Parameterization of geometric characteristics for extreme waves in shallow water

Abstract

This study presents an empirical parameterization of wave steepness and asymmetries used in the characterization of extreme waves in nearshore environment. A large amount of experimental datasets is analyzed for determining possible values of the wave geometric parameters. Results indicate that the steepness and asymmetries of extreme waves increase with water depth become shallower. For the data used here, the local relative wave height Hs/d play a crucial role in determining the geometric parameters of extreme waves different from that in deep water. A set of empirical formulas developed based on data analysis establish relationship between the wave geometric parameters and other parameters of engineering interest. Specifically, the first formula expresses the extreme wave steep as a function of the local relative wave height. The second formula defines the skewness and asymmetry for extreme waves as a function of the local Ursell number. From comparisons of the fitted results for different bottom slope, it is shown that the bottom slope has a negligible effect on the variations in crest-rear steepness, mean steepness and horizontal asymmetry, but obviously affects the crest-front and vertical asymmetry of extreme waves.