International Scale of River Difficulty
The following classifications are according to American Whitewater.
If rapids on a river generally fit into one of the following classifications,
but the water temperature is below 50°F or if the trip is an extended one
into a wilderness area, the river should be considered one class more difficult than normal.
- Class I
- Fast moving water with riffles and small waves. Few obstructions, all obvious and
easily missed with little training. Risk to swimmers is slight; self-rescue is easy.
- Class II: Novice
- Straightforward rapids with wide, clear channels which are evident without scouting.
Occasional maneuvering may be required, but rocks and medium-sized waves are easily missed
by trained paddlers. Swimmers are seldom injured and group assistance, while helpful,
is seldom needed. Rapids that are at the upper end of this difficulty range are designated "Class II+".
- Class III: Intermediate
- Rapids with moderate, irregular waves which may be difficult to avoid and which can
swamp an open canoe. Complex maneuvers in fast current and good boat control in tight
passages or around ledges are often required; large waves or strainers may be present
but are easily avoided. Strong eddies and powerful current effects can be found,
particularly on large-volume rivers. scouting is advisable for inexperienced parties.
Injuries while swimming are rare; self-rescue is usually easy but group assistance may
be required to avoid long swims. Rapids that are at the lower or upper end of this
difficulty range are designated "Class III-" or "Class III+" respectively.
- Class IV: Advanced
- Intense, powerful but predictable 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 fast maneuvers under pressure. A fast, reliable eddy turn may
be needed to initiate maneuvers, scout rapids, or rest. Rapids may require "must" moves above
dangerous hazards. Scouting may be necessary the first time down. Risk of injury to swimmers
is moderate to high, and water conditions may make self-rescue difficult. Group assistance for
rescue is often essential but requires practiced skills. A strong eskimo roll is highly recommended.
Rapids that are at the lower or upper end of this difficulty range are designated
"Class IV-" or "Class IV+" respectively.
- 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 high end of the scale, several of these factors may be combined.
Scouting is recommended but may be difficult. Swims are dangerous, and rescue is often
difficult even for experts. A very reliable eskimo roll, proper equipment, extensive experience,
and practiced rescue skills are essential. Because of the large range of difficulty that exists
beyond Class IV, Class 5 is an open-ended, multiple-level scale designated by class
5.0, 5.1, 5.2, etc... each of these levels is an order of magnitude more difficult than the last.
Example: increasing difficulty from Class 5.0 to Class 5.1 is a similar order of magnitude as
increasing from Class IV to Class 5.0.
- Class VI: Extreme and Exploratory Rapids
- 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 be impossible.
For teams of experts only, at favorable water levels, after close personal inspection and taking
all precautions. After a Class VI rapids has been run many times, its rating may be changed to an
apppropriate Class 5.x rating.
For more information on river classifications and safety see the
American Whitewater web site.
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