Forecasting the long-term activity of deep-seated landslides via groundwater flow and slope stability modelling

Large (deep-seated) landslides present complex geometries,
rock/soil properties, and kinematical behavior. Complex
geometries are due to the presence of several sliding zones, while
complex properties typically result from the dilation, compression,
or fatigue of geologic materials. Kinematical behavior is often
episodic, with periods of stability followed by periods of enhanced
slope movements owing to shear strength reduction in response to
groundwater pressure changes. These mechanisms complicate our
capacity in forecasting the long-term activity and thus, the choice
of a strategy for hazard management. This technical note introduces
a method for predicting the long-term activity of deepseated
landslides based on one-way coupled hydromechanical
numerical modelling. The method is applied to analyse the longterm
stability of a deep-seated compound slide in the Swiss Jura
Mountains. Results indicate that, under natural groundwater pressure
changes, the analysed compound slide will continue to move
in an episodic fashion in response to groundwater levels in the
slope, without developing velocities greater than several centimeters
per year. This example demonstrates how one-way coupled
hydromechanical modelling constrained by field data is a reliable
tool for assessing the long-term activity of deep-seated landslides
and helping the management of associated hazards.