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1. Get the equipment
You'll need your river clothes since you're going to be in the water a lot, as many heavy duty crowbars as you can get, come-alongs or winches, just basically your heavy hand equipment for moving rocks.
2. Decide on a location
You need to find a feature in the river with the potential for a hole. Generally what works best is two large pools connected by a single drop feature. The pool on the up stream side will give you the steady, non-aerated water supply that you need and the down stream side will provide you with the depth necessary to clear the riverbed during moves. In a best case scenario there will be a natural constriction of the river banks between the two pools.
3. Get to work
You're going to be wanting an inverted horseshoe shape, one where the curve bends around the downstream pool (if you can picture what I'm talking about). The first thing you need to do is collect a lot of large, flat boulders, about a meter in diameter at least, but you probably won't be able to move anything much larger. It is very important that they be as large as you can move them so they can resist the pressure that would normally push them down stream. And to be honest, they are still going to be moved around every year, so count on doing maintenance every year in spring.
Now take these rocks and build your inverted horseshoe shape along the riverbed. You want the rim of the ledge to be as smooth as possible. The notches between the rocks can act as sweet spots, areas where you can get your stern or bow through during low water conditions, so don't worry if you can't get the most perfect fit ever.
Now fill in the depression in the riverbed upstream from your new ledge. Again, the bigger the rocks that you use, the more resistance they will have to water pressure.
So what you have now should look like a new ledge in the river, at best a boring class I feature. Now you need to work on the next two parts: channeling the hole and building up the downstream pool.
The first thing to do is to get as many rocks out from immediately under the ledge as possible. Don't undermine the ledge you just built, just get the rocks out and make the area on the river bed which is going to be right below the seem as deep as possible. Building the down stream dam is probably what you should do next, and it's just a matter of putting in a dam several meters behind the hole feature. Done. Be sure to think about recovering from flips when you put in the dam, how much time you'll need versus, how close it has to be to raise the water level at the feature. It should also be smooth so that people don't knock it apart when they go over it. You might also consider making it into a ledge just like the one in the hole so that you can make a second hole later on, should the opportunity present itself.
Channeling the hole is where skill seems to take more of a role. You want the energy of the water to be channeled toward the middle of the hole without restricting the flow over the sides of the hole, and without creating a tongue in the middle that isn't retentive. Naturally, it's done by building up stone channeling walls on the upstream side of the hole which focus the water toward the center. It takes a lot of trial and error to figure this part out. Good luck.
That's about it. The rest involves tweaking the features to get the right hole effects. I'm not sure if the order that I've given you is the best, but it makes sense to me. If you have anymore questions, ask someone else, because as I said I am not an expert on this, just an observer.
Date of original publication on PLAYAK.COM: February 25 2000