October 13, 2022 10 min read

Whitewater Rapids Classification System

Paddle boarders on a calm river rapids

If you’re taking your paddling up a notch and tackling rivers where rapids are present, then it is essential that you understand the classes of the rapids, the levels of the water, and if you’re experienced enough to paddle down them in the first place.

This article is going to cover the classification of rapids, water levels, and canoeists' competence so you can get a feel for how difficult or easy your next whitewater kayaking adventure will be. 

Rapid Classes

Rapids vary in their intensities from smooth flat water in class A to extreme and often deadly waters in class VIs. As I’m sure you can imagine, understanding the difficulty of the waters you’ll be paddling in is extremely important. If a beginner paddler with very little rapid paddling experience paddled down a river with class VI rapids, then they would pretty much be signing their death wish. 

Whitewater rapids are categorized into seven different classes, which we will get into below. We also wanted to mention that if you’re paddling down the Grand Canyon stretch of the Colorado River, then the rapids are categorized into a class 1 to 10 system, which roughly parallels the class I - IV rapid scale. 

Class A

Class A shouldn’t even be categorized as rapids as it is essentially lake water that is flat, still, and manageable by paddlers of all abilities. 

Class I

Class I rapids are again basically flat waters, however, there may be small and irregular waves. Waters in the class I category will have very few rocks, occasional sand banks, and hardly any significant obstacles. 

Beginner paddlers who have perfected their paddling strokes will be able to tackle class I rapids without any problems or supervision.

Class II

Next up are Class II rapids which feature small waves, short bends, and clear, open passages. These waters will have medium-quick flowing water and a few obstructions that intermediate paddlers can safely and confidently navigate.

Class III

Class III rapids have an intermediate difficulty level due to the numerous irregular and high waves, the small drops, the counter-currents, the rocks, and the eddies. Class IIIs will also have narrow clear passages that require some experience to navigate.

The obstacles that come with a class III rapid can easily flip a canoe or kayak if the paddler isn’t experienced enough. Luckily, self-rescue is possible, but you may require some help. 

If you’re thinking about paddling a class III rapid, then you should also know that these rapids come in class III- and a class III+ difficulty. Class III- rapids are slightly easier to navigate as they’re on the easier end of the class III intensity, whereas class III+ rapids are on the more difficult end and should only be paddled by experienced paddlers.

Class IV

River surrounded by trees

Class IV rapids are difficult, powerful, and long rapids that are of an advanced level. Only paddlers with experience and whitewater skills should even attempt to paddle down them as the waves are large and turbulent. With that being said, however, the waves are predictable, and if you’re experienced, you’ll find them a pleasant challenge while paddling. 

Rapids in the Class IV category also feature falls, eddies, and obstacles that are dangerous and challenging to navigate. Self-rescues are extremely difficult to perform, so it is highly recommended to make advanced preparations for rescues and to always travel in groups.

Similar to class III rapids, class IV rapids can also be further graded to class IV - and class IV+, with the latter being even more difficult. Canoeists should only tackle class IV rapids if their canoes are fully equipped with flotation bags.

Class V

Class V rapids are extremely difficult and of an expert level. Class Vs are characterized by violent rapids that are long, turbulent, and continuous, and they have abrupt drops, unpredictable and very large waves, and holes and steep gradients. 

If you’re planning on attempting to paddle down a class V rapid, then it is crucial that you plan rescue preparations ahead of time as self-rescue is exceptionally difficult, and swimming is extremely dangerous. Only highly experienced paddlers in specially equipped kayaks, whitewater canoes, or crafts should even attempt a class V rapid. 

When it comes to the grade of a class V river, they’re classified from 5.0 - 5.9 based on the river's difficulty. It goes without saying that class V rapids on the higher end of the scale are reserved for only the elite. 

Class VI

Now, we highly recommend that no paddler even try to tackle class VI rapids as they can be fatal to even the most experienced paddler. Class VIs have extremely turbulent and erratic waves and dangerous hazards that require precise boat handling.

These waters are only navigable when water conditions and water levels are favorable, but even then, they should only be paddled by those of Olympic ability. Rescue is near enough impossible on class VI rapids, and paddlers should take every safety precaution imaginable. 

