The Aziza Cave is situated in the High Atlas Mountains, on the Tazougart Plateau, within the province of Errachidia in southeastern Morocco. The cave entrance is located approximately 30 m above the bed of the Oued Guir River. The system reaches a maximum surveyed depth of 90 m, with its lowest point at an elevation of 969 m above sea level, and extends over a total mapped length exceeding 4 km. The cave is segmented into several sections by a series of sumps. The passages situated beyond of the sumps extend for more than 1.3 km and exhibit morphological features distinct from those observed in the downstream sections. Located within the Saharan bioclimatic zone, the Aziza Cave hosts seven bat species that use the site at different times of the year, each occupying specific zones within the system. As a result, the composition and distribution of the cave's chiropteran assemblage vary seasonally. Topographic and photogrammetric surveys conducted in conjunction with behavioral observations of bat activity within the cave provide evidence for the influence of bat ethology on biocorrosion processes. Several sections of the cave display characteristic morphologies and notable enlargements that appear to be associated with their biogenic activity. The observed morphologies are closely associated with bat species that occupy the cave during the spring and summer seasons, forming large, densely aggregated colonies. The cave further displays a complex and diverse mineral assemblage, largely influenced by the presence of phosphate-and sulfate-bearing minerals. The detection of hexahydrite, epsomite, and vivianite constitutes a rare mineralogical occurrence within cave systems.
This article examines the dual role of the North American beaver (Castor canadensis) as both an ecosystem engineer and an emerging hydrological hazard. Combining a multidisciplinary review of scientific literature with a media-based analysis of 24 documented dam failure events in Qu & eacute;bec, the study investigates how beaver activity shapes hydrological, geomorphological, ecological, and biogeochemical processes. While dam construction promotes wetland restoration, biodiversity, sediment storage, and hydrological resilience, sudden summer dam failures can generate localized flooding and damage transportation networks and private infrastructure. Results show that media coverage predominantly frames beaver-related events through narratives of risk, crisis, and institutional liability, marginalizing the broader (geo)ecological functions documented in scientific research. This event-driven framing contributes to a governance focus on reactive intervention rather than long-term ecosystem-based management. In response, this study advocates integrated watershed governance approaches that combine citizen-based monitoring, hydraulic modeling, and zoogeomorphological perspectives to improve hazard assessment, risk anticipation, and adaptive management strategies. By bridging biophysical processes and socio-institutional dynamics, this paper provides one of the first integrative analyses linking beaver-induced geomorphic activity with civil protection frameworks. It argues for a shift from crisis-oriented control toward coexistence-based management, recognizing beavers as co-constructors of fluvial landscapes within socio-ecological resilience and nature-based adaptation strategies.
Cliffs are significant breeding habitats for numerous species of seabirds. Yet, few studies have investigated the relationship between seabirds and cliffs, particularly regarding spatial and temporal variation in cliff characteristics and seabird nesting patterns. This study aims to address this gap by focusing on the nesting site selection of kittiwakes and guillemots in relation to geomorphological dynamics. The study followed a three-step approach, starting with identifying factors controlling geomorphological dynamics in Icelandic cliffs, leading to a typology of geomorphological functioning, and finally assessing whether there is a correlation between geomorphological instability and seabird nest site selection. To do so, a diachronic series of photographs from Skoruvikurbjarg cliff (Northeast Iceland) and Krysuvikurberg cliff (Southwest Iceland) was analyzed using photographic comparison, which was then confirmed by on-site observations. The factors identified as having the greatest influence on the stability of cliffs, specifically the site (sheltered or seafront) and its profile (rectilinear or rugged), give rise to three main types of geomorphological functioning of cliffs. Geomorphological dynamics appear to have limited influence on seabird nest site selection, as the most stable type was progressively abandoned by seabirds, and no evidence of pre-or post-adaptation in response to geomorphological instability was observed. Nevertheless, this interdisciplinary study, combining ecology and geomorphology, highlights the value of long-term visual records in documenting both physical and population changes over time, offering insight into conservation priorities.
