Nadia Senechal

ON THE IMPACT OF A SERIES OF SEVERE STORMS ON A DOUBLE-BARRED SANDY COAST: DUNE EROSION AND MEGACUPS EMBAYMENTS

The winter of 2013/2014 was outstanding in terms of the available energy to move sediment and caused large-scale unprecedented erosion of the Gironde coast (France), comprising the onset of megacusp embayments cutting the dune with a typical alongshore and cross-shore lengthscale of O (100 m) and O(10 m), and a dune erosion scarp height often exceeding 10 m. Megacusps are found to be coupled to the outer crescentic sandbar and triggered by the outstandingly high-energy, long-period and normally-incident storm wave event Hercules on January 6-7. Our observations indicate that both the antecedent outer sandbar morphology and storm wave characteristics, including period and angle of incidence, govern patterns of beach and dune erosion along open multiple-barred sandy coasts during severe storms.