Investigating Retrofits to Improve Water Quality and Reduce Streambank Erosion in Aging Flood Control Basins in Northeast Ohio

Abstract Submission: Prior to regulations passed in 2003, flood control was the sole management objective of stormwater basins constructed in Ohio. As a result, many stormwater basins in developments constructed prior to 2003 fail to retain and slowly release runoff during frequently occurring small storm events, providing little to no water quality benefits nor mitigating erosion in receiving streams. Simple retrofits these basins (e.g., adding orifices, weirs, and other flow mitigation features to existing outflow structures) could improve their water quality benefits while reducing the occurrence of downstream erosion and maintaining flood control capacity. Many developed areas in the Cuyahoga River, Chagrin River, and Rocky River watersheds and Lake Erie Direct Tributaries have many pre-2003 stormwater basins that could potentially be retrofitted to reduce stream impairments. This presentation will highlight the results of extensive pilot-scale modeling to evaluate the benefits of retrofits to flood control basins in Aurora and Mayfield Heights, Ohio. The benefits and challenges of two modeling approaches (i.e., PCSWMM and HydroCAD) will be compared to develop retrofit strategies designed to meet current regulations (i.e., slowly release runoff from a 0.9-in storm event over a 48hr period) while reducing opportunities for downstream erosion in smaller storm events. Findings from this research can inform similar retrofit efforts targeting flood control basins to bolster the water quality benefits and mitigate downstream erosion of aging stormwater infrastructure designed under outdated regulations.

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