Kostarisk joint research laboratory has received government funding managed by the French National Research Agency under the France 2030 Investment Plan (ref. ANR-16-IDEX-0002).
Publications
[hal-05497633] Numerical Analysis of the Dynamics of a Wave Energy Hotspot in Southwest France
Feb 6, 2026 3:41 PM - HAL : Dernières publications
This work aims to improve our understanding of the wave dynamics at Belharra, a wave energy hotspot on the French Basque coast. A combination of spectral and phase-resolving wave models enables analysis of how the incident swell conditions and tide level affect the wave field in the coastal and local scales. We carry out a detailed wave-by-wave investigation of the local conditions for a wide range of scenarios, and draw comparisons with field data. Regional and local bathymetric features control the concentration of swell energy at this location. Longperiod swells from directions around 300°-315°generate the most energetic local conditions. Lower tides lead to greater breaking intensities, albeit with weaker wave amplifications.
[hal-05481614] Experimental and Numerical Study of Impulse Waves Generated by Water Releases on a Slope
Jan 28, 2026 1:01 PM - HAL : Dernières publications
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[hal-05481593] Numerical Analysis of the Dynamics of a Wave Energy Hotspot in Southwest France
Jan 28, 2026 12:56 PM - HAL : Dernières publications
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[hal-05481488] Étude des forces d’impact d’un écoulement de nappe sur un mur vertical
Jan 28, 2026 12:31 PM - HAL : Dernières publications
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[hal-05481454] Etude de l'impact d'une tempête extrême sur la Grande Plage de Biarritz en présence d'une digue amovible en sacs de sable
Jan 28, 2026 12:25 PM - HAL : Dernières publications
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[hal-05390837] Wave-driven amplification of surf-zone bottom stress on rough seabeds
Dec 1, 2025 1:44 PM - HAL : Dernières publications
The present paper proposes a unified view of the wave-driven amplification of the wave-averaged bottom shear stress in rough seabed contexts, covering both co-and opposing wave/current cases. The analysis is first based on a series of field observations performed over the Flysch rocky shore platform of Socoa. The momentum balance is examined locally, separating the net effect of the waves on the depth-and wave-averaged momentum budget, based on velocity and pressure measurements. The present observations confirm that, in the presence of complex seabed topography, the bed shear stress is an important component of the momentum balance. The results highlight two distinct regimes depending on the breaking activity due to the intricate composition between waves and mean currents in the wave averaged shear stress. In moderately developed undertow conditions, the bottom stress brings a negative contribution to the wave momentum balance, and acts to to promote wave setdown, while in conditions of depth-limited wave breaking saturation the bed friction acts to increase the wave setup. A novel empirical parameterization of the mean bottom stress under combined waves and current is proposed. The in-situ findings are complemented by a series of wave-resolving simulations on idealized closed and open beaches, confirming the complex effect of waves on the time-averaged water circulation.
[hal-05376444] Wave energy hotspots - a numerical study of wave processes at Belharra, South West of France
Nov 21, 2025 2:08 PM - HAL : Dernières publications
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[hal-05262420] Field study of post-overtopping flow impacts on a vertical wall at the crest of an upper-beach dike
Sep 16, 2025 10:44 AM - HAL : Dernières publications
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[hal-05228503] First and second force peaks generated by a surge impact on a wall with and without overtopping
Aug 28, 2025 6:07 PM - HAL : Dernières publications
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[hal-05003862] Modélisation à phase résolue de la transformation des vagues en zone de déferlement sur des fonds rugueux idéalisés
Mar 24, 2025 7:38 PM - HAL : Dernières publications
La compréhension et la prévision des processus de submersion dans les environnements rocheux nécessitent de prendre en compte la rugosité du fond, qui joue un rôle clé dans les processus de transformation des vagues et dans la dynamique littorale générale. Le présent travail vise à mettre en œuvre une paramétrisation de la dissipation induite par la rugosité dans les modèles de vagues 3D non hydrostatiques à phase résolue, basé sur le code Symphonie (MARSALEIX et al., 2019). Le modèle modifié est confronté à des expériences de laboratoire réalisées sur une zone de surf à pente linéaire (DEALBERA et al., 2024). Différentes vagues irrégulières y ont été testées sur diverses configurations de rugosité du fond (représentées par des configurations en blocs de tailles et de distributions différentes). La génération de vagues et la dissipation induite par le déferlement ont d'abord été paramétrées par rapport aux données de laboratoire sur fond lisse. Les différents cas de rugosité ont ensuite été étudiés sur la base de deux stratégies distinctes pour la paramétrisation du frottement du fond, à savoir l'approche par la contrainte de fond et l'approche par la traînée volumique de canopée. La performance de ces deux approches est ainsi évaluée en comparant les résultats du modèle et les mesures du profil cross-shore de la hauteur significative des vagues pour différentes configurations de fond. Sur la base de ce travail, des recommandations sur le choix des paramétrisations de la dissipation du fond seront prescrites pour chaque environnement.
