Dune recovery after storm erosion on a high-energy beach: Vougot Beach, Brittany (France)

On 10th March 2008, the high energy storm Johanna hit the French Atlantic coast, generating severe dune erosion on Vougot Beach (Brittany, France). In this paper, the recovery of the dune of Vougot Beach is analysed through a survey of morphological changes and hydrodynamic conditions. Data collection focused on the period immediately following storm Johanna until July 2010, i.e. over two and a half years. Results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic. Dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre- and post-storm dune toe, and reducing impacts of the storm surge. Dune recovery started in the month following the storm event and is still ongoing. It is characterised by the construction of “secondary” embryo dunes, which recovered at an average rate of 4–4.5 cm per month, although average monthly volume changes varied from − 1 to 2 m 3.m − 1 . These embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune. These dune-construction processes were facilitated by growth of vegetation on low-profile embryo dunes promoting backshore accretion. After more than two years of survey, the sediment budget of the beach/dune system showed that more than 10,000 m 3 has been lost by the upper tidal beach. We suggest that seaward return currents generated during the storm of 10th March 2008 are responsible for offshore sediment transport. Reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross-shore sediment redistribution inducing net erosion in the tidal zone. ► Storm dune erosion was generated by extreme water inducing 6 m maximum dune retreat. ► Initiation of dune recovery was immediate and still ongoing 2.5 years after the storm. ► Dune regeneration was largely determined by the creation of accommodation space. ► Dune regeneration led to embryo dunes recovery at an average rate of 4–4.5 cm/month. ► Sediment supply to the dune was provided by sand eroded to the upper intertidal beach.