Impacts of Climate Change and Variability 

on Transportation Systems and 

Infrastructure: Gulf Coast Study, Phase I 

U.S. Climate Change Science Program 

Synthesis and Assessment Product 4.7 

March 2008 
FEDERAL EXECUTIVE TEAM 

Acting Director, Climate Change Science Program: William J. Brennan 

Director, Climate Change Science Program Office: Peter A. Schultz 

Lead Agency Principal Representative to CCSP, 

Director, Office of Safety, Energy, and Environment, 

U.S. Department of Transportation: Linda L. Lawson 

Product Lead, Air Quality Team Leader, 

Federal Highway Administration, U.S. Department 

of Transportation: Michael J. Savonis 

Collaborating Agency Lead, Chief Scientist, 

Global Change Research, U.S. Geological Survey, 

U.S. Department of the Interior: Virginia R. Burkett 

Chair, Synthesis and Assessment Product Advisory Group 

Associate Director, National Center for Environmental 

Assessment, U.S. Environmental Protection Agency: Michael W. Slimak 

Synthesis and Assessment Product Coordinator, 

Climate Change Science Program Office: Fabien J.G. Laurier 

Special Advisor, National Oceanic and Atmospheric 

Administration: Chad A. McNutt 

EDITORIAL TEAM 

Editor, Cambridge Systematics: Joanne R. Potter 

Scientific Editor, U.S. Geological Survey: Virginia R. Burkett 

Editor, Federal Highway Administration: Michael J. Savonis 

Technical Advisor, Climate Change Science Program Office: David J. Dokken 

Disclaimer: This document, part of the Synthesis and Assessment Products described in the U.S. Climate Change Science Program 

(CCSP) Strategic Plan, was prepared in accordance with Section 515 of the Treasury and General Government Appropriations Act for 

Fiscal Year 2001 (Public Law 106-554) and the information quality act guidelines issued by the Department of Transportation pursuant to Section 515. The CCSP Interagency Committee relies on Department of Transportation certifications regarding compliance with 

Section 515 and Department guidelines as the basis for determining that this product conforms with Section 515. For purposes of compliance with Section 515, this CCSP Synthesis and Assessment Product is an “interpreted product” as that term is used in Department 

of Transportation guidelines and is classified as “highly influential”. This document does not express any regulatory policies of the 

United States or any of its agencies, or provide recommendations for regulatory action. 
Impacts of Climate Change and Variability on Transportation 

Systems and Infrastructure: Gulf Coast Study, Phase I 

Synthesis and Assessment Product 4.7 

Report by the U.S. Climate Change Science Program 

And the Subcommittee on Global Change Research 

Coordinating Lead Authors

Michael J. Savonis, Federal Highway Administration 

Virginia R. Burkett, U.S. Geological Survey 

Joanne R. Potter, Cambridge Systematics 

LIST OF AUTHORS 

Executive 

Summary 

Lead Authors: Joanne R. Potter, Cambridge Systematics (CS); Michael J. Savonis, 

Federal Highway Administration (FHWA); and Virginia R. Burkett, U.S. Geological 

Survey (USGS) 

Chapter 1 Lead Authors: Robert C. Hyman, CS; Joanne R. Potter, CS; Michael J. Savonis, 

FHWA; Virginia R. Burkett, USGS; and Jessica E. Tump, CS 

Chapter 2 Lead Authors: Virginia R. Burkett, USGS; Robert C. Hyman, CS; Ron Hagelman, 

Texas State University, San Marcos; Stephen B. Hartley, USGS; and Matthew 

Sheppard, Bureau of Transportation Statistics 

Contributing Authors: Thomas W. Doyle, USGS; Daniel M. Beagan, CS; Alan 

Meyers, CS; David T. Hunt, CS; Michael K. Maynard, Wilbur Smith Associates 

(WSA); Russell H. Henk, Texas Transportation Institute (TTI); Edward J. Seymour, 

TTI; Leslie E. Olson, TTI; Joanne R. Potter, CS; and Nanda N. Srinivasan, CS 

Chapter 3 Lead Authors: Barry D. Keim, Louisiana State University (LSU); Thomas W. Doyle, 

USGS; and Virginia R. Burkett, USGS 

Contributing Authors: Ivor Van Heerden, LSU; S. Ahmet Binselam, LSU; Michael 

F. Wehner, Lawrence Berkeley National Laboratory; Claudia Tebaldi, National Center 

for Atmospheric Research (NCAR); Tamara G. Houston, National Oceanic and 

Atmospheric Administration (NOAA); and Daniel M. Beagan, CS 

Chapter 4 Lead Authors: Robert S. Kafalenos, FHWA; Kenneth J. Leonard, CS 

Contributing Authors: Daniel M. Beagan, CS; Virginia R. Burkett, USGS; Barry D. 

Keim, LSU; Alan Meyers, CS; David T. Hunt, CS; Robert C. Hyman, CS; Michael K. 

Maynard, WSA; Barbara Fritsche, WSA; Russell H. Henk, TTI; Edward J. Seymour, 

TTI; Leslie E. Olson, TTI; Joanne R. Potter, CS; Michael J. Savonis, FHWA 

Chapter 5 Lead Authors: Kenneth J. Leonard, CS; John H. Suhrbier, CS; Eric Lindquist; Texas 

A&M University 

Contributing Authors: Michael J. Savonis, FHWA; Joanne R. Potter, CS; Wesley R. 

Dean, Texas A&M University 

Chapter 6 Lead Authors: Michael J. Savonis, FHWA; Virginia R. Burkett, USGS; Joanne R. 

Potter, CS 

Contributing Authors: Thomas W. Doyle, USGS; Ron Hagelman, Texas State 

University, San Marcos; Stephen B. Hartley, USGS; Robert C. Hyman, CS; Robert S. 

Kafalenos, FHWA; Barry D. Keim, LSU; Kenneth J. Leonard, CS; Matthew 

Sheppard, Bureau of Transportation Statistics; Claudia Tebaldi, NCAR; Jessica E. 

Tump, CS 

FEDERAL ADVISORY COMMITTEE 

Committee Member Title 

Vicki Arroyo Director of Policy Analysis, Pew Center on Global Climate 

Change 

Philip B. Bedient Professor of Engineering, Rice University 

Leigh B. Boske Associate Dean and Professor of Public Affairs, Lyndon B. 

Johnson School of Public Affairs, The University of Texas at 

Austin 

Alan Clark Director of Transportation Planning, Houston-Galveston Area 

Council 

Fred Dennin Regional Administrator, Region 3, Federal Railroad 

Administration 

Paul S. Fischbeck Professor of Social and Decision Sciences, Carnegie Mellon 

University 

Anthony Janetos Director, Joint Global Change Program Research Institute, 

University of Maryland 

Thomas R. Karl Director, National Climatic Data Center, National Oceanic and 

Atmospheric Administration 

Rob Lempert Senior Scientist, RAND 

Gilbert Mitchell Chief, Geodetic Services Division, National Geodetic Survey, 

National Oceanic and Atmospheric Administration 

Chris C. Oynes Gulf of Mexico Regional Director, Minerals Management Service 

Harold “Skip” Paul Director of Research, Louisiana Department of Transportation and 

Development 

Tom Podany Assistant Chief, Planning, Programs, and Project Management 

Division, U.S. Army Corps of Engineers, New Orleans District 

Burr Stewart Strategic Planning Manager, Port of Seattle 

Elaine Wilkinson Executive Director, Gulf Regional Planning Commission 

John Zamurs Air Quality Section Head, Environmental Analysis Bureau, New 

York State Department of Transportation 

Acknowledgments 

We wish to thank the following for their contributions to this report. 

This report has been peer reviewed by the individual members of the Federal Advisory Committee (FAC) to this 

study. FAC members were chosen for their diverse perspectives and technical expertise. The selection of 

reviewers and the expert review followed the OMB’s Information Quality Bulletin for Peer Review. We gratefully 

acknowledge the Committee members for their dedicated and generous contribution of their time, expertise, and 

thoughtful review. They are: Vicki Arroyo, Director of Policy Analysis, Pew Center on Global Climate Change; 

Philip B. Bedient, Professor of Engineering, Rice University; Leigh B. Boske, Associate Dean and Professor of 

Public Affairs, Lyndon B. Johnson School of Public Affairs, The University of Texas at Austin; Alan Clark, 

Director of Transportation Planning, Houston-Galveston Area Council (HGAC); Fred Dennin, Regional 

Administrator, Region 3, Federal Railroad Administration; Paul S. Fischbeck, Professor of Social and Decision 

Sciences, Carnegie Mellon University; Anthony Janetos, Director, Joint Global Change Program Research 

Institute, University of Maryland; Thomas R. Karl, Director, National Climatic Data Center, National Oceanic and 

Atmospheric Administration; Rob Lempert, Senior Scientist, RAND; Gilbert Mitchell, Chief, Geodetic Services 

Division, National Geodetic Survey, National Oceanic and Atmospheric Administration (NOAA); Chris C. Oynes, 

Gulf of Mexico Regional Director, Minerals Management Service (MMS); Harold “Skip” Paul, Director of 

Research, Louisiana Department of Transportation and Development; Tom Podany, Assistant Chief, Planning, 

Programs, and Project Management Division, U.S. Army Corps of Engineers, New Orleans District; Burr Stewart, 

Strategic Planning Manager, Port of Seattle; Elaine Wilkinson, Executive Director, Gulf Regional Planning 

Commission; and John Zamurs, Air Quality Section Head, Environmental Analysis Bureau, New York State 

Department of Transportation. We also want to thank Pasquale Roscigno, MMS; and David Levinson, National 

Climatic Data Center, NOAA; for their input and technical support. We thank Ashby Johnson, HGAC, and Diana 

Bauer, EPA, for their invaluable reviews and suggestions. The public review comments and peer review 

comments received on drafts of this report, along with responses to these comments, are publicly available at: 

http://www.climatescience.gov/Library/sap/sap4-7/default.php. 

We gratefully acknowledge past and present representatives from the U.S. Geological Survey and the U.S. DOT 

Center for Climate Change and Environmental Forecasting who helped fund, plan, scope and review technical 

information that led up to the final report. Special thanks go to Greg Smith, Director, and the staff of the USGS 

National Wetlands Research Center (NWRC) for hosting the research team, and for providing technical and staff 

support to the research effort. We are deeply indebted to Connie Herndon and Beth Vairin, NWRC technical 

editors, whose edits improved the readability and cohesiveness of the final manuscript. We thank the many people 

who helped over the course of this multiyear study, and wish to explicitly recognize Jane Bachner, Paul Marx, 

Kay Drucker, Karrigan Bork, Clare Sierawski, Brigid DeCoursey, Donald Trilling, Jan Brecht-Clark, April 

Marchese, and James Shrouds for their assistance. 

We wish to acknowledge Michael MacCracken whose drive and steady encouragement helped to propel us in the 

early years. 

A number of public and private agencies generously lent their time and insights to this report. We thank the 

Houston-Galveston Area Council and the City of Galveston for hosting the Advisory Committee meetings. We are 

very grateful to the many individuals from the private sector and local and state governments who were interviewed 

or who otherwise shared their perspectives on the significance of climate change to their work. Their insights and 

perspectives of how climate change considerations may affect their decisions are reflected in this report. 

Finally, we also wish to thank our University and agency co-authors whose lives were impacted by Hurricanes 

Katrina and Rita – for their persistence in delivering material for this study and for their timely responses to 

reviews, despite tremendous personal challenges and losses. 
Recommended Citations 

For the Report as a Whole: 

CCSP, 2008: Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast 

Study, Phase I. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change 

Research [Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.)]. Department of Transportation, Washington, DC, USA, 

445 pp. 

For the Chapters: 

For the Executive Summary 

Potter, J.R., V.R. Burkett, and M.J. Savonis, 2008: Executive Summary. In: Impacts of Climate Change and 

Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate 

Change Science Program and the Subcommittee on Global Change Research [Savonis, M. J., V.R. Burkett, and J.R. 

Potter (eds.)]. Department of Transportation, Washington, DC, USA. 

For Chapter 1 

Hyman, R.C., J.R. Potter, M.J. Savonis, V.R. Burkett, and J.E. Tump, 2008: 1.0 Why Study Climate Change Impacts 

on Transportation? In: Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: 

Gulf Coast Study, Phase I. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global 

Change Research [Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.)]. Department of Transportation, Washington, 

DC, USA. 

For Chapter 2 

Burkett, V.R., R.C. Hyman, R. Hagelman, S.B. Hartley, M. Sheppard, T.W. Doyle, D.M. Beagan, A. Meyers, D.T. 

Hunt, M.K. Maynard, R.H. Henk, E.J. Seymour, L.E. Olson, J.R. Potter, and N.N. Srinivasan, 2008: Why Study the 

Gulf Coast? In: Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast 

Study, Phase I. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change 

Research [Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.)]. Department of Transportation, Washington, DC, USA. 

For Chapter 3 

Keim, B.D., T.W. Doyle, V.R. Burkett, I. Van Heerden, S.A. Binselam, M.F. Wehner, C. Tebaldi, T.G. Houston, and 

D.M. Beagan, 2008: How is the Gulf Coast Climate Changing? In: Impacts of Climate Change and Variability on 

Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate Change Science 

Program and the Subcommittee on Global Change Research [Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.)]. 

Department of Transportation, Washington, DC, USA. 

For Chapter 4 

Kafalenos, R.S., K.J. Leonard, D.M. Beagan, V.R. Burkett, B.D. Keim, A. Meyers, D.T. Hunt, R.C. Hyman, M.K. 

Maynard, B. Fritsche, R.H. Henk, E.J. Seymour, L.E. Olson, J.R. Potter, and M.J. Savonis, 2008: What are the 

Implications of Climate Change and Variability for Gulf Coast Transportation? In: Impacts of Climate Change and 

Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate 

Change Science Program and the Subcommittee on Global Change Research [Savonis, M. J., V.R. Burkett, and J.R. 

Potter (eds.)]. Department of Transportation, Washington, DC, USA. 

For Chapter 5 

Leonard, K.J., J.H. Suhrbier, E. Lindquist, M.J. Savonis, J.R. Potter, W.R. Dean, 2008: How Can Transportation 

Professionals Incorporate Climate Change in Transportation Decisions? In: Impacts of Climate Change and 

Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate 

Change Science Program and the Subcommittee on Global Change Research [Savonis, M. J., V.R. Burkett, and J.R. 

Potter (eds.)]. Department of Transportation, Washington, DC, USA. 

For Chapter 6 

Savonis, M.J., V.R. Burkett, J.R. Potter, T.W. Doyle, R. Hagelman, S.B. Hartley, R.C. Hyman, R.S. Kafalenos, B.D. 

Keim, K.J. Leonard, M. Sheppard, C. Tebaldi, J.E. Tump, 2008: What are the Key Conclusions of this Study? In: 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I.

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [Savonis, 

M. J., V.R. Burkett, and J.R. Potter (eds.)]. Department of Transportation, Washington, DC, USA.
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Table of Contents 

Table of Contents 

Executive Summary.................................................................................................... ES-1 

1.0 Why Study Climate Change Impacts on Transportation? ............................. 1-1 

1.1 The Climate is Changing............................................................................... 1-2 

1.2 How Will Changes in Climate Affect Transportation?................................. 1-4 

1.2.1 What are the Challenges to Research?................................................ 1-5 

1.3 State of Science Regarding Climate Change Impacts on Transportation ..... 1-6 

1.3.1 Overview of State of Practice ............................................................. 1-7 

1.3.2 Major Sponsors Conducting Related Research .................................. 1-8 

1.3.3 State of Technical Analysis ................................................................ 1-10 

1.3.4 Impacts, Assessment, and Adaptation ................................................ 1-11 

1.3.5 Direct Climate Impacts on Transportation Addressed in 

Existing Literature .............................................................................. 1-12 

1.3.6 Indirect Climate Impacts on Transportation Addressed in 

Existing Literature .............................................................................. 1-15 

1.3.7 Decision Making Processes and Tools ............................................... 1-17 

1.4 Conclusions Drawn from Current Literature on the State of Research ........ 1-20 

1.5 Gulf Coast Study Selection, Objectives, and Organization .......................... 1-23 

1.5.1 Study Selection ................................................................................... 1-23 

1.5.2 Gulf Coast Study Objectives and Three Phases.................................. 1-24 

1.5.3 Study Organization and Oversight...................................................... 1-25 

1.5.4 Characterizing Uncertainty ................................................................. 1-26 

1.6 Sources .......................................................................................................... 1-26 

1.6.1 References........................................................................................... 1-26 

1.6.2 Background Sources ........................................................................... 1-34 

2.0 Why Study the Gulf Coast? ............................................................................... 2-1 

2.1 Overview of the Study Region...................................................................... 2-1 

2.1.1 Regional and National Significance ................................................... 2-1 

2.1.2 Study Area Boundaries ....................................................................... 2-2 

2.1.3 Structure of This Chapter.................................................................... 2-3 

2.2 The Transportation System in the Gulf Coast Region .................................. 2-3 

2.2.1 Overview of the Intermodal Transportation System in the Gulf 

Coast Region....................................................................................... 2-3 

2.2.2 Modal Characteristics ......................................................................... 2-6 

2.3 Gulf Coast Physical Setting and Natural Environment................................. 2-16 

2.3.1 Geomorphology .................................................................................. 2-16 

2.3.2 Current Elevation and Subsidence...................................................... 2-18 

2.3.3 Sediment Erosion, Accretion, and Transport...................................... 2-19 

2.3.4 Land Use and Land Cover .................................................................. 2-20 

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Table of Contents 

2.4 Social and Economic Setting ........................................................................ 2-21 

2.4.1 Population and Development Trends.................................................. 2-22 

2.4.2 Employment, Businesses, and Economic Drivers .............................. 2-23 

2.4.3 Societal Vulnerability ......................................................................... 2-25 

2.5 Conclusions................................................................................................... 2-27 

2.6 Sources .......................................................................................................... 2-28 

2.6.1 References........................................................................................... 2-28 

2.6.2. Background Sources ........................................................................... 2-30 

3.0 How is the Gulf Coast Climate Changing?....................................................... 3-1 

3.1 Temperature, Precipitation, and Runoff........................................................ 3-3 

3.1.1 Historical Data Sources ...................................................................... 3-3 

3.1.2 General Circulation Model Applications for the Study Area ............. 3-4 

3.1.3 Water-Balance Model......................................................................... 3-5 

3.1.4 Temperature and Runoff Trends......................................................... 3-6 

3.1.5 General Circulation Model Results and Future Climate Scenarios .... 3-7 

3.1.6 Changes in Daily Temperature ........................................................... 3-8 

3.1.7 Changes in Specific Temperature Maxima Affecting Transportation 3-10 

3.1.8 Increasing Daily Precipitation Extremes ............................................ 3-12 

3.2 Hurricanes and Less Intense Tropical Storms............................................... 3-12 

3.2.1 Assessing Trends in Historical Hurricane Frequency and Intensity... 3-13 

3.2.2 Gulf Coast Hurricane History............................................................. 3-15 

3.2.3 HURASIM: Model Application......................................................... 3-15 

3.2.4 Historical Storm Frequency across the Northern Gulf Coast 

Study Region....................................................................................... 3-15 

3.2.5 Temporal and Spatial Analysis of Hurricane Landfall ....................... 3-16 

3.2.6 Patterns of Hurricane Wind Direction ................................................ 3-17 

3.2.7 Modeling Climate Change Effects on Tropical Cyclones into the 

21st Century......................................................................................... 3-18 

3.3 Sea Level Rise and Subsidence..................................................................... 3-18 

3.3.1 Historical and Projected Global Sea Level Trends............................. 3-19 

3.3.2 Tide Records, Sea Level Trends, and Subsidence Rates along the 

Central Gulf Coast .............................................................................. 3-20 

3.3.3 Sea Level Rise Scenarios for the Central Gulf Coast Region............. 3-21 

3.4 Storm Surge................................................................................................... 3-23 

3.4.1 Predicting Storm Surge with the SLOSH Model................................ 3-23 

3.4.2 Future Sea Level Rise and Storm Surge Height ................................. 3-25 

3.5 Other Aspects of Climate Change with Implications for 

Gulf Coast Transportation............................................................................. 3-25 

3.5.1 Wind and Wave Regime ..................................................................... 3-26 

3.5.2 Humidity and Cloudiness.................................................................... 3-27 

3.5.3 Convective Activity ............................................................................ 3-27 

3.6 Conclusions................................................................................................... 3-28 

3.7 References ..................................................................................................... 3-31 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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4.0 What are the Implications of Climate Change and Variability for Gulf 

Coast Transportation? ....................................................................................... 4-1 

4.1 Climate Drivers and their Impacts on the Transportation System............... 4-2 

4.1.1 Effects of Warming Temperatures...................................................... 4-2 

4.1.2 Effects of Precipitation Levels and Patterns....................................... 4-3 

4.1.3 Relative Sea Level Rise ...................................................................... 4-4 

4.1.4 Storm Activity..................................................................................... 4-7 

4.1.5 Climate Impacts on Freight Transport................................................ 4-8 

4.2 Climate Impacts on Transportation Modes ................................................... 4-10 

4.2.1 Highways ............................................................................................ 4-10 

4.2.2 Transit ................................................................................................. 4-15 

4.2.3 Freight and Passenger Rail ................................................................. 4-18 

4.2.4 Marine Facilities and Waterways ....................................................... 4-25 

4.2.5 Aviation .............................................................................................. 4-30 

4.2.6 Pipelines.............................................................................................. 4-37 

4.2.7 Implications for Transportation Emergency Management ................. 4-43 

4.3 Impacts and Adaptation: Case Examples in the Study Region .................... 4-49 

4.3.1 Impacts of Hurricane Katrina on Transportation Infrastructure ......... 4-49 

4.3.2 Evacuation during Hurricane Rita ...................................................... 4-54 

4.3.3 Elevating Louisiana Highway 1.......................................................... 4-55 

4.4 Conclusions................................................................................................... 4-56 

4.5 Sources .......................................................................................................... 4-58 

4.5.1 References........................................................................................... 4-58 

4.5.2 Background Sources ........................................................................... 4-62 

5.0 How Can Transportation Professionals Incorporate Climate Change in 

Transportation Decisions? ................................................................................. 5-1 

5.1 Considering Climate Change in Long-Range Planning and Investment ...... 5-2 

5.1.1 Overview of the Surface Transportation Planning 

and Investment Processes ................................................................... 5-2 

5.1.2 Current State of Practice in Incorporating Climate 

Change Considerations ....................................................................... 5-7 

5.1.3 Challenges and Opportunities to Integrating Climate Information .... 5-13 

5.2 Conceptual Framework for Assessing Potential Impacts on Transportation 5-16 

5.2.1 Factors of Concern: Exposure, Vulnerability, Resilience, 

and Adaptation.................................................................................... 5-17 

5.2.2 Framework for Assessing Local Climate Change Impacts 

on Transportation................................................................................ 5-21 

5.3 Conclusions................................................................................................... 5-25 

5.4 Sources .......................................................................................................... 5-26 

5.4.1 References ............................................................................................ 5-26 

5.4.2 Background Sources............................................................................. 5-28 

6.0 What are the Key Conclusions of this Study?.................................................. 6-1 

6.1 Trends in Climate and Coastal Change......................................................... 6-2 

6.2 Transportation Impacts.................................................................................. 6-4 

6.3 Implications for Planning.............................................................................. 6-6 

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iv

6.4 Future Needs ................................................................................................. 6-7 

6.5 References ..................................................................................................... 6-9 

 Appendix A: Gulf Coast Study GIS Datasets.................................................. A-1 

 Appendix B: Additional Data on Social and Economic Setting..................... B-1 

 Appendix C: Additional Rail Data................................................................... C-1 

 Appendix D: Water Balance Model Procedures............................................. D-1 

 Appendix E: HURASIM Model Description................................................... E-1 

 Appendix F: Projecting Future Sea Level Rise with the SLRRP Model...... F-1 

 List of Selected Acronyms 

 Glossary of Terms 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Tables 

List of Tables 

1.1 Impacts of climate change on transportation identified in the literature, 

1987-2006............................................................................................................. 1T-1 

2.1 Study area counties and Federal Information Processing Standard 

(FIPS) codes ......................................................................................................... 2T-1 

2.2 Gulf Coast study area centerline miles of highway, by classification and 

ownership ............................................................................................................. 2T-2 

2.3 Equipment, annual service, and passengers for fixed-route bus operations in the 

study area, 2004.................................................................................................... 2T-3 

2.4 Freight railroads in the Gulf Coast study area...................................................... 2T-4 

2.5 Domestic and international waterborne tonnage of study area ports, 2003 .............. 2T-5 

2.6 Tonnage on study area inland and coastal waterways, 2003................................ 2T-6 

2.7 Passenger enplanements and cargo tonnage for select commercial service and 

industrial airports in the study area, 2005 ............................................................ 2T-7 

2.8 Land use of the central Gulf Coast study area as defined by the 1992 National 

Land Cover Dataset.............................................................................................. 2T-8 

2.9 Top 10 industries in the study area by employment percentage, 2000 ................ 2T-9 

3.1 Projected global average surface warming and sea level rise at the end of the 

21st century ........................................................................................................... 3T-1 

3.2 United States Historical Climatology Network (USHCN) stations within the 

seven climate divisions of the central Gulf Coast region..................................... 3T-2 

3.3 List of GCMs run with the three SRES emission scenarios (A1B, A2, and B1) 

for this study......................................................................................................... 3T-3 

3.4 Scenarios of temperature change (°C) from an ensemble of GCMs for the 5th, 

25th, 50th, 75th, and 95th percentiles for the A1B scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-4 

v
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Tables 

List of Tables 

(continued) 

3.5 Scenarios of precipitation change (percent) from an ensemble of GCMs for the 

5th, 25th, 50th, 75th, and 95th percentiles for the A1B scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-4 

3.6 Scenarios of temperature change (°C) from an ensemble of GCMs for the 5th, 

25th, 50th, 75th, and 95th percentiles for the A2 scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-5 

3.7 Scenarios of precipitation change (percent) from an ensemble of GCMs for the 

5th, 25th, 50th, 75th, and 95th percentiles for the A2 scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-5 

3.8 Scenarios of temperature change (°C) from an ensemble of GCMs for the 5th, 

25th, 50th, 75th, and 95th percentiles for the B1 scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-6 

3.9 Scenarios of precipitation change (percent) from an ensemble of GCMs for the 

5th, 25th, 50th, 75th, and 95th percentiles for the B1 scenario for 2050 relative to 

1971-2000 means ................................................................................................. 3T-6 

3.10 Days above 32.2 °C (90 °F) and mean daily temperature in the study area for 

datasets running through 2004 ............................................................................. 3T-7 

3.11 Modeled outputs of potential temperature increase (°C [°F]) scenarios for 

August .................................................................................................................. 3T-8 

3.12 Saffir-Simpson Scale for categorizing hurricane intensity and damage potential 3T-8 

3.13 GCM model-selection options based on data availability for the USGS SLRRP 

and CoastClim models for generating future sea level rise projections............... 3T-9 

3.14 USGS SLRRP model results showing the mean land surface elevations subject 

to coastal flooding for the Gulf Coast region by 2050 and 2100 ......................... 3T-10 

3.15 Regional grid cell counts and normalized indices of sea level rise relative to 

global mean sea level projections for northern Gulf Coast tide gage locations 

by different GCM models used in CoastClim simulations................................... 3T-10 

3.16 CoastClim model results showing the mean sea level rise (cm) for the Gulf 

Coast region by 2050 and 2100............................................................................ 3T-11 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Tables 

List of Tables 

(continued) 

3.17 Seven SLOSH basin codes, name descriptions, and storm categories included 

in the central Gulf Coast study region and simulation trials from Mobile, AL, to 

Galveston, TX ...................................................................................................... 3T-12 

3.18 SLRRP model parameters and results showing the mean sea level rise 

projections for the Gulf Coast region by 2050 and 2100 ..................................... 3T-12 

4.1 Relative sea level rise (RSLR) modeled by using SLRRP................................... 4T-1 

4.2 Relative sea level rise (RSLR) modeled by using CoastClim.............................. 4T-1 

4.3 Relative sea level rise impacts on Gulf Coast transportation modes: percentage 

of facilities vulnerable.......................................................................................... 4T-1 

4.4 Storm surge impacts on Gulf Coast transportation modes: percentage of 

facilities vulnerable .............................................................................................. 4T-2 

4.5 Relative sea level rise impacts on highways: percentage of 

facilities vulnerable .............................................................................................. 4T-2 

4.6 Storm surge impacts on highways: percentage of facilities vulnerable ............... 4T-2 

4.7 Relative sea level rise impacts on rail: percentage of facilities vulnerable.......... 4T-2 

4.8 Railroad-owned and -served freight facilities in the Gulf Coast study region at 

elevation of 122 cm (4 ft) or less.......................................................................... 4T-3 

4.9 Vulnerability from sea level rise and storm surge by rail distance and number 

of facilities............................................................................................................ 4T-4 

4.10 Storm surge impacts on rail: percentage of facilities vulnerable ......................... 4T-4 

4.11 Amtrak stations projected to be impacted by storm surge of 5.5 and 7.0 m (18 

and 23 ft) .............................................................................................................. 4T-5 

4.12 Relative sea level rise impacts on ports: percentage of facilities vulnerable ....... 4T-5 

4.13 Storm surge impacts on ports: percentage of facilities vulnerable....................... 4T-5 

4.14 FAA recommended runway lengths for hypothetical general aviation airport .... 4T-6 

vii
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Tables 

viii 

List of Tables 

(continued) 

4.15 Summary of impacts of temperature change to runway length (general aviation) 

under three climate scenarios ............................................................................... 4T-7 

4.16 Commercial aircraft runway length takeoff requirements ................................... 4T-8 

4.17 Airports located on 100-year flood plains............................................................ 4T-10 

4.18 Gulf Coast study area airports vulnerable to submersion by relative sea level 

rise of 61 to 122 cm (2 to 4 ft).............................................................................. 4T-10 

4.19 Gulf Coast study area airports vulnerable to storm surge .................................... 4T-11 

4.20 Hurricane impacts on toll revenue in Florida....................................................... 4T-12 

5.1 Urbanized area metropolitan planning organizations (MPO) in the Gulf Coast 

study area.............................................................................................................. 5T-1 

5.2 Level of decision maker concern about climate stressors .................................... 5T-2
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

List of Figures 

1.1 Gulf coast study design ........................................................................................ 1F-1 

1.2 Lexicon of terms used to describe the likelihood of climate outcomes ............... 1F-2 

2.1 Map of study area, which extends from Mobile, AL, to 

Houston/Galveston, TX........................................................................................ 2F-1 

2.2 Study area counties and Federal Information Processing Standard (FIPS) codes.. 2F-2 

2.3 Metropolitan planning organizations (MPO) in the study area............................ 2F-3 

2.4 Combined truck flows shipped domestically from Louisiana, 1998.................... 2F-4 

2.5 Navigable inland waterways impacting the study area, shown as named 

waterways............................................................................................................. 2F-5 

2.6 National network of Class I railroads................................................................... 2F-6 

2.7 Intermodal facilities in the study area .................................................................. 2F-7 

2.8 Highways in the study area .................................................................................. 2F-8 

2.9 Total and truck annual vehicle miles of travel (VMT) on nonlocal roads, 2003 . 2F-9 

2.10 Nonlocal bridges in the study area ....................................................................... 2F-10

2.11 Freight railroad traffic density (annual millions of gross ton-miles per mile) in 

the study area........................................................................................................ 2F-11 

2.12 Sunset Limited route map, Houston, TX, to Mobile, AL, segment ..................... 2F-12 

2.13 Freight handling ports and waterways in the study area ...................................... 2F-13 

2.14 Barge tow on the Mississippi River ..................................................................... 2F-14 

2.15 Study area airports................................................................................................ 2F-15 

2.16 Surface geology of the southeastern United States .............................................. 2F-16 

ix
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

List of Figures 

(continued) 

2.17 Relative elevation of counties in the study area ................................................... 2F-17 

2.18 Map of terrestrial ecoregions within and adjacent to the study area .................... 2F-18 

2.19 U.S. Census Bureau Metropolitan Statistical Areas within the study area .......... 2F-19 

2.20 Population density in study area, 2004................................................................. 2F-20 

2.21 Estimated population change in study area, 2000 to 2005 ................................... 2F-21 

2.22 Mean travel time to work in the study area.......................................................... 2F-22 

2.23 Manufacturers’ shipments in thousands of dollars, 1997..................................... 2F-23 

2.24 Social vulnerability index for the study area........................................................ 2F-24 

2.25 Persons in poverty in the study area..................................................................... 2F-25 

2.26 Persons aged 65 and older in the study area......................................................... 2F-26 

3.1 CO2 emissions, SO2 emissions, and atmospheric CO2 concentration through 

2100 for the six “marker/illustrative” SRES scenarios and the IS-92a scenario.... 3F-1 

3.2 United States climate divisions of the central Gulf Coast study area .................. 3F-1 

3.3 Grid area for the GCM temperature and precipitation results presented in 

Section 3.1.5 of this report ................................................................................... 3F-2 

3.4 Scatterplot of seasonal temperature and precipitation predictions by an 

ensemble of GCMs for the Gulf Coast region in 2050 created by using the 

SRES A1B emissions scenario............................................................................. 3F-3 

3.5 Temperature variability from 1905 to 2003 for the seven climate divisions 

making up the Gulf Coast study area ................................................................... 3F-4 

3.6 Precipitation variability from 1905 to 2003 for the seven climate divisions 

making up the Gulf Coast study area ................................................................... 3F-5 

3.7 Variability and trends in model-derived surplus (runoff) and deficit from 1919 

to 2003 for the Gulf Coast study area................................................................... 3F-6 

x 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

List of Figures 

(continued) 

3.8 Probability density functions for seasonal temperature change in the Gulf Coast 

study area for 2050 created by using the A1B emissions scenario ...................... 3F-7 

3.9 Probability density functions for seasonal precipitation change in the Gulf 

Coast study area for 2050 created by using the A1B emissions scenario ............ 3F-8 

3.10 Quantile estimates of monthly precipitation for the 2- to 100-year 

return period ......................................................................................................... 3F-9 

3.11 Quantile estimates of monthly average runoff for the 2- to 100-year 

return period ......................................................................................................... 3F-10 

3.12 Quantile estimates of monthly average deficit for the 2- to 100-year 

return period ......................................................................................................... 3F-11 

3.13 The change in the warmest 10 percent of July maximum and minimum 

temperatures at each station across the entire United States, for 1950-2004....... 3F-12 

3.14 Historical time series from stations within 500 km of Dallas, TX, showing 

anomalies of the number of days above 37.7°C (100°F), for 1950-2004 ............ 3F-13 

3.15 The current and future probabilities of having 1 to 20 days during the summer 

at or above 37.8°C (100°F) in or near Houston, TX ............................................ 3F-14 

3.16 Mean model predicted change (°C) of the 20-year return value of the annual 

maximum daily averaged surface air temperature ............................................... 3F-15 

3.17 Number of times on average, over a 20-year period, that the 1990-1999 annual 

maximum daily averaged surface air temperature 20-year return value 

levels would be reached ....................................................................................... 3F-16 

3.18 Mean model-predicted fractional change of the 20-year return value of the 

annual maximum daily averaged precipitation .................................................... 3F-17 

3.19 Geographic distribution of hurricane landfalls along the Atlantic and Gulf 

Coast regions of the United States, from 1950 to 2006........................................ 3F-18 

3.20 Frequency histogram of landfalling storms of tropical storm strength or greater 

in Grand Isle, LA, summarized on a 5-year basis, for the period 1851-2005 ...... 3F-19 

3.21 Hemispherical and global mean sea surface temperatures for the period of 

record 1855 to 2000.............................................................................................. 3F-20 

xi
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

List of Figures 

(continued) 

3.22 Sea surface temperature trend in the main hurricane development region of the 

North Atlantic during the past century................................................................. 3F-21

3.23 Sea surface temperature trend in the Gulf of Mexico region produced by using 

the ERSST v.2 database ....................................................................................... 3F-22 

3.24 The location and intensity of Hurricane Katrina at intervals of 6 hours show 

two intensification events..................................................................................... 3F-23 

3.25 Frequency histogram of tropical storm events for coastal cities across the Gulf 

of Mexico region of the United States over the period of record from 1851 to 

2006...................................................................................................................... 3F-24 

3.26 Frequency analysis of storm events exhibiting Category 1, 2, and 3 winds or 

higher across the Gulf Coast study area ............................................................... 3F-25 

3.27 Latitudinal gradient of declining storm frequency of Category 1 hurricanes or 

greater from Grand Isle, LA, inland..................................................................... 3F-26 

3.28 Storm frequency variation for 15-, 30-, and 50-year intervals for Category 1 

storms or greater for the most active grid location across the Gulf Coast study 

region.................................................................................................................... 3F-27 

3.29 Simulated wind rows and direction of wind force derived from the HURASIM 

model for one of the most active grid cell locations in the study area at Grand 

Isle, LA................................................................................................................. 3F-28 

3.30 Potential increase in the number of hurricanes by the year 2050 and 2100......... 3F-29 

3.31 Tide gauge records and mean sea level trend line for three northern Gulf Coast 

tide stations at Pensacola, FL, Grand Isle, LA, and Galveston, TX..................... 3F-30 

3.32 Merged results of Category 2 through 5 hurricane surge simulations of a slowmoving storm approaching from the southeast .................................................... 3F-31 

3.33 Color schemes illustrate the difference in surge inundation between a Category 

3 and Category 5 storm approaching the southeastern Louisiana coast from the 

southeast. .............................................................................................................. 3F-32 

3.34 Comparison of lidar and National Digital Elevation Data (DEM) for eastern 

Cameron Parish, LA............................................................................................. 3F-33 

3.35 Trend in summer wave height (1978-2005) in the mid-Gulf of Mexico.............. 3F-34 

xii 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

List of Figures 

(continued) 

4.1 Highways at risk from a relative sea level rise of 61 cm (2 ft) ............................ 4F-1 

4.2 Highways at risk from a relative sea level rise of 122 cm (4 ft) .......................... 4F-2 

4.3 National Highway System (NHS) Intermodal Connectors at risk from a relative 

sea level rise of 122 cm (4 ft)............................................................................... 4F-3 

4.4 Hurricane Katrina damage to U.S. Highway 90 at Bay St. Louis, MS ................ 4F-4 

4.5 Highways at risk from storm surge at elevations currently below 5.5 m (18 ft).. 4F-5 

4.6 Highways currently at risk from storm surge at elevations currently below 7.0 

m (23 ft)................................................................................................................ 4F-6 

4.7 National Highway System (NHS) intermodal connectors at risk from storm 

surge at elevations currently below 7.0 m (23 ft)................................................. 4F-7 

4.8 Fixed bus routes at risk from a relative sea level rise of 122 cm (4 ft), New 

Orleans, LA .......................................................................................................... 4F-8 

4.9 Fixed transit guideways at risk from a relative sea level rise of 122 cm (4 ft), 

Houston and Galveston, TX ................................................................................. 4F-9 

4.10 Fixed transit guideways at risk from storm surge at elevations currently below 

5.5 m (18 ft), New Orleans, LA ........................................................................... 4F-10 

4.11 Fixed transit guideways at risk from storm surge at elevations currently below 

5.5 m (18 ft), Houston and Galveston, TX........................................................... 4F-11 

4.12 Fixed bus routes at risk from storm surge at elevations currently below 5.5 m 

(18 ft), New Orleans, LA...................................................................................... 4F-12 

4.13 Fixed bus routes at risk from storm surge at elevations currently below 5.5 m 

(18 ft), Houston and Galveston, TX..................................................................... 4F-13 

4.14 Rail lines at risk due to relative sea level rise of 61 and 122 cm (2 and 4 ft) ...... 4F-14 

4.15 Railroad-owned and -served freight facilities at risk due to relative sea level 

rise of 61 and 122 cm (2 and 4 ft) ........................................................................ 4F-15 

4.16 Rail lines at risk due to storm surge of 5.5 and 7.0 m (18 and 23 ft) ................... 4F-16 

xiii
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Figures 

xiv 

List of Figures 

(continued) 

4.17 Railroad-owned and -served freight facilities at risk due to storm surge of 5.5 

and 7.0 m (18 and 23 ft) ....................................................................................... 4F-17 

4.18 Amtrak facilities at risk due to storm surge of 5.5 and 7.0 m (18 and 23 ft) ....... 4F-18 

4.19 Freight handling ports facilities at risk from relative sea level rise of 61 and 

122 cm (2 and 4 ft) ............................................................................................... 4F-19 

4.20 Freight handling ports facilities at risk from storm surge of 5.5 and 7.0 m (18 

and 23 ft) .............................................................................................................. 4F-20 

4.21 Boeing 757-200 takeoff runway requirements for design purposes..................... 4F-21 

4.22 Gulf Coast study area airports at risk from storm surge....................................... 4F-22 

4.23 Landside pipelines having at least one GIS link located in an area of elevation 

0 to 91 cm (3 ft) above sea level in the study area ............................................... 4F-23 

4.24 Evacuation route highways potentially vulnerable from storm surge of 5.5 m 

(18 ft).................................................................................................................... 4F-24 

4.25 Risks to Amtrak Facilities due to relative sea level rise and storm surge ............ 4F-25 

4.26 Population over age 65 impacted by Hurricane Katrina ...................................... 4F-26 

4.27 Airports affected by Hurricane Katrina winds. .................................................... 4F-27 

5.1 How will climate change affect transportation decisions?................................... 5F-1 

5.2 SAFETEA-LU planning factors........................................................................... 5F-2 

5.3 Steps in the transportation planning process ........................................................ 5F-3 

5.4 Relationship of transportation planning timeframe and infrastructure service 

life to increasing climate change impacts............................................................. 5F-4 

5.5 A risk-assessment approach to transportation decisions. ..................................... 5F-4 

5.6 Degree of risk and importance of system or facility performance inform the 

level of adaptation investment.............................................................................. 5F-5 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Abstract 

Abstract 

Climate affects the design, construction, safety, operations, and maintenance of transportation infrastructure and systems. The prospect of a changing climate raises critical questions 

regarding how alterations in temperature, precipitation, storm events, and other aspects of 

the climate could affect the nation’s roads, airports, rail, transit systems, pipelines, ports, 

and waterways. Phase I of this regional assessment of climate change and its potential 

impacts on transportation systems addresses these questions for the region of the U.S. central Gulf Coast between Galveston, Texas and Mobile, Alabama. This region contains 

multimodal transportation infrastructure that is critical to regional and national 

transportation services. 

Historical trends and future climate scenarios were used to establish a context for examining the potential effects of climate change on all major transportation modes within the 

region. Climate changes anticipated during the next 50 to 100 years for the central Gulf 

Coast include warming temperatures, changes in precipitation patterns, and increased storm 

intensity. The warming of the oceans and decline of polar ice sheets is expected to accelerate the rate of sea level rise globally. The effects of sea level rise in most central Gulf 

Coast counties will be exacerbated by the sinking of the land surface, which is accounted 

for in this assessment. 

The significance of these climate factors for transportation systems was assessed. Warming 

temperatures are likely to increase the costs of transportation construction, maintenance, 

and operations. More frequent extreme precipitation events may disrupt transportation 

networks with flooding and visibility problems. Relative sea level rise will make much of 

the existing infrastructure more prone to frequent or permanent inundation – 27 percent of 

the major roads, 9 percent of the rail lines, and 72 percent of the ports are built on land at or 

below 122 cm (4 feet) in elevation. Increased storm intensity may lead to increased service 

disruption and infrastructure damage: More than half of the area’s major highways 

(64 percent of Interstates; 57 percent of arterials), almost half of the rail miles, 29 airports, 

and virtually all of the ports are below 7 m (23 feet) in elevation and subject to flooding 

and possible damage due to hurricane storm surge. Consideration of these factors in 

today’s transportation decisions and planning processes should lead to a more robust, 

resilient, and cost-effective transportation network in the coming decades. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-1

Executive Summary 

Lead Authors: Joanne R. Potter, Michael J. Savonis, Virginia R. Burkett 

The changing climate raises critical questions for the transportation sector in the United 

States. As global temperatures increase, sea levels rise, and weather patterns change, the 

stewards of our Nation’s infrastructure are challenged to consider how these changes may 

affect the country’s roads, airports, rail, transit systems, and ports. The U.S. transportation 

network – built and maintained through substantial public and private investment – is vital 

to the Nation’s economy and the quality of our communities. Yet little research has been 

conducted to identify what risks this system faces from climate change, or what steps 

managers and policy makers can take today to ensure the safety and resilience of our vital 

transportation system. 

This study: The Impacts of Climate Change and Variability on Transportation Systems 

and Infrastructure: Gulf Coast Study, Phase I has investigated these questions through a 

case study of a segment of the U.S. central Gulf Coast. The research, sponsored by the 

U.S. Department of Transportation (DOT) in partnership with the U.S. Geological Survey 

(USGS), has been conducted under the auspices of the U.S. Climate Change Science 

Program (CCSP). The study is 1 of 21 “synthesis and assessment” products planned and 

sponsored by CCSP. The interdisciplinary research team included experts in climate and 

meteorology; hydrology and natural systems; transportation; and decision support. 

A case study approach was selected for this research as an approach that would generate 

useful information for local and regional decision makers, while helping to develop 

research methodologies for application in other locations. In defining the study area, the 

DOT sought to design a project that would increase the knowledge base regarding the risks 

and sensitivities of all modes of transportation infrastructure to climate variability and 

change, the significance of these risks, and the range of adaptation strategies that can be 

considered to ensure a robust and reliable transportation network. The availability of 

reliable data, interest of local agencies and stakeholders, and transferability of findings 

were also important criteria in selecting the study area. This study focuses on those climate 

factors which are relevant to the Gulf Coast; in other areas different aspects of climate 

change may be significant. The modeled climate projections and the specific implications 

of these scenarios for transportation facilities are specific to the Gulf Coast study area 

However, the methods presented in this report can be applied to any region. 

This report presents the findings of the first phase of a three phase research effort. The 

ultimate goal of this research is to provide knowledge and tools that will enable 

transportation planners and managers to better understand the risks, adaptation strategies, 

and tradeoffs involved in planning, investment, design, and operational decisions. The 

objective of Phase I was to conduct a preliminary assessment of the risks and 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-2 

vulnerabilities of transportation in the region, after collecting and integrating the range of 

data needed to characterize the region – its physiography and hydrology, land use and land 

cover, past and projected climate, current population and trends, and transportation 

infrastructure. Subsequent phases will conduct more detailed analyses. Phase II will 

conduct an in-depth assessment of risks to transportation in a selected location, reporting 

on implications for long-range plans and impacts on safety, operations, and maintenance. 

This phase will also develop a risk assessment methodology and identify techniques to 

incorporate environmental and climate data in transportation decisions. Phase III will 

identify and analyze adaptation and response strategies and develop tools to assess these 

strategies, while enumerating future research needs. 

 The Gulf Coast Study Area 

The Gulf Coast study area includes 48 contiguous coastal counties in four States, running 

from Houston/Galveston, TX, to Mobile, AL. This region is home to almost 10 million 

people living in a range of urban and rural settings and contains critical transportation 

infrastructure that provides vital service to its constituent States and the Nation as a whole. 

It is also highly vulnerable to sea level rise and storm impacts. A variety of physical 

datasets were compiled for review and use by the project research team. Most of the 

spatial data is organized in GIS formats or “layers” that can be integrated to assess the 

vulnerability and risks of the transportation infrastructure in the study area and inform the 

development of adaptation strategies. 

Physical and Natural Environment 

The coastal geography of the region is highly dynamic due to a unique combination of 

geomorphic, tectonic, marine, and atmospheric forcings that shape both the shoreline and 

interior land forms. Due largely to its sedimentary history, the region is low lying; the 

great majority of the study area lies below 30 m in elevation. Due to its low relief, much of 

the central Gulf Coast region is prone to flooding during heavy rainfall events, hurricanes, 

and lesser tropical storms. Land subsidence is a major factor in the region, as sediments 

naturally compact over time. Specific rates of subsidence vary across the region, 

influenced by both the geomorphology of specific locations as well as by human activities. 

Most of the coastline also is highly vulnerable to erosion and wetland loss, particularly in 

association with tropical storms and frontal passages. It is estimated that 56,000 ha (217 

mi2

) of land were lost in Louisiana alone during Hurricane Katrina. Further, many Gulf 

Coast barrier islands are retreating and diminishing in size. The Chandeleur Islands, which 

serve as a first line of defense for the New Orleans region, lost roughly 85 percent of their 

surface area during Hurricane Katrina. As barrier islands and mainland shorelines erode 

and submerge, onshore facilities in low-lying coastal areas become more susceptible to 

inundation and destruction. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-3

The Gulf Coast Transportation Network 

The central Gulf Coast study area’s transportation infrastructure is a robust network of 

multiple modes – critical both to the movement of passengers and goods within the region 

and to national and international transport as well: 

• The region has 17,000 mi (27,000 km) of major highways – about 2 percent of the 

Nation’s major highways – that carry 83.5 billion vehicle miles of travel annually. The 

area is served by 13 major transit agencies; over 136 providers offer a range of public 

transit services to Gulf Coast communities. 

• Roughly two-thirds of all U.S. oil imports are transported through this region, and 

pipelines traversing the region transport over 90 percent of domestic Outer Continental 

Shelf oil and gas. Approximately one-half of all the natural gas used in the United 

States passes through or by the Henry Hub gas distribution point in Louisiana. 

• The study area is home to the largest concentration of public and private freight 

handling ports in the United States, measured on a tonnage basis. These facilities 

handle a huge share – around 40 percent – of the Nation’s waterborne tonnage. Four of 

the top five tonnage ports in the United States are located in the region: South 

Louisiana, Houston, Beaumont, and New Orleans. The study area also has four major 

container ports. 

• Overall, more than half of the tonnage (54 percent) moving through study area ports is 

petroleum and petroleum products. Additionally, New Orleans provides the ocean 

gateway for much of the U.S. interior’s agricultural production. 

• The region sits at the center of transcontinental trucking and rail routes and contains 

one of only four major points in the United States where railcars are exchanged 

between the dominant eastern and western railroads. 

• The study area also hosts the Nation’s leading and third-leading inland waterway 

systems (the Mississippi River and the Gulf Intracoastal) based on tonnage. The inland 

waterways traversing this region provide 20 States with access to the Gulf of Mexico. 

• The region hosts 61 publicly owned, public-use airports, including 11 commercial 

service facilities. Over 3.4 million aircraft takeoffs and landings take place at these 

airports annually, led by the major facilities at George Bush Intercontinental (IAH), 

William P. Hobby, and Louis Armstrong New Orleans International. IAH also is the 

leading airport in the study area for cargo, ranking 17th in the Nation for cargo tonnage. 

Given the scale and strategic importance of the region’s transportation infrastructure, it is 

critical to consider the potential vulnerabilities to the network that may be presented by 

climate change. A better understanding of these risks will help inform transportation 

managers as they plan future investments. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-4 

 The Gulf Coast Climate Is Changing 

The research team’s assessment of historical and potential future changes in the Gulf Coast 

study region draws on publications, analyses of instrumental records, and models that 

simulate how climate may change in the future. The scenarios of future climate referenced 

in this report were generated by the National Center for Atmospheric Research (NCAR) by 

using an ensemble of 21 different atmosphere-ocean coupled general circulation models 

(GCM) for the Gulf Coast region. Model results, climatic trends during the past century, 

and climate theory all suggest that extrapolation of the 20th century temperature record 

would likely underestimate the range of change that could occur in the next few decades. 

While there is still considerable uncertainty about the rates of change that can be expected, 

there is a fairly strong consensus regarding the direction of change for most of the climate 

variables that affect transportation in the Gulf Coast region. Key findings for the study 

region include: 

• Rising relative sea levels – Relative sea level in the study area is likely to increase at 

least 0.3 meter (1 foot) across the region and possibly as much as 2 meters (6 to 7 feet) 

in some parts of the study area. Relative sea level rise (RSLR) is the combined effect 

of the projected increase in the volume of the world’s oceans (eustatic sea level 

change), which results from increases in temperature and melting of ice, and the 

projected changes in land surface elevation at a given location due to subsidence of the 

land surface. The highest rate of relative sea level rise will very likely be in the central 

and western parts of the study area (Louisiana and East Texas), where subsidence rates 

are highest. The analysis of a “middle range” of potential sea level rise of 0.6 to 

1.2 meters (2 to 4 feet) indicates that a vast portion of the Gulf Coast from Houston to 

Mobile may be inundated over the next 50 to 100 years. The projected rate of relative 

sea level rise for the region is consistent with historical trends, other published regionspecific analyses, and the IPCC 4th Assessment Report findings, which assumes no 

major changes in ice sheet dynamics. 

• Storm activity – Hurricanes are more likely to form and increase in their destructive 

potential as the sea surface temperature of the Atlantic and Gulf of Mexico increase. 

The literature indicates that the intensity of major storms could possibly increase by 10 

percent or more. This indicates that Category 3 storms and higher may return more 

frequently to the central Gulf Coast and thus cause more disruptions. Rising relative 

sea level will exacerbate exposure to storm surge and flooding. Depending on the 

trajectory and scale of individual storms, facilities at or below 9 meters (30 feet) could 

be subject to direct storm surge impacts. 

• Warming temperatures – All GCMs available from the Intergovernmental Panel on 

Climate Change (IPCC) for use in this study indicate an increase in average annual 

Gulf Coast temperature through the end of this century. Based on GCM runs under 

three different emission scenarios developed by the IPCC Special Report on Emissions 

Scenarios (SRES) (the low-emissions B1, the high-emissions A2, and the mid-range 

A1B scenarios), the average temperature in the Gulf Coast region appears likely to 

increase by at least 1.5°C ± 1°C (2.7°F ± 1.8°F) during the next 50 years. Extreme high 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-5

temperatures are also expected to increase – with the number of days above 32.2°C 

(90°F) very likely to increase significantly across the study area. Within 50 years the 

probability of experiencing 21 days a year with temperatures of 37.8°C (100°F) or 

above is greater than 50 percent. 

• Changes in precipitation patterns – Some analyses, including the GCM results from 

this study, indicate that average precipitation will increase in this region while others 

indicate a decline of average precipitation during the next 50 to 100 years. In either 

case, it is expected that average runoff could decline, due to increasing temperatures 

and resulting higher evapotranspiration rates. While average annual rainfall may 

increase or decrease slightly, the intensity of individual rainfall events is likely to 

increase during the 21st century. 

In the near term, the direction and scale of these modeled outcomes are consistent 

regardless of the assumptions used for level of greenhouse gas emissions: Model outputs 

are relatively similar across a range of IPCC SRES emission scenarios for the next four 

decades. However, long-range projections (modeled to 100 years) do vary across 

scenarios, with the magnitude of impacts indicated being more severe under higheremission assumptions. 

 Climate Change Has Implications for Gulf Coast Transportation 

The four key climate drivers in the region: rising temperatures, changing precipitation 

patterns, rising relative sea levels, and increasing storm intensity, present clear risks to 

transportation infrastructure in the study area. These factors can be incorporated into 

today’s transportation decisions to help prepare for and adapt to changing environmental 

conditions. 

• Warming temperatures may require changes in materials, maintenance, and 

operations. The combined effects of an increase in mean and extreme high 

temperatures across the study region are likely to affect the construction, maintenance, 

and operations of transportation infrastructure and vehicles. Higher temperatures may 

also suggest areas for materials and technology innovation to develop new, more heattolerant materials. Some types of infrastructure deteriorate more quickly at 

temperatures above 32.2°C (90°F). As the number of very hot days increases, different 

materials may be required. Further, restrictions on work crews may lengthen 

construction times. Rail lines may be affected by more frequent rail buckling due to an 

increase in daily high temperatures. Ports, maintenance facilities, and terminals are 

expected to require increased refrigeration and cooling. Finally, higher temperatures 

affect aircraft performance and the runway lengths that are required. However, 

advances in aircraft technology are expected to offset the potential effects of the 

temperature increases analyzed in this report, so that current runway lengths are likely 

to be sufficient. The effects of increases in average temperatures and in the number of 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-6 

very hot days will have to be addressed in designing and planning for vehicles, 

facilities, and operations. 

• Changes in precipitation patterns may increase short-term flooding. The analysis 

of future annual precipitation change based on results of climate model runs is 

inconclusive: some models indicate an increase in average precipitation and some 

indicate a decrease. In either case, the hotter climate may reduce soil moisture and 

average run-off, possibly necessitating changes in right-of-way land management. The 

potential of changes in heavy rainfall may have more significant consequences for 

transportation; more frequent extreme precipitation events may result in more frequent 

flooding, stressing the capacity of existing drainage systems. The potential of extreme 

rainfall events and more frequent and prolonged flooding may disrupt traffic 

management, increase highway incidents, and impact airline schedules – putting 

additional strain on a heavily used and increasingly congested system. Further, 

prolonged flooding – inundation in excess of one week – can damage pavement 

substructure. 

• Relative sea level rise may inundate existing infrastructure. To assess the impact of 

relative sea level rise (RSLR), the implications of rises equal to 61 cm and 122 cm (2 

and 4 ft) were examined. As discussed above, actual RSLR may be higher or 

somewhat lower than these levels. Under these scenarios, substantial portions of the 

transportation infrastructure in the region are at risk: 27 percent of the major roads, 

9 percent of the rail lines, and 72 percent of the ports are at or below 122 cm (4 ft) in 

elevation, although portions of the infrastructure are guarded by protective structures 

such as levees and dikes. While protective structures will continue to be an important 

strategy in the area, rising sea levels significantly increase the challenge to 

transportation managers in ensuring reliable transportation services. Inundation of even 

small segments of the intermodal system can render much larger portions impassable, 

disrupting connectivity and access to the wider transportation network. 

• Increased storm intensity may lead to greater service disruption and 

infrastructure damage. This study examined the potential for flooding and damage 

associated with storm surge levels of 5.5 m and 7.0 m (18 ft and 23 ft). These modeled 

outputs are comparable to potential surge levels during severe storms in the region: 

Simulated storm surge from model runs across the central Gulf Coast demonstrated a 

6.7- to 7.3-m (22- to 24-ft) potential surge for major hurricanes. These levels may be 

conservative; surge levels during Hurricane Katrina (rated a Category 3 at landfall) 

exceeded these heights in some locations. The specific location and strength of storm 

surges are of course determined by the scale and trajectory of individual tropical 

storms, which are difficult to predict. However, substantial portions of the region’s 

infrastructure are located at elevations below the thresholds examined, and recent 

storms have demonstrated that major hurricanes can produce flooding miles inland 

from the location of initial landfall. With storm surge at 7 m (23 ft), more than half of 

the area’s major highways (64 percent of Interstates; 57 percent of arterials), almost 

half of the rail miles, 29 airports, and virtually all of the ports are subject to flooding. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

ES-7

Other damage due to severe storms is likely, as evidenced by the damage caused by 

Hurricanes Katrina and Rita in 2005. Damage from the force of storm surge, high 

winds, debris, and other effects of hurricanes can be catastrophic, depending on where a 

specific hurricane strikes. This study did not examine in detail these effects; the 

cumulative direct and indirect impacts of major storms need to be further analyzed. 

However, given the expectation of increasing intensity of hurricanes in the region, 

consideration should be given to designing new or replacement infrastructure to 

withstand more energy-intensive, high-category storms. 

 Climate Change Considerations Need to Be Incorporated in 

Transportation Decisions 

This preliminary assessment raises clear cause for concern regarding the vulnerability of 

transportation infrastructure and services in the central Gulf Coast due to climate and 

coastal changes. The effects of potential climate changes, particularly when combined with 

other factors such as subsidence, are likely to be significant. These changes threaten to 

cause both major and minor disruptions to the smooth provision of transport service 

through the study area. As transportation agencies work to meet the challenges of 

congestion, safety, and environmental stewardship – as well as maintaining transportation 

infrastructure in good repair – addressing the risks posed by a changing climate can help 

ensure that the substantial investments in the region’s infrastructure are protected in the 

coming decades by appropriate adaptation strategies. 

While several of the impacts of climate change identified above are significant, 

transportation planners and managers can incorporate effective adaptation strategies into 

transportation decisions today. Some level of adaptation will be required in the near term 

to address the effects of climate change processes that are underway. Concentrations of 

greenhouse gases already in the atmosphere will further force climate changes for the next 

three to four decades. The scale of adaptation required over the longer term – through this 

century – will be shaped in part by future emissions levels, as projections of loweremission scenarios demonstrate lesser impacts. 

Transportation Planning Processes 

Transportation decisions are made by a number of different entities, both public and 

private, and transportation infrastructure is financed through a range of government and 

private investments. Within the study area, four State departments of transportation 

(DOTs) – for Texas, Louisiana, Mississippi, and Alabama – and 10 Metropolitan Planning 

Organizations (MPOs) lead surface transportation planning, in close coordination with 

local governments. To use Federal funding, these agencies must adhere to Federal 

requirements for surface transportation planning and investment. These laws are contained 

in Titles 23 and 49 of the United States Code (USC) and were most recently amended in 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Executive Summary 

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August 2005 by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A 

Legacy for Users (SAFETEA-LU), the latest six-year authorization of Federal funding for 

surface transportation. 

In surface transportation management, separate but coordinated long-range transportation 

plans are cooperatively developed on a statewide basis by each State DOT and for each 

urbanized area by an MPO. The long-range transportation plan is developed with a 

minimum of a 20-year forecast period, with many areas using a 30-year timeframe. These 

plans provide a long-range vision of the future of the transportation system, considering all 

passenger and freight modes and the intermodal system as a whole. The planning and 

investment process is highly collaborative; transportation agencies need to work in 

partnership with natural resource agencies, communities, businesses, and others as they 

chart a course for the transportation network that will meet multiple goals, supporting 

mobility, economic development, community, safety, security, and environmental 

objectives. 

While climate and environmental projections inherently have a degree of uncertainty, this 

is not unusual to transportation. Transportation decision makers are well accustomed to 

planning and designing systems under conditions of uncertainty on a range of factors – 

such as future travel demand, vehicle emissions, revenue forecasts, and seismic risks. In 

each case, decision makers exercise best judgment using the best information available at 

the time. In an ongoing iterative process, plans may be revised or refined as additional 

information becomes available. Incorporating climate information and projections is an 

extension of this well developed process. 

Similarly, environmental considerations have long played a role in the planning and 

development of transportation projects. As awareness of the complex interactions among 

environmental factors and transportation systems has grown, the transportation community 

has assumed increasing responsibilities for environmental stewardship. Integration of 

climate factors into transportation decisions continues this trend. However, interviews with 

a number of transportation managers in the region confirmed that most agencies do not 

consider climate change projections per se in their long-range plans, infrastructure design, 

or siting decisions. This appears to be changing, spurred in part by the devastating effects 

of Hurricanes Katrina and Rita. The damage caused by these storms highlighted the need 

to incorporate more information and model data related to climate change and other longterm shifts in environmental conditions as transportation plans are developed and 

implemented. 

New Approaches to Incorporate Climate Information 

The incorporation of climate factors into transportation decisions may require new 

approaches. 

• Planning timeframes – The timeframes generally used for the Federal transportation 

planning process – 20 to 30 years – are short compared to the multidecadal period over 

which climate changes and other environmental processes occur. The longevity of 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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ES-9

transportation infrastructure – which can last beyond a century – argues for a long 

timeframe to examine potential impacts from climate change and other elements of the 

natural environment. While the current timeframe is realistic for investment planning, 

agencies need to consider incorporating longer-term climate change effects into their 

visioning and scenario planning processes that inform their long-range plans. 

• Risk assessment approach – Given the complexities of climate modeling and the 

inherent uncertainties regarding the magnitude and timing of impacts of climate factors, 

the deterministic methods currently used to support decisions cannot fully address the 

range of potential environmental conditions that transportation managers need to 

consider. Adopting an iterative risk management approach would provide 

transportation decision makers, public officials, and the public a more robust picture of 

the risks to – and level of resilience of – various components of the transportation 

network. 

A conceptual framework and taxonomy for consideration of climate factors was 

developed. This approach incorporates four key factors that are critical to 

understanding how climate change may impact transportation: 

− Exposure: What is the magnitude of stress associated with a climate factor (sea 

level rise, temperature change, severe storms, precipitation) and the probability that 

this stress will affect a transportation segment or facility? 

− Vulnerability: Based on the structural strength and integrity of the infrastructure, 

what is the potential for damage and disruption in transportation services from this 

exposure? 

− Resilience: What is the current capacity of a system to absorb disturbances and 

retain transportation performance? 

− Adaptation: What response(s) can be taken to increase resilience at both the facility 

(e.g., a specific bridge) and system levels? 

Adaptation Strategies 

Ultimately, the purpose of a risk assessment approach is to enhance the resilience of the 

transportation network. Analysis of these factors can help transportation decision makers 

identify those facilities most at risk and adopt adaptation strategies to improve the 

resilience of facilities or systems. Structures can be hardened, raised, or even relocated as 

need be, and – where critical to safety and mobility – expanded redundant systems may be 

considered as well. 

What adaptation strategies are employed, and for which components of the system, will be 

determined considering the significance of specific parts of the network to the mobility and 

safety of those served, the effects on overall system performance, the cost of 

implementation, and public perceptions and priorities. Generally speaking, as the 

importance of maintaining uninterrupted performance increases, the appropriate level of 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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investment in adaptation for high-risk facilities should increase as well. This study does 

not make recommendations about specific facilities or adaptation strategies, but rather 

seeks to contribute to the information available so that States and local communities can 

make more informed decisions. 

 Future Research Would Benefit Decision Makers 

The analysis of how a changing climate might affect transportation is in its infancy. While 

there is sufficient information today to begin to assess risks and implement adaptation 

strategies, further development of data and analysis would help planners, engineers, 

operators, and maintenance personnel as they create an even more robust and resilient 

transportation system, ultimately at lower cost. Key research opportunities include: 

• Integrated climate data and projections – It would be useful to the transportation 

community if climatologists could continue to develop more specific data on future 

impacts. Higher resolution of climate models for regional and subregional studies 

would support the integration of region-specific data with transportation infrastructure 

information. More information about the likelihood and extent of extreme events, 

including temperature extremes, storms with associated surges and winds, and 

precipitation events, could be utilized by transportation planners. 

• Risk analysis tools – In addition to more specific climate data, transportation planners 

also need new methodological tools to address the uncertainties that are inherent in 

projections of climate phenomena. Such methods are likely to be based on probability 

and statistics as much as on engineering and materials science. The approaches taken 

to address risk in earthquake-prone areas may provide a model for developing such 

tools. 

• Region-based analysis – The impacts that a changing climate might have on an area 

depends on where the region is and its natural environment. Replication of this study in 

other areas of the country could help determine the possible impacts of climate change 

on transportation infrastructure and services in those locations. Transportation in 

northern climates will face much different challenges than those in the south. Coastal 

areas will similarly face different challenges than interior portions of the country. 

Further, additional analysis on demographic responses to climate change, land use 

interactions, and secondary and national economic impacts would help elucidate what 

impacts climate will have on the people and the Nation as a whole, should critical 

transportation services in the region be lost. 

• Interdisciplinary research – This study has demonstrated the value of crossdisciplinary research that engages both the transportation and climate research 

communities. Continued collaboration will benefit both disciplines in building 

methodologies and conducting analyses to inform the Nation’s efforts to address the 

implications of climate change. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

1.0 Why Study Climate Change 

Impacts on Transportation? 

Lead Authors: Robert C. Hyman, Joanne R. Potter, Michael J. Savonis, Virginia R. 

Burkett, and Jessica E. Tump 

Transportation is such an integral part of daily life in the United States that few pause to 

consider its importance. Yet the Nation’s strong intermodal network of highways, public 

transit, rail, marine, and aviation is central to our ability to work, go to school, enjoy leisure 

time, maintain our homes, and stay in touch with friends and family. U.S. businesses 

depend on reliable transportation services to receive materials and transport products to 

their customers; a robust transportation network is essential to the economy. In short, a 

sound transportation system is vital to the Nation’s social and economic future. 

Transportation professionals – including planners, designers, engineers, financial 

specialists, ecologists, safety experts, and others – work hard to ensure that U.S. 

communities have access to safe and dependable transportation services. 

Given the ongoing importance of the Nation’s transportation system, it is appropriate to 

consider what effect climate change may have on this essential network. Through a 

regional case study of the central Gulf Coast, this report begins to examine the potential 

implications of climate change on transportation infrastructure, operations, and services. 

Investments in transportation are substantial and result in infrastructure that lasts for 

decades. Transportation plans and designs should, therefore, be carefully considered and 

well informed by a range of factors, including consideration of climate variability and 

change. Climate also affects the safety, operations, and maintenance of transportation 

infrastructure and systems. This research investigates the potential impacts of climate 

variability and change on transportation, and it assesses how planners and managers may 

incorporate this information into their decisions to ensure a reliable and robust future 

transportation network. This report does not contain recommendations about specific 

facilities or adaptation strategies, but rather seeks to contribute to the information available 

so that States and local communities can make more informed decisions when planning for 

the future. 

Four key questions guide this investigation: 

1. How important are the anticipated changes in climate? 

2. Can we anticipate them with confidence? 

3. What information is useful to transportation decisions? 

4. How can decision makers address uncertainty? 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

The answers to these questions require first developing an understanding of how the 

climate is changing and the range of potential climate effects and then considering the 

relevance of these changes to transportation. 

To set the context for this regional case study, this chapter first provides in section 1.1 an 

overview of how climate change is occurring globally, based on current scientific research. 

Section 1.2 introduces the questions these changes raise for the transportation sector and 

the research required to support effective responses to climate change. Section 1.3 

provides a synthesis of the state of existing research regarding the impacts of climate 

change on transportation, discussing the focus of current investigations – both in terms of 

specific climate factors and individual transportation modes, major findings, and what 

entities are sponsoring and conducting this research. Section 1.4 draws conclusions from 

this literature review to identify what is known – and what research questions remain – on 

this multifaceted topic. Section 1.5 then discusses how the U.S. Department of 

Transportation (DOT) selected the Gulf Coast region for its first case study of the potential 

impacts of climate change on transportation and describes the objectives and organization 

of the research effort. 

 1.1 The Climate is Changing 

The natural “greenhouse” effect is an essential component of the planet’s climate process. 

Naturally occurring greenhouse gases – carbon dioxide, methane, and nitrous oxide – 

effectively prevent part of the heat radiated by the Earth’s surface from otherwise escaping 

to space. In the absence of these greenhouse gases, the Earth’s temperature would be too 

cold to support life as we know it today. 

However, atmospheric concentrations of greenhouse gases have increased markedly since 

the industrial age began. The concentration of carbon dioxide (CO2) in the atmosphere has 

been increasing due to the combustion of fossil fuels and, to a lesser extent, land use 

changes. Direct atmospheric measurements made over the past 50 years have documented 

the steady growth in carbon dioxide concentrations. In addition, analysis of ice bubbles 

trapped in ice cores show that atmospheric carbon dioxide has increased by roughly onethird since 1750. Atmospheric concentration of CO2 was 379 parts per million (ppm) in 

2005, compared to a preindustrial level of 280 ppm (IPCC, 2007). Other heat-trapping 

gases – methane and nitrous oxide – also are increasing as a result of human activities. 

Finally, once in the atmosphere these greenhouse gases have a relatively long life time, on 

the order of decades to centuries, which means that the atmospheric warming taking place 

today will continue. 

Temperature has increased and is projected to continue to do so. Temperatures have 

been rising over the last century, with more rapid increases since 1970 than earlier. 

According to the International Panel on Climate Change (IPCC) Working Group I Fourth 

Assessment Report (AR4), average global temperatures increased 0.74°C (1.33°F) during 

the past 100 years, with most of that increase – 0.65°C (1.17°F) experienced in the last 50 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

years. Recent years have set record highs; 11 of the past 12 years were the warmest years 

on record since 1850. While some of this change may be due to natural variability, human 

activities have contributed to the Earth’s warming. The IPCC report finds with very high 

confidence that the globally averaged net effect of human activities since 1750 has been 

one of warming. The last major challenge to whether the planet was warming or not was 

resolved in April 2006 with publication of “Temperature Trends in the Lower Atmosphere” 

(U.S. Climate Change Science Program, Synthesis, and Assessment Product 1.1, 2006). 

This study reconciled the remaining analytical issues regarding differences between surface 

and satellite temperature readings. 

The climate models used to estimate temperature changes agree that it will be warmer in 

the future. According to the IPCC report, global average warming is expected to be about 

0.4°C (0.72°F) during the next 20 years. Even if the concentrations of all greenhouse gases 

and aerosols had been stabilized at 2000 levels, warming of 0.2°C (0.36°F) would be 

expected during this period (IPCC, 2007). Over the longer term, the IPCC models project 

average global temperature increases ranging from 1.1°C (1.98°F) to 6.4°C (11.5°F) by the 

end of the 21st century, although climate responses in specific regions will vary. These 

projections are the result of reviewing a robust set of global climate models under a variety 

of future scenarios – using a range of assumptions for future economic activity and energy 

use – for the Earth as a whole. 

The average increase in temperature may not be as important to the transportation 

community as the changes in extreme temperature, which also are expected to increase. 

Over the last 50 years, the frequency of cold days and nights has declined, while hot days, 

hot nights, and heat waves have become more frequent. The number of days with 

temperature above 32°C (90°F) and 38°C (100°F) has been increasing since 1970, as has 

the intensity and length of periods of drought. The IPCC report finds that it is virtually 

certain that the next century will witness warmer and more frequent hot days and nights 

over most land areas (IPCC, 2007). 

Precipitation patterns are changing, and more frequent intense precipitation events 

are expected. Over the past century precipitation amounts have increased in several 

regions – including the eastern parts of North and South America – while drying has been 

observed in other regions in Africa and Asia. During the 21st century, the IPCC (2007) 

anticipates that increases in the amount of precipitation are very likely in high latitudes, 

while decreases are likely in most subtropical land regions, continuing observed patterns in 

recent trends. While total average levels of precipitation will vary by region, the incidence 

of extreme precipitation events is expected to increase. 

According to NOAA analyses, the magnitude of the highest precipitation events has been 

increasing since 1970. A Simple Daily Intensity Index that examines the total precipitation 

for the United States divided by the number of days with precipitation clearly demonstrates 

an increase in average intensity from 1970 to 2005. These observed increases in extreme 

precipitation are not only in keeping with observational analyses but also with model 

projections for the future. The IPCC AR4 (2007) concludes that heavy precipitation events 

will continue to become more frequent during the coming decades. 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

Sea level is rising, and the rate of change is likely to accelerate. As the Earth warms, 

two changes are occurring that are causing sea levels to increase: glacial melting and 

thermal expansion of the oceans. Sea level rise is perhaps the best documented and most 

accepted impact of climate change. The IPCC reports that – on a global level – the total 

20th century rise is estimated to be 0.17 m (0.56 ft) and that global sea level rose at an 

average rate of 1.8 mm (0.07 inches) per year between 1961 and 2003. Excluding rapid 

changes in ice flow, the IPCC model-based projections for global sea level rise over the 

next century across multiple scenarios range from 0.18 to 0.59 m (0.59 to 1.94 ft). Should 

the melting of the land-based polar ice caps accelerate, sea level could rise much higher. 

The intensity of severe storms is expected to increase. It is likely that future tropical 

cyclones (typhoons and hurricanes) will become more intense, with larger peak wind 

speeds and heavier precipitation (IPCC, 2007). (There is insufficient evidence to identify 

changing trends for other storm phenomenon, such as tornadoes, hail, and lightning [IPCC, 

2007]; these types of storm activity are not addressed by this report.) There are several 

aspects of tropical storms that are relevant to transportation: precipitation, winds, and 

wind-induced storm surge. All three tend to get much worse during strong storms. Strong 

storms tend to have longer periods of intense precipitation, and wind damage increases 

exponentially with wind speed. The primary concern with hurricanes is for strong storms 

of Categories 3, 4, and 5. These storms have considerably more destructive energy. For 

example, a Category 5 storm may have winds only twice as fast as a Category 1 storm, but 

its kinetic energy is over four times that of a Category 1 storm. 

Chapter 3.0 of this report provides a detailed discussion of how the climate is changing in 

the central Gulf Coast study area. 

 1.2 How Will Changes in Climate Affect Transportation? 

That the climate is changing leads to a number of intriguing and critically important 

questions for transportation. For the transportation community – the planners, engineers, 

builders, operators, and stewards of our Nation’s roads, airports, rail, transit systems, and 

ports – the primary question is how such changes will affect infrastructure and associated 

services and the trillions of dollars of investment these facilities represent. Transportation 

services are vital to our economy and quality of life. Individuals use transportation not 

only to get to and from work but for a wide variety of personal travel. Further, as 

producers seek to reduce warehousing costs through “just-in-time” delivery, transportation 

systems increasingly are functioning in effect as mobile warehouses. This places new 

stresses on service providers to make sure that economic goods are delivered on time. As 

the number of vehicles – and miles traveled – continues to grow, congestion on our 

roadways is an increasing concern. 

Nationally, we invest about $110 billion annually in highways and transit alone. Federal 

investment in passenger rail approaches $2 billion a year. Add to this the considerable 

investment made by the private sector in freight rail, airports, and ports, and it is clear that 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

the value that we place on these systems is enormous. Any disruption to the goods and 

services provided through the U.S. transportation network can have immediate impacts 

ranging from the annoying, such as flight delays due to severe weather, to the catastrophic, 

such as the chaos wrought by Hurricanes Katrina and Rita. 

The question of how a changing climate might affect transportation infrastructure and 

services led the U.S. DOT, under the auspices of its Center for Climate Change and 

Environmental Forecasting (hereafter “the Center”), to hold a first-ever workshop on 

October 1-2, 2002. Cosponsored by the Environmental Protection Agency, the Department 

of Energy, and the U.S. Climate Change Science Program, the workshop brought together 

noted climate scientists, top transportation executives and practitioners, and experts in 

assessment research, environment, planning, and energy. This interdisciplinary group was 

charged to explore the potential impacts of climate change for transportation and to 

delineate the research necessary to better understand these implications. In preparation, the 

Center commissioned a series of white papers on overviews of climate change, regional 

case studies, potential system impacts, and environment and planning. The workshop 

participants identified significant gaps in the knowledge and processes necessary to fully 

incorporate climate science information into transportation decisions and developed a 

framework to pursue future research in this multifaceted area of investigation. The twoday session deepened practitioners’ understanding of the significance of climate change for 

transportation and led to a firm commitment by the U.S. DOT to pursue needed research. 

The current Gulf Coast Study was designed to begin to address the research needs 

identified at this important forum. 

1.2.1 What are the Challenges to Research? 

Several research challenges must be met to successfully incorporate climate information 

into transportation decisions. Framing this new area of research is a complex undertaking 

that requires a new style of interdisciplinary work among scientists, planners, engineers, 

and policy makers. 

• Articulating data and information needs – First, transportation practitioners need to 

be able to articulate the types of climate data and model projections that will be 

relevant to transportation decisions: What information could lead a public or private 

transportation agency to change a transportation investment plan, road location, or 

facility design? Determining what climate information is useful includes identifying 

the appropriate regional scale and timeframe for climate scenarios, as well as the types 

of climate factors that could result in a revised decision. Generating this practical 

information may require scientists to analyze and portray existing data in different ways 

in order to be useful to transportation decisions. 

• Identifying most relevant climate information – At the same time, climate scientists 

need to be able to explain to transportation and planning professionals what information 

is available today that may be relevant to transportation decisions. The pace of climate 

science is advancing rapidly, and new and increasingly reliable climate findings are 

being released regularly. The sheer volume of significant climate information poses a 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

major challenge to the scientific community: How can scientists effectively translate 

the findings of basic research into information that can be understood by other 

professions – and the general public – and be applied to the choices transportation 

managers need to make? 

• Integrating multiple environmental factors – Further, climate factors need to be 

considered, not in isolation, but as part of a broader set of social and ecological factors 

that provide the context for thoughtful and informed transportation decisions. This will 

require that natural scientists and geospatial specialists work with transportation 

planners to integrate climate information into maps and data addressing other 

environmental factors. Incorporating new types of information – including longerrange climate scenario projections – may require the transportation community to adopt 

new approaches to planning and visioning exercises that engage a broader range of 

stakeholders and subject matter experts. 

• Incorporating uncertainty – An additional challenge is learning how to incorporate 

uncertainty in transportation decisions – how to assess risk and vulnerability of the 

transportation system and individual facilities given a range of potential future climate 

conditions. While transportation practitioners historically have planned and designed 

to meet established standards – for weight loads, flood levels, temperature extremes, 

etc. – today’s transportation planner needs to consider the most effective strategies to 

ensure a robust transportation system across a broader range of possible futures, 

potentially encompassing longer timeframes and a wider variety of impacts. This 

challenge may require new approaches to design and investment that use probabilistic, 

rather than deterministic, analysis. 

To begin to explore these complex research questions, the team conducted a review of 

existing literature regarding climate change impacts on transportation to determine the state 

of science. 

 1.3 State of Science Regarding Climate Change Impacts 

on Transportation 

What is the state of knowledge about climate change impacts on transportation? The 

research team undertook a review of the literature to assess the depth and breadth of 

existing research that specifically examines changes in climate and the resulting 

implications for transportation infrastructure and services. 

Although there is a large body of research concerning climate change and how 

transportation contributes to greenhouse gas emissions, less work has been done 

concerning the impacts of climate change on transportation. A review of existing literature 

indicates that the impacts of climate change on transportation is an emerging area of 

research and one that is growing steadily more sophisticated. As a new field, the level of 

analysis given to the variety of subtopics within this broad area of research has been 

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uneven; some aspects of climate change impacts on transportation have received much 

greater scrutiny than others depending on the particular concerns of individual authors and 

research sponsors. 

1.3.1 Overview of State of Practice 

Although there are relevant studies going back at least two decades, the pace of 

investigation has accelerated in more recent years. Several studies were conducted in this 

field in the late 1980s and early 1990s as international agreements on climate change were 

first under serious discussion (Marine Board, 1987; Hyman, 1989; Black, 1990; Irwin and 

Johnson, 1990). However, citations from this period are relatively infrequent, and as 

recently as 1998, the U.S. Federal Highway Administration (1998) found relatively little 

literature on this topic. Since then, the citations show growing recognition of climate 

impacts on transportation as an issue; research on this topic was highlighted in the United 

States’ Third National Communication (U.S. Department of State, 2002). In fact, the 

majority of references cited are from the new millennium (table 1.1). 

In addition to the growing number of research efforts, the analytic rigor of studies – 

particularly in the use of climate information – has progressed as well. While early 

discussions tend to be exploratory in nature, recent work has incorporated more 

sophisticated climate information and model outputs, addressed issues of uncertainty, and 

begun to examine the implications of climate factors on specific regions and infrastructure. 

This trend is likely to continue as awareness of the issues grows within the transportation 

community and decision makers seek improved information and tools to assess risks and 

adaptation strategies. 

The literature encompasses a wide variety of studies conducted for different time periods, 

sponsored by a range of organizations, and undertaken for different purposes. General 

characteristics of the literature reviewed are described below: 

• Key climate factors examined – The major climate factors most often discussed in the 

literature in terms of transportation impacts are temperature, precipitation, and sea level 

rise. Some articles explicitly dealt with storm activity or storm surge. (These climate 

factors are also analyzed as significant drivers in the Gulf Coast Study.) Many northern 

studies also examined permafrost thawing and navigation issues relating to ice cover on 

seaways and inland waterways. 

• Modal focus – Information on modes is uneven. The majority of articles dealt with 

highways and marine transport; other modes such as rail, aviation, and transit were not 

as well represented. Relatively few articles addressed pipelines or emergency 

management issues in the context of climate change. 

• Geographic focus – Much of the work done in this field has a national or regional 

focus; only the IPCC (1996 and 2001) has considered the topic at a truly global level. 

The Arctic Climate Impacts Assessment (Instanes et al., 2005) is a rare example of 

transnational regional study, in that it focused on impacts throughout the Arctic nations. 

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In addition, some studies focused on specific urban areas (Kirsten et al., 2004; Suarez, 

2005; Greater London Authority, 2005). 

• Climate zones examined – The literature does not examine all climate zones equally 

or in proportion to the amount of transportation infrastructure present. In particular, 

transportation in Arctic climates received substantial study, as warming impacts already 

are being observed in those regions. Many other studies looked at temperate climates, 

as in the United States or Europe. Australian studies were among the few that 

examined desert climates or hot climates. In addition, most of the literature focused on 

the industrialized world. 

• Timeframe examined – Most studies examined time horizons of 50- to 100-years into 

the future, consistent with the timescale of projections and scenarios often used in the 

climate literature. Though this is well beyond the 20- to 30-year planning horizons 

typically used in transportation planning, it was noted in the literature that some 

infrastructure (such as bridges) is designed with life expectancies of 100 years or more 

(Eddowess et al., 2003; Wooler, 2004; Norwell, 2004). Other researchers eschewed 

timescales and instead chose specific thresholds to consider. For instance, Marine 

Board (1987) chose to examine the impacts of 0.5-, 1.0-, and 1.5-m (1.6-, 3.3-, and 4.9-

foot) rises in sea levels, without specifying a projected year for when these might take 

place. Finally, several Arctic studies focused on changes presently occurring, as in 

Grondin’s (2005) study of the effect of thawing permafrost on airfields and roads in 

Nunavik due to increasingly warmer winters. 

