Stormwater Runoff Response under Changing Climate and Land Uses in Large-scale coastal-urban-natural environments

This study investigates the standalone and combined impacts of climatic and land cover changes on stormwater runoff and compares the historical and future stormwater runoff scenarios for coastal-urban-natural environments. A large-scale process based hydrologic model has been developed for the Southwest Florida Basin by using the modeling platform of U.S. Environmental Protection Agency (EPA)'s Storm Water Management Model 5.1. The model was calibrated and validated with daily streamflow observations at six major rivers of the study basin during 2010s (20042013). We computed stormwater runoffs for 2050s (20442053) and 2080s (20762085) by incorporating climatic features from the Coupled Model Intercomparison Projects fifth phase (CMIP5) global climate models (GCMs) (20 models) from the multivariate adaptive constructed analogs (MACA) and future land cover projections from US EPA under two Representative Concentration Pathways (RCP) - RCP 4.5 and RCP 8.5 scenarios. The simultaneous changes in climate and land cover exhibited linear responses of runoff. The projected concurrent changes in climate and land cover would lead to an increase in the mean annual basin runoff volume by 26%, 28%, 24%, and 17% under the 2080s-RCP 4.5, 2050s-RCP 4.5, 2050s-RCP 8.5, and 2080s-RCP 8.5 scenarios respectively. The findings of this study will provide crucial insights and guidelines for proactive management of stormwater flooding infrastructures in similar coastal urban-natural environments across the world.