Earlier this summer a lot of media attention was given to a mass rescue of over 20 people in a flash rip at Sydney’s Maroubra Beach. While the actual number of people rescued was exaggerated, it does raise the question: what exactly is a flash rip?
There are different types of offshore flowing rip currents on our beaches and most attention is given to those that sit in deeper channels between sandbars that can stay in place for days, weeks and even months. These channelised rips appear as narrow, darker gaps of greener water between the whitewater of waves breaking on the adjacent shallow sandbars and are thought to be the main cause of surf drownings on our beaches. But are they?
Flash rips are significantly different and also very dangerous. They form suddenly when a large group of waves (a wave set) breaks, or some randomly big waves break, causing the local water level to rise and force a sudden flow of water offshore. They only last for a minute or so before disappearing and are totally unpredictable. They tend to occur on days when the waves are messy and they can pop up and disappear all along the beach, including between the flags. They also look different and appear as offshore moving clouds of turbulent, bubbly whitewater and clouds of sand. They don’t flow particularly fast, but as they tend to form off of sandbars, they can quickly move people into deeper water.
Flash rips are usually the main cause of mass rescues on beaches because a group of people standing on a sandbar in relatively safe depths (and between the flags!) can suddenly lose their footing when the water level rises and be taken offshore out of their depth. That’s not good for poor or inexperienced swimmers! Often you’ll hear reports of mass rescues being caused by a collapsing sandbar, which is totally incorrect. Sandbars don’t collapse, it’s a physical impossibility and a total myth. Guaranteed it’s a flash rip.
In some ways flash rips are the most dangerous type of rip because you can’t see them until they happen, but the good news is that they generally don’t take you that far offshore before stopping. If you even find yourself caught in a flash rip, or any rip current, the best thing is to stay afloat and signal for help if you need it.
It’s hard to find good photographs of flash rips because they happen so fast, but there’s a few on the Rip of the Month page on my website:
www.scienceofthesurf.com. It’s well worth a look. Last month was also the 15-year anniversary of the Rip of the Month – that’s a whole lot of rip photos!
A new edition of Dr Rip’s Essential Beach Book is out now. Visit www.unsw.press/DrRip or Collins Booksellers Thirroul