1.3.2 Major Sponsors Conducting Related Research 

Studies on the impacts of climate change on transportation have been conducted by a 

variety of researchers and organizations, including governmental agencies, academic 

researchers, and the private sector, reflecting the range of stakeholders with an interest in 

the topic. These studies incorporate a variety of approaches and can be found as standalone assessments of transportation impacts or as one aspect of a broader examination of 

climate impacts. 

Two very significant impact assessment efforts have dealt with this issue in a limited 

fashion. The IPCC’s multivolume assessment reports (IPCC, 1996; IPCC, 2001) discussed 

the topic in general terms, particularly noting the vulnerability of transportation 

infrastructure in coastal zones and permafrost regions to climate impacts, with the 2001 

report broadly discussing some transportation operations impacts and more detail on 

Europe-specific concerns, such as impacts to aviation operations and river navigation. 

Similarly, the U.S. National Assessment, which represents one of the broadest 

examinations of climate impacts to date in the U.S., did not include transportation as a 

sector of interest (National Assessment Synthesis Team, 2000). However, some of the 

regional studies conducted under the umbrella of the national assessment process did 

examine transportation impacts, most notably the Metro East Coast and Alaska studies 

(Zimmerman, 2002a; Weller et al., 1999). The 2002 U.S. DOT report, The Potential 

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1-9

Impacts of Climate Change on Transportation: Summary and Discussion Papers, contains 

15 discussion papers addressing potential climate impacts on various modes of 

transportation across the Nation and a summary of priority research needs. The importance 

of weather and climate and its potential impacts on the Nation's transportation system was 

studied in Weather Information for Surface Transportation: A National Needs Assessment 

Report (OFCM, 2002). The report established national needs and requirements for weather 

information associated with decision-making for surface transportation operation modes 

including highway, transit, rail, marine, pipeline, and airport ground operations. It was 

issued as part of the cross-agency Weather Information for Surface Transportation (WIST) 

initiative, supported by the Federal Committee for Meteorological Services and Supporting 

Research (FCMSSR) and the agencies it represents. 

The United Kingdom (U.K.) Climate Impacts Programme, an initiative similar to the U.S. 

National Assessment, specifically included impacts on the transportation sector in the 

overall assessment and in each of the regional reports prepared under its umbrella. The 

Canadian and Australian governments also have commissioned studies to examine 

transportation impacts of special interest to them – Canada with permafrost concerns and 

interest in the opening of the Northwest Passage; Australia with dry land salinity impacts 

due to its unusual soil and climatic conditions (Andrey and Mills, 2003; Norwell, 2004). 

References to research on this topic also were seen for New Zealand, Finland, and the 

Netherlands (Kinsella and McGuire, 2005; Ministry of Housing, Spatial Planning, and the 

Environment, 2001). A small number of city agencies also have commissioned studies 

examining impacts to their own transportation networks, such as in Seattle and London 

(Soo Hoo, 2005; Greater London Authority, 2005). 

Many studies also were identified in engineering and transportation journals, ranging from 

transportation-specific publications such as the National Academy of Science 

Transportation Research Board’s (TRB) Transportation Research Review to more general 

sources such as Civil Engineering – ASCE or the Journal of Cold Regions Engineering, and 

even some transportation trade journals (Barrett, 2004). A small number of private sector 

reports, all from the U.K., were identified, including one study from a ports company and 

two from the insurance industry (ABP Marine Environmental Research, Ltd., 2004; 

Dlugolecki, 2004; Climate Risk Management and Metroeconomica, 2005). 

Finally, though many nongovernmental organizations (NGO) are engaged in research and 

policy advocacy related to climate change, we found few NGOs producing literature on 

climate impacts on transportation. For instance, the Union of Concerned Scientists (UCS) 

and the Pew Center on Global Climate Change have both published multiple reports on 

impacts and adaptation (see the UCS regional impact studies1

 and Easterling, 2004), yet 

transportation implications have received little direct attention in these reports. 

 

1 http://www.ucsusa.org/global_warming/science. 
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1.3.3 State of Technical Analysis 

The level of technical analysis in current research regarding their use of climate data and 

modeling varies, depending both on when the study was done and the magnitude of the 

study. Early studies, for instance, focused on CO2-doubling scenarios (i.e., examining an 

equilibrium state at an unspecified point in the future), because standardized emissions and 

climate change scenarios had not yet been developed for researchers to use (Hyman, 1989; 

Black, 1990; Irwin and Johnson, 1990). Later studies took advantage of the climate 

projections developed by the IPCC process or by other large modeling efforts, such as the 

United States and United Kingdom national assessments. Several studies demonstrated 

advanced approaches to climate modeling, making use of multiple climate models and 

regional models to generate projections of climate variables (Instanes et al., 2005; Kinsella 

and McGuire, 2005; National Assessment Synthesis Team, 2000; Entek UK Limited, 

2004). Other studies took more simplified approaches, using global temperature or sea 

level rise projections as the basis for examining potential impacts. A few studies did not 

use climate modeling at all, instead relying on historical trend data (Sato and Robeson, 

2006; ABP Marine Environmental Research Ltd., 2004). 

In many cases, climate variables produced by global or regional climate models were used 

as inputs into secondary effects models relevant for specific transportation questions. For 

example, Cheng (2005) used permafrost models to assess the impact of rising temperatures 

on road and rail structures in Tibet. Lonergan et al. (1993) integrated climate projections 

into snowfall and ice cover models for northern Canada to understand climate impacts on 

freight shipments via ice roads and waterways. 

On the whole, relatively few studies attempted to quantify the estimated costs, benefits, or 

effects on performance resulting from climate change; more commonly, they identified 

potential impacts without a quantitative assessment. Some examples of the kinds of 

quantitative analyses performed include: 

• Hyman et al. (1989) estimated that it would cost more than $200 million (in 1989 

dollars) to elevate affected Miami streets to compensate for rising groundwater levels 

due to sea level rise and that increases in winter temperatures and decreases in snowfall 

would reduce Cleveland’s snow and ice control budget by 95 percent (about $4.4 

million, or nearly 2 percent of the city’s operating budget). 

• Kirshen et al. (2004) estimated an 80 percent increase in traveler delays due to 

increased incidence of flooding in the Boston area. They also tested overall monetary 

and environmental costs for three adaptive strategies, finding that aggressive adaptation 

strategies proved less costly in the long run than doing nothing. 

• Kinsella and McGuire (2005) estimated the approximate cost of retrofitting or 

redesigning New Zealand’s road bridges to accommodate increased precipitation (and 

higher stream flows). They found that although designing for climate change increased 

initial costs by about 10 percent, over the life of the structure the incremental cost was 

small (less than 1 percent) due to the decreased probability of climate-related damage. 

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• Olsen (2005) conducted a Monte Carlo simulation of total annual losses to shippers on 

the Mississippi River from having to switch to more expensive modes of transport 

when barge travel is restricted due to low or high water flows. He found that future 

losses could range from $1.5 million to $41 million per year, compared to an historical 

average of $12 million per year. 

• Associated British Insurers used insurance catastrophe models to examine the financial 

implications of climate change through its effects on severe storms (Climate Risk 

Management and Metroeconomica, 2005), estimating that climate change could 

increase the annual costs of flooding in the United Kingdom almost 15-fold by the 

2080s under high-emissions scenarios. 

Studies also have been done on the cost of severe storms on transportation networks, which 

will provide useful data for future studies relating them to climate change. For instance, 

Grenzeback and Lukmann (2006) summarize some costs to the transportation network 

resulting from Hurricane Katrina. Although they do not attempt a full accounting of these 

costs, they note that infrastructure restoration costs will run into the billions of dollars – 

replacement of the I-10 Twin Span Bridge between New Orleans and Slidell, LA, alone 

will cost $1 billion and of the CSX rail line another $250 million. 

1.3.4 Impacts, Assessment, and Adaptation 

A review of the literature indicates that the potential impacts of climate changes on 

transportation are geographically widespread, modally diverse, and may affect both 

transportation infrastructure and operations. Indeed, numerous transportation impacts were 

discussed in the literature. However, the degree to which a study discussed an impact 

varied; some studies addressed impacts at length, while others gave an impact only a 

passing mention. A complete list of impacts and adaptations addressed in the literature, 

along with references, can be found in table 1.1. 

Four major categories of climate change factors are addressed most frequently in the 

literature. These closely parallel the major factors addressed later in this report’s study of 

the Gulf Coast region. These climate factors and their major impacts are: 

1. Increasing temperatures, which can damage infrastructure, reduce water levels on 

inland waterways, reduce ice cover in the Arctic, and melt permafrost foundations; 

2. Increasing precipitation, which can degrade infrastructure and soil conditions; 

3. Rising sea levels, which can inundate coastal infrastructure; and 

4. Changes in storm activity, which can damage infrastructure and operations due to 

increased storm intensity, though winter snowstorms may decrease in frequency. 

A summary of the literature findings regarding these impacts, and their corresponding 

adaptation measures, is presented below. This is followed by a brief discussion of the 

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indirect or secondary impacts on the economy, environment, population, and security of a 

region. 

[INSERT TABLE 1.1 Impacts of Climate Change Identified in the Literature 1987-2006] 

1.3.5 Direct Climate Impacts on Transportation Addressed in 

Existing Literature 

Increasing Temperatures 

Increasing temperatures have the potential to affect multiple modes of transportation, 

primarily impacting surface transportation. The transportation impacts mentioned most 

often in the literature included pavement damage; rail buckling; less lift and fuel efficiency 

for aircraft; and the implications of lower inland water levels, thawing permafrost, reduced 

ice cover on seaways, and an increase in vegetation. These are discussed in greater detail 

below: 

• Pavement damage – The quality of highway pavement was identified as a potential 

issue for temperate climates, where more extreme summer temperatures and/or more 

frequent freeze/thaw cycles may be experienced. Extremely hot days, over an extended 

period of time, could lead to the rutting of highway pavement and the more rapid 

breakdown of asphalt seal binders, resulting in cracking, potholing, and bleeding. This, 

in turn, could damage the structural integrity of the road and/or cause the pavement to 

become more slippery when wet. Adaptation measures mentioned included more 

frequent maintenance, milling out ruts, and the laying of more heat resistant asphalt. 

• Rail buckling – Railroads could encounter rail buckling more frequently in temperate 

climates that experience extremely hot temperatures. If unnoticed, rail buckling can 

result in derailment of trains. Peterson (2008) noted, “Lower speeds and shorter trains, 

to shorten braking distance, and lighter loads to reduce track stress are operational 

impacts.” Adaptation measures included better monitoring of rail temperatures and 

ultimately more maintenance of the track, replacing it when needed. 

• Vegetation growth – The growing season for deciduous trees that shed their leaves 

may be extended, causing more slipperiness on railroads and roads and visual 

obstructions. Possible adaptation measures included better management of the leaf 

foliage and planting more low-maintenance vegetation along transportation corridors to 

act as buffers (Wooler, 2004). 

• Reductions in aircraft lift and efficiency – Higher temperatures would reduce air 

density, decreasing both lift and the engine efficiency of aircraft. As a result, longer 

runways and/or more powerful airplanes would be required. However, one analyst 

projected that technical advances would minimize the need for runway redesign as 

aircraft become more powerful and efficient (Wooler, 2004). 

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• Reduced water levels – Changes in water levels were discussed in relation to marine 

transport. Inland waterways such as the Great Lakes and Mississippi River could 

experience lower water levels due to increased temperatures and evaporation; these 

lower water levels would mean that ships and barges would not be able to carry as 

much weight. Adaptation measures included reducing cargo loads, designing vessels to 

require less draft, or dredging the water body to make it deeper. 

• Reduced ice cover – Reduced ice cover was generally considered a positive impact of 

increasing temperatures in the literature. For example, a study conducted by John D. 

Lindeberg and George M. Albercook, which was included in the Report of the Great 

Lakes Regional Assessment Group for the U.S. Global Change Research Program, 

stated, “the costs of additional dredging [due to lower water levels] could be partially 

mitigated by the benefits of additional shipping days on the [Great] Lakes caused by 

less persistent ice cover” (Sousounis, 2000, p. 41). Additionally, arctic sea passages 

could open; for example, the Arctic Climate Impact Assessment noted, “projected 

reductions in sea-ice extent are likely to improve access along the Northern Sea Route 

and the Northwest Passage” (Instanes et al., 2005, p. 934). However, negative 

environmental and security impacts also may result from reduced ice cover as well 

from as the increased level of shipping. These are discussed below in the subsection on 

indirect impacts (Section 1.3.6.). 

• Thawing permafrost – The implications of thawing permafrost for Arctic 

infrastructure receive considerable attention in the literature. Permafrost is the 

foundation upon which much of the Arctic’s infrastructure is built. The literature 

consistently noted that as the permafrost thaws the infrastructure will become 

unstable – an effect being experienced today. Roads, railways, and airstrips are all 

vulnerable to the thawing of permafrost. Adaptation measures vary depending on the 

amount of permafrost that underlies any given piece of infrastructure. The literature 

suggested that some assets will only need rehabilitation, other assets will need to be 

relocated, and different construction methods will need to be used, including the 

possibility of installing cooling mechanisms. According to the Arctic Research 

Commission, “roads, railways, and airstrips placed on ice-rich continuous permafrost 

will generally require relocation to well-drained natural foundations or replacement 

with substantially different construction methods” (U.S. Arctic Research Commission 

Permafrost Task Force, 2003, p. 29). 

• Other – Other impacts of increasing temperatures included a reduction in ice loads on 

structures (such as bridges and piers), which could eventually allow them to be 

designed for less stress, and a lengthening of construction seasons due to fewer colder 

days in traditionally cold climates. 

Increasing Precipitation 

Increases in precipitation will likely affect infrastructure in both cold and warm climates, 

although in different ways. Increases in the frequency and intensity of the precipitation 

could impact roads, airstrips, bikeways/walkways, and rail beds. The literature suggested 

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most of the impact would be felt in the more rapid deterioration of infrastructure. 

According to a report released by Natural Resources Canada (2004, p. 138), “accelerated 

deterioration of these structures may occur where precipitation events and freeze-thaw 

cycles become more frequent, particularly in areas that experience acid rain.” Other 

impacts of increased flooding include subsidence and heave of embankments (ultimately 

resulting in landslides), and deterioration in water quality due to run-off and sedimentation. 

Adaptation measures included monitoring infrastructure conditions, preparing for service 

delays or cancellations, and replacing surfaces when necessary (Warren, 2004). Although 

mentioned less frequently, some attention was given in the literature to bridge scour from 

increased stream flow. Bridge scour could cause abutments to move and damage bridges. 

Rising Sea Levels 

Sea level rise could impact coastal areas. While incremental sea level rise impacts may not 

be as immediate or severe as the storm activity, the impacts could nevertheless affect all 

modes of transportation. Low-level roads and airports are at risk of inundation, and ports 

may see higher tides. Titus (2002, p. 139) concluded “the most important impact of sea 

level rise on transportation concerns roads. In many low-lying communities, roads are 

lower than the surrounding lands, so that land can drain into the streets. As a result, the 

streets are the first to flood.” Adaptation measures include more frequent maintenance, 

relocation, and the construction of flood-defense mechanisms (such as dikes) (Titus, 2002). 

Although mentioned less often in the literature, deeper water caused by sea level rise could 

permit greater ship drafts in ports and harbors. 

Changes in Storm Activity 

Storm activity was discussed as an issue for all climates, impacting both inland areas and 

coastal areas. Impacts most frequently mentioned in the literature include storm surges that 

could potentially cause damage to coastal areas and a decrease in winter snowstorms (with 

more winter precipitation falling as rain). These are discussed in greater detail below: 

• Increased storm activity or intensity – In coastal areas, increased storm activity or 

intensity could lead to an increase in storm surge flooding and severe damage to 

infrastructure, including roads, rails, and airports. These effects could be exacerbated 

by a rise in sea level. In addition, coastal urban areas, like New York City, could 

potentially see storm surges that flood the subway system. As Zimmerman (2002a, p. 

94) noted, “transportation systems are traditionally sited in low-lying areas already 

prone to flooding.” She went on to state that, “New York City alone has over 500 

miles of coastline, much of which is transgressed [sic] by transportation infrastructure – 

roadways, rail lines, and ventilation shafts, entrances and exits for tunnels and transit 

systems, many are at elevations at risk of being flooded even by traditional natural 

hazards” (p. 94). Adaptation measures included construction of barriers to protect 

against storm surges, relocating infrastructure, and preparing for alternative traffic 

routes (Zimmerman, 2002a). 

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Other impacts related to storm activity included an increase in wind speed and an 

increase in lightning. Increased wind speeds could damage signage and overhead 

cables. Increased lightning strikes could cause electrical disturbances disrupting 

electronic transportation infrastructure, like signaling. 

• Reduced snowfall – A decrease in winter snowstorms could potentially relieve areas 

that typically see large amounts of snow from some of the cost of maintaining winter 

roads. Natural Resources Canada concluded, “empirical relationships between weather 

variables and winter maintenance activities indicate that less snowfall is associated with 

reduced winter maintenance requirements. Thus, if populated areas were to receive less 

snowfall and/or experience fewer days with snow; this could result in substantial 

savings for road authorities” (Warren et al., 2004, pp. 138-139). 

1.3.6 Indirect Climate Impacts on Transportation Addressed in 

Existing Literature 

Four secondary, or indirect, impacts were addressed to some degree in the literature: 

economic, environmental, demographic, and security impacts. 

Economic 

The economic impact of climate change received considerable attention. Some studies 

made an attempt to approximate the cost of replacing infrastructure or to place a monetary 

figure on loss of specific aspects of system performance, such as traffic disruptions. For 

example, Suarez et al. (2005, p. 240), when discussing the effects flooding could have on 

the Boston Metro area, stated, “over the period 2000 to 2100, the results indicate that 

delays and trips lost (i.e., canceled trips) increased by 80 percent and 82 percent under the 

climate change scenario. While this is a significant increment in percentage terms, the 

magnitude of the increase is not enough to justify a great deal of infrastructure 

improvements.” 

The economic implications of impacts on freight were particularly studied. Three climate 

factors were analyzed in most depth: changing inland water levels, specifically on the 

Great Lakes; thawing permafrost and warmer temperatures in traditionally colder climates; 

and the potential opening of the Northwest Sea Passage through the Canadian Arctic as a 

result of sea ice melt. These are discussed in greater detail below: 

• Changing inland waterway levels – Quinn analyzed the economic impacts of lower 

water levels in the Great Lakes, which would require ships to lighten their loads 

because of lower water levels. According to Quinn (2002, p. 120), “a 1,000-foot bulk 

carrier loses 270 tons of capacity per inch of lost draft.” If lower water levels occur on 

a regular basis, Great Lakes shippers are likely to see less profit and will run the risk of 

the freight being transported by competing modes (e.g., rail or truck). A few analyses 

considered the impacts of rising inland water levels (Olsen, 2005). 

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• Increasing temperatures in northern regions – Other analysts assessed the economic 

impacts of warming temperatures on trucking in northern regions. Typically, trucks are 

allowed to carry more weight when the underlying roadbeds are frozen, and some 

Arctic regions are served by ice roads over the tundra in winter. If temperatures 

increase and northern roads thaw before their usual season, truckloads may have to be 

reduced during the traditionally higher weight-limit trucking season. This impact 

already is occurring in some regions of the United States and Canada. As a result, a 

few highway authorities are adjusting their weight restrictions based on conditions, 

rather than linking them to a given date (Clayton et al., 2005). 

• Opening of the Northwest Passage – The literature indicated that the reduction of 

waterway ice cover and the eventual opening of an Arctic Northwest Passage have by 

far the largest economic consequences of all the impacts. The passage could provide an 

alternative to the Panama Canal and stimulate economic development in the Arctic 

region (Johnston, 2002). 

Environmental 

A small number of environmental impacts have been addressed in the literature to date, 

focusing on the effects of specific adaptation responses to changing climate and weather 

conditions. These included the potential of increased dredging of inland waterways, 

reduced use of winter road maintenance substances, and the environmental impact 

increased shipping could have on the Arctic. 

• Dredging – Dredging of waterways – in response to falling water levels – could have 

unintended, harmful environmental impacts. According to the Great Lakes Regional 

Assessment, “in a number of areas the dredged material is highly contaminated, so 

dredging would stir up once buried toxins and create a problem with spoil disposal” 

(Sousounis, 2000, p. 30). 

• Increased shipping in the Arctic – The transportation benefits of the Northwest 

Passage could be offset by the negative environmental impacts associated with its use, 

particularly oil spills (Struck, 2006). Johnston (2002, p. 153) noted that there is 

“serious concern on the part of many Inuit and other residents that regular commercial 

shipping will, sooner or later, cause serious harm to the Arctic ecology.” 

• Reduced winter maintenance – Some positive environmental impacts also were 

mentioned, particularly in relation to milder winter weather in northern regions. For 

example, according to Warren et al. (2004, p. 139) “less salt corrosion of vehicles and 

reduced salt loadings in waterways, due to reduced salt use” during winter months 

could positively impact the environment. According to Natural Resources Canada, 

“experts are optimistic that a warmer climate is likely to reduce the amount of 

chemicals used, thus reducing costs for the airline industry, as well as environmental 

damage caused by the chemicals” (Warren et al., 2004, p. 139). 

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Demographic 

Demographic shifts were rarely addressed in the literature. A few reports raised the 

potential for shifts in travel destinations and mode choices. For instance, in a U.K. Climate 

Impacts Programme Report on the West Midlands it was noted: “higher temperatures and 

reduced summer cloud cover could increase the number of leisure journeys by road. There 

could be a possible substitution from foreign holidays if the climate of the West Midlands 

becomes more attractive relative to other destinations, reducing demand at Birmingham 

International Airport” (Entek UK Limited, 2004, p. 24). In addition, the Arctic regions, 

located near the Northwest Passage, could see an influx of population (Entek UK Limited, 

2004). 

Security 

Security was identified as an issue in relation to the Northwest Passage. Given the 

enormous changes the development of the Northwest Passage would precipitate, it is no 

surprise that global diplomacy, safety, and security is of concern. Johnston (2002, p. 152) 

stated, “even if the remoteness of the Northwest Passage seems to make it an unlikely 

target for terrorists, security concerns will centrally have to be factored in to any major 

undertaking in the Arctic or elsewhere that would be perceived by enemies as an important 

component of the North American economy.” If the Northwest Passage does become 

practical for shipping, security, ownership, maintenance, and safety of the waterway will 

become an issue. Indeed, the U.S. Navy already had begun thinking about the implications 

of an ice-free Arctic during a symposium held in April 2001 (Office of Naval Research, 

2001). Sovereignty issues also will need to be resolved to clarify whether the passage will 

be considered international or Canadian waters (Johnston, 2002). 

1.3.7 Decision Making Processes and Tools 

Until recently, studies typically concluded with recommendations for additional analysis of 

uncertainty, thresholds, and prioritization of actions. Recent work has begun to respond to 

this need, but the field still has a long way to go. Some reports have begun to make 

suggestions for institutional changes necessary to integrate climate impacts into the 

decision making processes for transportation planning and investment. Studies have 

suggested some approaches to more adequately dealing with uncertainty. Finally, several 

studies have attempted to develop methodologies that can integrate potential climate 

impacts into risk prioritization processes, decision trees, and other decision support tools. 

The following sections discuss institutional changes that were identified in the literature, 

evaluate the manner in which uncertainty and probability was addressed, and present four 

case studies highlighting different methodologies used in risk analysis and impact 

assessment. 

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Institutional Changes 

On the whole, analysis and recommendations concerning needed changes in standard 

design practice or institutional changes are beginning to emerge but are at a nascent stage. 

A few recent studies illustrate this point: 

• Urban-scale planning – Two recent studies developed recommendations for London 

and Seattle. The Greater London Authority (2005) urged transportation decision 

makers to incorporate climate into routine risk management procedures, build 

adaptation measures into new infrastructure when appropriate, and make certain that 

whatever measures are taken are flexible and easily adaptable to future climatic 

changes. However, the report gave little direction on how they should go about this; 

suggestions about how and when officials should incorporate these adjustments were 

not well defined. Likewise, a 2005 Seattle study, authored by the city auditor, 

recommended that the Seattle Department of Transportation “identify, prioritize, and 

quantify the potential effects of climate change impacts; and plan appropriate responses 

to changes in the region’s climate” (Soo Hoo et al., 2005, p. 12). A specific 

institutional recommendation made was the synchronization of sea level rise 

assumptions among Seattle’s various city agencies (for instance, in the assumptions 

made for construction of seawalls) (Soo Hoo et al., 2005). 

• Arctic maritime regulatory regime – For the Arctic, several studies identified the 

need for a new regulatory system to govern ships in Arctic waters. Johnston (2002) 

recommended a new “transit management regime” be developed for the Northwest 

Passage to clarify Canadian and international responsibilities and jurisdiction over 

maritime passage, and the Arctic Marine Transport Workshop (Brigham, 2004) 

suggested the development of harmonized safety and environmental measures for the 

larger Arctic region. 

• General planning considerations – Several other reports recommended that as a first 

step a process be developed for including climate impacts in planning. For instance, 

the Northern Ireland assessment recommended that a formalized policy on climate 

impacts be developed within three years (Smyth et al., 2002), and Associated British 

Ports indicated that it planned to periodically re-examine potential impacts to ports in 

order to see if their assessment changes with new information (ABP Marine 

Environmental Research Ltd., 2004). Interestingly, Norwell (2004) noted that planning 

for sea level rise already has been incorporated into planning documents in several 

Australian States. 

In general, the mismatch between typical planning horizons and the longer-term 

timeframe over which climate impacts occur appears to be a barrier to incorporating 

climate change factors in decision making. For example, Kinsella and McGuire (2005) 

concluded that for infrastructure with replacement horizons of less than 25 years, there 

was no need to consider longer-term climate effects in the present day, as the 

infrastructure would turn over before it became a problem. 

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Uncertainty and Probability 

The literature indicates that only recently have analysts begun to address the issue of 

transportation risk assessment and decision making under uncertainty. Even now, the 

analytical sophistication of studies that attempt to address these concerns is in its infancy. 

The studies consistently showed awareness of the uncertainty of climate projections, 

quoting ranges for potential climate changes. However, probabilistic approaches were not 

implemented in the literature reviewed and were rarely discussed. Nor was there a focus 

on the development of “robust” strategies that can bear up under multiple possible futures 

or other strategies designed specifically to deal with decision making under uncertainty. 

Dewar and Wachs (forthcoming) note that this is a gap in transportation planning more 

generally and not simply in the matter of climate change. They call for a paradigmatic shift 

in transportation planning approaches. 

Several studies did discuss possible approaches to the issue of uncertainty and decision 

making, without applying them to specific cases. For example, Meyer (forthcoming) noted 

that, “in recent years, many engineering design analyses have been incorporating more 

probabilistic approaches into their design procedures that account for uncertainty in both 

service life and in environmental factors.” He continued, “In considering wind speeds, for 

example, probabilities of different wind speeds occurring based on an underlying 

distribution of historical occurrences are used to define a design wind speed. Other 

analysis approaches are incorporating risk management techniques into the tradeoff 

between design criteria that will make a structure more reliable and the economic costs to 

society if the structure fails.” Furthermore, Dewar and Wachs (forthcoming) discuss a 

wide variety of conceptual decision making tools that could be considered when designing 

frameworks to understand how to incorporate climate uncertainty into transportation 

infrastructure decisions. 

Approaches to Risk Analysis and Impact Assessment 

Among those studies that attempted to implement a risk analysis or impact assessment 

framework for a particular transportation system, a number of different approaches were 

taken. For instance, Associated British Ports demonstrates an approach to risk evaluation 

that relies on expert elicitation to make a judgment on risk levels for U.K. ports (ABP 

Marine Environmental Research Ltd., 2004). Risk was broken into four themes: 

(1) flooding; (2) insurance; (3) physical damage; and (4) disruption. Port managers were 

asked to evaluate the risk level of each impact by indicating whether they thought it was a: 

(1) very low risk; (2) low risk; (3) moderate risk; (4) high risk; or (5) very high risk. Using 

this methodology, the study concluded that storm surge events represent the biggest threat 

to U.K. ports. 

For the U.K. rail network, Eddowess et al. (2003) developed a framework for prioritizing 

risks that integrates the probability that a particular climate effect would impact the rail 

industry (“risk likelihood”) with the scale of the impact, if it did occur (“risk impact”). The 

“risk likelihood” essentially combined an assessment of the present-day vulnerability to 

specific climate factors with projections of how they might change under global climate 

change scenarios, while the “risk impact” took into account the severity of a given impact, 

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the amount of infrastructure affected, and the ability to adapt to the change. Their study 

did not, however, explicitly specify thresholds for when a given level of adaptation was 

worth implementing. 

Transit New Zealand developed a methodology for determining thresholds for taking 

action by using a two-stage process (Kinsella and McGuire, 2005). The first stage 

constituted a decision tree that examined the necessity of taking action in the near term. 

No action was deemed necessary if (1) it was determined that a given impact was unlikely 

to occur before 2030, (2) the impact would not occur within the design life of the facility 

(for facilities with lifetimes of less than 25 years), or (3) current standards would 

adequately address the climate impact. If present-day action was deemed necessary, the 

second stage analysis determined the feasibility of taking action by comparing the costs of 

doing nothing, retrofitting the infrastructure, or designing all new infrastructure with future 

climate changes in mind. 

Finally, the Climate's Long-term Impacts on Metro Boston CLIMB report develops tools 

for scenario analysis tools and decision support for Boston decision makers to use in 

understanding climate impacts. Specifically, the researchers developed a dynamic 

analytical modeling tool to help policy and decision makers assess changes in climate and 

in socioeconomic and technological developments and to understand their associated 

interrelated impacts on Boston’s infrastructure system as a whole. The model allows users 

to input climate drivers in order to assess performance impacts and potential adaptation 

strategies for infrastructure systems, including transportation (Kirshen et al., 2004). 

 1.4 Conclusions Drawn from Current Literature on the 

State of Research 

Assessing the literature on the impacts of climate change on transportation as a whole, it 

becomes apparent that there are a number of areas in which more research is needed on 

potential impacts of climate change on transportation. Many authors noted that research on 

the potential impacts of climate change on transportation systems is limited. Warren et al. 

(2004) note that though much work has been done on adaptation to climate change in 

general, relatively little concerns climate impacts on transportation systems – to date, 

transportation research has been focused on emission-reduction strategies. Other authors 

noted the need for more research on specific impacts or modes. For instance, in their study 

of seasonal weight limits on prairie highways, Clayton et al. (2005) noted that there was 

essentially no transportation and climate impacts literature on their topic to draw upon. 

Work in this field has so far been focused on the initial stages of risk assessment and 

adaptation; i.e., building a basic understanding of the issues involved. In general, the 

literature review shows that some work has been done on collecting data, assessing 

impacts, and evaluating the significance of these risks. Less work has been done to 

develop methodologies for assessment or to systematically evaluate adaptation strategies. 

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Work to develop decision support tools to facilitate these processes has received little 

formal attention. The state of research in each analytic area is summarized below. 

Collecting data needed to assess transportation vulnerability to climate impacts. 

Some credible work on data collection and analysis has been done for selected modes and 

facilities in specific regions. Researchers have been able to make use of the good data on 

transportation networks and transportation engineering practice that exists for most of the 

developed world. 

Most studies used climate projections consistent with long-term IPCC global projections as 

the basis for their analyses. However, few studies considered a broader range of plausible 

climate futures that could occur, such as scenarios, including additional feedbacks or abrupt 

climate change. In addition, few studies addressed the implications of changes in 

temperature or precipitation extremes. 

In addition, there are significant gaps in data collection and analysis for several modes and 

for transportation infrastructure in hot or tropical climates, such as are found in the 

southwestern and southeastern portions of the United States. Most of the available 

literature addresses temperate or Arctic climates. 

Developing knowledge about potential impacts. Researchers considered a wide variety 

of potential impacts on transportation, and significant work has been done for selected 

modes and facilities. However, a number of important gaps were found in the current 

literature, most notably the lack of quantitative assessment and dearth of literature on 

operations, network, performance, and secondary impacts: 

• Quantitative assessment – Most studies to date have been qualitative. More 

quantitative assessments of impacts, along with the development of quantitative 

analytical methodologies, will provide needed information for decision makers. 

• Operations impacts – The implications of climate change impacts on operations (both 

normal and emergency) are not as well explored as they are for physical infrastructure. 

Most of the existing literature on operations is focused on a select few issues such as 

waterborne freight and winter maintenance. 

• Network and performance impacts – Relatively few studies (Kirshen et al., 2004; 

Suarez et al., 2005) focused on the network-level impacts of climate change. Most 

focused on the facility level (impacts to a type of facility, for instance, rather than 

system-level impacts on the whole network), and few measured performance impacts. 

• Secondary impacts – Several secondary impacts mentioned in the literature but not 

discussed in-depth could provide useful avenues for further study. These include shifts 

in transportation demand due to climate-induced changes in economic activity and 

demographics; the impact of a warming climate on air quality (which influences 

transportation investment decisions); and other environmental impacts related to 

climate change that may intersect with transportation decision making in relation to 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

ecosystem and habitat preservation, water quality and stormwater management, 

mitigation strategies, safety, and system and corridor planning. 

Assessing the significance of these risks. Work in this area is largely qualitative. Though 

many researchers were able to communicate an assessment of which risks were significant 

enough to require further study, few produced quantitative assessments of cost or 

performance impacts. In particular, more work is needed regarding the economic 

implications of climate impacts on transportation facilities and systems. Relatively few 

studies addressed this quantitatively from an overall life-cycle benefits/costs framework. 

Developing a methodological approach for assessment. Most studies used a similar 

basic approach (identify climate effects of concern, assess potential risks for specific 

modes/facility types, and identify potential adaptations). However, very few attempted to 

develop a generalized approach or consider the ramifications of translating their approach 

to other modes/regions. 

Identifying strategies for adaptation and planning. Most studies dealt with adaptation 

from a facility engineering approach, rather than a strategic or systems performance level. 

Thus, it is largely specific design adaptations appropriate for particular types of facilities 

that were identified in the literature (for instance, insulating railbeds to prevent permafrost 

melt or raising roads to protect them against sea level rise). 

Nonetheless, beginning elements of larger adaptation strategies were recognized in the 

literature. There is a general understanding of the differences between likely short- and 

long-term effects and acknowledgment that different approaches might be needed at 

different points in time (Meyer, forthcoming). In addition, some studies recognized that 

institutional change is necessary and recommended institutional processes for examining 

impacts and deciding on adaptations. 

Significantly, almost no research has been done on how climate change can be incorporated 

into the long-range transportation planning process. Issues to address in future research 

include the mismatch between the timeframe of 20- and 30-year long-range plans and the 

50- and 100-year projections of climate impacts; how to address the potential for nonlinear 

or abrupt changes in climate systems in a planning process; and how to make planning 

decisions that account for uncertainty in climate projections. 

Developing decision-support tools. Very little work has been done to develop decisionsupport tools for transportation managers and planners. The field is sufficiently new that 

there has likely been little demand from transportation decision makers for such tools; 

rather they are only now beginning to learn about the potential impacts they might face in 

the future.

One of the most important gaps in this area is the lack of probabilistic approaches to 

address uncertainty. More sophisticated methodologies to incorporate uncertainty will 

need to be developed for transportation decision makers in order for them to incorporate 

climate change into transportation planning. Currently, uncertainty is rarely incorporated 

in a probabilistic sense in the literature on climate impacts on transportation (though the 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

existence of uncertainty is acknowledged and expressed through the use of ranges in the 

climate factors and sometimes the use of scenarios). In addition, little attention is given to 

decision making practices under uncertainty, such as the development of adaptation 

strategies that are robust across multiple potential futures. 

In summary, research on the potential impacts of climate change on transportation is an 

emerging field and one that has shown a remarkable upturn in interest and activity over the 

past few years. This has coincided with greater interest in the subject of adaptation in 

general, as recognition has grown that some degree of climate change is inevitable in the 

coming decades, even as steps are taken to reduce future emissions. Considerable work 

remains to be done in bringing this field to a greater level of maturity, including 

investigations of impacts not yet thoroughly examined and developing strategies, 

methodologies, and tools that decision makers at all levels can use to both assess the 

importance of climate impacts and identify ways to respond. 

 1.5 Gulf Coast Study Selection, Objectives, and Organization 

1.5.1 Study Selection 

To advance research on the implications of climate change for transportation, the U.S. 

DOT Center for Climate Change solicited and reviewed a range of project concepts. A 

case study approach was selected as an initial research strategy that would both generate 

concrete, useful information for local and regional decision makers as well as help to 

develop a prototype for analysis in other regions and contribute to research methodologies 

for broader application. 

In selecting the study, U.S. DOT considered the extent to which the research would: 

• Increase the knowledge base regarding the risks and sensitivities of transportation 

infrastructure to climate variability and change, the significance of these risks, and the 

range of adaptation strategies that may be considered to ensure a robust and reliable 

transportation network; 

• Provide relevant information and assistance to transportation planners, designers, and 

decision makers; 

• Build research approaches and tools that would be transferable to other regions or 

sectoral analyses; 

• Produce near-term, useful results; 

• Address multiple aspects of the research themes recommended by the 2002 workshop; 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

• Build on existing research activities and available data; and 

• Strengthen U.S. DOT partnerships with other Federal agencies, State and local 

transportation and planning organizations, research institutions, and stakeholders. 

Based on these criteria, the U.S. DOT selected a study of the Gulf Coast as the first of a 

series of research activities that its Center for Transportation and Climate Change will 

pursue to address these research priorities. 

There are several intended uses for the products of this study. First, the findings of the 

study will help inform local and regional transportation decision makers in the central U.S. 

Gulf Coast region. While focused on one region of the United States, it is expected that 

this study will provide a prototype for analysis in other regions. The study findings will 

contribute to research methodologies in this new area of investigation. For example, 

Phase I has identified priority databases and methodologies for the integration of data for 

analysis in a GIS format, developed formats for mapping products, and developed criteria 

for assessing and ranking infrastructure sensitivities to the potential impacts of climate 

variability and change. Each of these outputs will offer useful information and example 

methodologies for use in research activities in other locations, as well as in decision 

making processes for transportation and planning in other areas. This research also is 

intended to help scientists and science agencies better understand the transportation 

sector’s information needs, leading to improved data and better decision support. 

1.5.2 Gulf Coast Study Objectives and Three Phases 

The Gulf Coast Study has been organized into three phases, as depicted in figure 1.1. This 

report presents the findings of Phase I. The objectives of the overall study are to: 

• Develop knowledge about potential transportation infrastructure sensitivities to climate 

changes and variability through an in-depth synthesis and analysis of existing data and 

trends; 

• Assess the potential significance of these sensitivities to transportation decision makers 

in the central U.S. Gulf Coast region; 

• Identify potential strategies for adaptation that will reduce risks and enhance the 

resilience of transportation infrastructure and services; and 

• Identify or develop decision support tools or procedures that enable transportation 

decision makers to integrate information about climate variability and change into 

existing transportation planning and design processes. 

The two primary objectives of Phase I of the central Gulf Coast transportation impact 

assessment were to: (1) collect data needed to characterize the region – its physiography 

and hydrology, land use and land cover, past and projected climate, current population and 

trends, and transportation infrastructure; and (2) demonstrate an approach for assessing 

risks and vulnerability of transportation at regional and local scales. The results of this 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

analysis are presented in this report. The methodologies developed during Phase I of the 

study can be applied to assess transportation risk and vulnerability at a community, county, 

or regional level. 

Phase II of the study will entail an in-depth assessment of impacts and risks to selected 

areas and facilities (as identified in Phase I) and will contribute to the development of riskassessment tools and techniques that can be used by transportation decision makers to 

analyze the vulnerability of other areas. 

The objectives of Phase III are to identify the range of potential adaptation strategies 

available to Federal, regional, and local transportation managers to respond to the risks 

identified in Phases I and II; to identify the potential strengths and weaknesses of these 

responses; and to develop an assessment tool that may assist transportation managers in 

selecting adaptation strategies appropriate to their agency, community, or facility, and to 

the identified sensitivity to climate change. 

[INSERT FIGURE 1.1 Gulf Coast Study Design] 

1.5.3 Study Organization and Oversight 

The Gulf Coast Study is 1 of 21 “synthesis and assessment” products planned and 

sponsored by the U.S. Climate Change Science Program (CCSP). The primary objective of 

the CCSP is to provide scientific information needed to inform public discussions and 

government and private sector decision making on key climate-related issues. This project 

is one of seven projects organized under CCSP Goal 4, which is “to understand the 

sensitivity and adaptability of different natural and managed ecosystems and human 

systems to climate and related global changes” (CCSP, 2003, p. 20).

Led by the U.S. DOT in collaboration with the U.S. Geological Survey (USGS), this study 

was conducted through a groundbreaking interdisciplinary approach that integrated natural 

science disciplines with expertise in risk assessment, transportation, and planning. The 

U.S. DOT and USGS convened a research team with expertise in multiple fields based on 

each agency’s mission and core capabilities. The USGS coordinated the provision of 

scientific research support, coordinating expertise in climate change science and impacts 

assessment; meteorology; hydrology; storm surge analysis and modeling; risk analysis; and 

economics. Cooperators from Louisiana State University, the University of New Orleans, 

and Texas A&M University assisted in the data collection aspects of Phase I and in 

developing a framework for assessing risk and vulnerability. (The U.S. DOT assembled 

expertise in transportation planning, engineering, design, and operation.) Cambridge 

Systematics, Inc., (CS) a transportation consulting firm, supported the coordination and 

design of the study, assisted in organizing the data, and provided transportation experts 

with expertise in ports, rail, highways and transit, pipelines, aviation, emergency 

management, and transportation planning and investment. The CS Transportation Analysis 

Team included consultant support from Wilbur Smith Associates and the Texas 

Transportation Institute. The U.S. DOT’s Bureau of Transportation Statistics (BTS) 

supported geospatial and other data collection and analysis related to transportation, 

working in coordination with USGS geospatial experts. Collectively, this group of 

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Chapter 1: Why Study Climate Change Impacts on Transportation? 

scientists and transportation experts has served as the research team conducting Phase I of 

the study. 

The Secretary of Transportation, following the guidelines of the Federal Advisory 

Committee Act (5 U.S.C. App. 2) or “FACA,” established a U.S. DOT Advisory 

Committee on Synthesis and Assessment Product 4.7: Impacts of Climate Variability and 

Change on Transportation Systems and Infrastructure – Gulf Coast Study, Phase I. The 

committee provides technical advice and recommendations in the development of this 

product for the CCSP. The committee provides balanced, consensual advice on the study 

design, research methodology, data sources and quality, and study findings. The 

committee functions as an advisory body to the two Federal agencies leading the research 

project. 

This product adheres to Federal Information Quality Act (IQA) guidelines and Office of 

Management and Budget (OMB) peer review requirements. Background sources of 

information, included as illustrative material and to provide context, are clearly identified 

as such at the end of the list of sources in each chapter. 

1.5.4 Characterizing Uncertainty 

Some degree of uncertainty is inherent in any consideration of future climate change; 

further, the degree of certainty in climate projections varies for different aspects of future 

climate. Throughout this report, the research team has adopted a consistent lexicon first 

developed by the IPCC to indicate the degree of certainty that can be ascribed to a 

particular potential climate outcome. As presented in figure 1.2, the “Degree of 

Likelihood” ranges from “Impossible” to “Certain,” with different terminology used to 

describe different ranges of statistical certainty as supported by available scientific 

modeling and analysis. The analytic approach required to characterize uncertainty for each 

climate factor (e.g., temperature, precipitation, sea level rise, storm surge) is discussed in 

detail in the relevant section of this report. 

[INSERT FIGURE 1.2 Uncertainty Lexicon] 

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2002. Center for Climate Change and Environmental Forecasting, U.S. Department of 

Transportation, Washington, D.C. 

Potter, J.R., 2002: Workshop Summary. In: The Potential Impacts of Climate Change on 

Transportation Workshop, October 1-2, 2002. Center for Climate Change and 

Environmental Forecasting, U.S. Department of Transportation, Washington, D.C. 

Potter, J.R. and M.J. Savonis, 2003: Transportation in an Age of Climate Change: What 

are the Research Priorities? TR News, 227, July-August, 26-31. 

Quinn, F.H., 2002: The Potential Impacts Of Climate Change On Great Lakes 

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Workshop, October 1-2, 2002. Center for Climate Change and Environmental 

Forecasting, U.S. Department of Transportation, Washington, D.C. 

1-31
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

Rosenzweig, C. and W.D. Solecki (Eds.), 2001: Climate Change and Global City: The 

Potential Consequences of Climate Variability and Change – Metro East Coast. 

Report for the U.S. Global Change Research Program, National Assessment of the 

Potential Consequences of Climate Variability and Change for the United States, 

Columbia Earth Institute, New York, 224 pp. 

Rossetti, M.A., 2002: Potential Impacts Of Climate Change On Railroads. In: The 

Potential Impacts of Climate Change on Transportation Workshop, October 1-2, 2002. 

Center for Climate Change and Environmental Forecasting, U.S. Department of 

Transportation, Washington, D.C. 

Rossiter, L., 2004: Climate Change Impacts on the State Highway Network: Transit New 

Zealand’s Position. Transit New Zealand, Auckland, New Zealand, July. 

Ruth, M. (Ed.), 2006: Smart Growth and Climate Change: Regional Development, 

Infrastructure and Adaptation. Edward Elgar Publishing, Cheltenham, United 

Kingdom. 

Sato, N. and S.M. Robeson, 2006: Climate Change and Its Potential Impact on WinterRoad Maintenance: Temporal Trends in Hazardous Temperature Days in the United 

States And Canada. In: TRB 85th Annual Meeting, January 22, 2006, Washington, 

D.C., page 13. 

Smith, O.P. and G. Levasseur, 2002: Impacts Of Climate Change On Transportation 

Infrastructure in Alaska. In: The Potential Impacts of Climate Change on 

Transportation Workshop, October 1-2, 2002. Center for Climate Change and 

Environmental Forecasting, U.S. Department of Transportation, Washington, D.C. 

Smith, O., 2006: Trends in Transportation Maintenance Related to Climate Change. 

North Carolina State University Center for Transportation and the Environment 2nd

Workshop on Impacts of Global Climate Change On Hydraulics and Hydrology and 

Transportation, March 27, 2006, Washington, D.C. 

Smyth, A., W.I. Montgomery, D. Favis-Mortlock, and S. Allen (Eds.), 2002: Implications 

of Climate Change for Northern Ireland: Informing Strategy Development. Scotland 

and Northern Ireland Forum for Environmental Research (SNIFFER). 

Soo Hoo, W.K., M. Sumitani, and S. Cohen, 2005: Climate Change Will Impact the 

Seattle Department of Transportation. City of Seattle, Office of City Auditor, Seattle, 

Washington, August 9. 

Sousounis, P.J., and J.M. Bisanz (Eds.), 2000: Preparing for a Changing Climate: The 

Potential Consequences of Climate Variability and Change Great Lakes Overview. 

Report for the U.S. Global Change Research Program. October. 

Suarez, P., W. Anderson, V. Mahal, and T.R. Lakshmanan, 2005: Impacts of Flooding 

and Climate Change on Urban Transportation: A Systemwide Performance 

1-32 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

Assessment of The Boston Metro Area. Elsevier Transportation Research Part D 10. 

Pages 231-244. 

Three Regions Climate Change Group, 2005: Consultation Document – Adapting to 

Climate Change: A Checklist for Development, Guidance on Designing Developments 

in a Changing Climate. London, United Kingdom, February. 

Titus, J., 2002: Does Sea Level Rise Matter To Transportation Along The Atlantic Coast? 

In: The Potential Impacts of Climate Change on Transportation Workshop, 

October 1-2, 2002. Washington, D.C. 

Trilling, D.R., 2002: Notes on Transportation into the Year 2025. In: The Potential 

Impacts of Climate Change on Transportation Workshop, October 1-2, 2002. Center 

for Climate Change and Environmental Forecasting, U.S. Department of 

Transportation, Washington, D.C. 

U.S. Arctic Research Commission Permafrost Task Force, 2003: Climate Change, 

Permafrost, and Impacts on Civil Infrastructure. Special Report 01-03, U.S. Arctic 

Research Commission, Arlington, Virginia. 

U.S. Climate Change Science Program (CCSP), 2003: Vision for the Program and 

Highlights of the Scientific Strategic Plan. Climate Change Science Program and the 

Subcommittee on Global Change Research, Washington, D.C. July. 

U.S. Department of State, 2002: Chapter 6: Impacts and Adaptation. In: U.S. Climate 

Action Report 2002. Washington, D.C., May. 

U.S. Federal Highway Administration (FHWA), 1998: Transportation and Global 

Climate Change: A Review and Analysis of the Literature. Office of Environment and 

Planning, Federal Highway Administration, U.S. Department of Transportation, 

Washington, D.C. June. 

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Climate-Change Assessment. Report for the U.S. Global Change Research Program. 

Utah State University, Logan, Utah: IV + 240 pages. 

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Change Impacts and Adaptation: A Canadian Perspective, [Lemmen, D.S. and F.J. 

Warren, eds.]. Climate Change Impacts and Adaptation Directorate Natural Resources 

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Potential Consequences of Climate Variability and Change: Alaska. Report for the 

U.S. Global Change Research Program, Center for Global Change and Arctic System 

Research, Fairbanks, Alaska, December. 

1-33
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

Wilkinson, R., 2002: Preparing for a Changing Climate – The Potential Consequences of 

Climate Variability and Change. A Report of the California Regional Assessment 

Group. Report for the U.S. Global Change Research Program, September. 

Wooler, S., 2004: The Changing Climate: Impact on the Department for Transport. 

Department for Transport, London, United Kingdom. 

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Support of Terrain Evaluation and Route Selection in the Mackenzie River Valley – 

Summary Report. Geological Survey of Canada, August. 

Wu, S.-Y., B. Yarnal, and A. Fisher, 2002: Vulnerability of Coastal Communities to Sea 

Level Rise: A Case Study of Cape May County, New Jersey, U.S.A. Climate 

Research 22, 255-270. 

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Lessons from the New York Area. In: The Potential Impacts of Climate Change on 

Transportation Workshop, October 1-2, 2002. Center for Climate Change and 

Environmental Forecasting, U.S. Department of Transportation, Washington, D.C. 

Zimmerman, R., 2002b: Global Warming, Infrastructure, and Land Use in the 

Metropolitan New York Area: Prevention and Response. In: Global Climate Change 

and Transportation: Coming to Terms. Eno Transportation Foundation, pages 55-63. 

1.6.2 Background Sources 

ABP Marine Environmental Research Ltd., 2004: Climate Change 2003 Port 

Template: Findings from the First Assessment. Report Number R.1061, Associated 

British Ports – Head Office, March.

Easterling, W. III, B.H. Hurd, and J.B. Smith, 2004: Coping with Global Climate 

Change: The Role of Adaptation in the United States. Pew Center on Global Climate 

Change. June. 

Entek U.K. Limited, 2000: The Potential Impacts of Climate Change on the East 

Midlands – Summary Report. East Midlands Sustainable Development Round Table, 

Warwickshire, England, July. 

Entek U.K. Limited, 2004: The Potential Impacts of Climate Change in the West 

Midlands. Sustainability West Midlands, United Kingdom, January. 

Land Use Consultants, CAG Consultants, and SQW Ltd., 2002: Living with Climate 

Change in the East of England Summary Report. East of England Sustainable 

Development Round Table, England, United Kingdom, September. 

1-34 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation? 

1-35

Struck, D., 2006: Melting Arctic Makes Way for Man: Researchers Aboard Icebreaker 

Say Shipping Could Add to Risks for Ecosystem. Washington Post, November 5, 

page A01. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 1: Why Study Climate Change Impact

Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation STemperature IncreaseIncreased Summer Temperatures 

Highway asphalt rutting Proper design/construction, 

milling out ruts, more maintenance, overlay with more rut-resistant asphalt 

(1) Wooler, Sarah. 2004. (2) Andrey and Mills. 200(3) Hass, et al. 2006. (4) Black, William. 1990. (5) Meyers, Michael. 2006(6) Barrett, et al. 2004. (7) Marbek Resource Cons(8) Kerr, Andrew, et al. 19(9) Warren, et al. 2004. (10) Entek U.K. Limited. 20(11) Entek U.K. Limited. 20(12) Lockwood, Steve. 2006(13) Kinsella, Y. and McGu(14) Mills and Andrey. 200(15) OFCM. 2002.

Rail buckling Potential for derailment and 

malfunction of track sensors and signal sensors, increased travel time due to speed restrictions, increased risk of hazardous material spill 

Speed restrictions, reducing frequency of some services, better air conditioning for signals. Improve systems to warn and update dispatch centers, crews, and stations. Inspect and repair tracks, track sensors, and signals. Distribute advisories, warnings, and updates regarding the weather situation and track conditions. 

(1) Wooler, Sarah. 2004. (2) Eddowes, M.J., et al. 2(3) Kerr, Andrew, et al. 199(4) Warren, et al. 2004. (5) Entek U.K. Limited. 20(6) Land Use Consultants, (7) Smyth, et al. 2002. (8) Kerr, Andy. 2001. (9) Entek U.K. Limited. 20(10) Rossetti. 2002. (11) OFCM. 2002. 

More airport runway length and fuel needed because of less dense air 

New planes designed to takeoff more efficiently 

(1) Wooler, Sarah. 2004. (2) Andrey and Mills. 200(3) Irwin and Johnson. 199(4) Warren, et al. 2004. (5) Entek U.K. Limited. 20(6) Smyth, et al. 2002. (7) Entek U.K. Limited. 20

Heat/Lack of ventilation on underground urban transit systems 

Personnel health/safety risk, heat exhaustion, engine/equipment heat stress. Overcrowding, failed, or delayed service will only compound the problem. Could cause passengers to avoid taking public transportation (mode shift). 

Install better ventilation systems, climate monitoring systems, personnel safety and equipment monitoring systems. 

(1) Wooler, Sarah. 2004. (2) Greater London Author(3) OFCM. 2002. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Tables 1T-2 Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation STemperature Increase (continued)

Health and safety risks from heat stress to highway, transit, and pipeline system operators, maintenance personnel, and passengers; including increased risk of collisions/spills of hazardous cargo, control system integrity 

Improve systems to advise operators, monitor personnel, and take prescribed and precautionary measures 

(1) OFCM. 2002. 

Low water levels on inland waterways 

Increased shipping costs; shift to other modes (rail, truck) 

Changes to navigation, dredging of channels, flow augmentation 

(1) Wooler, Sarah. 2004. (2) Andrey and Mills. 2003(3) Olsen, et al. 2005. (4) Black, William. 1990. (5) Irwin and Johnson. 199(6) U.S. Federal Highway A

Environment and Planni

(7) U.S. Department of Stat(8) Institute for Water Resou

Engineers. 2004. 

(9) Sousounis, Peter J. and J(10) National Assessment Sy(11) Marbek Resource Consu(12) D’Arcy, Pierre. 2004. (13) Warren, et al. 2004. (14) Entek U.K. Limited. 20(15) Ministry of Housing, Sp

Environment, The Nethe

(16) Ruth, Matthais. 2006. (17) Quinn. 2002. 

Thermal expansion of bridges Frequent detours, traffic 

disruptions 

Increased ongoing maintenance (1) Cohen, Susan, Soo Hoo, 

Megumi. 2005. 

Overheating of diesel engines Adaptation of cooling systems (1) Entek U.K. Limited. 20Increased vegetation – leaf fall Ineffective braking of rail cars, 

visual obstruction 

Vegetation management, plant low-maintenance vegetation as buffer 

(1) Wooler, Sarah. 2004. (2) Eddowes, M.J., et al. 20(3) Land Use Consultants, e(4) Smyth, et al. 2002. (5) Kerr, Andy. 2001. (6) Entek U.K. Limited. 20(7) Kinsella, Y. and McGuir

Changes to landscape/biodiversity Highway agency owns many 

medians. Increased pest management. Impact on wetlands commitments 

Different types of vegetation may have to be considered 

(1) Wooler, Sarah. 2004. (2) Kinsella, Y. and McGuir(3) Mortenson and Bank. 2
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 1: Why Study Climate Change Impact

Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation STemperature Increase (continued)Increased Summer Temperature and Decreased Precipitation 

Less rain to dilute surface salt may cause steel reinforcing in concrete structures to corrode (Australia) 

Better protect reinforcing in saline environments 

1) Norwell, Gary. 2004. 

Increased Winter Temperatures 

Reduction in cold weather rail maintenance 

Fewer broken rails, excessive wheel wear, and frozen switches 

(1) Andrey and Mills. 2002

Longer construction season Drier and warmer days (1) Andrey and Mills. 2003

(2) Kinsella, Y. and McGuir

Thawing Permafrost (United States, Canada, China) 

Road, rail, airport, pipeline embankments will fail and shallow pile foundations could settle 

Potential for fewer construction problems in long run 

Crushed rock cooling system, insulation/ground refrigeration systems, rehabilitation, relocation, mechanically stabilize embankments against ground movement, remove permafrost before construction 

(1) Instanes et al.. 2005. (2) Brown, Jeff. 2005. (3) Cheng, Guadong. 2005. (4) Hass, et al. 2006. (5) Black, William. 1990. (6) Irwin and Johnson. 1990(7) U.S. Arctic Research Co

Task Force. 2003. 

(8) Weller, Gunter, et al. 19(9) Grondin et al. 2005. (10) Wright, Fred. 2001. (11) Warren, et al. 2004. (12) Ruth, Matthais. 2006. (13) Smith and Levasseur. 20(14) Caldwell et al. 2002. 

Reduction of Freezing Season for Ice Roads (Arctic) 

Roads unusable during certain seasons 

Shorter shipping season, higher maintenance costs, higher lifecycle costs, seasonal mode shift 

Reconstruction of severely damaged infrastructure with less frost-susceptible foundation (geosynthetic barrier), retrofitting road side drains 

(1) Instanes et al.. 2005. (2) Lonergan, et al. 1993. (3) Andrey and Mills. 2003(4) Hass, et al. 2006. (5) Weller, Gunter, et al. 19(6) Marbek Resource Consu(7) Clayton et al. (and Mont(8) Warren, et al. 2004. (9) Lockwood, Steve. 2006
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Tables 1T-4 Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation S

Precipitation Increase

Increased Winter Precipitation – Rain/Snow 

Flooding of roads/airport runways/bikeways and walkways (frequency and magnitude will increase) 

Infrastructure deterioration (quicker with acid rain), impacts on water quality, travel and schedule delays, loss of life and property, increased safety risks, increased risks of hazardous cargo accidents 

Seek alternative routes, improve flood protection, risk assessment for new roads, emergency contingency planning, ensure bridge openings/culverts sufficient to deal with flooding, improve drainage, improved asphalt/concrete mixtures, perform adequate maintenance, and minimize repair backlogs 

(1) Wooler, Sarah. 2004. (2) Andrey and Mills. 2003(3) Irwin and Johnson. 1990(4) U.S. Department of State(5) Kirshen, Paul H. and Ma(6) Intergovernmental Panel (7) Sousounis, Peter J. and J

(8) Wilkenson, Robert. 200(9) Meyers, Michael. 2006. (10) Barrett, et al. 2004. (11) Kerr, Andrew, et al. 199(12) Warren, et al. 2004. (13) Entek U.K. Limited. 20(14) Land Use Consultants, e(15) Smyth, et al. 2002. (16) Kerr, Andy. 2001. (17) Entek U.K. Limited. 20(18) Norwell, Gary. 2004. (19) Kinsella, Y. and McGuir(20) Rossiter, Lisa. 2004. (21) Smith, Orson. 2006. (22) OFCM. 2002. 

Flooding of rails Service disruption, increased 

malfunctions of track or signal sensors, wash-outs and mud slides, increased risk of hazardous material spills 

Engineering solutions, increase advisories, warnings and updates to dispatch centers, crews, and stations. Modify operations for current or forecast conditions. 

(1) Wooler, Sarah. 2004. (2) Irwin and Johnson. 1990(3) Eddowes, M.J., et al. 20(4) Entek U.K. Limited. 20(5) Smyth, et al. 2002. (6) OFCM. 2002. 

Bridge scour Speed restrictions, closure to 

traffic, new materials, better maintenance 

(1) Wooler, Sarah. 2004. (2) Hass, et al. 2006. (3) Kirshen, Paul H. and Ma(4) Meyers, Michael. 2006. (5) Eddowes, M.J., et al. 20(6) Smith, Orson. 2006. (7) OFCM. 2002. 

Flooding of underground transit systems 

Power outages (third rail blowouts), complete loss of service in affected areas, drowned passengers 

Pumping systems (1) Wooler, Sarah. 2004. 

(2) Zimmerman, 2002a and (3) OFCM. 2002. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 1: Why Study Climate Change Impact

Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation S

Precipitation Increase(continued)

Flooding of inland marine transportation waterways 

Interruptions of river navigation and other inland waterway activities (ferries, boating, commerce, port operations, lock operations) 

(1) Intergovernmental Panel (2) Ning, Zhu H., et al. 200(3) OFCM. 2002. 

Pipeline system flooding and damage from scouring away pipeline roadbed or unearthing buried pipelines 

Disruption of fuel delivery, pipeline sensor failure, disruption of construction or maintenance cycles, leaks or other pipeline failures 

(1) OFCM. 2002. 

Increased Precipitation and Increased Summer Temperatures 

Highway, rail, and pipeline embankments at risk of subsidence/heave 

Landslides Fill cracks and carry out more 

maintenance 

(1) Wooler, Sarah. 2004. (2) Instanes et al.. 2005. (3) Cohen, Susan, Soo Hoo, 

Megumi. 2005. 

(4) Wilkenson, Robert. 200(5) Weller, Gunter, et al. 19(6) Eddowes, M.J., et al. 20(7) Konuk, Ibrahim. 2005. (8) Marbek Resource Consu(9) Kerr, Andrew, et al. 199(10) Warren, et al. 2004. (11) Entek U.K. Limited. 20(12) Land Use Consultants, e(13) Smyth, et al. 2002. (14) Entek U.K. Limited. 20(15) Kinsella, Y. and McGuir(16) Rossiter, Lisa. 2004. (17) duVair et al. 2002. (18) OFCM. 2002. 

Concrete deterioration (1) Wooler, Sarah. 2004. 

(2) U.S. Department of Stat(3) OFCM. 2002. 

More frequent and larger slushflow avalanches (Arctic) Incorporate potential risk into planning process for new 

settlements, detection systems, temporary closures 

(1) Instanes et al.. 2005. (2) Marbek Resource Consu(3) Warren, et al. 2004. (4) Stethem, Chris, et al. 20

Altered runoff patterns (Arctic) Disruption of the ice-water 

balance 

(1) Instanes et al.. 2005. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Tables 1T-6 Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation S

Glacial Melting/Thermal Expansion of Oceans 

Sea Level Rise Erosion of coastal highways Construction of sea walls (1) Wooler, Sarah. 2004. 

(2) Black, William. 1990. (3) U.S. Federal Highway A

Environment and Planni

(4) Marbek Resource Consu(5) Norwell, Gary. 2004. (6) Kinsella, Y. and McGuir(7) Ruth, Matthais. 2006. (8) Hyman, William, et al. (9) Titus, 2002. (10) OFCM. 2002. 

Higher tides at ports/harbor facilities 

 Damage to docks and terminals 

(1) Wooler, Sarah. 2004. (2) Black, William. 1990. (3) U.S. Department of Stat(4) Kirshen, Paul H. and Ma(5) Smyth, et al. 2002. (6) Ministry of Housing, Sp

Environment, The Nethe

(7) Caldwell et al. 2002. (8) OFCM. 2002. 

Deeper water Permit greater ship drafts (1) Andrey and Mills. 2003

(2) Kerr, Andrew, et al. 199(3) Titus. 2002. 

Low-level aviation infrastructure at risk 

Relocation or protection of facilities 

(1) Andrey and Mills. 2003(2) Committee on Engineeri

Relative Mean Sea Leve

(3) Warren, et al. 2004. (4) Ruth, Matthais. 2006. (5) Hyman, William, et al. 

Less bridge clearance (1) Cohen, Susan, Soo Hoo, 

Megumi. 2005. 

(2) Committee on Engineeri

Relative Mean Sea Leve

(3) Norwell, Gary. 2004. (4) Hyman, William, et al. 1(5) OFCM. 2002. 

More search and rescue operations 

Obtain more vessels with emergency towing capabilities, better weather forecasting, change seasonal classifications of waters around coast, change ship/boat design 

(1) Wooler, Sarah. 2004. (2) Marbek Resource Consu(3) OFCM. 2002. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 1: Why Study Climate Change Impact

Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation SStorm ActivityStorm Surges Coastal road flooding Increased VMT and VHT; 

increased number of road accidents, evacuation route delays, disruption of transit services, stranded motorists. 

Seawalls, build more redundancy into system, support land use policies that discourage development on shoreline, design and material changes, pumping of underpasses, raise roads 

(1) Choo, Kristin. 2005. (2) U.S. Federal Highway A

Environment and Planni

(3) Intergovernmental Panel 

(4) Suarez, Pablo et Al. 200(5) Rosenzweig, Cynthia an(6) Wilkenson, Robert. 200(7) National Assessment Sy(8) Meyers, Michael. 2006. (9) Committee on Engineeri

Relative Mean Sea Leve

(10) Greater London Authori

Railway flooding Safety risks to personnel and 

equipment (possible injury or death from accidents); rail and railway roadbed damage; disruption of rail traffic; rail sensor failure likely; increased risk of hazardous material spill. 

Seawalls, raising rails (1) Black, William. 1990. 

(2) Committee on Engineeri

Relative Mean Sea Leve

(3) Kerr, Andrew, et al. 199(4) Greater London Authori(5) OFCM. 2002. 

Subway flooding Flood barriers (1) Choo, Kristin. 2005. 

(2) Black, William. 1990. (3) Greater London Authori(4) Ruth, Matthais. 2006. (5) Zimmerman, 2002. 

Port flooding/damage Damage to ports facilities from 

vessels tied alongside. 

Reduce “cope” level at ports to reduce likelihood of water flowing across docks; construct flood defense mechanisms 

(1) ABP Marine Environme(2) Committee on Engineeri

Relative Mean Sea Leve

(3) Entek U.K. Limited. 20(4) Land Use Consultants, e(5) OFCM. 2002. 

Increased Frequency/Magnitude of Storms 

 Damage to infrastructure on roads, railways, pipelines, seaports, airports 

Closures or major disruptions of roads, railways, airports, transit systems, pipelines, marine systems and ports; emergency evacuations; travel delays 

(1) Instanes et al.. 2005. 

(2) Smyth, et al. 2002. (3) Ruth, Matthais. 2006. (4) OFCM. 2002. (5) Intergovernmental Panel 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Tables 1T-8 Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation SStorm Activity (continued)Increased Wind Speeds Bridges, signs, overhead cables, 

railroad signals, tall structures at risk 

Design structures for more turbulent wind conditions, build with better material, use “smart” technologies to detect abnormal events 

(1) Wooler, Sarah. 2004. (2) Meyers, Michael. 2006. (3) Eddowes, M.J., et al. 20(4) Kerr, Andrew, et al. 199(5) Kerr, Andy. 2001. (6) Kinsella, Y. and McGuir(7) OFCM. 2002. 

Roadways: loss of visibility from drifting snow, loss of stability/maneuverability, lane obstruction (debris), treatment chemical dispersion, 

(1) OFCM. 2002. 

Railways: Rail car blow over; schedule delays; increased risk of hazardous material spill 

(1) OFCM. 2002. 

Ship handling becomes difficult (1) OFCM. 2002. Impacts on airport ground operations: increased incidence of foreign objects present in aircraft movement areas, maintenance at high locations on large aircraft impeded/slowed, snow removal and de-icing operations affected 

(1) OFCM. 2002. 

Lightning/Electrical Disturbance 

Disruption to transportation electronic infrastructure, signaling, etc. 

Risk to personnel from lightning, maintenance activity delays, rail and aircraft refueling operations delayed, track signal sensor malfunction resulting in possible train delays and stops, threats to barge tow equipment, communications and data distribution from pipeline sensors may fail 

(1) Wooler, Sarah. 2004. (2) Eddowes, M.J., et al. 20(3) OFCM. 2002. 

Fewer Winter Storms Less snow/ice for all modes Improved mobility/safety, reduced 

maintenance costs, less pollution from salt, decrease in vehicle corrosion 

(1) Andrey and Mills. 2003(2) Black, William. 1990. (3) Irwin and Johnson. 1990(4) Intergovernmental Panel 

(5) Barrett, et al. 2004. (6) Marbek Resource Consu(7) Kerr, Andrew, et al. 199(8) Warren, et al. 2004. (9) Entek U.K. Limited. 20(10) Land Use Consultants, e(11) Entek U.K. Limited. 20(12) Wooler, Sarah. 2004. (13) Kinsella, Y. and McGuir(14) Hyman, William, et al. (15) Pisano et al. 2002. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 1: Why Study Climate Change Impact

Table 1.1 Impacts of climate change on transportation identified in the literature, 1987-20

Climate Impact Potential Infrastructure Impact Potential Operations Impact Adaptation SIce MeltingReduced Ice Cover (Canada, Alaska, Great Lakes) 

Reduced ice loading on structures, such as bridges or piers 

(1) Instanes et al.. 2005. 

New northern shipping routes Shorten shipping distance and 

delivery time, security concerns, environmental risks, lawdiplomacy issues, Inuit unease 

Develop a “transit management regime” for area 

(1) Instanes et al.. 2005. (2) Johnston, Douglas. 2002(3) Brigham, Lawson and B(4) Office of Naval Research

Oceanographer of the Na

(5) National Assessment Sy(6) Marbek Resource Consu(7) Warren, et al. 2004. (8) Smith and Levasseur. 20(9) Caldwell et al. 2002. 

Lengthened season for float planes 

(1) Black, William. 1990. (2) Irwin and Johnson. 1990

Longer shipping season (1) Wooler, Sarah. 2004. 

(2) Andrey and Mills. 2003(3) Black, William. 1990. (4) Irwin and Johnson. 1990(5) U.S. Federal Highway A

Environment and Planni

(6) Sousounis, Peter J. and J(7) National Assessment Sy(8) Warren, et al. 2004. (9) Ruth, Matthais. 2006. (10) Caldwell et al. 2002. 

Multiyear ice, in low concentrations, will be hazard to ships and naval submarines 

New ship/submarine design or modifications 

(1) Brigham, Lawson and B(2) Office of Naval Research

Oceanographer of the Na

Earlier River Ice Breakup (United States, Canada) 

Ice-jam flooding risk (1) Instanes et al.. 2005. 

(2) Hass, et al. 2006. (3) Smith and Levasseur. 20

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Figures 

1F-1

Figure 1.1 Gulf Coast study design.

Conduct in-depth 

assessment of risks 

to transportation in 

selected locations

Develop tool(s) to 

assess adaptation

and response 

strategies

Impacts on safety, 

operations, and 

maintenance 

Identify and 

analyze adaptation

and response 

strategies 

Task 6

Evaluate/ 

recommend 

specific areas of 

Phase II Analysis

Task 1

Define region 

boundaries; 

organize expert 

panel

Implications 

for long-range 

plans 

Potential impacts 

on existing 

infrastructure 

Phase I

Phase III*

Phase II*

Task 4

Conduct 

preliminary risk 

and vulnerability 

assessment 

Products Detailed report

Integrated databases

and GIS maps 

Selected focus 

for preliminary 

assessment 

Final overview 

assessment report 

and Phase II 

recommendations 

Products

Summary of 

strategies 

Summary report and 

recommendations 

Products Assessment tool(s) 

Summary of 

long-range 

plans

Task 3 .

Characterize 

vulnerabilities 

and define

pilot location

Draft regional 

overview assessment 

report, conceptual 

framework, and risk 

factors ranking 

Task 2

Collect, synthesize, 

and integrate 

baseline data

Weather, climate, 

and other 

environmental 

trends and 

projections

Critical 

infrastructure 

locations data 

Economic data

Social, political, 

and demographic 

data

Develop risk 

assessment 

template 

Risk assessment 

template 

Identify additional 

research needs 

Identify techniques 

to incorporate 

environment/climate 

data in transportation 

decisions

Report on decision 

tools integration 

*Study design of Phases II and III will be refined based on findings of Phase I.

Task 5

Prepare review 

of existing 

literature 

Literature 

review
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 1: Why Study Climate Change Impacts on Transportation?: Figures 

1F-2 

Figure 1.2 Lexicon of terms used to describe the likelihood of 

climate outcomes. 

Source: Karl et al., 2006. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2.0 Why Study the Gulf Coast? 

Lead Authors: Virginia R. Burkett, Robert C. Hyman, Ron Hagelman, Stephen B. Hartley, 

and Matthew Sheppard 

Contributing Authors: Thomas W. Doyle, Daniel M. Beagan, Alan Meyers, David T. Hunt, 

Michael K. Maynard, Russell H. Henk, Edward J. Seymour, Leslie E. Olson, Joanne R. Potter, 

and Nanda N. Srinivasan 

 2.1 Overview of the Study Region 

2.1.1 Regional and National Significance 

The Phase I Study area includes 48 contiguous coastal counties in 4 States, running from 

the Galveston Bay region in Texas to the Mobile Bay region in Alabama. This region is 

home to almost 10 million people living in a range of urban and rural settings, contains 

some of the Nation’s most critical transportation infrastructure, and is highly vulnerable to 

sea level rise and storm impacts. 

This area has little topographic relief but is heavily populated. Given its low elevation and 

the regional climate, the area is particularly vulnerable to flooding and storm surges that 

accompany hurricanes and tropical storms – almost half of the Nation’s repetitive flood 

damage claims are paid to homeowners and businesses in this region. These effects may be 

exacerbated by global sea level rise and local land subsidence. 

In addition, the central Gulf Coast’s transportation modes are both unique and 

economically significant. The study area contains transportation infrastructure that is vital 

to the movement of passengers and a variety of goods domestically and internationally. 

Ports and pipeline infrastructure represent perhaps the most conspicuous transport modes in 

the region. Some of the Nation’s most important ports, such as the ports of HoustonGalveston, South Louisiana, and New Orleans are found in the study area. The Port of 

South Louisiana, for example, is a critical agricultural export center. Agricultural 

producers in the Midwest depend on the continued operation of this port to ship their 

products for international sale. Likewise, disruptions in the functioning of pipelines and 

fuel production and shipping facilities in the study region have broad domestic and 

international impacts. Roughly two-thirds of all U.S. oil imports are transported through 

this region, and pipelines traversing the region transport over 90 percent of domestic Outer 

Continental Shelf oil and gas. 

2-1
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

The importance of these marine facilities and waterways to the study area, and to the 

Nation as a whole, is difficult to overstate. These are vital National resources, providing 

essential transportation and economic services. While some of these functions could be 

considered “replaceable” by facilities and waterways elsewhere, many of them – by virtue 

of geography, connections to particular industries and markets, historic investments, or 

other factors – represent unique and largely irreplaceable assets. 

In addition to ports and pipelines, the study region contains critical air, rail, highway, and 

transit infrastructure. Passenger and freight mobility depend both on the functioning of 

each mode and the connectivity of the modes in an integrated transport network. The 

efficacy of evacuation during storms is an important determinant of the safety and wellbeing of the region’s population. The region sits at the center of transcontinental trucking 

and rail routes and contains one of only four major points in the United States where 

railcars are exchanged between the dominant eastern and western railroads. 

The region is experiencing a population shift from rural to urban and suburban areas. 

Much of the population inhabiting the study area, as well as the transportation 

infrastructure supporting them, reside in low-lying areas vulnerable to inundation and 

flooding. In addition, parts of the population face challenges that may make it more 

difficult for them to adapt to the conditions imposed by a changing climate, such as 

poverty, lack of mobility, and isolation. Some of Louisiana’s rural counties and the urban 

centers of New Orleans and Mobile County, AL, have particularly high proportions of 

vulnerable citizens. 

2.1.2 Study Area Boundaries 

This initial study focuses on the central portion of the low-lying Gulf of Mexico coastal 

zone. The study region extends from Mobile, AL, to Galveston, TX, as shown in 

figure 2.1. The study area encompasses all coastal counties and parishes along that stretch 

of the Gulf of Mexico as well as their adjacent inland counties (figure 2.2). In addition, the 

boundaries of the study area were extended so that all portions of Metropolitan Planning 

Organizations (MPOs) within a two-county swath of coastline would be included 

(figure 2.3). Table 2.1 provides the resulting list of counties and parishes included in the 

study area. 

[INSERT FIGURE 2.1: Map of study area] 

[INSERT FIGURE 2.2: Study area counties and Federal Information Processing Standard 

(FIPS) codes] 

[INSERT FIGURE 2.3: Metropolitan planning organizations in the study area] 

[INSERT TABLE 2.1: Study area counties and Federal Information Processing Standard (FIPS) 

codes] 

2-2 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2.1.3 Structure of This Chapter 

The following sections provide a more detailed overview of the central Gulf Coast study 

region, as follows: 

• Section 2.2 describes the transportation system in the study area; 

• Section 2.3 describes the physical setting and natural environment of the study area, 

including factors that make it more susceptible to climate change impacts; and 

• Section 2.4 discusses the social and economic setting, including factors that make 

portions of the population more vulnerable to climate impacts. 

 2.2 The Transportation System in the Gulf Coast Region 

The transportation network of the Gulf Coast study area comprises a complex system of 

multiple modes that enables both people and goods to move throughout the region and 

supports national and international transport. While roadways are the backbone of the 

region’s transportation system, the viability of the network as a whole depends on reliable 

service connections across all modes. Section 2.2.1 provides an introduction to passenger 

travel, freight transport, intermodal facilities, and emergency management in the Gulf 

Coast study area, while Section 2.2.2 provides an in-depth look at each of the 

transportation modes present in the region. Climate impacts to this transportation system 

are then discussed in Section 4.0. The transportation facility location information cited and 

shown in maps throughout the report is from the National Transportation Atlas Database 

(BTS, 2004). 

2.2.1 Overview of the Intermodal Transportation System in the Gulf 

Coast Region 

Passenger Travel 

Passenger travel in the Gulf Coast study area is accommodated by a variety of modes, 

including highway, transit, rail, and aviation. Roads are the most geographically extensive 

system in the study area, and autos traveling on the highways serve as the principal mode 

for passenger travel. Some of those highways, particularly I-10/I-12, serve substantial 

national travel that is passing through the study area. The 27,000 km (17,000 mi) of major 

highways within the study area comprise about 2 percent of the Nation’s major highways. 

These highways carry 134 billion vehicle km of travel (83.5 billion vehicle mi of travel) 

annually. 

Public transit provides an important function – particularly in urban areas – by carrying 

passengers more efficiently (in densely populated areas) than they could be carried in autos 

2-3
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

and thus relieving congestion. Further, transit provides essential accessibility to those 

passengers who do not own or cannot rely on autos for transportation. Lower-income 

workers rely heavily on city and intercity bus services for basic needs: getting to and from 

work, transporting children to school or childcare services, and shopping. The majority of 

transit ridership in the study area is carried by scheduled bus services. Other transit 

services available include light rail, ferries, and unscheduled paratransit vans and 

minibuses. 

Intercity passenger rail services are provided by the National Railroad Passenger 

Corporation (Amtrak), which operates three long-distance routes connecting the study area 

to other parts of the nation. Passenger rail services are not extensive, but they do supply an 

alternative mode of transportation and are important to certain segments of the population. 

Airports are critical in connecting local, regional, and national economies, as well as the 

global economy. Several major airports serve the larger cities of the study area; in 

addition, numerous airports outside of the major metropolitan markets serve smaller 

municipal markets, and many provide general aviation services. Smaller regional airports 

are critical infrastructure elements as they are often used for the movement of emergency 

medical supplies and patients. 

Freight Transport 

The Gulf Coast Study area is a critical crossroads for the Nation’s freight network, with 

marine, rail, pipeline, trucking, and air cargo all represented. A large portion of the 

Nation’s oil and gas supply originates in the study area, either as domestic production or 

imports. New Orleans provides the ocean gateway for much of the U.S. interior’s 

agricultural production and is a major interchange point for freight railroads. Products are 

shipped from the study area to points throughout the United States. Figure 2.4 depicts 

Federal Highway Administration (FHWA) Freight Analysis Framework data describing 

combined domestic truck flows originating in Louisiana (FHWA, 2004). 

[INSERT FIGURE 2.4: Combined truck flows shipped domestically from Louisiana] 

The pipeline network along the Gulf of Mexico coast is vital to the supply and distribution 

of energy for national use everywhere east of the Rocky Mountains. Approximately onehalf of all the natural gas used in the United States passes through or by the Henry Hub gas 

distribution point in Louisiana. The pipelines originating in this region provide a low-cost, 

efficient way to move oil and gas long distances throughout the United States. 

The study area also is home to the largest concentration of public and private freight 

handling ports in the United States, measured on a tonnage basis. These facilities handle a 

huge share – around 40 percent – of the Nation’s waterborne tonnage. The study area also 

hosts the Nation’s leading and third leading inland waterway systems (the Mississippi 

River and the Gulf Intracoastal Waterway) based on tonnage. The inland waterways 

traversing this region provide 20 States with access to the Gulf of Mexico, as shown in 

figure 2.5. 

[INSERT Figure 2.5 Navigable inland waterways impacting the study area, shown as named 

2-4 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

waterways] 

The rail links in the study area provide crucial connectivity to the national rail network for 

ports in the region and, via intermodal facilities, the major highway freight corridors. 

Figure 2.6 shows the network of major freight railroads nationwide, illustrating an obvious 

divide between the eastern railroads and the western railroads along the Mississippi River. 

New Orleans is one of four major gateways nationwide where the dominant eastern and 

western railroads interchange transcontinental shipments (Chicago, St. Louis, and Memphis 

are the others). At New Orleans, for example, CSX interchanges over 1,000 cars per day 

with the western railroads. A disruption to any of the four major gateways has implications 

for the entire U.S. rail network. 

[INSERT Figure 2.6 National network of Class I railroads] 

Intermodal Facilities 

Intermodal facilities are critical infrastructure facilities that enable the transfer of goods and 

passengers between different transport modes. These facilities are critical to transportation 

logistics processes and provide a key link in industrial and public sector supply chains. 

There are more than 100 intermodal facilities in the study area. Figure 2.7 shows the 

locations of these facilities in the study area, with coded symbols for the various mode 

combinations handled at each. Unsurprisingly, many of these facilities are clustered in the 

port and rail hubs of New Orleans and Houston. 

[INSERT Figure 2.7: Intermodal facilities in the study area] 

Emergency Management 

Interstates and arterial roadways provide the majority of the transportation infrastructure 

for emergency management and evacuation along the Gulf Coast. While public 

transportation facilities exist, they typically rely on the highway system; there are no large 

scale transit systems operating on separate right-of-ways. This substantial reliance on a 

single mode of transportation represents a risk if the highway infrastructure is damaged or 

made inaccessible during an emergency. 

Existing infrastructure may be able to handle local evacuations and diversions such as in 

the case of spilled hazardous material from a tanker truck or risk from a point source 

event – like a ruptured pipeline. However, network-wide roadway capacity is not designed 

nor built to handle large-scale evacuations or emergencies. Further, evacuation protocols 

require time-sensitive actions that existing roadway infrastructure cannot accommodate. 

The limitations of the existing infrastructure to accommodate a major evacuation during a 

broad-scale emergency were dramatically illustrated during the 2005 hurricane season. As 

Hurricane Rita demonstrated, evacuating a substantial portion of the population from a 

major metropolitan area is problematic and, in many ways, difficult to accomplish in a 

timely and orderly fashion. The “normal” condition of the already capacity-constrained 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-6 

transportation infrastructure does not allow for a major ramp-up of evacuation capabilities 

during daylight hours in major urban areas. 

Managing the transportation infrastructure and leveraging its available capacity is highly 

dependent upon: (1) means for gathering real-time traffic information and (2) robust and 

integrated communication systems that are consistent across regional jurisdictional 

boundaries. In this regard, the state of practice within the region varies considerably. 

Advanced transportation management systems such as the TranStar Traffic Management 

Center in Houston and a similar array of intelligent transportation system (ITS) 

technologies and a traffic control center in New Orleans represent relatively new and 

effective advancements in obtaining accurate real-time data upon which to base 

transportation system management decisions. On the other hand, the interagency and 

interjurisdictional communication systems in the Gulf Coast region are sometimes 

independent from one another, with multiple radio systems in use by emergency responders 

in each State. 

2.2.2 Modal Characteristics 

Highways 

Highway Network and Usage 

Highways provide the overwhelming majority of the public transportation infrastructure in 

the Gulf Coast study area. There are 28,154 centerline km (17,494 centerline mi) of 

highway in the study region (table 2.2, figure 2.8) (FHWA, 2005). Highway facilities in 

the Gulf Coast study area are primarily owned and operated by the state departments of 

transportation (DOT). Roads are classified as: 

• Interstates – Highways that are designated as part of the Dwight D. Eisenhower 

National System of Interstate and Defense Highways; 

• Arterials – Highways that provide longer through travel between major trip generators 

(larger cities, recreational areas, etc.); 

• Collectors – Roads that collect traffic from the local roads and also connect smaller 

cities and towns with each other and to the arterials; and 

• Local – Roads that provide access to private property or low-volume public facilities. 

