‘100-year-storm’ batters Mississauga, but city says damage could have been much worse

Although some parks and sports fields in Mississauga are still closed following last week’s torrential rainstorm, the city says the damage could have been significantly worse without strong stormwater infrastructure in place to mitigate the floods.

Today, the city offered reporters a peek behind the stormwater management curtain, saying that the municipality’s “critical but largely invisible” infrastructure system ensured the municipality wasn’t decimated by the flooding that closed roads, filled basements and waterlogged huge swaths of the GTA.

In a news release, the city said that on July 16, the GTA experienced a “100-year storm,” with approximately 106 mm of rainfall covering the area in just a few hours. To put things in perspective, the area typically sees 75 mm of rainfall over the entire month of July.

At Pearson Airport in Mississauga’s northeast end, an Environment and Climate Change Canada weather station recorded 122.9 mm of rain between last Monday and Tuesday. It was the most rain received in any one area across southern Ontario.

While insurance claims made throughout the GTA in the wake of widespread property damage could reach $1 billion, Mississauga officials say things could have been worse if the city hadn’t had a strong stormwater management system in place. Stormwater refers to rain or melted snow that flows or runs off properties and roads and drains along streets, ditches, storm drains, and watercourses into Lake Ontario.

Stormwater funding and maintenance

In 2016, Mississauga introduced a stormwater fee, which officials say helps operate and maintain the system. Funding from the fee is used to clean out the catchbasins, which collect water, trap debris and prevent litter and other pollutants from ending up in local creeks.

A household’s stormwater charge is based on the type of property and the number of hard surfaces on the property.

According to the city, the stormwater drainage system is one of the largest assets owned and operated by the municipality, with an estimated replacement value of $7.6 billion. City officials say Mississauga has more than 1,900 kilometres of storm sewer pipes in its drainage system. If laid out end-to-end, these pipes would connect Mississauga to Winnipeg.

According to the city, the stormwater drainage system includes more than 51,000 catchbasins, 270 kilometres of ditches, 150 kilometres of creeks, and 81 stormwater management facilities (including ponds, underground storage, and low-impact development facilities) that help to collect, drain, and clean the city’s rainwater runoff before it enters Lake Ontario, the source of residents’ drinking water.

While flooding did occur during the storm, the city says its system was able to handle most of the rain.

“Maintaining this system lessens the risk of flooding, reduces creek erosion and protects water quality. This is important as it protects you, your property, aquatic habitats, wildlife and Lake Ontario,” the city said in a news release.

According to the city, the stormwater system safeguards against unpredictable storms. Last June, Mississauga approved its first Stormwater Master Plan, Build Beautiful, which aims to improve the system and ensure it can adapt in the future.

Stormwater projects

While the city calls the infrastructure “largely invisible,” you can see telltale pieces in major public places. One significant project is Lake Saigon, a stormwater management pond located at Matheson Blvd E. and Hurontario Street. The pond protects flood-susceptible lands downstream within the Cooksville Creek watershed.

You can also spot a stormwater drain at Celebration Square.

Climate change and rainfall

While storms like the one that hit last week are rare–the last comparable event occurred in 2013–experts say climate change could trigger more unpredictable storms and weather events and that temperatures climbing just one degree can significantly impact the environment.

“It’s important that we manage stormwater to reduce flooding risk to your property, lower erosion of our creeks and limit the amount of pollution entering Lake Ontario,” the city said.

While the city has praised the system for mitigating the impacts of the recent floods, it says funding is needed to ensure the municipality’s pipe reserve fund remains robust, as pipes will need to be replaced as they age. As of now, the system is fully funded for the next 10 years due to the stormwater fees.

“The city is seeking a commitment from all levels of government and is advocating for additional funding to help bridge the infrastructure gap. This is crucial for underlining priorities, such as stormwater infrastructure, that are vital to the safety of our community,” the city said.