Societal landslide and flood risk in Italy

Abstract

Abstract.We assessed societal landslide and flood risk to the population of Italy. The assessment was conducted at the national (synoptic) and at the regional scales. For the assessment, we used an improved version of the catalogue of historical landslide and flood events that have resulted in loss of life, missing persons, injuries and homelessness in Italy, from 1850 to 2008. This is the recent portion of a larger catalogue spanning the 1941-year period from 68 to 2008. We started by discussing uncertainty and completeness in the historical catalogue, and we performed an analysis of the temporal and geographical pattern of harmful landslide and flood events, in Italy. We found that sites affected by harmful landslides or floods are not distributed evenly in Italy, and we attributed the differences to different physiographical settings. To determine societal risk, we investigated the distribution of the number of landslide and flood casualties (deaths, missing persons, and injured people) in Italy, and in the 20 Italian Regions. Using order statistics, we found that the intensity of a landslide or flood event -measured by the total number of casualties in the event -follows a general negative power law trend. Next, we modelled the empirical distributions of the frequency of landslide and flood events with casualties in Italy and in each Region using a Zipf distribution. We used the scaling exponent s of the probability mass function (PMF) of the intensity of the events, which controls the proportion of small, medium, and large events, to compare societal risk levels in different geographical areas and for different periods. Lastly, to consider the frequency of the events with casualties, we scaled the PMF obtained for the individual Regions to the total number of events in each Region, in the period 1950-2008, and we used the results to rank societal landslide and flood risk in Italy. We found that in the considered period societal landslide risk is largest in Trentino-Alto Adige and Campania, and societal flood risk is highest in Piedmont and Sicily.

Assessment of data availability for the development of landslide fatality curves

“…Previous scientifically published quantification on fatalities are, as far as we know, calculated frequency rates for average number of fatalities per event, year, month, day, intensity, area of occurrence or expressed as the number of deaths per 100,000 inhabitants for a given population over a predefined time period (Cascini et al 2008;Giannecchini and D'Amato Avanzi 2012;Guzzetti et al 2005b;Hilker et al 2009;Pereira et al 2014;Salvati et al 2010). Methodologically, the studies differ concerning which observation inclusion criteria that are used when deriving a fatality (or mortality) rate.…”

“…Guzzetti et al (2005b) combined the number of missing people with the number of deaths when estimating fatalities. Salvati et al (2010) also included injured humans as well as those killed and declared missing. Giannecchini and D'Amato Avanzi (2012) did not distinguish between flood and landslide fatalities.…”

“…Among the scientifically published literature, an extensive portion focuses on Italian landslide scenarios. Several studies base their research on variations of the same historical landslide catalogs (e.g., Guzzetti et al 2003Guzzetti et al , 2006Salvati et al 2010). Analyses of experienced risk factors affecting fatality rates can, however, serve as input to risk assessments and disaster response by increasing the understanding of vulnerable groups and ease assistance in the direct aftermath of a disaster (Agrawal et al 2013).…”

Landslide Societal Risk in Portugal in the Period 1865–2015

“…Landslides activity usually causes direct human impacts (fatalities, injuries), but the quantitative assessment of landslide societal risk has been developed in a limited number of studies performed at global (Petley 2012), European (Haque et al 2016) and national scales (Guzzetti 2000;Salvati et al 2010;Pereira et al 2016). …”

Risk-based analysis of monitoring time intervals for landslide prevention

“…Landslide is one of the most dangerous disasters in terms of occurrence frequency and damage severity that result in loss of human life and social infrastructure (Petley, 2012;Kjekstad and Highland, 2009;Guzzetti, 2000;Salvati et al, 2010). 30 Nat.…”