Search

To study on a regional basis, the relation between fluvial sediment delivery and coastal erosion, the historical record of coastline migration of Sicily was analyzed with respect to the estimated sediment delivery to the coast obtained from the spatially distributed sediment delivery WaTEM/SEDEM model. The latter was directly acquired from the ESDAC database as a 25 m pixel layers, being based on the combination between the RUSLE model and a transport capacity routing algorithm. At the same time, the coastline-evolution (accretion/retreatment) data for 1960/1994 and 1994/2012 intervals were processed. This dataset, provided by ISPRA (Italian Institute for Environmental Protection and Research), is made by vectorial polygons, corresponding to erosion or accretion areas obtained by the intersection between two coastlines. The dataset contains polygons related to the 1960-1994 and 1994-2012 periods. Once a common baseline was extracted from 2019 satellite images, 22 Physiographic Units (PU) were identified. The PU was defined based on geomorphologic criteria and by assuming a null net sediment budget (null sediment transport between two PU neighboring). Each coastal PU was connected to its contributing fluvial basins, also assigning the expected sediment delivery at the coastline. To perform the analysis, cross profiles along the coastline were generated and intersected with the polygons, calculating a response value, in terms of retreatment or accretion, to each of the cross-profile centroids. Finally, for each PU, the cumulated variations were computed. PUs with significant cumulative variations (more than 2 km) in at least one of the two epochs were identified and three different patterns were detected: accretion/retreatment, retreatment/accretion, and retreatment/retreatment. The response observed for the different PUs was then analyzed considering estimated sediment delivery, recognizing coherent (large sediment delivery = accretion) and incoherent (large sediment delivery = retreatment) behaviors, which have been interpreted as controlled by the history of soil/coastal erosion management practices. In particular, in spite of a very high expected sediment delivery, more than three-quarters of the Powered by TCPDF (www.tcpdf.org) Tyrrhenian coast resulted as affected by a marked retreat in 60-94 (same tens of meters) and a moderate accretion in 94-12, as the result of extensive coastal works which have been realized to mitigate coastal erosion.

Calanchi (singular calanco) represent a typical example of badlands in the Italian peninsula, which rapidly evolve on clayey terrains such as the widespread Pliocene-Pleistocene marine clays. The present study aimed at investigating the role of the slope morphometry on the typology and distribution of morphogenetic processes in a calanchi area located in southern Italy. The research included detailed geomorphological surveying, morphometric and statistical analysis. The study area was first subdivided into individual hydrographic units (HUs), for which field survey allowed to identify the dominant denudation processes, their intensity and the distribution of the associated landforms (pipes, rills, gullies, landslides). The morphometry of each HU was characterized by calculating the Morphometric Slope Index (MSI) on a reconstructed digital elevation model (DEM). By statistically comparing the morphogenetic and morphometric data, the influence of the slope morphometry on the type, distribution and evolution of the calanchi erosion process has been highlighted. In particular, through a Cluster Analysis the groups of HUs having similar dominant processes were identified and, by applying the Analysis of the Variance, the effect of the MSI on the identified clusters was analysed. Two clusters were identified which revealed the relative importance of morphogenetic processes and the strict connection between surface and subsurface landforms. These two clusters were discriminated by the MSI value (high MSI favoured mass movements, whilst low MSI favoured gully erosion and piping), highlighting the importance of slope morphometry in driving the morphogenetic hillslope processes.

This study aims at evaluating the performance of the Maximum Entropy method in assessing landslide susceptibility, exploiting topographic and multispectral remote sensing predictors. We selected the catchment of the Giampilieri stream, which is located in the north-eastern sector of Sicily (southern Italy), as test site. On 1 October 2009, a storm rainfall triggered in this area hundreds of debris flow/avalanche phenomena causing extensive economical damage and loss of life. Within this area a presence-only-based statistical method was applied to obtain susceptibility models capable of distinguishing future activation sites of debris flow and debris slide, which where the main source of failure mechanisms for flow or avalanche type propagation. The set of predictors used in this experiment comprised primary and secondary topographic attributes, derived by processing a high resolution digital elevation model, CORINE land cover data and a set of vegetation and mineral indices obtained by processing multispectral ASTER images. All the selected data sources are dated before the disaster. A spatially random partition technique was adopted for validation, generating 50 replicates for each of the two considered movement typologies in order to assess accuracy, precision and reliability of the models. The debris slide and debris flow susceptibility models produced high performances with the first type being the best fit. The evaluation of the probability estimates around the mean value for each mapped pixel shows an inverted relation, with the most robust models corresponding to the debris flows. With respect to the role of each predictor within the modelling phase, debris flows appeared to be primarily controlled by topographic attributes whilst the debris slides were better explained by remotely sensed derived indices, particularly by the occurrence of previous wildfires across the slope. The overall excellent performances of the two models suggest promising perspectives for the application of presence-only methods and remote sensing derived predictors. Copyright © 2016 John Wiley & Sons, Ltd.

