Classification of Rapids, Water Level, and Canoeists
Part of the planning of a trip entails knowing what to expect on your trip. This is not so difficult to figure out when you are paddling on a lake. For paddling on a river, however, you should learn about the ratings given to rapids and water level.
Rapids
The International Rating system classifies rapids as follows:
Class A: Lake water. Still. No perceptible movement.
Class I.- Easy. Smooth water; light riffles; clear passages, occasional sand banks and gentle curves. The most difficult problems might arise when paddling around bridges and other obvious obstructions.
Class II.- Moderate. Medium-quick water; rapids with regular waves; clear and open passages between rocks and ledges. Maneuvering required. Best handled by intermediates who can maneuver canoes and read water.
Class III.- Moderately difficult. Numerous high and irregular waves; rocks and eddies with passages clear but narrow and requiring experience to run. Visual inspection required if rapids are unknown. Open canoes without flotation bags will have difficulty. These rapids are best left to canoeists with expert skills.
Class IV- Difficult. Long and powerful rapids and standing waves; souse holes and boiling eddies. Powerful and precise maneuvering required. Visual inspection mandatory. Cannot be run in canoes unless the craft is decked or properlyequipped with flotation bags. Advance preparations for possible rescue work important.
Class V- Extremely difficult. Long and violent rapids that follow each other almost without interruption. River filled with obstructions. Big drops and violent currents. Extremely steep gradient. Even reconnoitering may be difficult. Rescue preparations mandatory. Can be run only by top experts in specially equipped whitewater canoes, decked craft, and kayaks.
Class VI.- Extraordinarily difficult. Paddlers face constant threat of death because of extreme danger. Navigable only when water levels and conditions are favorable. This violent whitewater should be left to paddlers of Olympic ability. Every safety precaution must be taken.
Water Level
The characteristics of a river can change remarkably as the water level rises or falls. As you might expect, a set of Class II rapids can become raging Class IV when the water is abnormally high following spring runoff or heavy storms. Conversely, a Class IV can turn into a shallow pussycat when the water level is low in the late summer. Even normally calm stretches become turbulent and dangerous at flood stage, because the force of currents slammed this way and that by rocks and obstructions creates powerful and dangerous surface conditions.
An International Rating system has also been devised to describe river flow. The classification for a specific river may change from season to season; the following letter designations are used to describe water level and rate of flow:
L, or Low. Below-normal levels for the river. Below-normal depth may interfere with good paddling. Shallows may turn into dry banks and low areas become muddy sandbars.
M, or Medium. Normal river flow. Medium water generally is used to describe good water for rivers with slight gradients and enough depth for passage on the steeper sections.
MH, or Medium High. Higher than normal. Faster flow on gentle gradients. The best flow for more difficult river sections with enough water for passage over low ledges and through rock gardens.
H, or High. Water is becoming difficult to handle. he river is well above normal stage. Canoeists may refer to the strong currents as "heavy." Small debris may come floating by, a warning that the river is dangerous and better left to skilled kayakers or canoeists whose craft are supported by flotation bags.
HH, or High-High. Very heavy water. Hydraulics are complex. Even slight gradients become treacherous. Debris frequent. Only for experts.
F, or Flood. Abnormally high water, overflowing the banks; current extremely violent; low-lying areas underwater. TV crews show up to shoot tape for the evening news. Not for any boaters except those with appropriate equipment on dangerous rescue missions.
