Rainfall intensity in the Genoa Metropolitan Area (Northern Mediterranean): secular variations and consequences

According to historical papers the Genoa Metropolitan Area (GMA) is affected by floods since the Middle Ages. Anyhow in the last years an increase in flash floodings has been registered; recently in 2014, at least 4 floods took place, three of them in Fall.Then, secular pluviometric variations were analysed. The research analyses the pluviometric data recorded at Genoa University (since 1833) and Chiavari (since 1877) stations, which represent, respectively, the central and the eastern zone of the GMA along the coast. Weather data recorded at Isoverde and Giacopiane Dam (since 1925) stations allow to complete the analysis in the hinterland of GMA, respectively in the western valley and eastern mountain. The analysis was based on mean annual, seasonal and monthly rainfall, rainy days and rainfall rate (the ratio between the formers) for the 4 stations. Furthermore, annual maximum data of hourly rainfall for Pontecarrega (Bisagno stream, the most hit valley in Genoa) and Giacopiane Dam stations were analysed. The annual rainfall does not show any trend while significant decreases for rainy days have been highlighted. As a consequence, the rainfall rate increase in the coastal and mountain stations. Also, hourly rainfall at 3 and 6 hours increase. These facts can be related with the intensification of flash flood events measured in the last decade. So, interventions to reduce flood risk in the GMA are no more postponing