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Landslides cause fatalities, widespread damages and economic losses. Quite frequently, they are triggered by rainfall. Many studies have investigated the relationships between rainfall characteristics and landslide events. This paper reviews the two main approaches, physical and hydrological, for modelling such relationships. In the physical approach, the influence of rainfall on slope stability is commonly analysed in terms of groundwater infiltration, pore pressure changes and balance between shear stresses and resistances, therefore a considerable amount of hydrogeological, morphological and geotechnical data is required. In the hydrological approach, a statistical-probabilistic study of rainfall series and dates of occurrence of slope movements is instead carried out. Both types of methods are briefly presented, with examples from real applications to study cases in Southern Italy. In particular, the recent reactivations of a large rockslide in Northern Calabria have been modelled by means of physical and hydrological approaches. In addition, shallow landslides in Calabria, Campania and Sicily have been modelled by employing hydrological approaches. Strengths and weaknesses of the adopted methods are discussed, together with the causes that may have hindered better results for the considered cases. For the methods illustrated through real application cases, research perspectives are discussed, as well as their possible use in early warning systems. [ABSTRACT FROM AUTHOR]

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

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

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

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

Earth observation data are useful to analyze the impact of climate-related variables on geomorphological processes. This work aims at evaluating the impact of rainfall on slow-moving landslides, by means of a quantitative procedure for identifying satellite-based displacement clusters, comparing them with rainfall series, and applying statistical tests to evaluate their relationships at the regional scale. The chosen study area is the Basento catchment in the Basilicata region (southern Italy). Rainfall series are gathered from rain gauges and are analyzed to evaluate the presence of temporal trends. Ground displacements are obtained by applying the P-SBAS (Parallel Small BAseline Subset) to three datasets of Sentinel-1 images: T146 ascending orbit, and T51 and T124 descending orbits, for the period 2015–2020. The displacement series of the pixels located in areas mapped as landslides by the Italian Landslide Inventory and sited within rain gauge influence regions (defined as 10 km circular buffers) are studied. Those displacement series are analyzed and compared to the rainfall series to search for correlations, by employing statistical and non-parametric tests. In particular, two landslides are selected and investigated in detail. Significant results were obtained for the T124 descending orbit for both landslides, for a 3-day cumulative rainfall and a 7-day delay of the slope response. Challenges in the whole procedure are highlighted and possible solutions to overcome the raised problems are proposed. Given the replicability of the proposed quantitative procedure it might be applied to any study area. [ABSTRACT FROM AUTHOR]

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

Shallow flowslides, debris flows and debris avalanches are rainfall-induced landslides consisting in the shear failure of few metres of soils (or in some cases even less than a metre), which greatly increase downslope in volume and flow velocity. The southern Italian region of Campania has been historically affected by such events involving pyroclastic soils mainly resting on steep carbonate slopes. This paper deals with the analysis of factors influencing the occurrence of flow-like landslides, adopting the Lattari Mts. in Campania as a case study. The results of two investigation campaigns carried out in the area allowed effective large-scale geological and geotechnical characterization to be set up. Stratigraphic profiles, mean physical properties and typical friction angles at the critical state for each soil layer were investigated. The effect of suction on peak and critical shear strength, whose drop is responsible for soil failure, was analysed. Using detailed information on both the stratigraphic and geotechnical features of the soils involved in past flow-like landslides, typical triggering models were selected, representing locally recurrent geomorphologic conditions at the basin scale. The identified models were adopted for slope stability analyses carried out on four cross-sections of flowslides occurring prior to the event, to back-analyse the triggering conditions. From the evidence on the triggering mechanisms and the results of analyses, the infinite slope approach is not always suitable to model slope stability conditions properly, because the onset of landslides is also affected by local topographic and stratigraphic factors. • Flow-like landslides can be triggered due to local features. • Local topographic irregularities can be represented by roads, tracks, scarps and terraces. • Infinite slope model can be suitable to model only slopes characterized by angles higher than 39–40°. • Local natural and anthropic factors can affect the results of slope stability analysis. • The triggered landslides occurred when the 3-months precedent rainfall exceeded the 40 years average value. [ABSTRACT FROM AUTHOR]

In landslide-prone areas the magnitude of events is related to recurring rainfall intensity. In a large sector of the Sannio Apennines (Southern Italy), predictive mapping of recurrent shallow landslides was undertaken by combining deterministic and probabilistic predictive approaches. This, with the aim to minimize the negative influence of the uniform distribution of the initial water table depth in steady condition that usually influence the theoretical instability resulting from the application of methods for large-scale estimation. The deterministic approach was performed by means of the Transient Rainfall Infiltration and Grid-based Regional Slope-stability model to obtain triggering maps in multi-temporal transient pore-water pressures. The optimized physical modeling was validated by back-analysis on large-magnitude landslide events which occurred in 2003 by means of the introduction of two cross-mapping correlation indexes. Subsequently, different predictive scenarios were proposed for different probabilistic return periods of the rainstorm events. The output data permitted the definition of a linear log regression curve to estimate the theoretical instability of the study area. This curve is defined as a function of cumulative precipitation, duration and return periods of the possible rainfall events. [ABSTRACT FROM AUTHOR]