Green roofs

Saint Mary's University research green roof

Green roofs are important stormwater management tools that reduce the volume of stormwater  leaving the site by capturing and retaining rainfall and returning precipitation to the atmosphere through evapotranspiration. They are ideal for improving stormwater management in urban areas as they make use of existing roof space. To learn more about green roofs, I spoke with a group of Saint Mary's University grad students who are researching green roof plant communities (thanks Steph, Amy and Tobi!). 


There are two types of green roofs - intensive and extensive. Intensive green roofs have deep soils which can support a wide variety of plant species, including larger shrubs and trees.  They are used for both aesthetic and functional purposes. Intensive roofs require maintenance and care, much like a typical home garden. Extensive green roofs use less soil (layer can range between 2 - 20cm)  which makes them much lighter, but also limits the variety of plants that can be grown in such shallow conditions. Grasses, mosses and sedum species are commonly used.  Extensive green roofs require little to no maintenance. Some roofs may need irrigation for the first year while the plants are establishing, but they can then be left entirely on their own. 


Green roofs can be installed in three ways. Soil can be brought to the roof top and placed on top of the required waterproofing, filtering and insulation layers then planted with selected vegetation. More typically, green roofs are installed as small modules or vegetation trays that contain soil, plants and a shallow gravel layer to ensure the contents are secure on windy rooftop conditions. A third option, known as pre-cultivated vegetation blankets, are composed of soil and vegetation mats that can simply be rolled out onto the rooftop. 

Green roof modules

Green roof layers including pre-cultivated vegetation blanket (www.xeroflor.ca)

Along with improving stormwater management, other benefits associated with green roofs include increasing the life time of roofs, creating urban wildlife habitat, improving energy efficiency of the building, improving air quality and reducing the urban heat island effect. 


The city of Toronto has introduced a Green Roof Bylaw that requires the construction of green roofs on all new buildings of a certain size. You can read more about Toronto's bylaw here.

Engineered Wetlands

Appleton-Middleton Engineered Wetland Photo: www.abydoz.com

When the aging sewage treatment plants needed upgrades in the towns of Appleton and Glenwood in Newfoundland and Labrador, they took an innovative approach to improving stormwater and sewage treatment by implementing an engineered wetland. The towns were concerned  the quality of discharge that was entering the Gander River which was not meeting Provincial or Federal standards and about the increasing maintenance costs required by the older systems.


The newly constructed engineered wetland provides secondary treatment of wastewater, is cost-effective and has greatly improved the water quality discharged into the Gander River. This project was the Atlantic winner of the Watershed Awards, which recognizes community climate change adaptation efforts and is awarded by Insurance Bureau of Canada and the Federation of Canadian Municipalities. Check out this great video to see how the engineered wetland works. Video provided by the Insurance Bureau of Canada.

Retrofit Assessment - University Avenue Fire Station

Spring is in the air, which means we are moving closer to breaking ground on our stormwater retrofit project! To help us come up with a site design plan, we are incorporating suggestions from our site assessments with Dr. Jiri Marsalek (Environment Canada, Burlington). In this video, Dr. Marsalek discusses the opportunities and limitations to improve stormwater management at the University Avenue Fire Hall. This is the second of three candidate sites, so one more video of our third possible site follow.

We'd love you to get involved in this project by letting us know which location you think should become Nova Scotia's first stormwater demonstration site.

Kitchener approves stormwater credit

Interesting article from Exchance Magazine (March 5, 2012):

Stormwater Credit Policy Gets the Nod from City Council

Kitchener – A new stormwater credit program approved by Kitchener city council will offer incentives to property owners who actively decrease the volume of stormwater and pollution coming off their properties.

The proposed stormwater rate credit, which comes into effect Oct. 1, 2012 encourages private property owners to reduce total runoff and pollutants that leach into the stormwater management system, through already existing or proposed stormwater facilities or through best management practices.

Because the stormwater rate billing system needs to be modified and application forms created, those customers who are eligible for the credits will not see the adjustment until October. The eligible credits will be applied retroactively to Jan. 1, 2011, for all eligible property owners who apply before March 1, 2013.

“The stormwater credit policy is a strong environmental initiative that will help the community protect water resources for present and future generations,” said Grant Murphy, director of engineering services.

Two policies are included within the credit:

Non-residential and multi-residential property owners who pay the stormwater rate are eligible to apply for up to 45 per cent credit. Three components will be considered: flood prevention, pollution reduction and educational programs.

Residential property owners can also apply for up to 45 per cent credit, based on the volume of stormwater diverted from the municipal stormwater system from their property.

Since May 2011, the cities of Kitchener and Waterloo have worked together to develop the stormwater credit policy as part of the shared services initiative. Public consultations were held to get feedback on five potential credit or rebate options.

In 2011, the City of Kitchener altered the funding approach of its stormwater program, moving it from the tax base to a user-pay system. The rate, based on the amount of impervious area on each property, creates dedicated, sustainable funding for costs associated with stormwater management (SWM). The more impervious area an individual property owner has, the greater the amount of runoff and pollutants from the property and, consequently, the greater the demand on the city’s SWM system.

The City of Kitchener has been recognized by both the Association of Municipalities of Ontario and the Ontario Good Roads Association for its industry-leading approach to delivering stormwater utility services.