The Impact Of Urban Pluvial Flooding On Emergency Medical Services For Highly Vulnerable Populations

In the context of global change and rapid urbanization,pluvial flash flood（PFF）disasters in urban areas are frequent.As a particular industry to ensure the safety of people’s lives,emergency medical services are susceptible to time,so they are highly susceptible to the impact of the pluvial flash flood.As a highly vulnerable group,the elderly and children have a high demand for emergency medical services,and traffic delays and even paralysis caused by the pluvial flash flood undoubtedly increase the risk of disasters for vulnerable populations.Therefore,quantitatively assessing the impact of the urban pluvial flash floods on emergency medical services for highly vulnerable people has become an important topic in flood disaster research.Based on the two-dimensional hydrodynamic model Flood Map-Hydroundation2 D,this study selects the high-vulnerability unit（nursing home）in downtown Shanghai as the research object and simulates the pluvial flash flood under different reproduction periods combined with the "flood depth-speed" curve,constructs the urban transportation network under the pluvial flash flood,and uses Arc GIS network analysis and other methods to carry out research,from the three aspects of distance cost,time cost,and economic cost.The impact of the pluvial flash flood on emergency medical services for highly vulnerable populations was revealed.The main conclusions are as follows:（1）In the study on the characterization of urban pluvial flash floods,numerical simulations of storm flooding under different scenarios are carried out based on a twodimensional hydrodynamic model,and the depth of road water is extracted from the simulation results,the threshold value "30cm" is used to set the road traffic condition and to construct a hazard analysis of the flooded traffic network.The results show that the depth and extent of inundation increase as the return period increases;the percentage of disrupted road networks in the study area is 0.3%,1.6%,and 7.5%for the 5,2,0 an100-yearar storm inundation scenarios respectively,with disrupted roads scattered throughout the study area.（2）In the pluvial flash flood traffic simulation,the real-time traffic speed is indirectly obtained through the "path planning" function of Auto Navi Map,and the traffic road network in the central urban area under the pluvial flash flood scenario is constructed based on the "inundation depth-speed" curve.The results show that the average speed of the road during normal peak and peak hours is 24.3km/h and 20.9km/h,respectively,and the impact of medium to medium intensity rainstorms（5 years and 20years）on the highways and expressways in the study area is more obvious,and the speed of roads of all levels in the study area is reduced by 20%-47% due to the rainstorm event in the 100 years.（3）In the study of the emergency medical response to pluvial flash floods to highly vulnerable people,based on the service area analysis in the Arc GIS road network analysis module,the service area of the emergency center of 8,12,15 minutes was calculated;the number and percentage of various highly vulnerable people within the service range of the emergency medical center under different rainstorm intensities were counted to assess the flood risk of vulnerable people;the high vulnerability unit（nursing home）was used as the research object,and the shortest path and response time of the emergency center-nursing home were determined based on the "fastest path".The results show that the emergency center can basically cover the entire area within 15 minutes during normal peak hours,and with the increase in the recurrence period,the service area of the emergency center,the accessibility of emergency medical services for vulnerable people,and the response time of high-vulnerability units also show obvious nonlinear changes.（4）In the study of emergency medical services for highly vulnerable people to pluvial flash floods,the path with the shortest time cost of emergency center-nursing home-hospital was determined by "Finding the nearest facility" in the Arc GIS road network analysis module,and the distance cost,time cost and economic cost of emergency medical services in nursing homes under the scenario of the pluvial flash flood were calculated.The results show that the distribution of nursing homes,hospitals,and emergency centers in the central urban area is more concentrated,nearly half of the nursing homes have a distance cost of less than 3km of emergency medical services under normal conditions,and the probability of uninterrupted emergency medical services in nursing homes caused by heavy rains in 5 years and 20 years is small,and the distance cost is extended by 16 km under the scenario of rainstorms in a hundred years;the duration of emergency medical services during normal peaks and peak hours is 22 minutes and 24 minutes,respectively,when the peak hours encounter rainstorms once in a century.The cost of medical service time is delayed by up to 67 minutes.The economic cost and distance cost distribution of emergency medical services are consistent,and the indirect loss caused by the delay of large-scale nursing home emergency services located at the outer ring border caused by the centenary rainstorm event exceeds 100,000 yuan.