SOMMAIRE - u-bordeaux.fr€¦ · à barre(s) dominées par l’action de la houle Titre du projet...

PROGRAMME JEUNES CHERCHEUSES ET JEUNES

CHERCHEURS

EDITION 2010

Projet BARBEC

DOCUMENT SCIENTIFIQUE

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Acronyme BARBEC

Titre du projet en français

Rôle des interactions morphologiques dans la dynamique globale des systèmes de plages sableuses à barre(s) dominées par l’action de la houle

Titre du projet en anglais

Role of morphological interactions in governing the whole wave-dominated sandy BARred-BEaCh system

Comité d’Evaluation référence (CE)1

SIMI 6 – Système Terre, environnement, risques

Aide totale demandée

158 760 € Durée du projet 36 mois

SOMMAIRE

1. CONTEXTE ET POSITIONNEMENT DU PROJET / CONTEXT AND POSITIONNING OF

THE PROPOSAL ............................................................................... 3

2. DESCRIPTION SCIENTIFIQUE ET TECHNIQUE / SCIENTIFIC AND TECHNICAL

DESCRIPTION ................................................................................. 4

2.1. État de l'art / Background, state of art ........................................................ 4

2.2. Objectifs et caractère ambitieux/novateur du projet / Rationale highlighting the originality and novelty of the proposal .................................. 6

3. PROGRAMME SCIENTIFIQUE ET TECHNIQUE, ORGANISATION DU PROJET / SCIENTIFIC AND TECHNICAL PROGRAMME, PROJECT MANAGEMENT..................... 8

3.1. Programme scientifique et structuration du projet / Scientific programme, specific aims of the proposal ...................................................................... 8

3.2. Coordination du projet (Tâche 1) / Project management (Task 1) ................... 9

3.3. Description des travaux par tâche / Detailed description of the work organised by tasks ..................................................................................10

3.3.1 Tâche 2 / Task 2: Physical modelling of cross-shore hydrodynamics and morphodynamics 10

3.3.2 Tâche 3 / Task 3: Numerical modelling of cross-shore sandbar behaviour 11

3.3.3 Tâche 4 / Task 4: Numerical modelling of 3D surfzone sandbar behaviour 13

3.3.4 Tâche 5 / Task 5: Swash motions and beach face behaviour 15

3.4. Calendrier des tâches, livrables et jalons / Planning of tasks, deliverables and milestones .......................................................................................18

1 Indiquer la référence du CE choisi pour l’évaluation du projet (cf. tableaux page 3 et 4 du texte de

l’appel à projets)


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4. STRATEGIE DE VALORISATION DES RESULTATS ET MODE DE PROTECTION ET

D’EXPLOITATION DES RESULTATS / DATA MANAGEMENT, DATA SHARING, INTELLECTUAL PROPERTY AND RESULTS EXPLOITATION ................................ 19

5. ORGANISATION DU PROJET / PROPOSAL ORGANISATION .............................. 20

5.1. Description, adéquation et complémentarité des participants / Relevance and complementarity of the partners within the consortium ..........................20

5.2. Qualification du porteur du projet / Qualification of the principal investigator ............................................................................................24

5.3. Qualification, rôle et implication des participants / Contribution and qualification of each project participant ......................................................25

6. JUSTIFICATION SCIENTIFIQUE DES MOYENS DEMANDES / SCIENTIFIC

JUSTIFICATION OF REQUESTED BUDGET ................................................. 25

7. ANNEXES .................................................................................... 28

7.1. Références bibliographiques / References ...................................................28

7.2. Biographies / CV, Resume ........................................................................31

7.3. Implication des personnes dans d’autres contrats / Involvement of project particpants to other grants, contracts, etc… ................................................37


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1. CONTEXTE ET POSITIONNEMENT DU PROJET / CONTEXT AND POSITIONNING OF THE PROPOSAL

Over the last decades, population density along the coast has increased to the point that nowadays nearly half of the world population lives in coastal areas. This trend, which has been forecast to further increase, has occurred for a variety of reasons, including access to food, transport, generally milder climates and in more recent years for lifestyle reasons. Among all the coastal environments sandy coasts are nowadays one of the most attractive areas generating significant amounts of tourist revenue and creating thousands of businesses and employment opportunities. Wide and healthy sandy beaches are therefore of major interest from the perspective of recreational and economic activity. In contrast to these positive economic and lifestyle assets, wave-dominated sandy beaches are the most unpredictable, dynamic and vulnerable coastal systems, especially in the context of global warming and sea level rise.

Nearshore sandy patterns along wave-dominated beaches cover a wide and striking variety of temporal and spatial scales of variability. Of these morphological features, surfzone sandbars are one of the most intriguing, dynamical and complex patterns (Stive & Reniers, 2003). They are alongshore ridges of sand that are typically observed in the 0- to 10-m depth nearshore region. Nearshore sandbars provide natural protection for beaches by causing waves to dissipate away from the shoreline through depth-induced breaking resulting in lower inshore wave energy. During major storms nearshore sandbars substantially reduce the intensity of swash zone processes and potential extreme wave run-up which is the critical component to inundation as well as dune and cliff erosion.

Surfzone sandbars display highly-complex behaviour which is seemingly at odds with their simple rhythmicity. Most of the time, 3D morphological rhythmic or quasi-rhythmic features are observed, which can be viewed as an alongshore sequence of horns (shoal) and bays (cross-shore troughs) alternating shoreward and seaward of a line parallel to the beach with a wavelength on the order of several times the surf zone width. These 3D patterns are often part of an accretionary, down-state sequence developing from an alongshore-uniform beach state (Wright and Short, 1984) following a storm event (Figure 1). The resulting nearshore patterns are the so-called crescentic sandbars and rip channels (Van Enckevort et al., 2004; Castelle et al., 2007a). During severe storms, 3D sandbars are rapidly reshaped into a shore-parallel linear bar with concurrent erosion of the the beach face.

Figure 1. Beach morphologies surveyed with millimeter accuracy during the MODLIT 2D experiment at the “Laboratoire d'Hydraulique de France” (LHF) facility (Castelle et al., 2009) which shows a down-state sequence (Wright & Short, 1984) typically observed in the field. The beach evolves from a typical rhythmic bar and beach morphology (a,b,c) to a transverse bar and rip morphology (d,e,f) which progressively tends toward an almost featureless terrace-like morphology (g,h).These 3D morphologies were not shaped by the investigators but formed through the positive feedback between flow (waves and currents), sediment transport and the evolving morphology (that is, self-organization). Colorbar and solid black line indicate the seabed elevation in meter and the shoreline position, respectively.


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Crescentic sandbar and rip channels guide and constrain intense wave-driven circulations into strong offshore currents through the bays which endanger the safety of recreational beach users as they are the cause of the majority of rescues (90% in Australia) and fatalities (in Australia, on average, someone drowns in a rip every 2-3 days). Mega-cusps and dune erosion are also associated with rip current circulations (Thornton et al., 2007). Dune erosion occurs at the embayment of mega-cusps (Short and Hesp, 1982) which are a shoreline signature (also known as “hot-spots”) of rip current presence. Accordingly, shoreline evolution and hot spots are strongly related to surfzone sandbar dynamics and swash zone processes. However, how nearshore sandbar geometry impacts the spatial variability in intensity of inshore circulations and swash zone processes and resulting mirrored shoreline patterns (Figure 2) remain poorly understood.

Figure 2. Aerial photographs of a single-barred beach of the New South Wales Coast (Australia) displaying (a) a 180◦out-of-phase relationship of inner-bar patterns and shoreline rhythms with inner-bar bays systematically facing a seaward bulge in the shoreline and (b) an in-phase relationship between inner-bar patterns and shoreline rhythms (photographs are courtesy of Prof. A.D. Short in Castelle et al., in press-a)

So far, except in scarce papers, international coastal community systematically studies in isolation each of the elements in these wave-dominated nearshore systems, that is, offshore geological templates, surfzone sandbar(s) and the beach face and studies encompassing all these elements are non-existent. However there has been recently evidence that the behaviour of the individual elements of the surfzone system contrasts with the behaviour of the whole interconnected system, suggesting that the approach of studying each element in isolation can result in dangerously contradictory results. The work we propose in ANR BARBEC is to target the beach system as a whole to investigate how each element behaves in relation to the others, ultimately to understand the beach system as a whole. Our proposed work is thus to combine non-linear morphodynamic modelling, both existing and novel high-quality in-situ dataset and innovative physical modelling to explore high-energy sandy barred-beach dynamics.

2. DESCRIPTION SCIENTIFIQUE ET TECHNIQUE / SCIENTIFIC AND TECHNICAL DESCRIPTION

2.1. ÉTAT DE L'ART / BACKGROUND, STATE OF ART

Over the last decade considerable progress has been made in both the observation of cross-shore sandbar behaviour (Thornton et al., 1996; Gallagher et al., 1998, Hoefel & Elgar, 2003; Ruessink et al., 2009; Grasso et al., 2009b) and the identification of hydrodynamic processes relevant to on/offshore sandbar migration (Drake & Calantoni, 2001; Hoefel & Elgar, 2003; Ruessink et al., 2007b). During storms, intense wave breaking on the bar crest drives strong offshore-directed currents ("undertow") that transport sediment seaward, resulting in rapid (O(10m/day)) offshore sandbar migration concurrent to erosion of the beach. During weakly to nonbreaking, yet sufficiently energetic, wave conditions the near-bed wave-skewness driven bedload transport results in slow (0(1m/day)) onshore sandbar migration concurrent with accretion of the beach. Although this hypothesis is widely accepted by the coastal community, extensive measurements of velocity/acceleration skewness along beaches with a variety of profiles is strongly lacking.

In the cross-shore direction, the interactions between bars in multiple-barred settings have been recently touched upon. The observations of Ruessink & Terwindt (2000) and numerical modelling of


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Aarninkhof et al. (1998) and Masselink (2004) indicated that the morphodynamic feedback, driven for example by the position and geometry of adjacent sandbars, might be a critical parameter governing the behaviour of the whole system. This morphological feedback is, however, still very poorly understood, particularly for the morphological feedback between the sandbar(s) and the beach face. Following a decadal storm Castelle et al. (2007b) measured abnormally high erosion rates during both a second and a third, yet much less energetic, successive storm wave events. The authors established this behaviour could be explained by the outer-bar decay (Ruessink et al., 2009) following the decadal storm, which as a result did not provide any significant natural protection during the subsequent two storm events. There was however no definitive evidence for this hypothesis as no detailed hydrodynamic measurements were collected. Recently during the ECORS-Truc Vert’08 international field measurements (Sénéchal & Ardhuin, 2008), Almar et al. (in press) highlighted the potential key role of morphological settings (i.e. the presence of a subtidal outer bar and its shape) in governing inner-bar behaviour and the beach evolution during storms and the double sandbar system as a whole. The nature of these complex feedbacks have not yet been adequately identified. While recent numerical modelling studies started to accurately explore cross-shore sandbar behaviour on the time scale of weeks to months (Ruessink et al., 2007b; Kuriyama, 2009; Castelle et al., in press-c) they still strive to simulate the sandy bed evolution in water depths typically smaller than 0.5 m because of major issues when incorporating swash zone processes in their model. A typical solution is to ignore sediment transport in small water depths (Ruessink et al., 2007b) despite its known significance (Masselink et al., 2009). Because of this limitation, at this stage, cross-shore morphodynamic feedbacks between sandbar(s) and the beach face cannot be explored through numerical models. Despite the importance of swash hydrodynamics in determining wave-induced erosion (Ruggiero et al., 1996; Sallenger, 2000; Ruggiero et al., 2001), recent reviewers (Butt and Russell, 2000; Elfrink & Baldock, 2002) highlighted the lack of sufficient knowledge within this region. During storms, it is now widely acknowledged that the swash spectra are dominated by infragravity motions (typically less than 0.05Hz). At this stage there are no extensive quantitative measurements of swash under highly dissipative energy conditions with the notable exception of the work of Ruessink et al. (1998). However this last study was restricted to the investigation of the dependence of swash parameters on environmental conditions such as short-wave height, period, and local beach slope. The authors did not allow the assumptions raised by Holland & Holman (1999) under intermediate to reflective conditions to be investigated, about a possible decoupling between surf and swash motions. This link is critical to the success of the numerical modelling approach.

The emergence and dynamics of 3D surfzone sandbars and shoreline geometry has puzzled scientists for decades (Stive & Reniers, 2003). Coco & Murray (2007) reviewed the international coastal community’s sweeping shift from forcing template to self-organization theories for explaining the formation and subsequent evolution of rhythmic surfzone sandbars (among other nearshore patterns). The cross-shore and alongshore edge-wave patterns (i.e. longshore periodic gravity long waves trapped to the shoreline by refraction and reflection), that are spatially-organized structures in the hydrodynamics, were hypothesized to become imprinted on the seabed (Bowen & Inman, 1971; Carter et al., 1973; Holman & Bowen, 1982). This hydrodynamic template forcing became widely accepted (Komar, 1998; Short, 1999), despite a number of possible objections progressively raised by several authors (Sonu, 1972; Bryan & Bowen, 1997; Bowen, 1997; Holman, 2000; Van Enckevort et al., 2004). Most importantly, the edge-wave (template) theory, which only assumes a passive response of the incipient sediment patterns to the template in the hydrodynamics (Carter et al., 1973), was incompatible with the nonlinear and open nature of natural nearshore systems. In other words, the template theory does not account for the feedback between hydrodynamics (waves and currents), sediment processes and the evolving morphology which may play a key role in spontaneous formation of nearshore patterns. Only recently the template forcing theory has been challenged by the development of self-organization models based on this feedback. Linear stability models (Deigaard et al., 1999; Falqués et al., 2000; Calvete et al., 2005), restricted to the initial development (linear regime) of the 3D patterns, and later nonlinear morphodynamic models (Damgaard et al., 2002; Reniers et al., 2004; Castelle et al., 2006; Klein & Schuttelaars, 2006; Drønen & Deigaard, 2007; Smit et al., 2008; Garnier et al., 2008), allowing the simulation of the formation and subsequent nonlinear evolution of 3D features, have established that 3D surfzone sandbars can be formed through self-organization mechanisms alone and do not require template in the hydrodynamics.


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Noteworthy, nonlinear morphodynamic models are based on the depth-averaged approach as, at this stage, debates remain within the scientific community on how to implement wave-driven 3D circulations (see for instance Mellor, 2003,2008; Ardhuin et al., 2008a, 2008b). Despite these recent major scientific advances turbulence-closure remains a major issue in surf zone and ongoing work is in progress to implement a suitable 3D wave-current modelling strategy in the nearshore (for instance Post-doctorate A.-C. Benis (SHOM/EPOC) and PhD student C. Gandon (SHOM/EPOC) supervised by F. Ardhuin, ANR EPIGRAM). As a result of the uncertainty in the hydrodynamics, coastal scientists remain far from being able to accurately implement sediment transport in such 3D models and to undertake nonlinear morphodynamic modelling of wave-dominated beaches. Accordingly, for mathematical, numerical and computation time issues, nonlinear morphodynamic modelling based on a hydrodynamic depth-averaged approach have been used over the last few years and are expected to remain to be used for a significant number of years from now.