Local roads serve mainly a land-access function, carry little of the demand for 

transportation compared to the Interstates and the arterial roadways, and are not included as 

part of the highways studied in this report.1

 State DOTs administer 100 percent of the 

 

(Footnote continued on next page...) 

1

 According to FHWA’s Highway Statistics, while local roads represent 75 percent of the miles of the 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-7

centerline miles on interstate highways, 60 percent of the centerline miles on arterial 

highways, and 50 percent of the centerline miles on collector highways. 

[INSERT Table 2.2: Gulf Coast study area centerline miles of highway, by classification and 

ownership] 

[INSERT Figure 2.8: Highways in the study area] 

The volumes on the interstate, arterial, and collector roads are primarily on the State-owned 

highways, to an even greater extent than that of centerline miles. Of the 83.5 billion annual 

vehicle miles of travel (VMT) in the study area, 63.7 billion (76.3 percent) of that travel is 

on State-owned nonlocal roads (FHWA, 2005). 

State-owned nonlocal roads carry an even larger share of truck volumes. As shown in 

figure 2.9, 92 percent of the truck VMT is on State roads. Additionally, while truck VMT 

is 7.5 percent of the total VMT, which compares closely to national truck percentages of 

volumes, trucks represent 9.1 percent (5.7 billion of 63.7 billion) of traffic on all Stateowned roads and 10 percent of the VMT (2.4 billion of 24.4 billion) of all traffic on Stateowned interstate highways (FHWA, 2005). 

[INSERT Figure 2.9: Total and truck annual vehicle miles of travel (VMT) on nonlocal roads, 

2003] 

Intermodal Connectors 

Access to intermodal facilities is most often provided by highways. Because this access 

function is critical to the viability of other modes, States have been given the authority to 

designate major intermodal passenger and freight terminals and the road connectors 

between these terminals and the National Highway System (NHS) as NHS intermodal 

connectors. The NHS intermodal connectors for the Gulf Coast study area were identified 

from an FHWA database (FHWA, 2006). The official listing of the NHS Intermodal 

Terminals and Connectors includes the following: 

• Ferries/Ports: 

− Five ferry terminals served by 25 intermodal connector segments totaling 478.2 km 

(297.1 mi); and 

− Twenty-three ports served by 54 intermodal connector segments totaling 380.9 km 

(236.7 mi). 

• Bus/Transit: 

− One intercity bus terminal served by 12 intermodal connector segments totaling 

 

Nation’s highways (Table HM-18), they carry less than 0.2 percent of the Nation’s vehicle miles of travel 

(VMT) (Table HM-44) (FHWA, 2005). 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

26.7 km (16.6 mi); 

− Two multipurpose passenger terminals served by nine intermodal connector 

segments totaling 13.0 km (8.1 mi); and 

− Eight public transit stations served by 14 intermodal connector segments totaling 

17.7 km (11.0 mi). 

• Railroads: 

− Two Amtrak stations (Houston and New Orleans) served by four intermodal 

connector segments totaling 3.9 km (2.4 mi); and 

− Thirteen rail freight terminals served by 23 intermodal connector segments totaling 

49.4 km (30.7 mi). 

• Pipelines: 

− Four pipeline terminals served by seven intermodal connector segments totaling 

30.7 km (19.1 mi). 

• Airports: 

− Six airports served by 24 intermodal connector segments totaling 44.7 km (27.8 

mi). 

Bridges 

Highway bridges are structures that carry the highway over a depression or an obstruction, 

such as water, a highway, or railway. As shown in figure 2.10 there are almost 8,200 

bridges that serve nonlocal roads in the study area. The overwhelming majority, 80 

percent, of those bridges are owned by the States. Of those State bridges, almost 80 

percent serve interstate or arterial highways. Seventy-five percent of the bridges in the 

study area pass over water, making them susceptible to scour of their piers by water runoff 

(FHWA, 2001). 

[INSERT Figure 2.10: Nonlocal bridges in the study area (National Bridge Inventory (NBI) 

latitude and longitude location)] 

Eighty-one percent of the bridge structures are concrete compared to 15 percent of the 

bridges which are steel, and 80 percent of the road surface on bridge decks are concrete 

compared to 16 percent that are asphalt (FHWA, 2001). 

Other Facilities 

While roads and bridges are the primary facilities that comprise the highway system in the 

Gulf Coast Study area, highway agencies own and operate many ancillary facilities 

necessary to operate and maintain the highway system. These facilities include 

maintenance buildings and facilities, truck weight and inspection stations, rest areas, toll 

2-8 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

booths, traffic controls/signs, luminaries, fences, guardrails, traffic monitoring equipment, 

etc. 

Transit 

The American Public Transportation Association (APTA) lists over 136 public transit 

providers that serve the Gulf Coast study area (APTA, 2005). Most of those providers 

offer transportation as a social service to elderly, disabled, or low-income passengers. 

These transit providers include 13 major transit agencies that receive funding from the 

Federal Transit Administration (FTA) and are included in the National Transit Database 

(NTD) (FTA, 2005). Statistical information on transit services in the study region have 

been drawn from this database. 

By far the largest transit networks in the study area are found in Houston and New Orleans. 

As an illustration, in 2003 the NTD listed Houston as having almost $88 million in 

citywide transit revenues and New Orleans with almost $35 million –while no other city in 

the study area topped $4 million. 

Fixed Guideway (Light Rail) 

There are three transit agencies that operate fixed guideway rail service in the Gulf study 

Area. Fixed guideway rail service carries passengers in vehicles moving on fixed light 

rails. The service operated by the Regional Transit Authority (RTA) in New Orleans and 

Metro in Houston consists of street cars operated by overhead power lines, over 47 km (29 

mi) and 27 km (17 mi) of routes, respectively. The service operated by Island Transit in 

Galveston consists of heritage streetcars powered by diesel and operated on rails, on 29 km 

(18 mi) of route. These light-rail services account for a relatively small portion of total 

transit passengers in the study area: the New Orleans light rail service carried 8.9 million 

passengers in 2004, Houston’s carried 5.4 million, and Galveston’s carried 40,000. By 

comparison, fixed-route bus services in the study area carried 10 times as many passengers 

in 2004 (FTA, 2005). 

Fixed-Route Buses 

Not including the ridership for HART/Hub City Transit (Hattiesburg, MS), Lake Charles 

Transit System, LA, and Saint Bernard Urban Rapid Transit which was not reported, fixedroute bus service in the Gulf Coast study area in 2004 carried 139 million passengers 

traveling 650 million passenger mi for an average trip length of 7.6 km (4.7 mi). 

Table 2.3 shows data on equipment, service levels, and ridership for fixed-route bus service 

of the 13 major transit agencies in the Gulf Coast study area. Houston’s Metro, New 

Orleans’ RTA, and Jefferson Transit provide a small portion of this service as Bus Rapid 

2-9
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-10 

Transit (BRT).2 A total of 586 route km (364 route mi) of BRT are provided in the study 

area, of which 558 km (347 mi) are in the Houston area (FTA, 2005). 

[INSERT Table 2.3: Equipment, annual service, and passengers for fixed-route bus operations 

in the study area, 2004] 

Paratransit 

Transit agencies also provide special services to elderly, disabled, and other disadvantaged 

passengers. These paratransit services are offered in addition to accessible service on the 

fixed routes and are typically offered in smaller buses or vans with door-to-door service for 

passengers on a demand-responsive, flexible schedule. Twelve agencies in the study area 

offer paratransit service annually carrying 2.3 million passengers over 24 million passenger 

mi for an average trip of 17.1 km (10.6 mi) per trip. By far the largest paratransit provider 

in the study area is Houston’s Metro, which accounts for 80 percent of the paratransit 

vehicles in the region, 64 percent of the passengers, and 69 percent of the passenger miles. 

Other Facilities 

In addition to transit vehicles and guideways, transit agencies may own other facilities to 

serve vehicles or riders. According to the 2004 NTD, within the Gulf Coast Study area 10 

transit agencies own 86 terminals and transfer stations. Those terminals are most numerous 

in the light-rail systems operated by the New Orleans RTA and the Houston Metro. Also 

included are the terminals associated with passenger ferries within the study area. 

Other facilities include vehicle maintenance facilities, of which the NTD lists six major 

facilities owned by six transit agencies. In addition, transit agencies also own numerous 

small passenger shelters and signs and other controls that are neither inventoried nor 

located in the NTD. 

Rail 

The Gulf Coast region has an extensive rail network, with east-west lines linking the 

southern United States, north-south lines paralleling the Mississippi River, and diagonal 

lines connecting the region to the northeastern and northwestern U.S. Six of the seven 

class I railroads in the United States serve the study region, along with several short 

lines.3,4

 These railroads support important regional industries, such as chemicals, paper, 

 

2

 i.e., scheduled bus service on fixed guideways or HOV lanes. 

3

 Railroad classification is determined by the Surface Transportation Board. In 2004, a class I railroad was 

defined as having $289.4 million or more in operating revenues. A class II railroad, often referred to as a 

regional railroad, was defined as a non-class I line-haul railroad operating 563 km (350 mi) or more with 

operating revenues of at least $40 million. Class III railroads, or short lines, are the remaining non-class I 

or II line-haul railroads. A switching or terminal railroad is a railroad engaged primarily in switching 

and/or terminal services for other railroads. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-11

lumber, and international trade. The Gulf Coast region also serves as a critical junction for 

national freight movements, with New Orleans serving as a major gateway between the 

eastern and western railroads (most rail freight using New Orleans infrastructure is 

interchanging rather than originating or terminating in New Orleans). 

Intercity passenger rail services are provided by the National Railroad Passenger 

Corporation (Amtrak). Amtrak operates nationwide routes through the region over track 

owned by the class I railroads. Passenger rail services are not extensive, but they do supply 

an alternative mode of transportation and are important to certain segments of the 

population. 

Freight Rail 

Six class I railroads operate in the study region: Burlington Northern Santa Fe (BNSF); 

Canadian National Railway (CN); CSX; Kansas City Southern Railroad (KCS); Norfolk 

Southern (NS); and Union Pacific (UP). 

Figure 2.11 shows the annual density of traffic on the rail lines in the Gulf Coast study 

region (BTS, 2004). The most densely used lines (60 million to 99.9 million gross tonmiles per mile per year [mgtm/mi]) are short segments in Houston, TX, and New Orleans, 

LA. In the 40 to 59.9 mgtm/mi category is part of the UP line between Houston and New 

Orleans, some segments around Houston, and the CSX line east of Mobile. The 20 to 

39.9 mgtm/mi range includes the remainder of the UP line into New Orleans, the CSX line 

between Mobile and New Orleans, the NS line into New Orleans, and several lines around 

Houston. 

[INSERT Figure 2.11: Freight railroad traffic density (annual millions of gross ton-miles per 

mile) in the study area] 

In addition to track infrastructure, there are 94 major freight facilities (owned and served 

by rail lines) in the study region, including rail yards, intermodal terminals, and 

transloading facilities.5

 These facilities originate and terminate rail traffic, reclassify 

inbound railcars to outbound trains for through traffic, and interchange railcars between 

railroads. They include facilities owned by the railroads and nonrailroad-owned facilities 

that depend on rail service, such as ports. Although these facilities can be found 

throughout the region, there are clearly two major hubs: New Orleans and Houston. 

 

4

 Canadian Pacific Railway is the only North American class I railroad not serving the study region. 

5

 A transloading facility handles “nonflowing” commodities transferred between railcars and trucks for 

customers without direct rail service. Examples include steel, lumber, and paper. A transflow facility 

handles “flowing” commodities transferred between railcars and trucks, such as corn syrup, petroleum 

products, and plastic pellets. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

Table 2.4 provides a more complete description of the railroads operating in the Gulf Coast 

study area, showing the geographical service area and primary commodities hauled by 

each. A complete list of freight rail facilities in the study area is provided in appendix C. 

[INSERT Table 2.4: Freight railroads in the Gulf Coast study area] 

Passenger Rail 

The National Railroad Passenger Corporation (Amtrak) offers three intercity passenger rail 

services in the Gulf Coast study Region: City of New Orleans, Crescent, and Sunset 

Limited. The City of New Orleans provides north-south passenger service between New 

Orleans, LA, and Jackson, MS, Memphis, TN, and Chicago, IL, over track owned by CN. 

The Crescent provides service between New Orleans, Atlanta, GA, Washington D.C., 

Philadelphia, PA, and New York City, NY. Both the City of New Orleans and the Crescent 

services travel north from New Orleans and have relatively little track mileage in the study 

area. 

The Sunset Limited, however, traverses a distance of 4,448 km (2,764 mi) between 

Orlando, FL and Los Angeles, CA, and makes stops throughout the Gulf Coast study 

region, as shown in figure 2.12. East of New Orleans, the service runs along the coast and 

has been indefinitely suspended since Hurricane Katrina occurred in 2005. However, even 

before Katrina, the Sunset Limited was one of the lowest ridership long-distance trains 

operated by Amtrak, with fewer than 100,000 passengers per year according to Amtrak 

ridership reports. A complete list of Amtrak stations in the study area is provided in 

appendix C. 

[INSERT Figure 2.12: Sunset Limited route map, Houston, TX – Mobile, AL segment] 

Marine Facilities and Waterways 

Freight Handling Ports and Waterways 

Ports can be comprised of a single facility or terminal, but most are actually made up of a 

mix of public and private marine terminals within a given geographic region along a 

common body of water. The U.S. Army Corps of Engineers identifies almost 1,000 public 

and private freight handling facilities throughout the study area, including different 

terminals within various defined port areas. These are mapped in figure 2.13. Major port 

complexes include, from west to east: 

• Port of Freeport, TX; 

• Ports of Houston, Texas City, and Galveston, TX; 

• Ports of Port Arthur and Beaumont, TX; 

• Port of Lake Charles, LA; 

2-12 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-13

• Mississippi River ports of Baton Rouge, South Louisiana, New Orleans, St. Bernard 

(included in the New Orleans district by the U.S. Army Corps of Engineers), and 

Plaquemines, LA; 

• Ports of Bienville, Gulfport, Biloxi, and Pascagoula, MS; and 

• Port of Mobile, AL. 

[INSERT Figure 2.13 Freight handling ports and waterways in the study area] 

Waterborne Freight Types and Volumes 

Table 2.5 shows that four of the top five ports in the United States, as measured by annual 

tonnage of goods handled by the port, are located in the study area. South Louisiana – at 

almost 199 million tons – is the Nation’s leading tonnage port, while Houston – at over 190 

million tons – ranks second. Collectively, study area ports handle almost 40 percent of all 

tonnage moved through all U.S. ports. 

The study area also includes 4 of the Nation’s top 30 container ports6, including Houston, 

TX (number 11), New Orleans, LA (number 19), Gulfport, MS (number 21), and Freeport, 

TX (number 30) (AAPA, 2004). 

Along with these fixed marine facilities, the study area hosts critically important navigable 

marine transportation networks. Among the most significant are the Gulf Intracoastal 

Waterway, a protected coastal route running from the Texas-Mexico border to Appalachee 

Bay in Florida; the Mississippi River and its tributaries; and the Tombigbee, Tennessee, 

and Black Warrior rivers, feeding the Mobile River in Alabama. These inland waterways 

and their associated lock structures (numbering in the hundreds) provide 20 States with 

access to the Gulf of Mexico, mostly through the Mississippi River and the TennesseeTombigbee River systems. Tonnage data (table 2.6) shows that largest volumes are on the 

Mississippi River (almost 213 million tons between Baton Rouge and New Orleans and 

116 million tons between New Orleans and the Gulf of Mexico) and the Gulf Intracoastal 

Waterway (almost 118 million tons) (Institute for Water Resources, 2003). In fact, these 

two systems comprise the Nation’s leading and third leading inland waterway systems by 

tonnage. Agriculture and other industries depend on efficient, reliable inland water 

transportation to move goods downriver to ports in Louisiana and Alabama, where goods 

are transloaded from domestic barges to international vessels. Petroleum, chemicals, and 

bulk products utilize the Gulf Intracoastal Waterway as an alternative to congested 

highway and rail corridors within the region. 

[INSERT Table 2.5: Domestic and international waterborne tonnage of study area ports, 2003] 

[INSERT Table 2.6: Tonnage on study area inland and coastal waterways, 2003] 

 

6

 Ports with the ability to load and unload container ships, and transfer the shipping containers to or from 

other modes of travel, usually rail or truck. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2-14 

[INSERT Figure 2.14: Barge tow on the Mississippi River] 

Key Commodities and Industries 

Overall, more than half of the tonnage (54 percent) moving through study area ports is 

petroleum and petroleum products – gasoline, fuel oil, natural gas, etc. This is not 

surprising, as the Gulf is a major petroleum producing and processing region, and an 

estimated 60 percent of U.S. petroleum imports passes through Gulf gateways. Of the rest, 

the majority – around 18 percent – is made up of food and farm products such as grains and 

oilseeds. Around 12 percent is chemicals, and the remaining commodities – around 

4 percent to 6 percent each – are crude materials, manufactured goods, and coal (Institute 

for Water Resources, 2003). 

There are important differences between ports in different parts of the study area. The 

Alabama and Mississippi ports specialize in coal, petroleum, manufactured (containerized) 

goods, and crude materials. In contrast, around 38 percent of tonnage through the 

Mississippi River ports consists of food and farm products, much of it related to the 

transloading of barge traffic from the Nation’s interior, with petroleum accounting for 

another 30 percent of tonnage. The western Louisiana and Texas ports are dominated by 

petroleum, which represents 75 percent of their tonnage. 

Nonfreight Marine Facilities 

The study area also hosts a large array of nonfreight maritime uses. The U.S. Army Corps 

of Engineers database lists around 800 nonfreight facilities (including unused berths) in the 

study area. These serve a variety of functions, including commercial fishing; vessel 

fueling, construction, repair, and outfitting (including shipyards); marine construction 

services (channel dredging and maintenance, construction of berths and other facilities); 

government and research facility docks; recreational and commercial vessel berthing; 

passenger ferry and cruise docks; and support for offshore oil facilities. 

Aviation 

The system of airports analyzed in the Gulf Coast Study includes 61 publicly owned, 

public-use airports. Private facilities are excluded from the sample as are the 387 heliports 

located in the study area.7

 Twenty-eight of these airports (more than 45 percent) are in 

Louisiana, 16 are in Texas, 9 are in Mississippi, and 8 are in Alabama. 

There are over 3,800 aircraft based at publicly owned, public-use airports in the study area. 

Over 3.4 million aircraft takeoffs and landings take place at these airports annually, with 

the majority of operations taking place at commercial service airports. 

 

7

 Heliports primarily serve hospitals, office buildings, and oil and gas industry facilities. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

Of these 61 airports, 44 are general aviation airports, 11 are commercial service, 4 are 

industrial, and 2 are military, as described below: 

• Commercial service airport (CS) – Commercial service airports primarily 

accommodate scheduled passenger airline service. Two Houston airports led the region 

in passenger enplanements in 2005 (George Bush Intercontinental Airport [IAH] and 

William P. Hobby [HOU]), followed by Louis Armstrong New Orleans International 

[MSY]. 

• Military airfield (MIL) – Military Airfields accommodate strictly military aircraft and 

are off limits to civilian aircraft. The two active military airfields in the study area are 

Keesler Air Force Base [AFB] in Mississippi and the New Orleans Naval Air 

Station/Joint Reserve Base. Keesler AFB is notable for being the home of the 53rd

Weather Reconnaissance Squadron, the “Hurricane Hunters,” who fly aircraft into 

tropical storms and hurricanes to gather weather data. 

• Industrial airport (IND) – Industrial airports are airports that can accommodate both 

commercial and privately owned aircraft. Typically, an industrial airport is used by 

aircraft service centers, manufacturers, and cargo companies, as well as general 

aviation aircraft. The four industrial airports in the study area are former military 

airfields, designed to accommodate the largest aircraft. None of them have scheduled 

passenger service. 

• General aviation airport (GA) – General aviation airports accommodate aircraft 

owned by private individuals and businesses. 

In addition to leading the region in passenger enplanements, George Bush Intercontinental 

IAH in Houston also is the leading airport in the study area for cargo tonnage, processing 

75 percent of all cargo enplaned in the study area. It ranks 17th nationally for cargo, with 

387,790 annual tons (ACI, 2005). Louis Armstrong New Orleans International ranked 

second for cargo, followed by Mobile Downtown, an industrial airport. 

Table 2.7 details the passenger enplanements and cargo tonnage for the major study area 

airports. Figure 2.15 identifies the location of airports in the study area. 

[INSERT Table 2.7: Passenger enplanements and cargo tonnage for select commercial service 

and industrial airports in the study area, 2005] 

[INSERT Figure 2.15: Study area airports] 

Pipelines 

The pipeline system in and around the Gulf Coast is a major transporter of gas, petroleum, 

and chemical commodities. It links many segments of the country with energy sources 

located on the Gulf Coast. Unlike other transportation systems, pipelines are singularly a 

transportation system for bulk commodities that have little or no time sensitivity for 

product delivery. The entire pipeline network is privately funded and held. The onshore 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

portion is principally regulated by the Office of Pipeline Safety (OPS), within the United 

States. Department of Transportation, Pipeline and Hazardous Materials Safety 

Administration (PHMSA). Regulation focuses on safe operations to protect people, the 

environment, and the national energy supply. Off-shore pipelines are regulated by the U.S. 

Department of the Interior, Minerals Management Service. 

There is a total of 42,520 km (26,427 mi) of onshore liquid (oil and petroleum product) 

transmission and natural gas transmission pipelines in the Gulf Coast area of study, with 

some extended sections beyond its boundaries. This includes 22,913 km (14,241 mi) of 

onshore natural gas transmission pipelines and 19,607 km (12,186 mi) of onshore 

hazardous liquid pipelines (PHMSA, 2007). The liquid pipelines are concentrated in Texas 

while the natural gas pipelines are concentrated in Louisiana. 

Approximately 49 percent of U.S. wellhead natural gas production either occurs near the 

Henry Hub, which is the centralized point for natural gas futures trading in the United 

States, or passes close to the Henry Hub as it moves to downstream consumption markets. 

The Henry Hub is located near the town of Erath in Vermilion Parish, LA. The Henry Hub 

interconnects nine interstate and four intrastate pipelines, including: Acadian, Columbia 

Gulf, Dow, Equitable (Jefferson Island), Koch Gateway, LRC, Natural Gas Pipe Line, Sea 

Robin, Southern Natural, Texas Gas, Transco, Trunkline, and Sabine’s mainline. 

 2.3 Gulf Coast Physical Setting and Natural Environment 

The unique natural environment and geology of the Gulf Coast study region brings its own 

set of considerations and challenges in designing the built environment. Some of these 

physical characteristics, such as low topography, high rates of subsidence, and predilection 

for coastal erosion, significantly increase the vulnerability of the area to climate change 

impacts. A robust transportation system must accommodate the natural features of this 

landscape. 

A variety of physical datasets were compiled for phase I of the Gulf Coast study and posted 

on a Web site for review and use by the project research team (appendix A). Most of the 

spatial data is organized in GIS-type formats or “layers” that can be integrated for the 

purposes of assessing the vulnerability and risks of the transportation infrastructure in the 

study area and informing the development of adaptation strategies in phases II and III of 

the study, respectively. Examples of the spatial data products developed for the study are 

presented in the following sections. 

2.3.1 Geomorphology 

The Gulf Coast region of the United States is in the physiographic province called the 

southeastern Coastal Plain, which is a broad band of territory paralleling the Gulf and 

South Atlantic seacoast from North Carolina to Texas, with a deep extension up the 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

Mississippi River valley. The Coastal Plain is relatively flat, with broad, slow-moving 

streams and sandy or alluvial soils (figure 2.16). 

Much of the land area in the Coastal Plain is overlain with sediments deposited during the 

Holocene or Recent Age epoch, i.e., during the past 10,000 years. The remainder of the 

Coastal Plain surface consists primarily of late Cretaceous deposits (65 to 100 million years 

old). These sedimentary rocks, deposited mostly in a marine environment, were later 

uplifted and now tilt seaward; part of them form the broad, submerged Continental Shelf. 

Coastal Plain deposits overlap the older, more distorted, Paleozoic and Precambrian rocks 

immediately to the north and west (more than 250 million years old) (U.S. Geological 

Survey [USGS], 2000a). 

The center of the study area is dominated by the Mississippi Embayment, a geologic 

structural trough in which the underlying crust of the Earth forms a deep valley that 

extends from the Gulf Coast inland to the confluence of the Ohio and Upper Mississippi 

Rivers. The Lower Mississippi Valley occupies the center of the inland part of the 

embayment and ranges from 30– to 180–km (20–to 110–mi) wide. Large rivers, such as 

the Mississippi, Arkansas, and Ohio Rivers, have flowed through this region, carved the 

surface, and deposited clay, silt, sand, and gravel, collectively called alluvium. 

Nearly annually, the Mississippi River and its tributaries flood vast areas of the lower 

alluvial valley. Traditionally, these floods have lasted for several months and a few for 

even longer periods. For example, the great flood of 1927 occurred from April to June 

when the lower Mississippi River system stored the equivalent of 60 days of discharge in 

its 22–million-acre alluvial valley. The river flows through the Lower Mississippi River 

Valley in a 15- to 30-km (10- to 20-mi) wide meander belt, and historical and prehistoric 

records indicate the river is continually creating new channels and abandoning old ones. 

The alluvium provides the rich soils for massive agricultural development. 

Where the Mississippi River empties into the Gulf of Mexico, old deltas are abandoned and 

new ones formed. This Mississippi River deltaic plain lies at the center of the Gulf Coast 

study area. During the formation of the deltaic plain, millions upon millions of tons of 

sediment were deposited in a series of overlapping delta lobes that are presently in various 

phases of abandonment and deterioration. The barrier island chains off the coast of 

Louisiana are remnant features of old deltas that are naturally eroding and retreating 

landward as sea level rises. Erosional forces dominate this part of the central Gulf Coast 

landscape. 

[INSERT FIGURE 2.16: Surface geology of the southeastern United States.] 

Due largely to its sedimentary history, land along the central Gulf Coast tends to be low 

and flat and is dissected by numerous slow-moving streams or bayous that drain runoff 

from the Coastal Plain and the adjacent uplands. The central Gulf coastal zone includes 

many barrier islands and peninsulas, such as Galveston Island, TX, Grand Isle, LA, and the 

land between Gulfport and Biloxi, MS. These landforms protect numerous bays and inlets. 

The low-lying areas of the central Gulf Coast region are (or were) primarily marshland and 

wetland forests. 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

Erosion, sediment transport and deposition, and changes in elevation relative to mean sea 

level (i.e., subsidence, discussed in greater detail below) are the main land surface 

processes that interact with climate change and variability in a manner that could adversely 

affect transportation in the study area. Erosion is exacerbated by increased water depth, 

increased frequency or duration of storms, and increased wave energy – and all of these 

changes could potentially accompany an increase in the temperature of the atmosphere. 

2.3.2 Current Elevation and Subsidence 

The great majority of the study area lies below 30 meters in elevation (figure 2.17) (USGS, 

2004). Due to its low relief, much of the central Gulf Coast region is prone to flooding 

during heavy rainfall events, hurricanes, and lesser tropical storms. The propensity for 

flooding is higher in areas that are experiencing subsidence (i.e., the gradual lowering of 

the land surface relative to a fixed elevation). Near the coastline, the net result of land 

subsidence is an apparent increase in sea level. 

Land subsidence is a major factor in the study region. The rate of subsidence varies across 

the region and is influenced by both the geomorphology of specific areas as well as by 

human activities. Parts of Alabama, Texas, and Louisiana are experiencing subsidence 

rates that are much higher than the 20th–century rate of global sea level rise of 1-2 mm/year 

(IPCC, 2001). For example, in the New Orleans area the average rate of subsidence 

between 1950 and 1995 was about 5 mm/year (Burkett et al., 2003), with some levees, 

roads, and artificial-fill areas sinking at rates that exceed 25 mm/year (Dixon et al., 2006). 

As a result of subsidence, which was accelerated by the forced drainage of highly organic 

soils and other human development activity, most of the city of New Orleans is below sea 

level. 

[INSERT FIGURE 2.17: Relative elevation of study area counties (delineated in blue)] 

Subsidence in the Houston-Galveston-Baytown region is associated primarily with 

groundwater withdrawals, which peaked in the 1960s. By the mid 1970s, industrial 

groundwater withdrawals had caused roughly two meters of subsidence in the vicinity of 

the Houston Ship Channel, and almost 8,300 km2

 (3,200 mi2) of land in this region had 

subsided more than one foot. The growing awareness of subsidence-related flooding in 

southeastern Texas prompted the 1975 Texas Legislature to create the Harris-Galveston 

Coastal Subsidence District, which was authorized to regulate ground water withdrawals 

and promote water conservation programs (Coplin and Galloway, 1999). Shallow oil and 

gas withdrawals also have contributed to subsidence in southeast Texas (Coplin and 

Galloway, 1999) and coastal Louisiana (Morton et al., 2005). Recent geological and 

geophysical investigations suggest that subsidence across the Central Gulf Coast is 

occurring more rapidly than previously thought (Shinkle and Dokka, 2005; Dixon et al., 

2006). 

Recognizing the increasing trend in flooding in the region, the Federal Emergency 

Management Agency (FEMA) currently is updating its Base Flood Elevations Maps of the 

region. However, even new elevation maps can be outdated within just a few years due to 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

the high rates of subsidence in some parts of the study area (American Geophysical Union 

[AGU], 2006). 

While the Gulf Coast is considered at very low risk for earthquakes, it does have hundreds 

of subsurface faults that can be expressed at the surface by differences in elevation, by the 

zonation of plant communities, or by patterns of wetland loss (Morton et al., 2005). 

Generally, these faults run parallel to the shoreline and are displaced “down to the coast” 

due to the slow sliding of thick sediments towards the Gulf of Mexico. Subsidence and 

subsurface fluid withdrawals can activate shallow faults and cause ground failure along 

highways and beneath buildings. Since the late 1930s, 86 active faults in the HoustonGalveston area have offset the land surface by slow seismic creep at rates of up to 2.5 cm 

per year (Holzer and Gabrysch, 1987; Coplin and Galloway, 1999). 

2.3.3 Sediment Erosion, Accretion, and Transport 

The northern Gulf of Mexico coastal zone is highly dynamic due to a unique combination 

of geomorphic, tectonic, marine, and atmospheric forcings that shape both the shoreline 

and interior land forms. Most of coastline of the study area is classified as “highly 

vulnerable” to erosion (Theiler and Hammar-Close, 1999). The retreat of shoreline of the 

reticulated marshes that dominate much of the coastal zone is often translated to “wetland 

loss,” which occurs via submergence of land or erosion of the land/water interface. 

Highest erosion and wetland loss rates are associated with tropical storms and frontal 

passages. It is estimated that 56,000 ha (217 mi2) of land were lost in Louisiana alone 

during Hurricane Katrina (Barras, 2006). 

The barrier islands of the central Gulf Coast region are shaped continually by wind and 

wave action and changes in sea level, including the short-term increase in sea level 

associated with storm surge. The Chandeleur Islands, LA, which serve as a first line of 

defense for the New Orleans region, are extremely vulnerable to intense tropical storms, 

having lost 85 percent of their surface area during Hurricane Katrina (USGS, 2007). As 

barrier islands and mainland shorelines erode and submerge, onshore facilities in low-lying 

coastal areas become more susceptible to inundation and destruction. Many Gulf Coast 

barrier islands are retreating and diminishing in size, with the most significant breaching 

and retreat occurring during storms and frontal passages. The combined effects of beach 

erosion and storms can lead to the erosion or inundation of other natural coastal systems. 

For example, an increase in wave heights in coastal bays is a secondary effect of sandy 

barrier island erosion in Louisiana where increased wave heights have enhanced erosion 

rates of bay shorelines, tidal creeks, and adjacent wetlands (Stone and McBride, 1998; 

Stone et al., 2003). 

Theiler and Hammar-Close (1999) assessed the relative importance of six variables that 

influence coastal erosion rates and developed a coastal vulnerability index (CVI) for the 

Gulf Coast region. Their analyses indicated that geomorphology and tide range are the 

most important variables in determining the CVI for the Gulf of Mexico coast, since both 

variables reflect very high vulnerabilities along nearly the entire shoreline. Wave height, 

relative sea level rise, and coastal slope explain the large-scale (50-200 km alongshore) 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

variability of erosion rates. They concluded that erosion and accretion rates contribute the 

greatest variability to the CVI at short spatial scales. Rates of shoreline change, however, 

are the most complex and poorly documented variable in this dataset developed by the 

USGS. To best understand where physical changes may occur, large-scale variables must 

be clearly and accurately mapped, and small-scale variables must be understood on a scale 

that takes into account their geologic and environmental influences. Marshes that receive 

sufficient inputs of mineral or organic sediments, for example, can offset the potential for 

submergence due to subsidence and sea level rise (Rybczyk and Cahoon, 2002). 

Sediments eroded by winds, tides, and waves are transported generally towards shore and 

continually reworked into a mosaic of wetlands, shallow bays, and barrier islands. Some 

sediments, however, are lost to the Gulf or deposited along the shoreline to the east or west 

of the study area. Nearshore currents east of the mouth of the Mississippi River carry 

sediments eastward. To the west of the Mississippi River delta, the predominant direction 

of this nearshore drift is westward. 

At the geographic center of the study area, the Mississippi River alluvial or deltaic plain 

has been built on the continental shelf during the past 6,000 years, during a period of 

relatively slow sea level rise when most of the world’s present deltas were formed 

(Woodruffe, 2003). In recent times, sediments that would be delivered to the Mississippi 

River delta marshes via seasonal overbank flooding have been cut off by levees and deep 

channel dredging of the Mississippi River for navigation (Reed, 2002). Thousands of miles 

of smaller navigation channels, access canals to oil and gas fields, and other development 

activities have contributed to the vulnerability of the Mississippi River deltaic plain to 

sediment deprivation and land loss (Minerals Management Service [MMS], 1994).

2.3.4 Land Use and Land Cover 

Land use of the Gulf Coast study area was defined by using the National Land Cover 

Dataset (NLCD). The NLCD consists of 21 classifications, of which 19 were found in this 

study area. The data were collected from the Landsat Thematic Mapper satellite in the 

early to middle 1990s and are of 30–meter resolution. Table 2.8 summarizes this data for 

the study area. 

The central Gulf Coast study area covers an area of approximately 1 million ha (23.4 

million acres or 36,485 mi2

). Land cover is dominated by wetlands (32.4 percent), 

agriculture (19/1 percent), and upland forests (17.7 percent). The study area can be broadly 

divided into six ecological units based on Bailey’s classification of U.S. ecoregions 

(Bailey, 1976) (figure 2.18). Land cover within the study area has strong similarities from 

east to west across the study area and appears to be influenced more by soils, topography, 

and human activity than by climatic differences. Natural plant community distributions are 

generally oriented along north/south gradients, reflecting salinity, water level, and 

disturbance regimes. 

Nonurbanized land use in the region is devoted mainly to Federal/State protected lands, 

large-scale commercial agriculture, and relatively undeveloped wetlands associated with 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

the Mobile River in Alabama; the Pearl River in Mississippi and Louisiana; the 

Mississippi, Atchafalaya, and Calcasieu Rivers in Louisiana; and the Neches, Sabine, and 

Trinity Rivers in Texas. In addition to contributing to the formation of wetlands running 

inland from the coast, each of these rivers intersects or connects with the Gulf Intracoastal 

Waterway, and each forms the basis for urbanized port areas, of varying sizes, adjacent to 

the coast. 

[INSERT Table 2.8: Land use of the central Gulf Coast study area as defined by the 1992 

National Land Cover Dataset] 

[INSERT Figure 2.18: Map of terrestrial ecoregions within and adjacent to the study area] 

 2.4 Social and Economic Setting 

Transportation networks exist to facilitate the movement of people and goods and are an 

integral part of a region’s social and economic fabric. The need for these networks, or 

transportation demand, therefore, is defined by demographic and economic 

considerations – connecting population centers, providing access to economic resources, 

etc. It is important, therefore, to understand the people and the economy that exist in the 

Gulf Coast study region in order to assess the significance of climate impacts on its 

transportation systems. 

The Gulf Coast study region, like many parts of the country, has been growing in 

population and economic activity and has become increasingly urbanized in recent decades. 

These trends were seriously disrupted by the 2005 hurricanes, which caused massive 

property damage and wide-scale relocation of residents in affected areas. It is too early to 

know what long-term impacts Hurricanes Katrina and Rita will have on the region’s 

population distribution. 

According to the U.S. Census Bureau estimates for 2004, the 48 counties of the designated 

study area are home to about 9.7 million people. Within the region are 419 cities, towns, 

and villages (defined as “places” by the U.S. Census Bureau), ranging in population from 

less than 50 residents to nearly 2 million. A quick perusal of the interstate and highway 

map illustrates, to some degree, the interconnectedness of the region. The majority of these 

places are served by a vast land- and water-based transportation grid designed to move 

people and goods eastward and westward along the coast, as well as into and out of the 

United States via Gulf of Mexico port facilities. 

Figure 2.19 illustrates the degree to which urbanized zones have spread throughout the 

study area. Population growth and industrialization in the region are continuing to urbanize 

the central coast of the Gulf of Mexico. Nonetheless, major contrasts remain among urban, 

suburban, and rural settings within the region. 

Mean household income for the study area population was lower than for the nation 

($53,600 per household compared to $56,500 in the Nation). The study region also 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

experiences higher poverty rates (15.6 percent of all persons compared to 12.4 percent in 

the Nation), and higher rates of children below 5 years living in poverty (17.4 percent 

compared to 12.5 percent nationally). The demographic distribution showed a slightly 

younger population when compared to the Nation (52.8 percent of the population was less 

than 35 years, compared to 49.3 percent nationwide). 

[INSERT FIGURE 2.19: U.S. Census Bureau Metropolitan Statistical Areas in study area] 

2.4.1 Population and Development Trends 

Before the impacts of the hurricanes in 2005 were fully realized, the region had 

experienced an average population growth rate from 1990 to 2000 of 16 percent, with an 

additional 5 percent growth estimated for the period from 2000 to 2004 (figures 2.21 and 

2.22). Measured in terms of building permits issued, the region has experienced an overall 

housing growth rate of 12 percent during the period of 1997 to 2002. However, a wide 

variation in growth rates exists among counties in the study area, including 17 counties 

(primarily rural) that have experienced declines in building permit issuance over this 

period. 

[INSERT FIGURE 2.20: Population density in study area, 2004] 

[INSERT FIGURE 2.21: Estimated population change in study area, 2000 to 2005] 

Population and housing growth patterns for the region are dominated by urban-rural 

migration and the increasing suburbanization of the larger urban areas of 

Houston/Galveston, TX, Baton Rouge/New Orleans, LA, Hattiesburg, MS, and Mobile, 

AL. Rural counties along the western and central portions of the Louisiana coast, which 

tend to be dominated by wetland landscapes of the Atchafalaya and Mississippi Rivers, 

have experienced low and/or declining population growth over this period. These counties 

primarily host agricultural economies, and, like many similar rural counties in the United 

States, they have been experiencing slowly declining population growth rates for many 

decades. 

Urban growth has been primarily characterized by spatial expansion around existing 

urbanized areas. In the case of Houston/Galveston, growth has been focused on those 

counties surrounding the core county of Harris, especially due to the residential and 

commercial expansion along I-10 to the west and I-45 to the south and east. The Baton 

Rouge/New Orleans area is experiencing a similar suburbanization process focused on the 

“Northshore” of Lake Pontchartrain. This growth in “bedroom” communities on the 

Northshore is supported by commuter pathways along I-12 and I-10 and the Lake 

Pontchartrain Causeway. Baton Rouge continues to grow eastward toward these 

Northshore counties, and the New Orleans metro area has been undergoing the same crosslake residential migration for many years. One of the numerous impacts of Hurricane 

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Chapter 2: Why Study the Gulf Coast? 

2-23

Katrina appears to be an acceleration of this trend among residents of Orleans and 

St. Bernard Counties,8 as many residents are finding the Northshore communities more 

affordable or attractive despite the greater commute into New Orleans. Mobile, AL, 

appears to be experiencing a similar pattern of suburbanization as the greatest growth is 

taking place in the less densely populated county of Baldwin east of Mobile Bay. 

Figure 2.22, “Mean Travel Time to Work,” illustrates this trend toward suburbanization in 

the region. 

[INSERT FIGURE 2.22: Mean travel time to work in study area] 

It is still too early to know what the long-term impacts of Hurricane Katrina will be on 

regional demographics. Some locations, particularly New Orleans, experienced major 

shifts. According to the 2005 American Community Survey Special Product for the Gulf 

Coast Area (U.S. Census Bureau, 2005), in the months following the storm, the New 

Orleans Metropolitan Statistical Area [MSA] showed a 30 percent drop in population, 

accompanied by a nearly 4-year increase in median age (from 37.7 years to 41.6 years). 

The civilian labor force dropped from nearly 600,000 to about 340,000. The survey 

measured higher median incomes for those remaining, indicating that more higher-income 

workers in relatively stable professions have tended to stay in place, while lower-income, 

low-skilled workers have been more likely to relocate. Many people moved to other 

locations within the study area, such as the Houston-Galveston and Baton Rouge areas, 

while others left the study area entirely. 

2.4.2 Employment, Businesses, and Economic Drivers 

Energy production, chemical manufacturing, and commercial fishing dominate the 

economy of the study region. While the economy in the overall area has grown, certain 

parts of the region have not shared in this development. Table 2.9 shows the top 10 

industries in the study area by employment, according to the 2000 Census (U.S. Census 

Bureau, 2007). On the whole, these mirror national-level census results. Differences 

include a smaller share of workers employed in manufacturing (11.6 percent in the study 

region, compared to 14 percent in the Nation) and a larger share in construction (8.6 

percent in the Gulf Coast area compared to 6.8 percent in the Nation). In addition, a much 

larger share of study area workers are employed in extraction industries (2.2 percent in the 

study area, versus 0.3 percent nationally). 

[INSERT TABLE 2.9: Top 10 industries in the study area by employment percentage, 2000] 

The study region is host to nationally significant concentrations of several industries: 

• Oil and natural gas production and refining – Much of the U.S. domestic oil 

 

8

 The U.S. Census Bureau term “County” is used here for consistency in Louisiana, rather than the more 

common term “Parish.” Both indicate the same political unit. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

production is supported by facilities in the Gulf of Mexico region – fixed oil platforms 

and mobile rigs, transportation systems, refineries, storage facilities, and distribution 

systems. An estimated 60 percent of all U.S. energy imports come through port 

facilities in the Gulf of Mexico region. 

• Chemical and petrochemical manufacturing – Due to the presence of petroleum and 

natural gas supplies and infrastructure, the Gulf is a leading center for the U.S. 

chemical industry, which generally relies on expensive investments in fixed 

infrastructure. 

• Commercial fishing – This is a multibillion dollar industry that is critical to the 

economies of many Gulf States. 

As of 2003, the study area hosted approximately 214,768 private business establishments 

employing approximately 3,691,883 employees. The region experienced a 4 percent 

growth both in the number of establishments during the period from 1998 to 2003, and in 

the total number of employees. Despite this overall growth, certain counties have 

experienced decline and/or stagnation in businesses development. The growth versus 

decline patterns very closely match the same patterns as the population and housing 

discussed earlier, with suburbanizing counties on the periphery of the larger urban areas 

realizing most of the growth. Most notable again are the counties currently expanding 

westward and southward around Houston/Galveston, TX, west of Baton Rouge, LA, the 

counties of Louisiana’s Northshore area, and Baldwin County west of Mobile Bay, AL. 

Orleans and Jefferson Counties, LA, (constituting the bulk of metro New Orleans) again 

stand out as having a relatively high rate of business decline in recent years, while the 

counties to the east and north have flourished. 

Most rural counties have experienced decline or stagnation in terms of total businesses and 

total employees. These patterns again reflect the overall development and growth that is 

characterized by suburbanization in the region. In some areas, this trend may be more 

related to technological change in agriculture or petroleum extraction methods than a true 

decline in the general economy. 

Counties with port facilities or Mississippi River access dominate the manufacturing 

shipments measured in dollar amounts (figure 2.23). Retail sales patterns, on the other 

hand, exhibit a less rational spatial pattern and seem to be tied to idiosyncratic changes in a 

small sample of counties. For instance the county of Waller, TX, in the farthest 

northwestern corner of the Houston area, registers a top value in terms of retail sales but a 

low value in terms of manufacturer’s shipments. Much of this can be explained by the 

establishment of the Katy Mills Mall, which has caused the county to develop from one 

dominated by agriculture and industry to one based on a growing retail economy in recent 

years. Small-scale changes in the economic structure or productivity of specific sectors 

may be behind other local trends. 

[INSERT FIGURE 2.23: Manufacturers shipments in thousands of dollars, 1997] 

2-24 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

2.4.3 Societal Vulnerability 

Social vulnerability measures are important both as general background to the regional 

demographics but also to understand implications for future infrastructure needs and for 

emergency management. In this case, vulnerability refers to the inability of a social group 

to respond to, adapt to, or avoid negative impacts resulting from extreme or significant 

long-term deviations from average environmental conditions. 

Generally, vulnerability assessments are conducted in respect to a single risk or hazard 

(flooding, radioactive release, drought, hurricane evacuation, etc.). For this study, the 

“hazards” are the anticipated impacts of climate change and variability, specifically as it 

relates to transportation interests. Since this encompasses multiple changes over a 

protracted time period, it is difficult, at this spatial and temporal scale, to comprehensively 

measure those features of the current social landscape that will be most vulnerable to future 

changes as they occur. Therefore, numerous social measures were included in this analysis 

in an effort to describe the most general patterns of vulnerability. The attributes included 

in this social vulnerability index are: 

1. Percent persons reporting disabilities for civilian noninstitutionalized population five 

years and over; 

2. Percent total population: Age 14 and below; 

3. Percent total population: 65 years and over; 

4. Percent households: Two-or-more-person household; family households; maritally 

single; with own children under 18 years; 

5. Percent households: All languages; linguistically isolated; 

6. Percent population 25 years and over: No high school graduate (includes equivalency); 

7. Percent below study area median household income in 1999; 

8. Percent households: With public assistance income; 

9. Percent population for whom poverty status is determined: Income in 1999 below 

poverty level; 

10. Percent housing units: Mobile home; 

11. Percent housing units: Built 1969 or earlier; 

12. Percent occupied housing units: No vehicle available; 

13. Percent occupied housing units: Renter occupied; 

14. Specified owner-occupied housing units: Percent below study area median value; and 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

15. Specified owner-occupied housing units: Percent housing units with a mortgage; 

contract to purchase; or similar debt; with either a second mortgage or home equity 

loan, but not both. 

To illustrate how these multiple attributes can be agglomerated, these 15 measures were 

subjected to an indexing process to create a continuum of vulnerability at both the countyand block-group scale (most vulnerable, more vulnerable, less vulnerable, and least 

vulnerable). In future phases of this research, particularly for in-depth analysis of one site, 

the attributes included in this index can be changed or statistically weighted in response to 

particular transportation management or other concerns at that site. Figure 2.24 maps this 

vulnerability index for the study region. Maps depicting conditions within the region for 

each of the 15 societal attributes are contained in appendix B. 

A number of patterns emerge from these measures of vulnerability. The first is the obvious 

pattern of counties with high degrees of social vulnerability expressed in the central portion 

of the Louisiana section of the study area. These counties correspond with the physical 

feature of the Atchafalaya River valley, the western portions of the Mississippi River 

valley, and the wetland landscapes produced by both. One can interpret from this analysis 

that these populations, if faced with extreme changes in their physical environments, will 

find coping with those changes extremely difficult. Many of these counties are 

traditionally rural, impoverished areas (figure 2.25). Also included is the urban-core 

county of Orleans, which ranks extremely high on many of the vulnerability measures 

included here. 

However, poverty alone does not explain the higher rankings. These counties also tend to 

rank high in presence of disabled populations, persons over 65 (figure 2.26), absence of a 

vehicle per household, presence of single parents, linguistic isolation, and a number of 

other attributes. It can be argued that these are all dimensions of impoverishment. 

However, it is not the simple fact that a person is poor that makes them vulnerable; rather it 

is the context that widespread poverty can create in terms of public services, durability of 

infrastructure, access to egress, etc., acting together that make a community vulnerable to 

extreme environmental change. 

To a lesser degree, this pattern of vulnerability extends southeastward into the delta region 

of central Louisiana. Other counties with similar characteristics outside central Louisiana 

tend to be rural and tertiary to urban-suburban growth. Exceptions to this statement are the 

heavily industrialized counties around Beaumont and Port Arthur, TX, Lake Charles, LA, 

and St. Bernard County, LA. The rapidly urbanizing county of Mobile, AL, also falls into 

this category of vulnerability. 

Counties that tend to have fewer vulnerability characteristics are those on the periphery of 

large urban areas that were described earlier as undergoing the fastest rates of 

suburbanization. Again, this trend is tied heavily to overall income patterns but is not fully 

explained by that single attribute. For instance, these counties also tend to have higher 

rates of children per capita and more manufactured housing. It can be assumed that, at 

least for the time being, the populations of these counties will be better prepared to cope 

with the negative impacts of extreme environmental change. 

2-26 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

From a transportation perspective, it also might be assumed that these areas will have 

special needs for transportation infrastructure in coming years. Vulnerable areas may need 

more services and infrastructure in the future to help them reduce their vulnerability – and 

to cope with destructive natural events – such as severe storms – as they occur. 

[Insert Figure 2.24: Social vulnerability index for study area] 

[Insert Figure 2.25: Persons in poverty in study area] 

[Insert Figure 2.26: Persons aged 65 and older in study area] 

 2.5 Conclusions 

The central Gulf Coast study area contains transportation infrastructure that is vital not just 

to the movement of passengers and goods within the study area but also to the national 

transportation network and economy. However, the geomorphology of the region makes it 

particularly sensitive to certain climate impacts. Due largely to its sedimentary history, the 

region is low-lying – much of it below 5 m – with little topographical relief. Much of the 

region experiences high rates of subsidence as these sediments naturally compact over 

time, while high rates of erosion mean that sections of coastline are literally washed away 

after tropical storms and hurricanes. As a result, the region is particularly vulnerable to the 

effects of sea level rise and storm activity. 

In keeping with national trends, the region is experiencing a shift in population from rural 

to urban areas and increasing suburbanization of the larger urban areas. Much of the 

infrastructure supporting this population is located in vulnerable, low-lying areas. Parts of 

the population face vulnerabilities that may make it more difficult for them to adapt to the 

conditions imposed by a changing climate. This pattern of vulnerability is most focused in 

the rural counties of central coastal Louisiana, the urban core of New Orleans, and to a 

lesser extent southeastward into the delta region of Louisiana, and also into the rapidly 

urbanizing Mobile County, AL. On average, the population of the study area shows lowerincome levels and higher poverty rates than the rest of the nation. 

The following section will present the climate changes projected for the study area, while 

section 4.0 will discuss the resulting impacts to transportation systems in the central Gulf 

Coast region. 

2-27
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

 2.6 Sources 

2.6.1 References 

Airports Council International (ACI), 2005: 2005 North America Final Traffic Report. 

Airports Council International – North America, Washington, D.C. 

American Public Transportation Association (APTA), 2005: Public Transportation 

Fact Book. Washington, D.C., page 86. (Available on-line at http://www.apta.com/

research/stats.) 

Bailey, R.G., 1976: Ecoregions of the United States. USDA Forest Service, Intermountain 

Region, Ogden, Utah, map, scale 1:7,500,000. 

Barras, J.A., cited 2006: Land area change in coastal Louisiana after the 2005 hurricanes – 

a series of three maps. U.S. Geological Survey Open-File Report 2006-1274. 

(Available on-line at http://pubs.usgs.gov/of/2006/1274/. Accessed October 18, 2006.) 

Bureau of Transportation Statistics (BTS), 2004: National Transportation Atlas 

Database (NTAD) 2004. U.S. Department of Transportation, Washington, D.C., 

CD-ROM. (Available on-line at http://www.bts.gov/publications/national_

transportation_atlas_database/.) 

Burkett, V.B., D.B. Zilkoski, and D.A. Hart, 2003: Sea level rise and subsidence: 

Implications for flooding in New Orleans, Louisiana. In: USGS Subsidence Interest 

Group Conference (Prince, K.R., and D.L. Galloway (Eds.)). Proceedings of the 

Technical Meeting, Galveston, Texas, 27–29 November 2001, Open-File Report Series 

03-308, Water Resources Division, U.S. Geological Survey, Austin, Texas, pages 

63-70. 

Coplin, L.S. and D. Galloway, 1999: Houston-Galveston, Texas. Managing coastal 

subsidence. In: Land Subsidence in the United States (Galloway, D., D.R. Jones, and 

S.E. Ingebritsen (Eds.)). U.S. Geological Survey Circular 1182, U.S. Geological 

Survey, pages 35-48. 

Dixon, T.H., F. Amelung, A. Ferretti, F. Novali, F. Rocca, R. Dokka, G. Sella, S.-W. Kim, 

S. Wdowinski, and D. Whitman, 2006: Subsidence and flooding in New Orleans. 

Nature, 441, 587-588. 

Federal Highway Administration (FHWA), 2001: 2001 National Bridge Inventory 

Database. Office of Infrastructure, Washington, D.C. 

Federal Highway Administration (FHWA), 2004: Freight Analysis Framework. Freight 

Management and Operations, Office of Operations, Washington, D.C. (Dataset) 

2-28 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast? 

Federal Highway Administration (FHWA), 2005: Highway Statistics 2004. Office of 

Highway Policy Information, Washington, D.C. 

Federal Highway Administration (FHWA), cited 2006: Official NHS Intermodal 

Connector Listing. Office of Planning, Environment, and Realty, Washington, D.C. 

(Available on-line at http://www.fhwa.dot.gov/hep10/nhs/intermodalconnectors/.) 

Federal Transit Administration (FTA), 2005: 2004 National Transit Database. 

Washington, D.C. (Available on-line at http://www.ntdprogram.com/NTD/ntdhome.nsf.) 

Holzer, T.L., and R.K. Gabrysch, 1987: Effect of ground-water level recoveries on fault 

creep, Houston, Texas. Ground Water, 25, 392–397. 

Institute for Water Resources, 2003: Waterborne Commerce of the United States. 

Waterborne Commerce Statistics Center, Navigation Data Center, U.S. Army Corps of 

Engineers, Arlington, Virginia. 

Minerals Management Service (MMS), 1994: Backfilling Canals as a Wetland 

Restoration Technique in Coastal Louisiana. MMS Publication 94-0026, Minerals 

Management Service, Washington, D.C. 

Morton, R.A., J.C. Bernier, J.A. Barras, and N.F. Ferina, 2005: Rapid Subsidence and 

Historical Wetland Loss in the Mississippi Delta Plain: Likely Causes and Future 

Implications. U.S. Geological Survey Open-File Report 2005-1216, 115 pages. 

Pipeline and Hazardous Materials Safety Administration (PHMSA), 2007: Annual 

Reports: National Pipeline Mapping System. PHMSA, U.S. Department of 

Transportation, Washington, D.C. 

Reed, D.J., 2002: Sea level rise and coastal marsh sustainability: geological and 

ecological factors in the Mississippi delta plain. Geomorphology, 48, 233–243. 

Rybczyk, J.M. and D.R. Cahoon, 2002: Estimating the potential for submergence for two 

subsiding wetlands in the Mississippi River delta. Estuaries, 25, 985–998. 

Shingle, K.D. and R.K. Dokka, 2004: Rates of Vertical Displacement at Benchmarks in 

the Lower Mississippi Valley and the Northern Gulf Coast. NOAA Technical Report 

NOS/NGS 50, National Oceanic and Atmospheric Administration, U.S. Department of 

Commerce, Washington, D.C., 135 pages. 

Stone, G.W., J.P. Morgan, A. Sheremet, and X. Zhang, 2003: Coastal land loss and wavesurge predictions during hurricanes in Coastal Louisiana: implications for the oil and 

gas industry. Coastal Studies Institute, Louisiana State University, Baton Rouge, 

page 67. 

Stone, L., A. Huppert, B. Rajagopalan, H. Bhasin, and Y. Loya, 1999: Mass coral 

bleaching: a recent outcome of increased El Niño activity? Ecology Letters, 2, 325-

330. 

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Chapter 2: Why Study the Gulf Coast? 

2-30 

Thieler, E.R. and E.S. Hammar-Klose, 2000: National Assessment of Coastal 

Vulnerability to Future Sea Level Rise: Preliminary Results for the U.S. Gulf of 

Mexico Coast. U.S. Geological Survey Open-File Report 00–179. Available on-line at 

<http://pubs.usgs.gov/dds/dds68/>, viewed June 28, 2005. 

U.S. Census Bureau, 2005: Special Product for the Gulf Coast Area. American 

Community Survey Office, Washington, D.C. (Available on-line at http://

www.census.gov/acs/www/Products/Profiles/gulf_coast/index.htm.) 

U.S. Census Bureau, cited 2007: United States Census 2000. Washington, D.C. 

U.S. Geological Survey (USGS), 2000: The coastal plain. In: A Tapestry of Time and 

Terrain: The Union of Two Maps – Geology and Topography. U.S. Geological 

Survey, Reston, Virginia. Available on-line at http://tapestry.usgs.gov/features/

13coastalplain.html, viewed June 20, 2006. 

U.S. Geological Survey (USGS), 2004: National Elevation Dataset (NED). U.S. 

Geological Survey, EROS Data Center, Sioux Falls, South Dakota. (Available on-line 

at http://ned.usgs.gov/.) 

U.S. Geological Survey (USGS), 2007: Predicting flooding and coastal hazards. Sound 

Waves Monthly Newsletter, U.S. Geological Survey, Coastal and Marine Geology 

Program, June, page 1. 

Woodroffe, C.D., 2003: Coasts: Form, Process and Evolution. Cambridge University 

Press, Cambridge, United Kingdom, page 623. 

2.6.2 Background Sources 

American Association of Port Authorities (AAPA), 2004: North America Port 

Container Traffic 2004. American Association of Port Authorities, Alexandria, 

Virginia. (Available on-line at http://www.aapa-ports.org/Industry/content.cfm? 

ItemNumber=900&navItemNumber=551). 

American Geophysical Union, 2006: Hurricanes and the U.S. Gulf Coast: Science and 

Sustainable Rebuilding. American Geophysical Union, Washington, D.C., page 30. 

(Available on-line at http://www.agu.org/report/hurricanes/, viewed June 29, 2006.) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-1

Table 2.1 Study area counties and Federal Information Processing Standard 

(FIPS) codes. 

County name State FIPS Name State FIPS1

Baldwin Alabama 003 St. Tammany Louisiana 103 

Mobile Alabama 097 Tangipahoa Louisiana 105 

Acadia Louisiana 001 Terrebonne Louisiana 109 

Ascension Louisiana 005 Vermilion Louisiana 113 

Assumption Louisiana 007 West Baton Rouge Louisiana 121 

Calcasieu Louisiana 019 Forrest Mississippi 035 

Cameron Louisiana 023 George Mississippi 039 

East Baton Rouge Louisiana 033 Hancock Mississippi 045 

Iberia Louisiana 045 Harrison Mississippi 047 

Iberville Louisiana 047 Jackson Mississippi 059 

Jefferson Louisiana 051 Lamar Mississippi 073 

Jefferson Davis Louisiana 053 Pearl River Mississippi 109 

Lafayette Louisiana 055 Stone Mississippi 131 

Lafourche Louisiana 057 Brazoria Texas 039 

Livinston Louisiana 063 Chambers Texas 071 

Orleans Louisiana 071 Fort Bend Texas 157 

Plaquemines Louisiana 075 Galveston Texas 167 

St. Bernard Louisiana 087 Hardin Texas 199 

St. Charles Louisiana 089 Harris Texas 201 

St. James Louisiana 093 Jefferson Texas 245 

St. John the Baptist Louisiana 095 Liberty Texas 291 

St. Landry Louisiana 097 Montgomery Texas 339 

St. Martin Louisiana 099 Orange Texas 361 

St. Mary Louisiana 101 Waller Texas 473 

1

The FIPS county code is a number that uniquely identifies each county in the United States. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-2 

Table 2.2 Gulf Coast study area centerline miles of highway, by classification 

and ownership. (Source: Cambridge Systematics from 2004 

Highway Performance Monitoring System database for Gulf Coast 

study supplied by the Bureau of Transportation Statistics) 

 State County Municipal Other Total 

Interstate 1,096 0 0 0 1,096 

Arterials 4,484 794 2,268 105 7,651 

Collector 4,390 1,776 2,016 35 8,747 

Total 9,970 2,570 4,284 140 17,494 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-3

Table 2.3 Equipment, annual service, and passengers for fixed-route bus 

operations in the study area, 2004. (Source: Cambridge 

Systematics from 2004 National Transit Database) 

 Passengers Revenue 

Agency Urban Area Vehicles Type of Vehicle1 (000) 

Miles 

(000) 

Miles

(000) 

Hours

(000) 

Metropolitan Transit 

Authority of Harris 

County, MTAHC (Metro) 

Houston, 

Texas 

1,434 210 articulated 

diesel buses, 

1224 diesel buses

87,940 504,902 44,097 3,051 

New Orleans Regional 

Transit Authority (RTA) 

New Orleans, 

Louisiana 

367 367 diesel buses 38,202 92,252 10,655 748 

Capital Area Transit 

System (CATS) 

Baton Rouge, 

Louisiana 

74 5 CNG buses, 

51 diesel buses,

18 diesel vans 

4,805 15,749 3,172 159 

Jefferson Transit (JeT) New Orleans, 

Louisiana 

63 59 diesel buses,

4 diesel vans 

4,192 19,581 2,276 149 

Lafayette Transit System 

(LTS) 

Lafayette, 

Louisiana 

22 22 diesel buses 1,156 4,856 536 41 

Island Transit (IS) Galveston, 

Texas 

20 11 diesel buses,

9 diesel vans 

940 1,454 555 45 

The Wave Transit 

(The Wave) 

Mobile, 

Alabama 

31 26 diesel buses,

5 diesel vans 

860 5,233 1,371 97 

Beaumont Municipal 

Transit System 

Beaumont, 

Texas 

19 1 CNG bus, 

18 diesel buses 

662 2,858 729 52 

Coast Transit Authority Gulfport-Biloxi,

Pascagoula, 

Mississippi 

18 16 diesel buses,

2 LPG buses 

534 2,672 770 61 

Port Arthur Transit (PAT) Port Arthur, 

Texas 

11 10 diesel buses,

1 diesel van 

125 935 235 14 

Hattiesburg Area Readi 

Transit, Hub City Transit 

(HART) 

Hattiesburg, 

Mississippi 

5 3 gasoline buses,

2 diesel vans 

N/A N/A N/A N/A 

Lake Charles Transit 

System (LCTS) 

Lake Charles, 

Louisiana 

8 8 diesel buses N/A N/A N/A N/A 

Saint Bernard Urban Rapid 

Transit (SBURT) 

New Orleans, 

Louisiana 

9 8 diesel buses, 

1 diesel van 

N/A N/A N/A N/A 

Total 2,081 139,416 650,492 64,396 4,417 

1 CNG – Compressed Natural Gas 

LPG – Liquified Propane Gase 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-4 

 Table 2.4 Freight railroads in the Gulf Coast study area. (Source: Bureau of 

Transportation Statistics, 2004) 

Railroad Class Service Area Primary Commodities 

Acadiana Railway III Crowley, LA, through Eunice and 

Opelousas, to Bunkie, LA. 

Agricultural products, edible oils, and 

general freight. 

Alabama and Gulf Coast 

Railway 

III Pensacola, FL, to Columbus, AL. 

Extensions to Mobile, AL, via Norfolk 

Southern trackage. 

Paper industry: logs, woodchips, chlorine, 

sodium chlorate, hydrogen peroxide, rolled 

and boxed paper, and kaolin clay. 

Burlington Northern 

Santa Fe Railway 

I Over 32,000 route miles in western U.S. 

Operate between Houston and New Orleans.

Coal, grains, intermodal, lumber, and 

chemicals. 

Canadian National 

Railway (formerly 

Illinois Central Gulf) 

I Over 19,000 route miles in U.S. and 

Canada. Serves Mobile and New Orleans 

via north-south route. 

Petroleum, chemicals, grain, fertilizers, 

coal, metals, minerals, forest products, 

intermodal, and automotive. 

CSX Transportation I Over 22,000 route miles in eastern U.S. 

Operate between Florida and New Orleans 

along I-10 corridor. 

Coal, chemicals, autos, minerals, 

agricultural products, food, consumer 

goods, metals, forest and paper products, 

and phosphates and fertilizer. 

Kansas City Southern I Operates approximately 3,100 route miles 

in central and southeastern U.S. Serves 

New Orleans and Lake Charles, LA, Port 

Arthur and Galveston, TX, and Mexico. 

Agriculture, minerals, general merchandise, 

intermodal, autos, and coal. 

Lake Charles Port and 

Harbor District 

Switching Owned by the Port. Switches traffic for 

Union Pacific. 

Port traffic. 

Louisiana and Delta 

Railroad 

III Multiple branches connected by trackage 

rights on Union Pacific between Lake 

Charles and Raceland, LA. 

Carbon black, sugar, molasses, pipe, rice, 

and paper products. 

Mississippi Export 

Railroad 

 Escatawpa River at Evanston, MS, to port 

at Pascagoula, MS. 

Transloading services for intercoastal and 

river barges or vessels. 

New Orleans and Gulf 

Coast Railway 

III Westwego, LA, to Myrtle Grove, LA. Food products, oils, grains, petroleum 

products, chemicals, and steel products. 

New Orleans Public Belt 

Railroad 

Switching Serves Port of New Orleans along the 

Mississippi River and Industrial Canal. 

Exports: lumber, wood products, and 

paper. Imports: metal products, rubber, 

plastics, and copper. Domestic: clay, 

cement, and steel plate. 

Norfolk Southern 

Corporation 

I Over 21,000 route miles in eastern U.S. 

Operate from Birmingham to Mobile, AL, 

and New Orleans, LA. 

Agriculture, autos, chemicals, coal, 

machinery, intermodal, metals, construction material, paper, clay, forest products. 

Pearl River Valley 

Railroad 

III Goodyear, MS, to Nicholson, MS. Lumber and forest products. 

Port Bienville Railroad Switching Port Bienville Industrial Park, Hancock 

County, MS. 

Plastic resins and other goods for industrial 

park tenets. 

Sabine River and 

Northern Railroad 

III Between Buna and Orange, TX. Wood chips, chemicals, and other raw 

materials for the paper industry. Finished 

paper and lumber products. 

Terminal Railway 

Alabama State Docks 

Switching Operates over 75 miles in the Mobile, AL, 

area, serving the port and local industries. 

Port cargo. 

Timber Rock Railroad 

Company 

III De Ridder, LA, west through Merryville to 

Kirbyville, TX. 

Forest products and rock. 

Union Pacific Railroad I Over 32,000 route miles in western U.S. 

Operate between Houston and New 

Orleans. 

Chemicals, coal, food, forest products, 

grains, intermodal, metals, minerals, and 

autos. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-5

Table 2.5 Domestic and international waterborne tonnage of study area ports, 

2003. (Source: U.S. Army Corps of Engineers, Navigation Data 

Center)

National Rank Port 2003 Short Tons 

1 South Louisiana, Louisiana 198,825,125 

2 Houston, Texas 190,923,145 

4 Beaumont, Texas 87,540,979 

5 New Orleans, Louisiana 83,846,626 

9 Texas City, Texas 61,337,525 

10 Baton Rouge, Louisiana 61,264,412 

11 Plaquemines, Louisiana 55,916,880 

12 Lake Charles, Louisiana 53,363,966 

14 Mobile, Alabama 50,214,435 

23 Pascagoula, Mississippi 31,291,735 

24 Freeport, Texas 30,536,657 

27 Port Arthur, Texas 27,169,763 

Gulf Coast Study Area Total 932,231,248 

National Total 2,394,251,814 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-6 

Table 2.6 Tonnage on study area inland and coastal waterways, 2003. 

(Source: U.S. Army Corps of Engineers, Waterborne Commerce of 

the United States, 2003) 

Waterways Segments Within Study Area 2003 Short Tons (Millions) 

Mississippi River, Baton Rouge to New Orleans, LA 212.9 

Mississippi River, Mouth of Ohio to Baton Rouge, LA 185.5 

Gulf Intracoastal Waterway, TX-FL 117.8 

Mississippi River, New Orleans, LA, to Gulf of Mexico 115.8 

Gulf Intracoastal Waterway, Port Allen Route, LA 24.3 

Black Warrior and Tombigbee Rivers, AL 21.0 

Atchafalaya River, LA 9.8 

Tennessee-Tombigbee Waterway, AL and MS 5.2 

Red River, LA 4.2 

Chocolate Bayou, TX 3.3 

Petit Anse, Tigre, Carlin bayous, LA 2.5 

Ouachita and Black Rivers, AR and LA 2.2 

Bayou Teche, LA 1.4 

Subtotal for Waterway Segments Within Study Area 705.9 

Subtotal for Full Gulf Coast and Mississippi River Systems, including 

Waterway Segments Within or Connecting to Study Area 

1,650.5 

National Total of All Major Inland and Coastal Waterway Segments 1,717.0 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-7

Table 2.7 Passenger enplanements and cargo tonnage for select commercial 

service and industrial airports in the study area, 2005. 

 2005 

Associated 

City 

FAA 

Code State County Airport Name 

Airport 

Type 

Passenger 

Enplanements 

Cargo 

Tonnage 

Mobile MOB Alabama Mobile Mobile Regional CS 638,953 582 

Mobile BFM Alabama Mobile Mobile Downtown IND 0 44,000a

Lake Charles LCH Louisiana Calcasieu Lake Charles Regional CS 43,250a 2a

Lake Charles CWF Louisiana Calcasieu Chennault International IND 0 75 

Baton Rouge BTR Louisiana East Baton Rouge Baton Rouge 

Metropolitan, Ryan 

Field 

CS 973,625 5,663 

New Orleans MSY Louisiana Jefferson Louis Armstrong New 

Orleans International 

CS 7,775,147 66,123 

Lafayette LFT Louisiana Lafayette Lafayette Regional CS 343,301 6,774 

Hattiesburg HBG Mississippi Forrest Bobby L Chain Muni CS 8,000a 

Gulfport GPT Mississippi Harrison Gulfport-Biloxi 

International 

CS 769,669 

Houston EFD Texas Harris Ellington Field CS 53,947 15 

Houston HOU Texas Harris William P. Hobby CS 8,252,532 7,000 

Houston IAH Texas Harris George Bush 

Intercontinental/ 

Houston 

CS 39,684,640 387,790 

Beaumont/ 

Port Arthur 

BPT Texas Jefferson Southeast Texas 

Regional 

CS 43,0381 

Study Area 

Total 

 58,586,102 517,418 

National 

Total 

 738,629,000 30,125,644

Source: Alabama airports from http://www.brookleycomplex.com/cargo/statistics.asp. Louisiana airports from the 

Airports Council International and U.S. DOT BTS T100 data. Texas airports from http://www.citydata.com/us-cities/The-South/Houston-Economy.html. Wilbur Smith Associates. National totals from Bureau 

of Transportation Statistics (http://www.bts.gov/programs/airline_information/air_carrier_traffic_statistics/

airtraffic/annual/1981-2001.html) and Airports Council International. 

Note: CS: Commercial Service Airport 

IND: Industrial Airport 

1

 Estimated. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-8 

Table 2.8 Land use of the central Gulf Coast study area as defined by the 

1992 National Land Cover Dataset. (Source: National Land Cover 

Dataset, U.S. Geological Survey)

Land Use Category Area (Hectares) Percent of Total 

Water 508,735 5.38% 

Low-Intensity Residential 250,032 3.00% 

High-Intensity Residential 106,637 1.13% 

Commercial, Industrial, Transportation 152,744 1.62% 

Bare Rock, Sand, Clay 14,126 0.15% 

Quarries, Strip Mines, Gravel Pits 3,921 0.04% 

Transitional from Barren 92,835 0.98% 

Deciduous Forest 492,245 5.21% 

Evergreen Forest 1,175,278 12.44% 

Mixed Forest 861,726 9.12% 

Shrubland 23,096 0.24% 

Orchard, Vineyard 5 Negligible 

Grasslands, Herbaceous 123,576 1.31% 

Pasture, Hay 1,213,343 12.84% 

Row Crops 591,105 6.26% 

Small Grains 694,855 7.35% 

Urban, Recreation Grasses 83,476 0.88% 

Woody Wetlands 1,087,093 11.50% 

Emergent Herbaceous Wetlands 1,974,788 20.90% 

Total 9,449,615 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Tables 

2T-9

Table 2.9 Top 10 industries in the study area by employment percentage, 

2000. (Source: United States Census 2000, U.S. Census Bureau, 

2007)

Industry 

Percent of Study Area 

Employment 

Retail Trade 11.6 

Manufacturing 11.6 

Health Care and Social Assistance 10.2 

Educational Services 8.9 

Construction 8.6 

Accommodation and Food Services 6.4 

Professional, Scientific, and Technical Services 6.2 

Other Services (except Public Administration) 5.2 

Transportation and Warehousing 4.8 

Public Administration 4.3 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-1

Figure 2.1 Map of the study area, which extends from Mobile, AL, to 

Houston/Galveston, TX. (Source: U.S. Census Bureau; ESRI, 

Inc.; National Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-2 

Figure 2.2 Study area counties and Federal Information Processing Standard 

(FIPS) codes. (Source: U.S. Census Bureau; ESRI, Inc.; National 

Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-3

Figure 2.3 Metropolitan planning organizations (MPO) in the study area. 

(Source: U.S. Census Bureau; ESRI, Inc.; National 

Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-4 

Figure 2.4 Combined truck flows shipped domestically from Louisiana, 1998. 

(Source: U.S. Department of Transportation Federal Highway 

Administration, Freight Management and Operations, Office of 

Operations) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-5

Figure 2.5 Navigable inland waterways impacting the study area, shown as 

named waterways. (Source: U.S. Department of Transportation) 

Missouri Illinois

Ohio

Upper 

Mississippi

Lower

Mississippi

Arkansas White

Atchafalaya

Black

Tennessee

Cumberland

Black Warrior

Alabama

GIWW

Mobile

Red Tombigbee

Inland Navigable 

System
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-6 

Figure 2.6 National network of Class I railroads. 

(Source: Federal Railroad Administration Office of Policy, 

U.S. Department of Transportation) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-7

Figure 2.7 Intermodal facilities in the study area. (Source: Bureau of 

Transportation Statistics, U.S. Department of Transportation) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-8 

Figure 2.8 Highways in the study area. (Source: Cambridge Systematics 

analysis of U.S. Department of Transportation data) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-9

Figure 2.9 Total and truck annual vehicle miles of travel (VMT) on 

nonlocal roads, 2003. (Source: Cambridge Systematics, 

from 2004 Highway Performance Monitoring System database 

for Gulf Coast study supplied by the Bureau of Transportation 

Statistics, U.S. Department of Transportation) 

0

10,000

20,000

30,000

40,000

50,000

60,000

Annual VMT (in Millions)

Total Truck Total Truck Total Truck

Interstate Arterial Collector

Road Classification

State County Municipal Other
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-10 

Figure 2.10 Nonlocal bridges in the study area (National Bridge Inventory 

[NBI] latitude and longitude location). (Source: Cambridge 

Systematics analysis of U.S. Department of Transportation data) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-11

Figure 2.11 Freight railroad traffic density (annual millions of gross ton-miles 

per mile) in the study area. (Source: Bureau of Transportation 

Statistics, U.S. Department of Transportation) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-12 

Figure 2.12 Sunset Limited route map, Houston, TX, to Mobile, AL, segment.

(Source: Amtrak) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-13

Figure 2.13 Freight handling ports and waterways in the study area. 

(Source: Cambridge Systematics analysis of U.S. Army Corps 

of Engineers data) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-14 

Figure 2.14 Barge tow on the Mississippi River. 

(Source: U.S. Army Corps of Engineers) 

. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-15

Figure 2.15 Study area airports. (Source: Bureau of Transportation 

Statistics, U.S. Department of Transportation) 

Note: CS: Commercial Service 

GA: General Aviation 

IND: Industrial 

MIL: Military 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-16 

Figure 2.16 Surface geology of the southeastern United States. 

White line denotes inland extent of the Gulf Coastal Plain, 

and grey area is Holocene alluvium. (Source: U.S. Geological 

Survey, 2000a) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-17

Figure 2.17 Relative elevation of counties in the study area (delineated in 

blue). All areas shown in bright orange are below 30–m 

elevation. (Source: U.S. Geological Survey) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-18 

Figure 2.18 Map of terrestrial ecoregions within and adjacent to the study 

area. (Modified from Bailey, 1975) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-19

Figure 2.19 U.S. Census Bureau Metropolitan Statistical Areas within the 

study area. (Source: U.S. Census Bureau; ESRI, Inc.; National 

Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-20 

Figure 2.20 Population density in the study area, 2004. (Source: U.S. Census 

Bureau; ESRI, Inc.; National Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-21

Figure 2.21 Estimated population change in the study area, 2000 to 2005. 

(Source: U.S. Census Bureau; ESRI, Inc.: National 

Transportation Safety Bureau)
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-22 

Figure 2.22 Mean travel time to work in the study area. (Source: U.S. Census 

Bureau; ESRI, Inc.; National Transportation Safety Bureau)
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-23

Figure 2.23 Manufacturers’ shipments in thousands of dollars, 1997. 

(Source: U.S. Census Bureau; ESRI, Inc.; National 

Transportation Safety Bureau)
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-24 

Figure 2.24 Social vulnerability index for the study area. (Source: U.S. 

Census Bureau; ESRI, Inc.; National Transportation Safety 

Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-25

Figure 2.25 Persons in poverty in the study area. (Source: U.S. Census 

Bureau; ESRI, Inc.; National Transportation Safety Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 2: Why Study the Gulf Coast?: Figures 

2F-26 

Figure 2.26 Persons aged 65 and older in the study area. (Source: U.S. 

Census Bureau; ESRI, Inc.; National Transportation Safety 

Bureau) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

3.0 How Is the Gulf Coast 

Climate Changing? 

Lead Authors: Barry D. Keim, Thomas W. Doyle, and Virginia R. Burkett 

Contributing Authors: Claudia Tebaldi, Ivor Van Heerden, S. Ahmet Binselam, Michael F. 

Wehner, Tamara G. Houston, and Daniel M. Beagan 

The central Gulf Coast is one of warmest, wettest regions in the United States, where 

annual rainfall averages over 150 cm (60 inches) per year (Christopherson, 2000). Since 

there is very little topographic relief, changes in precipitation and runoff could have a 

dramatic impact on fragile Gulf Coast ecosystems and coastal communities by changing 

the hydroclimatology of the region. Changes in runoff are important to virtually all 

transportation modes in the Gulf Coast region. Interstate highways in Houston and New 

Orleans, for example, are occasionally flooded by locally intense rainfall, and several State 

and local highways are closed due to high rainfall at least once every five years. Even 

ports can be affected by high rainfall and runoff to shallow coastal waterways. Changes in 

temperature and moisture regime also are relevant to many aspects of transportation 

planning, construction, and maintenance. Airport runway length requirements, for 

example, are determined by mean maximum temperature for the hottest month of the year. 

As the climate and sea surface warm, we can anticipate an increase in the intensity of 

hurricanes making landfall along the Gulf of Mexico coastline. As the ocean warms and 

ice sheets decline, sea level rise is likely to accelerate, which has serious implications for 

the Gulf Coast region where much of the land is sinking (subsiding) due to local geological 

processes and human development activity. 

This chapter summarizes the direct and indirect effects of climate change that are most 

likely to affect transportation in the Gulf Coast region. The key climate “drivers” 

examined in the study region are: 

• Temperature; 

• Precipitation; 

• Sea level rise; and 

• Hurricanes and less intense tropical storms. 

The interactive effects of these drivers, coupled with ongoing environmental processes in 

the region, are discussed in the following sections. This chapter presents scenarios of 

future climate change in addition to analysis of historical trends. While the environmental 

trend information for the study area is compiled from region-specific data sources, a 

regional model of future climate was not available for the Gulf Coast study area. One 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

approach that is widely used to identify plausible changes in climate at a regional scale is to 

extract output from general circulation models run at a global scale. This approach was 

used in this study and is described in the following sections of the report. Specific 

implications of the scenarios of future climate for each mode of transportation are 

discussed in the subsequent chapter of this report. 

Intended Use of Climate and Emissions Scenarios in the Context of This Report 

A “scenario” is a plausible description of possible future conditions and is generally 

developed to inform decision making under uncertainty. Building and using scenarios can 

help people explore what the future might look like and the likely challenges of living in it 

(Shell International, 2003). Scenarios are distinct from assessments, models, and similar 

decision-support activities, although they can provide important inputs to these activities. 

Scenarios also can be distinguished from precise statements about future conditions, which 

may be referred to as “forecasts” or “predictions.” Compared to these, scenarios tend to 

presume lower predictive confidence, because they pertain to processes for which weaker 

causal understanding or longer time horizons increase uncertainties (Parson et al., 2007). 

Climate scenarios describe potential future climate conditions and are used to inform 

decision making relative to adaptation and mitigation. Scenarios can be constructed for 

higher order aspects of climate change and its impacts, such as future changes in sea level, 

drought and storm intensity, or vegetation distribution. Scenarios of relative sea level rise, 

for example, in a subsequent section of this report were constructed by combining climatechange scenarios with information about coastal subsidence and other specific regional 

characteristics. The climate and sea level rise scenarios discussed in this report identify 

plausible potential future conditions for the Gulf Coast region. They are intended to frame 

the analysis of potential risks and vulnerability within the transportation sector. 

The Earth’s climate is determined, in part, by the concentration of atmospheric greenhouse 

gases and particulates that absorb infrared radiation (heat) reflected from the Earth’s 

surface. Human activity is increasing greenhouse gas and particulate emissions, which has 

resulted in an increase in the Earth’s temperature (Intergovernmental Panel on Climate 

Change [IPCC], 2001, 2007). In order to assess how the climate may change in the future, 

future emissions must be specified. The Intergovernmental Panel on Climate Change 

(IPCC) has conducted three exercises to generate scenarios of 21st century greenhouse-gas 

emissions, the most recent being the IPCC Special Report on Emissions Scenarios (SRES) 

(Nakicenovic and Swart, 2000). To explore the potential effects on transportation, we 

selected a range of emissions futures from the SRES report, including the low-emissions 

B1 scenario, the mid-range A1B scenario, and the high-emissions A2 scenario. The AIFI 

scenario, which assumes the highest reliance on fossil fuels during this century, also was 

added to the SRES scenarios used to assess the effects of sea level rise. 

The SRES A1B scenario assumes a balance across all energy sources, meaning it does not 

rely too heavily on any one particular source, including fossil fuels. It is, therefore, based 

on the assumption that improvement rates apply to all energy sources and end-use 

technologies. The A2 scenario assumes that economic development is primarily regionally 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

oriented and that per capita economic growth and technological change are more 

fragmented and slower than for the other emission scenarios. The B1 scenario assumes a 

high level of social and environmental awareness with an eye toward sustainability. It 

includes an increase in resource efficiency and diffusion of cleaner technologies (IPCC, 

2001). These three emission scenarios are among the six “marker/illustrative scenarios” 

selected for climate model simulations in the IPCC’s Third and Fourth Assessment Reports 

(IPCC, 2001, 2007) (figure 3.1). The B1 scenario lies at the lower extreme end of the 

potential changes in atmospheric CO2 concentrations during this century, while the A1B 

emission scenario is considered a middle-of-the-range scenario in terms of the 

hypothesized rate of greenhouse gas emissions. The A2 scenario is among the higher end 

of the SRES scenarios in terms of both CO2 and SO2 emissions. The influence of SRES 

emission scenarios on global temperature simulations is presented in table 3.1. 

 3.1 Temperature, Precipitation, and Runoff 

The climate of the study area is influenced by remote global factors, including the El Niño 

Southern Oscillation, and regional factors such as solar insolation. Due to the influence of 

the nearby Gulf of Mexico, the region is warmer and moister than most other continental 

regions at this latitude. Rainfall across the study area has little seasonality, with slightly 

higher rainfall values in spring and summer relative to fall and winter. The region enjoys 

mild winters, which are occasionally interrupted by cold air masses extending far south 

from the northern pacific or the Arctic, which brings low temperatures and freezing 

conditions. Rainfall in the region is dependent upon a variety of processes, including 

frontal passages in the winter and spring (Twilley et al., 2001). Short-lived, unorganized 

thunderstorms fueled by afternoon heating and moisture are common in the study area and 

associated, in part, with a prominent sea/land breeze (Ahijevych et al., 2003). 

