55 research outputs found
Preliminary 3-D finite element analysis of the triggering mechanism of an occasional reactivation of a large landslide in stiff clays
In December 2013 a large landslide occurred along a clay slope located at the south-western outskirts of the Montescaglioso
village (Basilicata, Southern Italy) as a consequence of intense and prolonged rainfalls that presumably
caused a significant increment of the pore water pressures in the slope. The slope is formed of stiff clays belonging
to the formation of the Subappennine Blue Clays, which are over-consolidated and characterized by medium
plasticity. According to aerial photos dating back to 1950s, the slope was already affected by previous landslide
processes, so that the examined landslide process can be classified as an occasional reactivation according to the
well-known classification of Cruden & Varnes (1996). Also, during the last decades several man-made actions in
the area resulted in strong changes in the original water surface network that could have played some role in the
slope reactivation. Based on displacement data, obtained from a monitoring system installed few days after the
phenomenon, and still in function, at present the landslide does not show relevant signs of activity.
Preliminary 2-D and 3-D finite element analyses have been carried out to investigate the factors that controlled
the mechanism of reactivation of the landslide. The numerical model has been setup based on the available
topographical, geological and geomorphological information, the geotechnical properties of the involved soils
and the information concerning the piezometric regime in the slope. The results indicate that the mobilized
shear strength of the clays ranges between the typical post-peak and residual values for this type of material and
confirmed that the strong increment of the pore water pressures in the slope induced by the exceptional rainfalls
occurred in the previous days can be identified as the main triggering factor of the reactivation
Sinkhole susceptibility evaluation in Apulia, southern Italy
In some regions in Italy sinkholes are frequent and pose a serious threat to structures and infrastructures. Apulia region is largely affected by sinkholes of both natural and anthropogenic origin, due to the karst nature of large portions of the regional territory and to high diffusion of artificial cavities. For this reasons, susceptibility, hazard and risk posed by sinkholes must be estimated in order to gain more insights into their spatial and temporal distribution, and to apply appropriate risk management and to take proper mitigation strategies. In order to estimate the susceptibility to sinkholes in Apulia, the ensemble statistical modelling proposed by Rossi et al. (2010) and later refined by Rossi & Reichenbach (2016) is used. This allows assessing susceptibility using differentiated statistical approaches, quantifying accurately the modelling performances, and evaluating the associated uncertainty. In order to obtain accurate and reliable results thematic layers related to the sinkholes occurrence were carefully evauated and selected. This contribution shows the preliminary results of the analyses to evaluate the susceptibility to natural sinkholes, which used as training dependent (i.e. grouping) set, data extracted from the regional inventory of natural caves, edited by the Apulian Speleological Federation (www.catasto.fspuglia.it), and as validation set the natural sinkholes occurred in Apulia, collected in the chronological catalogue of sinkholes in Italy (Parise & Vennari, 2013, 2017). Appropriate thematic layers, were selected heuristically on the base of the knowledge on the triggering mechanisms and the nature of the phenomenon gained previously in the study area. Resulting regional-scale susceptibility map will be appropriately validated. The methodological
procedure will be applied to the evaluation of susceptibility for anthropogenic sinkholes as well
Automated reconstruction of rainfall events responsible for shallow landslides
Over the last 40 years, many contributions have
identified empirical rainfall thresholds (e.g. rainfall intensity
(I ) vs. rainfall duration (D), cumulated rainfall vs. rainfall
duration (ED), cumulated rainfall vs. rainfall intensity (EI))
for the possible initiation of shallow landslides, based on
local and global inventories. Although different methods to
trace the threshold curves have been proposed and discussed
in literature, a systematic study to develop an automated procedure
to select the rainfall event responsible for the landslide
occurrence has only rarely been addressed. Objective
criteria for estimating the rainfall responsible for the landslide
occurrence play a prominent role on the threshold values.
In this paper, two criteria for the identification of the
effective rainfall events are presented. The first criterion is
based on the analysis of the time series of rainfall mean intensity
values over 1 month preceding the landslide occurrence.
The second criterion is based on the analysis of the trend
in the time function of the cumulated mean intensity series
calculated from the rainfall records measured through rain
gauges. The two criteria have been implemented in an automated
procedure that is written in the R language. A sample
of 100 shallow landslides collected in Italy from 2002
to 2012 was used to calibrate the procedure. The cumulated
event rainfall (E) and duration (D) of rainfall events that triggered
the documented landslides are calculated through the
new procedure and are fitted with power law in the D, E diagram.
