Chilko River Expeditions
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International River Classifications
I : Easy
Flatwater to occasional rapids characterized by low, regular waves. Obstructions such as
rocks are easy to avoid. The best route down the river is easily recognized and easy to
Class II : Medium
Frequent rapids characterized by high regular waves up to three feet in height. Easy to
medium chutes, ledges, or falls. Back eddies and different currents are easy to negotiate.
The best route is easy to recognize and manoeuvre.
Class III : Difficult
Numerous rapids with high, irregular waves, rollers, breakers, and back eddies. This will
require skilled manoeuvring. Chutes, falls, and ledges are considered difficult.
Class IV: Very Difficult
Long, difficult sections of rapids with high irregular waves, breakers, powerful back
eddies, whirlpools, sharp bends, and constricted canyons. Chutes, falls, and ledges have
powerful rollers and undertow.
Class V: Extremely Difficult
Long sections of continuous violent rapids with very high irregular waves. Most of the
waves are unavoidable. The current is usually very fast with powerful eddies and
whirlpools. River routes are usually complicated.
All whitewater Class VI rapids are considered nearly impossible and extremely
dangerous. These rivers are run only in the best of conditions.