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The results of a geomorphological survey carried out in the urban area of Palermo are described. The study area is located in the northern margin of Western Sicily and is part of the SE-verging Alpine orogenic belt (Catalano et al., 2013). An E-W mountain range (Sicilian Apennines) is the topographical expression of this belt (Di Maggio et al., 2017). In the Palermo area, the physical continuity of the mountain range is broken by a large topographically-depressed coastal area. This area is set on a half-graben and is characterized by a plain (Conca d’Oro plain), opened to sea and surrounded by wide scarps hundreds of meters tall to the inland. The wide and tall scarps are abandoned coastal cliffs derived from original fault scarps. Large talus slopes bound the scarps at their base. A very slight dipping wedge of Calabrian coastal and shallow water clastic deposits from few to tens of meters thick crops out in the Conca d’Oro plain. These deposits (Marsala synthem, ISPRA 2013) lie on Meso-Cenozoic rocks with strong angular unconformities. Along the plain, a Middle- Upper Pleistocene succession of marine terraces develops from 0 m up to 150 m a.s.l. These terraces are characterized by large and well-preserved polycyclic wave-cut surfaces which in turn are down-cut by some river valleys from few to ten meters deep. The city of Palermo rises along the marine terrace surfaces and the river valleys of the Conca d’Oro plain. Over the last 2700 years, the urban area of Palermo has been affected by remarkable man-made changes to the topographic surface and to the drainage network. The main changes consist of: filling of river valleys; concreting, diversion and burial of riverbeds; excavation of aqueduct tunnel (qanat) and underground or open quarries; massive nourishment of the coast areas by means of demolition materials of the Second World War. Geomorphological setting, man-made changes, and urban development up to the talus slope expose the city of Palermo a hydraulic, sinkhole, and landslide risks. To facilitate study on urban planning and environmental risk assessment, a geomorphological map of the urban area of Palermo has been achieved through field surveys, multitemporal analysis of aerial photographs and topographic map, consultation of historical documents, and stratigraphic and topographic reconstructions from numerous wells.

Le aree carsiche gessose della Sicilia hanno attirato l’attenzione di naturalisti e geologi sin dalla seconda metà del 1800. Tuttavia, gli studi sul carsismo nei gessi non hanno visto una costante evoluzione nel tempo; infatti, dopo un lungo periodo di indifferenza, è solo a partire dagli anni ’80 del secolo scorso, che si è assistito ad un rinnovato interesse verso questa tematica, inizialmente grazie alla realizzazione di numerose campagne di esplorazione in diverse aree carsiche gessose della Sicilia da parte di alcuni gruppi speleologici siciliani, e in un secondo momento grazie all’interesse mostrato dall’Istituto di Geologia (oggi Dipartimento di Scienze della Terra e del Mare) dell’Università di Palermo, che ha intrapreso una serie di ricerche sistematiche su differenti aspetti del carsismo nelle evaporiti siciliane. Tali ricerche condotte fino ad oggi, in collaborazione anche con altri Atenei e Istituzioni di ricerca italiani e stranieri e gruppi speleologici siciliani, hanno consentito di ampliare significativamente le conoscenze sui fenomeni carsici nei gessi della Sicilia. Le aree carsiche nei gessi della Sicilia rappresentano dei complessi di eccezionale interesse scientifico, paesaggistico e didattico sia per la grande abbondanza e varietà di forme carsiche superficiali e sotterranee, uniche in tutto il Bacino del Mediterraneo, sia per la loro collocazione geografica ed ambientale, che si estende dalle fasce costiere alle valli fluviali, dalle conche lacustri alle colline e agli altopiani. Le forme carsiche di superficie spaziano dalle piccole sculture in roccia (karren) alle forme di medie e grandi dimensioni, quali doline, valli fluvio-carsiche, polje. Oltre duecento grotte, con sviluppi fino a 2 km e profondità di oltre 100 m, sono state esplorate. Grazie all’intensificarsi degli studi che hanno avvalorato sia l’interesse scientifico, sia quello naturalistico e culturale del carsismo nei gessi siciliani, diverse aree carsiche gessose in Sicilia sono oggi sottoposte a tutela essendo state inserite nell’ambito di aree protette, quali riserve naturali, parchi regionali, siti della Rete Natura 2000, geositi e geoparchi. Attualmente ricercatori e speleologi cooperano, anche con gli enti gestori delle aree protette, per incrementare le conoscenze sulle aree gessose dell’isola e per favorire la loro valorizzazione, fruizione e tutela. The gypsum karst areas of Sicily attracted the attention of naturalists and geologists since the second half of the 1800s. After a long period of indifference, only since the 80s of the last century some Sicilian speleological groups and the Institute of Geology (now Department of Earth and Marine Sciences) of the University of Palermo, in collaboration also with Italian and foreign universities, conducted new researches increasing significantly the knowledge on gypsum karst phenomena. The gypsum karst areas in Sicily are sites of exceptional scientific and cultural interest, for the great abundance and variety of surface and underground karst forms and for their geographical and environmental position, extending from coastal areas to river valleys, from lake basins to hills and plateau. The surficial karst forms range from small rock sculptures (karren) to medium and large forms, such as dolines, fluvial-karst valleys and polje. Over two hundred caves, with developments up to 2 km and a depth of over 100 m, have been explored. Thanks to increase of studies that confirmed the scientific and the naturalistic and cultural interest of gypsum karst in Sicily, several areas are now protected as nature reserves, regional parks, sites of the Natura 2000 Network, geosites and geoparks. Actually, researchers and speleologists cooperate, also with the management of the protected areas, to grow the knowledge on the Sicilian gypsum areas and favor their exploitation, enjoyment and protection.

