DIY Bridge

[2manyrocks]

Part of the problem is, over the last 20 years, the creek has moved a bit. It used to just flow across the drive after heavy rains. Now water runs and hits my driveway at the east end (bank) of the drive then doglegs west, with half the water turning south after about 30 ft and the rest of the water running down my drive 40-50’ before running south. I have an easement 30 ft wide X about 200 ft to the county road. The creek has another dogleg to the east just after my easement. That property owners has told me that I can have the area dredged to help with the flow.
Thanks for commenting.

The photo you posted looks like a very awkward situation to deal with.

Could you please explain what you think has caused the creek to move? Is there more runoff upstream from development or something? Did the existing creek bed fill up with material? Are there obstructions to flow downstream that didn't use to be there?

Would you happen to have an old photo of the area before this got this way?

 

[ArlyA]

Creeks, rivers and even big lake shore lines move all the time. This is why I recommend building bridges or roadways over culverts high and with big capacity.

 

[WranglerX]

Two thoughts here.....

1. Build a true bridge high and wide...

2. If you use culverts cement them in solid with good upstream and downstream headwalls so if they are blocked, water can flow over as typical of a "ford"...

Below are pictures of if you have unseasonal rains as 4-5 inches in 7-10 hours and the 36 inch culvert under county road is partially blocked and you only get about a 25-30% flow through it..... Granted flow was excessive this year and a lot of water came really fast from upstream where there is fire burn scar from recent wildfire and there was nothing to hold back dirt and debris.. Yes water was over 4 feet deep and there is about 18 inches of "new" dirt over what was a nice green "meadow" 24 hours earlier...
Red arrows shows where blocked culver is located....

Below is a creek that in worst of times in past years flowed 3-4 feet wide and maybe 12-18 inches deep.... Was up over 10 feet wide and 4 feet deep in some area of where it crossed my property...

 

[WranglerX]

looking at his pictures it appears that he is crossing at an angle. If so that is part of the problem.

A little creative backhoe or mini excavator work can change flow directions, don't think that is real issue, but type of crossing (bridge/culverts) is still problem to be decided on...

 

[Eagle1]

Personal opinion from someone living in flash flood county in the Ozarks. Do what ever it takes to have your drive cross the creek at 90 degrees. Then deal with the crossing, I have one of those low flow creeks that become 150 foot wide and over 3 foot deep in the flood area and a 15+ foot channel.in extreme cases, over 12" of rain in less than 6 hours. Design something that can withstand over topping or let the overflow go around your crossing.
In my case I have 4 four foot culverts and drive is humped over those. When they can't cope the water goes around the crossing. One the exit of the property I have a 20+ foot wide 4 foot deep outflow and a 120' wide emergency route. I have seen 3' foot of water in the emergency route with 7 foot going the normal route.
Around here there a lot of concrete low water crossings and even those get flipped at times.
I use concrete railroad ties (free) as low water crossing in places as do many around here. SO far have not see any of them wash away. We put them so they follow the current not the wide side across the current.

Then deal with the flood damage after the fact, just a fact of life here. Sometimes it takes weeks to get county roads working again.

 

[4570Man]

That creek would promptly wash out double 3ft culverts. You’re just throwing money away at that point. A 3ft culvert has 7 sf of area so 14 sf with 2 of them. Even if the water is only 1ft deep it’s 100sf of water at 100 ft fire. 100 foot of water can’t come close to fitting through 14 sf. A semi trailer or rail car bridge is the most affordable way to cross that.

 

[4570Man]

Remember that at saturation the 3 foot culvert allows more water through than (2) 24" culverts. [1017 sq ft vs (2x 452 sq ft.)]

Based on the pictures you've posted though, they both will blow out at saturation.

You’re correct that the 36” culvert has more than double the area of a 24” but your math is incorrect.

 

[dodge man]

I get roughly 7 sf for a 36” culvert and 6.3 sf for two 24” culverts.

My degree is in civil engineering and it’s fairly easy to design something like this. You calculate the drainage area, the precipitation is calculated in inches per hour, usually from standard charts for the state and then you calculate the flow. You also have to know something about the runoff area, like how much is paved, how much in crops, trees, grass etc. Then sizing the culverts is based on nomographs which these days is probably in a computer setup.

Normally a culvert like this is based on a 5 year, 10 year, or 25 year flood. It makes a big difference in size. I’d probably design if for a 5 year flood and then anything above that goes over the top. If it’s concrete I don’t see a problem with that.

I am not a civil engineer either, I am a land surveyor, so I’d find someone local to help figure it. Soil conservation might be free.

 

[Jstpssng]

I’d be very willing to have the work done for that amount of money. I figured 40 tons of rock and maybe 20 yds3 of concrete. The culvert pipe is $2600, for the two pipe. Do you do this kind of work or know someone in my area that does?

No, I don't do that type of work; but we often have water crossings done. You would do well to have somebody come look at it who knows more about your area. If I recall, you are in Wisconsin. This Contact Details might be a good place to start. At the very least he can tell you who to talk to. You also may be eligible for some type of NRCS funding.

