Recently, ECMWF has released a new generation of reanalysis, acknowledged as ERA5, able to deliver a comprehensive, free, and operative picture of the past weather, exploiting the data assimilation ...of historical observations from different sources (satellite, in situ, multiple variables) for both atmospheric and soil variables. Experiences concerning flooding issues suggest that ERA5 could support also landslide investigations. In this sense, a number of questions may be raised: (i) can ERA5 data be reliable in reproducing rainfall histories leading to a landslide event? (ii) can ERA5 soil moisture estimations be reliable proxies for antecedent slope wetness condition? (iii) can ERA5 be implemented in a landslide early warning system to improve the performances? This study tries addressing these questions referring to some historical Campanian events (Southern Italy) with a special focus on the fully investigated event occurred in Nocera Inferiore on March 4, 2005. The study shows the following: (i) ERA5 precipitation can appropriately reproduce actual rainfall histories leading to the events occurred in the last years; (ii) ERA5 soil moisture may act as proxy of slope wetness conditions; (iii) ERA5 data could be easily implemented in LEWSs in areas poorly covered by field monitoring networks.
This work examines the hydrological behaviour of a silty volcanic layer exposed to the atmosphere for 3 years under vegetated conditions. The layer was extensively monitored to measure energy fluxes, ...water fluxes, and internal variables (suction, water content, water storage, and temperature). Measurements were used to build representations of the layer's behaviour patterns depending on its surface covering, comparing the behaviour in vegetated conditions with behaviour observed under bare conditions over the previous 4 years. Results show that during cold- dry periods, differences in terms of fluxes and hydrological variables between the bare and vegetated conditions reduce to negligible levels, but increase significantly during hot-dry and transition periods. As the soil forming the layer was selected to have the same intrinsic and state properties as the layer in a specific rainfall-induced landslide case history that occurred in Nocera Inferiore (South Italy) in 2005, the experimental results are used to re-interpret such a landslide, considering the effects of vegetation and referring to a coupled thermohydraulic model. The experimental results are used to calibrate the model, and this is then used to interpret around 10 years of meteorological variables recorded at the landslide site, including the landslide time. Comparison with interpretations made previously as a bare soil hypothesis shows how neglecting the effects of vegetation might imply a loss in prediction accuracy of soil state variables (suction and water storage) related to the slope stability.
A highway embankment founded on a sloping tectonised marly-sandstone flysch formation located in the Apennines chain (Italy) has been affected for about 30 years by continuous slow movements. Given ...the strategic importance of the involved infrastructure, different investigation and monitoring campaigns have been carried out to get information about the properties of the involved soils and collect data about the displacements and piezometric regime. Field monitoring, in particular, reveals that the observed displacements result from a failure mechanism involving both the embankment and the foundation soils. However, significant gaps in monitoring jeopardize the possibility to assess the long-term trends in the displacements and piezometric regime and the significance of weather forcing in regulating the phenomena. To address such research questions, a procedure, easily transferable in different contexts, is proposed and applied to the test case: a simple hydrological proxy indeed permits evaluating the rate of movement featured by weatherinduced seasonal variability. Such a mechanical response has been confirmed by the results of a simplified numerical model aimed at finding out the main features of the observed kinematics accounting for a hydrological balance of the involved area.
•Poor performances of 21 empirical models for R-factor estimation are highlighted.•A new model for R-factor estimation is calibrated at the rain gauge scale.•The calibrated model is applied on four ...different gridded rainfall datasets.•Comparison of the new model against a reference dataset shows good performances.•Four R-factor maps with different spatial resolutions are provided for 1981–2010.
The paper considers a methodology to assess rainfall erosivity in Italy for the recent decades (1981–2010), building on datasets and materials freely available, such as those included within the Climate Data Store (CDS) of the Copernicus Climate Change Service (C3S). Twenty-one referenced empirical models to assess rainfall erosivity (R-factor) based on coarse rainfall data are tested and compared; then, a custom model is calibrated, with the support of seasonal rainfall pattern clustering by means of the Self-Organizing Map. Moreover, a large database of sub-hourly rainfall observations, covering the period 2002–2011, is collected and used for validation. Model performances are analysed at the point-scale of the rain gauges and at the spatial scale of different relevant gridded rainfall products: the fifth generation of ECMWF ReAnalysis (ERA5, ERA5-Land), the gridded European observational dataset (E-OBS), all included in the CDS, and SCIA-ISPRA (the Italian standard rainfall gridded dataset).
New Hydrological Insights from the Region
The proposed methodology provides four alternatives of spatially distributed rainfall erosivity datasets covering Italy with diverse levels of reliability. Analysis of results shows that the best performance is achieved by the combined use of the custom model and the SCIA-ISPRA dataset, followed by ERA5-Land, with the main source of error lying in the use of an empirical model instead of the rigorous model for R-factor estimation, and secondly in the use of gridded rainfall data instead of point-scale rainfall observations.