In this work, we assessed gully erosion susceptibility in two adjacent cultivated catchments of Sicily (Italy) by employing multivariate adaptive regression splines and a set of geo-environmental variables. To explore the influence of hydrological connectivity on gully occurrence, we measured the changes of performance occurred when adding one by one nine predictors reflecting terrain connectivity to a base model that included contributing area and slope gradient. Receiver operating characteristic (ROC) curves and the area under the ROC curve were used to evaluate model performance. Gully predictive models were trained in both the catchments and submitted to internal (in the calibration catchment) and external (in the adjacent one) validation, using samples extracted both from all cells of the catchments and only from cells located along flow concentration axes. Model evaluation on the entire catchments shows outstanding predictive performance of models that either include or do not include the predictors selected to reflect potential hydrological connectivity. Conversely, area under the ROC curve values measured on flow concentration axes reveals that almost all the additional predictors improve the performance of the base model, but the most enhanced increase of accuracy occurs when upstream drainage density of each landscape position is included as predictor of gully occurrence.

Many river systems in Europe suffer from human pressure. For this reason the European Water Framework Directive (WFD; 2000/60/EC) was created for river basin and floods management. In 2010 the Italian Environmental Minister issued the WFD and a protocol for the stream hydromorphological evaluation, analysis, and monitoring was established (IDRAIM). The Morphology Quality Index (MQI) is part of this procedure and defines the deviation of present geomorphic reach situation from reference conditions. It is composed by Indicators of Geomorphological Functionality (IGF), Indicators of Artificiality (IA) and Indicators of Channel Adjustments (ICA). The present work aims at illustrating the calculation of IGF in 34 river catchments located in the Eastern part of Sicily (Italy). The procedure was characterized by three main steps: i) subdivision of the river network into relatively homogeneous reaches depending on landscape units, valley setting, channel slope; ii) evaluation of confinement classes (the percentage of banks not directly in contact with the alluvial plain but with hillslopes or ancient terraces) and confinement index (the ratio between the alluvial plain width and the channel width); iv) identification of river morphological typologies (sinuosity, braiding and anastomosing indices). In order to calculate the IGF, GIS analysis, photo interpretation, historical data collection and geomorphological fieldwork were integrated. Results showed that the IDRAIM procedure for the calculation of the IGF can be successfully applied for the Sicilian Rivers. However, being the Sicilian rivers mainly characterized by a torrential regime, some adjustments of the IGF procedure could be suggested.

Urban-geomorphology studies in historical cities provide a significant contribution towards the broad definition of the Anthropocene, perhaps even including its consideration as a new unit of geological time. Specific methodological approaches to recognize and map landforms in urban environments, where human-induced geomorphic processes have often overcome the natural ones, are proposed. This paper reports the results from, and comparison of, studies conducted in coastal historical cities facing the core of the Mediterranean Sea – that is, Genoa, Rome, Naples, Palermo (Italy) and Patras (Greece). Their settlements were facilitated by similar climatic and geographical contexts, with high grounds functional for defence, as well as by the availability of rocks useful as construction materials, which were excavated both in opencast and underground quarries. Over centuries, urbanization has also required the levelling of relief, which was performed by the excavation of heights, filling of depressions and by slope terracing. Consequently, highly modified hydrographic networks, whose streams were dammed, diverted, modified in a culvert or simply buried, characterize the selected cities. Their urban growth, which has been driven by maritime commercial activities, has determined anthropogenic coastal progradation through port and defence or waterfront works. Aggradation of artificial ground has also occurred as a consequence of repeated destruction because of both human and natural events, and subsequent reconstruction even over ruins, buried depressions and shallow cavities. As a result, the selected cities represent anthropogenic landscapes that have been predominately shaped by several human-driven processes, sometimes over centuries. Each landform represents the current result, often from multiple activities with opposing geomorphic effects. Beyond academic progress, we believe that detecting and mapping these landforms and processes should be compulsory, even in risk-assessment urban planning, because of the increase of both hazards and vulnerability as a result of climate-change-induced extreme events and extensive urbanization, respectively.

