International Scale of River Difficulty

This code has been prepared using the best available information and has been reviewed by a broad cross-section of whitewater experts. The code, however, is only a collection of guidelines; attempts to minimize risks should be flexible, not constrained by a rigid set of rules. Varying conditions and group goals may combine with unpredictable circumstances to require alternate procedures. This code is not intended to serve as a standard of care for commercial outfitters or guides.

The Scale

International Scale of River Difficulty (see Section VI of the Safety Code of American Whitewater for complete descriptions)

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, recent floods, 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 the water is cold or if the river itself is remote and inaccessible.

The links below lead to the 3 parts of a list of examples of commonly run rapids that fit each of the classifications. Rapids of a difficulty similar to a rapid on this list are rated the same. Rivers are also rated using this scale. An overall river rating should take into account many factors including the difficulty of individual rapids, remoteness, hazards, etc. Each rapid is rated at a specific range of levels. Note that under some circumstances a paddler may find that similarly rated rapids seem to differ an extraordinary amount due to unusual factors that may include boat type, weather, fatigue, and limited experience on certain types of whitewater.

The story behind the American Whitewater rating scale project:

1998 Revisions to the Safety Code of American Whitewater Complete, May-June, 1998

Upgrading the American Version of the International Scale of River Difficulty, Sept-Oct, 1997

American Whitewater adds benchmark rapids to the International Scale of River Difficulty, Nov-Dec, 1997

Rating Survey Letter (used to solicit input to the benchmarked rapids)

Standard Rated Rapids: Class I-III
Standard Rated Rapids: Class IV
Standard Rated Rapids: Class V

For additional copies please write to:

American Whitewater
PO Box 1540, Cullowhee, NC 28723

Copyright 1998, American Whitewater

Join AW and support river stewardship nationwide!