O. Monfort et al., Beach cusp characteristics and the hydrodynamic conditions of formation inmacrotidal environments, B SOC GEOL, 171(6), 2000, pp. 649-656
Beach cusps are sometimes present on the upper foreshore of sandy beaches a
long the northwest coast of France characterised by very large tidal ranges
. These forms were observed on the high tidal zone of Luc-sur-Mer in the "b
aie de Seine" during morphodynamic surveys conducted between May and July 1
996. Topographic surveys showed these cusps to be depositional features. Th
e profile and incident wave characteristics do not favour the theory of cus
p formation based on the presence of subharmonic edge waves, while the spac
ing between the horns is in disagreement with the theory of "self-organisat
ion''. The wave record on the lower beach shows, at the time of their appea
rance, two incident wave trains each with a specific direction and period.
The observed beach cusps appear to be induced by the intersection of these
two wave trains, thus confirming, for the first time in the field observati
ons, experiments conducted in laboratory.