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-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-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-04670939] DEVELOPMENT AND VALIDATION OF A MODELLING CHAIN TO QUANTIFY COASTAL FLOODING EXPOSURE AT AN ENGINEERED BEACH
Aug 13, 2024 4:19 PM - HAL : Dernières publications
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[hal-04576062] Monitoring the morphological evolution of the beach of Zarautz through coastal videometry.
Jun 3, 2024 1:40 PM - HAL : Dernières publications
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[hal-04586661] Development and validation of a process-based coastal flooding Early Warning System -Zarautz beach
Jun 3, 2024 1:38 PM - HAL : Dernières publications
In the recent years, coastal cities exposure to storm impact have led to the development of Early Warning Systems, assisting authorities in the setting of their strategy to protect people and limit damages to buildings and infrastructures caused by coastal flooding. This study focuses on the development and validation of a process-based coastal flooding Early Warning System at the Zarautz beach, a highly urbanized embayed beach. The system estimates the hazard level through a scale that relates mean overtopping discharge values with hazard levels. The mean overtopping discharge is computed through a phase-resolving process-based numerical model that accounts for wave transformation processes in the nearshore zone and hydrodynamics induced by wave interactions with coastal structures. The assessment of the system accuracy is performed by comparing the computed hazard levels with those derived from images captured by a coastal videometry station during a series of potentially hazardous events with different intensities. The use of different hazard level estimation scales shows great variability in the system performance. The best system configuration shows an accuracy of 87% of hit, 4% of miss and 9% of fail. The results closely align with those achieved using the currently operational Early Warning System in Zarautz.
[hal-04583186] Analysis of the coastal flooding exposure of embayed beaches at a regional scale using a video monitoring network: Basque Coast (Spain)
May 22, 2024 2:44 PM - HAL : Dernières publications
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[hal-04576068] Numerical study to quantify the role of morphological parameters in the coastal flooding: Zarautz beach
May 15, 2024 2:54 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-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-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-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-03881962] Field observations and numerical modeling of swash motions at an engineered embayed beach under moderate to energetic conditions
Dec 2, 2022 11:38 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-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-03200067] Tsunami Impact on a Detached Breakwater: Insights from Two Numerical Models
Apr 16, 2021 1:46 PM - HAL : Dernières publications
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[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-02398282] Infragravity period oscillations in a channel harbor near a river mouth
Dec 7, 2019 11:23 AM - HAL : Dernières publications
Port of Bayonne, located in SW France, is a channel harbor situated near the river mouth of the Adour. Long-period oscillations have repeatedly caused snapping of mooring lines of berthed ships and have led to wave resonances in an adjacent marina (seiche). To investigate mechanisms for generation of theses oscillations, a field campaign was carried out during a one-year return-period storm (Hs = 6 m and Tp = 15 s): four pressure sensors were deployed inside the port. To complement the data and to better understand the governing processes that lead to the wave transformations in Port of Bayonne, the storm event was computed with the Boussinesq-type model, BOSZ. The data confirm the model results, which show generation of long infragravity (IG) waves by the incident swell around the harbor entrance and free propagation of these waves without amplification over far distances inside Port of Bayonne. Excited by these long waves, resonance oscillations are only noticeable in a small enclosed marina. Though the IG-waves are not causing substantial changes to the water level along the harbor channel, they are suspected to excite the ships' eigen modes, which consequently results in mooring problems.
[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-02154266] Characterization of Seiches in Small-Harbors
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154273] Numerical Study of the Undular Bore Impact on the Composite Breakwater of Port of Soma during the Tohoku Tsunami
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[hal-02154260] Étude des tempêtes et de leur impact sur les plages 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-02154254] Marine Flooding Processes by Local Runup on Biarritz Beaches
Jun 12, 2019 8:29 PM - HAL : Dernières publications
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[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-02154263] Contribution of IG Waves to Local Runup and Flooding:Beach of Biarritz
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-02154024] Modélisation numérique de l'impact des tempêtes sur une plage de poche partiellement aménagée
Jun 12, 2019 6:14 PM - HAL : Dernières publications
La protection des zones côtières contre les vagues de tempête peut être assurée soit de façon naturelle, dans le cas de la présence d'un cordon dunaire, soit par des ouvrages maritimes sur les sites anthropisés. La plage de Zarautz, située au fond d'une baie, sur la côte basque espagnole, présente les deux types de protection sur un même linéaire. Des études récentes, basées sur l'analyse d'images vidéo et de levés topographiques réalisés avant et après une séquence de tempêtes, ont mis en évidence des variations morphologiques distinctes en fonction du niveau d'anthropisation de la plage. Afin de mieux comprendre la réponse de ce type de plage hybride à des événements fortement énergétiques, un modèle morphodynamique a été mis en place. Cette étude présente dans un premier temps la calibration du modèle en se basant sur un événement particulier ayant eu lieu en février 2012. Les résultats des simulations réalisées avec les paramètres optimaux, sont ensuite analysés en considérant différents secteurs de plage. L'étude présente ensuite les différentes phases d'évolution du profile de plage et du cordon dunaire au cours de la séquence de tempêtes.
