1. REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) for Construction Sites
Predicting Soil Erosion By Rainfall and Overflow
Presented by: Guangyan Griffin, P.E.,
Northern Region Construction
Alaska Department of Transportation and Public Facilities
T2 Research Project
Preface:
In early 2007, I was given a task to write a paper about adopting revised universal soil loss equation (RUSLE) in construction best management practice in Alaska. It started with fund from construction overhead and lately become a T2 research project aiming for an implementation of RUSLE in DOT construction projects. The report is for providing detailed guidance to ADOT&PF and consultants for RUSLE, and step-by-step examples of how to use RUSLE in a construction project on different phases. The content is be straight forward and user friendly that an engineer with little or no construction background can estimate soil loss with correct parameters provided by the guidance.
The final paper is near the completion and will be available soon.

2. OBJECTIVES Understand erosion processes Learn RUSLE and its factors
RUSLE’s application on construction sites

3. Erosion and Sedimentation
Erosion is a process of detachment and transport of soil particles by erosive agents.
Erosive Agents
Raindrop impact
Overland flow surface runoff from rainfall
The definition of Erosion is a process of detachment and transport of soil particles by: raindrop impact, and overland flow surface runoff from rainfall.
Sedimentation is the deposition of eroded material.
Sedimentation is the deposition of eroded material.

4. Here is a familiar schematic of these 5different types of erosion.

5. FACTORS AFFECTING EROSION
Climate
Soil
Topography
Land use
Cover
Supporting practices
Erosion is greatest where rainfall amount and intensity are highest.
Some soils are naturally more erodible than are other soils.
Steep and long slopes produce more erosion than do short and flat slopes.
Land use has a huge effect on erosion. Exposing the soil to raindrop and surface runoff dramatically increases erosion.

6. EROSION IS A CONCERN Degrades soil resource
Causes downstream sedimentation
Produces sediment which is a pollutant
Produces sediment that carries pollutants
Some of the reasons why we are concerned about erosion.

7. EROSION PREDICTION AS A TOOL
Evaluate impact of erosion prior to construction
Manage BMPs more effectively and economically
Doing it right the first time
Serve as technical rationale
Concept:
Estimate erosion rate under different conditions
The principal use of erosion has been a tool to guide conservation planning on agricultural fields.
It has also been a major tool used to estimate soil loss in the construction sites.

8. OVERVIEW OF RUSLE
RUSLE background
Where RUSLE applies
RUSLE factors

9. RUSLE HISTORY BACKGROUND
Zingg’s equation (1940)
Smith and Whitt’s equation (1947)
US Dept. of Agriculture: Agri. HandBooks
AH-282 (1965) – USLE, Wischmeier and Smith
AH-537 (1978) – Wischmeier and Smith
AH-703 (1997) – RUSLE, Renard and Froster
Office of Surface Mining Manual (mined, reclaimed land, construction sites) (1998)
Computer software:
- RUSLE1 (1992)
- RUSLE2 (2001)
RUSLE is a result of a century long erosion researches, starting with the desire to find out what cause soil loss that impact crop production.
Early erosion research by Ewald Wollny in Early erosion measurement in US in US established Federal erosion experiment stations in 1929
Zingg’s equation, Zingg is often credited with the development of the first erosion prediction equation used to evaluate erosion problems and select conservation practices to reduce excessive erosion. Zingg's equation was a simple expression that related soil erosion to slope steepness and slope length.
Smith and Whitt’s equation (1947), added terms to Zingg's equation to reflect the influence of cover and management on soil erosion.
It did not emphasize differences in rainfall erosivity or soil among locations. Thus, rainfall-erosivity and soil-erodibility terms were added to the Zingg and the Smith and Whitt equations.
AH-282, Predicting rainfall-erosion losses from cropland east of the Rocky Mountains (USLE). Wischmeier and Smith
AH-537, Predicting rainfall-erosion losses – a guide to conservation planning.
AH-703, A guide to conservation planning with the revised universal soil loss equation (RUSLE). Renard and Froster

10. RUSLE BACKGROUND
From the theory of erosion process that the soil loss is caused by rain drop impact and the overland flow.
Consists of a set of mathematical equations

11. RUSLE APPLICATIONS Cropland Pastureland Rangeland
Disturbed forest land
Construction sites
Surface mine reclamation
Military training lands
Parks
Waste disposal/landfills
RUSLE has nationwide and worldwide applications on the areas of agriculture, construction, mining and reclamation for site evaluation and planning, and aid to the decision process of selecting erosion control measures.

