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Unmanned Aerial Systems, or drones, are very helpful tools for managing open-pit mining operations and developing ecological restoration activities. This article presents a method for identifying water erosion processes in active quarries by means of drone imagery remote sensing, in the absence of pre-existing imagery or mapping for comparison. A Digital Elevation Model (DEM) with a spatial resolution (SR) >10 cm and an orthophoto with an SR >2.5 cm were generated from images captured with a drone and their subsequent photogrammetric processing. By using Geographical Information Systems tools to process the DEM, a detailed drainage network was obtained, the areas of detected water erosion were separated, and the watersheds in the gullies identified. Subsequently, an estimated DEM before the erosive processes was reconstructed by interpolating the gully ridges; this DEM serves as a reference for the relief before the erosion. To calculate the volume of eroded material, the DEM of Differences was calculated, which estimates the volume difference between the previously estimated DEM and the current DEM. Additionally, we calculated the material necessary for the geomorphological adaptation of the quarry and the slope map, which are two valuable factors closely related to the monitoring of erosive processes. The results obtained allowed us to identify the erosion factors quickly and accurately in this type of mining. In the case of water-filled quarries, it would be important to characterize the subsurface relief. Essentially, the presented method can be applied with affordable and non-invasive materials to create digital grid maps at 10 cm resolution, obtaining data ready for 3D metrics, being a very practical landscape modelling tool for characterizing the restoration evolution of open-pit mining spaces, This research was funded by the Government of Catalonia through the project “Research and Innovation in the process and restoration of extractive activities” and by the European Union through the LIFE project “New Life for Drylands” (LIFE20 PRE/IT/000007)., Peer Reviewed, Postprint (published version)

La ladera del estribo derecho de la presa de Yesa está afectada por un gran paleodeslizamiento que mostró movimientos significativos en invierno de 2012-2013. Desde el año 2013, cuando se presentaron la gran mayoría de informes geológicos sobre el caso, se han realizado nuevos sondeos (39) y nuevos inclinómetros (30). Presentamos aquí los primeros resultados de la actualización del modelo geológico-geotécnico de la ladera. Se ha realizado un análisis 3D de la geometría de las dos superficies de rotura mayores y nuevos perfiles geológicos que siguen la dirección de desplazamiento, variable ladera abajo. Por otra parte, se han ensayado a corte directo ocho muestras de planos de estriados en testigos de sondeo, correspondientes a superficies de rotura. Los ensayos sugieren que el ángulo de fricción residual de las superficies de rotura es de unos 19º., Postprint (published version)

Los desprendimientos rocosos son los procesos de inestabilidad de laderas que causan un mayor número de víctimas en España, así como importantes pérdidas económicas. En esta contribución se presenta la cuantificación del impacto de los desprendimientos rocosos obtenida a partir del vaciado documental, fundamentalmente prensa escrita. Se han recopilado 990 eventos ocurridos entre 1802 y 2021 que han causado víctimas (cerca de 1400 muertos y más de 2000 heridos). El análisis del inventario permite evaluar el impacto de los desprendimientos rocosos y su evolución en contextos muy diversos como las laderas edificadas, las excavaciones a cielo abierto, los ferrocarriles, las carreteras y en el entorno natural. Se constatan dos tendencias contrapuestas. Mientras que la peligrosidad y el riesgo disminuyen a medida que se acumulan las actuaciones estabilizadoras y preventivas en los entornos de las poblaciones y líneas de ferrocarril, el número de incidentes se incrementa por el aumento de la movilidad en carretera y la mayor frecuentación en el medio natural (mayor exposición). En otro apartado se realiza una primera estimación de las inversiones realizadas por distintas administraciones en la estabilización desmontes y laderas rocosas y para reducir el riesgo por desprendimientos. Finalmente, se presenta un ejemplo, detallado paso a paso, para mostrar el potencial de los inventarios de desprendimientos rocosos para evaluar de manera cuantitativa el riesgo directo e indirecto en carreteras., Este trabajo se enmarca dentro de las actividades del proyecto GeoRisk con referencia PID2019-103974RB-I00 y que está financiado por MCIN/ AEI/10.13039/501100011033., Postprint (published version)

This paper presents a procedure for tracking rockfall trajectories and extracting kinematic parameters from both the impacts and the resultant fragments. A set of full scale rockfall experiments was performed in a quarry located in Vallirana, Barcelona (Spain). The study site was chosen due to the presence of a rigid discontinuity surface, inclined at 42° in the middle of the slope, whose configuration was expected to favor the breakage of the blocks. The trajectories of the blocks released and of the resultant fragments were recorded with three video cameras. A C++ program was specifically developed to track the 3D trajectory of blocks and fragments, and measure velocities before and after the impact. Two different modules were implemented, one for the blocks that break and one for those that do not. The trajectory of a non-fragmented block is obtained by comparing it to its 3D model. In this way, both the center of mass position and the orientation of the block are tracked. For fragmented blocks, the local coordinates of the fragments determined from the images are converted to terrain coordinates using the program we developed. A total of 16 blocks and 36 rock fragments after impact were tracked. The parameters obtained were georeferenced and linked to a common system of 3D terrestrial coordinates. The captured parameters allow obtaining the velocity distribution of fragments, the coefficient of restitution, and energy balance for the blocks that break. To our knowledge, this is the first attempt to capture kinematic parameters of rock fragments that result from the impact and breakage of rock blocks in full-scale tests. Although the analysis of the rockfall fragmentation phenomenon is beyond of this work, we have compared the performance of the fragmented and unbroken blocks. To this purpose, we have built 3D models of the rock fragments generated using images captured with a drone. The results indicate that blocks that fragment show higher rebound velocities an, Peer Reviewed, Postprint (published version)

Shallow slope failures triggered by rainfall commonly pose considerable risks in mountainous areas. In order to delineate areas where landslides are more prone to occur within a region, we have designed and developed a Python QGIS plugin named Fast Shallow Landslide Assessment Model (FSLAM). The plugin integrates a simplified hydrological model and a geotechnical model based on the infinite slope theory and contains two principal modules: runoff and slope stability modelling. It can output up to 15 raster maps describing the hydrological and stability conditions in a short computational time. Firstly, we explain the design of graphical user interface and the elements of the plugin. Then, the Berguedà area in NE Spain is used as case study to present the procedure of the plugin application. The results show that the accuracy of landslide susceptibility assessment performed by FSLAM-plugin is high and the computing time is only a few minutes., This study was partly funded by the Spanish national projects SMuCPhy and EROSLOP (BIA 2015-67500-R and PID2019-104266RB-I00/AEI/10.13039/501100011033). Zizheng Guo acknowledges the financial support of China Scholarship Council for his research at UPC BarcelonaTECH, Fundamental Research Funds for National Universities, China University of Geosciences (Wuhan), and China Shaanxi Province key research program (No.2019ZDLSF07-07-02)., Peer Reviewed, Postprint (author's final draft)

Los deslizamientos superficiales desencadenados por precipitaciones intensas pueden causar daños importantes en diferentes tipos de infraestructuras e incluso provocar pérdidas de vidas humanas. La ocurrencia de estos deslizamientos está directamente relacionada con futuros cambios (climáticos y de usos de suelo). Por ello es necesario disponer de herramientas para planificar el territorio y de esta manera contribuir a la reducción del riesgo asociado a estos procesos. En este estudio, se presenta un nuevo modelo de susceptibilidad llamado FSLAM basado en la teoría del talud infinito. El modelo calcula las presiones de agua en el suelo mediante dos modelos hidrológicos que incorporan la lluvia antecedente y la lluvia desencadenante. FSLAM es un modelo de código abierto que se ha implementado en un plugin de QGIS para su uso. El modelo FSLAM se ha aplicado y validado en cuatro áreas de centenares de kilómetros cuadrados del Pirineo (Andorra y Val d’Aran), del Pre-Pirineo (Berguedà) y de la Cordillera Prelitoral Catalana (Montseny). Se ha evaluado su eficiencia mediante el análisis ROC (Receiver Operating Characteristic) mostrando unos valores de precisión (accuracy) altos y satisfactorios a pesar de las incertidumbres de muchos parámetros de suelo. Mediante FSLAM se ha analizado la influencia de los efectos del cambio climático y de futuros cambios en los usos y cubiertas del suelo en la susceptibilidad a generar deslizamientos en la zona de la Val d’Aran. Los resultados indican que los cambios en las cubiertas del suelo, especialmente la transformación de prados y arbustos a bosques, aumenta la estabilidad global en la zona de estudio. Por el contrario, el aumento de precipitación diaria para un periodo de retorno de 100 años provoca una reducción de la estabilidad. Sin embargo, el efecto del cambio de las cubiertas del suelo es más importante que el cambio en las condiciones pluviométricas y, por ello, la estabilidad global en esta zona de estudio aumentará en el f, El presente estudio ha sido financiado por dos proyectos nacionales: SMuCPhy (BIA 2015-67500-R) y EROSLOP (PID2019-104266RB-I00/AEI/10.13039/501100011033)., Postprint (published version)

