identification of vulnerable zones of shahid bahonar district of mashhad metropolis from passive defense viewpoint using analytic method of weighted overlay (wo) in gis

1. introduction with regard to natural and human urban threats and risks which endanger security of the residents, ensuring urban safety and passive defense issues, especially before being hit by crisis and in peace situation such as natural disasters, war, etc., are the most significant duties of urban practitioners and planners. the main criterion of passive defense viewpoint is to increase the defense factor in time of war and its related crises in a city. due to aggregation of human, decision centers, and monetary and cultural capitals, the criterion has an active role in stability and cohesion of spatial regions of the country. these issues, along with report of human settlement released by united nation in 2007 concerning safety and security reinforcement of cities, precisely defined the necessity of focusing on aspects of safety and passive defense enhancement in design system and urban planning (mahmoudinejad, 2009, 53). on the other hand, components and indexes by which we can identify vulnerable urban areas and zones from passive defense viewpoint are provided only through design system and planning framework. accordingly, the major concern of the present article is failure in identification of urban areas and zones from passive defense viewpoint in shahid bahonar district of mashhad which cause vulnerability against probable damages of human and natural risks and disasters. the main objective of the study was to identify vulnerable zones of passive defense in shahid bahonar district of mashhad city. in this regard, theoretical principles of the research were presented using analysis of the related literature, and then shahid bahonar district is evaluated. since it was a qualitative analysis, analytic spatial maps were provided in accordance with extracted components and indexes of the literature. by weighting the data layers using the delphi and ahp techniques, vulnerable points and zones of the desired area has been identified via evaluation and analysis of weighted overlay method and based on the obtained results the related strategies were drawn up 2. study area shahid bahonar district of mashhad metropolis, as a discrete urban zone, with 152 hectare area is located in sixth region of mashhad municipality. in terms of pattern and tissue combination, the area is formed organically and is considered as a worthless worn-out tissue around mashhad city holy shrine. the existence of a passing lane (mashhad-sarakhs road) tears the zone apart and brings about physical rupture of the tissue. strategic location of metropolis of mashhad in east of country have doubled the necessity of attention (asas shahr shargh, 2010). location of residence like shahid bahonar district in the vicinity of such a metropolis directs a special safety and security attention to this region. it is worth mentioning that shahid bahonar district, after being recognized as a part of mashhad city in 2008, has went through renovation process. therefore, paying attention to vulnerable zones of passive defense could have positive effect in development and renovation process of the district. 3. material and methods the project was conducted in mixed method. various models and techniques have been employed to investigate and evaluate the urban vulnerable factors and elements of passive defense. analytical models and techniques of this research included spatial link method, analytical model of weighted overlay, delphi model, and hierarchical analysis model (ahp) which will be explained later. space syntax with spatial arrangement is one the useful techniques of urbanization for understanding complexity and spatial-functional relationships of a city. based on existing spatial relationships and behavioral patterns (movement in spaces) and amount of integration of lines, this technique analyzes the structure of a city (abbaszadegan, 2002) and investigates walking movement in the district. using delphi, as a systematic method in research in accordance with extraction of experts or panellists opinions on a certain problem via questionnaire, will provide the areas of optimal decision making and improvement of effective strategies (ahmadi, 2008, p. 177). experts’ opinions determine the level of significance of vulnerable factors and elements of the city. analytical hierarchy process (ahp) is a flexible, powerful, and simple method for making decision in situations that decision making criteria make it hard to select among the alternatives (zebardast, 2001, p. 13). ahp is initiated by identification and prioritization of decision making elements. these elements include objectives, criteria or indexes and probable options being used in the prioritization (zebardast, 2001). in this method, significance weight of criteria and sub-criteria in each vulnerable section of the district is calculated according to binary comparison and significant factor of each criterion is determined. the method of geographical information system (gis) is by analytic function of weighted overlay (wo). this method has been applied for interpolation of weighted layers in environment with the aim of obtaining comprehensive analysis of various and heterogeneous inputs (arcgis, 2013). the method is used for determining urban vulnerable zones of passive defense based on information layers of vulnerable factors and elements of city. 4. results and discussion in this section, after realization of corresponding significance of vulnerable factors and elements of shahid bahonar district by specialists and experts' opinion in a group judgment using delphi method, ahp is used for weighting and prioritizing of existing criteria and sub-criteria. the final score of this analysis indicated the importance of each criterion and sub-criteria in weighted overlay process and concerning these scores the overlay of existing layers was evaluated in databank by weighted overlay analyzer. by applying this method, vulnerable areas and zones of passive defense is shown based on the amount of vulnerability in the form of final map. regarding factors and elements and vulnerable zones of passive defense and high vulnerability range of the district (26 percent) in status quo, it can be said that: - passive defense principles were not regulated in locating land uses and operational canons. - major and leading centers were located in areas with high population and traffic. - if the case of damage to main access of the tissue, communication system is totally paralyzed. - the existence of only one communicative access from passing stream at the east of district. - mono central structure increases the vulnerability degree in critical situation. generally, it can be said that spatial organization of the district cannot properly manage and tackle with crises and military and security risks. conclusion based on the obtained results of the previous section, following strategies could be formulated for enhancing safety and passive defence in shahid bahonar district of mashhad: - building new peripheral access to improve the link of existing tissue with the main access according to the map of vulnerability rating - improving distribution, combination, and placement of functions and urban spaces (urban spaces). - designing shelters and open spaces in the city concerning existing surrounding open spaces. - locating relief centers with regard to existing vulnerable zones in middle zones and around the district. - paying attention to modification of access and communicative network to enhance integration (regarding mono central structure that increases range of vulnerability in critical situations). - locating elements and major infrastructure of the city regarding passive defense criterion to change the mono-center pattern. - building capacity and prioritizing of access to services and critical facilities (water, food, etc.) in crisis regarding map of vulnerable zones. - forecasting and locating of alarm systems regarding map of vulnerable zones. - increasing urban accesses via existing stream of the city based on map of vulnerable zones. - informing and creating the culture to enhance public participation as central core of passive defense. geographic information system (gis) is dynamic, efficient, and powerful system in collecting, managing, and analyzing data. using this system in relation to new analytic techniques like spatial arrangement analysis, facilitate the possibility of strategic planning in passive defense. in addition, by applying the employed methods and processes of this study, we could identify factors and elements of passive defense damage and prioritization regarding the existing criteria. identification of vulnerable zones of passive defense of the city, in the case that improve the existing damages and risks, is useful and operational and the prerequisite of that is pre-crisis management. by placing in an active and overall process, pre-crisis management must engage all related urban institutions and organizations. it is only in this case that we have the possibility of formation of safe cities consistence with passive defense principles or in other words, resilient cities, against possible crises