The WW (white water) scale, internationally recognised by the ICF (International Canoe Federation), has the following levels/classifications.
It should be noted that along any route down the river the level of difficulty may vary hugely according to the water flow, which is affected by the season, rain, and by thawing ice. Sudden changes, including changes in speed, may occur in the space of a few hours due to the closing off of flows and/or due to unforeseen obstacles (fallen trees, for example). Rivers that are too empty or too full (with too little/too much flow) cannot be classified.
N.B. The phrase “morta” (of “acqua morta”) refers to the edge of the river, on the margins of the main currents, where the water is still or headed upstream.
The classification used by Ckfiumi is as follows:
The WW scale is defined as follows:
Relatively smooth water flow with small, regular waves distributed sparsely across the surface. Light currents and easily identified and avoidable eddies. Wide rapids without obstacles, with an easy-to-follow, straight route. Slight gradient.
Torrent with easily avoidable obstacles, large, highly visible areas of still water. The route is easily identifiable and requires some wide manoeuvring. The descent is exciting and satisfying but not scary.
Torrent with a series of moderately difficult rapids interspersed with small lakes, waves and whirlpools that may interrupt the descent and immerse the kayak, without blocking it completely. Rapids with obstacles requiring decisive and effective manoeuvres. The kayaker must know how to turn, carry out duffek strokes, and execute an Eskimo roll. The kayaker must have experience and be confident dealing with real rapids.
Large and irregular waves and whirlpools, which must be avoided using quick decision-making and by choosing the correct direction. Difficult rapids requiring excellent and precise manoeuvring techniques. Narrow and choppy areas of water next to the river banks which are difficult to access and where it is challenging to remain still. Swimming in level IV water is dangerous and it is difficult for guides to intervene, therefore kayakers must be able to confidently execute an Eskimo roll in any situation. An assessment of the risks should be carried out prior to launching in sections of level 4 white water. Often, rapids are not more challenging than level III, but both their quantity and the length of the route raise the difficulty level.
Very difficult, dangerous
Deep whirlpools that can trap or capsize kayaks and canoeists. Bankside areas unusable as places to stop. Rapids have multiple, large obstacles, narrow passages, violent and sudden waves and currents. Kayakers/canoeists must have reliable technique, training and quick reactions. Level V sections are not fun, even for experts – they are extremely difficult, challenging and dangerous.
This level represents the limit of navigable water. At this level, courage and an excessive passion for risk are as fundamental as an optimum technique. Some are able to manage sections of level VI water, but even a minor error is fatal.
Routes for amateurs and tourists are usually up to level III. In safe conditions (with emergency assistance on standby) they may include short passages or sections at level IV. The highest competitive levels (slalom) generally take place in sections of water at level IV – and occasionally level V – with appropriate rescue and emergency services.