Evaluation of Distributed BMPs in an Urban Watershed – High Resolution Modeling for Stormwater Management

Abstract:

Urbanization presents challenging water resource problems for communities worldwide. The hydromodifications associated with urbanization results in increased runoff rates and volumes and increased peak flows which can lead to increased erosion and stream destabilization, decreased evapotranspiration, decreased ground water recharge, increases in pollutant loading, and localized anthropogenic climate change or Urban Heat Islands. Stormwater management is shifting from a drainage-efficiency focus to a natural systems focus. The natural system focus, referred to as Low Impact Development (LID), or Green Infrastructure, uses best management practices (BMPs) to reduce the impacts caused by urbanization hydromodification. Currently there are two modeling approaches used to evaluate BMPs in urban watersheds, conceptually-based coarse resolution hydrologic models and high-resolution physically-based models. Conceptual urban hydrology-hydraulic models typically are used to determine peak flow hydrographs within a watershed based on uniform rainfall, the basins size, shape, and percent of impervious land cover. Physically-based hydrologic models simulate integrated surface and subsurface water flow. Here, we use high-resolution physically based hydrologic models of the urban hydrologic cycle with explicit inclusion of the built environment. We compare the inclusion and exclusion of LID features to evaluate the parameterizations used to model these components in more conceptually based models. Differences in response are discussed and a road map is put forth for improving LID representation in commonly used urban water models.