Metodologie di analisi e definizione di soglie di eventi pluviometrici che hanno innescato colate rapide e frane superficiali in un'area dell'arco alpino nord-orientale

Debris flows and shallow landslides, due to the high velocity, in recent decades have caused the most damage in Italy both in terms of casualties that economic losses. The triggering is in almost all cases related to intense rainfall events. For these types of landslides one of the main risk mitigation measures is the adoption of early warning systems based on rainfall thresholds that identify the critical amount of precipitation for landslide initiation. The aim of this research is the development of objective, repeatable and exportable methodologies for the identification, analysis and characterization of rainfall events responsible for the triggering of shallow landslides and debris flows and the definition of empirical rainfall thresholds. The study area is the province of Trento (6,208 km2), located in the north-eastern Alps, and characterized by complex orography, with 70% of the area at an altitude above 1,000 m. 260 debris flows and shallow landslides with known date of occurrence in the study area have been extracted from the Italian Landslide Inventory (Progetto IFFI) and descriptive statistical analysis related to the main landslide controlling factors have been performed in order to assess the representativeness of the sample with known date of activation respect to the total debris flows and shallow landslides of Trento province. An objective and rigorous statistical methodology has been defined for the identification of the beginning of the triggering event based on the critical duration, that is the minimum dry period duration separating two stochastically independent rainy periods. The critical duration has been calculated for each rain gauge of the study area and its variability during the months of the year has been analysed. An analysis of the rainfall spatial variability in a neighbourhood of the landslide detachment zone has been then carried out through the examination of the Monte Macaion radar maps during some summer convective events, the comparison of rainfall records of rain gauges located in a 10 km buffer around the landslide, and the calculation of the Pearson's correlation coefficient between pairs of neighbouring rain gauges. An automatic procedure for the identification and characterization of the triggering rainfall event has been developed, which provides in output the event duration, cumulated rainfall and average intensity, the maximum rainfall height for fixed durations (from 5 minutes to 96 hours), the cumulated antecedent rainfall (from 1 to 30 antecedent days), the maximum return period of the event, the duration, rainfall amount and intensity associated with the maximum return period. The following rainfall thresholds have been then calibrated with the frequentist approach: cumulated event rainfall-duration (E-D) and average intensity-duration (I-D), which represent the rainfall event in its entirety, and rainfall amount-duration and intensity-duration associated with the event maximum return period (ETR-DTR and ITR-DTR), which consider the most critical portion of the event therefore responsible for the landslide triggering. In the absence of information about the landslide time of activation, the end of the triggering event has been identified using two criteria: the rainfall peak intensity and the last registration of the day. The relationship between rainfall thresholds and some environmental landslide controlling factors (i.e. lithology, land use and elevation) has been analysed and finally the contribution of antecedent rainfall has been evaluated. The main outcomes of the research are: the good applicability of the methodology adopted for the objective identification of the beginning of the triggering event, the low representativeness during convective summer events of the rainfall information recorded at the nearest rain gauge with respect to the precipitation over the landslide source area, the influence of the two criteria for the identification of the end of the event on the thresholds coefficients

Metodologie di analisi e definizione di soglie di eventi pluviometrici che hanno innescato colate rapide e frane superficiali in un'area dell'arco alpino nord-orientale

Debris flows and shallow landslides, due to the high velocity, in recent decades have caused the most damage in Italy both in terms of casualties that economic losses. The triggering is in almost all cases related to intense rainfall events. For these types of landslides one of the main risk mitigation measures is the adoption of early warning systems based on rainfall thresholds that identify the critical amount of precipitation for landslide initiation. The aim of this research is the development of objective, repeatable and exportable methodologies for the identification, analysis and characterization of rainfall events responsible for the triggering of shallow landslides and debris flows and the definition of empirical rainfall thresholds. The study area is the province of Trento (6,208 km2), located in the north-eastern Alps, and characterized by complex orography, with 70% of the area at an altitude above 1,000 m. 260 debris flows and shallow landslides with known date of occurrence in the study area have been extracted from the Italian Landslide Inventory (Progetto IFFI) and descriptive statistical analysis related to the main landslide controlling factors have been performed in order to assess the representativeness of the sample with known date of activation respect to the total debris flows and shallow landslides of Trento province. An objective and rigorous statistical methodology has been defined for the identification of the beginning of the triggering event based on the critical duration, that is the minimum dry period duration separating two stochastically independent rainy periods. The critical duration has been calculated for each rain gauge of the study area and its variability during the months of the year has been analysed. An analysis of the rainfall spatial variability in a neighbourhood of the landslide detachment zone has been then carried out through the examination of the Monte Macaion radar maps during some summer convective events, the comparison of rainfall records of rain gauges located in a 10 km buffer around the landslide, and the calculation of the Pearson's correlation coefficient between pairs of neighbouring rain gauges. An automatic procedure for the identification and characterization of the triggering rainfall event has been developed, which provides in output the event duration, cumulated rainfall and average intensity, the maximum rainfall height for fixed durations (from 5 minutes to 96 hours), the cumulated antecedent rainfall (from 1 to 30 antecedent days), the maximum return period of the event, the duration, rainfall amount and intensity associated with the maximum return period. The following rainfall thresholds have been then calibrated with the frequentist approach: cumulated event rainfall-duration (E-D) and average intensity-duration (I-D), which represent the rainfall event in its entirety, and rainfall amount-duration and intensity-duration associated with the event maximum return period (ETR-DTR and ITR-DTR), which consider the most critical portion of the event therefore responsible for the landslide triggering. In the absence of information about the landslide time of activation, the end of the triggering event has been identified using two criteria: the rainfall peak intensity and the last registration of the day. The relationship between rainfall thresholds and some environmental landslide controlling factors (i.e. lithology, land use and elevation) has been analysed and finally the contribution of antecedent rainfall has been evaluated. The main outcomes of the research are: the good applicability of the methodology adopted for the objective identification of the beginning of the triggering event, the low representativeness during convective summer events of the rainfall information recorded at the nearest rain gauge with respect to the precipitation over the landslide source area, the influence of the two criteria for the identification of the end of the event on the thresholds coefficients

