In the framework of the NOPP project “Hurricane Coastal Impacts” Deltares USA, Deltares Netherlands, USGS, NRL-SSC and IHE Delft are developing a forecasting system that can compute hurricane impacts of flooding, erosion and structural damage along the US Gulf of Mexico coast and the Eastern Seaboard.
The first version of the CoSMoS (COastal Storm MOdelling System) model system to compute flooding and erosion is set up and ready to be tested on the first hurricane events of the 2022 season. The model chain contains a number of model components:
At the largest scale we run a HurryWave wave model for the entire North Atlantic (tier 1 in Figure 1), driven by COAMPS (during hurricane events) and GFS (during non-hurricane time intervals) wind fields. Nested in this North Atlantic model are more detailed models with higher resolution along the US East Coast and Gulf of Mexico (GoM) (Tier 2), with at the highest resolution coastal wave models at Tier 3. With these models we can compute the nearshore wave conditions.
Figure 1: HurryWave wave model domains at level Tier 1 (North Atlantic), Tier 2 (US East Coast and Gulf of Mexico) and Tier 3 (detailed coastal wave models).
Surge and flood models
We also run SFINCS (Leijnse et al., 2021) surge and flooding models at two levels. Surge and tide is computed in two SFINCS models for the US East Coast and the Gulf of Mexico (Figure 2, Tier 1), with flood models at Tier 2 covering the Gulf of Mexico coast, and the Eastern Seaboard south of the Chesapeake Bay. SFINCS models for the Mid-Atlantic and New England are under development. With these models we can compute the surge and tide levels, and the overland flood depth and duration. SFINCS flood models at Tier 2 is run at a 200-meter resolution but with an innovative subgrid approach which means that flood depths at 3-meter resolution can be resolved.
Figure 2: Coastal SFINCS models (Tier 1) and SFINCS overland flood models (Tier 2).
Erosion and structural damage model
The SFINCS and Hurrywave models finally drive hundreds of 2D XBeach (Roelvink et al., 2009) morphodynamic models. At the moment we have implemented XBeach models along all sandy coastlines in the Gulf of Mexico, and along the Outer Banks of North Carolina (Figure 3). These models will output coastal erosion and sedimentation and give input to a module to compute structural damage of houses (under development).
Figure 3: Top: locations with sandy coastlines in the Eastern USA (courtesy USGS) and bottom: detail of the implemented Xbeach models along the Mississippi, Alabama and Florida Panhandle coasts.