While green roofs have been used for centuries worldwide, their introduction into Vietnam urban environment is much more recent. The control of storm-water runoff is a pressing issue in most urban areas. This research, therefore, evaluated the effectiveness of green roofs in the management of storm water and mitigation of urban flooding via considering such parameters as peak flow reduction, reduction of storm water runoff flow, peak flow delay time, total delay time (from the beginning of the rain until peak flow is reached). The three green roof models covered by gravel, sand and planting soil (one without irrigation, one planted with flowers and vegetables and manual irrigation, and one with automatic drip irrigation system) were studied in comparison with a conventional roof, which contains no green layer. Research results show that installed green roofs can reduce the peak flow up to 50% and increase total delay time up to 30 minutes. In the aspect of water retaining, the non-irrigation green roof model was shown to be the best.
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