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The prediction and prevention of landslide hazard is a challenging topic involving the assessment and quantitative evaluation of several elements: geological and geomorphological setting, rainfalls, and ground motion. This paper presents the multi-approach investigation of the Nevissano landslide (Asti Province, Piedmont, NW Italy). It shows a continuous and slow movement, alongside few paroxysmal events, the last recorded in 2016. The geological and geomorphological models were defined through a field survey. An inventory of the landslide's movements and rainfall records in the period 2000–2016 was performed, respectively, through archive investigations and the application of "Moving Sum of Daily Rainfall" method, allowing for the definition of rain thresholds for the landslide activation (105 mm and 193 mm, respectively, in 3 and 30 days prior to the event). The displacements over the last 8 years (2016–2023) were monitored through an innovative in-continuum monitoring inclinometric system and Earth Observation (EO) data (i.e., relying on Interferometric Synthetic Aperture Radar, or InSAR data): it gave the opportunity to validate the rainfall thresholds previously defined. This study aims to provide information to public authorities for the appropriate management of the site. Moreover, the proposed workflow could be adopted as a guideline for investigating similar situations. [ABSTRACT FROM AUTHOR]

Flow-like landslides are recognized to be the most destructive slope movements and to threaten human life. They may occur in several geological settings, as is the case of the pyroclastic soil covers resting on either igneous, or carbonate, bedrocks. The pyroclastic soil strata involved in these shallow landslides typically are partially saturated over the whole year. Intense rainfall, considered at hourly time scale, represents the triggering factor because it causes the decrease in matric suction and the consequent decrease in soil shear strength. However, it is recognized as the role of the hydromechanical slope behavior, the vegetation cover, and the geomorphological irregularities on shallow landslide hazard. These factors should be properly simulated in physically based predictive models of the failure onset to set up a reliable early warning system (EWS). This paper presents a new coupled thermohydraulic modeling of a pyroclastic soil cover in Campania, accounting for several slope factors that may predispose landslide activation, including the geomorphological local irregularities. The Mount Faito test site, in the Lattari Mountains (Southern Italy), has been adopted as a prototype slope for the geomorphological and hydromechanical scenarios of reference because of the extensive field and laboratory characterizations of the soil strata already available from previous studies. Once validated with these data, the numerical model has been used to estimate the slope response to critical rainfall scenarios. Such numerical estimations have been then compared to the instability predictions currently provided by empirical approaches, defined in terms of the intensity and duration of rainstorms threshold of shallow landslide activations. By comparison between the empirical and physically based approaches, the crucial role of antecedent slope hydraulic conditions and the geological setting for implementing reliable EWS, reducing false alarms, is proved. [ABSTRACT FROM AUTHOR]

Broad mountainous areas in the western Campania (southern Italy), where young pyroclastic deposits extensively outcrop, frequently experience rainfall-induced slope movements of different degrees of mobility, causing heavy damage and fatalities. Such landslides cannot be easily mitigated, and the implementation of physically based early warning systems is still not able to predict the post-failure evolution of slope movements and the exposed areas at risk. This paper is devoted to overcoming this limit. To this end, the mechanical characterization of pyroclastic soil, carried out through an extensive laboratory testing program, is presented and compared with those of two other ashy soils of different depositional mechanisms. The results show that the depositional mode influences soil properties; to begin with, it affects the unsaturated shear strength, whose intercept of cohesion is up to 5 kPa higher in ashes of flow deposition than in airfall ash deposits. The saturated undrained soil response allowed for the identification of different levels of susceptibility to the liquefaction of pyroclastic deposits, which is one of the main factors governing the post-failure evolution of landslides. Gathering all the acquired information, including saturated and unsaturated soil shear strength, permeability function, and water retention curves, into a soil database, it was possible to present all data under a unitary framework. Finally, the implementation of the proposed flowchart for a simplified assessment of post-failure evolution to be employed in regional early warning systems can enhance our knowledge of the areas at risk. [ABSTRACT FROM AUTHOR]

Cultural heritage is one of the most exceptional resources characterizing the Italian territory. Archaeological heritage, i.e., the archaeological sites with different types of archaeological artifacts, strongly contributes to enriching the national and international cultural heritage. Nevertheless, it is constantly exposed to external factors, such as natural deterioration, anthropic impact, and climate-related hazards, which may compromise its conservation. In Italy, many archaeological areas are affected by significant soil settlements that involve a large part of monuments. This paper focuses on the landslide hazard assessment of the archaeological site of Pietrabbondante (Molise region, Italy). The impact of the expected rainfall regimes, according to the EURO-CORDEX projections, on slope stability conditions were evaluated through the application of a physically based model that couples a hydraulic and a mechanical model to evaluate slope stability evolution due to pore pressure changes. Given the unavoidable lack of knowledge of the geotechnical soil properties in an archaeological heritage area, the proposed method considered the random uncertainty of soil parameters by means of a probabilistic approach in order to assess the stability conditions in terms of probability of occurrence of a landslide. The results of this study provide a reference for the safety assessment and preventive conservation of archaeological areas characterized by high cultural value. [ABSTRACT FROM AUTHOR]

Earth flows are complex gravitational events characterised by a heterogeneous displacement pattern in terms of scale, style, and orientation. As a result, their monitoring, for both knowledge and emergency purposes, represents a relevant challenge in the field of engineering geology. This paper aims to assess the capabilities, peculiarities, and limitations of different remote sensing monitoring techniques through their application to the Pietrafitta earth flow (Southern Italy). The research compared and combined data collected during the main landslide reactivations by different ground-based remote sensors such as Robotic Total Station (R-TS), Terrestrial Synthetic Aperture Radar Interferometry (T-InSAR), and Terrestrial Laser Scanner (TLS), with data being derived by satellite-based Digital Image Correlation (DIC) analysis. The comparison between R-TS and T-InSAR measurements showed that, despite their different spatial and temporal resolutions, the observed deformation trends remain approximately coherent. On the other hand, DIC analysis was able to detect a kinematic process, such as the expansion of the landslide channel, which was not detected by the other techniques used. The results suggest that, when faced with complex events, the use of a single monitoring technique may not be enough to fully observe and understand the processes taking place. Therefore, the limitations of each different technique alone can be solved by a multi-sensor monitoring approach. [ABSTRACT FROM AUTHOR]

Detailed and accurate geomorphological historical landslide inventory maps are an invaluable source of information for many research topics and applications. Their systematic preparation worldwide has been advised by many researchers as it may foster our knowledge on landslides, their spatial and temporal distribution, their potential interaction with the built environment, their contribution to landscape dynamics, and their response to climate change in the past. Due to the extreme variability of the morphological and radiometric elements that can reveal historical landslides, geomorphological historical landslide inventory maps are produced by expert interpretation, which makes it a time-consuming and expensive process, which often discourages wide-area mapping activities. In this paper we present a new geomorphological historical landslide inventory map for a 1460 km 2 area in the Daunia Apennines, the north-western sector of the Apulia (Puglia) region, in southern Italy. The inventory contains 17 437 landslides classified according to relative age, type of movement, and estimated depth. Landslides were mapped according to rigorous and reproducible criteria applied by two teams of expert photo interpreters to two sets of stereoscopic aerial photographs taken in 1954/55 and 2003. The dataset consists of a digital archive publicly available at 10.1594/PANGAEA.942427 (Cardinali et al., 2022). [ABSTRACT FROM AUTHOR]

