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Home arrow Conservation arrow Ridley Creek Deflector Project 8-22-2009
Ridley Creek Deflector Project 8-22-2009 Print
Written by Greg Shaffer   
Wednesday, 26 August 2009

Deflector Greg Fred & Steve Despite a last minute call for volunteers, high heat and humidity, a late delivery and a rock pile that was not nearly as close to the creek as I had hoped — 5 tons of rock have been added to the deflector immediately upstream of the bridge pool. Fred Dewees, brand new club member Steve Buck, and I waited an hour for the delivery before we started carrying and tossing stones.  A little later, Ed Collier got the word and pitched in with fresh muscles just at the right time.  Everyone worked hard, but we were able to finish the job in less than 2 hours of working time.

When the work was proposed, I was told we would need 5-6 tons of stone.  I erred on the safe side and got 5.  Although I am glad we didn't have any more to move with just the four of us, I think we are going to need another 5-10 tons of stone before we will be finished with this deflector.  The angle between the bank on the downstream side and the point of the deflector in the stream should be 60 degrees or less.  I am going to measure it out, but I don't think we are there yet.

Several people have asked what the deflector is supposed to do.  To get a precise answer, I consulted the book Better trout habitat: a guide to stream restoration and management by Christopher J. Hunter, Tom Palmer, Ellen Meloy, Montana Land Reliance (Trust):

The partial barrier to water flow deflects current towards the opposite bank.  By partially blocking flow, the deflector causes water to back up or pile up to some degree, which results in increased water depth and velocity. The water scours a pool just downstream and opposite the deflector. A portion of the stream's sediment is deposited in the lee of the structure.  Thus, a bar forms downstream, and on the same bank as the structure.

In this case, I think it should also reduce errosion of the bank downstream and adacent to the deflector.  Below is a picture of the work site after the rain we had from Hurricane Bill.  As you can see, more stone is needed to bring the new newly added area up to the appropriate level.

 

Saturday 8-24-2009 High Water
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