There is a rapid classification system used to compare river difficulty.
The system is not exact as rivers don’t always fit easily into one category and a rafter’s experience and knowledge of a river might classify it as a different level of class, but it’s a good starting point for knowing what to expect from a river.
Rapid Classification System
Is fast moving water with small waves. Little training is required and there is little risk to swimmers. This level of rapids is perfect for floating down the river in a tube.
Involves wide, clear channels that are easy to maneuver. Assistance is rarely needed, although those with little to no experience in rafting might benefit from assistance in paddling and maneuvering to learn the proper way to raft.
Is for advanced rafters. These rivers are powerful, but still predictable, requiring precise boat handling. Large, unavoidable waves and constricted passages demand fast maneuvers from experienced rafters. Risk of injury is more significant here because water conditions make self-rescue difficult.
Has moderate, irregular waves that can be difficult to avoid. This level requires complex maneuvers involving fast currents and good raft control in tight passages. Large waves and strainers can be present but avoided, and most of these rivers will have a guide assisting in the maneuvering and handling of the river.