Also called ephemeral gully erosion, this process occurs when water flows in narrow channels during or immediately after heavy rains or melting snow. A gully is sufficiently deep that it would not be routinely destroyed by tillage operations whereas rill erosion is smoothed by ordinary farm tillage. The narrow channels, or gullies, may be of considerable depth , ranging from 1 to 2 feet to as much as 75 to 100 feet. Gully erosion is not accounted for in the universal soil loss equation. In a few states gully erosion is substantial, but in most areas more soil is lost through sheet erosion and rill erosion.