Green roofs can significantly reduce the amount of rain water that would otherwise run off an impervious roof surface.
Green roof stormwater runoff.
A typical extensive green roof of 3 5 inches depth will reduce the volume of runoff by about 55 in central pennsylvania and attenuate the peak runoff rates to the level of the pre development land use.
Stormwater runoff that comes from downspouts rushes onto roads picking up copper from brake pads fuel and chemicals.
Green roofs are very effective stormwater bmps.
Green roofs aim to help eliminate excess stormwater.
Their major drawback is the initial cost.
Green roofs can help to reduce both storm water volume rate of run off entering the drainage system.
Green roof runoff does contain concentrations of some nutrients and other parameters but values are in line with other planted systems.
Due to the volume reduction actual nutrient loadings from.
They capture water when it rains slowly releasing it through evaporation and plant use.