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1
Ke^
8/11/2019 AH 503 Wichmeier
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U . S .
Departmentof
A f ^ '
Nat ionalAgricuJturalL..
Division
o f
L en d i n g
PRFDirTINC
^ ^ ' ^ ' ^ ' ' ^ ^ ' ^ ^ ' ^ ' ^
R A I N F A L L
E R O S I O N
LOSSES
A
GUIDE
TO
CONSERVATIONPLANNING
S u p e r s e d e s
AgricultureHandbook
N o .
282,
' 'Predict ing
R a i n f a l l - E r o s i o nLo s s e sF r o mC r o p l a n dE a s to f
the
R ocky
M o u n t a i n s
Sciencea n d
d u c a t i o n
Administration
UnitedS t a t e s
Department
of
Agriculture
in
o o p e r a t i o n
with
P u r d u e
griculturalxperiment
t a t i o n
U S D A
olicy
o e s
o t
ermitiscrimination
e c a u s efg e ,a c e ,o l o r ,
a t i o n a lrigin,e x,r
religion.nye r s o nho
e l i e v e s
e
r
he
a s
e e n
i s c r i m i n a t e d
g a i n s t
n
n y
SDA-related
activity
s h o u l d
write immediately
to
the
Se c r e t ar y
of
Agriculture, Washington, D. C. 20250.
8/11/2019 AH 503 Wichmeier
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A B S T R A C T
Wischme ie r ,
W.
.,
n d
mith,
.D .
978.
r e dict ing
a i n f a l l
ros ion
o s s e s a
g u i d eoo n s e r v a t i o nl a n n i n g .
.S.e p a r t m e n tfgr icul ture,griculture
H a n d b o o k
N o .
537.
The
Universal o il
os squation
USLE)
nables
lannerso
predictheaverageateofsoil
erosion
or a c h
easible
alter-
nativeombination
f
cropystemndmanagement
ractices
in
ssociation
with specifiedoil
ype,
ainfall
attern,
nd
topography.When
h e s e
redicted
osses
re
ompared
with
given
oil
os solerances,
hey
rovidepecificuidelines
or
effectingrosion
ontrol
within
pecified
imits
he
quation
groups
he
umerous
nterrelated
hysical
nd
anagement
parameters
hatnfluence
rosionatender
six
major
actors
whosesite-specific
values
can
e
expressed
numerically.
A
half
century
ferosionesearch
n
many
tates
a s
supplied
nfor-
mationromwhich teastpproximate
alues
f
heS LE
factors a n
e
obtainedorspecifiedarmieldsorothersmall
erosion
rone
reas
hroughout
he
United
tates.
ables
nd
charts
presentedn
his
handbookmake
his
nformationeadily
available
or
ield
s e.
ignificant
imitations
n
he
vailable
dataare
identified.
The
S LEs
an
rosion
model
designed
o
computeongtime
average
oilo s s e sromheetand
ill
rosionnderspecified
conditions.
t
s
also
useful
or
construction
i tes
and
other
non-
agricultural
onditions,
ut
t
o e s
ot
redict
eposition
nd
d o e sotcomputesediment
yields
rom
gully,
streombank,
and
streambederosion.
K e y w o r d s :
Conservationpractices,conservationillage,construc-
tion
i tes,
crop
canopy,
crop
e q u e n c e ,
delivery
atios,
ero-
sion
actors,
erosionndex,
rosionrediction,
rosionol-
erances,
rosivity,r o s s
rosion,
minimumillage,
o-till,
rainfall
characteristics,
ainfall
data,
esidue
mulch,
unoff,
sediment,
ediment
elivery,
lopeffect,
wateruality,
soilerodibility.
Forsaleby
theSuperintendent
ofDocuments,
U.S.
GovernmentPrintingO f l B i c e
8/11/2019 AH 503 Wichmeier
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C O N T E N T S
U.S.
i^gnT-*--.
/ . ..
NaionaM
''' W
D V i s i o nof''^^^'^
eitsWIie
..
