Flood map revision removes hundreds of West Island properties from high-risk zone

In total, 17 cities and municipalities — primarily in the greater Montreal area and further west of the island — are now no longer considered in a flood zone, according to a new draft of the government map that indicates flood plains in the province.

Mayors and experts say Quebec government rushed out early versions of the map, which included errors

Beaconsfield Mayor George Bourelle said Tuesday that the city is examining the revised draft. (Simon Nakonechny/CBC)

The Quebec government has revised a flood map that was going to ban construction work on hundreds of properties in the West Island.

In total, 17 cities and municipalities — primarily in the greater Montreal area and further west of the island — are now no longer considered in a flood zone, according to a new draft of the government map that indicates flood plains in the province.

The map was initially released in June, as part of the province's response to wide-scale spring flooding. It was first revised in July. The latest draft was released Monday.

Earlier versions of the map had labelled large parts of the West Island as a "special intervention zone," where both reconstruction and new construction were put on hold.

But in its August incarnation, swaths of Montreal, Pierrefonds, Roxboro, Beaconsfield, Dorval, L'Île-Dorval, Pointe-Claire, Notre-Dame-de-l'Île Perrot, Pincourt and Châteauguay were declared safe to build on.

Smaller portions of Senneville, Beauharnois, Léry, Sainte-Anne-de-Bellevue, Vaudreuil-Dorion, Saint-Étienne-de-Beauharnois and Saint-Louis-de-Gonzague were also taken out of the special intervention zone.

Flood maps 'puzzling,' says river management expert 

Municipal Affairs Minister Andrée Laforest has said the province-wide flood map was created by including areas flooded in 2017 and 2019 and by using historical data of identify zero-to-20-year flood zones — where the chance of flooding each year is greater than five per cent.

Any homeowner whose property sustained more than 50 per cent flood damage in 2017 or 2019, as well as homes designated as being at high risk of flooding ended up in the "special intervention zone."

But after it was first released, the map attracted criticism from mayors who found large portions of their municipality marked as a special intervention zone.

Vaudreuil-Dorion Mayor Guy Pilon accused the government of rushing to release the map, which he said contained errors caused by clouds obscuring satellite imagery.  

An earlier version of the flood map, seen here, placed Pointe-Claire, Baie d'Urfé, Dorval and Beaconsfield in a high-risk zone. None of the municipalities flooded in 2017 or 2019. (Quebec Ministry of Municipal Affairs and Housing)

Moreover, Pointe-Claire, Baie D'Urfé, Dorval and Beaconsfield all found themselves labelled as high-risk flood zones, even though they weren't affected by flooding this spring, or in 2017.

"Most people — I have to say, myself included — are a bit puzzled because it's not a very complicated thing to do, in the sense that water was either there [or it wasn't]," said Pascale Biron, a geography professor at Concordia University who specializes in river management

She agreed that clouds were to blame for some of the problems, as was the poor image resolution of some of the satellite imagery. But the more fundamental issue, she said, was a flawed process on the part of the government. 

"The problem is really that they created this map rather quickly," she said.

The government, she added, did things "backwards" by only consulting with municipalities after the map was created, and not before.

West Island mayor relieved

Beaconsfield Mayor George Bourelle said he is "very pleased" with the latest revision. "It looks like we've been completely removed from the flood-zone map."

He said that the province's decision to initially include 152 of Beaconsfield's waterfront properties in the flood zone wasn't supported by data.

"Initially, they wanted to put a whole blanket on areas they suspected would be flooded," he said.

The municipality of Pierrefonds-Roxboro was one of the harder-hit areas by the spring floods of 2017. Parts of the borough were removed from the flood map. (CBC Archives)

Bourelle said Beaconsfield has always respected the zero-to-20-year flood zone restrictions. He said he was able to prove that in a meeting with Laforest last Friday.

Municipalities have until August 19 to signal any further adjustments that need to be made on the flood maps.

The revision is a joint effort between Quebec's Ministry of Municipal Affairs and the Environment Ministry.

With files from Elysha Enos and Verity Stevenson


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

Become a CBC Member

Join the conversation  Create account

Already have an account?