Rapids are sections of a river where the river bed has a relatively steep

gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gr ...

, causing an increase in water

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

and

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

. Rapids are

hydrological Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...

features between a ''run'' (a smoothly flowing part of a stream) and a '' cascade''. Rapids are characterized by the river becoming shallower with some

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...

s exposed above the flow surface. As flowing water splashes over and around the rocks, air bubbles become mixed in with it and portions of the surface acquire a white color, forming what is called "

whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...

". Rapids occur where the bed material is highly resistant to the erosive power of the stream in comparison with the bed downstream of the rapids. Very young streams flowing across solid rock may be rapids for much of their length. Rapids cause

water aeration Water aeration is the process of increasing or maintaining the oxygen saturation of water in both natural and artificial environments. Aeration techniques are commonly used in pond, lake, and reservoir management to address low oxygen levels or ...

of the stream or river, resulting in better water quality. Rapids are categorized in classes, generally running from I to VI. A Class 5 rapid may be categorized as Class 5.1-5.9. While Class I rapids are easy to navigate and require little maneuvering, Class VI rapids pose threat to life with little or no chance for rescue.

River rafting A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

sports are carried out where many rapids are present in the course. File:Rapids before the Rhine Falls.jpg, Rapids featuring whitewater, close to the

Rhine Falls , photo = File:SBB RABe 514 DTZ Rheinfall.jpg , photo_width = 280 , photo_caption = Rhine Falls with Rheinfall Bridge and Laufen Castle , location = On the border between the cantons of Schaffhausen and Zürich next to Schaffhausen, i ...

File:Violent water below Niagara Falls.jpg, Violent water below

Niagara Falls Niagara Falls () is a group of three waterfalls at the southern end of Niagara Gorge, spanning the border between the province of Ontario in Canada and the state of New York in the United States. The largest of the three is Horseshoe Fall ...

File:RapidsonMississippiRiverOntario.jpg, Rapids on the

Mississippi River (Ontario) The Mississippi River is a tributary of the Ottawa River in Eastern Ontario, Canada which has no relation with the Mississippi River in the United States. It is in length from its source at Mackavoy Lake, has a drainage area of , and has a mean ...

in Pakenham, Ontario, Canada. File:Rapids on Maumee River above Toledo, Ohio - DPLA - 84b5711224c89b44832b7e7d0f6c27c9 (page 1).jpg, Historical image of the river rapids on the Maumee River in Ohio File:Uusimaa, Finland - panoramio - pan-opticon (22).jpg, The

Kuhakoski Kuhakoski (; literally meaning "zander rapids") is a rapids near the village of Perttula in Nurmijärvi, Finland.

rapids in

Uusimaa Uusimaa (; sv, Nyland, ; both lit. 'new land') is a region of Finland. It borders the regions of Southwest Finland, Tavastia Proper (Kanta-Häme), Päijänne Tavastia (Päijät-Häme), and Kymenlaakso. Finland's capital and largest city, ...

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

References

External links

Rapids entry
in National Geographic's encyclopedia Fluvial landforms Limnology Rivers Water streams {{River-stub

See also

References

External links