Evolutionary behaviour of the Tessina landslide

The Tessina Landslide, a complex movement which has been active for over the past 50 years in the Alpago area of Belluno (Italy), was triggered in October 1960. As it is typical of Tertiary Flysch formations, its evolution has been characterized by periodical medium-large roto-translational slides in the source area evolving into earthflows, often jeopardizing the safety of the lower valley. Both the landslide and earth flows have been extensively monitored and studied over the past few decades. The main aim is a better understanding of their evolution mechanisms and the selection of appropriate mitigation strategies to reduce risk to the valley below. This paper presents data recorded by two real-time monitoring systems that have recently been installed in the area. The first system measures groundwater pressure and the displacements in a lateral section of the landslide that plays a crucial role in the stability of the entire area. The second, a new photogrammetric-based system which daily photographs the upper basin affected by the roto-translational movements, will permit us to evaluate the mechanisms triggering the earth flows. The data collected until now at the site have made it possible to better understand the stability of the various sections as well as the processes involved in earth flow formation. This information will make it possible to evaluate the effectiveness of future mitigation measures. Finally, a new black-box model that will predict the mobility of the lateral section of the landslide has been developed, and its performance has been compared to that of a viscous model commonly used to analyse slow-moving landslides.