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Freeze-thaw cycles and rainfall as triggering factors of mass movements in a warm Mediterranean region: The case of the Tramuntana Range (Majorca, Spain)
Abstract
Between 2008 and 2010, the island of Majorca (Spain) experienced the coldest and wettest winters of the last 40 years. Accumulated
rainfall was twice the average and values of intense rainfall up to 296 mm/24 h were recorded, very similar to those calculated
for a return period of 100 years. Additionally, high precipitation coincided with anomalous, low temperatures, with abundant
snowfall and freezing in the highest zones of the Tramuntana Range, in the northwest sector of the island. As a result, 34
mass movements were recorded on the range, which seriously affected the road network in an area of great importance for tourism,
as it welcomes 8.5 million visitors each year. Fourteen rockfalls, 1 rock avalanche, 15 landslides and 4 karstic collapses
were inventoried. The geological structure, formed by a series of NW overlapping thrusts, determines the distribution as well
as the failure pattern of the movements. Thus, the northern face of the range registered 68% of the mass movements: nine rockfalls
with planar failure took place as well as all the landslides recorded. Likewise, south-facing slopes have been affected by
longer runout rockfalls with a wedge-type failure. The thorough analysis of the meteorological data shows that most of the
movements have taken place after antecedent rainfall over 800 mm. Additionally, the rockfalls have also occurred after several
freeze–thaw cycles, being a determining and unusual factor in this warm region. Intense rainfall >90 mm/24 h also caused rockfalls
as well as exceptional very intense rainfall >120 mm/24 h caused landslides. The results aim to contribute to the design of
an early warning system coordinating emergency, infrastructure services and meteorological centres in a region of high risk.
... The most significant took place in the Pyrenees in 1937Pyrenees in , 1940Pyrenees in and 1982 in the Cantabrian range in 1983, and in the Baetic ranges in the winter of 1996-1997, all of them were related to unusual and abundant precipitations (Corominas 2006). Finally, another abnormal situation took place in Majorca (Balearic Islands) for the period spanning from 2008 to 2010, when a combination of persistent and intense precipitations caused a large number of slope failures (Mateos et al. 2012). ...
... In the Tramuntana Range, short torrents with small drainage basins characterise the region. Taking into account the predominance of limestone lithologies, karstic aquifers and numerous water springs (around 700) characterise the hydrogeological behaviour of this region (Mateos et al. 2012). ...
... There is no evidence in the historical record (Mateos 2006) of any similar event, not only for the number of events but also for their magnitude. Mateos et al. (2012) carried out a thorough analysis of the landslides/rockfalls triggered during this period and their relationship with meteorological data. As a general overview, they report for this period values of accumulated rainfall twice the average and values of daily rainfall up to 300 mm. ...
In the present work, spectral analysis has been applied to determine the presence and statistical significance of climate cycles in long-term data series from different rainfall and gauging stations located in the Tramuntana Range, in the north-western sector of the island of Majorca. Climate signals recorded previously in the Mediterranean region have been identified: the ENSO, NAO, HALE, QBO and Sun Spot cycles as well as others related to solar activity; the most powerful signals correspond to the annual cycle, followed by the 6-month and NAO cycles. The incorporation of data derived from gauging stations contributes to better climate signal detection as local and exceptional influences are eliminated. Simulations have been performed for each rainfall/gauging station, using the most significant climate cycles obtained by means of the power spectrum. A good correlation between rainfall/flow values and simulated cycles has been obtained. The NAO and ENSO cycles are the most influential in the rainy periods, and specifically the NAO cycle, where a good correlation between episodes of high rainfall/flow and high values of ANAOI can be observed. At a second stage, landslides dated and recorded in the Tramuntana Range since 1954 (174 events) have been correlated with the simulated cycles obtaining good results, as the landslide events match rainfall peaks well. The correlation for the past decade (since 2005), when a detailed landslide inventory is available, also reveals a coincidence between landslide events and climate cycles, and specifically NAO and ENSO cycles. That is the case of the period 2008-2010, when numerous mass movements took place, and when the largest movement of the inventory was recorded. Results show a potential rainy period in the Tramuntana Range for the coming years (with maximum values around year 2021) when conditions similar to those related to the 2008-2010 event, could take place again. The methodology presented in this work can contribute to the prediction of temporal, extreme hydrological events in order to design short/medium-term mitigation strategies on a regional scale.
... La Serra de la Tramuntana se localiza en la parte noroeste de la isla ( Fig. 1) y se caracteriza por presentar una topografía escarpada, lo que junto con su complejidad geológica y un clima mediterráneo, favorece que se produzcan frecuentes movimientos de ladera (Mateos y Azañón 2005). En este sentido, los desprendimientos de roca son el tipo de movimiento de ladera más común en la Serra de la Tramuntana (Mateos et al., 2012), debido al predominio geológico de macizos rocosos jurásicos compuestos principalmente por calizas y dolomías. Así, históricamente, existen multitud de registros de desprendimientos rocosos acontecidos en la Serra. ...
... Como resultado de esta particular situación climatológica, se registraron 34 movimientos de ladera que afectaron seriamente a la red de carreteras, así como a zonas urbanas. El inventario para este periodo incluye: 14 caídas de roca, 1 avalancha de rocas, 15 deslizamientos de tierra y 4 colapsos kársticos (Mateos et al., 2012). En este trabajo se describe el desprendimiento acontecido en el Puig de Son Poc, situado en la zona sur de la Serra de la Tramuntana (municipio de Bunyola) el 6 de marzo de 2013. ...
... La mayor parte de las caídas de rocas que ocurren en la Serra de Tramuntana son provocadas por: (a) Lluvias intensas concentradas en cortos periodos de tiempo, estimándose un umbral desencadenante en torno a 90 mm por 24 h (Mateos et al., 2007); (b) Tras la ocurrencia de varios ciclos de hielo-deshielo previos a la rotura, cuando el macizo rocoso se encuentra 5 parcialmente saturado en agua, rellenando las grietas y diaclasas (Mateos et al., 2012). ...
Estabilidad de taludes en rocas y análisis de desprendimientos Análisis del desprendimiento rocoso de Son Poc (Mallorca) mediante modelización 3D RESUMEN En el municipio de Bunyola, situado en la cara sur de la Serra de Tramuntana de la isla de Mallorca, y después de un periodo de intensas lluvias y bajas temperaturas, se produjo, en la mañana del 6 de marzo de 2013, un desprendimiento rocoso en el Puig de Son Poc (493 m). El evento, de tipo vuelco, provocó la movilización de un volumen aproximado de 4000 m 3 de roca, el cual, y posteriormente al impacto, se fragmentó en numerosos bloques que se desplazaron a lo largo de la ladera. Las trayectorias seguidas por los bloques con dirección SE alcanzaron varias viviendas produciendo graves daños materiales. Para realizar el análisis del desprendimiento rocoso, se ha utilizado el software RocPro3D para determinar y reproducir las trayectorias seguidas por los bloques en 3-dimensiones, las velocidades estimadas y las energías alcanzadas, así como las alturas, impactos y los puntos de parada o máximo alcance.
... Are particularly susceptible the outcrops of Cretaceous and Eocene flysch in the Basque Country due to the unfavorable arrangement of the layers and the low strength marls of facies Keuper in Asturias. Similarly, large instabilities have been generated in the northern coast of Majorca, Balearic Islands ( Figure 10.4) (Mateos 2012;Mateos et al., 2013a). ...
... In this region, the maximum precipitation takes place during the autumn months due to the arrival of the first high cold air masses, which contrast with the high temperature retained by the sea. This phenomenon is known as "gota fría'' (cold air pool), in which heavy storms are accompanied by intense rainfall with episodes of up to 300 mm in 24 hours (Mateos, 2012). ...
... Additionally, high precipitation coincided with anomalous, low temperatures and freezing in the highest zones of the range. As a result, 34 mass movements were recorded on this region (Mateos et al., 2012). Most of the rockfalls started in rocky massifs when there were several freeze-thaw cycles in the days prior to the failure, when the temperature hovered at around 0 • C, regardless of whether the maximum daily rainfall were overly intense (around 30 mm). ...
In Spain, landslides are phenomena mostly concentrated in the mountainous areas and
coastal cliffs. Even though many of them have a natural origin, the activity in some
locations has increased as a result of changes in land use and due to excavations. The
increasing use of mountainous areas for tourism, has led to an unusual frequentation in
clearly unstable areas. New roads and human settlements are spreading towards places
in which slides, rockfalls and other type of movements occur relatively frequently, thus
increasing the risk to population. Climate change is expected to produce the increase
of temperatures in the Iberian Peninsula. The future rainfall pattern is, however, still
uncertain. Despite of this, all models predict an increase of the intense precipitation
events across the whole country with the subsequent occurrence of debris flows and
shallow landslides.
... Weathering may be composed of different origins according to the physical nature of rock, geological structure of the rock mass, existence of rock joints and fractures, climatic zone, etc. (Javey 1972;Clark and Small 1982;Derruau 1996;Matsuoka 2008). In the case of rocky cliffs in mountainous areas, field observations suggest that freezing is a prominent phenomenon (Fahey and Lefebure 1988;Wegmann and Gudmundsson 1999;Frayssines and Hantz 2006;Amitrano et al. 2010Amitrano et al. , 2012Mateos et al. 2012). In 1666, the destructive power of ice formation was revealed by Huygens (1666) who succeeded in bursting a gun barrel filled with liquid water by winter freezing. ...
... During the formation of ice crystals, molecules are arranged in a regular hexagonal lattice with hydrogen bonds (Berthier 1958;Teixeira 2001), with a distance between molecules that makes the network less compact than the liquid state. The specific volume of ice is well above that of liquid water (Lliboutry 1964) and the corresponding volume increase is about 9 % at atmospheric pressure. This basic data was used in different ways to estimate the stress generated by freezing in materials. ...
... The solution to this problem can be deduced from the classical solutions in linear elasticity for displacement and stress fields in a hollow sphere (Pouya 1991;Salençon 2002). Lliboutry (1964) developed a model based on the same idea but replacing the infinite elastic matrix, in an approximate way, by some elastic interaction of the ice and the walls of the rock crack, and taking also into account the air initially dissolved in water and freed during the freezing process. The estimations obtained by these two models are given in Table 1, with the parameters for ice and rock (limestone) defined in Table 2. ...
In mountainous areas, freezing is a prominent phenomenon for weathering processes in rock walls. A freezing front penetrates rock crack networks and causes its propagation. To study the evolution of rock mass stability, a suitable model of stress generated by freezing in open rock cracks is needed. This stress evaluated by the simple volume expansion model in a closed crack is too high to be realistic. In this paper, we present an assessment method for this stress and some results. Different experiments on notched limestone specimens submitted to freeze–thaw cycles were performed. Three different tight limestones (Larrys, Chamesson, Pierre de Lens) were tested. Actually, the stress generated by freezing begins to grow at the top of the notch where an ice plug is created and makes it possible for higher stresses to develop in deeper parts of the notch. Consequently, the stress induced by freezing depends on the geometry of the open crack represented by the notch. This value is, however, limited by the permeability of the surrounding rock matrix. A model of the stress evolution generated by freezing along an open crack was established and its envelope curve, named maximum stress, was parameterized. This maximum stress generated by freezing along the crack is completely defined by knowledge of the pore network of the limestone matrix and the geometry of the crack.
... For rock that contains natural fractures (e.g., veins, fissures, joints, flaws, and faults, etc.) in cold regions, the influence of repeated freeze-thaw (F-T) and disturbed stress on rock damage evolution is crucial to the long-time stability of rock structures (Mateos et al., 2012;Wang et al., 2020bWang et al., , 2020cWang et al., , 2020d. When rock mass experiences repeated F-T cycles, water-ice phase transformation occurs within the natural fractures, and rock volume will expand by 9% due to the generation of frost heaving force (Niu et al., 2019;Tan et al., 2011;Wang et al., 2020b;Zhou et al., 2019a). ...
... However, almost all those studies are focused on intact rock subjected to freezethaw treatment, and the freeze-thaw responses of the naturally fractured rocks are not well understood. Actually, it has been proved that fractures are more sensitive to freeze-thaw than rock matrix, water-ice phase transformation easily occurs within the natural fractures (Mateos et al., 2012;Tan et al., 2011). Huang et al. (2018) carried out laboratory tests on rock-like materials with a single crack under F-T and uniaxial compression conditions, and studied the crack growth characteristics and frost heaving cracking behavior. ...
The naturally fractured rock in the open pit slope is susceptible to irreversible damage caused by fatigue loads related to freeze-thaw weathering, blasting vibration, earthquakes and tramcar traffic. To ensure the safety of rock mass and reveal how natural fracture affects the damage modelling characteristics is of great concern. Hence, this work aims at investigating the fatigue damage evolution of rock from volumetric deformation caused by F-T and cyclic loads. The rock structural deterioration and damage accumulation were investigated as well as the stimulated natural fracture pattern. Results show the frost heaving force acted on natural fracture results in the rock volumetric changes. The damage variable expressed by volumetric strain presents a linear relationship with freeze-thaw cycles. In addition, the axial, lateral and volumetric strain of marble exposed to cyclic loads present a two-stage pattern, they first increase quickly and then get to steady and last for a long time. A new fatigue damage model was established by considering the freeze-thaw damage and mechanical damage simultaneously. The proposed coupling damage model can well describe rock damage accumulation. Moreover, the CT images further reveal the influence of the natural fracture on rock volumetric deformation and the final damage accumulation. It is suggested that the opening-mode natural fractures contribute a lot to rock freeze-thaw deformation and fatigue deformation.