Mountain areas are subject to various types of hydrological hazards such as torrential floods and debris flows. They are also particularly sensitive to climate and societal changes that lead to the emergence of new risk situations. To meet the challenges of managing and anticipating these risks, floods must be documented as exhaustively as possible over the long term. However, existing chronologies tend to cover a too large spatial scale, most often outside the mountain context, and do not take sufficient account of the complexity of the processes involved. In this article, a 420-year flood chronology has been reconstructed using data extracted from the Vallouise-Pelvoux multi-risk inventory. The accuracy and regularity of the sources made it possible to (i) identify 278 flood episodes that affected one or more torrents and/or torrential rivers in response to the same synoptic hydrometeorological conditions over the period 1600-2020 in Vallouise area, (ii) analyze their typology and consequences, (iii) identify six "active" periods separated by periods with much fewer floods, whose temporal distribution is broadly consistent with that of existing chronologies in other contexts, (iv) highlight a change in seasonality. The spatio-temporal evolution of the typology of individual events was also studied, showing, over the last 30 years, a shift in the proportion of torrential river and torrent events in favor of the latter.. An initial effort at contextualization allowed these results to be compared with climatic, societal, and source changes in order to formulate hypotheses as to their cause. Approaches for further exploration of the gathered information are proposed.
A detailed systemic analysis of the hydrometeorological event of Oct. 14-15, 2018, made it possible to identify, for the first time, all the predisposing, triggering, and aggravating/mitigating factors that explain the genesis, impacts, and management of the event in the Aude watershed. Attention then focused on one of the parts of the watershed that received the highest cumulative rainfall, namely the Rieu Sec watershed, a right-bank tributary of the Orbiel River in the Minervois. It has been shown that the Oct. 2018 event was extraordinary in several respects (meteorology; hydrology; geomorphology; sediment budget; specific degradation rate; impact on riparian vegetation; recurrence interval estimated at 204-378 yrs). A model of small, mountainous watersheds (< 40 km2) functioning is proposed, in which high-magnitude/low-frequency flood events play a key role. The significant variability in precipitation observed from one sub-watershed to another complicates the management of rainfall and floods. The challenge for the future lies in improving flood forecasting, and the effective dissemination of these forecasts.
Grain-size distribution is a key parameter for understanding torrential dynamics, whether through hydraulic or geomorphological approaches. However, such data are highly site-specific, particularly in torrential environments where acquisition is especially challenging due to the wide range of particle sizes and their strong spatial heterogeneity. To facilitate the collection ofgrain-size data, methods have been developed over the pastfour decades to measure particle sizes directly from very high-resolution images. These methods long remained imperfect. The recent democratization of artificial intelligence tools has enabled the development of detectors whose performance now ofiers the potential for widespread application. This paper presents the grain-size detector GALET, a software tool that automatically measures visible particles in an image. Based on a neural network, GALET enables exhaustive grain-size measurement from high-resolution orthophotographs, notably acquired using drones. Two case studies illustrate its application: the Ullion catchment (Alpes-Maritimes) and the Ca & iuml;ros torrent, both impacted by Storm Alex in 2020. These case studies demonstrate GALETs'ability to map grain-size distributions over large areas and to identify significant morphological structures, contributing to a better understanding of torrential processes. Such tools open promising perspectives for hydro-sedimentary modelling, the study ofgrain-size sorting, and the standardization of geomorphological indicators. This approach helps strengthen the links between geomorphology and hydraulics by transforming qualitative observations into quantitative data usable for both research and operational management.
Red wood ants (RWA) of the Formica rufa group are keystone species and ecosystem engineers that play a geomorphologically important but underestimated role in the boreal and temperate forest ecosystems of Europe. As mound-building species, they dig galleries in loose materials to form their underground nests and create meter-scale landforms (i.e., mounds or anthills) above the soil surface corresponding to the epigeal part of their nests. Mainly composed of organic matter, but also containing a mineral fraction, the mounds serve as microhabitats for many associated species (i.e., myrmecophiles), so the conservation of these biogenic landforms is relevant for a whole range of other taxa. The aim of this zoogeomorphological study is to examine the spatial distribution and temporal evolution of RWA mounds in a temperate forest landscape of Northwestern France through a 5-year monitoring study (2020-2024). The methodological protocol combines exhaustive GPS mapping of anthills on a forest area of 62 ha, and monitoring of 13 strip transects with morphometric measurements of mounds achieved each year at the same period. Main findings show that (i) the densities of RWA mounds vary greatly over space, mainly depending on forest stand types (with a preference for mixed-conifer stands) and slope gradient (with a preference for flat or low-gradient topography); (ii) anthills are dynamic landforms that change rapidly in terms of location, shape, size and volumes, mainly in response to interannual climate variability and anthropogenic disturbances. Future work will focus on deciphering the possible relationships between RWA mound distribution, geogenic gases and tectonic faults, and on conducting a systematic inventory of myrmecophilous organisms in and around large nests, which may reveal unexpected biodiversity associated with RWA mounds.
