Green Roof Runoff Impact

Enhanced stormwater management and water quality.

Green roof runoff impact.

Green roof facilities act as a reduction of impervious surfaces where the largest or almost integrally the rainfall volumes produces runoff flowing into the urban drainage system. With a green roof however the setup for routing the event is more complex. In summer a green roof can typically retain between 70 80 of the runoff green roofs can help to reduce the surface run off entering the drainage system. Another important benefit of green roofs is their ability to reduce and slow stormwater runoff in urban environments.

Green roofs can retain nearly all storm related precipitation during the summer months with lower retention during the winter months 20. 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. In summer a green roof can typically retain between 70 80 of the runoff.

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. The current paper has focused on the analysis of the impact of green roof construction on stormwater production. Impact of a green roof on individual rainfall events just as a stormwater basin can be modeled to show what effect each basin is expected to have on a specific runoff hydrograph a green roof can also be modeled. Due to the volume reduction actual nutrient loadings from green roofs are less than asphalt roofing runoff or otherwise manageable at the downspout.

Green roof runoff does contain concentrations of some nutrients and other parameters but values are in line with other planted systems. Because rooftops and streets in cities are hard surfaces the volume and velocity of stormwater runoff increases tremendously and is a major source of flooding and pollution worldwide. The stormwater management benefit provided by green roofs lies in the ability of the soil media and plants to retain stormwater increase evapotranspiration and allow stormwater runoff to be released gradually to receiving waters at decreased flow rates.