[hal-05003858] Phase-resolved modeling of surf zone wave transformation over idealized rough bottoms
Mar 24, 2025 7:32 PM - HAL : Dernières publications
Rough rocky seabeds dominate world's coastlines, making accurate modeling of wave transformation in such environments essential for understanding coastal processes and hazards. Wave breaking and friction are critical drivers of wave dissipation over rough seabeds, especially in the surf zone. Phase-resolved wave models, often relying on classical bed shear stress or canopy drag approaches, can fail to capture these processes due to limitations in their physical assumptions, especially for large roughness elements typical of rocky seabeds. The present study adapts the Bulk Canopy Drag (BCD) parameterization, inherited from vegetation and porous media studies, into the 3D non-hydrostatic phase-resolved SYMPHONIE model to simulate wave dissipation over rough seabeds. The model was tested against laboratory experiments (LEGOLAS), using controlled irregular wave forcing propagating over a rough ramp. Results reveal that turbulent drag dominates the outer surf zone, while inertial drag plays a key role in the inner surf zone. A combined optimization of these influences achieved strong agreement with experimental measurements under one irregular wave forcing and a specific bottom configuration. These findings underscore the importance of accurately incorporating both turbulent and inertial contributions into wave dissipation models for the rocky surf zone. The proposed BCD approach provides a promising framework for improving phase-resolved modeling of wave dynamics, with potential applications for more complex field conditions. Future work will aim to extend the approach to diverse roughness configurations and refine empirical coefficients for broader scalability and in situ applicability.
[hal-04822168] Physical processes explaining the second force peak generated during a surge impact on a vertical wall
Dec 6, 2024 9:19 AM - HAL : Dernières publications
This paper presents an in-depth study of the impact of a surge on a vertical wall using incompressible and compressible RANS model simulations of a classical dam break experiment over a dry bed. The model allows access to the detailed flow structure and pressure field at any instant, which provides valuable complementary information to measurements. Our study focuses on the second force peak, which is often the largest one and for which the literature does not really provide a clear explanation. Before and after this peak, the pressure on the wall is governed by the flow kinematics in the area. Before the peak, an overpressure appears at the root of the reflected jet, corresponding to the violent interaction between the incoming surge and the run-down flow. At the peak instant, the situation suddenly changes, due to the collapse of the reflected jet onto the incoming flow, trapping an air cavity. As in the classical case of direct wave impact on a wall with a trapped air pocket, this process generates an additional strong uniform pressure field in the air cavity, which propagates to the water and nearby boundaries due to the water confinement effect. This compressible effect, which varies depending on the capacity of air to escape the cavity, explains the formation of the second force peak. Finally, the 3D incompressible model provides a much more reliable estimate of the second force peak than the 2D incompressible model. This is likely due to the air escape phenomenon, which occurs when the experimental initial conditions are not perfectly 2D. Although it is unlikely that the 3D simulation perfectly reproduces the experimental flow, nevertheless, with more or less comparable air escape, the computation results appear consistent.
[hal-04784864] Numerical Simulation of The Impact Forces Generated by a Swash-Type Flow on an Overtopped Obstacle
Nov 15, 2024 11:54 AM - HAL : Dernières publications
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[hal-04720458] CoastCams: A MATLAB toolbox making accessible estimations of nearshore processes, mean water levels, and morphology from timestack images
Oct 11, 2024 5:47 PM - HAL : Dernières publications
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[hal-04442134] The role of roughness geometry in frictional wave dissipation
Feb 6, 2024 5:27 PM - HAL : Dernières publications
Bottom friction dissipation is a key factor for wave attenuation in nearshore environments presenting complex geomorphological structures, such as rocky or coral shores. The present paper reports on a series of laboratory experiments performed in a wave flume with controlled wave conditions and seabed structures. Using the frequency-integrated shortwave analysis and classical models for bottom friction and breaking dissipation, the wave friction factor and the hydraulic roughness parameter were estimated from the experimental data. The former varies from 0.17 to 98 while the latter varies from 0 to 0.291 m. The observations reveal the combined influence of several topographical metrics, including the standard deviation, the skewness, the directionality and the effective slope of the seabed elevation. A metric-based multi-varied model for the hydraulic roughness parameter is proposed and confronted with other field data recovered on coral and rocky shores.
[hal-04284058] Improving Wave Run-up Forecasts – Benefits from Phase-resolving Models
Nov 14, 2023 11:55 AM - HAL : Dernières publications
Presented at: Coastal Structures Conference 2019, Hannover, Germany, September 30th – October 2nd, 2019
[hal-04283870] Efficient Numerical Computations of Long-Wave Run-Up and Their Sensitivity to Grid Nesting
Nov 14, 2023 11:03 AM - HAL : Dernières publications
Computation of long-wave run-up has been of high interest in the fields of ocean sciences and geophysics-particularly for tsunami and river flood modeling. An accurate calculation of run-up and inundation requires the numerical model to account for a sequence of critical processes-each of them posing a different challenge to the numerical solution. This study presents the strategic development of a numerical solution technique for Shallow Water Equations with a focus on accuracy and efficiency for long-wave run-up. The present model is based on an explicit second-order Finite Volume scheme over a staggered grid that efficiently achieves fundamental properties such as well-balance and preservation of shock fronts without the need for computationally expensive solvers. The streamlined code serves as a foundation for the implementation of nested grids. Computations of commonly used long-wave benchmark tests showcase that accurate predictions of local extreme run-up can often be achieved with highly refined yet spatially focused nested grids. Strategic grid nesting can lead to stable and accurate solutions of run-up at locations of interest and reduce the computational load to a fraction of what is usually necessary for a comparable solution over a single grid.
