Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-i
CHAPTER 5: ESTIMATING EROSION ON CONSTRUCTION SITES USING
THE REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE)
TABLE OF CONTENTS
5.1
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.2
REVIEW OF RUSLE AND FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.3
EXAMPLES OF HOW THE REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) IS USED
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.3.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.3.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.3.3 Example 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.3.4 Example 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.4
TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Table 5.1.  Soil Erodibility Factors (K), Soil Loss Tolerance Factors (T), and Hydrologic Soil Groups
of the A, B and C Horizons, U.S. Virign Islands Soil Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Table 5.2.a.  Topographic Adjustment Factors (LS) for Slope Percent and Slope Length . . . . . . 5-7
Table 5.2.b.  Topographic Adjustment Factors (LS) for Slope Percent and Slope Length . . . . . . 5-8
Table 5.2.c.  Topographic Adjustment Factors (LS) for Slope Percent and Slope Length . . . . . . 5-9
Table 5.3.  Cover Index Factor (C) for Construction Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
Table 5.4.  Practice Factor (P) for Surface Conditions for Construction Sites . . . . . . . . . . . . . 5-10
Table 5.5.  Adjustment Factors (M) for Estimating Monthly and Portions of Annual Soil Loss . 5-11
Table 5.6.  Approximate Soil Weights in Pounds per Cubic Foot and Conversion Factors . . . . 5-11
Table 5.7.  USDA Texture Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
5.5
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-ii
Environmental Protection Handbook
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-1
[Eq. 5-1]
CHAPTER 5: ESTIMATING EROSION ON CONSTRUCTION SITES
USING THE REVISED UNIVERSAL SOIL LOSS EQUATION (USLE)
Prepared in 1995 by Maria Montes, Agronomist, USDA-NRCS Caribbean Area, 
Modified in 2002 by Julie Wright, Natural Resources Program Supervisor, UVI-CES
5.1
INTRODUCTION
The development of the Universal Soil Loss Equation (USLE) began in 1940 as a cooperative effort by the State
Experiment Stations, the Science and Education Administration, the Soil Conservation Service (now the Natural
Resources Conservation Service), and the National Weather Service. The USLE has been reviewed and updated many
times since it was first developed. The last major revision began in 1987, and the current form now used is called the
Revised Universal Soil Loss Equation (RUSLE). The Soil and Water Conservation Society (SWCS, www.swcs.org) is
currently marketing RUSLE software. 
RUSLE is an erosion model designed to predict long-term annual soil loss carried by runoff from fields and rangeland
under specific cropping and management conditions (USDA-NRCS, 1995). It is also applicable to non-agricultural
conditions such as construction sites. RUSLE retains the equation structure of USLE, but the technology for evaluating
these factors has been altered and new data added. RUSLE has been computerized to assist with calculations, and three
databases for deriving these factors have been developed.
Even though the RUSLE is only an estimate, it is still the best method available to estimate soil erosion. The information
that is used in predicting soil erosion is constantly being updated. However, great care must be taken to ensure that the
RUSLE is used correctly. A basic knowledge of the factors used in calculating soil loss is essential. For assistance with the
use of the RUSLE, please contact the University of the Virgin Islands Cooperative Extension Service or the USDA Natural
Resources Conservation Service. 
An alternative method was developed by Colorado State University, in collaboration with USGS, Island Resources
Foundation, Inc., and the Virgin Islands National Park. Their GIS-based road surface erosion model (ROADMOD)
estimates road surface erosion and sediment delivery from a digitized road network (MacDonald, et. al., 1997) utilizing
data collected in the early 1990s on St. John. Input data for this model include an ASCII file, exported from a GIS, that
lists road segments and segment characteristics such as segment identification number; connections to and from other
segments; segment length, width, and slope; road surface (paved or unpaved); whether the segment is a discharge location;
and a factor to proportionalize flow if it is split between downstream segments (MacDonald, et. al., 1997). The model
uses a predictive equation:
where
E is the cross-sectional road erosion in cubic meters per meter of road length per year, or square meters,
A is the upslope road drainage area in square meters, and
S is the segment slope as a decimal.
For information on utilizing this model to predict road surface erosion in the Virgin Islands, please contact Dr. Lee H.
