Search

Landslide hazards have significant social, economic, and environmental impact. This work provides a critical review of the main existing literature using satellite data for mapping landslides. We created and examined an extensive bibliographic database from Web of Science (WoS) consisting in 291 outputs from > 1,000 authors who studied almost 700,000 landslides across all continents, for a total of 52 countries represented with China and Italy on top of the list with more authors. The outputs are equivalent to ~ 5% of the whole landslide-related production for the period 1996–2022, with a 600% increase in the number of papers after 2014 driven by the availability of Sentinel-1 and Sentinel-2 data. Analysis of the geographical location across the 66 different countries analysed shows that, within the total number of contributions, the satellite imagery was used to detect and map two main types of landslides: flows and slides. When specified in the manuscripts, the events have been triggered by rainfall (104 cases), earthquakes (32 cases), or both (17 cases). Slope instabilities in these areas were predominantly identified through manual detection (40%); but since 2020, the advent of artificial intelligence is suppressing all other techniques. Despite the undisputed progress of EO-based landslide mapping over the last 26 years, which makes it a consolidated tool for many landslide-related applications, challenges still remain for an effective and operational use of EO images for landslide detection and mapping, and we provide a perspective for future applications considering the existing and the planned SAR satellite missions. [ABSTRACT FROM AUTHOR]

In the last 10 years, also due to climate change, extreme rain events have affected the Basilicata region (southern Italy) causing landslides and floods that have damaged urban fabric, commercial activities and transport infrastructures. In many of these cases, the civil protection system, involving national (DPC) and regional (DRPC) Civil Protection Departments, was activated to manage the emergency phase in cooperation with local administrations and scientific institutions, which in this context are referred to as competence centres (CdCs). Among the latter, the Institute of Methodologies for Environmental Analysis (IMAA) of the Italian National Research Council (CNR) has been frequently involved in carrying out geophysical investigations in landslide areas, especially during the post-event phase. This paper reports the main results of the in-field geophysical surveys carried out in two areas of the Basilicata region affected by significant landslides in the last 10 years. The aim of the surveys was to provide the DRPC technicians with a useful subsoil geophysical model to improve the knowledge of the geological setting of the slope, to reconstruct the geometry of landslide body and to highlight high water content areas, in order to support the decision-making process. At the end of the paper, a discussion follows with the lessons learned from each case study along with recommendations on how to possibly improve the application of geophysical techniques in landslide investigations in order to further increase their impact. [ABSTRACT FROM AUTHOR]

Landslide early warning systems (LEWS) can be categorized into two groups: territorial and local systems. Territorial landslide early warning systems (Te-LEWS) deal with the occurrence of several landslides in wide areas: at municipal/regional/national scale. The aim of such systems is to forecast the increased probability of landslide occurrence in a given warning zone. The performance evaluation of such systems is often overlooked, and a standardized procedure is still missing. This paper describes a new Excel user-friendly tool for the application of the EDuMaP method, originally proposed by (Calvello and Piciullo 2016). A description of indicators used for the performance evaluation of different Te-LEWS is provided, and the most useful ones have been selected and implemented into the tool. The EDuMaP tool has been used for the performance evaluation of the "SMART" warning model operating in Piemonte region, Italy. The analysis highlights the warning zones with the highest performance and the ones that need threshold refinement. A comparison of the performance of the SMART model with other models operating in different Te-LEWS has also been carried out, highlighting critical issues and positive aspects. Lastly, the SMART performance has been evaluated with both the EDuMaP and a standard 2 × 2 contingency table for comparison purposes. The result highlights that the latter approach can lead to an imprecise and not detailed assessment of the warning model, because it cannot differentiate among the levels of warning and the variable number of landslides that may occur in a time interval. [ABSTRACT FROM AUTHOR]

In different areas of the world, shallow landslides represent a remarkable hazard inducing fatalities and economic damages. Then, the evaluation about potential variation in frequency of such hazard under the effect of climate changes should be a priority for defining reliable adaptation measurements. Unfortunately, current performances of climate models on sub-daily scales, relevant for heavy rainfall events triggering shallow landslides, are not reliable enough to be used directly for performing slope stability analysis. In an attempt to overcome the constrains by gap in time resolution between climate and hazard models, the paper presents an integrated suitable approach for estimating future variations in shallow landslide hazard and managing the uncertainties associated with climate and sub-daily downscaling models. The approach is tested on a small basin on Amalfi coast (southern Italy). Basing on available basin scale critical rainfall thresholds, the paper outlines how the projected changes in precipitation patterns could affect local slope stability magnitude scenarios with different relevances as effect of investigated time horizon and concentration scenario. The paper concludes with qualitative evaluations on the future effectiveness of the local operative warning system in a climate change framework. [ABSTRACT FROM AUTHOR]

Thickness and stratigraphic settings of soils covering slopes potentially control susceptibility to initiation of rainfall-induced shallow landslides due to their local effect on slope hydrological response. Notwithstanding the relevance of the assessment of hazard to shallow landsliding at a distributed scale by approaches based on a coupled modelling of slope hydrological response and slope stability, the spatial variability of soil thickness and stratigraphic settings are factors poorly considered in the literature. Under these premises, this paper advances the well-known case study of rainfall-induced shallow landslides involving ash-fall pyroclastic soils covering the peri-Vesuvian mountains (Campania, southern Italy). In such a unique geomorphological setting, the soil covering is formed by alternating loose ash-fall pyroclastic deposits and paleosols, with high contrasts in hydraulic conductivity and total thickness decreasing as the slope angle increases, thus leading to the establishment of lateral flow and an increase of pore water pressure in localised sectors of the slope where soil horizon thickness is less. In particular, we investigate the effects, on hillslope hydrological regime and slope stability, of irregular bedrock topography, spatial variability of soil thickness and vertical hydraulic heterogeneity of soil horizons, by using a coupled three-dimensional hydrological and a probabilistic infinite slope stability model. The modelling is applied on a sample mountain catchment, located on Sarno Mountains (Campania, southern Italy), and calibrated using physics-based rainfall thresholds derived from the literature. The results obtained under five simulated constant rainfall intensities (2.5, 5, 10, 20 and 40 mm h−1) show an increase of soil pressure head and major failure probability corresponding to stratigraphic and morphological discontinuities, where a soil thickness reduction occurs. The outcomes obtained from modelling match the hypothesis of the formation of lateral throughflow due to the effect of intense rainfall, which leads to the increase of soil water pressure head and water content, up to values of near-saturation, in narrow zones of the slope, such as those of downslope reduction of total soil thickness and pinching out of soil horizons. The approach proposed can be conceived as a further advance in the comprehension of slope hydrological processes at a detailed scale and their effects on slope stability under given rainfall and antecedent soil hydrological conditions, therefore in predicting the most susceptible areas to initiation of rainfall-induced shallow landslides and the related I-D rainfall thresholds. Results obtained demonstrate the occurrence of a slope hydrological response depending on the spatial variability of soil thickness and leading to focus slope instability in specific slope sectors. The approach proposed is conceived to be potentially exportable to other slope environments for which a spatial modelling of soil thickness would be possible. [ABSTRACT FROM AUTHOR]

