Ben, are you asking if logs can be used as water harvesting berms? That's how I use them. Even though I have a lot of rocks, there are some places where it's easier to use logs or piles of brush, so I do. Eventually they will rot away, but before then they will have helped stabilize slopes so plants can grow.
Idle dreamer
joke time: What is brown and sticky? ... ... ... A stick! Use it to beat this tiny ad!