PIANC Smart Rivers 2022

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As currently the importance of maintaining the steady state of the significant tidal shoals and the navigation channels in a bifurcated estuary standing out, mainly due to the consideration for the both the environmental protection and economic development, the urgency of the research for the inner evolution mechanism of the morpho dynamics in a large-scale estuary with sophisticated natural and anthropogenic forces has been increased, especially in the Yangtze River Estuary. This study focuses on the bathymetric evolution mechanism of the Yangtze River Estuary, aimed to explore the relationship between the main control factors and the estuarine bathymetry variation in recent years and in the next few decades. The methods used in this study include the analysis of the recent bathymetric data of the tidal shoals and the channels, and the establishment of a large scale two-dimensional mathematical model which is fully calibrated and verificated on the bases of the recent measurement data. Firstly, the comparisons were made between the bathymetric data of different period gathered in recent years and it is clarified that the different change modes really exists along the estuary, which mainly result from the different positions of the shoals and channels spread in the estuary. Especially, the distinctness show how the forces of the tide and riverine current are balanced along the estuary from the upper reach to the lower reach and finally the mouth part. 
Although the man-made engineering buildings such as the jet and walls surely have exerted certain influences on the morphological variation in their protection areas, the areas locates in upper reach prefer to eroding more than the lower reach and the mouth area show most deposition trend comparing with other parts. Secondly, the hydraulic data of the channels which includes the north 
Passage and the south passage shows the navigation project have deeply influenced the the movement of both the current and sediment in which the south passage generally presents more suitable trend for navigation. Thirdly, the two-dimensional mathematical model stimulated both the short term and the long term of the estuary, and the results showed that in the short term erosion and deposition are nearly balanced in the mouth area , however , in the long term , the estuary present a trend of general erosion. This research further explore the evolution mechanism of the shoals and channels in an estuary both influenced from river and tide, and clarify the relationship between the bathymetric changes between different parts and it can offer certain useful suggestion and thoughts for the further integrated management of the estuary.

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