WIND EROSION FORCES IN THE

UNITED STATES AND THEIR USE

IN PREDICTING SOIL LOSS

Asriculture Handbook No. 346

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE

in cooperation with

Kansas Agricultural Experiment Station
Contents

Page

Source and description of wind data 1

Method of analysis 2

Magnitude of wind erosion forces 2

Prevailing wind erosion direction 2

Preponderance of wind erosion forces in prevailing wind erosion

direction 2

Distance across field along direction of wind erosion force vectors. _ 3

Results and discussion 3

Relative magnitude of wind erosion forces 3

Orientation of barriers, stripcrops, and other erosion control practices 3

EquiValentfield width 4

Examples of field applications 6

Determination of potential wind erodibility of farm fields 6

Determination of barrier spacing 8

Literature cited 8

Appendix 16

Washington, D.C. Issued April 1968

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price26 cents
WIND EROSION FORCES IN THE UNITED STATES AND THEIR USE

IN PREDICTING SOIL LOSS

By E. L. SKIDMOBE, research soil scientist, and N. P. WOODRUFF, research investigations leader, Soil and Water Conservation

Research Division, Agricultural Research Service

Soil blowing of agricultural lands is a serious

problem in arid and semiarid regions and on sandy

soils of the United States. Soil loss from a given

cultivated field depends on cloddiness, surface

roughness, and surface moisture of the soil; on

amount, kind, and orientation of the vegetation;

on wind velocity or force; and on distance across

the field along the direction of the wind force

(11)} Information on soil and residue effects on

erosion is available in considerable detail (7, 11).

However, published information on wind forces

for use in determining amoimts of wind erosion

and for designing wind erosion control practices

is meager and is limited to specific areas of the

United States (6,8),

This handboak furnishes detailed information on

wind erosion forces for locations throughout the

United States for use in assessing erodibility of

field soils and in designing control practices to

combat the ravages of wind erosion.

The data presented include (1) relative magnitude of wind erosion forces or the capacity of the

wind to cause erosion on unprotected soils, (2)

prevailing wind erosion direction, and (3) preponderance of wind erosion forces in the prevailing

wind erosion direction. These factors indicate,

respectively, potential need for wind erosion protection, proper orientation of erosion control

measures, and relative merits of proper orientation

of the control methods. The data are presented by

months for 212 locations.

A brief description of analysis is presented.

Method of analysis in more detail is available

elsewhere (10),

SOURCE AND DESCRIPTION OF WIND DATA

Determining magnitude and direction of wind

erosion forces requu-es analyses of detailed wind

data. Detailed wmd data of hourly observations

of windspeed and direction are scarce. Of the many

stations reporting climatological data, only a few

record these hourly observations. Those that do

are generally airports or military bases. Percent

frequency of windspeed and direction are given

in Air Force Smnmaries of Surface Weather Observations (A-B Summaries) ; Navy Summaries of

Monthly Aerological Records (SMAR); and Environmental Data Service publications, Local

Climatological Data—Supplement and Summary

of Hoiu-ly Observations. These wind-data summaries were obtained from the National Records

* Italic numbers in parentheses refer to Literature Cited,

p. 8.

Center, Asheville, N.C., and were used in the

analysis described here.

Available data are for relatively short periods

of time, especially data from military installations

that were active only during World War II. The

recording period for most of the data used ranged

from 5 to 10 years, as detailed in table 1 (Appendix) .

No effort was made to correct heights of observations to a standard because they were not

known at all locations and an attempted correction

might not be accurate. Windspeed-height relationships must be known to mate valid corrections.

Since these relationships are affected by such

factors as temperature gradients, surrounding

buildings, and surface conditions, they cannot be

predicted accurately for the sundry unknown

conditions.
AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

METHOD OF ANALYSIS

The analysis is based on the principle that the

capacity of a wind to cause soil movement is

proportional to windspeed cubed times the duration of the wind.

Several investigators (i, 3, 12) found that when

windspeed was greater than that required barely

to move the sou, the rate of soil movement was

directly proportional to friction velocity cubed.

Friction velocity U^^ is related to velocity profile

as expressed by

^*^5.75 loi z¡k ^^^

where Uz is the windspeed at height z and k is

roughness length. Over a specified type of surface

and height, z and k are constant (1, 5). Therefore,

Ui^ is proportional to C/g, and rate of soil movement is proportional to windspeed cubed after the

windspeed attains some minimum or threshold

speed reqidred to initiate soil movement.

Threshold speeds were reported by Chepil {2)

to range from 13 to 30 miles per hour at 1-foot

height, depending on the history of the field. A

threshold speed of about 11 miles per hour at 1.2

feet was indicated for the conditions of another

investigation (S). Malina {9) reported data of

O'Brien and Rindlaub in which the amount of

sand transported was proportional to windspeed

cubed after windspeed reached a "critical velocity''

of 13.4 feet per second (9.1 miles per hour).

Wind data are commonly reported in climatolog|ical records by speed groups. One common

division is between 12 and 13 miles per hour.

That corresponds closely to the reported minimum

windspeed required to initiate soil movement.

Therefore, windspeeds 12 miles per hour and less

are considered nonerosive and were not used in

computations reported here.

Magnitude of Wind Erosion Forces

The magnitude of a wind erosion force vector

ry is obtained by summing, for all speed groups

with windspeeds greater than 12 miles per hour,

the i)roduct of mean windspeed cubed and a

duration factor for a specified direction as expressed by equation 2

ri=S mji

i=^l

(2)

where U\ is the mean windspeed within the ith

speed group cubed./< is a duration factor expressed

as the percentage of total observations that occur

in the jth direction within the ith speed group.

The sub i's indicate direction and take values

from 0 to 15, inclusive, representing the 16 principal compass directions. They are numbered

counterclockwise starting with east, which is

arbitrarily taken as the initial side of the coordinate system. Hence, r^=o ^^^ ^i=i ^^^ wind

erosion force vectors pointing east and eastnortheast, respectively.

The sum of the magnitudes of the wind erosion

force vectors for all directions gives the total

magnitude of wind erosion forces tor the location

and is expressed by equation 3. The value obtained by evaluating equation 3 for some location

indicates the relative capacity of the wind to

cause soil blowing at the particular location.

16 «

FT-T, S u%j,,

y=o i=i (3)

Prevailing Wind Erosion Direction

The magnitude of erosion forces parallel to a

particular direction can be obtained from the wind

erosion force vectors. If p is an imaginary straight

line intersecting at the origin of a polar coordinate

system and <f}j is the angle between r^ and the imaginary line p, the amoimt of erosion forces

caused by r^ that occur parallel to p \B r^ cos 4>j.

The total wind erosion forces parallel to p as a

function of the orientation of p are

16

^l!=Z;^i|cos(jX22.5-ö)l (4)

where 6 is the angle between ^ and the initial side.

Similarly, the sum of the wind erosion forces

perpendicular to i? is

16 i'±=So|sin(iX22.5-^)| (5)

Obtaining an orienting line i? so the ratio of the

wind erosion forces parallel to line p to those

perpendicular to line ^, symbolized by Ä, is

maximum tends to maximize wind erosion forces

parallel to p and to minimize wind forces perpendicular to p. Hence, when It is maximum, p is

oriented in the prevailing wind erosion direction

BEPreponderance of Wind Erosion Forces in Prevailing

Wind Erosion Direction

The value of B maximum (Ä^) indicates the

preponderance of wind erosion forces in the

prevailing wind erosion direction. The greater the

value of Rm, the greater the prevalence of the

prevailing wind erosion direction. A value for

Rm of 1.0 indicates no prevailing wind erosion

direction and a wind barrier would be equally

effective in any direction, whereas an Rrn, of 2.0

indicates a prevailing wind erosion direction with

wind erosion forces twice as great parallel as

perpendicular to prevailing wind erosion direction.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS

Distance Across Field Aiong Direction of Wind Erosion

Force Vectors

Since rate of soil movement begins at zero on

the windward sides of isolated strips of land and

increases with distance downwind (4, 5), it is

necessary to know the distance across the field

along the direction of wind erosion force vectors.

The distance depends on the angle of deviation

of the wind erosion force vectors from right angles

to field strip. That is visualized when one represents a field strip by drawing parallel lines on two

sides of a wind erosion rose and extending each

arm of the rose to the boundaries. The length of

the arm then represents the distance wind would

travel in traversing the field strip along the

direction of the wind erosion force vector. When

a force vector is at right angles to the field strip,

the distance traveled is equal to field width. As

the angles of deviation mcrease, the distance

across the field increases as the reciprocal of the

cosine (secant) of the angle of deviation.

It is convenient to express the angle of deviation

of wind erosion force vector from right angles to

field strip as a function of prevaiUng wind erosion

direction, and angle of deviation of prevailing

wind erosion direction from right angles to field

strip.

Aj=:jX22.5-en±A (6)

where Aj is angle of deviation of jth wind erosion

force vector from right angles to field strip, OR is

prevailing wind erosion direction with east as

zero reference, and A is angle of deviation of

prevaiHng wind erosion direction from right angles

to field strip. When dß is clockwise and counterclockwise of right angles to barrier, A is subtracted and added, respectively, in equation 6.

Therefore, the distance across field of width

W along the direction of Avind erosion force vector

Vj is

Dj=Wsec (iX22.5-ÖÄ±4) (7)

By multiplying the distance across field along

the direction associated with each vector by the

portion of the total wind erosion forces represented

by each wind erosion vector, a distribution of

wind erosion forces traveling various distances to

traverse the field is obtained.

RESULTS AND DISCUSSION

The data were analyzed on a high-speed digital

computer by the previously described methods.

Magnitude of wind erosion forces, prevailing

wind erosion direction, and preponderance of

wind erosion forces in the prevaiHng wind erosion

direction are presented in table 1 (Appendix) for

212 locations in the United States.

Relative iMagnltude of Wind Erosion Forces

The magnitude of wind erosion forces was above

1,000 for some months at some locations in the

Great Plains (e.g., Wichita, Kans.; Great Falls,

Mont.). Some coastal areas never reached 100

(e.g., Tallahassee and Jacksonville, Fla.), whereas

other locations were never below 400 (e.g., Wichita

and Great Falls).

Generally wind erosion forces are greatest in

the spring and least in the summer; however, that

is not true for all locations. Wind erosion forces

were greatest in the summer for some (e.g.,

Laredo, Tex.; Riverside, Calif.) and greatest in

the mnter for others (e.g.. Great Falls, Mont.;

Windsor Locks, Conn.).

Orientation of Barriers, Stripcrops, and Otiier Erosion

Controi Practices

For maximum protection against wind erosion

forces, an erosion control practice should be

oriented perpendicular to the prevailing wind

erosion direction. The prevaiHng wind erosion

direction is consistently the same throughout the

year for some locations but varies considerably

for others.

One should orient wind barriers, stripcrops,

and other erosion control practices for the time

of year when field and climatic conditions are

most conducive to blowing, i.e., when wind forces

are maximum, when soil is dry and deficient in

cover and cloddiness, and when crops are most

susceptible to damage.

The protection given by a barrier depends not

only on the characteristics of the barrier and its

orientation relative to the prevailing wind erosion

direction but also on the preponderance of wind

erosion forces in the prevaihng wind erosion

direction R^.

As an example, in figure 1 we compare the percent of wind erosion forces traveling various

distances to traverse a field in December at

Great Falls, Mont. (Ä,„=3.6) and in April at

Midland, Tex. (R^=l.l),

In figure 1, a, for Midland at A=0° (.field strip

at right angles to prevailing wind erosion direction), 80 percent of the wind erosion forces travel

distances equal to or greater than l.l W, and 32

percent travel twice the field width. However,

for Great Falls when Rrr, is larger (3.6), only 40

and 11 percent of the wind erosion forces travel

distances equal to or greater than 1.1 and 2.0 W",

respectively. In figure 1, 6, where the field strip

deviates 40*" from right angles to prevailing wind

erosion direction, the angle of deviation makes

very little difference at Midland where Rm is

small. However, the percentages for Great FaUs

at A=4:0'' are much larger than for A=0° and

are shghtly larger than for Midland.
AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

UJ

Ü

100

90

80

70

60

50

40

30

20

10

a. A » 0

GREAT FALLS Hü R,„-3.6

MIDLAND EMI R„- I.I b. A «40

I.I 1.2 1.5 2.0 l.i 1.2 1.5 2.0

FIGURE 1.—Percent of wind erosion forces traveling distances equal to or greater than some value k times field width in

traversing field strip of width W, when angle of deviation of prevailing wind erosion direction from right angles to

field strip is 0° and 40° for (a) and (&), respectively, at Great Falls, Mont., and Midland, Tex.

As Bm approaches unity (the smallest value

Eossible for Em)) the unportance of a particular

airier orientation lessens. Wind erosion forces

that occur parallel are equal to those that occur

perpendicular to barrier regardless of barrier

orientation.

It follows that as Rm gets larger, more attention

should be given to proper orientation of the barrier,

as illustrated in figures 2-6. These charts give

the percent of wind erosion forces that travel

some specified multiple k of field width in traversing a field strip as a function of Rm and ^.

In general, as Rm gets larger, the percent of wind

erosion forces traveling more than 1.5 times the

field width decreases for small angles of deviation

of the prevailing wind erosion direction from right

angles to field strip. However, for large angles of

deviation, the percent of wind erosion forces

traveUng 1.5 times the field width in traversing

field strip increases. That fact should be considered when determining equivalent field width

for use in the wind erosion equation and the

distance between barriers.

Equivalent Field Width

Use of distance U across the field along the

prevailing wind erosion direction in the wind

erosion equation is based on the wind traveling

distance L' in traversing the field. Unless all wind

erosion forces occur along the prevailing wind

erosion direction, some of the wind will travel

distances greater than Z' in traversing the field.

Also, at angles of deviation greater than zero, some

wind wiU travel less than U in traversing a field

strip. A measure of equivalent field width based

on the preponderance of wind erosion forces in the

prevaihng wind erosion direction as well as deviation of right angle of the strip from preyaiUng

wind erosion direction would be more meaningful.

