The topic of the present study is the comparison of numerical simulations to records of real events of spreading of mud/debris-flow on torrent alluvial fans. This application is based on 2 events which occurred in the Wartschenbach (Austria, 1997) and the Varunasch (Switzerland, 1987) torrents. The numerical model is based on the two-dimensional form of the shallow-water-equations and a Herschel-Bulkley constitutive equation for the flowing material. Arcview GIS is used to generate the model input data and represent the results of computations. The methods used to deduce the model input data from available records are presented and discussed. For each case examined, the computed map of deposits, is compared to related descriptions of real events. A good concordance between model predictions and reality is observed. An analysis of the sensitivity of the model to variations of input parameters values is also carried out. The dominating effect of the quality of the digital elevation model, of rheological parameters values (especially the yield stress) and of the volume assessment on the accuracy of the result is established. However, the influence of the accuracy of input parameters values remains variable from one case to another.