I just bought 14 acres that's mostly rock but has lots of trees. It's a real tinderbox and there was a big deadly fire in the area a few years ago, so my plan is to thin the trees, partially cut through the branches so the trees lay flat, and lay them in lines on contour, anchoring them in spots with big boulders, and weaving the limbs and underbrush together to increase the density. As I complete the tree piles, I plan to rearrange rocks above to funnel some portion of the runoff into these tree walls, which will eventually turn them into hugelculture style beds.
I've done this in a few small spots as experiments and it only takes a few seasons for them to start filling with rocks and dirt and solidifying into actual swales.
It seems like a lot of work, but the trees need thinned out anyway, and don't need to get processed, or hauled very far, and gravity and rain end up doing most of the work hauling heavy stuff in.
On some particularly steep sections, I've thought about anchoring steel cable at the top of the hill and tying the tree piles into it to keep them from washing down the mountain.
