Wave transformation modeling at Cape Fear River entrance, North Carolina

Wave transformation in the region of Cape Fear, NC, is investigated through field measurements and application of the numerical spectral wave model STWAVE. Field data on offshore and nearshore directional waves, high-resolution bathymetry, tide, and wind were collected starting in the fall of 2000. The applicability of using offshore gauge data as input along the model boundary was evaluated by additional modeling on a coarse grid extending seaward beyond the influence of irregular shelf bathymetry. Model evaluation is presented based on three storm events. For nearshore model and gauge results paired in time, the root-mean-square error in wave height is 0.2-0.5 m and in wave direction is 14-24 deg. The relative importance of accurate bathymetry, tide, wind, nonlinear wave-wave interactions, and spectral shape (measured versus parameterized) are examined with model sensitivity studies. Impacts on potential longshore transport computations are also considered. High-resolution bathymetry is found to be most significant in reducing model versus gauge differences. Use of parametric input spectra gave comparable results to input of measured two-dimensional spectra for the selected storms.