Author(s): Yuya Kimiwada; Norio Tanaka; Takehito Zaha
Linked Author(s): Norio Tanaka
Keywords: No Keywords
Abstract: The 2011 Great East Japan tsunami revealed the weaknesses of a coastal embankment as a tsunami mitigation strategy and instead showed that a compound defence system might be more appropriate as a tsunami mitigation strategy. Current defence systems include coastal forest, moat and an embankment. This study was conducted to elucidate at which arrangement a compound defence system would provide the optimum tsunami mitigation benefits, i. e. the maximum reduction in fluid force and delay in arrival time of the tsunami wave. A flume with a quickly lifting gate was used to make a surge-type flow. Wave gauges and a velocity meter were placed inside this flume to measure the tsunami arrival time, velocity and the water depth. With this information, the fluid force index u h (where u: velocity and h: inundation depth) behind the compound defence system was calculated. The results showed that a compound defence system in the order of embankment, moat, and vegetation from the shore line can reduce fluid force index around 80%, which is most effective compared with other arrangements.