As Quebec becomes wetter from climate change, landslide risks increase
MONTREAL — Climate change is likely to increase the frequency of weather events that trigger landslides in Quebec, such as the one that killed two people a week ago, said a researcher who studies natural hazards.
Jacques Locat, professor emeritus at Université Laval, says climate change models predict that southern Quebec will receive between 5 and 14 percent more rainfall by 2050. events, will make the frequency of landslides in the province more likely.
“The impact of climate change on landslides in Quebec will primarily be related to precipitation,” Locat, co-founder of a research lab at the university that studies natural hazards, said in a recent interview.
Heavy rainfall in Quebec’s Saguenay-Lac-St-Jean region on Saturday contributed to several landslides, including one that led to the deaths of two people.
That landslide, Locat said, appears to have been caused by erosion along the Éternité River and saturation of the levee above the river, both of which caused sandy material on top of the clay soil to slide down.
Quebec is at risk of experiencing more “shallow landslides,” Locat said, which are generally accompanied by soil conditions that are particularly prone to erosion and become quickly saturated with water.
Locat said two factors lead to superficial landslides: soil erosion at the bottom of slopes — caused by water but also human activity — which makes them steeper, and soil saturation at the top of slopes, which causes material to slide down .
“Erosion is the cause of many landslides along watercourses and so climate change may have an effect on the frequency and significance of water level rises and perhaps have an impact on surface landslides,” Locat said.
About 40 percent of landslides in Quebec’s St. Lawrence River valley — a region where they are especially common in the province — are caused by erosion that results from human activities, he said. Landslides also occur around Gatineau, Que., near Ottawa; in the Charlevoix region, northeast of Quebec City; and the Gaspé Peninsula.
All those regions lie on a clay plain created by a sea that disappeared about 10,000 years ago. That clay soil can become unstable, and landslides are part of the natural evolution of that kind of landscape, he said.
Last summer, more than 70 households were evacuated in La Baie, Que., part of the city of Saguenay, after a landslide destroyed a vacant home, and officials feared further slides. In 1971, a landslide in another part of that town killed 31 people and the commune of St-Jean-Vianney was abandoned.
Locat said what is likely the deadliest landslide in Quebec history occurred in 1908 in Notre-Dame-de-la-Salette, Que., about 25 miles northeast of Ottawa, and killed 33 people. However, Locat, who studied the event for a 2017 paper, found that the landslide occurred across the river from town and created a kind of “tsunami” that projected ice onto the community, causing death.
Research published by Natural Resources Canada in May 2021 showed that Quebec had the country’s second highest number of fatal landslides between 1771 and 2019: 239. Only British Columbia had more, with 356. Quebec was followed by Newfoundland and Labrador, who had experienced 103, and Alberta, where there were 73.
But Locat said Quebec may have a higher number of recorded landslides than other parts of the country because of its settlement patterns. About 80 percent of Quebec’s population lives on the clay plain where landslides occur, he said, adding that the province was settled earlier than other parts of Canada, giving Quebecers more opportunity to capture the phenomenon compared to other Canadians.
This report from The Canadian Press was first published on July 7, 2023.
