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UMR 6143 "Morphodynamique Continentale et Côtière"

Le laboratoire Morphodynamique Continentale et Côtière (M2C) est une Unité Mixte de Recherche (UMR 6143) créée en 1996. Il est rattaché au CNRS (INSU en principal et INEE en secondaire), à l’Université de Caen Normandie (UNICAEN) et à l’Université de Rouen Normandie (URN).
Les recherches du laboratoire M2C s’intéressent à la caractérisation et à la modélisation de la dynamique des processus naturels et des différents compartiments, le long du continuum TERRE-MER, à différentes échelles de temps et d’espace. Les recherches s’organisent en 3 thèmes :
  • Bassins versants
  • Estuaire
  • Côtier

 

Ces recherches sont réalisées avec une approche interdisciplinaire intégrant des chercheurs spécialisés en mécanique, géosciences, océanographie et hydrologie, microbiologie et biologie des organismes.

En raison de la réponse qu’elles constituent aux attentes des gestionnaires, collectivités et industriels, les activités que nous menons en matière de valorisation s’inscrivent dans le cadre de différentes recherches appliquées.

Nos recherches couplent la mesure in situ grâce à de nombreux équipements dédiés (voir rubrique plateaux techniques), des approches expérimentales et de modélisations numériques.

Dépôts

1 279


Evolution des dépôts

 

Dernières publications

Here we present an experimental campaign delving into the complex interplay between sand dune morphology and tidal current dynamics. Employing particle image velocimetry (PIV) measurements, we conducted diverse series of laboratory flume experiments to scrutinize the hydrodynamic influence of dunes on steady currents, both aligned and opposed to the dune asymmetry. Our experiments sought to replicate the hydrodynamics occurring over the tidal dune field of the Goulet de Brest, located in Brittany, France. The Goulet hosts well-formed and highly dynamic dunes shaped by intense tidal currents. Notably, these currents exhibit a distinctive asymmetry, with ebb flows prevailing towards the southwest in contrast to the opposite flood flows. The resulting tidal asymmetry is vividly mirrored in the dune profiles, showcasing an accentuated asymmetry in the southeast part of the field, where dunes grow taller in shallower waters. Conducted in a bidirectional current-permitting flume, each experimental series encompassed varied hydrodynamic conditions, such as ebb and flood, aligned or opposed to the dune asymmetry, and different bottom roughnesses. We utilized sediment mixtures that were progressively coarser, transitioning from a smooth to a fully rough flow regime. The PIV flow measurements provided unprecedented spatial resolution, slightly larger than 1 mm, and temporal resolution sampling data at a frequency of 200 Hz. These measurements were taken at the central dune crest and along the neighboring trough. At the inlet, lower-frequency point measurements were conducted using a Vectrino-II ADV Nortek, ensuring the stability of inlet currents during different PIV acquisitions. Analysis of the collected data unveiled a rich tapestry of turbulent processes and boundary layer dynamics. The identified detachment and reattachment points of the boundary layer, along with their spatio-temporal oscillations, revealed an intermittent advection of coherent turbulent structures downstream from the dune crest proceeding further downward along the lee side in the boundary layer and upward in the water column up to the free surface. These deepened our understanding of the intricate interactions between boundary layer dynamics and turbulence. Additionally, by scrutinizing the vertical current profile along the dune, we estimated the equivalent bottom roughness and local shear stresses, providing crucial insights into the drag imposed by the dunes, with potential implications for sediment transport processes. In essence, this dataset stands as a cornerstone in unraveling the intricate relationship between tidal dune morphology and coastal current dynamics. It underscores the potential of PIV measurements for investigating such large-scale phenomena under controlled conditions. Furthermore, the collected database can inform the development, validation, and sensitivity analysis of new numerical models aiming at the investigation of those fine-scale processes taking place at the interface of sand dunes and tidal current which control sediment transport and thus shape coastal areas.