This paper investigates the possibility to detect the short-time evolution of the slow-moving Vomice earth flow, located in the northeastern sector of the Calabria region (South Italy), by combining the information obtained from two different drone flights, carried out in February 2019 and June 2022, with field surveys. The obtained results consisted of delimiting all landslide bodies constituting the Vomice earth flow, detecting landslide types and the state of activity, as well as identifying spatial and volumetric changes. The obtained results showed that depletion and transition zones of the Vomice earth flow are active, while the accumulation zone appears prevalently dormant. Particularly, in the analyzed period, the depletion zone was characterized by local collapses of the main scarps where several slides evolving in earth flows caused more than 20 m of retrogressive fail upslope. The maximum elevation changes observed in these zones were about ±5 m. The volume of the material mobilized by mass movements was about 114.2 × 103 m3, whereas the volume of the accumulated material was approximately 92.7 × 103 m3. The transition zone was affected by several slow earthflows that re-mobilized the displaced material located in the middle portion of the landslide and reached the accumulation zone. Overall, the results of this study demonstrated the practicality and feasibility of using UAV tools for detecting the short-time evolution of a large landslide. [ABSTRACT FROM AUTHOR]

Transferability of knowledge from well-investigated areas to a new study region is gaining importance in landslide hazard research. Considering the time-consuming compilation of landslide inventories as a prerequisite for landslide susceptibility mapping, model transferability can be key to making hazard-related information available to stakeholders in a timely manner. In this paper, we compare and combine two important transfer-learning strategies for landslide susceptibility modeling: case-based reasoning (CBR) and domain adaptation (DA). Care-based reasoning gathers knowledge from previous similar situations (source areas) and applies it to solve a new problem (target area). Domain adaptation, which is widely used in computer vision, selects data from a source area that has a similar distribution to the target area. We assess the performances of single- and multiple-source CBR, DA, and CBR–DA strategies to train and combine landslide susceptibility models using generalized additive models (GAMs) for 10 study areas with various resolutions (1, 10, and 25 m) located in Austria, Ecuador, and Italy. The performance evaluation shows that CBR and combined CBR–DA based on our proposed similarity criterion were able to achieve performances comparable to benchmark models trained in the target area itself. Particularly the CBR strategies yielded favorable results in both single- and multi-source strategies. Although DA tended to have overall lower performances than CBR, it had promising results in scenarios where the source–target similarity was low. We recommend that future transfer-learning research for landslide susceptibility modeling can build on the similarity criterion we used, as it successfully helped to transfer landslide susceptibility models by identifying suitable source regions for model training. [ABSTRACT FROM AUTHOR]

Detailed and accurate geomorphological historical landslide inventory maps are an invaluable source of information for many research topics and applications. Their systematic preparation worldwide has been advised by many researchers as it may foster our knowledge on landslides, their spatial and temporal distribution, their potential interaction with the built environment, their contribution to landscape dynamics, their response to climate change in the past. Due to the extreme variability of the morphological and radiometric elements that can reveal historical landslides, geomorphological historical landslide inventory maps are produced by expert interpretation, which makes it a time consuming and expensive process, which often discourages wide area mapping activities. In this paper we present a new geomorphological historical landslide inventory map for a 1,460 km² area in the Daunia Apennines, the northern-western sector of the Apulia (Puglia) region, in Southern Italy. The inventory contains 17,437 landslides classified according to relative age, type of movement and estimated depth. Landslides were mapped according to rigorous and reproducible criteria applied by two teams of expert photo interpreters to two sets of stereoscopic aerial photographs taken in 1954/55 and 2003. The dataset consists of a digital archive publicly available at https://doi.pangaea.de/10.1594/PANGAEA.942427 (Cardinali et al., 2022). [ABSTRACT FROM AUTHOR]

Transferability of knowledge from well-investigated areas to a new study region is gaining importance in landslide hazard research. Considering the time-consuming compilation of landslide inventories as a prerequisite for landslide susceptibility mapping, model transferability can be key to making hazard-related information available to stakeholders in a timely manner. In this paper, we compare and combine two important transfer-learning strategies for landslide susceptibility modelling: case-based reasoning (CBR) and domain adaptation (DA). CBR gathers knowledge from previous similar situations (source areas) and applies it to solve a new problem (target area). DA, which is widely used in computer vision, selects data from a source area that has a similar distribution to the target area. We assess the performances of single- and multiple-source CBR, DA and CBR-DA strategies to train and combine landslide susceptibility models using generalized additive models (GAMs) for 10 study areas with various resolutions (1 m, 10 m and 25 m) located in Austria, Ecuador, and Italy. The performance evaluation shows that CBR and combined CBR-DA based on our proposed similarity criterion was able to achieve performances comparable to benchmark models trained in the target area itself. Particularly the CBR strategies yielded favourable results in both single- and multi-source strategies. DA tended to have overall lower performances than CBR; yet, it had promising results in scenarios when the source-target similarity was low. We recommend that future transfer learning research for landslide susceptibility modelling can build on the similarity criterion we used, as it successfully helped to achieve landslide susceptibility model transfers by discovering suitable training datasets from various regions. [ABSTRACT FROM AUTHOR]

Recent events, including the floods in central Europe in May 2021, have highlighted how climate change is giving rise to scenarios that were neither foreseen nor predictable. One problem this poses is the need to rethink the logic of various environmental constraints that are often based on return times of 20-50 years or 100-200. A single event does not change the statistical expectations for the recurrence of the event itself, but the recurrence of several extraordinary events in a few years is a clear indication of a changing trend. The prevention of the effects of such events is based on the definition of the areas at greater or lesser risk specifically based on the return times of the exceptional events, so it is foreseeable that a series of territorial plans, mostly carried out a few decades ago, will have to be updated or re-executed from scratch. These reworkings will be able to take advantage of the opensource software and open spatial data that have become available in the meantime, facilitating the entire process, and making it more open and shareable. In this paper we tested on a real case (the May 1999 pyroclastic flows in Campania, southern Italy) the actual possibility of implementing a model for forecasting such events using only open-source software and open data. It has been demonstrated that the entire process can be carried out using only open-source resources and it has been verified that the predictions of the hazard and risk model obtained with only input data prior to the event, give an output prediction that is significantly coincident with the events that actually occurred as documented by the authorities. [ABSTRACT FROM AUTHOR]

The paper describes the multitemporal landslide inventory map prepared for the urban areas of Motta Montecorvino and Volturino, two municipalities located in the Southern Apennines (Apulia Region, Italy). These territories show a high propensity to landslides of different types and magnitude, which periodically interfere with the anthropic structures and infrastructures. For the study area, the spatial and temporal distribution of landslides is detected for the period between 1954 and 2003, through the visual interpretation of multiple sets of black and white digital stereoscopic aerial photographs at different scales. The analysis reveals locally high frequency of landslide occurrence and built-up areas on existing landslides, either on the body or on the crown areas. In particular, we show that over the years new residential areas were developed despite the presence of large old mass movements. [ABSTRACT FROM AUTHOR]

Starting on 24th August 2016, Central Italy was struck by a six-month earthquake sequence that caused 303 victims and extensive major damages to urban areas and infrastructures, in some cases entire villages needed complete rebuilding. In this paper we present a map that portrays the overall susceptibility to multiple landslide types and the exposure to landslides of the rural-urban areas of the Castelsantangelo sul Nera Municipality, a typical village of the central Italian Apennine. The map is based on a procedure that ingests geomorphological data and models and groups the individual landslide susceptibility maps in a joint susceptibility and exposure map based on expert-defined criteria. The procedure has been applied to built-up and to undeveloped areas to highlight their exposure and was used as a tool for planning post-seismic reconstruction. We advise that such maps are used also as basic tool for ordinary urban planning. [ABSTRACT FROM AUTHOR]

