Towards a novel quantitative approach for rockfallhazard assessment[Vers une nouvelle approche quantitative pour l’évaluation de l’aléa de chute de blocs]

Rockfall hazard assessment constitutes a major challenge for mountainous territories. Climate change and evolution of urbanisation have been deeply modifying our relationship with rockfall hazard and have increased significantly the number of stakes exposed. A precise quantification of this hazard is thus necessary in order to ensure an appropriate risk management. However, the complexity of the phenomenon and the multiplicity of real parameters make the establishment of such quantification particularly delicate. Herein, we introduce an original quantitative approach based on a probabilistic framework enabling to precisely quantify the resulting hazard by combining several intermediate probabilities. A methodological application in an operational context is proposed to demonstrate its potential use. Hypothesis, approximation criteria, and effects due to data are discussed and put in perspective with current practices. We also illustrate the approach with two examples, one of which is applied to the Saint-Eynard mountain in the French Alps.