REVISED UNIVERSAL SOIL LOSS EQUATION Version 1.06

1
REVISED UNIVERSAL SOIL LOSS EQUATIONVersion 1.06

• (RUSLE 1.06)

2
REVISED UNIVERSAL SOIL LOSS EQUATIONVersion 1.06

• Part I Model Development

3
What is RUSLE 1.06?

• It is a DOS-based model for estimating soil loss
  from hillslopes caused by raindrop impact and
  overland flow based on earlier versions of RUSLE
  and the Universal Soil Loss Equation that should
  work on Windows operating systems Windows95
  through Windows XP

4
What is RUSLE 1.06?

• It is a DOS-based model for estimating soil loss
  from hillslopes caused by raindrop impact and
  overland flow based on earlier versions of RUSLE
  and the Universal Soil Loss Equation that should
  work on Windows operating systems Windows95
  through Windows XP
• New ability to estimate sediment yield by
  estimating deposition on low-slope or dense
  vegetation areas

5
What is RUSLE 1.06?

• It is a DOS-based model for estimating soil loss
  from hillslopes caused by raindrop impact and
  overland flow based on earlier versions of RUSLE
  and the Universal Soil Loss Equation that should
  work on Windows operating systems Windows95
  through Windows XP
• New ability to estimate sediment yield by
  estimating deposition on low-slope or dense
  vegetation areas
• RUSLE 1.06 is especially designed to be used on
  mined lands, construction sites, and reclaimed
  lands

6
What is RUSLE 1.06?

• It is a DOS-based model for estimating soil loss
  from hillslopes caused by raindrop impact and
  overland flow based on earlier versions of RUSLE
  and the Universal Soil Loss Equation that should
  work on Windows operating systems Windows95
  through Windows XP
• New ability to estimate sediment yield by
  estimating deposition on low-slope or dense
  vegetation areas
• RUSLE 1.06 is especially designed to be used on
  mined lands, construction sites, and reclaimed
  lands
• Limitations
• - It does not estimate gully or
  stream-channel erosion, it estimates soil
• loss only from rill and interrill
  erosion
• - Soil losses are long term average
  amounts, not specific rainfall event
• estimates

7
What is RUSLE 1.06? (cont.)

• - Provides soil loss estimates, not soil
  loss absolutes, and is the best
• technology available at this time

8
What is RUSLE 1.06? (cont.)

• - Provides soil loss estimates, not soil
  loss absolutes, and is the best
• technology available at this time
• - Limits have been established for which
  hillslope length and gradient
• have been verified

9
What is RUSLE 1.06? (cont.)

• - Provides soil loss estimates, not soil
  loss absolutes, and is the best
• technology available at this time
• - Limits have been established for which
  hillslope length and
• gradient have been verified
• - Does not produce watershed-scale
  sediment yields and

10
What is RUSLE 1.06? (cont.)

• - Provides soil loss estimates, not soil
  loss absolutes, and is the best
• technology available at this time
• - Limits have been established for which
  hillslope length and gradient
• have been verified
• - Does not produce watershed-scale sediment
  yields and
• - Caution should be applied when used in
  geographical areas beyond
• that for which it has been developed
  (such as mountainous or
• undisturbed forested areas).
• For more information on the limitations that
  apply to the USLE which would also be applicable
  to RUSLE 1.06, see Wischmeier, W.H. 1976. Use
  and misuse of the universal soil loss equation.
  J Soil and Water Cons. 31(1)5-9.

11
Development of RUSLE 1.06

• Is the USLE still good enough to use?
• Can RUSLE 1.04 be used or modified for minelands,
  construction sites and reclaimed lands?
• Is either better than the other?

12
Development of RUSLE 1.06

• A Task Working Group established in 1997 by Joe
  R. Galetovic, Tech. Coordinator, Office of
  Technology, OSMRE, Western Regional Coordinating
  Center, Denver CO
• The groups objective was to evaluate the
  usefulness of RUSLE 1.04 to provide soil loss
  estimates for lands disturbed by mining and
  construction activities and/or modify it if
  necessary
• Chair of the working group was Dr. Terrence Toy,
  Dept. of Geography, Univ. of Denver

13
Development of RUSLE 1.06 (cont.)

• Chapter authors and other working group members
  included
• Ken Renard, USDA, ARS (retired)
• Glenn Weesies, USDA, NRCS
• Stephan Schroeder, ND Public Service
  Commission
• William Kuenstler, USDA, NRCS
• Gary Wendt, Peabody Western Coal Co.
• Richard Warner, Dept. Agricultural
  Engineering, Univ. of Kentucky
• William Agnew, Revegetation Environmental
  Consultants
• Scott Davis, USDI, BLM
• James Spotts, OSM, Appalachian Regional
  Coordinating Center
• Co-editors of the guidelines manual were Dr. Toy
  and Dr. George Foster, USDA, ARS
• Additional technical and programming support was
  provided by Dr. Foster and Dr. Daniel Yoder,
  Univ. of Tennessee

14
Informational Sources

• Most of the information for this presentation is
  covered in the following
• Toy, Terrence J. and George R. Foster
  (co-editors). 1998. Guidelines for the Use of
  the Revised Universal Soil Loss Equation (RUSLE)
  Version 1.06 on Mined Lands, Construction Sites,
  and Reclaimed Lands. OSM, Western Regional
  Coordinating Center, 1999 Broadway, Suite 3320,
  Denver, CO. 80202-5733
• Toy, T.J., G.R. Foster, and K.G. Renard. 1999.
  RUSLE for mining, construction, and reclamation
  lands. J. Soil and Water Conservation 54(2)
  462-467.
• Renard, K.G., G.R. Foster, G.A. Weesies, D.K.
  McCool, and D.C. Yoder. 1997. Predicting Soil
  Erosion by Water A Guide to Conservation
  Planning with the Revised Universal Soil Loss
  Equation (RUSLE). USDA, Agricultural Handbook
  No. 703, 404 pp.