In this paper, a geomorphological map of Pescara del Tronto area (Sibillini Mts, Marche Region) is presented. The work focuses on the geomorphological analysis performed in a zone strongly struck by the 2016–2017 seismic sequence of Central Apennines. The geomorphological map (1:7,500 scale) was obtained through an integrated approach that incorporates geological-geomorphological field mapping and geomorphological profile drawing, supported by air-photo interpretation and GIS analysis. The main purpose of the work is to describe a geomorphological approach for representing and mapping the evidence of several debris flows and landslides recognized in the framework of seismic microzonation (SM) activities. Finally, in order to elevate geomorphological maps into effective tools for land management and risk reduction, it could provide a scientific and methodological basis to demonstrate that accurate mapping provides important information, readily available for local administrations and decision-makers, for the implementation of sustainable territorial planning and loss-reduction measures. [ABSTRACT FROM AUTHOR]

Starting on 24th August 2016, Central Italy was struck by a six-month earthquake sequence that caused 303 victims and extensive major damages to urban areas and infrastructures, in some cases entire villages needed complete rebuilding. In this paper we present a map that portrays the overall susceptibility to multiple landslide types and the exposure to landslides of the rural-urban areas of the Castelsantangelo sul Nera Municipality, a typical village of the central Italian Apennine. The map is based on a procedure that ingests geomorphological data and models and groups the individual landslide susceptibility maps in a joint susceptibility and exposure map based on expert-defined criteria. The procedure has been applied to built-up and to undeveloped areas to highlight their exposure and was used as a tool for planning post-seismic reconstruction. We advise that such maps are used also as basic tool for ordinary urban planning. [ABSTRACT FROM AUTHOR]

The paper describes the multitemporal landslide inventory map prepared for the urban areas of Motta Montecorvino and Volturino, two municipalities located in the Southern Apennines (Apulia Region, Italy). These territories show a high propensity to landslides of different types and magnitude, which periodically interfere with the anthropic structures and infrastructures. For the study area, the spatial and temporal distribution of landslides is detected for the period between 1954 and 2003, through the visual interpretation of multiple sets of black and white digital stereoscopic aerial photographs at different scales. The analysis reveals locally high frequency of landslide occurrence and built-up areas on existing landslides, either on the body or on the crown areas. In particular, we show that over the years new residential areas were developed despite the presence of large old mass movements. [ABSTRACT FROM AUTHOR]

• Novel prognostic method for bridge SHM based on InSAR analysis. • Applied Element Method to simulate the behaviour of bridges up to total collapse. • Combination of InSAR monitoring and numerical modelling. • Estimation of residual service life of bridges affected by slow deformation phenomena. • Application to the Albiano-Magra Bridge case study collapsed in 2020. This paper proposes an innovative approach for structural prognosis of bridges, that combines displacement information obtained by Synthetic Aperture Radar Interferometry (InSAR), applied to satellite data, with structural and collapse analysis performed through numerical modelling. The purpose of this multidisciplinary approach is to recognize potentially critical conditions and predict the time to failure of bridges affected by slow deformation phenomena, such as slow landslide-induced movements. The methodology involves advanced pre- and post-processing techniques for satellite SAR acquisitions, which allow tracking two-dimensional displacement evolution of multi-span bridges with properly defined error bounds, and uses numerical modelling to simulate damage propagation and structural behaviour up to total collapse. The effectiveness of the proposed synergy between remote displacement measurements and numerical collapse analysis is exemplified through the application to the Albiano-Magra Bridge in Italy, which collapsed on April 8th, 2020. The results have allowed to identify the triggering cause of the collapse and have provided an estimate of the residual service life of the bridge, with increasing reliability as the available satellite monitoring period gets longer. The work demonstrates that a combined analysis considering both satellite measurements and numerical modelling can improve the comprehension of the phenomena concerning the structural collapse due to slow deformations and its prevention. [ABSTRACT FROM AUTHOR]

Slope failures are the result of various predisposing factors (geo-structural and morphological conditions, topography, geotechnical characteristics, etc.). In an ordinary phase, a typical slope stability analysis includes the identification of factors that can trigger a slope failure, its mechanisms, the modelling of stability conditions and their assessment during critical situations. To define the predisposing and triggering factors, integrated monitoring represents an essential and powerful tool. In this paper, referring to the case study of a medium-deep landslide that occurred in Calabria (Southern Italy) during the winter of 2009–2010, a method and means of defining an emergency geotechnical model ( smart geotechnical model ) using a geological model are proposed. The definition of both models considers the resources that may be obtained in an emergency and the short time available to achieve the objectives (protection of public and private safety, restoration of normal conditions, etc.). The proposed method allows the orderly and systematic acquisition, under emergency conditions, of data that are useful for the management of a particular situation and for defining an initial cognitive state of the problem. These elements can be particularly effective in both emergency (to manage risk using progressively quantitative knowledge) and ordinary conditions to plan, design, realize and manage definitive measures for risk adaptation, mitigation and reduction. Moreover, the same knowledge can provide useful references to typify landslides that occur in similar geo-environmental contexts. [ABSTRACT FROM AUTHOR]

This paper presents the results obtained by an audio-magnetotelluric (AMT) survey carried out crossing the western sector of Montemurro village (Southern Italy) affected by an intense hydrogeological instability. The AMT investigation was aimed to settle the question concerning the possible prosecution toward SE of the Eastern Agri Fault System whose surficial evidences could be blinded by extensive landslides phenomena and by anthropization of the territory. The AMT profile was oriented in NE-SW direction, orthogonal to the main geological structures of the investigated area. It crossed longitudinally the area affected by instability. The AMT model provides new insights on already known faults (i.e. Montemurro Faults) and imaged their in-depth immersion thus answering to still open geological question in the investigated areas. Furthermore, the high resolution of the model allowed the imaging of the boundaries, in terms of resistivity contrast, between material affected/unaffected by the sliding dynamics or characterized by an higher water content. The results provide new knowledge about the geological and geoelectrical structures in the area. They will be fully integrated with the results of the on-going research activities in the area and will represent an additional step for the multiscale and multiparametrical characterization of the Agri Valley geological setting. [ABSTRACT FROM AUTHOR]

The triggering of shallow landslides in granular deposits is highly controlled by the groundwater regime, namely, the pore water pressure distribution, which directly affects soil shear strength. The slope hydraulic state is usually variable over time and space due to the high variability of atmospheric loads at the ground surface and local geologic conditions, such as stratigraphic irregularities and preferential groundwater flow paths. The unfavourable combination among critical geomorphological and topographical settings with stratigraphic and hydrogeological features are commonly recognized as predisposing factors of flowslides and debris flow occurrences. This paper proposes a multidisciplinary approach that combines geological, geophysical and geotechnical investigations to identify the role of local geological and geotechnical factors on the groundwater regime in slopes prone to flow-like landslides. The study is based on seasonally repeated electrical resistivity tomography measurements integrated with geotechnical numerical modelling of hydraulic phenomena affecting the soil cover. The latter is used to analyse the effects of the stratigraphic variability in terms of the geometry, continuity, and thickness of the soil horizons on the groundwater regime over time. The proposed approach has been applied to a test site located on the northern slope of Faito Mt. in the Lattari/Sorrento Peninsula mountain chain (southern Italy), an area historically affected by many rapid instability phenomena, such as flow-like landslides and flash floods. Both geophysical and geotechnical models obtained for the test site were cross-checked and validated, providing significant insights into the hydraulic response of the soil cover to rainfall and its hydraulic interaction with the underlying bedrock. Specifically, the integrated approach proved that i) the buried paleo-morphology of the bedrock severely affects the pore water distribution in the soil cover and ii) ashy soil fills the upper karst portion of the bedrock, providing a hydraulic connection of the water flow infiltrating from the topsoil downwards. • The local geological factors severely affect flowslide's occurrence. • Geophysical modelling provides spatial distribution of water content in the slope. • Geotechnical models study the effects of local factors on hydraulic slope behaviour. • Bedrock paleo-morphology heavily affects pore water into soil cover. • Soil-filled fractures of the bedrock represent hydraulic connection of water flow. [ABSTRACT FROM AUTHOR]

