Need to solve flooding for old bridge

[Stonewilled]

I have a bridge that I've repositioned over a creek in a flood plane. Pretty sandy soil on both sides. A few trees upstream and downstream on both sides. More on the side I'm standing on and fewer/further on the side she's on. That is a 3-4 inch diameter water oak growing at the corner next to the side she is on. (South bank)... Edit: water will rise up to 2-3 feet over the top of this bridge.

 

[RjCorazza]

I don't see how you can solve that with water 2-3' over that bridge. Maybe build a large arched bridge?

 

[Stonewilled]

I was thinking ballasts and rings so it can slide up rebar hammered down into soil with a sledge as far as I can?

 

[Stonewilled]

What do you think would happen if I anchored it with rebar to a Mass of concrete and kept it held down? Would flood waters just destroy it?

 

[Stonewilled]

Or chain it to large trees upstream on both ends?

 

[jyoutz]

What do you think would happen if I anchored it with rebar to a Mass of concrete and kept it held down? Would flood waters just destroy it?

Probably

 

[Stonewilled]

It has been in that bottom for ten years. With privet growing through it holding it in place. But that's when it was sitting squarely on level ground. I know that just the fact that it is over the creek means it will be subjected to far greater forces. But will it be that significantly different? Can anyone link to some good reading that covers these sorts of topics?

 

[rumwrks]

I dunno.. 2-3' of water can be a hell of a lot of force. A lot depends on how fast it's moving though.. 6" of fast water does a lot more damage than 2' of slow...

Whats the soil under it down lower? That is how deep does the sand go?

I think my best shot would be to dig three holes 4-5' or more depending on the soil.. deep and 12-18" across on each end right under each of the three beams and fill those holes plumb full of concrete with concrete post anchors between the concrete piers and the beams. There will be some .. erosion effects from water eddying around all of that that I don't know how to model.

 

[ultrarunner]

When my friend bought a similar property I said nice raft you got.

He looked puzzled and said the seller had to rebuild it as part of the sale.

I said what happened to the old one and he said washed away.

Sure enough the second winter his 2 year old bridge washed away.

 

[bcp]

Using a long cable, anchor only one upstream corner very well. When the creek floods, the bridge can swing out to the side of the main current. Drag it back into position afterwards.

If you fight it, you will lose, sooner or later. Let it go with the flow, then reposition it.

Bruce