The effectiveness of coastal vegetation as a barrier to mitigate a tsunami greatly depends on the magnitude of tsunami and vegetation structure. This paper summarizes a series of laboratory experiments that investigated the upstream flow structure and energy loss due to a hydraulic jump in a steady super-critical flow. The characteristics of the jump were determined against vegetation of variable density ([Formula: see text], where [Formula: see text] of each cylinder in cross-stream direction, [Formula: see text] of cylinder), thickness (dn, where [Formula: see text] of cylinder, [Formula: see text] of cylinders in the stream-wise direction per unit of cross-stream width), and initial Froude number (Fro, where Froude number is obtained from a model without vegetation in the flume). In super-critical flow ([Formula: see text]–1.83), a weak hydraulic jump formed on upstream side of vegetation. The height of the jump, its location, and the resulting energy loss were increased by increasing both the vegetation density and thickness. Due to reduced reflection at vegetation front, the drag force against sparse vegetation ([Formula: see text]/[Formula: see text]) was higher compared to intermediate ([Formula: see text]/[Formula: see text]) and dense ([Formula: see text]/[Formula: see text]) vegetation. Under these conditions, the maximum energy reduction due to a weak hydraulic jump reached 9.4% for dense vegetation while it was 8.1% and 7.8% for intermediate and sparse vegetation, respectively.

中文翻译：

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上游不同密度和厚度植被形成的水跃特征

沿海植被作为减轻海啸屏障的有效性在很大程度上取决于海啸的幅度和植被结构。本文总结了一系列实验室实验，这些实验研究了在稳定的超临界流中由于水跃而导致的上游流动结构和能量损失。跳跃的特征是根据不同密度的植被确定的（[公式：见文本]，其中[公式：见文本]每个圆柱体在横向流方向，[公式：见文本]圆柱体），厚度（dn，其中 [公式：见正文] 圆柱体 [公式：见正文] 每单位横流宽度沿流向的圆柱体 [公式：见正文]，初始弗劳德数 (Fr○，其中弗劳德数是从水槽中没有植被的模型获得的）。在超临界流动（[公式：见正文]–1.83）中，植被上游侧形成弱水跃。通过增加植被密度和厚度，跳跃的高度、位置和由此产生的能量损失都增加了。由于植被正面的反射减少，对稀疏植被的阻力（[公式：见文本]/[公式：见文本]）与中间（[公式：见文本]/[公式：见文本]）相比更高，并且密集的（[公式：见正文]/[公式：见正文]）植被。在这些条件下，由于弱水跃导致的最大能量减少对于密集植被达到 9.4%，而对于中间植被和稀疏植被分别为 8.1% 和 7.8%。