@Trying, with your sleeper backdrop plan, would it be visible from behind?
It seems that any digging is out due to the cables that you found later, but maybe a "No Dig" sleeper feature could be the go. How about laying a sleeper on its side & fastening it to a base plank (forming a T shape), with a bracket plate:
Fixing plate
Flip it over, fix another bracket plate on the other side, but before you prop it up, hammer a long tent peg into the ground about a metre to the side, & tie an end of some cord to it at ground level. Then hammer in another tent peg into the ground, the width of your intended finished feature width, plus a metre on the other side. Now prop your first sleeper T piece into position, run the cord over the top of the now erect sleeper & tie it off to the other tent peg on the other side.
Repeat until all vertical sleepers are in place.
We aren't done yet, we need to stabilse the sleepers so they don't fall sideways, without the ugly cord.
My first suggestion would be to drill small pilot holes into the back of each sleeper, the same height from the ground, & drive a screw into each, but not flush, leave them slightly proud.
Here's the fun bit river babe, scrounge some high breaking point fishing line, tie it off to one of the tent pegs, then tie knot in succession to each of the small screws that you put in, finishing it off with tying it off to the other tent peg.
This is all for naught if it presents a tripping hazard, so please get back to me on it.
