Impact of climate change on beach erosion in the Basque Coast (NE Spain)

Abstract

In the present study, we addressed the potential impact of climate change on coastal erosion along the 28 beaches of the Basque Coast (150 km). A shoreline evolution model including cross-shore and alongshore sediment transport formulations, short- and long-term processes and hard structure treatment is developed. The historical analysis of the shoreline evolution is performed by forcing the model with waves and storm surges from reanalysis data, and with tides from in situ water level measurements. The model is calibrated and validated by using morphological information derived from the KostaSystem coastal video monitoring system. The analysis of the future impact of climate change on the sandy beaches is carried out using two sea level projections (RCP 4.5 and RCP 8.5 scenarios) and their confidence intervals, combined with synthetic wave series that allowed a probabilistic fashion outcome. The results show that the shoreline mean erosion due to both short- and long-term processes is in the range of 10-45 m under the RCP 4.5 scenario and 14-66 m under RCP 8.5 by the year 2100, which indicate the great vulnerability of the beaches of the Basque Coast. Still, the response of the studied systems is highly variable, owing to the intrinsic characteristic of each site. This result points to the difficulty of taking general management measures and highlights the need for management strategies at the local level.