Decadal morphological evolution of the mouth zone of the Yangtze Estuary in response to human interventions

Decadal morphological evolution of the mouth zone of the Yangtze Estuary in response to human interventions

Zhu, C. (TU Delft Coastal Engineering; East China Normal University)
Guo, Leicheng (East China Normal University)
van Maren, D.S. (TU Delft Environmental Fluid Mechanics; Deltares)
Tian, Bo (East China Normal University)
Wang, Xianye (East China Normal University)
He, Qing (East China Normal Univeristy)
Wang, Zhengbing (TU Delft Coastal Engineering; East China Normal University; Deltares)

2019

The morphology of the Yangtze Estuary has changed substantially at decadal time scales in response to natural processes, local human interference and reduced sediment supply. Due to its high sediment load, the morphodynamic response time of the estuary is short, providing a valuable semi-natural system to evaluate large-scale estuarine morphodynamic responses to interference. Previous studies primarily addressed local morphologic changes within the estuary, but since an overall sediment balance is missing, it remains unclear whether the estuary as a whole has shifted from sedimentation to erosion in response to reduced riverine sediment supply (e.g. resulting from construction of the Three Gorges Dam). In this paper we examine the morphological changes of two large shoals in the mouth zone (i.e. the Hengsha flat and the Jiuduan shoal) using bathymetric data collected between 1953 and 2016 and a series of satellite images. We observe that the two shoals accreted at different rates before 2010 but reverted to erosion thereafter. Human activities such as dredging and dumping contribute to erosion, masking the impacts of sediment source reduction. The effects of local human intervention (such as the construction of a navigation channel) are instantaneous and are likely to have already resulted in new dynamic equilibrium conditions. The morphodynamic response time of the mouth zone to riverine sediment decrease is further suggested to be >30 years (starting from the mid-1980s). Accounting for the different adaptation time scales of various human activities is essential when interpreting morphodynamic changes in large-scale estuaries and deltas.

channel–shoal system
human activities
morphology
response time
Yangtze Estuary

http://resolver.tudelft.nl/uuid:954a05de-b6af-4fab-bd2c-239e9cddd757

https://doi.org/10.1002/esp.4647

2019-11-06

0197-9337

Earth Surface Processes and Landforms, 44 (12), 2319-2332

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2019 C. Zhu, Leicheng Guo, D.S. van Maren, Bo Tian, Xianye Wang, Qing He, Zhengbing Wang