Landforms along the Pacific, Gulf of Mexico, and Atlantic coastlines for the conterminous United States are attributed with the relative vulnerability of horizontal erosion due to sea-level rise to characterize coastal zone stability. The position and extent of landforms are geospatially indexed as line-events where these coastal zone features are intersected by the linear-referenced 2013 - 2014 U.S. Geological Survey National Hydrography Dataset Coastline, which corresponds to the National Oceanic and Atmospheric Administration (NOAA) 2013 - 2014 mean high water level datum delineated in intertidal zones open to oceans, behind barrier coasts in bays, lagoons, and estuaries, and sometimes where tidal currents reach upstream (landward) of the embayed foreshore water bodies. The geospatial data provide baseline landform characterization of conterminous U.S. coastlines to assist in analyses and models used in coastal zone mapping, management, and protection of populated community infrastructures and economies, and to evaluate and protect ecological systems.
The geospatial coastline attribution data are created using the U.S. Geological Survey Hydrography Event Management (HEM) tool . Landforms, or geomorphology in intertidal zones were identified using high spatial resolution (1-meter) imagery from the U.S. National Agriculture Aerial Imagery Program and digital data maintained by the U.S. Fish and Wildlife Service National Wetlands Inventory Wetlands Mapper and Coastal Barriers Resource System Maps. In addition, state, federal, and academic studies are referenced where these have been used to characterize geologic frameworks or to ensure that the right landform is identified from imagery. Landform types and associated vulnerability to horizontal erosion classes, including 1 (very low) through 5 (very high), were adopted from the geomorphology categories and coastal vulnerability index developed and reported through the Department of Energy Carbon Dioxide Information Analysis Center.
Geomorphology and risk line-event vector data sets for glaciated and non-glacial terrain characterize the majority of the conterminous US NHDCoastline in estuarine landform settings commonly ranked with a moderate or moderately high risk of erosion (Risk 3 or 4, respectively). Often, in areas such as Chesapeake Bay, VA, Albemarle Bay, NC, Mobile Bay, AL., and San Francisco Bay, CA projected MHW occurs in large embayments protected from the open ocean by barrier coast complexes. Important to coastal zone communities developed on or near barrier spits and islands that intersect MHW, these features are ranked with the highest risk of erosion, Risk 5. A summary of NHDCoastline Geomorphology and Risk line-event geodata for each Pacific, Gulf, and Atlantic coast states indicates the majority of landform risk rankings range between Risk 3 and Risk 5. Risk 3 landforms account for 19, 52, and 35 percent, and Risk 4 landforms account for 33, 24, and 30 percent of the Pacific, Gulf, and Atlantic NHDCoastline, respectively. Comprising 37 percent of coast landforms, Risk 5 features are most common on the Pacific coast. Landforms ranked as Risk 5 features comprise 24 and 28 percent of the Gulf and Atlantic NHDCoastline, respectively.
