|Yang Xuhai,Xiong Haibin,Li Yitian,Li Sixuan.Adjustment mechanism of the typical sandbars in the lower Jingjiang River after the impoundment of the Three Gorges Reservoir. J. Lake Sci.2021,33(3):819-829. DOI:10.18307/2021.0321
|三峡工程运行后长江中下游河道洲滩普遍冲刷萎缩，航道条件极不稳定.为探究影响洲滩演变的主控因素，采用近期水文、泥沙和地形观测资料，以下荆江铁铺水道广兴洲边滩为例，分析了边界条件、水沙过程及整治工程等因素对洲滩调整特征的影响程度.结果表明：洲滩组成中的细沙（0.125 mm<d<0.25 mm）占比较大，抗冲性较弱，是滩体冲刷的前提条件.三峡工程运行后广兴洲边滩年际间呈冲刷萎缩趋势，水沙条件变化是洲滩变形的主导因素，滩体冲淤变化与漫滩流量（Q>15000 m3/s）有一定关系，其持续时间越长，一般表现为滩体面积越小；汛期悬移质分组沙输移过程中，细沙的大幅减少导致边滩萎缩明显，其影响程度比漫滩流量更大.滩体冲淤变形特征与前3年漫滩流量下平均水流冲刷强度的相关性最好.守护工程实施后，漫滩流量下平均水流冲刷强度仍然较大，但滩体后退趋势得以抑制且小幅淤积，工程效果得以充分发挥.
|关键词: 洲滩演变 水沙过程 守护工程 漫滩流量 水流冲刷强度 三峡水库
|Adjustment mechanism of the typical sandbars in the lower Jingjiang River after the impoundment of the Three Gorges Reservoir
Yang Xuhai1, Xiong Haibin1, Li Yitian1, Li Sixuan2
1.State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, P. R. China;2.Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan 430010, P. R. China
|After the operation of the Three Gorges Project (TGP), the sandbars in the middle and lower reaches of the Yangtze River were scoured and atrophic mostly, resulting in the channel conditions extremely unstable. In order to explore the dominant factors affecting the evolution of sandbars, combined with the recent hydrologic, sediment, and topographic observation data, the Guangxingzhou point bar of Tiepu reach of the lower Jingjiang is taken as an example to analyze the adjustment characteristics of sandbars and their response to boundary conditions, flow and sediment processes and remediation projects. The results show that most of the fine sand in the composition of the sandbars are weak in resistance to erosion, which is the precondition for the erosion of sandbars. After the operation of the TGP, the Guangxingzhou point bar has a tendency of erosion and shrinkage year by year. The change of flow and sediment conditions is the dominant factor of the deformation of the sandbars, there is a relationship between the variation of the Guangxingzhou point bar and over-bar discharge (Q>15000 m3/s), and the longer days last, generally the smaller the sandbar is. The amount of bed material in flood season is greatly reduced, especially the decrease of fine sand (0.125 mm<d<0.25 mm), making the point bar shrink significantly, the impact of which is greater than over-bar discharge. There is a significant correlation between the area of the Guangxingzhou point bar and the average fluvial erosion intensity of over-bar disscharge in the first three years. After the implementation of the revetment project, the receding trend of the point bar is restrained, the area is stable and increased slightly, indicating that the revetment project has been fully effective.
|Key words: Evolution of point bar flow and sediment process revetment project over-bar discharge average fluvial erosion intensity Three Gorges Reservoir