Many people are confused when hearing the phrase “International Scale of River Difficulty,” which is a standard scale used to measure or rate the safety of any particular river or single rapid. The river grade reflects the technical difficulty and skill level required associated with any particular section of a river.
There are six levels, classes or grades and then a number, the scale on which the river is graded is neither fixed nor linear. When a river or rapid is given a number grade and then a plus or minus sign, it is to denote if the section rates higher or lower on the scale of difficulty.
The class of a river or rapid is bound to change with the level of the water and higher water usually means rapids are more treacherous. However, there are some rapids which could be easy to maneuver at a high flow because there are some washed out areas. When a river is at flood stage, even rapids can contain highly dangerous or catastrophic materials which can be unpredictable. Some rivers with high volumes of fast moving water will need to have someone expert behind the wheel of the boat, if not it could mean the boat would capsize and people could possibly drown.
The specific river grading system in America is an expanded and more detailed version of the international one, which is typically used by floaters, white water organizations and others. In the US, classes include the following: (classes of water in Missouri only are the ones discussed here)
- Class I: fast moving water with small waves and ripples, risk to swimmers is slight, being rescued is fairly easy. Few obstructions in the water, all are readily witnessed and easy to avoid with a bit of training.
- Grade II: rapids with clear, wide channels, occasional maneuvering may be necessary. Swim with caution and rapids at the upper ends of the scale are considered to have a difficulty range of Class II+.
- Class III: irregular waves on rapids could be difficult to avoid and could capsize and swamp an open canoe. Complex maneuvering in fast currents is necessary and large waves may be present, scouting is necessary for those individuals that have little to no experience. It is recommended to take a group along for people that are not strong swimmers to avoid these conditions.
When wanting to take a vacation on one of the many bodies of water in Missouri, it is always advisable to preplan. Having the right supplies, the best equipment and skilled help along the way is strongly encouraged, but should not deter anyone from making the most of the majestic beauty of Missouri’s lakes and rivers.