Suppose that by using the wind erosion equation

(11) we have determined that the travel distance

U of wind in traversing a field strip should not

exceed 150 feet to control erosion to a tolerable

amount. We now desire to determine the width of

a field strip so that no more than 50 percent of the

wind erosion forces will travel more than 150 feet

in traversing the field strip. Some percentage other

than 50 could be selected, but 50 is desirable because haK of the wind erosion forces will travel

farther and half not so far, so 50 represents the

median travel distance; also, it is the percentage

best used with figures 2-6.

To illustrate, let us use Rm of 1.1 and 3.6 in

combination with A values of 0^ and 40°. The

median distances that wind erosion forces will

travel in traversing the field strip are determined

by interpolation from figures 2-6.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS

FIGURE 2.—^Percent of wind erosion forces traveling distances

equal to or greater than k times field width in traversing

field strip for conditions of nonexisting prevailing wind

erosion direction (Äm=1.0) and all values of A. Rm is

ratio of wind erosion forces that are parallel to those that

are perpendicular to prevailing wind erosion direction.

Magnitude of Rm indicates preponderance of wind

erosion forces in prevailing wind erosion direction. A is

angle of deviation of prevailing wind erosion direction

from right angles to field strip.

90 B^v

80^^^^x^^^^

70

\\\\^

H. 60

Z

tu 50 Ü

S ^°

Û- 30^^^^«=.

20

10 ^^^^-^^^^^^^^A- 5°

0

III!

1.0 1.5 2.0 2.5

k

3.0 3.5

FIGURE 4.—Percent of wind erosion forces traveling

distances equal to or greater than k times field width in

traversing field strip for Rm=2A and various values

of A

FIGURE 5.—Percent of wind erosion forces traveling

distances equal to or greater than k times field width in

traversing field strip for Äm=3.0 and various values

of A

FIGURE 3.—Percent of wind erosion forces traveling

distances equal to or greater than k times field width

in traversing field strip for Am=1.5 and various values

of A.

Remember that k times field width equals

distance traveled by a specified percentage of

wind erosion forces in traversing field strip and

hoW equals median travel distance. Therefore,

divide 150 by k^o to obtain width of field strip W50

required if no more than 50 percent of the wind

erosion forces travel more than 150 feet in traversing the field—the specified conditions of Rm

and A.

Results are given in table 2 and are compared

kvith width of field W^' based on distance across

the field along the prevailing wind erosion direction

^th disregard of the preponderance of wind

erosion forces in the prevailing wind erosion

direction.

FIGURE 6.—Percent of wind erosion forces traveling k

times field width or greater in traversing field strip for

An»=3.8 and various values of A,
AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 2.—Determination qf width of field strip

W50 for median travel distance of 160 feet and of

width of field strip WL' SO distance across field

in prevailing wind erosion direction is ISO feet

when preponderance of wind erosion forces (Rm)

is 1.1 and 3,6 and angle of deviation (A) is 0°

and 40''

Rm A ^50 Wßo WL'

1.1- --- --

r (') / 0

I 40

/ 0

I 40

L8

L9

LI

2.1

Feet

83

79

136

71

Feet

150

3.6

116

150

116

When Em equals 1.1, the angle of deviation

of strip from right angles to prevailing wind

erosion direction only sHghtly affects Wso, whereas when i?TO equals 3.6, an increase in angle of

deviation from 0° to 40° reduces Wm from 136

to 71 feet.

EXAMPLES OF FIELD APPLICATIONS

Data in this handbook can be used in several

ways to design wind erosion control practices.

Two examples are illustrative.

Determination of Potential Wind Erodibiiity of Farm

Fieids

The amount of erosion JE, expressed in tons

per acre per annum, that could occur from a

given agricultural field can be expressed as £'=

/(/^í:^í7^i^F), where r is a soil erodibihtj

index, K^ is a soil ridge roughness factor, C is

a cHmatic factor, U is field length along the prevaihng wind erosion direction, and V is equivalent

quantity of vegetative cover {11).

Assume we wish to use the equation and the

information given in this handbook to determine

the potential erosion E that might occur in March

and October from a field with a 1,320-foot northsouth width in the vicinity of Midland, Tex.

Since the field is flat and smooth, soil ridge rough-

\

0

Ü

<

</> Ul

Z

X

3 0.7 \ À

/

0

UJ \

V y

/

SOIL RID

V y

2 3 4 5 6 7 8

SOIL RIDGE ROUGHNESS Kr (INCHES)

ness Äi.=0 and soil ridge roughness factor -^'=1.0

(fig. 7). Because it has 800 pounds per acre of flat

wheat stubble, V, the equivalent vegetative cover,

is 2,500 (fig. 8). (For other vegetative covers, refer

to iigs. 9 and 10.) Since dry sieving indicates that

25 percent of the soil fractions are greater than

0.84 mm. in diameter, /'=86 (table 3). (7', the

climatic factor, appears in figures 11-22 for January through December. The factor is 102 percent

for March and 64 percent for October. In this

example we shall use median travel distance Z?6o

for L'. Ao may be determined from this handbook

in the foUowing manner :

(1) Refer to data in table 1 (Appendix) for

Midland, Tex. Find direction equal to 45° in

March and 90° in October, thus indicating the

prevailing wind erosion direction has an angle of

FIGURE 7.—Chart to determine soil ridge roughness factor

K* from soil ridge roughness Kr.

4 6 8 10 12 14 16 18 20 22 24 26

V (THOUSANDS OF EQUIVALENT POUNDS PER ACRE)

FIGURE 8.—Chart to determine V from W or W from V of

standing and flat anchored small grain stubble with any

row width up to 10 inches, including stover.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS

TABLE 3.—SoU erodibility I ßr soils with dif event percentages oj nonerodible

fractions as determined by standard dry sieving ^

Dry soil fractions

>0.84 mm.

(percent)

Unitsr

Tens

1

0

acre

10..._ 134

20 98

30 74

40 56

50 38

60 21

70 12

80 2

Tons

per

Tons

per

acre

310

131

95

72

54

36

20

11

Tons

per

acre

250

128

92

71

52

33

19

10

Tons

per

acre

220

125

90

69

51

31

18

Tons

per

acre

195

121

88

67

50

29

17

7

Tons

per

acre

180

117

86

65

48

27

16

6

Tons

per

acre

170

113

83

63

47

25

16

4

Tons

per

acre

160

109

81

62

45

24

15

3

Tons

per

acre

150

106

79

60

43

23

14

3

Tons

per

acre

140

102

76

58

41

22

13

2

I

1 For fully crusted soil surface, regardless of soil texture, erodibility / is, on the average,

about one-sixth of that shown.

deviation A with reference to the north-south

field width of 45° in March and 0° in October.

Also note from these data that preponderance or

Rm equals 1.2 in March and 1.9 in October.

(2) To find D^ for March, use figures 2 and 3

to determine ho. For A=45°, find ä:5O=1.90

when Rm=1.0 and 1.85 when Rjn=l.5. Since

actual Rm=1.2j then by interpolation ¿50=1.88

and D5o=kso field widths 1.88X1,320=2,480.

(3) To find Z>5o for October, use figures 3 and 4

to determine ¿go- For A=0°, find k50=lM when

Äm=1.5 and 1.18 when ^,^^=2.1. Since actual

Rm=l'9j then by interpolation ¿5o=1.22 and

060=1.22X1,320=1,610.

14

13 /^

12

UJ,|

.s^y

<^u^^^

.^^

^

Q. 9

^

/ .

«V

Z ^

2 7

fee

§ ^

r 3

a:

2

1

X

/y/^

//

\^/ /

Y

>/

/

0

f

Values of /'=86, Í3L' = 1.0, <7'=102 in March

and 64 m October, i?5o=2,480 m March and

1,610 in October, and 17=2,500 may now be

used in the wind erosion equation E=j{r,K\

C%UjV) to determine potential soil losses of 40

tons per acre in March and 21 tons per acre in

October. The procedure for making these calculations is as follows:

(1) Determine E2=rK\ £'2=86X1.0=86 tons

per acre.

(2) Determine E^=rK'C\ £3=86X1.0x1.02

=88 tons per acre in March. £3=86X1.0X0.64

=55 tons per acre in October.

(3) Determine E^=rK'GJ{U)

(a) i'=Z}60=2,480 feet in March and 1,610

feet in October.

4 6 8 10 12

(THOUSANDS OF EQUIVALENT POUNDS PER ACRE)

FIGURE 9.—Chart to determine V from R' or R' from V of

live or dead small grain crops in seedling and stooling

stage, above surface of ground, for crop in 3-inch-deep

furrow as created by deep-furrow drill on smooth ground.

276-724 0-68—2

12 14 16 18 20 22 24 26

(THOUSANDS OF EQUIVALENT POUNDS PER ACRE)

28 30 32

FIGURE 10.—Chart to determine V from R' or R' from V

of standing and flat grain sorghum stubble of average

stalk thickness, leafiness, and quantity of tops on ground.
8 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

(b) Use figurai 23 to obtain E^, Cut out

movable Ez=rK'C^ scale. For March, place it

along E2=rK^ ordinate so that 88 on movable

scale coincides with 86 on ordinate. From movable

scale move to ri^ht down along 86 interpolated

between curved lines 80 and 90 to intersection

of i'=2,480 feet, then move horizontally left to

movable E^ scale and read E^=rK'Cy{L')=S2

tons per acre. For October, place movable scale

E2 ordinate so that 55 on movable scale coincides

with 86 on ordinate. Again from movable scale

move to right down along 86 interpolated between curved lines 80 and 90 to intersection of

i'= 1,610 feet, then move horizontally left to

movable E^ scale and read £'4=50 tons per acre.

(4) Determme E,=E=rK'C%U)f{V)

(a) V as determined from figure 8 for 800

pounds per acre of residue B' is 2,500 equivalent

pounds per acre.

(b) Use figure 24 to determine E^=E, For

March, start with £'4=82 on abscissa of figure

24. Move vertically upward to intersection of

F=2,500, then move horizontally left to ordinate E.

E=4:0 tons per acre. For October, start with

£4=50 on abscissa of figure 24, move vertically

to intersection of y=2,500 and horizontally to

ordinate and read E=21 tons per acre.

Because these soil loss values are rather high, a

farm operator might next logically ask'*How much

additional residue above the 800 pounds per acre

would this field need to prevent soil losses from

exceeding a tolerable 5 tons per acre?'' That question can be answered by substituting 5 tons per

acre for E in the equation and solving for V. If

that is done using the field conditions for /', K\

C^j and L' indicated above, one finds that 1,800

Eounds per acre of flattened wheat stubble would

e requu:ed in March and 1,320 pounds per acre

in October. Thus, 1,000 pounds per acre more

residue than the existing 800 pounds would be

required for adequate protection in March, but

only an additional 520 pounds per acre would be

needed in October.

Determination of Barrier Spacing

For an example of determining barrier spacing,

assume we desire to establish windbreaks to reduce

wind erosion of wheat and fallow fields near Goodland, Kans. Information from table 1 indicates

that wind erosion forces are greatest in March and

April when fields are susceptible to wind erosion.

It is decided to design for conditions when wind

erosion forces are greatest. Other pertinent information from table 1 indicates that the prevailing

wind erosion direction is 112°, north-northwest,

and preponderance or R^ is 2.5 and 2.1 for March

and April, respectively. Since the field Hes along

grid hues and prevailing wind erosion direction is

only 22° from north-south, it is decided to orient

the barrier east-west.

It is decided to base the distance between barrier strips on the distance traveled by 50 percent

of the wind in traversing the field strip, or the

median travel distance. Based on properties of the

barrier to be established and degree of protection

desired, it is decided that the median travel distance should not exceed SOH. H is barrier height.

By using figure 4 and interpolating, it is found for

Ä;„=2.1 and A=22° that median travel distance

is 1.5 (¿50) times the field width PF. If we equate

that distance (1.5 W) to 30H and solve for W, we

obtain 20H. Therefore, based on the design criteria and average wind conditions of the area,

wind barriers should be spaced 20 times their

height.

LITERATURE CITED

(1) BAGNOLD, R. A.

1943. THE PHYSICS OF BLOWN SAND AND DESERT

DUNES. 265 pp. ^ William Morrow & Co.,

New York.

(2) CHEPIL, W. S.

1945. DYNAMICS OF WIND EROSION: II. INITIATION OF SOIL MOVEMENT. SoU Sci. 60 (5) :

397-411.

(3)

(4)

(6)

(6)

1945. DYNAMICS OF WIND EROSION: III. THE

TRANSPORT CAPACITY OF THE WIND. Soil

Sei. 60 (6): 475-480.

1957. WIDTH OF FIELD STRIPS TO CONTROL WIND

EROSION. Kans. Agr. Expt. Sta. Tech.

Bui. 92, 16 pp.

and MILNE, R. A.

1941. WIND EROSION OF SOIL IN RELATION TO

SIZE AND NATURE OF EXPOSED AREA. Sci.

Agr. 21 (8): 479-487.

SiDDOWAY, F. H., and ARMBRUST, D. V.

1964. PREVAILING WIND EROSION DIRECTION IN

THE GREAT PLAINS. Jour. Soü and Water

Conserv. 19 (2): 67-70.

(7) and WOODRUFF, N. P.

1963. THE PHYSICS OF WIND EROSION AND ITS

CONTROL. Adv. in Agron. 15: 211-302.

(8) JOHNSON, W. C.

1965. WIND IN THE SOUTHWESTERN GREAT

PLAINS. U.S. Agr. Res. Serv. Conserv.

Res. Rpt. No. 6, 65 pp.

(9) MALINA, F. J.

1941. RECENT DEVELOPMENTS IN THE DYNAMICS

OF WIND EROSION. Amer. Geophys. Union

Trans., pp. 262-284..

