Abstract
Most of coastal structures, especially coastal dikes were destroyed by the 2011 Tohoku Tsunami. It was reported that one of the most important causes was the failure of back slope of dikes due to scouring. It is assumed that probability of leading tsunami overflow landward is effective to study robustness of coastal dikes toward the tsunami. In this study, a numerical model using CADMAS-SURF/3D has been applied to clarify the difference of tsunami external force toward back slope of dikes due to structure spectification and to make suggestions for mechanism of robustness and design of coastal dikes. As a result, in order to restraint scouning at back slope of dikes, exceptng method of moderateing the back slope, streamline at top of inner slope and back slope were proposed.
