soil erosion detachment, transportation and deposition of soil material types of erosion...

Download Soil Erosion Detachment, Transportation and deposition of soil material Types of Erosion 1.Geological erosion 2.Accelerated erosion

Post on 03-Jan-2016

232 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Soil ErosionDetachment, Transportation and deposition of soil material

    Types of Erosion

    Geological erosion

    Accelerated erosion

  • Geological Erosion

    It is also called natural erosion or normal erosion

    The erosion which is undisturbed by human activity

    Types

    Water erosion

    Wind erosion

  • Water Erosion

    Removal of soil mass by running water from snow and ice melt,and transporting it usually downhill

    Forms of water Erosion

    Sheet erosion

    Rill erosion

    Gully erosion

  • Sheet Erosion

    Uniform removal of soil in thin layers resulting from sheet or over land flow of water occuring in thin layers

    It causes the color of land to chang gradually from dark to light,usually this change in color is accompnied by progressive decline in yield

  • Rill ErosionIt is the advanced satge of sheet erosion

    When sheet erosion continues for sometime and the land is neglected rills start deepning and widening so tht runoff concetrates through them.These rills then go on developing with the passage of time and prove fore runners of gullies.this stage of erosion is called rill erosion

  • Gully ErosionIt is the advanced stage of rill erosion

    Stages of gully development

    Formation of rills by sheet washingDeepning and cutting of rills Start of under cutting of rocksEating of backwards and uphill by gullies

  • Process of Water Erosion

    Detachment

    Transportation

    Deposition

  • Damages of Water ErosionWashing of soil

    Loss of fertile soil

    Increase runoff

    Top soil removal

    Decrease infiltration capacity

    Stones will be left

    Effect on wild life

  • Wind ErosionErosion which is caused by wind is called wind erosion

    In Pakistan, 40 % area is affected by wind erosion e.g Thal, Cholistan and D. G. Khan

    It occurs in

    Dry lands

    In arid and semi arid areas

  • Process of Wind ErosionInitiation of soil movementThe turbulance of wind, together with its velocity is responsible for starting the movement of soil in wind erosion processMinimum velocity of wind required to initiate soil movement is called threshhold velocity of wind.It greatly depends upon the size of soil grainThere is a range of threshold velocities for any soil depending upon previous history of field

  • 2. Transportation of Soil

    Transportability of soil depends upon the size of soil particles

    Fine dust once lifted, may be carried to great distances from the eroding areas

  • 3. Deposition of Atmospheric Load

    Material carried either in suspension or saltation is deposited primarly when the wind velocity decrease

    The process of picking up and depositing material is continuous is due to variable character of wind and to the nature and process of saltation

  • Modes of Sand TransportDepending upon wind force, sand particles and mass

    a.Saltation

    Progression of particles in succesive jumps

    Size of particles 0.1 to 0.5 in diameter most susceptible

  • b. Surface CreepThe soil particles with diameter 0.5-1 mm are too heavy to be moved by saltation but are pushed along the surface by the impact of particles to surface creep.

  • c. SuspensionVery fine dust particles less than 0.05mm in diameter are carried in true suspension,The amount of sand transported in suspension is only a very small portion of total.

  • DamagesLoss of fertilityAccumulation of materialsUprooting of seedlingsWeed seed transportationCovering of roads and railway tracksAir pollutionDamage of agri. machinery

  • 2.Accelerated ErosionThe deterioration of soil as a result of mans activities is called accelerated erosion.

    It is also called abnormal erosion

    It is associated with changes in natural vegetation and soil conditions.

  • Kinds of intensities of soil erosion

    Kind of erosionIntensity of hazardAffected area (mha)Water erosion (11.18mha)Sheet &rill erosionSheet &rill erosionRill &gully erosionGully erosion

    SlightModerateSevereVery severe

    0.403.583.753.45

  • Kinds of intensities of soil erosion

    Kind of erosionIntensity of hazardAffected area (mha)Wind erosion (4.73mha)Light wind erosionModerate wind erosionSevere wind erosion

    SlightModerateSevere

    2.560.501.67