Water Levels

Man whitewater rafting

The scale of river difficulty can change tremendously if the water level rises or falls. If the water level of class II rapid, for example, becomes abnormally high after a storm, then these waters can quickly turn into a class IV rapid. Alternatively, if the water levels in a class IV drop, then the difficulty of the stretch of water also lowers, and intermediate paddlers may even find the once extremely difficult rapids now a breeze. 

It’s important to remember that stretches of water, no matter how calm they are, can become exceptionally dangerous during floods. This danger arises because the forces given off by currents slamming into rocks create treacherous conditions for both swimmers and paddlers. 

Below is an international rating system for water levels that are used to describe the level and the rate of flow: 

  • Low (L)- Low water levels will interfere with paddling as shallow waters may turn into dry banks and muddy sandbars. 
  • Medium (M)- Medium waters are used to describe waters that are normal for that particular river. They have slight gradients, and there will be enough depth for paddling on the steeper sections of the river. 
  • Medium-High (MH) - Medium-High water levels are typically higher than normal and flow slightly faster on the river's gentle gradients. These waters provide the best flow for difficult sections of the river and provide paddlers with enough passage to paddle over low ledges.
  • High (H)- High waters are above normal and difficult to handle. There will be strong currents in high waters, and only experienced kayakers or canoeists whose canoes are equipped with adequate flotation bags should paddle in these waters.
  • High-High (HH)- High-High waters are extremely treacherous with debris and extremely strong currents. Reserved for only experts with good boat control. 
  • Flood (F)- Floods are abnormally higher waters that overflow the banks of the river. Currents during flood levels are violent, and no boaters should even think about paddling until the water levels have lowered.

Canoeists Competence

If you’ve been wondering about your canoeist competence rank, then compare your experience to the ratings below. 

  • Class I - Beginner paddlers who are familiar with basic strokes and can paddle a tandem canoe from either the bow or stern in flat waters.
  • Class II - Paddlers who can handle slightly more advanced whitewater strokes while paddling on their own or those who can perform these strokes in a tandem canoe from either the bow or stern. Class II canoeists should be able to read water and paddle regular rapids confidently. 
  • Class III - Intermediate paddlers with the ability to negotiate rapids by sequenced maneuvers. These paddlers should be able to skillfully paddle either the bow or stern end of a tandem canoe, or they should be able to paddle class II rapids in a kayak or solo canoe. 
  • Class IV - Expert paddlers who can paddle class III or class IV rapids from the bow or stern of a tandem canoe. These paddlers may also be able to paddle a fully equipped solo canoe or kayak, and they will be able to understand and execute maneuvers in high water.
  • Class V - The best of the best who have incredible paddling experience, training to lead a group, and good judgment of the waters. 

Risks Associated With Strong Rapids

Man paddle boarding on whitewater

Whitewater paddling is an extreme sport, and like all other extreme sports, there are some risks that should always be considered before each and every paddle.

  • Drowning- Obviously, when there is water involved, there is always the risk of drowning. If you attempt to tackle waters that are too advanced for your level, your kayak or canoe could flip, and the force of the rapids could pull you under.
  • Hypothermia- Rapids are often cold, and if you’re paddling outside during the summer months, the water will be even colder. Even wet suits or dry suits aren’t able to block out all the effects of cold weather and water, so hypothermia can be a real issue.
  • Overexertion- If you’re out of shape, then overexertion from paddling can cause heart attacks and, in some cases, sudden death. 
  • Hitting objects in the water- Rivers and rapids are filled with objects, most commonly rocks that can cause a great deal of damage to both you and your craft if you happen to smash into one. 
  • Getting stuck in river features- If you get tipped out of your craft, then there is also the risk of you getting stuck in holes, pinned on rocks, or trapped in downed trees. The force of the water prevents you from freeing yourself, which is one of the scariest things about whitewater paddling as you only have so long before you run out of air. 

What Can Change a River’s Classification?

One of the main factors that change the classification of a river is its water level. Water levels can often increase the difficulty of a river, however, some rapids also become more technical and harder to navigate when the waters are low.