MacDonald, Department of Earth Resources, Colorado State University, Fort Collins, CO 80523-1482 or Island
Resources Foundation, Inc. at www.irf.org.
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-2
Environmental Protection Handbook
[Eq. 5-2]
5.2
REVIEW OF RUSLE AND FACTORS
The method described herein is based on the Revised Universal Soil Loss Equation (RUSLE) and it is used to predict soil
loss from sheet and rill erosion. The rate of erosion as estimated by RUSLE depends on six factors: (1) rainfall energy
and intensity, (2) soil erodibility, (3) land slope steepness and length of slope, (4) soil surface cover conditions (such as
grass, woodland, pavement, or no cover), and (5) land management practice used. These factors may be assigned
quantitative values to be used in estimating soil loss. However, this method does not account for soil loss by gully erosion.
The Revised Universal Soil Loss Equation is:
where
A =
The estimated average annual soil loss from sheet and rill erosion caused by rainfall and its associated overland
flow (in tons per acre). For volume estimates, Table 5.6 may be used to convert tons per acre to cubic yards
based on soil textures.
R =
The factor for annual rainfall erosivity - a measure of the erosive force of rainfall. R represents differences in
erosivity among locations in the Caribbean area. For the Virgin Islands, the R factor is a constant of 250 for St.
Croix and St. Thomas and 240 for St. John.
K =
The soil erodibility factor. The K factor is based on soil type listed in the 1995 Revised Soil Survey of the Virgin
Islands. K values for the Virgin Islands are found in Table 5.1.
L =
The slope length factor calculates the effect of slope length on erosion.
S =
The slope steepness factor calculates the effect of soil steepness on erosion. The slope length and slope steepness
are usually combined into a single topographic factor (LS) and computed from Tables 5.2.a - 5.2.c. Table 5.2.a
is for low ratios of rill to interrill erosion, such as rangeland and other undisturbed soil conditions with cover.
Table 5.2.b is for moderate ratios of rill to interrill erosion, such as row-cropped agricultural areas and other
moderately consolidated soil conditions with little to moderate cover. Table 5.2.c is for high ratios of rill to
interrill erosion, such as for freshly prepared construction sites and other highly disturbed areas with little or no
cover. Table 5.2.a is typically used to estimate pre-development conditions, and Table 5.2.c to estimate
conditions during construction.
C =
The soil cover and management factor represents the effect of plants, soil cover, soil biomass, and soil disturbing
activities on erosion. The C factor is also called the cover index and can be used to represent the effect of land
cover or treatment that may be used to protect construction sites. The C factor zone for the Virgin Islands is
Southern Slopes. The appropriate C factor can be selected from Table 5.5. 
P =
The management practice factor is the ratio of soil loss that occurs with certain conservation practices (like
conservation tillage) compared to that of no practice. P factors for a combination of practices are computed as
the product of P factors for the individual practices. Refer to Table 5.4 for P factors.
Table 5.6 provides the approximate soil weights of soil textures to convert tons per acre to cubic yards; and Table 5.7
provides USDA Texture Abbreviations.
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-3
A disturbed site of 15 acres near Christiansted, St. Croix. The soil is Glynn gravelly loam and the B
horizon is completely exposed. The average slope is 8% and the length is 200 feet.
5.3
EXAMPLES OF HOW THE REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) IS USED
5.3.1 Example 1
Problem:  Determine the estimated soil loss from this site if it was scraped up and down the slope with a bulldozer and
remains unprotected for one year.
Solution:   The rainfall factor, R, for St. Croix is 250 (given on page 5-1). Refer to Table 5.1 and determine that
the K value for the B horizon of Glynn gravelly loam is 0.20. Note that the K values are not always the same for
the B and C horizons of some soils. (Table 5.7 provides texture and modifiers for abbreviations given in Table 5.1).
Refer to Table 5.2c to determine the topographic adjustment factor (LS) for length and percent of slope. The length and
slope data are not multiplied together in the formula, but are developed mathematically from a complex equation. They
may be obtained directly from Table 5.2. Find 8% in the left-hand column and move horizontally to read 1.72
under slope length 200 feet. To find quantities not included in Table 5.2, one may interpolate between gradients and
slope lengths to estimate the required LS or use the closest factor.
Table 5.3 provides the cover index factor, C, for planning conditions. Note that the C-factor for exposed soil is 1.0.
