Towards the Development of a Storm Erosion EWS for the French Aquitaine Coast

Alexandre Nicolae Lerma (1) , Thomas Bulteau (1) , Héloïse Muller (1) , Clément Decarsin , Raphaël Gillet , François Paris (1) , Mélanie Biausque (2) , Nadia Senechal (2) , Bruno Castelle (2)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 EPOC - Environnements et Paléoenvironnements OCéaniques

Towards the development of a storm erosion EWS for the French Aquitanian coast. The 230-km long Aquitaine sandy coast, SW France, is vulnerable to erosion hazards owing to its full exposure to Atlantic storm waves. Since 2015, the Observatory of the Aquitaine Coast and several academic and local partners have developed a network to better survey and forecast storm-driven morphological changes at regional scale. This paper presents the implementation of an early warning system (EWS) with the primary objective to alert the network members 2-3 days ahead in order to perform pre-storm and post-storm surveys. Regional bulletins are edited to identify the most exposed coastal sections. At local scale, tests are realized on two morphological indicators used to forecast qualitatively and quantitatively the likelihood of beach and dune erosion. The two indicators (namely the Collision Regime Indicator, CRI, and the Eroded Volume Indicator, EVI, were calibrated and further validated at two nearby beaches where extensive morphological data are collected regularly: bimonthly surveys from 2009 to 2015 at Truc Vert beach and surveys every 2 to 7 days during the winters since 2015 at Biscarrosse beach. Results indicate promising performance, with the CRI predicting collision regime when front dune erosion was indeed observed, and the EVI predicting fairly accurate eroded sediment volume on cross shore beach profile. Nevertheless, more extensive validation of the CRI and EVI is needed to extend the indicators to the entire Aquitaine coast and for a wide range single storms and storm clusters.

Domaines: Géomorphologie

Alexandre Nicolae Lerma, Thomas Bulteau, Héloïse Muller, Clément Decarsin, Raphaël Gillet, et al.. Towards the Development of a Storm Erosion EWS for the French Aquitaine Coast. Journal of Coastal Research, 2018, SI 85, 5 p. ⟨10.2112/SI85-001.1⟩. ⟨hal-01719953⟩