Rockfall Activity Index (RAI): A lidar-derived, morphology-based method for hazard assessment

•The Rockfall Activity Index (RAI) for assessing rockfall hazards is introduced.•The RAI is a morphology-based approach that utilizes high-resolution point clouds.•Field assessment indicates that the RAI matches the observed performance of slopes.

In this paper, we introduce the Rockfall Activity Index (RAI), a point cloud-derived, high-resolution, morphology-based approach for assessing rockfall hazards. With the RAI methodology, rockfall hazards are evaluated in a two-step procedure. First, morphological indices (local slope and roughness) are used to classify mass wasting processes acting on a rock-slope. These classifications are then used with estimated instability rates to map rockfall activity across an entire slope face. The rockfall hazard is quantified as the estimated annual kinetic energy produced by rockfall along 1-m length segments of a slope face. Field assessment of the RAI method at multiple study sites indicates that the morphology-derived classification and hazard assessment routines provide results that closely match the observed behavior and performance of rock slopes.