长江口悬沙动力特征与输运模式

Characteristics of Suspended Sediment Dynamics and Transport Pattern in Changjiang River Estuary

本项研究用ADCP在长江河口进行高频、高分辨率三维流速和声学浊度的定点观测,通过对定点站位潮周期内的悬沙浓度、流速和盐度的分析,计算悬沙输运率;悬沙输运机制分析表明平流作用、斯托克斯漂移效应在悬沙输运中占据主导地位。此外,从河口内向河口外,潮周期内的水动力特征与悬沙净输运具有明显的地域性差异,主要表现在悬沙输送的贡献因子、盐度的垂向混合和分布特征、垂向流速等方面。在拦门沙下游和口外地区,悬沙均向西、北方向输送,而拦门沙上游则向东、南方向输送。这种悬沙输运格局,对于长江口拦门沙及附近最大浑浊带的形成有着重要的作用。

The acoustic Doppler current profiler （ADCP） is wildly used to measure current velocities in recent years. In this contribution, the high-frequency velocity data are measured by using the 600Hz ADCP at three stations in the Changjiang estuary. Subsequently the tidal variations of suspended sediment concentration, velocity and salinity of different stations are analyzed, and the suspended sediment transport rate and mechanism are also calculated. As the three stations are situated in different parts of Changjiang estuary, and are subjected to different hydrodynamics, their sediment transport, salinity vertical mixing, vertical current speed, and net suspended sediment transport direction in tidal cycle show an obvious regional difference. The suspended sediment transport in the estuary is dominated by river flow, the storks drift, tidal dispersion also play an important role in the suspended sediment transport. Furthermore, such transport directions, which were directed towards west and north downstream of bar shoal and out of Changjiang estuary, and east and south upstream of the bar shoal, play a more important role in the forming of turbidity maximum of Changjiang estuary.