Spatial Evaluation of Access to Urban Free Spaces During the Post-Earthquake Periods Using Hub and Genetics Optimization Algorithms (Case Study: City of GORGAN)

Awareness of citizens' access to urban free spaces at post-earthquake period can be critical for crisis management. Identifying these points at pre-earthquake period can lead to reasonable decision at an unstable and uncertain time of post-earthquake. In the present study, the process of access of citizens of Gorgan to urban free spaces in the post-earthquake period has been evaluated. For this purpose, an Integrated combination of GIS and genetic algorithm have been used. Regarding to the optimal allocation in the GIS environment, two flexible and non-flexible scenarios with and without consideration of road blocking constraints were considered. For this purpose, for the first scenario, 48 pieces of land and for the second scenario, 153 pieces of land were considered as destination points. In solving the allocation problem using the genetic algorithm, six different scenarios with the lowest cost of population transfer from origin points (demographic block centers) to destination points (free spaces) were considered. By accepting the assumption of probabilistic conditions at post-earthquake, the general results of the research show that in the event of an intense earthquake, by according to blocking road in a non-flexible condition, 24% and in a flexible condition, 35% of the population has access to free spaces. This value in the flexible scenario would be 35% and 47% respectively. The results of hub problem solving by genetic algorithm are similar to the flexible scenario without considering the blocking roads.