Purpose
f
andbook
History
f
o il
o s s
quations
S o i llo s solerances
S o i l
o s squation
Rainfallnd
runoffactor
R )
Rainfall
erosion
index
Raluesorhawndnowmelt
SoilerodibilityactorK )
Definition
factor
Values
f
or
pecific
o i l s
S o i l erodibility
nomograph
0
Topographic
actor
(LS)
2
Slope-effect
chart 2
Slope-length
effect 4
Percent
slope
5
Irregular
slopes
6
Changes
ns o i lypeor
cover
along
he
slope
6
Equationoro il
etachment
o nuccessive
segments
of
a
slope
7
Coverndmanagement
actor
C ) 7
Definitionfactor 7
Cropstage
periods
8
Quantitative
valuations
f
crop
nd
management
effects
8
S o i lo s satios
0
E r o s i o nindexistribution
ata
1
Procedure
orerivingocal
alues
8
Support
racticeactor
P )
4
Contouring
4
Contourtripcropping 6
Terracing
7
Applying
he
o ilo s squation 0
Predictingroplando il
o s s e s
0
Determining
lternative
and
s e
and
reatment
combinations
2
Construction s i t e s 4
Estimating
upslope
ontributions
owatershed
ediment
yield
5
Accuracy
f
SL Eredictions
7
References 8
Appendix 0
Estimatingercentages
of
canopy
nd
mulchovers0
Probability
alues
fEl
n
he
nitedStates 0
Computingheerosion
ndexrom
ecording-rain
age
ecords
0
Conversion
to
metric
ystem
1
D 5
8/11/2019 AH 503 Wichmeier
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T A B L E S
1
. C o m p u t e d
values
or
oils n
erosionesearch
stations
2.Approximatevalues
of
he o ilerodibilityfactor,K,or 0benchmark
soi ls
nHawaii
3.Values of
he
opographicactor,
LS,
or
specific
ombinations of
lope
ength
and s t e e p n e s s
2
4.~Estimated
relative
oil losses
rom
u ccess iv eequal-length
egments
f niform
slope ......5
5.Rat io
of
soil
oss
from
cropland
o
corresponding
oss
from
continuous
fallow
2
5 A . - ~ A p proximo
te
soil
ossatiosorcotton 5
5- - B. Soi l
oss
atiosorconditions
not
evaluated
nable 6
5 C S o i l
ossatiospercent)forcropstage
4
whenstalksarechopped
and
distributedwithout
soil
illage
5- - D. Fac tors
o
credit
esidual
f fects
ofurned
o d 6
6. Perc entagesofheaverageannual lwhich
normally
ccu r s
between
January
and
he
ndicated
ates.Computedorhe
eographic
areas
hown
n
igure
.
8
7.MonthlydistributionofElatse l ec ted
ain
gageocations
9
8 . S a m p l e
working
able
or
derivation
of
otation
C
value
0
9. Mul c hactorsand
engthimits
orconstruction
lopes 1
10.Factor
C
value
or
permanent
pasture,
ange,
and
dle
and
2
1 1 .FactorC
valuesfor
undisturbed
orest
and 3
12.-Factor
Cor
mechanicallyprepared
woodland
i tes
4
13.Pvaluesandslope-length
imits
orcontouring *
14.P
values,
maximumstrip
widths,andslope-length
imits
or
contourstripcropping6
15.Palues
or
ontour-farmed
erracedields 7
16.Maximum
ermissible
C
values
T/RKLS)
or
R
= 80 ,
K=0.32,
and1
=
5
3
17.Observed
ange
and
0-,0-,
and ercent
probabilityvaluesoferosion
indexat
a c h
f
81
key
ocations
2
18.Expected
magnitudes
ofsingle-storm
Elndex
values 4
19.Kineticenergy
of
ainfall
expressed
noot-tonsperacrepern c hofain6
20.Kineticenergy
ofainfall
xpressed
n
metric
on-meters
er
ectare
er
entimeters
ofain
.6
F I G U R E S
1.Average
annual
alues
of
he
ainfall
rosion
ndex
map)
e
tween
ages
and
2. Est i matedaverageannualvalues
of
herainfall
erosionndex
n
Hawaii
3,The
soilerodibilitynomograph
1
4.Slope-effect
chart topographic
actor,
S ) ...
3
5.Influence
of
vegetative
canopy
n
effective
El
values
9
6.Combined mulchnd
anopy
f fectswhenaverageall
istancef
rops
from
canopy
o
he
ground
s
about
0
nc hes
9
7.Combinedmulchndanopy
f fects
whenverage
all
istance
f
rops
fromcanopyohe
ground
sabout
0
nc hes 9
8.Typical
l-distribution
curves
orhree
ainfall
atterns 7
9.Keymap
or
selectionof
applicable
El-distribution
data
romable 7
10. Rel a t i on
of
percent
coverodryweightof
uniformly
distributedesidue
mulch0
11. Sl ope- ef fec t
chart
or
metric ystem 8
8/11/2019 AH 503 Wichmeier
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PREDICTING
R A I N F A L L
EROSION
LOSSES
A
GUIDE
TOC O N S E R V A T I O NP L A N N I N G
WaiterH.