This paper concerns a study of slope dynamics in the Nunavik region (northern Qu & eacute;bec), specifically on a northern slope of Lepage Island, at Lake Wiy & acirc;sh & acirc;kim & icirc;. This area, characterized by a subarctic climate, features active geomorphological processes. The aim of this study is to document the evolution of a slope that consists of a coarse debris talus in the apical zone, followed by a forested slope below a flat area, with particular attention to slope dynamics and recent geomorphological activity. Fieldwork includes topographical profiles of the slope, an inventory of the morphometric properties of the rock debris, and visual estimation of the vegetal cover on the clasts. Dendrochronology methods were also used to identify the periods of disturbances in black spruce growth, and suggest recurrent surface instabilities since 1790. Results show that the upper part of the slope is dominated by large and coarse boulders with continuous vegetation cover, indicating little recent geomorphological activity on the majority of the slope. In contrast, the lower part shows signs of destabilization, notably after 1980. Results indicate that current geomorphological processes, such as snow avalanches, rockfall or landslides, are limited, although there are sings of past readjustments and recent disturbances.
The Vexin is a natural and historical territory located in the northwest of the Paris Basin. It presents a series of landforms illustrating the process of seepage erosion, i.e., an inconspicuous but permanent erosion process linked to the emergence of groundwater. These landforms develop at different levels of the sedimentary pile, mainly above the transitions between clays and sands that crop out in the Ypresian and Rupelian levels. The resulting elementary geomorphological features are natural amphitheaters in steep-walled valley heads and residual hills or outliers. At a larger scale, typical dendritic hydrographic networks are observed. The timing of valley head retreat is addressed using archaeological data. The discussion focuses on the respective roles of seepage and runoff in the formation of landscapes and on the possible links between seepage and slope dynamics. We finally suggest that, thanks to its preserved natural heritage, the Vexin has all the resources to become a major spot for studying and teaching erosion processes.
On June 21, 2024, the hamlet of La B & eacute;rarde (Ecrins massif) was devastated by an exceptional torrential flood. Following the event, the French government asked the ONFs'RTM department, assisted by some thirty scientists, to carry out a retroanalysis of the event. The flood resulted from the combination of an extreme rain-on-snow event and the drainage of a temporary supraglacial lake (and likely other water retention into the glacier), having mobilized a large quantity of available material in the Bonne Pierre sub-basin. This text presents the main geomorphological findings. A detailed geomorphological map was drawn up after the event. The results reveal three main areas of erosion and deposition: (i) the proglacial margin, where the main channel was widened and deeply incised, (ii) the Bonne Pierre proglacial fan, and (iii) the alluvial fan on which the B & eacute;rarde hamlet is built. Sediment balances based on a comparison of 2021 and 2024 LiDAR HD data show that the volumes mobilized from the glacier front to the torrential cone (at the level of the hamlet of La B & eacute;rarde) are of the order of 300,000 m(3) and that the volume accumulated on this cone is around 200,000 to 230,000 m(3). The difference would correspond to the volume exported downstream by the V & eacute;n & eacute;on river. A prospective analysis shows that it is not possible to exclude the occurrence of a new flood of similar magnitude in the future, especially in the context of the climate change. The flood of June 21, 2024 should therefore be considered as a reference flood to be taken into account when drawing up urban development plans, and in protection scenarios for the hamlet of La B & eacute;rarde.
