The ASCE/EWRI Impervious Surface Task Committee

Estimates of impervious surface cover are frequently needed by a wide range of hydrologic models that predict water quantity and water quality. Although imperviousness is a landscape characteristic that is easily understood, methods for quantifying imperviousness vary widely and are often not well-documented in published studies. Preliminary work by this committee indicates that estimates of imperviousness can easily vary by a factor of 2 to 10 based on a comparison of two very common approaches. The consequences of such variability effect the interpretation of findings from basic research, effect operational analysis and design decisions that practicing hydrologic engineers make daily, and effect policy aimed at protecting environmental and water resources. This paper summarizes the objectives and planned activities of the Impervious Surface Task Committee. The author is the chairman of this committee and the committee membership currently in composed of members of the Watershed Management and Surface Water technical committees.