The term debris flow is associated with a wide variety of phenomena as debris slides, debris torrents, debris floods, mudflows, mudslides, hyper-concentrated flows and lahars (in volcanic slopes). In historical times, they frequently occurred in Campania Region (Southern Italy) producing damage and casualties. In this paper, more than 200 events described as "debris flow" between 1924 and 2020 were collected. They are mainly located in the central sector of the region, which is characterized by pyroclastic deposits resting on steep carbonate and volcanic slopes and highly prone to hydrogeological hazards. Debris flow events registered in the region were classified as "gravity processes" (flow-like landslides, FL) or "fluvial processes" (flash floods, FF). This classification is fundamental for designing effective early warning systems and risk mitigation plans, since the two phenomena are triggered by different types of rainfall events and are responsible for damages of different magnitude. In this study, a large rainfall database was explored to identify the time scales and seasonality of the two classes of rainfall events, respectively triggering the two phenomena. [ABSTRACT FROM AUTHOR]

The Ancona landslide is a complex, deep-seated landslide displaying composite rotational-translational kinematisms and affecting a large urban area in the Ancona municipality on the Adriatic coast of central Italy. The landslide was reactivated with a large and destructive event on 13 December 1982 following a long period of precipitation and has remained active since. This paper focuses on the estimation of the landslide kinematics (more specifically, the horizontal and vertical components of average yearly velocity) for subsequent estimation of risk for a set of 39 buildings as presented in a companion paper. The study relies both on the processing of inclinometer and radar interferometer monitoring data through statistical procedures. Triggering factors are not investigated. Outputs from the two sets of monitoring data are compared quantitatively and qualitatively. The inherent limitations in available data are discussed. The validity of the quantitative results in the context of the risk estimation effort is discussed. [ABSTRACT FROM AUTHOR]

This paper illustrates the quantitative estimation of specific risk (i.e., the product of hazard and vulnerability) for 39 buildings located upon the Ancona landslide based on the characterization of landslide kinematics presented in a companion paper. Hazard is quantified based on intensity, intended as the damaging potential of the kinetic and/or geometric attributes of the landslide, and is expressed in terms of expected exceedance of preset cumulative displacement thresholds for a set of five reference time intervals, ranging from 1 to 100 years. The estimation of hazard relies sequentially on (1) Monte Carlo simulation of displacement series, with sampling distributions of average yearly displacement defined on the basis of the statistical processing of inclinometer and radar interferometer data; and (2) the subsequent spatialization of displacement using radial basis interpolation as described in the companion paper. The vulnerability of the set of buildings relies on a quantitative model in which vulnerability is a function of landslide intensity and the resilience of the buildings. Resilience is a function of a set of indicators including structural type, age, and foundation type and is temporally variable due to the progressive structural degradation. Hazard, vulnerability, and specific risk are estimated for the set of five aforementioned reference time intervals. The magnitude and temporal dependence of hazard, vulnerability, and specific risk are assessed critically. [ABSTRACT FROM AUTHOR]

The reconnaissance, mapping and analysis of kinematic features of slow-moving landslides evolving along medium-deep sliding surfaces in urban areas can be a difficult task due to the presence and interactions of/with anthropic structures/infrastructures and human activities that can conceal morphological signs of landslide activity. The paper presents an integrated approach to investigate the boundaries, type of movement, kinematics and interactions (in terms of damage severity distribution) with the built environment of a roto-translational slow-moving landslide affecting the historic centre of Lungro town (Calabria region, southern Italy). For this purpose, ancillary multi-source data (e.g. geological-geomorphological features and geotechnical properties of geomaterials), both conventional inclinometer monitoring and innovative non-invasive remote sensing (i.e. A-DInSAR) displacement data were jointly analyzed and interpreted to derive the A-DInSAR-geotechnical velocity (DGV) map of the landslide. This result was then cross-compared with detailed information available on the visible effects (i.e. crack pattern and width) on the exposed buildings along with possible conditioning factors to displacement evolution (i.e. remedial works, sub-services, etc.). The full integration of multi-source data available at the slope scale, by maximizing each contribution, provided a comprehensive outline of kinematic-geometric landslide features that were used to investigate the damage distribution and to detect, if any, anomalous locations of damage severity and relative possible causes. This knowledge can be used to manage landslide risk in the short term and, in particular, is propaedeutic to set up an advanced coupled geotechnical-structural model to simulate both the landslide displacements and the behavior of interacting buildings and, therefore, to implement appropriate risk mitigation strategies over medium/long period. [ABSTRACT FROM AUTHOR]

This paper shows the results of a study aimed at quantitatively estimating—in terms of direct (repair) costs, at large scale (1:5000)—the slow-moving landslide risk to a road network assumed as undamaged as well as the consequences to the same network in damaged conditions. The newly conceived methodological approaches address some challenging tasks concerning (i) the hazard analysis, which is expressed in terms of probability of occurrence of slow-moving landslides with a given intensity level that, in turn, is established based on empirical fragility curves, and (ii) the consequence analysis, which brings to the generation of time-dependent vulnerability curves. Their applicability is successfully tested in a case study in the Campania region (southern Italy) for which both very high-resolution DInSAR data and information gathered from in situ surveys on the severity of damage sustained by the selected road sections are available. Benefits associated with the use of the obtained results in informed decision-making processes are finally discussed. [ABSTRACT FROM AUTHOR]

In the last ten thousand years, the explosive activity of some volcanic centers has blanketed with pyroclastic soils the major part of Campania Region, Southern Italy. Experience shows that the sloping deposits may be mobilized by long-lasting precipitations, leading to rapid and sometimes catastrophic flow-type slope movements. This paper summarizes the present knowledge on this subject based on the results of both laboratory tests and experiments and on a review of the main data provided by field surveys. In particular, a careful examination and analysis of the available elements highlight the key role played by lithological and morphological details on failure and post-failure mechanisms, thus affecting landslide hazard. In fact, it is shown that deposition mode and grain size, slope angle, and morphology strongly affect the type of post-failure movement, which may take the features of a debris avalanche, of a debris flow, or of a flowslide and may lead (or not) to soil liquefaction, a mechanism that strongly affects both displacement rate and run-out. [ABSTRACT FROM AUTHOR]

Statistical analyses have been often used for landslide susceptibility zoning at small to medium scale when relevant base and thematic maps are available. Since the beginning of the last decade, images remotely acquired by spaceborne Synthetic Aperture Radar (SAR) and processed via Differential SAR Interferometry (DInSAR) proved extremely useful for non-invasive and non-destructive monitoring of displacements of the topographic surface. The present paper proposes an original procedure for the definition of the state of activity of slow-moving landslides via the combined use of multivariate statistical analyses and DInSAR data. The procedure is based on the following essential elements: distinction between terrain units used for computational purposes and the final zoning units; independent statistical and DInSAR analyses and activity models leading to first-level state of activity zoning maps; a consistency model between statistical and DInSAR analyses; two confidence and combination models leading, respectively, to second- or third-level state of activity zoning maps. The application in a test area including 19 municipalities in southern Italy, where slow-moving landslides are widespread and accurately mapped by using geomorphological criteria, allowed the generation of the three above-mentioned levels of zoning maps. The results were successfully crosschecked by exploiting a different DInSAR dataset and the results of previous works based on the use of slow-moving landslide-induced damage to facilities surveys. [ABSTRACT FROM AUTHOR]

The geometric and kinematic characterization of landslides affecting urban areas is a challenging goal that is routinely pursued via geological/geomorphological method and monitoring of ground displacements achieved by geotechnical and, more recently, advanced differential interferometric synthetic aperture radar (A-DInSAR) data. Although the integration of all the above-mentioned methods should be planned a priori to be more effective, datasets resulting from the independent use of these different methods are commonly available, thus making crucial the need for their standardized a posteriori integration. In this regard, the present paper aims to provide a contribution by introducing a procedure that, taking into account the specific limits of geological/geomorphological analyses and deep/surface ground displacement monitoring via geotechnical and A-DInSAR data, allows the a posteriori integration of the results by exploiting their complementarity for landslide characterization. The approach was tested in the urban area of Lungro village (Calabria region, southern Italy), which is characterized by complex geological/geomorphological settings, widespread landslides and peculiar urban fabric. In spite of the different level of information preliminarily available for each landslide as result of the independent use of the three methods, the implementation of the proposed procedure allowed a better understanding and typifying of the geometry and kinematics of 50 landslides. This provided part of the essential background for geotechnical landslide models to be used for slope stability analysis within landslide risk mitigation strategies. [ABSTRACT FROM AUTHOR]

