International Scale of River Difficulty, created by American Whitewater, (…not very international in my opinion)
Class I: Easy
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.
Class II: Novice
Straightforward rapids with wide, clear channels which are evident without scouting. Occasional maneuvering may be required, but rocks and medium-sized waves are easily avoided by trained paddlers. Swimmers are seldom injured and group assistance, while helpful, is seldom needed. Rapids that are at the upper end of this difficulty range are designated Class II+.
Class III: Intermediate
Rapids with moderate, irregular waves which may be difficult to avoid and which can swamp an open canoe. Complex maneuvers in fast current and good boat control in tight passages or around ledges are often required; large waves or strainers may be present but are easily avoided. Strong eddies and powerful current effects can be found, particularly on large-volume rivers. Scouting is advisable for inexperienced parties. Injuries while swimming are rare; self-rescue is usually easy but group assistance may be required to avoid long swims. Rapids that are at the lower or upper end of this difficulty range are designated Class III- or Class III+ respectively.
Class IV: Advanced
Intense, powerful but predictable rapids requiring precise boat handling in turbulent water. Depending on the character of the river, it may feature large, unavoidable waves and holes or constricted passages demanding fast maneuvers under pressure. A fast, reliable eddy turn may be needed to initiate maneuvers, scout rapids, or rest. Rapids may require “must make” moves above dangerous hazards. Scouting may be necessary the first time down. Risk of injury to swimmers is moderate to high, and water conditions may make self-rescue difficult. Group assistance for rescue is often essential but requires practiced skills. For kayakers, a strong roll is highly recommended. Rapids that are at the lower or upper end of this difficulty range are designated Class IV- or Class IV+ respectively.
Class V: Expert
Extremely long, obstructed, or very violent rapids which expose a paddler to added risk. Drops may contain large, unavoidable waves and holes or steep, congested chutes with complex, demanding routes. Rapids may continue for long distances between pools, demanding a high level of fitness. What eddies exist may be small, turbulent, or difficult to reach. At the high end of the scale, several of these factors may be combined. Scouting is recommended but may be difficult. Swims are dangerous, and rescue is often difficult even for experts. Proper equipment, extensive experience, and practiced rescue skills are essential.
Because of the large range of difficulty that exists beyond Class IV, Class V is an open-ended, multiple-level scale designated by class 5.0, 5.1, 5.2, etc. Each of these levels is an order of magnitude more difficult than the last. That is, going from Class 5.0 to Class 5.1 is a similar order of magnitude as increasing from Class IV to Class 5.0.
Class VI: Extreme and Exploratory Rapids
Runs of this classification are rarely attempted and often exemplify the extremes of difficulty, unpredictability and danger. The consequences of errors are severe and rescue may be impossible. For teams of experts only, at favorable water levels, after close personal inspection and taking all precautions. After a Class VI rapid has been run many times, its rating may be changed to an appropriate Class 5.x rating.
Personal Opinion
The fact is that no two people will give you the same definition of class I, let alone class V, or if there even is a class VI. How, as a community, especially an international community, are we supposed to talk about the rating system? My suggestion would be to continue with the cumbersome I-V (or VI) scale. Then, I firmly suggest that people talk more about what really defines this I-V grading scale. The following are some of the factors that I consider when contemplating a river section.
Regional Differences
It seems like every region that I go to, there is some kind of hazard that the locals are so accustomed to that they no longer realize that it’s an issue, or at best they have become blissfully complacent to the local hazard. Colorado; you are going to pin on road or train debris. California; poison everything, plants, more plants, snakes, aaand there is always a reservoir you have to paddle across at the take out. Southeast; there is no water. You will skip off a damp rock and then land on a slightly damper rock. Pacific Northwest; there are trees… everywhere. Minnesota; ice undercuts lining the shores! New Zealand: SIEVES! (Personal anecdote: coming up to a rapid I was told that there was a really sketchy piece of wood at the bottom of the rapid. Upon entering the rapid, half of the water quickly funneled into a sieve on the right. A bit further into the rapid, another quarter of the water disappeared into a sieve on the left. And at the very bottom of the rapid there was a small branch barely sticking out from the left shore). Zambia; crocs, hippos, baboons, elephants, oh my! Peru; Access. Cotahuasi Canyon is the deepest gorge in the world! Towering peaks reach 20,000 feet on both sides, hiking out isn’t even fathomable. Every place has a local hazard. It doesn’t matter how accustomed to them you have become, it is imperative to know that these are true hazards. You need to be able to properly share these regional issues to paddlers that aren’t acquainted with the region.
Vessel
That 300 cfs creek run might be wide open in a kayak, but sure is technical, or next to impossible, in a raft. Our preferred craft for the descent will drastically change our personal opinions of the rating structure.
Aging
The years keep ticking by, and we don’t revisit section ratings. This is most apparent to me on the Gauley River in West Virginia. Iron Ring was considered a class VI rapid until not that long ago. Sweets (not a) Falls is still talked about as being class V (there is flat water above a ramp of water that splashes into a small non-retentive wave, backed up by a quarter mile pool). On the other end of the spectrum are the things that are being run for the first time… tomorrow. With new equipment ramping up the learning curve and a huge amount of whitewater media being produced on obscure rivers around the globe, the pace at which we are raising the bar has continued to escalate. We are now consistently paddling sections that were unimaginable mere years ago.
Paddling Partner
Another key consideration: who are you paddling with? It turns out Darin McQuoid and my girlfriend rate sections slightly differently. That is ok, but you need to understand what you’re in for. If the person you’re about to go paddling with usually runs really hard class V and they tell you it’s super mellow class III (of course class III is mellow for them), this might be exactly the time to start pestering them for more beta. On the other hand, when you meet the paddler at the put in that is gripped and sweating bullets, and tells you it’s “pretty gnarly class III+++”, again, it might be time to get more beta.
