What is the depth threshold that classifies a valley as a gully?

A valley is classified as a gully when it reaches a specific depth threshold that indicates its formation through erosion and water flow. When the depth is one foot or more, the characteristics of the valley shift from a simpler drainage way to a more defined gully shape. This depth allows for significant water movement which contributes to further erosion and the deepening of the channel over time.

The threshold is significant because it represents the point at which the erosion process intensifies, leading to a wider and deeper channel as compared to shallower valleys. Depths less than one foot typically do not exhibit the same level of erosion and do not possess the pronounced features associated with gullies. Thus, defining gullies begins at this one-foot mark, making it a critical benchmark in understanding the classification of landforms created by erosive processes.