Abstract
Abstract. Damaging Hydro-geologic Events (DHEs), defined as landslides and floods caused by heavy or prolonged rainfall, represent an important source of economic damages. We propose an approach to classify DHEs, considering 1) meteorological antecedent conditions, 2) the season during which the event occurs, 3) the return period of maximum daily rainfall triggering the event, 4) geographic sectors hit, 5) types of triggered damaging phenomena; and 6) induced damage. We applied this approach to a case study of time series of DHEs that occurred over 85 years in Calabria (southern Italy). We analysed 13 DHEs that, between 1921 and 2005, triggered landslides, floods and secondary floods, causing severe damage and tens of causalities all over the Calabria region. During the analysed events, 64% of Calabria's municipalities suffered many types of damage. The most relevant rain phenomena and the largest damages were caused by the persistent effects of perturbations on Calabria, which were preceded by the appearance of low-pressure fields in two different areas located westwards. We sorted the events into three types based on geographic damage distribution and types of triggered phenomena and induced damage. The first two types are characterised by similar severity levels, while the third shows the highest severity, in terms of both damage and victims. Independent of the type of event, the S-SE and E sectors of the region are the most frequently affected by DHEs. As regards human life, floods are the most dangerous type of phenomenon, causing the highest number of fatalities. Our analysis indicates a decreasing frequency of DHEs during the study period, and an absence of the most severe type for more than 50 years. The number of victims is also decreasing over time.
Highlights
Prolonged and/or intense rainfall can trigger damaging phenomena, such as landslides, floods and secondary floods, causing damage and fatalities. These periods of bad weather and triggered phenomena can be defined as Damaging Hydro-geological Events (DHEs) (Petrucci and Polemio, 2003; Petrucci et al, 2009)
The analysis has identified some major types of DHEs that can be distinguished according to the following features: 1) types of damaging phenomena triggered; 2) geographic sectors hit; 3) season in which the event occurred; 4) antecedent meteorological conditions; 5) return period of maximum daily rainfall triggering the event; and 7) induced damage
Data concerning DHEs that occurred in Calabria can be gathered from two main sources: a) ASICal (Aree Storicamente Inondate in Calabria) is a database of landslides and floods that occurred in Calabria during the past centuries; it was produced by a joint research project of the CNR-IRPI of Cosenza and the Department of Soil Defence of Calabria University (Petrucci and Versace, 2004)
Summary
Prolonged and/or intense rainfall can trigger damaging phenomena, such as landslides, floods and secondary floods (stagnancy of rain on low permeability surfaces), causing damage and fatalities As a whole, these periods of bad weather and triggered phenomena can be defined as Damaging Hydro-geological Events (DHEs) (Petrucci and Polemio, 2003; Petrucci et al, 2009). Polemio: Damaging hydro-geologic events characterisation zones of areas likely to be damaged during DHEs (Petrucci and Pasqua, 2008). All of this information can be used in both urban planning and emergency plan preparation, aiming to forecast and reduce damage induced by DHEs
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