(10) SKIDMORE, E. L.

1965. ASSESSING WIND EROSION FORCES: DIRECTION AND RELATIVE MAGNITUDES. Soil

Sci. Soc. Amer. Proc. 29 (5): 587-590.

(11) WOODRUFF, N. P., and SIDDOWAY, F. H.

1965. A WIND EROSION EQUATION. Soil Sci.

SOC. Amer. Proc. 29 (5): 602-608.

(12) ZiNGG, A. W.

1953. WIND-TUNNEL STUDIES OF THE MOVEMENT

OF SEDIMENTARY MATERIAL. 5th Hydraul.

Conf. Proc, Iowa Inst. Hydraul. Bui. 34,

pp. 111-135.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS

JANUARY

CLIMATIC FACTOR C'

FIGURE 11.—Wind erosion climatic factor C (percent) for January.

FEBRUARY

CLIMATIC FACTOR C'

FIGURE 12.—Wind erosion climatic factor C (percent) for February.
10 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

MARCH

CLIMATIC FACTOR C

FIGURE 13.—Wind erosion climatic factor C (percent) for March.

APRIL

CLIMATIC FACTOR C

FIGURE 14.—Wind erosion climatic factor C (percent) for April.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 11

MAY

CLIMATIC FACTOR C'

FIGURE 15.—Wind erosion climatic factor C" (percent) for May.

JUNE

CLIMATIC FACTOR C

FIGURE 16.—Wind erosion climatic factor C (percent) for June.
12 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

JULY

CLIMATIC FACTOR C

FIGURE 17.—Wind erosion climatic factor C (percent) for July.

AUGUST

CLIMATIC FACTOR C'

FIGURE 18.—Wind erosion climatic factor C (percent) for August.
WIND EROSION FORCES AISTD THEIR USE IN PREDICTING SOIL LOSS 13

SEPTEMBER

CLIMATIC FACTOR C

FIGURE 19.—Wind erosion climatic factor C (percent) for September.

OCTOBER

CLIMATIC FACTOR C'

FIGURE 20.—Wind erosion climatic factor C (percent) for October.
14 AGBICULTÜBE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

NOVEMBER

CLIMATIC FACTOR C'

FIGURE 21.—Wind erosion climatic factor C (percent) for November.

DECEMBER

CLIMATIC FACTOR C'

FIGURE 22.--Wind erosion climatic factor C (percent) for December.
o

CO SOIL LOSS £2= TK' (TONS/ACRE/ANNUM)

o

PLACE MOVABLE SCALE HERE

Cu

Oí

X 10,000 s? 8,000

^m SjOOO

o3 4,000

DO m 3.000

g: m '^

3) 2.000

g 0 0

^

is

1,000

800 II 600

0

or 400

300

=° 1- 200

H"^ 0

H >

'%%

m CD Z 2

0

60

0 *^ 40

S| m "D 30

Í9 ^2 20

^ <

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10

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/ // y///// J ^UjZt^ttii/tutti y.'yyV./ y

r

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r

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r r 0//

J.v/lUi/lUuul

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'¿//////¿ ^ /y j/ j^j^ ///

wÎy^2Z '^y./^ y/ y

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///^///V\y/

/,/2/^>^^'^/¿ Z^^__._

yyy y /^

//

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^^',^/y^^/y^^^ {/....._

< .^^

^ .

y <,/r yyVA<;;:^<: /AV.'^tyy!y^^^^^A. y /^ ^y/;<^ /

y

^

yÍ/^<y. >; ^y\ ÍÍ/^y;."l^ yA/yy

^^

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H

Ö3

O

CD

S

»*1

O

S3

O

02

3

i

O

q

CUT HERE

SOIL LOSS E= TK'C* OR E^= iVC'flL') (TONS/ACRE/ANNUM )

3 4

T

o

I

ai

i

O CJiooiO 000 O

Il I III

— — lAJ IV Vi O cji Q en o

I I T I I

O

O

I

ro

o

— — ro h3 fu ro ro o4 0jojoic>i^-l^4^

o> 00 o ro 4^ en œOrJ4^a>œoM^

- O o Q o o o o 000000000 .

I I I I M I T I I I I I I I I I I I I I I I

o

CO

CO

CD Ü1
16 AGRICULTURE HANDBOOK 346i, U.S. DEPT. OF AGRICULTURE

2 34568 10 20 30 40 6080KX> 200300

E- I'K'C'fd:) (TONS/ACRE/ANNUM)

FIGURE 24.—Chart to determine soil loss E=^I'K*C'f{L')f{y) from soil loss Ei=rK^C%U) and from vegetative cover

factor V. Chart can be used in reverse to determine V needed to reduce soil loss to any degree.

APPENDIX

TABLE 1.—Relative magnitude^ prevailing wind erosion direction,^ and preponderance oj wind erosion jorces

in prevailing wind erosion direction Jor 212 locations in S9 States by months

Item Jan. Feb. Mar. Apr, May Jime July Aug. Sept. Oct. Nov. Dec.

Anchorage, Alaska

(Jan. 1956 - Dec. 1960)

Magnitude 66

68

2.0

108

68

3.4

75

90

2.7

48

90

2.7

115

90

3.4

73

90

3.1

63

90

2.7

42

90

3.2

66

90

3.1

56

90

3.2

45

90

3.1

36

Direction 90

Preponderance 3.1

Fairbanks, Alaska

(Jan. 1956 - Dec. 1960)

Magnitude. i 3

45

2.6

12

45

2.9

28

45

2.5

30

45

1.3

68

45

1.9

34

23

2.1

40

23

2.2

24

23

2.4

31

23

2.0

25

23

2.5

9

45

1.3

2

Direction 45

Preponderance 3.3

( Jan.-S(

Ajo, Ariz.

3pt. 1942; Nov. 1942 - Dec. 1 946)

Magnitude 54

90

1.9

73

90

2.1

91

113

1.2

83

45

1.2

80

45

1.4

95

67

1.8

69

45

1.3

44

90

1.2

62

68

1.6

37

90

1.5

24

90

1.7

28

Direction _ 90

Preponderance 1.4

Douglas, Ariz.

(Nov. 1942 - Nov. 1945)

Magnitude __ 84

69

1.3

140

67

1.6

230

45

1.5

294

23

1.4

177

22

1.5

215

45

1.6

80

113

1.4

37

135

1.4

69

180

1.5

86

180

1.8

74

180

1.0

53

Direction 90

Preponderance 1.0

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 17

TABLE 1—Relative magnitude, 'j^revailing wind erosion direction,^ and preponderan^^e of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Kingman, Ariz.

(Mar. 1943 - June 1945)

Magnitude- _ 150

45

2.9

244

67

1.7

337

67

2.6

256

45

2.8

280

45

2.7

329

45

3.6

225

45

2.4

181

45

2.9

162

45

1.9

98

45

1.5

83

45

2.0

66

90

1.6

Direction

Preponderance

Phoenix, Ariz.

(May 1950 - Apr. 1955)

Magnitude 45

180

L5

101

157

L4

74

158

L6

93

180

1.7

89

113

L4

62

135

L5

131

90

1.5

97

135

L7

76

112

L7

34

90

L6

29

90

1.0

38

113

1.4

Direction

Preponderance

Prescott, Ariz.

(Jan. 1953 - Jan. 1963)

Magnitude 69

68

L7

128

68

1.4

194

45

1.7

236

67

2.0

242

67

2.7

204

45

2.3

103

45

1.9

75

67

1.6

88

67

2.0

85

68

2.1

76

68

2.2

57

68

1.5

Direction

Preponderance

Tucson, Ariz.

(Sept. 1952 - Jan. 1963)

Magnitude 93

157

2.6

82

158

1.7

101

158

L6

121

180

L4

132

22

1.7

91

158

1.2

96

157

1.5

63

157

1.6

70

157

2.1

107

157

2.3

106

157

3.4

87

157

2.6

Direction

Preponderance

Yuma, Ariz.

(Sept. 1952 - Jan. 1963)

Magnitude _ 62

90

2.6

90

90

2.1

89

113

1.5

111

157

1.5

108

135

L7

107

113

2.2

139

113

3.0

114

113

2.5

43

112

1.9

45

113

1.4

62

90

2.4

59

90

2.7

Direction

Preponderance

Arcata, Calif.

(Dec. 1949 - Nov. 1958)

Magnitude 159

135

2.3

154

135

2.8

183

135

3.3

172

135

3.9

192

135

4.4

140

135

6.6

80

135

6.9

54

135

5.0

53

135

3.6

81

114

2.1

93

135

3. 1

126

135

2.5

Direction

Preponderance^.^

Bishop, Calif.

(Jan. 1948 - Jan. 1957)

Magnitude 170

90

4. 1

234

90

40

409

90

3.2

299

90

2.6

305

90

2.0

256

90

2.4

170

112

2.1

176

90

2.3

175

90

2.5

242

90

3.6

222

90

5.7

161

90

^ Q

Direction

Preponderance

Blythe, Calif.

(Aug. 1942 - May 1944)

Magnitude 110

90

2.3

108

90

2.4

172

90

2.2

132

45

2.3

226

90

1.4

216

45

2.1

136

90

1.9

166

90

3.9

59

90

1.8

103

67

1.9

127

90

4.2

90 Direction _ 113

Preponderance 1 Q

See footnote at end of table.
18 AGRICULTURE HANDBOOK 346, U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderance oj wind erosion jorces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May- June July Aug. Sept. Oct. Nov. Dec.

China Lake, Calif.

(Apr. 1945 - Dec. 1959)

Magnitude

Direction

PreponderanceMagnitude

Direction

Preponderance.

Magnitude

Direction

PreponderanceMagnitude

Direction

Preponderance290 370 539 553 504 431 282 274 241 272 236

67 45 45 45 45 45 45 67 45 45 45

L6 L7 L7 L6 1.8 2.0 2.1 2.4 2.4 L9 1.6

El Centro Calif.

(Feb. 1945 - Apr. 1946; Nov. 1946 - Feb. 1958)

155 203 299 344 393 311 92 90 101 128 142

22 22 22 22 22 180 180 180 180 180 180

L6 2.0 2.9 3.6 3.8 3.7 2.1 2.3 2.6 4.-1 L6

Fort BragfiC.Calif.

(June 1943 - May 1945)

135 237 180 182 103 102 44 65 51 56 80

157 135 135 135 113 135 112 113 113 135 157

2.3 2.3 2.3 4.3 4.1 4.5 3.9 3.7 4.5 3.6 1.7

Fresno, Calif.

(May 1950 - Apr. 1955)

70 65 92 73 Ill 77 27 17 27 52 36

113 135 135 135 135 157 157 157 135 112 135

2.7 2.9 3.1 2.6 2.2 4.6 42 3.1 2.4 L9 2.0

194

45

1.7

117

22

1.4

103

135

L6

79

135

2.0

Marysville, Calif.

(Aug. 1943 - Oct. 1944)

Magnitude 141

113

3.3

187

135

4.3

188

135

3.0

121

135

3.2

131

135

6.4

195

135

4.6

101

135

3.6

61

113

3.2

47

135

4.9

54

135

4.6

36

135

9.3

150

Direction _- _ 112

Preponderance. 1.9

Merced, Calif.

(Jan. 1942 - Nov. 1946; Dec. 1947 - Dec. 1952)

103 96 173 141 127 137 69 49 55 58 52

135 135 113 113 113 113 113 113 113 113 135

3.8 3.5 3.3 4.2 3.3 3.6 40 40 3.6 3.6 3.5

Magnitude

Direction

Preponderance.

91

135

4 1

Palmdale, Calif.

(Jan. 1934 - Dec. 1941; Nov. 1948 - Nov. 1952)

Magnitude

Direction

Preponderance.

210 267 326 349 407 368 285 216 176 179 148

23 45 23 45 45 45 45 45 45 45 22

L8 2. 1 L6 2.0 2.4 42 5.7 5.0 4 3 2.4 L9

(Jan. 1933

158

45

L7

Riverside, Calif.

Dec. 1934; Feb., Apr. - June 1935; Feb. 1936 - July 1941; Sept. 1941 - May 1953)

Magnitude

Direction

Preponderance

68 74 80 94 107 119 124 112 81 53 50

67 112 157 157 157 157 135 157 157 157 23

1.2 L2 1.6 2.0 2.5 2.8 3,6 3.7 3.1 2.3 1. 1

58

21

L4

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 19

TABLE 1.—Relative magnitude^ prevailing wind erosion directiony^ and preponderance ofwind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Salinas, Calif.

(Aug. 1941 - Dec. 1944)

Magnitude 275

135

6.8

169

135

45

166

135

3.5

207

157

2.8

140

158

3.0

160

158

3.3

156

157

3.4

146

135

3.2

103

135

42

91

135

3.0

116

135

42

152

Direction _ 135

Preponderance 5.3

San Diego, Calif.

(Jan. 1951 - Dec. 1960)

Magnitude 72

90

L5

81

90

1.5

105

90

1.4

96

68

L3

66

22

1. 1

37

67

1.2

19

157

L3

20

22

1.1

24

157

L5

34

67

L4

81

90

1.4

57

Direction 113

Preponderance 1.3

San Miguel Island, Calif,

(Feb. 1940 - June 1942)

Magnitude 427

113

2.8

721

113

4.0

1,142

113

2.6

1,417

113

40

1,627

135

3.2

1,626

135

41

854

157

5.4

1,095

135

2.6

713

135

2.6

640

157

46

616

156

3.5

709

Direction 113

Preponderance 3.6

Santa Rosa, Calif.

(Apr. 1943 - Dec. 1945)

Magnitude * 36

135

3. 1

106

90

L9

109

68

1.6

131

135

1.6

96

68

L4

109

111

1.4

93

90

2.7

72

112

2. 1

36

90

1. 6

53

90

1.7

27

90

1. 5

55

Direction 90

Preponderance 48

Stockton, Calif.

