Storm response and multi-annual recovery of eight coastal dunes spread along the Atlantic coast of Europe

Résumé En

Coastal dunes are natural barriers against coastal flooding, and represent large sources of sediment to mitigate coastal erosion, besides being a natural habitat for many living beings. Yet, these complex environments are threatened by sea level rise and possibly enhanced storminess in the future. Most of the studies on coastal dune erosion and recovery from storms are either site specific or focus on a short-time scale, from months to a couple of years. Here, airborne LiDAR data collected from 2011 to 2020 at eight diverse coastal dunes, spread from NW England to SW France, were analysed to study their response, and recovery from the most energetic extreme storms wave conditions since at least 1948. Results show that the 2013/14 winter was the first or second largest erosive event (from −14 to −290 m3/m dune volume loss) from 2011 to 2020 at all sites. The magnitude of storm-driven sand volume loss was mainly controlled by dune face slope (r = 0.84). Dunes with steeper pre-storm slopes lost the largest volumes of sand. At a dune scale, the scarping height was also well correlated to the dune face slope at sites where storm response was characterized by limited alongshore variability. Dune recovery was site specific (no recovery, partial, complete, excess), with dunes that either progressively returned to their pre-storm morphology or were reshaped while recovering. Percentage of dune sand volume recovery was well correlated to the local and long-term satellite-derived shoreline change rate computed from 1984 to 2021 (r = 0.81), suggesting that dune recovery is mainly controlled by the local coastal sediment budget. The rate of dune crest elevation increase (from 4.2 to 12 cm/year) at four of the study sites from 2011 to 2020, largely exceeded sea level rise rate over the past decade (3.3 ± 0.7 mm/year). These results provide key insight into the contrasting resilience of some of the most exposed coastal dunes along the Atlantic coast that recover at different rates following the same sequence of extreme storms