Wischmeier
ndDwight.Smith ^
PURPOSE
FA N D B O O K
Scientific
lanningoro ilndwateronserva-
t i o n
equires
nowledge
of
he
elationsetween
t h o s e
actors
hat
causeo s sofo ilndwaterand
t h o s e
hatelpo
educe
uch
o s s e s .
ontrolled
studiesnieldlotsndmallwatershedsave
supplieduch
aluable
nformationegarding
these
omplexactor
nterrelations.ut
he
reat-
e s t
ossibleenefits
rom
uchesearch
an
e
realized
nly
when
he
indings
re
onverted
o
sound
ractice
n
he
umerousarmsandther
erosionrone
reashroughouthe
ountry.
pe-
cificuidelinesre
eeded
orelectinghe
on-
trol
ractices
est
suited
o
he
articularneeds
f
each
site.
The
o ilo s s
rediction
rocedure
resented
n
this
andbook
rovides
uch
uidelines.
he
ro-
cedure
ethodically
ombines
esearchnforma-
t i o n
rom
any
o u r c e soevelop
esign
ata
forach
onservation
lan.
Widespread
ield
x-
perience
or
more
han
wo
decades
as
roved
t
highlyaluable
as
a
onservationlanninguide.
Theprocedure
is
founded
o n
anempirical
s o i lo s s
equation
hatselieved
o
e
pplicable
wher-
everumericalaluesftsactorsrevailable.
R e s e a r c h
has
uppliednformationrom
which
t
least
pproximate
alues
of
hequation'sactors
can
e
btainedor
pecific
arm
ieldsr
ther
small
and
reas
hroughoutmost
fhenited
States.
ables
nd
harts
resented
n
his
and-
book
make
his
nformation
eadily
vailable
or
field
u s e .
This
evision
fhe
965andbook64)pdates
the
content
and
ncorporates
newmaterial
hat
has
been
vailable
nformally
r
rom
cattered
e-
search
eports
n
rofessionalournals.
ome
f
theriginalhartsnd
ablesreevised
oon-
form
ith
dditional
esearch
indings,
nd
ew
ones
re
eveloped
oxtendhe
sefulness
f
theo ilo s squation.n
ome
nstances,xpand-
ing
able
orchart
ufficientlyomeetheeeds
for
widespread
ieldpplication
equiredrojec-
tion
fmpirical
actorelationships
ppreciably
beyond
he
hysical
imitsf
he
ata
romwhich
the
elationshipswere
erived.
stimates
btained
in
his
manner
re
he
est
nformation
vailable
for
heonditions
hey
epresent.
owever,
he
instances
re
dentifiednheiscussions
f
he
specificrosion
actors,
ables,ndharts.Major
research
eedsreuggested
yhese
iscussions
and
ere
ecently
ummarized
n
n
vailable
publication
y
Stewartandthers42).
HISTORY
F
OIL
OSSQ U A T I O N S
Developing
quations
o
alculate
ield
o il
o s s
beganbout
940
n
he
ornelt.heo ilo s s
estimatingrocedure
eveloped
nhat
egion
between 1940
and 1956 has been generally re-
^
Retired.ormer
esearch
tatistician
water
anagement).
ci -
ence
nd
ducation
dministration
SEA),
nd
rofessormeritus,
agriculturalngineering,urdueniversity,
est
afayette,nd.;
and agricultural
engineer,
SEA,
Beltsville,
Md.
ferred
o
as
he
lope-practice
method.
ingg
64)^
publishednquationn
940elatingo il
o s s
rateoengthandercentageof
slope.
The
ollow-
ing
ear.
mith38,
9)
dded
rop
and
onserva-
tionracticeactors
nd
he
oncept
fpecific
s o i ll o s simit,
oevelop
raphical
methodor
Numbers
n
arentheses
refer
o eferences
p.
8.
8/11/2019 AH 503 Wichmeier
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UNITED
T A T E S
EPARTMENT
F
GRICULTURE,AGRICULTURE
ANDBOOKUMBER37
determiningonservationracticesnhelbynd
associated
o i l s
f
heMidwest.
rowningnds-
sociates
)
dded
o ilnd
anagement
actors
and
repared
e tof
ables
o
implifyields e
of
he
quation
n
owa.
esearch
cientistsnd
operationsersonnel
f
he
oilonservation
Ser-
vice
S C S )n
heorthentral
tates
workedo-
gether
n
eveloping
he
lope-practice
quation
for
u s ethroughout
theCornBelt.
A
ational
ommittee
et
nhion
946
o
adapthe
Corneltquationoroplandnther
regions.
hi s
ommittee
eappraised
heorn
elt
factoraluesnd
dded
ainfall
actor.
he
resulting
ormula,
enerally
nownsheus-
grave
quation
31),
as
een
idelysed
or
estimatingrossrosionromwatershedsnlood
abatementrograms.
raphical
olutionf
he
equation
wasublished
n
95219)
andsed
y
the
SC S
n
he
Northeastern
States.
