Author(s): Nguyen Xuan Dao; Mohammad Bagus Adityawan; Hitoshi Tanaka; Pengzhi Lin
Keywords: 2011 Tohoku tsunami; Numerical model; Shore-parallel canal; Tsunami energy dissipation; Turbulence flow
Abstract: The Great East Japan Earthquake and Tsunami of 2011 had caused huge damage to people and civil infrastructure around Japan. This large -scale disaster has been provided many valuable practical lessons regarding the huge consequences and potential impact of megaearthquake and megatsunamis. There have been many studies on the effects of construction solutions such as coastal embankment, breakwater, as well as non-structural solutions such as pine trees, mangrove forest, and coastal dunes for reducing tsunami energy when it spreads in coastal areas. But the fact that most of these solutions only make significant in the case of relatively small tsunami events; in terms of multiple defense against largest tsunamis, there is a need to combine multiple solutions together. In addition, there have rarely been discussed the effectiveness of canal to reduce the tsunami impacts. Thus, the main objectives of this research are to investigate the effectiveness o f a shore-parallel canal on tsunami mitigation. Numerical model is presently a valuable tool to assess the tsunami risks. Since shallow water equation (SWE) cannot be realistically captured breaking waves near the shoreline; thus a numerical model based on Reynolds Averaged Navier-Stockes (RANS) equations was developed to account for the effects of wave-induced turbulence on the coastal embankment and canal. In this study, a NEWFLUME model is applied to simulate the recent Great East Japan Earthquake and Tsunami 2011 along the coast of Sendai. Numerical results revealed that the Kita-Teizan Canal which is parallel with the shoreline of Sendai coast has reduced the energy of tsunami. In addition, estimated time of tsunami arrival was delayed due to the effect of canal comparison with the case without canal. Overall, the results of this research show that the effectiveness of the canal which is parallel to the shoreline in terms of multiple defence against largest tsunami.