Landslide inventory and rockfall risk assessment of the Monte Pellegrino Oriented Nature Reserve area (Sicily)

In the last 20 years the natural oriented reserve of Monte Pellegrino is affected by several rockfall events. This sector of the Northern Sicily is a strategic urban area and represent the most important element of both the religious and cultural tradition and landscape for the city of Palermo.The rockfalls are here the major natural threats and represent a relevant risk of people, structures and infrastructures and prevents the economic and social development that could be made by high tourist potential of the area. For the above mentioned reasons a detailed geological and geotechnical study in order to define a quantitative risk analysis is now being carried out, concurrently with the implementation of the landslide inventory essential for analysis and monitoring. Monte Pellegrino, located along the Alpine orogenic belt (Catalano et al., 2013) in the emerged Sicilian fold and thrust belt, is an isolated carbonate massif characterized by the presence of poor rock masses and steeply sloping hillsides. The quantitative risk analysis was performed through several steps and taking into account the provisions of directive which is in force in the local institutions. The spread of a rockfall depends on many control factors such as geological setting and geomechanical features for both source area and below area, it is therefore necessary to define different input elements: an inventory of landslides, a database of factors and a dataset that contains the results of the on-site inspections like the geostructural and geomorphological data. The archive of landslides occurred over a period of 20 years was created; the spatial database (constructed in accordance with the standards) contains information on the identification code and date of the event, location, type, involved lithology and related thematic maps. Other thematic maps are those requirements deriving from the factors layers as tectonic features, morphological characteristics, geometric attributes of the slope, type of coverage, structures and infrastructures, trajectory of the block and the stop point. The above mentioned steps allow the implementation and calibration of the model for rockfall analysis; in particular, by means back-analysis stage it is possible to determine the restitution and friction coefficients through a comparison of the points where the rock blocks stop in the simulation with the rockfall history stop points. The next step we took is to produce the map of those areas with different degree of risk defined through the density of the trajectories reconstructed through the model. Finally, are presented here two between the cases studied needed to set up the forecasting model for the rockfall trajectories. Catalano R., Valenti V., Albanese C., Accaino F., Sulli A., Tinivella U., Gasparro Morticelli M., Zanolla C., Giustiniani M., 2013 – Sicily fold-thrust belt and slab roll-back: the SI.RI.PRO. seismic crustal transect. Journal of the Geological Society, 170, 451–464

Carta Geomorfologica del bacino idrografico del Rio Spinasanta e note illustrative(Sicilia centro-settentrionale).

Geomorphological map of the Rio Spinasanta river basin and illustrative notes (Central-northern Sicily). The present paper aims to illustrate the geomorphological map of the Rio Spinasanta river basin, in which landforms recognizable on the area are mapped and distinguished according to the responsible geomorphological process. The Rio Spianasanta river is a tributary of the head sector of the Imera Settentrionale river and is contiguous to the regional water divide that separate the northward and southward flowing Sicilian rivers; the geomorphological map has been produced using as support a topographic map on scale 1:10,000. The geomorphological map has been carried out by means of different methodologies, namely geological and geomorphological field surveys, analysis of aerial photos and orthophotos.Moreover, the geomorphological characterization of the area has been supported by the study of the pluviometric conditions and by the analysis of the landforms’ spatial distribution; the latter, which has been carried out using a GIS software, allowed to evaluate the density of landforms on the classes of the lithology parameter and on the classes of slope angle and aspect. The GIS analysis showed that the combinations of the selected parameters control the intensity of the processes and the spatial distribution of the shaped landforms; this fact led to different landscapes recognizable in the studied area. The landforms mapped in the Rio Spinasanta river basin have been distinguished according to the modeling processes in: a) landforms shaped by water erosion processes; b) landforms produced by gravitational processes

Malta and Sicily Joined by Geoheritage Enhancement and Geotourism within the Framework of Land Management and Development

