APPLICATION OF THE MATTEROCK METHODOLOGY FOR CLIFF DANGER EVALUATION

The traditional ''Cliff'' type danger map, based on a phenomena map, h as the inconvenience to reflect a past danger. It is only valid for ev ents of the same size. Because the mechanisms of mobilization are not taken into account, the phenomena map might miss the large rockslides, like the one which occurred in Randa, and which are due to a long and irreversible degradation process and occur rarely at the same place. By advocating to replace the phenomena map by the hazard map, MATTEROC K suggests a real diagnosis for the danger map. Its originality is to work on the probability of mobilization (dangerousness) of the hazard and to use probabilistic analysis for assessing the probability of int ersection between the discontinuities which are able to dissociate roc ks from the cliff.