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Coastal and Continental Morphodynamics laboratory

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The "Coastal and Continental Morphodynamics" laboratory (M2C) is a Joint Research Unit (UMR 6143) created in 1996, under the supervision of the French National Center for Scientific Research (CNRS), the university of Caen Normandie (UNICAEN) and the university of Rouen Normandy (URN). The staff of the laboratory includes 86 persons: 37 researchers, 21 engineers and technicians, 28 PhD students. The research of the M2C laboratory focuses on the characterization and modeling of natural processes dynamics in different compartments along the LAND-SEA continuum, at different scales of time and space. The research is organized into 5 themes:
  • Watershed
  • Estuary
  • Coastal


This research is carried out with an interdisciplinary approach integrating researchers specialized in mechanics, geosciences, oceanography, hydrology, microbiology and ecology of organisms. Our research combines in-situ measurements with numerous dedicated equipment, experimental approaches and numerical moodeling.

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Last publications

This study investigates the valorization of dredged sediments containing high and low organic matter (OM) content with alkali-activated ground granulated blast furnace slag (GGBS) and conventional hydraulic binders (HB). The objective is to develop a sustainable material with the necessary qualities for road construction. Research is conducted on dredged sediments from the French port of Cherbourg (CHER-ALL sediments) and the dam in the Maurienne Valley of France (MOR-ALL sediments), with high and low levels of OM content, respectively. After the determination of physico-chemical and mineralogical characteristics, high organic CHER-ALL sediments were first valorized using conventional HB and then co-valorized using low carbon footprint alkaline activated byproducts (AAB). The alkali activation of the byproduct (GGBS) was performed with a chemical activator named NeoliX. AAB and HB were utilized to treat the dredged sediments to compare their mechanical performances as well as environmental impacts. In terms of mechanical performance, the obtained results revealed that AAB outperformed traditional HB, and concerning the environmental impacts, byproducts have no carbon footprint except for their transportation. As a consequence, AAB has also been utilized to co-valorize the sediments from the Maurienne dam (MOR-ALL sediments) as well. AAB co-valorization of these two sediments (CHER-ALL and MOR-ALL) with varying degrees of OM content facilitates an understanding of the effects of OM concentration on mechanical properties. The high OM content of the CHER-ALL sediment (>17%), regardless of the proposed mixing with traditional HB, proved to impede the valorization, since the 28-day UCS did not exceed 1 MPa. The CBR as well as ultimate tensile strength (UTS) testing confirms the reported trends from the UCS experiments. In addition, the presence of a high OM concentration significantly decreased the mechanical properties of dredging sediments co-valorized with AAB. However, depending on the mass percentage of sediment (wt%) in the mix design, it was achievable to attain the required minimum strength value of 1 MPa with 30% and 70% of CHER-ALL and MOR-ALL sediments, respectively. Even if the OM content of sediments is high, alkaline activation can be employed to co-valorize them, as demonstrated by these encouraging results. The quantity of sediment to be co-valorized is depend upon their OM content.

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The Hall-Vinen-Bekharevich-Khalatnikov (HVBK) model is widely used to numerically study quantum turbulence in superfluid helium. Based on the two-fluid model of Tisza and Landau, the HVBK model describes the normal (viscous) and superfluid (inviscid) components of the flow using two Navier-Stokes type equations, coupled through a mutual friction force term. This feature makes the HVBK model very appealing in applying statistical tools used in classical turbulence to study properties of quantum turbulence. A large body of literature used low-order statistics (spectra, or second-order structure functions in real space) to unravel exchanges between the two fluids at several levels. The novelty in this study is to use a theoretical approach based on first principles to derive transport equations for the third-order moments for each component of velocity. New equations involve the fourth-order moments, which are classical probes for internal intermittency at any scale, revealing the probability of rare and strong fluctuations. Budget equations are assessed through Direct Numerical Simulations (DNS) of the HVBK flow based on accurate pseudo-spectral methods. We simulate a forced homogeneous isotropic turbulent flow with Reynolds number of the normal fluid (based on Taylor's microscale) close to 100. Values from 0.1 to 10 are considered for the ratio between the normal and superfluid densities. For these flows, an inertial range is not discernible and the Restricted Scaling Range (RSR) approach is used to take into account the Finite Reynolds Number (FRN) effect. We analyse the importance of each term in budget equations and emphasize their role in energy exchange between normal and superfluid components. Some interesting features are observed: i) transport and pressure-related terms are dominant, similarly to single-fluid turbulence; ii) the mathematical signature of the FRN effect is weak in the transport of the third-order moment, despite the low value of the Reynolds number; iii) for the normal fluid at very low temperatures, the mutual friction annihilates the effects of viscosity within the RSR. The flatness of the velocity derivatives is finally studied through the transport equations and their limit for very small scales, and it is shown to gradually increase for lower and lower temperatures, for both the normal fluid and the superfluid. This similarity highlights the strong locking of the two fluids. The flatness factors are also found in reasonable agreement with classical turbulence.

