Publications

2021

• Empirical modeling of beach evolution combining cross-shore and longshore processes
  
  • Chataigner Teddy
  , 2021. Sandy coasts are highly dynamic environments subject to erosion and marine flooding hazards, which are a threat to populations and economical activities near the coastline: methods and tools are needed to address coastal challenges, including models to predict future shoreline evolution at seasonal to decadal time scales and at beach to regional spatial scales. This PhD work is focused on improving the performance of empirical approaches based on a simplified representation of the dominant physical process, in particular by coupling a longshore one-line model with an equilibrium cross-shore model.The goal is to improve the cross-shore model prediction skill for long (decadal to centennial) time scales and to include the coast potentially more dominated by longshore processes. The empirical equilibrium shoreline change model of Yates et al. (2009), modified by Lemos et al. (2018) is used to model cross-shore processes, and a simple one-line approach is used to model longshore processes.The coupled model is implemented, validated and analyzed at the well-studied Narrabeen Beach (Australia). A sensitivity analysis is performed on the longshore model to errors in the forcing wave conditions, and an important sensitivity to errors in the wave direction is highlighted. Then, a method is proposed to correct a previously observed behavior of the one-line model generating a change in the coastline planform orientation that is not observed in the survey data, by assuming that it is due to biases in the forcing wave direction. Using a Monte Carlo approach, a set of relatively small wave angle biases is found to correct the model reorientation. Then, 7 combined models, with different ways of coupling the cross-shore model, the longshore model and a linear trend term, are implemented and tested at Narrabeen Beach to evaluate the model performance at reproducing the shoreline position at different temporal scales. Three criteria are used for this inter-comparison, based on the time scale at which the model skill in reproducing shoreline variability is assessed: short (~monthly), medium (seasonal) and long (pluri-annual) temporal scales.With the overall objective to extend the timescale of shoreline change predictions using empirical models such as the coupled model presented herein, 3 existing methods to predict long-term (from 10 to 100 years) shoreline change were tested at Vougot Beach (France) to examine the differences between existing methods, as well as the uncertainties of such long-term predictions. This work pointed out the uncertainties and the complexity of generating long term forcing conditions, that include potential climate change impact, when performing long-term predictions. It also highlights the necessity to improve the methods used to take into account changes in water levels in the equilibrium shoreline change model.
• Drafting of 2 swimmers
  
  • Bolon Baptiste
  • Pretot Charlie
  • Clanet Christophe
  • Larrarte Frédérique
  • Carmigniani Rémi Arthur
  , 2021, pp.1 p.. Open water swimming is a very tactical sport. As in cycling, competitors often swim in peloton formations. Therefore, their position in the group is crucial to optimize drafting, either to preserve their physical strength, to quickly pass a lead swimmer or to impede the passing of an opponent. This work is an experimental study of the drag on 2 swimmers scaled models.
• Energies and forces during pole vault flight
  
  • Quentin Lustig
  • Homo Sébastien
  • Brisard Sébastien
  • Clanet Christophe
  • Carmigniani Rémi Arthur
  , 2021. When looking at the evolution of the world records and yearly best performances of world class pole vault jumpers, we observe a stagnation of the best performance below the 6.20m mark, with a current world record held by Armand Duplantis at 6.18m. Yet, on closer inspection, the number of athletes able to pass the 6.10m mark is small (only 3 in the world). How to explain such a difference in level ? In the present study, we aim to quantify the energy transfers and the interaction forces between the athlete and the pole during an international competition. To this end, during the Paris Diamond League in August 2021, we used two cameras attached on top of the pole vault standards. Over 80 jumps were recorded and one jump exceeded the 6m mark. The scene is calibrated and triangulation makes it possible to deduce the 3D deformation of the pole and trajectory of the athletes. A quasi-static approach is used to evaluate the energy stored in the pole and the forces between the pole and the jumper during the jump. Our findings confirm that a significant part of the potential energy at release is due to the jumper activity after take-off (in the present case about 20%). This analysis also makes it possible to identify different important phases of the vault for which the athlete inputs or loses energy. These successive phases can be qualitatively observed by the coach. We now provide a methodology to quantify these phases. A similar analysis of the dynamics of vaulting will also be discussed.
• Hydrodynamic modelling for early warning of sanitary risks in open swimming waters
  
