Experimental meandering river with chute cutoffs
Experimental meandering river with chute cutoffs
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DOI：
10.1029/2011jf002314
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发表时间：
2012-09
影响因子：
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通讯作者：
W. M. Dijk;W. V. D. Lageweg;M. Kleinhans
中科院分区：
文献类型：
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作者：
W. M. Dijk;W. V. D. Lageweg;M. Kleinhans
辫状河在实验室中相对容易产生，而动态曲流河在最初的弯曲形成之后并没有持续存在。曲流的理论解释是由平面扰动引起的弯曲不稳定性，它向下游对流。在这项研究中，我们通过实验验证了上游扰动和溜槽切断发展在曲流河道模式的演化和动力学中的重要性。最初的直道有一个横向移动的上游入口点，泥沙饲料中添加了粉砂大小的二氧化硅粉，以形成洪泛平原。我们用滚动条获得了一条动态蜿蜒的河流。弯曲生长由斜槽切断交替形成，斜槽切断横跨点杆。当一个通道被一个插销断开时，保持了蜿蜒。斜槽分叉处的弯曲输沙，形成新的洪泛平原，而另一个河道变宽。实验结束时，河漫滩呈现曲流河道、点坝、溜槽、废弃河道和部分淤积河道，河漫滩表面具有与天然曲流砾石河床相似的微粘性。认为动态曲流砾石河床形成的充分必要条件是上游持续的动态扰动和漫滩的形成。
[1] Braided rivers are relatively simple to produce in the laboratory, whereas dynamic meandering rivers have not been sustained beyond initial bend formation. Meandering is theoretically explained by bend instability growing from planimetric perturbation, which convects downstream. In this study, we experimentally tested the importance of upstream perturbation and chute cutoff development in the evolution and dynamics of a meandering channel pattern. The initial straight channel had a transversely moving upstream inlet point and silt-sized silica flour was added to the sediment feed to allow floodplain formation. We obtained a dynamic meandering river with scroll bars. Bend growth was alternated by chute cutoffs that formed across the point bars. Meandering was maintained as one channel was disconnected by a plug bar. The curvature at the chute bifurcation transported sediment and build a new floodplain, while the other channel widens. At the end of the experiment, the fluvial plain exhibited a meandering channel, point bars, chutes and abandoned and partially filled channels with a slightly cohesive floodplain surface similar to natural meandering gravel bed rivers. We conclude that the necessary and sufficient conditions for dynamic meandering gravel bed river are a sustained dynamic upstream perturbation and floodplain formation.