The usability of the IdroGEO web platform for the dissemination of information on landslides and floods in Italy

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Landslides monitoring techniques review in the Geological Surveys of Europe

ABSTRACT: Landsliding is the downslope movement of surface material under the force of gravity, initiated when gravitational and other types of shear stresses within the slope exceed the shear strength of the material that forms the slope. Often, landslides pose a physical and environmental threat to communities living in landslide-prone areas. While much landslide research focuses on monitoring techniques to define the background of the landslide (extent, volume, velocity, magnitude) one of the main goals of the Geological Surveys (GS) are to support and understand the regional and local geology to identify areas susceptible to landslides.N/

Landslide databases in the Geological Surveys of Europe

Acceso electrónico sólo desde el IGMELandslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km2 landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm2 (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.Earth Observation and Geohazards Expert Group (EOEG), EuroGeoSurveys, the Geological Surveys of Europe, BélgicaGeohazards InSAR Laboratory and Modeling Group, Instituto Geológico y Minero de España, EspañaRisk and Prevention Division, Bureau de Recherches Géologiques et Minières, FranciaEngineering Geology Department, Institute of Geology and Mineral Exploration, GreciaGeoHazard team, Geological Institute of Romania, RumaníaGeological Survey of Slovenia, EsloveniaCroatian Geological Survey, CroaciaItalian Institute for Environmental Protection and Research, Geological Survey of Italy, ItaliaSwiss Federal Office for the Environment, SuizaGeological Survey of Austria, AustriaPolish Geological Institute, National Research Institute, PoloniaGeological Survey of Ireland, IrlandaCzech Geological Survey, República ChecaFederal Institute for Geosciences and Natural Resources, AlemaniaGeological Survey of Norway, NoruegaCyprus Geological Survey, ChipreGeological Survey of Sweden, SueciaInstitut Cartogràfic i Geològic de Catalunya, EspañaBritish Geological Survey, Reino UnidoGeological Survey of Slovakia, EslovaquiaGeological Survey of Lithuania, LituaniaFederalni zavod za geologiju, Bosnia y HerzegovinaGeological Survey of Estonia, EstoniaLaboratório Nacional de Energia e Geologia, PortugalGeological Survey of Hungary, HungríaNorwegian Water and energy Directorate of Norway, Norueg

Sediment transport time series in the Tiber river

The hydrologic regime of the Tiber River basin in central Italy has been impacted considerably in the last decades by intensive anthropic activities, and hydraulic works in particular (e.g. hydropower reservoirs, land use modification). In the Tiber River the wash load, in particular, plays an important role in sediment transport, and the knowledge of this hydrological variable is very important for the evaluation of medium-long-term dynamic of shoreline, and the evaluation of reservoir landfill. The Ripetta flow gauge, located in downtown Rome, has been continuously monitoring the daily discharge for decades, while daily sediment load measurements are available only for short terms. In this research, the yearly sediment rate is simulated using a simple stochastic model based on the evaluation of sediment rating curves. The sediment rating curve, i.e. the average relation between discharge and suspended sediment concentration for a specific location, is estimated using a power law model. The fitting curve, obtained by regression analysis, lacks the physical characterization of the phenomenon, often represented by the empirical evidences of erosion severity and the erosional power of river. Model results provide useful insights on the impact of recent hydraulic works on the sediment transport regime

Identification and characterization of rainfall events responsible for triggering of debris flows and shallow landslides

