Multi-temporal analysis of the geomorphic evolution of the failure surface of the Vajont Landslide

Abstract

Landslides are among the most common type of hazard that affect mountainous regions. While the impact of the single landslide is often localized and limited to the influence area, in some cases, the occurrence of major events can result in significant and long-lasting social, economic, and environmental impacts that extend beyond the area directly affected by the event. These major landslides involve the sudden detachment of large volumes of rock mass and cause significant disturbance of in-situ stress field due to slope debuttressing and reduction in lateral support, which often result in conditions of limit equilibrium affecting the remaining part of the slope. Effects of such limit equilibrium conditions can range from a long term, gradual morphological evolution of the slope due to progressive detachment of material, to the development of multistage landslides, involving the failure of volumes of rock mass
similar in magnitude and impacts to the original event. In this work, we investigate the post-failure morphological evolution of the daylighting rupture surface and deposit of one of the most important historical landslides, the 1963 Vajont Slide. A preliminary investigation of a pair of airborne laser scanner (ALS) datasets, collected in 2017 and 2023, is undertaken to assess and compute the change in elevation across selected areas within the rupture surface. Based on a three-dimensional change detection analysis, the observed volumetric changes of selected, inferred rockfall events are estimated. Terrestrial and airborne photographs are also used to identify the unstable volumes that have progressively detached, as well as the damage features that outlined these unstable blocks. Finally, we discuss the long-term evolution of the slope with focus on progressive damage accumulation and its spatial relationship with inherited, tectonic structures. Ultimately, this contribution is intended to highlight the important role of post-slope failure damage accumulation on the long-term stability of rock slopes, emphasizing the critical role that post-failure monitoring and analysis can play in outlining the residual landslide hazard and, in some instances, the potential development of multi-stage landslides.