How to properly size a culvert for Drainage ditch..?

[fried1765]

You also need to consider how wide the stream is where you want to cross. If you collect a wide slow moving stream into a narrow channel it will have to speed up and then when it exits the narrow channel it will start to dig a narrow channel below the exit point. Then you will have a gully that will expand downward the flow path. I would say you will need to use several smaller diameter culverts but I am no civil engineer either.

A single 20" diameter culvert will provide nearly 50% more flow than two 12" culverts, and will be much less suceptible to plugging from debris.

 

[mikester]

Looks to me like your land is flat like a pancake with nowhere for drainage to go...aka lowland flood area. You could start with drainage swails to move the surface water. I'm guessing it's a springtime only problem?

 

[skeets]

Where does the water flow down stream? That might be your first choice to get the water out before you worry about a pipe. I mean it the water cannot discharge away from where you want to cross, the the pipe becomes a moot point. Just MHO

 

[Daren Todd]

There should not be a need to cut any type of 20' pipe for that proposed application.

OP stated he was only looking for 10' long not 20' long. If he decides to go 10ft' long and 2- 12" culverts. He can purchase one 20ft stick in plastic and cut in half himself with a chainsaw and use both pieces

Around here you can't purchase a 10ft culvert. They sell them in 20ft sticks

 

[fried1765]

OP stated he was only looking for 10' long not 20' long. If he decides to go 10ft' long and 2- 12" culverts. He can purchase one 20ft stick in plastic and cut in half himself with a chainsaw and use both pieces

Around here you can't purchase a 10ft culvert. They sell them in 20ft sticks

As before:
Any 12" corrugated pipe, or pipes, is not the best idea.
12" corrugated pipe is readily plugged by debris.

Any diameter poly pipe ("plastic") is a very poor idea if trying to minimize earthen cover.
With... adequate earth cover..... poly pipe is the best choice.

 

[Daren Todd]

As before:
Any 12" corrugated pipe, or pipes, is not the best idea.
12" corrugated pipe is readily plugged by debris.

Any diameter poly pipe ("plastic") is a very poor idea if trying to minimize earthen cover.
With... adequate earth cover..... poly pipe is the best choice.

I agree with you, so your kicking a dead horse. When you quoted me to begin with, I mentioned that poly would be a easy to cut down. And that sent you on your previous tangent.

 

[fried1765]

I agree with you, so your kicking a dead horse. When you quoted me to begin with, I mentioned that poly would be a easy to cut down. And that sent you on your previous tangent.

I understand.
Because poly is easy to cut,..... it is obviously the best material for the OP's project?
Got it now!

 

[Daren Todd]

I understand.
Because poly is easy to cut,..... it is obviously the best material for the OP's project?
Got it now!

You really need to work on your reading comprehension and then apply it by rereading my posts

 

[Drifthopper]

Thanks for all the replies.
I'l try to answer all questions and throw some comments of my own.........
I like the "one " big pipe solution.....
I'm involved with the a local snowmobile club, and when we put.... say..... ( 2 ) 12 " culverts side by side.... or ( 2 ) drain pipes they would aways plug up or get washed out in the springs rains.... so from working with the club... i like one big pipe idea.

I like poly over steel.... lighter, easy to handle, and seems more available on Craigs list and market place.

In my area... Western NY, There are several ads on the local market place for sections or cut offs.... i've seen 8' pcs, , 10 ' 12' ...different diameters.... and one ad ... buy the 20 " er and he'll cut it to whatever, so. i think i'll go with plastic.
and.....as others posted.... I know.... the larger the diameter, the price really jumps up.

Skeets... it flows off the propety. in the pics, the 4 wheeler is propably 50 - 60 yds up stream of the fence line / property line. I could probably go on their land, but it gets wooded and brushy. But... it flows better thru their area then the grassy area where the wheeler is at.

mikester.... ya.... spring time mainly. it does stay soft in the summer, but last summer was the 1st yr with my tractor so i kept cutting the grass.... sometimes as high as the hood..... and after keeping it knocked down and short, it dryed out toward Aug / Sept.
But its low land, and just real loamy. i'd would hate like heck to get the tractor stuck down there.