The Gulf Coast, like much of the world, has experienced significant changes in climate 

over the past century. With continued increases in atmospheric greenhouse gases and their 

radiative forcing, the Earth’s climate is expected to change even more rapidly during the 

21st century (IPCC, 2007). Computer-based climate simulation models are used to study 

the present climate and its responses to past perturbations like variation in the sun’s output 

or major volcanic eruptions. They also are used to assess how the future climate would 

change under any specified scenario of greenhouse-gas emissions or other human activity 

(Parson et al., 2007). 

3.1.1 Historical Data Sources 

Changes in the historical climatology of the study area were investigated from an empirical 

perspective relying on instrumental records. The assessment of the present climate and 

20th-century trends was built around climatic data from the United States Climate Division 

Datasets (CDD) (Guttman and Quayle, 1996) and the United States Historical Climate 

Network (USHCN) (Karl et al., 1990; Easterling et al., 1996). Since CDD were used in a 

portion of this analysis, caution needs to be taken with data from 1905 to 1930, which are 

3-3
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

synthesized from statewide data as described by Guttman and Quayle (1996) and therefore 

are not true averages of data from within a climate division. 

Empirical trends and variability were analyzed for temperature and precipitation at the 

CDD level for the climate divisions along the Gulf Coast from Galveston, TX, to Mobile, 

AL, including Texas Climate Division 8, Louisiana Divisions 6-9, Mississippi Division 10, 

and Alabama Division 8 (figure 3.2). 

Keim and others (2003) showed that CDD can have spurious temperature trends. Our 

analysis synthesized CDD consisting of averages of stations within each division from the 

USHCN (table 3.2). The Filnet data have undergone numerous quality assurances and 

adjustments to best characterize the actual variability in climate. These adjustments take 

into consideration the validity of extreme outliers, time of observation bias (Karl et al., 

1986), changes in instrumentation (Quayle et al., 1991), random relocations of stations 

(Karl and Williams, 1987), and urban warming biases (Karl et al., 1988). Furthermore, 

missing data were estimated from surrounding stations to produce a nearly continuous 

dataset for each station. 

Monthly averages from the USHCN stations from 1905 to 2003 within each climate 

division were then averaged annually, thereby constructing an alternative “divisional data” 

annual time series. The year 1905 was selected as a starting point because it represents a 

common period of record for all but one of the USHCN stations utilized in the study – the 

exception is Fairhope, AL, beginning in 1919. Fairhope was maintained because it is the 

only USHCN station available in Alabama Climate Division 8. Only USHCN FILNET 

stations with a continuous monthly record of temperature from January 1905 through 

December 2003 were included in the analysis, with the exception of Fairhope. USHCN 

precipitation data were not as serially complete as temperature, and there were fewer 

stations available. As a result, this study incorporated the original CDD for precipitation, 

which seems reasonable given results of Keim and others (2005). 

3.1.2 General Circulation Model Applications for the Study Area 

The scenarios of future climate referenced in this report were extracted from an ensemble 

of up to 21 different atmosphere-ocean general circulation model (GCM) efforts, which 

contributed the results of their simulations in support of the IPCC’s Fourth Assessment 

Report, and are labeled “Coupled Model Intercomparison Project 3” (CMIP3). Gridded 

output limited to the study area was extracted from each GCM. Figure 3.3 shows the study 

region and the boundaries used to subset the global grid of a typical GCM output. Results 

are presented as spatial averages across the entire area. The GCMs were run under three 

forcings, the low-emissions B1, the high-emissions A2, and the mid-range A1B scenarios 

from the IPCC’s SRES (Nakicenovic and Swart, 2000). 

Scenarios of future temperature and precipitation change for the middle of the 21st century 

were derived from the regional GCM runs. Scatter diagrams were produced to convey the 

range of output of the models with respect to present conditions following the procedures 

of Ruosteenoja et al. (2003) (figure 3.4). Probability density (or distribution) functions 

3-4 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

(PDF) were developed by applying the method of Tebaldi and others (2004, 2005). Data 

forming the basis of the PDF estimation is an ensemble of historical and future climate 

simulations (from which temperature and precipitation are extracted). Output of 

temperature and precipitation (averaged for area l and seasonal fluctuations) from up to 21 

different GCMs under the three different scenarios was considered for two 20-year periods, 

one representative of recent climatology (1980-1999) and one representative of the future 

mid-century time slice (2040-2059). Thus scenarios of “climate change” are to be 

interpreted with respect to these two time periods and conditional on the SRES A1B, A2, 

and B1 scenarios (Nakicenovic and Swart, 2000). While the results from the GCM runs 

are indeed plausible, they should be interpreted as mid-, high-, and low-range results, 

respectively, among the SRES scenarios of the potential changes in temperature and 

precipitation. 

The statistical procedure synthesizes the multimodel ensemble of projections into a 

continuous PDF by applying a Bayesian method of estimation. At the core of the method 

is the idea that both observed and modeled temperature and precipitation contribute 

information to the estimate, so that different models will be differently “weighted” in the 

final probabilistic projections on the basis of their differential skill in reproducing observed 

climate. The method used also considered the convergence of different models when 

producing future trajectories, rewarding models that agree with one another and 

downweighting outliers. In the version of the statistical procedure applied here, the latter 

criterion is discounted, ensuring that even model projections that disagree with the 

consensus inform the shape of the final PDFs. This choice is made as a result of two 

considerations: the ensemble of GCMs at our disposal is not made of independent models 

(there are components and algorithms in common, for example), so rewarding agreement is 

somewhat questionable when one can argue that the agreement is not independently 

created. The second consideration has to do with the width of the PDFs produced, since 

enforcing the convergence criterion has the effect of narrowing the width of the PDFs to a 

range even smaller than the original ensemble range. It is well understood that the range of 

uncertainty addressed by this particular ensemble of models is limited when compared to 

the whole range of sources of uncertainty that can be listed, when examining climate 

change projections. Thus we preferred to produce conservative estimates of the uncertainty 

(i.e., larger rather than smaller). The result of applying the statistical analysis to the GCM 

output are PDFs of temperature and precipitation change (the latter as absolute values or 

percent change with respect to historical precipitation averages) from which any percentile 

can be derived. 

3.1.3 Water-Balance Model 

The primary tool used to investigate the hydroclimatology of the study area was a modified 

Thornthwaite Water Balance Model as described by Dingman (2002). The Thornthwaite 

model is simply an accounting of hydroclimatological inputs and outputs. Monthly values 

of temperature, precipitation, and potential evapotranspiration – called reference 

evapotranspiration – were entered into the budget, and parameters such as rain/snow ratios, 

soil moisture, soil moisture deficits, and runoff were calculated. The water balance was 

3-5
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

modified slightly by using an alternative reference evapotranspiration (ETo) term than that 

originally used by Thornthwaite to provide a better estimate of ETo in the central Gulf 

Coast region. As with any monthly water balance, atmospheric and terrestrial variables 

(such as ETo, soil moisture, runoff, etc.) were parameterized by using bulk terms. A 

description of the procedures used to estimate evapotranspiration, soil moisture, and other 

components of the water balance model are presented in appendix D. 

3.1.4 Temperature and Runoff Trends 

Results from our analysis of temperature variability during 1905 to 2003 indicate that the 

1920s or 1930s was generally the warmest decade for the various Gulf Coast climate 

divisions (figure 3.5). After a step down in the temperature in the late 1950s, the coolest 

period occurs in the 1960s, while a warming trend is evident for all seven climate divisions 

beginning in the 1970s and extending through 2003. Of the seven climate divisions, LA6, 

LA8, and MS10 have slight but significant cooling trends at an α ≤.05 over the 98-year 

period of record. Precipitation variability shows that the 1940s and 1990s were the wettest 

decades, while the 1950s was generally the driest (figure 3.6). Although all of the climate 

divisions at least suggest long-term patterns of increasing rainfall, only MS10 and AL8 

have trends that are significant at an α ≤.05. 

Data for each of the seven climate divisions were amalgamated into a regional dataset, by 

month, and the continuous monthly water balance model was run. In a typical year, ETo is 

low in winter and early spring, and most rainfall is converted to runoff because soil 

moisture storage remains at, or near, capacity. As temperatures rise in late spring and early 

summer and the number of hours of daylight increases, ETo also increases. 

Evapotranspiration will often exceed rainfall in July, August, and September, which leads 

to soil moisture utilization, on the average. Then in late fall, precipitation often exceeds 

ETo leading to recharge of soil moisture. Regional trends in model-derived runoff shows 

large inter-annual variability with the high values in the 1940s and from 1975 to 2003 

(figure 3.7). Despite the variability, a long-term trend was detected in the data at an α ≤.05, 

and the trend line indicates a 36 percent increase in runoff over the time period. Moisture 

deficits show high values from the mid-1940s through the mid-1960s, with 1998 to 2000 

also high (figure 3.7) but without any long-term trends during that period. 

Historical monthly extremes of precipitation, runoff, and deficit in the Gulf Coast Region 

were analyzed to provide a focus for this portion of the analysis. In the empirical record, 

there is some evidence of an increase in precipitation extremes in the United States and in 

the Gulf south. Karl et al. (1995) shows that one-day extreme rainfall events have 

increased in portions of the United States, and Keim (1997) shows heavy rainfall events 

have increased in the south-central United States. These heavy rainfall events have very 

likely contributed the increases in runoff found in this study. 

The period 1971 to 2000 serves as the baseline climatology for this analysis. Using water 

balance output for this 30-year period, partial duration series (PDS) are generated for the 

three variables. A PDS includes the number of events (monthly extremes) equal to the 

number of years under examination, which is 30 in this case. As such, the 30 largest 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

monthly totals of precipitation, runoff, and deficit were extracted and then fit to the beta-p 

distribution, as recommended by Wilks (1993), and the 2-, 5-, 10-, 25-, 50-, and 100-year 

quantile estimates are determined for each. These data serve as a baseline for assessing 

potential future changes in extremes of precipitation, runoff, and deficit. 

3.1.5 General Circulation Model Results and Future Climate Scenarios 

To explore how the regional climate may change over the next 50 years, output from an 

ensemble of GCM runs used by IPCC for the Fourth Assessment Report (2007) was 

analyzed. Scatterplots and probability density functions of average temperature and 

precipitation change were derived from the GCM ensemble output for the IPCC SRES 

greenhouse gas emissions scenarios labeled A1B, A2, and B1. The results presented in the 

following discussion are based on GCMs (table 3.3) that contributed runs to the IPCC 

archive used in the IPCC’s Fourth Assessment Report and are consistent with the 

temperature and precipitation projections reflected in IPCC Fourth Assessment Report 

(2007). 

The GCM results run with the A1B, A2, and B1 emissions scenarios suggest a warmer 

Gulf Coast region, with the greatest increase in temperature occurring in summer and 

lowest increases in winter (tables 3.4, 3.6, and 3.8). This is consistent with another 

analysis of historical data that shows a significant increase in summer minimum 

temperature across the Gulf Coast study area between 1950 and 2002 (Groisman et al., 

2004). 

Although the climate model output for the A1B, A2, and B1 emissions scenarios 

demonstrate a large degree of similarity, the A1B scenario was retained for more detailed 

analysis since it is considered “mid-range” of the IPCC emissions scenarios. Also, we note 

that the major differences in CO2 concentrations under the IPCC SRES scenarios occur 

after 2040 (figure 3.1), which helps explain why temperature and precipitation do not vary 

widely among the GCM experiments with the high-, low-, and mid-range emissions 

scenarios (tables 3.4 to 3.9). Stated another way, the climate scenarios presented in these 

tables are not likely to change significantly during the next three to four decades by 

mitigation measures that would reduce emissions, although mitigation measures could 

substantially affect the climate in the latter half of this century. Probability density 

functions for seasonal temperature and precipitation change through 2050 are presented in 

figures 3.8 and 3.9, respectively. 

Hourly or daily precipitation extremes cannot be reliably simulated by current GCM 

experiments. The percentiles (i.e., the 5th, 50th, and 95th percentiles) from the A1B PDFs 

were used as a proxy for assessing potential changes to hydrological extremes across the 

region. These percentiles stretch the range of output from all 21 GCMs, while also 

providing the middle of the PDF, or region under the curve where there is most agreement 

between the models (i.e., 50th percentile). The 1971-2000 temperature and precipitation 

data therefore were modified seasonally according to the predicted changes presented in 

tables 3.5, 3.7, and 3.9 for each of the three quartiles. The water-balance model was then 

rerun using the three quartile datasets to simulate the hydrology under these altered climate 

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Chapter 3: How is the Gulf Coast Climate Changing? 

conditions. These datasets provided the means necessary to produce new PDS of 

precipitation, runoff, and deficit for additional extreme value statistical testing. 

The 2-, 5-, 10-, 25-, 50-, and 100-year return periods for mean monthly precipitation show 

only modest differences between the current climate and the projected climate in 2050 at 

the three PDF percentiles (figure 3.10). As expected, there is a decrease in monthly 

precipitation extremes at the 5th percentile for the less rare return periods (2- to 25-year), 

relative to the current climate, which would be expected given the reduction in 

precipitation by up to 36 percent in summer. However, given the shape of the beta-p 

distribution, the 100-year precipitation event is slightly larger than the baseline. Results for 

the 50th percentile indicate that the less rare return periods are on par with current climate 

patterns, but that the rare return periods may have modestly larger storms. At the 95th

percentile, storms are generally larger across the board. 

Monthly runoff extremes show a very different relationship to the current climate. At both 

the 5th and 50th percentiles, there is a dramatic reduction in projected runoff (figure 3.11). 

The mid-range of the GCMs suggests a decline in runoff relative to the 1971-2000 baseline 

period. Runoff rates are lower because precipitation is somewhat reduced, but perhaps 

more importantly, the projected increases in temperature also lead to increases in potential 

and actual evapotranspiration, and evapotranspiration rates are highest in the Gulf and 

southeastern United States compared to other regions (Hanson, 1991). An increase in 

actual evapotranspiration, without any increase in precipitation, translates into a reduction 

in runoff rates. However, at the 95th percentile, precipitation increases anywhere from 9 to 

26 percent, depending on season. 

Extremes in monthly deficit show a more complex pattern between the quartiles and over 

the various return periods (figure 3.12). The 5th percentile shows much larger deficits 

occurring relative to the 1971-2000 baseline. This is especially relevant at the two-year 

return period, which is nearly 30 percent larger in magnitude/intensity than in the current 

climate. This observation makes sense because as temperatures become somewhat 

warmer, thereby increasing potential evapotranspiration, there also are substantial 

reductions in precipitation. The net effect of this combination would be an increase in 

deficits (and drought intensity). Smaller reductions in precipitation at the 50th percentile 

dampen the increases in deficits. At the 95th percentile, increases in temperature are more 

than offset by the dramatic increases in precipitation, with deficits substantially reduced in 

their intensity. 

3.1.6 Changes in Daily Temperature 

To examine trends in extreme temperature for the study area, daily maximum temperature, 

and minimum temperature were analyzed from 1950 through 2005. The historical analysis 

presented uses a dataset and tools developed for an analysis of North American extremes 

based on the daily data set from the USHCN (National Oceanic and Atmospheric 

Administration [NOAA], 2006). Temperature indices of transportation sensitive 

parameters were created on a station basis and then averaged together. For localized 

analyses, anomalies of the indices for all stations within 500 km of the target location were 

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Chapter 3: How is the Gulf Coast Climate Changing? 

averaged together. For the U.S. time series, anomalies of station-level indices were first 

averaged into 2.5° latitude by 2.5° longitude grid boxes. Where a grid box did not have 

any stations, the values of the indices from neighboring grid boxes were interpolated into 

that grid box in order to make the averaging area more spatially representative. The grid 

box values were then averaged on an area-weighted basis to create U.S. time series. The 

time series figures show the annual values and a smoothed line derived from a locally 

weighted regression (Lowess filter; Cleveland et al., 1988). An advantage of a Lowess 

filter is that it is not impacted very much by one extreme annual value that might occur in 

an El Niño year, and therefore it depicts the underlying long-term changes quite well. 

The number of very hot days has been increasing on average across the United States. 

Figure 3.13 shows the average change since 1950 in the warmest 10 percent of July 

maximum and minimum temperatures at each station. The positive trend in minimum 

temperatures implies significantly warmer nights. The maximum temperature decreased 

after a period of south-central U.S. droughts in the 1950s and has been increasing ever 

since. 

Temperature trends across the Gulf States region are not as pronounced as they are 

nationally due to the moderating effect of the proximate Gulf of Mexico waters. 

Figure 3.14 shows the anomaly in the number of days above 100 o

F averaged over stations 

within 500 km of Dallas, TX. Although centered outside the Gulf States region considered 

in this report, many of the stations are well within it, and this figure is certainly 

representative of the behavior of Gulf States extreme temperatures in the recent past. Note 

the cooling following the 1950s droughts. Also, note that the magnitude of interannual 

variations is considerably larger than any trend. 

Notwithstanding this absence of a detectible trend in the number of days exceeding a high 

threshold temperature, it is very likely that in the future the number of very hot days will 

substantially increase. Figure 3.15 shows a prediction of the average number of days 

exceeding 37.8 o

C (100 oF) in the June-July-August (JJA) season 25 years, 50 years, and 90 

years into the future under the SRES A2 scenario for Houston, TX, the closest station to 

Galveston, TX, with available data. The algorithm used for this prediction exploits current 

observations as well as predictions of the JJA average temperature from 17 of the climate 

models contained in the WGNE-CMIP3 database prepared for the IPCC Fourth 

Assessment Report. Twenty-five years from now, the probability of a week (although not 

necessarily continuous) of 37.8 o

C temperatures in this region is greater than 50 percent. 

Fifty years from now, the overall heating is such that the probability of three weeks of 37.8 o

C temperatures is greater than 50 percent. Note that results obtained under either the B1 

or A1B forcing scenarios would be statistically indistinguishable from these results until 

well after the mid-century mark. 

Climate models predict that the extreme temperature events could change more than the 

average climate over the course of the next century (IPCC, 2007). One way of quantifying 

this is to consider 20-year return values of the annual maximum of the daily average 

temperature. The 20-year return value is that value that is exceeded by a random variable 

once every 20 years on average over a long period of time. Such an event is truly rare, 

occurring only three or four times over the course of a typical human lifetime. Generalized 

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3-10 

extreme value theory provides a robust statistical framework to perform these calculations 

(Zwiers and Kharin, 1998; Wehner, 2005). Figure 3.16 shows the predicted change in this 

quantity at the end of 21st century under the SRES A1B scenario from a mean model 

constructed from 10 models from the WGNE-CMIP31 database. Over the Gulf States 

region, this extreme value change is about 1°C greater than the change in the average 

temperature. Another way to put this in perspective is to consider the frequency with 

which currently considered rare events will be encountered in the future. Figure 3.17 

shows the number of times in a 20-year period that the 1990-1999 return value would be 

reached near the end of the century. The purple shaded regions exceed 10 times; hence, 

currently considered rare events are likely to happen every other year or more frequently. 

3.1.7 Changes in Specific Temperature Maxima Affecting Transportation 

Transportation analysts have identified several specific attributes of temperature change of 

concern in transportation planning. Changes in annual days above 32.2 °C (90 °F) and 

maximum high temperature, for example, will impact the ability to construct and maintain 

transportation facilities. Concrete loses strength if it is set at air temperatures greater than 

32.2 °C and the ability of construction workers and maintenance staff to perform their 

duties is severely curtailed at temperatures above 32.2 °C degrees. In order to properly 

design for the thermal expansion of concrete and steel elements of transportation facilities, 

knowledge of the maximum expected temperatures is required. 

Since global climate models are integrated at spatial scales around 200 km, a linear 

regression analysis was used to downscale relationships between the three variables of 

greatest concern at the localized scale of a weather station to the transportation sector. 

Historical data from the USHCN for eight observation stations in the Gulf Coast study area 

were analyzed to determine highest temperature of record, mean number of days at 

minimum temperature 32.2 °C or higher, and mean daily temperature. Table 3.10 shows 

the reported observations for the eight weather stations for days above 32.2 °C and the 

associated annual and July mean daily temperatures. 

Based on the relationship established in the regression analysis of the historical data, 

changes in mean and extreme temperatures were calculated for the study area relevant to 

the temperatures in 2050 and 2100, as predicted by the global climate models used in this 

study. The analysis focused on the relationship between mean daily temperature, output 

from the climate models at 200-km scales, and the desired values downscaled to local 

spatial scales: number of days above 32.2 °C and the highest temperature of record. 

Comparisons were made to each of the annual mean daily temperatures and mean daily 

temperatures for the month of July to determine which relationship better provided the 

desired forecast variables. 

 

1

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3-11

A linear regression of days above 32.2 °C (90 °F) as an independent variable for the 

stations shown was undertaken for each of the annual mean daily and the July mean daily 

temperatures as the dependent variables. The regression of observed days above 32.2 °C 

versus annual mean daily temperature showed that for each rise by 0.6 °C (1 °F) in annual 

mean daily temperature there is an associated 3.9-day increase in the annual days above 

32.2 °C. However, the data for New Orleans falls outside the trend line for this 

relationship.2 The regression of days above 32.2 °C versus July mean daily temperature 

showed that for each rise by 0.6 °C (1 °F) in July mean daily temperature there is an 

associated 10-day increase in the annual days above 32.2 °C.3

The regression of observed high temperature versus annual mean daily temperature 

suggested that for each rise by 0.6 °C (1 °F) in annual mean daily temperature there is an 

associated 0.3 °C (0.6° F) rise in high temperature. However, this relationship only has an 

R-squared of 0.10, largely because the data for New Orleans falls outside the trend line. 

The regression of high temperature versus July mean daily temperature showed that for 

each rise by 0.6 °C (1 °F) in July mean daily temperature there is an associated 1.2 °C (2 

°F) rise in the high temperature.4

The mean daily temperature for the study area is 27.6 °C (81.7 °F). Based on the 

relationships established above, this implies that the existing high temperature should be 

approximately 40.6 °C (105 °F). For each additional 0.6 °C (1° F) degree increase in July 

mean daily temperature that is forecasted by the GCMs, this high temperature can be 

expected to increase by 1.2 °C (2 °F). Using the relationship developed, this implies that 

the baseline/historical number of days above 32.2 °C (90 °F) is approximately 77 days. For 

each additional increase of 0.6 °C (1 °F) in July mean daily temperature that is forecasted 

by the GCMs, the number of days above 32.2 °C (90 °F) can be expected to increase 

approximately 10 days.. 

Airport runway length in the United States is generally calculated based on the mean 

maximum temperature (that is, the average of the daily high temperatures) during the 

hottest month of the year during the prior 30-year record. August is the month with the 

highest monthly mean maximum temperature in the Gulf Coast study area. Mean 

maximum temperature is reported by NOAA for 283 NOAA stations across the United 

States, six of which are located in the study area. The average mean maximum temperature 

for the hottest month of the year from these six stations is 33.1 °C (91.6 °F). To verify this, 

we determined the 30-year mean maximum temperature data (1972 to 2002) from the 

Carbon Dioxide Information Analysis Center (CDIAC), which encompasses 12 reporting 

stations located in the study area. CDIAC data provides station elevation data as well as 

latitude and longitude data. The average mean maximum temperature from the 12 CDIAC 

 

2

 As a result, this relationship only has an R-squared of 0.27. 

3

 With an R-squared of 0.61 if New Orleans is included and 0.77 if New Orleans is excluded from the 

analysis. 

4

 The R-squared associated with this data is 0.42 if New Orleans is included and 0.89 if New Orleans is 

excluded from the analysis. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

stations is 33.0 °C (91.4 °F) (table 3.11). The airport section in the subsequent chapter 

deals more specifically with this dataset in an analysis of how runway length may be 

impacted by changes in temperature during the next 50 to 100 years. 

3.1.8 Increasing Daily Precipitation Extremes 

As mentioned above, current generation climate models are limited in their ability to 

simulate individual storms by a lack of horizontal resolution. From a simple theoretical 

argument (Allen and Ingram, 2003), it is expected that extreme precipitation events should 

become more intense as the climate warms. The IPCC (2007) concluded that the frequency 

of heavy precipitation events had increased over most areas during the past century and that 

a continued increase in heavy precipitation events is very likely during the 21st century. 

The largest rainfall rates occur when a column of air is completely saturated and 

precipitates out nearly completely. The Clausius-Claperyon relationship dictates that as the 

air temperature increases, the atmosphere has the ability to hold more water vapor. Hence, 

under a warmer climate, it is very likely that specific humidity will increase both on 

average and in extreme saturation conditions. Extreme-value analysis of model output for 

daily precipitation in the Gulf States region, similar to the analysis discussed above with 

daily surface air temperatures, reveals a predicted increase of around 10 percent in the 20-

year return value of the annual maximum of daily averaged precipitation, as shown in 

figure 3.18. The coarse horizontal resolution of the climate models used in this analysis 

results in an underestimation of extreme precipitation events (Wehner, 2005). 

Furthermore, these models lack the resolution to simulate tropical cyclones, a further 

source of extreme precipitation events. However, these deficiencies likely cause the 

prediction errors to be conservative, and it is likely that daily mean precipitation levels that 

are currently rare will become more commonplace in the future. 

 3.2 Hurricanes and Less Intense Tropical Storms 

Tropical cyclones (called hurricanes in the Atlantic and Gulf Coast regions) pose a severe 

risk to natural systems, personal property, and public infrastructure in the Gulf Coast 

region, and this risk will likely be exacerbated as the temperature of atmosphere and sea 

surface increase. Whereas loss of life from hurricanes has decreased in recent decades, 

property losses due to rapid population growth and economic development of coastal areas 

has increased (Herbert et al., 1997; Pielke and Pielke, 1997; Pielke and Landsea, 1998). 

Hurricanes have their greatest impact at the coastal margin where they make landfall and 

sustain their greatest strength. Severe beach erosion, surge overwash, inland flooding, and 

windfall casualties are exacted on both cultural and natural resources. Transportation 

facilities – roads, rails, pipelines, airports, ports – in coastal counties will likely be 

subjected to increasing hurricane intensity in the coming decades. Changes in Atlantic 

Basin hurricane formation and the behavior of hurricanes that make landfall in the Gulf 

Coast region have important implications for transportation planning, design, and 

maintenance in the short and long term. 

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3.2.1 Assessing Trends in Historical Hurricane Frequency and Intensity 

Understanding hurricane frequency and landfall patterns is an important process in 

calculating insurance liabilities and rates for coastal communities as well as forecasting 

future risk under a changing climate. Several studies have shown that landfalling 

hurricanes are more or less frequent for given coastal reaches of the United States (see 

figure 3.19) and within given decades over the recorded history of North Atlantic storms 

(Simpson and Lawrence, 1971; Ho et al., 1987; Neumann, 1991; Jarrell et al., 1992; Gray 

et al., 1997; Pielke and Pielke, 1997; Neumann et al., 1999; Vickery et al., 2000). While 

different methods have been employed to calculate landfall probabilities at the state and 

county levels, there is general agreement that south Florida, the Carolinas, and the western 

Gulf Coast are most frequently impacted by major hurricanes (figure 3.19). 

Studies of multidecadal hurricane variability and cycles have been complicated by the 

relatively short period of available and reliable data. Landfall counts of tropical storms and 

hurricanes at Grand Isle, LA, produced with a hurricane simulation model, HURASIM, 

(Doyle and Girod, 1997) (appendix E) for five-year periods from 1951 through 2005 show 

periods of greater and lesser hurricane history with short- and long-term variability 

(figure 3.20). If there is any pattern, historical records exhibit episodic hurricane activity 

rather than trends toward more frequent or stronger hurricanes, despite the most recent 

period of intense hurricane activity. While the long-term frequency trend of named storms 

within the Atlantic Basin has remained fairly constant, interannual variability is prominent 

particularly among major hurricanes (Gray, 1990; Landsea et al., 1992; Gray et al., 1997; 

Goldenberg et al., 2001; Bell and Chelliah, 2006). Hurricane spawning patterns have been 

linked to regional oscillation cycles, Atlantic thermohaline circulation, and African West 

Sahel rainfall patterns that have improved our understanding and forecasting of hurricane 

activity in the North Atlantic Basin (Gray et al., 1997; Landsea et al., 1999). 

Increased tropical storm activity is likely to accompany global warming as a function of 

higher sea surface temperatures, which have been observed globally (figure 3.21). The 

kinetic energy of tropical storms and hurricanes is fueled from the heat exchange in warm 

tropical waters. An increase in sea surface temperature (SST) from global climate change 

is likely to increase the probability of higher sustained winds per tropical storm circulation 

(Emanuel, 1987; Holland, 1997; Knutson et al., 1998). Sea surface temperature has 

increased significantly in the main hurricane development region of the North Atlantic 

during the past century (Bell et al., 2007) (figure 3.22) as well as in the Gulf of Mexico 

(Smith and Reynolds, 2004) (figure 3.23). 

Many scientists have evaluated the relationships between 20th-century warming and 

hurricane intensity, with some suggesting that the incidence of intense hurricanes over the 

past decade for the Atlantic basin could signal the beginning of an El Nino-Southern 

Oscillation (ENSO) related cycle of increased hurricane activity (Gray, 1984; O’Brien et 

al., 1996; Saunders et al., 2000). Henderson-Sellers et al. (1998) found no discernible 

trends in global hurricane trends with respect to number, intensity, or location during the 

past century. More contemporary analysis of the upswing in intense hurricane activity 

since the 1990s demonstrates that the proportion of intense, more destructive hurricanes 

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Chapter 3: How is the Gulf Coast Climate Changing? 

has increased in some ocean basins, including the North Atlantic, concomitant with rising 

sea surface temperature (Emanuel, 2005; Hoyos et al., 2006; Mann and Emanuel, 2006; 

Trenberth and Shea, 2006; Webster et al., 2005). Some studies conclude that the increase 

in recent decades is due to the combination of natural cyclical events (such as the North 

Atlantic Oscillation) and human-induced increases in sea surface temperature (Elsner, 

2006). 

Ocean currents that regulate heat content also appear to play an important role in the 

intensity of hurricanes when atmospheric conditions are favorable (Shay, 2006). In the 

Gulf of Mexico, the Loop Current is a heat conveyor that can build a heat reservoir 

spanning 200-300 km in diameter and 80-150 m in depth that is generally oriented towards 

the central Gulf Coast (figure 3.24) (Jaimes et al., 2006). Satellite-based and in situ 

measurements support the hypothesis that the warm water brought into the Gulf of Mexico 

by the Loop Current played an important role in the rapid intensification of Hurricanes 

Katrina, Rita, and Wilma (Jaimes et al., 2006). 

Santer et al. (2006) used 22 climate models to study the possible causes of increased SST 

changes in the Atlantic and Pacific tropical cyclogenesis region, where SST increased from 

0.32 °C to 0.67 °C (0.57 – 1.21 °F) over the 20th century. Their analysis suggests that 

century-timescale SST changes of this magnitude cannot be explained solely by unforced 

variability of the climate system. In experiments in which forcing factors are varied 

individually rather than jointly, human-caused changes in greenhouse gases are the main 

driver of the 20th-century SST increases in both tropical cyclogenesis regions. Ouuchi et 

al. (2006) used an atmospheric general circulation model at 20-km horizontal resolution to 

directly simulate the relationship between the tropical storm cycle and SST. This hurricane 

resolving model produced seasonal tropical storm statistics under present day conditions 

and was capable of hurricane force winds. When driven with the SST anomalies taken 

from A1B scenario experiments, the model produced fewer tropical storms everywhere 

except the North Atlantic Basin, where an increase was predicted. Tropical storms were 

more intense on average in all basins in these modeling experiments. 

These results and those from similar studies suggest that as radiative forcing and SST 

continue to increase, hurricanes will be more likely to form in the Atlantic and Pacific 

Basins and more likely to intensify in their destructive capacity. In its Fourth Assessment 

Report, the IPCC (2007) concludes that: 

• There is observational evidence for an increase of intense tropical cyclone activity in 

the North Atlantic since about 1970, correlated with increases of tropical sea surface 

temperatures; 

• Multidecadal variability and the quality of the tropical cyclone records prior to the 

beginning of routine satellite observations in about 1970 complicate the detection of 

long-term trends in tropical cyclone activity; and 

• There is no clear trend in the annual numbers of tropical cyclones. 

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Chapter 3: How is the Gulf Coast Climate Changing? 

3.2.2 Gulf Coast Hurricane History 

Gulf coast ecosystems are exposed to varying degrees of hurricane disturbance as 

influenced by storm frequency, periodicity, and duration. Figure 3.25 shows that tropical 

storm landfall across the Gulf of Mexico Basin increases geometrically from west to east. 

Because most storms spawn in tropical waters in the eastern Atlantic there is a greater 

probability for eastern landmasses on the same latitude to incur tropical storms (Elsner, 

1999). Temporal patterns of the past century reveal periods of relatively frequent 

hurricanes as well as inactive periods for most of the Gulf Coast region. The relatively 

calm period of record for hurricanes from the 1950s through the 1970s has some hurricane 

specialists purporting an increase in North Atlantic storms over the past decade related to 

ENSO oscillations and general warming trends (Elsner and Kara, 1999). Palynological and 

geological studies offer another means to reconstruct the regional history of hurricane 

activity over several centuries coincident with species changes and sedimentary overwash 

indicative of surge heights and storm intensity. One study of lake sediments in coastal 

Alabama suggests that major hurricanes of a Category 4 or 5 struck the Alabama coast with 

a frequency of about 600 years during the past three millennia (Liu and Fearn, 1993). 

3.2.3 HURASIM: Model Application 

HURASIM is a spatial simulation model of hurricane structure and circulation for 

reconstructing estimated windforce and vectors of past hurricanes. The model uses 

historical tracking and meteorological data of dated North Atlantic tropical storms from 

1851 to present. A description of the HURASIM model is presented in appendix E. 

The HURASIM model was applied in a hindcast mode to reconstruct hurricane windfields 

across the Gulf Coast region from Galveston, TX, to Pensacola, FL, on a 10-km grid basis 

for the period of record from 1851 to 2003. The model calculated windspeed and direction 

for every 15 minutes of storm movement retaining only wind events of 30 mph or greater 

for all proximal storms and grid cells within the study region. Storm tracking for calendar 

years 2004 and 2005 have not been added to the Hurricane Database (HURDAT) dataset as 

yet and, therefore, have been omitted from this analysis despite record storm activity that 

may be associated with multidecadal cycles and/or current global warming trends. 

3.2.4 Historical Storm Frequency Across the Northern Gulf Coast 

Study Region 

HURASIM model results were categorized by storm class based on the commonly used 

Saffir-Simpson scale over a 153-year period from 1851 to 2003 to gain an historical 

perspective of recurrence potential and spatial distribution of storm events along the 

northern Gulf Coast between Galveston, TX, and Pensacola, FL. Table 3.12 outlines the 

Saffir-Simpson scale for categorizing storms by intensity associated with range of 

windspeed. Storms on the Saffir-Simpson scale also have been ascribed typical storm 

surge levels based on observations during the 20th century. For example, NOAA states that 

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storm surge during landfall of a Category 1 hurricane is “generally 4 to 5 feet above 

normal,” and a Category 3 hurricane storm surge is “generally 9 to 12 feet above normal” 

(NOAA, 2007). In the Gulf Coast region, however, storm surge is highly variable for a 

given class of storm on the Saffir-Simpson scale in the Gulf Coast region. For example, 

Hurricane Camille, a Category 5 hurricane at landfall, had a peak storm surge in coastal 

Mississippi of 7.6 m (25 ft), while the storm surge associated with Hurricane Katrina (a 

Category 3 hurricane at landfall) had peak storm surge of 8.5 m (28 ft) (Graumann et al., 

2005). 

Figure 3.26 shows the frequency patterns of storm events with Category 1, 2, and 3 winds 

or higher across the study region. Results show that storm frequency by storm class is 

highest for southeastern coastal Louisiana than elsewhere and lowest in inland locations, 

decreasing with increasing latitude. Secondary locations with high hurricane incidence 

include Galveston, TX, and the Mississippi coast. Coastal reaches west of Galveston, TX, 

the chenier plain of southwest Louisiana, and northwest Florida have experienced low to 

moderate hurricane frequency respectively. The highest frequency of Category 3 storm 

winds or greater for the entire region are seven storms over the 153-year period, equivalent 

to four to five storms per century. Based on the historical perspective alone, transportation 

planners should expect at least one major hurricane of Category 3 or greater to strike the 

northern Gulf Coast every 20 years. Over the same 20 years, planners can expect another 

Category 2 hurricane and two Category 1 hurricanes for a combined incidence rate of at 

least one hurricane every five years. While this rate is indicative of the worst-case grid 

location coastwide and over the entire historical record, the chance for storm track 

convergence elsewhere within the region is expected to be similar. However, storm 

frequency may be influenced by multidecadal variability such that some sites may 

experience higher incidence depending on the timeframe and whether it spans periods of on 

and off cycles. 

3.2.5 Temporal and Spatial Analysis of Hurricane Landfall 

The northern Gulf Coast exhibits spatially disjunct patterns of storm strikes related to the 

landfall tracks and storm categories (figure 3.27). Of storms exceeding Category 3-level 

winds between 1851 and 2003, the HURASIM model counted a maximum of seven storms 

equal to a recurrence interval of one major hurricane every 22 years for southeastern 

Louisiana. Hurricane tracking records are available from 1851 to present, but data 

accuracy was greatly improved at the turn of the century with expanded and instrumented 

weather stations and since 1944 when aircraft reconnaissance of tropical storms was 

instituted. HURASIM model output was analyzed by segmented time periods to determine 

short-term return frequencies of tropical storms to account for cyclical behavior and data 

accuracy for successive intervals of 15, 30, and 50 years of the longer 153-year record from 

1851 to 2003. Data analysis focuses on the maximum potential return interval of storms by 

category according to the Saffir-Simpson scale. Given the prospect of questionable data 

accuracy of storm history and multidecadal storm cycling, it was deemed prudent to report 

storm frequencies for different time intervals to establish upward bounds of storm 

recurrence probabilities for catastrophe planning and assessment akin to worst-case 

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Chapter 3: How is the Gulf Coast Climate Changing? 

scenarios. Shorter time windows are likely to exhibit a wide range of storm recurrence 

probabilities (both high and low) relative to longer periods. 

The shorter the period of observation, the greater the probability of inflating the calculated 

return interval. Figure 3.28 shows the storm frequency for 15-, 30-, and 50-year intervals 

for Category 1 storms or greater for the most active grid location across the study area. 

The most active time period historically for all time intervals was the latter 19th century, 

despite concerns of data accuracy for this period. These data show a potential maximum of 

storm incidence of three to five hurricanes every 10 years, nearly twice the strike frequency 

for the entire 153-year record. The lowest incidence of hurricane activity within the Gulf 

Coast study region for all time intervals spans the 1970s and 1980s with two to three 

hurricanes for every 10 years. These historical hurricane return intervals provide an 

expected range of .2 and .5 probability that a hurricane may strike a given coastal county 

within the study region that can be used to guide coastal planning and preparation. Recent 

hurricane studies spurred by the upswing in hurricane activity of the 1990s and early 21st

century reveal the highly variable and cyclical nature of hurricane activity in the Northern 

Gulf of Mexico, as well as the need for reliable datasets that can be used to quantify longterm trends and relationships with sea surface temperature (Goldenberg et al., 2001). 

3.2.6 Patterns of Hurricane Wind Direction 

The HURASIM model outputs wind direction during storm landfall, which often relates to 

storm impact based on exposure to direct wind force. Road signs, for example, may be 

more prone to damage or destruction depending on their orientation to circulating storm 

winds. Because most storms approach the coast from the Gulf of Mexico on a northerly 

track, approaching storm winds are easterly and northeasterly on account of the 

counterclockwise rotation of North Atlantic tropical storms. Figure 3.29 displays 

simulated wind rows and direction of wind force derived for one of the most active grid 

cell locations in the study region at Grand Isle, LA, for tropical storm and hurricane 

conditions over the 153-year period of record. The concentration of wind rows is westerly 

and southerly for tropical storm events in accordance with prevailing storm approach from 

the south. Hurricane-force winds and direction at Grand Isle demonstrate a distinct shift to 

southwesterly and southeasterly directions as a result of major hurricanes passing to the 

east. As hurricanes pass inland of a given site, yet sustain their strength, backside winds in 

the opposite direction can occur. The length of each wind row is a function of the total 

number of 15-minute intervals of storm track interpolation and passage extracted from the 

HURASIM model. Longer wind rows are indicative of more frequent occurrences. Wind 

row data and polargrams have been generated for each grid cell within the Gulf Coast study 

region so that local and regional characterization of wind direction can be determined. 

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3.2.7 Modeling Climate Change Effects on Tropical Cyclones into the 

21st Century 

Early theoretical work on hurricanes suggested an increase of about 10 percent in wind 

speed for a 2 °C (4 °F) increase in tropical sea surface temperature (Emanuel, 1987). A 

2004 study from the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, 

that utilized a mesoscale model, downscaled from coupled global climate model runs, 

indicated the possibility of a 5 percent increase in the wind speeds of hurricanes by 2080 

(cf. IPCC, 2001). To explore how climate change could affect 21st century hurricane 

intensity, windspeeds of hurricanes during 1904 to 2000 were modeled and then projected 

to increase from 5 to 20 percent over the equivalent forecast period of 2004 to 2100. Storm 

tracking for calendar years 2004 and 2005 have not been added to the HURDAT 

(NOAA/NCDC) dataset as yet and, therefore, have been omitted from this analysis despite 

record storm activity in 2005 that may be associated with multidecadal cycles and/or 

current global warming trends. Future storm intensities were calculated by multiplying the 

historical wind reconstructions with the proportional increase based on the forecast year 

relative to a ramping increase to 5, 10, 15, and 20 percent by the year 2100. The theoretical 

and empirical limits of maximum hurricane intensity appear to be highly correlated with 

SSTs (Miller, 1958; Emanuel, 1986, 1988; Holland, 1997). While climatologists debate 

the weight of contributing factors, including SST, modeling and recent empirical evidence 

suggest that a 10 percent or more increase in potential intensity is plausible under warming 

conditions predicted for the 21st century (Emanuel, 1987; Camp and Montgomery, 2001; 

Knutson and Tuleya, 2004). 

Due to the differences in multidecadal hurricane activity over the 20th century, it was 

appropriate to evaluate the potential increase in storm frequency relative to the period of 

record. Figure 3.30 shows the potential increase in storm frequency by years 2050 and 

2100 under a climate change scenario that supposes increased ramping of hurricane 

intensity concomitant with warming sea surface temperatures projected at 5, 10, 15, and 20 

percent over the 21st century. Results show that an increase of one to two hurricanes above 

the historical frequency can be expected by year 2050 and up to four added hurricanes by 

year 2100. The potential gain of four hurricanes over the next century from a 20 percent 

increase in storm intensities nearly doubles the strike probability of the historical record. 

Not only will hurricane incidence increase under these assumptions, but individual storms 

will be stronger such that more catastrophic storms are likely to develop regardless of 

landfall location. These models and simulated data provide transportation planners with 

discrete and generalized probabilities of potential hurricane impact based on past and future 

climate. 

 3.3 Sea Level Rise and Subsidence 

Changes in climate during ice ages and warming periods have affected sea levels and 

coastal extent, as evidenced from geologic records. Currently, global sea level is on the 

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rise and is likely to accelerate with continued fossil fuel consumption from modernization 

and population growth (IPCC, 2001, 2007). As sea level rises, coastal shorelines will 

retreat, and low-lying areas will tend to be inundated more frequently, if not permanently, 

by the advancing sea. Subsidence (or sinking) of the land surface already is contributing to 

the flooding of transportation infrastructure in many Gulf Coast counties. In order to 

assess the vulnerability of transportation systems to inundation due to sea level rise, an 

integrated assessment of all important influences on coastal flooding must be considered. 

Relative sea level rise (RSLR) is the combined effect of an increase in ocean volume 

resulting from thermal expansion, the melting of land ice (“eustatic” sea level rise), and the 

projected changes in land surface elevation at a given location. 

In this section, global sea level trends are first reviewed, including a comparison of IPCC 

findings in the Third and Fourth Assessments. This is followed by an examination of sea 

level rise and subsidence in the study region. The application of two different models to 

project RSLR in the region is then discussed, and a summary of the modeled range of 

projected RSLR to 2100 is presented. 

3.3.1 Historical and Projected Global Sea Level Trends 

Sea level has risen more than 120 m since the peak of the last ice age (about 20,000 B.P.) 

and over the 20th century by 1-2 mm/year (Douglas, 1991, 1997; Gornitz, 1995; IPCC, 

2001). The rate of global sea level rise since 1963 is estimated at 1.8 mm/year (IPCC, 

2007). More recent analysis of satellite altimetry data for the period from 1993 to 2003 

shows a global average rate of sea level rise of about 3.1 (2.4-3.8) mm per year. Whether 

the faster rate since 1993 reflects decadal variability or a long-term acceleration over the 

20th-century rate is unclear. There is high confidence, however, that the rate of observed 

sea level rise was greater in the 20th century compared to the 19th century (IPCC, 2007). 

The rate of sea level rise in the world ocean basins varied significantly during the 20th

century. Sea level rise during the 21st century is projected to have substantial geographical 

variability as well. The historical rate of sea level rise calculated from tide gauge records, 

and satellite altimetry is much higher in the Gulf of Mexico than in many other ocean 

basins (see IPCC, 2007, Working Group I, page 412). 

The IPCC Third Assessment Report (TAR) (2001) projected an increase of 0.09-0.88 m in 

average global sea level by year 2100 with a mid-range estimate of 0.45 m. The range of 

projected sea level rise through 2100 is slightly lower and narrower in the IPCC Fourth 

Assessment Report (AR4) (see table 3.1). The midpoint of the projections in sea level rise 

differs by roughly 10 percent, and the ranges in the two assessment reports would have 

been similar if they had treated uncertainties in the same way (IPCC, 2007). As noted 

earlier, the IPCC 2007 sea level rise projections do not include rapid dynamical changes in 

ice flow from Greenland or Antarctica. If realized, some of the model-based projections 

could more than double the rate of sea level rise over the past century. 

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3.3.2 Tide Records, Sea Level Trends, and Subsidence Rates along the Central 

Gulf Coast 

Changes in mean water level at a given coastal location are affected by a combination of 

changes in sea level in an ocean basin and by local factors such as land subsidence. Gulf 

Coastal Plain environments, particularly in the central and western parts of the Gulf Coast 

study area, are prone to high rates of land surface subsidence attributed to soil 

decomposition and compaction, deep fluid extraction (Morton et al., 2001, 2002; White and 

Morton, 1997), and the lack of sediment deposition. For example, the Mississippi River 

delta region demonstrates relative sea level rates of 10 mm/year, tenfold greater than 

current eustatic sea level rise (Penland and Ramsay, 1990; Gornitz, 1995). Cahoon et al. 

(1998) measured subsidence rates for several Gulf Coast sites ranging from a low of 2.7 

mm/year in the Big Bend region of northwest Florida up to 23.9 mm/year for coastal 

Louisiana. Some of the forces driving shallow subsidence apparently included seasonal 

changes in water levels and a periodic occurrences of major storms. 

The National Ocean Service (NOS), a division of NOAA, validates and reposits historical 

water level records at primary tide stations along the coasts and Great Lakes of the United 

States. Historic data from tide stations located within the Gulf Coast study region have 

been downloaded from the NOS web site at <http://tidesandcurrents.noaa.gov> in graphical 

and digital formats to be used in model simulations for projecting future sea level rise. 

Three tide stations at Pensacola, FL, Grand Isle, LA, and Galveston, TX, comprise the most 

reliable long-term tide records corresponding with the eastern, central, and western 

coverage of the study area (figure 3.31). The mean sea level trend for these gauges shows 

Grand Isle, LA, with the highest rate at 9.85 mm/year, followed by Galveston, TX, at 6.5 

mm/year, and Pensacola, FL, at the lowest rate of 2.14 mm/year. These trend values are 

indicative of the high rates of local subsidence in Louisiana and Texas relative to the more 

stable geology underlying the Florida Panhandle. Multiple studies have extracted 

subsidence rates from these and other tide gauges within the Gulf Coast sector with some 

variability in rate estimates and methodology that mostly reaffirm regional patterns of 

generally high or low subsidence trends (Swanson and Thurlow, 1973; Penland and 

Ramsay, 1990; Zervas, 2001; Shinkle and Dokka, 2004). 

Long-term tide gauge records are among the most reliable measures of local and regional 

subsidence. However, tide records also include the long-term trend of eustatic sea level 

change, which over the last century has been estimated at 1.7-1.8 mm/year on a global 

basis (Douglas, 1991, 1997, 2001; IPCC, 2001, 2007; Holgate and Woodworth, 2004). 

Accounting for historical eustatic change in accord with the global average equates to 

regional subsidence rates of 8.05 mm/year for Grand Isle, LA, and the Mississippi River 

deltaic plain; 4.7 mm/year for Galveston, TX, and the chenier plain; and 0.34 mm/year for 

Pensacola, FL, and Mississippi/Alabama Sound of the central Gulf Coast. The high 

subsidence rate of the Mississippi River Delta region at Grand Isle, LA, is more than four 

times greater than the historical eustatic trend of the last century and will account for a 

relative rise in sea level approaching 0.81 m by the year 2100, apart from future eustatic 

changes. Some areas within the coastal zone of Louisiana have subsidence rates exceeding 

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3-21

20 mm/year, demonstrating the potential range and variability within a subregion (Shinkle 

and Dokka, 2004). 

Subsidence rates across a broad region like the Gulf Coast are highly variable on a local 

scale even within a representative coastal landform such as the Mississippi River deltaic 

plain or chenier plain. Many factors contribute to the rate and process of subsidence at a 

given locale by natural compaction, dewatering, and subsurface mineral extractions. 

Releveling surveys of benchmark monuments and well heads provide additional evidence 

and rates of rapid subsidence (Morton et al., 2001, 2002; Shinkle and Dokka, 2004). An 

extensive releveling project of the Lower Mississippi River coastal plain of first-order 

benchmarks along major highway corridors provides an expansive network of measured 

subsidence rates (Shinkle and Dokka, 2004). Oil and gas extractions in coastal Louisiana 

and southeastern Texas have accelerated local subsidence and wetland loss concomitant 

with production (Morton et al., 2001, 2002). Releveling projects in large cities such as 

New Orleans and Houston-Galveston have demonstrated high subsidence rates related to 

sediment dewatering and groundwater pumping, increasing the vulnerability to local 

flooding (Gabrysch, 1984; Zilkowski and Reese, 1986; Gabrysch and Coplin, 1990; 

Holzschuh, 1991; Paine, 1993; Galloway et al., 1999; Burkett et al., 2002). 

3.3.3 Sea Level Rise Scenarios for the Central Gulf Coast Region 

Two different sea level rise models were used to assess the range of sea level change that 

could be expected in the study area during the next 50 to 100 years. The Sea Level Rise 

Rectification Program (SLRRP) (see appendix F) is a model developed by the U.S. 

Geological Survey to explore the combined effects of future sea level change and local 

subsidence on coastal flooding patterns. CoastClim is a commercially available model that 

allows users to select GCM and emissions scenarios to predict sea level change within 

GCM grid cells over oceans. Table 3.13 outlines the selection list of GCM models that 

were available for use with SLRRP and the CoastClim models at the time of this study. 

SLRRP projects future sea level rise for select tide gauge locations by rectifying the 

historical tide record of monthly means for the period of record and adding the predicted 

global mean eustatic sea level change obtained from IPCC (2001).5

 The tidal data input for 

the SLRRP model is composed of mean monthly water levels, which captures both shortterm seasonal deviations and long-term trends of sea level change. Monthly values are 

derived from averaged hourly recordings for each month. A mean sea level trend is 

calculated for each tide gauge station, which includes both the local subsidence rate of 

 

5

 The sea level rise estimates from the IPCC Fourth Assessment Report were not available when the sea level 

rise simulations were run for this study. The projected range of sea level change in the IPCC Fourth 

Assessment Report (2007) has an upper limit that is slightly lower and a lower limit that is slightly greater 

than the projections contained in the IPCC Third Assessment Report (2001). The IPCC Fourth Assessment 

Report also indicates, however, that the rate of historical sea level rise was greater in the Gulf of Mexico 

than in most other ocean basins, so the global average rate may tend to underestimate the rate of change in 

the study area. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

vertical land movement and the eustatic rate of global sea level change for the period of 

record. Data records are given in stage heights for different tidal datums such as mean low 

water, mean tide level, and mean high water, which were rectified to the North American 

Vertical Datum of 1988 (NAVD88) to readily compare with land-based elevations of roads 

and other transportation infrastructure. Monthly extremes data also were used in this study 

to show that daily highs within a month can exceed the monthly average by as much 0.284 

m and 0.196 m for Galveston, TX, and Pensacola, FL, respectively. (SLRRP model 

procedures and inputs are explained in further detail in appendix F.) 

The SLRRP model indicates that surface elevations between 47.8 cm and 119.6 cm 

(NAVD88) will be inundated by sea level rise through 2050, dependent on geographic 

location, emissions scenario, and GCM forecast. The SLRRP model suggests that surface 

elevations between 70.1 cm and 199.6 cm (NAVD88) will be inundated by sea level rise 

through 2100, again dependent on geographic location, emissions scenario, and GCM 

forecast. Table 3.14 provides SLRRP model results showing the mean land surface 

elevations (cm, NAVD88) subject to coastal flooding for Galveston, TX, Grand Isle, LA, 

and Pensacola, FL, by 2050 and 2100 based on averaged output for all seven GCM models 

for the A1F1, B1, A1B, and A2 emissions scenarios. 

The CoastClim V.1. model is another database tool for extracting predicted sea level for a 

given location, GCM, and emissions scenario much like the SLRRP model. CoastClim has 

a global database to predict regional patterns of sea level change associated with grid cell 

output of inclusive GCM models. CoastClim’s user-friendly interface allows the user to 

select the region of interest from a global map. With a mouse click on the shoreline map, 

CoastClim picks the closest GCM grid cell and extracts a normalized index of regional sea 

level change relative to the global mean sea level. The normalized index is derived as a 

ratio or scaling factor for the average pattern of sea level change for the region or grid cell 

resolution divided by the global mean sea level change for the forecast period of 2071 to 

2100. Table 3.15 shows the equivalent normalized index for each of seven GCM model 

selections for Galveston, TX, Grande Isle, LA, and Pensacola, FL. The different models 

display a variable range of grid cell resolution and projected sea level response above and 

below the global mean from 0.88 to 1.04 for the northern Gulf Coast region. The user also 

can select from six SRES emissions scenarios (A1B, A1F1, A1T, A2, B1, and B2) to run 

for a given GCM application. CoastClim displays the predicted outcome in relative sea 

level rise above zero in tabular and graphical format from 1990 to 2100. 

CoastClim was used to generate predicted outcomes for seven different GCM models, six 

SRES scenarios, and three greenhouse gas forcing conditions of low, mid, and high for a 

total of 126 individual sea level rise curves for the 21st century. Results indicate that sea 

level rise will vary with both the selected model and emissions scenario. The high 

emissions A1F1 outcome for all GCM models predicts the highest rates of sea level change 

among SRES options, with a minimum eustatic sea level rise of 0.67 m by 2100, maximum 

potential rise of 1.55 m, and a mid-range around 1 m depending on model selection. The 

CoastClim model shows that relative sea level will rise between 12.68 cm and 75.42 cm by 

2050, dependent on-site location, emissions scenario, and GCM forecast. By 2100, 

CoastClim predicts a potential sea level rise between 23.64 cm and 172.06 cm depending 

on-site location, emission scenario, and GCM forecast. Table 3.16 displays the CoastClim 

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model results of the mean predicted sea level rise (cm) for the Gulf Coast region by 2050 

and 2100 under high, mid-, and low IPCC (2001) scenarios based on combined output for 

all seven GCM models for the A1F1, B1, A1B, and A2 emissions scenarios. However, 

these same eustatic rates are captured in the SLRRP model but rectified to a geodetic 

datum and local tidal conditions that more accurately reflect the potential for coastal 

flooding. 

 3.4 Storm Surge 

Storm surge is a wave of water that is pushed onshore by the force of the winds in the right 

quadrant of hurricane approach that can often inundate shoreline and inland areas up to 

many miles, length, and width. The added wave energy from advancing storms combines 

with normal tides to create the hurricane storm tide, which increases mean water levels to 

record heights, usually inundating roadways and flooding homes and businesses. The level 

of surge in a particular area is determined by the slope of the offshore continental shelf and 

hurricane intensity. The stronger the hurricane and the shallower the offshore water, the 

higher the surge will be. This advancing surge combines with the normal tides to create the 

hurricane storm tide, which can increase the mean water level 15 ft or more. In addition, 

wind-driven waves are superimposed on the storm tide. This rise in water level can cause 

severe flooding in coastal areas, particularly when the storm tide coincides with the normal 

high tides. 

3.4.1 Predicting Storm Surge with the SLOSH Model 

NOAA’s National Weather Service forecasters model storm surge using the SLOSH (Sea, 

Lake, and Overland Surges from Hurricanes) model. NOAA and the Federal Emergency 

Management Agency (FEMA) use SLOSH to predict potential height of storm surge so as 

to evaluate which coastal areas are most threatened and must evacuate during an advancing 

storm. The SLOSH model is a computerized model run by NOAA’s National Hurricane 

Center (NHC) to estimate storm surge heights and winds resulting from historical, 

hypothetical, or predicted hurricanes by taking into account storm barometric pressure, 

size, forward speed, track, and wind force. The model accounts for astronomical tides by 

specifying an initial tide level but does not include rainfall amounts, riverflow, or winddriven waves. SLOSH also considers the approach or angle of hurricane landfall, which 

can effectively enhance surge height of westerly and northwesterly approaching storms 

along the northern Gulf Coast. Graphical output from the model displays color-coded 

storm surge heights for a particular area in feet above the model’s reference level, the 

National Geodetic Vertical Datum (NGVD), which is the elevation reference for most 

maps. Emergency managers use output data and maps from SLOSH to determine which 

areas must be evacuated for storm surge. 

Modeling, theory, and recent empirical evidence suggest that hurricane intensity is likely to 

increase in the Gulf Coast region (see prior section on hurricanes). Even if hurricanes do 

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Chapter 3: How is the Gulf Coast Climate Changing? 

not become more intense, however, sea level rise alone will increase the propensity for 

flooding that will occur when hurricanes make landfall in the Gulf Coast region. To assess 

the combined potential effects of hurricanes and sea level rise on the Gulf Coast 

transportation sector, a database of storm surge heights for Category 3 and 5 hurricanes 

was developed by using NOAA’s SLOSH model for all coastal counties (extending inland 

from coastal counties along the Gulf of Mexico to those counties incorporating I-10) for the 

study area. Resulting surge elevations were overlaid on ArcViewTM representations of each 

study area, enabling views of the study area in its entirety and minimum graphic 

representations at the county/parish level. 

The NHC developed the SLOSH model to predict storm surge potential from tropical 

cyclones for comprehensive hurricane evacuation planning. The SLOSH models requires 

grid-based configurations of near-shore bathymetry and topography on a basin level. The 

NHC has defined 38 basins in the Atlantic and Pacific Oceans of which there are 14 

subbasins that define the offshore and onshore geomorphology of the Gulf Coast shoreline 

from the Florida Keys to the Laguna Madre of Texas. SLOSH model simulations were 

performed for a merged suite of SLOSH basins (n=7) that covers the central Gulf Coast 

between Galveston, TX, and Mobile, AL, (table 3.17). SLOSH output were compiled for 

28 simulation trials to extract surge levels for varying storm intensities (Categories 2-5) 

and landfall approaches. A sample simulation of surge height predictions are shown based 

on combined output for storms of Category 2, 3, 4, and 5 approaching the eastern half of 

the study area (Louisiana, Mississippi, and Alabama) on different azimuths (figure 3.32). 

Storm intensity, speed, and direction produces different storm surge predictions. Model 

simulation trials conducted for the SLOSH basin that covers New Orleans involved 

calibration and validation checks with historical storms and flood data. 

Study area SLOSH applications involved the collection, synthesis, and integration of 

various geospatial information and baseline data for the central Gulf Coast region relevant 

to storm surge model implementation and predictions, with the following objectives: 

• To derive a database of storm surge heights for Category 3 and 5 hurricanes by using 

NOAA’s SLOSH model for all coastal counties (extending inland from coastal counties 

along the Gulf of Mexico to those counties incorporating I-10), for the study area 

spanning Galveston, TX, to Mobile, AL; 

• To overlay the resulting surge elevations on ArcViewTM representations of each study 

area, enabling views of the study area in its entirety and minimum graphic 

representations at the county level; 

• To add topographic contours at 1-m intervals to the study area datasets; and 

• To color code storm surge heights based on surge elevation in meters. 

The integration of SLOSH output with local geospatial data will be particularly useful in 

phase II of the study, which will involve an assessment of transportation impacts for a 

particular county or Metropolitan Planning Organization (MPO) within the study area. 

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3.4.2 Future Sea Level Rise and Storm Surge Height 

Sea level rise can be incorporated into surge height predictions from SLOSH simulations 

for future years by elevating surge levels in proportion to the amount of rise for any given 

scenario (figure 3.33). Sea level change will be particularly important in influencing this 

coastal area, since the land already is subject to flooding with supranormal tides and surge 

and rainfall events of even smaller, less powerful, tropical storms. Improved spatial detail 

and vertical accuracy of coastal elevations will greatly enhance predictions of the spatial 

extent of flooding from projected sea level rise and storm surges. Lidar imagery used in 

this project for coastal Louisiana offers distinct advantages for modeling purposes and 

graphical representation over other available Digital Elevation Model (DEM) data sources 

such as the National Elevation Dataset (figure 3.34). Also, it is expected that storm surges 

superimposed on higher mean sea levels will tend to exacerbate coastal erosion and land 

loss. During Hurricanes Rita and Katrina, for example, 562 km2

 (217 mi2) of land in 

coastal Louisiana was converted to open water (Barras, 2006), and the Chandeleur Island 

chain was reduced in size by roughly 85 percent (USGS, 2007). The implications of the 

loss of these natural storm buffers on transportation infrastructure have not been quantified. 

Surge analyses were conducted for the Gulf Coast study area by reviewing historical tide 

records and simulated hurricane scenarios based on the NOAA SLOSH model. Highest 

tide records for over 70 coastal tide stations were obtained from historical records within 

the study area, with the highest recorded surge of 6.2 m (20.42 ft) (NAVD88) at Bay 

St. Louis, MS, in the wake of a northerly approaching Category 5 storm, Hurricane Camille 

(1969). After Hurricane Katrina (2005), high watermark surveys in New Orleans proper 

and east along the Gulf Coast in Mississippi revealed storm surge heights approaching 8.5 

m (28 ft) mean sea level (m.s.l.). Simulated storm surge from NOAA SLOSH model runs 

across the central Gulf Coast region demonstrate a 6.7-7.3-m (22-24-ft) potential surge 

with major hurricanes of Category 3 or greater without considering a future sea level rise 

effect. Storm approach from the east on a northwesterly track can elevate storm surge 0.3-

1.0 m (1-3 ft) in comparison to a storm of equal strength approaching on a northeasterly 

track. The combined conditions of a slow churning Category 5 hurricane making landfall 

on a westerly track along the central Gulf Coast under climate change and elevated sea 

levels indicate that transportation assets and facilities at or below 9 m (30 ft) m.s.l. are 

subject to direct impacts of projected storm surge. 

 3.5 Other Aspects of Climate Change with Implications for 

Gulf Coast Transportation 

Temperature, precipitation, runoff, sea level rise, and tropical storms are not the only 

components of Gulf Coast climate that have the potential to change as the temperature of 

the atmosphere and the sea surface increase. Changes in wind and wave regime, 

cloudiness, and convective activity could possibly be affected by climate change and would 

have implications for some modes of transportation in the Gulf Coast region. 

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Chapter 3: How is the Gulf Coast Climate Changing? 

3.5.1 Wind and Wave Regime 

There have been very few long-term assessments of near surface winds in the United 

States. Groisman and Barker (2002) found a decline in near surface winds of about 

-5 percent during the second half of the 20th century for the United States, but they suggest 

that a stepwise increase in the number of wind-reporting stations noticeably reduced the 

variance of the regionally averaged time series. They note that most reporting stations are 

located near airports and other developed areas. They did not attribute the decrease to 

climate change or land use change. Warming trends can be expected to generate more 

frequent calm weather conditions typical of summer months and generally characterized by 

lower winds than more windy conditions typical of cold-season months (Groisman et al.,

2004). 

Few studies have been made of potential changes in prevailing ocean wave heights and 

directions as a consequence of climate change, even though such changes can be expected 

(Schubert et al., 1998; McLean et al., 2001). In the North Atlantic, a multidecadal trend of 

increased wave height has been observed, but the cause is poorly understood (Guley and 

Hasse, 1999; Mclean et al., 2001). Wolf (2003) attributes the increasing North Atlantic 

wave height in recent decades to the positive phase of the North Atlantic Oscillation, which 

appears to have intensified commensurate with the slow warming of the tropical ocean 

(Hoerling et al., 2001; Wang et al., 2004). Changes in wave regime will not likely be 

uniform among ocean basins, however, and no published assessments have focused 

specifically on how climate change may affect wind and wave regime in the Gulf of 

Mexico. One 3-year study of wave and wind climatologies for the Gulf of Mexico (Teague 

et al., 1997) indicates that wave heights and wind speeds increase from east to west across 

the Gulf. This particular study, which is based on TOPEX/POSEIDEN satellite altimetry 

and moored surface buoy data, also indicates seasonality with the highest wind speeds and 

wave heights in the fall and winter. 

Scenarios of future changes in seasonal wave heights constructed by using climate model 

projections for the northeastern Atlantic indicated increases in both winter and fall seasonal 

means in the 21st century under three forcing scenarios (Wang et al., 2004). The IPCC 

(2007) concludes that an increase in peak winds associated with hurricanes will accompany 

an increase in tropical storm intensity. Increasing average summer wave heights along the 

U.S. Atlantic coastline are attributed to a progressive increase in hurricane activity between 

1975 and 2005 (Komar and Allan, 2007). Wave heights greater than 3 m increased by 0.7 

to 1.8 m during the study period, with hourly averaged wave heights during major 

hurricanes increasing significantly from about 7 m to more than 10 m since 1995 (Komar 

and Allan, 2007). A more recent study of wave heights in the central Gulf of Mexico 

between 1978 and 2005 suggests a slight increase, but the trend is not statistically 

significant (Komar and Allan, 2008) (figure 3.35). 

If tropical storm windspeed increases as anticipated (see section 3.2.8), this will tend to 

have a positive effect on mean wave height during the coming decades. Wave heights in 

coastal bays also will tend to increase due to the combined erosional effects of sea level 

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Chapter 3: How is the Gulf Coast Climate Changing? 

rise and storms on coastal barrier islands and wetlands (Stone and McBride, 1998; Stone et 

al., 2003). 

3.5.2 Humidity and Cloudiness 

As the climate warms, the amount of moisture in the atmosphere is expected to rise much 

faster than the total precipitation amount (Trenberth et al., 2003). The IPCC (2007) has 

concluded that tropospheric water vapor increased over the global oceans by 1.2 ± 0.3 

percent per decade from 1988 to 2004, consistent in pattern and amount with changes in 

SST and a fairly constant relative humidity. Several studies have reported an increase in 

the near surface specific humidity (the mass of water vapor per unit mass of moist air) over 

the United States during the second half of the past century (Sun et al., 2000; Ross and 

Elliot, 1996). Sun et al. (2000) found that during 1948 to 1993, the mean annual specific 

humidity under clear skies steadily increased at a mean rate of 7.4 percent per 100 years. 

Gaffen and Ross (1999) analyzed annual and seasonal dewpoint temperature, specific 

humidity, and relative humidity at 188 first-order weather stations in the United States for 

the period from 1961 to 1995. (Relative humidity is a measure of comfort based on 

temperature and specific humidity.) Coastal stations in the southeastern United States 

were moister than inland stations at comparable latitude, and stations in the eastern half of 

the country had specific humidity values about twice those at interior western stations. 

This dataset also shows increases in specific humidity of several percent per decade and 

increases in dewpoint of several tenths of a degree per decade over most of the country in 

winter, spring, and summer, with nighttime humidity trends larger than daytime trends 

(Gaffen and Ross, 1999). In the southeastern United States, specific humidity increased 2 

to 3 percent per decade between 1973 and 1993 (Ross and Elliot, 1996), and this trend is 

expected to continue. 

3.5.3 Convective Activity 

Sun et al. (2001) documented a significant increase in total, low, cumulonimbus, and 

stratocumulus cloudiness across the United States during 1948 to 1993. The largest 

changes in the frequency of cumulonimbus cloudiness occurred in the intermediate 

seasons, especially in the spring. The increase in the frequency of cumulonimbus cloud 

development is consistent with the nationwide increase in the intensity of heavy and very 

heavy precipitation observed by Karl and Knight (1998) and Groisman et al. (2004). 

Cumulonimbus clouds are commonly associated with afternoon thunderstorms in the Gulf 

Coast region. The historical and projected increase in summer minimum temperatures for 

the study area suggest an increase in the probability of severe convective weather (Dessens, 

1995, Groisman et al., 2004). 

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Chapter 3: How is the Gulf Coast Climate Changing? 

 3.6 Conclusions 

The empirical climate record of the past century, in addition to climate change scenarios, 

was examined to assess the past and future temperature and hydrology of the central Gulf 

Coast region. The empirical record of the region shows an annual temperature pattern with 

high values in the 1920s-1940s, with a drop in annual temperatures in late 1950s, which 

persisted through the 1970s. Annual temperatures then began to climb over the past three 

decades but still have not reached the highs of previous decades. The timing of the 

increase in Gulf Coast temperatures is consistent with the global “climate shift” since the 

late 1970s (Karl et al., 2000 and Lanzante, 2006) when the rate of temperature change 

increased in most land areas. 

Annual precipitation in the study area shows a suggestion toward increasing values, with 

some climate divisions, especially those in Mississippi and Alabama, having significant 

long-term trends. There also is a modeled long-term trend of increasing annual runoff 

regionwide. Over the entire record since 1919, there was an increase in rainfall that, 

combined with relatively cool temperatures, led to an estimated 36 percent increase in 

runoff. Modeled future water balance, however, suggests that runoff is expected to either 

decline slightly or remain relatively unchanged, depending upon the balance of 

precipitation and evaporation. Moisture deficits and drought appear likely to increase 

across the study area, though model results are mixed. These findings are consistent with 

the IPCC (2007), which concludes that it is very likely that heat waves, heat extremes, and 

heavy precipitation events over land will increase during this century and that the number 

of dry days (or spacing between rainfall events) will increase. Even in mid-latitude regions 

where mean precipitation is expected to decrease, precipitation intensity is expected to 

increase (IPCC, 2007). 

Changes in rainfall beyond the study area can play an important role in the hydrology of 

the coastal zone. Weather patterns over the Mississippi River basin, which drains 41 

percent of the United States, and other major drainages contribute to the total runoff in the 

Gulf Coast region. Several recent modeling efforts suggest an increase in average annual 

runoff in the eastern half of the Mississippi River watershed, while drainage west of the 

Mississippi and along the southern tier of states is generally predicted to decrease (Milly et 

al., 2005; IPCC, 2007). In the case of the Mississippi River, drainage to the coast is not 

presently a major factor in terms of flooding of infrastructure, because the river is levied 

and only a small portion of its flow reaches the marshes and shallow waters of the 

Louisiana coastal zone. Drainage of the Mississippi River and other rivers to the coast, 

however, is important in maintaining coastal soil moisture and water quality. The decline 

of approximately 150,000 acres of coastal marsh in southern Louisiana in 2000 was 

attributed to extreme drought, high salinities, heat and evaporation, and low river discharge 

(State of Louisiana, 2000). 

As stated earlier, climate models currently lack the spatial and temporal detail needed to 

make confident projections or forecasts for a number of variables, especially on small 

spatial scales, so plausible “scenarios” are often used to provide input to decision making. 

Output from an ensemble of 21 general circulation models (GCMs) run with the three 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

emissions scenarios indicate a wide range of possible changes in temperature and 

precipitation out to the year 2050. The models agree to a warmer Gulf Coast region of 

about 1.5 °C ± 1 °C, with the greatest increase in temperature occurring in the summer. 

Based on historical trends and model projections, we conclude that it is very likely that in 

the future the number of very hot days will substantially increase across the study area. 

Due to the non-normality of temperature distributions over the five Gulf States, extreme 

high temperatures could be about 1oC greater than the change in the average temperature 

simulated by the GCMs. 

Scenarios of future precipitation are more convoluted, with indications of increases or 

decreases by the various models, but the models lean slightly toward a decrease in annual 

rainfall across the Gulf Coast. However, by compounding changing seasonal precipitation 

with increasing temperatures, average runoff is likely to remain the same or decrease, while 

deficits (or droughts) are more likely to become more severe. 

Each of the climate model and emissions scenarios analyzed in this report represent 

plausible future world conditions. As stated earlier, GCMs currently lack the spatial and 

temporal detail needed to make projections or forecasts, so plausible “scenarios” are often 

used to provide input to decision making. These models also lack the capacity for 

simulating small-scale phenomena such as thunderstorms, tornadoes, hail, and lightning. 

However, climate models do an excellent job of simulating temperature means and 

extremes. Hourly and daily precipitation and runoff extremes are much more difficult to 

simulate due to horizontal resolution constraints. However, based on observational and 

modeling studies the IPCC (2007) and numerous independent climate researchers have 

concluded that more intense precipitation events are very likely during this century over 

continental land masses in the Northern Hemisphere. 

Recent empirical evidence suggests a trend towards more intense hurricanes formed in the 

North Atlantic Basin, and this trend is likely to intensify during the next century (IPCC, 

2007). In the Gulf region, there is presently no compelling evidence to suggest that the 

number or paths of tropical storms have changed or are likely to change in the future. 

Convective activity, heavy precipitation events, and cloudiness all appear likely to increase 

in the Gulf Coast region as the climate warms. 

Change in the rate of sea level rise is dependent on a host of interacting factors that are best 

evaluated on decadal to centennial time scales. Two complimentary modeling approaches 

were applied in this study to assess the potential rise in sea level and coastal submergence 

over the next century. Both models were used to estimate RSLR by 2050 and 2100 under a 

range of greenhouse gas emissions scenarios. Both models account for eustatic sea level 

change as estimated by the global climate models and also incorporate values for land 

subsidence in the region based on the historical record. One model, CoastClim, produces 

results that are closer to a simple measure of future sea level change under the scenarios of 

future climate. A similar model, SLRRP, also incorporates values for high and low tidal 

variation attributed to astronomical and meteorological causes, which are pulled from the 

historical record. The SLRRP model is rectified to the NAVD88 that is commonly used by 

surveyors to calculate the elevations of roads, bridges, levees, and other infrastructure. The 

tide data used in the SLRRP model is based on a monthly average of the mean high tide 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

(called mean high higher water) for each day of the month. The SLRRP results capture 

seasonal variability and interannual trends in relative sea level change, while the CoastClim 

results do not. 

The three long-term tide gauge locations analyzed in this study represent three subregions 

of the study area: Galveston, TX (the chenier plain); Grand Isle, LA (the Mississippi River 

deltaic plain); and Pensacola, FL (Mississippi/Alabama Sound). For each of these gauges, 

we examined potential range of relative sea level rise through 2050 and 2100 using the 

SRES B1, A1B, A2, and A1F1 emissions scenarios based on the combined output of 7 

GCMs (table 3.14). Results for the year 2100 generated with CoastClim range from 24 cm 

(0.8 ft) in Pensacola to 167 cm (5.5 ft) in Grand Isle. Results for the year 2100 from 

SLRRP, which as noted above accounts for historical tidal variation, are somewhat higher: 

predicted relative sea level ranges from 70 cm (2.3 ft, NAVD88) in Pensacola to 199 cm 

(6.5 ft, NAVD88) in Grand Isle. 

Storm surge simulations accomplished basin-specific surge height predictions for a 

combination of storm categories, track speeds, and angled approach on landfall that can be 

summarized by worst-case conditions to exceed 6 to 9 m (20 to 30 ft) along the central 

Gulf Coast. Storm attributes and meteorological conditions at the time of actual landfall of 

any storm or hurricane will dictate actual surge heights. Transportation officials and 

planners within the defined study area can expect that transportation facilities and 

infrastructure at or below 9 m of elevation along the coast are subject to direct and indirect 

surge impacts. Sea level rise of 1 to 2 m (3-6 ft) along this coast could effectively raise the 

cautionary height of these surge predictions to 10 m (33 ft) or more by the end of the next 

century. 

Changes in climate can have widespread effects on physical and biological systems of lowlying, sedimentary coasts. However, the large and growing pressures of development are 

responsible for most of the current stresses on Gulf Coast natural resources, which include: 

water quality and sediment pollution, increased flooding, loss of barrier islands and 

wetlands, and other factors that are altering the resilience of coastal ecosystems (U.S. 

Environmental Protection Agency, 1999). Human alterations to freshwater inflows through 

upstream dams and impoundments, dredging of natural rivers and engineered waterways, 

and flood-control levees also have affected the amount of sediment delivered to the Gulf 

coastal zone. Roughly 80 percent of U.S. coastal wetland losses have occurred in the Gulf 

Coast region since 1940, and predictions of future population growth portend increasing 

pressure on Gulf Coast communities and their environment. Sea level rise will generally 

increase marine transgression on coastal shorelines (Pethick, 2001) and the frequency of 

barrier island overwash during storms, with effects most severe in coastal systems that 

already are stressed and deteriorating. An increase in tropical storm intensity or a decrease 

in fresh water and sediment delivery to the coast would tend to amplify the effects of sea 

level rise on Gulf Coast landforms. 

Our assessment of historical and potential future changes in Gulf Coast climate section 

draws on publications, analyses of instrumental records, and models that simulate how 

climate may change in the future. Model results, climatic trends during the past century, 

and climate theory all suggest that extrapolation of the 20th-century temperature record 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing? 

would likely underestimate the range of change that could occur in the next few decades. 

The global near-surface air temperature increase of the past 100 years is approaching levels 

not observed in the past several hundred years (IPCC, 2001); nor do current climate 

models span the range of responses consistent with recent warming trends (Allen and 

Ingram, 2002). Regional “surprises” are increasingly possible in the complex, nonlinear 

Earth climate system (Groisman et al., 2004), which is characterized by thresholds in 

physical processes that are not completely understood or incorporated into climate model 

simulations; e.g., interactive chemistry, interactive land and ocean carbon emissions, etc. 

While there is still considerable uncertainty about the rates of change that can be expected 

(Karl and Trenberth, 2003), there is a fairly strong consensus regarding the direction of 

change for most of the climate variables that affect transportation in the Gulf Coast region. 

Key findings from this analysis and other published studies for the study region include: 

Warming Temperatures – An ensemble of GCMs indicate that the average annual 

temperature is likely to increase by 1-2 °C (2-4 °F) in the region by 2050. Extreme high 

temperatures also are expected to increase, and within 50 years the probability of 

experiencing 21 days a year with temperatures of 37.8 °C (100 °F) is greater than 50 

percent. 

Changes in Precipitation Patterns – While average annual rainfall may increase or 

decrease slightly, the intensity of individual rainfall events is likely to increase during the 

21st century. It is possible that average soil moisture and runoff could decline, however, 

due to increasing temperature, evapotranspiration rates, and spacing between rainfall 

events. 

Rising Sea Levels – Relative sea level is likely to rise between 1 and 6 ft by the end of the 

21st century, depending upon model assumption and geographic location. The highest rate 

of relative sea level rise will very likely be in the central and western parts of the study area 

(Louisiana and East Texas) where subsidence rates are highest. 

Storm Activity – Hurricanes are more likely to form and increase in their destructive 

potential as the sea surface temperature of the Atlantic and Gulf of Mexico continue to 

increase. Rising relative sea level will exacerbate exposure to storm surge and flooding. 

Depending on the trajectory and scale of individual storms, facilities at or below 9 m (30 ft) 

could be subject to direct storm surge impacts. 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Tables 

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Table 3.1 Projected global average surface warming and sea level rise at the 

end of the 21st century (IPCC, 2007). These estimates are assessed 

from a hierarchy of models that encompass a simple climate 

model, several Earth models of intermediate complexity (EMIC), 

and a large number of atmosphere-ocean global circulation models 

(AOGCM). Sea level projections do not include uncertainties in 

carbon-cycle feedbacks because a basis in published literature is 

lacking (IPCC, 2007). 

 Temperature Change 

(°C from 2090-2099 

Relative to 1980-1999) 

Sea Level Rise 

(m) from 2090-2099 

Relative to 1980-1999) 

Case 

Best 

Estimate 

Likely 

Range 

Model-Based Range, 

Excluding Future Rapid 

Dynamical Changes in Ice Flow 

Constant Year 2000 Concentrations 0.6 0.3-0.9 NA 

B1 Scenario 1.8 1.1-2.9 0.18-0.38 

A1T Scenario 2.4 1.4-3.8 0.20-0.45 

B2 Scenario 2.4 1.4-3.8 0.20-0.43 

A1B Scenario 2.8 1.7-4.4 0.21-0.48 

A2 Scenario 3.4 2.0-5.4 0.23-0.51 

A1F1 Scenario 4.0 2.4-6.4 0.26-0.59 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.2 United States Historical Climatology Network (USHCN) 

stations within the seven climate divisions of the central 

Gulf Coast region. 

Climate Division (CD) USHCN Stations 

Texas CD 8 Danevang, Liberty 

Louisiana CD 7 Jennings1

Louisiana CD 8 Franklin, Lafayette 

Louisiana CD 9 Donaldsonville, Houma, New Orleans, Thibodaux 

Louisiana CD 6 Amite, Baton Rouge, Covington 

Mississippi 10 Pascagoula, Poplarville, Waveland 

Alabama CD 8 Fairhope 

1

 The Jennings climate record only dates back to the late 1960s. As a result, CD 7 is made up of an average 

of Liberty, TX, to the west and Lafayette, LA, to the east. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.3 List of GCMs run with the three SRES emissions scenarios 

(A1B, A2, and B1) for this study. Not all model runs were 

available from the IPCC Data Centre for each SRES scenario. 

A1B A2 B1 

Temperature Precipitation Temperature Precipitation Temperature Precipitation 

CCCMA CCCMA.T63 BCCR BCCR BCCR BCCR 

CCCMA.T63 CNRM CCCMA CNRM CCCMA CCCMA.T63 

CNRM CSIRO CNRM CSIRO CCCMA.T63 CNRM 

CSIRO GFDL0 CSIRO GFDL0 CNRM CSIRO 

GFDL0 GFDL1 GFDL0 GFDL1 CSIRO GFDL0 

GFDL1 GISS.AOM GFDL1 GISS.ER GFDL0 GFDL1 

GISS.AOM GISS.EH GISS.ER INMCM3 GFDL1 GISS.AOM 

GISS.EH GISS.ER INMCM3 IPSL GISS.AOM GISS.ER 

GISS.ER IAP IPSL MIROC.MEDRES GISS.ER IAP 

IAP INMCM3 MIROC.MEDRES ECHAM IAP INMCM3 

INMCM3 IPSL ECHO MRI INMCM3 IPSL 

IPSL MIROC.HIRES ECHAM CCSM3 IPSL MIROC.HIRES 

MIROC.HIRES MIROC.MEDRES MRI PCM MIROC.HIRES MIROC.MEDRES

MIROC.MEDRES ECHAM CCSM HADCM3 MIROC.MEDRES ECHAM 

ECHO MRI PCM HADGEM1 ECHO MRI 

ECHAM CCSM3 HADCM3 ECHAM CCSM3 

MRI PCM HADGEM1 MRI PCM 

CCSM HADCM3 CCSM HADCM3 

PCM PCM 

HADCM3 HADCM3 

HADGEM1 
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Table 3.4 Scenarios of temperature change (°C) from an ensemble of GCMs 

for the 5th, 25th, 50th, 75th, and 95th percentiles for the A1B scenario 

for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter 0.18 0.95 1.42 1.89 2.56 

Spring 1.22 1.55 1.80 2.04 2.38 

Summer 1.24 1.66 1.94 2.23 2.70 

Autumn 1.31 1.69 1.93 2.22 2.62 

Table 3.5 Scenarios of precipitation change (percent) from an ensemble of 

GCMs for the 5th, 25th, 50th, 75th, and 95th percentiles for the A1B 

scenario for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter -13.30 -5.95 -1.79 2.49 9.01 

Spring -21.07 -11.04 -5.04 1.80 10.17 

Summer -36.10 -17.77 -6.39 6.25 26.24 

Autumn -8.20 0.46 5.97 12.05 21.50 
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Table 3.6 Scenarios of temperature change (°C) from an ensemble of GCMs 

for the 5th, 25th, 50th, 75th, and 95th percentiles for the A2 scenario 

for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter 0.2 1.0 1.5 2.0 2.9 

Spring 0.8 1.3 1.7 2.0 2.6 

Summer 1.1 1.5 1.8 2.1 2.5 

Autumn 1.0 1.5 1.8 2.1 2.6 

Table 3.7 Scenarios of precipitation change (percent) from an ensemble of 

GCMs for the 5th, 25th, 50th, 75th, and 95th percentiles for the A2 

scenario for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter -12.7 -5.7 0.4 5.6 13.6 

Spring -22.9 -12.8 -6.0 0.5 10.3 

Summer -31.2 -15.0 -5.2 5.9 21.3 

Autumn -7.3 1.3 7.0 12.7 22.1 
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Table 3.8 Scenarios of temperature change (°C) from an ensemble of GCMs 

for the 5th, 25th, 50th, 75th, and 95th percentiles for the B1 scenario 

for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter -0.31 0.44 1.02 1.53 2.32 

Spring 0.67 1.05 1.32 1.62 2.03 

Summer 0.64 1.09 1.35 1.63 2.03 

Autumn 0.62 1.04 1.33 1.62 2.07 

Table 3.9 Scenarios of precipitation change (percent) from an ensemble of 

GCMs for the 5th, 25th, 50th, 75th, and 95th percentiles for the B1 

scenario for 2050 relative to 1971-2000 means. 