Perceptions of risk are a key issue when seeking to develop systems, practices and policies to protect local populations. This is particularly evident when risk mitigation strategies involve non-structural measures such as relocation and warning systems which presuppose the active involvement of the communities in question. This study adopts an interdisciplinary approach to studying the perceptions, knowledge and opinions on landslide risk amongst residents in Sarno, a small town in Southern Italy which was hit by disastrous landslides on 5-6 May 1998. The paper presents the results of a survey conducted in the months of March, April and May 2013 using a purpose-designed questionnaire. The survey was conducted using face-to-face interviews with 100 residents, 60 of whom live inside the so-called 'red zone', a territory declared at high residual risk soon after the events of 1998. The questionnaire included questions relating to perceived risk exposure, trust in institutions responsible for risk management, evaluations of risk mitigation measures and the early-warning strategy. The results of the study clearly emerges, amongst other issues, that the organisms which are responsible for risk management in Sarno need to develop more effective communication strategies in order to transmit knowledge about the actions implemented to reduce landslide risk in the area. [ABSTRACT FROM AUTHOR]

This paper presents a mass flow model that includes gravity force, material stresses, drag force and topography effects solving a set of hyperbolic partial differential equations by using a so-called depth-averaged technique. The model is non-linear and general enough to tackle various problems of interest for geophysics and environmental engineering, such as the dynamic evolution of flow-like avalanches, the dam break problem (involving only water flow) and the generation of tsunami waves by landslides. The model is based on a Eulerian fluid solver, using a second-order central scheme with a minmod-like limiter; is tested against a number of typical benchmark cases, including analytical solutions and experimental laboratory data; and also compared with other numerical codes. Through this model, we study a historical tsunamigenic event occurred in 1783 in Scilla, Italy, that resulted to be catastrophic with a toll exceeding 1500 fatalities. The landslide is reconstructed by a mixture debris flow, and results are compared with the observational data and other numerical simulations. [ABSTRACT FROM AUTHOR]

Active landslides are generally characterized by variations in displacement rate in response to cumulated precipitation. Velocities that are only exceeded in a limited number of days during the year might be considered as critical events, since they might determine, or prelude to, a significant evolution of the landslide. The purpose of this paper is to present a novel approach based on the use of receiver operating characteristic (ROC) curves for assessing cumulated precipitation thresholds that can provide early warning for the occurrence of critical events such as the exceedance of rare displacement rates. The approach has been developed and tested in the Piagneto landslide, an active complex rock slide-debris slide in the Northern Apennines of Italy, for which a 5-year continuous surveying monitoring dataset is available. On the basis of the first 4 years of monitoring data (training dataset), threshold curves relating cumulative precipitation (mm) to precipitation moving windows (days) have been generated by using different benchmarks that, in literature, are used to estimate the maximum predictive performance of ROC curves. These threshold curves have been successfully validated using the last 1 year of monitoring data (validation dataset). They have then been used to simulate how they might help defining different early warning levels in due advance. The proposed methodology can be replicated in any landslide for which a monitoring dataset that includes recurrent acceleration events in response to precipitation is available. [ABSTRACT FROM AUTHOR]

In this paper, we present preliminary results of the IPL project No. 198 'Multi-scale rainfall triggering models for Early Warning of Landslides (MUSE).' In particular, we perform an assessment of the geotechnical and hydrological parameters affecting the occurrence of landslides. The aim of this study is to improve the reliability of a physically based model high resolution slope stability simulator (HIRESSS) for the forecasting of shallow landslides. The model and the soil characterization have been tested in Northern Tuscany (Italy), along the Apennine chain, an area that is historically affected by shallow landslides. In this area, the main geotechnical and hydrological parameters controlling the shear strength and permeability of soils have been determined by in situ measurements integrated by laboratory analyses. Soil properties have been statistically characterized to provide more refined input data for the slope stability model. Finally, we have tested the ability of the model to predict the occurrence of shallow landslides in response to an intense meteoric precipitation. [ABSTRACT FROM AUTHOR]

A case study of a debris slide (estimated volume of about 35,000 m) is described in this paper. This slide occurred in April 2009 in the North Western Italian Alps (Aosta valley) and damaged the SR25 road along the Valgrisenche valley. Ground investigations started with severe safety and logistic issues being posed. Given the need to open as soon as possible the road, the design of the landslide stabilization works was carried out using a 'design as you go' approach. The stabilization measures were conceived to be flexible in order to allow for changes and integration during construction, in line with the progressive refinement of the geological-geotechnical slope model being developed. Back analysis by means of the limit equilibrium method (LEM) and the finite element method (FEM) was used. Groundwater level rise following heavy rainfall and spring snow melting was found to be the main cause of the debris slide. The stabilization works were designed by using both the LEM and FEM methods. The stability conditions of the engineered slope were assessed based on the available performance monitoring data. [ABSTRACT FROM AUTHOR]

In the Campania region (southern Italy), sloping pyroclastic surfaces in partially saturated conditions are frequently affected by flow-like landslides and shallow slip. In this context, safeguarding human life is entrusted to early warning systems (EWSs), typically based on empirical precipitation intensity-duration thresholds that may suffer from missed and false alarms. Indeed, the consequences of heavy rainfall depend on the hydraulic conditions in the soil before the rainstorm. If this aspect is neglected, precipitation intensity-duration thresholds can fail. However, although the current hydraulic condition in the soil is a discriminating factor, it is rarely measured and taken into account. In this regard, the present study focuses on the assessment of the role of the groundwater conditions for the initiation of shallow landslides, and it may be the first step towards the implementation of an innovative early warning system. At this aim, a numerical approach to reproduce the current hydraulic condition in the slope is presented. This study is based on the back-analysis of two debris flows that occurred in the Campania region by means of uncoupled hydromechanical numerical modelling. The stratigraphy and hydromechanical characteristics of the soil layers are known due to surveys and investigations carried out at an experimental test site set up a few kilometres from the two debris flows that occurred. The results show that in the slopes examined, the hydraulic state in the soil before landslide triggering was correctly reproduced through an infiltration analysis starting a few months before, in which rainfall recorded on site was imposed as an entering flow at ground level. Moreover, it was shown that the water storage in the entire loose soil cover was an effective indicator of the average hydraulic state of the slope; more than local variables, such as matric suction and water content. [ABSTRACT FROM AUTHOR]

Landslide risk assessment is fundamental in identifying risk areas, where mitigation measures must be introduced. Most of the existing methods are based on susceptibility assessment strongly site-specific and require information often unavailable for damage quantification. This study proposes a simplified methodology, specific for rainfall-induced shallow landslides, that tries to overcome both these limitations. Susceptibility assessed from a physically-based model SLIP (shallow landslides instability prediction) is combined with distance derived indices representing the interference probability with elements at risk in the anthropized environment. The methodology is applied to Gioiosa Marea municipality (Sicily, south Italy), where shallow landslides are often triggered by rainfall causing relevant social and economic damage because of their interference with roads. SLIP parameters are first calibrated to predict the spatial and temporal occurrence of past surveyed phenomena. Susceptibility is then assessed in the whole municipality and validated by comparison with areas affected by slide movements according to the regional databases of historical landslides. It is shown that all the detected areas are covered by points where the SLIP safety factor ranges between 0 and 2. Risk is finally assessed after computation of distances from elements at risk, selected from the land use map. In this case, results are not well validated because of lack of details in the available regional hydrogeological plan, both in terms of extension and information. Further validation of the proposed interference indices is required, e.g., with studies of landslide propagation, which can also allow considerations on the provoked damage. [ABSTRACT FROM AUTHOR]

