When are the River Rapids to Dangerous and what the Different Class Ratings Mean for Rivers & CFS

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Use this chart below to get yourself familiar with the different river conditions and Know when it is safe to be on a river. What does the River Class mean?

International Scale of River Difficulty

Class I.	Easy	Waves small, passages clear; no serious obstacles
Class II	Medium	Rapids of moderate difficulty with passages clear.
Class III	Difficult	Waves numerous, high, irregular; rocks; eddies; rapids with passages clear though narrow, requiring expertise in maneuvering.
Class IV	Very Difficult	Long rapids; waves powerful, irregular; dangerous rocks; boiling eddies; powerful and precise maneuvering required.
Class V	Extremely Difficult	Exceedingly difficult, long and violent rapids, following each other almost without interruption; riverbed extremely obstructed; big drops; violent currents; very steep gradient.
Class VI	Unrunnable	Don't even try - if you fall in (hopefully with a life preserver and helmet) float down feet first to avoid the rocks hitting your tail bone and try to get to the side to crawl out.
P	Portage	Boats must be carried along the river bank to get around an unrunnable stretch of river.

Flow rates or CFS (Cubic Feet per Second)
CFS is another indication of the condition of the river.
So it's good idea to have this information too when planning a rafting trip.
A river that has10,000 CFS is going to be a wild ride.

You might also look at the Reynolds Number.

Flow information on west coast Rivers

River Levels and Flow Forcast

Water Data.usgs.gov

General Water Safety Tips

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