Erosion?

I’ve sectioned off a part of my yard with rocks to plant some azaleas in the fall. My property line is separated by deteriorated railroad ties. On the other side of the ties is my neighbor’s property, which slopes off to their driveway. Is there anything I can do on my side of the property to further prevent erosion? I’ve placed a row of repurposed bricks alongside the old railroad ties, and then layered some (natural) mulch over top. I’m working on cultivating some composted soil, and will build up the garden patch with it once I plant the bushes. But as I add more soil to the area, I keep noticing holes reappear. And I’m beginning to wonder if there’s something more that I’m gonna need to do to stop the erosion, since the yard basically drops off when it reaches the property line. I was considering adding another row of large rocks on top of the bricks. Or purchasing larger blocks. New railroad ties are a bit cumbersome. I’m trying to do what’s in my control, on my side of the property line. Suggestions welcomed!