The continental shelf morphology offshore of western Sicily suggests that during the Last Glacial Maximum (LGM, 20 ka cal BP), two of the Egadi Islands, Favignana and Levanzo, were connected to Sicily by a wide emerged plain, while Marettimo was only separated from the other islands by a narrow channel. We studied the relative sea-level variation from the LGM until today, focussing on two important time slices: the Mesolithic (9.5–13 ka cal BP) and the Neolithic (6.5–7.5 ka cal BP). In this research, we discuss a sea-level rise model by means of geomorphological, archaeological and geophysical observations and new radiocarbon dating of marine and terrestrial fossil fauna. The results enabled us to provide a detailed palaeogeographical reconstruction of the focal area from the LGM until they became isolated. The evidence that has emerged from this research, in particular the radiometric data, supports the hypothesis that seafaring in the western Mediterranean area may have started between the early Mesolithic and late Epigravettian (between 8.4 and 13.5 ka cal BP), although it probably became a well-established practice only during the Neolithic.

In landslide susceptibility modeling, the selection of the mapping units is a very relevant topic both in terms of geomorphological adequacy and suitability of the models and final maps. In this paper, a test to integrate pixels and slope units is presented. MARS (Multivariate Adaptive Regression Splines) modeling was applied to assess landslide susceptibility based on a 12 predictors and a 1608 cases database. A pixel-based model was prepared and the scores zoned into 10 different types of slope units, obtained by differently combining two half-basin (HB) and four landform classification (LCL) coverages. The predictive performance of the 10 models were then compared to select the best performing one, whose prediction image was finally modified to consider also the propagation stage. The results attest integrating HB with LCL as more performing than using simple HB classification, with a very limited loss in predictive performance with respect to the pixel-based model.

The results of a geomorphological study carried out in the urban area of Palermo are summarized in a thematic map. Field survey, analysis of aerial photographs and topographic maps, consultation of historical documents and maps, stratigraphic and topographic reconstruction from numerous wells and subsoil data, and bibliographic search were performed, in order to display the geomorphological changes produced by man over time in a densely populated area and to define the Anthropocene of the study area. Palermo town rises along large marine terrace surfaces cut by small river valleys and bordered by wide degraded and abandoned coastal cliffs. Over the last 2700 years, this area was affected by remarkable man-made changes to topographic surface and underground, exposing large areas of the city to hydraulic, sinkhole, and landslide risks, and increasing the levels of seismic susceptibility. In light of these results, the produced map is useful for urban planning studies.

The main topic of this research was to evaluate the effect in the performance of stochastic landslide susceptibility models, produced by differences between the triggering events of the calibration and validation datasets. In the Caldera Ilopango area (El Salvador), MARS (multivariate adaptive regression splines)-based susceptibility modeling was applied using a set of physical–environmental predictors and two remotely recognized landslide inventories: one dated at 2003 (1503 landslides), which was the result of a normal rainfall season, and one which was produced by the combined effect of the Ida hurricane and the 96E tropical depression in 2009 (2237 landslides). Both the event inventories included shallow debris—flow or slide landslides, which involved the weathered mantle of the pyroclastic rocks that largely outcrop in the study area. To this aim, different model building and validation strategies were applied (self-validation, forward and backward chrono-validations), and their performances evaluated both through cutoff-dependent and -independent metrics. All of the tested models produced largely acceptable AUC (area under curve) values, albeit a loss in the predictive performance from self-validation to chrono-validation was observed. Besides, in terms of positive/negative predictions, some critical differences arose: using the 2009 extreme landslide inventory for calibration resulted in higher sensitivity but lower specificity; conversely, using the 2003 normal trigger landslide calibration inventory led to higher specificity but lower sensitivity, with relevant increase in type-II errors. These results suggest the need for investigating the extent of such effects, taking multitrigger intensities inventories as a standard procedure for susceptibility assessment in areas where extreme events potentially occur.

