Impervious Surfaces

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Source NOAA Coastal Change Analysis Program (C-CAP); National Land Cover Database; Thurston Regional Planning Council
Data Table Impervious Surfaces by Watershed
Map Thurston County Watersheds
Explanation Watersheds or basins that have an impervious land cover of more than 10% are generally assumed to have degraded water quality. Two watersheds in Thurston County were near or above this level in 2014: Henderson Inlet, with approximately 17.3% impervious surface coverage, and Budd/Deschutes with 9.4%.

Impervious Surfaces

Impervious surfaces include roads, driveways, rooftops, and other compact surfaces which do not allow rain to infiltrate into the soil and groundwater. Watersheds with large areas of impervious surfaces tend to have more runoff, which increases erosion and washes pollutants directly into streams and lakes.

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