Technical and human aspects of historic rockslide dammed lakes and landslide dam breaches

The historical presentation of some 12 major landslide dam cases in the Alps which occurred between the first centuries AD and the present time and for which significant information is available, allows the formulation of specific conditions which are generally met, with respect to the development of the phenomena, their direct and indirect consequences on the population and the possible prevention and mitigation actions that can be carried out. Then three major recent cases in Switzerland and South America in which the human preventive action was essential to save many lives and estates are briefly commented, especially with respect to the need of a fast and organized action by the Civil Defence, the Army and the local authorities, in order to avoid more dramatic consequences due to the formation and subsequent breaching of the landslide dam lake. This analysis points out the necessity of properly assessing the potential landslide scenarios and the related risks so as to limit the possible consequences of such dramatic events in the future.