The guys in this raft do not escape during the minute of the video, but this suggestion is proffered at Fuck Yeah Fluid Dynamics:
One of the perils of whitewater sports is getting stuck in what paddlers call a “hole” or a “hydraulic”. This river feature forms just downstream of large obstacles like rocks or low-level dams. As water pours over the obstacle and into its shadow, the flow forms a recirculating vortex-like zone. Immediately next to the obstacle, water is pulled upstream toward the obstacle and then down toward the bottom of the river. This makes the hydraulic very dangerous and hard to escape. Note in the video how the raft is held in place by the upstream motion of the water at the surface of the hydraulic. The rafters are preventing their craft from flipping over by weighing down the side experiencing the upward flow of the vortex. Escaping a hydraulic usually requires getting near its edge, where its current is weaker. If swimming, the best way to escape is to swim toward the bottom of the river and then downstream with the current of the hydraulic rather than against it at the surface.It would take a braver person than me to shed a life preserver and dive to the bottom of a vortex in order to escape it.
Who said to shed your life preserver? The water is already heading for the bottom - you do not shed your life preserver, you simply go with the flow and aid the current by swimming for the bottom. Removing your life jacket would be a very stupid move in this situation.
ReplyDeleteIn reality, it doesn't take much swimming either. Just letting the current take me down has been enough to eject me from recirculating holes in rapids.
In this case, you can see that the person outside the boat is already being pulled downstream by the current. He's apparently trying to hang onto the boat and stay with it when it kicks out of the hole. I think he should have had the person in the boat dive out and then let go of the boat himself. He's tiring himself out just trying to hang onto the boat. Once the boat was empty, it would likely flip but would soon kick out of the hole.
ReplyDeleteAs a former expert-level whitewater rafter, I, too, have heard about swimming to the bottom, etc. But the problem is that unless you are purposely going into a hole to test this theory, you are falling in without the slightest intention of doing so.
ReplyDeleteThink of a firehose being turned on your face. Panic starts almost immediately if you get a mouth full. Worse, you are being "Maytagged" so badly that you not only can scarcely think, but you are also being flailed about such that you likely cannot even reach your buckles (assuming you could think to do so).
I've only fallen out one time, but it was bad enough. I fell out on "Corkscrew" on the Chattooga River/Section 4 (north Georgia). Just that quick I was in some primitive survival mode that constituted reaching, grasping, and saying (perhaps in my mind), "Jesus, help!"
As you might have deduced, I did not drown. But I have surfed plenty of holes--some unintentionally. The men in the video are "high-siding"--saying on the highest side of the boat to prevent capsize. But when you are in the drink and don't have a boat to hold onto...I don't imagine many people think to shuck their vest.
Fortunately, most people finally get washed out or someone helps them get out.
Thanks, Aaron. I am recurrently amazed by the variety of expertise and experience of readers of this blog.
Deletethanx for making this instructional video private and unavailable to the public. The last thing anyone wants it to give out instruction that might save someones life. Awesome.
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