Gulf Coast communities are being increasingly threatened by the compound flood hazards of tide, surge, wind, rain, and waves induced by tropical cyclones. Accurate predictions of flooding, erosion, and damage to infrastructure and threats to human life are essential to emergency management and long-term adaptation planning. This presentation describes the operational use of the Coastal Storm Modeling System [CoSMoS) to generate real-time hazard predictions along the Gulf Coast. CoSMoS has been developed for over fifteen years in collaboration between Deltares and USGS, and has been deployed across the country for both operational and long-term projection applications.

CoSMoS for the Gulf Coast integrates three numerical models to forecast compound flooding from the offshore to the coast: (1) the fast HurryWave model to forecast basin-scale wave period, wave height, and direction from COAMPS-TC meteorological predictions; (2) the SFINCS model to forecast total water level with tide, surge, and overland flooding depth and area; and (3) XBeach to forecast nearshore wave transformation, infragravity waves, coastal erosion, and dune breaching. The system produces 6-hourly operational forecasts.

During the 2024 hurricane season, real-time forecasts were generated for Hurricanes Beryl, Debby, Francine, Helene and Milton, Francine. Validation with observations demonstrates the accuracy of the modeling chain: maximum water levels simulated with a root-mean-square error (RMSE) of 22 cm compared with NOAA tide gauges, and wave heights with RMSE of 65 cm compared with air-dropped drifter buoys. Computed flooding in Tampa Bay during Hurricane Helene was well correlated with observations and local press reports. XBeach morphodynamic predictions correctly forecasted dune breaching and channel re-opening at Midnight Pass, Florida, during Hurricanes Helene and Milton. The accuracy of the model conveys confidence for emergency decision-making and long-term planning.

Having established this modeling framework and operational accuracy during extreme storms in the Gulf, CoSMoS is now perfectly positioned for additional applications in the region, including evaluating the risk associated with sea level rise and future storms, and the loss of coastal habitats (e.g, tidal wetlands), as well as the risk-reduction benefits of coastal habitat conservation and restoration.