How Are Rapids Classified?

When navigating a body of water, it’s vital that you are aware of how that water will behave. Making sure you know what to expect should be an essential part of your preparation. You should never take on a river or a rapid that you don’t have the skill for, or serious harm could come your way.

Whitewater kayaking gif

What Is The International Scale Of Difficulty?

The International Scale of Difficulty is used to rate the technical difficulty and level of skill that is necessary to pass through this section of the river. If you are a kayaker, a canoeist, or a fan of whitewater rafting, this method of rapids classification should come in handy.

Class I – VI

If you have spent any time on a river, you know that the current can get pretty intense in certain spots. If you plan on navigating turbulent rivers, you ought to know how these rapids are classified and whether you have the necessary skills to safely navigate them.

The International Scale of Difficulty system is merely a guide, though. The level of difficulty of these rapids is subjective, as no two people will experience the same rapids in the same way. The degree of difficulty will also depend on several factors including water level, the time of year and weather conditions.

Whitewater yakking

Within the International Scale of Difficulty, there are 6 categories.

Class I

A beginner should be able to navigate Class I rapids with ease. You can expect fast-moving water with small waves and some riffles. If there are any obstructions, they will be obvious, and you should be able to avoid them. Should trouble occur, it will be easy to rescffffffffffffffffue yourself, and there should be minimal risk to swimmers.


Class II

These rapids are still fairly simple, though you need at least some experience. When navigating Class II rapids, you will experience wide channels with a clear line of sight. There will be more obstacles and you might need to do some basic maneuvering, but it should still be simple enough given adequate training.

Klamath River
From the Bureau of Land Management FLikr –

Class III

Calling for an intermediate skill level, Class III rapids require some skill to safely navigate. You can expect moderate waves that are quite difficult to avoid. You need to be able to complete complex maneuvers to avoid obstacles as well as make it through fast currents and tight passages. Swimming is still relatively safe, and self-rescue is possible, though you might want some assistance.

Class IV

Meant for those with decent levels of experience, the Class IV rapid is an advanced classification. There will be powerful rapids that are nevertheless predictable, and you need to be capable of precisely handling the vessel through these intense waters. Some rivers may have tight passages, unavoidable obstacles or waves, and other dangerous hazards. There is a moderate to high risk for swimmers and self-rescue is often difficult.

a group of smiling men on their boat
From the Bureau of Land Management FLikr –

Class V

Extensive experience is required for navigating class V rapids, as these really need elevated levels of skill to get through safely. You can expect lengthy stretches of violent waters filled with obstructions. There will likely be sudden drops, large waves, and steep, narrow passageways. Rapids may continue for quite a distance before returning to calm water. As well as skill, you’ll also need to have a significant level of overall fitness. Swimming is dangerous, and rescue is difficult even for those with experience. Class V rapids also contain many other sub-designations such as 5.0, 5.1, and 5.2. Changing from 5.1 to 5.2 is just as difficult as stepping up from IV to V.

Class VI

These rapids are rarely attempted because they are far too dangerous for anyone who does not have extensive expertise in maneuvering rapids. These rapids are unpredictable and full of danger. They should only be attempted by expert teams. Swimming and rescue are nearly impossible, and mistakes often prove fatal.


Effect Of Water Level & Weather Conditions

Weather affects many things, including the classification level of rapids. If it’s been rainy, for example, the water level will be higher. Often, rapids become more difficult when the water is high, because the flow is faster and more powerful. When there has been heavy rainfall, there might also be more debris and obstacles in your way while navigating the river.


However, sometimes more skill is needed when the water level is low, so make sure you pay close attention to your surroundings. Weather conditions can also change the shape and duration of rapids, prompting a change in their classification.

Gear Required For Whitewater Kayaking

Before you head out to your adventure on the river you need to be prepared. There is plenty of gear required if you want to enjoy whitewater kayaking safely.

Personal Flotation Device (PFD): You should always wear your PFD on the water, no matter what the conditions are. It could save your life. Rapids are notorious for pulling things underwater, and your PFD will help ensure you stay above the water.

Helmet: When we say rapids are intense, we mean it. If you’re navigating rapids, you are quite likely to tip over and risk suffering a head injury climb. Wearing your helmet gives an additional layer of protection while enjoying the river. Look for a helmet specifically designed for whitewater sports.

Spare Paddle: When going through rapids, it’s probable that you will either lose a paddle or break one. As you don’t want to be up a creek without your paddle, it’s sound practice to keep a spare one with you. Look for one that is collapsible or sectional so you can easily break it down and keep it with you in the kayak.

Clothing: You need to ensure you have proper clothing while you are paddling. Even if the air is warm, the water is likely cold. You should invest in a wetsuit or drysuit and make sure you have good footwear, too – it’s no fun cutting your feet on sharp rocks because you neglected to think about shoes.

Don’t overlook other safety gear such at ropes, whistles, and knives, as well as a friend with whom you can navigate the river.

Final Word

Take inventory of your ability and skills before setting out for the river and only attempt rafting on a river that will suit them. Check weather conditions and any other crucial information before you set out paddling. Safety is of the utmost importance, but you can still have fun!