, and Coastal Policies 

9542 New York State does not have written policies or regulations pertaining specifically to 

9543 sea-level rise in relation to coastal zone management, although sea-level rise is becoming 

9544 recognized as a factor in coastal erosion and flooding by New York State Department of 

9545 State (DOS) in the development of regional management plans. 

 9546 
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9547 Policies regarding management and development in shoreline areas are primarily based 

9548 on three laws. Under the Tidal Wetlands Act program, the Department of Environmental 

9549 Conservation (DEC) classifies various wetland zones and adjacent areas where human 

9550 activities may have the potential to impair wetland values or adversely affect their 

9551 function; permits are required for most activities that take place in these areas. New 

9552 construction greater than 9.3 square meters (sq m) (100 square feet [sq ft]), excluding 

9553 docks, piers, and bulkheads) as well as roads and other infrastructure must be set back 

9554 22.9 m (75 ft) from any tidal wetland, except within New York City where the setback is 

9.1 m (30 ft)73 9555 . 

 9556 

9557 The Waterfront Revitalization and Coastal Resources Act (WRCRA) allows the DOS to 

9558 address sea-level rise indirectly through policies regarding flooding and erosion hazards 

9559 (NOAA, 1982). Seven out of 44 written policies related to management, protection, and 

9560 use of the coastal zone address flooding and erosion control. These polices endeavor to 

9561 move development away from areas threatened by coastal erosion and flooding hazards, 

9562 to ensure that development activities do not exacerbate erosion or flooding problems and 

9563 to preserve natural protective features such as dunes. They also provide guidance for 

9564 public funding of coastal hazard mitigation projects and encourage the use of 

9565 nonstructural erosion and flood control measures where possible (NYS DOS, 2002). 

 9566 

9567 Under the Coastal Erosion Hazard Areas Act program, the DEC identified areas subject 

9568 to erosion and established two types of erosion hazard areas (structural hazard and natural 

 

73 Article 25, Environmental Conservation Law Implementing Regulations-6NYCRR PART 661. 
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protective feature areas) where development and construction activities are regulated74 9569 . 

9570 Permits are required for most activities in designated natural protective feature areas.

9571 New development (e.g., building, permanent shed, deck, pool, garage) is prohibited in 

9572 nearshore areas, beaches, bluffs, and primary dunes. These regulations, however, do not 

9573 extend far inland and therefore do not encompass the broader area vulnerable to sea-level 

9574 rise. 

9575 

9576 New York State regulates shore protection structures along estuaries and the ocean coast 

9577 differently. The state’s Coastal Erosion Hazard Law defines coastal erosion hazard areas 

as those lands with an average erosion rate of at least 30 cm (1 ft) per year.75 9578 Within 

9579 those erosion hazard areas, the local governments administer the programs to grant or 

deny permits, generally following state guidelines.76 9580 Those guidelines requires that 

9581 individual property owners first evaluate non-structural approaches; but if they are 

9582 unlikely to be effective, hard structures are allowed (New York State, 2002a). 

 9583 

9584 Shoreline structures, which by definition include beach nourishment in New York State, 

9585 are permitted only when it can be shown that the structure can prevent erosion for at least 

9586 thirty years and will not cause an increase in erosion or flooding at the local site or 

9587 nearby locations (New York State, 2002a). Setbacks, relocation, and elevated walkways 

9588 are also encouraged before hardening. 

 9589 

 

74 Environmental Conservation Law, Article 34 

75 § New York Environmental Conservation Law 34-0103 (3)(a) 

76 § New York Environmental Conservation Law 34-0105 
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9590 Currently, all of the erosion hazard areas are along the open coast. Therefore, the state 

9591 does not directly regulate shore protection structures along estuarine shores. However, 

9592 under the federal Coastal Zone Management Act, New York's coastal management 

9593 program reviews federal agency permit applications, to ensure consistency with policies 

9594 of the State's coastal management program (NOAA, 2008; USACE, 2007). The state has 

9595 objected to nationwide permit 13 issued by the Corps of Engineer’s wetlands regulatory 

9596 program (see Section 12.2.2 in Chapter 12), which provides a general authorization for 

9597 erosion control structures (NYS DOS, 2006). The effect of that objection is that 

9598 nationwide permit 13 does not automatically provide a property owner with a permit for 

9599 shore protection unless the state concurs with such an application (NYS DOS, 2006). 

9600 The state has also objected to the application of nationwide permits 3 (which includes 

9601 maintenance of existing shore protection structures) and 31 (maintenance of existing 

9602 flood control activities) within special management areas (NYS DOS, 2006). 

 9603 

9604 Similar to the New York metropolitan area, the policies for Long Island reflect the fact 

9605 that the region is intensely developed in the west and developing fast in the east. Much of 

9606 the South Shore, particularly within Nassau County, is already developed and has already 

9607 been protected, primarily by bulkheads. The Long Island Sound Management Program 

9608 estimates that approximately 50 percent of the Sound’s shoreline is armored (NYS DOS, 

9609 1999). 

9610 

9611 Some of the South Shore’s densely developed communities facing flooding problems, 

9612 such as Freeport and Hempstead, have already implemented programs that call for 

9613 elevating buildings and infrastructure in place and installing bulkheads for flood 
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9614 protection. The Town of Hempstead has adopted the provisions of the state’s Coastal 

9615 Erosion Hazards Area Act, described in Section A1.B of this Appendix, because erosion 

9616 and flooding along Nassau County’s ocean coast have been a major concern. The Town 

9617 of Hempstead has also been actively working with the U.S. Army Corps of Engineers 

9618 (USACE) to develop a long-term storm damage reduction plan for the heavily developed 

9619 Long Beach barrier island (USACE, 2003). 

 9620 

9621 Beach nourishment and the construction of flood and erosion protection structures are 

9622 also common on the island. For example, in the early 1990s USACE constructed a 

9623 substantial revetment around the Montauk Lighthouse at the eastern tip of Long Island 

9624 and after a new feasibility study has proposed construction of a larger revetment (Bleyer, 

9625 2007). USACE is also reformulating a plan for the development of long-term storm 

9626 damage prevention projects along the 134 kilo (km) 83 mile [mi]) portion of the South 

9627 Shore of Suffolk County. As part of this effort, USACE is assessing at-risk properties 

9628 within the 184 square kilometer (sq km) (71 square miles [sq mi]) floodplain, present and 

9629 future sea-level rise, restoration and preservation of important coastal landforms and 

9630 processes, and important public uses of the area (USACE, 2008b). 

 9631 

9632 To obtain state funding for nourishment, communities must provide public access every 

9633 800 m (0.5 mi) (New York State, 2002b). In 1994, as terms of a legal settlement between 

9634 federal, state, and local agencies cooperating on the rebuilding of the beach through 

9635 nourishment, the community of West Hampton provided six walkways from the 

9636 shorefront road to allow public access to the beach (Dean, 1999). In communities that 
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9637 have not had such state-funded projects, however, particularly along portions of the bay 

9638 shore communities in East Hampton, South Hampton, Brookhaven, and Islip, public 

9639 access to tidal waters can be less common (NYS DOS, 1999). 

 9640 

9641 The Comprehensive Coastal Management Plan (CCMP) of the Peconic Bay National 

9642 Estuary Program Management Plan calls for “no net increase of hardened shoreline in the 

9643 Peconic Estuary”. The intent of this recommendation is to discourage individuals from 

9644 armoring their coastline; yet this document is only a management plan and does not have 

9645 any legal authority. However, towns such as East Hampton are trying to incorporate the 

9646 plan into their own programs. In 2006, the town of East Hampton adopted and is now 

9647 enforcing a defined zoning district overlay map that prevents shore armoring along much 

9648 of the town’s coastline (Town of East Hampton, 2006). Despite such regulations, 

9649 authorities in East Hampton and elsewhere recognize that there are some areas where 

9650 structures will have to be allowed to protect existing development. 

 9651 

9652 The New York Department of State (DOS) is also examining options for managing 

9653 erosion and flood risks through land use measures, such as further land exchanges. For 

9654 example, there is currently an attempt to revise the proposed Fire Island to Montauk Point 

9655 Storm Damage Reduction Project to consider a combination of nourishment and land use 

9656 measures. One option would be to use beach nourishment to protect structures for the 

9657 next few decades, during which time development could gradually be transferred out of 

9658 the most hazardous locations. Non-conforming development could eventually be brought 
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9659 into conformance as it is reconstructed, moved, damaged by storms or flooding, or other 

9660 land use management plans are brought into effect. 

 9661 

9662 A1.B. New York Metropolitan Area

9663 The New York metropolitan area has a mixture of elevated and low-lying coastlines. 

9664 Low-lying land within 3 m of mean sea level (Gornitz et al., 2002) include the borough 

9665 of Queens’ northern and southeastern shore, respectively (where New York’s two major 

9666 airports, LaGuardia and John F. Kennedy International Airport, are located); much of the 

9667 recreational lands along Jamaica Bay’s Gateway National Recreation Area (e.g., Floyd 

9668 Bennett Field, Jamaica Bay Wildlife Refuge, Fort Tilden, Riis Park); and the Staten 

9669 Island communities of South Beach and Oakwood Beach. In New Jersey, the heavily 

9670 developed coast of Hudson County (including Hoboken, Jersey City, and Bayonne) is 

9671 also within 3 m, as is much of the area known as the Meadowlands (area around Giants 

9672 Stadium). Other areas with sections of low-lying lands are found in Elizabeth and 

9673 Newark, New Jersey (near Newark Airport). The area also includes the ecologically9674 significant Raritan Bay-Sandy Hook habitat complex at the apex of the New York region 

9675 (also known as the New York Bight), where the east-west oriented coastline of New 

9676 England and Long Island intersects the north-south oriented coastline of the mid-Atlantic 

9677 at Sandy Hook. 

 9678 

9679 Given its large population, the effects of hurricanes and other major storms combined 

9680 with higher sea levels could be particularly severe in the New York metropolitan area. 

9681 With much of the area’s transportation infrastructure at low elevation (most at 3 m or 
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9682 less), even slight increases in the height of flooding could cause extensive damage and 

9683 bring the thriving city to a relative standstill until the flood waters recede (Gornitz et al., 

9684 2002). 

 9685 

9686 Comprehensive assessments of the vulnerability of the New York City metropolitan area 

9687 are found in Jacob et al. (2007) and Gornitz et al. (2002). Jacob et al. summarize 

9688 vulnerability, coastal management and adaptation issues. Gornitz et al. details the 

9689 methodology and results of a study that summarizes vulnerability to impacts of climate 

9690 change, including higher storm surges, shoreline movement, wetland loss, beach 

9691 nourishment and some socioeconomic implications. These assessments use sea-level rise 

9692 estimates from global climate models available in 2002. Generalized maps depicting 

9693 lands close to sea level are found in Titus and Richman (2001) and Titus and Wang 

9694 (2008). 

 9695 

9696 If sea-level rise impairs coastal habitat, many estuarine species would be at risk. This 

9697 Section provides additional details on the possible environmental implications of sea9698 level rise for the greater New York metropolitan area, including New York City, the 

9699 lower Hudson River, the East River, Jamaica Bay, the New Jersey Meadowlands, Raritan 

9700 Bay and Sandy Hook Bay. The following subsections discuss tidal wetlands, beaches, 

9701 tidal flats, marsh and bay islands, and shallow waters. (Sections A1.A.2 and A1.D.2 

9702 discuss the statewide coastal policies of New York and New Jersey.) 

 9703 

9704 Tidal Wetlands. Examples of this habitat include: 
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9705  Staten Island: The Northwest Staten Island/Harbor Herons Special Natural 

9706 Waterfront Area is an important nesting and foraging area for herons, ibises, egrets, 

9707 gulls, and waterfowl (USFWS, 1997). Several marshes on Staten Island, such as 

9708 Arlington Marsh and Saw Mill Creek Marsh, provide foraging areas for the birds of 

9709 the island heronries. Hoffman Island and Swinburne Island, east of Staten Island, 

9710 provide important nesting habitat for herons and cormorants, respectively (Bernick, 

9711 2006). 

9712  Manhattan: In the marsh and mudflat at the mouth of the Harlem River at Inwood 

9713 Hill Park (USFWS, 1997) great blue herons are found along the flat in winter, and 

9714 snowy and great egrets are common from spring through fall (NYC DPR, 2001). 

9715  Lower Hudson River: The Piermont Marsh, a 412 hectare (ha) (1,017 acre [ac]) 

9716 brackish wetland on the western shore of the lower Hudson River has been 

9717 designated for conservation management by New York State and the National 

9718 Oceanic and Atmospheric Administration (NOAA) (USFWS, 1997). The marsh 

9719 supports breeding birds, including relatively rare species such as Virginia rail, 

9720 swamp sparrow, black duck, least bittern, and sora rail. Anadromous and freshwater 

9721 fish use the marsh’s tidal creeks as a spawning and nursery area. Diamondback 

9722 terrapin reportedly nest in upland areas along the marsh (USFWS, 1997). 

9723  Jamaica Bay: Located in Brooklyn and Queens, this bay is the largest area of 

9724 protected wetlands in a major metropolitan area along the U.S. Atlantic Coast. The 

9725 bay includes the Jamaica Bay Wildlife Refuge, which has been protected since 1972 

9726 as part of the Jamaica Bay Unit of the Gateway National Recreation Area. Despite 

9727 extensive disturbance from dredging, filling, and development, Jamaica Bay remains 
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9728 one of the most important migratory shorebird stopover sites in the New York Bight 

9729 (USFWS, 1997). The bay provides overwintering habitat for many duck species, and 

9730 mudflats support foraging migrant species (Hartig et al., 2002). The refuge and 

9731 Breezy Point, at the tip of the Rockaway Peninsula, support populations of 214 

9732 species that are state or federally listed or of special emphasis, including 48 species 

9733 of fish and 120 species of birds (USFWS, 1997). Salt marshes such as Four Sparrow 

9734 Marsh provide nesting habitat for declining sparrow species and serve 326 species of 

9735 migrating birds (NYC DPR, undated). Wetlands in some parts of the bay currently 

9736 show substantial losses (Hartig et al., 2002). 

9737  Meadowlands: The Meadowlands contain the largest single tract of estuarine tidal 

9738 wetland remaining in the New York/New Jersey Harbor Estuary and provide critical 

9739 habitat for a diversity of species, including a number of special status species. 

9740 Kearney Marsh is a feeding area for the state-listed endangered least tern, black 

9741 skimmer, and pied-billed grebe. Diamondback terrapin, the only turtle known to 

9742 occur in brackish water, is found in the Sawmill Wildlife Management Area 

9743 (USFWS, 1997). 

9744  Raritan Bay-Sandy Hook: The shorelines of southern Raritan Bay include large 

9745 tracts of fringing salt marsh at Conaskonk Point and from Flat Creek to Thorn’s 

9746 Creek. These marshes are critical for large numbers of nesting and migrating bird 

9747 species. The salt marsh at Conaskonk Point provides breeding areas for bird species 

9748 such as green heron, American oystercatcher, seaside sparrow, and saltmarsh sharp9749 tailed sparrow, as well as feeding areas for herons, egrets, common tern, least tern, 

9750 and black skimmer. In late May and early June, sanderlings, ruddy turnstones, 
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9751 semipalmated sandpipers, and red knots feed on horseshoe crab eggs near the mouth 

9752 of Chingarora Creek. Low marsh along the backside of Sandy Hook spit provides 

9753 forage and protection for the young of marine fishes, including winter flounder, 

9754 Atlantic menhaden, bluefish, and striped bass, and critical habitat for characteristic 

9755 bird species of the low marsh such as clapper rail, willet, and marsh wren (USFWS, 

9756 1997). 

9757 

9758 Estuarine Beaches. Relatively few areas of estuarine beach remain in the New York City 

9759 metropolitan area, and most have been modified or degraded (USFWS 1997; Strange 

9760 2008a). In Jamaica Bay, remaining estuarine beaches occur off Belt Parkway (e.g., on 

9761 Plumb Beach) and on the bay islands (USFWS, 1997). Sandy beaches are still relatively 

9762 common along the shores of Staten Island from Tottenville to Ft. Wadsworth. The 

9763 southern shoreline of Raritan Bay includes a number of beaches along Sandy Hook 

9764 Peninsula and from the Highlands to South Amboy, some of which have been nourished. 

9765 There are also beaches on small islands within the Shrewsbury-Navesink River system 

9766 (USFWS, 1997). 

 9767 

9768 Although limited in area, the remaining beaches support an extensive food web. Mud 

9769 snails and wrack-based species (e.g., insects, isopods, and amphipods) provide food for 

9770 shorebirds including the piping plover, federally listed as threatened (USFWS, 1997). 

9771 The beaches around Sandy Hook Bay have becoming important nestling places in winter 

9772 for several species of seals (USFWS, 1997). The New Jersey Audubon Society reports 

9773 that its members have observed gulls and terns at the Raritan Bay beach at Morgan on the 
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9774 southern shore, including some rare species such as black-headed gull, little gull, 

9775 Franklin’s gull, glaucous gulls, black tern, sandwich tern, and Hudsonian godwit. 

9776 Horseshoe crabs lay their eggs on area beaches, supplying critical forage for shorebirds 

9777 (Botton et al., 2006). The upper beach is used by nesting diamondback terrapins; human9778 made sandy trails in Jamaica Bay are also an important nest site for terrapins in the 

9779 region, although the sites are prone to depredations by raccoons (Feinberg and Burke, 

9780 2003). 

 9781 

9782 Tidal flats. Like beaches, tidal flats are limited in the New York City metropolitan region, 

9783 but the flats that remain provide important habitat, particularly for foraging birds. Tidal 

9784 flats are also habitat for hard and soft shell clams, which are important for recreational 

9785 and commercial fishermen where not impaired by poor water quality. Large 

9786 concentrations of shorebirds, herons, and waterfowl use the shallows and tidal flats of 

9787 Piermont Marsh along the lower Hudson River as staging areas for both spring and fall 

9788 migrations (USFWS, 1997). Tidal flats in Jamaica Bay are frequented by shorebirds and 

9789 waterfowl, and an intensive survey of shorebirds in the mid-1980s estimated more than 

9790 230,000 birds of 31 species in a single year, mostly during the fall migration (Burger, 

9791 1984). Some 1,460 ha (3,600 ac) of intertidal flats extend offshore an average of 0.4 km 

9792 (0.25 mi) from the south shore of the Raritan and Sandy Hook Bays, from the confluence 

9793 of the Shrewsbury and Navesink Rivers, west to the mouth of the Raritan River. These 

9794 flats are important foraging and staging areas for migrating shorebirds, averaging over 

9795 20,000 birds, mostly semipalmated plover, sanderling, and ruddy turnstone. The flats at 

9796 the mouth of Whale Creek near Pirate’s Cove attract gulls, terns, and shorebirds year 
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9797 round. Midwinter waterfowl surveys indicate that an average of 60,000 birds migrate 

9798 through the Raritan Bay-Sandy Hook area in winter (USFWS, 1997). Inundation with 

9799 rising seas will eventually make flats unavailable to short-legged shorebirds, unless they 

9800 can shift feeding to marsh ponds and pannes (Erwin et al., 2004). At the same time, 

9801 disappearing saltmarsh islands in the area are transforming into intertidal mudflats. This 

9802 may increase habitat for shorebirds at low tide, but it leaves less habitat for refuge at high 

9803 tide (Strange 2008a). 

 9804 

9805 Shallow water habitat. This habitat is extensive in the Hudson River, from Stony Point 

9806 south to Piermont Marsh, just below the Tappan Zee Bridge (USFWS, 1997). This area 

9807 features the greatest mixing of ocean and freshwater, and concentrates nutrients and 

9808 plankton, resulting in a high level of both primary and secondary productivity. Thus, this 

9809 part of the Hudson provides key habitat for numerous fish and bird species. It is a major 

9810 nursery area for striped bass, white perch, tomcod, and Atlantic sturgeon, and a wintering 

9811 area for the federally endangered shortnose sturgeon. Waterfowl also feed and rest here 

9812 during spring and fall migrations. Some submerged aquatic vegetation (SAV) is also 

9813 found here, dominated by water celery, sago pondweed, and horned pondweed (USFWS, 

9814 1997). 

 9815 

9816 Marsh and bay islands. Throughout the region, these islands are vulnerable to sea-level 

9817 rise (Strange 2008a). Between 1974 and 1994, the smaller islands of Jamaica Bay lost 

9818 nearly 80 percent of their vegetative cover (Strange 2008a, citing Hartig et al., 2002). 

9819 Island marsh deterioration in Jamaica Bay has led to a 50 percent decline in area between 
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9820 1900 and 1994 (Gornitz et al., 2002). Marsh loss has accelerated, reaching an average 

9821 annual rate of 18 ha (45 ac) per year between 1994 and 1999 (Hartig et al., 2002). The 

9822 islands provide specialized habitat for an array of species: 

9823  Regionally important populations of egrets, herons, and ibises are or have been 

9824 located on North and South Brother islands in the East River and on Shooter’s 

9825 Island, Prall’s Island, and Isle of Meadows in Arthur Kill and Kill van Kull 

9826 (USFWS, 1997). 

9827  North and South Brother Islands have the largest black crowned night heron colony 

9828 in New York State, along with large numbers of snowy egret, great egret, cattle 

9829 egret, and glossy ibis (USFWS, 1997). 

9830  Since 1984, an average of 1,000 state threatened common tern have nested annually 

9831 in colonies on seven islands of the Jamaica Bay Wildlife Refuge (USWFS, 1997). 

9832  The heronry on Carnarsie Pol also supports nesting by great black-backed gull, 

9833 herring gull, and American oystercatcher (USFWS, 1997). 

9834  The only colonies of laughing gull in New York State, and the northernmost 

9835 breeding extent of this species, occur on the islands of East High Meadow, Silver 

9836 Hole Marsh, Jo Co Marsh, and West Hempstead Bay (USFWS, 1997). 

9837  Diamondback terrapin nest in large numbers along the sandy shoreline areas of the 

9838 islands of Jamaica Bay, primarily Ruler’s Bar Hassock (USFWS, 1997). 

9839 

9840 A1.C. New Jersey Shore

9841 The New Jersey shore has three types of ocean coasts (see Chapter 3 of this Product). At 

9842 the south end, Cape May and Atlantic Counties have short and fairly wide “tide-
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9843 dominated” barrier islands. Behind the islands, 253 sq km (97 sq mi) of marshes 

9844 dominate the relatively small open water bays. To the north, Ocean County has “wave 

9845 dominated” coastal barrier islands and spits. Long Beach Island is 29 km (18 mi) long 

9846 and only two to three blocks wide in most places; Island Beach to the north is also long 

9847 and narrow. Behind Long Beach Island and Island Beach lie Barnegat and Little Egg 

9848 Harbor Bays. These shallow estuaries range from 2 to 7 km (about 1 to 4 mi) wide, and 

9849 have 167 sq km (64 sq mi) of open water (USFWS, 1997) with extensive eelgrass, but 

9850 only 125 sq km (48 sq mi) of tidal marsh (Jones and Wang, 2008). Monmouth County’s 

9851 ocean coast is entirely headlands, with the exception of Sandy Hook at the northern tip of 

9852 the Jersey Shore. Non-tidal wetlands are immediately inland of the tidal wetlands along 

most of the mainland shore77 9853 . 

 9854 

9855 A1.C.1 Environmental Implications

9856 There have been many efforts to conserve and restore species and habitats in the barrier 

9857 island and back-barrier lagoon systems in New Jersey. Some of the larger parks and 

9858 wildlife areas in the region include Island Beach State Park, Great Bay Boulevard State 

9859 Wildlife Management Area, and the E.B. Forsythe National Wildlife Refuge (Forsythe 

9860 Refuge) in Ocean and Atlantic counties. Parts of the Cape May Peninsula are protected 

9861 by the Cape May National Wildlife Refuge (USFWS, undated[a]), the Cape May Point 

9862 State Park (NJDEP, undated) and The Nature Conservancy’s (TNC’s) Cape May 

9863 Migratory Bird Refuge (TNC, undated). 

 9864 

 

77 For comprehensive discussions of the New Jersey shore and the implications of sea level rise, see Cooper 

et al. (2005), Lathrop and Love (2007), Najjar et al. (2000) and Psuty and Ofiara (2002)
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9865 Tidal and Nearshore Nontidal Marshes. There are 18,440 ha (71 sq mi), 29,344 ha (113 

9866 sq mi), and 26,987 ha (104 sq mi) of tidal salt marsh in Ocean, Atlantic, and Cape May 

9867 counties, respectively (Jones and Wang, 2008). The marshes in the study area are keeping 

9868 pace with current local rates of sea-level rise of 4 millimeters (mm) per year, but are 

9869 likely to become marginal with a 2 mm per year acceleration and be lost with a 7 mm per 

9870 year acceleration, except where they are near local sources of sediments (e.g., rivers such 

9871 as the Mullica and Great Harbor rivers in Atlantic County) (Strange 2008b, interpreting 

9872 the findings of Reed et al., 2008). 

9873 

9874 There is potential for wetland migration in Forsythe Refuge, and other lands that preserve 

9875 the coastal environment such as parks and wildlife management areas. Conservation 

9876 lands are also found along parts of the Mullica and Great Egg Harbor Rivers in Atlantic 

9877 County. However, many estuarine shorelines in developed areas are hardened, limiting 

9878 the potential for wetland migration (Strange, 2008b). 

 9879 

9880 As marshes along protected shorelines experience increased tidal flooding, there may be 

9881 an initial benefit to some species. If tidal creeks become wider and deeper fish may have 

9882 increased access to forage on the marsh surface (Weinstein, 1979). Sampling of larval 

9883 fishes in high salt marsh on Cattus Island, Beach Haven West, and Cedar Run in Ocean 

9884 County showed that high marsh is important for mummichog, rainwater killifish, spotfin 

9885 killifish, and sheepshead minnow (Talbot and Able, 1984). The flooded marsh surface 

9886 and tidal and nontidal ponds and ditches appear to be especially important for the larvae 

9887 of these species (Talbot and Able, 1984). However, as sea level rises, and marshes along 

9888 hardened shorelines convert to open water, marsh fishes will lose access to these marsh 
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9889 features and the protection from predators, nursery habitat, and foraging areas provided 

9890 by the marsh (Strange 2008b). 

 9891 

9892 Loss of marsh area would also have negative implications for the dozens of bird species 

9893 that forage and nest in the region’s marshes. Initially, deeper tidal creeks and marsh pools 

9894 will become inaccessible to short-legged shorebirds such as plovers (Erwin et al., 2004). 

9895 Long-legged waterbirds such as the yellow-crowned night heron, which forages almost 

9896 exclusively on marsh crabs (fiddler crab and others), will lose important food resources 

9897 (Riegner, 1982). Eventually, complete conversion of marsh to open water will affect the 

9898 hundreds of thousands of shorebirds that stop in these areas to feed during their 

9899 migrations. The New Jersey Coastal Management Program estimates that some 1.5 

9900 million migratory shorebirds stopover on New Jersey’s shores during their annual 

9901 migrations (Cooper et al., 2005). Waterfowl also forage and overwinter in area marshes. 

9902 Mid-winter aerial waterfowl counts in Barnegat Bay alone average 50,000 birds 

9903 (USFWS, 1997). The tidal marshes of the Cape May Peninsula provide stopover areas for 

9904 hundreds of thousands of shorebirds, songbirds, raptors, and waterfowl during their 

9905 seasonal migrations (USFWS, 1997). The peninsula is also an important staging area and 

9906 overwintering area for seabird populations. Surveys conducted by the U.S. Fish and 

9907 Wildlife Service from July through December 1995 in Cape May County recorded more 

9908 than 900,000 seabirds migrating along the coast (USFWS, 1997). 

 9909 

9910 As feeding habitats are lost, local bird populations may no longer be sustainable (Strange, 

9911 2008b). For example, avian biologists suggest that if marsh pannes and pools continue to 
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9912 be lost in Atlantic County as a result of sea-level rise, the tens of thousands of shorebirds 

9913 that feed in these areas may shift to feeding in impoundments in the nearby Forsythe 

9914 Refuge. Such a shift would increase shorebird densities in the refuge ten-fold and reduce 

9915 population sustainability due to lower per capita food resources and disease from 

9916 crowding (Erwin et al., 2006). 

 9917 

9918 Local populations of marsh nesting bird species will also be at risk where marshes drown. 

9919 This will have a particularly negative impact on rare species such as seaside and sharp9920 tailed sparrows, which may have difficulty finding other suitable nesting sites. According 

9921 to a synthesis of published studies in Greenlaw and Rising (1994) and Post and Greenlaw 

9922 (1994), densities in the region ranged from 0.3 to 20 singing males per hectare and 0.3 to 

9923 4.1 females per hectare for the seaside and sharp-tailed sparrows, respectively (Greenlaw 

9924 and Rising, 1994). Loss and alteration of suitable marsh habitats are the primary 

9925 conservation concerns for these and other marsh-nesting passerine birds (BBNEP, 2001). 

 9926 

9927 Shore protection activities (nourishment and vegetation control) are underway to protect 

9928 the vulnerable freshwater ecosystems of the Cape May Meadows (The Meadows), which 

9929 are located behind the eroding dunes near Cape May Point (USACE, 2008a). Freshwater 

9930 coastal ponds in The Meadows are found within about one hundred meters (a few 

9931 hundred feet) of the shoreline and therefore could easily be inundated as seas rise. The 

9932 ponds provide critical foraging and resting habitat for a variety of bird species, primarily 

9933 migrating shorebirds (NJDEP, undated). Among the rare birds seen in The Meadows by 

9934 local birders are buff-breasted sandpipers, arctic tern, roseate tern, whiskered tern, 
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9935 Wilson’s phalarope, black rail, king rail, Hudsonian godwit, and black-necked stilt 

9936 (Kerlinger, undated). The Nature Conservancy, the United States Army Corps of 

9937 Engineers (USACE), and the New Jersey Department of Environmental Protection 

9938 (NJDEP) have undertaken an extensive restoration project in the Cape May Migratory 

9939 Bird Refuge, including beach replenishment to protect a mile-long stretch of sandy beach 

9940 that provides nesting habitat for the piping plover (federally listed as threatened), creation 

9941 of plover foraging ponds, and creation of island nesting sites for terns and herons (TNC, 

9942 2007). 

 9943 

9944 Estuarine Beaches. Estuarine beaches are largely disappearing in developed areas where 

9945 shoreline armoring is the preferred method of shore protection. The erosion or inundation 

9946 of bay islands would also reduce the amount of beach habitat. Many species of 

9947 invertebrates are found within or on the sandy substrate or beach wrack (seaweed and 

9948 other decaying marine plant material left on the shore by the tides) along the tide line of 

9949 estuarine beaches (Bertness, 1999). These species provide a rich and abundant food 

9950 source for bird species. Small beach invertebrates include isopods and amphipods, blood 

9951 worms, and beach hoppers, and beach macroinvertebrates include soft shell clams, hard 

9952 clams, horseshoe crabs, fiddler crabs, and sand shrimp (Shellenbarger Jones, 2008a). 

 9953 

9954 Northern diamondback terrapin nest on estuarine beaches in the Barnegat Bay area 

9955 (BBNEP, 2001). Local scientists consider coastal development, which destroys terrapin 

9956 nesting beaches and access to nesting habitat, to be one of the primary threats to 

9957 diamondback terrapins, along with predation, road kills, and crab trap bycatch (Strange, 
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9958 2008b, citing Wetland Institute [undated]). 

 9959 

9960 Loss of estuarine beach could also have negative impacts on various beach invertebrates, 

9961 including rare tiger beetles (Strange, 2008b). Two sub-species likely exist in coastal New 

9962 Jersey: Cicindela dorsalis dorsalis, the northeastern beach tiger beetle, which is a 

9963 federally listed threatened species and a state species of special concern and regional 

9964 priority, and Cicindela dorsalis media, the southeastern beach tiger beetle, which is state9965 listed as rare (NJDEP, 2001). In the mid-1990s, the tiger beetle was observed on the 

9966 undeveloped ocean beaches of Holgate and Island Beach. Current surveys do not indicate 

9967 whether this species is also found on the area’s estuarine beaches, but it feeds and nests in 

9968 a variety of habitats (USFWS, 1997). The current abundance and distribution of the 

9969 northeastern beach tiger beetle in the coastal bays is a target of research (State of New 

9970 Jersey, 2005). At present, there are plans to reintroduce the species in the study region at 

9971 locations where natural ocean beaches remain (State of New Jersey, 2005). 

 9972 

9973 Tidal Flats. The tidal flats of New Jersey’s back-barrier bays are critical foraging areas 

9974 for hundreds of species of shorebirds, passerines, raptors, and waterfowl (BBNEP, 2001). 

9975 Important shorebird areas in the study region include the flats of Great Bay Boulevard 

9976 Wildlife Management Area, North Brigantine Natural Area, and the Brigantine Unit of 

9977 the Forsythe Refuge (USFWS, 1997). The USFWS estimates that the extensive tidal flats 

9978 of the Great Bay alone total 1,358 ha (3,355 ac). Inundation of tidal flats with rising seas 

9979 would eliminate critical foraging opportunities for the area’s abundant avifauna. As tidal 

9980 flat area declines, increased crowding in remaining areas could lead to exclusion and 
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9981 mortality of many foraging birds (Galbraith et al., 2002; Erwin et al., 2004). Some areas 

9982 may become potential sea grass restoration sites, but whether or not “enhancing” these 

9983 sites as eelgrass areas is feasible will depend on their location, acreage, and sediment type 

9984 (Strange, 2008b). 

 9985 

9986 Shallow Nearshore Waters and Submerged Aquatic Vegetation (SAV). The Barnegat 

9987 Estuary is distinguished from the lagoons to the south by more open water and SAV and 

9988 less emergent marsh. Within the Barnegat Estuary, dense beds of eelgrass are found at 

9989 depths under 1 m, particularly on sandy shoals along the backside of Long Beach Island 

9990 and Island Beach, and around Barnegat Inlet, Manahawkin Bay, and Little Egg Inlet. 

9991 Eelgrass is relatively uncommon from the middle of Little Egg Harbor south to Cape 

9992 May, particularly locations where water depths are more than 1 m, such as portions of 

9993 Great South Bay (USFWS, 1997). 

 9994 

9995 Seagrass surveys from the 1960s through the 1990s indicate that there has been an overall 

9996 decline in seagrass beds in Barnegat Estuary, from 6,823 ha (16,847 ac) in 1968 to an 

9997 average of 5,677 ha (14,029 ac) during the period 1996 to 1998 (BBNEP, 2001). 

9998 Numerous studies indicate that eelgrass has high ecological value as a source of both 

9999 primary (Thayer et al., 1984) and secondary production (Jackson et al., 2001) in estuarine 

10000 food webs. In Barnegat Estuary eelgrass beds provide habitat for invertebrates, birds, and 

10001 fish that use the submerged vegetation for spawning, nursery, and feeding (BBNEP, 

10002 2001). Shallow water habitat quality may also be affected by adjacent shoreline 

10003 protections. A Barnegat Bay study found that where shorelines are bulkheaded, SAV, 
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10004 woody debris, and other features of natural shallow water habitat are rare or absent, with 

10005 a resulting reduction in fish abundance (Byrne, 1995). 

 10006 

10007 Marsh and Bay Islands. Large bird populations are found on marsh and dredge spoil 

10008 islands of the New Jersey back-barrier bays. These islands include nesting sites protected 

10009 from predators for a number species of conservation concern, including gull-billed tern, 

10010 common tern, Forster’s tern, least tern, black skimmer, American oystercatcher, and 

10011 piping plover (USFWS, 1997). Diamondback terrapins are also known to feed on marsh 

10012 islands in the bays (USFWS, 1997). 

 10013 

10014 Some of the small islands in Barnegat Bay and Little Egg Harbor extend up to about 1 m 

10015 above spring high water (Jones and Wang, 2008), but portions of other islands are very 

10016 low, and some low islands are currently disappearing. Mordecai (MLT, undated) and 

10017 other islands (Strange, 2008b) used by nesting common terns, Forster’s terns, black 

10018 skimmers, and American oystercatchers are vulnerable to sea-level rise and erosion 

10019 (MLT, undated). With the assistance of local governments, the Mordecai Land Trust is 

10020 actively seeking grants to halt the gradual erosion of Mordecai Island, an 18-ha (45-ac) 

10021 island just west of Beach Haven on Long Beach Island (MLT, undated). Members of the 

10022 land trust have documented a 37 percent loss of island area since 1930. The island’s 

10023 native salt marsh and surrounding waters and SAV beds provide habitat for a variety of 

10024 aquatic and avian species. NOAA National Marine Fisheries Service considers the island 

10025 and its waters Essential Fish Habitat for spawning and all life stages of winter flounder as 

10026 well as juvenile and adult stages of Atlantic sea herring, bluefish, summer flounder, scup, 
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10027 and black sea bass (MLT, undated). The island is also a strategically-located nesting 

10028 island for many of New Jersey’s threatened and endangered species, including black 

10029 skimmers, least terns, American bitterns, and both yellow-crowned and black-crowned 

10030 night herons (MLT, 2003). 

 10031 

10032 Sea-level fens. New Jersey has identified 12 sea-level fens, encompassing 126 acres. This 

10033 rare ecological community is restricted in distribution to Ocean County, New Jersey, 

10034 between Forked River and Tuckerton, in an area of artesian groundwater discharge from 

10035 the Kirkwood-Cohansey aquifer. Additional recent field surveys have shown possible 

10036 occurrences in the vicinity of Tuckahoe in Cape May and Atlantic counties (Walz et al., 

10037 2004). These communities provide significant wetland functions in the landscape as well 

10038 as supporting 18 rare plant species, of which one is state-listed as endangered. (Walz et 

10039 al., 2004). 

 10040 

10041 A1.C.2 Development, Shore Protection, and Coastal Policies 

10042 At least five state policies affect the response to sea-level rise along New Jersey’s 

10043 Atlantic Coast: the Coastal Facility Review Act, the Wetlands Act, the State Plan, an 

10044 unusually strong public trust doctrine, and the state’s strong support for beach 

10045 nourishment—and opposition to both erosion-control structures and shoreline retreat—

10046 along ocean shores. This section discusses the latter policy; the first four are discussed in 

10047 Section A1.D.2 of this Appendix. 

 10048 
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10049 In 1997, then-Governor Whitman promised coastal communities that “there will be no 

10050 forced retreat,” and that the government would not force people to leave the shoreline. 

10051 That policy does not necessarily mean that there will always be government help for 

10052 shore protection. Nevertheless, although subsequent administrations have not expressed 

10053 this view so succinctly, they have not withdrawn the policy either. In fact, the primary 

10054 debate in New Jersey tends to be about the level of public access required before a 

10055 community is eligible to receive beach nourishment, not the need for shore protection 

10056 itself (see Chapter 8 of this Product). 

10057 

10058 With extensive development and tourism along its shore, New Jersey has a wellestablished policy in favor of shore protection along the ocean78 10059 . The state generally 

10060 prohibits new hard structures along the ocean front; but that was not always the case. A 

10061 large portion of the Monmouth County shoreline was once protected with seawalls, with 

10062 a partial or total loss of beach (Pilkey et al., 1981). Today, beach nourishment is the 

10063 preferred method for reversing beach erosion and providing ocean front land with 

10064 protection from coastal storms (Mauriello, 1991). The entire Monmouth County shoreline 

10065 now has a beach in front of the old seawalls. Beach nourishment has been undertaken or 

10066 planned for at least one community in every coastal county from Middlesex along Raritan 

10067 Bay, to Salem along the Delaware River. Island Beach State Park, a barrier spit along the 

10068 central portion of Barnegat Bay just north of Long Beach Island, is heavily used by New 

10069 Jersey residents and includes the official beach house of the Governor. Although it is a 

 

78 For example, the primary coastal policy document during the Whitman administration suggested that 

even mentioning the term “retreat” would divide people and impede meaningful discussion of appropriate 

policies, in part because retreat can mean government restrictions on development or simply a decision by 

government not to fund shore protection (see NJDEP, 1997). Governor Whitman promised coastal mayors 

and residents that “there will be no forced retreat.” 
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10070 state park, it is currently included in the authorized USACE Project for beach 

nourishment from Manasquan to Barnegat Inlet. In the case of Cape May Meadows79 10071 , 

10072 environmental considerations have prompted shore protection efforts (USACE, 2008a). 

