Landslide risk assessment: the Passo della Morte case study (Eastern Italian Alps).

Large landslide, especially large slow-moving landslide, do not always show clear sign of deformation. The detection of displacements may come through monitoring although it is difficult to implement when large areas are involved and when cost effectiveness is an issue. Besides large landslides are usually located along major valleys due to the cumulated effect of tectonic effects and geomorphological constraints. Major transport routes and other infrastructures are also located along major valleys since they are usually the location of larger settlements due to the historical preference of building where there is more sunlight, the valley floor is flatter, streams are less active and commerce is easier. In this work we present a situation in which the design and construction of a new infrastructure, a road tunnel, did not take into account the presence of a large slow-moving landslide thus increasing the costs of variation during construction, reparations and maintenance. In order to plan properly mitigation works it was first of all fundamental to delineate the style of activity of the different portions of the affected slope and to characterize properly their cinematics. The paper describes the investigation strategy adopted and its different phases to detect and focus on the most hazardous phenomena and prioritize interventions.