(Feb. 1941 - June 1946)

Magnitude , _ 80

35

4.0

105

134

2.2

125

135

2.5

110

135

2.0

158

180

L7

185

180

2.4

56

180

3. 1

54

180

2.9

49

158

2.5

52

135

3.7

33

135

2.1

76

Direction 135

Preponderance 2.3

Thermal, Calif.

(July 1943 - Feb. 1945)

Magnitude-- __ __ 17

113

2.4

95

113

2.6

127

113

2.3

214

113

4 3

176

113

3.0

238

113

4 4

115

113

3.7

103

113

43

95

113

41

53

113

2.6

40

113

2.8

21

Direction 135

Preponderance _-_ 3.4

(Jan. 1942-

Victorville, Calif.

Feb. 1946; May-Sept. 1948; Sept. 1 950 - Jiline 1957)

Masmitude 224

77

1.1

311

180

L2

392

19

L3

413

180

L4

342

180

L3

283

45

1. 1

159

90

2.0

147

90

1.8

134

90

1.4

145

22

1.2

192

22

L3

218

Direction _> - 22

Preponderance 1.4

Denver, Colo.

(May 1950 - Apr. 1955)

Magnitude 265

135

1.2

448

135

1.1

423

157

LO

476

112

L2

251

112

L2

326

111

1.2

281

112

L8

152

90

L3

209

112

1.6

158

90

1.1

276

180

L3

332

Direction- 90

Preponderance L3

See footnote at end of table.
20 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitude, prevailing wind erosion direction^^ and preponderance oj wind erosion forces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

La Junta,

(Nov. 1942 -

Colo.

June 1945)

Magnitude _ _- 215

22

L5

334

158

1. 1

461

23

L3

533

90

1.1

430

45

1.1

562

45

L5

267

23

LO

270

67

1.4

261

44

L3

240

22

L3

330

90

1.3

211

Direction 180

Preponderance 1.3

Pueblo,

(Mar. 1950 -

Colo.

Feb. 1955)

Mairnitude- 357

157

1.6

364

113

1.2

451

180

1.6

352

68

L3

266

45

L4

393

67

1.3

193

90

1.2

182

113

1. 1

139

67

L2

152

157

1. 1

289

158

L4

402

Direction 157

Preponderance 1.5

Bridgeport, Conn.

(Jan.-Apr. 1953; Mar. 1960 - May 1963)

Magnitude

Direction

Preponderance348 340 387 406 234 145 136 151 274 302 327

157 135 157 157 180 45 180 23 45 22 113

L2 1.3 L2 L5 1.2 1.6 L3 1.7 1.5 L3 1.6

506

157

L4

Hartford, Conn,

(Jan. 1950 - May 1963)

Magnitude 190

135

L8

179

135

L8

221

135

1,5

273

112

2.0

128

90

L5

96

90

L6

59

90

1.4

68

90

L5

80

90

L8

102

90

L4

155

135

1.3

137

Direction 135

Preponderance 1.6

Stratford, Conn.

(Dec. 1942; Aug. 1943 - June 1944)

Magnitude 268

135

1.3

339

157

2.3

231

157

L4

200

45

L4

138

45

1.6

151

68

L6

241

66

1.3

140

45

2.5

246

23

2.5

200

158

L5

264

Direction 180

Preponderance 1.6

Windsor Locks, Conn.

(Sept. 1941 - Oct. 1944)

Magnitude

Direction

Preponderance190 351 246 224 100 94 46 39 76 134 137

135 135 113 135 90 90 90 90 90 135 113

L8 4.6 1. 3 1.9 2. 1 2.0 L6 1.7 1.7 1.5 L9

265

135

2.0

Wilmington, Del.

(Jan. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance.

192 227 257 182 105 94 59 63 82 110 135

135 157 135 135 112 135 112 90 90 22 135

L7 2.0 1.8 1.3 1. 1 1.2 1.4 L3 L4 1. 1 L7

136

157

1.4

Avon Park, Fla.

(Dec. 1943 - Sept. 1945)

Magnitude

Direction

Preponderance145 142 153 225 134 71 34 68 222 323 104

112 68 90 45 23 180 113 22 22 45 90

1.5 1.6 L2 1.6 2.0 1.2 1.2 1.7 1.8 2. 1 1.5

140

90

2.4

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PRÎ3DICTING SOIL LOSS 21

TABLE 1.—Relative magnitudej prevailing wind erosion direction,^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Cape Canaveral, Fla.

(Aug. 1950 - Feb. and Apr. 1954; Apr. 1956 - July 1962)

Magnitude

Direction

Preponderance179 235 225 206 152 95 79 74 174 227 169

113 135 113 135 158 135 135 135 180 45 113

1.5 1.4 1.4 L4 L3 L3 L6 L3 1. 1 1.4 L3

166

115

L4

Daytona Beach, Fla.

(Jan. 1953 - May 1963)

Magnitude

Direction

Preponderance163 216 188 216 150 109 74 75 153 165 132

68 45 45 22 22 22 180 23 23 45 90

L2 1. 2 1. 1 1.3 1.6 1.7 1. 6 1.7 1.7 2.0 1.4

127

90

1.3

Fort Myers, Fla.

(Jan. 1943 - Nov. 1945)

Magnitude

Direction

Preponderance.

72 93 148 129 100 61 32 48 106 162 68

67 45 45 23 22 180 169 22 23 45 45

L4 L3 L3 1.4 2.0 1.2 1.2 1.6 1.7 1.9 L8

78

68

2. 1

Homestead, Fla.

(Feb. 1943 - Nov. 1944; May, June, Aug.-Nov. 1945; Jan. 1956 - Dec. 1960)

Magnitude

Direction

Preponderance143 185 259 264 196 130 61 76 171 98 134

158 158 180 180 180 180 158 180 180 22 23

1. 2 1. 4 1. 3 2.0 2. 4 2. 5 2. 5 2.5 1. 7 2. 2 1. 6

137

158

1.3

(AF)r. 1949

Jacksonville, Fla.

- Feb. 1950; Oct. 1950 - Jan . 1963)

Magnitude - _ 45

45

L3

83

23

L5

68

180

L5

69

180

1.6

31

180

L8

23

22

L7

14

180

L5

14

45

1.5

31

45

1.9

42

45

1.9

37

45

1.2

40

Direction 45

Preponderance 1, 3

(Aug. 1952

Key West, Fla.

- June 1953; June 1960 - May 1963]

Magnitude - _ 210

90

1. 1

231

135

1.3

257

135

L6

293

157

1.3

193

158

2. 1

170

157

1.8

97

135

L7

99

158

2.2

173

180

L2

205

45

L9

220

45

L5

247

Direction 67

Preponderance 1.5

Orlando, Fla.

(Jan. 1953 ^ May 1954; July 1954 - May 1963)

Magnitude

Direction

Preponderance128 152 151 143 98 76 56 48 80 85 93

135 135 135 156 180 180 112 180 21 23 90

1.2 1.1 1. 1 1. 1 L4 L2 1. 1 L3 1.3 L3 L4

106

112

L2

Pensacola, Fla.

(Jan. 1952 - Dec. 1962)

Magnitude 134

90

L6

163

68

1.5

182

90

1. 8

158

135

1.6

119

112

1.6

74

90

L8

44

90

1.5

25

67

1. 3

45

68

1. 1

45

113

1.6

97

90

2.0

93

Direction 113

Preponderance 1.5

See footnote at end of table.
22 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitude^ prevailing wind erosion direction^^ and preponderance oj wind erosion forces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May- June July Aug. Sept. Oct. Nov. Dec.

Perry Field, Fla.

(May 1944 - May 1945)

Magnitude

Direction

Preponderance. »

41 91 62 85 26 12 16 10 15 93 22

90 67 45 68 45 45 45 45 45 135 112

L8 3.8 L6 3.0 3.2 4. 0 2.5 2.2 2.2 L3 2.3

22

90

1.3

Sarasota, Fla.

(July 1942 - May 1944)

104 124 178 125 109 31 19 25 37 85 109

90 90 68 68 21 45 113 67 45 68 68

L6 L6 L6 L3 1.4 L3 L3 L3 2.3 L7 L6

Magnitude

Direction

Preponderance- » _

106

90

L6

Tallahassee, Fla.

(Aug. 1952 - May 1963)

Magnitude

Direction

Preponderance.

65 75 87 79 36 23 17 15 24 27 40

112 90 90 90 90 90 90 23 45 90 112

L8 1.5 L7 L7 L4 L2 L5 1.2 1.5 L2 1.9

42

112

2. 1

Tampa, Fla.

(May 1941 - June 1947; Aug. 1947 - Dec. 1951)

Magnitude

Direction

Preponderance.

150 210 220 185 135 127 58 79 170 197 162

90 112 68 22 180 180 158 22 45 45 67

1.3 1.2 1.0 1. 1 L3 L3 L2 1.3 L4 2.0 1.7

156

68

1.6

Vero Beach, Fla.

(Jan. 1949 - Dec. 1964)

Magnitude

Direction

Preponderance.

137 167 198 196 176 107 89 112 130 237 141

157 158 135 22 23 22 180 43 23 23 23

L5 1. 2 1.3 L3 L6 1.6 1.6 1. 1 1. 8 2. 4 1. 1

162

158

1. 2

West Palm Beach, Fla.

(Jan. 1953 - May 1963)

Magnitude

Direction

Preponderance.

211 221 211 249 165 97 80 83 162 235 218

157 157 135 157 180 158 157 158 22 23 22

1.3 1.5 1.6 L6 1.6 L5 2.3 L8 1.8 2. 1 L4

205

180

1. 3

Albany, Ga.

(Oct. 1941 - June 1946; Feb. 1948 - Sept. 1953)

Magnitude. _ __ 104

92

1.3

124

90

1.2

136

112

1.3

93

135

L2

64

48

1. 1

42

23

L4

26

45

1.4

25

45

1.2

45

45

1.6

35

45

L5

56

157

L3

63

Direction 154

Preponderance 1. 1

Athens, Ga.

(Oct. 1955 - May 1963)

Magnitude

Direction

Preponderance

140 170 183 158 55 55 41 29 58 66 115

180 180 158 22 22 22 45 23 23 23 180

L4 L4 L5 L4 L6 L3 15 L5 2.0 1.8 L5

116

180

L4

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 23

TABLE 1—Relative magnitibde, prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Bainbridge, Ga.

(Oct. 1942 - Dec. 1944)

Magnitude

Direction

Preponderance.

90

45

1. 1

114

110

1.0

146

112

1.4

128

45

1. 2

61

23

1. 1

52

113

1. 1

51

45

1.5

53

45

1.3

73

23

1.9

63

45

L3

58

135

L5

101

180

L2

Marietta, Ga.

(Sept. 1946 - June 1947; Jan. 1948 - Feb. 1957)

Magnitude

Direction

Preponderance.

191 187 235 213 126 91 86 80 84 105 147

135 157 135 157 155 158 180 157 180 157 135

L5 1.5 1.5 1. 5 1. 3 1.4 L2 L4 1.5 L5 L9

161

157

1. 7

Savannah, Ga.

(Mar. 1953 - Feb. 1963)

Magnitude

Direction

Preponderance.

86 118 139 129 65 58 38 43 76 63 60

158 180 180 158 180 180 67 r)7 22 45 180

1.5 1.6 1. 3 L2 1.2 1.2 1.2 1. 1 1. 2 1.9 1.3

74

180

1.4

Valdosta, Ga.

(Apr. 1942 - May 1946)

Magnitude

Direction

Preponderance.

75 96 105 79 48 54 37 28 52 59 48

180 45 90 67 23 22 45 45 23 23 180

L2 1.0 1. 1 1.2 1.2 L4 1.4 1. 7 2.3 1.6 1.3

67

23

1. 3

Waycross, Ga.

(Dec. 1942 - July 1944)

Magnitude

Direction

Preponderance.

31 41 41 71 45 36 25 18 55 66 26

157 157 180 180 157 180 90 23 23 23 90

L3 1.7 1.2 1. 2 1. 7 1.7 1.2 3.0 2.6 2. 1 2. 1

52

67

1.2

Boise, Idaho

(Mar. 1950 - Feb. 1955)

Magnitude

Direction

Preponderance

329 278 361 268 215 163 124 182 121 315 196

135 135 135 135 135 135 135 157 135 157 135

3.4 4. 9 2.9 3.1 2.6 2.7 2.2 1.7 2.7 2.3 3.5

Magnitude

Direction

Preponderance.

207 309 359 405 314 303 226 176 173 257 177

157 135 157 157 157 157 157 135 157 135 157

2.2 2.6 2. 4 2.5 2. 3 2.0 2. 1 2. 1 2.3 3.0 2.4

252

135

3.0

Mountain Home, Idaho

(Jan. 1932 - Feb. 1933; July 1943 - Oct. 1945; May-Nov. 1949; Apr. 1951 - Nov. 1957)

179

157

2.3

Pocatello,

(May 1950 -

Idaho

Apr. 1955)

Magnitude.- 541

90

2.0

532

67

1.5

584

23

2.2

510

23

2.6

425

23

L8

382

45

L6

331

45

L3

183

45

L3

312

23

2. 1

351

23

L5

470

45

1.3

454

Direction 67

Preponderance 1. 6

See footnote at end of table.
24 AGRICULTURE HANDBOOK 346, U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitude^ j^revailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in S9 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Bellevüle, 111.

(Jan.-Dec. 1938; Mar. 1939 - July 1953)

Magnitude

Direction

Preponderance.

291 315 353 308 168 115 57 44 77 107 239

135 135 157 135 135 180 22 112 88 112 135

1.9 L9 1.6 1.3 1,4 1. 0 1. 1 1.0 1. 1 1. 3 1.4

212

135

1.6

Glenview, 111.

(Mar. 1945 - Nov. 1959)

Magnitude

Direction

Preponderance.

338 341 458 441 292 144 94 76 131 204 284

45 24 67 67 67 67 67 67 67 6? 67

1.3 1. 1 L7 1.7 2.3 2. 0 2.0 2.5 2.0 1.8 1.4

269

45

1. 3

Lawrenceville, 111.