10073 The area’s critical freshwater ecosystem is immediately behind dunes that have eroded 

10074 severely as a result of the jetties protecting the entrance to the Cape May Canal. 

 10075 

10076 Some coastal scientists have suggested the possibility of disintegrating barrier islands 

10077 along the New Jersey shore (see Chapter 3). Although the bay sides of these islands are 

10078 bulkheaded, communities are unlikely to seriously consider the option of being encircled 

10079 by a dike as sea level rises (see Box A1.2). Nevertheless, Avalon uses a combination of 

10080 floodwalls and checkvalves to prevent tidal flooding; and Atlantic City’s stormwater 

10081 management system includes underground tanks with checkvalves. These systems have 

10082 been implemented to address current flooding problems; but they would also be a logical 

10083 first step in a strategy to protect low-lying areas with structural solutions as sea level 

rises80 10084 . Other authors have suggested that a gradual elevation of barrier islands is more 

10085 likely (see Box A1.2). 

 10086 

10087 Wetlands along the back-barrier bays of New Jersey’s Atlantic coast are likely to have 

10088 some room to migrate inland, because they are adjacent to large areas of non-tidal 

10089 wetlands. One effort at the state level to preserve such coastal resources is the state’s 

10090 Stormwater Management Plan, which establishes a special water resource protection area 

10091 that limits development within 91.4 m (300 ft) along most of its coastal shore (NJDEP 

 

79 The Meadows are within Cape May Point State Park and the Nature Conservancy’s Cape May Migratory 

Bird Refuge. 

80 See Chapter 5 of this Product for explanation of structural mechanisms to combat flooding. 
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10092 DWM, 2004). Although the primary objective of the regulation is to improve coastal 

10093 water quality and reduce potential flood damage, it serves to preserve areas suitable for 

10094 the landward migration of wetlands. 

 10095 
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10096 

10097 

 10098 

BOX A1.2: Shore Protection on Long Beach Island 

The effects of sea-level rise can be observed on both the ocean and bay sides of this 29-km (18-mi) long 

barrier island. Along the ocean side, shore erosion has threatened homes in Harvey Cedars and portions of 

Long Beach township. During the 1990s, a steady procession of dump trucks brought sand onto the beach 

from inland sources. In 2007, the USACE began to restore the beach at Surf City and areas immediately 

north. The beach had to be closed for a few weeks, however, after officials discovered that munitions 

(which had been dumped offshore after World War II) had been inadvertently pumped onto the beach. 

High tides regularly flood the main boulevard in the commercial district of Beach Haven, as well as the 

southern two blocks of Central Avenue in Ship Bottom. Referring to the flooded parking lot during spring 

tides, the billboard of a pizza parlor in Beach Haven Crest boasts “Occasional Waterfront Dining.” 

U.S. EPA’s 1989 Report to Congress used Long Beach Island as a model for analyzing alternative 

responses to rising sea level, considering four options: a dike around the island, beach nourishment and 

elevating land and structures, an engineered retreat which would include the creation of new bayside lands 

as the ocean eroded, and making no effort to maintain the island’s land area (U.S. EPA, 1989; Titus et al., 

1991). Giving up the island was the most expensive option (Weggel et al., 1989; Titus, 1990). The study 

concluded that a dike would be the least expensive in the short run, but unacceptable to most residents due 

to the lost view of the bay and risk of being on a barrier island below sea level (Titus, 1991). In the long 

run, fostering a landward migration would be the least expensive, but it would unsettle the expectations of 

bay front property owners and hence require a lead time of a few generations between being enacted and 

new bayside land actually being created. Thus, the combination of beach nourishment and elevating land 

and structures appeared to be the most realistic, and U.S. EPA used that assumption in its nationwide cost 

estimate (U.S. EPA, 1989; Titus et al., 1991). 

Long Beach Township, Ship Bottom, Harvey Cedars, and Beach Haven went through a similar thinking 

process in considering their preferred response to sea-level rise. In resolutions enacted by their respective 

councils, they concluded that a gradual elevation of their communities would be preferable to either dikes 

or the retreat option. In the last ten years, several structural moving companies have had ongoing 

operations, continually elevating homes (see Figure 12.5). 

.

Box Figure A1.2 Street flooding in Long Beach Island, New Jersey at one of the higher tides. 
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10099 A1.D. Delaware Estuary 

10100 A1.D.1 Environmenal Implications 

10101 On both sides of Delaware Bay, most shores are either tidal wetlands or sandy beaches 

10102 with tidal wetlands immediately behind them. In effect, the sandy beach ridges are 

10103 similar to the barrier islands along the Atlantic, only on a smaller scale. Several 

10104 substantial communities with wide sandy beaches on one side and marsh on the other side 

10105 are along Delaware Bay—especially on the Delaware side of the bay. Although these 

10106 communities are potentially vulnerable to inundation, shoreline erosion has been a more 

10107 immediate threat to these communities. Detailed discussions of the dynamics of Delaware 

10108 shorelines are found in Kraft and John (1976). 

 10109 

10110 Delaware Bay is home to hundreds of species of ecological, commercial, and recreational 

10111 value (Dove and Nyman, 1995). Unlike other estuaries in the Mid-Atlantic, the tidal 

10112 range is greater than the ocean tidal range, generally about 2 m. In much of Delaware 

10113 Bay, tidal marshes appear to be at the low end of their potential elevation range, 

10114 increasing their vulnerability to sea-level rise (Kearney et al., 2002). Recent research 

10115 indicates that 50 to 60 percent of Delaware Bay’s tidal marsh has been degraded, 

10116 primarily because the surface of the marshes is not rising as fast as the sea (Kearney et 

10117 al., 2002). One possible reason is that channel deepening projects and consumptive 

10118 withdrawals of fresh water have changed the sediment supply to the marshes 

10119 (Sommerfield and Walsh, 2005). Many marsh restoration projects are underway in the 

10120 Delaware Bay (cf. Teal and Peterson, 2005): dikes have been removed to restore tidal 

10121 flow and natural marsh habitat and biota; however, in some restoration areas invasion by 
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10122 common reed (Phragmites australis) has been a problem (Abel and Hagan, 2000; 

10123 Weinstein et al., 2000). 

 10124 

10125 The loss of tidal marsh as sea level rises would harm species that depend on these 

10126 habitats for food and shelter, including invertebrates, finfish, and a variety of bird species 

10127 (Kreeger and Titus, 2008). Great blue herons, black duck, blue and green-winged teal, 

10128 Northern harrier, osprey, rails, red winged blackbirds, widgeon, and shovelers all use the 

10129 salt marshes in Delaware Bay. Blue crab, killifish, mummichog, perch, weakfish, 

10130 flounder, bay anchovy, silverside, herring, and rockfish rely on tidal marshes for feeding 

10131 on the mussels, fiddler crabs, and other invertebrates and for protection from predators 

10132 (Dove and Nyman, 1995). 

 10133 

10134 Delaware Bay is a major stopover area for six species of migratory shorebirds, including 

10135 most of the Western Hemisphere’s population of red knot (USFWS, 2003). On their 

10136 annual migrations from South America to the Arctic, nearly a million shorebirds move 

10137 through Delaware Bay, where they feed heavily on invertebrates in tidal mudflats, and 

10138 particularly on horseshoe crab eggs on the bay’s sandy beaches and foreshores (Walls et 

10139 al., 2002). Horseshoe crabs have been historically abundant on the Delaware Bay shores. 

10140 A sea-level rise modeling study estimated that a 6-centimeter (cm) (2-ft) rise in relative 

10141 sea level over the next century could reduce shorebird foraging areas in Delaware Bay by 

10142 57 percent or more by 2100 (Galbraith et al., 2002). 

 10143 
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10144 Invertebrates associated with cordgrass stands in the low intertidal zone include grass 

10145 shrimp, ribbed mussel, coffee-bean snail, and fiddler crabs (Kreamer, 1995). Blue crab, 

10146 sea turtles, and shorebirds are among the many species that prey on ribbed mussels; 

10147 fiddler crabs are an important food source for bay anchovy and various species of 

10148 shorebirds (Kreamer, 1995). Wading birds such as the glossy ibis feed on marsh 

10149 invertebrates (Dove and Nyman, 1995). Waterfowl, particularly dabbling ducks, use low 

10150 marsh areas as a wintering ground. 

10151 

10152 Sandy beaches and foreshores account for the majority of the Delaware and New Jersey 

10153 shores of Delaware Bay. As sea level rises, beaches can be lost if either shores are 

10154 armored or if the land behind the existing beach has too little sand to sustain a beach as 

10155 the shore retreats (Nordstrom, 2005). As shown in Table A1.1, so far only 4 percent 

10156 (Delaware) and 6 percent (New Jersey) of the natural shores have been replaced with 

10157 shoreline armoring. Another 15 percent (Delaware) and 4 percent (New Jersey) of the 

10158 shore is developed. Although conservation areas encompass 58 percent of Delaware 

10159 Bay’s shores, they include only 32 percent of beaches that are optimal or suitable habitat 

10160 for horseshoe crabs (Kreeger and Titus, 2008).

 10161 

10162 Beach nourishment has been relatively common along the developed beach communities 

10163 on the Delaware side of the bay. Although beach nourishment can diminish the quality of 

10164 habitat for horseshoe crabs, nourished beaches are more beneficial than an armored 

10165 shore; most beach nourishment along the New Jersey shore of Delaware Bay has been 

10166 justified by environmental benefits (Kreeger and Titus, 2008; USACE 1998b,,c). 
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 10167 

Table A1.1 The shores of Delaware Bay: Habitat type and conservation status of shores suitable for horseshoe 

crabs. 

Shoreline length Delaware New Jersey New Jersey and 

Delaware 

By Habitat Type (percent of bay shoreline km % km % % 

Beach 68 74 62 42 54 

Armored Shore 3.7 4 8.3 6 5 

Organic 20 22 78 53 41 

Total Shoreline 91 100 148 100 100 

By Indicator of Future Shore Protection (km) 

Shore Protection Structures 2.7 2.9 5.1 3.4 3

Development 13 15 5.7 3.8 8 

By Suitability for Horseshoe Crab (percent of Bay shoreline 

Optimal Habitat 31.3 34 26.0 18 24 

Suitable Habitat 10.5 12 5.1 3.5 6.6 

Less Suitable Habitat 29.0 32 49.0 33 33 

Unsuitable Habitat 20.0 22 67.0 46 37 

Within Conservations Lands by Suitability for Horseshoe Crab (percent of equally suitable lands) 

Optimal Habitat 12.9 41 9.6 37 39 

Optimal and Suitable Habitat 13.6 33 9.8 32 32 

Optimal, Suitable, and Less Suitable Habitat 32.2 46 43.3 54 50 

All Shores 44.7 49 92.7 63 58 

 

 Source: Kreeger and Titus (2008), compiling data developed by Lathrop et al. (2006). 

 10168 

10169 Many Delaware Bay beaches have a relatively thin layer of sand. Although these small 

10170 beaches currently have enough sand to protect the marshes immediately inland from 

10171 wave action, some beaches may not be able to survive accelerated sea-level rise even in 

10172 areas without shoreline armoring, unless artificial measures are taken to preserve them 

10173 (Kreeger and Titus (2008). For example, Delaware has already nourished beaches with 

10174 the primary purpose of restoring horseshoe crab habitat (Smith et al., 2002)(see Box 

10175 A1.3.). 

 10176 

 10177 

 10178 
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 10179 

10180 BOX A1.3: Horseshoe Crabs and Estuarine Beaches 

10181 

10182 The Atlantic horseshoe crab (Limulus polyphemus), an ancient species that has survived virtually 

10183 unchanged for more than 350 million years, enters estuaries each spring to spawn along sandy beaches. The 

10184 species has experienced recent population declines, apparently due to overharvesting as well as habitat loss 

10185 and degradation (Berkson and Shuster, 1999). 

10186 

10187 

10188 

10189 

10190 

10191 

10192 

10193 

10194 

10195 Population Status and Sea-Level Rise 

10196 In Delaware Bay, as elsewhere along its range, horseshoe crabs depend on narrow sandy beaches and the 

10197 alluvial and sand bar deposits at the mouths of tidal creeks for essential spawning habitat. A product of 

10198 wave energy, tides, shoreline configuration, and over longer periods, sea-level rise, the narrow sandy 

10199 beaches utilized by horseshoe crabs are diminishing at sometimes alarming rates due to beach erosion as a 

10200 product of land subsidence and sea-level increases (Nordstrom, 1989; Titus et al., 1991). At Maurice Cove 

10201 in Delaware Bay, for example, portions of the shoreline have eroded at a rate of 4.3 m per year between 

10202 1842 and 1992 (Weinstein and Weishar, 2002); an estimate by Chase (1979) suggests that the shoreline 

10203 retreated 150 m landward in a 32-year period, exposing ancient peat deposits that are believed to be 

10204 suboptimal spawning habitat (Botton et al., 1988). If human infrastructure along the coast leaves estuarine 

10205 beaches little or no room to transgress inland as sea level rises, concomitant loss of horseshoe crab 

10206 spawning habitat is likely (Galbraith et al., 2002). Kraft et al. (1992) estimated this loss, along with 

10207 wetland “drowning”, as greater than 90 percent in Delaware Bay (about 33,000 ha). 

10208 

10209 Horseshoe Crab Spawning and Shorebird Migrations 

10210 Each spring, horseshoe crab spawning coincides with the arrival of hundreds of thousands of shorebirds 

10211 migrating from South America to their sub-Arctic nesting areas. While in Delaware Bay, shorebirds feed 

10212 extensively on horseshoe crab eggs to increase their depleted body mass before continuing their migration 

10213 (Castro and Myers, 1993; Clark, 1996). Individual birds may increase their body weight by nearly one-third 

10214 before leaving the area. There is a known delicate relationship between the horseshoe crab and red knots 

10215 (Baker et al., 2004). How other shorebirds might be affected by horseshoe crab population decline is 

10216 uncertain (Smith et al., 2002).

10217 Numerous other animals, including diamondback terrapins, and Kemp’s ridley sea turtles, 

10218 rely on the sandy beaches of Delaware Bay to lay eggs or forage on invertebrates such as 

10219 amphipods and clams. When tides are high, numerous fish also forage along the 

10220 submerged sandy beaches, such as killifish, mummichog, rockfish, perch, herring, 

10221 silverside, and bay anchovy (Dove and Nyman, 1995). 
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 10222 

10223 A1.D.2 Development, Shore Protection, and Coastal Policies

10224 A1.D.2.1 New Jersey 

10225 Policies that may be relevant for adapting to sea-level rise in New Jersey include policies 

10226 related to the Coastal Facility Review Act (CAFRA), the (coastal) Wetlands Act of 1970, 

10227 the State Plan, an unusually strong public trust doctrine, and strong preference for beach 

10228 nourishment along the Atlantic Ocean over hard structures or shoreline retreat. This 

10229 Section discusses the first four of these policies (nourishment of ocean beaches is 

10230 discussed in Section A1.C of this Appendix). 

 10231 

10232 CAFRA applies to all shores along Delaware Bay and the portion of the Delaware River 

10233 south of Killcohook National Wildlife Area, as well as most tidal shores along the 

10234 tributaries to Delaware Bay. The act sometimes limits development in the coastal zone, 

10235 primarily to reduce runoff of pollution into the state’s waters (State of New Jersey, 2001). 

10236 Regulations promulgated under the Wetlands Act of 1970 prohibit development in tidal 

10237 wetlands unless the development is water-dependent and there is no prudent alternative 

10238 (NJAC 7:7E-2.27 [c]). Regulations prohibit development of freshwater wetlands under 

10239 most circumstances (NJAC 7:7E-2.27 [c]). The regulations also prohibit development 

10240 within 91.4 m (300 ft of tidal wetland, unless the development has no significant adverse 

10241 impact on the wetlands (NJAC 7:7-3.28 [c]). These regulations, like Maryland’s Critical 

10242 Areas Act (see Section A1.E.2), may indirectly reduce the need for shore protection by 

10243 ensuring that homes are set back farther from the shore than would otherwise be the case 

10244 (NOAA 2007, see Section 6.2 in Chapter 6). For the same reason, existing restrictions of 
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10245 development in nontidal wetlands (see Section 10.3) may also enable tidal wetlands to 

10246 migrate inland. 

 10247 

10248 The New Jersey state plan provides a statewide vision of where growth should be 

10249 encouraged, tolerated, and discouraged—but local government has the final say. In most 

10250 areas, lands are divided into five planning areas. The state encourages development in (1) 

10251 metropolitan and (2) suburban planning areas, and in those (3) fringe planning areas that 

10252 are either already developed or part of a well-designed new development. The state 

10253 discourages development in most portions of (4) rural planning areas and (5) land with 

10254 valuable ecosystems, geologic features, or wildlife habitat, including coastal wetlands 

10255 and barrier spits/islands (State of New Jersey, 2001). However, even these areas include 

10256 developed enclaves, known as “centers” where development is recognized as a reality 

10257 (State of New Jersey, 2001). The preservation of rural and natural landscapes in portions 

10258 of planning areas (4) and (5) is likely to afford opportunities for wetlands to migrate 

10259 inland as sea level rises. Nevertheless, New Jersey has a long history of building dikes 

10260 along Delaware Bay and the Delaware River to convert tidal wetlands to agricultural 

10261 lands (see Box 5.1) and dikes still protect some undeveloped lands. 

 10262 

10263 

10264 

10265 

10266 

10267 

10268 

10269 

10270 

10271 --Start text box-- 

10272 

10273 BOX A1.4: The Gibbstown Levee, New Jersey 

10274 
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10275 The Gibbstown Levee along the Delaware River in New Jersey once served a function similar to the dikes 

10276 in Cumberland County, preventing tidal inundation and lowering the water table to a level below mean sea 

10277 level. When the dike was built 300 years ago (USACE, undated[a]), the tides were 1 m lower and the 

10278 combination dike and tide gate kept the water levels low enough to permit cultivation. But rising sea level 

10279 and land subsidence have left this land barely above low tide, and many lands drain too slowly to 

10280 completely drain during low tide. Hence, farmland has converted to non-tidal wetland. 

10281 

10282 By keeping the creek a meter or so lower than it would be if it rose and fell with the tides, the levee 

10283 improves drainage during rainstorms for Greenwich Township. Nevertheless, it is less effective today than 

10284 when the sea was 50 to 100 cm lower. During extreme rainfall, the area can flood fairly easily because the 

10285 tide gates have to be closed most of the day. Heavy rain during a storm surge is even more problematic 

10286 because for practical purposes there is no low tide to afford the opportunity to get normal drainage by 

10287 opening the tide gate. Evacuations were necessary during hurricane Floyd when part of this dike collapsed 

10288 as a storm tide brought water levels of more than ten feet above mean low water (NCDC, 1999). 

10289 

10290 Officials in Greenwich Township are concerned that the dikes in Gloucester County are in danger of 

10291 failing. “The Gibbstown Levee was repaired in many places in 1962 by the U.S. Army Corps of Engineers 

10292 under Public Law 84-99” (USACE, 2004). Part of the problem appears to be that most of these dikes are 

10293 the responsibility of meadow companies originally chartered in colonial times. These companies were 

10294 authorized to create productive agricultural lands from tidal marshes. Although harvests of salt hay once 

10295 yielded more than enough revenue to maintain the dikes, this type of farming became less profitable during 

10296 the first half of the twentieth century. Moreover, as sea level has continued to rise, the land protected by the 

10297 dikes has mostly reverted to marsh (Weinstein et al., 2000; Abel et al., 2000). Revenues from these lands, 

10298 if any, are insufficient to cover the cost of maintaining the dikes (DiMuzio, 2006). As a result, the dikes are 

10299 deteriorating, leading officials to fear a possible catastrophic dike failure during storm, or an increase in 

10300 flood insurance rates (DELO, 2006). The officials hope to obtain federal funding (DELO, 2006). 

10301 

10302 Even if these dikes and their associated tide gates are fortified, the dry land will gradually be submerged 

10303 unless pumping facilities are installed (see Section 6.2 in Chapter 6), because much of the area is barely 

10304 above low tide even today (Titus and Wang 2008). Although freshwater marshes in general seem likely to 

10305 be able to keep pace with rising sea level (Reed et al., 2008), wetlands behind dikes do not always fare as 

10306 well as those exposed to normal tidal currents (Reed et al., 2008). Over longer periods of time, increases in 

10307 salinity of the Delaware River resulting from rising sea level and reduced river flows during droughts could 

10308 enable saltwater to invade these fresh marshes (Hull and Titus, 1986), which would convert them to open 

10309 water ponds. 

10310 

10311 If pumping facilities are not sufficient for a daily pumping of all the very low lands protected by the dikes, 

10312 the primary impact of the dikes could be to prevent flooding from storm surges and ordinary tides. For the 

10313 isolated settlements along Marsh Dike Road and elsewhere, elevating homes and land surfaces may be 

10314 possible; although property values are less than along the barrier islands, sources for fill material are closer. 

10315 One could envision that Gibbstown, Bridgetown, and other more populated communities could be encircled 

10316 with a ring dike with a pumping system that drains only the densely developed area; or they too may 

10317 elevate land as the sea rises.

10318 

10319 --End box--

10320 
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10321 In Cumberland County, salt marsh has been reclaimed for agricultural purposes for more 

10322 than 200 years (Sebold, 1992 and references therein). Over the last few decades, many of 

10323 the dikes that were constructed have been dismantled. Some have failed during storms. 

10324 Others have been purchased by conservation programs seeking to restore wetlands, most 

10325 notably Public Service Enterprise Group (PSEG) in its efforts to offset possible 

10326 environmental effects of a nuclear power plant. Although the trend is for dike removal, 

10327 the fact that diked farms have been part of the landscape for centuries leads one to the 

10328 logical inference that dikes may be used to hold back a rising sea once again. Cumberland 

10329 County has relatively little coastal development, yet the trend in coastal communities that 

10330 have not become part of a conservation program has been for a gradual retreat from the 

10331 shore. Several small settlements along Delaware Bay are gradually being abandoned. 

 10332 

10333 The state plan contemplates a substantial degree of agricultural and environmental 

10334 preservation along the Delaware River and its tidal tributaries in Salem and lower 

10335 Gloucester County. An agricultural easement program in Gloucester County reinforces 

10336 that expectation. Farther up the river, in the industrial and commercial areas, most of the 

10337 shoreline is already bulkheaded, to provide the vertical shore that facilitates docking—but 

10338 the effect is also to stop coastal erosion. The eventual fate of existing dikes, which protect 

10339 lightly developed areas, is unclear (Box A1.4). 

10340 

10341 The public trust doctrine in New Jersey has two unique aspects. First, the public has an 

10342 easement along the dry beach between mean high water and the vegetation line. Although 

10343 other states have gradually acquired these easements in most recreational communities, 
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10344 few states have general access along the dry beach. As a result, people are entitled to 

10345 walk along river and bay beaches. The laws of Delaware and Pennsylvania, by contrast, 

10346 grant less public access along the shore. In most states, the public owns the land below 

10347 mean high water. In these two states, the public owns the land below mean low water. 

10348 The public has an easement along the wet beach between mean low and mean high water, 

10349 but only for navigation, fishing, and hunting—not for recreation (see Chapter 8 of this 

10350 Product for additional details) 

 10351 

10352 Second, the New Jersey Supreme Court has held that the public is entitled to 

perpendicular access to the beach81 10353 . The holding does not mean that someone can 

10354 indiscriminately walk across any landowner’s property to get to the water, but it does 

10355 require governments to take prudent measures to ensure that public access to the water 

accompanies new subdivisions82 10356 . 

 10357 

10358 As trustee, the New Jersey Department of Environmental Protection has promulgated 

10359 rules preserving the public trust rights to parallel and perpendicular access. The 

10360 regulations divide new construction (including shore protection structures) into three 

10361 classes: single family homes (or duplexes); development with two or three homes; and all 

10362 other residential and nonresidential development. Along most of the tidal Delaware 

10363 River, any development other than a single family home requires a public walkway at 

10364 least 3 m (10 ft) wide along the shore. By contrast, along Delaware Bay, areas where one 

 

81 Matthews v Bay Head Improvement Association, 471 A.2d 355. Supreme Court of NJ (1984). 82 Federal law requires similar access before an area is eligible for beach nourishment. 
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10365 might walk along the beach rather than require a walkway, the regulations have a more 

10366 general requirement for public access. (See Table A1.2). 

Table A1.2 New Jersey Regulatory Requirements for (Parallel) Access along, and (Perpendicular) to 

the Shore for New Development or Shore Protection Structures Along Delaware Estuary.

 Single Family4 Two or Three Residential 

Structures5

All other Development6

Designated Urban 

Rivers1

No 

requirement 

Along the shore: 20-ft 

preservation buffer, including 

10-ft wide walkway 

To the shore: 10-ft wide 

walkway every half mile. 

Along the Shore: 30-ft 

preservation buffer, including 

16-ft wide walkway 

To the Shore: 20-ft wide 

preservation buffer, including 

10-ft wide walkway, every half 

mile 

Beaches along 

Major Bodies of 

Water2

Access along 

and to the 

beach is 

required. 

Access along and to the beach 

is required. 

Access along and to the beach 

is required. 

All other coastal 

areas (except 

Hudson River) 

No 

requirement 

Alternative access on site or 

nearby. 

Access along the beach and 

shore is required. 

1

 Within this region, Cohansey River within Bridgeton, Maurice River within Millville, and Delaware 

River from the CAFRA boundary upstream to the Trenton Makes Bridge (Trenton). Also applies to 

Arthur Kill, Kill Van Kull west of Bayonne Bride, Newark Bay, Elizabeth Riber, Hackwnsask River, 

Rahway River, and Raritan River. 

2

 Delaware Bay within this region. Also Atlantic Ocean, Sandy Hook Bay, and Raritan Bay. 3 See Section B of this Appendix for Hudson River requirements. 

4 NJAC 7:7E-8.11 (f)(6-7) 

5 NJAC 7:7E-8.11 (f)(4-5) 

6 NJAC 7:7E-8.11 (d-e) 

 10367 

10368 A1.D.2.2 Delaware 

10369 Kent County does not permit subdivisions—and generally discourages most 

10370 development—in the 100-year coastal floodplain, as does New Castle County south of 

the Chesapeake and Delaware Canal83 10371 . Because the 100-year floodplain for storm surge 

10372 extends about 2 m above spring high water, which is often more than one kilometer 

10373 inland, the floodplain regulations often require a greater setback than the erosion-hazard 

10374 (see e.g., A1.G.2) and environmental (e.g., A1.E.2 and A1.F.2) setbacks elsewhere in the 

10375 mid-Atlantic. Thus, a greater amount of land may be available for potential wetland 

 

83 See Kent County Ordinances § 7.3 and New Castle Ordinance 40.10.313 
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10376 migration (see Section 6.2 in Chapter 6). Nevertheless, if sea level continues to rise, it is 

10377 logical to assume that this buffer would not last forever. 

 10378 

10379 Preservation easements and land purchases have also contributed to a major conservation 

10380 buffer (DDA, 2004), which would leave room for wetlands to migrate inland as sea level 

10381 rises (see Chapter 6.2). The state is purchasing agricultural preservation easements in the 

10382 coastal zone, and a significant portion of the shore is in Prime Hook or Bombay Hook 

10383 National Wildlife Refuge. The majority of the shore south of the canal is part of some 

10384 form of preservation or conservation land. 

 10385 

10386 A1.D.2.3 Pennsylvania 

Pennsylvania84 is the only state in the nation along tidal water without an ocean coast85 10387 . 

10388 As a result, the state’s sensitivity to sea-level rise is different than other states. Floods in 

10389 the tidal Delaware River are as likely to be caused by extreme rainfall over the watershed 

10390 as storm surges. The Delaware River is usually fresh along almost all of the Pennsylvania 

10391 shore. Because Philadelphia relies on freshwater intakes in the tidal river, the most 

10392 important impact may be the impact of salinity increases from rising sea level on the 

10393 city’s water supply (Hull and Titus, 1986). 

 10394 

10395 The state of Pennsylvania has no policies that directly address the issue of sea-level 

rise86 10396 . Nevertheless, the state has several coastal policies that might form the initial basis 

 

84 This section only addresses the Pennsylvania side of the river because Section C in this Appendix 

addressed the policy context for shore protection in New Jersey. 

85 This statement also applies to the District of Columbia. 86 Philadelphia’s flood regulations do consider sea level rise. 
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10397 for a response to sea-level rise, including state policies on tidal wetlands and floodplains, 

10398 public access, and redeveloping the shore in response to the decline of water-dependent 

10399 industries. 

 10400 

10401 Tidal Wetlands and Floodplains 

Pennsylvania’s Dam Safety and Waterway Management Rules and Regulations87 10402 require 

10403 permits for construction in the 100-year floodplain or wetlands. The regulations do not 

10404 explicitly indicate whether landowners have a right to protect property from erosion or 

10405 rising water level. A permit for a bulkhead or revetment seaward of the high-water mark 

10406 can be awarded only if the project will not have a “significant adverse impact” on the 

10407 “aerial extent of a wetland” or on a “wetland’s values and functions”. A bulkhead 

10408 seaward of the high-water mark, however, eliminates the tidal wetlands on the landward 

10409 side. If such long-term impacts were viewed as “significant,” permits for bulkheads could 

10410 not be awarded except where the shore was already armored. But the state has not viewed 

10411 the elimination of mudflats or beaches as “significant” for purposes of these regulations; 

10412 hence it is possible to obtain a permit for a bulkhead. 

 10413 

10414 The rules do not restrict construction of bulkheads or revetments landward of the high 

10415 water mark. However, they do prohibit permits for any “encroachment located in, along, 

10416 across or projecting into a wetland, unless the applicant affirmatively demonstrates 

that...the ... encroachment will not have an adverse impact on the wetland...”88 10417 . 

 

87 These regulations were issued pursuant to the Dam Safety and Encroachment Act of 1978. Laws of 

Pennsylvania, The Dam Safety and Encroachments Act of November 26, 1978, P.L. 1375, No. 325. 

88 Pennsylvania Code, Chapter 105. Dam Safety and Waterway Management, Pennsylvania Department of 

Environmental Protection, 1997. Subchapter 105.18b. 
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10418 Therefore, shoreline armoring can eliminate coastal wetlands (or at least prevent their 

inland expansion89 10419 ) as sea level rises by preventing their landward migration. Like the 

10420 shore protection regulations, Pennsylvania’s Chapter 105 floodplains regulations consider 

10421 only existing floodplains, not the floodplains that would result as the sea rises. 

10422 

10423 Public Access 

10424 Public access for recreation is an objective of the Pennsylvania Coastal Zone 

10425 Management program. This policy, coupled with ongoing redevelopment trends in 

10426 Pennsylvania, may tend to ensure that future development includes access along the 

10427 shore. If the public access is created by setting development back from the shore, it may 

10428 tend to also make a gradual retreat possible. If keeping public access is a policy goal of 

10429 the governmental authority awarding the permit for shore protection, then public access 

10430 need not be eliminated, even if shores are armored (see Titus, 1998 and Table A1.2). 

 10431 

10432 Development and Redevelopment 

10433 Industrial, commercial, residential, recreational, wooded, vacant, transportation, and 

10434 environmental land uses all occupy portions of Pennsylvania’s 100-km coast. Generally 

10435 speaking, however, the Pennsylvania coastal zone is consistently and heavily developed. 

10436 Only about 18 percent of the coastal area is classified as undeveloped (DVRPC, 2003). 

10437 Much of the shoreline has been filled or modified with bulkheads, docks, wharfs, piers, 

 

89 Chapter 3 of this Product concludes that most tidal wetlands in Pennsylvania are likely to keep pace with 

projected rates of sea level rise. However, that finding does not address erosion of wetlands at their seaward 

boundary. Even though wetlands can keep vertical pace with the rising water level, narrow fringing 

wetlands along rivers can be eliminated by shoreline armoring as their seaward boundaries erode and their 

landward migration is prevented. Moreover, even where the seaward boundary keeps pace, preventing an 

expansion of wetlands might be viewed as significant. 
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10438 bulkheads, revetments and other hard structures over the past two centuries (DVRPC, 

10439 2000). 

 10440 

10441 The Pennsylvania coast is moving from an industrial to a post-industrial landscape. The 

10442 coastal zone is still dominated by manufacturing and industrial land uses, but a steady 

10443 decline in the industrial economy over the past 60 years has led to the abandonment of 

10444 many industrial and manufacturing facilities. Some of these facilities sit empty and idle; 

10445 others have been adapted for uses that are not water dependent. 

 10446 

10447 A majority of Pennsylvania’s Delaware River shore is classified as developed, but sizable 

10448 expanses (especially near the water) are blighted and stressed (DVRPC, 2003). Because 

10449 of the decaying industrial base, many residential areas along the Delaware River have 

10450 depressed property values, declining population, high vacancy rates, physical 

10451 deterioration, and high levels of poverty and crime (DVRPC, 2003). Many—perhaps 

10452 most—of the refineries, chemical processing plants, and other manufacturing facilities 

10453 that operate profitably today may close in the next 50 to 100 years. (DVRPC, 2003) 

 10454 

10455 New paradigms of waterfront development have emerged that offer fresh visions for 

10456 southeastern Pennsylvania’s waterfront. In late 2001, Philadelphia released the 

10457 Comprehensive Redevelopment Plan for the North Delaware Riverfront—a 25-year 

10458 redevelopment vision for a distressed ten-mile stretch of waterfront led by the design firm 

10459 Field Operations. Delaware County, meanwhile, developed its Coastal Zone 

10460 Compendium of Waterfront Provisions (1998) to guide revitalization efforts along its 
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10461 coast. Likewise, Bucks County just finished a national search for a design firm to create a 

10462 comprehensive plan outlining the revitalization of its waterfront. Meanwhile, the 

10463 Schuylkill River Development Corporation produced the Tidal Schuylkill River Master 

10464 Plan. 

 10465 

10466 All of these plans and visions share common elements. They view the region’s 

10467 waterfronts as valuable public amenities that can be capitalized on, and they view the 

10468 estuary as something for the region to embrace, not to turn its back on. They emphasize 

10469 public access along the water’s edge, the creation of greenways and trails, open spaces, 

10470 and the restoration of natural shorelines and wetlands where appropriate (DRCC, 2006). 

 10471 

10472 A1.E. The Atlantic Coast of Virginia, Maryland, and 

10473 Delaware (including coastal bays)

10474 Between Delaware and Chesapeake Bays is the land commonly known as the Delmarva 

10475 Peninsula. The Atlantic coast of the Delmarva consists mostly of barrier islands separated 

10476 by tidal inlets of various sizes (Theiler and Hammar-Klose, 1999; Titus et al., 1985). 

10477 Behind these barrier islands, shallow estuaries and tidal wetlands are found. The large 

10478 area of tidal wetlands behind Virginia’s barrier islands to the south are mostly mudflats; 

10479 marshes and shallow open water are more common in Maryland and adjacent portions of 

10480 Virginia and Delaware. The barrier islands themselves are a small portion of the low land 

10481 in this region (Titus and Richman, 2001). The northern portion of the Delaware shore 

10482 consists of headlands, rather than barrier islands (see Chapter 3 of this Product). 

 10483 
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10484 A1.E.1 Environmental Implications 

10485 Tidal Marshes and Marsh Islands. The region’s tidal marshes and marsh-fringed bay 

10486 islands provide roosting, nesting, and foraging areas for a variety of bird species, both 

10487 common and rare, including shorebirds (piping plover, American oystercatcher, spotted 

10488 sandpiper), waterbirds (gull-billed, royal, sandwich, and least terns and black ducks) and 

10489 wading birds such as herons and egrets (Conley, 2004). Particularly at low tide, the 

10490 marshes provide forage for shorebirds such as sandpipers, plovers, dunlins, and 

10491 sanderlings (Burger et al., 1997). Ducks and geese, including Atlantic brants, 

10492 buffleheads, mergansers, and goldeneyes, overwinter in the bays’ marshes (DNREC, 

10493 undated). The marshes also provide nesting habitat for many species of concern to federal 

10494 and state agencies, including American black duck, Nelson’s sparrow, salt marsh sharp10495 tailed sparrow, seaside sparrow, coastal plain swamp sparrow, black rail, Forster’s tern, 

10496 gull-billed tern, black skimmers, and American oystercatchers (Erwin et al., 2006). 

 10497 

10498 The marshes of the bay islands in particular are key resources for birds, due to their 

10499 relative isolation and protection from predators and to the proximity to both upland and 

10500 intertidal habitat. For example, hundreds of horned grebes prepare for migration at the 

10501 north end of Rehoboth Bay near Thompson’s Island (Ednie, undated). Several bird 

10502 species of concern in this region nest on shell piles (shellrake) on marsh islands, 

10503 including gull-billed terns, common terns, black skimmers, royal tern, and American 

10504 oystercatchers (Erwin, 1996; Rounds et al., 2004). Dredge spoil islands in particular are a 

10505 favorite nesting spot for the spotted sandpiper, which has a state conservation status of 

10506 vulnerable to critically imperiled in Maryland, Delaware, and Virginia (Natureserve, 
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10507 2008). However, marsh islands are also subject to tidal flooding, which reduces the 

10508 reproductive success of island-nesting birds (Eyler et al., 1999). 

 10509 

10510 Sea-level rise is considered a major threat to bird species in the Virginia Barrier 

10511 Island/Lagoon Important Bird Area (IBA) (Watts, 2006). Biologists at the Patuxent 

10512 Wildlife Research Center suggest that submergence of lagoonal marshes in Virginia 

10513 would have a major negative effect on marsh-nesting birds such as black rails, seaside 

10514 sparrows, saltmarsh sharp-tailed sparrows, clapper rails, and Forster’s terns (Erwin et al., 

10515 2004). The U.S. Fish and Wildlife Service considers black rail and both sparrow species 

10516 “birds of conservation concern” because populations are already declining in much of 

10517 their range (USFWS, 2002). The number of bird species in Virginia marshes was found 

10518 to be directly related to marsh size; the minimum marsh size found to support significant 

10519 marsh bird communities was 4.1 to 6.7 ha (10 to 15 ac) (Watts, 1993). 

 10520 

10521 The region’s tidal marshes also support a diversity of resident and transient estuarine and 

10522 marine fish and shellfish species that move in and out of marshes with the tides to take 

10523 advantage of the abundance of decomposing plants in the marsh, the availability of 

10524 invertebrate prey, and refuge from predators (Boesch and Turner, 1984; Kneib, 1997). 

10525 Marine transients include recreationally and commercially important species that depend 

10526 on the marshes for spawning and nursery habitat, including black drum, striped bass, 

10527 bluefish, Atlantic croaker, sea trout, and summer flounder. Important forage fish that 

10528 spawn in local marsh areas include spot, menhaden, silver perch, and bay anchovy. 
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10529 Shellfish species found in the marshes include clams, oysters, shrimps, ribbed mussels, 

10530 and blue crabs (Casey and Doctor, 2004). 

 10531 

10532 Salt Marsh Adaptation to Sea-level Rise. Salt marshes occupy thousands of acres in 

10533 eastern Accomack and Northampton counties (Fleming et al., 2006). Marsh accretion 

10534 experts believe that most of these marshes are keeping pace with current rates of sea-level 

10535 rise, but are unlikely to continue to do so if the rate of sea-level rise increases by another 

10536 2 mm per year (Strange 2008c, interpreting the findings of Reed et al., 2008). However, 

10537 some very localized field measurements indicate that accretion rates may be insufficient 

10538 to keep pace even with current rates of sea-level rise (Strange, 2008d). For instance, 

10539 accretion rates as low as 0.9 mm per year (Phillips Creek Marsh) and as high as 2.1 mm 

10540 per year (Chimney Pole Marsh) have been reported (Kastler and Wiberg, 1996), and the 

10541 average relative sea-level rise along the Eastern Shore is estimated as 2.8 to 4.2 mm per 

10542 year (May, 2002). 

