长江河口徐六泾节点的动态特征

EVOLUTIVE FEATURE OF THE NODAL POINT OF XULIUJING IN THE CHANG-JIANG ESTUARY

本文根据南通河段和长江河口南支河段河床演变过程,应用经验正交函数(EOF)分析徐六泾节点的变化特征,分析表明:徐六泾节点断面的复杂变化可以用前三个经验正交函数来表征,它们反映了三种不同的变化过程即主要趋势、局部形态变化和短周期变化。徐六泾节点断面演变的主要趋势表现为深槽的不断刷深和缩窄,局部形态变化是由上游南通河段河槽变化引起的,短周期变化是由长江水量的变化引起的。上述三种变化分别占节点断面总变化的78％,9.9％和3.6％。因此,如何控制南通河段河势的变化,对徐六泾节点的长期稳定是相当重要的。

According to the evolution processes of the Nan Tong channel and the South B-ranch channel of the Changjiang estuary, the empirical orthogonal eigenfunction (EOF) was used to analyse the variation of the nodal point of Xuliujing. The complicated variation of the transverse section at Xuliujing can be characterized by three ofthogonal eigenfunctions corresponding to the three largest eigenvalues. They represent three different evolution precesses respectively,the major trend, the change in shape and the short-period change. The major trend is that the central channel is deepened and narrowed. The change in shape is induced by the evolution of upstream Nan Tong Channel. The short-period change is caused by the variation of flow discharge of the Changjiang river. These three evolution processes account for about 78%, 9.9% and 3.6% respectively of the total variation of the transverse section. As a consequence, the control on upstream channel evolution is important for stabilizing the nodal point of Xuliujing,