Development of a Long Term Monitoring Network of Sensitive Clay Slopes in Québec in the Context of Climate Change

Abstract

The Government of Québec recently initiated the deployment of a vast groundwater pressures monitoring network in postglacial marine clays to document their variations in time and improve our understanding of the relationship between failure initiation and climate in clay slopes. This project aims at evaluating the impacts of climate change on clay-slope stability and how it can be integrated in landslide risk management to improve public safety. Hydrogeological data will be acquired at sites located throughout the Québec Province's post-glacial clay deposits to create a public georeferenced index of typical hydrogeological conditions. The project goes beyond the characterization of groundwater pressures and their variations in clay slopes. Indeed, slope deformation will be measured at several sites. Also, two sites in flat terrain will be instrumented in order to evaluate mechanical properties of clay layers in simple 1-D conditions and groundwater recharge. The unsaturated clay crust in slopes susceptible to superficial landslides will be characterized and instrumented. The current lifetime of the monitoring project has been set to a period of 25 years.

Hydrogeology of a complex Champlain Sea deposit (Quebec, Canada): implications for slope stability

“…Previous work has shown that pore pressures in the soil are highest during the Spring, due to increased precipitation and/or snowmelt-derived infiltration (Cloutier et al 2017). However, changing climatic conditions are likely to alter several key parameters used in the forecasting of landslide hazards, namely precipitation, the extent and thickness of snow cover, wind speed, and the number and timing of zero-degree days (Comenga et al 2013).…”

“…The Sainte-Anne-de-la-Pérade site presented here was selected to evaluate water infiltration and pore pressure variations. To ensure one-dimensional conditions for groundwater flow analysis, the site was located at a distance sufficiently remote (450 m) from the slope scarp near the river (e.g., a Type 2 site, Cloutier et al 2017; Figure 1). Interestingly, due to the complexity of the local stratigraphy and river morphology, the detailed analysis of the infiltration and groundwater flow shown below indicates that the 1-D hypothesis does not apply here.…”

“…The present study is part of a major inter-agency effort focused on understanding potential changes in climatic conditions, and the effects such changes could have on landslide activity in Quebec. As part of this effort, a series of instrumented sites representing various morphological conditions were established, and data from one such site is reported herein (Cloutier et al 2017).…”

Field performance of four vibrating-wire piezometer installation methods

“…In the province of Quebec, 89% of the population lives within the extent of the Champlain Sea formations, which were deposited by seawater invasion after the Wisconsin glaciation and are prone to landslides (Demers et al 2014). In response to the landslide risk posed by these formations, the Quebec Ministry of Transport (MTQ) has deployed an extensive network of vibrating-wire piezometers (VWP) to monitor spatial and temporal variation of pore pressures in clay slopes (Cloutier et al 2017). This type of piezometer provides a number of advantages over the traditional hydraulic piezometer design, very small amounts of liquid are required for measurement; measurement accuracy is very high; response times to changes in water pressure are very quick; and it is possible to transmit observed responses over long distances (McKenna, 1995).…”

Deep Hydraulically‐Active Fractures in Sensitive Clay Deposits: Implications for Groundwater Flow and Slope Stability

“…To determine the extent to which these classical conceptual models represent the groundwater flow dynamics in these hillslopes, an analysis of seasonal water level fluctuations was performed on data from a large network of multilevel vibrating-wire piezometers (VWP) in the St. Lawrence River Valley and Saguenay-Lac St-Jean Lowlands in Quebec, Canada (Cloutier et al, 2017). Cross-correlation of these time series was used to determine whether local groundwater flow systems were characterized by the slow, matrix-driven flow assumed in Lafleur and Lefebvre (1980), or whether the variations in hydraulic head could only be explained by rapid flow within a fracture network, as first proposed by Keller et al (1989).…”