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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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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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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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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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Past primary productivity is tracked in lake sediments to reconstruct environmental changes. However, the resolution of the routinely used destructive techniques is not suitable for the analysis of a large number of samples due to cost. Non-destructive analysis of chlorophyll-a performed by hyperspectral imagery enables the quick determination of indices of past primary productivity. Eighteen indices used in paleo-environmental reconstruction were inventoried to define the best index capable of tracking chlorophyll-a by this technique. All the indices were applied to hyperspectral data measured on the sediment of Lake Bresson, in which detrital organic matter input is likely to skew chlorophyll-a identification, and the results were compared with concentrations measured by a routinely used destructive analysis. The 18 indices all produced a different result and only three indices were positively correlated with chlorophyll-a concentrations (n = 28, p < 0.0001). The detrital organic matter impacts chlorophyll-a characterization and shows the bias produced by the sediment matrix variations. Moreover, artificial modification of the sediment matrix revealed an impact of the mineral phase. To tackle this issue, the indices are normalized by two proxies of the sediment components. This new approach reduces the impact of detrital organic matter, hence the sediment matrix variations also reduce the normalization of the chlorophyll-a indices by a specific proxy of the mineral phase. These results identify the impact of local geochemical features that limit past primary productivity assessment and show the necessity of characterizing the sediment composition prior to tracking the chlorophyll-a by hyperspectral imaging.

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Abstract Although parasite infection and pollution are common threats facing wild populations, the response of the gut microbiota to the joint impact of these stressors remains largely understudied. Here, we experimentally investigated the effects of exposure to Polycyclic Aromatic Hydrocarbons (PAHs) and infection by a common acanthocephalan intestinal parasite ( Pomphorhynchus sp. ) on the gut microbial flora of a freshwater fish, the European chub ( Squalius cephalus ). Naturally infected or uninfected individuals were exposed to PAHs at environmentally realistic concentrations over a five-week period. Characterization of the gut bacterial community through 16S rRNA gene amplicon sequencing revealed that parasitic infection was a more structuring factor of bacterial diversity and composition than PAH exposure. Specifically, chub infected by Pomphorhynchus sp. harbored significantly less evenly represented gut bacterial communities than the uninfected ones. In addition, substantial changes in sequence abundance were observed within the main bacterial phyla, including the Firmicutes , Fusobacteriota , Actinobacteriota , and Proteobacteria . Again, these compositional changes correlated with host infection with Pomphorhynchus sp. , confirming its pivotal role in gut microbial assemblage. Overall, these results highlight the importance of defining the parasitic status of individuals when conducting microbial ecotoxicological analyses at the digestive tract level, as this should lead to better understanding of microbiota modulations and help to identify microbial markers specifically associated with chemicals.

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A feasibility study on Usumacinta River sediment-based bricks for resilient housing adapted to both climate change and seismic risks is performed on laterally loaded reduced-scale walls. Mortar formulations with different volume ratios of lime and sand (2/1, 1/2, 1/4, 1/6) are prepared while different types of sediment-based bricks are thoroughly investigated, manufactured and strength characterized. Commercial fired bricks as reference bricks completed the set of bricks tested (FRS: Fired River Sediment-based brick (at 850 °C); LRS: Lime treated River Sediment-based unfired brick (1.5% of lime addition); NRS: Natural fiber Reinforced river Sediment-based unfired brick and FR: commercial Fired Reference brick made without sediment). Walls of different sizes were built with these types of bricks and mortars. Tests under lateral in-plane loads of walls i.e. pushover tests, were conducted. The most significant results are as follows: (1) the addition of lime increases the strength of the mortar; (2) the wall size effect is observed for wall built with reference bricks (FR) and mortar ratio (1/2), where, large walls (LW), intermediate walls (IW) and small walls (SW) exhibiting maximum load of about 1200 N, 440 N and 260 N respectively. Rocking failure mode is the most observed unlike shear and sliding mode which are rarer. (3) maximum load measured during a pushover test performed on walls with sediment-based bricks provides a satisfactory average of 130 N, which exceeds the strength recommended for light buildings; The failure mode is sliding for fired bricks and rocking for unfired bricks. (4) the sediment-based bricks walls give an interesting ductility to pushover test while (2.6-40). These results show promising perspectives on the possibility of using the Usumacinta River sediment-based bricks in walls for light constructions under seismic loading.

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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