This dataset represents data derived from the NLCD dataset and the National Hydrography Dataset version 2.1(NHDPlusV2) (see Data Sources for links to NHDPlusV2 data and NLCD). Attributes were calculated for every local NHDPlusV2 catchment and accumulated upstream catchments to provide watershed-level metrics for imperviousness values within the NLCD.

        This data set is derived from the NLCD Impervious Surfaces raster(imp2011) which describes percent imperviousness (continuous data type).  Values indicate the degree to which the area is composed of impervious anthropogenic materials (e.g., parking surfaces, roads, building roofs). This raster was produced based on a decision-tree classification of circa 2011 Landsat satellite data.(see Data Structure and Attribute Information for a description of each metric).