New maps would officially make part of Sainte-Marthe a flood zone

A new set of flood maps will increase the number of homes located in the flood zone in Sainte-Marthe-sur-le-Lac, if they are approved.

When water from the Lake of Two Mountains breached a dike in the municipality northwest of Montreal late last month, 800 homes flooded. But only two of those homes were actually located in the flood zone defined by current maps.

On the new maps, drafted by experts with the Montreal Metropolitan Community (CMM), up to 1,500 homes in the southern part of the town would be part of the flood zone — many of which were evacuated when this year's flooding began.

The experts were recently convened on an emergency basis to come up with new maps for the municipalities that border the Lake of Two Mountains and the Des Prairies and Mille Îles rivers.

They decided the revamped maps won't consider dikes to be a form of protection, which would change the size of flood zones in towns along those waterways.

"The fact that the dike [in Sainte-Marthe-sur-le-Lac] gave way means we have to be careful," said engineer Pierre Dupuis.

The new maps will break down the threat of flooding within a flood zone, categorizing areas as low, moderate or high risk.

In Sainte-Marthe-sur-le-Lac, the changes mean the flood maps will look much like they did in the 1970s, before the dike was built. The official flood zone shrunk after the dike's construction.

'It makes no sense,' mayor says

Mayor Sonia Paulus said if those changes are made, it will be "dramatic" for the residents of her community.

She said the dike has been there for 40 years, and until now, it has protected residents.

"If we put all those people in a flood zone overnight, just consider their mortgage renewal, it won't go well, the value of the property will decrease," she said.

"I'm thinking of all the people who will have to move.... I can't uproot them. Where do you want me to send them? We don't have enough land to keep them here. They will have to move."

"It makes no sense."

Denis Martin, who heads the regional county municipality of Deux-Montagnes, which includes Sainte-Marthe-sur-le-Lac, said he understands Paulus's frustration.

"But we can't deny there's a risk. We saw the result two weeks ago. We have to acknowledge there is a risk, even if there's a dike," he said.

He added, however, that the fact there is a risk doesn't mean residents won't be insured and can't keep living there, because the risk is small.

Members of the CMM will vote on whether to approve the maps June 20. The province will then have 60 days to adopt them.