Simulation And Exposure Analysis Of Typhoon Storm Surge In Shanghai Based On One-dimensional Two-dimensional Hydrodynamic Model

In the context of global warming and sea level rising,increasing storm surges disasters lead to severe losses and impacts on urban inhabitants,properties and functions,particularly in the interruption to public services.Storm surges from tropical cyclones,as one of the most devastating natural hazards in Shanghai,have caused considerable personal injury and property damage in the history.During the research period,the researcher collects a great number of literatures and research data.On the advanced bases,an one-dimensional and two-dimensional hydrodynamic model was established to simulate typhoon storm surge in Shanghai.Based on the hydrological model,the submergence ranges and submergence depth of storm surges encountered in different scenarios in Shanghai under different scenarios were calculated,then,the population exposure in extreme inundation scenarios was analyzed.The followings are main conclusions of the research:1.Under the no protection scenario,the impact of typhoon storm surge on the urban inundation range in different return periods is different.In general,the inundation area continuously expands with the increase of the return period;when the return period is 50 years,the inundation area is 789.98 km2,accounting for 15% of the area of Shanghai except the three islands,with an average depth of submergence of 0.579 m.When it was 10,000 years,the inundation area reached 1273.5 km2,accounting for about 50% One-fourth of the area,with an average inundation depth of 0.554 m.From the spatial analysis results,it can be seen that the inner core of Shanghai downtown,Songjiang and Jinshan areas are prone to submerge,which is mainly due to the submergence of low elevation(2-2.5m)in these areas.2.In the context of considering the flood prevention wall,there are some floodwalls in the embankment and flooding may occur.Based on the comparison of data and field surveys,six dyke-weak sections were selected for the flood-diverging scenarios that may be caused by typhoon storm surges.Two-dimensional hydrodynamic models were used to simulate the submerged scenarios of typhoon storm surges in four return periods.The results showed that only the dike was inundated.Submergence occurs in a local area near point O1,O2,O3,so it can be considered that other flood dikes are less dangerous to submerge.Diandi Point O3 has the highest risk of submergence,with an inundation area of 37 km2 at 10,000-year recurrence,and double the inundation flooded area over the 200-year recurrence period.3.Under the scenario of overtopping in 10,000 years return period,the number of communities affected by inundation reached 706 and the number of affected persons reached 1.49 million,mainly concentrated in the central urban area.Among them,there are 42 communities with more than 5,000 people affected,mostly in Putuo District and Baoshan District.The inundation depths of most inundation areas are all below 0.5m.The main inundation areas are southeastern Baoshan,southern Yangpu,southern Hongkou,southern Zhabei,southern Putuo,western Jing'an and Pudong,with the highest number being 108.88 Million people,affecting 437 communities.1% inundation area inundation depth of 1m or more,concentrated in the southeast corner of Hongkou District and the southwest corner of Yangpu District,affecting 13 communities,the number of more than 20,000 people.4.Under the hypothetical scenario,the population aged mainly in flooded areas is mainly distributed along the junction of Xuanzangbang and Huangpu River and the junction of Suzhou Creek and Huangpu River.The flooded population is about 100,000,of which nearly 70% of the population under flooded age The average inundation depth of the community is 0.5m or less,most of which are 432 communities located along the Yunzhamaha in Jiading,Baoshan,northern Huangpu and northern Pudong and the downtown area along the confluence of Suzhou Creek and Huangpu River.191 communities flooded depth of 0.5-1m,flooded population of about 30,000 people.Social vulnerability in this part of the community is high.Mainly in the west of Jing'an,the northern part of Huangpu,Hongkou,the southern part of Yangpu and the northeast corner of Changning along the junction of the Huangpu River and Suzhou River at the Huangjing River Interchange.There are 13 inundation communities with a depth of 1m or more,with a total of 13 affected sub-communities Fewer than two thousand people,70% of the communities have high social vulnerabilities.Mainly located in Hongkou District near the Huangpu River Department.According to the spatial distribution of social vulnerability of the elderly population,the distribution of high value areas is mainly distributed in the central urban areas of the Suzhou Creek,especially in Jing'an District and Huangpu District,while the low value areas cover the coastal areas of Yunzhamaha Inundation area in most areas and Pudong.The median is mainly staggered distribution in the downtown area of high value zone.In view of the above conclusion,Flood controled engineering measures such as flood control walls and seawalls can largely alleviate typhoon storm surge inundation.Once the overtopping occurs,firstly,we should focus on strengthening the weaknesses of the existing seawall so that they all meet the design criteria.Second,improve the existing emergency plan,in the event of floodwall break,should use the low tide period of the temporary floodwall repair section,and transfer evacuation of the affected area personnel and property.The proportion of middle-aged people in urban centers,the high proportion of widows who are divorced,and the number of elderly people who live alone,and most of the central urban areas is old urban areas,and those old houses are of an obsolete structure may cause the elderly population to deal with weak floods and social vulnerabilities,government and society should pay more attention.In addition,there are some deficiencies in the study.Firstly,due to the lack of actual flooding of typhoon storm surges data in historically similar scenarios,it is difficult to compare the simulation results.Secondly,because any two typhoon storm surge tides are not consistent,the boundary conditions of the tide level also have large uncertainties in the process of model establishment.And,the ground subsidence in the downtown area.The decrease of the river networks and the increase of the impervious surface will lead to the decrease of evapotranspiration and infiltration and the increase of direct runoff,which will also aggravate the occurrence of flood inundation disasters.These results provide the basis for the design and planning of flood control system in Shanghai.And we don't consider about multiple encounters in this study,the inundation in the downtown area may be worse than the simulation results.