What is Soil Erosion?
Soil erosion by water occurs when individual soil particles become detached and are then transported and deposited. There are 4 main types of erosion by water:
What are the consequences?
Effects of soil erosion are numerous and can occur on- or off-site from the erosion source.
On-site erosion effects include:
| Off-site erosion effects include:
|
What causes it?
Climate
Climate, particularly, rainfall is the primary driver of soil erosion by water. Rainfall is not only the main agent of detachment of soil particles but also the principal source of water running over the soil surface. The erosivity of the rainfall depends on the intensity and duration of a rainfall event as well as of the mass, diameter and velocity of the raindrops. In cold climate regions, however, freezing-thawing cycles can also play a key role in detachment, while snowmelt can be an important additional source of runoff.
There are two main runoff generating processes:
- infiltration excess overland flow - occurs when rainfall intensity exceeds a soil’s infiltration capacity
- saturation overland flow - occurs when a soil’s water storage capacity has been exceeded.
Soil Properties
Soil properties strongly determine a soil’s infiltration and storage capacities and, thus how it responds to rainfall events. Low infiltration or storage capacities can result in excess overland flows causing soil erosion.
Human activities
Arguably, human activities have become the most important driver of soil erosion by water in modern times and places, especially those witnessing strong increases in population and/or rapid advances in slope- and landscape engineering capabilities, including inappropriate ploughing and soil compaction from heavy machinery.
How can it be measured or assessed?
The table below lists key and/or proxy indicators for soil threats identified by the RECARE project.
| Soil threat | Soil Threat indicators |
|---|---|
| Soil erosion by water | Area affected by soil erosion (km2) and/or extent of area affected by soil erosion (%) |
| Magnitude of soil erosion/deposition or sediment delivery (tons) |
The table below lists key indicators, the purpose of the indicator and methods used for measuring soil erosion by water.
| Indicators | Purpose | Methods |
|---|---|---|
| Soil loss by water erosion | Measure/estimate transport of soil particles by rainsplash/splash erosion | Splash boards as well as funnels and cups of various designs <15-20 cm 1, 5 |
| Portable rainfall simulators 5 | ||
| Measure/estimate transport of soil particles by sheet flow/inter-rill erosion | Micro-plots, field rainfall simulators 1, 5 | |
| Measure/estimate transport of soil particles by sheet and concentrated overland flow | Large-enough plots (“Wischmeier” plot) typically >10 m long 1, 5 | |
| Produce erosion risk map | Modelling expert opinion or extrapolation of erosion plot data 2 3 4 7 | |
| Magnitude of sediment delivery | Measure transport of soil particles beyond the hillslope | Sediment yield = streamflow’s suspended sediment concentration x discharge 8 |
| Area affected bysoil erosion and/or deposition | Determine status of cumulative soil erosion | Cross-sectional area of the rills/gullies across a slope |
| Mapping erosion features using aerial photogrammetry, 3-D laser scanning & satellite imagery 1 |
How can it be prevented or remediated?
Different measures are available to control soil erosion by water. The most appropriate measure to use is dependent on the local situation, but the key principle is maximisation of rainfall infiltration in soils in situ.
| Agronomic measures | Vegetative measures | Structural measures | Management measures |
|---|---|---|---|
| Contour cropping | Vegetative cover | Terracing | Integrated management of micro-catchment |
| Mulching & residue management | Vegetative strips | Dams & silt fencing | Policy, law and regulation |
| Tillage management | Grassed waterways | Stone bunds | |
| Strip contour cropping | Temporary and permanent seedings | Impoundment | |
| Gravel access path |
Case Study Experiments
How does it interact with other soil threats?
Soil erosion by water can have an important impact on other soil threats especially on a decline in soil organic matter (SOM), flooding risk, and a decline in soil biodiversity.
How does it affect soil functions?
- Biomass production - direct effect, for example by removal of seeds, or indirectly by reducing rooting space for plant support and reducing available soil water and soil nutrient pool
- Gene pool - if the removal of an organism by runoff is significant in terms of its existing population
- Physical heritage - from changes in the aspect of the landscape, particularly from gully erosion raw materials – providing for example use of sands accumulated in river beds for civil construction purposes.
- Cultural heritage - the removal and re-deposition of archaeological artefacts as well as through the burial of archaeological artefacts under eroded sediments
 Presentation Slides |  Fact Sheet (PT) |
References
1 Morgan, R.P.C., 2005. Soil erosion and conservation. Blackwell Publishing Ltd., Bodmin. ISBN 1-405-1781-8, 304 pp
2 Cerdan, O., Govers, G., Le Bissonnais, Y., et al., 2010. Rates and spatial variations of soil erosion in Europe: A study based on erosion plot data. Geomorphology 122, 167-177.
3 Kirkby, M.J., Jones, R.J.A., Irvine, B. et al. 2004. Pan-European Soil Erosion Risk Assessment: The PESERA Map, Version 1 October 2003.
4 Panagos, P., Borrelli, P., Poesen, J., Ballabio, C., Lugato, E., Meusburger, K., Montanarella, L., Alewell, .C. 2015. The new assessment of soil loss by water erosion in Europe. Environmental Science & Policy. 54: 438-447
5 Jones, A., Panagos, P., Barcelo, S. et al. 2012: The state of soil in Europe. EUR 25186 EN – Joint Research Centre. JRC Reference Reports, Publication Office of the European Union, Luxembourg, ISSN 1018-5593, 71 pp.
6 Huber, S., Prokop, G., Arrouays, D., et al., 2008. Environmental assessment of soil for monitoring. Volume I indicators & criteria. EUR 23490 EN/1, Office for the Official Publications of the European Communities, Luxembourg, DOI 10.2788/93515, 339pp
7 Stolte, J., Tesfai, M., Øygarden, L., Kværnø, S., Keizer, J., Verheijen, F., Panagos, P., Bilbao, C and Hessel, R., (2015). Soil threats in Europe. JRC Technical Report.
8 OECD, 2013. Soil. Water and wind erosion. In: OECD Compendium of Agri-environmental Indicators. OECD Publishing. http://dx.doi.org/10.1787/9789264186217-9-en..
9 Vanmaercke, M., Maetens, W., Poesen, J., et al., (2012). A comparison of measured catchment sediment yields with measured and predicted hillslope erosion rates in Europe. J. Soils Sediments 12(4), 586–602.
10 Chappell, A. Baldock, J. Sandermand, J. (2016) The global significance of omitting soil erosion from soil organic carbon cycling schemes. Nature Climate Change 6, 187–191
Useful links
- FAO UN - Global map: Predicted soil loss in ton/ha/year
- FAO UN - Global map: Vulnerability to wind erosion
- FAO UN - Keeping the land alive: Soil erosion - its causes and cures (1983)
- WWF - Soil erosion and degradation
- Joint Research Centre European Soil Portal
- EU report - Research for AGRI Committee – Preserving agricultural soils in the EU
- North Dakota State University - Soil erosion: Processes (YouTube)
- The soil erosion site - Information gateway for soil erosion
- Soil erosion & hydroseeding - Trade journal
- European Communities - Water erosion and compaction (2009)
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Ontario Ministry of Agriculture, Food and Rural Affairs Fact Sheet
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A RECARE video link to a presentation explaining soil erosion can be viewed here.