Se presentan dos casos en canteras donde se trabaja a partir de un modelo 3D del terreno obtenido mediante la reconstrucción fotogramétrica con dron. El primer caso se centra en la delimitación detallada de una masa rocosa inestable y se comparan los resultados de análisis de estabilidad realizados con cuatro metodologías: test cinemático, equilibrio límite mediante el programa RocPlane y equilibrio límite con métodos numéricos en 2D y 3D mediante los programas Slide2D y Slide3D, todos ellos de Rocscience. Se comparan los resultados obtenidos considerando distintos valores de cohesión y ángulo de fricción obtenidos de ensayos de laboratorio sobre el plano de deslizamiento y se debate sobre las incertidumbres que controlan la estabilidad como la presencia de agua y la cohesión. El segundo caso muestra el estudio de una propuesta de geometría futura de taludes muy verticales en una cantera. Se analiza, por un lado, la estabilidad de la geometría futura propuesta y se contrasta con las roturas existentes y, por otro lado, se comparan simulaciones de desprendimientos con la geometría actual y con la propuesta. Se utiliza el programa RockGIS desarrollado en la UPC que permite realizar simulaciones de desprendimientos en 3D y considerando el fenómeno de la fragmentación. Se debate sobre las ventajas e inconvenientes de la geometría propuesta en relación a la estabilidad de los taludes y del riesgo asociado a los desprendimientos. Los dos casos muestran el potencial de realizar un vuelo dron y trabajar a partir de un modelo 3D detallado de la cantera: la caracterización del patrón de discontinuidades de forma masiva, la caracterización de los mecanismos de rotura, la delimitación de volúmenes potencialmente inestable, la definición de la geometría necesaria para realizar análisis de estabilidad en 2D y 3D, así como el escenario donde realizar simulaciones de desprendimientos 3D., Postprint (published version)

La gestión del riesgo en corredores viales por movimientos del terreno, tales como, inestabilidades de laderas, desmontes y terraplenes, tanto en macizo rocoso como en suelos, es un ámbito en el que el empleo de sistemas de clasificación del riesgo han de estar en continuo desarrollo y actualización, facilitando al gestor de la infraestructura una herramienta para priorizar las actuaciones e inversión. La clasificación RHRS “Rockfall Hazard Rating System” empleada por los autores, se descompone en características del terreno, de infraestructura, y frecuencias, habiendo sido aplicada en diferentes ubicaciones y entornos, con la finalidad de desarrollos de Planes de Inversión Estratégicos. Las inestabilidades potenciales en suelos, tanto en taludes como terraplenes, presentes en los corredores analizados, han sido evaluadas en peligrosidad con una metodología análoga al RHRS adaptada a los suelos y denominada SHRS (Soil Hazard Rating System)., Postprint (published version)

Se presenta el fenómeno de la fragmentación en desprendimientos rocosos, su análisis y un modelo para entender y reproducir la fragmentación. En 2017 se publicó una primera versión del modelo de fragmentación fractal “Rockfall Fractal Fragmentation Model” que ha sido mejorado en diversos aspectos. Este comunicado describe el fenómeno de la fragmentación en desprendimientos rocosos y sus implicaciones en la definición del peligro y el riesgo asociados a los desprendimientos rocosos. Se muestran un conjunto de inventarios de desprendimientos rocosos donde se observa un comportamiento claramente fractal de la distribución de volúmenes de bloques en los depósitos. Se propone un conjunto de mejoras para el modelo de fragmentación fractal y se ajustan los parámetros del modelo para reproducir los casos inventariados. Las mejoras del modelo permiten generar distribuciones de fragmentos que siguen leyes fractales “scale-variant” o “scale-invariant”, es decir, que se ajusta a una ley potencial (recta en escala doble logarítmica) o pueden adaptar-se en función del tamaño de fragmento respectivamente. Las mejoras también permiten garantizar el balance de masa y condicionar los parámetros del modelo a las superficies nuevas generadas. Los resultados muestran una relación entre la energía potencial en el primer impacto y la nueva superficie generada, así como con los parámetros del modelo de fragmentación. Este modelo se ha implementado en el simulador de caída de bloques RockGIS que permite realizar simulaciones en 3D considerando o no la fragmentación y analizar así sus implicaciones sobre la peligrosidad en términos de multi-impacto y zona afectada. Finalmente, estos nuevos resultados en términos de peligrosidad tienen consecuencias en los análisis cuantitativos del riesgo asociados a desprendimientos rocosos., Postprint (published version)

La fragmentación en desprendimientos rocosos es un fenómeno complejo y poco comprendido que afecta a la evaluación del peligro y del riesgo. Sólo algunos modelos de simulación de caídas de rocas lo consideran explícitamente. RockGIS es un programa de simulación numérica de desprendimientos rocosos que considera la fragmentación, empleando una aproximación puntual de la masa y un modelo de rebote mediante coeficientes de restitución. Su principal innovación es la implementación del modelo de fragmentación fractal (Rockfall Fractal Fragmentation Model, RFFM) para distribuir la masa al romper los bloques. Los parámetros del modelo de fragmentación se calculan según las condiciones cinemáticas de cada impacto para reproducir diferentes escenarios de fragmentación. El funcionamiento de RockGIS ha sido verificado y validado mediante ensayos a escala real y en diversos desprendimientos rocosos naturales. En esta contribución presentamos la evolución de RockGIS en los últimos años y su aplicación a diversos casos de estudio., Este estudio ha sido desarrollado en el marco del Proyecto de Investigación “Caracterización y modelado de desprendimientos de rocas” con el acrónimo RockModels, financiado por el Ministerio de Economía y Competitividad de España, y cofinanciado por la Agencia Estatal de Investigación (AEI) y el Fondo Europeo de Desarrollo Regional (FEDER) sobre el marco del Plan Estatal de Investigación Científico-Técnica e Innovación con código de referencia BIA2016-75668-P (AEI/FEDER,UE) y el proyecto de investigación “Avances en el análisis cuantitativo del riesgo de caída de rocas (QRA) incorporando desarrollos en geomática (GeoRisk)” con referencia PID2019-103974RB-I00, financiado por MCIN/AEI/10.13039/501100 011033, Ministerio de Ciencia e Innovación (MCIN) y la Agencia Estatal de Investigación (AEI)., Postprint (published version)

En este artículo, se presenta un experimento de campo diseñado para estudiar los fenómenos de interacción termo-hidráulicos suelo-atmosfera en taludes de dos orientaciones distintas: norte y sur. El experimento consiste en un terraplén instrumentado sometido a condiciones meteorológicas naturales (radiación solar, atmosférica y del suelo, infiltración, escorrentía, evaporación, evapotranspiración y viento.). Se han obtenido series de datos de larga duración y alta frecuencia (medidas cada 5 mins durante 4 años) incluyendo variables atmosféricas, temperatura. contenido de agua, potencial del agua y flujo de calor a distintas profundidades en el suelo, Los datos se han interpretado numéricamente mediante el código Elementos Finitos (Code_Bright) que resuelve problemas acoplados termo-hidro-mecánicos e incluye una condición de contorno específica para modelar acciones atmosféricas. Los resultados del modelo numérico se pueden comparar favorablemente con las mediciones y proporcionan valiosas informaciones sobre el efecto de la orientación de la ladera para su respuesta frente a acciones climáticas presentes y futuras., El estudio fue financiado por el proyecto de investigación nacional “Slope mass-wasting under climate change” (smucphy.upc.edu) otorgado por el Gobierno de España (número de referencia del proyecto BIA 2015-67500-R) y cofinanciado por AEI/FEDER, UE., Postprint (published version)

La evaluación del riesgo y el diseño de medidas de protección frente a desprendimientos de rocas requieren la predicción de las posibles trayectorias de los bloques susceptibles de desprenderse, así como la velocidad y la energía de llegada a las zonas que se deban proteger. Considerar la fragmentación introduce desafíos adicionales al modelado, tales como la energía disipada durante la fragmentación y la distribución de la energía restante entre los nuevos fragmentos. Para aclarar algunos de estos puntos se realizó un experimento a escala real, en el que se observaron las trayectorias de 16 bloques y de los fragmentos generados tras el impacto, empleando tres cámaras de video de alta velocidad. Para determinar la posición espacial de los bloques, hemos desarrollado un programa que permite calcular las velocidades, los momentos lineales, las energías en el instante anterior y posterior al impacto y, finalmente, los coeficientes de restitución asociados al impacto, Peer Reviewed, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els països, Postprint (published version)