The
o ilo s s
quation
resented
nhisand-
book
as
ecome
nown
sheniversaloil
L o s s
quation
U S L E ) .
egardless
f
hetherhe
designation
sully
ccurate,
he
ame
oes
is-
tinguish
his
quationrom
heegionallyased
s o i lo s sequations.TheSL Ewasdevelopedathe
National
unoffndoil
o s s
ata
enter
stab-
lished
n954y
he
cience
nd
ducation
d-
ministration
formerlygricultural
esearcher-
vice)
n
ooperation
with
urdueniversity.
ed-
eral-State
ooperative
esearchrojects
t
9o-
c a t i o n s ^
ontributed
more
han
0,000
plot-years
of
basic
unoff
ndo ilo s s
ataohisenter
or
summarizingnd
verall
tatisticalnalyses.
fter
1960,
ainfall
imulators22)perating
rom
ndi-
ana,
Georgia,
Minnesota,
andNebraska
were
used
onieldlots
n16
states
o
fillome
of
hegapsn
the
ata
eeded
or
actor
valuation.
Analysesfhisargessemblyfasic
ata
provided
everal
major
mprovements
orhe
o il
l o s squation
53):a)
ainfallrosion
ndex
evaluated
rorn
ocal
ainfallharacteristics;b)
quantitativeo ilrodibilityactor
hat
sevaluated
directly
rom
o ilroperty
data
andsndependent
of
opography
nd
ainfallifferences;
c)
method
f
valuating
ropping
nd
management
effectsnelationo
ocal
limaticonditions;nd
(d)
method
f
ccounting
or
ffectsof
nterac-
tions
etween
rop
ystem,roductivity
evel,
ill-
age
ractices,
ndesiduemanagement.
Developmentsi n c e
965
haveexpandedhe
u s e
of
he
o il
o s s
quation
y
roviding
echniques
for
stimating
ite
alues
f
ts
actors
or
ddi-
tionalands e s ,
limatic
conditions,
ndmanage-
ment
ractices.
hese
avencluded
o il
rodi-
bilityomographor
armland
nd
onstruction
areas
58);
opographic
actors
or
rregular
lopes
(72,5);
over
actors
orangendoodland
(57);
over
ndmanagementffects
fonserva-
tion
illage
ractices54);rosion
redictionn
construction
reas61,4,
5);
stimated
rosion
indexalues
or
he
Western
tates
ndawaii
(5,
,
5);o ilrodibilityactors
or
enchmark^
Hawaiio i l s9);and
mprovedesignand
valua-
tion
of
rosioncontrol
support
practices
7,6).
Research
s
ontinuing
with
mphasisonobtain-
ing
etternderstanding
f
he
asicrinciples
and
r o c e s s e s
f
water
rosion
nd
edimentation
and
evelopment
fundamental
models
apable
of
redicting
pecific-stormo il
o s s e sndeposi-
tion
y
verland
iow
JO ,
7,
2,
6,
2).
he
fundamental
modelsave
eenelpful
or
nder-
standing
heactors
nhe
ield
o il
o s s
quation
and
or
nterpreting
he
plotdata.
SOIL
O SS
O L E R A N C E S
The
erm
soil
o s solerance
enotes
hemaxi-
mumlevelfo ilrosion
hatwillermit
igh
level
of
crop
productivity
to
be
sustained
eco-
nomicallyandndefinitely.
^
The
ataereontributed
y
ederal-Stateooperativee-
searchrojects
the
ollowing
ocations:
atesville,
rk.;
ifton
and
atkinsville,
a.;
ixon
prings,
oliet,
nd
rbana,II.;a -
fayette,
nd.;
larinda,
astaa,eaconsfield,ndependence,nd
Seymour,owa;
ays,
ans.;aton
ouge,
a.;
resque
sle,
Maine;
Bentonarbor
nd
a s t
ansing,
ich.;
orris,
inn.;
olly
Springs and State
College,
M i s s . ;Bethany
and
McCredie, Mo.;
Hastings,
ebr.;
eemerville,
arlboro,
nd
ew
runswick,.J.;
Ithaca,
eneva,
nd
Marcellus,
.Y.;
tatesville
nd
aleigh,
.C.;
Coshocton
nd
anesville,
hio;herokeenduthrie,
kla.;
Stateollege,a.;
lemsonnd
partanburg,
.C.;adison,
S.Dak.;
noxvillend
reeneville,
enn.;emple
ndyler,
ex.;
Blacksburg,
a.;ullman,
ash.;
aCrosse,
adison,nd
wen,
Wis.;and
Mayaguez,
.R .
8/11/2019 AH 503 Wichmeier
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PREDICTING
AINFALLROSION
OSSES-A
GUIDE
O
ONSERVATION
PLANNING
The
major
purposeofthe
o il
o s sequation
s
o
ethodical
ecisionmaking
n
onservation
n ite
asis.he
quation
nables
lanner
oredict
he
verageate
fo il
or
ach
f
arious
lternative
ombina-
ofcrop
system,
management
echniques,
and
ractices
on
any
particular
site.
