Got the old bridge re decked

[kenny thomas]

As I have said before, I don't really understand the bridges. Particular in such narrow and shallow channels.

Couple 36" culverts and some riprap and call it good.

I am no expert on the subject but my FIL is. He's installed culvert pipes for many years and he said there is a drastic difference in 1 pipe vs 2 or big culvert vs bridge. I experienced this at my house. Had an 18" culvert pipe in that was constantly being overflowed by the creek. So I put 2 18" culverts in. Got better but didn't solve problem. My FIL said to put in 1 36" pipe. Didn't make sense to me. But it worked. I think it has to do with with the disruption on flow when you force it thru 2 pipes vs 1 or a culvert vs bridge. I'm sure somewhere out there are some formulas for this. I know he measures the ditch size to calculate culvert size.

A single 36" will handle almost double the volume of water that 2-18" will plus won't stop up nearly as easily with sticks and whatever else is in the stream.
The total acreage of the drainage has a lot to do with the flow during a flood also.
There are charts that show area, slope, and ground cover to determine culvert size.
In almost every case a bridge is better.

 

[Nesikep]

As I have said before, I don't really understand the bridges. Particular in such narrow and shallow channels.

Couple 36" culverts and some riprap and call it good.

I am no expert on the subject but my FIL is. He's installed culvert pipes for many years and he said there is a drastic difference in 1 pipe vs 2 or big culvert vs bridge. I experienced this at my house. Had an 18" culvert pipe in that was constantly being overflowed by the creek. So I put 2 18" culverts in. Got better but didn't solve problem. My FIL said to put in 1 36" pipe. Didn't make sense to me. But it worked. I think it has to do with with the disruption on flow when you force it thru 2 pipes vs 1 or a culvert vs bridge. I'm sure somewhere out there are some formulas for this. I know he measures the ditch size to calculate culvert size.

a 36" pipe has 4x the flow of an 18" (surface of a circle quadruples when you double the diameter)

 

[Nesikep]

our creek washed out a 36 one year (1997?).. got some sticks and big rocks in front of it.. they have a 48" in there now, most of the year it has about 3" of water in it

 

[Silver]

The little creek this bridge is on has washed out it's share of 48" culverts. When spring run off hits it's very dramatic for a few days. This bridge is set up so that at high water the creek overflows around the west side of the bridge, just before the water hits the bridge beams. I have dirt and log crossings that I fix up every year, but I can't patch them until the spring run off is done. I need to be able to get machinery and haul cattle across the creek before this time, so whether I like it or not I do need the security of having a reliable bridge to accomplish this.
I will hopefully be hauling more sandstone to another dirt crossing this year. I think if I can get enough rock on it it may withstand a pretty good overflow. Time will tell.

 

[kenny thomas]

As I have said before, I don't really understand the bridges. Particular in such narrow and shallow channels.

Couple 36" culverts and some riprap and call it good.

I am no expert on the subject but my FIL is. He's installed culvert pipes for many years and he said there is a drastic difference in 1 pipe vs 2 or big culvert vs bridge. I experienced this at my house. Had an 18" culvert pipe in that was constantly being overflowed by the creek. So I put 2 18" culverts in. Got better but didn't solve problem. My FIL said to put in 1 36" pipe. Didn't make sense to me. But it worked. I think it has to do with with the disruption on flow when you force it thru 2 pipes vs 1 or a culvert vs bridge. I'm sure somewhere out there are some formulas for this. I know he measures the ditch size to calculate culvert size.

a 36" pipe has 4x the flow of an 18" (surface of a circle quadruples when you double the diameter)

You are correct. My eyes are still cloudy.

 

[BFE]

Instead of buying bridge plank, we used a couple old 210 tanks cut and flattened to "plank" our only field bridge. Noisiest bridge in the country!
We drove oilfield pipe, wired cattle panels to the pipe, and filled the gap with rip rap to make wing walls. Works great, no forms to work with, cheaper than concrete.