15
Erosion Definitions

• Erosion This involves a group of processes by
  which soil is moved from its point of origin in a
  field to another place in the field or off the
  field entirely. This soil movement involves
  detachment, transport, and deposition processes.

16
Erosion Definitions

• Erosion This involves a group of processes by
  which soil is moved from its point of origin in a
  field to another place in the field or off the
  field entirely. This soil movement involves
  detachment, transport, and deposition processes.
• Soil loss This is soil particles or aggregates
  actually removed from a hillslope segment. The
  amount actually be negative if deposition on the
  segment exceeds erosion. Losses caused by water
  runoff may be in the form of interrill, rill, or
  gully erosion.

17
Erosion Definitions

• Erosion This involves a group of processes by
  which soil is moved from its point of origin in a
  field to another place in the field or off the
  field entirely. This soil movement involves
  detachment, transport, and deposition processes.
• Soil loss This is soil particles or aggregates
  actually removed from a hillslope segment. The
  amount actually be negative if deposition on the
  segment exceeds erosion. Losses caused by water
  runoff may be in the form of interrill, rill, or
  gully erosion.
• Sediment yield This is the fraction of eroded
  soil which leaves the hillslope. The sediment
  delivery ratio is the ratio between soil loss and
  erosion (values range from essentially 0 to 1).

18
RUSLE 1.06 Model

• RUSLE 1.06 consists of many mathematical
  equations derived from erosion research data to
  estimate soil loss

19
RUSLE 1.06 Model

• RUSLE 1.06 consists of many mathematical
  equations derived from erosion research data to
  estimate soil loss
• The model retains the same structure of that of
  the USLE, namely
• A R K L S C P
  
• Where A Average annual soil loss
  (tons/acre/year)
• R Rainfall/runoff erosivity
  factor
• K Soil erodibility factor
• L Hillslope length
• S Hillslope steepness
• C Cover management factor
• P Support practice factor

20
Soil Loss Estimation (A)

• Average annual and seasonal interrill and rill
  erosion

21
Soil Loss Estimation (A)

• Average annual and seasonal interrill and rill
  erosion
• Estimated accuracy of the estimated soil loss
  values
• 1ltAlt4 tons/ac/year 50
• 4ltAlt30 tons/ac/year 25
• 30ltAlt50 tons/ac/year 50
• Least accurate when Alt1 or Agt50
  tons/ac/year
• See article by Risse, L.M., M.A. Nearing, A.D.
  Hicks, and J.M. Laflen. 1993. Error assessment
  in the Universal Soil Loss Equation. J Soil Sci.
  Soc. Am. 57(3)825-833.

22
Rainfall/Runoff Erosivity (R)

• Factor is composed of the average annual sum of
  total storm kinetic energy during rainfall from a
  record of at least 22 years
• See article by Wischmeier,W.H. and D.D. Smith.
  1958. Rainfall energy and its relationship to
  soil loss. Am. Geophy. Union Trans.
  39(2)285-291.

23
Rainfall/Runoff Erosivity (R)

• Factor is composed of the average annual sum of
  total storm kinetic energy during rainfall from a
  record of at least 22 years
• Values are given for more than 1000 locations in
  the western U.S. to account for mountainous
  effects
• See article by Wischmeier,W.H. and D.D. Smith.
  1958. Rainfall energy and its relationship to
  soil loss. Am. Geophy. Union Trans.
  39(2)285-291.

24
Rainfall/Runoff Erosivity (R)

• Factor is composed of the average annual sum of
  total storm kinetic energy during rainfall from a
  record of at least 22 years
• Values are given for more than 1000 locations in
  the western U.S. to account for mountainous
  effects
• Effect of water ponding on the surface can
  account for a reduction in the rainfall erosivity
  and can be factored into the R value in RUSLE
  1.06
• See article by Wischmeier,W.H. and D.D. Smith.
  1958. Rainfall energy and its relationship to
  soil loss. Am. Geophy. Union Trans.
  39(2)285-291.

25
Rainfall/Runoff Erosivity (R)

• Factor is composed of the average annual sum of
  total storm kinetic energy during rainfall from a
  record of at least 22 years
• Values are given for more than 1000 locations in
  the western U.S. to account for mountainous
  effects
• Effect of water ponding on the surface can
  account for a reduction in the rainfall erosivity
  and can be factored into the R value in RUSLE
  1.06
• Most accurate where rainfall exceeds 20
  inches/year
• See article by Wischmeier,W.H. and D.D. Smith.
  1958. Rainfall energy and its relationship to
  soil loss. Am. Geophy. Union Trans.
  39(2)285-291.

