(Montreal) Climate change could increase the frequency of weather events that cause landslides in Quebec, like the one that killed two people a week ago, warns a researcher who studies natural hazards.
Jacques Locat, professor emeritus at Laval University, says climate change models predict that southern Quebec will receive between 5 and 14% more rain by 2050.
According to his research, the increase in precipitation, coupled with the expected increase in extreme rainfall events, could increase the frequency of landslides.
“The impact of climate change, with regard to landslides, will mainly be linked to precipitation,” explained in an interview Mr. Locat, who is co-founder of the Laboratory for Studies on Natural Risks.
Last Saturday, torrential rains in the Saguenay–Lac-Saint-Jean region contributed to several landslides, including one that killed two people.
This landslide, Locat said, appears to have been caused by erosion along the Eternity River and saturation of the embankment above, both of which caused sandy materials to slide down onto the ground. clayey.
Quebec is at risk of having more “shallow landslides,” according to Locat, which typically involves soil conditions that are particularly susceptible to erosion and rapid waterlogging.
According to Mr. Locat, two factors lead to surface landslides: soil erosion at the bottom of the slopes — caused by water, but also human activity — which makes them steeper, and soil saturation at the crest of slopes, which causes materials to slide downhill.
“Climate change could have an effect on the frequency of floods, and/or their importance and perhaps an impact on surface landslides,” he argued.
Regions most at risk
About 40% of landslides in Quebec’s St. Lawrence River Valley — an area where they are particularly common in the province — are caused by erosion resulting from human activities, he said. Landslides also occur around Gatineau, in the Charlevoix region and on the Gaspé Peninsula.
All these regions are located on a clay plain left by a sea that disappeared about 10,000 years ago. This clay soil can become unstable and landslides are part of the natural evolution of this type of landscape, he said.
Last summer, more than 70 households were evacuated in La Baie, part of the city of Saguenay, after a landslide destroyed an empty house; the authorities feared further slides. In 1971, a landslide in this same region killed 31 people and led to the abandonment of the village of St-Jean-Vianney.
According to Mr. Locat, the deadliest landslide in Quebec history occurred in 1908 in Notre-Dame-de-la-Salette, about 40 kilometers northeast of Ottawa, and killed 33 people. However, the researcher, who studied the event for a 2017 paper, found that the landslide had occurred across the river from the city and triggered a kind of “tsunami” that had threw ice on the community and caused fatalities.
Research published by Natural Resources Canada in May 2021 showed that between 1771 and 2019, Quebec ranked second in Canada for the number of deadly landslides, with a total of 239. Only British Columbia had some. recorded more, with 356. Quebec was followed by Newfoundland and Labrador, with 103, and Alberta, where there were 73.
But Locat noted that Quebec may have a higher number of recorded landslides than other parts of the country due to its settlement patterns. About 80% of Quebec’s population lives in the clay plain where landslides occur, he said, adding that the province was settled earlier than other parts of Canada, providing Quebecers with an opportunity more widespread to register the phenomenon compared to other Canadians.