Landslide susceptibility may be evaluated by defining statistical relationships between the spatial distribution of past slope failures and the variability of landslide triggering factors. In this research, susceptibility to landsliding was assessed by employing multivariate adaptive regression splines (MARS), a statistical model that has been rarely used to this aim. The experiment was carried out in an area of central Sicily (Italy), which is severely affected by shallow landslides mainly occurring during the wet autumn- winter semester. Bedrock lithology and a set of primary and secondary topographic attributes were exploited as proxies of main landslide driving factors. The robustness of the procedure and the predictive skill of the susceptibility models were evaluated by calibrating and validating the models on different samples of raster cells. Stable cells (absence of landslides) of these samples were selected using two different methods: i) a random selection of individual stable cells; ii) a selection of cells intersecting circles randomly distributed within the stable sectors of the study area. The fit of the models to calibration and validation samples was quantitatively assessed by drawing receiver operating characteristic (ROC) curves and by calculating the area under the ROC curve (AUC). The validation results indicate high accuracy and stability of the models, demonstrating the ability of MARS to effectively predict the spatial distribution of landslides. Moreover, a better performance was observed for models trained and tested using circular groups of stable cells.

Gulling is a complex process depending on several factors and involving a wide range of sub-processes. Different types of gullies were distinguished and described in literature. Their contribution to soil erosion changes in relation with the typology and their presence is influenced by different controlling factors. Mapping and classifying gullies is crucial for monitoring soil erosion. So far, no systematic definition of morphological characteristics of the different types of gullies and of their controlling factors has been made. The present work aims to suggest an innovative approach to automatically classify gullies by integrating remote sensing, GIS and a classification algorithm. The study was carried out in three subcatchments (20km2) of the Platani River basin, located in southwest Sicily (Italy). Two gullies inventories (2014 and 2008 years), containing more than 400 erosion features, were prepared by integrating Google Earth and aerial orthophotographs images and further field checks. Once mapped, gullies were classified by using the location in the landscape, the morphology and the dominant erosion process leading to their formation as criteria. Several primary and secondary topographic attributes were selected as independent variables in the classification model. The Classification and Regression Tree (CART) algorithm was used to predict the location of the different types of gullies and describe the influence of the different factors taking part of the model. The results, described in terms of AUC values, show high model accuracy. CARTbased gully classification is quicker and more objective than traditional methods. Moreover, the suggested method provided important information about which is the dominant erosion process leading to gullies formation.

The determination of soil properties is considerable challenge when it is aimed to evaluate the spatial distribution of one or more parameters across significant surfaces. In fact, terrain sampling and field data are punctual measurement; therefore, quantitative models are needed to predict the spatial distribution of soil attributes. The spatialization of field and laboratory data is a very important information in landslide studies. Raster layers displaying soil properties can be used both for statistical models and for the parameterization of physically based models. The purpose of this work is to produce a detailed hydrological and mechanical characterization of the soil affected by shallow landsliding processes. The study area is located in Messina (Southern Italy) where a debris flow event occurred on the 1st October 2009. In particular, two small and independent (2 km2) hydrological units were chosen: Racinazzi and Saponarà catchments. The sample sites were selected using a provisional predictive pedologic model based on the topographic attributes Topographic Wetness Index and Steepness of slope. The field analyses were aimed to determine soil thickness, hydraulic conductivity and other soil mechanical properties. The fieldwork was carried out using: (1) Dynamic Cone Penetrometer (2) Amoozemeter (3) Auger sampler. The laboratory analysis of the collected samples have performed in order to characterize granulometry and the Atterberg limits. Stochastic approaches have been then adopted to regionalize the punctual information for each of the collected properties resulting in robust spatial distributions used to characterize landslide prone conditions. The results show the slope instability mainly affect the terraced areas characterized by the presence of a thin layer of soil which, according to the laboratory analysis, testifies an incomplete pedogenesis.

Shallow landslide and debris flows are among the most dangerous natural hazards triggered by extreme meteorological events. These phenomena have recently caused catastrophic scenarios in Italy (e.g. in Sarno-Quindici and Giampilieri) and, according to expected changes in the climate pattern, an increasing frequency of these phenomena is expected. The aim of this research is to assess the debris flow susceptibility in the Giampilieri area (Sicily) using a spatially-distributed debris flow runout model based on topographic information. The application of the model starts with the identification of the source areas from which debris flows are propagated on the basis of frictional laws and flow direction algorithms. The area selected for this study is located in the Ionian sector of the Peloritanian area in Sicily, in the South part of Messina (Sicily) and includes the villages of Giampilieri, Briga Itala and Scaletta Zanclea. There, the 1st October 2009 thousands of debris and mud flows were activated by a cumulative rainfall of about 160 mm in 6 hours, which followed two previous rainfalls events occurred on16th September (76 mm in six hours) and 23rd – 24th September (190 mm in 10 hours). Among the catchments hit by the 2009 event, the Giampilieri basin (10 km2) has been chosen as sub area in order to set the algorithms for the spreading assessment and the friction parameters of the model. In this catchment, a complete inventory of the source areas and accumulation zone was created by photointerpretation of post event images. Moreover, volume and velocity estimations of the mobilized material have been carried out. The susceptibility was evaluated using the source areas of the 2009 event and its accuracy was estimated by the comparison of the results with the accumulation areas and the velocity and volume estimated. In a second step we performed the analysis at the medium scale on the whole area hit by the 2009 event using the parameters calibrated on the Giampilieri basin. The presented approach of debris flow susceptibility analysis demonstrates that a simple assessment of the debris flow spreading calculated using defined source areas and calibrated on past events, provided good results for consequent hazard and risk studies.