(Jan. 1943 - Jan. 1946)

Magnitude

Direction

Preponderance102 167 195 203 113 87 47 46 25 72 117

135 112 45 135 67 67 45 55 90 68 113

1. 3 L2 1.6 1. 1 1.8 1.7 L8 L6 L8 1. 3 1,2

79

158

1. 2

Park Ridge, 111.

(Oct. 1946 - Jan. 1957)

Magnitude

Direction

Preponderance.

393 434 502 519 376 246 158 137 245 292 464

180 158 180 22 45 45 67 45 45 67 180

L2 L3 1. 4 L2 1, 4 1.2 1.3 1.5 L2 1.4 L2

371

22

L2

Peoria, 111.

(Aug. 1949 - Mar. 1952; Sept. 1956 - May 1963)

Magnitude

Direction

Preponderance _

207 238 307 301 182 107 68 57 115 146 279

113 157 180 157 90 68 90 90 90 112 135

1.3 L4 1.2 L3 1.2 1.3 L3 1.5 1. 7 1. 5 1. 3

184

135

1.2

Rantoul, 111.

(July 1936 - Feb. 1961)

Magnitude

Direction

Preponderance.

317 362 377 415 288 193 97 86 137 170 312

67 135 22 67 68 46 45 68 68 90 90

1. 1 1. 1 1. 1 L2 1.4 1. 3 L5 1.6 1. 5 1.4 1.2

262

112

1. 2

Rockford, 111.

(Nov. 1958 - May 1963)

Magnitude

Direction

Preponderance147 166 215 248 191 113 77 87 121 147 210

23 180 22 22 45 23 22 67 67 23 26

1.2 1. 4 L6 1.3 1.2 1.9 L3 L6 1.4 1. 1 1. 1

167

158

1.2

Bunker Hill, Ind.

(Feb.-Oct. 1945; Dec. 1955 - Apr. 1962)

Magnitude

Direction

Preponderance-__

215 336 376 412 321 160 109 103 148 170 307

22 180 45 23 45 46 45 67 67 32 23

1. 3 1. 7 L5 L3 1.5 1.4 L6 1.6 1. 4 1. 3 L5

266

44

L4

See footnote at end of table.
WIND EROSION FORCES AND »THEIR USE IN PREDICTING SOIL LOSS 25

TABLE 1—Relative magnitude^ prevailing wind erosion directionj^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Columbus, Ind.

(May 1943 - June 1945; July 1949 - June 1957)

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction „.

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

See footnote at end of table

228 231 288 243 159 100 66 60 76 120 220

90 68 22 90 68 67 45 67 90 90 135

1.3 1. 1 LO 1. 1 L5 1.4 1.2 1.4 1.6 1.6 1. 1

181

90

1. 1

Madison, Ind.

(Nov. 1941 - Apr. 1944)

198 245 324 263 180 63 51 60 79 135 185

21 180 158 22 112 68 22 68 112 112 23

L5 1.4 1.4 1. 1 1. 1 1.2 1.4 L3 1.5 1.2 1.2

200

180

1.6

South Bend, Ind.

(Aug. 1952 - May 1963)

226 262 331 292 223 128 90 77 132 150 259

45 180 180 135 112 112 112 90 90 90 45

1.2 1.2 1.3 1. 1 1, 1 1. 3 1.2 1.3 1.3 1.2 1.4

Burlington , Iowa

(Oct. 1949 - Sept. 1954)

369 339 731 345 266 152 98 80 138 226 433

157 157 180 157 22 68 45 90 135 68 135

1. 8 1.3 1. 2 1. 4 1. 3 1.3 1.2 1. 3 1.2 1.6 1.3

Des Moines, Iowa

(Aug. 1950 - July 1955)

458 545 732 693 533 388 287 164 251 303 598

135 135 135 135 112 67 135 112 135 113 135

1.5 1. 1 1. 4 1.6 1.3 1. 1 1. 3 1.2 1. 1 L5 1.7

241

45

1.2

310

158

1. 1

543

135

1.3

Dodge City, Kans.

(Jan. 1956 - Dec. 1960)

423 517 741 755 620 539 350 411 499 497 572

90 90 90 90 90 90 90 90 90 90 90

2. 1 2.0 2. 4 L7 2.2 2.4 2. 1 2.5 2.8 2.5 2.2

505

90

2. 3

Goodland, Kans.

(Jan. 1956 - Jan. 1961)

196

112

2.0

280

112

2.5

454

112

2. 5

429

112

2. 1

319

90

1.9

326

90

1.9

202

90

2. 0

220

90

2.2

249

90

2.7

260

112

2,4

337

113

2. 3

269

112

2.4

Olathe, Kans.

(Jan. 1947 - Aug. 1953)

230 262 355 303 216 177 91 85 132 151 241

90 90 90 90 90 68 68 68 90 90 90

L7 1.6 1.6 L3 1.6 1.8 2.2 L9 2.0 2.0 1.6

217

90

1.5
26 AGRICULTURE HANDBOOK 346^ U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitudey prevailing wind erosion directiony^ and preponderance oj wind erosion forces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

(Jan.

Salina,

1943-

Kans.

July 1956)

Magnitude

Direction _ _ _

313

90

2.0

383

90

L9

479

90

L8

479

90

1.6

340

90

1.8

368

90

2.0

231

90

2. 1

228

90

2.0

351

90

2.7

313

90

2. 1

337

112

L8

258

90

Preponderance 1. 7

Topeka,

(Mar. 1950 -

Kans.

Feb. 1955)

Magnitude- _ _ 373

90

1.5

433

112

L5

872

90

L6

585

112

1. 4

718

45

L2

425

90

L7

281

90

1.5

334

112

1.2

298

90

2.0

310

90

2.2

388

112

1.5

476

Direction _ _ _ 90

Preponderance - _ _ _ _ L6

Wichita,

(Aug. 1949 -

Kans.

July 1954)

Magnitude- _ ^__ 598

90

2.5

868

90

2. 1

1, 408

90

1.6

855

90

2. 1

1,025

90

2. 1

939

90

2.3

511

90

2. 1

422

90

1.9

590

90

2.3

636

90

2.9

672

90

2, 1

685

Direction 90

Preponderance _ _ L8

Bangor, Maine

(Jan. 1942 - Mar. 1945; Mar. 1948- Oct. 1949; Mar. 1951 - July 1956)

Magnitude

Direction

Preponderance.

331 376 328 288 195 144 121 144 183 175 242

113 113 113 112 112 90 112 113 112 112 112

1.9 1.7 1.7 L5 L6 L6 1.5 L4 1.6 L6 L7

271

135

1.9

Brunswick, Maine

(Dec. 1951 - Oct. 1962)

Magnitude

Direction

Preponderance.-

235 223 216 182 140 94 73 66 94 119 130

90 112 112 90 90 68 90 68 68 90 90

L9 L6 L5 L6 L9 L8 L5 L8 2.0 L5 L4

178

90

1.5

Caribou, Maine

(Aug. 1952 - May 1963)

Magnitude

Direction

Preponderance

379 377 447 323 260 189 150 136 189 226 260

157 158 157 157 135 135 157 157 158 157 158

L8 1.6 L9 L7 L5 L2 L3 L4 1.3 L6 L6

325

158

L6

Aberdeen, Md.

(Oct. 1936 - July 1953)

Magnitude

Direction

Preponderance

194 276 295 243 132 81 54 66 83 128 194

135 135 135 135 90 68 68 68 68 90 135

L3 L9 L6 1.3 L3 1.3 L6 L7 L4 L4 L5

173

135

1.5

Annapolis, Md.

(Mar. 1945 - Mar. 1960)

Magnitude

Direction

Preponderance.

172 237 263 206 125 77 57 50 73 82 145

135 135 135 112 90 90 90 90 90 90 135

L8 L9 L7 L5 1.5 1.8 2.0 2.0 2.0 L2 L4

143

135

1.7

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 27

TABLE 1—Relative magnitude, prevailing wind erosion direction,^ and preponderance ofmnd erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Frederick. Md,

(July 1947 - Oct. 1953)

Magnitude

Direction

Preponderance.

161 193 345 173 70 35 22 21 36 67 151

157 135 135 135 135 135 157 135 135 135 157

2.6 2.9 4.0 2. 1 1.9 1.9 2.3 L3 L8 1.8 2.6

110

157

2.8

Bedford, Mass.

(Feb. 1943 - Aug. 1962)

Magnitude

Direction

Preponderance269 259 287 256 170 126 89 100 125 177 221

157 157 158 158 180 23 45 45 67 22 157

L4 1.5 1.3 1. 2 1. 1 L4 L4 L3 1.2 L3 1. 1

265

158

1. 5

Chicopee Falls, Mass.

(Apr. 1941 - Dec. 1952)

Magnitude

Direction

Preponderance.

265

113

L5

366

135

2.0

320

112

1.6

314

112

L6

221

90

L6

164

90

L9

109

90

2. 1

97

90

2. 1

134

90

L9

206

90

L7

259

90

L5

278

135

L6

(Aug. 1952 - Nov. 1954; Jan. 1955

îîantucket Ivlass

Sept. 1957; Apr. 1958 - Nov. 1960; July 1961 - May 1963)

Magnitude

Direction

Preponderance.

511

135

1.4

530

157

L4

603

158

1. 3

518

67

1.3

295

45

L6

244

45

L9

191

45

1.9

214

66

L6

283

67

L5

403

45

1.3

436

135

1. 2

492

158

1.3

Worcester, Mass.

(Nov. 1959 - May 1963)

Magnitude

Direction

Preponderance.

216

22

1.9

205

22

2. 1

227

23

1.5

216

180

L7

82

22

L7

34

45

L8

16

22

L8

27

45

2.2

76

45

3.2

98

23

2.2

137

22

L4

177

22

L6

Battle Creek, Mich.

(Oct. 1942 - Apr. 1945; Dec. 1948 - Dec. 1954)

Magnitude

Direction

Preponderance.

288

22

L4

318

22

1.4

368

22

L6

324

180

L4

206

23

L5

162

22

1.5

118

22

L5

89

180

1.3

169

180

L3

154

45

L2

253

45

L3

324

45

L5

Cadillac, Mich.

(Dec. 1948 - Sept. 1953)

Magnitude

Direction

Preponderance. _ _

379 346 414 330 325 249 159 132 228 276 347

22 22 158 158 45 45 23 45 24 67 67

1. 4 L3 1.2 L5 L4 L2 L3 1.4 1.2 L4 1.2

354

23

L5

Flint, Mich.

(Dec. 1956 - May 1963)

Magnitude

Direction

Preponderance..

155 167 212 313 128 67 45 36 63 96 187

45 180 22 22 23 22 22 45 45 45 45

1. 4 1.4 1.6 L4 L3 L6 1. 4 L8 L2 L2 L6

145

45

1.5

See footnote at end of table.
28 AGRICULTURE HANDBOOK 346, U.S. DEFT. OF AGRICULTURE

TABLE. 1—Relative magnitude, prevailing wind erosion direction,^ and preponderance oj wind erosion jorces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

Item

Magnitude

Direction

Preponderance.

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Marquette

(Jan.-Dec. 1948; Dec.

, Mich.

1949- Nov. 1955)

118 123 193 199 184 143 100 93 131 125 128

90 112 90 90 90 90 68 90 90 90 90

L8 L8 L9 L7 2. 1 L8 L9 2.9 1. 7 2.0 L8

91

90

1. 8

Mount Clemens, Mich.

(Dec. 1936 - July 1953)

Magnitude

Direction

PreponderanceMagnitude

Direction

Preponderance364 368 364 315 182 143 104 100 156 206 341

45 45 45 67 90 69 68 90 90 68 67

L5 L2 L2 L3 L3 L3 L4 L5 L6 L5 L4

Muskegon, Mich.

(Jan.-May 1953; Jan. 1960 - May 1963)

240 233 256 268 169 122 82 74 102 141 254

22 180 22 45 65 45 45 67 67 67 45

1.7 L6 L4 L2 L5 L7 L4 2.3 L4 L4 1.5

320

45

L4

139

180

1. 1

Oseoda, Mich.

(July 1943 - Dec. 1945; Dec. 1950 - May 1958)

Magnitude

Direction

Preponderance187 224 261 265 186 140 107 109 137 199 181

112 135 180 31 43 180 22 45 22 46 44

L2 L2 L2 L3 1. 1 1. 1 1. 1 L3 L2 L2 1. 1

211

135

1. 0

Pellston, Mich.

(Jan. 1948 - Aug. 1954)

Magnitude

Direction

Preponderance324 263 328 272 255 180 164 117 183 225 279

180 180 180 180 180 22 22 22 22 22 158

1.4 L7 L6 L5 L5 L8 2.0 L7 L5 1. 3 L4

304

180

L4

Sault Sainte Marie, Mich.

(Aug. 1952 - May 1963)

Magnitude

Direction

Preponderance.

130 136 154 186 164 102 71 61 106 118 176

158 157 157 157 157 157 157 157 157 157 157

L8 2.3 2.5 2.9 2.5 2.6 3.1 2.2 2.3 2.3 L9

142

158

2. 1

Traverse City, Mich.

(Mar.-Oct. 1945; Jan. 1948 ~ Sept. 1953)

Magnitude

Direction

Preponderance.

410 343 433 331 262 205 144 127 254 310 431

67 68 68 68 67 45 67 67 68 68 90

1.3 L3 1.4 L4 L6 L7 1.6 1.6 L5 L7 1.7

376

45

L3

Ypsilanti, Mich.

(Jan. 1948 - Dec. 1957)

Magnitude

Direction

Preponderance

308 292 434 342 234 169 132 110 161 188 340

22 180 180 180 180 180 180 180 180 22 22

1.5 L6 L9 L8 L5 1.6 L6 L3 1.5 1.3 L6

302

22

1.5

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 29

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderance oj wind erosion jorces

in prevailing wind erosion direction jor 212 locations in 39 States by moTi^A^—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Duluth, Minn.