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Marine aggregate extraction represents an opportunity to face the depletion of terrestrial aggregate resources. The environmental effects of this activity have been assessed in several studies, leading to the formulation of recommendations to mitigate its effects. This study investigates its environmental impacts in a coarse, high-current environment with low-intensity extraction, a unique scenario not extensively studied before. Employing multivariate analyses and a trophic group approach, it examines complex responses at both species and community levels. Results indicate a decline in biodiversity, promoting the establishment of r-selected species, particularly filter feeders. Although site restoration timelines remain uncertain, initial indications suggest rapid recovery (2–3 years) for this site. The study also discusses methodological challenges in sampling these low-intensity dredged sites and emphasizes the need for new indices tailored to this pressure and coarse sediments under strong hydrodynamics. These insights offer valuable directions for future research.

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Sediment cores from three major French watersheds (Loire, Meuse and Moselle) have been dated by 137Cs and 210Pbxs from 1910 (Loire), 1947 (Meuse) and 1930 (Moselle) until the present in order to reconstruct trajectories of plastic additive contaminants including nine phthalate esters (PAEs) and seven organophosphate esters (OPEs), measured by gas chromatography–mass spectrometer (GC–MS–MS). Historical levels of ∑PAEs were higher than those of ∑OPEs in the Loire and the Moselle sediments, while ∑PAEs and ∑OPEs contents were of the same order of magnitude in the Meuse sediments. Although increases in concentrations do not evolve linearly, our results clearly indicate an increase in OPEs and PAEs concentrations from the 1950–1970 period onwards, compared with the first half of the 20th century. Our results show that, ∑OPE contents increase gradually over time in the Loire and Meuse rivers but evolve more randomly in the Moselle River. Trajectories of ∑PAEs depend on the river and no generality can be established, suggesting sedimentary reworking and/or local contamination. Data from this study allowed comparisons of contents of ∑OPEs and ∑PAEs between rivers, with ∑OPE concentrations in the Moselle River > Meuse River > Loire River, and concentrations of ∑PAEs in the Loire River > Moselle River > Meuse River. Among all PAEs, di(2-ethylhexyl) phthalate (DEHP) was the most abundant in all sediment samples, followed by diisobutyl phthalate (DiBP). Tris (2-chloroisopropyl) phosphate (TCPP) was the most abundant OPE in sediments of the three rivers. In addition, strong positive Pearson correlations were observed between organic matter (OM) parameters and OPE concentrations, and to a lesser extent, between OM parameters and PAE concentrations. This is particularly true for the Moselle River and for the Loire River, but less so for the Meuse River.

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137Cs is a long-lived man-made radionuclide introduced in the environment worldwide at the early beginning of the nuclear Era during atmospheric nuclear testing’s followed by the civil use of nuclear energy. Atmospheric fallout deposition of this major artificial radionuclide was reconstructed at the scale of French large river basins since 1945, and trajectories in French nuclearized rivers were established using sediment coring. Our results show that 137Cs contents in sediments of the studied rivers display a large spatial and temporal variability in response to the various anthropogenic pressures exerted on their catchment. The Loire, Rhone, and Rhine rivers were the most affected by atmospheric fallout from the global deposition from nuclear tests. Rhine and Rhone also received significant fallout from the Chernobyl accident in 1986 and recorded significant 137Cs concentrations in their sediments over the 1970–1985 period due to the regulatory releases from the nuclear industries. The Meuse River was notably impacted in the early 1970s by industrial releases. In contrast, the Seine River display the lowest 137Cs concentrations regardless of the period. All the rivers responded similarly over time to atmospheric fallout on their catchment, underlying a rather homogeneous resilience capacity of these river systems to this source of contamination.

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Collaborations internationales

 

 

 

 

Site de Caen

Morphodynamique Continentale et Côtière

Université de Caen Normandie (Campus 1)

24 rue des Tilleuls

14000 Caen Cedex

https://hal-normandie-univ.archives-ouvertes.fr/

 

Site de Rouen

Morphodynamique Continentale et Côtière

Université de Rouen Normandie (bâtiment Blondel Nord)

Place Emile Blondel

76821 Mont-Saint-Aignan Cedex