In this study, statistical models of earth-flow susceptibility were prepared using logistic regression. The analyses were carried out in a small (51 km2) basin of western Sicily, where 1,376 earth-flows were identified. To predict the spatial distribution of the mapped landslides, outcropping lithology and seven topographic attributes were exploited as explanatory variables. Before calculating these variables, a reconstruction of the pre-failure topography was performed. To evaluate the predictive skill and the robustness of the models, two groups made of five random subsets of earth-flows and stable cells were prepared. Absences of the first group were selected as individual cells whereas those of the second group where picked up using circular areas randomly distributed within the stable portions of the basin. The largely satisfactory accuracy and stability of the models demonstrated the reliability of the reconstructed pre-landslide topography. Furthermore, models prepared with the circular groups of absences showed better predictive skills.

Debris flows are among the most hazardous phenomena in nature, which typically take the form of multiple-occurrence regional landslide events triggered by intense driving inputs such as storms or earthquakes. The main tasks of this study were to verify whether cell-based susceptibility models is capable of predicting debris flow initiations in the Giampilieri catchment (southern Italy) and to explore the relationships between the pixel size of the adopted mapping units in terms of predictive performances of the derived models. The Giampilieri catchment is a small area (10km 2 ) hit by a storm on the 1 st October 2009 which resulted in the triggering of more than one thousand landslides and caused severe damages and 37 fatalities.

In the recent years advanced statistical methods and GIS tools have been frequently used to assess landslide susceptibility. The latter is estimated by establishing statistical relationships between landscape characteristics and spatial distribution of past slope-failures. These are mapped mainly by recognizing changes on slope morphology produced by gravity. Despite of this, most of the researches on landslide susceptibility do not consider that slope-failures modify topography and associate high probability of landsliding with topographic characteristics that differ from those that led slope-failures. In this research we analyzed landslide susceptibility in the basin of the Malvello river with two statistical methods: binary logistic regression and multivariate adaptive regression splines. The study area, which extends for 51 km2 in western Sicily (Italy), is characterized by large outcroppings of clays and marls and is severely affected by shallow landslides. Bedrock lithology and land use were included as predictive variables, in addition to a set of primary and secondary topographic attributes. The latter were derived from a digital elevation model where altitude of areas hosting landslides was interpolated from adjacent undisturbed portions of the slopes. We assume that these artificial surfaces represent the old topography more efficiently respect to the morphology of depletion and accumulation zones of landslides. Ten random samples, with the same number of positive and negative cases, were used to train and test the susceptibility models. Accuracy, as well as overfitting and robustness of the models, were evaluated by drawing receiver operating characteristic (ROC) curves and calculating the area under the ROC curve. In addition of comparing the performance of the statistical methods, the validation results allowed us to highlight advantages/drawbacks of reconstructing original topography of slope-failures when mapping landslide susceptibility.

The SUFRA project is based on a three level susceptibility mapping. According to the availability of more detailed data, the three scale for susceptibility mapping are increased respect to the ones suggested by the TIER group to 1:100,000, 1:50,000 and 1:25,000/1:10,000. The mapping levels exploit climatic, soil use (CORINE2009) and seismic informative layers, differentiating in the details of the core data (geology and topography), in the quality and resolution of the landslide inventory and in the modelling approach (Tab. 1). SUFRA_100 is based on a heuristic approach which is applied by processing a geologic layer (produced by ARTA integrating pre-CARG 1:100,000 geologic maps); the DEM exploited are IGMI 250m and the mapping units are 1km side square cells. Models are validated with respect to the PAI LIPs (Landslide Identification Points) which are reclassified adopting a simplified scheme. Output cuts of SUFRA100 will be referred to administrative boundaries (provinces). SUFRA50 is based on statistical analysis of new CARG geologic maps and 20m (ITA2000) - 2m (ATA2007) DEM. The mapping units are 500m and 50m cells, hydrographic and hydro-morphometric units. The landslide inventory is the IFFI2012_LIPs (first level) which is the result of the conversion in IFFI format of the PAI archive, which will be supported by remote landslide mapping (exploiting the ATA2007 aerial photos), according to the IFFI first level approach. Validation of the models will be performed exploiting both random spatial partition and temporal partition methods. Output cuts of SUFRA50 will be based on physiographic (basin) and administrative (municipalities) boundaries. SUFRA10/25 is based on statistical analysis of new CARG geologic maps (remotely and field adapted) and 2m (ATA2007) DEM. The mapping units are the slope units (SLUs) which are derived by further partitioning the hydro-morphometric units so to obtain closed morphodynamic units. The landslide inventories is the IFFI2012 which is the results of a field supported (on focus) landslide remote systematic mapping, according to the IFFI full level approach. Examples of SUFRA_100, SUFRA_50 and SUFRA_10 are presented for some representative key sector of Sicily. First results attest for the feasibility and goodness of the proposed protocol. The SUFRA program aims at enabling the regional governmental administration to cope with landslide prevision, which is the required operational concept in land management and planning. PAI has been a great advance with respect to the “pre-SARNO” conditions, but it is very exposed to fail: it is a blind approach for new activations; it is critically dependent on the quality of the landslide inventories; it cannot project the susceptibility outside the landslide areas

