From Academic Kids

This page discusses whitewater rapids. For the scandal involving former U.S. President Bill Clinton, see Whitewater scandal.
Whitewater on the river Guil ()
Whitewater on the river Guil (French Alps)

Whitewater is formed in a rapid, when a river's gradient drops enough to form a bubbly, or aerated and unstable current; the frothy water appears white. The term is also used loosely to refer to less-turbulent but still agitated flows.

Three factors, separately or in combination, can create rapids: gradient, constriction, and obstruction.

The gradient of a river is the rate at which it loses elevation along its course. This loss determines the river's slope, and to a large extent its rate of flow. Shallow gradients produce gentle, slow rivers while steep gradients are associated with raging torrents.

Constrictions can form a rapid when a river's flow is forced into a narrower channel. This pressure causes the water to flow more rapidly (hence the name) and to react differently to riverbed events (rocks, drops, etc.)

Lastly, there is obstruction. A boulder or ledge in the middle of a river or near the side can obstruct the flow of the river, and can also create a "drop" (over the boulder) and "hydraulics" or "holes" where the river flows back on itself--perhaps back under the drop--often with fearful results for those caught in its grasp. (Holes, or hydraulics, are so-called because their foamy, aerated water provides less buoyancy and can feel like an actual hole in the river surface.) If the flow past the obstruction is less violent, often an eddy is formed; eddies may be swirling and whirlpool-like, or simply sheltered areas where boaters can stop to rest, scout or leave the main current.

These days the term has a broader meaning, applying to any river or creek that has a significant number of rapids and the term is also used as an adjective describing boating on such rivers. Ex. One of his hobbies is whitewater kayaking.


Classification of whitewater

The most widely used grading system is the International Grading System, where whitewater (either individual rapids, or the entire river) is classed in six categories from class I (the easiest and safest) to class VI (the most difficult and most dangerous). The grade reflects both the technical difficulty and the danger associated with a rapid, with grade I referring to flat or slow moving water with few hazards, and grade VI referring to the hardest rapids which are very dangerous even for expert paddlers, and are rarely run. Grade-VI rapids are often wrongly downgraded to grade-V or V+ if they have been run successfully many times. Harder rapids (for example a grade-V rapid on a mainly grade-III river) are often portaged. The term is French for carrying i.e. the boater lands and carries the boat around the rapid. A rapid's grade is not fixed, since it may vary greatly depending on the water depth and speed of flow. Some rapids may be easier at high flows because rapids are covered or "washed-out and others may be easier at low flows when the currents are slower.

  • Class 1 - no rapids, smooth flowing water
  • Class 2 - some rough water
  • Class 3 - whitewater but very safe for larger rafts
  • Class 4 - whitewater for experienced rafters only
  • Class 5 - whitewater for experts only
  • Class 6 - impassable

Features found in white water

one any given rapid there can be a multitude of different features change the layout of a river.


Strainers are formed when an object blocks the the passage of larger objects but alows the flow of water to continue like a big strainer. These objects can be very dangerous. Strainers are formed by many different objects from the obivious like storm grates over tunnels to trees that have fallen into a river to rebar from broken concrete structures in the water. if in an emergancy(ie being swept into one) it is often best to try and climb on top of strainer so as not to be pinned against the strainer under the water.

White Water Hydraulic

White Water Hydraulics, often referd to as holes, are formed when water pours over the top of a submerged object causing the water down stream to flow back over the top of the water rushing over the submerged object. hydraulics can be dangerous you float enough to stay stuck in the recirculating water. the more dangerous types of hydraulics are formed by lowhead damns and similar types of obstruction where the sides of the hydralic are blocked by an object making it impossible to slip off the side of the hydraulic.


Waves are formed in a similar manure to hydraulics and are sometimes also considered hydraulics as well. Waves are noted by the large smooth face on the water rushing down. Sometimes a particularly large wave will also be fallowed by a wave train, or a long series of waves.

Scientificly waves are called laminar, but the White Water world has also included waves with turbulance into the definition of waves.


are formed when a large flow of water runs into a large obstruction causing water to boil up against the face of the obstruction. pillows can be dangerous because oftentimes the object that forms the pillow is undercut and so objects can be swept underunderwater possibly to be entraped.


are formed on the down stream face of an obstruction. they are calm spots where the downward movement of water is partially or fully arrested.

