Gully Erosion Control
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Written by: D. Hilborn - Agricultural Engineering Service, Resources and Planning/OMAFRA; R.P. Stone - Agricultural Engineering Service, Resources and Planning/OMAFRA |
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Introduction
Throughout Ontario, especially in areas with deep sand plains, high stream banks or long sloping valleys, extensive gully erosion problems occur. Large quantities of valuable agricultural soils are lost each year to gully erosion.
Gully erosion is an advanced stage of rill erosion where surface channels have been eroded to the point where they can not be smoothed over by normal tillage operations.
Figure 1. An active gully in a sand plain area.
Often, gullies can be prevented if good land conservation measures are practiced on the farm. Good tillage and cropping practices increase the absorptive capacity of the soil resulting in less run-off and also protect the land surface from erosion. Surface and tile water should be conveyed from lands through proper waterways so as not to create potential gully problems. Buffer strips should be located at potential gully start points such as open ditches or deep depressions.
The saying "A Stitch in Time Saves Nine" is also valid for gully erosion control. Often a potential large gully problem can be solved if discovered and controlled early in its formation.
Figure 2. A gully located on clay soil. A grassed waterway shown in Figure 3 was used to solve this problem.
Causes of Gully Formation
Increase in flow of surface (or subsurface) water
An increase in water flow can be due to several reasons such as improvement of drainage channels upstream, removal of water holding areas upstream (such as a swamp or bush), enlargement of the watershed or a change in tillage and cropping program in the watershed.
Decrease of soils resistance to erosion
There are several ways that a soils resistance to erosion can be reduced such as elimination of a vegetative cover, breakdown of soil structure due to poor tillage and cropping practices, constant saturation by a trickling tile or compaction by tractor wheels.
Sloughing and mining at the bottom of the gully
Sloughing occurs at the base of a gully due to a strong spring, a constant saturation of the area by a pond or the eroding power of a waterfall from a higher to lower elevation, e.g. cultivated field to eroded channel. As the undermining process continues, the gully head moves upstream and enlarges in width and depth.
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