 5th 25th 50th 75th 95th

Winter -9.77 -4.37 -0.52 3.36 9.51 

Spring -16.94 -7.96 -2.94 2.41 11.38 

Summer -27.06 -14.16 -3.36 7.43 24.19 

Autumn -7.83 -0.06 5.63 11.13 19.40 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.10 Days above 32.2 °C (90 °F) and mean daily temperature in the 

study area for datasets running through 2004. The start date 

varies by location (note the number of years of observed data). 

Years of Annual Days Normal Mean Daily (°F) 

Station Observed Data Above 90 °F Annual July 

Mobile, AL 42 74 66.8 81.5 

Baton Rouge, LA 45 84 67.0 81.7 

Lake Charles, LA 40 76 67.9 82.6 

New Orleans, LA 58 72 68.8 82.7 

Meridian, MS 40 80 64.7 81.7 

Houston, TX 35 99 68.8 83.6 

Port Arthur, TX 44 83 68.6 82.7 

Victoria, TX 43 106 70.0 84.2 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.11 Modeled outputs of potential temperature increase (°C [°F]) 

scenarios for August. 

Mid-Term Potential (2050 Scenarios) Long-Term Potential (2100 Scenarios) 

Temperature Increase by Scenario Percentile: °C (°F) Temperature Increase by Scenario Percentile: °C (°F) 

Scenario 5th 50th 95th Scenario 5th 50th 95th

A1B 1.6 (2.9) 2.5 (4.5) 3.4 (6.1) A1B 3.0 (5.4) 3.9 (7.0) 5.0 (9.0) 

B1 0.9 (1.6) 1.8 (3.2) 2.6 (4.7) B1 1.8 (3.2) 2.7 (4.9) 3.6 (6.5) 

A2 1.1 (2.0) 2.3 (4.1) 3.4 (6.1) A2 3.3 (5.9) 4.7 (8.5) 6.0 (10.8) 

Note: Lowest/highest changes in bold. 

Table 3.12 Saffir-Simpson Scale for categorizing hurricane intensity and 

damage potential. Note that maximum sustained wind speed 

is the only characteristic used for categorizing hurricanes. 

Saffir-Simpson Scale 

and Storm Category 

Central Pressure 

(mbar) 

Maximum Sustained 

Wind Speed (mph) Damage Potential 

1 980 74-95 Minimal 

2 965-979 96-110 Moderate 

3 945-964 111-130 Extensive 

4 920-944 131-155 Extreme 

5 < 920 >155 Catastrophic 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.13 GCM model-selection options based on data availability for the 

USGS SLRRP and CoastClim models for generating future sea 

level rise projections. There are 3 GCM model datasets shared 

between SLRRP and CoastClim and a total of 11 GCM models 

and datasets altogether. 

SLRRP GCM Listing CoastClim GCM Listing 

CSIRO_Mk2 CGCM1 

CSM 1.3 CGCM2 

ECHAM4/OPYC3 CSIRO_Mk2 

GFDL_R15_a GFDL_R15_b 

HadCM2 GFDL_R30_c 

HadCM3 HadCM2 

PCM HadCM3 

Notes: CGMC1, CGCM2: Canadian Global Coupled Model . 

 CSIRO_Mk2: Commonwealth Scientific and Industrial Research Organisation [Australia] –. 

 CSM 1.3: Climate Simulation Model (NCAR) 

 ECHAM4/OPYC3: A coupled global model developed by the Max-Planck-Institute for 

Meteorology (MPI) and Deutsches Klimarechenzentrum (DKRZ) in Hamburg, Germany 

GFDL_R15a, R15b, R30c: Geophysical Fluid Dynamics Laboratory 

HADCM2, HADCM3: Hadley Centre Coupled Model. 

 PCM: Parallel Climate Model – DOE/NCAR 
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Table 3.14 USGS SLRRP model results showing the mean land surface 

elevations (cm [NAVD88]) subject to coastal flooding for the Gulf 

Coast region by 2050 and 2100 under a high, mid, and low scenario 

based on combined output for all seven GCM models for the A1F1, 

B1, A1B, and A2 emissions scenarios. 

Year 2050 Low Year 2100 Low 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 83.0 80.9 83.4 83.4 Galveston, TX 130.7 117.0 124.9 127.0 

Grand Isle, LA 107.5 106.0 108.8 106.3 Grand Isle, LA 171.2 159.7 168.7 167.6 

Pensacola, FL 48.0 47.8 48.4 53.7 Pensacola, FL 83.9 70.1 78.2 75.2 

 

Year 2050 Mid Year 2100 Mid 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 88.9 86.7 88.7 88.8 Galveston, TX 146.0 129.5 137.1 140.8 

Grand Isle, LA 113.6 111.8 114.2 111.8 Grand Isle, LA 185.3 171.4 180.2 181.3 

Pensacola, FL 53.9 53.6 53.7 60.0 Pensacola, FL 99.2 82.6 90.3 89.3 

 

Year 2050 High Year 2100 High 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 94.8 92.5 93.9 94.3 Galveston, TX 161.3 142.0 149.3 154.5 

Grand Isle, LA 119.6 117.6 119.6 117.3 Grand Isle, LA 199.6 183.1 191.7 195.1 

Pensacola, FL 59.8 59.4 58.9 66.3 Pensacola, FL 114.5 95.0 102.5 103.5 

Table 3.15 Regional grid cell counts and normalized indices of sea level rise 

relative to global mean sea level projections for northern Gulf 

Coast tide gage locations by different GCM models used in 

CoastClim simulations. 

Normalized SLR Index 

CoastClim 

Models 

Gulf Coast Grid 

Cell Count 

Galveston, TX Grand Isle, LA Pensacola, FL 

CGCM1 5 0.89 0.89 0.89 

CGCM2 5 1.04 1.04 0.95 

CSIRO_Mk2 3 0.90 0.94 0.94 

GFDL_R15_b 2 0.94 0.88 0.89 

GFDL_R30_c 6 0.98 1.01 1.01 

HadCM2 2 1.02 1.02 1.02 

HadCM3 7 1.03 1.00 0.96 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.16 CoastClim model results showing the mean sea level rise (cm) for 

the Gulf Coast region by 2050 and 2100 under a high, mid, and low 

scenario based on combined output for all seven GCM models for 

the A1F1, B1, A1B, and A2 emission scenarios. 

Year 2050 Low Year 2100 Low 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 40.5 39.2 40.2 39.6 Galveston, TX 81.8 72.4 76.3 78.6 

Grand Isle, LA 60.6 59.3 60.3 59.8 Grand Isle, LA 118.8 109.3 113.3 115.6 

Pensacola, FL 14.2 13.0 14.0 14.2 Pensacola, FL 33.6 24.3 28.2 32.0 

 

Year 2050 Mid Year 2100 Mid 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 46.2 44.3 45.8 44.8 Galveston, TX 101.8 84.9 92.2 95.4 

Grand Isle, LA 66.4 64.4 66.0 64.9 Grand Isle, LA 138.9 121.8 129.3 132.4 

Pensacola, FL 20.0 18.1 19.6 19.8 Pensacola, FL 53.5 36.8 44.1 49.3 

 

Year 2050 High Year 2100 High 

 A1FI B1 A1B A2 A1FI B1 A1B A2 

Galveston, TX 54.3 51.6 53.8 52.1 Galveston, TX 130 103.7 115.5 119.3 

Grand Isle, LA 74.5 71.7 73.9 72.3 Grand Isle, LA 167.3 140.7 152.5 156.4 

Pensacola, FL 28.1 25.3 27.5 27.5 Pensacola, FL 81.6 55.6 67.2 73.9 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Table 3.17 Seven SLOSH basin codes, name descriptions, and storm 

categories included in the central Gulf Coast study region and 

simulation trials from Mobile, AL, to Galveston, TX. 

Basin Code Basin Name Storm Category 

EMOB Elliptical Mobile Bay Cat2, Cat3, Cat4, Cat5 

NBIX MS – Gulf Coast Cat2, Cat3, Cat4, Cat5 

MS2 New Orleans Cat2, Cat3, Cat4, Cat5 

LFT Vermilion Bay Cat2, Cat3, Cat4, Cat5 

EBPT Elliptical Sabine Lake Cat2, Cat3, Cat4, Cat5 

EGL2 Elliptical Galveston Bay (2002) Cat2, Cat3, Cat4, Cat5 

PSX Matagorda Bay Cat2, Cat3, Cat4, Cat5 

Table 3.18 SLRRP model parameters and results showing the mean sea level 

rise projections for the Gulf Coast region by 2050 and 2100 under 

a high, mid, and low scenario based on combined output for all 

seven GCM models for the A1F1 emission scenario. 

Model Parameters Scenarios 

Louisiana-Texas

Chenier Plain 

Louisiana 

Deltaic Plain 

MississippiAlabama Sound 

Tide Gauge Galveston, TX Grand Isle, LA Pensacola, FL 

Sea Level Trend (mm/yr) 6.5 9.85 2.14 

Subsidence (mm/yr) 4.7 8.05 0.34 

Sea Level Rise by 2050 (cm, NAVD88) High 94.8 119.6 59.8 

 Mid 88.9 113.6 53.9 

 Low 83.0 107.5 48.0 

Sea Level Rise by 2100 (cm, NAVD88) High 161.3 199.6 114.5 

 Mid 146.0 185.3 99.2 

 Low 130.7 171.2 83.9 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Figure 3.1 CO2 emissions, SO2 emissions, and atmospheric CO2

concentration through 2100 for the six “marker/illustrative” 

SRES scenarios and the IS92a scenario (a “business as usual” 

scenario, IPCC [1992]). (Source: IPCC, 2001) 

Figure 3.2 United States climate divisions of the central Gulf Coast 

study area. Empirical trends and variability were analyzed for 

temperature and precipitation at the Climate Division Dataset- 

(CDD) level for the climate divisions along the Gulf Coast from 

Galveston, TX, to Mobile, AL, including Texas Climate Division 8, 

Louisiana Divisions 6-9, Mississippi Division 10, and Alabama 

Division 8. These climatic divisions cover the entire central Gulf 

Coast study area. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

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Figure 3.3 Grid area for the GCM temperature and precipitation results 

presented in section 3.15 of this report, which is a subset of the 

global grid of a typical GCM output. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

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Figure 3.4 Scatterplot of seasonal temperature and precipitation predictions 

by an ensemble of GCMs for the Gulf Coast region in 2050 

created by using the SRES A1B emissions scenario. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

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Figure 3.5 Temperature variability from 1905 to 2003 for the seven climate 

divisions making up the Gulf Coast study area. The level of 

significance in long-term temperature trend within each division 

was determined at a≤0.05. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

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Figure 3.6 Precipitation variability from 1905 to 2003 for the seven climate 

divisions making up the Gulf Coast study area. The level of 

significance in long-term precipitation trend within each division 

was determined at a≤0.05. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Figure 3.7 Variability and trends in model-derived surplus (runoff) and 

deficit from 1919 to 2003 for the Gulf Coast study area. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

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Figure 3.8 Probability density functions for seasonal temperature change in 

the Gulf Coast study area for 2050 created by using the A1B 

emissions scenario. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 3: How is the Gulf Coast Climate Changing?: Figures 

3F-8 

Figure 3.9 Probability density functions for seasonal precipitation change in 

the Gulf Coast study area for 2050 created by using the A1B 

emissions scenario. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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Figure 3.10 Quantile estimates of monthly precipitation for the 2- to 100-year 

return period generated by using the 1971 to 2000 baseline period 

relative to GCM output for the A1B emissions scenario at the 5, 

50, and 95 percent quartiles. 

0

100

200

300

400

500

600

2-year 5-year 10-year 25-year 50-year 100-year

Precipitation in mm

71-00 5th 50th 95th
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Figure 3.11 Quantile estimates of monthly average runoff for the 2- to 100-

year return period generated by using the 1971 to 2000 baseline 

period relative to GCM output for the A1B emissions scenario at 

the 5, 50, and 95 percent quartiles. 

0

50

100

150

200

250

300

350

2-year 5-year 10-year 25-year 50-year 100-year

Runoff in mm

71-00 5th 50th 95th
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Figure 3.12 Quantile estimates of monthly average deficit for the 2- to 100-

year return period generated by using the 1971 to 2000 baseline 

period relative to GCM output for the A1B emissions scenario at 

the 5, 50, and 95 percent quartiles. 

0

50

100

150

200

250

2-year 5-year 10-year 25-year 50-year 100-year

Deficit in mm

71-00 5th 50th 95th
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Figure 3.13 The change in the warmest 10 percent of July maximum and 

minimum temperatures at each station across the entire United 

States, for 1950-2004. Note that the number of days above the 90th

percentile in minimum temperature is rising faster than it is in 

maximum temperature. 
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Figure 3.14 Historical time series from stations within 500 km of Dallas, TX, 

showing anomalies of the number of days above 37.7 °C (100 °F), 

for 1950-2004. 
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Figure 3.15 The current and future probabilities of having 1 to 20 days during 

the summer at or above 37.8 °C (100 °F) in or near Houston, TX, 

under the A2 emissions scenario. 
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Figure 3.16 Mean model predicted change (°C) of the 20-year return value of 

the annual maximum daily averaged surface air temperature 

under the A1B emissions scenario in the Gulf States region. This 

analysis compares the 1990-1999 period to the 2090-2099 period. 
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Figure 3.17 Number of times on average, over a 20-year period, that the 1990-

1999 annual maximum daily averaged surface air temperature 20-

year return value levels would be reached under the SRES A1B 

2090-2099 forcing conditions. Under 1990-1999 forcing 

conditions, this value is defined to be one. 
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Figure 3.18 Mean model-predicted fractional change of the 20-year return 

value of the annual maximum daily averaged precipitation under 

the SRES A1B in the Gulf States region. This analysis compares 

the 1990-1999 period to the 2090-2099 period.
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Figure 3.19 Geographic distribution of hurricane landfalls along the Atlantic 

and Gulf Coast regions of the United States, from 1950 to 2006. 

(Source: NOAA, National Climate Data Center, Asheville, NC) 
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Figure 3.20 Frequency histogram of landfalling storms of tropical storm 

strength or greater in Grand Isle, LA, summarized on a 5-year 

basis, for the period 1851-2005. (Source: NOAA National 

Hurricane Research Division) 

0

1

2

3

4

5

6

7

1851 - 1855

1856 - 1860

1861 - 1865

1866 - 1870

1871 - 1875

1876 - 1880

1881 - 1885

1886 - 1890

1891 - 1895

1896 - 1900

1901 - 1905

1906 - 1910

1911 - 1915

1916 - 1920

1921 - 1925

1926 - 1930

1931 - 1935

1936 - 1940

1941 - 1945

1946 - 1950

1951 - 1955

1956 - 1960

1961 - 1965

1966 - 1970

1971 - 1975

1976 - 1980

1981 - 1985

1986 - 1990

1991 - 1995

1996 - 2000

2001 - 2005
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Figure 3.21 Hemispherical and global mean sea surface temperatures for the 

period of record from 1855 to 2000. (Source: NOAA, National 

Climate Data Center, Asheville, NC) 
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Figure 3.22 Sea surface temperature trend in the main hurricane development 

region of the North Atlantic during the past century. Red line 

shows the corresponding 5-yr running mean. Anomalies are 

departures from the 1971–2000 period monthly means. 

(Source: Bell et al., 2007) 
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Figure 3.23 Sea surface temperature trends in the Gulf of Mexico region 

produced by using the ERSST v.2 database. The plot includes the 

SST anomalies averaged annually, as well as the anomalies 

determined from the averages for August only and the JulySeptember peak of the hurricane season. 

(Source: Smith and Reynolds, 2004) 

ERSST v.2: Extended Reconstructed Sea Surface Temperatures, version 2. 
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Figure 3.24 The location and intensity of Hurricane Katrina at intervals of 6 

hours show two intensification events. Circles indicate data from 

National Hurricane Center advisories showing storm intensity (TS 

and TD stand for tropical storm and tropical depression, 

respectively): (a) Intensification is not correlated with sea surface 

temperature (from POES high-resolution infrared data); (b) In 

contrast, the intensifications correlate well with highs in the ocean 

dynamic topography (from Jason 1,TOPEX, Envisat, and GFO sea 

surface height data). The Loop Current can be seen entering the 

Gulf south of Cuba and exiting south of Florida; the warm-core ring 

(WCR) is the prominent high shedding from the Loop Current in 

the center of the Gulf. (Source: Scharroo et al., 2005) 

Envisat: An advanced polar-orbiting Earth observation satellite of the European Space Agency 

that \provides measurements of the atmosphere, ocean, land, and ice 

GFO: Satellite program of U.S. Navy GEOSAT Follow-On (GFO) program to maintain 

continuous ocean observations 

Jason-1: NASA satellite monitoring global ocean circulation 

POES: Polar Observational Environmental Satellite 

TOPEX: TOPEX/Poseidon is a CNES and NASA satellite monitoring ocean surface topography. 
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Figure 3.25 Frequency histogram of tropical storm events for coastal cities 

across the Gulf of Mexico region of the United States over the 

period of record from 1851 to 2006. 

0

50

100

150

200

250

300

Brownsville, Tx

Raymondville, Tx

Sarita, Tx

Corpus Christi, Tx

Port Lavaca, Tx

Bay City, Tx

Galveston, Tx

Port Arthur, Tx

Lake Charles, La

Lafayette, La

Baton Rouge, La

New Orleans, La

Gulfport, Ms

Mobile, Al

Pensacola, Fl

Fort Walton Beach, Fl

Panama City, Fl

Apalachicola, Fl

St. Marks, Fl

Cross City, Fl

Cedar Key, Fl

Brooksville, Fl

St. Petersburg, Fl

Venice, Fl

Fort Myers, Fl

Marco, Fl

Key Largo, Fl

Miami, Fl
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Figure 3.26 Frequency analysis of storm events exhibiting Category 1, 2, and 3 

winds or higher across the Gulf Coast study area. 
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Figure 3.27 Latitudinal gradient of declining storm frequency of Category 1 

hurricanes or greater from Grand Isle, LA, inland, illustrating the 

reduction of storm strength over land away from the coast, for the 

period 1951-2000.
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Figure 3.28 Storm frequency variation for 15-, 30-, and 50-year intervals for 

Category 1 storms or greater for the most active grid location 

across the Gulf Coast study region. 
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Figure 3.29 Simulated wind rows and direction of wind force derived from the 

HURASIM model for one of the most active grid cell locations in 

the study area at Grand Isle, LA, for tropical storm and hurricane 

conditions over the 153-year period of record, 1851 - 2003. 
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Figure 3.30 Potential increase in the number of hurricanes by the years 2050 

and 2100, assuming an increase in hurricane intensity at 5, 10, 15, 

and 20 percent concomitant with warming sea surface 

temperatures projected. 
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Figure 3.31 Tide gauge records and mean sea level trend line for three 

northern Gulf Coast tide stations at Pensacola, FL, Grand Isle, 

LA, and Galveston, TX, corresponding with the eastern, central, 

and western coverage of the study area (1900-2000). 
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Figure 3.32 Merged results of Category 2 through 5 hurricane surge 

simulations of a slow-moving storm approaching from the 

southeast (toward northwest in database), generated by using 

SLOSH model simulations. 
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Figure 3.33 Color schemes illustrate the difference in surge inundation 

between a Category 3 and Category 5 storm approaching the 

southeastern Louisiana coast from the southeast. 
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Figure 3.34 Comparison of lidar and National Digital Elevation Data (DEM) 

for eastern Cameron Parish, LA. The advantages of using a lidarderived topography are many, particularly as the effects of 

climate change are likely to be subtle in the short term but 

significant for this low-lying coast where 1 ft of added flooding 

will impact a large land area. 
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Figure 3.35 Trend in summer wave height (1978-2005) in the mid-Gulf of 

Mexico. (Figure source: Komar and Allan, 2008; data source: 

NOAA National Buoy Data Center, Stennis, MS) 
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4.0 What Are the Implications of 

Climate Change and Variability 

for Gulf Coast Transportation? 

Lead Authors: Robert S. Kafalenos, Kenneth J. Leonard 

Contributing Authors: Daniel M. Beagan, Virginia R. Burkett, Barry D. Keim, Alan 

Meyers, David T. Hunt, Robert C. Hyman, Michael K. Maynard, Barbara Fritsche, Russell 

H. Henk, Edward J. Seymour, Leslie E. Olson, Joanne R. Potter, Michael J. Savonis 

The major climate drivers discussed in chapter 3.0 have significant implications for the 

transportation system in the Gulf Coast region. This chapter provides an overview, in 

section 4.1, of the impacts of climate change on the region’s transportation infrastructure. 

It starts with a summary organized around the primary climate effects addressed in 

chapter 3.0 (temperature, precipitation, sea level rise, and storm activity) and continues 

with a discussion of freight and private sector concerns. In section 4.2, it shifts to a more 

detailed discussion organized by transportation mode; this subsection ends by summarizing 

and discussing freight and private sector concerns involving multiple modes. Finally, we 

use a series of case studies in section 4.3 to illustrate some of the effects of the 2005 

hurricanes on transportation. 

Based on the analysis of the climate scenarios relayed in chapter 3.0, climate change is 

likely to have the largest impact on highways, ports, and rail, particularly through sea level 

rise and storm surge. Temperature increases, particularly temperature extremes, are likely 

to increase energy consumption for refrigerated storage as well as rail and highway 

maintenance. Bridges, included in multiple modes, also could be affected by changes in 

precipitation, particularly through changes in peak stream flow. Changes in severe weather 

patterns (thunderstorms) or cloud cover could affect flight operations. See tables 4.3 

through 4.6 for summary statistics. 
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 4.1 Climate Drivers and Their Impacts on the 

Transportation System 

This section focuses on the main impacts on transportation facilities and features (e.g., 

bridges) resulting from the primary climate drivers: temperature, precipitation, sea level 

rise, and storm activity, and summarizes some of the issues that affect multiple modes.1

 

While each climate factor has implications for the transportation network, relative sea level 

rise (RSLR) and storm activity have the potential to cause the most serious damage to 

transportation infrastructure in this study region. The relative significance of different 

climate factors will vary from region to region. The section closes with a look at key crossmodal issues, particularly private sector involvement and the potential for climate impacts 

in the Gulf Coast region to disrupt freight movements outside the study region. 

As noted in Chapter 3.0, the climate impacts on transportation infrastructure assessed in 

this study rely on the combination of an understanding of historical climate trends and 

future projections from general circulation models (GCM). While model results imply that 

change will be gradual and linear, it should be noted that regional “surprises” are 

increasingly possible in the complex, nonlinear Earth climate system (Groisman et al., 

2004), which is characterized by thresholds in physical processes that are not completely 

understood or incorporated into climate model simulations; e.g., interactive chemistry, 

interactive land and ocean carbon emissions, etc. While there is still considerable 

uncertainty about the rates of change that can be expected (Karl and Trenberth, 2003), there 

is a fairly strong consensus concerning the direction of change for most of the climate 

variables that affect transportation in the Gulf Coast region. 

4.1.1 Effects of Warming Temperatures 

Based on the results presented in chapter 3.0 for the Gulf Coast subset of the GCM runs 

performed for the IPCC Fourth Assessment Report (2007), the average temperature in the 

Gulf Coast region appears likely to increase by at least 1.5 °C ± 1 °C (2.7 °F ± 1.8 °F) 

during the next 50 years. While changes in average temperatures have some implications 

for transportation infrastructure and services, the more significant consideration is the 

potential change in temperature extremes. As the number of days that the temperature is 

above 32 °C (90 °F) increases – rising in the next century to as much as 115 days (plus or 

minus 16 days) per year from the current level of 77 days – stress will increase on both the 

infrastructure itself and on the people who use and provide transportation services. 

Temperature extremes are most likely to cause the greatest maintenance problems. The 

greater frequency of very hot days will lead to greater need for maintenance of roads and 

 

1

 Aside from introductory and summary sections, the climate drivers are not addressed in order of relative 

importance but rather are discussed in the same order throughout this chapter for purposes of consistency: 

temperature, precipitation, sea level rise, and storm activity. 
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asphalt pavement (although some paving materials may handle temperature extremes better 

than others), rail tracks and freight facilities, some vehicles, and facility buildings and 

structures due to degradation in materials. Further, construction and maintenance 

schedules may be affected, as work crews may be unable to work during extreme heat 

events. For aviation, longer runways may be required, although this will probably be offset 

by advancements in engine technology and airframe materials. 

Increases in temperatures also are likely to increase energy consumption for cooling. This 

applies particularly to freight operations, including ports where energy is required to 

provide for refrigeration, as well as to trains and truck operations. Air conditioning 

requirements for passengers also can be expected to increase, which may lead to a need for 

additional infrastructure at terminal facilities. This has both environmental and economic 

costs and may pose a public health concern to vulnerable populations during emergency 

situations. 

4.1.2 Effects of Precipitation Levels and Patterns 

Precipitation and Runoff 

In this study, annual and monthly (January and July) precipitation totals are examined. 

Changes in mean precipitation levels appear to have a less significant effect on 

transportation than do sea level rise, storm surge, and temperature extremes. However, the 

potential exists for increased intensity in individual precipitation events, which would 

likely affect transportation network operations, safety, and storm water management 

infrastructure. Runoff resulting from such events could lead to increased peak streamflow, 

which could affect the sizing requirement for bridges and culverts. 

As reported in chapter 3.0, the climate models show relatively wide variance in average 

precipitation projections, with plausible scenarios showing annual rainfall potentially 

increasing or decreasing by as much as 13 percent by 2050 and by ± 15 percent by 2100. 

However, regardless of whether average precipitation rises or falls, higher temperatures are 

expected to result in more rapid evaporation. This would result in declining soil moisture 

and decreased runoff to rivers and streams. The size and extent of natural habitats adjacent 

to highways may be altered, resulting in changes in some plant and animal communities. 

These ecological changes may have implications for environmental mitigation strategies 

and commitments. 

While changes in annual average precipitation may have some effects, change in the 

intensity of individual rainfall events is likely to be the more significant implication for the 

transportation system. An increase in the intensity or frequency of heavy downpours may 

require redesign of storm water management facilities for highway, bridges and culverts, 

ports, aviation, and rail. Severe weather events are correlated to higher incidence of 

crashes and delays, affecting both safety and mobility. Further, aviation services can be 

disrupted by intense rainfall events as well as an increase in the probability of severe 

convective weather. No attempt is made in this study to quantify potential changes in 

intensity under the climate scenarios presented in chapter 3.0. 
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4.1.3 Relative Sea Level Rise 

Background 

Scenarios of 61 cm and 122 cm (2 and 4 ft) of relative sea level rise were selected as inputs 

to our analysis of potential transportation impacts in the study area. These scenarios were 

selected based on the range of projected relative sea level rise (discussed in chapter 3.0) of 

24-199 cm (about 1-7 ft, depending on location, GCM, and a given emission scenario from 

the Special Report on Emissions Scenarios (SRES). Even the lowest end of the range of 

increase in relative sea level has the potential to threaten a considerable proportion of the 

transportation infrastructure in the region. Future planning, construction, and maintenance 

activities should be informed by an understanding of the potential vulnerabilities. This 

subsection begins with a summary of the relative sea level rise analysis conducted for this 

study (see chapter 3.0 for the full discussion) and continues by summarizing the potential 

effects of relative sea level rise on the transportation modes. 

As noted in chapter 3.0, RSLR is the combined effect of the projected increase in the 

volume of the world’s oceans (eustatic sea level change), which results from increases in 

temperature and melting of ice, and the projected changes in land surface elevation at a 

given location. In the Gulf Coast region, change in land surface elevation change is 

dominated by subsidence, or sinking, of the land surface. While sea level may continue to 

rise incrementally, the potential for abrupt increases in relative levels cannot be dismissed. 

Gradual and relatively consistent rates of sea level increases will be more easily addressed 

by transportation planners and designers than would more abrupt or discontinuous changes 

in water levels. No analysis is conducted regarding the implications of a catastrophic 

degree of sea level change that would result from major changes in the rate of land ice 

decline (e.g., a rapid collapse of the Greenland Ice Sheet). 

Two different sea level rise models were used to estimate potential RSLR in the study area. 

Both models were used to estimate relative sea level rise by 2050 and 2100 under the 

greenhouse gas emissions scenarios considered in this study (see chapter 3.0 for more on 

the scenarios). Both models account for eustatic sea level change and land subsidence in 

the region based on the historical record. One model, CoastClim, produces results that 

approximate future change in RSLR under the climate scenarios. A similar model, SLRRP, 

also incorporates values for high and low tidal variation attributed to astronomical and 

meteorological causes, which are pulled from the historical record. The tide data used is 

based on a monthly average of the mean high tide (mean higher high water) for each day of 

the month. The SLRRP results presented in the study are the highest predicted monthly sea 

level elevations by 2050 and 2100. Thus, the SLRRP results capture seasonal variability 

and interannual trends in sea level change, while the CoastClim results do not. 

Results for the low- and high-range RSLR cases are summarized in tables 4.1 and 4.2. 

(See tables 3.14 and 3.16 for the full range of results.) Analysis was conducted for three 

long-term tide gage locations, as subsidence rates vary substantially across the region: 

regional subsidence rates are 4.7 mm/year (0.19 in/year) for Galveston, TX, and the chenier 

plain; 8.05 mm/year (0.32 in/year) for Grand Isle, LA, and the Mississippi River deltaic 

plain; and 0.34 mm/year (0.013 in/year) for Pensacola, FL, and the Mississippi/Alabama 
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Sound of the central Gulf Coast. Results generated using CoastClim range from 24 cm (0.8 

ft) in Pensacola to 167 cm (5.5 ft) in Grand Isle. Results from SLRRP, which as noted 

above accounts for historical tidal variation, are somewhat higher, with predicted sea level 

ranging from 70 cm (2.3 ft) in Pensacola to 199 cm (6.5 ft) in Grand Isle (North American 

Vertical Datum 88 [NAVD88]). 

[INSERT Table 4.1: Relative sea level rise (RSLR) modeled using SLRRP] 

[INSERT Table 4.2: Relative sea level rise (RSLR) modeled using CoastClim] 

This phase I analysis broadly examines the potential effects of sea level rise on the region 

as a whole; the results related in this study should not be used to predict specific impacts on 

any single location at a specific point in time. Impacts were analyzed assuming two 

different levels of relative sea level rise; 61 cm (2 ft) and 122 cm (4 ft). From a regional 

perspective, the selection of this range for analysis is clearly supported by the model 

results. In fact, given that the results range from 24 cm to 199 cm (0.8 to 6.5 ft), analyzing 

for 61- and 122-cm (2- and 4-ft) increases in RSLR may be overly conservative from a 

regional perspective. For both Galveston and especially Grand Isle, analyzing at the 122-

cm (4-ft)level is conservative, given that the high-range scenario results modeled to the 

year 2100 range from 130 cm (4.3 ft) to 199 cm (6.5 ft) for these two areas. In the case of 

Pensacola, given that three of the four values that define the range of the results are above 

61 cm (2 ft), this level should be considered a conservative input value. The 122-cm (4-ft) 

level, however, is representative of the high-range scenario results (114 cm or 3.8 ft) for 

Pensacola. 

The effect of existing flood control works has not been addressed in this study. Many 

existing facilities at lower elevations are protected by levees and other physical structures, 

which are intended to provide resistance to storm surge. The present land-based elevation 

data allows us to identify general geographic zones of potential risk and to identify areas 

that merit further study. More detailed future assessments of specific sites and facilities 

should consider the presence and viability of protective structures as part of an analysis of 

risk and vulnerability at those locations. 

As discussed in chapter 3.0, RSLR will not be uniform across the region. This study’s 

results are meant to give a broad indication of where relative sea levels could be by the 

year 2100 and what infrastructure could be affected as a result of the analysis under the 61- 

and 122-cm (2- and 4-ft) RSLR scenarios. This analysis provides a first approximation of 

potential vulnerabilities and provides insights for transportation planners; more detailed 

analyses can then be conducted to further assess specific locations and facilities that may 

be at risk. Phase II of this study will examine specific sublocations within the region and 

incorporate location-specific projections of future RSLR. 

Impact on Transportation 

Relative sea level rise poses the greatest danger to the dense network of ports, highways, 

and rail lines across the region. An increase in relative sea level of 61 cm (2 ft) has the 

potential to affect 64 percent of the region’s port facilities, while a 122-cm (4-ft) rise in 
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relative sea level would affect nearly three-quarters of port facilities. This is not surprising 

given that port facilities are adjacent to a navigable water body. For highways and rail, 

while the percentages are lower, the effect also is quite large. About a quarter of arterials 

and interstates, nearly half of the region’s intermodal connector miles, and 10 percent of its 

rail miles would be affected by a 122-cm (4-ft) rise. Because goods are transferred to and 

from ports by both trucks and rail, service interruptions on selected segments of 

infrastructure are likely to affect much more than these percentages imply due to the 

disruption to network connectivity. For example, an increase in relative sea level of 61 cm 

(2 ft) would affect 220 km (137 mi) of I-10 east of New Orleans, which could affect onroad transport of both people and goods into and out of New Orleans and, to a lesser extent, 

Houston. Similarly, while less than 10 percent of rail miles would be affected, most of the 

rail lines linking New Orleans to the rail system could be affected. This could hinder 

freight movements in the region, especially since New Orleans is the main east-west link 

for rail located in the region, one of four in the United States. While airports in the region 

are less directly vulnerable to sea level rise, the vulnerability of roads and rail lines serving 

them affects the passenger and freight services these facilities provide as well. See 

table 4.3 for a summary of this information. 

[INSERT TABLE 4.3 – Relative sea level rise impacts on Gulf Coast transportation modes: 

percentage of facilities vulnerable.] 

Relative sea level rise is likely to have an impact on the other modes as well. While bus 

routes can be adjusted over time should facilities no longer be of use, light rail facilities are 

not so easily moved; some of the light rail routes in Galveston and New Orleans would be 

affected by a 61-cm (2-ft) rise. Airports would not escape the direct and indirect effects of 

relative sea level rise; New Orleans International airport, at 122-cm (4 ft), and two other 

smaller airports could be affected directly by higher sea levels. Others could be affected 

indirectly if the roads and connectors leading to them are flooded. 

The data and analysis for both relative sea level rise and storm surge are based on land area 

elevations, rather than facility elevations. Facility elevations generally were not readily 

available for this phase of the study in a consolidated and geospatial format. The elevation 

of land areas was determined from the National Elevation Dataset (NED) maintained by 

the United States Geological Survey (USGS) (USGS, 2004). Mapping data for 

transportation infrastructure was obtained from the U.S Department of Ttransportation’s 

(DOT) Bureau of Transportation Statistics (BTS, 2004). 

The NED has a horizontal resolution of 30 m (98 ft). Since the positional accuracy of the 

transportation facilities is plus or minus 80 m (262 ft), the elevation data is sufficient only 

to make general conclusions about transportation facilities that are vulnerable to flooding. 

While some sections of the transportation network – particularly roads and rail lines – may 

be elevated, it is important to note that inundation of even short segments of the system can 

shut down significant portions of the broader network due to the essential connectivity 

provided by these segments. Furthermore, such inundation can undermine infrastructure’s 

foundations and substructures. 
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4.1.4 Storm Activity 

As discussed in chapter 3.0, the intensity of hurricanes making landfall in the Gulf Coast 

study area is likely to increase. In addition, the climate analysis indicates that the number 

of hurricanes may increase as the temperature of the sea surface continues to warm. 

Simulated storm surge from model runs across the central Gulf Coast at today’s elevations 

and sea levels demonstrated a 6.7- to 7.3-m (22- to 24-ft) potential surge for major 

hurricanes of Category 3 or greater. Based on recent experience, even these levels may be 

conservative; surge levels during Hurricane Katrina (rated a Category 3 at landfall) 

exceeded these heights in some locations. 

Many of the region’s major roads, railroads, and airports have been constructed on land 

surfaces at elevations below 5 m (16.4 ft). Storm surge poses significant risk to 

transportation facilities2 due to the immediate flooding of infrastructure, the damage caused 

by the force of the water, and secondary damage caused by collisions with debris. While 

surges at varying heights may disrupt operations and damage infrastructure, the effects of 

storm surges of 5.5 and 7 m (18 and 23 ft) were assessed for the purposes of this analysis. 

This assessment does not take into account the possible dampening of surge effects due to 

distance inland from coastal areas and the buffering qualities of both ecological systems 

(barrier islands, wetlands, marshes) and the built environment. The analysis identifies 

portions of the transportation network that are at land elevations below 5.5 and 7 m (18 and 

23 ft) as an initial indication of areas and facilities that may be at risk and warrant more 

detailed analysis. Areas significantly inland from the coast or protected by buffering 

systems may be less vulnerable, depending on site-specific coastal geomorphology and the 

characteristics of individual storm events. 

As shown clearly by Hurricanes Katrina and Rita, storm surge has the potential to cause 

serious damage and loss of life in low-lying areas. As considered in this study, much of the 

region’s infrastructure is vulnerable to storm surges on the order of 5.5 to 7 m (18 to 23 ft), 

though the specific infrastructure that would be flooded depends on the characteristics of a 

given storm, including its landfall location, wind speed, direction, and tidal conditions. 

As in the case of relative sea level rise, ports, highway, and rail are the transportation 

facilities that would be most directly affected by storm surge. Ports have the most 

exposure, because 98 percent of port facilities are vulnerable to a storm surge of 5.5 m (18 

ft). Fifty-one percent of arterials and 56 percent of interstates are located in areas that are 

vulnerable to a surge of 5.5 m (18 ft), and the proportions rise to 57 and 64 percent, 

respectively, for a surge of 7 m (23 ft). Some 73 percent of intermodal connector miles are 

vulnerable to surges of 5.5 or 7 m (18 ft or 23 ft). Thirty-three percent of rail lines are 

 

2

 Bridges may be of particular interest in this regard. Phase II of this study, which will include an in-depth 

analysis of a single location within the study region, is expected to include a systematic analysis of the 

potential impacts of climate change on bridges, because bridges play a key role across multiple modes, and 

their failures can produce bottlenecks. 
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vulnerable to a storm surge of 5.5 m (18 ft); this proportion climbs to 41 percent vulnerable 

at 7 m (23 ft). Twenty-nine airports are vulnerable to a surge of 7 m (23 ft), and one major 

commercial service facility – New Orleans International – also is vulnerable to a 5.5-m 

(18-ft) surge. Vulnerability of the region’s infrastructure to storm surge is summarized in 

table 4.4. 

[INSERT TABLE 4.4. Storm surge impacts on Gulf Coast transportation modes: percentage of 

facilities vulnerable] 

The effects of storms on the transportation network go beyond the impacts of storm surge. 

Severe winds and rainfall events throughout the study region can cause damage and 

flooding, disrupting system performance. Wind damage risk contours were not mapped as 

part of this project. Experience shows that the highest hurricane velocities are experienced 

along the coasts, diminishing as storms move inland, but that severe damaging winds can 

be sustained well inland. Hurricanes also spawn tornados, which can have substantially 

higher velocities over much smaller areas. The entire study area is within 100 mi of the 

Gulf of Mexico shoreline, and all of it could be considered potentially vulnerable to 

significant wind damage. As noted in chapter 3.0, while historical and projected increases 

in summer minimum temperatures for the study area suggest an increase in the probability 

of severe convective weather (Dessens, 1995; Groisman et al., 2004), GCMs currently lack 

the capacity for simulating small-scale phenomena such as thunderstorms, tornadoes, hail, 

and lightning. 

One factor that complicates the effects of both storm surge and relative sea level rise is the 

condition of the barrier islands. As noted in section 3.5.1, wave heights in coastal bays will 

tend to increase due to the combined erosional effects of sea level rise and storms on 

coastal barrier islands and wetlands. As the barrier islands erode, their role in shielding 

Gulf Coast waterways and infrastructure from the effects of waves will diminish, which 

means their ability to protect coastal infrastructure from waves at current sea levels and 

future sea levels, as well as from storm surge, will likely diminish. 

Any facility subject to flooding may incur structural damage or be rendered inoperable due 

to debris or other obstructions. Restoring facility and system performance necessitates 

considerable time and investment on the part of facility owners. The secondary economic 

costs to both businesses and communities who rely on these transportation networks could 

be considerable as well, depending on the time required to restore system performance. 

This report does not attempt to estimate the total costs of protecting, maintaining, and 

replacing Gulf Coast transportation infrastructure due to damage caused by climate change. 

It does, however, include a case study on Hurricane Katrina in section 4.3.1 that provides 

examples of the efforts associated with addressing the impacts of the hurricane. 

4.1.5 Climate Impacts on Freight Transport 

The private sector has made massive investments in transportation infrastructure in the 

Gulf Coast study area, a large portion of which revolves around moving freight. Almost all 
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of the roads and major airports are publicly owned, but the vehicles that operate over them, 

and the commercial and freight services that they accommodate, are private. Many of the 

ports are private, and the vessels and commercial services using them are private. Almost 

all of the Nation’s rail infrastructure is privately owned and operated. 

Disruption of privately owned infrastructure can have huge costs for the owners and users 

of these facilities. Repair costs for the more than 65-km (40-mi) CSX railroad segment 

damaged in Hurricane Katrina, $250 million, could be dwarfed by the costs of moving the 

line if the company chose to relocate the line further inland; Congressional proposals have 

considered authorizing $700 million in Federal funding to help relocate the damaged 

portion of the CSX segment. This is just a small share of the 1,915 km (1,190 mi) of rail 

line in the study area that are vulnerable to sea level rise and storm surge. Critical 

transportation-dependent industries – petroleum, chemical, agricultural production and 

transportation, etc. – are heavily concentrated in the study area. The private sector, 

therefore, has a significant interest in the impacts of climate change on transportation 

infrastructure, because it potentially affects hundreds of billions of dollars annually in 

commercial activity over study area roads, railroads, airports, seaports, and pipelines. 

One of the key issues that draws the private sector into the discussion of climate impacts on 

transportation is the movement of freight. The private sector has proven adept at using 

intermodal freight systems – involving ports, highways, rail, and aviation – to transport 

goods as inexpensively as possible. However, this lean and efficient system is vulnerable: 

a disruption that seemingly affects a limited area or a single mode can have a ripple effect 

throughout the supply chain. 

The loss of direct freight transportation service or connectivity in the Gulf Coast would 

likely have a substantial impact beyond the transportation provider and the local economy. 

 The interruption of freight transportation service in the Gulf Coast could impact the 

distribution of goods nationally and, therefore, impact the national economy. Costs of raw 

materials or products that have to be rerouted or transported by an alternate mode would 

likely increase to absorb higher transportation costs. Further, most businesses and 

industries that once held large inventories of products have shifted to low inventory, justin-time delivery business models, managing much of their inventories in transit. Therefore, 

they have lower tolerance for delays in shipment and receipt of goods and now demand 

greater reliability and visibility from their freight carriers. This system is very cost 

effective, but it leaves shippers with little cushion when the freight transportation system 

fails. A large failure such as that caused by a hurricane can quickly disrupt thousands of 

supply chains, undermining the operations and profitability of many shippers, carriers, and 

customers. For example, after Hurricane Katrina, CSX rerouted trains and experienced an 

increase in operating costs of the railroad through increased fuel usage, crew costs, 

equipment delays, and a loss of overall system capacity. Other freight transportation 

impacts included the disruption in the distribution of petroleum by pipelines and the failure 

of ships being able to make port along the Gulf Coast. An increase in transportation costs 

such as these is likely to increase the price of the final product and could jeopardize the 

national and global competitiveness of affected businesses.
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 4.2 Climate Impacts on Transportation Modes 

This section begins with an in depth examination of the impacts of climate change on each 

individual mode. It continues by looking at how these impacts could affect emergency 

management and evacuation and closes with a look at key cross-modal issues. 

4.2.1 Highways 

As in most parts of the nation, roads are the backbone of the transportation network in the 

Gulf Coast. Highways3 are the chief mode for transporting people across the region, and 

together with rail, highways are essential for moving freight throughout the region and to 

other parts of the United States. Thus, impacts to the highway network could serve as 

choke points to both passenger and freight traffic that emanates in or flows through the 

region. While temperature and precipitation changes have some implications for highway 

design and maintenance, the key impacts to the highway network result from relative sea 

level rise and storm surge. 

Temperature 

Impacts related to projected changes in average temperatures appear to have moderate 

implications for highways, while increases in extreme heat may be significant. 

Maintenance and construction costs for roads and bridges are likely to increase as 

temperatures increase. Further, higher temperatures cause some pavement materials to 

degrade faster, requiring earlier replacement. Such costs will likely grow as the number of 

days above 32 °C (90 °F) – projected to grow from the current average of 77 days to a 

range of 99 to 131 days over the next century – increases and as the projected maximum 

record temperatures increase in the region. 

While maintenance and construction costs are expected to rise as the number of very hot 

days increase, the incremental costs have not been calculated as part of this analysis. These 

additional, excessive temperature-related costs are incorporated into the total maintenance 

and construction costs for all pavements and bridges. Changes in materials used may help 

reduce future temperature-induced maintenance costs. For example, Louisiana Department 

of Transportation and Development (DOTD) has begun to use asphalts with a higher 

polymer content, which helps pavement better handle higher temperatures, though at a 

higher initial cost than standard asphalt. 

There are measures that could be taken to mitigate the loss in productivity associated with 

maintenance and construction, such as evening work hours, but these measures also would 

 

3

 As noted in chapter 2.0, this report focuses on interstates, arterials, and collectors, but not local roads. 
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increase costs. In subsequent phases of this study, the implications on construction, 

maintenance, and operation budgets in specific sublocations should be examined. 

The designs of steel and concrete bridges and of pavements in the study area typically are 

based on a maximum design temperature of 46 °C (115 °F) to 53 °C (125 °F). The 

increase in maximum record temperatures implied by the climate model projections are less 

than these values, although under the climate scenarios they would approach those values 

over the next century. It may be prudent for future designers of highway facilities to 

ensure that joints in steel and concrete bridge superstructures and concrete road surfaces 

can adequately accommodate thermal expansion resulting from these temperatures. The 

State DOT design manuals generally establish the maximum design temperature at a value 

near 53 °C (125 °F), well above the current maximum recorded temperatures in the study 

area, but as temperatures increase there may well be more failures of aging infrastructure. 

Consideration should be given to designing for higher maximum temperatures in 

replacement or new construction. 

Precipitation 

As previously noted, the analysis generally indicates little change in mean annual 

precipitation (152 cm or 60 inches per year) through either 2050 or 2100, but the range of 

possible futures includes both reductions and increases in seasonal precipitation. In either 

case, the analysis points to potential reductions in soil moisture and runoff as temperatures 

and the number of days between rainfall events increase. The research team analyzed 

average annual precipitation separately from potential changes in intensity of rain events. 

Under a scenario of insignificant change or a reduction in average precipitation, coupled 

with drier soils and less runoff, there would be decreases in soil moisture, which may result 

in a decline of slides in slopes adjacent to highways. It also would mean less settling under 

pavements, with a decrease in cracking and undermining of pavement base courses. While 

uniform decreases in runoff could reduce scouring of bridge piers in rivers and streams, 

greater frequency of high-intensity events could result in more scour. Stresses on animal 

and plant populations brought about by higher temperatures and changes in rainfall patterns 

could make it more difficult and expensive to mitigate the impacts of highway 

development on the natural environment. 

Pavement settling, bridge scour, and ecosystem impacts may not be significantly impacted 

by modest increases in average annual rainfall because of the effects of increasing 

temperature on evaporation rates. However, while potential changes in average annual 

precipitation are likely to have minor impacts, an increase in the intensity of individual 

rainfall events may have significant implications for highways. An increase in the 

frequency of extreme precipitation events – as discussed in chapter 3.0 – would increase 

accident rates, result in more frequent short-term flooding and bridge scour, as well as 

more culvert washouts, and exceed the capacity of stormwater management infrastructure. 

More instances of intense rainfall also may contribute to more frequent slides, requiring 

increased maintenance. However, some states, such as Louisiana, already address 

precipitation through pavement grooving and sloping and thus may have adequate capacity 

to handle some increase in precipitation. 
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Relative Sea Level Rise 

As discussed above, the effects of 61- and 122-cm (2- and 4-ft) RSLRs were analyzed to 

assess their implications on highways. The presence or absence of protective structures 

was not considered in this baseline analysis but would be an important factor in subsequent 

sublocation assessments. 

As shown in figure 4.1, the majority of the highways at risk from a 61-cm (2-ft) increase in 

relative sea level are located in the Mississippi River delta near New Orleans. The most 

notable highways at risk are I-10 and U.S. 90, with 220 km (137 miles) and 235 km (146 

miles), respectively, passing through areas that will be below sea level if sea levels rise by 

61 cm (2 ft). Overall, 20 percent of the arterial miles and 19 percent of the interstate miles 

in the study area are at elevations below 61 cm (2 ft) and thus are at risk from sea level rise 

unless elevated or protected by levees (table 4.5). 

The majority of the highways at risk from a 122-cm (4-ft) increase in relative sea level are 

similarly located in the Mississippi River Delta near New Orleans (figure 4.2). The most 

notable highways at risk remain I-10 and U.S. Highway 90, with the number of miles 

increasing to 684 km (425 mi) and 628 km (390 mi) passing through areas below sea level, 

respectively. Overall, 28 percent of the arterial miles and 24 percent of the interstate miles 

are at elevations below 122 cm (4 ft). Currently, about 130 mi (209 km) or about 1 percent 

of major highways (interstates and arterials) in the study region are located on land that is 

at or below sea level. 

As shown in figure 4.3, many of the National Highway System (NHS) intermodal (IM) 

connectors pass through low-lying areas concentrated in the Mississippi River Delta, where 

sea level rise is expected to have the most pervasive impact. Intermodal connectors are 

primarily necessary to provide highway access for various transportation facilities, such as 

rail, ports, and airports, some of which will be below sea level with a relative sea level rise 

of 61 to 122 cm (2 to 4 ft). Of the 1,041 km (647 mi) of IM connectors, 238 km (148 mi), 

or 23 percent, are at risk to a 61-cm (2-ft) increase in relative sea levels; and a total of 444 

km (276 mi), or 43 percent, are at risk to a 122-cm (4-ft) increase. In addition to the 

terminals at risk under the 61-cm (2 ft) RSLR scenario (the New Orleans International 

Airport, Port Fourchon, most rail terminals in New Orleans, ferry terminals in New 

Orleans, and ferry terminals outside of the Mississippi River Delta in Galveston and 

Houston), additional terminals at risk under the 122 cm (4 ft) RSLR scenario include port 

facilities in Lake Charles, Galveston, Pascagoula, and Gulfport. 

The cost of various adaptation options – including relocating, elevating, or protecting 

highways and IM connectors – is not addressed by this study. Additionally, the costs of 

right-of-way and environmental mitigation for relocating or elevating such facilities are 

unknown at this time. The adaptation and investment plans for specific facilities will be 

determined by local and regional decision makers. 

As discussed in section 4.2.1, the available elevation data for the study area is sufficient to 

make first order conclusions about roads that are at risk of flooding; it does not indicate the 

elevation of specific highways. However, it is worth noting that the loss of use of a small 
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individual segment of a given highway may make significant portions of that road network 

impassable. Further, even if a particular interstate or arterial is passable, if the feeder roads 

are flooded, then the larger road becomes less usable. 

[INSERT FIGURE 4.1: Highways at risk from a relative sea level rise of 61 cm (2 ft)] 

[INSERT [FIGURE 4.2.: Highways at risk from a relative sea level rise of 122 cm (4 ft)] 

[INSERT FIGURE 4.3: NHS Intermodal Connectors at risk from a relative sea level rise of 122 

cm (4 ft)] 

[INSERT TABLE 4.5: Relative sea level rise impacts on highways: percentage of facilities 

vulnerable] 

Storm Activity 

As discussed in chapter 3.0, the intensity of hurricanes making landfall or striking in the 

Gulf Coast study area can be expected to increase. About half of the region’s arterial miles 

and about three-quarters of the IM connectors are vulnerable to a storm surge of 5.5 m (18 

ft), and these proportions are even higher for a 7-m (23-ft) storm surge. 

Surge Wave Crests and Effects on Bridges 

The wave energy during storm surge events is greatest at the crest of the wave. The 

facilities most at risk are bridge decks and supports that are constructed at the wave heights 

reached during a storm. The impact of the 2005 hurricanes vividly illustrated some of the 

factors involved in infrastructure vulnerability (see section 4.3.1.) While only a small 

percentage of the study area’s bridges are located at the shore and have bridge decks or 

structures at these heights, when storm waves meet those bridges the effect is devastating; 

spans weighing 300 tons were dislodged during Hurricane Katrina. Although these bridges 

are few in number compared to the over 8,000 bridges on the functionally classified 

system, over two dozen bridges were hit by wave surges resulting from Hurricane Katrina 

and experienced serious damage. 

An example is shown in figure 4.4. In perhaps the most spectacular example, the Bay 

St. Louis Bridge on U.S. Highway 90, which links Bay St. Louis and Henderson Point, 

MS, was destroyed by Hurricane Katrina’s storm surge. The 3.2-km- (2-mi-) long bridge 

was recently replaced at a cost of $267 million, with two lanes in each direction and a 

shared-use path. At it highest point, the new bridge reaches 26 m (85 ft) above the bay, 17 

m (55 ft) higher than its predecessor (Nossiter, 2007; Sloan, 2007). 

Design features such as lack of venting along the length of the span, solid railings 

(preventing water from flowing through), and lack of connectors anchoring the spans to the 

pilings or corrosion in existing connectors made some bridges more susceptible than others 

to the force of the water during Katrina. In the absence of standard American Association 

of State Highway and Transportation Officials (AASHTO) design factors for storm surge, 

both the Louisiana DOTD and Mississippi DOT have developed their own approaches to 
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designing for future storms. For instance, Louisiana DOTD is developing standards calling 

for new bridges to be elevated beyond a 500-year event for the main span (9.1-11.6 m, or 

30-38 ft) and a 100-year event for transition spans close to shore. In addition, new bridges 

will be designed with open railings to reduce the impact of pounding water (Paul, 2007). 

Mississippi also has adopted more stringent design standards and is rebuilding the Biloxi 

Bay and St. Louis Bay bridges as high-rise structures, to keep the bridge decks above 

future storm surges. 

As the sea level rises, the coastline will change. Bridges that were not previously at risk 

may be exposed in the future. Additionally, bridges with decks at an elevation below the 

likely crest of storm surges, based on experience from previous storms, will be below water 

during the storm event and not subject to wave damage. Only data regarding the height of 

bridges above navigable channels was available to this study – a small portion of all 

bridges in the region. Therefore, a full analysis of the possible impacts of wave crests on 

bridges was not feasible. 

[INSERT FIGURE 4.4 Hurricane Katrina damage to Highway 90 at Bay St. Louis, MS] 

Surge Inundation 

Figures 4.5 and 4.6 show areas potentially vulnerable to surge inundation at the 5.5- and 7- 

m (18- and 23-ft) levels and identifies interstate and arterial highways that pass through 

these risk areas. As illustrated, a substantial portion of the highway system across the 

study area is vulnerable to surge inundation: 51 percent of all arterials and 56 percent of 

the interstates are in the 5.5-m (18-ft) surge risk areas. At the 7-m (23-ft) level, these 

percentages increase only slightly: 57 percent of all arterials and 64 percent of the 

interstates are in 7-m (23-ft) surge risk areas (table 4.6). 

The risk from surge inundation for NHS IM connectors is even greater than that for all 

highways. Seventy-three percent of IM connector miles are located in areas that would be 

inundated by a 5.5-m (18-ft) surge, and the proportion of IM connectors that is vulnerable 

at the 7-m (23-ft) level is only slightly higher (see figure 4.7). 

As noted above, the elevation data is sufficient to make only general conclusions about 

roads that are at risk of inundation. Local conditions for specific segments and facilities 

may be important, and individual roads that may be vulnerable should be studied in detail. 

While inundation from storm surges is a temporary event, during each period of inundation 

the highway is not passable, and after the surge dissipates, highways must be cleared of 

debris before they can function properly. Of particular concern is that a substantial portion 

of all of the major east-west highways in the study area, particularly I-10/I-12, are at risk to 

storm surge inundation in some areas, and during storm events and the recovery from these 

events, all long-distance highway travel through the study area is likely to be disrupted. 

The expense of these poststorm cleanups can be considerable and is often not included in 

State DOT budgets. For instance, the Louisiana DOTD spent $74 million on debris 

removal alone following Hurricanes Katrina and Rita (Paul, 2007). In the 14 months 

following the hurricanes, the Mississippi DOT spent $672 million on debris removal, 
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highway and bridge repair, and rebuilding the Biloxi and Bay St. Louis bridges 

(Mississippi DOT, 2007). See section 4.3.1 for a fuller discussion of poststorm cleanup 

costs. 

Moreover, data from the Louisiana DOTD suggests that prolonged inundation can lead to 

long-term weakening of roadways. A study of pavements submerged longer than three 

days during Katrina (some were submerged several weeks) found that asphalt concrete 

pavements and subgrades suffered a strength loss equivalent to two inches of pavement. 

Portland concrete cement pavements suffered little damage, while composite pavements 

showed weakening primarily in the subgrade (equivalent to one inch of asphalt concrete). 

The study estimated a $50 million price tag for rehabilitating the 320 km (200 mi) of 

submerged state highway pavements and noted that an additional 2,900 km (1,800 mi) of 

nonstate roads were submerged in the New Orleans area. The data was collected several 

months after the waters had receded; there has not been a subsequent analysis to test 

whether any strength was restored over time (Gaspard et al., 2007). 

[INSERT FIGURE 4.5 Highways at risk from storm surge at elevations currently below 5.5 m 

(18 ft)] 

[INSERT FIGURE 4.6 Highways currently at risk from storm surge at elevations currently 

below 7.0 m (23 ft)] 

[INSERT FIGURE 4.7 NHS Intermodal Connectors at risk from storm surge at elevations 

currently below 7.0 m (23 ft)] 

[INSERT TABLE 4.6: Storm surge impacts on highways: percentage of facilities vulnerable] 

Wind 

Wind from storms may impact the highway signs, traffic signals, and luminaries 

throughout the study area. The wind design speed for signs and supports in the study area 

is typically 160 to 200 km/h (100 to 125 mi/h). These designs should accommodate all but 

the most severe storm events. More significant safety and operational impacts are likely 

from debris blown onto roadways and from crashes precipitated by debris or severe winds. 

4.2.2 Transit 

Transit in the region consists of bus systems as well as light rail in New Orleans, Houston, 

and Galveston. While bus routes could be affected by relative sea level rise, transit 

operators can presumably adjust their routes as needed, particularly since the location of 

transit users and routes also might change. Storm surge could be a more serious, if 

temporary, issue. For the light rail systems in New Orleans and Galveston, an increase in 

relative sea level of 61 or 122 cm (2 or 4 ft) would affect at least some of the routes, 

especially in New Orleans; storm surge of 5.5 or 7.0 m (18 or 23 ft) would have an even 

greater impact. The light rail system in Houston would not likely be affected. Projected 

rises in temperature could lead to greater maintenance and air conditioning costs and an 
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increased likelihood of rail buckling for the light rail systems. If the intensity of 

precipitation increases, accident rates could be expected to increase. If total average annual 

precipitation increases, it could lead to higher accident rates. 

Temperature 

Given the temperature projections noted in chapter 3.0, temperature stresses on engines and 

air conditioning systems could possibly affect vehicle availability rates, disrupting overall 

scheduled service. Since these additional, excessive temperature-related costs are included 

in the total maintenance and construction costs of transit agencies, it is possible that those 

amounts will at a minimum increase by an amount proportional to the increase in the 

number of days above 32 °C (90 °F). 

Furthermore, temperature increases, especially increases in extremely high temperatures, 

will cause increases in the use of air conditioning on buses to maintain passenger comfort. 

This will exacerbate the issue of vehicle availability rates and raise costs due to increased 

fuel consumption. 

Increases in (record maximum) temperatures are likely to only impact fixed guideway rail 

networks and have little or no impact on bus or paratransit systems, aside from the vehicle 

maintenance issues noted above. As discussed in greater detail in section 4.2.3, rail 

networks are subject to “sun kinks” (the buckling of sections of rail) at higher 

temperatures; sun kinks are likely to occur more frequently as (record maximum) 

temperatures increase. The possibility of rail buckling can lead to speed restrictions to 

avoid derailments. The track used by the trolley systems in Galveston and New Orleans 

have expansion joints that generally are not significantly affected by sun kinks, while 

Houston’s METRORail uses continuously welded rail (CWR) track. CWR track lacks 

expansion joints and thus is more prone to sun kinks. 

Precipitation 

The climate model results point to potential increases or decreases in average annual 

precipitation. If precipitation increases, it very likely would lead to an increase in accidents 

involving buses, as well as increased costs and disruptions associated with such accidents. 

The same also is likely if the intensity of precipitation increases. Even an increase in 

roadway accidents not involving buses will lead to congestion that could disrupt bus 

schedules. 

Relative Sea Level Rise 

If relative sea level increases to an extent that transit service would pass through areas 

under water in the future, either the connectivity provided by that transit would be lost or 

corrective actions to reroute the transit would be needed. Since the vast majority of transit 

service is provided by buses, schedules and routes can be modified easily, though the same 

is not true for terminals and maintenance facilities. Therefore, minimal impact on bus 

systems is expected from RSLR. For light rail systems in the region, however, RSLR 
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could potentially be a much more serious issue. Moving tracks and permanent facilities is 

a major undertaking; tracks would need to be protected or moved to higher ground. 

With the exception of the RTA and St. Bernard buses in New Orleans and a small portion 

of the routes traveled in Galveston, bus and paratransit service is not expected to be 

affected by either a 61- or 122-cm (2- or 4-ft) increase in relative sea levels. If bus routes 

are not affected, ancillary facilities such as terminals and maintenance facilities may not be 

affected either. Figure 4.8 shows the effect of a 122-cm (4-ft) rise in relative sea level on 

fixed bus routes in New Orleans. This clearly illustrates the vulnerability of the transit 

network in New Orleans without levees or other protection. 

[INSERT FIGURE 4.8 Fixed bus routes at risk from a relative sea level rise of 122 cm (4 ft), 

New Orleans] 

The New Orleans streetcars system operated by the RTA and some small portions of the 

streetcar system operated by Island Transit in Galveston are similarly at risk of inundation 

at either the 61- or 122-cm (2- or 4-ft) sea level rise scenarios. Like the city itself, portions 

of many of the streetcar routes in New Orleans currently are below sea level, and it is only 

the levee system that maintains the ability of these streetcars to function. In contrast, the 

fixed transit system in Houston is not at risk at these levels, as show in figure 4.9. 

[INSERT FIGURE 4.9 Fixed transit guideways at risk from a relative sea level rise of 122 cm 

(4 ft), Houston and Galveston] 

Storm Activity 

Transit facilities passing through areas at elevations at or below 5.5 and 7.0 m (18 and 23 

ft) were identified. As shown in figures 4.10 and 4.11, the fixed transit systems in New 

Orleans and Galveston are very likely to be affected by any storms that generate surges of 

5.5 m (18 ft) or more. This inundation would affect service during and immediately after a 

storm, though it would not likely result in long-term disruptions. 

[[INSERT FIGURE 4.10: Fixed transit guideways at risk from storm surge at elevations 

currently below 5.5 m (18 ft), New Orleans] 

[INSERT FIGURE 4.11: Fixed transit guideways at risk from storm surge at elevations 

currently below 5.5 m (18 ft), Houston and Galveston] 

Fixed bus route systems also are at risk to storm surges. The bus route systems that are 

vulnerable to storm surges of 5.5 m (18 ft) include all the systems except those in Baton 

Rouge, Beaumont, and Houston (figure 4.12 and 4.13). At 7.0 m (23 ft), the risk of storm 

surge inundation also extends to the fixed bus routes in Beaumont. 

The risk of inundation by storm surge is that the bus routes could not operate on flooded or 

obstructed roads. It also should be noted that in low surge events, even if the buses can 

operate, their utility would be influenced by whether pedestrian facilities are passable and 
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riders can walk to bus stops. Consideration should be given to developing contingency 

plans for alternative routes during storms. 

[INSERT FIGURE 4.12: Fixed bus routes at risk from storm surge at elevations currently below 

5.5 m (18 ft), New Orleans] 

[INSERT FIGURE 4.13: Fixed bus routes at risk from storm surge at elevations currently below 

5.5 m (18 ft), Houston and Galveston] 

Storm Winds 

The transit infrastructure that is most vulnerable to impacts by the winds associated with 

increases in the number of intense storms are the overhead catenary lines that power street 

cars in New Orleans and Houston. Transit signs and control devices also are subject to 

wind damage. 

However, rather than wind damage to transit facilities, the most widespread impact may be 

from fallen trees and property debris blocking the streets on which transit routes operate. 

This impact would occur during and immediately after storm events and should be 

addressed by highway clean up operations. 

Storm Waves 

With the exception of light rail and Bus Raid Transit (BRT) systems, transit equipment can 

be moved away from areas subject to wave impacts, and therefore, storm wave impacts 

during surge events are not expected to impact most transit systems. Even in the case of 

fixed guideways, storm waves will mostly affect areas immediately on the shoreline, which 

is not where fixed guideway facilities in the New Orleans and Houston systems are located. 

However, the trolley tracks in Galveston are at risk to these impacts. 

4.2.3 Freight and Passenger Rail 

Rail lines in the region play a key role in transporting freight and a minor role in intercity 

passenger traffic. Much of the traffic on class I rail lines in the region is for transshipments 

as opposed to freight originating or terminating in the region (figure 2.12). Rail 

connectivity and service also is vital to the functioning of many, if not most, of the marine 

freight facilities in the study area. 

Of the four main climate drivers examined in this study, storm surge could be the most 

significant for rail. One-third of the rail lines in the study region are vulnerable to a storm 

surge of 5.5 m (18 ft), and 41 percent are vulnerable to a storm surge of 7.0 m (23 ft). 

Fifty-one freight facilities and 12 passenger facilities are vulnerable to storm surges of 7.0 

m (23 ft). Sea level rise is of less concern for rail; a 122-cm (4-ft) RSLR would affect less 

than 10 percent of rail miles, as well as 19 freight facilities and no rail passenger facilities. 

Temperature increases could raise the danger of rail buckling, but would be unlikely to 
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necessitate design changes. Projected precipitation patterns do not indicate that design 

changes are warranted to prevent increased erosion or moisture damage to railroad track. 

Temperature 

The level of average temperature increases discussed in chapter 3.0 is unlikely to require 

immediate design changes to track or other rail infrastructure, as these ranges generally fall 

within the current standards for existing rail track and facilities. However, the increase in 

temperature extremes – very hot days – could increase the incidence of buckling or “sun 

kinks” on all the rail tracks in the study area. This occurs when compressive forces in the 

rail, due to restrained expansion during hot weather, exceed the lateral stiffness of the 

track, causing the track to become displaced laterally. The amplitude of track buckles can 

reach 75 cm (30 inches) or more. 

Track buckling occurs predominately on continuously welded track, though it also can 

occur on older jointed track when the ends of the track become frozen in place. Track 

buckling is most prevalent on an isolated hot day in the springtime or early summer, rather 

than mid to late summer when temperatures are more uniformly hot. Buckling also is more 

likely to occur in alternating sun/shade regions and in curves. 

The most serious problem associated with track buckling is derailments. A derailment can 

occur when a buckled section of track is not observed in time for the train to safely stop. 

One way to overcome this is through blanket slow orders. In hot weather (more than 35 

°C, or 95 °F), railroads issue blanket slow orders (generally to reduce all train speeds by 16 

km/h or 10 mi/h) to help prevent derailments caused by buckling. This has several 

negative consequences, such as longer transit times, higher operating costs, shipment 

delays, reduced track capacity, and increased equipment cycle time leading to larger fleet 

sizes and costs. Reduced train speeds similarly affect passenger rail schedules, causing 

delays in travel schedules. 

Research into improved track design and installation has greatly reduced the derailments 

attributable to buckling. For example, concrete crossties with improved fasteners can 

withstand greater track stress than wooden ties with spikes. During installation, the rail is 

prestressed to a target neutral temperature. Since the track is more stable when the rail is in 

tension at temperatures below the neutral temperature, the target neutral temperature is 

generally 75 percent of the expected maximum temperature of the region. In the Gulf 

Coast region, the neutral temperature is typically 38 °C (100 °F), while 32 °C (90 °F) is 

used in more northern climates. Prestressing can occur either thermally (by actually 

heating the steel during installation) or mechanically by stretching the steel to introduce the 

desired stress prior to fastening it to the crossties. 

A temperature change of 1.5 °C (2.7 °F) over the next 50 years may slightly raise the 

neutral temperature used for installation but would have little impact on track design 

otherwise. A temperature increase in this range would not necessitate replacing existing 

track. It would most likely be replaced as part of normal maintenance, upgrades to handle 

increased traffic volumes, or replacement due to storm surge or other catastrophic events. 

The typical cost to upgrade track can vary greatly depending upon the type of upgrade, the 
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slope and curvature, and the number of bridges and tunnels. Costs to replace track range 

from $0.3 million to $1.9 million per kilometer ($0.5 million to $3 million per mile), 

excluding any additional right-of-way expenses. 

If incidences of buckling rise it will be increasingly important to develop improved 

methods of detection. It is relatively easy to detect a broken rail by running a light electric 

current through track, but manual observation remains the best method for identifying track 

buckling. Research is underway to develop improved methods that measure temperature 

and stress of the track.4

The projected increases in average temperature and number of hot days, coupled with 

possible increases in humidity, would create serious safety concerns for workers in rail 

yards and other rail facilities and would require investments to protect rail workers. This 

might include increases in crew size to allow for more frequent recovery breaks or greater 

use of climate-controlled facilities for loading and unloading the railcars. Regardless of the 

solution, providing the necessary relief for workers will lead to increased operating or 

capital expenses, which will be reflected in higher transportation costs. 

Precipitation 

The primary impacts on rail infrastructure from precipitation are erosion of the track 

subgrade and rotting of wooden crossties. Erosion of the subgrade can wash away ballast 

and weaken the foundation, making the track unstable for passage of heavy locomotives 

and railcars. Ballast is typically granite or other hard stone used to provide a flat, stable 

bed for the track, and also to drain moisture from the track and ties. Without ballast, 

wooden crossties would rot at a faster rate, leading to more buckling and unstable track. 

As with buckling, subgrade erosion and rotting crossties are difficult to detect using 

methods other than visual inspection. This situation is improving, though, through remote 

sensing advances that detect standing water and air pockets. 

The precipitation projections do not indicate that design changes are warranted to prevent 

increased erosion or moisture damage to railroad track, even with a potential change of 

13 percent in precipitation levels. The runoff projections point to even fewer problems 

with erosion over the next century than are present today, due to possibly less precipitation 

and slightly higher temperatures. However, if the frequency and/or the intensity of extreme 

rainfall events increases, it could lead to higher rates of erosion and railroad bridge scour, 

as well as higher safety risks and increased maintenance requirements. 

 

4

 Much of the material in this section was developed through personal communication with David Read, 

Principal Investigator, Transportation Technology Center, Inc., an Association of American Railroads 

subsidiary located in Pueblo, CO. 
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Relative Sea Level Rise 

The effects on rail lines and facilities of relative sea level of 61 and 122 cm (2 and 4 ft) 

over the next 50 to 100 years were analyzed. The obvious impacts for both of these sea 

level rise scenarios are water damage or complete submersion of existing rail track and 

facilities. These ground elevations affect the vulnerability of rail segments to storm surge 

as well.5

 Table 4.7 indicates the percent of rail lines and facilities vulnerable to sea level 

rise at 6-1 and 122-cm (2- and 4-ft) levels. Currently, about 50 miles or about 2 percent of 

rail lines in the study region are located on land that is at or below sea level. 

[INSERT Table 4.7: Relative sea level rise impacts on rail: percentage of facilities vulnerable] 

Figure 4.14 displays the rail network, used by both freight trains and Amtrak, with the 

RSLR elevation projections. Rail lines located in areas with a ground elevation of 0 to 61 

cm (0 to 2 ft) are vulnerable to a relative sea level rise of 61 cm (2 ft) or more. Lines 

located in slightly higher areas, with a ground elevation of 61 to 122 cm (2 to 4 ft), are 

vulnerable to a relative sea level rise of 122 cm (4 ft). 

Most of the rail lines in and around New Orleans would likely be impacted by RSLR. The 

heavily traveled CSX line between Mobile and New Orleans, which was damaged during 

Hurricane Katrina, also is at risk, as are several area short lines. A listing of the rail lines 

impacted if relative sea level rises 61 cm (2 ft) includes the following: 

• Most rail lines in and around New Orleans; 

• Burlington Northern Santa Fe (BNSF) line between Lafayette and New Orleans; 

• Canadian Nation (CN) line into New Orleans; 

• CSX line between Mobile and New Orleans; 

• CSX line north of Mobile; 

• Louisiana and Delta Railroad west of New Orleans; 

• Portions of the Mississippi Export (MSE) rail line in Mississippi; 

• The New Orleans and Gulf Coast Railway line between New Orleans and Myrtle 

Grove, LA; 

• Norfolk Station (NS) line into New Orleans; 

• Portions of the Port Bienville Railroad; 

 

5

 It should be noted that many existing facilities at low elevations are protected by levees and other physical 

structures, which provide some resistance to gradual changes in sea level and the impacts of storm surge. 

The effects of existing or planned protections were not addressed by this study. Even with this protection, 

the infrastructure described in this study is potentially still at risk. 
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• Segments of the Union Pacific (UP) line west of New Orleans; and 

• Various segments of track around Lake Charles and Galveston. 

[INSERT FIGURE 4.14: Rail lines at risk due to relative sea level rise of 61 and 122 cm (2 and 

4 ft)] 

Further degradation of these lines is very likely to occur should relative sea level increase 

by 122 cm (4 ft), with additional problems on the Kansas City Southern (KCS) route into 

New Orleans, the NS line north of Mobile, and selected track segments around Beaumont 

and Houston. 

Figure 4.15 shows the potential impacts of RSLR on railroad-owned and served facilities in 

the study region. Facilities located at less than 61 cm (2 ft) of elevation are very likely to 

be affected by a rise in relative sea level of 61 cm (2 ft). These include the KCS, NS, and 

UP rail yards in the New Orleans area. Facilities between 61 and 122 cm (2 and 4 ft) of 

elevation are very likely to be affected by a rise in relative sea level of 122 cm (4 ft). A 

listing of facilities with elevation 122 cm (4 ft) or less is contained in table 4.8. A listing of 

all freight rail facilities in the Gulf Coast study region, along with their elevation grid 

codes, is provided in appendix C. 

[INSERT FIGURE 4.15: Freight railroad-owned and served facilities at risk due to relative sea 

level rise of 61 and 122 cm (2 and 4 ft)] 

[INSERT TABLE 4.8 Freight railroad-owned and served facilities in the Gulf Coast study 

region at elevation of 122 cm (4 ft) or less] 

A related issue is how railroad customers will respond to these rising relative sea levels and 

storm surge, and how these decisions will affect the demand for rail services. For example, 

to what extent will customers choose to relocate or modify their shipping and production 

patterns? Some industries, most notably the ports, need to remain at or near the water’s 

edge to send and receive shipments. There will be a continued need for rail service into 

these locations. Other rail customers, however, may begin to relocate to higher ground or 

to different regions entirely. This will in turn affect the type and scale of rail network 

needed to meet the demand for inbound and outbound freight shipments. While it is 

difficult to predict the future choices of rail customers, it seems likely that climate change 

will negatively impact growth in goods movement at the lower elevations, and thus could 

lead to significantly reduced, and costlier, rail service in the region. 

Turning to passenger rail service, none of the Amtrak passenger rail stations are at a high 

risk of impact due to a 122-cm (4-ft) increase in relative sea level. However, the rail lines 

used by Amtrak are at risk. These include the Sunset Limited routes between Mobile and 

New Orleans on the CSX-owned track and between New Orleans and Houston on the UPowned track. 

Table 4.9 summarizes the impacts of RSLR and storm surge on the freight and passenger 

rail lines and facilities in the region. These calculations are based on ground-level 

elevations of the rail facilities. All facilities and lines at low elevations are included, even 
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though some are surrounded by higher land that may block rising sea levels. The actual 

inland flow of water due to higher relative sea levels was not available for this study. 

[INSERT TABLE 4.9: Vulnerability from sea level rise and storm surge by rail distance and 

number of facilities] 

One final factor, not directly addressed by the maps and tables discussed in this section, is 

the extent to which rising relative sea levels create a higher water table that leads to 

additional flooding during periods of normal precipitation. As the water table rises, the 

ground is less able to absorb normal rainfall. This could cause frequent flooding of rail 

track and facilities beyond the levels identified in the maps and tables. 

Storm Activity 

Hurricane Katrina provided a vivid example of the devastating impacts of severe storm 

events to the rail system in the Gulf Coast study area. Making landfall on August 29, 2005, 

Katrina caused damage to all of the major railroads in the region. BNSF, CN, KCS, and 

UP all suffered damage, mostly to yards in and around New Orleans. CSX track and 

bridges also were damaged. NS had nearly 8 km (5 mi) of track washed away from the 

9.3-km- (5.8-mi-) long Lake Pontchartrain Bridge. By September 13, 2005, most of these 

railroads had resumed operations into New Orleans, at least on a partial basis. There were 

still yards that had not fully opened, though this was due to a mixture of storm damage to 

the yard and customers not being fully operational. By October 8, 2005 most rail service 

on these carriers had been restored, except CSX (Association of American Railroads, 

2005). (See section 4.3.1 for more on the impacts of the 2005 hurricanes.)

Figure 4.16 illustrates the rail lines most at risk from storm surge at the 5.5- and 7.0-meter 

(18- and 23-ft) marks. One-third of the rail lines in the study region are vulnerable to a 

storm surge of 5.5 m (18 ft), and 41 percent are vulnerable to a storm surge of 7.0 m (23 ft) 

(table 4.10). This includes the heavily traveled CSX line from New Orleans to Mobile and 

the UP and BNSF lines from New Orleans to Houston. Cities at risk include Mobile, 

Gulfport, Biloxi, New Orleans, Baton Rouge, Lafayette, Lake Charles, Beaumont, Port 

Arthur, and Galveston. 

Similarly, figure 4.17 shows the potential impacts of storm surge on railroad-owned and 

served facilities in the study region. Facilities at less than 5.5 m (18 ft) of elevation have 

the highest risk of 5.5-m (18-ft) storm surge impacts. These include 43 percent of the rail 

facilities in the study region. An additional 11 facilities are between 5.5 and 7.0 m (18 and 

23 ft) of elevation and are very likely to be affected by a 7.0-m (23-ft) storm surge. A 

listing of all freight rail facilities in the Gulf Coast study region, along with their elevation 

grid codes, is provided in appendix C. 

Figure 4.18 shows the risks for Amtrak passenger rail stations due to storm surge at 5.5 and 

7.0 m (18 and 23 ft). The data indicates that there is low risk overall to Amtrak stations 

from storm surge, but the nine stations listed in table 4.11 are very likely to be affected by a 

storm surge of 5.5 m (18 ft). Two of the stations, Galveston and La Marque, TX, do not 

have direct passenger rail service but are connected to the Amtrak services by bus. At the 
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7.0-m (23-ft) storm surge level, an additional three stations are likely to be affected: New 

Iberia, LA, and Bay St. Louis and Biloxi, MS. A listing of all Amtrak stations in the Gulf 

Coast study region, along with their elevation grid codes, is provided in appendix C. 

[INSERT FIGURE 4.16 Rail lines at risk due to storm surge of 5.5 and 7.0 m (18 and 23 ft)] 

[INSERT Figure 4.17 Freight railroad-owned and served facilities at risk due to storm surge of 

5.5 and 7.0 m (18 and 23 ft)] 

[INSERT TABLE 4.10: Storm surge impacts on rail: percentage of facilities vulnerable] 

[INSERT FIGURE 4.18 Amtrak facilities at risk due to storm surge of 5.5 and 7.0 m (18 and 23 

ft)] 

[INSERT TABLE 4.11: Amtrak stations projected to be impacted by storm surge of 5.5 and 7.0 

m (18 and 23 ft)] 

Railroad Response to Hurricane Damage 

In the immediate aftermath of a hurricane, one of the largest problems facing railroad 

operators who are trying to restore service is safety issues at road-rail, at-grade crossings. 

Without power to operate the crossing gates, the railroads either need to manually flag each 

crossing or not run the trains. The larger railroads purchase electric generators that can be 

deployed after a hurricane to operate the gates, thus allowing trains to offer emergency 

response services and resume economic activity. For prolonged outages, as was the case 

with Hurricane Katrina, the railroads need to reeducate the public on the dangers of 

at-grade crossings once train service resumes. 

Other short-term responses are directed at protecting revenues and controlling costs. 

Business customers within a region impacted by a hurricane are likely facing the same 

difficulties as the railroads and may not be fully operational. Once a company is fully 

operational, though, a railroad needs to be ready to offer service or risk losing business to 

other railroads, trucks, or barges. Delays in rail service availability can lead to a long-term 

loss of revenue. The other issue is continued long-haul service to businesses outside of the 

impacted area. After Hurricane Katrina, CSX rerouted trains that previously passed 

through the New Orleans gateway to junctions at St. Louis and Memphis. This extra 

routing increases the operating costs of the railroad through increased fuel usage, crew 

costs, equipment delays, and a loss of overall system capacity. There is a strong financial 

incentive to return to normal operations as soon as possible after a catastrophic event. 

The long-term response of the railroads to increased storm intensity currently is being 

evaluated. The railroads are participating with both public and private groups to identify 

the best ways to serve the Gulf Coast region in the future. CSX Chief Operating Officer 

Tony Ingram stated, “We are open to ideas that are in the best interests of CSX, its 

customers, and its communities.” Mr. Ingram further stated, “Our recent rebuild of the 

Gulf Coast line restores vital service and underscores our commitment, but does not 

foreclose other long-term alternatives for the rail line.” (CSX, 2006a). 
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One obvious response is to begin relocating rail track and facilities further away from 

coastal areas and making expanded use of intermodal shipping. For example, CSX 

recently announced a new 1,250-acre integrated logistics center (ILC) in Winter Haven, 

FL, to serve the Tampa and Orlando markets. This ILC will include truck, rail, and 

warehousing for the storage and transfer of consumer goods to these two urban markets 

(CSX, 2006b). Although this ILC location was driven by proximity to the expanding 

Tampa and Orlando markets and the availability of affordable land – rather than as a risk 

reduction strategy – it does provide an interesting model for redesigned approaches to longhaul shipping by using inland locations and trucks to serve sensitive coastal markets. 

Other proposals have included the relocation of CSX rail lines in Mississippi. As 

proposed, the rail relocation would occur in the Gulfport area and would bypass the Bay 

St. Louis Bridge that was damaged by Hurricane Katrina. However, much of the rail line 

on this CSX route might remain in storm surge danger, as illustrated in figure 4.16. 

Another issue related to moving rail lines further away from coastal areas is that it will, in 

most cases, move passenger rail service further from population centers. The highest 

density populations tend to occur along coastal regions, making it the most desirable 

location for passenger rail stations. If the rail track is moved further inland to areas with 

lower population density, it would have a negative impact on intercity service and the 

potential of any future commuter passenger rail service that might be warranted by 

population growth along the coast. On the other hand, this effect could be obviated if rail 

facilities and passenger centers migrate inland in tandem, but coordinated responses cannot 

be assumed, in part because the entities involved – private rail companies, citizens, and 

governments – face different decisions related to the impacts of climate change, and their 

decision making processes are also necessarily different. 

The temperature and precipitation changes projected under the climate scenarios and 

models used in this study likely would not necessitate any rebuilding of rail facilities or any 

significant design changes in the Gulf Coast study area rail network. The larger issue is 

damage due to RSLR, storm surge, and hurricanes. Rail lines totaling 1,915 km (1,190 mi) 

and 40 rail facilities are at risk from storm surge as examined above. (See figures 4.16 and 

4.17.) Railroads may begin slowly relocating track and facilities further away from coastal 

areas, though this will be largely driven by customer location and needs. Increased use of 

rail-truck transloading from ILCs further from the coast might be an alternative. Any effort 

to move rail lines from the higher density coastal areas will have a negative impact on 

intercity passenger rail ridership and the potential utility of the line for commuter rail 

service as the population along the coast increases. 

