Gaetano Robustelli

Application and validation of bivariate GIS-based landslide susceptibility assessment for the Vitravo river catchment (Calabria, south Italy)

The Calabria (Southern Italy) region is characterized by many geological hazards among which landslides, due to the geological, geomorphological, and climatic characteristics, constitute one of the major cause of significant and widespread damage. The present work aims to exploit a bivariate statistics-based approach for drafting a landslide susceptibility map in a specific scenario of the region (the Vitravo River catchment) to provide a useful and easy tool for future land planning. Landslides have been detected through air-photo interpretation and field surveys, by identifying both the landslide detachment zones (LDZ) and landslide bodies; a geospatial database of predisposing factors has been constructed using the ESRI ArcView 3.2 GIS. The landslide susceptibility has been assessed by computing the weighting values (Wi) for each class of the predisposing factors (lithology, proximity to fault and drainage line, land use, slope angle, aspect, plan curvature), thus evaluating the distribution of the landslide detachment zones within each class. The extracted predisposing factors maps have then been re-classified on the basis of the calculated weighting values (Wi) and by means of overlay processes. Finally, the landslide susceptibility map has been considered by five classes. It has been determined that a high percentage (61%) of the study area is characterized by a high to very high degree of susceptibility; clay and marly lithologies, and slope exceeding 20° in inclination would be much prone to landsliding. Furthermore, in order to ascertain the proposed landslide susceptibility estimate, a validation procedure has been carried out, by splitting the landslide detachment zones into two groups: a training and a validation set. By means of the training set, the susceptibility map has first been produced; then, it has been compared with the validation set. As a result, a great majority of LDZ-validation set (85%) would be located in highly and very highly susceptible areas. The predictive power of the model is considered reliable, since more than 50% of the LDZ fall into 20% of the most susceptible areas. The reliability of the susceptibility map is also suggested by computing the SCAI index, true positive and false positive rates; nevertheless, the most susceptible areas are overestimated. As a whole, the results indicate that landslide susceptibility assessment based on a bivariate statistics-based method in a GIS environment may be useful for land planning policy, especially when considering its cost/benefit ratio and the need of using an easy tool.

Facies analysis and depositional architecture of shelf-type deltas in the Crati Basin (Calabrian Arc, south Italy)

This study focuses on facies analysis and depositional architecture of the Arente shelf-type delta, located at the southernmost margin of the Pleistocene Crati Basin (northern Calabria, southern Italy). Tectonically-controlled Gilbert deltas are extensively discussed in the literature, whereas few works document shelf-type deltas and factors controlling sedimentation. This paper contributes to these issues, with a special focus on evaluating eustatic and tectonic control on depositional architecture also by considering the occurrence of coeval Gilbert-delta systems.The Arente delta complex represents part of the coarse-grained sediments presently exposed along the eastern margin of the Crati Basin. It was sourced from the rising Sila Massif to the E and shows an overall westerly progradation.Conventional sedimentological analysis allowed to distinguish seven different facies associations. Well-exposed sections, at the basin margin, generally show an overall upward transition, locally basinward, from mouth-bar conglomerates and sandstones, to deltafront sandstone, to offshore mudstones. Facies distribution and arrangement are interpreted as the record of a shoal-water fan delta.Depositional processes were clearly influenced by the high sediment input, with a dominance of hyperpycnal deposits.Based on the occurrence of a series of bounding surfaces indicating abrupt drowning stages, the Arente deltaic succession can be divided into 5 distinct transgressive-regressive sequences.The fining and the thinning upward trend of the whole succession and the stacked landward-stepping architecture of the transgressiveregressive sequences, i.e. the E-directed retrogradational behavior of the Arente delta complex indicate that.Tectonic subsidence provided the accommodation space for the deposition of the delta complex, for the marked local backstepping of the system, and for the progressive drowning of bedrock. Highfrequency sea level fluctuations led to the repeated arrangement of the facies associations; in particular, the stacking of the individual deltaic sequences separated by transgressive surfaces suggests amplitudes of eustatic sea-level changes of a few tens of metres, thus representative of a higher-order cyclicity. The differing internal architecture, if compared to the steeply-dipping foreset beds of the Gilbert-type delta cropping out to the N of the study area, is interpreted as due to a decrease in displacement toward the southern tip of the Crati system fault.

