True, but they compensate by using a hand-thrown drag chute to accelerate deployment. It seems to go by a variety of names though. Here is an article that mentions it but not the part about it being thrown.
- The waterfall creates air currents that suck back in.
- Again, why would the canoe, travelling at the same velocity as the water, have enough momentum to get more distance than the water does? Unless you imagine the person paddling really really hard …
I guess I didn’t mention that I’m an experienced skydiver; I’ve made over 1,000 jumps (but no BASE jumps). For shorter BASE jumps they hold the large pilot chute in their hand and throw it into the wind shortly after jumping. The main canopy is folded into a back-pack container, often held shut with velcro. Opening shock is minimal due to low airspeed.
For longer BASE jumps they use a rig similar to what skydivers use. The main canopy is folded into a deployment bag, then into the back-pack container. The pilot chute is stowed in a pocket on the bottom of the container. They delay opening until they build up some airspeed, then reach back & pull out the pilot chute and throw it into the wind. The pilot chute pulls out the deployment bag, then the main canopy. The slower deployment reduces opening shock (and the likelihood of injury) at higher airspeed.
Most skydivers (and BASE jumpers) use this type of throw-out pilot chute. Very few use a ripcord and spring-loaded pilot chute.
It would take a pretty strong air current to suck a canoe with at least one occupant back into the water. And the OP didn’t say, but there could be 2 or more people paddling really really hard, so I can imagine (for the purposes of the story) the canoe going faster than the current. Not very likely, but I think it’s possible.
You’re the experienced skydiver - if the chute is large enough to slow down the descent to a safe speed, then isn’t it large enough that it will go where the air current takes it, even if that air current isn’t “pretty strong”? Unless you imagine some really powerful initial momentum. Now for comparison, the world record for rowing a four man team, in a light weight competition shell, with a strong tailwind, is roughly 12 mph. (Based on times on the standard 2 km course.) Two in a much less hydrodynamic, much heavier, canoe, that also has the big parachute on board … even if they weren’t actually spending all their paddling energy to stay upright … ? Um, a bit less you think? Alternatively the BASE jumper is probably hitting 15 to 18 mph at the cliff edge to get that 10 feet out.
If you want to see what an experienced kayaker going over a waterfall actually looks like check out this. Note: he doesn’t have any more momentum than the water. Here’s a two-man kayak with a view from the top. Note: the speed of the water, that they’d have to be going faster than to get momentum to clear, doesn’t speed up until the last little bit.
Look at those videos and tell me if you still think it is possible. (Mind you they show it is possible to run some pretty scary high falls. No parachute though.)
As I said, even a round parachute can be modified to have some forward drive. When I said he would have to use a round parachute I was thinking in practical terms. A gliding ram-air canopy requires at least some training to control. But for the story the canoeist could have that training and use a ram-air canopy, which has a forward speed of 20-25 mph, enough to glide away from the water fairly quickly. And a parachute, even a large one, is not very heavy at all. They’re made of nylon. A 300 sq. ft. canopy (large enough for a person and a canoe) weighs less than 20 lbs.
The kayakers, as you say, don’t have any more momentum than the water. But they’re not trying to go faster than the water. They’re barely paddling at all. And as you said, the water doesn’t speed up until the last little bit. If you’re going with the current without paddling, would you really have to paddle that hard to go faster than the water? Relative to the current aren’t you motionless? So how much effort would it take to go faster than the water? So yes, I still think it’s possible.
Enough to get to BASE jumper speed and clear the water by more than a foot or so? Yes, you’d need to be paddling very very hard - again, compare to the world records for a four man team in a competition lightweight shell with a tailwind - and in fast moving water effort is needed to just keep the kayak or canoe straight and upright.
Okay, a Jet Ski could possibly get enough speed to get the clearance a chute would need. (She really thought that would work?)
Someone tried a Jet Ski with a parachute over Niagara Falls once … unfortunately his chute didn’t open. Look at the picture though and tell me if he would have had enough clearance if it did.
It’s been done
Top boat speed is very non linear. It take a racing canoe or kayak and Olypmic paddlers to get in the over 10 mph range. However, me with my girly arms and my short fat barge of a canoe can easily do a burst of 6mph relative to water.
Also, its not hard to keep upright in fast moving water. It depends on whether its smooth flowing or more like a rapids/obstacle course.
Now whether something like 6mph forward motion relative to the water and a chute that will also carry you forward is enough to not get “sucked” back into water is a different issue (though I think it is in the realm of probably doable if you do it right and things go right).
I’ve gone over a six foot fall (I tell people it was eight, it felt like twenty). For a huge drop, maybe a 40ish pound kayak, with the paddler secured to the boat and wearing a chute would work.