  • Angelotti Natalia
  • Vinçon-Leite Brigitte
  • Carmigniani Rémi
  , 2021. Swimming in open water involves sanitary risks related to the presence of pathogenic microorganisms. To ensure the safety of bathers, a regulatory monitoring in the bathing area, based on faecal indicator bacteria (FIB), is required. Analysis of FIB concentrations can take more than 10 hours with in situ devices and more than 24 hours in the laboratory. Hence monitoring and forecasting of the sanitary conditions in urban bathing sites are essential for decision-making on their possible closure and its duration. In this paper, TELEMAC-3D hydrodynamic model was used to compute the time and space distribution of water temperature, velocity and contaminant tracers considering hydrometeorological conditions that can cause noticeable changes on the transfer time of the contaminant to the bathing area. The study site, La Villette, is an urban canal-basin system with a bathing area, located in Paris. The objectives focus on (i) how thermal stratification affects the transfer time of upstream contamination to the bathing area; (ii) the use of conductivity to track water quality changes after a storm event and (iii) the simulation of conductivity variation.
• Time-scales of a dune-beach system and implications for shoreline modelling
  
  • Montaño Jennifer
  • Coco Giovanni
  • Chataigner Teddy
  • Yates Marissa L.
  • Le Dantec Nicolas
  • Suanez Serge S.
  • Gagigal Laura
  • Floc'H France
  • Townend Ian
  Journal of Geophysical Research: Earth Surface, American Geophysical Union/Wiley, 2021, 126 (11), pp.e2021JF006169. Understanding the interactions between dune systems and beaches is critical to determining the short-term shoreline response and the long-term resilience. In this study, almost 15 years of monthly beach/dune measurements were analysed for three different profiles at Vougot Beach, France to understand and predict shoreline changes from intra- to multi-annual time- scales. Four migration modes: advance/retreat (translation modes) and steepening/flattening (rotation modes) were identified through a centroid analysis. The analysis showed that translation and rotation can occur simultaneously, with long-term trends of beach retreat and profile steepening (lower beach retreating and upper beach advancing), which was interrupted by two energetic wave events causing profile flattening (lower beach advancing and upper beach retreating). These two observations are evidence of how the sediment contribution resulting from the dune erosion events temporarily caused a large advance in the shoreline position. A recent modelling approach that accounts for different time-scales is applied to predict the shoreline changes, showing significant improvements in comparison to a traditional shoreline equilibrium model when time-scales related with the dune erosion and recovery are considered. The results showed that the dune system affects the beach profile evolution both spatially, with different impacts at different elevations along the cross-shore profile, and temporally, by periodically redistributing the sediment in the system. (10.1029/2021JF006169)
  DOI : 10.1029/2021JF006169
• Subaquatic Relaxed Eddy Accumulation: A new technique to resolve benthic solute fluxes
  
  • Calabro Souza Guilherme
  • Dubois Philippe
  • Saad Mohamed
  • Lorke Andreas
  • Noss Christian
  • Boudahmane Lila
  • Lauret Olivier
  • Brigitte Vinçon-Leite
  • Jodeau Magali
  • Moilleron Régis
  • Lemaire Bruno J.
  , 2021. The transport across the sediment-water interface of solutes, dissolved oxygen, nutrients and contaminants is of major importance for biogeochemical cycles and water quality in aquatic ecosystems. This exchange depends not only on biogeochemical processes and on temperature, but also strongly on near-bed currents. Eddy covariance measurements in a lake showed that oxygen benthic fluxes can vary over minutes to hours. However, the corresponding dynamics of nutrient and contaminant fluxes is still not fully understood. Common techniques fail to capture the turbulence-driven fluxes of interfacial transport for most chemical species, particularly in situ and at high temporal resolution. At the land-atmosphere interface, this issue is addressed with the relaxed eddy accumulation (REA), a conditional sampling technique. Samples are accumulated at constant flow rate in separated containers depending on the direction of the vertical flow. The vertical flux is finally assumed to be proportional to the concentration difference of sample pairs, which might be analysed in situ or at lab. The adaptation of the technique for measuring fluxes through the sediment-water interface is presented here. A portable prototype was developed, embedding both relaxed eddy accumulation and eddy covariance as a reference technique for validation. Vertical Dissolved oxygen fluxes were measured during ca. 10 min accumulation periods, at ca. 15 cm above the sediment, in spring and summer and at different sites: a laboratory flume with an artificial oxygen flux, a river branch, a creek, a shallow lake and an experimental lake. Oxygen fluxes measured with both techniques showed a good agreement, which validates both the technique and the prototype. The new device proves to be a promising tool to access benthic fluxes at high frequency over a flat sediment-water interface. First time series of nutrient fluxes will be presented.
• Prévisions d'ensemble hydrologiques et hydrauliques pour la vigilance crues
  
