Study On The Impact Of The Utilization Of The Yangtze River Estuary Beach On Flood Control And Tide Control

Since the 1950s,the Yangtze Estuary has carried out a series of tideland reclamation projects,such as regulation of the deep-water channel,siltation and reclamation,and construction of reservoirs,which have gradually changed the shape of the estuary and caused changes in the estuary coastline,hydrodynamic environment,and intensified flood disasters.In view of the important position of the Yangtze River estuary area in the development of the national economy,it is necessary to study in detail the comprehensive impact of the accumulation and utilization of tideland on the flood-carrying and tide-receiving of the Yangtze River estuary,and to assess the flood control safety of the Yangtze River estuary.This paper established a 2-D numerical model of the Yangtze River estuary’s water flow,and based on this,the changes in the hydrodynamic environment of the Yangtze River estuary under the four-year tideland reclamation scenarios in 1958,1997,2002,and 2016 were simulated and calculated.Through comparative analysis,we obtained the specific influence range of tideland reclamation on the flood,the velocity of typical cross-sections,and tidal prism.Which provides data support for scientific decision-making for flood control and tidal control.The main research contents are as follows:(1)The current situation of tideland reclamation at home and abroad is reviewed,and related parameters such as runoff characteristics,tidal level characteristics,tidal current characteristics and sediment characteristics of the Yangtze River estuary are analyzed by using a long series of hydrological data.(2)The basic equations and numerical calculation methods involved in the plane 2-D water flow numerical model are clarified,the hydrodynamic model of the Yangtze River estuary is established,and the model parameters are calibrated according to the existing hydrological data.In general,the model can simulate the water flow characteristics of the Yangtze River estuary better,and obtain a more realistic tide level and tidal current process.(3)The large-scale reclamation of the Yangtze River estuary caused a rise in the water level of local and entire waters.The change range of water level near the outer sea is smaller.The water level around the project is more obvious,with a maximum of 0.1m;it has little impact on the entire water area,with an average height of about 0-0.02m.The impact on the Yangtze River estuary flood control is small,and the project is safer(4)After the large-scale reclamation of tideland in the Yangtze River Estuary from 1958 to 2016,the average maximum velocity of the cross-sections changed significantly,and the average maximum velocity of most cross-sections appeared earlier.The greater the upstream inflow,the greater the change in flow velocity,and the change in the north branch is generally greater than that in the south branch.(5)After the reclamation of the Yangtze River estuary between 1958 to 2016,the tidal prism of the typical sections in the lower reaches of the Xuliujing River showed a decreasing trend.The closer to the open sea,the smaller the change,and the larger the upstream inflow of the same section,the smaller the change.Under the representative flow,the largest fluctuations in rising and falling tides are-32.17%and-57.12%respectively;under a 50-year flood,the largest fluctuations in rising and falling tides are-31.25%and-80.92%respectively;under a 100-year flood,The largest fluctuations in rising and falling tides reached-31.22%and-84.00%.The protection and efficient use of tidal flat resources support the sustainable development of the coastal economy.The overall and systematic simulation of water(tidal)flow,changes in river port lines,and flood control and tide protection are carried out to reveal the interaction between tidal flat resource utilization and related constraints.The relationship between them will make the planning more reasonable,the development more scientific,and the protection more effective,so as to realize the efficient development and protection of tidal flat resources in a real sense.