Wind erosion

wind erosion and its control measures, factor affecting wind erosion, mechanics of wind erosion, types of soil transportation, suspension, saltation and surface creep, windbreak, shelterbelt, sand duns

1. Subject
Soil and Water Conservation Engineering
Topic
Wind Erosion
Dr. Sanjay Singh Chouhan
Assistant Professor
JNKVV-College of Agriculture
Powarkheda, Hoshangabad

2. Wind Erosion
•Winderosionisanaturalprocessthat
movessoilfromonelocationto
anotherbywindpower.
•Winderosioncanbecausedbyalight
windthatrollssoilparticlesalongthe
surfacethroughtoastrongwindthat
liftsalargevolumeofsoilparticles
intotheairtocreateduststorms.
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College of Agriculture, Powarkheda
•Whilewinderosionismostcommonindesertsandcoastalsanddunesand
beaches,certainlandconditionswillcausewinderosioninagriculturalareas.
•So,itiswindthatdrivestheerosion,butit’smainlythelandscapeandconditionof
thelandwhichleadstothemostdamagingwinderosionandcancausesignificant
economicandenvironmentaldamage.
•Winderosion,inIndia,iscommonlyobservedinaridandsemi-aridareaswhere
theprecipitationisinadequate,e.g.RajasthanandsomepartsofGujarat,Punjab
andHaryana.

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College of Agriculture, Powarkheda
Wind Erosion Damages
•Winderosiondamageslandandnaturalvegetationbyremovingsoilfrom
oneplaceanddepositingitatanotherlocation.
•Itcausessoilloss,drynessanddeteriorationofsoilstructure.
•Mostseriousdamagecausedbywinderosionisthechangeinsoiltexture.
•Productivitylosses:Smallerparticlesofsoilaremoresubjectto
movementbywindassilt,clayandorganicmatterareremovedfromthe
surfacesoilbystrongwind,leavingthecoarse,lesserproductivematerial
behind.
•Sedimenttransportanddepositionaresignificantfactorsinthegeological
changeswhichoccuronthelandaroundusandoverlongperiodsoftime
areimportantinthesoilformationprocess.

5. •Humanhealthasairbornedustcancauseasthma
andotherhealthproblems.
•Theenvironmentwhendustchokescreeksand
depositsunwantednutrientsandsalt,
threateningplantsandanimalsandcausingblue
greenalgalblooms.
•Propertyasbuiltstructurescanbesandblasted
bywind-blowndustandburiedinblownsand.
•Economicactivitywhenduststormsdisrupt
commercialactivitiesandtransport,andcreate
theneedforextracleaning.
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6. •Climate
•Soil
•Surface roughness
•Topography
•Vegetative cover
•Organic matter content
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Factors Affecting Wind Erosion

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College of Agriculture, Powarkheda
Climate
•Theclimaticfactorsthataffectthewinderosionarethecharacteristicsofwind
itself(velocityanddirection)inadditiontotheprecipitation,humidityand
temperature.
Soil
•Soilmoistureconditions,texture,structure,densityofparticlesarethesoil
characteristicsthatinfluencetheSoilcloudinessandthuserosionbywind.

8. Surface roughness
•Rough surface leads to reduction in soil loss by the reducing the wind velocity uptoa
certain point and result in less soil loss.
•Rough surface also trapping the saltating soil particles and reduce the wind erosion
•In general, greater the soil roughness, lower the wind velocity against the ground and
lower is the rate of erosion.
Topography
•The land pattern also affect the rate and amount of soil loss caused by wind. If the
slope of land is not equal i.e., undulating soil leads to less soil loss than the plain area.
Soil surface characteristics depend upon the soil topography
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9. VegetativeCover
•Surfacefeatureslikevegetationorotherartificialcover(mulching
etc)havetheprotectiveeffectonwinderosionproblemas
surfacecoverincreasestheroughnessoverthelandsurfaceand
thusreducestheerosivewindforceonthelandsurface.
OrganicMatterContent
•Theorganiccontentinthesoilleadstoreductioninsoilerosion
duetobindingpropertiesoftheorganicmatterinthesoil.
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10. Mechanics of Wind Erosion.
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11. The overall occurrence of wind erosion could be described in
three distinct phases.
These are:
1.Initiation of Movement
2. Transportation
3. Deposition
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Mechanics of
Wind Erosion

