Land gradient described as the vertical rise divided by the horizontal run and expressed in percent. For engineering purposes, slope is expressed as horizontal distance over vertical distance (e.g., a slope of "3 to 1" (3/1) is one with 1 vertical unit for every 3 horizontal units). A slope of "6 to 1" (6/1) is much flatter than a slope of "2 to 1" (2/1).