High-resolution Mapping of Urban Land Use Intensity in Watersheds of the St. Louis River Estuary

Abstract

Agriculture and development are the source of a multitude of environmental stressors influencing coastal ecosystems, including sediment and nutrient runoff, alterations to hydrologic and thermal regimes, delivery of pollutants and loss of habitat. Many studies have addressed the effects of land use on aquatic ecosystem, but fundamental issues of scale remain unresolved. Land use data are common inputs to environmental indicator development, hydrologic models such as SWMM or HSPF, and decision support models such as the EPA National Stormwater Calculator. The difference in areal estimates of urban land cover between NLCD and higher resolution land classification can result in significant differences in predicted amounts of runoff and infiltration. Using these data to develop remediation strategies using green or gray infrastructure could potentially result in costly errors through under or over-engineering retention structures. For this reason, we initiated this project to expand the Stueve et al. (2014) methodology, which focused on a single watershed, to multiple urban watersheds entering the St. Louis River Estuary (SLRE). We then used these data to develop indices of urban land use intensity, focusing on impervious surface, building footprints, building heights and height diversity within municipal parcels. Finally, we assessed the relationship of these urban land use intensity indices to water quality data collected in nine tributary watersheds of the St. Louis River.