I am a big fan of sheet mulch gardening. It is a life inoculating, less weedy, less work, major output to minimum input gardening method. Sheet mulching also biomimicks nature in the way that nature creates soil and rich life filled organic matter by adding layer upon layer of decaying leaves, twigs, grasses, etc… Nature does not till. Most often when we create a sheet mulched garden bed it will usually ends up being, also, a raised bed. This in most cases is a great positive benefit in sheet mulching. However when designing gardens in the desert we want to design specifically to the shade and adapt methods that harvest every last drop of rain water. In order to do this we must switch the thinking from raised beds to sunken beds. By digging a small trench and using that trench as the area where we build the sheet mulched garden we will have created a sunken garden bed. At the same time we take the earth material we removed from the trench to make raised pathways. These aids in shade and creates valuable micro climate for desert species.
