Two 100-year storms hit Mississauga in a month; failing infrastructure costing residents millions

The wall of rain that swamped much of Mississauga August 17 brought as much as 128.3 millimetres in some areas, surpassing a record just over a year ago. 

The widespread flooding marked the second time in a month the city was overcome by a “once-in-a-century” storm that caused problems across the city, resulting in traffic disruptions, dangerous road conditions, closures and hundreds, maybe thousands of overwhelmed basements. 

The City reported that by Saturday afternoon, all creeks and rivers through Mississauga were either at capacity or flooding into parks and surrounding greenspaces. Warnings about the potential for heavy rainfall remained in effect throughout the course of the weekend, with localized precipitation amounts predicted to range between 100 and 200 millimetres over three days.

The numbers varied across Mississauga with the hardest hit areas receiving around 170 millimetres of rainfall. Las Vegas receives an average of about 100 millimetres of rain over an entire year. Toronto gets approximately 800.

The 2013 flood that impacted much of Mississauga and the GTA seemed, at the time, like a foreshadowing of what our emerging climate reality holds in store. Last month, when the storm that caused flooding of the same magnitude ravaged the city, local elected officials began contemplating how to protect their municipality from the inevitable impacts of our warming planet. Now, after another severe event, this time even worse, immediate solutions are more critical than ever.

As such storms become increasingly frequent, the City’s own climate projections anticipate rainfall to increase in volume and intensity. “Extreme events like lightning and thunderstorms, snowstorms, freezing rain, hail, powerful winds, droughts, wildfires, flooding and storm surges are expected to become more intense due to a warmer and hotter future climate,” staff warn. 

Climate change experts have highlighted events like these as evidence of how global warming is changing weather patterns, emphasizing that storms like the one on July 16th, which brought more than 106 millimetres of rainfall, and this past weekend, could become more commonplace. 

“Every degree of temperature change, even one degree warmer, can impact our environment significantly,” the City explained. “This could mean more widespread flooding with rainfall levels expected to increase in volume and intensity, with more frequent and intense precipitation. It’s important that we manage stormwater to reduce flooding risk to [residents’] property, lower erosion of our creeks and limit the amount of pollution entering Lake Ontario.”

Acknowledging Mississauga faced yet another unprecedented storm within a month, Mayor Carolyn Parrish assured residents the City is making “significant investments” in its stormwater infrastructure to better prepare and protect residents and infrastructure from future events.  

“These efforts are part of our broader strategy to increase our resilience and make sure we are prepared for future weather challenges,” she explained in a statement. “The scale of this flooding event, and the one on July 16th, has tested our systems, and we are actively assessing how we can further improve and adapt our infrastructure to meet these ever-changing demands.”
 

Emergency crews tended to people stranded in the flooding throughout Saturday and into Sunday over the weekend.

(Mississauga Fire/X)

While residents were once again left to deal with the burden of basement flooding, parks and roads submerged; and trails inaccessible, the City says that without the presence of its stormwater infrastructure, the situation could have been much worse.

The impacts of the 2013 storm changed how the City viewed its approach to managing stormwater, and made it clear Mississauga needed to increase its investment into its aging infrastructure. In the years since, flood prevention has become more of a priority. The City is spending millions of dollars annually to upgrade its stormwater infrastructure, but is it enough?

With the amount of precipitation increasing and more severe rain events expected more frequently, this increased threat is weighing on municipalities to expand stormwater management response in the event of potential flooding. Mississauga’s Climate Change Action Plan shows severe weather events are set to occur every six years as opposed to a previously estimated 40 years, and 70 millimetres more in annual rainfall, according to the City’s 2050 climate projections.

To lessen the risks of flooding, the City’s stormwater system acts as a barrier to collect and redistribute rainwater runoff to a receiving reservoir, among other functions. The stormwater drainage system is one of the largest assets owned and operated by the municipality, with the 2024 Corporate Asset Management Plan estimating the City’s infrastructure to have a replacement value of $7.6 billion.

The City’s stormwater charge has helped to offset some of the costs associated with maintaining this system by generating funding for ongoing management and repairs. The charge generated $44.6 million in revenue for the City in 2022 (the latest available data) and was previously estimated to increase to $47.3 million by 2025. The charge was part of the 22 action items laid out in the City’s official Stormwater Master Plan, which was approved by council in June 2023.  

Since 2016, the City of Mississauga has invested over $231.5 million in stormwater infrastructure. This year, $33.7 million was put toward stormwater as part of the capital budget with plans to invest $342.5 million over the next decade (approximately $51 million, on average, per year). The Pointer previously reported an additional $30 million per year from 2024 to 2123 is required to fully fund the City’s stormwater pipe program and maintain Mississauga’s aging stormwater pipes.

Councillor Chris Fonseca, who represents one of the areas often hardest hit by flooding, is putting pressure on staff to report back in response to her motion when council reconvenes in September.

(Alexis Wright/The Pointer Files) 

Although it is an impossible feat to update the City’s entire stormwater system immediately, Councillor Chris Fonseca brought forward a motion in July in an effort to increase the City's response following the July 16th storm. As the councillor representing one of the hardest hit areas, her motion requested staff report back to council with options on how to best mitigate the flood damage from any future storm events. 

“We need to come up with immediate solutions,” Fonseca told councillors and staff during the July 31st meeting. “I do believe there's things we can do, immediate things, that may have to happen in the short term, mid term and then longer term, but we definitely need to act now to address the flooding that has been occurring over many, many years in the City of Mississauga.” 

The motion asked that the City continue partnering with the Region of Peel and surrounding conservation authorities on finding solutions to mitigate flooding and provide flood protection to residents and businesses. This, it added, includes exploring improved flood forecasting and monitoring systems, flood detection and emergency management.

“My motion stressed the urgency for staff to report back to Council in September based on the findings related to the July 16th storm event and provide commentary on immediate, short term, mid-term and long-term actions the City should consider in regard to matters in and outside the Capital Plan,” Councillor Fonseca said in a statement. “In light of the August 17th and 18th storms aftermath, I have reiterated to staff the urgency of having a report come to council in September with actionable items that could support residents and businesses.”

A spokesperson from the City told The Pointer in an email staff are planning to bring a report forward in September in response to Councillor Fonseca’s motion on improvements to the City’s flood mitigation. 

“Clean-up efforts continue, including the removal of debris from sidewalks, roads and trails,” a press release from the City explained on Monday. “The City is still assessing the financial impacts to the Corporation and is working alongside its local and Regional partners, like the Region of Peel and Credit Valley Conservation, to collect data and insights about the severity of this weekend’s flooding.”  

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Twitter: @mcpaigepeacock

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