Increasing the cover or soil protection decreases the C-factor accordingly. Refer to Table 5.4 for the practice factor, P.
The P-factor for a compact, smooth, bulldozer-scraped surface is 1.3.  
To determine the annual soil loss on this site, enter the above underlined data into the RUSLE and compute the erosion
for these conditions as follows:
A = RKLSCP = 250 x 0.20 x 1.72 x 1.0 x 1.3 = 111.8 tons per acre
A = 111.8 tons/acre x 15 acres = 1677 tons of soil lost on that site in one year!!!
To convert this amount to volume, use Table 5.6. Note that for the loam texture of the Glynn soil, one cubic foot of
material weighs approximately 90 pounds. Each ton of soil equals 0.82 cubic yards (yd3). Thus, 1677 tons times 0.82
yd3/ton = 1375 cubic yards of soil eroded in one year from the site.
5.3.2 Example 2
Problem:  Determine the soil loss from this site during the period from June 1 to September 1.
Solution:  Refer to Table 5.5 to obtain the St. Croix adjustment, M, factor for the period.  During this period, 6 +
7 + 11 = 24% of the average annual soil loss for these conditions will occur.  Therefore, 24% of 1677 tons
is calculated as:
A = 0.24 x 1677 = 402.5 tons eroded between June 1 and September 1, or
A = 0.24 x 1375 = 330 cubic yards of soil eroded between June 1 and September 1.
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-4
Environmental Protection Handbook
5.3.3 Example 3
Problem:  Determine the soil loss from this site during the period from November 1 to March 30, when hay mulch at
a rate of 2 tons per acre has been applied.
Solution:  Refer to Table 5.3 for the C-factor for hay mulch at 2 tons per acre (0.02), and Table 5.5 to obtain
the M factor for this period (M = 14 + 9 + 5 + 4 + 4 = 36%).  Use the USLE to calculate the soil loss:
A = RKLSCP = (250 x 0.20 x 1.72 x 0.02 x 1.3) x 0.36
A = 0.81 tons per acre for November 1 to March 30 with hay mulch protection
A = 0.81 x 15 = 12.1 tons for November 1 to March 30 with hay mulch protection
A = 12.1 tons x 0.82 yd3/ton = 9.9 yd3 for November 1 to March 30 with hay mulch
5.3.4 Example 4
To determine soil loss from gullies, we cannot use the USLE but must compute soil loss by direct measurement.  
Problem:  A gully has formed that is 60 feet long and averages 2 feet wide by 1 foot deep.
Solution:  A = 60 feet x 2 feet x 1 foot = 120 cubic feet of soil.  For a gravelly loam, Table 5.6, we compute the weight
to be 120 ft3 x 90 lbs/ft3 = 10,800 pounds.  To convert to tons, divide by 2000 pounds/ton.  Therefore, A = 10800 ÷
2000 = 5.4 tons of soil eroded from the site.
5.4
TABLES
Table 5.1.  Soil Erodibility Factors (K), Soil Loss Tolerance Factors (T), and Hydrologic Soil Groups of the A, B and C Horizons, Virgin Islands Soil
Series (USDA-NRCS, 1995).