The results are discussed by comparing the D, E pairs
calculated by the automated procedure and the ones by the
expert method
Automated reconstruction of rainfall events responsible for shallow landslides
Abstract. Over the last 40 years, many contributions have identified empirical rainfall thresholds (e.g. rainfall intensity (I) vs. rainfall duration (D), cumulated rainfall vs. rainfall duration (ED), cumulated rainfall vs. rainfall intensity (EI)) for the possible initiation of shallow landslides, based on local and global inventories. Although different methods to trace the threshold curves have been proposed and discussed in literature, a systematic study to develop an automated procedure to select the rainfall event responsible for the landslide occurrence has only rarely been addressed. Objective criteria for estimating the rainfall responsible for the landslide occurrence play a prominent role on the threshold values. In this paper, two criteria for the identification of the effective rainfall events are presented. The first criterion is based on the analysis of the time series of rainfall mean intensity values over 1 month preceding the landslide occurrence. The second criterion is based on the analysis of the trend in the time function of the cumulated mean intensity series calculated from the rainfall records measured through rain gauges. The two criteria have been implemented in an automated procedure that is written in the R language. A sample of 100 shallow landslides collected in Italy from 2002 to 2012 was used to calibrate the procedure. The cumulated event rainfall (E) and duration (D) of rainfall events that triggered the documented landslides are calculated through the new procedure and are fitted with power law in the D, E diagram. The results are discussed by comparing the D, E pairs calculated by the automated procedure and the ones by the expert method
First evaluation of the damage related to alluvial events in torrential catchments of Campania (southern Italy), based on a historical database
<p><strong>Abstract.</strong> This study presents an historical database of alluvial events in torrential catchments of Campania region, southern Italy. Detailed scrutiny and critical analysis of the existing literature, and of the data inventory available, allowed us to build a robust database consisting of about 500 events. Being this study the first step of a longer project, aimed at eventually reaching an hazard analysis, information about time and site of occurrence are known for all the events. The outlet zone of torrential catchments (represented mainly by alluvial fans or fan deltas) are highly urbanized in Campania region, thus collecting information about past events could provide useful information on future events, in terms of damage, and of spatial and temporal occurrence as well. In section 1 we introduce the issue of alluvial events in Italy. Existing database and published studies on hydrogeological events, in particular regarding Campania region, are presented in section 2, where we also discuss the importance of using the historical sources, and their limits and drawbacks. The geological and geomorphological settings of Campania region are introduced in section 3. Then, in section 4, we present our database by illustrating its general structure and the methodology used in collecting information. Statistical and data analysis carried out on the collected data are presented in section 5. Aimed at performing a complete hazard analysis, analysis on rainfall data and the application of numerical models on alluvial events will be the future steps.</p>
Rainfall thresholds for shallow landslide occurrence in Calabria, southern Italy
Abstract. In many areas, rainfall is the primary trigger of landslides. Determining the rainfall conditions responsible for landslide occurrence is important, and may contribute to saving lives and properties. In a long-term national project for the definition of rainfall thresholds for possible landslide occurrence in Italy, we compiled a catalogue of 186 rainfall events that resulted in 251 shallow landslides in Calabria, southern Italy, from January 1996 to September 2011. Landslides were located geographically using Google Earth®, and were given a mapping and a temporal accuracy. We used the landslide information, and sub-hourly rainfall measurements obtained from two complementary networks of rain gauges, to determine cumulated event vs. rainfall duration (ED) thresholds for Calabria. For this purpose, we adopted an existing method used to prepare rainfall thresholds and to estimate their associated uncertainties in central Italy. The regional thresholds for Calabria were found to be nearly identical to previous ED thresholds for Calabria obtained using a reduced set of landslide information, and slightly higher than the ED thresholds obtained for central Italy. We segmented the regional catalogue of rainfall events with landslides in Calabria into lithology, soil regions, rainfall zones, and seasonal periods. The number of events in each subdivision was insufficient to determine reliable thresholds, but allowed for preliminary conclusions about the role of the environmental factors in the rainfall conditions responsible for shallow landslides in Calabria. We further segmented the regional catalogue based on administrative subdivisions used for hydro-meteorological monitoring and operational flood forecasting, and we determined separate ED thresholds for the Tyrrhenian and the Ionian coasts of Calabria. We expect the ED rainfall thresholds for Calabria to be used in regional and national landslide warning systems. The thresholds can also be used for landslide hazard and risk assessments, and for erosion and landscape evolution studies, in the study area and in similar physiographic regions in the Mediterranean area
Brief Communication: Rapid mapping of landslide events: the 3 December 2013 Montescaglioso landslide, Italy
We present an approach to measure 3-D surface deformations caused by large,
rapid-moving landslides using the amplitude information of high-resolution,
X-band synthetic aperture
radar (SAR) images. We exploit SAR data captured by the COSMO-SkyMed
satellites to measure the deformation produced by the 3 December 2013
Montescaglioso landslide, southern Italy. The deformation produced by the
deep-seated landslide exceeded 10 m and caused the disruption of a
main road, a few homes and commercial buildings. The results open up the
possibility of obtaining 3-D surface deformation maps shortly after the
occurrence of large, rapid-moving landslides using high-resolution SAR data
Extreme rainfall events in karst environments: the case study of September 2014 in the Gargano area (southern Italy)
In the first week of September 2014, the Gargano Promontory (Apulia, SE Italy) was hit by an extreme rainfall
event that caused several landslides, floods and sinkholes. As a consequence of the floods, two people lost their
lives and severe socio-economic damages were reported. The highest peaks of rainfall were recorded between
September 3rd and 6th at the Cagnano Varano and San Marco in Lamis rain gauges with a maximum daily rainfall
(over 230 mm) that is about 30% the mean annual rainfall.
