Abstract
It has become known that the existing tsunami breakwaters are insufficient for sheltering harbors and coastal areas as seen in the incidence of destructive tsunami triggered by 2011 great Tohoku earthquake in East Japan, especially in ria bays of Sanriku Area such as Ofunato Bay. Amplification of tsunami heights in a ria bay is one of major causes of the big disaster. In order to mitigate the tsunami disaster, layout of breakwaters at the mouth of the bay has been studied theoretically by numerical simulations. Breakwaters in multi rows, especially double rows of breakwaters, are typical. Focusing on the harbor oscillations for various tsunami period conditions, effectiveness of proposed layouts of the breakwater was examined extensively.