Fragmentation is a common feature of rockfall that exerts a strong control on the trajectories of the generated blocks, the impact energies, and the runout. In this paper, we present a set of four real-scale rockfall tests aimed at studying the fragmentation of the rocky blocks, from the global design of the field procedure to the data analysis and the main results. A total of 124 limestone, dacite, or granite blocks ranging between 0.2 and 5 m3 were dropped from different heights (8.5 to 23.6 m) onto four slopes with different shapes (single or double bench) and slope angles (42º to 71º). The characteristics of the blocks, in particular the size, surface texture and joint condition, were measured before the drops. The trajectories of the blocks and both the initial and the impact velocities were tracked and recorded by means of three high-speed video cameras. A total of 200 block-to-ground impacts have been studied. On average, 40% of the blocks broke upon impact on the slope or on the ground, making it necessary to measure the fragments. The initial and final sizes of the blocks/fragments were measured by hand with tape, though photogrammetric techniques (UAV and terrestrial) were also used for comparison purposes. The information gathered during the field tests provides a deep insight into the fragmentation processes. On the one hand, the high-resolution slow-motion videos help to describe when and how the block breakage takes place and the spatial distribution of the pieces. On the other hand, it is possible to compute the block trajectories, the velocities, and the energy losses using videogrammetry. The results include, for instance, a block average fragmentation of 54% and 14% for the limestone and granitoids, respectively; the systematic inventory of the size fragments, which may be used for fitting the power law distributions; and after each breakage, the total angle of aperture occupied by the fragments has been measured, with values in the range 25º–145º., The authors acknowledge the support of the Spanish Ministry of Economy and Competitiveness for the research projects RockRisk (BIA2013-42582-P), RockModels (BIA2016-75668-P, AEI, ERDF/FEDER, UE) and GeoRisk (PID2019-103974RB-I00/AEI/10.13039/501100011033). GeoRisk is funded by the Agencia Estatal de Investigación (AEI) on the framework of the Plan for Scientific-Technical Research and Innovation. The support of the Spanish Ministry of Education (grants to the second and third authors, codes FPU13/04252 and BES-2014-069795, respectively) and the BBVA Foundation (thirteenth author’s contract) is also appreciated. The collaboration of Canteras Hermanos Foj and Canteras Ponderosa S.A., Marc Janeras, and S. Moreno is greatly acknowledged. Finally, we thank two anonymous reviewers and the Editor who helped to improve the structure and content of the final version. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature., Peer Reviewed, Postprint (published version)

The Gloria storm rainfalls affected Catalonia from 20 to 23 January 2020 and triggered multiple landslides, some of which affected buildings and infrastructures (such as roads and railways). This paper presents the rainfall and landslide datasets collected during the event, and evaluates the performance of a regional landslide early warning system (LEWS) during the Gloria storm applying a fuzzy verification method. The majority of the inventoried landslides can be classified as slides, involving a limited volume of sediment (up to 10 m3), and were triggered in cut slopes along linear infrastructures. Rainfall accumulations were significant in the whole region, especially in the Montseny area, where over 450 mm were registered in 96 h. Generally, the LEWS computed moderate and high warnings in the areas where large rainfall amounts were recorded, and showed good correspondence with the locations where landslides were reported. The fuzzy verification method has been applied using neighbouring windows of different sizes to obtain scale-dependant information on the LEWS performance. The skill of the LEWS considerably improves when enlarging the neighbouring window size from 500 m to 1 km., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The first author is supported by a grant from the Secretariat of Universities and Research of the Ministry of Business and Knowledge of the Generalitat de Catalunya. This work has been partly funded by the EC H2020 project ANYWHERE (DRS-01–2015–700099) and the Spanish national projects SMuCPhy and EROSLOP (BIA 2015–67500-R and PID2019–104266RB–I00/AEI/)., Peer Reviewed, Postprint (published version)

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-021-01775-6, It is widely accepted that future environmental changes will affect rainfall-induced shallow slides in high-mountain areas. In this study, the Val d’Aran region located in the Central Pyrenees was selected to analyze and quantify the impacts of land use and land cover (LULC) and climate changes on regional landslides susceptibility. We analyzed 26 climate models of the EURO-CORDEX database focussing on the future rainfall conditions. The IDRISI TerrSet software suite was used to create the future LULC maps. These two inputs were analyzed individually and in a combined way defining 20 different scenarios. All these scenarios were incorporated in a physically based stability model to compute landslides susceptibility maps. The results showed that both environmental conditions will considerably change in the future. The daily rainfall will increase between 14 and 26% assuming a return period of 100 years. This intensification of precipitation will produce an overall decrease of the stability condition in the study area. Regarding the LULC prediction, the forest area will significantly increase, while in particular grassland, but also shrubs decrease. As a consequence, the overall stability condition improves, because the root strength is higher in forest than in grassland and shrubs. When we analyzed the combined impacts, the results showed that the positive effect of LULC changes is larger than the negative influence of rainfall changes. Hence, when combining the two aspects in the future scenarios, the stability condition in the study area will improve., This study was funded by the national research project EROSLOP (PID2019-104266RBI00/AEI/10.13039/501100011033) of the Spain Government. Zizheng Guo acknowledges the financial support of China Scholarship Council for his research at UPC BarcelonaTECH, and Fundamental Research Funds for National Universities, China University of Geosciences (Wuhan)., Peer Reviewed, Postprint (author's final draft)

Fatal landslides are a widespread geohazard that have affected millions of people and have claimed the lives of thousands around the globe. A change in climate has significantly increased the frequency and magnitude of rainfall, which affect the susceptibility of slopes to shallow landslides. This paper presents a methodological framework to assess the future changes in extreme and seasonal rainfall magnitudes with climate model projections. This framework was applied to project summer rainfall over Wanzhou County, China, using an ensemble of four regional climate models (RCMs) from the East Asian domain of the Coordinated Downscaling Experiment (CORDEX) under the Phase 5 Coupled Intercomparison Modeling Project (CMIP5). The results find that extreme daily rainfall was projected to decrease in the mid-21st century, with an uncertainty measured by a coefficient of variation between 5% and 25%. The mean seasonal rainfall is projected to increase in the mid-21st century up to a factor of 1.4, and up to a factor of 1.8 in the late-21st century. The variation in the mid21st century ranged from 10% to 35%, and from 30% to 50% in the late-21st century. This case study delivered a proof-of-concept for a methodological framework to derive shallow landslide-triggering rainfall scenarios under climate change conditions. The resulting spatially distributed climate change factors (CCFs) can be used to incorporate future rainfall scenarios in slope susceptibility models and climate impact assessments., Peer Reviewed, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (updated version)

The effect of climate change on soil loss processes in mountainous areas represents a current and critical problem. In this work, this issue is addressed through the analysis of the stability of different types of slopes subjected to climatic actions by 1D thermo-hydraulic numerical modeling and the infinite slope approach. The study aims to establish an average value of the safety factor, its variance and the probability of failure for the conditioning factors. The atmospheric values incorporated in the stability calculations are from regional climate change predictive models. The correlation data considers the most appropriate climate change projection for our study area located in the Central Pyrenees (Spain). Current reports, when considering the Mediterranean area, predict a rise in temperature up to 4.8 ° C for the largest projections of greenhouse gas emissions, which influence thermal flux and heat transfer patterns and mass storage processes, hydraulic conductivity values, changes in saturation degrees and liquid pressures. While the rainfall in the winter season decreases, the intensity and duration remain through all stability analysis as one of the parameters with the greatest influence of all climatic factors, by directly intervening in the increase in pore fluid pressures. The application of an infinite slope model for the analysis of the safety factor allows a stability analysis when evaluating the responses of the numerical model Code Bright. Code Bright incorporates the problem of flow and balance of water, air and energy, and the reaction to atmospheric scenarios for different soil types and the thermal and hydraulic properties that influence the development of the slope failure. The evolution of the safety factors related to the atmospheric variables describes the components of the instability and the sensitivity of the constitutive parameters of the soil. Other factors such as heterogeneous resistances within the coupled model allow us to describ, We thank the entire team of the SMuCPhy project and its funding by the Spain Government (BIA 2015-67500-R) and AEI/FEDER, UE, and supported partially by the SENACYT Foundation – Panama., Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (published version)

