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Faunsdale, AL | Short of building a road that will stay high and dry during a major flood, you are going to have trouble.
If you use small culverts to keep a road surface dry in low flow situations, you’ll soon get erosion on the downstream side of the road during overflows and eventually it’ll undercut your road even if you concrete it in. Only way to make this work is to extend the concrete well past the roadway and down to the stream bed. Huge rip-rap might stay put on the downstream side, but the normal 12” stuff not so much. We usually started out with the culvert(s) laying in stream bed and use rip-rap over them and build up roadway and then pour concrete over all of it to hold it all together.
Long term this invariably results in the water on the downstream side swirling around and undercutting the slab. Not enough of a flume down off the roadway and nothing to dissipate the energy of the water.
A good solution if you can deal with shallow water at times is to actually excavate the roadway across the stream and pour concrete level with stream bed. This will not blow out or get undercut since there’s no turbulence as the water goes over it. You may have a little silt on it or have to drive through low water but it’ll stay there. Obviously when water gets up a little you can’t cross where you would be able to keep going if you had culverts.
I’ve seen one that was done this way with cross ties instead of concrete. As long as it’s not raised above the surface of the stream bed it’ll work. Best to have a little silt on top of it for insurance. Any elevation and the turbulence will work on it starting on the downstream side.
Edited by ccjersey 2/20/2025 15:08
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Crossing a creek.