Most of the previous studies suggested the absence of interaction, thus precluding the possibility of self-organization at the scale of individual bars (Houser & Greenwood, 2005). Instead, Castelle et al. (in press-a) demonstrated that the morphodynamic feedback driven by the depth variability along one sandbar with respect to a second is critical to the understanding and prediction of the whole system, corroborating earlier observations in Ruessink et al. (2007a). This can be considered as a novel mechanism that blurs the distinction between self-organization and template theories. Indeed on the one hand, the inshore horizontal circulation patterns and resulting inner-bar rip channel development are forced by the more seaward outer-bar geometry through wave refraction and wave-breaking across the outer bar, which implies the presence of a template in the morphology (outer-bar geometry), i.e., a forcing template. On the other hand, the simulated inner-bar rip channels also formed through the positive feedback between hydrodynamics (waves and currents), sediment processes and the evolving bathymetry, that is, self-organization. Castelle et al. (in press-b) additionally found that the typical alongshore variability in inner-bar rip-channel scale is indicative of a mixture of self-organization and morphological coupling rather than self-organization alone, suggesting that morphological coupling may thus be more important to understanding and predicting the evolution of inner-bar rip channels than previously envisaged, and potentially extendable to other nearshore patterns. Overall we recently demonstrated that, in contrast to the earlier nearshore literature, elements in wave-dominated nearshore systems, such as sandbars, rip channels and the beach itself, must not be studied in isolation.

Another major issue in understanding and modelling the evolution of 3D surfzone sandbar is the reshaping of crescentic planshape and bar/rip morphology into shore-parallel linear bar during storms (up-state sequence following the classification of Wright & Short, 1984). For storm wave conditions, at this stage, all the existing nonlinear morphodynamic models still develop crescentic patterns and bar/rip morphologies while in nature these conditions would result in bar straightening. This constitutes a major limitation of nonlinear morphodynamic models.

The importance of morphological feedbacks for understanding and predicting the beach system as a whole has been very recently discussed in the nearshore literature. Our research group pioneered in this field (Ruessink et al., 2007a, Castelle et al., 2007b, in press-a, in press-b; Almar et al., in press) and the present proposal aims at further exploring the complex feedbacks that drive wave-dominated sandy beach dynamics.

2.2. OBJECTIFS ET CARACTÈRE AMBITIEUX/NOVATEUR DU PROJET / RATIONALE HIGHLIGHTING THE ORIGINALITY AND NOVELTY OF THE PROPOSAL

Scientific objectives and novelty of the proposal:

International coastal community systematically has studied each element of wave-dominated nearshore systems in isolation, that is, offshore geological templates, surfzone sandbar(s) and the beach face. Except in very scarce field observation studies, investigations encompassing all these elements are non-existent. With the present ANR BARBEC, we propose to target the beach system as a whole to investigate in detail how each element behaves with respect to the others to understand the beach system as a whole. To fill the gap in our understanding of the behaviour of wave-dominated sandy beaches there is a need of both combining different innovative approaches (i.e. numerical modelling, physical modelling and remote sensing of the nearshore region) as well as acquiring and analysing high-quality dataset. This will be achieved through an in-depth


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collaboration between EPOC and LEGI as well as with international institutions (Utrecht University, NIWA, University of Waikato and Naval Postgraduate School), the development of new experiments (Task 2) as well as the analysis of unique dataset recently gathered through MODLIT (Tasks 3 and 4) and ECORS-Truc Vert’08 (Task 5) experiments.

While only recently beach profile models identified hydrodynamic processes relevant to on/offshore sandbar migration (Drake & Calantoni, 2001; Hoefel & Elgar, 2003; Ruessink et al., 2007b), at this stage there are no extensive quantitative measurements of undertow / near-bed velocity skewness / near-bed acceleration skewness. These data are crucial for understanding how and why these hydrodynamic characteristics evolve with respect to wave conditions and beach morphology. New and innovative cross-shore experiments will be undertaken at LEGI to acquire for the first time such data (Task 2). Additional vertical flow profile measurements will be acquired along the beach profile to assess the vertical flow shear and its potential role in cross-shore sediment transport. These data will be crucial to the development and validation of our beach profile evolution model (Castelle et al., in press-c) in Task 3. Up to now, cross-shore models ignore morphological evolution driven by swash zone processes. Swash zone processes will be implemented in the beach profile model in a parametric way as recent studies (Tinker et al., 2009) proposed some cross-shore sediment transport formulas compatible with the energetic-type approach used in our numerical models. This will allow investigation of how surfzone sandbar behaviour impacts the upper part of the beach together with observations in Task 5.

Coupling of shoreline rhythms with surfzone sandbars have been widely observed in the field. At this stage no numerical model investigated how and why sandbars are mirrored at the shoreline. We recently developed a nonlinear morphodynamic model able to simulate shoreline undulations coupled to the sandbar geometry (Figure 3). According to our recent investigations on coupling mechanisms in double sandbar systems (Castelle et al., in press-a, in press-b) we plan for the first time to investigate the mechanisms driving sandbar/shoreline coupling (Task 4). This will be undertaken in concert with Task 5 when investigating the impact of sandbars on the inshore swash zone processes and resulting accretion/erosion patterns. Our research group additionally speculates that morphological feedback may be the key parameter for understanding and predicting intriguing links between offshore sorted bedforms (when present), surfzone sandbar(s) and shoreline hotspots (Schupp et al., 2006), as well as the dynamics of the beach system as a whole.

Figure 3. Simulated beach morphology with superimposed wave-induced current field at t = 40 days starting from an alongshore-uniform single-barred beach (time-invariant wave forcing with shore-normal waves, Hs = 1 m, Tp = 10 s) with colorbar indicating water depth in meters. Our nonlinear morphodynamic model (improved since the version presented in Castelle et al., in press-a, in press-b) reproduces bar/rip morphology with mega-cusps as erosive features of rip current systems. Reproducing the up-state sequences observed in the field is a major limitation of nonlinear morphodynamic models. We hypothesize that a change of dominance from horizontal circulation patterns to vertical mass flux compensation (i.e. undertow) during intense breaking waves drives the straightening of surfzone sandbars. The recent advances in cross-shore sediment transport modelling (Ruessink et al., 2007b; Kuriyama, 2009; Castelle et al., in press-c) together with findings in Tasks 2 and 3 for the first time render possible to test this hypothesis through the implementation of new cross-shore sediment transport formulations into the nonlinear morphodynamic model of 3D beach evolution (Task 4).

In the context of EPOC and LEGI:

It is noteworthy that the topic of wave-dominated sandy beach morphodynamics is a rather new field of research in both teams. In EPOC, quantitative field measurements of wave-driven circulations and beach morphological evolution, as well as the development of hydrodynamic and morphodynamic models started in the early 00’s. Within only a few years EPOC acquired


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internationally-acknowledged expertise in both field and numerical approaches of sandy beach dynamics. International recognition has been recently increased thanks to the development of cutting-edge nonlinear morphodynamic model which has produced results that are novel and relevant to the nearshore community (Castelle et al., in press-a, in press-b). Also, the success of the ECORS-Truc Vert’08 international field experiment (Sénéchal & Ardhuin, 2008) has further promoted the activities of EPOC and linkages with international scientists. The same applies for LEGI in the field of physical modelling of wave-dominated beaches, and more particularly in recent years the morphodynamics, as they developed innovative experimental strategy (Grasso et al., 2009a, 2009b; Grasso, 2009) that can reproduce nearshore bar behaviour observed in the field.

Therefore, this research project leans on a current internationally-acknowledged expertise of EPOC (Team METHYS) and LEGI (Team HOULE) in the field of wave-dominated sandy beach morphodynamics. This project is a unique opportunity to unite and combine complementary approaches and stimulate fruitful collaboration between young researchers. Joint research has already been undertaken by all the researchers involved in this proposal. Within EPOC numerous journal papers have been jointly published by the participants. More recently, within the framework of the MODLIT Project (2007-2010), EPOC and LEGI initiated fruitful collaboration based on the combination of physical and numerical modelling. BARBEC project will strengthen these collaborations between the young researchers, working on complementary topics and benefiting from the experience of senior researchers. Noteworthy BARBEC will also lean on the continuous collaboration with various internationally-acknowledged senior and young researchers from The Netherlands, New Zealand and the USA. BARBEC will therefore enforce collaborations of EPOC and LEGI with international institutions.

Awaited scientific outputs:

Overall, we plan that BARBEC will increase our understanding of wave-dominated beach systems. This knowledge will directly emerge from the analysis of the innovative physical and numerical modelling experiments as well as the video analysis of both the beach face evolution and swash processes during severe storms.

Another important outcome of BARBEC will be the development of two nonlinear morphodynamic models able to simulate the evolution of the sandy beach system during both up-state and down-state sequences from the nearshore to the beach face. The cross-shore and 3D numerical model will be mostly devoted to medium-term simulations (from weeks to years) and short-term simulations (from days to months), respectively.

3. PROGRAMME SCIENTIFIQUE ET TECHNIQUE, ORGANISATION DU PROJET / SCIENTIFIC AND TECHNICAL PROGRAMME, PROJECT MANAGEMENT

3.1. PROGRAMME SCIENTIFIQUE ET STRUCTURATION DU PROJET / SCIENTIFIC PROGRAMME, SPECIFIC AIMS OF THE PROPOSAL

To answer our questions and manage the project we will develop 5 tasks:

- Task 1 - Project management: The objective of this task will be to organize meetings, to collect and synthesize the 6-month reports of the different tasks, to ensure that the tasks are working in synergy and to balance the budget. In addition, a website devoted to BARBEC will be developed and updated at regular intervals

- Task 2 - Physical modelling of cross-shore sandbar behaviour: The general objective of this task will be to grasp extensive quantitative measurements of undertow / near-bed velocity skewness / near-bed acceleration skewness along a variety of equilibrium beach profiles. Additional experiments will be undertaken to both identify and quantify the respective contribution of these parameters on the net cross-shore sediment transport and offshore/onshore sandbar migration.


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- Task 3 - Numerical modelling of cross-shore sandbar behaviour:

The general objective of this task will be to develop a beach profile evolution model able to simulate both cross-shore sandbar and beach face behaviours on time scales from weeks to years with reasonably low computational costs. The model developed during BARBEC will be validated and further used to investigate of the morphological feedbacks between surfzone sandbar(s) and the beach face.

- Task 4 - Numerical modelling of 3D sandbar behaviour: The general objective of this task will be to develop a nonlinear morphodynmic model able to simulate both down-state an up-state sequences of intermediate wave-dominated beaches. It will be used to investigate how each element of the nearshore system (offshore geological patterns / sandbar(s) / shoreline rhythms) behave with respect to the others as well as to address the potential mechanisms responsible for up-state sequences.

- Task 5 - Swash motions and beach face behaviour: The general objective of this task will be to fill the gap in previous swash studies by analysing new video data acquired during highly dissipative conditions and by exploring possible interactions with the bar systems and beach face evolution. ECORS-Truc Vert’08 field experiment video data constitutes a unique data set of 6-weeks 2-Hz continuous video survey in presence of four large storms with offshore significant wave heights exceeding 5 m comprising a 10-year return period storm which caused historical damage on the SW coast of France. There will be strong interactions between the tasks throughout the duration of the project: • Task 1 will ensure that the other tasks are working in synergy • Task 2 will provide quantitative information on wave-nonlinearities to drive sediment transport

and simulate beach profile evolutions in Task 3, as well as data for model validation. • Task 3 will provide improved cross-shore sediment transport formula to be implemented in

nonlinear morphodynamic model of 3D surfzone sandbars in Task 4 • Task 5 (and 2) will provide key information of swash motions and beach face behaviour to be

taken into account in the numerical models (Tasks 3 and 4) • Tasks 4 and 5 will in concert explore possible explanation for sandbar/shoreline couplings

during both storm and post-storm conditions

3.2. COORDINATION DU PROJET (TACHE 1) / PROJECT MANAGEMENT (TASK 1)

Tâche 1 / Task 1 : Project Management – Person in charge : B. Castelle, participants: Task leaders (H. Michallet, N. Sénéchal, V. Marieu)

The project management will be considered as a task in itself. The objective of this task will be to organize meetings, to collect and synthesize the 6-month reports of the different tasks, to ensure that the tasks are working in synergy and to balance the budget. This Task will also ensure that the deadlines in the planning of tasks, deliverables and milestones (cf. Section 3.4) are met.

Meetings will be organized every 4 months by videoconference between the task leaders to discuss the possible problems to overcome, to discuss the recent progress of the project and to ensure a good and constant synergy between the tasks. General meetings will be organized every 12 months in Bordeaux to present the results by task. Another meeting will be organized in Grenoble during year 2 of BARBEC.

A website devoted to BARBEC will be developed and updated at regular intervals. A secured part will be used for data sharing between the BARBEC participants, and an open access will be designed for general public outreach, with a general description of the general interests of BARBEC and the synoptic results of the different tasks.


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3.3. DESCRIPTION DES TRAVAUX PAR TÂCHE / DETAILED DESCRIPTION OF THE WORK ORGANISED BY TASKS

3.3.1 TÂCHE 2 / TASK 2: PHYSICAL MODELLING OF CROSS-SHORE HYDRODYNAMICS AND MORPHODYNAMICS – Person in charge H. Michallet / Participants: J. Chauchat, PhD student, F. Grasso, B. Castelle The general objective of this task will be to grasp extensive quantitative measurements of undertow / near-bed velocity skewness / near-bed acceleration skewness to provide unique quantitative information on how these key hydrodynamic parameters evolve with respect to wave conditions and beach morphologies as well as their respective contribution of these on the net cross-shore sediment transport and offshore/onshore sandbar migration. Noteworthy this dataset will be crucial to accurately develop and validate the numerical beach profile model in Task 3.

To achieve this objective we will (a) undertake a number of extensive hydrodynamic measurements on a variety of equilibrium profiles and (b) subsequently offshore/onshore sandbar migration events. Concurrently (c) we will explore if there are potential missing key processes in bed response that are not yet included in numerical models.

For a few years, laboratory experiments on cross-shore beach morphodynamics are performed at LEGI (Michallet et al., 2007, Grasso et al. 2009a, 2009b). A lightweight sediment (density 1.19) model is used in order to fulfil a Shields number and Rouse number scaling to reproduce natural sediment transport processes (bedload, suspended load and sheet flow, Grasso et al., 2009b). Wave forcings conforming to a JONSWAP spectrum are imposed over long periods (up to more than a hundred hours) so to reach equilibrium beach profiles. Onshore/offshore bar migrations have been observed as transients states (Grasso et al. 2009a). Very recently, a set of experiments indicated that a equilibrium barred profiles may be also be reached which motivates further physical experiemnts.

