Effects of vegetation distribution on experimental river channel dynamics
Effects of vegetation distribution on experimental river channel dynamics
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DOI：
10.1002/2013wr013574
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发表时间：
2013-11
影响因子：
5.4
通讯作者：
W. M. Dijk;R. Teske;W. Lageweg;M. Kleinhans
中科院分区：
文献类型：
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作者：
W. M. Dijk;R. Teske;W. Lageweg;M. Kleinhans
河道动态、洪泛区发育和河岸植被之间存在强烈的反馈。早期的实验研究表明，均匀分布的河岸植被如何导致从辫状河到单线河的转变，因为河岸植被稳定了河岸，并将洪泛平原的流量集中到渠道中。这些实验测试了风播分布的植被，即，自然界中的许多河岸物种也是水栖分布的，即，流动的水。本研究的目的是实验测试不同的影响是水文和风播分布的植被对渠道格局和动力学。试验在宽3m、长10m的水槽中进行。我们比较了两种形式的植被分布方法的实验，以对照实验没有植被。为了独立地量化作为种子密度和植被年龄的函数的河岸退缩率，我们使用了一个小的河岸侵蚀试验。与其他工作一致，均匀分布的植被减少了河岸后退，通常稳定了河岸，收紧了曲流弯道。植被种子分布的流量在洪水期间定居在海拔较低的均匀分布的植被相比。内弯曲植被稳定了一部分的点坝和水力阻力的植被坝迫使水进入渠道和在河漫滩。因此，沉积物沉积在上游的植被斑块。我们的结论是，洪水过程中，种子分布的流量导致岛屿编织：一个不规则的多线程的河流与稳定的植被酒吧，而植被均匀分布在一个单一的线程曲流河的洪泛平原增加弯曲度和减少弯曲波长。这意味着流量变化和植被沉降行为的组合对河流的形态和动力学有很大的影响。实验方法开辟了广泛的可能性，探索高度控制的水文生物地貌相互作用。
Strong feedbacks exist between channel dynamics, floodplain development, and riparian vegetation. Earlier experimental studies showed how uniformly distributed riparian vegetation causes a shift from a braided to a single‐thread river because riparian vegetation stabilizes the banks and focuses discharge off the floodplains into channels. These experiments tested anemochorously distributed vegetation, i.e., by wind, whereas many riparian species in nature are also distributed hydrochorously, i.e., by flowing water. The objective of this study is to test experimentally what the different effects are of hydrochorously and anemochorously distributed vegetation on channel pattern and dynamics. The experiments were carried out in a flume of 3 m wide and 10 m long. We compared experiments with the two forms of vegetation distribution methods to control experiments without vegetation. To independently quantify bank retreat rate as a function of seed density and vegetation age, we used a small bank erosion test. In agreement with other work, the uniformly distributed vegetation decreased bank retreat, often stabilized banks and tightened meander bends. Vegetation seeds distributed by the flow during floods settled at lower elevations compared to the uniformly distributed vegetation. Inner bend vegetation stabilized a part of the point bar and hydraulic resistance of the vegetated bar forced water into the channel and over the floodplain. As a result, sediment was deposited upstream of vegetation patches. We conclude that seeds distributed by the flow during floods lead to island braiding: a patchy multithread river with stable vegetated bars, whereas vegetation uniformly distributed on the floodplain of a single‐thread meandering river increases sinuosity and decreases bend wavelength. This implies that the combination of discharge variations and vegetation settling behavior has a large effect on the morphology and dynamics of rivers. The experimental approach opens up a wide range of possibilities to explore hydro‐bio‐geomorphological interactions with a high degree of control.