Climate change impact on waves and longshore sediment flux of the Aquitanian coast

Coastal sediment dynamics are controlled by a set of hydrodynamics factors likely to be modified by climate change. Waves are a dominant factor in the dynamics of the Aquitanian coast. In order to analyse the climate change impact, we set up a wave model and carried out simulations for present (1961-2000) and future (2061-2100) climates. The analysis of future wave conditions in the Bay of Biscay highlights a generalized decrease of wave heights and a clockwise rotation of summer waves and winter swell, relatively to present climate. Along the Aquitanian coast, the wave height decrease is also significant. However, bathymetric refraction induces a reduction of the clockwise rotation, particularly in winter swell. The calculation of longshore sediment fluxes at the Biscarrosse beach, using empirical formulae, shows that the projected wave changes would result in a decrease of longshore fluxes (up to 10 %). This decrease is associated with wave height decrease in the coastal area. Finally, the listing of the uncertainties related to the different steps of this study suggests potential tracks to improve the future sediment fluxes assessment, for instance by considering a larger number of climate models or by modelling waves in the breaking zone.