Effects of bathymetric complexities and wind generation in a coastal wave propagation model

A new wave modelling strategy has been developed by Holthuijsen et al. (1989) for estimating wave heights for engineering applications in coastal areas. This strategy as well as the original model itself of Holthuijsen et al. (1989), called HISWA, are being used in several engineering applications. This paper examines two aspects of this model: its ability to adequately predict wave properties in regions with complex bathymetry where diffraction effects are likely to be important, and its ability to model wave growth due to wind. The former is of interest because the model is based on the energy-balance equation and does not explicitly incorporate diffraction. Other such models deal with this through artificial bounds on the energy, whereas HISWA does not. It is therefore necessary for the engineer to be aware of its performance in such situations. Investigations are therefore performed using hydraulic model data and the results of other mathematical models that are known to adequately handle such bathymetric configurations. For complex bathymetries, the model is found to give good simulations for sea-states with considerable directional spreading. As the degree of spreading decreased or for certain special wave conditions, model performance was marginal. Finally, the model is used to study the physics of wave decay and wind-induced growth in Saginaw Bay (Michigan) using prototype data.