River Rapid Classification - Classes I-VI
If river rapids generally fit into one of the following classifications, but the water temperature is below 50 degrees, or if the trip is an extended one in a wilderness area, the river should be considered one class more difficult than normal.
Class I – Moving water with a few riffles and small waves; few or no obstructions.
Class II – Easy rapids with waves up to three feet, and wide, clear channels that are obvious without scouting; some maneuvering is required.
Class III – Rapids with high, irregular waves often capable of swamping an open canoe; narrow passages that often require complex maneuvering; may require scouting from shore.
Class IV – Long, difficult rapids with constricted passages that often require precise maneuvering in very turbulent waters. Scouting from shore is often necessary, and conditions make rescue difficult. Generally not possible for open canoes: boaters in covered canoes and kayaks should be able to Eskimo roll.
Class V – Extremely difficult, long, and very violent rapids with highly congested routes that nearly always must be scouted from shore. Rescue conditions are difficult and there is significant hazard to life in event of mishap. Ability to Eskimo roll is essential for kayaks and canoes.
Class VI – Difficulties of Class V carried to the extreme of navigability. Nearly impossible and very dangerous. For teams of experts only, after close study and with precautions taken.