I used to think class I and calm flatwater are the same thing, but I was told they are not. Is there a name for calm/flatwater classification? Also, for ocean whitewater, is it the same scale (class I-V) like with river whitewater?

I think flatwater/flatwater river is pretty universally understood terminology, but someone may have something more official?
In an ocean environment, the certification systems of the ACA and BCU use 1-5. It’s classified by wind speed, current speed, wave height, and surf height in the ACA. In an ocean environment, you could find level 5 surf height with level 1 wind speed and current speed. Or you could paddle in an area with little fetch and have level 5 wind with low level waves and or current. Much like a section of river can change at different flow levels, any section of water can change levels based upon these parameters. I think it’s important to expose yourself to upper levels independently in a carefully controlled way before stacking them all together. You don’t want to be learning how your kayak behaves and how to maneuver it fully exposed to 20 knot winds for the first time at the same time you’re taking on short-period 3 - 4’ waves for the first time. The great thing is that there are ways to accomplish this.
So similar, but different.

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Fat water is what most call non-whitewater.

Here is a summary of the ACA flatwater level classifications:

That said, it is not as well understood/known/used as the whitewater class system.

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Whitewater classifications in the US most often follow the stratification scheme that originated with the American Whitewater Association using a Class I through Class V designation. Later a Class VI was added. The exception is the Colorado River which generally rates rapids using a numerical 1 through 10 stratification scheme.

Flat water, even moving flat water is not the same as Class I whitewater. Whitewater implies that there are at least some features, waves, drops, and/or obstacles to be avoided. In other words, there are rapids even though they may be simple and unobstructed in Class I.

Flat water on the other hand, is generally featureless even though it may be moving relatively rapidly. Moving flat water is sometimes classified A, B, or C depending on current velocity. I have seen different current velocity boundaries used to denote these classifications but for class A moving flat water current velocity is generally less than around 2 miles per hour, class B 2 to 4 mph, and Class C above 4 mph. I think a more useful way for an individual to grade moving flat water is to consider it Class A if you can relatively easily paddle upstream against the current, at least for a short time. Class B would indicate a current velocity that allows you to maintain your position relative to the stream bed bottom by paddling fairly hard, at least for a short time, and class C would indicate a current velocity that you could not overcome even for a short while paddling as hard as you can. So depending on the boat and the strength and proficiency of the paddler(s) the velocity boundaries between Class A, B, and C moving flat water might vary a bit.

So in class A moving flat water you could attain upstream at least for short periods, class B would allow you to ferry from one side of the stream to a point directly across on the other side, but you might have to work pretty hard to do so, and with class C you should expect to aim for a target significantly downstream when contemplating a forward (upstream) ferry.

The descriptions that have been used by American Whitewater for rapids of the various levels of difficulty have changed a bit over the years. Here is a link that gives the descriptions at present:

And here is American Whitewater’s description of a Class I rapid:

“Fast moving water with riffles and small waves. Few obstructions, all obvious and easily missed with little training. Risk to swimmers is slight; self-rescue is easy.”

But once again, for something to be called Class I whitewater there has to be a rapid or rapids, not just moving flat water.


Classification systems are important.
I have used the whitewater system for decades, but the ocean classification is new to me. Thanks for posting it.

Now we just need to get people to stop exaggerating what they paddle.

Whitewater experience can really help your open water skills.

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I never knew how ocean conditions were rated either. Greatly appreciated. I see that I self restrict myself to a specific category, but I think I drop one level regarding surf.

Surprising to see L4 can be done in a sit-on -top.

You sit on top guys are commited.

A classification system is a great place to start. Just understand that things are not static. Weather (especially wind and storms) can really change things on open water and rising or falling water levels certainly change how you run rapids. This idea seems pretty simple but it is surprising how this alludes many folks.

The whitewater classification system attempts to classify difficulty and danger into one category. Generally this works pretty well but changing conditions sometimes throw the system out of kilter.

There has been a tendency in the whitewater realm to downgrade the rating of rapids as they become more familiar. Increasing skill levels, better boat designs, and familiarity (regulated water levels) have all contributed to downgrading. There is also a tendency for individuals to downgrade things they’ve done well and increase the rating of rapids they end up swimming.

When you do things out of the norm the aw ratings go out the window. Tomorrow, I plan to run the middle gauley river. 2300-2800 cfs is a typical release level. It was running 630 cfs when I checked it this morning and I expect it to be in that neighborhood tomorrow. Typical runs are done in Sept and Oct. with a good deal of support nearby if something happens (Park Service, Commercial Rafting Companies, large groups of private boaters). I won’t be surprised if the two of us are the only folks on the water tomorrow. The lines change in a lot of the rapids. It is just a different gauley experience than what most folks think of. Less splashy but steeper and more technical. The colder water, cool air temps and lack of other resources will keep me a bit conservative. Play is likely to be nonexistant with an emphasis on clean lines and keeping boat spacing tight in case someone swims. You change up the approach to match the conditions.

We will probably push with our hands on a sneak route to get through “chainsaw” which is normally a straight forward class III. Stuff changes and people have different strengths. I’m better right now at bouncing off of rocks than boating big water which requires more physicality and could lead to a longer swim. My sweet spot for most of the local runs in my area is a good bit lower than the norm or what I used to do.

A large part of whitewater boating is “situational awareness”. The more you understand the situation the better you can mitigate the risks. So how can you learn this? Hooking up with more experienced folks can help. Doing personal first descents on rivers within your skillset is another good way. On familar rivers try harder moves, routes, and play more.

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the way a lot of ww boaters view flatwater is a bit different than the formal classification system

boogie water- water that is much easier than the rest of run, it may contain rapids or just swift current but any rapids are mild compared to the rest of the run, water is moving at a good pace but the goal is to get through it quickly to get to the rest of the run or takeout

flatwater- this water
may have some current and may even contain some class Is but lacks excitement

dreaded flatwater- not moving, little or no current, involves paddling short uncomfortable boats that are designed to turn. Dreaded flatwater often occurs at the end of run when you are tired from taking multiple swims earlier in the day and is frequently accompanied by a head wind


I did mild WW in a canoe when I was in my 20s. I love open water. You guys can have it and hats off to you!

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Well said. you took the words right outta my mouth.

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