Study of urban water storage tanks from the perspective of passive defense using Delphi, FEMA, and AHP hierarchical analysis

 This study was aimed to investigate the principles and foundations of passive defense, study the types of drinking water storage tanks, identify threats in urban water tanks and prioritize passive defense measures to reduce water tank threats.

 In this study, in order to identify threats in the field of drinking water storage tanks and identify hazards and risk assessment, a combination of Delphi and FEMA methods was used. Moreover, AHP hierarchical analysis was adopted in order to prioritize the types of tanks from the passive defense criteria point of view. Ethical considerations were observed in all stages of the study.

 According to experts, important threats with a high destructive effect in the field of water storage resources included "chemical and biological contaminants" that can endanger the health of water and consumers. Indeed, “air and missile bombings”, "fixed suicide bombings" and "individuals and vehicles" can cause the destruction of reservoir structures and disrupt water supply operations. Moreover, threats related to psychological warfare and soft warfare, including "rumors of water pollution", "psychological operations and personnel evacuation", "process sabotage" and "cyber-attacks" could result in chaos in the society. Accordingly, based on the aggregation of experts' opinions and the points given to water reservoirs in terms of exposure to threats, buried ground reservoir with a score of 0.386, semi-buried ground reservoir with a score of 0.246, elevated reservoir with a score of 0.225 and ground reservoir with a score of 0.143 were respectively prioritized for use as urban water storage tanks.

 According to the results of this study, it is suggested to avoid the implementation of visible water reservoirs, and if possible, the reservoirs should be designed and implemented as buried. If it is not economically justified, the reservoir should be semi-buried with embankment and necessary modifications to the structure. Implement and finally use passive defense measures including camouflage, deception, etc. Evaluation of reservoirs in Sari city showed that the condition of these facilities is not favorable in terms of passive defense requirements, especially in rural areas and small reservoirs.