I don't like the bridge idea.... again, from working with the snowmobile club where putting in the snowmobile trails, ya.... we have some bridges on our trail system, but it seams culverts last longer and work out better.

I know i'll have to bring some fill in, the only thing i have is my front loader to move fill.
this crossing will only be for the tractor and 4 wheelers.
.

A question for those following this thread......
how far down will i have to dig to get the pipe to drain properly..?
I know its hard to answer with out seeing the land...... but i don't what to put the pipe too deep, or too shallow.

 

[Henro]

A question for those following this thread......
how far down will i have to dig to get the pipe to drain properly..?
I know its hard to answer with out seeing the land...... but i don't what to put the pipe too deep, or too shallow.

Late to the party, but my comment would be that the pipe doesn’t drain anything. It just carries water through it. In order for the pipe to carry water, you need the water on the exit side of the pipe to be lower than the water on the entrance side of the pipe. (Not totally true, but for drainage purposes probably true)

In your picture if you put a pipe, with the top below the surface of the water, water might flow through the Pipe, or might flow over the Pipe, or flow to the sides of the pipe, but it wouldn’t help with your water problem. The water level is set by the restriction on the property at the exit point beyond where the pipe would be placed.

So I think the starting point is how high does the water level get, worst case? The top of the pipe certainly should be above that level, for it to carry any water through it in practical terms.

I guess my point is that you need to worry about where the top of the pipe should be, and not where the bottom needs to be.

Now if what you’re really looking to do is to build the surface up higher than the highest point where water is worst case, then you get to the point of trying to determine the size of a pipe you need for the amount of flow that goes across your property. This is not a drainage issue.

I guess in my mind, I got sidetracked because you mentioned drainage, but in reality, you might not be interested in drainage at all.

 

[fried1765]

Thanks for all the replies.
I'l try to answer all questions and throw some comments of my own.........
I like the "one " big pipe solution.....
I'm involved with the a local snowmobile club, and when we put.... say..... ( 2 ) 12 " culverts side by side.... or ( 2 ) drain pipes they would aways plug up or get washed out in the springs rains.... so from working with the club... i like one big pipe idea.

I like poly over steel.... lighter, easy to handle, and seems more available on Craigs list and market place.

In my area... Western NY, There are several ads on the local market place for sections or cut offs.... i've seen 8' pcs, , 10 ' 12' ...different diameters.... and one ad ... buy the 20 " er and he'll cut it to whatever, so. i think i'll go with plastic.
and.....as others posted.... I know.... the larger the diameter, the price really jumps up.

Skeets... it flows off the propety. in the pics, the 4 wheeler is propably 50 - 60 yds up stream of the fence line / property line. I could probably go on their land, but it gets wooded and brushy. But... it flows better thru their area then the grassy area where the wheeler is at.

mikester.... ya.... spring time mainly. it does stay soft in the summer, but last summer was the 1st yr with my tractor so i kept cutting the grass.... sometimes as high as the hood..... and after keeping it knocked down and short, it dryed out toward Aug / Sept.
But its low land, and just real loamy. i'd would hate like heck to get the tractor stuck down there.

I don't like the bridge idea.... again, from working with the snowmobile club where putting in the snowmobile trails, ya.... we have some bridges on our trail system, but it seams culverts last longer and work out better.

I know i'll have to bring some fill in, the only thing i have is my front loader to move fill.
this crossing will only be for the tractor and 4 wheelers.
.

A question for those following this thread......
how far down will i have to dig to get the pipe to drain properly..?
I know its hard to answer with out seeing the land...... but i don't what to put the pipe too deep, or too shallow.

I really do not think anyone can reasonably answer your "how far down will I have to dig" question, without seeing your particular location.
As a possible guide: sewer drain lines must slope at least 1" per 10', and that is a smooth pipe absolute minimum pitch!

