A Place-based Tool for Assessing Cumulative Impervious Surface Outcomes of Proposed Development Scenarios

Impervious surface cover is commonly used as an environmental indicator for land use and watershed planning. The net quantity of impervious surface added per quantity of residential and commercial development, including the added impervious at the development site as well as the offsite impacts associated with the development (e.g., roads, other infrastructure), can serve as a partial measure of the net impacts of site development. The comparison of net impervious surface growth rates can be used as a partial surrogate for predicting the relative impacts of alternative land development proposals on water quality, flood control infrastructure, stream erosion, groundwater recharge, and habitat. While a variety of approaches are currently used to estimate impervious cover, these approaches are limited in a number of ways for comparing alternative land use scenarios. To attempt to address these limitations and to fill unmet needs, a nationwide remote sensing and regression analysis was undertaken. The result is an impervious surface growth model (ISGM) capable of predicting the net increase in impervious cover at the census block group scale as a function of quantities of residential and commercial development added and relative centrality of the block group within a metropolitan regional context. This tool has potential for applications to urban planning and policy development as well as watershed and drainage planning. This paper presents the process used to develop the ISGM, evaluates the reliability of the ISGM, and discusses applications of the ISGM and potential future enhancements.