 10543 

10544 In some areas, marshes may be able to migrate onto adjoining dry lands. For instance, 

10545 lands in Worcester County that are held for the preservation of the coastal environment 

10546 might allow for wetland migration. Portions of eastern Accomack County that are 

10547 opposite the barrier islands and lagoonal marshes owned by The Nature Conservancy are 

10548 lightly developed today, and in some cases already converting to marsh. In unprotected 

10549 areas, marshes may be able to migrate inland in low-lying areas. From 1938 to 1990 

10550 mainland salt marshes on the Eastern Shore increased in area by 8.2 percent, largely as a 

10551 result of encroachment of salt marsh into upland areas (Kastler and Wiberg, 1996). 
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 10552 

10553 The marsh islands of the coastal bays are undergoing rapid erosion; for example, Big 

10554 Piney Island in Rehoboth Bay experienced erosion rates of 10 m (30 ft) per year between 

10555 1968 and 1981, and is now gone (Swisher, 1982; Strange et al., 2008). Seal Island in 

10556 Little Assawoman Bay is eroding rapidly after being nearly totally devegetated by greater 

10557 snow geese (Strange, 2008c). Island shrinking is also apparent along the Accomack 

10558 County, Virginia shore; from 1949 to 1990, Chimney Pole marsh showed a 10 percent 

10559 loss to open water (Kastler and Wiberg, 1996). The United States Army Corps of 

10560 Engineers (USACE) has created many small dredge spoil islands in the region, many of 

10561 which are also disappearing as a result of erosion (Federal Register, 2006). 

 10562 

10563 Sea-Level Fens. The rare sea-level fen vegetation community is found in a few locations 

10564 along the coastal bays, including the Angola Neck Natural Area along Rehoboth Bay in 

10565 Delaware and the Mutton Hunk Fen Natural Area Preserve fronting Gargathy Bay in 

10566 eastern Accomack County (VA DCR, undated [a][b]). The Division of Natural Heritage 

10567 within the Virginia Department of Conservation and Recreation believes that chronic sea10568 level rise with intrusions of tidal flooding and salinity poses “a serious threat to the long10569 term viability” of sea-level fens (VA DCR, 2001). 

 10570 

10571 Shallow Waters and Submerged Aquatic Vegetation (SAV). Eelgrass beds are essential 

10572 habitat for summer flounder, bay scallop, and blue crab, all of which support substantial 

10573 recreational and commercial fisheries in the coastal bays (MCBP, 1999). Various 

10574 waterbirds feed on eelgrass beds, including brant, canvasback duck, and American black 
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10575 duck (Perry and Deller, 1996). Shallow water areas of the coastal bays that can maintain 

10576 higher salinities also feature beds of hard and surf clams (DNREC, 2001). 

 10577 

10578 Tidal Flats. Abundant tidal flats in this region provide a rich invertebrate food source for 

10579 a number of bird species, including whimbrels, dowitchers, dunlins, black-bellied 

10580 plovers, and semi-palmated sandpipers (Watts and Truitt, 2002). Loss of these flats could 

10581 have significant impacts. For example, 80 percent of the Northern Hemisphere’s 

10582 whimbrel population feeds on area flats, in large part on fiddler crabs (TNC, 2006). The 

10583 whimbrel is considered a species “of conservation concern” by the United States Fish and 

10584 Wildlife Service, Division of Migratory Bird Management (USFWS, 2002). 

 10585 

10586 Beaches. Loss of beach habitat due to sea-level rise and erosion below protective 

10587 structures could have a number of negative consequences for species that use these 

10588 beaches: 

10589  Horseshoe crabs rarely spawn unless sand is at least deep enough to nearly cover 

10590 their bodies, about 10 cm (4 inches [in]) (Weber, 2001). Shoreline protection 

10591 structures designed to slow beach loss can also block horseshoe crab access to 

10592 beaches and can entrap or strand spawning crabs when wave energy is high (Doctor 

10593 and Wazniak, 2005). 

10594  The rare northeastern tiger beetle depends on beach habitat (USFWS, 2004b). 

10595  Photuris bethaniensis is a globally rare firefly located only in interdunal swales on 

10596 Delaware barrier beaches (DNREC, 2001). 
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10597  Erosion and inundation may reduce or eliminate beach wrack communities of the 

10598 upper beach, especially in developed areas where shores are protected (Strange, 

10599 2008c). Beach wrack contains insects and crustaceans that provide food for many 

10600 species, including migrating shorebirds (Dugan et al., 2003). 

10601  Many rare beach-nesting birds, such as piping plover, least tern, common tern, black 

10602 skimmer, and American oystercatcher, nest on the beaches of the coastal bays 

10603 (DNREC, 2001) 

 10604 

10605 Coastal Habitat for Migrating Neotropical Songbirds. Southern Northampton County is 

10606 one of the most important bird areas along the Atlantic Coast of North America for 

10607 migrating neotropical songbirds such as indigo buntings and ruby-throated hummingbirds 

10608 (Watts, 2006). Not only are these birds valued for their beauty but they also serve 

10609 important functions in dispersing seeds and controlling insect pests. It is estimated that a 

10610 pair of warblers can consume thousands of insects as they raise a brood (Mabey et al., 

10611 undated). Migrating birds concentrate within the tree canopy and thick understory 

10612 vegetation found within the lower 10 km (6 mi) of the peninsula within 200 m (650 ft) of 

10613 the shoreline. Loss of this understory vegetation as a result of rising seas would eliminate 

10614 this critical stopover area for neotropical migrants, many of which have shown consistent 

10615 population declines since the early 1970s (Mabey et al., undated) 

 10616 

10617 A1.E.2 Development, Shore Protection, and Coastal Policies 

10618 A1.E.2.1 Atlantic Coast 
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10619 Less than one-fifth of the Delmarva’s ocean coast is developed, and the remaining lands 

10620 are owned by private conservation organizations or government agencies. Almost all of 

10621 the Virginia Eastern Shore’s 124-km (77-mi) ocean coast is owned by the U.S. Fish and 

Wildlife Service, NASA, the State, or The Nature Conservancy90 10622 . Of Maryland’s 51 km 

10623 (32 mi) of ocean coast, 36 km (22 mi) are along Assateague Island National Seashore. 

10624 The densely populated Ocean City occupies approximately 15 km (9 mi). More than 

10625 three-quarters of the barrier islands and spits in Delaware are part of Delaware Seashore 

10626 State Park, while the mainland coast is about evenly divided between Cape Henlopen 

10627 State Park and resort towns such as Rehoboth, Dewey Beach, and Bethany Beach. With 

10628 approximately 15 km of developed ocean coast each, Maryland and Delaware have 

10629 pursued beach nourishment to protect valuable coastal property and preserve the beaches 

10630 that make the property so valuable (Hedrick et al., 2000). 

 10631 

10632 With development accounting for only 15 to 20 percent of the ocean coast, the natural 

10633 shoreline processes are likely to dominate along most of these shores. Within developed 

10634 areas, counteracting shoreline erosion in developed areas with beach nourishment may 

10635 continue as the primary activity in the near term. A successful alternative to beach 

10636 nourishment, as demonstrated by a USACE (2001a) and National Park Service project to 

10637 mitigate jetty impacts along Assateague Island, is to restore sediment transport rates by 

10638 mechanically bypassing sand from the inlet and tidal deltas into the shallow nearshore 

10639 areas that have been starved of their natural sand supply. Beginning in 1990, the USACE 

10640 and the Assateague Island National Seashore partnered to develop a comprehensive 

 

90 A few residential structures are on Cedar Island, and Cobbs and Hog Islands have some small private 

inholdings (Ayers, 2005).
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10641 restoration plan for the northern end of Assateague Island. The “North End Restoration 

10642 Project” included two phases. The first phase, completed in 2002, provided a one-time 

10643 placement of sand to replace a portion of sand lost over the past 60 years due to the 

10644 formation of the inlet and subsequent jetty stabilization efforts. The second phase is 

10645 focused on re-establishing a natural sediment supply by mechanically bypassing sand 

from the inlet and tidal deltas into the shallow nearshore areas91 10646 . 

 10647 

10648 A1.E 2.2 Coastal Bay Shores 

10649 The mainland along the back-barrier bays has been developed to a greater extent than the 

10650 respective ocean coast in all three states (MRLCC, 2002; MDP, 2001; DOSP, 1997). 

10651 Along the coastal bays, market forces have led to extensive development at the northern 

10652 end of the Delmarva due to the relatively close proximity to Washington, Baltimore, and 

10653 Philadelphia. Although connected to the densely populated Hampton Roads area by the 

10654 Chesapeake Bay Bridge-Tunnel, southern portions of the Delmarva are not as developed 

10655 as the shoreline to the north. Worcester County, Maryland, reflects a balance between 

10656 development and environmental protection resulting from both recognition of existing 

10657 market forces and a conscious decision to preserve Chincoteague Bay. Development is 

10658 extensive along most shores opposite Ocean City and along the bay shores near Ocean 

10659 City Inlet. In the southern portion of the county, conservation easements or the Critical 

10660 Areas Act preclude development along most of the shore. Although the Critical Areas 

10661 Act encourages shore protection, and conservation easements in Maryland preserve the 

10662 right to armor the shore (MET, 2006), these low-lying lands are more vulnerable to 

 

91 See <http://www.nps.gov/asis/naturescience/resource-management-documents.htm> 
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10663 inundation than erosion (e.g., Titus et al., 1991) and are therefore possible candidates for 

10664 wetland migration. 

 10665 

10666 Of the three states, Maryland has the most stringent policies governing development 

10667 along coastal bays Under the Chesapeake and Atlantic Coastal Bays Critical Areas 

10668 Protection Program, new development must be set back at least 100 ft from tidal wetlands 

or open water92 10669 . In most undeveloped areas, the statute also limits future development 

density to one home per 20 ac within 305 m (1000 ft) of the shore93 10670 and requires a 61-m 

(200-ft) setback.94 10671 In Virginia, new development must be set back at least 30 m (100 ft). 

10672 (see Section A1.F.2 in this Appendix for additional discussion of the Maryland and 

10673 Virginia policies.) The Delaware Department of Natural Resources has proposed a 30-m 

10674 (100-ft) setback along the coastal bays (DNREC, 2007); Sussex County currently 

requires a 15-m (50-ft) setback95 10675 . 

 10676 

10677 While shore protection is currently more of a priority along the Atlantic Coast, preventing 

10678 the inundation of low-lying lands may eventually be necessary as well. Elevating these 

10679 low areas appears to be more practical than erecting a dike around a narrow barrier island 

10680 (Titus, 1990). Most land surfaces on the bayside of Ocean City were elevated during the 

10681 initial construction of residences (McGean, 2003). In an appendix for U.S. EPA’s 1989 

10682 Report to Congress, Leatherman (1989) concluded that the only portion of Fenwick 

 

92 Maryland Natural Resources Code §8-1807(a). Code of Maryland Regulations §27.01.09.01 (C); 

93 Code of Maryland Regulations §27.01.02.05(C)(4). 

94 Maryland Natural Resources Code §8-1808.10 

95 Sussex County, DE. 2007. Buffer zones for wetlands and tidal and perennial non-tidal waters. §115-193, 

Sussex County Code. Enacted July 19, 1988 by Ord. No. 521. 
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10683 Island where bayside property would have to be elevated with a 50 cm rise in sea level 

10684 would be the portion in Delaware (i.e., outside of Ocean City). He also concluded that 

10685 Wallops Island, South Bethany, Bethany, and Rehoboth Beach are high enough to avoid 

10686 tidal inundation for the first 50 to 100 cm of sea-level rise. The Town of Ocean City has 

10687 begun to consider how to respond to address some of the logistical problems of elevating 

10688 a densely developed barrier island (see Box A1.5). 

 10689 

10690 The Maryland Coastal Bays Program considers erosion (due to sea-level rise) and 

10691 shoreline hardening major factors contributing to a decline in natural shoreline habitat 

10692 available for estuarine species in the northern bays (MCBP, 1999). Much of the shoreline 

10693 of Maryland’s northern coastal bays is protected using bulkheads or stone riprap, 

10694 resulting in unstable sediments and loss of wetlands and shallow water habitat (MCBP, 

10695 1999). Armoring these shorelines will prevent inland migration of marshes, and any 

10696 remaining fringing marshes will ultimately be lost (Strange 2008c). The Coastal Bays 

10697 Program estimated that more than 600 ha (1,500 ac) of salt marshes have already been 

10698 lost in the coastal bays as a result of shoreline development and stabilization techniques 

10699 (MCBP, 1999). If shores in the southern part of Maryland’s coastal bays remain 

10700 unprotected, marshes in low-lying areas would be allowed to potentially (see Chapter 4) 

10701 expand inland as sea level rises (Strange 2008c). 

 10702 

 10703 

 10704 

 10705 
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10706 --Start box-- 

 10707 

10708 BOX A1.5: Elevating Ocean City as Sea Level Rises 

10709 

10710 Logistically, the easiest time to elevate low land is when it is still vacant, or during a coordinated 

10711 rebuilding. Low parts of Ocean City’s bay side were elevated during the initial construction. As sea level 

10712 rises, the town of Ocean City has started thinking about how it might ultimately elevate. 

10713 Ocean City’s relatively high bay sides make it much less vulnerable to inundation by spring tides than other 

10714 barrier islands. Still, some streets are below the 10-year flood plain, and as sea level rises, flooding will 

10715 become increasingly frequent. 

10716 However, the town cannot elevate the lowest streets without considering the implications for adjacent 

10717 properties. A town ordinance requires property owners to maintain a 2 percent grade so that yards drain 

10718 into the street. The town construes this rule as imposing a reciprocal responsibility on the town itself to not 

10719 elevate roadways above the level where yards can drain, even if the road is low enough to flood during 

10720 minor tidal surges. Thus, the lowest lot in a given area dictates how high the street can be. 

10721 As sea level rises, failure by a single property owner to elevate could prevent the town from elevating its 

10722 streets, unless it changes this rule. Yet public health reasons require drainage, to prevent standing water in 

10723 which mosquitoes breed. Therefore, the town has an interest in ensuring that all property owners gradually 

10724 elevate their yards so that the streets can be elevated as the sea rises without causing public health 

10725 problems. 

10726 The Town of Ocean City (2003) has developed draft rules that would require that, during any significant 

10727 construction, yards be elevated enough to drain during a 10-year storm surge for the life of the project, 

10728 considering projections of future sea-level rise. The draft rules also state that Ocean City’s policy is for all 

10729 lands to gradually be elevated as the sea rises. 

10730 --End box-- 

 10731 

10732 A1.F Chesapeake Bay 

10733 The Chesapeake Bay region accounts for more than one-third of the lowland in the Mid10734 Atlantic (see Titus and Richman 2001). Accordingly, the first subsection (A1.F.1) on 

10735 vulnerable habitat, development, and shore protection) divides the region into seven 

10736 subregions. Starting with Hampton Roads, the subsections proceed clockwise around the 

10737 Bay to Virginia’s Middle Peninsula and Northern Neck, then up the Potomac River to 

10738 Washington, D.C., then up Maryland’s Western Shore, around to the Upper Eastern 

10739 Shore, and finally down to the Lower Eastern Shore. The discussions for Virginia are 

10740 largely organized by planning district; the Maryland discussions are organized by major 
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10741 section of shore. The second subsection compares the coastal policies of Maryland and 

Virginia that are most relevant to how these states respond to rising sea level96 10742 . 

 10743 

10744 A1.F.1 Inundation, Development and Shore Protection, and Vulnerable Habitat 

10745 A1.F.1.1 Hampton Roads 

10746 Most of the vulnerable dry land in the Hampton Roads region is located within Virginia 

10747 Beach and Chesapeake. These low areas are not, however, in the urban portions of those 

10748 jurisdictions. Most of Virginia Beach’s very low land is either along the back-barrier bays 

10749 near the North Carolina border, or along the North Landing River. Most of Chesapeake’s 

10750 low land is around the Northwest River near the North Carolina border, or the along the 

10751 Intracoastal Waterway. The localities located farther up the James and York Rivers have 

10752 less low land. An important exception is historic Jamestown Island, which has been 

10753 gradually submerged by the rising tides since the colony was established 400 years ago 

10754 (see Box 10.1 in chapter 10). 

 10755 

10756 Development and Shore Protection 

10757 Norfolk is home to the central business district of the Hampton Roads region. 

10758 Newport News has similar development to Norfolk along its southern shores, with bluffs 

10759 giving rise to less dense residential areas further north along the coast. The city of 

10760 Hampton is also highly developed, but overall has a much smaller percentage of 

10761 commercial and industrial development than Norfolk or Newport News. 

 

96 As this report was being finalized, a comprehensive study of the impacts of sea level rise on the 

Chesapeake Bay region was completed by the National Wildlife Federation (Glick et al., 2008). 
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 10762 

10763 Outside of the urban core, localities are more rural in nature. These localities find 

10764 themselves facing mounting development pressures and their comprehensive plans 

10765 outline how they plan to respond to these pressures (e.g., Suffolk, 1998; York County, 

10766 1999; James City County, 2003; Isle of Wight County, 2001). Overall, however, the 

10767 makeup of these outlying localities is a mix of urban and rural development, with historic 

10768 towns and residential development dotting the landscape. 

 10769 

10770 Virginia Beach has sandy shores along both the Atlantic Ocean and the mouth of 

10771 Chesapeake Bay. Dunes dominate the bay shore, but much of the developed ocean shore 

10772 is protected by a seawall, and periodic beach nourishment has occurred since the mid10773 1950s (Hardaway et al., 2005). Along Chesapeake Bay, by contrast, the Virginia Beach 

10774 shore has substantial dunes, with homes set well back from the shore in some areas. 

10775 Although the ground is relatively high, beach nourishment has been required on the bay 

10776 beaches at Ocean Park (Hardaway et al., 2005). Norfolk has maintained its beaches along 

10777 Chesapeake Bay mostly with breakwaters and groins. Shores along other bodies of water 

10778 are being armored. Of Norfolk’s 269 km (167 mi) of shoreline, 113 km (70 mi) have been 

10779 hardened (Berman et al., 2000). 

 10780 

10781 Overall trends in the last century show the dunes east of the Lynn Haven inlet advancing 

10782 into the Bay (Shellenbarger Jones and Bosch, 2008c). West from the inlet, erosion, beach 

10783 nourishment, and fill operations as well as condominium development and shoreline 

10784 armoring have affected the accretion and erosion patterns (Hardaway et al., 2005). Along 
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10785 the shores of Norfolk, the rate of erosion is generally low, and beach accretion occurs 

10786 along much of the shore (Berman et al., 2000). Most of the shore along Chesapeake Bay 

10787 is protected by groins and breakwaters, and hence relatively stable (Hardaway et al., 

10788 2005). On the other side of the James River, the bay shoreline is dominated by marshes, 

10789 many of which are eroding (Shellenbarger Jones and Bosch, 2008c). . 

 10790 

10791 Since 1979, Virginia Beach has had a “Green Line”, south of which the city tries to 

10792 maintain the rural agricultural way of life. Because development has continued, Virginia 

10793 Beach has also established a “Rural Area Line,” which coincides with the Green Line in 

10794 the eastern part of the city and runs 5 km (3 mi) south of it in the western portion. Below 

10795 the Rural Area Line, the city strongly discourages development and encourages rural 

10796 legacy and conservation easements (VBCP, 2003). In effect, the city’s plan to preserve 

10797 rural areas will also serve to preserve the coastal environment as sea level rises 

10798 throughout the coming century and beyond (see Sections 6.1.3, 6.2, 10.3). To the west, by 

10799 contrast, the City of Chesapeake is encouraging development in the rural areas, 

10800 particularly along major corridors. Comprehensive plans in the more rural counties such 

10801 as Isle of Wight and James City tend to focus less on preserving open space and more on 

10802 encouraging growth in designated areas (Isle of Wight, 2001; James City County, 2003). 

10803 Therefore, these more remote areas may present the best opportunity for long-range 

10804 planning to minimize coastal hazards and preserve the ability of ecosystems to migrate 

10805 inland.

 10806 

10807 Vulnerable Habitat
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10808 Much of the tidal wetlands in the area are within Poquoson’s Plum Tree Island National 

10809 Wildlife Refuge. Unlike most mid-Atlantic wetlands, these wetlands are unlikely to keep 

10810 pace with the current rate of sea-level rise (Shellenbarger Jones and Bosch, 2008c, 

10811 interpreting the findings of Reed et al., 2008). The relative isolation of the area has made 

10812 it a haven for over 100 different species of birds. The refuge has substantial forested dune 

10813 hummocks (CPCP, 1999), and a variety of mammals use the higher ground of the refuge. 

10814 Endangered sea turtles, primarily the loggerhead, use the near shore waters. Oyster, 

10815 clams, and blue crabs inhabit the shallow waters and mudflats, and striped bass, mullet, 

10816 spot, and white perch have been found in the near shore waters and marsh (USFWS, 

10817 undated[b]). 

 10818 

10819 The wetlands in York County appear able to keep pace with the current rate of sea-level 

10820 rise. Assuming that they are typical of most wetlands on the western side of Chesapeake 

10821 Bay, they are likely to become marginal with a modest acceleration and be lost if sea10822 level rise accelerates to 1 cm per year (Shellenbarger Jones and Bosch, 2008c, 

10823 interpreting the findings of Reed et al., 2008). Bald eagles currently nest in the Goodwin 

10824 Islands National Estuarine Research Reserve (Watts and Markham, 2003). This reserve 

10825 includes intertidal flats, 100 ha (300 ac) of eelgrass and widgeon grass (VIMS, undated), 

10826 and salt marshes dominated by salt marsh cordgrass and salt meadow hay. 

10827 

10828 A1.F.1.2 York River to Potomac River 
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10829 Two planning districts lie between the York and Potomac rivers. The Middle Peninsula 

10830 Planning District includes the land between the York and Rappahannock rivers. The 

10831 Northern Neck is between the Rappahannock and Potomac rivers. 

 10832 

10833 Development and Shore Protection 

10834 A large portion of the necks along Mobjack Bay has a conservation zoning that allows 

10835 only low-density residential development “in a manner which protects natural resources 

in a sensitive environment97. 10836 The intent is to preserve contiguous open spaces and protect 

the surrounding wetlands98 10837 . The county also seeks to maintain coastal ecosystems 

10838 important for crabbing and fishing. As a result, existing land use would not prevent 

10839 wetlands and beaches along Mobjack Bay from migrating inland as sea level rises. 

 10840 

10841 Gloucester County also has suburban country side zoning, which allows for low density 

residential development, including clustered sub-developments99 10842 along part of the Guinea 

10843 Neck and along the York River between Carter Creek and the Catlett islands. These 

10844 developments often leave some open space that might convert to wetlands as sea level 

10845 rises even if the development itself is protected. The county plan anticipates development 

10846 along most of the York River. Nevertheless, a number of areas are off limits to 

 

97 Gloucester County Code of Ordinances, accessed through Municode Online Codes: 

<http://livepublish.municode.com/22/lpext.dll?f = templates&fn = main-j.htm&vid = 10843>: “The intent 

of the SC-1 district is to allow low density residential development....Cluster development is encouraged in 

order to protect environmental and scenic resources.” 

98 Gloucester County Code of Ordinances, accessed through Municode Online Codes; 

<http://livepublish.municode.com/22/lpext.dll?f = templates&fn = main-j.htm&vid = 10843> 

99 Definition of suburban countryside in Gloucester County Code of Ordinances, accessed through 

Municode Online Codes: <http://livepublish.municode.com/22/lpext.dll?f = templates&fn = mainj.htm&vid = 10843>: “The intent of the SC-1 district is to allow low density residential 

development....Cluster development is encouraged in order to protect environmental and scenic resources.” 
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10847 development. For example, the Catlett islands are part of the Chesapeake Bay National 

Estuarine Research Reserve in Virginia, managed as a conservation area100 10848 . 

 10849 

10850 Along the Northern Neck, shoreline armoring is already very common, especially along 

10851 Chesapeake Bay and the Rappahannock Rivers shores of Lancaster County. Above 

10852 Lancaster County, however, development is relatively sparse along the Rappahannock 

10853 River and shoreline armoring is not common. Development and shoreline armoring are 

10854 proceeding along the Potomac River. 

 10855 

10856 Vulnerable Habitat 

10857 Like the marshes of Poquoson to the south, the marshes of the Guinea Neck and adjacent 

10858 islands are not keeping pace with the current rates of sea-level rise (Shellenbarger Jones 

10859 and Bosch, 2008a, interpreting the findings of Reed et al., 2008). For more than three 

10860 decades, scientists have documented their migration onto farms and forests (Moore, 

10861 1976). Thus, the continued survival of these marshes depends on land-use and shore 

10862 protection decisions. 

 10863 

10864 Upstream from the Guinea Neck, sea-level rise is evident in the York River’s tributaries, 

10865 not because wetlands are converting to open water but because the composition of 

10866 wetlands is changing. Along the Pamunkey and Mattaponi Rivers, dead trees reveal that 

10867 tidal hardwood swamps are converting to brackish or freshwater marsh as the water level 

10868 rises (Rheinhardt, 2007). Tidal hardwood swamps provide nesting sites for piscivorous 

 

100 See the Research Reserve’s web page at <http://www.vims.edu/cbnerr/about/index.htm>. 
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10869 (fish eating) species such as ospreys, bald eagles, and double-crested cormorants 

10870 (Robbins and Blom, 1996). 

 10871 

10872 In Mathews County, Bethel Beach (a natural area preserve separating Winter Harbor 

10873 from Chesapeake Bay) is currently migrating inland over an extensive salt marsh area 

10874 (Shellenbarger Jones and Bosch, 2008a). The beach is currently undergoing high erosion 

10875 (Berman et al., 2000), and is home to a population of the Northeastern beach tiger beetle 

10876 (federally listed as threatened) and a nesting site for rare least terns, which scour shallow 

10877 nests in the sand (VA DCR, 1999). In the overwash zone extending toward the marsh, a 

10878 rare plant is present, the sea-beach knotweed (Polygonum glaucum) (VA DCR, 1999). 

10879 The marsh is also one of few Chesapeake Bay nesting sites for northern harriers (Circus 

10880 cyaneus), a hawk that is more commonly found in regions further north (VA DCR, 1999). 

10881 As long as the shore is able to migrate, these habitats will remain intact; but eventually, 

10882 overwash and inundation of the marsh could reduce habitat populations (Shellenbarger 

10883 Jones and Bosch, 2008a). 

10884 

10885 A1.F.1.3 The Potomac River 

10886 Virginia Side. Many coastal homes are along bluffs, some of which are eroding (Bernd10887 Cohen and Gordon, 1999). Lewisetta is one of the larger vulnerable communities along 

10888 the Potomac. Water in some ditches rise and fall with the tides, and some areas drain 

10889 through tide gates. With a fairly modest rise in sea level, one could predict that wetlands 

10890 may begin to take over portions of people’s yards, the tide gates could close more often, 

10891 and flooding could become more frequent. Somewhat higher in elevation than Lewisetta, 
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10892 Old Town Alexandria and Belle Haven (Fairfax County) both flood occasionally from 

10893 high levels in the Potomac River. 

 10894 

10895 Maryland Side. Much of the low-lying land is concentrated around St. George Island and 

10896 Piney Point in St. Mary’s County, and along the Wicomico River and along Neal Sound 

10897 opposite Cobb Island in Charles County. Relatively steep bluffs, however, are also 

10898 common. 

 10899 

10900 Development and Shore Protection 

10901 West of Chesapeake Bay, the southwestern shoreline of the Potomac River is the border 

between Maryland and Virginia101 10902 . As a result, islands in the Potomac River, no matter 

10903 how close they are to the Virginia side of the river, are part of Maryland or the District of 

10904 Columbia. Moreover, most efforts to control erosion along the Virginia shore take place 

10905 partly in Maryland (or the District of Columbia) and thus could potentially be subject to 

Maryland (or Washington, D.C.) policies102 10906 . 

 10907 

10908 Development is proceeding along approximately two-thirds of the Potomac River shore. 

10909 Nevertheless, most shores in Charles County, Maryland are in the resource conservation 

10910 area defined by the state’s Critical Areas Act (and hence limited to one home per 20 ac) 

10911 (MD DNR, 2007). A significant portion of Prince George’s County’s shoreline along the 

10912 Potomac and its tributaries are owned by the National Park Service and other 

10913 conservation entities that seek to preserve the coastal environment (MD DNR, 2000). 

 

101 See Maryland v. Virginia, 540 US (2003) 102 The Virginia Shore across from Washington, D.C. is mostly owned by the federal government, which 

would be exempt from District of Columbia policies. 
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 10914 

10915 In Virginia, parks also account for a significant portion of the shore (ESRI, 1999). In 

10916 King George County, several developers have set development back from low-lying 

10917 marsh areas, which avoids problems associated with flooding and poor drainage. Water 

10918 and sewer regulations that only apply for lot sizes less than 10 acres may provide an 

10919 incentive for larger lot sizes. In Stafford County, the CSX railroad line follows the river 

10920 for several miles, and is set back to allow shores to erode, but not so far back as to allow 

10921 for development between the railroad and the shore (ADC, 2008a). 

 10922 

10923 Vulnerable Habitat 

10924 The Lower Potomac River includes a diverse mix of land uses and habitat types. 

10925 Freshwater tidal marshes in the Lower Potomac are found in the upper reaches of tidal 

10926 tributaries. In general, freshwater tidal marshes in the Lower Potomac are keeping pace 

10927 with sea-level rise through sediment and peat accumulation, and are likely to continue to 

10928 do so, even under higher sea-level rise scenarios (Strange and Shellenbarger Jones, 

10929 2008a, interpreting the findings of Reed et al., 2008). 

 10930 

10931 Brackish tidal marshes are a major feature of the downstream portions of the region’s 

10932 rivers. In general, these marshes are keeping pace with sea-level rise today, but are likely 

10933 to be marginal if sea level rise accelerates by 2 mm per year, and be lost if sea level 

10934 accelerates 7 mm per year (Strange and Shellenbarger Jones 2008a, interpreting the 

10935 findings of Reed et al., 2008). Loss of brackish tidal marshes would eliminate nesting, 

10936 foraging, roosting, and stopover areas for migrating birds (Strange and Shellenbarger 
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10937 Jones, 2008a). Significant concentrations of migrating waterfowl forage and overwinter 

10938 in these marshes in fall and winter. Rails, coots, and migrant shorebirds are transient 

10939 species that feed on fish and invertebrates in and around the marshes and tidal creeks. 

10940 (Strange and Shellenbarger Jones, 2008a). The rich food resources of the tidal marshes 

10941 also support rare bird species such as bald eagle and northern harrier (White, 1989). 

 10942 

10943 Unnourished beaches and tidal flats of the Lower Potomac are likely to erode as sea 

10944 levels rise. Impacts on beaches are highly dependent on the nature of shoreline protection 

10945 measures selected for a specific area. For example, the developed areas of Wicomico 

10946 Beach and Cobb Island are at the mouth of the Wicomico River in Maryland. Assuming 

10947 that the shores of Cobb Island continue to be protected, sea-level rise is likely to 

10948 eliminate most of the island’s remaining beaches and tidal flats (Strange and 

10949 Shellenbarger Jones, 2008a). 

 10950 

10951 Finally, where the cliffs and bluffs along the Lower Potomac are not protected (e.g., 

10952 Westmoreland State Park, Caledon Natural Area), natural erosional processes will 

10953 generally continue, helping to maintain the beaches below (Strange and Shellenbarger 

10954 Jones, 2008a). 

 10955 

10956 Above Indian Head, the Potomac River is fresh. Tidal wetlands are likely to generally 

10957 keep pace with rising sea level in these areas (see Chapter 4 of this Product). 

10958 Nevertheless, the Dyke Marsh Preserve faces an uncertain future. Its freshwater tidal 

10959 marsh and adjacent mud flats are one of the last major remnants of the freshwater tidal 
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10960 marshes of the Upper Potomac River (Johnston, 2000). A recent survey found 62 species 

10961 of fish, nine species of amphibians, seven species of turtles, two species of lizards, three 

10962 species of snakes, 34 species of mammals, and 76 species of birds in Dyke Marsh 

10963 (Engelhardt et al., 2005). Many of the fish species present (e.g., striped bass, American 

10964 shad, yellow perch, blueback herring) are important for commercial and recreational 

10965 fisheries in the area (Mangold et al., 2004). 

 10966 

10967 Parklands on the Mason Neck Peninsula are managed for conservation, but shoreline 

10968 protection on adjacent lands may result in marsh loss and reduced abundance of key bird 

10969 species (Strange and Shellenbarger Jones, 2008b). The Mason Neck National Wildlife 

10970 Refuge hosts seven nesting bald eagle pairs and up to 100 bald eagles during winter, has 

10971 one of the largest great blue heron colonies in Virginia, provides nesting areas for hawks 

10972 and waterfowl, and is a stopover for migratory birds. 

 10973 

10974 A1.F.1.4 District of Columbia 

10975 Within the downtown area, most of the lowest land is the area filled during the 1870s, 

10976 such as Hains Point and the location of the former Tiber and James Creeks, as well as the 

10977 Washington City Canal that joined them (See Box 5.2 in Chapter 5). The largest low area 

10978 is the former Naval Air Station, now part of Bolling Air Force Base, just south of the 

10979 mouth of the Anacostia River, which was part of the mouth of the Anacostia River during 

10980 colonial times. A dike protects this area, where most of the low land between Interstate10981 295 and the Anacostia River was open water when the city of Washington was originally 

10982 planned. 
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 10983 

10984 Development and Shore Protection 

10985 The central city is not likely to be given up to rising sea level; city officials are currently 

10986 discussing the flood control infrastructure necessary to avoid portions of the downtown 

10987 area from being classified as part of the 100-year floodplain. Nevertheless, natural areas 

10988 in the city account for a substantial portion of the city’s shore, such as Roosevelt Island 

10989 and the shores of the Potomac River within C&O Canal National Historic Park. 

 10990 

10991 As part of the city’s efforts to restore the Anacostia River, District officials have 

10992 proposed a series of environmental protection buffers along the Anacostia River with 

10993 widths between 15 and 90 m (50 and 300 ft). Bulkheads are being removed except where 

10994 they are needed for navigation, in favor of natural shores in the upper part of the river and 

10995 bioengineered “living shorelines” in the lower portion (DCOP, 2003). 

 10996 

10997 Vulnerable Habitat 

10998 The Washington, D.C. area features sensitive wetland habitats potentially vulnerable to 

10999 sea-level rise. Several major areas are managed for conservation or are the target of 

11000 restoration efforts, making ultimate impacts uncertain. The wetlands around the 

11001 Anacostia River are an example. Local organizations have been working to reverse 

11002 historical modifications and restore some of the wetlands around several heavily altered 

11003 lakes. Restoration of the 13-ha (32-ac) Kenilworth Marsh was completed in 1993; 

11004 restoration of the Kingman Lake marshes began in 2000 (USGS, undated). Monitoring of 

11005 the restored habitats demonstrates that these marshes can be very productive. A recent 
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11006 survey identified 177 bird species in the marshes, including shorebirds, gulls, terns, 

11007 passerines, and raptors as well as marsh nesting species such as marsh wren and swamp 

11008 sparrow (Paul et al., 2004). 

 11009 

11010 Roosevelt Island is another area where sea-level rise effects are uncertain. Fish in the 

11011 Roosevelt Island marsh provide food for herons, egrets, and other marsh birds (NPS, 

11012 undated). The ability of the tidal marshes of the island to keep pace with sea-level rise 

11013 will depend on the supply of sediment, and increased inundation of the swamp forest 

11014 could result in crown dieback and tree mortality (Fleming et al., 2006). 

 11015 

11016 A1.F.1.5 Western Shore: Potomac River to Susquehanna River 

11017 The Western Shore counties have relatively little low land, unlike the low counties across 

11018 the Bay. The Deal/Shady Side peninsula (Anne Arundel County) and Aberdeen Proving 

11019 Grounds (Harford County) are the only areas with substantial amounts of low-lying land. 

11020 The block closest to the water, however, is similarly low in many of the older 

11021 communities, including parts of Baltimore County, Fells Point in Baltimore (see Box 

11022 A1.6), downtown Annapolis, North Beach, and Chesapeake Beach, all of which flooded 

11023 during Hurricane Isabel. 

 11024 

11025 Between the Potomac and the Patuxent Rivers, the bay shore is usually a sandy beach in 

11026 front of a bank less than 3 m (10 ft) high. Cliffs and bluffs up to 35 m (115 ft) above the 

11027 water dominate the shores of Calvert County (Shellenbarger Jones and Bosch, 2008b). 
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11028 The shores north of Calvert County tend to be beaches; but these beaches become 

11029 narrower as one proceeds north, where the wave climate is milder. 
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11030 BOX A1.6: Planning for Sea-level Rise in Baltimore 

11031 Only 3.2 percent of the City of Baltimore’s 210 sq km (81 sq mi) of land is currently within the coastal 

11032 floodplain. This land, however, includes popular tourist destinations such as Inner Harbor and the Fells 

11033 Point Historic District, as well as industrial areas, some of which are being redeveloped into mixed use 

11034 developments with residential, commercial, and retail land uses. The map below depicts the areas that the 

11035 city expects to be flooded by category 1, 2, 3 and 4 hurricanes, which roughly correspond to water levels of 

11036 1.78 m (6 ft), 3.0 m (10 ft), 4.2 m (14 ft), and 5.5 m (18 ft) above North Amercan Vertical Datum 

11037 (NAVD88). Approximately 250 homes are vulnerable to a category 1, while 700 homes could be flooded 

11038 by a category 2 hurricane (Baltimore, 2006). As Hurricane Isabel passed in September 2003, water levels 

11039 in Baltimore Harbor generally reached approximately 2.4 m (8 ft) above NAVD, flooding streets and 

11040 basements, but resulting in only 16 flood insurance claims (Baltimore, 2006). 

11041 

11042 The city’s All Hazards Plan explicitly includes rising sea level as one of the factors to be considered in land 

use and infrastructure planning103 11043 . The All Hazards Plan has as an objective to “develop up-to-date research 

11044 about hazards” and a strategy under that objective to “study the threat, possible mitigation and policy 

11045 changes for sea-level rise.” As a first step toward accurate mapping of possible sea-level rise scenarios, the 

11046 city is exploring options for acquiring lidar. Policies developed for floodplain management foreshadow the 

11047 broad methods the city is likely to use in its response. 

11048 

11049 

11050 

11051 

11052 

11053 

11054 

11055 

11056 

11057 

11058 

11059 

11060 

11061 

11062 

11063 

11064 

11065 

11066 

11067 Box Figure A1.6 Inundation Zone for Baltimore Harbor under category 1,2,3, and 4 hurricanes. 

11068 

11069 Property values are high, and there is a long-standing practice of armoring shores to facilitate port-related 

11070 activities and more recently, protect waterfront structures from shore erosion. In most areas, there is not 

11071 enough room between the harbor and waterfront buildings to fit a dike. Even where there is room, the loss 

11072 of waterfront views would be unacceptable in tourist and residential areas (see Section 6.5 in Chapter 6; 

11073 Titus, 1990). In addition, storm sewers, which drain by gravity into the harbor, would have to be fit with 

11074 pumping systems. 

11075 

11076 Fells Point Historic District This historic community has 24 ha (60 ac) within the 100-year flood plain. 

11077 Fells Point is a Federal Historic District and pending approval as a Local Historic District. The row houses 

11078 here were built predominantly in the early to mid-nineteenth century and cannot be easily elevated. 

11079 Elevating brick and stone structures is always more difficult than elevating a wood frame structure. But 

11080 because row houses are, by definition, attached to each other, elevating them one at a time is not feasible. 