Task 2a: Velocity measurements over equilibrium beach profiles (H. Michallet, J. Chauchat, PhD student, F. Grasso)

Until now, wave dissipation, velocity skewness, and acceleration skewness were not measured directly but computed from the free surface elevation time series. Dissipation peaks coincide with bottom slope transitions as higher energy dissipation occurs with milder bottom slope sections. While acceleration skewness promotes onshore sediment transport, the estimated velocity skewness may promote offshore sediment transport through phase lag effects in the sheet flow layer or over rippled beds. These preliminary conclusions are deduced from measurements of the net sediment transport at sections where the undertow was relatively weak. The undertow was previously estimated from the time-averaged continuity equation (Dally & Brown, 1995; Cienfuegos et al., 2010). No direct measurements of the velocities have been performed yet. Our proposed new experiments will pave this gap.

Velocity measurements will be undertaken with acoustic systems. A Nortek© Vectrino+ Acoustic Doppler Velocimeter (ADV) will be used as well as an ADV Profiler developed at LEGI (Hurther et al., 2007; Hurther & Lemmin, 2008; Mignot et al., 2009). This latter instrument enables the measurement of the 3 components of the velocity at high frequency (50 Hz) every 3 mm over the entire vertical profile. Experiments with equilibrium beach profiles will allow a very detailed characterization of the near bed velocities and undertow vertical profiles all along the flume. This will enable to determine robust relationship between wave non-linearities deduced from the measurements of surface elevations and velocities. The wave transformation modelling will then be improved to predict undertow intensity, velocity and acceleration skewness from surface displacements measurements, which are much easier to obtain simultaneously at several locations along the flume for the transient offshore/onshore bar migrations in Task 2b.

Task 2b: Migrating sandbars and beach face evolution (H. Michallet, J. Chauchat, PhD student, F. Grasso, B. Castelle)

A close inspection of morphological changes and related wave properties for varying wave climates is required for improving numerical models. Grasso (2009) showed that a simulated storm event can reproduce offshore (onshore) bar migration during the rising (waning) phase. For such rapidly


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EDITION 2010

Projet BARBEC


11/37

evolving beach profiles (bar migration rate of about 1 m per hour in the experiments), the sediment transport can be very large. The velocity measurements will be associated to sediment concentrations obtained from Fiber Optical Sensors. For these experiments, most of the wave gauges will be gathered in the bar region and the swash zone. The aim here is to collect data on instantaneous sediment transport rate and wave property changes during bar migration for comparison with the numerical results (Task 3). The beach face evolution will also be recorded simultaneously. A large number of new offshore/onshore bar migration physical experiments will allow to accurately measure hydrododynamics and sediment transport associated with different time-varying wave condition scenarios, as well as beach face evolution.

For the beach face, low frequency waves known as surf beat resulting from the breaking of the wave groups constitute a dominant mechanism of the swash dynamics. Low frequency waves have been characterised for a few beach profiles in the LEGI flume (Michallet et al., 2007). The aim here will be to evaluate the coupling between the long waves and both bar and beach face evolutions to be implemented in the model in a parametric way in Task 3.

Task 2c: Dominant processes in bed response at the wave scale and implications on long-term beach evolutions (H. Michallet, J. Chauchat)

At present the scientific community is focusing on developing statistical parameterizations of wave processes (e.g. wave skewness) to be used in sediment transport models. Potential effects of water in/exfiltrating through the bed are not taken into account. Experimental and theoretical approaches need to be conducted to clarify the relative importance of these effects. Austin et al. (2009) have shown that velocity and acceleration skewness should be dominant processes for moderate wave conditions in the surf zone. In contrast, Michallet et al. (2009) have shown that liquefaction due to pressure fluctuations within the bed is often observed as waves break on a coastal structure. Besides, bed ventilation is an important process in the swash zone dynamics (e.g. Butt et al., 2001). In this context, the aim of the present task is two-fold: firstly to provide measurements of the bed response at the wave scale in the surf and swash zones and secondly to determine if there is a real need to include bed ventilation effects in sediment transport models in the future. The experimental facility described above enables a close inspection of the bed dynamics at the wave scale. Pressure variations in the bed, depth of sediment disturbance, velocity fluctuations and sediment concentrations just above the bed can be recorded simultaneously. Such measurements will be undertaken in the framework of the PhD thesis of Céline Berni (Sept. 2008 – Aug. 2011). The available measurement devices presented above are usually deployed in the surf zone. Adjustments are required to undertake accurate measurements in the swash zone. In particular, acoustic instruments are inadequate for measuring velocities in the highly-aerated swash flows. On the other hand, video systems such as Digital Correlation Image Velocimetry can produce accurate measurements in the roller of breaking waves (Govender et al., 2009).

3.3.2 TÂCHE 3 / TASK 3: NUMERICAL MODELLING OF CROSS-SHORE SANDBAR BEHAVIOUR – Person in charge V. Marieu/ Participants: B. Castelle, PhD student, H. Michallet, P. Bonneton, J. Chauchat and international collaboration (B. G. Ruessink – Utrecht University) The general objective of this task will be to develop a beach profile evolution model able to simulate both cross-shore sandbar and beach face behaviours on time scales from weeks to years with reasonably low computational costs.

In order to achieve this objective we will (a) further develop a beach profile evolution model (Castelle et al., in press-c) which, at this stage, presents a number of important limitations. The model will integrate (b) the scientific advances realized in Task 2 for equilibrium beach profiles. Then the model will (c) be validated with data acquired in Task 2 for onshore/offshore sandbar migrations as well as with a number of observations of sandy beaches worldwide. This will allow investigation of the morphological feedbacks between surfzone sandbar(s) and the beach face in the cross-shore direction.

Task 3a: Numerical development (V. Marieu, PhD student, B. Castelle, J. Chauchat, P. Bonneton)


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EDITION 2010

Projet BARBEC


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Recently we developed a simple coupled, wave-averaged, waves-currents-beach profile evolution model (Castelle et al., in press-c). Inspired by the work of Hsu et al. (2006) a new energetic-type (Bailard, 1981) parameterization of sediment transport induced by near-bed velocity and acceleration skewness was implemented. The model reproduces the onshore and offshore sandbar migration during low and high energy conditions, respectively. Comparison with a 2-month period field observation of a double-barred beach (Castelle et al., 2007b) showed encouraging results.

During the development of the beach profile evolution model a number of limitations have been pointed out. The most relevant issues were (1) significant change of default parameters from a site to another, (2) neglection of swash zone compartment, and (3) model blow-ups during severe storms. Because our objective is to keep low computational cost to eventually undertake long-term simulations of beach profile evolution we will not implement more complex and time-consuming advection/diffusion sediment transport schemes (Ruessink et al., 2007b). We will therefore keep an energetic-type approach which is also consistent with the wish of accounting for swash zone processes. The importance of swash zone processes in the overall behaviour of the nearshore morphology is now well-known (Elfrink & Baldock, 2002). Recent major advances have been done in the estimation of cross-shore sediment transport in the swash zone (Masselink et al., 2009; Tinker et al., 2009). The proposed formulas are compatible with our approach. Accordingly, parameterization of swash zone excursion and maximum run-up (existaing data and analysis in Task 5a) will be implemented to adapt a consistent sediment transport shape function in the swash zone. Several classic schemes have been tested in the model for the resolution of the sediment conservation equation, in order to compute the bed evolution. It appeared that most of the schemes induce spurious oscillations of the bedform or even model blow-ups, due to the peak of sediment fluxes near breaking point. The best results were obtained using the non-oscillatory central scheme developed by Marieu et al. (2008) for ripple morphodynamics. However the numerical diffusion induced by this scheme needs to be fully controlled, as being a function of sediment fluxes gradient times the morphological time step. At first, an adaptative morphological time step will be developed both to control the scheme numerical diffusion and to improve computation-time efficiency of our model. Second, the model will perform on two independent grids, one for hydrodynamics computations and the other for morphodynamics computations, allowing a better control of the morphological model. Communications between both grids will be performed by interpolating sediment fluxes on the morphodynamics grid and the bedform on the hydrodynamics grid. A validation of these improvements will also be useful for task 4 as they will be integrated in the morphodynamic model of 3D beach evolution.

Task 3b: Integration of results of Task 2 in the model (PhD student, B. Castelle, V. Marieu, J. Chauchat, B.G. Ruessink)

Direct measurements of wave height, undertow, near-bed velocity and acceleration skewness will be gathered through Task 1 for a variety of equilibrium beach profiles. This key information will be used to calibrate the hydrodynamic module of our numerical model. Formulations proposed by Kuriyama (1991, 2009) to estimate near-bed acceleration and velocity skewness will be tested and, presumably improve to encompass the shoaling, surf and inner surf zones. On the other hand undertow measurements will allow for the first time an accurate validation of the flow module. Additional vertical profiles of velocity will give information of the representativeness of the punctual velocity measurements for undertow estimation in the model.

Given that near-bed velocity and acceleration skewness and undertow constitute the relevant hydrodynamic processes driving cross-shore sediment transport and that these measurements will be available for a variety of equilibrium beach profiles, their respective contributions to the net cross-shore sediment transport will be assessed. Among other findings this will allow a quantitative description of the respective contribution of the three hydrodynamic processes driving cross-shore sediment transport with respect to accretive / erosive events. Potential additional missing key processes identified in Task 2c may also have to be implemented in the model. Sediment transport in the swash zone will not be addressed within Task 3b.

Task 3c: Comparison/validation of the model (PhD student, B. Castelle, V. Marieu, B. G. Ruessink, H. Michallet, J. Chauchat)

The validation of the beach profile model will be undertaken using data gathered from physical experiments and natural sandy beaches worldwide. The objective will be to accurately simulate


CHERCHEURS

EDITION 2010

Projet BARBEC


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both onshore/offshore sandbar migration (laboratory experiments and natural beach data) and beach face evolution (natural beach data).

The model will be applied to existing laboratory experiment studies in which a number of onshore/offshore sandbar migration events have been identified and accurately quantified through high-frequency bathymetric surveys (Grasso et al., 2009a). A first step will be to assess why and how the new version of the model improves simulation of cross-shore sandbar behaviour. The former version of the model (Castelle et al., in press-c) experiences difficulties in simulating both sandbar behaviour when welding to the shore and offshore sandbar migration for high-energy wave events. The ability of the model in simulating cross-shore sandbar migration rates is also highly-contrasting with respect to wave characteristics at the wavemaker (significant wave height Hs and peak wave period Tp). We therefore plan to first focus on the ability of the updated version of the model (Tasks 3a and 3b) to simulate offshore and onshore sandbar migration rates for a wide variety of offshore wave conditions without requiring changes of the default parameters in the sediment transport formulas. Another important issue will be to simulate the equilibrium profiles that were experimentally reached in Grasso et al. (2009a) as well as in the new experiments in Task2b.

Comparison of the model with natural sandy beach behaviour will be a major objective of Task 3. We will consider highly-contrasting sandy beaches (i.e. single-barred/double-barred beaches, low-energy/high-energy coasts) to accurately validate our model. A number of existing field data will be used (Castelle et al., 2007b; Ruessink et al., 2007b; Van Maanen et al., 2008) from beaches in Japan, Australia, New Zealand and The Netherlands. This will allow validation of the model on the time scale of months. This will also be the unique opportunity in Task 3 to evaluate the ability of the model to simulate the morphological evolution of the beach face during both severe storms (Castelle et al., 2007b) and continuous low-energy accretionnary periods (Ruessink et al., 2007b; Van Maanen et al., 2008) which has never been touched upon so far in the literature. This will enable in-depth investigation of the morphological feedbacks in the cross-shore direction between surfzone sandbar(s) and beach face. This is a very ambitious and challenging aspect of BARBEC and we expect to make significant progress in this field.

3.3.3 TÂCHE 4 / TASK 4: NUMERICAL MODELLING OF 3D SURFZONE SANDBAR BEHAVIOUR – Person in charge B. Castelle/ Participants: V. Marieu, PhD student, P. Bonneton and international collaborations (B. G. Ruessink – Utrecht University, G. Coco – NIWA) The general objective of this task will be to develop a nonlinear morphodynmic model able to simulate both down-state an up-state sequences of intermediate wave-dominated beaches. It will be used to investigate how each element of the nearshore system (offshore geological patterns / sandbar(s) / shoreline rhythms) behaves with respect to the others as well as to address up-state sequences.

In order to achieve this aim, we need to (a) further develop a nonlinear morphodynamic model to (b) explore theoretically coupling mechanisms and coupling patterns for down-state sequences. For up-state-sequences we will (c) investigate the potential driving mechanisms for sandbar reshaping into shore-parallel linear sandbar during storms to obtain a nonlinear morphodynamic model suitable for both down-state and up-state sequences to be validated with (d) recent unique physical modelling evolutions (MODLIT) and natural beach evolutions.

Task 4a: Numerical developments (V. Marieu, B. Castelle, P. Bonneton)

Nonlinear morphodynamic models have been recently developed at EPOC. The depth-averaged wave-driven circulation and sediment transport module are currently MORPHODYN (Castelle et al., 2006) or MARS2D (Bruneau, 2009), both coupled to SWAN (Delft Hydraulics). Within BARBEC we will develop an independent sediment transport and morphological evolution model, SediMorph, to be coupled to these circulation models.

Non-oscillatory central schemes are very diffusive, which prevent their use for the resolution of the sediment conservation equation on the coarse grids used with nearshore circulations models. However, as they perform well for steep slopes or for high peaks in the sediment flux, nearshore morphodynamic models would really benefit from these schemes. The use of an independent model


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EDITION 2010

Projet BARBEC


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for morphodynamic computations will allow the use of a proper grid for these schemes, fine enough to limit numerical diffusion without penalising the overall time-efficiency of the coupled models. SediMorph will benefit from the validation performed on the cross-shore model in task 3. A dynamic coupling will be performed between the wave model, the circulation model and the sediment transport and morphodynamic model. This will be performed using Palm dynamic parallel coupler, developed by CERFACS. It will improve the overall execution speed, will allow grid to grid interpolations, and the entire system will be managed and monitored through the graphical user interface.

A major issue in nonlinear morphodynamic modelling is numerical blow-ups as 3D sandbar patterns usually develop without diffusive mechanism to dump the instabilities resulting in continuously growing 3-dimensionnality. To overcome this, a solution is to implement a down-slope sediment transport contribution with respect to a hypothesized alongshore-uniform beach profile (Garnier et al., 2008). This enables investigation of the temporal change in shape, wavelength and amplitude of the 3D sandbar patterns resulting from merging and splitting (Van Enckevort et al., 2004). This approach is currently developed at EPOC (see for instance preliminary result in Figure 3). Such a modelling strategy will be used to explore nonlinear regime of 3D sandbar systems and coupling mechanisms (Task 4b). At this stage sediment transport induced by undertow and wave non-linearities (near-bed acceleration and velocity skewnesses) are assumed to balance in our sediment transport computations. Using numerical developments and validation in Task 3, the new cross-shore sediment transport formulations will be implemented in our nonlinear morphodyanmic model to explore down-state and, more particularly, up-state sequences.

Task 4b: Theoretical modelling of couplings in nearshore systems (B. Castelle, V. Marieu, B. G. Ruessink, G. Coco, N. Sénéchal)

The recent work in Castelle et al. (in press-a, in press-b) showed that strong morphological feedbacks occur in double sandbar systems. In particular the authors showed that the typical alongshore variability of inner-bar rip channels is indicative of coupling mechanisms while it was previously thought to prove absence of coupling. Only numerical modelling could identify this role of couplings. It strongly motivates additional theoretical investigations of coupling mechanisms in wave-dominated beach settings, now encompassing sandbars, shoreline rhythms and offshore geological templates.

