The Evaluation of the Effect of Extensive Green Roof on the Reduction of Urban Runoff (Case Study of Residential Buildings in Region 6 of Tehran)

In recent years the importance of flood control and management in urban areas has increased due to the development of urbanization and environmental pollution. The green roof technology is used in many parts of the world and seems an appropriate technique to reduce runoff. The lack of surface water collection systems has caused the flow of water on the streets in Tehran. The aim of this study is to simulate the effect of extensive green roof of residential buildings to reduce urban runoff in Tehran. For this purpose, a survey of the study area was performed in GOOGLE EARTH, and the area of the roof of buildings were analyzed using AUTOCAD software. Then, simulated green roof performance based on mass balance for a typical roof and three extensive green roofs with the soil thickness of 25 mm and the vegetation area of 25%, 50% and 75% and the hydraulic relationships between water and soil were compared using CROPWAT software. The results show that the highest decrease in runoff for extensive green roof with the vegetation of 25%, 50% and 75% is respectively 12/59%, 24/59% and 36/58% in comparison with the typical roof. The study shows whenever the vegetation area of the green roof is more; the run-off from the similar rainfall will be less. Thus, the green roof can be raised as a method to reduce runoff in Tehran.