Get NHD Data
Quick Links for data download:
The National Hydrography Dataset (NHD) is stored in a geodatabase implementation of the NHD model. This provides great flexibility and efficiency to allow the data to work well in analysis using a geographic information system (GIS). To maximize the capability of the NHD, users should download the data in a file-based or personal geodatabase known as NHDinGEO. For those using the NHD to create simple maps, a shapefile version known as NHDinSHAPE also is available.There are Five ways to access the data. These methods are based on the organization of hydrographic data into hydrologic units. These are drainage areas nested in a four-level hierarchy with a 2-digit identifier for each level.
Using the NHD Viewer, additional data themes can be overlaid to help identify the area of interest. These themes include shaded terrain, boundaries, transportation, cities, map graphics, aerial imagery, and others. You can also visit EPA's Surf Your Watershed Web site if you need to locate the subbasin of interest to you, or don't know the subbasin number. The NHD data are stored and made available at two levels of resolution: one is nominally at 1:24,000-scale known as high resolution, and the other is at 1:100,000-scale known as medium resolution. A limited amount of data are available at nominally 1:5,000-scale known as local resolution. The high resolution level may contain a mixture of scales at 1:24,000-scale or higher.
The NHD data are organized into several forms of geometry and into several supporting tables:
Geometry: The geodatabase contains two Feature Datasets of geometry. The Hydrography feature dataset contains the NHD whereas the Hydrographic Units feature dataset contains the Watershed Boundary Dataset (WBD).
Two other feature classes are used to represent features. NHDLine contains linear features not core to the network, and NHDPoint contains hydrography related point features.
Finally, an additional three feature classes represent point, line, and area data events that behave as map features and linearly referenced events. Streamgages, which are point features, can be displayed and identified in the network through linear referencing with a network address. These feature classes are NHDPointEventFC, NHDLineEventFC, and NHDAreaEventFC.
Tables: Information about the NHD also can be obtained in a series of associated tables. This includes metadata stored in NHDFeaturetoMetadata and NHDMetadata, sources given in NHDSourceCitation, identification of model and data version given in NHDProcessingParameters, flow relations given in NHDFlow, reach code histories given in NHDReachCrossReference, the domain of feature codes given in NHDFCode, and others.
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