This is the American version of a rating system used to
compare river difficulty throughout the world. This system is not
exact; rivers do not always fit easily into one category, and regional
or individual interpretations may cause misunderstandings. It is no
substitute for a guidebook or accurate first-hand descriptions of a run.
Paddlers attempting difficult runs in an unfamiliar area should act
cautiously until they get a feel for the way the scale is interpreted
locally. River difficulty may change each year due to fluctuations in
water level, downed trees, recent floods, geological disturbances, or
bad weather. Stay alert for unexpected problems!
As river difficulty increases, the danger to swimming paddlers becomes
more severe. As rapids become longer and more continuous, the challenge
increases. There is a difference between running an occasional class-IV
rapid and dealing with an entire river of this category. Allow an extra
margin of safety between skills and river ratings when the water is
cold or if the river itself is remote and inaccessible.
Examples of commonly run rapids that fit each of the classifications are presented in the attached document, "International Scale of River Difficulty - Standard Rated Rapids." Rapids
of a difficulty similar to a rapids on this list are rated the same.
Rivers are also rated using this scale. A river rating should take into
account many factors including the difficulty of individual rapids,
remoteness, hazards, etc.
The six difficulty classes:
List of Class I thru III Rated Rapids
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.
List of Class I thru III Rated Rapids
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+”.
List of Class III Rated Rapids
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.
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.
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.
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.
