Earthquake-induced sinkholes in Calabria

The attention on sinkholes phenomena has greatly increased in the last years, in the aftermath of the many events that have affected built-up areas in Italy and abroad. This has brought to a wider use of the term sinkholes, that is nowadays used also for events related to anthropogenic cavities, and/or to phenomena linked to occurrence of earthquakes. At this latter regard, the investigation of the surface effects triggered by seismic activity often poses some problems in discriminating between liquefaction phenomena and occurrence of sinkholes in alluvial plains. Especially when historical sources are examined, the descriptions and reports are typically similar, and when field evidence of the phenomena are no more recognizable, distinguishing one phenomenon from the other may be actually impossible. Starting from the above assumption, the contribution presents an analysis of the events induced by earthquakes in Calabria, for which historical documentation has been found. Among the case studies, worth to be mentioned is the 1783 seismic sequence, that struck central-southern Calabria and produced remarkable effects at the surface. A critical scrutiny of the available historical documentation is presented, integrated with description of the main geological and morphological features of the affected areas, in the attempt to identify seismically-triggered sinkholes, and to perform a preliminary analysis of the relationships between seismic parameters (magnitude, intensity, epicentral distance) and sinkholes

Populating a catalogue of rainfall events that triggered shallow landslides in Italy

In Italy, rainfall induced landslides - including soil slips and debris flows - occur every year, claiming lives and causing severe economic damages. In the 61-year period 1950-2010, such phenomena have caused more than 6400 casualties (SALVATI et alii, 2010). During 2011, 25 people have been either killed or wounded by landslides. As a result, the prediction of slope failures triggered by rainfall is of primary importance for decision makers and civil protection authorities. The predictive ability for rainfall induced landslides is still limited due to the complexity of the problem, to the number of the involved variables, and to the methodological approaches that are not always rigorous. As regards shallow landslides, a team of researchers working at CNR-IRPI (Italian National Research Council, Institute of Research for Geo-Hydrologic Protection) is carrying out a research project funded by the Italian national Department for Civil Protection (DPCN), aimed at defining regional and subregional rainfall thresholds

Rainfall events able to trigger shallow landslides in Calabria (Southern Italy).

In Calabria, la disponibilità di oltre 45000 eventi piovosi a scala di tempo di cinque minuti ha permesso di precisare la struttura temporale e la distribuzione spaziale, da assumere come input per i modelli completi di versante. Lo studio è stato condotto proponendo un semplice ed efficace metodo di classificazione automatica dei profili di pioggia

Catalogue of Rainfall Events with Shallow Landslides and New Rainfall Thresholds in Italy

In Italy, rainfall-induced shallow landslides are frequent and harmful phenomena. The prediction of their occurrence is of social significance for civil protection purposes. For the operational prediction of rainfall-induced shallow landslides empirical rainfall thresholds based on the statistical analysis of past rainfall conditions that triggered slope failures are commonly used. The paper describes a catalogue of 1981 rainfall events, which caused 2408 shallow landslides in Italy in the period 1996–2012. Information on rainfall-induced landslides was collected searching chiefly online newspaper archives, blogs, and fire brigade reports. For each documented failure, we reconstructed the triggering rainfall conditions (rainfall duration D and cumulated rainfall E) using national and regional rain gauge networks. We analysed the rainfall conditions to determine new ED rainfall thresholds for Italy. The calculated thresholds can be implemented in a landslide forecasting system to mitigate landslide hazard and risk

A preliminary attempt to determine the landslide hazard in Italy.

Determining landslide hazard at the national scale remains a difficult task. However, such a complex task needs to be accomplished to mitigate the landslide consequences, including loss of lives and economic and environmental damages. For administrative purposes, the Italian territory (303,000 km sq.) is subdivided in 20 regions that cover a large variety of natural environments, most of which are subject to landslide hazards. To determine landslide hazard in such a complex and diversified territory, the many natural and anthropogenic variables, and their variations, must be considered. In Italy, the Italian national Civil Protection Department (DPC), an office of the Prime Minister, is in charge of managing natural and human-made hazards, and the associated risk. For landslide (and flood) hazards, the DPC has subdivided the Italian territory into 134 “alert zones” (AZ), decided based on administrative and hydrological criteria. Here, we describe the results of a preliminary effort made by our research group – in the framework of a larger effort to forecast landslide hazard and risk in Italy – to describe landslide hazard in each AZ. For the purpose, we summarized in a specifically designed form the geographical, morphological, geological and landslide information available for each AZ. The form also contains general information on past landslide events and on the vulnerability to landslides of the AZ. We obtained the morphological information from the SRTM DEM with a grid resolution of 90 m 90 m, and the geological and lithological information from the Geological Map of Italy, at the 1:500,000 scale, published by the Italian Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA). We used the morphological (terrain elevation and terrain gradient) and the lithological information to subdivide the Italian territory in three main morphological domains (plains, hills and mountains), and we computed the proportion of the three domains in each AZ. We determined the type, abundance and distribution of landslides in each AZ heuristically, based on our experience aided by the critical evaluation of existing official documents and maps, including: (i) the maps produced by the national Inventory of Landslide Phenomena in Italy (IFFI), (ii) the maps associated to the geo-hydrological (landslide and flood) hazard plans (PAI), and (iii) other landslide maps prepared by our Institute (CNR IRPI) for parts of Italy. We obtained information on the damage to the population caused by landslides in Italy from a catalogue of historical landslides (and floods) with human consequences compiled by Salvati et al. (2010), and information on sinkholes failures from a catalogue of natural and human-induced sinkhole failures in Italy recently compiled by Parise & Vennari (2013). For each AZ, the dates of the most damaging events were identified, and the number of landslide fatalities, casualties and evacuated people were calculated. These figures provide a quantitative measure of the intensity of the landslide consequences in each AZ. The ensemble of the information collected provides a comprehensive – albeit preliminary – evaluation of the hazard posed by landslides in the Italian territory, and the basic data for proceeding to determine the related vulnerability

SANF: National warning system for rainfall-induced landslides in Italy

In Italy, rainfall-induced slope failures occur every year, claiming lives and causing severe economic damage. We have designed and implemented a landslide warning system, named SANF (an acronym for national early warning system for rainfall-induced landslides), to forecast the possible occurrence of rainfall-induced landslides in Italy. The system is based on: (i) rainfall thresholds for possible landslide occurrence, (ii) sub-hourly rainfall measurements obtained by a national network of 1950 rain gauges, and (iii) quantitative rainfall forecasts. Twice a day, the system compares the measured and the forecasted rainfall amounts against pre-defined ID thresholds, and assigns to each rain gauge a probability of landslide occurrence. This information is used to prepare synoptic-scale maps showing where rainfall-induced landslides are expected in the next 24 hours