RReedduucciinngg VVuullnneerraabbiilliittyy iinn FFiivvee NNoorrtthh CCaarroolliinnaa CCooaassttaall CCoommmmuunniittiieess:: A MODEL APPROACH FOR IDENTIFYING,,,, MAPPING AND MITIGATING COASTAL HAZARDS Prepared by: Duke University Program for the Study of Developed Shorelines Division of Earth and Ocean Sciences Duke Nicholas School of the Environment Prepared for: North Carolina Division of Emergency Management North Carolina Department of Crime Control and Public Safety August 2001 TABLE OF CONTENTS INTRODUCTION: OVERVIEWOVERVIEW AND FINDINGS................................................................................................ ........................................................................................................................................................................................................................................................................................................................................II Lessons Learned and the Ten Rules of Coastal Hazard Mitigation ................................................................................................................................................... ii Hazards, Economics and Politics ....................................................................................................................................................................................................iv CHAPTER 1: THE NORTH CAROLINA COAST................................COAST....................................................................................................................................................................................................................................................................................................................................................................................................................1 THE GEOLOGIC FRAMEWORK OF THE NORTH CAROLINA COAST ....................................................................................................................................................1 Southern Province ..........................................................................................................................................................................................................................1 Northern Province..........................................................................................................................................................................................................................2 NORTH CAROLINA BARRIER ISLANDS................................................................................................................................................................................................2 HOW BARRIER ISLANDS BEGAN.........................................................................................................................................................................................................3 The Role of the Shoreface in Barrier Island Evolution .......................................................................................................................................................................3 BEACH DYNAMICS.............................................................................................................................................................................................................................5 Sand/Sediment...............................................................................................................................................................................................................................5 Waves and Wind ...........................................................................................................................................................................................................................6 Vegetation .....................................................................................................................................................................................................................................8 BEACH FEATURES..............................................................................................................................................................................................................................9 Beach Shape ..................................................................................................................................................................................................................................9 Offshore Bars .................................................................................................................................................................................................................................9 Berms..........................................................................................................................................................................................................................................10 Beach Cusps.................................................................................................................................................................................................................................10 Swash Marks, Ripple Marks, and other Bedforms ...........................................................................................................................................................................11 Groundwater on the Beach ...........................................................................................................................................................................................................11 Beach Erosion ..............................................................................................................................................................................................................................11 Dunes..........................................................................................................................................................................................................................................12 NORTH CAROLINA ESTUARIES ........................................................................................................................................................................................................14 Estuaries of the Southern Province.................................................................................................................................................................................................14 Estuaries of the Northern Province.................................................................................................................................................................................................15 Estuaries and Development ...........................................................................................................................................................................................................15 NORTH CAROLINA INLETS ..............................................................................................................................................................................................................16 WHAT'S HAPPENING TO THE BARRIER ISLANDS TODAY?.................................................................................................................................................................16 Island Migration..........................................................................................................................................................................................................................16 CHAPTER 2: COASTAL HHAZARDSAZARDS AND HAZARDOUS PROCESSES ................................................................................................ ............................................................................................................................................................................................................ 19 WHAT ARE NATURAL HAZARDS?.....................................................................................................................................................................................................19 HOW NATURAL ARE NATURAL HAZARDS?.......................................................................................................................................................................................19 HAZARDOUS EVENTS ......................................................................................................................................................................................................................19 Hurricanes and Tropical Storms....................................................................................................................................................................................................19 Mid-Latitude Storms (Extra-Tropical Cyclones).............................................................................................................................................................................20 HAZARDOUS PROCESSES 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