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. The research methodology focused on the analysis of those variables that control the water routing when high peak flows exceed the drainage-system capacity. The model incorporates five parameters: distance to the drainage channels, topography (heights and slopes), Flow accumulation, and urban land use. In this paper, we present an approach for determining impact of rain water harvesting on flood hazard zoning using a geographic information system and Analytic Hierarchy Process.
