TSUNAMI MITIGATION EFFECT AND TREE BREAKING SITUATION OF DAHURIAN LARCH COASTAL FORESTAT SIX GROWTH STAGES UNDER THINNING MANAGEMENT OF TREES
TSUNAMI MITIGATION EFFECT AND TREE BREAKING SITUATION OF DAHURIAN LARCH COASTAL FORESTAT SIX GROWTH STAGES UNDER THINNING MANAGEMENT OF TREES
复制标题
间伐管理下达胡里安落叶松沿海林地六个生长阶段的海啸减缓效应及树木折断情况
DOI：
10.3850/38wc092019-0738
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
H. Torita
中科院分区：
文献类型：
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作者：
Y. Igarashi;N. Tanaka;Hajime Sato;H. Torita
沿海森林可以消散一部分海啸能量，但有产生浮木的风险。在不破坏林木的情况下，通过数值模拟和水槽试验对海岸带森林的作用和极限进行了研究。为了减轻海啸能量，日本北海道局计划建立一个由沿海森林和任何人工结构（如堤坝）组成的混合防御系统。无论树木是否被破坏，混合防御系统的有效性都可能发生变化。根据生长情况定期进行间伐管理，使木材质量良好。因此，本研究的目的是探讨如何间伐管理影响海岸森林的缓解效果和树木断裂情况对6个生长阶段，使用二维深度平均海啸流模型。结果表明，幼龄海岸林由于胸径和冠高的增长，其破碎率高于生长良好的海岸林。另一方面，即使将树木折断的影响计入在内，幼林的海岸林后方的海啸缓和效果也比发达林大，因为折断的方式不是“树干折断（树冠部分折断）”，而是“倾覆（树冠部分淹没在水下）”，即使折断后阻力变小，也能保持。这是由于幼林树冠高度小，密度大。
Coastal forest can dissipate a part of tsunami energy but has a risk of producing driftwood. There are many studies about the effect and limit of coastal forest by numerical simulation and/or flume experiment when the trees are not broken. To mitigate tsunami energy, a hybrid defense system consisting of a coastal forest and any artificial structure like an embankment are planned by the Hokkaido Bureau in Japan. The effectiveness of the hybrid defense system could be changed whether the trees are broken or not. The thinning management is regularly held according to the growth situation for making woods quality good. Therefore, the objective of this study is to investigate how the thinning management affects the mitigation effect and tree breaking situation against six growth stages of coastal forest by using two-dimensional depth-averaged tsunami flow model. The results show, the breaking rate of the young coastal forest is higher than that of a well-grown coastal forest due to the growth of tree diameter and tree crown height. On the other hand, the tsunami mitigation effect behind coastal forest of young forest is larger than that of well-grown forest even including the effect of tree breaking, as the breaking pattern is not ‘tree trunk breakage (tree crown part is broken off)’, but ‘overturn (tree crown part is submerged under water)’, and the resistance can be kept after breaking even though it becomes smaller. This is because that the tree crown height of young forest is small, and the density is high.