Erosion control measures

principles of erosion control, Agronomical measures of water erosion, contour cropping, strip cropping, contour strip cropping, mulching, bunding, terracing, bund, contour bund, graded bund, tarraces, bench terraces

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

2. Principles of Erosion Control
•Itisbettertocontroltheinitiationofsoilerosionthanreclaim
anerodedland.
•Forthispurpose,everypieceoflandinawatershedshouldbe
usedproperlyinaccordancewithitscapability.
•Landshouldbeusedinsuchamannersothatnoerosionor
deteriorationoflandtakesplaceevenafterprolongeduse.
•Suitableagronomicalpracticedshouldbefollowedtoprotect
thelandfromtheenergyofthefallingraindropandsurfaceflow.
•Differenttillageandagronomicalpracticesarerequiredtobe
followedtoachievethedesiredeffects.
JNKVV-College of Agriculture, Powarkheda 2

3. JNKVV
-
College of Agriculture,
Powarkheda
3
Agronomical Measures of Water Erosion Control
•Insoilandwaterconservation,theagronomical
measureisamoreeconomical,longlastingand
effectivetechnique.
•Agronomicconservationmeasuresfunctionby
reducingtheimpactofraindropsthroughinterception
andthusreducingsoilerosion.
•Theyalsoincreaseinfiltrationratesandtherebyreduce
surfacerunoff.Widelyusedagronomicmeasuresfor
watererosioncontrolare:
1.ContourCropping 2.StripCropping
3.Mulching

4. Contour
Cropping

5. Contour Cropping
•ContourCroppingisaconservationfarming
methodthatisusedonslopestocontrolsoil
lossesduetowatererosion.
•Contourcroppinginvolvesplantingcropsacross
theslopeinsteadofupanddowntheslope.
•Useofcontourcroppingprotectsthevaluable
topsoilbyreducingthevelocityofrunoffwater
andinducingmoreinfiltration.
•Contourcroppingismosteffectiveonslopes
between2-10%.
5

6. Strip Cropping
JNKVV-College of Agriculture, Powarkheda 6

7. 7
JNKVV
-
College of Agriculture, Powarkheda
Strip Cropping
•Stripcroppingisthepracticeofgrowingstripofcropshavingpoorpotentialfor
erosioncontrol,suchasrootcrop,cereals,etc.,alternatedwithstripsofcrops
havinggoodpotentialsforerosioncontrol,suchasfoddercrops,grasses,etc.,
whichareclosegrowingcrops.
•Strip cropping is a more intensive farming practice than contour farming.
•Strip cropping is laid out by using the three methods:

8. Contour Strip Cropping
Incontourstripcropping,alternate
stripsofcroparesownmoreorless
followingthecontours,similarto
contouring.
Suitablerotationofcropsandtillage
operationsarefollowedduringthe
farmingoperations.
JNKVV-College of Agriculture, Powarkheda 8

9. Field Strip Cropping
•Inafieldlayoutofstripcropping,strip
ofuniformwidtharelaidoutacrossthe
prevailingslope,whileprotectingthe
soilfromerosionbywater.
•Toprotectthesoilfromerosionby
wind,stripsarelaidoutacrossthe
prevailingdirectionofwind.
•Suchpracticesaregenerallyfollowedin
areaswherethetopographyisvery
irregular,andthecontourlinesaretoo
curvyforstrictcontourfarming.
JNKVV-College of Agriculture, Powarkheda 9

10. Buffer Strip Cropping
•Bufferstripcroppingispracticedwhere
uniformstripofcropsarerequiredtobe
laidoutforsmoothoperationsofthe
farmmachinery,whilefarmingona
contourstripcroppinglayout.
•Bufferstripoflegumes,grassesand
similarothercropsarelaidoutbetween
thecontourstripsascorrectionstrips.
•Bufferstripsprovideverygood
protectionandeffectivecontrolofsoil
erosion.
JNKVV-College of Agriculture, Powarkheda 10

