Investigating the Impact of Climate Change on Landslide activity in the French Alps

The evolution of future rainfall regime (intensity, frequency, season) induced by climate change is likely to change the intensity and frequency of hydro-meteorological induced hazards. Several studies already suggest that the frequency of landslide occurrence should increase with climate change. In this context, the quantification of the local evolution of the rainfall triggering conditions constitutes a key step.

In this study, we detect and analyse landslide-prone rainfall events in an ensemble of 15 climate model simulations dynamical downscaled and bias-corrected at a 8km resolution and quantify their changes over the period 2006-2100. Three greenhouse gas emission scenarios (or Representative Concentration Pathways) are analysed: RCP2.6, RCP4.5, and RCP8.5. A statistical analysis is conducted to identify predominant trends across models, applied to the 23 mountainous massifs of the French Alps at different altitudes.

Our results highlight contrasted evolutions depending on the massif, altitude, season and scenario. In the northern and western Alpine massifs, our projections suggest a significant increase of the annual frequency of landslide-prone events, which is further pronounced under high GHG emission scenarios. These changes are also found for the southern, with a lesser magnitude, however. The extreme trends are also significantly increasing. This is particularly true for the Northern massifs and for high altitudes. The cumulative rainfall associated with the landslide-prone events clearly shows some differences between North and South of the Alps, with a higher increase of cumulative rainfall for extreme events in the South than in the North. These future evolutions also exhibit a clear seasonal dependence, with more pronounced changes in winter and spring. Our findings provide a scientific basis for guiding adaptation strategies in mountainous regions.