The redaction of landslide inventory is a fundamental task for risk management and territorial planning activities. The availability of synthetic aperture radar imagery, especially after the launch of Sentinel-1 mission, enables to systematically update landslide inventories covering wide areas in a reduced time frame and at different scales of analysis. In this work, SAR data processed from the fully automatic P-SBAS pipeline have been adopted to update the Italian national landslide database. Specifically, a matrix has been introduced by comparing past landslide state of activity obtained with Envisat data (2003–2010) and that computed with Sentinel-1 (2014–2018). The state of activity was defined by obtaining the projected velocity along the slope dip direction. The analysis involved about 56,000 landslides which showed at least one Sentinel-1 measurement point, of which 74% were classified as dormant, having annual average velocity < 7 mm/year (considering a value of two times the standard deviation) and 26% as active (mean velocity > 7 mm/year). Furthermore, a landslide reliability matrix was introduced on the landslide inventory updated with S1 data, using the measurement point (MP) density within each landslide and the standard deviation of the mean Vslope value of each landslide. In this case, the analysis revealed that more than 80% of landslides has values of reliability from average to very high. Finally, the 2D horizontal and vertical components were computed to characterize magnitude and direction of every type of landslides included in this work, showing that spreadings, deep-seated gravitation slope deformations, and slow flows showed a main horizontal movement, while complex and translational/rotational slides had more heterogeneity in terms of deformation direction. Hence, the work demonstrated that the application of fast and automatically nationwide Sentinel-1 MTInSAR (multi-temporal interferometry SAR) may provide a fundamental aid for landslide inventory update. [ABSTRACT FROM AUTHOR]

Mountain landslides have occurred in countries such as Italy regularly throughout recorded history, often resulting in fatalities. Because of this, policies that would reduce landslide fatality risk need to be carefully formulated. As a first step in the exploration of preferences for these risk-reducing policies, we examine public perceptions of risk for landslides and related events. Subjective probabilities for others who might die in a landslide, as well as one's own subjective probability of death, are elicited for a sample of visitors and residents of a region in Italy prone to landslides. We present one portion of the sample with scientific information and allow them to update their risk estimate if they so choose, allowing the role of such information to be tested. The subjective probabilities are then used to construct risk-related attributes in a pivot-design version of a conventional stated choice model. Larger risk changes as departures from the baseline risk are found to be significant in explaining choices. [ABSTRACT FROM AUTHOR]

Earthquake-induced landslides represent a significant seismic hazard since they can largely increase the damage and losses due to a seismic event, an issue that must be considered in land-use and risk management purposes. However, it can be difficult to consider all the natural variables, such as geotechnical parameters, that predispose the occurrence of landslides under a specific dynamic triggering, especially for wide areas. Among these, the most important and critical ones to quantify at large scale, are represented by the hydraulic conditions in both unsaturated and saturated media. For this reason, in this work we present a newly developed GIS tool that was specifically designed for the automation of a pseudo-dynamic Newmark model to estimate the co-seismic displacements over wide areas. The tool takes into account reactivations of landslides under different rupture mechanisms and parametrically weighs the role of variable initial soil moisture or pressure head conditions, as well as the influence of ground shaking resulting from local amplification effects. The proposed tool was tested in the Molise region (central-southern Italy), where almost 23,000 existing landslides have been selected for evaluating potential reactivations. The obtained results point out the importance of local conditions on the displacement amount, even by considering a unique return period of the seismic action. Strengths and weaknesses of the proposed model have been also highlighted in view of potential future applications in the framework of co-seismic landslide risk assessment and mitigation measures. [ABSTRACT FROM AUTHOR]

Triggering mechanisms and causative processes of deep-seated gravitational slope deformations (DSGSD) in Alpine and high mountain areas include, among others, post-glacial de-buttressing, earthquake-induced ground shaking, or co-seismic surface faulting. Distinguishing between climatic or tectonically driven factors is challenging since faults and fracture systems can play both an active and/or passive role in the process initiation. We applied an integrated approach, including morpho-structural analysis, geologic field survey, a paleoseismological approach applied to trenching, radiocarbon dating and detailed sedimentological analysis, to a DSGSD located in the Cavargna Valley (N Italy), an area that was never occupied by extensive ice tongues in the Upper Pleistocene and Holocene. We were able to document at least two phases of movement from the Middle Holocene onwards and related triggering factors. Thanks to the comparison with dated lacustrine turbidites in the Alpine Lakes, we argue a seismic triggering for the landslide onset, with a possible source located in southern Switzerland, close to the Insubric Line. The later evolution of the landslide was instead driven by climatic predisposing conditions (humid and cold), instead, corresponding to a phase of enhanced slope instability. [ABSTRACT FROM AUTHOR]

Landslides represent a serious worldwide hazard, especially in Italy, where exposure to hydrogeological risk is very high; for this reason, a landslide quantitative risk assessment (QRA) is crucial for risk management and for planning mitigation measures. In this study, we present and describe a novel methodological approach of QRA for slow-moving landslides, aiming at national replicability. This procedure has been applied at the basin scale in the Arno River basin (9100 km2, Central Italy), where most landslides are slow-moving. QRA is based on the application of the equation risk = hazard (H) × vulnerability (V) × exposure (E) and on the use of open data with uniform characteristics at the national scale. The study area was divided into a grid with a 1 km2 cell size, and for each cell, the parameters necessary for the risk assessment were calculated. The obtained results show that the total risk of the study area amounts to approximately 7 billion €. The proposed methodology presents several novelties in the risk assessment for the regional/national scale of the analysis, mainly concerning the identification of the datasets and the development of new methodologies that could be applicable over such large areas. The present work demonstrates the feasibility of the methodology and discusses the obtained results. [ABSTRACT FROM AUTHOR]

This research proposes a conceptual approach for analysis and numerical modelling of the hydromechanical behaviour of large landslides, applied to one of the source areas of the Corvara earthflow (Dolomites, Italy). The approach consists of two steps: forward calculation and inverse analysis. For the forward calculations, the geological model of the slope considering several shear zones delimitating landslide units was developed, based on a detailed dataset of field investigation and monitoring data. A viscoplastic constitutive model was used to describe the time-dependent material behaviour, i.e. the creep, of the shear zones. The transient distribution of pore water pressure in the slope was considered by means of an additional purely hydrogeological model. These results were used as averaged hydraulic boundary conditions in the calculation of stress and deformation fields with the continuum finite element method (FEM). The numerical model was then calibrated against ground surface displacement rates measured by D-GPS, by iteratively varying the material parameters of the shear zones. For this task, an inverse analysis concept was applied, based on statistical analyses and an evolutionary optimisation algorithm. The inverse modelling strategy was further applied to gather statistical information on model behaviour, on the sensitivity of model parameters and on the quality of the obtained calibration. Results show that the calibrated model was able to appropriately simulate the displacement field of the earthflow and allow the requirements, difficulties and problems, as well as the advantages and benefits of the proposed numerical modelling concept to be highlighted. [ABSTRACT FROM AUTHOR]