Oggigiorno, la valutazione della diversa importanza delle variabili geoambientali nel determinare le condizioni di suscettibilità da frana di un’area è uno dei problemi più attuali della geologia. L’uso ed il confronto di due differenti approcci statistici, ha consentito di stimare le condizioni di predisposizione all’instabilità gravitativa dei versanti, per un esteso settore settentrionale della catena appenninica siciliana, ricadente all’interno delle tavolette I.G.M.I. nn. 259 I SE “Scillato” e 259 II NE “Caltavuturo”. L’area oggetto della sperimentazione, estesa circa 200 Km2, è stata suddivisa in maniera semi-automatica in 1827 unità idro-morfologiche o unità di versante. Per ciascun’unità di versante, è stato definito un set di 15 proprietà fisico-ambientali (caratteristiche geologiche, di uso del suolo, attributi topografici primari e secondari), che rappresentano le variabili indipendenti capaci di descrivere i fattori di controllo della stabilità dei versanti. Nell’area era disponibile un archivio di 233 frane di colamento che erano state riconosciute sulla base di fotointerpretazione e controlli di campo condotti nel 1999. In occasione della presente ricerca, utilizzando immagini GoogleTM relative al 2008, è stato realizzato un nuovo archivio eventi contenente 55 attivazioni successive. Per caratterizzare le condizioni di stabilità di ciascuna unità di mappatura, si sono utilizzate due differenti aree diagnostiche: il centroide di ogni area in frana (LC) e l’intera sua area di rottura (AR). Per definire il modello di suscettibilità sono state utilizzate due differenti tecniche di regressione: la Forward Logistic Regression (FLR) e Multivariate Adaptive Regression Splines (MARS). In particolare, si sono utilizzate le frane mappate al 1999 per allenare i modelli e le successive 55 attivazione per la validazione degli stessi. I due metodi sono stati applicati per ciascuna delle due aree diagnostiche, al fine di confrontare anche, per una stessa metodologia, la capacità previsionale offerta. I modelli di suscettibilità ricavati mostrano caratteristiche comuni, selezionando quali variabili indipendenti di maggiore impatto sulle condizioni di stabilità delle unità di mappatura: la pendenza e la lunghezza dell’unità di versante, l’uso del suolo, il comportamento litotecnico atteso dei terreni, la litologia affiorante, le condizioni geomorfologiche, la curvatura longitudinale al versante e l’indice di erosione potenziale. I modelli di regressione costruiti utilizzando quale area diagnostica il punto centroide del movimento franoso hanno performance previsionali (AUC = 0.693) inferiori ai modelli di regressione logistica implementati utilizzando l’intera area di rottura (AUC = 0.722). Il metodo MARS, pur selezionando le stesse variabili predittive, ha raggiunto maggiori prestazioni sia con il modello di previsione costruito sui punti centroidi (AUC > 0.90), sia con quello che utilizza l’intera area di rottura (ROC = 0.84), con un errore GCV sempre minore di 0.09. Entrambi gli approcci statistici hanno prodotto complessi algoritmi che riflettono la complessità dell’area oggetto dello studio e l’interdipendenza tra il set di variabili geoambientali e la franosità. Dai risultati ottenuti con entrambi gli approcci, si evidenzia che l’uso delle unità di versante come unità di mappatura di base, unitamente al punto centroide quale area di attivazione dell’unità morfologica, si presta alla costruzione di un modello di suscettibilità con buone prestazioni previsionali, consentendo un indubbio risparmio in termini di risorse economiche e temporali e, anche e soprattutto, di limitare fortemente gli eventuali errori di mappatura delle forme franose derivate dall’intervento di un operatore.

The studied area is located within two Sicilian districts– Scillato and Caltavuturo. Studied area is 200 km2. This territory is affected by large landslides very strongly. In the course of the research these districts were divided into 2 million square units of 10 × 10 m. Values of landslide factors were assessed within each unit. Using method of logistic regression allowed us to select the most significant factors and to make the landslide susceptibility map. Landslide hazard analys was made with 3 models, which analyze different diagnostic areas (places, where landslides are trigger usually). The results indicate that the using of the buffer zone with radius 50 m around the highest point of the landslide show the most accurate results.

