Urban Water Challenge and Urban Runoff Management Scenarios (Case study: Parts of Bandar Abbas City)

Urban development is associated with an increase in impervious areas and simultaneously with changes in the hydrological cycle. This increases the amount of runoff from rain, resulting in a faster runoff regime with shorter delay times and higher peaks. Therefore, the risk of flooding, which is one of the most dangerous natural disasters, increases. The studied area is part of the city of Bandar Abbas, which is highly subject to growth and development. Inappropriate drainage system and heterogeneous development of the city, regardless of comprehensive urban planning criteria in the past decades, have led to flooding in the urban area even due to rainfall with a small return period. Therefore, in this study, an attempt was made to investigate the areas sensitive to flooding through simulating the operation of the surface runoff drainage system and evaluate the best management practices for flood control and their impact on flood volume reduction. To this end, by means of EPA-SWMM software and in order to control the runoff, we evaluated three management practices including bioretention cells, green roof and swale in parts of Bandar Abbas city. The results indicated that the green roof management solution had the best performance compared to other solutions with an average reduction of 18.8 percent of the runoff peak, and 12.5 percent reduction in runoff velocity. The results of this study also revealed that the network in the non-BMP mode for the 10-year return period had a flow rejection of 18%, which was reduced by implementing the green roof scenario to 1% of the network. Therefore, the green roof management practice was selected as the best solution to reduce peak and flow velocity in the studied area.