Located in the northern, rain-shadow zone (< 300 mm/yr) of the Nepal Himalaya, Kagbeni village (2810 m, 420 inhabitants, at the junction between Jhong Khola and Kali Gandaki) was affected by a disastrous, unusual hyper-concentrated flood on August 13, 2023. It caused significant damage to property and infrastructure (cost estimated at USD 7.4 millions), fortunately without fatalities. For several years, increased rainfall has been recorded at Jomsom station (2720 m), a trend confirmed by residents. However, no single extreme rainfall event that could have triggered the flood was recorded at Jomsom station or in CHIRPS rainfall data for the Jhong Khola valley. Considering the geomorphological context, we hypothesized that the flood event was most likely triggered by a landslide-lake outburst. The landslide existence and source area (upstream from Chhiongur gorges) were confirmed by analysis of Sentinel-1 InSAR coherence time series. Downstream, the flood spread over the entire valley floor, as evidenced by new deposits, bank cuttings and reactivation of landslides providing additional debris and making downstream flooding even more destructive (bridges, buildings, livestock, orchards...). The volume of debris transported was estimated at 647,000 m(3), followed by rapid post-flood re-incision (215,000 m(3)). The inhabitants of Kagbeni also contributed to disasters by settling on very low terraces and encroaching on the Jhong Khola riverbed. Upstream of the village, the Upper Mustang Road bridge also amplified the damage through a bottleneck effect: its concrete deck collapsed, and its transport was very destructive downstream. Given the general trend towards climate change, the probability of future, similar flash floods remains high in Kagbeni, yet some residents have rebuilt their homes and continue to live on hazardous floodplains. We suggest some measures for preventing future risks, such as (i) applying the Freedom Space for Rivers concept to avoid encroachment of floodplains by anthropogenic activities, and (ii) managing a concrete ford-type structure instead of poorly calibrated bridge deck along the Upper Mustang Road. More generally, a nationwide natural risk-reduction policy should be implemented.
This article looks at the connection between slope processes and torrential dynamics in mountain catchments in the context of current climate change. The aim is to show that a chain of processes triggered by rock face destabilization is only possible under certain conditions, depending on the morphology of the watershed. Three basins are analyzed: (i) the Vallonbrun basin, partially glaciated, affected by a rock fall in 2017 detached from a permafrost rock wall, (ii) the Vallois basin, with voluminous slope deposits, affected by debris flows in 1971, 2001 and 2018, and (iii) the Cros de la Vache site, with walls where the presence of permafrost is possible, characterized by a recent sedimentary transfer combining avalanche, gravity and torrential processes. Using aerial images and orthophotographs, and during field work, the various processes and their evolution were identified and mapped using GIS. Geomorphological and diachronic maps were produced to highlight the connectivity factors for each basin: (i) strong connectivity between the torrent and the deposits at Les Vallois, where the steep slope enables rapid transit; (ii) slopes and proglacial margin disconnected from the torrent at Vallonbrun, where the low gradient of the valley prevents the transit of sediments, which remain stored upstream; (iii) an intermediate situation at Cros de la Vache, where the slopes are only connected to the torrent by a few scree cones, and where the transit of materials is interrupted on several sections of the torrent and the downstream basin is disconnected from the upstream sector. Models based on these three sites show that processes linked to cryospheric degradation are not always connected to the hydrographic network and therefore do not systematically lead to torrential hazards downstream.
Hydrogeomorphology makes use of various data notably hydrology and topography, which are necessary to analyse the change in river courses. It lays the foundation of a flood mapping technique done either by delineating the various river beds or by identifying the various features. Following this approach, this paper analyses the flood hazard on the Cameroonian side of the upper B & eacute;nu & eacute; valley, from the Lagdo dam moving downstream to the B & eacute;nu & eacute;- Faro confluence. The uniform geomorphology of this plain and the increasing human dynamics prone to flood occurrence of increasing magnitude, accompanied mostly by human and material loss. Efforts made to manage such floods are generally localized and inefficient due to limited knowledge of the spatial and temporal dynamics of floods, which can be explained by various technical and financial constraints. The literature review, geomatic techniques mobilised and field observations showed that applying hydrogeomorphology in the Benue Valley reveals a functional flood plain covering a surface area of about 135 km2 and shelters 4 groups of features namely: erosional features (11 %), sedimentation features (30 %), stable features (51 %) and the humid areas (8 %). Such spatial aggregation presents a categorized flood map based on three flood gradients: high (N3: 3000 m3/s in Garoua), average (N2: 2000 m3/s), and low (N1: 1500 m3/s). Finally, hydrogeomorphology is presented as a potential tool for the management of river corridors.
