WhiteWater

Whitewater is formed in a rapid, when a river 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.

The term "whitewater" also has a broader meaning, applying to any river or creek itself that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater kayaking whitewater rafing.

What Causes Whitewater?

Three factors, separately or in combination, can create whitewater 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 whitewater torrents.

Constrictions can form whitewater 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 passes next to the obstruction, an eddy may form behind the obstruction; although eddies are typically sheltered areas where boaters can stop to rest, scout or leave the main current, they may be swirling and whirlpool-like. As with hydraulics (which are, essentially, eddies turned at a 90-degree angle), the power of eddies increases with the flow rate.

You should go whitewater rafting - it is alot of fun!