The instrumental monitoring of torrential catchments is a fundamental research task that provides necessary information to improve our understanding of the mechanisms of debris flows. While most monitoring sites include meteorological sensors and analyze the critical rainfall conditions, very few contain soil moisture measurements. In our monitoring site, the Rebaixader catchment, 11 debris flows and 24 debris floods were detected during the last 9 years. Herein, the initiation mechanisms of these torrential flows were analyzed, focusing on the critical rainfall conditions and the soil water dynamics. Comparing the temporal distribution of both rainfall episodes and torrential flows, the Kernel density plots showed maximum values for rainfalls at the beginning of June, while the peak for torrential flows is on July 20. Thus, the antecedent rainfall, and especially the soil moisture conditions, may influence the triggering of torrential flows. In a second step, a new updated rainfall threshold was proposed that included total rainfall duration and mean intensity. The analysis of soil moisture data was more complicated, and no clear trends were observed in the data set. Therefore, additional data have to be recorded in order to quantitatively analyze the role of soil moisture on the triggering of torrential flows and for the definition of thresholds. Some preliminary results show that the soil moisture at the beginning of a rainfall event affects the maximum increase of soil moisture, while a slight trend was visible comparing the initial soil moisture with the necessary rainfall amount to trigger a torrential flow., The study is funded by the national research project called “Slope 260 mass-wasting under climate change (SMuCPhy)” granted by the Spain Government (project reference number BIA 2015-67500-R) and co-funded by AEI/FEDER, UE. We thank the reviewers for their comments, which significantly improved the quality of the manuscript., Peer Reviewed, Postprint (author's final draft)

The understanding of the conditioning factors and of the mechanisms involved in rockfalls are requirements for a successful risk assessment and for the prevention of future events. In that respect, the detailed documentation of past event may contribute to this goal. This communication presents methodologies based on UAV surveys to collect detailed documentation of a rock failure as fast as possible to allow the opening of the affected road. The Castell de Mur rock mass failure was a catastrophic mass movement involving around 18.000 m3 and causing 2 fatalities. We use this case to show the possibilities of immediate UAV surveys to create products and models to characterize and document a rock mass failure. The photogrammetric products (orthophoto, Digital Elevation Model, 3D Point cloud and 3D texturized mesh) are used to characterize the rock failure obtaining: high-resolution topographic maps; the block size distribution of fragments in the deposit; the total mobilized volume estimated; the distribution of rock bridges from scar image analysis; and finally, the identification of the involved joint sets and interpretation of the failure mechanism. These products may be used to characterize the failure and to identify the key features for subsequent stability analysis. The realization of the UAV flight has allowed us to collect detailed information about the failure scar and the rockfall debris that would otherwise have been lost after the clean-up of the site and implementation of the remedial works., This study was supported by the ROCKMODELS research project (BIA2016-75668-P, AEI/FEDER.UE) funded by the Spanish Ministry of Economy and Competitiveness. We are grateful to the Road Department of the Diputació de Lleida, for all the support provided., Postprint (published version)

El uso de técnicas geomáticas y modelos 3D del terreno en el estudio de riesgos naturales se ha incrementado notablemente en las últimas décadas. En este trabajo nos centramos en la caracterización de discontinuidades del macizo rocoso, con el objetivo de identificar el volumen de salida potencialmente inestable, necesario para evaluación de la peligrosidad de los desprendimientos rocosos. La zona de estudio es Pala de Morrano (PN Aigüestortes). A partir de vuelos fotogramétricos desde plataformas aéreas (RPAS y helicóptero) se generaron dos modelos 3D y un tercero desde cobertura terrestre. Se completaron los datos con un TLS (Terrestrial Laser Scanning), que se asumió como ground truth. La caracterización se realiza mediante el plugin Fast Marching de Cloud Compare, sobre estos modelos. Los modelos generados tienen una notable completitud, mayor al 95%, destacando la combinación de terrestre y helicóptero sin apenas oclusiones (98%). Se concluye que para el objetivo fijado de la obtención de las familias de discontinuidades todos los modelos fotogramétricos son válidos, destacando que el generado por fotogrametría terrestre es el que presenta mayor similitud con el obtenido con el TLS, siendo el óptimo en base a su coste-beneficio, seguido del generado por fotogrametría desde multicóptero, Peer Reviewed, Postprint (published version)

Rainfall-induced landslides represent an important threat in mountainous areas. Therefore, a physically-based model called “Fast Shallow Landslide Assessment Model” (FSLAM) was developed to calculate large areas (>100 km2 ) with a high-resolution topography in a very short computational time. FSLAM applies a simplified hydrological model and the infinite slope theory, while the two most sensitive soil properties regarding slope stability (cohesion and friction angle) can be stochastically included. The model has five necessary input raster files including information of soil properties, vegetation, elevation and rainfall. The principal output is the probability of failure (PoF) map. The Principality of Andorra was selected as case study, where FSLAM was successfully applied and validated using the existing landslide inventory. The PoF raster file of Andorra (including 19 million cells) was calculated in only 2 min. Therefore, an accurate calibration of the input parameters was easy, which strongly improved the final outcomes., Peer Reviewed, Postprint (author's final draft)

Fragmentation in rockfalls reduces the size of the blocks and increases the number of fragments. It affects the runout and the impact energies, having implications in the associated hazard and therefore in the subsequent risk. In some rockfall events, a young debris cover is formed during the first impacts, with a substantial reduction of the particle size. The large number of small particles generated in the debris cover suggests that beside the breakage of the particles, comminution by crushing and grinding may also occur during the impact. This contribution presents the results of the comminution tests carried out in the laboratory.A set of one, three and five stacked bricks of different colors were released. The tests aim at verifying and quantifying the following hypotheses for the brick located in the lower position of the stack: i) the fragments generated should be smaller, ii) the number of fragments generated should increase, and iii) both effects should intensify as the number of the stacked bricks increases. A total of 78 reduced scale tests were carried out using a set of stacked bricks that were dropped from a height of 4.26 m. The resulting fragments were separated by colors according to their initial position in the stacking and sieved obtaining the grain size distribution. A high-speed camera was used to record and interpret each test. A 3D photogrammetric reconstruction after each test was generated to register the final deposit. The obtained grain size distributions confirm the proposed hypothesis. Confinement reduces the maximum fragment size while increases substantially the total number of generated fragments and those effects increase with the number of stacked bricks., Postprint (published version)

The analysis of the impacts of future environmental changes on rainfall-induced landslides is of great importance. Recent studies have shown that these changes will affect the frequency and magnitude of shallow slides and debris flows. In this study, we focused on the effects of climate changes as well as land use and land cover (LULC) changes on rainfall-induced slope failures at regional scale. A newly developed physically-based susceptibility model was applied and the Val d’Aran area, located in the Central Pyrenees (Spain), was selected as study site. First, the catastrophic landslide episode, which affected the Val d’Aran area in June 2013, was used for a preliminary validation of the susceptibility model. Then, the future LULC changes until the end of the 21th century were simulated in the study area and incorporated in the regional landslide model. The results revealed an overall increase of stability in the future, because of the larger area of forest and the consequent higher cohesion due to augmented root strength. In the next step, the impacts of future climate changes were calculated including a higher rainfall intensity. We assumed an increase of 15%, which corresponds to the last findings obtained from the ensemble of regional climate models using RCP 4.5 and 8.5 scenarios. This increase in rainfall intensity produced a reduction of the overall slope stability in the study area. However, comparing the effects produced by LULC and rainfall changes revealed that the LULC changes have a greater influence than the changes related to the rainfall conditions. This means that the overall stability in the study area slightly improves in the future. Multiples assumptions and simplifications were introduced in these preliminary calculations of the future landslide susceptibility, and additional simulations are necessary to confirm the observed trends. Nevertheless, the results seem to be coherent with the outcomes of other recent studies and give some valuable i, The study was funded by the national research project called “Slope mass-wasting under climate change” (smucphy.upc.edu) granted by the Spain Government (project reference number BIA 2015-67500-R) and co-funded by AEI/FEDER, UE., Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (published version)

The stability and erosion of natural and man-made slopes is influenced by soil-vegetation-atmosphere interactions and the thermo-hydro-mechanical slope conditions. Understanding such interactions at the source of slope mass-wasting is important to develop land-use planning strategy and to promote environmentally adapted mitigation strategies, such as the use of vegetation to stabilize slopes and control erosion. Monitoring is essential for calibrating and validating models and for better comprehending the physical mechanisms of soil-vegetation-atmosphere interactions. We approached this complex problem by means of an experimental work in a full-scale monitored embankment, which is divided into four instrumented partitions. These partitions are North or South-faced and present a bare and vegetation cover at each orientation. Our main findings show that vegetation enhances rainfall infiltration and decreases runoff, which reduces slope stability and surficial erosion, while plant transpiration induces higher suctions and hence slope stability. Concerning thermal aspects, vegetation reduces the incidence of net solar radiation and consequently heat flux. Thus, daily temperature fluctuations and evaporation decreases. However, the effect of vegetation in the development of dryer soil conditions is more significant than the orientation effect, presenting higher drying rates and states at the North-vegetated slope compared to the South-bare slope., This research was funded by the national researchs projects called “Slope mass-wasting under climate change (SMuCPhy, project reference number BIA 2015-67500-R)” and “Multiscale analysis of soil erosion in steep slopes (EROSLOP, project reference number PID2019-104266RB-I00) granted by the Ministry of Economy and Competitiveness of Spain and co-funded by AEI/FEDER, UE., Peer Reviewed, Postprint (published version)

