Updated: Dec 6, 2022
The force behind a lateral wave is created by the angle of the wave to the main current, the volume of current / percentage of the river’s volume going into the wave, the backside of the wave, and the curl.
As with most features, a lateral wave may be an obstacle to avoid and counteract or a tool to aid in getting you where you need to be. As we progress as boaters, more and more we find ourselves letting the river do the work and that what used to be a scary obstacle to avoid is now a fun feature to play with. All it takes is a change in perspective for fearsome features to become fun. How does this change come about? Our society likes to tell us that people are afraid of the unknown, which I’ve seen hold true on the river for many folks. For instance, many paddlers and rowers like to watch someone else go first at the scout. The unknown factor is, “how will this feature affect my boat?” and the answer is always “it depends.” So let’s think about the different ways we can control how our raft interacts with a lateral wave and make it fun.
Photo: Selway River, Idaho. Where would you hit these laterals?
I like to break down the style of boating first and identify a person’s goals for the rapid before thinking about ways to engage with a lateral wave. For our purposes here, let us consider two distinct styles or approaches. One approach is to consider the wave an obstacle that must be overcome or countered in order to get to where you need to be in the river. The lateral is in the way of a clean line. The second approach will consider the lateral wave as a tool to move you. Letting the river move you will feel out of control at first, introducing that unknown factor; so in a boaters’ progression we start with countering the wave and once that feels predictable, we move toward using it.
Countering a lateral will require you to judge the force it has to move your boat, you know this as “reading water”. Countering the wave will create the desired result of breaking through it without altering your lateral placement in the river.
Using a lateral will require you to judge the force behind it exceptionally well; you know that as “advanced water reading”. Using the lateral wave will help you achieve your goal of moving your boat’s position laterally across the river or changing your angle as you crest the wave. Or both. (Surf, quartering, typewriter).
Using a lateral is up next in the reading water series, more on that later!
Which brings us to:
Reading water: Lateral Waves, Countering a Lateral.
The force behind a lateral wave is created by several factors, the most important for rafters being the angle of the wave to the main current, the volume of current / percentage of the river’s volume going into the wave, the backside of the wave, and the curl.
Angle: the sharper (more acute) the angle, the more force the wave has to reject you. Generally match the angle of your boat to the angle of the wave so that your raft is perpendicular (90) to the wave. You will hear this called “T - up” and “square up.” Be careful not to confuse the angle of the wave with the angle at which the current is entering it, or with your angle to the bank; they are all separate considerations.
For more advanced reading of water, pay attention to the upstream end of the lateral versus the downstream end. The upstream face is typically a sharper angle, with a little curl where it begins. As you hit the wave, the bow and stern of your raft are interacting with different currents.
Avoid having your bow swept downstream by sharpening your angle upstream slightly to compensate for that moment of torsion if you enter high on the lateral. Brace with your oars or paddle as your ride up the face of the lateral and take a stroke at the peak of the foam pile, crasher, or curler in order to pull you through to the backside of the crest. Matching your angle 90 degrees or less to the angle of the wave will help you counter it.
Volume: The more volume the lateral has, the more powerful it could be. A high volume river can have bigger features, but those waves don’t necessarily convey extreme force without also having a sharp angle, being backed up, or curling. In addition to overall volume, consider the percentage of the river’s volume that is being pushed into the lateral. The higher the percentage, the more unavoidable it is as well. With high volume waves, you will want to match the power of the wave with momentum.
Think Grand Canyon downstream ferry angle. The downstream ferry is used because pulling is stronger than pushing. The faster you are moving and the heavier your boat is, the better you will be able to counter the wave’s volume. Your boat should be going faster than the current. Momentum equals speed times mass, so the lighter you are, the faster you should be going and the harder you should row or paddle. Empty boats can start building speed later than loaded boats, it will take an empty boat less time to reach terminal velocity, ahem, maximum speed.
Photo: Boat Eater, Illinois River, Oregon. Hitting the V where two laterals meet with max momentum.
Backup. The water (or wall, as the case may be) behind the lateral backs it up. Think about this the same way you consider a hole to be more of a keeper if it is backed up by a rock. The lateral itself is likely created by the cliff wall or bank of the river, which the main flow was trying to drive straight through. The current was refracted by this wall, creating the lateral.
The wall is not always made of rock, sometimes a wall of water is piled up in an eddy, and I have seen lateral waves form off eddy fences. Laterals can also form off midstream rocks with eddies behind them or off alluvial fans from creek mouth blowouts or landslides. A lateral backed up by a rock wall will be almost impossible to break through…and you wouldn’t want to, because you would hit the cliff! Think Granite Rapid on the Grand Canyon. A lateral backed by an eddy fence or boil can hold as much rejection power (if not more, because it’s actively pushing back at you) as a rock wall. If water behind the wave is not aerated, as with a boil, it will literally be heavier and carry more force than foamy white aerated water. Pay attention to the color and turbidity, it matters. Mud water is heavier than clear water. Lastly, a lateral backed up by a mild eddy, aerated water, alluvial fans, or a low point in the river will hold the least force.
Photo: Rio Cotahuasi, Peru. The lateral top left is too powerful, we chose to line the boats around.
Curl. Some lateral waves will curl over at the peak instead of cresting and falling back on themselves in foam and white. Try to identify which part of the wave you could see through the hollow barrel of. Avoid that. A large lateral wave that forms a barrel creates the added challenge of countering it without flipping. The reason a big curler can flip a raft is because the heavy water curling becomes over vertical before crashing! Follow the main current with your eye, could your raft become vertical while on the face of the curler? Consider hitting this feature above or below the barrel if the height of the wave is more than half the length of your raft. Hitting the lateral high with the intent to break through will set you up to be on the backside and miss the barrel, however, if you misjudge you will be set up to enter the most powerful portion of the wave. A more conservative approach would be to hit it downstream of the barrel if possible or avoid the feature entirely.
Photo: No Name, Crooked River, Oregon. The main feature is a lateral barrel wave on the left that feeds into a mid stream hole. Check out the curl on that bad boy.
Stay tuned for the rest of the Reading Water Series, up next is Using a Lateral Wave. Thanks!