Earth Science

Delineating Watershed Boundaries Using The National Map

The National Elevation Dataset, the elevation layer of The National Map, is the framework for a multi-layered hydrologic database called the Elevation Derivatives for National Applications (EDNA). Using valuable flow direction characteristics within the EDNA, an elevation-derived watershed tool is available to delineate and download watershed boundaries by selecting a point anywhere within the conterminous United States. The tool was developed by the U.S. Geological Survey, Earth Resources Observation and Science Center, Topographic Science, and is available online at



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