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, 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 water is cold or if the river itself is remote and
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.
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.
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 is 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
Class V: Expert. Extremely long, obstructed, or very violent
rapids which expose a paddler to above average endangerment. 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 mandatory
but often difficult. Swims are dangerous, and rescue is difficult even
for experts. A very reliable eskimo roll, proper equipment, extensive
experience, and practiced rescue skills are essential for survival.
Class VI: Extreme. One grade more difficult than Class V.
These runs 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. This class does
not represent drops thought to be unrunnable, but may include rapids
which are only occasionally run.