Inland Flood
UrbanFootprint Inland Flood combines the FEMA National Flood Hazard Layer (NFHL) and U.S. Environmental Protection Agency (EPA) Estimated Floodplain Map of the Conterminous U.S datasets to produce a gap-free continuous 100-year flood zone layer for the United States.
Our algorithm considers the FEMA National Flood Hazard Layer (NFHL) as "truth" for indicating the 100-year floodplain. However, gaps may exist in the FEMA datasets where the maps may not exist, have not been digitized, or where the area is explicitly stated as unknown. We use the EPA data to fill gaps in the FEMA datasets. FEMA includes datasets for the entire United States.
The U.S. Environmental Protection Agency (EPA) Estimated Floodplain Map of the Conterminous U.S. identifies areas estimated to be inundated by a 100-year flood, also known as the 1% annual chance flood. This dataset completes areas FEMA has not yet mapped, representing about 30% of the contiguous United States. These data are developed using random forest classification of nationally available biophysical datasets. A value of 1 indicates that the asset is in the 100-year floodplain, and a value of 0 indicates that it is not.
EPA includes datasets for CONUS only. Therefore, coverage over Alaska and Hawaii is based on FEMA data. Across the continental United States, though, combining EPA with FEMA datasets provides substantial improvements over FEMA alone.