Abstract:

Based on the mechanism decomposition method, mechanisms of sediment transport in Nanhui tidal flat have been assessed with field data. The traditional mechanism decomposition method was improved in this study by dividing the suspended sediment into 4 groups (62.5～250μm, 16～62.5μm, 3.9～16μm, 0.5～3.9μm) according to the grain size and analyzing each group separately.  The results reveal that the transport of suspended sediment of different groups was controlled by different mechanisms. The transport of clay and fine silt was controlled by advection terms and tidal pumping terms. With respect to the transport of coarse silt and fine sand, tidal pumping terms and shear diffusion terms caused by the variation in the form of the vertical profiles of velocity and suspended sediment concentration both played main roles. Meanwhile, by comparing the main mechanisms contributing to the sediment transport of the same group in different water depths, it is found that the contribution of tidal pumping terms decreased sharply when suspended sediment was transported from deepwater area to shallow water area, and the trend didn't change with the variation in the tide type and grain size