河流原木对河岸侵蚀潜力的影响:用单个原木进行的水槽研究

IF 4.6 Q2 ENVIRONMENTAL SCIENCES
Nuosha Zhang, I. Rutherfurd, M. Ghisalberti
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引用次数: 9

摘要

摘要河岸树木减少了河岸侵蚀,这是公认的。然而,倒下的树木会增加河岸侵蚀,因为水流在原木及其根板和河岸之间发生偏转和加速,增加了边界剪应力,侵蚀了河岸。这种侵蚀导致水力变化,但也可能是恢复河流木材负荷的一个问题。在对这一现象的首次定量研究中,我们开发了一个理论水力模型,根据一系列测井特征(形态、角度、与河岸的距离)和流动特征,利用连续性和能量损失原理来估计单个测井曲线附近的近岸速度。水槽实验支持理论模型,并表明单个原木几乎可以使近岸速度增加一倍。测井曲线所占的分流通道面积(堵塞比)和测井曲线与河岸之间的距离是控制近岸流速的关键因素。原木与河岸的夹角越小,侵蚀速率越低,而且侵蚀向下游延伸越远。随着原木落入河道后形态的变化,岸坡侵蚀可能会迅速发展,但随着时间的推移会减慢;并向下游迁移。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Effect of instream logs on bank erosion potential: a flume study with a single log
Abstract It is well established that riparian trees reduce bank erosion. However, fallen trees can increase bank erosion as the flow is deflected and accelerated between the log and its root-plate and the bank face, increasing the boundary shear stress and eroding the bank. This erosion contributes to hydraulic variability but can also be a concern in restoring wood loads in rivers. In this first quantitative study into this phenomenon, we develop a theoretical hydraulic model to estimate the near-bank velocity around a single log using principles of continuity and energy loss for a range of log characteristics (morphology, angle, distance from the bank) and flow characteristics. Flume experiments support the theoretical model and suggest that a single log can almost double the near-bank velocity. The fractional channel area taken up by the log (blockage ratio) and the distance between the log and the bank are key factors governing the near-bank velocity. The smaller the angle of the log with the bank the lower the erosion rate, but also the further downstream the erosion extends. As the morphology of the log changes after falling into the channel, bank erosion potentially develops quickly, but slows over time; and migrates downstream.
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CiteScore
7.10
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