Class I

Easy, fast moving water with riffles and small waves. Few obstructions; all obstacles are obvious and are easily missed with little training.

Class II

Novice. Straight forward rapids with wide clear channels which are evident without scouting. Occasional maneuvering may be required. Rocks and medium sized waves are easily missed.

Class III

Intermediate. Irregular waves and narrow channels. Complex maneuvers in fast current and good boat control in tight passages or around ledges is often required; very large waves and holes maybe present but are avoidable. Strong eddies and powerful current effects are found on higher volume rivers.

Class IV

Advanced. Intense, powerful rapids requiring precise boat handling in turbulent water. Depending on the character of the river, it may feature large unavoidable waves and holes or constricted passages demanding complex maneuvers very quickly.

Class V

Expert. Extremely long, obstructed and very violent rapids. Drops may contain large, unavoidable waves and holes or steep congested chutes with complex demanding routes. Rapids may continue for long distances between pools demanding a high level of fitness. What eddies exist may be small turbulent or difficult to reach. At the high end of the Class V scale, several of these factors may be combined to constitute very dangerous rapids.

Class VI

Virtually impassable. These run exemplify the extremes of difficulty unpredictability and danger. The consequences of errors are very severe and rescue may be impossible. For teams of experts only at favorable water levels after close personal inspection and taking all precautions.