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Rafting the North Fork of the Shoshone

Understanding The International Scale of River Difficulty

Rivers are around the globe are rated using the International Scale of River Difficulty, which utilizes six “classes” to rate both specific river features, as well as entire river sections. This system is not exact and rivers do not always fit easily into one class or category. Regional or individual interpretations may cause misunderstandings, which is why it is helpful to have a basic working knowledge of the system in order to better prepare yourself for questions and considerations that come up when looking to book a rafting trip.

The Levels of Difficulty According to American Whitewater

It is important to remember that river ratings can change based on water levels and season. Be sure to inquire about what the timing of your trip will mean for the classification of that particular river section. Contact us.

Class I Rapids

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.

Red Rock Canyon and Full Canyon

a small boat in a body of water with a mountain in the background

Example of Class I on the Shoshone River

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+”.

Red Rock Canyon and Full Canyon

a man riding a surfboard on top of a mountain

Example of Class II in the Red Rock Canyon on the Shoshone River

Class III: 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.

North Fork Full Day Adventure

Example of Class III on the North Fork of the Shoshone

Class IV: 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.

Intermediate and Advanced Rafting and Packrafting


Example of Class IV in the upper Shoshone Canyon

Class V: 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.

a group of people riding on a raft in the water

Example of Class V on the Gualey River in West Virginia

Class VI: Extreme and Exploratory Rapids

These 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.

a man riding a wave on top of a body of water

Example of Class VI from the Zambezi River in Zimbabwe


How to Choose the Right River Trip

There are many factors that go into finding the right river trip for you and your group. These factors might include length of time, location, costs involved, or the time of year. River ratings or classifications are also important factors to consider — as well as your experience levels, risk tolerance, or how much excitement you are looking for. These are important questions to ask of the rest of your group as well. Almost all of our trips are suitable for a very wide range of experience levels, with most of our trips being rated between Class II-III.

We encourage you to also consider the following:

  1. Does the river guide/outfitter have your safety and well-being as a priority?
  2. Are the guides certified in Wilderness Medicine and Swiftwater Rescue?
  3. Is the equipment in good condition and is there proper gear and equipment being provided?
  4. Does the outfitter or guide ask preemptive questions or offer insight in order to reduce risk? i.e. safety orientations, questions about medical history, questions about experience and physical ability levels, etc.

By keeping these considerations in mind, you will be able to feel more confident that the river trip you are choosing is truly right for you.

a group of people sitting on a raft in a forest