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This is a Washington State extract downloaded from the USGS in March 2019 and projected into WA State Plane Coordinates North. Strahler Stream Order has been added. NHDArea contains many additional water-polygon features. One of the more important is the stream/river feature. It represents the areal extent of the water in a wide stream/river with a basic set of attributes. These polygons typically encompass NHDFlowline artificial paths that represent the stream network. Artificial path carries the critical attributes of the stream/river, whereas NHDArea represents the geometric extent.
The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. This high-resolution NHD, generally is developed at 1:24,000/1:12,000 scale, but many areas of Washington State have been improved to 1:4800 scale. NHD data was originally developed at 1:100,000-scale and exists at that scale for the whole country. Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water bodies. Reaches are also defined on waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee. Stream Orders in Washington State range from 1 to 10. The smallest headwater streams are a 1, and the Columbia River is a 10. |