The main purpose of this study is to investigate wave deformation over a coral reef and wave overtopping characteristics around a vertical seawall by carrying out hydraulic model experiments and numerical computations with a two-dimensional numerical wave flume based on a VOF method ‘CADMAS-SURF’. The comparison of the numerical and experimental results reveals that the CADMAS-SURF can reproduce well the experimental results regarding wave deformation and wave overtopping rate. The results also indicate that the mean water level increases due to successive wave breaking over the reef and wave setup takes place remarkably. The wave overtopping rate for the reef topography is found to be much larger than one on the mild slope.
The passage of tropical cyclones such as tropical storms and typhoons causes sea level rise around coastlines due to atmospheric pressure depression and strong wind, resulting in high waves, storm surges and wave overtopping. Especially, violent wave overtopping over road revetments induces not only human and property damages but also traffic accidents in low visibility conditions and the isolation of interregional transportation networks. Photo 1 exemplifies wave overtopping of road revetment in Okinawa Main Island, which is one of the typhoon prone areas in Japan. Wave overtopping characteristics in Okinawa Islands are said to be complicated since the sea areas have wide coral reefs with very shallow water depth and waves propagate with the repeat of wave breaking over the reef. However, countermeasures against wave overtopping have not been sufficiently taken yet. It is, thus, of extremely importance to fully comprehend wave overtopping characteristics of coastal revetments to prevent wave overtopping-induced disasters. A number of experimental and numerical studies on wave overtopping have ever been done in order to estimate wave overtopping rate and take a countermeasure for the protection of human and property damages by wave overtopping.