[hal-04000424] Laboratory study of wave hydrodynamics in the surf zone in presence of roughness
Feb 22, 2023 12:47 PM - HAL : Dernières publications
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[hal-04000367] Etude en laboratoire de l’hydrodynamique des vagues dans la zone de déferlement en présence de macro-rugosités
Feb 22, 2023 12:29 PM - HAL : Dernières publications
L'étude, la compréhension et la modélisation des processus physiques marins sont des facteurs-clés pour anticiper les risques de submersion du littoral. L'hydrodynamique des vagues n'est pas encore complètement, appréhendée et modélisée sur les fonds rugueux et/ou à forte pente, notamment l'effet des macro-rugosités sur la dissipation par frottement. Une série d'expériences en canal à houle a été menée afin d'améliorer la compréhension des phénomènes physiques et de connecter l'hydrodynamique à la bathymétrie du fond en pente en comparant un fond lisse de référence et un fond présentant des macro-rugosités. Après avoir extrait la composante incidente de la houle à partir des données d'élévation de la surface libre le long du profil de plage, la dissipation d'énergie est estimée à partir du gradient de flux d'énergie. Sur le fond lisse de référence, les paramètres d'un modèle de déferlement classique ont été optimisés pour chaque cas de houle irrégulière et réutilisés pour estimer la dissipation par déferlement sur le fond rugueux. Ceci nous permet de séparer les contributions du déferlement et du frottement en utilisant la rugosité hydraulique comme paramètre de calibrage sur les données expérimentales. Les résultats obtenus nous permettent de discuter le lien entre rugosité hydraulique et géométrie du fond, ainsi que la validité du modèle de frottement à des rugosités plus importantes.
[hal-03948133] Bayesian networks to predict storm impact using data from both monitoring networks and statistical learning methods
Jan 20, 2023 6:47 AM - HAL : Dernières publications
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[hal-03882074] Effects of a groyne field on inner bar dynamics: Anglet, France
Dec 2, 2022 12:12 PM - HAL : Dernières publications
Groynes are usually designed to limit beach erosion by mitigating longshore sediment transport. However, little is known about their side effects on inner-bar morphodynamics in double sandbar systems. While most of the studies are focused on natural systems where the outer-bar morphology drives inner-bar dynamics (offshore to nearshore process), this work focuses on the role of groynes on the inner bar dynamics (nearshore to offshore process). The study is based on 3-years field observations carried out at the beach of Anglet in the south-west of France. This engineered beach is 4 km long, limited by a rocky headland in the south and a 1 km long jetty at the entrance of the Adour river in the North. The study area concerns the south part of the beach and includes a series of four groynes, unevenly spaced and extending about 100 m seaward. Morphology changes observations were derived from images collected with a video system (http://sirena.univ-pau.fr/), and bi-annual topo-Bathymetric surveys. A special attention was paid to study the mechanisms controlling the observed morphology changes using the XBeach numerical model. Data analysis reveals that the study site is dominated by a double sandbar system. Both bars can evolve from reasonably alongshore-uniform to crescentic bars. Surprisingly, the beach may show episodes where the inner bar evolves from alonghsore uniform to non-uniform despite an alongshore uniform outer bar. Numerical results corroborate that the formation of inner bar crescentic features can be formed without the presence of an outer non-uniform bar under certain wave conditions for the study site. This study shows that inner bar evolution in the presence of groynes can be controlled by topographic rip channels and not only by morphological coupling as usually observed on natural double sandbar systems.
[hal-03882004] ALTERNATIVE IMAGE STABILIZATION METHOD FOR COASTAL VIDEO MONITORING SYSTEMS
Dec 2, 2022 11:51 AM - HAL : Dernières publications
The use of shore-based video systems has become a very popular and accessible low-cost tool for coastal monitoring given their capability to deliver continuous and high-resolution temporal data over large enough spatial scales. However, the reliability of the final image products can be compromised by external factors, sometimes overlooked, that can alter the image geometry over time. In particular, unwanted camera movement, produced either by thermal or mechanical effects, can lead to significant geo-rectification errors if not properly corrected. This study addresses an alternative straightforward method to stabilize an either continuous or subsampled image sequence based on state-of-the-art techniques and available routines.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/xX1CrvPQpK8
[hal-03881989] Predicting seiche hazard for coastal harbours along the northern and western coasts of France
Dec 2, 2022 11:45 AM - HAL : Dernières publications
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[hal-03881973] Spatial distribution of wave energy over complex coastal bathymetries: Development of methodologies for comparing modeled wave fields with satellite observations
Dec 2, 2022 11:41 AM - HAL : Dernières publications
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[hal-03830551] Video-Based Nearshore Bathymetric Inversion on a Geologically Constrained Mesotidal Beach during Storm Events
Oct 26, 2022 3:35 PM - HAL : Dernières publications
Although geologically constrained sandy beaches are ubiquitous along wave-exposed coasts, there is still a limited understanding of their morphological response, particularly under storm conditions, which is mainly due to a critical lack of nearshore bathymetry observations. This paper examines the potential to derive bathymetries from video imagery under challenging wave conditions in order to investigate headland control on morphological beach response. For this purpose, a video-based linear depth inversion algorithm is applied to three consecutive weeks of frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France). Video-derived bathymetries are compared against in situ topo-bathymetric surveys carried out at the beginning and end of the field experiment in order to assess the performance of the bathymetric estimates. The results show that the rates of accretion/erosion within the surf zone are strongly influenced by the headland, whereas the beach morphological response can be classified into three main regimes depending on the angle of wave incidence θp: (1) under deflection configuration (θp>0°), the alongshore sediment transport was trapped at the updrift side of the headland, promoting sand accretion. (2) Under shadowed configuration (θp<0°), the interruption of the longshore current drove a deficit of sand supply at the downdrift side of the headland, leading to an overall erosion in the surf zone. (3) Under shore-normal configuration (θp=0°), rip channels developed, and up-state beach transition was observed. A comparison between video-derived bathymetries and surveys shows an overall root mean square error (RMSE) around 0.49 to 0.57 m with a bias ranging between −0.36 and −0.29 m. The results show that video-derived bathymetries can provide new insight into the morphological change driven by storm events. The combination of such inferred bathymetry with video-derived surface current data is discussed, showing great potential to address the coupled morphodynamics system under time-varying wave conditions.
