Roberto Coscarelli

Influence of the North Atlantic Oscillation on winter rainfall in Calabria (southern Italy)

Seasonal rainfall amounts, directly responsible for availability of water resources on a specified area, are strongly dependent on the climate system. In order to highlight some features of such dependence, generally circulation indexes based on the difference in the sea level pressure between two geographic areas are taken into account. In the present study, the relationships between winter rainfall series observed in the Calabria region (southern Italy) and the North Atlantic Oscillation Index (NAOI) have been analysed. Firstly, a correlation analysis between precipitation and the NAOI was performed. Subsequently, the influence of the different phases of the NAO on the winter precipitation has been detected by a composite analysis, and by identifying changes in the behaviour of the probability density functions (gamma distribution) fitted on monthly rainfall. The results evidence a clear link existing between the phases of the climatic index and the amount of winter rainfall.

Time evolution of landslide damages to buildings: the case study of Lungro (Calabria, southern Italy)

In the last decades, building damage caused by landslides in urban areas has increased due to the rapid growth of urbanization even on landslide-prone slopes. This work presents the analysis results of landslide damage evolution by means of a macrodamage index in relation to the characteristics of landslides. The study area is located in southern Italy, and is affected by slow-moving landslides, which, over time, have caused relevant effects on the buildings. A series of geological and geomorphological studies and field surveys, supported by monitoring via conventional geotechnical techniques, allowed us to classify four categories of landslides based on the following criteria: landslide movement, type of material and estimated depth. Detailed field surveys aimed at evaluating distribution and evolution of the damage to buildings located within and near the unstable area were carried out in 2005 and 2011. The evaluation of the macrodamage index in two different years enabled us to directly correlate the features of the landslide categories and their effects on the urban fabric.

Slope movements induced by rainfalls damaging an urban area: the Catanzaro case study (Calabria, southern Italy)

Calabria is one of the Italian regions mostly affected by mass movements. The case study of a densely populated neighborhood (Ianò) located in the central-western sector of Calabria is presented. The several landslides triggered in February 2010 caused heavy damages to the built area, infrastructures and productions of this neighborhood, and increased the risk for the inhabitants. The results obtained through field surveys, photo interpretation, analyses of rainfall data and of the urban fabric evolution, historical survey on the reports of the damages caused by landslides, have enabled to formulate hypotheses on the potential causes that triggered landslide events and produced severe consequences on the area. These results have revealed that almost all landslides of February 2010 are partial reactivations of pre-existing landslide deposits. Moreover, the analyses have indicated a critical role of cumulative rainfalls over an interval of 15 days. However, the severe damage framework is explained through an unplanned urbanization which took place across the years on an area characterized by a high level of instability per se. Some buildings have been erected in proximity of or within pre-existing landslide scarps; in other cases, buildings have been constructed even inside the landslide bodies.

Shallow landslides triggered by consecutive rainfall events at Catanzaro strait (Calabria–Southern Italy)

This paper describes the activities conducted for the development of a thematic map of shallow landslides (and other landforms) resulting from by consecutive rainfall events during the fall-winter seasons of 2008/2009 and 2009/2010 in the Catanzaro Strait (Central Calabria, South Italy). The methodology is based on the interpretation of Google Earth high-resolution satellite images (post-event images are dated 19th March 2010), followed by processing and management of the collected data through a geographic information system. The inventory covers a wide area (692 km2) and includes 3483 shallow landslides and many other geomorphological features (zones of incipient shallow landslides and areas affected by soil erosion) related to the 2008–2010 rainfall events. The map produced may provide useful data to define shallow landslide events, develop landscape evolution models and characterise active geomorphic processes. Furthermore, the map may also be used as a basic tool to produce landslide or erosion susceptibility maps, which can be used for land-use planning strategies and landslide hazard analyses.