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The present study analyses the spatio-temporal structuration of the molluscan fauna from four tidal channels of the Gulf of Gabès. A total of 26 stations were sampled at four seasons from March 2016 to January 2017, leading to the identification of 2695 individuals and 57 species. The species richness and abundances are higher in autumn than in other seasons. The fauna is dominated by seven species, three gastropods [Cerithium scabridum Philippi, 1848, Bittium reticulatum (da Costa, 1778) and Tricolia speciosa (Megerle von Mühfleld, 1824)] and four bivalves [Abra alba (W. Wood, 1802), Loripes orbiculatus Poli, 1791, Varicorbula gibba (Olivi, 1792) and Peronaea planata (Linnaeus, 1758)], which are characteristic of habitats with detritus accumulation and seagrass meadows. These dominant species are commonly recorded in lagoons and coastal shallow waters of the Mediterranean Sea. The structure of the molluscan fauna is linked to the location of tidal channels in the Gulf of Gabès. Abundances are lower in the Mimoun channel than in the other channels, especially the Maltine channel which shows a great accumulation of organic matter and high abundances of molluscs. Low abundances are found in high-energy hydrodynamic zones with gravel sediment; conversely, the presence of macrophytes (mainly in seagrass meadows) increases molluscan diversity. Comparisons with other sites in the shallow waters of the Tunisian coast and lagoons show that the taxonomic diversity of molluscs of the tidal channels of the Gulf of Gabès is equivalent to that reported elsewhere, but the abundance per m2 is among the lowest levels recorded here. Moreover, most of the dominant species found in the Gulf of Gabès tidal channel are reported as dominant in other studies covering the Mediterranean Sea. A distance-based redundancy analysis shows that depth, sediment type and the presence of marine phanerogams and filter-feeder bivalves on fine sands and gravels account for the structure of mollusc assemblages associated with each channel.

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The present study aims at reconstructing mid-to late Holocene paleoenvironmental evolution of the Tahaddart lower estuary (NW of Morocco) and to find possible sedimentary evidence of past marine submersion events (storm surges and tsunamis). This is achieved through the study of four sedimentary cores and by using a multiproxy approach that combines sedimentological, geochemical and foraminiferal analyses. Radioisotope measurements of 210Pbex, 137Cs and 14C were used to provide a chronological framework of the studied cores. The results show that the Tahaddart lower estuary has evolved from a bay-like environment characterized by very shelly sandy facies (i.e., marine phase) between ∼6800 and ∼625 cal BP, to an estuarine system after ∼625 cal BP, with a dominance of fine-grained sediments (i.e., estuarine phase). We further identified several sedimentary deposits that we interpret as possible marine submersion events. Two events were identified in the marine phase at ∼3800 cal BP and ∼2700 cal BP, in coherence with previously documented marine high-energy deposits located on the Atlantic Iberian coast. In the estuarine phase of the cores, two other events were detected and dated at ∼625 cal BP and ∼200 cal BP. The latter coincides with the 1755 CE Lisbon tsunami (195 cal BP).

