Investigating the Impacts of Green Roofs' Vegetation Properties on Their Function in Controlling Urban Runoffs

The continuous replacement of permeable surfaces, that could previously infiltrate stormwater runoffs, with asphalt, concrete, and other impervious surfaces in urban areas, in addition to the numerous environmental damages caused by the transfer of pollutants, and heavy metals by these runoffs to the municipal water systems indicate a critical need to enhance the control of stormwater runoffs in urban areas. Green roofs have been shown to be one of the most effective best management practices in controlling urban runoffs. Considering the relatively short history of this technology, the impact of the green roof's components in controlling runoffs needs further identification. This paper focuses on the impacts of the vegetation-related factors through a review of the research findings. These impacts are discussed in three categories of 1) plants' resistance, 2) irrigation needs, 3) plants dependence on fertilization and pesticides. For each of the factors, recommended policies are provided. In addition, potentials for future studies that can fill the gap of inconsistent findings, and limited or non-existing knowledge about the green roof hydrological performance are discussed.