Soil erosion by water constitutes a serious problem affecting various countries. In the last few years, a number of studies have adopted statistical approaches for erosion susceptibility zonation. In this study, the Stochastic Gradient Treeboost (SGT) was tested as a multivariate statistical tool for exploring, analyzing and predicting the spatial occurrence of rill–interrill erosion and gully erosion. This technique implements the stochastic gradient boosting algorithm with a tree-based method. The study area is a 9.5 km 2 river catchment located in central-northern Sicily (Italy), where water erosion processes are prevalent, and affect the agricultural productivity of local communities. In order to model soil erosion by water, the spatial distribution of landforms due to rill–interrill and gully erosion was mapped and 12 environmental variables were selected as predictors. Four calibration and four validation subsets were obtained by randomly extracting sets of negative cases, both for rill–interrill erosion and gully erosion models. The results of validation, based on receiving operating characteristic (ROC) curves, showed excellent to outstanding accuracies of the models, and thus a high prediction skill. Moreover, SGT allowed us to explore the relationships between erosion landforms and predictors. A different suite of predictor variables was found to be important for the two models. Elevation, aspect, landform classification and land-use are the main controlling factors for rill–interrill erosion, whilst the stream power index, plan curvature and the topographic wetness index were the most important independent variables for gullies. Finally, an ROC plot analysis made it possible to define a threshold value to classify cells according to the presence/absence of the two erosion processes. Hence, by heuristically combining the resulting rill–interrill erosion and gully erosion susceptibility maps, an integrated water erosion susceptibility map was created. The adopted method offers the advantages of an objective and repeatable procedure, whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies.

Secondo la ormai classica definizione di W.A.P. Wimbledon un geosito è "una qualsiasi località, area o territorio in cui è possibile definire un interesse geologico-geomorfologico per la conservazione". L'istituzione di un geosito viene a rappresentare un ulteriore strumento normativo da utilizzare pe la salvaguardia e la tutela del paesaggio, particolarmente efficace in regioni, come quella siciliana, caratterizzate da una notevole geodiversità.

The main assumption on which landslide susceptibility assessment by means of stochastic modelling lies is that the past is the key to the future. As a consequence, a stochastic model able to classify past known landslide events should be able to predict a future unknown scenario as well. However, storm-triggered multiple debris flow events in the Mediterranean region could pose some limits on the operative validity of such an expectation, as they are typically resultant of a randomness in time recurrence and magnitude and a great spatial variability, even at the scale of small catchments. This is the case for the 2007 and 2009 storm events, which recently hit north-eastern Sicily with different intensities, resulting in largely different disaster scenarios. The study area is the small catchment of the Itala torrent (10 km2), which drains from the southern Peloritani Mountains eastward to the Ionian Sea, in the territory of the Messina province (Sicily, Italy). Landslides have been mapped by integrating remote and field surveys, producing two event inventories which include 73 debris flows, activated in 2007, and 616 debris flows, triggered by the 2009 storm. Logistic regression was applied in order to obtain susceptibility models which utilize a set of predictors derived from a 2 m cell digital elevation model and a 1 : 50 000 scale geologic map. The research topic was explored by performing two types of validation procedures: self-validation, based on the random partition of each event inventory, and chrono-validation, based on the time partition of the landslide inventory. It was therefore possible to analyse and compare the performances both of the 2007 calibrated model in predicting the 2009 debris flows (forward chrono-validation), and vice versa of the 2009 calibrated model in predicting the 2007 debris flows (backward chrono-validation). Both of the two predictions resulted in largely acceptable performances in terms of fitting, skill and reliability. However, a loss of performance and differences in the selected predictors arose between the self-validated and the chrono-validated models. These are interpreted as effects of the non-linearity in the domain of the trigger intensity of the relationships between predictors and slope response, as well as in terms of the different spatial paths of the two triggering storms at the catchment scale.

Pantelleria is a volcanic island located in the Strait of Sicily, 95 km far from the Sicilian coastline and 67 km from Cape Bon (Tunisia). The volcanological history of the island begins approximately 324 ka BP and the last eruptive event was a submarine eruption that occurred on 1891 A.D. Eruptive activity was characterized by seven very intense explosive events, the latest being the Green Tuff (44 ka). They have all produced ignimbrite sheets that covered large sectors of the island. The landscape of the island mirrors the variety of the eruptive styles and their interplay with volcano-tectonics. The most evident geomorphological features are represented by: (i) the mantle-like distribution of the Green Tuff ignimbrite; (ii) the arcuate remnants of the two large caldera collapses, and (iii) the intracalderic scoria cones, lava domes and lava fields. A very dense distribution of dry walls, built since Roman times, perfectly integrate the volcanic landscape, preventing from erosion and rock falls.

