Assessment Method Of Spatial Layout Of Urban Emergency Shelter

As an important part of urban disaster prevention and mitigation system,emergency shelters,which comprise public places for evacuation,rescue,and relocation during sudden disaster events.The spatial layout of urban emergency shelters directly influences the city's ability to withstand disasters.Therefore,it is necessary to scientifically and rationally evaluate the spatial layout of the existing emergency shelters.Although the research on the rationality of emergency shelter layout is very extensive,many factors,such as difficulty in obtaining data,low universality of evaluation models and large research scale,and so on,lead to low credibility and poor accuracy of evaluation results,which means that the existing evaluation system of emergency shelter layout is not perfect.Thus,it is necessary to explore a reliable and effective evaluation method for assessing emergency shelter's layout,which is of great scientific significance not only to the emergency shelter but also to other public facilities.To address the above limitations with respect to the evaluation on the rationality of the layout of emergency shelters,this study constructs and improves the current evaluation method system of the layout of emergency shelters from the integration of evacuation differences of different populations,high spatial resolution population distribution,and the catchment sizes of emergency shelter and population.Taking the main urban area of Lanzhou as an example,the feasibility and advantages of the improved method are verified and proved,and the rationality of the spatial layout of shelters in the study area is measured by the improved method.The basic contents and main conclusions of this research are as follows:(1)At the community scale,this study proposed an improved evaluation method for assessing urban large-scale emergency shelter's layout considering the evacuation differences of different age groups.First,the evacuation differences of different age groups were integrated into the traditional accessibility model.Then,the accessibility and crowdedness of emergency shelters were analyzed in the different evacuation time threshold scenarios.In addition,the hot spot analysis and Gini coefficient were respectively applied to measure the cold hot spot change and fairness of accessibility.The results show that: compared with the traditional accessibility model,the improved accessibility model can more reasonably obtain the emergency shelter accessibility in the vulnerable groups gathering area;when the evacuation time threshold is short,the overall accessibility is poor,and the vast majority of communities belong to the lowest and low-accessibility;with the increasing of evacuation time threshold,the communities with low accessibility are gradually concentrated in the southwest of Chengguan,and show a high significant cold spot;The Gini coefficient further confirms that there is a serious inequitable phenomenon in the emergency shelter accessibility among residents at the community scale;there is an obvious dependence between the crowdedness and accessibility,and the crowdedness of emergency shelters in high,accessibility areas is often small.(2)Taking the buildings as residential areas to evaluate the rationality of the spatial layout of small shelters in part of Chengguan.First,the influence factor of population size and travel limit distance were introduced to improve the traditional gravity model.Then,travel friction coefficient was determined by the sensitivity analysis of .Based on the improved gravity model,the accessibility and crowdedness of shelters were analyzed from the perspective of multiple evacuation distances.The results show that: the higher value often leads to larger difference in accessibility,but smaller spatial heterogeneity;when the evacuation distance threshold is short,the residential areas with high-accessibility are mainly concentrated around emergency shelters;with the increasing of evacuation distance,emergency shelter accessibility presents decline from northeast to southwest;there are few residential areas with low accessibility,and the crowdedness shows the opposite trend compared to the accessibility.(3)Based on a 100 × 100 m population grid,this study developed an improved2 SFCA method with variable catchment sizes to describe emergency shelter accessibility in Lanzhou's core area and compared with the traditional 2SFCA method.Furthermore,we used bivariate local Moran's I to identify the spatial relationships between emergency shelter accessibility and population density.The results show that the traditional 2SFCA method underestimates accessibility in densely populated areas with dispersed emergency shelters.Shelter accessibility in the study area is unevenly distributed,with the lowest levels of accessibility in densely populated areas.There is an obvious spatial mismatch between the accessibility of emergency shelters and the population density,and the central and western part of Chengguan has a serious shortage of emergency shelters.