The second factor that can change the river’s difficulty is the type of boat that you’re paddling as rafts would be able to tackle more challenging waters than a kayak, for example.

And lastly, the rapids may change classification after events like floods, landslides, and storms, which have changed the shape of the river. Rivers will change over time and with that, so will the rapid classes associated with them. It’s always best to keep updated on the waters you wish to paddle in to ensure you aren’t putting yourself in danger. 

How to Decide if You Should Paddle That Particular River

Before you paddle rapids of any level, you first need to evaluate three main rapid water elements. The first is your ability, the second is the class of the rapids, and the third is the water level in that particular river.

If you’ve mastered basic paddling skills and have been practicing on flat waters for a while, then you’re more than likely able to paddle class I rapids. From there, once you’ve gained further practice paddling down rivers with faster-moving waters, you can progress to the next level.

Never put yourself in danger by paddling in waters you aren’t ready for. Slow and steady wins the race, and you should always do your research on the water conditions and rapid classes before you set foot in a kayak or a canoe. 

Safety Tips for Whitewater Rafting

Group of people whitewater rafting

No matter what type of rapids you’re paddling in, it is crucial that you take some necessary precautions to ensure your safety at all times. 

  • Paddle with a professional - If it’s your first time tackling rapids, then it’s best to take a professional with you who can show you the ropes and teach you some important tips and tricks. 
  • Wear a PFD- You should always wear a PFD when paddling, especially in rapids and fast-moving waters. Personal flotation devices could save your life in unpredictable currents or in turbulent water. 
  • Wear a helmet- Along with a PFD, you should always wear a helmet to protect your head from any collisions on obstacles or submerged rocks. 
  • Be a competent swimmer - If you can’t swim confidently, then you should never tackle rapids. Basic swimming is an essential part of any water sport, so make sure you’re competent in the water before heading out to the rapids. 
  • Take a throw bag with you - Throw bags are a sack filled with a rope that can be used to rescue you if you fall out of your kayak, raft, or canoe. 
  • Listen to your guide- If you’re paddling with a guide, then always follow their instructions. They’re the experts and they know the rapids better than you do. 
  • Don’t panic - When things go wrong in rapids, they go wrong fast, and it’s important that you don’t panic. When we panic, we don’t act accordingly, so keeping a cool head can make all the difference.


🏆 What do class 1 and 2 rapids look like?

Class I rapids will look like moving water with very few obstructions and a handful of small waves. Class II rapids, on the other hand, will be slightly faster moving water with clear channels and small waves.

👍 What Is a class 2 rapids?

Class II rapids are medium-quick flowing waters that feature small waves, open passages, and short bends with a few obstructions. 

🏝️ What are level 4 rapids?

Level 4 or IV rapids are powerful and long rapids that are extremely difficult to navigate. These rapids will feature large and turbulent waves, falls, obstacles, and eddies, all of which are dangerous and challenging to paddle. 

Self-rescues in level 4 rapids are extremely difficult to perform, and you would need to make advanced plans for rescue if you decide to paddle down them. 

❓ Is it safe to paddle down rapids?

Some rapids are safe to paddle down, and others are not. Whether or not you could class a rapid as safe will come down to your paddling experience and the current water levels in the river. Here are the rapid classes and what level of paddling you’d need to be able to tackle them:

  • Class I - Beginner 
  • Class II - Intermediate
  • Class III - Advanced
  • Class IV - Expert
  • Class V - Olympic 

📦 How to determine what rapids are safe to paddle down?

To determine what rapids are safe to paddle down, you will need to combine three different factors. The first is the class of the rapid, the second is your paddling skills, and the third is the current water levels of the river. 

Beginner paddlers should only tackle class I rapids, for example, as they have very small currents and waves that won’t pose much of a challenge. More experienced paddlers can slowly make their way up the class list as long as the conditions in the river are deemed suitable. 

You should always remember that the water levels can alter the class of the rapids, so the class I, you paddled down last week may now be a class III because the water levels in the river have risen.

Jay Regan
Jay Regan

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