12. Landscape RUSLE Area Overland flow Interrill Rill
Gully (Concentrated flow)
This slide shows the portion of the landscape where interrill-rill (sheet) erosion may occur.
The dashed lines on the left show the RUSLE area that is depicted in the upper right hand corner of the screen and the dashed line on the left side represents a subwatershed divide for a the two concentrated flow watersheds.

13. RUSLE FACTORS A = R K L S C P
R- Rainfall-runoff erosivity factor
K- Soil erodibility factor
L- Slope length factor
S- Slope steepness factor
C- Cover-management factor
P- Supporting practices factor
The next few slides will give a brief overview of RUSLE.

14. EROSIVITY - R
22 years or longer rainfall data gathered by weather stations.
Single storm
Energy x 30 minute intensity
Annual-sum of daily values
Average annual-average of annual values
Monthly value=average annual x fraction that occurs on a given month
Erosivity is a measure of the forces actually applied to the soil by the erosive agents of raindrop impact, waterdrops falling from plant canopy, and surface runoff.
Studies show that erosion is directly related to the climate not only with rainfall duration but also with its intensity. The rainfall-runoff erosivity R-factor, or sometimes called Erosion Index EI, is calculated based on rainfall kinetic energy of the storm (E in ft-tons/acre-inch) times the maximum 30 min intensity (I30 in inch/hr) as given by Wischmeier and Smith (1978). It represents the combined energies of raindrop impact and water runoff causing soil particles to be detached and transported.

15. EROSIVITY - R Measure of erosivity of climate at a location
Las Vegas, NV 8 Phoenix, AZ 22 Anchorage, AK 26 Denver, CO 40 Fairbanks, AK 48 Syracuse, NY 80 Juneau, AK 101 Minneapolis, MN 110 Chicago, IL 140 Richmond, VA 200 Dallas, TX 275 Birmingham, AL 350 Charleston, SC 400 New Orleans, LA 700
Erosivity varies greatly by locations. We have
Las Vegas, NV 8
Anchorage, AK 26
Fairbanks, AK 48
New Orleans, LA 700
Climate is about 100 times more erosive in New Orleans than in Las Vegas.

16. R-factor for Alaska
Retrieved from USDA RUSLE2 computer program data file at fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm.
AK is broken into climate zones per common resource areas (CRA)
Way to acquire an R-Factor:
Determine the climate zone ID in which the construction project is located from the map
Look up the R-factor from the table
2. Instead of breaking the state down to counties like low 48, State of AK is broken into climate zones according to Common Resource Areas (CRA).

17. Alaska Rainfall erosivity map.
Here is the map will be use conjuction with the table coming up next. The shaded area represents Common Resource Area or CRA and also represents different climate zone. The number represents its climate zone ID.
Use as an example. So if I have a project in zone

18. Common Resource Areas
Key Locations
Climate Zone ID
Ri, Monthly
R, Annual
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Middleton Islands
220.1a
2.5
4.2 17 13 12 3 52
Alexander Archipelago
Craig, Ketchikan, Wrangell, Sitka, Juneau, Hoonah, Yakutat, Cordova, Wooded Islands
220.1b
4.4
8.9 28 21 20
6.7 89
Seldovia Area
Portlock, Port Graham, Seldovia
220.2
1.3
4.6
4.1
2.2 25
Lower Kenai Peninsula
Ushagat Island, E. Chuguch Island, Ragged Island, Chiswell Islands
220.3
4.8 10
9.2
2.4 41
Seward Area
Seward
220.4
2.7
4.9 15
3.6 53
Inner Prince William Sound
Whittier, Chenega
220.5
6.2 36 34 24
6.6
120
Kodiak Island Area
Kodiak, Chiniak, Afognak, Akhiok
221.1
6.8
Sitkinak-Chirikof Island Area
Chirkof Island, Aghlyuk Island, Kiliktagik Island
221.2
2.9 14 11 54
S. Alaska Coastal Mountains
Hyder, Snettisham, Skagway, Haine, Thompson Pass
222.1
6.3 45 35 33
9.6
140
Valdez Valley
Valdez
222.2
6.4 27 22 18 80
Cook Inlet Mountains
Rainy Pass, Cantwell, Sutton, Girdwood
223.1 44 42 19
170
Turnagain Area
Hope
223.2
1.7 4 16
Chugach Mountain Valleys
Eagle River
223.3
0.46
3.8
1.4
Homer-Fox River Area
Homer
224.1
0.91 2
7.5 6
5.3 23
Small River Areas
Anchor Pt, Ninilchik, Nikolaevsk
224.2
0.69
3.3
3.1
Ninilchik Uplands
224.3
0.78
1.5
Kenai Coastal Lowlands
Clam Gulch, Kaslof, Kenai, Nikiski
224.4
0.58
Kenai Lowlands
224.5
0.55
3.4
1.2
Kenai Foothills
Soldotna, Sterling
224.6
0.6
3.9
Anchorage Bowl
Anchorage, Birchwood
224.7
0.38
1.1 26
MatSu Lowlands
Wasila, Palmer
224.8 1
2.6
9.1
7.2 32
Knik Lowlands
Willow, Houston, Big Lake, Goose Bay, Pt Mackenzie
224.9
1.9
2.8
8.7
Then we can look down the table Climate Zone ID column and find 222.1, R = 140.

