Green roof performance towards management of runoff water quantity and quality: A review

This review paper addresses the role of green roofs in urban drainage considering both management of water quantity and quality. Results from investigation of full scale installations as well as from laboratory models are reviewed. The following factors affecting runoff dynamics from green roofs are discussed: type of green roof and its geometrical properties (slope); soil moisture characteristics; season, weather and rainfall characteristics; age of green roof; vegetation. Design parameters as suggested by different authors are also reviewed. Factors which affect influence of a green roof on runoff water quality are discussed in general terms followed by the review of data regarding concentrations of phosphorus, nitrogen, and heavy metals in green roof runoff, its’ pH, and first flush effect. Linking among fertilization, runoff pollution and vegetation development is given a particular focus. The review indicates clearly that there is a need for more research into a green roof performance in an urban environment. The differences measured by few existing studies between the early years performance of green roofs and the later years indicate a need for long term monitoring of green roofs.