 

103 Baltimore (City of Baltimore Department of Planning) 2006 “All Hazards Plan for Baltimore City” 

Adopted by Baltimore City Planning Commission April 20, 2006 at 6, 10-11. 
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11081 Many of these homes have basements, which already flood. FEMA regulations do not permit basements in 

11082 new construction in the floodplain and treats (44 CFR §60.3[c] [2]) existing basements as requiring 

11083 mitigation. Possible mitigation for basements includes relocation of utilities, reinforcement of walls, and 

11084 filling. 

11085 

11086 In theory, homes could be remodeled to add stairways and doors to convert what is now the second floor to 

11087 a first floor and convert the first floors to basements. But doing so would reduce the livable space. 

11088 Moreover, federal and local preservation laws, as well as community sensibilities, preclude adding third 

11089 stories to these homes. Elevating streets is also problematic because below-grade utilities need to be 

11090 elevated. In the last decade only one street (one block of Caroline Street) has been elevated specifically to 

11091 reduce flooding. 

11092 

11093 FEMA Flood Hazard Mapping and Sea-level Rise 

11094 

11095 Baltimore City is a participating jurisdiction in the National Flood Insurance Program through its regulation 

11096 of development in the floodplain and through overall floodplain management. The city is currently funded 

11097 through the Cooperative Technical Partnership (CTP) to update its flood maps. Federal flood mapping 

11098 policies require that Flood Insurance Rate Maps be based on existing conditions (see Section 10.7.5.3 in 

11099 Chapter 10). Therefore, the floodplain maps do not consider future sea level rise. As a result, the city will 

11100 be permitting new structures with effective functional lifespan of 50 to 100 years but elevated only to 

11101 current flood elevations. One strategy to surmount this limitation is to add “freeboard,” or additional 

11102 elevation to the effective BFE. Baltimore already requires one additional foot of freeboard. 

11103 

11104 The City of Baltimore is concerned, however, that 0.3 to 0.6 additional meters of freeboard is inequitable 

11105 and inefficient. If flood levels will be, for example, 1 meter higher than the flood maps currently assume, 

11106 then lands just outside the current flood boundary are also potentially vulnerable. If the city were to add 1 

11107 meter of freeboard to property in the floodplain, without addressing adjacent properties outside the 

11108 floodplain, then adjacent property owners would have divergent requirements that city officials would find 

11109 difficult to justify. (see Figure 10.6.) 

11110 

11111 

11112 

11113 Baltimore has two regional sewerage plants. One of them, the Patapsco Wastewater Treatment Plant, sits 

11114 on ground that is less than two meters above mean sea level and floods occasionally (see Box Figure A1.6). 

11115 The facility itself is elevated and currently drains by gravity into the Patapsco River (USGS 7.5-minute 

11116 map series). With a significant rise in sea level, however, pumping will be needed and possibly additional 

11117 protections against storms (Smith, 1998: Titus et al., 1987, . Numerous streets, with associated conduits and 

11118 utility piping, are within the existing coatal floodplain and would potentially be affected by sea-level rise 

11119 (see Box Figure A1.6). 

11120 

11121 --End box-- 

 11122 

11123 Development and Shore Protection 

11124 The Western Shore was largely developed before the Maryland’s Critical Areas Act was 

11125 passed. Stone revetments are common along the mostly developed shores of Anne 

11126 Arundel and Baltimore Counties. Yet Calvert County has one of the only shore protection 

11127 policies in the nation that prohibits shore protection along an estuary, even when the 

Infrastructure 
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11128 prohibition means that homes will be lost. Calvert County’s erosion policy is designed to 

11129 preserve unique cliff areas that border Chesapeake Bay. 

 11130 

11131 The county allows shoreline armoring in certain developed areas to protect property 

11132 interests, but also bans armoring in other areas to protect endangered species and the 

unique landscape104 11133 . Cliffs in Calvert County are separated into categories according to 

11134 the priority for preservation of the land. Although a county policy prohibiting shore 

11135 protection would appear to run counter to the state law granting riparian owner the right 

11136 to shore protection, to date no legal challenges to the cliff policy have been made. The 

11137 state has accepted the county’s policy, which is embodied in the county’s critical areas 

11138 plan submitted to the state under the Critical Areas Act. Recognizing the potential 

11139 environmental implications, living shoreline protection is becoming increasingly 

11140 commonplace along the Western Shore. 

 11141 

11142 Vulnerable Habitat

11143 A range of sea-level rise impacts are possible along the western shore of Chesapeake 

11144 Bay, including potential loss of key habitats. First, marshes are expected to be marginal 

11145 with mid-range increases in sea-level rise, and to be lost with high-range increases in sea11146 level rise (Shellenbarger Jones and Bosch, 2008b, interpreting the findings of Reed et al., 

11147 2008). The ability to migrate is likely to determine coastal marsh survival as well as the 

11148 survival of the crustaceans, mollusks, turtles, and birds that depend on the marshes. In 

11149 upper reaches of tributaries, however, marsh accretion is likely to be sufficient to counter 

 

104See also Nationwide Permits 3 (Maintenance), 31 (Maintenance of Existing Flood Control Facilities) 

and 45 (Repair of Uplands Damaged by Discrete Events). 72 Federal Register 11092-11198 (March 12, 

2007).
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11150 sea-level rise (Shellenbarger Jones and Bosch, 2008b, interpreting the findings of Reed et 

11151 al., 2008). Several key locations warrant attention: 

11152  In the Jug Bay Sanctuary, along the upper Patuxent River, marsh inundation is 

11153 causing vegetation changes, compounding stress on local bird species 

11154 (Shellenbarger Jones and Bosch, 2008b). 

11155  Cove Point Marsh in Calvert County is a 60-ha (150-ac) freshwater, barrier-beach 

11156 marsh. Numerous state-defined rare plant species are present, including American 

11157 frog’s-bit, silver plumegrass, various ferns, and unique wetland communities 

11158 (Steury, 2002), as well as several rare or threatened beetle species. With current 

11159 rates of sea-level rise, the marsh is continuing to migrate, but will soon hit the 

11160 northern edge of local residential development. 

11161  The potential loss of the wide mudflats at Hart-Miller Island would eliminate 

11162 major foraging and nesting areas for several high conservation priority species 

11163 (Shellenbarger Jones and Bosch, 2008b). 

11164  Given the extent of development and shoreline armoring in Anne Arundel County 

11165 and Baltimore City/County, both intertidal areas and wetlands are likely to be lost 

11166 with even a modest acceleration in sea-level rise (Shellenbarger Jones and Bosch, 

11167 2008b). 

 11168 

11169 Beach loss, particularly in St. Mary’s, Calvert, and Anne Arundel Counties along 

11170 Chesapeake Bay, may occur in areas without nourishment. In general, beach loss will 

11171 lead to habitat loss for resident insects (including the Northeastern beach tiger beetle, 
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11172 federally listed as threatened) and other invertebrates, as well as forage loss for larger 

predators such as shorebirds (Lippson and Lippson, 2006)105 11173 . 

 11174 

11175 The Calvert County cliffs represent unique habitat that could be degraded by sea-level 

11176 rise; however, the cliffs are not likely to be lost entirely. The Puritan tiger beetle and 

11177 Northeastern beach tiger beetle, both federally listed, are present in the area 

11178 (Shellenbarger Jones and Bosch, 2008b). While natural erosion processes are allowed to 

11179 continue in the protected cliff areas in the southern portion of the county, shoreline 

11180 protections in the more northern developed areas are increasing erosion rates in adjacent 

11181 areas (Wilcock et al., 1998). 

 11182 

11183 A1.F.1.6 Upper Eastern Shore

11184 The Eastern Shore above Rock Hall is dominated by bluffs and steep slopes rising to 

11185 above 6 m (20 ft). Tolchester Beach, Betterton Beach, and Crystal Beach are typical in 

11186 that regard. From Rock Hall south to around the middle of Kent Island, all of the land 

11187 within a few kilometers of the Chesapeake Bay or its major tributaries consists of low11188 lying land. 

 11189 

11190 Between the Choptank River and Ocohannock Creek along the Eastern Shore of 

11191 Chesapeake Bay lies one of the largest concentrations of land close to sea level. Water 

11192 levels in roadside ditches rise and fall with the tides in the areas west of Golden Hill in 

11193 Dorchester County and several necks in Somerset County. Many farms abut tidal 

11194 wetlands, which are gradually encroaching onto those farms. Some landowners have 

 

105 For more detail on beach habitats and the species that occur in the mid-Atlantic region, see 

Shellenbarger Jones (2008a). 
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11195 responded by inserting makeshift tide gates over culverts, decreasing their own flooding 

11196 but increasing it elsewhere. Throughout Hoopers Island, as well as the mainland nearby, 

11197 there are: numerous abandoned driveways that once led to a home but are now ridges 

11198 flooded at high tide and surrounded by low marsh or open water; recently abandoned 

11199 homes that are still standing but surrounded by marsh; and dead trees still standing in 

11200 areas where marsh has invaded a forest.

11201 

11202 Development and Shore Protection 

11203 Along the Chesapeake Bay, recent coastal development has not placed a high value on 

11204 the beach. The new bayfront subdivisions often provide no public access to the beach, 

11205 and as shores erode, people erect shore-protection structures that eventually eliminate the 

11206 beach (see Chapter 6 of this Product; Titus, 1998). Some traditional access points have 

11207 been closed (Titus, 1998). Maintaining a beach remains important to some of the older 

11208 bay resort communities where residents have long had a public beach—but even 

11209 communities with “beach” in the name are seeing their beaches replaced with shore 

11210 protection structures. 

 11211 

11212 Maryland’s Critical Areas Act, however, is likely to restrict the extent of additional 

11213 development along the Eastern Shore of Chesapeake Bay to a greater extent than along 

11214 the Western Shore. The resource conservation areas where development is discouraged 

11215 include half of the Chesapeake Bay shoreline between the Susquehanna and Choptank 

11216 Rivers. Among the major tributaries, most of the Sassafras, Chester, and Choptank Rivers 

11217 are similarly preserved; the Act did not prevent development along most of the Wye, Elk, 
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11218 and North East Rivers. Existing development is most concentrated in the northern areas 

11219 near Interstate-95, Kent Island, and the various necks near Easton and St. Michaels. 

 11220 

11221 Vulnerable Habitat 

11222 Above Kent Island. The environmental implications of sea-level rise effects in the upper 

11223 Chesapeake Bay are likely to be relatively limited. The Susquehanna River provides a 

11224 large (though variable) influx of sediment to the upper Chesapeake Bay, as well as almost 

11225 half of Chesapeake Bay’s freshwater input (CBP, 2002). This sediment generally is 

11226 retained above the Chesapeake Bay Bridge and provides material for accretion in the tidal 

11227 wetlands of the region (CBP, 2002). The other upper Chesapeake Bay tributaries 

11228 characteristically have large sediment loads as well, and currently receive sufficient 

11229 sediment to maintain wetlands and their ecological function. As such, the upper 

11230 Chesapeake Bay will continue to provide spawning and nursery habitat for crabs and fish, 

11231 as well as nesting and foraging habitat for migratory and residential birds, including bald 

11232 eagles and large numbers of waterfowl. Likewise, while some of the beaches may require 

11233 nourishment for retention, the general lack of shoreline protections will minimize 

11234 interferences with longshore sediment transport. Hence, beaches are likely to remain 

11235 intact throughout much of the region (Shellenbarger Jones, 2008b). 

11236 

11237 Two areas in the upper bay—Eastern Neck and Elk Neck—appear most vulnerable to 

11238 sea-level rise effects. First, Eastern Neck Wildlife Refuge lies at the southern tip of 

11239 Maryland’s Kent County. Ongoing shoreline protection efforts seek to reduce erosion of 

11240 habitats supporting many migratory waterfowl and residential birds, as well as turtles, 
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11241 invertebrates, and the Delmarva fox squirrel, federally listed as endangered. In many 

11242 marsh locations, stands of invasive common reed are the only areas retaining sufficient 

11243 sediment (Shellenbarger Jones, 2008b). Local managers have observed common reed 

11244 migrating upland into forested areas as inundation at marsh edges increases, although 

11245 widespread marsh migration of other species has not been observed (Shellenbarger Jones, 

11246 2008b). The three-square bulrush marshes on Eastern Neck have been largely inundated, 

11247 as have the black needle rush marshes on Smith Island and other locations, likely causes 

11248 of reductions in black duck counts (Shellenbarger Jones, 2008b). 

 11249 

11250 Other sea-level rise impacts are possible in Cecil County, in and around the Northeast 

11251 and Elk Rivers. The headwaters of the rivers are tidal freshwater wetlands and tidal flats, 

11252 spawning and nursery areas for striped bass and a nursery area for alewife, blueback 

11253 herring, hickory shad, and white perch, as well as a wintering and breeding area for 

11254 waterfowl (USFWS, 1980). Accretion is likely to be sufficient in some areas due to the 

11255 large sediment inputs in the Upper Bay. Where accretion rates are not sufficient, wetland 

11256 migration would be difficult due to the upland elevation adjacent to the shorelines. These 

11257 conditions increase the chances of large tidal fresh marsh losses (Shellenbarger Jones, 

11258 2008b). Other sensitive Cecil County habitats exist such as the cliffs at Elk Neck State 

11259 Park and the Sassafras River Natural Resource Management Area, which will be left to 

11260 erode naturally losses (Shellenbarger Jones, 2008b). Finally, marsh loss is possible in and 

11261 around the Aberdeen Proving Ground in Harford County. The Proving Ground is 

11262 primarily within 5 m of sea level and contains 8000 ha (20,000 ac) of tidal wetlands. 

 11263 
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11264 Kent Island to Choptank River. The central Eastern Shore region of Chesapeake Bay 

11265 contains diverse habitats, and sea-level rise holds equally diverse implications, varying 

11266 greatly between subregions. Large expanses of marsh and tidal flats are likely to be lost, 

11267 affecting shellfish, fish, and waterfowl populations (Shellenbarger Jones, 2008c). Several 

11268 subregions merit consideration: 

11269  Marshes along the Chester River are likely to be marginal with moderate sea-level 

11270 rise rate increases (Shellenbarger Jones, 2008c, interpreting the findings of Reed 

11271 et al., 2008; see Chapter 4 of this Product). 

11272  Loss of the large tidal flats exist at the mouth of the Chester River (Tiner and 

11273 Burke, 1995) may result in a decline in the resident invertebrates and fish that use 

11274 the shallow waters as well as the birds that feed on the flats (Shellenbarger Jones, 

11275 2008c; Robbins and Blom, 1996). 

11276  The Eastern Bay side of nearby Kent Island has several tidal creeks, extensive 

11277 tidal flats, and wetlands. Existing marshes and tidal flats are likely to be lost (see 

11278 Chapter 4) (although some marsh may convert to tidal flat). Increasing water 

11279 depths are likely to reduce the remaining SAV; a landward migration onto 

11280 existing flats and marshes will depend on sediment type and choice of shoreline 

11281 structure (Shellenbarger Jones, 2008c). 

11282  Portions of the Wye River shore are being developed. If these shores are protected 

11283 and the marshes and tidal flats in these areas are lost, the juvenile fish nurseries 

11284 will be affected and species that feed in the marshes and SAV will lose an 

11285 important food source (MD DNR, 2004). 

 11286 
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11287 Certain key marsh areas are likely to be retained. The upper reaches of tributaries, 

11288 including the Chester and Choptank Rivers, are likely to retain current marshes and the 

11289 associated ecological services. Likewise, Poplar Island will provide a large, isolated 

11290 marsh and tidal flat area (USACE, undated[b]). In addition, the marshes of the Wye 

11291 Island Natural Resource Management Area support a large waterfowl population (MD 

11292 DNR, 2004). Maryland DNR will manage Wye Island to protect its biological diversity 

11293 and structural integrity, such that detrimental effects from sea-level rise acceleration are 

11294 minimized (MD DNR, 2004). 

 11295 

11296 Beach loss is also possible in some areas. The Chesapeake Bay shore of Kent Island 

11297 historically had narrow sandy beaches with some pebbles along low bluffs, as well as 

11298 some wider beaches and dune areas (e.g., Terrapin Park). As development continues, 

11299 however, privately owned shores are gradually being replaced with stone revetments. The 

11300 beaches will be unable to migrate inland, leading to habitat loss for the various resident 

11301 invertebrates, including tiger beetles, sand fleas, and numerous crab species 

11302 (Shellenbarger Jones, 2008c). Shorebirds that rely on beaches for forage and nesting will 

11303 face more limited resources (Lippson and Lippson, 2006). Likewise, on the bay side of 

11304 Tilghman Island, the high erosion rates will tend to encourage shoreline protection 

11305 measures, particularly following construction of waterfront homes (MD DNR, undated). 

11306 Beach loss, combined with anticipated marsh loss in the area, will eliminate the worms, 

11307 snails, amphipods, sand fleas, and other invertebrates that live in the beach and intertidal 

11308 areas and reduce forage for their predators (Shellenbarger Jones, 2008c). 

 11309 
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11310 A1.F.1.7. Lower Eastern Shore 

11311 Approximately halfway between Crisfield on the Eastern Shore and the mouth of the 

11312 Potomac River on the Western Shore, are the last two inhabited islands in Chesapeake 

11313 Bay unconnected by bridges to the mainland: Smith (Maryland) and Tangier (Virginia). 

11314 Both islands are entirely below the 5-ft elevation contour on a USGS topographic map. 

11315 Along the Eastern Shore of Northampton County, by contrast, elevations are higher, often 

11316 with bluffs of a few meters. 

 11317 

11318 Development and Shore Protection 

11319 Along Chesapeake Bay, islands are threatened by a combination of erosion and 

11320 inundation. Wetlands are taking over portions of Hoopers and Deal Islands, but shore 

11321 erosion is the more serious threat. During the middle of the nineteenth century, watermen 

11322 who made their living by fishing Chesapeake Bay made their homes on various islands in 

11323 this region. Today, Bloodsworth and Lower Hoopers Islands are uninhabitable marsh, 

11324 and the erosion of Barren and Poplar Islands led people to move their homes to the 

11325 mainland (Leatherman, 1992). Smith Island is now several islands, and has a declining 

11326 population. Hoopers and Deal Islands are becoming gentrified, as small houses owned by 

11327 watermen are replaced with larger houses owned by wealthier retirees and professionals. 

 11328 

11329 Virtually all of the beaches along Chesapeake Bay are eroding. Shore erosion of beaches 

11330 and clay shores along the Chester, Nanticoke, and Chester Rivers is slower than along the 

11331 Bay but enough to induce shoreline armoring along most developed portions. The lower 
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11332 Eastern Shore has a history of abandoning lowlands to shore erosion and rising sea level 

11333 to a greater extent than other parts of the state (Leatherman, 1992). 

 11334 

11335 Today, Smith and Tangier are the only inhabited islands without a bridge connection to 

11336 the mainland. Government officials at all levels are pursuing efforts to prevent the loss of 

11337 these lands, partly because of their unique cultural status and—in the case of Tangier—a 

11338 town government that works hard to ensure that the state continues to reinvest in schools 

11339 and infrastructure. The USACE has several planned projects for halting shore erosion, but 

11340 to date, no efforts are underway to elevate the land (USACE, 2001b; Johnson, 2000). The 

11341 replacement of traditional lifestyles with gentrified second homes may increase the 

11342 resources available to preserve these islands. 

 11343 

11344 The mainland of Somerset County vulnerable to sea-level rise is mostly along three 

11345 necks. Until recently, a key indicator of the cost-effectiveness of shore protection was the 

availability of a sewer line106 11346 . As sea level rises, homes without sewer may be 

11347 condemned as septic systems fail. The incorporated town of Crisfield, in the 

11348 southernmost neck, has long had sewer service, which has been recently expanded to 

11349 nearby areas. The town itself is largely encircled by an aging dike. Deal Island, no longer 

11350 the thriving fishing port of centuries gone by, still has moderate density housing on most 

11351 of the dry land. 

 11352 

11353 Wicomico County’s low-lying areas are along both the Wicomico and Nanticoke Rivers. 

11354 Unlike Somerset, Wicomico has a large urban/suburban population, with the Eastern 

 

106 The mounds systems have made it possible to inhabit low areas with high water tables. 
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11355 Shore’s largest city, Salisbury. Planners accept the general principals of the state’s 

11356 Critical Areas Act, which discourages development along the shore. 

 11357 

11358 Much of coastal Dorchester County is already part of Blackwater Wildlife Refuge. The 

11359 very low land south of Cambridge that is not already part of the refuge is farmland. 

11360 Because most of the low-lying lands west of Cambridge are within Resource 

11361 Conservation Areas (CBCAC, 2001), significant development would be unlikely under 

11362 the state's Critical Areas Act (see Section A1.F.2). On the higher ground along the 

11363 Choptank River, by contrast, many waterfront parcels are being developed. In July 2008, 

11364 the State of Maryland Board of Public Works approved the purchase of 295 ha (729 ac) 

11365 of land along the Little Blackwater River, near the town to Cambridge in Dorchester 

11366 County. Funded by the state’s Program Open Space, the purchase will allow for the 

11367 preservation and restoration of more than two-thirds of a 434-ha (1,072-ac) parcel that 

was previously slated for development107 11368 . 

 11369 

11370 Vulnerable Habitat 

11371 On the lower Eastern Shore of Chesapeake Bay in Maryland, habitats vulnerable to sea11372 level rise are diverse and include beaches, various types of tidal marsh, non-tidal 

11373 marshes, and upland pine forests. 

 11374 

11375 Narrow sandy beaches exist along discrete segments of shoreline throughout the region, 

11376 particularly in Somerset County. Given the gradual slope of the shoreline, one might infer 

 

107 See <http://www.dnr.state.md.us/dnrnews/pressrelease2007/041807.html> 
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11377 that these habitats could accommodate moderate sea-level rise by migrating upslope, 

11378 assuming no armoring or other barriers exist. Many of the beaches provide critical 

11379 nesting habitat for the diamondback terrapin (Malaclemys terrapin), and proximity of 

11380 these nesting beaches to nearby marshes provides habitat for new hatchlings (see Box 

11381 A1.7) 

11382 Start Box******* 

11383 

11384 BOX A1.7: The Diamondback Terrapin, Malaclemys terrapin

11385 The diamondback terrapin, Malaclemys terrapin, comprising seven subspecies, is the only turtle that is 

11386 fully adapted to life in the brackish salt marshes of estuarine embayments, lagoons, and impoundments 

11387 (Ernst and Barbour, 1972). Its range extends from Massachusetts to Texas in the narrowest of coastal strips 

11388 along the Atlantic and Gulf coasts of the United States (Palmer and Cordes, 1988). Extreme fishing 

11389 pressure on the species resulted in population crashes over much of their range so that by 1920 the catch in 

11390 Chesapeake Bay had fallen to less than 900 pounds. The Great Depression put a halt to the fishery, and 

11391 during the mid-twentieth century, populations began to recover (CBP, 2006). Although a modest fishery 

11392 has been reestablished in some areas, stringent harvest regulations are in place in several states. In some 

11393 instances, states have listed the species as endangered (Rhode Island), threatened (Massachusetts), or as a 

11394 “species of concern” (Georgia, Delaware, New Jersey, Louisiana, North Carolina, and Virginia). In 

11395 Maryland, the status of the northern diamondback subpopulation is under review (MD DNR, 2006). 

11396 

11397 Effects of Sea-level Rise 

11398 The prospect of sea-level rise, along with land subsidence at many coastal locations, increasing human 

11399 habitation of the shore zone and shoreline stabilization, places the habitat of terrapins at increasing risk. 

11400 Loss of prime nesting beaches remains a major threat to the diamondback terrapin population in 

11401 Chesapeake Bay (MD DTTF, 2001).Because human infrastructure (i.e., roadways, buildings, and 

11402 impervious surfaces) leaves tidal salt marshes with little or no room to transgress inland, one can infer that 

11403 the ecosystem that terrapins depend on may be lost with concomitant extirpation of the species. 

11404 End Box******** 

 11405 

11406 Of the 87,000 ha (340 sq mi) of tidal marsh in the Chesapeake Bay, a majority is located 

11407 in the three-county lower Eastern Shore region (Darmondy and Foss, 1979). The marshes 

11408 are critical nursery grounds for commercially important fisheries (e.g., crabs and 

11409 rockfish); critical feeding grounds for migratory waterfowl; and home to furbearers (e.g., 

11410 muskrat and nutria). 

 11411 

11412 Areas of Virginia’s Eastern Shore are uniquely vulnerable to sea-level rise since large 

11413 portions of Northampton and Accomack counties lie near sea level. Because most of the 
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11414 land in the two counties is undeveloped or agricultural, the area also has a high potential 

11415 for wetland creation relative to other Virginia shorelines.

 11416 

11417 Most notably, the bay side of northern Accomack County is primarily tidal salt marsh, 

11418 with low-lying lands extending several kilometers inland. Unprotected marshes are 

11419 already migrating inland in response to sea-level rise, creating new wetlands in 

11420 agricultural areas at a rate of 16 ha (40 ac) per year (Strange, 2008e). Given the 

11421 anticipated lack of shoreline protection and insufficient sediment input, the seaward 

11422 boundaries of these tidal wetlands are likely to continue retreating (Strange, 2008e, 

11423 interpreting the findings of Reed et al., 2008). The upland elevations are higher in 

11424 southern than northern Accomack County, however, making wetland migration more 

11425 difficult. 

 11426 

11427 The salt marshes of Accomack County support a variety of species, including rare bird 

11428 species such as the seaside sparrow, sharp-tailed sparrow, and peregrine falcon (VA 

11429 DCR, undated [a][b]). Growth and survival of these species may be reduced where shores 

11430 are hardened, unless alternative suitable habitat is available nearby. Furthermore, long11431 term tidal flooding will decrease the ability of nekton (i.e., free-swimming finfish and 

11432 decapod crustaceans such as shrimps and crabs) to access coastal marshes. 

11433 

11434 A1.F.2 Baywide Policy Context 

11435 Chesapeake Bay’s watershed has tidal shores in Virginia, Maryland, the District of 

11436 Columbia, and Delaware. Because the shores of Delaware and the District of Columbia. 
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11437 account for a small portion of the total, this subsection focuses on Virginia and Maryland. 

11438 (The federal Coastal Zone Management Act’s definition of “coastal state” excludes the 

District of Columbia108 11439 .) 

 11440 

11441 Coastal management officials of Maryland have cooperated with the U.S. EPA since the 

11442 1980s in efforts to learn the ramifications of accelerated sea-level rise for their activities 

11443 (AP, 1985). Increased erosion from sea-level rise was one of the factors cited for the 

11444 state’s decision in 1985 to shift its erosion control strategy at Ocean City from groins to 

11445 beach nourishment (AP, 1985). The state also developed a planning document for rising 

11446 sea level (Johnson, 2000), and sea-level rise was a key factor motivating Maryland to 

11447 become the second mid-Atlantic state to obtain lidar elevation data for the entire coastal 

11448 floodplain. 

 11449 

11450 Neither Maryland nor Virginia has adopted a comprehensive policy to explicitly address 

11451 the consequences of rising sea level. Nevertheless, the policies designed to protect 

11452 wetlands, beaches, and private shorefront properties are collectively an implicit policy. 

11453 Both states prevent new buildings within 30.5 m (100 ft) of most tidal shores; Maryland 

11454 also limits the density of new development in most areas to one home per 8 ha (20 ac) 

11455 within 305 m (1,000 ft) of the shore. Virginia allows most forms of shore protection. 

Maryland encourages shore protection109 11456 , but discourages new bulkheads in favor of 

11457 revetments or nonstructural measures (MD DNR, 2006). Both states have programs to 

11458 inform property owners of nonstructural options and have created programs and 

 

108 16 USC §1453 (4) 

109 Code of Maryland Regulations§ 27.01.04.02.02-03 
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11459 educational outreach efforts to train marine contractors on “living shoreline” design and 

11460 installation techniques. Both states work with the federal government to obtain federal 

11461 funds for beach nourishment along their respective ocean resorts (Ocean City and 

11462 Virginia Beach); Virginia also assists local governments in efforts to nourish public 

11463 beaches along Chesapeake Bay and its tributaries. Summaries of these land use, wetlands, 

11464 and beach nourishment policies follow. 

 11465 

11466 During 2007, both states established climate change commissions to inform policy 

11467 makers about options for responding to sea level rise and other consequences of changing 

climate110 11468 . The Maryland Commission on Climate Change is charged with developing a 

climate action plan to address both the causes and consequences of climate change111 11469 . Its 

11470 interim report (MCCC, 2008) recommends that the state (1) protect and restore natural 

11471 shoreline features (e.g., wetlands) and (2) reduce growth and development in areas 

11472 vulnerable to sea-level rise and its ensuing coastal hazards. The Virginia commission has 

11473 an Adaptation Subgroup. 

 11474 

11475 A1.F.2.1 Land Use 

11476 The primary state policies related to land use are Maryland’s Chesapeake and Atlantic 

11477 Coastal Bays Critical Area Protection Act, Virginia’s Chesapeake Bay Preservation Act, 

11478 and Virginia’s Coastal Primary Sand Dunes & Beaches Act. 

 11479 

 

110 Maryland Executive Order (01.01.2007.07); Virginia Executive Order 59 (2007). 111 Maryland Executive Order (01.01.2007.07).
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11480 Maryland Chesapeake Bay and Atlantic Coastal Bays Critical Area Protection Act. The 

11481 Maryland General Assembly enacted the Chesapeake Bay Critical Area Protection Act in 

1984 to reverse the deterioration of the Bay112 11482 . (The statute now applies to Atlantic 

11483 coastal bays as well; see Section A1.E.2) The law seeks to control development in the 

11484 coastal zone and preserve a healthy bay ecosystem. The jurisdictional boundary of the 

11485 Critical Area includes all waters of Chesapeake and Atlantic Coastal Bays, adjacent 

wetlands113, dry land within 305 m (1,000 ft) of open water114 11486 , and in some cases dry land 

within 305 m inland of wetlands that are hydraulically connected to the bays115 11487 . 

 11488 

The act created a Critical Areas Commission to set criteria and approve local plans116 11489 . 

11490 The commission has divided land in the critical area into three classes: intensely 

11491 developed areas (IDAs), limited development areas (LDAs), and resource conservation 

areas (RCAs)117 11492 . Within the RCAs, new development is limited to an average density of 

one home per 8 ha (20 ac)118 and set back at least 61 m (200 ft)119 11493 , and the regulations 

11494 encourage communities to “consider cluster development, transfer of development rights, 

11495 maximum lot size provisions, and/or additional means to maintain the land area necessary 

to support the protective uses”120 11496 . The program limits future intense development 

 

112 Chesapeake Bay Critical Areas Protection Act, Maryland Code Natural Resources §8-1807. 113 i.e. all state and private wetlands designated under Natural Resources Article, Title 9 (now Title 16 of 

the Environment Article). 

114 Maryland Code Natural Resources §8-1807(c)(1)(i)(2). 115 Lands that are less than 1,000 ft from open water may be excluded from jurisdiction if the lands are 

more than 1,000 ft from open water, and the wetlands between that land and the open water are highly 

functional and able to protect the water from adverse effects of developing the land. Maryland Code 

Natural Resources §8-1807(c)(1)(i)(2) and §8-1807(a)(2). 

116 Maryland Code Natural Resources §8-1808. 117 Code of Maryland Regulations §27.01.02.02(A). 118 Code of Maryland Regulations §27.01.02.05(C)(4). 

119 Maryland Code Natural Resources §8-1808.10 The required setback is only 100 feet for new 

construction on pre-existing lots. 

120 Code of Maryland Regulations §27.01.02.05(C)(4). 
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11497 activities to lands within the IDAs, and permits some additional low-intensity 

11498 development in the LDAs. However, the statute allows up to 5 percent of the RCAs in a 

county to be converted to an IDA121 11499 , although a 61-m (200-ft) buffer applies in those 

11500 locations. 

 11501 

11502 The three categories were originally delineated based on the land uses of 1985. Areas that 

11503 were dominated by either agriculture, forest, or other open space, as well as residential 

areas with densities less than one home in 2 ha (5 acres), were defined as RCAs122 11504 . Thus, 

11505 the greatest preservation occurs in the areas that had little development when the act was 

11506 passed, typically lands that are far from population centers and major transportation 

11507 corridors—particularly along tributaries (as opposed to the Bay itself). The boundary of 

11508 the critical area was based on wetland maps created in 1972. MCCC (2008) pointed out 

11509 that rising sea level and shoreline erosion had made that boundary obsolete in some 

11510 locations. As a result, the Legislature directed the Critical Areas Commission to update 

the maps based on 2007 to 2008 imagery, and thereafter at least once every 12 years123 11511 . 

 11512 

11513 The Critical Areas Program also established a 30.5-m (100-ft) natural buffer adjacent to 

tidal waters, which applies to all three land categories124 11514 . No new development activities 

are allowed within the buffer125 11515 , except water-dependent facilities. By limiting 

11516 development in the buffer, the program prevents additional infrastructure from being 

11517 located in the areas most vulnerable to sea-level rise. In some cases, the 30.5-m buffer 

 

121 Code of Maryland Regulations §27.01.02.06. 122 Code of Maryland Regulations §27.01.02.05. 

123 Maryland House Bill 1253 (2008) §3. 124 Code of Maryland Regulations §27.01.00.01 (C)(1). 125 Code of Maryland Regulations §27.01.00.01 (C)(2). 
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11518 provides a first line of defense against coastal erosion and flooding induced by sea-level 

rise. But the regulations also encourage property owners to halt shore erosion126 11519 . 

Nonstructural measures are preferred, followed by structural measures127 11520 , with an eroding 

11521 shore the least preferable (Titus, 1998). 

 11522 

Virginia Chesapeake Bay Preservation Act. The Chesapeake Bay Preservation Act128 11523 

11524 seeks to limit runoff into the bay by creating a class of land known as Chesapeake Bay 

11525 Preservation Areas. The act also created the Chesapeake Bay Local Assistance Board to 

implement129 and enforce130 11526 its provisions. Although the act defers most site-specific 

development decisions to local governments131 11527 , it lays out the broad framework for the 

preservation areas132 11528 and provides the Board with rulemaking authority to set overall 

criteria133. The Board has issued regulations134 11529 defining the programs that local 

governments must develop to comply with the act135 11530 . 

 11531 

11532 All localities must create maps that define the locations of the preservation areas, which 

are subdivided into resource management areas136 11533 and resource protection areas 

 

126 Code of Maryland Regulations§ 27.01.04.02. 02 127 Code of Maryland Regulations§ 27.01.04.02. 03. 128 Code VA §10.1-2100 et seq. As of August 8, 2003, the Act was posted on the Virginia Legislative 

Information System website as part of the Code of Virginia at: <http://leg1.state.va.us/cgibin/legp504.exe?000+cod+TOC10010000021000000000000>. 

129 Code VA §10.1-2102. 130 Code VA §10.1-2104. 131 Code VA §10.1-2109. 132 Code VA §10.1-2107(B). 133 Code VA §10.1-2107(A). 134 Chesapeake Bay Preservation Area Designation and Management Regulations (9 VAC 10-20-10 et. 

seq.). 

135 9 Virginia Administrative Code §10-20-50. 136 The act also provides for Resource Management Areas (RMAs) which are lands that, if improperly used 

or developed, have the potential to diminish the functional value of RPAs. Finally, areas in which 

development is concentrated or redevelopment efforts are taking place may be designated as Intensely 
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(RPAs)137 11534 . RPAs include areas flooded by the tides, as well as a 30.5 m (100-ft) buffer 

inland of the tidal shores and wetlands138 11535 . Within the buffer, development is generally 

11536 limited to water dependent uses, redevelopment, and some water management facilities. 

11537 Roads may be allowed if there is no practical alternative. Similarly, for lots subdivided 

11538 before 2002, new buildings may encroach into the 30.5 m buffer if necessary to preserve 

11539 the owner’s right to build; but any building must still be at least 15.2 m (50 ft) from the 

shore139 11540 . Property owners, however, may still construct shoreline defense structures 

11541 within the RPA. The type of shoreline defense installed is not regulated (beyond certain 

11542 engineering considerations). Consequently, hard structures can be installed anywhere 

11543 along Virginia’s shoreline. 

 11544 

11545 Virginia Coastal Primary Sand Dunes & Beaches Act. Virginia’s Dunes and Beaches Act 

11546 preserves and protects coastal primary sand dunes while accommodating shoreline 

11547 development. The act identifies eight counties and cities that can adopt a coastal primary 

11548 sand dune zoning ordinance, somewhat analogous to a Tidal Wetlands ordinance: 

11549 Accomack, Northampton, Virginia Beach, Norfolk, Hampton, Mathews, Lancaster, and 

11550 Northumberland (Hardaway et al., 2001); all but Hampton and Accomack have done so. 

11551 The act defines beaches as (1) the shoreline zone of unconsolidated sandy material; (2) 

11552 the land extending from mean low water landward to a marked change in material 

11553 composition or in physiographic form (e.g., a dune, marsh, or bluff); and (3) if a marked 

 Developed Areas (IDAs) and become subject to certain performance criteria for redevelopment. Private 

landowners are free to develop IDA and RMA lands, but must undergo a permitting process as well to 

prove that these actions will not harm the RPAs. 

137 9 Virginia Administrative Code §10-20-70. 138 9 Virginia Administrative Code §10-20-80 (B). 

139 9 Virginia Administrative Code §10-20-130 (4). 
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11554 change does not occur, then a line of woody vegetation or the nearest seawall, revetment, 

11555 bulkhead or other similar structure. 

 11556 

11557 A1.F.2.2 Wetlands and Erosion Control Permits 

11558 Virginia. The Tidal Wetlands Act seeks to “...preserve and prevent the despoliation and 

11559 destruction of wetlands while accommodating necessary economic development in a 

11560 manner consistent with wetlands preservation” (VA Code 28.2-1302). It provides for a 

11561 Wetlands Zoning ordinance that any county, city, or town in Virginia may adopt to 

11562 regulate the use and development of local wetlands. Under the ordinance, localities create 

11563 a wetlands board consisting of five to seven citizen volunteers. The jurisdiction of these 

11564 local boards extends from mean low water (the Marine Resources Commission has 

11565 jurisdiction over bottom lands seaward of mean low water) to mean high water where no 

emergent vegetation exists, and slightly above spring high water140 11566 where marsh is 

11567 present. The board grants or denies permits for shoreline alterations within their 

11568 jurisdiction (Trono, 2003). The Virginia Marine Resources Commission has jurisdiction 

11569 over the permitting of projects within state-owned subaqueous lands and reviews projects 

11570 in localities that have no local wetlands board by virtue of not having adopted a wetland 

zoning ordinance141 11571 . 

 11572 

Maryland. The Wetlands and Riparian Rights Act142 11573 gives the owner of land bounding on 

11574 navigable water the right to protect their property from the effects of shore erosion. For 

11575 example, property owners who erect an erosion control structure in Maryland can obtain 

 

140 The act grants jurisdiction to an elevation equal to 1.5 times the mean tide range, above mean low water. 

141 Virginia Administrative Code §28.2. 142 Maryland Environmental Code §16-101 to §16-503. 
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a permit to fill vegetated wetlands143 11576 and fill beaches and tidal waters up to 3 m (10 ft) 

seaward of mean high water144 11577 . In addition, Maryland’s statute allows anyone whose 

11578 property has eroded to fill wetlands and other tidal waters to reclaim any land that the 

owner has lost since the early 1970s145 11579 . (USACE has delegated most wetland permit 

approval to the state146 11580 .) Although the state has long discouraged bulkheads, much of the 

11581 shore has been armored with stone revetments (Titus, 1998). 

 11582 

11583 Shore protection structures tend to be initially constructed landward of mean high water, 

but neither Virginia nor Maryland147 11584 require their removal once the shore erodes to the 

11585 point where the structures are flooded by the tides. Nor has either state prevented 

11586 construction of replacement bulkheads within state waters, although Maryland 

11587 encourages revetments. 

