Morphological evolution of the channel-shoal system in the South Channel of the Changjiang Estuary during 1958–2018: Causes and future trends

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 Changjiang (Yangtze River) Estuary as a typical example to investigate adjustment mechanism its future trend. combined approaches bathymetric data analysis process-based modeling (Delft3D) are applied. Quantitative morphological changes indicates that experienced remarkable during 1958–2018. Periodic evolution was identified, including shoal migration, incision emergence under natural conditions before mid-1980s. Since then, fluvial sediment decline local human intervention have interrupted periodic processes. After 1986, river discharge started decline, converted net erosion, both mid-channel at bifurcation node tail Ruifeng Shoal showed significant scour. Process-based hydrodynamic simulations revealed northern rotation mainstream downstream Wusong triggered erosion Shoal, while unordered sand mining in approximately 2002 enhanced shrinkage. In addition, self-adjustment transverse section shape resulted abnormal accretion 2002–2007. Afterward, underwent overall decreased low level (<150 Mt/a). Five stages pattern accretion/erosion status past 60 years were defined, i.e., stage (1958–1965), (1978–1986), slow (1986–1997), scour shrinkage (1997–2007) (2007–2018). Model prediction evolutionary trend within most likely continue 2015–2050. Further extremely may threaten riverbed sustainable development this large-scale estuary. Future work on adaptive strategies varying recommended.