12. Initiation of Movement
•Thesoilparticlesarefirstdetachedfromtheirplacebytheimpact
andcuttingactionofwind.
•Thesedetachedparticlesarethenreadyformovementbythe
windforces.
•Afterthisinitiationofmovement,soilparticlesaremovedor
transportedbydistinctmechanisms.
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13. Transportation
•Thetransportationofthesoilparticlesareofthreedistincttypesandoccurdepending
uponsizeofthesoilparticles.Suspension,SaltationandSurfacecreeparethethreetypes
ofsoilmovementortransportwhichoccurduringwinderosion.
•Whilesoilcanbeblownawayatvirtuallyanyheight,themajority(over93%)ofsoil
movement/transportationtakesplaceatorwithinonemeterheightfromlandsurface.
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14. Deposition
•Depositionofsoilparticlesoccurswhenthegravitationalforceis
greaterthantheforcesholdingtheparticleintheair.
•Thisgenerallyhappenswhenthereisadecreaseinthewind
velocitycausedbyvegetativeorotherphysicalbarrierslike
ditchesorbenches.
•Raindropsmayalsotakedustoutofair.
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15. Types of soil movement or transport which occur during wind erosion
Thetransportationofthesoilparticlesareofthreedistincttypesandoccurdependingupon
sizeofthesoilparticles.
•Whilesoilcanbeblownawayatvirtuallyanyheight,themajority(over93%)ofsoil
movement/transportationtakesplaceatorwithinonemeterheightfromlandsurface.
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S.No.Types of Soil
Movement
Soil Particles Size% of Transported
Soil Weight
1 SuspensionLess then 0.1 mm3 to 40%
2 Saltation0.1 mm to 0.5 mm50 to 75%
3 Surface creep0.5 mm to 2.0 mm5 to 25 %

16. 1.Suspension
•Itoccurswhenveryfinedirtanddustparticlesareliftedintotheatmosphere.
•Theycanbethrownintotheairthroughimpactwithotherparticlesorbythewinditself.
•Theseparticlescanbecarriedveryhighandbetransportedoververylongdistancesin
theatmospherebythewinds.
•Soilmovedbysuspensionisthemostspectacularandeasiesttorecognizeamongthe
threeformsofmovement.
•Thesoilparticlesoflessthan0.10mmsizearesubjectedtosuspensionandaround3to
40%ofsoilweightsarecarriedbythesuspensionmethodofsoiltransportunderthe
winderosion.
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17. 2. Saltation
•Themajorfractionofsoilmovedbythewindisthroughtheprocessofsaltation.
•Saltationmovementiscausedbythepressureofthewindonsoilparticlesaswellasby
thecollisionofaparticlewithotherparticles.
•Soilparticles(0.1to0.5mm)moveinaseriesofbouncesand/orjumpsanddependingon
soiltype,about50to75%ofthetotalweightofsoiliscarriedinsaltation.
•Soilparticlesmovedintheprocessofsaltationcancauseseveredamagetothesoil
surfaceandvegetation.
•Theytravelapproximatelyfourtimeslongerindistancethaninheight.
•Whentheystrikethesurfaceagaintheyeitherbouncebackintotheairorknockothersoil
particlesfromthesoilmassintotheair.
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18. 3.SurfaceCreep:
•Thelargeparticleswhicharetooheavytobeliftedintotheairaremovedthroughaprocess
calledsurfacecreep.
•Inthisprocess,theparticlesarerolledacrossthesurfaceaftercomingintocontactwiththe
soilparticlesinsaltation.
•Inthisprocessthelargestoftheerosiveparticleshavingdiametersbetween0.5to2mm
aretransportedandaround5to25%ofthetotalsoilweightsarecarriedinthisfashion.
•Overall,themassofsoilmovedbywindisinfluencedprimarilybyparticlesize,gradationof
particles,windvelocityandthedistancealongtheerodingarea.
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19. Estimation of Soil Loss Due to Wind Erosion
Anequationintheformofuniversalsoillossequationhasbeendevelopedandcanbeused
forestimatingsoillossbywind.However,theevaluationoftheconstantsintheequationfor
winderosioniscomparativelydifficultthantheuniversalsoillossequation.
Theequationisoftheform,
E = IRKFCWDB
Where,
Eissoillossbywinderosion,Iissoilcloddinessfactor,Rissurfacecoverfactor,Kissurface
roughnessfactor,Fissoiltexturalclassfactor,Cisfactorrepresentinglocalwindcondition,
Wisfieldwidthfactor,DiswinddirectionfactorandBiswindbarrierfactor.
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Wind Erosion Control
Measures