This paper presents the main results of the GB-InSAR (ground based interferometric synthetic aperture radar) monitoring of the Capriglio landslide (Northern Apennines, Emilia Romagna Region, Italy), activated on 6 April 2013. The landslide, triggered by prolonged rainfall, is constituted by two main adjacent enlarging bodies with a roto-translational kinematics. They activated in sequence and subsequently joined into a large earth flow, channelizing downstream of the Bardea Creek, for a total length of about 3600 m. The displacement rate of this combined mass was quite high, so that the landslide toe evolved with velocities of several tens of meters per day (with peaks of 70-80 m/day) in the first month, and of several meters per day (with peaks of 13-14 m/day) from early May to mid-July 2013. In the crown area, the landslide completely destroyed a 450 m sector of provincial roadway S.P. 101, and its retrogression tendency exposed the villages of Capriglio and Pianestolla, located in the upper watershed area of the Bardea Creek, to great danger. Furthermore, the advancing toe seriously threatened the Antria bridge, representing the "Massese" provincial roadway S.P. 665R transect over the Bardea Creek, the only strategic roadway left able to connect the above-mentioned villages. With the final aim of supporting local authorities in the hazard assessment and risk management during the emergency phase, on 4 May 2013 aerial optical surveys were conducted to accurately map the landslide extension and evolution. Moreover, a GB-InSAR monitoring campaign was started in order to assess displacements of the whole landslide area. The versatility and flexibility of the GB-InSAR sensors allowed acquiring data with two different configurations, designed and set up to continuously retrieve information on the landslide movement rates (both in its upper slow-moving sectors and in its fast-moving toe). The first acquisition mode revealed that the Capriglio and Pianestolla villages were affected by minor displacements (at an order of magnitude of a few millimeters per month). The second acquisition mode allowed to acquire data every 28 seconds, reaching very high temporal resolution values by applying the GB-InSAR technique. [ABSTRACT FROM AUTHOR]

The Crati Graben is a depression of Plio-Holocene age mainly controlled by extensional N–S striking faults and WNW–ESE transcurrent faults, in its northern and southern extremity. It is characterized by high landslide susceptibility due to the particular geo-structural pattern and seismotectonic characters. Landslides involve many villages, infrastructure and food crops, bringing serious economic and social damage. The seismotectonic and landslidesMain Mapof the Crati Graben, described in this paper, represents an update in detail of the framework of landslide risk areas and shows the main active and recent faults of the Crati Graben. The landslides and the faults, have been identified and classified, originally at detail scale (1:5000) and, then, represented at 1:50,000 scale. The geo-structural and geomorphological data were analysed in a geographic information system. The work has revealed a correlation between the trend of faults with respect to the distribution of landslides and of the historical and instrumental seismicity. The work presents an updated knowledge framework of risk conditions of the study zone, where risk areas related to slope instability are hierarchically classified according to the destructive potential of landslides. This document may be therefore a useful reference in planning and prioritising in the design of interventions for the safety of slopes and waterways. [ABSTRACT FROM AUTHOR]

This paper presents the results of geomorphological investigations carried out in Basilicata region (Southern Italy) in the sector of the youngest foredeep (Bradano trough) relative to most of the communal territory of Pisticci. The importance of the chosen area mostly lies in the presence of diffuse running-water landforms and landslides affecting urban areas. The geomorphological processes are linked with Quaternary tectonic uplift affecting the Apennine front-Bradanic foredeep sectors. A series of field surveys, supported by aerial photo interpretation, have led to the production of a geomorphological map at 1:35,000 scale which outlines the main processes and related landforms recognised in the study area. The latter are the result of the complex interplay of structural, gravitational and fluvial processes. Particular attention has been devoted to the recognition, identification and mapping of landslides which affect the slope, locally giving rise to hazardous conditions. [ABSTRACT FROM AUTHOR]

This paper deals with a quantitative risk analysis, performed using the rockfall risk management (RO.MA.) method, for a road affected by rockfalls. This approach allows evaluating the rockfall risk, also considering existing protection devices. Rockfall hazard and risk were assessed for an important and very busy road stretch linking Positano to Amalfi in the Campania region of southern Italy. An estimate of the rockfall return periods for assigned volume classes was obtained using the magnitude-frequency curves (MFCs) computed through the analysis of a rockfall inventory covering a time span from 1996 to 2008. For rockfall volumes of 0.1, 1.0, and 10 m, using a 2D trajectory simulating code, the involved kinetic energies and run-out distances of boulders that may hit the road were calculated. The risk, expressed as the annual probability of a fatal accident for the three rockfall hazard scenarios has been evaluated both without and with protection devices, respectively. The total final risk is given by the sum of partial risks related to the three scenarios. The analysis showed that regardless of whether there are any rockfall protection devices, the total risk remains almost constant. This is due to the wide spread of slopes protected with inadequate restraining metallic nets characterized by decreasing catching capacities, as possible rockfall magnitude increases. The individual risk is not acceptable, and some actions are requested in order to lower it. [ABSTRACT FROM AUTHOR]

Abstract: In this paper all the phases for the realization of the early warning system for the rockslide of Torgiovannetto in Central Italy are described. The landslide consists in a 182,000m3 rock wedge threatening two roads which are important for local transportation. The present work encompasses all the components of an early warning system, including the geological knowledge, the risk scenarios, the kinematic characterization of the landslide, the choice and installation of the monitoring system, the setting of appropriate alarm levels and the definition of plans of civil protection. The focus is on practical and logistical issues met in all these phases and the counter-measures adopted. At present the system consists in 13 wire extensometers, 1 thermometer, 1 rain gauge and 3 cameras. Should a velocity threshold be exceeded by two or more sensors, the attention level would be entered, causing improved monitoring and surveillance. In case the behavior of the landslide changes and, by using expert judgment and forecasting methods, an imminent failure is hinted, then an alarm is issued and the upper road is closed. This paper can provide ideas and solutions for a landslide early warning system that aims to be simple, flexible, versatile and with a low probability of giving false alarms. [Copyright &y& Elsevier]