(Aug. 1949 - July 1954)

Magnitude

Direction

Preponderance.

731 773 917 920 637 486 304 298 453 779 897

158 180 157 180 180 22 180 22 180 22 157

L9 L6 L3 L7 L7 2.0 L7 L5 L8 L3 L6

622

157

L7

International Falls, Minn.

(Jan. 1956 ~ Jan. 1961)

Magnitude

Direction

Preponderance122 155 120 246 212 127 88 92 153 200 234

158 180 157 158 158 157 158 135 135 157 157

L4 L5 L3 L4 1. 3 1. 4 L5 1.3 1. 3 2. 3 1. 5

158

158

1.9

Minneapolis, Minn.

(Nov. 1949 - Oct. 1954)

Magnitude

Direction

Preponderance.

316 358 421 467 543 387 273 212 325 292 437

135 157 158 157 158 157 90 90 135 135 135

L5 1.7 L4 L5 1. 3 1.3 LO L2 L4 L6 L7

328

157

1.4

Rochester, Minn.

(Jan. 1956 - Jan. 1960)

Magnitude

Direction

Preponderance189 191 199 337 245 172 106 133 179 220 292

113 135 135 135 113 112 113 90 90 113 135

2.0 L9 L7 L8 L6 L8 L7 2. 1 2.0 2. 1 L6

237

113

1.6

Billings, Mont.

(Oct. 1949 - Sept. 1954)

Magnitude

Direction

Preponderance.

503 552 499 584 480 451 326 338 351 332 528

23 22 135 90 135 90 90 112 112 112 134

L4 L2 L3 L3 L3 1. 1 L4 L4 L5 L2 LO

514

159

L2

Cut Bank, Mont.

(Dec. 1942 - Nov. 1944)

Magnitude

Direction

Preponderance.

881 933 1,076 686 574 49 Î 525 407 567 453 341

180 180 180 180 180 23 180 180 180 180 22

4.5 3.3 2.2 2.3 L9 L3 2.5 2.5 2. 1 L9 2.6

425

180

4.4

Glasgow, Mont.

(Dec. 1942 - Nov. 1943; Jan. 1948 ^ Mar. 1957)

Magnitude

Direction

Preponderance.

198 176 314 370 373 337 193 216 235 201 202

157 156 157 157 157 158 158 157 157 157 157

2.9 3.0 2.8 2. 1 2.2 2.2 2.3 2,3 2.6 3.9 3.6

192

157

3.6

Great Falls, Mont.

(Aug. 1950 - July 1955)

Magnitude

Direction

Preponderance. .

1,189 1,283 876 828 732 732 407 469 522 837 999

45 45 45 23 22 22 23 22 23 45 45

3.2 3.3 L9 L6 L8 L6 L6 L5 L9 2. 1 3.5

,315

45

3.6

See footnote at end of table.
30 AGRICULTURE HAI^DBOOK 346^ U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitude^ prevailing wind erosion directionj^ and preponderance oj wind erosion jorces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Helena, Mont.

(Nov. 1949 - Oct. 1954)

Magnitude

Direction

Preponderance.

208 248 184 243 265 217 187 123 173 153 205

90 180 158 157 158 158 157 157 157 180 22

1.4 L8 1.6 L5 L6 1.8. L 4 1. 4 L7 L2 1. 3

269

157

1. 2

Lewistown, Mont.

(Aug. 1950 - July 1955)

Magnitude

Direction

Preponderance.

347 305 414 245 269 146 776 189 188 187 133

180 180 180 158 157 157 135 158 157 157 45

L7 1.4 2. 1 L9 2.7 2.0 L5 2. 1 L6 L5 L5

374

44

L6

Miles City, Mont.

(Jan. 1948 - July 1953)

Magnitude

Direction

Preponderance.

207 176 319 391 307 283 214 166 196 226 247

135 157 157 135 157 158 135 135 135 157 157

L8 L7 2. 1 2.6 2,0 L8 L6 L6 1.9 2.3 3. 1

184

157

2.5

Missoula, Mont.

(Aug. 1950 ~ July 1955)

Magnitude

Direction

Preponderance.

173 136 173 193 188 191 149 154 145 99 63

158 158 158 22 180 180 157 135 135 112 157

L5 L4 L5 1.4 L2 L3 L5 L2 L2 L5 L6

98

157

L6

Grand Island, Nebr.

(Jan. 1956 - Dec. 1960)

Magnitude

Direction

Preponderance.

262 281 435 471 377 341 211 221 264 312 418

112 112 112 90 90 90 90 90 90 112 112

2.2 2. 1 L6 L6 L7 2.0 L6 L9 2.2 2.4 L9

323

112

2. 1

Lincoln, Nebr.

(Oct. 1942 - June 1955)

Magnitude

Direction

Preponderance.

259 331 439 427 325 228 140 151 148 177 293

112 113 112 112 113 112 112 112 112 112 113

2.4 L5 1.5 L6 1.6 L6 1.8 L5 L8 L7 2. 1

233

112

2. 1

North Platte, Nebr.

(Jan. 1956 - Dec. 1960)

Magnitude

Direction

Preponderance.

136 160 364 412 320 206 124 162 193 236 325

112 112 112 112 112 112 112 112 90 112 112

2.3 2.6 2. 1 2.6 2.2 2.4 2.0 2.6 2.4 3. 1 3.0

239

112

3.4

Omaha, Nebr.

(Nov. 1949 - Oct. 1954)

Magnitude

Direction

Preponderance

405 452 848 623 802 360 230 202 236 283 416

113 113 113 135 90 112 101 112 112 112 113

2.9 L7 1.7 L9 L7 L6 L7 L3 2.0 L9 2. 1

391

112

2. 1

See footnote at end of table.
WIND EROSION FORCES AND ^THEIR USE IN PREDICTING SOIL LOSS 31

TABLE 1.^—Relatim magnitude, prevailing wind erosion direction,^ and preponderance of wind erosion jorces

in prevailing wind erosion direction jor 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar, Apr. May June I July Aug. Sept. Oct. Nov. Dec.

Scottsbluff, Nebr.

(Jan. 1943^- Sept. 1944)

Magnitude

Direction

Preponderance.

299 412 427 413 341 346 179 188 134 174 290

158 157 135 135 113 156 135 135 90 135 113

2. 1 2.0 L9 L6 1.7 L6 1.4 i.é 1. 3 2. 3 2.9

154

158

2.7

Fallón, Nev.

(Apr. 1950 - Dec. 1958)

Magnitude

Direction

Preponderance.

133 151 204 173 157 135 63 43 33 73 68

45 67 23 180 180 158 158 22 135 23 111

L6 1.5 L2 1.4 L2 L8 L5 1.5 1. 1 1.5 L2

107

90

L5

Las Vegas, Nev.

(Jan. - Mar. 1952; Aug. 1952 - Deg. 1962)

Magnitude

Direction

Preponderance.

124 242 330 350 395 327 244 208 179 171 108

90- 90 67 45 67 45 45 67 45 67 68

L8 1. 4 L7 L9 2.2 2.6 2.0 2.0 2.6 L9 L8

120

90

L8

Mercury, Nev.

(Apr. 1951 - June 1953)

Magnitude

Direction

Preponderance.

240 338 379 232 284 293 139 146 113 96 133

90 90 68 90 68 90 89 90 90 90 90

2.8 2. 1 2. 2 2. 2 2. 3 2. 9 1.3 3.2 2.8 2.8 3.2

279

90

3.7

Reno, Nev.

(Sept. 1952 - Jan. 1963)

Magnitude

Direction

Preponderance.

151 165 188 191 157 130 96 94 68 84 81

90 90 112 113 157 157 157 158 135 112 90

2.2 2.1 1.3 1.6 1.6 2.4 2.4 2.7 1.2 1.5 2.1

110

90

2.2

Tonopah, Nev.

(Apr. 1951 - Feb. 1956)

Magnitude

Direction

Preponderance.

203 425 551 487 . 513 410 215 252 215 305 281

113 135 135 135 135 113 112 90 112 135 135

3.0 3.0 3.2 2L7 2.3 2.3 2.1 2.6 2.6 2.5 3.1

269

113

2.6

Concord, N.H.

(Jan. 1953 - May 1963)

Magnitude

Direction

Preponderance.

96 94 126 99 65 38 29 22 32 60 60

135 135 135 135 135 135 135 135 135 135 135

2.8 2.8 2.2 2.0 2.2 1.8 2.1 1.8 1.6 1.9 2.0

80

135

3.0

Manchester, N.H.

(Oct. 1941 - Oct. 1949; Mar. 1951 - Oct. 1953)

Magnitude

Direction

Preponderance.

167 253 217 221 114 99 61 36 66 100 141

135 135 156 157 135 135 112 135 113 113 135

1.7 1.6 1.4 1.6 1.3 1.2 1.3 1.5 1.4 1.5 1.5

207

158

1.8

See footnote at end of table.
32 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitude^ prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by moníA«—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Portsmouth, N.H.

(Apr. 1956 - Mar. 1961)

Magnitude

Direction ^

Preponderance!

177 199 183 150 138 115 79 48 86 97 90

135 157 157 157 157 158 135 113 112 135 135

1.4 1.9 1.6 1.4 1.4 1.2 1.4 1.2 1.1 1.4 1.4

140

135

1.4

Atlantic City, N.J.

(July 1958 - May 1963)

Magnitude

Direction

Preponderance

365 360 384 333 179 133 96 70 150 217 281

158 158 158 158 157 146 90 68 135 180 157

2.2 2.0 1.9 1.6 1.3 1.2 1.2 1.3 1.2 1.1 1.7

321

157

1.6

Lakehurst, N.J.

(Mar. 1945 - Sept. 1949; Nov. 1949 - Dec. 1959)

Magnitude 275

180

1.8

327

180

2.0

355

180

1.9

262

22

1.5

178

22

1.7

107

23

1.8

72

45

2.1

56

45

1.7

71

45

1.7

96

23

1.8

198

22

1.6

206

Direction. 180

Preponderance 1.8

Trenton, N.J.

(Aug. 1942 - Mar. 1946; Aug. 1948 - Aug. 1956)

Magnitude _ _ _ 218

158

1.2

215

157

1.6

255

158

1.4

221

158

1.2

117

158

1.2

80

21

1.2

48

45

1.4

63

45

1.1

87

68

1.4

136

23

1.2

179

157

1.5

198

Direction _ _ 158

Preponderance 1.4

Albuquerque, N. Mex.

(Jan. 1949 - Dec. 1953)

Magnitude _ _ _ 396

158

1.8

354

157

1.6

591

157

1.5

554

157

1.4

601

158

1.3

450

135

1.5

438

135

1.4

387

157

1.9

271

157

1.4

270

135

1.3

190

158

1.4

271

Direction 157

Preponderance 1.5

Hobbs, N. Mex.

(Jan. 1942 ~ Dec. 1946)

Magnitude. _ 183

22

1.8

328

180

1.5

45*^

23

2.1

381

180

1.3

309

23

1.2

310

90

1.3

766

90

1.6

107

68

1.8

121

67

2.7

115

68

1.8

208

45

1.7

145

Direction

Preponderance

23

1.3

Rosweü, N. Mex.

(July 1942 - Dec. 1952)

Magnitude 133

68

1.6

160

80

1.5

301

67

1.3

235

68

1.7

238

90

1.6

226

90

2.0

94

90

2.2

84

112

2.0

92

90

2.6

99

90

2.2

96

68

1.4

105

Direction-_ _ _ _ 90

Preponderance 1.5

Geneva, N.Y.

(Apr. 1952 - Mar. 1953)

Magnitude

Direction

Preponderance

141 280 167 169 188 157 198 96 70 207 224

135 157 113 90 113 112 68 90 90 90 90

2.0 1.9 1.8 2.4 2.4 1.8 2.8 2.1 2.3 2.1 1.8

154

90

1.4

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 33

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderanx^e of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

New York, N.Y.

(Apr. 1945 - Aug. 1957)

Magnitude

Direction

Preponderance.

431 481 523 399 305 198 153 136 182 241 434

158 158 158 158 158 113 112 90 112 180 180

1.6 1.9 1.7 1.5 1.1 1.4 1.4 1.2 1.1 1.1 1.5

437

158

1.7

Niagara, N.Y.

(June 1951 - July 1960; Nov.-Dec. 1961; Jan. 1962 - July and Oct. 1962)

Magnitude

Direction

Preponderance.

347 320 276 230 171 143 130 126 174 212 246

23 23 44 45 45 45 45 45 45 45 45

1.7 1.5 1.6 2.0 1.6 1.8 2.1 2.2 1.7 1.7 1.8

344

23

2.0

Plattsburgh, N.Y.

(Jan. 1956 - Dec. 1962)

Magnitude

Direction

Preponderance.

104

157

1.3

153

135

1.3

137

135

1.6

122

135

1.6

126

135

2.0

90

135

1.8

66

135

1.6

63

135

2.1

72

113

1.8

94

135

2.1

109

113

1.3

94

113

1.5

Rome, N.Y.

(July 1942 - Mar. 1955)

Magnitude

Direction

Preponderance.

177 230 231 177 131 79 56 41 70 85 140

158 157 157 157 157 135 157 157 157 135 157

2.7 3.1 2.6 2.5 2.5 2.1 1.7 2.1 1.9 1.7 2.2

178

158

2,5

Schenectady, N.Y.

(Sept. 1950 - Feb. 1953; June 1953 - Aug. 1955)

Magnitude

Direction

Preponderance.

203 193 254 238 195 117 117 128 146 115 179

157 157 157 157 157 158 158 157 157 157 158

5.6 2.8 2.4 1.6 2.6 2.2 2.5 1.9 1.5 2.1 2.0

131

157

2.7

Westhampton Beach, N.Y.

