曹双,程龙,李洁,等. 2020年流域性大洪水下长江下游干流河道演变分析[J]. 水利水运工程学报,2023(4):1-11. doi: 10.12170/20221130002
引用本文: 曹双,程龙,李洁,等. 2020年流域性大洪水下长江下游干流河道演变分析[J]. 水利水运工程学报,2023(4):1-11. doi: 10.12170/20221130002
(CAO Shuang, CHENG Long, LI Jie, et al. Analysis of evolution in the lower Yangtze River under the effect of the great basin flood in 2020[J]. Hydro-Science and Engineering, 2023(4): 1-11. (in Chinese)). doi: 10.12170/20221130002
Citation: (CAO Shuang, CHENG Long, LI Jie, et al. Analysis of evolution in the lower Yangtze River under the effect of the great basin flood in 2020[J]. Hydro-Science and Engineering, 2023(4): 1-11. (in Chinese)). doi: 10.12170/20221130002

2020年流域性大洪水下长江下游干流河道演变分析

Analysis of evolution in the lower Yangtze River under the effect of the great basin flood in 2020

  • 摘要: 自2003年三峡水库蓄水以来,长江下游水沙特性发生了显著变化,2020年夏长江流域发生了流域性大洪水。在分析三峡水库蓄水以来长江下游水沙特性变化的基础上,结合2020年洪水期的水情、沙情,利用实测河床地形及大断面资料,分析长江下游干流湖口至江阴多年河道冲淤特性,探讨2020年洪水作用下长江下游河床冲淤变化及河势演变特性。研究表明:自三峡水库蓄水以来,长江下游年均径流量变化较小,输沙量锐减,水沙关系发生明显改变;湖口至江阴河段1998—2006年有淤有冲,2006年后呈单向冲刷状态,且滩槽普冲,在2020年流域性大洪水作用后,长江下游河道延续这一冲刷特征,冲刷强度明显增强,各水位河槽冲刷强度为2016—2020年平均值的2.0~2.8倍;大通以上河段冲刷强度小于下游河段;长江下游分流格局总体稳定,但铜陵河段成德洲汊道有主支汊易位趋势,多次测得右汊分流比超过左汊;扬中河段支汊发展,分流比呈持续微增趋势;河势总体稳定,尚有多个江心洲边滩冲刷明显,铜陵沙首度出现撇岸切滩现象,扬中等局部江段江心洲高滩陡坎有条崩发生;河床纵向仍有冲刷,河道束窄段横断面形态进一步窄深化。对大洪水条件下河道冲淤演变特性的分析研究,有利于更加全面系统地掌握长江下游河道的河势演变规律。

     

    Abstract: Since the impoundment of the Three Gorges Reservoir (TGR) in 2003, the flow-sediment characteristics of the lower Yangtze River have changed significantly. In the summer of 2020, the Yangtze River basin experienced a great basin flood second only to those of 1954 and 1998 since the founding of PRC. Based on the analysis of the flow and sediment characteristics of the lower Yangtze River since TGR operation, the characteristics of multi-year river erosion and deposition in the lower Yangtze River from Hukou to Jiangyin were analyzed, and the characteristics of riverbed erosion and deposition and riverbed evolution under the effect of the 2020 flood were discussed, using the topographic and cross-sectional data. The study showed that the average annual runoff of the lower Yangtze River had changed little since TGR was impounded, but sediment transport had decreased sharply and the relationship between flow and sediment transport had changed significantly. The Hukou-Jiangyin reach had both erosion and deposition from 1998 to 2006, and turned to unidirectional erosion in both channel and beach after 2006. After the 2020 flood, the lower Yangtze River continued and enlarged this erosion characteristic, with the erosion intensity at different water levels enlarged by 2.0 to 2.8 times comparing to the average value during 2016 to 2020. The erosion intensity of the reaches upstream of Datong was less than that of the downstream reaches. The overall pattern of diversions in the lower Yangtze River was stable. But there was a tendency for the main branch to shift in the Chengdezhou branching channel, with the right branching diversion ratio exceeding that of the left in several measurements. The anabranch developed in the Yangzhong reach, with a continuous trend of slight increase in the diversion ratio. The river was generally stable, while a number of sandbanks eroded significantly. Tonglingsha experienced shore-cutting for the first time. And avalanches occurred in some central islands in river sections such as the Yangzhong reach. The riverbed was eroded in the longitudinal direction as before, and the cross-sectional pattern of the narrower sections was further narrowed and deepened. Analysis on the evolution characteristics of river channel erosion and deposition under great flood conditions is conducive to a more comprehensive and systematic grasp of the riverbed evolution of the lower Yangtze River.

     

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