Toronto residents got a taste of the future in 2013 when almost 130 mm of rain fell in a couple of hours on a hot and humid July afternoon. Toronto’s aging stormwater system was just too small to handle the water. Shortly after the rain started, water entered subway and hydro stations, turned roads and transportation corridors into mini lakes and flooded countless basements.

Toronto had a repeat performance in 2017 followed by high lake levels that started flooding homes on Toronto Island and beaches along the lakefront.

With the climate crisis, these floods will only get worse: more severe rain events means greater rainfall and more flooding. Add to that, we have had decades of development that has prioritized hard surfaces over surfaces that soak up water: when the water hits hard surfaces, it quickly overwhelms the stormwater system. Always looking for the lowest point, the water makes its way into basements and other low lying areas.

Much of the older parts of Toronto also have combined sewer overflows (CSOs). These are old pipes that carry stormwater and raw sewage from homes and buildings. Normally, these old pipes carry the water and sewage to treatment plants where the pollutants are removed from the water before it flows back into Lake Ontario. But when there is a heavy rain, the old pipes can’t handle all the water. Overflow pipes empty into rivers across the city sending raw sewage into our rivers and then the lake. Which is why beaches are often closed right after a heavy rainfall.

Certain neighbourhoods in Toronto are more prone to flooding than others. Being in low-lying areas close to creeks and rivers or beside the lake increases the likelihood of flooding causing you personal harm. But flooding harms the rest of us as well.

Floods damage transportation infrastructure like roads and subways as well as electrical systems. This requires a lot of tax dollars to repair. Floods also mean insurance payouts, leading to higher insurance premiums that we all have to pay. And, of course floods take a toll on our mental and physical health.

To learn more about flooding in Toronto, especially which areas are most prone to flooding visit the TRCA.

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