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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Hydro-morphodynamic evolution in a 90 degrees movable bed discordant confluence with low discharge ratio
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Hydro-morphodynamic evolution in a 90 degrees movable bed discordant confluence with low discharge ratio

机译：低排放比的90度可移动床不协调汇合处的水动力形态演化

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摘要

Confluences with low discharge and momentum ratios, where narrow steep tributaries with high sediment load join a wide low-gradient main channel that provides the main discharge, are often observed in high mountain regions such as in the upper-Rhone river catchment in Switzerland. Few existing studies have examined the hydro-morphodynamics of this type of river confluence while considering sediment discharge in both confluent channels. This paper presents the evolution of the bed morphology and hydrodynamics as observed in an experimental facility with a movable bed. For that purpose, one experiment was carried out in a laboratory confluence with low discharge and momentum ratios, where constant sediment rates were supplied to both flumes. During the experiment, bed topography and water surface elevations were systematically recorded. When the bed topography reached a steady state (so-called equilibrium) and the outgoing sediment rate approximated the incoming rate, flow velocity was measured at 12 different points distributed throughout the confluence, and the grain size distribution of the bed surface was analyzed. Typical morphodynamic features of discordant confluences such as a bank-attached bar and a flow deflection zone are identified in this study. Nevertheless, the presence of a marked scour hole in the discordant confluence and distinct flow regimes for the tributary and main channel, differ from results obtained in previous studies. Strong acceleration of the flow along the outer bank of the main channel is responsible for the scour hole. This erosion is facilitated by the sediment discharge into the confluence from the main channel which inhibits bed armoring in this region. The supercritical flow regime observed in the tributary is the hydrodynamic response to the imposed sediment rate in the tributary. Copyright (c) 2015 John Wiley & Sons, Ltd.
机译：低流量和动量比的汇合处通常是在高山地区（如瑞士的罗纳河上游集水区），狭窄的陡峭支流具有高的泥沙负荷，而宽的低梯度主河道提供了主要的流量。很少有研究研究这种河流汇合处的水动力形态，同时考虑了两个汇合渠中的泥沙排放。本文介绍了在具有可移动床的实验设备中观察到的床形态和流体动力学的演变。为此目的，在具有低流量和动量比的实验室汇合处进行了一项实验，在这两种汇流中提供恒定的沉积速率。在实验过程中，系统地记录了床的地形和水面高程。当床的地形达到稳态（所谓的平衡）并且流出的沉积速率接近流入的速率时，在整个汇合处分布的12个不​​同点处测量流速，并分析床表面的粒度分布。在这项研究中确定了不合流汇合的典型形态动力学特征，例如，堤坝连接的水坝和水流偏转区。然而，支流和主干道的不合流汇合处存在明显的冲刷孔，流动方式不同，这与以前的研究结果有所不同。沿主通道外堤的流动强烈加速是冲刷孔的原因。沉积物从主通道汇入汇合处会加剧这种侵蚀，从而抑制了该区域的床身装甲。在支流中观察到的超临界流态是对支流施加的沉积速率的水动力响应。版权所有（c）2015 John Wiley＆Sons，Ltd.

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