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DEGRADATION AND CONTROL PROCESSES |
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Degradation process:
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Gully erosion. Water erosion by concentrated surface runoff.
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Description:
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As rill erosion advances, channels get deeper. The terrain becomes dissected, which prevents access and makes cultivation with farm machinery impossible. This stage is known as gully erosion. Water separates and transports particles from the bottom of channels and sides and landslides may occur. This generates important quantities of loose matter which, when transported, may have negative effects further downstream. This process is due to a hydrological disturbance in the area.
Importance: great in arid and semi-arid areas.
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Soil functions affected:
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Biomass production (reduction of crop yields and the need for greater inputs), environmental function (filtration), hydrological function, reduction of carbon sequestration, function for preventing offsite effects (sediment supply during floods, silting up of dams).
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Diagnostic criteria:
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The terrain is dissected by deep channels which cannot be eliminated by applying normal cultivation techniques.
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Click on the image
Concentrated runoff erosion:
gullies. Anoia.
(J. Porta)
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Click on the image
Concentrated runoff erosion:
Gullies in abandoned fields.
Les Garrigues (J. Porta)
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Click on the image
Increases in the rate of gully erosion of poorly consolidated materials may be very rapid: the original fields have disappeared. Urgell (M. A. Aran)
Click on the image
Progressive silting up
of the Terradets reservoir
due to the accumulation of
eroded matter from the
drainage basin
(J. Porta)
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Prevention and control:
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Prevent and control possible changes in the hydrological system associated with the construction of roads, drains, the paving of streets, and fires, etc. Once established, gully erosion can be difficult to control. Hydrological correction measures should be implemented
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