... Hard rocks predominate, especially Jurassic limestone and dolostone, which constitute the framework of the mountains. These conditions determine frequent rockfalls, which have caused significant damage, specifically to the road network [18,30,126]. The Ma-10 road is a strategic road and constitutes the main transportation corridor on the northern face of the Tramuntana range. ...
... During the spanning period 2009-2017, the rockfall inventory collected by the Road Maintenance Service of Mallorca showed a total of 22 significant rockfalls in the area where the wildfire took place (Figure 12). Before the wildfire in 2013, 7 rockfalls were recorded in the burned section of the road between 2009 and 2013; 4 of them took place in 2010 when the island of Mallorca experienced the coldest and wettest winters of the last 40 years [126]. After the 2013 wildfire, between 2013 and 2017, a considerable increase in rockfalls was observed in the same section; a total of 15 rockfalls, which double the number of events for the pre-fire period (2009)(2010)(2011)(2012)(2013). ...
Understanding processes and conditions that lead to rockfalls during and after a wildfire in different geological contexts is crucial since this phenomenon is one of the major hazards in mountainous regions across Europe. Spain is one of the European countries with the highest rate of wildfires, and rockfalls cause high economic and social impact, with many fatalities every year. The increase of rockfalls during and after wildfires is connected with the merging of different factors, not only in the detached area but also in the propagation and potentially affected area. When wildfire occurred, many actions take place: changes in the mechanical conditions of the rocks, the loss of protective capacity from vegetation, the effect induced by firefighting activities and/or the impact by the high temperatures in the adopted protective measures. After the wildfire, there is an increase in frequency and intensity of rockfalls in the burned area, causing a major impact of rockfalls on not only road networks and built-up areas but also people living. Additionally, the removal of vegetation by wildfires causes an increase in the risk perception, related not only to detached blocks but also to the general appearance of the rock mass. In this review, the main factors that influence the occurrence of rockfalls after a wildfire are analyzed, and three actual case studies in Spain are presented to support the variety of conclusions obtained.
... These phenomena can progressively lead to the development of weak sectors within the rock mass that have the potential to evolve into failures. In fact, small-size failures usually originate from highly jointed rock masses that have been stressed by recurrent forcing, such as rainfalls and daily thermal cycles that can induce freezing and thawing events (Matsuoka and Sakai 1999;Gunzburger et al. 2005;Mateos et al. 2012;Collins and Stock 2016;Dietze et al. 2017;Matsuoka 2019). All of these factors are responsible for the accumulation of inelastic deformations within the rock mass, leading to permanent damage, i.e., the non-negligible reduction of mechanical strength. ...
... Similar outcomes were noted by Arosio et al. (2018), who analysed a three-year-long micro-seismic record collected on a limestone cliff. Regarding thermal forcing, the relevance of daily temperature variations and freeze-thaw cycles in the predisposition of rock falls has been widely documented (Mateos et al. 2012;Walbert et al. 2015;D'Amato et al. 2016). Additionally, the analysis of micro-seismic and acoustic emission datasets can help in monitoring ongoing damaging processes at a smaller scale (from metric to centimetric) (Xu et al. 2014a;Zhou et al. 2018;Colombero et al. 2018) since the inelastic strain associated with thermal oscillations is released as micro-seismic and acoustic emissions (Occhiena et al. 2012;Collins et al. 2014;Weber et al. 2018). ...
This study reports a comparative analysis of the environmental conditions and micro-seismicity recorded on a rock wall resulting from an intense meteorological event. The findings are focused on a quarry wall located in the Acuto Field Laboratory (Central Italy), where multi-parametric environmental monitoring is operating and an Artificial intelligence Camera Prototype has been placed to detect rock falls reaching a railway target. Six accelerometers were installed to detect micro-seismic events caused by the expected strong thermal transient caused by the Buran storm on February 2018. Within a few hours, a steep decrease in the average air and rock mass temperature down to 8 °C was recorded, and −4 °C and −8 °C were reached for the rock and air temperatures, respectively. A total of 103 micro-seismic events were analysed with respect to both rainfall and thermal forcing: while no correlation with rainfall was reported, the steep thermal transient was responsible for the strain effect that occurred during the heating phase of the rock mass following the Buran storm. An elastic deformation event with a maximum daily amplitude of 165 μ strain was recorded by the strain gages installed on the mm-joints due to the rock heating and cooling caused by the variation in temperature. The collected evidences show the relevance of short thermal transients in modifying stress conditions within rock masses and their relationship to a peculiar micro-seismic response. The main outcomes established the key role played by integrated monitoring systems to better understand the relationship between vibrational behaviour and environmental forcings in terms of understanding the precursors to rock failure.
... Aquesta mateixa combinació de possibles efectes, pot suposar un increment notable de danys als talussos de les obres públiques (xarxa de carreteres, ferroviària, urbanitzacions, etc.), amb majors erosions i un augment de les necessitats de manteniment. A escala major, a la Serra de Tramuntana, la relació entre pluges d'elevada intensitat i els moviments massius de sòl o de grans masses de roques ha estat estudiat a fons els últims anys [2]- [4], i alguns autors creuen que la freqüència d'aquests intensos moviments massius probablement augmentarà degut al canvi climàtic [5], [6]. A la Serra de Tramuntana, els 34 moviments massius reportats al període 2008-2010 varen suposar una situació excepcional de la que no existeixen antecedents històrics (des del segle XVII). ...
... A la Serra de Tramuntana, els 34 moviments massius reportats al període 2008-2010 varen suposar una situació excepcional de la que no existeixen antecedents històrics (des del segle XVII). Aquests moviments varen tenir lloc com a resultat de la confluència de pluges intenses (>90 mm/24 h), independentment de la temperatura, o degut a la saturació dels massissos rocosos (pluja acumulada > 800 mm) i diversos cicles de gel-desgel en els dies previs al trencament [2], el que també es relacionaria amb el possible augment de la freqüència i intensitat d'altres fenòmens meteorològics extrems (cicles gel-desgel). Aquesta elevada activitat a la Serra de Tramuntana ha seguit després del període esmentat, per exemple amb l'esllavissament de Son Poc a l'any 2013, que va suposar la caiguda de 4000 m 3 de roques [3]. ...
Versió original de l’autor* de l’apartat “4. El canvi climàtic – 4.2 Infraestructures” de l’Estudi sobre la prospectiva econòmica, social i mediambiental de les societats de les Illes Balears a l’Horitzó 2030 (CES-UIB 2019).
Aquest apartat dedicat a l’impacte del canvi climàtic a les infraestructures de les Illes Balears va ser reduït al llibre finalment publicat per falta d’espai. Es prega citar, sempre que sigui possible, el document original amb ISBN: 978-84-09-09772-2.
... Dilatation of rock mass and partial blocks, together with freeze-thaw cycles, is determined by temperature cycles (Weber et al. 2017 ). Rockfall events can also be triggered by severe rainfall (Maria et al. 2012 ) or high-velocity wind gusts (Sass 2005 ). These can be quantified using weather stations. ...
Rock mass characterization and rockfall/rock slope stability monitoring methods are one of the fastest evolving research areas in the field of geosciences. Traditionally, simple mapping, geodetical or geotechnical methods are used. The ongoing rapid development of monitoring methods is conditioned by engineering challenges when new infrastructure is nowadays being constructed in complicated geological conditions. These are represented by mountainous areas, deep gorges with steep slopes, or even active landslide sites. Traditional methods can be used within these monitoring demanding sites and bring high-quality monitoring results, sometimes with higher precision than modern state-of-art methods. This chapter reviews traditional rock slope stability monitoring methods and discusses their advantages, applicability, and strong/weak sides. Traditional methods are compared against newly introduced, modern state-of-art methods.
... During this period, the surface soil underwent a freeze-thaw cycle within one day, resulting in crisscross cracks on the slope. Freeze-thaw cracks provided an advantageous channel for the infiltration of rainfall and snowmelt (Mateos et al. 2012). ...
The Lashagou landslide group in Gansu Province, China, is a typical shallow loess landslide group caused by artificial slope cutting. In April 2018, local sliding of the landslide group damaged houses and blocked the G310 highway, leading to the relocation of the Lashagou village, which aroused widespread concern. Unfortunately, the spatiotemporal displacement characteristics and failure modes of the landslide remain unknown. In this study, a method for the estimation of two-dimensional deformation of landslides, based on the local parallel flow model, was presented. This method only needs two orbital synthetic aperture radar (SAR) images with different imaging geometries, and has high accuracy verified by global satellite navigation system (GNSS) observations. In practice, we first obtained the surface velocity and time series deformation of the ascending and descending orbits. The best-fit sliding direction and inclination of the landslide movement were then inverted by combining satellite imaging geometry and surface velocity. Furthermore, the two-dimensional deformation of the Lashagou landslide group in the sliding and normal directions was obtained. We found that the landslide was in the accelerated deformation stage during the wet season and the deformation was mainly concentrated in the northern part of the Lashagou village. The snowmelt and continuous rainfall were the main factors in the landslide deformation. In addition, the landslide surface displacement characteristics and deep stress states can be linked using a combination of two-dimensional deformation, combined deformation, and inclination, which provides evidence that landslide movement is controlled by one or more deep continuous structural planes. Our research shows that the two-dimensional deformation retrieval method can be applied to gravity-driven translational landslides to help prevent and mitigate landslide hazards.
... Rock failure is the main cause to many geological disasters, such as collapse, landsliding and tunnel collapse. Rock failures caused by temperature change and fatigue loading can lead to serious losses (Mateos et al., 2012;Strunden et al., 2015;Cui et al., 2022;Huang et al., 2018;Song et al., 2021). The freeze-thaw deterioration (Nicholson et al., 2000;Bayram, 2012;Freire-Lista et al., 2015;Ghobadi et al., 2015;Gao et al., 2020;Wang et al., 2021;Li et al., 2022) and fatigue (e.g. ...
Acoustic emission and thermal infrared signals are related to the process of rock breaking. In this paper, the acoustic emission and thermal infrared signals of rock are obtained during the loading process of indoor granite freeze-thaw cycle test and uni-axial compression test. Then the acoustic emission signals sent out during rock breaking are analyzed by short-time Fourier transform to get the peak frequency. infrared radiation thermographic sensor is applied to monitor and record the temperature change on the surface of rock so as to get the influence of thermal infrared radiation characteristics during rock materials deformation and breaking. Under the same axial stress, the samples passing through more freeze-thaw cycles have higher surface temperature. Both acoustic emission and thermal infrared temperature show that tensile failure is the main failure factor to granite samples. As freeze-thaw effect results in more micro fissures inside rock, the granite samples develop in the tendency of large breakage increases and small breakage decreases. This phenomenon shows that freeze-thaw cycle could restrict the heat release of granite sample.
... An example of this abnormal situation took place on Mallorca (Spain) in the period 2008-2010, when a combination of persistent precipitation and low temperature caused an unusual number of slope failures. This had a great impact on the regional economy, which revolves exclusively around tourism (Mateos et al., 2012). 18 MORLEs during the past 10 years were reported by 11 Geological Surveys (Mateos et al., 2020), with a total of approximately 150 fatalities and severe economic impacts. ...
Many fields of research relevant to climate-change-related policy are grounded in geological sciences-far more than is generally recognised by the public or policy makers. These fields include management of marine environments, urban development, groundwater , landslide risk, understanding the geochemistry of soils and water, and securing raw materials. Through the concerted collaborative efforts, over many years, of EuroGeoSurveys-the Geological Surveys of Europe-national datasets bearing on these and other areas have been harmonised at European scale and delivered through an online digital platform, the European Geological Data Infrastructure. This vast store of baseline data, information, and knowledge is crucial for informed pan-European decision making and is considered the core of a future Geological Service for Europe. De nombreux domaines de recherche per-tinents pour les politiques liées au change-ment climatique sont fondés sur les sciences géologiques-bien plus que ce qui est géné-ralement reconnu par le public ou les déci-deurs. Ces domaines incluent la gestion des milieux marins, l'aménagement urbain, les nappes phréatiques, les risques de glisse-ment de terrain, la compréhension de la géochimie des sols et de l'eau et la sécurisa-tion des matières premières. Depuis de nom-breuses années, grâce aux nombreux efforts de collaboration concertés des EuroGeoSur-veys-les services géologiques d'Europe-les ensembles de données nationaux portant sur ces domaines (ainsi que d'autres) ont été harmonisés à l'échelle européenne et fournis via une plateforme numérique en ligne-le European Geological Data Infrastructure. Cette vaste banque de données, d'informations et de connaissances est cruciale pour une prise de décision paneu-ropéenne éclairée et est considérée comme le coeur d'un futur service géologique pour l'Europe. Muchos campos de investigación concerni-entes con el cambio climático están relacio-nados con las ciencias geológicas-mucho más de lo que es reconocido por el público o por los responsables de políticas guber-namentales. Estos campos incluyen manejo de ambientes marinos, desarrollo urbano, aguas subterráneas, riesgos de deslizami-entos, la comprensión de la geoquímica de suelos y agua y el aseguramiento de mate-rias primas. A través de esfuerzos colabo-rativos mancomunados por muchos años de EuroGeoSurveys-Servicios Geológicos Europeos-se han integrado a escala euro-pea, bases de datos nacionales, relaciona-das con estos temas y otras áreas, para que estén disponibles en plataformas digitales en línea a través de la agencia Geológica de Datos de Infraestructura Europea. Este gran almacenamiento de datos es base de referencia, información y conocimiento, crucial para la toma de decisiones técni-cas a nivel pan-Europeo y se considera el núcleo central, clave para un futuro Servicio Geológico Europeo. scales, requiring decision-making that is resilient in the face of such rapid changes at local to Pan-European and even global scale.
... Rainfall Rainfall is a major factor for rockfalls in mountainous regions (Mateos et al. 2012). Annual average rainfall of Mogao Grottoes is 39 mm, but the average annual evaporation is 4348 mm, which is 111 times as high as the average annual precipitation (Liu et al. 2020a, b). ...
