Hope you have solid base and lots of drainage behind those walls.
Our city contracted a series of similar retaining walls some 10 years ago and nearly all now need to be redone as frost heaving is doing serious damage.
Mfg specs call for gravel base below frost line with serious drainage and geotextile plus gravel backfill.
Looks great however.
We did the same with the gravel. Back filled with gravel all the way to the bottom and back about 4 feet and added drain pipe. Only about a foot of dirt on the top of the gravel. Did ours in 2005.I have 40 tons of gravel on the outside of the walls and my soil is pure beach sand beyond that, so heaving isn't an issue.