[hal-03011157] Using Random forest and Gradient boosting trees to improve wave forecast at a specific location
Sep 14, 2022 11:05 AM - HAL : Dernières publications
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[hal-03602283] Automatic Creation of Storm Impact Database Based on Video Monitoring and Convolutional Neural Networks
Mar 9, 2022 6:34 AM - HAL : Dernières publications
Data about storm impacts are essential for the disaster risk reduction process, but unlike data about storm characteristics, they are not routinely collected. In this paper, we demonstrate the high potential of convolutional neural networks to automatically constitute storm impact database using timestacks images provided by coastal video monitoring stations. Several convolutional neural network architectures and methods to deal with class imbalance were tested on two sites (Biarritz and Zarautz) to find the best practices for this classification task. This study shows that convolutional neural networks are well adapted for the classification of timestacks images into storm impact regimes. Overall, the most complex and deepest architectures yield better results. Indeed, the best performances are obtained with the VGG16 architecture for both sites with F-scores of 0.866 for Biarritz and 0.858 for Zarautz. For the class imbalance problem, the method of oversampling shows best classification accuracy with F-scores on average 30% higher than the ones obtained with cost sensitive learning. The transferability of the learning method between sites is also investigated and shows conclusive results. This study highlights the high potential of convolutional neural networks to enhance the value of coastal video monitoring data that are routinely recorded on many coastal sites. Furthermore, it shows that this type of deep neural network can significantly contribute to the setting up of risk databases necessary for the determination of storm risk indicators and, more broadly, for the optimization of risk-mitigation measures.
[hal-03411135] Wave-Filtered Surf Zone Circulation under High-Energy Waves Derived from Video-Based Optical Systems
Nov 2, 2021 8:11 AM - HAL : Dernières publications
This paper examines the potential of an optical flow video-based technique to estimate wave-filtered surface currents in the nearshore where wave-breaking induced foam is present. This approach uses the drifting foam, left after the passage of breaking waves, as a quasi-passive tracer and tracks it to estimate the surface water flow. The optical signature associated with sea-swell waves is first removed from the image sequence to avoid capturing propagating waves instead of the desired foam motion. Waves are removed by applying a temporal Fourier low-pass filter to each pixel of the image. The low-pass filtered images are then fed into an optical flow algorithm to estimate the foam displacement and to produce mean velocity fields (i.e., wave-filtered surface currents). We use one week of consecutive 1-Hz sampled frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France) under high-energy conditions with significant wave height ranging from 0.8 to 3.3 m. Optical flow-computed velocities are compared against time-averaged in situ measurements retrieved from one current profiler installed on a submerged reef. The computed circulation patterns are also compared against surf-zone drifter trajectories under different field conditions. Optical flow time-averaged velocities show a good agreement with current profiler measurements: coefficient of determination (r2)= 0.5–0.8; root mean square error (RMSE) = 0.12–0.24 m/s; mean error (bias) =−0.09 to −0.17 m/s; regression slope =1±0.15; coherence2 = 0.4–0.6. Despite an underestimation of offshore-directed velocities under persistent wave breaking across the reef, the optical flow was able to correctly reproduce the mean flow patterns depicted by drifter trajectories. Such patterns include rip-cell circulation, dominant onshore-directed surface flow and energetic longshore current. Our study suggests that open-source optical flow algorithms are a promising technique for coastal imaging applications, particularly under high-energy wave conditions when in situ instrument deployment can be challenging.
