DROWNING the NORTH CAROLINA COAST: Sea-Level Rise and Estuarine Dynamics 0056102
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0056101 By Stanley R. Riggs and Dorothea V. Ames DROWNINGPublished by North Carolina Sea Grant DROWNING THE NORTH CAROLINA COAST: Sea-Level Rise and Estuarine Dynamics 0056102 ON THE FRONT COVER. Pre-Hurricane Isabel photograph of the lower portion of sediment bluff that occurs along the Chowan River estuary western shoreline. The red star, on the satellite image inside the back cover, indicates the specific site location. This bluff is approximately 75 feet high and consists of a lower clay bed that is about 30 feet thick (to the top of this photograph), with an overlying sand bed that is 45 to 50 feet thick. Because bluff shorelines normally erode at average rates between –2.0 and –2.5 ft/yr (Table 8-1-3) and because the lower sediment bank is composed of clay, there is no sand beach preserved on the eroded wave-cut scarp and platform (Fig. 4-2-1). Notice the red dotted line along the wave-cut scarp and compare this to the respective location on the post-Hurricane Isabel photograph on the back cover. Photograph was taken in August 2003. See the back cover for the post-Hurricane Isabel photograph of the same site and inside back cover for a satellite image showing the site location and post- Hurricane Isabel, sediment-laden, estuarine water conditions. 0056103 By Stanley R. Riggs and Dorothea V. Ames DROWNINGPublished by North Carolina Sea Grant DROWNING THE NORTH CAROLINA COAST: Sea-Level Rise and Estuarine Dynamics NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES Division of Coastal Management 225 North McDowell Street Raleigh, NC 27602 and NORTH CAROLINA SEA GRANT North Carolina State University Box 8605, Raleigh, NC 27695-8605 Drowning the North Carolina Coast • 1 0056104 DROWNING THE NORTH CAROLINA COAST: SEA LEVEL RISE AND ESTUARINE DYNAMICS Copyright© 2003 by North Carolina Sea Grant Written by Stanley R. Riggs and Dorothea V. Ames Edited by Ann Green • Designed by Linda J. Noble Published by North Carolina Sea Grant NC State University • Box 8605 • Raleigh, NC 27695-8605 919/515-2454 • www.ncseagrant.org • UNC-SG-03-04 • North Carolina Sea Grant • National Oceanic and Atmospheric Administration • NC Division of Coastal Management • Albemarle-Pamlico National Estuary Program East Carolina University • US Geological Survey • National Park Service • US Fish & Wildlife Service North Carolina Printed and bound in the United States of America First Printing: December 2003 • ISBN 0-9747801-0-3 2 • Drowning the North Carolina Coast 0056105 D R O W N I N G T H E N O R T H C A R O L I N A C O A S T : Table of Contents • List of Tables ............................................................................................................................................................................. 6 • List of Figures ........................................................................................................................................................................... 7 • Acknowledgments .................................................................................................................................................................. 11 • Disclaimer ............................................................................................................................................................................... 11 • Chapter 1. Introduction .......................................................................................................................................................... 12 1.1. The Coastal Dilemma ....................................................................................................................................................... 13 1.2. The Estuarine Shoreline .................................................................................................................................................... 13 1.3. Conclusions .................................................................................................................................................................... 15 • Chapter 2. Geologic Framework of the North Carolina Coastal System ............................................................................. 16 2.1. Physical Setting of the Coastal System .............................................................................................................................. 17 2.2. North Carolina Coastal Provinces ...................................................................................................................................... 17 2.3. Geologic Controls of Coastal Provinces ............................................................................................................................. 20 2.3.A. Southern Coastal Province ..................................................................................................................................... 20 2.3.B. Northern Coastal Province ...................................................................................................................................... 21 2.3.C. Consequences of the Geologic Differences ............................................................................................................. 21 2.4 Shorelines and Storms ...................................................................................................................................................... 22 2.4.A. The Flow of Energy ................................................................................................................................................ 22 2.4.B. Role of Barrier Islands and Their Inlet/Outlet Systems ................................................................................................ 23 2.4.C. Role of Paleotopography in Estuarine Dynamics ....................................................................................................... 23 • Chapter 3. Character of Drowned-River Estuarine System ................................................................................................. 24 3.1. Types of Estuarine Basins ................................................................................................................................................. 25 3.2. The Estuarine Basins ........................................................................................................................................................ 25 3.2.A. Basin Morphology .................................................................................................................................................. 25 3.2.B. Basin Sediments ................................................................................................................................................... 27 3.3. Back-Barrier Sounds ........................................................................................................................................................ 29 3.3.A. Back-Barrier Sounds of the Northern Province .......................................................................................................... 29 3.3.B. Back-Barrier Sounds of the Southern Province ......................................................................................................... 31 3.4. Trunk Estuaries ................................................................................................................................................................ 31 3.4.A. Trunk Estuaries of the Northern Province .................................................................................................................. 31 3.4.B. Trunk Estuaries of the Southern Province ................................................................................................................. 33 3.5. Tributary Estuaries ............................................................................................................................................................ 35 Table of Contents • 3 0056106 C O N T I N U E D : Table of Contents • Chapter 4. Types of Estuarine Shorelines ............................................................................................................................. 36 4.1. Shoreline Types ............................................................................................................................................................... 37 4.2. Sediment Bank Shorelines ................................................................................................................................................ 37 4.2.A. General Characteristics .......................................................................................................................................... 37 4.2.B. Strandplain Beaches .............................................................................................................................................. 38 4.3. Organic Shorelines ........................................................................................................................................................... 40 4.3.A. Swampforest Shorelines ......................................................................................................................................... 41 4.3.B. Marsh Shorelines ................................................................................................................................................... 43 4.4. Combination Shorelines ...................................................................................................................................................