The influence of wildfires on the occurrence of shallow landslides and related triggering mechanisms

Gravitational phenomena, like shallow landslides and debris flows, are very common in Italy due to the orographic and geological features of the territory, two mountain chains go all across the nation indeed (Alps and Apennines). It has already been demonstrated that it is impossible to avoid them all occurring; that is why prevention measures and studies are needed to decrease the damages and victims that such phenomena could cause. Exploiting the database of the Piemonte Region and Regional Agency of Environmental Protection of Piemonte (ARPA Piemonte), an attempt has been made to investigate the variations of soils affected by wildfires. Numerous studies have demonstrated that hydrological characteristics’ variations due to wildfire have to be examined. Whether these correlations have been sufficiently demonstrated for debris flows around the world, as analyzed in a recent article by Tiranti et al., (2021) in Piemonte, for the shallow landslides have not been made many studies in this regard and it is not yet clear how a wildfire could predispose shallow landslides. Critical rainfall values are usually one of the main triggering factor to consider, but as it is presented in this thesis, a significant and long-term predisposing factor able to increase the effect of rainfall in triggering shallow landslides must be considered: the dead vegetation that remains on the slope even several years after the passage of the fire triggered by strong winds. To obtain useful information for the aim of the thesis project it was necessary to search for new data (unpublished data) by field surveys focused on some case studies. The research work was conducted by contacting various professionals and public administrations in order to acquire technical reports on wildfire and landslide events and carry out field investigation in the areas of interest.