[hal-03044435] Field Observations of Wave-induced Headland Rips
Mar 1, 2021 10:18 AM - HAL : Dernières publications
Most of rip-current field experiments have focused on persistent rips along rip-channeled sandy beaches or transient rips along reasonably alongshore-uniform surf-zone morphology, while experiments on rip flowing against structures are scarce. In October 2018, a 3-week field experiment was performed at Anglet beach, SW France, aiming at examining the dynamics of high-energy rip currents in complex settings. The beach is barred with prominent inherited geology, characterized by the presence of a 500-m headland and a natural submerged reef. A large array of in-situ instruments was deployed to capture the temporal and spatial variability of rip flow circulations, including ADCPs, surf-zone drifters and video monitoring. The latter allowed to identify a wide range of rip-flow patterns. Among these patterns, a high-intensity rip current flowing against the headland was a dominant feature for obliquely incident waves. Such a boundary rip current was driven by the deflection of the longshore current against the headland, peaking at 0.7 m/s (5-min time-and depth-averaged) 800-m offshore in 12-m depth for a moderate storm event with 4-m obliquely incident waves. Very-lowfrequency (O(1h) and O(30min)) fluctuations of this rip current were observed around low tide. Measurements of the vertical structure of the rip reveal that the deflection rip was more vertically-sheared as the water depth increases, with higher velocities near the surface, which is typical of a theoretical rip head structure.
[hal-03043459] A Simple and Efficient Image Stabilization Method for Coastal Monitoring Video Systems
Dec 7, 2020 1:01 PM - HAL : Dernières publications
Fixed video camera systems are consistently prone to importune motions over time due to either thermal effects or mechanical factors. Even subtle displacements are mostly overlooked or ignored, although they can lead to large geo-rectification errors. This paper describes a simple and efficient method to stabilize an either continuous or sub-sampled image sequence based on feature matching and sub-pixel cross-correlation techniques. The method requires the presence and identification of different land-sub-image regions containing static recognizable features, such as corners or salient points, referred to as keypoints. A Canny edge detector (CED) is used to locate and extract the boundaries of the features. Keypoints are matched against themselves after computing their two-dimensional displacement with respect to a reference frame. Pairs of keypoints are subsequently used as control points to fit a geometric transformation in order to align the whole frame with the reference image. The stabilization method is applied to five years of daily images collected from a three-camera permanent video system located at Anglet Beach in southwestern France. Azimuth, tilt, and roll deviations are computed for each camera. The three cameras showed motions on a wide range of time scales, with a prominent annual signal in azimuth and tilt deviation. Camera movement amplitude reached up to 10 pixels in azimuth, 30 pixels in tilt, and 0.4°in roll, together with a quasi-steady counterclockwise trend over the five-year time series. Moreover, camera viewing angle deviations were found to induce large rectification errors of up to 400 m at a distance of 2.5 km from the camera. The mean shoreline apparent position was also affected by an approximately 10-20 m bias during the 2013/2014 outstanding winter period. The stabilization semi-automatic method successfully corrects camera geometry for fixed video monitoring systems and is able to process at least 90% of the frames without user assistance. The use of the CED greatly improves the performance of the cross-correlation algorithm by making it more robust against contrast and brightness variations between frames. The method appears as a promising tool for other coastal imaging applications such as removal of undesired high-frequency movements of cameras equipped in unmanned aerial vehicles (UAVs).
[hal-02383838] Identifying 2010 Xynthia Storm Signature in GNSS-R-Based Tide Records
Nov 28, 2019 10:13 AM - HAL : Dernières publications
In this study, three months of records (January-March 2010) that were acquired by a geodetic Global Navigation Satellite Systems (GNSS) station from the permanent network of RGP (Réseau GNSS Permanent), which was deployed by the French Geographic Institute (IGNF), located in Socoa, in the south of the Bay of Biscay, were used to determine the tide components and identify the signature of storms on the signal to noise ratio (SNR) during winter 2010. The Xynthia storm hit the French Atlantic coast on the 28th of February 2010, causing large floods and damages from the Gironde to the Loire estuaries. Blind separation of the tide components and of the storm signature was achieved while using both a singular spectrum analysis (SSA) and a continuous wavelet transform (CWT). A correlation of 0.98/0.97 and root mean square error (RMSE) of 0.21/0.28 m between the tide gauge records of Socoa and our estimates of the sea surface height (SSH) using the SSA and the CWT, respectively, were found. Correlations of 0.76 and 0.7 were also obtained between one of the modes from the SSA and atmospheric pressure from a meteorological station and a mode of the SSA. Particularly, a correlation reaches to 0.76 when using both the tide residual that is associated to surges and atmospheric pressure variation.
[hal-02337105] Hydrodynamics and SPM transport in an engineered tidal estuary: the Adour river (France)
Oct 29, 2019 12:54 PM - HAL : Dernières publications
The present paper reports on a series of field experiments aiming to characterise the functioning of a man-engineered strongly forced salt-wedge estuary : the lower estuary of the Adour river, France. Bottom-moored velocity measurements and surface boat surveys have been performed under low river discharge conditions, for both neap and spring tides, in order to provide a well-documented reference framework to understand the dynamics of water masses, turbulence and suspended particulate matter (SPM) transport in the lower estuary. An additional campaign has been carried out in high river discharge conditions. This first documented in-situ study of the Adour lower estuary demonstrates its variability in terms of hydrological regimes, from salt-wedge to partially mixed regimes depending on tidal and discharge conditions. Turbulent properties showed a significant response to the variations of salinity structure, with higher values when stratification is minimal. At spring tide, a tidal variation between mixing conditions on the ebb and the flood is revealed by ADCP measurements, with higher values extended up to the surface during the ebb. The link between turbulent mixing and suspended sediment concentration is straightforward during the ebb. During the flood, the suspended sediment concentration (SSC) seems related to the salt-wedge entrance re-suspension and stratification-induced turbulence damping. No stable Estuarine Turbidity Maximum (ETM) has been observed during the field experiment in the lower Adour estuary.
