Stabilizing river bank with water activated foam

[dpa]

Hi all,
A client has a home on the banks of a river in Washington State. During flood conditions the bank undergoes scouring. The bottom of the scoured area is 3 feet above the current water lever and goes up another 2 feet with a horizontal dimension of 18 to 20 inches. The supports for the deck are five feet from the edge of the bank which is a sheer drop of 14 feet to the current water level. We would like to stabilize the soil with a water activated foam which is potable water approved.

The soil is mostly rounded rocks from 6 inches to 10 inches with sand and a little gravel in between. The area is almost all rock with very little sand or gravel. Imagine a slice of fruit cake with very little flour binding it together. Flood waters scour the sand near the surface of the bank and then loose rocks tumble down to the edge of what is the current water level.

What we are not sure of is whether sand consolidated with foam will withstand the scouring forces. The amount of sand exposed to scouring is just small areas between the rocks. The bank is essentially a rock pile.

Does anyone have experience with the use of foam in an embankment exposed to rushing water?

About ten years ago we used a similar approach on a rip rap wall where the ground above was being undermined by wave action from a lake but the forces there were much smaller.

Thanks for any help
dpa

 

[cvg]

sounds like a very expensive science project. Might be better to construct a gabion wall. You have all the material you need already.

 

[chicopee]

If you can do without the sand, use rip rap to line the bank.

 

[beej67]

Gabion walls quite often collapse into the creek if they're on the exterior bend, which it sounds like this may be. If there's room to expand the floodplain (e.g. create a floodplain at all) on the opposite side, then that might help reduce the velocity in the creek, so some Rosgen approaches might help the problem.

If I was married to hard armoring the bank as my only solution, I would hand place riprap before I did gabions, and I'd leave a big pile of riprap on my land to replace any that falls in during floods.

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