Difficulty Level of Rapids

Difficulty Levels of Rapids

The Grand Canyon stretch of the Colorado River often uses a different rating system for rapids. The Class 1-10 system that is used in the Grand Canyon roughly parallels Classes I-V on the International Scale of River Difficulty (ISRD). In the Grand Canyon, Classes 1-2 equal ISRD Class I, Classes 3-4 equal ISRD Class II, Classes 5-6 equal ISRD Class III, Classes 7-8 equal ISRD Class IV and Classes 9-10 equal ISRD Class V.

Rapids are rated using the International Scale of River Difficulty (ISRD). This is an American system that is used to rate the technical difficulty levels of rapids or stretches of river on a scale of 1-6 in order to give rafters an idea of the skill level needed to navigate a specific waterway. The six categories in the International Scale of River Difficulty are referred to as “classes.” Many rivers are given a general classification, but contain sections with rapids both below and above that grade. Classes of specific waterways may change frequently due to shifts in weather patterns, water level fluctuations, geological disturbances, downed trees and more. 

Below is the American Whitewater Association’s summary of classes:

Class I Rapids – 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 Rapids – 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 Rapids – 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 Rapids – 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 lower or upper end of this difficulty range are designated “Class IV-” or “Class IV+” respectively.

Class V Rapids – Expert Extremely long, obstructed, or very violent rapids which expose a paddler 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 Rapids – Extreme and Exploratory Rapids These whitewater rafting 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.

The Grand Canyon stretch of the Colorado River often uses a different rating system. The Class 1-10 system that is used in the Grand Canyon roughly parallels Classes I-V on the International Scale of River Difficulty (ISRD). In the Grand Canyon, Classes 1-2 equal ISRD Class I, Classes 3-4 equal ISRD Class II, Classes 5-6 equal ISRD Class III, Classes 7-8 equal ISRD Class IV and Classes 9-10 equal ISRD Class V.

Both the Grand Canyon’s Class 1-10 scale and the International Scale of River Difficulty are effective and invaluable in allowing a rafter to decide whether or not a particular course is within his or her own ability level. They’re useful, albeit subjective, as they’re based on expert’s opinions and subject to change without advance warning. In determining what course may be best for you, use sound judgement and don’t be afraid to ask. We’re here to help you with any and all questions you may have regarding your rafting trip. Contact us here at Advantage Grand Canyon for more information at 888-244-2224 or click below to search for your Grand Canyon rafting trip!

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