When
hese
o s s e saneompared
with
o ilo s s
or
hat
ite,
hey
rovidepecificguide-
or
ffectingrosionontrol/ithinhepec-
imits.nyroppingnd
managementom-
orwhichhepredictederosion
rate
se s s
he
olerance
ayexpected
orovide
rosion
ontrol.
rom
heatisfactory
ndicated
y
his
rocedure,
he
ne
uitedo articular
arm
r
thernter-
may
thenbeselected.
S o i l
o s s
olerances
ranging
rom
5
o
2
t/A/year
heo i l s
fhe
nited
tates
wereerived
y
cientists,
gronomists,
eologists,
oil
on-
nd
ederal
ndStateesearch
ead-
rst
ix
egionalorkshops
n
96 1nd
962.
onsidered
n
defininghese
imits
ncluded
epth,
hysical
ropertiesnd
therharac-
ffectingootdevelopment,ully
reven-
n-field
edimentroblems,
eeding
o s s e s ,
rganicattereduction,
nd
lantutrient
eep,medium-textured,
moderately
er-
o il
hat
as
ubsoil
haracteristics
avor-
or
plant
growthhasa
reater
olerance
han
withhallow
oot
ones
righ
ercentages
hale
t
he
urface.idespreadxperience
shown
heseo ilo s solerances
o
eeasible
enerally
dequate
or
ustaining
igh
ro-
evels
ndefinitely.
omeo i l s
with
eep
favorable
oot
zones
mayexceed
he5-tolerance
without
o s sof
sustainedroductivity.
Soil
o s s
imits
re
ometimesstablishedri-
marily
or
water
uality
ontrol.
he
riteriaor
definingieldo il
o s simitsor
his
urpose
re
not
heames
hose
or
olerances
esigned
o
preserve
roplandroductivity.
oilepth
s
ot
relevantor
ffsite
ediment
ontrol,ndniform
limits
nrosionateswillllow
ange
nhe
quantities
f
ediment
er
nit
rea
hat
re
e-
livered
oa
iver.
Soil
material
eroded
rom
a
ield
slopemayedepositednhe
ieldoundaries,n
terracehannels,nepressional
reas,
r
nlat
or
vegetated
areas
raversed
y
he
overland
low
before
t
reaches
a
iver.
The
erosion
amageshe
cropland
n
hichtccurs,
utedimente-
posited
eartslaceoforiginsotdirectlyele-
vant
for
water
quality
control.
Ifhe
o il
o s s
olerance
esigned
orustained
cropland
roductivityails
o
ttain
he
esired
water
quality
standard,
lexibleimitshat
consider
otheractorshouldeeveloped
ather
han
uniformlyoweringheo il
o s s
olerance.
hese
factorsncludeistancefheieldrommajor
waterway,heediment
ransport
haracteristics
of
he
nterveningrea,
ediment
omposition,
needs
f
hearticular
odyf
waterbeingro-
tected,andheprobablemagnitude
of
luctuations
in
ediment
oads
42).
i m i t s
f
ediment
ield
wouldrovide
ore
niformater
uality
on-
trol
han
oweringheimits
no il
ovement
fromield
lopes.
hey
wouldlso
equire
ewer
restrictions
nropsystemelectionor
ieldsrom
which
nly
mallercentages
f
he
roded
o il
becomeoff-farmsediment.
SOIL
OS S
Q U A T I O N
Therosionate
tiven
ite
setermined
he
articular
way
n
which
he
evels
n
u-
hysical
ndanagementariables.
are
that
ite.
hysical
easurementsf
o s sorach
f
he
arge
numberf
ossible
n
which
he
evelsf
hese
ariable
an
ccur
nder
ield
onditions
would
ot
eeasible.o ilo s squations
were
evelopedo
onservationlannersorojectimited
ata
o
he
many
ocalitiesndonditions
aveoteen
irectly
epresentednhee-
TheSL E
snrosion
model
esigned
o
re-
dict
he
ongtime
verage
o il
o s s e s
n
unoff
frompecific
ield
reas
n
pecified
ropping
nd
management
ystems.
idespread
ield
s eas
substantiated
ts
sefulnessndalidity
orhis
purpose.
tslsopplicable
or
uch
onagricul-
tural
conditionss
onstruction
i t e s .
