by John Lull
(editor’s note: This week, Tsunami Ranger and earth scientist John Lull ‘splains the difference between river hydraulics and water dynamics present in ocean rock gardens)
At first glance the whitewater in ocean rock gardens looks very similar to a whitewater river. You’ll see waves, aerated rough water, rocks, currents, and swirling chaotic conditions. They share some characteristics, but are actually very different environments. If you are a river kayaker, many of the skills you use in the river will transfer to paddling in ocean rock gardens, and vice versa, but you’ll need to understand and learn how to handle the different dynamics. I’m going to outline some of the similarities and, more importantly, the differences between river and ocean whitewater. Probably the closest features to a river in the marine environment are tidal rips that form in bays and constricted passages between the open sea and inland waterways. But for this article I’m going to focus on ocean rock gardens.
This will be an overview. We can get into more details in the comments if you wish.
Similarities between rivers and ocean rock gardens
Rough water and waves are present in both river rapids and ocean rock gardens. So you’ll need all your rough water kayaking skills, including boat control, edging, balance, bracing, swimming skills, and rolling (especially in a closed deck kayak). In rock gardens, currents are induced by surging waves and to some extent they behave just like the current in a river. There is an important difference that I’ll discuss below. These currents move through and between rocks, as they do in a river, and in both cases you can ride the current. Good maneuvering skill, especially a good draw stroke, is necessary in both situations.
In a river, eddies can be used to stop, hang out, rest, and even scout the next rapid. You can also use them as launching points for surfing a standing wave, or making your next move. Similarly, in rock gardens there are often ‘safe zones’ behind rocks (on the shoreward side), where you are relatively protected from the waves and can rest, scout the area, and time your next move. These zones are not the same thing as an eddy, but can be used in a similar fashion.
And now for the most important similarity: They are both fun and exciting places to mess around in a kayak!
Differences between rivers and ocean rock gardens
Waves are a primary feature in both river and ocean whitewater, but the nature of the waves is different. In the ocean, the wave form is moving through the water and the water is only moving up and down in a circular fashion as the wave passes through. In a river, the wave form is stationary and the water is moving through it, as a current. This has important ramifications for a kayaker. If you surf a wave in the river, you’ll be standing still (facing upstream). You might move back and forth on the wave face, but you won’t be going anywhere. When surfing a wave in an ocean rock garden, you’ll be moving with the wave. You’ll have to be aware of where that wave is taking you!
The waves in a river stay in one place and don’t change much, at any given flow rate. The waves in ocean rock gardens constantly change in both size and power, and they can even arrive from different directions. This wave variation in the ocean might be the most important difference. The result is constantly changing dynamics, depending on the size of the waves. When you scout an ocean rock garden, you have to watch several sets of waves to see what happens, especially what happens when the larger wave sets move through. Seemingly benign conditions in a rock garden can suddenly explode into a surging cauldron when a wave set arrives. The action will intensify with each wave in the set.
The current in a river is constant and moves in one direction (with the exception of an eddy, where the current moves in the opposite direction). The wave-induced currents in an ocean rock garden are not constant and they move back and forth, first moving into the rocks, then reversing and moving back out. These currents are actually wave surge and they tend to ricochet around, between and over rocks like a berserk pinball machine, unlike river current which is more channelized.
A very important result of the different type of current in a river vs. ocean rock garden is how it affects a kayaker when broached on a rock. A river current will tend to trap you against the rock if you happen to get broached sideways, so you need to lean into a rock in the river and present your hull to the current. Otherwise the current will flip you and trap you against the rock. If the wave surge in an ocean rock garden carries you sideways into a rock, you lean away from the rock and present your hull to the rock. The surge will reverse direction and flow back off the rock, taking you with it. And your hull will take the impact instead of your body.
A pour-over in the river might look the same as a pour-over in the ocean, but there is one important difference. In the river, when water flows over a ledge, a ‘hole’ or ‘hydraulic’ forms on the downstream side and can trap you. When this happens you have to work your way out by moving to the side of the hole to escape. In the ocean, a similar hydraulic may form at the bottom of a pour-over, but if you get trapped, it will only be temporary and you’ll be released, or pushed elsewhere, when the wave recedes.
Paddling in whitewater is fun and challenging, whether you paddle rivers or ocean rock gardens. Many kayaking skills transfer from one regime to the other, but you’ll have to adjust to the different water dynamics and learn to adjust to either environment. The river tends to be more of a steady-state situation, whereas the ocean is in constant flux and will change by the minute.
