National Park Service

U.S. Department of the Interior

Natural Resource Stewardship and Science

Cape Hatteras National Seashore

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2015/964
ON THE COVER

Sea oats are a vital component to dune formation at Cape Hatteras National Seashore.

National Park Service photograph.

THIS PAGE

The sun rises over Cape Point at Cape Hatteras National Seashore.

National Park Service photograph.
Cape Hatteras National Seashore

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2015/964

Courtney A. Schupp

National Park Service

Geologic Resources Division

Geologic Resources Inventory

PO Box 25287

Denver, CO 80225

May 2015

US Department of the Interior

National Park Service

Natural Resource Stewardship and Science

Fort Collins, Colorado
ii NPS Geologic Resources Division

The National Park Service, Natural Resource Stewardship and Science office in Fort 

Collins, Colorado, publishes a range of reports that address natural resource topics.

These reports are of interest and applicability to a broad audience in the National Park 

Service and others in natural resource management, including scientists, conservation 

and environmental constituencies, and the public.

The Natural Resource Report Series is used to disseminate comprehensive information 

and analysis about natural resources and related topics concerning lands managed by 

the National Park Service. The series supports the advancement of science, informed 

decision-making, and the achievement of the National Park Service mission. The series 

also provides a forum for presenting more lengthy results that may not be accepted by 

publications with page limitations.

All manuscripts in the series receive the appropriate level of peer review to ensure that 

the information is scientifically credible, technically accurate, appropriately written for 

the intended audience, and designed and published in a professional manner. This 

report received informal peer review by subject-matter experts who were not directly 

involved in the collection, analysis, or reporting of the data.

Views, statements, findings, conclusions, recommendations, and data in this report do 

not necessarily reflect views and policies of the National Park Service, U.S. Department 

of the Interior. Mention of trade names or commercial products does not constitute 

endorsement or recommendation for use by the U.S. Government.

Printed copies of this report are produced in a limited quantity and they are only 

available as long as the supply lasts. This report is available from the Geologic Resources 

Inventory website (http://www.nature.nps.gov/geology/inventory/

gre_publications.cfm) and the Natural Resource Publications Management website 

(http://www.nature.nps.gov/publications/nrpm/). To receive this report in a format 

optimized for screen readers, please email irma@nps.gov.

Please cite this publication as:

Schupp, C. A. 2015. Cape Hatteras National Seashore: Geologic Resources Inventory 

report. Natural Resource Report NPS/NRSS/GRD/NRR—2015/964. National Park 

Service, Fort Collins, Colorado.

NPS 603/128571, May 2015
CAHA Geologic Resources Inventory Report iii

Contents

Lists of Figures and Tables ........................................................................................... iv

Executive Summary ....................................................................................................... v

Products and Acknowledgments................................................................................. ix

Geologic Setting and Significance................................................................................ 1

Geologic and Environmental Features and Processes ................................................. 9

Oceanographic Conditions.........................................................................................................................................11

Sediment Transport Processes....................................................................................................................................11

Capes and Cape-Associated Shoals ............................................................................................................................13

Inlets .........................................................................................................................................................................14

Estuaries....................................................................................................................................................................17

Freshwater Aquifer ....................................................................................................................................................18

Barrier Island Evolution and Behavior..........................................................................................................................20

Simple and Complex Barrier Island Model...................................................................................................................23

Geologic Influences on Island Habitats .......................................................................................................................25

Barrier Island System Unit Mapping............................................................................................................................26

Barrier Island System Units (East Carolina University Field Survey Map)........................................................................26

Barrier Island System Units (North Carolina Geological Survey Remote Sensing Map)...................................................38

Paleontological Resources..........................................................................................................................................40

Geologic Resource Management Issues ..................................................................... 43

Shoreline Erosion.......................................................................................................................................................43

Coastal Vulnerability and Sea-Level Rise......................................................................................................................44

Hurricane Impacts and Human Responses ..................................................................................................................49

Inlet Modifications.....................................................................................................................................................51

Recreational and Watershed Land Use .......................................................................................................................55

Coastal Engineering and Shoreline Armoring..............................................................................................................60

Highway 12 Transportation Corridor ..........................................................................................................................61

Geomorphic Mapping................................................................................................................................................62

Paleontological Resource Inventory, Monitoring, and Protection .................................................................................62

Additional Information Needs ....................................................................................................................................63

Geologic History .......................................................................................................... 65

Miocene (23 million to 5.3 million years ago) .............................................................................................................65

Pliocene (5.3 million to 2.6 million years ago).............................................................................................................65

Quaternary (2.6 million years ago to present) .............................................................................................................65

Geologic Map Data...................................................................................................... 71

Geologic Maps ..........................................................................................................................................................71

Source Maps..............................................................................................................................................................71

GRI GIS Data..............................................................................................................................................................71

GRI Map Posters........................................................................................................................................................72

Map Unit Properties Tables ........................................................................................................................................72

Use Constraints..........................................................................................................................................................72

Glossary........................................................................................................................ 73

Literature Cited............................................................................................................ 81

Additional References ................................................................................................. 93

Appendix A: Scoping Participants .............................................................................. 94

Appendix B: Geologic Resource Laws, Regulations, and Policies............................. 95

GRI Products CD ................................................................................................ attached

Map Posters and Map Unit Properties Tables.................................................in pocket
iv NPS Geologic Resources Division

List of Figures

Plate 1. Map of Cape Hatteras National Seashore.............................................................................................in pocket

Figure 1. Regional map showing the location of Cape Hatteras National Seashore. .......................................................1

Figure 2. Bathymetry (in meters) and dimensions of the Albemarle-Pamlico Estuarine System........................................2

Figure 3. Water resources and habitat..........................................................................................................................4

Figure 4. Geologic time scale. ......................................................................................................................................5

Figure 5. Cross-sectional topographic view of the marine terraces. ...............................................................................5

Figure 6. General stratigraphic column for Cape Hatteras National Seashore.................................................................6

Figure 7. Location of significant features (table 1) in Cape Hatteras National Seashore. .................................................9

Figure 8. Schematic illustration of overwash fan development. ...................................................................................12

Figure 9. Map of major currents.................................................................................................................................13

Figure 10. Map of potential for new inlet opening. ....................................................................................................14

Figure 11. Map of inlet vulnerability index..................................................................................................................14

Figure 12. Schematic illustrations of inlet formation. ..................................................................................................15

Figure 13. Location and duration of historic and modern inlets along the Outer Banks................................................16

Figure 14. Distribution (wt%) of calcium carbonate content in Pamlico Sound. ...........................................................18

Figure 15. Schematic cross section of a strandplain beach. .........................................................................................19

Figure 16. Sediment size distribution in Pamlico Sound, following the Wentworth classification..................................19

Figure 17. Schematic cross sections illustrating the diversity of strata underlying the Outer Banks. ..............................20

Figure 18. Bathymetric map of Cape Hatteras National Seashore from Oregon Inlet to Hatteras Village.......................21

Figure 19. Schematic cross section showing a regressive shoreface during progradation (sea-level fall) and a 

progressive shoreline during transgression (sea-level rise)............................................................................................23

Figure 20. Diagram showing cross-section profiles and dominant vegetation of the model forming the basic 

framework of the geomorphic mapping presented in this report. ...............................................................................24

Figure 21. Historic shoreline positions. .......................................................................................................................44

Figure 22. Schematic graphic illustrating major causes of sea-level change..................................................................45

Figure 23. Projected sea-level rise by 2100 (in meters). ...............................................................................................46

Figure 24. Map of coastal vulnerability .......................................................................................................................47

Figure 25. Map showing potential coastal responses to three sea-level rise scenarios. .................................................48

Figure 26. Buxton Inlet...............................................................................................................................................52

Figure 27. Inlet formation during Hurricane Isabel. .....................................................................................................52

Figure 28. Elevation and bathymetry of Isabel Inlet.....................................................................................................53

Figure 29. Isabel Inlet transects. .................................................................................................................................53

Figure 30. Oregon Inlet..............................................................................................................................................54

Figure 31. Aerial image of Oregon Inlet, stabilizing terminal groin and revetment, and erosion and accretion 

resulting from the hard stabilization...........................................................................................................................54

Figure 32. Drainage ditches near Cape Hatteras. ........................................................................................................57

Figure 33. Map of polluted (“303(d)”) waterways.......................................................................................................58

Figure 34. Stabilization and relocation........................................................................................................................61

Figure 35. Paleogeographic reconstructions for the northern Albemarle Embayment during the Late 

Pleistocene and Holocene. .........................................................................................................................................67

Figure 36. Paleogeographic reconstructions for the southern Pamlico Basin during the Holocene................................68

List of Tables

Table 1. Significant features at Cape Hatteras National Seashore discussed in this report. ...........................................10

Table 2. Coastal water-quality monitoring criteria used by the NPS Southeast Coast Network......................................18

Table 3. Summary of barrier island system units as mapped by East Carolina University...............................................27

Table 4. Summary of barrier island system units as mapped by the North Carolina Geological Survey..........................38

Table 5. Rates of relative sea-level rise in northeastern North Carolina for the last 18,000 years ..................................45

Table 6. The rate of sea-level rise will determine the responses of coastal wetlands and their driving processes. ..........49

Table 7. The Saffir-Simpson Hurricane Wind Scale .....................................................................................................50

Table 8. Existing and potential stressors that are affecting or may affect Cape Hatteras National Seashore 

habitats.....................................................................................................................................................................56

Table 9. Geology data layers in the Cape Hatteras National Seashore GIS data............................................................72
CAHA Geologic Resources Inventory Report v

Executive Summary

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National 

Park Service (NPS) Inventory and Monitoring Program. The Geologic Resources Division 

of the NPS Natural Resource Stewardship and Science Directorate administers the GRI. 

This report synthesizes discussions from a scoping meeting for Cape Hatteras National 

Seashore (North Carolina) held on 3–5 April 2000 and convened by the Geologic Resources 

Division to determine geologic resources, the status of geologic mapping, and geologic 

resource management issues and needs. It is a companion document to previously 

completed GRI digital geologic map data.

Cape Hatteras National Seashore is part of the North 

Carolina Outer Banks, a barrier island chain within the 

Atlantic Coastal Plain physiographic province. It was 

established to preserve the wild and primitive character 

of the dynamic barrier islands, to protect diverse plant 

and animal communities, and to provide for recreation 

that is compatible with its natural and cultural resources.

Most of the barrier islands are long and narrow, 

separated from the mainland by wide, shallow sounds. 

The islands provide diverse barrier island habitats that 

are controlled and sustained by natural coastal 

geomorphological processes and human modifications. 

These habitats support native mammals, reptiles, 

amphibians, many types of marine invertebrate, and 

several species listed federally as threatened or 

endangered. The park provides important avian 

breeding, migratory, and wintering habitats. The rich and 

productive estuary includes large areas of marshland and 

submerged aquatic vegetation, and the inland forests 

protect freshwater aquifer recharge areas.

The Outer Banks of North Carolina are intimately 

associated with several key periods of US history. 

American Indians were the first inhabitants and

Europeans arrived in 1584. In the early 1800s, 

lighthouses and US Lifesaving Service stations were 

established to support increased maritime traffic. In 

1903, the Wright brothers made their first powered 

flights in Kitty Hawk. Increased road access to the 

islands during the 20th century led to the growth of 

residential and tourist populations on the Outer Banks.

The Outer Banks are geologically young. The geologic 

framework of Cape Hatteras was constructed by the 

cyclic rise and fall of relative sea level. This framework 

controls the sediments available to the modern barrier 

island, and the ways in which the island responds to 

natural and anthropogenic processes. About 5.3 million 

years ago, sea level was much higher and marine 

sediments were deposited across much of what is now 

the coastal plain. During multiple glacial episodes (ice 

ages) beginning 2.6 million years ago, sea level rose and 

fell many times, and rivers incised the previously 

deposited marine strata, leaving a paleotopography that 

controls the estuarine geometry and bathymetry and the 

location of the barrier islands. These paleoriver channels 

were then backfilled and buried by Holocene sediments 

during the last 10,000 years as sea level rose to its present 

level. As a result, the sediments underlying the modern 

barrier island are a complex assemblage of marine, 

coastal, estuarine, riverine, and other Coastal Plain 

deposits, ranging from compact peat and mud to 

unconsolidated to semi-consolidated sands, gravels, and 

shell beds.

Modern coastal processes (storms, waves, tides, 

sediment transport, inlet dynamics, and sea-level change) 

shape the landforms and rework the thick Quaternary 

sediments. Due to the reworking of these older 

sediments, much of the present Outer Banks is less than 

3,000 years old, and some island segments are less than 

500 years old. Storms, waves, and winds continue to 

shape the islands, along with anthropogenic activities 

such as dune construction, nearshore dredging, inlet and 

shoreline stabilization, and beach renourishment.

This report is supported by two digital maps of the 

surficial geology of Cape Hatteras National Seashore, 

each with unique sets of geomorphic units. The map 

developed by Ames and Riggs (2006a–j) and described by 

Riggs and Ames (2006) is based on a model of barrier 

island evolution developed from time-slice, processresponse studies of sequential aerial photography, in 

concert with detailed field surveys. It describes four 

geomorphic groups: beach, overwash-plain, polydemic, 

and anthropogenic features. The map developed by 

Hoffman et al. (2007a–g) shows the classification of 

surficial features based on remotely sensed data. It 

describes four geomorphic groups: intertidal, supratidal, 

relict, and anthropogenic.

This GRI report was written for resource managers to 

support science-informed decision making. It may also 

be useful for interpretation. The report was prepared 

using available geologic information, and the NPS 

Geologic Resources Division conducted no new 

fieldwork in association with its preparation. Chapters of 

the report discuss distinctive geologic and environmental

features and processes within Cape Hatteras National 

Seashore, highlight geologic issues facing resource 

managers, describe the geologic history leading to the 

present-day landscape, and provide information about 

the GRI geologic map data. Posters (in pocket) illustrate 
vi NPS Geologic Resources Division

these data. The Map Unit Properties Tables (in pocket) 

summarize report content for each map unit on the two 

maps.

Noteworthy geologic and environmental features and 

processes at Cape Hatteras National Seashore include 

the following:

• Oceanographic Conditions. The Outer Banks is a 

storm- and wave-dominated barrier island system with 

low tidal ranges.

• Sediment Transport Processes. Waves, wind, and 

storm surge move sediment through the inlets and 

along and across the islands. The longshore transport 

rate is very high. The framework geology controls 

sediment availability and type. New sediment comes 

from the eroding shoreface, updrift beaches, capeassociated shoals, and inlet deltas.

• Capes and Cape-Associated Shoals. Cape Hatteras and 

Diamond Shoals separate two major ocean currents 

and biological regimes. The cold-water Labrador 

Current flows southward to meet the warm-water Gulf 

Stream, which flows northward. Their interaction and 

the resulting oceanographic and atmospheric 

responses are controlled by the geography of the 

continental margin, Cape Hatteras and Diamond 

Shoals, and the underlying geology.

• Inlets. New inlets open during storms, when storm 

surge breaches the island from the ocean or estuarine 

side. Tidal currents deposit sediment, building flood 

and ebb tidal deltas, which are important for the island 

sediment budget, marsh building, and long-term island 

evolution. Inlets are dynamic and essential 

components of barrier islands and associated riverine 

and estuarine systems. Only three modern inlets are 

currently present, but up to 30 inlets have opened and 

closed along the Outer Banks in the last 400 years.

• Estuaries. Pamlico and Roanoke sounds provide fish 

nursery and foraging habitats, and support several 

seagrass species. Water quality is good in most areas, 

but is impacted by septic leachate and other riverine 

pollutant input. Estuarine sediments are derived from 

shoreline erosion, continental shelf, and ongoing 

biogenic production.

• Freshwater Aquifer. The shallow groundwater is 

recharged through rainfall, and is depleted through 

anthropogenic withdrawal, evapotranspiration 

through surface vegetation, and surface drainage from 

uplands. It can also be affected by impoundments and 

drought. These influences can, in turn, alter hydrologic 

processes, wetland function, and vegetation 

community distribution, composition, diversity, and 

structure.

• Barrier Island Evolution and Behavior. The modern 

coastal geomorphology results from interaction among 

the underlying geologic framework, fluctuating rates 

of relative sea-level change, coastal oceanographic 

processes, and anthropogenic modifications.

• Simple and Complex Barrier Island Model. The 

majority of islands at Cape Hatteras National Seashore 

are simple barrier islands, which are young, sediment 

poor, and narrow with low topography. They are 

particularly vulnerable to sea-level rise and 

anthropogenic modifications. Complex barriers are 

older, sediment rich, and wide with high elevations, 

numerous beach ridges, and large dune fields.

• Geologic Influences on Island Habitats. Barrier island 

habitats are controlled by elevation above mean sea 

level, cross-island location relative to the ocean beach, 

and the tidal and salinity characteristics of the adjacent 

ocean, estuarine waters, and shallow groundwater.

• Barrier Island System Units (Field Survey Map). This 

map, one of two maps supporting this GRI, relies on a 

model of barrier island evolution developed from 

time-slice, process-response studies based on aerial 

photography in concert with modern field surveys of 

Riggs and Ames (2006).

• Barrier Island System Units (Remote Sensing Map). 

This map, one of two maps supporting this GRI, relies 

on remotely sensed data and incorporates the fieldsurvey map findings of Hoffman et al. (2007g).

• Paleontological Resources. Quaternary-age fossil 

marine invertebrates, marsh peat, and trees are 

abundant on the beaches of Cape Hatteras National 

Seashore. They are derived from the adjacent 

continental shelf and erosion of older beach and inlet 

sediments that constitute the shoreface seaward of the 

beach. Their ages vary from a few centuries to tens and 

hundreds of thousands of years old.

Geologic issues of particular significance for resource 

management at Cape Hatteras National Seashore were 

identified during a 2000 GRI scoping meeting and 

follow-up discussions. They include the following:

• Shoreline Erosion. Erosion of the ocean and estuarine 

shorelines threatens infrastructure and cultural 

resources. Natural overwash and inlet processes, if 

allowed to occur, would supply new sediment to the 

island interior and to the estuarine shoreline and 

shallow back-barrier shoals, which would in turn 

support development of marsh and seagrass habitat.

• Coastal Vulnerability and Sea-Level Rise. Global sea 

level is rising. Portions of the park are highly 

vulnerable due to their low topography and the high 

rate of relative (local) sea-level rise, which increase the 

rate of shoreline erosion and the potential for 

overwash, inlet formation, and wetland location and 

migration. Impacts will vary along the coast, 

depending on the underlying geologic framework and 

other factors. A considerable increase in sea level may 

cause the geomorphic stability of the barrier islands to 

reach a tipping point, resulting in increased landward 

migration and breaching, reduction in size, and 

possibly even submergence.

• Hurricane Impacts and Human Responses. The park is 

frequently impacted by storm winds, waves, and surges 

that move sand across and off of the islands. Future 

climate change may alter the frequency and intensity 

of storms impacting the barrier islands. Storms erode 

protective dunes and damage Highway 12 through 

overwash, undermining, and inlet formation. In recent 

years, these impacts have been addressed by 
CAHA Geologic Resources Inventory Report vii

immediate inlet infilling, dune restoration, and the 

relocation of overwash deposits back toward the 

ocean. These practices prevent natural increases in 

island elevation and width, as well as their landward 

migration as sea level rises.

• Inlet Modifications. The major inlets through the 

Outer Banks are actively maintained through dredging 

and stabilization to maintain navigability. However, 

new inlets are often closed artificially to protect 

infrastructure. Anthropogenic modifications of an 

inlet, such as dredging and coastal engineering 

structures, disrupt its ability to expand and shrink in 

response to storms, to bypass sediment between 

islands, to exchange sediment between flood and ebb 

tidal deltas, and to migrate laterally.

• Recreational and Watershed Land Use. Natural 

landscape and coastal processes have been disturbed 

by coastal settlement and development, dune 

construction and stabilization, off-road vehicle use, 

stormwater runoff, and nutrient inputs at the local and 

watershed levels.

• Coastal Engineering and Shoreline Armoring. State 

regulations prohibit the construction of hard 

stabilization structures without a special permit. Beach 

nourishment is an expensive and temporary solution 

that is often implemented to maintain beach width and 

protect beachfront development. Relocation and site 

selection are longer-term alternatives to protect 

infrastructure from erosion.

• Highway 12 Transportation Corridor. Highway 12, 

including Bonner Bridge over Oregon Inlet, provides 

the only road access to the park and adjacent island 

communities, but it is very vulnerable to shoreline 

erosion and storm overwash and has been damaged 

repeatedly in the last 50 years. Plans to replace the 

bridge and vulnerable portions of the highway are 

controversial. Longer-term development 

considerations would include new landward bridge 

routes or alternate transportation systems, such as 

ferries.

• Geomorphic Mapping. An understanding of 

geomorphic processes and landform evolution is 

critical to park manager’s ability to prepare for the 

island’s response to coastal processes and its evolution 

throughout the coming decades.

• Paleontological Resource Inventory, Monitoring, and

Protection. A paleontological resource summary was 

produced for the park in 2009. There are a variety of 

challenges to managing fossil resources in a coastal 

park including determination of what constitutes a 

fossil and educating the public about what nonfossil 

materials beachcombers are allowed to collect.

• Additional Information Needs. Efforts to manage and 

protect park resources would benefit from new 

products, including terrestrial and aquatic habitat 

maps, septic system surveys, and assessment of 

estuarine benthic health. A resource stewardship 

strategy has been identified as a future management 

need.
CAHA Geologic Resources Inventory Report ix

Products and Acknowledgments

The NPS Geologic Resources Division partners with institutions such as Colorado State 

University, the US Geological Survey, state geological surveys, local museums, and 

universities to develop GRI products. This chapter describes those products and 

acknowledges contributors to this report.

GRI Products

The objective of the Geologic Resources Inventory is to 

provide geologic map data and pertinent geologic 

information to support resource management and 

science-informed decision making in more than 270 

natural resource parks throughout the National Park 

System. To realize this objective, the GRI team 

undertakes three tasks for each natural resource park:

(1) conduct a scoping meeting and provide a summary

document, (2) provide digital geologic map data in a 

geographic information system (GIS) format, and (3) 

provide a GRI report (this document). These products 

are designed and written for nongeoscientists.

Scoping meetings bring together park staff and geologic 

experts to review and assess available geologic maps, 

develop a geologic mapping plan, and discuss geologic 

features, processes, and resource management issues that 

should be addressed in the GRI report. Following the 

scoping meeting, the GRI map team converts the 

geologic maps identified in the mapping plan to digital 

geologic map data in accordance with the GRI data 

model. After the map is completed, the GRI report team 

uses these data, as well as the scoping summary and 

additional research, to prepare the GRI report.

The compilation and use of natural resource information 

by park managers is called for in the 1998 National Parks 

Omnibus Management Act (section 204), 2006 National 

Park Service Management Policies, and the Natural 

Resources Inventory and Monitoring Guideline (NPS75). The “Additional References” chapter and Appendix 

B provide links to these and other resource management 

documents and information.

Additional information regarding the GRI, including 

contact information, is available at: 

http://www.nature.nps.gov/geology/inventory/. The 

current status and projected completion dates of 

products are available at: http://www.nature.nps.gov/

geology/GRI_DB/Scoping/Quick_Status.aspx.

Acknowledgments

Additional thanks to: Dorothea Ames and Stanley Riggs

(Department of Geologic Sciences, East Carolina 

University), Rebecca Beavers (NPS Geologic Resources 

Division), Katie KellerLynn (Colorado State 

University), Rob Thieler (US Geological Survey), and 

Linda York (NPS Southeast Region). Mark Dowdle

(Cape Hatteras National Seashore) coordinated park 

review of this report. Laura Pickens (Cape Hatteras 

National Seashore) provided updated park boundary file 

for use in report graphics and posters. Trista 

Thornberry-Ehrlich (Colorado State University) 

drafted many of the graphics in this report and wrote a 

previous version of the report. Kathleen Farrell (North 

Carolina Geological Survey) reviewed, and Jeffrey 

Matthews (Write Science Right) edited, a previous 

version of the report.

Author

Courtney A. Schupp (NPS Geologic Resources Division)

Review

Stanley Riggs (East Carolina University)

Dorothea Ames (East Carolina University)

Linda York (NPS Southeast Region)

Darrell Echols (NPS Southeast Region)

Jason Kenworthy (NPS Geologic Resources Division)

Editing

Jennifer Piehl (Write Science Right)

Report Formatting and Distribution

Jason Kenworthy (NPS Geologic Resources Division)

Rebecca Port (NPS Geologic Resources Division)

Source Maps

Dorothea V. Ames and Stanley R. Riggs (East Carolina 

University, detailed geomorphology maps)

Charles W. Hoffman, Brian P. Coffey, and Amy N. Ward 

(North Carolina Geological Survey, geomorphology 

maps)

GRI Digital Geologic Data Production

Stephanie O’Meara (Colorado State University)

GRI Map Poster Design

Kari Lanphier (Colorado State University)

Max Jackl (Colorado State University)

Georgia Hybels (Colorado State University)

GRI Map Poster Review

Georgia Hybels (Colorado State University)

Rebecca Port (NPS Geologic Resources Division)

Jason Kenworthy (NPS Geologic Resources Division)
CAHA Geologic Resources Inventory Report 1

Geologic Setting and Significance

This chapter describes the regional geologic setting of Cape Hatteras National Seashore and 

summarizes connections among geologic resources, other park resources, and park stories.

Park Setting

The Geologic Resource Inventory (GRI) maps created 

for the present report include three sites (plate 1) 

managed as part of the National Park Service (NPS) 

Outer Banks Group and located on the North Carolina 

Outer Banks and the Atlantic coast of North America

(fig. 1). Wright Brothers National Memorial was 

originally designated on 2 March 1927 as Kill Devil Hill 

Monument National Memorial; it was transferred to the 

NPS from the War Department on 10 August 1933 and 

re-designated as Wright Brothers National Memorial on 

1 December 1953 (NPS 2005). The park, which 

commemorates the first successful controlled power 

flight at the site where it occurred in 1903, is located in 

Kill Devil Hills, North Carolina, and comprises 173 ha 

(428 ac; plate 1) (NPS 2005). Fort Raleigh National 

Historic Site is located on 207 ha (513 ac) at the northern 

end of Roanoke Island, which is situated between Bodie 

Island and mainland North Carolina (plate 1). The park, 

authorized on 5 April 1941, preserves and interprets the 

first English colony in North America and the history of 

the many peoples who lived on Roanoke Island.

The present GRI report focuses on the third site, Cape 

Hatteras National Seashore, which was authorized on 17 

August 1937 (Public Law 50 Stat. 669, as amended in 

1940 by Public Law 54 Stat. 702). After several land 

acquisitions, its boundaries were established on 12 

January 1953, making it the first designated national 

seashore. Its stated purpose is to permanently preserve 

the wild and primitive character of the ever-changing 

barrier islands, protect the diverse plant and animal 

communities sustained by coastal island processes, and 

provide for recreational use and enjoyment that are 

compatible with the preservation of the distinctive 

natural and cultural resources of the nation’s first 

national seashore (NPS 2011).

Cape Hatteras National Seashore is a long and narrow 

park that comprises multiple barrier islands (fig. 1; plate 

1). It includes 108 km (67 mi) of beach along the Dare 

and Hyde county coastlines, and composes a portion 

(14,326 ha [35,400 ac]) of the island chain known as the 

North Carolina Outer Banks. The national seashore 

includes portions of Bodie, Hatteras, and Ocracoke 

islands and is bounded by Ocracoke Inlet to the south, 

Whalebone Junction to the north, the Atlantic Ocean to 

the east, and Pamlico Sound to the west. Pamlico Sound 

is connected to Albemarle Sound by Roanoke and 

Croatan sounds, which bound Roanoke Island at Fort 

Raleigh National Historic Site (fig. 1). The boundary of 

Cape Hatteras National Seashore is the mean low tide 

line on the ocean side, and it extends 46 m (150 ft) from 

the shore into Pamlico Sound on the estuarine side 

(Mallin et al. 2006).

Figure 1. Regional map showing the location of Cape 

Hatteras National Seashore. The black box indicates the 

extent of plate 1 (in pocket), a detailed map of Cape 

Hatteras National Seashore (red area). Map by Trista 

Thornberry-Ehrlich (Colorado State University) with 

basemap by Tom Patterson (National Park Service), available 

at: http://www.shadedrelief.com/physical/index.html

(accessed 26 March 2014).

The coastal plain of northeastern North Carolina has 

very low topography (less than 0.06 m elevation per 

horizontal kilometer [0.3 ft/mi]) (Corbett et al. 2008) and 

an average seaward gradient of approximately 0.01°, or 

0.10 m per horizontal kilometer (5.3 ft/mi) (Mallinson et 

al. 2010a). As a result, shoreline recession related to sealevel rise has removed 130 km2 (50 mi2

) of marsh and
2 NPS Geologic Resources Division

Figure 2. Bathymetry (in meters) and dimensions of the Albemarle-Pamlico Estuarine System. Map by Trista ThornberryEhrlich (Colorado State University) after figure 1 in Wells and Kim (1989).
CAHA Geologic Resources Inventory Report 3

estuarine shoreline in northeastern North Carolina in the 

past 25 years (Riggs and Ames 2003). Seaward of the 

Outer Banks barrier islands, the base of the modern 

shoreface occurs at a depth of approximately 15 to 20 m 

(49 to 66 ft) below present sea level (Mallinson et al. 

2010a). The shelf break occurs at a depth of 

approximately 50 m (164 ft) about 20 km (12 mi) east of 

Cape Hatteras (Mallinson et al. 2010a); the slope of the 

ocean floor deepens rapidly from this point to about 50 

to 100 km (31 to 62 mi) offshore (Mallin et al. 2006).

Most islands in the park are less than 400 m (0.25 mi) 

wide (Pendleton et al. 2004), but widths vary from about 

180 m (590 ft) near Hatteras Village to nearly 5 km (3.1 

mi) at Cape Hatteras. Dune crests along Cape Hatteras 

National Seashore can reach elevations of 10 m (33 ft), 

whereas dune toe and winter storm berm elevations are 

fairly constant at about 3 m (10 ft) (Elko et al. 2002). 

Isolated points within inland dune fields reach heights of 

approximately 18 m (60 ft) above sea level (Harris and 

Wilder 1964). Westward, beyond the dune ridges, sand 

flats as wide as 300 m (1,000 ft) slope gently down to the 

sounds. The flats are generally less than 3 m (10 ft) above 

sea level. Immediately adjacent to the sounds, along the 

western shores of most of the barrier islands, are salt 

marshes and some isolated, irregular sand ridges. 

Migrating inlets separate the barrier islands and are 

subject to considerable change during major storms, 

when new inlets may form or old ones may close 

(Winner 1975).

The islands provide diverse barrier island habitats that 

support native mammals, reptiles, amphibians, and many 

types of marine invertebrate. Cape Hatteras National 

Seashore habitats also support several species listed 

federally as threatened or endangered: seabeach 

amaranth (Amaranthus pumilus), piping plover 

(Charadrius melodus), and loggerhead (Caretta caretta), 

green (Chelonia mydas), and leatherback (Dermochelys 

coriacea) sea turtles (NPS 2010). The American Bird 

Conservancy has designated the park as a Globally 

Important Bird Area because it contains important avian 

breeding, migratory, and wintering habitats (NPS 2012). 

It supports 360 documented bird species that use the 

islands’ habitats for nesting, resting, or feeding (NPS 

2011). These populations include species listed by the 

North Carolina Wildlife Resources Commission 

(NCWRC) as of special concern, such as colonial 

waterbirds (least tern [Sterna antillarum], common tern 

[Sterna hirundo], and black skimmer [Rynchops niger]), 

American oystercatcher (Haematopus palliatus), and 

Wilson’s plover (Charadrius wilsonia), and the gull-billed 

tern (Sterna nilotica), which is listed by the NCWRC as 

threatened (NPS 2010).

The Albemarle-Pamlico Estuarine System (fig. 2) is the 

second largest estuary in the United States, containing 

extensive marshes that support a rich and productive 

ecosystem (Corbett et al. 2008). Pamlico Sound is up to 

45 km (28 mi) wide (Corbett et al. 2008). Croatan Sound, 

which connects the Roanoke/Albemarle drainage system 

to Pamlico Sound and the Atlantic Ocean, ranges in 

width from 4.2 km to 8 km (2.6 to 5 mi) and has an 

average depth of 5 m (16 ft), with depths of up to 7.5 m 

(25 ft) in the northwest–southeast-trending channel 

(Riggs et al. 1992; Parham et al. 2007).

Ocracoke, Oregon, and Hatteras inlets affect physical, 

hydrologic, and geomorphic processes within the park. 

Ocracoke Island has significant fresh and brackish water 

resources, including a vast brackish marsh near South 

Point Road, a freshwater marsh near the northern end of 

the island in the vicinity of the ferry terminal, and 

temporary ponds. Tidal creeks (fig. 3A, 3B) are present 

on Ocracoke, Hatteras, and Bodie islands (Mallin et al. 

2006).

Wider and higher portions of the islands support 

maritime forests, such as Buxton Woods on Hatteras 

Island and near Ocracoke Village on Ocracoke Island. 

Approximately one-third of the 405-ha (1,000-ac) 

Buxton Woods is within park boundaries (NPS 2012). 

Buxton Woods contains many freshwater swales, or 

sedges, that serve as important wildlife habitat (fig. 3C) 

(Mallin et al. 2006). The mature broad-leaved evergreen 

forest and shrub (fig. 3D), freshwater marsh, and bog 

habitats of Buxton Woods support a diverse assemblage 

of aquatic, terrestrial, and avian species. Buxton Woods 

also overlies, protects, and provides for recharge of an 

important freshwater aquifer (NPS 2012). Small maritime 

forest is also found in the Bodie Island and Whalebone 

Junction areas.

The Outer Banks of North Carolina are intimately 

associated with several key periods of US history. Native 

Americans were the first inhabitants. Early European 

settlers tried to establish a colonial base on the northern 

end of Roanoke Island in 1584, a settlement now known 

as the Lost Colony; the next significant European 

settlement developed in 1663 on Colington Island 

(Dolan and Lins 1986). As settlement increased, inlets 

became vital transportation routes for maritime traffic, 

which struggled through rough surf and shoals to reach 

the North Carolina coast; the many shipwrecks inspired 

the coast’s nickname, “the graveyard of the Atlantic.” To 

aid coastal navigation, historic lighthouses were built in 

1823 and 1870, and the US Lifesaving Service 

(forerunner to the US Coast Guard) set up a series of 

lifesaving stations on the Outer Banks (Stover 2008). In 

1903, the Wright brothers made their first powered 

flights on the sandy flats of Kitty Hawk. Increased road 

access to the islands led to the growth of residential and 

tourist populations in the Outer Banks. Cape Hatteras 

National Seashore received nearly 2.2 million visitors in 

2014 (National Park Service 2015).

Geologic Setting

The Outer Banks lie along the Atlantic passive 

continental margin, which has experienced little tectonic 

activity since widespread rifting during the Mesozoic Era 

(252 to 66 million years ago) (fig. 4) initiated the 

formation and opening of the Atlantic Ocean. As rifting 

progressed, extensive marine, coastal, and riverine 

deposits infilled the western edge of the Atlantic Basin. A 

wedge-shaped deposit of sediments formed, thickening 

in a seaward direction and attaining a maximum
4 NPS Geologic Resources Division

Figure 3. Water resources and habitat. A,B) Ocracoke, Hatteras, and Bodie islands have significant fresh and brackish water 

resources, including tidal creeks, marshes, and temporary ponds. C) Buxton Woods contains many wetlands and freshwater 

swales, or sedges, that serve as important wildlife habitat. D) Buxton Woods is a mature broad-leaved evergreen forest and 

shrub habitat. Photographs by Matthew McIver (A) and Michael Mallin (B, C, D) (University of North Carolina Wilmington) 

extracted from Mallin et al. (2006), plates 2, 4, 8, 9.

thickness of about 3,000 m (9,800 ft) at Cape Hatteras 

(Lawrence and Hoffman 1993); the sediment includes 

deposits of Cretaceous through Quaternary age (Brown 

et al. 1972).

The geologic framework of Cape Hatteras was 

constructed by the cyclic rise and fall of relative sea level 

(Colquhoun 1969; Richards et al. 1971). This framework 

controls the sediments available to the modern barrier 

island, and the ways in which the island responds to 

natural and anthropogenic processes. Island size and 

shape are largely dependent on sediment supply (Riggs 

and Ames 2006). Some of these earlier sediments have 

been reworked so recently that portions of the Outer 

Banks are less than 500 years old, and the oldest barrier 

island beach ridges on the Outer Banks date to about 

3,000 years before present (Mallinson et al. 2007; Riggs et 

al. 2011).

The surface of the Atlantic Coastal Plain is 

predominantly characterized by a series of welldeveloped paleoshorelines and terraces that step down 

in elevation and decrease in age toward the Atlantic coast 

(fig. 5) (Wells and Kim 1989; Farrell et al. 2003; Tweet et 

al. 2009). Seven river basins dissect the coastal plain, so 

that its low-relief, flat, eastward-dipping coastwise 

terraces are separated by incised valleys with terraced 

borders (Colquhoun 1966). The Suffolk paleoshoreline 

has regional extent and is one of the youngest 

Pleistocene shorelines preserved on the North Carolina 

Coastal Plain.

Between the Cape Lookout High to the south and the 

Norfolk Arch to the north, thick Quaternary deposits fill 

a regional depositional basin called the Albemarle 

Embayment (Ward and Strickland 1985; Riggs et al. 1995, 

2011; Foyle and Oertel 1997). This embayment is 

dissected by Pleistocene river valleys, which incised the 

underlying Pliocene erosion surface and subsequently 

filled with younger coastal and shelf sediments (Riggs et 

al. 1995). Croatan and Roanoke sounds are drowned 

lateral tributary creeks that flowed northward into the 

paleo–Roanoke River (now Albemarle Sound) (Riggs et 

al. 1992). Roanoke Island is a remnant of the interstream 

divide that separated the Roanoke River and Pamlico 

Creek drainages (Parham et al. 2007).

Sea-level cycles and the paleodrainage system deposited 

a complex assemblage of marine, coastal, estuarine, 

fluvial, and other Coastal Plain deposits (fig. 6) 

(Mallinson et al. 2008a). Relict Pleistocene inlets, which 

were infilled when sea level rose, may constitute up to 

75% of Hatteras and Pea Islands (Mallinson et al. 2009). 

Relict flood-tidal delta deposits, which now underlie the 

narrowest portions of the islands, are generally overlain 

by marsh peat and storm overwash sediments; relict 

channel-fill sediments occur under the widest portions 

of the island (Mallinson et al. 2009).
CAHA Geologic Resources Inventory Report 5

Figure 4. Geologic time scale. The divisions of the geologic time scale are organized with the oldest at the bottom and 

youngest at the top. Boundary ages are in millions of years ago (MYA). Major life history and tectonic events occurring in 

North Carolina are included. Bold lines indicate major boundaries between eras. Graphic by Trista Thornberry-Ehrlich 

(Colorado State University), using dates from the International Commission on Stratigraphy 

(http://www.stratigraphy.org/index.php/ics-chart-timescale; accessed 27 April 2015).

Figure 5. Cross-sectional topographic view of the marine terraces (green text) and paleoshorelines (brown text) of the North 

Carolina Coastal Plain. Graphic by Trista Thornberry-Ehrlich, modified after figure 3 in Daniels et al. (1984).
6 NPS Geologic Resources Division

Era Period Epoch Age* Rock/Sediment Unit Description Cenozoic

Quaternary

Holocene 0.01–

present

Barrier island facies (to 6 

m below MSL**)

Fine to medium quartz sand with some 

gravel; peats associated with modern 

marshes and swamp forests.

Estuarine bay facies (6 to 

12 m below MSL)

Old fluvial (river) channels filled with 

coarse fluvial sand and gravel, overlain by

thick accumulations of organic-rich, 

estuarine mud.

Pleistocene

0.078–

0.038

Barrier island sand facies 

(12 to 16 m below MSL).

Clean barrier-island sand, sandy open 

shelf, bay, inlet, and possibly fluvialchannel deposits. Outcrops on the lower 

portion of the lower foreshore and across 

the modern sea floor, and forms part of 

major bathymetrically high features 

known as the Albemarle and Platt shoals

Estuarine bay facies (16 

to 20 m below MSL).

Fossiliferous estuarine mud with oyster 

shells and other estuarine fauna. 

Outcrops on the lower portion of the 

lower foreshore and across the modern 

sea floor. Part of major bathymetrically 

high features known as the Albemarle 

and Platt shoals.

0.18–0.08

Nearshore marine facies, 

underlain by marine 

deposits, underlain by 

marine erosion 

(ravinement) surface (21 

to 35 m below present 

MSL).

Represents period of interglacial sea-level 

rise and transgression. Muddy quartz 

sand with mollusks and a major soil 

profile along the upper surface. Eroded 

and modified by overlying sediment 

sequence.

0.55–0.22

Inner shelf facies (sand 

and shell), underlain by 

estuarine bay facies (silt 

and clay) (35 m to more 

than 50 m below present 

MSL).

Older sequences are separated by 

surfaces created during periods when no 

sediment was deposited, or sediment 

was deposited but later removed through 

erosion. 

0.8-0.55

Muddy, low-oxygen shelf 

deposits (40-43 m below 

present MSL)

Pleistocene interglacial

Marine deposits (43-47 m

below present MSL) Pleistocene glacial 

1.2 – 0.8

Sandy open shelf, bay, 

and inlet deposits (47 –

55 m below present MSL)

Sequence boundary at about 55 m below 

present MSL

Tertiary

Neogene

Pliocene 5.3–2.6

Yorktown Formation (or 

lateral equivalent) (more 

than 55 m below present 

MSL)

Muddy, fine-grained marine sediments 

deposited in reduced-oxygen, open-shelf 

conditions at midshelf depths. 

Paleotopography may control modern 

bathymetric features. Southwardthickening, steeply inclined, southwardprograding beds.

Miocene 23–5.3 none

Inner to middle neritic (shallow marine) 

sand and silty clay beds. Parallel bedding 

with gently dipping beds.

*Age is in millions of years before present and indicates the time spanned by the associated epoch or period. Rock/sediment units obtained in 

drill cores correspond to various epochs and periods, but do not encompass the entire age range, as indicated in the age column.

**MSL = mean sea level.

Figure 6. General stratigraphic column for Cape Hatteras National Seashore. The column is based on interpretations by 

Riggs et al. (1992), Parham et al. (2007), and Culver et al. (2008b) of multiple sediment cores obtained along the barrier 

island from Nags Head to Oregon Inlet, North Carolina. Colors are standard colors approved by the US Geological Survey to 

indicate different time periods on geologic maps.
CAHA Geologic Resources Inventory Report 7

The modern barrier island system of North Carolina 

consists of a thin veneer of modern sands that covers 

marsh peats, tidal-flat muds, fluvial sands and gravels, 

bay-fill sands and muds, flood-tidal delta sands, and 

inlet-fill sands and gravels (Riggs et al. 1995). Coastal 

processes (storms, waves, tides, sediment transport, inlet 

dynamics, and sea-level rise) continue to shape the 

landform and rework the thick Pliocene and Quaternary 

sediments. The morphology of the islands can change 

quickly during major storms due to surge overwash, 

rapid erosion, and inundation (Winner 1975). 

Anthropogenic activities, such as dune construction, 

nearshore dredging, inlet and shoreline stabilization, and 

beach renourishment, also control the ways in which the 

barrier island system evolves.

The dominant sediment size on the barrier islands is 

sand, which is concentrated on beaches, in dunes and 

inlets, and on tidal bars. The sand is composed primarily 

of quartz, with minor amounts of heavy minerals, organic 

matter, and shell debris (Johnson et al. 1986; Tweet et al. 

2009). Finer-grained, muddy deposits are associated with 

back-barrier environments. The present continental 

shelf consists of reworked surficial siliciclastic sands that 

form shelf sand ridges (Swift et al. 1978) interspersed 

with outcrops of Pleistocene calcareous sandstone and 

estuarine mud.

The subaqueous Diamond Shoals extend 15 km (9 mi) 

seaward from Cape Point, at the tip of Cape Hatteras. 

The cape separates two major ocean currents and 

biological regimes: the Labrador Current, which is north 

of the cape and moves cold water southward, and the 

tropical Gulf Stream, which is south of the cape and 

moves warm water northward (Mallinson et al. 2009). 

Alongshore sediment transport is currently directed 

toward the tips of capes (Swift 1976; McNinch and Wells 

1999), and the shoals can move dramatically in response 

to changes in oceanographic conditions (Mallinson et al. 

2009).
CAHA Geologic Resources Inventory Report 9

Geologic and Environmental Features and Processes

This chapter describes noteworthy natural features and processes in Cape Hatteras 

National Seashore. Discussions during the scoping meeting (3–5 April 2000) 

for Cape Hatteras National Seashore provided 

opportunities to develop a list of geologic and 

environmental features and processes operating in the 

park, including the following:

• Oceanographic Conditions

• Sediment Transport Processes

• Capes and Cape-Associated Shoals

• Inlets

• Estuaries

• Freshwater Aquifers

• Barrier Island Behavior and Evolution

• Simple and Complex Barrier Island Model

• Geologic Influences on Island Habitats

• Barrier Island System Units (ECU Field Survey Map)

• Barrier Island System Units (NCGS Remote Sensing 

Map)

• Paleontological Resources

Significant features within Cape Hatteras National 

Seashore mentioned in this text are listed on table 1 and 

mapped on figure 7. See also plate 1 (park map; in 

pocket).

Coastal natural resources are located in a transition zone 

between terrestrial and marine environments, and as 

such, include resources and characteristics of both types 

of environments. Coastal environments—shaped by 

waves, tides, wind, and geology—may include tidal flats, 

estuaries, river deltas, wetlands, dunes, beaches, barrier 

islands, bluffs, headlands, and rocky tidepools. The 

National Park Service manages 85 ocean, coastal, and 

Great Lakes parks with more than 18,000 km (11,200 

miles) of shoreline (Curdts 2011). Of that total, 444 km 

(276 miles) are within Cape Hatteras National Seashore,

1.6 km (1.0 miles) are within Fort Raleigh National 

Historic Site, and none are mapped within Wright 

Brothers National Memorial (Curdts 2011).

More than 120 parks are close to the coast, even though 

some do not manage a shoreline, and are vulnerable to 

sea-level rise, lower lake levels, salt water intrusion, and 

inundation during coastal storms (Beavers et al. in 

review; see “Resource Management Issues” chapter). 

The NPS Geologic Resources Division Coastal Geology 

website, http://nature.nps.gov/geology/

coastal/index.cfm, provides additional information.

Coastal change in the Cape Hatteras region is a product 

of geologic and oceanographic factors in combination

Figure 7. Location of significant features (table 1) in Cape 

Hatteras National Seashore. A) Northern portion. B) 

Southern portion. Map annotated by Jason Kenworthy (NPS 

Geologic Resources Division). Imagery from Esri World 

Imagery basemap layer using imagery Esri, DigitalGlobe, 

GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, 

IGN, IGP, swisstopo, and the GIS User Community.
10 NPS Geologic Resources Division

Table 1. Significant features at Cape Hatteras National Seashore discussed in this report. Features are listed 

from north to south. Refer to figure 7 for location.

Significant Feature Type of Feature Notes

Croatan Sound Estuary Connects the Roanoke/Albemarle drainage system to 

Pamlico Sound and the Atlantic Ocean.

Roanoke Island Island

A remnant of the interstream divide that separated the 

Roanoke River and Pamlico Creek drainages. Site of early 

(1584) European settlement now known as the Lost 

Colony.

Roanoke Sound Estuary Separates Roanoke Island from the barrier island chain.

Whalebone Junction Island section

Former salt marsh islands that were part of the flood tidal

delta for the paleo–Roanoke Inlet, which closed around 

1817.

Bodie Island Island section Supports small maritime forest, elevated dune ridges, and 

freshwater aquifers.

Oregon Inlet Inlet

Inlet stabilization (e.g., terminal groin construction) causes 

downdrift erosion, but provides some protection for the 

current configuration of Highway 12.

Hatteras Flats Estuarine shoals

Broad and shallow platform composed of coalesced relict 

flood tidal deltas and overwash sand shoals. Extends along 

the west side of the barrier islands between Oregon Inlet 

and Ocracoke Island.

Dare Headland Submarine headland Controls morphology of the northern Pamlico Sound in the 

area between Oregon Inlet and Cape Hatteras.

Pea Island Island section

Site of many former inlets, resulting in extensive flood-tidal

delta deposits and overwash sediments. High shoreline 

erosion rate. Vulnerable to future inlet breaching despite 

continued dune construction and renourishment.

Loggerhead Hills Overwash fan

This massive overwash fan on Pea Island covers the flood

tidal delta of Loggerhead Inlet, which was frequently open 

between about 1650 and 1870.

Hatteras Island Island section Has accretionary shoreface, wide beaches, continuous dune 

ridges, and well-developed maritime forest.

Buxton Woods Ridge and swale complex Old section of complex Hatteras Island supports forests, 

freshwater swales, and aquifer.

Wimble Shoals and Kinnakeet 

Shoals Submarine ridges

Offshore hardbottom features composed of carbonatecemented sandstones and mudstones. Ridges influence 

wave refraction and wave setup. Oriented from the northnortheast to the south-southwest along Hatteras Island 

north of the cape.

Diamond Shoals at 

Cape Hatteras Cape-associated shoals Separates two ocean currents, biological regimes, and 

sediment transport directions.

Hatteras Inlet Inlet One of only three inlets along the northern Outer Banks. 

No bridge crosses it. 

Ocracoke Island Island

Supports some fresh- and brackish-water resources and 

limited maritime forest. Interior dunes are isolated single 

ridges. Frequently overwashed.

Ocracoke Inlet Inlet

One of only three inlets along the northern Outer Banks. 

No bridge crosses it. Southern boundary of Cape Hatteras 

National Seashore.

Pamlico Sound Estuary Supports diverse plant and animal communities. Threatened 

by increased pollutant loading.
CAHA Geologic Resources Inventory Report 11

with human modifications and climate-driven changes. 

Major storms often cause changes that may persist for 

weeks to a decade or more (Zhang et al. 2002, 2004; List 

et al. 2006; Riggs and Ames 2007). Complex interactions 

between nearshore sand bodies and underlying geology 

influence beach morphology over time (Riggs et al. 1995; 

Honeycutt and Krantz 2003; McNinch 2004; Browder 

and McNinch 2006; Miselis and McNinch 2006; Schupp 

et al. 2006).

Oceanographic Conditions

The Outer Banks are wave-dominated barrier islands. 

Mean significant wave heights at Cape Hatteras are 1.2 to

1.3 m (3.9 to 4.3 ft), based on data from 1976 through 

1995 (Pendleton et al. 2004). Mean wave period is 6 s,

with a standard deviation of 2.4 s, and the predominant 

wave direction is from south to southeast (Wamsley et al. 

2009). Astronomical tidal range is less than 1 m (3.3 ft), 

based on data from the National Oceanic and 

Atmospheric Administration/National Ocean Service

(NOAA/NOS) ocean tide gauges at the Cape Hatteras 

fishing pier and the Field Research Facility at Duck, 

North Carolina (Pendleton et al. 2004). Storm waves and 

storm surges exceed these average magnitudes and drive 

significant physical changes on the island and in the 

estuary; these forcings are described in detail in the 

“Geologic Resource Management Issues” chapter.

The Gulf Stream off of North Carolina is located 

seaward of the continental shelf-slope break. It moves 

northward toward Cape Hatteras, and its dynamic 

current drives the predominantly counterclockwise 

circulation in Raleigh Bay through frictional forcing. 

Filaments of the Gulf Stream sometimes flow landward 

up onto the shelf, bringing nitrogen-enriched water 

within 10 km (6.2 mi) of the shoreline (Mallin et al. 2006).

At the Cape, the Gulf Stream meets the southwardmoving Labrador Current (see the “Capes and CapeAssociated Shoals” section).

Sediment Transport Processes

The barrier islands at Cape Hatteras National Seashore 

are continuously modified by natural processes and 

human activities (Ames and Riggs 2006j). They are

reshaped by the constant movement of sand by wind, 

waves, and currents (Dolan and Lins 1986).

Shifting shorelines are recorded not only by historical 

maps, but also by the appearance on eroding ocean 

beaches of peat deposits and tree stumps in the surf zone. 

These deposits are remnants of back-barrier marshes and 

forests that grew on the landward side of the barrier 

islands (Dolan and Lins 1986). Steadily rising sea level is 

causing net beach recession, which results in increased 

wave energy on the dunes and subsequent overwash and 

build-up of the interior sand flats and tidal marshes on 

the sound sides of the islands. The net effect of this 

process in response to rising seas is upward and 

landward (westward) migration of the barrier islands 

(Dolan and Godfrey 1972).

Aeolian Transport

Average wind speeds are 15 km (9.3 mi)/h, but speeds 

can reach 48 km (30 mi)/h in every month of the year 

(Wells and Kim 1989). Winds blow primarily from the 

south to southwest between April and August and from 

the north to northwest between September and 

February. Annually, average strong winds blow most 

frequently from the north and northeast, resulting in 

overall average southward and southwestward aeolian 

sand transport (Havholm et al. 2004). A fetch of 100 km 

(62 mi) is possible when winds blow along the axis of 

Pamlico Sound (Wells and Kim 1989).

As detailed in the “Estuaries” section, wind drives 

circulation in Pamlico Sound (Wells and Kim 1989), and 

major wind-driven tides can cause sediment erosion and 

transport. Storm winds, described in the “Hurricane 

Impacts and Human Responses” section of the 

“Geologic Resource Management Issues” chapter, also 

move significant amounts of sand into the island interior 

and estuary, and help to build and shape dunes.

Wave Transport

Waves and wave-induced currents produce a very high 

net southerly sand transport, estimated to be 590,000 m3

(772,000 yd3

) per year, along the northern Outer Banks 

toward Cape Hatteras (Inman and Dolan 1989). In 

comparison, net northerly sediment transport in 

southern Virginia, just north of the Outer Banks, is only 

160,000 m3 (209,000 yd3

) per year (Inman and Dolan 

1989). The depth of closure, a measure used in coastal 

engineering models and defined as the depth beyond 

which sediment transport relative to beach dynamics 

does not occur, is estimated to be 18.6 m (61 ft) at Nags 

Head and 21.6 m (70.8 ft) off Cape Hatteras (Everts 1978,

as cited in Moore et al. 2007).

Despite the high rate of alongshore sediment transport, 

some areas of the shoreface and inner shelf are devoid of 

sand. A thin layer of modern beach sand commonly 

overlies shoreface sediment, which consists of relict 

fluvial and estuarine sediments (muddy sands, mud, and 

sometimes rock), but these underlying sediments are 

sometimes exposed in the surf zone and nearshore areas 

(shoreline to 5 km [3.1 mi] offshore) from Wilmington to 

Nags Head (Pearson 1979; Snyder 1993; Riggs et al. 1995; 

Miselis and McNinch 2006).

Overwash

Overwash is an important process in building island 

elevation, expanding marsh platforms, and creating and 

maintaining early-succession habitat.

When small storm surges produce waves that overtop the 

island berm and erode the dune ridge, sediment is 

deposited in small overwash fans on the ocean side of the 

barrier. Large storm events can drive meters of water 

across the island berm, resulting in large, arcuate 

overwash ramps that bury the back-barrier platform 

marshes and may even build shallow shoals in the estuary 

(fig. 8) (Riggs et al. 2009). These processes move 

sediment on top of and across the island, building island
12 NPS Geologic Resources Division

Figure 8. Schematic illustration of overwash fan development. When waves carry sand across the beach, sediment is 

deposited as small overwash fans on the ocean side of the barrier. Large storm events can drive meters of water across the 

island, resulting in large overwash ramps that bury the back-barrier platform marshes and may even build shallow shoals in 

the estuary. Graphic by Trista Thornberry-Ehrlich (Colorado State University) after online figure by NPS and University of 

Maryland Center for Environmental Science (2012).

elevation and width. The change in elevation 

subsequently controls the locations of post-storm 

habitats and revegetation (e.g., scrub shrub, high and low 

marsh) (Riggs and Ames 2006).

When a major storm erodes the shoreface sand, flattens 

island topography, and buries vegetation across the 

island, a low and wide island area results. On islands 

without fixed features, such as forested berms or houses, 

the resulting overwash plain will form broad overwash 

ramps that diminish gradually into the back-barrier and 

estuarine habitats. On islands with fixed features, a more 

irregular geometry of arcuate back-barrier shoals and 

associated tidal channels will form, and the overwashed 

sediments will evolve into the classic “molar-tooth”

structure. In this formation, the lower overwash ramp is 

dominated by platform marshes in the intertidal zone,

with back-barrier shoals in the subtidal and submarine 

zones. The platform marshes are separated by active tidal 

channels that move water and sediment onto and off of 

the supratidal portion of the middle overwash ramp,

which is often dominated by interior marsh or algal flats 

(Riggs and Ames 2006).