19. SOIL ERODIBILITY - K
Measure of K-factor under standard unit plot condition
72.6 ft long, 9% slope, tilled continuous fallow, up and down hill tillage
Represent the uniform soil at upper 6”of the subsoil (not topsoil) in a construction site
Major factors
Texture
Organic matter
Structure
Permeability
Erodibility is a measure of the susceptibility(inverse of resistance) of the soil to erosion.
A key point is that soil erodibility is determined under the standard reference condition where management effects have been eliminated by maintaining the unit plots in a continuous tilled, fallow conditions for a number of years.
The K value that is used if for the soil fines, but the influence of rock fragments in the soil profile should be considered in setting K values.
The effects of rock fragments on the soil surface is considered in the cover-management computations.

20. Obtain Soil Data Options: Perform gradation analysis
sand
silt
clay
Options:
Information in Alaska Soil Survey Report published by NRCS.
Using soil-erodibility nomograph chart or equation.
Use regression equations in AH-703, Renard et al. (1997).

21. Here is soil-erodibility nomograph published by USDA in 1971
Here is soil-erodibility nomograph published by USDA in It has five soil parameters: percent silt and very fine sand, percent sand, organic matter, and classes for structure and permeability.
In 1978, a nomograph equation was published (see bottom part of the chart).
M is represented the product of two primary particle size fractions.
OM is organic matter
s, p are classes of structure and permeability
The nomograph has its limitation, which does not applied to volcanic or organic soil. If the soil sample has particles larger than 2mm in diameter, then K value has to be adjusted to account for rock fragments.

22. Approximate K Values for Construction Soil Material
Soil Type
USCS Classifications
Percent Passing 3”
Percent Passing #10
Percent Passing #200
K-Factor
Sandy gravel, little or no fines1
GW, GP
85-100
15-35
0-5
0.02
Sandy Gravel1
20-40
5-7
0.04
Silty sandy gravel 1
GP-GM
20-50
7-10
0.05
25-55
10-15
0.08
Silty gravel, Silty sandy gravel 1
30-55
15-25
Gravelly sand2
SP-SM --
90-100
10-25
0.20
Coarse sand, sand, loam fine sand2 SM
75-100
15-40
Silty gravel, silty sand2
GM, SM
65-95
35-50
0.17
Silt loam2 ML
70-90
0.37
Sandy loam2
0.32
Fine sandy loam, loam2
ML, SM
80-100
20-60
Clay loam, gravelly loam, cobbly loam2 CL
55-75
Silty clay, clay, cobbly silty clay2
75-90
Rock, shotrock, ripped rock 1 GP
20-30
< 15
This is a table I made for your use. It lists some approximate K values for construction soil material.
1. K value is calculated through Soil-Erodivity Nomograph.
2. Information is from National Resources Conservation Services (NRCS) soil survey of Alaska.
If we know the gradation and soil description, we can know certain type of soil k-factor if it falls in these particle size range.

23. TOPOGRAPHY - LS Slope length (L) and steepness (S) are major factors
Watershed topography affects erosion rate and sediment transport
Steep slopes typically result in rapid runoff
Long slopes acuminate more runoff
These are the main variables that determine how topography affects erosion.

