technical tour
A field trip is offered to illustrate various aspects of the problem of highly retrograde landslides in sensitive clays, several of which will have been discussed during the workshop. This tour will allow participants to discover four sites located within the boundaries of the Champlain Sea. The sites included in this tour have been affected to varying degrees by issues related to landslides in sensitive clays, including some very recent cases that have led to changes in the initial program. In addition to the sites included in the tour, additional information will be provided throughout the tour in the form of audio clip for other cases located along the road.
Date of field trip: Thursday, Octobre 2, 2025
Meeting place: Musée de la Civilisation de Québec
Departure from and return to Quebec City: 7:30 a.m. - 5 p.m.
Tour cost: 150$ + taxes (Price in Canadian dollars (CAD). Taxes (9.975% QST + 5% GST) may apply)
Registration opens on April 1, when you register for the conference (see Registration section). Hurry, places are limited. Bring appropriate clothing and footwear for the time of year to enjoy the visit (raincoat, warm clothes, walking shoes, etc.), as the weather can be changeable.
1st stop – Saint-Thuribe
The first stop, originally planned at a site of a deep rotational landslide that occurred in April 2022 in Saint-Alban, was replaced by a very recent case, where a strongly retrogressive landslide occurred on July 15, 2025, in the neighboring village of Saint-Thuribe, cutting off an intermunicipal collector road and sweeping away a residence. Covering an area of approximately 3 hectares, this landslide is a combined case of “flowslide and spread.” This site will allow us to observe the characteristics specific to these two failure mechanisms, as described by Therrien et al. during the workshop. This case also illustrates the effects of debris on a “C” type watercourse, as described by Turmel et al. during the workshop. The presence of a system of subvertical cracks visible in the walls of the landslide will allow for discussion of their origin and effects, particularly in relation to the topics addressed by Lemieux et al. and Routhier et al. during the workshop. Finally, this recent case will provide an opportunity to discuss how emergencies are handled when such events occur in Quebec, a topic that will also be addressed during the last stop of the day in Sainte-Monique.
2nd stop – Sainte-Geneviève-de-Batiscan
The second stop is located on Rue des Brumes, in Sainte-Geneviève-de-Batiscan. At this location, preventive excavation and rockfill work were carried out on the opposite bank of the Batiscan River. The geotechnical properties of the clay, the presence of active erosion at the foot of the slope, and the specific topographical conditions predisposed the site to a potential second-generation highly retrogressive landslide. A numerical simulation study of debris propagation showed that residents of Rue des Brumes, located on the alluvial plain opposite the slope under study, could be threatened, particularly by a potential tsunami. This stop will provide an opportunity to discuss the work that has been done to protect residents and the various analyses that have been carried out.
In addition, large-scale preventive stabilization work is currently under study to protect the heart of the village. Rockfill work on the Veillet River, located near the site, is expected to cover approximately 1.5 km long and is the subject of a multidisciplinary partnership to harmonize the work with the natural habitat.
3rd stop – Nicolet
The third stop is in Nicolet, where a flowslide, followed by a spread landslide phase (composite landslide), occurred on November 12, 1955. This landslide had major repercussions, as it occurred in the downtown area. It swept away a school, part of the Episcopal building, a gas station and three houses, and claimed the lives of 3 people. The landslide occurred while rockfill work was underway to protect the riverbank from erosion. Although the cathedral was spared by the landslide, it had to be demolished because its foundations had been weakened. However, some elements of the cathedral were salvaged, including the richly crafted vault, which was used in the construction of what is now the Centre des arts populaires. Dinner will be held inside this building and will provide an opportunity to discuss the historical aspects of this movement.
4th stop – Sainte-Monique-de-Nicolet
The last stop will be in Sainte-Monique-de-Nicolet, replacing the site originally planned in Pierreville. A small 1.5-hectare flowslide began on May 20 at this location, sweeping away a residence and two secondary buildings and cutting off an intermunicipal collector road. The landslide, which has two distinct stepped failure surfaces, began along a small “D” type ravine (as described by Turmel et al. during the workshop). This site also allows us to observe the different effect that the debris had when it reached the Nicolet River (“A” type), compared to the case of the first stop. Furthermore, a comparison of lidar surveys from 2013, 2022, and 2024 revealed that the stream bank, at the point where the phenomenon began, had eroded by approximately 2.4 meters during this period, reaching a height of 10 meters, which is reminiscent of the Gjerdrum case in Norway in December 2020. This site therefore highlights the value of new tools, such as lidar surveys, for monitoring the evolution of areas potentially exposed to highly retrogressive landslides, as illustrated by several presentations at the workshop. The issue of emergency response will also be addressed.