CLASSIFICATION OF RAPIDS IN RAFTING

Rafting and white-waterrafting are recreational outdoor activities which use an inflatable raft to navigatea river or other body of water. This is often done on white-water or differentdegrees of rough water.

Rapids are hydrologicalfeatures between a run (a smoothly flowing part of a stream) and a c
ascade. Rapids are characterised by the river becoming shallower with somerocks exposed above the flow surface.

‘White Water’ Rafting. …White-water is formed in a rapid, when a river’s gradient increases enough todisturb its laminar flow and create turbulence, i.e. form a bubbly, or aeratedand unstable current; the frothy water appears white. The term is also usedloosely to refer to less-turbulent but still agitated flows.

The International Ratingsystem classifies Rapids / Water Level / Canoeists as follows:

Rapids

A skier is aware that ablack diamond run is a lot steeper and more difficult than a green circleslope. Rapids, like ski slopes, vary in their intensity. The InternationalRating system classifies rapids as fol
lows:

Class A: Lake water. Still. Noperceptible m
ovement.

Class I – Easy. Smooth water;light riffles; clear passages, occasional sand banks and gentle curves. Themost difficult problems might arise when paddling around bridges and otherobvious obstructions.        

Class II – Moderate. Medium-quickwater; rapidswith regular waves; clear and open passages b
etween rocks and ledges. Manoeuvring required. Best handled by intermediateswho can manoeuvre canoes and read water.

Class III – Moderately difficult.Numerous high and irregular waves; rocks and eddies with clear but narrowpassages requiring experience to run. Visual inspection required if rapids areunknown. Open canoes without flotation bags will have difficulty. These rapidsare best left to canoeists with expert skills.

Class IV – Difficult. Long andpowerful rapids and standing waves; souse holes and boiling eddies. Powerfuland precise manoeuvring required. Visual inspection mandatory. Cannot be run incanoes unl
ess the craft is decked or properly equipped with flotation bags. Advancepreparations for possible rescue work important.

Class V – Extremely difficult.Long and violent rapids that follow each other almost without i
nterruption. River filled with obstructions. Big drops and violent currents.Extremely steep gra
dient. Even recce may be difficult. Rescue preparations mandatory. Can berun only by exper
ts in specially equipped white-water canoes, decked craft, and kayaks.

Class VI – Extraordinarilydifficult. Paddlers face constant threat of death because of extreme d
anger. Navigable only when water levels and conditions are favourable. Thisviolent white-watersho
uld be left to paddlers of Olympic ability.Every safety precaution must bestrictly adhered to.

Water Level

The characteristics of ariver can change remarkably as the water level rises or falls. As you mightexpect, a set of Class II rapids can become raging Class IV when the water is abnormallyhigh following spring runoff or heavy storms. Conversely, a Class IV can turninto a shallow pussy-cat when the water level is low in the late summer. Evennormally calm stretches become turbulent and dangerous at flood stage, becausethe force of currents slamming this way and that on the rocks and obstructionscreates powerful and dangerous surface conditions.

An International Ratingsystem has also been devised to describe river flow. The classification for aspecific river may change from season to season;the following letterdesignations are used to describe water level and rate of flow.

‘L’ or Low. Below-normallevels for the river. Below-normal depth may interfere with good p
addling. Shallows may turn into dry banks and low areas become muddy sandbars.

‘M’ or Medium. Normal riverflow. Medium water generally is used to describe good water for rivers withslight gradients and enough depth for passage on the steeper sections.

‘MH’ or Medium High. Higherthan normal. Faster flow on gentle gradients. The best flow for more difficult river sections with enough water for passage over low ledges andthrough rock gardens.

‘H’ or High. Water becomesdifficult to handle. The river is well above normal stage. Canoeists may referto the strong currents as “heavy.” Small debris may come floating by. A warningthat the riv
er is dangerous and better left to skilled kayakers or canoeists whosecrafts are supported by floatation bags.

‘HH’ or High-High. Very heavywater. Hydraulics are complex. Even slight gradients become t
reacherous. Debris is frequent. Only for experts!

‘F’ or Flood. Abnormally highwater, overflowing the banks; current extremely violent; low-lying areasa
re underwater. TV crews show up to shoot for the  news. Not for any boaters except those with ap
propriate equipment on dangerous rescue missions.

Canoeists

The Appalachian MountainClub rates canoeists on a scale of I through V. Check your competence againsttheir ratings:

Class I – Beginner. Is familiarwith basic strokes and can handle a tandem canoe competently from the bow orstern in flat water, solo canoeist is familiar with basic strokes.

Class II – Novice. Can handle moreadvanced white-water strokes solo or in either bow or stern of a t
andem canoe. Knows how to read water; can negotiate easy and regular rapidswith assurance.

Class II I- Intermediate. Cannegotiate rapids requiring linked sequence of manoeuvres,  understands and can use eddy turns and basicbow-upstream techniques; is skilled in either bow or stern of a tandem canoe;can paddle Class II rapids in a solo canoe or a kayak.

Class IV – Expert. Has establishedability to run difficult (Class III and Class IV) rapids in bow or stern of atandem craft, can paddle solo in a properly equipped canoe or kayak;understands and can manoeuvre in heavy (Class H) water.

Class V – Leader. Is an expertcanoeist; possessesthe experience, judgment, and training to lead a group ofany degree of skill on any navigable waterway and in the wilderness. A&W