A thread in MPSIMS got me wondering about this. There is a video of a guy in a kayak going off of Palouse Falls in WA, a drop of 186 feet. Other kayakers have taken similar, if less precipitous plunges without any serious injury. How is this possible? Hitting water from that height would be like hitting a wall, it would seem. And then there are the tons of water coming down behind you.
So what are the physics of this? How do these people survive the drops and why isn’t the kayak itself crumpled or destroyed in the process? Thanks.
This is just an educated guess but I think the key is that they ride the kayak through a waterfall. The person and the kayak most certainly would not survive in they just dropped into regular water from anywhere else like a tall bridge. However, the bottom of the waterfall is extremely turbulent and bubbly rather than flat and hard like the normal water surface. The deceleration isn’t instant like it would be for calm water and that is the key. It is a similar idea to jumping from a building into a pit of soft pellets rather than the ground.
Palouse Falls is also uniquely suited for that stunt because it has a ridiculously large plunge pool, but relatively low water flow. That’s because the canyon and drop off were formed by the gigantic Lake Missoula Floods during the last ice age, and the modern snake river has just taken advantage of the channel.
Okay, but still: 186 feet is a hell of a drop. I would think there would at least be some whiplash, although I suppose if the boater leaned forward and formed a vee with his arms and body, it might lessen that effect.
GreasyJack: I know all about glacial Lake Missoula and have read Bretz’s Flood, which is a very interesting book. The scab-lands of eastern Washington are fascinating geology, and Palouse Falls is right at the top.
Since the water is traveling with them, and continuing to travel downward at the water surface, it greatly increases the distance over which deceleration occurs. The world record high dive into still water is from a similar height, btw.
From what I understand the only thing sticking out of the kayak was the top of his (helmet-wearing) head. The aerodynamic kayak would have basically been like a bullet hitting the water, but since there was such a deep splash pool there was lots of room to decelerate before hitting the bottom.