Hosting precious superb murals and painted sculptures from the fourth to the fourteenth century, the UNESCO word heritage site Mogao Grottoes are one of the most famous sites of Buddhist art. Although several reinforcement projects had been implemented, frequent rockfalls originated from the slope atop the cliff of Mogao Grottoes can be observed, representing a significant risk to both relics and tourists. Therefore, it is important to assess the rockfall hazard of the slope of Mogao Grottoes for the preventive protection as well as to inform future management decisions. In this study, rockfall hazard of the slope of Mogao Grottoes was assessed by using Analytic Hierarchy Process (AHP), Fuzzy-AHP (F-AHP) and AHP-TOPSIS methods and then the performances were evaluated by receiver operating characteristic curve (ROC) and area under curve (AUC). To execute these methods, a high-resolution digital surface model was first captured through UAV digital photogrammetry technology without contact. Belonging to four hazard levels (Very high, high, low and very low), the slope was divided into 10 units based on the slope topography. The hazard assessment result shows that 80% of the total slope units are at low rockfall hazard level and 20% slope units are at very high/high level, respectively. Moreover, loose debris and rainfall are confirmed as the most active causative factors. The result of AUC, ROC and recorded rockfall events reveal that the F-AHP is the most suitable method. Besides, this study also holds the potential applications of the F-AHP in the rockfall assessment for many other grottoes carved in conglomerate strata in Dunhuang.
... Yuan et al. (2021) investigated the degree of soil damage under freeze-thaw cycles and showed that the voids are expanded and further inter-connected as the number of freeze-thaw cycles increases. Many researchers have studied the effect of freeze-thaw cycles as a landslide trigger (Krautblatter and Moser 2009, Mateos et al. 2012, Macciotta et al. 2015, Macciotta et al. 2017a, Pratt et al. 2019. Fahey and Lefebure (1988) monitored the bedrock freeze-thaw at an actively eroding bedrock exposure on the Niagara Escarpment in southern Ontario. ...
Managing the risks associated with landslides requires adequately understanding the factors that affect their state of activity. Of these, weather is a known factor in landslides. Alberta Transportation (AT) is managing the geohazard associated with a 500 m long, 60 m high weak sedimentary rock slope adjacent to Highway 837 (Site C018) in central Alberta with a long history of landslides. Preliminary studies show that a relationship exists between weather and three distinct failure modes at this site: earthflows, rockfalls, and slides of frozen slabs of heavily weathered material. The climatic data at the site have been analyzed for each landslide, and the corresponding weather signature that led to each landslide has been investigated. Results allow for a probabilistic approach to quantify the weather-landslide relationship at this site. RÉSUMÉ La gestion des risques associés aux glissements de terrain nécessite une compréhension adéquate des facteurs qui affectent leur état d'activité. Parmi ceux-ci, la météo est un facteur connu dans les glissements de terrain. Alberta Transportation (AT) gère le géorisque associé à une faible pente rocheuse sédimentaire de 500 m de long et 60 m de haut adjacente à l'autoroute 837 (site C018) dans le centre de l'Alberta avec une longue histoire de glissements de terrain. Des études préliminaires montrent qu'il existe une relation entre les conditions météorologiques et trois modes de défaillance distincts sur ce site: les coulées de terre, les chutes de pierres et les glissements de dalles gelées de matériaux fortement altérés. Les données climatiques sur le site ont été analysées pour chaque glissement de terrain, et la signature météorologique correspondante qui a conduit à chaque glissement de terrain a été étudiée. Les résultats permettent une approche probabiliste pour quantifier la relation météo-glissement de terrain sur ce site.
... Freeze-thaw weathering is an important factor resulting in deterioration of rock structure and the associated stability of rock engineering in cold regions. Various rock mass instability events emerge in high-altitude and alpine regions (Mateos et al. 2012;Zhou et al. 2016;Kong et al. 2018;Forte et al. 2021), and the irreversible freeze-thaw damage of rock mass after repeated freeze-thaws have attract the attention of many scholars and engineers. Generally, a 9% volume expansion occurs when water freezes to ice, while ice exerts multidirectional tensile stress (i.e., frost heaving force) on rock and would lead to pore expansion and new micro-cracks. ...
Rock structural deterioration induced by coupled freeze–thaw and stress disturbance are a great concern for jointed rock mass during rock constructions in cold regions. Previous studies focused on fracture evolution of intact rock or flawed rock under freeze–thaw–static loads, but the coupling effect of freeze–thaw and cyclic loads on the pre-flawed hollow-cylinder rock is not well understood. This work investigated the influence of freeze–thaw on rock microstructure change and fatigue mechanical behaviors. Testing results show that rock strength, volumetric strain, and lifetime decrease with increasing F–T number. The stiffness degradation caused by cyclic loads is also impacted by the previous freeze–thaw damage. Additionally, the AE ring count and energy count decrease with the increase of F–T treatment. Large fracture signals are captured for rock that has smaller F–T cycles and at the stress-increasing moment. The AE b-value increases with F–T cycles, and it decreases rapidly near rock failure. Spectral analysis indicates that large-scaled cracking is prone to form for a sample having high F–T cycles. Moreover, 2D CT images reveal the differential crack network pattern at rock bridge segments and how it is affected by the previous freeze–thaw damage. The crack coalescence and hole collapse patterns and the associated structural deterioration of the rock bridge segment are obviously influenced by the F–T treatment.
... In many civil and mining engineering, repeated freeze-thaw (F-T) weathering results in the deterioration of rock structure and the geomechanical properties, and therefore severely impacts the stability of rock engineering. Plenty of geological hazards have emerged in the cold regions mainly caused by the F-T cycle, such as such as landslides, debris and rockfall etc. [1][2][3][4]. Under freeze thaw conditions, a 9% volumetric expansion occurs when water turns to ice [5][6][7][8], frost heaving pressure promotes the development of new micro-cracks and thus does great damage on rock engineering. ...
... As a last operation, we performed sensitivity analyses to investigate the role of water pressure and seismic actions as potential triggering factors for rockfall events [68]. As regards the first factor, different authors analyzed the water effect on rockfall/rockslide occurrence, evaluating both critical water heights within upslope tension cracks [69,70] and freeze-thaw episodes in cold areas, where ice which forms within cracks can lead to failure [71][72][73]. In this study, water pressure (u) variation was simulated through the "Percentage Filled Fissures" option in Swedge®, which allows to specify the average height of water within joint surfaces as a percentage of the completely water-filled state. ...
Archaeological areas in the mountain region of central Italy can be seriously threatened by geological hazards, and efforts are required to preserve cultural heritage. The Lucus Angitiae is a pre-Roman site located along the western edge of the Fucino Basin, the largest continental depression of central Apennines. The carbonate slope overhanging the area is affected by active rockfall processes from two main rock escarpments. In this paper, rockfall assessment was pursued through a 3D kinematic modelling, performed by adopting a probabilistic approach. Specific attention was dedicated to the choice and calibration of the input data, based on field evidence and a literature review. Two different sizes of wedge-shaped rock blocks were identified on rock escarpments, and specific stability analyses were performed. Sensitivity analyses accounting for possible triggering factors, such as water pressure increase and seismic action, were also carried out, together with an investigation of the seismological characteristics of the area. The results of the numerical simulations were used to design effective countermeasures in the framework of a mitigation plan for protection of the archaeological site. Finally, clues of gravity-driven slope deformations at the slope scale were documented, framing the rockfall process in a wider geological scenario.
... These conditions determine frequent rockfalls, which have caused significant damage during the past decades (Mateos et al., 2016). Special events took place during 2009, 2010 and 2013, when the island of Mallorca experienced very cold and wet winters (Mateos et al., 2012). These freezing, wet conditions triggered numerous rockfalls with severe damages, in special to dwellings and holiday apartment (Fig. 11). ...
Landslides have great socio-economic impacts in urban areas. The increasing consumption of land resources for urban purposes is leading to a large augmentation in people living in prone-locations to landslides. Spain is a clear example of this, where some dramatic, recent cases of landslides in new urban environments are analyzed. We show the methodologies and tools employed for characterizing and monitoring the landslide cases, using preferably remote sensing and numerical modeling. The survey of the three Spanish cases reveals that no adequate previous site investigation studies were carried out and the lack of effective building regulations were major drivers of landslide-damage.
... For example, the loess landslide in Gaoling District of Xi'an, Shaanxi in China is closely related to the seasonal freeze-thaw cycle, which is manifested by the destruction of pore structure and strength deterioration of the loess body under freeze-thaw conditions (Li et al., 2020). Additionally, the rockfalls have also occurred after several freeze-thaw cycles, being a determining factor in the Tramuntana Range, in the northwest sector of the island of Majorca (Spain) (Mateos et al., 2012). Therefore, it is a key scientific problem to evaluate the damage state of soil under long-term freeze-thaw cycles. ...
In permafrost regions, roads and soil slopes experience freeze–thaw cycles annually and the soil characteristics (such as strength and conductivity) change irreversibly. Several studies have been conducted on the evaluation of soil damage using soil mechanics principles and electrical measurements. Owing to the limitations of previous studies, such as low efficiency and the inapplicability of real-time testing for assessing damages, a real-time quantitative test method for assessing the damage degree of layered soil subjected to freeze–thaw cycles based on electrical measurements is proposed. An electrical measurement device was developed for testing the electrical parameters of multilayer soil. Combined with electrical measurements, freeze–thaw cycle tests were performed. The resistivity of each layer of soil under freeze–thaw cycles was determined. Additionally, microstructural parameters of the multilayered soil were determined through computed tomography to investigate the changes in the soil microstructure during freeze–thaw cycles. The porosity and pore distribution characteristics of the multilayered soil under freeze–thaw cycles were obtained using image processing methods, such as median filter and K-means clustering. As the number of freeze–thaw cycles increased, the soil porosity increased, and the pore structure became less complex. Based on the relationship between the soil resistivity and the microstructural parameters, the soil damage mechanism was described, and a damage factor was introduced in developing the model. Furthermore, the dynamic damage process of the multilayered soil under freeze–thaw cycles was evaluated using the damage model, and the settlement was used to verify the results. And the damage model can be applied to evaluate the damage state of soil in permafrost region
... In mountain and cold plateau areas, gravelly soil, a mixed soil consisting of fine soils and gravel particles, is widely distributed and susceptible to frequent F-T cycles due to high altitude and seasonal variations (Nyberg, 1993;Mateos et al., 2012;Qu et al., 2019). Besides, it also exists extensively in glacial tills, mudflows, landslides and colluvial soil deposits (Dong et al., 2017Luo et al., 2019). ...
Gravelly soils, characterized by a mixture of soil matrix and gravel aggregates, are widely distributed in high mountain and cold plateau areas. These soils are frequently subjected to freeze-thaw actions, and the hydraulic conductivity is crucial for analyzing hydrological processes and geological hazards. This study aims to investigate hydraulic conductivity in gravelly soils containing various contents of gravel particle fraction under cyclic freeze-thaw. The results show that the hydraulic conductivity in gravelly soils significantly depends on gravel content, confining stress, number of F-T cycles and initial water content. The presence of gravel particles modifies the porosity and pore connectivity/tortuosity in soil matrix, as well as affects the clay-gravel interfaces. With increasing gravel content, the overall gravel assembly transforms from a state of floating in the clay matrix to forming a contacted skeleton structure. Thus, the extensively developed loose clay-gravel interfaces due to F-T cycles result in a significant increase in hydraulic conductivity. Increasing confining pressure significantly reduces the clay matrix void ratio and thereby decreases the hydraulic conductivity, while no longer recovers the degradation in clay-gravel interfaces induced by F-T cycles. Different initial compacted water content provides different soil structures, divided by the optimum water content (wopt). A prominent increase of hydraulic conductivity after F-T cycles occurs in samples compacted at the dry side of wopt, while a slighter increase at its wet side.
... Under susceptible conditions, rockfalls occurrence can be determined by a variety of natural processes, acting both over short or long term. Seismic shaking/acceleration or rainfall-induced pore pressure increases can be easily recognised as short-term rockfall triggers, whereas it is more difficult to identify long-term triggers, for example, related to frost and thaw cycles or thermal rock movements and expansions (Luckman, 2013;Mateos et al., 2012). ...
Modelling rockfall phenomena is complex and requires various inputs, including an accurate location of the source areas. Source areas are controlled by geomorphological, geological, or other geoenvironmental factors and may largely influence the results of the modelling. In the Canary Islands, rockfalls are extremely common and pose a major threat to society, costing lives, disrupting infrastructure, and destroying livelihoods. In 2011, the volcanic event on the island of El Hierro triggered numerous rockfalls that affected strategic infrastructures, with a substantial impact on the local population. During the emergency, the efforts performed to map the source areas and to model the rockfalls in the considerably steep landscape characterising the island were not trivial. To better identify the rockfall source areas, we propose a probabilistic modelling framework that applies a combination of multiple statistical models using the source area locations mapped in the field as the dependent variable and a set of thematic data as independent variables. The models use as input morphometric parameters derived from the Digital Elevation Model and lithological data as an expression of the mechanical behaviour of the rocks. The analysis of different training and validation scenarios allowed us to test the model sensitivity to the input data, select the optimal model training configuration, and evaluate the model applicability outside the training areas. The final map obtained from the model for the entire island of El Hierro provides the probability of a given location being a potential source area and can be used as the input for rockfall runout simulation modelling.