What is your take on John’s description of river vs ocean whitewater? Please post your comments or questions below this essay.
Fat Paddler says
Great post! I’ve spent most of my life playing in the surf in one form or another, and feel like I have a good handle on surf water dynamics. As a newbie to rock gardening, I’m learning about the changing dynamics of waves and current in the rocks, which has been a fun (and sometimes painful!) learning curve. Recently, I got the opportunity to go river white water kayaking and was astounded at the difference. For example, if I get hit broadside in surf I lean into the wave, extend my paddle out and side surf until its time to self-right. In white water, you have to lean away from the current and moving water, to stop being dragged under by the hydraulics. Fortunately I learnt this lesson in a relatively safe rapid, and when the inevitable happened I was able to swim to safety and take stock of what happened. I literally had to try to re-train my thinking on handling dynamic water, which was terrifying in some ways, but exciting in more! I’ve now spent much more time studying eddies, and eddy-lines, and areas where currents stop/change/reverse, and can only think this will help me more when exploring rocks in the future. Clearly I still have a lot to learn, but I’m going to enjoy throwing a little creek running into my paddling regime as well. Cheers, FP
Scott Becklund says
I agree and have both a similar feeling and experience as Fat Paddler. I’ve always felt as if we ocean kayakers were cheating. The ocean gives us second and third chances. She releases us after we screw up before she comes again.
John I’d love to watch a river with you someday. Not only to discuss the geology,stream morphology and limnology but to help understand what the heck the fresh stuff is doing.
Thank you both. Keep it up.
Fat Paddler says
Scott, I couldn’t agree more. Watching river hydraulics made it clear to me why this type of water was so dangerous, and made me thankful for the occasional beatings I get on ocean-side rocks – at least I get beaten and released!!
Rainer Lang says
I agree with the differences in regard to hydraulics. Ocean white water being mostly cyclical; river whitewater being mostly constant, based on flow rates.
On an early whitewater trip, the real eye opener was the concept of Gradient. Where the riverbed loses elevation, causing the water to increase in speed. We scouted the run by looking down hill. Basically we were going down a rock staircase with thousands of cubic feet of water.
Eric Soares says
I like the “catch and release” philosophy of the ocean. Once you get in a river, it’s all downhill! 🙂
Seriously, John’s essay points out some strong differences between rivers and ocean rock gardens, as FP, Scott, and Rainer have indicated. I think it’s worthwhile for sea kayakers of all stripes to do some river time, and it wouldn’t hurt river runners to learn about the hydrodynamics of surf and ocean rock gardens.
Moulton Avery says
Lovely article, John. It really does a great job of illustrating the different dynamics in both environments. What a great sport!
One thing I haven’t encountered in rivers is waves coming from many directions at the same time, reflecting off obstructions and occasionally amplifying each other. That’s not to say that rivers can’t be chaotic, just that this particular type of chaos, where you can can get hit from multiple directions at the same time, is rare in rivers but seems to be a common feature of ocean rock gardens. As far as catch and release goes, I think the ocean is a far more dangerous and demanding environment. Ditto large bodies of open water. Both have the capacity to be grimly unrelenting in a way that rivers can seldom match, and our strength, both mentally and physically, is all too finite. One of the most harrowing incident reports I’ve ever read involved a mate in your area who got trapped in a sea cave and had one hell of a time making it out alive.
With respect to currents and leaning, I think the turning force we’re trying to counteract is exactly the same whether the venue is river or ocean; it just feels different at times. In rivers, when peeling out of an eddy, the moving water contacts the upriver side and bottom of your hull and the resulting force tries to flip you “upstream”, so you counter by leaning downstream, away from the force of the current. The same principle holds true for tide races.
In ocean waves, the water between the trough and the peak is moving up the wave face the same way it does on a standing river wave, so when you lean into the wave, you’re still leaning away from the force of the current. A breaking wave that’s pushing you sideways towards shore only feels different because it’s your boat that’s moving, rather than the water directly underneath it. The evil forces trying to capsize you, however, are exactly the same.