U.S. Department of Agriculture
Natural Resources Conservation Service 
CB Table 2
6/13/95
Survey Area:
VIRGIN ISLANDS OF THE UNITED STATES
Soil Data for RUSLE
Map Unit Symbol
Component Name
Surface Texture
Percent of Map Unit
Hydrologic
Group
Kf
T*
Rock Cover %
AcD
ANNABERG
GR-L
60
D
.12
1
30
AcD
CRAMER
GR-CL
20
C
.08
2
25
AcE
ANNABERG
GR-L
60
D
.12
1
30
AcE
CRAMER
GR-CL
20
C
.08
2
25
AcF
ANNABERG
GR-L
60
D
.12
1
30
AcF
CRAMER
GR-CL
20
C
.08
2
25
AcG
ANNABERG
GR-L
60
D
.12
1
30
AcG
CRAMER
GR-CL
20
C
.08
2
25
AmD
ANNABERG
GR-L
50
D
.12
1
30
AmD
MAHO BAY
GR-L
30
D
.22
2
15
AmE
ANNABERG
GR-L
50
D
.12
1
30
AmE
MAHO BAY
GR-L
30
D
.22
2
15
AmF
ANNABERG
GR-L
50
D
.12
1
30
AmF
MAHO BAY
GR-L
30
D
.22
2
15
AmG
ANNABERG
GR-L
50
D
.12
1
30
AmG
MAHO BAY
GR-L
30
D
.22
2
15
AqA
AQUENTS
VAR
90
D
5
NO DATA
ArB
ARAWAK
GR-L
85
B
.12
2
25
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Map Unit Symbol
Component Name
Surface Texture
Percent of Map Unit
Hydrologic
Group
Kf
T*
Rock Cover %
Environmental Protection Handbook
5-5
ArC
ARAWAK
GR-L
85
B
.12
2
25
ArD
ARAWAK
GR-L
85
B
.12
2
25
ArE
ARAWAK
GR-L
85
B
.12
2
25
ArF
ARAWAK
GR-L
85
B
.12
2
25
BrB
ROCK OUTCROP
UWB
90
D
NO DATA
BsB
BEACHES
S
90
D
5
10
BtB
BEACHES
STX-S
90
D
5
NO DATA
CaA
CARIB
CL
85
D
.26
5
5
CbB
CINNAMON BAY
L
85
B
5
5
CgC
CINNAMON BAY
GR-L
85
B
.17
5
10
CvC
CRAMER
CL
50
C
.08
2
15
CvC
VICTORY
L
30
B
.22
3
20
CvD
CRAMER
CL
50
C
.08
2
15
CvD
VICTORY
L
30
B
.22
3
20
CvE
CRAMER
CL
50
C
.08
2
15
CvE
VICTORY
L
30
B
.22
3
20
CvF
CRAMER
CL
50
C
.08
2
15
CvF
VICTORY
L
40
B
.22
3
20
DoE
DOROTHEA
CL
80
C
.17
5
10
DoE
SUSANNABERG
CL
15
D
.12
2
30
DoF
DOROTHEA
CL
80
C
.17
5
10
DoF
SUSANNABERG
CL
15
D
.12
2
30
DoG
DOROTHEA
CL
80
C
.17
5
10
DoG
SUSANNABERG
CL
15
D
.12
2
30
FsD
FREDRIKSDAL
GRV-CL
50
D
.22
1
35
FsD
SUSANNABERG
CL
30
D
.12
2
30
FsE
FREDRIKSDAL
GRV-CL
50
D
.22
1
35
FsE
SUSANNABERG
CL
30
D
.12
2
30
FsF
FREDRIKSDAL
GRV-CL
50
D
.22
1
35
FsF
SUSANNABERG
CL
30
D
.12
