COMBINED MITIGATION EFFECTS OF FOREST, HILL AND SEAWALL AGAINST TSUNAMI

Abstract

 The construction of "green hills" in the lowland areas of the damaged Tohoku region are underway as a symbol of the reconstruction due to the mitigating effects that some hills contributed to during the 2011 huge tsunami event. In this study, after comparing the individual mitigation effects of a vegetation, dune and seawall against a tsunami, the combined mitigation effects of these elements were experimentally studied. It is shown that the countermeasure comprising of vegetation, dune and seawall can effectively reduce flood depth, flow rate, and specific energy, as well as further delay the tsunami arrival time. An examination of the amount of water transported by a tsunami to the area behind the coupled countermeasure shows the effectiveness of the comprehensive countermeasures.