Danielle Maltais

Ph.D., Emeritus Professor

Department of Human and Social Science, Université du Québec à Chicoutimi (UQAC), Saguenay, Québec, Canada

During and after a landslide: it's not just clay that suffers consequences, it's people too

On the evening of May 4, 1971, the population of the municipality of Saint-Jean-Vianney (Saguenay–Lac-Saint-Jean) fell victim to a severe and deadly landslide that engulfed 41 houses within minutes, creating a massive chasm and causing the deaths of 31 people of all ages. This article presents the results of a qualitative study conducted 29 years after the disaster, involving 42 adults interviewed in a semi-structured format. The participants in the study recalled the events that affected them the most, the emotions they experienced, and the consequences they faced in the months and years following the landslide. The findings show that, regardless of their level of exposure, all respondents were deeply affected by what they had experienced and felt that the event had profoundly disrupted many aspects of their lives.

Serge Leroueil

Ph.D., Emeritus Professor

Department of Civil and Water engineering , Université Laval, Quebec, Canada

Landslides in sensitive clays from southern Québec and Ontario – A Review

Over the last 20 years or so, numerous landslides, mainly flowslides and spreads from the provinces of Québec and Ontario, have been investigated in detail in collaborative projects between the Québec ministère de la Sécurite 
publique, ministère des Transports et de la Mobilite durable and Université Laval, Québec. These studies have recently been synthesized in two papers, one on flowslides and one on spreads. The aim of the present study is to 
examine the similarities and the differences between the factors characterizing each group of landslides, the ultimate objective (not reached yet) being to determine which type of landslide could occur at a given location and what would be its characteristics.

Jean-Sébastien L'Heureux

Ph.D, Head of Natural Hazards department

Norwegian Geotechnical Institute (NGI), Trondheim office, Norway

The impact of mitigation work in quick clay zones – An example from Skjelstadmark, Norway

Quick clay landslides pose significant threats to human lives, infrastructure, and the environment. This paper summarizes nearly three decades of mitigation work in the Skjelstadmark region, where extensive measures were implemented to reduce landslide risk along approximately 28 km of river channels and tributaries. The mitigation strategy combined erosion control, slope relief, and counter fills, resulting in a substantial decrease in sediment transport and landslide activity. Environmental benefits included improved water quality and enhanced fish habitats. Socio-economic benefits were also significant, safeguarding lives, protecting infrastructure, and preserving agricultural lands. The cost-benefit analysis demonstrates the economic viability of these measures, highlighting the importance of proactive risk management. This study provides valuable insights into effective mitigation strategies for quick clay landslides, emphasizing the need for continued monitoring and maintenance to ensure long term effectiveness.

Dominique Turmel

Ph.D., Professionnal engineer

Direction de la géotechnique et de la géologie, Ministere des Transports et de la Mobilité durable, Québec, Canada

Landslide dams and debris in sensitive clays of eastern Canada: review of characteristics and consequences

Highly retrogressive landslides as well as rotational landslides are of common occurrence in Quebec’s post-glacial sensitive clay deposits. Due to their scale, debris from these landslides often partially or totally obstruct the watercourses along which they occur, leading to significant water retention upstream. Beyond the immediate hazards posed by the sudden release of these water masses, the resulting temporary dams cause long-term disruptions to the natural environment, sometimes lasting for decades. This paper examines several cases of landslide-induced dams in Quebec, highlighting their economical, environmental and societal impacts and exploring the various ways, sometimes catastrophic, but generally gradual, in which water flow was eventually restored. Examples of remedial work are also presented, and when this is required.