Mid-Atlantic Gardening: New Projects in the Mid-Atlantic almost spring 2013, 1 by coleup

coleup wrote:
To chime in again , it will take a while for liriope musceri (the clumping kind not stricata, the running kind) to form enough of a border edge to prevent erosion so I like Sall's suggestion. As to concerns for maintenance, when the new shoots appear the old fronds will die back and lok 'ratty' But, since this will be for edging a lawn, just set lawn mower at highest setting and trim them before new shoots emerge (like now or last week) Easy peasy. New mulch will cover any stragglers. It takes about 4-5 years before any divide the clumps might even become an issue. And, you can always fill in with more plants as you have time and inclination (oops freudian slope) as you won't have to use climbing gear to do so.

SS Rain gardens can be at the bottom of hills or slopes, or at the top, before runoff erodes and destabilizes the slope/hill.
Happy, I was suggesting a 'rain garden' at the top of your hill to manage the runoff from the back of your property as you described it last year on this thread
http://davesgarden.com/community/forums/t/1261201/
I'm seeing 'rain garden' to the top of hill area on right side of your pic.