White Water Craft

There are many different types of white water craft that people use to get down a rapid. Here is a short list of them.

White Water Kayak differs from sea kayaks and recreactional kayaks in that it is specialized to deal with moving water better. they are often shorter and more manuverable then sea kayaks and are specially designed to deal with water flowing up onto their decks. See Whitewater kayaking

Raft also often used as a whitewater craft, see Whitewater rafting

Cat Raft similar to a raft but with two pontoons on either side of the craft which are bridged by a suport carriage where the occupants sit.

Canoe Often made of fiberglass, kevlar, plastic or a combination of the three for strength and durability. White water Canoes often have large Airbags to prevent the boat from being Swamped.

The Scientific investigation of White Water Events

fluid mechanics

North American White Water


Whitewater in Canada

Whitewater Recreation in Canada

Whitewater in the United States

East Coast Rivers

Rivers in the eastern section of the United States are usually considered "technical," which means that due to lesser water volume, rafters/kayakers must often direct their craft through boulder-strewn sections of river, through narrow channels, through shoals, and so forth. This requires a degree of "river reading" skill, paddling precision, and so forth.

  • Ocoee River - ??, Tennessee
  • New River - Oak Hill, West Virginia
  • Green River - Ashville, North Carolina
  • French Broad - ??, Tennessee
  • Nolichucky - ??, North Carolina

In the eastern United States, there are several "must do" rivers for paddlers. For beginners, there is the Nantahala in North Carolina. It is a relatively gentle river, with the final rapid having the propensity to send paddlers in for a cold, exhilarating swim.

The next step up--and the most fun you can have before things "get scary"--is the Ocoee River just west of Cleveland, Tennessee. The 1996 Olympic Canoe/Kayak Whitewater Slalom Competition was held on this world-class river. A special section was contructed for the venue, but the "lower" Ocoee is the classic--and best--ride. What makes this river special is that it is almost continuous whitewater. Many river are "drop-pool" rivers, with rapids far apart. Not the Ocoee. Within ten seconds of your first paddle stroke, you will be in a serious class IV rapid. While there are some challenging rapids on the Ocoee, most of the rapids are very forgiving. If you fall in, you'll get a good scare, but will very likely be pulled back into the boat within 30 seconds.

The New River in West Virginia is the next step up. It is a "grown-up" Ocoee river. Larger rapids, fairly close together (except for the long wait for the first one--"Surprise").

The Chattooga (Sections 3 and 4) outside of Clayton, Georgia can, at high water, be thrilling to the point of fear. Huge rapids, big drops, and thunderous power, this river is a challenge for even experts.

The Gauley River in West Virginia, especially at the "Fall Draw Down" (when the reservoir is drained) is a world-class ride. Huge rapids, many of the listed as "class V+" (which is shorthand used for insurance purposes). A true challenge is to do the upper and lower Gauley in a single day. It's twenty-four miles of big rapids and lots of paddling.

Then there is the river that only the most hardcore rafters and kayakers of the east know about or raft: The Russell Fork Gorge. Located in the Breaks Interstate Park on the border of Kentucky and Virginia, this river drops 150 ft. per mile in the gorge. Huge and fearful drops. Advanced paddlers only. El Horrendo is the showcase rapid due to its size. The best description of that rapid would be "something like a 45 degree waterfall."

West Coast Rivers

In the western United States, the more noted rivers (e.g., Grand Canyon) have much larger water volumes, and thus require a different set of rafting skills. Western rafters also navigate many small, low volume rivers, some with much steeper descents than eastern rivers, however, since the mountains are newer in the west, the hazard from undercut rocks, a problem in the east, is replaced by more frequent log jams created primarily by logging activities near the rivers.

The big water rivers usually do not require the precision paddling of smaller rivers, but have larger rapids and longer wilderness trips are available due to the greater length and water flow of the big rivers. The smaller rivers and creeks boated by most rafters offer many exciting one or two day trips with difficulty levels from I to VI.

In the west, most rafters start on the American and work their way up to the Rogue, the Illinois, the Toulomne, the Salmon, the Snake, and then the big water rivers like the Green and Colorado through the Grand Canyon, or the Fraser in British Columbia, and many Alaskan streams where you will get tired of eating fresh salmon and have to carry a cannon to keep the bears away.

