Sainte-Marthe is built on a lake bed. How did that happen?

This week's flooding has raised questions about how municipalities have been allowed to develop so close to the water or, in the case of Quebec's Sainte-Marthe-sur-le-Lac, on the lake bed itself.

This week's flooding forces a rethink about Quebec's storied connection to water

Flooded streets are seen from an aerial view in St-Marthe-sur-le-Lac, Que.
Homes and cars in Sainte-Marthe-sur-le-Lac, Que., were flooded Saturday when the dike protecting it from the Lake of Two Mountains was breached. (Paul Chiasson/Canadian Press)

Like many of the suburbs that dot Montreal's North Shore, Sainte-Marthe-sur-le-Lac was home only to summer cottages not so long ago.

The area routinely flooded when the Lake of Two Mountains swelled in the spring.

Then a dike — a grassy knoll packed with gravel and earth — was built in 1980.

With the dike's construction, the municipality grew, as it allowed more people to build year-round homes closer to the lake.

The town's logo even pays homage to the dike, represented as a swerving blue line separating "firm ground" from the Lake of Two Mountains.

With low taxes, waterfront views and its proximity to the city, Sainte-Marthe has grown rapidly, its population more than doubling from 8,300 in 1995 to 18,000 in 2016.

The lake was routinely the site of flooding in the 1970s, before the dike was constructed. (Radio-Canada Archives)

But since the dike burst Saturday — forcing thousands from their homes — there have been questions about a lack of government oversight and whether authorities should have acted more quickly in improving the structure.

The dike was inspected after the historic flooding two years ago, and plans were in place to repair it this fall.

But the disastrous breach has prompted broader concerns about how municipalities in the Montreal area have allowed their waterfronts to be developed.

'There is a nonsense there'

In Sainte-Marthe, the construction of the dike allowed much of the town to be built, effectively, on the actual lake bed.

"I think the focus and the question is, what kind of circumstances over the last several decades led to large urban areas completely [dependent] on a system of dikes," François Brissette, a hydrologist and professor at the École de Technologie Supérieure, told CBC Montreal's Daybreak.

"There is a nonsense there. And that's the key problem that should be looked at."

Brissette said proper bylaws and regulations would have prevented people from building homes on flood plains.

"There would have never been a need for those dikes, and there would have never been dike failures, and there would have never been all the problems we are witnessing now," he said.

The lure of property taxes

Municipalities' dependence on property tax revenues has driven the expansion onto their waterfronts.

"For them, the house with the nice view of the river brings a lot of taxes. And if they want to develop a new library or whatever plan they have, they need money," said Pascale Biron, a professor of geography, planning and environment at Concordia University.

Biron said decisions about zoning and flooding mitigation measures should be made at the provincial level, taking into account the full impact of those decisions on the watershed.

Sainte-Marthe-sur-le-Lac was once limited to summer cottages but it has grown considerably in recent years, like much of the region north of Montreal. (CBC)

In the spring, the rain and snowmelt has to go somewhere, she explained.

"You need an overall approach," she said.

"If you put levees and dikes everywhere, the risk might be that water is routed faster downstream."

An elderly couple returned to their home in Sainte-Marthe-sur-le-Lac this week to retrieve some belongings. But with flood waters still high, they weren't allowed to stay. (Ivanoh Demers/Radio-Canada)

A river needs to breathe

Experts point to European countries, like the Netherlands, where authorities have stopped building up dikes and, instead, moved them back, to allow the river to "breathe" during the spring runoff.

Martine Chatelain, a spokesperson for the environmental group Eau Secours, said although Quebecers have a strong connection to the water, it may be time to rethink the assumption we should live right next to it.

"It's beautiful, that's true," said Chatelain, who grew up on a lake in the Laurentians. "But it doesn't always make sense."

When asked Wednesday whether the government plans to allow the reconstruction of the dike in Sainte-Marthe-sur-le-Lac, Quebec Premier François Legault said no decision has yet been made.

"Do we have to build all of it, a part of it? It will have to be studied," he said.

Legault said he wants to have a broader look at what's defined as a flood zone.

"It's not an easy process to redefine a flood zone, but I think it's important that we do so.

"With what happened in 2017 and this year, it's clear that we're in for a new impact with what's happening every spring."

For some in Sainte-Marthe-sur-le-Lac, the cleanup has already begun. (Alison Northcott/CBC)


Benjamin Shingler is a senior writer based in Montreal, covering climate change, health and social issues. He previously worked at The Canadian Press and the New Brunswick Telegraph-Journal.

With files from Alison Northcott and CBC Montreal's Daybreak