[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-02153974] Sliding of Caisson Submitted to Water Wedge Impact: Analytical Calculation and CFD Verifications
Jun 12, 2019 6:12 PM - HAL : Dernières publications
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[hal-02153976] Numerical Simulation of Tsunami Flooding Downstream a Quay Wall
Jun 12, 2019 6:12 PM - HAL : Dernières publications
In this paper, the interaction of a tsunami and a quay wall is studied numerically with focus on the water volume flooding the downstream part of the quay. The model solves the Navier-Stokes equations using the VOF method. It is first validated on two cases close to the study configuration. Then flooding discharge are calculated considering two wave inputs (solitary wave, break flow over wet bottom) and increasing amplitudes. The differences are significant. The solitary wave give a short duration flooding due to its dependency between amplitude and frequency. The dam break flow produces flooding bursts followed by a steady residual flooding which may be the parameter of importance in this problem.INTRODUCTIONTsunamis are long waves whose destructive power has been illustrated in several dramatic recent events (e.g., the Tohoku tsunami in 2011). Vertical walls, designed for tsunami protection (i.e., tsunami seawall) or for other purpose (e.g., harbor quay wall) are known to be e\ₓient structures able to reduce tsunami impact inland by reflecting wave energy o\₋shore instead of allowing the whole wave energy transfer by run-up like beaches. However, depending on tsunami features, part of the wave may spill over the wall.The problem has already been studied in several papers. Fukui et al. (1963) and Shi-igai and Kono (1970) used quasi steady formulation of the flow over a weir to approach the overtopping volume. Iwasaki and Togashi (1968) studied the transformation of tsunami waves at a vertical quay wall using U-C characteristics in shallow water theory. Applications were made using solitary wave input signal. Ozhan and Yalciner (2011) applied the weir analogy to study the overtopping of solitary wave above vertical wall.More recently, Hsiao and Lin (2010) studied the overtopping of a solitary wave over a sloping seawall experimentally and by RANS modeling. Mizutani and Nakamura (2011) carried out an equivalent study but based on a half sinusoidal long wave and with a vertical quay wall. Baldock et al. (2012) studied the overtopping of solitary tsunami bore on sloped structure. Interaction between bores and vertical walls was more specifically studied in the context of loading determination (e.g., Togashi (1986)).
[hal-02153691] Risk Mapping Assessment by Means of Probabilistic Storm Scenarios in a Partially Engineered Beach: Anglet, France
Jun 12, 2019 4:00 PM - HAL : Dernières publications
The characterisation of storms and the associated damage level is essential to design correct risk mitigation strategies. The study site, an engineered beach located in the South West of France, is exposed to frequent storm events. The objective of the present work is twofold: (1) to obtain a risk map along the different sectors of the beach and (2) to find risk indicators suitable for the present study site. The storm scenarios are obtained from a hindcast database that includes 66 years of wave parameters. Six storm types have been chosen to be representative of the extreme wave climate of the study site based on the energy flux (EF) threshold. The beach response to storm events is alongshore non-uniform and closely linked to the cross-shore position of the seawall. Total storm power combined with water level and beach volume/width seems to be the best set of risk indicators for the present study site.
[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-02153680] Validation of a Navier-Stokes Model to Study Flip-through Impacts on a Composite Breakwater
Jun 12, 2019 3:59 PM - HAL : Dernières publications
Two validation cases of the Navier-Stokes VOF (Volume-Of-Fluid) model THETIS are presented in this study: uplift pressures on a rubble mound due to wave impacts and flip-through impacts on a vertical wall. The first validation case demonstrates the ability of the model to reproduce uplift pressure overall variations due to wave impacts inside a porous rubble mound. The presence of a marked pressure peak in the porous medium is also stressed. Then, the flip-through phenomenon is modeled using the THETIS model. These results are compared with other numerical data computed with a potential model. The Navier-Stokes simulations which take into account water and air, underestimate pressures along the wall. The wave interface is modified by the presence of air, which is not considered in the potential model, and this seems to be enough to generate such pressure differences. A better agreement between the two models is obtained while lowering the surrounding gas density to almost zero. \textcopyright Société Hydrotechnique de France, 2017.
[hal-02146089] Numerical Simulation of Flip-through Impacts of Variable Steepness on a Vertical Breakwater
Jun 3, 2019 5:47 PM - HAL : Dernières publications
This paper focuses on the analysis of the flow field and pressures generated by flip-through impacts on a vertical breakwater. A multiphase Navier\textendashStokes model is used as a numerical wave tank to analyse the influence of interface steepness on pressures and forces generated in the real configuration of a breakwater caisson. The numerical simulations consist in a solitary wave propagating over a reef and impacting a caisson breakwater placed over a porous rubble mound. After careful validation, the model allows us to make an in-depth investigation of three flip-through impacts with different incidence angles at impact (least steep, medium steep and steepest flip-through impact). The main characteristics of flip-through impacts are identified for the three cases: no air entrapped, presence of an ascending jet with large accelerations and large pressures. The focusing phase before impact introduced by Lugni et al. [30] is only observed for the steepest case. The understanding of the process of this extreme impact is improved by analysing velocities and accelerations for the three cases. Pressures and forces are shown to be directly linked to the flip-through impact inclination at impact. The flow field and pressure variations inside the porous rubble mound are also analysed in this study.
[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-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.
[hal-01167585] Déplacement d'une structure soumise à l'impact d'un front d'onde
Jun 24, 2015 6:37 PM - HAL : Dernières publications
<p>Ce travail porte sur l'étude théorique du déplacement d'une structure soumise à des impacts caractérisés par des signaux variables de pression instantanée et une même valeur d'impulsion de pression. L'impact étudié est celui d'un front d'onde (e.g. front de tsunami, rupture de barrage, etc.). Dans cet article, on étudie le cas idéal de l'impact d'une masse d'eau dont la surface libre rectiligne présente un angle donné avec l'horizontale (i.e., cas du jet triangulaire). L'impulsion de pression est calculée à partir des lois semi-empiriques qui permettent de définir le champ de pression généré par l'impact d'un jet triangulaire. Ces lois semi-empiriques ont elle même été obtenues à partir des simulations numériques avec le code Thetis. Finalement, la force exercée par l'impact et le déplacement final du caisson sont calculés en fonction de l'angle d'inclinaison de l'interface. </p>