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The analysis of geological processes threatening people and properties in a populated region should be based on a comprehensive knowledge of historical events and related characteristics. This type of information is essential for predisposing event scenarios, validating prediction models, and planning risk mitigation measures. Such activities may be more complex in some geological settings, where urban settlements are exposed to multi-hazard conditions. This is the case of the densely populated Campi Flegrei volcanic area located in the Campania region, southern Italy. Here, volcanic and seismic hazards are associated with landslides, floods, and coastal erosion, which are playing a relevant role in the landscape modification. The CAmpi Flegrei LAndslide Geodatabase (CAFLAG), here presented, provides information related to 2302 landslides that occurred in the continental, coastal, and insular sectors of the study area during the 1828–2017 time interval. Data associated with the collected landslide events highlight the characteristics of both landslides and of the affected sites. Most of the cataloged mass movements consist of rock falls affecting rocky slopes formed by lithified volcanic rocks, such as tuff or ignimbrite. In addition, rainfall-induced earth and debris slides translating into debris avalanches or rapid flows are widespread along steep slopes mantled by weakly welded pyroclastic airfall deposits, similarly to other areas of the region. The highest density of landslides is concentrated along the coastline, where mass movements are contributing to the retreat of coastal cliffs, and along inland slopes exposed towards the western directions, where most of the storm systems come from. Temporal information shows peaks of landslides in the years 1986, 1997, and 2005. A total of 127 people lost their lives as a consequence of 53 cataloged landslides, with a frequency of deadly events observed however to have decreased since the early 1980s. This information will be useful to analyze mortality and risk conditions still affecting the population of the Campi Flegrei caldera, which should be fully addressed with advanced knowledge and accurate scenarios. The full database is freely available online at 10.4121/14440757.v2 (Esposito and Matano, 2021). [ABSTRACT FROM AUTHOR]

Steep slopes covered by loose unsaturated pyroclastic deposits widely dispersed in Campania, Southern Italy, are often subjected to shallow landslides that turn into fast debris flows causing a large amount of damage and many casualties, triggered by heavy and persistent precipitation. The slope of Cervinara, located around 40 km northeast of Naples, was involved in a destructive flowslide between 15 and 16 December 1999, triggered by a rain event of 325 mm in 48 h. Hydrometeorological monitoring activities have been carried out near the landslide scarp of 1999 since 2017 to assess the water balance and to identify major hydrological processes involving the cover and the shallow groundwater system developing in the upper part of the underlying limestone fractured bedrock. Since 1 December 2022, a remotely accessible low-cost network has been installed to expand the field hydrological monitoring. The use of a network of low-cost capacitive sensors, communicating within the domain of Internet of Things (IoT) technology, aiming at dispersed monitoring of soil moisture, has been tested. Specifically, the tested prototype network allows measurements of the soil water content at two different points, communicating through a Wi-Fi-based IoT system using ESP32 boards. The ThingSpeakTM IoT platform has been used for remote field data visualization. Based on the obtained results, the prototype of this IoT-based low-cost network shows the potential to expand the amount of hydrological data, suitable for setting up early warning systems in landslide-prone areas. [ABSTRACT FROM AUTHOR]

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

Abstract: Campania Region (Italy), one of the most densely populated areas in Europe, is probably the one with the highest risk of landslide. A large part of the region is covered by unsaturated cohesionless pyroclastic deposits subjected to rainfall-induced landslides. According to experience, these can display different features and magnitude. The most catastrophic landslides are liquefied debris flows which periodically occur on steep slopes, causing death and destruction in areas located downslope. Therefore, zoning of those areas which can be the source of liquefied debris flow is necessary. The paper reports some useful elements for zoning based on infinite slope analysis, accounting for the results of recent research on the mechanics of rainfall-induced landslides in pyroclastic soils. [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]

Debris flows that have occurred in the area of San Martino Valle Caudina (Campania, Southern Italy) are described by geomorphological and hydrological analyses, focusing on the recent event of December 2019. This area can be considered a key example for studying debris-flow phenomena involving the pyroclastic mantle that covers the karstified bedrock along steep slopes. A hydrological analysis of the time series of the maximum annual rainfall, of durations of 1, 3, 6, 12 and 24 h, was carried out based on a new approach to assess rainstorm magnitude. It was quantified by measuring the deviation of the rainfall intensity from the normal conditions, within a specified time period. As the time series of annual maxima are typically skewed, a preliminary transformation is needed to normalize the distribution; to obtain the Z-value of the standard normal distribution, with mean µ = 0 and standard deviation σ = 1, different probability distribution functions were fitted to the actual data. A specific boxplot was used, with box width Z = ±1 and whiskers length Z = ±2. The deviations from these values provide the performance of the distribution fits. For the normalized time series, the rates shown by the trends and relative significance were investigated for the available time series of 11 rain gauges covering the Western–Central Campania region. The most critical condition for the debris-flow initiation appears to occur when a severe or extreme rainfall has a duration ≥ 12 h. The trend analysis did not detect statistically significant increases in the intensity of the rainfall of duration ≥ 6 h. [ABSTRACT FROM AUTHOR]

On the 4th and 5th of March 2005, about 100 rainfall-induced landslides occurred along volcanic slopes of Camaldoli Hill in Naples, Italy. These started as soil slips in the upper substratum of incoherent and welded volcaniclastic deposits, then evolved downslope according to debris avalanche and debris flow mechanisms. This specific case of slope instability on complex volcaniclastic deposits remains poorly characterized and understood, although similar shallow landsliding phenomena have largely been studied in other peri-volcanic areas of the Campania region underlain by carbonate bedrock. Considering the landslide hazard in this urbanized area, this study focused on quantitatively advancing the understanding of the predisposing factors and hydrological conditions contributing to the initial landslide triggering. Borehole drilling, trial pits, dynamic penetrometer tests, topographic surveys, and infiltration tests were conducted on a slope sector of Camaldoli Hill to develop a geological framework model. Undisturbed soil samples were collected for laboratory testing to further characterize hydraulic and geotechnical properties of the soil units identified. In situ soil pressure head monitoring probes were also installed. A numerical model of two-dimensional variably saturated subsurface water flow was parameterized for the monitored hillslope using field and laboratory data. Based on the observed soil pressure head dynamics, the model was calibrated by adjusting the evapotranspiration parameters. This physically based hydrologic model was combined with an infinite-slope stability analysis to reconstruct the critical unsaturated/saturated conditions leading to slope failure. This coupled hydromechanical numerical model was then used to determine intensity–duration (I-D) thresholds for landslide initiation over a range of plausible rainfall intensities and topographic slope angles for the region. The proposed approach can be conceived as a practicable method for defining a warning criterion in urbanized areas threatened by rainfall-induced shallow landslides, given the unavailability of a consistent inventory of past landslide events that prevents a rigorous empirical analysis. [ABSTRACT FROM AUTHOR]