Vertical movements in the Ionian margin of the Sila Massif (Calabria, Italy)

Detailed geological-geomorphological investigations, carried out in the Ionian coastal belt between the Trionto River and the Colognati River, allowed us to set up a tectonic-sedimentary model of the northern flank of the Sila Massif during Pliocene-Pleistocene times. The study area is characterised by a distinct step-like topography displaying a well-preserved flight of coastal plain (alluvial/marine) terraces, arranged in five altimetric orders (T1 to T5). The deposition of sandy-clayey marine sediments of Middle Pliocene age ( CTSL Unit ) and beach sandstones grading upward to gray silty clays, referred to the Emilian-Sicilian ( Bisciglia Unit ) on the basis of micropaleontological analysis, has been related to a phase of subsidence, likely induced by the activity of E-W trending extensional faults. The Bisciglia Unit grades westward into conglomerates, sandstones and silty-clay sediments forming part of juxtaposed and superimposed deltaic (and subordinate alluvial/beach) deposits. A phase of subaerial landscape modelling, starting from the Middle Pleistocene, marks the end of subsidence and the onset of a rapid uplift which, interacting with eustatic sea-level changes, gave rise to the five orders of terraces. The uplift rate of the whole area, inferred by correlating the terrace surfaces with the paleoclimatic curve proposed by Bintanja et alii (2005), is 0.65 ± 0.1 mm yr −1 . However, the contemporaneous occurrence of extensional fault activity in the area induced variations in the uplift rates, which actually range between 0.52 and 0.88 mm yr _1 in relation to the distance from the fault trace. These data highlight the competing role of fault activity and regional uplift in controlling vertical movements and surface topography at the local scale.

Using Tephrochronology and palynology to date the MIS 13 lacustrine sediments of the Mercure basin (Southern Apennines – Italy)

The paper deals with the chronostratigraphy of the lacustrine infilling of the Mercure basin, an intramontane depression of the Southern Apennines, located along the Calabria-Lucania boundary.A preliminary tephrochronologic investigation and pollen analyses were carried out on the infilling succession exposed along V-shaped tributary valleys of the Mercure river. Lithological and chemical features of the thickest and best preserved tephra layer were fully characterised, and single crystal 40Ar/39Ar dating was performed yielding an age of 514±16 ka. Pollen analyses revealed the occurrence of warm and humid interglacial conditions that were correlated to MIS 13 on the basis of the age determination. The chemical compositions of glasses indicate that the Sabatinian volcanic field is the most probable source of the investigated tephra layer. Although chemical features support a correlation with the Tufo Giallo della Via Tiberina multiphase eruption that occurred between 561 and 548 ka, the integration of tephrochronology and pollen analysis points to a younger age, falling within MIS 13. We propose a correlation with one of the four explosive events that occurred in the Latial district from 514 to 449 ka. The Mercure tephra layer, owing to its age and great distance from the presumed source, represents a valid correlating tool for MIS 13 in central-southern Italy.

Geomorphological map of the Crotone Province (Calabria, South Italy)

Abstract Please click here to download the map associated with this article. The geomorphological map described covers an area of about 1,720 km, located on the northeastern part of Calabria (south Italy); it contributes to the understanding of both long-term landscape evolution and present-day trends of the Crotone Province. The map, at a 1:75,000 scale, integrates information coming from geomorphological analysis of relief, air photo interpretation and fieldwork. It documents the interplay between tectonic and climatic controls at different temporal and spatial scales. Several remnants of planation surfaces, developed during late Miocene-early Pliocene, result from ancient landscape fragmentation and uplift since the Late Pliocene. Marine and alluvial terraces reflect complex cycles of erosion and deposition, possibly in relation to climate and tectonism during most of the Quaternary. Finally, the present landscape is heavily affected by slope denudational processes such as mass movements, running water processes and wave action. This map may provide the basis for further analyses, representing a useful tool for land management as well as the initial step for the assessment of geomorphological hazard and risk.

