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The paper presents measurements of sediment deposition in the navigation channel of Changjiang Estuary during the construction of the world largest jetty-spur system. A significant change of sediment deposition pattern is found after the second stage of the project, which extended the previous 25 km long jetties built in the first stage to about 50 km. The measurements show that the main deposition region migrated from the lower reach to upper reach of the navigation channel, with the strongest deposition occurred at the upper middle reach. The physical mechanisms inducing the migration of the sediment deposition region are studied numerically using the finite-volume coastal ocean model (FVCOM). Model results reveal that the tidal currents as well as the sediment processes in the northern passage are greatly changed by the structures. With the extension of the structures, suspended sediment concentration decreases at the upper reach and increases at the lower reach, resulting in a seaward migration of turbidity maximum in the northern passage. The changes of suspended sediment concentration distributions are mainly caused by the adjustments of tidal currents at ebb. The analysis based on the local momentum balance identifies two mechanisms causing these adjustments.

An unstructured grid, Finite Volume Coastal Ocean Model (FVCOM) is used to study hydrodynamics and large-scale structure impacts in Changjiang Estuary. Field measurements conducted after the construction of the large-scale channel–jetty system are used to assess numerical results. The agreements between simulated and measured water levels, depth-averaged current velocities and tidally averaged longitudinal salinity distributions are excellent, as indicated by predictive skills higher than 0.94. The predictive skills for time series of salinity show a large range, from 0.97 to 0.62, in different measurement locations. The impacts of two 50 km long jetties and tens of spurs on the estuarine circulations as well as salinity distribution are investigated using comparisons of numerical results with and without jetty structures. Results reveal that the jetty structures intensify currents in the navigation channel and generate strong shear and vortices in jetty–spur blocks, which enhance turbulent mixing and degrade salinity stratification in the channel. The large-scale structures not only affect the flow field in the northern passage, but also play an important role in redistributing freshwater runoff in the multi-channel system, resulting in estuary-scale adjustments of circulations and salinity distribution.

In this paper, the wet-dry grid point method (WDM) with generalized curvilinear computation grids is introduced with the aim of presenting a kind of effective numerical model for real-time forecasting of storm surge flooding. To realize this general WDM method, generalized 2-D shallow sea dynamic equations in curvilinear co-ordinates are derived, and the contravariant components of the velocity vector are employed for easily realizing boundary conditions and making the wet-dry point judgement criterion more reasonable. As the generalized equations are not limited to a specific co-ordinate transformation, a self-adaptive grid generation method, which optimizes simultaneously grid smoothness, orthogonality and variation in cell volumes, is then proposed to meet the needs of WDM with varying spacing grids. The paper also provides a numerically stable difference scheme and this scheme is proved accurate by the verification calculation of observed storm surge.