A stochastic model for the analysis of the temporal change of dry spells

In the present paper a stochastic approach which considers the arrival of rainfall events as a Poisson process is proposed to analyse the sequences of no rainy days. Particularly, among the different Poisson models, a non-homogeneous Poisson model was selected and then applied to the daily rainfall series registered at the Cosenza rain gauge (Calabria, southern Italy), as test series. The aim was to evaluate the different behaviour of the dry spells observed in two different 30-year periods, i.e. 1951–1980 and 1981–2010. The analyses performed through Monte Carlo simulations assessed the statistical significance of the variation of the mean expected values of dry spells observed at annual scale in the second period with respect to those observed in the first. The model has then been verified by comparing the results of the test series with the ones obtained from other three rain gauges of the same region. Moreover, greater occurrence probabilities for long dry spells in 1981–2010 than in 1951–1980 were detected for the test series. Analogously, the return periods evaluated for fixed long dry spells through the synthetic data of the period 1981–2010 resulted less than half of the corresponding ones evaluated with the data generated for the previous 30-year period.

Stochastic analysis of long dry spells in Calabria (Southern Italy)

A deficit in precipitation may impact greatly on soil moisture, snowpack, streamflow, groundwater and reservoir storage. Among the several approaches available to investigate this phenomenon, one of the most applied is the analysis of dry spells. In this study, a non-homogeneous Poisson model has been applied to a set of high-quality daily rainfall series, recorded in southern Italy (Calabria region) during the period 1981–2010, for the stochastic analysis of dry spells. Firstly, some statistical details of the Poisson models were presented. Then, the proposed model has been applied to the analysis of long dry spells. In particular, a Monte Carlo technique was performed to reproduce the characteristics of the process. As a result, the main characteristics of the long dry spells have shown patterns clearly related to some geographical features of the study area, such as elevation and latitude. The results obtained from the stochastic modelling of the long dry spells proved that the proposed model is useful for the probability evaluation of drought, thus improving environmental planning and management.

Sensitivity to desertification of a high productivity area in Southern Italy

Calabria (Southern Italy) is one of the Italian regions most affected by desertification phenomena. This study presents a detailed analysis of the sensitivity to desertification of an economically important agricultural area in the province of Crotone. The Environmentally Sensitive Areas methodology, developed during the European Union MEDALUS project, has been applied by means of a consistent set of pedological, vegetation, climatic and management data of the study area. Analysis of 15 biophysical and social-economic indicators and an evaluation of 4 Quality Indices allowed the classification of the study area into potential, fragile and critical areas in relation to desertification. The main result is a pronounced sensitivity to desertification of the area: about 46% of the land emerges as being already affected by degradation phenomena, falling within the worst class (‘critical’), while about 39% of the area belongs to the ‘fragile’ class.

Recent damaging events on alluvial fans along a stretch of the Tyrrhenian coast of Calabria (southern Italy)

Debris flow and flood phenomena constitute the main natural hazards on alluvial fans. These processes, often occurring during intense rainfall events, may put many communities living on fan surfaces at high risk. This article focuses on an area along the Tyrrhenian coast of Calabria (southern Italy) where a set of mountain front alluvial fans has developed on the narrow coastal plain. This area has been heavily exploited, and tourism constitutes an important source of income. Rainfall events occurring in 2009, 2010 and 2011, albeit not significantly intense, induced debris flows endangering the population and damaging private property and infrastructures. The analysis highlighted that in the study area the risk due to debris flow and the vulnerability of the area have increased as a consequence of both the reactivation of construction processes in the alluvial fan feeder basin and the intense development of human activities in the same areas. The construction of protection facilities and the loss of the historical accounts of past catastrophic events have encouraged this development. Given the characteristics of the study area, the choice and design of the most appropriate measures need particular attention.

A combined stochastic analysis of mean daily temperature and diurnal temperature range

In this paper, a stochastic model, previously proposed for the maximum daily temperature, has been improved for the combined analysis of mean daily temperature and diurnal temperature range. In particular, the procedure applied to each variable sequentially performs the deseasonalization, by means of truncated Fourier series expansions, and the normalization of the temperature data, with the use of proper transformation functions. Then, a joint stochastic analysis of both the climatic variables has been performed by means of a FARIMA model, taking into account the stochastic dependency between the variables, namely introducing a cross-correlation between the standardized noises. The model has been applied to five daily temperature series of southern Italy. After the application of a Monte Carlo simulation procedure, the return periods of the joint behavior of the mean daily temperature and the diurnal temperature range have been evaluated. Moreover, the annual maxima of the temperature excursions in consecutive days have been analyzed for the synthetic series. The results obtained showed different behaviors probably linked to the distance from the sea and to the latitude of the station.