This paper proposes a morphoevolutionary model for western Sicily. Sicily is a chain–foredeep–foreland system still being built, with tectonic activity involving uplift which tends to create new relief. To reconstruct the morphoevolutionary model, geological, and geomorphological studies were done on the basis of field survey and aerial photographic interpretation. The collected data show large areas characterized by specific geological, geomorphological, and topographical settings with rocks, landforms, and landscapes progressively older from south to north Sicily. The achieved results display: (1) gradual emersion of new areas due to uplift, its interaction with the Quaternary glacio-eustatic oscillations of the sea level, and the following production of a flight of stair-steps of uplifted marine terraces in southern Sicily, which migrates progressively upward and inwards; in response to the uplift (2) triggering of down-cutting processes that gradually dismantle the oldest terraces; (3) competition between uplift and down-cutting processes, which is responsible for the genesis of river valleys and isolated rounded hills in central Sicily; (4) continuous deepening over time that results in the exhumation of older and more resistant rocks in northern Sicily, where the higher heights of Sicily are realized and the older forms are retained; (5) extensional tectonic event in the northern end of Sicily, that produces the collapse of large blocks drowned in the Tyrrhenian Sea and sealed by coastal-marine deposits during the Calabrian stage; (6) trigger of uplift again in the previously subsiding blocks and its interaction with coastal processes and sea level fluctuations, which produce successions of marine terraces during the Middle–Upper Pleistocene stages.

The Capo San Vito peninsula is located along the north-westernmost sector of the Sicilian coastline. It is characterized by a complex geomorphological setting, where a large variety of coastal, gravity-induced and karst landforms allow the visitor to easily detect the interactions between Quaternary tectonics and climate changes as well as morphodynamic processes responsible for shaping the landscape. Thanks to natural reserves, the peninsula preserves a typical Mediterranean natural environment, marked by spectacular and suggestive landforms.

The aim of this study is to analyze the susceptibility conditions to gully erosion phenomena in the Magazzolo River basin and to test a method that allows for driving the factors selection. The study area is one of the largest (225 km2) watershed of southern Sicily and it is mostly characterized by gentle slopes carved into clayey and evaporitic sediments, except for the northern sector where carbonatic rocks give rise to steep slopes. In order to obtain a quantitative evaluation of gully erosion susceptibility, statistical relationships between the spatial distributions of gullies affecting the area and a set of twelve environmental variables were analyzed. Stereoscopic analysis of aerial photographs dated 2000, and field surveys carried out in 2006, allowed us to map about a thousand landforms produced by linear water erosion processes, classifiable as ephemeral and permanent gullies. The linear density of the gullies, computed on each of the factors classes, was assumed as the function expressing the susceptibility level of the latter. A 40-m digital elevation model (DEM) prepared from 1:10,000-scale topographic maps was used to compute the values of nine topographic attributes (primary: slope, aspect, plan curvature, profile curvature, general curvature, tangential curvature; secondary: stream power index; topographic wetness index; LS-USLE factor); from available thematic maps and field checks three other physical attributes (lithology, soil texture, land use) were derived. For each of these variables, a 40-m grid layer was generated, reclassifying the topographic variables according to their standard deviation values. In order to evaluate the controlling role of the selected predictive variables, one-variable susceptibility models, based on the spatial relationships between each single factor and gullies, were produced and submitted to a validation procedure. The latter was carried out by evaluating the predictive performance of models trained on one half of the landform archive and tested on the other. Large differences of accuracy were verified by computing geometric indexes of the validation curves (prediction and success rate curves; ROC curves) drawn for each one-variable model; in particular, soil texture, general curvature and aspect demonstrated a weak or a null influence on the spatial distribution of gullies within the studied area, while, on the contrary, tangential curvature, stream power index and plan curvature showed high predictive skills. Hence, predictive models were produced on a multi-variable basis, by variously combining the one-variable models. The validation of the multi-variables models, which generally indicated quite satisfactory results, were used as a sensitivity analysis tool to evaluate differences in the prediction results produced by changing the set of combined physical attributes. The sensitivity analysis pointed out that by increasing the number of combined environmental variables, an improvement of the susceptibility assessment is produced; this is true with the exception of adding to the multi-variables models a variable, as slope aspect, not correlated to the target variable. The addition of this attribute produces effects on the validation curves that are not distinguishable from noise and, as a consequence, the slope aspect was excluded from the final multi-variables model used to draw the gully erosion susceptibility map of the Magazzolo River basin. In conclusion, the research showed that the validation of one-variable models can be used as a tool for selecting factors to be combined to prepare the best performing multi-variables gully erosion susceptibility model.