 

[woodsy]

Had a similar situation, potential place on my woods road to get stuck only in a ravine that drains 10-12 acres. Local hardware store had a sale on the 10" x 20'
poly culvert pipe couple years back, $120 out the door. Cut it in 1/2 at the store with a sawzall for easy transport and ended up with a 15' culvert. It has never overflowed or plugged up and only seen it 1/2 full after a 3" rainfall event. it pitches about 6" in that span.
I didn't want to spend much and this worked great. Been over it with a 2 ton tractor many times, tough culverts the poly ones.
I did haul in some buckets of rocks to solidify the base before putting the culvert in then packed the culvert in crushed stone, under, beside and 6" over.

 

[fried1765]

Had a similar situation, potential place on my woods road to get stuck only in a ravine that drains 10-12 acres. Local hardware store had a sale on the 10" x 20'
poly culvert pipe couple years back, $120 out the door. Cut it in 1/2 at the store with a sawzall for easy transport and ended up with a 15' culvert. It has never overflowed or plugged up and only seen it 1/2 full after a 3" rainfall event. it pitches about 6" in that span.
I didn't want to spend much and this worked great. Been over it with a 2 ton tractor many times, tough culverts the poly ones.
I did haul in some buckets of rocks to solidify the base before putting the culvert in then packed the culvert in crushed stone, under, beside and 6" over.

For a little 4,000 pound tractor, I can certainly understand that would work just fine.

 

[motionclone]

Get a laser and figure out elevations on your land so you know where its the lowest. Dig a ditch 2 ft deep through the wet area to the lowest area you figured out with the laser and hopefully you will have at least a couple feet of drop between the two. That will drain the wet area. Might take a year or so to fully dry everything out.

Put the culvert in the ditch and cover it with gravel where you want your crossing.

 

[Motion]

Besides plastic or sprial metal pipe, consider checking with a scrap yard for used pipe or if there's a plant that makes RCP and Arch pipe they may have second for a good price. I believe multiple pipes would be better. No mater what you go with, per the pictures you will need lots and lots of good quality fill up to and including mucking out to provide a good base for the culverts. Be reminded double wall plastic pipe floats.

 

[mikester]

A question for those following this thread......
how far down will i have to dig to get the pipe to drain properly..?
I know its hard to answer with out seeing the land...... but i don't what to put the pipe too deep, or too shallow.

You need to dig down DEEP ENOUGH to get slope and flow from point A to point B is the answer.

Get out a transit or laser level and start measuring elevation and distances for your answer.

 

[Henro]

You need to dig down DEEP ENOUGH to get slope and flow from point A to point B is the answer.

Get out a transit or laser level and start measuring elevation and distances for your answer.

I may be wrong, but it sounds like the neighboring property is close to the same level as the OP's, so digging a ditch would not help, unless the OP could also extend that ditch across the neighboring property, to a point where the level drops off.

 

[fried1765]

Before I decided to build a bridge, I considered a culvert. I found a site using Google that sizes culverts based on the drainage area it services, design rainfall, etc. Try searching 'culvert sizing' or 'how to size culvert'.
Use 12" bare minimum to reduce plugging. And set the bottom of the culvert 3-4" below the ditch invert. It'll fill up a little to match the bottom of the ditch.

The concept of 4" depth setting is good .....except...
If using a 12" diameter pipe, that only leaves 8" for water to pass.
8" for flow, is almost a guarantee for a pipe to plug from debris.

 

[fried1765]

I may be wrong, but it sounds like the neighboring property is close to the same level as the OP's, so digging a ditch would not help, unless the OP could also extend that ditch across the neighboring property, to a point where the level drops off.

Yup!
You done broke da code for this particular drainage issue!

 

[PoTreeBoy]

The concept of 4" depth setting is good .....except...
If using a 12" diameter pipe, that only leaves 8" for water to pass.
8" for flow, is almost a guarantee for a pipe to plug from debris.

Well, maybe 10", going by o.d. But that's why 12" minimum. Even that requires periodic maintenance. OP would do well to include headwalls anyway, since he's scrimping on culvert length.