Percent impervious surface for selected Chesapeake Bay watersheds

This dataset contains watershed means of estimated percent impervious surfaces for three time periods: 1992, 2002, and 2012. Estimates are based on coefficients derived from comparing land use of the 2012 NAWQA Wall-to-wall Anthropogenic Land-use Trends (NWALT) product to the 2011 National Land Cover Database (NLCD) imperviousness, then applying those coefficients to previous years (1974-2002) of the NWALT dataset.