A statistical approach was employed to model the spatial distribution of rainfall-triggered landslides in two areas in Sicily (Italy) that occurred during the winter of 2004–2005. The investigated areas are located within the Belice River basin and extend for 38.5 and 10.3 km 2 , respectively. A landslide inventory was established for both areas using two Google Earth images taken on October 25th 2004 and on March 18th 2005, to map slope failures activated or reactivated during this interval. Geographic Information Systems (GIS) were used to prepare 5 m grids of the dependent variables (absence/presence of landslide) and independent variables (lithology and 13 DEM-derivatives). Multivariate Adaptive Regression Splines (MARS) were applied to model landslide susceptibility whereas receiver operating characteristic (ROC) curves and the area under the ROC curve ( AUC ) were used to evaluate model performance. To evaluate the robustness of the whole procedure, we prepared 10 different samples of positive (landslide presence) and negative (landslide absence) cases for each area. Absences were selected through two different methods: (i) extraction from randomly distributed circles with a diameter corresponding to the mean width of the landslide source areas; and (ii) selection as randomly distributed individual grid cells. A comparison was also made between the predictive performances of models including and not including the lithology parameter. The models trained and tested on the same area demonstrated excellent to outstanding fit ( AUC > 0.8). On the other hand, predictive skill decreases when measured outside the calibration area, although most of the landslides occur where susceptibility is high and the overall model performance is acceptable ( AUC > 0.7). The results also showed that the accuracy of the landslide susceptibility models is higher when lithology is included in the statistical analysis. Models whose absences were selected using random circles showed a significantly better performance when learning and validation samples were extracted from the same area; whereas, conversely, no significant difference was observed when testing the models outside the training area.

This work deals with an integrated geomorphological and chemical–physical study of “calanchi” landforms in two sites (Ottosalme and Catalfimo) of NW Sicily (southern Italy), developed on dominant silty-clay deposits. The calanchi fronts are characterized by different morphological features and dominant geomorphic processes. Sharp knife-edged ridges and concentrated water runoff dominate at Ottosalme, and smoother landforms affected by mass movements (mud flows and translational slides) prevail at Catalfimo. We focused on some geochemical and physical parameters such as pH , total dissolved salts, sodium adsorption ratio ( SAR ), porosity, plastic and liquid limits as possible causes of the above differences, with special emphasis on their role in discriminating the behavior of peculiar microforms, such as a weathered outer crust and the corresponding inner massive portion (unweathered substrate). Our results show that the main chemical–physical features of calanchi morphologies and microforms often display no clear correlations with respect to those reported in the existing literature, pointing to a higher complexity of patterns and behaviors. In particular, all samples consist of dispersive material ( SAR values > 10), but a more plastic and liquid behavior at Catalfimo can explain a higher occurrence of landslides and smoother morphology than at Ottosalme. Higher SAR values at Ottosalme well explain the dominance of concentrated water erosion. The chemical behavior of the studied microforms is better described by pH being alkaline with higher values in the inner substrate than the outer crust, and appears to minimize the effects of all other parameters and their responses to other external controlling factors. Lower SAR values in the crust suggest that clay dispersivity is not the prominent factor controlling its surface detachment and mobility downslope, which is more likely promoted by its higher porosity and consequent water absorption than the inner portion, with changes in the saturation state, shear strength and water pressure.

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.

