Flood risk in Italy

During the 20th century, floods in Italy have killed or injured more than 4750 people in at least 916 fatal flood events, at 739 different sites (Salvati et al., 2010). In the same period, the number of homeless and evacuees caused by inundations exceeded 530 000. These figures indicate that flood risk to the population is severe and widespread in Italy. Consequently, establishing flood risk levels is a problem of both scientific and societal interest. Estimates of individual and collective risk levels in Italy were first determined by Salvati et al. (2003), and were revised by Guzzetti et al. (2005a,b) and by Salvati et al. (2010). In this Chapter, we use an improved version of the catalogue of flood events with human consequences in Italy (Salvati et al., 2003, 2010; Guzzetti et al., 2005b) to update the existing estimates of individual and societal flood risk in Italy and in the 20 Italian regions. Next, we investigate the temporal and the geographical variations of flood risk in Italy, and we compare the national flood risk levels to the levels of risk posed by other natural hazards, including landslides, earthquakes and volcanic activity. Here, we use the term fatalities to indicate the sum of the deaths and the missing persons caused by a harmful flood event. Casualties indicate the sum of fatalities and injured people. Evacuees are people forced to abandon their homes temporarily, while the homeless are people that lost their homes. Human consequences encompass casualties, homeless people and the evacuees. A fatal event is an event that resulted in fatalities. Individual risk is the risk imposed by a hazard to any unidentified individual. Societal (or collective) risk is the risk imposed by a hazard on society as a whole.