A gully doesn't appear overnight. It starts as a small furrow caused by concentrated runoff, and if left unchecked, it becomes a channel that can deepen by several meters and advance tens of meters a year up the slope.
It is one of the most severe forms of soil degradation in the Mediterranean landscape—and also one of the conditions that responds best to a well-planned intervention combining engineering work and revegetation with native species.
In this article, we explain what a gully is, why it advances, and how a revegetation process is designed to stabilize it in the long term.
What is a gully, and why does it spread?
A gully forms when runoff water repeatedly concentrates at a single point, without vegetation cover or obstacles to dissipate its energy. The water erodes the substrate, deepening the channel, and with each rainfall event, the process feeds back on itself:
- The head of the gully is moving back up the slope (upward erosion)
- The riverbed deepens and widens
- The destabilized side slopes collapse and contribute more sediment
- Once soil is lost, it cannot be recovered—without intervention, this degradation is virtually irreversible
The most vulnerable areas are those that combine steep slopes, poorly structured soils (loam, clay, and soils degraded by continuous tillage), and a lack of vegetation cover—a common combination in olive groves and woody crops on slopes in the southern part of the Iberian Peninsula.
Why Technical Work Alone Is Not Enough
Retaining dikes, gabions, or stepped structures slow the energy of the water and are, in many cases, essential for halting the immediate advance of an active gully. But a structure without vegetation has a limited lifespan: the substrate remains exposed, without the structure or biological activity needed to sustain it in the long term.
Revegetation is what turns an emergency response into a permanent solution.
The Role of Vegetation in Controlling Gully Erosion
Plant cover works on several fronts at once:
- Roots physically anchor the substrate and reduce the risk of slope failure
- The vegetation cushion the direct impact of rain on bare soil
- Plant biomass provides organic matter, improving soil structure and infiltration capacity
- The cover slows down surface runoff, reducing its erosive potential
Stages of Revegetation of a Gully
Phase 1 — Stabilization of the edges and headwall
The immediate goal is to halt the encroachment and cover the exposed soil as soon as possible. Priority is given to species that establish quickly and have a dense root system:
- Lygeum spartium — albardín, an extraordinarily hardy steppe grass that plays a key role in degraded soils and on steep slopes
- Stipa tenacissima — esparto grass, with a deep root system, is a key factor in erosion control in the southeastern part of the Iberian Peninsula
- Brachypodium distachyon — a fast-growing annual, useful as a pioneer cover in the first growing season
Phase 2 — Colonization of the river channel and side slopes
Once the edges have been stabilized, species are introduced to reinforce the interior of the gully and improve the soil:
- Anthyllis cytisoides — Albaida, a pioneer shrub that is highly resistant to poor and eroded soils
- Medicago spp. — clover, a legume that establishes itself quickly and fixes nitrogen in depleted soil
- Atriplex halimus — osagra, tolerant of degraded soils with some salinity, commonly found in gullies on loamy substrates
Phase 3 — Consolidation with structural shrubbery
In the final phase, shrubbery is added to provide the site with lasting stability and functional biodiversity:
- Retama sphaerocarpa — broom, a nitrogen-fixing plant and a structural component of the Mediterranean scrub
- Salvia rosmarinus — rosemary, a natural colonizer of poor, dry soils
- Cistus spp. — rockroses, which are very hardy and naturalize well in degraded areas
Gullies in olive groves: a specific challenge
The expansion of olive groves on slopes over the past few decades has made gully control a priority for much of southern Spain. This is precisely the challenge addressed by the project INNOLIVAR, focused on innovative solutions for erosion and gully control in Andalusian olive groves—an area in which we contribute our technical expertise on native species for revegetation.
The logic is the same as with any gully: it's not enough to stop the water; you have to restore the vegetation cover to the soil so that it can sustain itself.
Why Require Certified Native Seeds in These Projects
In restoration projects funded with public money or subject to an Environmental Impact Statement, the traceability of the seeds used is not optional. Seed certification refers to the standards that guarantee that the species used are truly suitable for the receiving ecosystem—without the risk of invasive behavior or failure to establish.
CANTUESO in Gully Control
At CANTUESO, we have been working with Iberian wild flora for over 25 years and maintain our own germplasm bank with more than 850 species, including those most effective in controlling erosion and gullies. We are the only company in Spain with an organic production certificate (CAE) for wild flora.
We provide guidance on the composition of phase-based mixtures, tailored to the slope, soil type, and degree of degradation of each gully.
Do you have an active gully on your property or in your project?
Our technical team helps you design a phased revegetation strategy.
📩 info@cantuesoseeds.com · +34 957 323 580
CANTUESO Natural Seeds — Finca La Jarilla, Villarrubia, Córdoba
The only company in Spain with an organic certification (CAE) for the production of wildflowers