Abstract
In the Great East Japan Earthquake, we clarified that Ohtanabe fishing ports have fully function as tsunami mitigation using tsunami simulation. The process in which tsunami develops or propagates is very different depending on the presence or absence of the fishing ports. Especially, if there were not the fishing ports, the tsunami height increases more than 60% at the front of Ohtanabe seawall and the inundation height increases twice at the area inside the seawall. Furthermore, there will be also strongly possibility that the large amount of water is stored within the seawall for a long stretch of time. Therefore, we learned from the disaster that a multilayered defense system should be built to minimize damage in the event of a disaster that overwhelms disaster prevention infrastructures.