Gary Allen says
I’m afraid I must respectfully disagree with Moulton above. I’ve spent considerable time surfing, doing extended ocean and bay crossings, and in ocean rock gardens. I’ve also done as much, if not more, whitewater river rafting/paddling in up to class V water. As Scott comments, the ocean gives you second and third chances, and things generally set up slowly–it’s more like, “Here comes the wave, I see it coming, it’s almost here, now it’s here, whoa!” On the other hand in a complex river rapid with multiple obstacles such as exposed rocks, holes, submerged logs, etc., it’s all about fast twitch reflexes and immediate response. And the consequences of a screwup are more severe if for no other reason than the basic fact that the water moves through the wave on the river. If you get stuck in a keeper hole or wedged between rocks on the river, you’re in serious trouble. There are more kayak fatalities on rivers than in the ocean. But it’s all a matter of degree, of course, depending on the cfs of the river flow, the complexity of the rapid, etc. All that being said, both environments are beautiful in their own ways, but the vast wilderness of the ocean is the one that speaks more to me.
Doug Lloyd says
If I were to take my little bottle of whiteout I don’t think anything Moulton wrote would be redacted other than the “evil forces” are not really evil – just molecules of water helplessly being manipulated by flow/swell and river/ocean topographic features, etc., obviously. I also think it is difficult comparing apples and oranges even though both are fruit and so finding the similarities wasn’t too bad an idea by Mr. Avery. However, both rivers and ocean rock gardens have rating systems. The Ranger’s SCRS when correctly resulting in a too high value to be safe rating as when applied to a heavy swell zone impacting the shoreline of a continental land mass where injury and possible death may be likely subsequent to a capsize may indeed compare favourably with a Class VI rapid. I have certainly seen Class VI in Northern Pakistan and up through the Hindu Kush meltwater regions when I lived in Pakistan and I’ve also played near the edges of 30 foot winter swell off my coastline as I skirted the edges of the rock garden zones; neither would I consider survivable (coming out of my boat in Class VI or going into the rock garden is said heavy swell) – at least for my skill levels. But Gary is right, your average Class III or short IV run compared to a heavy day on the Mendocino coast doesn’t compare favourably. The linearity and forced flow downstream requires a great deal of split-second decision making and the skills to move the kayak where it needs to go. Creek boating in higher gradients in the higher Class ranges gets even more consequential.
I have played off the north outer jetty of the Columbia River Bar and the degree of skill and fast-response, reflex action is so intense it can’t even be described with ocean breakers steeply spilling without warning from multiple directions under tidal flow conditions; but even in that there is a scope and breadth that doesn’t require the same intense fast-twitch responsiveness that a river may require to avoid a trajectory leading to probable complications or death. One of the reasons I gave up Island winter river paddling was because river routing in swelled water conditions saw water coursing through bush and low tree lines which were just too dangerous if you missed your line and there were rapid river morphology changes. The only other observation I have – and you can chuck any of this if you want – is that a lot of white water paddlers are doing the park and play thing now, as are ocean paddlers playing around pourovers and slapwall features, etc. In both pursuits most pick conditions and degrees of severity they are comfortable with though we do see white water injuries and deaths remaining high, though this may be due to increased incidences of running waterfalls and taking on challenging rivers for their difficulty thresholds.
I like playing narrow river bars where the action is tight and intense with rock garden peripheries that add confusion and a dynamic of unpredictability that requires both fast-twitch responsiveness and poor outcomes if you misalign trajectory. Nitnat Narrows was a place I frequented in the 1980’s along the West Coast Trail on Vancouver Island. My brother in law runs commercial fishing trips out of Nitnat. Lake, over the bar. Local knowledge is paramount he’d agree. Many have died here over the years.
John Lull says
Moulton, your last paragraph in the post above is exactly right on! I’ll follow up with more and also answer a lot of these comments tomorrow.
I’ve been off line for a few days and just got home from a music gig. It’s late, I’m tired, and so I’ll catch up tomorrow.
Eric Soares says
Moulton above mentions that in rivers he hasn’t experienced “waves coming from many directions at the same time, reflecting off obstructions and occasionally amplifying each other.” Neither have I. However, I just read a great story by Doug Ammons in KAYAK SESSIONS magazine about the Stikine River in Canada, which scared the bejeezus out of me. Talk about waves from everywhere rebounding and amplifying. Whew.
A few years ago I scouted the Yellowstone River in Jellystone Park, and wow, it was impressive with all its compressed hydraulics, multidimensional waves and then the big falls. Gulp. My point? In rivers and in ocean rock gardens all kinds of chaotic wave action can occur–and that’s what makes “whitewater” so exciting in manifold ways.