4.2.4 Marine Facilities and Waterways 

Due to their location, marine facilities are most vulnerable to storm surge and relative sea 

level rise. Marine facilities include both freight and nonfreight facilities: ports, marinas, 

and industry-support facilities. Virtually all of the region’s port facilities, or 98 percent, 

have the potential to be inundated by a storm surge of 5.5 m (18 ft), and 99 percent would 

be affected by a surge of 7.0 m (23 ft). A RSLR of 61 cm (2 ft) has the potential to affect 
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64 percent of the region’s port facilities, while a 122-cm (4-ft) rise in relative sea level 

would affect nearly three-quarters of the port facilities. Impacts related to increased 

temperatures and changes in precipitation are expected to include increased costs related to 

maintenance as rising temperatures place greater stress on facilities, higher energy costs for 

refrigeration, and changes in the quantity and type of products shipped through the region 

as production and consumption patterns change both in and outside the region due to 

climate change. 

Marine facilities and waterways are vital to the region and to the Nation as a whole. As 

noted in chapter 2.0, the study area is one of the Nation’s leading centers of marine 

activity. Much of the region’s economy is directly linked to waterborne commerce. and in 

turn, this waterborne commerce supports a substantial portion of the U.S. economy. 

While some of these functions could be considered “replaceable” by facilities and 

waterways elsewhere, many of them – by virtue of geography, connections to particular 

industries and markets, historical investments, or other factors – represent unique and 

essentially irreplaceable assets. It might be possible to provide capacity equivalent to the 

Gulf Intracoastal Waterway or the Mississippi River on land, via highway and/or rail. It 

might even be possible to provide landside connections to, and sufficient capacity at, 

alternative international seaports, but the capital costs to provide such “replacement 

capacity” would undoubtedly be huge, and the costs to system users would be dramatically 

higher, if not prohibitively higher. 

Higher Temperatures 

Higher temperatures may affect port facilities in three key ways. First, higher temperatures 

will increase costs of terminal construction and maintenance, particularly of any paved 

surfaces that will deteriorate more quickly if the frequency of high temperatures increases. 

Many terminals – especially container and automobile handling terminals – have very large 

and open paved surfaces for storing cargo that in some cases can range up to hundreds of 

paved acres, while most others have at least some open paved area for storage. Nearly all 

provide on-terminal circulation space for trucks and wheeled terminal equipment. All such 

areas would be vulnerable to higher temperatures. Second, higher temperatures will lead to 

higher energy consumption and costs for refrigerated warehouses or “reefer slots” 

(electrical plug-ins for containers with on-board cooling units). Third, higher temperatures 

would likely lead to increased stress on temperature-sensitive structures. Container 

handling cranes, warehouses, and other marine terminal assets are made of metals. With 

increasing record temperatures and days over 32 °C (90 °F), it may be necessary to design 

for higher maximum temperatures in replacement or new construction. On the other hand, 

most dock and wharf facilities are made of concrete and lumber, which are generally less 

sensitive to temperature fluctuations. It is possible that lock and dam structures could be 

affected, although this will require further investigation. While this analysis examines 

existing facilities, it should be noted that development of new types of surfaces and 

structures that can better tolerate high temperatures, for example, would counteract some 

adverse impacts. 
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Temperature changes in other parts of the country may prompt some changes in 

consumption and production patterns in the United States that in turn would affect shipping 

patterns in the study region. Compared to the freight movement patterns of today, 

increases in temperature in the southeast or other regions could possibly lead to increases in 

shipments of coal or other energy supplies that pass through the region’s ports. (This 

assumes that the current mix of power plants and fuels remains the same; however, changes 

in energy consumption patterns and improvements in energy efficiency are certainly 

possible, which could lead to changes in demand for fossil fuels.) Additionally, 

temperature changes in other regions could possibly lead to changes in the quantity and 

location of grain production, thus changing shipping patterns involving Gulf Coast ports; 

such changes could have economic ramifications for the Nation as a whole as well as for 

regional ports. 

Precipitation 

As noted previously, projections of future annual average rainfall suggest a slight increase 

or decrease in average annual precipitation depending on choice of GCM and emissions 

scenario. The prospect of more intense precipitation events, as indicated in chapter 3.0, 

could require the capacity of some stormwater retention and treatment facilities to be 

increased. The handling of stormwater can be a significant expense for container 

terminals, auto terminals, and other terminals with large areas of impervious surface. 

Increasing environmental regulatory requirements also may add to costs of adapting 

stormwater handling infrastructure. 

Relative Sea Level Rise 

Typically, the highest portion of the marine terminal is the wharf or pier structure, where a 

vessel actually berths. Structures and open storage areas behind the wharf or pier may be 

at the same level or may be lower. The highway and rail connections serving the terminal 

will be at land level, unless they are on bridge structures. Depending on their design, 

different terminals will have different areas of particular vulnerability with respect to 

RSLR. 

It is important to note that many existing facilities at low elevations are protected by levees 

and other physical structures, which should provide resistance to gradual changes in sea 

levels. The specific effects of existing protections have not been considered in this study. 

For facilities that are not appropriately protected, either by elevation or by structures, rising 

water levels pose an increased risk of chronic flooding, leading in the worst case to 

permanent inundation of marine terminal facilities, either completely or in part, and 

rendering them inoperable. 

Of freight facilities in the study area, about 72 percent are vulnerable to a 122-cm (4-ft) rise 

in relative sea level. Of the 994 freight facilities in the United States Army Corps of 

Engineers (USACE) database, 638 (64 percent) are in areas with elevations between 0 and 

61 cm (2 ft) above sea level, and another 80 (8 percent) are in areas with elevations 

between 61 and 122 cm (2 and 4 ft). More than 75 percent of facilities are potentially 
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vulnerable in Beaumont, Chocolate Bayou, Freeport, Galveston, New Orleans, Pascagoula, 

Plaquemines, Port Arthur, Port Bienville, and Texas City; between 50 percent and 

75 percent of facilities are potentially vulnerable in Gulfport, Houston, Lake Charles, 

Mobile, South Louisiana, and the Tenn-Tom. Only Baton Rouge, with 6 percent of 

facilities potentially at risk, appears to be well-positioned to avoid impacts of sea level rise 

(see figure 4.19). 

A similar situation faces nonfreight facilities. Seventy-three percent of study area marine, 

nonfreight facilities in the study area are potentially vulnerable to a 122-cm (4-ft) increase 

in relative sea level. Of the 810 nonfreight facilities in the USACE database, 547 (68 

percent) are in areas with elevations between 0 and 61 cm (2 ft) above sea level, and 

another 47 (6 percent) are in areas with elevations between 61 and 122 cm (2 and 4 ft). 

More than 75 percent of facilities are potentially vulnerable in Beaumont, Chocolate 

Bayou, Freeport, Galveston, New Orleans, Pascagoula, Plaquemines, Port Arthur, the 

Tenn-Tom, and Texas City; between 50 percent and 75 percent of facilities are potentially 

vulnerable in Houston, Lake Charles, Mobile, and South Louisiana. Twenty-seven percent 

of Gulfport facilities and no Baton Rouge facilities are potentially at risk (see table 4.10). 

Navigable depths are likely to increase in many harbors and navigation channels as a result 

of rising sea levels. This could lead to reduced dredging costs, but higher costs where 

rising water levels require changes to terminals. The functionality and/or protections of 

lock and dam structures controlling the inland waterway system also may be impacted by 

relative sea level rise. 

Various indirect impacts could potentially affect operations and need for ports. As 

discussed in earlier sections, impacts on highways and rail connections could affect the 

ability to utilize and transport goods to and from affected ports. Rail connections to the 

Ports of New Orleans, Mobile, Pascagoula, and Gulfport/Biloxi are at greatest risk. 

Production and consumption patterns within the study area are likely to be significantly 

affected by changes in sea level, which could lead to increased demand for certain types of 

shipments and reduced demand for others. As residential populations relocate from 

affected areas, demand for transported goods would decline. Similarly, as commercial 

activities relocate, transportation services would shift with them. Further, shifts in 

population could cause labor shortages for transportation and commercial facilities. 

[INSERT TABLE 4.12: Relative sea level rise impacts on ports: percentage of facilities 

vulnerable] 

[INSERT FIGURE 4.19: Freight handling ports facilities at risk from relative sea level rise of 

61 and 122 cm (2 and 4 ft)] 

Storm Activity: Water and Wind Damage 

While the actual facilities that would be flooded depend on the particulars of a given 

storm – the landfall location, direction, tidal conditions, etc. – fully 99 percent of all study 

area facilities are vulnerable to temporary and permanent impacts resulting from a 7.0-m 
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(23-ft) storm surge, while almost 98 percent are vulnerable to temporary and permanent 

impacts resulting from an 5.5-m (18-ft) storm surge (figure 4.20 and table 4.13). All 

facilities are vulnerable to wind impacts. Similar to sea level rise, storm surge impacts on 

highway and rail connections could affect the ability to utilize ports for transport of goods 

to and from affected ports. 

As evidenced by Katrina, fast moving water can be incredibly damaging to marine 

facilities. Water can physically dislodge containers and other cargo from open storage 

areas, knock down terminal buildings, damage or destroy specialized terminal equipment, 

damage wharf and pier structures, temporarily inundate and submerge large areas, and 

undermine or damage pavement and foundations. Wind has its most damaging effects on 

unreinforced terminal structures, such as metal warehouses that feature large surface areas 

and relatively light construction. Much of Katrina’s damage to the Port of New Orleans – 

which mostly escaped water damage – was due to wind tearing off warehouse roofs and 

doors. 

Wind and water can result in navigation channels becoming inoperable due to blockages 

and/or loss of markers. One of the first recovery tasks following Katrina was locating and 

clearing the channel in the Mississippi River, allowing it to reopen to barge and vessel 

traffic. Wind and water also can affect the location and protection afforded by the barrier 

islands that help define the Gulf Intracoastal Waterway. 

[INSERT FIGURE 4.20: Freight handling ports facilities at risk from storm surge of 5.5 and 7.0 

m (18 and 23 ft)] 

[INSERT TABLE 4.13: Storm surge impacts on ports: percentage of facilities vulnerable] 

Further, as mentioned earlier, highway and rail connectivity is vital to the functioning of 

nearly all port facilities in the study area. The road and rail facilities that are potentially at 

risk of surge at 5.5 and 7.0 m (18 and 23 ft) are shown in figures 4.5, 4.6, 4.7, 4.16, and 

4.17. While the actual highways that would be flooded depends on the particulars of a 

given storm, a substantial portion of the highway system is at risk of surge inundation, 

including roads in all four states in the study area. The resulting potential loss of access to 

ports is obviously a critical vulnerability to reliable intermodal operations. 

Secondary Impacts 

Water levels in navigable rivers, and thus the ability to move freight, would be affected by 

higher or lower levels of precipitation, evapotranspiration, and runoff occurring outside the 

region. Such changes in the Mississippi River Basin could affect the ability to use the 

upper Mississippi River and its tributaries to export grain and other commodities from the 

Midwest and Great Plains States through Gulf Coast ports. Dredging operations and 

changes in water control facilities and marine terminals at up-river ports could be needed to 

maintain access to them. Freight transport by truck and rail outside the study region could 

increase if river transport is curtailed. Estimation of these effects would require the 

application of models and data from outside of the study area to incorporate up-river 

hydrology. 
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Demand for freight services that include use of Gulf Coast ports also could be influenced 

by changes in precipitation and temperature outside the study region. For example, 

changes in the amount and frequency of precipitation as well as temperature levels could 

affect demand for U.S. grain products overseas, just as changes in the same climate drivers 

in the United States could affect the ability of U.S. grain producers to supply export 

markets and domestic consumers. Such changes could have implications for Gulf Coast 

ports in particular, as well as for national highway and rail systems. 

Similarly, transport of energy supplies through Gulf Coast ports could be influenced by 

changes in temperature across the globe. Increases in temperature in the United States 

could affect the demand for energy products transported through Gulf Coast ports; demand 

for natural gas and coal to power electricity plants in the southeast, for example, could lead 

to greater production and/or importation of natural gas and liquefied natural gas (LNG) 

LNG through the ports and could put downward pressure on coal exports through the Gulf 

in favor of domestic consumption. On the other hand, coal exports through Gulf Coast 

ports could increase as export demand increased. Of course, climate mitigation policies 

could lead to significant shifts in preferred energy resources, leading to changes in energy 

transport demand. Such changes would have implications for pipelines (natural gas, 

petroleum), as well as rail (coal) and ports (coal). These secondary effects may prove to be 

important in the future, and such changes need to be monitored closely to track and adapt 

to changing demand levels. 

4.2.5 Aviation 

It is possible that existing patterns and intensity of severe weather events could be 

adversely affected by climate change, and such events could have the greatest impacts on 

aviation. These changes in severe weather may be widespread geographically such that 

they could profoundly affect the operational aspects of aviation and overall air traffic and 

air space management. If the climate becomes wetter, more general aviation pilots would 

need to learn to fly by instruments or avoid flying during inclement weather. Increased 

precipitation also could affect commercial service operations, particularly by raising the 

potential for delays. However, it should be noted that predicting how severe weather 

patterns would change as a result of climate change is extremely difficult and uncertain. 

Ultimately, the impact on the operational aspects of aviation could potentially supersede 

the overall magnitude of combined effects on aviation due to other factors discussed below 

A total of 29 airports could be vulnerable to a storm surge of 7.0 m (23 ft). The analysis 

suggests that 3 airports may be vulnerable to an increase in RLSR of 1.2 m (4 ft). 

Temperature increases considered by this report would indicate a small increase in baseline 

runway length requirements, assuming other relevant factors are held constant; however, 

the changes will very likely not be sufficient, especially accounting for ongoing 

technological change in commercial aircraft, to have any substantial impact on runway 

length requirements. Nevertheless, aircraft manufacturers may want to determine whether 

the generic hot day temperatures used in their specifications for civilian aviation aircraft 

are sufficiently high. 
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Temperature 

Runway Design and Utilization 

Required runway length is a function of many variables, including airport elevation, air 

temperature, wing design, aircraft takeoff weight and engine performance, runway 

gradient, and runway surface conditions.6

 Runways are designed to accommodate the 

most stringent conditions aircraft can experience. Climate model simulations as discussed 

in chapter 3.0 have conclusively noted that future change in climate will be accompanied 

by increases in temperature. Generally speaking, the higher the temperature the longer the 

runway that is required. In fact, initial runway construction planning takes into account, as 

a matter of course, a range of temperatures that can very well capture the extent of the 

increase in mean maximum temperature derived from the model results. If increases in 

temperature exceed the range initially expected, then considerations for additional 

adjustment in runway length may be necessary, depending on other relevant considerations 

such as payload and elevation. However, this is considered unlikely. 

With rising temperatures, it is possible that there could be an impact on aircraft 

performance that would warrant aircraft manufacturers considering field length 

requirements in their design specifications. However, current trends in aircraft design 

point to shorter takeoff distances as airframes become lighter and engines become more 

powerful. Thus, due to technological innovation, runway length requirements may 

actually decrease even if temperatures increase. 

Forecasting aircraft manufacturer’s product offerings beyond 20 to 30 years is speculative, 

but trends toward increased fuel efficiency, more powerful engines, and lighter weight 

aircraft are anticipated to continue, which could offset the need for longer runway length as 

temperatures rise. Analysis of passenger jet aircraft performance indicates that newer 

aircraft entering the market over the last 50 years use less runway length per pound of 

aircraft. A comparison of two similar Boeing aircraft illustrates this point: the Boeing 

737-200 aircraft entered commercial service in 1968 with an engine thrust of 6,580 kg 

(14,500 lb) and a per passenger seat thrust ratio of 53 kg (117 lb). In 2008, the company’s 

first 787-800 “Dreamliner,” made of up to 50 percent light weight composite products, will 

enter service. Compared to its predecessor, the 737-200, the GE Aircraft Engines on the 

787 will provide more than four times as much thrust and twice as much engine thrust per 

passenger seat. This design, paired with more fuel efficient engines, translates into 

increased fuel efficiency, producing fuel savings up to 20 percent versus similar sized 

aircraft as well as shorter takeoff distances. 

In order to better understand how changes in temperature could affect the current 

generation of aircraft, we looked at both general aviation and civil aviation applications. 

 

6

 These variables affect the performance of departing aircraft in particular; landing aircraft use less runway 

because of decreased landing weight (from fuel usage), as compared to take-off weight, and the use of flap 

settings. 
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Generally, assessments of required runway length are conducted along two tracks for 

general aviation and civil aviation airports, and our analysis below reflects this difference:7

• Using the procedures outlined in the Federal Aviation Administration (FAA) Advisory 

Circulars (AC) (for general aviation aircraft); and 

• Using the manufacturer’s performance curves, published by aircraft manufacturers8

(primarily large commercial service aircraft). 

General Aviation 

While planning for runway design generally accounts for a range of temperatures, this 

analysis of general aviation airports looks solely at how changes in assumptions about 

temperature would affect the baseline analysis of runway length requirements for a 

hypothetical general aviation airport by using the FAA’s Airport Design for 

Microcomputers software.9 The software allows for four variable inputs: airport elevation; 

runway slope measured in difference in elevations at each end of the runway; mean 

maximum temperature for the hottest day of the month; and runway conditions. Aircraft 

performance during takeoff varies significantly based on runway elevation, although 

generally speaking, there is only moderate difference in runway length needed between an 

airport at sea level and one at 91 m (300 ft) above sea level. Runways located in 

mountainous areas, however, have significantly longer runways than those at sea level. 

Mean maximum temperature is used by airport planners to identify the average hottest 

temperature during the hottest month of the year. Generally speaking, longer runways are 

required at hotter temperatures. Requirements for wet runways, which have less friction 

for braking or slowing the aircraft, are set out in regulation. 

Table 4.14 lists the FAA design standards for a hypothetical general aviation airport and 

shows that all small airplanes (defined as having a maximum takeoff weight of less than 

5,670 kg or 12,500 lb) could operate in the study area with a 1,308-m (4,290-ft) runway on 

days as hot as 33 °C (91.5 oF). On cooler days, less runway length is required. Large 

aircraft with maximum takeoff weights greater than 5,670 kg (12,500 lb) require longer 

runways. As noted in table 4.14, 1,637 m (5,370 ft) of runway is recommended to 

accommodate 75 percent of large airplanes up to 27,200 kg (60,000 lb) at up to a 60 

percent useful load when runway surfaces are wet. Wet runway conditions require more 

length, and these conditions are typically used when calculating runway length. 

 

7

 The approach is not completely different. The FAA AC provides design guidance for both small aircraft 

and large aircraft by using the charts within the AC or directing the reader to obtain manufacturer 

performance charts for small or large aircraft. The FAA AC also stipulates what design procedure to apply, 

based on whether or not Federal dollars are involved, e.g., funding through the Airport Improvement 

Program (AIP). 

8

 Runways at military airports are designed to military aircraft specifications. 

9

 It should be noted that the FAA Airport Design for Microcomputer software is solely for planning 

purposes and not for design, since the software generates roughly estimated lengths. 
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[INSERT Table 4.14 FAA recommended runway lengths for hypothetical general aviation 

airport] 

While planning for airport construction generally accounts for a range of temperatures, this 

analysis looks solely at how changes in assumptions about temperature would affect the 

baseline results generated using the FAA’s Airport Design for Microcomputers. The 

research team analyzed the effect of changes in mean maximum temperature for the hottest 

month of the year on runway length requirements as indicated by the climate scenarios 

reviewed in chapter 3.0. Mean maximum temperature was the only variable changed; 

airport elevation, centerline elevation, and runway surface conditions (wet) were held 

constant.10 The 5th, 50th, and 95th percentile temperature increases demonstrated in 

scenarios A1B, B1, and A2 were applied to the FAA design standards for the hypothetical 

airport presented. The increases in runway length based on the increase in temperature 

associated with each scenario are discussed below. Mean maximum monthly temperature 

is derived by averaging the daily high temperature for the month with the highest average 

maximum temperature, which for the Gulf Coast is August. The projected temperature 

increases used were then added to the base year’s mean maximum monthly temperature. 

The current average mean maximum temperature is estimated to be 33 °C (91.4 °F), based 

on 1972-2002 data from 12 research stations from the Carbon Dioxide Information 

Analysis Center (CDIAC) located in the region. For example, for scenario A1B the 50th

percentile temperature increase of 2.5 °C (4.5 °F) was added to the 33 °C (91.4 °F) base 

year mean maximum temperature, indicating that in 2050 the mean maximum temperature 

is projected to be 35.5 °C (95.9 °F). 

Below is a brief discussion of the results of this analysis that indicates the range of 

potential changes in baseline runway length requirements under the climate scenarios, 

conveying the full range of results based on the models and scenarios. For 2100, we point 

out the lowest and highest results. These results indicate the change in baseline runway 

length requirements for this hypothetical airport by using the FAA’s airport design 

software, given a specific change in mean max temperature. 

The analysis confirms that generally speaking, the possible increases are quite small. 

Given the long lead times and ongoing changes in aircraft technology, this means that 

possible temperature increases most probably will have little effect on runway length for 

commercial aircraft. 

The potential temperature increases for the month of August are summarized in 

chapter 3.0, table 3.11. Over the longer term (to 2100), the analysis indicates an increase 

of between 1.8 °C (3.2 °F) (B1, 5th percentile) and 6 °C (10.8 °F) (A2, 95th percentile). An 

increase at the lower end would indicate a potential need to increase runway length by 9 m 

(30 ft) for small aircraft and by 12 to 15 m (40 to 50 ft) for large general aviation aircraft. 

At the 95th percentile, an increase of 6 °C (10.8 °F) could require lengthening the runway 

 

10 One hundred percent of all large aircraft category is seldom used in runway design since very few airports 

experience the entire spectrum of large general aviation aircraft operations. 
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by 30 to 46 m (100 to 150 ft) for small airplanes and by 40 to 219 m (130 to 720 ft) for 

large aircraft. 

Generally speaking, the possible increases in baseline runway length requirements are very 

low, especially for small aircraft (see table 4.15). The scale of these runway length 

requirement increases range from 8 to 16 percent for corporate jets to 2 to 3 percent for 

light general aviation aircraft. While these limited analyses are illustrative of the potential 

influence of temperature increase on runway length based on existing aircraft technology, 

whether more detailed analyses would need to be conducted would be decided by airport 

managers on a case by case basis in order to determine possible investment considerations. 

[INSERT Table 4.15: Summary of impacts of temperature change to runway length (general 

aviation) under three climate scenarios (SRES Scenarios A2, B1, and A1B)] 

Commercial Service Airports 

Commercial service, military airfields, and industrial airport master plans determine the 

size of “critical” aircraft anticipated to operate at an airport in the future, then design the 

runway system to accommodate the critical aircraft. Runways at commercial airports are 

designed by using aircraft manufacturer’s specifications. Figure 4.21 is a table showing 

runway lengths for airport design issued by Boeing for the 757-200 aircraft. These 

specifications provide length of runway required for aircraft based on payload, 

temperature, and elevation. In general, the higher the temperature, elevation, and payload 

weight, the longer the runway needs to be to accommodate the aircraft (figure 4.21). 

[INSERT FIGURE 4.21 B757-200 takeoff runway requirements for design purposes] 

Commercial airliners offer versatility in their ability to operate at a wide assortment of 

airports throughout the world. Large wide-body aircraft such as the Boeing 747 are 

designed to seat over 300 passengers and operate at international gateway airports such as 

Houston, whereas narrow-body aircraft designed for medium-sized markets seat 100 to 200 

passengers and serve markets such as Tallahassee, FL, and Baton Rouge, LA. Regional 

jets seat 34 to 70 passengers and serve markets such as Lake Charles Regional Airport in 

Louisiana. 

Airport master plans determine the size of “critical” aircraft anticipated to operate at an 

airport in the future, then design the runway system to accommodate these critical aircraft. 

Unlike general aviation airports that rely on the FAA airport design software to calculate 

runway length requirements, runways at commercial airports are designed by using aircraft 

manufacturer’s specifications. Once airports go into service, it is the pilot’s responsibility 

to calculate aircraft performance on a given day prior to takeoff based on the following: 

ambient temperature, aircraft gross takeoff weight (GTW), airfield elevation, wind velocity 

and direction, and runway surface slope and drag. Thus, on hot days the pilot can make 

adjustments in cargo or passenger loads in order to takeoff on a runway, given its length. 

On days when the temperature is higher than the aircraft specs contemplate, the airliner 

would need to lower its weight to accommodate the higher temperatures. 
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Table 4.16 lists the required runway lengths for three groups of aircraft, fully loaded, for a 

generic hot day (a standard day temperature of 15 °C (59 °F) plus 15 °C (27 °F), for a total 

of 30 °C (86 °F)) and compares the manufacturer’s specifications with the primary runway 

lengths of the 11 commercial service airports in the study area. Shortfalls in runway length 

for specific aircraft are presented in italics. Houston Bush Intercontinental (IAH) is the 

fourth largest market in the United States and is the only international gateway airport in 

the study area. Other airports in the study area do not require the same runway lengths 

since wide-body aircraft do not operate at these airports on a scheduled basis. On the 

opposite end of the spectrum, regional jets typically operate at Lake Charles Regional 

(LCH), Hattiesburg (HBG), and Beaumont/Port Arthur (BPT). These airports are designed 

to accommodate regional jets and turboprop aircraft and have shorter runway lengths. The 

other commercial airports in the study area are designed to accommodate medium-haul, 

narrow-body jets. 

As shown in the discussion above, the maximum temperature contemplated by this study is 

39 °C (102.2 °F), which is 33 °C (91.4 °F) plus 6 °C (10.8 °F), based on scenario A2 for 

the year 2100. This maximum temperature is 9 °C (16.2 °F) higher than the generic hot 

day. Therefore, aircraft manufacturers may want to consider the extent to which the use of 

a standard day temperature of 15°C (59°F) plus 15°C (27°F) as a measure of a typical hot 

day will continue to be applicable for aircraft design or whether to increase this 

temperature based on any projected temperature increase associated with a change in 

climate. 

[INSERT TABLE 4.16: Commercial aircraft runway length takeoff requirements] 

Temperature Conclusions 

As is the case today, pilots will need to address how temperature increases may affect 

aircraft takeoff performance capabilities and payload requirements, and airports will need 

to address any such increases in the context of current runway utilization and future runway 

design. Given past trends, it is likely that future aircraft will be able to operate on shorter 

runways. Airports serving large commercial aircraft in the future, however, are anticipated 

to continue to utilize aircraft manufacturer’s specifications to determine runway lengths. 

Precipitation 

In general, airlines, airports, and aircraft operate more efficiently in dry weather conditions 

than wet. Weather is a critical influence on aircraft performance and the outcome of the 

flight operations while taking off, landing, and while aloft. Precipitation affects aircraft 

and airports in several ways such as decreasing visibility, slowing air traffic by requiring 

greater separation between aircraft, and decreasing braking effectiveness. On the ground, 

effects include creating turbulence, increasing the risk of icing of wings, and affecting 

engine thrust. 

The climate scenarios for the years 2050 and 2100 developed as part of this research 

generally indicate that the Gulf Coast study area could become a warmer but drier climate. 

However, the models do indicate the possibility that the climate could be warmer with 
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increased annual precipitation. In either scenario, the increased intensity of individual 

rainfall events is likely. 

Implications of a drier climate to airport and aircraft operations may include positive and 

negative effects. Less precipitation would most likely reduce aircraft and air traffic delays; 

reduce periods of wet surfaces on runways, taxiways, and aprons; and in the winter months, 

reduce the risk of wing icing. A drier climate also may increase the number of days of 

visual flight rules11 (VFR) operations. A warmer climate with less precipitation may, 

however, increase convective weather (turbulence), as well as increase the number and 

severity of thunderstorms. In addition, increased water vapor in the atmosphere, 

particularly during the summer months, may increase haze and reduce pilot visibility, 

thereby reducing the number of VFR days. 

A wetter climate would reduce the number of VFR-operating time periods and would 

impact the general aviation sector. General aviation pilots would either learn to fly in 

instrument flight rules (IFR) conditions by becoming “instrument rated” or not fly during 

periods of reduced visibility and precipitation. In order for pilots to fly in IFR conditions, 

aircraft flight decks must be equipped with complex navigation instruments, which is a 

significant investment for aircraft owners. 

Increased extreme precipitation events also would impact commercial service aircraft 

operations. During severe thunderstorm activity it is not unusual for an airline to cancel 

flights or at a minimum experience delays in operations. Navigation in heavy precipitation 

is possible and currently occurs on a daily basis in the national air system. However, 

precipitation almost always creates delays, particularly at the most congested airports. 

If the Gulf Coast study area climate proves to have more intense precipitation events, 

airport planners and engineers would need to consider the implications of periods of 

increased heavy rainfall in airport design and engineering. This is particularly true of 

airports located on floodplains in the study area since they are more susceptible to flash 

flood events. Eight of the 61 airports in the study area are located on 100-year floodplains. 

These airports are identified in table 4.17. 

[INSERT TABLE 4.17: Airports located on 100-year flood plains] 

Relative Sea Level Rise 

As indicated in chapter 3.0, RSLR scenarios developed as part of this research indicate that 

coastal zones in the Gulf Coast study area are very likely to be inundated by rising sea level 

combined with geologic subsidence. As a result, some airport infrastructure would most 

likely be susceptible to erosion and flooding. 

 

11 Visual flight rules (VFR) are a set of aviation regulations under which a pilot may operate an aircraft, if 

weather conditions are sufficient to allow the pilot to visually control the aircraft’s attitude, navigate, and 

maintain separation with obstacles such as terrain and other aircraft. 
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Geographic information system (GIS) analysis indicates three airports in the study area 

would be below mean sea level (MSL) if relative sea level increases by 122 cm (4 ft). 

Each of these airports currently is protected by preventive infrastructure such as dikes and 

levees, which will need to be maintained. If feeder roads in the area are inundated, 

however, access to these airports may be disrupted. Table 4.18 lists these airports and their 

elevations. All three airports are located in Louisiana and range from New Orleans 

International (122 cm or 4 ft elevation), one of the study area’s large commercial service 

airports, to South LaFourche (30 cm or 1 ft), a very small general aviation facility. The 

third is a military airport, New Orleans Naval Air Station Joint Reserve Base (NASJRB 

New Orleans) (91 cm or 3 ft). 

[INSERT Table 4.18 Gulf Coast study area airports vulnerable to submersion by relative sea 

level rise of 61 to 122 cm (2-4 ft)] 

Storm Activity 

Both storm surge and hurricane force winds can damage airport facilities. As indicated in 

chapter 3.0, the study team analyzed the vulnerability of facilities to storm surge heights of 

5.5 and 7.0 m (18 and 23 ft). At these elevations a variety of airports in the region would 

be vulnerable to the impacts of storm surge, though this depends on the specific 

characteristics of each individual storm event, including landfall location, wind speed, wind 

direction, tidal conditions, etc. 

Figure 4.22 depicts airports within the study that are vulnerable to storm surges of 5.5 or 7 

m (18 or 23 ft). Table 4.19 lists these airports by location, type, and elevation. There are 

22 airports in the 0- to 5.5-m (18-ft) MSL category and seven airports in the 5.8- to 7-m 

(19- to 23-ft) MSL category. This list includes some major airports in the region, such as 

New Orleans International. Also, the commercial service airport in Lake Charles, LA, 

would be vulnerable. See section 4.3.1 for a discussion of the wind impacts of the 2005 

hurricanes on airport facilities. 

[INSERT FIGURE 4.22: Gulf Coast study area airports at risk from storm surge] 

[INSERT TABLE 4.19: Gulf Coast study area airports vulnerable to storm surge] 

4.2.6 Pipelines 

There is a combined total of 42,520 km (26,427 mi) of onshore liquid (oil and petroleum 

product) transmission and natural gas transmission pipelines in the Gulf Coast area of 

study, as shown in figure 4.23.12 This includes 22,913 km (14,241 mi) of onshore natural 

gas transmission pipelines and 19,607 km or 12,186 mi of onshore hazardous liquid 

 

12 This includes some extended pipeline sections beyond the boundaries of the study, because GIS coding of 

links included segments that spanned both inside and outside the study area. 
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pipelines (Pipeline and Hazardous Materials Safety Administration [PHMSA], 2007). This 

region is essential to the distribution of the Nation’s energy supply through pipeline 

transportation, and historically the landside pipelines have been relatively secure from 

disruption by increased storm activity and intensity. A number of risks and vulnerabilities 

to climate-related impacts have been revealed, however, particularly for submerged or very 

low elevation pipelines. PHMSA of the U.S. DOT has jurisdiction over onshore pipeline 

facilities and some offshore pipeline facilities. PHMSA has jurisdiction over offshore 

pipeline facilities that are exposed or are hazards to navigation when the offshore pipeline 

facilities are between the mean watermark and the point where the subsurface is under 4.6 

m (15 ft) of water as measured from mean low water. The U.S. Department of the Interior 

Minerals Management Service (MMS) has jurisdiction over about 36,000 miles of offshore 

pipelines in the Gulf of Mexico. 

[INSERT FIGURE 4.23 – Landside pipelines having at least one GIS link located in an area of 

elevation zero to 91 cm (3 ft) above sea level in the study area] 

Some historical weather events have resulted in only minor impacts on pipelines, with the 

notable exceptions of Hurricanes Andrew, Ivan, Katrina and Rita, which caused fairly 

extensive damage to underwater pipelines, and flooded distribution lines in areas where 

houses were destroyed. Storm surge and high winds historically have not had much impact 

on pipelines – either onshore transmission lines or offshore pipelines – since they are 

strong structures, well-stabilized, and/or buried underground. Yet offshore pipelines have 

been damaged in relatively large numbers on occasion, as during Hurricanes Andrew and 

Ivan. Temperature shifts resulting from climate scenario projections are not expected to 

have much direct or indirect impact on pipelines. Increases or decreases in precipitation – 

either long-term or in the frequency or extent of droughts or inundation – could impact soil 

structure. Sea level rise would likely have little direct effect but could affect water tables, 

soil stability, and the vulnerability of pipelines to normal wave action as well as sea surge. 

Changes in soil structure, stability, and subsidence – whether undersea, landside, or in 

wetlands or transition elevations – could play an important role in pipeline-related risks. 

However, there is little information on this topic outside of earthquake risks. There has 

recently been concern about how wave action could affect the seabed, either by 

liquefying/destabilizing the sand or silt surface above a buried pipeline or by gradually 

eroding away seabed that had been covering the pipeline. It is unclear at present whether a 

changing climate might lead to conditions that exacerbate these effects and cause additional 

damage. 

The possible effects on pipelines from climate change – storm surge and extreme winds, 

temperature shifts, precipitation changes, and sea level rise – were considered in this 

analysis. Both pipeline companies and governmental agencies have considered pipeline 

risks, vulnerability, and safety and have well-developed inspection, maintenance, and 

response plans. However, these plans do not appear to address a number of risks that may 

be arising. This study did not examine the adequacy of those plans. While some issues 

regarding impacts have been addressed here, there is still significant uncertainty about the 

overall risk to pipelines from climate change. 
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Importance of Pipeline Operations in the Study Area 

Onshore natural gas transmission pipelines are primarily located in Louisiana. 

Approximately 49 percent of natural gas wellhead production either occurs near the Henry 

Hub, which is the centralized point for natural gas futures trading in the United States or 

passes close to the Henry Hub as it moves to downstream consumption markets. The 

Henry Hub – located near the town of Erath in Vermillion Parish, north central Louisiana – 

interconnects nine interstate and four intrastate pipelines, including: Acadian, Columbia 

Gulf, Dow, Equitable (Jefferson Island), Koch Gateway, Louisiana Resources Company 

(LRC), Natural Gas Pipe Line, Sea Robin, Southern Natural, Texas Gas, Transco, 

Trunkline, and Sabine’s mainline. 

Temperature 

Pipelines are more protected than other types of infrastructure from the effects of 

temperature changes projected for the region due to the moderating and insulating effects 

of soil and water. The great majority of the transmission pipeline system is buried under at 

least 91 cm (3 ft) of soil cover, both onshore and offshore. Federal regulations require that 

all pipelines in navigable waters be buried. Moreover, pipelines are designed to carry 

product at significant temperature variations (natural gas is pressurized in their system, 

while petroleum products are heated considerably above ambient temperatures). There is 

extensive experience with pipelines in much more extreme ambient temperature conditions 

(Alaska, Saudi Arabia, West Africa) than would be expected in the Gulf States region. Sea 

temperatures will vary even less than land temperatures. Thus, there is not expected to be 

any significant effect on pipelines due to direct effects from increased (or decreased) 

temperatures. 

Precipitation Changes 

Sustained periods of increases or decreases in precipitation, whether over months or the 

cumulative effect across years, can cause substantial soil changes due to drought or 

saturation. Changes in water tables may occur both from local climate changes as well as 

from global effects such as sea level rise. An increase in water table level or increased 

surface water runoff can cause erosion or slumping (collapse) of the soil surface, thereby 

leading to potential for pipeline exposure. 

In the lowland and marsh areas particularly associated with the coastal regions of 

Louisiana, the soil is being washed away due to storm activity. With the disappearance of 

the soil, the pipelines in these regions are losing cover. 

Detailed analysis of geology and pipeline-specific conditions are required to draw more 

precise conclusions regarding the potential for serious disruption of the transmission 

pipeline system from climate-related soil changes. Nonetheless, this is an area of concern, 

because a considerable and unpredictable portion of the pipeline system could be 

vulnerable to these climate change and sea level induced impacts. 
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Another vulnerability is from expected short-term changes (such as torrents and floods), 

where significant change in water flow rate and water flow energy are a result of increased 

precipitation. Risk analysis of the impacts of extreme events is required to determine 

appropriate adaptation or mitigation actions. 

Storm Impact Preparation, Mitigation, and Response 

Wave action during storms may impact pipelines. For offshore pipelines, in instances 

where significant subsidence occurs and the pipeline segment is exposed, that section is 

exposed to wave action. High-energy waves may subject a pipeline to stress levels it was 

not designed to withstand, causing a fracture. An exposed offshore pipeline also could be 

vulnerable to lateral and vertical displacement, exposure to vessel traffic and fishing trawls, 

or rupture by currents, which may be very important in this context. 

Pipeline operating companies are required to have an emergency plan in place to cover all 

known or expected situations that may require response to repair the pipeline system due to 

damage, including, storms, excavation, and even sabotage or terrorist attack. Pipeline 

systems are segregated by sections between valves in order to allow isolation and shutdown 

of segments for routine maintenance, malfunctions, or response to emergency incidents. 

During shutdowns, pipelines are pressurized at the value given in the emergency plan 

design, and all valves are closed to prevent flow problems during the rest of the event and 

to facilitate repair. The operating portion of the emergency plan generally presumes that 

operations will be interrupted for a period of only up to 10 days. 

As soon as a storm or other event dissipates in the pipeline area of concern, the pipeline 

response team initiates their response plan. An inspection begins as a visual flyover the 

pipeline in the affected region to examine it for exposure or other obvious indications of 

damage. Some damage also can be detected through sensors measuring pressure in 

different pipeline segments or through other physical indicators, although these approaches 

may miss some damage (e.g., structural damage not yet causing a leak) or not be able to 

isolate damage location more precisely. If damage is apparent, then a thorough closeup 

inspection will take place, including divers if necessary. After damage has been identified, 

a repair team initiates repairs. 

The damages caused to pipelines by Hurricanes Andrew and Ivan were severe and fairly 

widespread throughout the storm front region, as documented by the MMS study discussed 

below (Skinner, 2006). After Ivan, oil refineries had ample products to supply, but the 

pipelines could not deliver due to damages. In contrast, damage to pipelines from Katrina 

and Rita was relatively minor; most pipelines were ready to take product but were 

hampered by the lack of available product due to refinery damage and/or power shortages. 

One representative of a hazardous liquid pipeline company stated that, prior to Ivan, 

obtaining pipeline maintenance and repair contract commitments was relatively easy, “a 

foregone conclusion of commitment,” but after Katrina and Rita, it has become 

increasingly difficult to obtain solid commitments from suppliers to respond to emergency 

calls. While suppliers are still offering contracts, the commitment is now only an offering 

to put the customer on a response list for a front-end fee. There is no longer a guarantee 
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that the supplier will respond to an emergency call within a fixed time period or otherwise 

provide service, because all their assets and personnel may be engaged in a prior 

commitment. 

Response capabilities and reliability have thus declined, even while the acknowledged 

storm threat has increased due to Ivan’s illustration of a previously unknown level of 

damage. Furthermore, while there were emergency operating plans before Ivan that 

matched the committed response time, we now know that responses may take longer, and 

operating plans will need to be adapted to meet these eventualities. 

Hurricane Damage Studies 

One of the more substantial studies of hurricane damage to pipelines in the Gulf of Mexico 

was done by Det Norske Veritas (DNV) Technology Services upon a request from the 

MMS (Skinner, 2006). This was an assessment of damage to the Gulf of Mexico offshore 

pipelines resulting from the passage of Hurricane Ivan in September 2004. The DNV study 

also summarized the impacts of Hurricanes Andrew, Lili, Katrina, and Rita. 

Hurricane Ivan reached Category 5 strength three times and was a Category 3 hurricane 

when it made landfall. Hurricane Ivan resulted in approximately 168 pipeline damage 

reports, although the vast majority of Gulf of Mexico offshore pipelines performed well 

during its passage. According to the MMS DNV report, the impact on the environment 

from pipeline spills was minimal. The majority of pipeline damage occurred at or near 

platform interfaces, in areas of mudflows, or as a result of an indirect hurricane impact, 

such as platform failure or anchor dragging. Localized failures at pipeline crossings and 

excessive movements in shallow water depths indicate that more hurricane-resistant design 

considerations might be needed on a site-specific basis but do not warrant industry-wide 

design or construction code revisions. The report suggests that design assumptions used 

for shallow water pipelines need to be evaluated in areas dominated by silty soils, 

particularly where self-burial is intended as the method of installation. 

Hurricane Andrew passed through the Gulf of Mexico in August 1992 as a Category 4 

storm. It damaged more than 480 pipelines and flow lines. Prior to Hurricane Andrew, 

minimal damage to pipelines had been experienced as a result of passing hurricanes, with 

combined pipeline failures from hurricanes for the period of 1971 through 1988 resulting in 

about 100 damage reports. Most of the pipeline failures were in depths less than 30 m (100 

ft) of water. 

Hurricane Lili was a Category 4 storm offshore in the Gulf of Mexico and was downgraded 

to a Category 2 hurricane at landfall in October 2002. There were 120 pipeline damage 

reports to the MMS following Hurricane Lili. The majority of the pipeline failures in Lili 

occurred in small diameter pipelines with no apparent correlation for age, which also was 

true for damages reported from Andrew. 

According to the MMS, there were 457 offshore oil and gas pipelines that were damaged as 

a result of Hurricanes Katrina and Rita (MMS Press Release, 2006). Most of the damage 

was relatively minor. Disruptions also occurred due to power outages, and pipeline 
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operators procured portable electric power generators necessary to resume operations. The 

closure of major pipelines originating in the Gulf of Mexico region in the wake of both 

storms served to exacerbate the petroleum product supply situation (EIA, 2005). 

Storm Activity: Erosion 

The above information and an interview with a hazardous liquids (mostly petroleum 

products) pipeline company revealed that damage from erosion and soil stability due to 

storm wave action has focused new interest on this phenomenon. The results of Hurricane 

Ivan, when erosion occurred in waters up to 76 m (250 ft) in depth, demonstrated that this 

effect can occur at depths previously considered impervious. The problem and solution is 

still being investigated in joint industry programs, along with Office of Pipeline Safety and 

MMS. 

Erosion typically has been found to occur in what the industry has termed “ultra shallow 

waters.” This phenomenon was prevalent from Hurricane Ivan (Skinner, 2006) but almost 

completely lacking from Hurricanes Katrina and Rita. This indicates that risk is not only 

due to storm intensity but also may be based on more complex meteorological and fluid 

dynamics factors, making the risk less predictable than assumed. 

In ultra shallow waters where erosion occurs, the general concurrence of industry 

specialists is that the seabed is “liquefying” (when the sand or silt shifts from a wet solid to 

a suspended state) in certain wave-action conditions. Pipeline design incorporates negative 

buoyancy (a present regulatory requirement and previously considered good design 

practice), but, if the sands are liquefying, the negative buoyancy may become positive and 

the pipeline ends up on the seabed surface. Documentation shows that the seabed level has 

not changed in these occurrences, but the pipeline has changed its elevation from 0.9 m (3 

ft) below the seabed surface to resting on the surface. While possible solutions are being 

developed, impacts from more frequent or severe storms currently can be considered a 

vulnerability of the pipeline system (EIA, 2005). 

Storm Activity: Increased Storm Severity 

In the Gulf Coast area of study, transmission pipelines have been designed to maintain their 

integrity for a (historical) 100-year storm event. Interviews with natural gas transmission 

pipeline company representatives indicate that the potential of pipeline damage due to 

increased storm activity or increased severity of storms is considered to be of marginal 

concern. They framed the issue as: to what extent can increased weather damage be 

effectively planned for, and what level of risk exposure should be assumed, beyond 

regulatory requirements? While there is an extensive regular inspection process that may 

identify weaknesses that could be expanded by a storm or by more gradual soil structure 

changes, it only partially prepares for and mitigates potential storm damage. 

Discussions regarding the potential for transmission pipeline damage consistently centered 

on the issue that nearly all the transmission lines are buried with 0.9 m (3 ft) of top cover, 

more in urban and populated areas, and they are regularly inspected for integrity. There is 

a need to better understand issues regarding damage to exposed pipeline portions (which 
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may be the most vital), such as valves, pumping stations, etc., and damage to underground 

portions from previously unconsidered factors, such as changing water tables and soil 

subsidence due to sea level changes.. 

Researchers interviewed MMS regulatory officials in the New Orleans, LA, office 

regarding the effects they see concerning climate change. The offshore pipelines are 

regulated by MMS regarding design, construction, operations, and maintenance 

requirements. MMS representatives indicated that they do not anticipate increased storm 

severity and frequency will appreciably affect the pipelines under their regulatory authority 

in the Gulf of Mexico. (Note that MMS’ authority ends at the State/Federal boundary 

offshore.13) It is unclear whether their comments took into account the changing soil 

structure and shoreline in the region. They based their comments on the fact that the 

subject pipelines are at substantial depth, and the pipelines are buried 0.9 m (3 ft) below sea 

floor level or anchored to piers designed to prevent pipeline movement on the sea floor. It 

is not certain how this accounts for the results of Hurricane Ivan and the findings of the 

DNV study. 

Secondary Impacts 

The level of oil and natural gas products moved via pipelines could be influenced by 

changes in temperature across the globe. Increases in temperature in the United States 

could affect the demand for energy products transported through the Gulf Coast; demand 

for natural gas (and coal) to power electricity plants in the southeast, for example, could 

lead to greater production and/or importation of natural gas through study region pipelines. 

Furthermore, climate mitigation policies designed to reduce carbon emissions could favor 

natural gas over other fossil fuels, thus promoting greater exploration and production of 

natural gas and importation of LNG, with clear implications for pipelines. 

Further study is necessary before firm conclusions can be drawn regarding the vulnerability 

of onshore and offshore pipelines. Relatively significant damage has occasionally 

occurred, yet other storms have produced only minor damage. Recent investigations have 

raised concerns about seabed conditions under which pipelines exhibit some vulnerability. 

It is a matter of further research whether climate change will exacerbate those conditions or 

whether the interface between onshore and offshore pipelines might be affected. 

4.2.7 Implications for Transportation Emergency Management 

Without proactive planning, climate change could complicate evacuation efforts in the 

region. As noted above, some highways, the chief mode for evacuation, are very likely to 

be inundated permanently as relative sea level rises and periodically when areas are 

flooded by storms. Further, higher temperatures could make evacuations more 

problematic, particularly in situations where there is severe congestion; higher 

 

13 The State/Federal boundary is 3 mi offshore in the study area except in Texas, where it is 10 mi offshore. 
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temperatures lead to greater air conditioning usage, making it more likely that vehicles will 

run out of fuel and block traffic. Large-scale emergency management is further challenged 

by the changing demographics of the region: an increasing percentage of residents are 

older and/or have special needs. Also, recent experience with evacuations suggests that 

congestion on key evacuation routes poses serious challenges to evacuating residents 

quickly. The need for interoperable communications systems across the region, currently 

lacking, will be heightened as the number of emergencies increases with climate change. 

A robust emergency management system is highly dependent on the viability of the 

region’s transportation infrastructure. Ensuring the capability to both evacuate residents, 

and move emergency responders and services into affected areas will require purposeful 

adaptation and, thus, focused investment in the transportation system. This section 

examines the implications for transportation emergency management of the potential 

impacts to highways and to transit and passenger rail that were presented earlier in this 

report. Many of these routes are expected to become increasingly vulnerable to higher sea 

levels and storm surge. 

This section also highlights some of the lessons learned from recent hurricane evacuation 

experiences and examines some of the issues related to the varied – and often 

incompatible – communications system found across the region. 

Further analysis and development of institutional consensus is necessary to more fully 

understand the implications of climate change on transportation emergency management. 

However, the preliminary vulnerability issues raised here are illustrative of the kinds of 

interactions that climate change and variability may cause for emergency management 

planning and operations. These issues are compounded by the changing demographics in 

the region. 

There are two key types of emergency management/climate change scenarios. The first 

involves complications for emergency response activities given climate impacts. For 

example, unusable roads caused by higher sea levels could disrupt road connectivity, 

increasing the time needed for emergency response vehicles to reach fires, medical 

emergencies, etc. The second involves situations where the climate impact itself causes the 

emergency; e.g., where hurricane induced flooding or a sudden rise in relative sea levels 

forces people to evacuate a particular area. 

Temperature 

As discussed in chapter 3.0, both mean and extreme temperatures are very likely to 

increase in the Gulf Coast region over the next 50 to 100 years. The increase in 

temperatures could cause more air conditioning usage during some evacuations and could 

further diminish mobility. Vehicles using air conditioning during storm evacuations, 

particularly on congested roads, would contribute to roadside blockages as fuel is depleted 

and vehicles are abandoned. Furthermore, an increase in temperatures, especially 

maximum temperatures, coupled with a growing number of special needs residents in the 

Gulf Coast study area means that more lives could be vulnerable in the absence of 

electrical power and air conditioning in the aftermath of a storm. 
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Relative Sea Level Rise 

As noted above, interstates and arterials tend to serve as the major evacuation routes for 

emergencies in the Gulf Coast study area. This substantial reliance on a single mode of 

transportation may endanger many people if the highway infrastructure is damaged or 

made inaccessible because of relative sea level rise. If the relative sea level increases such 

that portions of evacuation routes are under water then the essential connectivity and 

evacuation provided by those highways would be lost. This will be particularly important 

for large-scale evacuations dependent on east-west routes. Of course, as sea levels rise 

over time population centers may shift to higher elevations; the segments of evacuation 

routes that will be most critical are likely to change with these shifts in community 

locations. Furthermore, if the increase in relative sea level is gradual, infrastructure 

development would likely follow the movement of population centers. 

As discussed in section 4.2.1, the majority of the highways vulnerable to a 61- and 122-cm 

(2- and 4-ft) rise in relative sea level are located in the Mississippi River Delta region near 

New Orleans. The most prominent vulnerable highways are I-10, with 220 km (137 miles) 

and U.S. Highway 90 with 235 km (146 mi) passing through areas likely to be below sea 

level with a 61-cm (2-ft) rise in relative sea level. Overall, 19 percent of the interstate 

miles and 20 percent of the arterial miles are at elevations below 61 cm (2 ft). With a 122 

cm (4-ft) rise, the miles affected increase to 684 km (425 mi) of I-10 and 628 km (390 mi) 

of U.S. Highway 90. Overall, 24 percent of the interstate miles and 28 percent of the 

arterial miles currently are at elevations below 122 cm (4 ft). 

Storm Activity 

As noted in chapter 3.0, studies suggest that as radiative forcing (that is, greenhouse gas 

[GHG] concentrations) and sea surface temperatures continue to increase, hurricanes may 

be more likely to form in the Atlantic and Pacific and more likely to intensify in their 

destructive capacity. Storm surge disperses debris that blocks highways and makes many 

roads, including evacuation routes, impassable. In addition, storm surge may damage 

bridges and other structures, potentially compromising mobility for extended periods. 

While the actual highways that would be flooded and impacted by debris depends on the 

specific characteristics of any given storm, a substantial portion of the highway system is 

vulnerable to surge inundation, including roads in all four States in the study area. The 

areas that are potentially vulnerable to 5.5- and 7.0-m (18- and 23-ft) storm surge levels are 

shown in section 4.2.1 above. At the 5.5-m (18-ft) level, 51 percent of all arterial highways 

and 56 percent of the interstates in the study area are affected (figure 4.24). At 7.0 m (23 

ft), these percentages rise to 57 percent of all highways and 64 percent of the interstates. 

[INSERT FIGURE 4.24 Potential evacuation route highways vulnerable from storm surge of 5.5 

meters (18 ft)] 

Although not traditionally used for evacuation and emergency management purposes, 

railroads also could provide a transportation choice, especially for evacuees with special 

needs. Figure 4.25 illustrates the impacts on Amtrak facilities due to relative sea level rise 
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and storm surge and identifies the Amtrak stations that are vulnerable to storm surge at the 

5.5-m (18-ft) level. 

[INSERT FIGURE 4.25 Risks to Amtrak Facilities due to relative sea level rise and storm surge] 

Other Considerations Affecting the Success of Emergency Management 

The issues below are important from the perspective of managing emergencies and 

protecting people. Highlighting these issues is important because they are relevant to 

preparing for potential emergencies, some of which could be related to the impacts of 

climate change. 

Adapting Emergency Management Plans 

Effective emergency evacuation plans must be living documents that incorporate current 

and anticipated conditions, procedures, and resources. Climate change will likely 

exacerbate the need to update these plans and procedures. The 2005 hurricane season 

highlighted the need to reassess the appropriate level of investment for emergency 

management planning. As discussed, the climate analysis indicates a rise in temperature 

and relative sea level for the Gulf Coast region. These changes – coupled with continued 

increases in overall population, and of particular concern, major increases in the elderly 

and special needs populations – translate into a difficult situation for emergency 

evacuations in the Gulf Coast region without thoughtful and proactive planning. 

The requirement to transport those with special needs is especially challenging along the 

Gulf Coast, where many elderly people live in rural areas. Figure 4.26 illustrates the State 

and county/parish boundaries and the population over 65 that were impacted by Hurricane 

Katrina. 

[INSERT FIGURE 4.26 Population over age 65 impacted by Hurricane Katrina] 

Interdependent Communications Infrastructure 

Successful emergency management depends not only on the transportation infrastructure 

but also on interdependent communications infrastructure that allows emergency 

management personnel and responders to dynamically accommodate changing needs and 

infrastructure availability. Lessons learned from recent events indicate that significant 

breakdowns in communication can occur across multiple jurisdictions and agencies during 

major emergencies. Although not linked to or caused by changes in climate characteristics 

directly, cell phones and land lines quickly become unreliable both before and after major 

regional emergencies. Changes in climate may exacerbate this dynamic as greater 

penetration of storm surge and wind fields may disable the “day-to-day” communications 

infrastructure. 

A recent study released by First Response Coalition, a public safety group, suggests that 

many wireless communications systems in hurricane-prone states are still unlikely to 

function well during major regional emergencies. Communication plans and infrastructure 
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remain largely uncoordinated, even after concerted efforts to improve these dynamics 

following the 2005 hurricane season (First Response Coalition, 2006). 

The use of new surveillance technologies such as unmanned aerial vehicles (UAV) may 

help ameliorate problems with existing communications systems that would be exacerbated 

by future storm events. These relatively new, but increasingly efficient and more 

affordable devices, could be effective new tools in the critical 72-hour period leading up to 

evacuations, as well as postevent recovery and response operations. These and other 

strategies may serve as a new means of acquiring and relaying real-time information when 

existing infrastructure is disabled during a storm. 

Traffic Management 

Traffic management related to emergency evacuations will become increasingly critical as 

the population in the Gulf Coast region grows. This may lead to increased instances such 

as that experienced during Hurricane Rita in 2005, when Galveston’s long-standing plan to 

evacuate to Houston was complicated by the evacuation of Houston itself. Many 

Galveston (and other) residents tried to evacuate “through Houston,” only to encounter 

hours of gridlock in the oversaturated transportation system that already was filled with 

Houston residents evacuating from the approaching storm. Other coastal communities in 

the region could fare similar evacuation problems in future storms. Also, as storm impacts 

and the resulting evacuations do not follow State lines, it is important that States not only 

plan for evacuations of their own residents but also account and allow for potential 

multistate evacuations that cross multiple State boundaries. 

Critical Care Facilities and Shelters for Those with Special Needs 

The predicted changes in climate over the next century will make the care of those with 

special needs more complex and problematic. In the instance of “sheltering in place,” 

increased attention and planning will need to be given to auxiliary power and backup 

communication systems to sustain critical health services and to maintain acceptable 

quality of life (air conditioning, water supply, etc.). 

The 2005 hurricane season also produced numerous instances of evacuees with special 

needs arriving at their “designated shelters,” only to be turned away due to lack of capacity 

or the facility not even being open. Many of these shelters that denied evacuees shelter 

received funding from the U.S. Department of Homeland Security to support the facility 

infrastructure and operation. With evacuee demands only expected to increase in the 

future, the need to ensure reliable shelter services becomes increasingly important. 

Local Development Policies 

As it relates to the ability to support regional evacuations during emergencies, the potential 

for climate impacts – particularly storm surge and wind field during major hurricanes – 

should be mapped (and otherwise illustrated) to determine probable zones of risk. This 

information can inform local development policies and guide the location of new housing 

and critical care facilities to areas of lower vulnerability. 
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Fiscal Impacts 

Revenue data collected by the State of Florida indicates that hurricane weather events 

reduce toll collection and increase toll system costs. As shown in table 4.20 below, the 

Florida 2004 hurricane season cost the State’s tolled facilities $62,600,000 (Ely, 2005). 

These financial impacts could negatively impact the fiscal viability of toll projects that are 

used for evacuation routes in emergencies. The toll operating agencies in Florida recognize 

their toll facilities as evacuation routes and are working to suspend payment of tolls in the 

event of a hurricane (Warren, 2005). 

[INSERT TABLE 4.20 Hurricane impacts on toll revenue in Florida] 

Increased frequency and severity of hurricanes might pose a challenge to the fiscal 

strategies of toll facilities, may discourage the trend to finance future infrastructure with 

tolls, and may thereby reduce infrastructure that can be used for emergency evacuation. If 

too much of an area is inundated for an extended period there may be a reduction in vehicle 

trips below the threshold needed to support repayment of bonds. For example, beaches that 

had served as a destination for toll bridges could be flooded by rising sea levels and no 

longer support tourism. This could in turn affect toll revenues and ultimately undermine 

the financial viability of key segments of evacuation routes. Bridge tolls in the 

northwestern Florida region (Garcon Point and Mid-Bay Bridges) offer one illustration of 

this potential impact. 

Highways provide the majority of transportation infrastructure for emergency operations. 

There are limited public transportation capabilities that operate on separate rights-of-way. 

This substantial reliance on a single mode of transportation could endanger many residents 

if the highway infrastructure is damaged or made inaccessible. 

The prospect of climate change may require more frequent changes to emergency 

management plans and procedures. After the 2005 hurricane season, many public agencies 

are reassessing the appropriate level of investment for this activity. Recent events, as well 

as the climate change projections discussed in this report, highlight the need to develop 

action plans for worst-case scenarios. With predictions of a warmer Gulf Coast climate, 

more intense storms and hurricanes, and rising relative sea levels, the future design of 

critical infrastructure and emergency evacuation plans will need to incorporate increased 

challenges to our emergency management system. 
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 4.3 Impacts and Adaptation: Case Examples in the 

Study Region 

While sections 4.1 and 4.2 analyze the potential future impacts of climate change on the 

region, this section focuses on the impacts associated with Hurricanes Katrina and Rita. 

The challenges of responding to severe weather events are all too familiar to transportation 

managers in the Gulf Coast. The hurricane season of 2005 was devastating for many 

communities in the study area. As the region rebuilds, some areas are incorporating 

changes to infrastructure design to help systems better withstand flooding and storm surge. 

The lessons learned from the costs of clean up and repair can help managers assess the 

implications of infrastructure damage as they consider future adaptation options. The 

following case examples illustrate the issues confronting managers working to ensure a 

safe and reliable transportation system. 

4.3.1 Impacts of Hurricanes Katrina and Rita on Transportation 

Infrastructure 

Hurricane Katrina, which made landfall on August 29, 2005, was the most destructive and 

costliest natural disaster in the history of the United States and the deadliest hurricane since 

the 1928 Okeechobee Hurricane. Over 1,800 people lost their lives during Hurricane 

Katrina, and the economic losses totaled more than $100 billion (Graumann et al., 2006). 

More than 233,000 km2 (90,000 mi2

) were declared disaster areas. While a single storm 

cannot be attributed to climate change, the impacts of Hurricanes Katrina and Rita in 2005 

illustrate the types of impacts that would occur more frequently if the Gulf Coast were to 

experience more Category 4 and 5 hurricanes in the future. 

The storm had a devastating impact on much of the transportation infrastructure of coastal 

Mississippi, Louisiana, and Alabama, causing major damage to highways, railroads, ports, 

and airports. Damage was caused by flooding, pounding waves, and high winds. In 

addition, when the floodwaters subsided, an enormous amount of debris still had to be 

removed before transportation networks could function. Forty-six million yd3

 of debris 

were removed from Mississippi alone (from all locations, not just transportation facilities). 

Louisiana DOTD spent $74 million on debris removal following Hurricanes Katrina and 

Rita (Paul, 2007). 

Through aggressive action by public and private transportation managers, many major 

transportation facilities were reopened relatively quickly considering the level of damage. 

Most of the study area highways, rail lines, pipelines, ports, and airports were back in 

service within weeks to a month. Limited access across the I-10 Twin Span Bridge was 

available within two months and nearly full access achieved within five months. The 

heavily damaged CSX Gulf Coast mainline and its bridges were reopened six months after 

being washed out by Hurricane Katrina. The worst damaged facilities were the river and 

bay bridges that carry U.S. Highway 90 along the edge of the Gulf Coast. Though much of 

the roadway and three of the six badly damaged crossings were repaired within about three 
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months, the three remaining bridges took considerably longer to repair or replace. The last 

of these bridges, the Biloxi-Ocean Springs Bridge, is scheduled to reopen in November 

2007, more than two years after Katrina. In all, the price tag of cleanup and reconstruction 

effort will run into the billions of dollars: the Louisiana Recovery Authority estimated 

costs exceeding $15 billion for Louisiana alone (Louisiana Recovery Authority, 2006). 

Mississippi spent more than $1 billion on cleanup and bridge replacement. (Mississippi 

DOT, 2007). 

By most accounts, the impact of Hurricanes Katrina and Rita on national-level freight 

flows was modest because of redundancy in the national transportation system and timing. 

Truck traffic was able to divert to parallel east-west interstate routes that avoided the 

collapsed bridges and other barriers. Railroad operators were able to reroute intermodal 

and carload traffic that was not bound directly for New Orleans through Memphis and 

other Midwest rail hubs. Most of the Mississippi river ports and the Mississippi inland 

waterway were back in service in time to handle the peak export demand later in the fall of 

2005. Major pipelines suffered relatively little damage and were able to open within days 

as electrical power was restored (Grenzeback and Lukmann, 2006). 

The following text outlines some of the key impacts by mode. 

Roads 

The most significant impacts to roads were to the numerous bay and river crossings 

throughout the region. While the effects were limited in some locations and damage was 

repaired within days, in some coastal sections prominent elements of the transportation 

network remained closed many months after the storm. The worst damage was focused in 

the area along and to the south of the I-10/I-12 corridor, including U.S. Highway 90, State 

Highway 1, and the Lake Pontchartrain Causeway in Louisiana, as well as I-110 in 

Mississippi. Three major bridge crossings along the route were destroyed and two more 

sustained significant damage. The damage was largely caused by the immense force of 

wave action on the bridge spans, many of which were not sufficiently tied down to the 

bridge pilings to resist movement (figure 4.4). Spans weighing 300 tons were dislodged by 

the hurricane. 

Inundation also caused structural problems along many miles of roadway. More than 50 

km (30 mi) of coastal U.S. Highway 90, which runs through the beachfront communities of 

Mississippi, were completely inundated by the storm. At a cost of $267 million, the 3.2-

km (2-mi), four-lane Bay St. Louis Bridge (U.S. Highway 90) reopened on May 17, 2007. 

The total request for emergency repairs to Mississippi highways alone after Katrina is $580 

million (Mississippi Gulf Coast Regional Planning Commission, 2006). Much of the 

paved surface between Pass Christian and Biloxi buckled or dropped into sinkholes; in 

places it took weeks to repair washouts and to remove many feet of sand from the road 

surface: More than 3,200 km (2,000 mi) of roads were submerged in Louisiana, and the 

Louisiana DOTD found indications that prolonged inundation can lead to long-term 

weakening of roadways. A study of pavements submerged longer than three days (some 

were submerged several weeks) found that asphalt concrete pavements and subgrades 
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suffered a strength loss equivalent to 5 cm (2 in) of pavement (Gaspard et al., 2007). The 

estimate for rehabilitating a portion of these roads, 320 km (200 mi) of submerged State 

highway pavements, amounted to $50 million. 

The expense of poststorm cleanup and repair can be considerable. The Louisiana Recovery 

Authority estimated that the cost of rebuilding infrastructure (defined as roads, bridges, 

utilities and debris removal) damaged by the hurricanes would cost $15-18 billion. 

Louisiana DOTD spent $74 million on debris removal; as of June 2007, Mississippi DOT 

had spent $672 million on debris removal, highway and bridge repair, and rebuilding the 

Biloxi and Bay St. Louis bridges; it expects to spend an additional $330 million in the 

subsequent 18 months (Mississippi DOT, 2007; Louisiana Recovery Authority, 2006). 

Also, debris removal is not completely benign in terms of further impact; heavy trucks 

removing debris in Louisiana also damaged some roadways (Paul, 2007). 

Rail 

The rail infrastructure in coastal Mississippi and Louisiana suffered major damage that 

took weeks or months to repair. The worst storm damage was focused on a 160-km (100-

mi) section of CSX’s Gulf Coast line between New Orleans and Pascagoula, Mississippi. 

CSX had to restore six major bridges and more than 65 km (40 mi) of track, much of which 

was washed out or undermined. Damage was so extensive on the line that CSX required 

more than 5 months and $250 million to complete repairs and to reopen the line. It would 

take many times that if the company wanted to relocate the line further inland. In addition, 

New Orleans is a major rail freight interchange point for east-west rail traffic, and the 

railroads needed to reroute intermodal and carload traffic that was not bound directly for 

New Orleans through other rail hubs in Memphis and St. Louis, which increased operating 

expenses (Grenzeback and Lukmann, 2006). 

Ports 

Due to their low-lying locations, the ports were susceptible to damage from all effects of 

Hurricane Katrina– high winds, heavy rains, and especially the storm surge. Container 

cranes were knocked down, storage sheds blown apart, and navigational aids lost. In 

Gulfport, MS, the storm surge pushed barges hundreds of feet inland and scattered 40-ft 

containers throughout downtown Gulfport. The storm sank nearly 175 barges near New 

Orleans, disrupting navigation on the river; however, almost all ports in the central Gulf 

Coast were able to reopen within a month of Katrina’s landfall. Nonetheless, damage was 

costly: more than $250 million has been allocated to repair, rebuild, and expand the Port of 

Gulfport in the wake of Hurricane Katrina (Grenzeback and Lukmann, 2006). 

Fortunately, the timing of the storm prevented a catastrophic impact on U.S. agricultural 

exports. Gulf Coast ports typically handle 55 percent to 65 percent of U.S. raw corn, 

soybean, and wheat exports. Since the bulk of U.S. corn and soybean harvest moves down 

the Mississippi River from October to February, the ports were generally able to restore 

operations in preparation for this critical season, although agriculture still faced increased 
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shipping costs due to a shortage of barges. The severe damage to Gulfport (which 

specializes in importing containerized bananas and winter fruits from Central and South 

America) did result in a regional shortage of tropical fruits, because major fruit importers 

such as Dole, Chiquita, and Crowley were forced to reroute shipments to Port Everglades, 

FL, or Freeport, TX, at extra expense (Grenzeback and Lukmann, 2006). 

Airports 

A number of airports in the study area received significant damage from the strong winds, 

flooding rains and embedded tornadoes associated with Hurricane Katrina. Airports 

sustained damage to passenger terminals, maintenance facilities, and navigational devices. 

Power outages also took air traffic control facilities offline and darkened nighttime runway 

lights. As a result, some airports were closed for days and weeks while necessary repairs 

could be made, but relief flights were flown in before the airport facilities were fully 

reopened. 

Louis Armstrong New Orleans International Airport, the third largest airport in the Central 

Gulf Coast, sustained damage to its roofs, hangars, and fencing, but had no significant 

airfield damage despite sitting only 122 cm (4 ft) above sea level (making it the second 

lowest lying international airport in the world, after Schiphol International in The 

Netherlands). For the first few weeks of September, the airport was open only to military 

aircraft and humanitarian flights, but reopened to commercial flights on September 13, 

2005. On the other hand, Lakefront Airport, one of the busiest general aviation facilities in 

the Gulf Coast and located directly on Lake Pontchartrain to the north of the New Orleans 

city center, suffered extensive damage, with a number of terminals and hangars destroyed. 

It took 7 weeks before it could even reopen for daytime operations. Gulfport-Biloxi 

International, the fifth busiest commercial airport in the central Gulf Coast, was also hard 

hit by the storm. Located less than a mile inland, between U.S. Highway 90 and I-10 in 

Gulfport, the airport’s terminal building, taxiways, cargo facility, general aviation facility, 

and rental car facility sustained an estimated $50 million to $60 million in damage. The 

airport reopened to commercial flights on September 8 and returned to its normal volume 

of traffic in February 2006 (Grenzeback and Lukmann, 2006). 

Fifty-eight airports were surveyed on how they were affected by Hurricanes Katrina and 

Rita – the extent of damage either hurricane caused, the ability of the airports to cope with 

the damage, and the use of the airports for emergency management. Twenty-nine airports, 

or 50 percent, responded to the survey. Forty-eight percent of respondents pointed to the 

following as some of the main reasons for closure: electrical outage (19 percent), wind 

damage (16 percent), and debris on runways (12 percent) were the top three reasons 

identified. Civil, military, and passenger airline operations were affected by the hurricanes. 

Figure 4.23 identifies airports affected by Hurricane Katrina’s winds. GIS analysis 

indicates 16 airports experienced winds exceeding 161 km/h (100 mi/h) during Hurricane 

Katrina, including New Orleans International, Gulfport-Biloxi, and Hattiesburg 

commercial service airports. These airports are located in southeastern Louisiana and 

south-central Mississippi. USGS data also indicates that nine airports impacted by 

Hurricane Rita experienced winds exceeding 161 km/h (100 mi/h), including two 
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commercial service airports: Beaumont-Port Arthur in Texas and Lake Charles Regional in 

southwestern Louisiana. Survey responses indicated additional implications to aircraft 

operations as follows: 

• Civil aircraft operations were closed at 12 airports. The average length of closure to 

civil aircraft operations was 209 hours, and the maximum observed closure was 1,152 

hours. Lakefront Airport in New Orleans, an outlier, was closed for 48 days and skews 

the data. When removing this airport from the data field, the average length of time 

closed to civil aircraft operations is 35 hours. It is noteworthy that although many 

airports “opened” soon after the hurricanes passed, many were without electricity and 

were only open during daylight hours. 

• Military aircraft operations were closed at eight airports. The average length of closure 

to military aircraft operations at civil airports was 33 hours, and the maximum observed 

closure was 96 hours. 

• Two commercial service airports, Lake Charles Regional and Houston’s William P. 

Hobby, reported passenger airline operations were suspended at their airport. 

[INSERT FIGURE 4.27 Airports affected by Hurricane Katrina winds] 

Hangar facilities also were damaged by Hurricanes Katrina and Rita. Thirty-eight percent 

of responding airports suffered damage to T-hangars, which are long rectangular structures 

with 12 to 20 “bays” that store single-engine and small twin-engine aircraft. Forty-five 

percent of responding airports experienced damage to conventional hangars, which are 

designed to store large aircraft and are 18 by 18 m (60 by 60 ft) to 30 by 30 m (100 by 100 

ft) in size. Conventional hangars are also 6 to 9 m (20 to 30 ft) in height to accommodate 

large aircraft with high tails. 

Pipelines 

The major petroleum and petroleum-product pipelines servicing the study area received 

relatively little physical damage from the effects of Hurricanes Katrina and Rita, but could 

not operate reliably due to massive power outages in the wake of the storms and by 

interruptions to the supply of fresh product to transport due to refinery shutdowns, causing 

shortages of petroleum products in parts of the Nation. Even so, most of these systems 

were able to resume partial service within days of the storm and full service within a week. 

At the peak of the disruption caused by Hurricane Katrina, 11 petroleum refineries were 

shut down, representing 2.5 million barrels per day or 15 percent of U.S. refining capacity, 

and all major pipelines in the area were inoperable due to power outages. By September 4, 

5 days after the storm, eight major petroleum refineries remained shut down (representing 

1.5 million barrels per day or nine percent of U.S. refining capacity); however, all of the 

major crude or petroleum product pipelines had resumed operation at either full or near-full 

capacity (Grenzeback and Lukmann, 2006). 
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4.3.2 Evacuation During Hurricane Rita 

Emergency evacuation is a key strategy to cope with hurricanes in the low-lying Gulf Coast 

study region. The evacuation of Houston/Galveston, the largest metropolitan area in the 

study region, prior to Hurricane Rita presents a case study of the difficulties of evacuating 

large urban areas and some lessons learned for future emergency planning. 

Unlike New Orleans, much of Houston is high enough to be out of the storm surge zone; 

thus, Galveston and the low-lying eastern areas are generally supposed to evacuate first. 

However, Houstonians learned during Tropical Storm Allison (2001) that precipitation 

alone can cause massive flooding in the city from overflowing bayous and lack of drainage. 

With images of the devastation wrought by Hurricane Katrina fresh on their minds, up to 

2.5 million people attempted to evacuate the Houston/Galveston area in the days before 

Rita’s projected landfall (Mack, 2005) – twice as many people as the area’s evacuation 

planning was developed for (Durham, 2006). In fact, only about half of these people lived 

in evacuation zones (Feldstein and Stiles, 2005). 

Evacuees faced massive congestion, with 160-km (100-mi) traffic jams reported 

(Breckinridge et al., 2006). One fifth of the evacuees spent more than 20 hours on the road 

to leave the area; only half completed the trip in less than 10 hours (Mack, 2005). 

Worsening the congestion, households traveled in multiple cars in order to get valuable 

property out of harm’s way: the Texas Transportation Institute (TTI) estimated that on 

average there were 1.2 occupants per vehicle, versus the 2.1 occupants generally assumed 

in evacuation planning (Durham, 2006). In an effort to ease congestion, officials 

improvised a last-minute contraflow system on some highways, which was not part of their 

original evacuation plan. Fuel shortages plagued travelers as gasoline stations on the 

evacuation routes were overwhelmed by demand. Tragically, 23 nursing home evacuees 

died when their bus caught fire on the road. 

Following the storm, the Houston-Galveston Area Evacuation and Response Task Force 

identified several lessons learned from the experience and recommendations for the future 

(Durham, 2006): 

• Evacuation plans should be practiced extensively prior to the hurricane season to reveal 

problems ahead of time. 

• Plans should include a system for removing disabled vehicles – during Rita, an 

effective incident management service was available only within the Houston city 

limits. As a result, vehicle breakdowns caused significant bottlenecks along the 

evacuation routes. 

• Contraflow plans should be developed well in advance, but operations are not a 

panacea. Emergency planners will need to consider the numerous drawbacks of 

implementing contraflow strategies: They require intensive use of law enforcement 

and other personnel, disrupt day-to-day operations in areas not evacuating, and make it 

more difficult to move emergency vehicles and supplies back into the area. 
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• Thorough planning is necessary for evacuees with special needs, including ensuring an 

adequate supply of vehicles, identifying destination(s) capable of supporting their 

needs, and providing personnel sufficient training to ensure a safe trip. 

The Rita evacuation also demonstrated the importance of accounting for human behavior. 

“Too few” people evacuated New Orleans before Katrina, but “too many” evacuated the 

Houston-Galveston area (Breckinridge et al., 2006). Evacuation orders are meant to 

reinforce the fundamental strategy of “run from the water, hide from the wind”; however, 

in the case of Rita it seems many evacuees ran from the wind. Similarly, the tendency of 

households to take as many vehicles with them as possible is a logical way to protect 

property but counterproductive during a mass evacuation. This illustrates the need to better 

understand the range of potential reactions by residents during a crisis and how best to 

communicate with the public to facilitate effective emergency management. 

4.3.3 Elevating Louisiana Highway 1 

Louisiana currently is in the process of upgrading and elevating portions of Louisiana 

Highway 1, a road that is very important both locally and nationally. It connects Fourchon 

and Port Fourchon to Leeville and Golden Meadow to the north. The project is broken into 

multiple phases and includes a four-lane elevated highway between Golden Meadow, 

Leeville, and Fourchon to be elevated above the 500-year flood level; and a bridge at 

Leeville with 22.3-m (73-ft) clearance over Bayou LaFourche and Boudreaux Canal. 

Construction has begun on both the $161 million bridge project and a segment of the road 

south of Leeville to Port Fourchon (Wilbur Smith, 2007). 

Hurricane Katrina’s impact on the energy infrastructure helped raise the profile of the 

dangers facing and the importance of Louisiana Highway 1. The highway floods even in 

low-level storms, and in addition to the effects of storm surge, the existing infrastructure 

also faces threats from very high rates of coastal erosion and subsidence (Smith, 2006). 

The importance of this part of the Gulf Coast, and thus Highway 1, to the Nation’s energy 

supply and infrastructure cannot be overstated. It is the only roadway linking Port 

Fourchon and the Louisiana Offshore Oil Port (LOOP) to the Nation. Port Fourchon 

supports 75 percent of deepwater oil and gas production in the Gulf of Mexico, and its role 

in supporting oil production in the region is increasing. The LOOP, located about 32 km 

(20 mi) offshore, plays a key role in U.S. petroleum importation, production, and refining 

as it links daily imports of 1 million barrels and production of 300,000 barrels of oil in the 

Gulf of Mexico to 50 percent of U.S. refining capacity. Locally, the road is the key route 

for transporting machinery and supplies to Port Fourchon and offshore oil workers and also 

for exporting seafood from the region. Perhaps most importantly, it is the evacuation route 

for south Lafourche and Grand Isle, as well as some 5,000 offshore oil workers (LA 1 

Coalition, 2007a and b). 
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 4.4 Conclusions 

The results of this investigation shows a wide range of possible impacts on transportation 

infrastructure and services across the Gulf Coast study area. Given the uncertainties 

inherent in modeling and the complexities of the natural processes involved, this analysis 

does not attempt to pinpoint the precise timing of climate effects but rather provides a 

broad assessment of potential impacts during the coming decades. These findings provide 

a critical overview for transportation planners and managers of the potential implications of 

climate factors and indicate areas of vulnerability that warrant consideration by decision 

makers. Future investment decisions should be informed by the potential risks identified in 

this study. 

Some of the most evident impacts are related to RSLR and storm surge. A 122-cm (4-ft) 

increase in relative sea level could inundate a substantial portion of the transportation 

infrastructure in the region: 28 percent of the arterials, 43 percent of the IM connectors, 

and 20 percent of the rail miles. Nearly three quarters of ports could be affected, as well as 

three airports, including Louis Armstrong International in New Orleans. Impacts 

associated with storm activity are more acute, although confined to the specific locations of 

individual storm events. Some 51 percent of arterials and 56 percent of interstates, along 

with almost all ports, a third of rail lines, and 22 airports are vulnerable to a storm surge of 

5.5 m (18 ft), should such a surge occur. As the potential of higher-intensity storms 

increases and sea level rises, the vulnerability of infrastructure to storm surge becomes 

increasingly significant. 

The direct impacts of climate factors on specific facilities can have much broader 

implications than implied by the percentages and maps contained in this chapter. Damage 

to critical links in the intermodal network can disrupt connectivity throughout the region. 

These disruptions can be relatively short term, as in the case of precipitation and some 

storm surge and weather events; moderate, as in the case of shut-downs to conduct 

maintenance required to repair pavement surfaces caused by higher temperatures or storm 

surges; or long-term interruptions of service caused by inundation and damage to entire 

segments of infrastructure due to storm surge or permanent sea level rise. 

The safety impacts associated with climate impacts deserve further in-depth analysis 

beyond this effort. Storm activity and storm surge in particular have the most direct 

implications for safety. These include accidents caused by: debris caused by storms, 

washed-out roads during or after storms, or evacuations before storms. Furthermore, the 

other key climate drivers, including changes in precipitation patterns, temperature, and 

relative sea level rise, could have important safety impacts as well. 

In addition to these regional impacts, the vulnerabilities of Gulf Coast transportation will 

have nationwide significance that merit further investigation. The resilience of Gulf Coast 

transportation infrastructure capabilities has implications for the country’s ability to 

transport many key commodities into and out of the United States, including petroleum and 

natural gas, agricultural products, and other bulk goods. 
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Data and Research Opportunities 

This study identified needs for additional data and research that would further advance 

understanding of the implications of climate change for transportation. These include 

information and investigation in the following areas: 

• Integration of site-specific data – The integration of site-specific elevation and 

location data in a GIS-compatible format would greatly facilitate investigation of the 

impacts of climate change and the natural environment on transportation. This data 

should include information on transportation facilities as well as on protective 

structures such as levees and dikes 

• Additional and refined climate data and projections – Further development of 

environmental trend data and climate model projections tailored to transportation 

decision makers is needed to facilitate integration of climate information into 

transportation decisions. In addition, specific data on other climate factors not fully 

addressed in this study would be valuable. These factors include wind speeds, isolated 

hot days, and fog. 

• Effects of climate change on freight transport demand – Research is needed on the 

perspectives, investment considerations, relocation plans, and adaptation strategies of 

private sector shippers and freight transportation providers and how their requirements 

may evolve due to climate change and shifts in market demand. 

• Demographic response to climate change – High-population density creates 

increased need for both passenger transport and movement of consumer goods. 

Population change will be driven by multiple factors, possibly including changing 

environmental conditions. Projections of population density along coastal regions and 

their impact on the demand for freight and passenger services need to be explored. 

• Design standards and reconstruction and adaptation costs – Additional case 

information would be valuable regarding the costs of rebuilding transportation facilities 

following severe storms. Research is needed on how local agencies are adapting design 

standards during reconstruction (or construction of new facilities) to increase the 

resilience of their facilities, such as changes in bridge height or construction, use of 

new materials, and changes in design criteria. Analysis of the range of adaptation 

options available and the costs and benefits of specific strategies would help inform 

State and local transportation planners and decision makers. 

• New materials and technologies – Research is needed to develop materials that can 

better withstand higher temperatures and drier or wetter conditions and technologies 

that can help us better adapt to the effects of climate change. 

• Pipelines – A more complete examination of pipeline impacts from climate change and 

adaptation strategies is warranted. 

• Land use and climate change interactions – Research is required to investigate how 
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various land use development and environmental management strategies in vulnerable 

areas affect the magnitude of climate change impacts on communities and 

transportation infrastructure. A comparative analysis of current, international best 

practices in land use and building codes, particularly in coastal regions, could provide 

useful information to U.S. transportation and planning agencies. 

• Emergency management planning/coordination/modeling – Additional study on 

successful approaches in coordinating emergency management planning among public 

agencies and major private sector entities in at-risk areas could identify opportunities 

for improved coordination, public-private partnering, and risk reduction. Development 

and application of simulation modeling should be considered to illustrate the increasing 

challenges of evacuating major urban areas and evaluate mitigation strategies. 

Collection and evaluation of real-time data gathered during emergencies is needed to 

determine its possible use to first responders, operating agencies, the media, and the 

general public. Changes in communication and information technology infrastructure 

also should be explored. 

• Secondary and national economic impacts – More in-depth research into the 

secondary economic impacts to the region and Nation of freight disruption would 

benefit understanding of national trends and vulnerabilities and inform development of 

appropriate policies. 

• Site-specific impacts – This assessment considers scenarios of change for the counties 

that comprise the central Gulf Coast. More detailed analysis is desirable since specific 

transportation facilities will ultimately be affected by climate change. This will require 

development of climate data and information that is specific to much smaller 

geographic areas, in addition to detailed analyses of specific facilities. 

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<http://www.mcema.net/sa_procs.html>, viewed December 2006. 

National Assessment Synthesis Team (U.S.). Climate Change Impacts on the United 

States: The Potential Consequences of Climate Variability and Change. Cambridge 

University Press, Cambridge, 2001. Available on-line at: <http://www.usgcrp.gov/

usgcrp/Library/nationalassessment/foundation.htm>, viewed December 2005.> 

Paul, H., 2007: Impacts of Climate Change and Variability on Transportation Systems and 

Infrastructure: Gulf Coast Study. Presented at Impacts of Climate Change and 

Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Federal Advisory Committee Meeting, May 16-17, 2007. 

