Rainwater harvesting (RWH) is a part of best management practices (BMPs) that recycles and reuses runoff in order to meet the expected demands. RWH can also provide an additional benefit, which is runoff reduction or capture. In this study, RWH systems throughout the entire office and residential buildings in the city of Hamadan are evaluated in order to reduce the risk of flooding. The adopted approach for this purpose is the analytic hierarchy process (AHP)-based multi-criteria decision analysis technique. In this paper, in order to investigate the impact of rainwater harvesting on flood risk zoning, the role of RWH on flood hazard mapping is firstly assessed and in the next step, by composing this mapping with the vulnerability parameters, the final map, called flood risk mapping, is attained.
