water erosion

Soil and water conservation engineering, water erosion, types of water erosion, splash erosion, sheet erosion, rill erosion, gully erosion, stream bank erosion, coastal erosion

1. Soil and Water Conservation
Engineering
Topic: Soil Erosion
by
Dr. Sanjay Singh Chouhan
Assistant Professor
College of Agriculture, JNKVV,
Powarkheda, Hoshangabad
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2. •“Soil and Water Conservation” term is similar to the
conservation of energy, momentum and mass.
•It is applied for conserving the soil and water against
several atmospheric agents such as waterand
wind.
•The most fundamental and dominating problem
which is tackled by this subject is the ‘soil erosion’.
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Soil and Water Conservation

3. Soil
•Soilistheuppermostlayeroftheearth'scrust
andconsistsofweatheredanddisintegrated
mineralsmixedwithorganicsubstances.
•Itsdepthisvariable:insomeplacesthereisno
soil,insomeplacesthesoillayerismany
metersdeep.
•However,itislittleexaggerationtosaythat,the
top30cmofsoilsupportsallhumanand
animallife.
•Thisthinlayerislargelyresponsibleforboththe
physicalsupportandnutritionalofplantgrowth.
3JNKVV-College of Agriculture, Powarkheda

4. Soil Erosion
•SoilerosionistheprocessbywhichsoilisremovedfromtheEarth'ssurfaceby
exogeneticprocessessuchaswindorwaterflow,andthentransportedand
depositedinotherlocations.
•Ingeneral,soilerosionimpliesthephysicalremovaloftopsoilbyvariousagents,
includingrain,waterflowingoverandthroughthesoilprofile,wind,glaciersor
gravitationalpull.
•Landandwaterarethemostpreciousnaturalresourcesthatsupportandsustain
theanthropogenicactivities.

5. JNKVV-College of Agriculture, Powarkheda
Soilerosionisinitiatedby
detachmentofsoilparticles
duetoactionofrain.The
detachedparticlesare
transportedbyerosion
agentsfromoneplaceto
anotherandfinallyget
settledatsomeplaceleading
tosoilerosionprocess.
Differentsoilerosion
processesareshowninFig.
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Mechanics of Soil Erosion

6. Causes of Soil Erosion
•Indiscriminate cutting of trees,
•Overgrazing of the vegetative cover and
•Forest fires.
(1) Destruction of Natural Protective Cover by
•Keeping the land barren subjecting it to the action of rain and wind,
•Growing of crops that accelerate soil erosion,
•Removal of organic matter and plant nutrients by injudicious cropping
patterns
•Cultivation along the land slope, and
•Faulty methods of irrigation.
(2) Improper Use of the Land
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7. Effects of Soil Erosion
•Loss of productive soil
•Deposition of sand on productive fields
•Silting of lakes and reservoirs
•Silting of drainage and irrigation channels.
•Lowering of water table
•Fragmentation of land
•Damage to seacoast and formation of sand dunes.
•Disease and public health hazards.
•Soilserodedbywatergetdepositedonriverbeds,thusincreasingtheirleveland
causingfloods.Thesefloodssometimehavevariousextremeeffects,suchaskilling
humanandanimalsanddamagingvariousbuildings.
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8. •Soil erosion decreases the moisture supply by soil to the plants for their growth. It
also affects the activity of soil micro-organisms thus deteriorating the crop yield.
•Top layer of soil contains most of the organic matter and nutrients, loss of this soil
reducing soil fertility and affecting its structure badly.
•Wind erosion is very selective, carrying the finest particles -particularly organic
matter, clay and loam for many kilometres. There the wind erosion causes losses of
fertile soils from highly productive farming areas.
•Sheetsofsandtravellingclosetotheground(30to50meters)candegradecrops.
•Winderosionreducesthecapacityofthesoiltostorenutrientsandwater,thus
makingtheenvironmentdrier.
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9. Factors affecting Soil Erosion
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Hydrology
(Rainfall, Runoff)
Topography
(Soil, Slope)
Wind
Soil surface coverTillage practices

10. Soil erosion can broadly be categorized into two types
1.Geologic Erosion
2.Accelerated Erosion.
Types of Soil Erosion

11. •Under natural undisturbed conditions an equilibrium is established between the climate of
a place and the vegetative cover that protects the soil layer.
•Vegetative covers like trees and forests retard the transportation of soil material and act as
a check against excessive erosion.
•A certain amount of erosion, however, does take place even under the natural cover. This
erosion, called geologic erosion, is a slow process and is compensated by the formation of
soil under the natural weathering process.
•Its effect are not of much consequence so far as agricultural lands are concerned.
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Geological Erosion

12. When land is put under cultivation, the natural balance existing between the soil, its
vegetation cover and climate is disturbed. Under such condition, the removal of surface soil
due to natural agencies takes places at faster rate than it can be built by the soil formation
process. Erosion occurring under these condition is referred to as accelerated erosion. Its
rates are higher than geological erosion. Accelerated erosion depletes soil fertility in
agricultural land.
Ex: Water Erosion, Wind Erosion
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Accelerated Erosion

