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大型水库的兴建深刻改变了下游水沙输移特点,进而导致河床演变规律显著调整,水库下游弯曲河型对水沙过程改变响应敏感,是水库下游河床演变、航道整治、河势控制等方面研究的关键区域。本文基于1996-2016年的实测水文、地形资料,对长江三峡水库下游弯曲河型的演变规律及其驱动机制开展研究,结果表明:(1)三峡水库蓄水前,下荆江存在“凸淤凹冲”、“凸冲凹淤”两类弯曲河型,而三峡水库蓄水后均表现为“凸冲凹淤”的一致性规律;(2)在水库拦沙作用的影响下,下荆江河段平滩河槽存在累积性冲刷现象,冲刷部位集中于枯水河槽与基本河槽之间的低滩,冲淤部位调整主要由变化的流量过程所驱动,上游河势、河道边界以及支流入汇等因素均有一定驱动作用;(3)在三峡水库蓄水后缺乏大洪水的情况下,凸岸水流挟沙力随流量增加逐渐增强,水流对凸岸冲蚀力度在平滩流量级附近(20000~25000 m3/s)达到最强,平滩流量附近流量级的持续时间超过20天时,弯曲河道发生凸冲凹淤现象。而悬沙中造床粗沙的减少,增强了水流冲刷强度,加剧了凸岸的冲蚀程度。
The construction of large reservoirs has profoundly changed the characteristics of downstream water and sediment transport, leading to a significant adjustment of the riverbed evolution rule. The curved river patterns in the lower reaches of the reservoirs are sensitive to the changes in water and sediment processes, which are the study of riverbed evolution, channel regulation and river regime control in the lower reaches of the reservoir The key area. Based on the measured hydrological and topographical data from 1996 to 2016, this paper studies the evolution and driving mechanism of the curved river patterns in the lower reaches of the Three Gorges Reservoir in the Yangtze River. The results show that: (1) Before the impoundment of the Three Gorges Reservoir, The two types of curved river are concave bump and concave bump, while the Three Gorges reservoir implies the consistent law of convex bump. Second, Under the influence, there is a cumulative scour phenomenon at the lower bank of Pingjiang River in the lower Jingjiang River. The erosion sites are concentrated on the low bank between the lower and lower basins. The adjustment of the scouring and silting sites is mainly driven by the changing flow process. The upper reaches of the river and the border of the river (3) Under the condition of the lack of major flood after the impoundment of the Three Gorges Reservoir, the sediment-carrying capacity of the coastal flow gradually increases with the increase of the flow rate, and the erosion intensity of the flow to the bank is at the level of the flat beach Near the flow rate level (20000 ~ 25000 m3 / s) reaches the strongest, and when the duration of the flow rate near the flat beach flow exceeds 20 days, the phenomenon of convex and concave depression occurs in the curved river. The reduction of sediment-making coarse sand in sand-suspending sediments enhances the intensity of water erosion and aggravates the erosion of the embankments.