Citation

Hasan H, Dodd N, Garnier R. Journal of Geophysical Research: Oceans 2009; 114(C7): 2008JC005031.

Copyright

(Copyright © 2009, William Byrd Press for John Hopkins Press)

DOI

10.1029/2008JC005031

PMID

unavailable

Abstract

The instability leading to the formation of rip currents in the nearshore for normal waves on a nonbarred, nonerodible beach is examined with a comprehensive linear stability numerical model. In contrast to previous studies, the hypothesis of regular waves has been relaxed. The results obtained here point to the existence of a purely hydrodynamical positive feedback mechanism that can drive rip cells, which is consistent with previous studies. This mechanism is physically interpreted and is due to refraction and shoaling. However, this mechanism does not exist when the surf zone is not saturated because negative feedback provided by increased (decreased) breaking for positive (negative) wave energy perturbations overwhelms the shoaling/refraction mechanism. Moreover, turbulent Reynolds stress and bottom friction also cause damping of the rip current growth. All the nonregular wave dissipations examined give rise to these hydrodynamical instabilities when feedback onto dissipation is neglected. When this feedback is included, the dominant effect that destroys these hydrodynamical instabilities is the feedback of the wave energy onto the dissipation. It turns out that this effect is strong and does not allow hydrodynamical instabilities on a planar beach to grow for random seas.

Keywords: Drowning; Drowning Prevention; Water Safety

Language: en