The first vegetation to recolonize the island is salt

tolerant, particularly on the middle and lower overwash 

ramps, with the early development of salt marsh grasses 

in the intertidal zone and high salt marsh grasses and mat 

algae in the supratidal zone. With time, the middle and 

upper portions of the overwash ramp will revegetate with 

grasses such as Spartina patens and dune grasses. Earlysuccession plants can generally tolerate subsequent 

overwash events and are important in stabilizing 

sediment on the back side of the island. Wrack, dead 

plant material from the marsh and aquatic vegetation, 

forms a series of fringing berms around the platform 

marshes and absorbs much of the wave energy coming 

onto the marsh during small storm tides (Riggs and Ames 

2006).

The increased elevation of the island reduces the 

frequency and extent of overwash events. The ocean 

shoreline will then slowly recede, moving the island 

berm farther inland, narrowing the island, and ultimately 

eliminating the middle overwash zone. As the island 

narrows, overwash can again reach the back barrier; 

marsh platforms and associated tidal channels are buried 

by overwash sediment as the island berm and beach 
CAHA Geologic Resources Inventory Report 13

move landward over the molar-tooth structure (Riggs 

and Ames 2006).

Sediment Sources

New sediment for the northern Outer Banks ocean 

shoreline usually comes from four sources (Riggs and 

Ames 2006):

1)Fossil sands and gravels that were deposited as river 

deltas on the adjacent continental shelf during prior 

low sea-level conditions and that now occur on the 

shoreface;

2)Diamond Shoals, which extends from Cape Hatteras 

across the continental shelf and contains large 

amounts of sediment that can periodically supply 

volumes of new sand to the downstream beaches of 

Buxton Woods;

3)Erosion of shoreface sediments, including barrier 

island sand, estuarine valley-fill muddy sands, and 

mudstone;

4)Inlet ebb and flood tidal deltas, which can provide 

sediment to island segments adjacent to present-day or 

paleo-inlets.

The majority of beaches along the barrier island are 

composed of quartz sand, with small concentrations of 

black heavy mineral sand and river gravel in some areas. 

All three of these sediment types were ultimately derived 

from erosion of the Piedmont and Appalachian 

mountains and transported by rivers to the coast in past 

millennia (Riggs et al. 2008a). The black sands are 

composed of various types of very hard and chemically 

stable heavy mineral. The dominant minerals are 

illmenite and magnetite, with smaller proportions of red 

minerals (garnet and rutile) and the rare pale-green and -

blue minerals (tourmaline, zircon, and apatite). These 

minerals are heavier and denser than quartz and calcite, 

and their grain sizes are usually fine to very fine sand. 

They often appear in the upper portions of a post-storm 

beach and are particularly concentrated around inlets 

and capes (Riggs et al. 2008a).

Shell fragments from organisms presently living in the 

surf zone, along the shoreface, and on the continental 

shelf are also present in varying amounts. Most of the 

shells on today’s beaches are fossils. Fossil shells include 

oysters (Ostrea virginica) that lived in back-barrier 

estuaries; were buried in mud and peat, where they were 

stained gray or black; and were then exposed in the surf 

zone as the barrier island migrated westward over the 

earlier marsh deposits (Riggs et al. 2008a). These oysters 

are usually a few hundred to a few thousand years old. 

Fossil shells that have been stained orange with iron are 

usually tens to hundreds of thousands of years old. When 

sea level was more than 120 m (400 ft) below present sea 

level, these shells were subaerially exposed and stained 

with iron oxide within the surficial soil profile on what is 

now the continental shelf offshore of the modern barrier 

island (Riggs et al. 2008a).

Capes and Cape-Associated Shoals

Cape Point and the associated Diamond Shoals, which 

extend 15 km (9 mi) seaward from Cape Point, are part of

a high-energy and mobile sand shoal system that 

responds dramatically to changes in oceanographic 

conditions (Mallinson et al. 2009). This cross-shelf shoal 

system creates dangerous boating conditions, but 

provides excellent fishing opportunities. The system 

separates two major ocean currents and biological 

regimes (fig. 9). North of the cape, the Labrador Current 

moves cold water southward; south of the cape, the Gulf 

Stream and its associated warm water move northward 

and host a different set of tropical fauna and flora. The 

two water masses meet at Diamond Shoals (Mallinson et 

al. 2009). Alongshore sediment transport is currently 

directed toward the tips of capes (e.g., it moves 

southward north of Cape Hatteras and northward south 

of the cape, so that the sediment loads meet and are 

deposited at Diamond Shoals) (Swift 1976; McNinch and 

Wells 1999).

Figure 9. Map of major currents. Cape Point and the 

associated Diamond Shoals, which extend 15 km seaward 

from Cape Point, are part of a high-energy system that is 

highly mobile and responds dramatically to changes in 

oceanographic conditions. The shoals separate two major 

ocean currents and biological regimes. Graphic by Trista 

Thornberry-Ehrlich (Colorado State University).

The locations of Cape Hatteras and the other Carolina 

capes (Capes Lookout, Fear, and Romain) are all likely 

controlled by the underlying geologic framework (Swift 

et al. 1972; Moslow and Heron 1981; Popenoe 1985). The 

findings of a recent study (Thieler and Ashton 2011) 

suggest that the Carolina capes are dynamic, self-
14 NPS Geologic Resources Division

organized features in which the shoreline responds to 

high-angle waves (wave crests that approach the coast at 

a large angle), and that they continue to evolve.

Inlets

The number and size of inlets between barrier islands are

in equilibrium with the volume of water discharged from 

the rivers and entering and exiting the estuaries due to 

tides. At Cape Hatteras National Seashore, new inlets 

open during powerful storms and old inlets may close 

due to rapid influxes of sediment (Dolan and Godfrey 

1972). In areas with minimal tidal range, such as northern 

North Carolina and Cape Hatteras National Seashore, 

inlets act primarily as outlets for freshwater flowing from 

rivers to estuaries, resulting in fewer inlets and longer 

barrier islands than in southern North Carolina 

(Mallinson et al. 2008b). The formation and location of 

new inlets are difficult to predict, but the potential for 

inlet formation exists everywhere along the simple 

barrier islands of the Outer Banks (fig. 10), with 

likelihood depending on six major variables: storm event 

dynamics, physical geometry of coastal compartments,

island geomorphology, framework geology, estuarine 

geometry and dynamics, and human modifications (fig. 

11) (Riggs and Ames 2006).

An inlet through a barrier island is created when storms 

drive surges across and through the island from the 

ocean or estuarine side (FitzGerald and Hayes 1980).

The inlet widens by erosion and collapse of the adjacent 

bank, and deepens as flow scours the channel (Wamsley 

et al. 2009). Margin shoals are often formed immediately

Figure 10. Map of potential for new inlet opening. The 

potential for a new inlet to open varies by location along 

the Outer Banks. Potentials illustrated in this figure are

based on measurements of subaerial island volume. 

Categories are defined by quartiles of the total number of 

sample sites measured. Note that inlets opened in the last 

century are in areas mapped as “Very High Potential” (red). 

Figure 20 from Mallinson et al. (2008b).

Figure 11. Map of inlet vulnerability index. The likelihood that an inlet will form at a given location along the Outer Banks 

depends on at least six major variables: storm event dynamics, physical geometry of coastal compartments, island 

geomorphology, framework geology, estuarine geometry and dynamics, and human modifications. Text and figure 12 from 

Riggs and Ames (2006).
CAHA Geologic Resources Inventory Report 15

Figure 12. Schematic illustrations of inlet formation. Inlet formation and shoreline recession are important components of 

barrier island evolution. A) Active flood and ebb tidal deltas (FTDs and ETDs, respectively) form in association with an inlet. 

B) As the inlet closes, the ETD collapses, causing temporary and localized shoreline accretion, while adjacent areas continue 

to erode. A molar-tooth platform marsh and marsh islands develop on FTD shoals, increasing island width. C) Continued 

shoreline erosion narrows the island more rapidly in areas underlain by fine FTD sediments, while slower erosion occurs 

where coarse sands are associated with the inlet throat channel. D) The narrow portion of the island breaches during a 

storm and cross-island flow and downcutting create a new inlet. Erosion accelerates in adjacent areas underlain by fine FTD 

sediment, continuing the evolutionary succession. Graphic redrafted by Trista Thornberry-Ehrlich (Colorado State 

University) after figure 3 and text from Mallinson et al. (2008b)

after the inlet opens. Sufficient depth of scour in the inlet 

allows the interchange of freshwater and ocean water,

even after the storm has subsided, and tidal flow 

continues to widen and deepen the channel. If the inlet 

flow is strong enough to flush littoral drift-derived 

sediments faster than they are introduced, the inlet is 

maintained (Wamsley et al. 2009). When water volume 

decreases, the channel begins to shoal (Mallinson et al. 

2008b). Most inlets are temporary features of elevated 

water levels and last only a few days (Dolan and Lins 

1986). Non-migrating inlets are usually ephemeral 

features, opening and closing on a time scale of months 

to years (Mallinson et al. 2010b).

Tidal currents construct a flood tidal delta on the 

estuarine side of the barrier island and an ebb tidal delta 
16 NPS Geologic Resources Division

Figure 13. Location and duration of historic and modern inlets along the Outer Banks. Graphic by Trista Thornberry-Ehrlich 

(Colorado State University), created with information from Fisher (1962), Dolan and Lins (1986), and Mallinson et al. (2010b).
CAHA Geologic Resources Inventory Report 17

on the ocean side, where sediment is deposited as the 

swiftly moving tide dissipates into larger water bodies 

(fig. 12A) (Riggs et al. 2009). These delta shoals are 

important components of the coastal sediment budget 

and the long-term evolution of the barrier islands, 

allowing a platform for marsh development (Dolan and 

Lins 1986) and for island migration as sea level rises 

(Riggs et al. 2009; Mallinson et al. 2010b). Flood-tidal

delta deposits provide the major volume of sediments 

beneath the Outer Banks (Mallinson et al. 2010b). 

Migrating inlets provide sediment to the back-barrier 

system through the growth of spits and the longevity of 

the inlet's existence. The deltaic deposits widen the 

island in back-barrier areas adjacent to the inlet throat 

(Mallinson et al. 2010b).

After an inlet closes, sand from the flood tidal deltas is 

incorporated into the island as intertidal marsh flats 

known as molar-tooth platform marshes (fig. 12B), 

which may be segmented by the old delta channel 

system. As overwash buries the marsh, the channels are 

filled with sand (fig. 12C). The barrier migrates over this 

former marsh, which often crops out on the beach and 

upper shoreface during storms. As storm surge flows 

over the narrow portions of a barrier island, the exposed 

marsh peat surface resists erosion while the adjacent 

sand-filled tidal channels are easily eroded, producing 

new inlet channels (fig. 12D) (Mallinson et al. 2008b; 

Riggs et al. 2009).

Ebb tidal deltas also store sand and episodically release it

to nearby beaches and coastal systems. Waves and 

currents rework the ebb-tidal delta sand into shoals, 

which migrate alongshore and merge with the beach 

downdrift of the inlet (Mallinson et al. 2008b). The 

exchange of water through new inlets also moves 

nutrients, organisms, and sediment out of and into backbarrier sounds (Dolan and Lins 1986; Ames and Riggs 

2006j).

Historic Inlets

As many as 30 inlets have opened and closed along the 

Outer Banks since the first European presence in this 

area 400 years ago (fig. 13) (Dolan and Lins 1986), and 

approximately 70% to 85% of the Outer Banks have had 

at least one inlet in the past 500 years (Riggs et al. 2009). 

On Pea Island, North Carolina, New Inlet was open 

numerous times between 1650 and 1945, and 

Chicinacommock Inlet was open irregularly between 

about 1650 and 1775. Loggerhead Hills (a massive 

overwash fan) covers the flood tidal delta of Loggerhead 

Inlet, which was frequently open between about 1650 

and 1870 (Riggs et al. 2009). Whalebone Junction, at the 

foot of the causeway to Roanoke Island, is located on 

former salt marsh islands that were part of the flood tidal

delta of the paleo–Roanoke Inlet, which closed around 

1817 (Mallinson et al. 2008b).

Only three major inlet systems now connect the entire 

Albemarle-Pamlico Estuarine System to the ocean. 

Ocracoke Inlet, open since at least 1584, has undergone 

maintenance dredging at various times, including 1828–

1835, 1895–1905, and 1942–1961 (Riggs and Ames 2007). 

Oregon Inlet, which was opened by a hurricane in 1846, 

has a history of dredging and stabilization that is 

described in detail in the “Geologic Resource 

Management Issues” chapter. Hatteras Inlet, which also 

opened during a hurricane in 1846, has typical inlet 

features, including a small, well-developed ebb tidal delta 

on the ocean side, an extensive flood tidal delta of 

shallow sand flats on the estuarine side, and a long 

prograding spit on the northeastern (updrift) side of the 

inlet (Mallinson et al. 2009). Vegetation on this 

accretionary spit increases with distance from the inlet, 

indicating decades of inlet migration to the southwest.

Estuaries

Pamlico Sound is an important fishing resource, and 

provides nursery and foraging habitats for mid-Atlantic 

fish species (Paerl et al. 2006). Three seagrass species are 

present along the eastern sides of Pamlico and Roanoke 

sounds: Zostera marina (eelgrass), Halodule wrightii

(shoalgrass), and lesser abundances of Ruppia maritima

(widgeongrass) (Ferguson et al. 1988, as cited in Mallin et 

al. 2006).

Roanoke Sound, west of Bodie Island, and Pamlico 

Sound, west of the rest of the park, are both polyhaline 

with salinities of 18 to 29 practical salinity units (psu) 

(Mallin et al. 2006). Tide range within the AlbemarlePamlico lagoonal system is low (10 cm [3.9 in] or less; 

more around the inlets) (Wells and Kim 1989). Coves 

and tidal creeks have variable estuarine salinities, 

depending on local rainfall, which averages about 143 cm

(56 in)/year (Mallin et al. 2006).

Pamlico Sound receives freshwater from five major 

watersheds and has a surface area of 435,000 ha (110,000 

ac)(Giese et al. 1985). Recent estimates indicate that the 

sound contains 16.9 × 109 m3 (2.2 × 1010 yds3) of water, 

with an annual turnover of 1.7 years (Burkholder et al. 

2004, as cited in Mallin et al. 2006). This long residence 

time is the result of the sound’s limited connection with 

the Atlantic Ocean, which occurs primarily through three 

narrow, shallow inlets (Paerl et al. 2006). Circulation is 

dominated by wind-driven currents. Average currents in 

Pamlico Sound are 10 to 26 cm (3.9 to 10.2 in)/s, with a 

high speed of 69 cm (27 in)/s recorded during a squall 

and a low speed of 0.5 cm (0.2 in)/s (Wells and Kim 

1989). The winds driving the currents also presumably 

influence the bottom sediments through processes of 

wave resuspension (Wells and Kim 1989).

Estuarine water-quality data for Cape Hatteras National 

Seashore are collected monthly at one continuousmonitoring station located near the Ocracoke 

Lighthouse, at the southern end of Ocracoke Island. In 

2011, the monthly data recorded consistently good 

conditions for water quality, dissolved oxygen, and 

chlorophyll a, and fair conditions for dissolved nitrogen 

and phosphorus (see table 2 for condition definitions) 

(NPS 2012; Wright et al. 2012). Benthic conditions in the 

estuary and ocean were rated as good (healthy) (NPS 

2012). 
18 NPS Geologic Resources Division

Table 2. Coastal water-quality monitoring criteria used by the NPS Southeast Coast Network, based on 

thresholds set by the US Environmental Protection Agency (2005). 

Rating Water Clarity 

(k)1

Chlorophyll a

(ug/L)

Total Dissolved 

Nitrogen2 (mg/L)

Total Dissolved 

Phosphorus2

(mg/L)

Dissolved 

Oxygen 

(mg/L)

Good <2.3 <5 <0.1 <0.01 >5

Fair 2.30–2.99 5–20 0.1–0.5 0.01–0.05 2–5

Poor >2.99 >20 >0.5 >0.05 <2

Table and notes reproduced from table 3 in Wright et al. (2012).

1

Light attenuation coefficients (k) were used to assess water clarity conditions using criteria categories in Smith et al. (2006), which are 

comparable to the US Environmental Protection Agency (2005) criteria for the assessed water bodies.

2

US Environmental Protection Agency nutrient criteria use dissolved inorganic nitrogen and dissolved inorganic phosphorus, which are close 

approximations of total dissolved nitrogen and total dissolved phosphorous.

Estuarine Sediments

Wells and Kim (1989) thoroughly described the 

sediments in the Albemarle-Pamlico Sound System. 

These sediments are derived from four major sources: 

rivers, shoreline erosion, continental shelf, and 

autochthonous biogenic production of fauna and flora. 

Minor contributions are derived from silt and sand 

transported by storm wind and water from the barrier 

islands and from periodically unvegetated agricultural 

fields on the mainland. Riverine input is mostly silt and 

clay with high organic content. Biogenic material in the 

form of shell fragments (fig. 14) represents less than 2% 

of bottom sediments throughout much of Pamlico 

Sound, but more than 16% of sediments at Ocracoke, 

Hatteras and Oregon inlets, where shell fragments are 

transported from adjacent Outer Banks beach 

environments. High concentrations of shell fragments 

(8% to 16%) in the central basin and seaward of the 

Pamlico and Neuse rivers may be related to preferential 

growth of oysters in these regions.

Wells and Kim (1989) also described sediment transport 

into the sound. Shoreline erosion by direct wave attack 

provides the major source of coarse sediment, mainly 

from high banks and bluffs that are undercut during 

storms, then collapse as slump blocks onto the beach (fig. 

15). Erosion rates of 1 to 3 m (3.3 to 10 ft)/year are 

sufficient to create beaches along the estuarine 

shorelines. Most of the sand in Core Sound and central 

and eastern Pamlico Sound is derived from barrier 

islands and offshore sediments carried through inlets 

and overwash fans, as evidenced by the similarity in 

texture between sound and barrier-island sediments and 

the decreasing landward percentage of garnet and yellow 

quartz. The three inlets influencing Cape Hatteras 

National Seashore are high-energy, wave-dominated 

features with flood tidal deltas that account for 

approximately half of the medium-grained sand in the 

estuarine system. Extensive washover fans and former 

inlets have also contributed sand to nearly all of Core 

Sound.

Figure 14. Distribution (wt%) of calcium carbonate content 

in Pamlico Sound. Highest concentrations occur at inlets 

where shell fragments are transported from the oceanside 

surf zone. Figure redrafted by Trista Thornberry-Ehrlich 

(Colorado State University) after figure 5 in Wells and Kim 

(1989), as modified from Pickett (1965).

Grain size in Pamlico Sound decreases away from crossestuarine finger shoals, toward the center of the sound

and quiet-water environments near drowned tributary 

mouths and protected mainland embayments (fig. 16). 

Along the mainland side of Pamlico Sound are areas of 

sandy mud characterized by sediment mottled by 

burrowing organisms. The deeper central part of the 

sound has homogeneous sediment that lacks sand and 

burrowing organisms (Wells and Kim 1989).

Freshwater Aquifer

The popularity of Cape Hatteras National Seashore has 

placed increasing demands on natural resources and 

visitor use facilities. An understanding of the potable
CAHA Geologic Resources Inventory Report 19

Figure 15. Schematic cross section of a strandplain beach. 

Strandplain beaches are common shoreline shapes on the 

estuarine sides of complex barrier islands in Cape Hatteras 

National Seashore, and are the dominant forms of 

sediment-bank estuarine shorelines along the mainland. 

Shoreline erosion occurs by direct wave attack during high 

astronomical, wind, and storm tides and provides a major 

source of sand sediment for an adjacent strandplain beach. 

As the sediment banks are undercut, slump blocks collapse 

onto the beach, where they are reworked by wave energy. 

Graphic redrafted by Trista Thornberry-Ehrlich (Colorado 

State University) after figure 4-2-1 in Riggs and Ames 

(2003).

Figure 16. Sediment size distribution in Pamlico Sound, 

following the Wentworth classification. Figure redrafted by 

Trista Thornberry-Ehrlich (Colorado State University) after

figure 7 in Wells and Kim (1989).

groundwater supply is critical to protect and ensure the 

optimal use of this resource.

Surficial water aquifers consist of porous and permeable 

sediments capable of storing and transmitting useable 

quantities of water. These aquifers extend from a water 

table at or below the land surface down to an underlying 

confining layer of silt and clay. On barrier islands, 

surficial fresh groundwater may occur as a lens-shaped 

mass floating atop denser salty water, with an intervening

mixing zone (Harris and Wilder 1964; Winner 1975). 

Below the confining layer of the surficial aquifer, other 

confined or semi-confined aquifers may occur between 

additional confining silt and clay beds (Brown 1960; 

Harris and Wilder 1964; Winner 1975). The depth of 

freshwater below the land surface and the thickness of 

the aquifers vary along the Outer Banks.

On Hatteras Island, the Buxton Woods surficial aquifer 

consists of an upper permeable layer up to 12 m (39 ft) 

thick, with a semi-confining layer of silts and fine sands 

below it. A lower aquifer ranges from 12 to 24 m (39 to 79 

ft) in thickness. It is generally a layer of shell and shell 

hash underlain by a 13-m- (43-ft-) thick confining layer 

of silty to clayey sand. This deep aquifer continues to 

supply a portion of local drinking water, although most 

freshwater is currently derived from brackish water in 

deeper (70 m [230 ft]) wells that is treated by reverse 

osmosis (Anderson et al. 2000, as cited in Mallin et al.

2006). On Ocracoke Island, drinking water is sourced 

from brackish water obtained from a 189-m- (620-ft-) 

deep aquifer that is purified by a reverse osmosis 

treatment system located on Cape Hatteras National 

Seashore property in Ocracoke Village.

Brown (1960) reported the presence of two fresh 

groundwater aquifers at the southern end of Bodie 

Island. The upper aquifer lies 0 to 6 m (20 ft) below the 

surface and is composed of medium- to fine-grained 

quartz sand with shell fragments. The water level varies

with rainfall, evapotranspiration, and tides. The lower 

aquifer, at a depth of 9 to 13 m (29 to 42 ft), is composed 

of coarse- to medium-grained quartz sand with shell 

fragments. It is separated from the upper aquifer by a 

layer of sandy silt and clay that is 3 m (9 ft) thick. 

Underlying the lower aquifer is a silty clay layer that is 5 

m (18 ft) thick and prevents intrusion of the underlying 

saline water.

The Outer Banks fresh groundwater supply is recharged 

through rainfall and depleted through residential use, 

evapotranspiration from the surface and vegetation, and 

surface drainage from wetlands (Mallin et al. 2006). 

Annual average rainfall ranges from 114 to 140 cm (45 to 

55 in) and is greatest between July and October (Brown 

1960; Kimrey 1960). Most rainwater enters the aquifer

directly, with little to no surface runoff; the amount of

groundwater available is thus related directly to the 

amount and frequency of precipitation (Brown 1960; 

Harris and Wilder 1964; Winner 1975). Runoff typically 

occurs only when significant rainfall saturates the 

ground. Some freshwater ponds exist, but they are often 

ephemeral (Winner 1975; Ames and Riggs 2006a–i).
20 NPS Geologic Resources Division

Fresh surficial groundwater tends to move away from the 

central part of the island, toward the ocean and sound, at 

an average of about 0.3 m (1 ft) per day (Harris and 

Wilder 1964; Winner 1975). Test drilling and water 

sampling have indicated that subsurface lateral 

permeability is greater than vertical permeability (Brown 

1960). The downward and outward movement of 

freshwater recharge maintains the freshwater lens atop 

the saline water until storm overwash events add 

saltwater to the freshwater, creating a brackish resource 

that persists for some period of time.

Groundwater systems and aquifers can be affected by 

impoundments, weather conditions (e.g., drought), and 

water withdrawal for anthropogenic needs. The 

combination of these influences can, in turn, alter 

hydrologic processes, wetland function, and the 

distribution, composition, diversity, and structure of

vegetation communities (NPS 2012). Water levels have 

declined in two of the three wells, located on the Coastal 

Plain, that the NPS Southeast Coast Network monitors 

as indicators of park resource conditions (NPS 2012): a 

surficial aquifer well just south of Plymouth, North 

Carolina (130 km [80 mi] northwest of Cape Hatteras) 

with a 25-year quarterly record, and a deeper well in the 

Castle Hayne aquifer just north of Washington, North 

Carolina (150 km [90 mi] northwest of Cape Hatteras) 

with an 8-year daily record (Wright 2012). Withdrawal of 

freshwater will change the balance between the 

freshwater lens and underlying saltwater, due to the 

resulting encroachment of adjacent saltwater bodies 

(Brown 1960; Harris and Wilder 1964; Winner 1975).

Areas favorable for fresh groundwater development are 

not likely to be inundated by saltwater and subject to 

only rare overwash from the largest storms (Winner 

1975). Areas such as the high and wide island mass at 

Buxton Woods and a smaller area at the southern end of 

Bodie Island (dunes near Theoff Point) fit these criteria 

(Brown 1960; Winner 1975). Higher areas in the central 

parts of the narrower islands (e.g., Ocracoke Island) have 

more frequent saltwater overwash. Overwash from 

Hurricane Emily in 1993 caused an increase in chloride 

levels in the Buxton Woods Aquifer from the normal 

level of 40 mg/L (milligrams per liter, equal to parts per 

million) to 280 mg/L; this level remained above 100 mg/L 

for eight months (Anderson 2002, as cited in Mallin et al. 

2006). The Environmental Protection Agency has set a 

secondary standard of 250 mg/L chloride in drinking 

water due to effects related to taste and corrosion.

Barrier Island Evolution and Behavior

The modern coastal geomorphology of the Cape 

Hatteras region results from interaction among the 

antecedent topography, varying magnitudes of relative 

sea-level change, variable fluvial input, and coastal 

oceanographic processes (Mallinson et al. 2010a). Thus, 

to understand large-scale barrier behavior along the 

Outer Banks, the geologic framework must be 

considered.

Geologic Framework

At the broadest scale, Coastal Plain sediments sit atop 

bedrock basement characterized by broad structural 

highs (the Carolina Platform High, underlying the region

Figure 17. Schematic cross sections illustrating the diversity of strata underlying the Outer Banks. 1) Location of cross-island 

(A–A’) and along-island (D–D’) geologic sections along the Outer Banks. 2) West–east geologic cross section extending from 

Stetson Pit (A) eastward into the Atlantic Ocean (A’), showing seven stacked Quaternary depositional sequences (labeled 

DS-1 through DS-7), and major sediment facies of each depositional sequence. DS-7 is the Holocene depositional sequence. 

3) North–south geologic cross section extending from the north side of Kitty Hawk Bay (D) southward through Nags Head 

and to the south side of Oregon Inlet (D’), showing portions of at least three stacked Quaternary depositional sequences 

and major sediment facies of each. Graphic redrafted by Trista Thornberry-Ehrlich (Colorado State University) after figures 

1, 2, and 5 in Riggs et al. (1992).
CAHA Geologic Resources Inventory Report 21

between Myrtle Beach, South Carolina, and Cape Fear, 

North Carolina) and lows (the Albemarle Embayment, 

which is the shallow flank of the Salisbury Embayment 

and is slowly subsiding in the northern coastal zone from 

Cape Lookout, North Carolina, to the Virginia state line) 

(Riggs et al. 2011). Cape Hatteras beaches are perched 

atop pre-existing Pleistocene, Tertiary, and Cretaceous

sediments. Locally, a Quaternary sequence (50 to 70 m 

[160 to 230 ft] thick) of soft sediments (slightly indurated 

to unconsolidated mud, muddy sand, sand, and peat) fills 

the Albemarle Embayment depositional basin (Riggs et 

al. 1995).

Superimposed on the regional stratigraphy between 

southeastern Virginia and Cape Hatteras is a flooded, 

ancient drainage system consisting of a series of 

Pleistocene paleofluvial channels (Riggs et al. 1995, 1996; 

Thieler et al. 2001; Boss et al. 2002; Schwartz and 

Birkemeier 2004; Mallinson et al. 2005; Miselis and 

McNinch 2006) that incised the Quaternary strata across 

the regional shoreface. When sea level rose following the 

lowstands of the Last Glacial Maximum, these channels 

filled with Pleistocene and Holocene coastal sediments,

including bedded sequences of muddy estuarine 

sediments, fine to medium sands, and, where inlets or 

rivers were present, coarse sands and gravel that now 

outcrop in the shoreface (fig. 17) (Boss et al. 2002; 

McNinch 2004; Mallinson et al. 2005; Browder and 

McNinch 2006; Miselis and McNinch 2006; Culver et al. 

2008b; Mallinson et al. 2010a, 2010b). Large interstream 

areas of older sediments separate the paleovalleys (Riggs 

et al. 1995).

The modern estuaries behind the barrier islands occur 

within the flooded paleovalleys of the Roanoke, 

Pamlico/Tar, and Neuse rivers (Mallinson et al. 2010a). 

Ocracoke Inlet, the southern boundary of Cape Hatteras 

National Seashore, has historically been relatively stable, 

appearing on maps as far back as 1590, likely because it 

occurs within the fluvial paleovalley of Pamlico Creek 

(Riggs and Ames 2003; Mallinson et al. 2010a). A major 

erosional hotspot presently occurs north of the Wright 

Brothers National Memorial in Kitty Hawk, where the 

paleo–Roanoke River Valley passes beneath the northern 

Outer Banks (Mallinson et al. 2010a).

Mallinson et al. (2009) estimated that paleo-inlet

channels constitute up to 75% of Hatteras and Pea 

islands, resulting from the cutting of inlets into older 

flood tidal deltas that formed when barrier islands 

existed farther seaward. These flood-tidal delta deposits 

are generally overlain by marsh peat and storm overwash 

sediments. Channel-fill sediments occur under the 

widest portions of the island. Narrow portions of the 

island are underlain by flood-tidal delta and overwash 

sediments (Mallinson et al. 2009).

The Hatteras Flats (fig. 18) occur on the western side of 

the barrier islands between Oregon Inlet and Ocracoke 

Island. This broad and shallow platform, which is 

composed of coalesced relict flood tidal deltas and 

overwash sand shoals, extends up to 8 km (5 mi) into 

Pamlico Sound and is in water depths of less than 1 to 2

Figure 18. Bathymetric map of Cape Hatteras National 

Seashore from Oregon Inlet to Hatteras Village. Hatteras 

Flats is an extensive shallow shoal system that occurs on the 

west side of the barrier islands between Nags Head and 

Ocracoke Inlet. The shoals are composed of relict flood tidal

deltas and overwash sand shoals. Wimble and Kinnakeet 

shoals are offshore hardbottom features composed of 

Pleistocene carbonate-cemented sandstones and 

mudstones. The green feature is the modern barrier island. 

Map annotated by Jason Kenworthy (NPS Geologic 

Resources Division) using the National Oceanic and 

Atmospheric Administration National Geophysical Data 

Center’s Bathymetry and Digital Elevation Models viewer 

(DEM Hillshades layer), available online: 

http://maps.ngdc.noaa.gov/viewers/bathymetry/?layers=no

s_hydro&minx=-200&maxx=-50&miny=10&maxy=70

(accessed 19 May 2014).

m (3 to 6 ft) (Mallinson et al. 2011). From Oregon Inlet 

south to Rodanthe, the flats slope gradually into Pamlico 

Sound. From Rodanthe southward to Avon, the western 

side of these flats has a high-angle slope that drops from 

0.5 m (1.6 ft) or less into 3 to 4 m (9.8 to 13 ft) water 

depth (Mallinson et al. 2009).
22 NPS Geologic Resources Division

Influence of the Geologic Framework on Modern Processes

Sediment availability for the North Carolina barrier 

islands is significantly influenced by the geologic 

framework of older stratigraphic units occurring beneath 

and seaward of the shoreface. The variability in age, 

origin, and composition of units within the geologic 

framework interacts with coastal processes to determine 

the three-dimensional shoreface morphology, 

composition and texture of beach sediments, and 

shoreline recession rates (Riggs et al. 1995).

Perched barrier islands such as the Outer Banks do not 

develop a classic shoreface profile of equilibrium because 

they consist of thin and variable layers of surficial beach 

sand on top of older eroding stratigraphic units 

characterized by a variety of lithologies, compositions, 

and geometries (Riggs et al. 1995). A shoreface composed 

of compact muds, limestones, or sandstones is more 

resistant to erosion than are unconsolidated sands or soft 

muds, and thus exerts a greater effect on the island and 

nearshore morphology. Also, along many parts of the 

Cape Hatteras National Seashore coastal system, 

bathymetric shoal features occur on the inner shelf and 

modify incoming wave and current energy, which in turn 

affects the patterns of sediment erosion, transport, and 

deposition on adjacent beach faces (Riggs et al. 1995).

Older sediments cropping out on the eroding shoreface 

characterize submarine headlands or submerged 

morphological features upon which the barrier-estuarine 

system is perched. Submarine headlands commonly 

occur on the inner shelf as bathymetric highs seaward of 

the modern shoreface. These bathymetric high areas 

modify incoming waves between Kill Devil Hills and 

Cape Hatteras. Erosional remnants (submarine 

headlands) control changes in the orientation of the 

barrier islands, occurrence of minor cape structures on 

the barrier beach, and a series of offshore ridge and shoal 

structures (Riggs et al. 1995).

Between Oregon Inlet and Cape Hatteras, the barrier 

system is perched on a major submarine headland (the 

Dare Headland), which controls the morphology of the 

northern Pamlico Sound in this area (fig. 17). This area is 

characterized by four distinctive coastal features (fig. 18) 

(Riggs et al. 1995):

1)a major change in barrier island orientation at 

Rodanthe;

2)a series of bathymetric highs (Wimble and Kinnakeet 

shoals) on the inner shelf associated with each of 

several minor capes that intersect the lower beachface 

at acute angles;

3)minor cape structures (associated with Wimble and 

Kinnakeet shoals) on the barrier beach in Rodanthe 

and Avon, with rapidly receding beach segments 

occurring between the structures; and

4)Hatteras Flats, a broad, shallow platform bound on the 

west by a vertical scarp up to 3 m (9 ft) high, located on 

the back side of the barrier island in Pamlico Sound 

south of Rodanthe.

Transgressive (erosional) shorefaces occur along a large 

portion of the barrier islands at Cape Hatteras National 

Seashore, between Nags Head and Ocracoke (Riggs et al. 

1995). These areas of pronounced erosion are generally 

characterized by irregular and steep beach geometry with 

discontinuous, highly scarped dune ridges and abundant 

overwash fans. Estuarine peat and mud deposits are 

characteristic and were overrun by barrier island systems 

as they migrated inland (westward) in response to 

ongoing sea-level rise. Storms often expose these 

deposits within the surf zone and upper shoreface 

following significant beach sand removal.

Regressive (accretionary) shorefaces (fig. 19) occur on 

Hatteras Island, southwest of Cape Hatteras. These 

features are characterized by progradational geometries, 

beach ridge accretion, and dune development with wide 

beaches and continuous dune ridges. They occur along 

barrier island stretches with adequate sediment supplies, 

often in association with headlands, cape structures, and 

inlets, which are the sources of new sediment (Riggs et al. 

1995).

Channel-dominated inlet-fill shorefaces exist at Bodie 

Island and numerous beach segments of Pea, Hatteras, 

and Ocracoke islands. These features form when 

historic, ephemeral inlets close and their channels fill 

with beach sand from prograding spits. As sea level rises, 

the shoreface recedes and the upper portion, underlain 

by inlet fill, rapidly erodes and produces relatively 

steeper beach slopes. This erosion produces a sediment 

supply for adjacent beach segments that tend to have 

slightly wider beaches with much slower erosion rates 

(Riggs et al. 1995).

A major portion of the Kitty Hawk area, north of the 

Wright Brothers National Memorial, is underlain by a 

channel-dominated valley-fill shoreface. Historically, 

this area was dominated by the paleodrainage of the 

Roanoke River/Albemarle Sound estuarine system. With 

initial drowning of the river system and development of 

the barrier islands, the channel complex was backfilled 

with estuarine mud sediments, which can be fairly 

cohesive. As the barrier island continues to recede over 

the backfilled channel deposits due to ongoing sea-level 

rise, the mud-filled channel erodes more slowly, 

producing relatively shallower slopes. The eroded 

sediments are fine grained and tend to be transported 

offshore, instead of supplying adjacent beaches. The net 

result for adjacent beaches is relatively higher rates of 

shoreline recession (Riggs et al. 1995).

Wimble and Kinnakeet shoals occur in the nearshore 

area of the Hatteras Island portion that has a north–

south orientation. The shoals are ridges with 

north/northeast–south/southwest orientations at angles 

of about 25° to 30° to the shoreline and up to 6 m (20 ft) 

relief (fig. 18) (Mallinson et al. 2009). These offshore 

hardbottom features are relict erosional Pleistocene 

features composed of carbonate-cemented sandstones 

and mudstones (Boss and Hoffman 2001). These shoals 

influence wave refraction and wave setup (Cox 1996), 

thereby affecting the large-scale behavior of this coastal 
CAHA Geologic Resources Inventory Report 23

Figure 19. Schematic cross section showing a regressive shoreface during progradation (sea-level fall) and a progressive 

shoreline during transgression (sea-level rise). Graphic by Trista L. Thornberry-Ehrlich (Colorado State University) after 

information provided by Kathleen Farrell (North Carolina Geological Survey, senior geologist, written communication, 13 

August 2010) and Stanley Riggs (East Carolina University, professor, written communication, 30 December 2013).

segment. The shoreface profile directly off the two shoal 

features is steep, but the shoreface and adjacent beach 

are broad and shallow with relatively low erosion rates

where these shoal features intersect the barrier island

(Mallinson et al. 2009).

Broad fields of nearshore, shore-oblique, unconsolidated 

sandbars that are 200 to 1,000 m (660 to 3,280 ft) wide 

and up to 1 km (0.6 mi) long occur in the nearshore area 

of the northern Outer Banks (north of Oregon Inlet). A 

gravel layer outcrops in the troughs between these bars. 

These persistent features coincide with the locations of 

paleochannels in the shoreface (McNinch 2004; Browder 

and McNinch 2006; Miselis and McNinch 2006) and are 

spatially correlated with onshore hotspots of shoreline 

variability and, in some places, zones of long-term 

(decadal-scale) erosion (List et al. 2006; Schupp et al. 

2006). The bar morphology is similar to others 

documented in the surf zone and nearshore areas along 

the northern Atlantic coast (Niedoroda and Tanner 

1970; Swift et al. 1972; Stubblefield and Swift 1976; Swift 

and Field 1981; Wright and Short 1984; Lippman and 

Holman 1990; McBride and Moslow 1991; Konicki and 

Holman 2000).

These bars occur as bands of coarse and fine sediment 

that are oriented perpendicular or oblique to the 

shoreline. Studies of these sorted bedforms, known as 

rippled scour depressions, suggest that these features are

self-reinforcing and repeating, responding to alongshore 

and cross-shore flows, and associated with long-shore 

sediment transport (Murray and Thieler 2004). These 

rippled scour depressions are believed to control the 

distribution, texture, and composition of surficial 

sediments and inner-shelf bathymetry (Thieler et al. 

2001), while underlying geology may control the 

shoreface profile shape (Thieler et al. 1995).

Despite the tendency for shorelines to smooth out over 

time, the northern Outer Banks has persistent large-scale 

curvatures (Lazarus and Murray 2011). The greater 

availability of coarse paleochannel substrate may hold 

the large-scale curvature of the shoreline in place 

through interactions with patterns of alongshore 

sediment flux, allowing shore-oblique bars and gravellined troughs to persist despite a wave climate that tends 

to focus erosion at such promontories. In that case, the 

large-scale shoreline curvature could change the wavedriven alongshore sediment transport, which, in turn, 

affects shoreline change over long spatial and temporal 

scales (Lazarus and Murray 2011).

Simple and Complex Barrier Island Model

Riggs and Ames (2006) developed a model of Outer 

Banks barrier island evolution by integrating aerial 

photographs (1932–2003), topographic data (1852–2003), 

and field studies to evaluate the responses of 

geomorphic-ecologic systems to sea-level rise, storms, 

and human modification. The model describes two basic 

types of barrier island (simple and complex) in the area 

between Kitty Hawk and Cape Lookout, North Carolina 

(fig. 20).
24 NPS Geologic Resources Division

Figure 20. Diagram showing cross-section profiles and dominant vegetation of the model forming the basic framework of 

the geomorphic mapping presented in this report. A) Simple barrier islands are young, with active barrier components 

dominated by inlet and overwash processes, and are generally transgressive, with landward migration. B) A complex 

barrier island forms when a simple barrier island migrates into and accretes onto an older barrier island segment. When the 

sand supply is locally abundant, a complex barrier island can form through the construction of beach ridges and backbarrier dune fields, resulting in the seaward progradation of the barrier segment. The older, complex segment of the barrier 

island is shaded brown, and the welded, younger, overwash-dominated portion of the barrier island is tan. Graphic 

redrafted by Trista Thornberry-Ehrlich (Colorado State University) after figure 28 from Riggs and Ames (2006).

Simple Barrier Islands

Simple barrier islands constitute about 70% of North 

Carolina’s ocean shoreline (Riggs et al. 2011). This type 

of barrier island is sediment poor and narrow, with low 

elevations and surface morphology that is generally 

young (less than 500 years old). These islands are 

presently active and have developed in response to a 

fairly recent set of environmental conditions and 

processes (Riggs and Ames 2006). They are actively 

transgressing upward and landward in response to storm 

events. They are dominated by storm-surge overwash, in 

which much of the sand is incorporated into overwash 

fans, building island elevation; island width is built by the 

opening and closing of shallow, migratory inlets, with 

sand incorporated into flood tidal deltas (Riggs and 

Ames 2006).
CAHA Geologic Resources Inventory Report 25

Three primary features compose a simple barrier island: 

beach, overwash plain (upper, middle, and lower 

overwash ramps), and sound features (fig. 20) (Ames and 

Riggs 2006j). The morphology of each simple barrier 

island varies due to differences in storm patterns, sand 

supplies, shoreline erosion rates, underlying geologic 

structure, and anthropogenic impacts.

The ocean and estuarine shorelines of a simple barrier 

island erode due to poor sediment supply in combination 

with rising sea level. Eventually the island becomes so 

narrow that a major storm overwashes it or forms a new 

inlet and tidal delta. These processes build island 

elevation and width. Where human modifications, such 

as constructed dune ridges, impede inlet formation and 

overwash, new sediment does not reinforce the island's 

height and width, and the island continues to narrow.

When a vegetated island is overwashed, the vegetative 

cover breaks the hydraulic flow; this process causes the

rapid dumping of overwash sediment, building elevation 

on the ocean side of the island. Over time, this process 

steepens the upper overwash ramp and minimizes the 

middle overwash ramp. As the ocean shoreline continues 

to recede, the island narrows and steepens, with the 

upper ramp totally eliminating the middle ramp and 

eventually burying the platform marshes that form the 

lower overwash ramp. The upper overwash ramp 

becomes a sediment bank shoreline covered with scrub 

shrub along the estuary (Riggs and Ames 2006).

Simple barrier islands in the Outer Banks include most of 

Cape Hatteras National Seashore and Pea Island 

National Wildlife Refuge, including most of Ocracoke 

Island and the island segments between the villages of 

Hatteras and Frisco, Buxton and Avon, Avon and Salvo, 

Rodanthe and Oregon Inlet, and Oregon Inlet and Nags 

Head (Riggs et al. 2009).

Complex Barrier Islands

Complex barrier islands constitute about 25% of North 

Carolina’s ocean shoreline (Riggs et al. 2011). This type 

of barrier island is older, more sediment rich, and wider 

than simple barrier islands, with higher elevations. 

Complex islands are generally composed of beach ridge 

and swale morphology, with extensive dune fields 

spanning them from the oceanfront toward the sound. 

These accretionary beach ridges are generally not 

forming under modern processes. Older portions of 

these islands represent multiple stages of formation 

dating back to 3,000 years before present; they are 

remnants of a previous set of climatic and environmental 

conditions and processes. A narrow, simple overwashdominated barrier segment is often welded onto the 

oceanfront, resulting in an abnormally high and wide 

barrier island (Riggs and Ames 2006). These islands have 

little potential for the formation of new inlets or 

occurrence of small-scale overwash, other than along the 

front side of the barrier (Riggs et al. 2009).

The estuarine shorelines associated with complex barrier

islands are generally scarped, with wave-cut cliffs and 

terraces in older upland sediment units or along the 

thicker peat deposits of the platform marshes (Riggs and 

Ames 2006). The upper 15 to 30 cm (6 to 12 in) of the 

peat layer contains a dense living root mass, below which 

the peat is soft and erodible (Riggs et al. 2008a). At low 

tide, waves erode the softer peat, causing the 

overhanging peat layer to fall (Riggs et al. 2008a). 

Strandplain beaches form in front of the erosional scarps 

if sand is available from the eroding shoreline, adjacent 

shallow estuarine waters, or as windblown sand from the

dune fields (Riggs and Ames 2006).

Kitty Hawk, Nags Head Woods, and Buxton Woods are 

examples of well-developed complex islands; they 

formed when a major sand source was available and as a 

result are sand rich and very wide and high, with 

extensive multidirectional and truncated sets of beach 

ridges, associated wetland swales, and often extensive 

dune fields. The southern shore of Buxton Woods 

continues to accrete new beach ridges composed of sand 

derived from Diamond Shoals during specific storm 

events (Riggs and Ames 2006).

Poorly developed complex barrier islands form when no 

major sand source is available. They are sand poor, with 

moderate widths and elevations and a few simple sets of 

low beach ridges separated by wide, wetland swales 

(Riggs and Ames 2006). Much of the older segment of 

such an island is buried by marsh expansion as sea level 

rises. Hatteras Village is located on moderately 

developed complex islands, and the villages of Rodanthe, 

Waves, Salvo, and Avon are on poorly developed 

complex islands (Riggs et al. 2009). Ocracoke Village is 

on a complex barrier island that was still being formed 

until recently, when human modifications intensified 

(e.g., following the 1962 Ash Wednesday storm) (Riggs 

and Ames 2006).

Geologic Influences on Island Habitats

Island habitats are controlled by elevation above mean 

sea level (MSL), cross-island location on the barrier, and 

the tidal and salinity characteristics of shallow 

groundwater and associated estuarine water. The 

minimal vegetation on a low, overwash-dominated 

barrier island must be salt tolerant. Wider, higher islands 

with infrequent saltwater inundation allow for the 

establishment of mixed and freshwater-dominated plant 

species (Riggs and Ames 2006).

Twenty-four terrestrial mammal species are present in 

the region extending from Nags Head to Ocracoke, 

including the non-native feral pig. Ocracoke Island has 

much lower mammalian diversity than Hatteras Island, 

with only six species represented. This relative lack of 

diversity has been attributed to the lack of maritime 

forest, fewer freshwater wetlands, and frequent 

overwash from hurricanes and nor’easters (Webster and 

Reese 1992, as cited in Mallin et al. 2006). Mammals 

utilizing fresh and salt marshes as habitat include the 

Cryptotis parva parva (least shrew), Sylvilagus palustris 

palustris (marsh rabbit), Oryzomys palustris palustris

(marsh rice rat), Microtus pennsylvanicus nigricans

(meadow vole), Ondatra zibethicus macrudon, (muskrat), 

Myocastor coypus bonariensis (nutria, an invasive 
26 NPS Geologic Resources Division

species), Mustela vison mink (mink), and Lutra 

canadensis lataxina (river otter). The park also provides 

important habitat for neotropical migrant landbirds, 

waterbirds, shorebirds, and marsh birds throughout the 

year.

Barrier Island System Unit Mapping

This report is supported by two digital maps of Cape 

Hatteras National Seashore surficial geology, each 

developed using a distinct methodology and resulting in 

a unique set of geomorphic units and different area of 

coverage.

The first map, developed by Riggs and Ames (2006; table 

3), classifies geomorphic units based on a model of 

barrier island evolution developed from processresponse studies and modern field surveys of the North 

Carolina Outer Banks (Riggs and Ames 2006). This

detailed map covers portions, but not all, of the northern 

Outer Banks and Cape Hatteras National Seashore.

Products of the Riggs and Ames mapping informed the 

North Carolina Geological Survey’s development of a 

second map, which classifies surficial features using 

remotely sensed data (Hoffman et al. 2007g; table 4). The 

map includes complete areal coverage of Cape Hatteras 

National Seashore. In locations where anthropogenic 

development has occurred atop natural features, this

map depicts the natural underlying unit, rather than the 

more recent anthropogenic feature. For example, the 

Fore-island Dune Complex, which has been significantly 

modified, was not differentiated as an anthropogenic 

feature (Hoffman et al. 2007g). Preliminary mapping for 

this second map was completed prior to Hurricane Isabel 

(September 2003), and thus does not incorporate the 

impacts of that storm to the Cape Hatteras National 

Seashore shoreline (Hoffman et al. 2007g).

Barrier Island System Units (East Carolina University 

Field Survey Map)

The field-based map developed by Riggs and Ames 

(2006) identifies subgroups and units of the following 

regional geomorphic features: beach, overwash-plain, 

polydemic, and anthropogenic features (table 3). Each 

feature description includes detailed descriptions of 

geomorphic units and dominant vegetation. The unit 

descriptions provided below are taken primarily from 

Riggs and Ames (2006), and supplemented by 

information from publications where cited.

In predominantly urban areas, where severe 

modification of the landscape has occurred, the regional 

geomorphic features (beach, overwash-plain, and 

polydemic features) are drawn within the urban 

boundary, but the detailed geomorphic units are 

included only to the extent possible and where they 

remain obvious.

Submarine sand bodies in the sound behind the barrier 

islands were not mapped, although these features are 

abundant and critically important to barrier island 

evolution and associated estuarine ecosystems. They 

supply width to the back sides of the barrier islands and 

interact with the lower overwash ramp habitats to form 

the underlying framework for expansion of the lower 

overwash ramp onto the back-barrier shoals over time. 

The back-barrier shoals should be incorporated into 

future maps of the barrier islands.

Beach Features

Ocean Beach Unit

The ocean beach extends from the wet-dry ocean 

shoreline to the bases of natural dune fields or scarped 

dunes or dune fields. Where no dune is present, the 

beach extends to the island berm crest, which is the crest 

of an overwash island, represents the highest point on 

the overwash plain, and separates surface water flow 

between the ocean and back-barrier estuary.

Macroscopic vegetation is sparse in this unit. However, 

wrack commonly occurs along the upper swash lines 

associated with the storm beaches. The wrack may 

consist of offshore algae (Sargassum spp.), dune grasses, 

estuarine submerged aquatic vegetation, or estuarine 

marsh grasses.

Beaches and adjacent marine waters are used for mating 

and nesting by sea turtles, mainly Caretta caretta

(loggerhead sea turtle), which is listed federally as 

threatened, and Chelonis mydas (green sea turtle), but 

also by Lepidochelys kempii (Kemp’s Ridley sea turtle) 

and Dermochelys coriacea (leatherback sea turtle), which 

is listed federally as endangered (Mallin et al. 2006). On 

average, 75 sea turtle nests were found on park lands 

annually between 1992 and 2004 (Mallin et al. 2006).

Inlet Flat Unit

Inlet flats occur adjacent to modern inlets or paleo-inlets. 

An inlet flat is a gently ramped surface that slopes 

gradually from the ocean-beach berm toward the inlet 

and estuary and forms during regular overwash events. 

Waves and tidal currents interact during high-water 

overflow conditions associated with spring tides and 

small storm tides. Active inlet flats are unvegetated. The 

vegetation on older inlet flats often consists of mixed 

grasses that include Spartina patens. Fine-grained areas 

in the lower portions of inlet flats are frequently 

dominated by microbial mats.

Inlet Spit Unit

An inlet spit consists of one or more subparallel and 

curved ridges that occur adjacent to a modern inlet or a 

paleo-inlet. It is dominated by curved ridge structures on 

a gentle ramped flat that results from regular overwash 

events and forms by the combined interaction of waves 

and tidal currents during high-water overflow conditions 

associated with high tides, spring tides, or small storm 

tides. Higher ridges that formed in response to previous 

storm events can be subsequently truncated, breached, 

or even enlarged by the accretion of secondary ridges. An 

older inlet spit often contains small active dune fields 

that form subsequent to spit formation. Paleo-inlet spits

no longer occur as beach features, but occur in several 

locations on the barrier and are now classified as 

polydemic features.
CAHA Geologic Resources Inventory Report 27

Table 3. Summary of barrier island system units as mapped by East Carolina University.

Group Subgroup or Map Unit (symbol)

Beach Features Ocean Beach (BF_ocbeach)

Inlet Spit and Flat (BF_spit_flt)

Overwash-Plain Features

Upper Overwash Ramp

Sparse to unvegetated (UO_unveg)

Grass (UO_grass)

Scrub Shrub (UO_scrb_shrb)

Foredune (UO_fdune)

Urban (UO_urbdune)

Middle Overwash Ramp

Sparse to Unvegetated (MO_unveg)

Grass (MO_grass)

Scrub Shrub (MO_scrb_shrb)

Forest (MO_forest)

Interior Marsh (MO_intmarsh)

Isolated Dunes (MO_isodune)

Ringed Dunes and Beach Ridges (MO_rdune_br)

Urban Dune (MO_urbandune)

Paleo-Inlet Spit (MO_p_inl_spt)

Lower Overwash Ramp

Platform Marsh (LO_pf_marsh )

Fringing Berm (LO_fring_brm)

Standplain Beach (LO_spln_bch)

Back-Barrier Berm (LO_bk_br_bm)

Polydemic Features

Tidal Creeks and Tidal Channels (PF_tidal)

Pond (PF_pond)

Transverse Ridges (PF_trnv_dune)

Dune Flat (PF_dune_flat)

Dune Field (PF_dunef)

Sparse to Unvegetated Dune Field (PF_dune_unvg)

Grass Dune Field (PF_dune_grss)

Forested Dune Field (PF_dune_fors)

Urbanized Dune Field (PF_dune_urb)

Algal Flat (PF_algal_flt)

Ridge and Swale (PF_rdg_swl )

Swale Marsh (PF_swl_marsh)

Paleo-Inlet Spit (PF_p_inl_spt)

Anthropic Features

Constructed Dune-Ridges (AF_cn_dune_r)

Constructed Interior Dune-Ridges (AF_cn_idune)

Road/parking Areas (AF_rd_prk)

Dredge Channels/Spoils(AF_drdge)

Excavations (AF_excavate)

Anthropic Overprint (AF_an_overpr)
28 NPS Geologic Resources Division

New and active inlet spits are unvegetated or grassed 

with Spartina patens. The vegetation on older inlet spits 

often consists of mixed grasses that include Spartina 

patens and a small growth of scrub shrub.

Overwash-Plain Features

Upper Overwash Ramp Unit

The upper overwash ramp begins at an island’s berm 

crest, which is the highest point on an overwashdominated barrier island. The upper overwash ramp 

extends gently downslope to the middle overwash ramp, 

more steeply to the lower overwash ramp, or,

occasionally, directly into the adjacent estuary with an 

eroding sediment-bank shoreline. The upper overwash 

ramp is a slightly undulating, high and dry surface that 

frequently contains small isolated dunes, and is often 

characterized by a shell gravel pavement resulting from 

overwash events. A natural dune field or anthropic 

constructed dune ridge generally occurs on the upper 

overwash ramp along the island berm crest. In the latter 

situation, the ocean side of the upper overwash ramp 

begins at the depositional or scarped boundary at the top 

of the ocean beach. As the major source of dune sands is 

directly off the beach, most natural dune fields are

superimposed on the uppermost portion of the upper 

overwash ramp.

Upper Overwash Ramp: Sparse to Unvegetated

The upper overwash ramp is predominantly subaerial 

and may be overwashed during storms by ocean waves 

that transport sand across the beach and berm onto it, 

occasionally reaching the sound. This process builds 

island elevation and erodes the beach and foredunes. 

Recent overwash deposits have no macrovegetation.