26
Soil Erodibility (K)

• Represents the susceptibility or resistance of
  soil to detachment by either raindrop impact or
  overland flow and the potential of the soil to
  generate runoff measured under very specific unit
  plot conditions

27
Soil Erodibility (K)

• Represents the susceptibility or resistance of
  soil to detachment by either raindrop impact or
  overland flow and the potential of the soil to
  generate runoff measured under very specific unit
  plot conditions
• Major factors affecting K include
• - Texture
• - Clay - Very cohesive and resistant
  to erosion
• - Silt - Easily detached,
  susceptible to crusting, high runoff
• potential
• - Sand Easily detached, not easily
  transportable, low runoff
• potential
• - Silt loam Moderately resistant
  to detachment, moderate to
• high runoff
  potential,

28
Soil Erodibility (K)

• Represents the susceptibility or resistance of
  soil to detachment by either raindrop impact or
  overland flow and the potential of the soil to
  generate runoff measured under very specific unit
  plot conditions
• Major factors affecting K include
• - Texture
• - Clay - Very cohesive and resistant
  to erosion
• - Silt - Easily detached,
  susceptible to crusting, high runoff
• potential
• - Sand Easily detached, not easily
  transportable, low runoff
• potential
• - Silt loam Moderately resistant
  to detachment, moderate to
• high runoff
  potential,
• - Organic matter aids in particle
  cohesiveness, generally increases
• 
  infiltration,

29
Soil Erodibility (K) (cont.)

• - Structure Affects mainly detachment
  and infiltration, and

30
Soil Erodibility (K) (cont.)

• - Structure Affects mainly detachment
  and infiltration, and
• - Permeability Affects the amount of
  potential runoff.

31
Soil Erodibility (K) (cont.)

• - Structure Affects mainly detachment
  and infiltration, and
• - Permeability Affects the amount of
  potential runoff.
• For example, a general combination of
  the effects of texture and
• permeability on runoff would be as
  follows
• 
  Permeability
  Potential
• Texture Code
  Rate (in/hr) Runoff
• SiC, C 6 (Very slow)
  lt0.04 High
• SiCL, SC 5 (Slow)
  0.04 0.08
• SCL, CL 4 (Slow to
  moderate) 0.08 0.20
• L, SiL, Si 3 (Moderate)
  0.20 0.80
• LS, SL 2 (Moderately
  rapid) 0.80 2.40 Low
• S 1 (Rapid)
  gt2.40 Very
  Low
• (For soils that tend to seal or develop
  surface crusts, it is recommended that the
  permeability class be lowered by one or two
  classes)

32
Soil Erodibility (K) (cont.)

• Values for disturbed soils should be computed
  using the soil-erodibility nomograph process
  within the model using values representing the
  upper 6 inches of the fill material recognizing
  that the nomograph does not apply to organic
  soils or soils of volcanic origin (Hawaii)

33
Soil Erodibility (K) (cont.)

• Values for disturbed soils should be computed
  using the soil-erodibility nomograph process
  within the model using values representing the
  upper 6 inches of the fill material recognizing
  that the nomograph does not apply to organic
  soils or soils of volcanic origin (Hawaii)
• Although RUSLE 1.06 currently calculates a
  time-varying K, problems have arisen at certain
  locations and this calculation in RUSLE will most
  likely be removed in the near future. Thus care
  should be used whenever this information is
  presented.

34
Soil Erodibility (K) (cont.)

• Effects of rock fragments 0.75 inch in diameter
  or more in the
• profile are accounted for in the nomograph
  process within the
• model for the estimation of K (rock
  fragments on the surface are
• taken into account in the C factor) to
  reflect influences on
• permeability.

35
Soil Erodibility (K) (cont.)

• Effects of rock fragments 0.75 inch in diameter
  or more in the
• profile are accounted for in the nomograph
  process within the
• model for the estimation of K (rock
  fragments on the surface are
• taken into account in the C factor) to
  reflect influences on
• permeability.
• Soil loss estimate accuracies
• - Most accurate for medium textured soils
  such as loams and silt
• loams
• - Moderately accurate for fine-textured
  soils such as sandy clay, silty
• clay, and clay, and
• - Acceptable accuracy for coarse-textured
  soils such as sands and
• loamy sands

36
Hillslope Length and Gradient Factor (LS)

• Definition Effect of slope gradient and length
  on soil loss as compared to unit plot conditions

37
Hillslope Length and Gradient Factor (LS)

• Definition Effect of slope gradient and length
  on soil loss as compared to unit plot conditions
• Generally speaking, as hillslope length and/or
  hillslope gradient increase, soil loss increases
  because
• 1. As length increases, the progressive
  accumulation of runoff in the
• downslope direction generally results
  in greater transport
• capability,
• 2. As slope gradient increases, the
  velocity and erosivity of the
• runoff increases thereby creating the
  possibility of increased soil
• loss due to increased transport
  capacity, and
• 3. As runoff amount and velocity increase,
  the runoff itself may cause
• additional detachment. In fact, if
  runoff becomes deep enough,
• raindrop impact detachment may become
  minimal and all the
• detachment may come from the runoff.

