Risk Assessment Of Storm Surge Disaster In Coastal Cities

Due to the influence of global warming and sea level rise,the economic losses of storm surge disasters in coastal areas of China are fluctuating and the risk of storm surge disasters has increased significantly.Shanghai is the core area of China's social and economic development,and it is also a high-risk area for storm surge disasters in China.In order to reduce the impact of typhoon storm surge disasters in Shanghai coastal areas,and enhance disaster prevention,mitigation and emergency response capabilities of this city,we took Jinshan District as example to evaluate its risk of storm surge.It can be used as a typical case to study the risk assessment of storm surge disasters in coastal areas.It can also the coastal areas as typical cases to carry out risk assessment of storm surge disasters according to local conditions,further improve and develop the theory and methods of risk assessment,so as to reduce and mitigate casualties and property losses caused by storm surge disasters.Based on the ADCIRC model,this paper establishes a storm surge numerical model covering the entire East China Sea,and locally encrypts the coastal and terrestrial grids in the Jinshan District.The grid focuses on the defense projects such as the seawall,the reserve pond and the Shanghai-Hangzhou highway.The grid has a maximum resolution of 100m.The applicability test was carried out on the model using the collected measured data.The verification results show that the average relative error between the simulated maximum and the maximum simulated water and the measured value of the 30 stations is 4.60%and 7.71%,respectively,which can better reflect the typhoon.The model is indeed credible during the tidal level and water increase along the Hangzhou Bay.Five types of typhoon 950hPa,940hPa,930hPa,920hPa and 910hPa were selected as the basic path to construct a typhoon data set for risk assessment.The maximum tidal level was calculated by superimposing the maximum water addition on the high tide level of the astronomical tide to simulate different typhoons.The maximum possible submergence range and submerged water depth in Xiajinshan District were assessed for risk.The results show that there is no risk of submergence in the Jinshan area under the typhoon of 950hPa and 940hPa.The inundated area of Jinshan District under typhoon930hPa is 92.29 km~2,the submerged water depth is less than 1m,the risk of storm surge disaster is low and medium grade,and the medium risk is mainly distributed in Shanyang Town.The inundated area of Jinshan District under typhoon 920hPa is 343.61 km~2,and the maximum submerged water depth is 3.76m.Except for the risk of no flooding in Fengjing Town,the remaining towns have the risk of storm surge disaster inundation,and the high risk is mainly concentrated in Sanyang Town.Haitang section along the coast.The Jinshan area under the typhoon 910hPa level was fully flooded,with an inundation area of 482.65km~2 and a maximum submergence depth of 4.37m.The hazard level and scope were further expanded,and the high risk was distributed in Shanyang Town and Petrochemical Street.The higher risk was mainly distributed in Shanyang Town,Petrochemical Street and Jinshanwei Town;Caojing,Tinglin,Zhangyan,Langxia,Luxiang and Zhujing are mainly low-grade,and most of Fengjing Town is non-hazardous,and its risk of submergence is only Limited to the edge of the town of Zhujing,at a low level.The Shanghai-Hangzhou Highway and the main and auxiliary ponds,as the second line of defense,have played a role in retaining water to a certain extent,weakening the degree of flooding in the Jinshan District and reducing the risk of flooding in the Jinshan District.Based on land use types,typhoon storm surge disaster vulnerability index of land use was established.The socioeconomic vulnerability evaluation index system is established from three aspects:social,economic and disaster-resisting ability.According to GIS spatial analysis,typhoon storm surge disaster vulnerability assessments both in land use and socioeconomic aspects were carried out.The results indicated that the vulnerability of Shihua Street,Shanyang Town and Tinglin Town is generally higher than that of other towns.The vulnerability of other towns is generally in the lower-middle level,and the areas with higher vulnerability levels are residential areas and industrial agglomeration.Taking the hazards and vulnerability assessment results into consideration,we calculated and assessed the risk spatial distribution of the simulated typhoon storm surge disasters.With the increase of typhoon,the risk of storm surges increases.The risk level of the coastal areas is higher than that of the inland areas,and the coastal areas of the central and western regions are higher than the southeast coast.The high-risk areas of typhoon storm surge disasters mainly concentrated on Shanyang Town and Shihua Street,while the other towns were at medium and low risk.