Analysis of landslide Susceptibility and Tree Felling Due to an Extreme Event at Mid-Latitudes: Case Study of Storm Vaia, Italy

Storm Vaia on 29 October 2018, hit northeastern Italy and produced extensive damage in the immediacy of the event, including extensive tree felling in some places, as well as debris flow or earth flow landslides. This study aims to assess the susceptibility of the area following extreme events by evaluating the environmental criticality during strong winds and intense precipitation. Specifically, tree felling susceptibility due to wind and landslide susceptibility due mainly to precipitation were analysed by taking into consideration the geomorphological and environmental criticality of the areas under study. In particular, the area was modelled using fluid dynamics software, allowing an understanding of wind accelerations in relation to morphology, showing excellent agreement between the tree falls that occurred during the event and the areas with the highest wind gusts. With regard to landslides, an algorithm was prepared through GIS software that took into account the debris and earth flows that were activated during the extreme event in question, allowing the creation of a susceptibility map that delineated areas of high potential hazard. The final result is a landslide and tree-fall susceptibility map that determines the fragility of the territory during an extreme event. The procedures applied in the study area can be considered as a working method that allows critical values to be obtained for extreme events that can produce damage to the environment and beyond. It follows that this research also has an immediate application purpose by helping the political decision-maker in the choice of interventions to be implemented.