A first step will be to explore the validity of common assumptions in numerical modelling the dynamics of nearshore 3D sandbars. A strong assumption in Castelle et al. (in press-a, in press-b), which is common to all the other nonlinear morphydanamic modelling exercises of sandbar behaviour (Damgaard et al., 2002; Reniers et al., 2004; Castelle et al., 2006; Klein & Schuttelaars, 2006; Drønen & Deigaard, 2007; Smit et al., 2008; Garnier et al., 2008) is consideration of time-invariant forcing. We will first assess the representativeness of time-invariant forcing with respect to time-varying forcing. We suspect that time-invariant forcing plays a key role in the ubiquitous merging/splitting of crescents and rip channels in the field as well as in the typical quasi-rhythmicity (rather than rhythmicity) of field sandbar patterns. Another strong assumption in all the previous numerical modelling studies of 3D sandbar pattern is ignorance of tides. Our numerical model can account for tidal elevation variations. We will investigate the impact of tidal range on the growth rate, shape and rhythmicity of emerging 3D sandbar patterns.

Couplings between sandbar(s) and shoreline rhythms will be explored through nonlinear morphodynamic modelling. First these investigations will be undertaken without accounting swash zone processes. We will investigate coupling of bar/rip systems with shoreline undulations. A more complex investigation of sandbar/shoreline coupling will address how crescentic patterns are mirrored at the shoreline as in-phase or 180° out-of-phase coupling can occur (Figure 2). We plan to undertake the same modelling strategy as in Castelle et al. (in press-a). Limitations of the modelling strategy will be identified as well as the potential requirement for accounting for swash zone processes to accurately reproduce sandbar/shoreline couplings. This will be done in concert with Task 5c.

Intriguing recent observations of nearshore systems suggest the presence of shoreline hotspots linked with offshore geological features (McNinch, 2004; Browder & McNinch, 2006; Schupp et al., 2007). These observations typically feed the debate of template theories versus self-organization mechanisms and can be considered as reminiscent of coupling mechanisms in double sandbar


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EDITION 2010

Projet BARBEC


15/37

systems explored in Castelle et al. (in press-a, in press-b). Based on our work on coupling in double sandbar systems and our projected studies on sandbar/shoreline coupling, we will merge the 2 studies to investigate the nearshore system as a whole, that is, encompassing shoreline undulation (and erosional hot-spots), sandbar(s) and offshore geological template. We will aim at understanding why and how offshore geological templates can impact sandbars and shoreline patterns, and particularly hot-spots.

Task 4c: Mechanism responsible for up-state sequences (B. Castelle, B. G. Ruessink, T.D. Price)

In the field, 3D surfzone sandbars are reshaped into shore-parallel linear bar during storms (up-state sequence) with concurrent erosion of the beach. Reproducing up-state sequences observed in the field is a major limitation of nonlinear morphodynamic models. We hypothesize that a change of dominance from horizontal circulation patterns to vertical mass flux compensation (i.e. undertow) during intense breaking waves drives the straightening of surfzone sandbars. Findings in Tasks 2 and 3 for the first time render possible to test this hypothesis through the implementation of new cross-shore sediment transport formulations into nonlinear morphodynamic models of 3D beach evolution. Such implementation may not be sufficient to explain the unknown mechanism responsible for up-state sequence. If so, we plan to implement simpler sediment transport formulations (with a restricted number of free parameters), in a similar way as earlier numerical investigations that rendered possible to identify the mechanisms responsible for down-state sequences (for instance Falquès et al., 2000).

This is without a doubt the most challenging, ambitious and risky part of our project. However we think this issue must be addressed through BARBEC as modelling up-state sequences of sandy beaches is one of the most critical scientific unknown in surfzone sandbar behaviour which strongly limits the validity of wave-dominated beach morphodynamic models that are commonly used to explore and propose engineering practices. We expect to make significant progress in understanding and predicting these crucial up-state sequences.

Task 4d: Comparison/Validation of the model (PhD student, B. Castelle, B. G. Ruessink, T.D. Price, H. Michallet)

As described above, a significant part of Task 4 will be devoted to theoretical studies. These are strongly required given the numerous unknowns in nearshore sandbar modelling and wave-dominated beach behaviour in general. According to the scientific advances reached in Tasks 4b and 4c we plan to confront numerical modelling to observations. First we will apply the nonlinear morphodynamic model to the 2D MODLIT physical experiments (Castelle et al., 2009; Figure 1) during which a full down-state sequence has been for the first time both observed and quantified with concurrent millimetric accuracy bathymetric surveys and highly-dense eulerian and lagrangian measurements. This unique high-quality dataset is currently analysed within project MODLIT and will be available for model validation during BARBEC.

Confrontation of the model with natural beaches will also be done in collaboration with B.G. Ruessink and PhD student Timothy Price who will explore 9-year dataset of a double sandbar system on the Gold Coast (Australia). Timothy Price will use recently developed techniques to inversely model image-intensity into bathymetric maps (Van Dongeren et al., 2008) to quantify the beach bathymetry which will be used to initialize the nonlinear morphodynamic model and further validate the morphological evolutions.

3.3.4 TÂCHE 5 / TASK 5: SWASH MOTIONS AND BEACH FACE BEHAVIOUR PERSON IN CHARGE N. SÉNÉCHAL / Participants: V. Marieu, B. Castelle, and international collaborations (K. Bryan – University of waikato, G. Coco – NIWA, JHM MacMahan - NPS) The general objective of this task will be to fill the gap in previous swash studies by new analysis of existing data collected during highly dissipative conditions (ECORS-Truc Vert’08 field experiment) and by exploring possible interactions between swash, offshore bar system and beach face evolution.

In order to achieve this aim, we need to (a) analyse high-quality dataset of swash motions to quantify swash elevation during storms and to (b) address wavenumber characteristics of swash


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EDITION 2010

Projet BARBEC


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motions. This will enable investigating (c) the role of swash motions in the interaction between the beach face and offshore sandbar(s).

The ECORS-Truc Vert’08 field experiment provides a unique data set of 6-weeks 2-Hz continuous video survey in presence of four large storms with offshore significant wave heights exceeding 5 m. One of the storms, characterized by a 10-year return period, wave heights up to 8.2 m and a wave period of 18 sec, caused historical damage on the coast (a century-old pier was destroyed). This dataset will be analysed in Task 5. Noteworthy, the programs developed in Task 5 will be progressively implemented in the permanent video station at Biscarrosse Beach for both scientific and coastal protection purposes

Task 5a: Environmental parameters and storm extreme statistics (N. Sénéchal, V. Marieu, G. Coco, K. Bryan)

Flow variations in the swash will be measured by collecting pixels along a cross-shore transect from 10-minute sequences of video images into a single image (a timestack). The alongshore distance between each timestack will range between 10 m and a few tens of meters. This spacing will depend on beach morphology, wave conditions and our ability to automate the method. The swash edge is clearly identifiable in the timestacks by the sharp contrast of white foam carried by the flow against the reddish colour of the sand on the beach face. Run-up excursion is defined as the relative difference between successive minima and maxima. Both types of images, time-averages and timestacks, can be rectified and the pixel coordinates in the images transformed into a real-world coordinate system. Although this method is not new in itself, we will develop innovative techniques for automation. Indeed previous works, based on this kind of approach (Ruessink et al., 1998; Ruggiero et al., 2004, Stockdon et al., 2006) generally resorted to manual detection of the swash. According to the amount of data available, manual detection would be possible but would not allow use of the whole dataset, given the number of manual operators needed. Moreover, the digitization is subjective and varies between operators, particularly of the backwash (minima). Our team is still working on an improvement of the method in collaboration with international teams. Using the daily topographic surveys, the horizontal excursion of swash can then be transformed into vertical elevation. Using multiple linear regression we will then investigate the dependence of swash parameters on environmental conditions such as short-wave height, period, and local beach slope under very highly dissipative conditions. These elevations, in turn, can be used as input into a storm impact model (Sallenger, 2000). To make comparisons with previous studies, each environmental parameter will be re-evaluated: using reverse shoaling to deep water using linear wave theory (assuming a shore-normal propagation) to evaluate offshore conditions or to get the breaking wave heights. Our data will be then compared to the most recent empirical parameterization proposed in the literature (review in Stockdon et al., 2006). Our data collected using extreme storms will allow extension of the empirical parameterization to highly dissipative conditions associated with Iribarren ranging from very small to intermediate. Extending our empirical models to highly-energetic conditions is critical to our ability to predict and mitigate against these type of decadal scale storms. Both infragravity and incident contributions will be evaluated. In particular, the intriguing possibility of saturation of infragravity components under these conditions will be evaluated as suggested by previous works which dealt with lower energy conditions (Ruessink et al., 1998; Ruggiero et al., 2004).

Task 5b: Coupling or decoupling effects between surf and swash processes (N. Sénéchal, G. Coco, K. Bryan, JHM MacMahan)

The specific frequency and wavenumber characteristics of swash motions are of interest because of the existence of alongshore-propagating swash motions and the potential coupling of these swash motion with alongshore patterning in morphological features (Ciriano et al., 2005). Previous work indicated the presence of both gravity motions (including both edge and leaky wave modes) and nondispersive, nongravity waveforms (Holland & Holman, 1999) in swash data. The authors suggested that surf and swash zone motions may be decoupled, yet there is clear evidence that surfzone processes drive beachface dynamics. For example, dune erosion has been associated with rip current circulations (Thornton et al., 2007), occurring at the embayments of mega-cusps (Short and Hesp, 1982). Therefore our first key question concerns the nature of the observed alongshore-propagation motions. Are they the shoreline signature of surfzone processes, or are they generated within the swash zone. This question will be addressed by estimating wavenumber frequency


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spectra using the iterative maximum likehood estimator (IMLE) developed by Pawka (1982;1983) applied to vertical swash elevation time series collected during the ECORS-Truc Vert’08 experiment. Our video data at the shoreline will be coupled to alongshore synchronized PUV arrays deployed on the inner bar system in the surf zone (dataset of one of our international collaborators, Dr. JH MacMahan) which will allow the degree of coupling to be measured. In particular, conditions including high infragravity activity over the bar-trough system will be compared to conditions including low infragravity activity.

Task 5c: Horizontal Coupling between swash processes and morphology (N. Sénéchal, V. Marieu, B. Castelle, G. Coco, K. Bryan, JHM MacMahan)

Only few studies have looked at the concomitant behaviour of sandbars and beachface dynamics during storm conditions. It has been suggested, using both field observations (Coco et al., 2003; Ruessink et al., 2007a; Castelle et al., 2007) and numerical modelling (Castelle et al., in press-a, in press-b; Coco & Calvete, 2009) that coupling might occur between sandbars, and between the inner sandbar and the shoreline. We will use field observations (daily surveys operated during ECORS-Truc Vert’08) to characterize morphological changes occurring as a result of different storms. We will analyze if and how such changes are affected by coupling between sandbars and the beach face and how the beach face and swash motions potentially interact.

We will aim at determining if the swash motions and alongshore morphology patterns are coupled. If so, which is likely, we will assess if it is the morphology that predominantly impacts the hydrodynamics or the other way around, and in which condition (storm/post-storm). We will also investigate the impact of the inner and outer bar systems on the swash motions and the potential mirrored shoreline patterns (Figure 2) in concert with Task 4b. The method used here will be similar to the one developed in Task 4b. Datasets with similar offshore conditions but contrasting beach morphologies will be selected and compared both at low and high tide conditions.

Another approach will be evaluated. The effectiveness of various sediment transport mechanisms is roughly correlated with flow velocity so prediction of erosional and accretive events on the beach face requires knowledge of swash flow fields to improve our understanding of this area. They have been many high-quality in situ data-set collected in this area (Masselink & Hughes, 1998; Butt & Russell, 1999, Osborne & Rooker, 1999; Masselink et al., 2009) but they generally concern a small grid or cross-shore array of instruments. Because of the spatial non-uniformities exhibited by the beach face and also because of the wavenumber-frequency structure of the swash (Task 4b), in situ measurements are often not suitable to study horizontal flow structure of swash zone on large area. The method, here, will lie on a PIV (particle image velocimetry) approach. This method has been widely used in laboratory field experiments and more recently in river studies. Concerning the swash zone, Holland et al. (2001) recently applied PIV methods. Because our data set consists in 6 weeks of continuous high frequency (2 Hz) images, this approach is completely appropriate. Vincent Marieu evaluated the possibility of using this method during his post-doctoral fellowship. It looks very promising, even if much technical work will be necessary before using it. The obtained results will be discussed in comparison to the swash elevations and velocity measurements planned in the physical experiments (Task 2c).


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3.4. CALENDRIER DES TÂCHES, LIVRABLES ET JALONS / PLANNING OF TASKS, DELIVERABLES AND MILESTONES

For each task we give in the table below the workplan with task leader in bold, underline.

Tasks Year 1 Year 2 Year 3

4 8 12 16 20 24 28 32 36

Task 1 Project coordination

B. Castelle, V. Marieu, H. Michallet, N. Sénéchal

Task 2 Physical modelling of cross-shore sandbar

behaviour

H. Michallet, J. Chauchat, PhD

student, F. Grasso, B. Castelle

2a- Velocity measurements over equilibrium profiles

2b- Migrating sandbars and beach face evolution

2c- Dominant processes in bed response at the wave scale

and implication in long terms beach evolutions

Task 3 Numerical Modelling of cross-shore sandbar

behaviour

V. Marieu, B. Castelle, PhD student,

H. Michallet, P. Bonneton, J.

Chauchat, B. G. Ruessink

3a- Numerical developments

3b- Integration of results of Task 1 in the model

3c- Comparison/validation of the model

Task 4 Numerical modelling of 3D

surfzone sandbar behaviour

B. Castelle, V. Marieu, PhD student, B. G. Ruessink, G. Coco, P. Bonneton

4a- Numerical developments

4b- Theoretical modelling of couplings in nearshore

systems

4c- Mechanism responsible for up-state sequences

4d- Comparison/validation of the model

Task 5 Swash motions and beach face behaviour

N. Sénéchal, V. Marieu, B. Castelle, K. Bryan, G. Coco, JHM

MacMahan

5a- Environmental parameters and storm extreme statistics

5b- Coupling or decoupling effects between surf and

swash processes

5c- Horizontal Coupling between swash processes and

morphology


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Below we present the deliverables and milestones with delivery date. In addition, one report will be delivered every 6 months.

