The rapids of the rivers are classified according to their technical difficulty, established in period of normal flow. This difficulty may vary depending on the flow of the river. The following classification was established by the decree of May 4, 1995 of the Ministry of Youth and Sports.
Class I = easy:
Regular course, regular waves, small eddies, simple obstacles.
Class II = moderately difficult:
(free passage) irregular course, irregular waves, medium eddies, weak eddies and rapids, simple obstacles in the current, small thresholds.
Class III = difficult:
(visible passage) high irregular waves, large eddies, eddies and rapids. Boulder, small falls, various obstacles in the current.
Class IV = very difficult:
(passage not visible in advance, reconnaissance generally necessary) continuous big waves, powerful and fast rollers. Rocks obstructing the current, higher falls with abseils.
Class V = extremely difficult:
(inevitable recognition) waves, eddies, rapids in the extreme. Narrow passages, very high falls with difficult entrances and exits.
Class VI = limit of airworthiness:
(generally impossible) possibly navigable according to the water levels. Great risks.