Works carried out to monitor the displacements of the Vallcebre landslide (Pyrenees range, NE of Spain) since 1987 are presented. The landslide, which extends over an area of about 0.8 km2 and affects more than 20 × 106 m3, has experienced displacements of up to one meter per year in some points and periods. It has been periodically monitored since 1987, using a wide range of surface and in-hole techniques: triangulation with theodolite, Terrestrial Photogrammetry, Electronic Distance Measurement, GNSS-GPS, inclinometers, wire extensometers, piezometers, DInSAR (satellite) and GBSAR (terrestrial). The results obtained using new techniques are compared with those obtained with GNSS-GPS and a wire extensometer, and checked against fixed stable points. From this comparison, we conclude that even though wire extensometers and inclinometers may have the highest precision, in practice, all systems play potentially valuable roles in providing meaningful data for monitoring at different study stages. In the near future, we envisage the installation of a Distributed Fiber Optic array to monitor the risk with a certain space and time continuity. After the evaluation of the precision and advantages of the different methods, the complementary use of some of them is strongly recommended., The three decades work summarized here has been funded mainly by EC and Spanish Research Projects. In chronological order: TESLEC (Temporal stability and activity of landslides in Europe with respect to climatic change; EC; contract EV5V-CT94.0454); NEWTECH (New technologies for landslide hazard assessment and management in Europe; EC contract ENV4-CT96-0248 and Spanish CICYT contract AMB96-2480-CE); CICYT project (Cartografía de la susceptibilidad a los deslizamientos del terreno en el área del Alto Llobregat … Vallcebre mediante los SIG; Spanish CICYT contract AMB97-1091-C06); MODEVALL (Modelación hidrológico-mecánica del deslizamiento de Vallcebre; Spanish Science and Education Ministry, MEC, contract CGL2005-05282); SAFELAND (Living with landslide risk in Europe: Assessment, effects of global change, and risk management strategies; EC, 7thFP, grant agreement 226479); PYRMOVE (Research network funded by AGAUR, Government of Catalonia; grant number 2014CTP00051); PYRMOVE (Prevention and cross-border management of risk associated with landslides; funded by Interreg V-A, POCTEFA, and by the European Regional Development Fund, ERDF; project EFA364/19). The last project is still active., Peer Reviewed, Postprint (published version)

There is an increasing need for quantitative rockfall hazard and risk assessment that requires a precise definition of the terms and concepts used for this particular type of landslide. This paper suggests using terms that appear to be the most logic and explicit as possible and describes methods to derive some of the main hazards and risk descriptors. The terms and concepts presented concern the rockfall process (failure, propagation, fragmentation, modelling) and the hazard and risk descriptors, distinguishing the cases of localized and diffuse hazards. For a localized hazard, the failure probability of the considered rock compartment in a given period of time has to be assessed, and the probability for a given element at risk to be impacted with a given energy must be derived combining the failure probability, the reach probability, and the exposure of the element. For a diffuse hazard that is characterized by a failure frequency, the number of rockfalls reaching the element at risk per unit of time and with a given energy (passage frequency) can be derived. This frequency is relevant for risk assessment when the element at risk can be damaged several times. If it is not replaced, the probability that it is impacted by at least one rockfall is more relevant., We are grateful for the financial support by the French research project C2ROP., Peer Reviewed, Postprint (published version)

Real-scale fragmentation tests provide high quality data in order to study the fragmentation pattern of rock blocks. In the tests carried out, the initial rock mass, in terms of both volume and shape, was reconstructed by means of 3D photogrammetry. The fragments size distribution of the bocks tested was measured by hand using a tape. The drop tests were performed in four different sites, releasing a total of 124 blocks and measuring 2907 fragments. The obtained fragment size distributions may be well fitted using power laws. The survival rate (Sr), which is the proportion of remaining block shows a wide range of values. Observing the fragment distribution, two parameters are needed to characterize the fragmentation: the number of fragments produced and Sr. The intensity of the fragmentation is expressed by the exponent of the fitted power laws. Although the results are highly variable and show a stochastic behavior of the fragmentation, we have identified different patterns that reflect some local test conditions, This research was funded by the Spanish Ministry of Economy and Competitiveness and co-funded by the Agencia Estatal de Investigación (AEI) and The European Regional Development Fund (ERDF/FEDER, UE), grant number BIA2016-75668-P (AEI/FEDER, UE)., Peer Reviewed, Postprint (published version)

The sensitive mountain catchment of Portainé (Eastern Pyrenees, Iberian Peninsula) has recently experienced a significant change in its torrential dynamics due to human disturbances. The emplacement of a ski resort at the headwaters led to the surpassing of a geomorphological threshold, with important consequences during flood events. Consequently, since 2008, channel dynamics have turned into sediment-laden, highly destructive torrential flows. In order to assess this phenomenon and to acquire a holistic understanding of the catchment’s behaviour, we carried out a field work-based multidisciplinary study. We considered the interaction of the various controlling factors, including bedrock geology, geomorphological evolution, derived soils and coluvial deposits, rainfall patterns, and the hydrological response of the catchment to flood events. Moreover, anthropogenic land-use changes, its consequential hydrogeomorphic effects and the role of vegetation were also taken into account. Robust sedimentological and geomorphological evidence of ancient dense debris flows show that the basin has shifted around this threshold, giving rise to two different behaviours or equilibrium conditions throughout its history: alternating periods of moderate, bedload-laden flows and periods of high sediment-laden debris flow dynamics. This shifting could have extended through the Holocene. Finally, we discuss the possible impact of climate and global change, as the projected effects suggest future soil and forest degradation; this, jointly with more intense rainfalls in these mountain environments, would exacerbate the future occurrence of dense sediment-laden flows at Portainé, but also in other nearby, similar basins., Peer Reviewed, Postprint (published version)

The research focuses on the assessment of the conditions for debris flow triggering in three very active mountain catchments. The study areas are the following: Rudan torrent (Vodo di Cadore, Mount Antelao in the Dolomites, Italy), Chiesa torrent (Pieve di Livinallongo, Mount Col di Lana, in the Dolomites, Italy) and Rebaixader torrent (border between the regions of Catalonia and Aragon, Axial Pyrenees area, Spain). Due to the differences among these basins and related source areas where debris flows originate, the knowledge on the link between geomorphic conditions and driving mechanisms for debris flow activation is outlined. The study of debris flow initiation is carried out through a hydrological approach and a slope stability analysis. The hydrological analysis is supported by the calibration of intensity-duration curves of triggering rainfalls coupled with a distributed rainfall-runoff model. The analysis is corroborated using literature equations to compute critical discharges for sediment motion at the different levels of terrain deformation. The main results highlight the following: (i) a quite narrow range of triggering water discharges (0.03–0.16 m3/s) and shear stresses (267–413 N/m2), promoting a new insight on the specific hazard mitigation; (ii) the quantification of a second stage of bed breakage, in some circumstances capable of amplifying the debris flow magnitude; and (iii) a minimum critical rainfall duration needed to effectively entrain the phenomenon (12–22 min) that might help to define more precise alert conditions. Finally, the geomorphologic differences among basins revealed two main typologies in terms of driving the triggering mode: flow rate dominant in the Rudan-type basins and mixed (flow rate plus slope stability conditioned) in the Chiesa-Rebaixader-type basins., Peer Reviewed, Postprint (author's final draft)

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-020-01425-3, This work presents a prototype landslide early warning system (LEWS) adapted to real-time performance over the region of Catalonia (NE Spain). The system uses high-resolution rainfall information obtained from weather radar observations and susceptibility maps to issue a qualitative warning level at a regional scale. To study the influence of the mapping unit on the LEWS outputs, susceptibility maps obtained for Catalonia based on (i) pixels of different sizes and (ii) hydrological subbasins have been compared. The susceptibility has been derived using a simple fuzzy logic approach combining slope angle and land cover data. The susceptibility maps for the different mapping units have then been employed to run the LEWS for a period of 7 months (warm season of 2010). For each configuration, the performance, interpretability of the warnings, and computational requirements have been compared to assess the suitability of each mapping unit for their use in the LEWS in real time. The configuration using pixels of 30-m resolution as mapping units seems to be the best as a compromise between resolution, performance, and computational cost. However, from an end-user’s real-time perspective, the interpretation of the warnings can be difficult. Therefore, summarizing and visualizing the warnings, which are computed over the high-resolution grid, by subbasins is proposed as the best option., This work has been partially funded by the EC H2020 project ANYWHERE (DRS-01-2015-700099) and the Spanish project SMuCPhy (BIA 2015-67500-R). Also, the first author is supported by a grant from the Secretariat of Universities and Research of the Ministry of Business and Knowledge of the Generalitat de Catalunya., Peer Reviewed, Postprint (author's final draft)