38
Hillslope Length and Gradient Factor (LS) (cont.)

• Hillslope Length
• - Defined as the distance from the point of
  origin of the runoff or
• overland flow to the point where either
  deposition begins or the
• runoff becomes concentrated in a
  well-defined channel

39
Hillslope Length and Gradient Factor (LS) (cont.)

• Hillslope Length
• - Defined as the distance from the point of
  origin of the runoff or
• overland flow to the point where either
  deposition begins or the
• runoff becomes concentrated in a
  well-defined channel
• - L factor has a value of 1 for a unit plot
  72.6 feet in length with a
• gradient of 9 under fallow conditions
  using the equation
• L (? /
  72.6)m
• where ? is hillslope length and the
  exponent m is a variable slope-
• length exponent related to the ratio of
  rill to interrill erosion
• designated as ß in the formula m ß / (
  1 ß )

40
Hillslope Length and Gradient Factor (LS) (cont.)

• Hillslope Length
• - Defined as the distance from the point of
  origin of the runoff or
• overland flow to the point where either
  deposition begins or the
• runoff becomes concentrated in a
  well-defined channel
• - L factor has a value of 1 for a unit plot
  72.6 feet in length with a
• gradient of 9 under fallow conditions
  using the equation
• L (? /
  72.6)m
• where ? is hillslope length and the
  exponent m is a variable slope-
• length exponent related to the ratio of
  rill to interrill erosion
• designated as ß in the formula m ß / (
  1 ß )
• - L values remain at 1 if soil loss is
  entirely generated by interrill
• erosion but will increase linearly with
  length if rill erosion
• dominates

41
Hillslope Length and Gradient Factor (LS) (cont.)

• Rill to interrill ratio A function of soil
  texture and general land use, its effect on the
  calculation of the L factor is a major change in
  RUSLE 1.06 versus earlier versions. Values have
  been programmed into the model to adjust the
  calculated L factor using the soil texture and
  land use inputted by the user.

42
Hillslope Length and Gradient Factor (LS) (cont.)

• Rill to interrill ratio A function of soil
  texture and general land use, its effect on the
  calculation of the L factor is a major change in
  RUSLE 1.06 versus earlier versions. Values have
  been programmed into the model to adjust the
  calculated L factor using the soil texture and
  land use inputted by the user.
• - Texture effects on rill to interrill
  ratio
• High (gt85) silt soils are assumed to
  have high rill to interrill ratio
• Silt loams are assumed to have high to
  moderate ratios
• Soils high in sand are assumed to have
  moderate to low ratios
• High clay (gt35) soils are assumed to
  have low ratios

43
Hillslope Length and Gradient Factor (LS) (cont.)

• Rill to interrill ratio A function of soil
  texture and general land use, its effect on the
  calculation of the L factor is a major change in
  RUSLE 1.06 versus earlier versions. Values have
  been programmed into the model to adjust the
  calculated L factor using the soil texture and
  land use inputted by the user.
• - Texture effects on rill to interrill
  ratio
• High (gt85) silt soils are assumed to
  have high rill to interrill ratio
• Silt loams are assumed to have high to
  moderate ratios
• Soils high in sand are assumed to have
  moderate to low ratios
• High clay (gt35) soils are assumed to
  have low ratios
• - General land use effects
• Mined or construction lands high ratio
• Croplands and disturbed forests
  moderate ratio
• No-till cropland, pastures, rangelands
  low ratio

44
Hillslope Length and Gradient Factor (LS) (cont.)

• Length (cont.)
• - Soil loss estimates are not as sensitive
  to this factor as to gradient
• thus the difficulty in establishing the
  point of origin of overland
• flow will not cause large errors

45
Hillslope Length and Gradient Factor (LS) (cont.)

• Length (cont.)
• - Soil loss estimates are not as sensitive
  to this factor as to gradient
• thus the difficulty in establishing the
  point of origin of overland
• flow will not cause large errors
• - Areas of micro-depressional deposition of
  sediment does not
• constitute the end of the slope length

46
Hillslope Length and Gradient Factor (LS) (cont.)

• Length (cont.)
• - Soil loss estimates are not as sensitive
  to this factor as to gradient
• thus the difficulty in establishing the
  point of origin of overland
• flow will not cause large errors
• - Areas of micro-depressional deposition of
  sediment does not
• constitute the end of the slope length
• - Main area of deposition to terminate
  slope length occurs on
• concave hillslopes and can be found using
  a rule of thumb
• If no signs of deposition are present on
  a concave slope profile, it
• can be assumed that deposition begins
  where the gradient is ½ of
• the average gradient for the concave
  hillslope profile. Thus if the
• average slope gradient is 10, then
  deposition would presume to
• begin at the location where the slope
  gradient is 5.

