Dynamic of a meso to macro-tidal double barred beach: inner bar response

Three years of daily video images on the intermediate double-barred open beach Biscarrosse in a meso-to macrotidal environment (South-West, France) permit to study the dynamic of an inner bar system under high energetic conditions. Morphological changes were monitored through low-tide daily video imagery from May 2007 to April 2010. The imagery were classified according a visual morphological classification. We observed that despite high energetic conditions (mean annual Hs was 1.66m), the inner bar exhibited mostly complex 3D patterns, TBR and LTT states being the most frequently observed states. The results also indicated that both up-state and down-state transitions were dependent on the previous beach state and that no 'jump' to the highest beach state was observed. The associated weighted mean value of SI for Biscarrosse are very similar to the one observed for Narrabeen Beach (in a micro-tidal environment) but higher than the one observed at Truc Vert beach, situated about 30kms northward of Biscarrosse. These observations raise the question of possible slow and long-term adjustment of the beach to wave conditions.