Abstract
Many breakwaters suffered from the huge tsunami caused by the East Japan great earthquake disaster in 2011. It is reported that harbor side mound scoring by the tsunami overflow was one of the main causes of collapse of breakwaters. In this paper, we examined the differences of conditions when collaping occurred and did not occur by hydraulic model tests.We showed the ramming down angle of overflow and the point of action to breakwater mounds de-pended on water depth of overflow. And the most dangerous water level was not necessarily the peak level. In addition, we showed the coping of mounds had big effects in collapse of breakwaters.It is very important to know the most dangerous water level precisely in examining countermeasures for preventing harbor side mound scoring by tsunami overflow.
