The suspended sediment transportation and its mechanism in strong tidal reaches of the North Branch of the Changjiang Estuary

As the effect of natural accreting processes and artificial reclamation, the river channel of the North Branch in the Changjiang Estuary has narrowed significantly, and the position of summit of the funnel-shape has moved down. As an important strong tidal bifurcation of the Changjiang Estuary, the transport characteristics of suspended sediment in the North Branch is deserving of further discussion and research by considering the changes in river morphology and sediment load from the Changjiang drainage area.According to the continuousl observation of flow and sediment during one spring-neap tide cycle in April 2010, together with historical data from different locations, the obtained results are as follows: the current is strong and suspended scdiment content(SSC) comparatively high in the North Branch, the process curve of the SSC shows a pattern of "unimodal-bimodal-unimodal"in a half 14 d cycel. Lagrangian advection and tidal pumping effect are two main constituents of sediment transport in the North Branch, with spatial variations.Touxing Port can be considered as a transition, where Lagrangian sediment transport dominantes in the upper mouth and the tidal pumping in the lower section. As for the net sediment transport flux, it moved seaward in upper mouth and landward in the lower section. The result suggests a turbidity maximum due to sediment accumulation around the summit.