Building a bridge in a flood plain?

[paintman161]

I want to build a bridge over a creek, it is about 40'-0" from edge to edge. Most of the year the creek is below the surrounding banks. But once maybe twice a year (depends on how much rain or snow melt) it does flood the surrounding areas but goes down within 2 days. I would like to make it 5' wide to drive an ATV across.

Is there any way to do this without having the bridge float away when the water floods the area?

thanks!

 

[SPYDERLK]

Any way you could create a small bridge on wheels that you could remove when threatened?

 

[Depmandog]

How high above the creek banks does the water rise during the flood events? Is the approach to the bridge location flat or could you build a XXX foot long bridge that would span the area that floods?

We need more info before we can give any decent answers. Keep this in mind, flowing water is mighty powerful. A 40' bridge is a healthy DIY project to start with. Adding on another major technical component (floating bridge, removable bridge, super long bridge, etc) will turn this into a major project. Not trying to dissuade you, just injecting a dose of reality.

Can we get some pictures or a site drawing to look at? From the bridge deck to the deepest part of the creek - how deep?

 

[paintman161]

no way to put it on wheels, the area is flat except where it goes up to the old railroad bed but that would be over 1000' bridge. The locations per google is: 43.300903,-77.844253 thats the approximate location i want the bridge as that would be on the edge of the property line.

 

[rd_macgregor]

A number of years ago, I built a 6' wide X 40' long footbridge across a (small) stream and flood plain. I bought steel square tubing and pounded it into the ground on each side of the stream channel and at intervals across the flood plain, then installed cross members and beams (all PT) with PT deck boards. It clears the stream by nearly 4' at normal flow and has 12 to 18" of clearance over the flood plain. It is mostly for foot traffic, but it has had ATV traffic as well. Now, I wish I had built it sturdy enough for my tractor to cross.

 

[ideburger]

Be aware of any permit requirements. I build bridges for a living and the US Army Corps of Engineers don't care much for unpermitted work in their jurisdiction. You should be ok with them if you stay above the ordinary high water mark.

When flooded, if the water velocity high? Bridges that end up under water are difficult to keep in place.

 

[bcp]

Build a bridge that can float, a strong, pivoting anchor on one end, and just a rest for the other end. Let a large flood swing it.

Bruce

 

[paintman161]

this is kind of what i was thinking, not sure the barrels would allow it to float or not though, may be too heavy?

 

[GLyford]

Just a thought here...

What's the bed of the stream like? Deep silt, or gravel? If it's relatively level gravel, how about building a concrete pad about 8' square, and 4' below your regular crossing height, with a veritical wall up to the road way height. On the other bank, put in a ramp that ends in another concrete pad, except now maybe just 6" to a foot below roadway height. You have basically just made a loading dock and a rest for the kingpin plate for a highway trailer.

Then get a used 40' flatbed trailer that will no longer pass road inspection. It already has the wheels and everything. Hook a chain to it and pull it across and out the ramp when foods threaten. Even if the floods take it away or wrap it around a tree, dig the debris off your concrete pads and buy another old flatbed trailer and you're back in business.

Even if the stream has a muddy bottom, you might be able to put in enough large rocks to make a stable enough bottom to wheel your trailer across when you need to.

 

[GLyford]

Another option: how about starting with a mobile home chassis? Leave at least one set of axles on it.