Deliverables and milestones

Task Title and substance of the deliverables and milestones Delivery date in months

2 Physical modelling of cross-shore sandbar behaviour

Technical note for the new experimental set-up 26 Dataset on velocity and acceleration skewness and undertow for a variety of equilibrium profiles

16

Dataset on sandbar migration for a variety of wave conditions 24 Final report and publications 36

3 Numerical modelling of cross-shore sandbar behaviour

Numerical beach profile model for cross-shore sandbar migration 24 Numerical beach profile model encompassing sandbar and swash zone 28 Validate beach profile model 36 Final report and publications 36

4 Numerical modelling of 3D surfzone sandbar behaviour

Numerical model adapted for long-term simulations 8 Dynamically parallel coupled nonlinear morphodynamic model 24 Nonlinear morphodynamic model suitable for both up-state and down-state sequences 36

Final report and publications 36 5 Swash motions and beach face behaviour

Dataset on swash motions during ECORS’08 24 Final report and publications 36

4. STRATEGIE DE VALORISATION DES RESULTATS ET MODE DE PROTECTION ET D’EXPLOITATION DES RESULTATS / DATA MANAGEMENT, DATA SHARING, INTELLECTUAL PROPERTY AND RESULTS EXPLOITATION

Scientific communication

The questions we address in BARBEC concern the morphodynamics of high-energy wave-dominated sandy beaches. We plan to investigate the beach system as a whole, that is, from offshore geological templates to the dune foot, encompassing surfzone sandbar(s) and the beach face. Nearshore studies, and particularly those dealing with sandy shores, have received increasing attention by the scientific community in recent years. Understanding and predicting wave-dominated beach dynamics is therefore increasingly represented in international conferences and journals. The participation to these international conferences and publications in international peer-reviewed journal will be priority during the 3 years of the project.

Data management and data sharing

A web site will be developed and updated on a regular basis. A significant part of the web site will be open access (see below). For the duration of BARBEC, the other part will be secured to the participants of BARBEC for data sharing purposes. We plan to share the published data with the coastal community at the end of the project. Publications from BARBEC project (or their references depending on copyrights) will be posted on the website as soon as accepted.

Public scientific outreach

The open access will be designed for general public outreach, with a description of the general interests of BARBEC and the synoptic results of both the experiments and numerical modelling exercises. Results from BARBEC will also be presented during conferences and lectures for public outreach. This will be partly done with the Association OCEAN with which EPOC and BARBEC


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researchers already worked with, as there is a rising need in society to better understand the potential response of coastal systems to climate change.

General scientific and technical outcomes

Overall, we plan that BARBEC will increase our understanding of wave-dominated beach systems. This knowledge will directly emerge from the analysis of the innovative physical and numerical modelling experiments as well as the video analysis of both beach face evolution and swash processes during severe storms. Despite this is not a primary objective of BARBEC, results and developments during the project will also allow a more accurate evaluation of potential response of sandy coastlines to climate change.

Results obtained from our analysis will provide highly-valuable information on how sandy beaches evolve with respect to storms and post-storm conditions on the time scale of weeks to months. Such information will be of use for improving (in a parametric way) longer-term models (for instance one-line-type models, which are not addressed in BARBEC) which are used to simulate large-scale (O(1-100 km)) shoreline evolutions. These models currently ignore the role of sandbars as well as their strong nonlinear behaviour and potential role in shoreline response.

On a more technical point of view, a number of video-imagery techniques will be developed to quantify beach response and swash zone processes. These programs will be fully compatible with commercial and non-profit shore-based video remote sensing systems (ARGUS, KOSTA, Cam-Era, etc) which are an alternative low cost tool to remotely survey coastal areas. These systems are increasingly used worldwide for coastal management issues, and their use is expected to further increase within the next few years. During BARBEC, programs will be progressively implemented in the permanent video stations at Biscarrosse, which is a highly-vulnerable populated sandy beach.

Another important outcome of BARBEC will be the development of two nonlinear morphodynamic models able to simulate the evolution of the sandy beach system during both up-state and down-state sequences. The cross-shore and 3D numerical model will be mostly devoted to medium-term simulations (from weeks to years) and short-term simulations (from days to months), respectively. At this stage, there is no research or commercial numerical model able to simulate the overall evolution of wave-dominated beaches in the presence of time-varying wave and tide conditions and, particularly, during severe storms. While this kind of model is sometimes tentatively used to provide prediction of beach response during storms (despite there is obviously missing physics) our effort will be to improve hydro-sedimentary processes. Our goal is not to sell a model at the end of BARBEC, but this will be a first key step to the development of operational accurate sandy beach evolution models.

5. ORGANISATION DU PROJET / PROPOSAL ORGANISATION

5.1. DESCRIPTION, ADÉQUATION ET COMPLÉMENTARITÉ DES PARTICIPANTS / RELEVANCE AND COMPLEMENTARITY OF THE PARTNERS WITHIN THE CONSORTIUM

The BARBEC project will allow young researchers, working on complementary research areas and approaches, to unite on an innovative topic that has only been very little addressed at the international level: how each element of the nearshore system behaves with respect to the others and how morphologic feedbacks govern the beach system as a whole.

All members of the team share a common expertise in nearshore physical processes and morphodynamics. BARBEC will benefit from the strong expertise of young and senior researchers who are already internationally well known: Bruno Castelle (numerical modelling and physical analysis of wave-dominated sandy beach dynamics), Nadia Sénéchal (field and video analysis of wave-driven nearshore circulations and morphodynamics), Hervé Michallet (physical modelling of wave-dominated beaches), Vincent Marieu (Numerical modelling and Remote Sensing techniques), Philippe Bonneton (Numerical modelling) and Julien Chauchat (Sediment transport modelling and hydrodynamics). Complementarities also arise from the different spatial and temporal scales studied by each member of the group.


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All these researchers also have a strong experience in the education and training of students at both the Master and PhD levels, which allows considering education of new researchers as a priority within BARBEC.

Detailed description of the participants and their relevance to BARBEC objectives:

UMR EPOC, University of Bordeaux:

Dr. Bruno Castelle, CR2/CNRS, 32 years (CV in section 7.2) acquired an expertise in the observation and numerical modelling of the morphodynamics of wave-dominated sandy coasts through his PhD at EPOC (2004) and later during his post-doctorate at Griffith University (2005-2007). Overall, training and expertise of Bruno Castelle lie in numerical modelling, but he also works on physical modelling and observational techniques such as current and wave measurements, bottom mapping and remote sensing (video and satellite) through national and international collaborations. After a few years focussing on wave-driven circulations and larger-scale morpho-sedimentary behaviour of sandy coasts (post-doctorates at Griffith University and EPOC), he recently resumed work on nearshore sandbar modelling (MODLIT). Within this framework he conducted numerical modelling of double sandbar systems: new and unexpected results (Castelle et al., in press-a, in press-b) on coupling mechanisms between the different elements of the nearshore system largely contributed to this proposal.

Dr. Nadia Sénéchal, Assistant Professor, HDR 33 years (CV in section 7.2) acquired an expertise in the field measurements and observation of hydrodynamic processes through her PhD (2003). In particular, she worked on wave energy dissipation and energy transfer through nonlinear triad interactions. She started her work on beach morphodynamics as a young appointed as assistant Professor at university Bordeaux 1/ EPOC (2004), working both a long term data series and intensive field experiments. In particular, she deployed the first permanent video system for coastal morphodynamics purposes in France in 2007. She recently defended her HDR (2009) on morphodynamics and physical processes on sandy beaches. Overall, training and expertise of Nadia Sénéchal lie in field measurements and observations techniques such as current and wave measurements, bottom mapping and remote sensing (video and satellite). She supervised an international (France, GB, USA, The Netherlands, New Zealand, Australia) multi-institutional (16 teams) field experiment on beach morphodynamics under storm conditions in 2008. She spent 4 months as invited scientist at the National Institute of water and Atmospheric Research in New Zealand in 2009, working on swash dynamics using video data and morphodynamics of the shoreface. She supervised one PHD on high frequency beach morphodynamics from video data (Rafael Almar defended his PhD in September 2009, he is currently post-doctorate in Chile).

Dr. Vincent Marieu, research engineer/CNRS, 33 years (CV in section 7.2) worked in various fields of oceanography during his early carrier as an engineer. In particular, he developed an expertise in numerical modelling and remote sensing techniques. During his PhD, he focussed on ripple dynamics which led to the development of morphodynamic numerical models. He is currently applying his knowledge of morphodynamic and numerical modelling to develop a general morphodynamic model for sandy bedforms, which will be coupled to various waves/currents codes. His knowledge of numerical modelling and video remote sensing will be very useful for both sandbar modelling and swash dynamics using video data.

Dr. Philippe Bonneton, DR2/CNRS, 46 years acquired an expertise in geophysical fluid dynamics through his PhD at CNRM (1992) and after his entrance to CNRS at IMFT (1993-1997). His past research interests were mainly focused on the dynamics of waves and turbulence in stratified fluids (15 journal papers). Since 1998, he is working on the modelling of wave-induced circulation and beach morphodynamics (35 journal papers). He is in charge of the METHYS team (EPOC), which is mainly involved in the field of nearshore hydrodynamics and sedimentary processes. He is the coordinator of the MODLIT project (SHOM-INSU, 2008-2010) that federated 11 teams (8 from France, 1 from Chile, 2 from the Netherlands) which, in particular, initiated the present collaboration EPOC/LEGI in the framework of the combination of numerical and physical modelling.


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UMR LEGI, University of Grenoble :

Dr Hervé Michallet, CR1, 41 years (CV in section 7.2) acquired an expertise in fluid mechanics through his PhD at LEGI (1995) and during post-doctoral periods at University of Western Australia (1997), UMR INLN (1998) and LEGI. Overall, training and expertise of Hervé Michallet lie in physical modelling, but he also worked on numerical modelling and field experiments. His past research interests include the dynamics of long internal waves, turbulent suspensions of cohesive sediments, soil liquefaction at coastal structures. For a few years he focused on the wave dynamics in the surf zone and induced sediment transport. He was the coordinator of a project (INSU-LEFE/IDAO, 2001-2009) that federated about 50 researchers from 15 French institutes for sharing knowledge on the hydrodynamics of the coastal zone. He participated in 2007 to experiments in the Large Oscillating Wave Tunnel of Deltares (Delft, NL) in the framework of the transnational access to European large scale facilities program (project TRANSKEW-HydralabIII). He was in charge of measuring velocity profiles down to the bed for studying the sediment tansport induced by skewed waves and currents. He was the principal investigator in 2008 on large scale experiments (30 m x 30 m LHF wave tank, Figure 1) that aimed at reproducing the hydrodynamics and morphodynamics of rip currents. He recently co-supervised a PhD on physical modelling of beach morphodynamics (Grasso et al., 2009a, 2009b) that showed the relevance of this approach for the present project.

Dr Julien Chauchat, Assistant Professor, 31 years (CV in section 7.2) acquired an expertise in sediment transport modelling during his PhD (2007) and his post-doctorate at the University of Provence in Marseille (2008-2009). His research mainly concerns numerical modelling of sediment transport using two-phase approach with a special focus on small scale processes, at the scale of the sediment particles: fluid-particles turbulent interactions in dilute flows (suspended-load) and particle-particle interactions in dense flows (bed-load). He has just been recruited as Assistant Professor at LEGI in order to develop his research in connection with research activities carried out by the HOULE Team in coastal morphodynamics and more especially on cross-shore sandbar migration. His expertise on physical and numerical modelling of sediment transport processes will be very useful for the determination of sediment transport parameterization from the experiments (Task 2).

Description of International Collaborators: As explained earlier in this proposal our project will also lean on international collaborations with young and senior international researchers whose expertises are internationally-acknowledged. Despite they will not lead any research given in this proposal we consider that they are part of this project in the framework of continuously increasing collaborations and exchanges with their institution in the field of wave-dominated beaches:

Dr. Gerben Ruessink (Utrecht University, The Netherlands), Associate Professor in Coastal Morphodynamics, 39 years, obtained his PhD in 1998 with the highest honour from Utrecht University on a field-based study of the hydrodynamics and sediment transport across subtidal sandbars. Between 1998 and 2000 he was a post-doctoral research assistant with the same university and organized and executed the international Coast3D project. In 2000 he joined the Marine and Coastal Management group of the research institute WL|Delft Hydraulics, where he focused on applied coastal problems. Since 2002 he is Associate Professor at Utrecht University and heads the research group "Morphodynamics of sandy coastal environments". In 2004 he was awarded a prestigous Early Career Award from the Dutch Organisation for Scientific Research. He has investigated in particular the processes responsible for cross-shore sandbar migration on time scales of weeks to seasons and the resulting predictability of sandbar migration, and he has pioneered inner-outer sandbar coupling. The development and use of numerical models, together with the analysis of data obtained from remote sensing and extensive in-situ field experiments, has earned his research group international reputation as a leading group in nearshore science. His main current research interests are the interaction between the subtidal bar zone, the intertidal beach and the dune area, especially under high-energy wave conditions, and the potential effect of climate change on coastal evolution. He is currently supervising 4 PhD students and 2 post-doctoral research assistents. He has (co-)authored more than 50 peer-reviewed journal publications, over


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60 conference contributions, and is Associate Editor for the Journal of Geophysical Research - Oceans.MSc

MSc Timothy Price (Utrecht University, The Netherlands), PhD student, 27 years obtained his MSc degree with the highest honour in 2007 fromUtrecht University. He explored the relevance of shoaling waves, breaking waves and swash to the evolution of the intertidal beach using field data and numerical modelling. He is currently a PhD student and focuses on inner-outer bar coupling and bar straightening using a 9-year data set of daily video images of the Gold Coast, Australia and numerical models. He will conduct part of his work in close co-operation with Dr. B. Castelle during a 6-month stay at EPOC, Bordeaux. During this period he will work on the numerical modelling of coupling mechanisms in double sandbar systems using the Gold Coast dataset to ensure comprehensive and quantitative evaluation of coupling mechanisms explored theoretically in Castelle et al. (in press-a, in press-b). He will interact with PhD student on numerical modelling in Task 4d. Timothy Price has (co-)authored 4 peer-reviewed journal publications.

Dr Florent Grasso (Utrecht University, The Netherlands), Post-doc, 27 years acquired an expertise in physical modelling of sandy beaches during his PhD at LEGI (defended in 2009). He investigated hydrodynamics and morphodynamics of cross-shore beach profiles. Florent Grasso showed the relevance of physical modelling; particularly to study sediment transport associated with equilibrium beach profiles and sandbar migrations. He collaborated actively with French and European research projects (INSU-LEFE/IDAO, DGA/RELIEF-MODLIT, Beachmed-e INTERREG IIIC). In January he was appointed as post-doc at Utrecht University, working in the Coastal Group with Gerben Ruessink. This project aims at analysing and modelling the sediment transport in shallow water under extreme wave conditions. Florent Grasso will be involved in the examination of the physical results in Task 2 as he was pioneer in the physical modelling strategy.

Dr Giovanni Coco (NIWA, New Zealand), 38 years is a coastal scientist at the National Institute of Marine Studies (New Zealand) and he works in the area of nearshore processes over a range of scales using a range of modeling techniques. Over the years he has published several contributions on the formation of beach cusps in the swash zone, surf zone sandbars and offshore bedforms. He also leads the national network of video-monitoring stations in New Zealand and has developed software to analyze patterns in shoreline and sandbar position. Some of his most recent work explores the development and evolution of crescentic patterns in double-barred systems using a morphodynamic model based on linear stability analysis. He has also published papers on cross-shore sandbar evolution and video observations of swash and surf zone processes. He is Associate Editor for the Journal of Geophysical Research – Earth Surface. Dr Coco will interact with all participants in areas ranging from numerical modeling to field observations.

