Instrumental Monitoring of a Slow-Moving Landslide in Piedmont (Northwest Italy) for the Definition of Rainfall Thresholds

TL;DR

This study investigates a slow-moving landslide in Italy and defines rainfall thresholds that trigger movement, using field data and satellite observations.

Contribution

The study introduces a workflow combining field surveys, rainfall analysis, and Earth Observation data to define and validate landslide activation thresholds.

Findings

Rainfall thresholds of 105 mm (3 days) and 193 mm (30 days) were defined for landslide activation.

InSAR and inclinometric data validated the thresholds and confirmed the slow movement of the landslide.

The proposed workflow can guide similar landslide investigations and management strategies.

Abstract

The prediction and prevention of landslide hazard is a challenging topic involving the assessment and quantitative evaluation of several elements: geological and geomorphological setting, rainfalls, and ground motion. This paper presents the multi-approach investigation of the Nevissano landslide (Asti Province, Piedmont, NW Italy). It shows a continuous and slow movement, alongside few paroxysmal events, the last recorded in 2016. The geological and geomorphological models were defined through a field survey. An inventory of the landslide’s movements and rainfall records in the period 2000–2016 was performed, respectively, through archive investigations and the application of “Moving Sum of Daily Rainfall” method, allowing for the definition of rain thresholds for the landslide activation (105 mm and 193 mm, respectively, in 3 and 30 days prior to the event). The displacements over the last 8 years (2016–2023) were monitored through an innovative in-continuum monitoring inclinometric system and Earth Observation (EO) data (i.e., relying on Interferometric Synthetic Aperture Radar, or InSAR data): it gave the opportunity to validate the rainfall thresholds previously defined. This study aims to provide information to public authorities for the appropriate management of the site. Moreover, the proposed workflow could be adopted as a guideline for investigating similar situations.

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