High Resolution Measurement and Analysis of Sediment Dynamics in Bottom Boundary Layer of the Macro Tidal Estuary

Key words: 
• tripod /
• bottom boundary layer /
• suspended sediment /
• resuspension /
• sediment transport

Abstract: The field experiment gained continuous temperature, salinity, current velocity, turbidity data synchronously in several layers through the tripod platform. The tripod performed stability during the field experiment, and it can be applied in high resolution measurement of sediment dynamics and transport in shallow sea. The results showed that there was residual current which towards land in bottom boundary layer and gradually decreased during observation periods, which was caused by asymmetric of flood and ebb flow, strong wind and density circulation also affected the residual current strength. Bottom shear stress was greater than threshold shear stress in most time of observation periods, so sediment can be transported and even resuspended significantly. The response of suspended sediment concentration to dynamics was different in flood and ebb, spring and neap tide, changes of hydrodynamic, length of acceleration and deceleration periods of tidal current, the available erosion sediment, settlement of sediment of above water were the reasons of changes of suspended sediment concentration; asymmetric sediment transportation of flood and ebb tide lead to suspended sediment net transport to inside of estuary in bottom boundary layer.