21. Wind Erosion Control
•Asuitablesurfacesoiltextureisthebestkeytowinderosion
protection.
•Properlymanagedcropresidues,carefullytimedsoiltillage,and
accuratelyplacedcropstripsandcropbarrierscanalleffectively
reducewinderosion.
•Properlanduseandadaptationofadequatemoistureconservation
practicesarethemaintoolswhichhelpinwinderosioncontrol.
•Intheabsenceofcropresidue,soilroughnessorsoilmoisturecan
reducethewinderosioneffectively.
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22. Principle of Wind Erosion Control
1.The measures to reduce the surface wind
velocity.
2.The Measures to improve the soil
characteristics.
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Measures to Reduce the
Surface Wind Velocity
Vegetative
Temporary
Crop
management
Permanent
Windbreak
Shelterbelt
Tillage
Primary &
Secondary Tillage
Mulching of Crop
Residues
Strip Cropping
Mechanical
Obstacles
Construction
Fence, Walls,
Stone packing,
Terraces, Bunds
Principle-1

24. Vegetative Measures
•Itisoneofthemosteffectiveandeconomicalmeanstoreducetheeffectofwindonthe
soil.
•Itretardsthewindvelocitynearthegroundsurfaceandcontrolerosion.
•Itkeepthesoilroughandridgedtoeitherpreventanymovementinitiallyortoquickly
trapbouncingsoilparticlesinthedepressionsoftheroughsurface.
•Fromthebasicconcept,thevelocityofwinddecreasesnearthegroundsurfacebecause
oftheresistanceofferedbythevegetation.
•Vegetativemeasurescanbeoftwotypesandtheuseofthesemeasuresdependsupon
theseverityoferosion,(1)Temporaryand(2)Permanent.
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25. Temporary Measures
•Theyconsistofgrowingoferosionresistantcropsi.e.groundnut,
legumes,grasses,berseemetc.whicharemoreeffectivefor
erosioncontrolthentheinter-tilledcrops.
•Theeffectivenessisdependentuponthestageofgrowth,density
ofcover,rowdirection,widthofrows,kindofcropsandclimatic
conditions.
•Theyshouldhaveabilitytogrowwithrapidspeedagainstthewind
andalsobeabletowithstandforalongtime.
•Theyshouldprovideadensevegetativecoverduringcritical
seasonoftheyear.
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26. Permanent Measures
•Theyconsistofplantingoftrees,
shrubsandgrassesforprotectingthe
landagainstwinderosion.
•They are two types:
1.Windbreak
2.Shelterbelts
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27. Wind Breaks

28. Wind Breaks
•Thetermwindbreakisdefinedasanytypeofbarriereithermechanicalorvegetativeused
forprotectingtheareaslikebuildingapartments,orchardsorfarmsteadsetc.fromblowing
winds.
•Thewindbreakactsasfencingwallaroundtheaffectedareas,normallyconstructedbyone
rowormaximumuptotworowsacrosstheprevailingwinddirection.
•Thisisapermanentvegetativemeasurewhichhelpsinthereductionofwinderosion.
•Itreducesthewindspeedupto60-80%onleewardside.
•Thewindbreakreducesthewindspeedontheleewardsideat200mawayupto20%only
andintheareaasat300maway,thereisnoeffectatall.Thereforeatanintervalof300m,
suchwindbreaksshouldberepeated.
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29. Wind Breaks
Design
1.One leg
2.Two legs

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31. Shelter Belts
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Shelter Belts
•Shelterbelt is more effective for reducing the impact of wind movement than the
wind break. Apart from controlling wind erosion, it provides fuel, reduces
evaporation and protects the orchard from hot and cold winds.
•A shelterbelt is a longer barrier than the wind break, is installed by using more than
two rows, usually at right angle to the direction of prevailing winds.
•The rows of belt can be developed by using shrubs and trees.
•It is mainly used for the conservation of soil moisture and for the protection of field
crops, against severe wind erosion.