Upper Overwash Ramp: Grass

This unit is part of the overwash-plain features group 

and the upper overwash ramp subgroup. As the upper 

overwash ramp decreases in elevation away from the 

ocean beach, fresh groundwater dominates and rises,

allowing an increased vegetative cover that grades 

successively from the xeric community to the grass flat 

and scrub shrub communities on the upper overwash 

ramp. The grass community is dominated by the 

following species:

• Uniola paniculata (sea oat)

• Spartina patens (salt meadow hay)

• Andropogon scoparius (broomstraw rush)

• Hydrocotyle bonariensis (pennywort)

• Cakile edentula (sea rocket)

Where the uppermost portion of the upper overwash 

ramp is dominated by salty groundwater or a relatively 

deep freshwater table, the surface is characterized by a 

xeric vegetation community. These communities have 

low species diversity and are dominated by sparse 

growth of the following species:

• Gaillardia pulchella (firewheel)

• Opuntia spp. (prickly pear cactus)

• scattered Juniper virginiana (eastern red cedar)

• irregular and splotchy growth of lichens and moss on

the sand surface

Upper Overwash Ramp: Scrub Shrub

As the upper overwash ramp decreases in elevation away 

from the ocean beach, fresh groundwater dominates and 

rises relative to the land surface, resulting in an increased 

vegetative cover that grades successively from the xeric 

community to the grass flat and scrub shrub 

communities on the upper overwash ramp. Where the 

upper overwash ramp is very wide with a significant 

natural dune field or constructed dune ridge, an 

extensive scrub shrub community expands in the 

oceanward direction. This community is dominated by 

the following species, along with abundant grasses and 

vines:

• Baccharis halimifolia (salt myrtle)

• Myrica cerifera (wax myrtle)

• Ilex vomitoria (yaupon holly)

• Iva frutescens (marsh elder)

• Myrica pensylvanica (bayberry)

• Juniper virginiana (eastern red cedar)

• Spartina patens (salt meadow hay)

• Smilax spp. (cat brier)

• Toxicodendron radicans (poison ivy)

• Parthenocissus quinquefolia (Virginia creeper)

Upper Overwash Ramp: Foredune

Natural foredunes are frequently absent, particularly in 

regions where constructed dune ridges have been built 

and maintained by human efforts. In areas where such

dune ridges have not been built or regularly maintained, 

natural foredunes often form along the uppermost 

portion of the overwash plain. Foredune size depends 

largely on sand availability. The dunes have an irregular 

geometry and are variable in size and number. As the 

wind blows in many different directions throughout the 

seasons, any single dune is built and modified 

continuously through time with abundant blowouts, cut 

and fill structures, and scarping along the ocean side or 

along overwash channels through the dune field. 

Foredunes occasionally develop concentric rings of 

alternating vegetated and unvegetated areas.

Foredunes are mostly vegetated with Uniola paniculata 

(sea oats). However, on the back side of a large dune field 

or as the distance from the ocean increases, salt spray is 

diminished, with a corresponding increase in vegetation 

diversity. Plants that commonly occur on the lee side of 

the dune field include the following:

• Spartina patens (salt meadow hay)

• Cakile edentula (sea rocket)

• Solidago sempervirens (goldenrod)

• Myrica cerifera (wax myrtle)

• Occasionally Juniper virginiana (eastern red cedar) and 

groundcover plants such as Hydrocotyle bonariensis 

(pennywort)
CAHA Geologic Resources Inventory Report 29

Overwash channels may occur between foredunes on the 

upper overwash plain. These shore-perpendicular 

features are formed by oceanside overwash events that 

scour interdunal channels and may become isolated, 

ephemeral ponds due to overwash deposition during the 

waning stages of a storm event.

Middle Overwash Ramp Unit

The middle overwash ramp is a relatively flat and dry to 

slightly wet surface that slopes gently away from the 

upper overwash ramp. The boundary between the upper 

and middle overwash ramps is characterized by a 

dramatic step down when the island segment is heavily 

vegetated. The dense scrub shrub or forest vegetation 

disrupts the storm-surge flow, causing rapid deposition 

of sediments during overwash events. The step down is 

generally composed of sand with interbeds of beach shell 

gravel.

The middle overwash ramp may be very extensive on a 

wide island, particularly in the presence of a welldeveloped molar-tooth structure with major tidal 

channels on the lower overwash ramp. In contrast, the 

middle overwash ramp may be absent on a narrow 

island. In this situation, the upper overwash ramp is steep 

and drops directly onto the lower overwash ramp or 

even into the back-barrier estuary, with an eroding 

sediment-bank shoreline supplying sand for 

development of an estuarine strandplain beach.

Vegetation on the middle overwash ramp displays 

downslope zonation as a direct function of water table 

depth, frequency and magnitude of overwash events, and 

time since the last overwash event. Storm events that 

deposit new overwash sediment may also rip up and/or 

bury existing vegetation. The resulting increase in middle 

overwash ramp elevation resets the clock with respect to 

the location and succession of dominant vegetation that 

emerges in the years following the overwash event.

Middle Overwash Ramp: Sparse to Unvegetated

Immediately after a major storm event that delivers a new 

overwash fan across the middle overwash ramp, the 

sediment surface is essentially an unvegetated flat. 

However, in subsequent years, grasses begin to develop 

and the new overwash plain slowly evolves into one of 

the following dominant vegetation groups, depending 

upon subsequent storm and flooding patterns; elevation, 

width, and dissection of the middle overwash ramp with 

tidal channels; and composition and location of the 

groundwater table.

Middle Overwash Ramp: Grass

When the upper portion of the middle overwash ramp 

frequently receives minor amounts of salt spray, aeolian 

sand, and overwash sediment, the flats will be dominated 

by the following:

• Spartina patens (salt meadow hay)

• Andropogon scoparius (broom straw)

Middle Overwash Ramp: Scrub Shrub

When the upper portion of the middle overwash ramp 

has not been impacted recently by major storm events 

and overwash sediment fans, the flats are dominated by 

scrub shrub. Established scrub shrub disrupts flow 

during small overwash events, resulting in deposition of 

the overwash sediment as a series of “stair” steps within 

the scrub shrub flat. Large overwash events can kill or 

partially or entirely uproot the scrub shrub, resetting the 

process of vegetation succession.

The scrub shrub flat is dominated by the following 

species:

• Baccharis halimifolia (salt myrtle)

• Myrica cerifera (wax myrtle)

• Ilex vomitoria (yaupon holly)

• Iva frutescens (marsh elder)

• Myrica pensylvanica (bayberry)

• Juniper virginiana (eastern red cedar)

• Spartina patens (salt meadow hay)

• Smilax spp. (cat brier)

• Toxicodendron radicans (poison ivy)

• Parthenocissus quinquefolia (Virginia creeper)

Middle Overwash Ramp: Forest

In the absence of major storm events and overwash 

sediment fans, the scrub shrub flats can locally evolve 

into a forest-dominated middle overwash ramp 

characterized by larger growth with a well-developed 

overstory. Establishment of a forest within the middle 

overwash ramp indicates that overwash events are rare,

due to a low frequency of major storm activity, low rates 

of ocean shoreline recession, and/or the presence of a 

large natural dune field or large constructed dune ridges. 

However, a large overwash event can kill trees and erode 

out large portions or all of the forest. Such an event 

resets the process of vegetation succession.

The forested flat is dominated by the following:

• Pinus sp. (pine)

• Quercus virginiana (live oak)

• Juniper virginiana (eastern red cedar)

Almost all forested flats contain a major understory of 

shrubs, including the following:

• Myrica cerifera (wax myrtle)

• Ilex vomitoria (yaupon holly)

• Smilax sp. (cat brier)

• Toxicodendron radicans (poison ivy)

• Vitis rotundifolia (muscadine grape)

The shrubs and vines occur throughout the forest, but 

their densest growth is generally near the periphery.

Middle Overwash Ramp: Interior Marsh

The lower portion of the middle overwash ramp is in the 

supratidal zone, which has a high water table that is 

frequently flooded by irregular wind and storm tides 
30 NPS Geologic Resources Division

with estuarine waters flowing through associated tidal 

channels. This process can result in the formation of vast 

algal mats and interior marsh. With time and subsequent 

overwash events, the elevation of the middle overwash 

ramp increases and the irregularly flooded algal flats and 

interior marsh may evolve into dry grass flats.

The interior marsh is characterized by organic-rich 

sandy soil with a water table that fluctuates from a few 

inches below ground level to above ground level,

depending on rainfall and irregular wind tides. The 

interior marsh of this irregularly flooded wind-tidal 

system is similar to the high marsh of the regularly 

flooded astronomically tidal system.

The interior marsh grades into the platform marsh of the 

lower overwash ramp with a gentle decline in elevation 

that ranges from a few feet to a few inches above MSL. 

The interior marsh has a sand substrate, whereas the 

substrate in the platform marsh is generally sandy peat, 

with less sand content and more organic matter. 

Submerged aquatic vegetation and marsh-grass wrack 

are blown into the interior marsh through tidal channels 

during storm flooding.

The dominant vegetation of the interior marsh is 

extremely variable, depending on the frequency of 

flooding and the water chemistry. Higher-salinity marsh 

plants include the following:

• Spartina alterniflora (smooth cordgrass)

• Spartina patens (salt meadow hay)

• Juncus roemerianus (black needlerush)

• Distichlis spicata (saltgrass)

• Borrichia frutescens (sea oxeye)

Dominant plants in areas characterized by lower-salinity 

to freshwater conditions include the following:

• Scirpus robustus (soft-stemmed bulrush)

• Cladium jamaicense (sawgrass)

• Phragmites australis (common reed)

• Spartina cynosuroides (giant cordgrass)

• Typha angustiflora (cattail)

Middle Overwash Ramp: Isolated Dunes

Small-scale isolated dunes are common on the sparse to 

unvegetated portions of active middle overwash ramps 

and within the algal flats that frequently occur on the 

ramps’ lower portions. Isolated dunes in these habitats 

are particularly active and move across the flats during 

the dry season. These dunes may have almost any 

geometry due to the multiplicity of wind and water 

dynamics affecting the middle overwash ramp.

The density and diversity of vegetation on a stable dune 

generally increase over time, with Spartina patens (salt 

meadow hay) or scrub shrub predominating. Vegetation 

spreads inward toward the dune nucleus until a major 

flood event occurs, destroying the dune or reworking it 

into a regular ringed beach ridge, as described below.

Middle Overwash Ramp: Ringed Dunes and Beach Ridges

An isolated dune that becomes stabilized by grasses on a

sparse to unvegetated or algal flat–dominated middle 

overwash ramp increases in size over time by ringed 

accretion around a portion or the entirety of the dune. 

Grasses around the nucleus dune trap sand during the 

dry seasons, forming smaller dunes. The flats then 

become flooded during subsequent stormy seasons that 

rework the new perimeter dune sands, forming beach 

ridges that ring all or part of the nucleus dune. The 

isolated ringed dunes can become quite large, with 

numerous ringed structures around their perimeters. 

Flowing currents resulting from a major overwash event 

can truncate the dunes and cause blowouts within the 

nucleus dune, resulting in complicated dune geometries. 

A major flood event may severely truncate or destroy a 

ringed dune.

The same process occurs when the middle overwash 

ramp encroaches on an older component of the barrier 

island, such as Ocracoke and Portsmouth villages. 

During dry periods, windblown sands are trapped 

against the stabilized land mass; during stormy periods, 

these sands are reworked into a beach ridge by water that 

floods the middle overwash ramp. These beach ridges 

run subparallel to the portion of the land mass that has 

trapped the sands.

Isolated ringed dunes on the middle overwash ramp may 

initially be stabilized by Spartina patens (salt meadow 

hay) and Borrichia frutescens (sea oxeye). The density 

and diversity of vegetation on a large stabilized dune may 

increase over time to include scrub shrub.

Middle Overwash Ramp: Paleo-inlet Spit

When an inlet opens through a barrier island segment, 

the upper overwash ramp is generally eliminated and the 

existing middle overwash ramp becomes the location of 

inlet spit formation. An inlet spit consists of one or more 

subparallel ridges that occur adjacent to an existing inlet 

or paleo-inlet. The spits are slightly curved ridge 

structures occurring at oblique angles to the ocean 

shoreline. The spit geometry results from two forces: the 

flow dynamics of regular, high spring tide, and small 

storm-tide overwash events that rework windblown 

sands deposited along the inlet during dry periods. 

During a tidal event, a higher inlet spit ridge that formed 

in response to a previous storm event may be truncated 

or breached, or may develop an accreted secondary 

ridge. Older inlet spits may contain small active dune 

fields, particularly after vegetation has been established. 

When an inlet closes and an upper overwash ramp 

reforms in front of the inlet spit, the spit becomes a 

paleo-inlet spit preserved on the middle overwash ramp.

Vegetation is absent on an active inlet spit. However, an

inlet spit may be abandoned with the development of a 

younger spit as the inlet migrates. The older, abandoned 

inlet spit becomes grassed and, over time, may even 

become vegetated with scrub shrub.
CAHA Geologic Resources Inventory Report 31

Lower Overwash Ramp Unit

The lower overwash ramp is a flat, wet, intertidal surface 

that extends into the back-barrier estuary. It is usually 

made up of an extensive platform marsh with a thin (<1 

m [3.3 ft]) sandy peat substrate on a fine sand base. The 

lower overwash ramp may be very extensive on a wide 

island, particularly true in the presence of a welldeveloped molar-tooth structure with tidal channels 

cutting through the lower overwash ramp into the 

lowermost portion of the middle overwash ramp. In 

contrast, the middle overwash ramp and even the lower 

overwash ramp may be absent on a narrow island. In this

case, the upper overwash ramp is steep and drops 

directly onto the lower overwash ramp or into the backbarrier estuary with a strandplain beach.

The lower overwash ramp is also characterized by strong 

vegetation zonation across the flat, which is controlled 

by salinity gradients and water-level fluctuations caused 

by the regular astronomical tides (in the vicinity of inlets) 

and by irregular wind tides that occur within the adjacent 

estuarine water body. The outer edge of the platform 

marsh is generally an erosional scarp along the higherenergy, open shorelines and associated tidal channels. 

However, marsh shorelines in more protected 

embayments occur as ramps sloping gradually onto 

shallow back-barrier shoals.

Lower Overwash Ramp: Platform Marsh

The platform marsh is the major component of the lower 

overwash ramp. It is irregularly flooded by wind tides, 

except near inlets, where it is also flooded by small, 

regular astronomical tides. The platform marsh is 

characterized by a thin (<1 m [3.3 ft]) peat or sandy peat 

substrate that is permanently saturated with standing 

water and grades downward into a fine sand base. Tidal

creeks form extensive drainage networks in many 

platform marsh environments, with occasional small 

ponds scattered within the marsh. The marshes have a 

low diversity of vegetation that is strongly zoned 

subparallel to the outer marsh perimeter and the backbarrier berms occurring within the platform marsh.

Platform marshes are often cut with shore-perpendicular 

tidal channels to produce molar-tooth structures on the 

lower overwash ramp. Both ends of the tidal channels 

shallow, flatten, and broaden out into deltaic lobes. The 

tidal deltas are deposited by flooding through the tidal 

channels and may be intertidal or supratidal sand bodies. 

Fine-grained sediments of the tidal deltas are frequently 

bound by algae (microbial organisms) and occasionally 

sparsely vegetated with Spartina patens (salt meadow 

hay).

Platform marshes slope slightly toward the sound and

end abruptly at the estuarine shoreline with an erosional, 

undercut scarp that ranges from a few centimeters to <1 

m (3.3 ft) above the estuarine floor. In areas with 

sufficient sand, the soundward edge of a platform marsh 

may contain a strandplain beach located in front of and 

burying the scarp. The outer perimeters of most platform 

marshes contain elevated fringing berms just landward of 

and parallel to the erosional scarps. This fringing berm is 

generally <1 m (3.3 ft) high and is composed of a mixture 

of fine sand and wrack.

Wrack, which plays a critical role in the platform marsh,

occurs as small to large irregular patches or in shoreparallel rows that represent different storm water levels. 

Wrack deposits are composed of dead submerged 

aquatic vegetation or marsh vegetation, occur at varying 

distances within the marsh as a function of water-level 

elevation, and are products of specific events and 

therefore in various stages of decay.

Depressions may form in a marsh as a result of the 

accumulation of multiple wrack deposits in the same area 

over time, which prevents recolonization and causes

some peat compaction. Depressions below MSL pond 

water. Ponds within the platform marsh may vary from 

hypo- to hypersaline, depending on groundwater flow, 

weather (wet versus dry season), and location relative to 

active inlets. Marsh plants that colonize a decomposing 

wrack pile or shallow pond differ markedly from the 

predominant marsh grasses in platform marshes.

The dominant platform marsh grasses in the northern 

Outer Banks study area include Spartina patens (salt 

meadow hay) or Spartina alterniflora (smooth cordgrass) 

growing in narrow fringes along outer platform marsh

perimeters. The outer fringe of a marsh may be severely 

eroded and even stripped of vegetation. The eroded 

areas often have Juncus roemerianus (black needlerush) 

at the water’s edge, and Salicornia bigelovii (annual 

marsh glasswort) may colonize the stripped zone. The 

platform marsh grades inward to vast areas of Juncus 

roemerianus (black needlerush). In the proximity of 

major inlets, the Spartina alterniflora fringe becomes 

more expansive at the expense of Spartina patens, and 

replaces Juncus roemerianus (black needlerush) on most 

of the platform.

Thick wrack deposits kill the underlying dominant 

platform marsh vegetation. As wrack decomposes, rows 

or patches of different plants locally recolonize the 

denuded areas. The type of recolonizing vegetation is a 

function of elevation and salinity, with dominant plants 

including Borrichia frutescens (sea oxeye), Salicornia 

bigelovii (annual marsh glasswort), Salicornia virginica 

(perennial marsh glasswort), Distichlis spicata (saltgrass), 

with small growth of the scrub shrub species Myrica 

cerifera (wax myrtle), Iva frutescens (marsh elder), and 

Baccharis halimifolia (salt myrtle).

Lower Overwash Ramp: Fringing Berm

Most sound-side shorelines within platform marshes are 

composed of scarped and undercut sandy peat banks 

that range from a few centimeters to 1 m (3.3 ft) in 

height. Storms deposit one or more elongate fringing 

berms parallel to the shore at regular distances from the 

sound shoreline. The most prominent fringing berm is 

generally <10 m (33 ft) inside of the marsh perimeter and 

is a product of the average storm surge resulting from the 

most common winter storms. These fringing berms are 

composed of submerged aquatic vegetation wrack 

and/or marsh-grass wrack mixed with sand and other 
32 NPS Geologic Resources Division

debris; they may be up to 1 m (3.3 ft) thick in rows 1 to 3 

m (3.3 to 10 ft) wide. As the scarped marsh peat erodes 

along the shorelines over time, the fringing berm is 

systematically moved landward in response to the 

cumulative impact of many annual winter storms. 

Depending upon the exposure, the marsh grasses in front 

of the fringing berm may be ripped off by the wave 

energy, leaving a barren peat surface exposed. This 

surface is frequently colonized by Salicornia bigelovii.

The fringing berms are generally dominated by Spartina 

patens (salt meadow hay) and Spartina cynosuroides 

(giant cordgrass), with some woody shrubs, including 

Myrica cerifera (wax myrtle), Iva frutescens (marsh 

elder), and Baccharis halimifolia (salt myrtle). The back 

side of the fringing berm drops off more abruptly, with 

vegetation grading into vast areas of Juncus roemerianus 

(black needlerush). The fringing berm plant assemblage 

also occurs in the transition zone between platform 

marsh and back-barrier berms.

Lower Overwash Ramp: Strandplain Beach

Small strandplain beaches frequently occur in front of 

the eroded scarps of adjacent platform marshes,

particularly where cross-barrier island features (e.g., 

transverse ridges, ridge and swale complexes) intersect 

the estuarine shoreline or where back-barrier shoals are 

well developed within the adjacent estuary. The presence 

and development of a strandplain beach are often 

temporary or seasonal; its presence is in part a direct 

function of storm frequency, abundance, and patterns.

An active strandplain beach generally has no 

macrovegetation. However, during extended calm 

periods, such as the warm summer months, various types 

of algae may temporarily stabilize the sand on these 

beaches.

Lower Overwash Ramp: Back-Barrier Berm

Back-barrier berms are sand deposits on top of the lower 

overwash ramp that form in response to the interaction 

between estuarine and oceanic storm dynamics. They 

generally occur as major depositional features that are 

not subparallel to the estuarine shoreline, in contrast to

small-scale fringing berms. Rather, these features are 

farther inland and occur as ridges that are subparallel to 

the larger-scale overwash plain. Back-barrier berms tend 

to be <2 m (6.6 ft) high and <25 m (82 ft) wide, and are 

composed totally of clean sand. Occasionally, the lateral 

ends adjacent to the tidal channels have a recurved 

geometry that turn into the island.

Barrier island segments that have a lower overwash ramp

with a well-developed molar-tooth structure also 

commonly have one or two arcuate back-barrier berms 

that occur on the platform marsh and extend the entire 

length of the large-scale lobate overwash plain. 

Individual back-barrier berms within this system occur 

along the width of the platform marsh and between 

adjacent tidal channels.

Vegetation on back-barrier berms is primarily scrub 

shrub, particularly on smaller and lower features. At the 

highest elevation, the vegetation becomes sparse and 

consists mainly of Juniper virginiana (eastern red cedar) 

and Spartina patens (salt meadow hay), with large 

unvegetated areas of exposed sand. In addition, 

abundant Baccharis halimifolia (salt myrtle), Iva 

frutescens (marsh elder), Myrica cerifera (wax myrtle),

and Ilex vomitoria (yaupon holly) may be present.

Some larger and higher back-barrier berms contain 

maritime forests consisting of various Pinus spp. (pine),

Quercus virginiana (live oak), and Juniper virginiana 

(eastern red cedar) that form an overhead canopy. 

Shrubs such as Baccharis halimifolia (salt myrtle), Iva 

frutescens (marsh elder), Myrica cerifera (wax myrtle),

and Ilex vomitoria (yaupon holly) grow as an understory 

and mainly near the forest periphery.

Polydemic Features

Polydemic features are those that occur in or inhabit two 

or more regions on a barrier island. Thus, these features 

are products of processes that can occur within any 

portion of the overwash plain or over several different 

portions of the overwash plain of the simple barrier 

island model.

Examples of polydemic features include overwash 

channels (described in the “Upper Overwash Ramp”

section), paleo-inlet spits (described in the Middle 

“Overwash Ramp Unit” section), and tidal deltas 

(described in the “Lower Overwash Ramp” section). 

Other major polydemic features are described below.

Tidal Channel Unit

Tidal channels, also known as tidal creeks, generally 

form on flood tidal deltas and persist after the inlet is 

closed, when the shallow shoals evolve into platform 

marshes. Tidal channels are common in platform 

marshes, particularly in areas adjacent to major inlets 

where astronomical tides are prevalent. The channels are 

often truncated by the overwash ramp as it migrates onto 

the platform marsh. However, tidal channels 

occasionally extend from the lower overwash ramp well 

into the middle overwash ramp and even into the upper 

overwash ramp on some island segments. These 

segments are generally characterized by rapidly eroding 

ocean shorelines, where the upper overwash ramp of the 

migrating barrier has moved landward onto the lower 

overwash ramp in direct response to major storms and 

resulting overwash events. The uppermost reaches of 

these tidal channels tend to be freshwater and fed 

directly from the groundwater occurring in high portions 

of the upper overwash ramp.

An active overwash plain will completely bury the 

headwaters of tidal channels. Water flow onto and off of 

the overwash plain carries significant volumes with 

sufficient energy to erode the tidal channels occurring 

between segments of the platform marsh. Over time,

these portions of the tidal channels are eroded laterally 

and vertically to produce channels between platform 

marsh segments. The resulting geomorphology has a

classic molar-tooth structure. These shore-perpendicular 

tidal channels connect the middle overwash ramp 
CAHA Geologic Resources Inventory Report 33

directly with the estuary and move overwash water off 

the island during ocean-overwash events; they also carry 

estuarine storm-tide water into algal flats and interior 

marshes on the middle overwash ramp. The tidal 

channels tend to be deep (up to 3 to 4 m [10 to 13 ft]) and 

extend completely through the platform marsh, with 

steeply scarped peat shorelines along the edges. Each end 

of a tidal channel (inner and outer edges of the lower 

overwash ramp) shallows, flattens, and broadens out into 

small-scale deltaic lobes of the submarine structures.

The tidal channel perimeters within the upper overwash 

ramp and uppermost reaches of the middle overwash 

ramp are generally dominated by freshwater, with 

perimeter marshes dominated by Scirpus robustus (softstemmed bulrush), Cladium jamaicense (sawgrass), 

Spartina cynosuroides (giant cordgrass), Typha 

angustiflora (cattail), and Phragmites australis (common 

reed). The vegetation along the fringes of the tidal 

channels is dominated by Juncus roemerianus (black 

needle rush) marsh grass, which expands laterally into 

the platform marshes of the lower overwash ramp.

Pond Unit

Ponds form in many different places within the general 

overwash plain in response to very different sets of 

processes. Consequently, ponds tend to be ephemeral, 

with variable water composition. The presence of many 

ponds is a direct function of the patterns, frequencies, 

and abundance of storms and rainfall. During times of 

frequent storms and abundant rainfall, most ponds are

filled with salt- or freshwater, depending on their 

locations within the barrier system. Ponds may become 

wetland marshes during intermediate periods; during 

periods of low rainfall, they may become algal flats or 

even dry up completely.

The following list contains general descriptions of 

important features of ponds occurring on simple barrier 

islands.

1)In regions without constructed dune ridges, storm 

overwash channels flow through the frontal dune 

fields on the island berm crest of the upper overwash 

ramp. These channels frequently leave a series of 

shore-perpendicular, ephemeral ponds after a storm 

subsides. They are commonly filled by windblown 

sand or overwashed sediment. These ponds initially 

contain saltwater, but those that persist through time 

may become brackish and ultimately freshwater ponds 

controlled by rain and groundwater.

2)Back-barrier berms that form on the platform marshes 

of the lower overwash ramp are frequently breached 

by storm surges, producing a series of smaller, 

elongate, shore-perpendicular tidal channels. After a 

storm surge recedes, low depressions in the centers of 

tidal channels become a series of ponds in the backbarrier berms. These ponds are often permanent and 

are initially saline, but freshen over time.

3)Some active tidal channels are located between 

platform marshes within the molar-tooth structure on 

the lower overwash ramp. As fan delta sands build up 

and become stabilized by marsh grasses, the outside 

and inside edges of these tidal channels may become 

blocked, forming ponds. Because these ponds are at 

MSL, they are flooded by both spring and storm tides 

and generally remain brackish.

4)Small, irregular, and shallow ponds occur frequently 

within the interior marshes of the middle overwash 

ramp and the platform marshes of the lower overwash 

ramp. In some marshes, these ponds are extremely 

abundant. They can form in several different ways.

a)Many platform marshes contain shallow (<0.5 m [1.6 

ft] deep) ponds that appear to form in response to 

large wrack accumulations that kill the underlying 

grasses. As unvegetated patches in the marsh dry 

out, peat compaction, in concert with possible 

oxidation of some peat, leaves shallow depressions 

that become filled with water. This water is generally 

brackish, with variable salinity ranging from hypoto hypersaline, depending on season and weather 

conditions.

b)A few platform marshes appear to be in a 

constructive mode, with marsh growing onto the 

shallowest portions of the back-barrier sand shoals. 

Slightly deeper (<0.5 m [1.6 ft]) areas have become 

ponds with gradual slopes around the edges. These 

ponds are interconnected to adjacent estuaries and 

have similar salinities.

c) Some platform marshes appear to be in a destructive 

mode, with slightly deeper (<1 m [3.3 ft]) ponds. The 

edges of these ponds are erosional and consist of 

scarped peat that drops off abruptly into deeper 

water. This results in a platform marsh with a 

“Swiss-cheese” fabric of ponds that have variable 

salinity ranging from hypo- to hypersaline,

depending on season and weather conditions.

5)After an inlet through a barrier island closes, the floodtidal delta sand shoals quickly evolve into intertidal 

marsh islands that separate the many tidal channels 

radiating out from the main inlet channel. As the ocean 

shoreline recedes and the barrier migrates on top of 

the flood tidal delta, overwash begins to fill portions of 

the channels from the front side while storm surges fill 

portions from the estuarine side. The remaining long, 

linear, and relatively deep ponds have various

orientations; they occur along the boundary between 

the middle and lower overwash ramps or within floodtidal delta marshes.

Ponds vary in size, substrate composition, pH, 

vegetation, and water color; water chemistry is similar to 

that of local groundwater (Mallin et al. 2006). Ephemeral 

ponds, which may contain water for a few weeks or 

years, are polydemic; a survey of several on northern 

Ocracoke Island in August 2004 found that they had 

dimensions of 100 m2 (1,076 ft2

) and about 0.5 m (1.6 ft) 

mean depth, with temperatures ranging from 31° to 33°C, 

salinities of 5 to 14 psu, and dissolved oxygen 

concentrations of 5.3 to 10.5 mg/L (72% to 140% 

saturation) (Mallin et al. 2006).
34 NPS Geologic Resources Division

Ephemeral ponds provide important breeding habitat for 

amphibians and reptiles and support vertebrates, 

crustaceans, insects, mollusks, annelids, rotifers, and 

other species (Mallin et al. 2006). Fish living in the ponds 

came from overwash and intentional stocking. Species 

include Lepomis gibbosus (pumpkinseed), Cyprinodon 

variegatus (variegated minnow), Gambusia a. holbrooki 

(mosquitofish), Fundulus confluentus (marsh killifish), 

Micropterus salmoides (largemouth bass), Lucania parva 

(rainwater killifish), Anguilla rostrata (American eel), 

Fundulus heteroclitus (mummichog), Lepomis 

machrochirus (bluegill), Cyprinus carpio (carp), and 

Menidia beryllina (inland silversides) (Mallin et al. 2006). 

Mammals utilizing freshwater ponds include muskrats, 

otter, Procyon lotor lotor (raccoon), and Odocoilus 

virginianus virginianus (white-tailed deer) (Mallin et al. 

2006).

Transverse Ridge Unit

Transverse ridges are long, low, and fairly straight 

geomorphic ridges oriented transverse to a barrier island. 

They can form in several different ways.

In one mechanism, scattered and isolated dune sands are 

reworked into elongate beach ridges by waves or stormsurge floodwaters that are temporarily ponded on an 

overwash plain. These ridges are often low (<1 m [3.3 ft] 

high), narrow (1 to 3 m [3.3 to 10 ft] wide), and up to 

several hundred meters long.

A second mechanism builds large transverse ridges that 

incorporate huge volumes of sand as elongate dune 

structures extending transversely across the upper and 

middle overwash ramps. These sediment-rich dune 

features may occur along active inlets on the inlet sides of 

older inlet spits, or downwind from unvegetated sand

flats. In either case, aeolian-driven sands accumulate 

along the edges of existing features during dry periods. 

The sand is trapped and stabilized by dune vegetation. 

During subsequent storms, active overwash across the 

overwash plain or inlet spit can truncate the dune 

structure, leading to further elongation and producing a 

complicated dune structure characterized by erosion and 

overwash blowouts. Large-volume transverse dune

ridges occurring within a barrier island may be important 

evidence for the existence of former inlets.

Active transverse ridges have large unvegetated areas of 

exposed sand, with some areas stabilized by Uniola 

paniculata (sea oat) and Spartina patens (salt meadow 

hay). Older and less active portions of transverse dune 

ridges are vegetated primarily with scrub shrub,

including Baccharis halimifolia (salt myrtle), Iva 

frutescens (marsh elder), Myrica cerifera (wax myrtle),

Ilex vomitoria (yaupon holly), and Juniper virginiana 

(eastern red cedar). Old transverse ridges are dominated 

by maritime forests consisting of various pine species

(Pinus spp.), Quercus virginiana (live oak), and Juniper 

virginiana (eastern red cedar). These trees form an 

overhead canopy along with massive growths of various 

vines, including Smilax sp. (cat brier), Toxicodendron 

radicans (poison ivy), and Vitus rotundifolia (muscadine 

grape). The shrubs and vines occur throughout the 

forest, but their densest growth is generally near the 

periphery.

Dune Flat Unit

When an island segment has ample sediment supply, 

aeolian processes during non-storm tide conditions can 

transport large volumes of sand landward of the island 

berm. This process creates a broad, rolling sand flat with 

an elevation significantly higher (2 to 3 m [6.6 to 10 ft]) 

than those of the island berm and upper overwash ramp. 

The surface of the aeolian dune flat ranges from very flat 

to slightly undulating, with <2 m (6 ft) of relief related to 

small-scale deflation and dune features.

When sufficient sediment is available, an aeolian dune 

field may form on top of a far more extensive aeolian 

dune flat. In this situation, the dune flat forms a broad 

platform that generally encircles the perimeter of the

dune field. Such features are very important in the region 

extending from Kitty Hawk to Whalebone Junction, 

where aeolian dune flats have helped to build a barrier 

segment that is higher than most segments dominated by 

inlets and overwash. This difference has attracted 

development, resulting in almost total urbanization of 

this island segment.

Dominant vegetation on the pre-1930s aeolian dune flats 

differed markedly from that found after the 1930s 

between Kitty Hawk and Whalebone Junction. Frost 

(2000) described the dominant vegetation in the early 

1900s based on regional photographs taken by the 

Wright Brothers between 1900 and 1912 in the area 

extending from Kill Devil Hills to Kitty Hawk. Because 

the aeolian dune flats have clean, well-sorted dune sands

and higher elevations than overwash plains, a major 

freshwater aquifer frequently rises to the land surface. 

This process creates broad damp areas and shallow 

ponds dominated by algae and freshwater marsh plants, 

respectively. The small dunes rose above the water table 

and were dominated by Spartina patens (salt meadow 

hay) during non-stormy periods. Aeolian dune flats 

farthest from the ocean were usually stabilized by scrub 

shrub species and ultimately became forested with Pinus 

spp. (pine), Ilex vomitoria (yaupon holly), and Quercus 

virginiana (live oak).

In the 1930s, barrier island modification and 

urbanization began in earnest. Following bridge 

construction from the mainland to the barrier islands 

and paving of Highway 12 in the Kitty Hawk to Nags 

Head area in the early 1930s, initial construction of 

barrier-dune ridges in the late 1930s, and extensive 

construction of oceanfront motels and houses, the 

character of vegetation on the aeolian dune flats changed 

dramatically. The beach, which had been the major 

source of sand for aeolian and overwash transport 

processes, was cut off from the dune flats, decreasing the 

effects of wind and associated salt spray. In response, the 

aeolian dune flats were successively vegetated by an 

extensive growth of scrub shrub, followed by pine and 

live oak forests. Today, most dune flats in this area are

fully developed, with lots, homes, and a highly urbanized 

understory of lawns and gardens, as well as the
CAHA Geologic Resources Inventory Report 35

occasional occurrence of an upperstory of pine and live 

oak woods.

Dune Field Unit

When island segments have large sediment supplies and 

are dominated by aeolian processes, natural dune fields

form on top of the aeolian dune flats. During non-storm 

tide conditions, strong winds transport large volumes of 

sand landward from the barrier beach and berm. This 

process results in the development of an active dune 

field, with dune elevations ranging from 3 to 25 m (10 to 

82 ft) or more. In the region extending from Kitty Hawk 

to Whalebone Junction, sediments are provided by 

paleo–Roanoke River delta deposits associated with 

previous climatic conditions and sea-level stands. 

Consequently, much of this barrier segment is dominated 

by the extensive development of dune fields.

Before urban development in the 1930s, large individual 

dunes (e.g., Jockey’s Ridge) with elevations of up to 45 m 

(148 ft) formed. The dune fields generally have a

complex geomorphic character consisting of 

depositional dunes produced by different kinds of storm 

(e.g., fall to spring nor’easters, summer southwesters, and 

summer to fall tropical storms) with multiple wind 

directions. The dune fields are further complicated by 

severe erosional dynamics in concert with the influence 

of upper water tables that result from the wet temperate 

climatic conditions, producing abundant over-steepened 

slopes. These dune fields frequently override forested 

habitats on the back sides of barrier islands, which 

further complicates their depositional, erosional, and 

stabilization patterns.

Back-barrier dune fields may contain numerous buried 

soil profiles. These buried soils reflect various shifts in 

past climatic conditions, such as storms or dry-season 

fires that re-activated dune deposition, and periods of 

wet or fair weather that fostered vegetative stabilization 

of the dune fields (Havholm et al. 2004).

Dominant vegetation on the natural dune fields before 

the 1930s differed markedly from that occurring post1930s. From 1900 through 1912, many natural dune 

fields, including those in front of Kitty Hawk Woods and 

Kitty Hawk Bay (e.g., Kill Devil Hill), on the front side of 

Nags Head Woods (e.g., Run Hill and Jockey’s Ridge), 

and the Seven Sisters dune field in Nags Head Cove and 

the village of Nags Head, were active and essentially

barren of vegetation (Frost 2000). The minor vegetation 

that did exist on these active dunes consisted of scattered 

grasses, including Spartina patens (salt meadow hay). 

Swales between many of the dunes contained shallow, 

freshwater ephemeral ponds dominated by algae and 

freshwater wetland vegetation.

After the establishment of Kill Devil Hill Monument 

National Memorial in 1927, work began in 1929 to 

stabilize with grass the Kill Devil Hill active dune utilized 

by the Wright Brothers. Construction of the first flight 

monument on top of Kill Devil Hill was completed in 

1932, before this land was transferred to the NPS in 1933 

(NPS 2002).

In the past (pre-1970s), dune fields occurring closest to 

the ocean front (e.g., Seven Sisters) tended to be most 

active, whereas those furthest from the ocean (e.g., Nags 

Head Woods) tended to be heavily forested. By the early 

1970s, the ocean front had been completely developed 

and urbanization moved rapidly soundward and into the 

natural dune fields. The remaining Kill Devil Hills were 

quickly developed, followed by Nags Head Cove, the 

north end of Jockey’s Ridge, and the Kitty Hawk dune 

field. Lastly, the village at Nags Head developed the 

southern half of the Seven Sisters dune field. Urban 

development in front of the dune fields cut off the sand 

source from the beach and modified and raised the wind 

field; the construction of houses and pavement and 

establishment of grass, urban gardens, and trees quickly 

stabilized the active dune fields.

Grass Dune Field Unit

Grass was planted in 1929 to stabilize the Kill Devil Hill 

active dune, which was utilized by the Wright Brothers 

and newly designated as the Kill Devil Hill National 

Memorial.

Forested Dune Field Unit

The major portion of Nags Head Woods dune field, 

which is situated on the back side of a wide island 

segment, has historically been heavily forested. Today, 

the high dunes generally contain a mature stand of mixed 

hardwood and pine forest with a perimeter zone of scrub

shrub on the low dune flank along the estuarine side. 

Scrub shrub vegetation generally constitutes a 

transitional zone that occurs within the storm tide zone 

and grades downslope to the intertidal platform marsh of 

the lower overwash ramp.

Algal Flat Unit

Algal flats usually occur in the lower supratidal portion 

of a natural, overwash-dominated barrier island segment 

with a broad middle overwash ramp. They are especially 

common in the presence of a well-developed molartooth structure with tidal channels that dissect the lower 

overwash ramp. The low elevation and high water table 

enable irregular wind and storm tides to flood the middle 

overwash ramp frequently with estuarine waters flowing 

through the tidal channels. The algal flats form in 

response to fluctuating habitat conditions, which range 

from fresh groundwater or rainwater to hypersaline 

waters due to local ponding and evaporation of ocean or 

estuarine waters. With time and subsequent overwash 

events, the elevation of the middle overwash ramp 

increases and the irregularly flooded algal flats may be 

taken over by interior marsh or may shift to dry grass 

flats.

Algal flats also occur in other habitats, including 

ephemeral ponds or depressions characterized by fresh 

to hypo- to hypersaline water conditions. As the water 

table in these ponds drops, the damp floor of the 

depression frequently develops an algal mat. This mat is 

periodically ripped up or buried by subsequent storm 

events. Hypersaline ponds may evaporate, leaving salt 

flats that become vegetatively zoned with Salicornia 

bigelovii (annual marsh glasswort), and Salicornia 
36 NPS Geologic Resources Division

virginica (perennial marsh glasswort), forming rings 

around the peripheries of the depressions that, in turn,

may be surrounded by an outer zone of Distichlis spicata 

(saltgrass) and Borrichia frutescens (sea oxeye).

Ridge and Swale Unit

Ridge and swale geomorphic units occur as sets of 

subparallel couplets consisting of low, regular sand 

ridges and adjacent shallow low swales. The sand ridges 

tend to be linear to slightly curved, uniform features that 

rarely exceed 3 m (10 ft) in elevation. These shoreline 

features formed during a temporary higher stand of sea 

level or a series of storm surge deposits (Riggs and Ames 

2006).

Lower swales between successive beach ridges represent 

beach deposition during periods characterized by slightly 

lowered sea level or non-stormy periods. These swales 

are generally dominated by wetlands. They are filling 

with organic peat deposits that are thickest on the 

estuarine side and thin up onto the subsequent ridge. 

The centers of many swales, particularly those close to 

the estuary, contain open water. Over the years, many of 

the swales have been dredged and opened up as 

navigation channels, with the dredge spoil disposed of on 

adjacent marshes or the low flanks of adjacent ridges.

The most extensive and best developed sets of ridge and 

swale structures form Buxton Woods and Kitty Hawk 

Woods. Buxton Woods (located between Frisco and 

Buxton) is the largest maritime forest on the Outer Banks 

and is approximately 1,630 ± 200 years old (Mallinson et 

al. 2009). It is composed of multiple sets of ridge and 

swale structures occurring at slightly different angles, 

with each set bounded by a major erosional truncation, 

suggesting oscillating sets of events at several different 

time scales. The first set of ridges was built along the 

present Pamlico Sound shoreline and trends northeast–

southwest. The formation of younger east–west-trending

ridges built the island southward (Mallinson et al. 2009).

The Buxton Woods unit contains many freshwater 

ponds and marshes (locally known as sedges) that 

support wildlife. This area was impacted in 1994 by 

Hurricane Emily, which damaged pine forests; the 

resulting breakage allowed for subsequent insect 

infestation. Opening of the pine canopy enabled the 

establishment of hardwood forests in competition with 

the pines, returning this forest habitat to conditions like 

those preceding heavy logging for ship timbers in the 

1800s and early 1900s (Mallinson et al. 2009).

Ridge and swale structures are dominant geomorphic 

units on complex barrier islands and are not products of 

overwash-dominated barrier island dynamics. No such

structure is currently forming on the northern Outer 

Banks. Rather, the ridge and swale island segments were 

produced by processes prevailing in an earlier 

evolutionary stage of the barrier system. Age-dating of 

some structures has indicated that they formed during a 

prior sea-level highstand event or as sea level was rising 

under variable sediment supply and wave energy 

conditions (Mallinson et al. 2009). Most barrier islands 

have since collapsed, and the modern barrier islands 

began to reform about 500 years ago (Sager and Riggs 

1998; Riggs et al. 2000; Grand Pre 2006; Culver et al. 

2007). Thus, the modern inlet and overwash-dominated 

barrier island components have migrated into and 

become welded onto the older barrier island, which had

ridge and swale structures, as exemplified by the Kitty 

Hawk Woods island segment.

Similar ridge and swale features occur on the land masses 

occupied by Ocracoke and Hatteras villages. However, 

these ridge structures are rarely 2 m (6.5 ft) high and are 

spaced much farther apart compared to those in Kitty 

Hawk. They have wide marsh-filled swales. Many of the 

sand ridges have already been buried by the vertical 

growth of peat in response to the ongoing rise of sea 

level.

Because most ridge and swale structures are older than 

surrounding areas of the barrier island and occur on the 

back sides of barrier island segments, they tend to be 

dominated by heavy vegetative cover, except where they 

have been urbanized. The sand ridges have thick forests 

with mature stands of mixed hardwood and pine. 

Because the ridges are not very high, the forest grades 

downslope into an extensive growth of transitional scrub 

shrub vegetation in the supratidal zone, where adjacent 

swales are connected to the estuary. The swales are 

dominated by wetland vegetation. Land-locked swales 

and segments far from the estuaries are dominated by 

swamp forests or linear ponds surrounded by swamp 

forest.

Swale Marsh Unit

When swales are connected to the estuary, the swamp 

forest sequentially grades toward the estuary to 

freshwater and then brackish-water marshes. The 

brackish marshes generally have freshwater zones

immediately adjacent to the ridges due to groundwater 

discharge from these ridges. This habitat grades outward 

into a middle zone dominated by Juncus roemerianus 

(black needlerush) and a broad outer zone dominated by 

Spartina cynosuroides (giant cordgrass) in low brackish 

estuaries, Spartina patens (salt meadow hay) in middle 

brackish estuaries, and Spartina alterniflora (smooth 

cordgrass) in high brackish estuaries.

Anthropic Features

Constructed Dune Ridge Unit

Constructed dune ridges are linear, ocean shoreline–

parallel ridges that are built by sand transportation and 

bulldozing, then vegetated by the planting of grass. The 

size of these features is highly variable. In general, they 

are built over long beach segments and are up to 15 m (49 

ft) wide at the base and up to 5 m (16 ft) tall. The 

purposes of these structures are to prevent the 

disruption of barrier island infrastructure by storm 

overwash and inlets, and to protect building 

superstructures and associated roads. They are built on 

the normal beach-overwash plain profile, which is in 

equilibrium with normal ocean dynamics. However, 

newly constructed dune ridges tend to be severely out of 
CAHA Geologic Resources Inventory Report 37

equilibrium and are rapidly scarped on the ocean side 

and readily eroded by storm surges.

The initial construction of dune ridges began in the late 

1930s with the establishment of Works Progress 

Administration and Civilian Conservation Corps work

camps. Ridges were initially built over the entire distance 

from the Virginia state line and Ocracoke Inlet utilizing 

many different sand-trapping methods, but they have not 

been maintained throughout this entire coastal stretch. 

Thus, some island segments contain only partial or 

terminated ridges. The constructed dune ridges have 

been rebuilt frequently in urbanized areas and in narrow 

island segments where Highway 12 occurs close to the 

ocean shoreline. Many island segments have multiple 

constructed dune ridges along with remnants of “goingto-sea” highways. In a few areas with sufficient sediment 

supply, the beaches tend to be very wide and shallow 

with low net erosion rates. Some dune ridges built within 

these wide beach segments have been naturally modified 

over time into natural dune fields, which are usually 

quite wide and high and comprise many irregularly 

shaped and scoured dunes with numerous small 

overflow channels.

Sand fencing has historically been used to stop and trap 

moving sand, creating long, linear constructed dune

ridges that are up to 1 m (3.3 ft) high and hundreds of 

meters long. In the early 20th century, this method was 

also used routinely on unvegetated and algal flats within 

middle overwash ramps to preventing the sanding over 

of roads, ponds, and other features. Many of these 

constructed oceanfront dune ridges persist today 

because ongoing maintenance has minimized overwash 

and fostered the expansion of stable vegetation on the 

island.

Immediately after constructed dune ridges are built or 

rebuilt, they are planted with grass or implanted with 

sand fencing in an effort to stabilize the structure. The 

preferred vegetation along the oceanfront tends to be 

Uniola paniculata (sea oats) or Ammophila breviligulata

(American beachgrass). In the island interior, the 

preferred stabilization vegetation tends to be Spartina 

patens (salt meadow hay). Old constructed dune ridges 

or sequences of two or three inner ridges frequently

become vegetated with scrub shrub, including Baccharis 

halimifolia (salt myrtle), Iva frutescens (marsh elder),

Myrica cerifera (wax myrtle), Ilex vomitoria (yaupon 

holly), and Juniper virginiana (eastern red cedar).

Road/Parking Area Unit

Major highways in urban areas and paved roads and 

parking areas outside of the major urban areas have been 

mapped. Paved roads and parking lots within urban areas 

are not included on the map.

Dredged Channel/Spoils Unit

A dredged channel or drainage ditch is evidence of 

sediment removal. Some removed sediment (referred to 

as spoil) has been pumped or transported off site and 

deposited as fill material to raise land elevations for 

urban development. More often, the sediment removed 

from a dredged channel is deposited immediately 

adjacent to the structure being dredged, creating linear

ridges or series of circular piles along one or both sides of 

the channel. These dredge spoil piles generally raise the 

elevation of adjacent land from a few centimeters to 1 m 

(3.3 ft); they are generally mapped as a single geomorphic 

unit with a dredged channel.

Spoil that is utilized to raise land elevations for urban 

development can support any kind of vegetation. Where 

spoil is placed within the marsh supratidal zone as linear 

ridges or concentric piles, the dominant vegetation is 

composed of transitional-zone species, including 

Baccharis halimifolia (salt myrtle), Iva frutescens (marsh 

elder), Spartina patens (salt meadow hay), and Spartina 

cynosuroides (giant cordgrass) or scrub shrub. Where the 

spoil is deposited above the supratidal zone, vegetation 

includes Myrica cerifera (wax myrtle), Ilex vomitoria 

(yaupon holly), Myrica pensylvanica (northern 

bayberry), Pinus spp. (pine), Juniper virginiana (eastern 

red cedar), Spartina patens (salt meadow hay), Smilax 

spp. (cat brier), and Toxicodendron radicans (poison ivy).

The drainage ditches contain abundant periphyton, 

particularly during warmer months, and (in an August 

2005 sample) consisted largely of floating mats of the 

blue-green alga Microcoleus lyngbyaceus intermixed with 

pennate diatoms (Mallin et al. 2006). Harpacticoid 

copepods, rotifers, protozoans, and nematodes graze on 

smaller algae and bacteria in the mat (Mallin et al. 2006). 

These ditches may be loci of intense microbial food web 

interactions, and may be important resources to small or 

young fish utilizing the marsh (Mallin et al. 2006).

Excavation Unit

Sand was commonly mined from portions of the barrier 

islands for construction of dune ridges or as fill material 

for roads or buildings elsewhere on the islands. The 

resulting holes have filled with water, becoming lakes or 

ponds that range from large, irregularly shaped 

structures to smaller square or rectangular structures. 

This unit also includes dredged harbors and marinas.

Where spoil is placed around an excavation as road bed

within the supratidal zone, the dominant vegetation 

includes transitional-zone species, such as Baccharis 

halimifolia (salt myrtle), Iva frutescens (marsh elder),

Spartina patens (salt meadow hay), and Spartina 

cynosuroides (giant cordgrass) or scrub shrub. Where the 

spoil rises above the supratidal zone, vegetation includes

Myrica cerifera (wax myrtle), Ilex vomitoria (yaupon 

holly), Myrica pensylvanica (northern bayberry), Pinus 

spp. (pine), Juniper virginiana (eastern red cedar),

Spartina patens (salt meadow hay), Smilax spp. (cat 

brier), and Toxicodendron radicans (poison ivy).

Anthropic Overprint Unit

This category includes all major urban areas with dense 

patterns of buildings and roads. All urban areas, as well 

as campgrounds, Coast Guard stations, marinas, and 

cemeteries within Cape Hatteras National Seashore, the 

Pea Island Wildlife Refuge, Jockey’s Ridge State Park, 

and Wright Brothers Historical Monument are mapped 
38 NPS Geologic Resources Division

as an anthropic overprint. This unit includes paved roads 

and parking lots, but does not include dirt roads, power

lines, or buildings. In predominantly urban areas, this 

unit includes only major state highways. Geomorphic 

features were mapped only where they remained in a 

recognizable and partially natural state within these 

highly modified areas.

Barrier Island System Units (North Carolina Geological 

Survey Remote Sensing Map)

Hoffman et al. (2007g) developed a geomorphic map of 

Cape Hatteras National Seashore using remotely sensed 

data. Descriptions of the processes and timing of unit 

formation are based on interpretation, rather than fieldbased studies. The map identifies the following 

geomorphic units in the intertidal, supratidal, relict, and 

anthropogenic groups (table 4). The unit descriptions 

provided below are taken primarily from Hoffman et al. 

(2007g), and supplemented by information from 

publications where cited.

Intertidal Group

Beach Unit

The beach is defined as the area between the 1998 

wet/dry ocean shoreline (North Carolina Division of 

Coastal Management [NCDCM] 2003) and the toe of the 

Fore-island Dune Complex (delineated using a 

combination of slope and aerial imagery). Storms and 

high lunar tides subject the beach area to periodic 

flooding, particularly near inlets, where the beach merges 

laterally with sand flats of the Spit Complex Subgroup.

Sand Flat Unit

Sand flats are part of the Spit Complex Subgroup. They 

occur adjacent to the three active inlets in the mapped

area. They are unvegetated and have low (<1.2 m [4 ft]) 

elevations and relief. They are subject to regular tidal 

flooding and overwash. Sand flats may contain areas of 

episodically ponded water and small isolated dunes, and 

seasonally may become encrusted with algae. Sand flats 

merge with the beach where the Fore-island Dune 

Complex first develops behind the beach.

Table 4. Summary of barrier island system units as mapped by the North Carolina Geological Survey.

Group Subgroup or Map Unit (symbol)

Intertidal

Beach (beach)

Spit Complex Sand Flat (sand_flat)

Ridge and Swale (ridge_swale)

Marsh Platform (pf_marsh)

Intertidal and Supratidal Beach and Fore-Island Dune 

Complex Dune Saddle (dnesadl_bch)

Supratidal

Fore-Island Dune Complex 

Subgroup Dune Ridges (dunerdge)

Interdune Swale and Dune 

Ridge (intswale_dr)

Dune Saddle and Dune Ridge 

(dnesadl_dr)

Overwash Complex Subgroup

Overwash Flat (owflat)

Overwash Flat and Overwash Channel (owflt_owchn)

Overwash Fan (owfan)

Isolated Dune (isodune)

Interior Dune (intdune)

Interior Marsh (intmarsh)

Back-Barrier Berm (bk_br_brm)

Relict

Relict Beach Ridge Complex (rel_bch_rdge)

Relict Spit Complex (rel_splt)

Water Body (water)

Anthropogenic

Airport/Landing Strip (airport_land)

Commercial/Industrial Facility (comm_indust)

Dredge/Spoil (drdge)

Filled (filled)

Erosion Control Structure (ersn_ctrl_st)

Excavation (excavate)

Dike (dike)

Waterfowl Impoundment (wtrfwl_impnd)
CAHA Geologic Resources Inventory Report 39

Sand flats support tens of thousands of shorebirds 

representing at least 21 species annually. These areas are 

critical foraging sites for piping plovers breeding in the 

park, as well as migrating and wintering piping plovers 

from the Atlantic Coast and Great Lakes populations, 

currently listed federally as threatened and endangered, 

respectively (Mallin et al. 2006).

Ridge and Swale Unit

The arcuate ridge and swale unit, part of the Spit 

Complex Subgroup, occurs adjacent to the three active 

inlets. Where present, this unit is situated lateral to the 

sand flat and merges toward the island interior with the 

Fore-island Dune and Overwash complexes. Ridges and 

swales typically trend subparallel to the axis of a barrier 

and then curve toward the back of the island as they 

approach an inlet. Ridges range from incipient features 

to well-formed continuous structures to heavily 

dissected remnants. These units represent older, more 

stable portions of spit complexes.

Marsh Platform Unit

Marsh platforms are extensive on the back sides of 

barrier islands and along tidal creeks that cut into them. 

These areas are low lying (generally <0.6 to 0.9 m [2 to 3 

ft] in elevation) and subject to regular tidal flooding. 

They are located along the sound-side shoreline. When 

they are located significantly inland of back-island tidal 

creeks, they are often found in depressions associated 

with relict features, such as the swales between relict 

beach ridges in the Buxton area or mid-island lows 

behind former sand flats.

Marsh platforms are relatively stable features and are 

quite extensive in parts of the barrier system. Juncus and 

Spartina patens are the dominant grass species inhabiting

these platforms. A peat layer up to several feet thick has 

developed in concert with rising sea level and the 

associated increase in marsh elevation. Where sediment 

supply is insufficient for marsh aggradation into the 

sound, wave energy may undercut the peat and cause 

local shoreline recession. Updip (island-ward) areas are 

prone to storm overwash, which supplies sand to the 

marsh platforms’ interior margins and raises their

elevations above tidal influence. As this process 

continues, the Overwash Complex builds onto the marsh 

platform area.

Supratidal Group

Dune Ridge Unit

Dune ridges are part of the Fore-island Dune Complex 

Subgroup, which is a shoreparallel unit of higher 

elevation that occurs between the beach and island 

interior units. Dune ridges are the most prominent and 

extensive portions of the Fore-island Dune Complex. 

They are linear and shoreparallel. Dune heights vary, but 

generally are less than 6 m (20 ft). Dune toe elevations are 

typically 1.8 to 2.4 m (6 to 8 ft) on the front (ocean) side 

and 1.2 to 2.4 m (4 to 8 ft) on the back (island interior) 

side.

Intradune Swale Unit

Intradune swales are part of the Fore-island Dune 

Complex Subgroup. They are closed, relatively low-lying 

areas within dune complexes. These linear troughs are 

less than 3 m (10 ft) in elevation and occur between dune 

ridges.

