Assessing hydro- and sediment dynamics of hurricane-induced compound flooding using a dynamically coupled ocean-river modeling suite

We introduced WRF-Hydro to the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System to simulate the water and sediment dynamics during the compound flooding caused by Hurricane Florence in 2018 in the Cape Fear River watershed. The river model (WRF-Hydro) is coupled with the ocean model component (ROMS) along the land-ocean boundary where water level information is exchanged dynamically. A newly developed physics-based, fully distributed soil erosion and sediment transport model, WRF-Hydro-Sed, was used to represent the sediment dynamics in the watershed. Calculated river and surface runoff from hurricane-induced precipitation is ten times the volume of the Cape Fear River Estuary. The models performance in water-level simulation is largely improved (0.3-1.0 m) in the upper Cape Fear Estuary, NC. The spatial-temporal distribution of soil erosion was largely controlled by the rainband structure evolution and slow storm movement. Diagnostic analysis indicates that the compound flooding process can be categorized into four different stages: swelling, local wind dominated, transition, and river dominated.