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Conséquences de la crue extrême du 2 octobre 2020 dans la vallée de la Roya (Alpes Maritimes) sur les réseaux de transport et de communication : leçons pour la reconstruction

2023, Fouache, Eric, Marchiel, Adrien, Rabaute, Alain, Desruelles, Stéphane, Gorini, Christian, Bianchi, Nicoletta, Kerverdo, Raphaël, Lafuerza, Sara

Le 2 octobre 2020, le passage de la tempête « Alex » a favorisé le déclenchement de précipitations « méditerranéennes » exceptionnellement intenses dans les vallées côtières des Alpes-Maritimes, notamment celle de la Roya. Ces pluies ont provoqué de nombreux processus hydro-géomorphologiques dévastateurs, crues glissements de terrain et éboulements principalement. Les destructions, qui ont frappé des infrastructures modernes et anciennes, ont été considérables, avec des conséquences sociales et économiques dramatiques. La majorité des ponts ont été détruits entre Tende et Breil-sur-Roya, ainsi que de grandes sections de routes et de voies ferrées. Les réseaux électriques, d’alimentation en eau et de fibre optique ont aussi été interrompus. L’isolement des villages a duré plusieurs mois et la reconstruction n’est pas achevée au 12 décembre 2022. À l’initiative d’enseignants-chercheurs de Sorbonne Université, un groupe de recherche, intitulé « Story : Risques et sociétés dans le bassin de la Roya : analyse pluridisciplinaire et multi-temporelle, des versants à la mer », s’est constitué, avec pour objectif d’associer des spécialistes des géosciences et de sciences humaines en vue (i) d’analyser la catastrophe d’octobre 2020, (ii) de restituer l’histoire des risques, de leur gestion et de leur perception et (iii) d’élaborer, avec les acteurs locaux, des recommandations pour la reconstruction de leur territoire, avec l’objectif de réduire les impacts des futurs événements extrêmes. Cet article présente les résultats préliminaires issus d’observations de terrain et d’analyses de données collectées. Le caractère exceptionnel de la crue est confirmé par la destruction d’une quantité inédite de ponts par une crue dans la vallée. Un facteur aggravant a été la construction au XXe siècle des routes en remblai dans le lit du fleuve. La voie ferrée a été plus affectée par les éboulements et les glissements de terrain induits par l’épisode hydro-climatique. La cartographie des secteurs détruits nous conduit à faire des recommandations, parfois en contradiction avec les directives retenues par les services de l’aménagement dans leur reconstruction très rapide des infrastructures. Nous discutons enfin les difficultés à concilier les perceptions des différents acteurs, le nécessaire temps de la recherche pas toujours facile à articuler avec l’urgence de la reconstruction et la nécessité vitale de désenclaver des secteurs qui sinon risquent d’être définitivement abandonnés par les populations.

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Review on Late Pleistocene-Holocene relative sea-level changes in Kuwait : New evidence from Failaka island

2021, Pavlopoulos, Kosmas, Fouache, Eric

New results from fieldwork carried out on Failaka island testify to relative sea-level fluctuations during Late Pleistocene and Holocene. This study is based on analysing, sampling and dating geomorphological sea-level indicators, including beach ridges or beachrocks. The results have been compared and harmonised with recalibrated data from pre-existing literature to reconstruct the relative sea-level local chronology. The vertical displacement identified may have induced coastline mobility and significant environmental changes and impacted the human occupation in Failaka and along the coastal areas of Kuwait. Eventually, the results highlight the impact of large-scale crustal deformations on regional relative sea-level variations.

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The contribution of simulated lithostratigraphy in the geoarchaeological research of the Athenian Basin during the Holocene

2020, Pavlopoulos, Kosmas, Fouache, Eric, Vandarakis, D., Vouvalidis, K., Kapsimalis, V.

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Geomorphological changes in the coastal area of Farasan Al-Kabir Island (Saudi Arabia) since mid Holocene based on a multi-proxy approach

2018, Pavlopoulos, Kosmas, Fouache, Eric, Koukousioura, O., Triantaphyllou, M., Vandarakis, D., Marion de Procé, S., Chondraki, V., Kapsimalis, V.

The geomorphological evolution of the southeastern coastal area of Farasan Al-Kabir Island (Saudi Arabia) is revealed by the mapping of modern landforms and a multi-proxy and high spatial resolution study including grain size, particulate organic carbon, mineralogy, element geochemistry, benthic foraminifera analysis and radiocarbon dating of a 3.3-m long sediment core. The modern geomorphological features comprise a variety of arid landforms, such as plateau, cliffs and pediments of Pleistocene coral limestones, playa depressions located on plateau surfaces, alluvial fans, butte and sandy beaches. The mid Holocene evolution of the borehole area is resulted from the detailed analysis of five sedimentary units detected along the core Matar-1, and includes three distinct stages: (a) from 5253 ± 223 y cal BP to 3138 ± 223 y cal BP, carbonate coarse-grained material consisting of coral fragments, molluscs, calcareous algae and benthic foraminifera are deposited on a shallow marine fringing reefal platform, which becomes progressively a nearshore backreef (around 3675 ± 215 y cal BP), and later (around 3138 ± 223 y cal BP) a reef ramp; (b) since 3040 ± 220 y cal BP the borehole area obtains the characteristics of a high-energy beach that receives increasing inputs of terrigenous material; (c) subsequently, a supratidal backshore setting is established influenced mostly by terrestrial processes and occasionally by marine processes, as it is indicated by the decreasing and sometimes sporadic presence of benthic foraminifera, and recently, a sedimentary veneer consisting of terrigenous, carbonate and evaporite material is formed by terrestrial, mainly wadi and aeolian, processes. © 2018 Elsevier Ltd and INQUA

