Influence of bed roughness on dune and megaripple generation

Déborah Idier (1) , Dominique Astruc (2) , Suzanne J.M.H. Hulscher (3)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 IMFT - Institut de mécanique des fluides de Toulouse
3 Water Engineering and Management

Richards [1980] conjectured that megaripples of the continental shelf are due to a seabed instability in the presence of seabed ripples. Towards a better understanding of this megaripple formation process, we use a morphodynamical numerical model to investigate the bed roughness influence on the bed load–induced linear stability of a sandy bed. We find that the linearly most amplified mode shifts from a dune mode (grain roughness) towards a megaripple mode (large bed roughness). Then, we discuss how megaripples could be generated over a flat bed and over dunes.

Mots clés: Marine Geology and Geophysics; Marine sediments-processes and transport; Oceanography-General-Continental shelf processes; Oceanography-General-Numerical modeling; Oceanography-Physical-Currents; Marine Geology and Geophysics-Seafloor morphology and bottom photography

Domaines: Planète et Univers [physics]; Sciences de la Terre; Océanographie

Déborah Idier, Dominique Astruc, Suzanne J.M.H. Hulscher. Influence of bed roughness on dune and megaripple generation. Geophysical Research Letters, 2004, 31, pp.L13214. ⟨10.1029/2004GL019969⟩. ⟨hal-00557292⟩