长江口外海滨典型断面悬沙通量计算

Suspended sediment flux at the typical cross sections in the offshore area of Changjiang Estuary

长江河口的口外海滨地区是河流和海洋之间的过渡区域和长江入海泥沙扩散、堆积的主要场所 ,也是与杭州湾、江苏海域等邻近水域进行水、沙交换的过往之地。本文运用目前较为成熟和可靠的机制分解法和等面积时变网格法分别对口外海滨地区典型断面的悬沙通量进行了估算 ,两种方法计算得到的通量结果方向一致 ,量级相同。结果表明 ,长江流域来沙出口门后 ,大约 2 7%向南进入杭州湾 ,向东入海的有 2 0 %左右 ,还有 9%左右的泥沙向北进入江苏海域 ,剩余的大约 4 4 %的泥沙在水下三角洲地区沉积下来。就各输沙项而言 ,平流作用输沙贡献最大 ,潮泵作用输沙量次之 ,垂向净环流和垂向潮振荡切变项的相对贡献较小。

The offshore area of Changiiang estuary is the transitional area of river and ocean,where water and sediment are always transporting towards the sea,and exchanging with Hangzhou bay and alongshore the north of Jiangsu sea area.The method of mechanism analyses and equal_area grids were used in this paper to calculate the suspended sediment flux in the typical cross sections in the study area. The results indicate 44 per cent of sediment from the Changjiang river deposits in the submarine delta, more than 27 percent of remainders transport to the south_east into the alongshore of Hangzhou bay, only 9 per cent of sediment exchanges with the sediment alongshore the north of Jiangsu sea area,and about 20 per cent of total sediment transport to the sea.Advective sediment flux is the most important item,and the tidal pumping effect is the second important item,and the vertical gravitational circulation and vertical tidal oscillation shear contribute little to the total sediment discharge.