南汇近岸水域近底层泥沙运动和边滩沉积  

Near bottom sediment movement and sidebank deposition for the Nanhui offshore waters

作　　者：陈沈良[1] 谷国传[1] 李玉中[1] 

机构地区：[1]华东师范大学河口海岸国家重点实验室,上海200062

出　　处：《东海海洋》2003年第4期15-25,共11页Donghai Marine Science

基　　金：国家自然科学基金资助项目(40276027);教育部科学技术重点资助项目(01079)

摘　　要：根据长江口南汇近岸水域17个站的水文泥沙同步观测资料,阐述了该水域近底层泥沙的流速、悬沙浓度的分布和变化。经无量纲潮流动力值的计算表明,研究区存在一个包络南汇边滩先向东南继而向南延伸的舌状高能量区,与高悬沙浓度分布区相一致。通过对悬沙运动和涨、落潮周期流向的分析,揭示了长江口向杭州湾底层泥沙输移的规律,其底层泥沙输移主要集中在低潮位时段,输移时间约占潮周期的36%,其中以南汇边滩向杭州湾输移的时间为最长,大、小潮都在5h以上,与其相关联,在芦潮港水域下层存在着一股东西向的高悬沙浓度的水体。据盐度、潮流、悬沙浓度等要素,并结合絮凝沉降分析得出,南汇边滩的沉积强度是潮滩>潮下带>深水区;边滩舌尖前缘水域的泥沙沉积时间与水体出现向东偏南或向西流的时间一致,这可视为近年来南汇水下沙嘴向东偏南伸展的原因之一。The distributions of near\|bottom current velocity and suspended sediment for the Nanhui offshore waters are analyzed based on seventeen multi\|ship synoptic surveys. The calculation of tidal current dynamics indicates that a high\|energy area, covering around the Nanhui nearshore, stretches first southeastward then southward, which is consistent with the distribution of high suspended sediment concentration. The analysis of suspended sediment movement and current directions over a tidal period indicates that the sediment transport from the Changjiang Estuary to the Hangzhouwan Bay mostly concentrates at low tide, accounting for about 36 percent of a tidal period, in which the transport time from the Nanhui nearshore to the Hangzhouwan Bay is the longest, near 6 hours during spring tides, correspondingly in the meanwhile, in the bottom layer of the Luchaogang waters exists a high sediment concentration column with east\|west direction. Finally, according to the synthetical analysis of salinity, tidal current and suspended sediment, combined with flocculation deposition, the depositional intensity for the Nanhui nearshore is greater in the nearshore area than that in the offshore area, and the weakest in the deep water area. And it is found that at the front edge of Nanhui tongue\|like sidebank, the depositional time is consistent with the southeasterly or westerly current, which shows, in a certain extent, the Nanhui Spit has extended southeastward for recent years.

关 键 词：近底层泥沙 潮流动力 边滩沉积 南汇水域 泥沙运动 

分 类 号：P737.14[天文地球—海洋地质]