A wave overtopping rate for a seawall on coral reef may be evaluated with the estimation diagrams of it on sloping beach, which is proposed by Goda & Kishira (1975).To do this, Miyakuni et al. (2008) have suggested that wave set-up and surf-beat should be added to the design water depth which is applied on them. Moreover, Hirayama et al. (2009) have indicated that such design conditions on a coral reef can be calculated by using the Boussinesq-type wave transformation model developed by Hirayama & Hiraishi (2005).
In this study, an applicability of such estimation method is verified with the results of model experiments which are carried out on a horizontal basin, and it is confirmed that the calculations of wave transformation on coral reef should be conducted with the topography installed the designed seawalls. Moreover, a drain installed behind seawall can reduce wave overtopping rate in case that the water surface of drainage would keep lower level in the drain.