Watershed-scale green stormwater infrastructure optimization and distribution in US Urban areas

Watershed-scale green stormwater infrastructure benefits communities by reducing peak flows, lowering runoff volume, and improving streamflow quality. Despite these advantages, many cities still have unmanaged stormwater runoff, meaning the potential benefits of green infrastructure can be maximized when systems are placed in optimized watershed locations. Across 20 urban areas in the US, treatment of runoff from impervious surfaces ranges from 0.1% to 71%, with a median of <12%. Simulation-optimization tool (OSTRICH-SWMM) optimized the placement of bioretention cells, swales, and permeable pavements at three treatment levels — 14%, 42%, and 70% — to minimize the runoff volume of approximately 10-year storms in urban watersheds in Cleveland, Ohio and Denver, Colorado. Overall, permeable pavements showed even spatial distribution and the largest hydrologic effects. Cost effectiveness was maximized by bioretention cells and swales, which were similarly distributed across subcatchments. Optimization is most useful for low to moderate treatment levels and discretized SWMM models. Many US cities treat stormwater from <14% of impervious surfaces.Treatment level and number of subcatchments influenced evenness of optimized green infrastructure.Permeable pavements tend to reduce peak flow and total flow volume more than bioretention cells and swales.At 42% treatment, bioretention cells and swales are most cost-effective. Many US cities treat stormwater from <14% of impervious surfaces. Treatment level and number of subcatchments influenced evenness of optimized green infrastructure. Permeable pavements tend to reduce peak flow and total flow volume more than bioretention cells and swales. At 42% treatment, bioretention cells and swales are most cost-effective.