Search

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]

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]

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]

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]

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]

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]

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]

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]

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]