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Groundwater level (GWL) simulations allow the generation of reconstructions for exploring the past temporal variability of groundwater resources or provide the means for generating projections under climate change on decadal scales. In this context, analyzing GWLs affected by low-frequency variations is crucial. In this study, we assess the capabilities of three deep learning (DL) models (long short-term memory (LSTM), gated recurrent unit (GRU), and bidirectional LSTM (BiLSTM)) in simulating three types of GWLs affected by varying low-frequency behavior: inertial (dominated by low-frequency), annual (dominated by annual cyclicity) and mixed (in which both annual and low-frequency variations have high amplitude). We also tested if maximal overlap discrete wavelet transform pre-processing (MODWT) of input variables helps to better identify the frequency content most relevant for the models (MODWT-DL models). Only external variables (i.e., precipitation, air temperature as raw data, and effective precipitation (EP)) were used as input. Results indicate that for inertial-type GWLs, MODWT-DL models with raw data were notably more accurate than standalone models. However, DL models performed well for annual-type GWLs, while using EP as input, with MODWT-DL models exhibiting only minor improvements. Using raw data as input improved MODWT-DL models compared to standalone models; nevertheless, all models using EP performed better for annual-type GWLs. For mixed-type GWLs, while using EP as input, MODWT-DL models performed well, with substantial improvements over standalone models. Using raw data as input, improvement of MODWT-DL models is marginal compared to that of standalone models; nevertheless, they perform better than standalone models with EP. The Shapley Additive exPlanations (SHAP) approach used to interpret models highlighted that they preferentially learned from low-frequency in precipitation data to achieve the best simulations for inertial and mixed GWLs. This study showed that MODWT-based input pre-processing is highly suitable to better simulate low-frequency varying GWLs.

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Biological invasions are one of the main global threats to biodiversity in terrestrial, freshwater and marine ecosystems worldwide, requiring effective inventorying and monitoring programs. Here, we present an updated list of non-indigenous species in French marine and transitional waters. Focused on eukaryote pluricellular species found throughout the three metropolitan French marine regions (Western Mediterranean Sea, Bay of Biscay and the Northern Seas), a total of 342 non-indigenous, including 42 cryptogenic, species are listed as having been introduced since the 13th century. The majority of the species originated from the temperate Northern Pacific. They mainly arrived through both ballast and hull fouling and also are associated with shellfish farming activities. Most of them have been introduced since the 1970s, a time when maritime and aquaculture trade intensified. Despite important human-aided opportunities for species transfer between the three marine regions (for instance, via recreational boating or aquaculture transfers), only a third of these NIS are common to all regions, as expected due to their environmental specificities.

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Embedding PCMs in building materials has attracted great interest due to their ability to store thermal energy. Storage of heat and cold is an efficient way to save energy. Considering a lightweight earth-based material, mixture of soil with a high straw content, the present work aims to improve its thermal properties by using phase change materials (PCM). In this investigation, a laboratory experimental campaign and subsequent numerical analysis were carried out to examine the impact of incorporating PCM within the lightweight earth-based material. Materials' hygro-thermal properties (thermal conductivity, specific heat capacity and water vapor permeability), determined experimentally in laboratory, have been considered to calculate energy consumption and occupant's comfort in a typical single-family housing. Experimental results showed an improvement of the lightweight earth-based material thermal conductivity and specific heat capacity, as well as a slight reduction in its water vapor permeability depending on the PCM content. These modifications in the lightweight earth-based material properties lead to predict an improvement of occupants' thermal comfort and a reduction of energy consumption in buildings that will be made with such a material. Finally, this study underlined the existence of an optimal phase change temperature regarding climate in which the building evolves.

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Coastal barriers are dynamic systems, the morphology and architecture of which are controlled by local hydrodynamics, sea-level fluctuations at different timescales, geological heritage and sediment composition. Coastal barriers may be composed of siliciclastic sediments, bioclastic sediments, or a mixture of both. Mixed siliciclastic–bioclastic sediments (as common as ‘pure’ sediments) are still little represented in the literature. Changes in sediment composition could affect sedimentary processes which are involved in the construction and stability of coastal barriers due to a different hydrodynamic behaviour between bioclastic and siliciclastic particles. In this study, wave-flume experiments were used to investigate the role of sediment compositional mixing on the morphology and architecture of coastal barriers. Three different siliciclastic/bioclastic mixtures were exposed to regular wave forcing, together with mean water level fluctuations to create regressive and transgressive depositional units. Compositional mixtures responded similarly in first-order to mean water-level fluctuations, with the formation of a bar at low water level. Its subsequent on-shore migration and reworking as berm deposits during rising water level stages, and with the formation of washover deposits during high water level stages. In detail, the increasing content of bioclastic sediment increased the beachface slope and reduced the length of washover deposits. The faster aggradation of washover sheets with bioclastic-rich mixtures accelerated the barrier recovery after a submersion and breaching event. A strong segregation between the siliciclastic and the bioclastic grains was observed in the different depositional units, which is attributed both to the coarse size (grain-size control) and to the flat-shape (compositional control) of the bioclastic particles.