On the 1st of October 2009, the area centred on the village of Giampilieri (Messina), on the Ionian side of the Peloritan belt, suffered thousands of landslides activated in the time lapse of about five hours, which caused 36 victims, more than 100 injured and more than 0.5M€ of damage to structures. This unprecedented phenomenon was triggered by an exceptional meteorological event, recorded at the foothills with 250mm of rain in just 8 hours; this amount of rainfall was cumulated to two previous events (16/IX: 75mm; 23/IX: 190mm) for a total amount of more than 500mm in less than two weeks. Due to the peculiar triggering conditions a huge number of debris flows involved the shallow weathered layer of the outcropping lithologies, consisting of phyllites of the Mandanici Units, mica schists of the Mela Units and medium to high grade Varisic metamorphic rocks. The purpose of this study is to evaluate the exportability of a landslide susceptibility model, obtained by using logistic regression method, within a training hydrographic unit (the “Torrente Briga” catchment) to predict the landslide spatial distribution in a test hydrographic units (the “Torrente Giampilieri” catchment). Both the basins extend for about 10km2. Exporting procedures for susceptibility model are in fact of great importance to optimize the survey costs or when facing phenomena which are locally triggered, such as the ones activated under extreme rainfall events; in fact, in this cases the landslide scenario used to train the statistical model is local and spatially more limited than the extension of while investigated area. In this research we prepared a susceptibility model by means of forward logistic regression in the “Torrente Briga” catchment (871 landslides, regressing an optimized set of computed physicalenvironmental predictors and obtaining the log-function which was then applied to the “Torrente Giampilieri” catchment (1121 landslides). By using a 2m cell DEM (from which we calculated and tested a large set of primary and secondary topographic attributes) and some thematic maps (geology and land use), the following predictors have been selected: height, slope, stream power index, topographic wetness index, profile and plan curvatures, landform classification, outcropping geology, landuse. Unstable slope conditions were assigned to the cells within a 2.9m neighbourhood of the landslide identification points (located on the highest point of the landslide areas). Models were built by merging the unstable cells with an equal number of randomly selected stable cells. To assess the sensitivity of the models with respect to the selection, 8 extractions were performed for each of the two basins, obtaining 8 models for the “Torrente Briga” area and 8x8 exporting combination, for the “Torrente Giampilieri”. The results attest for a high performance of the models, as we obtained excellent AUC both for the the 8 Briga models (>0.84) and the 64 exported Giampilieri models (>0.8). High steepness, low height, plan concave and profile convex curvatures, together with south and south-west verging slopes, are the main controlling factors of debris flow initiations in the two areas.

In the framework of a regional landslide susceptibility study in southern Sicily, a test has been carried out in the Tumarrano river basin (about 80 km2) aimed at characterizing its landslide susceptibility conditions by exporting a ‘‘source model’’, defined and trained inside a limited (about 20 km2) representative sector (the ‘‘source area’’). Also, the possibility of exploiting Google Earth TM software and photo-images databank to produce the landslide archives has been checked. The susceptibility model was defined, according to a multivariate geostatistic approach based on the conditional analysis, using unique condition units (UCUs), which were obtained by combining four selected controlling factors: outcropping lithology, steepness, plan curvature and topographic wetness index. The prediction skill of the exported model, trained with 206 landslides, is compared with the one estimated for the whole studied area, by using a complete landslide archive (703 landslides), to see to what extent the largest time/money costs needed are accounted for. The investigated area stretches in the fore-deep sector of southern Sicily, where clayey rocks, mainly referring to the Numidian Flysch and the Terravecchia Formations, largely crop out. The results of the study confirm both the exploitability of Google Earth TM to produce landslide archive and possibility to adopt in assessing the landslide susceptibility for large basin, a strategy based on the exportation of models trained in limited representative sectors.

L’attuale versione del PAI (Piano Stralcio per l'Assetto Idrogeologico) disponibile per il territorio siciliano è fortemente dipendente dallo scenario di dissesti passati censiti e catalogati, sulla base dei quali, utilizzando un sistema di matrici di valutazione, è possibile ricavare le condizioni di rischio geomorfologico associato. Questo stadio costituisce un primo grande avanzamento delle conoscenze a partire dal quale è ora necessario procedere alla valutazione della suscettibilità da frana e all’adozione dunque di uno strumento di analisi territoriale con carattere previsionale. La realizzazione di una cartografia della suscettibilità da frana a scala regionale pone d’altra parte una serie di problemi di approccio e di tecnica realizzativa, che derivano dalla necessità di trovare un compromesso tra estensione territoriale e risoluzione dei modelli previsionali e, dunque, di risoluzione dei dati necessari in ingresso. Il progetto SUFRA muove dalla stessa analisi metodologica del progetto TIER ma, alla luce della disponibilità per il territorio siciliano di tematismi geologici con maggiore dettaglio e inventari delle forme franose densamente popolati, diverge da questo sia nei dati in ingresso sia nei metodi di costruzione dei modelli, che vengono implementati per la valutazione della suscettibilità nei tre livelli in Sicilia. Tutti i livelli di mappatura sfruttano strati informativi con informazioni riguardo alla geologia, al clima, all’uso del suolo e ai dati sismici. Il progetto SUFRA mira dunque a realizzare una cartografia a varia scala della suscettibilità, articolata secondo i tre livelli: SUFRA100 (scala 1:100,000), SUFRA50 (scala 1:50,000) e SUFRA25/10 (scala 1:25,000 o 1:10,000). SUFRA100 è basato su un approccio euristico utilizzando un DEM con cella di 250 metri derivato dall’IGMI. Le unità di mappatura sono celle quadrate di 1 km di estensione. I modelli sono validati rispetto ai LIP (punti identificazione della frana) che vengono riclassificati con adozione di una semplificazione in due sole principali tipologie (frane di scarpata e frane di versante) dell’archivio PAI, disponibile per tutto il territorio regionale. La rappresentazione di uscita, a questo livello saranno limiti amministrativi come quelli comunali o provinciali. SUFRA50 si basa sull'analisi statistica sfruttando la disponibilità delle nuove carte geologiche (CARG) e un DEM ottenuto ricampionando a celle di 20 metri di lato il DEM ATA2007/08. L’inventario delle frane, utilizzato per questo livello è l’IFFI2012_LIP (solamente il primo livello) che è il risultato della conversione in formato IFFI dell'archivio PAI, che sarà supportato e implementato da un controllo remoto delle aree individuate (sfruttando le foto aeree ATA2007). La rappresentazione di uscita del SUFRA50 sarà basata su confini fisiografici (bacini idrografici) e/o amministrative (comuni). SUFRA10/25 si basa sull'analisi statistica delle carte CARG (verificate con un lavoro di campagna) e sfruttando l’alta risoluzione del DEM ATA2007. Le unità di mappatura di base corrispondono alle unità di versante (SLU), derivate da una nuova ripartizione delle unità idromorfometriche in modo da ottenere unità con coerenza morfodinamica. Gli inventari di frana sono il risultato di una successiva implementazione dell’archivio IFFI2012, controllato e verificato da remoto e con indagini di campo. Esempi di SUFRA_100, SUFRA_50 e SUFRA_10 sono stati realizzati per qualche settore rappresentativo di diversi contesti geologici e geomorfologici Siciliani. I primi risultati attestano per la fattibilità e la bontà del protocollo proposto.

