珠江黄茅海河口洪季侧向余环流与泥沙输移

2012年洪季对珠江黄茅海河口湾侧向动力结构与泥沙输移过程进行了系统观测,采用动量平衡和泥沙通量机制分解等方法,分析了河口流、温盐和泥沙侧向分布特征以及泥沙输移过程,探讨了侧向动量平衡与泥沙输移机制。洪季黄茅海河口存在明显的侧向流,西滩和北槽均形成表层向东、底层向西的两层侧向流,拦门沙滩顶呈现表、底层向西、中层向东的三层侧向流,而拦门沙前缘侧向流整体向西。河口湾纵向净泥沙通量表现为北槽向海、西滩向陆,拦门沙滩顶及其前缘均向海;侧向净泥沙通量表现为滩顶及其前缘均向西,西滩向东、北槽向西。这种侧向泥沙辐聚过程是高浓度悬沙聚集于滩槽界面的重要原因,向陆净通量是西滩回淤的重要原因。滩槽间侧向余环流动量平衡主要是侧向斜压梯度力、科氏力和侧向平流作用。欧拉平流输运在侧向泥沙输运中起主要作用,潮泵效应也起重要作用。

Lateral residual circulation and sediment transport during the flood season in the Huangmaohai Estuary,Pearl River

Systematic observations of lateral flows and sediment transport were conducted in the 2012 flood season in a wide and shallow estuary of Huangmaohai,Pearl River. The lateral distributions of flows,salinity and sediment were identified,and the lateral dynamics and the mechanism of sediment transport were examined. Lateral flows were found to indeed occur in the estuary. A two-layer lateral residual flow developed on the west shoal and in the North Channel,a three-layer lateral residual flow developed on the top of the mouth shoal,and a lateral residual flow was directed westwards downstream of the mouth shoal. Net longitudinal sediment dispersal appeared that seaward transports occur in the deep channel,landward transports on the west shoal,and seaward transports on and downstream of the mouth shoal. Net lateral sediment transport existed that the westward transport appears on and downstream of the mouth shoal,while the westward transport occurs in the North Channel and the eastward transport on the west shoal. The reverse lateral sediment transport between the channel and the shoal resulted in the sediment convergence near the deep channel. The landward sediment fluxes on the west shoal plays an important role in the deposition of the west shoal. The mean lateral momentum balance showed that a clockwise lateral residual circulation (looking landwards) is controlled by the interaction between Coriolis effect and lateral baroclinic forcing. Lateral advection influences greatly the lateral dynamics,which has been regarded to be unimportant. The mechanism decomposition of lateral sediment fluxes over a tidal cycle showed that the lateral sediment transport is driven mainly by the Eulerian advection and tidal pumping.