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
If you open the box, you will find Heisenberg strangling Shrodenger's cat. And waving this tiny ad:
October Rocket Mass Heater days! Wheaton Labs October 11-17