Soil erosion is a natural process of landform and landscape evolution involving the detachment, transport and deposition of mineragenic and organic sediments. This process is naturally occurring but can be exacerbated by human activity, such as farming. Land-cover change and intensification of farming are widely linked to accelerated soil erosion.
Especially in semi-arid landscapes the impacts of climate change strengthen the vulnerability of landscapes to soil erosion and the existing cycles of natural resource degradation will be exacerbated.
Anti-erosion measures are all actions to reduce the vulnerability of landscapes to soil-erosion processes. The key to erosion control is preventing the detachment of soil particles and reducing the volume of runoff. These measures include a broad range of technical and biological soil-treating actions and the rehabilitation of degraded areas as well as changes in land-use planning and agricultural management. These measures often involve the creation of a physical barrier. Due to different environmental conditions anti-erosion measures vary accordingly to the specific ecological conditions.
Rainwater Harvesting Systems, e.g. Water Spreading Weirs, often function as anti-erosion measures as their principle is to capture potentially damaging rainfall and runoff. They combine those benefits with the accumulation, storage and provision of rainwater for agricultural use. In some cases further stabilization measures are required to stop erosion completely.
Examples of anti-erosion-measures include (see GIZ 2012 for further information):
- Strip farming
- Permeable rock dams
- Permeable rock dikes
- Sand dune stabilization
- Hand-dug trenches
- Contour stone bunds
- Semi-circular bunds
- Nardi/Vallerani trenches
- Grass strips
- Water spreading weirs
- Small-scale dams
Soil conservation through vegetation and reforestation
As the amount of bare soil one a site is a good indicator of the soil’s vulnerability to erosion and degradation, good soil coverage is an essential element in soil conservation programs.
A vegetation cover reduces the erosive power of impacting raindrops and thus splash erosion, furthermore it reduces the volume of water reaching the soil surface.
In the long term, vegetation influences the fluxes of water and sediments by increasing the soil aggregate stability and cohesion and by improving water infiltration. Therefore anti-erosion measures which include the planting of specific species and reforestation-programs play an important role in the context of water and soil protection.
The influence of the vegetation is mainly attributed to the aboveground biomass. Differences between species appear due to their individual plant morphologies and plant components. Canopy cover played a major role in runoff and soil loss reduction in this study from Bochet et al. (2006). In the early growth stages of cereals and grasses, roots could be relatively more important with respect to soil erosion reduction than in later plant stages when the aboveground biomass overrules the effects of the plant roots. It is obvious that the influencing role of plant roots on water erosion will largely depend on root type and their spatial distribution.
References and further reading
GIZ (2012): Good Practices in Soil and Water Conservation - a contribution to adaptation and farmer's resilience towards climate change in the Sahel
GIZ, KfW (2012): Water-spreading weirs for the development of degraded dry river valleys
GIZ (1988): Erosionsbekämpfung in Parana, Brasilien
Lüdemann, F.(1995): Ressourcensicherung im Sahel
Rima Mekdaschi Studer, Hanspeter Lininger (2013): Water Harvesting: Guidelines to Good Practice
E. Bochet, J. Poesen, J.L. Rubio (2006): Runoff and soil loss under individual plants of a semi-arid Mediterranean shrubland: influence of plant morphology and rainfall intensity. In: Earth Surf. Process. Landforms31, 536–549