Montreal needs to build greener, smarter to face the coming floods, experts say

Another week, another storm rains down on Montreal. A month's worth of rain pounded the city in a torrential downpour Thursday afternoon.  Homes were flooded, sections of major highways were closed, sewers overflowed and hundreds of thousands of Montrealers lost power. 

Days after the floodwaters have begun to recede, Montrealers are still cleaning up the mess. But as climate change promises more floods and extreme weather events that will erode Quebec's infrastructure, climate scientists and sustainability researchers warn Montreal needs to move fast to adapt and reinforce its buildings, bridges, sewers and roads — before the next storms strike.

"I have never seen this kind of rainfall except for when I was in the monsoon area," said  Philippe Gachon, a professor of hydroclimatology at L'Université du Québec à Montréal (UQAM). 

Gachon had predicted more extreme, higher-intensity downpours, but even he was shocked by just how much rain fell on the city in a short time.

He says Montreal is increasingly vulnerable to flooding, and researchers from different disciplines have to work with engineers and policymakers to better prepare the province as a whole for that reality. The group he heads, Réseau Inondations InterSectoriel du Québec (RIISQ), works toward that goal. 

Riding out the storm

On Friday, city of Montreal spokesperson Philippe Sabourin said the city is taking action in different forms. On top of plans to more than halve greenhouse gas emissions — a major driver of climate change — by 2030, the city is also taking more immediate steps to mitigate the damage caused by flooding.

The city is building three new underwater reservoirs to help drain heavy rainfall into water treatment plants without overflowing, said Sabourin. At the same time, he said the city is building more greenspaces, which naturally absorb excess rainfall instead of draining the water directly into neighbourhood sewers.

According to Dominique Ollivier, chair of the city of Montreal's executive committee and councillor for the borough of Rosemont–La Petite-Patrie, the city's infrastructure — much of which was built in the 1960s — urgently needs reinforcement.

"We are investing more than half a billion dollars a year to make our streets more resilient, changing the pipes, planting trees and building overhangs to retain water," said Ollivier.

WATCH | Décarie Expressway flooded again 36 years later:

Two massive storms left the Décarie Expressway under water, almost exactly 36 years apart

1 year ago

Duration 1:29

On July 14,1987, 102.2 mm of rain drenched the city, flooding the city's arterial highway. The improvements made to the expressway since have certainly helped, but they're not enough to prevent significant flooding when the city is hit by major storms.

Louis-André Bertrand, spokesperson for Quebec's Transport Ministry, said the ministry is investing $535 million over the next decade to adapt the province's roadways and reduce the impact of erosion.

Building bridges higher and adding rocks to coastal roads — especially along the St. Lawrence River — are some ways of mitigating damage, said Bertrand.

Building away from the water

Gonzalo Lizarralde, professor of architecture at Université de Montréal, knows full well the havoc flooding can wreak on a city's homes and buildings. On Thursday, the rainwater flooded his office at the university.

He says any plan to build or adapt buildings to cope with extreme weather vulnerabilities needs to be weighed against the carbon footprint the action would incur.

Meanwhile, the tendency in Quebec to build around rivers and lakes means people who live nearby repeatedly have their homes filled with gushing waters, just as in the floods of 2019 and 2017, said Lizarralde, who is also a researcher at RIISQ.

"In an ideal world we wouldn't build in flood-prone areas," he said.

For people at greatest risk of flooding, adaptation may mean relocating away from flood-prone areas, says Lizarralde. At the same time, he says building new homes for people away from flood zones might produce more emissions than staying put. 

As for how our buildings are powered, Lizarralde says too many are reliant on single systems for their power, a dependance that leaves people at risk of losing electricity when a storm hits.

The cost of short-term fixes

Alexandra Lesnikowski, assistant professor in the department of geography, planning and environment at Concordia University, says there is no quick and easy fix.

"There's no kind of silver bullet to help us tackle the issue of flooding," said Lesnikowski, who  also heads the Concordia Climate Change Adaptation Research Lab.

She says municipalities need to update aging infrastructure and reflect on how our communities can evolve, changes that could be enormously expensive for Canadian cities.

However, Lesnikowski says the price of more reactive measures in responding to chronic stressors like rainfall is even more expensive, a price tag of about $2 billion a year over the next few decades.

"Proactively adapting saves us huge amounts of money long term, as opposed to just continuing to react to these extreme events when they happen," said Lesnikowski.

Ollivier agrees, and she is calling on more funding from the Quebec government to make the transition.

"There should be an investment of $2 billion a year for the next 20 years," said Ollivier.

"What you have to understand is that every time we have an event like that we have to work in an emergency and that costs a lot more than if we can plan all the work that needs to be done over the next 10 years," said Ollivier.