Abstract
In order to examine the stability of caisson breakwater against Tsunami which flow over the top of caisson, wave flume experiments and numerical calculations were carried out. As a result of experiments, it is shown that the water surface elevation observed behind the caisson breakwater reached the maximum (or minimum) value earlier than that observed in front of the caisson did and this may decrease the stability of the caisson. As for numerical calculations, the water particle velocity which flow over the top of caisson is very large and large scale turbulence was computed behind the caisson. This large velocity and the turbulence may cause the caisson overturning, which was observed in the experiments.