Pipeline and Hazardous Materials Safety Administration (PHMSA), 2007: Annual 

Reports: National Pipeline Mapping System. PHMSA, U.S. Department of 

Transportation, Washington, D.C. 

Plans Branch, Louisiana Office of Homeland Security and Emergency Preparedness, 

2006: Pelican Parish Planning Guidance and Crosswalk for Parish Multi-Hazard 

Emergency Operations Plans. March 2006. Available on-line at: <http://www.ohsep.

louisiana.gov/plans/PELICAN%20CROSSWALK06F.doc>, viewed December 2006. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation? 

4-62 

Skinner, John, 2006: Pipeline Damage Assessment from Hurricane Ivan. Det Norske 

Veritas Technology Services, Department of Interior, Minerals Management Services 

report. Available on-line at: <http://www.mms.gov/tarprojects/553.htm>. 

Sloan, Kim, 2007: Bay St. Louis Bridge Open. Mississippi DOT Public Affairs. 17 May 

2007. Available on-line at: <http://www.gomdot.com/newsapp/newsDetail.aspx?

referrer=list&id=529200710349>, viewed 10 July 2007. 

State of Alabama, Emergency Operations Plan, April 20, 2006: Available on-line at: 

<http://ema.alabama.gov/Misc/Alabama%20EOP%202006.pdf>, viewed December 

2006. 

State of Louisiana, Office of Homeland Security and Emergency Preparedness, 

Emergency Operations Plan. April 2005. Available on-line at: 

<http://www.lsuhsc.edu/hcsd/loep.pdf>, viewed December 2006. 

Transportation Research Board, Special Report 281, Transportation Pipelines and Land 

Use, Washington, D.C., 2004, page 47. 

U.S. Census Bureau: Areas Affected by Hurricane Katrina (Revised). Available on-line 

at: <http://ftp2.census.gov/geo/maps/special/HurKat/Katrina_Pop_65+_v2.pdf>, 

viewed May 2006. 

U.S. Department of Transportation (DOT) in Cooperation with U.S. Department of 

Homeland Security, 2006: Catastrophic Hurricane Evacuation Plan Evaluation: A 

Report to Congress. Available on-line at: 

<http://www.fhwa.dot.gov/reports/hurricanevacuation/index.htm>. 

U.S. Geological Survey (USGS), 2004: National Elevation Dataset (NED). U.S. 

Geological Survey, EROS Data Center, Sioux Falls, South Dakota. [Available on-line 

at http://ned.usgs.gov/] 

Warren, C.L., et al., 2005: Toll Suspension Plan during Hurricanes. Transportation and 

Expressway Authority Membership of Florida (TEAMFL). 

Wilbur Smith Associates, 2007: LA 1 Improvements. Available on-line at: 

<http://www.la1project.com/index.cfm>, viewed 3 July 2007. 

4.5.2 Background Sources 

Association of American Railroads, 2005: Back on Track, Issue 2, September 16, 2005, 

and, Back on Track, Issue 5, October 7, 2005. Available at: <www.aar.org>. 

CSX, Press Release: January 19, 2006. CSX Takes First Steps Toward New Logistics 

Center. Available at: <www.csx.com>. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation? 

4-63

CSX, Press Release: January 18, 2006. CSX Transportation to Reopen Vital Gulf Coast 

Rail Line. Available at: <www.csx.com>. 

Feldstein, D. and M. Stiles, 2005: Too Many People and No Way Out. Houston 

Chronicle, Houston, Texas, September 25. 

Grenzeback, L. R., A. T. Lukmann, 2008: Case Study of the Transportation Sector’s 

Response to and Recovery from Hurricanes Katrina and Rita. In: The Potential 

Impacts of Climate Change on U.S. Transportation. The National Research Council, 

National Academy of Science, Transportation Research Board and Department of 

Earth and Life Sciences, Washington, D.C. 

LA 1 Coalition, 2007: Highway Challenge, LA Highway 1: Gateway to the Gulf. 

Available on-line at: <http://www.la1coalition.org/highway.html, viewed June 2007. 

LA 1 Coalition, 2007: The Importance of LA Highway 1 to our Region and our Nation. 

Available on-line at: <http://www.la1coalition.org/highway_02.html>, viewed June 

2007. 

Mack, K., 2005: Most Say They’d Evacuate Again. Houston Chronicle, Houston, Texas, 

November 10. 

Nossiter, Adam, “A Bridge Restores a Lifeline to a Battered Town,” The New York 

Times, May 24, 2007. Available at: <http://www.nytimes.com/2007/05/29/us/

nationalspecial/29bridge.html?ex=1338091200&en=24a98c1c1216af01&ei=5088&par

tner=rssnyt&emc=rss>, viewed 10 July 2007. 

Smith, Elliot Blair, 2006: Road to Recovery Sinking into Gulf. USA Today, 18 July 2006. 

Available on-line at: <http://www.usatoday.com/money/2006-07-17-new-orleansusat_x.htm>, viewed 3 July 2007. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-1

Table 4.1 Relative sea level rise modeled by using SLRRP. 

 Low Range High Range 

Galveston, TX 117 cm (3.8 ft) 161 cm (5.3 ft) 

Grand Isle, LA 160 cm (5.2 ft) 199 cm (6.5 ft) 

Pensacola, FL 70 cm (2.3 ft) 114 cm (3.8 ft) 

Table 4.2 Relative sea level rise modeled by using CoastClim. 

Projected 

Subsidence 

by 2100 

RSLR, B1- 

Low Range 

Subsidence, 

Percent of 

Low Range 

RSLR, A1F1-

High Range 

Subsidence, 

Percent of High 

Range 

Galveston, TX 51.7 cm (1.7 ft) 72 cm (2.4 ft) 71.8% 130 cm (4.3 ft) 39.7% 

Grand Isle, LA 88.6 cm (2.9 ft) 109 cm (3.5 ft) 81.3% 167 cm (5.5 ft) 53.0% 

Pensacola, FL 3.7 cm (0.12 ft) 24 cm (0.8 ft) 15.4% 82 cm (2.7 ft) 4.5% 

Table 4.3 Relative sea level rise impacts on Gulf Coast 

transportation modes: percentage of facilities vulnerable. 

Relative Sea 

Level Rise 

Interstate 

Highways Ports (Freight) Rail Lines Airports 

61 cm (2 ft) 19% 64% 5% 1 airport 

122 cm (4 ft) 24% 72% 9% 3 airports 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-2 

Table 4.4 Storm surge impacts on Gulf Coast transportation modes: 

percentage of facilities vulnerable. 

Storm Surge 

Height 

Interstate 

Highways 

Ports 

(Freight and Nonfreight) Rail Lines Airports 

5.5 m (18 ft) 56% 98% 33% 22 airports 

7.0 m (23 ft) 64% 99% 41% 29 airports 

Table 4.5 Relative sea level rise impacts on highways: percentage of 

facilities vulnerable. 

Relative Sea Level Rise Arterials Interstates Intermodal Connectors 

61 cm (2 ft) 20% 19% 23% 

122 cm (4 ft) 28% 24% 43% 

Table 4.6 Storm surge impacts on highways: percentage of 

facilities vulnerable. 

Storm Surge Height Arterials Interstates Intermodal Connectors 

5.5 m (18 ft) 51% 56% 73% 

7.0 m (23 ft) 57% 64% 73% 

Table 4.7 Relative sea level rise impacts on rail: percentage of 

facilities vulnerable. 

Relative Sea Level Rise 

Rail Lines 

(track miles) 

Rail Freight 

Facilities (94) 

Rail Passenger 

Stations (21) 

61 cm (2 ft) 5% 12% 0 

122 cm (4 ft) 9% 20% 0 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-3

Table 4.8 Railroad-owned and -served freight facilities in the Gulf Coast 

study region at elevation of 122 cm (4 ft) or less. 

Name Modal Access City State 

Elevation 

cm (ft) 

KCS Rail and truck Metairie LA < 0 

Larsen Intermodal, Inc. Rail and truck Metairie LA < 0 

New Orleans Cold Storage and Warehouse, Ltd. Rail and truck Metairie LA < 0 

Port of Gulfport Truck, port, rail Gulfport MS < 0 

Port of Galveston Truck, port, rail Galveston TX < 0 

NS – New Orleans, Louisiana Rail and truck New Orleans LA 0-30 (0-1) 

UP Intermodal Facility Rail and truck Avondale LA 0-30 (0-1) 

Port of Freeport Truck, port, rail Freeport TX 0-30 (0-1) 

Dry Storage Corporation of Louisiana Rail and truck Kenner LA 30-61 (1-2) 

DSC Logistics Rail and truck Kenner LA 30-61 (1-2) 

Yellow Terminal Rail and truck New Orleans LA 30-61 (1-2) 

BNSF – New Orleans, Louisiana Rail and truck Westwego LA 61-91 (2-3) 

BNSF 539 Bridge Rail and truck Westwego LA 61-91 (2-3) 

BNSF Intermodal Facility Rail and truck New Orleans LA 61-91 (2-3) 

Intermodal Cartage Company Truck, port, rail New Orleans LA 61-91 (2-3) 

Transflo Rail and truck New Orleans LA 61-91 (2-3) 

BNSF 101 Avonda Rail and truck Avondale LA 91-122 (3-4) 

Downtown Transfer, Inc. Rail and truck Avondale LA 91-122 (3-4) 

Port of New Orleans Truck, port, rail New Orleans LA 91-122 (3-4) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-4 

Table 4.9 Vulnerability from sea level rise and storm surge by rail distance 

and number of facilities. 

 Cumulative 

Elevation Risk 

Gridcode 

Ground Elevation 

m (Ft) 

Length of Railway 

Segments Vulnerable 

km (mi) 

Freight Facilities 

Vulnerable 

Passenger Facilities 

Vulnerable 

0 and 1 <0.3 (<1) 26 (86) 8 0 

2 0.3-0.6 (1-2) 45 (146) 11 0 

3 0.6-0.9 (2-3) 58 (191) 16 0 

4 0.9-1.2 (3-4) 81 (267) 19 0 

5 1.2-1.5 (4-5) 126 (412) 22 0 

6 1.5-5.5 (5-18) 294 (966) 40 9 

7 5.5-7.0 (18-23) 363 (1,190) 51 12 

8 >7.0 (>23) 894 (2,934) 94 21 

Table 4.10 Storm surge impacts on rail: percentage of facilities vulnerable. 

Storm Surge Height 

Rail Lines 

(Track Miles) 

Rail Freight 

Facilities (total of 94) 

Rail Passenger 

Stations (total of 21) 

5.5 m (18 ft) 33% 43% 43% 

7.0 m (23 ft) 41% 54% 57% 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-5

Table 4.11 Amtrak stations projected to be impacted by storm surge of 

5.5 and 7.0 m (18 and 23 ft). 

Station State Amtrak Services 

5.5-m (18-ft) Storm Surge 

Mobile AL Sunset Limited1

Pascagoula MS Sunset Limited1

Lake Charles LA Sunset Limited 

New Orleans LA City of New Orleans, Crescent, Sunset Limited 

Schriever LA Sunset Limited 

Slidell LA Crescent 

Beaumont TX Sunset Limited 

Galveston TX Service by bus 

La Marque TX Service by bus 

7.0-m (23-ft) Storm Surge 

New Iberia LA Sunset Limited 

Bay St. Louis MS Sunset Limited1

Biloxi MS Sunset Limited1

1 Stations are currently inactive due to Hurricane Katrina. 

Table 4.12 Relative sea level rise impacts on ports: percentage of 

facilities vulnerable. 

Ports 

Relative Sea Level Rise Freight Nonfreight 

61 cm (2 ft) 64% 68% 

122 cm (4 ft) 72% 73% 

Table 4.13 Storm surge impacts on ports: percentage of facilities vulnerable. 

Storm Surge Height 

Ports 

(Freight and Nonfreight) 

5.5 m (18 ft) 98% 

7.0 m (23 ft) 99% 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-6 

Table 4.14 FAA recommended runway lengths for hypothetical general 

aviation airport. (Source: U.S. DOT Federal Aviation 

Administration, Airport Design Version 4.2D) 

Airport Data 

Airport Elevation 30 

Maximum Difference in Runway Centerline Elevation (feet) 1 

Temperature (°F) 91.5 

Runway Condition Wet 

Small Airplanes 

Small Airplanes with Approach Speeds of Less than 30 Knots 330 

Small Airplanes with Approach Speeds of Less than 50 Knots 870 

Small Airplanes with Less than 10 Passenger Seats 

75 Percent of these Small Airplanes 2,530 

95 Percent of these Small Airplanes 3,100 

100 Percent of these Small Airplanes 3,660 

Small Airplanes with 10 or More Passenger Seats 4,290 

Large Airplanes 

Large Airplanes of 60,000 Pounds1 or Less 

75 Percent of these Large Airplanes at 60 Percent Useful Load 5,370 

75 Percent of these Large Airplanes at 90 Percent Useful Load 7,000 

100 Percent of these Large Airplanes at 60 Percent Useful Load 5,500 

100 Percent of these Large Airplanes at 90 Percent Useful Load 8,520 

1

 Maximum takeoff weight. 

.
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 4: What are the Implications of Climate Change and Variability for Gulf C

Table 4.15 Summary of impacts of temperature change to runway length (general aviation) unde

scenarios (SRES scenarios A2, B1, and A1B). (Source: U.S. DOT Federal Aviation A

(FAA) Airport Design Version 4.2D) 

50th Percentile 

2050 Climate Scenarios 210

Analysis Category Base Year A2 B1 A1B A2 Possible Mean Maximum Temperature of Hottest Month, °C (°F) 33.0 (91.4) 

35.2 

(95.5) 

34.8 

(94.6) 

35.5 

(95.9) 

37.7 

(99.9) 

Runway Length Analysis by Aircraft Type 

Runway Length 

m (Ft) Runway Length Percent I

Small Airplanes with Less than 10 Passenger Seats 

 75 Percent of these Small Airplanes 771 (2,530) 1.6% 1.2% 1.6% 3.2%  95 Percent of these Small Airplanes 945 (3,100) 1.3% 1.0% 1.6% 2.9%  100 Percent of these Small Airplanes 1,116 (3,660) 1.6% 1.1% 1.6% 3.3% 

Small Airplanes with 10 or More Passenger Seats 1,308 (4,290) 1.6% 1.2% 1.9% 3.3% Large Airplanes of 60,000 Pounds or Less 

 75 Percent of these Large Airplanes at 60 Percent Useful Load 1,637 (5,370) 0.9% 0.7% 1.1% 2.4% 

 75 Percent of these Large Airplanes at 90 Percent Useful Load 2,134 (7,000) 2.1% 0.9% 2.7% 7.9% 

 100 Percent of these Large Airplanes at 60 Percent Useful Load 1,676 (5,500) 2.5% 1.6% 3.3% 8.0% 

 100 Percent of these Large Airplanes at 90 Percent Useful Load 2,597 (8,520) 6.8% 4.9% 7.9% 16.3% 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 4T-8 

Table 4.16 Commercial aircraft runway length takeoff requirements. 

Commercial Service Airport Primary Runway Length

EFD IAH HOU BPT MSY LFT BTR LCH 

Aircraft Group 

Aircraft 

Type1

Required 

Runway Length2 2,744 3,658 2,317 2,057 3,080 2,332 2,135 1,981 

A. Measured in Meters 

747-400 3,170 -426 488 -853 -1,113 -90 -838 -1,035 -1,189 

MD 11 3,597 -853 61 -1,280 -1,539 -517 -1,265 -1,462 -1,615 

Wide-Body 

777-200LR 3,505 -762 153 -1,188 -1,448 -426 -1,173 -1,370 -1,524 

737-900 2,652 92 1,006 -335 -594 428 -320 -517 -671 

DC-9-15 2,499 244 1,159 -182 -442 580 -167 -365 -518 

737-800 2,225 518 1,433 92 -168 855 107 -90 -244 

MD-80 2,195 549 1,463 123 -137 885 137 -60 -213 

737-300 2,012 732 1,646 305 46 1,068 320 123 -30 A300-600 1,981 762 1,677 336 76 1,098 351 154 0 737-500 1,920 823 1,738 397 137 1,159 412 215 61 A319 1,859 884 1,799 458 198 1,220 473 276 122 757-200 1,829 915 1,829 488 229 1,251 503 306 152 

Medium-Haul3

Narrow Body 

737-600 1,768 976 1,890 549 290 1,312 564 367 213 

Regional Jets and ERJ 145 1,951 793 1,707 366 107 1,129 381 184 30 Turboprops ERJ 135 1,951 793 1,707 366 107 1,129 381 184 30 

CRJ 1,829 915 1,829 488 229 1,251 503 306 152 

DASH8-300 1,554 1,189 2,103 763 503 1,525 778 580 427 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructu

Chapter 4: What are the Implications of Climate Change and Variability for Gulf C

Table 4.16 Commercial aircraft runway length takeoff requirements. (continued) 

Commercial Service Airport Primary Runway Lengths 

EFD IAH HOU BPT MSY LFT BTR LCH 

Aircraft Group 

Aircraft 

Type1

Required 

Runway Length2 9,001 12,001 7,602 6,750 10,104 7,651 7,004 6,500 

B. Measured in Feet 

747-400 10,400 -1,399 1,601 -2,798 -3,650 -296 -2,749 -3,396 -3,900 MD 11 11,800 -2,799 201 -4,198 -5,050 -1,696 -4,149 -4,796 -5,300 

Wide-Body 

777-200LR 11,500 -2,499 501 -3,898 -4,750 -1,396 -3,849 -4,496 -5,000 

737-900 8,700 302 3,301 -1,098 -1,950 1,404 -1,049 -1,696 -2,200 

DC-9-15 8,200 801 3,801 -598 -1,450 1,904 -549 -1,196 -1,700 

737-800 7,300 1,701 4,701 302 -550 2,804 351 -296 -800 MD-80 7,200 1,801 4,801 402 -450 2,904 451 -196 -700 737-300 6,600 2,401 5,401 1,002 150 3,504 1,051 404 -100 

A300-600 6,500 2,501 5,501 1,102 250 3,604 1,151 504 0 737-500 6,300 2,701 5,701 1,302 450 3,804 1,351 704 200 

A319 6,100 2,901 5,901 1,502 650 4,004 1,551 904 400 

757-200 6,000 3,001 6,001 1,602 750 4,104 1,651 1,004 500 

Medium-Haul3

Narrow Body 

737-600 5,800 3,201 6,201 1,802 950 4,304 1,851 1,204 700 

Regional Jets and ERJ 145 6,400 2,601 5,601 1,202 350 3,704 1,251 604 100 Turboprops ERJ 135 6,400 2,601 5,601 1,202 350 3,704 1,251 604 100 

 CRJ 6,000 3,001 6,001 1,602 750 4,104 1,651 1,004 500 

DASH8-300 5,100 3,901 6,901 2,502 1,650 5,004 2,551 1,904 1,400 

1 MD 11 aircraft runway length based on standard day +18°C (33°F). All other aircraft based on standard day +15°C (27°F). 2 Assumes all elevations at sea level. 3 Medium-Haul are aircraft weights for 800 miles of fuel on-board. 

EFD Houston Ellington Field MSY New Orleans International MOB Mobile Regio

IAH Houston Intercontinental LFT Lafayette Regional GPT Gulfport BiloHOU Houston Hobby BTR Baton Rouge Metropolitan HBG Hattiesburg RBPT Beaumont/Port Arthur Regional LCH Lake Charles Regional
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-10

Table 4.17 Airports located on 100-year flood plains. (Sources: Wilbur Smith 

Associates; USGS) 

Associated City State Airport Name 

Gonzales LA Louisiana Regional 

Sulphur LA Southland Field 

Galliano LA South Lafourche 

New Orleans LA Lakefront 

Reserve LA St. John The Baptist Parish 

Thibodaux LA Thibodaux Municipal 

Winnie/Stowell TX Chambers County-Winnie Stowell 

Galveston TX Scholes International at Galveston 

Table 4.18 Gulf Coast study area airports vulnerable to submersion by 

relative sea level rise of 61 to 122 cm (2 to 4 ft). 

State Associated City Airport Name 

Airport 

Type 

Elevation

in Feet 

Louisiana Galliano South LaFourche GA 1 

Louisiana New Orleans New Orleans NAS JRB MIL 3 

Louisiana New Orleans Louis Armstrong-New Orleans International CS 4 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Tables 

4T-11

Table 4.19 Gulf Coast study area airports vulnerable to storm surge. 

(Sources: U.S. DOT FAA Records, April 2006; FEMA Storm 

Inundation Data) 

State Associated City Airport Name Airport Type 

Elevation 

m (ft) 

Airports 0 to 5.5 m (18 ft) Elevation 

Alabama Gulf Shores Jack Edwards General Aviation 4.9 (16)

Alabama Mobile Dauphin Island Airport General Aviation 1.5 (5)

Louisiana Abbeville Abbeville Chris Crusta Memorial General Aviation 4.6 (15)

Louisiana Crowley Le Gros Memorial General Aviation 5.2 (17)

Louisiana Galliano South LaFourche General Aviation 0.3 (1)

Louisiana Gonzales Louisiana Regional General Aviation 4.6 (15)

Louisiana Houma Houma-Terrebonne General Aviation 3.0 (10)

Louisiana Jeanerette Le Maire Memorial General Aviation 4.3 (14)

Louisiana Lake Charles Lake Charles Regional Commercial Services 4.6 (15)

Louisiana Lake Charles Chennault International Industrial 5.2 (17)

Louisiana New Orleans New Orleans NAS JRB Military 0.9 (3)

Louisiana New Orleans Louis Armstrong-New Orleans International Commercial Services 1.2 (4)

Louisiana New Orleans Lakefront General Aviation 2.4 (8)

Louisiana Patterson Harry P. Williams Memorial General Aviation 2.7 (9)

Louisiana Reserve St. John The Baptist Parish General Aviation 2.1 (7)

Louisiana Sulphur Southland Field General Aviation 3.4 (11)

Louisiana Thibodaux Thibodaux Municipal General Aviation 2.7 (9)

Louisiana Welsh Welsh General Aviation 5.5 (18)

Mississippi Pascagoula Trent Lott International General Aviation 5.2 (17)

Texas Beaumont/Port Arthur Southeast Texas Regional General Aviation 4.6 (15)

Texas Galveston Scholes International at Galveston General Aviation 1.8 (6)

Texas Orange Orange County General Aviation 4.0 (13)

Airports 5.6 – 7.0 m (19 to 23 ft) Elevation 

Alabama Mobile Mobile Downtown Industrial 5.8 (19)

Louisiana Iberia Acadiana Regional Industrial 6.1 (20)

Louisiana Jefferson Davis Jennings General Aviation 6.1 (20)

Mississippi Hancock Stennis International Industrial 7.0 (23)

Mississippi Harrison Keesler AFB Military 6.1 (20)

Texas Brazoria Brazoria County General Aviation 6.7 (22)

Texas Chambers Chambers County-Winnie Stowell General Aviation 6.4 (21)
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: Impacts on Climate Variability and Change of Transportation in the Gulf Coast: Tables 

4T-12 

Table 4.20 Hurricane impacts on toll revenue in Florida. (Source: Ely, 2005) 

Hurricane Season 2004 

Millions 

Entity Estimated Revenue Loss Estimated Damage Costs Estimated Total Loss 

Turnpike System $32.21 $8.50 $40.71 

FDOT-Owned (5) 2.48 1.33 3.81 

Garcon Point 0.27 0.22 0.49 

Mid-Bay 0.52 0.25 0.77 

MDX 1.03 0.00 1.03 

Bob Sikes 0.30 1.76 2.06 

THCEA 1.44 0.00 1.44 

OOCEA 9.07 1.50 10.57 

Lee County 0.70 0.87 1.57 

Miami-Dade County 0.11 0.00 0.11 

Monroe (Card Sound) 0.04 0.00 0.04 

Total $48.17 $14.43 $62.60 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.1 Highways at risk from a relative sea level rise of 61 cm (2 ft). 

(Source: Cambridge Systematics analysis of U.S. DOT data) 

4F-1
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.2 Highways at risk from a relative sea level rise of 122 cm (4 ft). 

(Source: Cambridge Systematics analysis of U.S. DOT data) 

4F-2 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

4F-3

Figure 4.3 National Highway System (NHS) intermodal connectors at risk 

from a relative sea level rise of 122 cm (4 ft). (Source: Cambridg

Systematics

e 

 analysis of U.S. DOT data) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.4 Hurricane Katrina damage to U.S. Highway 90 at Bay St. Louis, 

MS. (Source: NASA Remote Sensing Tutorial) 

4F-4 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.5 Highways at risk from storm surge at elevations currently below 

5.5 m (18 ft). (Source: Cambridge Systematics analysis of U.S. 

DOT data) 

4F-5
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.6 Highways currently at risk from storm surge at elevations 

currently below 7.0 m (23 ft). (Source: Cambridge Systematics 

analysis of U.S. DOT data) 

4F-6 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.7 National Highway System (NHS) intermodal connectors at risk 

from storm surge at elevations currently below 7.0 m (23 ft). 

(Source: Cambridge Systematics analysis of U.S. DOT data) 

4F-7
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.8 Fixed bus routes at risk from a relative sea level rise of 122 cm (4 

ft), New Orleans, LA. (Source: Cambridge Systematics analysis of 

U.S. DOT data) 

4F-8 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.9 Fixed transit guideways at risk from a relative sea level rise of 122 

cm (4 ft), Houston and Galveston, TX. (Source: Cambridge 

Systematics analysis of U.S. DOT data) 

4F-9
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.10 Fixed transit guideways at risk from storm surge at elevations 

currently below 5.5 m (18 ft), New Orleans, LA. (Source: 

Cambridge Systematics analysis of U.S. DOT data) 

4F-10 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.11 Fixed transit guideways at risk from storm surge at elevations 

currently below 5.5 m (18 ft), Houston and Galveston, TX. 

(Source: Cambridge Systematics analysis of U.S. DOT data) 

4F-11
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.12 Fixed bus routes at risk from storm surge at elevations currently 

below 5.5 m (18 ft), New Orleans, LA. (Source: Cambridge 

Systematics analysis of U.S. DOT data) 

4F-12 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.13 Fixed bus routes at risk from storm surge at elevations 

currently below 5.5 m (18 ft), Houston and Galveston, TX. 

(Source: Cambridge Systematics analysis of U.S. DOT data) 

4F-13
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.14 Rail lines at risk due to relative sea level rise of 61 and 122 cm (2 

and 4 ft). Of the 4,722 km (2,934 mi) of rail lines in the region, 

235 km (146 mi), or 5 percent, are at risk from a relative sea level 

rise of 61 cm (2 ft) or less. An additional 195 km (121 mi), for a 

total of nine percent, are at risk from an increase of 61 to 122 cm 

(2 to 4 ft). (Source: Cambridge Systematics analysis of U.S. DOT 

data) 

4F-14 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.15 Railroad-owned and -served freight facilities at risk due to 

relative sea level rise of 61 and 122 cm (2 and 4 ft). 

Of the 94 facilities in the region, 11 are at risk from a 61-cm (2-ft) 

increase in relative sea level, and an additional 8 facilities are at 

risk from a 122-cm (4-ft) increase. (Source: Cambridge 

Systematics analysis of U.S. DOT data) 

4F-15
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.16 Rail lines at risk due to storm surge of 5.5 and 7.0 m 

(18 and 23 ft). Of the 4,722 km (2,934 mi) of rail lines in the 

region, 1,555 km (966 mi) are potentially at risk from a storm 

surge of 5.5 m (18 ft), and an additional 360 km (224 mi) are 

potentially at risk from a storm surge of 7.0 m (23 ft). (Source: 

Cambridge Systematics analysis of U.S. DOT data) 

4F-16 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.17 Railroad-owned and -served freight facilities at risk due to storm 

surge of 5.5 and 7.0 m (18 and 23 ft). Of the 94 facilities in the 

region, 40 are at risk from a storm surge of 5.5 m (18 ft) or less, 

and an additional 11 facilities are at risk from storm surge of 5.5 

to 7.0 m (18 to 23 ft). (Source: Cambridge Systematics analysis of 

U.S. DOT data) 

4F-17
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.18 Amtrak facilities at risk due to storm surge of 5.5 and 

7.0 m (18 and 23 ft). Of the 21 Amtrak facilities 

in the region, 9 are at risk from a storm surge of 7.0 m (18 ft) 

or less, and an additional 3 facilities are at 

risk from storm surge of 5.5 to 7.0 m (18 to 23 ft). (Source: 

Cambridge Systematics analysis of U.S. DOT data) 

4F-18 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.19 Freight handling port facilities at risk from relative sea level rise 

of 61 and 122 cm (2 and 4 ft). (Source: Cambridge Systematics 

analysis of U.S. Army Corps of Engineers data) 

4F-19
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.20 Freight handling port facilities at risk from storm surge of 5.5 and 

7.0 m (18 and 23 ft). (Source: Cambridge Systematics analysis of 

U.S. Army Corps of Engineers data) 

4F-20 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.21 Boeing 757-200 takeoff runway requirements for design purposes. 

(Source: The Boeing Company, 2002) 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.22 Gulf Coast study area airports at risk from storm surge. (Source: 

Cambridge Systematics analysis of U.S. DOT and USGS data) 

4F-22 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.23 Landside pipelines having at least one GIS link located in an area 

of elevation 0 to 91 cm (3 ft) above sea level in the study area. 

(Source: Texas Transportation Institute) 

4F-23
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.24 Evacuation route highways potentially vulnerable from storm 

surge of 5.5 m (18 ft). (Source: Cambridge Systematics analysis of 

U.S. DOT data) 

4F-24 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.25 Risks to Amtrak facilities due to relative sea level rise and 

storm surge. (Source: Cambridge Systematics analysis of U.S. 

DOT data) 

4F-25
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

Figure 4.26 Population over age 65 impacted by Hurricane Katrina. 

(Source: U.S. Census Bureau) 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 4: What are the Implications of Climate Change and Variability for Gulf Coast Transportation?: Figures 

4F-27

Figure 4.27 Airports affected by Hurricane Katrina winds. (Source: USGS) 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

5.0 How Can Transportation 

Professionals Incorporate 

Climate Change in 

Transportation Decisions? 

Lead Authors: Kenneth J. Leonard, John H. Suhrbier, Eric Lindquist 

Contributing Authors: Michael J. Savonis, Joanne R. Potter, Wesley R. Dean 

As the previous chapters have demonstrated, there is benefit to including long-term climate 

considerations in the development of transportation systems. In fact, climate factors are 

likely to affect decisions in every phase of the transportation management process: from 

long-range planning and investment; through project design and construction; to 

management and operations of the infrastructure; and system evaluation (figure 5.1). This 

chapter will explore how such concerns might be addressed in the continuing process of 

development and renewal of transportation infrastructure. To better understand this, an 

overview of the planning process as generally implemented today is provided, as well as 

specific consideration of transportation planning within the Gulf States. 

To rigorously address climate concerns, new approaches may be necessary. Since climate 

impacts occur into the future, and there is uncertainty as to the full magnitude and the 

timing of the impacts, deterministic methods as currently employed are ill suited to provide 

the type of information that current decision makers need. Instead it may be more fruitful 

to consider these impacts through a risk management approach to more effectively give 

transportation executives, elected officials, and the general public a more complete picture 

of the risks and potential solutions to climate impacts. The last section of this chapter 

begins the process of developing an alternate approach to planning with a conceptual 

framework for introducing more probabilistic approaches. Once fully operational, this type 

of methodology could lead to better information to address the changing climate. 

[INSERT FIGURE 5.1 How will climate change affect transportation decisions?] 

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Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

 5.1 Considering Climate Change in Long-Range Planning 

and Investment 

5.1.1 Overview of the Surface Transportation Planning 

and Investment Processes 

This section discusses how transportation planning and investment decisions are made in 

State and local governments and to some extent in private agencies. It reviews in particular 

the planning and decision making processes used by State departments of transportation 

(DOT) and metropolitan planning organizations (MPO). Specifically, it discusses the longrange planning taking place in the Gulf Coast study region and provides the results of a 

number of State DOT and MPO interviews. Finally, it discusses the challenge of how the 

planning process might be adapted to consider the potential impacts of climate change. 

The Federal Surface Transportation Planning Process 

Transportation planning processes vary with the type of agency (public or private), level of 

government (Federal, State, or local), mode of transportation, and other factors. This 

chapter will not attempt to provide an overview of all of them, but since the Federal 

government has specific requirements codified in law to cover the surface transportation 

planning process (for highways and transit investments), this chapter provides an 

illustrative example by using the Federal process. 

Surface transportation planning and investment decision making, employed to make use of 

Federal transportation funding, is conducted within the framework and requirements 

defined by the planning provisions contained in Titles 23 and 49 of the United States Code 

(USC), most recently amended in August 2005 by the Safe, Accountable, Flexible, Efficient 

Transportation Equity Act: A Legacy for Users (SAFETEA-LU). 

State DOTs and MPOs have lead transportation planning responsibilities, working in 

coordination with local governments. States and local governments may implement 

transportation infrastructure without Federal funding. These projects may be included 

within the framework of the Federal transportation process but could be implemented 

outside that framework. 

Within the Federal process for highways and transit, State DOTs and MPOs must comply 

with the planning requirements to be eligible and to receive Federal transportation funds. 

The state DOTs within the study area are the Alabama Department of Transportation, 

Louisiana Department of Transportation and Development (DOTD), Mississippi 

Department of Transportation, and Texas Department of Transportation. Ten MPOs exist 

within the study area, as identified in table 5.1. Each MPO consists of one or more 

urbanized areas exceeding 50,000 in population, with an urban area exceeding 200,000 in 

population also defined as a Transportation Management Area (TMA). 

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5-3

[Insert Table 5.1 Urbanized area Metropolitan Planning Organizations (MPO) in the Gulf Coast 

study area] 

The MPO’s planning activities are identified in the Unified Plan Work Program which 

covers a 2-year period for the purpose of maintaining short- and long-term transportation 

plans. It is within this program that MPO staff collect data on traffic and pedestrian counts, 

building permits, planned developments, and accident rates, etc.; analyze trends; and 

evaluate potential projects. Two principal products result from the transportation planning 

process: a long-range transportation plan and a transportation improvement program. 

These two products, then, provide the basis for more detailed project development – 

engineering, design, and construction.

Separate but coordinated long-range transportation plans are cooperatively developed on a 

statewide basis by a State DOT and for each urbanized area by an MPO. The long-range 

transportation plan is developed with a minimum of a 20-year forecast period, with many 

areas using a 30-year time horizon. The intent of a plan is to provide a long-range vision of 

the future of the surface transportation system, considering all passenger and freight modes 

and their interrelationships. As defined by SAFETEA-LU (23 USC 134 and 135), longrange plans, “shall provide for the development and integrated management and operation 

of transportation systems and facilities that will function as an intermodal transportation 

system.” The transportation planning process for TMAs is essentially identical to that in 

urbanized areas having a population between 50,000 and 200,000 except that a congestion 

management process (CMP) also is required. 

The transportation improvement program (TIP) is a separate document for the immediate 

future. It must be consistent with the long-range plan and provides the list of short-term (3 

years) priorities for construction. A TIP must be developed for each metropolitan area, and 

a Statewide Transportation Improvement Program (STIP) must be developed for the State 

that is consistent with the TIPs. The STIP must be approved by U.S. DOT. 

Environmental considerations have long played a role in the planning and development of 

transportation projects. Changes over time, though, have occurred in the manner in which 

environmental analyses have been conducted and the underlying legal framework in which 

these analyses are conducted. SAFETEA-LU, in section 6001, defines the following eight 

planning factors that should guide a transportation planning process and the development 

of projects, strategies, and services (figure 5.2):1

1. “Support the economic vitality of the United States, the States, nonmetropolitan areas, 

and metropolitan areas, especially by enabling global competitiveness, productivity, 

and efficiency; 

2. Increase the safety of the transportation system for motorized and nonmotorized users; 

 

1

 This list represents a refinement of a similar list contained in previous intermodal surface transportation 

legislation. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

3. Increase the security of the transportation system for motorized and nonmotorized 

users; 

4. Increase the accessibility and mobility of people and freight; 

5. Protect and enhance the environment, promote energy conservation, improve the 

quality of life, and promote consistency between transportation improvements and 

plans for state and local planned growth and economic development patterns; 

6. Enhance the integration and connectivity of the transportation system across and 

between modes throughout the State, for people and freight; 

7. Promote efficient system management and operation; and 

8. Emphasize the preservation of the existing transportation system.” 

[INSERT Figure 5.2 SAFETEA-LU Planning Factors] 

The SAFETEA-LU legislation requires that long-range transportation plans be developed 

in consultation with agencies responsible for land use management, natural resources, 

environmental protection, conservation, and historic preservation. Further, this 

consultation is to consider, where available, conservation plans or maps and inventories of 

natural or historic resources. This is typically a time- and labor-intensive effort requiring 

years to complete, with extensive public involvement that was made far more difficult by 

the 2005 hurricanes. The Gulfport MPO reports that in addition to the several years the 

overall effort took prior to 2005, the agency needed another year to reconsider the land use 

and demographic changes taking place as well as the Plan’s regional goals to make them 

consistent with the Governor’s Recovery Plan. 

An interesting question is the manner in which the impacts of climate change can be 

addressed in the list of eight planning factors and the associated consultative process. As 

will be discussed later in this section, while climate change is not now named as part of any 

of the eight factors, a number of them reflect considerations that are directly related to 

climate change. In addition to protecting, enhancing, and mitigating impacts on the 

environment, these include system preservation, system management and operation, safety, 

and economic vitality (see especially factors 1, 2, 6, and 8). 

Transportation plans, programs, and projects historically have been developed to meet the 

needs of future, projected, or planned land use, including population and employment 

patterns. In recent years, though, transportation and land use are being addressed in a much 

more interactive or coordinated manner. Rather than land use being viewed as driving 

transportation decisions, transportation investment and management decisions are 

increasingly being made collaboratively and in concert with growth management and 

economic development decisions. In this view, the manner in which transportation 

infrastructure is developed and managed is seen as one tool for helping to achieve desirable 

growth objectives. 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

The overall transportation planning and investment process is illustrated in figure 5.3 with 

an emphasis that is helpful in identifying where in this transportation planning process 

considerations related to climate change impacts potentially could be introduced. Using 

terminology that is consistent with current planning and strategic management approaches, 

separate steps are identified for establishing a long-range vision and for establishing goals, 

objectives, and performance measures. Developing an understanding of the problem is 

seen as occurring on a continuing and iterative basis throughout the planning process, 

including the analysis of data and evaluating tradeoffs and establishing priorities among 

candidate policies and projects. The process culminates with development of a long-range 

transportation plan, a short-range transportation improvement program, and project 

development and implementation. 

In terms of introducing climate-related changes into the long-range transportation planning 

and investment process, the potential exists at each step illustrated in figure 5.3. As shown, 

long-range environmental quality, economic development, mobility, and other desired 

conditions such as safety commonly are defined as part of a vision and accompanying 

mission statement and then translated into goals, objectives, and performance indicators. 

Thus, protection from climate change impacts could be introduced at these stages as well. 

Given these defined goals and objectives, strategies then are developed that are specifically 

designed to meet the agreed upon goals and objectives and are evaluated using the 

appropriate performance measures. Again, strategies could be developed that address 

climate change and variability. Similarly, climate change protection and mitigation 

strategies could be evaluated with respect to their potential impact on the transportation 

system. 

[INSERT Figure 5.3 Steps in the transportation planning process] 

Coordination in Transportation Planning 

The Federal transportation planning and investment process is highly collaborative in 

which transportation agencies work in partnership with natural resource agencies, 

communities, businesses, and others throughout the period of planning, programming, 

developing, implementing, and operating transportation projects. Transportation agencies 

are charged with helping to accomplish multiple transportation; economic development; 

environmental, community, safety, and security objectives. Going beyond the Federally 

mandated process, the continued development and operation of the multimodal network 

requires extensive coordination. 

Although planning and programming of the highway system, and its coordination with 

other modes of travel, are major responsibilities of the State DOT and the MPO, the actual 

development and operation of the transportation system is the responsibility of various 

levels of government and private agencies. States typically own and operate a relatively 

small portion of the road network but that portion (the Interstate System and arterial 

highways) usually accommodates the majority of the road travel. In some cases, States 

also own and operate local and state transit systems and freight rail lines. However, the 

majority of highway miles and transit systems are local responsibilities, and most of the 

Nation’s freight system and air passenger system is owned by the private sector. 

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Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

5-6 

Meeting the requirements of the Federal planning process is necessary as a condition of 

receiving Federal financial assistance. However, for States and MPOs the number of 

different organizations who have independent roles makes it important to have a 

collaborative decision making process, one that is based on valid and convincing 

information. At the MPO level, decisions are a collaboration of the individual local 

governments that comprise the MPO and serve on the policy board that is usually 

supported by the advice and analysis of a technical coordinating committee. 

At the State level, the ultimate decisions are typically made by the Governor and the State 

legislature2, with recommendations and advice coming from the State DOT. Decisions 

within the State DOT also occur at many levels and units within the organization. State 

DOT decisions encompass all aspects of the roadways under State jurisdiction: planning, 

engineering, operations, design, and construction. 

Most of the freight and part of the aviation and passenger systems are owned by the private 

sector. State DOT and MPO plans that make recommendations for these systems must get 

the concurrence from the private sector for implementation. In the vast majority of the 

cases, the private sector invests in their current system or a new system if they feel it is cost 

effective to do so. The State and MPO may have some influence through the planning 

process or through the provision of financial assistance. For instance, a railroad will not 

likely move a rail line unless it improves their return on investment or because the 

government helps finance it. 

Since the freight network is largely owned by the private sector, the long-range 

transportation planning process for both States and metropolitan areas ensures that the 

private users and providers of transportation are represented and their comments 

considered. In fact, the Federal planning regulations discussed above require that in 

developing or updating long-range transportation plans, States and MPOs shall have a 

process to allow freight shippers and providers of freight transportation services a 

reasonable opportunity to review and comment on key decision points and the proposed 

transportation plan. Planning agencies normally include private shippers and transportation 

providers on their plan advisory committees to guarantee representation early and 

throughout the planning process. 

For these systems to be effective at efficiently moving people and goods – as well as 

meeting the higher needs of society in terms of economic development and environmental 

enhancement – a high degree of coordination is crucial. In terms of meeting the particular 

challenges that climate change poses, each entity, whether public agency or private firm, 

needs to consider how climate stressors might affect their businesses. Further, these 

agencies need to work together to consider how climate changes affect the efficient 

movement of people, goods and services as a whole to take full advantage of system 

redundancy and resilience, explained later in this chapter. 

 

2

 Some DOTs, such as Mississippi’s, do not report to the Governor. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

5.1.2 Current State of Practice in Incorporating Climate 

Change Considerations 

In this Gulf Coast Study, representation of the private freight industry was sought during 

the development of the modal technical papers. For example, railroads were involved in 

the review of the rail technical paper, and discussions were held with the Association of 

American Railroads about possible impacts to rail lines from climate change such as “sun 

kinks” and the importance of prestressed rail track. The CSX Railroad provided significant 

information on hurricane Katrina impacts and adaptation strategies through public 

comments and the sharing of information. The CSX Railroad reported that it cost about 

$250 million to repair damage from Katrina, and the damage caused them to further 

consider relocating the rail line. The CSX Railroad is exploring the feasibility of new 

construction within the existing corridor but further inland. Also, increased use of 

alternative Mississippi River crossings (Baton Rouge/Vicksburg) is under study. 

Interviews included a private toll road authority and port employees for two separate ports 

(Galveston and Houston) that were publicly owned but privately operated facilities. The 

toll road representative expressed concern about potential impacts of sea level rise since the 

toll facilities do approach the coastline, particularly in the Houston metropolitan area. The 

port representatives also were concerned about the impacts of possible sea level rise and 

the impacts of increased precipitation on sedimentation of port channels and port runoff 

that could cause local flooding. In the next phase of the Gulf Coast Study, the private 

sector involvement will be intensified to determine what specific climate change impacts 

are possible and in detailing likely adaptation strategies and costs. 

Two approaches were utilized to determine how state DOTs and MPOs currently are 

addressing issues of climate change and also how climate change might be addressed in the 

future. The approaches involved: 

1. Obtaining and reviewing current long-range transportation plans, transportation 

improvement programs, and other recent documents for the States and selected MPOs 

within the study area, addressing infrastructure development, operation, and 

management; and 

2. Interviewing State DOT and representative MPO officials responsible for transportation 

planning within the study area. 

Some MPOs within the study region currently are in the process of updating their vision 

statements and long-range transportation plans. In some of these cases, MPOs are actively 

considering issues related to the potential effects of climate change and variability, 

including the impacts of hurricanes such as Katrina and Rita. The two aspects of climate 

that are receiving the most attention in these more recent planning activities are: 

(1) evacuation planning and management and (2) preventing infrastructure damage 

resulting from storm surge-related flooding. 

Long-range transportation plans, statewide transportation improvement programs, and 

annual reports were obtained, where available, from the Internet for the States of Alabama, 

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Mississippi, Louisiana, and Texas. In addition, the corresponding documents were 

similarly obtained for the following urban areas: 

• Mobile, AL (South Alabama Regional Planning Commission); 

• Hattiesburg, MS (Hattiesburg-Petal-Forrest-Lamar Metropolitan Planning 

Organization); 

• Gulfport, MS (Gulf Regional Planning Commission); 

• Lake Charles, LA (Imperial Calcasieu Regional Planning and Development 

Commission); 

• Lafayette, LA (Lafayette City-Parish Consolidated Government Metropolitan Planning 

Organization); 

• New Orleans, LA (Regional Planning Commission for Jefferson, Orleans, Plaquemine, 

St. Bernard and St. Tammany parishes); and 

• Houston and Galveston, TX (Houston-Galveston Area Council). 

None of the existing State and MPO documents examined here, all of which date from 

2000 to 2006, directly addresses or acknowledges issues of climate change and variability. 

This is, in part, due to their age; most were developed 2 to 4 years ago, prior to the recent 

increase of interest in climate change and the associated increase in the availability of 

climate change-related information. Also, most of these documents were prepared prior to 

Hurricanes Katrina and Rita, so the many actions being taken by State DOTs and MPOs in 

response to these two storms have only recently been included in updated and published 

documents. 

The following observations result from a review of these planning documents, organized 

into the following three categories: plans including missions and goals, planning activities, 

and prioritization criteria. 

State and Metropolitan Planning Organization Plans and Planning Activities 

Most of the state and MPO plans in the region include a mission or goals that include 

statements about providing environmentally sound transportation systems or preserving the 

quality of the environment and enhancing the quality of life. There also are goals that 

include strategies to encourage land use planning and to incorporate public transportation, 

walking, and bicycles. Essentially, all of the plans recognize the environmental impacts 

(excluding climate change) and issues related to transportation growth and expansion. The 

Louisiana long-range transportation plan defines 57 “mega projects,” whose evaluation 

criteria for development and implementation include environment, demonstrating contextsensitive design and/or sound growth management principles, and emergency evacuation 

capabilities. Nine of the 22 Priority “A” mega projects involve I-10, including construction 

of a six-lane I-10 Twin Span across Lake Pontchartrain. Other Priority “A” mega projects 

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located in evacuation areas include upgrading I-49 south of Lafayette and construction of a 

new two-lane road between U.S. Highway 90 and Louisiana Highway 3127. The HoustonGalveston long-range transportation plan identifies eight distinct ecological zones within 

the region and pays particular attention to the wetlands, which protect shoreline areas from 

erosion and serve as buffers from flooding. 

As mentioned above, however, some of the planning activities and infrastructure 

reconstruction since Hurricanes Rita and Katrina are being done to address the impacts of 

climate change. In Mississippi, the flooding that resulted from Hurricane Katrina has 

resulted in new design standards for the bridges that are being rebuilt and is serving as a 

catalyst for considerable debate on the interrelationships between land use and 

transportation investment within the coastal areas of the State. 

The Regional Planning Commission for the New Orleans urbanized area and the 

Mandeville/Covington and Slidell urbanized areas is refining its metropolitan 

transportation plan (MTP) for the New Orleans region so that it can provide a framework 

within which the projected climate change effects can be assessed and addressed. The 

Houston-Galveston Area Council (H-GAC) is in the process of conducting a visioning 

exercise, the results of which will then guide the development of an updated regional 

transportation plan. Since this is occurring post-Hurricane Rita, climate change and the 

means of reducing the risk of flooding have been raised in the outreach sessions and 

working meetings. 

In addition to including policies to provide maintain and improve the area’s intermodal 

systems, the States and MPOs in the study area also are including consideration of future 

uncertainties and evacuation management. The Mississippi transportation plan and 

associated STIP both acknowledge uncertainty in future year conditions in areas such as 

growth, air quality, road maintenance, and congestion. The STIP contains a section on 

planning and research that describes planning as looking at what has to be done today to be 

ready for an uncertain tomorrow. While climate change and variability are not explicitly 

mentioned in either the current plan or the STIP, and the major effects of climate change 

may not occur within the plan’s current 30-year timeframe, the stage certainly is set to both 

recognize and respond to potential issues of climate change in future planning activities. 

Following Hurricane Rita, the Governor of Texas established a task force on evacuation, 

transportation, and logistics. The report of this task force was completed and submitted on 

February 14, 2006. Twenty recommendations are made, including the development of 

contraflow plans for major hurricane evacuation routes, including some in the study area, 

such as north out of the Houston-Galveston metropolitan area on I-45, U.S Highway 290, 

U.S. Highway 59; west out of Houston on I-10; and north out of Beaumont on U.S. 

Highway 69. Evacuation routes represent one element of the operations and system 

management portion of the long-range transportation plan for the Houston-Galveston 

metropolitan area, with extra points given to evacuation routes in the prioritization of 

projects. Short-term recommendations to improve evacuation capabilities were developed 

in 2006. Longer-term evacuation priorities also are being assessed, some of which may 

require significant public investment over a period of many years, according to the task 

force report. These may include new evacuation routes, reconstruction of existing 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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evacuation routes, and reduction in the number and severity of traffic bottlenecks. The 

location of new development in flood- and storm-prone areas also is arising as an issue. 

Site Interviews with Transportation Representatives in the Gulf Coast Region 

In addition to reviewing planning documents and interviewing DOT and MPO officials as 

described above, another set of interviews was conducted between December 15, 2006, and 

January 10, 2007, to understand in more specific terms the issues facing the area selected 

for more intense study in Phase II of this effort. These interviews included a representative 

of each of the transportation modes represented in the site study area. The objective of the 

study site interviews was to consider the potential climate impacts at the level of the 

individual decision maker/planner. This information was used to develop and refine the 

conceptual framework for assessing potential impacts on transportation presented below. 

There were three general lines of inquiry used to generate a localized picture of climate 

change impacts and transportation decision making: 

1. Interviewees’ Perspectives on Climate Change – Respondents were asked about their 

perception of climate change, its potential impact on the respondent’s specific facility 

or system, and whether or not the respondent currently was incorporating climate 

change and variability science or indicators in their decision making and planning. 

2. Decision and Planning Processes in which Respondents are Involved – Interviewees 

were asked to describe the types of decisions they are engaged in at the facility and/or 

system level in their area of responsibility. The interview guide solicited responses in 

regard to the factors that were the most relevant to making facility or system decisions; 

the role of the respondent in the local decision and planning process and interactions 

with the State and Federal processes; what information was used for informing these 

decisions; and what threshold or tipping point factors would facilitate changes in policy 

or planning, both from the climate perspective and in general. 

3. Utility of the General Project Report Findings – Respondents were asked their opinions 

regarding the applicability of the climate scenarios and various report concepts that 

might be used in their analysis. The respondents were presented with a two-page 

summary of study findings – including climate scenarios for the study area, and the 

assessment of exposure, vulnerability, and resilience – for their review and input. 

The interviews were designed and conducted according to standard social science research 

methodologies and practices. The questions were open ended in order to solicit a range of 

responses as broad as possible. 

The interview subjects were contacted and interviewed by using a questionnaire approved 

by the Texas A&M University Institutional Review Board. As such, they were informed 

that their expressed opinions and any information they provide would be kept confidential 

and that they were free to refuse to answer any questions that made them uncomfortable. 

Because of the size and public nature of the research area, only limited references are made 

to the positions of these individuals within the hierarchy of their system or institution. 

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Fourteen individuals were interviewed, four of whom provided general context information 

on climate change and variability and the Galveston County area, and 10 of whom were 

formal interview subjects. These included: 

• An employee of Transtar, the Houston Traffic Management Center; 

• An individual responsible for evacuation in the Galveston County area,; 

• A representative of a toll road authority; 

• Employees of the City of Houston Aviation Department; 

• A county engineer; 

• Employees of the Texas DOT; and 

• Employees of the Ports of Galveston and Houston. 

Significance of climate considerations – Although the respondents were comfortable with 

the idea that climate conditions would be changing in the Gulf Coast area, most respondents 

reported that climate was not an issue that they considered in development of the plans and 

TIPS. The perceptions of the respondents were that climate change is an issue that has been 

of limited concern to the State and Federal agencies that affect their decision making, yet 

responses varied. Representatives of at least one agency indicated a strong belief that climate 

change should be treated as an issue of importance in the transportation planning of the 

region. In contrast, others indicated that climate change is not an issue that has received any 

official treatment. Several interviewees felt that future consideration of climate change 

would be directed by guidelines established by the Federal government. 

None of the interview subjects indicated they were using climate change data in their 

transportation decision making. However, the entire sample of interview subjects was 

convinced that climate change is a matter of some concern. 

Value of climate information – Findings from the general project synthesis report were of 

some use to the interview subjects. At least one interview subject indicated s(he) had not 

been concerned with climate change until s(he) saw the predictions for sea level and storm 

surge in the Galveston County area. The value of the specific predictions varied from one 

respondent to the next. Many respondents found sea level rise and storm surge information 

to be useful; however, they would like the projections to be for time periods more 

applicable to their own decision making timeframes. At least one respondent suggested 

that the elevations for storm surge and sea level should be selected from a range more 

relevant to the Galveston County area. Much of Galveston County is at an elevation of 4.6 

m (15 ft); the 5.5-m (18-ft) threshold used in the storm surge map was not as relevant as 

this decision maker would like. 

Perceived importance of individual climate factors – The degree to which respondents 

considered various climate stressors to affect the transportation infrastructure modes for 

which they were responsible is characterized in table 5.2 with a scale of low, limited, 

moderate, high, and highest perceived concern. 

[Insert Table 5.2 Level of decision-maker concern about climate stressors] 

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The high degree of concern exhibited by all respondents about storm frequency and 

magnitude as a stressor betrays the strong affective power of recent hurricanes on the 

hazard perceptions of respondents in the Galveston and Harris County area. The majority 

of subjects expressed their concern for storm frequency and magnitude in regards to the 

capacity of their infrastructure mode of responsibility to fully function during a hurricane 

evacuation, or in the case of the port, to be evacuated. An exception was the flood control 

subject who shared this fear but was primarily concerned about the ability of the drainage 

system to cope with severe storms. 

Temperature was of limited importance to the respondents with the exception of the 

Transtar subject who described his equipment as tested and hardened against temperature 

extremes and the airport representative who described temperature as a key variable in 

airport performance measures. The other airport representative was not as concerned about 

temperature. We account for this variation as a function of their respective roles. The 

second representative is involved in construction and does not directly grapple with 

operations logistics. Operations logistics are heavily determined by temperature because 

increased temperature reduces lift and results in an increase of the airport facility’s average 

annual delay of departures. 

Average precipitation was of limited importance to many of the respondents in comparison 

to extreme precipitation events. Of special interest was the flood control engineer who 

indicated that increases or decreases in average precipitation have limited effect on 

flooding. His concern was principally with precipitation events that could be categorized 

as high in intensity, frequency, and duration. The one interview subject who was directly 

and seriously concerned with overall precipitation levels was the port engineer, who linked 

average levels of precipitation to the sedimentation of port channels. The second port 

engineer and manager were concerned with precipitation as well, especially with the 

consequences of port runoff for local flooding. 

Sea level was of high importance to many of the interview subjects. The factor that 

governed the strength of this concern was proximity to the coast, moderated by the relative 

imperviousness of the infrastructure in question. For example, the toll road authority 

representative expressed a potential concern about sea level because the toll facility does 

approach the coast; however, this facility was designed to be elevated well above the surge 

levels predicted in the climate and vulnerability summaries, as well as the levels to which 

this respondent was previously familiar. Other respondents had broader purviews of 

responsibility such as multiple highways, the evacuation of residents, and facilities near sea 

level. These respondents expressed high concern about sea level rise. The port 

representatives characterized their concerns about sea level rise differently. One port 

engineer was highly concerned about sea level rise, but this respondent noted that his 

concern was coupled with his concern about local subsidence. The second port interview 

subject could imagine sea level rise having an impact on the region; however, the 

infrastructure elements of concern – piers – were rebuilt often enough that only a 

catastrophic degree of sea level rise would have any impact. This respondent explicitly 

stated that such an event was highly unlikely. 

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The responses in regards to questions about decision making thresholds were fairly 

uniform. Interview subjects suggested that the impetus to make fairly radical policy shifts 

could only come from higher levels of government and usually in response to a disaster. 

Otherwise, they simply did not have the autonomy or the access to funding to adopt new 

policies or planning approaches. 

Since these interviews were conducted, however, there appears to have been a shift in some 

of the expressed opinions due to the impacts of Hurricanes Katrina and Rita, as evidenced 

by adaptation measures being undertaken. For example, as detailed in chapter 4.0, the 

rebuilding of certain facilities, like U.S. Highway 90 in Mississippi, have taken into 

account the likely impacts of future storms. Further, the activities and opinions expressed 

to the study authors by State and local authorities indicate a much greater appreciation for 

the potential impacts of climate change than those of the interviewees. 

The involvement of private users and providers of freight transportation in these interviews 

was limited. Employees at two public ports that use private facilities and a private toll road 

authority representative were interviewed; however, the private sector’s involvement in the 

next phase of the study will be substantially expanded to capture specific impacts and 

adaptation activities. Also, additional insight to private sector impacts and adaptation 

considerations were learned from other regions of the study area in the aftermath of 

Hurricane Katrina. As an example, the CSX Railroad received extensive damage on the 

Gulf Coast, particularly in Mississippi and Louisiana, and had to consider alternative 

adaptation strategies such as rerouting, rehabilitation with strengthening, or relocation 

further inland. 

5.1.3 Challenges and Opportunities to Integrating Climate Information 

Transportation agencies consider a broad range of future conditions, including 

demographic, environmental, economic, and other factors. It is within this broader context 

that it is reasonable for some agencies to address the additional consideration of climate 

change over the lifetimes of their transportation facilities, to the extent possible. 

Over time, fundamental and significant changes may be desirable in the manner in which 

long-range transportation plans are developed and investment decisions are made. Similar 

to what transportation agencies are now doing to address freight, safety, economic 

development, environmental mitigation, and other emerging issues, considerations of 

climate change can be incorporated in each step of the transportation planning process, 

particularly during the earliest parts of the planning process – the formulation of a vision 

and the development of goals and objectives. 

Timeframes 

Long-range transportation plans are developed with a time horizon that typically extends 

20 to 30 years into the future. Most long-range transportation plans being developed today 

have time horizons of 2030 or 2035. However, as illustrated in figure 5.4, individual 

facilities being recommended in those plans will be designed with a considerably longer 

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service life. For instance, bridges being built today should last 60 to 80 years or more. 

Furthermore, bridges being proposed in the long-range plans will be designed to last 

beyond 2100. Although the timeframe for significant climate change might appear to be 

longer than most plan horizons, studies have found that the effects of climate change are 

being experienced today. And while climate change is typically thought of as a gradual, 

incremental process over many years, scientists expect that climate changes are likely to 

include abrupt and discontinuous change as well. To begin to adequately consider the 

implications of climate change, transportation planners would benefit from consideration of 

longer time horizons. Climate changes over longer time periods could be addressed as part 

of a long-term visioning that helps determine where transportation investments are needed 

and should be located. This process would inform the transportation planning process with 

supplementary information. For example, in the planning process depicted in figure 5.3, 

climate change could be added to the initial visioning step, along with other factors such as 

economic and environmental considerations. 

While it is difficult to know the planning horizons of private companies, given their 

proprietary nature, it is likely that their focus would benefit from an expanded time horizon 

as well. Since the infrastructure likely to be affected by future climate impacts is currently 

under development, planners and decision makers need to start now in considering how 

climate changes may affect them. 

[Insert Figure 5.4: Relationship of transportation planning timeframe and infrastructure 

service life to increasing climate change impacts] 

Land Use 

Responding to the potential effects of climate change, as demonstrated by the ongoing 

discussions in Texas, Louisiana, and Mississippi, may involve changes in the location of 

transportation facilities, housing, and business. Transportation planning already attempts 

to forecast these types of demographic and economic shifts. Potential changes in the future 

climate and its resulting impacts on the existing ecology may make such forecasting far 

more difficult. 

A further challenge for transportation planners and climate scientists is to better understand 

the interplay of the built environment with the local ecology toward the betterment of both. 

For example, barrier islands serve to protect existing infrastructure by reducing the impacts 

of major storms. Preservation of these ecologically sensitive coastal wetlands is one way 

of minimizing damage from hurricanes, by restoring critical buffer areas that absorb storm 

energy. Similarly, a variety of human activities are contributing to the current and 

projected rate of land subsidence, including but not limited to, the location and 

management of navigation channels. The impacts of climate change will likely make 

understanding and protecting these natural systems even more important, not only for their 

own sake but to prolong the viability of transportation infrastructure. The development of 

the full range of port, pipeline, and shipping facilities, and their supporting land 

transportation infrastructure, can be examined for their potential to either directly or 

indirectly affect coastal areas. In essence, this is extending the concept of “secondary and 

cumulative effects” (as required under the National Environmental Policy Act [NEPA]), to 

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include coastal ecology and storm protection. Similarly, strategies proposed to protect 

coastal areas should be screened for potential implications on the transportation system. 

Institutional Arrangements 

Existing institutional arrangements may not be sufficient for transportation agencies to 

fully address and respond to issues of climate change. Increased collaboration may be 

necessary for transportation planning and investment decision makers to effectively 

respond to climate change issues, including their partnering with climate change 

specialists. State DOTs and MPOs already are consulting with resource agencies such as 

natural resources, conservation, and historical preservation in the planning process. 

Collaborating on climate change might be a natural extension of that consultation process. 

It also will be necessary for State DOTs to collaborate within their agencies so that 

planning, engineering, and programming have a common understanding of the potential for 

climate change and the alternative responses possible. Likewise, the MPOs need to 

accomplish a similar effort with their local governments. Finally, for the vast amount of 

the transportation system owned by private agencies, climate change information must be 

made available to them so that their decisions can be coordinated with and compliment 

those of the public sector. In some cases, this may lead to public/private investment 

options. 

A New Approach 

Based on currently available climate change information, there appear to be important 

implications of climate change for the manner in which transportation investments are 

planned, developed, implemented, managed, and operated. This report shows that these 

implications are sufficiently significant that transportation planners should develop an 

improved understanding of climate change issues and reflect them in their decision making 

today. 

The long timeframe for climate change, as compared to the existing 20-year view of most 

transportation plans, makes the specification of its impacts considerably more difficult. 

Instead of relatively precise estimates of potential impacts that are needed for many aspects 

of transportation planning, broad ranges are more typically what climatologists currently 

can provide. Given this lack of certainty, climatologists are moving toward the 

determination of probabilities of potential impacts. 

Currently, the transportation planning process does not consider probabilities in 

determining future travel demand and ways to meet it.3

 Instead, transportation 

professionals generally rely on more deterministic methods that yield a single answer based 

 

3

 Steps have been made in this direction with the development of TRANSIMS, a new generation 

transportation simulation model, which employs sampling and statistical methods to generate future travel 

demand; however TRANSIMS is not yet in general use. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

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on the inputs - such as well accepted engineering, construction and other standards - along 

with professional judgment. 

Such methods are ill-equipped to addressing the uncertainties associated with the timing 

and magnitude of many climate change impacts. What is needed are new tools that can 

address the uncertainties associated with climate change and yet provide more useful 

information to the transportation community that would be used to create a more robust and 

resilient system. 

The following section provides a conceptual approach that represents the first step toward 

development of such a tool. It suggests a new approach to viewing both individual 

transportation facilities and the system as a whole, borrowing concepts and relationships 

from ecology, risk management, decision theory, and transportation practice. It proposes a 

way to help planners, designers, and engineers think through the potential harm that 

changing conditions in the natural environment might cause and the ability of the existing 

and proposed facilities to withstand such harm. 

 5.2 Conceptual Framework for Assessing Potential Impacts 

on Transportation 

While climate factors are not usually considered for transportation planning purposes, as 

shown in the previous section, some agencies are beginning to explore how they might be 

incorporated. This section attempts to provide a conceptual approach to how climate 

concerns – with their inherent uncertainties – might be addressed in a transportation 

context. This is a first step toward creation of a way to consider risk and uncertainty in 

transportation planning as an alternative to the largely deterministic approaches currently 

employed. Further refinement will be necessary in Phase II of this study to make this 

approach operational in a pilot test area. 

While the focus of this project is on a portion of the U.S. Gulf Coast, the intent is to 

develop a conceptual framework that lays the groundwork for an assessment that links 

climate change and transportation and to focus on this nexus by using a specific case as an 

illustration. Climate change impacts vary by region, with some areas being more 

vulnerable to some aspects of exposure than others. Regardless of the specific site 

characteristics related to this chapter, the general framework and relationships between 

information, decision maker, and process will be transferable to other situations. 

Developing a conceptual framework at this stage in the research, rather than a static tool or 

model, provides the transportation sector with the basic understanding of these 

relationships at this early stage of recognition of the potential impacts of climate change 

and variability on transportation infrastructure. 

This section focuses on: (1) a description of the basic factors that can be useful in an 

assessment of the potential impacts of climate change on transportation and (2) a 

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description of the development of a conceptual framework incorporating these basic 

components. 

5.2.1 Factors of Concern: Exposure, Vulnerability, Resilience, 

and Adaptation 

There are four major conceptual factors to consider climate concerns in transportation: 

exposure to climate stressors, vulnerability, resilience, and adaptation. These concepts and 

their definitions are borrowed from, and consistent with, ecological and hazard assessment 

practices and represent transportation infrastructure’s probable levels of exposure to 

damage from climate change factors, its capacity to resist such damage or disruption of 

service, and its ability to recover if damaged. For purposes of this project, we adapted the 

Intergovernmental Panel on Climate Change (IPCC) definitions of these concepts, in 

general, with reference to applied and theoretical applications for more specific or 

articulated examples. It was determined by the research team to closely approximate the 

IPCC terminology and methodology, as this also informs many other regional and sectoral 

assessments conducted in the United States and elsewhere. 

With specific regard to climate change, exposure comprises the “nature and degree to 

which a system is exposed to significant climatic variations” (IPCC, 2001, p. 987). 

Exposure also is often articulated as the probability of occurrence (the probable range of 

climate change stressors, such as sea level rise or increased rainfall) and the physical 

characterization of the local area. In this study, exposure is the combination of stress 

associated with climate-related change (sea level rise, changes in temperature, frequency of 

severe storms) and the probability, or likelihood, that this stress will affect transportation 

infrastructure. 

While there are different kinds of exposure (see Tobin and Montz, 1997, for a discussion), 

two types are applicable to this approach: perceived (based on the situational perspective 

of the particular decision maker) and predicted (based on “objective” measures). For 

predicted exposures, the following environmental impacts appear to be most relevant in the 

central Gulf Coast region, depending on the specific infrastructure component and location: 

• Sea level rise, historical trends, and predicted range (including rates of subsidence 

and/or erosion; 

• Temperature range, scenarios, and probability distribution functions (with special 

consideration to changes in extreme temperatures); 

• Precipitation range, scenarios, and probability distribution functions and intensity; and 

• Major storm characteristics (projected magnitude of storm surge and winds, as well as 

frequency). 

Vulnerability, in general, refers to the “potential for loss” (Tobin and Montz, 1997) due to 

exposure to a particular hazard. The IPCC defines vulnerability as: “the degree to which a 

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system is susceptible to, or unable to cope with, adverse effects of climate change, 

including climate variability and extremes. Vulnerability is a function of the character, 

magnitude, and rate of climate variation to which a system is exposed, its sensitivity, and 

its adaptive capacity” (IPCC, 2001, p. 995). More specifically for this project, 

vulnerability considers the structural strength and integrity of key facilities or systems and 

is defined as the resulting potential for damage and disruption in transportation services 

from climate change stressors. The vulnerability of a facility or system then depends on 

the level of exposure to which it is subject. 

The risk that a transportation facility or a system faces can be defined from these notions of 

exposure and vulnerability. Risk is the product of the probability that a facility will be 

exposed to a climate stressor of destructive (or disruptive, at the systems level) force times 

the damage that would be done because of this exposure. 

While transportation is frequently thought of as the built infrastructure, transportation’s 

value to society is the service or performance this system of facilities and operations 

provides to move goods and people. Loss of capacity is the reduction from full 

performance capacity for a particular transportation system or facility. For example, 

Berdica (2002) defines vulnerability to the road system as a problem of reduced 

accessibility. System vulnerabilities to specific locational risks will vary based on the 

performance expectations of those specific system segments. The loss in performance 

would be the reduction of system capacity measured according to the relevant metrics. For 

example, highway capacity would be measured in volume of traffic flow; a loss in 

performance would be gauged by the reduction of traffic flow capacity. 

It is important to note that vulnerability, like exposure, may be perceived differently among 

stakeholders and across modes. Key factors for the determination of transportation facility 

or system vulnerability may include: 

• Age of infrastructure element; 

• Condition/integrity; 

• Proximity to other infrastructure elements/concentrations; and 

• Level of service. 

The concept of resilience is used to refer to the restoration capacity of the infrastructure at 

the facility and system level. In general, resilience is defined as the “amount of change a 

system can undergo without changing state” (IPCC, 2001, p. 993). In the climate change 

context, resilience also refers to regenerative capacity, the speed of response and recovery 

of various system elements, and mitigation and adaptation efforts. It also is generally 

considered to be a “multidimensional concept, encompassing biogeophysical, 

socioeconomic and political factors” (Klein et al., 1998, p. 260). Adger et al. (2005) define 

resilience more specifically as the capacity of a system to absorb disturbances and retain 

essential processes. 

We can apply these concepts to the transportation context. System-level resilience is 

particularly important in the transportation sector because of the inherent connectivity of 

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transportation facilities. Resilience can be looked at as the ability of a transportation 

network to maintain adequate performance levels for mobility of goods and services 

through redundant infrastructure and services. The fact that one component is out of 

service may not be crucial in areas where alternative transportation facilities or services are 

available. For an individual facility such as a road or bridge, resilience can be thought of 

as how quickly full service can be restored either through repair or replacement. 

Key factors influencing resilience in our conceptual framework can be categorized across 

three dimensions: mode or structure (highway segment or port, for example), 

socioeconomic (political will and resources), and system-level factors. These factors may 

include: 

1. Mode/structure: 

− Repair/replacement cost; and 

− Replacement timeframe. 

2. Socioeconomic: 

− Public support; 

− Interorganization cooperation; 

− Economic resources; and 

− Social resources. 

3. System level: 

− Redundancy among components; 

− Essential service resumption; 

− System network connectivity; 

− Institutional capacity; and 

− Relevance of existing plans for response to events (e.g., floods). 

Transportation planners and decision makers may consider these factors (either formally or 

informally) and generate a basic perception of resilience. For example, for any given 

facility the relevant decision maker would have a general idea as to: (1) how much 

replacement would cost; (2) how long it would take; (3) the economic resources available 

for replacement; (4) public sentiment regarding replacement (or not); (5) how essential the 

facility is to system performance; and (6) whether or not plans exist for dealing with 

disruption of facility and/or system performance over the duration of the replacement time. 

This understanding of the resilience of the facility or system can be based on either the 

general feeling and experience of the decision maker, or it can be developed systematically 

with quantifiable measures. 

The IPCC defines adaptation as the: “adjustment to natural or human systems to a new or 

changing environment. Adaptation to climate change refers to adjustment in natural or 

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human systems in response to actual or expected climatic stimuli or their effects, which 

moderates harm or exploits beneficial opportunities” (IPCC, 2001, p. 982). An associated 

concept, adaptive capacity, refers to “the ability of a system to adjust to climate change 

(including climate variability and extremes) to moderate potential damages, to take 

advantage of opportunities, or to cope with the consequences” (IPCC, 2001, p. 982). 

In this project, we are interested in understanding adaptation as a decision that officials can 

make in response to perceptions or objective measurements of vulnerability or exposure. 

For example, given a certain climate change scenario, a decision maker may choose to 

advocate for certain adaptive policy responses beyond the status quo. This can be 

determined through interviews by asking such questions as: what is the planning horizon 

for this specific area; what factors (political and resource) constrain or encourage adaptive 

behavior in this area of concern; and what are the stakeholder perceptions of uncertainty in 

regard to the data and information provided and available for informed decision making 

(see Jones, 2001, for an example)? 

Adaptive strategies can be further delineated into three possible alternatives: protect, 

accommodate, and retreat. These adaptive responses are derived from the IPCC framework 

for assessing coastal adaptation options (Bijlsma et al., 1996). Within the context of our 

case study in a coastal region, the protection strategy might aim to protect the land from the 

sea by constructing hard structures (e.g., seawalls) as well as by using “soft measures” 

(e.g., beach nourishment, wetland restoration). Accommodation may call for preparing for 

periodic flooding by having operational plans in place to redirect traffic, for example, or 

cleaning up roadway obstacles to return to normal service. The retreat option would 

involve no attempt to protect the facility from the climate stressor. In an extreme case 

along a coastal area, for example, a facility or road segment could be abandoned under 

certain conditions (sea level rise, persistent storm surges that reduced the feasibility of 

replacement). From a system perspective, it could be determined that retreat is the best 

decision if the road segment could be relocated without loss of system service; if 

performance can be maintained through other system components; or if service is no longer 

required due to shifts in population and commerce. 

A related concept, threshold, also will be considered in the framework. Threshold has been 

defined as the point where a stimulus leads to a significant response (Jones, 2001; Parry, 

Carter, and Hulme, 1996). In the case of transportation decision making, we are interested 

in determining at what point within an assessment or decision process change is induced. 

A threshold can be quantified under certain circumstances (for example, the impact of 

temperature on pavement construction decisions), or it may be subjective, depending on the 

situation. Jones (2001) suggests two general thresholds for infrastructure: (1) economic 

write-off, when replacement costs less than repair and (2) a standard-derived threshold, 

when the condition of the infrastructure component falls below a certain standard. These 

variables can have both quantitative and qualitative characteristics. In this phase of the 

research, the focus is on determining qualitative characteristics and their general utility to 

decision makers (see Cutter et al., 2000, for a similar approach). 

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In summary, the following are working definitions that were applied in this section of the 

research. These definitions were developed in conjunction with the research team, the 

Federal Advisory Committee, and other experts. 

Exposure – The combination of stress associated with climate-related change (sea level 

rise, changes in temperature, frequency of severe storms) and the probability, or likelihood, 

that this stress will affect transportation infrastructure. 

Vulnerability – The structural strength and integrity of key facilities or systems and the 

resulting potential for damage and disruption in transportation services from climate 

change stressors. 

Resilience – The capacity of a system to absorb disturbances and retain essential processes. 

Adaptation – A decision that stakeholders can make in response to perceptions or 

objective measurements of vulnerability or exposure. Included in this concept is the 

recognition that thresholds exist where a stimulus leads to a significant response. 

Each of these four factors is critical in our understanding of how climate change may 

impact transportation in the study region. As illustrated in figure 5.5, an initial risk 

assessment for a facility or system will include analysis of the first three factors: exposure, 

vulnerability, and resilience. Once a risk assessment is conducted, choices for an 

appropriate adaptation strategy can be considered. The implementation of a particular 

adaptation strategy – to protect, accommodate, or retreat – will in turn affect subsequent 

risk assessments by changing one or more aspects of risk. The effectiveness of the 

adaptation strategy can be assessed by the degree of success in maintaining system or 

facility performance. 

[INSERT FIGURE 5.5: A risk assessment approach to transportation decisions] 

5.2.2 Framework for Assessing Local Climate Change Impacts 

on Transportation 

Having introduced the major factors for consideration in a climate change impact 

assessment, this section introduces the conceptual framework and outlines the input and 

outputs. This is followed by a description of an approach to implementing such a 

framework. 

In general, the objective is to illustrate how climate change/variability can be integrated 

into existing processes for transportation policy and decision making toward the 

development of adaptation strategies. Even at the conceptual level, this process can assist 

transportation decision makers in considering the potential impacts from climate change 

and variability on a wide range of transportation infrastructure components of any type, 

including air, rail, marine, transit, or highway, as well as the overall intermodal system. It 

is intended to be implemented primarily at the State or local scale, since climate impacts 

differ by region of the country. 

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The framework can help direct local decision makers in raising and to some extent 

answering such questions as: what are the likely changes in sea level (for example) in my 

area; how vulnerable is the transportation infrastructure related to this probability in my 

area; and at what point should decision makers seek adaptive strategies to address this? 

The resulting information can then be utilized for making adaptation decisions. 

Needed Data 

Previous chapters outlined the physical, infrastructure, and socioeconomic data that was 

collected and aggregated specifically for the Gulf Coast study area. This section discusses 

how this data serves to help assess the exposure and vulnerability of any transportation 

network. While not all of the data collected for this project would be available to local 

transportation stakeholders, much of the data is available and is being updated on a regular 

basis. 

Within this conceptual framework, the analysis begins with an assessment of what climate 

impacts can be determined with a relatively high degree of confidence. This is the basis for 

the exposure analysis, including some idea as to the probability that transportation facilities 

will be exposed to particular impacts. For the Gulf Coast Study, various climate scenarios 

were analyzed and probable impacts identified at the regional level, including sea level 

rise, increased storm intensity, extreme temperature increases, and potential ranges 

quantified. The infrastructure and services will be exposed to these impacts. 

The vulnerability of specific portions of the transportation infrastructure will depend on its 

location relative to the location of the impacts, as well as other characteristics. Sea level 

rise is a good example, as coastal infrastructure will be more vulnerable than inland 

facilities. Based on location, the physical characteristics of the region, and socioeconomic 

data, the vulnerability of transportation facilities can be assessed. 

From the probability of an exposure to a climate impact and the assessment of 

vulnerability, some idea of the risk the facility or the system faces can be determined. In 

order to do this, repair or replacement costs, economic losses, or other metrics of potential 

damage must be developed. In addition, precise estimates of risk would require 

quantitative estimates of exposure. Whether risk can be quantitatively determined remains 

to be seen. 

Resilience was not addressed in the first phase of the Gulf Coast analysis, but will be in the 

second phase. The analysis of resilience requires different data for systems versus facility 

consideration. At the systems level, an in-depth knowledge of the movement of goods and 

people is necessary to assess the potential for redundant services that can at least minimally 

maintain service. For facilities, the time and cost needed to bring damaged infrastructure to 

full performance would be critical. 

Outcomes 

Having considered how transportation facilities might be exposed and having determined 

their vulnerability and the resilience of the network, decision makers can then consider 

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Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

ways to improve transportation in the region to be more robust to the climate impacts 

identified. 

The primary outputs from the conceptual framework are policy recommendations or 

changes derived from the decision makers’ understanding and interpretation of the major 

factors (exposure, vulnerability, and resilience and adaptation) associated with climate 

change. Where appropriate, these recommendations should lead to capital, maintenance, or 

operational improvements that will result in a more robust and resilient network. 

The process of following the framework can be used to characterize the exposure of 

particular facility or system components to climate hazards; the vulnerability and resiliency 

of these elements; and the adaptation options available to the decision maker. Examples of 

potential thresholds or tipping points indicated for each of these factors targeted at each 

relevant transportation infrastructure element can then be used as input into the planning 

and decision processes available to the user. This output from the conceptual framework 

could be designated for the local level or State DOT level of planning. It will be up to the 

stakeholder or decision maker to determine how the assessment output would impact 

existing or proposed decision and planning processes at the relevant scale. 

Figure 5.6 illustrates the relationship between risk assessment and the value of performance 

to the type of adaptation strategy that may be selected. As the importance of maintaining 

uninterrupted performance increases, the appropriate level of investment in adaptation 

should increase as well, taking into account the degree of risk facing the specific facility or 

system. For example, maintaining a specific bridge may be essential to ensure safe 

evacuation of a particular community, because no other feasible evacuation routes or backup strategies are available. In this instance, transportation and regional planners may 

recommend that more conservative (and possibly more expensive) design standards be 

applied to protect that bridge in the event of a low probability – but high consequence – 

storm event in that location. Conversely, although a road segment may be assessed to be 

highly at risk, it may warrant less extensive adaptation investment because alternatives to 

that road are available to provide access and mobility, or a moderate disruption in service 

performance is not considered to be critical. 

[INSERT FIGURE 5.6: Degree of risk and value of performance inform level of adaptation 

investment] 

Making Use of Risk Assessment in Transportation Decisions 

The concepts presented in this chapter can be employed to begin the assessment of climate 

impacts in transportation planning and investment. Additional detail will be required for 

implementation, but this discussion offers an initial step toward a more complete 

consideration of risk and uncertainty in this type of assessment. As demonstrated, 

probabilities for some climate impacts are now available on a regional level, but 

probabilities for specific impacts on individual facilities or network components cannot yet 

be assigned with confidence. Furthermore, while some climate impacts can be reliably 

identified, data are lacking for others that may be important for transportation. 

Nonetheless, even at the conceptual level, this discussion may be useful for transportation 

5-23
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

planners as they begin to incorporate climate concerns in their consideration of new 

investments. 

Consider the following example of a bridge located near the coast that is scheduled for 

rehabilitation in 5 years. Based on the conceptual framework, the first step is to determine 

its exposure to stressors that may significantly impede the service it provides. 

If the bridge were located within the Gulf Coast study area, the analyses in chapters 3.0 and 

4.0 indicate the four main stressors of concern: sea level rise, storm surge, temperature 

increases, and heavy downpours giving rise to flooding. There may be others as well, and 

the analyst would do well to consider other potential impacts in consultation with natural 

resource experts. 

If the bridge falls within the area identified as likely to be flooded by a 61- to 122-cm (2- to 

4-ft) rise in sea level, more specific examination of the particular terrain is warranted to 

assess in greater detail the likelihood of flooding. If there are no mitigating factors, there is 

a relatively high probability that the area will flood within a 50- to 100-year time period. 

The next step is to determine the bridge’s vulnerability to sea level rise. How high is the 

bridge? How high are the approaches? How critical is the service it provides? Based on 

these and other considerations, the bridge’s vulnerability, in the context of its role within 

the larger network, can be assessed. If the bridge, or critical elements of it, are below 122 

cm (4 ft), it will likely flood within its projected lifespan. While more objective measures 

of vulnerability to the service flowing over the bridge would be desirable, at a minimum 

the analyst should be able to derive a qualitative determination of the bridge’s 

vulnerability. 

Judgment must be applied to assess the risk (probability of exposure times vulnerability) 

posed by flooding with current knowledge. Precise estimates of its components are not 

possible, but the direction and likely ranges are known, and from this a general sense of the 

risk can be inferred. If the bridge is heavily trafficked and vulnerable, the risk is high 

because the sea is rising, leading to permanent flooding, and the bridge’s period of service 

will be cut short before it reaches the end of its useful life. Since (in the example) the 

bridge is scheduled for rehabilitation, now would be an appropriate time to consider 

options. 

The adaptation options are to protect, accommodate, or retreat. Accommodation, which 

might include operational strategies to work around the flooding or simply live with it, 

does not appear to be viable since the flooding is permanent, and operational strategies like 

pumping the water out do not seem viable. Protection may include raising the bridge or its 

approaches or relocating the facility. Retreat, which in this case amounts to abandonment 

of the bridge, is likely the option of last choice since the bridge presumably provides a 

critical service. Engineering, design, landscape, and regional considerations will play 

crucial roles in the determination of the best option, as will the consideration of the 

additional resources necessary to best protect the bridge. Transportation agencies have 

extensive experience in exercising the judgment necessary to make these determinations. 

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Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

In similar fashion, each of the stressors can be assessed for their likelihood and the bridge 

examined for its vulnerability. Risk can be determined and options identified to prolong 

the bridge’s useful life and minimize disruptions to the critical service it provides. For 

stressors whose impacts are well understood, a higher level of analysis can and should be 

done to consider the potential for synergistic impacts that may be more severe than the 

individual effect. The end result of the analysis will be recommendations for investment 

whose implementation will result in a more robust and reliable transportation facility and 

system. Experience indicates that the total cost to transportation agencies will probably be 

lower than failing to consider these impacts when the full costs – capital, operating, and 

economic loss due to disrupted service – are included. 

