The excitement of running the rapids of a wild river in a raft or kayak rates high as an outdoor adventure, whether you go with a licensed company and guide or on your own.
If you have read about or considered river rafting or kayaking, you have probably seen the class or grade of a river run expressed in roman numerals from I (One) to VI (Six). This safety rating of a stretch of river or a specific rapid is according to the International Scale of River Difficulty (ISRD), a classification system based on river flows, rapid types, obstacles, etc. This scale in not fixed, but changes with conditions.
If you choose to raft or kayak without the benefit of a licensed guide, it is best to select river difficulty according to your experience as a river runner. A rafter or kayaker should begin by running easier classes and, over time, look to more difficult waters as know-how allows. This gradual learning method will help ensure your safety in what can be a violent and dangerous recreation.
Here is a review of the meanings of the six ISRD classifications:
Class or Grade I (Easy) – A Class I (One) stretch of water features long runs of flat, slow-moving water with minor wave action, no serious obstacles and is easy to navigate. The water is not dangerous if you must swim, and self-rescue is easy. Class or Grade II (Medium) – A Class II (Two) stretch of water may have straightforward rapids or small waves, small drops or ledges and eddies. It will be a clear route without prior inspection requirements. Suitable for any skill level. Class or Grade III (Moderate) – A Class III (Three) stretch will have a number of rapids, uneven wave action, moderate drops,, harder eddies, rocks with narrow passages requiring maneuvering skills. Some points of heavier water may dictate pre-run inspection from the riverbanks. Class or Grade IV (Difficult) – A Class IV (Four) section will have long and difficult rapids with irregular waves and often have a steep grade or dangerous rocks to navigate. Heavy eddy or whirlpool activity may be present. The features may also include powerful and unpredictable flows requiring precise handling, while others present a high danger risk for swimmers. A pre-run inspection and human support along the banks is recommended. Class or Grade V (Extremely Difficult) – A Class V (Five) rating means the river is like Class IV but with larger, more violent features and unpredictable flows. Usually, a Class V will have unavoidable dangers such as deep, relentless eddies and drops with steep grades. This class is unusual and presents a real risk for both the paddlers and the equipment. Expert handling is a must. A pre-run riverbank inspection is crucial. Rescue can be difficult and bank support with ample throw lines is always recommended. Class or Grade VI (Dangerous/Not Advised) – A Class VI (Six) section requires top technical skills only for runners with infinite experience and expert skills. A mid-river waterfall is an example of a Class VI element. There is a real risk of life. Many of these sections have never been successfully paddled before, or have led to serious injury or death. Bank support with rescue lines is always required, as is pre-run study prior to the run from all angles.
The grade of a river or rapid can change with the level of the water. High water during peak runoff can add danger and difficulty, although some rapids tend to be washed out with higher water, actually covering the features. However, high water levels can hide hazards from view, making the section more dangerous. On the other hand, low water levels often make passage through rapids easier to manage. Keep water levels at the time of your run in mind and consider what the levels can mean to the section’s grade.
This rating system varies from country to country. Because ratings come from paddlers who have run the river sections scored, the individual grade given really depends on the rater’s skill level, experience, bravery and risk-taking behavior. Be wary!
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