| 三峡大坝下游近坝段沙质河床形态调整及洲滩联动演变关系 |
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| 引用本文： | 赵维阳,杨云平,张华庆,张明进,袁晶,杨保岑.三峡大坝下游近坝段沙质河床形态调整及洲滩联动演变关系[J].水科学进展,2020,31(6):862-874. |
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| 作者姓名： | 赵维阳 杨云平 张华庆 张明进 袁晶 杨保岑 |
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| 作者单位： | 中铁大桥勘测设计院集团有限公司, 湖北 武汉 430056;河海大学水文水资源与水利工程科学国家重点实验室,江苏 南京 210098;交通运输部天津水运工程科学研究所工程泥沙交通运输行业重点实验室, 天津 300456;交通运输部天津水运工程科学研究所工程泥沙交通运输行业重点实验室, 天津 300456;长江水利委员会水文局, 湖北 武汉 430010;长江航道测量中心, 湖北 武汉 430010 |
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| 基金项目： | 国家重点研发计划资助项目（2018YFB1600400）；河海大学水文水资源与水利工程科学国家重点实验室开放研究基金资助项目（2017491211） |
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| 摘 要： | 大型水库运行改变了坝下游水沙条件，引起河床冲淤、洲滩形态等适应性调整，尤其是近坝段沙质河床的响应最为敏感。以三峡大坝下游近坝段沙质河段为研究对象，采用1955-2018年水沙数据与1975-2018年地形资料，研究了河床冲淤量及河床形态、洲滩形态演变及联动关系等。研究表明:伴随流域来沙量减少，1975-2018年河床为累积冲刷态势，枯水河槽冲刷量占总冲刷量的93.1%，同步发生洲滩面积减少、深泓下切；以2009年分界，滩槽冲淤逐渐由"低滩冲刷，高滩淤积"逐渐向"低滩、高滩均冲"转变；受来沙量锐减、河道采砂活动等影响，2013年以来河床冲刷强度显著增大，疏浚抛泥对滩槽冲淤的影响较小；航道工程实施前滩群演变关联性强，太平口心滩发育与头部下移引起腊林洲边滩上段面积减小并后退，对应腊林洲边滩尾部面积增大且淤宽，使得三八滩面积减小且右缘蚀退，金城洲逐渐由边滩演变为心滩；航道工程实施后太平口心滩与腊林洲边滩上段关联性减弱，受航道工程及疏浚抛泥等影响腊林洲边滩下段淤宽，引起三八滩维持面积持续减小、右缘后退及左移态势，促使金城洲萎缩且分散。
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| 关 键 词： | 河床形态 洲滩演变 人类活动 三峡工程 长江中游河段 |
| 收稿时间： | 2020-03-16 |
Adjustment patterns and causes of the morphology of sandy riverbed downstream of the Three Gorges Dam |
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| Affiliation: | 1.China Railway Major Bridge Reconnaissance Design Institute Co., Ltd. Wuhan 430056, China2.State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China3.Key Laboratory of Engineering Sediment, Tianjin Research Institute for Water Transport Engineering, Ministry of Transport, Tianjin 300456, China4.Bureau of Hydrology Changjiang Water Resources Commission, Wuhan 430010, China5.Changjiang Waterway Bureau Survey Center, Wuhan 430010, China |
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| Abstract: | The operation of the Three Gorges Reservoir has altered the water and sediment conditions downstream of the dam, resulting in adaptive adjustments in riverbed by scouring and silting, as well as shoal and beach morphology. In particular, the sandy riverbed in the near-dam segment demonstrates the most sensitive response. In this work, the first sandy river segment of the Yangtze River was studied, and water and sediment data from 1955 to 2018 as well as topographic data from 1975 to 2018 were used to quantitatively study the characteristics and causes of riverbed erosion and deposition as well as the shoal and beach morphology adjustment. The results demonstrated that the riverbed underwent cumulative erosion as the sediment inflow from the river basin decreased. The amount of erosion in the low-flow channel accounted for 93.07% of the total amount of erosion in the river channel, and the area of shoals. After the 175 m impoundment of the Three Gorges Project, the scouring intensity downstream of dam on the riverbed increased, the near-dam segment with the greatest scouring intensity moved down to the sandy river segment, and sand excavation accounted for 15.9% of the scouring amount of the beach-level channel. The law of scouring and silting gradually changed from "scouring on low beaches and silting on high beaches" to "scouring on low and high beaches" since the impoundment. At the same time, the channel showed thalweg downcutting, the fluviatile facies coefficient decreased. Before the implementation of the waterway project, the evolution of beach groups demonstrated strong correlation. The channel bar development and downward movement of the head of the Taipingkou waterway caused the area of the upper section of the Lalinzhou point bar to decrease and recede. The tail area of the Lalinzhou point bar increased and the siltation width increased correspondingly, causing the area of the Sanba beach to decrease, the right edge to be eroded and recede, and the position of the beach body gradually move left. After the implementation of the waterway project, the correlation of beach group evolution was gradually weakened and the correlation between the channel bar of the Taipingkou waterway and the upper section of the Lalinzhou point bar was weakened. Moreover, the lower section of the Lalinzhou point bar was widened due to the influence of the waterway project as well as dredging and mud dumping, and the area of Sanba beach continued to decrease, with the right edge receding and moving left, causing the Jinchengzhou shoal to shrink and gradually disperse. |
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