Dr Karin Bryan (University of Waikato, New Zealand), 40 years completed a PhD from the Department of Oceanography, Dalhousie University (Canada) in 1997, after which she undertook a Post Doctoral position at the National Institute of Water and Atmospheric Research (New Zealand). Since 2002, she has been a senior lecturer at the University of Waikato. Her doctoral work showed the existence of bar-trapping of edgewaves, both theoretically, and using frequency-direction spectra of longshore array data collected during the DELILAH experiments at DUCK, North Carolina. During her post-doctoral work, she derived a the theoretical background for converting turbulent frequency spectra to wave number spectra in all depths of water. She also developed the software needed for implementing the Cam-Era video network of beach cameras (rectification, lens distortion corrections, general image analysis) in New Zealand. At present she is working on techniques for detecting non-linear variations in swash timeseries, collected using video. She has been a team member on 4 large multi-institutional field experiments, and she has also been chief logistics organiser for a large NSF –funded experiment in New Zealand in 2001, jointly undertaken with Virginia Institute of Marine Sciences. However, her main contribution to this team will be expertise in statistics, data analysis and video techniques

Dr Jamie MacMahan (Naval Postgraduate School, USA), 37 years completed a PhD from the Department of Civil and Coastal Engineering, University of Florida (USA). In 2003, he was a National Research Council Postdoctoral Fellow at the Naval Postgraduate School (USA). From 2005-2007, he was an assistant professor at the University of Delaware (USA). Since 2007, he has been an assistant professor at the Naval Postgraduate School (US), and remains an adjunct faculty


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member at the University of Delaware. His doctoral work, explained infragravity rip current pulsations, discovered new very-low-frequency motions associated with rip currents, and described mean rip current characteristics from data collected during the RIP current EXperiment (RIPEX) in Monterey, CA (USA). During his doctorate, he developed GPS-equipped personal watercraft surveying system and participated in a number of field experiments located in California, Florida, Oregon, Washington, and Australia. During his post-doctoral work, he investigated wave-group forced surfzone vortical motions using field observations from the Sandyduck experiment at Duck, North Carolina. He also participated in the Nearshore Canyon Experiment, where he described low-energy rip currents. He wrote an overview manuscript on rip currents. Currently, he has developed inexpensive GPS-equipped drifters, which he has used to describe the Lagrangain flow behavior and mixing estimate in the surf zone associated rip-channeled beaches. Jamie interests revolve around understanding rip currents. He has published 15 papers associated with rip currents. He has actively participated in over 10 multi-institutional field experiments throughout the world. Jamie will be involved in the analysis of coherent alongshore lagged array located within the inner-bar system, which was obtained during the ECORS08 project at Truc Vert, France.

5.2. QUALIFICATION DU PORTEUR DU PROJET / QUALIFICATION OF THE PRINCIPAL INVESTIGATOR

Bruno Castelle acquired an expertise in wave-dominated sandy beach morphodynamics through his PhD at EPOC and his post doctorates at Griffith University and EPOC. A significant part of his research was predominantly devoted to numerical modelling of wave-driven nearshore circulations (6 journal papers) and surfzone sandbar / beach evolutions (7 journal papers). In addition, some of his research was mainly based on video-imagery techniques (4 journal papers), field measurements (5 journal papers) and more recently physical modelling (1 journal paper in preparation as 1st author). It must be noted that most of his research/publications were based on the combination of 2 to 3 of these approaches. In other words, these approaches were only scarcely undertaken in isolation and the investigations led by Bruno Castelle were always undertaken in collaboration with national and international investigators with complementary approaches and expertise. Accordingly he has the required scientific expertise to conduct Task 1 and to understand and exchange with the researchers involved in BARBEC in the other tasks.

As coordinator, Bruno Castelle has been recently established as the scientist in charge of managing 4 people of the METHYS team in the field of numerical modelling and physical analysis of hydro-sedimentary processes. One of his other tasks is to organize multidisciplinary seminars at EPOC (about 30 to 40 per year), attracting national and international researchers. Despite not being the project coordinator of the project MODLIT (RELIEFS/INSU, SHOM-DGA, 2007-2010; http://modlit.epoc.u-bordeaux1.fr/) as he was not permanent researcher at the time of submitting the proposal, he has been strongly involved in writing the proposal. In addition, he has been a leader in the numerical modelling aspects of this project and he was strongly involved in the physical experiments.

Despite BARBEC will be the first large-scale project Bruno Castelle will handle as coordinator, we think he has both the required scientific and management expertise to take in charge the BARBEC project and to conduct Task 1.


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5.3. QUALIFICATION, ROLE ET IMPLICATION DES PARTICIPANTS / CONTRIBUTION AND QUALIFICATION OF EACH PROJECT PARTICIPANT

Below is synthesized contributions and qualification of the participants:

Nom Prénom Emploi actuel

Unité de rattachement et Lieu

Discipline

Personne.

mois

Rôle/Responsabilité dans le projet

4 lignes max

Project Coordinator (Task 1) and Leader Task 4

CASTELLE Bruno CR2, CNRS

UMR EPOC, Talence

Numerical modelling of

sandbar dynamics

27(75%)

Numerical modelling of sandbar dynamics

Involved in Tasks 1 (10%), 2 (5%), 3(15%), 4 (40%) and 5 (5%)

Leader of Task 5 SENECHAL Nadia MdC, HDR UMR EPOC,

Talence

Field data analysis

27(75%)

Swash dynamics and beach face morphodynamics

Involved in Tasks 1 (5%), 4 (5%) and 5 (90%)

Leader of Task 3 MARIEU Vincent IR, CNS UMR EPOC,

Talence

Numerical modelling and

remote sensing

12(33%)

Numerical modelling and video analysis

Involved in Tasks 1 (12%), 3 (38%), 4 (25%) and 5 (25%)

Leader of Task 2 MICHALLET Hervé CR1, CNRS

UMR LEGI, Grenoble

Physical modelling of

wave-dominated beaches

12(33%)

Physical modelling of sandbar dynamics


CHAUCHAT Julien MdC UMR LEGI, Grenoble

Sediment transport

modelling and hydrodynamics

9(25%)

Analysis of sediment transport processes

Involved in Tasks 2 (66%) and 3 (34%)

BONNETON Philippe DR/CNRS UMR EPOC,

Talence Numerical modelling

4(11%)

Numerical modelling

Involved in Tasks 3 (25%) and 4 (75%)

PhD student X X Master 2 UMR EPOC,

Talence

Numerical and physical modelling

36 (100%)

Sandbar morphodynamics


6. JUSTIFICATION SCIENTIFIQUE DES MOYENS DEMANDES / SCIENTIFIC JUSTIFICATION OF REQUESTED BUDGET

The major point is that an appointed PhD student is essential to undertake our research project. Overall, our project does not require large amounts of money to operate. This justifies the fact that, given the significant manpower involved in BARBEC (127 pers.months), the percentage of mission cost is larger than the 5% recommended by ANR. This is also justified by the fact that a 4-month stay of PhD student at LEGI is required to be involved in the physical modelling experiments.

Accordingly, below we detail scientific and technical justification of requested budget:


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• Équipement / Equipment As outlined in our proposal, numerical modelling studies will require a very large number of simulations. While our beach profile model is rather light, our nonlinear morphodynmic model of 3D surfzone sandbars is much less time-efficient. In order to perform all the simulations and to test a large number of hypotheses, we need a multi-processors workstation to run the simulations in parallel. This workstation will be used for Tasks 3, 4 and 5c. The price of this workstation (Dell power edge + options) is 9 300 €. Coût HT + TVA non récupérable : 9 300 + (9 300*19,6%*80%) = 10 760 €

Total Equipment : 10 760 €

• Personnel / Staff

As described in section 3, our work proposal is innovative and very ambitious which also requires a lot of time to be spent in data analysis and numerical developments / validations to explore a number of scientific unknowns. This justifies the appointment of a 3-year PhD to complete the project. PhD student will be involved in Tasks 2 (20%), 3 (60%) and 4 (20%). Description: PhD student will assist some physical modelling experiments and will be involved in data analysis in collaboration with Hervé Michallet and Julien Chauchat. PhD student will be based in Bordeaux at EPOC (including a 4-month stay at LEGI during the physical experiments) as he will pursue numerical developments of the cross-shore sandbar model with Bruno Castelle and Vincent Marieu and will explore driving mechanism in cross-shore sandbar behaviour and beach face response. Accordingly he will be leader of Tasks 3b and 3c. In the end of BARBEC he will implement cross-shore sediment formulations in our nonlinear morphodynamic model of 3D surfzone sandbar behaviour. PhD student will be surpervised by Bruno Castelle at EPOC. Qualifications: The candidate is expected to assist data processing from the physical experiment, build and apply morphodynamic models, publish in international peer-reviewed journals and write a (paper) PhD thesis within the project duration of three years. Highly-motivated candidates with an MSc degree in Physical Oceanography, Hydrodynamics or another related field will be encouraged to apply. We will require good nearshore process knowledge and quantitative skills from the candidates. Noteworthy, given the very scarce French education in this field, experience in morphodynamic modelling will be an asset but not a condition. PhD Student 36 months 2 700 €/month 97 200 €

Total Staff : 97 200 €

• Prestation de service externe / Subcontracting

None

Total Subcontracting: 0 €

• Missions / Missions 1) Because our project leans on an-depth collaboration between EPOC and LEGI, with the development of novel physical experiments in which PhD student will be involved, a 4-month stay of PhD Student at LEGI including 1000 € / month for lodging and 2 return flights Bordeaux-Grenoble (1000 €) is required: 5000 €

2) 1 meeting in Grenoble during the physical experiment (1 return flight and 2-day stay for 3 persons from EPOC): 1500 € 3) 3 meetings of 2-day stay in Bordeaux for H. Michallet (LEGI): 1500 €


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4) National and international conferences, participations to workshops, which are essential for our research group to continuously exchange with international researchers and to communicate our results: 12 000 €

Total Missions: 20 000 €

• Dépenses justifiées sur une procédure de facturation interne / Internal expenses

None

Total Internal expenses: 0 €

• Autres dépenses de fonctionnement / Other expenses

1) Small equipment (< 4000 €) - 1 computer suitable for numerical modelling and data analysis + small equipment for PhD student: 3000 € - 1 computer suitable for video data analysis + small equipment in Task 5: 2500 € - NAS (3 To capacity) for physical experiment and video data storage: 700 € 2) Software licence - 2 Matlab licences with toolboxes for 3 years essential for PhD student data analysis and numerical model output processing (Tasks 2, 3 and 4) as well as for video analysis in Task 5: 3000 € 4) The permanent video station at Biscarrosse needs regular maintenance to operate continuously. Estimated cost for 3 years: 1500 € 5) Publications fees: 5000 € 6) The experimental facility at LEGI needs regular maintenance, as well as additional lightweight, particularly for the large number of experiments planned during BARBEC: 4000 € 7) In addition, small equipments (for website, video conference, etc) and consumables are required throughout the project: 5000 €

Total other expenses: 24 700 €

• Détail des coûts consolidés / Details of consolidated costs Below is a table detailing the consolidated cost for each position with respect to the synthesized table given in the submission document A: Position

Cost / month

Task 1 Pers.months

Task 2 Pers.months

Task 3 Pers.months

Task 4 Pers.months

Task 5 Pers.months

Total Pers.months

Cost

DR 7200

€/month 0,0 0,0 1,0 3,0 0,0 4,0 28 800 €

CR 6300

€/month 3,5 12,0 6,5 15,0 2,0 39,0 245 700 €

IR 6500

€/month 1,5 0,0 4,5 3,0 3,0 12,0 78 000 €

MdC 3200

€/month 1,5 6,0 3,0 2,0 23,5 36,0 115 200 €

Total 6,5 18,0 15,0 23,0 28,5 91,0 467 700 €

Total consolidated cost per Task: Task 1: 36 600 € Task 2: 94 800 €


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Task 3: 87 000 € Task 4: 142 000 € Task 5: 107 300 € Total consolidated cost: 467 700 €

7. ANNEXES

7.1. REFERENCES BIBLIOGRAPHIQUES / REFERENCES

Aarninkhof, S., C. Hinton, and K. Wijnberg (1998), On the predictability of nearshore bar behaviour, in Proc. of 26th Int. Conf. on Coast. Eng., pp. 2409–2422, ASCE, New York.

Almar, R., B. Castelle, B. G. Ruessink, N. Sénéchal, P. Bonneton and V. Marieu (in press), Two and three-dimensional double-sandbar system behavior under intense wave forcing and a meso-macro tidal range. Cont. Shelf Res.

Ardhuin, F., N. Rascle and K. A. Belibassakis (2008a), Explicit wave-averaged primitive equations using a generalized lagrangian mean, Ocean Modelling, 20, 35-60.

Ardhuin, F., A. D. Jenkins, and K. A. Belibassakis (2008b), Comments on “The three-dimensional current and surface wave equations”, J. Phys. Oceanogr., 38, 1340-1350

Austin, M., G. Masselink, T. O'Hare and P. Russell (2009), Onshore sediment transport on a sandy beach under varied wave conditions: Flow velocity skewness, wave asymmetry or bed ventilation? Marine Geology, 259, 86-101.

Bailard, J. A. (1981), An energetic total load sediment transport model for a plane sloping beach, J. Geophys. Res., 86, 10938-10954.

Bowen, A. J., and D. L. Inman (1971), Edge waves and crescentic bars, J. Geophys. Res., 76, 8662–8671.

Bowen, A. J. (1997), Patterns in the water: Patterns in the sand?, In Proc. of Coastal Dynamics ’97, pp. 1–10, ASCE, New York.

Browder, A. G. and J. E. McNinch (2006), Linking framework geology and nearshore morphology: Correlation of paleo-channels with shore-oblique sandbars and gravel outcrops, Mar. Geol., 231, 141-162.

Bruneau, N. (2009), Modélisation morphodynamique des plages sableuses, PhD Thesis Univ. Bordeaux (in French), 173p.

Bryan, K. R., and A. J. Bowen (1997), Can bar-trapped edge waves cause bar formation, bar movement or bar growth?, In Proc. of Coasts and Ports, pp. 1037–1042.

Butt, T., and P. Russell (2000), Hydrodynamics and cross-shore sediment transport in the swash zone of natural beaches: A review. J. Coastal Res., 16, 225-268.

Butt,T., P. Russell and I. Turner (2001), The influence of swash infiltration-exfiltration on beach face sediment transport: onshore or offshore? Coast. Eng., 42(1), 35-52.

Calvete, D., N. Dodd, A. Falqués, and S.M. Van Leeuwen (2005), Morphological development of rip channel systems: normal and near-normal wave incidence, J. Geophys. Res., 110, C10006, doi:10.1029/2004JC002803.

Carter, T. G., P. L. Liu, and C. C. Mei (1973), Mass transport by waves and offshore bedforms, Journal of the Waterways, Harbors and Coastal Engineering Division, 99, 165–184.

Castelle, B., P. Bonneton, and R. Butel (2006), Modeling of crescentic pattern development of nearshore bars: Aquitanian Coast, France, C. R. Geoscience, 338, 795–801.

