Ask Mr. Smarty Plants

What you need is erosion control, not a specific recommendation for plants. We will certainly recommend some grasses native to Berkeley County, West Virginia, but we don't want them to go down the hill with all the rest of your seed and topsoil. You already know, from bitter experience, that just throwing out some seeds won't work. Grasses are wonderful for erosion control because their long fibrous roots will grab hold of the soil and hold it (and the grasses) in place, but first you have to get the seeds to stay there long enough to root.

We don't know how large an area you need to cover.  If it is small you might be able to use grass plugs.  However, if it is a large area, seeds may be a better solution.  Since apparently the slope is steep you might consider using an erosion control blanket.  The erosion-control fabric works by slowing the runoff water and allowing sediments to fall out rather than be washed away. Seeds are sown under the erosion-control material and grow up through the matting when they germinate. You can also insert plants into the soil by cutting through the matting. The roots of the plants that are growing through the erosion-control material anchor the soil to stop the erosion. If you use erosion-control blankets made of biodegrable material, they will eventually disappear leaving the plants to control the problem.  Many nurseries carry this erosion control fabric.  

Now, we will go to our Native Plant Database, select on West Virginia, "grasses" under General Appearance, and "sun" (6 hours or more of sun daily) for Light Requirements, and click on "Combination Search." And right there, we ran into what may be your problem, even more than the erosion. Before we even begin listing plants, we determine what part of the state and what county we are being asked about. When we are searching for a plant, we begin with searching on the state it is listed as being native to. Then, we go to the bottom of the information webpage and click on "Find (plant Latin name) in USDA Plants." This takes you to a page from the USDA, with a map of the U.S. and Canada on which states in which that plant grows are green. Next step, we click on the state in question (West Virginia, in this case) and get a county outline map of where in that state the plant grows. Let us walk you through one grass that we chose as a demonstration. We went to the webpage on Calamagrostis canadensis (bluejoint), and clicked on the "Find (plant Latin name) in USDA Plants." There we clicked on the (green) outline of West Virginia. Behold, all of the three counties (which we assume includes Berkeley County) in the Panhandle are white. The counties just below them are green, and so are many other counties in the state. So, now we are going to give you links to 4 grasses that come close and let you look at the USDA Plant Profile for yourself.

Calamagrostis canadensis (bluejoint) - county map

Carex blanda (eastern woodland sedge)- county map

Schizachyrium scoparium (little bluestem) - county map

Sorghastrum nutans (Indiangrass) - county map

So, you see our problem, and these were the GOOD ones, where at least the counties where those grasses were native were close. The last two had the grass chosen in one of the 3 counties, the other two plus all the others we considered, none at all. We are wondering if perhaps the soil, you mentioned shale and clay, not ideal, could be a problem as well as the erosion. Because there are zillions of grasses, and certainly not all of them are in our Native Plant Database, we are going to suggest you contact the West Virginia University Extension Service for Berkeley County. If you are having this problem, so are a lot of other people in your area.  Perhaps they will have a list or pamphlet of erosion control grasses suitable to your site and your soil. 

From our Native Plant Image Gallery:

Calamagrostis canadensis

Carex blanda

Schizachyrium scoparium

Sorghastrum nutans