Green Roof Runoff Water Quality

Precipitation generally runs off the roof of a building into gutters and flows into a storm sewer.

Green roof runoff water quality.

A green roof also helps control storm water runoff and retention. Green roofs are very effective stormwater bmps. Because any runoff is filtered through the media and the plants there is potential for both cleansing and contamination. Green roofs sequester rain and carbon pollution as well.

Green roofs also moderate the temperature of the water that happens to run off improving water quality for marine life green roofs delay the time that runoff occurs reducing the number and volume of overflows in combined sewer systems csos. The following factors affecting runoff dynamics from green roofs are discussed. Age of green roof. Green roofs influence runoff quality through making the ph higher from values between 5 and 6 in rain water to over between 7 and 8 in green roof runoff water bliss et al 2009 czemiel berndtsson et al 2009 teemusk and mander 2007.

The increased urbanization of towns and cities has resulted in less green space and more impervious surfaces. Somewhere between 40 and 80 percent of the total volume of rain that falls on green roofs can be retained. Moreover the water that is. Overall total p concentrations were higher in green roof runoff than control roof runoff.

Green roofs can affect runoff quality in a number of ways. Green roofs can help to reduce both storm water volume rate of run off entering the drainage system. The media and plants act as a particle trap for dust and airborne particulates removing them from the runoff when it rains. Results from investigation of full scale installations as well as from laboratory models are reviewed.

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. Therefore green roofs have an important role to play in the urban realm. In general we observed lower no3 nitrate and nh4 concentrations in green runoff than control roof runoff with the exception of runoff from the built up system which had higher no3 concentrations than the control roof runoff. Most extensive green roofs will reduce stormwater flows on an annual basis by 50 green roofs also delay stormwater runoff but flow dynamics depend on climate and green roof design cincinnati civic garden center roof example rain event 12mm from july green roofs and water quantity.

Type of green roof and its geometrical properties slope. Their major drawback is the initial cost.