Integrating geomorphology, statistic and numerical simulations for landslide invasion hazard scenarios mapping

This paper highlights a multidisciplinary method for evaluating debris-flow invasion hazard, based on geological-geomorphological field survey and statistical analysis coupled with numerical simulations through Cellular Automata. The developed hazard assessment methodology consists of different consolidated techniques for the (a) identification of spatial susceptibility, i.e. potential landslide sources in previous unfailed slopes, (b) estimation of the probability of cover thickness involvement in initial landsliding, (c) evaluation of temporal probability and (d) numerical modeling of potential landslides. In this study, the SCIDDICA Cellular Automata landslide model has been considered and applied to the northern sector of Mount Pendolo (Sorrento Peninsula), which was affected by several landslides in historical time. Model calibration has been performed by considering past events of similar scale and type. Results of these simulations were satisfactory as proven by the comparison between real and simulated reference events. Several possible source areas have been hypothesized and a potential future landslide scenario has been simulated by using SCIDDICA. By associating to each simulation a spatial, magnitude and temporal probability, a landslide invasion hazard scenario was mapped. We developed an integrated approach for debris flow invasion hazard scenarios.Spatial, magnitude and temporal probabilities and runout were assessed.The SCIDDICA model was able to well simulate the considered case studies.The validity of the approach is related to the quality and accuracy of input data.By varying statistical hypotheses, different hazard scenarios can be mapped.

Geomorphological Map of the Ionian Area between the Trionto and Colognati River Catchments (Calabria, Italy)

Abstract Please click here to download the map associated with this article. This paper describes a geomorphological map representing a sector of the Ionian coastal belt, located in north-eastern Calabria, between the catchments of the Trionto and Colognati Rivers. The landforms have been distinguished according to their origin into: a) structural and tectonic-controlled landforms; b) gravity-induced landforms; c) landforms formed by running water; d) coastal and transitional landforms; e) anthropic landforms, using as support a simplified topographic map on scale 1:20,000. The geomorphological map provides information about the long-term evolution of the landscape and identifies the geomorphic processes presently active. Therefore, the map could be used in developing land management and planning guidelines.

Soil loss assessment in the Turbolo catchment (Calabria, Italy)

Soil loss caused by accelerated erosion is a growing problem in the Mediterranean belt in general, and in many parts of the Calabrian region (Southern Italy), in particular. It is due to the combination of peculiar geomorphological, pedological and climatic features, very often exacerbated by unsuitable land management. The aim of this study is to analyze and map soil loss by water-induced soil erosion at the catchment scale. Soil loss was quantified using the revised universal soil loss equation (RUSLE) model implemented in a geographical information system. The RUSLE is an empirical model which estimates the average annual soil loss that would generally result from splash, sheet and rill erosion. The analysis shows that total soil loss estimated in the study area is 16,470.88 t yr−1 with an average annual soil loss of 5.65 t ha−1 yr−1. Spatial variation and rates of soil erosion are mainly linked to land use, and the rate of soil erosion varies from less than 1 t ha−1 yr−1 in wooded areas to more than 40 t ha−1 yr−1 in barren land. In addition, the comparison between soil loss and slope maps shows that ∼47% of the estimated soil loss involves slopes with a gradient >20°. The map shows seven classes of soil loss, with 8% in the upper three classes and 51% in the lowest class.

Geomorphological Map of the area between Frosolone and Trivento (Molise, Italy)

Abstract Please click here to download the map associated with this article. A 1:50,000-scale geomorphological map of the area between the settlements of Frosolone and Trivento (Molise Region, Italy) is presented and discussed in this paper. Field surveys and air photo interpretations allowed the characterization of the main morphological landforms of the study area, drawn from the reduction of an original 1:5,000-scale field map. The landforms have been grouped on the basis of the main controlling factors, as follows: i) tectonic and structural landforms; ii) slope landforms; iii) karst landforms; iv) fluvial landforms. This map shows the distribution of the geomorphic processes presently active, as well as the main relic landforms. Consequently, the collected data aim to provide a useful and easy tool for land planning policy; in addition, since the study area represents a typical geomorphic scenario of the southern Apennines, the data produced could be used in developing more widely-applicable landscape evolution models.

The Use of Airborne LiDAR Data in Basin-Fan System Monitoring: An Example from Southern Calabria (Italy)

To analyse morphologic and volumetric changes within an active basin-fan system of about 0.250 km2 in Calabria (South Italy), we compare two high-resolution DTMs (50 cm) derived from aerial LiDAR surveys conducted in October 2012 and May 2013. The comparison allowed us to: (i) evaluate the magnitude of erosion-transport-sedimentation processes (ii) identify the extent of an active landslide within the feeder sub-basin, and (iii) confirm the fan, feeder channel and feeder basin dynamics obtained from previous works based on geological and geomorphological field surveys. The results demonstrate that the LiDAR techniques can be a useful tool for the monitoring of geomorphological changes in areas affected by severe erosion and depositional processes.