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Mannings for Ditch Liner

Mannings for Ditch Liner

(OP)
Hi, I recently read the thread about calculating the mannings roughness coefficients as I want to provide similar information on our Concrete Cloth ditch liner. Is there an agency that tests for a figure in the US. We produce this in the UK and Our US Distributor is asking for this info.

RE: Mannings for Ditch Liner

Manning's roughness for concrete can vary from .011 to .020 depending on finish, but .013 is pretty standard.  The quick way to get a number to use is pull up a table and find the material and finish that best describes your product, and just use that.  (see attachment - that's from Sturm: Open Channel Hydraulics, which he took from Chow)

If you're interested in actually figuring out the real number, any university with a substantial fluid mechs lab could do this for you.  You basically just put it in a long flume with tight controls on flowrate and flume slope, and plot depth versus flowrate and depth vs slope.  Measure depth as far away from the ends of the flume as possible.  (=normal depth)  It's been a while, but I think we did the procedure as a lab in undergrad at Georgia Tech.  

If you've got a big enough pump and a good source of free water, you could do the procedure yourself at your plant, out in the yard.  Could be fun.  

There may be other agencies or private corps that could help you out too.  I'll be interested to see some of the other responses.  If nobody points you in a better direction, shoot me an email and I'll try to track someone down at GT to talk to.

 

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Mannings for Ditch Liner

(OP)
Thanks Beej67, that is very helpful. I like your idea on testing it at the factory, we may give a go.

RE: Mannings for Ditch Liner

Make sure you get someone with a solid fluid mechs / open channel background to set the experiment up, because there's lots of little things you have to take into account, like channel geometry and whatnot.  The basic premise is simple though.  "Given this geometry, this slope, and this flowrate, what Manning's coefficient gives you this measured depth?"  Then repeat for different flow rates at different slopes and look at your data.  

That concrete cloth product looks neat.  Is there a US distributor in the south east?   

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Mannings for Ditch Liner

(OP)
Thanks again, yes we have a distributor based in Louisiana, he covers the South East.
Tracy Stewart & David Pedigo
Pedigo Concrete Solutions, L.L.C.
www.pedigoconcretesolutions.com

RE: Mannings for Ditch Liner

I would not recommend doing this yourself, it is beyond the capabilities of most and the results will be suspect if you do it yourself. Stick with a university lab and I would recommend the following which I have experience with:
Colorado State, Dr. Steven Abt and Utah State, Dr. Bill Rahmeyer.

RE: Mannings for Ditch Liner

Dr. Terry Sturm at Georgia Tech might also be someone worth speaking to.  (wrote the book I linked above)

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Mannings for Ditch Liner

(OP)
Thanks Gents, I really appreciate the help. One last question, any idea how much they would charge?

RE: Mannings for Ditch Liner

No clue.   

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Mannings for Ditch Liner

they often get work study / intern students to do much of the  work at very low compensation. I used to be one of those. Generally there will be a masters or PhD running the project, however they generally don't have high rates either. Generally not terribly expensive, but it depends  on what your scope of work is.

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