A conceptual morphodynamic model including storm impacts for microtidal barred beaches

International audienceThis paper introduces the main results of a large dataset concerning the impacts of storm events and recovery period on a microtidal double barred beach of the NW Mediterranean Sea (Lido de Sète, Gulf of Lions, South France). The objective is to discuss of the key control parameters among both the forcing conditions and the morphological state of the bar/beach system. Our new dataset (high frequency topo-bathymetries and ARGUS video) clearly demonstrates the importance of the morphological variations in bar pattern along the beach. The steady alongshore difference in the outer bar depth and distance (maintained by the N.O.M. variations) has a concrete influence on the modal inner bar state and sensitivity of bar and beach profile face to the erosive processes

Morphodynamique de la plage de Sète sous l'incidence d'une houle de tempête: expérimentation et modélisation

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Modélisation de la dynamique de sédimentaire de la plage de Sète. Le rechargement sédimentaire des barres sableuses sous-marines, une solution pour lutter contre l'érosion ?

International audienceno abstrac

Morphodynamique de la plage de Sète sous l'incidence d'une houle de tempête: expérimentation et modélisation

International audienceno abstrac

Modélisation de la dynamique de sédimentaire de la plage de Sète. Le rechargement sédimentaire des barres sableuses sous-marines, une solution pour lutter contre l'érosion ?

International audienceno abstrac

Déformation de la houle pendant une période de tempête sur une plage sableuse à barres: Expérimentation et modélisation

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Caractérisation hydrodynamique sur un littoral à barres festonnées du golfe du Lion (Leucate, France): mesures in-situ et modélisation

L'objet de cette communication est la caractérisation hydrodynamique d'un système double de barres festonnées en milieu microtidal. Pour comprendre l'évolution du littoral de Leucate-Plage (Languedoc-Roussillon, France), une campagne de mesures hydrodynamiques in-situ a été réalisée, puis complétée par une étude à l'aide du modèle numérique Quasi-3D SHORECIRC de la houle et des courants dans des conditions plus dynamiques non observées. Les mesures in-situ ont permis de réaliser des cartes de circulation hydrodynamique. Les données modélisées donnent des résultats proches de la réalité en terme d'intensité dans la zone de déferlement, en termes de direction et d'intensité dans la zone deshoaling. This paper deals with the hydrodynamic study of a microtidal double crescentic bars system. To understand the coastal evolution of Leucate-Plage (Languedoc- Roussillon, France), a hydrodynamic survey has been realized, added to numerical studies with Q-3D SHORECIRC model for more dynamic unobserved conditions. Hydrodynamic maps with observed data have been produced. The numeric hydrodynamic maps show good analogies in the shoaling zone but some difference in the surf zone

Net offshore bar migration variability at a regional scale: Inter-site comparison (Languedoc-Roussillon, France)

International audienceThe Languedoc-Roussillon coastline is a large unit stretching out over 200 km of sandy low coast in a wave dominated environment. The nearshore is characterized by a quasi continuous system of double sandbar that displays a wide range of typology. The interannual sandbar dynamic was investigated using 2D bathymetric profiles and 3D LiDAR imagery. This study has allowed determining the sandbar systems affected by the Net Offshore Migration (NOM). At a regional scale, conditions necessary to NOM development depend on the sandbar morphologies (crescentic or straight), the wave energy and the associated coastal orientation (low or high energy, sheltered area), the coastal structures (harbour and coastal defences) and the nearshore sedimentary budget. The areas where the NOM occurs show cycle dynamic differences. This regional inter-site comparison highlights that nearshore morphology and bar parameters seem to influence the nearshore bar behaviour. Interaction between the nearshore slope, width of the bar zone and the migration rate control the NOM duration. The sandbar volume and the regional wave climate influence also the migration rate of the system. On the Languedoc-Roussillon coast, the sediment grain size does not appear to influence the seaward bar migration

Hydrodynamique à l'échelle événementielle d'un système de barres festonnées dans le golfe du Lion (Leucate-plage, Aude)

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Beachrocks and lithified barriers in the Gulf of Lions (western Mediterranean Sea) as new markers of the last sea-level rise

The Gulf of Lions shelf (southern part of the French Mediterranean coast) displays several occurrences of beachrocks, thus offering an exceptional opportunity to determine the stages of the last marine transgression. These beachrocks crop out especially on the outer shelf and near the modern shoreline. In addition, several other exposures are located on the inner shelf between 10 m and 25 m). The absence of exposure on the middle shelf (water depths of 25 to 90 m) is probably related to a higher rate of sea-level rise. Most of the beachrocks occur at the top of two or three parallel and contiguous barriers. The seaward barriers are generally less lithified than the inner barriers. Each barrier displays an asymmetric profile, the seaward slope being more accentuated. This gently-dipping landward slope forms part of the outer trough resulting from resuspension due to enhanced turbulence at the barrier toe. Almost all of these beachrocks are coarse quartz-rich sandstones and conglomerates, whose large pore space has been first filled by magnesian calcite (ca 11 mol.% MgCO3), which predominantly fills the voids. Secondary sparites or microsparites, also composed of high-magnesian calcite, may develop locally in the last remaining voids. Finally, more rarely and very locally (for example, Pierres de Sète), a late-stage cementation of low-magnesian calcite is observed which expresses a brief episode of influence from a nearby freshwater groundwater table. δ18O and δ13C values reflect the relative geochemical homogeneity of these Gulf of Lions beachrocks. However, they are quite distinct from other marine cements, and in particular, those of the eastern Mediterranean, expressing lower temperatures and a lack of influence of dissolved carbon linked to terrigenous fluxes. Based on the radiocarbon ages of these calcitic cements, this study proposes new index points on sea-level positions in the Gulf of Lions from -95 to 108 m to -0.3 m water depths, between ca 18,583 a cal BP and 633 a cal BP