Compound Effect of Sea-Level Rise, Groundwater Rise, and Coastal Watershed Precipitation on Coastal Inundation

Abstract:

Compound effects correspond to events with multiple concurrent or consecutive drivers (e.g., coastal flooding, high tides, sea level rise, etc. ) leading to substantial impacts on the environment and communities. Also, under the changing climate, storm events projected to increase in frequency and intensity could (i) cause more intense precipitation-driven surface flows in coastal communities, and (ii) increase the risks of Sea-Level Rise (SLR)-driven uprising groundwater, which could contribute to the additional inundation and thus impacting more humans, and infrastructure. Although there is (limited) scientific literature available on projecting the inundation caused by SLR-driven groundwater rise, there is a distinct knowledge gap on understanding the compound effects of these phenomena considering the important hydrological and hydraulic considerations. To fill this knowledge gap, we developed a novel analytical framework to understand the movements of the surface flow under annual precipitation events considering its interaction with uprising groundwater and sea level rise. SLR-driven groundwater shoaling and emergence is assessed by generating and interpolated groundwater table surface, and subtracting the land-surface DEM from the groundwater table surface, and adding the desired amount of SLR using ArcGIS. In order to consider the compound effect of SLR, groundwater inundation, and precipitation-driven surface flow we performed a 2-dimensional, unsteady modelling of inundation under annual precipitation events, using groundwater inundation and SLR heights as boundary conditions. The framework is employed to develop the first comprehensive tool that effectively projects inundation in coastal communities under the frequent events from multiple sources. This modelling approach simulates the dynamics of compound inundation in a fine resolution, which is critical for devising proper flood management strategies. The focus of this study is on the underrepresented coastal communities like Imperial Beach and Alameda flatlands that typically encounter disproportionate environmental injustices due to the abundance of aged elements in their built infrastructure. These environmental injustices can emerge as overexposure to pollution and flooding issues because of compound effect of sea level rise and frequent precipitation-driven surface flows.