Abstract: The Apennine mountains of the Parma Province (Italy) are characterized by a young geological structure subjected to continuous morphological modification in many areas. As a consequence, several active landslides can be identified in this region. Among others, slow movements occurring over large areas are the typical type of instability in this zone. The slow but constant deformation process can induce major damage when interacting with major civil infrastructures such as bridges, roads and railways, but has a less severe effect on agricultural practice and smaller structures. Four different slope instability phenomena are analyzed in this paper. All the slopes are characterized by similar geological and hydrogeological features and by similar deformation rates. All slopes have been studied by means of experimental tests and numerical modelling in order to understand the failure mechanism and the evolution of slope movement. The deformation of each slope was monitored using superficial topographic control points and inclinometers, while its water level regime is controlled by means of discontinuous piezometric readings. The monitoring results, together with in-situ and laboratory testing, allowed a more detailed understanding of processes such as deformation under a constant active stress. The development of a numerical model was necessary to predict creep rates. Special attention has been given to the mineralogical components of the material involved in the unstable areas, in order to identify the material structure characterizing these types of landslides. This work is aimed to be a methodological study of a type of complex phenomena that are recurrent in a zone of the Apennines. These phenomena can be partly considered as mudslides acting in undrained loading condition along localized shear zones but creep gives a fundamental contribution to mass deformation that must also be considered in the phenomenon modelling to be able to obtain measured displacement rates. For this purpose creep tests have been performed in undrained conditions and modeled by a finite difference code for the calibration of relevant material mechanical parameters. The paper reports the description of the problems encountered to sample and to make experimentation on this kind of complex materials along with the obtained results and, at the end, gives some operative suggestions on how to overcome such difficulties. [Copyright &y& Elsevier]

The paper explores the potential of the satellite advanced differential synthetic aperture radar interferometry (A-DInSAR) technique for the identification of impending slope failure. The advantages and limitations of satellite InSAR in monitoring pre-failure landslide behaviour are addressed in five different case histories back-analysed using data acquired by different satellite missions: Montescaglioso landslide (2013, Italy), Scillato landslide (2015, Italy), Bingham Canyon Mine landslide (2013, UT, USA), Big Sur landslide (2017, CA, USA) and Xinmo landslide (2017, China). This paper aimed at providing a contribution to improve the knowledge within the subject area of landslide forecasting using monitoring data, in particular exploring the suitability of satellite InSAR for spatial and temporal prediction of large landslides. The study confirmed that satellite InSAR can be successful in the early detection of slopes prone to collapse; its limitations due to phase aliasing and low sampling frequency are also underlined. According to the results, we propose a novel landslide predictability classification discerning five different levels of predictability by satellite InSAR. Finally, the big step forward made for landslide forecasting applications since the beginning of the first SAR systems (ERS and Envisat) is shown, highlighting that future perspectives are encouraging thanks to the expected improvement of upcoming satellite missions that could highly increase the capability to monitor landslides' pre-failure behaviour. [ABSTRACT FROM AUTHOR]

Landslide dams are a particular kind of natural dam which forms when an earth or rock mass reaches a river channel causing its complete or partial blockage. Since 1995, the Earth Sciences Department of the University of Firenze has been running a project involving the inventory of landslide dams in the Northern Apennines, which currently contains more than 60 case studies. It is known that the geotechnical characterisation of landslide dams is closely related to the grain size distribution of the materials composing the dams. In particular, grain size exerts a control on dam stability, influencing the strength and the permeability of the dam material. The main purpose of this work is to contribute to grain size characterisation of landslide dams by giving an outline of the possible methods that can be used for grain size assessment and showing the results obtained from the case studies selected in the Northern Apennines. Indeed, despite its importance, there are few quantitative studies directed at determining grain size distribution of debris dams, mainly because customary bulk sieve analyses are impractical when dealing with materials often ranging in size from blocks tens of cubic metres in size, to microscopic particles. This paper presents results derived from the application of two main sampling methods on 42 landslide dams, (a) volumetric analysis and (b) grid by number analysis (here presented in two variants). These techniques allow us to obtain very similar grain size distributions for the coarser part of the debris material, while some differences persist for the finer fraction. The paper would also like to highlight the importance of getting accurate grain size data, with particular reference to the determination of the hydrograph derived from a landslide dam failure. Many deterministic models attempt to approach this problem, by taking into account only the median percentile (D50) of the cumulate grain size distribution. However, in most of the selected cases, a marked bimodal distribution was found in the frequency diagrams, so the fiftieth percentile (D50) is often one of the less representative grain size classes. It should thus be taken carefully into account that this choice could be misleading, as it is not necessarily justified by the physical evidence. [Copyright &y& Elsevier]

Landslide geodatabases, including inventories and thematic data, today are fundamental tools for national and/or local authorities in susceptibility, hazard and risk management. A well organized landslide geo-database contains different kinds of data such as past information (landslide inventory maps), ancillary data and updated remote sensing (space-borne and ground based) data, which can be integrated in order to produce landslide susceptibility maps, updated landslide inventory maps and hazard and risk assessment maps. Italy is strongly affected by landslide phenomena which cause victims and significant economic damage to buildings and infrastructure, loss of productive soils and pasture lands. In particular, the Messina Province (southern Italy) represents an area where landslides are recurrent and characterized by high magnitude, due to several predisposing factors (e.g. morphology, land use, lithologies) and different triggering mechanisms (meteorological conditions, seismicity, active tectonics and volcanic activity). For this area, a geodatabase was created by using different monitoring techniques, including remote sensing (e.g. SAR satellite ERS1/2, ENVISAT, RADARSAT-1, TerraSAR-X, COSMO-SkyMed) data, and in situ measurements (e.g. GBInSAR, damage assessment). In this paper a complete landslide geodatabase of the Messina Province, designed following the requirements of the local and national Civil Protection authorities, is presented. This geo-database was used to produce maps (e.g. susceptibility, ground deformation velocities, damage assessment, risk zonation) which today are constantly used by the Civil Protection authorities to manage the landslide hazard of the Messina Province. [ABSTRACT FROM AUTHOR]

In recent years, space-borne InSAR (interferometric synthetic aperture radar) techniques have shown their capabilities to provide precise measurements of Earth surface displacements for monitoring natural processes. Landslides threaten human lives and structures, especially in urbanized areas, where the density of elements at risk sensitive to ground movements is high. The methodology described in this paper aims at detecting terrain motions and building deformations at the local scale, by means of satellite radar data combined with in situ validation campaigns. The proposed approach consists of deriving maximum settlement directions of the investigated buildings from displacement data revealed by radar measurements and then in the cross-comparison of these values with background geological data, constructive features and on-field evidence. This validation permits better understanding whether or not the detected movements correspond to visible and effective damages to buildings. The method has been applied to the southwestern sector of Volterra (Tuscany region, Italy), which is a landslide-affected and partially urbanized area, through the use of COSMO-SkyMed satellite images as input data. Moreover, we discuss issues and possible misinterpretations when dealing with PSI (Persistent Scatterer Interferometry) data referring to single manufactures and the consequent difficulty of attributing the motion rate to ground displacements, rather than to structural failures. [ABSTRACT FROM AUTHOR]

Terraces are traditional engineered ecosystems that affect the hydro-geological equilibrium, slope stability, and local communities. The aims of this paper are (i) identifying environmental factors that affect terrace stability in the Amalfi Coast, (ii) defining agriculturalists' observations on environmental changes within that system and (iii) exploring potentiality of these observations to better define conservation strategies. All available data on physical and ecological factors recognized to affect the terrace system were collected and analyzed. Interviews were conducted with agriculturalists to obtain long-term observations on environmental factors that interact with this system. Landslides are more frequent where rainfall is high and during winter. Fires have an uneven annual distribution, with higher frequency during summers. Agriculturalists detailed complex interactions among environmental factors, economic elements, and terraces. These observations represent a valuable resource for defining causes and effects of abandonment and for better addressing conservation strategies. [ABSTRACT FROM AUTHOR]

