DIY Bridge

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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

 

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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.