  • Tiberi Anne-Laure
  , 2021. Cette thèse s’inscrit dans le cadre d’un partenariat entre le CEREMA (Centre d’Études et d’expertise sur les Risques, l’Environnement, la Mobilité et l’Aménagement), EDF R&D, le CERFACS (Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique) et le SCHAPI (Service Central d'Hydrométéorologie et d’Appui à la Prévision des Inondations). Afin de réaliser les cartes de vigilance bi-quotidiennes, le SCHAPI et les 19 SPC (Services de Prévision des Crues) répartis sur le territoire utilisent entre autres des résultats de modèles numériques généralement lancés de manière déterministe (prévisions météorologiques, modélisations hydrologique et hydraulique). L’objectif de la thèse est la mise en place et l’évaluation de prévisions d’ensembles hydrologiques et hydrauliques dans le cadre de la vigilance crue-inondation réalisée par les services de l’État afin de mieux appréhender et réduire les incertitudes dans un contexte de prévision à courte et moyenne échéance (24 heures). L’originalité de ce travail réside dans l’utilisation hybride de modèles à base physique et de modèles d’apprentissage sur un important volume de données. Dans cet objectif, les prévisions météorologiques forcent un modèle chaîné hydrologie-hydraulique afin de fournir des prévisions de débit et de hauteurs d’eau. Afin de prendre en compte les diverses sources d’incertitude liées aux modèles numériques, aux paramètres des modèles et aux données associées, l’approche déterministe est remplacée par une approche ensembliste ; on fournit ainsi un ensemble de prévisions de débits et hauteurs d’eau.Le bassin d’étude est le bassin versant de l’Odet situé dans le Finistère. La partie amont du bassin est modélisée par un modèle hydrologique (GRP ou MORDOR-TS). Il fournit une prévision de débit qui sert de forçage au modèle hydraulique 1D MASCARET, qui lui prévoit des hauteurs d’eau aux stations de vigilance en aval.Dans un premier temps, une étude de sensibilité globale (GSA) est menée sur les modèles hydrologiques et hydrauliques. Ceci est un préalable à la génération des prévisions d’ensemble. La GSA permet d’identifier les sources principales d’incertitude et ainsi de perturber les paramètres incertains significatifs pour la représentation des débits et des hauteurs d’eau prévus. La propagation de ces incertitudes aboutit à la création d’un ensemble brut pour l’hydrologie et pour l’hydraulique, les ensembles hydrologiques étant utilisés pour forcer les ensembles hydrauliques. Deux méthodes de correction des ensembles sont alors investiguées dans la thèse : la calibration statistique via la méthode des forêts aléatoires « Quantile Regression Forest » et la calibration par assimilation de données via un filtre de Kalman d’ensemble (EnKF). On a montré que ces deux approches améliorent significativement les performances de l’ensemble en termes de fiabilité et résolution. Enfin la comparaison des performances des prévisions d'ensemble est finalement réalisée pour l’hydrologie et l’hydraulique et des préconisations sont émises pour la génération opérationnelle de prévisions d’ensemble au sein des SPC
• Climate change impacts on coastal wave dynamics at Vougot Beach, France
  