You are in a tough spot, given the limitations. However, I would do some type of bridge as I described before.

 

[Jstpssng]

You’re correct that the 36” culvert has more than double the area of a 24” but your math is incorrect.

I get roughly 7 sf for a 36” culvert and 6.3 sf for two 24” culverts.

My degree is in civil engineering and it’s fairly easy to design something like this. You calculate the drainage area, the precipitation is calculated in inches per hour, usually from standard charts for the state and then you calculate the flow. You also have to know something about the runoff area, like how much is paved, how much in crops, trees, grass etc. Then sizing the culverts is based on nomographs which these days is probably in a computer setup.

Normally a culvert like this is based on a 5 year, 10 year, or 25 year flood. It makes a big difference in size. I’d probably design if for a 5 year flood and then anything above that goes over the top. If it’s concrete I don’t see a problem with that.

I am not a civil engineer either, I am a land surveyor, so I’d find someone local to help figure it. Soil conservation might be free.

Good points. That should have been cubic inches, not cubic feet. Doi!!!
We generally size culverts from measuring cross sections upstream and down stream. The culverts should be big enough to handle top of bank rain events. That can vary state by state.

 

[ning]

Good points. That should have been cubic inches, not cubic feet. Doi!!!
We generally size culverts from measuring cross sections upstream and down stream. The culverts should be big enough to handle top of bank rain events. That can vary state by state.

(square not cubic, obviously)

I’ve followed this dry creek bed about 5 miles. Above me there are 3 places where this creek & smaller creeks feeding into it cross the road. Each crossing has a low water concrete slab. The largest crossing is maybe 30 ft. The reason it’s so wide at my drive is because of it jogging west, east and then west again. I think just cleaning up the creek bed and taking the turns out will help tremendously.
What is FWIW mean? Thanks for commenting.

Before consulting with authorities, find out if it's a protected watershed or some other designation that might limit your ability to perform construction.
If so, keep that in mind when doing what you need to do.

 

[dodge man]

Your correct, if I convert to square inches your number is good.

 

[Streetcar]

Designing bridge that goes over a creek has been changing its bed exceeds my pay grade. Good luck!

A properly designed bridge locks the stream in place

 

[ning]

A properly designed bridge locks the stream in place

Unless the stream changes course above the bridge and just laughs at the old course with its bridge

 

[Streetcar]

I’d be very willing to have the work done for that amount of money. I figured 40 tons of rock and maybe 20 yds3 of concrete. The culvert pipe is $2600, for the two pipe. Do you do this kind of work or know someone in my area that does?

At my previous job, I did storm water modeling and calculations.
You need your water crossing to be mostly concrete, the gravel will wash away in high flow.
You will need well over 100 cy of concrete from quick glance at photos

 

[Streetcar]

Unless the stream changes course above the bridge and just laughs at the old course with its bridge

That usually is only a problem in coastal flat areas

 

[dodge man]

It’s true a stream will tend to meander more in flat areas but things will change everywhere. Often some event causes it, a land slide or a big tree can change things.

 

[garymartin63965]

I’ll see what I can find…

 

[airbiscuit]

Part of the problem is, over the last 20 years, the creek has moved a bit. It used to just flow across the drive after heavy rains. Now water runs and hits my driveway at the east end (bank) of the drive then doglegs west, with half the water turning south after about 30 ft and the rest of the water running down my drive 40-50’ before running south. I have an easement 30 ft wide X about 200 ft to the county road. The creek has another dogleg to the east just after my easement. That property owners has told me that I can have the area dredged to help with the flow.
Thanks for commenting.

I’ve followed this dry creek bed about 5 miles. Above me there are 3 places where this creek & smaller creeks feeding into it cross the road. Each crossing has a low water concrete slab. The largest crossing is maybe 30 ft. The reason it’s so wide at my drive is because of it jogging west, east and then west again. I think just cleaning up the creek bed and taking the turns out will help tremendously.
What is FWIW mean? Thanks for commenting.

It sounds like this whole area isn't very much higher than the creek. Again a sketch or map of the drive and creek(s) would be helpful.

 

[garymartin63965]

The photo you posted looks like a very awkward situation to deal with.

Could you please explain what you think has caused the creek to move? Is there more runoff upstream from development or something? Did the existing creek bed fill up with material? Are there obstructions to flow downstream that didn't use to be there?

Would you happen to have an old photo of the area before this got this way?

The creek only runs past my driveway after heavy rains. A lot of times it stops flowing on the surface and goes in

I agree with 4570man about the pipes being undersized.
The MAIN point I want to make is your crossing has NO protection on the bottom side for when the water goes over the top. Water will dig out the botttom side, and the erosian will work it's way upstream.

i don’t expect the 2 36” pipes to handle all the water during the really heavy rain. At that point the bridge will be more of a spillway. I hope is to be able to cross the creek sooner and not have wait more than a day or so. I think you’re right about needing concrete/a footing on the down stream side. I don’t need any washouts or water getting under the crossing.