Spatial Accessibility Of Urban Emergency Service During Flooding Disasters

As a highly concentrated area of social development and human activities,cities are highly vulnerable to flood disasters.In recent years,under the background of global change and rapid urbanization,extreme rainstorms and floods in urban areas have occurred frequently,and the danger of disasters has increased,posing a greater threat to urban socio-economic development and residents' lives and property.Under the influence of flood disasters,the response capacity of urban emergency services is also greatly limited.The service area and the rescue time to reach the destination are delayed,which makes it more difficult for residents in the disaster areas to rescue and evacuate.Therefore,research on the impact of flood disasters in urban areas on urban emergency response accessibility has become one of the hot issues in the field of social and disaster research.Based on the carding and analysis of previous research results,this paper uses the combination of FloodMap two-dimensional hydrodynamic model and ArcGIS network analysis,the Shanghai dawntown is used as an example research area to carry out the service accessibility study of river floods and heavy rains to urban critical infrastructure(119 fire rescue and 120 medical first aid)under different scenarios.The main research work and conclusions are as follows:(1)This paper uses the FloodMap 2D hydrodynamic model to simulate the flooding of the central city along the Huangpu River.2010,2030 and 2050 were selected to simulate the flooding extent and depth of the river flood in 100-year and 1000-year.Select 30 cm as the road interruption threshold caused by flood submergence.Refer to the “Technical Standards for Highway Engineering of the People's Republic of China(JTG B01-2003)” and the real-time traffic analysis report of Amap to set four types of road speeds(maximum speed limit S1,evening and weekend speed S2,daytime speed S3,and morning and evening peak speed S4).According to the best rescue time(5-15min)of 119 fire rescue and 120 medical emergency,a total of 168 complex scenarios were constructed through scientific combination of three factors: flood scenarios,road speed and facility rescue time.(2)This paper uses the Shanghai storm intensity formula and the Chicago rain type to calculate the rainfall and the rainfall process under the 5-year,20-year and 100-year recurring scenarios.And use the FloodMap two-dimensional hydrodynamic model to simulate the flooding under the three intrinsic recurrence periods.According to the realtime monitoring of Amap,four types of road speeds(S1,S2,S3 and S4)are obtained,and considering the rescue time of 119 and 120 facilities,96 composite scenarios can be constructed.(3)Based on the simulation results of flood disasters,the service area analysis tools in ArcGIS network analysis were used to study the service capabilities of fire rescue(119)and medical emergency(120)under different flood scenarios.Under 100-year and 1000-year of the river floods,as the flooding reappearance period increases,the city's emergency service capacity continues to decline;as the road speed decreases,the service area also shows a decreasing trend.The flooding of river floods is mainly concentrated in the coastal areas of the Huangpu River.Under the conditions of heavy rain,the 5-year rainstorm has little impact on the emergency response service capacity.The 15 min response time can cover almost the entire study area;the service area of the 119 and 120 rescue points in the 20-year and 100-year torrential rains are gradually increasing and the service area is decreasing.(4)The fastest path module in ArcGIS network analysis is used to calculate the fastest route of 119 fire and 120 emergency to kindergartens and nursing homes.With the increase of the river flooding and the recurrence period of the torrential rains,the flooded area is gradually increasing,and the number of rescue facilities located in the inundation area is also increasing.Up to seven emergency centers have lost their rescue capacity,and 139 kindergartens cannot obtain Emergency services should be provided.Due to the interruption of road traffic,the rescue time of some kindergartens and nursing homes has also been delayed.Under the influence of river floods,the fastest rescue time for the firefighting 119 and first aid 120 stations to the rescue point was postponed.The maximum delay is up to 22 min in the case of the extremely road speed and the 1000-year flood of 2050;under the influence of heavy rain,delays in the rescue time from 119 and 120 first-aid spots to nearly half of kindergartens and nursing homes in 100-year,and the longest delay can reach 36 min and 34 min,which is much than the best rescue time.The rescue time seriously affected the evacuation and resettlement of the affected people.The emergency response accessibility study under the background of urban flood disasters is a complex systematic project.It involves geography,disaster science,sociology and other fields.This paper only does the part of the exploration in emergency response space accessibility and rescue capability of urban public facilities.Relative to the expansion of the field of scientific theory and case studies is only the beginning.In future research,it is also necessary to consider the factors such as the duration of flooding and the flow rate in the flood flooding simulation,and build a comprehensive traffic network model based on GIS to more accurately simulate speed and response time.Formulate the best rescue route for first-aid points and re-planning and site selection of facilities,and provide scientific support for the management of urban disasters.