 11588 

11589 For the last several years, Maryland has encouraged the “living shorelines” approach to 

11590 halting erosion (e.g., marsh planting and beach nourishment) over hard structures and 

revetments over bulkheads148 11591 . Few new bulkheads are built for erosion control, and 

11592 existing bulkheads are often replaced with revetments. Nevertheless, obtaining permits 

11593 for structural options has often been easier (NRC, 2007; Johnson and Luscher, 2004). For 

 

143 See MD. CODE ANN., ENVIR. § 16-201 (1996); See Baltimore District (1996), app. at I-24, I-31. 

Along sheltered waters, the state encourages property owners to control erosion by planting vegetation. For 

this purpose, one can fill up to 35 feet seaward of mean high water. See MD. CODE ANN., ENVIR. § 16-

202(c)(3)(iii) (Supp. 1997). Along Chesapeake Bay and other waters with significant waves, hard structures 

are generally employed. 

144 MD. CODE ANN., ENVIR. § 16-202(c)(2). 145 MD. CODE ANN., ENVIR. § 16-201. 146 See Baltimore District (1996) §§ 1-5 147 The Maryland/Virginia border along the Potomac River is the low water mark. Courts have not ruled 

whether Maryland or Virginia environmental rules would govern a structure in Maryland waters attached to 

Virginia land. 

148 Maryland General Permit at 56, § A1(A)(1)(g). 
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11594 example, in the aftermath of Hurricane Isabel, many property owners sought expedited 

11595 permits to replace shore protection structures that had been destroyed by storms. 

11596 Maryland wanted to make obtaining a permit to replace a destroyed bulkhead with a 

11597 living shoreline as easy as obtaining a permit to rebuild the bulkhead; but the state was 

11598 unable to obtain federal approval. The permits issued by USACE authorized replacement 

11599 of the damaged structures with new structures of the same kind, but they did not 

11600 authorize owners to replace lost revetments and bulkheads with living shoreslines, or 

11601 even to replace lost bulkheads with revetments (Johnson and Luscher, 2004). 

 11602 

11603 Recognizing the environmental consequences of continued shoreline armoring, the 

Living Shoreline Protection Act of 2008149 11604 . Under the act, the Department of 

11605 Environment will designate certain areas as appropriate for structural shoreline measures 

11606 (e.g., bulkheads and revetments). Outside of those areas, only nonstructural measures 

11607 (e.g., marsh creation, beach nourishment) will be allowed unless the property owner can 

demonstrate that nonstructural measures are infeasible150 11608 . 

 11609 

11610 A1.F.2.3 Beach Nourishment and Other Shore Protection Activities 

11611 Virginia. Until 2003, the Board on Conservation and Development of Public Beaches 

11612 promoted maintenance, access, and development along the public beaches of Virginia. 

11613 The largest beach nourishment projects have been along the 21 km (13 mi) of public 

11614 beach along the Atlantic Ocean in Virginia Beach. During the last 50 years, the state has 

 

149 MD H.B. 273 (2008). 150 MD Code Environment §16-201(c) 
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11615 provided three percent of the funding for beach nourishment at Virginia Beach, with the 

11616 local and federal shares being 67 percent and 30 percent, respectively (VA PBB, 2000). 

 11617 

11618 Virginia has made substantial efforts to promote beach nourishment (and public use of 

11619 beaches) along Chesapeake Bay and its tributaries. Norfolk’s four guarded beaches serve 

11620 160,000 visitors each summer (VA PBB, 2000). When shore erosion threatened property, 

11621 the tourist economy, and local recreation, the Beach Board helped the city construct a 

11622 series of breakwaters with beachfill and a terminal groin at a cost of $5 million (VA PBB, 

11623 2000). State and local partnerships have also promoted beach restoration projects in 

11624 several other locations along Chesapeake Bay and the Potomac and York rivers. (see 

11625 Table A1.3). 

11626 

11627 Maryland. Maryland’s primary effort to protect shores along the bay is through the 

11628 Department of Natural Resource’s Shore Erosion Control Program. Until 2008, the 

11629 program provided interest-free loans and technical assistance to Maryland property 

11630 owners to resolve erosion problems through the use of both structural and nonstructural 

11631 shore erosion control projects; the program is now limited to “living shoreline” (see Box 

11632 5.3 in Chapter 5) approaches. The program provides contractor and homeowner training 

11633 to support the installation of “living shorelines”. The Department of Natural Resources 

11634 has been involved in several beach nourishment projects along Chesapeake Bay (see 

11635 Table A1.3), many of which include breakwaters or groins to retain sand within the area 

11636 nourished. 

 11637 
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11638 The Maryland Port Administration and the USACE have also used dredge spoils to 

11639 restore Poplar and Smith Islands (USACE, 2001b). Preliminary examinations are under 

11640 way to see if dredged materials can be used to restore other Chesapeake Bay islands such 

11641 as James and Barren Islands (Federal Register, 2006), or to protect valuable 

11642 environmental resources such as the eroding lands of the U.S. Fish and Wildlife Service 

11643 (USFWS) Blackwater National Wildlife Refuge (USFWS, 2008). 

 11644 

Table A1.3. Selected State Funded Beach Nourishment Projects Along Estuarine 

Shores in Maryland and Virginia 

 

Location City or County $Cost 

(Millions) 

Maryland (2001 to 2008)

North Beach Calvert n.a. 

Sandy Point Anne Arundel n.a. 

PT Lookout State Park St Mary’s n.a. 

Choptank River Fishing Pier Talbot n.a. 

Jefferson Island. St. Mary's n.a. 

Tanners Creek St. Mary's n.a. 

Bay Ridge Anne Arundel n.a. 

Hart and Mlllers Island. Baltimore County Co. n.a. 

Rock Hall Town Park Kent n.a. 

Claiborne Landing Talbot n.a. 

Terrapin Beach, Queen Anne’s n.a. 

Jefferson Is. Club - St Catherine 

Island 

St. Mary's n.a. 

Elms Power Plant Site St. Mary's n.a. 

 

Virginia (1995 to 2005) 

Bay Shore Norfolk 5.0 

Parks along James River Newport News 1.0 

Buckroe Beach Hampton 1.3 

Cape Charles Northampton 0.3 

Colonial Beach Westmoreland 0.3 

Aquia Landing Stafford 0.2 

Source: Maryland Department of Natural Resources; Virginia Board on Conservation and 

Development of Public Beaches 
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11645 

11646 A1.G North Caroina 

11647 A1.G.1 Introduction 

11648 North Carolina’s coastline is outlined by a barrier island system, with approximately 500 

11649 km (300 mi) of shoreline along the Atlantic Ocean. North Carolina’s winding estuarine 

11650 shorelines extend a total of approximately 10,000 linear km (6,000 mi) (Feldman, 2008). 

11651 There are three well-known capes along the coastline: Cape Hatteras, Cape Lookout, and 

11652 Cape Fear, in order from north to south. The “Outer Banks” of North Carolina include the 

11653 barrier islands and barrier spits from Cape Lookout north to the Virginia state line. Much 

11654 of this land is owned by the federal government, including Cape Lookout National 

11655 Seashore, Cape Hatteras National Seashore, Pea Island National Wildlife Refuge, and 

11656 Currituck National Wildlife Refuge. The Outer Banks also include several towns, 

11657 including Kitty Hawk, Nags Head, Rodanthe, and Ocracoke (see Section A1.G.4.2). 

11658 North and east of Cape Lookout, four rivers empty into the Albemarle and Pamlico 

11659 Sounds. Albemarle Sound, Pamlico Sound, and their tidal tributaries, sometimes 

11660 collectively called the Albemarle-Pamlico Estuarine System, comprise the second largest 

11661 estuarine system in the United States. 

 11662 

11663 Previous assessments of North Carolina's estuarine regions have divided the state’s 

11664 coastal regions into two principal provinces (geological zones), each with different 

11665 characteristics (e.g., Riggs and Ames, 2003). The zone northeast of a line drawn between 

11666 Cape Lookout and Raleigh (located about 260 km west of the cape) is called the Northern 

11667 Coastal Province, which includes the Outer Banks and most of the land bordering the 
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11668 Albemarle and Pamlico Sounds. It has gentle slopes, three major and three minor inlets, 

11669 and long barrier islands with a moderately low sediment supply, compared to barrier 

11670 islands worldwide (Riggs and Ames, 2003). The rest of the state’s coastal zone―the 

11671 Southern Coastal Province―has steeper slopes, an even lower sediment supply, short 

11672 barrier islands, and many inlets. 

 11673 

11674 The Albemarle-Pamlico Peninsula is the land between Albemarle and Pamlico Sounds, to 

11675 the west of Roanoke Island. The potential vulnerability of this 5,500 sq km (2,100 sq mi) 

11676 peninsula (Henman and Poulter, 2008) is described in Box A1.8. The majority of Dare 

11677 and Hyde counties are less than 1 m (approximately 3 ft) above sea level, as is a large 

11678 portion of Tyrell County (Poulter and Halpin, 2007). Along the estuarine shorelines of 

11679 North Carolina, wetlands are widespread, particularly in Hyde, Tyrell, and Dare counties. 

11680 North Carolina’s Division of Coastal Management mapped a total of more than 11,000 sq 

11681 km (4,400 sq mi) of wetlands in the 20 coastal counties in North Carolina (Sutter, 1999). 

11682 Wetlands types present include marshes, swamps, forested wetlands, pocosins (where 

11683 evergreen shrubs and wetland trees occupy peat deposits), and many other types (Sutter, 

11684 1999). 

 11685 

11686 Where the land is flat, areas a few meters above sea level drain slowly—so slowly that 

11687 most of the lowest land is nontidal wetland (Richardson, 2003). Because rising sea level 

11688 decreases the average slope between nearby coastal areas and the sea, it slows the speed 

11689 at which these areas drain. Some of the dry land within a few meters above the tides 

11690 could convert to wetland from even a small rise in sea level; and nontidal wetlands at 
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11691 these elevations would be saturated more of the time (McFadden et al., 2007; Moorhead 

11692 and Brinson, 1995). Wetland loss could occur if dikes and drainage systems are built to 

11693 prevent dry land from becoming wet (McFadden et al., 2007). 

 11694 

11695 The very low tide range in some of the sounds is another possible source of vulnerability. 

11696 Albemarle Sound, Currituck Sound, and much of Pamlico Sound have a very small tide 

11697 range because inlets to the ocean are few and far between (NOAA, 2008b). Some of the 

11698 inlets are narrow and shallow as well. Although Oregon and Ocracoke inlets are more 

11699 than 10 m (over 30 ft) deep, the inlets are characterized by extensive shoals on both the 

11700 ebb and flood sides, and the channels do not maintain depth for long distances before 

11701 they break into shallower finger channels. Like narrow channels, this configuration limits 

11702 the flow of water between the ocean and sounds (NOAA, 2008c). Thus, although the 

11703 astronomic tide range at the ocean entrances is approximately 90 cm (3 ft), it decreases to 

11704 30 cm (1 ft) just inside the inlets, and a few centimeters in the centers of the estuaries. It 

11705 is possible that rising sea level combined with storm-induced erosion will cause more, 

11706 wider, and/or deeper inlets in the future (Riggs and Ames, 2003; see Chapter 3 of this 

11707 Product). If greater tide ranges resulted, more lands would be tidally inundated. 

 11708 

11709 The configuration of the few inlets within the Northern Coastal Province reduces tidal 

11710 flushing and keeps salinity levels relatively low in most of the estuaries in this area 

11711 (Riggs and Ames, 2003). Salinity is relatively high at the inlets, but declines as one 

11712 proceeds upstream or away from the inlets. Also, there can be a strong seasonal variation 

11713 with lower salinities during the periods of maximum river discharge and higher salinities 
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11714 during periods of drought (Buzzelli et al., 2003). The salinity in Albemarle-Pamlico 

11715 Sound generally ranges from 0 to 20 parts per thousand (ppt), with the upper reaches of 

11716 the Neuse and Pamlico Rivers, Albemarle Sound and Currituck Sound having salinities 

11717 usually below 5 ppt (Caldwell, 2001; Tenore, 1972). (The typical salinity of the ocean is 

11718 35 ppt [Caldwell, 2001]). Some tidal marshes (which are irregularly flooded by the winds 

11719 rather than regularly flooded by astronomical tides) are thus unable to tolerate salt water 

11720 (Bridgham and Richardson, 1993; Poulter, 2005). In some areas, the flow of shallow 

11721 groundwater to the sea is also fresh, so the soils are unaccustomed to salt water, and 

11722 hence potentially vulnerable to increased salinity. 

 11723 

11724 BOX A1.8: Vulnerability of the Albemarle-Pamlico Peninsula and Emerging Stakeholder Response 

11725 

11726 Vulnerability to sea-level rise on the diverse Albemarle-Pamlico Peninsula is very high: about two-thirds of 

11727 the peninsula is less than 1.5 m (5 ft) above sea level (Heath, 1975), and approximately 30 percent is less 

11728 than 0.9 m (3 ft) above sea level (Poulter, 2005). Shoreline retreat rates in parts of the peninsula are already 

11729 high, up to 7.6 m (25 ft) per year (Riggs and Ames, 2003). The ecosystems of the Albemarle-Pamlico 

11730 Peninsula have long been recognized for their biological and ecological value. The peninsula is home to 

11731 four national wildlife refuges, the first of which was established in 1932. In all, about one-third of the 

11732 peninsula has been set aside for conservation purposes.

11733 

11734 The Albemarle-Pamlico Peninsula is among North Carolina’s poorest areas. Four of its five counties are 

11735 classified as economically distressed by the state, with high unemployment rates, along with low average 

11736 household incomes (NC Department of Commerce, 2008). However, now that undeveloped waterfront 

11737 property on the Outer Banks is very expensive and very scarce, developers have discovered the small 

11738 fishing villages on the peninsula and begun acquiring property in several areas—including Columbia 

11739 (Tyrrell County), Engelhard (Hyde County) and Bath (Beaufort County). The peninsula is being marketed 

11740 as the “Inner Banks” (Washington County, 2008). Communities across the peninsula are planning 

11741 infrastructure, including wastewater treatment facilities and desalination plants for drinking water, to 

11742 enable new development. Columbia and Plymouth (Washington County) have become demonstration sites 

11743 in the North Carolina Rural Economic Development Center’s STEP (Small Towns Economic Prosperity) 

11744 Program, which is designed to support revitalization and provide information vital to developing public 

11745 policies that support long-term investment in small towns (NC REDC, 2006). 

11746 

11747 There are already signs that sea-level rise is causing ecosystems on the Albemarle-Pamlico Peninsula to 

11748 change. For example, at the Buckridge Coastal Reserve, a 7,547-ha (18,650-ac) area owned by the North 

11749 Carolina Division of Coastal Management, dieback is occurring in several areas of Atlantic white cedar. 

11750 Other parts of the cedar community are beginning to show signs of stress. Initial investigations suggest the 

11751 dieback is associated with altered hydrologic conditions, due to canals and ditches serving as conduits that 

11752 bring salt and brackish water into the peat soils where cedar usually grows. Storms have pushed estuarine 

11753 water into areas that are naturally fresh, affecting water chemistry, peatland soils, and vegetation intolerant 

11754 of saline conditions (Poulter and Pederson, 2006). There is growing awareness on the part of residents and 

11755 local officials about potential vulnerabilities across the landscape (Poulter, et al., 2009). Some farmers 
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11756 acknowledge that salt intrusion and sea- level rise are affecting their fields (Moorhead and Brinson, 1995). 

11757 Researchers at North Carolina State University are using Hyde County farms to experiment with the 

11758 development of new varieties of salt-tolerant soybeans (Lee et al., 2004). Hyde County is building a dike 

11759 around Swan Quarter, the county seat (Hyde Country, 2008). 

11760 

11761 A variety of evidence has suggested to some stakeholders that the risks to the Albemarle-Pamlico Peninsula 

11762 merit special management responses. In fact, because so much of the landscape across the peninsula has 

11763 been transformed by humans, some have expressed concern that the ecosystem may be less resilient and 

11764 less likely to be able to adapt when exposed to mounting stresses (Pearsall et al., 2005). Thus far, no 

11765 comprehensive long-term response to the effects of sea-level rise on the peninsula has been proposed. In 

11766 2007, The Nature Conservancy, U.S. Fish and Wildlife Service, National Audubon Society, Environmental 

11767 Defense, Ducks Unlimited, the North Carolina Coastal Federation and others began working to build an 

11768 Albemarle-Pamlico Conservation and Communities Collaborative (AP3C) to develop a long-term strategic 

11769 vision for the peninsula. Although this initiative is only in its infancy, sea-level rise will be one of the first 

11770 and most important issues the partnership will address (Nature Conservancy, 2008). 

11771 The Nature Conservancy and other stakeholders have already identified several adaptive responses to sea11772 level rise on the Peninsula. Many of these approaches require community participation in conservation 

11773 efforts, land protection, and adaptive management (Pearsall and Poulter, 2005). Specific management 

11774 strategies that The Nature Conservancy and others have recommended include: plugging drainage ditches 

11775 and installing tide gates in agricultural fields so that sea water does not flow inland through them, 

11776 establishing cypress trees where land has been cleared in areas that are expected to become wetlands in the 

11777 future, reestablishing brackish marshes in hospitable areas that are likely to become wetlands in the future, 

11778 creating conservation corridors that run from the shoreline inland to facilitate habitat migration, reducing 

11779 habitat fragmentation, banning or restricting hardened structures along the estuarine shoreline, and 

11780 establishing oyster reefs and submerged aquatic vegetation beds offshore to help buffer shorelines (Pearsall 

11781 and DeBlieu, 2005; Pearsall and Poulter, 2005). 

11782 End box***

 11783 

11784 More than other areas in the Mid-Atlantic, the Albemarle-Pamlico Sound region appears 

11785 to be potentially vulnerable to the possibility that several impacts of sea-level rise might 

11786 compound to produce an impact larger than the sum of the individual effects (Poulter and 

11787 Halpin, 2007; Poulter et al., 2008). If a major inlet opened, increasing the tide range and 

11788 salinity levels, it is possible that some freshwater wetlands that are otherwise able to keep 

11789 pace with rising sea level would be poisoned by excessive salinity and convert to open 

11790 water. Similarly, if a pulse of salt water penetrated into the groundwater, sulfate reduction 

11791 of the organic-rich soil and peat that underlies parts of the region could cause the land 

11792 surfaces to subside (Hackney and Yelverton, 1990; Henman and Poulter, 2008; Mitsch 

11793 and Gosselink, 2000; Portnoy and Giblin, 1997). Moreover, a substantial acceleration in 
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11794 the rate of sea-level rise storms of the type described below could cause barrier islands to 

11795 be breached (see Chapter 3). Pamlico Sound (and potentially Albemarle Sound) could be 

11796 transformed from a protected estuary into a semi-open embayment with saltier waters, 

11797 regular astronomical tides, and larger waves (Riggs and Ames, 2003). 

 11798 

11799 A1.G.2 Shore Processes 

11800 A1.G.2.1 Ocean Coasts 

11801 North Carolina receives the highest wave energy along the entire east coast of the United 

11802 States and the northwest Atlantic margin (Riggs and Ames 2003). The coast of North 

11803 Carolina has shifted significantly over time due to storms, waves, tides, currents, rising 

11804 sea level, and other natural and human activities. These factors have caused variable 

11805 sediment transport, erosion, and accretion, along with the opening and closing of inlets 

11806 (see, e.g., Everts et al., 1983). 

 11807 

11808 The North Carolina Division of Coastal Management (NCDCM) has calculated long-term 

11809 erosion rates along the coastline adjacent to the ocean by comparing the location of 

11810 shorelines in 1998 with the oldest available maps of shoreline location, mostly from the 

11811 1940s. The average erosion rate was 0.8 m (2.6 ft) per year. Approximately 18 percent of 

11812 the ocean coastline retreated by more than 1.5 m per year (5 ft per year), 20 percent 

11813 eroded at an annual rate of 0.6 to 1.5 m (2 to 5 ft) per year, and 30 percent of the 

11814 coastaline eroded by 0.6 m (2 ft) per year or less. However, 32 percent of the coastline 

11815 accreted (NC DCM, 2003). The NCDCM recalculates long-term erosion rates about 
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11816 every five years to better track the dynamic shoreline trends and establish the setback line 

11817 that determines where structures may be permitted on the oceanfront (NC DCM, 2005). 

 11818 

11819 An analysis of shoreline change between approximately 1850 and 1980 in the area 

11820 between the northern border of North Carolina and the point 8 km west of Cape Hatteras 

11821 has been published. Data were averaged over 2 km reaches (stretches of coastline). 

11822 Across the areas where data were available during this time period, approximately 68 

11823 percent of the ocean shoreline retreated towards the mainland, while approximately 28 

11824 percent advanced (or accreted) away from the mainland, and 4 percent did not change 

11825 position (Everts et al., 1983). On average, the parts of the coastline between Ocracoke 

11826 Inlet and Cape Hatteras eroded an average of 4.5 m (14.8 ft) per year over 1852 to 1917, 

11827 8.3 m (27.2 ft) per year over 1917 to 1949, and 2.0 m (6.6 ft) per year over 1949 to 1980. 

11828 The average erosion rate over the study period along the parts of the coastline facing east 

11829 (between Cape Hatteras and Cape Henry, in Virginia) was 0.8 m (2.6 ft) per year. 

11830 However, the study indicates that the coastline from Cape Hatteras to Oregon Inlet 

11831 accreted slightly (an average of 0.4 m [1.3 ft] per year) over 1852 to 1917, eroded an 

11832 average of 2.9 m (9.5 ft) per year over 1917 to 1949, and eroded an average of 1.3 m (4.3 

11833 ft) per year over 1949 to 1980. North of Oregon Inlet, the coastline was stable, on 

11834 average, over 1852 to 1917; however, there was an average of 1.2 m (3.9 ft) per year of 

11835 erosion over 1917 to 1949 and an average of 0.3 m (1.0 ft) per year of erosion in 1949 

11836 to1980 (Everts et al., 1983). 

 11837 
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11838 The report cautions against predicting future shoreline change based on the limited data 

11839 available from surveys conducted since 1850. The authors observe that shoreline change 

11840 can be influenced by local features, such as inlets, capes, and shoals (Everts et al., 1983). 

11841 For example, shorelines north of the ridges of three offshore shoals intersecting North 

11842 Carolina’s ocean coast have retreated, whereas shorelines south of the ridges have 

11843 generally advanced (Everts et al., 1983). Everts et al. also point out that while geological 

11844 evidence indicates that the barrier islands have migrated landward over thousands of 

11845 years, the islands are presently narrowing from both sides, in part because overwash 

11846 processes cannot carry sand to the estuarine side due to island width and development 

11847 (Everts et al., 1983). 

 11848 

11849 More recently, researchers have used models to predict the amount of shoreline change 

11850 that might result from future sea-level rise, above and beyond the shoreline change 

11851 caused by other factors. For example, one analysis of statewide erosion rates over the past 

11852 100 years led researchers to estimate that a 1 m sea-level rise would cause the shore to 

11853 retreat an average of 88 m (289 ft), in addition to the erosion caused by other factors 

11854 (excluding inlets) (Leatherman et al., 2000a). Another study estimated that a rise in sea 

11855 level of 0.52 m between 1996 and 2050 would cause the shoreline at Nags Head to retreat 

11856 between 33 and 43 m, or between 108 and 144 ft (Daniels, 1996). 

 11857 

11858 Some researchers are concerned that the barrier islands themselves may be in jeopardy if 

11859 sea-level rise accelerates. According to Riggs and Ames (2003), about 40 km (25 mi) of 

11860 the Outer Banks are so sediment-starved that they are already in the process of 
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11861 “collapsing”. Within a few decades, they estimate, portions of Cape Hatteras National 

11862 Seashore could be destroyed by: (1) sea-level rise (at current rates or higher); (2) storms 

11863 of the magnitude experienced in the 1990s; or (3) one or more Category 4 or 5 hurricanes 

11864 hitting the Outer Banks (Riggs and Ames, 2003). Most of the Outer Banks between Nags 

11865 Head and Ocracoke is vulnerable to barrier island segmentation and disintegration over 

11866 the next century if the rate of sea-level rise accelerates by 2 mm per year—and portions 

11867 may be vulnerable even at the current trend (see Chapter 3.) 

11868 

11869 A1.G.3 Vulnerable Habitats and Species 

11870 Some wetland systems are already at the limit of their ability to vertically keep pace with 

11871 rising sea level, such as the remnants of the tidal marshes that connected Roanoke Island 

11872 to the mainland of Dare County until the nineteenth century. The pocosin wetlands can 

11873 vertically accrete by about 1 to 2 mm per year with or without rising sea level—when 

11874 they are in their natural state (Craft and Richardson, 1998; Moorhead and Brinson, 1995). 

11875 The human-altered drainage patterns, however, appear to be limiting their vertical 

11876 accretion—and saltwater intrusion could cause subsidence and conversion to open water 

11877 (Pearsall and Poulter, 2005). 

11878 

11879 A1.G.3.1 Estuarine Shoreline Retreat 

11880 The Pamlico and Albemarle Sounds, North Carolina’s smaller sounds, and the lower 

11881 reaches of the Chowan, Roanoke, Tar, and Neuse Rivers are affected by rising sea level 

11882 (Brinson et al., 1985). Rising sea level is not the primary cause of shoreline retreat along 

11883 estuarine shores in North Carolina. Storm waves cause shorelines to recede whether or 
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11884 not the sea is rising. A study of 21 sites estimated that shoreline retreat—caused by “the 

11885 intimately coupled processes of wave action and rising sea level”—is already eliminating 

11886 wetlands at a rate of about 3 sq km (800 ac) per year, mostly in zones of brackish marsh 

11887 habitat, such as on the Albemarle-Pamlico Peninsula (Riggs and Ames, 2003). 

 11888 

11889 Riggs and Ames (2003) compiled data collected across North Carolina shorelines, both 

11890 those that are adjacent to wetlands and those that are not. These data show that the vast 

11891 majority of estuarine shores in the region are eroding, except for the sound sides of 

11892 barrier islands (which one might expect to advance toward the mainland). Shores have 

11893 retreated almost 2 m (7 ft) per year, over periods as long as 30 years. Annual averages for 

11894 most shoreline types are less than 1 m per year, (Table A1.4) but annual maxima exceed 

11895 the average many-fold and can reach 8 m (26 ft) per year where the shoreline is 

11896 characterized by sediment bluffs or high banks. One or a few individual storm events 

11897 contribute disproportionately to average annual shoreline recession rates (Riggs and 

11898 Ames, 2003). 

Table A1.4 Estuarine shoreline erosion rates by shoreline type and the percent of total 

shoreline for each type. From Riggs and Ames (2003). 

Shoreline type 

Percent of 

shoreline 

Maximum rate 

per year (m) 

Average rate per year 

(m) 

Sediment Bank 38 

 Low bank 30 2.7 1.0 

 Bluff/high bank 8 8.0 0.8 

 Back-barrier strandplain beach <1 0.6 -0.21

Organic Shoreline 62 

 Mainland marsh 55 5.6 0.9 

 Back-barrier marsh <1 5.8 0.4 

 Swamp forest 7 1.8 0.7 

Human Modified Unknown 2.0 0.2 

Weighted Average2 2.7 1

 The negative erosion rate listed refers to this shoreline type, on average, accreting.

 2

11899 This weighted average excludes strandplain beaches and human-modified shorelines. 

11900 
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11901 An analysis of estuarine shoreline change is also included in Everts et al. (1983). The 

11902 authors calculated average erosion rates for the periods around 1850 to 1915 and 1915 to 

11903 1980. Between Nags Head and Oregon Inlet, the estuarine points analyzed between 1850 

11904 and 1915 showed both advance rates greater than 4 m (13 ft) per year and retreat rates of 

11905 close to 3 m (10 ft) per year. However, between 1915 and 1980, the estuarine points 

11906 analyzed in this region showed a range of approximately 1 m per year of retreat to less 

11907 than 1 m per year of advance. Study authors did not analyze the area adjacent to Oregon 

11908 Inlet or along most of Pea Island. Just north of Rodanthe, the earlier dataset shows 

11909 dramatic shoreline advance averaging 4 m per year, but the later dataset shows a 

11910 relatively stable shoreline. Just south of Rodanthe, there was slow advance during the 

11911 earlier period and slow retreat (of approximately 1 m per year or less) in the later period. 

11912 Between Avon and Salvo, both datasets show shoreline retreat at rates not exceeding 2 m 

11913 per year, with a slightly higher average rate of retreat in the later period than the earlier 

11914 period (taken from Figure 34, Everts et al., 1983). 

 11915 

11916 The study indicates that the average retreat rate across all the estuarine points analyzed 

11917 from 1852 to 1980 was 0.1 m (4 in) per year. However, this average masks an important 

11918 trend seen both north and south of Oregon Inlet. The rate of shoreline change gradually 

11919 changed from shoreline advance (movement towards the sounds) to shore retreat. The 

11920 rate of advance was almost 2.0 m per year from 1852 to 1917. Shores were generally 

11921 stable from 1917 to 1949, but they retreated over the period from 1949 to 1980. Erosion 

11922 was greater along estuarine shores facing west (an average of 1.2 m per year over 1852 to 

11923 1980) than those facing north or south (averaging 0.1 m per year over 1852 to 1980). The 
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11924 authors observed that these data indicate that the North Carolina barrier islands in the 

11925 study region did not appear to be migrating landward during the study period, but instead 

11926 they narrowed from both sides. The present rate of island narrowing averages 0.9 m (3.0 

11927 ft) per year. Available data indicate that sand washed over the barrier islands to the 

11928 estuarine side of islands (overwash) did not significantly affect shoreline change along 

11929 the estuary, particularly after the artificial dunes were constructed, a process that might 

11930 itself have caused erosion from the sound side because it removed sand from the 

11931 estuarine system (Everts et al., 1983). Away from the inlets connecting the Albemarle11932 Pamlico Estuarine System to the ocean, the authors conclude that the retreat of the 

11933 estuarine shoreline “can be accounted for mostly by sea level rise” (Everts et al., 

11934 1983). 

 11935 

11936 A1.G.3.2 Potential for Wetlands to Keep Pace with Rising Sea Level 

11937 Sections 4.3, 4.4, and 4.6 in Chapter 4 discuss wetland vertical and horizontal 

11938 development. In North Carolina, vertical accretion rates have, for the most part, matched 

11939 the rate of sea-level rise (see Section 4.6.2 in Chapter 4; Cahoon, 2003; Erlich, 1980; 

11940 Riggs et al., 2000). Vertical accretion rates as high as 2.4 to 3.6 mm per year have been 

11941 measured, but the maximum rate at which wetlands can accrete is not well understood 

11942 (Craft et al., 1993). Further, relative sea-level rise in North Carolina in recent years has 

11943 ranged from approximately 1.8 to 4.3 mm per year at different points along the North 

11944 Carolina coast (Zervas, 2004). As discussed in Section 4.6.2.2, wetland drowning could 

11945 result in some areas if rates of global sea-level rise increase by 2 mm per year and is 

11946 likely if rates increase by 7 mm per year. Day et al. (2005) suggest that brackish marshes 
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11947 in the Mississippi Delta region cannot survive 10 mm per year of relative sea-level rise. 

11948 Under this scenario, fringe wetlands of North Carolina’s lower coastal plain would 

11949 drown. However, swamp forest wetlands along the piedmont-draining rivers are likely to 

11950 sustain themselves where there is an abundant supply of mineral sediments (e.g., river 

11951 floodplains, but not river mouths) (Kuhn and Mendelssohn, 1999). As sea level rises 

11952 further and waters with higher salt content reach the Albemarle-Pamlico peninsula, the 

11953 ability of peat-based wetlands to keep up is doubtful, where the peat, root map, and 

11954 vegetation would first be killed by brackish water (Poulter, 2005; Portnoy and Giblin, 

11955 1997; Pearsall and Poulter, 2005). 

 11956 

11957 Finally, as described in Chapter 3, in a scenario where there are high rates of sea-level 

11958 rise, more inlets would likely be created and segmentation or disintegration of some of 

11959 the barrier islands is possible. This would cause a state change from a non-tidal to tidal 

11960 regime as additional inlets open, causing the Albemarle and Pamlico Sounds to have a 

11961 significant tide range and increased salinity, which would greatly disrupt current 

11962 ecosystems. In this scenario, wave activity in the sounds could change erosion patterns 

11963 and could impact wetlands (Riggs and Ames, 2003). 

 11964 

11965 A1.G.3.3 Environmental Implications of Habitat Loss and Shore Protection 

11966 Ecological/habitat processes and patterns. Some wetland functions are proportional to 

11967 size. Other functions depend on the wetland’s edges, that is, the borders between open 

11968 water and wetland. Many irregularly flooded marshes in coastal North Carolina are quite 

11969 large. In the absence of tidal creeks and astronomical tidal currents, pathways for fish and 
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11970 invertebrate movement are severely restricted, except when wind tides are unusually high 

11971 or during storm events. By contrast, the twice-daily inundation of tidal marshes by 

11972 astronomical tides increases connections across the aquatic-wetland edge, as does the 

11973 presence of tidal creeks, which allow fish and aquatic invertebrates to exploit intertidal 

11974 areas (Kneib and Wagner, 1994). Mobility across ecosystem boundaries is less prevalent 

11975 in irregularly flooded marshes, where some fish species become marsh “residents” 

11976 because of the long distances required to navigate from marshes to subtidal habitats 

11977 (Marraro et al., 1991). Where irregularly flooded marshes are inundated for weeks at a 

11978 time, little is known about how resident species adapt. These include, among other 

11979 species, several types of fish (e.g., killifish and mummichogs), brown water snakes, 

11980 crustaceans (various species of crabs), birds (yellowthroat, marsh wren, harrier, swamp 

11981 sparrow, and five species of rails), and several species of mammals (nutria, cotton rat, 

11982 and raccoon). North Carolina’s coastal marshes are also home to a reintroduced 

11983 population of red wolves, and sea-level rise could affect this population (see Box A1.9). 

 11984 

11985 Effects of human activities. Levees associated with waterfowl impoundments have 

11986 isolated large marsh areas in the southern Pamlico Sound from any connection with 

11987 estuarine waters. Impoundments were built to create a freshwater environment conducive 

11988 to migratory duck populations and thus eliminated most other habitat functions 

11989 mentioned above for brackish marshes. Further, isolation from sea level influences has 

11990 likely disconnected the impoundments from pre-existing hydrologic gradients that would 

11991 promote vertical accretion of marsh soil. If the impoundments were opened to an 
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11992 estuarine connection after decades of isolation, they would likely become shallow, open11993 water areas incapable of reverting to wetlands (Day et al., 1990). 

 11994 

11995 Drainage ditches, installed to drain land so that it would be suitable for agriculture and 

11996 timber harvesting, are prevalent in North Carolina. By the 1970s, on the Albemarle11997 Pamlico Peninsula, there were an estimated 32 km (20 mi) of streams and artificial 

11998 drainage channels per square mile of land, while the ratio in other parts of North Carolina 

11999 ranged from 1.4:1 to 2.8:1 (Heath, 1975). In Dare County, there are currently an 

12000 estimated 4 km of drainage ditch features per sq km (Poulter et al., 2008). In many cases, 

12001 ditches, some of which were dug more than a century ago to drain farmland (Lilly, 1981), 

12002 now serve to transport brackish water landward, a problem that could become 

12003 increasingly prevalent as sea level rises. Saltwater intrusion into agricultural soils and 

12004 peat collapse are major consequences of this process.

 12005 

12006 A number of tide gates have been installed on the Albemarle-Pamlico Peninsula to reduce 

12007 brackish water intrusion, but these will serve their purpose only temporarily, given 

12008 continued sea-level rise. One analysis indicates that plugging ditches in selected places to 

12009 reduce saltwater flow inland would be effective for local stakeholders. Another option is 

12010 to install new water control structures, such as tide gates, in selected locations (Poulter et 

12011 al., 2008). Plugging ditches would also help restore natural drainage patterns to the 

12012 marshes. 

 12013 

12014 A1.G.4 Development, Shore Protection, and Coastal Policies 
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12015 A1.G.4.1 Statewide Policy Context 

12016 Several North Carolina laws and regulations have an impact on response to sea-level rise 

12017 within the state. First, setback rules encourage retreat by requiring buildings being 

12018 constructed or reconstructed to be set back a certain distance from where the shoreline is 

12019 located when construction permits are issued. Second, North Carolina does not allow 

“hard” shoreline armoring 151 12020 such as seawalls and revetments on oceanfront 

shorelines152 12021 , preventing property owners from employing one possible method of 

holding back the sea to protect property153 12022 . Along estuarine shores, however, shoreline 

12023 armoring is allowed landward of any wetlands. The North Carolina Coastal Resources 

12024 Commission (CRC) is preparing new state regulations for the location and type of 

12025 estuarine shoreline stabilization structures to help encourage alternatives to bulkheads

12026 (NC CRC, 2008b; Feldman, 2008). The goals are similar to the “living shorelines” 

12027 legislation recently enacted in Maryland (see Section A1.F.2.2). Adding sand to beaches 

12028 (i.e., beach nourishment) is the preferred method in North Carolina to protect buildings 

12029 and roads along the ocean coastline. 

 12030 

12031 The state’s Coastal Area Management Act (CAMA) has fostered land use planning in the 

12032 20 coastal counties to which it applies. Regulations authorized by CAMA require local 

12033 land use plans to “[d]evelop policies that minimize threats to life, property, and natural 

12034 resources resulting from development located in or adjacent to hazard areas, such as those 

 

151 See Chapter 6 for an explanation of various shore protection options. 152 15A NCAC 07H.0101. 153 Some hard structures exist along North Carolina’s oceanfront shoreline (e.g., adjacent to inlets). Many 

were built before 1985 when the statute was enacted to ban new hard structures, or were covered by 

exception in the rules. The Legislature regularly considers additional exceptions, such as terminal groins 

for beach nourishment projects and jetties for stabilizing inlets. e.g. North Carolina SB599 (2007-2008). 
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12035 subject to erosion, high winds, storm surge, flowing, or sea level rise”. However, the 

12036 state’s technical manual for coastal land use planning (NC DCM, 2002) does not mention 

12037 sea-level rise. Accordingly, local land use plans either do not mention sea-level rise at all, 

12038 mention it only in passing, or explicitly defer decisions about vulnerable areas until more 

12039 information is available in the future (Feldman, 2008; Poulter et al., 2009). Nevertheless, 

12040 the regulatory requirement to consider sea-level rise may eventually encourage local 

12041 jurisdictions to consider how the communities most vulnerable to sea-level rise should 

12042 prepare and respond (Feldman, 2008). Land-use plans are updated regularly and are an 

12043 important tool for increasing public awareness about coastal hazards. 

 12044 

12045 CAMA and the state’s Dredge and Fill Law authorize the CRC to regulate certain aspects 

12046 of development within North Carolina’s 20 coastal counties. For example, the CRC 

12047 issues permits for development and classifies certain regions as Areas of Environmental 

12048 Concern (AECs, e.g., ocean hazard zones and coastal wetlands) where special rules 

12049 governing development apply. Land use plans are binding in AECs. In response to the 

12050 threat of damage to coastal structures from the waves, since 1980 North Carolina has 

12051 required new development to be set back from the oceanfront. The setbacks are measured 

from the first line of stable natural vegetation154 12052 . Single-family homes of any size—as 

12053 well as multi-family homes and non-residential structures with less than 5,000 sq ft of 

12054 floor area—must be set back by 60 ft or 30 times the long-term rate of erosion as 

12055 calculated by the state, whichever is greater. Larger multi-family homes and non12056 residential structures must be set back by 120 ft or the erosion-based setback distance, 

 

154 Local governments can request that an alternative vegetation line be established under certain 

conditions. Additional rules also apply when there is a sand dune between the home and the shoreline, to 

protect the integrity of the dune. 
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12057 whichever is greater. The setback distance for these larger structures is set as either 60 

times the annual erosion rate or 105 ft plus 30 times the erosion rate, whichever is less155 12058 . 

