Soil Erosion by Water

Abstract

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 beyond the tolerance limit. A tolerance range of 2–11 t ha−1 year−1 depending on soil types is accepted in the USA. There are places and situations where erosion rates are much higher than this limit, even as high as 100 t ha−1 year−1. 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 integrated for an efficient soil erosion control.