The Formative Processes And Application In Estuarine Regulation And Exploiture Of Out-bar And Inner-stream Topographty In Changjiang Estuary

Along with the faster economic economic globalization trend and modern construct step, the status of Shanghai port is continuously increased in domestic and international shipping market. The cargo volume is the biggest and the container throughput in Shanghai port is the third biggest in the word. Shanghai port is vital important to the sustainable development of economy and society in Shanghai. However, there is a lack of navigations and bank resources with deep water in Changjiang Estuary, which restrict the development of Shanghai port. In fact, there are some port and bank resources which have foreground in exploitation and use. Some of them are located in the reach of out-bar and inner-stream. Therefore, research on the protection and exploitation to the bank of out-bar and inner-stream is practical important.This paper will conbine with field measurement and inside analysis, qualitative analysis and quantitative analysis to research the formative mechanism and application in estuarine regulation and exploiture of out-bar and inner-stream topographty in Changjiang Estuary though the angle of dynamical, sedimention and geomorphology. GIS technology and mathematical statistics method are necessary. The research result as follows.1. The formative process of the three reach of out-bar and inner-stream in Changjiang Estuary has similar rules. At first, the channel is divided into flood channel and ebb channels by the sand sidge. Then under the effect of the ebb tidal currents, the sand ridge extends downstream and moves northward. Thus the out-bar and inner-stream effect appeared.2. The out-bar and inner-stream topographty in the Biandansha and Xinqiao channel of the South Branch formed in the end of 50's in the 20^th century, while the one in the Liuxiaosha Spit and the Liuxiao Flood Channel of the North Channel formed at the beginning of 80's in the 20^th century and the one in the Ruifengsha Spit and the South Changxing Channel of the South Channel formed at the beginning of 60's in the 20^th century. In recent years, the Down Biandansha is in instability and the Down Ruifengsha has almost disappeared. The out-bar and inner-stream topographties are facing with destruction.3. The common patten of out-bar and inner-stream topographty: the strong flood and ebb tidal currents is branching under the actions of Coriolis force in Changjiang Estuary. There is a reach with slow current between the route of the flood and ebb tidal currents. The sediment is prone to deposit and forms a sand ridge. Then the sand ridge extends downstream in rich sediment supply condition, and the channel is divided into the flood and ebb channels. While the sand ridge silts northward, the width of the flood channel will decrease, the water deep will increase and the beach will erode. The out-bar and inner-stream effect appeared.4. The condition to maintain the out-bar and inner-stream topographty: Retain the up mouth channels and let the runoff come into the flood channel. Control the location and width of gullies. Forbid sand-exploitation out of order.5. There are harbor-built condition and exploitation and use foreground in the out-bar and inner-stream reach. The regulation emphases in the South Branch are to build shoal-protected projects to stabilize the Biandansha and Biandansha channel, and maintain the sand discharge ratio between the South and North Channel. Dredging projects and reclaime projects can be used in the regulation and exploitation in the North Channel. The auther is apt to the dredging projects. And the regulation emphases in the South Channel are to stabilize the Ruifengsha Spit and insure the safty of the harbors on the bank.