Simulating Coupled Surge and River Flow and its Influence on Compound Inundation in an Idealized Test Case

Coastal compound flooding, the spatial and temporal co-occurrence of riverine flooding and coastal storm surge, has received much attention recently from both the oceanographic and hydrologic communities. Better prediction capabilities for this scenario are needed, given that the frequency of such events may be increasing. One approach is to couple a watershed model with a storm surge model, although there are several technical issues of this coupling that largely revolve around the physics needed to accurately resolve flow in rivers, coastal waters, and overbank areas. This study explores these challenges to improve our understanding of model coupling and its influence on overall coastal inundation. To focus on the interactions between the two flow regimes, numerical experiments are conducted in an idealized test case, using the ADCIRC model to simulate the flow dynamics and inundation processes. Specifically, we investigate various approaches to ingest along channel flows into ADCIRC, different finite element arrangements, and one-way versus two-way coupling strategies. The impacts of these factors on the flow and inundation characteristics are quantified. The lessons learned from this study are expected to contribute to the knowledge basis for both communities and help make progress on this challenging problem.