Abstract

River confluences are the key elements within fluvial systems, where three-dimensional flow fields and sedimentation patterns can have a substantial effect on the hydraulics, bed morphology of stream courses, and environments. The present study is configured to realize the alterations in bedload transportation and in bedform at confluence channel in relation to particular hydrological occurrences. It is anticipated that the patterns of the flow attributes following the confluence to be different from those in the conditions reported in other publication. Therefore, this article concisely reports the various flow aspects, examines the corresponding river bed patterns, and provides a brief description of the different flow properties. On the basis of field findings in response to fluctuation in the flow of contributory tributaries, the recorded morphological and sedimentological changes are explained. To accomplish this, bedload transport, bed surveys, and particle size distribution measurements were carried out at the study site during different hydrological seasons at intervals of two months from January 2018 to March 2019. The three major goals of this work were to comprehend the symmetry between two confluence channels, estimate bedload transport, and investigate the consequences of net fluvial behavior on bedform dynamics. The short-term impacts of stream flow irregularity on channel morphology and particle structures were discovered by repeated transect studies and bed material sampling at a small asymmetrical river junction. Results show that the confluence involves the shifting in the scour region, frequent erosion and deposition of sediments, and bar development at the downstream confluence as flow rate fluctuates following the hydrological changeability in the confluence channels. The average bedload at the confluence appears to be irregular in favor of the tributary, since two-thirds of the total bedload was carried across the shallow zone of the cross-section. A high speed digital camera was used to detect sand ripples, and video technique was utilized to obtain statistics on the presence of ripple geometries. Asymmetric two-dimensional ripples were observed in relatively calm weather conditions and in moderate winds. It was discovered that ripples generated by the two-dimensional flow were supplanted by flatbed circumstances and the normal two-dimensional wash-out ripples after the medium wind periods, demonstrating that the presence of a combined flow increases the induced bed shear stress.

中文翻译：

---

河流交汇处底质输送及其对河床形态的影响

摘要

河流交汇处是河流系统中的关键要素，其中三维流场和沉积模式会对水力学、河道河床形态和环境产生重大影响。本研究的目的是实现与特定水文事件相关的河床淤积输送和汇合河道河床形态的变化。预计汇合后的流动属性模式与其他出版物中报告的条件下的模式不同。因此，本文简明地报告了各种流量方面，研究了相应的河床模式，并对不同的流量特性进行了简要描述。根据对贡献支流流量波动的现场调查结果，对记录的形态和沉积变化进行了解释。为了实现这一目标，从 2018 年 1 月到 2019 年 3 月，在不同水文季节，每隔两个月在研究地点进行了底质输送、底床调查和颗粒尺寸分布测量。这项工作的三个主要目标是理解对称性。两个汇合河道之间的数据，估计底质输送，并研究净河流行为对河床动态的影响。通过在小型不对称河流交汇处进行反复样线研究和河床物质采样，发现了溪流不规则性对河道形态和颗粒结构的短期影响。结果表明，汇流区冲刷区移动，沉积物冲刷频繁，下游汇流处坝体发育，流量随汇流河道水文变化而波动。汇合处的平均河床荷载似乎不规则，有利于支流，因为总河床荷载的三分之二是通过横截面的浅层区域携带的。使用高速数码相机来检测沙波纹，并利用视频技术来获取波纹几何形状存在的统计数据。在相对平静的天气条件和温和的风中观察到不对称的二维波纹。结果发现，二维流产生的波纹被平板环境和中风期后正常的二维冲刷波纹所取代，这表明组合流的存在增加了诱导床剪切应力。