Cliff erosion: self-organisation of sand cliff material eroded by monochromatic waves

Bastien Caplain (1, 2) , Vincent Regard (2) , Dominique Astruc (1)

1 IMFT - Institut de mécanique des fluides de Toulouse
2 GET - Géosciences Environnement Toulouse

Laboratory experiments on cliff erosion were carried out in a monochromatic wave flume. Natural coarse sands are used to represent cliff erosion and bottom morphodynamics with a reasonable time scale. A bottom typology is established as a function of wave forcing, through the wave energy flux F and the surf similarity parameter ξ. The bottom types strongly depends on the surf similarity parameter at the breaker point ξb . Steep terraces (ξb > 0.48), one-bar profiles (0.42 < ξb < 0.48), gentle terraces (0.38 < ξb < 0.43) and double-bars profiles (ξb < 0.38) were observed. It can be translated into a Dean parameter Ω vs. Shields number Θb space to take into account sediment granulometry. Sediment grain diameter change has no noticeable influence on bottom typology. The bottom types depends more on the Dean parameter Ω than on the Shields number Θb . Finally, we explored cliff height effect: it does not modify the bottom typology established.

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Bastien Caplain, Vincent Regard, Dominique Astruc. Cliff erosion: self-organisation of sand cliff material eroded by monochromatic waves. 2013. ⟨hal-00790628⟩