Éditeur(s) : HAL CCSD
Résumé : International audience
Les plages sableuses constituent une frontière mobile et poreuse entre l'océan ouvert et la terre. La compréhension de la circulation dans les nappes de plage est importante pour une variété de processus physiques, biologiques et chimiques. On cherche à caractériser in-situ la dynamique souterraine sous la zone de swash. Le site atelier est la plage microtidale de Rousty (Camargue, France). L'étude, réalisée sur 48h les 13 et 14 décembre 2014, fait partie d'une plus grande campagne de mesure visant à caractériser la réponse hydro-morphologique de la plage de Rousty à une saison hivernale. La période présentée ici correspond à la phase de déclin d'une tempête modérée. La stratégie retenue dans le cadre de ce projet a été de déployer un réseau de15 capteurs de pression enterrés sous la zone de swash. Les caractéristiques des vagues incidentes, à la fois au large et dans la zone de surf interne, ont été mesurées conjointement à l'utilisation d'un LiDAR terrestre haute fréquence permettant de suivre la surface libre et l'évolution du lit sableux à haute fréquence sur la zone de swash. L'analyse des données moyennées dans le temps a mis en évidence la présence d'un schéma de circulation relativement robuste sous la zone de swash, qui se décale vers le large en suivant la descente du niveau moyen et la diminution de l'activité des vagues. La tendancedominante est un écoulement vers le large, avec une intensité maximale de l'ordre de 0.1mm/s modulé par des infiltrations et exfiltrations dans les parties hautes et basses de la zone de swash, respectivement. L'analyse haute fréquence à des événements de swash sélectionnés ont mis en évidence uncycle souterrain caractéristique.
XIV èmes Journées Nationales Génie Côtier – Génie Civil
toulon, France

hal-01357778
https://hal.archives-ouvertes.fr/hal-01357778

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This manuscript reports on a novel field experiment carried out on a microtidal beach in Camargue, France. For the first time in the field, a comprehensive description of the groundwater dynamics under sandy beach swash zone is presented. A cross-shore network of 15 buried pressure sensors is combined with terrestrial LiDAR measurements to study the swash-groundwater dynamics. The presented data focus on the decay of a moderate storm which allows to monitor the evolution of the groundwater pressure field in response to the retreat of the swash zone. Both horizontal and vertical head gradients are measured within the porous sand soil to estimate the groundwater flow field using Darcy’s law. Time-averaged analysis demonstrates the presence of a rather consistent groundwater circulation pattern under the swash zone, shifting offshore with the swash zone. The main tendency is an offshore directed flow, with infiltration/exfiltration in the upper/lower parts of the swash zone. Time-resolved analysis highlights the typical groundwater response to swash events which consists mainly of an overall infiltration flow during the bed inundation by the swash tongue, a seaward flow during the swash retreat and, for long backwash events, a localized exfiltration flow under the next incoming uprush.
ISSN: 0309-1708

hal-01412450
https://hal.archives-ouvertes.fr/hal-01412450
DOI : 10.1016/j.advwatres.2016.09.009

Éditeur(s) : HAL CCSD
Résumé : International audience
This communication reports on a field experiment carried out on a microtidal beach in Camargue, France. The analysis is built on the initial work presented by Sous et al. (2016) on swash-groundwater dynamics. The analysis of a cross-shore network of buried pressure sensors allows to monitor the watertable dynamics over the full 2013-2014 winter season. The pressure head gradients are observed to be primarily seaward, forced by a higher level at the landward boundary. The groundwater flux is driven by the relative fluctuations of Still Water Level and inland elevations. Rain and tides have a little effect. A nearly isolated groundwater circulation is driven by wave activity below the swash zone whatever the overall watertable gradient. Estimations of beach groundwater discharge over the Gulf of Beauduc reveal the importance of beach groundwater in the exchanges between coastal aquifer and open sea.
Coastal Dynamics 2017
Helsingor, Denmark

hal-01562908
https://hal.archives-ouvertes.fr/hal-01562908

Éditeur(s) : HAL CCSD Coastal Education and Research Foundation, Inc.
Résumé : International audience
Morphodynamics of sandy, macrotidal, embayed beaches is complex because of the numerous physical processes interacting at the same location over a wide range of temporal scales. As most of these processes are controlled by beach morphology, dynamic feedbacks are generally observed between hydro- and morphodynamics. Investigating short-term processes is essential in order to improve long term morphological prediction. A key question is to understand how beach slope reacts to forcing conditions, in particular the response time of the beach profile, how long the transient state lasts. This study deals with the spatial and temporal responses of beach morphology to varying incident conditions. Here we report main observations, preliminary results and on-going investigations on the DYNATREZ1 field campaign, which was conducted in the framework of the National Observation Service Dynalit. Beach profiles are shown to adapt rapidly to forcing conditions, within two days, with more intense variations observed in the high tide swash zone. The presence of infragravity waves and their dissipation on the beach is highlighted. It is likely that the very large variability in beach slope observed over a single neapspring cycle is responsible for the accordingly large variability in wave skewness, asymmetry and breaking processes, and thus in sediment fluxes and morphological changes.
ICS 2016 Sydney
Sydney, Australia

hal-01254465
https://hal.archives-ouvertes.fr/hal-01254465
DOI : 10.2112/SI75-075.1

Éditeur(s) : HAL CCSD Editions Paralia CFL
Résumé : The wave-dominated beach barrier of Villeneuve-Lès-Maguelone extends between Palavas and Frontignan (Gul f of Lions, northernmost Me diterranean Sea), along a slightly natural sandy protected area char acterized by typical and well-expressed morphologies. In the nearshore, the sea bottom shows one or two approximately rectilinear sand bars. In 2010-2011, we pe rformed a 6 month-long monitoring (autumn 2010/late spring 2011) of a 500 meter-long se gment along this sand barrier. We used RTK D-GPS offering centimeter resolution to acquire sets of elevation data on the beach and the upper shoreface. The study is innovative because a full morphologic monitoring was performed each time the wave/ wind conditions changed significantly. These changes were tracked in real-time thanks to a set of hydrodynamic equipments deployed at sea, including well-known DREAL buoys. We identify from well- documented data: (1) a beach reconstruction cycle at the shorelin e after a moderate storm event (wave height at 3-4 m) and (2) how a sand bar in the nearshore migrates to the shoreline and drives the shoreline shift.
ISSN: 1760-8716

hal-00854402
https://hal.archives-ouvertes.fr/hal-00854402
DOI : 10.5150/jngcgc.2012.023-C