Preliminary analysis of the November 10, 2014 rainstorm and related landslides in the lower Lavagna Valley (Eastern Liguria)

Abstract

On the evening of November 10, 2014, eight rainfall-induced shallow landslides were triggered on a slope in the lower Lavagna valley (eastern Liguria, Italy). Most of the shallow landslides were channelled as flows into steep hollows and reached the toe of the slope, where some sparse houses were built. One of these landslides impacted and destroyed a building located just at a steep channel outlet, causing two fatalities. Damage affected also agricultural terracing as well as some other buildings and a road running at the toe of the slope, which was buried for long tracts by landslide deposits. Since a few days after the landslides occurrence, various activities were carried out, with the aim of better understanding both the triggering and predisposing factors of landslides. These activities included field surveys, rainfall data analysis, topographic/thematic maps, DEM and aerial photo analyses, preliminary laboratory tests on soil samples. From the analyses performed, it seems that, in addition to the rainfall characteristics of the November 10, 2014 event, the antecedent rainfall may have played an important role as landslides predisposing factor. Other relevant predisposing factors can be referred to slope steepness, presence of hollows, stratigraphic and structural settings at the source areas and lack of maintenance of terracing. Investigations are still in progress to achieve a complete geotechnical and hydraulic characterization of soils. Furthermore, it is also expected to extend the analyses performed to the whole area affected by shallow landslides. However, we believe the results of this study can be helpful in shallow landslide modelling, hazard assessment and planning of appropriate risk mitigation measures.