19,000 homes at risk of landslides in Quebec

19,000 homes at risk of landslides in Quebec

and Philippe Langlois MISE À DAY

The inhabited areas of Quebec are increasingly vulnerable to landslides due to climate change. No less than 19,000 residences are under surveillance, as they are found in high-risk areas that have been listed by the government.

Map of residences most at risk
to landslides Note: To directly find your address, search using the magnifying glass on the map. Caption: Area most at risk Residence most at risk Landslide reported since January 2007 Methodology

The map and analysis of buildings located in areas most at risk of landslides were created from 'a combination of two separate files.

The first (red zones), produced by the Ministère des Transports (MTQ), locates the parts of the territory where the standards prescribed by the Government of Quebec must apply in relation to landslides. The determined areas are more vulnerable to ground movement due to several characteristics, including the nature of the ground or the elevation.

The second file includes all addresses in Quebec that are identified by a black dot. This is an official government data source. A point usually corresponds to the center of the building or the main entrance door. The Journal has highlighted all the points/addresses inside the areas most at risk of landslides.

The yellow points correspond to the landslides reported since January 2007. They come from the Ministry of Security public and are available as open data.

Caution:

*Even if it does not appear on the map, it is still possible that a building is in a higher risk area, and vice versa.

**The Journal has noted several inconsistencies between the official address data and the map generator used for this project. After verification, official sources are more precise as to the location of a building.

***This map has no legal value, the opinion of a professional is necessary to determine if your building is located in an area more at risk of landslides or not.

The important landslide that swept away a residence at the bottom of a cliff in the borough of La Baie, in Saguenay, on June 13, forced the evacuation of 76 houses in the same area. Unfortunately, some owners will never be able to return to their homes because the risks are too high.

To date, 41 municipalities manage sectors that are located in the heart of areas exposed to landslides. According to data compiled by Le Journal, no less than 19,000 residences and more than 1,000 commercial units are currently found in these areas across Quebec, not counting municipal infrastructure, institutional buildings and places resorts. 

These residences are mostly built on “sensitive” clay soils, prone to soil movement when disturbed. 

The government assures that these places are under surveillance and that preventive works are carried out.

Climate change 

These natural events, having consequences on Quebec's built heritage and the safety of populations, are set to grow more rapidly due to the climate crisis, say experts.

“Indeed, the vegetation changes, as does the soil,” explains Alain Bourque, director general of Ouranos, a consortium on regional climatology and adaptation to climate change. 

According to the Canadian Network education, fluvial erosion and increased water pressure in the ground “particularly during heavy rains or rapid snowmelt” can trigger subsidence.

“It means that a shift that should perhaps have taken place in 2085 could take place now. We can imagine that by 2100 there will be many more people who will have experienced landslides because the ground has become unstable. 

Top 10 cities with the most housing at risk of landslides

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Rank City units
1 Gatineau 5360
2 Shawinigan 2425
3 Saguenay 1895
4 Mascouche 827
5 Blainville 821
6 Three -Rivers 710
7 Chute-aux-Outardes 558
8 Alma 512
9 Sainte- Therese 512
10 Baie-Comeau 472

Source: Ministry of Transport and Ministry of Energy and Natural Resources of Quebec

Human intervention

This phenomenon is added to human activity, “such as excavation and construction work”, which usually acts as the main trigger or aggravating factor of landslides.  

“Everyone wanted to have beautiful views from the top of the embankments,” says professor emeritus Serge Leroueil. “At the time, we knew less about the risk. »

The geotechnical specialist, Mr. Leroueil believes that it “is credible” that climate change increases the risks. Increased rainfall can cause ground motions, he says, but he adds nuance; these are mostly “superficial”. 

Climate analyzed

The Ministry of Public Security, for its part, ensures that its analyzes and monitoring take now consider climate-related risks.

“The progress of research in the field of the impacts of climate change on certain types of landslides now makes it possible to take these parameters into account,” underlines Marie-Josée Montminy of the Ministère de la Sécurité publique.   

NUMBER OF PROPERTIES AT RISK OF SLIDES IN QUEBEC 

18,000 buildings*

19,000 residential units 

1000 commercial units  

  • A building can contain multiple units
  • The number of residences built in the constraint zone can change over time
  • Risk levels associated with landslides vary within the same stress zone. The probability of being affected by a landslide decreases as one moves away from an embankment.