With
ppropriateelection
f
ts
actor
alues,
theequationwill
ompute
he
average
o ilo s s
or
amulticropsystem,oraarticular
cropyearn
rotation,or
for
a
articular
cropstageperiodwithin
a
rop
ear.
t
omputes
heo il
o s s
oriven
8/11/2019 AH 503 Wichmeier
9/67
UNITED
TATES
E P A R T M E N T
F
G RICULTURE,G RICULTURE
ANDBOOK
U M B E R37
site she
product
ofsixmajor
actors
whosem o s t
likely
alues
t
articularocationan
e
x-
p r e s s e d
umerically.
rosion
variableseflected
by
these
actors
varyconsiderablyaboutheirmeans
from
torm
otorm,ut
ffects
f
he
andom
end
o
verage
ut
ver
xtended
periods.e c a u s e
f
he
npredictable
hort-time
n
he
evels
f
nfluential
ariables,
hov/ever,
resent
oilos s
quations
re
ubstan-
essaccurateor
prediction
f
specificevents
or
redictionfongtimeverages.
The
soillossequation
is
A=:RKLSCP
0)
s
hecomputed o iloss
per
unit
area,express-
edn
he
units
elect ed
or
K
andor
he
peri-
od
elect ed
or
.
n
ractice,h e s e
ares u -
allyoelect edhat
heyompute
n
o n s
percreer
ear,
utthernitsa ne
select ed.
he
ainfallandunoff
actor,s
henumberof
rainfallrosion
ndex
nits,lus
actor
or
runoff
rom
snowmelt
or
applied
water
where
s uch
unoff
issignificant.
K,
heo ilrodibility
actor,
s
heo ilossate
per
rosion
ndex
nit
or
specified
o il
s
measured
n
nitplot,
which
sdefined
s
a
2.6-ft
ength
f
niform
-percentlope
continuouslyn
clean-tilledallow.
,
he
lope-length
actor,s
heatio
f
o ilos s
from
hefieldslopeength
o
that
from 2.6-
ft
ength under
denticalonditions.
,
helope-steepnessactor,
she
atio
f
o il
loss
rom
he
field
slope
gradiento
hat
rom
a-percentlope
nder
therwise
dentical
conditions.
he
over
nd
managementactor,
she
atio
ofsoil
os s
rom
n
areawith
pecified
cover
and
anagement
ohat
rom
n
dentical
area
nilledcontinuousallow.
he
upport
ractice
actor,
s
he
atio
fo il
loss
with
upportractice
ike
ontouring,
stripcropping,
rerracingohatith
straight-rowarming
p
andown
he
slope.
The
oil
os s
quationnd
actor
valuation
charts
ere
nitially
eveloped
n
ermsfhe
Engl i shnits
commonly
s e d
nheUnited ta tes.
Theactordefinitions
arenterdependent,
ndi-
rec tonversionfc r e s ,ons,n c h e s ,nd
eeto
metricunitswouldnotproducethekindofintegers
thatwouldeesirableor
an
xpression
f
he
equation
n
hat
s y s t e m .
Therefore,
only
the
Engl ish
unitsre
s e d
nhenitial
resentation
f
he
equation
ndactorvaluation
aterials,
nd
their
counterparts
nmetric
units
are
given
n
he
Appendix
nder
o n v e r s i o n
o
etr icy s t e m .
Numericalaluesor
ac hf
heix
actors
were
erived
rom
nalyses
f
he
ssembled
e -
searc h
ata
nd
rom ational
Weather
ervice
precipitationecords.
or
most
onditions
nhe
United
ta tes,he
pproximate
aluesof
he
ac-
tors
or
anyparticular
it e
may
e
obtained
rom
charts
nd
ables
nhisandbook.ocalitiesr
countrieswhere
he
ainfallharacteristics,oil
types,
opographic
eatures,
r
arm
ractices
are
substantially
eyond
he
ange
fresent.S .
data
willind
h e s e
charts
nd
ables
ncomplete
anderhapsnaccurateorheir
conditions.
ow-
ever,
hey
will
provide
guidelines
hat
a n
educe
the
mount
f
ocal
esearch
eeded
o
evelop
comparable
charts
andables
or
heirconditions.
The
subsectionn
P r ed i ct i ngC r o p l a n d
Soi lLo s s -
e s ,age
0
llustrates
ow
o electactor
values
from
he
ablesandcharts.Readerswho
have
had
n o
experience
with
he
o il
oss
equationmay
wish
toeadhat ect ion
irst.
After
hey
have
eferred
to
he
ablesnd
igures
ndocated
he
alues
u s e d
n
hesample,heymay
move
eadily
o
he
intervening
etailed
iscussions
f
he
quation's
factors.
The
soil
os s
rediction
rocedure
s
more
valu-
able
s
guide
forselectionofpracticesif
the
s er
ha s
eneral
nowledge
f
he
rinciples
nd
factor
nterrelations
n
hich
he
quation
s
based.
Therefore,he
significance
of
a c h
actor
s
d i s c u s s e d
efore
resentingheeference
abler
chart
rom
which
ocalaluesmaye
btained.
Limitationsof
he
data
available
orevaluation
of
s o m e
ofhe
actors
are
also
pointed
out.