Dune Saddle Unit

Dune saddles are part of the Fore-island Dune Complex 

Subgroup. They are gaps or breaks along dune ridge lines 

of the fore-island dune system, with elevations of less 

than 3 m (10 ft). Elevations are even lower in more 

extensive low-lying island segments, such as in the 

central Rodanthe map area. Saddles are important 

features of the dune complex in that they represent 

potential high-water flow pathways along ridge lines that 

are vulnerable to coastal flooding during major storms.

Overwash Flat and Overwash Channel Unit

Overwash flat is the dominant unit of the Overwash 

Complex Subgroup. This complex occurs behind the 

Fore-island Dune Complex and in front of the marsh 

platform. This area is elevated relative to the marsh 

platform and tends to have low to moderate relief; 

elevations typically range from 0.61 to 2.4 m (2 to 8 ft)

and decrease gradually toward the sound side of the 

island. The Overwash Complex is a depositional feature 

receiving sand that is blown or washed over and through 

the Fore-island Dune Complex, most notably by storm 

events. Locally, the Overwash Complex extends into the 

sound.

Overwash flats represent the long-term accumulation of 

sand overwash behind the Fore-island Dune Complex.

Discrete events deposit sand in lobate forms, which then 

coalesce into a single geomorphic unit through 

reworking by wind, water, and humans. In the 

southeastern part of Ocracoke Island and a few other 

localities, individual overwash fans and linear overwash 

channels that cut through the fore-island dune during 

storm events were sufficiently preserved to permit 

mapping.

Overwash Fan Unit

The overwash fan unit is part of the Overwash Complex 

Subgroup.

Isolated Dune Unit

The isolated dune unit is part of the Overwash Complex 

Subgroup. These features occur within or soundward of 

the overwash flat area. They appear to have a variety of 

origins, including: 1) as remnants of former fore-island

dune ridges or large overwash fans, or 2) as 

constructional features caused by the trapping of sand by 

vegetation or anthropogenic features, such as sand 

fencing.

Interior Dune Unit

Interior dunes occur in several areas soundward of the 

Fore-island Dune Complex. They are larger than isolated 

dunes of the Overwash Complex. Interior dunes are 

significant geomorphic features of sizable areal extent, 

and are often the highest point on an island, with 

elevations of 3 to 27 m (10 to 90 ft). Most are vegetated. 
40 NPS Geologic Resources Division

Interior dunes range from isolated single ridges, as seen 

on Ocracoke Island, to more laterally extensive elevated 

features, such as on central Bodie Island.

Interior Marsh Unit

Interior marshes are not connected to ocean or sound

waters, but often are located adjacent to water bodies 

such as ponds. Interior marshes usually occur in the 

swales of extensive relict beach ridge complexes, such as 

those in the Buxton area, or in interior lows behind the 

Fore-island Dune Complex.

Back-Barrier Berm Unit

Back-barrier berms occur in the back portions of the 

barrier island system throughout much of Cape Hatteras 

National Seashore. They vary from very subtle linear 

features lying just slightly higher than the surrounding 

marsh platform to elevated (>3 m [10 ft]) features. Many 

berms form broad arcs in areas of apparent relict flood

tidal deltas, suggesting that wave reworking of delta sand 

bodies facilitated berm development. Other berms are of 

less intuitive origin.

Relict Group

Relict Beach Ridge Unit

The relict beach ridge unit occurs as sets of parallel 

ridges and swales in island-interior portions of the 

Buxton area, just west of Cape Hatteras. Most elevations 

are 3 to 4.6 m (10 to 15 ft) or less, but rise to 9 m (30 ft) in 

the Buxton complex. Swales between ridges often 

contain interior marsh and isolated water bodies.

Fisher (1967) originally mapped these ridges using aerial 

photographs. Truncation of parallel dune sets by later 

dune sets oriented at slightly different angles allows

delineation of individual sets of relict beach ridges and 

determination of relative age relationships. Fisher (1967) 

identified 13 sequences of ridge development in this area 

and termed this complex the “Hatteras group of relict 

beach ridges.” His analysis included dune ridges 

classified in this report as part of the modern Fore-island

Dune Complex.

A large, very complex interior dune dominates the 

Buxton-area landscape. Its morphology differs

considerably from that of the Relict Beach Ridge 

Complex. It has a boxwork-like pattern of spurs and 

connecting transverse ridges, with elevations 

approaching 18 m (60 ft).

Less-pronounced ridge and swale topography forms a 

portion of the complex barrier island in the Hatteras 

Village area. Despite considerable human modification 

of the landscape in this area, two sets of ridges can be 

recognized. Ridges in this area are less than 2.4 m (8 ft) in 

elevation, with some barely rising above the enveloping 

marsh platform in the soundward portion of the island.

Relict Spit Unit

Relict spits are subtle arcuate-shaped ridge and swale 

features located in mid- to back-island areas. They 

exhibit topography and geomorphic attributes 

characteristic of modern spit complexes, but lack 

connection to an active inlet. These areas have been

interpreted as older, inactive spit complexes that 

developed adjacent to former inlets. Relict spit 

complexes are notable in the vicinity of Avon and south 

of Buxton.

Water Body Unit

Water bodies that appeared to be ephemeral features, 

such as those occurring on sand flats or in intradune 

swales, were not mapped.

Anthropogenic Group

Airport/Landing Strip Unit

Airport landing strips occur in the Buxton, Ocracoke, 

and Wright Brothers Memorial map areas.

Commercial/Industrial Facility Unit

Facilities such as marinas, ferry terminals, and other large 

developments were mapped in this category.

Dredge Spoil Unit

Dredging is a very common practice for construction and 

modification of landforms throughout the map area. This 

map unit is reserved for specific positive-relief features 

that can be confidently identified, with a dredged 

waterway as the source of each spoil deposit. Older spoil 

islands may not have been recognized due to subsequent 

wave modification and vegetation.

Filled Unit

Filling of low-lying areas for development purposes has 

been and continues to be a common practice, especially 

in wetland areas. Evidence of artificial fill includes linear 

boundaries, odd juxtapositions with or within the marsh 

platform, or atypically high elevations in comparison 

with surrounding areas.

Erosion Control Structure Unit

Where the shoreline has been stabilized through 

hardening, structures sufficiently large to map at 1:24,000 

scale were included. The terminal groin at the north end 

of Pea Island is an example.

Excavation Unit

A limited number of low areas were recognized as 

artificially excavated, based on personal communication 

or inferred from imagery and elevation data.

Dike Unit

This map unit applies to dikes built for waterfowl 

impoundment areas in Pea Island National Wildlife 

Refuge.

Waterfowl Impoundment Unit

Several large water-filled impoundments occur in Pea 

Island National Wildlife Refuge.

Paleontological Resources

Cape Hatteras National Seashore is one of 258 NPS areas 

with documented paleontological resources as of April 

2015. Paleontological resources (fossils) are any evidence 

of life preserved in a geologic context (Santucci et al. 

2009). All fossils are non-renewable. Body fossils are any 

remains of the actual organism such as bones, teeth, 
CAHA Geologic Resources Inventory Report 41

shells, or leaves. Trace fossils are evidence of biological 

activity; examples include burrows, tracks, or coprolites 

(fossil dung). Fossils in NPS areas occur in rocks or 

unconsolidated deposits, museum collections, and 

cultural contexts such as building stones or archeological 

resources. The NPS Geologic Resources Division 

Paleontology website, http://www.nature.nps.gov/

geology/paleontology/index.cfm, provides more 

information.

Paleontological resources present opportunities for 

education, interpretation, and scientific research at Cape 

Hatteras National Seashore. They contain valuable 

information about the geologic history and recent 

evolution of the area. Documented fossils collected from 

the park are archived at the NPS Museum Resource 

Center (Suitland, Maryland) and the Southeast 

Archeological Center (Atlanta, Georgia) (Tweet et al. 

2009).

Mixed assemblages of Quaternary marine fossils are 

abundant on North Carolina beaches and can locally 

constitute up to 75% of beach shells (Riggs et al. 1995). 

Landward migration of the barrier islands exposes

remnants of forests and swamps that once grew on their

back sides. These remnant trees and organic peat 

deposits are generally hundreds to hundreds of

thousands of years old (Dolan and Lins 1986; Tweet et al. 

2009). Sediments eroded from relict inlet deposits 

provide another source of shell fragments and other 

fossils of pre-Holocene age (Herbert and Heron 1978; 

Tweet et al. 2009).

Although the geologic units at Cape Hatteras are young, 

older fossils are accessible by dredging and drilling 

operations and via offshore sources that are washed 

onshore. Culver et al. (2008a) drilled deep cores along 

the length of the northern Outer Banks and found 

Pliocene microfossils as deep as 60 m (200 ft) (between 

Nags Head and Whalebone Junction). Microfossils as 

old as Oligocene age have been recovered from deep 

cores at Cape Hatteras (Richards 1968; Tweet et al. 

2009), and even older fossils were found in the deep 

(3,061 m [10,044 ft]) exploratory well that Esso drilled 

near the Cape Hatteras Lighthouse more than 60 years 

ago (Coffey 1977). Other local subsurface and offshore 

remains include sponges, scaphopods, barnacles, 

bivalves, and gastropods (Tweet et al. 2009).

The offshore continental shelf produces a variety of 

fossils that may wash ashore, including those of algae, 

foraminifera, corals, bryozoans, mollusks, ostracodes, 

barnacles, and echinoids, as well as polychaete worm 

tubes (Macintyre and Milliman 1970; Cleary and Thayer 

1973; Culver et al. 2008b; Tweet et al. 2009). Vertebrate 

remains also wash ashore, including an Odobenus 

rosmarus (walrus) skull, radiocarbon dated to 36,760 ± 

570 years before present, that washed up on the beach at 

Salvo in 1990 (Stover 2002; Tweet et al. 2009). Other 

vertebrate remains known from the area include a nearly 

complete skull of a female Bootherium bombifrons

(Harlan’s muskox or woodland muskox), fragments of 

whale vertebrae, and a group of three auditory bullae 

(hollow structures enclosing part of the ear) from whales 

(McDonald and Ray 1993; Tweet et al. 2009).

Fossils in the park may also be associated with cultural 

resources, such as fossils altered or modified by humans 

(Kenworthy and Santucci 2006; Tweet et al. 2009). 

According to the archeological record, humans were not 

present on the Outer Banks before about 3,000 years ago;

at least 29 archeological sites predate European contact. 

Twenty of these sites have shell middens (refuse piles 

created by humans) or other shell relicts. Excavations at 

Fort Raleigh National Historic Site yielded artifacts from 

the late 16th century, including oyster shells associated 

with copper plates that may have been strung together 

for ornamental use (Thompson 1977; Tweet et al. 2009).

There are a variety of management issues associated with

paleontological resources in Cape Hatteras National 

Seashore. They are summarized in the “Paleontological 

Resource Inventory, Monitoring, and Protection” 

section.
CAHA Geologic Resources Inventory Report 43

Geologic Resource Management Issues

This chapter describes geologic features, processes, or human activities that may require

management for visitor safety, protection of infrastructure, and preservation of natural 

and cultural resources in Cape Hatteras National Seashore. The NPS Geologic Resources 

Division provides technical and policy assistance for these issues.

Geologic issues facing Cape Hatteras National Seashore 

include natural processes, anthropogenic influences, and 

natural processes exacerbated by anthropogenic 

influences. The GRI scoping meeting (NPS 2000) and 

subsequent discussions identified 11 major issues that are 

related to the park’s geology and that shape the park's 

resources:

• Shoreline Erosion

• Coastal Vulnerability and Sea-Level Rise

• Hurricane Impacts and Human Responses

• Inlet Modifications

• Recreational and Watershed Land Use

• Coastal Engineering and Shoreline Armoring

• Highway 12 Transportation Corridor

• Geomorphic Mapping Needs

• Paleontological Resource Inventory, Monitoring, and 

Protection

• Additional Information Needs

Resource managers may find Geological Monitoring

(Young and Norby 2009; http://go.nps.gov/

geomonitoring) useful for addressing these geologic 

resource management issues. The manual provides 

guidance for monitoring vital signs—measurable 

parameters of the overall condition of natural resources. 

Each chapter covers a different geologic resource and 

includes detailed recommendations for resource 

managers, suggested methods of monitoring, and case 

studies.

Parks developing monitoring protocols can contact their 

NPS Inventory & Monitoring Network. They can also 

consult suggested protocols such as the Geological 

Monitoring chapter about coastal features and processes

defined in Bush and Young (2009), which described 

methods and vital signs for monitoring the following 

coastal features and processes: (1) shoreline change, (2) 

coastal dune geomorphology, (3) coastal vegetation 

cover, (4) topography/elevation, (5) composition of 

beach material, (6) wetland position/acreage, and (7) 

coastal wetland accretion.

The NPS Water Resources Division, Ocean and Coastal 

Resources Branch website (http://www.nature.nps.gov/

water/oceancoastal/) has additional information about 

servicewide programs and the resources and 

management programs at the ocean, coastal, and Great 

Lakes parks. Shoreline maps of each park, along with 

shoreline and water acreage statistics from Curdts 

(2011), are available at http://nature.nps.gov/water/

oceancoastal/shorelinemaps.cfm.

Shoreline Erosion

Barrier islands recede when erosive forces exceed the 

ability of the sediment supply to replenish the beach 

system. Wave energy, sediment availability, sea-level 

change, and human activities vary and influence the 

balance between erosion and deposition (Dolan and 

Godfrey 1972).

Ocean shoreline change rates along Cape Hatteras 

National Seashore range from more than 2 m (6.5 ft)

accretion to more than 2 m (6.5 ft) erosion per year (fig. 

21), based on shoreline datasets from NOS T-Sheets and 

LiDAR data spanning 150 years (Pendleton et al. 2004). 

Erosional response and the post-storm shape of the 

shoreface profile are controlled by the degree of 

consolidation of sediments underlying the modern sand

sheet (Riggs et al. 1995).

Estuarine shoreline shape and recession rates are 

controlled by variables including fetch, offshore depth 

and slope, shoreline geometry, height and composition 

of sediment bank (e.g., low peat banks are more erodible 

than high clay banks), presence of fringing vegetation, 

presence of boat wakes, water level, size and shape of the 

associated water body, and storm frequency and 

intensity (Riggs and Ames 2003; Corbett et al. 2008). 

Estuarine shoreline change in the Albemarle-Pamlico 

Estuarine System ranges from 0.2 m (0.6 ft) accretion 

(back-barrier beaches) to 1 m (3.3 ft) erosion (mainland 

marshes) per year (Riggs and Ames 2003). Mainland 

marsh and low sediment banks, which are the most 

abundant estuarine shoreline types (85% of such features 

in northeastern North Carolina), tend to have the highest 

average erosion rates. Bluffs and high sediment banks, 

which are less abundant (8%), erode more slowly 

(approximately 0.8 m [2.6 ft]/year). Swamp forest 

shorelines are the least abundant shoreline type (7%) and 

have the lowest erosion rates (0.7 m [2.3 ft]/year) due to 

their low offshore gradients and the presence of trees 

that abate wave energy.

In some cases, erosion rates of ocean and estuarine 

shorelines are greater than rates of sediment 

replenishment, causing an island to narrow and 

potentially disappear as its cross-sectional profile 

steepens. This process may be reversed by a significant 

overwash event or the development of a flood tidal delta 

that supplies sediment in an inlet (Ames and Riggs 2006j).
44 NPS Geologic Resources Division

Figure 21. Historic shoreline positions. These maps span the 

past 150 years along Cape Hatteras National Seashore, 

collated from NOAA T-Sheets, NCDCM (2003) and LiDAR

data (Morton and Miller 2005). Ocean shoreline change 

rates range from more than 2 m (6.5 ft)/year accretion to 

more than 2 m (6.5 ft)/year erosion. Figure 12 from 

Pendleton et al. (2004).

Examples of narrow, low, oversteepened barrier 

segments, where erosion rates are highest and the

likelihood of inlet breaching in the future is high, include 

the island segment immediately north of Rodanthe, the 

southern portion of Pea Island, the Buxton and Isabel 

inlet areas, and northeastern Ocracoke Island (Ames and 

Riggs 2006j; Mallinson et al. 2008b). Within the estuary, 

shoreline erosion at Fort Raleigh National Historic Site

threatens visitor infrastructure (theatre), cultural 

resources (cemetery), and likely also unknown and 

unexcavated archeological resources (NPS 2007).

Coastal Vulnerability and Sea-Level Rise

Sea-level rise is caused by global climate warming in 

combination with regional and local effects of geologic, 

oceanographic, and atmospheric conditions, which vary 

spatially and temporally (fig. 22) (Williams 2013). Global, 

or eustatic, sea level refers to the global ocean elevation. 

On a global scale, sea level varies with changes in the 

volumes of ocean basins and ocean water, caused by 

expansion due to heat uptake and the addition of 

meltwater from ice sheets and glaciers. Relative local sealevel rise, as measured by the growth of salt-marsh peat, 

tide gauge records, and the submergence of human 

structures, refers to the combination of global rise with 

regional and local factors, such as sediment compaction 

and changes in ocean circulation patterns and wind 

patterns.

Historic Sea-Level Rise

Sea level has fluctuated over geologic time and over the 

past millennia (table 5). In the past century, global sea 

level has risen approximately 0.18 m (0.6 ft), a rate of 1.8 

mm (0.07 in) per year (Douglas 1997). A recent study 

(Sallenger et al. 2012) found that rates of relative sealevel rise are increasing three to four times faster along 

parts of the US Atlantic coast than globally. Since about 

1990, global sea level has risen 0.6 to 1.0 mm (0.02 to 0.04 

in) per year. In comparison, sea-level rise in the 1,000-km 

(600-mi) stretch of the coastal zone from Cape Hatteras, 

North Carolina, to north of Boston, Massachusetts, has 

increased 2 to 3.7 mm (0.08 to 0.14 in)/year. The authors 

expect this rate of increase to continue if global 

temperatures continue to increase. This sea-level-rise 

hotspot is consistent with the slowing of Atlantic Ocean 

circulation, which in turn may be related to changes in 

water temperature, salinity, and density in the subpolar 

North Atlantic.

Over the past 12,000 years, relative sea-level change 

along the North Carolina coast has varied as a function 

of latitude, with higher rates of rise in the north and 

lesser rates of rise in the south. This pattern is a function 

of the local geology as well as differential crustal 

subsidence and uplift (North Carolina Coastal Resources 

Commission [NCCRC] 2010). The rate of sea-level rise, 

based on microfossils from coastal marsh sites along the 

northern Outer Banks, was stable from 100 BCE (Before 

Common Era, preferred to “BC”) to 950 CE (Common 

Era, preferred to “AD”), then rose at a rate of 0.6 mm 

(0.02 in)/year until 1400 CE. It then stabilized again until 

the end of the 19th century before increasing again to a 

mean rate of 2.1 mm (0.08 in)/year beginning around 

1880–1920 (Kemp et al. 2011). Since 1963, sea level has 

been rising at an estimated rate of 4.5 ± 1.5 mm (0.18 ±

0.06 in) per year (Kemp et al. 2009). At Duck, North 

Carolina, short-term (1980–2000) tide gauge data 

indicate that sea level is rising about 4.5 mm (0.18 

in)/year (Zervas 2004, as cited in Riggs et al. 2008b). The 

rate of sea-level rise at Oregon Inlet Marina is 2.82 ± 0.44 

mm (0.11 ± 0.02 in) per year, based on tide gauge data 

from 1977–2006. In Beaufort, North Carolina (about 75 

km [47 mi] southwest of Ocracoke Island), the rate is 

2.57 ± 0.44 mm (0.10 ± 0.02 in)/year, based on tide gauge 
CAHA Geologic Resources Inventory Report 45

Figure 22. Schematic graphic illustrating major causes of sea-level change. Sea-level rise is caused by global climate 

warming in combination with regional and local effects of geologic, oceanographic, and atmospheric conditions, which vary 

spatially and temporally. Additional causes include terrestrial water storage, building of reservoirs, changes in runoff, 

seepage into aquifers, vertical land movements including delta subsidence, tectonic displacements, and glacial isostatic 

adjustment (Williams 2013). Graphic by Jane Hawkey and Jane Thomas (Integration and Application Network, University of 

Maryland Center for Environmental Science) available online: http://ian.umces.edu/imagelibrary/ (accessed 27 April 2015).

Table 5. Rates of relative sea-level rise in northeastern North Carolina for the last 18,000 years, based on 

studies of salt-marsh peat on Roanoke Island, North Carolina (as compiled by Riggs et al. 2011).

Time Period Rate of Sea-Level Rise Coastal Events

18,000–11,000 years ago 1.3 m (53 in)/100 years Shore zone migrates onto and across much 

of continental shelf.

11,000–8,000 years ago 0.53 m (21 in)/100 years Initial flooding of the drowned-river estuarine 

system.

8,000–3,500 years ago 0.25 m (10 in)/100 years

Formation of modern drowned-river 

estuarine system. Initial formation of barrier 

islands proximal to their modern location.

3,500–100 years ago 0.13 m (5 in)/100 years Development of modern barrier island 

system.

100 years ago–present 0.32 m (12.6 in)/100 years Increased rate of upslope migration and 

increased coastal engineering efforts.

late 20th century (1980–2000) 

(Duck, NC, tide gauge) 0.46 m (18 in)/100 years Continued increase in sea-level rise rate.

data from 1953–2006 (Zervas 2009). Data from NOAA 

(2013b) and summarized by Caffrey (2013) show that sea 

level has risen around Beaufort North Carolina at the 

rate of 2.8 mm (0.11 in) per year from 1953 to 2012.

Future Sea-Level Rise

Over the next century, differences in the rate of sea-level 

rise between the two regions of North Carolina are likely 

to be overwhelmed by the much larger global rise in sea 

level (NCCRC 2010). New models and scenarios used by 

the Intergovernmental Panel on Climate Change (IPCC)

predict that sea level will rise 0.26 to 0.98 m (0.85 to 3.2 

ft) by 2100 (fig. 23) (Church et al. 2013). Many recent 

assessments have proposed a projected 1-m (3.3-ft) 

global average sea-level rise by 2100 as a reasonable value 

to be used for planning purposes (Williams 2013). Some
46 NPS Geologic Resources Division

Figure 23. Projected sea-level rise by 2100 (in meters). Over 

the next century, global sea level will rise, although the 

magnitude of projections under various modeling scenarios 

varies. Figure 9 from Church et al. (2013).

estimates include the possibility that sea level may rise as 

much as 2 m (6.6 ft) by 2100 along the mid-Atlantic coast 

(Rahmstorf 2007). Models that also consider accelerated 

melting of glaciers and the Greenland and West Antarctic 

ice sheet, along with the relationship between sea level 

and temperature, predict that sea level may rise by 0.9 to 

1.2 m (2.9 to 3.9 ft) by the end of this century (Boesch 

2008; Karl et al. 2009; The World Bank 2012), with 

variable regional and temporal influences on local rates 

of sea-level rise depending on geophysical and 

oceanographic factors (Williams 2013).

Along the North Carolina coast, sea level is likely to rise 

0.4 to 1.4 m (1.25 to 4.6 ft) above the present level by 

2100, but not necessarily in a linear fashion (NCCRC 

2010). A 1-m (3.3-ft) rise is considered a good estimate 

for planning purposes because that rate requires only 

that the linear relationship between temperature and sea 

level noted in the 20th century remains valid for the 21st 

century (Rahmstorf 2007), and because it is not located 

at the upper or lower extreme of valid projections 

(NCCRC 2010).

Coastal Impacts of Sea-Level Rise

As sea level rises, various processes modify coastal 

landforms, causing cumulative impacts at a range of 

spatial and temporal scales (Williams 2013). Coastal 

evolution in response to sea-level rise and storms is 

influenced by several conditions, including geologic 

framework (underlying geology) and nearshore

bathymetry (Honeycutt and Krantz 2003; Browder and 

McNinch 2006; Miselis and McNinch 2006; Schupp et al. 

2006; Wikel 2008), characteristics of coastal landforms, 

coastal and nearshore oceanographic processes (i.e., 

waves, currents, circulation), sediment supply and 

transport, and human actions that alter sediment 

movement (e.g., jetties) (Williams 2013).

Different rates of sea-level rise are tied to the formation 

of particular types of landform. For example, global 

deltas formed approximately 8,000 years ago when rates 

of sea-level rise slowed to less than 10 mm (0.4 in)/year 

(Stanley and Warne 1994), and barrier islands and 

Atlantic wetlands formed when rates of sea-level rise fell 

below 5 to 7 mm (0.2 to 0.3 in)/year (Shennan and 

Horton 2002; Horton et al. 2009).

The northeastern North Carolina coastal plain is highly 

vulnerable to rising seas due to the low and narrow 

character of the barrier islands, the flat coastal plain 

surface extending many kilometers landward from the 

coast, and the accelerated rate of local sea-level rise 

relative to global rates (Williams 2013). All barrier islands 

of Cape Hatteras National Seashore are already within 

the 100-year flood zone (Pendleton et al. 2004).

Pendleton et al. (2004) evaluated the coastal vulnerability 

of Cape Hatteras National Seashore to sea-level rise 

based on six variables: (1) geomorphological type of 

shoreline, which dictates relative resistance to erosion; 

(2) historical shoreline change rate (erosion/accretion); 

(3) regional coastal slope, which indicates relative 

susceptibility to flooding; and three physical process 

variables that contribute to the inundation hazards of a 

coastline: (4) relative sea-level change, (5) mean 

significant wave height, and (6) mean tidal range. This 

study did not explicitly consider the types, frequencies, 

or intensities of storms and associated surge, which are 

also important variables affecting coastal vulnerability 

(Stanley Riggs, East Carolina University, professor, 

personal communication, 12 December 2013). Pendleton 

et al. (2004) found that the geomorphology of the Cape 

Hatteras region varies from highly vulnerable barrier 

islands with dunes to very highly vulnerable washoverand inlet-dominated barrier islands. Of the six equally

ranked variables, values for shoreline change, 

geomorphology, regional coastal slope, and significant 

wave height had the largest alongshore ranges, and 

therefore the strongest influence on the overall 

vulnerability score for each section of the island. Of the 

195 km (120 mi) of ocean and inlet shoreline mapped, 

54% was classified as having high or very high 

vulnerability, and 16% as having low vulnerability (fig. 

24).

Barrier islands likely have thresholds or tipping points of 

geomorphic stability, such that when limits of sea-level 

rise and storm activity are exceeded, or sediment supply 

rates decrease to an unstable level, they become unstable 

and prone to irreversible changes in form and position 

(Riggs and Ames 2003; Gutierrez et al. 2009; Moore et al. 

2010, 2011). These changes may result in increased 

landward migration, geomorphic change such as 

reduction in size or segmentation, or, in extreme cases, 

transformation of a barrier island into a subaqueous sand 

shoal (i.e., submergence of the barrier island) (Williams 

2013). Gutierrez et al. (2007) discussed the following 

indicators of threshold conditions:

• Increased rate of landward migration of the barrier

island

• Decreased barrier width and elevation of barrier island 

and sand dunes

• Increased frequency of storm overwash
CAHA Geologic Resources Inventory Report 47

Figure 24. Map of coastal vulnerability of the northeastern portion of the North Carolina barrier islands, including Cape 

Hatteras National Seashore, to sea-level rise. Vulnerability differs by location, depending on six main variables: 

geomorphology, shoreline change, coastal slope, relative sea-level rise, significant wave height, and tidal range. Figures 13 

and 14 from Pendleton et al. (2004).
48 NPS Geologic Resources Division

• Increased frequency of barrier island breaching and 

inlet formation and widening

• Barrier island segmentation

In the past, portions of the Outer Banks were segmented 

for periods of a few hundred years, and later reformed 

(Mallinson et al. 2005; Culver et al. 2008a). Given the 

potential for future increases in sea level and/or storm 

activity, threshold crossing may occur in the Outer 

Banks, and portions of these barrier islands could once 

again become segmented into submarine shoals 

(Gutierrez et al. 2009). Gutierrez et al. (2009) postulated

that if mid-Atlantic sea level rises 0.3 to 0.4 m (1 to 1.3 ft) 

by 2100, the majority of wave-dominated barrier islands 

along the mid-Atlantic coast will continue to experience 

morphological changes through erosion, overwash, and 

inlet formation, as they have over the last several 

centuries (fig. 25, table 6). Model results reported by 

Moore et al. (2007) suggest that a more rapid increase in 

sea level (up to 0.88 m [2.9 ft]) by 2100 would cause the 

Outer Banks to migrate 9.8 m (32 ft)/year, about 2.5 times 

more rapidly than at present but within the range of rates 

observed for rapidly migrating barrier islands elsewhere 

(e.g., in Louisiana). When sea level rises more quickly 

than the rate at which the shoreface can erode to provide 

sediment to the island, the island begins to disintegrate 

and a state change (threshold crossing) occurs (Moore et 

al. 2010). Human mitigation efforts, such as beach 

nourishment, result in little reduction in barrier island 

migration rates and barrier island vulnerability to 

collapse (Moore et al. 2007).

Mid-Atlantic wetlands are expected to keep pace with 

moderate rates of sea-level rise, but higher rates (e.g., 1 m 

[3.3 ft] by 2100) may result in the conversion of most 

tidal wetlands to open water bays and lagoons, although 

tidal wetlands with sufficient sediment input may prevail 

(Williams 2013). In North Carolina, vertical accretion 

rates of marshes have largely matched the rate of sealevel rise, but wetland drowning may occur if rates of 

global sea-level rise increase by 2 mm (0.08 in)/year and 

is likely if rates increase by 7 mm (0.28 in)/year (Feldman 

et al. 2009) (table 6). With a rise of 10 mm (0.4 in)/year, 

fringe wetlands of North Carolina’s lower coastal plain 

would drown, and peat-based wetlands would be 

unlikely to maintain elevation relative to sea level as the 

peat, root map, and vegetation would first be killed by 

brackish water. Creation of additional inlets due to sealevel rise would change the estuarine system from what is 

now a predominantly wind-driven tide to an 

astronomical tide–driven regime, increasing tide range, 

salinity, and wave activity, which would impact wetlands 

(Feldman et al. 2009).

Impacts of Sea-level Rise on Facilities

In addition to impacts on environmental features and 

processes, park facilities will also be impacted by rising 

sea level. The NPS developed a report entitled “Adapting 

To Climate Change in Coastal Parks: Estimating the 

Exposure of FMSS-Listed Park Assets to 1 m of SeaLevel Rise” (Peek et al. in press). This report includes the

Figure 25. Map showing potential coastal responses to three 

sea-level rise scenarios. If mid-Atlantic sea-level rise 

continues at the present rate, the majority of wavedominated barrier islands along the mid-Atlantic coast will 

almost certainly continue to undergo morphological 

changes through erosion, overwash, and inlet formation. 

Additional changes will occur under higher rates of sealevel rise. Figure 4 from Gutierrez et al. (2009).

geospatial location and approximate elevation of over 

10,000 assets in 40 coastal parks, based on information 

within the NPS Facilities Management Software System 

(FMSS) and supplemented with other datasets, 

collaboration with park staff, and field visits to locate 

assets. Assets were characterized based on their overall 

exposure to long-term (1 m) sea-level rise and associated 

storm vulnerability, and were categorized as having 

either high exposure or limited exposure to sea-level rise 

impacts. According to Peek et al. (in press), more than 

550 coastal assets are mapped within Cape Hatteras 

National Seashore and all of them are considered “high 

exposure” to 1 m of sea-level rise. Assets within Wright 

Brothers National Memorial and Fort Raleigh National 

Historic Site are included in the Cape Hatteras list.

Coastal Resource Management and Planning

The NPS Coastal Adaptation Handbook (RM 39-3; 

Beavers et al. in review, expected spring 2015) will 

provide climate change adaptation guidance to coastal 

park managers in Cape Hatteras National Seashore, Fort 

Raleigh National Historic Site, Wright Brothers National 

Memorial and the 115 other parks that have been 

identified by their regional offices as potentially 

vulnerable to sea-level change. Focus topics will include 

NPS policies relevant to climate change, guidance on 
CAHA Geologic Resources Inventory Report 49

Table 6. The rate of sea-level rise will determine the responses of coastal wetlands and their driving 

processes. Table 4.3 from Cahoon et al. (2009).

Scenario Vertical Accretion of 

Wetland Surface

Shoreline Erosion 

Rate

Sediment Supply

Non-drowning: historical exposure 

of wetlands (past hundreds to several 

thousand years) is predictive of 

future behavior. Vertical accretion 

will keep pace with rising sea level 

(about 2 to 4 mm [0.08 to 0.16 in] 

per year)

Keeps pace with rising 

sea level

Recent historical patterns 

are maintained

Low due to a lack of sources; 

vertical accretion mostly biogenic

Drowning: vertical accretion rates 

cannot accelerate to match rates of 

rising sea level; barrier islands remain 

intact

Wetlands undergo 

collapse and marshes 

break up from within

Rapid acceleration when 

erosion reaches collapsed 

regions

Local increases in organic and 

inorganic suspended sediments 

as wetlands erode

Barrier island breached: change to 

tidal regime throughout Pamlico 

Sound

Biogenic accretion 

replaced by inorganic 

sediment supply

Rapid erosion where high 

tides overtop wetland 

shorelines

Major increase in sediments and 

their redistribution; tidal creeks 

develop along antecedent 

drainages, mostly in former 

upland regions

evaluating appropriate adaptation actions, and 

adaptation opportunities for planning, incident 

response, cultural resources, natural resources, facilities 

and assets, and infrastructure. The handbook will also 

provide guidance on developing communication and 

education materials about climate change impacts, and it 

will detail case studies of the many ways that individual 

parks are implementing adaptation strategies for 

threatened resources.

Additional Reference Manuals that guide coastal 

resource management include NPS Reference Manual 

#39-1: Ocean and Coastal Park Jurisdiction, which can 

provide insight for parks with boundaries that may shift 

with changing shorelines (available at 

http://www.nps.gov/applications/npspolicy/DOrders.cf

m); and NPS Reference Manual #39-2: Beach 

Nourishment Guidance (Dallas et al. 2012) for planning 

and managing nourishment projects.

The NPS is also developing a cultural resources climate 

change response strategy that connects climate science 

with historic preservation planning. The summary report 

from the Preserving Coastal Heritage workshop in 2014 

identified and described six climate change adaptation 

options for cultural resources and cultural landscapes 

(no active intervention; offset stressors; improve 

resilience; manage change; relocate or facilitiate 

movement; document and release). Additional 

information about the workshop, and associated 

presentations and reports, are available at 

https://sites.google.com/site/democlimcult/ (National 

Park Service 2014; accessed 21 April 2015).

Hurricane Impacts and Human Responses

Hurricanes and other major storms are important drivers 

of geomorphological change along the Outer Banks, as 

the winds, waves, and storm surge move sand across and 

off of the islands. Riggs and Ames (2006) asserted that 

migration of the barrier islands upward and landward in 

a back-stepping motion would be driven by a single large 

storm or a series of smaller storm events with storm 

surges of 4 to 10 m (13 to 33 ft; category 3 or higher 

hurricanes on the Saffir-Simpson scale describing 

hurricane impacts; table 7). According to data compiled 

by Caffrey (2013) for Cape Hatteras visitor center and 

Cape Hatteras Lighthouse (Buxton), storm surges are 

projected to range from 2.4 m (7.9 ft) above current sea 

level (storm surge heights will change over time as sea 

level rises) for a category 2 at mean tide to 3.7 m (12.3 ft) 

for a category 5 at high tide. Caffrey’s (2013) compilation 

also indicates storm surges at Fort Raleigh National 

Historic Site from 1.9 m (6.1 ft) for a category 2 at mean 

tide to 3.6 m (11.7 ft) for a category 5 at high tide. Data 

for Wright Brothers National Memorial (see Caffrey 

2013) suggest the park would be “dry” during a category 

2 at mean tide with a storm surge of 4.5 m (14.9 ft) during 

a category 5 at high tide.

The chance that a hurricane will make landfall 

somewhere on the Outer Banks in a given year is 12%

(8.6-year expected return period), and the likelihood that

hurricane-speed winds will affect the Outer Banks in a 

given year is even higher (18%, equal to a 5.5-year

expected return period) (Smith et al. 2006). Although 

higher-category storms are rare—only one category 4 

storm (Hurricane Hazel in 1954) struck the North 

Carolina coast between 1851 and 2012 (NOAA 2013a)—

lower-category storms regularly cause significant erosion 

and infrastructure damage, as evidenced by Hurricane 

Isabel in 2013 (category 2) and Hurricane Sandy in 2012 

(category 1).

Ecological Impacts of Hurricanes on Estuaries

Perturbations caused by hurricanes affect Pamlico 

Sound’s phytoplankton communities, which account for
50 NPS Geologic Resources Division

Table 7. The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane's sustained wind 

speed. This scale estimates potential property damage. Hurricanes reaching category 3 and higher are 

considered major because of the potential for significant loss of life and damage.

Category Sustained Winds Types of Damage due to Hurricane Winds

1 

74–95 mph

64–82 kt

119–153 km/h

Very dangerous winds will produce some damage: well-constructed frame homes 

may sustain damage to roofs, shingles, vinyl siding, and gutters. Large branches of trees

will snap and shallowly rooted trees may be toppled. Extensive damage to power lines 

and poles likely will result in power outages that could last a few to several days.

2

96–110 mph

83–95 kt

154–177 km/h

Extremely dangerous winds will cause extensive damage: well-constructed frame 

homes could sustain major roof and siding damage. Many shallowly rooted trees will be 

snapped or uprooted and block numerous roads. Near-total power loss is expected, with 

outages that could last from several days to weeks.

3 (major)

111–129 mph

96–112 kt

178–208 km/h

Devastating damage will occur: well-built frame homes may incur major damage or 

removal of roof decking and gable ends. Many trees will be snapped or uprooted, 

blocking numerous roads. Electricity and water will be unavailable for several days to 

weeks after the storm passes.

4 (major)

130–156 mph

113–136 kt

209–251 km/h

Catastrophic damage will occur: well-built framed homes can sustain severe damage 

with loss of most of the roof structure and/or some exterior walls. Most trees will be 

snapped or uprooted and power poles downed. Fallen trees and power poles will isolate 

residential areas. Power outages will last weeks to possibly months. Most of the area will 

be uninhabitable for weeks or months.

5 (major) 

≥157 mph

≥137 kt

≥252 km/h

Catastrophic damage will occur: a high percentage of framed homes will be destroyed, 

with total roof failure and wall collapse. Fallen trees and power poles will isolate 

residential areas. Power outages will last for weeks to possibly months. Most of the area 

will be uninhabitable for weeks or months.

Information source: National Hurricane Center (2012), available online at: http://www.nhc.noaa.gov/aboutsshws.php (accessed 27 August 

2014).

at least 80% of primary production sustaining the food 

webs of the Pamlico Sound and its tributaries, according 

to a study by Paerl et al. (2006). This study found that an 

increase in the number of hurricanes with high rainfall 

and high flood production would lead to increased 

nutrient loading and greater frequency, intensity, and 

spatial coverage of phytoplankton blooms, as well as 

expansion of low oxygen conditions. In contrast, 

hurricanes with low rainfall result in lower nutrient 

inputs and low to moderate stimulation of primary 

production and phytoplankton biomass. Hurricanerelated flooding adds nutrients, organic material, 

sediments, and toxic chemicals to the estuary, and can 

enhance vertical stratification of the water column, 

which allows low oxygen conditions in the bottom water. 

The authors found that salinity levels in the sound can 

take months to return to normal pre-hurricane levels

(Paerl et al. 2006).

Impacts of Hurricanes on Infrastructure

Hurricanes, tropical storms, and nor’easters impact

infrastructure along the Outer Banks and in Cape 

Hatteras National Seashore through erosion of 

protective dunes, damage to Highway 12, and 

destruction of coastal buildings. Storms buckle asphalt 

roads and deposit thick beds of overwash sand, as 

occurred during Hurricane Sandy and nor’easters 

between October 2012 and March 2013. Storms also 

open new inlets through the barrier islands, as occurred 

during Hurricane Isabel in 2003 and Hurricane Irene in 

2011. Immediately following each storm, roads are 

repaired, inlets and breaches are filled, and overwash 

sand is pushed back toward the beach to create 

protective dunes (Riggs et al. 2008b, 2011; Saunders et al. 

2012). These practices stop natural landward migration 

by elevating and widening the barrier island, preventing 

sand from remaining on and moving across the island 

and through the inlets to the island’s estuarine shoreline. 

Ocean shoreline erosion continues, but the natural 

overwash processes that elevate and widen islands are 

prevented. For additional examples of human responses

to hurricane impacts, see the “Inlet Modifications” and 

“Highway 12 Transportation Corridor” sections of this 

chapter.

Impact of Climate Change on Hurricanes

Climate change is expected to increase hurricane 

intensity in the North Atlantic Basin, according to the 

2013 IPCC report (Kirtman et al. 2013). Saunders et al. 

(2012) stated that hurricanes have become stronger in 

the last 30 years, coinciding with an increase of 1.1°C 

(2°F) in sea-surface temperature where hurricanes form. 

Temperatures at Cape Hatteras National Seashore were 

0.67°C (1.2°F) warmer in 2000–2011 than during 1961–

2000, and a medium–high future emissions scenario 

projects that they will rise an average of 1.67°C (3°F; 
CAHA Geologic Resources Inventory Report 51

average daily summer temperatures up to 30.1°C

[86.2°F]) by 2051–2060 (Saunders et al. 2012). Saunders 

et al. (2012) believe that hurricanes have also increased 

average summer wave heights along the Atlantic 

coastline since 1975.

The strength of Atlantic hurricanes is likely to increase in 

this century, with higher peak winds, rainfall intensity, 

and storm-surge height and strength (Saunders et al. 

2012). An increase in storm activity will increase the rate 

and extent of ocean and estuarine shoreline erosion and 

associated land loss throughout the coastal system of 

North Carolina (Culver et al. 2008a). Additionally, 

increased storm activity will open new inlets, which will 

in turn affect estuarine physical and chemical dynamics, 

including increases in astronomical tidal range, salinity 

content, and water column mixing, and associated 

changes in nutrient dynamics and turbidity. These 

changes will impact fisheries, benthic ecosystems, and 

intertidal wetlands. Estuaries would also be impacted by 

changes in precipitation patterns that affect river flow, 

which in turn influence nutrient delivery and cycling, 

flushing rates, and salinity values in the estuaries. Each of 

these responses would influence the structure (e.g., plant 

and animal composition) and function (e.g., plant and 

animal production, nutrient cycling) of the estuarine 

system (Culver et al. 2008a).

Inlet Modifications

Inlet dynamics are a critical component of natural barrier 

island processes and sediment transport at Cape Hatteras 

National Seashore (see the “Geologic and Environmental 

Features and Processes” chapter for additional 

information). Inlet size and location shift in response to 

each storm, and a stable, deep channel is rarely 

maintained naturally (Riggs et al. 2009). Anthropogenic 

modifications of an inlet, such as dredging andcoastal 

engineering, disrupt the inlet’s ability to respond to 

storms, to bypass sediment between islands, to exchange 

sediment between flood and ebb tidal deltas, to migrate, 

and to provide sediment to downdrift shorelines (Riggs 

et al. 2009). Inlet stabilization is one of many examples of 

human efforts to protect coastal development from 

waves and flooding, to mitigate erosion, and to maintain 

navigation channels, which have often altered the 

behavior of coasts considerably (Williams 2013).

The navigability of some modern inlets through the 

Outer Banks is actively maintained through dredging. 

Newly opened inlets are often closed artificially to 

maintain the highway infrastructure. Only one inlet, 

Oregon Inlet, has been modified with a terminal groin

and revetment in an effort to stabilize it. Several effects of 

these management actions are described below.

Buxton Inlet: Filling and Dredging Increase Vulnerability

The Ash Wednesday nor’easter of March 1962 opened 

Buxton Inlet (fig. 26) through a narrow portion of 

Hatteras Island between the towns of Buxton and Avon. 

This inlet was 503 m (1,650 ft) wide and had a maximum 

depth of 3.7 m (12 ft) below National Geodetic Vertical 

Datum (NGVD) 29 (Wamsley et al. 2009). A bridge built 

over this inlet was destroyed in another nor’easter in 

December 1962. The US Army Corps of Engineers then 

filled the inlet in January and February 1963 by dredging 

sand from its flood tidal delta and the adjacent estuary. 

This flood tidal delta was mined again in the 1960s for a 

series of beach nourishment projects, which created a 

series of deep channels and holes (e.g., Canadian Hole) 

along the back of the barrier; such features persist in the 

area known as the Haulover (Mallinson et al. 2008b). 

These human modifications to the inlet and flood tidal 

delta, combined with impacts of storms to the sound side 

of the island, increased the rate of estuarine shoreline 

erosion and exacerbated island narrowing (Riggs and 

Ames 2006). Shoreline erosion between 1852 and 1998 

removed approximately 760 m (2,500 ft; 76%) of island 

width (Riggs et al. 2008). As a result, this location is 

vulnerable to future breaching (Mallinson et al. 2008b).

Isabel Inlet: Costly Infilling Does Not Reduce Vulnerability

In September 2003, Hurricane Isabel approached the 

North Carolina coast as a category 5 hurricane on the 

Saffir-Simpson scale (table 7); it had weakened to a 

category 2 storm by the time it made landfall (Smith et al. 

2006). At the point of landfall, maximum wind speeds 

were approximately 161 km/h (100 mph) and storm 

surges were 2 to 2.4 m (6.5 to 8 ft) above normal tide level 

(Wamsley et al. 2009).

The storm breached Hatteras Island about 10 km (6 mi) 

northeast of Hatteras Inlet between the villages of 

Hatteras and Frisco, where a previous inlet had been 

opened in 1933 (fig. 27). This area, a known erosion 

hotspot, is one of the narrowest and least elevated

sections of Hatteras Island (Sallenger 2003), with a longterm shoreline recession rate of about 0.9 to 1.2 m (3 to 4 

ft)/year (Overton and Fisher 2004). The breach was 

caused by elevated water levels and wave attack from the 

ocean side (Wamsley et al. 2009).

The 600-m- (1,970-ft-) wide inlet had three channels that 

formed through underlying, sand-filled tidal channels 

dissecting the platform marsh and peat deposits, which

are more resistant to erosion (fig. 28) (Riggs and Ames 

2006). According to Wamsley et al. (2009), peat 

outcroppings on the ocean sides of the small mid-inlet 

islands separating the three channels acted as an erosionresistant barrier. The easternmost channel had the 

highest flow volume. It was 99 to 107 m (325 to 350 ft) 

wide with scour depths of 6 m (20 ft) relative to North 

American Vertical Datum (NAVD) 88 and an ebb shoal 

that extended up to 381 m (1,250 ft) offshore in water 

depths of 1.2 to 1.8 m (4 to 6 ft) NAVD88. The middle 

channel had a peat terrace that resisted scouring and 

restricted flow to periods of higher tide elevations. The 

west channel was about 107 m (350 ft) wide with depths 

of 2.1 to 3 m (7 to 10 ft) NAVD88 and a rapidly changing 

morphology (fig. 29) (Wamsley et al. 2009).

The US Army Corps of Engineers sealed the Isabel Inlet 

breach 44 days after it had opened with sand dredged 

from the federally maintained ferry channel between 
52 NPS Geologic Resources Division

Figure 26. Buxton Inlet. Buxton Inlet formed during a 1962 nor’easter called the Ash Wednesday Storm. The yellow line in 

the left panel indicates the shoreline position in 1852. The blue, purple, red, white, and green lines and dates are the 

locations and times of westward relocation of North Carolina Highway 12. Red stars indicate the same geographic location 

in all three aerial photographs. Notice the engineered channel and dike in the 1953 photograph, the very well-developed 

flood tidal delta in the 1963 photograph, and the dredge holes produced to close Buxton Inlet visible in the 1963 

photograph. Figure 8 from Riggs and Ames (2006).

Figure 27. Inlet formation during Hurricane Isabel. Hurricane Isabel breached Hatteras Island in September 2003. The threechannel inlet was filled using dredged sand, and Highway 12 was rebuilt. The red arrows point to the same geographic 

locations on both oblique aerial photographs. This location remains vulnerable to future breaching. Figure 11 from 

Pendleton et al. (2004), created using US Geological Survey aerial photographs.
CAHA Geologic Resources Inventory Report 53

Figure 28. Elevation and bathymetry of Isabel Inlet. This map shows the land elevation (green to red colors) and water 

bathymetry (blue to purple colors) of Isabel Inlet, which was formed by Hurricane Isabel in 2003. The inlet had three 

channels, with depths of up to 6 m (20 ft), that were separated by erosion-resistant peat. Figure 7 from Freeman et al. 

(2004).

Figure 29. Isabel Inlet transects. Bathymetry and island topography of Isabel Inlet were surveyed along three transects from 

3 to 5 October 2003 and again from 13 to 16 October 2003 to evaluate changes in inlet morphology over time. Morphology 

changed rapidly. Figure 7 from Wamsley et al. (2009), created using photographs from North Carolina Department of 

Transportation.

Hatteras and Ocracoke islands, at an estimated cost of 

$6.5 million, excluding road and utility reconstruction 

(Smith et al. 2006). North Carolina Highway 12 was 

rebuilt in place. Because the inlet was filled before a flood 

tidal delta had been deposited, this area of the island 

remains just as vulnerable to future inlet formation as it 

was prior to Hurricane Isabel (Riggs and Ames 2006).

Oregon Inlet: Infrastructure Threatened by Migration

Oregon Inlet (fig. 30) opened during a hurricane on 7 

September 1846 near the current location of the Bodie 

Island lighthouse. It is the only inlet in the northern 

Outer Banks between Cape Hatteras and Cape Henry, 

Virginia, and it provides a transportation corridor 

between the Pamlico, Currituck, and Albemarle sounds 

and the Atlantic Ocean. The Herbert C. Bonner Bridge, 

completed in 1963, spans Oregon Inlet and connects 

with Highway 12 on Bodie Island to the north and Pea 

Island to the south. Since it was opened, the inlet has 

migrated approximately 4 km (2.5 mi) southward 

because of accretion on its north bank (Bodie Island) and 

erosion on its south bank (Pea Island). The rate of this 

migration has ranged from 23 to 165 m (75 to 541 ft) per 

year (Riggs et al. 2009).

The maintenance of a navigation channel through the 

inlet is challenging due to inlet dynamics and the amount 

of dredging required to hold the channel in place (Riggs
54 NPS Geologic Resources Division

Figure 30. Oregon Inlet. The inlet was stabilized by a terminal groin and revetment to stop southward migration, which 

undermined the Pea Island Bridge onramp for Highway 12. Bonner Bridge is visible near the center of the photograph. 

National Park Service photograph taken February 2015, available online: 

https://www.flickr.com/photos/capehatterasnps/16217489383/ (accessed 27 April 2015).

et al. 2011). A controversial proposal to stabilize the 

inlet’s location has been discussed and involves a pair of 

3.2-km- (2-mi-) long jetties (Riggs et al. 2009). Such 

jetties could have serious environmental consequences 

and have not yet been built. Jetties are built 

perpendicular or oblique to a shoreline to trap and hold 

sand being transported along the shoreline by longshore 

drift; they protect the attached shoreline from erosion

but starve downdrift beaches of sand. In 1989–1991, a 

938-m- (3,077-ft-) long terminal groin and rock 

revetment were built on the southern side of the inlet to 

prevent disconnection of the southern approach to 

Bonner Bridge from Pea Island (Riggs et al. 2009). This 

structure stopped the inlet’s southward migration, but a 

new downdrift beach equilibrium configuration 

developed (fig. 31) (Joyner et al. 1998). Geomorphic 

changes included the soundward accretion of the Bodie 

Island spit to the area of the navigation span of Bonner 

Bridge, which decreased the width of the inlet, in turn 

causing the channel to deepen and migrate southward 

toward the rock structures (Joyner et al. 1998).

From 1960 to 1983, an unknown volume of sand was 

dredged to maintain the navigability of Oregon Inlet and 

was deposited offshore in deep water (Riggs et al. 2009).

Between 1983 and 2009, 9.2 million m3 (12 million yd3

) of 

sediment was dredged from Oregon Inlet and artificially 

bypassed to Pea Island beaches between mileposts 1 and 

3 (Riggs and Ames 2011). As a result of inlet stabilization, 

and despite beach nourishment efforts, Pea Island’s 

ocean shoreline continues to erode at rates of up to 4 m 

(13 ft)/year, among the highest rates in North Carolina 

(Riggs et al. 2011).

The aging Bonner Bridge is decades past its planned date 

of decommissioning (1993). Adjacent sections of 

Highway 12 on Pea Island continue to be undermined by 

storm erosion and overwash. As of September 2014, 

work on replacing the bridge was suspended by court

Figure 31. Aerial image of Oregon Inlet, stabilizing terminal 

groin and revetment, and erosion and accretion resulting 

from the hard stabilization. Aerial imagery from ESRI World 

Imagery base layer (accessed 23 July 2013), annotation by 

Jason Kenworthy (NPS Geologic Resources Division).

ruling while NCDOT and the Southern Environmental 

Law Center (SELC) discuss a long-term solution that 

considers whether the 4 km (2.5 mi) bridge should be 

rebuilt in place or instead replaced by a 27 km (17 mi) 

bridge that bypasses areas particularly vulnerable to 

breaching (SELC 2014). More information on these 

issues is provided in the “Highway 12 Transportation 

Corridor” section of this chapter.
CAHA Geologic Resources Inventory Report 55

Recreational and Watershed Land Use

Disturbed Lands

Humans have disturbed the natural landscape and 

coastal processes at Cape Hatteras National Seashore in 

several ways: (1) coastal settlement and development; (2) 

extraction of oak maritime forests for shipbuilding; (3) 

early mosquito control and waterfowl management

efforts, which involved excavation of drainage ditches 

and construction of water control structures; (4) 

construction and vegetative stabilization of primary 

dunes along the length of the seashore; and (5) 

excavation of borrow ponds for roadbed material during 

road construction (NPS 2012). Current practices 

continue to disturb the ecosystem, including off-road 

vehicle (ORV) use and nutrient inputs at the local and 

watershed levels.

An increase in the area of impervious surfaces adjacent to 

the park has led to increased runoff of pollutantcontaining stormwater into Cape Hatteras National 

Seashore (Mallin et al. 2006). Increased impervious 

surface coverage in coastal areas is strongly correlated 

with increases in freshwater discharge, fecal coliform 

bacterial loading, shellfish area closures, and degradation 

of benthic biological communities (Mallin et al. 2001; 

Holland et al. 2004).

Increased development of lands adjacent to Wright 

Brothers National Memorial, along with increased 

population and demographic transformation of adjacent 

communities, have changed the uses of and use impacts 

on the park. Due to limited availability of non-federal 

lands, park staff is often pressured to permit land uses 

that are incompatible with park values (NPS 2005).

Water Quality

Cape Hatteras National Seashore faces several threats 

related to water quality (table 8) (Mallin et al. 2006). The 

long residence time (approximately 1.7 years) of Pamlico 

Sound waters fosters the sound’s high productivity, but 

also makes this nitrogen-limited estuary sensitive to 

excessive nutrient input and eutrophication (Paerl et al. 

2006). Fortunately, the distances between Outer Banks 

islands and the mainland likely protect the park from 

mainland sources of nutrients and pollutants to some 

degree (Mallin et al. 2006).

Nutrients and contaminants enter the estuary from 

several sources. Since the late 1950s, nutrient loading to 

the tributary rivers has increased by 50% in association

with increased agriculture, silviculture, urbanization, and 

industrialization. Increases in impervious surface area 

have increased stormwater runoff, with associated 

contaminants potentially degrading offshore water 

quality (Wright et al. 2012). Manmade drainage ditches 

affect water distribution and quality on Bodie and 

Hatteras islands; traffic crossing these ditches may 

contribute polycyclic aromatic hydrocarbons (fig. 32A) 

(Mallin et al. 2006). Estuarine waters at the southern end 

of Ocracoke Island receive effluent from the reverseosmosis drinking water plant, which discharges 122 m 

(400 ft) offshore; nitrogen concentrations exceed 5 mg/L 

and have the potential to cause localized algal blooms in 

nutrient-limited Pamlico Sound (Mallin et al. 2006).

Three other reverse-osmosis water plants operate 

elsewhere in Dare County at Kill Devil Hills, Stumpy 

Point, and Rodanthe. The Rodanthe/Waves/Salvo water 

treatment plant discharges into Blackmar Gut, 

approximately 0.8 km (0.5 mi) north of the southern 

boundary of Pea Island National Wildlife Refuge. 

Effluent from the water treatment plant had lower 

salinity but higher alkalinity and phosphorous 

concentrations compared with the average conditions of 

the receiving water (US Fish and Wildlife Service 2008). 

Due to the limited exchange between Blackmar Gut and 

Pamlico Sound, the potential that the effluent will impact 

sensitive resources in Pamlico Sound or Pea Island 

National Wildlife Refuge is low (US Fish and Wildlife 

Service 2008).

