River Difficulty Classifications
 
CLASS I

Moving water with a few ripples and small waves. Few or no obstructions.

CLASS II
Easy rapids with waves up to three feet and wide clear channels visible without scouting. Some maneuvering required.
CLASS III
Rapids with high irregular waves capable of swamping an open canoe. Narrow passages often requiring complex maneuvering and scouting from shore.
CLASS IV
Long, difficult rapids with constricted passages often requiring precise maneuvering in very turbulent water. Scouting from shore is often necessary, and conditions make rescue difficult. Not runnable in open canoes.
CLASS V
Extremely difficult, long and very violent rapids with highly congested routes nearly always require scouting from shore. Rescue conditions are difficult. Significant hazards to life in event of a mishap. Ability to Eskimo roll kayaks is essential.
CLASS VI
Nearly impossible to run and very dangerous. For teams of experts only after close study, having taken all precautions