Giovanni Gullà

Geometric and kinematic characterization of landslides affecting urban areas: the Lungro case study (Calabria, Southern Italy)

The geometric and kinematic characterization of landslides affecting urban areas is a challenging goal that is routinely pursued via geological/geomorphological method and monitoring of ground displacements achieved by geotechnical and, more recently, advanced differential interferometric synthetic aperture radar (A-DInSAR) data. Although the integration of all the above-mentioned methods should be planned a priori to be more effective, datasets resulting from the independent use of these different methods are commonly available, thus making crucial the need for their standardized a posteriori integration. In this regard, the present paper aims to provide a contribution by introducing a procedure that, taking into account the specific limits of geological/geomorphological analyses and deep/surface ground displacement monitoring via geotechnical and A-DInSAR data, allows the a posteriori integration of the results by exploiting their complementarity for landslide characterization. The approach was tested in the urban area of Lungro village (Calabria region, southern Italy), which is characterized by complex geological/geomorphological settings, widespread landslides and peculiar urban fabric. In spite of the different level of information preliminarily available for each landslide as result of the independent use of the three methods, the implementation of the proposed procedure allowed a better understanding and typifying of the geometry and kinematics of 50 landslides. This provided part of the essential background for geotechnical landslide models to be used for slope stability analysis within landslide risk mitigation strategies.

Chemical and minero-petrographic features of Plio-Pleistocene fine-grained sediments in Calabria, southern Italy

The composition of Plio-Pleistocene fine-grained sediments from different areas of Calabria (southern Italy), have been studied to unravel the interplay of provenance. The use of multivariate statistical methods ( e.g. , PCA) based on biplot, allows for the discrimination of different groups of sediments. The general chemical composition of the fine-grained samples reflects the mineralogical variation observed in the sediments, which are composed of phyllosilicates, quartz, calcite, dolomite and feldspars. The I-S mixed layers, 10 A-minerals (illite and micas) are the most abundant phyllosilicates, chlorite and kaolinite are present in variable amounts, and smectite and chlorite/smectite mixed layers are presents in trace amounts. These chemical and mineralogical variations are also confirmed by SEM analysis, which also demonstrates that phyllosilicates are characterized by open and folded structures with generation of neoformed clay minerals. Provenance proxies and element ratios testify greater input of felsic source rocks, with lack of a marked mafic-ultramafic detritus input for all studied sediments, and the minero-petrographical features of the studied fine-grained sediments. These chemical and mineralogical variations are also confirmed by SEM analysis showing abundant phyllosilicate minerals for Groups 1 (Crotone Basin) and 2 (Crati Graben) and high content of quartz and feldspars grains for Group 4 (Catanzaro Graben) samples, probably due to abundant siliciclastic input coming from plutonic-metamorphic source and associated Mesozoic to Miocene sedimentary sources (Sila and Serre Massifs), and abundant calcium-carbonate phases mainly related to the presence of planktonic calcareous microfossils (Globigerina and coccoliths) for Groups 3 (southern Ionian coast) and 5 (southern Tyrrhenian coast). Furthermore, paleogeographic reconstructions characterized by re-establishment of open-marine conditions in the Mediterranean following the Messinian salinity crisis at the beginning of the Pliocene, play an important role. A progressive increase in the connectivity of Mediterranean sub-basins with the Atlantic ( e.g. , sub-basins at the south of the Catanzaro Strait, characterized by normal water supply) and Paratethys ( e.g. , sub-basins at the north of the Catanzaro Strait, characterized by freshwater supply) can be envisaged during the Neogene period; this paleogeographic reconstruction may also explain the different composition among the studied samples.