  • Cache La Puder - a easy class 2 river with a small class 4 section and a class 5 waterfall. The Water fall is very dangerous because the last drop is unrunable. The water pours off a slab into a 2 foot wide crack and grinds anything that goes into it.
  • Gore Section of the Colorado - a nice class 4 river with two very nasty class 5 rapids. the first class 5, ????, is tighly surrounded by several large class 4 rapids. most of the water flow to the river left side of rapid where a very nasty and very sticky hole that runs into a large rock. The second Class 5 Rapid, Tunnel Rapid, is mostly comprised of a single large ledge. on the right side of the rapid is a very nasty and very sticky hole that is bordered by a large rock on the left preventing people from exiting. On the left side of the ledge the water is redirected right back into the large hole. the water is redirected by an undercut rock.
  • The Locksa River
  • Salmon River
  • Payet
  • Clarks Fork of the Yellow Stone
  • Snake River

European White Water

United Kingdom

Whitewater rivers in the UK are typically low volume and technical. In England and Wales rivers are typically less than 20 m³/s, and some are run with less than 1 m³/s (usually these involve skidding the kayak down steep rockslides and small waterfalls). In Scotland there are also a few bigger volume (up to about 50 m³/s) rivers.

Almost all runs in England and Wales need recent rain to be at a paddleable level, and many can only be run immediately after heavy rain. In Scotland some bigger rivers can be run for weeks after rain although as with the rest of the country, most need recent wet weather. The paddling season is year-round but the rivers are more often runnable in winter (the wettest months of the year being December and January).

Most runs offer only a few kilometres of whitewater and often several rivers can be run on a wet day. Some rivers consist of only a single rapid. Only a few rivers (such as the Findhorn and Spean in the Scottish Highlands) have more than a days' worth of paddling, and most of this tends to be grade III or less.

There is no natural whitewater in the (mainly flat) south and east of England. Here whitewater paddlers often go playboating at man made weirs. Hurley weir on the River Thames west of London is probably the most popular. There are several artificial whitewater courses, where water is pumped or diverted though a concrete channel containing obstacles to create rapids. There is a 28 m³/s artificial whitewater course on the Trent at Holme Pierrepont in Nottingham (at the National Watersports Centre), a 5 m³/s course on the Tees in Teesside, and smaller courses on the Nene at Northampton, and at Cardington.

Commercial rafting is limited to artificial whitewater courses (where it often provides the majority of the courses' income) and a few of the bigger and more reliable rivers, in particular the Tryweryn and the Orchy.

There are several sites off the west coast of Britain where strong tidal currents channeled between islands create big volume sections of whitewater. These include the Bitches in Pembrokeshire in Wales, and the Falls of Lora on the west coast of Scotland.

Legal access to whitewater is a big issue in England and Wales. The public are only allowed access to a tiny proportion of the available whitewater, and often this is restricted to a few months or even a few days per year. This limits commercial operations and the activities of clubs, but many individual kayakers still paddle illegally. Rivers are almost all private and access must be agreed with all of the riparian owners (the owners of the land either side of the river) and the owners of the fishing rights, otherwise canoeing or kayaking there is trespass (although landowners can do little other than tell trespassers to leave their property). Agreements rarely exist as there is no incentive for the owners of rivers to let anyone else use them. In Scotland, like most of the rest of the world, access to whitewater is legal and has never been illegal. It has been enshrined in law in the recent Scottish Land Reform act. The Right to Roam act in England explicitly excluded rivers.


Popular whitewater rivers in the Alps are mainly medium volume glacier-fed rivers with long continuous rapids and few big drops. The season is short (two or three months in early summer when the snow and glaciers are melting) but the whitewater is reliable in this period. Tourists come from around europe to kayak and raft--the most popular centres are Brianšon in the French alps, and the area around Landeck in Austria.

Whitewater in Norway

Norwegian whitewater rivers are typically steep pool-drop rivers with many waterfalls, and are run mainly by experienced kayakers. There are also bigger (sometimes glacier-fed) rivers which are sometimes rafted. The season lasts all summer, although some rivers only run after recent rain.

Norwegian waterfalls regularly feature on extreme kayaking videos. de:Wildwasser

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fluid Mechanics


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