In this paper, we present the upgraded version of RockGIS, a stochastic program for the numerical simulation of rockfalls and their fragmentation, based on a fractal model. The code has been improved to account for a range of fragmentation scenarios, depending on the impact conditions. In the simulation, the parameters of the fractal fragmentation model that define the sizes of the generated fragments were computed at each impact according to the kinematic conditions. The performance of the upgraded code was verified and validated by real-scale rockfall tests performed in a quarry. The tests consisted of the release of 21 limestone blocks. For each release, the size and spatial distribution of the fragments generated by the impacts were measured by hand and from orthophotos taken via drone flights. The trajectories of the blocks and the resulting fragments were simulated with the code and calibrated with both the volume distribution and the runout distances of the fragments. Finally, as all the relevant rockfall parameters involved were affected by strong uncertainty and spatial variability, a parametric analysis was carried out and is discussed., This work has been carried out with the support of the Spanish Ministry of Economy and Competitiveness thanks to a fellowship to the first author (BES-2014-069795) and in the framework of the research project RockModels (Ref. BIA2016-75668-P, AEI/FEDER, UE). The collaboration of Canteras Hermanos Foj (Barcelona metropolitan area, Spain) is gratefully acknowledged., Peer Reviewed, Postprint (published version)

There is intrinsic difficulty in the investigation of the largest volume of rockfalls that is expected in an area, which lies in the small number of large events, in registrable times. The maximum credible rockfall size has been associated with the properties of the rock mass discontinuities, as they delimit detachable rock blocks, and in particular with the penetration of those discontinuities that comprise rockfall sliding planes. In highly fractured rock masses, the evaluation of the penetration remains an issue. A probabilistic methodology is proposed, to measure the penetration of potential sliding planes into the interior of a rocky slope. The main hypothesis of the method is that the sliding plane persistence is interrupted along its two directions, at the intersection with two lateral discontinuity sets, as the latter displaces the former. Due to the displacement, the sliding planes are formed by quasi-planes that contain a maximum number of spacings of the intersecting joints, hence their size is restricted. The methodology requires as an input the spacing of the intersecting joint sets. Its application to a granodiorite slope confirms that for the study site, there is a maximum volume of rockfalls, excluding the possibility of large stepped failures and rupture of rock bridges. The maximum calculated persistence for the two existing sliding planes in the study site is, respectively, 28.0 m and 48.5 m. The maximum calculated sliding plane surfaces are, accordingly, 282.5 m2 and 289.3 m2. These results are compared against the observed scar dimensions at the study site, which have been retrieved alternatively, by processing a LiDAR point cloud. The results from the two alternative sources are similar, indicating that the methodology can be efficiently used to assess the sliding plane persistence and the expected maximum rockfall magnitude at the study site., Peer Reviewed, Postprint (published version)

The final publication is available at Springer via http://dx.doi.org/10.1007/s00603-019-01987-2, We present the performance of the rockfall fractal fragmentation model (RFFM) developed by Ruiz-Carulla et al. (Landslides 14(3):875–889. doi.org/10.1007/s10346-016-0773-8, 2017) and based on Perfect (Eng Geol 48:185–198, 1997). The RFFM combines disaggregation of the initial rock mass and breakage of the blocks. The model has been upgraded as to meet the mass balance, and to generate both a continuous decreasing and scale variant distribution of fragments volumes. The input of the model may be either a single block or a rock mass characterized by its In situ Block Size Distribution (IBSD). The measured fragment size distributions of seven inventoried rockfall events are used to calibrate the model. The results of the simulations fit well to the measured volume distributions. Our findings indicate that fragmentation is better characterized by the whole volume distribution of fragments generated and the increase of new surface area of the rock fragments. A relation has been observed between the potential energy of the first impact, the new surface area of fragments generated, and the model parameters. Although a greater number of parametric analyses and calibration exercises are required, this relation is proposed as a first approach to model rockfall scenarios., Peer Reviewed, Postprint (author's final draft)

In this work, we present a novel quantitative geographical information system-based procedure to obtain the magnitude (area) and frequency of medium to large first-time shallow slope failures. The procedure has been set up at the Barcedana Valley, in the Tremp Basin (Eastern Pyrenees). First, pixel-based susceptibility classes were defined using a slope stability index obtained with the physically based model SINMAP. The frequency calculated from the number of first-time failures recorded during the last 60 years was then assigned to each susceptibility class. We devised a procedure to estimate the size of potential failures by means of the aggregation of pixels within the boundaries of morphological slope units, optimized for the purpose. Finally, the landslide hazard was prepared using the magnitude-frequency matrix. Results show that a proper pixel clustering has been carried which avoids the generation of small groups of pixels with different susceptibility degrees within the same slope unit. For a given hill slope, the area of the cluster of pixels depends on the size of the slope unit, which is not unique as it depends on the criterion used to delineate them. Therefore, the latter is a key factor in the final results. In this study, we validated our results with the size distribution of the observed landslides. The methodology presented in this work can be applied using any susceptibility assessment method with a pixel-based output., Peer Reviewed, Postprint (published version)

The effects of land use and land cover (LULC) dynamics on landslide susceptibility are not fully understood. This study evaluates the influence of LULC on landslide susceptibility and assesses the historic and future LULC changes in a high mountain region. A detailed inventory map showing the distribution of landslides was prepared based on the 2013 episode in Val d'Aran, Pyrenees (Spain). This inventory showed that LULC clearly affected landslide susceptibility. Both the number of landslides and the landslide density triggered in grassland and meadow was highest (52% and 2.0 landslides/km2). In contrast, the landslide density in areas covered by forest and shrubs was much lower (15% and 0.4 landslides/km2, and 23% and 1.7 landslides/km2, respectively). Historical changes of LULC between 1946 and 2013 were determined by comparing aerial photographs. The results indicated that the forest and shrub areas increased by 68 and 65%, respectively; whereas grassland and scree areas decreased by 33 and 52%. Urban area also increased by 532%, especially between 1990 and 2001. Future LULC was predicted until 2097 using TerrSet software. The results showed that the forest area and urban area increased by 57 and 43%, severally; while shrubs, grassland and scree area decreased by 28, 46 and 78%, respectively. Heuristic and deterministic models were applied to create susceptibility maps, which classified the study area into four susceptibility degrees from very low to high. The maps were validated by the 2013 landslide dataset and showed satisfactory results using receiver operating characteristics curves and density graph method. Then, susceptibility maps until 2097 were calculated by the heuristic model and results revealed that landslide susceptibility will decrease by 48% for high-susceptible areas. In contrast, the areas of very-low susceptibility degree will increase 95%, while medium and low-susceptible areas will be more or less constant. This study only includes the effec, Postprint (author's final draft)

Risk mitigation for debris flows at regional scale is a challenge. Early warning systems are helpful in depicting the time and the location of future debris flows so that emergency responders can act in advance before the disaster takes place. Herein we present a prototype real-time regional early warning system for rainfall induced shallow landslides and debris flows for the region of Catalonia (northeastern Spain). The model issues a warning level combining susceptibility information and real-time rainfall triggering conditions obtained from weather radar observations and forecasts. Susceptibility maps have been derived using a fuzzy logic approach and two input variables, terrain slope and land cover. These maps have been obtained using (i) grid cells of different resolutions, and (ii) physical catchments (of first order) as terrain units. Although high resolution grid-cell maps show a more accurate representation of susceptibility over the region, maps based on catchments are more intuitive and better characterize the area affected by future debris flows. Rainfall triggering conditions are assessed by means of probabilistic intensity-duration thresholds obtained from literature. Finally, we have validated the early warning system and tested its performance for some important events from the last ten years that were either monitored in specific catchments, or were reported in unmonitored catchments. In general, the system has been able to satisfactorily forecast the time of occurrence of most of the analyzed past debris flow events., Postprint (published version)

Slopes undergoing deep-seated gravitational deformation create surface landforms that, if trenched and dated, yield critical data on slope kinematics. The northern slope of Pic d'Encampadana descends steeply 800 m down into the glaciated Valira d'Orient of Andorra and has long been known for its numerous antislope scarps (sackungen), indicative of deep-seated gravitational slope deformation (DSGSD). We excavated three trenches across antislope scarps and their adjacent troughs to date the deformation structures and to infer slope kinematics. Trough deposits have been disrupted by normal and reverse faulting, with the largest fault zone underlying the antislope scarp and dipping into the slope at 40°-80°. Trenches in the troughs expose fining-upward sequences of strata from which we interpret several cycles of: (1) episodic downdropping along graben faults and deepening of the topographic trough, (2) filling the trough with marginal colluvial and axial sag-pond sediments, followed by (3) a hiatus of soil profile development. The average time between deformation events in any one trench in the past 12–15 ka is about 3–3.5 ka. Deformation seems to have begun first in the lower part of the northern slope (1935 m elevation) about 15.3 ka, and had spread to the upper parts of the slope (2320 m) by 11.6 ka. Deformation in the lower slope ceased after 5.5 ka, but continued higher on the slope into the mid-late Holocene. The youngest deformation dated (1.4–1.6 ka) occurred in the highest trench on the slope. This pattern of younger deformation with increasing elevation has been documented at several other sites and has been ascribed to an upslope-migrating extensional stress field which originated at the base of the slope from glacial oversteepening and end-glacial debuttressing., Peer Reviewed, Postprint (author's final draft)

