Climate change impacts on urban stormwater best management practices

Abstract

Total maximum daily load (TMDL) studies determine the amount of contaminant(s) that can be discharged daily from point (waste load allocation-WLA) and nonpoint (load allocation-LA) sources including a margin of safety (MOS) and then layout the path for achieving these levels by reductions in loadings. This has caused environmental agencies to require best management practices (BMPs) for control of urban stormwater contributions. Design storms for volume-based and peak discharge BMPs are typically determined from historic precipitation and runoff records that do not adequately address the impacts of climate change. We examine a 10-year period of predicted flows in the Spokane River watershed under 2050 climate predictions to determine the amount of additional LA removal required to meet water quality goals. While the current TMDL proposes a 50% reduction of nonpoint loading, our results indicate this will not be adequate. The implication is that urban BMPs are currently inadequately designed to handle nonpoint pollution in areas projected to experience increased precipitation events. The problem is particularly acute for rain on snow events where BMP performance is already impaired.

Regenerating Sponge City to Sponge Watershed through an Innovative Framework for Urban Water Resilience

“…The appropriateness of UWM practices depends on specific site conditions, i.e., watershed size, space scale, and human activities, while no single standardized solution can be effective in all locations in terms of comprehensive and multiple-goal orientation [55]. The significant programs refer to sustainable urban drainage systems (SUDS) [39,56], low impact development (LID) [52,57,58], best management practices (BMP) [55,59], water sensitive urban design (WSUD) [60,61], and green infrastructure (GI) [62,63]. More details are presented in Table 2.…”

“…The water resilience module comprises five indicators: green and blue space ratio, river network connectivity, volume capture ratio of annual rainfall, composite runoff coefficient, and heat island mitigation. It helps address the disasters and challenges of climate change and extreme weather under conditions of uncertainty [59]. The sponge watershed system should respect the local landscape and balance urban development and nature conservation [58].…”