Experimental study of wave propagation characteristics on a simplified coral reef

The wave transformation over slope topography is widely studied,but most of studies are for common coastal slopes.This paper presents an experimental study of 2-D regular and irregular wave transformations on a simplified coral reef with a steep slope of 1:5 and a horizontal reef flat,focusing on the characteristics of the waves that break on the reef flat.The analyzed results show that the estimates of the wave breaking made by using the well-known previous formulae do not agree completely with the experimental results.When the waves break on a reef flat,the relative breaking wave height(H/d)b is related to the incident deep-water wave steepness and the relative water depth db/L0.Hence,a new criterion for breaking waves on a reef flat is proposed.Furthermore,in view of the fact that the local Ursell number is commonly used to parameterize the wave nonlinearity,the relationships among the skewness,the asymmetry,and the local Ursell number are also presented.Experimental data confirm that when the Ursell number is greater than 30,the absolute values of the skewness and the asymmetry on a reef flat are greater than those on a steep slope.