2
30
FsG
FREDRIKSDAL
GRV-CL
50
D
.22
1
35
FsG
SUSANNABERG
CL
30
D
12
2
30
GyA
GLYNN
GR-L
85
C
.20
5
10
GyB
GLYNN
GR-L
85
C
.20
5
10
GyC
GLYNN
GR-L
85
C
.20
5
10
HeA
HESSELBERG
C
85
D
.05
2
0
HeB
HESSELBERG
C
85
D
.05
2
0
HeC
HESSELBERG
C
85
D
o5
2
0
HgA
HOGENSBORG
CL
85
D
.26
5
0
HgB
HOGENSBORG
CL
85
D
.26
5
0
HgC
HOGENSBORG
CL
85
D
.26
5
0
JaB
JAUCAS
S
85
A
.08
5
0
JsD
JEALOUSY
GR-CL
50
C
.15
3
10
JsD
SOUTHGATE
GR-L
30
D
.22
1
25
JSE
JEALOUSY
GR-CL
50
C
.15
3
10
JSE
SOUTHGATE
GR-L
30
D
.22
1
25
JsF
JEALOUSY
GR-CL
50
C
.17
3
10
JsF
SOUTHGATE
GR-L
30
D
.22
1
25
LmC
LAMESHUR
GR-SL
85
A
.12
5
55
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Map Unit Symbol
Component Name
Surface Texture
Percent of Map Unit
Hydrologic
Group
Kf
T*
Rock Cover %
5-6
Environmental Protection Handbook
PaB
PARASOL
CL
85
B
.15
5
0
PaC
PARASOL
CL
85
B
.15
5
0
Pt
PITS
UWB
90
NO DATA
RdB
REDHOOK
STX-S
85
A
.08
5
65
SaA
SALT FLATS
SICL
90
D
5
No  DATA
SbA
SANDY POINT
SCL
50
D
.20
5
0
SbA
SUGAR BEACH
MUCK
40
D
3
0
SiA
SION
C
85
B
.05
4
5
SiB
SION
C
85
B
.05
4
5
SoA
SOLITUDE
GR-FSL
85
D
.20
5
20
SrD
SOUTHGATE
GRV-L
45
D
.22
1
30
SrD
ROCK OUTCROP
UWS
40
D
No DATA
SrE
SOUTHGATE
GRV-L
45
D
.22
1
30
SrE
ROCK OUTCROP
UWB
40
D
No DATA
SrF
SOUTHGATE
GRV-L
45
D
.22
1
30
SrF
ROCK OUTCROP
UWB
40
D
No DATA
SrG
SOUTHGATE
GRV-L
45
D
.22
1
30
SrG
ROCK OUTCROP
UWB
40
D
NO DATA
UbD
URBAN LAND
VAR
90
No DATA
UcC
URBAN LAND
VAR
80
No DATA
UcC
CINNAMON BAY
L
15
B
.17
5
5
UgC
URBAN LAND
VAR
80
NO  DATA
UgC
GLYNN
GR-L
15
C
.20
5
10
VsC
VICTORY
L
45
B
.22
3
20
VsC
SOUTHGATE
GR-L
40
D
.22
1
25
VsD
VICTORY
L
45
B
.22
3
20
VsD
SOUTHGATE
GR-L
40
D
.22
1
25
VsE
VICTORY
L
45
B
.22
3
20
VsE
SOUTHGATE
GR-L
40
D
.22
1
25
VsF
VICTORY
L
45
B
.22
3
20
VsF
SOUTHGATE
GR-L
40
D
.22
1
25
*The soil loss tolerance or permissible soil loss (“T” factor) is expressed in tons/acre/year.
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-7
Slope
(%)
Horizontal Slope Length (Feet)