12059 North Carolina is considering changes to its oceanfront setback rules, including 

12060 progressively larger setback factors for buildings with 10,000 sq ft of floor area or more 

(NC CRC, 2008a). Along estuarine shorelines, North Carolina has a 30-ft setback156 12061 and 

restricts development between 30 and 75 ft from the shore157 12062 . As the shore moves inland, 

12063 these setback lines move inland as well. 

 12064 

12065 As of 2000, the U.S. Army Corps of Engineers (USACE) participated in beach 

12066 nourishment projects along more than 51 km (32 mi) of North Carolina’s shoreline 

12067 (including some nourishment projects that occurred as a result of nearby dredging 

12068 projects), and nourishment along an additional 137 km (85 mi) of coastline had been 

proposed (USACE, 2000)158 12069 . If necessary, property owners can place large geotextile 

12070 sandbags in front of buildings to attempt to protect them from the waves. Standards apply 

12071 to the placement of sandbags, which is supposed to be temporary (to protect structures 

12072 during and after a major storm or other short-term event that causes erosion, or to allow 

time for relocation)159 12073 . Buildings are supposed to be moved or removed within two years 

of becoming “imminently threatened” by shoreline changes160 12074 . 

 12075 

 

155 15A NCAC 07H. 0305 - 0306. 156 15A NCAC 07H.0306.

157 15A NCAC 07H.0209

158 Although beach nourishment has been a common response to sea level rise in many areas along the 

coast, there has been a decline in the availability of suitable sand sources for nourishment, particularly 

along portions of the coast (Bruun, 2002). In addition, the availability of substantial federal funds allocated 

for beach nourishment has become increasingly questionable in certain areas, particularly in Dare County 

(Dare County, 2007; Coastal Science and Engineering, 2004). 

159 15A NCAC 07H.0308 

160 15A NCAC 7H.0306 (l) 
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12076 North Carolina officials are in the process of reassessing certain state policies in light of 

12077 the forces of shoreline change and climate change. Policy considerations have been 

12078 affected by numerous studies that researchers have published on the potential effects of 

12079 sea-level rise on North Carolina (Poulter et al., 2009). The state legislature appointed a 

12080 Legislative Commission on Global Climate Change to study and report on potential 

12081 climate change effects and potential mitigation strategies, including providing 

recommendations that address impacts on the coastal zone161 12082 . The Commission’s 

12083 recommendations have not yet been finalized, but an initial draft version offered such 

12084 suggestions as creating a mechanism to purchase land or conservation easements in low12085 lying areas at great risk from sea-level rise; providing incentives for controlling erosion 

12086 along estuarine shorelines using ecologically beneficial methods; creating a commission 

12087 to study adaptation to climate change and make recommendations about controversial 

12088 issues; and inventorying, mapping, and monitoring the physical and biological 

12089 characteristics of the entire shoreline (Feldman, 2008; Riggs et al., 2007). 

 12090 

12091 The CRC is also considering the potential effects of sea-level rise and whether to 

12092 recommend any changes to its rules affecting development in coastal areas (Feldman, 

12093 2008). In addition, NCDCM is developing a Beach and Inlet Management Plan to define 

12094 beach and inlet management zones and propose preliminary management strategies given 

12095 natural forces, economic factors, limitations to the supply of beach-quality sand, and 

12096 other constraints (Moffatt and Nichol, 2007).

12097 

12098 A1.G.4.2 Current Land Use 

 

161 See the “North Carolina Global Warming Act,” Session Law 2005-442.
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12099 Ocean Coast (from north to south). North Carolina’s ocean coast, like the coasts of most 

12100 states, includes moderate and densely developed communities, as well as undeveloped 

12101 roadless barrier islands. Unlike other mid-Atlantic states, North Carolina’s coast also 

12102 includes a major lighthouse (at Cape Hatteras) that has been relocated landward, a 

12103 roadless coastal barrier that is nevertheless being developed (described below), and 

12104 densely populated areas where storms, erosion, and sea-level rise have caused homes to 

12105 become abandoned or relocated. 

 12106 

12107 The northern 23 km (14 mi) of the state’s coastline is a designated undeveloped coastal 

12108 barrier under the Coastal Barrier Resources Act (CBRA) and hence ineligible for most 

12109 federal programs (USFWS, undated[c]) This stretch of barrier island includes two 

12110 sections of Currituck National Wildlife Refuge, each about 2 km (1 mi) long, which are 

12111 both off-limits to development. Nevertheless, the privately owned areas are gradually 

12112 being developed, even though they are accessible only by boat or four-wheel drive 

12113 vehicles traveling along the beach. The CBRA zones are ineligible for federal beach 

12114 nourishment and flood insurance (USFWS, undated[c]). 

 12115 

12116 Along the Dare County coast from Kitty Hawk south to Nags Head, federal legislation 

12117 has authorized shore protection, and USACE (2006b) has concluded that the proposed 

12118 project would be cost-effective. In some areas, homes have been lost to shoreline erosion 

12119 (Pilkey et al., 1998) (see Figure 12.6). Continued shore erosion has threatened some of 

12120 the through-streets parallel to the shore, which had been landward of the lost homes. 

12121 Given the importance of those roads to entire communities (see Section 12.2 in Chapter 
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12122 12) small sand replenishment projects have been undertaken to protect the roads (Town 

12123 of Kitty Hawk, 2005). The planned beach nourishment project does not extend along the 

12124 coast to the north of Kitty Hawk. Those beaches are generally not open to the public and 

12125 are currently ineligible for publicly funded beach nourishment. 

 12126 

12127 From Nags Head to the southwestern end of Hatteras Island, most of the coast is part of 

12128 Cape Hatteras National Seashore. A coastal highway runs the entire length, from which 

12129 one can catch a ferry to Ocracoke Island, carrying through traffic to both Ocracoke and 

12130 Carteret County. Therefore, the National Park Service must balance its general 

12131 commitment to allowing natural shoreline processes to function (see Chapter 12.1; NRC 

12132 1988) with the needs to manage an important transportation artery. In most cases, the 

12133 approach is a managed retreat, in which shores generally migrate but assets are relocated 

12134 rather than simply abandoned to the sea. Congress appropriated $9.8 million to move the 

12135 Cape Hatteras Lighthouse 1,600 ft (468 m) inland in 1999 (NPS, 2000) (see Figure 

12136 11.1a). The coastal highway has been relocated inland in places. Because it is essential 

12137 infrastructure, its protection would probably require maintaining the barrier island itself, 

12138 for example, by filling inlets after severe storms. A possible exception is where the 

12139 highway runs through Pea Island National Wildlife Refuge on the northern end of 

12140 Hatteras Island, just south of the bridge over Oregon Inlet. The federal and state 

12141 governments are considering the possibility that when a new bridge is built over Oregon 

12142 Inlet, it would bypass the National Wildlife Refuge and extend over Pamlico Sound just 

12143 west of Hatteras Island as far as Rodanthe (USDOI, 2007). 

 12144 
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12145 The undeveloped Portsmouth Island and Core Banks constitute Cape Lookout National 

12146 Sea Shore and lack road access. Cape Lookout is located on Core Banks. Shackleford 

12147 Banks, immediately adjacent to the southwest, is also roadless and uninhabited. 

12148 Southwest of Cape Lookout, the coast consists mostly of developed barrier islands, 

12149 conservation lands, and designated “undeveloped coastal barriers” that are nevertheless 

12150 being developed. Bogue Banks includes five large communities with high dunes and 

12151 dense forests (Pilkey et al., 1998). Bogue Banks also receives fill to widen its beaches 

12152 regularly. 

 12153 

12154 To the west of Bogue Banks are the barrier islands of Onslow County and then Pender 

12155 County. Some islands are only accessible by boat, and most of these are undeveloped. 

12156 North Topsail Beach, on Topsail Island, has been devastated by multiple hurricanes, in 

12157 part due to its low elevation and the island’s narrow width. Erosion has forced multiple 

12158 roads on the island to be moved. While some parts of North Topsail Beach are part of a 

12159 unit under the CBRA system, making them ineligible for federal subsidies, development 

12160 has occurred within them nonetheless (Pilkey et al., 1998). 

 12161 

12162 Further to the southwest are the barrier islands of New Hanover County, including Figure 

12163 Eight Island, which is entirely privately-owned with no public access to the beach, and 

12164 hence ineligible for public funding for beach nourishment (see Chapter 8). Wrightsville 

12165 Beach, like many other communities southwest of Cape Lookout, has an inlet on each 

12166 side. It is the site of a dispute to protect a hotel from being washed away due to inlet 

12167 migration (Pilkey et al., 1998). The USACE has made a long-term commitment to regular 
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12168 beach renourishment to maintain the place of the shoreline in Wrightsville Beach and 

12169 Carolina Beach (USACE, 2006a). An exception to North Carolina’s rules forbidding 

12170 hardened structures has been granted in Kure Beach, west of Carolina Beach, where stone 

12171 revetments have been placed on the oceanfront to protect Fort Fisher (which dates back to 

12172 the Civil War). These structures also protect a highway that provides access to the area 

12173 (Pilkey et al., 1998). Most of the beach communities in New Hanover County are 

12174 extensively developed. 

 12175 

12176 Some of the barrier islands in Brunswick County, close to the South Carolina state line, 

12177 are heavily forested with high elevations, making them more resilient to coastal hazards 

12178 (Pilkey et al., 1998). Holden Beach and Ocean Isle Beach, however, contain many 

12179 dredge-and-fill finger canals. Historically, at least two inlets ran through Holden Beach; 

12180 and storms could create new inlets where there are currently canals (Pilkey et al., 1998). 

 12181 

12182 Estuarine Shores. Significant urbanization was slow to come to this region for many 

12183 reasons. Most of the area is farther from population centers than the Delaware and 

12184 Chesapeake Estuaries. The Outer Banks were developed more slowly than the barrier 

12185 islands of New Jersey, Delaware, and Maryland. Most importantly, the land is mostly low 

12186 and wet. 

12187 

12188 Unlike the Delaware Estuary, North Carolina does not have a long history of diking tidal 

wetlands to reclaim land from the sea for agricultural purposes162 12189 . However, the state is 

 

162 Nevertheless, it has had a few short-lived projects, most notably Lake Matamuskeet.
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12190 starting to gain experience with dikes to protect agricultural lands from flooding. In 

12191 Tyrrell County, the Gum Neck has been protected with a dike for four decades. A dike is 

12192 under construction for the town and farms around Swan Quarter (Allegood, 2007), the 

12193 county seat of Hyde County (which includes Ocracoke Island). Hurricanes Fran and 

12194 Floyd led to federally-sponsored purchases of thousands of properties across North 

12195 Carolina’s eastern counties, facilitating the demolition or relocation of associated 

12196 structures. Pamlico County has encouraged people to gradually abandon Goose Creek 

12197 Island in the eastern portion of the county, by working with FEMA to relocate people 

12198 rather than rebuild damaged homes and businesses (Barnes, 2001). By contrast, in other 

12199 areas (e.g., parts of Carteret County), people took the opposite approach and elevated 

12200 homes.

 12201 

12202 Geography, coastal features, and community characteristics vary greatly along North 

12203 Carolina’s coast. Thus, one can assume that a variety of different planning and adaptation 

12204 strategies related to shoreline change and sea-level rise would be needed, particularly 

12205 over the long term. Scientists, managers, and community members in North Carolina 

12206 have undertaken a variety of efforts to better understand and begin to address potential 

12207 sea-level rise vulnerabilities and impacts. These research and collaborative efforts may 

12208 increase awareness, receptivity, and readiness to make informed coastal management 

12209 decisions in the future (Poulter et al., 2009). 

 12210 

12211 
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12212 APPENDIX 1 REFERENCES 

12213 * Indicates non-peer reviewed literature; available upon request 

12214 

12215 

12216 Abel, K.W. and S.M. Hagan, 2000: Effects of common reed (Phragmites australis) 

12217 invasion on marsh surface macrofauna: Response of fishes and decapod 

12218 crustaceans. Estuaries, 23(5), 633-646. 

12219 Abel, K.W., D.M. Nemerson, P.R. Light, and R.O. Bush, 2000: Initial response of fishes 

12220 to marsh restoration at a former salt hay farm bordering Delaware Bay. In: 

12221 Concepts and Controversies in Tidal Marsh Ecology, [Weinstein, M.P. and D.A. 

12222 Kreeger (eds.)]. Kluwer Academic Publishers, Dordrecht, the Netherlands, 

12223 * Allegood, J., 2007: Dike to protect Swan Quarter: Battered coastal village hopes to 

12224 hold back flooding from the next hurricane. Raleigh News and Observer, May 29, 

12225 2007.

12226 ADC (Alexandria Drafting Company), 2008: Stafford County, VA Street Atlas. 

12227 Langennscheldt Publishing Group, Duncan, SC, 60 pp.

12228 * AP (Associated Press), 1985: Doubled erosion seen for Ocean City. Washington Post, 

12229 November 14th. (Maryland Section). 

12230 Ayers, R.A., 2005: Human Impacts to Sensitive Natural Resources on the Atlantic 

12231 Barrier Islands on the Eastern Shore of Virginia. Virginia Department of 

12232 Environmental Quality, Coastal Zone Management Program, Richmond, 14 pp. 

12233 <http://www.deq.state.va.us/coastal/documents/task11-07-04b.pdf> 

12234 Baker, A.J., P.M. Gonzalez, T. Piersma, L.J. Niles, and I. de Lima Serrano do 

12235 Nacimento, 2004: Rapid population decline in Red Knots: fitness consequences of 

12236 decreased refueling rates and late arrival in Delaware Bay. Proceedings of the 

12237 Royal Society of London, B, 271, 875-882. 

12238 Barnes, J., 2001: North Carolina's Hurricane History. University of North Carolina 

12239 Press, Chapel Hill, NC, 336 pp. 
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12240 BBNEP (Barnegat Bay National Estuary Program, Scientific and Technical Advisory 

12241 Committee), 2001: Chapter 7 of The Barnegat Bay Estuary Program 

12242 Characterization Report.

12243 <http://www.bbep.org/Char_Rpt/Ch7/Chapter%207.htm> 

12244 Baltimore District, 1996: Maryland State Programmatic General Permit (MDSPGP). 

12245 U.S. Army Corps of Engineers, Baltimore. 

12246 Berkson, J. and C.N. Shuster Jr., 1999: The horseshoe crab: the battle for a true multiple12247 use resource. Fisheries, 24, 6-10. 

12248 Berman, M.R., H. Berquist, S. Dewing, J. Glover, C.H. Hershner, T. Rudnicky, D.E. 

12249 Schatt, and K. Skunda, 2000: Mathews County Shoreline Situation Report. 

12250 Special report in applied marine science and ocean engineering no. 364. 

12251 Comprehensive Coastal Inventory Program, Virginia Institute of Marine Science, 

12252 College of William and Mary, Gloucester Point, VA. 

12253 Bernd-Cohen, T. and M. Gordon, 1999: State coastal program effectiveness in 

12254 protecting natural beaches, dunes, bluffs, and rock shores. Coastal Management,

12255 27, 187-217. 

12256 Bernick, A.J., 2006: New York City Audubon’s Harbor Herons Project: 2006 Interim 

12257 Nesting Survey. Report prepared for New York City Audubon, New York, 22 pp. 

12258 Bertness, M.D., 1999: The Ecology of Atlantic Shorelines. Sinauer Associates, 

12259 Sunderland, MA, 417 pp. 

12260 * Bleyer, B., 2007: Erosion protection for Montauk lighthouse creates waves. Lighthouse 

12261 Digest. 

12262 <http://www.lighthousedigest.com/Digest/StoryPage.cfm?StoryKey=2636> 

12263 Boesch, D.F. and R.E. Turner, 1984: Dependence of fishery species on salt marshes: the 

12264 role of food and refuge. Estuaries, 7(4A), 460-468. 
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12265 Botton, M.L., R.E. Loveland, and T.R. Jacobsen, 1988: Beach erosion and geochemical 

12266 factors: influence on spawning success of horseshoe crabs (Limulus polyphemus) 

12267 in Delaware Bay. Marine Biology, 99(3), 325-332. 

12268 Botton, M.L., R.E. Loveland, J.T. Tanacredi, and T. Itow, 2006: Horseshoe crabs 

12269 (Limulus polyphemus) in an urban estuary (Jamaica Bay, New York) and the 

12270 potential for ecological restoration. Estuaries and Coasts, 29(5), 820-830. 

12271 Bridgham, S. D., and C. J. Richardson, 1993: Hydrology and nutrient gradients in North 

12272 Carolina peatlands. Wetlands, 13, 207-218. 

12273 Brinson, M.M., H.D. Bradshaw, and M.N. Jones, 1985: Transitions in forested wetlands 

12274 along gradients of salinity and hydroperiod. Journal of the Elisha Mitchell 

12275 Scientific Society, 101, 76-94. 

12276 Burger, J., 1984: Cited in New York State Department of State and the U.S. Fish and 

12277 Wildlife Service, Southern New England–New York Bight Coastal Ecosystems 

12278 Program. 1998. Shorebirds. South Shore Estuary Reserve, Technical Report 

12279 Series. 

12280 <http://www.nyswaterfronts.com/Final_Draft_HTML/Tech_Report_HTM/PDFs/

12281 C8A_Index_pdf.htm> 

12282 Burger, J., L. Niles, and K.E. Clark, 1997: Importance of beach, mudflat, and marsh 

12283 habitats to migrant shorebirds in Delaware Bay. Biological Conservation 79(2), 

12284 283-292. 

12285 Buzzelli, C. ., J.R. Ramus, and H.W. Paerl, 2003: Ferry-based monitoring of surface 

12286 water quality in North Carolina estuaries. Estuaries, 26, 975-984. 

12287 * Byrne, D.M., 1995: The effect of bulkheads on estuarine fauna: a comparison of littoral 

12288 fish and macroinvertebrate assemblages at bulkheaded and non-bulkheaded 

12289 shorelines in a Barnegat Bay Lagoon. In: Second Annual Marine Estuarine 

12290 Shallow Water Science and Management Conference, Atlantic City, NJ.

12291 Environmental Protection Agency, Philadelphia, PA, pp. 53-56. 
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12292 Cahoon, D.R., 2003: Storms as agents of wetland elevation change: their impact on 

12293 surface and subsurface sediment processes. Proceedings of the International 

12294 Conference on Coastal Sediments 2003, May 18-23, 2003, Clearwater Beach, 

12295 Florida. World Scientific Publishing Corporation, Corpus Christi TX.

12296 Caldwell, W.S., 2001: Hydrologic and Salinity Characteristics of Currituck Sound and 

12297 Selected Tributaries in North Carolina and Virginia, 1998-99. USGS water 

12298 resources investigation report 01-4097. U.S. Geological Survey, Raleigh, NC, 36 

12299 pp. 

12300 Casey, J. and S. Doctor, 2004: Status of finfish populations in the Maryland Coastal 

12301 Bays. In: Maryland’s Coastal Bays: Ecosystem Health Assessment 2004

12302 [Wazniak, C.E. and M.R. Hall (eds.)]. DNR-12-1202-0009. Maryland Department 

12303 of Natural Resources, Tidewater Ecosystem Assessment, Annapolis, chapter 8.4. 

12304 Castro, G. and J.P. Myers, 1993: Shorebird predation on eggs of horseshoe crabs during 

12305 spring stopover on Delaware Bay. Auk, 110(4), 927-930. 

12306 CBCAC ( Chesapeake Bay Critical Area Commission, Maryland Department of Natural 

12307 Resources), 2001: Chesapeake Bay Critical Area Line. 

12308 <http://www.marylandgis.net/metadataexplorer/full_metadata.jsp?docId=%7B480

12309 9747B-1DF0-4635-92D1-CE99AA1A84C1%7D&loggedIn=false> 

12310 * CBP (Chesapeake Bay Program), 2002: The Impact of Susquehanna Sediments on the 

12311 Chesapeake Bay. Scientific and Technical Advisory Committee Workshop 

12312 Report. May 2002 

12313 * CBP (Chesapeake Bay Program), 2006: Diamondback Terrapin. [web site] 

12314 <http://www.chesapeakebay.net/diamondback_terrapin.htm> 

12315 * Chase, C.M., 1979: The Holocene Geologic History of the Maurice River Cove and its 

12316 Marshes, Eastern Delaware Bay, New Jersey. MS Thesis, University of 

12317 Delaware, Newark, 129 pp. 
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12318 Clark, K., 1996: Horseshoe crabs and the shorebird connection. In: Proceedings of the 

12319 Horseshoe Crab Forum: Status of the Resource [Farrell, J. and C. Martin 

12320 (eds.)].University of Delaware Sea Grant College Program, Lewes, pp. 23-25. 

12321 * CLO (Cornell Laboratory for Ornithology), 2004: All About Birds: Piping Plover. [web 

12322 site] 

12323 <http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Piping_Plover_dtl.html

12324 > 

12325 Cohen, J.B., E.H. Wunker, J.D. Fraser, 2005: Substrate and vegetation selection by 

12326 piping plovers. Wilson Journal of Ornithology, 120(2), 404-407 

12327 Conley, M., 2004: Maryland Coastal Bays Aquatic Sensitive Areas Initiative Technical 

12328 Report. Prepared by the Maryland Department of Natural Resources, Coastal 

12329 Zone Management Division. 

12330 Cooper, M.J.P., M.D. Beevers, and M. Oppenheimer, 2005: Future Sea-level Rise and 

12331 the New Jersey Coast. Science, Technology, and Environmental Policy Program, 

12332 Woodrow Wilson School of Public and International Affairs, Princeton 

12333 University, Princeton, NJ, 37 pp. 

12334 <http://www.princeton.edu/~step/people/Oppenheimer%20Future%20of%20Sea

12335 %20Level%20Rise.pdf> 

12336 CPCP (City of Poquoson Comprehensive Plan), 1999: Environmental Element. 

12337 Poquoson, VA. <http://www.ci.poquoson.va.us/> 

12338 Craft, C.B. and C.J. Richardson, 1998: Recent and long-term organic soil accretion and 

12339 nutrient accumulation in the everglades. Soil Science Society of America Journal, 

12340 62, 834-843. 

12341 Craft, C.B., E.D. Seneca, and S.W. Broome, 1993: Vertical accretion in microtidal 

12342 regularly and irregularly flooded estuarine marshes. Estuarine, Coastal, and Shelf 

12343 Science, 37, 371-386. 
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12344 Daniels, R.C., 1996: An innovative method of model integration to forecast spatial 

12345 patterns of shoreline change: A case study of Nags Head, North Carolina. The 

12346 Professional Geographer, 48(2), 195-209. 

12347 Darmondy, R.G. and J.E. Foss, 1979: Soil-landscape relationships of tidal marshes of 

12348 Maryland. Soil Science Society of America Journal, 43(3), 534-541. 

12349 Day, R.H., R.K. Holz, and J.W. Day Jr., 1990: An inventory of wetland impoundments in 

12350 the coastal zone of Louisiana, USA: historical trends. Environmental 

12351 Management, 14(2), 229-240. 

12352 Day, J.W., Jr., J. Barras, E. Clairain, J. Johnston, D. Justic, G.P. Kemp, J.-Y. Ko, R. 

12353 Lane, W.J. Mitsch, G. Steyer, P. Templet, and A. Yañez-Arancibia, 2005: 

12354 Implications of global climatic change and energy cost and availability for the 

12355 restoration of the Mississippi delta. Ecological Engineering, 24(4), 253-265.

12356 DCOP (District of Columbia Office of Planning), 2003: Anacostia Riverparks Target 

12357 Area Plan and Riverwalk Design Guidelines. District of Columbia Office of 

12358 Planning, Washington, DC, 6 pp. 

12359 Dean, C., 1999: Against the Tide: The Battle for America’s Beaches. Columbia 

12360 University Press, New York, 279 pp. 

12361 DDA (Delaware Department of Agriculture), 2008: Delaware Agricultural Preservation 

12362 Program: Statewide District/Easement Maps. Dover, DE. 

12363 <http://dda.delaware.gov/aglands/forms/2008/062008JuneMap.pdf> 

12364 DNREC (Delaware Department of Natural Resources and Environmental Control), 

12365 undated: Discover Delaware’s Inland Bays. Document No. 40-01-01/03/03/01. 

12366 <www.dnrec.state.de.us/dnrec2000/Library/Misc/InlandBays> 

12367 DNREC (Delaware Department of Natural Resources and Environmental Control), 2001: 

12368 Inland Bays/Atlantic Ocean Basin Assessment. Report. Document No. 40-

12369 01/01/01/02. Published June 2001. 
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12370 DNREC (Delaware Department of Natural Resources and Environmental Control), 2007: 

12371 Inland Bays Pollution Control Strategy and Proposed Regulations. April 2007. 

12372 DNREC, Division of Water Resources, Dover, DE. 

12373 Doctor, S. and C.E. Wazniak, 2005: Status of horseshoe crab, Limulus polyphemus,

12374 populations in Maryland coastal bays. In: Maryland’s Coastal Bays: Ecosystem 

12375 Health Assessment 2004 [Wazniak, C.E. and M.R. Hall, (eds.)]. DNR-12-1202-

12376 0009. Maryland Department of Natural Resources, Tidewater Ecosystem 

12377 Assessment, Annapolis, chapter 8.7. 

12378 DOSP (Delaware Office of State Planning), 1997: Land Use/Land Cover. Dover, DE. 

12379 Dove, L.E. and R.M. Nyman (eds.), 1995: Living Resources of the Delaware Estuary. 

12380 Delaware Estuary Program Report Number 95-07. Partnership for the Delaware 

12381 Estuary, Wilmington, DE. 

12382 Dugan, J.E., D.M. Hubbard, M.D. McCrary, and M.O. Pierson, 2003: The response of 

12383 macrofauna communities and shorebirds to macrophyte wrack subsidies on 

12384 exposed sandy beaches of southern California. Estuarine, Coastal, and Shelf 

12385 Science, 58S, 25–40. 

12386 Ednie, A.P., Undated: Birding Delaware’s Prehistoric Past: Thompson’s Island at 

12387 Delaware Seashore State Park.

12388 <http://www.dvoc.org/DelValBirding/Places/ThompsonsIslandDE.htm> 

12389 Engelhardt, K.A.M., S. Seagle, and K.N. Hopfensperger, 2005: Should We Restore Dyke 

12390 Marsh? A Management Dilemma Fcing George Washington Memorial Parkway. 

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12392 National Capital Region, McLean, VA. 

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12394 Roanoke River Area, North Carolina. M.S. thesis, Department of Geology, 

12395 University of North Carolina, Chapel Hill, 83 pp.
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12396 Ernst, C.H. and R.W. Barbour, 1972: Turtles of the United States. University Press of 

12397 Kentucky, Lexington, 347 pp. 

12398 Erwin, R.M., 1996: Dependence of waterbirds and shorebirds on shallow-water habitats 

12399 in the mid-Atlantic coastal region: An ecological profile and management 

12400 recommendations. Estuaries, 19(2A), 213-219. 

12401 Erwin, R.M., G.M. Sanders, and D.J. Prosser, 2004: Changes in lagoonal marsh 

12402 morphology at selected northeastern Atlantic Coast sites of significance to 

12403 migratory waterbirds. Wetlands, 24(4), 891-903. 

12404 Erwin, R.M., G.M. Sanders, D.J. Prosser, and D.R. Cahoon, 2006: High tides and rising 

12405 seas: potential effects on estuarine waterbirds. In: Terrestrial Vertebrates in Tidal 

12406 Marshes: Evolution, Ecology, and Conservation [Greenberg, R. (ed.)]. Studies in 

12407 avian biology no. 32. Cooper Ornithological Society, Camarillo, CA, pp. 214-228. 

12408 Everts, C.H., J.P. Battley Jr., and P.N. Gibson, 1983: Shoreline Movements: Report 1, 

12409 Cape Henry, Virginia, to Cape Hatteras, North Carolina, 1849-1980. Technical 

12410 report CERC-83-1. U.S. Army Corps of Engineers, Washington, DC, and 

12411 National Oceanic and Atmospheric Administration, Rockville, MD, 111 pp. 

12412 Eyler, T.B., R.M. Erwin, D.B. Stotts, and J.S. Hatfield, 1999: Aspects of hatching 

12413 success and chick survival in gull-billed terns in coastal Virginia. Waterbirds, 22,

12414 54-59. 

12415 ESRI (Environmental Systems Research Institute), 1999: Parks. National Park Service 

12416 Washington, DC. 

12417 Federal Register, 2006: Availability of a Draft Integrated Feasibility Report and 

12418 Environmental Impact Statement for the Mid-Chesapeake Bay Island Ecosystem 

12419 Restoration Project in Dorchester County, on Maryland's Eastern Shore. Federal 

12420 Register Notices, 71(174), 53090-53091. 
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12421 Feinberg, J.A. and R.L. Burke, 2003: Nesting Ecology and Predation of Diamondback 

12422 Terrapins, Malaclemys terrapin, at Gateway National Recreation Area, New 

12423 York. Journal of Herpetology, 37(3), 517-526. 

12424 Feldman, R.L., 2008: Recommendations for responding to sea level rise: lessons from 

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12426 HI. American Society of Civil Engineers, Reston VA, pp. 15-27. 

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12429 Second approximation, version 2.2. Virginia Department of Conservation and 

12430 Recreation, Division of Natural Heritage, Richmond, VA. 

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12454 Science, 38 pp. 

12455 Hardaway, C.S., Jr., D.A. Milligan, L.M. Varnell, C. Wilcox, G.R. Thomas, and T.R. 

12456 Comer, 2005: Shoreline Evolution, Chesapeake Bay Shoreline, City of Virginia 

12457 Beach, Virginia.Virginia Institute of Marine Sciences, College of William and 

12458 Mary (Gloucester Point) and Virginia Department of Environmental Quality 

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12465 Sound Foundation, Groton, CT, pp. 61-65. 

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12469 Wetlands, 22(1), 71-89. 

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12473 Hedrick, C., W. Millhouser, and J. Lukens, 2000: State, Territory, and Commonwealth 

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12475 Resource Management Program policy series technical document 00-01. National 

12476 Oceanic and Atmospheric Administration, National Ocean Service. 

12477 Henman, J. and B. Poulter, 2008: Inundation of freshwater peatlands by sea level rise: 

12478 uncertainty and potential carbon cycle feedbacks. Journal of Geophysical 

12479 Research, 113, G01011, doi:10.1029/2006JG000395. 

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12482 1: Tidal Wetlands. EPA Long Island Sound Office, Stamford, CT, 25 pp. 

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12485 Delaware Estuary. Delaware River Basin Commission, West Trenton, NJ. 

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12488 the Swan Quarter Watershed Project). 

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12499 Elsevier, Amsterdam and Oxford, pp. 139-156. 
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12500 Jackson, E.L., A.S. Rowden, M.J. Attrill, S. Bossey, and M. Jones, 2001: The 

12501 importance of seagrass beds as habitat for fishery species. Oceanography and 

12502 Marine Biology Annual Review, 39, 269-303. 

12503 James City County, 2003: James City County Comprehensive Plan. Land Use (pp. 101-

12504 141) and Environment (pp. 42-67) Chapters. Williamsburg, Virginia. 

12505 Johnson, Z.P., 2000: A Sea Level Rise Response Strategy for the State of Maryland. 

12506 Maryland Department of Natural Resources, Coastal Zone Management Division, 

12507 Annapolis, 49 pp. 

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12515 overlay analysis of GIS data on coastal elevations, shore protection, and wetland 

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12519 Environmental Protection Agency, Washington, DC, pp. 45-67. 

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12525 Chesapeake and Delaware Bays. EOS Transactions of the American Geophysical 

12526 Union, 83(16), 173. 
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12530 Kneib, R.T., 1997: The role of tidal marshes in the ecology of estuarine nekton. 

12531 Oceanography and Marine Biology, an Annual Review, 35, 163-220. 

12532 Kneib, R.T. and S.L. Wagner, 1994: Nekton use of vegetated marsh habitats at different 

12533 stages of tidal inundation. Marine Ecology-Progress Series, 106, 227-238. 

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12535 warming. The Virginian-Pilot, October 6, 2006. 

12536 Kraft, J.C. and C.J. John, 1976: Introduction, the Geological Structure of the Shorelines 

12537 of Delaware. Delaware Sea Grant Technical Report, #DEL-SG-14-76. 

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12539 decline of the tidal saltmarsh lithosome: the Delaware estuary and Atlantic coastal 

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12543 Program, pp. 81-90. 

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12552 Climates I: Ecological and Ecophysiological Studies [Leith, H., (ed.)]. Backhuys 

12553 Publishers, Leiden, Netherlands, pp. 113-126. 
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12554 Kumer, J., 2004: Status of the endangered piping plover, Charadrius melodus, 

12555 population in the Maryland Coastal Bays. In Maryland's Coastal Bays: Ecosystem 

12556 Health Assessment. pp. 8-97. 

12557 Lathrop, R.G., Jr., and A. Love, 2007: Vulnerability of New Jersey’s Coastal habitats to 

12558 Sea Level Rise. Grant F. Walton Center for Remote Sensing and Spatial Analysis, 

12559 Rutgers University, New Brunswick, NJ, and American Littoral Society, 

12560 Highlands, NJ, 17 pp. <http://www.crssa.rutgers.edu> 

12561 Lathrop, R., M. Allen, and A. Love, 2006: Mapping and Assessing Critical Horseshoe 

12562 Crab Spawning Habitats in Delaware Bay. Grant F. Walton Center for Remote 

12563 Sensing and Spatial Analysis, Cook College, Rutgers University, New Brunswick, 

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12567 Climate Change on the United States. Appendix: B, Sea Level Rise. EPA 230-05-

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12571 Analogy approach to global climate analysis and response. In: Regions and 

12572 Global Warming: Impacts and Response Strategies [Schmandt, J. (ed.)]. Oxford 

12573 University Press. 

12574 Leatherman, S., K. Zhang, and B. Douglas, 2000: Sea level rise shown to drive coastal 

12575 erosion: A reply. EOS, Transactions of the American Geophysical Union, 81(38),

12576 437-441. 

12577 Lee, G.J., T.E. Carter, Jr., M.R. Villagarcia, Z. Li, X. Zhou, M.O. Gibbs, and H.R. 

12578 Boerma, 2004: A major QTL conditioning salt tolerance in S-100 soybean and 

12579 descendent cultivars. Theoretical and Applied Genetics, 109(8), 1610-1619. 
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12580 Lilly, J.P., 1981: A history of swamp land development in North Carolina. In: Pocosin 

12581 Wetlands [Richardson, C.J., (ed.)]. Hutchinson Ross, Stroudsburg, PA, pp. 20-30. 

12582 Lippson, A.J. and R.L. Lippson, 2006: Life in the Chesapeake Bay. Johns Hopkins 

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12584 * LISF (Long Island Sound Foundation), 2008: Plants & Animals of Hammonasset. Long 

12585 Island Sound Foundation, Groton, CT. 

12586 <http://www.lisfoundation.org/coastal_access/hamm_wildlife.html> 

12587 LISHRI (Long Island Sound Habitat Restoration Initiative), 2003: Long Island Sound 

12588 Habitat Restoration Initiative, Technical Support for Habitat Restoration, Section 

12589 5: Coastal Barriers, Beaches, and Dunes. EPA Long Island Sound Office, 

12590 Stamford, CT, 10 pp. <http://www.longislandsoundstudy.net/habitat/index.htm> 

12591 Mabey, S., B. Watts, and L. McKay, Undated: Migratory Birds of the Lower Delmarva: 

12592 A Habitat Management Guide for Landowners. The Center for Conservation 

12593 Biology, College of William and Mary, Williamsburg, VA. 

12594 Mangold, M.F., R.C. Tipton, S.M. Eyler, and T.M. McCrobie, 2004: Inventory of Fish 

12595 Species within Dyke Marsh, Potomac River (2001-2004). U.S. Fish and Wildlife 

12596 Service in conjunction with Maryland Fishery Resources Office, Annapolis, MD. 

12597 Marraro, P.M, G.W. Thayer, M.L. LaCroix, and D.R. Colby, 1991: Distribution, 

12598 abundance, and feeding of fish on a marsh on Cedar Island, North Carolina. In: 

12599 Ecology of a Nontidal Brackish Marsh in Coastal North Carolina [Brinson, 

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12601 Washington, DC, pp. 321-385. 

12602 Mauriello, M., 1991: Beach nourishment and dredging: New Jersey’s policies. Shore & 

12603 Beach, 59, 3. 
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12604 * May, M.K., 2002: Pattern and Process of Headward Erosion in Salt Marsh Tidal 

12605 Creeks. Master’s thesis, Department of Biology. Eastern Carolina University, 

12606 Greenville, NC, 133 pp. 

12607 MCBP (Maryland Coastal Bays Program), 1999: Today’s Treasures for Tomorrow: 

12608 Towards a Brighter Future. The Comprehensive Conservation and Management 

12609 Plan for Maryland’s Coastal Bays. Maryland’s Coastal Bays Program, Berlin, 

12610 MD, 181 pp. 

12611 MCCC (Maryland Commission on Climate Change), 2008: Interim Report to the 

12612 Governor and the Maryland General Assembly: Climate Action Plan. Maryland 

12613 Department of Environment, Baltimore, MD. 

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12615 wetlands: what is required? Hydrobiologia, 577, 5-15. 

12616 * McGean, T., 2003: City Engineer, Town of Ocean City, Maryland. Presentation to 

12617 Coastal Zone. 

12618 * MD DNR (Maryland Department of Natural Resources), Undated: Maryland Shoreline 

12619 Changes Online, from the Maryland Department of Natural Resources. 

12620 <http://shorelines.dnr.state.md.us/sc_online.asp> 

12621 * MD DNR (Maryland Department of Natural Resources), 2000: Maryland Atlas of 

12622 Greenways, Water Trails, and Green Infrastructure. Maryland Greenway 

12623 Commission. <http://ww.dnr.state.md.us/greenways/counties/princegeorge.html> 

12624 * MD DNR (Maryland Department of Natural Resources), 2004: Land and Water 

12625 Conservation Service. Wye Island NRMA Land Unit Plan. 

12626 * MD DNR (Maryland Department of Natural Resources), 2006: DNR receives approval 

12627 for diamondback terrapin conservation, Press Release, 2 August, 2006. 
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12628 * MD DNR (Maryland Department of Natural Resources), 2007: Bay Smart: A Citizen’s 

12629 Guide to Maryland’s Critical Area Program. 

12630 <http://www.dnr.state.md.us/criticalarea/download/baysmart.pdf>. 

12631 MD DTTF (Maryland Diamondback Terrapin Task Force), 2001: Findings and 

12632 Recommendations, Final Report to the Secretary of the MD DNR, September 

12633 2001, Executive Order 01.01.2001.05. 

12634 MET (Maryland Environmental Trust), 2006: Model Conservation Easement. 

12635 Annapolis, Md. <http://www.dnr.state.md.us/MET/model.html>

12636 Mitsch, W.J. and J.G. Gosselink, 2000: Wetlands. Van Nostrand Reinhold, New York, 

12637 3rd ed., 920 pp. 

12638 * MLT (Mordecai Land Trust), Undated: <http://www.mordecaimatters.org> 

12639 * MLT (Mordecai Land Trust), 2003: Mordecai Island - Habitat Value. 

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12641 Moffatt and Nichol, 2007: Scope of Work for Development of a Beach and Inlet 

12642 Management Plan for the State of North Carolina. Raleigh, NC, 5 pp. 

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12646 applied science and ocean engineering. Virginia Institute of Marine Science, 

12647 Gloucester Point, VA, 104 pp. 

12648 Moorhead, K.K. and M.M. Brinson, 1995: Response of wetlands to rising sea level in 

12649 the lower coastal plain of North Carolina. Ecological Applications, 5(1), 261-271. 

12650 Mushacke, F., 2003: Wetland loss in the Peconic estuary. Long Island Sound Tidal 

12651 Wetland Loss Workshop, June 24-25, 2003, Stony Brook, New York. Workshop 

12652 Proceedings and Recommendations to the Long Island Sound Study. 

12653 <http://www.longislandsoundstudy.net/habitatrestoration/more.htm> 
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12654 (MRLCC) Multi-Resolution Land Characteristics Consortium, 2002: Land Cover 1992. 