  • Dissayanake Pushpa
  • Yates Marissa L.
  • Suanez Serge S.
  • Floc'H France
  • Krämer Knut
  Journal of Marine Science and Engineering, MDPI, 2021, 9 (9), pp.1009. Wave dynamics contribute significantly to coastal hazards and are thus investigated at Vougot Beach by simulating both historical and projected future waves considering climate change impacts. The historical period includes a major storm event. This period is projected to the future using three globally averaged sea level rise (SLR) scenarios for 2100, and combined SLR and wave climate scenarios for A1B, A2 and B1 emissions paths of the IPCC. The B1 wave climate predicts an increase in the occurrence of storm events. The simulated waves in all scenarios show larger relative changes at the beach than in the nearshore area. The maximum increase of wave energy for the combined SLR and wave scenarios is 95%, while only 50% for the SLR-only scenarios. The effective bed shear stress from waves and currents shows different spatial variability than that of the wave height, emphasizing the importance of interactions between nearshore waves and currents. Increases in the effective bed shear stress (combined scenarios: up to 190%, and SLR-only scenarios: 35%) indicate that the changes in waves and currents will likely have significant impacts on the nearshore sediment transport. This work emphasizes that combined SLR and future wave climate scenarios need to be used to evaluate future changes in local hydrodynamics and their impacts. These results provide preliminary insights into potential future wave dynamics at Vougot Beach under different climate change scenarios. Further studies are necessary to generalize the results by investigating the wave dynamics during different storm periods and to evaluate potential changes in sediment transport and morphological evolution due to climate change. (10.3390/jmse9091009)
  DOI : 10.3390/jmse9091009
• Experimental and numerical characterization of swell type waves effect on wind sea growth with fetch
  
  • Villefer Antoine
  • Benoit Michel
  • Violeau Damien
  • Teles Maria João
  • Harris Jeffrey C.
  • Branger Hubert
  • Luneau Christopher
  , 2021.
• Chapter 3: Water level and discharge measurements
  
  • Larrarte Frédérique
  • Lepot Mathieu
  • Clemens-Meyer Francois
  • Bertrand-Krajewski Jean-Luc
  • Ivetić Damjan
  • Prodanović Dusan
  • Stegeman Bram
  , 2021, pp.35-104. The knowledge of water levels and discharges in urban drainage and stormwater management (UDSM) systems is of key importance to understand their functioning and processes, to evaluate their performance, and to provide data for modelling. In this chapter, devoted mainly to underground combined and separate sewer pipe systems, various methods and technologies are described and discussed. After an introduction to important aspects to deal with when measuring discharges in sewer systems, the following parts are presented successively: (i) measurement of water level with rulers, and pressure, ultrasonic and radar sensors, (ii) measurement of flow velocity with ultrasonic, Doppler, velocity profiler, free surface, and electromagnetic sensors, (iii) direct measurement of discharge with pre-calibrated devices, physical scale models, computational fluid dynamics modelling and use of pumping stations, and (iv) detection and/or measurement of infiltration into and exfiltration from sewers, with flow or pressure measurements, tracer experiments, distributed temperature sensing and geophysical methods. (10.2166/9781789060119_0035)
  DOI : 10.2166/9781789060119_0035
• Coordination and stroking parameters in the four swimming techniques: a narrative review
  
  • Seifert Ludovic
  • Carmigniani Remi Arthur
  Sports Biomechanics, Taylor & Francis (Routledge): SSH Titles, 2021, pp.1-17. (10.1080/14763141.2021.1959945)
  DOI : 10.1080/14763141.2021.1959945
• Influence of swell on wind-wave growth with fetch: an experimental and numerical study
  
  • Villefer Antoine
  • Teles Maria João
  • Benoit Michel
  • Violeau Damien
  • Harris Jeffrey C.
  • Branger Hubert
  , 2021.
• Investigation of the hydraulics in flooded housing estate
  