The monitoring of morphologic changes in high-mountain environments is an important, but complex task. Terrestrial as well as airborne laser scanning (TLS and ALS) and digital photogrammetry (DP) using Unnamed Aerial Vehicle (UAV) can determine recent variations. In contrast, changes that occurred 20 or more years ago, need generally the application of DP and historic aerial photograph. We compared these four geomatic techniques and the resulting digital elevation models (DEM) that ranged over a 70-year time span (1946–2016). The accuracy of the different models and also the effect of different cell size were analysed. The accuracy analysis of the resulting DEMs shows important drawbacks, when historic aerial photographs are used. In these DEMs, the error in elevation can be important and a detailed analysis of morphologic changes is limited. Nowadays, the combination of DP and UAV is the technique with best cost-benefit ratio, although TLS could reveal similar precision. However, the application of TLS is restrained by the complex morphology and the presence of vegetation, which produce many shadows. Finally, the erosion rate was determined in our catchment. The resulting values range between 0.06 and 0.16¿m3/m2/y, which coincides rather well with data observed in other studies., Peer Reviewed, Postprint (published version)

Debris flows represent one of the most dangerous types of mass movements, because of their high velocities, large impact forces and long runout distances. This review describes the available debris-flow monitoring techniques and proposes recommendations to inform the design of future monitoring and warning/alarm systems. The selection and application of these techniques is highly dependent on site and hazard characterization, which is illustrated through detailed descriptions of nine monitoring sites: five in Europe, three in Asia and one in the USA. Most of these monitored catchments cover less than ~10 km2 and are topographically rugged with Melton Indices greater than 0.5. Hourly rainfall intensities between 5 and 15 mm/h are sufficient to trigger debris flows at many of the sites, and observed debris-flow volumes range from a few hundred up to almost one million cubic meters. The sensors found in these monitoring systems can be separated into two classes: a class measuring the initiation mechanisms, and another class measuring the flow dynamics. The first class principally includes rain gauges, but also contains of soil moisture and pore-water pressure sensors. The second class involves a large variety of sensors focusing on flow stage or ground vibrations and commonly includes video cameras to validate and aid in the data interpretation. Given the sporadic nature of debris flows, an essential characteristic of the monitoring systems is the differentiation between a continuous mode that samples at low frequency (“non-event mode”) and another mode that records the measurements at high frequency (“event mode”). The event detection algorithm, used to switch into the “event mode” depends on a threshold that is typically based on rainfall or ground vibration. Identifying the correct definition of these thresholds is a fundamental task not only for monitoring purposes, but also for the implementation of warning and alarm systems, Peer Reviewed, Postprint (author's final draft)

The instrumental monitoring of torrential catchments is a fundamental research task and provides necessary information to improve our understanding on the mechanisms of debris flows. While most monitoring sites include meteorological sensors and analyze the critical rainfall conditions, only very few contain soil moisture measurements. In our monitoring site, the Rebaixader catchment, 11 debris flows and 24 debris floods were detected during the last nine years. Herein, the initiation mechanisms of these torrential flows were analyzed focusing on the critical rainfall conditions and the soil water dynamics. Comparing the temporal distribution of both rainfall episodes and torrential flows, the Kernel density plots showed maximum values for rainfalls at the beginning of June, while the peak for torrential flows is at July 20th. This means that highest probability of debris flows and debris floods triggering is about 1.5 months later than the one of rainstorms in the catchment. Thus, the antecedent rainfall and especially the soil moisture conditions may influence the triggering of torrential flows. In a second step, a new updated rainfall threshold was proposed including total rainfall duration and mean intensity. The analysis of soil moisture data was more complicated and no clear trends were observed in the dataset. Therefore, additional data has to be recorded in order to quantitatively analyze the role of soil moisture on the triggering of flows and for the definition of thresholds. Some preliminary results show that the soil moisture at the beginning of a rainfall event affects the maximum increase of soil moisture, while a slight trend was visible comparing the initial soil moisture with the necessary rainfall amount to trigger a torrential flow., Postprint (published version)

Transportation corridors such as roadways are often subjected to both natural instability and cut-slope failures, with substantial physical damage to the road infrastructure and threats to the circulating vehicles and passengers. In the early 2000s, the Gipuzkoa Provincial Council of the Basque Country in Spain noted the need for assessing the risk related to the geotechnical hazards of its road network, in order to assess and monitor their safety for road users. The quantitative risk assessment (QRA) was selected as a tool for comparing the risk of different hazards on an objective basis. Few examples of multi-hazard risk assessment along transportation corridors exist. The methodology presented here consists of the calculation of risk, in terms of probability of failure and its respective consequences, and it was applied to 84 selected points of risk (PoR) over the entire road network managed by the Gipuzkoa Provincial Council. The types of encountered slope instabilities that are examined are rockfalls, retaining-wall failures, and slow-moving landslides. The proposed methodology includes the calculation of the probability of failure for each hazard based on an extensive collection of field data, and its association with the expected consequences. Instrumentation data from load cells and inclinometers were used for the anchored walls and the slow-moving landslides, respectively. The expected road damage was assessed for each hazard level in terms of a fixed unit cost (UC). The results indicate that the risk can be comparable for the different hazards. A total of 21¿% of the PoR in the study area were found to be of very high risk., Peer Reviewed, Postprint (published version)

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-018-1087-9, Rockfalls are ubiquitous diffuse hazard in mountain regions, cliffs, and cutslopes, with the potential of causing victims and severely damaging buildings and infrastructures. A vast majority of detached rock masses break up when impacting the ground, generating multiple trajectories of rock fragments. In this paper, we present the quantitative risk analysis (QRA) of fragmental rockfalls. Fragmentation in rockfalls requires the redefinition of the probability of reach and the evaluation of the effect of multiple rock blocks trajectories on the exposure. An example of QRA was carried out at the Monasterio de Piedra, Spain, using RockGIS, a rockfall propagation model that takes fragmentation into account (Matas et al. Landslides 14:1565–1578, 2017). The results show that fragmentation has a significant but contrasting effect in the calculation of risk. The risk is reduced if the slope where blocks propagate is sufficiently long and gentle. The reason for this is that, compared to the unfragmented rock masses, the new fragments generated travel shorter distances with lesser kinetic energy. The effect disappears in case of large rockfalls. Conversely, the risk increases if the rock fragments propagate over steep slopes. The reason is that few blocks stop along the way while the generation of a cone of fragments increases the exposure. Our simulations also show that assuming a continuous flow of visitors or segregating the flow in groups of different number of people has only a minor influence on the results. Finally, we observed that the capability of the protection barriers to stop rockfalls of up to a few tens of cubic meters increases with fragmentation., Peer Reviewed, Postprint (author's final draft)

The objective of this work is to propose a standard classification of seismic signals generated by gravitational processes and detected at close distances (<1 km). We review the studies where seismic instruments have been installed on unstable slopes and discuss the choice of the seismic instruments and the network geometries. Seismic observations acquired at 13 unstable slopes are analyzed in order to construct the proposed typology. The selected slopes are affected by various landslide types (slide, fall, topple and flow) triggered in various material (from unconsolidated soils to consolidated rocks). We investigate high-frequency bands (>1 Hz) where most of the seismic energy is recorded at the 1 km sensor to source distances. Several signal properties (duration, spectral content and spectrogram shape) are used to describe the sources. We observe that similar gravitational processes generate similar signals at different slopes. Three main classes can be differentiated mainly from the length of the signals, the number of peaks and the duration of the autocorrelation. The classes are the “slopequake” class, which corresponds to sources potentially occurring within the landslide body; the “rockfall” class, which corresponds to signals generated by rock block impacts; and the “granular flow” class, which corresponds to signals generated by wet or dry debris/rock flows. Subclasses are further proposed to differentiate specific signal properties (frequency content, resonance, precursory signal). The signal properties of each class and subclass are described and several signals of the same class recorded at different slopes are presented. Their potential origins are discussed. The typology aims to serve as a standard for further comparisons of the endogenous microseismicity recorded on landslides., Peer Reviewed, Postprint (published version)

