In mountainous areas, rockfalls represent a major threat to human safety, public infrastructures and economic assets. Accurate mapping and qualification of risk areas are required so that public authorities can make secure and efficient decisions regarding urban planning. In France, Risk Prevention Plans (PPR) are standard documents that determine risk areas and building authorisations for ten-year periods. During the PPR revision of the town of Veyrier-du-Lac (France), we implemented a new methodology based on geomatics for rockfall risk assessment. Analysis of airborne laser scanning data, field data, 2D and 3D rockfall simulations was performed with geographic information system to accurately map hazard areas. The use of LiDAR data and algorithms allowed a refined delineation of risk maps with quantification of forest protection effect in
a complex environment. The coordination of information in a GIS improved the interactions between experts and decision makers.