Green Roofs to Improve Water Management

Green roofs are increasingly used as sustainable urban drainage system due to their positive impact on the storm water management. The mitigation consists in reducing the total outflow volume, while delaying the initial time of runoff and distributing the outflow over a longer time period. The retention, detention and infiltration processes promote the occurrence of adsorption and dissolution mechanisms throughout the green roof components generally limiting the total pollutant mass delivered on an event basis. An overview of the green roofs hydrologic performance metrics as well as experimental data to provide a quantitatively assessment is presented. Similarly the impact of green roof in altering storm water quality is examined based on the observed pollutant loads reported in the literature. Finally, the needs for future research and suggestions for green roofs integration in urban water mitigation strategies are discussed.