First-in-Canada building feature could prevent more floods in Mississauga: city

A first-in-Canada building feature located in Mississauga is being touted as a strategy that could help minimize water damage and even prevent widespread floods such as those that caught the city and residents off guard this past summer.

Mississauga is the first city in the country to use a Canadian Standards Association-compliant “smart blue roof system,” a building feature designed to capture and detain rainwater, the City of Mississauga said on Thursday.

Credit Valley Conservation’s administration building on Old Derry Road in the city’s north end is outfitted with a “blue roof” that can control and store as much as 60,000 litres of rainwater.

“During heavy rainfall, blue roofs can hold rainwater back, reducing and controlling the release of that water into city stormwater pipes to reduce flood risk,” city officials said in a news release. “This innovative system captures rainwater to reduce flooding impacts, conserve water and promote sustainability.”

CVC’s “blue roof,” constructed with the city’s help, has already proven effective, officials note, adding the collaborative project “demonstrates how both organizations are committed to finding innovative solutions for increasing climate challenges.”

Applied on a wider scale to other structures across Mississauga, city officials say the system has the potential to be a positive game changer.

“As weather patterns continue to change, widespread community adoption of technology like blue roofs can help to mitigate the impacts of heavy rainfall and storms,” the city said, referencing historic summer flooding that hit Mississauga and other parts of the GTA and southern Ontario several months ago.

Numerous city residents experienced basement flooding and other damage during severe rainstorms on July 16 and again on Aug. 17-18.

“Over the last few months, Mississauga has experienced two major weather events where flooding caused damage to both public and private property,” city officials said. “As climate change continues to evolve and more extreme weather patterns occur, cities like Mississauga are looking at innovative and adaptive drainage solutions, like blue roofs, to help with these challenges. Flooding can cause costly damage to homes, businesses and infrastructure. It can also disrupt essential services and utilities like transit and electricity. Ongoing flooding can also cause erosion, harm local ecosystems and cause debris and pollutants to contaminate our drinking water source, Lake Ontario.

“This smart blue roof initiative serves as a living lab and a template for future projects of this kind that fully support Mississauga’s goals to encourage sustainable development in response to climate change and stormwater mitigation efforts,” officials continued. “Widespread adoption of blue roof technology can help cities like Mississauga reduce flood risk and expand rainwater harvesting.”

The city said “blue roofs” have proven reliable elsewhere in helping to reduce the risk of flood damage. They’re also a cost-effective solution “to mitigate some of the impacts of climate change on stormwater infrastructure, promote environmental sustainability and offset water and cooling expenses in buildings with these systems.”

Whereas conventional building roofs are sloped to shed water and use gravity to pull water downwards and off the roof, “blue roofs” are designed to capture and detain rainwater.

Water held back using this system can be used in several ways, officials note, among them:

• some of the stored rainwater evaporates (cooling the building)
• stored water can be diverted and treated for desired uses inside the building
• some of the water may be used for irrigation on the property, particularly during dry weather spells
• diverting water from the roof to the property landscaping allows water to soak into the soil, which helps to slow the release of water into the city’s stormwater system
• harvesting rainwater can also help save the owner money on their water bill

Still, officials point to the most significant benefit as being one that helps prevent or minimize large-scale flooding.

“During floods, the smart blue roof can detain significant quantities of roof runoff that might otherwise contribute to downstream flooding or the surcharging of storm sewers,” the city said. “If the storage capacity of the roof is exceeded, then water is safely discharged through one of two overflow routes.”

(Cover photo and other photos: City of Mississauga)

This year, through a funding partnership with Credit Valley Conservation (CVC), Mississauga became the first city in Canada to host a smart blue roof to reduce the risk of flood damage.

Learn more: https://t.co/xxa4xi2Bqu@CVC_CA pic.twitter.com/ybTDsLSvjG

— City of Mississauga (@citymississauga) November 28, 2024