Wave Group Forcing of Rip Currents

Experiments have been performed in a laboratory wave basin investigating the effect of wave groups on rip currents. Results show a strong group signature in velocity time series measured in the rip neck. In some cases, mean quantities are also significantly affected. Velocity fluctuations with periods greater than the group period do not appear to be affected by the group forcing. Fundamental differences are found between flow at startup and at later times. These startup transients are extremely high, and the differences from later flow are hypothesised to be because wave-current interaction is not significant in the initial stages of flow development, and because large-scale circulation patterns have not yet developed.