River Rating Scale
From American Whitewater, this is the American version of the international scale of river difficulty.
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.
THE SIX DIFFICULTY CLASSES:
Class I: Easy. 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 upper end of this difficulty
range are designated "Class IV-" or "Class IV+" respectively.
Class V: 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. 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, It's rating may be changed to an appropriate Class 5.x rating.