Brazil has been affected by the occurrence of catastrophic mass movements, of the debris flow type, whose consequences are related to the rainfall intensity, the volume of material involved, the level of energy, and the coverage area of the movement. This research deals with the debris flow that occurred in Rio Príncipe, in Teresópolis, during the tragic disasters at the mountainous region of Rio de Janeiro State, in February 2011, after an unusual event of intense precipitation. The paper summarizes the studies carried out to understand the debris flow (or avalanche), with emphasis on the use of available empirical expressions and numerical methods for debris flow modelling. In the three-dimensional analysis of the debris flow, the DAN3D program was used, which allows the use of two constitutive models. The program was developed by McDougall and Hungr (2004), and corresponds to an improved version of the well-known DAN-W model. Despite the complexity of the Rio Príncipe mass movement, it was possible to obtain numerical results which were consistent with the field observations of the debris flow.