This communication reports on a field experiments carried out on the Ouano reef barrier, New Caledonia. The analysis is based on a cross-shore network of pressure sensors deployed across the reef flat and within the lagoon. Confirming existing observations, the measurements show the strong filtering role of the reef barrier on the incoming wave energy The swell energy is dissipated and transferred toward lower frequencies, including the so-called infragravity (IG) and very low frequency (VLF) waves. During energetic event (Hs=4.2m), IG and VLF significant wave heights on the reef flat are observed to reach 1.2 and 0.7m, respectively. A variety of long waves modes are observed on the reef, combining standing and progressive-dissipative modes. In any cases, the VLF and IG waves are much more developed over and close to the reef flat than further inside the lagoon.

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.

The purpose of this research work is to study the effect of specific surface s, the fluid–solid contact surface per volume unit, on the wave energy dissipation by porous structures consisting in dense arrays of emergent vertical cylinders. Experiments have been carried out in a 10 m long wave flume. Three cylinder diameters D are considered in order to study the effects of the specific surface while keeping the porosity constant. In a first series, the length of the porous zone is kept constant for the three cylinder diameters tested. The measurements, which include various wave teepness conditions, demonstrate the role of specific surface s on both wave attenuation and interference processes. The larger the specific surface is, the stronger the wave damping is. Damping is found to be almost proportional to 1/D when laminar, turbulent and inertial effects are of same order. Results are compared to numerical calculations based on either a constant rate of wave damping within the porous medium per unit wavelength or a quadratic damping developed using a force expression based on the work of [26]. This latter model, calibrated with drag and inertia coefficients, shows a good agreement with measurements. In a second series, both porous length and water depth are kept proportional to the cylinder diameter for the three diameters. Scale effects are then discussed and underline the importance of the flow regime within the porous medium.

This work aims to better understand the physical processes governing the wave propagation in a vertically shearedcurrent and the resulting nearshore circulation patterns. It is based on a high resolution hydro-morphodynamic fieldcampaign, ROUSTY2014, collecting a comprehensive hydro-morphodynamical dataset during a full winter season.The overall analysis highlights three main circulation patterns, largely controled by the bathymetric features and byco-working or competing wind and waves forcings. Regarding the vertical structuration of the circulation, most of fieldobservations shown seaward directed circulation with onshore component close to the air/sea surface whose intensityvaries according to incoming wave conditions. Forth, vertical shear increase when breaking happen close to sensorlocation and orientation of mean circulation depend on wind direction.

Propagation of water waves in coastal zones is mainly affected by the influence of currents and bathymetry variations. Models describing wave propagation in coastal zones are often based on the numerical solution of theMild Slope equation (Kirby, 1984). In this work, an extension of this equation is derived, taking into account the linear variation of the current with depth,which results in a constant horizontal vorticity, slowly varying horizontally, within the background current field. The present approach is based on the asymptotic expansion of the depth-integrated lagrangian, assuming the linear variation of the background currentwith depth. With the aid of selected examples the role of this horizontal vorticity, associated with the assumed background current velocity profile, is then illustrated and emphasized, demonstrating its effect on the propagation of water waves in coastal areas.

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.

Sloshing tests are performed on a rectangular tank filled with bottom-mounted vertical cylinders. The cylinders, in regular staggered arrangements, are first emergent then shortened to be fully submerged. Different porosities are achieved by varying the number of cylinders. The tank undergoes forced horizontal motion at frequencies around the natural frequency of the first sloshing mode. The free surface elevation and the hydrodynamic loads are measured. When resonance is attained, it means that the wavelength is exactly twice the length of the tank and that this wavelength and the sloshing frequency are related by a specific dispersion equation. From literature several theoretical dispersion equations are proposed in the emergent and submerged cases. New dispersion equations are offered based on the cylinder cluster being considered as an anisotropic porous medium. The latter ones provide the best agreement with the experimental results.