• 论文 •

### 长江河口的演变规律与水动力作用

1. 湘潭工学院资源勘查与城镇建设系,湘潭411201
• 收稿日期:1997-02-01 修回日期:1997-11-01 出版日期:1998-05-15 发布日期:1998-05-15

### THE EVOLUTIONAL RULE OF CHANGJIANG RIVER MOUTH AND HYDRODYNAMICE EFFECT

Gao Jin

1. Xiangtan Polytechnic University, Department of Resource Exploration and Municipal Construction, Xiangtan 411201
• Received:1997-02-01 Revised:1997-11-01 Online:1998-05-15 Published:1998-05-15

Abstract: The key problem in discussing evolutional rule of Changjiang river mouth is to study the developing rule of river mouth sandbars in each period. In the past, scholars studied the problem by geomophology and sedimetology method, while the author inquires into the problem with hydrodynamics method. Developing length and the arranged direction of sandbars can be calculated. In the paper, two questions are disscussed. 1. The theoretical analysis of the developing length of sandbars The theoretical formula of developing length Chongming island is as follows: l=S/Q2Q14b1b2 10-1 Due to the irregular shape of Chongming island and the unsymmetrical character of the water flow on both sides of the island, in order to simplify the calculation, we consider the south branch as one side of a right triangle and straighten the north branch as the hypotenuse of the right triangle, the length of another side is S . Q2/Q1 is ratio of flow for north branch to the total in ebb tide. b1b2 is the ratio of width between main channel and north branch. The cross section of river channel is supposed to be arc. When S =39 7 km, Q2/Q1 =12 4100 and b1b2 =5 962 53, we can getl=80 3 km. The theoretical value conforms to the practical length. 2. The evolutional rule of Changjiang River mouth and its environment significance An outstanding evolutional rule of the present Changjiang River mouth is that the main channel is gradully deflected towards south and the river mouth sandbars in different periods were arranged like wild geese flying from northwest to southeast. The effect of Coriolis force lies in that it controlls the difference of initial conditions for the channels of division flows, and this creates that the channels of division flows evolute towards different direction. The north branch is easily silted up and the south branch is developing further. In the near future, Chongming island will be connected with the land on the north bank and the second Chongming island will be formed, which is composesed of Changxin and Hengshan Island. The channel on its south side, South Harbour will be more narrow in width. These islands and the sea banks of Pudong in shanghai will be eroded. This is a potential environmental problem.

• P343.5