基于无人机航测黄河源弯曲河道泥沙亏损量计算

弯曲河流的河道冲淤变化在长时间尺度处于动态的平衡状况,其泥沙输移部分来自于凹岸冲刷与凸岸淤积的差值。2018年采用无人机航测获取黄河源典型弯曲河流(麦曲、哈曲、格曲和兰木错曲)连续弯道的低空影像数据,通过图像技术处理后生成高精度地形,进而提取单个弯道和连续弯道的断面地形,计算弯道凸、凹两侧断面面积和相邻断面间的差值。结果表明,凹岸侵蚀崩岸产生的泥沙量与凸岸点边滩淤积的泥沙量是不平衡的,即存在一个泥沙亏损量。对于单个弯道,兰木错曲单位河长的泥沙亏损量约为0.191 m^3,麦曲、哈曲和格曲单位河长的泥沙亏损量约为0.045 m^3,且相同河段的沿程亏损量具有不均匀性,其间接反映不同弯道横向的迁移速率具有差异性。

Calculation of bend-scale sediment balance in meandering rivers of Yellow River source based on UAV aerial survey

Erosion-deposition changes of meandering channels are a dynamic equilibrium process in the long-term time scale. The part of sediment load transport is roughly equal the difference between bank erosion in concave bank and point bar deposition in convex bank. In summer 2018,the Unmanned Aerial Vehicle (UAV) aerial survey was used to obtain high-resolution imagery data in four meandering rivers of Yellow River source(i.e.,Maiqu,Haqu,Gequ,and Lanmucuo Rivers),and the high-resolution topographic dataset were produced by post-processing of the Structure-for-Motion technology. Channel topography of cross sections of single bend and subsequent bends are extracted using ArcGIS. The differences of the cross-sectional area between convex and concave bank zone are calculated in single section and adjacent sections of meandering channels. Results demonstrate that sediment loss amount generated by bank collapse on concave bank and sediment deposition amount on convex bank are imbalanced,i.e.,a net loss of sediment amount existing. For a single bend,the sediment loss per unit channel length in Lanmucuoqu River is about 0.191 m³,and about 0.045 m³ on average in Maiqu,Haqu,and Gequ Rivers. Nonetheless,the sediment loss in the reach scale of meandering channel is non-uniformity that indirectly reflects the difference in lateral migration rates among different bends.