11. Mulching

12. 12
JNKVV
-
College of Agriculture, Powarkheda
Mulching
•Mulchisanymaterialthatisspreadorlaidoverthesurfaceofthesoilasacovering.
•Mulchesareusedtominimizerainsplash,reduceevaporation,controlweeds,reduce
temperatureofsoilinhotclimates,andmoderatethetemperaturetoalevelconducive
tomicrobialactivity.
•Italsohelpinbreakingtheenergyofraindrops,preventsplashanddissipationofsoil
structure,obstructtheflowofrunofftoreducetheirvelocityandpreventsheetandrill
erosion.
•Theyalsohelpinimprovingtheinfiltrationcapacitybymaintainingaconductivesoil
structureatthetopsurfaceofland.

13. Mechanical Measures
of Water Erosion
Control
1.Bunding
2.Terracing

14. Mechanical Measures of Water Erosion Control
•Mechanicalpracticesareengineeringmeasuresusedtocontrolerosionfromslopping
landsurfacesandthuslandsurfacemodificationisdoneforretentionandsafedisposalof
runoffwater.
Inthedesignofsuchpractices,thebasicapproachis:
1.Toincreasethetimeofstayofrunoffwaterinordertoincreasetheinfiltrationtime
forwater.
2.Todecreasetheeffectoflandslopeonrunoffvelocitybyinterceptingtheslopeat
severalpointssothatthevelocityislessthanthecriticalvelocity.
3.Toprotectthesoilfromerosioncausedbytherunoffwater.
JNKVV-College of Agriculture, Powarkheda 14

15. BundingMethods for Water Erosion Control
•Bundisanengineeringmeasureofsoilconservation,usedforcreatingobstructionacrossthepath
ofsurfacerunofftoreducethevelocityofflowingwater.
•Itretainstherunningoffwaterinthewatershedandthustohelpstocontrolsoilerosion.
•Bundsaresimplyembankmentlikestructures,constructedacrossthelandslope.
Different Types of Bunds
Contourbund:.Whenthebundsareconstructedalongthecontourswithsomeminordeviationto
adapttopracticalsituation,theyareknownascontourbunds.
Gradedbunds:Ifthebundsareconstructedwithsomeslope,theyareknownasgradedbunds.
Thechoiceofthetypesofbundisdependentonlandslope,rainfall,soiltypeand
purposeofthebundinthearea.
JNKVV-College of Agriculture, Powarkheda 15

16. Contour Bunds

17. Contour Bunds
Thecontourbundsarerecommendedforareaswith
•lowannualrainfall(<600mm)
•permeablesoils
•landslopeoflessthan6%.
Themainfunctionsofcontourbundsare:
1.It reduces the length of slope which in turn
reduces the soil erosion.
2.Thewaterisimpoundedforsometimeandgets
rechargedintothesoilwhichhelpsincrop
cultivation.
Contourbundsareoftwotypes:
1.Narrowbase
2.Broadbase
17

18. NarrowBase
•Innarrowbasecontourbundingsystem,thereisanobstructionforcrossingoffarm
implements;naturalvegetationscoverthesidesandmoreheightisallowedforsame
cross-section.
•Ithaslimitationsthat,thereisconsiderableareaislostinconstructingthebund;the
bundsectionisliabletogetaffectedbyerosionduetoraindropimpact,hence
requiresasinceremaintenance.
•Thenarrowbasecontourbundalsocausesobstructioninfarmingoperations.
Broad base
•Thebroadbasecontourbundingisconcerned,itdoesnotcreatehindrancein
farmingoperations;theentireareacanbekeptundercultivation.
•Ithassomelimitations,suchasdisturbanceofbund’ssectionduetocrossingoffarm
equipments,asresultthereisrequiredanattentivecareandmaintenance.
•Apartfromabove,thesoilofbundisalsoloosenedduringmovementoffarm
machineries,causingreductioninthesizeofbundinaveryshortperiod,unless
somepropermaintenanceisadopted.

