Video observations of rip currents on an embayed beach

Rip currents and their interaction with waves and underwater morphology are still poorly understood. This study presents a conceptual model demonstrating how rip channels respond to changes in wave conditions, focusing on wave energy and wave event duration. Past attempts to relate rip channels to wave conditions have not resulted in good relationships between rip characteristics (e.g. rip spacing) and waves. In order to address this problem, a 3.3 year rip channel data set was obtained using an improved computer-based technique to locate rips from video imagery. In this study we show how the scale of rip channels (i.e. cross-shore extent), previous wave conditions and the duration of high wave events determine how rip channels will evolve. Observations of six events when rip channels changed their spatial configuration are used to create a conceptual model for how rip channels respond to changes in the wave conditions. When rip channels are small in relation to the wave energy, these rips are more likely than larger rips (extending less than ∼70 m cross-shore) to evolve. Conversely when rip channels are large in relation to the wave energy, these rips are less likely to evolve than smaller rips (extending more than ∼80 m cross-shore).