GetWiki

{{Short description|River section with increased velocity and turbulence}}File:Rapids of Kern River, California, USA.webm|thumb|Rapids of Kern River, California, USA.]]Rapids are sections of a river where the river bed has a relatively steep gradient, causing an increase in water velocity and turbulence. Flow, gradient, constriction, and obstacles are four factors that are needed for a rapid to be created.

Physical factors

Rapids are hydrological features between a run (a smoothly flowing part of a stream) and a cascade. Rapids are characterized by the river becoming shallower with some rocks exposed above the flow surface.WEB, Rapids,weblink February 20, 2024, National Geographic, 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". 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 of the stream or river, resulting in better water quality.WEB, Rapids - redzet.lv,weblink 2024-05-01, www.redzet.lv, en, For a rapid to form, a necessary condition is the presence of a gradient, which refers to the river or stream's downward slope. When a river has a larger gradient, the water flows downhill faster.WEB, Rapids,weblink 2024-05-01, education.nationalgeographic.org, en, Gradients are typically measured in feet per mile.BOOK,weblink Stream Gradient, Creek Connections Topographic Map Module, This impacts the river's flow or discharge, which is measured as a volume of water per unit of time. The faster the water flows, the more likely a rapid will form.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.WEB, 2019-02-18, Whitewater Rapid Classification System - River Difficulty Classification,weblink 2022-08-21, kayakbase.com, en-US, River rafting sports are carried out where many rapids are present in the course.Constriction refers to when rivers flow through narrower channels, thus increasing the velocity of the water. This may also lead to the creation of obstructions due to sediment transportation and erosion. Obstacles may occur by human activity, natural landslides and earthquakes, or accumulation of sediment or debris. The more prominent these four factors are present in a river, the more likely that river is to be a rapid river.BOOK, Nelson, Stephen,weblink Streams and Drainage Systems, November 3, 2015,

Gallery

File:Rapids before the Rhine Falls.jpg|Rapids featuring whitewater, close to the Rhine FallsFile:Violent water below Niagara Falls.jpg|Violent water below Niagara FallsFile: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 in OhioFile:Uusimaa, Finland - panoramio - pan-opticon (22).jpg|The Kuhakoski rapids in Uusimaa, FinlandFile:Storforsen-17.JPG|Storforsen, rapids along the Ume River, Norrbotten, Sweden

See also

• Fluid dynamics
• 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

{{Commons category}}{{Reflist |refs=}}

• WEB, River Flow Changes Over Time {{!, EARTH 111: Water: Science and Society| accessdate = 2023-03-03| url =weblink}}
• WEB, Understanding Rivers, 2023-03-03,weblink
• WEB, Rivers and Streams, and erosional processes, 2023-03-03,weblink
• WEB, Wright, Nick, How Do Rapids Form in a River?, Whitewater Guidebook, 2023-03-03, 2020-08-14,weblink
• WEB, Attal, Mikaël, Impacts by Moving Gravel Cause River Channels to Widen or Narrow, Eos, 2023-03-03, 2021-09-24,weblink
• WEB, Water flow obstructions in watercourses - World Problems & Global Issues, The Encyclopedia of World Problems,weblink 2023-03-03,
• BOOK, Path of the Paddle, Bill, Mason, Northword Press, 1984, 9781559710046,
• BOOK, Geological Society of America, 978-0-8137-2398-3, 398, Sean D., Willett, Niels, Hovius, Mark T., Brandon, Donald M., Fisher, Brocard, G.Y., van der Beek, P.A., Tectonics, Climate, and Landscape Evolution, Influence of incision rate, rock strength, and bedload supply on bedrock river gradients and valley-flat widths: Field-based evidence and calibrations from western Alpine rivers (southeast France), 2023-03-03, 2006-01-01, 10.1130/2006.2398(07),weblinkweblink

External links

• Rapids entry in National Geographic's encyclopedia

{{river morphology}}{{Rivers, streams and springs}}{{Authority control}}