Moulton Avery says
Jeepers, mates; I stand corrected. Guess I was focusing more on the relative paucity of “bail-out” options if things turn sour on open water (distant shores, no eddys etc.) but reading and thinking about what you both wrote, I concede with respect to the overall number of objective hazards & how nimble the river runner has to be to avoid them. I’ve also seen some videos of folks succesfully running rivers (in Chile, for example) that looked terrifying and unrunnable to me, and in those cases, there certainly was water exploding from all directions.
Great post!!! It makes me excited for our upcoming whitewater kayaking season. Learning to kayak whitewater rivers hugely improved my overall paddling skills. It was intimidating at first because the river current is constant; whereas the ocean pulses (“catches and releases”) and lets you regroup. I like the technical aspects of river running – reading the water, picking out a line, and then executing the line. I still have to constantly remind myself on the river to hug the rocks (on the ocean it seems pretty intuitive to moon them).
Moulton Avery says
I think Doug makes an excellent point about comparing apples and oranges; some aspects of river and ocean paddling really don’t compare well at all. Also, after taking a peek at the sat photos of Nitnat Narrows, I can say without hesitation that I’d want a couple of stiff drinks before so much as sitting down to watch a video of that water on an ebb tide. Crikey, Doug, that’s a really big lake and a really tiny Pacific Ocean inlet.
While I agree with Gary and Scott’s observations about things generally setting up more slowly on the ocean, second and third chances, capture and release, and so forth, two contrasting variables I think we should consider about the ocean equation are the potential for rapid change and what I would describe as sustained intensity.
One distinction between river and ocean paddling pointed out by John Lull, Eric, and others, either here or elsewhere on this blog, is the fact that the ocean is more unpredictable than a river because of the rapidity with which conditions can change. Whether individually or in combination, variables like an increase in wind speed, a change in tidal flow, or the arrival of a larger wave set from the same or a different direction can very rapidly change the sea conditions from, say, a fun Class 2 to a jaw-clenching Class 4. Rivers don’t have a reputation for suddenly changing their ratings and springing that sort of change on you.
When paddling a long distance from shore, or a long way from a safe place to take out, open water paddling conditions also continue uninterrupted, hour after hour, with no possibility of a break in the action. While I recognize that we’re not exactly comparing apples and oranges, my point is that it’s one thing to have to paddle for 20 – 30 minutes through continuous rapids, and another thing entirely to have to paddle for 3 – 4 hours in comparable sea conditions. I don’t think many rivers feature that level of sustained intensity. That’s the variable that was on my mind when I wrote that open water paddling has the capacity to be grimly unrelenting in a way that rivers can seldom match.
John Lull says
Hey, thanks for all the cogent comments so far! I’ll give my take on a couple of points made, starting with Moulton’s observation about sidesurfing a breaking wave (or hole) in the river vs a breaking wave in the ocean.
As Moulton correctly points out, sidesurfing in the river is exacty the same technique as in the ocean. In both cases you are tilting the kayak into the break and presenting your hull on a planing angle to the moving water. Now read that sentence again. The only difference is that in the river the water is moving under your boat due to the current, while the boat is held stationary by the wave. In the ocean the moving water is a result of the wave pushing you along over the surface of the water. In either case you want your hull to plane, not catch an edge and flip. One mistake beginners often make in this situation is to lean their body into the wave, instead of tilting the boat. You might lean your body momentarily (especially in a large breaking ocean wave), but the critical thing is to set your boat on edge. And remember, a wave breaks upstream in a river. That can mess with your perceptions until you get used to the idea!
Regarding the relative danger of river vs ocean whitewater, that wasn’t really the focus of my article. I don’t think you can over-generalize, given the really wide range of conditions found in both environments. And of course, the risk factor is highly dependent on the paddler’s skill and experience. You can’t go by drowning statistics because far, far more boaters run rivers (in all sorts of craft, including kayaks, rafts, canoes, ‘rubber duckies’, etc) as opposed to paddling ocean whitewater/rock gardens. And I’ve seen many inexperienced yahoos on the river, myself included on my first-ever river run many years ago in a dime-store inflateable on a class IV river! Ah, the joy of ignorance.
Don’t let the ‘catch and release’ factor of ocean waves lull you into a sense of security. Sure, the first wave that pounds you into a dangerous slot in the rocks will release you, only to be followed by wave after wave giving you a continuous unrelenting pounding. And Murphy’s Law will dictate that each wave is larger than the last! Just ask BASK member Ken Manshard about his experience out at Point Bonita (outside the Golden Gate). Of course it doesn’t always happen this way, but in many situations it can.
