The American Whitewater Affiliation's International Scale of River 
Difficulty is a useful tool to determine the severity of sections in a 
river. These guidelines offer a general classification for rivers, but 
be aware that the system is not exact. Rivers do not always fit neatly 
into the various classifications, and regional interpretations of the 
classification system may create misunderstandings.


There is no substitute for a cautious approach to rivers with which a 
paddler is unfamiliar.

Moving water has three classifications:
          1. Class A   Flowing under 2 m.p.h.
          2. Class B   2 to 4 m.p.h.
          3. Class C   Greater than 4 m.p.h.
       
Whitewater has six classifications:

Class 1: Easy
* Few or no obstructions - all obvious and easily missed

* Fast-moving water with riffles and small waves

* Risk to swimmers is slight

* Self-rescue is easy


Class II: Novice
* Straightforward rapids with wide, clear channels that are obvious 
without scouting

* Occasional maneuvering may be required but rocks and medium-sized 
waves are missed easily by trained paddlers

* Swimmers are seldom injured and group assistance, while helpful, is 
seldom needed


Class III: Intermediate
* Rapids with moderate, irregular waves which may be difficult to avoid 
and capable of swamping an open canoe

* Complex maneuvers in fast current and narrow passages requiring good 
boat control frequently exist

* Large waves, holes and 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

* Chances of injury while swimming is low, but group assistance may be 
required to avoid long swims


Class IV: Advanced
* Intense, powerful rapids requiring precise boat handling in turbulent 
water

* Depending upon the character of the river, there may be long 
unavoidable waves and holes or constricted passages demanding fast 
maneuvers under pressure

* A fast, reliable eddy turn may be needed to negotiate the drop, scout 
rapids or rest

* Rapids may require "must" moves above dangerous hazards

* Scouting is necessary the first time

* Risk of injury to swimmers is moderate to high, and water conditions 
may make rescue difficult

* Group assistance is often essential but requires practiced skills

* A strong Eskimo roll is highly recommended


Class V: Expert
* Extremely long, obstructed or violent rapids which expose the paddler 
to above average risk of injury

* Drops may contain very large, unavoidable waves and holes or steep, 
congested chutes with complex, demanding routes

* Rapids often continue for long distances between pools or eddies, 
demanding a high level of fitness

* What eddies exist may be small, turbulent or difficult to reach

* Several of these factors may be combined at the high end of this class

* Scouting is mandatory

* Rescue is extremely difficult even for experts

* A very reliable Eskimo roll and above-average rescue skills are essential


Class VI: Almost Impossible
* Difficulties of Class V are carried to the limits of navigability

* Nearly impossible and very dangerous

* Risks are high and rescue may be impossible

* For teams of experts only at favorable water levels, after close study 
and with all precautions

* The frequency with which a rapid is run should have no effect on this 
rating as there are a number of Class VI rapids which are regularly 
attempted