Assessment of Future Stormwater Runoff Scenarios in the Suwannee River Basin under changing Climate and Land uses

We assessed the historical and future stormwater flooding scenarios for the lower Suwannee River Basin of Florida. The sensitivities of stormwater runoff to reference changes in climatic variables and land uses were determined by developing a large-scale process-based hydrologic model using the Storm Water Management Model (SWMM 5.1) of U.S. EPA. The model was calibrated and validated at two locations using observed daily mean stream flows during 2004-13. The total basin runoff was highly sensitive to the rainfall and imperviousness, while showing moderate sensitivities to changes in watershed evapotranspiration, slope, and roughness. The response of stormwater runoff under simultaneous hydro-climatic and climate-land cover perturbations were notably different than the summations of their individual contributions. We then incorporated the downscaled climatic projections of 20 GCMs, obtained from the coupled model intercomparison project (CMIP5) and future projections of percent impervious surface from U.S. EPA to compute stormwater budgets for historical (2010s = 2004-2013) and two future periods (2050s = 2044-2053, and 2080s = 2076-2085). Comparative synthesis of the historical and future stormwater flooding scenarios, along with the sensitivity analyses, provided valuable insights into the potential changes in runoff under the changing climate and land uses. Our findings will aid in efficient management of stormwater flooding in the Suwannee River Basin and similar large-scale watersheds across the globe.