长江口南港水动力及悬沙的时空分布特征

Temporal and spatial distribution characteristics of suspended sediment and hydrodynamics in Nangang water way of Yangtze estuary

通过2011年8月中旬一个大潮期间长江口南港某横断面上的5个定点水沙观测资料,分析了南港水动力及悬沙在潮周期及横断面上的分布特征。结果表明:在时间尺度上,南港潮位波动以半日分潮为主,日分潮较小;受径流及Stokes漂流的影响,涨潮流流速明显小于落潮流流速;含沙量随潮波动现象明显,波动频率是潮流的2倍;在空间尺度上,南港纵向流速最大值分布在南侧主槽,转流从北侧副槽率先开始;侧向流主要是由科氏力对纵向流的偏转作用形成;北侧副槽平均含沙量大于南侧主槽;半日潮流驱动下,平均含沙量在急流和憩流时刻将分别增大和降低;半日潮流和余流共同驱动下,在落急时刻和涨急时刻分别会增大和降低平均含沙量。

Based on the observation data of flow movement and suspended sediment concentration of 5 points on a crosssection of Nangang water way, Yangtze River estuary during the middle August, 2011, we analyzed the temporal and spatial variation characteristics of hydrodynamics and suspended sediment in the water way. The results show that, on the time scale, the domi- nant part of water level variation is semi - diurnal tide, and secondary is diurnal tide ; the current speed during flood is signifi- cantly larger than that during ebb period due to the river discharge and Stokes drift ; the variation frequency of suspended sedi- ment concentration （SSC） is obvious, doubling to that of tidal flow. For the spatial distribution of tidal current and residual cur- rent, their longitudinal maximum velocity occur in the main channel near south bank, correspondently, the slack flow takes place in secondary channel near the north bank ; the lateral flows are mainly induced by the Coriolis deflection action ; the mean SSC in northern secondary channel is much higher than that in the south main channel; the mean SSC would be increased due to the in- fluence of semidiurnal tide during maximum flood and maximum ebb, and decreased during flood slack and ebb slack; or in- creased due to the influence of semidiurnal tide and residual current during ebb period, and decreased during tidal surge.