In this paper, terrain susceptibility to earth-flow occurrence was evaluated by using geographic information systems (GIS) and two statistical methods: Logistic regression (LR) and multivariate adaptive regression splines (MARS). LR has been already demonstrated to provide reliable predictions of earth-flow occurrence, whereas MARS, as far as we know, has never been used to generate earth-flow susceptibility models. The experiment was carried out in a basin of western Sicily (Italy), which extends for 51 km 2 and is severely affected by earth-flows. In total, we mapped 1376 earth-flows, covering an area of 4.59 km 2 . To explore the effect of pre-failure topography on earth-flow spatial distribution, we performed a reconstruction of topography before the landslide occurrence. This was achieved by preparing a digital terrain model (DTM) where altitude of areas hosting landslides was interpolated from the adjacent undisturbed land surface by using the algorithm topo-to-raster. This DTM was exploited to extract 15 morphological and hydrological variables that, in addition to outcropping lithology, were employed as explanatory variables of earth-flow spatial distribution. The predictive skill of the earth-flow susceptibility models and the robustness of the procedure were tested by preparing five datasets, each including a different subset of landslides and stable areas. The accuracy of the predictive models was evaluated by drawing receiver operating characteristic (ROC) curves and by calculating the area under the ROC curve (AUC). The results demonstrate that the overall accuracy of LR and MARS earth-flow susceptibility models is from excellent to outstanding. However, AUC values of the validation datasets attest to a higher predictive power of MARS-models (AUC between 0.881 and 0.912) with respect to LR-models (AUC between 0.823 and 0.870). The adopted procedure proved to be resistant to overfitting and stable when changes of the learning and validation samples are performed. In conclusion, the highly acceptable predictive skill of the statistical models confirms the reliability of the procedure adopted to reconstruct the pre-failure topographic conditions. Such a method solves the conceptual problem arising when post-failure elevation data are the only source of topographic information available to model landslide susceptibility. Furthermore, with respect to other solutions proposed in the past, which identify as unstable the conditions of landslide surroundings, our approach allows for more accurate measurement of those variables (e.g. curvature, convergence index, topographic position index) that depend on the relative position of a cell with respect to its nearby pixels.

article i nfo Article history: This research aims at characterizing susceptibility conditions to gully erosion by means of GIS and multivariate statistical analysis. The study area is a 9.5 km 2 river catchment in central-northern Sicily, where agriculture ac- tivities are limited by intense erosion. By means of field surveys and interpretation of aerial images, we prepared a digitalmap of thespatial distribution of 260 gulliesinthestudy area.Inaddition,fromavailable thematicmaps, a 5 m cell size digital elevation model and field checks, we derived 27 environmental attributes that describe the variability of lithology, land use, topography and road position. These attributes were selected for their potential influence on erosion processes, while the dependent variable was given by presence or absence of gullies within two different types of mapping units: 5 m grid cells and slope units (average size = 2.66 ha). The functional re- lationships between gully occurrence and the controlling factors were obtained from forward stepwise logistic regression to calculate the probability to host a gully for each mapping unit. In order to train and test the predictive models, three calibration and three validation subsets, of both grid cells and slope units, were randomly selected. Results of validation, based on ROC (receiving operating characteristic) curves, attest for acceptable to excellent accuracies of the models, showing better predictive skill and more stable performance of the susceptibility model based on grid cells.