Sources: Departments of Municipal Affairs and Housing, Public Safety, Natural Resources, and Transportation

Top 10 addresses with the most units at risk of landslides < table class="top10addresses" cellspacing="0" cellpadding="0" border="0">

Name Address units

< th>Description Chartwell Domaine Cascade 695, 7e rue de la Pointe
Shawinigan 265 Home for independent retirees Terrasse Chavoin 23, Rue de la Soeur-Jeanne-Marie-Chavoin
Gatineau 206 Accommodation Fontainebleau Sunrise Living House 50, Boulevard des Châteaux
Blainville 103 Home for independent retirees Résidence Le Crystal 4715, Boulevard de la Grande- South Bay
Saguenay 62 Home for independent retirees ELK Property Management Limited 45, Rue Charles-Albanel
Gatineau 60 Accommodation 40 Louis-Vadeboncoeur 40, Rue Louis-Vadeboncoeur
Saint- Charles-Borromée 36 Housing 400 Riel Housing Cooperative 400 Riel Boulevard
Gatineau 35 Housing Résidence Mont-Bleu 100, Boulevard du Mont-Bleu
Gatineau 35 Intermediate resource CHSLD Isidore-Gauthier 5731, Avenue du Pont Nord
Alma 30 Home for non-autonomous retirees (includes CHSLDs) My Home 18, Rue Hamel
Gatineau 26 Housing

Source: Ministry of Transport and Ministry of Energy and Natural Resources of Quebec BEWARE OF LANDSLIDES 

VERY COSTLY FOR THE STATE

For ten years, Quebec has spent $71 million under financial assistance programs for landslide victims and to carry out ground movement prevention work. “As part of the emergency financial assistance programs, a total amount of more than $32 million was paid to individuals, owners of rental properties and businesses in connection with ground movement files. “, relates the spokesperson for the Ministry of Public Security (MSP), Marie-Josée Montminy. In addition, 13 landslide prevention projects costing $39 million have been completed or will be completed by 2025. 

HUNDREDS OF INCIDENTS

For five years, an average of 182 landslides have been recorded each year, particularly in more densely populated regions. Reports are identified by the ministry as “possible threats to life or property”. Movements are occurring in particular outside the areas identified on the government map. A total of 369 individual files have been opened over the past 10 years under financial assistance programs for homeowners. An average of $87,000 per file was paid. Public infrastructure such as roads are also victims of these subsidence. 

 

INCREASED MONITORING

The Ministry of Public Security ensures that a risk analysis for the built environment is carried out by its experts in order to “ensure safe land development”. The government determines the vulnerable zones which are then disseminated to the municipal environment through mapping. “This makes it possible to identify situations of concern where mitigation interventions are deemed necessary. Depending on the situation, financial support may be offered to the municipality and the citizens concerned to correct the situation,” explains MSP spokesperson Marie-Josée Montminy. Municipalities have an obligation to integrate it into their development plan. Quebec may request modifications for reasons of public safety. 

NO LOSS OF VALUE…FOR NOW

In 2018, Altus Group provided a study in Quebec City on the market value of La Baie properties located within landslide stress zones. Conclusion: there was no significant impact on the selling price. The panoramic view and the quality of the materials are the winning elements. However, in several cases, the certificate of location did not include clear information on the inclusion of residences in the zone, just like the real estate advertisements which emphasized the view. “If market participants…disregard the possibility of slippage occurring, the impact on prices may be skewed,” the report says.

< p>VULNERABLE PEOPLE 

According to the list of buildings that are located in areas of constraint due to the risk of landslides, the main buildings with high density are residences for the elderly and housing cooperatives. For example, the Chartwell Domaine Cascade residence in Shawinigan has 265 units according to data from the Ministry of Energy and is in a red zone. In Alma, the CHSLD Isidore-Gauthier is also found in one of the risk areas. Vacation resorts, such as the Chalets sur le Fjord in L'Anse-Saint-Jean, are also found in these areas, as well as institutional buildings such as schools and daycare services.

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CREDITS

Writing: Nicolas Lachance

Research, data compilation: Philippe Langlois, Bureau of investigation

Design, Integration, data visualization: Cécilia Defer

Direction, editorial creation: Charles Trahan< /p>