©Krzysztof Kowalik

Highlights

• Integrative approach to infer the evolution of avalanche risk and its drivers.
• Socio-economic factors play an important role in the evolution of risk.
• Incomplete reforestation of avalanche paths following land abandonment does not reduce the risk.
• Avalanche risk increased when urban areas became more exposed and vulnerable.

Abstract

Changes in mountain landscape can affect avalanche activity, causing changes in risk, potentially enhanced by a transition of the socio-environmental system and its underlying dynamics. Thus, integrative approaches combining biophysical and social sciences are required to assess changes in risk in all its dimensions. This study proposes a holistic methodology combining land cover change detection using advanced image processing techniques, geohistorical investigations and qualitative modelling of risk changes in order to infer the evolution of avalanche risk and its drivers in the upper Maurienne (French Alps) from 1860 to 2017. Results show that a continuous increase of forested areas associated with the retraction of agro-pastoral zones followed a period of land abandonment and depopulation. However, reforestation within avalanche paths remains largely incomplete and mostly absent in the majority of release areas, making a decrease in avalanche occurrence and propagation unlikely. This, combined with marked urban sprawl partially concentrated in avalanche prone areas, locally increased the exposure of residential settlements to avalanches. Hence, even if new defense structures have been set up, our analysis indicates that avalanche risk in the upper Maurienne increased through the study period. Even if local specificity related to physical dissimilarities and/or distinguished socio-economic trends always exist, our results may be valid for many high alpine valleys. Our approach is also transferable to other natural hazards, notably in wider mountain environments, as a contribution to the elaboration of effective adaptation strategies in a context of increasing risks related to combined climate change and socio-economic transitions.