长江河口南槽近期滩槽水沙输移特性分析

Characteristics of recent flow and suspended sediment transport in beachs and channels of South Channel of Yangtze River Estuary

为了深刻认识近期长江河口演变趋势,依据2005,2006年和2010年长江口南槽滩槽洪枯季实测水文泥沙数据,分析了主槽与浅滩的水动力条件及悬沙浓度的时空分布特征。利用机制分解法,研究了河口滩槽间泥沙输移及交换机制。研究结果表明,长江口南槽主要以往复流为主,落潮流速大于涨潮流速。随着水深变浅,水流流速过程线存在差异,使不同区域的水流挟沙能力和输沙过程不同。输沙以平流项输沙通量为主,但潮泵作用在南槽地区泥沙输移中也占有重要地位,形成"主槽出沙、浅水进沙"的输沙模式,促使南汇边滩前缘缓慢淤涨。

In order to understand the recent evolution trend of Yangtze River Estuary, according to the measured hydrological and sediment data on beach and channels of South Channel in flood and dry seasons of 2005, 2006 and 2010, the hydrodynamic conditions and the temporal - spatial distribution of suspended sediment in main channel and shallow beach are analyzed. The mechanism decomposition method is adopted to study the sediment transport and exchange mechanism. The result shows that the flow is reciprocated and the ebb current velocity is larger. Flow velocity process changes with depth, resulting in different sedi- ment - carrying capacity and sediment transport process in different areas. Sediment is transported mainly by adveetion term, but tidal pumping occupies an important position of suspended sediment transport in the south passage zone. The sediment flows out at main channel and comes in at shallow areas, which makes the front of Nanhui shoal deposit slowly.