12655 University of Virginia, Charlottesville. 

12656 Najjar, R.G., H.A. Walker, P.J. Anderson, E.J. Barro, R.J. Bord, J.R. Gibson, V.S. 

12657 Kennedy, C.G. Knight, J.P. Megonigal, R.E. O'Connor, C.D. Polsky, N.P. Psuty, 

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12660 Research, 14(3), 219-233. 

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12663 NatureServe, 2008: NatureServe Explorer: An online encyclopedia of life [web 

12664 application]. Version 7.0. NatureServe, Arlington, VA. 

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12666 NC CRC (North Carolina Coastal Resources Commission), 2008a: Draft rule language 

12667 approved by CRC for public hearing on March 27, 2008, 15A NCAC 07H. 0306. 

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12669 NC CRC (North Carolina Coastal Resources Commission), 2008b: Memorandum CRC12670 08-23 from Bonnie Bendell, DCM, to CRC re: Draft Amendments to the General 

12671 Permit for Bulkheads and Riprap, May 1, 2008. 

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12673 NCDC (National Climatic Data Center), 1999: Event Record Details: 16 Sept 1999, New 

12674 Jersey. <http://www4.ncdc.noaa.gov/cgi12675 win/wwcgi.dll?wwevent~ShowEvent~365151> 

12676 NC DCM (North Carolina Division of Coastal Management), 2002: Technical Manual 

12677 for Coastal Land Use Planning: A “How-To” Manual for Addressing the Coastal 

12678 Resources Commission’s 2002 Land Use Planning Guidelines. North Carolina 

12679 Division of Coastal Management, Raleigh, 63 pp. 

12680 <http://www.nccoastalmanagement.net/Planning/techmanual.pdf> 
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12681 NC DCM (North Carolina Division of Coastal Management), 2003: Coastal 

12682 Management News: CAMAgram: Spring 2003. 

12683 <http://dcm2.enr.state.nc.us/CAMAgram/Spring03/rates.htm> 

12684 NC DCM (North Carolina Division of Coastal Management), 2005: CAMA Handbook 

12685 for Development in Coastal North Carolina. NCDENR Division of Coastal 

12686 Management, Morehead City, NC, section 2. 

12687 <http://dcm2.enr.state.nc.us/Handbook/section2.htm> 

12688 NC (North Carolina) Department of Commerce, 2008: County Tier Designations. 

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12691 NC REDC (North Carolina Rural Economic Development Center), 2006: Small Towns 

12692 Initiative. NC Rural Economic Development Center, Raleigh, NC. 

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12695 Management Program, Albany, NY. 

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12697 NJDEP (New Jersey Department of Environmental Protection), Undated: Cape May 

12698 Point State Park. 

12699 <http://www.state.nj.us/dep/parksandforests/parks/capemay.html> 

12700 NJDEP (New Jersey Department of Environmental Protection), 1997: Coastal Report 

12701 Task Force, New Jersey Department of Environmental Protection, 1997, New 

12702 Jersey Coastal Report: A Framework Document for a Coastal Management 

12703 Partnership. 

12704 NJDEP (New Jersey Department of Environmental Protection), 2001: Cape May County 

12705 Rare Species and Natural Communities Presently Recorded in the New Jersey 

12706 Natural Heritage Database. 

12707 <http://www.nj.gov/dep/parksandforests/natural/heritage/textfiles/njcape.txt> 
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12708 NJDEP DWM (New Jersey Department of Environmental Protection Division of 

12709 Watershed Management), 2004: Stormwater Best Management Practices, 

12710 Appendix D. <http://www.njstormwater.org/tier_A/pdf/NJ_SWBMP_D.pdf> 

12711 NOAA (National Oceanic and Atmospheric Administration), 1982: Ocean & Coastal 

12712 Resource Management in New York. 

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12714 NOAA (National Oceanic and Atmospheric Administration), 2007: Construction 

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12717 NOAA (National Oceanic and Atmospheric Administration), 2008a: Bench Mark Data 

12718 Sheets: Duck Pier, NC. 

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12720 +Sheets> 

12721 NOAA (National Oceanic and Atmospheric Administration), 2008b: Make a Tide 

12722 Prediction, State and Region Listing: North Carolina. 

12723 <http://tidesandcurrents.noaa.gov/tides08/tpred2.html#NC> 

12724 NOAA (National Oceanic and Atmospheric Administration), 2008c: NOAA Nautical 

12725 Charts for North Carolina: Charts 11536 to 12205. 

12726 Nordstrom, K.F., 1989: Erosion control strategies for bay and estuarine beaches. Coastal 

12727 Management, 17, 25-35. 

12728 Nordstrom, K.F., 2005: Beach nourishment and coastal habitats: research needs to 

12729 improve compatibility. Restoration Ecology, 13(1), 215-222. 

12730 NPS (National Park Service), Undated: Description of Roosevelt Island. 

12731 <http://www.nps.gov/gwmp/pac/tri/backgrnd.html> 
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12732 NPS (National Park Service), 2000: Synopsis: Cape Hatteras Lighthouse. [NPS Cape 

12733 Hatteras National Seashore, Manteo, NC.] 

12734 <http://www.nps.gov/archive/caha/synopsis.htm> 

12735 NRC (National Research Council), 1988: Saving Cape Hatteras Lighthouse from the 

12736 Sea: Options and Policy Implications. National Academy Press, Washington, DC, 

12737 136 pp. 

12738 NRC (National Research Council), 2007: Mitigating Shore Erosion along Sheltered 

12739 Coasts. National Academies Press, Washington, DC, 174 pp. 

12740 NYC DPR (New York City Department of Parks and Recreation), Undated: Four 

12741 Sparrow Marsh Reserve. 

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12744 NYC DPR (New York City Department of Parks and Recreation), 2001: Inwood Hill 

12745 Park - Salt Marshes in New York City Parks. Oct. 1. 

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12748 NYDOS (New York Department of State) 2006: Department of State review of US Army 

12749 Corps of Engineers consistency determination for reissuance, modification, and 

12750 issuance of new nationwide permits and conditions. Letter to USACE Buffalo 

12751 and New York districts, December 8, 2006. New York Division of Coastal 

12752 Resources, Albany. 5 pp. 

12753 NYS DEC (New York State Department of Environmental Conservation), 2006: New 

12754 York’s Open Space Conservation Plan. 

12755 <http://www.dec.ny.us/opensp/index.html> 

12756 NYS DEC (New York State Department of Environmental Control), 2007: List of 

12757 Endangered, Threatened and Special Concern Fish & Wildlife Species of New 

12758 York State. Last revised August 8, 2007. <http://www.nynhp.org/> 
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12759 NYS DOS (New York State Department of State), 1999: Long Island Sound: Coastal 

12760 Management Program. 129pp. 

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12763 NYS DOS (New York State Department of State), 2002: State Coastal Policies, 

12764 Excerpted from the State of New York Coastal Management Program and Final 

12765 Environmental Impact Statement, Section 6, August 1982. 

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12767 Wildlife Habitats. <http://nyswaterfronts.com/waterfront_natural_narratives.asp> 

12768 (Multiple location-specific pieces can be found on the site). 

12769 NYS DOS and USFWS (New York State Department of State and United States Fish 

12770 and Wildlife Service), 1998: Shorebirds. South Shore Estuary Reserve, Technical 

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12805 Applications, 7(3), 1054-1063. 

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12861 3 pp. 

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12863 District of Columbia. University of Pittsburgh Press, Pittsburgh, PA. 
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12864 Rounds, R.A., R.M. Erwin, and J.H. Porter, 2004: Nest-site selection and hatching 

12865 success of waterbirds in coastal Virginia: Some results of habitat manipulation. 

12866 Journal of Field Ornithology, 75(4), 318. 

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12868 environmental implications of sea level rise. Section 3.1 in: Background 

12869 Documents Supporting Climate Change Science Program Synthesis and 

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12872 Protection Agency, Washington, DC, pp. 188-210. 

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12875 Background Documents Supporting Climate Change Science Program Synthesis 

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12878 Protection Agency, Washington, DC, pp. 290-293. 

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12887 peninsula. Section 3.12 in: Background Documents Supporting Climate Change 

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12892 Shellenbarger Jones, A. and C. Bosch, 2008b: Western shore Chesapeake Bay 

12893 shoreline. Section 3.16 in: Background Documents Supporting Climate Change 

12894 Science Program Synthesis and Assessment Product 4.1: Coastal Elevations and 

12895 Sensitivity to Sea Level Rise [Titus, J.G. and E.M. Strange (eds.)]. EPA 

12896 430R07004. U.S. Environmental Protection Agency, Washington, DC, pp. 284-

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12899 Hampton Roads. Section 3.11 in: Background Documents Supporting Climate 

12900 Change Science Program Synthesis and Assessment Product 4.1: Coastal 

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12902 EPA 430R07004. U.S. Environmental Protection Agency, Washington, DC, pp. 

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12905 Nourishment on Delaware Shore Beaches to Restore Habitat for Horseshoe Crab 

12906 Spawning and Shorebird Foraging. The Nature Conservancy: Wilmington, DE. 51 

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12908 Proection and Management System web page: 

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12918 State of New Jersey, 2001: New Jersey State Development and Redevelopment Plan. 

12919 <http://www.nj.gov/dca/osg/plan/stateplan.shtml> 
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12920 State of New Jersey, 2005: New Jersey Comprehensive Wildlife Conservation Strategy 

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12924 Maryland Naturalist 45(2), 1-28. 

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12941 Protection Agency, Washington, DC, pp. 251-257. 

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12950 Background Documents Supporting Climate Change Science Program Synthesis 

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12953 Protection Agency, Washington, DC, pp. 298-300. 

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12956 Background Documents Supporting Climate Change Science Program Synthesis 

12957 and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise

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12959 Protection Agency, Washington, DC, pp. 275-279. 

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12962 Background Documents Supporting Climate Change Science Program Synthesis 

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12965 Protection Agency, Washington, DC, pp. 280-283. 

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13117 inventory: Wilmington. Washington, D.C.: No. 39074-A1-EI-250. 

13118 USFWS (United States Fish and Wildlife Service), 1993: Species Account for the Red 

13119 Wolf. ><http://www.fws.gov/cookeville/docs/endspec/rwolfsa.html> 

13120 USFWS (United States Fish and Wildlife Service), 1996: Piping Plover (Charadrius 

13121 melodus) Atlantic Coast Population Revised Recovery Plan. Prepared by the 

13122 Atlantic Coast Piping Plover Recovery Team. U.S. Fish and Wildlife Service, 

13123 Hadley, MA, 245 pp. 

13124 USFWS (United States Fish and Wildlife Service), 1997: Significant Habitats and 

13125 Habitat Complexes of the New York Bight Watershed. U.S. Fish and Wildlife 

13126 Service, Charlestown, RI. <http://training.fws.gov/library/pubs5/begin.htm> 

13127 USFWS (United States Fish and Wildlife Service), 2002: Birds of Conservation Concern 

13128 2002. Division of Migratory Bird Management, Arlington, VA. Table 30. 

13129 <http://www.fws.gov/migratorybirds/reports/reports.html> 

13130 USFWS (United States Fish and Wildlife Service), 2004a: 2002-2003 Status Update: 

13131 U.S. Atlantic Coast Piping Plover Population. U.S. Fish and Wildlife Service, 

13132 Sudbury, MA, 8 pp. 

13133 <http://www.fws.gov/northeast/pipingplover/status/index.html> 
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13134 USFWS (United States Fish and Wildlife Service), 2004b: Eastern Shore of Virginia and 

13135 Fisherman Island National Wildlife Refuges Comprehensive Conservation Plan. 

13136 Chapter 3: Refuge and Resource Descriptions of Northeast Regional Office, 

13137 Hadley, MA. <http://library.fws.gov/CCPs/eastshoreVA_index.htm> 

13138 USFWS (United States Fish and Wildlife Service), 2008: Blackwater National Wildlife 

13139 Refuge. Wetland Restoration. <http://www.fws.gov/blackwater/restore.html>. 

13140 Last updated January 22, 2008. 

13141 USGS (United States Geological Survey), Undated: Anacostia Freshwater Tidal 

13142 Reconstructed Wetlands. 

13143 <http://www.pwrc.usgs.gov/resshow/hammerschlag/anacostia.cfm> 

13144 VA DCR (Virginia Department of Conservation and Recreation), Undated(a): Parkers 

13145 Marsh Natural Area Preserve Fact 

13146 Sheet.<http://www.dcr.virginia.gov/natural_heritage/natural_area_preserves/parke

13147 rs.shtml> 

13148 VA DCR (Virginia Department of Conservation and Recreation), Undated(b) : Mutton 

13149 Hunk Fen Natural Area Preserve. 

13150 <http://www.dcr.virginia.gov/natural_heritage/natural_area_preserves/muttonhun

13151 k.shtml> 

13152 VA DCR (Virginia Department of Conservation and Recreation), 1999: Bethel Beach 

13153 Natural Area Preserve, fact sheet. 

13154 <http://www.dcr.virginia.gov/natural_heritage/documents/pgbethel.pdf> 

13155 VA DCR (Virginia Department of Conservation and Recreation), 2001: The Natural 

13156 Communities of Virginia. Ecological Classification of Ecological Community 

13157 Groups. First Approximation. Division of Natural Heritage Natural Heritage 

13158 Technical Report 01-1, January 2001. 

13159 VA PBB (Virginia Public Beach Board), 2000: 20 Years of Coastal Management. 

13160 Richmond, Virginia: Board on Conservation and Development of Public Beaches. 
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13161 VBCP (Virginia Beach Comprehensive Plan), 2003: Introduction and General Strategy: 

13162 Policy Document. 

13163 * VIMS (Virginia Institute for Marine Science), Undated: Chesapeake Bay National 

13164 Estuarine Research Reserve in Virginia. Goodwin Islands. 

13165 <http://www.vims.edu/cbnerr/reservesites/goodwin.htm> 

13166 Walls, E.A., J. Berkson, and S.A. Smith, 2002: The horseshoe crab, Limulus polyphemus: 

13167 200 million years of existence, 100 years of study. Reviews in Fisheries Science, 

13168 10(1), 39-73. 

13169 Walz, K., E. Cronan, S. Domber, M. Serfes, L. Kelly, and K. Anderson, 2004: The 

13170 Potential Impacts of Open Marsh Management (OMWM) on a Globally Imperiled 

13171 Sea-level Fen in Ocean County, New Jersey. Prepared for the New Jersey 

13172 Department of Environmental Protection, Coastal Management Office, 18 pp. 

13173 Washington County, 2008: Return to the Heart of the Inner Banks. 

13174 <http://www.originalwashington.com/> 

13175 Watts, B.D., 1993: Effects of Marsh Size on Incidence Rates and Avian Community 

13176 Organization within the Lower Chesapeake Bay. Technical report CCBTR-93-03. 

13177 Center for Conservation Biology, College of William and Mary, Williamsburg, 

13178 VA, 53 pp. 

13179 Watts, B.D., 2006: Synthesizing Information Resources for the Virginia Important Bird 

13180 Area Program: Phase I, Delmarva Peninsula and Tidewater. Technical Report 

13181 CCBTR-06-05. Center for Conservation Biology, College of William and Mary, 

13182 Williamsburg, VA. 

13183 Watts, B.D. and C. Markham, 2003: The Influence of Salinity on Diet, Prey Delivery, 

13184 and Nestling Growth in Bald Eagles in the Lower Chesapeake Bay: Progress 

13185 Report. Technical Report CCBTR-03-06. Center for Conservation Biology, 

13186 College of William and Mary, Williamsburg, VA, 5pp. 
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13187 Watts, B.D. and B.R. Truitt, 2002: Abundance of shorebirds along the Virginia barrier 

13188 islands during spring migration. The Raven, 71(2), 33-39. 

13189 * Weber, R.G., 2001: Preconstruction horseshoe crab egg density monitoring and habitat 

13190 availability at Kelly Island, Port Mahon, and Broadkill Beach Study areas. 

13191 Prepared for the Philadelphia District Corps of Engineers, Philadelphia, PA. 

13192 December 2001. 

13193 Weggel, J.R., S. Brown, J. Escajadillo, P. Breen, and E. L. Doheny, 1989: The cost of 

13194 defending developed shorelines along sheltered water of the United States from a 

13195 two meter rise in mean sea level. In: The Potential Effects of Global Climate 

13196 Change on the United States. Appendix: B, Sea Level Rise. EPA 230-05-89-052. 

13197 Environmental Protection Agency, Washington, DC, pp. 3-1 to 3-90. 

13198 <http://epa.gov/climatechange/effects/coastal/appB.html> 

13199 Weinstein, M.P., 1979: Shallow marsh habitats as primary nurseries for fishes and 

13200 shellfish, Cape Fear River, North Carolina, United States. Fisheries Bulletin, 

13201 77(2), 339-357. 

13202 Weinstein, M.P. and L.L. Weishar, 2002: Beneficial use of dredged material to enhance 

13203 the restoration trajectories of formerly diked lands. Ecological Engineering, 

13204 19(3), 187-201. 

13205 Weinstein, M.P., K.R. Phillip, and P. Goodwin, 2000: Catastrophes, near-catastrophes, 

13206 and the bounds of expectation: Success criteria for macroscale marsh restoration. 

13207 In: Concepts and Controversies in Tidal Marsh Ecology [Weinstein, M.P. and 

13208 D.A. Kreeger (eds.)]. Kluwer Academic Publishers, Dordrecht, the Netherlands, 

13209 pp. 777-804. 

13210 * Wetlands Institute, Undated: Terrapin Conservation Program. 

13211 <http://www.terrapinconservation.org>. 

13212 White, C.P., 1989: Chesapeake Bay: Nature of the Estuary: A Field Guide. Tidewater 

13213 Publishers, Centreville, MD, 212 pp. 
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13214 Wilcock, P.R., D.S. Miller, R.H. Shea, and R.T. Kerhin, 1998: Frequency of effective 

13215 wave activity and the recession of coastal bluffs: Calvert Cliffs, Maryland. 

13216 Journal of Coastal Research, 14(1), 256-268. 

13217 York (York County, Virginia), 1999: Charting the Course to 2015: The York County 

13218 Comprehensive Plan. Yorktown, VA. 

13219 Zervas, C., 2004: North Carolina Bathymetry/Topography Sea Level Rise Project: 

13220 Determination of Sea Level Trends. NOAA technical report NOS CO-OPS 041. 

13221 NOAA National Ocean Service, Silver Spring, MD, 31 pp. 

13222 <http://tidesandcurrents.noaa.gov/publications/techrpt41.pdf> 

13223 

13224 
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13225 Appendix 2. Basic Approaches for Shoreline Change 

13226 Projections 

13227 Lead Author: Benjamin T. Gutierrez, USGS 

13228 Contributing Authors: S. Jeffress Williams, USGS; E. Robert Thieler, USGS 

 13229 

13230 While the factors that influence changes in shoreline position in response to sea-level rise 

13231 are well known, it has been difficult to incorporate this understanding into quantitative 

13232 approaches that can be used to assess land loss over long time periods (e.g., 50 to 100 

13233 years). The validity of some of the more common approaches discussed in this Appendix 

13234 has been a source of debate in the scientific community (see Section 3.1). This Appendix 

13235 reviews some basic approaches that have been applied to evaluate the potential for 

13236 shoreline changes over these time scales. 

13237 

13238 The Bruun Model. One of the most widely known models developed for predicting 

13239 shoreline change driven by sea-level rise on sandy coasts was formulated by Bruun 

13240 (1962, 1988). This model is often referred to as the ‘Bruun rule’ and considers the two13241 dimensional shoreline response (vertical and horizontal) to a rise in sea level. A 

13242 fundamental assumption of this model is that over time the cross-shore shape of the 

13243 beach, or beach profile, assumes an equilibrium shape that translates upward and 

13244 landward as sea level rises. Four additional assumptions of this model are that: 

13245 1. The upper beach is eroded due to landward translation of the profile. 
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13246 2. The material eroded from the upper beach is transported offshore and deposited 

13247 such that the volume eroded from the upper beach equals the volume deposited 

13248 seaward of the shoreline. 

13249 3. The rise in the nearshore seabed as a result of deposition is equal to the rise in sea 

13250 level, maintaining a constant water depth. 

13251 4. Gradients in longshore transport are negligible. 

13252 Mathematically, the model is depicted as: 

S

hB

L

R   

*

* 13253 (A2.1) 

13254 where R is the horizontal retreat of the shore, h* is the depth of closure or depth where 

13255 sediment exchange between the shore face and inner shelf is assumed to be minimal, B is 

13256 the height of the berm, L* is the length of the beach profile to h* , and S is the vertical rise 

13257 in sea level (Figure A2.1). This relationship can also be evaluated based on the slope of 

13258 the shore face, , as: 

R  S

  tan

1 13259 (A2.2) 

13260 For most sites, it has been found that general values of  and R are approximately 0.01 to 

13261 0.02 and 50*S to 100*S, respectively (Wright, 1995; Komar, 1998; Zhang, 1998). 

13262 

13263 A few studies have been conducted to verify the Bruun Model (Schwartz, 1967; Hands, 

13264 1980; also reviewed in SCOR, 1991; Komar, 1998; and Dean and Dalrymple, 2002). In 

13265 other cases, some researchers have advocated that there are several uncertainties with this 

13266 approach, which limit its use in real-world applications (Thieler et al., 2000; Cooper and 

13267 Pilkey, 2004, also reviewed in Dubois, 2002). Field evaluations have also shown that the 
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13268 assumption of profile equilibrium can be difficult to meet (Riggs et al., 1995; List et al., 

13269 1997). Moreover, the Bruun relationship neglects the contribution of longshore transport, 

13270 which is a primary mechanism of sediment transport in the beach environment (Thieler et 

13271 al., 2000) and there have been relatively few attempts to incorporate longshore transport 

13272 rates into this approach (Everts, 1985). 

13273 

13274 A number of investigators have expanded upon the Bruun rule or developed other models 

13275 that simulate sea-level rise driven shoreline changes. Dean and Maurmeyer (1983) 

13276 adapted and modified the Bruun rule to apply to barrier islands (e.g., the Generalized 

13277 Bruun Rule). Cowell et al. (1992) developed the Shoreline Translation Model (STM), 

13278 which incorporated several parameters that characterize the influence of the geological 

13279 framework into sea-level rise driven shoreline change for barrier islands. Stolper et al.

13280 (2005) developed a rules-based geomorphic shoreline change model (GEOMBEST) that 

13281 simulates barrier island evolution in response to sea-level rise. While these models can 

13282 achieve results consistent with the current understanding of sea-level rise driven changes 

13283 to barrier island systems, there is still need for more research and testing against both the 

13284 geologic record and present-day observations to advance scientific understanding and 

13285 inform management. 
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13286 

13287 Figure A2.1 Illustration showing the Bruun Model and the basic dimensions of the shore that are used as 

13288 model inputs.

13289 

13290 Historical Trend Extrapolation. Another commonly used approach to evaluate potential 

13291 shoreline change in the future relies on the calculation of shoreline change rates based on 

13292 changes in shoreline position over time. In this approach, a series of shorelines from 

13293 different time periods are assembled from maps for a particular area. In most cases, these 

13294 shorelines are derived from either National Ocean Service T-sheets, aerial photographs, 

13295 from Global Positioning System (GPS) surveys, or lidar surveys (Shalowitz, 1964; 

13296 Leatherman, 1983; Dolan et al., 1991; Anders and Byrnes, 1991; Stockdon et al., 2002). 

13297 The historical shorelines are then used to estimate rates of change over the time period 

13298 covered by the different shorelines (Figure A2.2). Several statistical methods are used to 
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13299 calculate the shoreline change rates with the most commonly used being end-point rate 

13300 calculations or linear regression (Dolan et al., 1991; Crowell et al., 1997). The shoreline 

13301 change rates can then be used to extrapolate future changes in the shoreline by 

13302 multiplying the observed rate of change by a specific amount of time, typically in terms 

13303 of years (Leatherman, 1990; Crowell et al., 1997). More specific assumptions can be 

13304 incorporated that include other factors such as the rate of sea-level rise or geological 

13305 characteristics of an area (Leatherman, 1990; Komar et al., 1999). 

13306 

13307 Because past shoreline positions are readily available from maps that have been produced 

13308 over time, the extrapolation of historical trends to predict future shoreline position has 

13309 been applied widely for coastal management and planning (Crowell and Leatherman, 

13310 1999). In particular, this method is used to estimate building setbacks (Fenster, 2005). 

13311 Despite this, relatively few studies have incorporated shoreline change rates into long13312 term shoreline change predictions to evaluate sea-level rise impacts, particularly for cases 

13313 involving accelerated rates of sea-level rise (Kana et al., 1984; Leatherman, 1984). 

13314 

13315 Historical trend analysis has evolved over the last few decades based on earlier efforts to 

13316 investigate shoreline change (described in Crowell et al., 2005). Since the early 1980s, 

13317 computer based Geographical Information System (GIS) software has been developed to 

13318 digitally catalog shoreline data and facilitate the quantification of shoreline change rates 

13319 (May et al., 1982; Leatherman, 1983; Thieler et al., 2005). At the same time, thorough 

13320 review and critique of the procedures that are employed to make these estimates have 

13321 been conducted (Dolan et al., 1991; Crowell et al., 1991, 1993, 1997; Douglas et al., 
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13322 1998; Douglas and Crowell, 2000; Honeycutt et al., 2001; Fenster et al., 2001; Ruggiero 

13323 et al., 2003; Moore et al., 2006; Genz et al., 2007). 

13324 

13325 Recently, a national scale assessment of shoreline changes that have occurred over the 

13326 last century has been carried out by the U.S. Geological Survey (Gulf Coast: Morton et 

13327 al., 2004; southeastern U.S. coast: Morton and Miller, 2005; California coast: Hapke et 

13328 al., 2006). In addition, efforts are ongoing to complete similar analyses for the 

13329 northeastern, mid-Atlantic, Pacific Northwest, and Alaskan coasts. 

13330 

13331 

13332 Figure A2.2 Aerial photograph of Fire Island, New York showing former shoreline positions and how 

13333 these positions are used to calculate long-term shoreline change rates using linear regression. The inset box 

13334 shows the shoreline positions at several points in time over the last 170 years. From the change in position 

13335 with time, an average rate of retreat can be calculated. This is noted by the slope of the line, m. The red line 

13336 in the inset box indicates the best fit line while the dashed lines specify the 95 percent confidence interval 

13337 for this fit. Photo source: State of New York GIS. 

13338 
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13339 The Sediment Budget. Another approach to shoreline change assessment involves 

13340 evaluating the sediment mass balance, or sediment budget, for a given portion of the 

13341 coast (Bowen and Inman, 1966; Komar, 1996; List, 2005; Rosati, 2005), as shown in 

13342 Figure A2.3. Using this method, the gains and losses of sediment to a portion of the 

13343 shore, often referred to as a control volume, are quantified and evaluated based on 

13344 estimates of beach volume change. Changes in the volume of sand for a particular setting 

13345 can be identified and evaluated with respect to adjacent portions of the shore and to 

13346 changes in shoreline position over time. One challenge related to this method is obtaining 

13347 precise measurements that minimize error since small vertical changes over these 

13348 relatively low gradient shoreline areas can result in large volumes of material (NRC, 

13349 1987). To apply this approach, accurate measurements of coastal landforms, such as 

13350 beach profiles, dunes, or cliff positions, are needed. Collection of such data, especially 

13351 those on the underwater portions of the beach profile, is difficult. In addition, high13352 density measurements are needed to evaluate changes from one section of the beach to 

13353 the next. While the results can be useful to understand where sediment volume changes 

13354 occur, the lack of quality data and the expense of collecting the data limit the application 

13355 of this method in many areas. 
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13356 

13357 

13358 Figure A2.3 Schematic of the coastal sediment budget (modified from Komar, 1996). Using the sediment 

13359 budget approach, the gains and losses of sediment from the beach and nearshore regions are evaluated to 

13360 identify possible underlying causes for shoreline changes. In this schematic the main sediment gains are 

13361 from: cliff erosion, coastal rivers, longshore transport, and cross-shore sediment transport from the 

13362 continental shelf. The main sediment losses are due to: offshore transport from the beach to the shelf and 

13363 wind transport from the beach to coastal dunes. 

13364 

13365 The Coastal Vulnerability Index. One approach that has been developed to evaluate the 

13366 potential for coastal changes is through the development of a Coastal Vulnerability Index 

13367 (CVI, Gornitz and Kanciruk, 1989; Gornitz, 1990; Gornitz et al., 1994; Thieler and 

13368 Hammar-Klose, 1999). Recently, the U.S. Geological Survey (USGS) used this approach 

13369 to evaluate the potential vulnerability of the U.S. coastline on a national scale (Thieler 

13370 and Hammar-Klose, 1999) and on a more detailed scale for the U.S. National Park 

13371 Service (Thieler et al., 2002). The USGS approach reduced the index to include six 

13372 variables (geomorphology, shoreline change, coastal slope, relative sea-level change, 

13373 significant wave height, and tidal range) which were considered to be the most important 
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13374 in determining a shoreline’s susceptibility to sea-level rise (Thieler and Hammar-Klose, 

13375 1999). The CVI is calculated as: 

6

fedcba CVI 13376  (A2.3) 

13377 where a is the geomorphology, b is the rate of shoreline change, c is the coastal slope, d

13378 is the relative sea-level change, e is the mean significant wave height, and f is the mean 

13379 tidal range. 

13380 

13381 The CVI provides a relatively simple numerical basis for ranking sections of coastline in 

13382 terms of their potential for change that can be used by managers to identify regions where 

13383 risks may be relatively high. The CVI results are displayed on maps to highlight regions 

13384 where the factors that contribute to shoreline changes may have the greatest potential to 

13385 contribute to changes to shoreline retreat (Figure A2.4).
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13386 

13387 Figure A2.4 Coastal Vulnerability Index (CVI) calculated for Assateague Island National Seashore in 

13388 Maryland. The inner most color-coded bar is the CVI estimate based on the other input factors (1 through 

13389 6). From Pendleton et al. (2004).

13390 
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13391 APPENDIX 2 REFERENCES

13392 * Indicates non-peer reviewed literature; available upon request

13393 

13394 Anders, F.J. and M.R. Byrnes, 1991: Accuracy of shoreline change rates as determined 

13395 from maps and aerial photographs. Shore and Beach, 59(1), 17-26.

13396 Bowen, A.J. and D.L. Inman, 1966: Budget of Littoral Sands in the Vicinity of Point 

13397 Arguello, California. Coastal Engineering Research Center technical memoradum 

13398 no. 19. [U.S. Army Corps of Engineers, Washington, DC], 56 pp. 

13399 Bruun, P., 1962: Sea-level rise as a cause of shore erosion. Journal of Waterways and 

13400 Harbors Division, 88, 117-130. 

13401 Bruun, P., 1988: The Bruun rule of erosion by sea-level rise: a discussion on large scale 

13402 two- and three-dimensional usages. Journal of Coastal Research, 4(4), 627-648. 

13403 Cooper, J.A.G. and O.H. Pilkey, 2004: Sea-level rise and shoreline retreat: time to 

13404 abandon the Bruun Rule. Global and Planetary Change, 43(3-4), 157-171. 

13405 Cowell, P.J., P.S. Roy, and R.A. Jones, 1992: Shoreface translation model: computer 

13406 simulation of coastal-sand-body response to sea level rise. Mathematics and 

13407 Computers in Simulation, 33(5-6), 603-608. 

13408 Crowell, M. and S.P. Leatherman (eds.), 1999: Coastal erosion mapping and 

13409 management. Journal of Coastal Research, Special issue 28, 196 pp. 

13410 Crowell, M., S.P. Leatherman, and M.K. Buckley, 1991: Historical shoreline change; 

13411 error analysis and mapping accuracy. Journal of Coastal Research, 7(3), 839-852. 

13412 Crowell, M., S.P. Leatherman, and M.K. Buckley, 1993: Shoreline change rate analysis: 

13413 long-term versus short-term. Shore and Beach, 61(2), 13-20.

13414 Crowell, M., B.C. Douglas, and S.P. Leatherman, 1997: On forecasting future U.S. 

13415 shoreline positions: a test of algorithms. Journal of Coastal Research, 13(4), 

13416 1245-1255.
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13417 Crowell, M., S.P. Leatherman, and B. Douglas, 2005: Erosion: historical analysis a 

13418 forecasting. In: Encyclopedia of Coastal Science [Schwartz, M.L. (ed.).] Springer, 

13419 the Netherlands, pp. 846-850. 

13420 Dean, R.G. and R.A. Dalrymple, 2002: Coastal Processes with Engineering 

13421 Applications. Cambridge University Press, New York, 475 pp. 

13422 Dean, R.G. and E.M. Maurmeyer, 1983: Models of beach profile response. In: CRC 

13423 Handbook of Coastal Processes [Komar, P.D. (ed.)]. CRC Press, Boca Raton, FL, 

13424 pp. 151-165. 

13425 Dolan, R., M.S. Fenster, and S.J. Holme, 1991: Temporal analysis of shoreline recession 

13426 and accretion. Journal of Coastal Research, 7(3), 723-744. 

13427 Douglas, B.C. and M. Crowell, 2000: Long-term shoreline position prediction and error 

13428 propagation. Journal of Coastal Research, 16(1), 145-152.

13429 Douglas, B.C., M. Crowell, and S.P. Leatherman, 1998: Consideration for shoreline 

13430 position prediction. Journal of Coastal Research, 14(3), 1025-1033. 

13431 Dubois, R.N., 2002: How does a barrier shoreface respond to a sea-level rise? Journal of 

13432 Coastal Research, 18(2), iii-v. 

13433 Everts, C.H., 1985: Sea-level rise effects on shoreline position. Journal of Waterway, 

13434 Port, and Coastal Engineering, 111(6), 985-999. 

13435 Fenster, M.S., 2005: Setbacks. In: Encyclopedia of Coastal Science [Schwartz, M.L. 

13436 (ed.)]. Springer, Dordrecht, the Netherlands, pp. 863-866. 

13437 Fenster, M.S., R. Dolan, and R.A. Morton, 2001: Coastal storms and shoreline change: 

13438 signal or noise? Journal of Coastal Research, 17(3), 714-720. 

13439 Genz, A.S., C.H. Fletcher, R.A. Dunn, L.N. Frazer, and J.J. Rooney, 2007: The 

13440 predictive accuracy of shoreline change rate methods and alongshore beach 

13441 variation on Maui, Hawaii. Journal of Coastal Research, 23(1), 87-105. 
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13442 Gornitz, V.M., 1990: Vulnerability of the east coast, USA to future sea-level rise. 

13443 Journal of Coastal Research, Special issue 9, 201-237. 

13444 * Gornitz, V.M. and P. Kanciruk, 1989: Assessment of global coastal hazards from sea 

13445 level rise. In: Coastal Zone ’89: Proceedings of the Sixth Symposium on Coastal 

13446 and Ocean Management, July 11-14, 1989, Charleston, SC. American Society of 

13447 Civil Engineers, New York, pp. 1345-1359. 

13448 Gornitz, V.M., R.C. Daniels, T.W. White, and K.R. Birdwell, 1994: The development of 

13449 a coastal risk assessment database: vulnerability to sea-level rise in the U.S. 

13450 southeast. Journal of Coastal Research, Special issue 12, 327-338. 

13451 Hands, E.B., 1980: Prediction of Shore Retreat and Nearshore Profile Adjustments to 

13452 Rising Water Levels on the Great Lakes. Coastal Engineering Research Center 

13453 technical paper TP 80-7. U.S. Army Corps of Engineers, Ft. Belvoir, VA, 199 pp. 

13454 Hapke, C.J., D. Reid, B.M. Richmond, P. Ruggiero, and J. List, 2006: National 

13455 Assessment of Shoreline Change: Part 3 Historical Shoreline Change and 

13456 Associated Land Loss along Sandy Shorelines of the California Coast. U.S. 

13457 Geological Survey open-file report 2006-1219. U.S. Geological Survey, Reston 

13458 VA, 72 pp. <http://purl.access.gpo.gov/GPO/LPS86269>

13459 Honeycutt, M.G., M. Crowell, and B.C. Douglas, 2001: Shoreline position forecasting: 

13460 impacts of storms, rate-calculation methodologies, and temporal scales. Journal of 

13461 Coastal Research, 17(3), 721-730. 

13462 Kana, T.W., J Michel, M.O. Hayes, and J.R. Jensen, 1984: The physical impact of sea 

13463 level rise in the area of Charleston, South Carolina. In: Greenhouse Effect and 

13464 Sea-level Rise: A Challenge for this Generation [Barth, M.C. and J.G. Titus 

13465 (eds.)]. Van Nostrand Reinhold, New York, pp. 105-150. 

13466 Komar, P.D., 1996: The budget of littoral sediments concepts and applications. Shore 

13467 and Beach, 64(3), 18-26. 
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13468 Komar, P.D., 1998: Beach Processes and Sedimentation. Prentice Hall, Upper Saddle 

13469 River, NJ, 2nd edition, 544 pp. 

13470 Komar, P.D., W.G. McDougal, J.J. Marra, and P. Ruggiero, 1999: The rational analysis 

13471 of setback distances: applications to the Oregon coast. Shore and Beach, 67(1), 

13472 41-49. 

13473 Leatherman, S.P., 1983: Shoreline mapping: a comparison of techniques. Shore and 

13474 Beach, 51(3), 28-33. 

13475 Leatherman, S.P., 1984: Coastal geomorphic responses to sea level rise: Galveston Bay, 

13476 Texas. In: Greenhouse Effect and Sea-level Rise: A Challenge for This 

13477 Generation [Barth, M.C. and J.G. Titus (eds.)]. Van Nostrand Reinhold, New 

13478 York, pp. 151-178. 

13479 Leatherman, S.P., 1990: Modeling shore response to sea-level rise on sedimentary 

13480 coasts. Progress in Physical Geography, 14(4), 447-464. 

13481 List, J.H., 2005: The sediment budget. In: Encyclopedia of Coastal Science [Schwartz, 

13482 M.L. (ed.)]. Springer, Dordrecht, the Netherlands, pp. 846-850. 

13483 List, J.H., A.H. Sallenger, M.E. Hansen, and B.E. Jaffe, 1997: Accelerated relative sea13484 level rise and rapid coastal erosion: testing a causal relationship for the Louisiana 

13485 barrier islands. Marine Geology, 140(3-4), 347-365. 

13486 May, S., W. Kimball, N. Grandy, and R. Dolan, 1982: The coastal erosion information 

13487 system (CEIS). Shore and Beach, 50(1), 19-25. 

13488 Moore, L., P. Ruggiero, and J. List, 2006: Comparing mean high water and high water 

13489 line shorelines: Should proxy-datum offsets be incorporated in shoreline change 

13490 analysis? Journal of Coastal Research, 22(4), 894-905. 

13491 Morton, R.A. and T.L. Miller, 2005: National Assessment of Shoreline Change: Part 2, 

13492 Historical Shoreline Changes and Associated Coastal Land Loss along the U.S. 

13493 Southeast Atlantic Coast. U.S. Geological Survey open-file report 2005-1401. 
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13494 U.S. Geological Survey, St. Petersburg, FL, 35 pp. 

13495 <http://pubs.usgs.gov/of/2005/1401/> 

13496 Morton, R.A., T.L. Miller, and L.J. Moore, 2004: National Assessment of Shoreline 

13497 Change: Part 1, Historical Shoreline Changes and Associated Coastal Land Loss 

13498 along the U.S. Gulf of Mexico. U.S. Geological Survey open file report 2004-

13499 1043. U.S. Geological Survey, St. Petersburg, FL, 44 pp. 

