Title: National Hydrography Dataset (NHD) 1:24,000
Originator:
Abstract:
The U.S. Geological Survey has
developed a National Hydrography Dataset (NHD). The
NHD is a comprehensive set of digital spatial data that contains information
about surface water features such as lakes, ponds, streams, rivers, springs and
wells. Within the NHD, surface water features are combined to form
"reaches," which provide the framework for linking water-related data
to the NHD surface water drainage network. These linkages enable the analysis
and display of these water-related data in upstream and downstream order.
The NHD is based upon the content of USGS Digital Line Graph (DLG) hydrography data integrated with reach-related information
from the EPA Reach File Version 3 (RF3). The NHD supersedes DLG and RF3 by
incorporating them, not by replacing them. Users of DLG or RF3 will find the
National Hydrography Dataset both familiar and
greatly expanded and refined.
The NHD is a national framework for assigning reach addresses to water-related entities, such as industrial discharges, drinking water supplies, fish habitat areas, wild and scenic rivers. Reach addresses establish the locations of these entities relative to one another within the NHD surface water drainage network, much like addresses on streets. Once linked to the NHD by their reach addresses, the upstream/downstream relationships of these water-related entities--and any associated information about them--can be analyzed using software tools ranging from spreadsheets to geographic information systems (GIS). GIS can also be used to combine NHD-based network analysis with other data layers, such as soils, land use and population, to help understand and display their respective effects upon one another. Furthermore, because the NHD provides a nationally consistent framework for addressing and analysis, water-related information linked to reach addresses by one organization (national, state, local) can be shared with other organizations and easily integrated into many different types of applications to the benefit of all.
While initially based on 1:100,000-scale data, the NHD is designed to incorporate and encourage the development of higher resolution data required by many users. The NHD is a living dataset that is updated bimonthly to incorporate the "best available" data. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee.
The dataset is provided in essentially two resolutions at this time. The first is the “medium” resolution based on
the 100K scale data; the second is the “high” resolution based on the 24K scale
data. As higher resolution data becomes available from state and local
governments and other sources, a third category will become more and more
common – “local” resolution data.
The Gateway serves the high resolution data only. Layers served are the following:
Flowline - streams, flowlines through 2-d features, connectors, ditches, pipelines.
Waterbody - examples – lake/pond, reservoir, swamp, ice mass.
Area - 2-d stream/river, inundation area, area to be submerged, bay/inlet, ocean.
Line - flume, gate, reef, tunnel, dam.
Point - spring, well, gaging station, water intake/outflow.
As a result, the gateway provides upto five(where available) maps for each hydrologic unit.
For a complete listing of Features and codes in each layer, go to: http://nhd.usgs.gov/NHDinGEO_FCodes_by_layer.pdf
The NHD home, http://nhd.usgs.gov/ provides a great deal of information about the NHD.
Format: vector lines – Arc shapefile
Spatial Reference Information: Decimal Degrees, North American Datum 1983