24. Hillslope Shape Convex Uniform Complex-Convex:concave
These are typical hillslope shapes.
Complex-Convex:concave
Complex-Concave:convex
Concave

25. Slope Length for Uniform Slope
SOIL LOSS
SEDIMENT
YIELD
SLOPE LENGTH
In this simple uniform slope, sediment yield, which is the amount of sediment delivered to the end of the slope equals soil loss. Slope length is measured from the top of the slope to the foot in the horizontal direction.
RUSLE
ESTIMATES
TO HERE

26. Slope Length for Complex Slope
Soil loss
Deposition
Sediment yield
This complex slope has a concave section where deposition occurs. The portion of the slope from the beginning of the slope to where deposition begins is the eroding portion of the slope.
Soil loss occurs on the eroding portion of the slope. It is this soil loss that would be used in conservation planning to protect this hillslope from excessive erosion.
Sediment yield is less than soil loss because of the deposition.
Sediment Yield = Soil Loss - Deposition
SLOPE LENGTH

27. Even though deposition occurs on a slope with strips, the entire slope length is used because the runoff that flows over the lower portion of the slope originated at the top of the hillslope slope.
Although deposition occurred, runoff flowed through the depositional area and through the strips to downslope areas.

28. Horizontal slope length (ft)
Values for LS for Construction Sites
Slope
Horizontal slope length (ft) %
<3 6 9 12 15 25 50 75
100
150
200
250
300
400
600
800
1000
0.2
0.05
0.06
0.5
0.07
0.08
0.09
0.10
0.11
0.12
0.13
1.0
0.14
0.15
0.17
0.18
0.19
0.20
0.22
0.24
0.26
0.27
2.0
0.16
0.21
0.25
0.28
0.33
0.37
0.40
0.43
0.48
0.56
0.63
0.69
3.0
0.30
0.36
0.41
0.50
0.57
0.64
0.80
0.96
1.10
1.23
4.0
0.38
0.47
0.55
0.68
0.79
0.89
0.98
1.14
1.42
1.65
1.86
5.0
0.23
0.31
0.46
0.58
0.86
1.02
1.16
1.28
1.51
1.91
2.25
2.55
6.0
0.54
0.82
1.05
1.25
1.43
1.60
1.90
2.43
2.89
3.30
8.0
0.32
0.45
0.70
0.91
1.72
1.99
2.24
2.70
3.52
4.24
4.91
10.0
0.35
0.39
1.20
1.46
1.92
2.34
2.72
3.09
3.75
4.95
6.03
7.02
12.0
0.49
0.71
1.15
1.54
1.88
2.51
3.07
3.60
4.09
5.01
6.67
8.17
9.57
14.0
0.51
0.85
1.40
1.87
2.31
3.81
4.48
5.11
6.30
8.45
10.40
12.23
16.0
0.62
0.67
1.64
2.21
2.73
3.68
4.56
5.37
6.15
7.60
10.26
12.69
14.96
20.0
0.76
0.84
1.24
2.10
2.86
3.57
4.85
6.04
7.16
8.23
10.24
13.94
17.35
20.57
25.0
0.93
1.04
1.56
2.67
3.67
4.59
7.88
9.38
10.81
13.53
18.57
23.24
27.66
30.0
0.72
1.08
3.22
4.44
5.58
7.70
9.67
11.55
13.35
16.77
23.14
29.07
34.71
40.0
0.53
1.13
1.37
1.59
2.41
5.89
7.44
10.35
13.07
15.67
18.17
22.95
31.89
40.29
48.29
50.0
0.97
1.31
1.62
2.91
5.16
7.20
9.13
12.75
16.16
19.42
22.57
28.60
39.95
50.63
60.84
60.0
1.07
1.47
1.84
2.19
3.36
5.97
8.37
10.63
14.89
18.92
22.78
26.51
33.67
47.18
59.93
72.15
This is a table from Wischmeier AH 537 for construction sites for unfrozen soil.
When we know a hillslope length of 50’ and slope of 50%, LS value can be found at 5.16.

