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

3. Geological Erosion It is also called natural erosion or normal erosion
The erosion which is undisturbed by human activity
Types
Water erosion
Wind erosion

4. 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

5. 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

6. Rill Erosion It 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

7. Gully Erosion It is the advanced stage of rill erosion
Stages of gully development
Formation of rills by sheet washing
Deepning and cutting of rills
Start of under cutting of rocks
Eating of backwards and uphill by gullies

8. Process of Water Erosion
Detachment
Transportation
Deposition

9. Damages of Water Erosion
Washing of soil
Loss of fertile soil
Increase runoff
Top soil removal
Decrease infiltration capacity
Stones will be left
Effect on wild life

10. Erosion 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

11. Process of Wind Erosion
Initiation of soil movement
The turbulance of wind, together with its velocity is responsible for starting the movement of soil in wind erosion process
Minimum velocity of wind required to initiate soil movement is called threshhold velocity of wind.It greatly depends upon the size of soil grain
There is a range of threshold velocities for any soil depending upon previous history of field

12. 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

13. 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

14. Modes of Sand Transport
Depending upon wind force, sand particle’s and mass
a.Saltation
Progression of particles in succesive jumps
Size of particles 0.1 to 0.5 in diameter most susceptible

15. b. Surface Creep
The soil particles with diameter mm are too heavy to be moved by saltation but are pushed along the surface by the impact of particles to surface creep.

16. c. Suspension
Very 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.

17. Damages Loss of fertility Accumulation of materials
Uprooting of seedlings
Weed seed transportation
Covering of roads and railway tracks
Air pollution
Damage of agri. machinery

18. 2.Accelerated Erosion
The deterioration of soil as a result of man’s activities is called accelerated erosion.
It is also called abnormal erosion
It is associated with changes in natural vegetation and soil conditions.

19. Kinds of intensities of soil erosion
Kind of erosion
Intensity of hazard
Affected area (mha)
Water erosion (11.18mha)
Sheet &rill erosion
Rill &gully erosion
Gully erosion
Slight
Moderate
Severe
Very severe
0.40
3.58
3.75
3.45

20. Kinds of intensities of soil erosion
Kind of erosion
Intensity of hazard
Affected area (mha)
Wind erosion (4.73mha)
Light wind erosion
Moderate wind erosion
Severe wind erosion
Slight
Moderate
Severe
2.56
0.50
1.67

21. Thanks