CHANGE OF OVERTOPPING TSUNAMI FLOW RATE FROM EMBANKMENT WITH THE ARRANGEMENT OF THE EMBANKMENT AND COASTAL FOREST

Abstract

 The Great East Japan tsunami has revealed the limit of hard solution by only sea embankment. Thereafter, a multiple defense system for Level2 tsunami that combined coastal forest and sea embankment is planned. This study is conducted to clarify the change of overflow rate from embankment with the location and thickness of coastal forest. Flume with sudden opening gate for making tsunami-like unsteady flow was used to investigate the change with various multiple defense models. The results indicates that seaside coastal forest can reduce overtopping flow rate than landward. Even when the seaside forest is thin, the flow pattern change in front of embankment increases the total reflection and decreases the overflow rate around 10%, although the forest itself does not increase the reflection.