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| Water quality || <font size=4><center>&#9684;</center></font size> || Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
 
| Water quality || <font size=4><center>&#9684;</center></font size> || Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
 
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| Water quantity/supply || <font size=6><center>&#9679;</center></font size> || Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
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| Water quantity/supply || <font size=4><center>&#9685;</center></font size> || Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
 
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| Energy savings || <font size=6><center>&#9679;</center></font size> ||  
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| Energy savings || <font size=4><center>&#9685;</center></font size> ||  
 
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| Climate resiliency || <font size=4><center>&#9681;</center></font size> || Provides some rate control. Impacts on carbon sequestration are uncertain.
 
| Climate resiliency || <font size=4><center>&#9681;</center></font size> || Provides some rate control. Impacts on carbon sequestration are uncertain.

Revision as of 21:19, 12 September 2022

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In development
image of target center green roof, Minneapolis, MN
Vegetation on the Target Center Arena green roof. vegetation consisted of a pregrown Sedum mat supplemented with 22 species of plugs and 16 species of seed native to Minnesota’s bedrock bluff prairies. Image Courtesy of The Kestrel Design Group, Inc.
image

Green roofs occur at the beginning of treatment trains. Green roofs provide filtering of suspended solids and pollutants associated with those solids, although total suspended solid (TSS) concentrations from traditional roofs are generally low. Green roofs provide both volume and rate control, thus decreasing the stormwater volume being delivered to downstream best management practices (BMPs).

Green infrastructure and multiple benefits

Green infrastructure (GI) encompasses a wide array of practices, including stormwater management. Green stormwater infrastructure (GSI) encompasses a variety of practices primarily designed for managing stormwater runoff but that provide additional benefits such as habitat or aesthetic value.

There is no universal definition of GI or GSI (link here fore more information). Consequently, the terms are often interchanged, leading to confusion and misinterpretation. GSI practices are designed to function as stormwater practices first (e.g. flood control, treatment of runoff, volume control), but they can provide additional benefits. Though designed for stormwater function, GSI practices, where appropriate, should be designed to deliver multiple benefits (often termed "multiple stacked benefits". For more information on green infrastructure, ecosystem services, and sustainability, link to Multiple benefits of green infrastructure and role of green infrastructure in sustainability and ecosystem services.

Benefit Effectiveness Notes
Water quality
Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
Water quantity/supply
Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
Energy savings
Climate resiliency
Provides some rate control. Impacts on carbon sequestration are uncertain.
Air quality
Habitat improvement
Use of perennial vegetation and certain media mixes promote invertebrate communities.
Community livability
Aesthetically pleasing and can be incorporated into a wide range of land use settings.
Health benefits
Economic savings
Generally provide cost savings vs. conventional practices over the life of the practice.
Macroscale benefits
Individual bioretention practices are typically microscale, but multiple bioretention practices, when incorporated into a landscape design, provide macroscale benefits such as wildlife corridors.
Level of benefit: ◯ - none; ; - small; - moderate; - large; - very high

Green Infrastructure benefits of green roofs

Because of their use of vegetation in conjunction with building design, green roofs provide multiple green infrastructure benefits.

  • Water quality: Green roofs provide stormwater treatment benefits, but because pollutant concentrations are generally low, these benefits are limited. Pollutant removal mechanisms include filtering, evaporation, transpiration, biological and microbiological uptake, and soil adsorption.

Green roofs employ engineered media that is effective at removing solids, most metals, and most organic chemicals. Green roofs are generally not effective at retaining phosphorus because of the organic matter content in the media. They therefore are likely to lose phosphorus during the first years after establishment, but may gradually retain phosphorus over time.

Design considerations

Maximizing specific green infrastructure (GI) benefits of green roofs requires design considerations prior to constructing the practice. While site limitations cannot always be overcome, the following recommendations maximize the GI benefit of green roofs.

  • Water quality
  • Water quantity/supply
  • Climate resiliency
  • Habitat
  • Community livability
  • Health benefits
  • Economic benefits

Recommended reading

References