I didn’t forget to follow up on this! Unfortunately the coordinator that was responsible for planning the plant layout is gone visiting home for the next month, and the other coordinator didn’t know as much about it (beyond that the coordinator that sets this up knows a lot about it!). Another volunteer remembered what I was talking about and was able to tell me that they were utilizing both a combination of rocks to slow down the water flow (giving it more time to absorb into the soil) that one of the plants being used is called mule fat (Baccharis salicifolia), and that it’s generally beneficial to plant within what’s known as a “plant guild” of plants that all tend to grow together and serve different functions in the ecosystem.
Sorry I couldn’t get you more info! If you want to wait longer I can follow up with more details once the coordinator that actually planned the layout and everything gets back, but I wanted to go ahead and let you know what I did find out in case that gives you a good jumping off point.