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Experimental Investigation for the Effects of Tree Arrangement in a Forest on Mitigating Tsunami

Author(s): Kosuke Iimura; Norio Tanaka; Kenji Harada; Katsutoshi Tanimoto

Linked Author(s): Norio Tanaka

Keywords: Tsunami; Coastal vegetation; Tree density

Abstract: Coastal vegetation is currently being introduced as a comprehensive strategy to mitigate the destructive force of tsunami. Some studies investigated quantitatively the coastal vegetation effects on mitigating tsunami, however, the effects of distribution of tree density in a forest on the reduction of tsunami energy have not been elucidated yet. The tsunami mitigation by the coastal vegetation were investigated experimentally by changing the tree density in a forest model under the constant vegetation thickness (dn, where d is the diameter of a tree trunk and n is the number of trunks in streamwise direction). In the experiments, water level, velocity, drag force, and run-up height were measured. Moreover, numerical simulation was performed for conditions as same as the experimental conditions, The simulated velocity behind the vegetation area were validated with the experimental studies. Under the same dn, the run-up height and maximum velocity behind the vegetation model for the dense case have become smaller than that for the sparse case. This implies that the coastal vegetation for tsunami mitigation should be as dense as possible, even if the vegetation thickness is the same.


Year: 2011

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