In the present research, two neighbouring calanchi fronts have been monitored by means of repeated readings on erosion pins, that were carried out between November 2006 and October 2008. During the monitoring period, a gauge station has been recording rainfalls, allowing us to compute the Rainfall-Runoff Erosivity Factor of the USLE model. The research highlighted: i) a general correspondence between rainfalls temporal trends and surface variation rhythms; ii) alternating erosion and deposition phases result in a retreat of the “calanchi” fronts.

Exploiting Google EarthTM to assess a landslide susceptibility model: a test in central Sicily. A landslide susceptibility multivariate model, based on the conditional analysis approach, has been derived in the Tumarrano river basin (about 78 km2), by intersecting a GIS grid layer, expressing some selected geo-environmental conditions (outcropping lithology, steepness, plan curvature and topographic wetness index), and a landslide vector archive, produced by a Google EarthTM aided remote survey. The analysis of the Google EarthTM images dated at 2006, allowed to recognize 733 landslides (30 rotational slides and 703 flows), almost exclusively affecting clay and sandy clay rocks. Validation procedures produced largely satisfactory results, which were analyzed in the domain of the success and prediction rate curves. The research confirms the goodness of the susceptibility assessment method, as well as the powerful of Google EarthTM as a tool to manage the need of new, detailed and multi-temporal landslide archives.

A GIS-analysis was carried out in a test basin of southern Sicily, the Magazzolo River basin, in order to assess susceptibility conditions to gully erosion phenomena. The linear density of ephemeral and permanent gullies computed within each class of nine environmental variables was used to generate a gully erosion susceptibility map for the area. A validation procedure carried out in order to test the reliability of the adopted method highlighted a clear correlation between the occurrence of gullies and the computed susceptibility levels

The aim of this work is to study the impact of vegetation cover on water erosion phenomena by exploiting an integrated approach to the assessment of soil loss rates. The investigated area is located in the western portion of the mountainous group named “Monti di Palermo” and occupies an area of approximately 475 km2; this area, which extends from sea level up to about 1,300 m, is mainly characterized by the presence of lithosols and luvisols laying above carbonate and terrigenous substrates. The assessment of erosion intensity was indirectly obtained by applying the RUSLE model, that allowed to estimate soil loss produced by rill-interrill erosion phenomena. Starting from topographical and thematic maps, pluviometric data and field surveys, a GIS grid layer, for each of the erosion control factors, was defined; by exploiting ArcView GIS 3.2 spatial analysis tools, all the factors’ grids were overlayed and multiplied to produce a grid map, made up of 89,001 square cells, showing the spatial variability of predicted erosion rates. The RUSLE application, here presented, distinguishes for the approach used to define the C factor (cover-management factor), which was calculated using a landscape and plant biodiversity map, rather than a land use one; this map was constructed by identifying and detecting plant communities with a phytosociological approach. The mean annual soil loss, which average value for the entire area is equal to 9.16 t ha-1 year-1, shows a spatial variability that is mainly controlled by the geographical distribution of topographic and cover-management factors. Sever soil erosion rates (>40 t/ha-1 year-1), in effect, fall on abandoned fields, grasslands and garrigues areas, characterized by high altitude values and steep slopes, often affected by fire. In order to detail the spatial variability of the C factor, the analysis was focused on the “Vallone San Vincenzo” river basin, that extends for 33 km2 in the NW sector of the “Monti di Palermo” region. In this area, analysis of high-resolution orthophotos and field surveys of the phytosociological associations allowed to discriminate, within vegetation categories, some sub-categories related to percentage of area covered by canopy of trees and undergrowth, type and height of vegetation; these sub-factors permitted to define a more detailed and reliable cover-management factor layer. By intersecting the latter with the others erosion factors layers, a mean annual soil loss map of “San Vincenzo” river basin was produced. The two differents approaches of evaluating the C factor result in different average values of mean annual soil loss rate in the “San Vincenzo” river basin; the second method provides an average value of soil loss equal to 9.3 t ha-1 year-1, which is about 10% lower than the correspondent one (10,6 t ha-1 year-1), obtained by applying the first method. This work reveals the possibility to define the C factor by exploiting phytosociological surveys; the latter permitted to comprise the effect of vegetation canopy and ground covers in reducing soil loss, providing a more comprehensive and multidisciplinary approach in evaluating water erosion.

