Mississauga should ramp up stormwater infrastructure after record rainfall, experts say | CBC News

Mississauga is continuing to clean up after record rainfall hit the city over the weekend, causing flash flooding that is prompting city officials and experts to call for expanding stormwater infrastructure to better prepare for the future.

The storm that affected a wide swath of southern Ontario and the Greater Toronto Area (GTA) marked the second time this summer that the city has been forced to respond to rapidly worsening extreme weather. 

Fire crews rescued 27 people from the water over the weekend, including stranded drivers and pedestrians, and eight people who were trapped in elevators that stopped working due to power surges or water flowing through the elevator shaft.

In a news release issued Monday, the city said rainfall amounts varied across Mississauga, with some areas of the city seeing as little as 6.2 millimetres and the hardest-hit areas receiving some 170 millimetres from Saturday to Sunday. 

Helen Noehammer, the city’s director of works, operations and maintenance, said the stormwater system is only designed to handle a similar weather event once every 10 years.

“This was probably right now looking [to be] at least a one-in-100-year event,” Noehammer said Monday. 

“What we’re seeing is climate change and the impacts of climate change, so we’re seeing these type of rainfall events happening more often, and I think the difference … is that they’re much more intense.”

The areas near Dixie Road and Dundas Street, Cooksville Creek, Streetsville, Malton, Lisgar, along with stretches of highways 401, 403 and 410 and the airport were all hard hit by the heavy rain. Some roads were closed as a result of localized pooling.

Storm a ‘disaster’ for many

Mississauga resident Jason Brown, who lives near Cooksville Creek, was waiting for nearly a month to finish renovating his kitchen when his garage — where he had stored brand new kitchen appliances and cabinetry that were set to be installed Saturday — flooded.

“Everything was underground and now it’s all ruined,” he said.

Brown, who lives in a condominium complex on Kirwin Avenue that backs onto Cooksville Creek, said his family was trying to keep the water out but couldn’t keep up with the pace of the rain.

“The system they have, it goes to the creek and when it goes to the creek and the creek is so high, the water won’t go out. It just surges back,” he said.

“Everything comes up the drain and there’s no stopping it. There’s nothing you can do,” he said.

Mississauga Mayor Carolyn Parrish said in a statement on Monday the city is “actively” assessing how it can improve its infrastructure in the face of such storms and is working with other levels of government to secure additional supports.

“I understand how challenging this situation is and appreciate the patience of our residents and businesses, as we work with local and regional partners to assess the damage and repair what was damaged,” Parrish said.

“Mississauga City Council remains committed to our community during this difficult time. Rest assured, we will continue to make investments in critical stormwater infrastructure to address these more frequent historic weather events.”

Parrish urged all residents to call 311 to provide their names and addresses and to document any damage with photos or videos, as well as inform their insurance providers as soon as possible.

Coun. Alvin Tedjo said the rainstorm aftermath was “disaster” for many across the city.

He said that given the region is experiencing heavy rainfall more often, the city should look at improving its infrastructure and reassessing its stormwater management measures.

“I think we’ve done a great job. We’ve done everything that we could,” Tedjo said in an interview Monday.

“But we never were able to anticipate this amount of water, this volume of rain, happening at the same time — let alone just weeks apart.”

City to expand on stormwater infrastructure

Tedjo, who is also a member of the city’s environmental action committee, said the city has plans to expand stormwater ponds, creeks and to improve stormwater mitigation on existing roads but needs it needs to work more quickly.

“We have a responsibility to make sure that we’re upgrading our infrastructure but also anticipating the challenges that we’re going to be getting on a more regular basis to make sure that we start changing those pieces now,” Tedjo said.

Since the city introduced a stormwater charge in 2016, it has invested more than $230 million to improve its stormwater system. 

Noehammer said future investments will be made taking into account the frequency of such storms.

Tim Duval, associate professor of physical geography at the University of Toronto Mississauga, said the effects of climate change suggest there needs to be a better method of analyzing data to predict future weather patterns for local regions.

“We need to rethink what our datasets are, the way we derive 100-year storms. We can only look at past records to help us predict the future and that’s fine in a time period say 50 years ago [when] the effects of climate change haven’t been ramping up as fast as they are now,” he said.

“Relying on a hydrograph or stream flow data set that’s based on 100 years of record from the past is proving now cannot be so sufficient moving forward.”

Residents advised to exercise caution

Crews are continuing to clean up debris from sidewalks, roads and trails on Monday, the city said. 

The city is advising residents to take exercise caution in all parks and trails, creeks, rivers or watersheds as well as in flooded areas. Residents are asked to follow all posted signs and barricades in the affected areas.

Most sports fields reopened on Monday after they were closed due to the weather conditions, but the following remained shut: 

• Courtney Park Cricket Pitch.
• All fields at Meadowvale Sports Park.
• Lisgar Fields Major Baseball Field.
• Dunton Fields, Major Softball Fields 1 and 2.
• All secondary fields in the Malton area.
• Quenippenon Major Baseball Field.

The city says it’s too early to estimate the total value of damage caused by the weekend storm, adding it is continuing to collect data.

The flooding comes after Toronto and surrounding areas experienced a major rain squall last month that left many parts of the city inundated.

WATCH | Anti-flood barriers tested in Mississauga in July, before second major rainstorm: 

Emergency crews test out anti-flood barriers in Mississauga

One week after Toronto was hit with major flooding across the city, humanitarian group GlobalMedic on Tuesday demonstrated new anti-flood barriers that it hopes will mitigate the next emergency. CBC’s Britnei Bilhete takes a look.

Initial estimates released on Monday put the total insured damage caused by flash flooding in Toronto and other parts of southern Ontario in July at more than $940 million.

The estimate by Catastrophe Indices and Quantification covered July 15-16, when torrential rain hit Toronto and the surrounding area and flooded major highways and Union Station, a key transit hub.

The Insurance Bureau of Canada estimated that severe weather in 2023 caused over $3.1 billion in insured damage across Canada.