Coastal geomorphology and vulnerability to sea level rise at the National Hydrography Dataset Coastline

National Hydrography Dataset (NHD) Coastline Geomorphology and Risk line-event feature classes are developed and used to characterize the extent and distribution of coastal landform features and the associated relative risk of horizontal erosion at Mean High Water levels (MHW) for the conterminous U.S. coastline. Created along the linear-referenced NHD Coastline using the Hydrographic Event Management (HEM) tool (http://nhd.usgs.gov/tools.html) in a geographic information system the digital data sets attribute the Pacific, Gulf, and Atlantic coasts. Attribution of the linear-referenced NHDCoastline for conterminous US states provides digital vector data identifying the occurrence and extent of landform types attributed with the relative risk of horizontal erosion. This geodata is used to generate risk line-events that quantify the percent and distribution of relative risk rankings as a guide for locating soft to stable shorelines. In a geographic information system, geomorphology and risk line-events to attribute the coast at MHW are created using coastal landform categories and the associated risk of horizontal erosion rankings published in US Coastal Hazards Database (CHDB) reports (Gornitz and White, 1992; 1994; Gornitz et al, 1997). The CHDB geomorphology category index is augmented to include a subtype for rocky, glaciated coast landforms and landforms originally deposited offshore but that are now exposed. Risk rankings for landforms intersected by MHW along coasts that open into oceans or large bays were determined through extraction and modification of the risk parameter classification developed at the University of Virginia, to create the Coastal Erosion Information System (CEIS) (May and others, 1982; 1983, Dolan and others, 1975; 1983; 1989). Previously integrated as one of seven parameters used to characterize coastal vulnerability to sea-level rise, in this study the risk of horizontal change ranking for landforms crossed by the NHDCoastline is independent of the six other physical parameters required to fully assess coastal vulnerability.