... Our study also converges with findings from the Bavarian Alps (Krautblatter and Moser, 2009) where a 5-yr record of rock fragments found in traps shows that 90% of all small-magnitude rockfalls were triggered by rainstorms. At larger scale, a similar dependency of rockfall from precipitation has been reported for non-glaciated cliffs in Burgundy (France; Delonca et al., 2014), the Tatras (Poland; Zielonka and Wronska-Walach, 2019), the Canadian Cordillera (Macciotta et al., 2015), Hong-Kong (Chau et al., 2003), the Tramuntana Range (Spain; Mateos et al., 2012) or the Japanese Alps (Matsuoka, 2019;Imaizumi et al., 2020). In the latter case, based on a coupled geomorphic and microclimatic monitoring, Matsuoka (2019) explains the increasing rockfall frequency by raised water pressure in rock joints or the lubrification of joints after rainfall. ...
To overcome the lack of historical archives at active rockfall environments, dendrogeomorphic techniques have been used extensively on forested slopes since the early 2000s and several approaches developed to extract rockfall signals from tree-ring records. Given the unpredictable nature of rockfall, these reconstructions are, in principle, of great help when it comes to relate fluctuations in rockfall activity to meteorological variables. Yet, so far, dendrogeomorphic time series were only rarely compared with meteorological records. Here, we ascribe this shortfall to the absence of clear guidelines on how to optimize the sampling strategy. In order to test this hypothesis, we capitalize on the extensive dataset of rockfall impacts recorded in trees growing in a mixed forest plot within the French Alps. We designed six different scenarios retrospectively and compared rockfall reconstructions with meteorological records. Our results demonstrate that reconstructions that include trees located in the most active segments of the plot (i.e. close to the cliff and over periods lacking multidecadal trends in the reconstruction) capture summer precipitation as the main driver of rockfall activity more clearly. This result is in line with monitoring studies from calcareous cliffs in the Alps located outside periglacial environments thus confirming the robustness of our approach.
... The number of days to be considered depends on the characteristics of the terrain and climate, which may vary widely depending on the local settings (Aleotti, 2004;Crozier, 1999;Garcia-Urquía, 2016;Glade et al., 2000;Guzzetti et al., 2007;Li et al., 2011;Ma et al., 2016;Wieczorek, 1987). For shallow landslides in slopes covered by permeable colluvium, where the interstitial pressure dissipates rapidly, the antecedent rainfall should not be so important, since the rainfall itself generates the hydrological conditions required for instability (Mateos et al., 2012). Also, the antecedent soil moisture conditions can be important for medium and long duration landslide trigger rainfall events (Zêzere et al., 2015). ...
Deba area is intensely affected by frequent shallow landslides triggered by rainfall. This contribution explores the role of rainfall in landslide activity during a quite long time span (60 years), from a large network of rainfall gauges and a complete inventory of landslides. Out of 1,180 landslides inventoried, more than 50% occurred simultaneously in 6 known dates, corresponding to 6 episodes triggering multiple landslides; 3,241 rainfall episodes have been automatically recognized and characterized in terms of rainfall amount and duration, providing a representative dataset that covers a wide range of movement types and behaviors.The relationship between rainfall episodes driving multiple movements simultaneously has not been explored in depth so far in northern Spain. The extraordinary character of the triggering rainfall has been assessed and empirical rainfall thresholds (total amount, and mean intensity), producing multiple landslides, have been found and compared with others described in the literature. Also, the meteorological conditions associated to those extreme events have been recognized: multiple landslide occurrences are triggered by extreme convective rainfall: intense, short and with limited horizontal extent, as well as a marked summer-autumn seasonality. This weather pattern is more characteristic of Mediterranean areas than of mild marine west-coast climates.
... Rainfall intensity and frequency, snow thickness and snow melting rate can change the soil matric suction and affect the shear strength (Subramanian et al., 2018;Yan Long et al. 2019). The magnitude of temperature, its frequency and duration of periodic changes also have a significant impact on the soil physical and mechanical parameters (Qi et al., 2006;Rosa et al., 2012;Zhou et al., 2016). Field observations and https://doi.org/10.1016/j.coldregions.2020.103181 ...
The instability of irrigation reservoir bank slopes in cold regions has seriously affected the benign development of irrigation areas and agricultural production in recent years. To predict and evaluate the slope failure caused by freeze-thaw cycles, a two-dimensional numerical model of thermo-hydro-mechanical multi physical fields of a reservoir soil bank slope is established based on field investigations, laboratory tests and prototype observations. The relationship between the sliding surface temperature and the soil mechanical parameters is proposed by a secondary development program. The generation of the cracks on the bank slope top is explained from the viewpoint of temperature. The hydrothermal changing process of the bank slope under the external temperature is analyzed and compared with the measured data. The long-term degradation process of the soil bank slope under freeze-thaw cycles is studied, and the evolution law of its safety factors with the hydrothermal variation at the sliding surface is quantitatively revealed. The results show that the freeze-thaw cycles have an obvious accelerating effect on the soil bank slope instability, and the safety factor is decreased by 10.43% after 5 freeze-thaw cycles, which directly leads to the bank slope failure
... At broader scale, similar dependency of rockfall to precipitations have been reported for nonglaciated cli by e.g. Delonca et al. (2014) in Burgundy (France), Zielonka and Wro«ska-Waªach (2019) in the Tatras Mountains (Poland),Macciotta et al. (2015) in the Canadian Cordillera,Chau et al. (2003) in Hong-Kong,Mateos et al. (2012) in the Tramuntana Range (Spain) or byMatsuoka (2019) in the Japanese Alps. The later, based on coupled geomorphological an microclimatic monitoring, explain increasing rockfall frequency by raise water pressure in rock joints or lubrication of joints after rainfalls(Matsuoka, 2019). ...
Rockfalls are one of the most common geomorphological processes in the steeply sloping environments. Despite their limited volumes, rockfalls pose a significant hazard, due to their rapid evolution, high velocity and impact energy, but their unpredictable occurrence hinders detailed investigation of their dynamics and drivers under natural conditions. As the relative influence of rainfall, snowmelt, temperature, or freeze–thaw cycles have long been identified, based on medium-term monitoring methods, as the main drivers of rockfall activity, increasing rockfall hazards triggered by climate change are a major concern expressed both in scientific and non-scientific media.At high altitude sites, unequivocal relationships have been established between heightened rockfall activity, permafrost thawing and global warming. By contrast, below the permafrost limit, in the absence of longer-term assessments of rockfall triggers and possible changes thereof, our knowledge of rockfall dynamics remains still lacunary as a result of the persisting scarcity of exhaustive and precise rockfall databases.Over the last two decades, dendrogeomorphology – based on the analysis of damage inflicted to trees after rockfall impacts – has been used to overcome certain limitations inherent to historical archives and reconstructions of rockfall activity have been developed. Paradoxically, tree-ring reconstructions have only rarely been compared with climatic data to precisely constrain the potential meteorological triggers of process activity or to detect potential influences of global warming mostly due to the absence of clear recommendations to derive reconstructions that optimally capture the climatic signal in rockfall-prone environments.In this context, this PhD thesis first aims at proposing clear methodological guidelines to optimize sampling strategies of trees so as to precisely quantify uncertainties in dendrogeomorphic reconstructions back in time. Our results clearly evidence that the high-resolution mapping of stems on the studied combined with a careful selection of tree-species located at the vicinity of the cliffs improve the robustness of our reconstructions at the Saint-Guillaume (mixed forest stand, Vercors massif, French Alps) and Valdrôme (monospecific planted forest stands, Diois massif, French Alps) studied plots.In the second part, we capitalize on rockfall activity derived from optimized reconstructions and on the high-spatio-temporal resolution of the SAFRAN reanalyses, to precisely identify the meteorological triggers of rockfall events. At the interannual scale, our results evidence that summer precipitations and intense rainfall-events are the main drivers at both sites while no clear impact of temperature or freeze-thaw cycles could be detected.Finally, we compare decadal fluctuations existing in both tree-ring records with climatic series available for the period 1959-2017 with the purpose to detect the potential impacts of global warming on rockfall activity. In the Vercors massif, we explain increasing rockfall activity observed in the reconstruction since 1959 by a rapid forest recolonization and the overrepresentation of young sensitive trees rather than by climate change. In the Diois massif, the absence of significant trend suggests that a premature warning of increasing rockfall hazard, is not supported by the existing data. Yet, the weak robustness of the multiple regression models used here, the limited increase of temperature at the study sites and the incompleteness of our tree-ring reconstructions suggest that these results have to be treated with cautiously. All in all, this PhD thesis clearly demonstrates the added-value of the dendrogeomorphic approach to reconstruct rockfall activity, assess the meteorological driver of past events as well as to detect the potential impacts of environmental changes on the process dynamics.
... The number of days to be considered 110 depends on the characteristics of the terrain and climate, which may vary widely depending on the local settings (Wieczorek, 1987;Crozier, 1999;Glade et al., 2000;Aleotti, 2004;Guzzetti et al., 2007;Li et al., 2011;Zêzere et al., 2015;Garcia-Urquía, 2016;Ma et al., 2016). For shallow landslides in slopes covered by permeable colluvium, where the interstitial pressure dissipates rapidly, the antecedent rainfall is not so important, since the rainfall itself generates the hydrological conditions required for instability (Mateos et al., 2012). Still, the antecedent rainfall is usually considered in this type of investigations. ...
Abstract. The Deba area is intensely affected by frequent shallow landslides triggered by rainfall. Relationships between rainfall and landslides in northern Spain, particularly for rainfall events driving multiple movements simultaneously, have not been explored in depth so far. This contribution explores the role of rainfall in landslide activity during a quite long time span, (60 years), from a large network of rainfall gauges and a complete inventory of landslides, and utilizing three different strategies of analysis. 1,180 landslides have been inventoried, and 3,241 rainfall episodes automatically recognized and characterized in terms of rainfall amount, duration and intensity. Antecedent rainfall has also been considered. Six episodes of intense rainfall, which have produced multiple landslides (> 50 % of the recent past occurrences) have been identified. The analysis provides different results: the extraordinary character of the triggering rainfall has been assessed, the meteorological conditions associated to those extreme episodes have been recognized and empirical rainfall threshold producing multiple landslides has been found (I = 7.7D-0.428) and compared with others described in literature. Results show that multiple landslide occurrences are triggered by extreme convective rainfall, intense, short and with limited horizontal extent, as well as a marked summer-autumn seasonality, characteristic of Mediterranean climate.
... The former, for most of catastrophic landslides, is the result of the comprehensive functions of long-and short-term factors. Long-term factor, such as climate (Bovis and Jakob 1999), rock weathering (Regmi et al. 2013), and freeze-thaw cycles (Mateos et al. 2012), can slowly change the properties of a slope body. For example, the formation of the Sangrumba landslide that occurred in Nepal Himalaya was mainly influenced by rock weathering that drastically decreased the strength of the rock (Regmi et al. 2013). ...
This paper investigates the setting, causes, and main dynamic characteristics of the landslide that occurred at Xinmo village, Diexi, Sichuan province, China, on June 24, 2017. By comparing the pre- and post-sliding DEMs, the landslide involved the failure of ≈ 3.0 × 10⁶ m³ rock mass from its source area, and had a final volume of ≈ 6.3 × 10⁶ m³. The landslide runout extended 2800 m horizontally and 1200 m vertically, and covered an area of ≈ 143.1 × 10⁴ m². Field investigation indicates that entrainment was one of the major causes of the increase in volume of landslide. To reproduce the behavior of the landslide runout, a depth-averaged continuum model that takes entrainment into consideration is applied. The simulated results generally agree well with the characteristics of the sliding path and distribution of the landslide deposit as observed in the field. It is demonstrated that entrainment plays a significant role in landslide mobility and volume. The final volume of the landslide is calculated about 6.21 × 10⁶ m³, which has more than double its initial volume.
... Changes in weather conditions (precipitation and temperature) influences mechanical response of rockmass by fluctuating pore water pressure, leaching, frost wedging and propagation of thermal stresses during thawing period. Previously, some researchers correlated metrological changes with landslide occurrence (D'Amato et al., 2016;Delonca et al., 2014;Douglas, 1980;Luckman, 1976;Mateos et al., 2012;Matsuoka, 1994;Perret et al., 2006;Sandersen et al., 1996;Sarro et al., 2014). In this study, an effort is made to check the control of precipitation and variations in temperature (freeze thaw) on rockfall occurrence. ...
... However, these are not suited to the implementation of an early-warning system, which in some scenarios may be the only viable option for reducing risk to tolerable levels. Other approaches propose to provide early-warning by linking the likelihood of rockfall to precipitation, freeze-thaw cycles, or other external triggers (Chau et al. 2003;Krautblatter and Moser 2009;Mateos et al. 2012). While noteworthy statistical correlations may be found, some problems remain. ...
Rockfalls are a recurrent cause of disruption for transportation corridors running along the bottom of U-shaped alpine valleys. In some scenarios, risk may effectively be reduced only by implementing an early-warning system able to give notice of incipient failures on the slope. This paper describes a successful example of rockfall forecasting and risk management in proximity of the Gallivaggio sanctuary (San Giacomo Valley, Central Italian Alps). Since 2016, a Ground-Based Synthetic Aperture Radar continuously monitored a roughly 500-m high, sub-vertical granitic slope. Monitoring data evidenced the presence and continued movement of a ~ 5000 m³ highly unstable mass, having a projected fall trajectory directly threatening the sanctuary and the adjacent segment of a national road. Traffic and access to the sanctuary were regulated by a sequence of alert thresholds, and restrictive orders were issued according to the activity of the instability. The rock mass eventually fell, and the failure-time was accurately predicted several hours in advance. Despite damage to both the road and buildings, the timely evacuation of the area prevented any loss of life. The case study provides a reference framework to better manage rockfall risk in areas where the installation of adequate protective barriers is not technically feasible.
