A multi-risk framework for assessing and ranking seismic and flood risks: an application in Italy-Slovenia transboundary region

To formulate suitable prevention and mitigation policies, risk assessment is the primary tool adopted by decision makers to understand and quantify the potential impacts resulting from hazardous events. In areas exposed to multiple hazards a joint analysis for quantifying and comparing all risks that potentially affect the territory is crucial. However, the evaluation of possible interactions among risks and their comparison could be a complex task. This paper illustrates the methodology for multi-risk assessment proposed within BORIS project (Cross BOrder RISk assessment for increased prevention and preparedness in Europe), focusing on the assessment of seismic and flood risk in the Eastern Alps cross-border area between Italy, Slovenia and Austria. Adopting a multi-layer single risk approach, the risk evaluation related to the investigated hazards is performed by independent analyses and the expected losses are compared and ranked through risk curves. To ensure the comparability of the risks, the same boundary conditions for the analysis (common area, time frame of analysis and metric to rep- resent the risk) as well as the same methodological approach to compute the probabilistic risk curves are defined. The harmonized methodology proposed is applied to a pilot transbounda- ry region at the Italy-Slovenia border, including 27 municipalities in Italy and 6 in Slovenia. The municipal scale is selected as a scale to represent and compare the risks and the metric to evaluate impacts is measured in terms of direct economic losses. Results in terms of Ex- pected Annual Losses (EAL) show in which municipality the overall risk is significantly high and in which town one risk could be more relevant than the other.