长江口北港上段河道枯季悬沙浓度垂向分布特征研究

基于2018年4月15日至4月24日在长江口北港主槽大小潮连续10天的定点水文泥沙观测资料，对枯季期间北港上段河道悬沙浓度的垂线分布特征进行了研究。结果表明：研究区域的悬沙浓度较低，大小潮平均值仅为0.17 kg/m3，悬沙浓度具有大潮显著高于小潮，涨落潮平均浓度接近的特点；水动力则具有大潮明显强于小潮、落潮明显强于涨潮的特点；观测期间的盐度值很低，平均值仅为0.16 psu，盐度的大小潮变化、涨落潮变化以及垂向变化都非常小，盐度密度分层对悬沙剖面影响微弱。在这种动力、泥沙和盐度环境下，大潮期间的悬沙剖面主要为斜线型和指数型；小潮期间的悬沙剖面有斜线型、垂线型和指数型，其中以斜线型占主导。通过Rouse公式拟合发现，大部分的实测悬沙剖面较符合Rouse公式，根据该公式计算得到的悬沙沉降速度介于0.36~2.89 mm/s。Soulsby公式能够对实测的斜线型和垂线型悬沙剖面进行较准确预测，平均误差控制在10%以内。

Vertical Profile of Suspended Sediment Concentration in the Upper Reach of North Channel in the Changjiang Estuary During the Dry Season

Based on the field observation data of current velocity and suspended sediment concentration (SSC) measured in the upper reach of North Channel in the Changjiang Estuary from 15th April to 24th April in 2018, the vertical distribution patterns of SSC during the neap and spring tides are studied. The results show the SSCs in the study area were relatively low, with the mean value of only 0.17 kg/m3. SSCs were higher in spring tide than in neap tide, and close to each other for the flood-mean and ebb-mean values. Tidal currents were much stronger in spring tide than in neap tide, and in ebb phase than in flood phase. Salinity was considerable low during the survey period, with the mean value of only 0.16 psu. The neap-spring variation, flood-ebb variation and vertical variation of salinity were all very small, indicating the impact of salinity-induced stratification on the SSC profile is negligible. In such hydrodynamics, sediment dynamics and salinity condition, the SSCs profiles during the spring tide were the linear type and exponential type. But during the neap tide the SSCs profiles were the linear type, vertical-line type and exponential type, and the linear profile was the dominant type. By fitting Rouse equation, we found that most of measured SSCs profiles fitted Rouse equation roughly, and the settling velocity of suspended sediment deduced by this equation is between 0.36-2.89 mm/s. Soulsby equation can accurately predict the observed linear and vertical-line types of SSC profiles, with the average error less than 10%.