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Principles of Soil and Water Conservation




  • In general, depth of soil varies from place to place to great extent. But the top 30 cm soil depth is very useful for both human being and wild life. This layer is continuously exposed to the action of atmospheric activities. Two main active forces, water and wind always tend to detach the top soil layer and to transport them from one placed to another.

    Soil Erosion:

    It is three phase phenomenon consisting the detachment of individual soil particles from the soil mass and their transport by erosive agents such as running water and wind when energy to transport the particles is not available then third phase called deposition take place.

    Definition:

    “It is defined as detachment, transportation and deposition soil particles from one place to another place under influence of wind, water or gravity forces”.

    Important Points:

    1. When eroding agents have sufficient capacity to transport more quantity of materials than the materials supplied through detachment then erosion is turned as “detachment limited “.

    2. When materials supplied are greater than materials transported then erosion is turned as transport limited.

    Two energy forms are involved in erosion process.

    a. Potential 
    b. Kinetic
     
    PE = m.g.h

    PE =potential energy in joules      
    M   = Mass of body in kg 
    G = acceleration due to gravity 
    H = elevation Difference.

    KE = ½ mv2

        KE = Kinetic energy 
        m = mass of body in kg
        V = Velocity of running water or falling raindrops

    3. A large amount of energy is lost against frictional resistance of soils surface.

    4. Only 3 to 4 % energy is remained with running water to detached soil particles.

    5. Critical water velocity responsible for soil erosion is a function of particle size.

    6. Critical velocity value increases with increase in grain diameter. (Greater than 0.5mm)

    7. Fine particles are harder to get e rode by water flow due to cohesiveness of play clay minerals.

    8. Soil particles of 0.01mm in diameter requires of flow velocity of 60m/s and to detached the soil particles but not deposited until the flow velocity reduces below 0.1m/s. d

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