长江河口南港枯季沙波对安全航行的影响研究

Estimated Effect of Bed Sediments and Sand Waves During Dry Season on the Safe Nautical Depth in the South Channel of the Changjiang River Estuary

基于1997年、2002年、2006年枯季长江河口南港床面形态的现场观测,分析沙波发育对水深的影响。结果表明:(1)枯季南港沙波一般分布于吴淞口至中段121°44.′5E细砂、粉砂质底床区间,呈逐年向下游扩大的趋势,发育尺度由西向东逐渐变小,河床沉积物粒度组成由上游至下游逐渐细化,分选性变差;(2)沙波波高一般为0.2～1.31m,平均为0.47m,波高沿程向下游递减,水深均处于15m的上段波高虽最大可达1.31m,但足以通行第四代集装箱船,而水深降至11.8m的中段,最大波高可达0.80m的沙波发育将直接影响第四代集装箱船的乘潮入港条件。

Bed sediments, sand waves and current velocities and directions were measured during the dry season in 1997,2002 and 2006 in the South Channel of the Changjiang River Estuary. In the view of results, we found that： （ 1 ） Downstream ward fining and decreasing sorting of the bed sediment grain size occurred during the dry season in the South Channel of the Changiiang Estuary. （2） Smaller spatial scale of sand waves with parallel and straight and systematic crests during the dry season than that during the flood season scattered within the channel bed composed of fine sands and coarse silts from Wusong outlet to the channel bed at latitude 121°44.5′E,and the spatial scales of sand waves from the western to the eastern decreased;sand waves were overlapped by a highly turbid liquid mainly composed of silts and the thickness at 10 ~ 20cm,located in the clay silt distributed area at the lower South Channel where the sand waves tended to vanish. The existing area of sand wave in South Channel expands to west annually, affected by the river regime changes in the branch of South and North Channel. Quite great seasonal variation of sand wave＇ s height might lead to the higher seasonally changeable regime of safe nautical depth at larger than 2m in the South Channel of the Changjiang Estuary.