International Scale of River Difficulty - Caution in Application

Caution in Application

Classifications can vary enormously, depending on the skill level and experience of the paddlers who rated the river. For example, at the 1999 International Conference on Outdoor Recreation and Education, an author of a paddling guide pointed out that there is too much variation in what is covered by the class I designation, and proposed making further distinctions within the Class I flat water designations and Class I+ moving water designations, with the goal of providing better information for canoeists, instructors leading trips, and families with young children.

The grade of a river or rapid is likely to change along with the level of the water. High water usually makes rapids more difficult and dangerous, although some rapids may be easier at high flows because features are covered or "washed-out". At spate/flood stage, even rapids which are usually easy can contain lethal and unpredictable hazards. Conversely, some rapids may be easier with lower water levels when dangerous hydraulics become easier to manage. Some rivers with high volumes of fast moving water may require little maneuvering, but will pose serious risk of injury or death in the event of a capsize.