Castelle, B., P. Bonneton, H. Dupuis, and N. Sénéchal (2007a), Double bar beach dynamics on the high-energy meso-macrotidal French Aquitanian Coast: a review, Mar. Geol., 245, 141–159.

Castelle, B., I. L. Turner, B. G. Ruessink and R. B. Tomlinson (2007b), Impact of storms on beach erosion: Broadbeach (Gold Coast, Australia), J. Coast. Res., SI 50, 534-539.

Castelle, B., Michallet, H., Marieu, V., Leckler, F., Dubardier, B., Lambert,A., Berni, C., Bouchette, F., Bonneton, P., Kimmoun, O., Sous, D. and Almar, R. (2009), A large−scale laboratory experiment of rip current circulations over a moveable bed : drifter measurements, In Proc. Coastal Dynamics’09, [CD-ROM], 14p

Castelle, B., B. G. Ruessink, P. Bonneton, V. Marieu, N. Bruneau, and T. D. Price (in press-a), Coupling mechanisms in double sandbar systems, Part 1: Patterns and physical explanation, Earth Surface Processes and Landforms.


CHERCHEURS

EDITION 2010

Projet BARBEC


29/37

Castelle, B., B. G. Ruessink, P. Bonneton, V. Marieu, N. Bruneau, and T. D. Price (in press-b), Coupling mechanisms in double sandbar systems, Part 2: Impact on alongshore-variability of inner-bar rip channels, Earth Surface Processes and Landforms.

Castelle, B., F. Grasso, V. Marieu, P. Bonneton and N. Bruneau (in press-c), Modelling beach profile evolutions, La Houille Blanche.

Cienfuegos, R., E. Barthélemy, and P. Bonneton (2010), A wave-breaking model for Boussinesq-type equations including roller effects in the mass conservation equation. J. Waterw., Port, Coastal, Ocean Eng., 136(1), 10-26.

Ciriano, Y., G. Coco, K. R. Bryan, and S. Elgar (2005), Field observations of swash zone infragravity motions and beach cusp evolution, Journal of Geophysical Research, 110, C02018, doi:10.1029/2004JC002485.

Coco, G., and A. B. Murray (2007), Patterns in the sand: from forcing templates to self organization, Geomorphology, 91, 271–290.

Coco, G. and D. Calvete (2009), The use of linear stability analysis to characterize the variability of multiple sandbar systems, In Proc. Coastal Dynamics’09, [CD-ROM], 11p

Dally, W., and C.A. Brown (1995), A modelling investigation of the breaking wave roller with application to cross-shore currents, J. Geophys. Res., 100(C2), 24873-24883.

Damgaard, J., N. Dodd, L. Hall, and T. Chesher (2002), Morphodynamic modeling of rip channel growth, Coastal Eng., 43, 199–221.

Deigaard, R., N. Drønen, J. Fredsøe, J. H. Jensen, and M. P. Jørgensen (1999), A morphological stability analysis for a long straight barred coast, Coastal Eng., 36, 171-195.

Drake, T.G. and J. Calantoni. 2001. Discrete-particle model for sheet flow sediment transport in the nearshore. Journal of Geophysical Research, 106(C9), 19,859-19,868

Drønen, N., and R. Deigaard (2007), Quasi-three-dimensional modelling of the morphology of longshore bars, Coastal Eng., 54, 197–215.

Elfrink, B. and T. Baldock (2002), Hydrodynamics and sediment transport in the swash zone: a review and perspectives, Coast. Eng., 45, 149-167.

Falqués, A., G. Coco, and D. A. Huntley (2000), A mechanism for the generation of wave-driven rhythmic patterns in the surf zone, J. Geophys. Res., 105, 24,071-24,088.

Gallagher, E. L., S. Elgar, and R. T. Guza (1998), Observation of sand bar evolution on a natural beach, J. Geophys. Res., 103, 3203-3215.

Garnier, R., D. Calvete, A. Falqués, and N. Dodd (2008), Modelling the formation and the long-term behavior of rip channel systems from the deformation of a longshore bar, J. Geophys. Res., 113, C07053, doi:10.1029/2007JC004632.

Govender, K., H. Michallet, M.J. Alport, U. Pillay, G.P. Mocke, & M. Mory (2009), Video DCIV measurements of mass and momentum fluxes and kinetic energies in laboratory waves breaking over a bar, Coastal Engineering, 56 (8), 876-885.

Grasso, F., H. Michallet, R. Certain and E. Barthélemy (2009a), Experimental flume simulation of sandbar dynamics, J. Coast. Res., SI 56, 54-58.

Grasso, F., H. Michallet, E. Barthélemy and R. Certain (2009b), Physical modeling of intermediate cross-shore beach morphology, J. Geophys. Res., 114, C09001.

Grasso, F. (2009) Modélisation physique de la dynamique hydro-sédimentaire des plages. PhD Thesis (in French), Univ. Joseph Fourier, Grenoble.

Hoefel, F., and S. Elgar (2003), Wave-induced sediment transport and sandbar migration, Science, 299,1885-1887.

Holland, K.T., and R.A. Holman (1999), Wavenumber-frequency structure of infragravity swash motions, J. Geophys. Res., 104, 13,479-13,488.

Holman, R. A., and A. J. Bowen (1982), Bars, bumps and holes: models for the generation of complex beach topography, J. Geophys. Res., 87, 457–468.

Holman, R. A. (2000), Pattern formation in the nearshore, In Proc. of River, Coastal and Estuarine Morphodynamics, pp. 141–162, Springer-Verlag, New York.

Houser, C., and B. Greenwood (2005), Hydrodynamics and sediment transport within the inner surf zone of a lacustrine multiple-barred nearshore, Marine Geology, 218, 27-63.

Hsu, T. –J., S. Elgar and R. T. Guza (2006), Wave-induced sediment transport and onshore sandbar migration, Coast. Eng., 53, 817-834.

Hurther, D., Michallet , H., & Gondran, X. (2007). Turbulent measurements in the surf zone suspension. J. Coastal Res., SI50, 297–301.


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Projet BARBEC


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Hurther, D. and U. Lemmin (2008), Improved turbulence profiling with field adapted acoustic Doppler velocimeters using a bi-frequency Doppler noise suppression method. Journal of Atmospheric and Oceanic Technology, 25(2), 452-463.

Klein, M. D., and H. M. Schuttelaars (2006), Morphodynamic evolution of double-barred beaches, J. Geophys. Res., 111, C06017, doi:10.1029/2005JC003155.

Komar, P. D. (1998), Beach processes and sedimentation, Prentice Hall. Kuriyama, Y. (1991), Investigation on cross-shore sediment transport rates and flow parameters in

the surf zone using field data, Report of the Port and Harbour Research Institute, 31(2), 3-58. Kuriyama, Y. (2009), Numerical model for bar migration at Hasaki, Japan, In Proc. Of Coastal

Dynamics’09, [CD-ROM], 12p. Mellor, G. (2003), The three-simensional current and surface wave equations, J. Phys. Oceanogr.,

33, 1978-1989. Mellor, G. (2008), Reply, J. Phys. Oceanogr., 38, 1351-1353. Marieu, V., P. Bonneton, D. L. Foster and F. Ardhuin (2008), Modeling of vortex ripple

morphodynamics, J. Geophys. Res., 113(C09007). Masselink, G. (2004), Formation and evolution of multiple intertidal bars on macrotidal beaches:

application of a morphodynamic model, Coastal Eng., 51, 713–730. Masselink, G., P. Russell, I. L. Turner, C. Blenkinsopp (2009), Net sediment transport and

morphological change in the swash zone of a high-energy sandy beach from swash event to tidal cycle time scales. Mar. Geol., 267, 18-35.

McNinch, J. E. (2004), Geological control in the nearshore: shore-oblique sandbars and shoreline erosional hotspots, Mid-Atlantic Bight, USA, Mar. Geol., 211, 121-141.

Michallet, H., Grasso, F., & Barthélemy, E. (2007), Long waves and beach profiles evolutions. J. Coastal Res., SI50, 221–225.

Michallet, H., M. Mory, & I. Piedra-Cueva (2009), Wave-induced pore pressure measurements near a coastal structure, J. Geophys. Res., 114, C06019.

Mignot, E., Hurther, D., Chassagneux, F.-X. and Barnoud, J.-M. (2009), A field study of the ripple vortex shedding process in the shoaling zone of a macro-tidal sandy beach. J. Coast. Res., SI 56, 1776 – 1780.

Pawka, S. (1983), Island shadows in wave directional spectra, J. Geophys. Res., 88, 2579-2591. Pawka, S. (1982), Wave directional characteristics on a partially sheltered coast. PhD thesis,

Scripps Inst. Of Oceanogr., Univ. of Calif., San Diego. Reniers, A. J. H. M., J. A. Roelvink, and E. B. Thornton (2004), Morphodynamic modeling of an

embayed beach under wave group forcing, J. Geophys. Res., 109, C01030, doi: 10.1029/2002JC001586.

Ruessink, B.G., M.G. Kleinhans, and P.G.L. Van den Beukel. (1998). Observations of swash under higly dissipative conditions. J. Geophysical Research, 103, 3111-3118.

Ruessink, B. G., and J. H. J. Terwindt (2000), The behaviour of nearshore bars on the time scale of years: a conceptual model, Mar. Geol., 163, 289–302.

Ruessink, B. G., G. Coco, R. Ranasinghe, and I. L. Turner (2007a), Coupled and noncoupled behavior of three-dimensional morphological patterns in a double sandbar system, J. Geophys. Res., 112, C07002, doi:10.1029/2006JC003799.

Ruessink B. G., Y. Kuriyama, A. J. H. M. Reniers, J. A. Roelvink and D. J. R. Walstra (2007b), Modeling cross-shore sandbar behavior on the time scale of weeks. Journal of Geophysical Research, 112, F03010, doi:10.1029/2006JF000730.

Ruessink, B. G., L. Pape and I. L. Turner (2009), Daily to interannual cross-shore sandbar migration: observations from a multiple sandbar system. Continental Shelf Research, 29, 1663-1677.

Ruggiero, P., P.D. Komar, W.G. McDougal, and R.A. Beach (1996), Extreme water levels, wave runup and coastal erosion. Paper presented at the 25th ICCE, Am. Soc. Of Civ. Eng., Orlando, Fla.

Ruggiero, P., P.D. Komar, J.J. Marra, W.G. McDougal, and R.A. Beach (2001), Wave runup, extreme water levels and the erosion of properties backing beaches. J. Coastal Res., 17, 407-419.

Ruggiero, P., R.A. Holman, and R.A. beach (2004). Wave run-up on a high-energy dissipative beach. J. Geophysical Research, 109, C06025, doi:10.1029/2003JC002160.

Sallenger, A.H. (2000), Storm impact scale for barrier islands. J. Coastal Res., 16, 890-895.


CHERCHEURS

EDITION 2010

Projet BARBEC


31/37

Schupp, C. A., J. E. McNinch and J. H. List (2006), Nearshore shore-oblique bars, gravel outcrops, and their correlation to shoreline change. Marine Geology, 233, 63-79.

Sénéchal, N., Ardhuin, F. (2008). ECORS Truc Vert’08 : a multi-institutional international nearshore field experiment. American Geophysical Union – Fall Meeting, 15-19 dec., San Francisco .

Short, A. D., and P. A. Hesp (1982), Wave, beach and dune interactions in South Eastern Australia, Mar. Geol., 48, 259–284.

Short, A. D. (1999), Handbook of Beach and Shoreface Morphodynamics, Wiley, Chichester. Smit, M. W. J., A. J. H. M. Reniers, B. G. Ruessink, and J. A. Roelvink (2008), The morphological

response of a nearshore double sandbar system to constant wave forcing, Coast. Eng., 55, 761–770.

Stive M.J.F., and A.J.H.M. Reniers (2003), Sandbars in motion. Science. 21, 1855-1856. Sonu, C. J. (1972), Field observation of nearshore circulation and meandering currents, J.

Geophys. Res., 77 (18), 3232–3247. Stockdon, H.F., R.A. Holman, P.A. Howd, and A.H. Sallenger Jr. (2006), Empirical parameterization

of set-up, swash, and runup. Coastal Engineering, 53, 573-588. Thornton, E. B., R. T. Humiston, and W. Birkemeier (1996), Bar/trough generation on a natural

beach, J. Geophys. Res., 101, 12,097-12,110. Thornton, E. B., J. H. MacMahan, and A. H. Sallenger Jr (2007), Rip currents, mega-cusps, and

eroding dunes, Mar. Geol., 240, 151–167. Tinker, J., T. O’Hare, G. Masselink, T. Butt and P. Russell (2009), A cross-shore suspended

sediment transport shape function parametrisation for natural beaches, Cont. Shelf Res., 29, 1948-1960.

Van Dongeren, A., N. Plant, A. Cohen, D. A. Roelvink (2008), Beach Wizard: Nearshore bathymetry estimation thourgh assimilation of model computations and remote observations, Coast. Eng., 55, 1016-1027.

Van Enckevort, I. M. J., B. G. Ruessink, G. Coco, K. Susuki, I. L. Turner, N. G. Plant, and R. A. Holman (2004), Observations of nearshore crescentic sandbars, J. Geophys. Res., 109, C06028, doi:10.1029/2003JC002214.

Van Maanen, B., P. J. De Ruiter, G. Coco, K. R. Bryan, and B. G. Ruessink (2008), Onshore sandbar migration at Tairua Beach (New Zealand): numerical simulations and field measurements, Marine Geology, 253, 99-106.

Wright, L. D., and A. D. Short (1984), Morphodynamic variability of surf zones and beaches: A synthesis, Mar. Geol., 56, 93–118.

7.2. BIOGRAPHIES / CV, RESUME

It must be noted that the 4 of the 5 permanent researchers who will dedicate more than 25% of their time to BARBEC in the next 3 years, and whose resume are attached, are at UMR EPOC and UMR LEGI and are considered as young researchers according to ANR criteria.


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EDITION 2010

Projet BARBEC


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CASTELLE Bruno, 32 year-old, 1 child (http://www.epoc.u-bordeaux.fr/indiv/Castelle/)

Past and present positions: • Since Oct. 2007: CR2/CNRS at UMR EPOC. Sandy Beach Morphodynamics • Feb 2007 – Sept 2007: Post-doctoral position at UMR EPOC. Wave-driven nearshore circulation

(ECORS, DGA/SHOM) • Jan 2005 – Jan 2007: Senior Research Assistant at Griffith Center for Coastal Management

(Griffith University, Australia). Wave climate and Gold Coast Shoreline Management Plan. • Oct 2004 – Dec 2004: Post-doctoral position at UMR EPOC: Modelling of sandy beach

morphodynamics • Sept 2001 – Sept 2004: PhD at UMR EPOC, Modelling of wave-dominated sandy beaches:

Application to the French Aquitanian Coast (PhD Supervisor: P. Bonneton) Other experiences: • Participation in national and international programs: PNEC ART7, PATOM, LEFE/IDAO (INSU),

Gold Coast Shoreline Management Plan, ECORS (DGA/SHOM), VULSACO (ANR), EPIGRAM (ANR), MODLIT (RELIEFS/INSU, DGA)

• (Co-)supervision of 4 1st year master students, 6 2nd year master students, 2 PhD students • Coordinator of Research Axe II in METHYS team (EPOC): Numerical Modelling and Physical

Analysis of hydro-sedimentary processes • Reviewer for Journal of Geophysical Research – Earth Surface, Journal of Geophysical Research

– Oceans, Marine Geology, Continental Shelf Research, Estuarine Coastal and Shelf Science, Ocean Engineering

• Member of 1 PhD Jury • Participation to 4 sandy beach field campaigns (PNEC 2001, BROADBEACH 2006, BISCA 2007,

ECORS 2008) Five most significant publications during the last 5 years: Castelle, B., Ruessink, B.G., Bonneton, P., Marieu, V., Bruneau, N., Price, T.D. (in press).

