International Whitewater Rating Scale

Class 1: Easy. Fast moving water with small waves. Few obstructions, all obvious and easily missed with little training. Risk to swimmers is slight; self-rescue is easy.

Class 2: Novice. Easy rapids with obvious wide, clear channels, no scouting. Occasional maneuvering required, but rocks and waves are easily missed by trained paddlers. Swimmers seldom injured and group assistance seldom needed. Rapids at upper end of rating are class 2+.

Class 3: Intermediate. Rapids with moderate, irregular waves; may be difficult to avoid,can swamp an open canoe. Complex maneuvers in fast current and good boat controlin tight passages or around ledges is required; large waves or strainers are present easily avoided. Strong eddies and powerful current effects. Inexperienced should scout. Injuries to swimmers rare; self-rescue possible but group assistance may be required to avoid long swims. Rapids at lower/upper end are Class 3- or Class 3+.

Class 4: Advanced. Intense, powerful but predictable rapids requiring precise boat handling in turbulent water. May be large, unavoidable waves and holes or constricted passages demanding fast maneuvers under pressure. A fast, reliable eddy turn needed for maneuvers, scout rapids, or rest. Rapids require must moves above dangerous hazards. Scouting necessary first time. Risk of injury to swimmers moderate to high, and water conditions may make self-rescue difficult. Group assistance for rescue is often essential but requires practiced skills. Rapids at upper/lower end are Class 4- or Class 4+.

Class 5: Expert. Extremely long, obstructed, or very violent rapids which expose a paddler to added risk. 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 end of the scale, several of these factors may be combined.Scouting recommended but may be difficult. Swims are dangerous, and rescue is often difficult even for experts. Proper equipment, extensive experience, and practiced rescue skills are essential. Rapids at the upper end are classed as 5.1, 5.2, etc.

Class 6: Extreme and exploratory. These runs have almost never been attempted and often exemplify the extremes of difficulty, unpredictability and danger. The consequences of errors are very severe and rescue may impossible. After a class 6 rapids has been run many times, it’s rating may be changed to an appropriate Class 5.x rating.