This is a basic guide to river classification. Every river is different, and different factors can influence classification (this includes length of rapid, weather conditions, wilderness considerations and type of boat).
We often use a + or – to indicate that a rapid is between classes.
Clear, wide channels with small waves. No obstructions or hazards.
Slightly larger, more frequent waves. Little or no obstructions or hazards. Little Maneuvering required.
Waves up to four feet in height. Some obstructions present. Maneuvering required.
Difficult with large frequent waves and obstructions. Skillful maneuvering required.
Large frequent waves which are often unavoidable. Technical rapids with many hazards and obstructions present.
The upper limit of navigation attempted only career risk takers.