Location: National Soil Erosion ResearchTitle: Erosion
Submitted to: Encyclopedia of Soil Science
Publication Type: Book / Chapter
Publication Acceptance Date: 7/9/2015
Publication Date: 9/15/2016
Citation: Flanagan, D.C. 2016. Erosion. In: Lal, R., Editor. Encyclopedia of Soil Science, 3rd Edition. Boca Raton, FL. CRC Press. pp. 742-745. https://doi.org/10.4324/9781315161860.
Technical Abstract: Erosion is the detachment of soil particles and transportation to another location. Wind erosion occurs when wind speed exceeds a critical threshold level, and loose soil particles or soil particles removed by abrasion then move in one of three ways: creep, saltation, and suspension. Erosion by water is typically by raindrops or by concentrated water flows on a soil surface. Raindrops vary in size from about 0.5 mm in diameter to 4 mm or larger and can reach terminal velocities of 10 m/s. The momentum of large drops at high speeds can result in soil compaction and ejection of water and sediment sprays (splash) at the point of impact.Water on a soil surface that does not infiltrate will flow downhill and typically coalesce into small channels or “rills.” When enough water is flowing in a rill, flow shear forces will act to detach soil from the channel bottom and sides. Rills are the major pathway for both water and sediment detached by raindrops and flow shear stress to move downslope and ultimately off of a piece of land. In larger channels, similar detachment due to flow shear forces can also occur that can produce different types of gullies, as well as additional soil loss from other processes including bank sidewall sluffing and headcutting. A number of practices are recommended to reduce or prevent erosion, including use of mulch or plant residues to protect the soil surface, terraces to reduce slope length and steepness, and grade control structures to safely transport water flow to lower elevations.