Dynamic analysis of riverbed evolution: Chengtong Reach of Yangtze Estuary

Abstract

This paper proposes a new approach to improve the analysis by extensively using the numerical model results. A 2D hydrodynamic model based on the Delft 3D suite is first set up and validated with the field measurement data. The model is then used to examine the hydrodynamic responses of the estuary to the change of local bathymetry or upstream discharge. This approach is applied to the Chengtong Reach of Yangtze Estuary as an example. The net discharge ratio (NDR) is used as an index to demonstrate the trend of channel development. The results show that the net discharge ratios (NDRs) at the main channels of Fujiangsha, Tongzhousha and Langshansha sub-reaches decrease with increase of upstream river discharge in general; however, the NDR at the main channel of Rugaosha sub-reach increases first, and then decreases with increase of upstream river discharge when the river discharge is larger than 45,000 m3/s. This difference is related to the local bathymetry as well as the ebb-dominated or flooddominated characters in those sub-reaches.