The stability of estuarine channel-shoal systems is important for port utilization,navigation maintenance,habitat protection and ecosystem service functions.This paper uses the South Channel of the Changjiang(Yangtze River)Estuary as a typical example to inves-tigate the channel-shoal adjustment mechanism and its future trend.The combined ap-proaches of bathymetric data analysis and process-based modeling(Delft3D)are applied.Quantitative analysis of morphological changes indicates that the South Channel experienced remarkable channel-shoal adjustment during 1958-2018.Periodic evolution was identified,including shoal migration,incision and emergence under natural conditions before the mid-1980s.Since then,fluvial sediment decline and local human intervention have interrupted the periodic processes.After 1986,as river sediment discharge started to decline,the South Channel converted to net erosion,and both the mid-channel shoal at the bifurcation node and the tail of the Ruifeng Shoal showed significant scour.Process-based hydrodynamic simula-tions revealed that the northern rotation of the mainstream downstream of Wusong triggered the erosion of the Ruifeng Shoal,while unordered sand mining at the shoal tail in approxi-mately 2002 enhanced shoal shrinkage.In addition,the self-adjustment of the transverse section shape resulted in abnormal accretion in 2002-2007.Afterward,the South Channel underwent overall erosion as sediment discharge decreased to a low level(＜150 Mt/a).Five stages of channel-shoal pattern adjustment and accretion/erosion status during the past 60 years were defined,i.e.,the accretion stage(1958-1965),remarkable channel-shoal ad-justment stage(1978-1986),slow erosion stage(1986-1997),shoal scour and shrinkage stage(1997-2007)and overall channel-shoal erosion stage(2007-2018).Model prediction of the evolutionary trend indicates that overall erosion within the South Channel is most likely to continue in 2015-2050.Further adjustment of the South Channel under extremely low sedi-ment discharge may threaten the riverbed stability and the sustainable development of this large-scale estuary.Future work on adaptive strategies for varying conditions is recom-mended.

LUAN Hualong;YAO Shiming;QU Geng;LEI Wentao

River Research Department,Changjiang River Scientific Research Institute,Wuhan 430010,China

地理学报（英文版）

[1]LUAN Hualong;YAO Shiming;QU Geng;LEI Wentao-.Morphological evolution of the channel-shoal system in the South Channel of the Changjiang Estuary during 1958-2018:Causes and future trends)[J].地理学报（英文版）,2022(11):2291-2310

Ruifeng,Wusong,justment

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