DIY Bridge

[airbiscuit]

Don’t have access to the computer right now but I used my phone and took some screenshots.
On this photo the yellow arrow shows points to the driveway. The blue arrows show the creek bed. You can see how the creek widens between the green and red arrows. That wide area in my drive is about 100. I think the dogleg is the biggest problem.

I took some liberties.

 

[nyone]

3ft deep and 70ft wide and your trying to put it through two 36in culverts? That dosnt sound right.

Theres a driveway down the road here that has a 6ft culvert it's in a mostly dry ravine and not a steep section.. I believe they put that culvert in 3x before they gave up.

 

[ArlyA]

Here is a few pics from the flood we had here when 6" of rain fell overnight. Its became to be known as "the Father Day flood of 2018". Something like 350 culverts and bridges got washed out. Lots and lots of culverts and bridges were made larger after that.

 

[dodge man]

It almost looks like the creek is doglegging at your driveway. I’ve seen people just build a concrete crossing, no pipes. Sometimes those hold up for a fairly long time.

 

[2manyrocks]

Water likes to take the path of least resistance. It's hitting that dogleg and doesn't like having to make the bend. So it is fanning out and the gravel is being deposited into the creek bed I'm guessing because the water velocity is slowing down at the dogleg.

Could you post a picture of the creekbed facing upstream and a picture facing downstream? Is the creekbed pretty much the same depth and about as full of gravel?

 

[keg99]

Lots of good info here. As mentioned, you need to know you drainage area and your storm volume and then you can decide on a culvert. Here is the chart I have used in the past. However, with the increased frequency of +100 year storms (or should I say 500 year storms back to back?!), you will be well served going to the next size up.

For this chart, the number of acres is your drainage area. Then pick the type of ground that is most common upstream. Find you square footage and convert that into a pipe diameter. [Keep in mind, this chart is for a 2.5" per hour rainfall event. If you think you might see more rain per hour, then you will need a different chart.]

Note my scribbles below. For a 113 acre drainage basin, I calculated the need for a 16 sq ft cross-sectional pipe. So I selected 60". Or you can do two pipes, as long as they equal 16 sq ft.

 

[dodge man]

Keg99 charts above are probably a simplification of what is a more complicated calculation. 2.5“ inches per hour of rainfall seems pretty low for where I live in Illinois but might not be a bad number to use. I think the OP is in Texas? We also often used a C factor lower than 0.4 around here but once again for Texas 0.4 might be a good number. The C number is a runoff coefficient. For example a concrete parking lot 95% of the water will runoff. For a partly sandy soiled farm field maybe only 15% of the rainfall runs off. For designing something like a driveway culvert its probably a great place to start with the above chart.

 

[WranglerX]

Aerial view sort of shows you didn't pay attention to creek channel over the years and allowed it to dogleg down the road instead of yearly maintenance to keep it where you want it... Water is like electricity it takes path of least resistance.... A little creative tractor work and some layers of coarse gravel and a shallow area where you want the water to flow is simple one day project...

Bridge or culverts or ford is long term solution ....

 

[Rockbadchild]

Aerial view sort of shows you didn't pay attention to creek channel over the years and allowed it to dogleg down the road instead of yearly maintenance to keep it where you want it... Water is like electricity it takes path of least resistance.... A little creative tractor work and some layers of coarse gravel and a shallow area where you want the water to flow is simple one day project...

Bridge or culverts or ford is long term solution ....

you such of a great help ... I don't know if you notice but the road goes across the creek and always did as long as it's been a road there is no way around it...

 

[rScotty]

That dogleg sure does look familiar!

A dogleg just like that caused a problem locally. Ultimately that dogleg was caused some 40 years before when a farmer decided to use his bulldozer to move the creek on his land. The creek was tiny, seasonal, and nobody cared.

The original farmer had moved on, lots had been created, the land became part of a town subdivision with new owners who bought and built. None of the new owners knew that the stream had been moved 30 or 40 years before.

Then along came some years with more than normal precipitation causing annual flooding problems on the new roads and driveways.

This was all a sort of local mystery until someone thought to dig out some old maps - then the cause of the problem became obvious.

The solution was to move the downstream section of the creek back to where it was originally, deepen the channel, and rock line the banks. Then the various upstream low water crossings and small bridges became effective.

rScotty