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SOIL EROSIONSoil erosion is a naturally occurring process that affects all landforms. In agriculture, soil erosion refers to the wearing away of a field's topsoil by the natural physical forces of water and wind or through forces associated with farming activities such as tillage.

Physical Process

Rainfall and surface runoff. Soil and water being splashed by the impact of a single raindrop. Rainfall, and the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.

Factors Affecting1. The amount and intensity of rainfall and wind velocity. 2. Topography with special reference to slope of land. 3. Physical and chemical properties of soil. 4. Ground cover its nature and extent.

The amount and intensity of rainfall and wind velocity

Rainfall is the most forceful factor causing erosion through splash and excessive run off.Rain drop erosion is splash, which results from the impact of water drops, directly on soil. Although the impact of rain drops on water in shallow streams may not splash soil, it does cause turbulence, providing a greater sediment carrying capacity. Large drop may increase the sediment carrying capacity of run off as much as 12 times.

Topography will special reference to slope of lands

Slope accelerates erosion as it increases the velocity of flowing water. Small differences in slope make big difference in damage. According to the laws of hydraulics, a four - time increase in slope doubles the velocity of flowing water. This doubled velocity can increase the erosive power four times and the carrying capacity by 32 times.

Ground cover, its nature and extent

The presence of vegetation ground cover retards erosion. Forests and grasses are more effective in providing cover than cultivated crops. Vegetation intercepts the erosive beating action of falling raindrops retards the amount and velocity of surface fun off, permits more water flow into the soil and creates more storage capacity in the soil. It is the lack of vegetation that creates erosion permitting condition.

FACTORS AFFECTING SOIL EROSION RATES

The amount and intensity of precipitation is the main climatic factor governing soil erosion by water. The relationship is particularly strong if heavy rainfall occurs at times when, or in locations where, the soil's surface is not well protected by vegetation. This might be during periods when agricultural activities leave the soil bare, or in semi-arid regions where vegetation is naturally sparse.

CLIMATE

VEGETATIVE COVER Vegetation acts as an interface between the atmosphere and the soil. It increases the permeability of the soil to rainwater, thus decreasing runoff. It shelters the soil from winds, which results in decreased wind erosion, as well as advantageous changes in microclimate. The roots of the plants bind the soil together, and interweave with other roots, forming a more solid mass that is less susceptible to both water and wind erosion. The removal of vegetation increases the rate of surface erosion.

TOPOGRAPHY The topography of the land determines the velocity at which surface runoff will flow, which in turn determines the erosivity of the runoff. Longer, steeper slopes (especially those without adequate vegetative cover) are more susceptible to very high rates of erosion during heavy rains than shorter, less steep slopes. Steeper terrain is also more prone to mudslides, landslides, and other forms of gravitational erosion processes

TECTONICS Tectonic processes control rates and distributions of erosion at the Earth's surface. If tectonic action causes part of the Earth's surface (e.g., a mountain range) to be raised or lowered relative to surrounding areas, this must necessarily change the gradient of the land surface. Because erosion rates are almost always sensitive to local slope (see above), this will change the rates of erosion in the uplifted area. Active tectonics also brings fresh, unweathered rock towards the surface, where it is exposed to the action of erosion.

PREVENTION By applying some relatively simple steps, you can control and prevent soil erosion! The four most common soil erosion prevention methods are vegetation, geotextiles, mulch, and retaining walls. 1) Vegetation: The simplest and most natural

way to prevent erosion is through planting vegetation. Plants establish root systems, which stabilizes soil and prevents soil erosion.

2)Geotextiles: Using geotextiles is an effectivemethod because it also stabilizes soil. When used in conjunction with growing vegetation, it is even more effective. There are three main types of geotextiles: woven, nonwoven, and coir.3)Mulch/Fertilizer: Applying a layer of mulch to the soil top allows the soil to slowly soak up water, as it protects against rain impact, and restores pH levels helping with erosion prevention.4)Retaining Walls: Retaining walls can be built around the area of erosion to prevent water run off. Runoff water leads to further erosion, and if used with other methods, retaining walls can be a very effective way to prevent soil erosion.

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