Septic leachate is a significant source of contamination. 

Human population has increased along the northern 

Outer Banks over the past 30 years, with summer tourists 

tripling the population and increasing nutrient and 

bacterial loads on septic systems (Mallin et al. 2006). 

Portions of the park on South Bodie Island receive 

nutrients and microbial pathogens via septic leachate 

from the town of Nags Head and from the movement of 

groundwater through the sandy saturated soils into 

drainage ditches within the park (fig. 32B) (Mallin et al. 

2006). Studies conducted in 1988 and 1995 showed that 

septic leachate has a considerable impact on drainage 

ditches on NPS land, and a lesser impact on marshes 

(Mallin et al. 2006). Septic leachate may sometimes enter 

the groundwater table; because much of the area has a 

seasonal water table of less than 0.76 m (2.5 ft), the

amount of unsaturated soil may be insufficient to provide 

proper aerobic treatment to wastewater entering the 

subsurface (Evans and Houston 2000, as cited in Mallin 

et al. 2006).

Estuarine water-quality sampling at 17 sites in Cape 

Hatteras National Seashore in 2010 yielded mostly good 

and fair water-quality ratings, with water from some 

areas containing elevated nitrogen and phosphorus

concentrations (Gregory and Smith 2011). However, 

many areas along the park’s estuarine shoreline have 

water bodies that were 303(d) listed as impaired between 

2006 and 2010 (fig. 33) (North Carolina Department of 

Environment and Natural Resources Division of Water 

Quality 2012), meaning that the existing controls on 

pollution are insufficient to attain or maintain applicable 

water quality standards. Some areas have been closed to 

shellfishing due to pathogens. Commercial fisheries 

landings in Pamlico Sound have been declining rapidly 

since 1980 and indicate major changes in the sound’s 

trophic dynamic structure, likely related to 

eutrophication, algal blooms, and hypoxia, and 

accelerated by overfishing and habitat destruction (Paerl 

et al. 2006).

Toxic blooms of Pfiesteria spp. in the waters of Cape 

Hatteras National Seashore are unlikely because this 

species prefers nutrient-enriched waters and more
56 NPS Geologic Resources Division

Table 8. Existing and potential stressors that are affecting or may affect Cape Hatteras National Seashore 

habitats. Redrafted after Mallin et al. (2006).

Ocracoke Island

Stressor Ocean 

beach

Sound 

shore

Tidal 

creeks GW Marsh FW ponds

Algal blooms L P P L E L

Toxic algae L P P L P X

Nutrient loading L E P L P L

Excessive nitrate L L L X L L

Fecal bacteria L E1 P X X L

Metals contamination E; Hg2 E; Hg2 P; Hg2 X X X

Toxic compounds X L P; PAHs X X X

Invasive species lionfish X X L E3 X

Habitat disruption E; ORVs L L L L P; ORVs

Hatteras Island

Stressor Ocean 

beach

Sound 

shore

Tidal 

creeks GW Ditches Sedges/swales

Algal blooms L P P L E L

Toxic algae L P P L P L

Nutrient loading L P P E E E

Excessive nitrate L L L E E L

Fecal bacteria E; drainage P P E E E

Metals contamination E; Hg2 E; Hg2 P; Hg2 X X X

Toxic compounds X E X X X E X

Invasive species P; lionfish X X L E3 X

Habitat disruption E; ORVs E; ORVs L E E P; drainage

Bodie Island

Stressor Ocean 

beach

Sound 

shore

Tidal 

creeks GW Ditches Sedges/swales

Algal blooms L P P P L E E

Toxic algae L P P L P X

Nutrient loading L P P E E E E

Excessive nitrate L L L E E E

Fecal bacteria E P L E E E

Metals contamination E; Hg2 E; Hg2 P; Hg2 X X X

Toxic compounds X E X X P; PAHs X

Invasive species P; lionfish E P L E3 X

Habitat disruption E; ORVs L L L L X

Legend

X no data to make judgment P potential problem

L low or no problem E existing problem

Notes: 1 = based on closed shellfishing area around developed canal community soundside; 2 = fish tissue consumption advisory by North 

Carolina Division of Water Quality; 3 = Phragmites is abundant in areas of the oligohaline marsh. GW = groundwater; FW = freshwater; Hg = 

mercury; PAH = polycyclic aromatic hydrocarbon; ORV = off-road vehicle. 
CAHA Geologic Resources Inventory Report 57

Figure 32. Drainage ditches near Cape Hatteras. A) Human -constructed drainage ditches affect water distribution and 

quality on Hatteras Island, and traffic crossing these ditches may contribute polycyclic aromatic hydrocarbons. ESRI World 

Imagery base layer (accessed 27 March 2014); annotation by Trista Thornberry-Ehrlich (Colorado State University). NPS 

boundary (2012; green line) courtesy Laura Pickens (Cape Hatteras National Seashore). B) Photograph of a ditch draining 

groundwater from Nags Head Village toward Pamlico Sound. Portions of Cape Hatteras National Seashore on South Bodie 

Island receive nutrients and microbial pathogens via septic leachate from the town of Nags Head and from the movement 

of groundwater through the sandy saturated soils into drainage ditches within the park. Photograph by Michael Mallin 

(University of North Carolina Wilmington) extracted from Mallin et al. (2006), plate 3.

estuarine conditions, but blooms are possible given the 

leaching of nutrients from septic systems adjacent to 

park waters (Mallin et al. 2006). Toxic blue-green algal 

blooms or nuisance algal blooms may occur in 

freshwater areas of the park, such as the nutrientenriched drainage ditches on Bodie Island, Hatteras 

Island swales that are impacted by runoff or septic 

system leachate, and tidal creeks, marshes, and ponds on 

Ocracoke Island. Swales may also be impacted by 

groundwater withdrawals in wellfield areas, which can 

disrupt habitat by limiting plant species richness and 

diversity in nearby swales, according to a study 

conducted on Hatteras Island (Mallin et al. 2006). 

Fortunately, however, Buxton Woods swales that are 

well within the park are insulated from anthropogenic 

impacts (Mallin et al. 2006).

Contact the NPS Water Resources Division 

(http://nature.nps.gov/water/) for assistance with water 

quality issues.

Off-Road Vehicles

Cape Hatteras National Seashore permits ORVs to drive 

and park on the beach seaward of the primary dune line 

via several access ramps. A 10-m (33-ft) backshore area 

seaward of the primary dune line is protected seasonally 

to allow for turtle and shorebird nesting, and additional 

protection buffers may be established when wildlife or 

nests are observed. Historically, beach driving at the 

seashore was for the purpose of transportation, not 

recreation. Improved access to the island, increased 

population, and popularity of sport utility vehicles have 

resulted in a dramatic increase in recreational vehicle use
58 NPS Geologic Resources Division

Figure 33. Map of polluted (“303(d)”) waterways. Multiple water bodies along the Cape Hatteras National Seashore 

estuarine shoreline were 303d listed as polluted in the state’s 2010 report. Stars indicate where images join. Figure created 

by Trista Thornberry-Ehrlich (Colorado State University) using information from the US Environmental Protection Agency 

“How’s My Watershed?” tool, available online: http://watersgeo.epa.gov/mywaterway/#/mywaterway/map.htm (accessed 

27 March 2014). Imagery from ESRI World Imagery base layer (accessed 27 March 2014).
CAHA Geologic Resources Inventory Report 59

on Cape Hatteras National Seashore beaches. Efforts to 

establish a balance among recreational access, various 

user groups, and habitat preservation has been 

controversial. New ORV policies were established 

through an Environmental Impact Statement in 

November 2010 and became active in February 2012 

(NPS 2010).

Studies conducted along beaches similar to those at Cape 

Hatteras National Seashore have shown that ORV use 

can have a variety of ecologic and geomorphic impacts. 

Driving on the unvegetated beach displaces sediment 

and may interfere with beach-dune morphology and 

evolution, but the sediment is not necessarily lost to the 

beach-dune system. A study conducted at Fire Island 

National Seashore, New York, estimated that 119,300 m3

(156,040 yd3) of sediment was displaced (but not 

necessarily lost to the beach-dune system) by 45,000 

vehicles annually (Anders and Leatherman 1987a, 

1987b), and a study performed on North Stradbroke 

Island, Australia, estimated 38,018 m3 (49,725 yd3)/year

sediment displacement for every 500 cars (Schlacher and 

Thompson 2008).

A recent study of the ORV zone at Assateague Island 

National Seashore, Maryland (Houser 2012; see GRI 

report by Schupp 2013), suggested that ORV use causes 

no net seaward loss of sediment from the beachface. 

Rather, ORV use disrupts the landward exchange of 

sediment between the beach and dune, preventing poststorm dune recovery. In comparison with those in

adjacent no-driving zones, dunes in the ORV zone were 

found to be smaller, shorter, farther landward, and more 

susceptible to scarping. This study also determined that 

sediment volume was greater on the leeward sides of 

dunes in the ORV zone, which reduces their resilience to 

storms, preventing the recovery of pre-disturbance 

height and elevation. This effect can accelerate shoreline 

retreat and island transgression in response to relative 

sea-level rise.

Off-road driving can also destabilize coastal dunes 

through direct damage to vegetation on backshore and 

embryo dunes, the precursors to larger stable dunes 

(Liddle and Greig-Smith 1975; Steiner and Leatherman 

1981; Anders and Leatherman 1987a). Loss of vegetation 

seaward of a dune can promote erosion of the dune toe 

and steepening of the seaward beach, which can lead to 

further erosion and scarping by astronomical and storm 

tides (Anders and Leatherman 1987a). In contrast, dunes 

in vegetated control sections extend seaward and 

provide greater protection during storms. Even a low 

frequency of ORVs can cause extensive degradation of 

vegetation and habitat, limiting seaward dune growth 

(Anders and Leatherman 1987a). Godfrey and Godfrey 

(1980) found that 50 vehicle passes on Cape Cod were 

sufficient to inhibit seaward dune development, resulting

in a scarped rather than sloped dune profile. The number 

of vehicles using a path makes little difference once 

vegetation has been impacted.

Off-road driving also has numerous biological impacts 

on habitats, organisms, and ecosystems. On the 

unvegetated beach, off-road driving limits the survival, 

abundance, and diversity of shorebirds, sea turtles 

(Leatherman and Godfrey 1979; Godfrey and Godfrey 

1980; Hosier et al. 1981; Wolcott and Wolcott 1984; 

Watson et al. 1996; Williams et al. 2004; Schlacher et al. 

2007) and invertebrates (Moss and McPhee 2006;

Schlacher et al. 2008), including ghost crabs, which can 

be crushed even in burrows located 30 cm (12 in) below 

the surface (Schlacher et al. 2007). Studies conducted at 

Assateague Island National Seashore have shown that 

ORV use limits the abundance of the tiger beetle 

(Cicindela dorsalis media), listed by the State of Maryland 

as rare (Knisley and Hill 1990); it also reduces migratory 

seabird species richness, abundance, size, number of 

roosts, and time spent foraging (Forgues 2010).

Dune Stabilization

On natural barrier island systems, broad beaches and 

beach berms absorb most storm wave energy, and 

remaining wave energy rapidly weakens as water flows 

between dunes and across islands (Dolan and Godfrey 

1972). Along the Outer Banks, however, a line of 

constructed dune ridges is maintained to protect roads 

and other infrastructure. This perception of the 

protective role of the dune ridges contributes directly to 

increased pressure to protect, maintain, and rebuild the 

artificial dunes.

The dunes were first built between 1936 and 1940 under 

the direction of the NPS, Civilian Conservation Corps,

and Works Progress Administration. Workers

constructed 1,258 km (782 mi) of dunes and erected 

nearly 914 km (568 mi) of sand fencing to create a 

continuous barrier dune ridge along the entire length of 

the Outer Banks, from the Virginia state line to Ocracoke 

(Dolan and Godfrey 1972; Riggs et al. 2009). The 

resulting dune ridge was up to 6 m (20 ft) high and in 

many places was backed by multiple rows of dune ridges. 

Other modifications followed, including the 

construction of 120 km (75 mi) of dikes and jetties, and 

planting of 2,650 ha (6,548 ac) grass and 3.4 million 

seedlings, trees, and shrubs until a nearly continuous 

band of vegetation blanketed the area (Riggs et al. 2009). 

Some stretches were not maintained and now contain 

only partial or terminated ridges (Ames and Riggs 2006j). 

In areas with adequate sediment supply, some 

constructed dune ridges have become incorporated into 

natural dune fields (Ames and Riggs 2006j).

Geomorphologists find determination of the point at 

which a man-made dune has become “natural” on the 

barrier islands difficult (Hoffman et al. 2007g). For 

example, prior to 1962, Ocracoke Village was growing 

southeastward as ringed dune-beach ridges formed 

naturally. Following the 1962 Ash Wednesday storm, a 

set of dune ridges was constructed using sand fences and, 

along with the adjacent overwash plain, was stabilized 

with vegetation. These features are currently heavily 

vegetated with dune grasses and scrub-shrub 

communities, and the previous overwash plain now 

supports marsh vegetation. Natural dune growth has 

ceased on the southeastern side of the village, and the 

northern side of the village is eroding at an approximate
60 NPS Geologic Resources Division

rate of 1.2 m (4 ft)/year in response to storm wind and 

waves from Pamlico Sound (Riggs and Ames 2006).

Artificial dune stabilization has greatly altered the 

ecosystem and geologic structure of Cape Hatteras 

National Seashore. Stabilized dunes have minimized 

natural overwash and inlet-formation processes, 

modified vegetation communities, and altered backbarrier estuarine processes. These effects have resulted 

in narrower beaches, a steeper shoreface, and deeper 

inshore water depths (Dolan and Lins 1986), as well as

increased wave energy dissipating on the shoreface, a 

steeper beach profile, increased turbulence, and 

accelerated mechanical weathering of sand into finer 

particles. As the buffering beaches erode away, wave 

energy and storm surges attack the dunes, causing rapid 

scarp formation while the system is out of equilibrium 

(Ames and Riggs 2006j). For example, 30 years after 

initial stabilization, several beaches on Hatteras Island 

had all but disappeared (Dolan and Godfrey 1972). 

Additionally, along the barrier segment between Avon 

and Buxton, maintained dunes have prevented inlet 

formation and minimized overwash, resulting in 

substantial island narrowing and the relocation of 

Highway 12 at least four times (fig. 26) (Riggs and Ames 

2006). Natural maintenance of this barrier island 

segment over the short term (months to years) and 

evolution over the long term (decades to centuries) in 

response to ongoing sea-level rise would require inlet 

formation followed by extensive overwash (Riggs and 

Ames 2006).

Back-barrier areas are also impacted by the dunes, which

cut off the overwash source of sediments, causing scarp 

development in landward marshes and decreasing the 

biological productivity of sound ecosystems. Dune 

stabilization also causes flooding behind the barrier 

dunes from the direction of the Pamlico Sound when 

strong northwest winds push water up against the 

western coasts of the barrier islands. This influx of water 

formerly flowed relatively freely between the dunes 

eastward and out to sea (Dolan and Lins 1986).

Coastal Engineering and Shoreline Armoring

NPS management policies (NPS 2006; see also 

“Appendix B”) require that natural shoreline processes 

be allowed to continue without interference and that 

anthropogenic impacts be mitigated. Exceptions require 

special evaluation and are granted for the protection of 

cultural or natural resources, safety during emergencies, 

and congressional directives. The 1984 General 

Management Plan for Cape Hatteras National Seashore 

allows for natural processes to continue with three 

exceptions for infrastructure and cultural resources: 

Highway 12, Ocracoke Village, and the Cape Hatteras 

lighthouse (Riggs et al. 2009).

Dallas et al. (2013) completed an inventory of 72 coastal 

engineering projects in or immediately adjacent to Cape 

Hatteras National Seashore. Forty-eight of these projects

are coastal structures (extending a total of 5,723 m 

[18,360 ft]), 17 are beach nourishment projects, five are 

dredging projects, and two are dune construction 

projects. That report also discusses impacts due to 

coastal engineering projects, as well as recommendations 

for further study and management.

Since 1985, state regulations disallowed the installation 

of hardened structures (e.g., jetties, groins, bulkheads, 

seawalls, and revetments) to prevent ocean shoreline 

erosion, and require that new construction be located a 

certain distance from the shoreline. However, Senate Bill 

151, the Coastal Policy Reform Act of 2013, permits the 

construction of up to four terminal groins at North 

Carolina inlets if structures or infrastructure are 

threatened by erosion. This act represents a significant 

change to the state’s coastal policy laws, which

previously required an imminent erosion threat and 

determination that nonstructural control methods (e.g.,

relocation) were impractical. Additional exceptions can 

be made to stabilize commercial navigation channels 

(including Oregon Inlet) and erosion-threatened bridges, 

and to protect historic sites (Riggs et al. 2008b). Many 

forms of estuarine shoreline armoring are permitted 

(NCDCM 2009). The state’s Coastal Area Management 

Act requires local land-use plans to contain policies that 

minimize threats to natural resources resulting from 

development in areas subject to erosion, storm surge, 

and sea-level rise, among other forces (Feldman et al. 

2009).

Seawalls and other structures that attempt to inhibit 

wave action are expensive and do not prevent sediment 

loss in front of the structures. Instead, they commonly 

accelerate erosion locally (Dolan and Godfrey 1972; 

Dolan and Lins 1986) and are aesthetically displeasing. 

Jetties and other structures designed to inhibit currents 

that transport sand cause localized erosion in the 

direction of longshore transport and adjacent to the 

structures (Dolan and Godfrey 1972).

Alternative erosion control structures, such as sandbags 

and beach renourishment, are permitted. The state 

allows the use of sandbags as a temporary measure to 

provide time to arrange for beach nourishment or to 

move a structure threatened by erosion. Unfortunately, 

bulkheads composed of sandbags act in a similar manner 

to those composed of rock or steel (fig. 34). The beach in 

front of the sandbags is lost to wave energy and erosion 

on adjacent beaches increases (Riggs et al. 2008b). Beach 

nourishment, another temporary solution, requires the 

availability of compatible sediment within a reasonable 

transport distance. The idea of artificial beach 

nourishment seems attractive because (1) placement of 

sand on a beach does not alter the suitability of the area 

for recreation, (2) addition of sediment does not always 

affect areas beyond the problem area, and (3) no 

structural debris must be removed if the effort fails

(Dolan and Godfrey 1972; Dolan and Lins 1986).

However, the sourcing of sufficiently large quantities of 

sand compatible with the eroding beach in terms of size 

and mineralogy can be difficult. Finer sands tend to wash 

away too quickly; coarser sands create artificial beach 

berms and impact nearshore habitats. Sources of large 

quantities of sand may be limited to offshore areas, such
CAHA Geologic Resources Inventory Report 61

Figure 34. Stabilization and relocation. Hard stabilization is 

not permitted in North Carolina except in special 

circumstances (e.g., Oregon Inlet). Short-term solutions 

include sandbags (top, along Highway 12 in Rodanthe; 

North Carolina Department of Transportation photograh). 

Relocation provides a longer-term solution, as in the case of 

moving the Cape Hatteras lighthouse to an inland location 

(bottom; NPS photograph by Mike Booher, February 1999, 

with move path cleared).

as Diamond Shoals and coastal inlets (Dolan and Lins 

1986). The means of obtaining suitable sand, such as 

dredging, can have substantial impacts on other areas 

(Dolan and Godfrey 1972). In North Carolina, the most 

commonly used nourishment sand is sourced from inlet 

deltas and channels; this sand is compatible, but its 

removal destabilizes the inlets and impacts longshore 

sediment transport and long-term sediment budgets for 

the barrier islands and inlets (Riggs et al. 2008b).

Between 1962 and 2011, over 7.8 million m3 (10.2 million 

yd3

) of sediment were emplaced on Cape Hatteras 

National Seashore beaches (Dallas et al. 2013).

Another feasible solution to protect infrastructure from 

shoreline erosion is to build or relocate structures farther 

away from the shoreline. One successful example is the 

relocation of the Cape Hatteras lighthouse, an iconic 

structure built in 1870 approximately 500 to 750 m (1,640 

to 2,460 ft) from the shoreline (fig. 34). By 1935, 

shoreline erosion threatened the structure, and coastal 

engineering projects to protect the lighthouse began in 

earnest. Early efforts included sand fencing and planting 

to foster dune growth. Beginning in 1966, successive 

engineering efforts included the construction and 

rebuilding of three groins; several beach nourishment 

projects; the use of rock revetments, nylon sandbags, and 

artificial seaweed; and the dumping of asphalt rubble 

onto the beach (Mallinson et al. 2009). In 1999, a new 

management approach was employed; the lighthouse 

and light station components were moved away from the 

eroding shoreline and rising sea level to a new location 

880 m (2,900 ft) inland, where they are available for 

public visitation (Mallinson et al. 2009).

Highway 12 Transportation Corridor

Highway 12 is the only road providing access to Cape 

Hatteras National Seashore and the only evacuation 

route for the 5,000 Outer Banks residents and additional 

tourists during hurricanes (plate 1). However, this road is 

very vulnerable to shoreline erosion and storm 

overwash, and has been repeatedly damaged in 

numerous places in the last few decades. Highway 12 has 

been destroyed repeatedly at two locations on Pea Island 

in recent years, during Hurricane Irene in 2011, 

Hurricane Sandy in 2012, and a series of nor’easters in 

2012–2013.

The northeastern half of Ocracoke Island, as well as the 

barrier segments from Frisco to Hatteras Village and 

from Buxton to Avon, have histories of inlet formation 

and continue to be vulnerable to these changes. In 

addition, the entire length of Pea Island (a U.S. National 

Wildlife Refuge) is vulnerable to inlet formation. Three 

locations were predicted to have a particularly high 

likelihood of becoming inlets during a major storm or 

series of storms (Riggs et al. 2009), and in fact the 

northernmost two of them did breach during Hurricane 

Irene in 2011:

• The historic location of New Inlet and associated 

flood tidal delta, approximately 11 km south of the 

inlet;

• A narrow island segment underlain by molar-tooth 

platform marsh with sand-filled overwash tidal 

channels, approximately 17 km south of Oregon Inlet; 

and

• The historic location of Chickinacommock Inlet, 

which is filled with sand and underlies the island, 

approximately 19 km south of the inlet.

Highway 12 is particularly vulnerable to overwash and 

storm damage at these three erosional hotspots, which

extend a total of almost 10 km (6 mi), half the length of 

Pea Island (Riggs et al. 2011).

Even with continued beach nourishment and dune ridge 

construction, the long-term viability of the Pea Island 

portion of Highway 12 is expected to be severely 

threatened by the narrowness of the island. Major 

changes in road location, by relocation to a back-barrier 

causeway or elevation as a causeway above the island 

within the lifespan of a new Oregon Inlet bridge, are 

required in the immediate future (Riggs et al. 2011).

As of September 2014, the long-term plan to replace the 

aging Bonner Bridge over Oregon Inlet (figs. 30 and 31) 
62 NPS Geologic Resources Division

and adjoining sections of Highway 12 continues to be 

mired in controversy. Court appeals had been filed to 

rescind permits issued for rebuilding of the adjoining Pea 

Island highway in its present location, with the possibility 

of building a permanent 4 km- (2.5 mi) bridge where a 

temporary bridge was constructed following Hurricane 

Irene in 2011. The Southern Environmental Law Center 

(2012) has argued that current plans to rebuild Bonner 

Bridge and other portions of Highway 12 on Pea Island 

would impact wildlife, habitat, and pristine beaches; 

would require expensive ongoing repairs in response to 

continued overwash and storm events; and involve

permitting in an inappropriately piecemeal fashion,

rather than as an entire project with cumulative impacts. 

An August 2014 court ruling suspended work on the 

bridge so that SELC and NCDOT could develop a longterm solution (SELC 2014).

The long-term future of maintaining a highway along a 

highly mobile barrier system is controversial and pits 

short-term economic development against long-term 

natural island dynamics (Riggs et al. 2009). Alternatives 

that consider the infrastructure’s long-term reliability 

include the implementation of a system of ferries and 

water taxis (Riggs et al. 2008b), and construction of a 

long bridge that bypasses vulnerable island areas and the 

Pea Island National Wildlife Refuge by running over 

Pamlico Sound with ramp access to Pea Island (Riggs et 

al. 2008b; SELC 2012). This bridge would be 27 km (17 

mi) long, with the Oregon Inlet portion built over the 

flood tidal delta and the deeper water of Pamlico Sound; 

the southern end of the bridge would come ashore at the 

village of Rodanthe (Riggs et al. 2011).

Geomorphic Mapping

An understanding of geomorphic processes and 

landform evolution along the Outer Banks is critical to 

park managers’ ability to prepare for the island’s 

response to coastal processes and its evolution 

throughout the coming decades. To describe the 

geomorphology of Cape Hatteras National Seashore, 

geologists produced maps of landforms and sedimentary 

facies. These maps, which are described in detail in the 

“Geologic and Environmental Features and Processes”

chapter and included in the map pocket, provide a 

snapshot of the landscape at a particular instant in 

geologic time. Examples of mapped features include 

beaches, dunes, overwash fans, relict inlets, and 

anthropogenic modifications.

The US Geological Survey, North Carolina Geological 

Survey, East Carolina University, and Virginia Institute 

of Marine Science participated in a North Carolina 

Geology Coastal Cooperative Research Program that 

includes the barrier islands of the Outer Banks of North 

Carolina. The goals of the cooperative research program 

were to develop a thorough understanding of (1) the 

Quaternary geologic framework of the northeastern 

North Carolina coastal system, (2) the processes that 

formed the coastal geologic system over the past 10,000 

years, and (3) the climatic and sea-level history that 

produced the modern coastal system of the Outer Banks 

(Ames and Riggs 2006j). Program techniques and 

products include seafloor mapping of the inner shelf 

(e.g., Capone et al. 2002a, 2002b) and nearshore (e.g.,

McNinch 2004; Miselis and McNinch 2006; Schupp et al. 

2006), shoreline surveys to determine storm event 

responses and erosional hotspot behavior (e.g., List et al. 

2006), core drilling to determine paleoenvironment

characteristics (e.g., Culver et al. 2008b; Mallinson et al. 

2010a), seismic and ground-penetrating radar surveys to 

map shallow stratigraphy beneath the estuary and islands 

(e.g., Mallinson et al. 2010a, 2011), airborne topographic 

mapping using LiDAR to detect elevation and beach and 

dune changes after storms (e.g., Hoffman et al. 2007g), 

and detailed field surveys to supplement the remotely 

sensed data (e.g., Ames and Riggs 2006j). These products 

address many of the needs expressed by park resource 

managers at Cape Hatteras National Seashore during the 

initial GRI scoping meeting (NPS 2000), and their 

findings are described in this report.

An understanding of the detailed processes and 

responses that led to development of the North Carolina 

Outer Banks and their associated geomorphic and 

ecologic systems provides a foundation for the 

development of long-term resource management 

strategies (Ames and Riggs 2006j).

Continued topographic surveys (e.g., LiDAR) are 

recommended to evaluate barrier island vulnerability, 

storm response, and potential changes in habitats. Postprocessed LiDAR data provide a reliable and costeffective representation of coastal dunes at Cape 

Hatteras National Seashore for volumetric change 

measurements (Woolard and Colby 2002). Although the 

nearshore seafloor is not contained within the 

boundaries of Cape Hatteras National Seashore, its 

habitats support organisms in the park (e.g., shorebird 

foraging, nesting sea turtles) and the benthos can be used 

as indicators of environmental health or change. For 

these reasons, park managers may want to consider the 

development of benthic habitat maps for the estuary and 

nearshore areas, to complement and enhance existing 

seafloor data.

Paleontological Resource Inventory, Monitoring, and 

Protection

Fossils within Cape Hatteras National Seashore are 

summarized by Tweet et al. (2009) and the 

“Paleontological Resources” section of this report. All 

paleontological resources are non-renewable and subject 

to science-informed inventory, monitoring, protection, 

and interpretation as outlined by the 2009 

Paleontological Resources Preservation Act (see 

Appendix B). As of April 2015, Department of the 

Interior regulations associated with the Act were being 

developed.

Beachcombers are allowed to collect unoccupied shells 

at Cape Hatteras National Seashore, but NPS (2006) 

policy states that fossils cannot be collected from NPS 

lands. The NPS defines a “fossil” as any remains of life 

preserved in a geologic context; although this definition 

does not include an arbitrary date separating older 

(fossil) from younger specimens, the term “geologic 
CAHA Geologic Resources Inventory Report 63

context” implies some degree of antiquity (Tweet et al. 

2009). Cape Hatteras National Seashore staff may need 

to consider refinement of the definition of a fossil, or of 

what beachcombers are allowed to collect, in concert 

with an outreach effort to educate visitors about 

paleontological resources and collection. Differentiation 

between true fossil material and the remains of coastal 

organisms that died recently can include documentation 

of the presence or absence of staining, boring by other 

invertebrates, and abrasion, and the measurement of 

trace element compositions. In general, older age is 

associated with more wear, staining, damage, and boring 

on a shell specimen (Tweet et al. 2009). Specimens 

collected at Cape Hatteras National Seashore are 

Pleistocene to Holocene in age (Tweet et al. 2009).

A field-based paleontological resource survey can 

provide detailed, site-specific descriptions and resource 

management recommendations that are beyond the 

scope of this report. Potential sources for paleontological 

expertise include Geologic Resources Division refreshertraining courses for NPS rangers, baseline 

paleontological inventories, and paleontological surveys. 

The 2009 paleontological summary for Cape Hatteras 

National Seashore includes a literature review, 

recognition of type specimens, species lists, and guidance 

for developing resource management plans (Tweet et al. 

2009). Brunner et al. (2009) presents a summary of 

paleontological resource management challenges 

associated with coastal parks and suggests policy-based 

resource management considerations. An additional 

resource, Santucci et al. (2009), details five methods and 

vital signs for monitoring in situ paleontological 

resources: (1) erosion (geologic factors), (2) erosion 

(climatic factors), (3) catastrophic geohazards, (4) 

hydrology/bathymetry, and (5) human access/public use.

Additional Information Needs

Cape Hatteras National Seashore staff could benefit 

from additional research or information related to the 

following issues:

• Benthic habitat maps of the estuary and nearshore 

(NPS 2000)

• Survey of septic systems to define present pollutant 

loading to ditches and marshes within the park (Mallin 

et al. 2006)

• Survey of benthic macroinvertebrates in park estuarine 

waters and tidal creeks to assess current benthic 

community health (Mallin et al. 2006)

• The Cape Hatteras National Seashore Foundation 

Statement (NPS 2011) identified a resource 

stewardship strategy as a future management need.
CAHA Geologic Resources Inventory Report 65

Geologic History

This chapter describes the surficial geomorphologic units, environments of formation, and 

evolutionary history of the modern barrier islands and estuaries in Cape Hatteras National 

Seashore.

The North Carolina barrier islands are very young in 

terms of geologic time. The geologic history occurred 

within the Cenozoic Era (the past 66 million years). The 

geologic story at Cape Hatteras National Seashore is one 

of cyclic rise and fall of relative sea level. The geologic 

framework controls the sediments available to the 

modern barrier island, and the ways in which the island 

responds to natural and anthropogenic processes. The 

oldest known parts of the Outer Banks, including the 

portion currently blocking the mouth of Albemarle 

Sound where Wright Brothers National Memorial is 

located, were formed less than 3,000 years ago (Culver et 

al. 2008b).

Modern-day coastal processes continue to shape the 

modern landforms and rework the Quaternary 

sediments (see the “Geologic and Environmental

Features and Processes” chapter for additional 

information on the influence of the geologic framework 

on modern coastal geomorphology). This chapter 

focuses on the Late Tertiary and Quaternary periods 

because older units occur in the subsurface and do not 

play an active role in modern coastal processes and issues 

along the Outer Banks.

Miocene (23 million to 5.3 million years ago)

During the Middle and Late Miocene, shelf sands were 

deposited under relatively low-energy conditions in the 

Albemarle Embayment, a regional depositional basin. 

Such conditions would have existed in a shelf basin 

protected from shelf currents by the Cape Lookout High 

to the south (Popenoe 1985). Upper units of early

Miocene and early Pliocene age are sandy to silty clay 

beds that were deposited in inner to middle neritic 

depths (Zarra 1989) of approximately 50 m (164 ft) with a 

sea level similar to today’s sea level (Greenlee and Moore 

1988).

Pliocene (5.3 million to 2.6 million years ago)

In the Early Pliocene, seas lapped over the eastern 

portion of the coastal plain in the region of present-day 

North Carolina (Richards 1968). This transgression 

deposited widespread marine sediments along the east 

coast, which document the last major marine advances 

over the coastal plain. The Yorktown Formation, a Late 

Miocene/Pliocene sequence of marine sediments, forms

part of the upper 5 to 50 m (16 to 164 ft) of the preHolocene sedimentary sequence below Pamlico Sound 

(Wells and Kim 1989). The upper surface of the 

Yorktown Formation was eroded during the Pliocene–

Pleistocene interval, when stream channels cut irregular 

depressions. The topography that it formed may be 

responsible for many of the modern bathymetric features 

in the lagoon, and may control the position of features 

such as Ocracoke Island and Ocracoke Inlet.

Quaternary (2.6 million years ago to present)

The Quaternary Period, which includes the Holocene 

and Pleistocene epochs, represents a time of dramatic 

climate and sea-level fluctuations. Early Pleistocene 

deposits mimic the orientation of the underlying 

Pliocene surface (Mallinson et al. 2010a).

The Albemarle Embayment, a regional depositional 

basin, is filled with sediments that were deposited during 

many sea-level fluctuations that occurred during the 

multiple glaciations and interglacial periods of the 

Quaternary (Riggs et al. 1995; Riggs and Ames 2006). 

Quaternary sediments in the Albemarle Embayment are 

up to 90 m (295 ft) thick (Culver et al. 2008b). They 

thicken northward and consist of slightly indurated to 

unconsolidated mud, muddy sand, sand, and peat 

(Popenoe 1985; Mallinson et al. 2005; Riggs and Ames 

2006; Culver et al. 2008b). Holocene deposits are thinner

and Pleistocene sediments occur within a few meters of 

the surface, except in paleovalleys such as the paleo–

Roanoke River drainage system (Culver et al. 2008b).

The Quaternary evolution of the continental shelf system 

has been influenced in part by the erosional topography 

inherited from the Pliocene surface (Mallinson et al. 

2010a). During multiple glacial episodes in the 

Pleistocene, fluvial channels cut into existing strata. 

These channels were then backfilled when sea level rose. 

On top of Pleistocene sediments located close to the 

surface, Holocene sea-level rise has deposited modern 

barrier island and estuarine sediments consisting of 

compact peat and mud and unconsolidated sands, 

gravels, and shell beds (Mallinson et al. 2010a).

Recent studies interpreted past climate conditions and 

depositional environments, and reconstructed 

environmental changes, by combining seismic 

stratigraphic data with micropaleontological 

(foraminifera, diatoms, and pollen) data from drill cores 

in the Cape Hatteras region of the northern Albemarle 

Embayment and Outer Banks (Culver et al. 2007, 2008b). 

Because the paleoenvironments preserved in the 

Quaternary section are generally the result of highstand 

warm climate and sea-level conditions, they may inform 

us about potential future environmental shifts that could 

occur if ongoing relative climate and sea-level changes 

continue (Culver et al. 2008b).
66 NPS Geologic Resources Division

Pleistocene (2.6 million years ago to 10,000 years ago)

Early through late Pleistocene sediments, which lie 

unconformably upon Late Pliocene deposits (Culver et 

al. 2008b), suggest an open inner- to mid-shelf marine 

environment (Mallinson et al. 2010a) with cooler climate 

conditions (Culver et al. 2008b).

The early Pleistocene Epoch was characterized by 

climate and sea-level changes with a periodicity of 

approximately 41,000 years, transitioning to a periodicity 

of 100,000 years between approximately 1 million and

800,000 years ago (Mallinson et al. 2010a). During glacial 

periods, when large volumes of Earth’s water were 

incorporated into glacial ice, sea level was lower and 

fluvial channels dissected coastal systems along the 

continental margin. When the ice melted during 

interglacial periods, the flooding that resulted from 

meltwater flow back into the oceans caused the 

backfilling of incised valleys with fluvial and estuarine 

sediments. The advancing shoreline and shoreface 

produced an erosional shoreface surface that migrated 

landward with rising sea level (Riggs et al. 1995) and 

truncated large portions of previously deposited coastal 

sediments (Mallinson et al. 2010a). Beneath the western 

part of Pamlico Sound, the Early Pleistocene inner shelf 

occurs at a depth of 20 to 40 m (66 to 131 ft); the mid- to 

outer-shelf lowstand terrace with shelf-sand ridge 

deposits occurs at a deeper level, about 45 to 70 m (148 

to 230 ft), beneath the modern barrier system and 

northern Pamlico Sound (Mallinson et al. 2010a).

Units of fine sand that record well-oxygenated, inner 

shelf environments from the mid-Pleistocene (600,000 to 

250,000 years ago) occur atop the Pleistocene open shelf 

deposits. These units are, in turn, overlain by muddy 

deposits of another cool climate and associated lower 

sea-level stand and brackish to freshwater conditions, 

also deposited in the mid-Pleistocene (Culver et al. 

2008b).

The magnitude of sea-level fluctuation increased during 

the Middle to Late Pleistocene (Mallinson et al. 2010a). 

During the last interglacial warm period (approximately 

125,000 years before present), when most of the world’s 

glaciers and many ice sheets on Greenland had melted, 

sea level was approximately 6 to 8 m (20 to 26 ft) higher 

than present (Williams 2013) and the shoreline was tens 

of miles west of its present location (Riggs et al. 2008b).

During the Last Glacial Maximum (approximately 21,000 

years before present), when much of North America and 

northern Europe was covered with ice sheets, sea level 

was 120 to 130 m (394 to 425 ft) lower than present and 

the coastal system occurred as far out as the present-day 

continental shelf (Williams 2013), which extended from 

15 km (10 mi) off modern Cape Hatteras to 100 km (62 

mi) seaward of the barrier islands at the present-day 

North Carolina/Virginia state line (Riggs et al. 2011). 

Thick Late Pleistocene units contain numerous filled 

fluvial valleys that were incised into older Pleistocene 

deposits (Culver et al. 2008b; Mallinson et al. 2010a),

suggesting that large rivers entered the area from the 

west along with their south- and north-flowing 

tributaries.

These drainage channels and the deposits that filled 

them have played a significant role in the evolution of the 

modern coastal system (Mallinson et al. 2010a). 

Paleodrainage systems may have a role in controlling the 

locations and similarities of the Carolina capes (Hatteras, 

Lookout, Fear, and Romain) (Swift et al. 1972; Moslow 

and Heron 1981).

Between 21,000 and 6,000 years ago, global sea level rose 

at an average rate of 10 mm (0.4 in)/year. During two 

brief warmer episodes, this rate may have reached 40 to 

50 mm (1.6 to 2 in)/year (Horton et al. 2009; Williams 

2013).

Near the end of the Pleistocene, approximately 12,000 

years ago, the landscape of the northern Albemarle 

Embayment was largely subaerial, and the paleo–

Roanoke River was still entrenched in a broad valley that 

cut 35 to 40 m (115 to 131 ft) into older Pleistocene 

deposits (fig. 35A) (Mallinson et al. 2005; Culver et al. 

2008b) and extended about 20 km (12 mi) offshore from 

Albemarle Sound (Culver et al. 2008b). This paleovalley 

was being refilled with Late Pleistocene to Holocene

fluvial/estuarine sediments (Boss and Hoffman 2001, as 

cited in Culver et al. 2008b; Boss et al. 2002, as cited in 

Culver et al. 2008b; Mallinson et al. 2005).

The current barrier islands are perched upon the 

Hatteras Flats Interstream Divide, a Pleistocene feature 

that separated the southwest-flowing Pamlico Creek 

from another creek to the east (Riggs and Ames 2006; 

Culver et al. 2007). By 11,000 years ago, the shoreline was 

about 30.5 m (100 ft) below present sea level (Riggs et al. 

2011).

Early to Middle Holocene (approximately 10,000 to 3,000 

years ago)

Between 11,000 and 8,000 years ago, sea level rose at a 

rate of 5.3 mm (0.21 in)/year, causing initial flooding of 

what is now the Albemarle Sound area, west of the 

modern barrier islands (fig. 35A) (Riggs et al. 2011). 

Marine waters flooded the paleo–Roanoke River, the 

Pamlico Creek drainage, and the Tar and Neuse river 

valleys west of the present barrier islands approximately 

9,000 to 7,000 years before present (Mallinson et al. 2005; 

Culver et al. 2007, 2008b). Around 7,000 years ago, sealevel rise continued and increased flooding up the 

drowned-river valleys formed Pamlico Sound (fig. 36A) 

(Culver et al. 2007; Mallinson et al. 2010b).

From 6,000 to 3,000 years ago, global sea level continued 

to rise at a slower rate of about 0.5 mm (0.02 in)/year 

(Williams 2013). By 5,000 years ago, the paleo–Roanoke 

River Valley had become an open embayment 

(Albemarle Bay) and had tidal exchange with the open 

Atlantic Ocean and estuarine environments to the west.

Colington Shoals had developed at the mouth of the bay 

(fig. 35B) (Mallinson et al. 2005; Culver et al. 2008b). 

Other fluvial valleys along the coast were also flooded by 

rising seas, and shoals and shoreparallel spits and
CAHA Geologic Resources Inventory Report 67

Figure 35. Paleogeographic reconstructions for the northern Albemarle Embayment during the Late Pleistocene and 

Holocene. Inset on panel D shows the location of the reconstruction maps. Gray areas and modern shorelines are shown as 

guides to changes occurring over time. Graphic by Trista L. Thornberry-Ehrlich (Colorado State University) after figure 14 in 

Culver et al. (2008b).
68 NPS Geologic Resources Division

Figure 36. Paleogeographic reconstructions for the southern Pamlico Basin during the Holocene. Graphic redrafted by Trista 

Thornberry-Ehrlich (Colorado State University) after figure 3 in Culver et al. (2007) and figure 7 in Mallinson et al. (2009).

barriers cut off open-marine access to local river 

channels, forming sounds (Culver et al. 2007, 2008b). 

Upward-fining, muddy units in Pamlico Sound, 

deposited approximately 4,070 to 4,340 years ago, 

indicate that conditions were highly brackish and

estuarine at that time as rising seas overtopped the 

Hatteras Flats Interstream Divide (fig. 36B) (Culver et al. 

2007).

Thieler and Ashton (2011) suggested that a cuspate 

foreland existed between Cape Hatteras and Cape 

Lookout in the Early Holocene, from about 9,000 to 

4,000 years ago. This cape was likely captured by the 

present-day capes.

Around 3,600 years ago, the shoreline was about 4.2 m 

(13.8 ft) below present sea level (Horton et al. 2009). By 

3,000 years ago, the initial configuration of barrier islands

had formed slightly seaward of their modern location 

(fig. 36C) (Riggs et al. 2011), effectively blocking the 

drowned river drainages to form semi-enclosed 

estuaries, including Pamlico Bay (Culver et al. 2007). 

Beach ridges began to develop north of the flooded 

paleo–Roanoke River Valley and formed Currituck 

Sound (Mallinson et al. 2005).
CAHA Geologic Resources Inventory Report 69

Late Holocene (approximately 3,000 years ago to present)

The rate of sea-level rise slowed episodically, eventually 

reaching a near still-stand (0 to 0.2 mm [0.008 in]/year) 

about 3,000 years ago (Williams 2013), when sea level 

was about 2.6 m (8.5 ft) below present MSL (Horton et 

al. 2009). According to Kemp et al. (2011), sea level in the 

region of present-day North Carolina was stable 1,060 to 

2,100 years ago (from 100 BCE to 950 CE). Sea level rose 

over the subsequent 450 years (950 to 1400 CE) at a rate 

of 0.6 mm (0.02 in)/year due to warming conditions, and 

then remained stable from 1400 CE until the end of the 

19th century due to cooler temperatures. As sea level 

rose, the ocean shorelines of simple barrier islands 

receded westward.

Between 2,500 and 1,500 years ago, several sets of beach 

ridges prograded to the east (fig. 35C), and barrier 

islands to the south of the paleo–Roanoke River Valley 

developed on top of flooded Late Pleistocene highs in 

the area between Oregon Inlet and Ocracoke Inlet (fig. 

36C) (Culver et al. 2008b).

According to core studies performed north of Cape 

Hatteras, islands partially collapsed into a submarine 

shoal system during intervals between 3,000 and 500 

years before present (Culver et al. 2007). Large portions 

of the southern Outer Banks were segmented, likely due 

to increased hurricane activity, during the Medieval 

Warm Period approximately 1,100 years before present 

(fig. 36D) (Mallinson et al. 2011). Major disruptions in 

barrier island continuity occurred between Ocracoke 

Inlet and Rodanthe (a 90-km [56-mi] section), including 

barrier segmentation on Ocracoke Island, between 

Hatteras Village and Frisco, between Buxton and Avon, 

in the Kinnakeet region, and on Pea Island (Mallinson et 

al. 2011). These processes allowed open marine 

environments to inundate the sound for varying periods 

of time before the barrier island system recovered. Vast 

amounts of sediment moved into Pamlico Sound, 

forming the shallows of Hatteras Flats, a vast submarine 

shoal west of the Cape Hatteras National Seashore 

barrier islands (fig. 36D) (Culver et al. 2007). As a result 

of these events, the sediments beneath the Outer Banks 

and Hatteras Flats are largely marine, with an extensive 

erosional surface at an average depth of approximately 9 

m (30 ft) below present sea level (Mallinson et al. 2010a). 

The widest portions of the Outer Banks at Rodanthe, 

Salvo, Kinnakeet, and Avon are underlain by migrating 

inlet sediments and associated spit and beach ridge 

deposits (Mallinson et al. 2010b).

Farther north, approximately 1,000 years ago, the beach 

ridges at Kitty Hawk ceased accumulating and 

prograding to the east (Mallinson et al. 2008a). Erosion 

started to move the shoreline westward, truncating the 

previously deposited beach ridges. Shoals that developed 

at the mouth of the embayment became subaerially 

exposed and are now known as Colington Island. Large 

back-barrier dunes formed on the western sides of local 

barrier islands (fig. 35D) (Havholm et al. 2004; Culver et 

al. 2008b). Inlets such as Kitty Hawk and Roanoke inlets 

began to form and migrate (Culver et al. 2008b). 

Roanoke Island remained connected to the mainland by 

a series of extensive salt marshes (Culver et al. 2008b).

The Little Ice Age occurred from approximately 1400 to 

1900 CE, with peak cooling occurring between 

approximately 1570 and 1650 CE (Mallinson et al. 2011). 

During this peak, as many as 20 inlets may have been 

open along the Outer Banks in an area that today has 

only four inlets (fig. 13) (Mallinson et al. 2011). The 

formation and maintenance of numerous paleo-inlets 

during the Little Ice Age are likely due to the increased 

frequency of nor’easter storms (Mallinson et al. 2011).

In theory, existing inlets are in equilibrium with the 

modern tidal prism. Newly opened inlets that are not in 

equilibrium will not be stable and will shoal quickly 

(Mallinson et al. 2011). Four possible explanations have 

been offered for the occurrence of so many inlets 

through the Outer Banks in the past:

1)Frequent and severe storms maintained an overall 

elevated wind-driven tidal prism (storm surge) that 

kept the inlets open.

2)Increased runoff from rivers due to storm patterns 

required more outlets through the barriers.

3)A threshold was crossed during the Medieval Warm 

Period and perhaps again during the Little Ice Age, 

causing island segmentation that allowed for a 

modified tidal regime and an increase in tidal prism to 

maintain the newly formed inlets.

4)Some combination of these conditions occurred

(Mallinson et al. 2011).

Most Outer Banks inlets have closed naturally over the 

last 300 years, likely due to more stable climate 

conditions, fewer storm impacts (hurricanes and 

nor’easters), and decreases in the average wind intensity 

and wave energy field in the mid-latitudes of the North 

Atlantic (Mallinson et al. 2011). The renewed 

development of the simple barrier islands returned 

Pamlico Sound to an estuarine state, with lower energy 

and deposition of organic-rich mud (Riggs et al. 2009). 

Thus, most back-barrier marshes and surficial 

geomorphic features on the simple barrier islands (from 

Pea Island to Portsmouth Island) formed within the last 

500 years (Riggs et al. 2009), after Columbus arrived in 

North America.

Modern Barrier System

Global sea level has risen at an average rate of 1.8 mm 

(0.07 in)/year over the past century (Douglas 1997), and 

at a rate of 0.6 to 1.0 mm (0.02 to 0.04 in)/year since 

about 1990 (Sallenger et al. 2012).

Recent local sea-level rise in the Outer Banks (table 5) 

has been higher than global sea-level rise. As detailed in 

the “Coastal Vulnerability and Sea-Level Rise” section, 

the rate of local sea-level rise in the Outer Banks 

increased to about 1.5 mm (0.06 ft)/year) in the beginning 

of the 19th century, with a resulting increase in the rate 

of upslope migration of the barrier islands (Riggs et al. 

2009). Beginning around 1880 to 1920, sea-level rose 

along the North Carolina coast at a mean rate of 2.1 mm 
70 NPS Geologic Resources Division

(0.08 in)/year (Kemp et al. 2011). Along the northern 

Outer Banks, sea level has been rising at rates between 

2.82 mm (0.11 in)/year), as measured at the Oregon Inlet 

Marina (1977–2006; Zervas 2009), and 4.5 mm (0.18 

in)/year) at Duck, North Carolina (1980–2000; Zervas 

2004, as cited in Riggs et al. 2008b).

Culver et al. (2007, 2008b) predicted that open shelf 

conditions will likely return to the Outer Banks region in 

the near future if the current trend of relative sea-level 

rise continues; the resulting barrier island collapse would 

substantially change the way in which the coastal 

population and its economy proceed.

Geomorphological processes continue to shape the 

dynamic barrier island system under the control of the 

underlying geologic framework, in concert with ongoing 

storm dynamics and sea-level rise. In addition, 

anthropogenic activity is one of the largest influences on 

modern barrier island morphology (see the “Geologic 

Resource Management Issues” chapter for additional 

information.) Stabilization of shorelines and dunes (with 

sandbags and constructed and interior dune ridges), 

beach renourishment, urban development, excavations, 

dredging, and road and bridge construction all influence

natural geomorphic processes (Ames and Riggs 2006j), 

and in turn the dependent natural habitats within Cape 

Hatteras National Seashore.
CAHA Geologic Resources Inventory Report 71

Geologic Map Data

This chapter summarizes the geologic map data available for Cape Hatteras National 

Seashore. Posters (in pocket) display the map data draped over imagery of the park and 

surrounding area. The Map Unit Properties Tables (in pocket) summarize this report’s 

content for each geologic map unit. Complete GIS data are included on the accompanying 

DVD and are also available at the GRI publications website: http://go.nps.gov/gripubs.

Geologic Maps

Geologic maps facilitate an understanding of an area’s 

geologic framework and the evolution of its present 

landscape. Using designated colors and symbols, these

maps portray the spatial distribution and temporal 

relationships of rocks and unconsolidated deposits. 

Geologic maps can be divided into two primary types:

surficial and bedrock. Surficial geologic maps typically 

encompass deposits that are unconsolidated and formed 

during the past 2.6 million years (the Quaternary Period). 

Surficial map units are differentiated by geologic process 

or depositional environment. These maps may also be 

referred to as “geomorphic.” Bedrock geologic maps 

encompass older, typically more consolidated 

sedimentary, metamorphic, and/or igneous rocks. 

Bedrock map units are differentiated based on age 

and/or rock type. Surficial (geomorphic) map data are 

provided for Cape Hatteras National Seashore that also 

cover Wright Brothers National Memorial and Fort 

Raleigh National Historic Site.

Geologic maps often depict geomorphic features, 

structural interpretations (such as faults or folds), and 

locations of past geologic hazards that may be 

susceptible to future activity. Anthropogenic features 

such as mines or quarries, as well as observation or 

collection locations, may be indicated on geologic maps. 

The American Geosciences Institute website, 

http://www.americangeosciences.org/environment/publi

cations/mapping, provides more information about 

geologic maps and their uses.

Source Maps

The GRI team digitizes paper maps and converts digital 

data to conform to the GRI GIS data model. The GRI 

digital geologic map product includes essential elements 

of the source maps such as map unit descriptions, a 

correlation chart of units, a map legend, map notes, cross 

sections, figures, and references.

This report is supported by two digital maps of Cape 

Hatteras National Seashore surficial geology, each 

developed using a distinct methodology and resulting in 

a unique set of geomorphic units and different area of 

coverage.

The first map, developed by Riggs and Ames (2006) and 

produced as Ames and Riggs (2006a–j) classifies

geomorphic units based on a model of barrier island 

evolution developed from process-response studies and 

modern field surveys of the North Carolina Outer Banks 

(Riggs and Ames 2006). This detailed map covers

portions, but not all, of the northern Outer Banks and 

Cape Hatteras National Seashore.

Products of the Riggs and Ames mapping informed the 

North Carolina Geological Survey’s development of a 

second map, which classifies surficial features using 

remotely sensed data as described by Hoffman et al. 

(2007g) and produced as Hoffman et al. (2007a–f). The 

map includes complete areal coverage of Cape Hatteras 

National Seashore.

GRI GIS Data

The GRI team implements a GIS data model that 

standardizes map deliverables. The data model is 

included on the enclosed CD and is also available at 

http://science.nature.nps.gov/im/inventory/geology/Geo

logyGISDataModel.cfm. This data model dictates GIS 

data structure, including layer architecture, feature 

attribution, and relationships within ESRI ArcGIS 

software. The GRI team digitized the data for Cape 

Hatteras National Seashore using data model version 1.4.

The GRI Geologic Maps website,

http://www.nature.nps.gov/geology/inventory/

geo_maps.cfm, provides more information about GRI 

map products.

GRI digital geologic data are included on the attached 

CD and are available through the NPS Integrated 

Resource Management Applications (IRMA) portal 

(https://irma.nps.gov/App/Reference/Search?SearchTyp

e=Q). Enter “GRI” as the search text and select a park 

from the unit list.

The following components are part of the data set:

• A readme file (caha_gis_readme.pdf) that describes

data formats, naming conventions, extraction

directions, use constraints, and contact information.

• Data in ESRI geodatabase and shapefile GIS format;

• Layer files with feature symbology (table 9);

• Federal Geographic Data Committee (FGDC)–

compliant metadata;

• An ancillary map information document 

(caha_geology.pdf) that contains information captured 

from source maps such as map unit descriptions; and

• ESRI map documents (cahg_geology.mxd; 

caha_geology.mxd) that display the digital geologic 

data.
72 NPS Geologic Resources Division

Table 9. Geology data layers in the Cape Hatteras National Seashore GIS data. The North Carolina Geological 

Survey data are compiled as caha_geology.mxd and on maps 1–7 (poster, in pocket). The East Carolina 

University data are compiled as cahg_geology.mxd and on sheets 1–10 (in pocket).

Data Layer Data Layer Code On Posters?

Geomorphic Ridge Lines GLF Yes

Anthropic Overprint Area (ECU data only) ANTHRO Yes

Geomorphic Contacts GLGA Yes

Geomorphic Units GLG Yes

GRI Map Posters

A poster of the GRI digital geologic data draped over 

aerial imagery of the park and surrounding area is 

included with this report. The poster (maps 1–7) displays 

the North Carolina Geological Survey data for Cape 

Hatteras National Seashore. The individual sheets 

(sheets 1–10) display the detailed East Carolina 

University data. Geographic information and selected 

park features have been added to the posters. Digital 

elevation data and added geographic information are not 

included in the GRI GIS data set, but are available online 

from a variety of sources. Contact GRI for assistance 

locating these data.

Map Unit Properties Tables

The Map Unit Properties Tables list the geologic time 

division, symbol, and a simplified description for each of 

the geologic map units in the GRI GIS data sets.

Following the structure of the report, the table 

summarizes the geologic features, processes, resource 

management issues, and history associated with each 

map unit.

Use Constraints

Graphic and written information provided in this report

is not a substitute for site-specific investigations. 

Ground-disturbing activities should neither be permitted 

nor denied based upon the information provided here.

Please contact GRI with any questions.