  • Doumic Augustin
  • Larrarte Frédérique
  • Rtimi Rajae
  • Goutal Nicole
  , 2021, pp.9 p., graph., photos.. Climate change is currently taking place at the scale of our planet, leading to aviolent response from the environment, particularly with regard to the water cycle. One of the risk is already floods. As an example, in France, the average annual costof damages caused by floods (and insured under the Natural Disaster plan) amounts to 520 million euros. In metropolitan France, nearly 17 million people, about aquarter of the national population, are exposed to the risk of flooding by overflowaccording to the preliminary flood risk assessment carried out by the State in 2011.And with climate evolution, floods will become more frequent and more intense. Onechallenge during floods is to be able to access to people refugee over buildings.In order to investigate the hydraulic context generated by the grouped obstaclesrepresentative of a submerged housing estate, both an experimental and numericalstudy is being conducted.We experimentally study the flow in the presence of rows of macro-roughnesses representative of a slightly emerged and of a submerged housing estate, and this for situations representing both current and more intense floods. Measurements of the velocity field will provide information on currents distribution that might affect an evacuation process. In parallel a numerical study is also conducted with the opensource code Saturne. The numerical results are compared to experimental results and this preliminary stupy opens the way to a systematic investigation. (10.1007/978-981-19-1600-7_19)
  DOI : 10.1007/978-981-19-1600-7_19
• Relevance of acoustic methods to quantify bedload transport and bedform dynamics in a large sandy-gravel-bed river
  
  • Le Guern Jules
  • Rodrigues Stéphane
  • Geay Thomas
  • Zanker Sébastien
  • Hauet Alexandre
  • Tassi Pablo
  • Claude Nicolas
  • Jugé Philippe
  • Duperray Antoine
  • Vervynck Louis
  Earth Surface Dynamics, European Geosciences Union, 2021, 9 (3), pp.423-444. Abstract. Despite the inherent difficulties in quantifying its value, bedload transport is essential for understanding fluvial systems. In this study, we assessed different indirect bedload measurement techniques with a reference direct bedload measurement in a reach of a large sandy-gravel-bed river. An acoustic Doppler current profiler (aDcp), the dune tracking method (DTM) and hydrophone measurement techniques were used to determine bedload transport rates by using calibration with the reference method or by using empirical formulas. This study is the first work which attempted to use a hydrophone to quantify bedload rates in a large sandy-gravel-bed river. Results show that the hydrophone is the most efficient and accurate method for determining bedload fluxes in the Loire River. Although further work is needed to identify the parameters controlling self-generated sediment noise, the calibration procedure adopted in this study allows a satisfactory estimation of bedload transport rates. Moreover, aDcp and hydrophone measurement techniques are accurate enough to quantify bedload variations associated with dune migration. (10.5194/esurf-9-423-2021)
  DOI : 10.5194/esurf-9-423-2021
• Viscoelastic flows of Maxwell fluids with conservation laws
  
  • Boyaval Sébastien
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2021, 55 (3), pp.807-831. We consider multi-dimensional extensions of Maxwell's seminal rheo-logical equation for 1D viscoelastic flows. We aim at a causal model for compressible flows, defined by semi-group solutions given initial conditions , and such that perturbations propagates at finite speed. We propose a symmetric hyperbolic system of conservation laws that contains the Upper-Convected Maxwell (UCM) equation as causal model. The system is an extension of polyconvex elastodynamics, with an additional material metric variable that relaxes to model viscous effects. Interestingly, the framework could also cover other rheological equations, depending on the chosen relaxation limit for the material metric variable. We propose to apply the new system to incompressible free-surface gravity flows in the shallow-water regime, when causality is important. The system reduces to a viscoelastic extension of Saint-Venant 2D shallow-water system that is symmetric-hyperbolic and that encompasses our previous viscoelastic extensions of Saint-Venant proposed with F. Bouchut. (10.1051/m2an/2020076)
  DOI : 10.1051/m2an/2020076
• Automatic Calibration of Bed Friction Coefficients to Reduce the Influence of Seasonal Variation: Case of the Gironde Estuary
  