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Relative Sea-Level Changes on the Southwestern Arabian Gulf since the Last Glacial Maximum

2022, Pavlopoulos, Kosmas, Fouache, Eric, Arhan, Damien

Several works have been carried out regarding Late Pleistocene–Holocene sea-level changes in the Arabian Gulf. Nevertheless, a global and regional approach is still lacking, and some critical issues remain unsolved. In this paper, a review and a reinterpretation of all published data regarding sea-level changes in the area have been completed and compared with new results obtained from fieldworks carried out in Failaka Island, Kuwait, and in Abu Dhabi Emirate, United Arab Emirates. This work relies mostly on studying geomorphological sea-level indicators, such as beach rocks and beach ridges besides combining archaeological data. Results show different trends in vertical movement within the studied area since the Last Glacial Maximum, which cannot be explained alone by the existing sea-level model, implying different, specific and local factors, such as tectonic deformations and diapirism.

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Stratigraphy of « MOUN1 » Drill Core : Discussion of Results

2021, Pavlopoulos, Kosmas, Chabrol, Antoine, Fouache, Eric, Goiran, Jean-Philippe

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Holocene relative sea-level variations and archeological implications, Abu Dhabi western region, United Arab Emirates

2020, Pavlopoulos, Kosmas, Fouache, Eric, Damien, Arhan

New results from fieldwork in the western region of the Emirate of Abu Dhabi showed meaningful differences in relative sea-level variations during Holocene and recorded unknown late marine highstands. These dynamics may have induced important environmental changes and affected human settlement. Surveys have been carried out in the Emirate of Abu Dhabi in order to construct local sea-level variations. These results rely on identifying, characterizing, and dating sea-level indicators and particularly beachrocks. Two main areas were studied: Ghagha island and Ras Khumays peninsula. Data obtained from our surveys highlight significant differences and suggest local processes that need to be understood. From an archeological perspective, this work helps to better understand human settlement dynamic through the Holocene.

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Geomorphology of the Kalamas river delta (Epirus, Greece)

2022, Pavlopoulos, Kosmas, Adrien Gonnet, Fouache, Eric, Charles Lecoeur

This article presents the geomorphological mapping of the Kalamas river delta in Thesprotia (Epirus, north-western Greece). The Kalamas (also known as Thyamis) is one of the three main deltas of this region. Detailed mapping was performed through analysis of field geomorphological surveys and interpretation of old maps, satellite images, aerial photos, and DEM. The evolution of the delta as well as its current morphology derives from complex interactions between alluvial, marine dynamics and human activities. Several palaeo-channels have been identified, and the recent morphology of the delta has been altered by the construction of a dam and the canalization of the river during the second half of the twentieth century. The coastline is complex, and mainly consists of lagoons, sandy barriers and sand spits. Since part of the delta has been prograding for about fifty years, the current dynamics indicate erosion as well as progressive submersion of these low coasts.

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Paleoenvironmental Evolution and Sea Level Change in Saronikos Gulf (Aegean Sea, Greece) : Evidence from the Piraeus Coastal Plain and Elefsis Bay Sedimentary Records

2021, Pavlopoulos, Kosmas, Fouache, Eric, Triantaphyllou, Maria V., Tsourou, Theodora, Kouli, Katerina, Koukousioura, Olga, Dimiza, Margarita D., Aidona, Elina V., Syrides, George, Antoniou, Varvara, Panagiotopoulos, Ioannis P., Vandarakis, Dimitris, Pallikarakis, Aggelos, Cheilaris, Sofia, Skampa, Elisavet, Goiran, Jean-Philippe

Thorough faunal (benthic foraminifera, ostracods, molluscs) and palynomorph analyses as well as magnetic susceptibility measurements performed on the Piraeus coastal plain sedimentary sequences have shed light on the paleoenvironmental evolution of the area since ca. 9000 cal BP. Benthic and palynomorph assemblages along with magnetic susceptibility suggest a typical lagoonal environment with significant freshwater inputs at the eastern part of the plain after 8700 cal BP. Between 7500 and 5400 cal BP, microfaunal assemblages, mollusc fauna and magnetic susceptibility suggest a shallow marine paleoenvironment, with Piraeus forming a tied island in the center of the bay. Since ca. 4800 cal BP a closed oligohaline lagoon is evidenced in the western part of the Piraeus plain further developed to a marsh after 2800 cal BP, while a coastal environment associated with the fluvio-deltaic system of Kifissos and Korydallos Rivers is continually developing to the west. Signs of cultivation and grazing activities in the area are evidenced since the Early Bronze Age, culminating during the Classical Period. A comparison with a well-dated marine record, recovered from the nearby shallow Elefsis Bay, provides a reasonable estimation of ~5 mm/yr for the absolute sea level rise rate in the inner Saronikos Gulf during the Mid-Holocene.

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Influence des centuriations romaines sur les dynamiques hydriques et éoliennes en Tunisie centre-orientale

2018, Fouache, Eric