Analysis of Riverbed Evolution of the Waigaoqiao Branch Channel of the Yangtze Estuary in Flood Period Under New Water and Sediment Conditions

With the change of sediment conditions in the Yangtze River Estuary, the river regime evolution pattern has entered a new stage. The overall trend has changed from siltation to erosion, and the impact of the evolution trend of overall river regime on local river regime needs to be further studied. Based on the hydrological and topographic data of flood season in 2020, this paper analyzes the riverbed change of Waigaoqiao branch channel during flood period under new water and sediment conditions. The river bed evolution law and causes of scouring and silting are analyzed statistically. Result shows that the water depth of branch channel decreases with the influence of channel dredging and river regime change in South Harbour under new water and sediment condition. During the flood period of 2020, the Waigaoqiao branch channel generally presents a continuous silting situation, mainly located in the front of Waigaoqiao Wharf (phase IV). The increase of sediment concentration caused by the flood and the scouring of shoal along the upstream of the branch channel are the main reasons for the silting of the branch channel. Based on the actual needs of waterway operation and maintenance, this paper puts forward relevant countermeasures and suggestions according to the analysis results.