Long-term effects of deep-seated landslides on transportation infrastructure: a case study from the Swiss Jura Mountains

Deep-seated landslides (DSLs) involve large-scale deformation and likely affect transportation infrastructure. Movement rates are in general very slow (less than a metre per year) with acceleration periods controlled by external factors such as the seasonal fluctuation of groundwater pressure. Acceleration response may change from season to season depending on hydrogeological conditions, changes in slope geometry and degradation of geological materials. More localized landslide types are associated with and develop within DSLs, such as rock falls, topples and debris slides. Management of hazards related to DSLs requires first the assessment of geological, hydrogeological and geomechanical processes. This is the starting point for developing a management strategy. This paper presents the characterization of a deep-seated landslide located in the Swiss Jura Mountains, Les Buges landslide, where a railway line, a power line and an aqueduct of regional importance cross the slide, as well as a highly frequented hiking trail beneath the landslide toe. Slide kinematics is governed by the geology and hydrogeology of the slope, which can be subdivided into two dominant bodies. A management strategy is subsequently discussed for this DSL. Les Buges is a good example illustrating that hazards related to deep-seated landslides must be tackled first of all by means of the observational method.