19. Graded
Bunds

20. Graded Bunds
•Agradedbundsystemisdesignedtodisposeofexcessrunoffsafelyformagriculturalfields.
•Agradedbundislaidoutwithalongitudinalslopegradientleadingtooutlet.
•Variationsinthegradeareprovidedatdifferentsectionsofthebundtokeeptherunoff
velocitywithinthedesiredlimitssoasnottocauseanysoilerosion.
Gradedbundsarelaidoutinareaswhere
•Thelandissusceptibletowatererosion
•Theareahaswaterloggingproblems
•Highrainfall(>600mm)and
•Relativelyimpervioussoil.

21. TERRACING
JNKVV-College of Agriculture, Powarkheda 21

22. Terraces
•A Terrace is an earth-embankment, constructed across the slope, to control runoff and
minimize soil erosion loss at highly slopping land (slope >10%).
•A terrace acts as an intercept to land slope, and divides the sloping land surface into
strips.
Terraces are classified into to two major types:
1.Broad-base terraces
2.Bench terraces.
•Broad-base terraces are adapted where the main purpose is either to remove or retain
water on sloping land suitable for cultivation.
•The purpose of bench terraces is mainly to reduce the land slope.
JNKVV-College of Agriculture, Powarkheda 22

23. JNKVV-College of Agriculture, Powarkheda 23
Bench Terrace Components

24. JNKVV-College of Agriculture, Powarkheda 24
Types of Terraces

25. Bench Terracing
•The original bench terrace system consists of a series of flat shelf-like areas that convert a steep
slope of 20 to 30% to a series of level, or nearly level benches.
•In other words, bench terracing consists of construction of series of platforms along contours cut
into hill slope in a step like formation.
•These platforms are separated at regular intervals by vertical drop or by steep sided and protected
by vegetation and sometimes packed by stone retaining walls.
•In hilly areas bench terraces is used for the purpose of converting hill slopes to suit agriculture.
•In some areas where the climatic conditions favour the growing of certain cash crops like potato,
coffee, the hill slopes are to be bench terraced before the area is put for cultivation of these crops.
•It also been adopted for converting sloping lands into irrigated fields or for orchard plantations.
JNKVV-College of Agriculture, Powarkheda 25

26. Types of Bench Terraces
Dependingonthepurposeforwhich
theyareused,benchterracesarealso
classifiedasfollows:
1.Hill-typebenchterraces:usedfor
hillyareaswithagradereversely
towardsthehill.
2.Irrigatedbenchterraces:level
benchesadoptedunderirrigated
conditions.
3.Orchardbenchterraces:narrow
widthterracesforindividualtrees.
JNKVV-College of Agriculture, Powarkheda 26

27. Depending upon the slope of
benches, bench terraces are
classified as.
(i)Bench terraces sloping
outward
(ii)Bench terraces sloping
inward
(iii)Bench terraces with
level top
JNKVV-College of Agriculture, Powarkheda 27

28. Bench Terraces Sloping Outward
•In bench terraces sloping outward, shoulder bund is essential even though such
a bund is provided in the other two types also for giving stability to the edge of
the terrace.
•In these terraces the rainfall thus conserved will have more time for soaking
into the soil.
Bench Terraces Sloping Inward
•Bench terraces with slopes inside are to be adopted in heavy rainfall areas
where a major portion of the rainfall is to be drained as surface runoff.
•In the case of these terraces, a suitable drain at the inward end of each of these
terraces is to be provided to drain the runoff.
•These drains ultimately lead to a suitable outlet.
•These are also known as hill-type terraces.
JNKVV-College of Agriculture, Powarkheda 28

29. 29
JNKVV
-
College of Agriculture,
Powarkheda
Bench Terraces with Level Top
•Benchterraceswithleveltoparesuitableforareasofmediumrainfall,evenly
distributedandhavingdeepandhighlypermeablesoils.
•Duetothefactthatnoslopeisgiventothebenchesitisexpectedthatthemost
oftherainfallcomingovertheareaistobeabsorbedbythesoilandverylittle
wateristogoassurfacedrainage.
•Thesetypesofterracesarealsousedwhereirrigationfacilitiesareavailableand
referredtoasirrigatedbenchterraces.

30. Thanks for listening…..
JNKVV-College of Agriculture, Powarkheda 30