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PREDICTING
R A I N F A L L
E R O S I O N L O S S E S - AGUIDEO
O N S E R V A T I O N PLANNING
R A I N F A L LANDU N O F FA C T O R
R )
Rillsnd
ediment
eposits
bserved
ftern
unusually
ntensestorm
ave
sometimes
e do
he
c onc l us i onhat
he
significanterosions
associated
withonly ew
storms,
or
hatt
s
solely unc-
tionfeak
ntensities.
owever,morehan0
years
of
measurements
n
many
S t a t e s
have
shown
that
hiss
othe as e
5 1 ) .he
atashow
hat
a
ainfall
actor s ed
oestimate
average
nnual
soil
ossmustncludehe
cumulative
f fectsofthe
many
moderate-sized
storms, swell she f fects
o fthe
occasionalsevereo n e s .
The
umerical
alue
s edor
n
he
oil
oss
equationmust
quantifyhe
aindrop
mpact
effect
a n d
must
alsorovide
elativenformation n
he
amount
ndate
of
unoff
ikelyo
e
associated
withhe
ain.
he
ainfall
rosionndexerived
by
Wischmeier49 )
appearso
meet
h e s e
equire-
m e n t s
etter
han
ny
ther
f
he
many
ainfall
parameters
nd
roupsf
arameters
ested
against
he
ssembled
lot
ata.
he
ocal
alue
of
his
ndexenerallyquals
or
he
o il
oss
equationndmay
ebtained
irectlyrom
he
map
n igure. owever,he
ndex
o esotn-
cludeheerosiveorcesofunofffromhaw,
snow-
melt,
r
rrigation.
rocedureor
valuating
for
ocations
wherehis
ypeofunoffssignificant
will
e
iven
nderheopic V a l u e s
or
Thaw
andS n o w m e l t .
Rainfall
r o s i o n
ndex
Th e
esearch
ata
ndicate
hat
when
actors
other
han
ainfall
re
eld
onstant,
torm
oil
lossesrom
ultivated
ieldsre
irectly
ropor-
tionalo ainstorm
arameter
dentified
s
he
El
defined
below)
49).
he
elation
f
soil
os s
o
thisarameter
s
inear,nd
ts
ndividualtorm
V alues
aredirectlyadditive.
he
u m
fhe
storm
E l
alues
or iveneriods umericalmea-
su r eofheerosive
otentialof
he
ainfall
within
thatperiod.
The
average
annual
otal
of
he
storm
E l
valuesn particularocality
s
heainfallero-
s ionndexor
hat
ocality.
e c a u s e
fpparent
cyclical
patterns
n
ainfalldata
33),
he
published
rainfallrosion
ndex
alues
wereasedn
2 -
yearstationrainfallrecords.
Rain
howersfes s
han
ne-half
nc hnd
separated
rom
therain
eriods
ymorehan
6
ours
eremittedrom
he
rosion
ndex
computations, nless
s
m u c h s0.25
nofain
ell
in
5
min.ExploratoryanalysesshowedhatheEl
values
or
uc h
ains
re
sually
oomall
or
practical
ignificance
nd
hat,
ollectively,
hey
have
ittle
ffect
n
onthly
ercentages
f
he
annual
l.
heo s t
f
bstracting
nd
nalyzing
4,000
ocation-yearsofainfall-intensity
atawas
greatly
educedy
adopting
he.5-in
hreshold
value.
ElParameter
By
efinition,
he
value
f
lor
iven
ain-
stormquals
he
roduct,
otal
torm
nergy
E)
times
he
maximum
0-min
ntensity
I30)/
where
is
n
undreds
f
oot-tons
er
acre
nd
3 0
s
n
inch eser
our
in/h).
ls
n
bbreviationor
energy-times-intensity,
andheermhouldot
e
considered
imply
an
nergyparameter.
he
data
show
hatainfall
energy,
tself,-is
not
ood
n-
dicatorferosive
otential.
he
torm
nergy
n-
dicateshe
olume
f
ainfall
nd
unoff,
ut
long,slow
ain
may
ave
he
a m e value s
shorter
aintu c h
igher
ntensity.aindrop
erosion
ncreases
with
ntensity. he
3 0component
indicates
he
rolonged-peak
ates
f
etachment
and
unoff.
heroducterm. l,s tatistical
interactionerm
hat
efiects
howotal
energyand
peak
nensityre
ombinedn
a c h
articular
storm.Technically,tndicates
how
particle
detach-
ment
scombined
withransportcapacity.
