# Dimensions of a ditch



## Bears Butt (Sep 12, 2007)

OK all you scientific and engineering types. If I have a water flow of 800 gallons per minute and I want to make a ditch to carry it, how deep and how wide does that ditch have to be?

In order that someone not drown if they fell into this ditch, let's limit the ditch to a max depth of 2 feet.

Thanks!


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## Fishrmn (Sep 14, 2007)

Gotta know the grade too. 

And someone can drown in an inch of water if they are face down and unconscious.


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## Bears Butt (Sep 12, 2007)

HMMMMM grade.......3%?


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## sawsman (Sep 13, 2007)

Bears Butt
So is any head space needed in the ditch or do you want the water flow running flush with the ground surface? Will it be rectangular? will the ditch be dirt, concrete or other? If it’s a dirt ditch, you need to consider silt containment, storm water, ditch erosion, slope/grade, vegetation and maintenance.
If we want to get technical…
:mrgreen:


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## wyogoob (Sep 7, 2007)

How much perimeter wetting will there be?

Is the soil:
Cohesive?
Granular?
Organic?


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## sawsman (Sep 13, 2007)

..and how do you know that the max flow is truly 800 gpm? V-Notch weir, rectangular, flume or flow meter? If flow meter, has it been calibrated?

Short answer to your question - the wider the better. You know, just to be safe.


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## Fishrmn (Sep 14, 2007)

I'd rather step over a ditch that's 4 feet deep and a foot wide, than a ditch that's a foot deep and 4 feet wide. :mrgreen:


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## Bears Butt (Sep 12, 2007)

YIKES!
I just want to run 800 gallons per hour down a dirt ditch to flood out onto 20 acres of very flat ground. The 800 gallons number comes from a very reliable source as they deal with this every day. The ground (dirt) gets very slick when wet and so, I wish to contain the water in a ditch that can be waded across without drowning the person should they slip and fall.

Is the soil:
Cohesive?
Granular?
Organic?

GEEZ! I have no idea.

If it’s a dirt ditch, you need to consider silt containment, storm water, ditch erosion, slope/grade, vegetation and maintenance.

Lots of silk expected. Storm water should not be too much of a problem. Ditch Erosion.....probably some sloughing from the sides. I would like to think sloping sides of the ditch would be preferred so as to allow wading across it. The grade is almost flat. Lots of vegetation grows where the ditch is planned and so I would expect it to grow back once the ditch was dug and maintenance would be performed probably once each year.

The water will be flushed through this ditch for up to 4 continual months in the year and not during the other 8 months.

I'd rather wade through a two foot deep ditch for 10 feet than slip and fall into a two foot wide ditch 6 feet deep


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## Fishrmn (Sep 14, 2007)

Turn the water loose. It'll cut its own path. _(O)_


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## wyogoob (Sep 7, 2007)

Make it 2 cubits deep by 3 cubits wide and you'll be fine.


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## Bears Butt (Sep 12, 2007)

I would think more like this:
De 3:11 For only Og king of Bashan remained of the remnant of 
giants; behold, his bedstead was a bedstead of iron; 
is it not in Rabbath of the children of Ammon? nine 
cubits was the length thereof, and four cubits the 
breadth of it, after the cubit of a man.


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## middlefork (Nov 2, 2008)

This is why I love this place


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## jahan (Sep 7, 2007)

You would be more than sufficient if you went with a trapezoidal channel with a bottom width of a half a foot, with 1:1 side slopes and a depth of 2'. That would give you a top width of 4.5 feet. PM if you have any questions or email me.


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## Bears Butt (Sep 12, 2007)

[attachment=0:ggcpqm0t]Trapezoid.png[/attachment:ggcpqm0t]

h = 2 ft.

I see. Very good Jahan. That looks like the answer I needed. You are the man! Thank you. And to you cubit guys...... _(O)_


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## Bears Butt (Sep 12, 2007)

Well folks, I met with the adjacent land owner on the site of the "ditch issue" and he does not want to change what is on his land....OK....But what about the water? We both agreed to let it flood and see what came of it.
I actually like this idea because the lay of the land should allow my property will receive about 1/3rd of the total volume of water, which will create exactly what I want and should not cause any undo problems like washouts or silting as the water has to travel nearly 300 yards through his place before getting to mine. He has lots of grass growing as well to stop any silt long before it gets to me. He is very happy to flood his place because of the same reason I am happy to get the water.
A win-win all around!
Thanks to everyone for the advise! Even the cubit guy. I thought for a long time about the 2X3 cubits and it would actually handle my 800 gal/min and even more. My problem is who's cubit do I use, mine is shorter than most.  I have saved the information in my favorites in case the other landowner decides a ditch would be better in the future!


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## wyogoob (Sep 7, 2007)

When Noah built the Ark a cubit was 17", the width of a normal adult man. Today a cubit is 18" (per Mr. Google). 


If you need any more advice Mr. Z, just holler, I had math all 6 years of high school.


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## Bears Butt (Sep 12, 2007)

:lol:


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## sawsman (Sep 13, 2007)

Good luck Bears Butt. What you gonna grow? Corn? Nightcrawlers?


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## manysteps (Sep 28, 2009)

800 gallons a minute is only good for growing one thing. The rest of you quackers will have to try and figure it out.


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## Utahgreenhead (Apr 28, 2009)

What will a cross section of the ditch look like? Rectangular, trapezoidal, circular. That will probably be the biggest variable that will make the most difference. That and the slope that you build it.


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