The NHD represents the national drainage networks and related surface water features including rivers, streams, canals, lakes, ponds, glaciers, coastlines, dams, and stream gauges. The NHD has attributed these features and includes classification and other characteristics, delineation, geographic name, position and related measures, a "reach code" through which other information can be related to the NHD including the direction of water flow. This network of reach codes allows analysis for tracing movement in upstream and downstream directions. The NHD can support many applications, such as making maps, geocoding observations, flow modeling, data maintenance, and stewardship.
The WBD represents drainage areas of the country in eight nested levels called hydrologic unit codes(HUCs).
Texas stretches across three HUC-2 regions encompassing the Arkansas-White-Red Region, Texas-Gulf Region and Rio Grande Region; furthermore, Texas contains over 6,450 HUC-12 Subwatershed. The NHD for Texas contains over 1.5 Million features.
The Markup Application is a web-based mapping tool allowing public users to submit edits, or markups, to the NHD, WBD, and NHDPlus HR. Users can log in with any gmail account to suggest corrections and improvements to the data using local knowledge. For more information and details on how to use the tool see the USGS new Markup App Video for help using the tool.
In Texas NHD Plus HR is currently available for all regions of Texas and beta QC is either in progress or completed.
The NHDPlus HR is built using:
The complete nationwide Watershed Boundary Dataset NHDPlus HR consists of vector and raster data layers. It includes a snapshot of the NHD and WBD at the time the NHDPlus HR was built, as well as the following components: