WP1 runs over the project duration and until all the work is completed. The work covered in WP1 entails all the subtasks needed to facilitate the efficient development of the project. This ranges from providing the necessary financial and administrative management to ensuring exchange of information among the partners and the correct evolution of the project providing scientific and technical coordination. A project management committee will be composed as follows: A. Beaudoin, G. Rousseaux and L. Furgerot. It will be completed by scientific tasks coordinators: WP2 T. Sauzeau, WP3 L. Furgerot, WP4 G. Rousseaux and WP5 A. Beaudoin. The CURIOSITY team (Pprime Institute) will oversee the management and coordination of BABA. It will inform the ANR of any event which might affect the implementation of the project. It will manage the planning of periodic meetings (one remote meeting per semester), writing and delivery of meetings minutes.  Moreover, this WP will ensure the effective interactions among the teams through the WP 2, 3, 4, 5 and 6. Technical monitoring will be performed by the project coordinator, in collaboration with the work package leaders. The technical management will rely upon the following activities: periodic progress meetings in combination with annual progress reports; monitoring the deliverables and milestones; keeping the project website up to date with relevant information. Progress reports delivered by task leaders will be distributed to all the partners and to the ANR.

 

Leader: A. Beaudoin (assistant professor at the University of Poitiers, scientific coordinator)

Email: anthony.beaudoin@univ-poitiers.fr

 

The question of water depth variations affecting the long-term tidal bore development can be understood thanks to the study of ancient bathymetric charts of estuaries (inner estuaries and tidal rivers would be better since the numerics and experiments won’t look to outer estuaries, see Florent Grasso et al. works). Retrospective work will thus be carried out on the Dordogne and also the Gironde estuary where the increasing ship draft has implied major bathymetric changes. The CRIHAM laboratory is still developing a technic for the optical recognition of nautical charts of hydrographic campaigns (Task 2.1) produced according to the rules of the hydrographic engineer Beautemps-Beaupré from 1820. Those maps will provide the expected data so as to create the data sets. The consequences of the tidal bore about the trade navigation on the estuaries will be studied thanks to the archives of the institutions who ruled the shipwrecks and the river banks management, so as to provide a chronology of the main events and their impact on the society, from a memorial point of view. In order to study the influence of the meteorology and the tide gauge on the tidal bore, the archives of the Shom, the ports of Bordeaux and Rochefort (Marine) will be collected and analysed (Task 2.3). As the estuaries of the MSM bay are not navigable, the data from old maps are scarcer. A study carried out in parallel at the M2C laboratory on the morpho-sedimentary trajectory of Normand estuaries over the past 2 centuries (TRESSE project) will complete the work (Task 2.2) with cores samples and analysis of old maps. The integration of data acquired by the Normandy coastline observation network for the MSM bay will also complete the work. Ancient bathymetry will feed the models developed by the TREFLE department (I2M Institute) and the CURIOSITY team (Pprime Institute).

 

Leader: T. Sauzeau (professor at the University of Poitiers)

Email: thierry.sauzeau@univ-poitiers.fr

WP3 will be dedicated to field measurements. The relationship between the bottom and the tidal bore will be studied in upstream of the Sée estuary (MSM bay) by the M2C laboratory and A. Crave (Research Scientist from Geosciences Rennes Laboratory – unfunded partner) and upstream of the Garonne River by the TREFLE department (I2M Institute) (sites instrumented as part of other projects). Several other members of the consortium will provide support to the WP teams during the various field campaigns, as was done in previous projects. Equipment sharing between sites is also anticipated. The selected sites have different characteristics providing an interesting variety of conditions for physical (WP4) and numerical modeling (WP5). WP3 focus on i) the impact of bathymetry on the generation of TJ&B and on the evolution of their shapes and celerity during propagation (hydrodynamics study), ii) the impact of TJ&B on the sediment transport and on the water/sediment interface (sediment liquefaction process) and iii) the impact of TB on coastal construction in the Garonne River. Studies on the Sée River will provide results on large time scales while studies on the Garonne River will focus on the most intense tidal bores. This study will span a longer period and a wider range of conditions than previous work, with a focus on the water-sediment interface (boundary layer and sediment liquefaction) and high-frequency processes (turbulence in the water column and aeration). WP3 is divided into 3 tasks: task 3.1, campaign preparation and instrument calibration; task 3.2, in situ measurements and task 3.3, data processing.

 

On the Sée River, two main stations will be instrumented: one located on a meandering section with sloped banks, and the other on a straight section with uniform banks, resembling an experimental open channel. These sites will be instrumented for one month in 2026 (covering two spring tide cycles), and bathymetric surveys will be conducted regularly along this river section (task 3.2). Bathymetric survey will provide morphology models for WP4 and WP5. The influence of channel morphology on the evolution of TJ&B shape and bore celerity along and across the channel will be studied with pressure sensors and LIDAR 2D (tasks 3.2 and 3.3). Velocity current and turbulent parameters will be also measured with 1 ADV (Acoustic Doppler Velocimeter) for high frequency punctual measurements and 1 ADCP (Acoustic Doppler Current Profiler) for an average measurement at several heights in water column. The boundary layer will be instrumented with a 1000kHz ADCP to increase the data quality near the bottom. The impacts of TJ&B on channel morphology (bottom and banks) will be quantified by measuring the SSC (Suspended Sediment Concentration) evolution during successive TJ&B and by detecting the water-sediment interface changes (task 3.3). The SSC will be measured using turbidity meters (punctual measurement and on water column) and the water/sediment interface changes (morphology and liquefaction processes) will be tracked using ALTUS sensors, echo sounder and regular bathymetric survey (between two tides). In addition, sedimentation plates will be installed on the banks under construction to perform sediment balances. Most of these instruments will be calibrated with specific sediment of site in the DEXMEX device based in Brest (IEM laboratory) in task 3.1. The impact of TB on coastal construction will not be addressed because the Sée river has very few structures on its riverbanks.

 

The Garonne River will rely on 0,5 to 1/year field campaigns during spring tides (high Froude – breaking bores) for 3 years to separate the year-long effects of the river flow from the instantaneous effect of breaking bore (task 3.2). The influence of channel morphology on the evolution of breaking TB and bore celerity along and across the channel will be studied by drone and fixed camera with Large Scale particle image velocimetry (LSPIV) approaches. The bore shape will be caught by a deep Multi-Camera Tracking system mounted on drone after a software (FUDAA) treatment (task 3.3.1). The same recordings will be also analysed using an optical flow (OF) technique for complementary validation and redundancy. Water column velocities will be also measure in 3 points along the river axis with 3 ADV at high frequency (200Hz) allowing to calculate the turbulent parameters. A bathymetric survey with echosounder will complete the data set at two scales (wide scale of 140ha and near field of 14ha). A specific study will be conducted on interfacial properties in the breaking roll to quantify environmental impacts of breaking front, with a network of high frequency phase detection probes and multiparameter sensors (DO, CO2, Ph, conductivity). This impact will be correlated to tidal bore momentum transport by the turbulent flow thanks to ADV measurements. The impact of breaking TB on the sediment transport will be studied along the main river channel as well as on the banks with turbidity meters, and on the water/sediment interface (liquefaction processes) with echosounder and pore pressure sensors to work on sediment resuspension and upstream advection. The characterization of the sediments in the laboratory will allow to refine the analysis (granulometry, composition, rheology) in task 3.1. Finally, the impact of breaking TB on coastal construction will be assessed for the first time with pressure and deformation sensors. This WP will contribute to better understand the natural TJ&B processes in 2 very different estuaries, which cannot be studied at full scale in laboratory facilities or with numerical simulations.

 

Leaders: L. F FURGEROT  (assistant professor at the University of Caen) and D. REUNGOAT (assistant professor at the University of Bordeaux)

Emails: lucille.furgerot@unicaen.fr and david.reungoat@u-bordeaux.fr

Task 4.1 will consist in open channel experiments in PHE of the Pprime Institute that will be carried out by the CURIOSITY team using our new TB generation method thanks to a volume inversion in time complementary to the usual closing gate method recently explored on a decametric scale with rigid variable bottoms such as sandbanks and obstacles like islands with reflection, interference and diffraction mechanisms. The TB wave will be characterized in Task 4.2 by Particle Image Velocimetry in vertical and horizonal planes, Laser Induced Fluorescence to measure the free surface in 1D h(x,t) with subpixel precision [Euvé et al., 2020] and checkerboard or starry night bottom patterns using refraction at the free surface in 2D h(x, y, t) with respect to a non-deformed interface. Experiments will be performed in Task 4.3 to test the TB classification by changing the bathymetry from a simple rectangular geometry then to a trapezoidal section then to scans of real bathymetry albeit rigid to simplify but scaled and designed with 3D printers/PVC/PMMA/polystirene shapes in the laboratory: the definition of the generalized Froude number due to Kelland (1840) based on the river section and the surface width of the river and not just the water depth as in the rectangular geometry will be used to extend the classification of the types of TB for actual river geometries: Ke = (Ur+Ub)/c where Ur is the current in the river that is a function of the flow rate and the section Ac of the channel of free surface width W, Ub is the speed of the TB and c = (g*Ac/W)½ is the speed of linear long gravity wave in the channel: the effect of amplitude of the bore on its speed will be scrutinized. The role of a bottom obstacle on the acceleration of the river current and the blocking of a TB generated when propagating against the current with or without a slope effect in a possibly tilting metric or decametric channels will be probed as well [Li and Chanson, 2018]. The death of the TB will be characterized experimentally in connection with both the slope and bathymetry (bottom obstacle, island, etc…) of our laboratory rivers. We will impose either constant flow rate or time-dependent flow rate since the pump can be controlled accordingly.