[hal-02162530] Validation of a 3D Numérical Model of the Adour River Plume Flow
Jun 21, 2019 9:19 PM - HAL : Dernières publications
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[hal-02154268] A Combined Numerical/Experimental Approach to Understand Stratification and Mixing Processes in the Adour Estuary
Jun 12, 2019 8:29 PM - HAL : Dernières publications
River plumes play a central role in the input and transport of dissolved and particulate matters that can lead to the dispersion of pollutants into coastal waters. Understanding the dynamics of river plumes is thus essential to evaluate the potential threat to coastal-marine ecosystems, in order to improve management and mitigation policies. The Adour estuary morphology combined with the competition between the tide and the river flow result in a partially stratified estuary. A dual approach, coupling field experiments and numerical modeling, has been carried out to better understand the physical processes that govern the Adour river plume hydrodynamics. A field campaign was performed inside the estuary in September 2017. Velocity profilers and high frequency point current-meters were moored, at two different stations inside the estuary, during one month. Series of salinity profiles were realized at four stations including mooring stations. Meanwhile, a numerical model has been developed based on the open source code TELEMAC-3D to investigate the interaction between light continental waters and heavy salty marine waters, focusing on the salt-wedge intrusion inside the estuary. The resulting density stratification playing a major role in the transfer of water masses and the transport of dissolved and particulate matters, its precise reproduction isone of the cornerstones of our study. Inside the estuary, a competition between density gradient and velocity/bottom shear regulates mixing processes. First comparisons between model and field data show a good agreement between measured and simulated water levels and velocity profiles. The correct representation of density stratification processes by the numerical model remains, as expected, a challenging issue. The choice of the turbulence model, which is of the foremost importance for a good representation of the interaction between water masses, will be discussed within the physical framework provided by field measurements
[hal-02154248] Propriétés statistiques des événements de tempêtes au large de la côte basque
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154243] Statistical Properties of Storm Waves in the Basque and Les Landes Coast, Bay of Biscay
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154256] Infragravity Period Oscillations in a Channel Harbor near a River Mouth
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154266] Characterization of Seiches in Small-Harbors
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154236] Turbulence Measurements in a Stratified Man-Controlled Estuary, the Adour Case
Jun 12, 2019 8:28 PM - HAL : Dernières publications
The Adour river is a partially stratified river flowing into the Basque Country coastal waters. The dynamics of estuarine waters and suspended matters, including density stratification, mixing, residence and renewal times, is controlled by the competition between the input of terrestrial waters with strongly varying discharge and suspended load and the meso-tidal fluctuations of the ocean level. Since pycnoclines can form a decisive barrier for exchange processes within a water body, it is important to better understand the processes that govern their evolution in particular for water quality studies. A turbulence-dedicated field campaign was performed in the lower estuary in September 2017. The instrumentation is based on fixed bottom moorings with high frequency point currentmeters and velocity profilers. During the well-mixed phases of the tidal cycles, the flow properties are in good agreement with the standard hypothesis of the canonical turbulent boundary layer in open channel flows. Measurements carried out during the arrival of the salt wedge at rising tide demonstrate the strong influence of density stratification on the flow dynamics. Both turbulent kinetic energy and momentum fluxes are damped by the density stratification, which consequently affect the mixing and resuspension processes near the river bed. A second series of experiments has been performed in order to identify the turbulent properties away from the bed. Instrumented lagrangian drifters have been deployed during the two-layers flow pattern in the estuary. The results again show the important effect of density stratification. The local measurements of small-scale turbulent processes will be placed and discussed in a more general contextaiming to describe the intra-estuary exchanges between river and ocean waters and the fate of dissolved and suspended matters
[hal-02154022] Numerical Study of Breakwater Failure Due to Tsunami-like Undular Bore Impacts: The Case of the Port of Soma.
Jun 12, 2019 6:14 PM - HAL : Dernières publications
The Tohoku tsunami, that impacted the Japanese coast in 2011, caused great damages on many offshore vertical breakwaters ranging from the erosion of the rubble mound to the partial displacement or total collapse of caissons. The breakwater failure mechanisms were function of the tsunami wave types that vary along the Japanese coast according to the bathymetry features. The Iwate coast, characterized by deep water depths and steep slopes, was mainly impacted by tsunami overflow leading in particular to the failure of the world's deepest breakwater of Kamaishi. In the shallow waters of the Sendai bay, observations showed that breakwaters protecting harbor entrances were impacted by short waves train resembling to undular bore. This work aims to investigate this latter type of tsunami wave impacts that are less reported in the literature. We chose to focus on the highly damaged offshore breakwater of Soma, located in the south part of the Sendai bay. The hydrodynamics conditions during the tsunami impact are investigated using the VARANS Thetis code (Desombre et al., 2012), which allows to simulate both the free surface flow and the flow inside the rubble mound simulated by a porous medium. The model is forced at the offshore boundaries by the Funwave Boussinesq code that describes the transformation of the tsunami waves from the source to the generation of undular bores in shallow waters. The study includes the computation of forces acting on the caissons. We discuss the relevance of describing the hydrodynamics at the short wave scale to assess breakwater stability in the course of tsunami-like undular bore impact. References Desombre, J., Morichon, D., & Mory, M. (2012). SIMULTANEOUS SURFACE AND SUBSURFACE AIR AND WATER FLOWS MODELLING IN THE SWASH ZONE. Coastal Engineering Proceedings, 1(33), 56.
