That illustration looks exactly like what you need. Indeed, if the berm was a hugelkulture mound, you would be keeping each level's rainfall on its level, rather than having it all pool at the bottom of the slope.
A 30 degree slope, even with heavy ground cover would send a lot of water to the bottom without some
earthworks along the slope. If done properly,
each elevation would be improved...especially the bottom, where, as you said, the soil would probably be too wet for most roots.
Each year, during the dry season, you could store your trimmings in the swales, and have a ready supply of
compost at each tier.