  • Huybrechts Nicolas
  • Smaoui Hassan
  • Orseau Sylvain
  • Tassi Pablo
  • Klein Fabrice
  Journal of Waterway, Port, Coastal, and Ocean Engineering, American Society of Civil Engineers, 2021, 147 (3), pp.05021004. An automatic procedure to identify the bed friction coefficient is tested on a 2D hydrodynamic model of the Gironde estuary (France). The proposed procedure involves an optimization algorithm based on evolution strategy, namely Covariance Matrix Adaptation Evolution Strategy. Without optimization, application of the same friction distribution to different hydrological conditions leads to significant relative error in water level prediction up to 20%–30%. For the tested configuration, 300 runs seemed to be sufficient to reach an optimal value whereas an additional 200 runs would help to gain an accuracy of a few millimeters (or 0.3%). In order to reach the same level of accuracy for the different hydrological configurations, it is necessary to adapt for each configuration of the bed friction coefficient. Such behavior tends to confirm a seasonal variation of the friction coefficient and this is particularly the case in the central part of the estuary. Different relationships of the friction coefficient according to the flowrate have been incorporated inside the 2D hydrodynamic model. These relationships effectively maintain an accurate prediction of the water levels close to 10% for a wide range of hydrological configurations. (10.1061/(ASCE)WW.1943-5460.0000632)
  DOI : 10.1061/(ASCE)WW.1943-5460.0000632
• Non-isothermal viscoelastic flows with conservation laws and relaxation
  
  • Boyaval Sébastien
  • Dostalík Mark
  , 2022, pp.337-364. We propose a system of conservation laws with relaxation source terms (i.e. balance laws) for non-isothermal viscoelastic flows of Maxwell fluids. The system is an extension of the polyconvex elastodynamics of hyperelastic bodies using additional structure variables. It is obtained by writing the Helmholtz free energy as the sum of a volumetric energy density (function of the determinant of the deformation gradient det F and the temperature θ like the standard perfect-gas law or Noble-Abel stiffened-gas law) plus a polyconvex strain energy density function of F, θ and of symmetric positive-definite structure tensors that relax at a characteristic time scale. One feature of our model is that it unifies various ideal materials ranging from hyperelastic solids to perfect fluids, encompassing fluids with memory like Maxwell fluids. We establish a strictly convex mathematical entropy to show that the system is symmetric-hyperbolic. Another feature of the proposed model is therefore the short-time existence and uniqueness of smooth solutions, which define genuinely causal viscoelastic flows with waves propagating at finite speed. In heat-conductors, we complement the system by a Maxwell-Cattaneo equation for an energy-flux variable. The system is still symmetric-hyperbolic, and smooth evolutions with finite-speed waves remain well-defined. (10.1142/S0219891622500096)
  DOI : 10.1142/S0219891622500096
• Finite volume arbitrary Lagrangian-Eulerian schemes using dual meshes for ocean wave applications
  
  • Ferrand Martin
  • Harris Jeffrey C.
  Computers and Fluids, Elsevier, 2021, 219, pp.104860. • Finite volume three-dimensional Navier-Stokes modeling of water wave propagation • Steep wave generation and propagation with Arbitrary Lagrangian-Eulerian scheme • Use of Compatible Discrete Operators shows improved accuracy and stability Finite volume Arbitrary Lagrangian-Eulerian schemes using dual meshes for ocean wave applications. For reasons of efficiency and accuracy, water wave propagation is often simulated with potential or inviscid models rather than Navier-Stokes solvers, but for wave-induced flows, such as wave-structure interaction, viscous effects are important under certain conditions. Alternatively, general purpose Navier-Stokes (CFD) models can have limitations when applied to such free-surface problems when dealing with large amplitude waves, run-up, or propagation over long distances. Here we present an Arbitrary Lagrangian-Eulerian (ALE) algorithm with special care to the time-stepping and boundary conditions used for the free-surfaces, integrated into Code_Saturne, and we test its capabilities for modeling a variety of water wave generation and propagation benchmarks, and finally consider interaction with a vertical cylinder. Two variants of the mesh displacement computation are proposed and tested against the discrete Geometric Conservation Law (GCL). The more robust variant, for highly curved or sawtoothed free-surfaces, uses a Compatible Discrete Operator scheme on the dual mesh for solving the mesh displacement, which makes the algorithm valid for any polyhedral mesh. Results for standard wave propagation benchmarks for both variants show that, when care is taken to avoid grids with excessive numerical dissipation, this approach is effective at reproducing wave profiles as well as forces on bodies. (10.1016/j.compfluid.2021.104860)
  DOI : 10.1016/j.compfluid.2021.104860
• Submersions marines sur le littoral atlantique français : 700 ans d'archives sociétales et environnementales pour une meilleure connaissance et gestion du risque
  
