The Comprehensive Study On Layout Optimization Of Urban Emergency Evacuation Sites Based On GIS

With the rapid development of the social economy and the growing population of the city,the vulnerability of urban lifeline is increasingly obvious.It has been witnessed that frequent heavy urban disasters caused widespread destruction and distress.The establishment and improvement of urban emergency evacuation system has becoming more and more important.The sites of urban emergency evacuation play an important role in the event of a disaster.The establishment of urban emergency shelters in China is late and in its developing stage now.With the financial support of the National Natural Science Foundation of China(No.41601568)and Open Fund of Tianjin Normal University,this paper uses the method of multi-level index model to comprehensively research the layout of urban emergency evacuation sites from the three aspects:the suitability evaluation of urban emergency evacuation sites,the optimization of layout and the selection of evacuation routes for disaster-affected residents.Firstly,ten evaluation indexes are selected from the three aspects of validity,accessibility and security.This paper takes gray correlation analysis as the suitablility evaculation method and uses entropy weight method to calculate the weights of evaluation indexes and establishes the suitability evaluation index system of city emergency evaculation site.Secondly,an evacuation population prediction-"product model" has been constructed to determine the objectives and principles for optimizing the layout of urban emergency evacuation shelters.Combining the number of evacuation populations in the city with the current status of the city,we use GIS spatial analysis techniques to determine the areas of urban emergency shelters that need to be added or expanded.Thirdly,without exceeding the capacity limit,based on alternative interpolation mechanism algorithm and with the aim of minimizing the total evacuation distance,this paper construted evacuation routes selection model for disaster-affected residents so as to find the best routes from disaster sites to emergency shelters.Finally,taking the Heping District of Tianjin as an example for verification,through eight-by-eight meter resolution,Google imagery has been used to have identified the 113 public security stations,45 fire stations,40 medical sites above Grade ?,and 127 refueling stations in downtown Tianjin.We can use visual interpretation to find out that 30 parks,squares,green spaces,playgrounds,and parking lots in the Heping District can serve as emergency shelters for the city,and their suitability evaluation analysis,layout optimization,and residents' routh selection are studied.The main conclusions of this article are as follows:(1)The suitability evaluation of urban emergency shelters is a multi-objective decision-making problem.Evaluation indicators should be established from the three aspects of validity,accessibility and safety.The results of suitability evaluation of urban emergency shelters found that the number of entrances to emergency shelters is more effective than accessibility and security,and has the largest contribution to the results of suitability evacuation.(2)The constructed "product model" can calculate quickly and easily the number of people who need shelter in the event of a disaster even if the data is difficult to obtain.(3)Replacing the interpolation principle can guarantee that with the limited capacity of shelters and uneven distribution of demand space,the goal of maximizing space continuity and minimizing the total travel costs of residents affected by disasters is achieved.(4)The results of suitability evaluation of the 30 emergency shelters in Heping,Tianjin are like this:10 are suitable,16 are appropriate and 4 are less suitable;the total number of evacuees in the Heping of Tianjin are predicted to be 48639,caculated by the "product model" method.The result shows that an emergency evacuation shelter needs to be built in the street of Quan Yechang of Heping.There are 30 shelters with a total of 294410.443m2 service area in Heping district.In disaster-affected resident evacuation route allocation,after accommodating all evacuees,2 shelters are full and the other 28 shelters still have some free space.Based on the self-developed emergency evacuation analysis tool SimpleMap,dynamic simulation of path selection was performed.The total travel cost of the disaster-affected residents to the evacuation facility is 3.03 X 104km.Using the shift-insertion algorithm,the total travel cost is 23.29%less than using the direct insertion algorithm.