This document discusses different forms of water erosion including splash/raindrop erosion, sheet erosion, rill erosion, and gully erosion. It provides details on each process and how they relate to each other in stages from small rills developing into larger gullies over time due to water flow. Additionally, it covers specialized forms of erosion like pedestal erosion and piping erosion as well as classification systems for gullies based on shape, activity level, and size.

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Different forms of
Water Erosion

2. Different Forms of Water Erosion
 Splash/ Raindrop Erosion
 Sheet Erosion
 Rill Erosion
 Gully Erosion

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Different Forms of Water Erosion

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 It results from soil splash caused by the
impact of falling torrential rain
 If raindrops strikes on the land covered with
thick blanket of vegetation the drop breaks
into a spray of clear water which slowly
finds its way into soil pores
Splash/ Raindrop Erosion

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 If the raindrop strikes bare soil considerable
splashing occurs
 These splashes gradually remove fine materials
from the soil and leave the land infertile by
leaving behind sand and gravel particles
 Splashes as much as 60 cm. high and 150 cm.
away
Splash/ Raindrop Erosion

6. Splash/ Raindrop Erosion

7. Sheet Erosion
 It is the removal of fairly uniform layer of soil
from land surface by the action of rainfall and
runoff water
 Sloping land having a shallow loose topsoil
overlying a compact subsoil are the most
susceptible to sheet erosion
 detected by the muddy colour of the run-off
from the fields

8. Sheet Erosion

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 small finger like rills are formed under landscape
 rills are smoothened by working of small
implements
 rills will increase not only in number but also in
shape and size
 These get wider and deeper
Rill Erosion

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 Rill erosion is more serious in soils having
shallow top soil
 transition stage between sheet and gully
erosion
Rill Erosion

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 advance stage of rill erosion
 Rills are small in size and can be destroyed by tillage
operations.
 If rills are not destroyed, the rills become larger in size and
shape due to prolonged occurrence of flow through them
and cannot be removed by tillage operations and these are
called gullies.
 Gullies unless stopped or controlled in the rill stage will get
deepened and widened.
 High intensity of flow of the run off increase the gully
dimensions.
 Large gullies and their network are called as ravines.
Gully Erosion

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Gully Erosion

13.  The rate of gully erosion mainly depends on the runoff
characteristics of the watershed, namely watershed area,
soil characteristics
Gully Erosion

14. Stages of Gully
Development
Formation Stage
It is beginning of formation of rills (small channels)
and development by downward scouring of the
soils

15. Stages of Gully Development
Development Stage
It is a stage where the upstream movement in the
gully head and enlargement of gully in depth and
width takes place

16. Stages of Gully Development
Healing Stage
It is the stage where the vegetation begins to
grow in the gullies

17. Stages of Gully Development
Stabilization Stage
Here the gully bed, reaches a stable condition
The gully walls reach a stable slope and vegetative
cover spreads over the gully surface

18. • Based on shape (U shape, V shape)
• Based on nature of gully flow (Active,
Inactive)
• Based on size (depth, width and side
slopes)
Gully Classification
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19. Types of Gullies – Based on shape
U or V shaped gullies
Gullies can be classified as U or V shaped gullies
based on the shape of their cross-section

20. U shaped
It is formed in areas where surface and subsurface soils are
weak and susceptible to erosion.
The flow velocity is less and this causes a continuous process of
caving in of the gully sides, forming U shape.
It is common in plains
V shaped
It is formed in areas where the subsoil is more resistant to
erosion.
The flow through this gullies is low, but velocity is very high due
to steep slope.
These gullies are formed in hilly areas with steep faces.
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21. U or V shaped gullies

22. Active and inactive gullies
Active gullies are those which continued to enlarge
and they will be recognized by the presence of loose
soils
Inactive gullies are that which doesn’t enlarge
further and is covered with vegetation on the side
slopes
Types of gullies

23. Classification of Gullies based on Depth
S.
No.
Symbol Description Specification
1. G1
Very small
gullies
Upto 3 m deep, bed width not more than
18 m, side slopes vary
2. G2
Small gullies Upto 3 m deep, bed width more than 18 m
and side slopes 8-15%
3. G3
Medium gullies Depth 3-9 m, bed width more than 18 m,
sides uniformly sloping between 8-15%
4. G4
Deep and
narrow gullies
(a) 3-9 m deep, bed width less than 18 m,
side slopes vary
(b) Depth more than 9 m, bed width varies
and the side slopes vary.

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• A ravine is generally a slope landform (larger
than a gully) of relatively steep (cross-sectional)
sides, on the order of 20 – 70 % in gradient.
Ravines

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Ravines

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• Landslides are simply defined as the
mass movement of rock, debris or earth
down a slope
• They often take place in conjunction
with earthquakes, floods and volcanoes.
Landslides

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• Landslides are caused when the
stability of a slope changes from a
stable to an unstable condition.
• A change in the stability of a slope can
be caused by a number of factors,
acting together or alone
Causes of Landslides

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• Ground water pressure acting to destabilize the
slope
• Loss or absence of vertical vegetative structure,
soil nutrients, and soil structure.
• Erosion of the toe of a slope by rivers or ocean
waves
• Weakening of a slope through saturation by
snowmelt, glaciers melting, or heavy rains
• Earthquakes adding loads to barely-stable slopes
• Volcanic eruptions
Natural Causes of Landslides

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• Vibrations from machinery or traffic.
• Earthwork which alters the shape of a slope,
or which imposes new loads on an existing
slope in shallow soils.
• Removal of deep-rooted vegetation that binds
colluvium to bedrock.
• Construction, agricultural, or forestry activities
which change the amount of water which
infiltrates into the soil.
Human Causes of Landslides

30. Specialized Forms of Water Erosion
Pedestal Erosion
 It results when a stone or tree
roots protrudes the soil by splash
erosion which removes the
surrounding soil
 It develops slowly over years and
is often found on patches in
grazing lands

31. Pinnacle Erosion
 This occurs often in gullies as
a result of deep vertical rills
until pinnacles are left in land
Specialized Forms of Water Erosion

32. Piping Erosion
 It is caused by the occurrence of interflows in soil
medium.
 It removes and transports soft soil particles.
 Such interflows are initiated by cracks, burrows in the soil
medium and are developed by the seepage of water
called piping.
Specialized Forms of Water Erosion

33. Slumping Erosion
 Sliding or mass movement of soil in the gullies
 It is usually a process of geological erosion
 It is prominent in high rainfall areas with deep soil
coastal erosion also causes slumping
Specialized Forms of Water Erosion

34. Fertility Erosion
It is the loss of plant nutrients by erosion
P is mainly lost along with the colloidal particles on the
surface is observed
N in the form of NO2 or NO3 is soluble and so can be
lost as solution with the runoff without any soil movement
occurring
Specialized Forms of Water Erosion