waterfall into a hidden water sump? I have a small stream running on my slightly sloping garden, make sure you get a decent pump as a trickle is going to make you need the loo!
We have a serious slope in our back garden, which is terraced with 3 levels. The original terracing of brick had sunk, and become cracked, not very attractive (photo 1). We pushed the upper terrace back, to create more flat space for our vegetable patch, and used railway sleepers (photo 2). These are much more flexible and kind on the eye, if there is any sinkage or movement of the soil. They can also be cut easily to create steps/curves, etc. Photo 3 shows the result, about 2 years after the work.
1 2 3
A more gentle slope in the front garden was altered by creating a raised bed, with sleepers again.
One of our retaining walls in the back garden (more sleepers!) is hidden by a mature Cotoneaster, so you could soften any retaining wall with some planting.
As you can tell, I'd recommend railway sleepers, although you can see from the above photo that we also still have some brick retaining walls.
KeenOnGreen, your garden looks stunning, a lot of hard work has gone into that, well done ?
If you are going to use sleepers length wise and more than two sleepers high, I would suggest you dig a trench and fill it with hardcore laying the sleepers on top of that to stop them sinking. Again, tie them in either to themselves using long screws or pinned into the ground using rebar.
If using bricks you will need to use engineering brick for a retaining wall. They are stronger and better at resisting water.