47
Hillslope Length and Gradient Factor (LS) (cont.)

• General Comments on Hillslope Length
• - Hillslope lengths rarely exceed 400 in
  natural landscapes
• - RUSLE 1.06 will not allow total slope
  length to exceed 1000 feet

48
Hillslope Length and Gradient Factor (LS) (cont.)

• General Comments on Hillslope Length
• - Hillslope lengths rarely exceed 400 in
  natural landscapes
• - RUSLE 1.06 will not allow total slope
  length to exceed 1000 feet
• - Accuracy for hillslope lengths of 35 to
  300 feet are the most accurate,
• moderately accurate for lengths of 20 to
  50 and 300 to 600 feet,
• poorest for slope lengths 600 to 1000
  feet

49
Hillslope Length and Gradient Factor (LS) (cont.)

• General Comments on Hillslope Length
• - Hillslope lengths rarely exceed 400 in
  natural landscapes
• - RUSLE 1.06 will not allow total slope
  length to exceed 1000 feet
• - Accuracy for hillslope lengths of 35 to
  300 feet are the most accurate,
• moderately accurate for lengths of 20 to
  50 and 300 to 600 feet,
• poorest for slope lengths 600 to 1000
  feet
• - Measurement of hillslope length can be
  either horizontal or along the
• hillslope (easier and more accurate for
  the latter, especially for longer
• hillslopes)

50
Hillslope Length and Gradient Factor (LS) (cont.)

• - Hillslope lengths from topographic maps
  and GIS databases are
• usually overestimated because of
  difficulty in ascertaining the point
• where overland flow begins and the ending
  point where the runoff
• becomes concentrated in a flow channel,
  and

51
Hillslope Length and Gradient Factor (LS) (cont.)

• - Hillslope lengths from topographic maps
  and GIS databases are
• usually overestimated because of
  difficulty in ascertaining the point
• where overland flow begins and the ending
  point where the runoff
• becomes concentrated in a flow channel,
  and
• - Hillslope lengths can be reduced by
  installing diversion channels
• or terraces. These will redirect upslope
  runoff away from the lower
• portions of the slope.

52
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient
• - Defined as the change in elevation per
  change in horizontal distance,
• expressed as a percentage,
• - For unit plots, a 9 gradient has a given
  S factor value of 1 and may
• vary above and below 1 depending on if
  the gradient is less than or
• more than that of a unit plot,

53
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient
• - Defined as the change in elevation per
  change in horizontal distance,
• expressed as a percentage,
• - For unit plots, a 9 gradient has a given
  S factor value of 1 and may
• vary above and below 1 depending on if
  the gradient is less than or
• more than that of a unit plot,
• - Soil losses increase more rapidly as the
  gradient increases than as
• the hillslope length increases,
• - Rill erosion is affected more than
  interrill erosion by changes in
• gradient,

54
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient
• - Defined as the change in elevation per
  change in horizontal distance,
• expressed as a percentage,
• - For unit plots, a 9 gradient has a given
  S factor value of 1 and may
• vary above and below 1 depending on if
  the gradient is less than or
• more than that of a unit plot,
• - Soil losses increase more rapidly as the
  gradient increases than as
• the hillslope length increases,
• - Rill erosion is affected more than
  interrill erosion by changes in
• gradient,
• - Can be measured in the field in several
  ways, can be estimated from
• aerial surveys but accuracy decreases as
  map scales decrease,

55
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient (cont.)
• - As previously mentioned in the opening
  statements, usually the area
• where the slope gradient is the greatest
  would be the area where the
• greatest erosion potential would also
  exist,

56
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient (cont.)
• - As previously mentioned in the opening
  statements, usually the area
• where the slope gradient is the greatest
  would be the area where the
• greatest erosion potential would also
  exist,
• - Usually slope gradients are not linear
  with slope length, thus RUSLE
• will allow a single complex slope to be
  defined through the use of up
• to 10 segments which describe the entire
  slope length, and

57
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient (cont.)
• - As previously mentioned in the opening
  statements, usually the area
• where the slope gradient is the greatest
  would be the area where the
• greatest erosion potential would also
  exist,
• - Usually slope gradients are not linear
  with slope length, thus RUSLE
• will allow a single complex slope to be
  defined through the use of up
• to 10 segments which describe the entire
  slope length, and
• - A RUSLE hillslope profile is not a single
  straight transect down the
• slope but rather the path a drop of
  runoff will take in proceeding
• down the slope.

58
Hillslope Length and Gradient Factor (LS) (cont.)

• Gradient accuracy
• - Accuracy of the S factor is greatest for
  slopes 3 to 20 percent
• - Moderate accuracy for slopes 1 to 3 and
  20 to 35 percent
• - Least accurate for slopes exceeding 35
  percent

59
Hillslope Length and Gradient Factor (LS) (cont.)

• General Comments
• - The greatest potential soil loss in the
  field is usually the area where
• the hillslope gradient is the largest
• - This factor is combined with hillslope
  length into a single
• topographic factor, LS, to define the
  ratio of soil loss from a given
• hillslope
• - User must select one of several
  appropriate general land uses (such
• as cropland, pasture, forest, etc.)

