It doesn’t matter what craft you choose to enjoy on the water from a raft to a kayak, SUP, or inflatable pizza wedge; holes are probably one of the most feared and talked about hazards on the river. While sieves and strainers may harbor the greatest danger on the water it is the ubiquitous hole that is most often faced as a serious challenge to any boater. Some commercial guides discuss holes in their safety talks while every first year guide gets the hydrology of how a hole works pounded into their heads from day one. Even the head guides and storied veterans of the river will talk about how you could park a bus in that one crazy hole on that river. One thing I do rarely hear in discussions about holes is how to navigate them. Understanding the hydrology is not enough to know what is really happening from a practical sense. I don’t know if your mentors ever talked about successfully navigating the feature, but mine rarely did. So how do we deal with these monsters of the river?

Look for the outflow

We know the hydrology diagrams never helped to establish a solution for the boater in this crux move. So what is the first thing you should be looking for? Outflow. Try to imagine where your boat will ideally travel through the rapid. Having trouble visualizing it? I like to throw a large floating object into the hole to see where it flushes out. It is important to take not of this, because if you mess up that stick will be you. There is another side to this though. That outflow is generally the path of least resistance. This can be located anywhere in the hole it could be on the side, in the gut, into a sieve, or worse…not at all (in which case it is probably a low head dam and you should most likely grab your boat and start portaging). So now that we know where the outflow is, how do you run it?

Sometimes you don’t

People give me a lot of crap for this, but sometimes I just flat don’t deal with the hole. Unless it is a river wide ledge hole there are many ways to work around holes. In many instances it is possible to simply avoid the hole by skimming the side of it. People claim if you didn’t run the guts of a rapid then you didn’t rally run a rapid. In some ways that is true, but in others that is a mix of fear and pure bravado talking. Sometimes there is a bus sized hole and given the circumstances it can really end a trip if you decide to play with that hole. What it really comes down to is a how likely is it that hole will cause an accident if you mess up and how likely are you to recover from that accident?

The Bad Stuff

All kinds of bad stuff can happen in a hole causing an accident. If you haven’t read our article on how accidents really happen this can shed some light on how you end up in the “Bad Stuff”. The short list of potential outcomes are commonly swims, dump trucks, flips, surfs. Less common outcomes can be terminal surfs (with or without you in the boat), lost gear, and flush drownings (if a swimmer gets recirculated).  All of these are consequences of potential failure. Part of understanding if you should run a particular hole is to understand what the likely consequences are and if you are willing to accept them. You can read more about of risk assessment on the river, but bear in mind that risk assessment skills are critical to being a better boater.

Aim for the weak spot

Ok you’ve scouted the rapid and we’ve talked about the bad stuff, so now you have decided to run the hole… Now that you know the consequences and the factors in play where do you go from here. Bravado says charge it, fear says avoid it, the river is saying something different though. In a natural river bed there are rarely perfect hydraulics. There is always a weak point in the flow of the recirculation in the hole. In one of my favorite rapids on the Slab Creek section of the South Fork of the American River there is a river wide ledge hole that looks mean and munchy at nearly any flow. If you take a closer look at this feature you will notice the flake in the middle. This creates an oddly angled hole with a weak point just left of center. This is the doorway to freedom. The thickness of the wave is the smallest at this point. This provides the doorway to freedom if you can punch through the wall at this point. Let’s look at another hole on the same section of river. This one is much bigger and meatier; however there is still a weak point in the wall that you could work with. The key ingredients now are tow back of the hole and power in your boat, but the difficult part becomes estimating these two forces.

Tow back

Tow back refers to the boil on the downstream side of the crest of the visible surface wave. Specifically this refers to the amount of water bubbling up and pouring back into the hole also known as the hydraulic jump. This zone creates the primary upstream force acting to encourage you into the bad stuff. Since the hole is trying to achieve equilibrium at all times you will also notice a pattern as to where this flow is the weakest. The weakest point of the tow back is often the weakest point of the wave. IF this is the case you have a prime way through he hole to safety. If this is not the case, then you have a bit of a dilemma and this is where things get tricky. Now you have to navigate not only through the weak point in the wall, but through the weak point of the tow back. This could require some careful route planning so you get the most downstream punch into the wall, but also the ability to hit that sweet spot in the tow back. To pile more onto the equation you also have to estimate the forces that the entire hydraulic jump is placing on your raft as you pass through it. Flow, hole depth, overall hydraulic jump size, boat shape, crew weight, and speed of downstream travel are all major factors in this estimate. There can be a lot of oversimplifications of this, but this estimate is best made through experience.

Boat Power

The power of your crew is the second important factor of getting through the hole successfully. By this point if you have been boating together for a while you should know the abilities and limitations of your crew. Estimating power is often the easiest part of this equation. Pay close attention in the calmer section of river to the overall weight of your boat, how tired your paddlers are, who the strongest paddlers are, who has the best endurance, if they can make full strokes coming into the hole, and estimated speed of downstream travel.

It’s not about luck

The key to successfully navigating a hole is not a matter of luck it is a simple question of physics. Is the downstream momentum of your boat enough to counteract the impulse of the hole? In other words is the net force on your boat at the moment you come into contact with the hydraulic jump positive (downstream) or Negative (upstream). If net force = positive you made it through, if net force = negative…bad stuff. Some people like to call this luck, but it truly is not luck. There are many factors involved with making this determination, so many that less experienced boaters tend to get overwhelmed and chalk it up to random chance of the universe rolling the dice in their favor. At its core making it through a hole is more about your ability to recognize the factors involved and correctly estimate the positive and negative amounts of force from each of those factors. The mark of the superior boater is to become better at making these estimations. The better you are at understanding the forces the better you become at running holes.