Rockslide-debris flow may cause catastrophic damages because of its high speed and long run-out distance. The influences of slope gradient and gully channel on the entrainment, deposition, and run-out behavior of this type of landslide were not sufficiently investigated by previous studies. To achieve a better understanding toward this type of landslide, a recent rockslide-debris flow that occurred in the Northern Apennines of Italy is studied through field investigation and numerical simulation. The run-out process of this landslide is simulated by an improved depth-averaged model, paying special attention to analyzing the influence of slope gradient and gully channel. The simulation results are compared with the detailed field data of entrainment and deposition distributions. It shows that the depth-averaged model can reasonably simulate the entrainment and deposition characteristic of this landslide by adopting different basal friction strengths for the rockslide region and debris flow region. Entrainment occurs in both high and low slope gradient zones. However, entrainment can only be observed in the high slope gradient zones, while in the low gradient zones, the post-failure topography shows accumulation and deposition. The simulation results also demonstrate that the presence of a gully channel is a key factor in determining landslide mobility and run-out distance. In comparison to a landslide with similar size and geological settings but without a gully channel, the run-out distance is much less, and the landslide does not develop into a flow. [ABSTRACT FROM AUTHOR]

Nowadays, several systems to set up landslide inventories exist although they rarely rely on automated or real-time updates. Mass media can provide reliable info about natural hazard events with a relatively high temporal and spatial resolution. The news publication about a natural disaster inside newspaper or crowdsourcing platforms allows a faster observation, survey, and classification of these phenomena. Several techniques have been developed for data mining inside social media for many natural events, but they have been rarely applied to the automatic extraction of "landslide events". This source of information allows continuous feedback from real world, and news concerning landslide events can be rapidly collected. In this work, the newspaper articles about landslides in Italy are automatically collected by an existing data mining algorithm, based on a semantic engine. The news has been analysed to assess their distribution over the territory and to verify the possibility of using them for hazard mapping purpose. In 10 years, from 2010 to 2019, the algorithm identified and geolocated 184322 articles referring to 32525 generical events ("news"). At first, the collected data underwent to a manual verification, followed by a classification based on news relevance, localization accuracy and time of publication. Then, these data have been used to identify the areas and the periods most affected by landslide phenomena. The analyses show that almost 42% of Italian municipalities have been affected by landslide. According to the results, the use of data mining is helpful for the creation of landslide databases where the day and the approximative location (municipality) of the possible landslide triggers are known. This database, in turn, can be used for scientific purposes, as the definition of the meteorological condition associated with landslide initiation, the validation of risk maps. It can also be used for a proper land use or risk mitigation planning, since the most landslide-prone municipalities can be defined. [ABSTRACT FROM AUTHOR]

This study presents the employment of automatic deep drainage systems to stabilize the Mendatica landslide, one of the largest relict landslides of western Liguria (north-western Italy). Despite the relict state of activity of the main landslide body, a residual kinematic still affects the sector of accumulation zone over which the small village of Mendatica is located and where sharp reactivations of the movements were frequently recorded after severe rainstorms. The aim of this research is to investigate both the efficiency and effectiveness of Electropneumatic Drains® during an extreme rainstorm based on geotechnical monitoring data. On the one hand, the continuous groundwater level measurements allowed to examine the performance of two alignments of wells equipped with electropneumatic pumps during a severe 5-day rainfall event occurred in November 2016, when cumulative rainfalls equalled approximately 800 mm at Mendatica. On the other hand, the subsurface displacements measured from inclinometers before and after the activation of the two draining diaphragms enabled the evaluation of the influence of the automatic deep drainage on the landslide kinematic. The analysis of the hydraulic response of the two drainage lines reveals that, despite the severity of the recorded rainfall values, the pumping wells efficiently worked during the rainstorm since they successfully controlled the increase of hydraulic heads. Furthermore, the outcomes of this study show that, under severe rain conditions, the presence of the Electropneumatic Drains® has mitigated the magnitude of the landslide displacements preventing the development of rapid accelerations of the slope movements. [ABSTRACT FROM AUTHOR]

Landslides hazard assessment requires the combination of spatial and temporal probabilities. In this work, we combine spatial modelling and regionalization of debris rainfall thresholds for assessing both these probabilities and map debris flows initiation hazard over 15 × 103 km2 of the Emilia-Romagna Apennines (Italy). In this area, debris flows are spatially and temporally less frequent than earth slides and earth flows. However, more than a hundred debris flows occurred in October 2014 and September 2015 during two large rainstorms clusters in Parma in Piacenza provinces; some tens of debris flows are reported to have occurred in the past and few others have occurred recently. Since landslides inventory maps used for land use planning only consider some large debris flows accumulation fans, and substantially no information is given on the slopes along which these phenomena might occur, this study aims to fill this gap by creating a hazard map using the evidences collected after the recent abovementioned multi-occurrence events. Different spatial statistical models (Frequency Ratio [FR], Weight of Evidence [WOE] and Logistic Regression [LR]), set up with various combinations of geo-environmental causal factors, have been trained using 60% of debris flow initiation points mapped after the 2014 and 2015 events. The predictive performances of the models have been compared by success rate curves using the remaining 40% of initiation points of the 2014 and 2015 events. The model with the best predictive capability (area under the curve > 0.96) has been further validated using the spatial distribution of other debris flows occurred in the period 1972–2016, and its outputs have been classified into spatial probability classes. Furthermore, the annual exceedance probability of recently published debris flows 3 h cumulated rainfall triggering thresholds has been calculated for in 185 rain gauges and regionalized by spatial interpolation. Finally, spatial and temporal probability maps ranked in a 0–1 range have been combined into a regional debris flows initiation hazard map that, on the basis of the return periods, is associated to different yearly probability values. The resulting hazard map classifies 0.87% of the area as high hazard, 2.83% as medium hazard, 0.5% as low hazard and the remaining 95.81% as null hazard. The spatial distribution of hazardous zones is quantitatively and qualitatively consistent with the spatial distribution of past debris flows. Furthermore, it is coherent with geomorphological common sense and it has proven sufficiently accurate in discriminating as hazardous the debris flows initiation zones of phenomena occurred after it was produced. On such a basis, despite its limitations, we consider the debris flows hazard map produced sufficiently reliable to integrate existing inventory maps in land-use regulation and emergency planning. [ABSTRACT FROM AUTHOR]

This study outlines the relationship between antecedent precipitations and activation of the translational rock-block slides (TRBSs). This type of landslide has the peculiarity to involve wide sectors of the sedimentary bedrock, and it is emblematic in the Langhe area, in the southern hilly part of Piemonte in the Tertiary Piemonte Basin. The Langhe hills are particularly renowned for the cultivation of valuable vineyards, and therefore, constitute a place of important economic and tourist interest. Furthermore, the high density of structures and infrastructures in this area exposes a number of elements to the activity of these large landslides. In order to minimize human and economic losses, it is particularly important to establish a warning system capable of providing announcement of activation of TRBSs with sufficient advance. In this direction, the Environmental Protection Agency of Piemonte (ARPA Piemonte) developed a precipitation-threshold-based model. The model is set up on an extensive collection of historical data about the landslides movements (since 1917) and the related complete meteorological dataset. The regional weather gauge network and the forecasted precipitation amount, including snow melt's contribution, provide input data to the model. Output model can be tested by observations derived by the regional landslides monitoring network consisting of inclinometers and groundwater gauges managed by ARPA Piemonte. [ABSTRACT FROM AUTHOR]