60
Cover-Management (C)

• Definition this factor represents vegetative,
  management and erosion-control practice effects
  that primarily affect the process of detachment
  on soil loss
• Similar to the other factors, the calculated C
  factor is the ratio of soil
• loss comparing the defined, existing
  surface conditions to that of a
• unit plot
• Has the greatest possible range of all factors

61
Cover-Management (C)

• Definition this factor represents vegetative,
  management and erosion-control practice effects
  that primarily affect the process of detachment
  on soil loss
• Similar to the other factors, the calculated C
  factor is the ratio of soil
• loss comparing the defined, existing
  surface conditions to that of a
• unit plot
• Has the greatest possible range of all factors
• There are 2 C-factor options in RUSLE 1.06
• 1. Time-invariant option
• - This option is used to document
  prior conditions that do not
• change significantly over time,
  i.e. rangeland or pastureland
• - Can be used after a few years after
  disturbance and reclamation
• when conditions affecting soil loss
  become more stable

62
Cover-Management (C) (cont.)

• C-factor options (cont.)
• 2. Time-variant option
• - Used when changes in vegetation and
  soil conditions significantly
• affect soil loss
• - These conditions may occur in the
  following ways
• a. Crop rotations using various
  numbers of years and crops
• b. Where the vegetation varies
  significantly at times within a year
• c. Changes in conditions
  following revegetation

63
Cover-Management (C) (cont.)

• RUSLE 1.06 uses soil-loss ratios (SLR) developed
  in sub-factor calculations to compute soil loss
  at any given time to that of standard conditions
  for 15-day periods throughout the entire period
  and then provides an overall rotational C value

64
Cover-Management (C) (cont.)

• RUSLE 1.06 uses soil-loss ratios (SLR) developed
  in sub-factor calculations to compute soil loss
  at any given time to that of standard conditions
  for 15-day periods throughout the entire period
  and then
• provides an overall rotational C value
• Sub-factors involved in calculating the SLR
  values include
• 1. Prior land use (PLU)
• - Reflects soil loosening effects by
  tillage operations
• - Highest during mining due to
  decreased biomass
• - High after tillage due to less
  consolidation and fewer stable
• aggregates
• - Soil is assumed to be fully
  consolidated 7 years after the last
• disturbance in the eastern US, but it
  may take up to 20 out west

65
Cover-Management (C) (cont.)

• 2. Canopy Cover
• - This is the vegetative cover above the
  soil surface that intercepts
• raindrops but does not contact the
  soil surface
• - Does not affect surface flow
  characteristics
• - Characteristics used in RUSLE include
  the percent of the surface
• covered by the canopy and the height
  from which the water
• droplets fall to the ground
  (effective fall height)

66
Cover-Management (C) (cont.)

• 2. Canopy Cover
• - This is the vegetative cover above the
  soil surface that intercepts
• raindrops but does not contact the
  soil surface
• - Does not affect surface flow
  characteristics
• - Characteristics used in RUSLE include
  the percent of the surface
• covered by the canopy and the height
  from which the water
• droplets fall to the ground
  (effective fall height)
• - Effective fall height varies with the
  vegetation type, density of the
• canopy, and the shape of the plants
• - The user should visualize the height
  from the ground to the
• canopy where most of the water drops
  would fall when more than
• one type of vegetation composes the
  canopy

67
Cover-Management (C) (cont.)

• 3. Surface cover
• - This is the material in contact
  with the soil that both intercepts
• raindrops and affects surface flow
  characteristics
• - Generally more effective on
  reducing interrill (lt10 slopes)
• than rill erosion (gt10 slopes)

68
Cover-Management (C) (cont.)

• 3. Surface cover
• - This is the material in contact
  with the soil that both intercepts
• raindrops and affects surface flow
  characteristics
• - Generally more effective on
  reducing interrill (lt10 slopes)
• than rill erosion (gt10 slopes)
• - May consist of live vegetation,
  litter, mulch, manufactured
• erosion-control products, and rock
  (gt0.75 inch)
• - To be effective it should either be
  anchored to the surface or
• of a big enough size not to be
  washed away by runoff
• - Adjustments are made in reducing
  effectiveness if material is not
• in contact with the soil surface
• - Varies depending on type of the
  dominant erosion, slope gradient,
• extent of contact, and the
  material itself

69
Cover-Management (C) (cont.)

• 3. Surface cover (cont.)
• - The user must select a land use from
  which RUSLE calculates a
• ß value that reflects the effectiveness
  of the surface cover

70
Cover-Management (C) (cont.)

• 3. Surface cover (cont.)
• - The user must select a land use from
  which RUSLE calculates a
• ß value that reflects the effectiveness
  of the surface cover
• For Example If the soil were bare
• ß0.025 Soil rill erosion is low relative to
  interrill erosion
• (flat slopes of lt2, short
  slopes lt15 feet)
• ß0.035 A mid-range value where equal
  rill/interrill erosion
• (typical medium-textured soils
  that are regularly disturbed)
• ß0.045 Coarse soils, low rainfall areas,
  cover strongly affects runoff
• ß0.050 Soil rill erosion is high relative to
  interrill erosion
• (steep slopes, long slopes,
  high silt soils, highly disturbed soils)

71
Cover-Management (C) (cont.)

• 4. Surface Roughness
• - This sub-factor takes into account
  the fields random roughness
• - Activities disturbing a soil leave
  two types of surface roughness
• a. Oriented
• - Ridges and furrows left
  behind a chisel plow, for example,
• that have a very
  recognizable surface pattern
• - This type is considered in
  the P factor