The Gargano Promontory is characterized by complex orographic conditions, with the highest elevation of about
1000 m a.s.l. The geological setting consists of different types of carbonate deposits affected by intensive development
of karst processes. The morphological and climatic settings of the area, associated with frequent extreme
rainfall events can cause various types of geohazards (e.g., landslides, floods, sinkholes). A further element enhancing
the natural predisposition of the area to the occurrence of landslides, floods and sinkholes is an intense
human activity, characterized by an inappropriate land use and management.
In order to obtain consistent and reliable data on the effects produced by the storm, a systematic collection of information
through field observations, a critical analysis of newspaper articles and web-news, and a co-operation with
the Regional Civil Protection and local geologists started immediately after the event. The information collected
has been organized in a database including the location, the occurrence time and the type of geohazard documented
with photographs.
The September 2014 extreme rainfall event in the Gargano Promontory was also analyzed to validate the forecasts
issued by the Italian national early-warning system for rainfall-induced landslides (SANF), developed by the Research
Institute for Geo-Hydrological Protection (IRPI) for the Italian national Department for Civil Protection
(DPC). SANF compares rainfall measurements and forecasts with empirical rainfall thresholds for the prediction
of landslide occurrence. SANF forecasts were compared to the documented landslides and discussed
Distribution and Features of Natural and Anthropogenic Sinkholes in Apulia
Sinkholes, of both natural and anthropogenic origins, represent the main geological hazard in Apulia, a region in southern Italy characterized for most of its extension by soluble rocks, with widespread presence of karst caves and man-made cavities. Occurrence of sinkholes in Apulia is described and analysed in this paper, by using the data extracted from the chronological database of sinkholes, produced by CNRIRPI
for the whole Italian territory. It appears that the frequency of documented events strongly increased in the last decades in Apulia, in the aftermath of a series of sinkholes that hit different parts of the region
A chronological catalogue of sinkholes in Italy: the first step toward a real evaluation of the sinkhole hazard
Among the many different types of geological hazards affecting the Italian territory, sinkholes have often been underestimated (if not neglected entirely), and only in some sectors of the country have they been effectively considered in hazard and risk analysis. Nevertheless, sinkholes affect large parts of Italy, covering the whole territory with a variety of typologies, and exhibit both natural and anthropogenic origin. The latter clearly originate from the long history of Italy, with the complex historical vicissitudes that have characterized this territory, during which different types of artificial cavities have been realized underground for different purposes in different epochs. Over time, many of these cavities have been abandoned, and the consequent loss of memory resulted in their inclusion in newly developed parts of towns, thus creating a serious risk to the built-up environment above.
Starting from these considerations, an archival research was started to collect information about the occurrence of sinkholes in Italy, with particular attention to their precise site and date of occurrence, in order to make an effort in assessing, respectively, the susceptibility and the hazard related to the particular phenomenon under study. As concerns date of occurrence, the accuracy of the information is provided (depending upon the amount of available data), with the highest quality when hour, day, month and year of occurrence are indicated, and a decrease in quality when one or more of these data are lacking. In order to be included in the database, at least some kind of temporal reference (even if general) of the sinkhole has to be known
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