Migration of sediment deposition due to the construction of large-scale structures in Changjiang Estuary

摘要

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.