 5.3 Conclusions 

Climate change and variability have not historically been considered in the planning and 

development of transportation facilities, and this was clearly expressed in the interviews 

conducted as part of this study. Until recently, it may not have been possible to effectively 

use climate data to serve as the basis of considerable capital investment due to its relative 

uncertainties. That appears to be changing. The destructive forces of Hurricanes Katrina 

and Rita have underscored the need to carefully consider the effects of the natural 

environment on transportation to a much higher degree. State, local, and possibly private 

(though less is known about their myriad approaches) transportation agencies are beginning 

to incorporate more information about the natural environment, including those effects 

wrought or exacerbated by climate change. 

With the advent of increasingly greater certainty about the regional effects of climate 

change and better tools to assist their examination, analyzing the impacts of climate and the 

natural environment has become possible. Clearly there is benefit to do so. Subsidence 

and climate-induced sea level rise, coupled with the likely increased severity of hurricanes, 

threaten infrastructure, potentially causing severe disruptions to essential transportation 

services or cutting short the useful lives of important facilities. Transportation planners 

across the United States would do well to follow the lead of progressive agencies in the 

Gulf Coast and other places to begin immediately to consider the impacts of climate change 

on the natural environment and thus on transportation facilities under their purview. 

This chapter introduces a taxonomy and conceptual approach toward incorporating climate 

change impacts in transportation planning. Standard deterministic approaches used in 

transportation planning will not suffice to address the timeframes and uncertainties that a 

changing climate poses. The approach is based on the quantitative or qualitative 

assessment of exposure to potentially disruptive impacts, examination of a facility’s (or a 

network’s) vulnerability, the risk of its loss, and possible adaptation strategies to mitigate 

these impacts and prolong service. It is premature to consider any formal changes to the 

established Federal transportation planning process. If for no other reason, the timeframes 

and other requirements such as fiscal constraint do not mesh well. Nonetheless, the 

consideration of climate impacts is possible and useful to transportation plans at all levels 

5-25
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

of government and the private sector. For instance, in the planning process shown in 

figure 5.3, climate change could be considered early on as part of a visioning process and 

later in the development and evaluation of alternative improvement strategies to consider 

future services and their location. Climate change could be considered in the project 

development process when design and engineering are addressed. Likewise, the concept of 

uncertainty and the use of risk analysis could be incorporated into the entire planning and 

project development process. 

 5.4 Sources 

5.4.1 References 

Adger, W. N., T.P. Hughes, C. Folke, S.R. Carpenter, and J. Rockström, 2005: SocialEcological Resilience to Coastal Disasters. Science, 309 (5737):1,036-1,039. 

Berdica, K., 2002: An Introduction to Road Vulnerability: What Has Been Done, Is 

Done, And Should Be Done. Transport Policy, 9(2):117-127. 

Bijlsma, L., C.N. Ehler, R.J.T. Klein, S.M. Khlshrestha, R.F. McLean, N. Mimura, R.J. 

Nicholls, L.A. Nurse, H Perez Nieto, E.Z. Stakhiv, R.K. Turner, and R.A. Warrick, 

1996: Coastal Zones and Small Islands. In: Climate Change 1995: Impacts, 

Adaptations, and Mitigation of Climate Change: Scientific-Technical Analysis. 

Contribution of Working Group II to the Second Assessment Report of the 

Intergovernmental Panel on Climate Change. [Watson, R.T., M.C. Zioyowera, and 

R.H. Moss, eds.] Cambridge University Press, Cambridge, United Kingdom, and New 

York, New York, USA, pages 289-324. 

Cutter, S.L., 2003: The Vulnerability of Science and Science of Vulnerability. Annals of 

the Association of American Geographers, 93(1):1-12. 

Cutter, S. L., J.T. Mitchell, and M.S. Scott, 2000: Revealing the Vulnerability of People 

and Place: A Case Study of Georgetown County, South Carolina. Annals of the 

Association of American Geographers, 90(4):713-737. 

Intergovernmental Panel on Climate Change (IPCC), 2001: Climate Change 2001: 

Impacts, Adaptation, and Vulnerability. J.J. McCarthy, O.F. Canziani, and N.A. 

Leary, et al. (Eds.). Contribution of Working Group II to the Third Assessment Report 

of the Intergovernmental Panel on Climate Change. New York, New York: 

Cambridge University Press. [Available on-line at: http://www.ipcc.ch/] 

Jones, R.N., 2001: An Environmental Risk Assessment/Management Framework for 

Climate Change Impact Assessment. Natural Hazards, 23: 197-230. 

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Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

Kelly, P.M. and W.N. Adger, 2000: Theory and Practice in Assessing Vulnerability to 

Climate Change and Facilitating Adaptation. Climatic Change, 47: 325-352. 

Klein, R.J.T., M.J. Smit, H. Goosen, and C.H. Hulsbergen, 1998: Resilience and 

Vulnerability: Coastal Dynamics or Dutch Dikes? The Geographical Journal, 164(3): 

259-268. 

Levina, E. and D. Tirpak, 2006: Adaptation to Climate Change: Key Terms. Paris: 

Organisation for Economic Cooperation and Development/International Energy 

Agency. 

Llort, Y., 2006: Transportation Planning in Florida. In: Statewide Transportation 

Planning: Making Connections. Transportation Research Circular E-C099, 

Transportation Research Board, Washington, D.C. 

Omenn, G.S., 2006: Grand Challenges and Great Opportunities in Science, Technology, 

and Public Policy. Science, 314: 1,696-1,704. 

Parry, M. and T. Carter, 1998: Climate Impact and Adaptation Assessment: Guide to the 

IPCC Approach. Earthscan Publications, Ltd., London, United Kingdom. 

Parry, M.L., T.R. Carter, and M. Hulme, 1996: What is Dangerous Climate Change? 

Global Environmental Change. 6(1):1-6. 

Power, M. and L.S. McCarty, 1998: A comparative Analysis of Environmental Risk 

Assessment/Risk Management Frameworks. Policy Analysis, 32(9): 224 A – 231 A. 

Presidential/Congressional Commission on Risk Assessment and Risk Management, 

1997: Framework for Environmental Health Risk Management: Final Report. The 

Presidential/Congressional Commission on Risk Assessment and Risk Management, 

Washington, D.C. 

Scheraga, J.D. and J. Furlow, 2001: From Assessment to Policy: Lessons Learned from 

the U.S. National Assessment. Human and Ecological Risk Assessment, 7(5): 

1,227-1,246. 

Schneider, S., J. Sarukhan, J. Adejuwon, C. Azar, W. Baethgen, C. Hope, R. Moss, N. 

Leary, R. Richels, J.P. van Ypersele, K. Kuntz-Duriseti, and R.N. Jones, 2001: 

Overview of Impacts, Adaptation, and Vulnerability to Climate Change. In: Climate 

Change: Impacts, Adaptation, and Vulnerability, the Contribution of Working 

Group II to the IPCC Third Assessment Report (TAR) of the Intergovernmental Panel 

on Climatic Change [J.J. McCarthy, O.F. Canziani, N.A. Leary, D.J. Dokken, and K.S. 

White, eds.] Cambridge University Press, Cambridge, United Kingdom, 75-103. 

Smit, B., I. Burton, and J.T.K Klein, 1999: The Science of Adaptation: A Framework for 

Assessment. Mitigation and Adaptation Strategies for Global Change, 4(3-4), 

199-213. 

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Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions? 

5-28 

Stern, P.C., and H.V. Fineberg, Eds., 1996: Understanding Risk: Informing Decisions in 

a Democratic Society. National Academies Press, Washington, D.C. 

Tobin, G.A., and B.E. Montz, 1997: Natural Hazards: Explanation and Integration. 

Guilford Press, New York City. 

U.S. Department of Transportation, 2006: SAP-4.7, Prospectus for Impacts of Climate 

Variability and Change on Transportation Systems and Infrastructure – Gulf Cast 

Study. Department of Transportation, Washington, D.C. 

5.4.2 Background Sources 

Baumert, K., and J. Pershing, 2004: Climate Data: Insights and Observations. Pew 

Center on Global Climate Change, Washington, D.C. 

VTPI, 2006: Online TDM Encyclopedia. Victoria Transport Policy Institute, Victoria, 

BC, Canada. [On-line at: http://www.vtpi.org/tdm/index.php] 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Tables 

5T-1

Table 5.1 Urbanized area metropolitan planning organizations (MPO) in the 

Gulf Coast study area. 

Urbanized Areas 2000 Population Metropolitan Planning Organizations 

Mobile, AL 354,943 Mobile Area Transportation Study 

Baton Rouge, LA 516,614 Capital Regional Planning Commission 

Houma, LA 108,474 Houma-Thibodaux MPO 

Lake Charles, LA 183,577 Imperial Calcasieu Regional Planning and 

Development Commission 

Lafayette, LA 215,061 Lafayette MPO 

New Orleans, LA; 

Slidell, LA; 

Mandeville-Covington, LA 

1,193,847 Regional Planning Commission of New Orleans 

Gulfport-Biloxi, MS; 

Pascagoula, MS 

363,987 Gulf Regional Planning Commission 

Hattiesburg, MS 80,798 Hattiesburg-Petal-Forest-Lamar MPO 

Houston, TX; 

Galveston, TX; 

Lake Jackson-Angleton, TX; 

Texas City, TX; 

The Woodlands, TX 

4,669,571 Houston-Galveston Area Council 

Beaumont, TX; 

Port Arthur, TX 

385,090 South East Texas Regional Planning Commission MPO
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Tables 

5T-2 

Table 5.2 Level of decision maker concern about climate stressors. 

Area of Interest of 

Interviewees Sea Level Precipitation Temperature Storm Frequency and Magnitude 

Traffic Management –

Transtar 

Moderate Moderate High High 

Emergency 

Management 

High Limited Limited High 

Toll Authority Low Limited Limited High 

Aviation Limited Moderate Highest High 

Aviation Limited Moderate Moderate High 

County Engineer High Limited Limited Highest 

Port Engineer High High Limited Highest 

Port Engineer Low High Limited Highest 

Flood Control – 

Houston 

Limited Limited Low Highest 

State Transportation 

Engineer 

Highest Limited Low High 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Figures 

5F-1

Figure 5.1 How will climate change affect transportation decisions? 

Climate Changes

and Variability

• Temperature change

• Precipitation change

• Accelerated 

sea level rise

• Increased storm surge and 

intensity

Transportation

Decision Making

• System planning

and investment

• Project development

• Operations

• Maintenance

• System assessment

Transportation

Impacts

• Location

• System design

• Design specifications

• Materials

• Safety

• Emergency management/

evacuation

• Replacement/

repair schedules

• Investment levels
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Figures 

5F-2 

Figure 5.2 SAFETEA-LU planning factors. Eight planning factors that should 

guide the development of plans, programs, and projects are identified 

in SAFETEA-LU. (Source: U.S. Department of Transportation) 

Plans,

Programs,

Projects

System

Preservation

Accessibility

and Mobility

Economic 

Vitality

Security

Operational 

Efficiency

Safety

Environmental

Quality

Intermodal 

Connectivity
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Figures 

5F-3

Other Sources 

for Project 

Ideas

Environmental

Quality

Economic 

Development

Mobility and 

Accessibility

Vision

Goals and 

Objectives

Performance

Measures

Long-Range 

(20-30 year)

Plan

Implementation 

of Strategies

Short-Range

(3-5 year)

Program

Alternative

Improvement 

Strategies

Data Analysis Methods

System

Operations

Evaluation

PoliciesOperations strategiesInfrastructure projectsStudiesRegulationsEducation and awarenessEnforcementFinancing strategiesPartnershipsCollaborative undertakings

Understanding 

the Problem

Figure 5.3 Steps in the transportation planning process. 

(Source: Adapted from Michael Meyer, Georgia Institute of Technology) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Figures 

5F-4 

Figure 5.4 Relationship of transportation planning timeframe and 

infrastructure service life to increasing climate change impacts. 

0 10 20 30 40 50 60 70 80 90 100

Project

Concept

Construction In Service

Engineering and Design

Adopted

Long-Range Plan

Years

Transportation Planning Process

Facility Service Life

Climate Impacts

Figure 5.5 A risk-assessment approach to transportation decisions. 

Risk Assessment Adaptation

Response

• Exposure

• Vulnerability

• Resilience

• Protect

• Accommodate

• Retreat

Greater

Resilience
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 5: How Can Transportation Professionals Incorporate Climate Change in Transportation Decisions?: Figures 

5F-5

Figure 5.6 Degree of risk and importance of system or facility performance 

inform the level of adaptation investment. 

High Risk/

Low Importance

High Risk/

Low Importance

Degree of Risk

Importance of System/Facility Performance

Low Risk/

Low Importance

Low Risk/

Low Importance

Low Risk/

Critical Importance

Low Risk/

Critical Importance

Highest Priorities:

High Risk/

Critical Importance

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-1

6.0 What Are the Key Conclusions 

of This Study? 

Lead Authors: Michael J. Savonis, Virginia R. Burkett, Joanne R. Potter 

Contributing Authors: Thomas W. Doyle, Ron Hagelman, Stephen B. Hartley, Robert C. 

Hyman, Robert S. Kafalenos, Barry D. Keim, Kenneth J. Leonard, Matthew Sheppard, 

Claudia Tebaldi, Jessica E. Tump 

The primary objectives of this phase of the Gulf Coast Study were to assemble the data 

needed for an analysis of the potential impacts on transportation; determine whether 

climate and ecological data could be usefully employed in such an assessment; identify and 

implement an assessment approach; and provide an overview of the potential impacts. The 

results are striking. They show that the data can provide useful information to 

transportation decision makers about the natural environment as it exists today, as well as 

the likely changes stemming from climate shifts. By using the historical data on the natural 

environment, an ensemble of climate models, a range of emissions scenarios, wellestablished literature on climate impacts, and a conservative approach toward 

interpretation, this study indicates that the potential impacts on transportation in the Gulf 

Coast are highly significant, as summarized below. 

While further study is needed to examine in more detail the impacts on specific 

transportation facilities, such as individual airports or rail terminals, this preliminary 

assessment finds that the potential impacts on infrastructure are so important that 

transportation decision makers should begin immediately to assess them in the 

development of transportation investment strategies. Phase II of this effort will examine 

one small part of the Gulf Coast study region in much more detail. While the significance 

of climate factors will vary across regions of the United States, responsible transportation 

agencies in other areas would do well to consider these types of impacts as well, since the 

decisions they make today may result in infrastructure that will last 50 to 100 years. While 

the timing and pace of these impacts cannot be specified with precision, the central Gulf 

Coast already is vulnerable to certain impacts, as demonstrated by the 2005 hurricane 

season. 

Given the characteristics of the climate system – especially the long periods of time 

greenhouse gases remain in the atmosphere and the virtually certain increases in carbon 

dioxide concentrations in the coming decades – some degree of impacts cannot be avoided. 

Based on analysis of different emissions scenarios, the magnitude of future impacts will 

depend on the amount of greenhouse gases emitted. While the modeled scenarios 

demonstrate very similar levels of climate impacts over the next 40 years, lower emission 

scenarios show lesser impacts in the longer term (60 to 100 years). If aggressive measures 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-2 

result in reduced emission levels globally, the climate impacts identified here may be on 

the lower end of the anticipated ranges. 

The study authors believe that prudent steps can be taken to fortify the existing 

transportation system, as warranted, after an evaluation of impacts on critical transportation 

facilities and systems. Structures can be hardened, raised, or even relocated as need be, 

and where critical to safety and mobility, expanded redundant systems may be considered 

as well. What adaptive strategies may be employed, the associated costs, and the relative 

effectiveness of those strategies will have to be determined on a case-by-case basis, based 

on studies of individual facilities and systemwide considerations. As transportation 

agencies struggle to meet the challenges of congestion, safety, and environmental 

mitigation – as well as maintaining transportation infrastructure in good repair – meeting 

the challenges posed by a changing climate poses a new and major hurdle toward creation 

of a more resilient transportation network in a time of increasingly scarce resources. 

Phase III of this effort will examine potential response strategies and develop methods to 

assist local decision makers in assessing the relative merits of various adaptation options. 

 6.1 Trends in Climate and Coastal Change 

The central Gulf Coast is particularly vulnerable to climate variability and change because 

of the frequency with which hurricanes strike, because much of its land is sinking relative 

to mean sea level and because much of its natural protection – in the form of barrier islands 

and wetlands – has been lost. While difficult to quantify, the loss of natural storm buffers 

will likely intensify many of the climate impacts identified in this report, particularly in 

relation to storm damage. 

• Relative Sea Level Rise – Since much of the land in the Gulf Coast is sinking, this area 

is facing much higher increases in relative sea level rise (the combination of local land 

surface movement and change in mean sea level) than most other parts of the U.S. 

coast. Based on the output of an ensemble of general circulation models (GCM) run 

with a range of Intergovernmental Panel on Climate Change (IPCC) emissions 

scenarios, relative sea level in the study area is very likely to increase by at least 0.3 m 

(1 ft) across the region and possibly as much as 2 m (6 to 7 ft) in some parts of the 

study area over the next 50 to 100 years. The analysis of even a middle range of 

potential sea level rise of 0.3 to 0.9 m (2 to 4 ft) indicates that a vast portion of the Gulf 

Coast from Houston to Mobile may be inundated in the future. The projected rate of 

relative sea level rise for the region during the next 50 to 100 years is consistent with 

historical trends, region-specific analyses, and the IPCC 4th Assessment Report (2007) 

findings, which assume no major changes in ice-sheet dynamics. 

Protective structures, such as levees and sea walls, could mitigate some of these 

impacts, but considerable land area is still at risk to permanent flooding from rising 

tides, sinking land, and erosion during storms. Subsidence alone could account for a 

large part of the change in land area through the middle of this century, depending on 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-3

the portion of the coast that is considered. Sea level rise induced by the changing 

climate will substantially worsen the impacts of subsidence on the region. 

• Storm Activity – The region is vulnerable today to transportation infrastructure 

damage during hurricanes and, given the potential for increases in the number of 

hurricanes designated as Category 3 and above, this vulnerability will likely increase. 

This preliminary analysis did not quantitatively assess the impact of the loss of 

protective barrier islands and wetlands, which will only serve to make storm effects 

worse. It also did not consider the possible synergistic impacts of storm activity over a 

sea that has risen by 0.6 to 1.2 m (2 to 4 ft). This potential would likely make a bad 

situation even worse, as well. 

• Average Temperature Increase – All GCMs used by the IPCC in its Fourth 

Assessment Report (2007) indicate an increase in average annual Gulf Coast 

temperature through the end of this century. Based on GCM runs under three different 

IPCC emission scenarios (A1B, A2, and B1), the average temperature in the Gulf Coast 

region appears likely to increase by at least 1.5 °C ± 1 °C (2.7 °F ± 1.8 °F) during the 

next 50 years, with the greatest increase in temperature occurring in the summer. 

• Temperature Extremes – With increases in average temperature also will come 

increases in extreme high temperature. Based on historical trends and model 

projections, it is very likely that the number of days above 32.2 °C (90 °F) will increase 

significantly across the study area; this has implications for transportation operations 

and maintenance. The number of days above 32.2 °C (90 °F) could increase by as 

much as 50 percent during the next 50 years. 

• Precipitation Change – Future changes in precipitation are much more difficult to 

model than temperature. Precipitation trends in the study area suggest increasing 

values, with some climate divisions, especially those in Mississippi and Alabama, 

having significant long-term trends. Yet while some GCM results indicate that average 

precipitation will increase in this region, others indicate a decline in average 

precipitation during the next 50 to 100 years. Because of this ambiguity, it is difficult 

to reach conclusions about what the future holds regarding change in mean 

precipitation. Even if average precipitation increases slightly, average annual runoff in 

the region could decline as temperature and evapotranspiration rates increase. 

• Extreme Rainfall Events – Average annual precipitation increased at most recording 

stations within the study area since 1919, and the literature indicates that a trend 

towards more rainfall and more frequent heavy downpours is likely. At this stage, 

climate modeling capacity is insufficient to quantify effects on individual precipitation 

events, but the potential for temporary flooding in this region is clear. In an area where 

flooding already is a concern, this tendency could be exacerbated by extreme rainfall 

events. This impact will become increasingly important as relative sea level rises, 

putting more and more of the study area at risk. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-4 

 6.2 Transportation Impacts 

Based on the trends in climate and coastal change, transportation infrastructure and the 

services that require them are vulnerable to future climate changes as well as other natural 

phenomena. While more study is needed to specify how vulnerable they are and what steps 

could be taken to reduce that vulnerability, it is clear that transportation planners in this 

region should not ignore these impacts. 

• Inundation from Relative Sea Level Rise – While greater or lesser rises in relative 

sea level are possible, this study analyzed the effects of relative sea level rise of 0.6 and 

1.2 m (2 and 4 ft) as realistic scenarios. Based on these levels, an untenable portion of 

the region’s road, rail, and port network is at risk of permanent flooding. 

Twenty-seven percent of the major roads, 9 percent of the rail lines, and 72 percent of 

the ports are at or below 122 cm (4 ft) in elevation, although portions of the 

infrastructure are guarded by protective structures such as levees and dikes. This 

amounts to more than 3,900 km (2,400 mi) of major roadways that are at risk of total 

inundation for the highway system alone. While flood protection measures will 

continue to be an important strategy, rising sea levels in areas with insufficient 

protection may be a major concern for transportation planners. Furthermore, the crucial 

connectivity of the intermodal system in the area means that the services of the network 

can be threatened even if small segments are inundated. 

While these impacts are very significant, they can be addressed and adaptive strategies 

developed if transportation agencies carefully consider them in their decisions. The 

effectiveness of such strategies will depend on the strategies selected and the magnitude 

of the problem because scenarios of lower emissions demonstrate lesser impacts. It 

may be that in some cases, the adaptive strategy may be wholly successful, while in 

others further steps may need to be taken. Adaptive strategies that can be undertaken to 

minimize adverse impacts will be assessed in phase III of this study. 

• Flooding and Damage from Storm Activity – As the central Gulf Coast is already is 

vulnerable to hurricanes, so is its transportation infrastructure. This study examined the 

potential for short-term flooding associated with a 5.5- and a 7.0-m (18- and 23-ft) 

storm surge. Based on these relatively common levels, a great deal of the study area’s 

infrastructure is subject to temporary flooding. More than half (64 percent of 

interstates; 57 percent of arterials) of the area’s major highways, almost half of the rail 

miles, 29 airports, and virtually all of the ports are subject to flooding. 

The nature and extent of the flooding depends on where a hurricane makes landfall and 

its specific characteristics. Hurricanes Katrina and Rita demonstrated that that this 

temporary flooding can extend for miles inland. 

This study did not examine in detail the potential for damage due to storm surge, wind 

speeds, debris, or other characteristics of hurricanes since this, too, greatly depends on 

where the hurricane strikes. Given the energy associated with hurricane storm surge, 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-5

concern must be raised for any infrastructure in its direct path that is not designed to 

withstand the impact of a Category 3 hurricane or greater. 

Climate change appears to worsen the region’s vulnerability to hurricanes, as warming 

seas give rise to more energetic storms. The literature indicates that the intensity of 

major storms may increase 5 to 20 percent. This indicates that Category 3 storms and 

higher may return more frequently to the central Gulf Coast and thus cause more 

disruptions of transportation services. 

The impacts of such storms need to be examined in greater detail; storms may cause 

even greater damage under future conditions not considered here. If the barrier islands 

and shorelines continue to be lost at historical rates and as relative sea level rises, the 

destructive potential of tropical storms is likely to increase. 

• Effects of Temperature Increase – As the average temperature in the central Gulf 

Coast is expected to rise by 0.5 °C to 2.5 °C (0.9 °F to 4.5 °F), the daily high 

temperatures, particularly in summer, and the number of days above 32.2 °C (90 °F) 

also will likely increase. These combined effects will raise costs related to the 

construction, maintenance, and operations of transportation infrastructure and vehicles. 

Maintenance costs will increase for some types of infrastructure because they 

deteriorate more quickly at temperatures above 32 °C (90 °F). Increase in daily high 

temperatures could increase the potential for rail buckling in certain types of track. 

Construction costs could increase because of restrictions on days above 32 °C (90 °F), 

since work crews may be unable to be deployed during extreme heat events and 

concrete strength is affected by the temperature at which it sets. Increases in daily high 

temperatures would affect aircraft performance and runway length because runways 

need to be longer when daily temperatures are higher (all other things being equal). 

While potentially costly and burdensome, these impacts may be addressed by 

transportation agencies by absorbing the increased costs and increasing the level of 

maintenance for affected facilities. 

• Effects of Change in Average Precipitation – It is difficult to determine how 

transportation infrastructure and services might be impacted by changes in average 

precipitation since models project either a wetter or a drier climate in the southeastern 

United States. In either case, the changes in average rainfall are relatively slight, and 

the existing transportation network may be equipped to manage this. 

• Effects of Increased Extreme Precipitation Events – Of more concern is the potential 

for short-term flooding due to heavier downpours. Even if average precipitation 

declines, the intensity of those storms can lead to temporary flooding as culverts and 

other drainage systems are overloaded. Further, Louisiana Department of 

Transportation and Development reports that prolonged flooding of 1 to 5 weeks can 

damage the pavement substructure and necessitate rehabilitation (Gaspard et al., 2007). 

The central Gulf Coast already is prone to temporary flooding, and transportation 

representatives struggle with the disruptions these events cause. As the climate 

changes, flooding will probably become more frequent and more disruptive as the 

intensity of these downpours will likely increase. As relative sea level rises, it appears 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-6 

likely that even more infrastructure will be at risk because overall water levels already 

will be so much higher. While these impacts cannot be quantified at present, 

transportation representatives can monitor where flooding occurs and how the sea is 

rising as an early warning system about what facilities are at immediate risk and 

warrant high-priority attention. In a transportation system that already is under stress 

due to congestion, and with people and freight haulers increasingly dependent on justin-time delivery, the economic, safety, and social ramifications of even temporary 

flooding may be significant. 

 6.3 Implications for Planning 

The network in the study area provides crucial service to millions of people and transports 

enormous quantities of oil, grain, and other freight. It is a network under increasing strain 

to meet transportation demand as the American public’s desire for travel and low-cost 

goods and services continues to grow. Even minor disruption to this system causes ripple 

effects that erode the resources of transportation agencies as well as the good will and trust 

of the public. Good stewardship requires that the transportation network be as robust and 

resilient as possible within available resources. 

This preliminary assessment raises clear cause for concern regarding the vulnerability of 

transportation infrastructure and services in the central Gulf Coast due to climate and 

coastal changes. These changes threaten to cause both major and minor disruptions to the 

smooth provision of transport service through the study area. Transportation agencies – 

bearing the responsibility to be effective stewards of the network and future investments in 

it – need to consider these impacts carefully. 

Steps can be taken to address the potential impacts to varying degrees. This study 

demonstrates that there is benefit to examining the long-term impacts of climate change on 

transportation. Climate data and model scenarios may be productively employed to better 

plan for transportation infrastructure and services, even if there is not as much information 

or specificity as transportation planners might prefer. State and local planners need to 

examine these potentialities in greater detail within the context of smaller study areas and 

specific facilities. But to effectively consider them, changes are likely necessary in the 

timeframes and approaches taken. 

• Planning Timeframes – Current practice limits the ability of transportation planners to 

examine potential conditions far enough into the future to adequately plan for impacts 

on transportation systems resulting from the natural environment and climate change. 

As such, insufficient attention is paid to longer-term impacts in some cases. The 

longevity of transportation infrastructure argues for a long timeframe to examine 

potential impacts from climate change and other elements of the natural environment. 

The current practice for public agencies of examining 20 to 30 years in the future to 

plan for transportation infrastructure may represent the limits of our sight for social, 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-7

economic, and demographic assessments, as well as for consideration of fiscal 

constraint and other Federal planning requirements. However, the natural environment, 

including the climate, changes over longer time periods and warrants attention – 

perhaps as part of a long-term visioning process that helps to determine where 

transportation investments are needed and should be located. Such an approach would 

inform the long-range planning process with valuable supplementary information. 

This study could not examine transportation decision making in the private sector in 

detail due to proprietary concerns and the numerous companies involved. Clearly, 

some companies, such as CSX Railroad, have responded to issues posed by the 2005 

hurricane season and made contingency plans to reroute service. Since the concerns are 

every bit as real for the private sector, these companies also would do well to plan for 

and implement adaptive strategies related to climate and other natural environment 

impacts. 

• Connectivity – In addition to analysis at the level of particular facilities – such as an 

airport, bridge, or a portion of rail line – it would be useful for planners to examine the 

connectivity of the intermodal system for vulnerability assessed at the local, regional, 

national, and international levels to long-term changes in the natural environment, 

including changes induced by climate. This helps to identify critical links in the system 

and ways to buttress them against exposures to climate factors or other variables, or to 

create redundancies to maintain critical mobility for directly and indirectly affected 

populations alike. 

• Integrated Analysis – From a transportation planning perspective, it is unnecessary 

and irrelevant to separate impacts due to climate change from impacts occurring from 

other naturally occurring phenomena like subsidence or storm surge due to hurricanes. 

In fact, such impacts are integrally related. Climate change is likely to increase the 

severity or frequency of impacts that already are occurring. Any impact that affects the 

structural integrity, design, operations, or maintenance that can be reasonably planned 

for should be considered in transportation planning. Efforts to restore ecological 

systems to redevelop protective buffers and reverse land loss may likewise help to 

protect transportation infrastructure from future climate impacts. 

 6.4 Future Needs 

The analysis of how a changing climate might affect transportation is in its infancy. While 

there is useful information that can be developed, the continued evolution of this type of 

study will serve to enhance the type of information that planners, engineers, operators, and 

maintenance personnel need to create an even more robust and resilient transportation 

system, ultimately at lower cost. This study begins to address the research needs identified 

in chapter 1.0 based on the current literature, but much more investigation is required. 

Based on the experience gained in conducting this study, research gaps are indicated in 

several chapters and specifically identified in chapter 4.0. Taken together, they indicate the 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-8 

following areas where more information is critical to the further estimation of the impacts 

of a changing climate on transportation infrastructure and services. 

• Climate Data and Projections – The transportation community would benefit from 

the continued development by climatologists of more specific data on projected future 

impacts. Higher resolution of climate models for regional and subregional studies 

would be useful. More information about the likelihood and extent of extreme events, 

including temperature extremes, storms with associated surges and winds, and 

precipitation events could be utilized by transportation planners. 

• Risk Analysis Tools – In addition to more specific climate data, transportation 

planners also need new methodological tools to address the uncertainties that are 

inherent in projections of climate phenomena. Such methods are likely to be based on 

probability and statistics as much as on engineering and material science. The 

approaches taken to address risk in earthquake-prone areas may provide a model for 

developing such tools. 

This study proposes a conceptual framework that may provide one way of approaching 

the development of new tools. More effort is needed to make the concepts presented 

here operational and thus useful to planners in the region. Specifically, more effort is 

needed to identify thresholds at which adaptive actions are warranted and taken. 

Monitoring short-term flooding due to increased downpours; relative sea level rise; and 

operating, maintenance, and construction costs serves as a good first step toward the 

identification of these thresholds. Eventually, it would be most useful to have 

standards of transportation service based on societal needs to guide future investments, 

and in some instances, changes in design standards may be indicated to ensure the 

desired levels of service. 

• Region-Based Analysis – Future phases of this study will examine in more detail the 

potential impacts specific to the Gulf Coast and determine possible adaptation 

strategies. In addition, information developed either in this or subsequent studies 

would be valuable on freight, pipelines, and emergency management in particular. 

Additional analysis on demographic responses to climate change, land use interactions, 

and secondary and national economic impacts would help elucidate what impacts 

climate will have on people and the Nation as a whole, should critical transportation 

services in the region be lost. However, the impacts that a changing climate might have 

depends on where a region is and the specific characteristics of its natural environment. 

The research conducted in this study should be replicated in other areas of the country 

to determine the possible impacts of climate change on transportation infrastructure and 

services in those locations. Transportation in northern climates will face much 

different challenges than those in the south. Coastal areas will similarly face different 

challenges than interior portions of the country. 

• Interdisciplinary Research – This study has demonstrated the value of crossdisciplinary research that engages both the transportation and climate research 

communities. Continued collaboration will benefit both disciplines in building 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Chapter 6: What are the Key Conclusions of this Study?

6-9

methodologies and conducting analyses to inform the Nation’s efforts to address the 

implications of climate change. 

 6.5 References 

Gaspard, K., M. Martinez, Z. Zhang, and Z. Wu., 2007: Impact of Hurricane Katrina on 

Roadways in the New Orleans Area. Technical Assistance Report No. 07-2TA, LTRC 

Pavement Research Group, Louisiana Department of Transportation and Development, 

Louisiana Transportation Research Center, March 2007, 73 pages. 

Intergovernmental Panel on Climate Change (IPCC), 2007: Climate Change 2007: 

The Physical Science Basis, Summary for Policy-Makers. Contribution of Working 

Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate 

Change. Geneva, Switzerland, 21 pages. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix A: Gulf Coast Study GIS Datasets 

A-1

Appendix A: Gulf Coast Study 

GIS Datasets 

Table A.1 Datasets in the geographic information system for the 

Gulf Coast study area. 

Topic Dataset 

National Elevation Dataset (NED) for Gulf Coast study area 

Lidar for coastal Louisiana 

Elevation/Subsidence 

LSRC/NGS Subsidence Measurement Network for LMRV 

(NOAA Tech Report 50) 

Pipeline data obtained from the U.S. DOT OPS National Pipeline Mapping 

System 

Road networks from TIGER data, 2003 

Individual State evacuation routes 

Railway network from TIGER data 

Rail networks (Source: Federal Railroad Administration, 2005) 

Amtrak stations (Source: Federal Railroad Administration, 2005) 

Fixed guideway transit facilities (Source: Bureau of Transportation Statistics, 

Federal Transit Administration) 

Airports (Source: Federal Aviation Administration, 2005) 

Ports (Source: U.S. Army Corps of Engineers, 2005) 

Intermodal freight terminals (Source: Bureau of Transportation Statistics, 2004) 

Transportation Infrastructure 

Navigable waterways (Source: U.S. Army Corps of Engineers) 

Landsat 5 Thematic Mapper (TM) satellite data at 90-m resolution 

Aerial Photography at 1-m resolution from the 1998 DOQQ 

Imagery and Topographic Maps 

Topographic Maps (DRG) at 1:24,000, 1:100,000, and 1:250,000 scales 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix A: Gulf Coast Study GIS Datasets 

A-2 

Table A.1 Datasets in the geographic information system for the 

Gulf Coast study area (continued). 

Topic Dataset 

Geology at 1:2,000,000 covering the study area 

1:500,000 for Louisiana 

State Soil Geographic Database (STATSGO) for Gulf Coast study area 

Soil Survey Geographic Database (SSURGO) in tabular form available for Gulf 

Coast study area 

National Land Cover Dataset (NLCD) 

Earth Sciences 

EcoRegions 

National Hydrographic Dataset (NHD) 

Federal Emergency Management Agency (FEMA) Q3 flood data 

Hydrology 

Hydrologic unit watershed coverage of Gulf Coast drainage 

Administrative Geography and Other Infrastructure 

Political boundaries (Source: U.S. Census) 

Demographic data (Source: U.S. Census) 

Urbanized areas (Source: U.S. Census) 

MPO planning boundaries (Source: BTS) 

Coastal and hazard planning districts (Source: FEMA) 

Petrochemical and energy resources (Source: EPA/CENSUS) 

Industrial centers (Source: EPA/CENSUS) 

Employment centers (Source: CENSUS) 

Government/Federal facilities (Source: USGS) 

Military bases (Source: MTMCTEA) 

Public health, education, service facilities (Source: CENSUS) 

Emergency response and safety facilities (Source: FEMA) 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-1

Appendix B: Additional Data 

on Social and Economic Setting 

Figure B.1 Persons reporting disabilities. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-2

Figure B.2 Children age 14 and under. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-3

Figure B.3 Single adult households with children. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-4

Figure B.4 Linguistically isolated households. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-5

Figure B.5 Percent of population with no high school diploma or equivalent. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-6

Figure B.6 Percent of population below/above median income of study area. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-7

Figure B.7 Percentages of persons receiving public assistance income. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-8

Figure B.8 Percent of housing units that are mobile homes. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-9

Figure B.9 Percent of housing built before 1970. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-10

Figure B.10 Percent of housing units reporting no vehicle. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-11

Figure B.11 Percent of housing units with a second mortgage or home equity loan. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting

B-12

Figure B.12 Number of building permits issued, 2002. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix B: Additional Data on Social and Economic Setting 

B-13

Figure B.13 Percent change in building permits issued, 1997 to 2002. 

Source: U.S. Census Bureau; ESRI, Inc.; National Transportation Safety Bureau. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix C: Additional Rail Data 

C-1

Appendix C: Additional Rail Data 

Table C.1 Freight rail facilities in the Gulf Coast study area. 

Name Mode Type City State Gridcode 

Kansas City Southern-Metairie-LA Rail & Truck Metairie LA 0 

Larsen Intermodal, Inc.-Metairie-LA Rail & Truck Metairie LA 0 

New Orleans Cold Storage & Warehouse Company, Ltd Rail & Truck Metairie LA 0 

Port of Gulfport Truck - Port – Rail Gulfport MS 0 

Port of Galveston Truck - Port – Rail Galveston TX 0 

NS-New Orleans-LA Rail & Truck New Orleans LA 1 

Up-Avondale-La-Intermodal Facility Rail & Truck Avondale LA 1 

Port of Freeport Truck - Port – Rail Freeport TX 1 

Dry Storage Corporation of Louisiana Rail & Truck Kenner LA 2 

DSC Logistics-Kenner-LA Rail & Truck Kenner LA 2 

Yellow-New Orleans-LA Terminal Rail & Truck New Orleans LA 2 

BNSF-New Orleans-LA Rail & Truck Westwego LA 3 

BNSF-New Orleans-LA-539 Bridge Rail & Truck Westwego LA 3 

BNSF-New Orleans-LA-Intermodal Facility Rail & Truck New Orleans LA 3 

Intermodal Cartage Company-New Orleans-LA Truck - Port – Rail New Orleans LA 3 

Transflo-New Orleans-LA Rail & Truck New Orleans LA 3 

BNSF-Avondale-LA-101 Avonda Rail & Truck Avondale LA 4 

Down South Transfer, Inc.-Avondale-LA Rail & Truck Avondale LA 4 

Port of New Orleans Truck - Port – Rail New Orleans LA 4 

CSX Intermodal-New Orleans-LA Rail & Truck New Orleans LA 5 

Dupuy Storage and Forwarding Corporation Rail & Truck New Orleans LA 5 

Port of Iberia Truck - Port – Rail New Iberia LA 5 

BNSF-Mobile-AL Rail & Truck Mobile AL 6 

CN-Mobile-AL Truck - Port – Rail Mobile AL 6 

Miller Transporters, Inc.-Mobile-AL Rail & Truck Prichard AL 6 

CN-New Orleans-LA Truck - Port – Rail New Orleans LA 6 

Continental Grain Co.-Westwego-LA Rail & Truck Westwego LA 6 

Hayes Dockside, Inc.-New Orleans-LA Rail & Truck New Orleans LA 6 

Illinois Central Railroad-New Orleans-LA Rail & Truck New Orleans LA 6 

Lake Charles Harbor and Terminal District-Lake CHA Rail & Truck Lake Charles LA 6 

LST (Floating Elevator)-Belle Chasse-LA Rail & Truck Belle Chasse LA 6 

NS Independent Bulk Transfer Terminal-Arabi-LA Rail & Truck Arabi LA 6 

Port of Lake Charles Rail & Port Lake Charles LA 6 

Port of South Louisiana Rail & Port Laplace LA 6 

Port of Pascagoula Truck - Port – Rail Pascagoula MS 6 

Houston Fuel Oil Terminal Co.-Houston-TX Rail & Truck Houston TX 6 

Miller Transporters, Inc.-Beaumont-TX Rail & Truck Beaumont TX 6 

Port Arthur-TX Rail & Truck Port Arthur TX 6 

Port of Orange Truck - Port – Rail Orange TX 6 

Port of Port Arthur Truck - Port – Rail Port Arthur TX 6 

Mobile Moving and Storage Rail & Truck Mobile AL 7 

Yellow-Mobile-AL Terminal Rail & Truck Mobile AL 7 

Aimcor Galveston Marine Terminal-Texas City-TX Rail & Truck Texas City TX 7 

ASW Supply Chain Services, LLC-Beaumont-TX Truck - Port – Rail Beaumont TX 7 

GATX Terminals Corporation-Galena Park-TX Rail & Truck Galena Park TX 7 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix C: Additional Rail Data 

C-2 

Table C.1 Freight rail facilities in the Gulf Coast study area (continued). 

Name Mode Type City State Gridcode 

PCI Transportation, Inc.-Houston-TX Rail & Truck Houston TX 7 

Port of Beaumont Truck - Port – Rail Beaumont TX 7 

UP-Laporte-TX Rail & Truck Strane TX 7 

Walton Barge Terminal-Houston-TX Truck - Port – Rail Houston TX 7 

Wilson Warehouse Co. of Texas, Inc.-Beaumont-TX Rail & Truck Beaumont TX 7 

Yellow-Beaumont-TX Terminal Truck - Port – Rail Beaumont TX 7 

Cargill Marketing Co. Inc. Truck - Port – Rail Eight Mile AL 8 

Meador Warehousing and Distribution, Inc.-Mobile-A Rail & Truck Mobile AL 8 

The Finch Companies-Mobile-AL Rail & Truck Mobile AL 8 

Acme Transfer-Baton Rouge-LA Rail & Truck Baton Rouge LA 8 

Agway Systems Inc. Rail & Truck Baton Rouge LA 8 

Branch Warehousing and Distribution Center, Inc.-l Rail & Truck Lafayette LA 8 

Innovative Waste Systems, Inc-Baton Rouge-LA Rail & Truck Baton Rouge LA 8 

Miller Transporters, Inc.-Baton Rouge-LA Rail & Truck Baton Rouge LA 8 

Port Manchac Distribution Center Rail & Truck Ponchatoula LA 8 

Yellow-Layfayette-La Terminal Rail & Truck Broussard LA 8 

Miller Transporters, Inc.-Hattiesburg-MS Rail & Truck Hattiesburg MS 8 

Miller Transporters, Inc.-Lumberton-MS Rail & Truck Lumberton MS 8 

Yellow-Gulfport-MS Terminal Rail & Truck Gulfport MS 8 

Adams Distribution Center, Inc.-Houston-TX Rail & Truck Houston TX 8 

BNSF-Houston-TX Rail & Truck Houston TX 8 

BNSF-Houston-TX-10000 Wal Rail & Truck Houston TX 8 

BNSF-Houston-TX-5500 Walli Rail & Truck Houston TX 8 

Care Terminal Truck - Port – Rail Houston TX 8 

Charles Emmons Pulpwood Co.-Cleveland-TX Rail & Truck Cleveland TX 8 

CSX Intermodal-Houston-TX Rail & Truck Houston TX 8 

General Stevedores, Inc.-Houston-TX Rail & Truck Houston TX 8 

Gulf Winds International, Inc.-Mykawa-TX Rail & Truck Mykawa TX 8 

Guthrie Lumber Sales Inc.-Houston-TX Rail & Truck Houston TX 8 

Intercontinental Terminals Co.-Houston-TX Rail & Truck Houston TX 8 

Intermodal Cartage Company-Houston-TX Truck - Port – Rail Houston TX 8 

International Distribution Corp.-Houston-TX Rail & Truck Houston TX 8 

MCC Transport, Inc.-Houston-TX Rail & Truck Houston TX 8 

Miller Transporters, Inc.-Houston-TX Rail & Truck Houston TX 8 

Oil Tanking Houston, Inc.-Houston-TX Rail & Truck Houston TX 8 

Palmer Logistics-Houston-TX Rail & Truck Houston TX 8 

Port of Houston Authority Truck - Port – Rail Houston TX 8 

Quality Carriers-Houston-TX Rail & Truck Houston TX 8 

South Coast Terminals, l.P.-Houston-TX-3730fm 196 Rail & Truck Houston TX 8 

Southern Warehouse Corporation-Houston-TX Rail & Truck Houston TX 8 

Tencon Industries, Inc.-Houston-TX Rail & Truck Houston TX 8 

Texas Rice Inc. Rail & Truck Houston TX 8 

Thompson Cargo Specialists, Inc.-Houston-TX Rail & Truck Houston TX 8 

Union Pacific Bulk Tainer Service-Spring-TX Rail & Truck Spring TX 8 

United DC, Inc Corporate Headquaters-Houston-TX894 Rail & Truck Houston TX 8 

United DC, Inc.-Houston-TX-1200 Lathr Rail & Truck Houston TX 8 

UP-Houston-TX-5500 Rail & Truck Houston TX 8 

Western Intermodal Services, Ltd.-Houston-TX Rail & Truck Houston TX 8 

Yellow-Houston-TX Terminal Truck - Port – Rail Houston TX 8 

Source: National Transportation Atlas Database (BTS, 2004). 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix C: Additional Rail Data 

C-3

Table C.2 Amtrak facilities in the Gulf Coast study area. 

Station/City State Gridcode 

Mobile AL 6 

Lake Charles LA 6 

New Orleans LA 6 

Schriever LA 6 

Slidell LA 6 

Pascagoula MS 6 

Beaumont TX 6 

Galveston TX 6 

Lamarque TX 6 

New Iberia LA 7 

Bay St. Louis MS 7 

Biloxi MS 7 

Bay Minette AL 8 

Baton Rouge LA 8 

Hammond LA 8 

Lafayette LA 8 

Gulfport MS 8 

Hattiesburg MS 8 

Picayune MS 8 

Houston TX 8 

South Houston TX 8 

Source: National Transportation Atlas Database (BTS, 2004). 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix D: Water Balance Model Procedures 

D-1

Appendix D: Water Balance 

Model Procedures 

Temperature and precipitation data were either the calculated historical values for the study 

area or the forecast-modified values under Special Report on Emissions Scenarios (SRES) 

scenario A1B. Reference evapotranspiration (ETo), was calculated by using the Turc 

(1961) model (Jensen et al., 1997; Fontenot, 2004). Turc was selected for use over the 

original Thornthwaite model (as described in Dingman 2002) because of its ability to more 

closely simulate FAO-56 Penman-Monteith ETo with a limited set of meteorological data 

(Fontenot, 2004). Allen (2003) defined the Turc equation for operational use: 

λ

8856.23 50

15

013.0 +

+ = S

mean

mean

TO

R

T

T

aET (1) 

where ETo is evapotranspiration (mm day-1), Tmean is the mean daily air temperature (°C), 

Rs is solar radiation (MJ m-2 day-1), and λ is the latent heat of vaporization (MJ kg-1). The 

coefficient aT is a humidity-based value. If the mean daily relative humidity (RHmean) is 

greater than or equal to 50 percent, then aT = 1.0. If the mean daily relative humidity is less 

than 50 percent, then aT has the value of: 

70

50 1 mean

T

RH

a − += (2)

Humidity data (historical or forecasted) were not available for the study area, so the 

assumption was made that the dew point temperature was equal to the mean monthly 

minimum temperature. This procedure is recommended by Allen et al. (1998) for 

approximating daily humidity values when measured values are not available. Solar 

radiation (Rs) was estimated by using the Hargreaves model as described by Allen et al. 

(1998): 

RSs MAX RTTkR aMIN = ( − ) (3) 

where Rs is the solar radiation as stated above, kRS is an adjustment coefficient, TMAX and 

TMIN are the mean daily maximum and minimum air temperatures (°C), and Ra is 

extraterrestrial radiation (MJ m-2 day-1). A value of 0.19 was used for kRS as suggested by 

Allen et al. (1998) for use in coastal locations. The Turc model was run by using the 

monthly temperature data and radiation data for the 15th – the midpoint – of each month. 

The values were then multiplied by the appropriate number of days in each month to create 

a monthly value for ETo. For simplicity, leap days were not included. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix D: Water Balance Model Procedures 

D-2 

After the basic input variables were prepared, the data were entered into the water balance 

model. First, by using the temperature data, the monthly precipitation was partitioned into 

rain and snow components, where: 

PFRAIN MMM •= (4)

( ) M PF MM SNOW 1 •−= (5) 

Where PM is the monthly precipitation and FM is a melt factor that is computed by using the 

following method: 

If TM ≤ 0° C: FM = 0 

If 0° C < TM < 6° C: FM = 0.167· TM 

If TM ≥ 6° C: FM = 1 (6) 

where TM is the mean monthly temperature (Dingman, 2002). FM also is used to determine 

the monthly snowmelt amount: 

( ) FMELT MM PACK m 1 + SNOWm •= − (7) 

with PACKm-1 being the water equivalent of the snow pack at the end of the previous 

month and SNOWm being the snow fall total of the current month. The previous month’s 

pack amount is calculated as: 

() () 1

2 1 1 − PACK m M M M •−+•−= PACKFPF m (8) 

The overall hydrological input into the model is defined by WM as: 

M RAINW m += MELTm (9) 

In this study, the probability of the study region having any significant snow amounts is 

low, but the variable was included to provide for the possibility in the forecasted model 

runs. 

Changes in soil moisture are calculated by using the following logic. If WM ≥ ETo, 

monthly evapotranspiration (ETM) occurs at the ETo rate. If ETM equals ETo, then soil 

moisture would increase or remain steady if the soil moisture already is at field capacity 

(Dingman, 2002). For the purposes of this study, field capacity (SOILMAX) has been set to 

150 mm (5.9 in). The monthly value for soil moisture is therefore: 

{ } [ ] ( ) SOILM M ETW O SOILm SOILMAX min , = +− −1 (10) 

where the soil moisture value is the lesser of the two values in the equation (Dingman, 

2002). If WM is less than ETo, then ETM is equal to the hydrological input (WM) and a 

drying factor: 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix D: Water Balance Model Procedures 

D-3

⎪⎭

⎪

⎬

⎫

⎪⎩

⎪

⎨

⎧

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ − += −−• −

MAX

OM M

M M m SOIL

WET

WET SOIL 1 exp1 (11)

where ETOM is the monthly Turc ETO value (Dingman, 2002). 

After computing soil moisture change, any excess water in the budget was declared as 

surplus. The monthly surplus parameter is synonymous with runoff in these wetland 

environments, as long lags are not common between the generation of surplus water and 

the resultant streamflow. If WM does not meet the environmental demand, then a deficit is 

created until WM meets the environmental demand. In this study, we retained surplus as an 

index for runoff and dismissed the modeled runoff term as invalid. 

 References 

Allen, R.G., 2003: REF-ET User’s Guide. University of Idaho Kimberly Research 

Stations: Kimberly, Idaho. 

Allen, R.G., L.S. Pereira, D. Raes, and M. Smith, 1998: Crop Evapotranspiration – 

Guidelines for Computing Crop Water Requirements. FAO Irrigation and 

Drainage Paper 56. Food and Agriculture Organization. Rome. 

Dingman, S.L., 2002: Physical Hydrology, 2nd Ed.: Upper Saddle River, New Jersey. 

Prentice Hall. 

Fontenot, R., 2004: An Evaluation of Reference Evapotranspiration Models in 

Louisiana. M.N.S. Thesis, Department of Geography and Anthropology, 

Louisiana State University. 

Jensen, D.T., G.H. Hargreaves, B. Temesgen, and R.G. Allen. 1997: Computation of 

ETo under Nonideal Conditions. Journal of Irrigation and Drainage Engineering 

123(5):394-400 

Turc, L., 1961: Evaluation des besoins en eau d’irrigation, evapotranspiration 

potentielle, formule climatique simplifee et mise a jour. (In French). Annales 

Agronomiques 12(1):13-49.

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix E: HURASIM Model Description 

E-1

Appendix E: 

HURASIM Model Description 

HURASIM is a spatial simulation model of hurricane structure and circulation for 

reconstructing estimated windforce and vectors of past hurricanes. The HURASIM model 

generates a matrix of storm characteristics (i.e., quadrant, windspeed, and direction) within 

discrete spatial units and time intervals specified by the user for any specific storm or set of 

storms. HURASIM recreates the spatial structure of past hurricanes based on a tangential 

wind function, inflow angle offset, forward speed, and radius of maximum winds. 

Figure E.1 (below) shows the graphic user interface of the HURASIM model for a 

windfield reconstruction of Hurricane Katrina (2005) making landfall southeast of New 

Orleans, LA. Data input for the model includes tracking information of storm position, 

latitude and longitude, and maximum sustained wind speed every six hours or less. The 

model offers a suite of mathematical functions and parameter sets for the tangential wind 

profile taken from other hurricane studies (Harris, 1963; Bretschneiger and Tamaye, 1976; 

Neumann, 1987; Kjerfve et al., 1986; Boose et al., 1994). The user can specify the set of 

functions that provide more or less robust constructions of the range and extent of 

estimated winds. 

Model output is user-specified for given geographic locations assigned by a given point or 

boundary area. Latitude and longitude for each study site location was supplied to the 

model to create a log of hurricane activity at 15-minute intervals for predicted winds above 

30 mi/h for the period of record (1851-2003). The model estimates a suite of storm 

characteristics (i.e., quadrant, wind speed, and direction) within discrete spatial units and 

time intervals specified by the user for designated storms, years, and study site locations. 

Profiles of estimated wind conditions for a given site application are stored by year and 

storm. Time intervals of storm reposition and speed for this study were generated every 15 

minutes. Minimum conditions of windspeed or distance can be set to parse the data output 

if warranted. In this study, windspeed estimates for any point or grid location were 

retained for further analysis if greater than 30 mi/h or tropical depression status. 

HURASIM has been used extensively for field and modeling studies to relate biological 

response to hurricane forcing. HURASIM model output from Hurricane Andrew was 

correlated with field data to construct data tables of damage probabilities by site and 

species and to determine critical windspeeds and vectors of tree mortality and injury 

(Doyle et al., 1995a, 1995b). HURASIM also has been applied to reconstruct probable 

windfields of past hurricanes for remote field locations and correlated with tree-ring growth 

patterns and direction of leaning trees and downed logs (Doyle and Gorham, 1996). 

HURASIM also has been used to construct landscape templates of past hurricane activity 

that are linked with landscape simulation models of coastal habitat (Doyle and Girod, 

1997). 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix E: HURASIM Model Description 

E-2 

 References 

Boose, E.R., 1994: Hurricane impacts to tropical and temperate forest landscapes. 

Ecological Monographs 64:369-400. 

Bretschneigder, C.L. and E.E. Tamaye, 1976: Hurricane wind and wave forecasting 

techniques. In: Proceedings of the 15th Coastal Engineering Conference, held 

Honolulu, Hawaii, July 11-17, (ASCE), Chapter 13, pages 202-237. 

Doyle, T.W., B.D. Keeland, L.E. Gorham, and D.J. Johnson, 1995a: Structural impact of 

Hurricane Andrew on forested wetlands of the Atchafalaya Basin in coastal 

Louisiana. Journal of Coastal Research 18:354-364. 

Doyle, T.W., T.J. Smith III, and M.B. Robblee, 1995b: Wind damage effects of Hurricane 

Andrew on mangrove communities along the southwest coast of Florida, USA. 

Journal of Coastal Research 18: 144-159. 

Doyle, T.W. and L.E. Gorham, 1996: Detecting hurricane impact and recovery from tree 

rings. In: J.S. Dean, Meko, D.M., and Swetnam, T.W., Tree-Rings, Environment and 

Humanity, Radiocarbon Press, Tucson, Arizona. Radiocarbon 1996, pages 405-412. 

Doyle, T.W. and G. Girod, 1997: The frequency and intensity of Atlantic hurricanes and 

their influence on the structure of south Florida mangrove communities. Chapter 7. 

pages 111-128. In: H. Diaz and R. Pulwarty (eds.), Hurricanes, Climatic Change and 

Socioeconomic Impacts: A Current Perspective, Westview Press, New York, New 

York, pages 325. 

Harris, D.L., 1963: Characteristics of the hurricane storm surge. U. S. Department of 

Commerce, Technical Paper No. 48, Washington, D.C., page 138. 

Neumann, C.J., 1987: The National Hurricane Center risk analysis program (HURISK). 

NOAA Technical Memorandum NWS NHC 38, Washington D.C., page 56. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix E: HURASIM Model Description 

E-3

Figure E.1 Graphic user interface of the HURASIM model displaying storm 

track and windfield reconstruction of Hurricane Katrina (2005) 

at landfall south of New Orleans, LA. Grid cell color schemes 

represent different categories of storm strength and a directional 

line of wind direction. 

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-1

Appendix F: 

Projecting Future Sea Level Rise 

with the SLRRP Model 

The Sea Level Rise Rectification Program (SLRRP) is a software package designed with a 

user-friendly interface to generate a suite of future sea level projections from various GCM 

models and scenario outputs obtained from the Intergovernmental Panel on Climate 

Change (IPCC) (2001). The SLRRP model allows the user to select a region-based tide 

station, GCM model, and SRES emissions scenario to generate a graph and output file of 

future sea level change. SLRRP rectifies the historical tide record and future eustatic sea 

level rise into a common datum (default = North American Vertical Datum of 1988 

[NAVD88]) to facilitate comparison with landbased features and elevations. The SLRRP 

model generates a sea level prediction by wrapping the historical mean monthly records for 

the period of record for all future years up to year 2100. Because the historical record 

retains the long-term trend of local subsidence and historical eustatic change, an adjustment 

of removing the historical eustatic rate is accomplished before adding the predicted eustatic 

sea level rise based on a selected IPCC model and scenario. SLRRP uses a historical 

eustatic sea level rate of 1.8 mm/year (0.071 in) conferred by several sources as the best 

estimate for the global-mean since 1963 (IPCC, 2001; Douglas, 1997). 

The SLRRP model uses a series of sequential pop-up windows to facilitate user selection of 

GCM models, scenarios, and manual entries for projecting future sea levels 

(figures F.1-F.3). The SLRRP and CoastCLIM models generate similar eustatic 

projections, but SLRRP retains the local tidal fluctuations that will contribute to short-term 

flooding above mean tides. The advantage of using the historical record includes the 

retention of the local variability and seasonality of sea level heights and the interannual 

variability and long-term climatic autocorrelation. 

The program gives the user options for saving graphical and digital formats of SLRRP 

predictions and generating a supplemental graph to visualize the timing and extent of 

yearly flooding potential for a given elevation (NAVD88) for a transportation feature. 

After generating a future sea level projection, the user can execute a seawater inundation 

option that builds another graph that plots the timing and rate of flooding for a selected 

land elevation (figure F.4). In effect, the model shows the prospective data and time period 

for which sea level will overtop a given landscape feature under a future changing climate. 

Flooding potential is the percentage of months within a year when there is inundation by 

seawater at a select land elevation determined by the user. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-2 

 References 

Douglas, B.C. 1997. Global sea rise: A redetermination. Surveys in Geophysics, 

Volume 18, pages 279-292. 

IPCC, 2001: Climate Change 2001: Impacts, Adaptation, and Vulnerability. 

Contribution of Working Group II to the Third Assessment Report of the 

Intergovernmental Panel on Climate Change [J.J. McCarthy, O.F. Canziani, N.A. 

Leary, et al. (Eds.)], New York, New York: Cambridge University Press. Page 944 

(Available on-line at http://www.ipcc.ch/). 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-3

Figure F.1 User interface and simulated graph of historical sea level rise 

from a sample SLRRP model application displaying the pop-up 

windows for selecting tide gauge stations and constructing a sea 

level function based on local subsidence. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-4 

Figure F.2 User interface and simulated graph of historical sea level rise 

from a sample SLRRP model application displaying the pop-up 

window for selecting a GCM model and SRES emissions scenario. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-5

Figure F.3 User interface and simulated graph of future sea level rise from a 

sample SLRRP model application displaying the historical trend 

line, datum relationship, and maximum historical storm surge 

stage for the selected tide gauge location. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Appendix F: Projecting Future Sea Level Rise with the SLRRP Model 

F-6 

Figure F.4 Sample flood graph displaying flood timing and extent based on 

the hydroperiod or percent of days within a calendar year that 

flooding is likely to occur for a given land elevation and sea level 

rise projection. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

List of Selected Acronyms 

List of Selected Acronyms 

AASHTO American Association of State and Highway Transportation Officials 

APTA American Public Transit Association 

BRT Bus Rapid Transit 

CCSP Climate Change Science Program 

CDIAC Carbon Dioxide Information Analysis Center 

CVI Coastal Vulnerability Index 

DEM Digital Elevation Model 

DOT Department of Transportation 

ENSO El Nino-Southern Oscillation 

FAA Federal Aviation Administration 

FHWA Federal Highway Administration 

FRA Federal Railroad Administration 

FTA Federal Transit Administration 

GCM General Circulation Model 

HURDAT HURricane DATabase 

IPCC Intergovernmental Panel on Climate Change 

MARAD Maritime Administration 

MPO Metropolitan Planning Organization 

NAVD88 North American Vertical Datum 88 

NBI National Bridge Inventory 

NED National Elevation Dataset 

NGVD National Geodetic Vertical Datum 

NHC National Hurricane Center 

NHS National Highway System 

NLCD National Land Cover Dataset 

NTD National Transit Database 

PDF Probability Density Function 

PHMSA Pipeline and Hazardous Materials Safety Administration 

SLOSH Sea, Lake, and Overland Surges from Hurricanes 

SLRRP Sea Level Rise Rectification Program 

SRES Special Report on Emissions Scenarios 

SST Sea Surface Temperature 

USCDD U.S. Climate Division Dataset 

USGS United States Geological Survey 

USHCN U.S. Historic Climate Network 

VMT Vehicle Miles of Travel 

WGNE-CMIP3 Working Group on Numerical Experimentation Coupled Model Intercomparison Project 

Phase 3 

Acronyms-1

Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-1

Glossary of Terms 

Accretion 

The process of soil buildup, generally through deposition. 

Adaptation 

Actions taken to reduce the vulnerability of natural and human systems against actual or 

expected climate change effects. Various types of adaptation can be distinguished, including 

anticipatory, autonomous, and planned adaptation. 

• Anticipatory Adaptation – Adaptation that takes place before impacts of climate 

change are observed. Also referred to as proactive adaptation. 

• Autonomous Adaptation – Adaptation that does not constitute a conscious response to 

climatic stimuli but is triggered by ecological changes in natural systems and by market 

or welfare changes in human systems. Also referred to as spontaneous adaptation. 

• Planned Adaptation – Adaptation that is the result of a deliberate policy decision, 

based on an awareness that conditions have changed or are about to change and that 

action is required to return to, maintain, or achieve a desired state. 

Adaptation Assessment 

The practice of identifying options to adapt to climate change and evaluating them in terms 

of criteria such as availability, benefits, costs, effectiveness, efficiency, and feasibility. 

Adaptation Benefits 

The avoided damage costs or the accrued benefits following the adoption and implementation of adaptation measures. 

Adaptation Costs

Costs of planning, preparing for, facilitating, and implementing adaptation measures, 

including transition costs. 

Adaptive Capacity 

The ability of a system to adjust to climate change (including climate variability and 

extremes) to moderate potential damages, to take advantage of opportunities, or to cope 

with the consequences. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-2 

Alluvium 

Sand, gravel, and silt deposited by rivers and streams in a valley bottom. 

Anthropogenic 

Resulting from or produced by human beings. 

Arterials 

Major streets or highways, many with multilane or freeway design, serving high-volume 

traffic corridor movements that connect major generators of travel. While they may provide 

access to abutting land, their primary function is to serve traffic moving through the area. 

Atmosphere 

The gaseous envelope surrounding the earth. The dry atmosphere consists almost entirely 

of nitrogen and oxygen, together with trace gases, including carbon dioxide and ozone.

Baseline/Reference 

The baseline (or reference) is the state against which change is measured. It might be a 

“current baseline,” in which case it represents observable, present-day conditions. It might 

also be a “future baseline,” which is a projected set of conditions, excluding the driving 

factor of interest. Alternative interpretations of the reference conditions can give rise to 

multiple baselines.

Basin 

The drainage area of a stream, river, or lake. 

Bus Rapid Transit (BRT) 

A rapid mode of bus transportation that can combine the quality of rail transit and the 

flexibility of buses. There are a broad range of features that can be considered elements of 

a BRT system, including a dedicated bus-only right-of-way, bus lane reserved for buses on 

a major arterial road or freeway, on-line stops or stations (like light rail stations), other 

forms of giving buses priority in traffic, faster passenger boarding, faster fare collection, 

and a system image that is uniquely identifiable. 

Carbon Cycle 

The term used to describe the flow of carbon (in various forms, e.g., carbon dioxide) 

through the atmosphere, ocean, terrestrial biosphere, and lithosphere. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-3

Carbon Dioxide (CO2) 

A naturally occurring gas fixed by photosynthesis into organic matter. A by-product of 

fossil fuel combustion and biomass burning, it is also emitted from land use changes and 

other industrial processes. It is the principal anthropogenic greenhouse gas that affects the 

earth’s radiative balance. It is the reference gas against which other greenhouse gases are 

measured, thus having a global warming potential of one. 

Climate 

Climate in a narrow sense is usually defined as the “average weather,” or more rigorously, 

as the statistical description in terms of the mean and variability of relevant quantities over 

a period of time ranging from months to thousands or millions of years. These quantities 

are most often surface variables such as temperature, precipitation, and wind. Climate in a 

wider sense is the state, including a statistical description, of the climate system. The classical 

period of time is 30 years, as defined by the World Meteorological Organization (WMO). 

Climate Change 

A change in the mean state or variability of the climate, whether due to natural variability 

or as a result of human activity, that persists for an extended period, typically decades or 

longer. This usage differs from that in the United Nations Framework Convention on 

Climate Change (UNFCCC), which defines “climate change” as: “a change of climate 

which is attributed directly or indirectly to human activity that alters the composition of the 

global atmosphere and which is in addition to natural climate variability observed over 

comparable time periods.” Also see climate variability. 

(Climate Change) Impact Assessment 

The practice of identifying and evaluating, in monetary and/or nonmonetary terms, the 

effects of climate change on natural and human systems. 

(Climate Change) Impacts 

The effects of climate change on natural and human systems. Depending on the consideration of adaptation, one can distinguish between potential impacts and residual impacts. 

• Potential Impacts – All impacts that may occur given a projected change in climate, 

without considering adaptation. 

• Residual Impacts – The impacts of climate change that would occur after adaptation. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-4 

Climate Model 

A numerical representation of the climate system based on the physical, chemical, and 

biological properties of its components, their interactions and feedback processes, and 

accounting for all or some of its known properties. The climate system can be represented 

by models of varying complexity (i.e. for any one component or combination of components a hierarchy of models can be identified, differing in such aspects as the number of 

spatial dimensions, the extent to which physical, chemical, or biological processes are 

explicitly represented, or the level at which empirical parameterisations are involved). 

Coupled atmosphere/ocean/sea-ice general circulation models (AOGCM or GCM) provide 

a comprehensive representation of the climate system. More complex models include 

active chemistry and biology. Climate models are applied, as a research tool, to study and 

simulate the climate, but also for operational purposes, including monthly, seasonal, and 

interannual climate predictions.

Climate Prediction 

A climate prediction or climate forecast is the result of an attempt to produce an estimate of 

the actual evolution of the climate in the future; e.g., at seasonal, interannual, or long-term 

time scales. Also see climate projection and climate scenario. 

Climate Projection 

The calculated response of the climate system to emission or concentration scenarios of 

greenhouse gases and aerosols, or radiative forcing scenarios, often based on simulations 

by climate models. Climate projections are distinguished from climate predictions in that 

the former critically depend on the emission/concentration/radiative forcing scenario used, 

and therefore, on highly uncertain assumptions of future socioeconomic and technological 

development. 

Climate Scenario 

A plausible and often simplified representation of the future climate, based on an internally 

consistent set of climatological relationships and assumptions of radiative forcing, typically constructed for explicit use as input to climate change impact models. A “climate 

change scenario” is the difference between a climate scenario and the current climate. 

Climate System 

The climate system is defined by the dynamics and interactions of five major components: 

atmosphere, hydrosphere, cryosphere, land surface, and biosphere. Climate system 

dynamics are driven by both internal and external forcing, such as volcanic eruptions, solar 

variations, or human-induced modifications to the planetary radiative balance, for instance 

via anthropogenic emissions of greenhouse gases and/or land use changes. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-5

Climate Variability 

Climate variability refers to variations in the mean state and other statistics (such as standard deviations, statistics of extremes, etc.) of the climate on all temporal and spatial scales 

beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability) or to variations in natural or anthropogenic external forcing (external variability). Also see climate change. 

Collectors 

In urban areas, streets providing direct access to neighborhoods as well as direct access to 

arterials. In rural areas, routes serving intracounty, rather than statewide travel. 

Commercial Service Airport 

Airport that primarily accommodates scheduled passenger airline service. 

Convection 

Generally, transport of heat and moisture by the movement of a fluid. In meteorology, the 

term is used specifically to describe vertical transport of heat and moisture in the atmosphere, especially by updrafts and downdrafts in an unstable atmosphere. The terms “convection” and “thunderstorms” often are used interchangeably, although thunderstorms are 

only one form of convection. 

Datum 

A reference point or surface against which position measurements are made. A vertical 

datum is used for measuring the elevations of points on the Earth’s surface, while a horizontal datum is used to measure positions on the Earth. 

Downscaling 

A method that derives local- to regional-scale (10 to 100 km) information from larger-scale 

models or data analyses. 

Drought 

The phenomenon that exists when precipitation is significantly below normal recorded levels, causing serious hydrological imbalances that often adversely affect land resources and 

production systems. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-6 

El Niño-Southern Oscillation (ENSO) 

El Niño, in its original sense, is a warmwater current that periodically flows along the coast 

of Ecuador and Peru, disrupting the local fishery. This oceanic event is associated with a 

fluctuation of the intertropical surface pressure pattern and circulation in the Indian and 

Pacific Oceans, called the Southern Oscillation. This coupled atmosphere-ocean phenomenon is collectively known as El Niño-Southern Oscillation. During an El Niño event, the 

prevailing trade winds weaken and the equatorial countercurrent strengthens, causing warm 

surface waters in the Indonesian area to flow eastward to overlie the cold waters of the 

Peruvian current. This event has great impact on the wind, sea surface temperature, and 

precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific 

region and in many other parts of the world. The opposite of an El Niño event is called La 

Niña. 

Emissions Scenario 

A plausible representation of the future development of emissions of substances that are 

potentially radiatively active (e.g., greenhouse gases, aerosols), based on a coherent and 

internally consistent set of assumptions about driving forces (such as demographic and 

socioeconomic development, technological change) and their key relationships. In 1992, 

the IPCC presented a set of emissions scenarios that were used as a basis for the climate 

projections in the Second Assessment Report (IPCC, 1996). These emissions scenarios are 

referred to as the IS92 scenarios. In the IPCC Special Report on Emissions Scenarios 

(SRES) (Nakićenović et al., 2000), new emissions scenarios – the so-called SRES scenarios – were published. 

Enplanements 

The total number of passengers boarding an aircraft, including both originating and connecting passengers. 

Ensemble 

A group of parallel model simulations used for climate projections. Variation of the results 

across the ensemble members gives an estimate of uncertainty. Ensembles made with the 

same model but different initial conditions only characterize the uncertainty associated 

with internal climate variability, whereas multimodel ensembles, including simulations by 

several models also include the impact of model differences. 

Erosion 

The process of removal and transport of soil and rock by weathering, mass wasting, and the 

action of streams, glaciers, waves, winds, and underground water. 

Evaporation 

The transition process from liquid to gaseous state. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-7

Evapotranspiration 

The combined process of water evaporation from the Earth’s surface and transpiration 

from vegetation. 

Exposure 

The combination of stress associated with climate-related change (sea level rise, changes in 

temperature, frequency of severe storms) and the probability, or likelihood, that this stress 

will affect transportation infrastructure. 

Extreme Weather Event 

An event that is rare within its statistical reference distribution at a particular place. Definitions of “rare” vary, but an extreme weather event would normally be as rare as or rarer 

than the 10th or 90th percentile. By definition, the characteristics of what is called “extreme 

weather” may vary from place to place. Extreme weather events may typically include 

floods and droughts. 

Fixed-Route Bus Service 

Service provided on a repetitive, fixed-schedule basis along a specific route with vehicles 

stopping to pick up and deliver passengers to specific locations; each fixed-route trip serves 

the same origins and destinations, unlike demand response and taxicabs. 

Fixed Transit Guideway 

A system of vehicles that can operate only on its own guideway constructed for that purpose 

(e.g., rapid rail, light rail). Federal usage in funding legislation also includes exclusive 

right-of-way bus operations, trolley coaches, and ferryboats as “fixed guideway” transit. 

Freight Handling Facility 

Marine facilities or terminals that handle freight. A given port or port area may contain 

multiple freight-handling facilities. 

General Aviation Airport 

Airport that primarily accommodates aircraft owned by private individuals and businesses. 

General Circulation Model (GCM) 

See climate model. 
Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I 

Glossary of Terms 

Glossary-8 

Greenhouse Effect 

The process in which the absorption of infrared radiation by the atmosphere warms the Earth. 

In common parlance, the term “greenhouse effect” may be used to refer either to the natural 

greenhouse effect, due to naturally occurring greenhouse gases, or to the enhanced (anthropogenic) greenhouse effect, which results from gases emitted as a result of human activities. 

Greenhouse Gas 

Greenhouse gases are those gaseous constituents of the atmosphere, both natural and 

anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum 

of infrared radiation emitted by the Earth’s surface, the atmosphere, and clouds. This property causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide 

(N2O), methane (CH4), and ozone (O3) are the primary greenhouse gases in the Earth’s 

atmosphere. Besides CO2, N2O, and CH4, the Kyoto Protocol deals with the greenhouse 

gases sulfur hexaflouride (SF6), hydrofluorocarbons (HFC), and perfluorocarbons (PFC). 

Gross-Ton Mile 

One ton of equipment or freight moved one mile. 

Hazardous Liquid 

Petroleum, petroleum products, liquefied natural gas (LNG), anhydrous ammonia, or a liquid that is flammable or toxic. 

Humidity 

Generally, a measure of the water vapor content of the air. Popularly, it is used synonymously with relative humidity. 

Hurricane 

A tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, in 

which the maximum one-minute sustained surface wind is 64 knots (74 mph) or greater. 

Industrial Airport 

Airports which can accommodate both commercial and privately owned aircraft and are 

typically used by aircraft service centers, manufacturers, and cargo companies, as well as 

general aviation aircraft. 

Infrastructure 

The basic equipment, utilities, productive enterprises, installations, and services essential 

for the development, operation, and growth of an organization, city, or nation. 
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Integrated Assessment 

An interdisciplinary process of combining, interpreting, and communicating knowledge 

from diverse scientific disciplines so that all relevant aspects of a complex societal issue 

can be evaluated and considered for the benefit of decision making. 

Intermodal Connector 

Highway providing access to intermodal facilities and designated as a National Highway 

System (NHS) Intermodal Connector. 

Intermodal Passenger Terminal 

A passenger terminal that accommodates several modes of transportation, such as intercity 

rail service, intercity bus, commuter rail, intracity rail transit and bus transportation, airport 

limousine service and airline ticket offices, rent-a-car facilities, taxis, private parking, and 

other transportation services. 

Intermodal Transportation 

Use of more than one type of transportation; e.g., transporting a commodity by barge to an 

intermediate point and by truck to destination. Often specifically refers to the use of cargo 

containers that can be interchanged between transport modes (i.e., motor, water, and air 

carriers) and where the equipment is compatible within the multiple systems. 

Interstate Highways 

Limited access, divided facility of at least four lanes designated by the Federal Highway 

Administration as part of the Interstate System, a system of freeways connecting and 

serving the principal cities of the continental United States. 

Invasive Species 

An introduced species that invades natural habitats. 

Land Use 

The total of human activities implemented in a certain land-cover type (a set of human 

actions). The social and economic purposes for which land is managed (e.g., grazing, timber extraction, conservation). 

Lidar (Light Detection and Ranging) 

A remote sensing technology that determines the distance to an object or surface by using 

laser pulses. 

Linguistically Isolated Household 

A household in which no person aged 14 and over speaks English at least “very well.” 
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Local Road 

Roads that provide access to private property or low-volume public facilities. 

Long-Range Transportation Plan (LRTP) 

A 20- to 30-year plan that provides a long-range vision of the future of the surface transportation system, considering all passenger and freight modes and their interrelationships. 

LRTPs are developed by MPOs as part of the Federally mandated planning process. 

Metropolitan Planning Organization (MPO) 

The forum for cooperative transportation decision making for a metropolitan planning area. 

Formed in cooperation with the state, it develops transportation plans and programs for the 

metropolitan area. For each urbanized area, an MPO must be designated by agreement 

between the Governor and local units of government representing 75 percent of the 

affected population (in the metropolitan area), including the central cities or cities as 

defined by the Bureau of the Census or in accordance with procedures established by 

applicable state or local law (23 U.S.C. 134(b)(1)/Federal Transit Act of 1991 Section 

8(b)(1)). 

Mitigation 

An anthropogenic intervention to reduce the anthropogenic forcing of the climate system; it 

includes strategies to reduce greenhouse gas sources and emissions and to enhance greenhouse gas sinks. 

Morphology 

The form and structure of an organism or land form, or any of its parts. 

Nonfreight Marine Facility 

Marine facilities not used for transporting or handling freight. Includes unused berths; 

commercial fishing facilities; vessel construction, repair, and servicing facilities; marine 

construction services; etc. 

Nonlinearity 

A process is called “nonlinear” when there is no simple proportional relation between 

cause and effect. 
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Paratransit 

Comparable transportation service required by the American Disabilities Act (ADA) for 

individuals with disabilities who are unable to use fixed-route transportation systems. 

Usually involves the use of demand-response systems, in which passengers or their agents 

contact a transit operator, who then dispatches a car, van, or bus to pick up the passengers 

and transport them to their destinations (also called “Dial-a-Ride”). 

Partial Duration Series (PDS) 

A series composed of all events during the period of record that exceed some set criterion; 

for example, all floods above a selected base, or all daily rainfalls greater than a specified 

amount. 

Probability Density Function 

A statistical function that shows how the density of possible observations in a population is 

distributed. 

Projection 

The potential evolution of a quality or set of quantities, often computed with the aid of a 

model. Projections are distinguished from predictions in order to emphasize that projections involve assumptions – concerning, for example, future socioeconomic and technological developments that may or may not be realized – and are, therefore, subject to substantial uncertainty. Also see climate projection and climate prediction. 

Radiative Forcing 

Radiative forcing is the change in the net vertical irradiance (expressed in Watts per square 

meter (Wm-2)) at the tropopause due to an internal or external change in the forcing of the 

climate system, such as a change in the concentration of CO2 or the output of the sun. 

Relative Humidity 

A dimensionless ratio, expressed in percent, of the amount of atmospheric moisture present 

relative to the amount that would be present if the air were saturated. Since the latter 

amount is dependent on temperature, relative humidity is a function of both moisture content and temperature. As such, relative humidity by itself does not directly indicate the 

actual amount of atmospheric moisture present. 

Resilience 

The capacity of a system to absorb disturbances and retain essential processes. 

Runoff 

That part of precipitation that does not evaporate and is not transpired. 
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Saffir-Simpson Scale 

A scale from 1 to 5 that describes a hurricane’s strength, where Category 1 is the weakest 

and Category 5 is the strongest hurricane. The categories are defined by wind speed. The 

scale of numbers is based on actual conditions at some time during the life of the storm; as 

the hurricane intensifies or weakens, the scale number is reassessed accordingly. 

Scenario 

A plausible and often simplified description of how the future may develop based on a 

coherent and internally consistent set of assumptions about driving forces and key relationships. Scenarios may be derived from projections but are often based on additional information from other sources, sometimes combined with a “narrative storyline.” Also see 

climate scenario and emissions scenario and Special Report on Emissions Scenarios 

(SRES).

Sea Level Rise 

An increase in the mean level of the ocean. Eustatic sea level rise is a change in global 

average sea level brought about by an increase in the volume of the world ocean. Relative 

sea level rise occurs where there is a local increase in the level of the ocean relative to the 

land, which might be due to ocean rise and/or land-level subsidence. In areas subject to 

rapid land level uplift, relative sea level can fall. 

Sea Surface Temperature 

The mean temperature of the ocean in the upper few meters. 

Socioeconomic Scenarios 

Scenarios concerning future conditions in terms of population, Gross Domestic Product, 

and other socioeconomic factors relevant to understanding the implications of climate 

change. Also see Special Report on Emissions Scenarios (SRES).

Specific Humidity 

In a system of moist air, the ratio of the mass of water vapor to the total mass of the system. 

Special Report on Emissions Scenarios (SRES) 

The storylines and associated population, Gross Domestic Product, and emissions scenarios 

associated with the Special Report on Emissions Scenarios (SRES) (Nakićenović, 2000), 

and the resulting climate change and sea level rise scenarios. Four families of 

socioeconomic scenario (A1, A2, B1, and B2) represent different world futures in two 

distinct dimensions: a focus on economic versus environmental concerns and global versus 

regional development patterns. 
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Storm Surge 

An abnormal rise in sea level accompanying a hurricane or other intense storm, whose 

height is the difference between the observed level of the sea surface and the level that 

would have occurred in the absence of the cyclone. Storm surge is usually estimated by 

subtracting the normal or astronomic tide from the observed storm tide. 

Subsidence 

A sinking down of part of the Earth’s crust, generally due to natural compaction of sediments or from underground excavation (such as the removal of groundwater). 

Surface Runoff 

The water that travels over the soil surface to the nearest surface stream; runoff of a drainage basin that has not passed beneath the surface since precipitation. 

Thermal Expansion 

In connection with sea level rise, this refers to the increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the 

ocean volume and hence an increase in sea level. 

Threshold 

The level of magnitude of a system process at which sudden or rapid change occurs. A 

point or level at which new properties emerge in an ecological, economic, or other system, 

invalidating predictions based on mathematical relationships that apply at lower levels. 

Transpiration 

The evaporation of water vapor from the surfaces of leaves through stomates. 

Transportation Improvement Program (TIP) 

A prioritized program of transportation projects to be implemented in appropriate stages 

over several years (i.e., 3 to 5 years). The projects are recommended from those in the 

transportation systems management element and the long-range element of the planning 

process. This program is required as a condition for a locality to receive Federal transit and 

highway grants. 

Tropical Storm 

A tropical cyclone in which the maximum 1-minute sustained surface wind ranges from 

34 to 63 knots (39 to 73 mph) inclusive. 
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Uncertainty 

An expression of the degree to which a value (e.g., the future state of the climate system) is 

unknown. Uncertainty can result from lack of information or from disagreement about 

what is known or even knowable. It may have many types of sources, from quantifiable 

errors in the data to ambiguously defined concepts or terminology, or uncertain projections 

of human behavior. Uncertainty can therefore be represented by quantitative measures 

(e.g., a range of values calculated by various models) or by qualitative statements (e.g., 

reflecting the judgment of a team of experts). 

United Nations Framework Convention on Climate Change (UNFCCC) 

The UNFCCC was adopted on May 9, 1992, in New York and signed at the 1992 Earth 

Summit in Rio de Janeiro by more than 150 countries and the European Community. Its 

ultimate objective is the “stabilization of greenhouse gas concentrations in the atmosphere 

at a level that would prevent dangerous anthropogenic interference with the climate system.” It contains commitments for all Parties. Under the Convention, Parties included in 

Annex I aim to return greenhouse gas emissions not controlled by the Montreal Protocol to 

1990 levels by the year 2000. The Convention entered in force in March 1994. 

Urbanization 

The conversion of land from a natural state or managed natural state (such as agriculture) 

to cities; a process driven by net rural-to-urban migration through which an increasing percentage of the population in any nation or region come to live in settlements that are 

defined as “urban centers.” 

Vehicle Miles of Travel (VMT) 

A unit to measure vehicle travel made by a private vehicle, such as an automobile, van, 

pickup truck, or motorcycle. Each mile traveled is counted as one vehicle mile, regardless 

of the number of persons in the vehicle. Generally, vehicle miles of travel are reported on 

an annual basis for a large area. 

Vulnerability 

The structural strength and integrity of key facilities or systems and the resulting potential 

for damage and disruption in transportation services from climate change stressors. 
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 References 

American Meteorological Society, accessed 2007: American Meteorological Society 

Glossary of Meteorology. Washington, D.C. Accessible at http://

amsglossary.allenpress.com/glossary.

Bureau of Transportation Statistics (BTS), accessed 2007: BTS Dictionary. U.S. 

Department of Transportation, Washington, D.C. Accessible at http://www.bts.gov/

dictionary/index.xml.

IPCC, 2007: Climate Change 2007: The Physical Science Basis, Summary for PolicyMakers. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. Geneva, Switzerland, 21 pages. 

National Weather Service, accessed 2007: National Weather Service Glossary. National 

Oceanic and Atmospheric Administration, Silver Spring, Maryland. Accessible at 

http://www.weather.gov/glossary/. 

USGS, accessed 2007: USGS Geologic Glossary. Reston, Virginia. Accessible at http://

wrgis.wr.usgs.gov/docs/parks/misc/glossaryAtoC.html. 

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Climate Change Science Program and 

The Subcommittee on Global Change Research 

William J. Brennan, Chair 

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Acting Director, Climate Change Science Program 

Jack Kaye, Vice Chair 

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