Does anyone know what makes waves/holes on rivers? I know that if the water goes over a rock etc, then a wave or hole is usually made, but why? does one level of water move faster/slower than the others?

Since im here, what about wave trains that appear after a hole or wave, but don't necessarily have an obstruction to create them?

thanks, GS

Check out this long post. Somewhere in the middle was something related to holes/waves and wave trains:

playak.com/index.php?option=com_joomlabo...=10844&catid=108

The formation of waves is caused by the deceleration of moving water into slack water or in to more slowly moving water. As water comes down from a drop it enters a space that is occupied by stagnant water. The immediate result is that it tries to displace the stagnant water and since there is no place for the water to go it rises upward briefly creating a standing wave.

For a classic example of this see the Himalaya rapid on Chile's Futaleufu River. Here the river, moving upwards of 40-50 kph enters a deceleration pool creating some of the most massive waves in the hemisphere. Check out the video section:

www.exchile.com/guide/index.php/Himalayas

In the case of Hydraulics the effect is more pronounced. The water upstream has a definite downward momentum and flows under the slackwater causing the slackwater to rise and then fall backward. The physics are a bit more complicated but are similar to the creation of a backward current in an eddy. In the case of a hydraulic this backward current occurs over the surface of the water. (ie, the water needs someplace to go after it rises) A great example of this can be found here:

www.dailymotion.com/video/xxmn1_painkiller-a-hawai-sur-loch

hope this helps...

PS.. the water behind a rock is definitely stagnant.

The answer to your question is - Phyisics. People who are very clever have pined these river features down on a peice of paper. I have tried but the paper always seems to get wet.

Some things that help to understand hydrology are:

Water has lots of mass so that when gravity gives the water energy it gets lots of it. Like a freight train it doesn't stop in a hurry.

Water likes to travel in straight lines, always!

Water is not compressable so it can rebound off it's self as well as off rocks and river banks. Rebounding you can find explained very well by watching a snooker match on BBC 2.

William Nealy's book \"Kayak\" has a lot of very well drawn pictures that do well to explain a quite complicated subject.

neilnt wrote:

William Nealy's book \"Kayak\" has a lot of very well drawn pictures that do well to explain a quite complicated subject.

Yeah, that book is really good. Highly recommended:yes:

Jim Snyders book also has some great information on rivers and their flow how wave trains are formed, waves, rocks what to look out for etc.. all in nice an easy picture format as well as text. Not to mention good tips on squirt moves, rock splats / playboating.

Squirt Boating and Beyond: How to Rip in Anything That Squirts by Jim Snyder
ISBN-10: 0897323734
ISBN-13: 978-0897323734

My copy is well thumbed and kept in the van at all times for a referance. Will also give a thumbs up for William Nealy's book \"Kayak\"