Massachusetts hydrologic unit subdivisions

Impervious surfaces such as paved roads, parking lots, and building roofs can
affect the natural streamflow patterns and ecosystems of nearby streams. This
data set summarizes the percent of impervious surface for hydrologic units in
Massachusetts using a newly available statewide 1-m binary raster dataset of
impervious surface for 2005. A hydrologic unit consists of all or part of a
drainage basin, or an area of coastal drainage. Hydrologic units subdivide
large drainage basins into discrete, non-overlapping areas. This is one of
three data layers in this data series publication.