NREM 301NREM 301ErosionErosion

D G B l dD G B l dDr. Greg BrulandDr. Greg Bruland

Geologic Geologic vsvs Accelerated Erosion WarmAccelerated Erosion Warm--UpUp1 2 3

www.wildmadagascar.org

4 5 6

Photo courtesy of Jim MansfieldPhoto USDA NRCS

7 8 9

2Photo USDA NRCS

Water Erosion

3

Photo courtesy of USDA NRCS

Detachment

D t h t &Detachment & Transport

4

5Zones of erosion & deposition in Guilin, ChinaZones of erosion & deposition in Guilin, China

6Mississippi Delta, MSMississippi Delta, MS

7South Shore Moloka‘iSouth Shore Moloka‘i

Types of Water Erosion

8

Streambank erosionStreambank erosion

9

USLE

A = R x K x LS x C x PWhere:A = Estimated Avg. Annual Soil Loss (T/ac-yr)R = Rainfall ErosivityK S il E dibili

Walter Wishmeier

K = Soil ErodibilityLS = Slope Length & SteepnessC C M tC = Cover-ManagementP = Supporting-Practice

10

Components of USLEp

Rainfall Erosivity Factor (R)Rainfall Erosivity Factor (R)

A = R x K x LS x C x PA R x K x LS x C x P

11

http://serc carleton edu/NAGTWorkshops/visualization/collections/soil erosion html

12

http://serc.carleton.edu/NAGTWorkshops/visualization/collections/soil_erosion.html

(Troeh et al. 2004)

13

Soil Erodibility Factor (K)Soil Erodibility Factor (K)

• Inherent soil erodibilityInherent soil erodibility• Rate of soil loss on a standard plot (72.6 ft

long on a 9% slope)long on a 9% slope)

A = R x K x LS x C x PA = R x K x LS x C x P

14

15

K factors are t b l t d f h iltabulated for each soil map unit in County Soil Surveys. y

16

17

K factor nomograph: K = (5 soil properties)

(Troeh et (al. 2004)

18

Slope Length & SteepnessSlope Length & Steepness Factor (LS)

LS is the ratio of expected soil loss per unit area of a particular field segmentunit area of a particular field segment compared to what would be lost from a 9% 72 6-ft-long slope with no cover9%, 72.6 ft long slope with no cover

A = R x K x LS x C x P

19

LS Lookup Tables

Example: Determine LS for ag field w/ slope of 5% & length of 400 ft.

20

Cover-Management Factor (C)Cover Management Factor (C)

A = R x K x LS x C x PA = R x K x LS x C x P

C = (5 subfactors)C = (5 subfactors)

C = PLU*CC*SC*SR*SM

21

22

23

Supporting-Practice (P) FactorSupporting Practice (P) Factor

• The fractional amount of erosion thatThe fractional amount of erosion that occurs when “special practices,” i.e. contour cultivation contour strip croppingcontour cultivation, contour strip cropping, & terracing, are used compared with erosion that would occur without themerosion that would occur without them.

A = R x K x LS x C x P

24

25

Example USLE Calculations

With conventional tillage:A= 170 x 0.26 x 1.62 x 0.20 x 1.0 = 14.3 t/a/yy

With conservation tillage:A = 170 x 0.26 x 1.62 x 0.11 x 1.0 = 7.9 t/a/y

With contour cultivation:With contour cultivation:A= 170 x 0.26 x 1.62 x 0.20 x 0.61 = 8.6 t/a/y

With cons. tillage & contour cult.:A = 170 x 0 26 x 1 62 x 0 11 x 0 61 = 4 8 t/a/y

26

A 170 x 0.26 x 1.62 x 0.11 x 0.61 4.8 t/a/y

Onsite: Gullying

28(www.wildmadagascar.org)

Offsite

High sediment loads in the Manambolo River (www.wildmadagascar.org)

29

Betsiboka River & estuary, image from Space Shuttle (NASA)

Water Erosion BMPs

1) Strip cropping) p pp g

2) Grassed waterways

3) Terraces3) Terraces

4) Conservation tillage

) ff5) Riparian buffers

30Photos courtesy of USDA NRCS.

Wind Erosion

31

Types of Wind Erosion

32

http://serc.carleton.edu/NAGTWorkshops/visualization/collections/soil_erosion.html

33

WEQE = (I’, K’, C’, L’, V)

Where:Where:E = Estimated Avg. Annual Soil Loss (T/ac-yr)I’ = Soil Erodibility K’ = Soil Ridge RoughnessC’ = ClimateL’ Width f fi ldL’ = Width of fieldV = Vegetative Cover

34

A l SAral Sea: Shrinking since 1960 due to diversion of water from 2 rivers (Syr Darya, Amu Darya) to

(Mussner 2005)

irrigate nearby crop land

35

36

•Salt concentration ↑ from 10 to >23‰, contributing to devastation of a once-thriving fishery.

•Local climate shifted, w/ hotter, drier summers & colder, longer winters.

•As water retreated, salty soil remained on exposed lake bed. Dust storms have blown up to 75,000 tons of this exposed soil annually, dispersing salt particles, pesticideannually, dispersing salt particles, pesticide residues.

•Air pollution caused widespread nutritional & i t il trespiratory ailments.

•Crop yields diminished.

37

(Perera 1993, Micklin 1992, Rich 1991, Perera 1988, United Nations Environment Programme 1992)

Wind Erosion BMPs

1) Conservation tillage

2) Barriers/Windbreaks

3) Moisture management3) Moisture management

4) Soil amendments

38(Photos courtesy of USDA NRCS)

Erosion Models• Water: USLE, MUSLE, RUSLE, RUSLE2, EPIC,

AGNPS, WEPP

• Wind: WEQ RWEQ WEPS39

• Wind: WEQ, RWEQ, WEPS

FallTypes ofof Mass Wast

Rotational slide/slump

Wast-ing

Translational slide

40

Flows

mudflow

debris flow

41

42