Grazing chickens on a steep hill

We're still working on our chicken pasture infrastructure, with the ultimate goal of having enough space so that our flocks don't overgraze the pastures during the summer lull.  Our laying flock has four moderately sized pastures, which usually keeps them happy, but our broiler flock only had one big and one small pasture until last week.  That's when my long-suffering husband fenced in another large pasture up the side of the hill in the powerline cut.

The good news about this pasture is that the shade from forest trees at the top gives our birds plenty of low-temperature foraging space in the summer.  The bad news is that the pasture is going to erode away if I don't get creative.

The powerline pasture had grown up in small trees since the last time the electric company came through and whacked the brush back, so the ground is relatively barren of small plants.  Our chickens think that's a great opportunity to scratch through leaves, but I'm afraid all the topsoil is going to end up on the downhill end in short order.  There are already big bare spots in the area closest to the coop where our lazy chickens hang out the most.

I'm open to suggestions on how to make this pasture sustainable.  The traditional option would be to finish clearing out the trees this fall and then to seed the ground with grasses and clovers.  From my experience in other pastures, I'm pretty sure that would require me to keep chicken feet off the sward for about a year as the pasture plants become established.

In the long run, I'd like the pasture to be more interesting than just grass, so I'm considering terracing the steepest parts.  If I added logs at intervals to produce retaining walls, I have a feeling our flock might create the terraces for me by scratching dirt downhill.  Then I could plant useful shrubs within those terraces, a bit like the Mexican idea of cepas.

Do you have experience grazing chickens on steep hills?  I'm all ears!