< 3
6
9
12
15
25
50
75
100
150
200
250
300
400
600
800
1000
0.2
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.5
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
1.0
0.12
0.12
0.12
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.15
0.15
0.16
0.16
0.17
0.17
2.0
0.20
0.20
0.20
0.20
0.20
0.21
0.23
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0.33
0.34
0.35
3.0
0.26
0.26
0.26
0.26
0.26
0.29
0.33
0.36
0.38
0.40
0.43
0.44
0.46
0.48
0.52
0.55
0.57
4.0
0.33
0.33
0.33
0.33
0.33
0.36
0.43
0.46
0.50
0.54
0.58
0.61
0.63
0.67
0.74
0.78
0.82
5.0
0.38
0.38
0.38
0.38
0.38
0.44
0.52
0.57
0.62
0.68
0.73
0.78
0.81
0.87
0.97
1.04
1.10
6.0
0.44
0.44
0.44
0.44
0.44
0.50
0.61
0.68
0.74
0.83
0.90
0.95
1.00
1.08
1.21
1.31
1.40
8.0
0.54
0.54
0.54
0.54
0.54
0.64
0.79
0.90
0.99
1.12
1.23
1.32
1.40
1.53
1.74
1.91
2.05
10.0
0.60
0.63
0.65
0.66
0.68
0.81
1.03
1.19
1.31
1.51
1.67
1.80
1.92
2.13
2.45
2.71
2.93
12.0
0.61
0.70
0.75
0.80
0.83
1.01
1.31
1.52
1.60
1.97
2.20
2.39
2.56
2.85
3.32
3.70
4.02
14.0
0.63
0.76
0.85
0.92
0.98
1.20
1.58
1.85
2.08
2.44
2.73
2.99
3.21
3.60
4.23
4.74
5.18
16.0
0.65
0.82
0.94
1.04
1.12
1.38
1.85
2.18
2.46
2.91
3.28
3.60
3.88
4.37
5.17
5.82
6.39
20.0
0.68
0.93
1.11
1.26
1.39
1.74
2.37
2.84
3.22
3.85
4.38
4.83
5.24
5.95
7.13
8.10
8.94
25.0
0.73
1.05
1.30
1.51
1.70
2.17
3.00
3.63
4.16
5.03
5.76
6.39
6.96
7.97
9.65
11.04
12.26
30.0
0.77
1.16
1.48
1.75
2.00
2.57
3.60
4.40
5.06
6.18
7.11
7.94
8.68
9.99
12.19
14.04
15.66
40.0
0.85
1.36
1.79
2.17
2.53
3.30
4.73
5.84
6.78
8.37
9.71
10.91
11.99
13.92
17.19
19.96
22.41
50.0
0.91
1.52
2.06
2.54
3.00
3.95
5.74
7.14
8.33
10.37
12.11
13.65
15.06
17.59
21.88
25.55
28.82
60.0
0.97
1.67
2.29
2.86
3.41
4.52
6.63
8.29
9.72
12.16
14.26
16.13
17.84
20.92
26.17
30.68
34.71
1 Such as for rangeland and other consolidated soil conditions with cover.
Table 5.2.a. Topographic Adjustment Factors (LS) for Slope Percent and Slope Length (USDA-NRCS Caribbean Area, 1995) for Rangeland.1
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-8
Environmental Protection Handbook
Slope
(%)
Horizontal Slope Length (Feet)