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Clostridium botulinum is the main causative agent of botulism, a neurological disease encountered in humans as well as animals. Nine types of botulinum neurotoxins (BoNTs) have been described so far. Amongst these “toxinotypes,” the A, the B and E are the most frequently encountered in humans while the C, D, C/D and D/C are mostly affecting domestic and wild birds as well as cattle. In France for instance, many cases and outbreaks are reported in these animal species every year. However, underestimation is very likely at least for avifauna species where the detection of dead animals can be challenging. Knowledge about BoNTs C, D, C/D, and D/C and the diseases they cause in animals and humans is still scarce and unclear. Specifically, the potential role of animal botulism outbreaks in cattle and poultry as a source of human illness needs to be further assessed. In this narrative review, we present the current knowledge about toxinotypes C, D, C/D, and D/C in cattle and poultry with, amongst various other aspects, their epidemiological cycles. We also discuss the zoonotic potential of these toxinotypes and some possible ways of risk mitigation. An adapted and effective management of botulism outbreaks in livestock also requires a better understanding of these less common and known toxinotypes.

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The mapping of the vertical and lateral variations in the physical properties of the few-meter cover layer over near-surface aquifers is important for hydrogeological modelling, particularly for the quantification of the recharge of groundwater systems. The first ground-based time-domain electromagnetic survey over a small catchment (Avesnelles, France) of the watershed of Orgeval (Seine basin) was carried out to determine discontinuities in the first silt layer as well as in the Brie multilevel aquifer limestone horizon. The results highlighted the following: (1) a good sensitivity of the time-domain electromagnetic survey to the presence of multi-decametric resistive sand lenses, particularly in a location where they were previously identified and (2) the interest in conducting a survey at a fine sampling step but extending to the meso-scale. To overcome the sampling issue over a watershed of several hundred square kilometres, we proposed numerically assessing the use of a prototype of low-cost airborne transient electromagnetic systems towed by light fixed-wing airplanes (with transmitting and receiving loops in the same plane). The present numerical analysis, in 1D for the vertical (i.e. thickness) variation and in 3D for the lateral extensions of localized sandy and resistive units, showed that a conductive few-meter cover can be mapped even with a system flying at 50 m with, however, the need of a priori constraint on the resistivity of the first layer to estimate its thickness variation as accurately as possible. Even if it did not bring more sensitivity to the layer thickness and despite the severe difficulty of practical implementation with a decametric emission loop, the vertical co-planar configuration potentially offered better near-surface lateral resolution (down to ∼40 m) to delineate the sandy units (discontinuities) within the silt layer (if units are at least 50 m in size) and provided better spatial constraints compared to the classical horizontal co-planar geometry used in the time-domain electromagnetic. Even if not aerodynamically in the plane of the emission loop, the measurement of the Hx component with a vertical dipole emission loop (PERPxz geometry for perpendicular) improved the lateral resolution (down to ∼20 m; still with at least 50 m size sand units) and confirmed that a geometry different from the classical horizontal co-planar configuration could be valuable.

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International collaboration (co-authors)



M2C lab. in Caen

Morphodynamique Continentale et Côtière
Université de Caen Normandie (Campus 1)
24 rue des Tilleuls
14000 Caen Cedex

M2C lab. in Rouen

Morphodynamique Continentale et Côtière
Université de Rouen Normandie (bâtiment Blondel Nord)
Place Emile Blondel
76821 Mont-Saint-Aignan Cedex