Soil erosion can occur anywhere if enough water flows over the surface, but no place is as obvious as a hillside. The ruts that are carved into the sides of hills and the blank surface that develops from washing out vegetation is noticeable. To prevent this, you must plant your trees, shrubs or grass properly.
Dig down in several spots to see if there is rock below the surface. If the land is rocky, then trees are the better plant to use, because the roots will grow out, around, and through rock to anchor themselves. If the soil is sandy or regular dirt, then grasses and shrubs work well and can put down enough roots to hold the soil fast.
Fill one of the holes with water and wait to see how long it takes to drain. If it takes less than an hour, then the soil drains well, and any vegetation will work fine. If it takes longer, then most of the water will run off the hill. In this case, you need grasses or shrubs that are drought tolerant. When you know the kind of soil you are dealing with, select trees, shrubs, or grasses that grow well in your area.
Lay down a landscape straw mesh over the hill. This will help keep the seedling plants or grass from washing away while their roots are getting established. If you are going to grow grass, cast the seed before putting down the mesh. Cast it out by hand according to the quantities suggested on the package.
Dig holes through the matting for plants. Make the holes deep enough so the tops of the root balls are at the surface. Set the plants in the holes and cover them with the soil you removed. If the grade of the hill will allow it, set a good-sized rock in front of each plant to keep it from washing away. By using the rocks and the mesh, the plants should stay in place until their roots establish.
Water the hillside to soak the new plants and seeds. Normally you would water deeply. However, if the hill doesn't soak well according to the drainage test, you might wash the soil and seeds away. In this case, water lightly a couple of times a day. Repeat watering each day for two weeks until roots start to establish and grass grows. Then reduce watering to twice a week for four to six weeks.