International Scale
of River Difficulty
Class I: Easy. Fast moving water
with riffles and small waves. Few obstructions, all obvius 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 stainers 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.
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 even for experts. Proper
equipment, extensive experience, and practiced rescue skills are
essential for survival.
Class VI: Extreme. One grade more difficult
than Class V. This 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.
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