Low head dam explained

yomchi

Found this useful.

http://www.youtube.com/watch?v=IPaCXSwjLA4&feature=related

irishlostboy

despite the fact that we as kayakers play with hydrolic features (meaning whitewater, not holes in particular) there is definately an under-education about the actual function of whitewater. how holes work is an important factor. how strainers work is another. another is how eddies work. there is a lot to it. how i learned is, back in the day i went to a little stream, chucked in a foamy i made, and watched what happened and tried to figure out why what happened, happened. i would be interested in hearing about other methods people have for teaching and learning about hydrolic function and effect.
full marks to yomchi for bringing this up. cheers

yomchi

The scary thing about these is that they seem so tame, compared to some of the more violent looking features. Compare what you see in the video to say the sluice channel up at Lucan. Sluice looks like a monster in high water but in reality it's very safe (from a retention point of view). The thing to remember with deep recirculators is that all the 'violence' is under the surface making them look like a treat to run.

Has anyone any first hand experience of one?

KenHy

Usefull video. The best example of a recirculating stoper like that around dublin would be either the big A on the boyne. Sluice isn't really a recirculating feature, its more of a wave.

As a rule of thumb, the louder and more visable a hole is, the less sticky it will be. Always look for the towback, in the video you can see the line where the water starts flowing upstream. You dont want to get caught in there! Another rule of thumb is if the towback is more than half the length of your boat don't even think about trying to get through!

yomchi

Yeh the Big A on the Boyne is a good example. There is a video somewhere on YouTube of a couple of college lads going down it in a blow up raft, they fall out of it just before the bar and with all the luck in the world they manage to find the chute. I reckon if they had any idea of the possible dangers involved they'd probably feel right stupid about it.

Sluice is just a big mess of water, there is a stopper thought just on the bend afaicr. My point is exactly what you say, the more noisy and violent looking the less danger compared to those silent low head dams.

999/112

Hope these are useful.

In the hydraulics [animated slide], text describing each feature should also run ... can't get it going at the moment!

Pigeon Reaper

Swift water rescue courses will cover these features in detail. I recommend doing a course if you ever get the opportunity.

Lochlannach

I got Franco Ferrerro's book "Whitewater safety and rescue" a while back and would recommend it for anyone who want's to learn to read and understand river features better. I now have a better understanding of a lot of the features though I must refresh soon.

irishlostboy

ya, franco's book is the business when it comes to all things rescue on rivers. definately the best for that. for actual understanding of whitewater i have to say i learned more from William Nealy's book, Kayak than any other single source. even ages pld it really is super relevent. find a preview here;
http://books.google.ie/books?id=_yuZFwZTQLEC&lpg=PA1&dq=william%20nealy&pg=PA1#v=onepage&q&f=false
you can pick it up for about a tenner.

yomchi

irishlostboy wrote: »

ya, franco's book is the business when it comes to all things rescue on rivers. definately the best for that. for actual understanding of whitewater i have to say i learned more from William Nealy's book, Kayak than any other single source. even ages pld it really is super relevent. find a preview here;
http://books.google.ie/books?id=_yuZFwZTQLEC&lpg=PA1&dq=william%20nealy&pg=PA1#v=onepage&q&f=false
you can pick it up for about a tenner.

Where would you get that? Chapters, Easons?

wet-paint

You can buy it online from the publishers, Pesda Press. I'm super impressed with them, they do great quality books, and they're real authorities on whatever they're talkign about.

And Ken, that rule of thumb doesn't work for Hypoxia! /fail

KenHy

Ah! That flushes (eventually)!

Truley

+ 1 for William Nealy's Kayak it's like the bible in this house!

Another book I found fantastic was Loel Collins Kayak Rolling. It teaches everything you need to know about rolling, not just for learning yourself but from a teaching perspective too. Very concise and easy to understand.