72
Cover-Management (C) (cont.)

• 4. Surface Roughness
• - This sub-factor takes into account
  the fields random roughness
• - Activities disturbing a soil leave
  two types of surface roughness
• a. Oriented
• - Ridges and furrows left
  behind a chisel plow, for example,
• that have a very
  recognizable surface pattern
• - This type is considered in
  the P factor
• b. Random
• - No recognizable pattern on
  the surface
• - Defined as the standard
  deviation of the elevation from a
• plane taken across a
  tilled area after oriented roughness is
• taken into consideration
• - Amount varies due to site
  condition, tillage implement, and
• soil texture and moisture

73
Cover-Management (C) (cont.)

• 4. Surface Roughness (cont.)
• For Example
• Random
  Soil Surface
• Tillage Operation Roughness (in)
  Disturbed ()
• Chisel sweeps 1.2
  100
• straight points 1.5
  100
• Disk , tandem 0.8
  100
• Drill, no-till 0.4
  60
• Plow, moldboard 1.9
  100
• Planter, no-till 0.4
  15
• From Agricultural Handbook 703

74
Cover-Management (C) (cont.)

• General Comments
• - Factor takes into consideration effects
  of 5 subfactors on soil loss
• - RUSLE is the most sensitive to this
  factor
• - Much time and preparatory information
  should be gathered prior
• to inputting data into the C factor
• - Imperative that plant types and sequences
  of operations be inputted
• in the correct sequence to insure
  accurate C factor calculations
• - Local NRCS offices may provide additional
  assistance in developing
• various sequence for use

75
Support Practice (P)

• This factor takes into consideration the effect
  of specific support practices on soil loss to the
  corresponding soil loss from a unit plot with
  tillage performed up and down the slope
• The support practices generally affect soil loss
  through their influence by reductions in the
  amount and rate of runoff, and/or changing the
  flow pattern or direction of the surface flow

76
Support Practice (P)

• This factor takes into consideration the effect
  of specific support practices on soil loss to the
  corresponding soil loss from a unit plot with
  tillage performed up and down the slope
• The support practices generally affect soil loss
  through their influence by reductions in the
  amount and rate of runoff, and/or changing the
  flow pattern or direction of the surface flow
• For time-invariant option P subfactors are
  contouring and terracing
• For time-variant option P subfactors are
  contouring, barrier strips or concave hillslope
  shape, terracing or sediment basins, and
  subsurface drainage

77
Support Practice (P) (cont.)

• Contouring
• - Common practice for mine reclamation
  activities
• - Tillage practices follow (or nearly so)
  the contour of the area across
• the hillslope

78
Support Practice (P) (cont.)

• Contouring
• - Common practice for mine reclamation
  activities
• - Tillage practices follow (or nearly so)
  the contour of the area across
• the hillslope
• - Ridges formed will redirect the overland
  flow across a less steep
• grade, thus
• a) Flows transport and detachment
  capacities are reduced, and
• b) If the grade is sufficiently flat,
  deposition may occur within the
• furrows between the ridges
• - If runoff collects in a low area, the
  ridges may be overtopped and
• concentrated flow erosion may occur

79
Support Practice (P) (cont.)

• Contouring (cont.)
• - Effectiveness depends upon factors such
  as hillslope length and
• gradient, soil type, surface cover, storm
  severity, and ridge height

80
Support Practice (P) (cont.)

• Contouring (cont.)
• - Effectiveness depends upon factors such
  as hillslope length and
• gradient, soil type, surface cover, storm
  severity, and ridge height
• - The contouring P subfactor approaches 1
  if
• a) R is high
• b) Infiltration capacity is low
• c) Hillslope length and gradient
  critical limits are exceeded, ie
• lengths may be as short as 50 feet
  for steep slopes (gt25) or
• as long as 1000 feet for flat slopes
  (lt2), and
• d) Ridge height is low.
• - Conversely, the contouring P subfactor
  approaches zero when the
• opposites are true

81
Support Practice (P) (cont.)

• For example Assume a 300-foot long
  hillslope with a 10 gradient
• and a hydrologic soil
  grouping of D (high runoff potential)
• 
  Contouring P subfactor value
• 
  Surface Cover
• Ridge Height (inches) 50
  Nearly Bare
• Very Low (0.5 2)
  1.00 1.00
• Moderate (3 4)
  0.70 0.95
• Very High (gt 6)
  0.41 0.89

82
Support Practice (P) (cont.)

• Terracing
• - Terraces divide the hillslope length into
  shorter segments and
• RUSLE hillslope profiles since water from
  upper terraces never runs
• down onto the lower terraces

83
Support Practice (P) (cont.)

• Terracing
• - Terraces divide the hillslope length into
  shorter segments and
• RUSLE hillslope profiles since water from
  upper terraces never runs
• down onto the lower terraces
• - Deposition within and along the terraces
  may trap much of the
• eroded soil from the areas between
  terraces, any erosion within the
• channels is not calculated by RUSLE

84
Support Practice (P) (cont.)

• Terracing
• - Terraces divide the hillslope length into
  shorter segments and
• RUSLE hillslope profiles since water from
  upper terraces never runs
• down onto the lower terraces
• - Deposition within and along the terraces
  may trap much of the
• eroded soil from the areas between
  terraces, any erosion within the
• channels is not calculated by RUSLE
• - Terraces may pond or divert runoff water
  to areas that can
• discharge the water in a non-dispersive
  nature, such as closed outlets,
• grassed waterways, rip-rapped channels,
  or underground outlets