[hal-02154026] Propriétés statistiques des événements de tempête au large de la côte Basque
Jun 12, 2019 6:14 PM - HAL : Dernières publications
Dans ce travail, nous proposons une étude statistique des vagues de tempête sur la côte basque française et espagnole à partir d'un jeu de données issu de simulations numériques. Ce jeu de données, hébergé sur le site des ports espagnols (Puertos del Estado), couvre la période 1958 à nos jours. Après avoir validé ces données en comparaison de nos propres mesures, nous avons fait appara\ⁱtre les événements de tempêtes, définis comme les événements extrêmes en termes d'énergie totale (i.e. l'intégrale du flux entre le début et la fin de la tempête). Puis nous avons analysé statistiquement les données obtenues et déterminé une classification permettant de dégager des groupements représentatifs de ces événements de tempête.
[hal-02153956] Oscillations portuaires forcées par les ondes infra-gravitaires dans un chenal de navigation
Jun 12, 2019 6:11 PM - HAL : Dernières publications
Le port de Bayonne, situé proche de l'embouchure de l'Adour, rencontre fréquemment des problèmes de tenu à quai des navires en période de tempête. Afin de comprendre l'origine de l'agitation du port, une campagne de mesures, composée d'un houlographe mouillé à 50 m de fond et de trois capteurs de pression déployés dans le port, est réalisée durant un épisode de tempête de période de retour de 1 an (Hs=5 m et Tp=16 s). Cet événement est également simulé avec un modèle numérique basé sur la résolution des équations de Boussinesq (BOSZ) afin de comprendre l'origine du forçage des oscillations mesurées dans le port. L'étude montre que les deux digues situées à l'embouchure de l'Adour assurent efficacement la protection du port contre la houle incidente en provoquant un amortissement de Hs de 85 % dans la bande de périodes des vagues courtes (5-25 s). L'agitation du plan d'eau est majoritairement contrôlée par les ondes infra-gravitaires (IG). En période de tempête des valeurs de Hs de 0,70 m dont 0,65 m dans les IG (30- 300 s) ont été mesurées à 1,4 km en amont du fleuve. Un dépôt sous-marin de dragage, situé entre 2,5 et 3,5 km des plages, provoque la levée des vagues et une augmentation de Hs de l'ordre de 20 %. Ce phénomène semble favoriser la génération d'ondes IG par interaction non linéaire entre les vagues courtes. En pénétrant dans le port, les ondes IG se propagent librement dans le fleuve et se dissipent progressivement par frottement. Cependant, elles conservent suffisamment d'énergie pour, d'une part, provoquer la résonance d'un port de plaisance situé à 1,4 km en amont de l'embouchure, et d'autre part probablement exciter les navires amarrés dont les périodes propres sont dans la bande IG.
[hal-02153676] Shoreline-Sandbar Dynamics at a High-Energy Embayed and Structurally-Engineered Sandy Beach: Anglet, SW France
Jun 12, 2019 3:59 PM - HAL : Dernières publications
Anglet beach, Basque Coast (SW France), is a 4-km long embayment bounded by a prominent headland in the South and by the southern Adour River training wall in the North. The beach is structurally-engineered with, within the embayment, 6 groins and 3 distinct sectors where the beach is backed by a seawall. The beach is high-energy intermediate, mostly double-barred, composed of medium to coarse sand with a steep beach face (∼1/10). In January 2013, a video system was installed at the Southern end of Anglet beach at about 70 m above mean sea level to monitor about 2 km of the southern beach of Anglet that includes 4 groins extending about 100 m seaward and a 1- km seawall backing the beach. The study period includes the winter 2013/2014 that was outstanding in terms of the available energy arriving at the coast with a 2-month-averaged significant wave height peaking at 3.6 m. Despite the extreme storm wave conditions during the winter 2013/2014, the outer bar crescentic patterns maintained and even further developed. The beach eroded by O(10 m) and, surprisingly and in contrast with the nearby northern open beaches, they recovered to their pre-winter 2013/2014 state within only a few months. Overall, Anglet beach appears to respond predominantly at individual storm frequency rather than at seasonal timescales, with the groins and headland acting as major controlling boundaries influencing beach state and dictating rip channel locations. \textcopyright Coastal Education and Research Foundation, Inc. 2016.
