عنوان مقاله [English]
Many Iranian cities are located on areas with moderate and high risk of urban crises. Gorgan city is one of the most vulnerable cities to earthquakes, drift, landslides, and etc. The geostrategic situation, the location of a part of the city on a steep slope, inattention to standards and norms in the radius of access to permeability indicators, inertial growth and inappropriate distribution of services in the city, inadequate access to the passage network and inadequate physical structure are the factors that necessitate to address the permeability of the urban texture of Gorgan city in the face of possible damage.The present study is an applied study with a descriptive-analytical method.In order to achieve the research goal, permeability indicators were extracted from relevant experts according to available resources and field studies through a hierarchical analytical method and data banks. In addition, the permeability of the indicators was measured based on non-active defense principles.Considering the different effects of the indices, the AHP-FUZZY method was used in the GIS environment to evaluate and prepare the permeability map of the city. Using the ARC GIS10.3 software, urban texture permeability of Gorgan was prepared through the overlap of final Raster Fuzzy. According to the findings of the research, about 50.40% of the Southern and marginal areas of Gorgan are exposed to low permeability and high vulnerability due to a large slope, low vacancy spaces, and a shortage of passageways, high density of bays and the density of bridge bridges against emergencies and possible urban damages.
Introduction: Security is one of the fundamental factors that do not lead to crisis in societies. The present era is the era of urban vulnerability, because as urban life becomes more complex, cities in different dimensions face natural hazards and technological crises on the one hand, and social-security crises on the other. Permeability factor as an important element in non-operational defense has a great impact on security and reduction of vulnerability in the city. Therefore, if a city is affected by natural or human disasters, the distance and access to the site in question will be of particular importance. Gorgan is one of the most vulnerable cities due to earthquake, landslide, due to high slope. Also, due to the lack of safe spaces, lack of open urban spaces for temporary accommodation in times of urban crisis, lack of proper access radius related to permeability, compactness and high population density in some areas of the city, inadequate access. According to the network of main passages, the high density of lanes in the city of Gorgan encourages us to recognize the permeability coefficient by applying passive defense principles. Therefore, the purpose of this study was to evaluate the permeability coefficient of physical tissue in Gorgan with emphasis on passive defense.
Methodology: This is a practical study with descriptive-analytical method. In the field of the collection of current information, two methods of field studies and documentary studies are used. In the field of research, the researcher-made questionnaire was used to collect information using questionnaire and observation techniques. To achieve the purpose of the study, indicators were extracted using available resources, research projects, statistics, existing books and articles, comprehensive and detailed plans. Considering the different coefficients of each of the selected indices in the physical permeability of Gorgan city, weighting method is based on AHP method based on a survey of 20 experts and urban planning and planning professors (7 experts, 7 people). Masters and 6 PhDs) in Couples Comparison Questionnaire in Academic and Academic Centers, Municipalities, Governments, Crisis Management Agency, Passive Defense Agency and Road and Urban Development Department. At this stage, the experts used linguistic terms based on the superiority of one criterion over another (or one class over another) and, accordingly, the pairwise comparisons matrix was formed. Finally, using the 10.3 ARC GIS software, each of the indices were fuzzy and were numerically zero to one. After this step, the fuzzy maps of each factor in the Map Algebra were multiplied and converted into fuzzy weighted layers by the Raster Calculator in their own weight obtained through the AHP method. Finally, after fuzzing and multiplying weights, Sum, Prodact, Gamma operators were implemented on the fuzzy layers. Finally, the final map was obtained using gamma operator which had the highest adaptation to the permeability of the physical tissue of Gorgan.
Results: Effective indices of tissue permeability of Gorgan city were merged with different weight values and permeability was shown using color spectrum. Accordingly, the areas with green and purple color spectrum, which cover about 26.58% of the target range, show a high degree of permeability, thus in the face of urban crises of the lowest. They are vulnerable. But the red and yellow color spectra, which cover about 50.40 percent of the range, are less susceptible to urban crises. Therefore, according to the final map, the level of permeability of Gorgan city is low and passive defense principles for access to urban open spaces are not well respected. Therefore, a strong focus on the permeability indices with the passive defense approach is an important step towards greater safety and vulnerability.
Conclusion: The results show that Gorgan, due to its high slope, is a prone area for urban crises, and is highly exposed to hazards and damages caused by natural disasters. And it is abnormal. In the event of an accident, there is likely to be a lot of damage to the city and due to the potential for widespread breakdowns, weaknesses and inadequacy of the network of passages and inadequate infrastructure to provide relief and temporary resettlement of the injured, there are many problems for citizens. It will come and make the city extremely in crisis.
Keywords: Urban Vulnerability, Permeability, urban non-operational defense, Fuzzy Logic, Gorgan City.