Integrating compound flood conditions through 2D hydraulic modeling for simulating flood risk processes in coastal cities

Low elevation coastal karst environments are highly vulnerable to flooding conditions due to climate change. Trends in rising global temperatures have increased the frequency and intensity of extreme precipitation, hydrometeorological phenomena and sea level rise, exacerbating the impact of pluvial, fluvial, coastal and groundwater flood hazards. Compound flooding events amplify flood hazards and pose a higher threat to residents and infrastructure in unison compared to independent phenomena. Recent advancements in coupling hydrologic and hydraulic modeling frameworks have improved our ability to account for the combined effects of extreme pluvial, fluvial, and coastal flood hazards. This innovation in the hydroinformatics field facilitates more robust estimation of inundation, in turn improving floodplain mapping and mitigation strategies. Although groundwater flooding is frequently overlooked in flood modeling due to its sporadic frequency worldwide and typically less severity compared to other flood hazards, the depth of the water table plays a crucial role in flood inundation dynamics, as high water table levels can diminish the soil infiltration rate and undermine the performance of storm drain systems, leading to chronic flooding scenarios. In this study, we apply a two-way coupling technique to develop an integrated surface-subsurface water model capable of simulating the compound flooding potential of rainfall, tides, and groundwater mechanisms for the Arch Creek Basin located in North Miami, Florida (US), a region particularly prone to intense precipitation, hurricanes, king tides, high water tables, sunny day flooding and SLR. The experiment suggests that groundwater-induced flooding is localized and influences the inundation area. In addition, copula-based statistical analyses were incorporated to simulate different combinations of flood drivers with predefined groundwater levels and sea level rise projections to characterize their relevance and impact in terms of inundation depth, extent, and building damage for current and future scenarios. The contributions of this research are substantial and go beyond the numerical simulation scope, as it supports numerous fields and real applications including flood management, urban planning and design, flood mapping and zoning, flood insurance policies and policy making.