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Whitewater Rapids: The Universal Classification Guide

There are a good number of white-water rivers in Canada with popular activities including canoeing, water-rafting, kayaking and wilderness exploration. Rapids are responsible for the appearance of ‘white’ waters. They are areas of lower water levels that cause the waves to beat against the exposed rocks, which aerates the water with air bubbles and it makes for a fun ride. Water naturally flows downstream and the goal is to move with that current. How do you know what those classes are or what they mean? This article explains it all. Before you read further, you may want to check out our glossary for some terms that will be used throughout.

How are rapids classified?

The international rating scale of river difficulty by the non-profit organization, American Whitewater, provides a guide to classify rivers and rapids. This rating is based on the width of the water channel, size and strength of waves, degree of obstructions present, ease of swimming and self-rescue. These correlate to the level of skill and experience required for navigation. The scale features Roman Numerals I-VI; from easy to most difficult. Additional symbols are also used, with a ‘-’ meaning that the class is at the lower end of difficulty for that level while a ‘+’ signifies the higher end of difficulty for that class.

During our expeditions, clients often ask, 'what class is the next rapid?' This is one of the toughest questions to answer as so many variables are involved.

Weather conditions, water temperatures and season, guide and client skill levels, remoteness and accessibility, number of and type of watercraft in the group (canoes, kayaks, whitewater rafts), water levels, and more are all contributory factors. Because of the variety of factors, the same rapid may be classified differently from week to week or month to month, based on the water level. Additionally, the classification process of rapids is very subjective. If two guides standing by a riverbank, While one guide rates a rapid C2, a less experienced guide standing right beside could rate the same river C3+.


So how are the classes of rapids generally determined?


Class I rapids:

A river with class I rapids is basically flat water, which is usually calm and only has small waves or riffles. There are hardly any rocks or significant obstacles. It is denoted easy because a beginner, who has mastered basic paddling strokes, can canoe or kayak with little or no supervision.

Class II rapids:

This next grade of rapids features small to medium waves, short bends, and a few obstructions that a person at novice level can safely negotiate. A Class II rapid that is close to the difficulty of III is denoted II+. Generally, these rivers are straightforward and self-rescue is possible.

Class III rapids:

Rapids classed III are considered intermediate level difficulty. When this difficulty is at the lower end of the class, it is denoted III- and when at the upper end, it is III+. The characteristics are medium but irregular waves with obstructions like small falls or drops, counter currents and eddies. These can succeed in flipping a canoe if care is not taken. Fortunately, self-rescue is possible in grade III rivers, even though it may require some help. Most of our trips fall within classes I-III and our guides at MHO Adventures are always eager to provide guidance and instructions on improving your paddling and navigating skills during our trips. 

Class IV rapids:

Class IV rapids are advanced level and should only be navigated by those who have the required skills. The waves are large, irregularly sized and turbulent, but they are relatively predictable and are a delight for the experienced canoeist. Other features of grade IV rivers include eddies, holes, falls and other obstacles that can be dangerous. Like the previous two classes, they can also be further graded as IV- or IV+.  However, self-rescues are difficult to perform in these rapids. It is therefore highly recommended to scout such rapids ahead of time and to travel in a group, even for skilled paddlers. MHO Adventures would be happy to plan a group trip for you with an experienced guide who is quite familiar with the river.   

Class V rapids:

This class is denoted Expert level. Class V rivers are characterized by a combination of the following: rapids that are turbulent or continuous and span a long distance, steep gradients with abrupt drops, large unpredictable waves, and the presence of holes. Due to the nature of these waters, it is often dangerous to swim in them. Apart from the fact that self-rescue is really difficult, rescuing another injured party is also challenging. Scouting the rapids is therefore very important, so is going with multiple canoes. Class V rivers are further classified 5.0-5.9, based on the perceived progression of difficulty. 

Class VI rapids

Only daredevils brave these rapids as they pose an extraordinary danger and a minor paddling mistake can be fatal. The mighty waves are turbulent and erratic. In addition, the rivers have obstructions that require a lot of skill and preparation to negotiate. These rivers have hardly been negotiated and the rapids are considered. It is nearly impossible to rescue anyone who gets into trouble here. 

Some of the more popular rapids from around the world have nicknames like Godzilla (Ocoee river), Celestial Falls (White River), Terminator (Futaleufu), Stairwell to Heaven, Commercial Suicide, and the Devil’s Toilet Bowl (all three in Zambezi river). Notable ones in Canada include Thunder House Falls of the Missinaibi River, Devil’s Cellar and White Horse Rapids of the Petawawa River.

What are the implications of the classes of rapids?

The classification system of a river is a universal numerical rating system and a good guideline. However, it is important to ALWAYS scout the entirety of any rapid that you want to run, even if you've been there before!!! This is why it is recommended that you hire experienced guides that you can trust. 

MHO Adventures has dedicated almost 3 decades to ensuring safe and unforgettable expeditions along white-water rivers across Canada. These rapids are our playground and our team knows which rapids are thrilling and which should simply be avoided. In those cases, our guides lead adventurers by portaging across until it is safe. Our expertise allows you to have maximum adventure and enjoyment while avoiding any unnecessary dangers. Most of our expeditions occur from late spring to summer, when water levels are more predictable and the weather is great. Do take a look at our all-inclusive expeditions and let us help you plan your next adventure!