Nature-based solutions: an effective approach for flood mitigation and resilience in the Quad Cities in future climate

Flooding, a major global climate hazard, increasingly threatens urban and low-income regions due to intensified rainfall from climate change. This study focuses on the Quad Cities: Davenport IO, Bettendorf IO, Moline IL, and Rock Island IL, to assess evolving flood risks and the effectiveness of Nature-based Solutions (NbS). Using CMIP6 climate models, 26 models were statistically downscaled with bicubic spline interpolation and bias-corrected using empirical quantile mapping (EQM). MIROC6 was selected for its superior performance (RMSE ~14%, NSE ~0.68) when compared U.S. Geological Survey (USGS) raingage data. Downscaled precipitation were ingested into SWMM+HEC-RAS to simulate runoff and flooding. Results reveal that NbS such as infiltration trenches, permeable pavements, and rooftop disconnections can reduce runoff by up to 37% in Rock Island and 14 - 30%, lowering peak runoff by 19% during extreme events. The findings guide climate-resilient urban planning and sustainable stormwater management in the face of future climate variability.