Lay perforated drainage tubing at base Water-soaked soil is the worst enemy of retaining walls because it exerts enormous pressure behind the wall. Adding good drainage behind block or stone walls is crucial for long-lasting, bulge-free walls. Start by laying perforated plastic drainage tubing along the base of the wall slightly above ground level so it can drain to daylight. Slope the tubing about 1/4 in. per foot.
I don't know when I will ever have enough rocks to make a wall, but it would certainly be doable to do a spiral in he space between pavers as in one of the pictures. I could use rocks from the landscaping around the house.