It does look like something you or Trish spoke of in a podcast: someone piled something together, took a picture, and posted it online as "here's an idea".
As distinct from trying it out for a season or two, to see how it worked, then improve it, THEN publish it as a GOOD idea.
The strange, criss-crossed irrigation mainlines suggest a lack of thought and planning at best. (I couldn't see any 1/4" or 1/8" takeoff lines at all.) Maybe they have several very fine low-flow sprayers or misters plugged right into the looped mainline, intended to water it so gradually that runoff and mudslides would be minimized. Until they got a heavy rain, as Jonna said.
It would be almost as pretty, but more functional, if they had used the same number of stones to make it wider and lower.
I forget, Dave, does your spiral just have a shallower slope, or is the soil level "stepped" or terraced as it goes around the spiral?
