Journal of Geographical Sciences ›› 2021, Vol. 31 ›› Issue (12): 1837-1851.doi: 10.1007/s11442-021-1925-x

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Quantitative relationship between channels and bars in a tidal reach of the lower Yangtze River: Implications for river management

YANG Yunping1,2(), ZHENG Jinhai1, ZHANG Wei1, ZHU Yude2,*(), CHAI Yuanfang3, WANG Jianjun2, WEN Yuncheng4   

  1. 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China
    2. Tianjin Research Institute for Water Transport Engineering, Ministry of Transport, Tianjin 300456, China
    3. Vrije Universiteit Amsterdam, Department of Earth Sciences, Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
    4. Nanjing Hydraulic Research Institute, Nanjing 210029, China
  • Received:2020-08-20 Accepted:2021-03-09 Online:2021-12-25 Published:2022-02-25
  • Contact: ZHU Yude E-mail:yangsan520_521@163.com;zhuyude2800@sina.com
  • About author:Yang Yunping, PhD and Research Assistant, E-mail: yangsan520_521@163.com
  • Supported by:
    National Natural Science Foundation of China(51809131);National Natural Science Foundation of China(U2040203);Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(2017491211);Fundamental Research Funds for Central Welfare Research Institutes(TKS20200404);Fundamental Research Funds for Central Welfare Research Institutes(TKS20200312)

Abstract:

Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions. The Fujiangsha reach is particularly difficult to manage, as it has many braided channels within the tidal fluctuation zone. In this study, hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion, flow diversion, shoals, and channel conditions. Since the Three Gorges Dam became operational and water storage was initiated, the Fujiangsha reach has shown an overall tendency toward erosion. Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017. Moreover, the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments. Deposition volumes of these sediments has varied significantly among different channels, but has mainly occurred in the Fubei channel. Furthermore, periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern, and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened. Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel. The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%, respectively, of the total amount of siltation in the Fubei channel.

Key words: tidal current, fluctuating reach, point and central bar, channel conditions, quantitative relationship, lower reaches of the Yangtze River, Fujiangsha reach