Rockfall hazards are fundamental problems for roadway safety in hilly areas. Monitoring rockfall activity along the 17 km long road from Chambon to La Grave is necessary to assess frequency, return period, and magnitude of rockfall events. According to historical inventory, more than 15 rockfall occurred between 1999 and 2020. Therefore, annual LiDAR measurements, with a point density of 40 to 189 points/m2, and more than 10’000 images from high-resolution cameras are used for detecting and evaluating rockfalls. Based on comparisons between 2020 and 2021, three rockfall sources totalling 200 m3 have been identified. Rock stability is assessed by analysing topography to identify potential rockfall sources using slope angle distribution (SAD) analysis and overhanging slopes from point clouds. Then, the trajectory from each identified source was simulated and verified using historical rockfall data. Thus, this combination of techniques better identifies and predicts deposited rockfall and impacts on infrastructures.
Slope movement processes like rockfalls (Varnes 1978) are common in mountainous areas, height rock walls have the capacity to generate large rockfalls that are developing talus at their toe on which the blocks rebound, fragmented and slide, stopping or not on it. Consequently, rockfall hazards can be high on these talus slopes. The risks for persons on roads and in houses that are built on these talus or located below these cliffs can be high (Volkwein et al. 2011).
Road access to La Grave is one road that connects Grenoble to Briançon in France. Along the side of the road is a cliff with a high slope, including several scree slopes. This area is constantly monitored for hazards as multiple hazards happened. So, this paper presents a case study to assess the sources of rockfalls and a statistical modelling of rockfall trajectories and an assessment of potentially impacted areas and infrastructures.
