Rainfall intensity in the Genoa Metropolitan Area: secular variations and consequences. (25th March 2018)

• Record Type: Journal Article
• Authors: Acquaotta, Fiorella; Faccini, Francesco; Fratianni, Simona; Paliaga, Guido; Sacchini, Alessandro
• Is Part Of: Weather. Volume 73:Number 11(2018)
• Page Start: 356
• Page End: 362
• Publication Date: 2018-03-25
• Subjects: Meteorology -- Periodicals; Weather -- Great Britain -- Periodicals; 551.1
• DOI: 10.1002/wea.3208
• Languages: English
• ISSNs: 0043-1656

Abstract

Abstract : According to historical papers, the Genoa Metropolitan Area (GMA) has been affected by floods since the Middle Ages. An increase in flash floods has been recorded over the last few years, and in 2014 at least four floods were observed, three of which occurred during autumn. Following these observations, the secular pluviometric variations for the region have been analysed. Pluviometric data recorded at the Genoa University station (since 1833) and Chiavari station (since 1877), which represent the central and the eastern zones of the GMA along the coast, have been analysed. Weather data recorded at the Isoverde station (since 1921) and Giacopiane Dam station (since 1925) have allowed the analysis to be completed in the western valley and eastern mountain regions of the GMA hinterland, respectively. This analysis was based on the mean annual, seasonal and monthly rainfall amounts, the number of rainy days and the rainfall rate (the ratio between the former and the latter) recorded at the four stations. Furthermore, the annual maximum hourly rainfall data have been analysed for the Pontecarrega station (at the Bisagno stream, the most affected valley in Genoa) and the Giacopiane Dam station. No trend was found for annual rainfall, though significant decreases were observed for the numbers of rainy days. As a result, an increase in the rainfall rate for the coastal and mountain stations was found. Moreover, an increase has also been found in the 3‐ and 6‐hourly rainfall values. These findings could be related to the intensification of flash flood events that has been observed over the last decade. Interventions to reduce flood risks in the GMA should therefore no longer be postponed. Abstract : The Genoa Metropolitan Area has exhibited an increase in flooding in recent years. This study analyses the pluviometric statistics collected by four weather stations based on annual, seasonal and monthly rainfall amounts and number of rainy days data; hourly rainfall data were also analysed. Monthly analysis highlights a decrease in rainfall amounts and the number of rainy days and a secular increase in the average daily rainfall rate, particularly in autumn. Also, the graphs of hourly rainfall show positive trend lines, and climate data more generally confirm the occurrence of increasingly intense rainfall over the last 50 years. This is consistent with the recently recorded increase in the number of flash floods.