Application of the SWAN Wave Model to Hurricane Generated Waves on the North Carolina Continental Shelf

The SWAN (Simulating WAves Nearshore) model, developed at Delft University of Technology was applied to reproduce waves during Hurricane Dennis off North Carolina from August 30, 1999 to landfall on September 5, 1999. Hurricane Dennis was a large, persistent tropical cyclone with an erratic path. Although Dennis was downgraded to a tropical storm as it made landfall, it produced waves in excess of 7 m in the model domain and extensively eroded dunes along the North Carolina coast. Two suites of non-stationary model runs were completed for August 30 through September 5. One set of model runs was driven with input from the parametric wind component of the NOAA Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model. The second set of model runs was driven with observed wind fields gridded by the NOAA Hurricane Research Division (HRD). The Shoaling Waves Experiment (SHOWEX) Shelf Bathymetry Data was used for the bathymetric grid. Default model formulations were used along with the Madsen formulation for bottom friction. The two suites of model results were compared and validated with data from NOAA buoy 44014 (47 m water depth) and the directional buoy located off Duck, NC (17 m water depth). SWAN model results were sensitive to resolution of wind input, bathymetric grid resolution, ocean level, and length of time step. Modeled wave climate during Hurricane Dennis compared best with wave data when high-resolution wind input and time steps on the order of minutes were used. The results of this modeling effort are being used to investigate the relationship between nearshore wave characteristics and dune change. (See related abstract by Sallenger et al.)