Wave transformation on a microtidal barred beach (Sète, France)

An instrumented field study of the cross-shore evolution of incident waves was conducted on the shoreface of a gentle sloping microtidal barred-beach (Sète, France). A spectral analysis of typical hydrodynamic conditions (storm, waning storm and fair-weather) was performed from a series of pressure sensor data and synchronized horizontal velocities and pressure data. Results highlight the role of sedimentary bars in the dissipation and the spectral redistribution of incident energy. At the approach to the coast, the bars act like regulators of energy arriving at the shore and non-linear energy transfers are observed from the gravity to infragravity domain, during breaking or non-breaking situations. Consequently, the ratio of infragravity to gravity wave spectral energy density increases shoreward as significant wave height decreases. The study of incident wave reflection shows that during storm conditions, no significant wave reflection is observed and the beach can be classified as dissipative. During fair-weather conditions, a significant reflection from the beachface is observed but the bars do not play any role in this reflection.