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 gradi ...
, 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 is a ...
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
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
) and a ''
cascade
Cascade, Cascades or Cascading may refer to:
Science and technology Science
*Cascade waterfalls, or series of waterfalls
* Cascade, the CRISPR-associated complex for antiviral defense (a protein complex)
* Cascade (grape), a type of fruit
* Bioc ...
''. 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 a ...
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
File:Violent water below Niagara Falls.jpg, Violent water below Niagara Falls
File:RapidsonMississippiRiverOntario.jpg, Rapids on the Mississippi River (Ontario) 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
The Maumee River (pronounced ) ( sjw, Hotaawathiipi; mia, Taawaawa siipiiwi) is a river running in the United States Midwest from northeastern Indiana into northwestern Ohio and Lake Erie. It is formed at the confluence of the St. Joseph and ...
in Ohio
File:Uusimaa, Finland - panoramio - pan-opticon (22).jpg, The Kuhakoski rapids in Uusimaa, Finland
See also
*
Fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
*
International scale of river difficulty - for classification of rapids
*
Rheophile - organisms that live in fast-flowing water
*
Riffle - A fast-moving portion of a stream without the vigor of a rapid
*
River rapids ride
References
*
External links
Rapids entryin
National Geographic
''National Geographic'' (formerly the ''National Geographic Magazine'', sometimes branded as NAT GEO) is a popular American monthly magazine published by National Geographic Partners. Known for its photojournalism, it is one of the most widely ...
's encyclopedia
Fluvial landforms
Limnology
Rivers
Water streams
{{River-stub