Landslides recurrently impact the Italian territory, producing huge economic losses and casualties. Because of this, there is a large demand for monitoring tools to support landslide management strategies. Among the variety of remote sensing techniques, Interferometric Synthetic Aperture Radar (InSAR) has become one of the most widely applied for landslide studies. This work reviews a variety of InSAR-related applications for landslide studies in Italy. More than 250 papers were analyzed in this review. The first application dates back to 1999. The average production of InSAR-related papers for landslide studies is around 12 per year, with a peak of 37 papers in 2015. Almost 70% of the papers are written by authors in academia. InSAR is used (i) for landslide back analysis (3% of the papers); (ii) for landslide characterization (40% of the papers); (iii) as input for landslide models (7% of the papers); (iv) to update landslide inventories (15% of the papers); (v) for landslide mapping (32% of the papers), and (vi) for monitoring (3% of the papers). Sixty-eight percent of the authors validated the satellite results with ground information or other remote sensing data. Although well-known limitations exist, this bibliographic overview confirms that InSAR is a consolidated tool for many landslide-related applications. [ABSTRACT FROM AUTHOR]

Recent research in Umbria, Italy, has shown that landslide susceptibility is controlled by a process called path-dependency, which describes how past landslides control the locations of future landslides. To date, landslide path-dependency has only been characterised in Italy. This raises the question of whether this process occurs in other geomorphic settings, and thus whether path-dependency should be more universally included in landslide susceptibility assessments. Therefore, the main aim of this paper is to investigate and quantify landslide path dependency in the Nepal Himalaya. This is achieved by applying several path dependent metrics to three monsoon-triggered landslide inventories for the central-eastern Nepal Himalaya. These inventories were developed at two different spatial and temporal resolutions. As such, we aim not just to quantify landslide path-dependency, but also to assess whether path dependency characteristics are resolution-dependent. We find strong evidence that landslide path dependency is occurring in Nepal, with all three inventories having more overlap between past and new landslides than expected from a random distribution, and a tentative observation that the expected degree of overlap between landslides decreases with time. Finally, whilst path-dependency is observable across both of the investigated inventory resolutions, we find that the rates and magnitudes of the quantified path dependent metrics are sensitive to inventory length, study region size and the size/type of landslides mapped. Overall, our results corroborate the path-dependency observations from Italy, confirming that this process does occur in other geomorphic settings, and thus suggesting that path-dependency should be explicitly and universally considered in landslide susceptibility approaches. [ABSTRACT FROM AUTHOR]

Abstract: The present work is focused on investigating the potential role of capillary barriers on the stability of layered soil deposits laying upon high permeability steep slopes. In presence of capillary barrier effects, often possible on a soil stratigraphy characterized by contrasting hydraulic properties (pyroclastics deposit over pumices, silt upon fractured bedrock, silt over sand) failure might originate in less permeable layers, where unsaturated conditions might provide a crucial contribution to stability. Basic ideas and considerations have been drawn from a peculiar case study, the catastrophic landslide occurred in Campania, Southern Italy, on May 1998, which is discussed in this paper from a different perspective. The areal extent of failures’ distribution, their dense concentration at the steeper and higher slopes, the extremely high number of initial failures occurred within a relatively short time span suggest that the intimate cause of the event is related at some extent to the soil state characteristic parameters rather than positive pore pressure pulses from water circulation in coarser layers or groundwater level rising from bedrock and springs. A widespread loss of soil strength related to saturation can contribute to explain such phenomena. Capillary barrier effects favor accumulation and lateral distribution of percolating rainfall and possibly divert flowlines downslope, thus leading to localized increases in water content and loss of strength. Diversion of percolating waters facilitates lateral redistribution of soil moisture along the slope with possible further localized saturation, because more permeable layers may act temporarily as barriers and not as drains, as one could expect. Numerical 2-D infiltration models with parameters calibrated versus laboratory data show a relevant influence of capillary barrier effects on infiltration in layered slopes with vertically stratified variations of hydraulic properties and point out significant localized moisture accumulation with possible consequences on slope stability. Landslide initiation phenomena in layered covers might thus be conditioned by the increase in saturation within the least permeable soil layers due to capillary barrier phenomena. [Copyright &y& Elsevier]

Abstract: This paper conducts a statistical analysis to determine shallow-landslide susceptibility in an approximately 7500-km2 region of the south-eastern Alps (South Tyrol, Italy). The study applies the weight of evidence (WofE) method, which is useful in determining landslide susceptibility in large areas with complex geological and geomorphological settings. The statistical analysis and landslide susceptibility mapping are based on 882 past landslides, three geometric/topographic factors and two anthropogenic factors, which are the most relevant landslide predisposing factors. The quality of the proposed model, particularly the fitting performance, was assessed; the landslide database was divided into a training set to obtain the model and a validation set to estimate the model quality. The results show that the developed susceptibility model predicts an acceptable percentage (75%) of landslides. Therefore, the model can be useful and reliable for land planners and decision makers also due to its cost-effectiveness ratio. [Copyright &y& Elsevier]

Abstract: Studying long term-evolution of gravitational slope evolution is a key to understanding deep-seated landslide processes. This paper deals with three large Deep-Seated Landslides (DSLs) at a front of a subalpine meridional chain, on the “La Marbrière” slope near the town of Grasse (Alpes-Maritimes, France). The geological framework controlling the stability and morphology of the DSLs is associated with thick and tamped Triassic layers of mudstone with gypsum overlain by highly faulted Jurassic limestone. Gravitational deformation affects the entire slope, involving a movement of about 1.1×108 m3 of rock material. It creates large disturbances in landscape morphology, such as scarps, counter-slope scarps, trenches and other typical gravitational morpho-structures. Geomorphological mapping coupled with deep electrical resistivity tomography (ERT) reveals a strong correlation between these morpho-structures and inherited brittle tectonic features. This observation relies on spatial and geometrical relations (on the surface and at the depth of more than 150m, checked by ERT) between the most persistent fault and the gravitational morpho-structures. The specific distribution of the morpho-structures on the basis of their morphological typologies and variations in the stage of evolution of three DSLs provides an interpretation of their kinematics during the last 400ka. It appears that soft substratums combined with inherited persistent anisotropies are key factors in the development of the DSLs. Indeed, outflow of mudstone due to the lithostatic pressure imposed by individual limestone compartments has led to general slope subsidence. Then, a progressive toppling of a rock mass may have led to the catastrophic rock collapse along bedding planes. The evolution of the DSLs can be divided into three distinct stages represented by three zones: a young collapse stage (zone 1), a pre-collapse stage (zone 2) and an old mature stage (>400ka, zone 3). As the DSLs occur on the same slope and in the same geological context, this area offers interesting perspectives for understanding factors controlling the long-term gravitational evolution of slopes. [Copyright &y& Elsevier]

Abstract: On October 9th 1963 a huge landslide fell into the Vajont artificial reservoir in Northern Italy, and displaced the water which overtopped the dam and produced a destructive wave that inundated the valley causing about 2000 casualties and complete devastation. The landslide has been the subject of many geological studies, and is one of the largest ever documented in literature. Nevertheless, only a small number of hydraulic analyses have been conducted relating the sliding motion to the consequent water waves and describing the formation of different waves and how they interfered with each other. A numerical model, capable of doing so, has not yet been presented. In this paper, a horizontal bi-dimensional finite volume model is proposed in order to study the wave generated by the Vajont landslide. We hereby introduce a moving wall reproducing the effects of the landslide. [Copyright &y& Elsevier]