 

Understanding these processes will allow better interpretation of field measurements for different sedimentary configurations (WP2). The resuspension processes will be tackled in an open channel by the HYDEE team (Pprime Institute). Quantitative 2D and 3D velocity and surface measurements in the flow but also for the sediment will also promote comparisons with the various numerical approaches proposed in the WP5. The mechanical forces related to the passage of TJ&B will be studied at first to better understand the flow, the exchanges between the breaking roller and the water column, the interaction between the upper sheared layers and the boundary layers. The associated physical quantities such as turbulence and pressure at the bottom of the channel, and flow shear over the bed and banks will be calculated from PIV measurements. These initial states of tidal bores will then be applied to sedimentary beds on which the type, distribution and shape of the sediments will be varied to understand the remobilization of the sediment, the forces applied to the sedimentary bed and the liquefaction in certain cases. Lagrangian measurements (LPT) and sediment surface topography will be carried out to follow non cohesive particles placed at the bottom of the channel as the erosion effect. The different mechanical solicitations (pressure, shear) will be characterized first in task 4.4 for different positive surges. Then the same conditions will be applied in task 4.5 for the Lagrangian transport and the bed erosion of a non-cohesive doped sediments to be able to follow simultaneously the flow and the sediment. The results will provide a benchmark for modelling validation in WP5 at a local scale. The bed erosion of cohesive sediments coming from the Garonne River (TREFLE) and the Sée channel (M2C) will be evaluated under different flow conditions to compare the mass transfer obtained by simulations in WP5. The rheological characterization of these sediments will focus on the determination of the yield stress which represents the minimal stress to occurs the flow of the material. This methodology has been applied in previous ANR project EMPHASE (Projet-ANR-19-FQSM-0003) on the Garonne sediments and will be performed in collaboration with M2C and TREFLE. Finally, the rheological properties of these cohesive sediments will be linked to the quantified erosion phenomenon.

 

Leaders: G. ROUSSEAUX (research director of CNRS) and L. DAVID (professor at the University of Poitiers)

Emails: germain.rousseaux@univ-poitiers.fr and laurent.david@univ-poitiers.fr

In WP5, we will attempt to address numerically the question of characterizing the hypodynamic processes and regimes having the largest potential impact on morphological modifications. It has highlighted the existence of two modes of propagation of a bore, of which one is essentially hydrostatic, the other fully non-hydrostatic. The second mode involving vertical kinematics of much larger magnitudes is clearly more prone to produce particle suspensions and may be more interesting for morphodynamical chances. Note that these modes have been not only produced in numerical models but observed in measurements in artificial and natural environments. In addition, one needs to account for the dynamics of vorticity and the interaction with the boundary layers, which for sure play a crucial role in the actual morphological modifications due to the bore. To address these issues, WP5 adds more levels of depth to the hierarchy of investigation tools used in BABA. More specifically, to complement laboratory and in situ measurements we will consider three family of models of increasing fidelity. The lowest level of fidelity is represented by depth integrated models for which we will make use of the solver TELEMAC2D. This model has the advantage of having a reduced computational cost which should allow its use for all the cases, including the in situ ones (WPs 2, 3 and 4). To include a richer description of the vertical dynamics, we will consider using the multi layer model implemented in TELEMAC3D (EDF). This model provides an intermediate fidelity prediction at moderate computational costs, which on one hand may allow to also include realistic simulations, but more importantly allows to exploit TELEMAC3D’s functionalities in terms of sediment modelling to go beyond purely hydrodynamic predictions and have some estimates for morphodynamical chances. The three-dimensional Navier-Stokes solver NOTUS allows to perform numerical simulations tackling processes with length scales range from several meters to the submillimetre scale, as well as all physical processes going from the propagation of the waves generated by the tidal bore to the secondary waves propagating upstream the river channel, including vorticity dynamics, and boundary layers development and separation. In order for WP5 to be a success, it is first necessary to define benchmarks based on simple geometries and in situ cases (Task 5.1). The simple geometries will be taken from scientific literature  and the project with the laboratory data obtained in WP4. The in situ cases will be given by WP2 and WP3. These benchmarks, defined in this way, will be used to perform code-to-code benchmarking and a comparison with fields measurements and laboratory experiments. Each model will be applied to all the benchmarks. This will correspond to one task per model, task 5.2 NOTUS, task 5.3 TELEMAC2D and task 5.4 TELEMAC3D.

 

Leaders: A. BEAUDOIN (assistant professor at the University of Poitiers) and P. LUBIN (professor at the University of Bordeaux)

Emails: anthony.beaudoin@univ-poitiers.fr and pierre.lubin@bordeaux-inp.fr

WP6 involves the publication of scientific articles and the participation in international conferences. More than half of the amount allocated to this task will be dedicated to the participation of international congresses. We plan to publish at least one scientific paper per year in international journals and two in congresses and conferences. The other half of resources requested in WP6 will be used for teaching and popularization of project-related research with the general audience. Dissemination of scientific and technical achievements and specific results will be performed by means of Open Access publications in scientific journals and conferences. A website will be created for both internal and external communications, collaborative work and knowledge management. With the support of partners establishments, the consortium members will take part in various communication activities: Nuit de la Recherche, Fête de la Science, Speed searching, The conversation, interventions in schools, Chab’aret des sciences, Osmose, Actu des Labos, video presentation, Pint of sciences, documentaries, etc.