(Aug. 1943 - Nov. 1945; June 1951 - Jan. 1959)

Magnitude

Direction

Preponderance.

274

135

1.2

268

157

1.5

315

158

1.2

275

22

1.2

224

45

1.2

179

45

1.4

148

45

1.8

172

45

1.6

217

45

1.6

236

23

1.3

280

89

1.1

247

158

1.2

Cherry Point, N.C.

(Mar. 1945 - Mar. 1959)

Magnitude

Direction

Preponderance.

199 219 274 281 169 132 108 125 155 143 129

67 67 67 67 67 67 67 67 67 67 67

1.7 1.7 2.0 2.6 2.9 2.5 2.8 2.2 2.5 2.3 2.0

140

68

1.7

Hatteras, N.C.

(Jan. 1953 - May 1963)

350 387 365 363 238 217 190 270 284 264 276

90 68 68 68 67 67 67 67 67 67 90

1.2 1.5 1.4 1.8 2.8 2.6 2.9 1.6 1.7 1.9 1.6

Magnitude

Direction

Preponderance.

318

68

1.3

See footnote at end of table.
34 AGRICULTURE HANDBOOK 346, U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States bi/months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Jacksonville, N.C.

(Jan. 1955 - Mar. 1959)

Magnitude 1

Direction

Preponderance- _

109 121 142 153 63 61 54 77 89 79 64

113 135 45 63 67 90 67 45 64 67 89

1.3 1.3 1.2 1.6 1.9 1.5 2.1 2.0 1.7 2.4 1.2

57

90

1.3

WeeksvHle, N.C.

(Mar.-Dec. 1945; May 1952 - Apr. 1954)

Magnitude

Direction

Preponderance.

115 99 138 128 68 51 36 57 77 46 64

68 68 45 67 45 67 45 45 45 68 112

1.9 2.0 1.5 2.7 1.7 1.6 3.1 2.4 3.8 2.0 3.1

94

67

1.6

Wilmingtonj N.C.

(Aug. 1952 - July 1953; Sept. 1959 - May 1963)

Magnitude

Direction

Preponderance192 264 247 217 123 132 83 97 160 117 203

90 90 112 68 68 90 68 68 90 90 90

1.4 1.5 1.1 1.3 2.0 2.1 2.5 1.6 1.4 2.0 2.0

170

90

1.4

Winston-Salem, N.C.

(Aug. 1952-May 1963)

Magnitude

Direction

Preponderance.

173 204 227 232 112 83 71 69 98 123 145

45 23 45 45 45 45 45 45 45 45 45

1.2 1.2 1.2 1.4 2.3 2.2 2.2 2.3 2.8 2.2 1.5

Bismarck, N. Dak.

(Aug. 1949 - July 1954)

134

45

1.3

Magnitude

direction

Preponderance.

303 301 574 581 575 729 292 327 316 362 503

135 157 125 135 135 157 135 113 135 135 135

1.7 2.0 1.3 1.7 1.8 1.7 1.5 L4 2.1 2.0 2.4

298

135

2.4

Fargo, N. Dak.

(Oct. 1949 - Sept. 1954)

Magnitude

Direction

Preponderance

614 565 713 1,002 790 838 414 400 491 649 769

113 113 113 135 113 135 113 112 135 135 113

2.5 2.0 L9 1.7 1.5 1.2 1.7 1.6 1.6 1.9 2.4

503

113

2.2

Grand Forks, N. Dak.

(Jan. 1949 - Dec. 1954; Mar. 1959 - Aug. 1960)

Magnitude

Direction

Preponderance

571 439 548 749 580 526 295 282 462 593 679

112 113 112 113 113 i«0 113 112 135 113 113

3.2 2.5 2.1 2,0 1.5 1.2 1.4 1.7 1.3 1.8 2.5

420

113

2.5

Minot, N. Dak.

(Dec. 1948-June 1960)

Magnitude

Direction

Preponderance

446 432 474 530 452 412 263 256 381 370 510

135 135 135 135 135 157 135 113 157 135 135

1.7 1.8 1.7 1.5 1.5 1.3 1.5 1.4 1.7 1.8 2.2

407

135

1.6

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 35

TABLE 1.—Relative magnitude^ prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Cincinnati, Ohio

(Jan. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance.

212 217 252 234 127 81 57 40 75 102 195

67 45 23 45 45 45 45 45 45 45 45

1.5 1.3 , 1.3 1.6 1.6 1.8 1.7 1.8 1.8 1.7 1.5

163

45

1.6

Cleveland, Ohio

(Jan. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance.

527 589 679 609 371 292 188 233 221 303 581

22 180 23 23 67 45 67 157 68 67 23

1.3 1.2 1.3 1.3 1.3 1.2 1.4 1.1 1.2 1.4 1.3

466

45

1.2

Columbus, Ohio

(Jan. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance

169 187 227 178 108 66 46 41 56 73 156

135 180 23 45 67 68 68 90 90 90 45

1. 1 1. 1 1.2 1.3 1.4 1.4 1.4 1.4 1.4 1.4 1.3

182

67

1.2

Dayton, Ohio

(Jan. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance.

292 326 358 282 162 100 69 49 80 115 283

158 180 180 22 23 45 24 45 67 46 23

1. 1 1.3 1.4 1.3 1.3 1.3 1.4 1.2 1.2 1.2 1.2

253

45

1.1

Toledo, Ohio

(Mar. 1950 - Feb. 1955)

Magnitude

Direction

Preponderance.

457 448 774 468 359 252 229 103 194 235 479

23 23 22 23 23 45 66 45 22 45 50

1.4 1.5 1.4 1.6 1.7 1.4 1.1 1.3 1.4 1.5 1.6

623

45

2.0

Magnitude

Direction

Preponderance.

Youngstown, Ohio

(Jan. 1951 - Dec. 1960)

254 271 297 215 138 97 67 55 87 126 269

22 180 22 22 22 23 45 68 45 45 23

1.4 1.5 1.6 1.4 1.2 1.1 1.3 1.3 1.3 1.3 2.0

252

23

1.7

Oklahoma City, Okla.

(Jan. 1949 - Dec. 1953)

Magnitude

Direction

Preponderance.

1,028 1,043 1,338 1,273 1,099 927 538 606 543 691 809

90 90 90 90 90 90 90 90 90 90 90

2.6 2.4 1.7 2.4 2.1 2.1 2.1 2.0 2.1 3.1 2.6

940

90

2.5

Tulsa, Okla.

(Jan. 1949 - Dec. 1953)

Magnitude

Direction

Preponderance. _

396 379 537 504 331 271 198 217 162 236 293

90 90 90 90 90 90 90 90 90 90 90

2.6 2.8 1.8 2.2 2.2 2.7 2.0 1.9 2.8 2.7 2.7

329

90

2.1

See footnote at end of table.
36 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderanx^e of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Gontmned

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov.

- Dec.

Astoria, Oreg.

(Feb. 1953 - Jan. 1963)

Magnitude

Direction

Preponderance175 162 143 114 86 81 108 79 76 98 170

67 68 67 68 135 135 135 135 90 67 68

1.6 1.6 1.5 1.2 1.3 1.7 3,1 2.1 1.4 2.3 2.1

180

67

1.8

Klamath Falls, Oreg.

(Jan. 1948 - Deo. 1954; Sept. 1959 - Aug. 1962)

Magnitude

Direction

Preponderance208 178 233 187 140 106 63 61 96 137 161

90 112 113 113 113 130 113 113 112 111 112

1.8 1.8 1.3 1.5 1.6 1.3 2.0 1.8 1.4 1.9 2.0

153

112

1.4

Medford, Oreg.

(Aug. 1950 - July 1955)

Magnitude

Direction

I^eponderance.

170 122 212 161 117 111 54 69 61 99 123

113 134 113 135 135 157 135 135 135 113 118

1.5 1.5 1.5 1.6 2.3 1.7 1.7 2.2 1.7 1.7 1.9

142

112

2.6

Pendleton, Oreg,

(Sept. 1952 - Jan. 1963)

Magnitude

Direction

Preponderance128 242 286 301 276 266 192 162 200 119 190

22 180 180 180 180 180 180 180 180 180 180

1.2 2,0 3.1 4,1 4.8 4.2 3.2 3.9 3.7 3.1 2.7

180

180

1.7

Portland, Oreg.

(Sept. 1951 - Dec. 1960)

Magnitude

Direction

Preponderance.

387 334 250 172 101 83 71 51 78 123 226

90 68 68 90 90 112 135 135 90 90 90

1. 1 L5 1.2 L5 1.4 1.3 1.8 L8 1.2 L6 1. 1

381

90

1.2

Redmond, Oreg.

(Aug., Sept., Dec. 1942; Jan. 1943 - Apr. 1944)

Magnitude

Direction

Preponderance159 122 238 181 159 120 122 80 73 144 69

90 112 135 135 135 135 135 135 113 90 90

1.6 L8 1. 6 1.7 2.6 1.9 2,7 2.7 3.2 1.7 1,5

164

90

2.4

Salem, Oreg.

(Jan. 1953 - Jan. 1963)

Magnitude

Direction

Preponderance136 134 129 80 42 30 37 35 47 64 116

90 90 90 90 90 68 90 90 90 90 90

6.6 5.4 3.8 2. 1 1.6 L4 L7 L8 2.6 4.5 5.6

131

90

5.5

Quonset Point, R.I.

(Mar. 1945 - Feb. 1959)

Magnitude 475

90

1.6

449

112

L3

459

90

1.5

451

90

1.6

324

68

2.0

222

68

2.2

133

68

2. 2

163

90

2. 1

213

90

2.2

324

68

2.0

388

90

1. 5

387

Direction _ _ 112

Preponderance 1. 3

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 37

TABLE 1.—Relative magnitude, prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Beaufort, S.C.

(Apr.-Nov. 1945; Nov. 1957 - Oct. 1961)

Magnitude

Direction

Preponderance52 109 55 105 49 35 23 10 66 37 47

23 180 168 90 180 67 68 45 45 45 68

1.2 1.7 1.6 1.3 1.4 1.5 1.9 1.3 1.6 2.3 1.2

56

45

1.3

Florence, S.C.

(Jan. 1958; Feb. 1959 - May 1963)

Magnitude

Direction

Preponderance68 100 99 98 42 40 23 18 39 34 78

67 45 45 45 45 67 67 67 45 67 67

2. 1 2.3 1.6 1.5 1.4 2.3 1.8 2.2 1.8 2. 1 1.9

64

45

Greenville, S.C.

(Jan. 1953 - Sept. 1962; Nov. 1962 - May 1963)

Magnitude

Direction _

Preponderance122 128 147 147 78 61 43 48 79 88 80

45 45 45 45 45 45 45 45 45 45 45

2.0 2.4 2.0 1.9 2.4 2. 1 2.0 2.3 3.3 2.7 2.3

89

45

2.3

Myrtle Beach, S.C.

(Nov. 1942 - June 1947; Jan. 1949 - Dec. 1954)

Magnitude

Direction

Preponderance68 102 110 116 86 83 81 66 47 39 53

45 45 45 67 67 68 67 68 45 45 23

1.3 1.2 1.2 1.3 1.8 1.7 2.3 2.0 1.4 1.3 1.2

59

23

1.4

Sumter, S.C.

(Jan. 1942 - May 1955)

Magnitude

Direction

Preponderance74 91 119 102 60 37 35 29 57 55 51

45 45 45 45 45 67 45 45 45 45 45

1.7 1.8 1.5 1.6 1.6 1.4 1.9 1.7 3. 1 2.3 1.9

58

45

1.7

Huron, S. Dak.

(Jan. 1956 - Dec. 1960)

Magnitude

Direction

Preponderance289 254 354 482 380 295 226 223 286 386 434

113 113 113 113 113 112 112 112 112 135 135

2.9 2.6 2.6 1.8 1.8 1.9 2.3 2.6 2.0 2.4 2.5

293

135

2.7

Rapid City, S. Dak.

(Sept. 1949 - Aug. 1959)

Magnitude

Direction

Preponderance.

538 459 748 545 423 328 332 306 383 430 695

113 113 113 113 113 113 113 113 113 113 113

2.7 2.9 3.0 2.4 2.0 2.4 2.4 2.3 2.7 2.6 3.0

586

135

2.9

Sioux Falls, S. Dak.

(Mar. 1950 - Feb. 1955)

Magnitude

Direction

Preponderance346 543 809 686 512 400 231 203 289 350 464

113 112 135 113 135 135 112 112 113 112 135

2.2 1.5 1.5 1.9 1.4 1.4 1.6 1.6 1.6 1.7 2.3

327

113

2.0

See footnote at end of table.
38 AGRICULTURE HANDBOOK 346, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relative magnitude, prevailing mind erosion direction,^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Amarillo, Tex.

(May 1950 - Apr. 1955)

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance .

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction

Preponderance

Magnitude

Direction ,

Preponderance

See footnote at end of table.

469 734 949 865 794 619 390 242 325 385 400

67 90 45 67 67 68 90 68 68 68 68

L9 L7 L3 L4 L3 L9 1. 4 1.9 2. 1 2.0 1.7

595

67

L8

Austin, Tex.

(Jan. 1949 - Dec. 1953)

264 234 260 248 204 164 110 157 124 144 215

90 90 104 90 90 90 90 90 90 90 90

2.3 L8 1. 7 L8 2. 1 L9 L7 L9 L9 2. 1 2.4

244

90

L8

Brownsville, Tex.

(Jan. 1949 - Dec. 1953)

463 454 577 608 591 416 328 267 207 216 279

113 113 113 135 135 135 135 135 113 135 113

3.6 2.6 2. 1 2. 1 3, 1 3.0 3.7 2.5 L4 L7 3.2

378

112

2.9

Corpus Christi, Tex.

(Jan. 1949 - Dec. 1953)

563 525 697 643 504 391 391 301 173 208 398

112 113 112 113 113 113 113 135 135 113 112

3. 1 3.0 2.4 2.3 2.3 3.4 2. 7 L8 L3 1.7 j 2.5

398

112

2.3

Dalhart, Tex.