Malta and Sicily, which lie at the centre of the Mediterranean Sea, share a long history and have unique geological and geomorphological features which make them attractive destinations for geotourism. In the framework of an international research project, a study for the identification, selection and assessment of the rich geological heritage of Malta and Sicily was carried out, aiming to create a geosite network between these islands. Based on the experience and outputs achieved in previous investigations on geoheritage assessment carried out in various morpho-climatic contexts, an integrated methodology was applied for the selection, numerical assessment and ranking of geosites. The selection phase was based on three main criteria-scientific, additional and use values-and led to the establishment of a list of 42 geosites (20 in Malta and 22 in Sicily). Besides being spectacular and attractive for tourists, these sites represent the main geomorphological contexts and the various stages of regional morphogenesis of the study areas. The sites selected were assessed quantitatively and ranked according to management and tourism criteria. The results provide both the necessary basic knowledge for joint conservation actions and policies in Malta and Sicily and the elements for creating a link between Malta and Sicily through geoheritage appraisal and tourism development

Malta and Sicily Joined by Geoheritage Enhancement and Geotourism within the Framework of Land Management and Development

Malta and Sicily, which lie at the centre of the Mediterranean Sea, share a long history and have unique geological and geomorphological features which make them attractive destinations for geotourism. In the framework of an international research project, a study for the identification, selection and assessment of the rich geological heritage of Malta and Sicily was carried out, aiming to create a geosite network between these islands. Based on the experience and outputs achieved in previous investigations on geoheritage assessment carried out in various morpho-climatic contexts, an integrated methodology was applied for the selection, numerical assessment and ranking of geosites. The selection phase was based on three main criteria—scientific, additional and use values—and led to the establishment of a list of 42 geosites (20 in Malta and 22 in Sicily). Besides being spectacular and attractive for tourists, these sites represent the main geomorphological contexts and the various stages of regional morphogenesis of the study areas. The sites selected were assessed quantitatively and ranked according to management and tourism criteria. The results provide both the necessary basic knowledge for joint conservation actions and policies in Malta and Sicily and the elements for creating a link between Malta and Sicily through geoheritage appraisal and tourism development

Landslide inventory and rockfall risk assessment of a strategic urban area (Palermo, Sicily)

This study concerns the assessment of the rockfall risk for two strategic sectors of the Mount Pellegrino, one of the most relevant place in the city of Palermo. During the last two decades, several rockfalls affected the study area setting up a serious threat to the people, structures and infrastructures preventing the economic and social development. For these landslides a detailed GIS inventory was realized; the most dangerous rockfalls occurred within the two study sectors. In both areas we have carried out detailed field surveys and the geo-mechanical characterization of the rock slopes. These analyses allowed to define the rock mass parameters, the set of discontinuities and the kinematics. The back analyses for the past events were conducted permitting to define the blocks trajectories using a numerical model for rockfall simulation. Through this procedure the hazardous areas have been identified and the map of the landslide risk was produced considering the possible spread of the blocks both on land and at sea. The results were exploited to compare this map with the existent map in the framework of the Sicilian Master Plan for hydrogeological risk (PAI), showing that the new risk areas are larger than those previously mapped

Investigating the Effects of Cell Size in Statistical Landslide Susceptibility Modelling for Different Landslide Typologies: A Test in Central–Northern Sicily

Optimally sizing grid cells is a relevant research issue in landslide susceptibility evaluation. In fact, the size of the adopted mapping units influences several aspects spanning from statistical (the number of positive/negative cases and prevalence and resolution/precision trade-off) and purely geomorphological (the representativeness of the mapping units and the diagnostic areas) to cartographic (the suitability of the obtained prediction images for the final users) topics. In this paper, the results of landslide susceptibility modelling in a 343 km2 catchment for three different types of landslides (rotational/translational slides, slope flows and local flows) using different pixel-size mapping units (5, 8, 10, 16 and 32 m) are compared and discussed. The obtained results show that the higher-resolution model (5 m) did not produce the best performance for any of the landslide typologies. The model with 8 m sized pixels displayed the optimal threshold size for slides and slope flows. In contrast, for local flows, an increasing trend of model prediction accuracy was reached with 32 m pixels, which was a higher value than that presented using 8 m pixels. The variable importance analysis demonstrated that the better performance of the 8 m cells was due to their effectiveness in capturing morphological conditions which favour slope instability (profile curvature and middle and high ridges)