Erosion control

I'm going to be doing some work on a friend's property, and one issue that I need to tackle is erosion control.

This is in the mountains of Western North Carolina, so the soil is pretty much just acidic red clay. This portion in particular sits at about a 60 degree angle and was disturbed in a previous building project, leaving it unstable. At the moment I'm considering putting in rhododendron and mountain mint, but I'd like to find a few other native perennials that could help stabilize this part. Any thoughts?

I'm afraid I can't be too much help - I don't have any experience with slopes that steep. but I can say on my 15-20 degree hill the Rhody works awesome. I have about 18 inch more soil on the uphill side of the plant than elsewhere. Sword Ferns if they grow near you can work wonders too

Come to think of it I've seen alders growing on slopes that steep in Austria. I nearly broke myself charging down a couple hundred foot section planted in primarily alder. They where holding the soil awesomely though. Alder - another thing to think about. They grow quick.

Check to see if the people at Soil Conservation (part of the USDA) can help you. The people here in TN came out, looked at our areas of erosion and gave us some great tips. They can even help you get grant money and do the work to fix things. If nothing else they should tell you the best things to plant.