Engineering geomorphological characterisation of the Vajont Slide, Italy, and a new interpretation of the chronology and evolution of the landslide

Abstract

Although the 1963 Vajont Slide in Italy has been extensively studied for over 50 years, its regional geological and geomorphological context has been neglected. In this paper, we use field observations and remote sensing data to elucidate the interaction between endogenic and exogenic processes that brought the north slope of Monte Toc to failure. We present the first detailed pre- and post-failure engineering geomorphology maps of the slide area. The maps delineate two main landslide blocks, several sub-blocks, compressional and extensional zones, and secondary failures in the deposit. The maps provide new insights into the kinematics, dynamics and evolution of the slide. Finally, we discuss the origin of Vajont Gorge and a prehistoric failure that occurred at the same location as the 1963 slide. We propose, as part of a newly developed multi-stage landscape evolution sequence, that the prehistoric failure was a deep-seated gravitational slope deformation (sackung) that initiated during deglaciation and\ud continued to slowly move until the catastrophic failure in 1963. We argue that the gorge was created by these deep-seated slow movements

New, simplified and improved interpretation of the Vaiont landslide mechanics

“…Semenza ( , 2010 highlighted a large mass that slid from the head of the east side and over-ran the main landslide deposit by up to 100 m. This mass, identified as the 'eastern lobe', retained its forest cover and therefore must have fallen after the flood wave had subsided. Wolter et al (2016) showed that similar but smaller masses had likewise slipped from the head of the west side and retained their trees intact, consistent with a single photograph in the Vaiont-focused tourist visitor centre in Erto that shows a more pronounced head scarp above the west side in daylight (i.e. not earlier than the morning of 10 October).…”

“…Toc. Indeed, we have discussed evidence of past landslides within or adjacent to the gorge, at least one of which blocked the lower part of the gorge causing it to fill up with alluvial sediment before a further landslide, triggered by rapid slope undercutting, deposited the mass of rock known as the 'Colle Isolato' on top of the infilled channel sediments (Dykes and Bromhead 2018;Wolter et al 2016).…”

Application of Remote Sensing to the Investigation of Rock Slopes: Experience Gained and Lessons Learned

“…The size and characteristics of the Vajont Slide were greatly affected by geological structures present in the area. The rupture surface was characterized by a chair-like shape, structurally controlled by the Erto Syncline [77]. The lateral and rear release surfaces of the slide were defined by the Col Tramontin Fault and the Col delle Erghene Fault, respectively [78].…”

Improvements in the integration of remote sensing and rock slope modelling

“…These techniques are therefore used in numerous types of cartographic application, from military and regional small-scale maps, to that of medium-and large-scale technical maps (topographic, geological, geomorphological, land use, etc.). Airplane/satellite photogrammetry is very useful in regional engineering-geological mapping and for detecting landslide related geomorphic landforms (Wolter et al, 2016;Mantovani et al, 2016, Clayton et al, 2017. Donati et al, 2017.…”