Transportation of suspended sediment in Shenjiamen offshore area of Zhoushan

Based on both the data of tidal current and suspended sediment collected from the sea area off Shenjiamen of the Zhoushan Islands, temporal and spatial variation in suspended sediment concentrations during neap and spring tides and their influence factors are discussed in this paper. The transportation characteristics of the suspended matter in the sea area are described by sediment net discharge rate and moving direction. Results show that suspended sediment concentration in the study area is higher than that in surrounding areas, owing to the inputs from the Yangtze, Qian Tang and other rivers as well as surrounding islands. In general, the suspended sediment concentration is spatially in a pattern decreasing from northeast to southwest. The highest sediment concentration appears at the C1 station in Lianhuayang sea, while the lowest at the C4 station in the Zhitouyang sea. Vertically, the suspended sediment concentrations gradually increase with the increase in water depth. The movement of suspended sediment from initiation to settlement is mainly udder the control of tidal movement. There is a high correlation between the suspended sediment concentration and the tidal current velocity. Flux mechanism decomposition shows that suspended sediment is mainly transported in a form of advection. Net transport rate in spring tide is greater than that in the neap tide period. To sum up, the sediment transport in the study area is in a trend towards the sea through channels.