Narrow Results

Yangtze Estuary deepwater channel improvement project started in 1998. The channel depth have been dredged from 7.0m (under Theoretical Lowest Water Level) to 8.5m, 10m and 12.5m. After the project, which formed the regulating line along the groins heads and adjusted the flow fields, deepened the mouth bar area and merged the ebb with flood channel, a faintly-curved channel was obtained in the North Passage. At the same time, in other passages such as in South Passage and North Channel, the mouth bar is still persisting after the project as long as mouth bar terrain has disappearing in north passage. In this study we will focus on the Yangtze Estuary, with major aims: (a) to reveal the evolution process through field data analysis before and after the project reveal, and compare the different evolution model of three main passages in Yangtze Estuary, (b) to understand and quantify the effect of measures like the navigation works on the natural morphological system, (c) to obtain more insight in the large-scale morphological development in estuaries and the underlying processes and mechanisms, with specific interest in the bifurcating channels and the development of the inter-tidal flats, (d) to predict the long-term impact of the human interventions to the large scale morphological development of the estuary, to understand and quantify the large-scale response of the morphological system to human interventions with emphasis to those related to navigation channels. It is aimed to improve our fundamental knowledge on small-scale processes around navigation channels and increase the understanding of the large-scale response of estuaries, to explain the complex phenomenon of the high siltation in the North Passage of Yangtze estuary. The results will be useful for a proper management of the estuary.

A state-of-art process-based model is applied to simulate the hydrodynamics in the Yangtze Estuary in China, as a basic step to acquaint ourselves with the morphological development and the effect of human interference in the estuary. A major improvement with respect to previous models for the Yangtze Estuary is that the present model covers the entire tidal region of the Yangtze River. Two curvilinear grids are used to adapt to the complex geomorphologic setting and the large spatial magnitude of the study area by applying domain decomposition techniques. The calibration of the model against extensive hydrodynamics data shows a good representation of observed hydrodynamics. With the present calibrated and validated model, the morphological evolution, as well as the effects of discharge regime change and sediment load reduction on the Yangtze Estuary can be carried on.