长江中游沙卵石-沙质河床过渡带冲刷趋势研究

通过30余年特别是三峡水库蓄水以来水文、地形、地质等实测资料的系统收集，对长江中游枝城-陈家湾沙卵石-沙质河床过渡带冲刷特性和发展趋势开展分析，其结果表明：虽然河段内自上而下呈现出卵石逐渐减少而沙质比例逐渐增多的渐变特点，但以昌门溪~马家店一带为界，上下游的洲滩组成、深泓形态、河床冲淤、水位下降等方面存在突变现象。在三峡水库蓄水后的冲刷过程中，虽然全河段内均出现了汊道冲刷、枯期河槽扩大的现象，但可以预计的是，河段内河势不会发生大的变化，而昌门溪以下河段难以抵御水位下降的溯源传递，马家店以上在枯水期将出现比现状更为严重的坡陡、流急、水浅现象。

Channel erosion processes in the gravel bed to sand bed transitional recch of the middle Yangtze River

Based on gauged data of hydrology, topography and geology that obtained in the past 30 years, especially in the post-dam period of the Three Georges Project, the channel erosion processes in the reach of Zhicheng to Chenjiawan in the middle Yangtze River is investigated. In this reach, it is demonstrated by geology data that bed material changes with the feature of gravel component decreasing and sand component increasing gradually in the streamwise direction. However, abrupt changes are found in the vicinity of Changmenxi-Majiadian section which lies in middle of this reach. This abrupt changes is revealed by the differences of sand bar deformation, thalweg degradation, channel erosion volume and water level lowering. After dam impoundment of the Three Georges Project, although secondry branch erosion and cross section enlargement are common in this reach, it is predicted that great changes of river regime will not take place due to resistent bed material. In the meanwhile, backward erosion caused by downstream water level lowering will develop and move upstream continuously, which will result in high gradient, swift velocity and shallow water depth in the unstream of Majiadian.