June 2018 (ROTM#114) Laguna Beach, California

One of the hardest types of rip currents to get decent photos of are flash rips. Flash rips tend to occur on flat beaches or on the seaward slopes of sand bars and form when large waves break causing the water level to rise, pushing the extra water back offshore as a narrow rip.

They don’t necessarily flow offshore that far or fast, but they are dangerous because they are so unpredictable and only last for a few minutes, before disappearing and reforming elsewhere or sometimes in the same location.

They also don’t look like the classic ‘dark gap’ rip, because they don’t occupy deep channels, but rather appear as turbulent, streaky water with clouds of sand moving offshore. However, we don’t really understand flash rips nearly as well as we do other types because of the difficulty in measuring and observing them.

 This month we’ve got a video which helps demonstrate flash rips really well, but it also raises a lot of questions. It was taken by Ryan Gates from the California State Lifeguards at Crystal Cove State Park in Laguna Beach, California. What’s interesting with this flash rip is how it formed.

The waves aren’t that big at all and break consistently at the shoreline. But it looks like there’s some sort of beach morphology which is focussing the swash from the breaking wave. The resulting backwash is therefore also quite concentrated and flows offshore as a narrow rip. It doesn’t go too far, but if you can’t swim it doesn’t matter. Deep water is deep water. Ryan also confirmed that the beach was very scalloped that day, likely with features known as beach cusps, and that small rips like this were forming in the embayments of the scallops/cusps.

 So is it a flash rip or what we call backwash (a swash rip)? An argument could be made for both, but this is definitely a fantastic example of a very different kind of rip that is probably more common than we think. Thanks Ryan and the California State Lifeguards!

Does backwash make a rip? Watch the video!