Some data sets are available online at no cost. Others require a distribution fee, or must be ordered on compact disc or tape. For more information, see About the USGS Geospatial Data Clearinghouse . Water Resources Investigations Report 93-4076 by J.R. Slack, Alan M. Lumb, and Jurate Maciunas Landwehr describes the HCDN and links to data sets by region. Data on current hydrologic conditions, flood impact information, and an archive of past flood summaries.
Some data is displayed in maps.
Information adapted from Water-Supply Paper 2294 defines hydrologic units and describes available maps. Links to free, online, digital spatial data sets are also provided. Active warnings for flash floods and other weather events. Updated every five minutes. Policy and claim statistics.