Long-term (1842-2006) morphological change and equilibrium state of the Changjiang (Yangtze) Estuary, China

Yonghong Wang, Ping Dong, Takashi Oguchi, Shenliang Chen, Huanting Shen

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    Abstract

    The 165 year morphological evolution of the Changjiang (Yangtze) Estuary
    and its long-term equilibrium characteristics have been investigated
    using 16 selected maritime charts from 1842 to 2006. These charts were
    digitized and analyzed with a GIS to provide quantitative estimates of
    geomorphologic changes below selected bottom elevations. The results
    show that the Changjiang Estuary has experienced overall erosion over
    this 165 year period, having been affected by several large erosion and
    deposition episodes. It is found that the overall volume changes are
    less than 10% and aspect ratios of <5 have increased from 2% to ca.
    30%. During this period, both coastlines and thalwegs have become
    straighter and more aligned with the propagation direction of offshore
    tidal current, indicating that the estuary is approaching dynamic
    equilibrium. Based on variations of aspect ratios and thalweg movements,
    five types of stable channels were identified. Significant
    topographical changes, including infilling after 1958 and erosion after
    1980, are principally associated with engineering work around the
    estuary and a reduction in sediment supply. Although human influence
    only notably occurred at certain locations in the estuary, such as
    upstream node of an estuary, it had a significant impact on the overall
    geomorphologic evolution. In addition to these anthropogenic effects,
    freshwater flow, sediment discharges, tide propagation and Coriolis
    force are also found to play important roles in channel development
    within the estuary. By contrast, changes in other factors such as sea
    level changes and wave climate were considered to be of relatively minor
    importance in the morphological evolution process of the estuary.

    Original languageEnglish
    Pages (from-to)71-81
    Number of pages11
    JournalContinental Shelf Research
    Volume56
    DOIs
    Publication statusPublished - 15 Mar 2013

    Keywords

    • SYSTEMS
    • The Changjiang Estuary
    • MERSEY ESTUARY
    • Long-term
    • Morphodynamics
    • UK
    • RIVER SEDIMENT
    • MOUTH
    • ENGLAND
    • CHANNEL
    • TRANSPORT
    • Channel stability
    • MORPHODYNAMIC EVOLUTION
    • SEA
    • Estuarine equilibrium

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