Coupling mechanisms in double sandbar systems, Part 1: Physical explanation and coupling patterns. Earth Surface Processes and Landforms.

Castelle, B., Ruessink, B.G., Bonneton, P., Marieu, V., Bruneau, N., Price, T.D. (in press). Coupling mechanisms in double sandbar systems, Part 2: impact on alongshore variability of inner-bar rip channels. Earth Surface Processes and Landforms

Castelle, B., Turner, I.L., Bertin, X., Tomlinson, R.B. (2009). Beach nourishments at Coolangatta Bay over the period 1987-2005 : impacts and lessons. Coastal Engineering, 56, 940-950

Castelle B., Bonneton P., Dupuis H., Sénéchal N. (2007). Double bar beach dynamics on the high-energy meso-macrotidal French Aquitanian coast: a review. Marine Geology, 245, 141-159.

Castelle, B., Bonneton, P., Sénéchal, N., Dupuis, H., Butel, R. and Michel, D. (2006). Dynamics of wave-induced currents over a multi-barred beach on the Aquitanian coast. Continental Shelf Research 26, 113-131.

Number of publication in journals: 27 (14 as 1st author) Number of international conference proceedings: 12 (6 as 1st author)


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EDITION 2010

Projet BARBEC


33/37

Nadia Sénéchal, 33 year-old, 2 children Past and present positions: • Since Oct. 2004: Assistant Professor at University Bordeaux 1/EPOC, coastal morphodynamics

and physical processes • Oct.2003-Aug. 2004: Lecturer at University Bordeaux 1/EPOC. • Oct. 2000 – Oct. 2003: PhD at UMR EPOC, Wave transformation over complex bathymetry in

the surf zone. (PhD supervisors: H. Dupuis, P Bonneton).

Experience in coordination and managing: • HDR (Habilitation à Diriger des Recherché) since 2009. • Principal investigator of an international multi-institutional nearshore field experiment (ECORS

Truc Vert’08, 6 countries and 16 teams involved). • Supervisor of 2 post-doctorates. • (Co-) supervisor of 1 PhD and 5 2nd year master students and 7 1st year master students. International Activities

a. Short stays abroad • Feb. – June 2009. Invited scientist at the National Institute of water and Atmospheric Research

(New Zealand). Contact person: Dr Giovanni Coco. • Dec. 2008 (1 week): Invited oral presentation at the AGU Fall Meeting, session Nearshore

processes. Contact person: Dr. Bret M. Webb • Dec. 2008 (1 week). Visiting scientist at Naval Postgraduate School (USA). Contact person: Dr.

Jamie MacMahan. b. Participation to scientific committee and review

• Member of the scientific committee of the ‘Second international Geography Symposium – Geomed2010 Mediterranean Environment’.

• Member of the scientific committee of the 10th International Coastal Symposium. • Reviewer for Journal of Geophysical Research-Ocean, Continental Shelf Research,

Environmental Modelling and Software, Journal of Coastal Research, Limnology and Oceanography.

Other experiences: • Participation in national and international programs: PNEC ART7, PATOM, LEFE/IDAO (INSU),

ECORS (DGA/SHOM), VULSACO (ANR), MODLIT (RELIEFS/INSU, DGA) • Member of 1 PhD Jury • Participation to 7 sandy beach field campaigns (4 as principal investigator) Five most significant publications during the last 5 years: Sénéchal N., Gouriou T., Castelle B., Parisot J.P., Capo S., Bujan S., Howa H. (2009).

Morphodynamic response of a meso- to macro-tidal intermediate beach based on a long-term data-set, Geomorphology, 107, 263-274.

Dehouck, A., Dupuis, H., Sénéchal, N. (2009). Pocket beach hydrodynamics: the example of four macrotidal beaches, Brittany (France). Marine Geology. 206, 1-17.

Emmanuel, I., Parisot, J.P., Michallet, H., Barthélémy, E., Sénéchal, N. (2009). Beach response to cumulative rare events. Journal of Coastal Research, SI 56, 1766-1770.

Almar R., Coco G., Bryan K.R., Huntley D.A., Short A.D., Sénéchal N. (2008). Video observations of beach cusp morphodynamics, Marine Geology, 254, 216-223.

Almar, R., Castelle, B., Ruessink, G., Sénéchal, N., Bonneton, P., Marieu, V. (2009). High-frequency video observation of a double sandbar system under high-energy wave forcing. Journal of Coastal Research, SI 56, 1706-1710.



CHERCHEURS

EDITION 2010

Projet BARBEC


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MARIEU Vincent, 33 year-old, 1 child Past and present positions: • Since Dec. 2008: IR2/CNRS at UMR 5805 EPOC. Numerical modelling and scientific computing • Oct 2007 – Sept 2008: Post-doctoral position at UMR EPOC. Video acquisition and PIV

techniques for detection of wave/current velocity during ECORS field experiment (DGA/SHOM) • Apr 2005 – Sept 2007: PhD at UMR 5805 EPOC. Modelling of vortex ripple dynamics (PhD

Supervisor: P. Bonneton) • Oct 2004 – Sept 2007 : Position at CLS, Toulouse : Calibration and validation of altimetry data

(Topex/Poseidon, Jason, ERS-2, Envisat, Geosat) • Sept 2002 – Sept 2004 : Fixed-term contracts at UMR 5805 EPOC : Wave transformation in the

surf zone. Classification of Arcachon lagoon soils using SPOT 5 remote sensing images. • Sept 2000 – Apr 2002 : Position at Samtech, Liège (Belgium) : Improvement of the finite

element model Samcef for axi-symmetric structures Other experiences: • Participation in national and international programs: ECORS (DGA/SHOM), EPIGRAM (ANR),

MODLIT (RELIEFS/INSU, DGA) • (Co-)supervision of 5 master students • Participation to ECORS sandy beach field campaign (SHOM/DGA, 2008), in charge of the video

system Five most significant publications during the last 5 years: Castelle, B., Ruessink, B.G., Bonneton, P., Marieu, V., Bruneau, N., Price, T.D. (in press) Coupling

mechanisms in double sandbar systems, Part 1: Physical explanation and coupling patterns. Earth Surface Processes and Landforms.

Castelle, B., Ruessink, B.G., Bonneton, P., Marieu, V., Bruneau, N., Price, T.D. (in press) Coupling mechanisms in double sandbar systems, Part 2: impact on alongshore variability of inner-bar rip channels. Earth Surface Processes and Landforms

Almar, R., Castelle, B., Ruessink, G., Sénéchal, N., Bonneton, P., Marieu, V. (2009). High-frequency video observation of a double sandbar system under high-energy wave forcing. Journal of Coastal Research, SI 56, 1706-1710.

Marieu, V., Bonneton, P., Foster, D. L., Ardhuin F. (2008). Modeling of vortex ripples morphodynamics. Journal of Geophysical Research, 113, C09007, doi:10.1029/2007JC004659.

Bonneton, P., Marieu, V., Dupuis, H., Sénéchal, N., Castelle, B. (2006). Wave transformation and energy dissipation in the surf zone : Comparison between a non-linear model and field data. Journal of Coastal Research, SI 39, P. 329-333.

Number of publication in journals: 11 (2 as 1st author) Number of international conference proceedings: 7


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EDITION 2010

Projet BARBEC


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MICHALLET Hervé, 41 year-old, 2 children

Past and present positions: • Since Oct. 1999: CR/CNRS (section 10) at UMR LEGI. Sandy Beach Morphodynamics • 1999: Post-doctoral position at UMR LEGI: Modelling cohesive sediment settling in a diffusive

turbulence. • 1998: Associate Lecturer at UJF Grenoble: Numerical study of generalized solitary waves. • 1997: Post-doctoral position at Center for Water Research, Univ. of Western Australia: Mixing

induced by long internal waves breaking on slopes • 1996: Post-doctoral position at UMR LEGI: Dynamics of long internal waves • Sept 1992 – Dec 1995: PhD at UMR LEGI, Theoretical and experimental study of interfacial

solitary waves (PhD Supervisor: E. Barthélemy) Other experiences: • Participation in national and international programs: MORSE (EC), COSINUS (EC), LIMAS (EC),

PNEC ART7, PATOM, LEFE/IDAO (INSU), ECORS (DGA/SHOM), MODLIT (RELIEFS/INSU, DGA), Beachmed-e (EC-INTERREG-IIIc), LITEAU-II, (MEDD)

• (Co-)supervision of 8 2nd year master students, 3 PhD students, 4 post-docs • Coordinator of LEFE/IDAO “Breaking zone hydrodynamics” project • Head of team “Houle” from LEGI since 2007 • Reviewer for Eur. J. Mech./B Fluids, Phys. Fluids, ASCE J. Waterway, Port, Coastal and Ocean

Engineering, Geophys. Res. Letter, Water Resources Res. • Member of 4 PhD Juries • Participation to 4 sandy beach field campaigns (LIMAS 2002-2003, BISCA 2007, ECORS 2008) Five most significant publications during the last 5 years: Camassa, R., Choi, W., Michallet, H., P.-O. Rusås, & Sveen, J.K. 2006. On the realm of validity of

strongly nonlinear asymptotic approximations for internal waves. J. Fluid Mech. 549, 1-23. Grasso, F., H. Michallet, E. Barthelemy, & R. Certain (2009), Physical modeling of intermediate

cross-shore beach morphology: transients and equilibrium states, J. Geophys. Res., 114, C09001.

Gratiot, N., Michallet, H., & Mory, M. 2005. On the determination of the settling flux of cohesive sediments in a turbulent fluid. J. Geophys. Res., 110, C06004.

Govender, K., H. Michallet, M.J. Alport, U. Pillay, G.P. Mocke, & M. Mory (2009). Video DCIV measurements of mass and momentum fluxes and kinetic energies in laboratory waves breaking over a bar, Coastal Engineering, 56 (8), 876-885.

Michallet, H., M. Mory, & I. Piedra-Cueva (2009), Wave-induced pore pressure measurements near a coastal structure, J. Geophys. Res., 114, C06019.



CHERCHEURS

EDITION 2010

Projet BARBEC


36/37

CHAUCHAT Julien, 31 year-old, 2 children

Past and present positions: • Since Sept. 2009: Assistant Professor at INP Grenoble - UMR LEGI. Sediment Transport

Modelling. • April 2008 - Sept. 2009: Post-doctoral position at UMR IUSTI - GEP Team (Marseille),

Development of a 3D two-phase numerical model for bed-load in laminar shearing flows. • Jul. 2007 – Jan. 2008: Post-doctoral position at UMR M2C (Caen), Use of rheometric data for

the improvement of sediment transport two-phase flow model. • Jun. 2003 – Jul. 2007: PhD at UMR M2C (Caen): Contribution to two-phase flow modelling for

sediment transport in estuarine and coastal zones. (PhD Supervisors: S. Guillou and K. D. Nguyen)

Other experiences: • Collaboration and participation in projects: ANR Dunes (E. Guazzelli, IUSTI/GEP), CETMEF (D.

Pham Van Bang). • (Co-)supervision of 1 1st year master student and 1 post-doc • Active member of the GDR Transport Solide Naturel (Natural Solid Transport). • Reviewer for Journal of Geophysical Research-Earth Surface, Journal of Fluid Mechanics and

Journal of Hydraulic Engineering. Five most significant publications during the last 5 years: Chauchat J. and M. Médale (in press), A 3D numerical model for incompressible two-phase flow of

a granular bed submitted to a laminar shearing flow. Computer Methods in Applied Mechanics and Engineering, doi:10.1016/j.cma.2009.07.007.

Nguyen K. D., S. Guillou, J. Chauchat and N. Barbry (2009,) A two-phase numerical model for suspended-sediment transport in estuaries. Advances in Water Resources, 32(8), 1187-1196, doi: 10.1016/j.advwatres.2009.04.001.

Chauchat J., S. Guillou, N. Barbry and K. D. Nguyen (2009). Simulation of the turbidity maximum in the Seine estuary with a two-phase flow model. C.R. Geosc., 341(7), 505-512, doi: 10.1016/j.crte.2009.04.002.

Chauchat J. and S. Guillou (2008), On turbulence closures for two-phase sediment-laden flow models, J. Geophys. Res. – Oceans, 113, C11017, doi :10.1029/2007JC004708.



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EDITION 2010

Projet BARBEC


37/37

7.3. IMPLICATION DES PERSONNES DANS D’AUTRES CONTRATS / INVOLVEMENT OF PROJECT PARTICPANTS TO OTHER GRANTS, CONTRACTS, ETC…

The investigators involved in BARBEC are already involved in various other projects. Noteworthy, most of these projects will finish in 2010. In addition, there is no project currently in preparation. Accordingly, BARBEC will be a major priority of the involved investigators within the next few years.

Part. Nom de la personne

participant au projet

Personne. mois

Intitulé de l’appel à projets

Source de financement

Montant attribué

Titre du projet Nom du coordinateur

Date début &

Date fin

EPOC

Bruno Castelle

18 (50%) RELIEFS/INSU-SHOM MODLIT P. Bonneton 2007-2010

2.5 (7%) ANR and LEFE-IDAO EPIGRAM Y. Morel 2008-2011

7 (20%) ANR VULSACO D. Idier 2007-2010

Nadia Sénéchal

2 (11%) LITEAU BARCASUD L. Goeldner Gianella

2010-2012

4.5 (75%) SYSTER/INSU

Processus hydro-sédimentaire et dynamique des plages sableuses

N. Sénéchal 2010-2010

Philippe Bonneton

0.5(1,5%) ANR and LEFE-IDAO EPIGRAM Y. Morel 2008-2011

2.4(7%) ANR MATHOCEAN D. Lannes 2009-2011

3(8%) ANR MISEEVA C. Vinchon 2008-2010

4(11%) RELIEFS/INSU-SHOM MODLIT P. Bonneton 2008-2010

LEGI

Julien Chauchat

24(66%) ANR DUNES F. Charru 2007-2010

Hervé Michallet

9(25%) RELIEFS/INSU-SHOM MODLIT P.Bonneton 2008-2010

1(8%) SYSTER/INSU

Processus hydro-sédimentaire et dynamique des plages sableuses

N. Sénéchal 2010-2010

SOMMAIRE - u-bordeaux.fr€¦ · à barre(s) dominées par l’action de la houle Titre du projet...

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