黄河源弯曲河流的河段尺度横向冲淤特征研究

Reach-scale lateral erosion and deposition of meandering rivers in the source region of the Yellow River

弯道横向迁移是弯曲河流周期性演变的主要特征,也是横向冲淤的累积性结果。为认识弯曲河流年际时间尺度下的河岸迁移规律,2018—2020年在黄河源麦曲和兰木错曲河段开展了连续3年的无人机航测。通过影像后处理技术生成高精度地形,对河段尺度的河岸迁移和弯道冲淤特征进行探讨。结果表明:边滩的淤积外延驱动边滩-凹岸宽度的变化,所以弯道河宽变化值超过0.1B(B为河宽)的河段总是位于弯顶段。两个弯曲河段凹冲凸淤特征明显,凹岸侵蚀峰值与凸岸淤积峰值在弯道出口段呈对称分布。麦曲河段的凸岸边滩冲淤共存,但整体淤长,凹岸岸线的冲退宽度反映了河岸侵蚀状况。

Lateral migration is an inevitable process of periodic evolution in a meandering river,which is an accumulated result of lateral erosion and deposition.In order to understand the bank migration of typical meandering rivers in the source region of the Yellow River on an interannual timescale,the channel topography was surveyed by Unmanned Aerial Vehicle(UAV)in Maiqu and Lamucuoqu Rivers from 2018 to 2020.Based on the high-resolution topography generated by the image post-processing technology,the characteristics of river bank migration and curve erosion and deposition on a reach scale are discussed.Results show that because the width change of“point barconcave bank”is dominated by the enlargement of point bar,the reach where the change of river width exceeds 10%is always at the apex of the bend.The feature of“concave bank erosion and convex bank deposition”in the meandering reach is distinct,and the peak values of concave bank erosion and convex bank deposition are symmetrically distributed along the channel at the outlet of the bend.Erosion and deposition coexist on the convex bank zone in the Maiqu River,though the deposition process is dominated in the long term.The width variation of concave bankline reflects the erosion volume along the channel.