On the river entrapment is a definite hazard, but most entrapment situations are easily avoided once you know what to look for.
Perhaps the biggest general hazard in ocean whitewater is the unpredicatibility of the waves. You can never know for absolute certainty that a rogue wave won’t arrive, even on the calmest day. I know at least one highly experienced, expert whitewater river kayaker (he knows who he is, and can respond here if he chooses) who told me straight out that the ocean is more dangerous due to the unpredictibility factor. I don’t entirely disagree, but as I mentioned above, you really don’t want to over generalize.
Dennis Kuhr says
Good post John. I have fond memories of running the South Fork American with you.
You mentioned the waves breaking up-river towards the end of your comments. To eloborate a little further, that means one must roll up-river(opposite your direction of travel), unlike down wave in the ocean.
John Lull says
Hey Dennis, yeah we had some great runs on the South Fork. Maybe we ought to get up there again next season.
You bring up an important point about rolling, but unless I misunderstood what you said (I probably did), I think it’s just the opposite of what you describe. It’s easy to get turned around and confused about which is the best side to roll in a dynamic situation. I’ll give my take on it, but first and most important, when upside down underwater there is no way to know for sure which way the current is moving, the wind is blowing, or the wave is moving. So the best course is to set up on your favorite side (if you have one) and roll. If you meet a lot of resistance, set up again on the other side and you’ll probably pop right up, assuming the reason you missed the first roll was due to current, wind, or wave action.
In a river, if you are moving at exactly the same speed as the current, you can roll either side. If something is slowing you down relative to the current, like a wave or hydraulic, you’ll need to roll up on the downstream side. That means you are rolling up on the breaking wave side, exactly the same as in the ocean (see below).
In the ocean, if you are being pushed shoreward by a breaking wave, it will be nearly impossible to roll up on the shoreward side, but very easy to roll up on the wave side (same as the river).
So the rule is: Roll up into the wave.
Finally, out on open water in a strong wind (20 knots +), you’ll need to roll up on the up-wind side.
In every one of the above cases, if you think really hard about it, you are rolling up on the side where the water is moving AWAY from your boat (downstream side in a river). Where the water is piling up on your boat, the ‘upstream side’, that water will tend to prevent you from rolling up. Remember it’s the relative movement that counts. When pushed by the wind or a wave on the ocean, the ‘upstream’ side is the direction you are moving across the water. Very confusing, I know. But go back and read the second paragraph again. Here it is in a nutshell:
If in wind, current, or a wave, try rolling on one side (you have a 50% chance of getting it right), and if that fails, roll on the other side.
Eric Soares says
I like your 50/50% chance rule, John. Most people should have enough air in their lungs for 2 rolling tries. If upside down, another indicator as to which is the best side to roll on is to start to move your paddle underwater to one side or the other. If there is lots of resistance, go to the other side, as that is the way the current (river or ocean) is going. In other words, go with the flow. It takes time to get sensitive enough to feel resistance or the lack of it, so practice!
But if you are stuck in a Current Chaos, which can happen in either environment, but is common in surfy rock gardens, and water is changing directions constantly under you, then you’ll have to do the Herculean roll (as hard as you can) and hope for the best.
On the point of which side to roll on when knocked over … I make a mental note while I’m paddling upright of which way I’m most likely to get knocked over and therefore decide beforehand I may need to roll on my dominant side or off-side.
John Lull says
Good idea, Tony. That works in some cases, but not all. If you’re sideways in a hole on the river, it’s pretty easy to remember which side is downstream and to roll on that side. Also, when sea kayaking in a strong side wind you should be able to remember which direction the wind is blowing; roll up on the upwind side.
However, in some situations, especially in ocean whitewater in rock gardens, it’s not at all obvious so you have to ready to switch sides if a repeated roll attempt fails.
I agree John that this doesn’t always work but its a good starting point that eliminates the guess work most of the time. Giving some thought to when this may not be effective, I can imagine one scenario such as getting knocked over by an incoming wave but being hit on the other side by it on the rebound if near cliffs.
Thanks for your response. I have your book “Sea Kayaking – Safety & Rescue. I can almost recite it word for word *lol*
John Lull says
Yeah, definitely it’s always best to make that first roll. And if you already know which side to come up on, you’re more likely to make it.
Glad you enjoyed the book. It was fun to write.