- Potential sediment delivery and runoff from abandoned fields in Southeast Spain: control or natural development?
- Soil Erosion and Dryland Farming conference
- Book/source title
- Abstracts Second International Symposium on Soil Erosion and Dryland Farming
- Pages (from-to)
- Institute of Soil and Water Conservation
- Document type
- Conference contribution
- Faculty of Science (FNWI)
- Institute for Biodiversity and Ecosystem Dynamics (IBED)
RECONDES is a three-year EU-funded project, which focus is to mitigate desertification processes by means of innovative techniques using vegetation in specific landscape configurations prone to severe degradation processes. One of the research themes is the impact of desertification on abandoned land and potential mitigation practices. Land abandonment is nowadays widely spread in Spain and is expected to increase. Previous research showed that gully erosion was higher on abandoned fields compared to similar cultivated fields. Especially fields that are terraced or have earth dams are prone to gully erosion after abandonment, due to restoration of the natural drainage pattern and piping in case of dispersive substrate. Main cause of increased erosion is the absence of ploughing and a low vegetation recovery, which results in sealing crusts and bare spots with low infiltration rates leading to more runoff and finally gully erosion.
The objective of this paper was to analyse the consequences of land abandonment on erosion and to provide effective eco-engineering techniques for mitigation of gully erosion. The study was carried out in the Carcavo basin, a semi-arid catchment in Southeast Spain. At catchment scale all abandoned fields were surveyed and characteristics of each field, gullies and terrace failures were described. One abandoned valley was surveyed at a more detailed scale to create a precise DTM and detailed aerial photographs were taken to study vegetation patterns.
The results reveal that gullies on abandoned fields are often located on critical positions at the transition of the hillslope to the channel. This means that when a gully becomes active the connectivity of runoff and sediment in the landscape increases considerably, with the negative off-site effects as a consequence. A reconstruction of eroded sediment from the DTM confirms the importance of gully erosion in terms of sediment losses. Overflow at the lowest point and piping seem to be the main causes of terrace failure. Especially the influence of piping increases in dispersive soils after abandonment, because the topsoil is not ploughed anymore and runoff can enter directly the subsoil through cracks and macro-pores that have been developed after abandonment. Two potential soil and water conservation practices are: (1) Maintenance of terraces and earth dams, as a result more water is retained, which increases the vegetation cover and that strengthens the terrace or earth dam. Only in dispersive soils the risk of piping remains. (2) Revegetation on critical spots in the landscape with indigenous species that grow fast and have dense rooting systems to bind the soil.
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