How to translate text using browser tools
1 March 2016 Bathymetric controls on very low frequency rip current motions
R. Jak McCarroll, Robert W. Brander, Ian L. Turner
Author Affiliations +

McCarroll, R.J.; Brander, R.W., and Turner, I.L., 2016. Bathymetric controls on very low frequency rip current motions. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 418-422. Coconut Creek (Florida), ISSN 0749-0208.

Time-averaged mean rip currents are forced by persistent gradients in dissipation over shallow bars and deep rip channels. Time-variable horizontal surfzone eddies, at the ∼10 min or very low frequency (VLF) range, are forced by stochastic wave breaking injecting vortical energy into the surfzone. Previous observations note that deep channel rips have greater variability of velocity while shallow channel rips exhibit greater variability in trajectory, this suggests a continuum of flow states that at present are poorly understood. This paper investigates the degree of bathymetric control on VLF motions illustrating how VLF motions manifest on different morphologies. Three field sites are investigated using low-pass filtered: (i) mean velocity; (ii) variable eddy velocity; (iii) directional standard deviation; and (iv) instantaneous vorticity. A VLF flow-type parameter is introduced to differentiate flow regimes, based on degree of bathymetric control. A novel classification scheme is introduced: (i) strong bathymetric control, with high mean velocities and rip cell oscillation; (ii) moderate control, with high mean velocities and variable VLF trajectories; and (iii) weak control, with low mean velocities and mobile eddies. Level of bathymetric control may be related to channel orientation, in addition to relative depth. This study improves our understanding of rip flow variability over short times frames, with implications for sediment transport and beach safety.

©Coastal Education and Research Foundation, Inc. 2016
R. Jak McCarroll, Robert W. Brander, and Ian L. Turner "Bathymetric controls on very low frequency rip current motions," Journal of Coastal Research 75(sp1), 418-422, (1 March 2016).
Received: 15 October 2015; Accepted: 15 January 2016; Published: 1 March 2016
intermediate beach
Lagrangian drifter
rip channel
rip variability
surf zone
Get copyright permission
Back to Top