Difficutly ratings for River Navigation The International Scale of River Difficulty is a standardized scale used to rate the safety of a stretch of river, or a single rapid. The grade reflects the technical difficulty and skill level required associated with the section of river.

Grade 1: Very small rough areas, might require slight maneuvering. (Skill Level: Very Basic)
Grade 2: Some rough water, maybe some rocks, might require some maneuvering.(Skill Level: Basic Paddling Skill)
Grade 3: Whitewater, small waves, maybe a small drop, but no considerable danger. May require significant maneuvering.(Skill Level: Experienced paddling skills)
Grade 4: Whitewater, medium waves, maybe rocks, maybe a considerable drop, sharp maneuvers may be needed. (Skill Level: Whitewater Experience)
Grade 5: Whitewater, large waves, possibility of large rocks and hazards, possibility of a large drop, requires precise maneuvering (Skill Level: Advanced Whitewater Experience)
Grade 6: Class 6 rapids are considered to be so dangerous as to be effectively unnavigable on a reliably safe basis. Rafters can expect to encounter substantial whitewater, huge waves, huge rocks and hazards, and/or substantial drops that will impart severe impacts beyond the structural capacities and impact ratings of almost all rafting equipment. Traversing a Class 6 rapid has a dramatically increased likelihood of ending in serious injury or death compared to lesser classes. (Skill Level: Successful completion of a Class 6 rapid without serious injury or death is widely considered to be a matter of great luck or extreme skill)

Specific location/national classifications

India

Grade I: Small, easy waves; mainly flat water

Grade II: Mainly clear passages; some areas of difficulty

Grade III: Difficult passages; narrow in places and with high waves

Grade IV: Very difficult, narrow and requiring precise maneuvering

Grade V: Extremely difficult. Very fast-flowing waters which can be maneuvered only by experts

Grade VI: For all practical purposes, unmanageable - even suicidal