长江口拦门沙地区的泥沙运动规律

依据１９８８年７月和１２月水文观测资料，通过流，盐，沙的综合分析，认识到长江口拦门沙地区的泥沙运动有与河口其他地区不同的特点，泥沙输移在水平面上和垂直面上存在着多种循环，潮流和盐水截留大量泥沙积聚的拦门沙地区，河口在盐淡水交锋地带，除了涨，落急时段外，发现在转流时期泥沙也可能产生再悬浮，从而形成一个潮周期中出现３次或４次再悬浮的特殊规律。

THE SEDHVIENT DYNAMICS IN THE CHANGJIANG RIVER ESTUARY MOUTH BAR AREA

Results analyzed current, salt, sediment based on hydrographic data ofChangiiang hiver mouth bar in July and Desember, 1988 were as follow. In theChangiiang mver Estuary mouth bar area sediment in the reach where runoffplays an important role moves seaward; sediment in the reach where tidal currentis the main force, moves landward; sediments in the reach where density curentplays an important role drculates vedically; and the sediment on the whole circu-lates in a plane under the impacts of the topography and current.The abundant sediment discharged from the Changjiang fover are trapped atthe mouth bar due to the effeCts of tidal current, runoff and mixing of salt- andfresh-water. There are two different mechanisms controlling the trapping of the sedi-ment by tidal current and salt water. The depositing centre may not be at one placebut in two densely depositing zones in the deep trough.It was found that the sediment of the mixing zone between salt-and fresh-waterwas resuspended three or four times during one tidal period. The reason is relatedto the mixing effect between salt water and fresh water.