Efficacy of Stormwater Control Measures for Extreme Precipitation in the Northern Midwest Region

Abstract Extreme precipitation events are a major driver of flood risk for urban areas with extensive impervious cover. Existing stormwater management infrastructure, much of which was constructed before our current best estimates for extreme precipitation values, is unlikely to sufficiently address the rising risks. This research modeled several potential broad stormwater management strategies in three different subwatersheds in Minnesota, USA using the US EPA’s storm water management model (EPA-SWMM). The stormwater management strategies included three storage-based approaches, one conveyance approach, and one infiltration approach. The performance of each scenario was measured by reduction in average model node depth from baseline and reduction in peak flow rate at the outlet. Adding new storage ponds ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="2,100 minus 5,100 normal m cubed" display="inline" overflow="scroll"> <mml:mn>2,100</mml:mn> <mml:mtext>−</mml:mtext> <mml:mn>5,100</mml:mn> <mml:mtext> </mml:mtext> <mml:msup> <mml:mi mathvariant="normal">m</mml:mi> <mml:mn>3</mml:mn> </mml:msup> </mml:math> of live storage) equipped with continuous monitoring and adaptive control (CMAC) systems to the watersheds was the most effective strategy modeled, followed by adding new storage ponds without CMAC, and the amount of storage added by each scenario (on a per area basis) was found to have a positive relationship with performance across precipitation depths and watersheds. The conveyance strategy, uniformly upsizing stormwater pipes, was found to decrease peak depths for upstream nodes while increasing peak depth for downstream nodes and increasing peak outlet flow rates for the 24-h, 100-year storm by 3.8%–16%.