... Original Paper new work is needed for a better understanding of the relation rainfall-landslides in this area. Apart from the northern area, other studies have been developed in the Iberian Peninsula, such as the thresholds calculated by Mateos et al. (2012) for the Tramuntana Range, Palenzuela et al. (2016) for the Betic Range, and the large number of studies conducted in Portugal (e.g., Marques et al. 2008;Zêzere and Trigo 2011;Zêzere et al. 2015;Vaz et al. 2018). ...
Landslides are one of the most serious geomorphological hazards in Asturias (NW Spain), where their temporal forecasting constitutes a key issue. The present work uses 559 records from the Principality of Asturias Landslide Database (BAPA) and daily precipitation data series from six rain gauges, gathered during a period of 8 hydrological years (2008–2016), to calculate empirical antecedent rainfall thresholds for the triggering of landslides. The methodology includes (i) the selection of a representative input dataset and (ii) the assessment of the performance of the thresholds through contingency tables and skill scores. On this basis, six local rainfall thresholds for different areas within Asturias have been calculated and compared, allowing progress towards a better understanding of the rainfall-landslides relationship in the NW of Spain. The analysis has highlighted the strong influence of (i) the climatic variability between areas and (ii) the different seasonal precipitation patterns on the landslide-triggering conditions. The antecedent rainfall plays a key role during the wet period while the intensity of the rainfall event is the most relevant factor during the dry period. These observations must be considered to successfully address the temporal forecasting of landslides.
... High-magnitude debris flow events may cause a disturbing impact of the dynamic equilibrium, resulting in longer relaxation periods with a frequent occurrence of low-magnitude hydrogeomorphic events. The recent evolution is, however, strongly influenced by climatic variables such as the number of freeze-thaw cycles, which influence the disintegration of the source area (Matsuoka et al. 1998;Mateos et al. 2012), and the rainfall intensity-duration control of debris flow/flood initiation (Guzzetti et al. 2008;Borga et al. 2014). ...
Headwater catchments are frequently prone to debris flows/floods. Dendrogeomorphic methods allow for the accurate dating of the frequencies and spatial patterns of these events. Nevertheless, a combined approach based on the sampling of increment cores from tree stems and the extraction of cross-sections of scarred roots has been rarely used together at one site to determine the headwater dynamics. Such sampling strategy was performed in the Rudohorský potok catchment (the Hrubý Jeseník Mountains, Eastern Sudetes, Czech Republic) to compile the debris flow/flood chronology and to describe the detailed spatial patterns in the studied sub-catchments. In total, 44 events of increased hydrogeomorphic activity during the last 110 years were identified based on the analysis of 860 growth disturbances from 322 trees and 85 roots. The largest events (debris flows) occurred in 1921, 1951, 1965, 1975, 1991, 1997, 2001 and 2010. Higher dynamics of hydrogeomorphic processes were investigated in the sub-catchment affected by deep-seated rockslides. The inclusion of root analyses facilitated the completion of the event chronology mainly during the last 20 years. With respect to the decreasing sensitivity of tree stems with increasing age to the recording of geomorphic disturbances, the root analysis helped to better illustrate the spatial imprint of recent debris flow events (especially the most recent one in 2010).
... Other coastal areas in the central and western Mediterranean have also been affected by landslides of different types, in various geological and geomorphological conditions. For instance, rock falls on the coast of Majorca (Baleares Islands, Spain) were recently described (Mateos et al. 2012(Mateos et al. , 2013(Mateos et al. , 2016aSarro et al. 2014); different landslides were also reported on the island of Malta (Mantovani et al. 2013) and the coasts of Amalfi and Maratea in the Campania and Basilicata Regions of southern Italy (Ciervo et al. 2016;Pellicani et al. 2016) and debris flows affecting the coast of the island of Ischia (Italy) were described by Nocentini et al. (2015) who applied dendrochronology techniques to assess potential landslide areas on that Tyrrhenian Sea island. ...
The Costa Tropical in Granada Province, in Southern Spain, was intensively developed during the 1980s and 90s. A complex of several residential communities was built on the eastern slope of the coastal Cerro Gordo hill (Almuñécar), on the pre-existing Calaiza landslide. This was not identified in the preliminary technical studies, thus giving rise to a set of incidents associated with this unforeseen unstable slope. To ensure sea views from all the houses, excavations and fillings were carried out, creating a stepped slope, on which the new foundations of structures and roads were located and subsequently damaged by an increasing number of cracks and deformations, leading to 42 houses becoming ruins in the period 2003–2016. Since 1990, annual and monthly rainfall has been variable in the area, and some rainfall peaks were eventually associated with damage proliferation, although more frequently damage was recorded during dry or low rainfall seasons, when water infiltrated from breaks in pipelines. This damage results from a combination of sliding and bad construction practices at increasing rates from dry to humid periods or during heavy rains. An overall perspective of the geotechnical and geomorphological features of the study area, the landslide reactivation, and its correlation with the damage evolution, as well as its legal consequences, is presented here.
... The main criterion in selecting the ALOS PALSAR imagery was the temporal spanning, as it covered a very rainy period on the island. During the period 2008 and 2010, the island of Mallorca experienced the coldest and wettest winters of the last 48 years with accumulated rainfall twice the average and values of daily rainfall up to 300 mm (Mateos et al. 2012). Additionally, high rainfall values coincided with low temperatures and freezing processes in the highest zones of the Tramuntana Range. ...
The Bàlitx area is located on the steep coastal side of the Tramuntana Range (Majorca), a mountainous region which was declared a World Heritage Site by UNESCO in 2011 in the cultural landscape category. The Bàlitx site was occupied by farming areas with dry stone constructions and water storing systems of both Roman and Islamic origin. The coastal landscape is characterised by a large fault escarpment of up to 260 m in height. Lateral spreading processes are favoured by local stratigraphy and tectonics in an energetic coastal dynamics scenario. Block spreading morphologies are identified along the escarpment, with large, rocky blocks of volumes up to 60 × 10³ m³ moving very slowly until their collapse. Consequently, a thick and highly karstified breccia deposit is accumulated at the base of the scarp. The lowest, oldest breccia outcrop has been dated (Th/U), and an age of 82.5 ± 5.6 kyr was obtained, reflecting the time span this process has been active. Additionally, numerous geomorphological slope features are identified in the area: landslides, rockfalls, and, more specifically, long and deep cracks in the hanging wall block of the fault, which also reveal active lateral spreading processes. Coastal dynamics have been investigated by interpreting offshore geophysical studies, bathymetry data and borehole information to determine the role of wave energy in the stability of the slope. Additionally, 14 SAR images from the ALOS PALSAR satellite have been exploited for the present work, covering a period spanning from 2007 to 2010, an anomalous rainy period in the region. Images were processed using the Persistent Scattered Interferometry (PSI) technique. PSInSAR results reveal that the rate of movement for the Bàlitx lateral spreading is extremely low (− 5.2 mm/year on average), but major activity has been detected in the NE sector, where velocity rates can reach values of up to − 16 mm/year Coastal dynamics in the area can explain this, as a small island generates wave refraction and reflection determining more intense erosive processes in the NE part, which lead to a greater destabilising effect on the slopes. A simple vulnerability approach has been developed to take the elements of cultural heritage into account. Vulnerability increases from SW to NE, in accordance with landslide activity. The Bàlitx case study could provide a testimony to the effects of mass movements and coastal dynamics in an exceptional example of Mediterranean agricultural landscape.
... In recent years, the population density along spanish coastlines, where 50% of the population live and tourism is most intensive (75.3 million of visitors in 2016), has led to generalized disturbance of coastal lands. Over 30% of the spanish coastline has been developed resulting in a large number of landslides affecting resorts, dwellings, apartment blocks and infrastructures (Mateos et al., 2012;notti et al., 2015;. Figure 4 shows some significant examples. ...
Damages and fatalities caused by geohazards have considerably increased in Europe during the last decades; urban pressure has led more people to live in flood plains, around seismically active areas and in zones prone to landslides. A lack of regulatory mechanisms in many countries to face geohazards within the ambit of urban planning, as well as poor land-use plans, have increased the risk and exacerbated the effects of natural disasters. Geohazards in Spain cause significant economic and social losses. Every year, nearly 25 people are killed while economic losses exceed 0.23% of GDP. Additionally, the indirect losses could be very important, in a country that lives from and for tourism. Geohazards are contemplated in the Spanish legislation within the ambits of the land regulations and the civil protection management, both in hands of the 17 autonomous communities of the country. The result is a large heterogeneity in approaches to geohazard mapping and different regional velocities about how to integrate efficiently Geoscience knowledge into the land-use and urban development policies. On a larger scale, Europe shows a similar situation to the Spanish one, with heterogeneous policies across borders and a lack of common methodological guides to elaborate geohazard maps. The present work reveals the need to stress a better integration of geohazards into land-use and urban planning across Europe by means of a legislative framework and homogenization of the national legislations. It is essential to understand that geohazards are an international problem that requires collaboration and mutual understanding guided by collective EU policy.
... Furthermore, many documented cases in other European countries exist and refer to long rainy periods which triggered a large number of landslides extending over large areas. An example of this abnormal situation took place in the Island of Mallorca (Spain) from the period 2008-2010 when a combination of persistent precipitations and low temperature caused an unusual number of slope failures; they produced a great impact on the regional economy of the island which revolves exclusively around tourism (Mateos et al. 2012). ...
Landslides 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.
... La mayoría de los movimientos de ladera se desencadenan fundamentalmente después de largos e intensos periodos de lluvias, pudiendo desencadenarse un gran número de deslizamientos en áreas extensas. Un ejemplo de esta situación se produjo en la isla de Mallorca (España) durante el período 2008-2010, cuando una combinación de precipitaciones persistentes y bajas temperaturas causaron un número inusual de roturas que generaron un gran impacto en la economía regional de la isla, basada principalmente en el turismo (Mateos et al., 2012;Mateos et al., 2013). ...
A pesar de que los movimientos de ladera son uno de los peligros geológicos más extendidos en España, faltan instrumentos legales, guías metodológicas oficiales y datos reales sobre sus impactos económicos y sociales. Así mismo existen, en la actualidad, distintos inventarios de movimientos de ladera generados por distintos organismos sin una aparente interrelación. En este trabajo, se analizan de manera conjunta las bases de datos de movimientos de ladera del Instituto Geológico y Minero de España y del Instituto Cartográfico y Geológico de Cataluña. En primer lugar, se analiza la distribución espacial de los distintos tipos de movimientos de ladera, y posteriormente, se analiza el grado de completitud de dichas bases de datos. Este trabajo pretende ser una invitación para que todos los organismos trabajen de manera conjunta en la armonización e integración de las bases de datos existentes de movimientos de ladera en España.
... Esta compleja relación lluvia-deslizamientos también se ha analizado desde la óptica de la experiencia de los evaluadores del riesgo geotécnico, quienes a partir de registros históricos y las características básicas de la lluvia, como la cantidad de precipitación diaria, proponen unos umbrales mínimos a partir de los cuales se pueden desencadenar fenómenos de remoción en masa. En este tipo de aproximaciones, los expertos seleccionan desde su experiencia el tipo de variable derivada de registros de lluvia y generan una explicación basada en la casuística de la relación lluvia-deslizamiento [4][5][6][7][8][9]. Por otro lado, Caine [10], Glade et al. [11], Jakob y Weatherly [12], Aleotti [13], Guzzetti et al. [3], Guzzetti et al. [14], Brunetti et al. [15], Li et al. [16] y Mathew et al. [17], entre otros, han generado funciones de tipo regresivo y/o probabilístico para la determinación de lluvias antecedentes, acumuladas, o intensidades de lluvia que generen deslizamientos en aproximaciones dirigidas por datos. ...
En el mundo se han propuesto múltiples relaciones lluvia-deslizamientos para sistemas de alerta temprana. Este trabajo presenta una base de datos que sintetiza el estado del arte de umbrales de lluvia que generan movimientos en masa en todo el mundo. Las relaciones más comunes lluvia-deslizamiento se procesan con el fin de analizar los datos en función de la clasificación climática de Köppen y el área para la cual fue generada. Los resultados muestran la amplia oferta disponible de tipos de parámetros derivados de lluvia que producen deslizamientos, unido con las diferencias considerables en los valores umbrales que pueden tomar dichos parámetros. Estos resultados se condensan en figuras comparativas de niveles umbrales de lluvia que generan deslizamientos propuestos en el mundo para diferentes parámetros. Del análisis de la información recopilada resulta evidente la necesidad de obtener parámetros y umbrales derivados de lluvia que generan deslizamientos para cada zona geográfica y climática específica, de forma tal que se pueda generar una base racional de conocimiento que permita establecer sistemas de alerta temprana de deslizamientos detonados por lluvias con baja variabilidad. Este trabajo aporta en la construcción del conocimiento del catálogo de posibles parámetros derivados de registros de precipitación que permiten generar umbrales de predicción de ocurrencia de deslizamientos. Los investigadores tendrán la posibilidad de buscar relaciones lluvia-deslizamiento, basadas en análisis estadísticos, con una amplia paleta de parámetros, más allá de las variables tradicionales de lluvia antecedente e intensidad ocurrida el día del deslizamiento.