This study stems from the theoretical principle that environment protection and conservation have evolved from a constraint-based approach aimed at designating protected areas, to an ecosystem-based approach intended to protect and preserve biodiversity. The said approach identifies the ecological networks as a possible solution to the need for an ecological-functional connection between natural and semi-natural areas and areas of cultural interest, with the ultimate aim of implementing widespread environment protection “covering” the whole territory. An ecological network can be understood either as a set of natural (or semi-natural) areas interconnected through linear infrastructure or, in a somewhat and detached manner, as relations and connections between actors, even regardless of the location of the linkages, which tend to cancel out any tendency to confine natural areas to numerous little islands each ignoring the other. On one side, the “paradigm of the network” used as an instrument of analysis and economic-functional interpretation of the territory is supported by some literature and an established reference scientific base; on the other, the “ecological network”, that is a system of ecological connectivity throughout the territory, is a relatively more recent interpretation system, which is consolidating its theoretical foundation and trying to find its own role among the territory management tools. In particular, the ecological connections between areas of natural interest represent a strategic hot issue, which has a number of cultural and economic impacts based on the enhancement of natural resources. Over time, however, such an issue has been interpreted in different manners. With respect to these topics, the study we wish to illustrate was carried out under the “Ecological Cross-border Networks Malta-Sicily” R.E.MA.SI. project funded by the Italy-Malta 2007-2013 operational programme, which represents a brick in the construction of the “cross-border network” for the preservation and enhancement of natural areas both as an “intangible network” for the exchange of information and good practices, and as a “tangible network” for the ecological-environmental interconnection of the natural sites in the areas under investigation. In this respect, our research focuses on specific European contexts by adopting an “open” cultural approach aimed at rebalancing the policies in force. As a result, the comparative study on Sicily and Malta is useful not only to point out any unresolved problems, but also to thoroughly investigate and critically analyse the strategies to be implemented. In the framework of the territorial strategy aimed at the ecological-functional connection of natural areas, promoted through the “ecological network”-based model, this study was intended to realize integrated actions and interventions in order to improve and disseminate information about some sites in Sicily and Malta (nature reserves, geosites and Natura 2000 sites). Concerning the general scope of the Italy-Malta Programme, Axis II (Environment, energy and risk prevention), our work contributed to identify, exchange and disseminate - at cross-border level - good practices for an environmentally-friendly management of the territory, with respect to both protected natural areas (Natura 2000 sites, nature reserves, etc.), and un-protected natural areas in two specific territories: the province of Agrigento (Sicily) and Malta . The Maltese Archipelago and Sicily share a number of similarities in terms of environmental features, geographical location (common sea, shared migration routes, morphological-evolutionary similarities, etc.), as well as cultural problems that often prevent the full enhancement of natural resources. To face the said problems, monitoring, protection and enhancement actions must be implemented in a cross-border manner, in order to compare the territories and exchange good practices, which may contribute to improving nature conservation levels, even in neighbouring territorial contexts. The cross-border dimension of the study satisfies the need for tackling the problems associated with landscape transformations, movements of avifauna, conservation of geosites in an integrated manner, so as to exchange information on the protection and development actions to run. We will achieve results applicable to the geographical area of the Strait of Sicily, which could however be replicated in other territories. The study has the added value of being cross-border, which means that the two territories have the chance: to share specialised knowledge and strategic resources for the dissemination and implementation of scientific research and for the management of protected natural areas and relevant sites within the European community; to spur dialogue and exchange of ideas, raise awareness and involve local communities in the enhancement of natural resources; and to define common strategies and establish future collaborations. The study carried out has a twofold general scope: on one side, to investigate and identify the models and ongoing trends of fragmentation; on the other, to interpret the elements upon which territory enhancement and protection projects can be designed. Overall, the research includes the following phases: 1. collecting information and data; 2. examining the exiting documents and identifying the conditions of potential consistency or conflict in the territories (territorial fragmentation); 3. checking the conditions of consistency and conflict, through onsite inspections and by questioning local operators; 4. determining the spatial components that define the conditions of ecological-functional connectivity of the territory. To deal with the various topics under study, we looked at the territory on one side, while also taking into account the regulations and planning tools existing in the field of environment protection and territory management. With respect to this reference framework, we identified the elements of consistency and the criticalities, taking into consideration both natural and anthropic factors of the territorial heritage, in Sicily and in Malta. For the interpretation of the fragmentation factors of the territory – aimed at identifying a potential cross-border ecological network – we used the QGis Desktop software, to digitally manage the data gathered during the first phase of the project. This approach led to the development of a Territorial Information System, which let us easily manage the multidisciplinary analyses carried out and became the base for the subsequent interpretation and proactive phase of this work. The map we have been working on, is the result of an Overlay Mapping, that is overlapping thematic maps of previously carried out analyses, in which every single feature (cartographic territorial object) is associated with an informative record; the data in the record can be queried. In the first place, the Overlay Mapping model made it possible to assess and draft general maps of factors having an impact, which define the spatial distribution and the magnitude levels of the impacts; secondly, it allowed us to verify whether the proposed ecological connections were compatible with the state of conservation of the resources, their sensitivity, the current uses and the potential ones. During the first interpretation phase, we assessed and determined the criteria to be used to identify and classify the factors of fragmentation and territorial conflict. In this case, the map represented the main systems the territory is made of: infrastructure system, settlements, the system of natural areas and areas of natural and cultural interest, as well as the natural and administrative elements that border the territory. Once the mapping for the interpretation phase was completed, we started to detect the fragmentation factors, according to the criteria previously set, and we made onsite inspections to check the results of the interpretation phase. Afterwards, we identified potential connections. Using the initial data and the ones interpreted during the first phase, we classified the main areas according to naturalness levels; by querying the TIS, we identified potential connections and the areas needing more or less prompt interventions. For further details on the analytical results, refer to the chapter written by Giampino, Lotta, Scaduto and Todaro. The impact of the study on the involved territories should be taken into account. Indeed, due to its own aim of interpreting the links between various issues, this work allows to single out the ecological-environmental components that can influence the territorial development guidelines, while respecting the peculiarities of each territory. Although the connections sound sectorial themes, they actually represent a binding element for territory management and establish a system-based vision. In our specific case study, the high level of vulnerability detected and, by contrast, the properties of a few ecological-environmental factors can outline the goals to be achieved in planning, and most of all in territory management. Based on this work, we can define the “rules” of territorial transformations, by identifying the elements of a high ecological-environmental value system capable of advancing solutions to solve the decay caused by modern economy.