V_DATUM
(
type: esriFieldTypeString, alias: V_DATUM, length: 6
, Coded Values:
[MSL: Mean Sea Level]
, [NAVD88: North American Vertical Datum 1988]
, [NGVD29: North American Geodetic Vertical Datum 1929]
, ...4 more...
)
Description: The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD), herein after referred to as the “Standard” (http://pubs.usgs.gov/tm/11/a3). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HU’s are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS) Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygons attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications. WBDHU8 represents the 8-digit hydrologic unit boundaries (previously referred to as Subbasins) and are part of the WBD delivery, but the boundaries are not editable by the WBD In-State Steward. Approximately 2,297 8-digit hydrologic units (Subbasins) are in the WBD,
Service Item Id: 73ee72886a0e40928e55f6a87ba28106
Copyright Text: Funding for the Watershed Boundary Dataset (WBD) was provided by the USDA-NRCS, USGS and EPA along with other federal, state and local agenies. Representatives from many agencies contributed a substantial amount of time and salary towards quality review and updating of the dataset in order to meet the WBD Standards. See dataset specific metadata for further information
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