Colorado Whitewater Adventure
International Scale of River Difficulty
The rating of rivers is subjective. Rivers also change due to water levels,
rocks that may shift on the riverbed, man-made influences, etc. On rivers
rated on this website, ratings are based on medium water levels and should
be used as a general guide. We have also used the minus or plus symbol
to show that a river run may be a bit easier or harder than most runs
of the same rating.
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. BOC note: Great for the whole family.
CLASS II: NOVICE
Straight forward 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. BOC note:
Great for the whole family.
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 are often required; large waves or strainers may be present
but are easily avoided. Strong eddies and powerful currents 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. BOC note: We
recommend swimming ability for class III rivers and up.
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 for kayakers is highly recommended. BOC
note: Good swimming ability is recommended. With a professional raft
guide, first time rafters with reasonable physical conditioning and a love
of excitement should enjoy this river difficulty.
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. A very reliable
Eskimo roll, proper equipment, extensive experience, and practiced rescue
skills are essential for survival. BOC note: Only for experienced
boaters/rafters in great physical shape that want the ultimate challenge.
CLASS VI: EXTREME
One grade more difficult
than Class V. These runs often exemplify the extremes of difficulty, unpredictably,
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 unrunable, but may include rapids which are
only occasionally run.