Making Sense of Rapid Classifications

Monumental Expeditions Info, Rafting

In this post we hope to improve ones understanding of the various rapid classifications, and how they can change with different water levels (CFS). The six point ratings scale used on the Arkansas River is common throughout the world. The higher the class the more difficult the section or rapids.

Whitewater Rapids Six Point Scale *

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    Class I

    Moving water, riffles, small waves.

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    Class II

    Easy rapids, waves, clear channels.

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    Class III

    Large waves, obstacles, narrow passages.

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    Class IV

    Long rapids, unavoidable waves, many obstacles.

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    Class V

    Violent rapids, extremely difficult, unseen hazards.

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    Class VI

    Unpredictable, dangerous, nearly impossible to run. Not run commercially.

*River conditions and ratings change with flow levels. Whitewater boating has risks at all ratings and levels.

Rapid classifications fluctuate as the water level, or flow, changes throughout the season. Generally starting off low but quickly rising as the high country warms up and the winter snowpack starts to melt. Then as the snowmelt disappears the river returns to more moderate flows for the rest of the season. Typically big water run-off occurs late May through early June.

Higher water generally translates into larger, more difficult rapids. CFS stands for Cubic Feet per Second. This is how we measure what the river is flowing. You can imagine that one CFS is equivalent to an over inflated basketball, so if the gauge reads 1,000 CFS, that means 1,000 basketballs are floating by the gauge every second!

The higher the CFS generally the bigger the rapids become, and many rapids form in areas where there were previously rocks that are now underwater. Many times higher CFS will increase a rapids difficulty rating. Be sure to contact us if you have questions about current CFS.

Some sections of the Arkansas that we raft come under a high water advisory issued by the AHRA, the managing agency of the headwaters. These sections close at the following levels. The Numbers (2400 CFS) and the Royal Gorge (3200 CFS). One benefit of the Arkansas River Headwaters encompassing over 100 miles is that there is always another section to do that is more appropriate for all ages and abilities.

A good example of how rapid classification can change with water levels is the Royal Gorge. Closure level is 3200 CFS. At just below this flow the gorge is a serious Class IV-V section, with giant rapids, swift current and few eddies. Around 2000 CFS is what most consider the ideal level. Big fun Class III-IV with few rocks and lots of rapids. When the river is really low, like in the early spring and fall, around 500 CFS the river gets technical and channelized. These low water trips can be extremely challenging too.

When the Royal Gorge is closed to commercial trips Monumental Expeditions, and every other outfitter, moves the Gorge trip upriver to the Bighorn Sheep Canyon section, which at and above 3200 CFS becomes big fun Class III-IV, and includes arguably one of the biggest Class V‘s on the river; Three Rocks Falls; aka Reefer Madness. The Bighorn Canyon trip then moves further up the canyon to where the rapids are still big and fun, but farther apart with more calmer waters.

Ultimately these ratings are a subjective thing, and can vary depending on conditions. The Arkansas River allows Monumental Expeditions to offer Class I Family Float trips, Class II-III trips on the Bighorn Sheep Canyon and Browns Canyon, and Class III-IV (V) trips on The Numbers and the Royal Gorge. So regardless of what the river is flowing at, adventure awaits! Let ME be your guide.

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