33. Shelter Belts
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34. Width of Shelter Belt
Itindicatesthenumberofrowsofplants,raisedintheshelterbeltorbreak.
Awindbreakinvolvesoneormaximumtworows,butashelterbelt
involvesmorethantworows.
The rows of plants should be raised in following trends:
a)The row of tallest trees should be arranged in the middle of
shelterbelt.
b)Shorter trees should be raised in the sides of tallest tree’s row.
c)The shrubs should be planted at the outer edge of belt.
Types of Shelter Belt
1.Right Angle Tringle Shelter Belt
2.Tringle Shelter Belt
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35. Shelter Belts
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36. Shelter Belts
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37. Tillage Practices
Tillagepracticesaregenerallyusedfor
moistureconservationsothat
erodibilityreduces.Thecommontillage
practicesare:
1.Primaryandsecondarytillage
2.Useofcropresidues
3.Stripcropping
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38. Primary and
Secondary Tillage
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39. Primary and Secondary Tillage
•The main aim is to produce a rough and cloddy surface of soil to resist the wind velocity.
•The soil should be ploughed soon after the rain for clod formation.
•A network of small ridges generally 100mm high is formed throughout the field, in the
direction normal to the prevailing wind.
•They do not obstruct the wind but also changes the wind direction between the ridges and
help in soil deposition.
•Rougheningcanbeusedinbothcropandpastureareas.Surfacerougheningaloneis
inadequateforsandysoilsbecausetheyproducefewclods.
•Ridgesthatarelowerthan100mmgetquicklyfilledwithsand,whilstthecrestoftheridge
thatishigherthan100mmtendstoerodeveryquickly.
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40. Use of Crop Residues
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Use of Crop Residues
•Cropresiduesknownasstubblemulchingactintwoways,theyreducethe
windvelocityoverthelandsurfaceandtraptheerodingsoilsonthesoil
surface.
•Amixtureofstrawandstubbleprovidesbetterprotectionagainstwinderosion.
•Italsohelpsinbetterabsorptionofrainfall,reduceraindroperosion,reduced
evaporationlosses,increaseinproductivitybyaddingorganicmatterinsoil.

42. Use of Zero Tillage

43. Use of Strip Cropping

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Field and Contour Strip Cropping
•Itconsistofalternatestripsofrowcropsandclosegrowingcropsinthesamefield.
•Thestripcroppingislaidoutgenerallyparalleltothefieldboundaryor
perpendiculartotheerosivewinddirection.
•Thewidthofthestripismaintainedsuchasitshouldnothamperthefarming
operationandshouldnotallowedmucherosion.
•Thecombinationofrowcropsthatpermiterosioni.e.maize,cotton,potato,bajra,
jowaretc.aresownwitherosionresistantcropsi.e.groundnut,legumes,grasses,
berseemetc.

45. Mechanical Measures
•This method consists of some mechanical obstacles, constructed
across the prevailing wind, to reduce the impact of blowing wind
on the soil surface.
•These obstacles may be fences, walls, stone packing etc., either in
the nature of semi-permeable or permeable barriers.
•The semi-permeable barriers are most effective, because they
create diffusion and eddying effects on their downstream face.
•Terraces and bunds also obstruct the wind velocity and control
the wind erosion to some extent.
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46. Principle-2
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Measures to
Improve Soil
Characteristics
Conserving the
soil moisture
Terracing,
Contouring,
Mulching
Selection of
Suitable Crops
Conditioning the
top soil
Crop management
practices, Crop
rotation, tillage
Addition of
manures and
organic matter

47. Conserving the Soil Moisture
•Theconservationofmoisture,particularlyinaridsemi-aridregionisimportant
bothforwinderosioncontrolandcropgrowth.
•Itcanbeachievedbyincreasingthesoilinfiltration,reducingevaporationlossand
preventingunnecessaryplantgrowth.
•Variouspracticessuchasterracing,contouring,mulchingandselectionofsuitable
cropsshouldbeadopted.
•Amongthemeasures,mulchingisoneofthemostsuitablepracticesused
successfullytocontrolwinderosion.
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48. Conditioning of the Top Soil
•Thewinderosionisgreatlyinfluencedbythetopsoilconditionasitaffectsthe
detachmentofsoilparticles.
•Adoptionsoftillagepracticestoproducenon-erosivesoilaggregatesisaneffective
method.
•Cropmanagementpractices,croprotation,tillage,additionofmanuresandorganic
matterhaveagreateffectonwinderosioncontrolastheyhelptodevelopagoodsoil
structureandabletowithstandwindvelocity.
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49. Sand Dunes
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50. Sand Dunes
•A ‘Dune’ is derived from English word ‘Dun’ means hilly topographical feature.
Therefore a sand dune is a mount, hill or ridge of sand that lies behind the part of the
beach affected by tides.
•They are formed over many years when windblown sand is trapped by beach grass or
other stationary objects.
•Dune grasses anchor the dunes with their roots, holding them temporarily in place,
while their leaves trap sand promoting dune expansion.
•Without vegetation, wind and waves regularly change the form and location of dunes.
•Dunes are not permanent structures.
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51. JNKVV-College of Agriculture, Powarkheda 51
Sand Dunes at Sea Beach Sand Dunes at Desert

52. Thanks for listening…..
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