Rock avalanches are complex phenomena that occur with a low frequency but which have a high destructive potential. As a consequence, the people who are responsible for the management of a territory are more and more interested in predicting the possible evolutions of well-known potential events. Tackling the above problems from a quantitative point of view, the RASH3D code, based on continuum mechanics concepts, has been here used to predict the evolution of a potential rock avalanche in the Western Italian Alps. A calibration-based approach, in which rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of past events similar to the landslide under investigation, is proposed to set rheological parameter values to be used for prediction purposes. The back-analysis of a 2⋅10 m rock avalanche located in the Divedro Valley, close to the area of the potential event, has then been analysed using both a frictional and a Voellmy rheology. The characteristics of the slope and the dynamics of the event have made the frictional rheology more suitable to come to the correct simulation of the historical case. The back-analysis results have contributed not only in the selection of the rheological parameter values but also in the choice of the type of rheological law to use in the carried out forward-analyses. [ABSTRACT FROM AUTHOR]

Slope stability is influenced by a number of factors that modify the resisting/acting force ratio control landslide initiation and movement velocity. Among these, artificial vibrations have been identified as an important degrading factor for soil strength, but it is not fully clear if they can trigger or modulate movements of clay landslides. To contribute to a better understanding of the potential effect of vibrations on landslide movement, also in terms of boundary conditions, we analyzed monitoring data acquired at the toe of the Pietrafitta landslide in southern Italy. This landslide adjoins the SS87 national road that suffered periodic closure due to landslide activity and in April 2016 operates daytime only for risk mitigation purpose. This condition promoted a better identification of a potential cause-effect relation between traffic vibration and landslide movement. Results from data analysis and landslide modeling suggest that in condition of incipient movement, artificial vibrations, also of limited amplitude, are able to directly initiate clay landslide movement that due to the viscous nature of the involved material exhibit a specific displacement pattern that is not consistent with a sliding block model. [ABSTRACT FROM AUTHOR]

In November 2016, an extreme rainfall event affected the Ligurian Alps (NW Italy). Consequently, several landslides and debris flows occurred in the upper Tanarello stream basin. In particular, the village of Monesi di Mendatica was severely damaged by two landslide phenomena: the activation of a rotational landslide, which caused the total collapse of two buildings and part of the main road, and the reactivation of a deep-seated planar massive and a complex landslide, which widely fractured most of the buildings in the village. The latter phenomenon was mostly unknown and had never been monitored prior to the 2016 event. Due to the extensive damage, the village of Monesi was completely evacuated, and the road connecting a ski resort area in the upper part of the valley was closed. Furthermore, a potentially dangerous situation related to the eventual progressive evolution of this landslide that could cause a temporary occlusion of the Tanarello stream still remains. For this reason, we defined the landslide behaviour, triggering conditions and chronological evolution leading to the 2016 event using a multidisciplinary approach. This approach consisted of field surveys, satellite DInSAR time series analyses, digital image correlation techniques, rainfall records analyses, postevent monitoring campaigns and subsurface investigation data analyses, and numerical modelling. This multidisciplinary approach enhanced our understanding of this landslide, which is fundamental to better comprehend its behaviour and possible evolution. [ABSTRACT FROM AUTHOR]

The morphological changes of unstable areas can be identified using different methodologies that allow repeated surveys over time. The integration between the data obtained from different remote sensing and ground-based techniques, characterized by different coverage, resolution, and precision, allows to describe the kinematic motion of landslides with high accuracy and details. The aim of this work is to monitor the displacements of the Patigno landslide, a deep-seated gravitational slope deformation located in the Northern Apennines (Zeri, Massa Carrara, Italy), using archival aerial photogrammetry (1975–2010), continuous GNSS observations (2004–2018), and multi-temporal InSAR data (2015–2019). The results obtained adopting the different techniques were cross-validated and integrated in order to better explain the kinematics of the landslides: the GNSS data analysis shows horizontal movements of about 43 mm/yr in the S-E direction and vertical deformations of 6.5 mm/yr, in agreement with the average displacement rates obtained from photogrammetry and InSAR processing. The analysis of multi-temporal aerial photogrammetric images allowed us to observe three sectors of the landslide body characterized by different velocities rates and planimetric directions, in agreement with the LOS InSAR displacement field. Furthermore, the correlation between the rainfall distribution and the GNSS time series shows an acceleration of the sliding movements after about 3–4 months of a strong rainfall period. This integrated approach allowed us to overcome the limitations of each technique and to provide a 44-year long monitoring of the Patigno landslide. We also show that a synergic use of ground-based and remote sensing methodologies can provide useful information for the planning of more effective landslide risk mitigation strategies. [ABSTRACT FROM AUTHOR]

Slopes covered with unsaturated shallow pyroclastic deposits, lying upon fractured limestone bedrock, are widespread in the mountains around Naples (southern Italy). Rainfall infiltration, reducing soil suction, eventually triggers shallow landslides. While drastic reduction of suction is unanimously recognized as the triggering mechanism, there is still debate about the hydrological processes controlling slope drainage and causing the establishment of landslide predisposing conditions. Field observations at the slope of Cervinara suggested that temporary storage of water in a perched aquifer, in the upper part of the fractured bedrock, may affect the leakage through the soil-bedrock interface. Hence, a physically based model, coupling flows in the unsaturated soil cover and in the perched aquifer, has been applied to three large rainfall events which occurred in December 1999 (when a landslide was triggered), January 2009, and November 2012. The results highlight that the different responses of soil and aquifer to precipitations, related not only to rainfall event characteristics (i.e., duration and mean intensity) but also to the initial conditions of the slope, determined by antecedent precipitations, can play a prominent role in the triggering of landslides. In fact, further simulations with synthetic rainfall events and different initial conditions provide a possible interpretation of the triggering of the landslide of December 1999, indicating that a soil profile with dry conditions at the base and a low level in the perched aquifer, typical of late autumn, can impede the drainage of infiltrating water through the soil-bedrock interface, thus favoring the build-up of pore pressure within the soil cover. [ABSTRACT FROM AUTHOR]

Landslide dams are a common hazard which threaten downstream human settlement or infrastructure, as their collapse may result in a flash flood. The danger is compounded by the amount of water accumulated; therefore, estimation of the time to failure becomes crucial for assessing engineering risk mitigation procedures. Dam dimension indices, descriptive multivariate analysis and logistic regression have been used to produce a static image of the dam conditions, estimating the probability of failure, but they provide no information of when a failure might occur. We propose a Bayesian model to predict the time to failure of landslide dams, based on imputing missing dam and reservoir measurements via an analysis of their covariate structure. The resulting data is then used in a Bayesian survival model which links the (censored) failure time to dam and reservoir variables. A case study on heterogeneous Italian events is presented, on which our model is tested. Results show that it is possible to produce a probabilistic model of time to failure. The length and height of dams, and the catchment area behind them, are identified as the most important covariates controlling the time to failure. The addition of area-based intercepts confirms the robustness of the methodology. Examples of potential results (forecasting) and possible generalizations of the model are presented. [ABSTRACT FROM AUTHOR]