Abstract: Rainfall-induced shallow landslides of flow type provide unstable masses which often travel long run-out distances with high velocities, thus posing a high societal risk when they affect large areas. Therefore, analysis of their spatial and temporal occurrence is relevant to landslide hazard assessment as the first step of the risk analysis. In order to address this issue, this paper outlines a multidisciplinary procedure that is applied to the May 1998 Sarno-Quindici landslides (southern Italy), whose spatial and temporal occurrence is not satisfactorily addressed in current literature. The spatial occurrence of the landslides is analysed using heuristic models for both the source and propagation areas. The temporal occurrence of the landslides is firstly compiled and then related to the cumulated rainfall, stratigraphy and hydraulic boundary conditions. Finally, the spatial and temporal occurrence of the main landslide triggering mechanism is modelled over the whole affected area by analysing the groundwater regime and slope stability conditions. The obtained results show that the spatial and temporal occurrence is strongly related to stratigraphy and hydraulic boundary conditions at both the slope and massif scales. They also highlight a suitable procedure for assessing the spatial and temporal occurrence of complex landslides over large areas. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we evaluate different methods to predict soil erosion processes. We derived different layers of predictor variables for the study area in the Northern Chianti, Italy, describing the soil–lithologic complex, land use, and topographic characteristics. For a subcatchment of the Orme River, we mapped erosion processes by interpreting aerial photographs and field observations. These were classified as erosional response units (ERU), i.e. spatial areas of homogeneous erosion processes. The ERU were used as the response variable in the soil erosion modelling process. We applied two models i) bootstrap aggregation (Random Forest: RF), and ii) stochastic gradient boosting (TreeNet: TN) to predict the potential spatial distribution of erosion processes for the entire Orme River catchment. The models are statistically evaluated using training data and a set of performance parameters such as the area under the receiver operating characteristic curve (AUC), Cohen''s Kappa, and pseudo R2. Variable importance and response curves provide further insight into controlling factors of erosion. Both models provided good performance in terms of classification and calibration; however, TN outperformed RF. Similar classes such as active and inactive landslides can be discriminated and well interpreted by considering response curves and relative variable importance. The spatial distribution of the predicted erosion susceptibilities generally follows topographic constraints and is similar for both models. Hence, the model-based delineation of ERU on the basis of soil and terrain information is a valuable tool in geomorphology; it provides insights into factors controlling erosion processes and may allow the extrapolation and prediction of erosion processes in unsurveyed areas. [Copyright &y& Elsevier]

Abstract: This paper describes the geometrical structure and the main kinematic features of an ancient and active landslide which develops in structurally complex formations of the Southern Apennines (Italy): a scaly clayey formation in the medium and lower part of the slope, and a stratified marly–calcareous rock formation in the upper part. The landslide 3D geometry was reconstructed by using topographic data, stratigraphies from continuous coring boreholes and inclinometer data. The analysis of the kinematic features was based on the measurement of deep and superficial displacements. Laboratory tests were carried out to evaluate shear strength parameters. It was found that in each investigated transversal section of the landslide channel the displacements can be considered uniform, and that the decrease of the displacement rates, from upslope to downslope, mostly depends on the increase in the areas of transversal sections, the “soil discharge” variations being slight. Stability analyses confirmed that shear strength close to the residual value is available on the slip surface. The large difference between residual strength and peak strength of the landslide material is consistent with the displacement uniformity. [Copyright &y& Elsevier]

The paper reports an investigation into the distribution and type of landslides in the Benevento province in southern Italy, between 2001 and 2008. Field mapping was undertaken at various scales up to 1:10,000 depending on the features identified. Landslide types were recognized within 5-group litho-technical sequences cropping out in the province, grouped according to their similar mechanical and lithological features. The analysis showed a widespread diffusion of Earth Flows, with reactivation linked to both rainfall and seismic events. They are structurally controlled related to bedding, stratigraphic/tectonic contact between more and less competent sequences and a high degree of tectonisation. [ABSTRACT FROM AUTHOR]

Abstract: For the generation of susceptibility maps on medium scales (1:25,000 to 1:50,000) using statistical techniques, a reliable landslide inventory is needed, together with factor maps used as inputs. This paper compares landslide susceptibility maps obtained with the same methodology but using different landslide inventories: the official Italian landslide inventory GeoIFFI for the Lombardy Region and a recently mapped inventory (DF2001). The analysis included four main steps: (i) preparation of debris flow inventories using both random and spatial partitions and factor maps as explanatory variables; (ii) calculation of accountability and reliability indices for a preliminary susceptibility analysis and selection of an appropriate combination of the factor maps for detailed analysis; (iii) evaluation and validation of the obtained susceptibility maps; and (iv) comparison of the results and selection of the final map. The study area is located in the Valtellina Valley in the Central Italian Alps. The analysis identified highly susceptible areas of shallow landslides that may generate debris flows. It was demonstrated that more precisely delimited source areas for landslide-induced debris flows produce better susceptibility maps. However, the improvement of these maps was relatively limited when the inventories were randomly subdivided. Higher improvements were observed after the subdivision of the inventories into three geographical parts with different geomorphological characteristics. Although the modelling showed very similar results if evaluation is made using standard techniques, the spatial pattern of the susceptibility maps was highly variable and dependent on the combination of the factor maps used. [Copyright &y& Elsevier]

During the 2002 eruption, the NW flank of Stromboli volcano (Southern Italy) experienced large landslides that produced tsunami waves with a maximum runup of 10 m in height. This paper focuses on the geomechanical behavior of the loose volcaniclastic layers, the weakest component of the deposit forming the volcano flank. Tests on the coarse-grained volcaniclastic soil and on the rock material forming the grains were conducted in dry conditions, a feature of the subaerial slope. The rock material, in spite of its high porosity, exhibits relatively high stiffness and strength due to the remarkable continuity of the solid skeleton. Accordingly, the volcaniclastic soil is characterized by high shear strength. During shear tests, however, significant grain crushing occurs, which partly explains the nonlinear shear strength envelope and the strain softening associated with contractive behavior. Grain crushing was also found to affect compressibility and its time dependency, investigated under oedometric conditions. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to analyze the reactivation mechanism of ancient earth flows, with a view to gleaning information that can subsequently be utilized to formulate a risk-reduction strategy. All considerations made herein are the result of direct experience and observation of actual events which have occurred over the past few decades in the Northern Apennines. Particular attention has been paid to the analysis of the evolution of landslides during actual reactivation, acknowledging a typical, recurring succession of events that precede the failure of the slope. The hazard assessment of these large landslide bodies, which are of slope scale, constitutes a thorny problem, especially in view of the inapplicability of traditional deterministic models such as limit equilibrium stability analysis. Nevertheless, a site-specific assessment of probability of reactivation of these large and ancient earth flows is fundamental to effective land-use planning. [Copyright &y& Elsevier]

The 2016 Italian seismic sequence was characterized by three main shocks that occurred on August 24th, on October 26th and 30th. The latter, a Mw 6.5 event, is the strongest seismic event recorded in Italy since the 1980, Mw 6.9 Irpinia Earthquake. In this time span between the first and the third shock of the 2016 sequence, more than 1000 seismic events of Mw greater than 3.0 and shallow hypocentral depth between 7 and 11 km were recorded, triggering more than of 1300 observed landslides. In this paper, the identification of the triggering models for four selected rock slides was performed together with the mechanical characterization of the affected rock masses both in situ and in laboratory. Large scale morphostructural setting was analysed to verify the role of regional tectonics in the failures. Discontinuity sets were identified at detail-scale using three-dimensional (3D) point clouds developed from structure from motion (SfM) reconstruction using unmanned aerial vehicles (UAVs). In situ and laboratory tests coupled to data from UAV 3D models were used for geomechanical characterization. Data were finally adopted as input of limit equilibrium static analyses, which allowed a better comprehension of the stability conditions prior to seismic events and clarify some aspects of the mobilized strength. • 3D Rockslides models were obtained from UAV surveys. • Structure from Motion (SfM) permitted to characterize the discontinuty sets. • The tectonic pattern of the area is controlled by NW-SE Quaternary faults. • Rockslides are locally controlled by more ancient discontinuity systems. • Failures of rock bridges were involved in the sliding. [ABSTRACT FROM AUTHOR]

