On the Occurrence of Extreme Rainfall Events Across Italy: Should We Update the Probability of Failure of Existing Hydraulic Works?

Every year, extreme rainfall events cause human deaths and economic losses around the world. Risk reduction strategies may involve the implementation of structural measures that are widely extended and financial relevant. Despite the high reliance on these mitigation measures, there might occur instances of overload, i.e. events with intensities exceeding the design value of these structures, that may have catastrophic consequences. In this framework, it is crucial to improve hydraulic works management, thus, we introduce a procedure at rain gauge scale for revising design variables throughout their operational lifespan. This enables us to enhance the assessment of the probability of failure of these works. Finally, we investigate instances where design variables experience overload during the recording period, thus assessing the occurrence of rare yet possible events. To this aim we find the most-suitable probability distribution to describe daily rainfall maxima in Italy. Specifically, we test the performance of four widely used bi-parametrical distributions with different tail behaviour, by analysing an impressive dataset consisting of 2282 rain gauges observations from 1860 to 2022. Our results show that: (1) 78