The Reach Address DatabaseThe Reach Address Database (RAD) stores the reach address of each Water Program feature that has been linked to the underlying surface water features (streams, lakes, etc) in the National Hydrology Database (NHD). These reach addresses record the geographic extent of Water Program features in both tabular and spatial formats. The reach addresses link to a static copy of the NHD obtained from the USGS. Periodically, EPA retrieves an updated version of the NHD from USGS and migrates all reach addresses in the RAD to this new version.
The only information about an individual Water Program feature stored in the RAD is its reach address. Additional descriptive information for each feature is stored in separate Water Program databases. A unique Water Program feature ID is used to relate the reach address for each Water Program feature found in the RAD with the other detailed data for that feature found in the separate databases. This unique Water Program feature ID is also called the Source Feature ID. The Water Program feature ID is the key for relating the event tables and shapefiles with the corresponding attribute information for that feature.