Introduction
The natural situation, way of dispersion of uses, position or placement of infrastructures and urban installations and equipment are assumed as safety considerations in analysis of topography and security planning and passive defense of city. Therefore, it is necessary to employ defensive and security approaches in the designs of urban development where this indicates both a link between performances of activities on one hand and defensive arrangements on the other hand. Fortification of urban defensive installations, anticipation of escape exits from risks, and improvement of the status of services which are required during the period of defense will be assumed as the foremost objectives in urban survey respectively. As the capital of Kurdistan province and the location of important administrative centers and the vital and significant facilities, the city of Sanandaj is of great importance. In addition, due to location of this city near Iraq and the same language spoken in Iraq’s Kurdistan region and recent presence of Israeli agents in this region, Sanandaj may be subject to political and military threats. With respect to the experiences of recent wars, especially U.S attacks on Iraq, the critical and vital points of this city have been recognized as centroids of the city, which, if damaged, could lead to the surrendering of the city. Therefore it is necessary to pay attention to the topology (positioning) of urban installations equipment with respect to passive defense approach in order to reduce such damages.
 
Materials and Methods
The methodology of this study is of descriptive- analytical type. In this regard, the authors have determined vulnerable points of this city in order to recognize the vulnerable elements and extents of this city by passive defense approach. Accordingly, a list of vulnerable elements of the city has been prepared using comments from 14 experts and these elements have been scored by means of Analytic Hierarchy Process (AHP) method. Initially data have been prepared as vulnerability maps based on any element in Arc Map software environment. Then weighting of elements have been done by AHP technique and binary comparison of them in ‘Expert Choice’ environment to solve AHP model. The order preference of parameters will be determined with respect to each other. The standardization (fuzzification) method has been adopted to determine the range of the city’s vulnerability based on scores. With respect to the conducted analyses on each of urban elements, the rate of vulnerability of Sanandaj city has been specified at five vulnerability level, i.e. very high, high, medium, low, and very low. Then SWOT model was employed to identify and to reduce vulnerability elements in Sanandaj city and Quantitative Strategic Planning Matrix (QSPM) model was employed for order-preference of strategies.
 
Results and Discussion
The highest vulnerability score belongs to vital artery (0.623). This criterion is divided into four following sub criteria in which reservoir and water treatment unit possess the highest scores. This is because of the location of this important infrastructure at the entrance of this city. Afterwards, crisis management centers are placed at second rank of vulnerability with score of 0.300. One of the reasons for concentration of offices at the central point of the city and inappropriate access of medical centers to communication network is related to pending position of city hill to hospital. The crisis management centers include two sub criteria of important offices and hospital and medical centers among which hospital and medical centers have been more vulnerable. After those, urban equipment and military, disciplinary, and supporting centers have higher vulnerability respectively. In terms of vulnerability rate, some of layers are overlapped to specify the most vulnerable parts in this city. The municipal region 5 and lesser part of regions 3 and 4 are vulnerable. Due to the placement of some centers with high- vulnerability in these regions, it is necessary to pay attention to passive defense principles out of which topology is one of their subsystems.
 
Conclusion
With respect to the implementation of scores from AHP model on maps of the studied zone, Sanandaj municipal region 5 has been known as the most vulnerable part of Sanandaj city because of its location in the vital artery and other important urban centers. Topology of vital and significant installations has not favorably followed passive defense approach. Thus, with respect to the derived information from the existing documents and evidences, the conducted field visits and analyses on the given centers represented that the principles of passive defense have not been observed in these installations and equipment. These centers have been located beside important and critical equipment in a centralized form and they have not been dispersed. This might increase the risk of attacks on these installations from the air and the ground. Similarly, duly efforts have not been made for camouflage and hiding these centers. What is clear so far is that, the subject of passive defense has not yet been addressed in urban designs prepared for the positions in Sanandaj city.