长江口横沙浅滩及邻近海域含沙量与沉积物特征分析

Analysis of the suspended sediment concentration and sedimentation around the Hengsha Shoal of the Yangtze Estuary and its adjacent region

长江口在河流动力和海洋动力相互作用和相互制约下,在河口口门形成了庞大的河口拦门沙系,在河口口外形成了巨大的水下三角洲.横沙浅滩是河口拦门沙系的重要组成部分.横沙浅滩含沙量不仅受到流域来水来沙条件的影响,更主要的是受到台风暴潮和寒潮大风的影响,除了大潮含沙量大于小潮含沙量的特征外,冬季含沙量大大大于夏季含沙量.横沙浅滩5 m水深含沙量的总体水平约为0.459 kg/m3.横沙浅滩邻近海域含沙量在向海方向上迅速降低.除潮汐大小含沙量呈现大小变化之外,冬季含沙量大于夏季含沙量是其主要特征.长江流域来沙近年来呈现减少趋势,邻近海域含沙量有所减少,局部海床出现冲刷现象.横沙浅滩沉积以细粉砂为主,水下三角洲沉积物以粘土质粉砂为主,横沙浅滩及邻近海域沉积物的平面分布和垂向分布均反映了横沙浅滩沉积物和水下三角洲沉积物的组合结构.拟建横沙浅滩挖入式港池和外航道沉积地层均为第四纪疏松沉积层,特别是水下三角洲地层,可挖性好,容易成槽,对工程建设有利.

Under the joint influences of the Changjiang River and ocean, the significant sandbar system has been produced in the river mouth, and the submarine delta in the outer deep region. Hengsha Shoal is one of the most important components in this sandbar system. The suspended sediment concentration is not only influenced by the upstream sediment input, but also affected by the storm surge and strong wind. The SSC during spring tide is mairdy bigger than that during neap tide. And the SSC of wintertime is higher than summer. The averaged SSC at the 5 m i- sobath is about 0. 459 kg/m3. The SSC shows a significant decreasing trend at the seaward direc- tion. Under the decreasing input from the Changjiang River recently, some part of the seabed shows a erosion pattern. The bed of Hengsha Shoal is mainly composited of silt, and the subma- rine delta is consisted of silt and clay. The submarine delta could be excavated for harbor and channel, which is favorable for the construction of planed harbor.