Minor inaccuracies may exist regarding the locations of 

geologic features relative to other geologic or geographic 

features on the poster. Based on the source map scale 

(1:24,000 for North Carolina Geological Survey data,

1:10,000 for East Carolina University data) and US

National Map Accuracy Standards, geologic features 

represented in the geologic map data are horizontally 

within 12 m (40 ft; 1:24,000-scale data) or 5 m (17 ft;

1:10,000-scale data) of their true locations.
CAHA Geologic Resources Inventory Report 73

Glossary

These brief definitions are for selected geologic terms relevant to this report. Definitions are 

based on those in the American Geosciences Institute Glossary of Geology (5th edition; 

2005). Additional terms are defined at

http://geomaps.wr.usgs.gov/parks/misc/glossarya.html.

absolute age. The geologic age (in years) of a fossil, rock,

feature, or event. The term is now in disfavor as it 

implies a certainty or exactness that may not be 

possible by present dating methods. See “isotopic age” 

and “radiometric age.”

accretion (sedimentary). The gradual addition of new 

land to old by the deposition of sediment, for example, 

on a beach by the washing up of sand from the sea.

accretion (streams). The filling-up of a stream bed as a 

result of such factors as silting or wave action.

aeolian. Describes materials formed, eroded, or 

deposited by or related to the action of wind.

aggradation. The building up of Earth’s surface by 

depositional processes.

amphibole. A group of silicate (silicon + oxygen) 

minerals composed of hydrous calcium and 

magnesium with the general formula 

(Ca2Mg5)Si8O22(OH)2.

amphibolite. A metamorphic rock consisting mostly of 

the minerals amphibole and plagioclase, with little or 

no quartz.

anticline. A fold, generally convex upward (“A”-shaped) 

whose core contains the stratigraphically older rocks. 

Compare with “syncline.”

apatite. A group of phosphate (phosphorus + oxygen) 

minerals composed of calcium together with fluorine, 

chlorine, hydroxyl, or carbonate in varying amounts 

and having the general formula 

Ca5(F,OH,Cl)(PO4,CO3)3.

aquiclude. A saturated geologic unit that is incapable of 

transmitting significant quantities of water under 

ordinary hydraulic gradients. Replaced by the term 

“confining bed.”

aquifer. A rock or sedimentary unit that is sufficiently 

porous to hold water, sufficiently permeable to allow 

water to move through it, and saturated to some level.

aragonite. A carbonate (carbon + oxygen) mineral of 

calcium, CaCO3; it is the second most abundant cave 

mineral after calcite and differs from calcite in its 

crystal structure.

astronomical tide. The periodic rise and fall of a body of 

water resulting from gravitational interactions between 

the Sun, Moon, and Earth. Synonymous with “tide,” 

but used to emphasize the absence of atmospheric 

influences.

back-barrier. Refers to areas along the landward 

(estuarine) side of a barrier island; it is influenced 

predominantly by estuarine processes such as lagoonal 

tides and landforms such as mudflats and overwash 

fans.

bank. A submerged ridge of sand in the sea, a lake, or a 

river, usually exposed during low tide or low water.

barrier island. A long, low, narrow island consisting of a 

ridge of sand that parallels the coast.

basement. The undifferentiated rocks, commonly 

igneous and metamorphic, that underlie rocks 

exposed at the surface, commonly sedimentary. In 

many regions the basement is of Precambrian age, but 

it may be much younger. Also, Earth’s crust below 

sedimentary deposits that extends down to the 

Mohorovicic discontinuity.

basin (sedimentary). Any depression, from continental to 

local scale, into which sediments are deposited.

bathymetry. The measurement of ocean or lake depths 

and the charting of the topography of the ocean or lake 

floor.

beach. A gently sloping shoreline covered with sediment, 

usually sand or gravel, extending landward from the 

low-water line to the place where there is a definite 

change in material, physiographic form, or permanent 

vegetation.

beach face. The section of the beach normally exposed 

to the action of wave uprush.

beachrock. A poorly to well-cemented sedimentary rock 

formed in the intertidal zone, consisting of sand and 

gravel cemented with calcium carbonate.

bed. The smallest sedimentary stratigraphic unit, 

commonly ranging in thickness from about 1 cm (0.4 

in) to 1 to 2 m (40 to 80 in) and distinguishable from 

beds above and below.

bedding. Depositional layering or stratification of 

sediments.

bedrock. Solid rock that underlies unconsolidated,

superficial material and soil.

benthic. Pertaining to the ocean bottom or organisms 

living on or in the substrate; also, referring to that 

environment.

berm. A low, impermanent, nearly horizontal or 

landward-sloping bench, shelf, or ledge on the 

backshore (zone above the high-water line) of a beach.

biotite. A dark-colored, shiny silicate mineral (silicon + 

oxygen) of the mica group composed of magnesium 

and/or iron, K(Mg,Fe)Si3O10(OH)2; characterized by 

perfect cleavage, readily splitting into thin sheets.

bioturbation. The reworking of sediment by organisms.

bivalve. Having a shell composed of two distinct, but 

equal or nearly equal, movable valves, which open and 

shut.

brachiopod. Any marine invertebrate belonging to the 

phylum Brachiopoda, characterized by two bilaterally 

symmetrical valves that are commonly attached to a 

substratum but may also be free. Range: Lower 

Cambrian to Holocene.
74 NPS Geologic Resources Division

breakwater. An offshore, generally shore-parallel 

structure that breaks the force of the waves.

bryozoan. Any invertebrate belonging to the phylum 

Bryozoa; characterized by colonial growth and a 

calcareous skeleton. Range: Ordovician (and possibly 

Upper Cambrian) to Holocene.

burrow. A tubular or cylindrical hole or opening, made in 

originally soft or loose sediment by a mud-eating 

worm, mollusk, or other invertebrate; may be later 

filled with clay or sand and preserved.

calcareous. Describes a substance that contains calcium 

carbonate. When applied to a rock name it implies that 

as much as 50% of the rock is calcium carbonate.

calcite. A carbonate (carbon + oxygen) mineral of 

calcium, CaCO3; calcium carbonate. It is the most 

abundant cave mineral.

calcium carbonate. A solid, CaCO3, occurring in nature 

as primarily calcite and aragonite.

cape. An extensive, somewhat rounded irregularity of 

land jutting out from the coast into a large body of 

water, either as a peninsula (e.g., Cape Cod, 

Massachusetts) or as a projecting point (e.g., Cape 

Hatteras, North Carolina). Also, the part of the 

projection extending farthest into the water.

carbonate. A mineral group composed of carbon and 

oxygen plus an element or elements; for example 

calcite, CaCO3; and dolomite, CaMg(CO3)2.

carbonate rock. A rock, for example, limestone, calcite, 

and dolomite, that consist primarily of carbonate 

minerals.

cement (sedimentary). Mineral material, usually 

chemically precipitated, that occurs in the spaces 

among the individual grains of sedimentary rocks, thus 

binding the grains together.

cementation. The process by which clastic sediments 

become lithified or consolidated into hard, compact 

rocks, usually through deposition or precipitation of 

minerals in the spaces among the individual grains of 

the sediment; may occur simultaneously with 

sedimentation or at a later time.

channel. A relatively narrow sea or stretch of water 

between two nearby landmasses, connecting two 

larger bodies of water.

chlorite. A group of silicate (silicon + oxygen) minerals 

composed of iron, magnesium, and aluminum with the 

general formula (Mg,Fe)6(AlSiO3)O10(OH)8.

chronology. The arrangement of events in their proper 

sequence in time.

chronostratigraphy. The branch of stratigraphy that 

deals with the age of strata and their time relations.

clay. Refers to clay minerals and sedimentary fragments 

that are less than 1/256 mm (0.00015 in) across.

clay mineral. Any mineral occurring in the clay-sized 

fraction with the understanding that size imposes 

physical and chemical characteristics.

coarse-grained. Describes a crystalline rock and texture 

in which the individual minerals are relatively large, 

specifically an igneous rock whose particles have an 

average diameter greater than 5 mm (0.2 in). Also, 

describes sediment or sedimentary rock and texture in 

which the individual constituents are easily seen with 

the unaided eye, specifically sediment or rock whose 

particles have an average diameter greater than 2 mm 

(0.08 in).

coastal plain. Any lowland area bordering a sea or ocean, 

extending inland to the nearest elevated land, and 

sloping very gently seaward; may result from the 

accumulation of material along a coast.

compaction. The process whereby fine-grained sediment 

is converted to consolidated rock.

confining bed. A body of relatively impermeable or 

distinctly less permeable material stratigraphically 

adjacent to one or more aquifers. Replaced the term 

“aquiclude.”

continental rise. Gently sloping region from the foot of 

the continental slope to the deep ocean abyssal plain; 

generally has smooth topography but may have 

submarine canyons.

continental shelf. The shallowly submerged—covered by 

water depths of less than 200 m (660 ft)—part of a 

continental margin that extends from the shoreline to 

the continental slope.

continental slope. The relatively steep slope from the 

outer edge of the continental shelf down to the more 

gently sloping ocean depths of the continental rise or 

abyssal plain.

core (drill). A cylindrical section of rock or sediment. 

usually 5–10 cm (2–4 in) across and up to several 

meters long, taken as a sample of the interval 

penetrated by a core bit, and brought to the surface for 

geologic examination and/or laboratory analysis.

cross section. A graphic interpretation of geology, 

structure, or stratigraphy based on mapped and 

measured geologic extents and attitudes, depicted in a 

vertical plane (i.e., a cut or profile view).

delta. The low, nearly flat, alluvial tract of land at or near 

the mouth of a river, commonly forming a triangular or 

fan-shaped plain of considerable area; resulting from 

the accumulation of sediment supplied by the river in 

such quantities that it is not removed by tides, waves, 

and currents.

delta fan. A deposit formed by the merging of an alluvial 

fan with a delta.

delta plain. The level or nearly level surface composing 

the landward part of a large or compound delta; 

strictly, an alluvial plain characterized by repeated 

channel bifurcation and divergence, multiple 

distributary channels, and interdistributary flood 

basins.

diatom. A microscopic, single-celled alga that secretes 

walls of silica, called frustules; lives in freshwater and 

marine environments.

discharge. The rate of flow of surface water or 

groundwater at a given moment, expressed as volume 

per unit of time.

drainage. The manner in which the waters of an area 

flow off in surface streams or subsurface conduits; 

also, the processes of surface drainage of water from 

an area by streamflow and sheet flow, and the removal 

of excess water from soil by downward flow.

drainage basin. The total area from which a stream

system receives or drains precipitation runoff.

dredge (engineering). A floating machine for excavating 

sedimentary material from the bottom of a body of 
CAHA Geologic Resources Inventory Report 75

water, raising it to the surface, and discharging it to the 

bank through a floating pipeline or conveyor, into a 

scow for removal, or, in the case of certain mining 

dredges, into the same body of water after removal of 

the ore mineral.

dune. A low mound or ridge of sediment, usually sand, 

deposited by the wind.

dune field. Extensive deposits of sand in an area where 

the supply is abundant; individual dunes resemble 

barchans but are highly irregular in shape and 

crowded.

ebb-tidal delta. A tidal delta formed on the seaward side 

of a tidal inlet.

electrical resistivity survey. A measure of the difficulty 

with which electric current flows through 

unconsolidated sediment and rock.

electromagnetic survey. An electrical exploration 

method based on the measurement of alternating 

magnetic fields associated with currents artificially or 

naturally maintained in the subsurface.

emergence. A change in the levels of water and land such 

that the land is relatively higher and areas formerly 

under water are exposed; results from either an uplift 

of land or fall of water level. Compare to 

“submergence.”

entrainment. The process of picking up and transporting 

sediment, commonly by wind or water.

ephemeral stream. A stream that flows briefly, only in 

direct response to precipitation, and whose channel is 

always above the water table.

erosion. The general process or group of processes that 

loosen, dissolve, wear away, and simultaneously move 

from one place to another, the materials of Earth’s 

crust; includes weathering, solution, abrasive actions, 

and transportation, but usually excludes slope 

movements.

estuary. The seaward end or tidal mouth of a river where 

freshwater and seawater mix.

eustatic. Describes a worldwide rise or fall in sea level.

evapotranspiration. Loss of water from a land area 

through transpiration (passage of water vapor from a 

living body through a membrane) of plants and 

evaporation from the soil and surface-water bodies. 

Also, the volume of water lost through 

evapotranspiration

facies (sedimentary). The depositional or environmental 

conditions reflected in the sedimentary structures, 

textures, mineralogy, fossils, and other components of 

a sedimentary rock.

fan delta. A gently sloping alluvial deposit produced 

where a mountain stream flows out onto a lowland.

feldspar. A group of abundant silicate (silicon + oxygen) 

minerals, comprising more than 60% of Earth’s crust 

and occurring in all types of rocks. Compare to “alkali 

feldspar” and “plagioclase.”

feldspathic. Describes a rock containing feldspar.

felsic. Derived from feldspar +silica to describe an 

igneous rock having abundant light-colored minerals 

such as quartz, feldspars, or muscovite; also, describes 

those minerals.

fetch. The area of the ocean surface over which a 

constant and uniform wind generates waves.

fine-grained. Describes a crystalline or glassy rock and 

texture in which the individual minerals are relatively 

small, specifically an igneous rock whose particles have 

an average diameter less than 1 mm (0.04 in). Also, 

describes sediment or sedimentary rock and texture in 

which the individual constituents are too small to 

distinguish with the unaided eye, specifically sediment 

or rock whose particles have an average diameter less 

than 1/16 mm (0.002 in), that is, silt-size particles and 

smaller.

flood-tidal delta. A tidal delta formed on the landward 

side of a tidal inlet.

floodplain. The surface or strip of relatively smooth land 

composed of alluvium and adjacent to a river channel, 

constructed by the present river in its existing regimen 

and covered with water when the river overflows its 

banks. A river has one floodplain and may have one or 

more terraces representing abandoned floodplains.

fluvial channel. A natural passageway or depression 

produced by the action of a stream or river.

foraminifer. Any protozoan belonging to the subclass 

Sarcodina, order Foraminiferida, characterized by the 

presence of a test of one to many chambers composed 

of secreted calcite (rarely silica or aragonite) or of 

agglutinated particles; most foraminifers are marine 

but freshwater forms are known. Range: Cambrian to 

Holocene.

foreshore. The part of the beach face that lies between 

the berm crest and the low water line, and that is 

shaped by waves and tides.

formation. Fundamental rock-stratigraphic unit that is 

mappable, lithologically distinct from adjoining strata, 

and has definable upper and lower contacts.

fossil. A remain, trace, or imprint of a plant or animal that 

has been preserved in the Earth’s crust since some past 

geologic time; loosely, any evidence of past life.

garnet. A hard silicate (silicon + oxygen) mineral with a 

glassy luster, and commonly well-defined crystal faces; 

characteristically dark red but occurs in a variety of 

colors.

gastropod. Any mollusk belonging to the class 

Gastropoda, characterized by a distinct head with eyes 

and tentacles and, in most, by a single calcareous shell 

that is closed at the apex, sometimes spiraled, not 

chambered, and generally asymmetrical (e.g., a snail). 

Range: Upper Cambrian to Holocene.

geodetic surveying. Surveying that takes into account the 

figure and size of Earth, with corrections are made for 

curvature; used where the areas or distances involved 

are so great that results of desired accuracy and 

precision cannot be obtained by plane (ordinary field 

and topographic) surveying.

geology. The study of Earth, including its origin, history, 

physical processes, components, and morphology.

geomorphology. The study of the general configuration 

of surface landforms and their relationships to 

underlying structures, and of the history of geologic 

changes as recorded by these surface features.

gradient. A degree of inclination (steepness of slope), or 

a rate of ascent or descent, of an inclined part of 

Earth’s surface with respect to the horizontal; 

expressed as a ratio (vertical to horizontal), a fraction 
76 NPS Geologic Resources Division

(such as m/km or ft/mi), a percentage (of horizontal 

distance), or an angle (in degrees).

granite. A coarse-grained, intrusive igneous (plutonic) 

rock in which quartz constitutes 10%–50% percent of 

the felsic (“light-colored”) components and the alkali 

feldspar/total feldspar ratio is generally restricted to 

the range of 65% to 90%; perhaps the best known of

all igneous rocks.

gravel. An unconsolidated, natural accumulation of 

typically rounded rock fragments resulting from 

erosion; consists predominantly of particles larger 

than sand, greater than 2 mm (1/12 in) across.

groundwater. That part of subsurface water that is in the 

zone of saturation, including underground streams.

hematite. An oxide mineral composed of oxygen and 

iron, Fe2O3.

heterogeneous. Consisting of dissimilar or diverse 

ingredients or constituents.

highstand. The interval of time during one or more 

cycles of relative sea-level change when sea level is 

above the edge of the continental shelf in a given area. 

Compare to “lowstand.”

hornblende. A silicate (silicon + oxygen) mineral of 

sodium, potassium, calcium, magnesium, iron, and 

aluminum; the most common mineral of the 

amphibole group; commonly black and occurring in 

distinct crystals or in columnar, fibrous, or granular 

forms in hand specimens.

hurricane. The term applied in the Northern Hemisphere 

for an atmospheric low-pressure system with a closed 

roughly circular wind motion that is counterclockwise; 

sustained near-surface wind speed equals or exceeds 

64 knots (73 mph).

hydrogeology. The science that deals with subsurface 

waters and related geologic aspects of surface waters, 

including the movement of groundwater; the 

mechanical, chemical, and thermal interaction of 

groundwater with the porous medium; and the 

transport of energy and chemical constituents by the 

flow of groundwater. Synonymous with 

“geohydrology.”

hydrology. The study of liquid and solid water 

properties, circulation, and distribution, on and under 

the Earth's surface and in the atmosphere.

ilmenite. An oxide mineral composed of oxygen, 

titanium, and iron FeTiO3; iron titanium oxide. It 

commonly contains considerable magnesium and 

manganese. Ilmenite is a common accessory mineral in 

basic igneous rocks (e.g., gabbro), and is also 

concentrated in mineral sands.

incision. Downward erosion by a stream, resulting in a 

deepened channel and commonly a narrow, steepwalled valley.

indurated. Describes a rock or soil hardened or 

consolidated by pressure, cementation, or heat.

induration. Hardening by heat, pressure, or the 

introduction of cementing material, especially the 

process by which relatively consolidated rock is made 

harder or more compact.

interdune. The relatively flat surface between dunes, 

commonly a long, troughlike, wind-swept passage 

between parallel dunes; may be covered with sand or 

sand free.

interfluve. The area between rivers, especially the 

relatively undissected upland or ridge between two 

adjacent valleys containing streams flowing in the same 

general direction.

intertidal. Pertaining to the benthic ocean environment 

or depth zone between high water and low water; also, 

pertaining to the organisms of that environment. 

Synonymous with “littoral.”

isostacy. The condition of equilibrium, comparable to 

floating, of the units of the lithosphere above the 

asthenosphere.

isotopic age. An age (in years) calculated from the 

quantitative determination of radioactive elements and 

their decay products. Synonymous with “radiometric 

age.”

lag gravel. An accumulation of coarse material remaining 

on a surface after finer material has been blown or 

washed away.

lagoon. A narrow body of water that is parallel to the 

shore and between the mainland and a barrier island; 

characterized by minimal or no freshwater influx and 

limited tidal flux, which cause elevated salinities. Also, 

a shallow body of water enclosed or nearly enclosed 

within an atoll.

lens. A sedimentary deposit that resembles a convex lens 

and is characterized by converging surfaces, thick in 

the middle and thinning out toward the edges.

lenticular. Resembling in shape the cross section of a 

lens.

light detection and ranging/LiDAR. A method and 

instrument that measures distance to a reflecting 

object by emitting timed pulses of light and measuring 

the time between emission and reception of reflected 

pulses; the measured interval is converted to distance.

limestone. A carbonate sedimentary rock consisting of 

more than 95% calcite and less than 5% dolomite.

lithofacies. A lateral, mappable subdivision of a 

designated stratigraphic unit distinguished from 

adjacent subdivisions on the basis of lithology.

lithology. The physical description or classification of a 

rock or rock unit based on characteristics such as 

color, mineral composition, and grain size.

lithostratigraphy. The branch of stratigraphy that deals 

with the description and systematic organization of the 

rocks of Earth’s crust into distinctive named units 

based on the lithologic character of the rocks and their 

stratigraphic relations.

littoral. Pertaining to the benthic ocean environment or 

depth zone between high water and low water; also, 

pertaining to the organisms of that environment. 

Synonymous with “intertidal.”

longitudinal dune. A long, narrow sand dune, usually 

symmetrical in cross profile, oriented parallel with the 

direction of the prevailing wind; characteristically 

wider and steeper on the windward side and tapering 

to a point on the leeward side; may be a few meters 

high and as much as 100 km (60 mi) long.

longshore current. A current parallel to a coastline 

caused by waves approaching the shore at an oblique 

angle.
CAHA Geologic Resources Inventory Report 77

lowstand. The interval of time during one or more cycles 

of relative sea-level change when sea level is below the 

edge of the continental shelf in a given area. Compare 

to “highstand.”

magnetite. An oxide mineral composed of oxygen and 

iron, Fe3O4; iron oxide. It commonly contains 

manganese, nickel, chromium, and titanium. It is a very 

common and widely distributed accessory mineral in 

rocks of all kinds, and occurs as a “heavy mineral” in 

sand.

marine terrace. A relatively flat-topped, horizontal or 

gently inclined, surface of marine origin along a coast, 

commonly veneered by a marine deposit (typically silt, 

sand, or fine gravel).

medium-grained. Describes an igneous rock and texture 

in which the individual crystals have an average 

diameter in the range of 1 to 5 mm (0.04 to 0.2 in.). 

Also, describes sediment or sedimentary rock and 

texture in which the individual particles have an 

average diameter in the range of 1/16 to 2 mm (0.002 to 

0.08 in), that is, sand size.

member. A lithostratigraphic unit with definable 

contacts; a subdivision of a formation.

mica. A group of abundant silicate (silicon + oxygen) 

minerals characterized by perfect cleavage, readily 

splitting into thin sheets. Examples include “biotite” 

and “muscovite.”

micaceous. Consisting of, containing, or pertaining to 

mica; also, resembling mica, for example, a “micaceous 

mineral” capable of being easily split into thin sheets.

mid-ocean ridge. The continuous, generally submarine 

and volcanically active mountain range that marks the 

divergent tectonic margins in Earth’s oceans.

mineral. A naturally occurring inorganic crystalline solid 

with a definite chemical composition or compositional 

range.

mud flat. A relatively level area of fine silt along a shore 

or around an island, alternately covered and 

uncovered by the tide, or covered by shallow water; a 

muddy tidal flat barren of vegetation.

mollusk. A solitary invertebrate such as gastropods, 

bivalves, and cephalopods belonging to the phylum 

Mollusca. Range: Lower Cambrian to Holocene.

muscovite. A light-colored silicate (silicon + oxygen) 

mineral of the mica group, KAl3Si3O10(OH)2, 

characterized by perfect cleavage in one direction and 

the ability to split into thin, clear sheets.

neoglacial. A period of glacial readvance during the late 

Holocene Epoch. The Little Ice Age (1500s to mid1800s) was the most recent.

neritic. Describes the ocean environment or depth zone 

between low tide and 200 m (660 ft), or between low 

tide and approximately the edge of the continental 

shelf. Also, describes the organisms living in that 

environment.

oligoclase. A silicate (silicon + oxygen) mineral of the 

plagioclase group, intermediate in chemical 

composition and crystallographic and physical 

characters between albite (NaAlSi3O8) and anorthite

(CaAl2Si2O8).

orogeny. A mountain-building event.

orthoclase. A colorless, white, cream-yellow, flesh-pink, 

or gray silicate (silicon + oxygen) mineral of the alkali 

feldspar group, KAlSi3O8, characterized by potassium 

ions in its crystal structure.

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface.

paleofluvial channel. A natural passageway or depression 

produced by the action of a stream or river at a 

particular time in the geologic past.

paleogeography. The study, description, and 

reconstruction of the physical landscape in past 

geologic periods.

paleontology. The study of the life and chronology of 

Earth’s geologic past based on the fossil record.

paleotopography. The topographic relief of an area at a 

particular time in the geologic past.

parabolic dune. Crescent-shaped dune with horns or 

arms that point upwind.

parent material. The unconsolidated organic and 

mineral material from which soil forms.

parent rock. Rock from which soil, sediment, or other 

rock is derived.

passive margin. A continental plate boundary where no 

plate-scale tectonism is taking place; plates are not 

converging, diverging, or sliding past one another.

peat. An unconsolidated deposit of semicarbonized plant 

remains in a water-saturated environment, such as a 

bog or fen, and of persistently high moisture content 

(at least 75%). It is an early stage or rank in the 

development of coal; carbon content is about 60% and 

oxygen content is about 30% (moisture-free). 

Structures of the vegetal matter may or may not be 

visible, depending on the degree of organic matter 

degradation.

pebble. A small rounded rock, especially a waterworn 

stone, between 4 and 64 mm (0.16 and 2.5 in) across.

perched aquifer. An aquifer that is separated from 

(“perched” above) the main body of groundwater by 

an unsaturated zone.

periphyton. Microorganisms, primarily algae and 

heterotrophic microbes, that coat rocks, plants, and 

other surfaces at the bottom of a body of water.

permeability. A measure of the relative ease with which a 

fluid moves through the pore spaces of a rock or 

unconsolidated deposit.

plagioclase. A silicate (silicon + oxygen) mineral of the 

feldspar group that contains both sodium and calcium 

ions that freely substitute for one another; 

characterized by striations (parallel lines) in hand 

specimens.

platform. Any level or nearly level surface.

porosity. The percentage of total void space in a volume 

of rock or unconsolidated deposit.

potassium feldspar. A feldspar mineral rich in potassium 

such as orthoclase, microcline, and sanidine.

potentiometric surface. A surface representing the total 

head of groundwater and defined by the level to which 

water will rise in tightly cased wells.

prodelta. The part of a delta below the level of wave 

erosion.

progradation. The seaward building of land area as a 

result of sedimentary deposition.
78 NPS Geologic Resources Division

pyroxene. A group of silicate (silicon + oxygen) minerals 

composed of magnesium and iron with the general 

formula (Mg,Fe)SiO3; characterized by short, stout 

crystals in hand specimens.

quartz. The only silicate (silicon + oxygen) mineral 

consisting entirely of silicon and oxygen, SiO2; silicon 

dioxide. Synonymous with “crystalline silica.”

quartzite. A medium-grained, nonfoliated metamorphic 

rock composed mostly of quartz; metamorphosed 

quartz sandstone.

radioactivity. The spontaneous decay or breakdown of 

unstable atomic nuclei.

radiocarbon age. An isotopic age expressed in years and 

calculated from the quantitative determination of the 

amount of carbon-14 remaining in an organic material. 

Synonymous with “carbon-14 age.”

radiolarian. Any actinopod (protozoan) belonging to the 

subclass Radiolaria, characterized by a siliceous 

skeleton and a marine pelagic environment. Range: 

Cambrian to Holocene.

radiometric age. An age (in years) calculated from the 

quantitative determination of radioactive elements and 

their decay products. Synonymous with “isotopic age.”

ravinement. An irregular junction that marks a break in 

sedimentation, such as an erosion line occurring where 

shallow-water marine deposits have “scooped down 

into” (or “ravined”) slightly eroded underlying beds; a 

small-scale disconformity caused by periodic invasions 

of the sea over a deltaic area. From the French 

meaning “hollowing out (by waters), gullying.”

rebound. Upward flexing of Earth’s crust. Synonymous 

with “upwarping.”

recharge. The addition of water to the saturated zone 

below the water table.

refraction. The deflection of a ray of light or of an energy 

wave (such as a seismic wave) due to its passage from 

one medium to another of differing density, which 

changes its velocity.

regression. Long-term seaward retreat of the shoreline 

or relative fall of sea level.

relative dating. The chronological placement and 

ordering of rocks, events, or fossils with respect to the 

geologic time scale and without reference to numerical 

ages.

relict. Describes a topographic feature that remains after 

other parts of the feature have been removed or have 

disappeared, for example, a “relict beach ridge” or a 

“relict hill.” Also, a landform made by processes no 

longer operative such as glaciated forms in the 

northern United States or sand dunes in rain forests.

rip current. A strong, narrow, surface or near-surface 

current of short duration (a few minutes to an hour or 

two) and high velocity (up to 2 knots), flowing seaward 

from the shore through the breaker zone at nearly 

right angles to the shoreline, appearing as a visible 

band of agitated water returning to the sea after being 

piled up on the shore by incoming waves and wind.

riprap. A layer of large, durable rock fragments placed in 

an attempt to prevent erosion by water and thereby 

preserve the shape of a surface, slope, or underlying 

structure.

rock. An aggregate of one or more minerals (e.g., granite), 

a body of undifferentiated mineral matter (e.g., 

obsidian), or a body of solid organic material (e.g., 

coal).

runup. The advance of water up the foreshore (between 

high- and low-water marks) of a beach, following the 

breaking of a wave.

rutile. A reddish-brown oxide mineral of titamium, TiO2.

saltation. A mode of sediment movement, driven by 

wind or water, whereby materials move through a 

series of intermittent leaps or jumps.

sand. A clastic particle smaller than a granule and larger 

than a silt grain, with a diameter ranging from 1/16 to 2 

mm (0.0025 to 0.08 in).

sand sheet. A large irregularly shaped plain of aeolian 

sand, lacking the discernible slip faces that are 

common on dunes.

saturated zone. A subsurface zone in which all the 

interstices are filled with water under pressure greater 

than that of the atmosphere; separated from the 

unsaturated zone (above) by the water table.

scarp. A steep cliff or topographic step resulting from 

displacement on a fault or as a result of slope 

movement or erosion. Synonymous with 

“escarpment.”

scour. The powerful and concentrated clearing and 

digging action of flowing air, water, or ice.

seagrass. Flowering plants from four families 

(Posidoniaceae, Zosteraceae, Hydrocharitaceae, and 

Cymodoceaceae) all in the order Alismatales, which 

grow in marine environments.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sedimentary. Pertaining to or containing sediment.

sedimentary rock. A rock resulting from the 

consolidation of loose sediment that has accumulated 

in layers; it may be “clastic,” consisting of mechanically 

formed fragments of older rock; “chemical,” formed 

by precipitation from solution; or “organic,” consisting 

of the remains of plants and animals. One of the three 

main classes of rock—igneous, metamorphic, and 

sedimentary.

sedimentation. The process of forming or accumulating 

sediment into layers, including the separation of rock 

particles from parent rock, the transportation of these 

particles to the site of deposition, the actual deposition 

or settling of the particles, the chemical and other 

changes occurring in the sediment, and the ultimate 

consolidation of the sediment into solid rock.

sequence. A rock-stratigraphic unit that is traceable over 

large areas and defined by sediment associated with a 

major sea level transgression–regression.

shoal. A relatively shallow place in a stream, lake, sea, or 

other body of water.

shoaling. To become shallow gradually, to fill up or block 

off with a shoal, or to proceed from a greater to a lesser 

depth of water.

shoreface. The zone between the seaward limit of the 

shore and the more nearly horizontal surface of the 

offshore zone; typically extends seaward to storm 

wave depth or about 10 m (30 ft).
CAHA Geologic Resources Inventory Report 79

silica. Silicon dioxide, SiO2, an essential constituent of 

many minerals, occurring as crystalline quartz, 

cryptocrystalline chalcedony, and amorphous opal.

silicate. A mineral group composed of silicon (Si) and 

oxygen (O) plus an element or elements, for example, 

quartz, SiO2; olivine, (Mg, Fe)2SiO4; and pyroxene, 

(Mg,Fe)SiO3; as well as the amphiboles, micas, and 

feldspars.

siliceous. Describes a rock or other substance containing 

abundant silica.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay, 1/256 to 

1/16 mm (0.00015 to 0.002 in) across.

silting. The deposition or accumulation of silt that is 

suspended throughout a body of standing water or in 

some considerable portion of it, especially the 

choking, filling, or covering with stream-deposited silt 

behind a dam or other place of retarded flow, or in a 

reservoir.

siltstone. A clastic sedimentary rock composed of siltsized grains.

slope. The inclined surface of any part of Earth’s surface, 

such as a hillslope. Also, a broad part of a continent 

descending into an ocean.

slump. A generally large, coherent slope movement with 

a concave failure surface and subsequent backward 

rotation relative to the slope.

soil. The unconsolidated portion of the Earth’s crust 

modified through physical, chemical, and biotic 

processes into a medium capable of supporting plant 

growth.

sorted. Describes an unconsolidated sediment consisting 

of particles of essentially uniform size.

sorting. The dynamic process by which sedimentary 

particles having some particular characteristic (such as 

similarity of size, shape, or specific gravity) are 

naturally selected and separated from associated but 

dissimilar particles by the agents of transportation.

specific conductance. The measure of discharge of a 

water well per unit of drawdown.

stage. A major subdivision of a glacial epoch, particularly 

one of the cycles of growth and disappearance of the 

Pleistocene ice sheets.

strand plain. A shore built seaward by waves and 

currents, extending continuously for some distance 

along the coast.

strata. Tabular or sheetlike layers of sedimentary rock; 

layers are visually distinctive from other layers above 

and below. The singular form of the term is stratum, 

but is less commonly used.

stratification. The accumulation, or layering, of 

sedimentary rocks as strata. Tabular, or planar, 

stratification refers to essentially parallel surfaces. 

Cross-stratification refers to strata inclined at an angle 

to the main stratification.

stratigraphy. The geologic study of the origin, 

occurrence, distribution, classification, correlation, 

and age of rock layers, especially sedimentary rocks.

stream. Any body of water moving under gravity flow in 

a clearly confined channel.

stream channel. A long, narrow depression shaped by the 

concentrated flow of a stream and covered 

continuously or periodically by water.

subaerial. Describes a condition or process that exists or 

operates in the open air on or immediately adjacent to 

the land surface.

subaqueous. Describes conditions and processes, or 

features and deposits, that exist or are situated in or 

under water.

submarine. Something situated or living under the 

surface of the sea.

submergence. A rise of water level in relation to land, so 

that areas of formerly dry land become inundated; 

results from either a sinking of the land or rise of water 

level. Compare to “emergence.”

subsidence. The sudden sinking or gradual downward 

settling of part of Earth’s surface.

supertidal. Describes a feature or process at an elevation 

higher than normal tidal range on a given shoreface.

terrestrial. Describes a feature, process, or organism 

related to land, Earth, or its inhabitants.

terrigenous. Describes material or a feature derived from 

the land or a continent.

theory. A hypothesis that has been rigorously tested 

against further observations or experiments; a 

generally accepted tenet of science.

topography. The general morphology of Earth’s surface, 

including relief and locations of natural and humanmade features.

tourmaline. A silicate (silicon + oxygen) mineral of 

sodium and aluminum whose composition varies 

widely because of substitutions of elements; occurs as 

a semi-precious stone in a wide variety of colors.

trace fossil. A fossilized feature such as a track, trail, 

burrow, or coprolite (dung), that preserves evidence of 

an organism’s life activities, rather than the organism 

itself. Compare to “body fossil.”

transgression. Landward migration of the sea as a result 

of a relative rise in sea level.

transverse dune. A dune that is elongated perpendicular 

to the prevailing wind direction; the leeward slope 

stands at or near the angle of repose of sand, whereas 

the windward slope is comparatively gentle.

travertine. A chemical sedimentary rock—the spongy or 

less compact variety is tufa—composed of precipitated 

calcium carbonate (predominantly calcite and 

aragonite) from spring-fed, heated and/or ambienttemperature waters.

unconfined groundwater. Groundwater that has a water 

table; that is, water not confined under pressure 

beneath a confining bed.

unconformity. A substantial break or gap in the geologic 

record where a rock unit is overlain by another that is 

not next in stratigraphic succession, resulting from 

either a change that caused deposition to cease for a 

considerable span of time or erosion with loss of the 

previously formed record.

undercutting. The removal of material at the base of a 

steep slope by the erosive action of water (such as a 

meandering stream), sand-laden wind in a desert, or 

waves along the coast.
80 NPS Geologic Resources Division

water table. The surface between the saturated zone and 

the unsaturated zone. Synonymous with “groundwater 

table” and “water level.”

wave base. The depth at which wave activity no longer 

stirs up sediments, usually at about 10 to 20 m (30 to 70 

ft) below water level.

wind tide. The change in still-water level that is caused 

by wind transport of the surface water.

Wisconsinan. Pertaining to the classical fourth glacial 

stage of the Pleistocene Epoch in North America, 

following the Sangamonian interglacial stage and 

preceding the Holocene Epoch.

zircon. A very durable silicate mineral (silicon + oxygen), 

ZrSiO4. When cut and polished, the colorless variety 

provides exceptionally brilliant gemstones.
CAHA Geologic Resources Inventory Report 81

Literature Cited

These references are cited in this report. Contact the Geologic Resources Division for 

assistance in obtaining them.

Ames, D. V., and S. R. Riggs. 2006a. Geomorphic 

framework of the North Carolina Outer Banks (Kitty 

Hawk to Whalebone Junction area digital data) (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006b. Geomorphic 

framework of the North Carolina Outer Banks (South 

Nags Head to Oregon Inlet area digital data (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006c. Geomorphic 

framework of the North Carolina Outer Banks (New 

Inlet to Rodanthe area digital data) (scale 1:10,000). 

East Carolina University, Greenville, North Carolina.

Ames, D. V., and S. R. Riggs. 2006d. Geomorphic 

framework of the North Carolina Outer Banks (South 

Salvo to No Ache Island area digital data) (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006e. Geomorphic 

framework of the North Carolina Outer Banks (Little 

Kinnakeet area digital data) (scale 1:10,000). East 

Carolina University, Greenville, North Carolina.

Ames, D. V., and S. R. Riggs. 2006f. Geomorphic 

framework of the North Carolina Outer Banks 

(Buxton Inlet digital data) (scale 1:10,000). East 

Carolina University, Greenville, North Carolina.

Ames, D. V., and S. R. Riggs. 2006g. Geomorphic 

framework of the North Carolina Outer Banks 

(Hatteras Village to Frisco area digital data) (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006h. Geomorphic 

framework of the North Carolina Outer Banks (Great 

Swash to Quork Hammock area digital data) (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006i. Geomorphic 

framework of the North Carolina Outer Banks 

(Ocracoke Village to The Plains area digital data) (scale 

1:10,000). East Carolina University, Greenville, North 

Carolina.

Ames, D. V., and S. R. Riggs. 2006j. Geomorphic 

framework of the North Carolina Outer Banks. East 

Carolina University, Greenville, North Carolina. 

Included in GRI GIS data products (see attached CD).

Anders, F., and S. Leatherman. 1987a. Disturbance of 

beach sediment by off-road vehicles. Environmental 

Geology 9:183–189.

Anders, F. J., and S. Leatherman. 1987b. Effects of offroad vehicles on coastal foredunes at Fire Island, New 

York. Environmental Management 11:45–52.

Anderson, W. P., D. G. Evans, and S. W. Snyder. 2000. 

The effects of Holocene barrier island evolution on 

water table elevations, Hatteras island, North Carolina. 

Hydrogeology Journal 8:390–404.

Anderson, W.P., Jr. 2002. Aquifer salinization from storm 

overwash. Journal of Coastal Research 18:413-420.

Beavers, R., C. Hawkins-Hoffman, and M. Koslow. In 

review. Chapter 1 Introduction. In: Beavers, R.L., A. 

Babson, and C. Schupp, editors. Coastal Adaptation 

Strategies Handbook. Natural Resource Report 

NPS/NRSS/GRD/NRR—2015/XXX. National Park 

Service, Fort Collins, Colorado.

Boesch, D. F., editor. 2008. Global warming and the free 

state: comprehensive assessment of climate change 

impacts in Maryland, report of the scientific and 

technical working group of the Maryland Commission 

on Climate Change. University of Maryland Center for 

Environmental Science, Cambridge, Maryland. 

http://www.umces.edu/sites/default/files/pdfs/global_

warming_free_state_report.pdf (accessed 24 

September 2012).

Boss, S. K., and C. W. Hoffman. 2001. Geologic 

framework derived from high-resolution seismic 

reflection, side-scan sonar, and vibracore data offshore 

Oregon Inlet to Duck, Dare County, North Carolina. 

US Minerals Management Service, International 

Activities and Marine Minerals Division 

(INTERMAR).

Boss, S. K., C. W. Hoffman, and B. Cooper. 2002. 

Influence of fluvial processes on the Quaternary 

geologic framework of the continental shelf, North 

Carolina. Marine Geology 183:45–65.

Browder, A. G., and J. E. McNinch. 2006. Linking 

framework geology and nearshore morphology: 

correlation of paleo-channels with shore-oblique 

sandbars and gravel outcrops. Marine Geology 

231:141–162.
82 NPS Geologic Resources Division

Brown, P. M. 1960. Ground-water supply of Cape 

Hatteras National Seashore Recreational Area. Report 

of Investigation RINEDJ. Groundwater Section, 

Division of Resource Planning and Evaluation, North 

Carolina Department of Natural and Economic 

Resources, Raleigh, North Carolina. 

https://irma.nps.gov/App/Reference/Profile/657642

(accessed 5 March 2014).

Brown, P. M., J. A. Miller, and F. M. Swain. 1972. 

Structural and stratigraphic framework, and spatial 

distribution of permeability of Atlantic coastal plain, 

North Carolina to New York. Professional paper 796. 

U. S. Geological Survey, Reston, Virginia.

Brunner, J., J. Kenworthy, and V. Santucci. 2009. 

Unauthorized fossil collecting from National Park 

Service shorelines: Servicewide policy and 

perspectives. Pages 319-323 in S. Weber, editor. 

Rethinking Protected Areas in a Changing World: 

Proceedings of the 2009 George Wright Society 

Biennial Conference on Parks, Protected Areas, and 

Cultural Sites. The George Wright Society, Hancock, 

Michigan. http://www.georgewright.org/

0956brunner.pdf (accessed 16 April 2015).

Burkholder, J., D. Eggleston, H. Glasgow, C. Brownie, R. 

Reed, G. Janowitz, M. Posey, G. Melia, C. Kinder, R. 

Corbett, D. Toms, T. Alphin, N. Deamer, and J. 

Springer. 2004. Comparative impacts of two major 

hurricane seasons on the Neuse River and western 

Pamlico Sound ecosystems. Proceedings of the 

National Academy of Sciences 101:9291–9296.

Bush, D. M., and R. Young. 2009. Coastal features and 

processes. Pages 47–67 in R. Young and L. Norby, 

editors. Geological monitoring. Geological Society of 

America, Boulder, Colorado. 

http://nature.nps.gov/geology/monitoring/coastal.cfm

(accessed 16 April 2015).

Caffrey, M. 2013. Sea level and storm surge trends for the 

state of the park report: Cape Hatteras National 

Seashore/Fort Raleigh National Historic Site/Wright 

Brothers National Memorial. University of Colorado, 

Boulder, Colorado and NPS Geologic Resources 

Division, Coastal Geology Program, Lakewood, 

Colorado.

Cahoon, D. R., D. J. Reed, A. S. Kolker, M. M. Brinson, J.

C. Stevenson, S. Riggs, R. Christian, E. Reyes, C. Voss, 

and D. Kunz. 2009. Coastal wetland sustainability. 

Pages 57–72 in J. G. Titus, coordinating lead author, 

and K. E. Anderson, D. R. Cahoon, D. B. Gesch, S. K. 

Gill, B. T. Gutierrez, E. R. Thieler, and S. J. Williams, 

lead authors. Coastal sensitivity to sea-level rise: a 

focus on the Mid-Atlantic region. A report by the U.S. 

Climate Change Science Program and the 

Subcommittee on Global Change Research. U. S. 

Environmental Protection Agency, Washington, DC.

http://downloads.globalchange.gov/sap/sap4-1/sap4-

1-final-report-all.pdf (accessed 23 September 2014).

Capone, M., E. Thieler, D. Nichols, and T. O'Brien. 

2002a. Archive of boomer subbottom data collected 

during USGS Cruise ATSV99045, northern North 

Carolina, October 9-27, 1999. Open-file report 01-380. 

U. S. Geological Survey.

Capone, M., E. Thieler, D. Nichols, and T. O'Brien. 

2002b. Archive of CHIRP subbottom data collected 

during USGS Cruise ATSV99045, northern North 

Carolina, October 9-27, 1999. Open-file report 2002-

215. U. S. Geological Survey.

Church, J. A., P. U. Clark, A. Cazenave, J. M. Gregory, S. 

Jevrejeva, A. Levermann, M. A. Merrifield, G. A. 

Milne, R. S. Nerem, P. D. Nunn, A. J. Payne, W. T. 

Pfeffer, D. Stammer, and A. S. Unnikrishnan. 2013. Sea 

level change. In T. F. Stocker, D. Qin, G.-K. Plattner, 

M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, 

V. Bex, and P. M. Midgley, editors. Climate change 

2013: the physical science basis. Contribution of 

Working Group I to the Fifth Assessment Report of 

the Intergovernmental Panel on Climate Change. 

Cambridge University Press, Cambridge, United 

Kingdom, and New York, New York. 

http://www.climatechange2013.org/images/report/W

G1AR5_Chapter13_FINAL.pdf (accessed 10 February 

2014).

Cleary, W. J., and P. A. Thayer. 1973. Petrography of 

carbonate sands on the Carolina continental shelf. 

Transactions - Gulf Coast Association of Geological 

Societies 23:288–304.

Coffey, J. C. 1977. Exploratory oil wells of North 

Carolina 1925-1976. Information circular 22. North 

Carolina Geological Survey, Raleigh, North Carolina.

Colquhoun, D. J. 1966. Geomorphology of river valleys 

in the southeastern Atlantic Coastal Plain. 

Southeastern Geology 7 (3):101–109.

Colquhoun, D. J. 1969. Coastal Plain terraces in the 

Carolinas and Georgia. Congress of the International 

Union for Quaternary Research 16:150–162.

Corbett, D. R., J. P. Walsh, L. Cowart, S. R. Riggs, D. V. 

Ames, and S. J. Culver. 2008. Shoreline change within 

the Albemarle-Pamlico Estuarine System, North 

Carolina. East Carolina University, Greenville, North 

Carolina. http://www.ecu.edu/icsp/

ICSP/Reports_files/EstuarineShorelineChangeDec200

8.pdf (accessed 10 December 2012).

Cox, M. O. 1996. Geologic control of nearshore wave 

energy: Wimble Shoals, North Carolina. PhD 

dissertation. Duke University, Durham, North 

Carolina.
CAHA Geologic Resources Inventory Report 83

Culver, S. J., C. A. Grand Pre, D. J. Mallinson, S. R. Riggs, 

D. R. Corbett, J. Foley, M. Hale, L. Metger, J. Ricardo, 

J. Rosenberger, D. G. Smith, C. W. Smith, S. W. Snyder, 

D. Twamley, K. Farrell, and B. P. Horton. 2007. Late 

Holocene barrier island collapse: Outer Banks, North 

Carolina. The Sedimentary Record 5:4–8.

Culver, S. J., O. Bin, J. Brewer, R. R. Christian, D. R. 

Corbett, S. Curtis, B. Edwards, L. King, P. Long, D. J. 

Mallinson, L. Novick, M. O'Driscoll, S. R. Riggs, and J. 

Rummel. 2008a. Global warming and coastal North 

Carolina: a response in two parts from East Carolina 

University to Senator Marc Basnight’s request 

concerning global warming. East Carolina University, 

Greenville, North Carolina. 

https://www.northcarolina.edu/nctomorrow/ECU_cli

mate_change_report.pdf (accessed 10 February 2014).

Culver, S. J., K. M. Farrell, D. J. Mallinson, B. P. Horton, 

D. A. Willard, E. R. Thieler, S. R. Riggs, S. W. Sndyer, J. 

F. Wehmiller, C. E. Bernhardt, and C. Hillier. 2008b. 

Micropaleontologic record of late Pliocene and 

Quaternary paleoenvironments in the northern 

Albemarle Embayment, North Carolina. 

Palaeogeography, Palaeoclimatology, Palaeoecology 

254:54–77.

Curdts, T. 2011. Shoreline length and water area in the 

ocean, coastal and Great Lakes parks: Updated 

statistics for shoreline miles and water acres (rev1b). 

NPS/WASO/NRR—2011/464. National Park Service, 

Fort Collins, Colorado. 

https://irma.nps.gov/App/Reference/Profile/2180595

(accessed 11 March 2015).

Dallas, K., J. Eshleman, and R. Beavers. 2012. National 

Park Service beach nourishment guidance. Natural 

Resource Technical Report. 

NPS/NRSS/GRD/NRTR—2012/581. National Park 

Service, Fort Collins, Colorado. 

https://irma.nps.gov/App/Reference/Profile/2185115

(accessed 11 March 2015).

Dallas, K., M. Berry, and P. Ruggiero. 2013. Inventory of 

coastal engineering projects in Cape Hatteras National 

Seashore. Natural resource technical report 

NPS/NRSS/GRD/NRTR—2013/713. National Park 

Service, Fort Collins, Colorado. 

https://irma.nps.gov/App/Reference/Profile/2193864

(accessed 15 May 2014).

Daniels, R. B., H. J. Kleiss, S. W. Buol, H. J. Byrd, and J. A. 

Phillips. 1984. Soil systems in North Carolina. Bulletin 

467. North Carolina Agricultural Research Service, 

North Carolina State University, Raleigh, North 

Carolina.

Dolan, R., and P. Godfrey. 1972. Dune stabilization and 

beach erosion; Cape Hatteras National Seashore, 

North Carolina. Natural resource report no. 5. 

National Park Service, Washington, DC.

Dolan, R., and H. Lins. 1986. The Outer Banks of North 

Carolina. Professional paper 1177-B. U. S. Geological 

Survey, Reston, Virginia.

http://pubs.usgs.gov/pp/1177b/report.pdf (accessed 2 

October 2012).

Douglas, B. C. 1997. Global sea rise: a redetermination. 

Surveys in Geophysics 18(2–3): 279–292.

Elko, N. A., A. H. Sallenger, Jr., K. Guy, and K. L. M. 

Morgan. 2002. Barrier island elevations relevant to 

potential storm impacts: 2, South Atlantic. Open-file 

report 2002-288. U. S. Geological Survey, St. 

Petersburg, Florida.

http://coastal.er.usgs.gov/hurricanes/publications/ofr02-288.pdf (accessed 8 January 2013).

Evans, D. G., and B. H. Houston. 2000. Assessing the 

impact of septic discharge on water quality on the 

Cape Hatteras National Seashore. Unpublished report, 

National Park Service Files, Ft. Raleigh, Manteo, 

North Carolina.

Everts, C. H. 1978. Geometry of profiles across inner 

continental shelves of the Atlantic and Gulf Coasts of 

the United States. U. S. Army Corps of Engineers 

Coastal Engineering Research Center, Fort Belvoir, 

Virginia.

Farrell, K. M., H. E. Mew, A. J. Keyworth, and T. W. 

Clark. 2003. Comprehensive landscape analysis, 

geomorphology, and sequence stratigraphy in eastern 

North Carolina’s Little Contentnea Creek watershed 

of the Neuse River Basin: methods for constructing 

reconnaissance-level geologic maps of a relict PlioPleistocene terrane. Carolina Geological Society, 

Annual Field Trip Guidebook Nov 14–16, 2003:1–17.

Feldman, R. L., J. G. Titus, and B. Poulter. 2009. North 

Carolina. Pages 229–238 in J. G. Titus, coordinating 

lead author, and K. E. Anderson, D. R. Cahoon, D. B. 

Gesch, S. K. Gill, B. T. Gutierrez, E. R. Thieler, and S. J. 

Williams, lead authors. Coastal sensitivity to sea-level 

rise: a focus on the Mid-Atlantic region. A report by 

the U.S. Climate Change Science Program and the 

Subcommittee on Global Change Research. Appendix 

1: state and local information on vulnerable species 

and coastal policies in the Mid-Atlantic. U. S. 

Environmental Protection Agency, Washington, DC. 

http://downloads.globalchange.gov/sap/sap4-1/sap4-

1-final-report-all.pdf (accessed 23 September 2014).

Ferguson, R. L., J. A. Rivera, and L. L. Wood. 1988. 

Submerged aquatic vegetation in the AlbemarlePamlico estuarine system. Project no. 88-10. National 

Marine Fisheries Service, National Oceanic and 

Atmospheric Administration, Beaufort Laboratory, 

Beaufort, North Carolina.
84 NPS Geologic Resources Division

FitzGerald, D. M., and M. O. Hayes. 1980. Tidal inlet 

effects on barrier island management. Pages 2355–2379 

in B. Edge, editor. Coastal Zone’80: Proceedings of the 

Second Symposium on Coastal and Ocean 

Management, Hollywood, Florida, November 17-20, 

1980. American Society of Civil Engineers, New York, 

New York.

Fisher, J. J. 1962. Geomorphic expression of former 

inlets along the Outer Banks of North Carolina. MS 

thesis. University of North Carolina, Chapel Hill, 

North Carolina.

Fisher, J. J. 1967. Development pattern of relict beach 

ridges, Outer Banks Barrier Chain, North Carolina. 

PhD dissertation. Department of Geology, University 

of North Carolina, Chapel Hill, North Carolina.

Forgues, K. 2010. The effects of off-road vehicles on 

migrating shorebirds at a barrier island in Maryland 

and Virginia. Master’s thesis. Trent University, 

Peterborough, Ontario, Canada.

Foyle, A. M., and G. F. Oertel. 1997. Transgressive 

systems tract development and incised-valley fills 

within a Quaternary estuary-shelf system: Virginia 

inner shelf, USA. Marine Geology 137:227–249.

Freeman, C. W., D. J. Bernstein, and H. Mitasova. 2004. 

Rapid response 3D survey techniques for seamless 

topo/bathy modeling: 2003 Hatteras Breach, North 

Carolina. Shore and Beach 72(2): 25–30.

http://www.geodynamicsgroup.com/p/wpcontent/uploads/2012/08/afreeman_pdf.pdf (accessed 

5 November 2012).

Frost, C. C. 2000. Studies in landscape fire ecology and 

pre-settlement vegetation of the southeastern United 

States. PhD dissertation, University of North Carolina, 

Chapel Hill, North Carolina.

Giese, G. L., H. B. Wilder, and G. G. Parker. 1985. 

Hydrology of major estuaries and sounds of North 

Carolina. Water-supply paper 2221. U. S. Geological 

Survey, Raleigh, North Carolina.

Godfrey, P.J. and M. Godfrey. 1980. Ecological effects of 

off-road vehicles on Cape Cod. Oceanus 23: 56-67.

Grand Pre, Candice A. 2006. Holocene 

paleoenvironmental change in Pamlico Sound, North 

Carolina: foraminiferal and stable isotopic evidence. 

MS thesis. Department of Geology, East Carolina 

University, Greenville, North Carolina.

Greenlee, S. M., and T. C. Moore. 1988. Recognition and 

interpretation of depositional sequences and 

calculation of sea-level changes from stratigraphic 

data—offshore New Jersey and Alabama Tertiary. 

Pages 329–356 in C. K. Wilgus et al., editors. Sea-level 

changes: an integrated approach. Memoir 42. Society 

of Economic Paleontologists and Mineralogists, Tulsa, 

Oklahoma.

Gregory, M. B., and K. A. Smith. 2011. Assessment of 

estuarine water and sediment quality at Cape Lookout 

and Cape Hatteras National Seashores, 2010. Natural 

resource data series NPS/SECN/NRDS—2011/179. 

National Park Service, Fort Collins, Colorado.

Gutierrez, B. T., S. J. Williams, and E. R. Thieler. 2007. 

Potential for shoreline changes due to sea-level rise 

along the U.S. Mid-Atlantic region. Open-file report 

2007-1278. U. S. Geological Survey, Reston, Virginia.

http://woodshole.er.usgs.gov/pubs/of2007-1278/

(accessed 5 August 2014).

Gutierrez, B. T., S. J. Williams, and E. R. Thieler. 2009. 

Ocean Coasts. Pages 43-56 in J. G. Titus, coordinating 

lead author, and K. E. Anderson, D. R. Cahoon, D. B. 

Gesch, S. K. Gill, B. T. Gutierrez, E. R. Thieler, and S. J. 

Williams, lead authors. Coastal sensitivity to sea-level 

rise: a focus on the Mid-Atlantic region. A report by 

the U.S. Climate Change Science Program and the 

Subcommittee on Global Change Research. U. S. 

Environmental Protection Agency, Washington, DC. 

http://downloads.globalchange.gov/sap/sap4-1/sap4-

1-final-report-all.pdf (accessed 23 September 2014).

Harris, W. H., and H. B. Wilder. 1964. Ground-water 

supply of Cape Hatteras National Seashore 

Recreational Area, North Carolina. Part 3. Report 

inventory 4. North Carolina Department of Water 

Resources, Raleigh, North Carolina.

Havholm, K. G., D. V. Ames, G. R. Whittecar, B. A. 

Wenell, S. R. Riggs, H. M. Jol, G. W. Berger, and M. A. 

Holmes. 2004. Stratigraphy of back-barrier coastal 

dunes, northern North Carolina and southern 

Virginia. Journal of Coastal Research 20:980¬999.

Herbert, J. R., and S. D. Heron, Jr. 1978. Relict inlets of 

Northern Core Bank: evidence from Holocene inlet fill 

and geomorphic features. Geological Society of 

America Abstracts with Programs 10(4):171.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007a. 

