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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >The effect of instream logs on river-bank erosion: Field measurements of hydraulics and erosion rates
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The effect of instream logs on river-bank erosion: Field measurements of hydraulics and erosion rates

机译：Instream Logs对河流侵蚀的影响：液压和侵蚀率的现场测量

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This is the first substantial field measurement of river-bank erosion around fallen logs in rivers. Whilst numerous studies have established that living trees can stabilize river banks, and that fallen trees can cause scour of the river bed, knowledge of bank erosion effects from logs is largely restricted to qualitative observations. Recent flume studies suggest that a single log can increase near-bank velocity (and thus erosion) and this increase is related to the blockage ratio of the log and the distance between the log and bank. However, hydraulic interactions between logs can reduce this increase or even decrease the near-bank velocity. These theories, developed in a straight flume, have not been tested in the field. We measured erosion rates (relative to controls) on river banks adjacent to 35 large logs for 2 years, and velocity distributions around 11 logs during a near-bankfull flow in anabranching channels of the River Murray, SE Australia. These channels have abundant large instream logs, consistent bank material, and consistent regulated high flows. The field results generally supported the velocity changes caused by single and multiple logs in the flume studies, with single logs increasing near-bank velocity, but with the hydraulic interactions between successive logs tending to reduce this increase. Flow patterns caused by logs adjacent to curved banks were more complicated as the local effects of logs reinforced or weakened recirculating flows. Instream logs did not change overall, average, bank erosion rates, but they tended to shift the erosion from bank top to bank toe. However, individual logs increased or decreased bank erosion rates in patterns that generally concur with the near-bank velocity changes predicted in flume studies: that isolated logs increased erosion rates whilst hydraulically interacting logs did not increase erosion rates. (c) 2020 John Wiley & Sons, Ltd.
机译：这是河流河流河流侵蚀的第一个大实场衡量河流中的日志。虽然众多的研究已经确定了生活树可以稳定河岸，并且落下的树木会导致河床的冲浪，从日志的银行侵蚀效果的知识在很大程度上仅限于定性观察。最近的水槽研究表明，单个日志可以增加近岸速度（并且因此侵蚀），并且这种增加与日志的封闭比率和日志和银行之间的距离有关。然而，日志之间的液压相互作用可以减少这种增加甚至降低近岸速度。这些理论，在直线上发展，尚未在该领域进行测试。我们测量了与35个大日志相邻的河岸上的侵蚀率（相对于对照）2年，以及在澳大利亚River Murray河的Anabranching频道的近乎银行流程中左右11个日志。这些通道具有丰富的大型仪器日志，一致的银行材料和一致的调节高流量。现场结果通常支持由SPUCUS研究中的单一和多个日志引起的速度变化，单数日志增加了近岸速度，但随着连续日志之间的液压相互作用倾向于减少这种增加。由弯曲库相邻的日志引起的流动模式更加复杂，因为原木的局部效应加强或削弱了再循环流动。仪器日志没有变化整体，平均，银行侵蚀率，但它们倾向于将银行顶部的侵蚀转移到银行脚趾。然而，各个日志增加或减少了通常会在水槽研究中预测的近岸速度变化的模式中增加或减少的银行侵蚀率：该隔离的日志增加了侵蚀速率，而液压相互作用的日志没有增加侵蚀速率。 （c）2020 John Wiley＆Sons，Ltd。

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