The Sedimentary & Accretion-Erosion Environment Of The Outer Navigation Channel In Changjiang Estuary

The water area outside of North Passage is part of the submerged delta in Changjiang estuary, and there is the outlet of the outer navigation channel in North Passage. In order to keep the navigation straightway and decrease sedimentation, it is necessary to know in detail the sediment conditions and the rules of erosion and siltation in the water area.Therefore, the author studies the sediment dynamic conditions and the rules of erosion and siltation outside of North Passage and its nearby areas in this thesis. By Contrasting a great deal of data about hydrologic, sediment and geomorphology, several characters have been found out. (1) In North Passage, the rectilinear current increases, the direction concentrates, the ebb tide duration becomes longer and tide ellipticity increases after compared with the past, so sediment will tend to diffuse easily and less silt. (2) Larger north-direction current has turn out in the north of the navigation, especially in upper and middle water. It can cause abundance sediment enter into the south area from North passage and Hengsha flat. (3) After the deep-water project being built, sediment on flat has been coarsened responding strong storms and currents along North Bank. And the coarse-sediment area has extended to nearby the mouth of navigation. It maybe cause the navigation silting. (4) When the height of storm wave is larger than 5.0m,the sediment on outer flats will suspend, and then increase the sediment concentration. (5) The main stream line of the distributary moving and swaying can affect the terrain change out of estuary. Recently, flow and sediment ratio of North and South passage is steady, so it is help to the terrain out of estuary. (6) The terrain change is not very acute outside of the North Passage under deluge or typhoon, and sediment is easy to silt in the north of the North Passage and easy to erode in the south. Now there is a eroded region outside of the North Passage, it can redound to Navigate.The study show, now the outlet navigation's direction is accordant with the flow and sediment dynamical condition, and it should be kept.