Undertow and longshore current profiles outside of the surf zone were analyzed using a canonical situation involving an alongshore-uniform barred beach. Forcing mechanisms due to the presence of surface gravity waves are of interest. As is customary for surf zone studies, dynamics related to wave breaking and associated wave rollers were included. Also considered were the effects of the wave orbital velocities on the bottom and surface boundary layers. The effect of Earth’s rotation in the dynamics is included through two mechanisms: (1) the Coriolis-Stokes stress that results from the effect of Earth’s rotation on the wave orbital velocities, and (2) the Coriolis terms in the cross-shore and alongshore momentum equations. Model results qualitatively reproduce observed undertow profile shapes inside and  just outside of the surf zone, as well as a few surf zone widths offshore and far offshore on the inner shelf. In particular, the results explain the surface-intensified undertow currents often observed outside the surf zone. The Coriolis-Stokes stress is not active inside the surf zone; but it is an important player, alongwith the other considered dynamics, in shaping the profiles outside of the surf zone. Themodel also suggests the presence of an alongshore current outside the surf zone that is generated owing to the effects of theCoriolis terms in themomentumequations.Ananalysis of the temporal spin-up behavior of the predictions suggest that circulation patterns strongly influenced by Earth’s rotation should be observable in the fieldwithin a fewhours after the onset of wave activity.

Özkan-Haller, H. Tuba
Short Description: 
This study sought to assemble a simple model of the cross-shore and alongshore flows in the outer surf zone that takes into account surf zone– forcing effects (e.g., wave forcing) as well as dynamics important to larger-scale flows (e.g., Coriolis effects
Product Number: 
Entry Date: 
Monday, May 12, 2014
10 pp.
Size and Format: 
8 1/2 x 11, online
Source (Journal Article): 
Journal of Waterway, Port, Coastal and Ocean Engineering
DOI Number (Journal Article): 
Year of Publication: