Stability of backwater‐influenced river bifurcations: A study of the Mississippi‐Atchafalaya system
Stability of backwater‐influenced river bifurcations: A study of the Mississippi‐Atchafalaya system
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受回水影响的河流分叉的稳定性：密西西比-阿查法拉亚水系的研究
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发表时间：
2012
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通讯作者：
D. Edmonds
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作者：
D. Edmonds
在本文中，我用数值模拟表明，水力回水剖面创建一个反馈，可能会稳定河流分叉。数值模型模拟了无旧河控结构的密西西比-阿查法拉亚河水系的水流和泥沙输移。结果表明，分叉的演化强烈依赖于分叉上游的流量。当上游流量大于12600 m3 s−1时，阿查法拉亚河的流量会随着时间的推移而增加，而密西西比河的流量则会减少。有趣的是，在上游流量低于12600 m3 s−1时，情况正好相反，密西西比河的流量增加，而阿查法拉亚河的流量减少。捕获方向的变化，因为回水剖面的每条河流在高和低流量足以反转水面斜率比。这些结果表明，捕获方向将在高流量和低流量下发生变化，这将通过防止一个通道的失控生长而具有稳定作用。考虑到这一点，我计算出，在没有旧河流控制结构的情况下，捕获不会发生灾难性的，而是阿查法拉亚河将捕获密西西比河从今天起的1300年。
In this paper I use numerical modeling to show that the hydraulic backwater profile creates a feedback that may stabilize river bifurcations. The numerical model simulates flow and sediment transport in the Mississippi‐Atchafalaya River system without the Old River Control Structure. The results show that bifurcation evolution strongly depends on the discharge upstream of the bifurcation. At upstream discharges greater than 12600 m3 s−1 the Atchafalaya River discharge increases through time at the expense of the Mississippi River. Interestingly, at upstream discharges lower than 12600 m3 s−1 the opposite occurs and the Mississippi River discharge increases at the expense of the Atchafalaya River. The capture direction changes because the backwater profile of each river varies enough at high and low discharge to invert the water surface slope ratio. These results suggest that the capture direction would change at high and low flow, which would have a stabilizing effect by preventing the runaway growth of one channel. Accounting for this, I calculate that in the absence of the Old River Control Structure capture would not happen catastrophically, but rather the Atchafalaya River would capture the Mississippi River in ∼300 years from present day.