Storms impacts on a sandy beach including seasonal recovery: alongshore variability and management influences
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Article de revue
Ce document a été publié dans
Revue Paralia. 2018-01-01, vol. 11, p. n02.1-n02.16
Résumé en anglais
Despite a global context of shoreline retreat, coastal areas and in particular sandy coasts
are increasingly attractive. To handle the problem of coastline retreat different
management strategies are deployed and among ...Lire la suite >
Despite a global context of shoreline retreat, coastal areas and in particular sandy coasts
are increasingly attractive. To handle the problem of coastline retreat different
management strategies are deployed and among them soft methods as windbreakers or
hard ones as seawalls. But all those methods are known to interfere in the natural
evolution of the beach/dune systems at different timescales. To underline potential
influences of management strategies on erosion and recovery periods, high frequency
DGPS surveys coupled with video images are recorded at a workshop-site exhibiting
various management strategies, Biscarrosse beach (SW of France) from November 2015
until September 2016. Results for the winter 2016 highlight a global erosion of the
beach associated to a dune foot retreat and an alongshore variability in the beach
response to events. The same patterns can be observed during the seasonal recovery
period (April to August), in particular a lag in the berm reconstruction in front of the
seawall. The LVI (Longshore Variation Index) reflects possible sediment processes
taking place between the different sections of the beach: while recovery seems to be
dominated by cross-shore exchanges in the unmanaged section, longshore sediment
processes seem to be the origin of the recovery in the managed section. This variability
could be linked to a permanent rip current visible (98% of observation) in front of the
seawall that could cause an offshore sediment export explaining both the lag in term of
recovery timescale and the different sediment processes involved during the recovery
period. During the erosion season, sediment exchanges between the beach and the dune
are limited due to the presence of seawalls and beach erosion and dune retreat in the two
ends on the wall accelerated.< Réduire
Mots clés en anglais
Coastal management
Alongshore variability
Sandy beach
Shoreline variations
Seasonal recovery
Rip currents
Longshore sediment transport