A Hierarchical Method for Soil Erosion Assessment and Spatial Risk Modelling

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Okoth, P.F.
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Wageningen University
Soil erosion can be defined as the detachment and translocation of soil particles by moving water or wind from their original locations to new depositional areas. Soil erosion is commonly recognised by incisions or depositional features it forms on the surface of the land (Laflen and Roose, 1997). The word erosion is derived from the Latin word erosio, meaning 'to gnaw away'. Distinguishable erosion features have been described by NiH et al. (1996) as 'finger prints' for evidence of erosion. Some examples of water erosion features include surface sheet-wash, rills, gullies and landslides (Nill et aI., 1996, Laflen and Roose 1997). Apart from rainfall and wind, soil erosion may also be caused by intensification of land use, tillage, construction structures, overgrazing, unregulated land use and deforestation. The destruction of land by water erosion has been recognised by many people over time. Many recognise it as a real problem and a threat to sustained agricultural production and soil productivity sustenance (examples are Bennett, 1939; Kilewe and Ulsaker, 1984; Lal, 1988; Dregne, 1982; NiH et aI., 1996; Gachene, 1995b; and Laflen and Roose, 1997). The currently known agents of erosion are water, gravity, ice and wind (Lal, 1990).