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River Rafting India
By sunil
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 White Water Rapids
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, which is difficult enough to tax the most experienced crew of rafters to the limit). The ability of a paddler, thrown from his raft, to swim through a rapid in safety is also a consideration when rapid grades are fixed.
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.
The grade of difficulty of any given section of whitewater will depend upon the degree of skill required to negotiate it, or indirectly, upon the nature of the obstruction that the raft crew needs to overcome.
Grades do vary when water levels vary. As a generalisation grades tend to go higher as water levels increases because of the steep nature of river gradients in this country. These grades are referred to as the NORMAL grade. Below are the general characteristics of the six grades of whitewater.
RAPID GRADE [1]
Rapids are small regular waves. The passage is clear an easy to recognise and negotiate. Care may be needed with obstacles like fallen trees and bridge piers.
RAPID GRADE [2]
Rapids with regular medium sized waves (less than 1 m); low ledges or drops; easy eddies and gradual bends. The passage is easy to recognise and is generally unobstructed although there may be rocks in the main current, overhanging branches or log jams.
RAPID GRADE [3]
Rapids with fairly high waves (1-2 m); broken water, stoppers and strong eddies; exposed rocks; small falls. The passage may be difficult to recognise from on the river and inspection from the bank may be required. Maneuvering to negotiate the rapids is required.
RAPID GRADE [4]
Difficult rapids with high, powerful, irregular waves; broken and confused water; often boiling eddies; strong stoppers; ledges; drops and dangerous exposed rocks. The passage is often difficult to recognise and inspection from the bank is preferable. Precise and sequential maneuvering is required.
RAPID GRADE [5]
Very difficult rapids with confused and broken water; large drops; violent and fast currents; abrupt turns; difficult powerful stoppers and fast boiling eddies; numerous obstacles in the main current. Detailed inspection from the bank is normally required and is strongly recommended for rapids not recently transited at the prevailing water level. Complex, precise and powerful sequential maneuvering is required. A buoyancy vest equipped swimmer risks injury and this is the extreme for commercial operations.
RAPID GRADE [6]
All previous difficulties increased to the limit of practicability. Nearly impossible, very dangerous and cannot be attempted without a definite risk of life. The rapids under this grade is also known as suicidal rapids.
To know more in details visit this site: http://www.questrails.com
About the Author
sunil is a desigener & author of www.questrails.com
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