Classification for whitewater is not fixed, since it may vary greatly depending on the water depth and speed of flow. On any given rapid there can be a multitude of different features which arise
from the shape of the riverbed and the velocity of the
water in the stream. The gradient of a river is the rate at which it loses elevation along its course. Constrictions can form a rapid when the river flow is forced into a narrower channel. Obstruction can be a ledge in the middle of the river or near the side which obstructs the flow. Ratings are pretty much subjective and the opinion of the person doing the rating. High water may make a rapid easier when it is washed out and in lower water more technical due to exposed obstacles. Three things to look at when scouting a rapid. The Gradient, attaining a line in the rapid, and difficulty getting out safely. This may also differ by the boaters experience and equipment. The other rating that is used is a Class 1-10 system used on some western U.S. rivers, most commonly on
the Grand Canyon stretch of the Colorado River. The 1-10 system roughly equates
to Classes I-V on the International Scale, with 1-2 somewhat equivalent to Class
I, 3-4 to Class II, 5-6 to Class III, 7-8 to Class IV and 9-10 to Class V. Location and the remoteness of the area may play a huge part in your decision to run the river. Checking the weather before you leave home may save your life. Rivers tend to rise quickly when it rains or warms suddenly sending down the snow pack. Pictured is a Maravia Mistral, Hermit rapids on the Grand Canyon. We also carry a full line of Aire rafts, perfectly suited for all rivers you would like to go on.
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 5: Expert. Extremely long, obstructed, or very violent rapids which expose a paddlers 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, its rating may be changed to an appropriate Class 5.x rating.
Other terms to be familiar with:
Strainers - Strainers are formed when an object blocks the passage of larger objects but
allows the flow of water to continue. These objects can be very dangerous, because the force of the water will pin an
object or body against the strainer and then pile up, pushing it down under
Holes - Holes, or "hydraulics", are formed when water pours over the top of a submerged object, causing the
surface water to flow back upstream toward the object. There are Smiling holes and Frowning holes. Smiling holes are generally play holes, fun places to surf, or catch an eddie. Looking down stream at the hole if the tail on either side is pointing down stream the hole is smiling.
Eddies - Eddies are formed, like hydraulics, on the downstream face of an obstruction. Unlike
hydraulics, eddies swirl on the horizontal surface of the water. Typically, they
are calm spots where the downward movement of water is partially or fully
arrested - a nice place to rest or to go upstream. However, in very
powerful water, eddies can have powerful, swirling currents which can flip boats ( Eddie Fence )
and from which escape can be very difficult.
Waves - Waves are noted by the large smooth face on the water rushing down. Sometimes a
particularly large wave will also be followed by a "wave train", a long series of waves. These standing waves can be smooth or, particularly the larger ones, can be breaking waves with laterals.
Sweepers - Trees fallen or leaning over the river, may not be fully submerged
Pillows - Pillows are formed when water runs into a large obstruction, and boils up on the face.
Undercut Rocks - Undercut rocks are rocks that have been worn down underneath the surface by the
river. They can be extremely dangerous features of a rapid because a person can
get trapped underneath them, under water.
Sieves - A major whitewater feature is a sieve, which is a narrow empty space that
water flows through between two obstructions, usually rocks.
Weirs & Low Head Dams - The most dangerous types of holes are formed by low head dams, because of the constant re-circulating current the only way out is on either end.
If can't find what you like or have questions please call 503-788-3077 or use our contacts page.
*Six Classifications were taken from American Whitewater