Classical rockfall simulations codes could be highly improved by defining models of the interactions between the falling rocks and the natural environment that integrate the variability associated with these interactions. Probabilistic models of the rebound of the rock on the soil and of the interaction of the rock with standing trees were developed. The probabilistic rebound model is based on the statistical analysis of numerical simulations of the impact of a rock on a soil using the Discrete Element Method. The procedure for the integration of the effect of forest is based on the probabilistic analysis of results from field experiments. The models allow the probabilistic calculation of the kinematics of the falling rock after interaction depending on the kinematics before interaction using a reduced number of easily identifiable field parameters. These models have been integrated into the trajectory simulation code Rockyfor3D. Comparisons of rockfall simulations using these models with field experiments have shown the efficiency of the approach.