After the 2011 Great East Japan tsunami, field observations have shown the possibility of an inland forest trapping tsunami-borne large driftwood (TLD). This research was conducted to understand the driftwood trapping capability by a forest patch downstream of a shoreline, considering a model scale driftwood with attention to the crown and roots of a tree. The results demonstrated that there are four types that driftwood gets trapped by an inland forest, with each trapping type exhibiting a different force on the trapping tree. A trapping type where the driftwood got trapped at the front face of an inland forest model (IFM) in a cross-stream position by one or more trunk(s) (Type FC) exhibited high force on the trunk, because of the high cross-sectional area of the driftwood against the flow. However, when the upstream trees’ (potential to being TLD) trunk length was small, the occurrence of this trapping type decreased. The results showed that the trunk length to tree height ratio of 0.18 had a trapping occurrence of 33%, while trunk length to tree height ratio of 0.06 had a trapping occurrence of 16%. The driftwood condition, in this case, was driftwood with roots. This study further demonstrated the behaviour of driftwood trapping by an inland forest and proposed a further improvement to tsunami mitigation, by elucidating its ability to trap tsunami-generated large driftwood as a function of trunk diameter at breast height.

中文翻译：

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内陆森林作为诱捕功能，可抵御海啸传播的大片破碎或被冲刷的树木

在2011年东日本大海啸之后，现场观察表明，内陆森林可能会困住海啸传播的大浮木（TLD）。进行这项研究是为了了解海岸线下游的一片森林中的浮木捕获能力，考虑模型规模的浮木并注意树冠和树根。结果表明，有四种类型的浮木被内陆森林捕获，每种捕获类型对捕获树表现出不同的作用力。浮木被一个或多个树干（FC型）在横流位置被内陆森林模型（IFM）的前表面困住的陷阱类型（FC型），因为交叉强度高截流的截面积。然而，当上游树木（可能为TLD）的树干长度较小时，这种诱捕类型的发生率会降低。结果表明，树干长与树高之比为0.18时有33％的诱捕发生，而树干长与树高之比为0.06时有16％的诱捕发生。在这种情况下，浮木的状况是带有根的浮木。这项研究进一步阐明了内陆森林诱捕漂流木的行为，并提出了进一步的缓解海啸的措施，方法是阐明其捕获海啸产生的大漂流木的能力，该能力随胸高的树干直径而变。而树干长与树高的比率为0.06，则有16％的诱捕发生。在这种情况下，浮木的状况是带有根的浮木。这项研究进一步阐明了内陆森林诱捕漂流木的行为，并提出了进一步的缓解海啸的措施，方法是阐明其捕获海啸产生的大漂流木的能力，该能力随胸高的树干直径而变。而树干长与树高的比率为0.06，则有16％的诱捕发生。在这种情况下，浮木的状况是带有根的浮木。这项研究进一步阐明了内陆森林诱捕漂流木的行为，并提出了进一步的缓解海啸的措施，方法是阐明其捕获海啸产生的大漂流木的能力，该能力随胸高的树干直径而变。