The Hunza-Nagar districts in northern Pakistan, nestled in the central Karakoram range, are known for their distinct climate and geology. However, the area is geologically unstable due to steep mountains, active faults, seismic zones, and sheared rock masses, leading to frequent landslides. This research aims to assess the comparative efficacy of three cutting-edge deep machine learning techniques (DMLTs), namely, the Universal Network U-Net, InceptionV3+, and DeeplabV3+, alongside three bivariate statistical models: Weight of Evidence (WofE), Intuitionistic Fuzzy Divergence (IF-D), and Frequency Ratio (FR), for Landslide Susceptibility Mapping (LSM) in Hunza-Nagar, North Pakistan. Initially, 148 landslide locations were marked, and 10 conditional factors were chosen to create a Landslide Inventory Map (LIM). The validation of landslide susceptibility models was assessed using several metrics: Area under the Curve (AUC), Density of Landslide Distribution (DLA), and the Seed Cell Area Index (SCAI). The evaluation of landslide susceptibility maps, produced through statistical models and DMLTs, revealed notable Prediction Rate Curves (PRC). Specifically, the WofE model achieved an 85 % PRC, the FR model reached 82 %, and the IF-D model also achieved an 85 % PRC. Furthermore, when estimating the performance of DMLTs using PRC, DeeplabV3+ established an 82 % success rate, InceptionV3+ reached 79 %, and U-Net achieved 80 %. In conclusion, the analysis designates that the WofE model, with an 85 % PRC and a D-value of 3.6, and the IF-D model, boasting an 85 % PRC and a D-value of 2.4, exhibited the highest prediction accuracy and classification ability.
The Gouffre site in Plougrescant is a Breton geotope listed in the inventory of remarkable geological objects in Brittany established in 1994 by the "Soci & eacute;t & eacute; G & eacute;ologique et Min & eacute;ralogique de Bretagne" (SGMB). These remarkable geological and geomorphological features have contributed to its tourist and cultural development by local authorities since the 1980s. Today, the Conservatoire du littoral, as the site manager, has to deal with the impact of ever-increasing visitor numbers and the aspirations/demands of a coastal population that has lived in this area since the 19th century. In this context, a morphosedimentary study of the gravel barriers and their relationship to the hydrological functioning of the sites' lagoons was carried out at the request of the Conservatoire du Littoral. The purpose of this assessment is to provide relevant scientific knowledge to guide and support the site's management and ecological restoration strategy. Although the morphological and sedimentary condition of the gravel barriers shows no major deterioration, the hydrological functioning of the lagoons has been compromised by a series of human interventions. This key issue must be addressed in the future to help restore the Gouffre site to the more natural state it had before human modifications.
The present study proposes a methodology for the visualization of cliff-top retreat velocity, using maps. This method is applied to the cliffs of La Flotte (R & eacute; Island, France). These cliffs are composed of sedimentary rocks, alternating carbonate, bioclastic limestone, and marl. The retreat at the cliff-top, a key indicator of the erosion of these geomorphological objects, is typically measured through time series analysis employing orthophotographs. However, these linear approaches are unable to adequately represent at once the spatial and temporal variability of the phenomenon. To address this issue, we have developed a methodology for generating strip graphs from multiscalar sources, encompassing both annual (UAV orthophotographs, 2021-2024) and decadal (IGN orthophotographs, 1950-2021) data. These strip graphs are derived from statistical results obtained with DSAS software, which compare cliff-top positions at varying dates. These strip graphs are then segmented to identify recurring areas of active erosion, particularly in the central and western parts of the cliffs studied. Uncertainties (georeferencing, digitizing, and resolution) are taken into account to eliminate unreliable values. This process, however, limits the exploitation of the results, as many transects are located within the periodic error margins. To compensate for this limitation, transects are cross-referenced with external indicators (landslides and scree cones inventories) to overcome uncertainty. A comparison of strip graphs and French regulatory mapping methods reveals that the former provides a more precise and localized assessment of erosive dynamics. However, using strip graphs requires additional information (geological, climatic, and marine characteristics) to explain the underlying mechanisms. This could be accomplished in the future. In conclusion, although subject to methodological constraints, strip graphs analysis is a relevant tool for spatializing medium-term cliff-top retreat velocity hazards, for coastal risk management.