< 3
6
9
12
15
25
50
75
100
150
200
250
300
400
600
800
1000
0.2
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.06
0.06
0.06
0.5
0.07
0.07
0.07
0.07
0.07
0.08
0.08
0.08
0.09
0.09
0.09
0.09
0.09
0.10
0.10
0.10
0.10
1.0
0.11
0.11
0.11
0.11
0.11
0.12
0.13
0.14
0.14
0.15
0.16
0.17
0.17
0.18
0.19
0.20
0.20
2.0
0.17
0.17
0.17
0.17
0.17
0.19
0.22
0.25
0.27
0.29
0.37
0.33
0.35
0.37
0.41
0.44
0.47
3.0
0.22
0.22
0.22
0.22
0.22
0.25
0.32
0.36
0.39
0.44
0.48
0.52
0.55
0.60
0.68
0.75
0.80
4.0
0.26
0.26
0.26
0.26
0.26
0.31
0.40
0.47
0.52
0.60
0.67
0.72
0.77
0.86
0.99
1.10
1.19
5.0
0.30
0.30
0.30
0.30
0.30
0.37
0.49
0.58
0.65
0.76
0.85
0.93
1.01
1.13
1.33
1.49
1.63
6.0
0.34
0.34
0.34
0.34
0.34
0.43
0.58
0.69
0.78
0.93
1.05
1.16
1.25
1.42
1.69
1.91
2.11
8.0
0.42
0.42
0.42
0.42
0.42
0.53
0.74
0.91
1.04
1.26
1.45
1.62
1.77
2.03
2.47
2.83
3.15
10.0
0.46
0.48
0.50
0.51
0.52
0.67
0.97
1.19
1.38
1.71
1.98
2.22
2.44
2.84
3.50
4.06
4.56
12.0
0.47
0.53
0.58
0.61
0.64
0.84
1.23
1.53
1.79
2.23
2.61
2.95
3.26
3.81
4.75
5.56
6.28
14.0
0.48
0.58
0.65
0.70
0.75
1.00
1.48
1.86
2.19
2.76
3.25
3.69
4.09
4.82
6.07
7.15
8.11
16.0
0.49
0.63
0.72
0.79
0.85
1.15
1.73
2.20
2.60
3.30
3.90
4.45
4.95
5.86
7.43
8.79
10.02
20.0
0.52
0.71
0.85
0.96
1.06
1.45
2.22
2.85
3.40
4.36
5.21
5.97
6.68
7.97
10.23
12.20
13.99
25.0
0.56
0.80
1.00
1.16
1.30
1.81
2.82
3.65
4.39
5.69
6.83
7.88
8.86
10.65
13.80
16.58
19.13
30.0
0.59
0.89
1.13
1.34
1.53
2.15
3.39
4.42
5.34
6.98
8.43
9.76
11.01
13.30
17.37
20.99
24.31
40.0
0.65
1.05
1.38
1.68
1.95
2.77
4.45
5.87
7.14
9.43
11.47
13.37
15.14
18.43
24.32
29.60
34.48
50.0
0.71
1.18
1.59
1.97
2.32
3.32
5.40
7.17
8.78
11.66
14.26
16.67
18.94
23.17
30.78
37.65
44.02
60.0
0.76
1.30
1.78
2.23
2.65
3.81
6.24
8.33
10.23
13.65
16.76
19.64
22.36
27.45
36.63
44.96
52.70
1 Such as for row cropped agricultural and other moderately consolidated soil conditions with little-to-moderate cover.
Table 5.2. b. Topographic Adjustment Factors (LS) for Slope Percent and Slope Length (USDA-NRCS Caribbean Area, 1995) for Cropland.1
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-9
Slope
(%)
Horizontal Slope Length (Feet)
< 3
6
9
12
15
25
50
75
100
150
200
250
300
400
600
800
1000
0.2
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.5
0.07
0.07
0.07
0.07
0.07
0.07
0.08
0.08
0.09
0.09
0.10
0.10
0.10
0.11
0.12
0.12
0.13
1.0
0.09
0.09
0.09
0.09
0.09
0.10
0.13
0.14
0.15
0.17
0.18
0.19
0.20
0.22
0.24
0.26
0.27
2.0
0.13
0.13
0.13
0.13
0.13
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
0.17
0.17
0.17
0.17
0.17
0.21
0.30
0.36
0.41
0.50
0.57
0.64
0.69
0.80
0.96
1.10
1.23
4.0
0.20
0.20
0.20
0.20
0.20
0.26
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
0.23
0.23
0.23
0.23
0.31
0.46
0.58
0.68
0.86
1.02
1.16
1.28
1.51
1.91
2.25
2.55
6.0
0.26
0.26
0.26
0.26
0.26
0.36
0.54
0.69
0.82
1.05
1.25
1.43
1.60
1.90
2.43
2.89
3.30
8.0
0.32
0.32
0.32
0.32
0.32
0.45
0.70
0.91
1.10
1.43
1.72
1.99
2.24
2.70
3.52
4.24
4.91
10.0
0.35
0.37
0.38
0.39
0.40
0.57
0.91
1.20
1.46
1.92
2.34
2.72
3.09
3.75
4.95
6.03
7.02
12.0
0.36
0.41
0.45
0.47
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
0.38
0.45
0.51
0.55
0.58
0.85
1.40
1.87
2.31
3.09
3.81
4.48
5.11
6.30
8.45
10.40
12.23
16.0
0.39
0.49
0.56
0.62
0.67
0.98
1.64
2.21
2.73
3.68
4.56
5.37
6.15
7.60
10.26
12.69
14.96
20.0
0.41
0.56
0.67
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
0.45
0.64
0.80
0.93
1.04
1.56
2.67
3.67
4.59
6.30
7.88
9.38
10.81
13.53
18.57
23.24
27.66
30.0
0.48
0.72
0.91
1.08
1.24
1.86
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
0.85
1.13
1.37
1.59
2.41
4.24
5.89
7.44
10.35
13.07
15.67
18.17
22.95
31.89
40.29
48.29
50.0
0.58
0.97
1.31
1.62
1.91
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
0.63
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
1 Such as for freshly prepared construction and other highly disturbed soil conditions with little or no cover.
Table 5.2. c. Topographic Adjustment Factors (LS) for Slope Percent and Slope Length (USDA-NRCS Caribbean Area, 1995) for Construction Sites.1
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-10
Environmental Protection Handbook
Type of Cover*
Factor C
Percent1
None (fallow or bare gr ound)
1.0
0.0
Temporary Seedings (90% stand)
Ryegrass (perennial type)
Ryegrass (annuals)
Small grain
Millet or sudan grass
0.05
0.10
0.05
0.05
95
90
95
95
Permanent Seeding (90% stand)
0.01
99
Sod (laid immediately)
0.01
99
Application Rate (tons/acre)
Mulch
Hay
Hay
Hay
Hay
Small grain straw
Wood chips
Wood cellulose
Fiberglass
0.50
1.00
1.50
2.00
2.00
6.00
1.75
0.50
0.25
0.13
0.07
0.02
0.02
0.06
0.10
0.05
75
87
93
98
98
94
95
95
Asphalt emulsion (1,250 gals/acre)
0.02
98
*  Fiber matting, excelsior, gravel and stone may also be used as protective cover.