[hal-02058605] A comparative study of models to predict storm impact on beaches
Mar 6, 2019 9:33 AM - HAL : Dernières publications
The storm impact scale of Sallenger (J Coast Res 890-895, 2000) was tested on a partially engineered beach. This scale is supposed to provide a convenient tool for coastal managers to categorize the storm impact at the shore. It is based on the relation between the elevation of storm wave runup and the elevation of a critical geomorphic or man-made structures in the present study. Two different approaches were tested to estimate the elevation of extreme storm wave runup: (1) a parametric model based on offshore wave conditions and local beach slope and (2) the XBeach process-based model that solves implicitly the runup. The study shows comparisons between impact regimes computed with the two methods and those derived from video observations acquired during 2 weeks while the site was battered by three consecutive storms. Storms scenario including wave conditions with higher return periods and different tidal range were also investigated. The advantages and disadvantages of the two methods used to compute extreme water level are then compared, and guidelines for the development of early warning system are drawn.
[hal-01891067] Assessment of Flooding Hazards at An Engineered Beach during Extreme Events: Biarritz, SW France
Oct 9, 2018 1:29 PM - HAL : Dernières publications
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[hal-01885867] Liga en Sud-Aquitaine. Causes et conséquences du développement de "neige marine" sur la côte Basque et le sud des Landes
Oct 2, 2018 3:09 PM - HAL : Dernières publications
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[hal-01627758] Wave propagation, breaking, and overtopping on a 2D reef: A comparative evaluation of numerical codes for tsunami modelling
Nov 3, 2017 11:20 AM - HAL : Dernières publications
In the framework of the French research project TANDEM dedicated to tsunami modelling, a series of benchmarks has been set up, addressing the various stages of a tsunami event: generation, propagation, run-up and inundation. We present here the results of five codes, involving both depth-averaged Boussinesq and fully 3D Navier-Stokes equations, aimed at being applicable to tsunami modelling. The codes are evaluated on a flow involving propagation, run-up, overtopping and reflection of the waves on two-dimensional reefs, and compared with the experimental data produced from a set of laboratory experiments carried out at the O.H.
[hal-01414781] Wave propagation breaking, and overtoping on a 2D reef : a comparative evaluation of numerical codes for tsunami modelling
Jan 10, 2017 2:04 PM - HAL : Dernières publications
In the framework of the French research project TANDEM dedicated to tsunami modelling, a series of benchmarks has been set up, addressing the various stages of a tsunami event: generation, propagation, run-up and inundation. We present here the results of five codes, involving both depth-averaged Boussinesq and fully 3D Navier-Stokes equations, aimed at being applicable to tsunami modelling. The codes are evaluated on a flow involving propagation, run-up, overtopping and reflection of the waves on two-dimensional reefs, and compared with the experimental data produced from a set of laboratory experiments carried out at the O.H. Hinsdale Wave Research Laboratory, Oregon State University (OSU, see Roeber et al., 2010 and Roeber and Chung, 2012).
[hal-01390692] A database of validation cases for tsunami numerical modelling
Nov 2, 2016 1:37 PM - HAL : Dernières publications
This work has been performed by a French national consortium within the framework of the national project Tandem, with aim to improve knowledge about tsunami risk on the French coasts. Workpackage #1 of this project was the opportunity to build a database of benchmark cases to assess the capabilities of 18 codes, solving various set of equations with different numerical methods. 14 test cases were defined from the existing literature with validation data from reference simulations, theoretical solutions or lab experiments. They cover the main stages of tsunami life: 1) generation, 2) propagation, 3) run-up and submersion, and 4) impact. For each case several of the numerical codes were compared in order to identify the forces and weaknesses of the models, to quantify the errors that these models may induce, to compare the various modelling methods, and to provide users with recommendations for practical studies. In this paper, 3 representative cases are selected and presented with an analysis of the results.
[insu-01387873] DYNALIT : Dynamique du Littoral et Trait de Côte
Oct 26, 2016 1:14 PM - HAL : Dernières publications
Le littoral, caractérisé par une grande diversitéd’environnements (plages sableuses ou rocheuses, cordonsdunaires, falaises, lagunes, estuaires...) est une zone très mobile etévolutive du fait de forçages hydrodynamiques et météorologiquessouvent intenses. Cet environnement est fragile, car soumis àl’impact d’activités humaines qui ne cessent d’augmenter (urbanisation,aménagements...), mais aussi aux effets du changementclimatique (élévation du niveau de la mer, modification durégime de houles, inondations). Comprendre le fonctionnementhydromorpho-sédimentaire des environnements littoraux est crucialpour prédire leur évolution et celle des écosystèmes associés.Le Service National d’Observation labellisé par le CNRS, (SNO)DYNALIT, - Dynamique du Littoral et du Trait de Côte a pourbut de constituer une base de données hydromorphologiques sur lelong terme de 29 sites ateliers représentatifs des environnementslittoraux français (côtes sableuses, falaises et embouchures) afin :- De mesurer la cinématique de ces environnements et du trait decôte associé ;- De mieux comprendre les interactions entre les processushydrodynamiques-transport sédimentaires-réponse morphologiqueassociés à la dynamique du littoral ;- Utiliser les observations pour améliorer notre connaissance desréponses de la morphologie des littoraux dans différents contextesde forçages météo-marins ;- D’utiliser ces observations pour analyser l’importance relativedes facteurs anthropiques et naturels sur la dynamique littorale ;- De se positionner en interlocuteur pour les responsables de ladéfinition et la mise en oeuvre des politiques de gestion des risqueslittoraux.