Page 82 - Soil Degradation, Conservation and Remediation

Chapter 3
Soil Erosion by Water

Erosion is a natural process of detachment of soil particles and their transport
and deposition at distant places by natural agents such as water, wind, glacier, and
gravity. Detachment of soil particles from aggregates primarily by raindrops and

flowing water and their transport by runoff water are involved in soil erosion by
water. Natural erosion is considered as normal erosion and is usually of little
concern from soil quality point of view because its rate is low and soil loss can be
naturally compensated by soil formation. Human actions such as deforestation,
overgrazing, over tilling, and shifting cultivation have accelerated soil erosion
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beyond the tolerance limit. A tolerance range of 2–11 t ha year depending on soil
types is accepted in the USA. There are places and situations where erosion rates are
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much higher than this limit, even as high as 100 t ha year . The principal types of
soil erosion by water are splash erosion, sheet erosion, interrill erosion, rill erosion,
gully erosion, landslides, and stream erosion. Soil erosion has on-site and off-site
effects. The on- site effects include loss of soil, loss of organic matter and nutrients,
damage to growing crops, exposure of plant roots, and decline in soil fertility and
productivity. The off-site effects are burrowing of crops and installations, siltation
of reservoirs, eutrophication of ponds and lakes, pollution of water, etc. Several
agronomic and engineering practices are employed for the control of water erosion.
These are no- tillage, minimum tillage, mulching, strip cropping, contour cropping,
contour strip cropping, and terracing, but several methods are needed to be inte-
grated for an efficient soil erosion control.

3.1 Geological and Accelerated Erosion

Erosion is the detachment of materials from earth surfaces such as rock and soil
from its original assemblage and position and transport to other places by various
agents, including water, wind, glacier, and gravity. Erosion has both on-site and off-
site effects. Earth materials from the mountains of the Himalayas are being torn out

K.T. Osman, Soil Degradation, Conservation and Remediation, 69
DOI 10.1007/978-94-007-7590-9_3, © Springer Science+Business Media Dordrecht 2014