On Modelling Wind-Waves in Shallow and Fetch Limited Areas Using the Method of Holthuijsen, Booij and Herbers

Abstract

A parametric discrete spectral model, MIKE 21 NSW, based on the equations presented by HOLTHUIJSEN, BOOIJ and HERBERS, 1989 (HBH) is used to compute the growth of wind-waves in the shallow and fetch limited waters off the coast of Lolland, Denmark. A simple procedure is used to obtain the HBH wind-wave growth coefficients from empirical deep water wave growth formula without the need of tuning. Simulations are carried out to assess the influence of wind-wave growth source functions, bottom friction, wave breaking and assumed spectral shape. Results indicate that for this limited fetch (about 20 km) in relatively shallow water (depths about 3-4m near measurement locations), the locally generated significant wave heights are not sensitive to bottom friction and depth induced wave breaking. Of the 5 wave growth formulas investigated, the best results were obtained using HBH coefficients corresponding to the SPM (1984) or the KAHMA & CALKOEN (1994) formulas. The results show that the method performs much better for calculating waves in shallow and fetch limited situations than a direct calculation with the SPM (1984) shallow water formula.