Earthquakes and freeze-thaw cycles are two important causes of landslides, but knowledge of their combined effect is limited. Therefore, a freeze-thaw test and large-scale shaking table tests were carried out to simulate the progressive deformation and failure mode of loess fill slopes. The process of frost-heaving deformation and seismic deformation was observed, and the failure mode was analyzed by comparing with the accelerations. The results showed that the slope stability decreased after freeze-thaw cycles. Freezing and thawing causes the crest and upper portion melted, and settled to the lower portion, creating frost-heaving zones and irreversible cracks. Comparisons between the freezing-thawing slope and nonfreezing-thawing slope allowed to highlight, through the analysis of seismic responses, the possible and not negligible effect of both frost-heaving spatial distribution of slope surface soil and freeze-thaw interface during the seismic shaking in initiation and development of landslides. The peak ground acceleration (PGA) amplification factors of freezing-thawing slope were higher, especially in the frost-heaving zones. Cracks in freezing-thawing slope developed faster and deformation was greater. The freeze-thaw interface became a potential slip surface and a multistep landslide suddenly occurred under 1.2 g seismic loads, while the nonfreezing-thawing slope was stable. The freezing-thawing slope shows a brittle superficial shear failure, and its failure mode is freeze-thaw cycles - forming potential sliding surface and irreversible cracks - slow expansion of cracks - rapid development and penetration of cracks - superficial shear sliding.
This work aims at investigating the fracture and instability behaviors of Xinjiang granite containing hole and fissures under freeze-thaw (FT) and cyclic loads using acoustic emission (AE) monitoring and X-ray computed tomography (CT) imaging. The stress path is sinusoidal load with decreasing frequency and increasing amplitude pattern. The experimental results reveal a sudden increase of volumetric strain and a sudden decrease of AE-b value. Their increasing rate becomes quick as cycle increases reflecting the rapid propagation of damage. The frequency of AE activities displays different proportions that is impacted by the FT cycle. The percentage of the low-frequency and high-frequency signals is relatively high and low respectively for a rock experiencing more FT cycles. The theoretical description of F-T influence coupled with mechanical performance are performed. Based on acoustic emission energy, a damage evolution model considering the coupling effect of freezing-thawing cycle and cyclic load is proposed, which can fit the experimental data well. A series of CT images reveal the influence of freeze-thaw on rock failure modes. Typical failure modes of double shear coalescence, single shear coalescence and single tensile coalescence failure modes were identified from the reconstructured CT images.
Multistage constant-amplitude-cyclic (MCAC) loading experiments were conducted on Tibet interbedded skarn to investigate and characterize fatigue mechanical behavior of the tested rock. Rock volumetric deformation, stiffness change, and fatigue damage evolution were analyzed along with the macroscopic failure morphology. The experimental results demonstrated that the volumetric deformation of the tested skarn was influenced by the interbed structure. Rock damage presented a two-stage pattern. The rock damage increased quickly at the beginning and subsequently became steady for long periods of time within a cyclic loading stage. A new damage evolution model was proposed on the basis of axial strain. Macroscopic failure morphology analysis revealed different fracture mechanisms, combining a tension-splitting mode, shear-sliding, and mixed shear-tension. In this study, the understanding of the anisotropic mechanical properties of interbedded skarn was highlighted, and this could contribute to the ability to predict the stabilities of rock engineering structures.
This work conducted laboratory tests considering the coupled freeze–thaw (FT) and variable-frequency–variable-amplitude cyclic loads on granite containing two fissures and a circular hole. The analysis is dedicated to reveal the deformation and energy rate characteristics. Testing results show that increasing FT cycle and loading level both accelerate rock damage. The rock subjecting to high FT cycle behaves much larger damage rate in terms of volumetric strain and dissipated energy. The warning strength is defined according to the volumetric strain rate and dissipated energy rate which can early issue a warning than the crack damage stress point. In addition, the rock instability precursor is proposed by monitoring the incremental rate of the radial strain and volumetric strain; drastic damage occurs when the volumetric rate exceeds the radial rate. Three typical crack coalescence modes of double shear coalescence, single shear coalescence, and single tensile coalescence were revealed.
For rock engineering in cold regions, rock is often subjected to coupled fatigue conditions of freeze-thaw (F-T) and stress disturbance. Rock fracture evolution and energy mechanism under room temperature and constant stress amplitude loading condition have been widely investigated. Yet the rock energy dissipation and damage evolution characteristics subjected to multiple level cyclic loading conditions are not well understood. In this work, multiple level cyclic compressive loading experiments were conducted using GCTS RTR 2000 rock mechanics system on marble with F-T treatment of 0, 20, 40 and 60 cycles. The fracture evolution and energy dissipation mechanism were analyzed as well as the damage evolution characteristics. The results indicate that F-T treatment strongly influences the fatigue mechanical behaviors of marble, with both fatigue strength and strain energy decreases and irreversible volumetric deformation increases with increasing F-T cycles. The incremental rate of dissipated energy becomes faster as cyclic loading level grows. In addition, a F-T-fatigue loads coupling damage variable was proposed by using the input total strain energy and the dissipated strain energy to describe the rock damage evolution after F-T treatment and experiencing fatigue loading. Moreover, a damage evolution model was first established based on the obtained coupling damage variable to describe the two-phase damage accumulation characteristics. Damage accumulation curve presents a first steady increase and then faster increase trend, the damage evolution model can good fit the experimental data.
Rock mass containing natural fractures is susceptible to freeze-thaw (F-T) weathering in cold regions and could result in the instability of rock engineering and even serious geological hazards. Yet the F-T action on the change of fracture physical characteristics and the associated fracturing evolution of naturally fractured rock is poorly understood. In this work, multi-level compressive cyclic loading experiments were performed to investigate the fracture evolution of naturally fractured granite using real time acoustic emission monitoring and post-test CT scanning. The results show that the aperture change of natural fracture is related to the fracture openness and filling characteristics, the open-type fracture is sensitive to F-T treatment and its aperture increases faster than the close-type and fill-type fractures. In addition, the stress strain curve pattern is impacted by the initial natural fracture volume. The AE activities at fatigue loading stage are weaker than the stress-increasing stage. The proportion of low frequency AE signals increases with increasing natural fracture volume, and the shear-sliding along natural fracture results in the occurrence of low-frequency signals. Moreover, interactions between the natural fracture and stimulated new fracture are visualized using CT scanning and it is found that the initial natural fracture volume impacts the failure mode and fracture network pattern. The testing results are expected to improve the understanding of the influence of natural fractures on rock damage and deformation in cold regions.
Este informe tiene como finalidad resumir los mecanismos existentes en España para gestionar los peligros geológicos ligados al clima, así como ofrecer datos actuales sobre los mismos: inundaciones, deslizamientos y desprendimientos rocosos, riesgos costeros, etc. El trabajo analiza una serie de cuestionarios compartidos a la comunidad científica, gestores de Emergencias, Protección Civil y planificación urbana/territorial, con la finalidad de identificar las debilidades y fortalezas en España en relación a:
- La coordinación y eficacia de los instrumentos de prevención.
- La gestión de las catástrofes.
- La rehabilitación de zonas siniestradas.
The deterioration mechanism and fatigue fracturing evolution of granite with two pre-existing flaws experiencing freeze–thaw (F-T) treatment are investigated in this work. The flaws in the rock sample were prepared as a combination of a horizontal flaw with an upper inclined flaw above the horizontal flaw according to the joint characteristics in an open pit slope. In-situ acoustic emission monitoring combined with the post-test 3D computed tomography (CT) technique was employed to reveal the fracture evolution behaviors of rock treated with 0, 50, and 80 freeze–thaw cycles. Results show that the freeze–thaw damage impacts the frost heaving force, cyclic deformation, AE activates, crack coalescence pattern and fatigue life of the granite samples. The accumulative AE count/energy decreases with increasing number of freeze–thaw cycles, and the accumulated AE count/energy in a loading stage gradually grows faster. In addition, AE spectral frequency analysis reveals the impact of previous freeze–thaw damage on the formation of the crack scale, the sample is prone to producing large scale cracks under high freeze–thaw treatment. Moreover, 3D reconstructed CT images present an internal crack network pattern, and the most striking finding is that a simple crack network forms for a sample experiencing high F-T fatigue damage. It is suggested that deterioration of the rock bridge structure is strongly impacted by the accumulative freeze–thaw damage. The testing results are helpful to understand the influence of freeze–thaw and fatigue loading on the fracture evolution characteristics of rock in cold regions.
La temperatura del planeta está experimentando una subida clara desde principios del siglo XX. De hecho, los 16 años más cálidos que se han vivido desde 1880 se han registrado en los últimos 20 años. A consecuencia del calentamiento de la atmósfera y del océano, las cantidades de nieve y hielo han disminuido y el nivel del mar ha subido. Además, algunos de los cambios observados desde los años cincuenta no habían tenido precedentes desde hace décadas o, en algunos casos, desde hace milenios. En estos momentos, parece claro que el calentamiento global observado está causado por el aumento de la concentración de gases de efecto invernadero (GEI) en la atmósfera, especialmente de dióxido de carbono, metano y óxido de nitrógeno, y que la actividad humana es la responsable de este aumento. De hecho, las concentraciones de GEI han llegado a los niveles más elevados de los últimos 800.000 años.
En cuanto a las Illes Balears, desde 199050 hasta 2008 las emisiones aumentaron un 70 %, una cifra notablemente superior a la media del Estado español (un 50 %). Durante los años de la crisis, hasta 2014, las emisiones disminuyeron, para volver a remontar a partir de aquel año. En 2016, las Balears emitieron un 39 % más de GEI que en 1990, lejos de los compromisos adoptados por España en el marco del Protocolo de Kyoto de 199751. Este aumento de emisiones nos aleja también, por ahora, de los objetivos establecidos en el marco del reciente Acuerdo de París, en el marco del cual la UE ha fijado una reducción de las emisiones del 40 % para el año 2030 respecto de las emisiones de 1990. Por sectores, el informe del Mapama de 2016 indica que el 42 % de las emisiones de las Balears están asociadas a la producción de energía eléctrica, el 37 % al transporte, el 4,7 % a los procesos industriales, el 3,8 % al tratamiento de residuos y el 2,3 % a la agricultura. Si desglosamos el consumo de energía, encontramos que en nuestra comunidad está dominado por el transporte terrestre (33 %) y aéreo (29 %), seguidos por el consumo residencial (13,8 %) y los servicios (13,5 %), mientras que es mucho más pequeña la contribución del sector primario (3,9 %), la industria (3,9 %) y los servicios públicos (2,7 %; CAIB, 2016). Hay que decir que en estos datos no se incluyen las emisiones “importadas”, generadas durante la producción en el exterior de bienes y servicios intermedios y finales demandados por los diferentes sectores y consumidores en las Illes Balears.
El calentamiento global tendrá unos efectos claros sobre el clima, tanto a nivel global como regional. Hay indicios que cuanto más se tarde en iniciar la reducción de emisiones, mayores serán los impactos y más difíciles de evitar o de adaptarse. El objetivo de este capítulo es hacer una revisión de los cambios observados hasta ahora y de los cambios proyectados para las próximas décadas en cuanto a variables ambientales, económicas y sociales en relación con el cambio climático. Hay que hacer énfasis en el hecho que los cambios serán más notables a medio y largo plazo (2050-2100); es decir, más allá de 2030, que es el horizonte temporal de este informe, pero las medidas para limitarlos y adaptarse se tienen que empezar a tomar ahora para que sean efectivas. A corto plazo, los cambios se harán también presentes (algunos ya han sido observados), pero su magnitud será más difícil de discernir de la variabilidad natural del clima. En cualquier caso, los cambios esperables a medio y largo plazo son tan importantes, y con consecuencias potencialmente tan graves, que se considera imprescindible que las Illes Balears cuenten con planes de adaptación y mitigación del cambio climático antes de 2030, dado que la puesta en práctica de estos planes requerirá tiempo y recursos.
También se quiere remarcar que en este capítulo nos centraremos únicamente en cuestiones vinculadas al cambio climático. Hay que tener en cuenta que hay otros problemas asociados al medio ambiente no causados directamente o principalmente por el cambio climático, que tienen una gran relevancia y que requerirían un estudio y una toma en consideración adecuadas a la hora de establecer una planificación responsable para las Balears de cara a 2030. Nos referimos, por ejemplo, a la sobreexplotación de recursos o a las diversas formas de contaminación (de acuíferos, del suelo, del aire...). Hay que tener presente, en todo caso, que estos problemas no necesariamente originados por el cambio climático se pueden ver agravados por este fenómeno.
Topographic, granulometric, morphometric, petrographic and vegetation surveys were conducted on the slopes of Tasiapik Valley, near Umiujaq (Nunavik), to document mass wasting processes and their geomorphological impact. Talus slopes, widespread at the foot of the steep rockwalls of Tasiapik Valley, are an important landscape feature in the area. The lithology of the slope deposits attest their local origin, namely the result of rockfalls coming from the adjacent wall. Locally, poor vegetation covering the clasts exhibits recently fallen debris; elsewhere, dense shrub cover has colonized the slopes demonstrating the low activity nowadays. On-going periglacial processes have led to extensive dismantling of the rockface, enabling for debris supply. Following the last deglaciation, paraglacial processes have potentially favoured slope instabilities. The use of automatic cameras during the winter 2017–2018 resulted in the observation of many snow-avalanche events; however few rockfall events have been observed. Spring snow avalanches have carried rock debris to the talus at the foot of the slope; snow also enabled debris redistribution on the slopes.
Llistat Bibliografia Naturalística de les Balears, M-O
The influence of meteorological conditions on rockfall occurrence has been often highlighted, but its knowledge is still not sufficient due to the lack of exhaustive and precise rockfall data bases. In this study, rockfalls have been detected in a limestone cliff by annual terrestrial laser scanning, and dated by photographic survey during 2.5 years. A near-continuous survey (1 photo each 10 mn) with a wide-angle lens have allowed dating 214 rockfalls larger than 0.1 m3, and a monthly survey with a telephoto lens, dating 854 rockfalls larger than 0.01 m3. The analysis of the two data bases shows that the rockfall frequency can be multiplied by a factor as high as 7 during freeze–thaw episodes and 26 when the mean rainfall intensity (since the beginning of the rainfall episode) is higher than 5 mm h−1. Based on these results, a 4-level scale has been proposed for predicting the temporal variations of hazard. The more precise data base and freeze–thaw episode definition make it possible to distinguish different phases in freeze–thaw episodes: negative temperature cooling periods, negative temperature warming periods and thawing periods. It appears that rockfalls occur more frequently during warming and thawing periods than during cooling periods. It can be inferred that rockfalls are caused by thermal ice dilatation rather than by dilatation due to the phase transition. But they may occur only when the ice melt, because the cohesion of the ice–rock interface can be sufficient to hold the rock compartment which has been cut.
