Characteristics and dynamics of crescentic bar events in an open, tideless beach

Abstract

Crescentic bar events at Castelldefels beach (NW Mediterranean) have been characterised using a 4.25 years dataset (October 2010-December 2014) of time-exposure video images. Crescentic bars are observed during 41% of the study period, with an irregular distribution of the events in the different years. The crescentic bars have a lifetime that varies from 1 to over 100 days, a mean wavelength of 245 m and a mean amplitude of 9 m. The bars are observed in relatively low-energetic wave conditions with a wide variety of wave angles. The formation of crescentic bars also depends on the antecedent bathymetry, in particular crescentic bar events only occur when the sandbar is located at least at 50 m from the shoreline. Crescentic bar destruction at Castelldefels beach is observed in both low- and high energetic wave conditions, but the angle of incidence is always oblique.