13. JNKVV
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College of Agriculture, Powarkheda
Water Erosion
•Watererosionisseeninmanypartsoftheworld.
•Infact,runningwateristhemostcommonagent
ofsoilerosion.
•Thisincludesriverswhicherodetheriverbasin,
rainwaterwhicherodesvariouslandforms,and
theseawaveswhicherodethecoastalareas.
•Watererodesandtransportssoilparticlesfrom
higheraltitudeanddepositstheminlowlying
areas.
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14. Factors
Affecting
Water
Erosion
JNKVV
-
College of Agriculture, Powarkheda
1.Climatic factors
•Rainfall charactersticsinclude amount, intensity, frequency and
duration of rainfall. All this have great effect of runoff and soil loss.
•Atmospheric temperature
•Wind velocity
2.Soil characteristics (infiltration rate and soil cover)
3.Vegetation: Vegetation create surface obstruction for direct falling of
raindrop on the land surface as well as in the flow path of surface
runoff.
4.Topographic factors: The land slop, length of slope and shape of
slope are the main topographic factors which influence the soil
erosion
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15. 1.Raindrop or Splash erosion,
2.Sheet erosion,
3.Rill erosion,
4.Gully erosion,
5.Stream bank erosion
6.Costal erosion
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Types of Water Erosion

16. •Thistypeofsoilerosionisbecauseoftheaction
ofraindrop.
•Thekineticenergyoffallingraindropdislodges
thesoilparticleandtheresultantrunoff
transportssoilparticles.
•Splasherosionisthefirststageofsoilerosionby
water.Itoccurswhenraindropshitbaresoil.
•Theexplosiveimpactbreaksupsoilaggregates
sothatindividualsoilparticlesare‘splashed’
ontothesoilsurface.
•Thesplashedparticlescanriseashigh0.60
meterabovethegroundandmoveupto1.5
meterfromthepointofimpact.
•Theparticlesblockthespacesbetweensoil
aggregates,sothatthesoilformsacrustthat
reducesinfiltrationandincreasesrunoff.
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Splash Erosion

17. Sheet Erosion
▪Sheeterosionistheremovalofsoilinthinlayers
byraindropimpactandshallowsurfaceflow.
▪Thisactioncalledskimmingandisprevalentinthe
agriculturalland.Itresultsinlossofthefinestsoil
particlesthatcontainmostoftheavailable
nutrientsandorganicmatterinthesoil.
▪Soillossissogradualthattheerosionusuallygoes
unnoticed,butthecumulativeimpactaccounts
forlargesoillosses.
▪Thistypeofsoilerosionismainlyresponsiblefor
lossofsoilproductivities.
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18. JNKVV
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College of Agriculture, Powarkheda
▪Soilsmostvulnerabletosheeterosionare
overgrazedandcultivatedsoilswherethereis
littlevegetationtoprotectandholdthesoil.
▪Earlysignsofsheeterosionincludebareareas,
waterpuddlingassoonasrainfalls,visiblegrass
roots,exposedtreeroots,andexposedsubsoilor
stonysoils.
▪Soildepositsonthehighsideofobstructionssuch
asfencesmayindicateactivesheeterosion.
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19. ▪Rillsformationistheintermittent
processoftransformingtogullyerosion.
▪Theadvanceformoftherillisinitial
stageofgullyformation.
▪Therillsareshallowdrainagelinesless
than30cmdeepand50cmwide.
▪Theydevelopwhensurfacewater
concentratesindepressionsorlow
pointsthroughpaddocksanderodes
thesoil.
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Rill Erosion

20. •Rillerosioniscommoninbare
agriculturalland,particularly
overgrazedland,andinfreshly
tilledsoilwherethesoil
structurehasbeenloosened.
•Therillscanusuallybe
removedwithfarmmachinery.
•Rillerosionismostlyoccursin
alluvialsoilandisquite
frequentinChambalriver
valleyinIndia.
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21. Gully Erosion

22. ▪Theadvancestageofrillsistransformed
intoinitialstageofgully.
▪Gullyformationareinitiatedwhenthe
depthandwidthoftherillismorethan50
cm.
▪Gulliesaredeeperchannelsthatcannotbe
removedbynormalcultivation.
▪Hillsidesaremorepronetogullyingwhen
theyclearedofvegetation,through
deforestation,over-grazingorother
means.
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Gully Erosion

23. Stream Bank
Erosion
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24. Stream Bank Erosion
•Streambankerosionoccurswherestreamsbegincuttingdeeper
andwiderchannelsasaconsequenceofincreasedpeakflowsor
theremovaloflocalprotectivevegetation.
•Generally,streambankerosionbecomesaproblemwhere
developmenthaslimitedthemeanderingnatureofstreams,where
streamshavebeenchannelized,orwherestreambankstructures
(likebridges,culverts,etc.)arelocatedinplaceswheretheycan
actuallycausedamagetodownstreamareas.
•Stabilizingtheseareascanhelpprotectwatercoursesfrom
continuedsedimentation,damagetoadjacentlandusesand
improvementofhabitatforfishandwildlife.
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25. Coastal erosion
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26. Coastal erosion
▪Thewaves,geologyandgeomorphologyare
thethreemajorfactorsthataffectthecoastal
erosion.
▪Wavesarethecauseofcoastalerosion.Wave
energyistheresultthespeedofthewind
blowingoverthesurfaceofthesea,thelength
offetchandthewindblowingtime.
▪Thegeologyofthecoastlinealsoaffectsthe
rateoferosion
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27. Thanks for listening…..
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