Formation And Law Of Evolution Processes Of The Jiuduansha Shoal Of The Changjiang Estuary

There exist a shoal and channel alternated mouth bar system near the Changjiang river mouth, from the south to the north, they are South Passage, Jiuduansha Shoal, North Passage, Eastern Hengsha Shoal, North Channel, Eastern Chongming Shoal and North Branch. Jiuduansha is a mouth bar, it is an important sedimentary geological body of the delta front, and a part of the mouth bar system of the Changjiang river mouth. Systematically research of the formation and the evolution is not only abound the estuary theory content of the estuarine geomordynamics and estuarine dynamic sedimentology, but also related to the practical problem of administration of navigation channel, the selection of Harbor sites and bank revetment and land reclamation, and even the comprehensive exploitation of the Changjiang estuary.The paper combined methods of the dynamic sedimentation and geomordynamics, GIS technology and DEM, historical datum and field survey datum, quantitative and qualitative analysis, systematically researched the sedimentary characteristics and formation and evolution processes of the Jiuduansha shoal.On behalf of sediments characteristics research of Jiuduansha shoal, mainly based on the field survey and samples taken from the Jiuduansha shoal and the South Passage and the North Passage during dry season and flood season in 2003, samples analyzed in the laboratory, deeply researched the parameters related with the sedimentary environment change during Jiuduansha formation, there are sediments size distribution, minerals formation, sedimentary structure and sedimentation rates and so on.On behalf of the formation and evolution processes of the Jiuduansha shoal research, mainly based on the sea chart from 1908 to 2001, through the GIS technology and Digital Elevation Model, relatively deeply researched the formation background, evolution processes, change after formation of the Jiuduansha shoal and evolution processes of the South Passage and the North Passage.Through the research mentioned above, not only emboldening the knowledge" of the formation and low of the evolution of the Jiuduansha shoal, but also the restrict relationship between Jiuduansha shoal and the South Passage and the North Passage.