Complex landslides, capable of reactivation, are typical slope movements in high relief areas. Due to their distribution, size and kinematics, these landforms represent a major hazard, posing a high risk to populations, settlements and infrastructures. This paper integrates geomorphological analyses, instrumental measurements and dendrochronological approaches in assessing a large, reactivated landslide system on the southern piedmont of Monte Sirino (southern Italy). The landslide system is associated with weak geological structures, earthquake activity, and rapid recent incision of the mid-Pleistocene Noce lake deposits. Potential reactivation triggers include a higher regional annual rainfall, one of the highest in southern Italy, and more frequent heavy snowfalls in recent decades. Reactivation of the Sirino landslide system has important implications for the motorway connecting Salerno and Reggio Calabria, which crosses it. The results of our study show that the slide is reactivated with an almost decadal frequency and that major reactivations are correlated to prolonged snowfall, which occurs with increasing frequency in the southern Apennines. The last observation suggests the need for similar studies on the behaviour of other landslide systems in the southern Apennines, performing integrated approaches such as geotechnical and dendrogeomorphological analysis. [ABSTRACT FROM AUTHOR]

Rainfall-induced shallow landslides occurring along slopes of mountains around the city of Naples (southern Italy), characterized by pyroclastic covers laying upon fractured limestone bedrock, pose serious threat to settlements and towns located at their foot. Although the triggering mechanism, related to suction reduction in the initially unsaturated soil cover is quite clear, there is still debate about the hydrological processes which predispose the slopes to failure. In this paper, the predisposing factors are analyzed with reference to two intense storms, both with about 300 mm rainfall, occurred in the same period of the year in 1999 and 2019. The two storms triggered several shallow landslides in an area of few km2 of the northeast-facing slopes of Partenio Mountains. The two events are compared analyzing both the characteristics of antecedent and event precipitations, as well as simulating the response of the slopes to rainfall with the help of a mathematical model. Specifically, two slopes are analyzed: one, near the town of Cervinara, where landslides were triggered only in 1999; another, near the town of San Martino Valle Caudina, where landslides occurred during both the events. The results of the model simulations indicate that rainstorm duration (shorter in 1999) and antecedent precipitation during the weeks before the event (smaller in 1999) are the main reasons of the different responses of the slopes to the two rainfall events. In fact, both drier initial conditions at the base of the soil cover and shorter storm duration limit the possibility of drainage of infiltrating water out of the soil cover through the soil-bedrock interface, thus favoring the suction reduction required for slope failure. The obtained results provide a key for the interpretation of landslides, often occurring in late autumn-early winter in the area. • Two landslides (1999 and 2019) on near slopes compared through mathematical modeling • Water leakage through soil-bedrock interface can prevent landslide triggering • Streams supplied by perched aquifer in the uppermost bedrock ensure slope drainage • Landslide predisposing conditions are controlled by soil moisture profile • Antecedent precipitation alone is not a proxy of landslide predisposing conditions [ABSTRACT FROM AUTHOR]

Abstract: The paper describes a methodology to detect landslide triggering scenarios in geological homogeneous areas and for some specific landslide categories. In these scenarios, the rainfall–landslide relationship as well as the pluviometric load conditions influencing slope instability have to be investigated. The methodology is applied to an area located in northern Calabria (Italy) and affected by widespread and different slope instability phenomena. Outcropped, fractured, and deeply weathered crystalline rock masses, determining geologic homogeneous conditions, are present. In the same area, suitable and homogeneous climatic features have also been found. According to the methodology adopted, the hydrologic analysis of rainfall time-series is initially carried out notwithstanding historical data concerning landslide mobilization, but using simple models to determine critical pluviometric scenarios for the three landslide categories: shallow, medium-deep, and deep. Landslide-triggering scenarios individualized according to this procedure are less significant as compared to the landslide mobilization detected in the study area by means of historical research and ascribed to the three landslide categories according to geomorphologic analysis. Subsequently, the possible landslide triggering scenarios are outlined by carefully investigating the hydrologic analysis limited to the periods identified according to the historical data. In the study area and approximately for all the areas characterized by the outcrop of fractured and deeply weathered crystalline rocks, significant triggering scenarios can be outlined. In particular, shallow landslide triggers could be activated by rainfall events with intensities exceeding 90 mm/day and/or with amounts exceeding 160 mm. As for medium-deep and deep landslides, triggering mechanisms are more complicated; and effective rainfall contribution must be taken into account compared to groundwater storage. Moreover, a more complex link between deep landslides and precipitation is confirmed. The results obtained to date highlight the potential of this methodology, which enables us to define and progressively improve the knowledge framework by means of a work sequence integrating different disciplinary tools and results. [Copyright &y& Elsevier]

Abstract: In May 1998, a prolonged period of rainfall caused disastrous landslides in the Sarno–Quindici area (Campania, Southern Italy). The landslides initiated as small debris slides, and developed into debris avalanches and debris flows involving the shallow pyroclastic deposits that lie on the steep, vegetated slopes of this area. In view of the potential for such events to occur again in this area, an understanding of the initial failure mechanism is crucial if assessments are to be made of the hazard levels. In this paper, the results of detailed surveys of the morphological characteristics of the source areas are presented. Statistical analyses and parametrical relationships have been performed on key parameters, demonstrating that the initial failures were associated with the presence of morphological discontinuities, such as limestone scarps and road cuts. Notably, the presence of man-made cuts appears to have been responsible for about the 60% of the initial debris slides. Morphometric analysis has shown that the debris avalanches are characterised by a typical triangular shape. Statistical analyses have been used to try to relate the apex angles to relevant geomorphological parameters. Allowing for differences in local morphology the findings show some significant correlation. [Copyright &y& Elsevier]

Abstract: The Tessina landslide is a large, seasonally active slope failure located on the southern slopes of Mt. Teverone, in the Alpago valley of NE Italy, consisting of a complex system that has developed in Tertiary Flysch deposits. The landslide, which first became active in 1960, threatens two villages and is hence subject to detailed monitoring, with high quality data being collected using piezometers, inclinometers, extensometers, and through the use of a highly innovative, automated Electronic Distance Measurement (EDM) system, which surveys the location of a large number of reflector targets once every 6 h. These systems form the basis of a warning system that protects the villages, but they also provide a very valuable insight into the patterns of movement of the landslide. In this paper, analysis is presented of the movement of the landslide, concentrating on the EDM dataset, which provides a remarkable record of surface displacement patterns. It is proposed that four distinct movement patterns can be established, which correspond closely to independently defined morphological assessments of the landslide complex. Any given block of material transitions through the four phases of movement as it progresses down the landslide, with the style of movement being controlled primarily by the groundwater conditions. The analysis is augmented with modelling of the landslide, undertaken using the Itasca FLAC code. The modelling suggests that different landslide patterns are observed for different parts of the landslide, primarily as a result of variations in the groundwater conditions. The model suggests that when a movement event occurs, displacements occur initially at the toe of the landslide, then retrogress upslope. [Copyright &y& Elsevier]