I would like to put a hugel or 2 on the hillside,
depending on how these are constructed, you might have problems. A large hugul, or one running cross slope (especially on contours), can catch and hold way too much
water, and the result is that can cause a landslide. The more your
wood is below grade, and your mound short, and the less continuous your mound is across the slope, the less issues you will have with this problem, from my understanding. Here's a great article/video about it:
jack spirko on hugul swales
While it is not recommended to plant trees
on hugul beds, it is great to do so beside the hugul, particularly down slope of it.
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