A seguito di un evento estremo di pioggia verificatosi il 1 ottobre 2009 in un settore circoscritto del versante ionico della Provincia di Messina, si sono sviluppati numerosi eventi franosi classificabili per la maggior parte come colate di fango e detrito a rapida evoluzione (debris-mud flows). Dai primi sopralluoghi effettuati, in assenza ancora di un censimento sistematico, si sono riconosciuti eventi in numero di oltre 500, che hanno interessato sia nei versanti interni dei bacini idrografici che sversano nello Ionio, sia sui rilievi direttamente prospicienti la costa. L’elevato numero di eventi occorsi ha consentito di dettagliare dal punto di vista morfologico i fenomeni avvenuti e di compiere preliminari analisi statistiche relative alle aree di innesco in rapporto con parametri geomorfologici, morfometrici, litologici e dello spessore di copertura. I rilievi sono stati condotti direttamente sul terreno, dall’alto tramite sorvoli su elicotteri messi a disposizione dalla Protezione Civile Nazionale, da ortofoto del 2000 e del 2008, da immagini satellitari. I dati così acquisiti successivamente sono stati successivamente elaborati e digitalizzati al fine di redigere una “Carta di censimento preliminare delle aree di innesco”, rappresentate da punti, di seguito indicati, in analogia con il sistema di archiviazione IFFI, con il termine “PIFF”, con particolare riferimento alle aree nell’immediato intorno degli abitati coinvolti. Tali dati sono stati poi trasposti in ambiente GIS, al fine sia di realizzare un database continuamente aggiornabile, condizione di primaria importanza in ragione della estrema dinamicità di modellamento dei versanti, sia di disporre di un database che consentisse di passare dall’analisi dei fenomeni all’analisi della pericolosità. In tal senso sono state elaborate le prime analisi statistico-descrittive relative ai 113 fenomeni censiti la cui distribuzione spaziale è stata messa in relazione con la variabilità geografica di parametri geologici, morfometrici, morfologici e di uso del suolo. Vengono inoltre espresse alcune considerazioni preliminari circa le soglie di innesco dei fenomeni.

The Madonie Natural Park is characterized by relevant zoological and botanic aspects and by geological features so remarkable that since 2001 it has been incorporated into the European Geoparks Network. The Park is marked by a wide massif know as Madonie Mountains. In this area, segment of the Maghrebide-Apenninic chain, successions of Meso-Cenozoic lithologies and late- and post-orogenic deposits occur. The geomorphological setting is extremely varied and includes many landscapes characterising several Sicilian areas; it results from the interaction between geomorphological processes, tectonic movements and climatic changes. It is possible to identify five distinct sectors, each corresponding to a particular landscape unit marked by a typical assemblage of landforms, related to the geological and structural setting and to a distinctive geomorphological agent.