  • Maanan Mohamed
  • Athimon Emmanuelle
  • Pouzet Pierre
  , 2021. Cette recherche, financée par la Fondation de France, avait pour objectifs : 1) de retracer l’histoire des submersions marines dans l’ouest de la France à l’aide d’approches pluridisciplinaires, 2) d’évaluer les impacts quantitatifs de ces évènements sur les sociétés littorales et 3) de définir la notion de « résilience sociétale » sous le prisme historique. La méthodologie repose sur une approche interdisciplinaire intégrant la sédimentologie (21 carottes sédimentaires ont été prélevées) et l’histoire du climat (19 888 documents historiques ont été dépouillés et analysés). Le cadre spatiotemporel de l'étude est localisé au niveau de la façade atlantique française, de la Petite mer de Gâvres à l'île de Ré, et couvrant une période allant du XIVe siècle à nos jours. Le couplage des données sédimentologiques avec les archives historiques a permis de caractériser seize évènements extrêmes à forts impacts environnementaux et sociétaux. L’un d’entre eux, survenu durant l’hiver 1351 – 1352 (n.st) AD, est qualifié d’« évènement millénaire ». Les résultats de cette recherche témoignent de l’adaptabilité des populations et de leur tolérance au risque de submersion marine à travers l’histoire. À travers cette lecture historique, ces différentes approches permettent d’accroître la connaissance des aléas côtiers, de contribuer à leur prévention et de proposer des outils prospectifs pour la gestion des risques côtiers.
• A new definition of the kinematic breaking onset criterion validated with solitary and quasi-regular waves in shallow water
  
  • Varing Audrey
  • Filipot Jean-Francois
  • Grilli Stephan
  • Duarte Rui
  • Roeber Volker
  • Yates Marissa L.
  Coastal Engineering, Elsevier, 2021, 164, pp.103755. A large body of work has been devoted to the accurate detection and simulation of wave breaking in coastal areas. It is a key process for a wide range of engineering activities and environmental issues. This has motivated the development of a variety of breaking onset criteria, such as kinematic criteria based on a maximum value (usually unity) of the ratio u c /c, of the horizontal particle velocity at the wave crest u c to its phase velocity c, both taken in the direction of wave propagation. Here, we investigate numerically the validity of this criterion in capturing breaking onset for solitary and quasi-regular two-dimensional shallow water waves using the Fully Nonlinear Potential Flow (FNPF) model by Grilli and Subramanya (1996). With this model, the propagation up to overturning of solitary waves over plane slopes, and solitary and quasiregular waves over a submerged bar, both initially specified as numerically exact FNPF waves, is simulated. In all cases, waves break as spilling or plunging breakers, initiated by the formation of a breaker jet near the wave crest. Results show that the location of the maximum fluid velocity u m on the free surface closely coincides with the location where the overturning jet is initiated. Based on this, a new breaking onset criterion is proposed as u m /c 1, which is shown to be more universal for accurately detecting wave breaking initiation than existing criteria based on the crest velocity. (10.1016/j.coastaleng.2020.103755)
  DOI : 10.1016/j.coastaleng.2020.103755
• NavTEL: an open-source tool for ship routing and underkeel clearance management in estuarine channels
  
