Explaining the white water rapid grade and the International Scale of River Difficulty

May 06, 2016 BY Paul McWilliams

If you’ve never been white water rafting or kayaking, looking downstream can be a daunting and even frightening experience. However, there is a white water rapid grade system called the International Scale of River Difficulty that is universally used to classify rivers difficulty.

white water rapid grade and International Scale of River Difficulty flickr image by PeterJBellis

Rafting, particularly with a reputable operator, is a relatively safe ‘extreme’ sport, kayaking is a little more risky. Although accidents do happen – they’re adventure sports after all, the universally used white water rapid grade scale means rafters and kayakers do not head out on waters they cannot handle.

So read of this article explaining the white water rapid grade and the International Scale of River Difficulty. It should stop you from thinking ‘they’re going to let me paddle down that, with no previous experience in a boat?’

White water rapid grade

The white water rapid grade scale, sometimes referred to by its full name – the International Scale of River Difficulty – is a standardised scale used to identify the safety of a stretch of river. A grading for each section of river is given which reflects the level of skill and technical ability that will be required to navigate it safely.

white water rapid grade and International Scale of River Difficulty flickr image by Dlm 7155

The are six levels in the rapid grade scale, ranging from class I to class VI, with class I being the easiest and calmest waters. The addition of a plus (+) or minus (-) sign after the class number also tells you if the rapids are at the easier or harder end of the rapid scale class.

International Scale of River Difficulty

The below rapic classifications help to show you what to expect from a river. However, in many cases rafting tour operators will take complete beginners on high classification rapids. This is because a team with lots of experience on a particular river massively reduces the risk making white water rafting accessible to all.

Class I – Easy

Characterised by  some fast moving water with small waves and riffles. There will be no or few obstructions which can be easily missed with only a little training. Swimming is relatively easy in the water, allowing for self rescue in most cases.

white water rapid grade and International Scale of River Difficulty Wikimedia image by Lisa_Aw

Class II – Novice

Rapids with wide clear channels that are fairly obvious routes. Some obstacles such as rocks may be in your path but can be easily avoided using basic paddling skills. If you do end up in the water, swimming is still fairly safe although some assistance may be needed at times.

Class III – Intermediate

This is a grade for intermediate paddlers that has rapids with moderate, irregular waves which can swamp a raft. There may be some tight passages and good boat control is needed to avoid obstacles. Powerful currents make swimming difficult and group assistance may be needed to avoid longer swims in the water.

Class IV – Advanced

Rapids for advanced paddlers. These are powerful but predictable rapids that nevertheless require good boat control and handling. There will be constricted passages that require a high skill level and larger waves that can’t be avoided.

white water rapid grade and International Scale of River Difficulty flickr image by Sascha Grab

Some rapids will require mandatory paddling manoeuvres and the risk when swimming is high. This level of rapid is recommended for a high skill level of paddler only.

Class V – Expert

Recommended for expert paddlers only, class V involves long, obstructed and violent rapids that pose a significant risk to any paddler. Waves and holes are steep and the routes both technically and physically demanding.

You will need to have all the correct equipment and extensive experience – or be rafting with a reputable operator that has vast experience of rafting that river. Swimming in these waters poses a substantial risk.

white water rapid grade and International Scale of River Difficulty flickr image by Steve

Class VI – Extreme/Exploratory

Historically river grade VI is reserved for rapids that are unnavigable. As you might expect from what has come before, these runs are extremely dangerous and may never have been attempted. Many consider the attempt of rafting them to be suicide and you will only make it through alive if very lucky.

However, some of the world best kayakers have attempted various class VI rapids – not always successfully. If a class VI has been safely negotiated numerous times by a number of kayakers, it may be downgraded to class V+.

White water rapid grading conclusions

While the International Scale of River Difficulty is clearly a very helpful tool for knowing what to expect on the river, it is not an exact science. Some rivers are given an overall grade of, say, class II but may contain some stretches of class IV rapids. Also class can change seasonally, and down to local weather conditions.

Who can go on rafting holidays flickr image by Fortherock

If you are rafting or kayaking on your own, you should thoroughly research a river before setting off and get advice on current conditions from a local. Better still, travel with someone who knows the river or book with a reputable rafting operator, or take a kayaking guide.

If our guide to white water rapid grade and explanation of the International Scale of River Difficulty had you tempted to head off rafting or kayaking check out our rafting discounts or kayaking discounts to get the best deal.


Kayaking, Rafting
Class I, Class II, Class III, Class IV, Class V, Eskimo Roll, Rapid Grading (Whitewater Classification), Whitewater (Rapids)

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