85
Support Practice (P) (cont.)

• Terracing
• - Terraces divide the hillslope length into
  shorter segments and
• RUSLE hillslope profiles since water from
  upper terraces never runs
• down onto the lower terraces
• - Deposition within and along the terraces
  may trap much of the
• eroded soil from the areas between
  terraces, any erosion within the
• channels is not calculated by RUSLE
• - Terraces may pond or divert runoff water
  to areas that can
• discharge the water in a non-dispersive
  nature, such as closed outlets,
• grassed waterways, rip-rapped channels,
  or underground outlets
• - Effectiveness depends upon climate,
  hillslope length and gradient
• between terraces, soil type, cover,
  terrace grade, and soil loss from
• inter-terrace space

86
Support Practice (P) (cont.)

• Terraces (cont.)
• - The P subfactor approaches 1 for
  terracing when
• a) R is high
• b) Infiltration capacity is low
• c) Terrace grade is greater than 2
• - Converse is true for the opposite
  conditions listed

87
Support Practice (P) (cont.)

• Terraces (cont.)
• - The P subfactor approaches 1 for
  terracing when
• a) R is high
• b) Infiltration capacity is low
• c) Terrace grade is greater than 2
• - Converse is true for the opposite
  conditions listed
• - Sediment delivery ratio
• a) New feature in RUSLE 1.06 terracing
  subfactor computations
• b) Is calculated based on the sediment
  load, size and density of the
• eroded particles reaching the
  terrace channel, and flow transport
• capacity

88
Support Practice (P) (cont.)

• Sediment Delivery Ratio (cont.)
• c) Also used for concave hillslope
  profiles where deposition may
• occur on the relatively flat toeslope
  positions
• i) Concavity must be very accurately
  defined because the degree of
• concavity significantly
  influences the SDR value through effects
• on the deposition rate
• ii) Concavity is calculated by
  dividing the upper slope gradient by
• the average slope of the
  hillslope in question
• iii) The greater the concavity, the
  smaller the SDR value becomes

89
Support Practice (P) (cont.)

• Sediment Control Barrier or Structures
• - Common ones used on mining, reclaimed
  lands, and construction
• sites include vegetative buffer strips,
  strawbale dikes, and silt fences
• - RUSLE assumes that these features are
  installed on the contour and
• are properly designed, installed, and
  maintained.

90
Support Practice (P) (cont.)

• Sediment Control Barrier or Structures
• - Common ones used on mining, reclaimed
  lands, and construction
• sites include vegetative buffer strips,
  strawbale dikes, and silt fences
• - RUSLE assumes that these features are
  installed on the contour and
• are properly designed, installed, and
  maintained.
• - Increased sediment deposition is the
  result of reducing overland flow
• velocity or ponding
• - Effectiveness decreases rapidly when
  slope gradients exceed 15
• and thus no values can be calculated
  within RUSLE 1.06 for those
• conditions

91
Support Practice (P) (cont.)

• Sediment Basins or Ponds
• - These are usually temporary structures
  designed to collect and store
• eroded sediments on site to prevent
  downstream damages to streams,
• lakes, and undisturbed soils
• - These must have regular maintenance,
  usually cleaning to remove
• collected sediments, to keep their
  effectiveness

92
Support Practice (P) (cont.)

• Sediment Basins or Ponds
• - These are usually temporary structures
  designed to collect and store
• eroded sediments on site to prevent
  downstream damages to streams,
• lakes, and undisturbed soils
• - These must have regular maintenance,
  usually cleaning to remove
• collected sediments, to keep their
  effectiveness
• - Collection of sediments is accounted for
  in the terracing P subfactor
• - SDR is sensitive to particle and/or
  aggregate sizes of the sediment
• reaching the basin or pond thus upslope
  deposition of large particles
• or aggregates is not recognized

93
SUMMARY (cont.)

• RUSLE 1.06 was designed for use for activities
  commonly associated with mined lands,
  construction sites, and reclaimed disturbed sites
• It is DOS based and is Windows compatible up
  through Windows XP
• Uses the same type of equation used in the USLE
  and previous version
• of RUSLE
• With properly inputted data, soil loss
  estimations are within 25 if
• soil losses are from 4 to 30 tons/acre and
  within 50 for estimations
• from 1 to 4 and from 30 to 50 tons/acre

94
SUMMARY (cont.)

• Please visit the references listed earlier for
  more detailed information on the various factors
  within RUSLE 1.06

95
Acknowledgements

• This presentation could not have been made
  available without the
• cooperation and financial support of the
  following organizations and personnel
• Office of Surface Mining, Western Regional
  Coordinating Center, Denver, Co and especially
  the help of Linda Wagner and Joe Galetovic
• Presentation reviewers Mr. Larry Larson of
  the ND Public Service Commission and Dr. Daniel
  Yoder, Univ. of Tennessee
• This presentation was written and narrated
  by Dr. Stephan A. Schroeder, Environmental
  Scientist, North Dakota Public Service
  Commission, Reclamation Division, Bismarck, ND