黄河下游游荡河段典型断面主槽与深泓横向摆动特点

Characteristics of section-scale lateral channel migration in the wandering reach of the Lower Yellow River

黄河下游河床频繁横向摆动会破坏河势稳定,研究游荡河段河床横向摆动的过程及特点对了解该河段河势演变的特点,进而指导整治工程建设具有重要意义。基于1999-2020年游荡河段汛后遥感图像及143个断面实测地形资料,计算了断面主槽和深泓的摆动宽度,探讨了二者之间的关系,并进一步分析了影响河床横向摆动的因素。研究结果表明:游荡河段河床横向摆动幅度中段大、上下两段小,96.5%的断面深泓平均摆幅大于主槽平均摆幅;典型断面河床横向摆动过程具有明显的阶段性特征,在同一阶段主槽与深泓的摆动趋势基本一致;水沙条件是影响河床横向摆动的主要因素,典型断面主槽及深泓的累计摆动宽度与累计水流冲刷强度呈良好的对数正相关关系;滩槽高差越大、工程靠溜越近,河床越不易发生摆动。

The frequent lateral migration of the channel in the Lower Yellow River(LYR)will destroy the stability of the river regime.It is of great significance to study the process and characteristics of lateral channel migration in order to understand the characteristics of river regime evolution and to guide the construction of river regulation works in the wandering reach of the LYR.Migration widths of main-channel and thalweg at section-scale were calculated based on the data covering remote sensing images and observed 143 cross-sectional profiles in the wondering reach of the LYR during the period from 1999 to 2020.Then the relationship between migration widths of main-channel and thalweg was discussed,and the factors affecting the lateral channel migration were further analyzed.It is found that:mean widths of lateral migration are larger in the middle reach and smaller in the upper and lower reaches.The average migration width of thalweg is larger than that of main-channel for 96.5%of the sections in the wandering reach;the lateral channel migration process at typical sections has obvious stages characteristics,and the lateral migration trends of main-channel and thalweg are basically similar at the same stage.The incoming flow and sediment are the main factors affecting lateral channel migration in the wandering reach,there is a significant positive logarithmic correlation between the cumulative migration widths of main-channel and thalweg at typical sections and the cumulative fluvial erosion intensity.The larger the elevation difference between floodplain and main channel,the closer the main channel is to the regulation works,the less likely the riverbed is to migrate.