Stormwater Management Options and Decision-Making in Urbanized Watersheds of Los Angeles, California

Hydrologic modeling is a crucial tool to understand the physical and hydrologic characteristics that contribute to water quality degradation in urban areas and the effectiveness of stormwater best management practices (BMPs) for meeting subsequent regulatory compliance. In this study, three highly urbanized watersheds, the Ballona Creek (BC), the Dominguez Channel (DC), and the Los Angeles River (LAR), located in Los Angeles, are modeled using the EPA's System for Urban Stormwater Treatment and Analysis INtegration (SUSTAIN). The primary goal is to identify the key characteristics that contribute to water quality impairment, analyze the efficacy of utilizing specific BMPs to comply with regulatory compliance, and discuss how results can inform optimal stormwater management plans for each watershed. The BC watershed has the least degraded water quality and multiple BMP scenarios result in elimination of exceedances, while the DC watershed has the most degraded water quality and none of the modeled BMP scenarios meet water quality regulations. The LAR watershed is a large, diverse watershed and results show better water quality compliance than the DC watershed despite land use characteristics that would indicate otherwise. Watersheds that reach compliance with multiple BMP types have more available options when considering ancillary benefits. Modeling results such as those presented here are critical for informing stakeholders' decision-making process and facilitating optimal BMP implementation for integrated water management.