Mass-movement, geologic structure and morphologic evolution of the Pizzotto–Greci slope (Calabria, Italy)

Abstract Deep-seated mass-movements of different types affect the Pizzotto–Greci slope in northwest Calabria, Italy. The slope is carved out of phyllitic rocks capped by gneissic layers. Its geological structure is extremely complicated by tectonic structures that pervasively cross the slope transversely and downslope. A large-scale gravitational deformation of sackung type affects the slope. On the upslope side a debris-flow source area feeds a large fan constructed by recurrent debris-flow deposits. Aggradation is consequently occurring along the stream at the base of the slope. In order to define the internal structure of the slope for a stability slope model, geological, geostructural, geomorphological, historical and dendrogeomorphologic studies, as well as direct geotechnical logs and indirect geophysical investigations have been carried out over a two-year project financed by the EC Environment Programme. The main aspects of the geological and geomorphological studies and some preliminary geotechnical data are presented here, along with a conceptual model aimed at describing the relationships between the mass-movements on the slope and the construction/destruction stages of the fan at the base of the slope. The model is based on the assumption that aggradation has a stabilising effect on the slope, thus debris-flow activity is reduced and, consequently, destruction of the fan occurs, bringing the slope again towards unstable conditions. The reactivation of mass-movement, however, leads to the reconstruction of the fan and the buttressing effect at the base of the slope is restored. Thus, the process is cyclic and self-regulating.

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.

Weathering grade and geotectonics of the western-central Mucone River basin (Calabria, Italy)

This paper illustrates the compilation of an engineering geological map based on structural architecture and weathering grade of crystalline rocks occurring in the central-western portions of the Mucone River basin (Sila Massif, Calabria, Italy). The map, drawn at 1:10,000 scale and covering an area of about 100 km2, was compiled by combining new geological and structural data with the results of a weathering-grade field survey. Five weathering classes, each characterized by comparable mechanical behaviour, have been mapped, from the class VI (residual and colluvial soils) to class II (slightly weathered rock). Both qualitative and semi-quantitative criteria (e.g. rock colour, discolouration processes, samples broken by hand and hammer, sound of the rock when it is struck by a geological hammer, Schmidt Hammer tests) were used to distinguish and map weathering-grade classes at outcrop scale. The thematic map presented in this paper aims to provide a useful tool for land planning policy, for the evaluation of geological and geotechnical hazard and for environmental and engineering perspectives of land use.

Empirical fragility and vulnerability curves for buildings exposed to slow-moving landslides at medium and large scales

Slow-moving landslides yearly induce huge economic losses worldwide in terms of damage to facilities and interruption of human activities. Within the landslide risk management framework, the consequence analysis is a key step entailing procedures mainly based on identifying and quantifying the exposed elements, defining an intensity criterion and assessing the expected losses. This paper presents a two-scale (medium and large) procedure for vulnerability assessment of buildings located in areas affected by slow-moving landslides. Their intensity derives from Differential Interferometric Synthetic Aperture Radar (DInSAR) satellite data analysis, which in the last decade proved to be capable of providing cost-effective long-term displacement archives. The analyses carried out on two study areas of southern Italy (one per each of the addressed scales) lead to the generation, as an absolute novelty, of both empirical fragility and vulnerability curves for buildings in slow-moving landslide-affected areas. These curves, once further validated, can be valuably used as tools for consequence forecasting purposes and, more in general, for planning the most suitable slow-moving landslide risk mitigation strategies.

Weathering grade in granitoid rocks: The San Giovanni in Fiore area (Calabria, Italy)

This paper illustrates the methodology and techniques for the compilation of a thematic (engineering) geological map based on detailed mapping of the weathering grade of crystalline rocks occurring in a portion of the Sila Massif close to the San Giovanni in Fiore Village (Calabria, Italy). The map (1:5000 scale), covering an area of about 20 km2, was compiled combining new geological and structural data with the results of a weathering grade field survey. The methodology, used to distinguish and map the weathering grade classes, was performed using qualitative criteria, semi-quantitative tests, and petrographic analysis of weathered rock samples. The Main Map, presented in this paper, aims to provide a useful tool for land-use planning, for geological hazard assessment and engineering perspectives.

The Use of DInSAR Data for the Analysis of Building Damage Induced by Slow-Moving Landslides

The paper aims at checking the contribution that DInSAR data, processed via different algorithms, can provide to the analysis of damages recorded to buildings located in slow-moving landslide affected areas. For this purpose, an urban area in Calabria region, southern Italy, was selected due to the availability of both DInSAR data since 1992 and historic information concerning damage data recorded via municipal ordinances. The combination of DInSAR data and the results of supplementary damage surveys allowed the preliminary investigation of a cause (maximum velocity)—effect (damage) relationship which, once validated, can be valuably used for damage analysis and forecasting.