We review the range of landslide processes and provide a vocabulary for describing the features of landslides relevant to their classification for avoidance, control or remediation.
El litoral de la Serra de Tramontana de la Isla de Mallorca está afectado por numerosos procesos de inestabi lidad en las laderas y escarpes que forman la costa. La cala de Banyalbufar, con un acantilado rocoso de más de 50 m de altura, es un ejemplo notable de ello, sufriendo frecuentes desprendimientos como el ocurrido en Septiembre de 1993, el último de importancia, en el que se produjo la caída de una cuña rocosa de unos 80 metros cúbicos de volumen. En este trabajo se analizan los procesos de inestabilidad que afectan a los taludes del acantilado, así como los factores condicionantes y desencadenantes que controlan los desprendimientos. A partir del conocimiento de los mecanismos de rotura y de la caracterización de estos diferentes factores, se rea liza una estimación de la peligrosidad y riesgo en el acantilado, como medida preventiva frente a futuros desprendimientos. La propuesta y diseño de medidas estabil izadoras queda fuera del ámbito de este trabajo, centrado en el aná lisis de los procesos naturales que sufre el acantilado.
Resumen: Entre los días 24 y 29 de marzo del año 1721 tuvo lugar en el Predio de Biniarroi, situado en el t.m de Mancor del Vall (Mallorca), un importante deslizamiento que afectó a unos 300.000 m 2 de tierras de labor, modificando totalmente la topografía original de la zona así como la red superficial de drenaje. Este deslizamiento y reactivaciones posteriores en los años 1816, 1857 y 1943 determinaron el abandono de este núcleo de población y de las tierras de cultivo. Gracias a la recuperación de documentos históricos que refieren los hechos ocurridos por testigos presenciales y al estudio y análisis del terreno, se ha podido reconstruir lo acontecido en el deslizamiento original, sus dimensiones y características, la tipología del movimiento y el mecanismo de rotura, así como los factores que desencadenaron dicho fenómeno. Abstract: Between 24 th March and 29 th March 1721, a great landslide took place in Biniarroi, a small village located in the municipality of Mancor del Vall (Majorca). The landslide affected more than 300.000 m 2 of agricultural land, completely modifying the original topography of the area, as well as the superficial drainage network. The occurrence of this landslide, and subsequent reactivations during the years 1816, 1857 and 1943, caused both the village of Biniarroi and the cultivated area to be abandoned. The recovery of historical documents about this event, including eyewitness accounts, and a detailed study of the area, have allowed us to reconstruct the original landslide, its magnitude and characteristics, the type of movement as well as the triggering factors of this natural phenomenon.
We review rainfall thresholds for the initiation of landslides world wide and propose new empirical rainfall thresholds for
the Central European Adriatic Danubian South-Eastern Space (CADSES) area, located in central and southern Europe. One-hundred-twenty-four
empirical thresholds linking measurements of the event and the antecedent rainfall conditions to the occurrence of landslides
are considered. We then describe a database of 853 rainfall events that resulted or did not result in landslides in the CADSES
area. Rainfall and landslide information in the database was obtained from the literature; climate information was obtained
from the global climate dataset compiled by the Climate Research Unit of the East Anglia University. We plot the intensity-duration
values in logarithmic coordinates, and we establish that with increased rainfall duration the minimum intensity likely to
trigger slope failures decreases linearly, in the range of durations from 20 minutes to ∼12 days. Based on this observation,
we determine minimum intensity-duration (ID) and normalized-ID thresholds for the initiation of landslides in the CADSES area.
Normalization is performed using two climatic indexes, the mean annual precipitation (MAP) and the rainy-day-normal (RDN).
Threshold curves are inferred from the available data using a Bayesian statistical technique. Analysing the obtained thresholds
we establish that lower average rainfall intensity is required to initiate landslides in an area with a mountain climate,
than in an area characterized by a Mediterranean climate. We further suggest that for rainfall periods exceeding ∼12 days
landslides are triggered by factors not considered by the ID model. The obtained thresholds can be used in operation landslide
warning systems, where more accurate local or regional thresholds are not available.
Large numbers of landslides can be associated with a trigger, for example, an earthquake or a large storm. We have previously hypothesized that the frequency-area statistics of landslides triggered in an event are well approximated by a three-parameter inverse-gamma distribution, irrespective of the trigger type. The use of this general distribution was established using three substantially complete and well-documented landslide event inventories: 11,000 landslides triggered by the Northridge California Earthquake, 4000 landslides triggered by rapidly melting snow cover in the Umbria region of Italy, and 9000 landslides triggered by heavy rainfall associated with Hurricane Mitch in Guatemala. In this paper, we examine further this general landslide distribution by using an inventory of 165 landslides triggered by heavy rainfall in the region of Todi, Central Italy. Our previous studies have shown the applicability of our general landslide distribution to events with 4000-11,000 landslides. This smaller inventory provides a critical step in examining the applicability of the general landslide distribution. We find very good agreement of the Todi event with our general distribution. This also provides support for our further hypothesis that the mean area of landslides triggered by an event is approximately independent of the event size.
Analysis of the spatial distribution of rockfall deposits at a regional scale (over an area of 250 km2 of northern Spain) using a cartographic database supported by a Geographic Information System (GIS) reveals several relationships between rockfall activity and environmental variables. Recent rockfall activity is inferred when recent scree is preserved at the bottom of the rock slopes. In order to identify the slope source areas of the scree we have mapped the deposit's drainage basin, applying topographic criteria, and we have combined these basins with the rock slopes map. A method for setting the basin boundaries automatically will replace manual cartography. This method is based on algorithms available within many commercial software programs and originally planned to analyse the behaviour of fluids over a topographic surface.The results obtained by combining the rockfall area source map with the geology and DTM show the relationships between the distribution of rockfall deposits and lithology, elevation and slope of the rockwall and a strong control of the joint type and density. Elevation influence on rockfall has been associated with climatic variations with elevation. Other variables, such as orientation, show complex influences that are difficult to interpret.
Rainfall-triggered landslides taking place in the Spanish Eastern Pyrenees have usually been analysed on a regional scale. Most research focussed either on terrain susceptibility or on the characteristics of the critical rainfall, neglecting a detailed analysis of individual events. In contrast to other mountainous regions, research on debris flow has only been performed marginally and associated hazard has mostly been neglected.
In this study, five debris flows, which occurred in 2008, are selected; and site specific descriptions and analysis regarding geology, morphology, rainfall data and runout were performed. The results are compared with worldwide data and some conclusions on hazard assessment are presented.
The five events can be divided into two in-channel debris flows and three landslide-triggered debris flows. The in-channel generated debris flows exceeded 10 000 m<sup>3</sup>, which are unusually large mass movements compared to historic events which occurred in the Eastern Pyrenees. In contrast, the other events mobilised total volumes less than 2000 m<sup>3</sup>. The geomorphologic analysis showed that the studied events emphasize similar patterns when compared to published data focussing on slope angle in the initiation zone or catchment area.
Rainfall data revealed that all debris flows were triggered by high intensity-short duration rainstorms during the summer season. Unfortunately, existing rainfall thresholds in the Eastern Pyrenees consider long-lasting rainfall, usually occurring in autumn/winter. Therefore, new thresholds should be established taking into account the rainfall peak intensity in mm/h, which seems to be a much more relevant factor for summer than the event's total precipitation.
The runout analysis of the 2008 debris flows confirms the trend that larger volumes generally induce higher mobility. The numerical simulation of the Riu Runer event shows that its dynamic behaviour is well represented by Voellmy fluid rheology. A maximum front velocity of 7 m/s was back-analysed for the transit section and even on the fan velocities larger than 2 m/s were obtained.
This preliminary analysis of the major Eastern Pyrenean debris flows represents the first background for future studies. Additional research on other events is necessary to support the results presented herein, and to properly assess and reduce hazard related to debris flows.
Climate and environmental changes associated with anthropogenic global warming are being increasingly identified in the European Alps, as seen by changes in long-term high-alpine temperature, precipitation, glacier cover and permafrost. In turn, these changes impact on land-surface stability, and lead to increased frequency and magnitude of natural mountain hazards, including rock falls, debris flows, landslides, avalanches and floods. These hazards also impact on infrastructure, and socio-economic and cultural activities in mountain regions. This paper presents two case studies (2003 heatwave, 2005 floods) that demonstrate some of the interlinkages between physical processes and human activity in climatically sensitive alpine regions that are responding to ongoing climate change. Based on this evidence, we outline future implications of climate change on mountain environments and its impact on hazards and hazard management in paraglacial mountain systems.
In Italy, rainfall is the primary trigger of landslides that frequently cause fatalities and large economic damage. Using a variety of information sources, we have compiled a catalogue listing 753 rainfall events that have resulted in landslides in Italy. For each event in the catalogue, the exact or approximate location of the landslide and the time or period of initiation of the slope failure is known, together with information on the rainfall duration D, and the rainfall mean intensity I, that have resulted in the slope failure. The catalogue represents the single largest collection of information on rainfall-induced landslides in Italy, and was exploited to determine the minimum rainfall conditions necessary for landslide occurrence in Italy, and in the Abruzzo Region, central Italy. For the purpose, new national rainfall thresholds for Italy and new regional rainfall thresholds for the Abruzzo Region were established, using two independent statistical methods, including a Bayesian inference method and a new Frequentist approach. The two methods proved complementary, with the Bayesian method more suited to analyze small data sets, and the Frequentist method performing better when applied to large data sets. The new regional thresholds for the Abruzzo Region are lower than the new national thresholds for Italy, and lower than the regional thresholds proposed in the literature for the Piedmont and Lombardy Regions in northern Italy, and for the Campania Region in southern Italy. This is important, because it shows that landslides in Italy can be triggered by less severe rainfall conditions than previously recognized. The Frequentist method experimented in this work allows for the definition of multiple minimum rainfall thresholds, each based on a different exceedance probability level. This makes the thresholds suited for the design of probabilistic schemes for the prediction of rainfall-induced landslides. A scheme based on four probabilistic thresholds is proposed. The four thresholds separate five fields, each characterized by different rainfall intensity-duration conditions, and corresponding different probability of possible landslide occurrence. The scheme can be implemented in landslide warning systems that operate on rainfall thresholds, and on precipitation measurements or forecasts.
The autumn of 2004 was particularly wet in Umbria, with cumulative rainfall in the period from October to December exceeding 600 mm. On 4?6 December and on 25?27 December 2004, two storms hit the Umbria Region producing numerous landslides, which were abundant near the town of Orvieto where they affected volcanic deposits and marine sediments. In this work, we document the type and abundance of the rainfall-induced landslides in the Orvieto area, in south-western Umbria, we study the rainfall conditions that triggered the landslides, including the timing of the slope failures, we determine the geotechnical properties of the failed volcanic materials, and we discuss the type and extent of damage produced by the landslides. We then use the recent event landslide information to test a geomorphological assessment of landslide hazards and risk prepared for the village of Sugano, in the Orvieto area. Based on the results of the test, we update the existing landslide hazards and risk scenario for extremely rapid landslides, mostly rock falls, and we introduce a new landslide scenario for rapid and very rapid landslides, including soil slides, debris flows and debris avalanches.
Tree-ring analysis has been used to reconstruct 22 years of rockfall behavior on an active rockfall slope near Saas Balen (Swiss Alps). We analyzed 32 severely injured trees ( L. decidua , P. abies and P. cembra ) and investigated cross-sections of 154 wounds.
The intra-annual position of callus tissue and of tangential rows of traumatic resin ducts was determined in order to reconstruct the seasonality of past rockfall events. Results indicate strong intra- and inter-annual variations of rockfall activity, with a peak (76%) observed in the dormant season (early October ? end of May). Within the growth season, rockfall regularly occurs between the end of May and mid July (21.4%), whereas events later in the season appear to be quite rare (2.6%). Findings suggest that rockfall activity at the study site is driven by annual thawing processes and the circulation of melt water in preexisting fissures. Data also indicate that 43% of all rockfall events occurred in 1995, when two major precipitation events are recorded in nearby meteorological stations. Finally, data on impact angles are in very good agreement with the geomorphic situation in the field.
A total of more than 140 000 kg of small-magnitude rockfall deposits was measured in eight rockfall collectors of altogether 940 m2 in size between 1999–2003 below a 400–600 m high rock face in the Reintal, German Alps. Measurements were conducted with a temporal resolution up to single days to attribute rockfall intensity to observed triggering events. Precipitation was assessed by a rain gauge and high-resolution precipitation radar. Intense rainstorms triggered previously unreported rockfall intensities of up to 300 000 g/(m2h) that we term "secondary rockfall event." In comparison to dry periods without frost (10−2g/(m2h)), rockfall deposition increased by 2–218 times during wet freeze-thaw cycles and by 56-thousand to 40-million times during secondary rockfall events. We obtained three nonlinear logistic growth models that relate rockfall intensity [g/(m2h)] to rainfall intensity [mm/h]. The models account for different rock wall intermediate storage volumes, triggering thresholds and storage depletion. They apply to all rockfall collector positions with correlations from R2=0.89 to 0.99. Thus, the timing of more than 90% of the encountered rockfall is explained by the triggering factor rainfall intensity. A combination of rockfall response models with radar-supported storm cell forecast could be used to anticipate hazardous rockfall events, and help to reduce the exposure of individuals and mobile structures (e.g. cable cars) to the hazard. According to meteorological recordings, the frequency of these intense rockfall events is likely to increase in response to global warming.
