Response Of Mouth Bars To The Sea Level Rise In The Yangtze Estuarine Waterways

The mouth bar in Yangtze estuarine waterways has significant influences on the transportation of the estuary, flood discharge and the construction of Shanghai Port. At the same time the Yangtze Estuary is facing serious challenge from the reduced sediment from upstream and the rising sea level. Based on the morphological evolution and evolution mechanisms of mouth bars of the Yangtze estuarine waterways, the response of mouth bars to sea level rise in the Yangtze Estuarine Waterways is studied.Here in this paper the morphological evolution and evolution mechanisms of mouth bars of the Yangtze estuarine waterways are studied by analyzing hundreds years of historical data and the latest profile maps of some main mouth bar channels in the Yangtze Estuary. The results are shown as followed:The mouth bars in North Branch move gradually from outside of the mouth to inside and form a huge sand bar there. In North Channel, the top of mouth bar migrate down-stream about 30 kilometers, and a channel bar has been developing since 2001. Two mouth bar tops had ever existed in North Passage, which retreated in 2010. The top of mouth bar in South Passage migrates to down-stream about 14 kilometers and the number of tops increases at first and then reduces to only one now. According to these analysis results, we can conclude that the evolution of mouth bar differs with the location. In North Branch it is directly related to large reclamation in Chongming Island, but in North Passage it has a close relationship with the Yangtze Estuary Deepwater Channel Regulation. However, the evolution of mouth bar in North Channel and South Passage is not only in connection with the Yangtze Estuary Deepwater Channel Regulation, but also the Reclamation in East Hengsha Shoal and the Qingcaosha Reservoir.Based on the morphological evolution and evolution mechanisms of mouth bars of the Yangtze estuarine waterways in the last 100 years, the response of mouth bars to long-term sea level change in the Yangtze Estuarine Waterways has been studied by using a Boolean network approach. With steady runoff, deficient sediment and channel constriction due to human activity, the response of mouth bars to sea level rise is shown as followed:The mouth bars of the Yangtze estuarine waterways moves gradually from outside of the mouth to inside and the water depth of the mouth bar is more shallow and length of the 10-m-contour of the mouth bar grow longer. With steady runoff, abundant sediment and channel constriction due to human activity, the response of mouth bars to sea level rise is shown as followed:The mouth bars of the Yangtze estuarine waterways also moves gradually from outside of the mouth to inside, but the water depth of the mouth bar is more deep and length of the 10-m-contour of the mouth bar grow shorter.