View topic - Artificial WWB channel-- Gradient/Length/Total Drop

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PostPosted: September 19th, 2011, 10:25 am 
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Location: Central Maine--Sheepscot Watershed
A question--what is the typical length, gradient, and total drop of an artificial whitewater course?

I used work on fish passage projects, and we woould occasionally get questions about whether a fishway could be designed to also serve for WW playboating or for "boat passage" at a dam.

In general, my sense from the ones I have seen is that the typical gradient and water velocities are considerable higher than desirable for ideal passage of most species, but would like input on what would be a "typical" course in terms of gradient, length, and overall drop.

Is there any potential at sites with relatively small head--say 10-15 feet?


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PostPosted: September 22nd, 2011, 7:49 am 
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Location: a bit south ofWinnipeg
Hi

there is plenty of evidence from the UK of salmon and other species using the canoe courses at Holme Pierrepont in Nottingham and the course at Teeside. HP has a drop of 7m, not sure about Teeside and both have recently been re-worked so am even less familiar with the hydraulics now. Salmon also use the welsh whitewater center on a flow controlled section of modified river- similar to the Ocoee. You could probably get more details by contacting the competitive section of the ACA. I did have a table showing length, gradient and flow volume for a range of courses when I was back in the UK.

It's going to depend very heavily on the design of the course but I would think the velocities in a canoe course are much more variable across the cross section of the channel due to the eddies created by the obstructions and would require very short periods of burst speed swimming. Some modern courses have pools specifically designed for freestyle play in holes creating an entirely different kind of flow to areas with surfing waves- the variation is probably much closer to a real river than a fish pass!

There's no reason why flow could not be reduced when paddlers are not using the course to encourage passage. One of the biggest issues may be to ensure that the downstream entrance of the course was in a place suitable for passage. There may be a conflict between placing it far enough upstream to encourage passage but not too close to a dangerous structure such as a low head dam that could drown paddlers.

On a slightly different topic passes to allow fish up and canoeists down are being built in the UK and Europe using large plastic brushes as baffles on the bed- very fish and boat friendly!

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PostPosted: September 22nd, 2011, 11:24 am 
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Location: Central Maine--Sheepscot Watershed
Thanks Chris. Very helpful.

Salmon are easy to pass. For us on the east coast, the most challenging species is probably shad.

Conceptually, I agree with your sense that a natural channel is a more "nature-like" than a traditional fishway, and therefore ought to provide better passage. Being able to demonstrate that to the satisfaction of a skeptic is a different matter.

My sense from eyeballing online photos of some of the Olympic WWB courses is that the gradient will likely result in water velocities and levels of turbulence that may be beyond what's desirable. A nice Class 1/II might be just the ticket for shad. :)


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PostPosted: September 22nd, 2011, 12:08 pm 
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To return to the original question -- what is the gradient of a WW course? I have to admit that I don't know the profiles of courses like Valleyfield, Minden, the Ottawa Pumphouse or Chalet Rapids on the Middle Mad but my guess would be that they lose at least 50-60 feet from start to finish. Even the very short Pumphouse loses at least 20 feet.

Some of the dedicated slalom paddlers probably know the specs by heart.


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PostPosted: October 1st, 2011, 9:45 pm 
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It is not as much as you think.
the Pump house does not drop too much vertically and is probably the gentlest of the 3 mentioned.
I would contact White Water Ontario, If I remember correctly Minden only drops about 40ft, lake to lake.
When you see it shut off it is pretty amazing.
For other courses you could contact American White Water for their specs on the Alanta course

http://en.wikipedia.org/wiki/Ocoee_Whit ... lom_course
Ocoee had a 1.9 percent drop or 19 m per KM

It would be easiest to contact local National Associations to get the contacts.

Just remember it does not have to be an "olympic" level course to be a good design for a training centre or play area for your average paddler.
The real tough courses would only cater to a few users and would not be worth the cost and would not attract higher use.
Jeff

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PostPosted: October 9th, 2011, 8:32 pm 
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The main contact in the UK is Chris Hawkesworth at the British Canoe Union. He is the facilities development officer (I think!) Yuo should be able to find his details on the website somewhere.

One problem is the trend to steeper courses to attract the rafting crowd. That will be how the new Olympic course in London makes it's money.

Shad are really dumb! I think they go through vertical slot passes but not sure about other designs. Yes salmon are easy. Most other species are better swimmers than we give them credit for. I guess it just depends on how efficient you want your pass to be!

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