流量非恒定性对河道演变影响机理的研究

河流流量在自然条件下大多都有一定的非恒定特性,它是河道演变的重要动力因素。为了增加流量非恒定性对河道演变规律的认识,课题开展了概化的物理模型河流试验,对不同流量过程作用下河道地形的变化进行了精细测量。模型试验包括三个组次:恒定流量试验、突变流量试验和渐变流量试验。突变流量试验和渐变流量试验的结果以恒定流量试验作为参考进行对比分析。试验结果表明:1在上游斜道和二次流作用下河道发展出滩槽结构,浅滩包括两个部分,滩面较高的部分起到导流的作用,使得水流主流蜿蜒向前,并保护了滩面较低的浅滩不受主流侵蚀作用;2流量的非恒定特性使得原有的滩槽结构不断破坏,岸滩变得平整,主流变浅;3具有较大流量波动强度(均方差)的流量过程具有更强的岸滩冲刷能力,使得河道展宽增加。

Study on river morphology dynamics under varying discharges

Fluctuation process of river discharge is a key factor to channel evolution, and discharge variation is common in natural rivers. In this study, physical model tests and fine measurements of river flow have been conducted to investigate channel evolution under discharge variations, with three sets of test conditions arranged, i.e. constant discharge, gradually varied discharge, and rapidly varied discharge. The results show that, shoal-pool structures develop in the channel under a combination of initial bending and secondary flow, covering two typical areas: the higher one that deflects the main flow, and the lower one that are sheltered. Fluctuations in discharge can destroy the existing shoal-pool structures, causing flatter shoals and shallower thalwegs, and the fluctuations of greater mean square deviation has greater bank erosion power hence leading to a wider river channel.