Background: I live in a neighborhood I learned used to be full of a lot of water until they installed some a big drainage detention area, etc, etc. Well, My back yard slopes down slightly from my the house, then after about 30 feet, the backyard slopes up steeply for about another 30 feet (give or take). At the bottom of the hill (going across the middle of my backyard), from looking at the neighborhood plat, is a 10' private drainage easement. This drainage easement raps all the way around the back of everybody's property to where the big drainage detention area is. We have had some pretty hard rain in the past. The neighborhood, lucklily, has never flooded. However, it looks like the ground, previously sodded, is too wet to stay grassy in my backyard. The grass on the sides of my house is great!
Anyway, as you can see from the pictures, I have put some straw down because I am having some erosion problems. Last year, my neighbor thought she was doing me a favor by spraying herbicide on my hill. Anyway, I put down grass seed and straw, but I fear this will not work. I am thinking about planting some Thuja Green Giants about 10' from the top of the hill to act as a privacy screen and erosion control (I will keep them trimmed to look like hedges). However, I'm not sure if Green Giants will work on my hill. Also, planting the Green Giants will act as a barrier to keep the kids from finding shortcuts through my backyard. (I live just between three schools!)
I need some advice on what I should plant to achieve these goals. I chose Green Giants because I heard they were great for privacy, required little maintenance, had great resistance to many things, and they were CHEAP. My soil, from the looks of it, holds water pretty darn well. I think it is clay-like. Anyway, with the hill, it might provide decent drainage? When it is hot, the ground is rocky and very dry. The hill gets good sun, but during the evening, half of the hill is shaded due to nearby trees. The area in TN that I live in has a hardiness zone of 6 (I believe).
Help. (Pictures Below)