Geomorphology of Bodie Island map area, Cape 

Hatteras National Seashore (scale 1:24,000). Digital 

publication plate 1 of 6. North Carolina Geological 

Survey, Raleigh, North Carolina.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007b. 

Geomorphology of Pea Island map area, Cape 

Hatteras National Seashore (scale 1:24,000). Digital 

publication plate 2 of 6. North Carolina Geological 

Survey, Raleigh, North Carolina.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007c. 

Geomorphology of Rodanthe map area, Cape Hatteras 

National Seashore (scale 1:24,000). Digital publication 

plate 3 of 6. North Carolina Geological Survey, 

Raleigh, North Carolina.
CAHA Geologic Resources Inventory Report 85

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007d. 

Geomorphology of Avon map area, Cape Hatteras 

National Seashore (scale 1:24,000). Digital publication 

plate 4 of 6. North Carolina Geological Survey, 

Raleigh, North Carolina.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007e. 

Geomorphology of Buxton map area, Cape Hatteras 

National Seashore (scale 1:24,000). Digital publication 

plate 5 of 6. North Carolina Geological Survey, 

Raleigh, North Carolina.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007f. 

Geomorphology of Ocracoke Island map area, Cape 

Hatteras National Seashore (scale 1:24,000). Digital 

publication plate 6 of 6. North Carolina Geological 

Survey, Raleigh, North Carolina.

Hoffman, C. W., B. P. Coffey, and A. N. Ward. 2007g. 

Geomorphic mapping of Cape Hatteras National 

Seashore. Digital publication. North Carolina 

Geological Survey, Raleigh, North Carolina.

Holland, A. F., D. M. Sanger, C. P. Gawle, S. B. Lerberg, 

M. S. Santiago, G. H. M. Riekerk, L. E. Zimmerman, 

and G. I. Scott. 2004. Linkages between tidal creek 

ecosystems and the landscape and demographic 

attributes of their watersheds. Journal of Experimental 

Marine Biology and Ecology 298:151–178.

Honeycutt, M. G., and D. E. Krantz. 2003. Influence of 

geologic framework on spatial variability in long-term 

shoreline change, Cape Henlopen to Rehoboth Beach, 

Delaware. Journal of Coastal Research Special Issue 

38:147–167.

Horton, B. P., W. R. Peltier, S. J. Culver, R. Drummond, 

S. E. Engelhart, A. C. Kemp, D. Mallinson, E. R. 

Thieler, S. R. Riggs, D. V. Ames, and K. H. Thomson. 

2009. Holocene sea-level changes along the North 

Carolina Coastline and their implications for glacial 

isostatic adjustment models. Quaternary Science 

Reviews 28:1725–1736.

Hosier, P. E., M. Kochhar, and V. Thayer. 1981. Off-road 

vehicle and pedestrian track effects on the seaapproach of hatchling loggerhead turtles. 

Environmental Conservation 8(02): 158–161.

Houser, C. 2012. Impact of over sand vehicles at 

Assateague Island National Seashore. Research report 

submitted to National Park Service. Texas A&M 

University, Department of Geography, College Station, 

Texas.

Inman, D. L., and R. Dolan. 1989. The Outer Banks of 

North Carolina: budget of sediment and inlet 

dynamics along a migrating barrier system. Journal of 

Coastal Research 5(2): 193–237.

Johnson, G. H., P. C. Peebles, G. M. Richmond, D. S. 

Fullerton, and D. L. Weide. 1986. Quaternary geologic 

map of the Hatteras 4° by 6° quadrangle, United States 

(scale 1:1,000,000). Miscellaneous investigations series 

I-1420 (NI-18). U. S. Geological Survey, Reston, 

Virginia.

Joyner, B. P., M. F. Overton, and J. S. Fisher. 1998. Poststabilization morphology of Oregon Inlet, NC. Coastal 

Engineering (1998) Conference Proceedings: 3124–

3137.

Karl, T. R., J. M. Melillo, and T. C. Peterson, editors. 

2009. Global climate change impacts in the United 

States. Cambridge University Press, New York, New 

York. 

http://globalchange.gov/publications/reports/scientific

-assessments/us-impacts (accessed 19 September 

2012).

Kemp, A. C., B. P. Horton, D. R. Corbett, S. J. Culver, R.

J. Edwards, and O. van de Plassche. 2009. The relative 

utility of foraminifera and diatoms in reconstructing 

late Holocene sea-level change in North Carolina. 

Quaternary Research 71:9–21.

Kemp, A. C., B. P. Horton, J. P. Donnelly, M. E. Mann, 

M. Vermeer, and S. Rahmstorf. 2011. Climate related 

sea-level variations over the past two millennia. 

Proceedings of the National Academy of Sciences 

108(27):11017–11022. doi: 10.1073/pnas.1015619108 

(accessed 5 February 2014).

Kenworthy, J. P., and V. L. Santucci. 2006. A preliminary 

investigation of National Park Service paleontological 

resources in cultural context: Part 1, general overview. 

Pages 70–76 in S. G. Lucas, J. A. Spielmann, P. M. 

Hester, J. P. Kenworthy, and V. L. Santucci, editors. 

America’s antiquities: 100 years of managing fossils on 

Federal lands. Bulletin 34. New Mexico Museum of 

Natural History and Science, Albuquerque, New 

Mexico.

Kimrey, J. O. 1960. Ground-water supply of Cape 

Hatteras National Seashore Recreational Area. Part 2. 

Report inventory 2. North Carolina Department of 

Water Resources, Raleigh, North Carolina.
86 NPS Geologic Resources Division

Kirtman, B., S. B. Power, J. A. Adedoyin, G. J. Boer, R. 

Bojariu, I. Camilloni, F. J. Doblas-Reyes, A. M. Fiore, 

M. Kimoto, G. A. Meehl, M. Prather, A. Sarr, C. Schär, 

R. Sutton, G. J. van Oldenborgh, G. Vecchi, and H. J. 

Wang. 2013. Near-term climate change: projections 

and predictability. Pages 953-1028 in T. F. Stocker, D. 

Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. 

Boschung, A. Nauels, Y. Xia, V. Bex, and P. M. 

Midgley, editors. Climate change 2013: the physical 

science basis. Contribution of Working Group I to the 

Fifth Assessment Report of the Intergovernmental 

Panel on Climate Change. Cambridge University Press, 

Cambridge, United Kingdom, and New York, New 

York. http://www.climatechange2013.org/

images/report/WG1AR5_Chapter11_FINAL.pdf

(accessed 25 September 2014).

Knisley, C. B., and J. M. Hill. 1990. Distribution and 

abundance of two tiger beetles Cicindela dorsalis media

and C. lepida at Assateague Island, Maryland, 1990. 

Final report to Maryland Department of Natural 

Resources, Natural Heritage Program, Annapolis, 

Maryland.

Konicki, K. M., and R. A. Holman. 2000. The statistics 

and kinematics of transverse sand bars on an open 

coast. Marine Geology 169: 69–101.

Lawrence, D. P., and C. W. Hoffman. 1993. Geology of 

basement rocks beneath the North Carolina Coastal

Plain. Bulletin 95. North Carolina Geological Survey, 

Raleigh, North Carolina.

Lazarus, E. D., and A. B. Murray. 2011. An integrated 

hypothesis for regional patterns of shoreline change 

along the Northern North Carolina Outer Banks. 

Marine Geology 281:85–90.

http://www.sciencedirect.com/science/article/pii/S002

5322711000223 (accessed 2 October 2012).

Leatherman, S. P., and P. J. Godfrey. 1979. The impact of 

off-road vehicles on coastal ecosystems in Cape Cod 

National Seashore: an overview. Report no. 34. 

University of Massachusetts and National Park Service 

Cooperative Research Unit.

Liddle, M. J., and P. Greig-Smith. 1975. A survey of 

tracks and paths in a sand dune ecosystem. II. 

Vegetation. Journal of Applied Ecology 12:909–930.

Lippman, T., and R. A. Holman. 1990. The spatial and 

temporal variability of sandbar morphology. Journal of 

Geophysical Research 95:11575–11590.

List, J. H., A. Farris, and C. Sullivan. 2006. Reversing 

storm hotspots on sandy beaches: spatial and temporal 

characteristics. Marine Geology 226:261–279.

http://www.sciencedirect.com/science/article/pii/S002

5322705003476 (accessed 15 January 2013).

Macintyre, I. G., and J. D. Milliman. 1970. Physiographic 

features on the outer shelf and upper slope, Atlantic 

continental margin, southeastern United States. 

Geological Society of America Bulletin 81(9):2577–

2597.

Mallin, M. A., S. H. Ensign, M. R. McIver, G. C. Shank,

and P. K. Fowler. 2001. Demographic, landscape, and 

meteorological factors controlling the microbial 

pollution of coastal waters. Hydrobiologia 460:185–

193.

Mallin, M. A., M. R. McIver, and V. L. Johnson. 2006. 

Assessment of coastal water resources and watershed 

conditions at Cape Hatteras National Seashore, North 

Carolina. Technical report NPS/NRWRD/NRTR2006/351. National Park Service, Fort Collins, 

Colorado. http://www.nature.nps.gov/

water/nrca/assets/docs/caha_coastal.pdf (accessed 25 

July 2013).

Mallinson, D., S. Riggs, S. Culver, R. Thieler, D. Foster, 

D. Corbett, K. Farrell, and J. Wehmiller. 2005. Late 

Neogene and Quaternary evolution of the northern 

Albemarle Embayment (Mid-Atlantic Continental 

Margin, USA). Marine Geology 217:97–117.

Mallinson, D. J., K. Burdette, S. Mahan, G. Brook, C. 

Smith, P. Parham, S. R. Riggs, and S. J. Culver. 2007. 

Assessing the chronostratigraphy of late Pleistocene 

and Holocene coastal lithosomes using optically 

stimulated luminescence techniques: intriguing results 

from NC and FL. Geological Society of America

Abstracts with Programs 39(2): 73, Abstract 119261.

GSA Southeastern Section Meeting, Savannah, 

Georgia, March 29-30, 2007.

Mallinson, D., K. Burdette, S. Mahan, and G. Brook. 

2008a. Optically stimulated luminescence age controls 

on late Pleistocene and Holocene coastal lithosomes: 

North Carolina. Quaternary Research 69:97–109.

Mallinson, D. J., S. J. Culver, S. R. Riggs, J. P. Walsh, D. 

Ames, and C. W. Smith. 2008b. Past, present and future 

inlets of the Outer Banks barrier islands, North 

Carolina. East Carolina University, Greenville, North 

Carolina, USA.

Mallinson, D. J., S. R. Riggs, S. J. Culver, D. Ames, B. P. 

Horton, and A. C. Kemp. 2009. The North Carolina 

Outer Banks barrier islands: a field trip guide to the 

geology, geomorphology, and processes. East Carolina 

University Department of Geological Sciences, 

Greenville, North Carolina.

Mallinson, D. J., S. J. Culver, S. R. Riggs, E. R., Thieler, D. 

Foster, J. F. Wehmiller, K. M. Farrell, and J. Pierson. 

2010a. Regional seismic stratigraphy and controls on 

the Quaternary evolution of the Cape Hatteras region 

of the Atlantic continental margin, USA. Marine 

Geology 268:16–33.
CAHA Geologic Resources Inventory Report 87

Mallinson, D. J., C. W. Smith, S. J. Culver, S. R. Riggs, and 

D. Ames. 2010b. Geological characteristics and spatial 

distribution of paleo-inlet channels beneath the outer 

banks barrier islands, North Carolina, USA. Estuarine, 

Coastal and Shelf Science 88(2):175–189.

http://www.sciencedirect.com/science/article/pii/S027

2771410001319 (accessed 2 October 2012).

Mallinson, D. J., C. W. Smith, S. Mahan, S. J. Culver, and 

K. McDowell. 2011. Barrier island response to late 

Holocene climate events, North Carolina, USA. 

Quaternary Research 76(1):46–57.

http://www.sciencedirect.com/science/article/pii/S003

3589411000640 (accessed 2 October 2012).

McBride, R. A., and T. F. Moslow. 1991. Origin, 

evolution, and distribution of shoreface sand ridges, 

Atlantic inner shelf, U.S.A. Marine Geology 97:57–85.

McDonald, J. N., and C. E. Ray. 1993. Records of musk 

oxen from the Atlantic Coastal Plain of North 

America. The Mosasaur 5:1–18.

McNinch, J. E. 2004. Geologic control in the nearshore: 

shore-oblique sandbars and shoreline erosional 

hotspots, Mid-Atlantic Bight, USA. Marine Geology 

211(1–2):121–141.

McNinch, J. E., and Wells, J. T. 1999. Sedimentary 

processes and depositional history of a capeassociated shoal, Cape Lookout, North Carolina: 

Marine Geology 158:233–252.

Miselis, J. L., and J. E. McNinch. 2006. Calculating 

shoreline erosion potential using nearshore 

stratigraphy and sediment volume: Outer Banks, North 

Carolina. Journal of Geophysical Research 

111:F02019.

Moore, L. J., J. H. List, S. J. Williams, and K. Patsch. 2011. 

Barriers on the brink: the complex intertwined roles of

geologic framework, sediment availability and sealevel rise in island evolution. Pages 272-285 in P. Wang, 

J. D. Rosati, and T. M. Roberts, editors. Coastal 

Sediments 2011. World Scientific, Miami, Florida.

Moore, L. J., J. H. List, S. J. Williams, and D. Stolper. 

2007. Modeling barrier island response to sea-level 

rise. Pages 1153-1164 in N. Kraus and J. Rosati, editors. 

Coastal Sediments 2007 (3). American Society of Civil 

Engineers, Reston, Virginia.

Moore, L. J., J. H. List, S. J. Williams, and D. Stolper. 

2010. Complexities in barrier island response to sea 

level rise: insights from numerical model experiments, 

North Carolina Outer Banks. Journal of Geophysical 

Research 115(F3):F03004.

Morton, R. A., and T. Miller. 2005. National assessment 

of shoreline change: part 2, historical shoreline 

changes and associated coastal land loss along the U.S. 

southeast Atlantic coast. Open-file report 2005-1401. 

U. S. Geological Survey. 

http://pubs.usgs.gov/of/2005/1401/ (accessed 5 

February 2014).

Moslow, T. F., and S. D. Heron. 1981. Holocene 

depositional history of a microtidal cuspate foreland 

cape: Cape Lookout, North Carolina. Marine Geology 

41:251–270.

Moss, D., and D. McPhee. 2006. The impacts of 

recreational four-wheel driving on the abundance of 

the ghost crab (Ocypode cordimanus) on a subtropical 

sandy beach in SE Queensland. Coastal Management 

34:133–140.

Murray, A. B., and E. R. Thieler. 2004. A new hypothesis 

for the formation of large-scale inner-shelf sediment 

sorting and rippled scour depressions. Continental 

Shelf Research 24:295–315.

National Hurricane Center. 2012. Saffir-Simpson 

Hurricane Wind Scale.

http://www.nhc.noaa.gov/aboutsshws.php (accessed 

27 August 2014).

National Oceanic and Atmospheric Administration. 

2013a. Tropical cyclones frequently asked questions. 

National Oceanic and Atmospheric Administration 

Hurricane Research Division, Virginia Key, Florida. 

http://www.aoml.noaa.gov/hrd/tcfaq/E19.html

(accessed 7 February 2014).

National Oceanic and Atmospheric Administration. 

2013b. Updated mean sea level trends, 8656483 

Beaufort, North Carolina. Available at: 

http://tidesandcurrents.noaa.gov/sltrends/sltrends_up

date.shtml?stnid=8656483 (accessed October 2013).

National Park Service. 2000. Geologic resources 

inventory workshop summary for the Outer Banks 

group: Cape Hatteras and Cape Lookout national 

seashores, Wright Brothers National Memorial, and 

Fort Raleigh National Historic Site. Internal report.

National Park Service Geologic Resources Division 

and Natural Resources Information Division, Denver, 

Colorado. http://www.nature.nps.gov/geology/

inventory/publications/s_summaries/CAHA_scoping_

summary_20000711.pdf (accessed 16 January 2013).

National Park Service. 2002. Historic structure report: 

Wright Brothers National Memorial Visitor Center. 

National Park Service Southeast Region Cultural 

Resources, Atlanta, Georgia.
88 NPS Geologic Resources Division

National Park Service. 2005. Strategic plan for Wright 

Brothers National Memorial October 1, 2006 -

September 30, 2011. Technical report. Wright Brothers 

National Memorial, Manteo, NC. 

http://www.nps.gov/wrbr/parkmgmt/upload/072307%

20WRBR%20Strategic%20Plan%202006-2011.pdf

(accessed 26 September 2014).

National Park Service. 2006. Management policies 2006. 

http://www.nps.gov/policy/mp/policies.html (accessed 

10 January 2013).

National Park Service. 2007. Fort Raleigh National 

Historic Site general management plan news, issue 2, 

spring 2007. Newsletter. http://parkplanning.nps.gov/

document.cfm?parkID=380&projectID=10965&docu

mentID=19088 (accessed 26 September 2014).

National Park Service. 2010. Cape Hatteras National 

Seashore off-road vehicle management plan final 

environmental impact statement. Cape Hatteras 

National Seashore, Manteo, NC. 

http://parkplanning.nps.gov/documentsList.cfm?parkI

D=358&projectID=10641 (accessed 26 September 

2014).

National Park Service. 2011. Cape Hatteras National 

Seashore foundation statement. NPS 603/110361. 

National Park Service, Denver, Colorado.

National Park Service. 2012. Inventory & monitoring 

program status report, 2011: Cape Hatteras National 

Seashore. Southeast Coast Network, National Park 

Service, Athens, Georgia.

National Park Service and University of Maryland 

Center for Environmental Science. 2012. Teach Ocean 

Science module “barrier islands and sea level rise.” 

http://www.teachoceanscience.net/teaching_resources

/education_modules/barrier_islands_and_sea_level_ris

e/learn/ (accessed 22 July 2013).

National Park Service. 2014. Preserving coastal heritage. 

Summary Report. April 3-4, 2014. Federal Hall, New 

York City, New York. https://sites.google.com/site/

democlimcult/ (accessed 7 October 2014).

National Park Service. 2015. National Park Service visitor 

use statistics. https://irma.nps.gov/Stats/Reports/Park

(accessed 20 April 2015).

Niedoroda, A.W., and W. F. Tanner. 1970. Preliminary 

study of transverse bars. Marine Geology 9:41–62.

North Carolina Coastal Resources Commission. 2010. 

North Carolina sea-level rise assessment report. North 

Carolina Coastal Resources Commission's Science 

Panel on Coastal Hazards, Raleigh, North Carolina.

http://dcm2.enr.state.nc.us/slr/NC%20SeaLevel%20Rise%20Assessment%20Report%202010%2

0-%20CRC%20Science%20Panel.pdf (accessed 10 

January 2013).

North Carolina Division of Coastal Management. 2003. 

Long-term average annual shoreline change study & 

setback factors. North Carolina Division of Coastal 

Management, Raleigh, North Carolina. 

http://portal.ncdenr.org/web/cm/downloadoceanfront-setback-factor-maps-1998-shoreline

(accessed 23 September 2014).

North Carolina Division of Coastal Management. 2009. 

Estuarine shoreline stabilization options. Online 

guidance. http://www.nccoastalmanagement.net/

estuarineshoreline/options.html (accessed 10 January 

2013).

North Carolina Department of Environment and 

Natural Resources Division of Water Quality. 2012. 

2012 overall integrated reporting water quality ratings. 

Digital dataset. North Carolina Department of 

Environment and Natural Resources Division of 

Water Quality, Raleigh, North Carolina. 

http://portal.ncdenr.org/web/wq/ps/mtu/assessment

(accessed 10 February 2014).

Overton, M. F., and J. S. Fisher. 2004. Hurricane Isabel 

and the NC 12 Hotspots. Shore and Beach 72(2):38–44.

Paerl, H. W., L. M. Valdes, A. R. Joyner, B. L. Peierls, M.

F. Piehler, S. R. Riggs, R. R. Christian, L. A. Eby, L. B. 

Crowder, J. S. Ramus, E. J. Clesceri, C. P. Buzzelli, and 

R. A. Luettich, Jr. 2006. Ecological response to 

hurricane events in the Pamlico Sound System, North 

Carolina, and implications for assessment and 

management in a regime of increased frequency. 

Estuaries and Coasts 29(6):1033–1045.

http://www.jstor.org/stable/4124836 (accessed 31 

October 2012).

Parham, P. R., S. R. Riggs, S. J. Culver, D. J. Mallinson, 

and J. F. Wehmiller. 2007. Quaternary depositional 

patterns and sea-level fluctuations, northeastern 

North Carolina. Quaternary Research 67:83–99.

Pearson, D. K. 1979. Surface and shallow subsurface 

sediment regime of the nearshore inner continental 

shelf, Nags Head and Wilmington areas, North 

Carolina. MS thesis, East Carolina University, 

Greenville, North Carolina.

Peek, K. M., R. S. Young, R. L. Beavers, C. H. Hoffman, 

B. T. Diethorn, and S. Norton. in press [2015]. 

Adapting to climate change in coastal national parks: 

Estimating the exposure of park assets to 1 m of sealevel rise. Natural Resource Report 

NPS/NRSS/GRD/NRR—2015/961. National Park 

Service, Fort Collins, Colorado. https://irma.nps.gov/.

Pendleton, E. A., E. R. Thieler, and S. J. Williams. 2004. 

Coastal vulnerability assessment of Cape Hatteras 

National Seashore (CAHA) to sea-level rise. Open-file 

report 2004-1064. U. S. Geological Survey, Reston, 

Virginia. http://pubs.usgs.gov/of/2004/1064/ (accessed 

24 October 2012).
CAHA Geologic Resources Inventory Report 89

Pickett, T. E. 1965. The modern sediment of Pamlico 

Sound, North Carolina. PhD dissertation, University 

of North Carolina, Chapel Hill, North Carolina.

Popenoe, P. 1985. Cenozoic depositional and structural 

history of the North Carolina margin from seismicstratigraphic analyses. Pages 125–188 in C. W. Poag, 

editor. Geologic evolution of the United States 

Atlantic margin. Van Nostrand Reinhold Co., New 

York, New York.

Rahmstorf, S. 2007. A semi-empirical approach to 

projecting future sea-level rise. Science 315:368–370.

Richards, H. G. 1968. The Tertiary history of the Atlantic 

Coast between Cape Cod and Cape Hatteras. 

Palaeogeography, Palaeoclimatology, Palaeoecology 

5(1):95–104.

Richards, H. G., D. J. Colquhoun, and R. L. Blanchard. 

1971. Pleistocene mollusks from boreholes in South 

Carolina. Notulae Naturae 445:1–11.

Riggs, S. R., and D. V. Ames. 2003. Drowning the North 

Carolina coast: sea-level rise and estuarine dynamics. 

Publication no. UNC-SG-03-04. North Carolina Sea 

Grant, Raleigh, North Carolina.

Riggs, S. R., and D. V. Ames. 2006. Barrier island 

evolution: a model for development of the geomorphic 

framework, North Carolina Outer Banks. East 

Carolina University, Greenville, North Carolina. 

Included in GRI GIS data products (see attached CD).

Riggs, S. R., and D. V. Ames. 2007. Effect of storms and 

barrier island dynamics on core banks (1960-2001), 

Cape Lookout National Seashore, North Carolina. 

Scientific investigations report 2006-5309. U. S. 

Geological Survey, Reston, Virginia.

Riggs, S. R., and D. V. Ames. 2011. Consequences of 

human modifications in Oregon Inlet to the downdrift Pea Island, North Carolina Outer Banks. 

Southeastern Geology 48(3):103–128.

Riggs, S. R., D. V. Ames, S. J. Culver, and D. J. Mallinson. 

2011. The battle for North Carolina’s coast: 

evolutionary history, present crisis, and vision for the 

future. The University of North Carolina Press, Chapel 

Hill, North Carolina.

Riggs, S. R., D. V. Ames, S. J. Culver, D. J. Mallinson, D. 

Reide Corbett, and J. P. Walsh. 2009. Eye of a human 

hurricane: Pea Island, Oregon Inlet, and Bodie Island, 

northern Outer Banks, North Carolina. Pages 43–72 in

J. T. Kelley, O. H. Pilkey, and J. A. G. Cooper, editors. 

America's most vulnerable coastal communities. 

Special paper 460-04. Geological Society of America, 

Boulder, Colorado.

Riggs, S. R., D. V. Ames, and K. R. Dawkins. 2008a. 

Coastal processes and conflicts: North Carolina’s 

Outer Banks. North Carolina Sea Grant, Raleigh, 

North Carolina. http://core.ecu.edu/geology/

riggs/Coastal-Processes-September-2008.pdf

(accessed 7 August 2012).

Riggs, S. R., W. J. Cleary, and S. W. Snyder. 1995. 

Influence of inherited geologic framework on barrier 

shoreface morphology and dynamics. Marine Geology 

126(1–4):213–234.

Riggs, S. R., S. J. Culver, D. V. Ames, D. J. Mallinson, D. 

Reide Corbett, and J. P. Walsh. 2008b. North 

Carolina’s coasts in crisis: a vision for the future. East 

Carolina University, Greenville, North Carolina.

Riggs, S. R., G. L. Rudolph, and D. V. Ames. 2000.

Erosional scour and geologic evolution of Croatan 

Sound, Northeastern North Carolina. 

FHWA/NC/2000-002. North Carolina Department of 

Transportation, Raleigh, North Carolina.

Riggs, S. R., S. W. Snyder, A. C. Hine, and D. L. Mearns. 

1996. Hardbottom morphology and relationship to the 

geologic framework: mid-Atlantic continental shelf. 

Journal of Sedimentary Research 66(4): 830-846.

Riggs, S. R., L. L. York, J. F. Wehmiller, and S. W. Snyder. 

1992. Depositional patterns resulting from highfrequency Quaternary sea-level fluctuations in 

northeastern North Carolina. Pages 141–153 in C. H. 

Fletcher III and J. F. Wehmiller, editors. Quaternary 

coasts of the United States: marine and lacustrine 

systems. Special publication 48. Society for 

Sedimentary Geology, Tulsa, Oklahoma.

https://sakai.udel.edu/access/content/user/42339/

Wehmiller_Pubs/Riggsetal1992.pdf (accessed 2 

October 2012).

Sager, E. D., and Riggs, S. R. 1998. Models for Holocene 

valley-fill history of Albemarle Sound, North Carolina. 

Pages 119–127 in C. Alexander, V. J. Henry, and R. 

Davis, editors. Tidalites: processes and products.

Special publication no. 61. Society for Sedimentary 

Geology, Tulsa, Oklahoma.

Sallenger, A. 2003. Before and after surveys document 

the impacts of Hurricane Isabel. Sound Waves 56: 5.

http://soundwaves.usgs.gov/2003/11/SW200311-

144.pdf (accessed 23 September 2014).

Sallenger, A. H., K. S. Doran, and P. A. Howd. 2012. 

Hotspot of accelerated sea-level rise on the Atlantic 

coast of North America. Nature Climate Change 2: 

884-888. http://dx.doi.org/10.1038/nclimate1597

(accessed 25 October 2012).
90 NPS Geologic Resources Division

Santucci, V. L., J. P. Kenworthy, and A. L. Mims. 2009. 

Monitoring in situ paleontological resources. Pages 189–

204 in R. Young and L. Norby, editors. Geological 

monitoring. Geological Society of America, Boulder, 

Colorado. 

http://nature.nps.gov/geology/monitoring/paleo.cfm

(accessed 5 May 2015).

Saunders, S., T. Easley, D. Findlay, K. Durdy, and T. 

Spencer. 2012. Atlantic National Seashores in Peril: 

The Threats of Climate Disruption. The Rocky 

Mountain Climate Organization, Louisville, CO, and 

Natural Resources Defense Council, New York, NY.

www.rockymountainclimate.org/images/AtlanticSeash

oresLow.pdf (accessed 10 January 2013).

Schlacher, T. A., L. Thompson, and S. Price. 2007. 

Vehicles versus conservation of invertebrates on sandy 

beaches: mortalities inflicted by off-road vehicles on 

ghost crabs. Marine Ecology 28:354–367.

Schlacher, T. A., and L. M. C. Thompson. 2008. Physical 

impacts caused by off-road vehicles to sandy beaches: 

spatial quantification of car tracks on an Australian 

barrier island. Journal of Coastal Research 24:234–242.

Schlacher, T. A., L. M. C. Thompson, and S. J. Walker. 

2008. Mortalities caused by off-road vehicles (ORVs) 

to a key member of sandy beach assemblages, the surf 

clam Donax deltoides. Hydrobiologia 610(1): 345-350.

Schupp, C. 2013. Assateague Island National Seashore: 

geologic resources inventory report. Natural resource 

report NPS/NRSS/GRD/NRR—2013/708. National 

Park Service, Fort Collins, Colorado.

http://www.nature.nps.gov/geology/inventory/gre_pu

blications.cfm (accessed 21 April 2015).

Schupp, C. A., J. E. McNinch, and J. H. List. 2006. 

Nearshore shore-oblique bars, gravel outcrops, and 

their correlation to shoreline change. Marine Geology 

233:63–79.

Schwartz, R. K., and W. A. Birkemeier. 2004. 

Sedimentology and morphodynamics of a barrier 

island shoreface related to engineering concerns, 

Outer Banks, NC, USA. Marine Geology 211:215–255.

Shennan, I., and B. P. Horton. 2002. Relative sea-level 

changes and crustal movements of the UK. Journal of 

Quaternary Science 16:511–526.

Smith, J .J., R. Dolan, and H. Lins. 2006. Hurricane 

history of the North Carolina Outer Banks (USA), 

1586 to 2004. Shore and Beach 74(3):19–23.

Snyder, S. 1993. Miocene geology of the Continental 

Shelf: Onslow Bay, North Carolina. North Carolina 

Division of Land Resources, Raleigh, North Carolina.

Southern Environmental Law Center. 12 December 

2012. Groups call on N.C. to provide reliable, longterm solution after Outer Banks Highway washed out 

again. Press release.

http://www.southernenvironment.org/newsroom/pres

s_releases/groups_call_on_n.c._to_provide_reliable_lo

ng-term_solution_after_outer/ (accessed 10 January 

2013).

Southern Environmental Law Center (SELC). 15 

September 2014. NCDOT and Conservation Groups 

Represented by SELC Discussing Possible Bonner 

Bridge Solutions. Press release. 

https://www.southernenvironment.org/news-andpress/press-releases/ncdot-and-conservation-groupsrepresented-by-selc-discussing-possible-bonnerbridge-solutions (accessed 25 September 2014).

Stanley, D. J., and A. G. Warne. 1994. Worldwide 

initiation of Holocene marine deltas by deceleration of 

sea-level rise. Science 265(5169):228–231.

Steiner, A. J., and S. P. Leatherman. 1981. Recreational 

impacts on the distribution of ghost crabs Ocypode 

quadrata Fab. Biological Conservation 20:111–122.

Stover, D. 2002. Fossil walrus skull found on the Outer 

Banks near Cape Hatteras. Park Paleontology 6(2):2.

Stover, D. 2008. Pea Island life-saving station, Rodanthe, 

North Carolina: Coast Guard Station #177. Historic 

Resource Study. National Park Service, Cape Hatteras 

National Seashore, Manteo, North Carolina.

Stubblefield, W. L., and D. J. P. Swift. 1976. Ridge 

development as revealed by sub-bottom profiles on the 

central New Jersey shelf. Marine Geology 20:315–334.

Swift, D. J. P. 1976. Coastal sedimentation. Pages 255–310 

in D. J. Stanley and D. J. P. Swift, editors, Marine 

sediment transport and environmental management. 

John Wiley and Sons, New York, New York.

Swift, D. J. P., and M. E. Field. 1981. Evolution of a 

classic sand ridge field: Maryland sector, North 

American inner shelf. Sedimentology 28:461–482.

Swift, D. J. P., B. W. Holliday, N. F. Avignone, and G. I. 

Shideler. 1972. Anatomy of a shoreface ridge system, 

False Cape, Virginia. Marine Geology 12:59–84.

Swift, D. J., G. Parker, N. W. Lanfredi, G. Perillo, and K. 

Figge. 1978. Shoreface-connected sand ridges on 

American and European shelves: a comparison. 

Estuarine and Coastal Marine Science 7(3):257–273.

Thieler, E. R., and A. D. Ashton. 2011. 'Cape capture': 

geologic data and modeling results suggest the 

Holocene loss of a Carolina Cape. Geology 39:339–

342.
CAHA Geologic Resources Inventory Report 91

Thieler, E. R., A. L. Brill, W. J. Cleary, C. H. Hobbs, III, 

and R. A. Gammisch. 1995. Geology of the Wrightsville 

Beach, North Carolina shoreface: implications for the 

concept of shoreface profile of equilibrium. Marine

Geology 126:271–287.

Thieler, E.R., O. H. Pilkey, Jr., W. J. Cleary, and W. C. 

Schwab. 2001. Modern sedimentation on the 

shoreface and inner continental shelf at Wrightsville 

Beach, North Carolina, U.S.A. Journal of Sedimentary 

Research 71:958–970.

Thompson, T. A. 1977. Archaeological resources at the 

Cape Hatteras National Seashore – a management 

study. Unpublished report. Technical Information 

Center, Denver, Colorado.

Tweet, J. S., V. L. Santucci, and J. P. Kenworthy. 2009. 

Paleontological resource inventory and monitoring—

Southeast Coast Network. Natural resource technical 

report NPS/NRPC/NRTR—2009/197. National Park 

Service, Fort Collins, Colorado.

United States Environmental Protection Agency. 2005. 

National coastal condition report II. EPA-620/R03/002. Office of Research and Development/Office of 

Water, Washington, DC. http://water.epa.gov/

type/oceb/2005_index.cfm (accessed 23 September 

2014).

U. S. Fish and Wildlife Service. 2008. Assessment of 

potential toxicity and aquatic community impacts 

associated with membrane and ion exchange water 

treatment facility effluents in coastal North Carolina. 

U. S. Fish and Wildlife Service, Raleigh, North 

Carolina. http://www.fws.gov/raleigh/pdfs/

wtpreport_608.pdf (accessed 10 February 2014).

Wamsley, T. V., K. K. Hathaway, and M. Wutkowski. 

2009. Hatteras Breach, North Carolina. Coastal and 

hydraulics laboratory engineering technical note 

ERDC/CHL CHETN-VI-43. U. S. Army Engineer 

Research and Development Center, Vicksburg, 

Mississippi.

Ward, L. W., and G. L. Strickland. 1985. Outline of 

Tertiary stratigraphy and depositional history of the 

US Atlantic Coastal Plain. Pages 87–123 in C. W. Poag, 

editor. Geological evolution of the United States 

Atlantic margin. Van Nostrand Reinhold, New York, 

New York.

Watson, J. J., G. I. H. Kerley, and A. McLachlan. 1996. 

Human activity and potential impacts on dune 

breeding birds in the Alexandria Coastal Dunefield. 

Landscape & Urban Planning 34:315–322.

Webster, W. D., and C. L. Reese. 1992. Mammalian 

zoogeography on North Carolina's barrier islands, 

with special reference to Cape Hatteras National 

Seashore. Pages 133–143 in C. A. Cole and K. Turner, 

editors. Barrier island ecology of the Mid-Atlantic 

Coast: a symposium. NPS/SERCAHA/NRTR 93/04. 

National Park Service, Denver, Colorado.

Wells, J. T., and S. Y. Kim. 1989. Sedimentation in the 

Albemarle-Pamlico lagoonal system: synthesis and 

hypotheses. Marine Geology 88(3–4):263–284.

Wikel, G. L. 2008. Variability in geologic framework and 

shoreline change: Assateague and Wallops islands, 

eastern shore of Virginia. Master’s thesis. Virginia 

Institute of Marine Science, The College of William 

and Mary, Williamsburg, Virginia.

Williams, J. A., V. L. Ward, and L. G. Underhill. 2004. 

Waders respond quickly and positively to the banning 

of off-road vehicles from beaches in South Africa. 

Wader Study Group Bulletin 104:79–81.

Williams, S. J. 2013. Sea-level rise implications for coastal 

regions. Journal of Coastal Research 63:184–196.

Winner, M. D., Jr. 1975. Ground-water resources of the 

Cape Hatteras National Seashore, North Carolina 

(scale 1:24,000). Hydrologic investigations atlas HA0540. U. S. Geological Survey, Reston, Virginia.

Wolcott, T. G., and D. L. Wolcott. 1984. Impact of 

offroad vehicles on macroinvertebrates of a midAtlantic beach. Biological Conservation 29:217–240.

Woolard, J. W., and J. D. Colby. 2002. Spatial 

characterization, resolution, and volumetric change of 

coastal dunes using airborne LIDAR; Cape Hatteras, 

North Carolina. Geomorphology 48(1–3):269–287.

The World Bank. 2012. Turn down the heat: why a 4o

C 

warmer world must be avoided. A report for the World 

Bank by the Potsdam Institute for Climate Impact 

Research and Climate Analytics. The World Bank, 

Washington, DC.

http://climatechange.worldbank.org/sites/default/files

/Turn_Down_the_heat_Why_a_4_degree_centrigrade

_warmer_world_must_be_avoided.pdf (accessed 8 

January 2013).

Wright, C. J. 2012. Groundwater conditions in Southeast 

Coast Network Parks, 2011. Natural resource data 

series NPS/SECN/NRDS—2012/326. National Park 

Service, Fort Collins, Colorado.

Wright, L. D., and A. D. Short. 1984. Morphodynamic 

variability of surf zones and beaches: a synthesis. 

Marine Geology 56:93–118.
92 NPS Geologic Resources Division

Wright, W., M. B. Gregory, and A. Rinehart. 2012. Fixed 

station water quality monitoring at Cape Hatteras 

National Seashore: 2010 data summary. Natural 

resource data series NPS/2012/NRDS—2012/367. 

National Park Service, Fort Collins, Colorado.

Young, R., and L. Norby, editors. 2009. Geological 

monitoring. Geological Society of America, Boulder, 

Colorado. http://nature.nps.gov/geology/

monitoring/index.cfm (accessed 23 September 2014).

Zarra, L. 1989. Sequence stratigraphy and foraminiferal 

biostratigraphy for selected wells in the Albemarle 

embayment, North Carolina. Open-file report 89-5.

North Carolina Geological Survey, Raleigh, North 

Carolina.

Zervas, C.E. 2004. North Carolina 

Bathymetry/Topography Sea Level Rise Project: 

Determination of Sea Level Trends. NOAA Technical 

Report NOS CO-OPS 041. National Oceanic and 

Atmospheric Administration, Silver Spring, Maryland.

Zervas, C. 2009. Sea level variations of the United States 

1854-2006. NOAA Technical Report NOS CO-OPS 

053. National Oceanic and Atmospheric 

Administration, Silver Spring, Maryland.

Zhang, K., B. Douglas, and S. Leatherman. 2002. Do 

storms cause long-term beach erosion along the U.S. 

East Barrier Coast? Journal of Geology 110(4):493–502.

Zhang, K., B. Douglas, and S. Leatherman. 2004. Global 

warming and coastal erosion. Climatic Change 64:41–

58.
CAHA Geologic Resources Inventory Report 93

Additional References

These additional references, resources, and websites may be of use to resource managers. 

Web addresses are valid as of April 2015. Refer to Appendix B for laws, regulations, and 

policies that apply to NPS geologic resources.

Geology of National Park Service Areas

NPS Geologic Resources Division (Lakewood, 

Colorado): http://nature.nps.gov/geology/

NPS Geologic Resources Inventory:

http://www.nature.nps.gov/geology/inventory/.

NPS Geoscientist-In-the-Parks (GIP) internship and 

guest scientist program:

http://www.nature.nps.gov/geology/gip/index.cfm

NPS Views program (geology-themed modules are 

available for Geologic Time, Paleontology, Glaciers, 

Caves and Karst, Coastal Geology, Volcanoes, and a 

variety of geologic parks): 

http://www.nature.nps.gov/views/

NPS Resource Management Guidance and Documents

1998 National parks omnibus management act: 

http://www.gpo.gov/fdsys/pkg/PLAW105publ391/pdf/PLAW-105publ391.pdf

Management Policies 2006 (Chapter 4: Natural resource 

management): 

http://www.nps.gov/policy/mp/policies.html

NPS-75: Natural resource inventory and monitoring 

guideline: 

http://www.nature.nps.gov/nps75/nps75.pdf

NPS Natural resource management reference manual 

#77: http://www.nature.nps.gov/Rm77/

Geologic monitoring manual (Young and Norby 2009)

http://nature.nps.gov/geology/monitoring/index.cfm

NPS Technical Information Center (TIC) (Denver, 

Colorado; repository for technical documents): 

http://www.nps.gov/dsc/technicalinfocenter.htm

Climate Change Resources

NPS Climate Change Response Program Resources: 

http://www.nps.gov/subjects/climatechange/resources

.htm

US Global Change Research Program: 

http://globalchange.gov/home

Intergovernmental Panel on Climate Change: 

http://www.ipcc.ch/

Geological Surveys and Societies

North Carolina Geological Survey

http://www.geology.enr.state.nc.us/

US Geological Survey: http://www.usgs.gov/

Geological Society of America: 

http://www.geosociety.org/

American Geophysical Union: http://sites.agu.org/

American Geosciences Institute: 

http://www.americangeosciences.org/

Association of American State Geologists: 

http://www.stategeologists.org/

US Geological Survey Reference Tools

National geologic map database (NGMDB): 

http://ngmdb.usgs.gov/

Geologic names lexicon (GEOLEX; geologic unit 

nomenclature and summary): 

http://ngmdb.usgs.gov/Geolex/geolex_home.html

Geographic names information system (GNIS; official 

listing of place names and geographic features): 

http://gnis.usgs.gov/

GeoPDFs (download searchable PDFs of any 

topographic map in the United States): 

http://store.usgs.gov (click on “Map Locator”)

Publications warehouse (many publications available 

online): http://pubs.er.usgs.gov

Tapestry of time and terrain (descriptions of 

physiographic provinces): 

http://tapestry.usgs.gov/Default.html

Water Quality Data Portals and Websites

North Carolina DENR Division of Marine Fisheries 

(shellfish closures due to pollution): 

http://portal.ncdenr.org/web/mf/proclamationspolluted-areas

North Carolina OneMap Geospatial Portal (including 

water quality data): http://data.nconemap.com/

geoportal/catalog/main/home.page

US Environmental Protection Agency How’s My 

Watershed? Tool: 

http://watersgeo.epa.gov/mywaterway/
94 NPS Geologic Resources Division

Appendix A: Scoping Participants

The following people attended the GRI scoping meeting for Cape Hatteras National 

Seashore, held on 3-5 April 2000. Discussions during that meeting supplied a foundation for 

this GRI report. The scoping summary document is available on the GRI publications 

website: http://go.nps.gov/gripubs.

2000 Scoping Meeting Participants

Name Affiliation Position

Tim Connors NPS Geologic Resources Division Geologist

Stephen Culver East Carolina University Professor of Geology

Nikki Ernst NPS Cape Hatteras National Seashore Cartographic Technician

Kathleen Farrell North Carolina Geological Survey Senior Geologist

Steve Harrison NPS Cape Hatteras National Seashore Resource Management Chief

Bruce Heise NPS Geologic Resources Division Geologist

Bill Hoffman North Carolina Geological Survey Chief Scientist

Stanley Riggs East Carolina University Professor of Geology

Michael Rikard NPS Cape Lookout National Seashore Resource Management Chief

Rob Thieler U.S Geological Survey Research Geologist

Keith Watson NPS Cape Hatteras National Seashore Resource Management Specialist
CAHA Geologic Resources Inventory Report 95

Appendix B: Geologic Resource Laws, Regulations, and 

Policies

The NPS Geologic Resources Division developed this table to summarize laws, regulations, 

and policies that specifically apply to National Park Service minerals and geologic 

resources. The table does not include laws of general application (e.g., Endangered Species 

Act, Clean Water Act, Wilderness Act, National Environmental Policy Act, or National 

Historic Preservation Act). The table does include the NPS Organic Act when it serves as the 

main authority for protection of a particular resource or when other, more specific laws are 

not available. Information is current as of April 2015. Contact the NPS Geologic Resources 

Division for detailed guidance.

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Paleontology

National Parks Omnibus 

Management Act of 1998, 16 

USC § 5937 protects the 

confidentiality of the nature and 

specific location of paleontological 

resources and objects.

Paleontological Resources 

Preservation Act of 2009, 16 

USC § 470aaa et seq. provides for 

the management and protection of 

paleontological resources on 

federal lands.

36 CFR § 2.1(a)(1)(iii) prohibits 

destroying, injuring, defacing, 

removing, digging or disturbing 

paleontological specimens or parts 

thereof.

Prohibition in 36 CFR § 13.35

applies even in Alaska parks, where 

the surface collection of other 

geologic resources is permitted.

Regulations in association with 2009 

PRPA are being finalized (April

2015).

Section 4.8.2 requires NPS to 

protect geologic features from 

adverse effects of human activity.

Section 4.8.2.1 emphasizes 

Inventory and Monitoring, 

encourages scientific research, 

directs parks to maintain 

confidentiality of paleontological 

information, and allows parks to buy 

fossils only in accordance with 

certain criteria.

Rocks and Minerals

NPS Organic Act, 16 USC § 1 et 

seq. directs the NPS to conserve all 

resources in parks (including rock 

and mineral resources), unless 

otherwise authorized by law.

Exception: 16 USC § 445c (c) –

Pipestone National Monument 

enabling statute. Authorizes 

American Indian collection of 

catlinite (red pipestone).

36 CFR § 2.1 prohibits possessing, 

destroying, disturbing mineral 

resources...in park units.

Exception: 36 CFR § 7.91 allows 

limited gold panning in 

Whiskeytown.

Exception: 36 CFR § 13.35 allows 

some surface collection of rocks and 

minerals in some Alaska parks (not 

Klondike Gold Rush, Sitka, Denali, 

Glacier Bay, or Katmai) by nondisturbing methods (e.g., no 

pickaxes), which can be stopped by 

superintendent if collection causes 

significant adverse effects on park 

resources and visitor enjoyment.

Section 4.8.2 requires NPS to 

protect geologic features from 

adverse effects of human activity.
96 NPS Geologic Resources Division

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Park Use of Sand and Gravel

Materials Act of 1947, 30 USC § 

601 does not authorize the NPS to 

dispose of mineral materials outside 

of park units.

Exception: 16 USC §90c 1(b) the 

non-wilderness portion of Lake 

Chelan National Recreation Area, 

where sand, rock and gravel may 

be made available for sale to the 

residents of Stehekin for local use 

as long as such sale and disposal 

does not have significant adverse 

effects on the administration of the 

National Recreation Area.

None applicable. Section 9.1.3.3 clarifies that only 

the NPS or its agent can extract 

park-owned common variety 

minerals (e.g., sand and gravel), and:

-only for park administrative uses;

-after compliance with NEPA and 

other federal, state, and local laws, 

and a finding of non-impairment;

-after finding the use is park’s most 

reasonable alternative based on 

environment and economics;

-parks should use existing pits and 

create new pits only in accordance 

with park-wide borrow 

management plan;

-spoil areas must comply with Part 6

standards; and

-NPS must evaluate use of external 

quarries.

Any deviation from this policy 

requires a written waiver from the 

Secretary, Assistant Secretary, or 

Director.
CAHA Geologic Resources Inventory Report 97

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Coastal Features and Processes

NPS Organic Act, 16 USC § 1 et. 

seq. authorizes the NPS to 

promulgate regulations to protect 

park resources and values (from, 

for example, the exercise of mining 

and mineral rights).

Coastal Zone Management Act, 

16 USC § 1451 et. seq. requires 

Federal agencies to prepare a 

consistency determination for every 

Federal agency activity in or outside 

of the coastal zone that affects 

land or water use of the coastal 

zone.

Clean Water Act, 33 USC § 

1342/Rivers and Harbors Act, 33 

USC 403 require that dredge and 

fill actions comply with a Corps of 

Engineers Section 404 permit.

Executive Order 13089 (coral 

reefs) (1998) calls for reduction of 

impacts to coral reefs.

Executive Order 13158 (marine

protected areas) (2000) requires 

every federal agency, to the extent 

permitted by law and the maximum 

extent practicable, to avoid 

harming marine protected areas.

36 CFR § 1.2(a)(3) applies NPS 

regulations to activities occurring 

within waters subject to the 

jurisdiction of the US located within 

the boundaries of a unit, including 

navigable water and areas within 

their ordinary reach, below the mean 

high water mark (or OHW line) 

without regard to ownership of 

submerged lands, tidelands, or 

lowlands.

36 CFR § 5.7 requires NPS 

authorization prior to constructing a 

building or other structure (including 

boat docks) upon, across, over, 

through, or under any park area.

Section 4.1.5 directs the NPS to reestablish natural functions and 

processes in human-disturbed 

components of natural systems in 

parks unless directed otherwise by 

Congress.

Section 4.4.2.4 directs the NPS to 

allow natural recovery of landscapes 

disturbed by natural phenomena, 

unless manipulation of the landscape 

is necessary to protect park 

development or human safety.

Section 4.8.1 requires NPS to allow 

natural geologic processes to 

proceed unimpeded. NPS can 

intervene in these processes only 

when required by Congress, when 

necessary for saving human lives, or 

when there is no other feasible way 

to protect other natural resources/ 

park facilities/historic properties.

Section 4.8.1.1 requires NPS to:

-Allow natural processes to continue 

without interference,

-Investigate alternatives for 

mitigating the effects of human 

alterations of natural processes and 

restoring natural conditions,

-Study impacts of cultural resource 

protection proposals on natural 

resources,

-Use the most effective and naturallooking erosion control methods 

available, and

-Avoid putting new developments in 

areas subject to natural shoreline 

processes unless certain factors are 

present.
98 NPS Geologic Resources Division

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Upland and Fluvial Processes

Rivers and Harbors 

Appropriation Act of 1899, 33 

USC § 403 prohibits the 

construction of any obstruction on 

the waters of the United States not 

authorized by congress or approved 

by the USACE.

Clean Water Act 33 USC § 1342

requires a permit from the USACE 

prior to any discharge of dredged 

or fill material into navigable waters 

(waters of the US [including 

streams]).

Executive Order 11988 requires 

federal agencies to avoid adverse 

impacts to floodplains. (see also 

D.O. 77-2)

Executive Order 11990 requires 

plans for potentially affected 

wetlands (including riparian 

wetlands). (see also D.O. 77-1)

None applicable. Section 4.1 requires NPS to manage 

natural resources to preserve 

fundamental physical and biological 

processes, as well as individual 

species, features, and plant and 

animal communities; maintain all 

components and processes of 

naturally evolving park ecosystems.

Section 4.1.5 directs the NPS to reestablish natural functions and 

processes in human-disturbed 

components of natural systems in 

parks, unless directed otherwise by 

Congress.

Section 4.4.2.4 directs the NPS to 

allow natural recovery of landscapes 

disturbed by natural phenomena, 

unless manipulation of the landscape 

is necessary to protect park 

development or human safety.

Section 4.6.4 directs the NPS to (1) 

manage for the preservation of 

floodplain values; [and] (2) minimize 

potentially hazardous conditions 

associated with flooding.

Section 4.6.6 directs the NPS to 

manage watersheds as complete 

hydrologic systems and minimize 

human-caused disturbance to the 

natural upland processes that deliver 

water, sediment, and woody debris 

to streams.

Section 4.8.1 directs the NPS to 

allow natural geologic processes to 

proceed unimpeded. Geologic 

processes...include...erosion and 

sedimentation...processes.

Section 4.8.2 directs the NPS to 

protect geologic features from the 

unacceptable impacts of human 

activity while allowing natural 

processes to continue.
CAHA Geologic Resources Inventory Report 99

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Soils

Soil and Water Resources 

Conservation Act, 16 USC §§ 

2011–2009 provides for the 

collection and analysis of soil and 

related resource data and the 

appraisal of the status, condition, 

and trends for these resources.

Farmland Protection Policy Act, 

7 USC § 4201 et. seq. requires 

NPS to identify and take into 

account the adverse effects of 

Federal programs on the 

preservation of farmland; consider 

alternative actions, and assure that 

such Federal programs are 

compatible with State, unit of local 

government, and private programs 

and policies to protect farmland.

NPS actions are subject to the FPPA 

if they may irreversibly convert 

farmland (directly or indirectly) to 

nonagricultural use and are 

completed by a Federal agency or 

with assistance from a Federal 

agency. Applicable projects require 

coordination with the Department 

of Agriculture’s Natural Resources 

Conservation Service (NRCS).

7 CFR Parts 610 and 611 are the US

Department of Agriculture 

regulations for the Natural Resources 

Conservation Service. Part 610

governs the NRCS technical 

assistance program, soil erosion 

predictions, and the conservation of 

private grazing land. Part 611

governs soil surveys and cartographic 

operations. The NRCS works with 

the NPS through cooperative 

arrangements.

Section 4.8.2.4 requires NPS to

-prevent unnatural erosion, removal, 

and contamination;

-conduct soil surveys;

-minimize unavoidable excavation; 

and

-develop/follow written prescriptions 

(instructions).
The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides 

scientific and other information about those resources; and honors its special responsibilities to American Indians, 

Alaska Natives, and affiliated Island Communities.

NPS 603/128571, May 2015
National Park Service

U.S. Department of the Interior

Natural Resource Stewardship and Science

1201 Oakridge Drive, Suite 150

Fort Collins, CO 80525

www.nature.nps.gov

EXPERIENCE YOUR AMERICATM












CAHA Map Unit Properties Table (East Carolina University Map), Page 1 of 6

Cape Hatteras National Seashore: Geomorphic Map Unit Properties Table (East Carolina University Map; 1:10,000 scale) Group Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

BEACH FEATURES (BF)

Ocean Beach 

(BF_ocbeach)

Inlet Spit and Flat 

(BF_spit_flt)

Beach: a sand body that extends 

from the wet/dry line to the base 

of a dune field, scarped dune, or 

island berm crest.

Inlet Spit and Flat: subparallel 

sand ridges adjacent to modern 

or paleo-inlets. Characterized by 

curved ridge structures on gently 

ramped flats. 

Sediment Transport Processes—Units are frequently inundated 

during storms and high tides. Ridges form in response to overflow 

conditions. Barrier islands are continuously reshaped by the constant 

movement of sand by wind, waves, and currents. Storm winds move 

sand into the island interior and estuary, and build dunes. Overwash

builds island elevation, expands marsh platforms and estuarine 

shoals, and creates and maintains early-succession habitat.

Inlets—Created when storms drive surges across and through the 

island from the ocean or estuarine side. It widens by erosion and 

collapse of the adjacent bank, and deepens as flow scours the 

channel. They provide sediment to the back-barrier system through 

the growth of spits and delta deposits, which become platform 

marshes when the inlet closes.

Barrier Island Evolution and Behavior—Sediment availability and 

shoreline erosion patterns are influenced by the geologic framework 

of older stratigraphic units occurring beneath and seaward of the 

shoreface.

Barrier Island System Units—Predominantly sand.

Paleontological Resources—Fossils may wash ashore or be 

exposed.

Shoreline Erosion—Ocean shoreline change rates range from -2 

m/yr to 2 m/yr. Erosion rates and breach potential are highest north 

of Rodanthe, southern Pea Island, the Buxton and Isabel inlet areas, 

and northeastern Ocracoke Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses—Storms move sand 

across and off the island, create overwash and breaches, and drive 

landward migration. Overwash adds saline water to surficial aquifers 

and groundwater.

Inlet Modifications—Inlet modifications disrupt the inlet’s ability to 

provide sediment to downdrift shorelines. Newly opened inlets are 

often closed artificially to maintain the highway infrastructure. The 

Oregon Inlet terminal groin and revetment stopped erosion of 

northern Pea Island, but soundward accretion of the Bodie Island spit 

has narrowed and deepened the inlet. Oregon Inlet stabilization 

causes shoreline erosion of up to 4 m/yr on Pea Island.

Recreational and Watershed Land Use—ORV use disturbs beach 

ecosystems, damages backshore vegetation, limits seaward dune 

development, and prevents post-storm dune recovery.

Coastal Engineering and Shoreline Armoring—Seawalls, 

bulkheads, and other structures to inhibit wave action are expensive 

and accelerate erosion in front of the structures. Temporary soft 

stabilization (sandbags) have similar effects but are permitted in 

North Carolina. There have been 17 recorded beach nourishment 

projects in the park. Most nourishment sand is sourced from inlet 

deltas and channels; its removal destabilizes the inlets and impacts 

regional sediment budgets. Between 1962 and 2011, over 7.8 million 

m3 of sediment were emplaced on park beaches.