Landslides often happen where they have already occurred in the past. The potential of landslides to reduce or enhance conditions for further landsliding has long been recognized and has often been reported, but the mechanisms and spatial and temporal scales of these processes have previously received little specific attention. Despite a preponderance of qualitative and anecdotal evidence, analysis has been limited. As a result, there is little consensus on the meaning of terms such as landslide repetition, recurrence, and reactivation. This source of confusion is evident when such terms are also used to describe systems where landsliding is prevalent but unrelated to landslide history. Recent findings, partly based on a rare multi-temporal landslide inventory for an area in Italy, show that the impacts of earlier landslides affect a substantial fraction of landslides, that landslides following earlier landslides differ from those that do not, and that accounting for the effect of previous landslides can improve susceptibility assessments. These findings await confirmation in other landslide-prone landscapes but show that consecutive landsliding deserves more attention, which requires consistent terminology. No such terminology is presently available, and we therefore propose it in this manuscript. We use the term "uncorrelated landsliding" to describe situations where landslides are common, but where a correlation with environmental variables such as terrain steepness is not implied. We propose "correlated landsliding" to describe situations where landslides are common and correlations with environmental variables exist, and "path-dependent landsliding" to describe situations where causal relations exist between consecutive landslides, for instance, when landslides occur at the scarp of previous landslides. These are situations where past landslides impact future landslides. Within the path-dependent category, we distinguish three subcategories based on the spatial distance between earlier and later landslides: "reactivation" or "continuation" if essentially the same material recommences or continues to slide, "local activation" if an earlier slide causes changes in a local hillslope that cause a later slide, and "remote activation" if an earlier slide causes changes elsewhere in the landscape that cause a later landslide. We use this proposed set of terms to outline some prominent knowledge gaps and potential research questions. [ABSTRACT FROM AUTHOR]

A complete landslide dam hazard management incorporates two assessment phases: the damming probability and the breach hazard. A prompt evaluation of the dam stability is crucial during the emergency to mitigate its consequences, but a reliable risk assessment can be realized only after the event has occurred, when the available time is very short. Therefore, it is necessary to develop tools able to help in mapping the spatial probability of damming over large areas for land-use planning, in order to better constrain consequence analysis and risk scenarios for setting up mitigation measures. In this work, a semi-automated GIS-based mapping methodology, based on a statistical correlation of morphometric parameters described by a morphological index, is proposed to spatially assess the likelihood of a river obstruction by landslide damming through two main mechanisms: the reactivation of existing landslides and the formation of new landslides. The two mapping methods (damming predisposition and damming probability) were used on a test area, the Arno River basin in Italy. The Eastern part of the basin resulted as the most susceptible to damming events in the whole basin. These are the highest mountain ridges in the basin (about 1600 m a.s.l.), characterized by calcareous, arenaceous, and marl lithology. The results are confirmed by the high concentration of the known historical landslide dams in the area according to existing inventories. [ABSTRACT FROM AUTHOR]

Hundreds of landslides were triggered by the mainshocks (up to Mw 6.5) that occurred in 2016 in Central Italy during the seismic sequence that originated in the Apennine and ended in January 2017. These landslides were studied via field-based investigation and remote sensing techniques during the weeks immediately after the mainshocks occurred. EarthQuake-triggered Landslides (EQtLs) mostly consisted of rockfalls and rockslides. The spatial distribution of the examined EQtLs with respect to the epicentres of the main shocks resulted in very good agreement with the available empirical curves of maximum distance vs. magnitude. Based on the collected dataset, approximately 70% of the landslides impacted transportation routes (national, provincial and secondary roads linking towns and mountain villages) since they principally detached from road cuts. The landslides caused traffic interruption, and some delayed rescue vehicles from reaching the zones most damaged by earthquakes; moreover, some landslides caused the temporary isolation of several localities in the epicentre area. Even if it seems obvious that road cuts favour slope failure under shaking conditions, the dataset reported here is the first one for Italy where such an effect is quantified. Moreover, a statistical analysis was conducted to explore the relationships between the spatial distribution of EQtLs and some selected causative factors, including both natural (i.e., earthquake and terrain) and anthropogenic factors (i.e., presence of roads and trackways). Among the considered combinations of causative factors (both natural and anthropogenic), this study demonstrates that the occurrence of the uphill road cuts at the bottom of deep incised V-shaped valleys strongly influenced the spatial clustering of the EQtL triggered in 2016 in Central Italy. [ABSTRACT FROM AUTHOR]

Understanding the mechanism of a landslide and its evolution is of fundamental importance in the risk management process. This work introduces an articulated approach to the problem, applying it to a specific case in the south of Italy where a gravitational movement insists on a section of an important highway. In recent years, the site has been investigated from a geomorphological and a lithological point of view, and a comprehensive geomechanical characterization has been carried out by means of on-site and laboratory tests. The area has been instrumented with a monitoring system composed of automatic inclinometers, piezometers, a rainfall station, and time domain reflectometry (TDR) cables. These sensors have monitored the deformation processes and their correlation with groundwater fluctuation. A 2D finite differences model (FDM) of the slope has been created, calibrated, and validated through back analysis, carried out using the monitoring data available. A secondary creep phenomenon, barely influenced by the water level rise due to occasional rainfall, has been identified and modeled using the Burgers viscoelastic constitutive model. Variations in the piezometric level were introduced and their effect accounted for the numerical model refinement. Once the improvements had been completed together with the reproduction of past events, a predictive analysis was carried out in order to forecast the most probable slope behavior relative to the incoming year. At the end of this phase, the infrastructure supervisor should have information about possible deformations to be compared with the near real-time monitoring outcomes and design assumptions. This procedure allows real-time monitoring of the compatibility of slope deformations with highway safety. [ABSTRACT FROM AUTHOR]

Despite abundant information on landslides, and on landslide hazard and risk, in Italy, little is known on the direct impact of event landslides on road networks and on the related economic costs. We investigated the physical and economic damage caused by two rainfall-induced landslide events in Central and Southern Italy, to obtain road restoration cost statistics. Using a GIS-based method, we exploited road maps and landslide event inventory maps to compute different metrics that quantify the impact of the landslide events on the natural landscape and on the road networks, by road type. The maps were used with cost data obtained from multiple sources, including local authorities, and specific legislation, to evaluate statistically the unit cost per metre of damaged road and the unit cost per square metre of damaging landslide, separately for main and secondary roads. The obtained unit costs showed large variations which we attribute to the different road types in the two study areas and to the different abundance of landslides. Our work confirms the long-standing conundrum of obtaining accurate landslide damage data and outlines the need for reliable, standardized methods to evaluate landslide damage and associated restoration costs that regional and local administrations can use rapidly in the aftermath of a landslide event. We conclude recommending that common standardized procedures to collect landslide cost data following each landslide event are established, in Italy and elsewhere. This will allow for more accurate and reliable evaluations of the economic costs of landslide events. [ABSTRACT FROM AUTHOR]

A process chain for the definition and the performance assessment of an operational regional warning model for rainfall-induced landslides, based on rainfall thresholds, is proposed and tested in a landslide-prone area in the Campania region, southern Italy. A database of 96 shallow landslides triggered by rainfall in the period 2003-2010 and rainfall data gathered from 58 rain gauges are used. First, a set of rainfall threshold equations are defined applying a well-known frequentist method to all the reconstructed rainfall conditions responsible for the documented landslides in the area of analysis. Several thresholds at different exceedance probabilities (percentiles) are evaluated, and nine different percentile combinations are selected for the activation of three warning levels. Subsequently, for each combination, the issuing of warning levels is computed by comparing, over time, the measured rainfall with the pre-defined warning level thresholds. Finally, the optimal percentile combination to be employed in the regional early warning system, i.e. the one providing the best model performance in terms of success and error indicators, is selected employing the 'event, duration matrix, performance' (EDuMaP) method. [ABSTRACT FROM AUTHOR]