Aeolianite (cemented dune sand) is commonly found along coastlines in South Africa, the Mediterranean, the Caribbean and Australia. Despite their widespread distribution, little is known about how aeolianite cliffs develop and the processes associated with their dynamics. This has implications for coastal sediment supply, responses to extreme events such as coastal storms, and the resilience of these rocky coastlines to climate change. This study examines the processes and patterns of aeolianite cliff development along the South African coast, where aeolianite has formed from the Middle Pleistocene onwards and where it outcrops along the contemporary coastline with cliffs up to 30 m high. Through field observations, measurements and mapping, the most significant processes associated with cliff development are identified. Unlike landslides and rockfalls that dominate rocky cliff development in other lithologies, aeolianite cliffs are mainly affected by small-scale physical, chemical and biological weathering processes that contribute to the granular disintegration of the cliff face. This is controlled by the detailed properties of aeolian units, such as bed thickness and bedding structures, the degree of cementation, and the presence of rhizoliths and case-hardened surfaces. Progressive mass loss from weaker aeolian units can then lead to structural collapse of the cliff face or when undercut by waves. These different weathering and erosion processes of aeolianite cliff development are strongly climatically controlled, suggesting that they are sensitive to any changes in external climatic conditions.
This study updates the data on the morphodynamic evolution of the Pas-de-Calais coastal cliffs, based on a diachronic analysis of cliff-top kinematics between 2000 and 2021, using the area-loss method. It also uses LiDAR datasets to conduct a three-dimensional topographic analysis, based on previously defined retreat zones. In analysing cliff retreat and morphological variations, 2D and 3D approaches complement each other, and help to identify recent erosion areas. The results reveal relatively high medium-term retreat rates across the study area (-0.26 m/year) and significant spatio-temporal variability. This variability is explained by the diversity of cliff types in terms of their hydrogeological characteristics, topomorphological configurations, and the magnitude and nature of anthropogenic impacts during the 20th century. Additionally, the low quality of the orthophotographs used in certain sectors may affect the accuracy of measurements and introduce significant uncertainty.
On October 2, 2020, Storm Alex triggered one of the most extreme torrential floods in recent years in France, causing severe damage in the V & eacute;subie and Roya valleys (southeastern France). In the V & eacute;subie, the floods induced exceptional sediment yields both in the main river and its tributaries. High-resolution pre-and post-event LiDAR data enabled the construction of a detailed sediment budget at the catchment scale. This study (i) contextualizes the storm-induced torrential event with other documented intense floods across the Alps and worldwide, and (ii) analyses the variability and controlling factors of the specific sediment yield in the V & eacute;subie tributaries. While Storm Alex ranks among the highest sediment yields recorded in the Alps, it is included in the variability domain of extreme headwater sediment production. Integrating these new data with existing Alpine records allows to refine an upper limit (the 99th percentile) for values of extreme sediment yields in the Alps. Variability in measurement methods across the literature underscores the suitability of systematically using high resolution topographic differencing for future extreme torrential events analyses. The observed specific sediment yield variability across the tributaries cannot be explained by rainfall forcings, making sediment availability the dominant control. We demonstrate that the specific sediment yield variability is best predicted by the proportion of sediment sources and the slope at the outlet measured on each catchment.
Rectilinear debris-mantled slopes, which are emblematic of periglacial environments, have a straight gradient from the base to the summit of the slope. Their inclination determines the evacuation of the debris supplied by frost shattering. Depending on lithology, slope gradient varies between 33 and 40 degrees. The central issue posed by these equilibrium profiles is how long it takes to shape them. Based on the study of slopes cut into the basalts of D & yacute;rafj & ouml;r & eth;ur in the Icelandic Westfjords, this contribution shows that such slopes are found in the most stable areas because their formation requires a long period of time under periglacial conditions. These slopes are less prevalent in the areas most affected by glacio-isostatic rebound and paraglacial rock-slope failures. Rectilinear debris-mantled slopes are developed in glacial valleys and have been preserved through glaciation periods. They therefore correspond to forms of glacial-interglacial iteration during which the role of glaciers was essential to scree evacuation, enabling the persistence of the rectilinear shape of the slopes.
