Investigating hurricane-induced compound flooding and sediment dispersal using coupled hydrology and ocean models

Abstract:

In events with extreme precipitation, the compound effects of river flooding and ocean surge can be extremely hazardous to vulnerable infrastructure. In addition, flooding leads to freshwater carrying pollutants, sediment, organic matter, and other debris can be released to the coastal ocean, contributing to beach closures, hypoxic events, and other ecosystem impacts. New tools are needed to simulate these complex coupled hydrologic and ocean processes. To achieve this, we have integrated WRF-Hydro into the framework of the Coupled Ocean Atmosphere Wave Sediment Transport modeling system (COAWST), offering the potential to investigate the role of three-dimensional land-ocean interaction processes in coastal storm hazards. A number of new features, including the coupling with the ocean model (ROMS) and a sediment yield and transport module, are introduced to the WRF-Hydro system recently. The COAWST model now features a seamless coupling between WRF-Hydro and ROMS via the exchange of water level and sediment at the land ocean boundary. Here, this new forecast model coupling is described, with an application to Hurricane Florence. Extreme precipitation during Hurricane Florence, which made landfall in North Carolina in September, 2018, led to breaches of hog waste lagoons, and wastewater treatment facilities. The pathways of these pollutants through the land-ocean system is investigated by quantifying the magnitude and spatiotemporal patterns of freshwater, tracers, and sediment. Model results will also be used to diagnose the cross-shelf exchange, along-coast transport and dilution of contaminants in the coastal ocean, providing useful information for mitigation efforts and actions to improve resilience to the compound flooding.