Modeling Compound Flooding from Hurricane Florence Using ADCIRC. Part I: Coastal Response

On September 14, 2018, Hurricane Florence made landfall near Wrightsville Beach, North Carolina. The slow-moving storm produced a costly combination of storm surge and extreme precipitation, causing record-setting flooding and stream flows at many locations in both southeastern North Carolina and northeastern South Carolina. According to the NOAA National Centers for Environmental Information, the hurricane caused damages totaling approximately $24 billion. Florence, along with other recent storms and coastal flooding events in the U.S., provides motivation to effectively model the hydrodynamics and hydrology of the low-lying transitional terrain between the upland and the shoreline in an effort to improve water level forecasting. This disastrous event provides a unique opportunity to study contributions from both storm surge and river discharge towards total water levels, which will give guidance for how best to model compound flooding in coastal transition zones. Herein, the Florence storm surge is computed using the ADCIRC coastal hydrodynamic model, and model skill is assessed using the parametric hurricane model (Generalized Asymmetric Holland Model – GAHM) used for forecasting and reanalysis winds provided by Ocean Weather, Inc. The model is run with and without inflows from available USGS river gauges throughout the region as a first pass for determining the impact of river flow/runoff on the simulated response. A second talk in this sequence provides a deeper analysis into available hydrologic model output for Florence and its coupling with ADCIRC.