Review of the literature on the reconstruction of the rainfall responsible for slope failures reveals that criteria for the identification of rainfall events are lacking or somewhat subjective. To overcome this problem, we developed an algorithm for the objective and reproducible reconstruction of rainfall events and of rainfall conditions responsible for landslides. The algorithm consists of three distinct modules for (i) the reconstruction of distinct rainfall events, in terms of duration ( D, in h) and cumulated event rainfall ( E, in mm), (ii) the identification of multiple ED rainfall conditions responsible for the documented landslides, and (iii) the definition of critical rainfall thresholds for possible landslide occurrences. The algorithm uses pre-defined parameters to account for different seasonal and climatic settings. We applied the algorithm in Sicily, southern Italy, using rainfall measurements obtained from a network of 169 rain gauges, and information on 229 rainfall-induced landslides occurred between July 2002 and December 2012. The algorithm identified 29,270 rainfall events and reconstructed 472 ED rainfall conditions as possible triggers of the observed landslides. The algorithm exploited the multiple rainfall conditions to define objective and reproducible empirical rainfall thresholds for the possible initiation of landslide in Sicily. The calculated thresholds may be implemented in an operational early warning system for shallow landslide forecasting. [ABSTRACT FROM AUTHOR]

We provide a step-by-step analysis and discussion of the 'PSI-based matrix approach', a methodology employing ground deformation velocities derived through Persistent Scatterer Interferometry (PSI) for the assessment of the state of activity and intensity of extremely to very slow landslides. Two matrices based on PSI data are designed respectively for landslides already mapped in preexisting inventories and for newly identified phenomena. Conversely, a unique intensity scale is proposed indiscriminately for both. Major influencing factors of the approach are brought to light by the application in the 14 km area of Verbicaro, in Northern Calabria (Italy). These include lack of PSI data within the landslide boundaries, temporal coverage of the available estimates, and need of field checks as well as the operative procedures to set the activity and intensity thresholds. For the area of Verbicaro, we exploit 1992-2011 PSI data from ERS1/2 and RADARSAT1/2 satellites, projecting them along the maximum slope directions. An activity threshold of ±5 mm/year is determined by applying the average projection factor of local slopes to the PSI data precision. The intensity threshold between extremely and very slow phenomena (16 mm/year) is reduced by ~20 % to account for temporal and spatial averages being applied to attribute representative velocities to each landslide. The methodology allows assessing the state of activity and the intensity for 13 of the 24 landslides premapped in the 2007 inventory and for two newly identified phenomena. Current limitations due to characteristics and spatial coverage of PSI data are critically tackled within the discussion, jointly with respective implications. [ABSTRACT FROM AUTHOR]

The active Ruinon rockslide is located on the left bank of the Frodolfo River valley (Valfurva, Italian Alps) and is developed on the Confinale deep-seated gravitational slope deformation. Ruinon landslide is a major hazard for valley inhabitants in that rapid movement might dam the stream and create a debris flow. The landslide is strongly controlled by preexisting structural features and is believed to have been triggered by postglacial debuttressing. Ground-based radar interferometry has been used to map surface deformation over time of the entire unstable zone of Ruinon landslide with high spatial resolution and at a very high temporal acquisition rate (about five images per hour). The activity of the landslide shows strong periodicity, with summer and autumn accelerations and winter deceleration. From a correlation between the landslide acceleration and a class of rainfall event, we deduce the specific rainfall conditions that accelerate the instability of the landslide area. The study results suggest an improved tool for early warning of events of potentially catastrophic landslide instability. [ABSTRACT FROM AUTHOR]

Rainfall thresholds represent the main tool for the Italian Civil Protection System for early warning of the threat of landslides. However, it is well-known that soil moisture conditions at the onset of a storm event also play a critical role in triggering slope failures, especially in the case of shallow landslides. This study attempts to define soil moisture (estimated by using a soil water balance model) and rainfall thresholds that can be employed for hydrogeological risk prevention by the Civil Protection Decentrate Functional Centre (CFD) located in the Umbria Region (central Italy). Two different analyses were carried out by determining rainfall and soil moisture conditions prior to widespread landslide events that occurred in the Umbria Region and that are reported in the AVI (Italian Vulnerable Areas) inventory for the period 1991-2001. Specifically, a 'local' analysis that considered the major landslide events of the AVI inventory and an 'areal' analysis subdividing the Umbria Region in ten sub-areas were carried out. Comparison with rainfall thresholds used by the Umbria Region CFD was also carried out to evaluate the reliability of the current procedures employed for landslide warning. The main result of the analysis is the quantification of the decreasing linear trend between the maximum cumulated rainfall values over 24, 36 and 48 h and the soil moisture conditions prior to landslide events. This trend provides a guideline to dynamically adjust the operational rainfall thresholds used for warning. Moreover, the areal analysis, which was aimed to test the operational use of the combined soil moisture-rainfall thresholds showed, particularly for low values of rainfall, the key role of soil moisture conditions for the triggering of landslides. On the basis of these results, the Umbria Region CFD is implementing a procedure aimed to the near real-time estimation of soil moisture conditions based on the soil water balance model developed ad hoc for the region. In fact, it was evident that a better assessment of the initial soil moisture conditions would support and improve the hydrogeological risk assessment. [ABSTRACT FROM AUTHOR]

On December 15, 2008, a rock slide of approximately 4,000 m occurred near San Severino di Centola (Cilento, Province of Salerno). The landslide occurred along very steep bedding planes intersected by tectonic joints affecting a rocky cliff. The landslide debris, formed by several boulders, came to a halt along the gentler slope below. Many blocks reached the slope base including the national road n° 562 and injuring a motorist on the road. Furthermore, the road suffered heavy damages causing a halt in traffic for many weeks. Several signs of the impacts were detected along the slope and on the road; also, the volumes of some boulders were measured. The area affected by block trajectories stretch down slope about 4,900 m. By means of 2D and 3D trajectory codes using the 'lumped-mass' method, it was possible to estimate more suitable impact energy restitution and rolling friction coefficients, to reconstruct rock fall trajectories, and to calculate total kinetic energies. Extending to the surrounding slope (surface about 2 ha) these data, a hazard scenario was carried out, displaying the pattern of iso-energy distribution curves calculated along 11 critical profiles, and zones exposed to 70% and 30% of frequencies of block transits and endpoints. Successively, with reference to the Swiss Federal Guidelines, another scenario was prepared on the basis of rock fall intensity values and the return period of the 2008 landslide event. In this way, it was possible to define areas of high, moderate and low hazard. The degrees of hazard are assigned according to their consequences for construction activity and outline zones where additional protection is required. The construction of a retaining embankment was believed suitable for local risk mitigation. [ABSTRACT FROM AUTHOR]

The World Landslide Forum (WLF) is a triennial mainstream conference aimed at gathering scientists, stakeholders, policy makers and industry members dealing with the management of landslide risk. The First World Landslide Forum, organised by the International Consortium of Landslides, UNESCO, WMO, Food and Agriculture Organization, UNISDR, UNU, UNEP, IBRD, UNDP, ICSU, WFEO, KU and the Japan Landslide Society, was held in 2008 at the United Nations University, Tokyo. The 1st WLF adopted the 2008 Tokyo Declaration 'Strengthening the International Programme on Landslides with UNISDR'. The Second World Landslide Forum has the objective to further develop the outcomes of the First Forum in Tokyo 2008 by providing a global cross-cutting information and cooperation platform for all types of organisations representing academia, United Nations organisations, governments, private enterprises and individuals that contribute to landslide research, practice, education and decision making and are willing to strengthen landslide and other related Earth system risk reduction strategies. The emphasis of this forum will be 'Putting Science into Practice' with special attention given to actual implementation of technology and research in everyday applications and procedures with the direct involvement of researchers, engineers, private enterprises, stakeholders as well as policy and decision makers. The abstract submission and pre-registration of participants was quite successful with 649 received abstracts and more than 800 participants at May 2011. The full organisation of the event is now in progress taking into consideration the new figure and interest in scientific community and stakeholders. [ABSTRACT FROM AUTHOR]