The WBD and HU Codes! Lily S. Niknami and Kimberly A. Jones, USGS   WBD (Watershed Boundary Dataset) and HUC (hydrologic unit codes).This dataset probably impacts every GIS'er whether you are assessing storm water run-off for your County or municipality, determining the impact of a post-wildfire debris flow, evaluating landslides and avalanches, or calculating spring streamflow estimates. […]