Experimental study of wave height, crest, and trough distributions of directional irregular waves on a slope

Presently, most studies of wave height distribution on slopes are based on normal incident unidirectional waves. In this study, the wave height, crest, and trough distributions of oblique incident unidirectional and multidirectional irregular waves on a 1:15 slope were experimentally investigated. The Composite Weibull Distribution fitted the experimental data well and could be applied to predict the wave height, crest, and trough distributions for unidirectional and multidirectional waves on the slope. The shape parameter with a constant value k2 = 3.6 in Composite Weibull Distribution proposed by Battjes and Groenendijk (2000) did not describe the actual variation of wave height distribution in the surf zone. The parameters' values in Composite Weibull Distribution were modified and the corresponding fitted formulas were proposed in this paper. The results showed that the fitting parameters' values of Composite Weibull Distribution between normal and oblique incident irregular waves, and between unidirectional and multidirectional irregular waves were slightly different. But the directional spreading had little effect on the fitting parameters' values for narrow directional spreading waves. These findings for a 1:15 slope can be referenced as a supplement to the conclusions of Battjes and Groenendijk (2000).