The reality is this: there is no such thing as "preventing" erosion. Erosion can never be prevented nor stopped; rather, erosion can never be brought to zero or not at all. But it can be reduced and minimized so that there is less loss to soil than what is considered undesirable. How to slow down or minimize erosion in such an area all depends on the slope and aspect (which direction the slope is facing) of this area. It also depends on your location. Often planting shrubs or allowing certain deep-rooted perennials (non-invasive, preferably, plus native ones, if possible) to grow in that area and not allowing any sort of disturbance to disrupt it--from animals to recreational vehicles--may be one solution to reduce erosion in such an area. Regular monitoring of this area and consistent restrictions to access this area will slowly turn it into a thriving plant community or an area that has lower erosion potential than what you have now.