The present work analyses the main weather patterns over the period 1981–2010 in the Central Apennines (Italy), drawing upon data from 23 monitoring stations spanning a wide elevation range (260–1750 ...m asl). Cluster analysis was used to identify homogeneous units and to verify the effectiveness of the bioclimatic classification by crossing the results derived from the application of hierarchical and non-hierarchical classification techniques. The results reveal a diversified picture of five clusters that depends on several factors as elevation, the geographic position within or outside the mountainous range, and the regional morphological traits. Although Mediterranean and Temperate climatic features coexist, the Mediterranean pattern in the southern areas and internal valleys better expresses the overall mixed characteristics of Central Italy. The use of a mixed methodology of hierarchic and partitioning methods of cluster analysis improves the bioclimatic classification, especially to quantify the level of humidity and the mediterraneity degree.
In the context of rainfall-induced landslides involving pyroclastic soils, the present work analyzes the influence of cover thickness on slope stability conditions. To this aim, the slope failure ...that occurred in Nocera Inferiore (4th March 2005) is selected as a reference test case, providing the actual weather forcing history that preceded the event, the hydraulic characterization of the soil involved, and the lowermost boundary condition (variously fractured calcareous bedrock underlying the cover). By maintaining unchanged soil hydraulic properties, the relationship between domain thickness, initial soil suction distribution, and slope instability induced by critical rainfall is investigated by numerical analyses. These refer to a rigid unsaturated domain subject to one dimensional flow conditions under the effects of incoming (precipitation) and outcoming (evaporation) fluxes applied at the uppermost boundary. The main outcomes indicate that critical event duration increases significantly with increasing the domain thickness. This relationship is strongly influenced by initial suction distribution. A linear relationship results for soil suction that is assumed to be constant at the beginning of the critical event. However, this relationship is quadratic if, by simulating the actual antecedent meteorological conditions, suction at the beginning of the critical event is the main function of the domain thickness. Additional numerical analyses were carried out to characterize the influence of a different lowermost boundary condition. Outcomes indicate that, for the same thickness, critical duration is substantially longer if the cover contact is with the same material as that of the cover.
Landslide early warning systems at regional scale are typically based on correlations between landslides that occurred in the past and rainfall monitoring data in order to identify trigger rainfall ...thresholds. Recently, the availability of large datasets of atmospheric measurements allows including additional variables, increasing the reliability of the models. However, conducting the analyses with traditional techniques can be quite complex and time-consuming. The purpose of this preliminary study is to demonstrate that machine learning techniques can be used to analyze monitoring data in order to select the most relevant variables for the triggering of shallow rainfall-induced landslides at regional scale. The models developed herein were tested in one of the alert zones defined by civil protection for the management of geo-hydrological risk in Campania region, Italy. Two data sources were used in the analysis. The atmospheric variables are derived from the ERA5-Land atmospheric reanalysis. The data on landslide events are retrieved from “FraneItalia”, a georeferenced catalog of landslides occurred in Italy developed by consulting online sources from 2010 onwards. The models developed were calibrated and validated in order to define combinations of rainfall variables and soil water content for the prediction of the occurrence of landslides. Finally, the performance of the models was assessed using statistical indicators derived from contingency matrices.
•European climatic loads for structural design need to be updated and harmonised.•European climate datasets (E-OBS, ERA5-Land) can be used to update thermal maps.•Methods to update thermal loads for ...design with the Eurocodes are tested for Italy.•European maps of climatic actions will help setup of national safety requirements.•Updated climatic actions will speed climate change adaptation of built environment.
The characteristic values of temperature corresponding to the maximum and minimum shade air temperature with an annual probability of being exceeded 0.02, used in the European construction standard for thermal actions (EN 1991-1-5:2003), are usually assessed at a country level and included in the National Annexes to that Eurocode part.
The paper aims to support national authorities on elaborating maps for thermal actions using publicly available datasets, consistent at a European level, and harmonised modelling approaches. In addition, these datasets are continuously updated, reflecting the current climate and capturing potential global warming variations.
The work investigates how updates in data and modelling could affect the characteristic values currently adopted in the Italian National Annexes to the Eurocodes. The main results show that: (i) the currently adopted number and locations of the weather stations result fairly representative of the patterns detected by exploiting additional datasets; ii) the statistical method plays an essential role in the assessment of characteristic values, i.e., the method adopted in the current Italian standard evaluates more conservative characteristic values of maximum temperature than Gumbel or Generalized Extreme Value distributions, but could err on the unsafe side for minimum ones; (iii) both E-OBS and ERA5-Land datasets represent two optimal products to be used as a common source of temperature values at European scale; (iv) moving towards an updated period for temperature data results on an increase of characteristic values of maximum temperature and limited variations in spatial extent and magnitude of characteristic values of minimum ones.
A significant part of the recent geotechnical literature concerning pyroclastic soils is focused on the characterization of the hydrological effects of precipitations and their implications for the ...stability conditions of unsaturated sloping covers. Recent experience shows that suction-induced strength reduction is influenced by various factors including hydraulic hysteresis. A deeper insight into the hysteretic water retention behavior of these materials and its effects upon their response to dry/wetting conditions is a major goal of this paper, which exploits the data provided by the monitoring of a volcanic ash. Based on the parameters retrieved from data calibration, the hydrological response of a virtual slope subject to one-dimensional rainfall infiltration is investigated by numerical analyses and compared with the results obtained through the usually adopted non-hysteretic approaches. The analysis demonstrates that considering the hysteretic behavior may be crucial for a proper evaluation of the conditions leading to slope failure.
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