Self-organized kilometer-scale shoreline sand wave generation: Sensitivity to model and physical parameters

Abstract : The instability mechanisms for self-organized kilometer-scale shoreline sand waves have been extensively explored by modeling. However, while the assumed bathymetric perturbation associated with the sand wave controls the feedback between morphology and waves, its effect on the instability onset has not been explored. In addition, no systematic investigation of the effect of the physical parameters has been done yet. Using a linear stability model, we investigate the effect of wave conditions, cross-shore profile, closure depth, and two perturbation shapes (P1: cross-shore bathymetric profile shift, and P2: bed level perturbation linearly decreasing offshore). For a P1 perturbation, no instability occurs below an absolute critical angle θc0≈ 40–50°. For a P2 perturbation, there is no absolute critical angle: sand waves can develop also for low-angle waves. In fact, the bathymetric perturbation shape plays a key role in low-angle wave instability: such instability only develops if the curvature of the depth contours offshore the breaking zone is larger than the shoreline one. This can occur for the P2 perturbation but not for P1. The analysis of bathymetric data suggests that both curvature configurations could exist in nature. For both perturbation types, large wave angle, small wave period, and large closure depth strongly favor instability. The cross-shore profile has almost no effect with a P1 perturbation, whereas large surf zone slope and gently sloping shoreface strongly enhance instability under low-angle waves for a P2 perturbation. Finally, predictive statistical models are set up to identify sites prone to exhibit either a critical angle close to θc0 or low-angle wave instability.
Type de document :
Article dans une revue
Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2017, 122, 〈http://onlinelibrary.wiley.com/doi/10.1002/2017JF004197/full〉. 〈10.1002/2017JF004197 〉
Liste complète des métadonnées

https://hal-brgm.archives-ouvertes.fr/hal-01590706
Contributeur : Déborah Idier <>
Soumis le : mercredi 20 septembre 2017 - 09:29:50
Dernière modification le : lundi 29 janvier 2018 - 13:04:01

Fichier

Idier_et_al-2017-Journal_of_Ge...
Fichiers produits par l'(les) auteur(s)

Identifiants

Collections

Citation

Déborah Idier, Albert Falqués, Jeremy Rohmer, Jaime Arriaga. Self-organized kilometer-scale shoreline sand wave generation: Sensitivity to model and physical parameters. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2017, 122, 〈http://onlinelibrary.wiley.com/doi/10.1002/2017JF004197/full〉. 〈10.1002/2017JF004197 〉. 〈hal-01590706〉

Partager

Métriques

Consultations de la notice

54

Téléchargements de fichiers

3