1  Percent soil loss reduction as compared with fallow or bare ground.
Table 5.3. Cover Index Factor (C) for Construction Sites (U.S. Department of Agriculture, Soil Conservation Service).
Surface Condition With No Cover
P Factor1
Compact and smooth, scraped with bulldozer or scraper up and down hill
1.3
Same condition, except raked with bulldozer root rake up and down hill
1.2
Compact and smooth, scraped with bulldozer or scraper across the slope
1.2
Same condition, except raked with bulldozer root rake across the slope
0.9
Loose as a disked plow layer
1.0
Rough irregular surface equipment tracks in all directions
0.9
Loose with rough surface greater than 12" depth
0.8
Loose with smooth surface greater than 12" depth
0.9
1  Values based on estimates.
Table 5.4. Practice Factor (P) for Surface Condition for Construction Sites (U.S. Department of Agriculture, Soil Conservation Service).
Chapter 5
Revised Universal Soil Loss Equation (USLE)
Environmental Protection Handbook
5-11
St. Croix & St. Thomas (R = 250)
St. John (R = 240)
Month
Percent
Percent
January
5
6
February
4
5
March
4
5
April
5
7
May
10
10
June
6
6
July
7
7
August
11
10
September
12
12
October
13
11
November
14
12
December
9
9
100
100
Table 5.5. Adjustment Factors (M) for Estimating Monthly and Portions of Annual Soil Loss (U.S. Department of Agriculture, Soil Conservation
Service).
Soil Texture*
Volume Weight (lbs/ft3)
Tons to Cubic Yards
Sands and loamy sands
110
0.67
Sandy loam
105
0.71
Fine sandy loam
100
0.74
Loam
90
0.82
Silt loam
85
0.87
Silty clay loam
80
0.93
Clay loam
75
0.99
Silty, sandy clay and clay
70
1.06
Aerated sediment
80**
0.93
Saturated sediment
60**
1.24
* Less than 2 mm particle size (includes gravelly and stony textural modifiers).
** These are the approximate aerated and saturated weights to be used at damaged sites (streams or reservoirs).
Table 5.6. Approximate Soil Weights in Pounds per Cubic Foot and Conversion Factors (U.S. Department of Agriculture, Soil Conservation
Service).
Chapter 5
Revised Universal Soil Loss Equation (USLE)
5-12
Environmental Protection Handbook
Texture Modifiers
CB - Cobbly
GRV - Very gravelly
CN - Channery
MK - Mucky
CNV - Very Channery
SR - Stratified
GR - Gravelly
ST - Stony
STV - Very stony
STX - Extremely stony
Textures
G - Gravel
SL - Sandy loam
COS - Coarse Sand
FSL - Fine sandy loam
S - Sand
VSFL - Very fine sandy loam
FS - Fine sand
L - Loam
VFS - Very fine sand
SIL - Silt loam
LCOS - Loamy coarse sand
SI - Silt
LS - Loamy sand
CL - Clay loam
LFS - Loamy fine sand
SICL - Silty clay loam
LVFS - Loamy very fine sand
SIC - Silty clay
COSL - Coarse sandy loam
C - Clay
MUCK - Muck
Table 5.7. USDA Texture Abbreviations (U.S. Department of Agriculture, Soil Conservation Service).
5.5
REFERENCES
MacDonald, L.H., D.M. Anderson, and W.E. Dietrich. 1997. “Paradise Threatened: Land Use and Erosion on St. John,
US Virgin Islands,” Environmental Management, Vol. 21, No.6, pp. 851-863, Springer-Verlag, New York.
USDA-NRCS. 1995. Soil Survey of the U.S. Virgin Islands, U.S. Department of Agriculture, Soil Conservation Service,
Caribbean Field Area, San Juan, PR.
USDA-NRCS. 1995. Revised Universal Soil Loss Equation (RUSLE) Handbook, Caribbean Area, U.S. Department of Agriculture,
Soil Conservation Service, Caribbean Field Area, San Juan, PR.
Wischmeier, W.H. 1976. “Cropland Erosion and Sedimentation,” Chapter 3 IN: Control of Water Pollution, Volume II,
USDA-EPA, U.S. Government Printing Office, Washington, DC.
Wischmeier, W.H. 1978. Predicting Rainfall Erosion Losses — A Guide to Conservation Planning, U.S. Department of
Agriculture, Agriculture Handbook #537.