Beachwatch : The effect of daily morphodynamics on seasonal beach evolution

Abstract

Not only the storm intensity, but also the capacity of the beach to recover during fair weather conditions, influences the erosion trends of beaches. Susanne Quartel concludes this in her thesis in which the daily changes of the intertidal beach of Noordwijk aan Zee, the Netherlands, are described. She used daily images, which were taken around low tide by a shore-based Argus-video system. Besides, height measurements were executed monthly on the beach of Noordwijk during a period of 3 years. Only storm events that last at least 30 hours with an average offshore root-mean-square wave height over 2 m and an offshore surge level exceeding 0.5 m result in a morphologic reset of the beach. The recovery of the lower parts of the intertidal beach takes several days, whereas the recovery of beach zones with higher elevations and near to the dunefoot may take several months and thus remain visible for an extended period. When a subsequent reset storm appears before the beach is fully recovered, the associated morphologic changes disorder the trend of seasonal beach evolution and may lead to structural erosion of the beach.