29. LS Factor for Complex Slope
break it down into several fairly uniform segments where the gradient changes, preferably into equal lengths
Number
of segments
Sequential number of segments
Slope Gradient (H:V)
50:1
20:1
15:1
12:1
10:1
8:1
6:1
5:1
4:1
3:1
2.5:1
2:1
1.75:1 2 1
0.76
0.67
0.65
0.63
0.62
0.61
0.6
0.59
0.58
0.57
0.56
1.24
1.33
1.35
1.37
1.38
1.39
1.4
1.41
1.42
1.43
1.44 3
0.53
0.51
0.48
0.47
0.46
0.44
0.43
0.42
0.41
0.4
1.06
1.05
1.04
1.03
1.29
1.45
1.47
1.48
1.5
1.52
1.53
1.54
1.55
1.56
1.57 4
0.45
0.39
0.37
0.36
0.35
0.34
0.33
0.32
0.94
0.89
0.88
0.87
0.86
0.85
0.84
0.83
0.82
0.81
1.16
1.20
1.21
1.22
1.23
1.32
1.46
1.49
1.58
1.59
1.6
1.62
1.63
1.64 5
0.40
0.3
0.29
0.28
0.27
0.26
0.79
0.75
0.74
0.72
0.71
0.7
0.69
0.68
1.28
1.30
1.31
1.34
1.36
1.61
1.65
1.66
1.67
1.68
This is also from AH 537 for complex slope LS value calculation. The way to do it is to break it down into several equal length of segments at slope gradient changes. This table provide a fraction factor multiplier to the value from the previous table.

30. Cover Management Factor C
The factor representing the site’s cover protection from rainfall impact.
The ratio of erosion between a specific ground cover and bare ground.
Bare ground condition is defaulted as 1, other ground covers are compared to the bare ground.

31. Cover-Management Effects
Raindrops intercepted by canopy cover
Raindrops not intercepted by canopy cover
Canopy cover
Intercepted rainfall falling from canopy cover
Ground cover
Ridges
This schematic illustrates the position of each cover effects.
Canopy cover like trees and bushes intercepts raindrops and reduce their energies.
Ground cover like grass, mulch, erosion control blanket, or rock cover also intercepts raindrops, slowdown runoff.
Live or dead roots increase infiltration , holding soil in place, in turn of reducing the runoff
Buried residue
Live roots
Dead roots

32. Erosion Control Technology Council (ECTC) http://www.ectc.org/
Industry authority in the development of standards, testing, and installation techniques
Rolled erosion control products (RECPs),
Hydraulic erosion control products (HECPs)
Sediment retention fiber rolls (SRFRs).
The organization, Erosion Control Technology Council provides standards of specification, testing and installation techniques for these products.

33. Table ECTC Standard Specification For Temporary Rolled Erosion Control Products (
For use where natural vegetation alone will provide permanent erosion protection.
ULTRA SHORT-TERM - Typical 3 month functional longevity.
Type
Product Description
Material Composition
Slope Applications*
Maximum Gradient
C Factor2, 5
1.A
Mulch Control Nets
A photodegradable synthetic mesh or woven biodegradable natural fiber netting.
5:1 (H:V)
< 0.10
1.B
Netless Rolled Erosion Control Blankets
Natural and/or polymer fibers mechanically interlocked and/or chemically adhered together to form a RECP.
4:1 (H:V)
1.C
Single-net Erosion Control Blankets & Open Weave Textiles
Processed degradable natural and/or polymer fibers mechanically bound together by a single rapidly degrading, synthetic or natural fiber netting or an open weave textile of processed rapidly degrading natural or polymer yarns or twines woven into a continuous matrix.
3:1 (H:V)
< 0.15
1.D
Double-net Erosion Control Blankets
Processed degradable natural and/or polymer fibers mechanically bound together between two rapidly degrading, synthetic or natural fiber nettings.
2:1 (H:V)
< 0.20
SHORT-TERM - Typical 12 month functional longevity.
2.A
2.B
2.C
An erosion control blanket composed of processed degradable natural or polymer fibers mechanically bound together by a single degradable synthetic or natural fiber netting to form a continuous matrix or an open weave textile composed of processed degradable natural or polymer yarns or twines woven into a continuous matrix.
This table is from ECTC, for erosion control blanket. It provides C-factor of a blanket according to the type and hill slope.

34. C-factor for Other Covers (Pitt, Clark and Lake, 2007; Fifield, 2004)
Type
Percent Ground Cover (%)
Temporary Grass 1
Permanent Grass2
Mechanically Cleared Site3
Not given
Hydraulic Mulching4
This table I created for your use, for these different type of ground covers.
It’s from the sources listed at top.

