A multidisciplinary investigation of deep-seated landslide reactivation triggered by an extreme rainfall event: a case study of the Monesi di Mendatica landslide, Ligurian Alps

Davide Notti,Piernicola Lollino,Nunzio Luciano Fazio,Aleksandra Wrzesniak,Niccolò Dematteis,Daniele Giordan,Francesco Zucca

doi:10.1007/s10346-021-01651-3

Abstract

In November 2016, an extreme rainfall event affected the Ligurian Alps (NW Italy). Consequently, several landslides and debris flows occurred in the upper Tanarello stream basin. In particular, the village of Monesi di Mendatica was severely damaged by two landslide phenomena: the activation of a rotational landslide, which caused the total collapse of two buildings and part of the main road, and the reactivation of a deep-seated planar massive and a complex landslide, which widely fractured most of the buildings in the village. The latter phenomenon was mostly unknown and had never been monitored prior to the 2016 event. Due to the extensive damage, the village of Monesi was completely evacuated, and the road connecting a ski resort area in the upper part of the valley was closed. Furthermore, a potentially dangerous situation related to the eventual progressive evolution of this landslide that could cause a temporary occlusion of the Tanarello stream still remains. For this reason, we defined the landslide behaviour, triggering conditions and chronological evolution leading to the 2016 event using a multidisciplinary approach. This approach consisted of field surveys, satellite DInSAR time series analyses, digital image correlation techniques, rainfall records analyses, postevent monitoring campaigns and subsurface investigation data analyses, and numerical modelling. This multidisciplinary approach enhanced our understanding of this landslide, which is fundamental to better comprehend its behaviour and possible evolution.

Highlights

Worldwide, there are many landslides that have the potential to reactivate
Past activity of the Monesi landslide The evidence collected from aerial photos and technical reports suggested the following: 1. According to the SCAI technical report, the Monesi di Mendetica landslide
1.01 part of the landslide at the contact between the landslide debris and the bedrock (Fig. 15a) and propagated upwards within the debris mass (Fig. 14b and Fig. 15b). These numerical results agreed with the field observations, as well as the satellite data and digital image correlation (DIC) analyses, which highlight that the highest displacement values were concentrated in the lowest portion of the slope, where the rotational landslide (L1) occurred (Fig. 15a)

Summary

Introduction

Many of them are not monitored by in situ measurement systems, and if they reactivate, the catastrophic phase cannot be directly registered In such cases, one of the initial activities carried out during a scientific or technical investigation is the identification of the recent landslide’s evolution and characterization of its kinematics. Rainfall thresholds perform better for shallow landslides or debris flows (Guzzetti et al 2008; Tiranti and Rabuffetti 2010) than for deep-seated landslides (Zêzere et al 2005; Guzzetti et al 2007; Gao et al 2018). Focusing on European cases, we note the Val Pola rock avalanche in the central Alps in 1987 (Crosta et al 2004), the Corniglio landslide in the Northern Apennines in 1994 (Bertolini and Pizziolo 2008), the Alpe Baranca DSGS in the NW Alps in 2000 (Ramasco and Troisi 2002), the Mount Gírová landslide in the West Carpathian in 2010 (Baroň et al 2011) and the Stogovce landslide in the Slovenian Alps in 2010 (Petkovšek et al 2011)

Methods

Results

Discussion

Conclusion