Floods in Montreal will happen again. Maybe soon. What can we do about it?

Annabelle Olivier · CBC News

· Posted: Jul 16, 2025 4:00 AM EDT | Last Updated: 11 minutes ago

Eva Szymkowiak was among the Montrealers starting the week dealing with the aftermath of a tempest that dumped much than 70 millimetres of rainfall implicit the metropolis successful conscionable a fewer hours. 

For the 2nd clip successful conscionable nether a year, the longtime nonmigratory of Montreal's Saint-Laurent borough, says her building's parking garage on Thimens Street was wholly flooded.

Last year, she says both their vehicles were ruined successful a flood. But connected Sunday, Szymkowiak says they saw the h2o accumulating from the tempest and she luckily had clip to move her car and pass others successful the building. 

One neighbour described seeing the manhole covers connected the thoroughfare being blown disconnected and the h2o making its mode into the gathering done the indoor garage. "Somehow this thoroughfare doesn't sorb [...] immense amounts of water," Szymkowiak said.

Szymkowiak and her neighbour are hoping the metropolis steps up to hole the problem. Faced with repeated flooding crossed aggregate boroughs, officials are attempting to find semipermanent solutions — immoderate adjacent introducing bylaws designed to mitigate flood hazard and exposure. 

'Every neighbourhood, each thoroughfare is different,' says mayor

Montreal Mayor Valérie Plante visited those impacted by flooding successful the city's Ahuntsic-Cartierville borough connected Monday. 

"There isn't a unsocial solution for the full territory," she said. "Every neighbourhood, each thoroughfare is different."

WATCH | The assistance you tin get aft your location is flooded: 

She pointed to assorted initiatives being carried retired by the metropolis to trim the interaction of flooding, including overhauling the sewer infrastructure successful high-priority areas and gathering greenish infrastructure, specified as sponge parks and retention basins.

Maja Vodanovic, the enforcement committee subordinate liable for water, said respective criteria assistance find which areas are precocious priority, including the fig of radical affected successful an area, whether it's successful a low-lying country oregon prone to flooding. 

Overhauling sewage web not the solution, says expert

Jean-Luc Martel, a prof successful the operation and engineering section astatine the École de technologie supérieur successful Montreal, said determination is often a batch of accent placed connected the request to redo the sewer network.

But retrofitting the sewage web arsenic a full would beryllium expensive, helium says. In immoderate cases, putting successful bigger pipes would conscionable displace the occupation by moving the h2o downstream.  

"It's not a question of the size and the capableness of the sewer network. They're not designed to woody with those events," said Martel. "That's not [its] job."

To mitigate flooding, boroughs have to look astatine what's happening astatine the surface, says Martel, and trim the magnitude of runoff making its mode into tempest sewers to debar overwhelming the network.

Green infrastructure tin help. He says homeowners tin besides bash their portion by having rainfall gardens and disconnecting gutters to let the h2o to beryllium absorbed by the lawn.

Ultimately, though, Martel says the main contented are basements.

"We request to truly question ourselves arsenic a society. Do we request basements?" said Martel.

"After the sewer is full, the h2o stays connected the aboveground and past it goes with gravity. It goes to the lowest point," helium said. 

Mitigating flood hazard and exposure 

With the strength and frequence of utmost rainfall acceptable to increase, the City of Montreal says it wants to marque it easier for homeowners to marque changes to make a much resilient home.

That tin see utilizing waterproof materials similar ceramic tiles successful flood-prone basements, oregon installing watertight store doors, says Maja Vodanovic, the enforcement committee member.

"We privation to marque it much simpler for those benignant of projects to spell through. We are moving connected changing our regulations to streamline those projects," Vodanovic said.

Regardless of the neighbourhood, oregon borough, the metropolis of Montreal said its RénoPlex program, for buildings with 1 to 5 dwellings, provides fiscal assistance to homeowners for renovations oregon flood extortion enactment connected their property.

The borough of Saint-Laurent has taken action and adopted a caller bylaw past period which will allow homeowners to level up downward sloping store entrances.

It also outlines conditions for parking batch layouts and states that caller driveways should beryllium designed successful a mode to forestall rainwater from flowing onto backstage property.

WATCH | Saint-Laurent's caller bylaw could assistance little flood hazard for immoderate homeowners:

But the borough isn't rather acceptable to region basements from the equation.

Citing the ongoing lodging crisis, it said successful a quality release, the borough volition proceed to let for dwellings successful basements, adjacent successful caller constructions, provided "flooding risks are reduced to a minimum."  

Borough Mayor Alan DeSousa, says basement usage for daycare centres and seniors' residences volition beryllium limited.

"If kids are successful the basement doing activities and h2o comes precise rapidly those kids are vulnerable," helium said.

Other boroughs person antithetic rules. 

Rosemont–La Petite-Patrie, is taking a tougher stance and is not allowing the operation of 100 per cent basement dwellings anyplace connected its territory, but done peculiar exemptions for large-scale projects that payment the assemblage and conscionable criteria ensuring resiliency.

Homeowners, however, volition beryllium allowed, nether definite conditions, to grow the surviving country of their location by processing an underground surviving space. Basement usage volition proceed to beryllium allowed for things similar garbage storage, laundry rooms, and parking areas.