35. Mulch (Mechanical) and Rock Cover (Wischmeier and Smith, 1978)
Type of Mulch
Mulch Rate (tons/acre)
Land Slope (%)
Max Length1 (ft)
C Factor
None
all - 1
Straw/hay,
tied down by anchoring and tacking equipment2
1-5
200
0.2
6-10
100
1.5
300
0.12
150 2
400
0.06
11-15
0.07
16-20
0.11
21-25 75
0.14
26-33 50
0.17
34-50 35
Crushed stone,
¼ to 1 ½ in
135
<16
0.05
21-33
240
<21
0.02
Wood chips 7
0.08 12 25
Another table from Agricultural Handbook for different mulching at various application rates and slopes.

36. Supporting Practices (P)
Conservation practices are controllable, experience-driven and interactive measures.
They can:
enhance the factors of cover and soil texture
mitigate the influence of rainfall and runoff
modify flow path length and steepness
It’s a controllable, experience-driven and interact measures.
What it does is:
enhance the factors of cover and soil texture
mitigate the influence of rainfall and runoff
modify flow path length and steepness

37. Supporting Practices Strips/barriers Diversions Impoundments
Buffer strips,
Filter fence,
Wattles
Straw bales,
Gravel bags
Diversions
Channel
Terrace
Impoundments
Sediment traps
Detention / retention pond
Strips and barriers slows runoff, reduce its transport capacity, and produce deposition.
Strips/barriers spread the runoff, reducing its erosivity.
Many type strips/barriers are used depending on land use.
Terraces/diversions are ridges-channels placed on the hillslope to intercept runoff.
In effect, terraces/diversions shorten slope length.
Terraces are channels on such flat grades that deposition occurs in them because transport capacity is less than incoming sediment load, provided the grade of the terrace channel is sufficient flat.
Diversions are design with a grade sufficiently steep that deposition doesn’t occur and with a grade sufficiently flat that erosion doesn’t occur.
Impoundments trap and retain runoff, giving sediment time to settle and be deposited.
Discharge for small basins can be discharged to an underground tile line thus eliminating concentrated flow at that point.
Storage of runoff in impoundments reduce flow rate, and thus reduce concentrated flow erosion.

38. P-factor for Construction Sites (Fifield 2004 and Foster & Toy 1998)
Surface Condition with No Cover
P-factor
Bare soil, trackwalks along contour
1.2
Bare soil, rough, loose surface
1.0
Bare soil, trackwalks up and down slope
0.9
Silt fence barrier, continuous berm, gravel filter 1, 2
0.6
Sediment containment systems (sediment traps/basin), rock check dam 3
Sandbag or bale barriers 1, 2
Rock barriers at sump location, diameter 1”-2” 1
0.8
Grass buffer strips, with minimum 50 ft width and 65% ground cover % basin slope
11% to 24% basin slope
This table I created from sources listed above. The higher the value is , the less effectiveness of the practice to reduce erosion.
Bare soil condition , trackwalk along contour actually increase erosion.
Sediment containment systems have P-factor ranged 0.1 – 0.9, depending on their capacity and working condition.

39. Examples
Steese Hwy R=31 Silty gravel (GM) K= % passing #10 35% passing # :1 Slope/60 ft long LS=4.9 RKLS = 26 Tons/acre/yr

40. Examples C=1, up and down slope trackwalking P= 0.9
70% perennial grass cover C=0.0275, P =1
Mulching C=0.02, tracked P=0.9
CP x RKLS = 0.9x26 = 23 Tons/acre/yr
CP x RKLS = x26 = 0.7 Tons/acre/yr
CP x RKLS = 0.02x0.9x26 = 0.5 Tons/acre/yr

41. Examples Valdez R=80 Silty gravel (GM) K=0.17 80 % passing #10
2.5:1 Slope/60 ft long LS=4.9
RKLS = 67 Tons/acre/year

42. Examples C=1, up and down slope trackwalking P= 0.9
70% perennial grass cover C=0.0275, P =1
Mulching C=0.02, tracked P=0.9
CP x RKLS = 0.9x67 = 60 Tons/acre/yr
CP x RKLS = x67 = 1.8 Tons/acre/yr
CP x RKLS = 0.02x0.9x67 = 1.2 Tons/acre/yr

43. SUMMARY
RUSLE is only for interrill and rill erosion, not for gully and channel erosion.
The result from RUSLE is estimated soil loss rate, cannot be interpreted as actual soil loss rate.
RUSLE AK use on unfrozen soil only