L’area di Scopello (Sicilia Nord-Occidentale) è da tempo oggetto di studi che, sulla base di osservazioni e rilievi geomorfologici, hanno consentito sia di riconoscere la presenza di frane superficiali e di fenomeni di deformazione gravitativa profonda di versante (DGPV), sia di ipotizzare cause e tipologie dei movimenti in atto, giungendo alla definizione di un primo modello interpretativo. I movimenti franosi si sviluppano lungo i settori costieri dell’area di Scopello, dove è a giorno un piano di sovrascorrimento del Miocene superiore, che vede la sovrapposizione di unità rigide, costituite da successioni carbonatiche meso-cenozoiche, su unità duttili, costituite, al tetto, da argille-marnose del Miocene medio-superiore. Le unità argillo-marnose sono interessate da processi di scalzamento ad opera dell’erosione marina, che determinano condizioni di instabilità nei pendii. L’assetto strutturale ereditato, l’erosione del mare ed i movimenti tettonici plio-quaternari sono le cause che hanno consentito l’attivazione di fenomeni di DGPV, per le cui velocità non sono tuttavia disponibili valutazioni quantitative di riferimento. Il presente lavoro riferisce sulla realizzazione di una rete di monitoraggio GPS dei fenomeni gravitativi in atto nell’era di Scopello e sull’esecuzione del «rilievo di zero», evidenziando come la precisione sul posizionamento 3-D dei suoi vertici sia adeguata alle ampiezze di massimo spostamento attese e, quindi, come la rete possa consentire, con rilievi successivi, il monitoraggio del campo degli spostamenti. The Scopello area (north-western Sicily; fig. 1) is affected by several landslide phenomena (AGNESI et alii, 1995), involving both surface mass movements and, mainly, Deep-seated Gravitational Slope Deformation (DsGSD) phenomena (see GOGUEL, 1978; SAVAGE & VARNES, 1987; DRAMIS & SORRISO-VALVO, 1994; CANCELLI & CASAGLI, 1995; HUTCHINSON, 1995; SORRISO-VALVO, 1995; CROSTA, 1996). The phenomena involve the external margin of an overthrust plane (ABATE et alii, 1998a), where a rigid carbonate tectonic unit (Trias-Oligocene) overlies a ductile clayey substratum (Middle-Upper Miocene). The upper carbonate bodies (fig. 2) are marked by an inner imbricate structure and are intensely faulted and fractured, determining the presence of several disjointed blocks of various size, constituting favorable conditions for DsGSD movements to occur. Within the carbonate relief the DsGSD phenomena are responsible for the existence of double crests, depression alignments and river valleys truncated at their head, due to differential settlements. The outermost sectors of the carbonatic slopes (figs. 2-3), affected by block movements, lateral spreads and large topples or falls, are the sites of rotated and/or rafted blocks, great escarpments and open or closed trenches and cracks (AGNESI et alii, 1989). Finally, the marlyclayey slopes show diagnostic landforms of flow and/or slide type surface movements (AGNESI et alii, 1987). The causes of the landslides (AGNESI et alii, 2000; AGNESI et alii, 2003) are: superposition of carbonate rocks over marly-clayey rocks; undercutting processes induced by coastal erosion along the landslide foot/tip; Quaternary tectonic movements. As a geomorphological model has already been established for the landslide, a multidisciplinary study has been implemented, in order to define best both its geometric and kinematic characteristics. The final aim of this study is to gain a mathematical model which allows the phenomena to be correctly described, so that fore- and back- projection can be implemented. The project involves geophysical surveys (resistivity prospecting), geodetic monitoring measurements (GPS) as well as geomorphological, hydrogeological and geotechnical analysis and modeling. In the present paper all the study activities needed in order to implement a monitoring network, requiring a multidisciplinary approach in order to optimize its geometry, are discussed: detailed geomorphological analysis and modeling; resistivity geophysical survey; design and setting up of a geodetic monitoring network. In order to define a monitoring network for the landslide, a detailed geomorphological analysis has been carried out, so that bodies having a different expected kinematic response have been discriminated at a detailed scale (fig. 2). A resistivity survey was also carried out to verify the geometry of the ductile substratum in the area (fig. 4). The GPS network (fig. 2) consists on 27 3D vertices, 7 of which (fig. 2): SC01, SC02, SC03, SC04, SC05, SC06 e SC07) are located outside the landslide area, so that these can constitute a reference system, in respect to which the displacements of the other 20 vertices can be calculated. The coordinates of SC05 point have been calculated by connections to two vertices (TRAP and VALD in fig. 1) of the IGM95 geodetic network. The non-fixed vertices are located in areas characterized by: a) outermost areas of the margin of the carbonate slab about to undergo disarticulation (SC26 e SC27); b) isolated carbonate bodies moving toward the sea (SC08, SC09, SC10, SC15, SC16, SC17, SC18, SC19, SC24 e SC25); c) large landslide cemented debris masses (SC14, SC20, SC21, SC22 e SC23); d) marly-clay substratum (SC11, SC12 e SC13). The expected movement ranges from: very slow (mm/year) rotational -translational (a); varying velocity (mm/year-cm/year) translational, rotational-translational or rotational, depending on the depth to which «the roots» of the carbonate blocks extend inside the substratum (b); slow (cm/year) translational (c); slow to quite fast (dm/year) rotational-translational (d). A preliminary survey has been carried out, in order to calculate the coordinates of the vertices SC02, SC04, SC05, SC06 that are not subject to the landslide movements and to individuate a polygon including all the vertices (fig. 5). Data have been collected in two 3 hours sessions, using geodetic double frequency receivers with a rate of 15s. Data collected have been processed using the software SKI-Pro, with standard parameters but using a cut-off angle of 20° to lower the noise and the average multipath and compensated fixing the SC05 vertex. The redundancy of the this survey is equal to 2, which is enough to give a good accuracy and reliability to the network (CARDINALI et alii, 1993). The uncertainty in 2D and 1D of the fixed vertices (at a confidence level of 95%) is shown in fig. 5, suggesting a precision of less than 1 cm for their location. The survey on the whole net has been carried out using GPS 7 receivers (4 on the fixed points and 3 on as many sites positioned on the landslide body) with sessions 6-9 hours long. A total of 92 baselines were measured having a redundancy of 4. The survey was carried out between 20th and 25th of June 2000, according to the time schedule of fig. 6 and the quality of data tested according to ESTER & MEERTENS (1999), verifying acceptable values for the multipaths, both in L1 and L2 (fig. 7). Sixteen independent recording sessions with duration of 3-4 hours have been completed and the frequency distribution of the 92 baseline lengths (fig. 8) is characterized by an average of 1.9 km. The residuals for the 138 resolved triangles is of about 3 p.p.m. The uncertainty in 2D and 1D (at a confidence level of 95%) is presented in fig. 9, showing error ellipses having semiaxes less than 6 mm long and the minor to major axis ratio greater than 0.8; the uncertainty for the heights is greater by a factor two. Residuals after compensation for the 138 triangles (figs. 10a-b) are much lower and generally don’t exceed 1 p.p.m., thanks to a good geometry both of the network and of the satellite configuration during the recording sessions. The research carried out allowed refinement of the geomorphological model that had been defined in the past for the gravitational phenomena at Scopello, on the basis of which a geodetic monitoring network was defined. Data of the zero survey have been processed showing that the monitoring system is able to describe the kinematic evolution of the area with a precision suitable for DsGSD phenomena.