Decadal link between longitudinal morphological changes in branching channels of Yangtze Estuary and movement of the offshore depo-center

Zhu Boyuan, Yao Yue, Alistair Borthwick, Wenjun Yu, Liang Enhang, Jinwu Tang, Yuanfang Chai, Yitian Li

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

In estuaries, the morphology of inland and offshore areas usually evolves synergistically. This study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo center (where sediment deposition rate is maximum) of the Yangtze River estuary, under intense human interference. Integrated data analysis is provided of morphology, runoff discharge, and ebb partition ratio from 1950 to 2017. Channel volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects. Ebb partition ratio and duration of discharge ≥ 60,000 m3 s 1 act as proxies for the water excavating force in branching channels and runoff intensity. It is found that deposition occurs in the lower/upper sub reaches (or further downstream/upstream channels) of the inland north/south branching channels, and the offshore depo center moves southward or southeastward, as runoff intensity grows; the reverse occurs as runoff intensity declines. This is because the horizontal circumfluence in the Yangtze Estuary rotates clockwise as ebb partition ratios of the north/south branching channels increase/decrease for increasing runoff, and conversely rotates anticlockwise for decreasing runoff. Land reclamation activities, the Deepwater Channel Project, and the Qingcaosha Reservoir have impacted greatly on longitudinal changes of morphology in the North Branch and the South Passage and on ebb partition ratio variations in the North/South Channel and the North/South Passage. Dam induced runoff flattening has enhanced deposition in the upper/lower sub reaches of the north/south branching channels and caused northward movement of the offshore depo center, except in areas affected by estuarine engineering projects. Dam induced longitudinal evolution of branching channel morphology and offshore depo center movement will likely persist in the future, given the ongoing construction of large cascade dams in the upper Yangtze and the completion of major projects in the Yangtze Estuary.
Original languageEnglish
Pages (from-to)2689-2705
JournalEarth Surface Processes and Landforms
Volume45
Issue number11
Early online date30 May 2020
DOIs
Publication statusPublished - 15 Sept 2020

Keywords / Materials (for Non-textual outputs)

  • Yangtze Estuary
  • longitudinal evolution
  • depo-center movement
  • ebb partition ratio
  • runoff discharge
  • human interference

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