Numerical Study On The Storm Surge And Floodplain In Beilun District, Ningbo City

China is one of the few countries in the world that is severely affected by marine disasters,especially storm surge and wave disasters,accounting for more than 90% of the total disaster losses.The impact of storm surge on our country is almost everywhere along the coast,especially in economically developed areas such as the Yangtze River Estuary,Hangzhou Bay,Minjiang Estuary and Pearl River Estuary.Beilun District of Ningbo City is located on the east coast of Zhejiang Province,and the main disasters are marine disasters.Typhoon is one of the most influential natural disaster.Therefore,Beilun District of Ningbo City is selected for numerical study of storm surge and floodplain.In order to meticulously portray the characteristics of urban roads and buildings,a model of storm surge and floodplain is established of the block scale.The resolution of the Beilun District land reached 5 to 10 meters.This paper will simulate storm surge and floodplain based on this model.Considering the Yong River runoff and not considering the seawall,the block-scale model of storm surge and floodplain can accurately simulate the storm surge and the total tide level of Typhoon No.5612.In order to investigate the impact of sensitive factors such as the underlying surface on the floodplain,sensitivity tests are designed in terms of frictional changes in the underlying surface,sea surface uplift,and the impact of super typhoon intensity on the storm surge and floodplain.Under the condition of considering the frictional changes at the bottom of the underlying surface,the maximum submerged area is reduced by 21.4% compared with the simulated experiment without considering the bottom friction change,and the submerged water depth in most regions is reduced by 0.1 to 0.2m.After the sea level rises by 0.5m,the maximum submerged area is increased by 26.93% compared with the submerged area without considering sea level uplift,and the submerged depth in most areas is increased by about 0.2m.Based on the typhoon path No.5612,we reference the changes in the pressure of the typhoon “Rammasun” landing at Hainan Island,China.The center pressure at the time of landing is set at 923 hPa to 905 hPa.After the typhoon landing strength is enhanced,compared with the simulated experiment without considering the super typhoon,the result of the simulation experiment with the intensity shows that the maximum submerged area increases by 35.57%,and the submerged depth in most areas increases by about 0.5m.Relying on the block-scale model of the storm surge and floodplain,the floodplain situation with dense neighborhoods and complex terrain can be simulated more rigorously,reflecting the distinctive features of the district scale.In the floodplain simulation,the effects of changes in bottom friction on the underlying surface,sea level rising,and typhoon intensity increasing cannot be ignored.