The gravel on the edge of my own steep driveway used to erode with each moderate rainstorm. I replaced the small 3/4-inch pieces of gravel with 3-inch stones. All of a sudden my problem disappeared.

Strong blacktop driveways are typically built using crushed angular gravel as a base. This gravel needs to be a minimum of 6 inches thick for light vehicle traffic such as cars and pickup trucks.