[Cob] Building retaining walls

[Wilderness Voice]

Just wondering if anyone has a good ideas for building retaining walls.
Back in the day we used to use used railroad ties with deadman to build retaining walls, but for ecological reasons that is not acceptable to me even if I could get RR ties which I can't.
I have thought about trying to get tires and use rebar and packed dirt, but wonder if they will hold  a hill?
Anyway, I figure you smart people may have some resource.
I have purchased my little 2 acre piece of forrested heaven and am now seeking to clear a little of it to build a cob house, but finding it difficult to find good info on drainage and retaining walls
thanks

       
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