Storm response of the upper intertidal zone on a gravel beach

Le résumé fourni par la source

• In a 42-year hindcast context: 2019–2020 can be considered an exceptionally energetic winter season; 2018–2019 moderate. • Video monitoring quantified upper-intertidal volume and shoreline changes. • Storm impact controlled by storm characteristics, tide range during storm impact, and previous beach morphology conditions. • Multiple regression (wave height + tide range during storm impact) explains 46 % of volume change related to storm event. • Storm clusters often erode but can also promote recovery during lower-energy phases. This paper investigates morphodynamics of a macrotidal gravel beach (Etretat, Normandy, NW France) during two consecutive winter seasons characterized by moderate (2018–2019) and exceptionally energetic (2019–2020) conditions according to a 42-year analysis of hindcasted wave data. Upper intertidal beach changes and shoreline data were derived from a video monitoring system. The results show that storm impacts were strongly influenced by the storm characteristics, the tide phasing, and more importantly, by the pre-existing conditions of the beach before the impact of the storms. A multiple regression including wave height and tide range during the storm event explained 46% of the variance of the volume change due to storm events. Storm clusters often cause beach erosion but can also contribute significantly to beach recovery.

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