A crazy guy I know took a kayak onto a bridge over a river. Not a huge drop, maybe twenty five feet? He secured himself into the boat and had two accomplices, one at either end, drop him off he bridge. Another guy filmed it. He landed sideways and fractured an arm and collarbone.
ETA: I think people are underestimating the difficulty of doing something like the OP’s idea.
If the jet skier in the second link deployed at the moment the picture was taken he would have no problem. Plenty of air around him. Same with the first link; if she deployed a parachute as she went over the edge it would inflate. Ram-air canopies are very efficient and open very fast. Skydivers use various techniques to slow down the opening and make opening shock survivable, such as the deployment bag I described upthread. They don’t need much clearance at all. They just need to catch air and they will inflate.
The canoeist in the OP wouldn’t have to store the canopy in any kind of container, he could have it folded in the bottom of the canoe and throw the pilot chute into the air as he goes over the edge. Inflation will be almost instantaneous. BASE jumpers have made jumps from cliffs less than 100 ft. high by laying the canopy out on the ground behind them and jumping (no running necessary), dragging the chute with them. It inflates immediately.
I wouldn’t try it myself, but the OP specifically said “Never mind feasible, would this be technically physically possible?” My answer is still Yes.
Edit; This is in reply to DSeid in post # 27.
Thanks for your reply, kayaker. How difficult would it be to get going faster than the current?
Thanks for your input, billfish. As long as the canoeist is going even a little faster than the current and is in open air, the parachute will inflate.
Depends on the design of the boat and the strength/endurance of the paddler. Last summer I wanted to rerun a fun stretch. I paddled upstream through decent current. It took me 15 minutes of difficult work, but I made it. It took under a minute to come back down.
I think the problem is that the speed of flow of a river or stream is deceptive. The water I am on flows between one and four miles an hour. When I take out after a day trip, I’ll have averaged faster than the current, but only by a small percentage.
Also, if you are going six mph, you do not “shoot” over the lip of the falls. The front of the boat begins falling as soon as center of gravity passes the precipice. It isn’t like a speed boat going 120 mph.
Bumershoot. I’d still be somewhat worried about air currents. Now we need a waterfall/aircurrent expert to tell us about that part. The manitude of the inward/downward iar currents is the issue. If its a small breeze, probably no big deal. If its sucking air in like hoover vacuum there could be problems.
Here is a graph that shows resistance vs boat speed. A decently fit person can paddle a canoe for hours on end at 3 to 4 mph. And as I said, I can provide a burst of say three times continuous output and hit 6mph or so. But you can see how steep the curve gets towards the end. And the further right you go the stepper those curves get, so it becomes obvious why you need an olympic crew to do those fast speeds. Also, as simplifieded rule of thumb (that is based on basic physics), top boat speed is a function of the square root of the boat length. So, keeping other things as “equal” as possible, a boat twice as long can be paddled about 1.4 times faster. Thats why kayaks and racing boats are long (long helps). And skinny also helps. Hence, long skinny yaks if you want to go "fast"er.
http://www.kudzucraft.com/articles/longboatmyth.php
Kayaker, its still FASTER than the water, about 6mph. Water doesn’t magically bring you back down to its speed now does it? I’ve gone over small drops too and my boat wasn’t glue to the water’s surface. The video’s I seen of people going over taller stuff they do actually arc out past the fall (and it often looks to me like they are NOT trying to paddle fast over the lip (and there might be good reason to do that if you aren’t doing it with a parachute)
If anyone is interested in real-world figures, I always take my GPS with me when I take out my canoe. I and my nephew were out one day, and we drifted with the current, measuring it at 0.5 mph, then went on a speed-run downstream back to where we put in, measuring 8.6 mph (8.1 after subtracting current) at max speed, but only briefly. We were only averaging about 7 or so faster than the current. That’s with two people paddling, all out. We didn’t go over any waterfalls. I’ll let someone else try that one. 
Do you have any links? Because the only ones I can find on YouTube (which I have linked to) show no such thing. Again, even a Jet Ski only gets several feet out, and a few feet of center of gravity out of a kayak built for speed isn’t even getting close to the end of the thing. And the end needs to clear the water falling down.
I don’t think that your ever going to get up enough speed to have any certainty of clearing the water and the downdrafts to ensure that your chute doesn’t collapse. Even if you did, there’s the problem of landing. You will hit fairly hard, without the ability to use your legs as shock absorbers. Then you’ll have a large collapsed canopy smother your boat. There better not be any more rapids.
If the canoeist is heading into the wind so he has his forward speed combined with the wind, and deploys as he goes over, the canopy will inflate very fast. As I said before, the canopy could be laying folded in the canoe. And it has a forward speed of 20-25 mph. Yes landing will be a problem, but the OP’s question is “would this be technically physically possible?” Like I said, I wouldn’t try it but I think it is possible.