Effects of vegetation on channel morphodynamics: results and insights from laboratory experiments
Effects of vegetation on channel morphodynamics: results and insights from laboratory experiments
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DOI：
10.1002/esp.1908
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发表时间：
2010-07
影响因子：
3.3
通讯作者：
M. Tal;C. Paola
中科院分区：
文献类型：
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作者：
M. Tal;C. Paola
一系列的实验室实验表明，河岸植被可以导致辫状河道自组织，并保持一个动态的，单线通道。实验的初始条件是在均匀排放下在无粘性砂中的稳态编织。从这里开始，一个实验包括重复的周期交替短时间的高流量与长时间的低流量，并在每个高流量结束时在床上均匀散布苜蓿种子。植物建立在新沉积的酒吧和地区的braidplain是无人居住在低流量。植物的存在具有逐渐集中高流量的效果，因此形成了一个单一的主导通道。单线通道可自动调节以承载高流量。植被也减缓了河岸侵蚀的速度。沿着点坝的沉积与沿着外弯的侵蚀相匹配，使河道能够发展弯曲并横向迁移，同时抑制河道分裂和新河道宽度的产生。实验通道自发地再现了许多机制，通过这些机制，自然蜿蜒的通道迁移并保持单一的主导通道，特别是弯曲生长和通道截断。与辫状系统，其中通道切换是一个几乎连续的过程，植被保持连贯的通道，直到批发分流通过切断和/或撕脱发生，由这一点以前的通道往往是非常不利的流量。因此，植被阻碍了多种渠道的共存。变化的流量是允许植物和流动之间的反馈表达的关键，并促进从编织到单线通道的过渡，然后动态地维持。版权所有© 2010约翰威利父子有限公司.
A series of laboratory experiments demonstrates that riparian vegetation can cause a braided channel to self‐organize to, and maintain, a dynamic, single‐thread channel. The initial condition for the experiments was steady‐state braiding in non‐cohesive sand under uniform discharge. From here, an experiment consisted of repeated cycles alternating a short duration high flow with a long duration low flow, and uniform dispersal of alfalfa seeds over the bed at the end of each high flow. Plants established on freshly deposited bars and areas of braidplain that were unoccupied during low flow. The presence of the plants had the effect of progressively focusing the high flow so that a single dominant channel developed. The single‐thread channel self‐adjusted to carry the high flow. Vegetation also slowed the rate of bank erosion. Matching of deposition along the point bar with erosion along the outer bend enabled the channel to develop sinuosity and migrate laterally while suppressing channel splitting and the creation of new channel width. The experimental channels spontaneously reproduced many of the mechanisms by which natural meandering channels migrate and maintain a single dominant channel, in particular bend growth and channel cutoff. In contrast with the braided system, where channel switching is a nearly continuous process, vegetation maintained a coherent channel until wholesale diversion of flow via cutoff and/or avulsion occurred, by which point the previous channel tended to be highly unfavorable for flow. Thus vegetation discouraged the coexistence of multiple channels. Varying discharge was key to allowing expression of feedbacks between the plants and the flow and promoting the transition from braiding to a single‐thread channel that was then dynamically maintained. Copyright © 2010 John Wiley & Sons, Ltd.