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==Overview==
==Overview==
[[Green roofs]] are engineered rooftop design features that allow the growth of [[vegetation]] on rooftops and have numerous benefits. These LID BMPs can also be referred to as vegetated roofs, rooftop gardens or eco-roofs. A green roof acts like a lawn, meadow or garden by intercepting and absorbing a portion of the rainwater or snowmelt that falls on it. The typical layers of a green roof (in ascending order from the roof surface) include a water-proofing membrane, drainage layer, lightweight growing media layer and the vegetation. Excess water that is not absorbed by the [[Plant selection|growing media]] or vegetation is collected by the underlying drainage layer, directed to [[Overflow|outlet]] structures and conveyed via the roof drainage system to another BMP or the municipal storm sewer system. A portion of the water absorbed by green roofs is returned to the atmosphere by evaporation and transpiration by plants. Green roofs are typically designed to retain precipitation from small to medium-sized (e.g., 5 to 25 mm rainfall depth) storm events. Overflow outlets are necessary to safely convey flows from major storm events.   
[[Green roofs]] are engineered rooftop design features that allow the growth of [[vegetation]] on rooftops and have numerous benefits. These LID BMPs can also be referred to as vegetated roofs, rooftop gardens or eco-roofs. A green roof acts like a lawn, meadow or garden by intercepting and absorbing a portion of the rainwater or snowmelt that falls on it. The typical layers of a green roof (in ascending order from the roof surface) include a water-proofing membrane, drainage layer, lightweight growing media layer and the vegetation. Excess water that is not absorbed by the [[Plant selection|growing media]] or vegetation is collected by the underlying drainage layer, directed to [[Overflow|outlet]] structures and conveyed via the roof drainage system to another BMP or the municipal storm sewer system. A portion of the water absorbed by green roofs is returned to the atmosphere by evaporation and transpiration by plants. Green roofs are typically designed to retain precipitation from small to medium-sized (e.g., 5 to 25 mm rainfall depth) storm events. Overflow outlets are necessary to safely convey flows from major storm events.   
[[File:Layers green roof.PNG|thumb|400px|Generalized cross-section view of a green roof showing key components and common layers that make up this LID BMP (TRCA, 2018)<ref name="example1" />]]


Some of the benefits of [[green roofs]] include:
Some of the benefits of [[green roofs]] include:
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*Can provide aesthetic value as attractive landscaped features. <br>
*Can provide aesthetic value as attractive landscaped features. <br>
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[[File:Layers green roof.PNG|thumb|400px|Generalized cross-section view of a green roof showing key components and common layers that make up this LID BMP (TRCA, 2018)<ref name="example1" />]]


{{textbox|Key components of Underground Infiltration Systems to pay close attention to are the:  
{{textbox|Key components of Underground Infiltration Systems to pay close attention to are the:  
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*[[Green roofs#Irrigation|Irrigation System]]
*[[Green roofs#Irrigation|Irrigation System]]
*[[Overflow|Overflow outlets]]}}
*[[Overflow|Overflow outlets]]}}
Trash, debris and sediment builds up at these locations and can prevent water from flowing into or out of the practice.


==Associated Practices==
==Associated Practices==
*'''[[Soakaways]]''': Typically service individual lots and receive only roof and walkway runoff but can also be designed to receive overflows from other BMPs (e.g., [[rainwater harvesting|rain barrels]] or [[Rainwater harvesting|cisterns]], [[rain gardens]], [[green roofs]]. Also known as infiltration galleries, French drains, [[Dry well|dry wells]] or soakaway pits.
*'''[[Green roofs#Design|Intensive green roofs]]''' contain greater than 15 cm depth of growing media, can be planted with deeply rooted plants (e.g., shrubs and trees) and can be designed to handle pedestrian traffic.
*'''[[Infiltration trenches]]''': Linear oriented soakaways designed to fit into narrow strips of land between structures or properties, or along road rights-of-way; can also receive road runoff with adequate pretreatment devices upstream of inlets.
*'''[[Green roofs#Design|Extensive green roofs]]''' consist of a thinner growing media layer (15 cm depth or less) and are typically planted with.
'''[[Green roofs#Design|Intensive green roofs]]''' contain greater than 15 cm depth of growing media, can be planted with deeply rooted plants (e.g., shrubs and trees) and can be designed to handle pedestrian traffic.
'''[[Green roofs#Design|Extensive green roofs]]''' consist of a thinner growing media layer (15 cm depth or less) and are typically planted with.
'''[[Blue roofs]]''' are systems that temporarily capture rainwater using the roof as storage and allow it to evaporate and/or to be used for non-potable requirements (i.e. irrigation, toilet flushing, truck washing) and ultimately offset potable water demands.
'''[[Blue roofs]]''' are systems that temporarily capture rainwater using the roof as storage and allow it to evaporate and/or to be used for non-potable requirements (i.e. irrigation, toilet flushing, truck washing) and ultimately offset potable water demands.


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