The analysis of seismic signals obtained from near-source triaxial accelerometer recordings of two sets of single-block rockfall experiments is presented. The tests were carried out under controlled conditions in two quarries in northeastern Spain; in the first test (Foj limestone quarry, Barcelona), 30 blocks were released with masses ranging between 475 and 11,480 kg. The second test (Ponderosa andesite quarry, Tarragona) consisted of the release of 44 blocks with masses from 466 to 13,581 kg. An accelerometer and three high-speed video cameras were deployed, so that the trajectories, velocities, and block fragmentation could be tracked precisely. These data were used to explore the relationship between seismic energy and rockfall kinetics (the latter obtained from video analysis). We determined absolute and relative values of seismic energy and used them to estimate rockfall volumes. Finally, the seismic signature of block fragmentation was assessed in both the frequency and time domains. The ratios of seismic energy after impact to kinetic energy before impact ranged between 10-7 and 10-4. These variables were weakly correlated. The use of seismic energy relative to impacting kinetic energy was preferred for the estimation of volumes. Block fragmentation impacts were dominated by higher acceleration spectrum centroid frequencies than those of nonfragmentation impacts: 56.62 ± 2.88 and 48.46 ± 4.39 Hz at Foj and 52.84 ± 12.73 and 38.14 ± 4.73 Hz at Ponderosa., Peer Reviewed, Postprint (published version)

Landslides are one of the most common and dangerous threats in the world that generate considerable damage and economic losses. An efficient landslide monitoring tool is the Differential Synthetic Aperture Radar Interferometry (DInSAR) or Persistent Scatter Interferometry (PSI). However, landslides are usually located in mountainous areas and the area of interest can be partially or even heavily vegetated. The inherent temporal decorrelation that dramatically reduces the number of Persistent Scatters (PSs) of the scene limits in practice the application of this technique. Thus, it is crucial to be able to detect as much PSs as possible that can be usually embedded in decorrelated areas. High resolution imagery combined with efficient pixel selection methods can make possible the application of DInSAR techniques in landslide monitoring. In this paper, different strategies to identify PS Candidates (PSCs) have been employed together with 32 super high-spatial resolution (SHR) TerraSAR-X (TSX) images, staring-spotlight mode, to monitor the Canillo landslide (Andorra). The results show that advanced PSI strategies (i.e., the temporal sub-look coherence (TSC) and temporal phase coherence (TPC) methods) are able to obtain much more valid PSs than the classical amplitude dispersion (DA) method. In addition, the TPC method presents the best performance among all three full-resolution strategies employed. The SHR TSX data allows for obtaining much higher densities of PSs compared with a lower-spatial resolution SAR data set (Sentinel-1A in this study). Thanks to the huge amount of valid PSs obtained by the TPC method with SHR TSX images, the complexity of the structure of the Canillo landslide has been highlighted and three different slide units have been identified. The results of this study indicate that the TPC approach together with SHR SAR images can be a powerful tool to characterize displacement rates and extension of complex landslides in challenging areas, Peer Reviewed, Postprint (published version)

Slope mass-wasting like shallow slides are mostly triggered by climate effects, such as rainfall, and soil–vegetation–atmosphere (SVA) interactions play a key role. SVA interactions are studied by a full-scale embankment with different orientations (North and South) and vegetation covers (bare and vegetated) in the framework of the prediction of climate change effects on slope stability in the Pyrenees. A clayey sand from the Llobregat river delta was used for the construction of the embankment and laboratory tests showed the importance of suction on the strength and hydraulic conductivity. Sixty sensors, which are mostly installed at the upper soil layer of the embankment, registered 122 variables at four vertical profiles and the meteorological station with a 5 min scan rate. Regarding temperature, daily temperature fluctuation at the shallow soil layer disappeared at a depth of about 0.5 m. There was great influence of orientation with much higher values at the South-facing slope (up to 55 °C at -1 cm depth) due to solar radiation. Regarding rainfall infiltration, only long duration rainfalls produced an important increase of soil moisture and pore water pressure, while short duration rainfalls did not trigger significant variations. However, these changes mostly affected the surface soil layer and decreased with depth., Peer Reviewed, Postprint (published version)

The final publication is available at Springer via http://dx.doi.org/10.1007%2Fs10346-017-0910-z, There exists a transition between rockfalls, large rock mass failures, and rock avalanches. The magnitude and frequency relations (M/F) of the slope failure are increasingly used to assess the hazard level. The management of the rockfall risk requires the knowledge of the frequency of the events but also defining the worst case scenario, which is the one associated to the maximum expected (credible) rockfall event. The analysis of the volume distribution of the historical rockfall events in the slopes of the Solà d’Andorra during the last 50 years shows that they can be fitted to a power law. We argue that the extrapolation of the F-M relations far beyond the historical data is not appropriate in this case. Neither geomorphological evidences of past events nor the size of the potentially unstable rock masses identified in the slope support the occurrence of the large rockfall/rock avalanche volumes predicted by the power law. We have observed that the stability of the slope at the Solà is controlled by the presence of two sets of unfavorably dipping joints (F3, F5) that act as basal sliding planes of the detachable rock masses. The area of the basal sliding planes outcropping at the rockfall scars was measured with a terrestrial laser scanner. The distribution of the areas of the basal planes may be also fitted to a power law that shows a truncation for values bigger than 50 m2 and a maximum exposed surface of 200 m2. The analysis of the geological structure of the rock mass at the Solà d’Andorra makes us conclude that the size of the failures is controlled by the fracture pattern and that the maximum size of the failure is constrained. Two sets of steeply dipping faults (F1 and F7) interrupt the other joint sets and prevent the formation of continuous failure surfaces (F3 and F5). We conclude that due to the structural control, large slope failures in Andorra are not randomly distributed thus confirming the findings in other mountain ranges., Peer Reviewed, Postprint (author's final draft)

Debris flows that involve loess material produce important damage around the world. However, the kinematics of such processes are poorly understood. To better understand these kinematics, we used a flume to measure the kinematics of debris flows with different mixture densities and weights. We used sensors to measure pore fluid pressure and total normal stress. We measured flow patterns, velocities, and depths using a high-speed camera and laser range finder to identify the temporal evolution of the flow behavior and the corresponding peaks. We constructed fitting functions for the relationships between the maximum values of the experimental parameters. The hydrographs of the debris flows could be divided into four phases: increase to a first minor peak, a subsequent smooth increase to a second peak, fluctuation until a third major peak, and a final continuous decrease. The flow depth, velocity, total normal stress, and pore fluid pressure were strongly related to the mixture density and total mixture weight. We defined the corresponding relationships between the flow parameters and mixture kinematics. Linear and exponential relationships described the maximum flow depth and the mixture weight and density, respectively. The flow velocity was linearly related to the weight and density. The pore fluid pressure and total normal stress were linearly related to the weight, but logarithmically related to the density. The regression goodness of fit for all functions was >0.93. Therefore, these functions are accurate and could be used to predict the consequences of loess debris flows. Our results provide an improved understanding of the effects of mixture density and weight on the kinematics of debris flows in loess areas, and can help landscape managers prevent and design improved engineering solutions., Peer Reviewed, Postprint (published version)

Rockfalls are frequent natural processes in mountain regions with the potential to produce damage. The quantitative risk analysis (QRA) is an approach increasingly used to assess risk and evaluate the performance of mitigation measures. In case of the fragmentation of the falling rock mass, some of the hypothesis taken in the QRA estimation for rockfalls have to be modified since a single block or rock mass can produce several fragments thus modifying the runout probability, the impact energies and exposure of the elements at risk. In this contribution, we present a procedure to account for the exposure in QRA analysis along linear paths using the fragmental rockfall propagation model RockGIS (Matas et al. 2017). The procedure is applied at the “Monasterio de Piedra”, Spain as part of a QRA., Postprint (published version)

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-018-1000-6, The debris flow (DF) and debris flood (DFD) activity in the Rebaixader catchment (Spanish Pyrenees) is analyzed in this study. The research is focused on how precipitation leads to the triggering of torrential floods and influences the sediment availability during the recharge period, in a supply-unlimited catchment. Two kinds of correlations are studied: (1) the correlation between the rainfall features (intensity and kinetic energy) and the DF/DFD triggering and (2) the correlation between the hyetograph and the DF/DFD volumes. The tested hypothesis was that a greater amount of rainfall during the recharge period would produce a greater DF/DFD volume. The period between two consecutive DF/DFD events is processed using a variable, the Erosion Index, originally developed for the Universal Soil Loss Equation. This analysis considered the rainfall time series and 22 DF/DFD events registered during the period 2009–2015. The results show that the precipitation of the recharge period does not seem to have a strong influence on the mobilized volumes. In many cases, a second DF/DFD event was triggered soon after the previous event, which highlighted the role of the first event in creating an unstable state of the catchment. Additionally, a threshold relationship between the kinetic energy of the rainfall event and the maximum rainfall intensity for a 30-min period seems to be a good criterion to discriminate between triggering and non-triggering rainfall events. The results show no clear trends with which to forecast the sediment volume from precipitation, weakening the role of rainfall characteristics in determining the return period of mobilized sediment volumes in catchments similar to the Rebaixader torrent., Peer Reviewed, Postprint (author's final draft)