Strategies to Mitigate Drought and Water Stress in Tehran through Nature-based Solutions (NbS), A Decision-making Based on Fuzzy Cognitive Maps (FCMs)

Drought and water stress in the metropolis of Tehran can adversely impact the environmental, social, economic, and political areas of life while increasing the vulnerability of the society and the city. Tehran’s resilience against drought has been exacerbated by a range of factors such as the management’s atomistical view of the integrated human-environmental system of the city, the loss of water resources, the disproportion between the change of land uses and the water capacities, as well as human interventions and the development of gray infrastructure. This situation has turned decision-making and identifying priorities regarding the water tension into a serious challenge. This research aims to provide multi-scale solutions to reduce drought based on the capacities of Tehran’s landscape and answer the question of what main risk reduction strategies can be adopted at the macro level and what appropriate tools are available at the micro level. To address this question, the experts’ opinions in collaborative panels were analyzed and the causes of Tehran’s vulnerability were identified through Fuzzy Cognitive Maps (FCMs) and related-driven scenarios. The findings show that the strategies for encountering and reducing the consequences of drought in Tehran are a combination of nature-based and gray solutions. Changing urban management strategies, modifying population patterns and city development, restoring natural ecosystems, and changing the mentality of citizens towards the issue of water shortage are other proposed solutions. Among Nature-based Solutions (NbS), river valleys play a key role in modifying the city’s development pattern. Using these solutions requires the adoption of integrated strategies at the institutional-physical levels along with the promotion of social and economic programs.