Stormwater Management by Green Roof

Urban impermeable areas such as roads, buildings and roofs produce a significant stormwater runoff.Under the big storm events, also caused by climate change especially, stormwater runoff may cause flooding, landslides and other water-related problems.Conventional drainage system doesn't have enough design capacity for reception all increased runoff.Green roofs perform very well as a stormwater management tool by providing reducing stormwater runoff generation.Additional benefits provided by green roofs (improved stormwater quality, improved aesthetics and environmental preservation etc.) makes this tool a desirable option for sustainable stormwater quality and quantity management.The main purpose of this paper is to present the design of green roofs and its roles and benefits in urban stormwater management.There are also presented experience in application and efficiency of green roof in different circumstances by reviewed some researches.Cities have paved over natural green spaces to make way for streets, homes, and commercial developments.Urban stormwater can be defined as the extreme runoff from pervious and impervious surfaces that include roofs, driveways, pavements, footpaths, and roads infrastructure characteristic of urban areas [1,2].In the developed urban areas, roof surface areas account for 40-50% of all total impervious surface areas.Also, climate change has caused more frequent and intense storms.The effects of global warming because of climate change is already increasing vulnerability of several urban areas around the world, through raising sea levels, inland floods, more frequent droughts, periods of increased heat, and the spread of diseases [3].Due to climate change and urbanization stormwater runoff rates, volumes and pollution are getting more and more increased.Technologies of stormwater management (SWM) systems need to be improved to account for the changes in the hydrologic cycle that results from urbanization and changes of runoff caused by climate changes [4,5].Approaches to stormwater management known as 'Sustainable (Urban) Drainage systems' (SUDS), 'Low Impact Development' (LID), or 'Best Management Practices' (BMPs), represent a diverse range of control procedures, which integrate stormwater quality and quantity control as well as enabling social and amenity perspectives to be incorporated into stormwater management approaches [6,7].For example, the aim of LIDs include: treating stormwater as close to the source as possible, decreasing impervious area, and implementing systems that have multiple functions (i.e.attenuating peak flow rates, storage of precipitation, delay of stormwater generation, infiltration, filtration, enhancing aesthetics, improve ecology) [8-10].The implementation of a stormwater control as a retrofit on vacant roofs could significantly reduce the impervious surface cover and help decrease stormwater runoff and pollution generation at the source.The goals of stormwater system design, is typically to preserve groundwater, prevent geomorphic changes in waterways, prevent Green roof design