The aim of this study is the development of objective and replicable methodologies for the identification, analysis and characterization of rainfall events responsible for the triggering of shallow landslides and debris flows, in order to define empirical rainfall thresholds. The study area is the province of Trento (6208 km2), located in the north-eastern Alps, and characterized by complex orography, with 70% of the area at an altitude above 1000 m. A rigorous statistical methodology has been defined for the identification of the beginning of the triggering event, based on the critical duration, i.e. the minimum dry period duration separating two stochastically independent rainy periods. The critical duration has been calculated for each rain gauge of the studied area and its variability during the months of the year has been analyzed. An analysis of the rainfall spatial variability in a neighborhood of the landslide detachment zone has been carried out. The adopted methods are: the examination of the Monte Macaion radar maps during some summer convective events, the comparison of rainfall records of rain gauges located in a 10 km buffer around the landslide, and the calculation of the Pearson's correlation coefficient between pairs of neighboring rain gauges. The following rainfall thresholds have been then calibrated with the frequentist approach and compared: average intensity–event duration (I–D), which represents the rainfall event in its entirety, and intensity–duration associated with the event maximum return period (IRP–DRP), which considers the most critical portion of the event. In the absence of information about the landslide time of activation, the end of the triggering event has been identified using two criteria: the rainfall peak intensity and the last registration of the day. The methodology adopted for the objective identification of the beginning of the triggering event has demonstrated good applicability for rainfall induced landslides. During convective summer events the low representativeness of the rainfall information recorded at the nearest rain gauge with respect to the precipitation over the landslide source area has been evaluated as a critical issue for rainfall threshold definition

Comparison of Logistic Regression and Random Forests techniques for shallow landslide susceptibility assessment in Giampilieri (NE Sicily, Italy)

The aim of this work is to define reliable susceptibility models for shallow landslides using Logistic Regression and Random Forests multivariate statistical techniques. The study area, located in North-East Sicily, was hit on October 1st 2009 by a severe rainstorm (225 mm of cumulative rainfall in 7 h) which caused flash floods and more than 1000 landslides. Several small villages, such as Giampilieri, were hit with 31 fatalities, 6 missing persons and damage to buildings and transportation infrastructures. Landslides, mainly types such as earth and debris translational slides evolving into debris flows, were triggered on steep slopes and involved colluvium and regolith materials which cover the underlying metamorphic bedrock. The work has been carried out with the following steps: i) realization of a detailed event landslide inventory map through field surveys coupled with observation of high resolution aerial colour orthophoto; ii) identification of landslide source areas; iii) data preparation of landslide controlling factors and descriptive statistics based on a bivariate method (Frequency Ratio) to get an initial overview on existing relationships between causative factors and shallow landslide source areas; iv) choice of criteria for the selection and sizing of the mapping unit; v) implementation of 5 multivariate statistical susceptibility models based on Logistic Regression and Random Forests techniques and focused on landslide source areas; vi) evaluation of the influence of sample size and type of sampling on results and performance of the models; vii) evaluation of the predictive capabilities of the models using ROC curve, AUC and contingency tables; viii) comparison of model results and obtained susceptibility maps; and ix) analysis of temporal variation of landslide susceptibility related to input parameter changes. Models based on Logistic Regression and Random Forests have demonstrated excellent predictive capabilities. Land use and wildfire variables were found to have a strong control on the occurrence of very rapid shallow landslides

Identification of independent storm events: Seasonal and spatial variability of times between storms in Alpine area

The aim of the paper is the identification of rain events that trigger landslides through the use of an exponential method to separate stochastic independent events. This activity is carried out within the definition of empirical rainfall thresholds for debris flows and shallow landslides. The study area is the Trento district, which is located in the northeast zone of an Alpine area. The work evaluates the factors that affect the variability in space and time of the critical duration of each rain gauge, defined as the minimum dry period duration that separates two rainy periods that are stochastically independent

IdroGEO: A Collaborative Web Mapping Application Based on REST API Services and Open Data on Landslides and Floods in Italy

The new national IdroGEO web platform allows the navigation, social sharing and download of data, maps, reports of the Italian Landslide Inventory, national hazard maps, and risk indicators. It is a tool for communication and dissemination of information to support decisions in risk mitigation policies, land use planning, preliminary design of infrastructures, prioritization of mitigation measures, management of civil protection emergencies, and environmental impact assessment. The challenges that have been faced during the design and development of the platform concern usability, access on multiple devices (smartphones, tablets, desktops), interoperability, transparency, reuse of information and software in the public sector, and improvement of the updating of the Italian Landslide Inventory. The methodologies and solutions adopted to address them include Progressive Web Application (PWA), Application Programming Interface (API), open standards, open libraries, and software. A landslide inventory management system has been developed via REST API for data entry and approval workflow in order to maintain the inventory in a distributed and collaborative manner. As a result, IdroGEO provides a public service for citizens, public administration, and professionals, using the “mobile first” approach and with scalable and reliable architecture. IdroGEO represents a solid infrastructure for the interoperability of data that serves as the foundation for creating a first knowledge-graph on landslides and the community who manages them