For a Little Comedy:
International System for Rating Rapids Class I, Easy. Fast moving water with riffles and small waves. Swimming is pleasant, shore easily reached. A nice break from paddling. Almost all gear and equipment is recovered. Boat is just slightly scratched. Class II, Novice. Straightforward rapids with wide, clear channels which are evident without scouting. Swimming to eddies requires moderate effort. Climbing out of river may involve slippery rocks and shrub-induced lacerations. Paddle travels great distance downstream requiring lengthy walk. Something unimportant is missing. Boat hits submerged rock leaving visible dent on frame or new gash in plastic. Class III, Intermediate. Rapids with moderate, irregular waves which may be difficult to avoid. Water is swallowed. Legs are ground repeatedly against sharp, pointy rocks. Several eddies are missed while swimming. Difficult decision to stay with boat results in moment of terror when swimmer realizes they are downstream of boat. Paddle is recirculated in small hole way upstream. All personal possessions are removed from boat and floated in different directions. Paddling partners run along river bank shouting helpful instructions. Boat is munched against large boulder hard enough to leave series of deep gouges. Sunglasses fall off. Class IV, Advanced. Water is generally lots colder than Class III. Intense, powerful but predictable rapids requiring precise swimming in turbulent water. Swimming may require `must’ moves above dangerous hazards. Must moves are downgraded to `strongly recommended’ after they are missed. Sensation of disbelief experienced while about to swim large drops. Frantic swimming towards shore is alternated with frantic swimming away from shore to avoid strainers. Rocks are clung to with death grip. Paddle is completely forgotten. One shoe is removed. Hydraulic pressure permanently removes waterproof box with all the really important stuff. Paddle partners running along stream look genuinely concerned while lofting throw ropes 20 feet behind swimmer. Paddle partners stare slack-jawed and point in amazement at boat which is finally pinned by major feature. Climbing up river bank involves inverted tree. One of those spring loaded pins that attaches watch to wristband is missing. Contact lenses are moved to rear of eyeballs. Class V, Expert. The water in this rapid is usually under 42 degrees F. Most gear is destroyed on rocks within minutes if not seconds. If the boat survives, it is need of about three days of repair. There is no swimming, only frantic movements to keep from becoming one with the rocks and to get a breath from time to time. Terror and panic set in as you realize your paddle partners don’t have a chance in heck of reaching you. You come to a true understanding of the terms maytagging and pinballing. That hole that looked like nothing when scouted, has a hydraulic that holds you under the water until your lungs are close to bursting. You come out only to realize you still have 75% of the rapid left to swim. Swim to the eddy? What #%^&*#* eddy!? This rapid usually lasts a mile or more. Hydraulic pressure within the first few seconds removes everything that can come off your body. This includes gloves, shoes, neoprene socks, sunglasses, hats, and clothing. The rocks take care of your fingers, toes, and ears. That $900.00 dry suit, well it might hold up to the rocks. Your paddle is trash. If there is a strainer, well, just hope it is old and rotten so it breaks. Paddle partners on shore are frantically trying to run and keep up with you. Their horror is reflected in their faces as they stare at how you are being tossed around! They are hoping to remember how to do CPR. They also really hope the cooler with the beer is still intact. They are going to need a cold one by the time you get out! Climbing out of this happens after the rapid is over. You will probably need the help of a backboard, cervical collar and Z-rig. Even though you have broken bones, lacerations, puncture wounds, missing digits & ears, and a concussion, you won’t feel much pain because you will have severe hypothermia. Enjoy your stay in the hospital: with the time you take recovering, you won’t get another vacation for 3 years. Class VI, World Class. Not recommended for swimming. © 2002 by David Petterson of Calgary Paddlers. Or for even more comedy, check out what was possibly the original grading system, from AW at the link below. It contains tons of very applicable information in a very sexist, dated journal. https://www.americanwhitewater.org/content/Journal/show-page/issue/3/page/28/year/1963/
The Hard Numbers
It’s time to give the I-V scale less importance, and place more emphasis on some hard figures.
Gradient. This seems pretty simple: how steep is the section? Depending on the region, this is given in FPM (Foot Per Mile) or for just about everywhere else in the globe, MPK (Meter Per Kilometer).
Volume. Again, this is not arbitrary. How much water is in the drainage? Measured by CFS (Cubic Foot per Second) or CMS (Cubic Meter per Second), and when stating these facts, give your interpretation of the flow (flood, high, medium, low). A quick side note here, the foot gauge or meter gauge or random graffiti or scribble on the bridge pylon or that specific “rock” is sometimes the only measure of volume available on more obscure sections. If this is so, do your best to relate this in at least an estimate of numerical volume so an outsider might be able to have a rough guess at what they’re getting themselves into.
With these two stats, most seasoned paddlers can start to build a mental picture of what they are signing themselves up for.
A couple of extreme examples of this in practice:
Yule Creek, CO, 640 FPM 300 CFS, Flood, Class V… ish!
Grand Canyon of the Colorado, AZ, 8FPM 12,000 CFS, Medium, Class IV… ish.
The Solution
In reality, there is no universal “fix” to the current rating system. It’s deeply entrenched in our sport, and getting away from it isn’t feasible. Compounding the issue, every time paddling has been picked up in a new region, the scale has been bastardized by the locals. The best option for us now is to truly be aware of the shortcomings of the I-V scale and to supplement this with more tangible beta. So when you’re looking for info on your next class IVish river, ask another question or two, will ya?Words by 4CRS team Member Chris Baer. Check out his personal blog whereisbaer.com for more!
