Analyzing Increases in Impervious Surface and the Effects on Hydrology and Water Quality in Big Sky, Montana

Abstract

At a resolution of 30 m, there was a 26% increase in impervious surface in the West Fork of the Gallatin watershed from 1990 to 2005. After assessing the negative effects of impervious surface increase on aquatic systems, this review concludes that freshwater ecosystem health is likely to be the primary object of concern. Specifically, stream biota is negatively affected by reduced base flow and increased sediment loads that result when a watershed is overlaid by more impervious surfaces. Effective impervious surfaces, or impervious surfaces with gray stormwater infrastructure, have the greatest effect on hydrology and thus aquatic communities. Unless stormwater best management practices (BMPs) are implemented, greater increases in impervious surface will further stress freshwater ecosystems in the West Fork watershed and Upper Gallatin River.