Highway 12 Transportation Corridor—Highway 12 is very 

vulnerable to shoreline erosion and storm overwash, and has been 

repeatedly damaged in numerous places in the last few decades. 

Debate over how to replace the route is ongoing.

Paleontological Resource Inventory, Monitoring, and

Protection— Beachcombers are allowed to collect unoccupied shells 

at Cape Hatteras National Seashore, but NPS policy states that fossils 

cannot be collected from NPS lands.

Beach unit is among the most indicative features of modern barrier 

island geomorphological processes. Spit and flat features are 

indicative of sand accretion during periodic overflow events and 

evolve in patterns. Cultural artifacts may wash ashore.

Habitat: Shorebird foraging. Wrack consisting of offshore algae 

(Sargassum spp.), dune grasses, submerged aquatic vegetation, and 

estuarine marsh grasses. Inlet spits support Spartina patens grasses, 

mixed grasses, and scrub shrub.
CAHA Map Unit Properties Table (East Carolina University Map), Page 2 of 6

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

OVERWASH-PLAIN FEATURES

UPPER OVERWASH RAMP (UO)

Sparse to 

Unvegetated 

(UO_unveg)

Grass

(UO_grass)

Scrub Shrub 

(UO_scrb_shrb)

Upper overwash ramp begins at 

the island berm crest with a 

slightly undulating surface and 

slopes of varying degrees to the 

middle overwash ramp, lower 

overwash ramp, or adjacent 

estuary. Small isolated dunes are 

present locally. 

Sparse to unvegetated: 

dominated by salty groundwater 

with a surface of xeric 

vegetation. 

Vegetative cover increases 

successively away from the 

beach to grass- and shrubdominated areas on the upper 

ramp. 

Shrub: communities expand 

oceanward on very wide ramps 

with dune fields or ridges.

Sediment Transport Processes—Barrier islands are continuously 

reshaped by the constant movement of sand by wind, waves, and 

currents. Overwash builds island elevation, expands marsh platforms 

and estuarine shoals, and creates and maintains early-succession 

habitat.

Inlets—Created when storms drive surges across and through the 

island from the ocean or estuarine side. It widens by erosion and 

collapse of the adjacent bank, and deepens as flow scours the 

channel. They provide sediment to the back-barrier system through 

the growth of spits and delta deposits, which become platform 

marshes when the inlet closes.

Freshwater Aquifers—Units have a relatively deep freshwater table 

or salty groundwater; farther from the beach, freshwater dominates 

and the water table rises. The dunes near Theoff Point at the 

southern end of Bodie Island are favorable for fresh groundwater 

development because they are unlikely to be inundated by salt water 

or overwash.

Barrier Island System Units—Predominantly sand with shell gravel 

pavements that may contain paleontological resources.

Shoreline Erosion—Ocean shoreline change rates range from -2 

m/yr to 2 m/yr. Erosion rates and breach potential are highest north 

of Rodanthe, southern Pea Island, the Buxton and Isabel inlet areas,

and northeastern Ocracoke Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion and landward migration.

Hurricane Impacts and Human Responses—Storms move sand 

across and off the island, create overwash and breaches, and drive 

landward migration. Overwash adds saline water to surficial aquifers 

and groundwater.

Highway 12 Transportation Corridor—Highway 12 is very 

vulnerable to shoreline erosion and storm overwash, and has been 

repeatedly damaged in numerous places in the last few decades. 

Debate over how to replace the route is ongoing.

Units record landward changes in morphology and vegetation in 

overwash ramp areas. Successive landform development and 

vegetation give important relative age dates for island development. 

Cultural artifacts may wash ashore.

Habitat: Xeric vegetation dominated by firewheel (Gaillardia 

pulchella), prickly pear cactus (Opuntia spp.), and scattered eastern 

red cedar (Juniperus virginiana), lichens, moss. Grass flat communities 

include sea oats (Uniola paniculata), salt meadow hay (Spartina 

patens), broomstraw rush (Andropogon scoparius), pennywort 

(Hydrocotyle bonariensis), sea rocket (Cakile edentula). Shrub habitat 

dominated by salt myrtle (Baccharis halimifolia), wax myrtle (Myrica 

cerifera), yaupon holly (Ilex vomitoria), marsh elder (Iva frutescens), 

bayberry (Myrica pensylvanica), eastern red cedar (Juniper virginiana), 

salt meadow hay (Spartina patens), cat brier (Smilax spp.), poison ivy 

(Toxicodendron radicans), Virginia creeper (Parthenocissus 

quinquefolia).

Foredune 

(UO_fdune)

Urban 

(UO_urbdune)

Foredune: natural features 

forming along the uppermost 

portion of the overwash plain 

with irregular geometry and 

variable size. Absent in areas 

where constructed dunes disrupt 

the natural sediment-supply 

process.

Sediment Transport Processes—Barrier islands are continuously 

reshaped by the constant movement of sand by wind, waves, and 

currents. Storm winds move sand into the island interior and estuary, 

and build dunes. Overwash builds island elevation.

Barrier Island System Units—Predominantly sand.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion and landward migration.

Hurricane Impacts and Human Responses—Units are 

continuously evolving through blowouts, cut and fill structures, and 

scarping. Sand inundation associated with active dunes.

Recreational and Watershed Land Use—ORV use disturbs beach 

ecosystems, damages backshore vegetation, limits seaward dune 

development, and prevents post-storm dune recovery.

Coastal Engineering and Shoreline Armoring—Seawalls, 

bulkheads, and other structures to inhibit wave action are expensive 

and accelerate erosion in front of the structures. Temporary soft 

stabilization (sandbags) have similar effects but are permitted in 

North Carolina. There have been 17 recorded beach nourishment 

projects in the park. Most nourishment sand is sourced from inlet 

deltas and channels; its removal destabilizes the inlets and impacts 

regional sediment budgets. Between 1962 and 2011, over 7.8 million 

m3 of sediment were emplaced on park beaches.

Natural dunes are rare in modern developed beach areas and serve as 

models for the evolution of barrier island systems.

Habitat: Locally vegetated by sea oats (Uniola paniculata) and on the 

lee side by salt meadow hay (Spartina patens), sea rocket (Cakile 

edentula), goldenrod (Solidago sempervirens), wax myrtle (Myrica 

cerifera), eastern red cedar (Juniper virginiana), and pennywort 

(Hydrocotyle bonariensis).

MIDDLE OVERWASH RAMP (MO)

Sparse to 

Unvegetated 

(MO_unveg)

Grass

(MO_grass)

Scrub Shrub 

(MO_scrb_shrb)

Forest

(MO_forest)

Middle overwash ramp is 

relatively flat, with a dry to damp 

surface. This unit occurs only on 

relatively wide islands.

Vegetation succession goes from 

unvegetated to grass to shrub to 

forest (if storm events are 

infrequent, ocean shoreline 

recession is slow, and/or a 

protective dune field is present).

Sediment Transport Processes—Overwash builds island elevation, 

expands marsh platforms and estuarine shoals, and creates and 

maintains early-succession habitat.

Freshwater Aquifer—Supply is recharged through rainfall and 

depleted through residential use, evapotranspiration from the surface 

and vegetation, and surface drainage from wetlands. Groundwater 

systems and aquifers can be affected by impoundments, weather 

conditions, and water withdrawal; these influences alter hydrologic 

processes, wetland function, and the distribution, composition, 

diversity, and structure of vegetation communities.

Barrier Island System Units—Predominantly sand. Erosion 

resistance is low to moderately low where forested.

Hurricane Impacts and Human Responses—Units are often 

slightly wet and inundated during storm events. Units are associated 

with infrequent, but pervasive, storm events that destroy or bury 

existing stabilizing vegetation. Overwash adds saline water to surficial 

aquifers and groundwater. Rainwater adds fresh water to surficial 

aquifers and groundwater.

Units form as a function of island size, sediment supply, overwash 

frequency, vegetation patterns, and island morphology. Unvegetated 

areas represent new overwash fans following major storm events.

May contain cultural resources.

Habitat: Grass species include salt meadow hay (Spartina patens) and 

broom straw (Andropogon scoparius). Scrub shrub species include salt 

myrtle (Baccharis halimifolia), wax myrtle (Myrica cerifera), yaupon 

holly (Ilex vomitoria), marsh elder (Iva frutescens), bayberry (Myrica 

pensylvanica), eastern red cedar (Juniper virginiana), salt meadow hay 

(Spartina patens), cat brier (Smilax spp.), poison ivy (Toxicodendron

radicans), Virginia creeper (Parthenocissus quinquefolia). Forest species 

include pine (Pinus spp.), live oak (Quercus virginiana), eastern red 

cedar (Juniper virginiana), wax myrtle (Myrica cerifera), yaupon holly 

(Ilex vomitoria), cat brier (Smilax spp.), poison ivy (Toxicodendron

radicans), and muscadine grape (Vitus rotundifolia).
CAHA Map Unit Properties Table (East Carolina University Map), Page 3 of 6

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

OVERWASH-PLAIN FEATURES

MIDDLE OVERWASH RAMP (MO)

Interior Marsh 

(MO_intmarsh)

Unit contains sandy, organic-rich 

soil with a high, fluctuating 

water table. Grades into 

platform marsh areas with a 

gentle decline in elevation, 

ranging from <1 m (39 in) to a 

few centimeters above mean sea 

level. 

Sediment Transport Processes—Frequently flooded by wind and 

storm tides and estuarine water flowing through tidal channels. 

Overwash builds island elevation, expands marsh platforms and 

estuarine shoals, and creates and maintains early-succession habitat.

Freshwater Aquifer—Supply is recharged through rainfall and 

depleted through residential use, evapotranspiration from the surface 

and vegetation, and surface drainage from wetlands. Groundwater 

systems and aquifers can be affected by impoundments, weather 

conditions, and water withdrawal; these influences alter hydrologic 

processes, wetland function, and the distribution, composition, 

diversity, and structure of vegetation communities.

Barrier Island System Units—Predominantly sand and peat. 

Erosion resistance is low.

Paleontological Resources—May contain pollen spores and other 

recent organic remains.

Hurricane Impacts and Human Responses—Overwash adds saline 

water to surficial aquifers and groundwater. Rainwater adds fresh 

water to surficial aquifers and groundwater.

Unit is interstitial between the middle overwash ramp and dry grass 

flat areas. Unit has a sandy substrate, in contrast to the peaty 

substrates of platform marsh areas.

Habitat: Algal mats, marsh vegetation including smooth cordgrass 

(Spartina alterniflora), salt meadow hay (Spartina patens), black 

needlerush (Juncus roemerianus), saltgrass (Distichlis spicata), sea 

oxeye (Borrichia frutescens), soft-stemmed bulrush (Scirpus robustus), 

sawgrass (Cladium jamaicense), common reed (Phragmites australis), 

giant cordgrass (Spartina cynosuroides), cattail (Typha angustiflora), 

depending on groundwater salinity.

Isolated Dunes 

(MO_isodune)

Ringed Dunes

and Beach 

Ridges 

(MO_rdune_br)

Urban Dune 

(MO_urbandune)

Paleo-inlet Spit 

(MO_p_inl_spt)

Isolated Dunes: common in 

unvegetated areas of the middle 

ramp, often on algal flats. 

Ringed Dunes: complicated 

geometries that form when 

isolated dunes are stabilized by 

vegetation through a process of 

dry-season sand trapping 

followed by wet-season 

reworking. 

Paleo-inlet Spits: subparallel 

ridges adjacent to inlets with 

curved ridge structures at 

oblique angles to the shoreline.

Barrier Island System Units—Predominantly sand. Hurricane Impacts and Human Responses—Units associated with 

sand inundation and can be prone to major storm flooding.

Units are typically fleeting and constantly evolving naturally and under 

human influence. Paleounits record past overflow and blowout 

events. Ringed dunes form around stabilized structures, such as 

Ocracoke Village.

Habitat: Isolated dunes may be stabilized by salt meadow hay 

(Spartina patens) or scrub shrub. Isolated ringed dunes may contain 

salt meadow hay (Spartina patens) and sea oxeye (Borrichia

frutescens).

LOWER OVERWASH RAMP (LO)

Platform Marsh 

(LO_pf_marsh)

The lower overwash ramp is a 

wet, flat, intertidal surface 

extending toward the backbarrier estuary, with strong 

vegetation zonation determined 

by salinity gradients. Marsh 

contains a <1-m- (3-ft-) thick 

peat or sandy peat substrate that 

is permanently water saturated. 

This unit often has tidal creek 

networks and occasional small 

ponds. Grades gently to a scarp 

abutting the estuary and a low 

fringing berm. 

Inlets—Created when storms drive surges across and through the 

island from the ocean or estuarine side. It widens by erosion and 

collapse of the adjacent bank, and deepens as flow scours the 

channel. They provide sediment to the back-barrier system through 

the growth of spits and delta deposits, which become platform 

marshes when the inlet closes.

Estuaries—Some sediment contributions is derived from erosion of 

the marsh shoreline.

Freshwater Aquifer—Supply is recharged through rainfall and 

depleted through residential use, evapotranspiration from the surface 

and vegetation, and surface drainage from wetlands. Groundwater 

systems and aquifers can be affected by impoundments, weather 

conditions, and water withdrawal; these influences alter hydrologic 

processes, wetland function, and the distribution, composition, 

diversity, and structure of vegetation communities.

Barrier Island System Units—Predominantly sand and peat. 

Frequently inundated and may locally contain quicksand or thick 

muck. 

Paleontological Resources—May preserve pollen.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses—Unit is constantly 

water saturated and should be avoided for infrastructure. Overwash 

adds saline water to surficial aquifers and groundwater. Rainwater 

adds fresh water to surficial aquifers and groundwater. High rainfall 

and flooding increases nutrients and sediments to the estuary, 

reduces estuarine salinity, and causes phytoplankton blooms.

Recreational and Watershed Land Use—Toxic and nuisance algal 

blooms may occur in tidal creeks, marshes, and ponds on

Ocracoke Island due to runoff or septic system leachate.

Wrack causes depressions, where it kills underlying marsh vegetation

and may eventually form ponds that vary from hypo- to hypersaline in 

wet/dry seasons. May preserve cultural artifacts.

Habitat: Decaying wrack deposits kill marsh platform vegetation, but 

are locally recolonized by sea oxeye (Borrichia frutescens), annual 

marsh glasswort (Salicornia bigelovii), perennial marsh glasswort 

(Salicornia virginica), saltgrass (Distichlis spicata), wax myrtle (Myrica

cerifera), marsh elder (Iva frutescens), salt myrtle (Baccharis

halimifolia).
CAHA Map Unit Properties Table (East Carolina University Map), Page 4 of 6

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

OVERWASH-PLAIN FEATURES

LOWER OVERWASH RAMP (LO)

Fringing Berm 

(LO_fring_brm)

Strandplain 

Beach 

(LO_spln_bch)

Back-Barrier 

Berm 

(LO_bk_br_bm)

Fringing Berms: up to 1 m (3 ft) 

in height and 1 to 3 m (3 to 9 ft) 

wide. These storm deposits are 

shore parallel <10 m (30 ft) from 

the edge of the platform marsh. 

Berm consists of mixed sand and 

peat. 

Strandplain Beaches: occur in 

eroded scarps and are often 

temporary or seasonal due to 

storm patterns. 

Back-Barrier Berms: form at the 

interface between estuarine and 

ocean storm–dominated systems 

and occur as ridges subparallel to 

the overwash plain. Berms are 

<2 m (6 ft) high and 25 m (77 ft) 

wide, and may have arcuate 

morphologies. 

Sediment Transport Processes—Low-lying areas are prone to 

inundation and some units are associated with storm surge events.

Storm winds move sand into the island interior and estuary. 

Overwash builds island elevation, and expands marsh platforms and 

estuarine shoals.

Inlets—Created when storms drive surges across and through the 

island from the ocean or estuarine side. It widens by erosion and 

collapse of the adjacent bank, and deepens as flow scours the 

channel. They provide sediment to the back-barrier system through 

the growth of spits and delta deposits, which become platform 

marshes when the inlet closes.

Barrier Island System Units—Predominantly peat and sand.

Shoreline Erosion—Estuarine shoreline change rates range from 

-1.2 m/yr (marsh) to 0.2 m/yr (beach). Estuarine erosion at Fort 

Raleigh NHS threatens infrastructure and cultural resources. The 

northern side of Ocracoke Village is eroding at 1.2 m/yr due to storm 

wind and waves from Pamlico Sound.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses—Storms move sand 

across and off the island, create overwash and breaches, and drive 

landward migration.

Recreational and Watershed Land Use—Constructed dune ridges 

have altered the park's ecosystem and geologic structure, minimized

overwash and inlet formation, modified habitat and back-barrier 

estuarine processes. They have resulted in narrower beaches, steeper 

shoreface, increased wave energy hitting the shoreface, marsh 

scarps, and decreased sound productivity.

Fringing berm buffers the lower overwash ramp from the sound and 

records timing of storm surge events. Units are strongly associated 

with storm events and may be present only temporarily. They record 

the evolution of the low-lying back-barrier area.

Habitat: Barren peat surfaces become colonized by Salicornia bigelovii, 

berms dominated by salt meadow hay (Spartina patens), giant 

cordgrass (Spartina cynosuroides), wax myrtle (Myrica cerifera), salt 

myrtle (Iva frutescens), black needlerush (Juncus roemerianus). Algal 

mats on strandplain beaches. Back-barrier berms provide habitat for 

eastern red cedar (Juniper virginiana), salt meadow hay (Spartina

patens), salt myrtle (Iva frutescens), marsh elder (Iva frutescens), wax 

myrtle (Myrica cerifera), and yaupon holly (Ilex vomitoria). Higher 

forested areas have pine (Pinus spp.), live oak (Quercus virginiana), 

eastern red cedar (Juniper virginiana), salt myrtle (Baccharis

halimifolia), marsh elder (Iva frutescens), wax myrtle (Myrica cerifera), 

and yaupon holly (Ilex vomitoria).

POLYDEMIC FEATURES (PF)

Tidal Creeks and Tidal 

Channels

(PF_tidal)

Pond

(PF_pond)

Tidal Creeks and Channels: form 

in platform marshes, may be fed 

by tides or fresh groundwater 

from higher island elevations. 

Overwash plain deposits may 

bury headwaters of creeks. 

Where tidal creeks erode 

between platform marsh 

segments, the classic molartooth geomorphology forms. 

Tidal channels are 3 to 4 m (9 to 

12 ft) deep, with steeply scarped 

peat shorelines. 

Ponds: formation, water 

composition, and duration in the 

general overwash plain vary. 

Many ponds are present as a 

function of the patterns, 

frequency, and abundance of 

storms and precipitation. 

Freshwater Aquifer—Supply is recharged through rainfall and 

depleted through residential use, evapotranspiration from the surface 

and vegetation, and surface drainage from wetlands. Groundwater 

systems and aquifers can be affected by impoundments, weather 

conditions, and water withdrawal; these influences alter hydrologic 

processes, wetland function, and the distribution, composition, 

diversity, and structure of vegetation communities.

Barrier Island System Units—Predominantly peat and sand. 

Erosion resistance is nonexistent. 

Paleontological Resources—May contain pollen.

Shoreline Erosion—Estuarine shoreline change rates range from

-1.2 m/yr (marsh) to 0.2 m/yr (beach).

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses Overwash adds saline 

water to surficial aquifers and groundwater. Rainwater adds fresh 

water to surficial aquifers and groundwater. High rainfall and 

flooding increases nutrients and sediments to the estuary, reduces 

estuarine salinity, and causes phytoplankton blooms.

Recreation and Watershed Land Use—Toxic and nuisance algal 

blooms may occur in tidal creeks, marshes, and ponds on Ocracoke 

Island due to runoff or septic system leachate.

Tidal creeks and channels are major forces of landscape change, 

eroding the upper platform areas. Ponds are constantly changing 

based on abundance of water and vary from open water to marshes 

and dried algal flats. May contain cultural resources.

Habitat: Perimeter areas may contain soft-stemmed bulrush (Scirpus

robustus), sawgrass (Cladium jamaicense), giant cordgrass (Spartina

cynosuroides), cat tail (Typha angustiflora), common reed (Phragmites

australis), and black needle rush (Juncus roemerianus). Ponds may 

contain algal mats and other marsh vegetation.

Transverse Ridges 

(PF_trnv_dune)

Dune Flat

(PF_dune_flat)

Transverse Ridges: long, low, 

straight ridges forming 

transverse to the long trend of a 

barrier island. Unit forms when 

temporarily ponded waves of 

storm surge rework dune sands 

or by truncation of a large dune 

system.

Dune Flats: form in areas of 

abundant sand supply as broad, 

rolling flat areas (elevation 2 to 3 

m [6 to 9 ft] higher than the 

island berm) downwind of the 

island berm. Maximum relief of 

sand flat areas is <2 m (6 ft). 

Sediment Transport Processes—Units are associated with active 

overwash and aeolian processes and are prone to sand and water 

inundation.

Barrier Island System Units—Predominantly sand.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses—Storms move sand 

across and off the island, create overwash and breaches, and drive 

landward migration. Overwash adds saline water to surficial aquifers 

and groundwater. Rainwater adds fresh water to surficial aquifers 

and groundwater.

Transverse dune ridges suggest former inlet locations. Dune flats 

record the anthropogenic impacts of urbanization on the barrier 

islands, as they become vegetated and stabilized when the sand 

supply is truncated by roads, structures, and other changes. Longstanding, stable dune flats support cultural resources at Kitty Hawk 

and Whalebone Junction.

Habitat: Vegetation ranges from nonexistent to some areas stabilized 

by sea oat (Uniola paniculata), salt meadow hay (Spartina patens), 

scrub shrubs such as salt myrtle (Baccharis halimifolia), marsh elder 

(Iva frutescens), wax myrtle (Myrica cerifera), yaupon holly (Ilex

vomitoria), and eastern red cedar (Juniper virginiana). The oldest, 

forested areas contain pine (Pinus spp.), live oak (Quercus virginiana), 

eastern red cedar (Juniper virginiana), cat brier (Smilax spp.), poison 

ivy (Toxicodendron radicans), and muscadine grape (Vitus

rotundifolia). Unit supports broad damp areas dominated by algae 

and freshwater marsh plants. Other species include salt meadow hay 

(Spartina patens), forests of pine (Pinus spp.), yaupon holly (Ilex

vomitoria), and live oak (Quercus virginiana).
CAHA Map Unit Properties Table (East Carolina University Map), Page 5 of 6

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

POLYDEMIC FEATURES (PF)

Dune Field

(PF_dunef)

Sparse to Unvegetated 

Dune Field 

(PF_dune_unvg)

Grassy Dune Field 

(PF_dune_grss)

Forested Dune Field 

(PF_dune_fors)

Urbanized Dune Field 

(PF_dune_urb)

Dune Fields: form atop dune flats 

when sand supply is sufficient. 

Dune heights range from 3 to 25 

m (9 to 77 ft) or more. Dune 

morphology varies with 

formation process and wind 

direction. Dune vegetation varies 

from nonexistent to forested and 

urbanized, depending on sand 

supply.

Infrastructure has stabilized dune 

areas at Kill Devil Hills, Nags 

Head Cove, the northern end of 

Jockey’s Ridge, Kitty Hawk, and 

the southern half of the Seven 

Sisters dune field.

Barrier Island System Units—Predominantly sand.

Paleontological Resources—May contain paleontological resources 

(paleosol horizons).

Recreational and Watershed Land Use—Constructed dune ridges 

have altered the park's ecosystem and geologic structure, minimized

overwash and inlet formation, modified habitat and back-barrier 

estuarine processes. They have resulted in narrower beaches, steeper 

shoreface, increased wave energy hitting the shoreface, marsh 

scarps, and decreased sound productivity. Along the barrier segment 

between Avon and Buxton, this has resulted in substantial island 

narrowing and four relocations of Highway 12.

Large sand supplies (from paleo–Roanoke River delta deposits) record 

previous climatic conditions and sea-level stands that built sedimentrich or complex barrier island segments. Unit features prominently in 

photographs by the Wright brothers. Kill Devil Hill was used by the 

Wright brothers and is now stabilized. Contains cultural resources 

(buried soil profiles that may record early settlement)

Habitat: Prior to 1930s stabilization efforts, dunes were virtually void 

of vegetation except some minor salt meadow hay (Spartina patens). 

Heavy forests on the Nags Head Woods dune field, unit supports 

mixed hardwood and pine forest with a scrub shrub perimeter.

Algal Flat

(PF-algal_flt)

Ridge and Swale 

(PF_rdg_swl)

Swale Marsh 

(PF_swl_marsh)

Paleo-inlet Spit 

(PF_p_inl_spt)

Algal Flats: dominate the lower 

supratidal portion of the 

overwash area and form in 

ephemeral ponds or depressions. 

Unit persists in highly fluctuating 

salinity. 

Ridges and Swales: subparallel 

couplets of low, regular sand 

ridges (<3 m [9ft] high) and 

adjacent shallow swales.

Sediment Transport Processes—Storm winds move sand into the 

island interior and estuary, and build dunes. Overwash builds island 

elevation.

Capes and Cape-Associated Shoals—Alongshore sediment 

transport is toward the tip of Cape Hatteras, so that the sediment 

loads from the south and from the north meet and are deposited at 

Diamond Shoals.

Inlets—Created when storms drive surges across and through the 

island from the ocean or estuarine side. It widens by erosion and 

collapse of the adjacent bank, and deepens as flow scours the 

channel. They provide sediment to the back-barrier system through 

the growth of spits and delta deposits, which become platform 

marshes when the inlet closes.

Estuaries—The sounds provide habitat for birds, seagrass, oysters, 

and mid-Atlantic fish. Most sand in Core Sound and central and 

eastern Pamlico Sound is derived from barrier islands and offshore 

sediments carried through inlets and overwash fans. Additional major 

contributions are from rivers, shoreline erosion and biogenic 

production.

Barrier Island System Units—Predominantly sand and peat. Algal 

flats are frequently flooded by waters of varying salinity.

Shoreline Erosion—Estuarine shoreline change rates range from

-1.2 m/yr (marsh) to 0.2 m/yr (beach).

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion, landward migration, and 

conversion of tidal wetlands to open water.

Hurricane Impacts and Human Responses—Overwash adds saline 

water to surficial aquifers and groundwater. Rainwater adds fresh 

water to surficial aquifers and groundwater.

Recreational and Watershed Land Use—Toxic and nuisance algal 

blooms may occur in Hatteras Island swales that are impacted by 

runoff or septic system leachate. Groundwater withdrawals can 

disrupt habitat by limiting plant species richness and diversity in 

nearby swales.

Algal mats can persist in conditions ranging from freshwater to 

hypersaline. No ridge and swale structure is forming today on the 

northern Outer Banks, but unit provides important age dates for sealevel highstand events. Units are among the oldest landforms present 

on the barrier islands. Many swales are dredged as navigational 

channels. May contain evidence of early settlements (<500 years old).

Habitat: Perimeter of algal flats contains annual marsh glasswort 

(Salicornia bigelovii), perennial marsh glasswort (Salicornia virginica), 

saltgrass (Distichlis spicata), and sea oxeye (Borrichia frutescens). Sand 

ridges are heavily vegetated with mixes of pine and hardwood. Swales 

are dominated by wetland vegetation.

ANTHROPOGENIC FEATURES (AF)

Constructed Dune 

Ridges

(AF_cn_dune_r)

Constructed Interior 

Dune Ridges 

(AF_cn_idune)

Constructed Dune Ridges and 

Interior Dune Ridges: linear, 

ocean-parallel sand ridges built 

by bulldozers, then artificially 

vegetated with grass. Generally 

about 15 m (45 ft) wide at the 

base and up to 5 m (15 ft) high. 

Barrier Island System Units—Predominantly sand.

Shoreline Erosion—Ocean shoreline change rates range from 

-2 m/yr to 2 m/yr. Erosion rates and breach potential are highest 

north of Rodanthe, southern Pea Island, the Buxton and Isabel inlet 

areas, and northeastern Ocracoke Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and 

inlet formation will continue to change island morphology. Sea-level 

rise may accelerate shoreline erosion.

Hurricane Impacts and Human Responses—Storms erode 

protective dunes.

Recreational and Watershed Land Use—Constructed dune ridges 

have altered the park's ecosystem and geologic structure, minimized

overwash and inlet formation, modified habitat and back-barrier 

estuarine processes. They have resulted in narrower beaches, steeper 

shoreface, increased wave energy hitting the shoreface, marsh 

scarps, and decreased sound productivity. Along the barrier segment 

between Avon and Buxton, this has resulted in substantial island 

narrowing and four relocations of Highway 12.

Units are out of equilibrium and are rapidly scarped on the ocean side 

and breached by storm surges. Units protect buildings and roads by 

preventing storm overwash and inlet migration. Units began in the 

1930s with Works Progress Administration and Civilian Conservation 

Corps work camps.

Habitat: Vegetation planted on these units includes sea oats (Uniola

paniculata), American beachgrass (Ammophila breviligulata), salt 

meadow hay (Spartina patens). Older ridges become vegetated with 

salt myrtle (Baccharis halimifolia), marsh elder (Iva frutescens), wax 

myrtle (Myrica cerifera), yaupon holly (Ilex vomitoria), and eastern red 

cedar (Juniper virginiana).
CAHA Map Unit Properties Table (East Carolina University Map), Page 6 of 6

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Resource Management Issues Geologic History and Habitat

ANTHROPOGENIC FEATURES (AF)

Road/Parking Areas

(AF_rd_prk)

Dredge Channels/Spoils 

(AF_drdge)

Excavations 

(AF_excavate)

Anthropic Overprint 

(AF_an_overpr)

Paved Areas: include roads, 

highways, and parking lots. 

Dredge Channels and Pits: 

sediment removal areas with 

most dredged material pumped 

offsite or deposited adjacent to 

the dredged area. Dredge often 

appears as linear ridges or 

rounded mounds. 

Excavations: artificially round or 

rectangular water features 

(including marinas and harbors) 

where sand was mined for 

constructed dune features. 

Anthropogenic Overprint: 

includes major urban areas with 

dense patterns of structures, 

parking lots, and roads.

Barrier Island System Units—Predominantly soil, sand, and gravel.

Inlet Modifications—The US Army Corps of Engineers sealed the 

2003 Hurricane Isabel Inlet breach using sand dredged from the 

federally maintained ferry channel between Hatteras and Ocracoke 

islands. Sand dredged from Oregon Inlet was deposited offshore 

from 1960 to 1983, and was artificially bypassed to Pea Island 

beaches between 1983 and 2009.

Recreational and Watershed Land Use—Impervious surface 

increases pollutant and nutrient runoff, degrading estuarine habitat.

Constructed drainage ditches affect water distribution and quality on 

Bodie and Hatteras islands. Toxic and nuisance algal blooms may 

occur in nutrient-enriched drainage ditches on Bodie Island.

Coastal Engineering and Shoreline Armoring—Seawalls, 

bulkheads, and other structures to inhibit wave action are expensive 

and accelerate erosion in front of the structures. Temporary soft 

stabilization (sandbags) have similar effects but are permitted in 

North Carolina. There have been 17 recorded beach nourishment 

projects in the park. Most nourishment sand is sourced from inlet 

deltas and channels; its removal destabilizes the inlets and impacts 

regional sediment budgets. Between 1962 and 2011, over 7.8 million 

m3 of sediment were emplaced on park beaches.

Highway 12 Transportation Corridor—Highway 12 is very 

vulnerable to shoreline erosion and storm overwash, and has been 

repeatedly damaged in numerous places in the last few decades. 

Debate over how to replace the route is ongoing.

Units record the human presence on the barrier islands. Units 

associated with urban development and access to natural areas. 

Anthropogenic unit includes cemeteries, monuments, Coast Guard 

stations, and camp grounds.

Habitat: Inundated dredged areas contain salt myrtle (Baccharis

halimifolia), marsh elder (Iva frutescens), salt meadow hay (Spartina

patens), giant cordgrass (Spartina cynosuroides), and scrub shrub. 

Above the supratidal zone, dredged areas contain wax myrtle (Myrica

cerifera), yaupon holly (Ilex vomitoria), northern bayberry (Myrica

pensylvanica), pine (Pinus spp.), eastern red cedar (Juniper virginiana), 

salt meadow hay (Spartina patens), cat brier (Smilax spp.), and poison 

ivy (Toxicodendron radicans).
CAHA Map Unit Properties Table (NC Geological Survey Map), Page 1 of 5

Cape Hatteras National Seashore: Geomorphic Map Unit Properties Table (North Carolina Geological Survey Map; 1:24,000 scale) Group Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Issues Geologic History and Habitat

INTERTIDAL FEATURES

Beach

(beach)

Area between the ocean shoreline 

(wet/dry line) and the toe of the 

Fore-island Dune Complex with a 

narrow, steep profile.

Sediment Transport Processes—Barrier islands are continuously reshaped 

by the constant movement of sand by wind, waves, and currents. Overwash 

builds island elevation and creates and maintains early-succession habitat.

Capes and Cape-Associated Shoals—Alongshore sediment transport is

toward the tip of Cape Hatteras, so that the sediment loads from the south 

and from the north meet and are deposited at Diamond Shoals.

Barrier Island Evolution and Behavior—Sediment availability and 

shoreline erosion patterns are influenced by the geologic framework of 

older stratigraphic units occurring beneath and seaward of the shoreface.

Barrier Island System Units—Predominantly sand. Periodic flooding 

during storms and high lunar tides, especially near inlets.

Paleontological Resources—Fossils may wash ashore or be exposed.

Shoreline Erosion—Ocean shoreline change ranges from -2 m/yr to 2 m/yr. 

Erosion rates and breach potential are highest north of Rodanthe, southern 

Pea Island, the Buxton and Isabel inlet areas, and northeastern Ocracoke 

Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion and landward migration.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches, and drive landward migration.

Inlet Modifications—Modifications disrupt sediment transport to downdrift

shorelines. Newly opened inlets are often closed artificially to maintain the 

highway infrastructure. The Oregon Inlet terminal groin and revetment 

stopped erosion of northern Pea Island, but soundward accretion of the Bodie 

Island spit has narrowed and deepened the inlet. Oregon Inlet stabilization 

causes shoreline erosion of up to 4 m/yr on Pea Island.

Recreational and Watershed Land Use—ORV use disturbs beach 

ecosystems, damages backshore vegetation, limits seaward dune 

development, and prevents post-storm dune recovery.

Coastal Engineering and Shoreline Armoring—Seawalls and other 

structures to inhibit wave action are expensive and accelerate erosion in front 

of the structures. Temporary soft stabilization (sandbags) have similar effects 

but are permitted in North Carolina. Most nourishment sand is sourced from 

inlet deltas and channels; its removal destabilizes the inlets and impacts 

regional sediment budgets. Between 1962 and 2011, over 7.8 million m3 of 

sediment were emplaced on park beaches.

Highway 12 Transportation Corridor—Highway 12 is very vulnerable to 

shoreline erosion and storm overwash, and has been repeatedly damaged in 

numerous places in the last few decades. Debate over how to replace the 

route is ongoing.

Paleontological Resource Inventory, Monitoring, and Protection—

Beachcombers are allowed to collect unoccupied shells at Cape Hatteras 

National Seashore, but NPS policy states that fossils cannot be collected from 

NPS lands.

Beach unit is among the most indicative features of modern 

barrier island geomorphological processes. Spit and flat 

features are indicative of sand accretion during periodic 

overflow events and evolve in patterns. Cultural artifacts may 

wash ashore.

Habitat: Active wave area habitat for shorebirds and other 

marine life.
CAHA Map Unit Properties Table (NC Geological Survey Map), Page 2 of 5

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Issues Geologic History and Habitat

INTERTIDAL FEATURES

SPIT COMPLEX

Sand Flat

(sand_flat)

Ridge and 

Swale 

(ridge_swale)

Sand Flats: unvegetated, low (<1 

m [4 ft]) elevation and relief; 

merge with the beach along the 

shoreline. 

Ridge and Swale: components 

situated lateral to sand flats, 

merging toward the interior and 

trending subparallel to the axis of 

the barrier island; curve toward 

the back of the island closer to the 

inlet. 

Sediment Transport Processes—Sand flats are subject to regular tidal 

flooding and overwash. Barrier islands are continuously reshaped by the 

constant movement of sand by wind, waves, and currents. Storm winds 

move sand into the island interior and estuary and build dunes. Overwash 

builds island elevation and creates and maintains early-succession habitat.

Capes and Cape-Associated Shoals—Alongshore sediment transport is 

toward the tip of Cape Hatteras, so that the sediment loads from the south 

and from the north meet and are deposited at Diamond Shoals.

Freshwater Aquifer—Supply is recharged through rainfall and depleted 

through residential use, evapotranspiration from the surface and 

vegetation, and surface drainage from wetlands. Groundwater systems and 

aquifers can be affected by impoundments, weather conditions, and water 

withdrawal; these influences alter hydrologic processes, wetland function, 

and the distribution, composition, diversity, and structure of vegetation 

communities. The dunes near Theoff Point at the southern end of Bodie 

Island are favorable for fresh groundwater development because they are 

unlikely to be inundated by salt water or overwash.

Barrier Island System Units—Predominantly sand. Ridge and swale areas 

represent older and more stable portions of the spit complex.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion and landward migration.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches, and drive landward migration.

Inlet Modifications—Soundward accretion of the Bodie Island spit has 

narrowed and deepened the stabilized Oregon Inlet.

Recreational and Watershed Land Use—ORV use disturbs beach 

ecosystems, damages backshore vegetation, limits seaward dune 

development, and prevents post-storm dune recovery. Toxic and nuisance 

algal blooms may occur in Hatteras Island swales that are impacted by runoff 

or septic system leachate. Groundwater withdrawals can disrupt habitat by 

limiting plant species richness and diversity in nearby swales.

Highway 12 Transportation Corridor—Highway 12 is very vulnerable to 

shoreline erosion and storm overwash, and has been repeatedly damaged in 

numerous places in the last few decades. Debate over how to replace the 

route is ongoing.

Sand flats are generally associated with first development of 

Fore-island Dune Complex.

Habitat: Algae crusts, episodic ponded water.

Marsh Platform 

(pf_marsh)

Unit is present along tidal creeks 

as low-lying areas (<1 m [2 to 3 ft] 

elevation) and developed in 

depressions between relict ridges 

or behind former sand flats. 

Approximately 1 m (several feet) 

of localized peat development 

during sea-level rise.

Sediment Transport Processes—Marsh areas are subject to regular tidal 

flooding and storm overwash. Barrier islands are continuously reshaped by 

the constant movement of sand by wind, waves, and currents. Storm winds 

move sand into the estuary. Overwash builds island elevation, expands

marsh platforms and estuarine shoals, and creates and maintains earlysuccession habitat.

Inlets—Created when storms drive surges across and through the island 

from the ocean or estuarine side. It widens by erosion and collapse of the 

adjacent bank, and deepens as flow scours the channel. They provide 

sediment to the back-barrier system through the growth of spits and delta 

deposits, which become platform marshes when the inlet closes.

Barrier Island System Units—Predominantly peat and sand (from 

overwash).

Paleontological Resources—May contain pollen.

Shoreline Erosion—Estuarine shoreline change rates range from -1.2 m/yr 

(marsh) to 0.2 m/yr (beach). The northern side of Ocracoke Village is eroding 

at -1.2 m/yr due to storm wind and waves from Pamlico Sound.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion, landward migration, and conversion of tidal 

wetlands to open water.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches. Overwash adds saline water to 

surficial aquifers and groundwater. Rainwater adds fresh water to surficial 

aquifers and groundwater. High rainfall and flooding increases nutrients and 

sediments to the estuary, reduces estuarine salinity, and causes 

phytoplankton blooms.

Recreational and Watershed Land Use —Toxic and nuisance algal blooms 

may occur in tidal creeks, marshes, and ponds on Ocracoke Island due to 

runoff or septic system leachate.

Marsh elevations correspond to sea level and are sensitive to 

sediment supply. May contain cultural resources.

Habitat: Grasses such as Juncus and Spartina patens.

INTERTIDAL AND SUPRATIDAL 

FEATURE

BEACH AND FORE-ISLAND 

DUNE COMPLEX

Dune Saddle 

(dnesadl_bch)

Gaps or breaks along dune ridges 

in beach and fore-island dune 

systems with elevations <3 m (10 

ft).

Sediment Transport Processes—Barrier islands are continuously reshaped 

by the constant movement of sand by wind, waves, and currents. Storm 

winds move sand into the island interior and build dunes. Overwash builds 

island elevation and creates and maintains early-succession habitat.

Inlets—Created when storms drive surges across and through the island 

from the ocean or estuarine side. It widens by erosion and collapse of the 

adjacent bank, and deepens as flow scours the channel. They provide 

sediment to the back-barrier system through the growth of spits and delta 

deposits, which become platform marshes when the inlet closes.

Barrier Island System Units—Predominantly sand. 

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology.

Hurricane Impacts and Human Responses—Saddles represent potential 

high-water flow pathways that are vulnerable to coastal flooding during 

storms. Storms move sand across and off the island, create overwash and 

breaches. Overwash adds saline water to surficial aquifers and groundwater. 

Rainwater adds fresh water to surficial aquifers and groundwater.

Important features for predicting future overwash channels or 

inlets.

Habitat: May provide local protection from prevailing winds.
CAHA Map Unit Properties Table (NC Geological Survey Map), Page 3 of 5

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Issues Geologic History and Habitat

SUPRATIDAL FEATURES

FORE-ISLAND DUNE COMPLEX

Dune Ridges 

(dunerdge)

Unit is present as prominent, 

linear, shore-parallel sand ridges 

separated by swales. As many as 

three distinct ridges crop out 

locally, with heights generally <7 

m (20 ft). Toe elevations are 2 to 3 

m (6 to 8 ft) toward the ocean 

and 1 to 3 m (4 to 8 ft) toward 

the island interior.

Barrier Island System Units—Predominantly sand.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches. Overwash adds saline water to 

surficial aquifers and groundwater. Rainwater adds fresh water to surficial 

aquifers and groundwater.

Recreational and Watershed Land Use—Constructed dune ridges have 

altered the park's ecosystem and geologic structure, minimized overwash and 

inlet formation, modified habitat and back-barrier estuarine processes. They 

have resulted in narrower beaches, steeper shoreface, increased wave energy 

hitting the shoreface, marsh scarps, and decreased sound productivity. Along 

the barrier segment between Avon and Buxton, this has resulted in 

substantial island narrowing and four relocations of Highway 12.

Form prominent and extensive portions of Fore-island Dune 

Complex, important sediment supply for the system. May 

contain cultural resources (artifacts).

Habitat: None documented.

FORE-ISLAND DUNE COMPLEX, DUNE RIDGE

Interdune Swale 

and Dune Ridge 

(intswale_dr)

Dune Saddle 

and Dune Ridge 

(dnesadl_dr)

Swales: closed, relatively low-lying 

areas in dune complexes with 

bases <3 m (10 ft) in elevation. 

Saddles: gaps or breaks along 

dune ridge lines with an elevation 

threshold of <2 m (10 ft).

Sediment Transport Processes—Barrier islands are continuously reshaped 

by the constant movement of sand by wind, waves, and currents. Storm 

winds move sand into the island interior and estuary, and builds dunes. 

Overwash builds island elevation, expands marsh platforms and estuarine 

shoals, and creates and maintains early-succession habitat.

Inlets—Created when storms drive surges across and through the island 

from the ocean or estuarine side. It widens by erosion and collapse of the 

adjacent bank, and deepens as flow scours the channel. They provide 

sediment to the back-barrier system through the growth of spits and delta 

deposits, which become platform marshes when the inlet closes.

Barrier Island System Units—Predominantly sand.

Shoreline Erosion—Erosion rates and breach potential are highest north of 

Rodanthe, southern Pea Island, the Buxton and Isabel inlet areas, and 

northeastern Ocracoke Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion.

Hurricane Impacts and Human Responses—Dune saddles represent 

potential high-water flow pathways or breach points that are vulnerable to 

coastal flooding during storms. Storms create overwash and breaches. 

Overwash adds saline water to surficial aquifers and groundwater. Rainwater 

adds fresh water to surficial aquifers and groundwater.

Recreational and Watershed Land Use—Toxic and nuisance algal blooms 

may occur in Hatteras Island swales that are impacted by runoff or septic 

system leachate. Groundwater withdrawals can disrupt habitat by limiting 

plant species richness and diversity in nearby swales.

Important features for predicting future overwash channels or 

inlets; if they remain stable, swales may become marshy areas.

Habitat: May provide local protection from prevailing winds.

OVERWASH COMPLEX

Overwash Flat

(owflat)

Overwash Flat 

and Overwash 

Channel 

(owflt_owchn)

Overwash Flats: long-term 

accumulations of sand overwash 

behind the Fore-island Dune 

Complex, often in lobate forms. 

Overwash Channels: linear 

features associated with cuts 

through the fore-island dune.

Sediment Transport Processes—Associated with overwash during 

seasonal high tides and storm events. Barrier islands are continuously 

reshaped by the constant movement of sand by wind, waves, and currents. 

Overwash builds island elevation, expands marsh platforms and estuarine 

shoals, and creates and maintains early-succession habitat.

Barrier Island System Units—Predominantly sand.

Shoreline Erosion—Ocean shoreline change rates range from -2 m/yr to 2 

m/yr. Erosion rates and breach potential are highest north of Rodanthe, 

southern Pea Island, the Buxton and Isabel inlet areas, and northeastern 

Ocracoke Island.

Coastal Vulnerability and Sea-Level Rise—Erosion, overwash, and inlet 

formation will continue to change island morphology. Sea-level rise may 

accelerate shoreline erosion and landward migration.

Hurricane Impacts and Human Responses—Units are frequently reworked 

during storms.

Flats are deposited as lobes in discrete events, then reworked 

by wind, water, and humans into large flats.

Habitat: Early-succession. Shorebird foraging. If stable for a 

sufficiently long period, can support vegetation.

Overwash Fan

(owfan)

Well defined locally as individual 

lobes from discrete storm events. 

Often with associated channels.

Sediment Transport Processes—Barrier islands are continuously reshaped 

by the constant movement of sand by wind, waves, and currents. Overwash

builds island elevation, expands marsh platforms and estuarine shoals, and 

creates and maintains early-succession habitat.

Barrier Island System Units—Forms during storm events and is prone to 

flooding. Predominantly sand.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches, and drive landward 

migration.Overwash adds saline water to surficial aquifers and groundwater.

Recreational and Watershed Land Use—Constructed dune ridges have 

minimized overwash and inlet formation.

Unit records discrete storm events (obvious on satellite 

imagery) and can be used to date overwash events during 

island development. Cultural resources (artifacts) may wash 

ashore during storms.

Habitat: Early-succession. Shorebird foraging. If stable for a 

sufficiently long period, can support vegetation.

Isolated Dunes 

(isodune)

Isolated dunes occur in the 

overwash flat area and/or farther 

inward as remnants of former 

fore-island dune ridges or as sand 

accumulations due to local traps. 

Barrier Island System Units—Predominantly sand. Unit is localized and 

can be associated with anthropogenic features.

Hurricane Impacts and Human Responses—Storms move sand across and 

off the island, create overwash and breaches, and drive landward migration

Recreational and Watershed Land Use—Constructed dune ridges have 

altered the park's ecosystem and geologic structure, minimized overwash and 

inlet formation, modified habitat and back-barrier estuarine processes. They 

have resulted in narrower beaches, steeper shoreface, increased wave energy 

hitting the shoreface, marsh scarps, and decreased sound productivity. Along 

the barrier segment between Avon and Buxton, this has resulted in 

substantial island narrowing and four relocations of Highway 12.

Isolated unit can be remnant of former dune ridge or form as 

a result of sand trapping by vegetation or fencing. Interior 

dune sand source is enigmatic; its identification requires more 

research.

Habitat: Vegetation may trap sand, forming isolated dunes.
CAHA Map Unit Properties Table (NC Geological Survey Map), Page 4 of 5

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Issues Geologic History and Habitat

SUPRATIDAL FEATURES

Interior Dunes

(intdune)

Interior Marsh

(inmarsh)

Back-Barrier Berm 

(bk_br_brm)

Interior Dunes: large-scale dunes 

that are the highest points of 

some islands (3 to 30 m [10 to 90 

ft] elevation). Can occur as single 

ridges or be more laterally 

extensive. 

Interior marshes: develop adjacent 

to water bodies, often in swales of 

relict beach ridge complexes or 

interior lowlands. 

Berms: subtle linear features 

adjacent to and slightly higher 

than marsh platforms. Up to 3 m 

(10 ft) high with complex internal 

morphology.

Inlets—Created when storms drive surges across and through the island 

from the ocean or estuarine side. It widens by erosion and collapse of the 

adjacent bank, and deepens as flow scours the channel. They provide 

sediment to the back-barrier system through the growth of spits and delta 

deposits, which become platform marshes when the inlet closes.

Barrier Island System Units—Interior Dunes and Back-Barrier Berm are 

sand. Interior Marsh is organic-rich sandy soil.

Paleontological Resources—May contain pollen.

Hurricane Impacts and Human Responses—Dune unit can inundate local 

areas with sand deposits. Units should be avoided for recreation due to active 

dune formation or delicate marsh habitat. Rainwater adds fresh water to 

surficial aquifers and groundwater.

Recreational and Watershed Land Use—Toxic and nuisance algal blooms 

may occur in swales on Hatteras Island, and in tidal creeks, marshes, and 

ponds on Ocracoke Island, that are impacted by runoff or septic system 

leachate. Groundwater withdrawals can disrupt habitat by limiting plant 

species richness and diversity in nearby swales.

Interior dune sand source is enigmatic; its identification 

requires more research. Marshes may be freshwater, berms 

tend to form in broad arcs of apparent relict flood tidal deltas, 

possibly due to the reworking of delta sand bodies by wave 

action.

Habitat: Vegetation stabilizes interior dunes, providing habitat 

for plants preferring well-drained conditions. Marsh vegetation 

is prominent. Berms support leafy vegetation.

RELICT FEATURES

Relict Beach Ridge 

Complex

(rel_bch_rdge)

Relict Spit Complex 

(rel_splt)

Water Body

(water)

Relict Beach Ridges: crop out as 

sets of parallel ridges and swales 

in interior portions of islands. 

Elevation reaches 0 m (30 ft). 

Relict Spits: subtle arcuate-shaped 

ridges and swales in back-island 

areas with no active inlet 

connection. 

Water Bodies: ponds, streams, and 

other perennial water features; 

does not include ephemeral 

features.

Capes and Cape-Associated Shoals—Alongshore sediment transport is 

toward the tip of Cape Hatteras, so that the sediment loads from the south 

and from the north meet and are deposited at Diamond Shoals.

Freshwater Aquifer—Supply is recharged through rainfall and depleted 

through residential use, evapotranspiration from the surface and 

vegetation, and surface drainage from wetlands. Groundwater systems and 

aquifers can be affected by impoundments, weather conditions, and water 

withdrawal; these influences alter hydrologic processes, wetland function,

and the distribution, composition, diversity, and structure of vegetation 

communities. The high and wide island mass at Buxton Woods are 

favorable for fresh groundwater development because they are unlikely to 

be inundated by salt water or overwash. 

Barrier Island System Units—Predominantly sand, and peat in local 

marshes. Erosion resistance is very low to low if vegetated.

Hurricane Impacts and Human Responses—Rainwater adds fresh water to 

surficial aquifers and groundwater.

Recreational and Watershed Land Use—Toxic and nuisance algal blooms 

may occur in drainage ditches on Bodie Island, in swales on Hatteras Island, 

and in tidal creeks, marshes, and ponds on Ocracoke Island, that are 

impacted by runoff or septic system leachate. Groundwater withdrawals can 

disrupt habitat by limiting plant species richness and diversity in nearby 

swales.

At least 13 sequences of relict beach ridges are mappable 

locally.

Habitat: Marsh vegetation in interior areas, leafy vegetation on 

dunes.

ANTHROPOGENIC FEATURES

Airport/Landing Strip

(airport_land)

Commercial/Industrial 

Facility

(comm_indust)

Airport: includes buildings and 

pavement near Buxton, Ocracoke, 

and Wright Brothers memorial 

areas.

Commercial Facilities: includes 

marinas, ferry terminals, parking 

lots, and buildings.

Barrier Island System Units—Predominantly sand, gravel, and building 

materials. Historical structures such as lighthouses and guard houses are 

associated with these units.

Recreational and Watershed Land Use—Impervious surface increases 

pollutant and nutrient runoff, degrading estuarine habitat.

Coastal Engineering and Shoreline Armoring—Seawalls, bulkheads, and 

other structures to inhibit wave action are expensive and accelerate erosion in 

front of the structures. Temporary soft stabilization (sandbags) have similar 

effects but are permitted in North Carolina.

Units record the history of human presence on the barrier 

islands.

Habitat: Plants and animals adaptable to human presence.

Dredge/Spoil

(drdge)

Filled

(filled)

Dredge/Spoil: includes features of 

positive relief with obvious source 

areas within waterways. There 

have been five recorded dredging 

projects within or immediately 

adjacent to the park.

Fill Areas: often include wetlands 

and exhibit linear boundaries and

atypically high elevations.

Estuaries—Most sand in Core Sound and central and eastern Pamlico 

Sound is derived from barrier islands and offshore sediments carried 

through inlets and overwash fans. Additional major contributions are from 

rivers, shoreline erosion and biogenic production.

Barrier Island System Units—Predominantly sand and clay. Erosion 

resistance is moderate to low.

Inlet Modifications—The US Army Corps of Engineers sealed the 2003 

Hurricane Isabel Inlet breach using sand dredged from the federally 

maintained ferry channel between Hatteras and Ocracoke islands. Sand 

dredged from Oregon Inlet was deposited offshore from 1960 to 1983, and 

was artificially bypassed to Pea Island beaches between 1983 and 2009.

Coastal Engineering and Shoreline Armoring—Most nourishment sand is 

sourced from inlet deltas and channels; its removal destabilizes the inlets and 

impacts regional sediment budgets. Between 1962 and 2011, over 7.8 million 

m3 of sediment were emplaced on park beaches.

Dredge spoil subject to wave modification and vegetation as 

natural processes overprint anthropogenic changes.

Habitat: Fill areas often abut and/or overprint former marsh 

areas. The sounds provide habitat for birds, seagrass, oysters, 

and mid-Atlantic fish.
CAHA Map Unit Properties Table (NC Geological Survey Map), Page 5 of 5

Group

Subgroup

Map Unit

(Symbol) Geologic Description Geologic and Environmental Features and Processes Geologic Issues Geologic History and Habitat

ANTHROPOGENIC FEATURES

Erosion Control 

Structure

(ersn_ctrl_st)

Excavation

(excavate)

Dike

(dike)

Waterfowl 

Impoundment 

(wtrfwl_impnd)

Erosion Control Structures: may 

include hardening, riprap, and 

other artificial sediment traps. 

There are 48 coastal engineering 

structures in or immediately 

adjacent to the park.

Excavation Areas: known from 

imagery and witness accounts, 

typically serving as spoil sources. 

There are 5 dredging projects in or 

immediately adjacent to the park.

Dikes: built for several waterfowl 

impoundment areas in Pea Island 

National Wildlife Refuge.

Estuaries—Most sand in Core Sound and central and eastern Pamlico 

Sound is derived from barrier islands and offshore sediments carried 

through inlets and overwash fans. Additional major contributions are from 

rivers, shoreline erosion and biogenic production.

Freshwater Aquifer—Groundwater systems and aquifers can be affected 

by impoundments, weather conditions, and water withdrawal; these 

influences alter hydrologic processes, wetland function, and the 

distribution, composition, diversity, and structure of vegetation 

communities

Barrier Island System Units—Predominantly sand and fill.

Hurricane Impacts and Human Responses—Structures may fail under 

extreme storm conditions.

Inlet Modifications—The US Army Corps of Engineers sealed the 2003 

Hurricane Isabel Inlet breach using sand dredged from the federally 

maintained ferry channel between Hatteras and Ocracoke islands.

Coastal Engineering and Shoreline Armoring—Seawalls, bulkheads, and 

other structures to inhibit wave action are expensive and accelerate erosion in 

front of the structures. Temporary soft stabilization (sandbags) have similar 

effects but are permitted in North Carolina. Most nourishment sand is 

sourced from inlet deltas and channels; its removal destabilizes the inlets and 

impacts regional sediment budgets. Between 1962 and 2011, over 7.8 million 

m3 of sediment were emplaced on park beaches.

Recreational and Watershed Land Use—Constructed drainage ditches 

affect water distribution and quality on Bodie and Hatteras islands. Toxic and 

nuisance algal blooms may occur in nutrient-enriched drainage ditches on 

Bodie Island.

Units document human attempts to stop, slow, or reverse 

natural barrier island processes.

Habitat: Plants and animals adaptable to human presence, 

waterfowl use impoundment areas.