Geomorphological study of the Fadalto landslide, Venetian Prealps, Italy

Abstract

This research deals with the Fadalto landslide (Lapisina Valley, Venetian Prealps), which took place in the Lateglacial and has continued its activity until today. Our aim is to recognize how the landslide failed, the causes of such failure and the activity of this landslide. The study of this landslide is important not only to understand the geomorphological history of this alpine area, and why the Piave River modified its course in the Late Pleistocene, but also the links with human activities, and specifically with the road and rail network. The geomorphological study, carried out by the interpretation of aerial photos and by a detailed field survey, has been integrated with a geological survey, geophysical investigations and a morphometric analysis (DTM). The Fadalto landslide is considered to be a rockslide reactivated in various phases, with different dimensions and with different characters (slides, slumps and flows). The landslides have been provoked by natural causes, both external and internal; the fundamental external causes are the retreat of the Würmian glacier and tectonic activity; the internal factors that decrease the shear resistance are the bedding planes and joints of the bedrock, the attitude of the rocks dipping towards the valley bottom and, as regards more recent failures, the presence of glacial deposits underlying the landslide debris. Besides, in recent times, we must also consider human activity as a cause of slope instability. As to the activity, the Fadalto landslide is defined “dormant”. This means that in this area there is a geomorphological risk connected with the important road and rail network of the Lapisina Valley.