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Geographically Isolated Wetlands (Non-Floodplain Wetlands) of the Conterminous United States

Published by U.S. EPA, Office of Research and Development | U.S. Environmental Protection Agency | Metadata Last Checked: January 27, 2026 | Last Modified: 2016-01-29T00:00:00.000+00:00
This data set represents the extent and approximate location of GIWs, also known as non-floodplain wetlands (NFWs), in the conterminous United States. NWI lacustrine systems and palustrine wetlands were determined to be “isolated” based on their geographic location (i.e., unconnected, based on a distance measure, to specific classes of NHD aquatic systems). GIWs were here considered geographically isolated when they were outside of 10 meters from select NHD lines and polygons or were not adjacent to NWI Riverine or Estuarine wetlands and (where applicable) outside of 10 meters from a coastline (e.g., oceans or Great Lakes).

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