You ask a distinguished question, but I would guess that more details are needed. My first thought is:
What is the slop or drop absent from the bed?
Is it an inground bed or on the surface?
Is there a swale? How deep?
What is your soil type?
There is probably a series of questions on rain plunge averages and surge?
Dwarf or full sized trees also enter into the question?
I am practicing more of the give the area a year or more to incorporate the Hugle beds before they get planted out. This will allow the new balance to be set before the plants start to use it.
As far as trees recede I am keeping the Hugle bed out of the canopy. But my Hugle beds are on what is close to flat but can be swampy in the wet season. Research the trees you are planting and building Guilds is the best advice I am getting.
Source: thesurvivalpodcast.com