  • Orseau Sylvain
  • Huybrechts Nicolas
  • Tassi Pablo
  • Kaidi Sami
  • Klein Fabrice
  Journal of Waterway, Port, Coastal, and Ocean Engineering, American Society of Civil Engineers, 2021, 147 (2), pp.04020053. NavTEL is a new decision support tool for the short-term (36 h) planning of ship routes and the management of underkeel clearance in estuarine navigation channels. NavTEL uses a deterministic method and is coupled with the TELEMAC-MASCARET system for numerical modeling of hydrodynamic and sediment transport in the estuary with a two-dimensional approach. In its present version, NavTEL allows (i) daily simulations to be automatically prepared and launched; and (ii) simulation outputs to be postprocessed to find the safest ship route and to predict underkeel clearances at specified locations. As the reliability of the results relies on the accuracy of water-level predictions, numerical simulations were performed with measured river discharges, storm surge forecasts, and time-varying friction coefficients for bed roughness. Even though NavTEL was initially developed for the Atlantic Port of Bordeaux located in the Gironde Estuary, its kernel has a modular structure allowing the tool to be adjusted to different port configurations and types of water bodies. Finally, examples of graphical outputs and reports generated by NavTEL are shown for an application of a container ship coming into the port of Bordeaux. (10.1061/(ASCE)WW.1943-5460.0000610)
  DOI : 10.1061/(ASCE)WW.1943-5460.0000610
• NavTEL: Open-Source Decision Support Tool for Ship Routing and Underkeel Clearance Management in Estuarine Channels
  
  • Orseau Sylvain
  • Huybrechts Nicolas
  • Tassi Pablo
  • Kaidi Sami
  • Klein Fabrice
  Journal of Waterway, Port, Coastal, and Ocean Engineering, American Society of Civil Engineers, 2021, 147 (2). (10.1061/(ASCE)WW.1943-5460.0000610)
  DOI : 10.1061/(ASCE)WW.1943-5460.0000610
• Hydrodynamics of a hyper-tidal estuary influenced by the world's second largest tidal power station (Rance estuary, France)
  
  • Rtimi Rajae
  • Sottolichio Aldo
  • Tassi Pablo
  Estuarine, Coastal and Shelf Science, Elsevier, 2021, 250, pp.107143. (10.1016/j.ecss.2020.107143)
  DOI : 10.1016/j.ecss.2020.107143
• Physically interpretable machine learning algorithm on multidimensional non-linear fields
  
  • Mouradi Rem-Sophia
  • Goeury Cédric
  • Thual Olivier
  • Zaoui Fabrice
  • Tassi Pablo
  Journal of Computational Physics, Elsevier, 2021, 428, pp.110074. In an ever-increasing interest for Machine Learning (ML) and a favorable data development context, we here propose an original methodology for data-based prediction of two-dimensional physical fields. Polynomial Chaos Expansion (PCE), widely used in the Uncertainty Quantification community (UQ), has long been employed as a robust representation for probabilistic input-to-output mapping. It has been recently tested in a pure ML context, and shown to be as powerful as classical ML techniques for point-wise prediction. Some advantages are inherent to the method, such as its explicitness and adaptability to small training sets, in addition to the associated probabilistic framework. Simultaneously, Dimensionality Reduction (DR) techniques are increasingly used for pattern recognition and data compression and have gained interest due to improved data quality. In this study, the interest of Proper Orthogonal Decomposition (POD) for the construction of a statistical predictive model is demonstrated. Both POD and PCE have amply proved their worth in their respective frameworks. The goal of the present paper was to combine them for a field-measurement-based forecasting. The described steps are also useful to analyze the data. Some challenging issues encountered when using multidimensional field measurements are addressed, for example when dealing with few data. The POD-PCE coupling methodology is presented, with particular focus on input data characteristics and training-set choice. A simple methodology for evaluating the importance of each physical parameter is proposed for the PCE model and extended to the POD-PCE coupling. (10.1016/j.jcp.2020.110074)
  DOI : 10.1016/j.jcp.2020.110074
• Large meandering bends with high width-to-depth ratios: Insights from hydro-sedimentological processes
  
  • Dominguez Ruben Lucas
  • Szupiany Ricardo
  • Tassi Pablo
  • Vionnet Carlos
  Geomorphology, Elsevier, 2021, 374, pp.107521. (10.1016/j.geomorph.2020.107521)
  DOI : 10.1016/j.geomorph.2020.107521