From October 2008 to January 2009, Majorca island was affected by a period of intense rainfall and low temperatures which triggered numerous slope movements, 12 being registered in the Tramuntana Range, some of which seriously affected the road network. On the night 19th December 2008, a rockfall on the eastern slope of the Puig de s'Alcadena (Alaro) took place, generating a rock avalanche with a length of 650 m. The rock avalanche destroyed the pine wood in its path, leaving a tongue of blocks over an area of 60.000 m2 and 300.000 m3 in volume. Some of the blocks have a volume of over 1,500 m3 and are several tones in weight. The wedge failure on the scarp of Puig de s 'Alcadena is produced on two planes which coincide with the main tectonic features of the Range. The fact that heavy and continuous rainfall (150 mm in 24 h and 672 mm of accumulated rainfall) coincided with unusually low temperatures (below O0C), was the triggering factor of the avalanche. Fortunately, no serious damage occurred.
This chapter presents a review of the situation concerning the various geomorphological hazards in the country, including some information about existing programmes for research, control and mitigation. With its great variety of climatic, geological and morphodynamic environments, Spain is subject to every kind of natural hazard: tsunamis, floods, volcanism, and mass movements. The whole of the territory is prone to some kind of geomorphological hazard but it is in the eastern and southern coastal strips that the risks are greatest. One of the main problems for the mitigation of geomorphological hazards in Spain is the lack of an appropriate regulatory framework for the incorporation of natural hazard assessments into land-use planning and management at the macro-, meso- and micro-planning levels. The coverage of hazard mapping is still far from complete or adequate, and much work remains to be done. There has been considerable diversity in the methods used for risk assessment and for the cartographic representation of natural hazards. An urgent need is to establish common, accepted methodologies and criteria, based on indicators defined as clearly as possible, and to standardize map legends and scales for different planning levels. Information programmes for the general public also need to be considerably expanded.
RESUMEN La ladera de la margen izquierda del Torrente de Fornalutx, junto al Valle de Sóller en la isla de Mallorca, ha sufrido una serie de movi-mientos en los años 1924, 1954, 1974 y 2002, todos ellos desencadenados por episodios de lluvias intensas y prolongadas durante varios días. En el año 2002, la posibilidad de taponamiento del torrente por la masa deslizada, puso en alerta a las autoridades de la isla y con-dicionó la realización de un estudio detallado de la zona. Este estudio incluyó la realización de perfiles geofísicos mediante sísmica de refracción y tomografía eléctrica; la ejecución de 4 sondeos mecánicos de reconocimiento, así como numerosos ensayos in situ y de labo-ratorio que tuvieron como objetivo determinar las propiedades hidráulicas y resistentes de los materiales de la ladera. El análisis e inter-pretación de los datos obtenidos pone de manifiesto la existencia de un deslizamiento principal de tipo planar, cuya superficie de rotura coincide con el contacto entre dos tipos de materiales de diferente naturaleza y propiedades resistentes. El deslizamiento (y sucesivas reactivaciones), aunque superficial, involucra un volumen de material de unos 300.000 m 3 y determina que la zona sea una de las de mayor riesgo por este tipo de procesos en la isla, debido a la cercanía del pueblo de Fornalutx. Palabras clave: caracterización geomecánica, deslizamientos, laderas, Mallorca, riesgo Landslides on the left side of the Fornalutx torrent (Majorca, Spain) ABSTRACT The slope on the left hand side of the Fornalutx Torrent, close to the Valley of Soller on the island of Majorca, has been affected by a series of movements in 1924, 1954, 1974 and 2002, all of which were triggered by episodes of intense and continuous rainfall. In 2002, the pos-sibility of the torrent being blocked by the material from the slide, alerted the island authorities to the need for a detailed study of the area. The work included a geophysical study of the slope, using seismic and electrical tomography techniques; the drilling of 4 boreholes as well as numerous in situ and laboratory tests, which aimed to determine the hydraulic and stress properties of the materials of the slope. The analysis of the data obtained clearly shows the existence of a planar main landslide and the breaking surface of which coincides with the contact between two types of materials of different nature and stress properties. The landslide, although very shallow, involves a vol-ume of material of 300,000 m 3 and means that the area is one of those at greatest risk on the island, due to the proximity of the village of Fornalutx.
This paper evaluates the usefulness of press archives as temporal
records of landslides in Asturias, northern Spain. It also shows the
potential for this kind of information in the establishment of
relationships between slope instability events and climatic parameters.
In this way, a search has been made of Asturian regional newspaper
archives, including data from the period between January 1980 and June
1995 (5290 newspapers reviewed). The methodology developed shows some
limitations, due to the low frequency of news items relating to
landslides and the lack of scientific data collected by correspondents.
Moreover, there is a bias towards instability events concerning people,
infrastructures and other human resources. Statistical analysis of 209
news items relating to slope instability is useful to establish the
geological and spatial location of landslides. Fifty-one point two
percent of them are situated in the Central Coal Basin, with a
sedimentary siliceous bedrock. Temporal data are accurate in 83.2% of
the cases. A comparison between climatic and slope instability events
reveals that 79% of the landslides developed during rainfall events,
associated with the monthly 24-h rainfall maximum values. Highest
landslide frequencies are reached in years with more than 1000 mm
rainfall, mainly in December and April.
This study investigates the relationships between climate changes and hillslope evolution in the Dolomites (eastern Alps, Italy), during the Late Quaternary, with particular attention paid to landslide processes. The basic premise is that modifications in landslide frequency may be interpreted as changes in the hydrological conditions of slopes, which are in turn controlled by climate.After the statistical analysis of a data set composed of 73 conventional radiocarbon ages, obtained from 24 landslides, four periods of enhanced landsliding have been identified: I. from 10,700 to 8400cal BP, between Younger Dryas and the Preboreal; II. from 8200 to 6900cal BP, during the older Atlantic; III. from 5800 to 4500cal BP, between Atlantic and Subboreal; and IV. from 4000 to 2100cal BP, between Subboreal and Subatlantic.These periods have been compared with different Lateglacial and Holocene paleoclimatic records, to check the correspondence between periods of enhanced landslide activity and cold and humid spells recognized at different spatial scales. As the records show, in the study areas, slope instability processes can be considered geomorphological indicators of climatic changes and to a certain extent reliable proxies of environmental evolution.
We examined information collected from 395 reports of slope-movement events during about the past 150 years in Yosemite National Park, central Sierra Nevada, California, to identify the most prevalent types of slope movements and their triggering mechanisms. Rock slides and rock falls have been more numerous than debris slides, debris flows, and miscellaneous slumps. Rock falls have produced the largest cumulative volume of deposits. About half of slope movements had unreported or unrecognized triggering events. Earthquakes and rain storms individually accounted for the greatest cumulative volumes of deposits from recognized triggers of all types of historical slope movements; snowmelt, human activities and freeze-thaw conditions accounted for only a small proportion of the volumes from reported triggers. A comparison of the historical and postglacial average annual rates of deposition from slope-movement processes in a portion of the Yosemite Valley indicates that, during the period 1851–1992, slope-movement processes have been producing about half the average rate of deposits than during the past 15,000 years.
The Tramuntana Range on the Island of Majorca has suffered numerous, damaging episodes caused by landslides. The historical inventory of these movements shows a clear correlation between landslide occurrence and intense rainfall. Most of the slides have occurred after short intense storms. The slope movements are mainly shallow failures, debris flows, debris slides and soil slips. Regional hazard assessment is carried out by combining the probability of the landslide rainfall threshold with the landslide susceptibility in the area. The correlation of the known dates of historical landslides since 1956 with rainfall data provided by the rain gauges nearest to the location of the slides, reveals that most of the movements take place when maximum 24-hour rainfall values are around 130 mm or above. This is the triggering threshold considered in the present work. A statistical analysis of intense rainfall has been carried out in the area, using the Gumbel probability distribution function, which allows us to obtain the maximum 24-hour rainfall values that are to be expected for return periods of 5, 10, 25 and 100 years and to locate the areas where the rainfall threshold is exceeded. In order to predict medium-term hazard, we have considered the probability of the occurrence of episodes of intense rainfall, exceeding 130 mm in 24 hours, for a period of 25 years. Prior to this work, a susceptibility study was made on the area, based on the inventory of the movements and the analysis of the different conditioning factors of the instability. A susceptibility map at 1 : 25,000 scale was designed which provides information on the spatial probability of occurrence of the landslides predicted in the area. As our objective was to determine the degree of hazard in the study area, we performed a spatial-temporal superposition on the general map of susceptibility and the probability map of intense rainfall exceeding 130 mm, for a return period of 25 years. This methodology allows us to obtain a hazard map which constitutes a feasible tool for regional hazard assessment.
French
Le Massif de la Tramuntana sur l'île de Majorque a subi de nombreux épisodes dévastateurs du fait de glissements de terrain. L'historique de ces mouvements indique une forte corrélation entre la survenue d'un glissement de terrain et de fortes chutes de pluie. La plupart de ces glissements de terrain sont ainsi survenus à la suite d'intenses orages de courte durée. Les mouvements des versants sont principalement constitués d'effondrements de terrains, avalanches ou glissements de débris, ainsi que d'éboulement des sols. L'une des méthodes d'évaluation des risques régionaux consiste à combiner la probabilité du seuil de chute de pluie avec la sensibilité aux glissements de terrain dans la région. La corrélation entre les dates connues des glissements de terrain historiques depuis 1956 avec les données de chutes de pluie fournies par les pluviomètres situés à proximité des sites des glissements de terrain démontre que la plupart des mouvements ont lieu lorsque les valeurs maximales de chutes de pluie sur une période de 24 heures sont supérieures ou égales à 130 mm. C'est là le seuil de déclenchement pris en compte par la présente étude. Une analyse statistique des fortes chutes de pluie a été menée dans la région, à l'aide de la fonction de distribution de probabilité de Gumbel, qui permet de déterminer les valeurs maximales de chutes de pluie sur une période de 24 heures, à prévoir pour des périodes de récurrence de 5, 10, 25 et 100 ans et permet de localiser les zones où le seuil de chutes de pluie est dépassé. Afin de prévenir le risque pour une zone, sur une période moyenne de temps, nous avons considéré la probabilité de la survenue d'épisodes de fortes chutes de pluie, au-delà de 130 mm en 24 heures, sur une période de 25 ans. Préalablement à la présente étude, une étude de sensibilité a été menée dans cette zone, fondée sur l'inventaire des mouvements et de l'analyse des différents facteurs qui conditionnent l'instabilité. Une carte de sensibilité au 1 : 25.000 a ainsi été conçue, afin de fournir des informations sur la probabilité spatiale de survenue de glissements de terrain dans la région. Dans la mesure où notre objectif était de déterminer le degré de risque dans la zone d'étude, nous avons réalisé une superposition spatio-temporelle sur une carte générale de sensibilité et sur la carte de probabilité de fortes chutes de pluie dépassant les 130 mm, sur une période de récurrence de 25 ans. Cette méthodologie nous permet d'obtenir une carte de risque, qui constitue un outil réalisable d'évaluation des risques dans une zone régionale.
This paper presents results of recent studies on distribution and category of landslides in one section of the Sichuan–Tibet Highway, adjacent to the northern side of the Yarlu Tsangpo Grand Canyon, Tibet, Southwestern China. In the tectonic setting predominated by compression and strike-slipping, active faults are dominant and result in the genesis of the great alpine relief together with fluvial incision and unloading. In this section, with a distance of about 290 km between Ranwu and Lulang, 34 landslides occurred. Among them, the 12 large and super-large landslides comprise the most dangerous part of the highway system to road users over the past 50 years. The landslides usually occurred in slopes comprised of moraine with a large thickness, fluvio-pluvial and lacustrine deposits and fractured rocks. Based on the examination of the physical geography, structural geology, Quaternary geology, stratigraphy and petrography, this paper presents the temporal-spatial distribution of landslides along the section and classification of them into three types with respect to mechanism and composites of landslides. Type 1. Landslide initiated at high elevation and transformed into a distal debris flow damming the river with a long reoccurrence interval
The landslides and rockfalls were studied in this paper from Xiangjiaba to Baihetan in the lower reach of Jinsha river. Their
volume, distribution density and landslide index were studied which indicated that there existed close relationships between
landslides and rockfalls and geological structure, stratum. The fold and faultage influenced on the stability of slope and
offered the geological condition to landslides and rockfalls. The physiognomy controlled their distribution. Slope angles
of landslides were 10°–50° and slope angles of rockfalls were mainly 35°–50° in the valley in the studied area. The results
indicated the geology and physiognomy of distribution area of the landslides and rockfalls in the studied area. They offered
the theoretical foundation to prevent and cure geological disaster and protect the water power engineering.
This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction.
The purpose of this study is to develop and apply the technique for landslide susceptibility analysis using geological structure in a Geographic Information System (GIS). In the study area, the Janghung area of Korea, landslide locations were detected from Indian Remote Sensing (IRS) satellite images by change detection, where the geological structure of foliation was surveyed and analysed. The landslide occurrence factors (location of landslide, geological structure and topography) were constructed into a spatial database. Then, strike and dip of the foliation and the aspect and slope of the topography were compared and the results, which were verified using landslide location data, show that foliation of gneiss has a geometrical relation to the joint or fault that leads to a landslide. Using the geometrical relations, the landslide susceptibility was assessed and verified. The verification results showed satisfactory agreement between the susceptibility map and the landslide location data.