长江河口北港河道泥沙特性及河床沙再悬浮研究

Sediment character and bed load resuspension in North Channel of Changjiang Estuary

基于北港上段和下段以及南支河道三个站点的7天连续同步水沙观测数据(包括潮流、悬沙含量和表层沉积物样品),通过对不同时刻悬沙浓度、悬沙和沉积物粒径组成分析,以及基于沙量平衡的粒度谱计算,对长江口北港河道泥沙特性和河床沉积物再悬浮作用进行了研究。结果表明:北港上段河道落潮时水动力强于涨潮,单宽输沙量表现为净向海输沙;河床沉积物颗粒较粗,细砂和粉砂含量可达90%以上;近底层悬沙浓度在一个涨或落潮周期内可存在两个峰值;河床沉积物再悬浮作用落潮强于涨潮。

Based on the measurements of the tidal velocity, suspended sediment concentration （SSC） and bed load samples, done simultaneously at three stations located in the upper reach and lower reach of the North Channel and the South Branch of the Changjiang Estuary from June 26th to July 2nd 2011, the sediment char acter and seabed sediment resuspension processes are studied by data analysis and the grain size spectral cal culation. The results indicate that the hydrodynamics during the flood tide was stronger than that during the ebb tide with seaward net sediment fluxes, which was due to the tidal asymmetry caused by tide wave deforma tion. The bed load was mainly composed of fine silt and clay, whose content was over 90%. The SSC near bed could reach its maximum twice during a single flood period or an ebb period. That was caused by the re suspension of fluid mud that settled on the seabed surface during the turn of tidal current and the resuspension of eroded fine particles from the bed load by strong tidal current, respectively. Thus the resuspension of the bed load in the North Channel was quite strong. However, the sediment supply from the bed load to the sus pended sediment was less than 35% of the total suspended sediment.