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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Impact of reach geometry on stream channel sensitivity to extreme floods
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Impact of reach geometry on stream channel sensitivity to extreme floods

机译：河段几何形状对河道对极端洪水敏感性的影响

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Predicting spatial and temporal variations in bank erosion due to extreme floods presents a long-standing challenge in geomorphology.We develop two methodologies for rapid, regional-scale assessments of stream reaches susceptible to channel widening. The first proposes that channel widening occurs when unit stream power exceeds a critical threshold (300W/m~2). The second is motivated by the observation that widening often occurs at channel bends. We introduce a new metric, the bend stress parameter, which is proportional to the centripetal force exerted on a concave bank. We propose that high centripetal forces generate locally high bank shear forces and enhance channel bank erosion. We test both metrics using the geomorphic signature of Tropical Storm Irene (2011) on the White and the Saxtons Rivers, Vermont. Specifically, we test if reaches where significant channel widening occurred during Irene required one or both metrics to exceed threshold values.We observe two distinct styles of channel widening.Where unit stream power and bend stress parameter are high, widening is usually due to bank retreat. Elsewhere widening is usually due to the stripping of the upstream end of midchannel islands. Excluding widening associated with the stripping of the heads of mid-channel islands, almost all the widening (> 98%) occurred along reaches identified as susceptible to widening. The combined metrics identify up to one-quarter of the reaches lacking susceptibility to channel widening.
机译：预测由于极端洪水而造成的河岸侵蚀的时空变化是地貌学方面的长期挑战。我们开发了两种方法，用于快速，区域范围内评估易受河道拓宽影响的河段。第一种建议是，当单位流功率超过临界阈值（300W / m〜2）时，发生信道扩展。第二个原因是观察到经常在通道弯曲处出现拓宽。我们引入了一个新的度量标准，即弯曲应力参数，该参数与施加在凹面堤岸上的向心力成比例。我们建议，高的向心力会在局部产生高的堤岸剪切力，并增强河道堤岸的侵蚀。我们使用热带风暴艾琳（2011）在佛蒙特州怀特河和萨克斯顿河上的地貌特征测试了这两个指标。具体来说，我们测试艾琳（Erene）期间是否达到显着的河道拓宽需要一个或两个指标都超过阈值的情况，我们观察到两种不同的河道拓宽样式，其中单位流功率和弯曲应力参数较高时，拓宽通常是由于堤岸撤退所致。其他地方的扩大通常是由于中河岛上游端的剥离所致。除了与中海岛屿头部剥离相关的拓宽以外，几乎所有的拓宽（> 98％）都发生在被确定为易于拓宽的河段。合并后的指标最多可确定四分之一的覆盖范围不易扩展渠道。

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