13500 <http://pubs.usgs.gov/of/2004/1043/> 

13501 NRC (National Research Council), 1987: Responding to Changes in Sea Level: 

13502 Engineering Implications. National Academy Press, Washington DC, 148 pp. 

13503 Pendleton, E.A., S.J. Williams, and E.R. Thieler, 2004: Coastal Vulnerability 

13504 Assessment of Fire Island National Seashore (ASIS) to Sea-level Rise. U.S. 

13505 Geological Survey open-file report 04-1020. [U.S. Geological Survey, Reston, 

13506 VA], 20 pp. <http://pubs.usgs.gov/of/2004/1020/> 

13507 Riggs, S.R., W.J. Cleary, and S.W. Snyder, 1995: Influence of inherited geologic 

13508 framework upon barrier beach morphology and shoreface dynamics. Marine 

13509 Geology, 126(1-4), 213-234. 

13510 Rosati, J.D., 2005: Concepts in sediment budgets. Journal of Coastal Research, 21(2), 

13511 307-322. 

13512 Ruggiero, P., G.M. Kaminsky, and G. Gelfenbaum, 2003: Linking proxy-based and 

13513 datum-based shorelines on a high-energy coastline: Implications for shoreline 

13514 change analyses. Journal of Coastal Research, Special issue 38, 57-82. 

13515 Schwartz, M.L., 1967: The Bruun theory of sea-level rise as a cause of shore erosion. 

13516 Journal of Geology, 75(1), 76-92. 

13517 SCOR (Scientific Committee on Ocean Research) Working Group 89, 1991: The 

13518 response of beaches to sea level changes: a review of predictive models. Journal 

13519 of Coastal Research, 7(3), 895-921. 
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13520 Shalowitz, A.L., 1964: Shore and Sea Boundaries; With Special Reference to the 

13521 Interpretation and Use of Coast and Geodetic Survey Data. Publication 10-1. 

13522 U.S. Department of Commerce, Coast and Geodetic Survey, Washington, DC, 

13523 749 pp. 

13524 Stockdon, H.F., A.H. Sallenger, J.H. List, and R.A. Holman, 2002: Estimation of 

13525 shoreline position and change using airborne topographic Lidar data. Journal of 

13526 Coastal Research, 18(3), 502-513. 

13527 Stolper, D., J.H. List, and E.R. Thieler, 2005: Simulating the evolution of coastal 

13528 morphology and stratigraphy with a new morphological-behavior model 

13529 (GEOMBEST). Marine Geology, 218(1-4), 17-36. 

13530 Thieler, E.R. and E. Hammar-Klose, 1999: National Assessment of Coastal Vulnerability 

13531 to Sea-level Rise--Preliminary Results for U.S. Atlantic Coast. U.S. Geological 

13532 Survey open-file report 99-593. U.S. Geological Survey, Reston, VA, 1 sheet. 

13533 <http://purl.usgs.gov/of/1999/of99-593/> 

13534 Thieler, E.R., O.H. Pilkey, R.S. Young, D.M. Bush, and F. Chai, 2000: The use of the 

13535 mathematical models to predict beach behavior for U.S. coastal engineering: a 

13536 critical review. Journal of Coastal Research, 16(1), 48-70. 

13537 Thieler, E.R., S.J. Williams, and R. Beavers, 2002: Vulnerability of U.S. National Parks 

13538 to Sea-Level Rise and Coastal Change. U.S. Geological Survey fact sheet FS 095-

13539 02. [U.S. Geological Survey, Reston, VA], 2 pp. <http://pubs.usgs.gov/fs/fs095-

13540 02/> 

13541 Thieler, E.R., E.A. Himmelstoss, J.L. Zichichi, and T.L. Miller, 2005: Digital Shoreline 

13542 Analysis System (DSAS) Version 3.0; An ArcGIS© Extension for Calculating 

13543 Shoreline Change. U.S. Geological Survey open-file report 2005-1304. U.S. 

13544 Geological Survey, Reston, VA. <http://pubs.usgs.gov/of/2005/1304/> 

13545 Wright, L.D., 1995: Morphodynamics of Inner Continental Shelves. CRC Press, Boca 

13546 Raton, FL, 241 pp. 
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13547 * Zhang, K., 1998: Twentieth Century Storm Activity and Sea Level Rise along the U.S. 

13548 East Coast and Their Impact on Shoreline Position. Ph.D. dissertation, 

13549 Department of Geography. University of Maryland, College Park, 266 leaves. 

13550 
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13551 Glossary

13552 access, lateral 

13553 the right to walk or otherwise move along a shore, once someone has reached the shore 

13554 

13555 access, perpendicular 

13556 a legally permissible means of reaching the shore from dry land 

13557 

13558 access point 

13559 a place where anyone may legally gain access to the shore; usually a park, the end of a 

13560 public street, or a public path; a place where perpendicular access is provided 

13561 

13562 accretion, lateral

13563 the extension of land by natural forces acting over a long period of time, as on a beach by 

13564 the washing-up of sand from the sea or on a floodplain by the accumulation of sediment 

13565 deposited by a stream 

13566 

13567 accretion, vertical 

13568 the vertical accumulation of a sedimentary deposit; the increase in thickness of a 

13569 sediment body as a result of sediment accumulation 

13570 

13571 active margin

13572 a continental margin characterized by volcanic activity and earthquakes occurring where 

13573 the edges of lithospheric plates are colliding; because these margins are largely confined 

13574 to the rim of the Pacific, this type of margin is also referred to as a Pacific margin; 

13575 compare with passive margin 

13576 

13577 armoring

13578 the placement of fixed engineering structures, typically rock or concrete, on or along the 

13579 shoreline to mitigate the effects of coastal erosion and protect structures; such structures 

13580 include seawalls, revetments, bulkheads, and rip-rap (loose boulders) 

13581 

13582 astronomical tides

13583 the alternating rise and fall of the ocean surface and connected waters, such as estuaries 

13584 and gulfs, that result from the gravitational forces of the moon and sun 

13585 

13586 avulsion

13587 a sudden cutting off or separation of land by a flood or by and abrupt change in the 

13588 course of a stream, as by a stream breaking through a meander or by a sudden change in 

13589 current whereby a stream deserts its old channel for a new one; OR rapid erosion of the 

13590 shore by waves during a storm 

13591 

13592 barrier island, (or sometimes just barrier)
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13593 a long, narrow coastal sandy island that is above high tide and parallel to the shore, and 

13594 that commonly has dunes, vegetated zones, and swampy terraces extending landward 

13595 from the beach

13596 

13597 barrier island roll-over

13598 the landward migration or landward transgression of a barrier island, accomplished 

13599 primarily over decadal or longer time scales through the process of storm overwash, 

13600 periodic inlet formation, and wind-blown transport of sand 

13601 barrier migration 

13602 refers to the movement of an entire barrier island or barrier spit in response to sea-level 

13603 rise, changes in sediment supply, storm surges or waves, or some combination of these 

13604 factors 

13605 

13606 barrier raising

13607 adding sediment to a barrier island or spit to increase its elevation; it is rarely done on a 

13608 large scale (e.g., the Galveston, Texas barrier island was raised after the hurricane of 

13609 1900) but individual lot owners sometimes import sediment to add elevation to their land, 

13610 especially if the land is prone to flooding 

13611 

13612 barrier spit

13613 a barrier island that is connected at one end to the mainland 

13614 

13615 bathymetry 

13616 the measurement of ocean depths and the mapping of the topography of the seafloor 

13617 

13618 beach

13619 the unconsolidated material that covers a gently sloping zone extending landward from 

13620 the low water line to the place where there is a definite change in material or 

13621 physiographic form (such as a cliff), or to the line of permanent vegetation (usually the 

13622 effective limit of the highest storm waves)

13623 

13624 beach nourishment

13625 the addition of sand, often dredged from offshore, to an eroding shoreline to enlarge or 

13626 create a beach area, offering both temporary shore protection and recreational 

13627 opportunities 

13628 

13629 berm

13630 a commonly occurring, low, impermanent, nearly horizontal ledge or narrow terrace on 

13631 the backshore of a beach, formed of material thrown up and deposited by storm waves 

13632 

13633 bluff

13634 a high bank or bold headland with a broad, precipitous, sometimes rounded cliff face 

13635 overlooking a plain or body of water 

13636 

13637 breakwater
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13638 an offshore structure (such as a wall or jetty) that, by breaking the force of the waves, 

13639 protects a harbor, anchorage, beach or shore area 

13640 

13641 breach 

13642 (n.) a channel through a barrier spit or island typically formed by storm waves, tidal 

13643 action, or river flow; breaches commonly occur during high storm surge cause by a 

13644 hurricane or extra-tropical storm; (v.) to cut a deep opening in a landform 

13645 

13646 bulkhead 

13647 a structure or partition to retain or prevent sliding of the land; a secondary purpose is to 

13648 protect uplands against damage from wave action 

13649 

13650 coastal plain

13651 any lowland area bordering a sea or ocean, extending inland to the nearest elevated land, 

13652 and sloping very gently seaward 

13653 

13654 coastal squeeze 

13655 the narrowing, potentially to the point of failure or elimination, of an environmental 

13656 system (typically a beach or marsh) that is trapped between the transgressing sea on one 

13657 side and an impassable barrier (e.g., a sea wall or bulkhead) on the other 

13658 

13659 coastal zone

13660 the area extending from the ocean inland across the region directly influenced by marine 

13661 processes 

13662 

13663 coastline

13664 the line that forms the boundary between the coast and the shore or the line that forms the 

13665 boundary between the land and the water 

13666 

13667 continental shelf 

13668 the gently sloping underwater region at the edge of the continent that extends from the 

13669 beach to where the steep continental slope begins, usually at depths greater than 300 feet 

13670 

13671 contour interval 

13672 the difference in elevations of adjacent contours on a topographic map 

13673 

13674 datum

13675 a quantity, or a set of quantities, that serves as a basis for the calculation of other 

13676 quantities; in terms of surveying and mapping, a datum is a point, line or surface used as 

13677 a reference in measuring locations or elevations 

13678 

13679 delta

13680 a low relief landform composed of sediments deposited at the mouth of a river that 

13681 commonly forms a triangular or fan-shaped plain of considerable area crossed by many 

13682 channels from the main river; forms as the result of accumulation of sediment supplied by 

13683 the river in such quantity that it is not removed by tidal or wave-driven currents 
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13684 

13685 DEM (digital elevation model) 

13686 the digital representation of the ground surface or terrain using a set of elevation data

13687 

13688 deposition

13689 the laying, placing, or throwing down of any material; typically refers to sediment 

13690 

13691 depth of closure 

13692 a theoretical depth below which sediment exchange between the nearshore (beach and 

13693 shoreface) and the continental shelf is deemed to be negligible 

13694 

13695 dike 

13696 a wall generally of earthen materials designed to prevent the permanent submergence of 

13697 lands below sea level, tidal flooding of lands between sea level and spring high water, or 

13698 storm-surge flooding of the coastal floodplain 

13699 

13700 discount rate 

13701 

13702 downdrift 

13703 refers to the location of one section or feature along the coast in relation to another; often 

13704 used to refer to the direction of net longshore sediment transport between two or more 

13705 locations (i.e., downstream) 

13706 

13707 dredge and fill 

13708 a process by which channels are dredged through wetlands or uplands to allow small boat 

13709 navigation, and dredge spoil is placed on the adjacent land area to raise the land high 

13710 enough to allow development; sometimes referred to as “lagoon development” or “canal 

13711 estates”; used extensively before the 1970s 

13712 

13713 dredge spoil disposal (dredged material placement)

13714 dredged material, or spoil, is material consisting of sediment or rock, excavated or 

13715 dredged from an underwater location and removed to a placement site or disposal area; in 

13716 the United States, designated areas must be coordinated with the Environmental 

13717 Protection Agency and resource agencies such as the U.S. Fish and Wildlife Service and 

13718 the National Marine Fisheries Service for environmental compliance, and with local 

13719 interests for capacity and acceptability 

13720 

13721 dune

13722 a low mound, ridge, bank or hill of loose, wind blown material (generally sand) either 

13723 bare or covered with vegetation, capable of movement from place to place but typically 

13724 retaining a characteristic shape 

13725 

13726 ebb current

13727 the tidal current associated with the decrease in height of the tide, generally moving 

13728 seaward or down a tidal river or estuary 

13729 
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13730 ebb-tide delta

13731 a large sand shoal commonly deposited at the mouths of tidal inlets formed by ebbing 

13732 tidal currents and modified in shape by waves 

13733 

13734 erosion

13735 the mechanical removal of sedimentary material by gravity, running water, moving ice, 

13736 or wind; in the context of coastal settings erosion refers to the landward retreat of a 

13737 shoreline indicator such as the water line, the berm crest, or the vegetation line; the loss 

13738 occurs when sediments are entrained into the water column and transported from the 

13739 source 

13740 

13741 erosion-based setback 

13742 a setback equal to an estimated annual erosion rate multiplied by a number of years set by 

13743 statute or regulation (e.g., 30 years) 

13744 

13745 estuary

13746 a semi-enclosed coastal body of water which has a free connection with the open sea and 

13747 within which sea water is measurably diluted with freshwater from land drainage; an inlet 

13748 of the sea reaching into a river valley as far as the upper limit of tidal rise, usually being 

13749 divisible into three sectors; (a) a marine or lower estuary, in free connection with the 

13750 open sea; (b) a middle estuary subject to strong salt and freshwater mixing; and (c) an 

13751 upper or fluvial estuary, characterized by fresh water but subject to daily tidal action; 

13752 limits between these sectors are variable, and subject to constant changes in the river 

13753 discharge 

13754 

13755 eustatic sea-level rise

13756 refers to worldwide rise of sea level that affects all oceans; eustatic rise has various 

13757 causes, but typically result from thermal expansion of ocean waters, and additions of 

13758 water from glaciers, ice caps, and ice sheets 

13759 

13760 extra-tropical storm

13761 refers to cyclonic weather systems, occurring in the middle or high latitudes (e.g., 

13762 poleward of the tropics) that are generated by colliding airmasses; these weather systems 

13763 often spawn large storms occurring between late fall and early spring 

13764 

13765 fetch

13766 the area of the open ocean over the surface of which the winds blow with constant speed 

13767 and direction, generating waves 

13768 

13769 flood current

13770 the tidal current associated with the increase in height of the tide, generally moving 

13771 landward or up a tidal river or estuary 

13772 

13773 flood-tide delta

13774 a large sand shoal commonly deposited on the landward side of a tidal inlet formed by 

13775 flooding tidal currents 
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13776 

13777 floodproofing

13778 a technique that is intended to limit the amount of damage that will occur to a building or 

13779 its contents during a flood (see also dry floodproofing and wet floodproofing)

13780 

13781 geologic framework 

13782 refers to the underlying geological setting, structure, and lithology (rock/sediment type) 

13783 in a given area 

13784 

13785 geomorphic or geomorphology 

13786 the external structure, form, and arrangement of rocks or sediments in relation to the 

13787 development of the surface of the earth 

13788 

13789 glacial rebound

13790 uplift of land following deglaciation due to the mass of the ice being removed from the 

13791 land surface which causes an isostatic response of the lithosphere

13792 

13793 global sea-level rise 

13794 the worldwide average rise in mean sea level (see eustatic sea level) 

13795 

13796 groin

13797 an engineering structure oriented perpendicular to the coast, used to accumulate littoral 

13798 sand by interrupting longshore transport processes; often constructed of concrete, 

13799 timbers, steel, or rock 

13800 

13801 high marsh

13802 the part of a marsh that lies between the low marsh and the marsh’s upland border; this 

13803 area can be expansive, extending hundreds of yards inland from the low marsh area; soils 

13804 here are mostly saturated but only flooded during higher-than-average tides 

13805 

13806 hydrodynamic climate

13807 the characteristics of nearshore or continental shelf currents in an area that typically result 

13808 from waves, tides, and weather systems 

13809 

13810 inlet 

13811 a small, narrow opening, recess, indentation, or other entrance into a coastline or shore of 

13812 a lake or river through which water penetrates landward, commonly refers to a waterway 

13813 between two barrier islands that connects the sea and a lagoon

13814 

13815 intertidal zone

13816 see littoral

13817 

13818 inundation

13819 refers to the submergence of land by water 

13820 

13821 isostasy
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13822 equilibrium condition whereby portions of the Earth’s crust are compensated (floating) 

13823 by denser material below 

13824 

13825 jetty 

13826 an engineering structure built at the mouth of a river or tidal inlet stabilize a channel for 

13827 navigation; designed to prevent shoaling of a channel by littoral materials and to direct 

13828 and confine the stream or tidal flow 

13829 

13830 lagoon

13831 a shallow coastal body of seawater that is separated form the open ocean by a barrier or 

13832 coral reef; the term is commonly used to define the shore-parallel body of water behind a 

13833 barrier island or barrier spit 

13834 

13835 levee 

13836 a wall, generally of earthen materials, designed to prevent riverine flooding after periods 

13837 of exceptional rainfall 

13838 

13839 lidar (LIght Detection And Ranging) 

13840 a remote sensing instrument that uses laser light pulses to measure the elevation of the 

13841 land surface with a high degree of accuracy and precision 

13842 

13843 lithology

13844 the description of rocks on the basis of characteristics such as color, mineral composition, 

13845 and grain size 

13846 

13847 lithosphere

13848 the solid portion of the Earth, including the crust and part of the upper mantle 

13849 

13850 littoral

13851 zone between high and low tide in coastal waters or the shoreline of a freshwater lake 

13852 

13853 littoral cell

13854 a section of coast for which sediment transport processes can be isolated from the 

13855 adjacent coast; within each littoral cell, a sediment budget can be defined that describes 

13856 sinks, sources, and internal fluxes 

13857 

13858 littoral drift

13859 the sedimentary material moved in the littoral zone under the influence of waves and 

13860 currents 

13861 

13862 littoral transport

13863 the movement of littoral drift in the littoral zone by waves and currents; includes 

13864 movement parallel and perpendicular to the shore 

13865 

13866 littoral zone

13867 a term describing the region on the shore occurring between high and low water marks 
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13868 

13869 living shoreline 

13870 refers to a shore protection concept where some or all of the environmental 

13871 characteristics of a natural shoreline are retained as the position of the shore changes 

13872 

13873 long lived 

13874 having a long lifetime or a long expected lifetime; long-lived infrastructure means 

13875 infrastructure that is likely to be in service for a long time 

13876 

13877 longshore current

13878 an ocean current in the littoral zone that moves parallel to the shoreline, produced by 

13879 waves approaching at an angle to the shoreline 

13880 longshore transport

13881 movement of sediment parallel to the shoreline in the surf zone by wave suspension and 

13882 the longshore current 

13883 

13884 low marsh 

13885 the seaward edge of a salt marsh, usually a narrow band along a creek or ditch which is 

13886 flooded at every high tide and exposed at low tide (also see high marsh for comparison) 

13887 

13888 marsh

13889 a frequently or continually inundated wetland characterized by herbaceous vegetation 

13890 adapted to saturated soil conditions (see also salt marsh) 

13891 

13892 mean high water

13893 a tidal datum; the average height of high water levels observed over a 19-year period 

13894 

13895 mean higher high water 

13896 the average of the higher high water height of each tidal day observed over the national 

13897 tidal datum epoch (see national tidal datum epoch

13898 

13899 mean sea level

13900 the 'still water level' (i.e., the level of the sea with high frequency motions such as wind 

13901 waves averaged out) averaged over a period of time such as a month or a year, such that 

13902 periodic changes in sea level (e.g., due to the tides) are also averaged out; the values of 

13903 MSL are measured with respect to the level of marks on land (called 'benchmarks') 

13904 

13905 metadata

13906 a file of information which captures the basic characteristics of a data or information 

13907 resource; representing the who, what, when, where, why and how of the data resource; 

13908 geospatial metadata are used to document geographic digital resources such as 

13909 Geographic Information System (GIS) files, geospatial databases, and earth imagery 

13910 

13911 metes and bounds 

13912 the boundary lines and limits of a tract that is described and characterized by placing all 

13913 data in the tract description as opposed to other references such as maps or plats 
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13914 

13915 mixed energy coast

13916 a coast in which the coastal landforms are shaped by a combination of wave and tidal 

13917 currents 

13918 

13919 moral hazard 

13920 a circumstance in which insurance, lending practices, or subsidies designed to protect 

13921 against a specified hazard induce people to take measures that increase the risk of that 

13922 hazard 

13923 

13924 mudflat 

13925 a level area of fine silt and clay along a shore alternately covered and uncovered by the 

13926 tide or covered by shallow water 

13927 

13928 national geodetic vertical datum of 1929 (NGVD29) 

13929 a fixed reference adopted as a standard geodetic datum for elevations; it was determined 

13930 by leveling networks across the United States and sea-level measurements at 26 coastal 

13931 tide stations; this reference is now superseded by the North American vertical datum of 

13932 1988 (NAVD88) 

13933 

13934 national tidal datum epoch (NTDE) 

13935 the latest 19-year time period over which NOAA has computed and published official 

13936 tidal datums and local mean sea-level elevations from tide station records; currently, the 

13937 latest NTDE is 1983-2001 

13938 

13939 nearshore zone

13940 refers to the zone extending from the shoreline seaward to a short, but indefinite distance 

13941 offshore, typically confined to depths less than 5 meters (16.5 feet) 

13942 

13943 nontidal wetlands 

13944 wetlands that are not exposed to the periodic change in water level that occurs due to 

13945 astronomical tides 

13946 

13947 nor’easter (northeaster)

13948 name given to the strong northeasterly winds associated with extra-tropical cyclones that 

13949 occur along East Coast of the United States and Canada; these storms often cause beach 

13950 erosion and structural damage; wind gusts associated with these storms can approach and 

13951 sometimes exceed hurricane force in intensity 

13952 

13953 North American vertical datum of 1988 (NAVD88) 

13954 a fixed reference for elevations determined by geodetic leveling, derived from a general 

13955 adjustment of the first-order terrestrial leveling networks of the United States, Canada, 

13956 and Mexico; NAVD88 supersedes NGVD29 

13957 

13958 100-year flood 
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13959 the standard used by the National Flood Insurance Program (NFIP) for floodplain 

13960 management purposes and to determine the need for flood insurance; a structure located 

13961 within a special flood hazard area shown on an NFIP map has a 26 percent chance of 

13962 suffering flood damage during the term of a 30-year mortgage 

13963 

13964 ordinary high water mark 

13965 a demarcation between the publicly owned land along the water and privately owned land 

13966 which has legal implications regarding public access to the shore; generally based on 

13967 mean high water, the definition varies by state; along beaches with significant waves, it 

13968 may be based on the line of vegetation, the water mark caused by wave runup, surveys of 

13969 the elevation of mean high water, or other procedures 

13970 

13971 overwash

13972 sediment that is transported from the beach across a barrier, and is deposited in an apron13973 like accumulation along the backside of the barrier; overwash usually occurs during 

13974 storms when waves break through the frontal dune ridge and flow landward toward the 

13975 marsh or lagoon 

13976 

13977 outwash plain

13978 braided stream deposit beyond the margin of a glacier; it is formed from meltwater 

13979 flowing away from the glacier, depositing mostly sand and fine gravel in a broad plain 

13980 

13981 passive margin

13982 type of continental margin occurring in the middle of a tectonic plate, consequently 

13983 tectonic activity is minimal; these margins are typified along the margins of the Atlantic 

13984 Ocean and often so it is often termed an Atlantic margin 

13985 

13986 pocket beach

13987 a typically small, narrow beach formed between two littoral obstacles, such as between 

13988 rocky headlands or promontories that occur at the shore 

13989 

13990 Public Trust Doctrine 

13991 a legal principle derived from English Common Law; the essence of the doctrine is that 

13992 the waters of the state are a public resource owned by and available to all citizens equally 

13993 for the purposes of navigation, hunting, fowling, and fishing, and that this trust is not 

13994 invalidated by private ownership of the underlying land 

13995 

13996 relative sea-level rise 

13997 the rise in sea level measured with respect to a specified vertical datum relative to the 

13998 land, which may also be changing elevation over time; typically measured using a tide 

13999 gauge 

14000 

14001 retreat 

14002 the act of moving inland 

14003 

14004 revetment 
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14005 a sloped facing of stone, concrete, etc., built to protect a scarp, embankment, or shore 

14006 structure against erosion by wave action or currents 

14007 

14008 river diversion 

14009 engineering approaches used to redirect the flow of water from its natural course 

14010 for a range of purposes; commonly used to by-pass water during dam construction, for 

14011 flood control, for navigation, or for wetland and floodplain restoration 

14012 

14013 rip-rap

14014 loose boulders placed on or along the shoreline as a form of armoring

14015 

14016 riverine flooding

14017 flooding of lands caused by the elevation of nontidal or tidal waters resulting from the 

14018 drainage of upstream areas, usually after periods of exceptional rainfall 

14019 

14020 roll-over 

14021 see barrier island roll-over

14022 

14023 rolling easement 

14024 an interest in land (by title or interpretation of the Public Trust Doctrine) in which a 

14025 property owner’s interest in preventing real estate from eroding or being submerged 

14026 yields to the public or environmental interest in allowing wetlands or beaches to migrate 

14027 inland 

14028 

14029 root mean square error 

14030 a measure of statistical error calculated as the square root of the sum of squared errors, 

14031 where error is the difference between an estimate and the actual value; if the mean error 

14032 is zero, it also equals the standard deviation of the error 

14033 

14034 salt marsh 

14035 a grassland containing salt tolerant vegetation established on sediments bordering saline 

14036 water bodies where water level fluctuates either tidally or nontidally (see also marsh) 

14037 

14038 saltwater intrusion 

14039 displacement of fresh or ground water by the advance of salt water due to its greater 

14040 density, usually in coastal and estuarine areas 

14041 

14042 sand bypassing 

14043 hydraulic or mechanical movement of sand from the accreting updrift side to the eroding 

14044 downdrift side of an inlet or harbor entrance; the hydraulic movement may include 

14045 natural movement as well as movement caused by man

14046 

14047 seawall

14048 a structure, often concrete or stone, built along a portion of a coast to prevent erosion and 

14049 other damage by wave action, often it retains earth against its shoreward face; a seawall is 

14050 typically more massive and capable of resisting greater wave forces than a bulkhead
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14051 

14052 sediment(s)

14053 solid materials or fragments that originates from the break up of rock and is transported 

14054 by air, water or ice, or that accumulates by other natural agents such as chemical 

14055 precipitation or biological secretions; solid material that has settled from being suspended 

14056 as in moving water or air 

14057 

14058 sediment broadcasting

14059 a technique in which sediment from an external source is spread onto salt marshes to 

14060 supply mineral material to enhance their growth 

14061 

14062 sediment supply 

14063 refers to the abundance or lack of sediment in a coastal system that is available to 

14064 contribute to the maintenance or evolution of coastal landforms including both exposed 

14065 features such as beaches and barrier islands, and underwater features such as the seabed 

14066 

14067 setback 

14068 the requirement that construction be located a minimum distance inland from tidal 

14069 wetlands, tidal water, the primary dune line, or some other definition of the shore 

14070 

14071 shoal

14072 a relatively shallow place in a stream, lake, sea, or other body of water; a submerged 

14073 ridge, bank, or bar consisting of or covered by sand 

14074 

14075 shore

14076 the narrow strip of land immediately bordering any body of water, especially a sea or 

14077 large lake; the zone over which the ground is alternately exposed and covered by the tides 

14078 or waves, or the zone between high and low water

14079 

14080 shoreface 

14081 the narrow relatively steep surface that extends seaward from the beach, often to a depth 

14082 of 30 to 60 feet, at which point the slope flattens and merges with the continental shelf 

14083 

14084 shoreline

14085 the intersection of a specified plane of water with the shore or beach; on National Ocean 

14086 Service nautical charts and surveys, the line representing the shoreline approximates the 

14087 mean high water line 

14088 

14089 shoreline armoring (see armoring)

14090 a method of shore protection that prevents shore erosion through the use of hardened 

14091 structures such as seawalls, bulkheads, and revetments 

14092 

14093 shore protection

14094 refers to a range of activities that focus on protecting land from inundation, erosion, or 

14095 storm-induced flooding through the construction of various structures such as jetties, 

14096 groins, or seawalls, or the addition of sediments to the shore (e.g., beach nourishment) 
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14097 

14098 significant wave height

14099 the average height of the highest one-third of waves in a given area 

14100 

14101 sill

14102 semicontinuous structures placed along the edge of a marsh in order to diminish wave 

14103 erosion of the marsh, usually made of stone; similar to breakwaters, except that 

14104 breakwaters are generally farther from the shore and have larger open spaces between 

14105 them 

14106 

14107 soft shore protection 

14108 a method of shore protection that prevents shore erosion through the use of materials 

14109 similar to those already found in a given location, such as adding sand to an eroding 

14110 beach or planting vegetation whose roots will retain soils along the shore 

14111 

14112 spit

14113 a fingerlike extension of the beach that was formed by longshore sediment transport; 

14114 typically, it is a curved or hook-like sandbar extending into an inlet 

14115 

14116 spring high water

14117 the average height of the high waters during the semi-monthly times of spring tides 

14118 (occurs at the full and new moons) 

14119 

14120 storm surge 

14121 an abnormal rise in sea level accompanying a hurricane or other intense storm, whose 

14122 height is the difference between the observed level of the sea surface and the level that 

14123 would have occurred in the absence of the cyclone 

14124 

14125 subsidence 

14126 the downward settling of material with little horizontal movement; the downwarping of 

14127 the earth’s crust relative to the surroundings 

14128 

14129 submergence 

14130 a rise of the water level relative to the land, so that areas that were formerly dry land 

14131 become inundated; it is the result either of the sinking of the land or a net rise in sea level 

14132 

14133 supratidal zone

14134 the shore area just above the high-tide level 

14135 

14136 surf zone

14137 the zone of the nearshore region where bore-like waves occur following breaking waves, 

14138 extending from the point where waves break to the wet beach 

14139 

14140 taxon (plural, taxa) 

14141 a general term applied to any taxonomic element, population, or group irrrespective 

14142 of its classification level 
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14143 

14144 threshold 

14145 in climate change studies, a threshold generally refers to the point at which the climate 

14146 system begins to change in a marked way because of increased forcing; crossing a 

14147 climate threshold triggers a transition to a new state of the system at a generally faster 

14148 rate 

14149 

14150 tidal datum 

14151 a base elevation used as a vertical from which to reckon heights 

14152 or depths; called a tidal datum when defined in terms of a certain phase of the tide 

14153 

14154 tidal freshwater marsh 

14155 marsh along rivers and estuaries close enough to the coastline to experience significant 

14156 tides by nonsaline water, vegetation is often similar to nontidal freshwater marshes 

14157 

14158 tidal inlet

14159 an opening in the shoreline through which water penetrates the land, thereby providing a 

14160 connection between the ocean and bays, lagoons, and marsh and tidal creek systems; the 

14161 main channel of a tidal inlet is maintained by tidal currents 

14162 

14163 tidal range 

14164 the vertical difference between normal high and low tides often computed as the 

14165 elevation difference between mean high water and mean low water; spring tide range is 

14166 the elevation difference between spring high water and spring low water 

14167 

14168 tidal wetlands

14169 wetlands that are exposed to the periodic rise and fall of the tides (see wetlands) 

14170 

14171 tide-dominated coast

14172 coast where the morphology is primarily a product of tidal processes 

14173 

14174 tide gauge 

14175 the geographic location where tidal observations are conducted and consisting of a water 

14176 level sensor, data collection and transmission equipment, and local bench marks that are 

14177 routinely surveyed into the sensors 

14178 

14179 tidelands 

14180 lands that are flooded during ordinary high water, and hence available to the public under 

14181 the Public Trust Doctrine

14182 

14183 tipping point

14184 a critical point in the evolution of a system that leads to new and potentially irreversible 

14185 effects at a rate that can either be much faster or much slower than forcing 

14186 

14187 transgression
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14188 the spread or extension of the sea over land areas, and the consequent evidence of such 

14189 advance; also, any change such as a rise in sea level that brings offshore deep-water 

14190 environments to areas formerly occupied by nearshore, shallow-water environments or 

14191 that shifts the boundary between marine and nonmarine deposition away from deep water 

14192 regions 

14193 

14194 updrift

14195 refers to the location of one section or feature along the coast in relation to another; often 

14196 used to refer to the direction of net longshore sediment transport between two or more 

14197 locations (i.e., upstream) 

14198 

14199 wave-dominated coast

14200 coast where the morphology is primarily a product of wave processes 

14201 

14202 wave refraction

14203 the process by which a water wave, moving in shallow water as it approaches the shore at 

14204 an angle, tends to be turned from its original direction so that the wave crest is more 

14205 parallel to shore; also can refer to the bending of wave crests by currents 

14206 

14207 wave run-up 

14208 the upper levels reached by a wave on a beach or coastal structure, relative to still-water 

14209 level 

14210 

14211 wet floodproofing

14212 

14213 wetlands 

14214 specifies those areas that are inundated or saturated by surface or ground water at a 

14215 frequency and duration sufficient to support, and that under normal circumstances do 

14216 support, a prevalence of vegetation typically adapted for life in saturated soils; wetlands 

14217 generally include swamps, marshes, bogs, and similar areas 

14218 

14219 wetland accretion 

14220 a process by which the surface of wetlands increases in elevation; see also accretion, 

14221 vertical

14222 

14223 wetland migration 

14224 a process by which tidal wetlands adjust to rising sea level by advancing inland into areas 

14225 previously above the ebb and flow of the tides 

14226 
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14227 Scientific Names—Chapter 5 Species

American black duck Anas rubripes 

American oystercatcher Haematopus palliatus 

Atlantic menhaden Brevoortia tyrannus 

Atlantic silverside Menidia spp. 

bald eagle Haliaeetus leucocephalus 

bay anchovy Anchoa mitchilli 

belted kingfisher Ceryle alcyon 

black rail Laterallus jamaicensis 

black skimmer Rynchops niger 

bladderwort Utricularia spp. 

blue crab Callinectes sapidus 

bluefish Pomatomus saltatrix 

brant Branta bernicla 

canvasback duck Aythya valisineria 

carp Family Cyprinidae 

catfish Order Siluriformes 

clapper rail Rallus longirostris 

common tern Sterna hirundo 

crappie Pomoxis spp. 

diamondback terrapin Malaclemys terrapin 

eastern mud turtle Kinosternum subrubrum 

elfin skimmer (dragonfly) Nannothemis bella 

fiddler crab Uca spp. 

Forster’s tern Sterna forsteri 

fourspine stickleback Apeltes quadracus 

grass shrimp Hippolyte pleuracanthus 

great blue heron Ardea herodias 

gull-billed tern Sterna nilotica 

herring Clupea harengus 

horseshoe crab Limulus polyphemus 

Kemp’s ridley sea turtle Lepidochelys kempii 

laughing gull Larus atricilla 

least bittern Ixobrychus exilis 

meadow vole Microtus pennsylvanicus 

minnows Family Cyprinidae 

mummichog Fundulus herteroclitus 

naked goby Gobiosoma bosci 

northern pipefish Syngnathus fuscus 

piping plover Charadrius melodus 

red drum Sciaenops ocellatus 

red knot Calidris canutus 

red-winged blackbird Agelaius phoeniceus 

ribbed mussel Geukensia demissa 
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sand digger Neohaustorius schmitzi 

sand flea Talorchestia spp. 

sandpiper Family Scolopacidae 

sea lettuce Ulva lactuca 

sea trout Salvelinus fontinalis 

shad Alosa sapidissima 

sheepshead minnow Cyprinodon variegatus 

shiners Family Cyprinidae 

spot Leiostomus xanthurus 

striped anchovy Anchoa hepsetus 

striped bass Morone saxatilis 

striped killifish Fundulus majalis 

sundew Drosera spp. 

sunfish Family Centrarchidae 

threespine stickleback Gasterosteus aculeatus 

tiger beetle Cicindela spp. 

weakfish Cynoscion regalis 

white croaker Genyonemus lineatus 

white perch Morone americana 

widgeon grass Ruppia maritima 

willet Catoptrophorus semipalmatus 

14228 

14229 
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14230 ACRONYMS AND ABBREVIATIONS 

14231 

14232 A–P Albemarle–Pamlico 

14233 ABFE Advisory Base Flood Elevations 

14234 AEC Areas of Environmental Concern ( 

14235 ASFPM Association of State Floodplain Managers 

14236 BFE base flood elevation 

14237 CAFRA Coastal Facility Review Act 

14238 CAMA Coastal Area Management Act 

14239 CBRA Coastal Barrier Resources Act 

14240 CCMP Comprehensive Coastal Management Plan 

14241 CCSP Climate Change Science Program 

14242 CORS continuously operating reference stations 

14243 CRC Coastal Resources Commission 

14244 CTP Cooperative Technical Partnership 

14245 CVI Coastal Vulnerability Index 

14246 CZM Coastal Zone Management 

14247 CZMA Coastal Zone Management Act 

14248 DDFW Delaware Division of Fish and Wildlife 

14249 DEC Department of Environmental Conservation 

14250 DEM Digital elevation Model 

14251 DFIRM digital flood insurance rate maps 

14252 FEMA Federal Emergency Management Agency 

14253 FGDC Federal Geographic Data Committee 

14254 FIRM Flood Insurance Rate Maps 

14255 FIS Flood Insurance Studies 

14256 GAO General Accounting Office (1982) 

14257 GAO General Accountability Office (2007) 

14258 GEOSS Global Earth Observation System of Systems 

14259 GIS geographic information system 

14260 GCN greatest conservation need 

14261 GPS Global Positioning System 

14262 HOWL highest observed water levels 

14263 IDA intensely developed area 

14264 IOOS Integrated Ocean Observing System 

14265 IPCC Intergovernmental Panel on Climate Change 

14266 IPCC CZMS Intergovernmental Panel on Climate Change Coastal Zone Management 

14267 Subgroup 

14268 LDA limited development area 

14269 LMSL local mean sea level 

14270 MHHW Mean Higher High Water 

14271 MHW Mean High Water 

14272 MLW Mean Low Water 

14273 MLLW Mean Lower Low Water 

14274 MSL mean sea level 

14275 NAI No Adverse Impact 
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14276 NAS National Academy of Sciences 

14277 NAVD North American Vertical Datum 

14278 NCDC National Climatic Data Center 

14279 NERRS National Estuarine Research Reserve System 

14280 NDEP National Digital Elevation Program 

14281 NED National Elevation Dataset 

14282 NFIP National Flood Insurance Program 

14283 NGVD National Geodetic Vertical Datum 

14284 NHP National Heritage Program 

14285 NHS National Highway System 

14286 NLCD National Land Cover Data 

14287 NMAS National Map Accuracy Standards 

14288 NOAA National Oceanic and Atmospheric Administration 

14289 NPS National Park Service 

14290 NRC National Research Council 

14291 NSSDA National Standard for Spatial Data Accuracy 

14292 NTDE National Tidal Datum Epoch 

14293 NWR National Wildlife Refuge 

14294 NWS National Weather Service 

14295 PORTS Physical Oceanographic Real-Time System 

14296 RCA resource conservation area 

14297 RMSE root mean square error 

14298 RPA resource protection area 

14299 SAV submerged aquatic vegetation 

14300 SFHA Special Flood Hazard Area 

14301 SRTM Shuttle Radar Topography Mission 

14302 SWFL still water flood level 

14303 TNC The Nature Conservancy 

14304 USACE United States Army Corps of Engineers 

14305 U.S. EPA United States Environmental Protection Agency 

14306 U.S. FWS United States Fish and Wildlife Service 

14307 U.S. DOT United States Department of Transportation 

14308 USGS United States Geological Survey 

14309 VA PBB Virginia Public Beach Board 

14310 WRCRA Waterfront Revitalization and Coastal Resources Act 

Box 9.1 

Ecological 

Effects of 

Sea Level 

Rise–NOAA 

North

Box 9.2 1991 

FEMA 

Study: 

Projected 

Impact of 

Relative Sea

The study 

notes that 

these 

numbers 

differ slightly 

from a

Box 9.3 A 

Maryland 

Case Study–

Implications 

for Decisionmakers:

Adult and 

juvenile 

piping plover 

foraging on a 

sandy beach 

near the

Piping plover 

nest 

BOX 

A1.9: 

Reintrod

uced 

populati

on of red