Evaluation of the wind hazard and risk during high-impact weather conditions on the natural and built environment in Liguria

The risk caused by natural hazards is extremely high and increasing. As major sources of hazardous events like floods, windstorms and hailstorms, the assessment of impacts from both cyclones and thunderstorms has gained a certain importance over time. That is in particular the case of the Mediterranean region, considered as one of the major hot-spots worldwide and whose peculiar characteristics makes the area particularly prone to both flood and wind risks. While the former has been long investigated over time, works involved on assessing the risk arising from windstorms are fewer and, in general, more devoted to study specific case studies, although the simultaneous occurrence of the two hazard categories in most of the cases. However, the greater likelihood of having more intense weather events as a result of a warming climate has also posed more attention, especially over the last decades, on windstorms in literature, posing a challenge in filling the gaps in the knowledge of their features. These works mainly resulted in numerical simulations of specific case studies associated with strong tornadoes or wet downbursts, and in statistical analysis of variables retrieved from past data like modeling reanalyses. Some other works, on the other hand, deeply investigated the wind-related risk from an engineering point of view, providing a wide range of approaches for modeling wind damage as a function of speed for specific building classes in different areas of the globe. The study presented in this dissertation explores these two points of view more devoted to the study of the hazard and provides an attempt to evaluate the wind-damage risk at the local scale. In the first part of the thesis, we simulate a thunderstorm event with an associated downburst at the surface that occurred in 2018 in Genoa by means of a high-resolution model. Such an investigation addresses the mesoscale mechanisms at the basis of downburst’s development in an environment characterized by complex orography, assessing the reliability of outcomes based on observations of a Windcube scanning LiDAR WLS400S, funded by the European Project THUNDERR and installed by the Giovanni Solari Wind Engineering and Structural Dynamics (GS-Windyn) Research Group of the University of Genoa. In the second part, an investigation of cyclones passing through the Ligurian Sea is carried out by means of a cyclone detection and tracking algorithm, originally developed for the Southern Emisphere at the University of Melbourne. The main features of the selected elements are analyzed in terms of spatial and temporal distributions, as well as areas of development, evaluating the risk caused by hazardous synoptic conditions from a climatological and probabilistic point of view. The last part addresses the wind-related damage which potentially affects all municipalities in the Ligurian region, based on reanalyses of the past and on the direct application of risk’s concept as a combined evaluation of the hazard, the vulnerability and the exposure of the local territory.