STONE: a computer program for the three-dimensional simulation of rock-falls

Rock-fall poses a continuous hazard in mountain areas worldwide. Despite the fact that rock fall is a simple landslide type to model, only a few attempts have been made to establish rock-fall hazard and the associated risk at regional scales. We developed a three-dimensional simulation program that generates simple maps useful to assess rockfall hazard, using GIS technology to manipulate existing thematic information available in digital format. The program requires as input a digital terrain model, the location of rock-fall detachment areas, the dynamic friction coefficient used to simulate the loss of velocity during rolling, and the coefficients for normal and tangential energy restitution at the impact points. The program allows for the natural variability of the input data by using a random component approach. Raster outputs include the count of rock-fall trajectories, the maximum velocity and the maximum height computed at each grid cell. Vector outputs consist of the planar (two dimensional) and the three-dimensional trajectories of the rock falls. The program outputs proved to be consistent with the results of other rock-fall simulation programs, to be reliable for modelling rock-fall in three-dimensional geomorphological settings, and to help in the quantitative assessment of rock-fall hazard over large areas.