High Resolution Measurement and Analysis of Sediment Dynamics in Bottom Boundary Layer of the Macro Tidal Estuary
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摘要: 现场试验表明，三角架观测系统稳定性良好，获取了边界层内多层位、连续的温、盐、流速、浊度同步观测数据，适用于浅海近底部沉积动力过程高分辨率观测及物质输运研究。观测结果显示：观测期间，边界层内存在向陆的余流，并呈现逐渐减小的趋势，其主要由涨、落潮流的不对称造成，大风天气和密度环流亦是影响余流强弱的重要因素；观测期间多数时刻底部切应力大于起动切应力，底质沉积物可产生明显的搬运甚至再悬浮；悬沙浓度对沉积动力的响应在涨、落潮，大、小潮阶段均有各自的特点，水动力的变化、潮流加/减速时间的长短、床面泥沙的供应量、上部水体泥沙的沉降是导致悬沙浓度变化的主要原因；底部边界层内，涨、落潮期间不对称输沙导致潮周期内悬沙净向河口湾内输运。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.
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Key words:
- tripod /
- bottom boundary layer /
- suspended sediment /
- resuspension /
- sediment transport
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