Flood risk to the population and its temporal variation in Italy

Floods pose a severe threat to the population of Italy. Quantitative flood risk levels to the population can be evaluated determining levels of individual risk. Using an updated version of an historical record of flood events with human consequences in Italy, we studied the temporal and the geographical distributions of events with casualties in the 1861 - 2013 period, and we determined individual flood risk for the whole Italy, and for five physiographical areas established classifying the Italian municipalities on their terrain elevation and the distance to the sea coast. To study individual flood risk, we determined flood mortality rates using Italian census data from 1861. To evaluate the temporal variation of flood mortality, we divided the historical record into three 50-year periods, and we calculated the average flood mortality for the periods, and their variations in the different physiographical zones. The results were compared to risk levels calculated for landslides, earthquakes, and volcanic activities, and with the perception that the population of Italy has of the risk posed by different natural hazards. The comparison revealed that the perception of the threat does not match the long-term risk posed to the population by floods, and by the other natural hazards.