(Nov. 1942 - Dec. 1945)

328 463 717 582 545 563 279 279 496 312 451

45 45 45 67 45 67 68 68 67 67 67

2.4 2.2 2.3 L8 2.0 2.2 2.3 2.3 2.8 2.6 2.0

358

67

2.2

DaUas, Tex.

(Jan. 1949 - Dec. 1953)

320 258 441 474 343 337 181 168 109 160 262

90 112 112 90 90 90 90 90 90 90 90

2.9 2.2 1.9 2.3 2.2 2.6 2. 1 L9 L9 2.5 L8

252

92

2. 1

Galveston, Tex.

(Jan. 1949 - Dec. 195a)

460 492 717 568 383 334 294 183 232 620 367

113 113 113 135 113 112 90 90 49 135 90

L9 L5 1. 4 1.3 1.9 2.2 2.3 L5 L4 L2 2.0

405

112

1. 3

Houston, Tex.

(Jan. 1949 - Dec. 1953)

429 371 482 542 425 236 167 200 135 482 386 365

112 112 112 113 113 90 90 112 45 22 90 112

1. 9 L6 L6 L8 L7 L9 L8 1.6 1.2 L4 1.6 L6
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 39

TABLE 1.—Relative magnitude, prevailing wind erosion direction,^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Laredo, Tex.

(Jan. 1943- Feb. 1945; Sept. 1946- Aug. 1955)

Magnitude

Direction

Preponderance175 222 320 409 437 496 433 357 240 228 196

115 135 135 135 135 135 135 135 135 135 113

L9 1.8 1.7 2.4 2.9 3. 5 3.8 3.2 1.7 2.2 L8

169

113

2. 0

Lubbock, Tex.

(Aug. 1942 - Dec. 1945; Jan. 1950- Dec. 1956)

Magnitude

Direction

Preponderance.

308 438 640 546 456 428 178 145 209 204 293

43 23 22 45 68 90 90 90 68 67 56

1. 3 1.2 1.5 1. 1 1. 3 1.9 2.0 1.5 2.0 L6 1.2

385

22

1. 2

Midland, Tex.

(Apr. 1940 - Oct. 1946)

Magnitude

Direction

Preponderance.

141 262 346 455 289 245 118 95 149 150 143

23 180 45 157 90 90 90 90 90 90 45

1.6 1. 1 1.2 1. 1 L5 1.8 L7 1.5 1.8 1.9 L4

166

90

1. 1

Port Arthur, Tex.

(May 1950-Apr. 1955)

Magnitude

Direction

Preponderance.

359 393 386 379 265 149 171 76 97 149 252

135 90 90 112 112 90 90 68 67 112 112

1.5 1.6 2.2 2. 1 2.3 1.6 L2 1. 3 1.3 1. 3 1. 4

320

112

1. 4

San Angelo, Tex.

(Jan. 1955 - Dec. 1960)

Magnitude

Direction

Preponderance.

250 331 472 381 299 239 189 118 182 192 255

45 45 66 67 90 90 90 90 68 68 67

L5 1.3 1. 1 1.5 L8 2.0 2.8 1.6 L8 L7 2. 1

400

45

2.7

San Antonio, Tex.

(Jan. 1949 - Dec. 1953)

Magnitude

Direction

Preponderance.

288 277 322 296 245 227 168 153 121 133 197

67 113 112 69 135 135 135 135 45 68 90

L6 L3 1.2 1. 1 L7 1.6 L9 1.7 L2 1.5 2. 1

226

90

1.6

(Oct. 1942 - Sept.

Waco, Tex.

1945; Jan. 1949-Dec.. 1955)

Magnitude. ______ ___ 260

90

2.5

230

90

2.4

311

90

2.5

277

90

2.4

232

90

2.5

243

90

3. 0

168

68

2.4

135

68

2.3

124

68

2.0

147

68

2.4

228

90

2.5

227

Direction 90

Preponderance 2.6

Wichita Falls, Tex.

(Apr. 1942 - Aug. 1955)

Magnitude

Direction

Preponderance

346 378 560 460 340 354 218 180 207 234 383

89 90 112 90 112 90 90 90 90 90 112

1.9 1.6 L5 1.8 1.9 2.3 L5 L4 1.8 2. 1 L6

339

90

L6

See footnote at end of table.
40 AGRICULTURE HANDBOOK 346, U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitudej prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for M2 locations in 39 States by months—Gontmued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Dugway, Utah

(June 1943-Jan. 1946; Dec. 1949- Nov. 1950; Jan. - May 1951; Dec. 1951-June 1957)

Magnitude

Direction

Preponderance.

79 106 149 169 174 182 122 132 109 84 72

90 90 90 90 90 90 90 90 90 90 90

4.0 3.2 2.8 1.9 2.0 2. 1 1.8 2.2 2.0 2.2 2.6

71

90

2.6

Ogden, Utah

(Oct. 1941 - Feb. 1946; June 1946- Dec. 1954)

Magnitude

Direction

Preponderance

227 246 258 259 282 272 290 301 278 263 202

90 45 90 67 23 23 22 23 22 22 23

1.4 1. 3 1. 3 1.2 1.3 1.2 1.9 1.6 2. 1 2.2 1.3

180

68

1. 1

Salt Lake City, Utah

(May 1950-Apr. 1955)

Magnitude

Direction*

Preponderance.

223

112

2.6

204

113

2.5

339

112

1.7

242

90

1.6

356

113

L7

402

113

1.7

211

90

1.6

301

113

L9

159

112

2.4

174

113

1.5

148

112

2. 4

206

112

2. 4

Wendover, Utah

(Aug. 1942 - Feb. 1946; June 1946 - May 1947; July 1947 - Nov. 1949)

Magnitude

Direction

Preponderance.

105

112

L4

100

135

1.9

168

135

L9

146

135

2. 1

114

135

1.6

135

113

L5

100

112

L4

107

113

1.3

74

135

L6

87

135

1.9

106

135

1.8

62

135

1.9

Blackstone, Va.

(Feb. 1949 - Dec. 1953)

Magnitude

Direction

Preponderance.

150

49

1.8

118

45

L2

154

67

L2

163

45

L6

84

45

1.9

55

45

L8

60

49

2.3

33

67

L6

41

67

L8

41

67

1.7

91

67

L5

85

45

1.3

Chincoteague, Va.

(Mar. 1945-June 1957)

Magnitude _ _ 320

135

L4

382

157

L3

415

158

L3

374

88

1. 1

244

45

1.2

181

42

1. 1

144

67

1. 5

142

67

L3

215

45

L7

246

45

L4

247

135

L3

244

Direction 149

Preponderance 1.3

Hampton, Va.

(Oct.-Dec. 1936; Feb. 1937-June 1953)

Magnitude

Direction

Preponderance.

369 462 463 374 265 198 166 178 267 298 311

90 90 68 90 68 67 67 68 68 90 90

1.5 1.3 1. 4 L5 1.5 L7 L9 L7 2, 1 2. 1 L6

336

90

L5

Oceana Va

(Mar. 1945- Jan. 1946; Feb. 1947- Aug.* 195a; Dec. 1951 - Feb. 1958)

Magnitude

Direction

Preponderance.

373

90

1.7

335

97

1. 1

417

45

1. 1

350

67

1.4

211

45

1.2

131

45

L5

103

45

2,2

115

23

L4

211

45

1.5

230

68

1.4

255

112

1.5

268

90

1.3

See footnote at end of table.
WIND EROSION FORCES AND THEIR USE IN PREDICTING SOIL LOSS 41

TABLE 1.—Relative magnitude, prevailing wind erosion direction^^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by months—Contmned

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Quantico, Va.

(Jan. 1945-Mar. 1960)

Magnitude

Direction

Preponderance.

88

113

1.7

99

113

1.4

116

135

1.3

112

90

1.2

57

90

1.4

34

90

1.2

27

90

1.6

23

90

1.5

40

90

L7

45

101

L3

62

112

1.5

53

113

1.5

Everett, Wash.

(Nov. 1938 - Nov. 1945; Jan. 1948 - June 1953)

Magnitude

Direction

Preponderance127 126 114 86 96 67 68 55 66 69 104

112 112 112 112 112 112 90 112 112 112 112

2.5 2.4 2.7 2.3 2.7 3.5 2.9 3.1 4.0 2.8 2.5

137

112

2,6

Kelso, Wash.

(Jan. 1948 - Aug. 1953)

Magnitude

Direction

Preponderance.

207 168 130 92 82 50 51 41 65 90 185

112 112 112 112 112 112 112 112 90 112 112

7.7 6.3 3.8 2.3 1.8 1.6 1.9 1.8 3.3 4.5 9.2

212

112

9.2

Tvloses Lake Wash

(June-Dec. 1943; Jan., May-Dec'1944; Apr. 1949 - Oct. 1957)

Magnitude

Direction

Preponderance

197 173 284 251 191 218 127 94 159 144 133

90 90 45 43 180 45 180 90 90 90 90

2.5 1.9 1.3 1.1 1.1 1.2 1.1 1.2 1.3 1.6 1.6

Magnitude

Direction

Preponderance

Olympia, Wash.

(Jan. 1953 - Dec. 1962)

123 114 120 101 47 43 36 38 45 79 107

68 67 67 45 23 45 45 45 45 68 67

3.1 2.9 2.3 2.3 2.2 2.3 2.3 2.3 2:3 2.6 2.8

Magnitude

Direction

Preponderance _ _ _

Spokane, Wash.

(Oct. 1949 - Sept. 1954)

267 217 199 175 145 131 92 87 80 241 186

67 67 45 45 45 67 67 67 45 68 67

4.1 2.8 2.5 3.1 3.4 2.1 1.9 1.6 2.6 3.4 3.9

143

90

1.9

136

67

3.1

208

67

3.5

Tacoma, Wash.

(Aug. 1940 - July 1953)

Magnitude

Direction

Preponderance

83 84 94 78 69 46 37 36 37 42 65

67 67 67 45 45 45 45 45 67 67 68

2.4 2.6 2.1 2.0 1.9 1.8 1.4 1.4 2.2 2.3 2.2

69

68

2.4

WaQa Walla, Wash.

(Jan., Feb., Apr.-Dec. 1945)

Magnitude

Direction

Preponderance

96 125 190 125 70 100 83 89 90 14 53

68 90 68 45 45 45 45 45 45 90 90

2.6 2.4 1.8 2.8 2.7 2.9 2.7 2.4 2.7 2.4 2.3

33

90

5.5

See footnote at end of table.
42 AGRICULTURE HANDBOOK 546, U.S. DEFT. OF AGRICULTURE

TABLE 1.—Relative magnitude^ prevailing wind erosion direction^ and preponderance of wind erosion forces

in prevailing wind erosion direction for 212 locations in 39 States by mon^A^—Continued

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Whidbey Island, Wash.

(Apr. 1945 - Mar. 1959)

Magnitude

Direction

Preponderance

399 359 314 220 122 90 67 41 101 235 385

135 135 135 135 180 180 45 180 135 135 135

2.7 2.5 1.9 1.7 1.4 1.7 1.6 1.2 2.2 2.7 2.8

453

135

2.8

Yakima, Wash.

(Jan. 1950 - Dec. 1962)

Magnitude

Direction

Preponderance

76 88 142 158 101 74 56 38 60 67 65

67 47 49 157 157 135 113 135 157 90 90

2.3 1.0 1.1 1.2 1.7 1.8 1.7 2.0 1.5 1.1 1,1

52

67

1.4

Green Bay, Wis.

(Aug. 1952 - July 1963)

Magnitude

Direction

Preponderance—

216 221 251 291 229 141 89 89 173 186 340

158 42 45 23 45 45 45 45 45 45 180

1.2 1.3 1.4 1.2 1.4 1.5 1.3 1.9 1.7 1.3 1.3

230

43

1.2

La Crosse, Wis.

(Nov. 1949 - Oct. 1954)

Magnitude

Direction

Preponderance.

247 232. 304 440 548 230 110 69 139 270 279

135 135 135 135 121 113 114 45 135 135 135

1.6 1.9 1.8 1.8 1.1 1.2 1.4 1.2 1.5 1.5 :L9

259

112

1.0

Madison, Wis.

(Jan. 1951 - Dec. 1960)

Mag^pitude

Direction

Preponderance.

204 250 366 358 244 160 113 86 156 172 302

135 180 20 180 22 23 22 45 23 23 180

1.2 1.3 1.4 1.5 1.3 1.3 1.3 1.3 1.3 1.1 1.4

202

22

1.2

Milwaukee, Wis.

(Jan. 1951 - Dec. 1960)

Magpiitude

Direction

Preponderance

490 666 811 644 544 360 250 247 340 467 784

45 45 67 45 45 67 68 45 67 90 I 45

1.2 1.2 1.3 1. 1 1.2 1.2 1,7 1.3 1.2 1.2 1,4

578

23

1.1

Cheyenne, Wyo.

(Sept. 1949-Aug. 1954)

Magnitude 1,116

180

2.4

1,227

180

1.7

1,319

180

1.2

935

135

1,5

751

158

1,4

542

157

1.3

400

113

1.5

336

135

1.2

480

158

1.4

581

157

1.7

835

158

1.9

970

Direction ______ 180

Preponderance 2.3

Sheridan, Wyo.

(Jan. 1956 - Nov. 1960)

Magnitude 143

135

3.4

190

135

2.5

245

135

3.0

281

135

3.1

207

135

2.7

156

135

3.1

-

110

135

2.4

146

135

2.5

143

135

3.0

201

154

3.2

322

135

3.4

250

Direction.- __ _. __ 158

Preponderance 2.3

1 Direction given in degrees measured counterclockwise with east 0°, north 90°, west 180°, and south 270°.

T!VU.S. GOVERNMENT PRINTING OFFICE : 1968—0-276-724