Analysis of influence of Deep Waterway Project on morphological change in North Passage of Changjiang Estuary

Based on the bathymetry data of the North Passage of the Changjiang Estuary,surveyed in Jan.1998 and Feb.2008,respectively,the characteristics of erosion and deposition distribution in the North Passage are discussed quantitatively in this paper.It is found that the morphology in the North Passage has been significantly changed due to the Deep Waterway Project.Major features of the erosion and deposition patterns are summarized as follows.1) The total volume of deposition was 3.37×108m3 in the study area with the average deposition thickness up to 1.03 m during ten years from Jan.1998 to Feb.2008.The volumes of deposition in the entrance,upper,middle and lower regions of the North Passage were about 16.5%,32.1%,29.6% and 21.8% of the total deposition volume,with the deposition thickness about 1.23m,1.12m,1.39m and 0.65m,respectively;2) The total volume of deposition within the dikes and groins was 3.50×108m3,in which 58.3% deposited in the north region of the navigation channel.The deposition thickness of the upper,middle and lower sections in north region was 3.94m,2.44m and 0.92m,respectively.The deposition thickness of the upper,middle and lower sections in south region was 3.32m,3.1m and 1.87m respectively;3) The main channel of the North Passage was mainly eroded,with the erosion thickness 1.40m in the upper section,and 0.1~0.79m in the lower section,except the middle section with the deposition thickness 1.28 m in the south part and 0.59m in the north one.The morphological change in the North Passage was mainly influenced by the Deep Waterway Project,especially the construction of dikes and groins.The dredging along the navigation channel and sediment dumping at several locations only affected the local sedimentation.The change of sediment load from the Changjiang River had no significant effect on the morphological change in the North Passage.