This document discusses different types of soil erosion, including water erosion and wind erosion. It provides definitions and descriptions of various types of water erosion, including raindrop erosion, sheet erosion, rill erosion, gully erosion, and stream bank erosion. It also discusses the processes of wind erosion, including saltation, suspension, and surface creep. The document is a lecture on soil erosion given by Prof. P. R. Kowe of the Department of Agricultural Engineering.

1. Course: ENGG-121
Course teacher,
Prof. P. R. Kowe
Dept. of Agricultural Engineering
Lecture 2.
Accelerated soil erosion - water and wind erosion definitions,
Types of water erosion
Prof. P. R. Kowe, Department of Agril. Engg.

2. Accelerated erosion (Abnormal erosion)
• It is due to man made activities, which have brought about changes in
natural cover and soil conditions.
• The activities includes;
Land preparation for raising crops
Land use patterns for building houses, infrastructures, industries, hill cutting,
deforestation, lack of soil conservation and watershed management
• The removal of surface soil takes place at a much faster rate than the soil
forming processes. Erosion on cultivated land is of accelerated type.
•It is also referred as anthropogenic or man-induced erosion. The
various forces involved in accelerated erosion are as follows:
1) Destabilizing force of water or wind, which removes and transports the soil
particles from one place to another
2) Restoring (retarding) forces which resist the erosion., Normally surface
characteristics offer resistance to the erosion.
.

3. Types of accelerated Erosion
i. Wind Erosion ii. Water erosion
• Raindrop/Splash erosion
• Sheet erosion
• Rill erosion
• Gully erosion
• Stream bank erosion
Prof. P. R. Kowe, Department of Agril. Engg.

4. Wind Erosion
• Definition: Wind erosion is the process
deposition of soil particles by
of detachment, transportation and
the
action of wind.
• A rare or absent vegetative cover, a
loose, dry and smooth soil surface,
large fields and strong winds all
increase the risk of wind erosion.
• Winds with velocities of less than 12-
19 km/hr rarely gives sufficient energy
at the soil surface to dislodge and put
into motion sand-sized particles.
Prof. P. R. Kowe, Department of Agril. Engg.

5. Process of Wind Erosion
Prof. P. R. Kowe, Department of Agril. Engg.
i) Saltation:
• Saltation occurs when the wind lifts larger
particles off the ground for short distances,
leading to sand drifts.
• Fine and medium sand-sized particles are
lifted a short distance into the air, dislodging
more soil as they fall back to the ground.
ii) Suspension:
• Suspension occurs when the wind lifts finer
particles into the air leading to dust storms.
• Very fine soil particles are lifted from the surface by the impact of saltation and carried high into
the air, remaining suspended in air for long distances.
(iii) Surface Creep:
• The movement of large soil particles along the surface of the soil after being loosened by the
impact of saltating particles.

6. Water Erosion
Prof. P. R. Kowe, Department of Agril. Engg.
Definition:
• It is the removal of soil from the exposed surface of land by the impact of raindrops and
running water including runoff from rainfall, melted snow & ice.
• It is affected by land slope, soil type, density of vegetative cover, amount of intensity of
rainfall.
A) Raindrop/Splash Erosion:
• Raindrop erosion or splash erosion results from the soil splash caused by the impact of
falling raindrops.
• Factors affecting raindrop erosion are :
a) Climate - Heavy rainfall and temperature
b) Soil - its inherent resistance to dispersion and its infiltration rate
c) Topography - steepness and length of slope
d) Plant cover – either living or the residue

7. • The falling raindrops break down soil
aggregates and detach soil particles from
the soil mass.
• Raindrop splash gradually removes the fine
materials from the soil.
• The impact of raindrops per unit area is
determined by the number and size of the
drops, and the velocity of the drops. Large
drops may increase the sediment carrying
capacity as much as 12 times.
• A single raindrop may splash wet soil as
much as 60 cm high and 150 cm away from
the spot.
• The factor affecting the direction and
distance of soil splash are wind, land slope,
soil surface conditions.
Prof. P. R. Kowe, Department of Agril. Engg.

8. Prof. P. R. Kowe, Department of Agril. Engg.
B) Sheet Erosion
• Def.- Sheet erosion is the removal of a fairly
uniform layer of soil from the land surface by
the action of rainfall and runoff.
• In sheet erosion soil is removed from the
surface in a thin layer or sheet of relatively
uniform thickness.
• This type of erosion is extremely harmful to
the land.
• It is common on lands having a gentle slope.
• It results in the uniform “skimming off the
cream” of the top soil with every hard rain.
• Areas where loose, shallow top soil overlies
light subsoil are most susceptible to sheet
erosion.

9. Prof. P. R. Kowe, Department of Agril. Engg.
C) Rill Erosion
• Def: It is the removal of soil by running water with
the formation of a series of small shallow branching
channels.
• There is no sharp line of demarcation where sheet
erosion ends and rill erosion begins.
• Rill erosion is more readily apparent than sheet
erosion.
• Rills develop when there is a concentration of
runoff water.
• If rill erosion is neglected it grows into large gullies.
• Rill erosion is more serious in soils having loose
shallow top soil.
• It may be regarded as a intermediate stage
between sheet erosion and gully erosion.
• Rills of small depth can be smoothed out by
ordinary farm tillage.

10. Prof. P. R. Kowe, Department of Agril. Engg.
D) Gully Erosion
• Def: It is the removal of soil by excessive
concentration of running water, resulting in the
formation of channels ranging in size from 30
cm to 10 m or more.
• Gully erosion is an advanced stage of rill
erosion.
• If the rills are not destroyed and detachment
continues, then it becomes wider and deeper
which forms gullies.
• Unattended rills get deepened and widened
every year and begin to attain the form of
gullies.
• During every rain, the rainwater rushes down
these gullies, increasing their width, depth and
length.
• Advanced and Last stage of erosion.

11. Prof. P. R. Kowe, Department of Agril. Engg.
E) Stream Bank Erosion
• Def: It is the scouring of material from the side
and bottom of the stream or water and the
cutting of bank by running water.
• It is mainly due to removal of vegetation, over
glazing or cultivation on the area near to the
stream bank.
• Also caused by water flowing over the sides of
the stream.