Th energy f ainstorm
s
unction
f
he
amount
of
ain
nd fall
he
torm's
omponent
intensities.edianaindrop
iz e
n c r e a s e sith
rain
ntensity
2),
nd
erminal
elocitiesof
ree-
falling
waterdrops
ncrease
with
ncreasedrop-
s ize
7 3 ) .
ince
he
energy
of
given
m a s s
n
o -
tion
sroportional
o
elocity-squared,
ainfall
energy
s
irectlyelatedo
ain
ntensity.he
relationship
sexpressed
y
heequation,
E=:
916+3 3 1
ogio,
(2 )
where
s
inetic
nergynoot-tons
ercre-
inchnd
s
ntensity
nnc hes
er
our62).
limitof n/h
smposed
n
y
he indinghat
median
ropsize
o e s
otontinueo
ncrease
whenntensitiesexceed n/h
7 ,5 ). he
energy
8/11/2019 AH 503 Wichmeier
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FIGURE1 . ^ A v e r a ge
n n ua l
v a l u e s
f
hea i n f a l l
rosion
n d e x .
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UNITED
TATES
E P A R T M E N T
F
G RICULTURE, AG RICULTURE
ANDBOOKUMBER
37
of
ainstorm
s
omputed
rom
ecording-rain
gage
data.
Thestorm
sdivided
nto
uc c ess i ven-
crements
f
ssentially
niformntensity,
nd
rainfallnergy-intensity
able
erived
rom
he
above
ormula
app.,
able 9)
s
s e d
o
compute
the
energyore a c hncrement.B e c a u s ethe
energy
equationndnergy-intensity
ableave
e e n
frequently
ublished
ith
nergy
xpressed
n
foot-tonser
cre-inch,
hisnit
was
etained
n
table
9.
owever,
oromputation
f
lalues,
storm
energy
s
expressed
n
hundreds
of
oot-tons
peracre.
Therefore,
energies
computed
by
the
pub-
lishedormula
or
able
9must e
dividedby 00
before
multiplying
by3 0
o
compute
E.)
I s o e r o d e n tMaps
L o c a lvalues
f
he
ainfall
rosion
ndex
may
be
taken
directly
fromhe
soerodent
maps,figures
I
nd
.
he
plotted
ines
n
he
maps
are
called
isoerodentse c a u s e
heyonnectoints
f
qual
rainfallerosivity.Erosi onndex
valuesfor
ocations
between
heines
re
obtained
y
inearnterpo-
lation.
Thesoerodent
map
n
heriginalersionf
this
handbook(64)
was
developed
from
22-year
s t a-
tion
ainfall
ecordsbycomputingheElvalueor
e a c h
torm
hatmet
he
previously
definedhresh-
old
criteria.soerodents
were
then
ocated
between
t hese
point
valueswithhe
help
of
published
ain-
fall
ntensity-frequency
ata
47 )
and
opographic
maps.
he
1
estern
tatesweremitted
rom
thenitial
ap
e c a u s eheainfall
atterns
n
this
ountainous
egion
re
poradic
nd
ot
enoughong-term,
ecording-rain
age
ecords
wereavailableoestablish
aths
of
equal
erosion
index
values.
The
soerodent
mapwasextendedohe
Paci f ic
Coast
n
97 6
y
s e
fon
estimating
rocedure.
Resultsofnvestigationsatthe
Runoff
and o il os s
DataCenter
at
Purdue
Universityshowedhathe
known
erosion
ndex
alues
n
he
Western
Plains
and
orth
Central
tatesouldepproximated
with
easonable
ccuracy
yheuantity
7 . 3 8
p2.i7^
where s
he
-year,-hainfall
mount
(55) ,
his
elationship
as
s e d
ith
ational
Weatherervice
sopluvial
maps
opproximate
erosionndexalues
or
he
Western
tates.
he
resulting
soerodents
areompatible
with
he
ew
pointvalueshatade e n
stablished
withinhe
II
Western
tatesand
a n
rovide
helpfulguides
foronservationlanning
n
iteasis.
ow-
ever,
hey
re
ess
recise
hanh o s eomputed
forthe37-Statearea,
wheremoredatawereavail-
able
nd
ainfall
atterns
re
ess
rotic. lso,
linear
nterpolations
etween
heines
willot
alwayseccuratenmountain
egionse c a u s e
values
f
he
rosion
ndexmay
hange
ather
abruptly
with levationhanges.he
point
values
thatwereomputed
irectly
rom
ong-term
ta -
tion
ainfallecordsnhe
Western
tates
re
n-
cludedn
able
7 ,
s
eference
points.
Figure
waseveloped
y
computing
hero-
s ionndex
forfirst-order
weatherstations
inHawaii
anderivinghe
elation f
h e s ealues
o
a-
tional
Weather
Service
ntensity-frequencydata
or
the
ive
ajorslands.
When
heresent
hort-
term,
ainfall-intensityecordsave
e e n
uffi-
cientlyengthened,
more
pointvalues
of
the
ndex
should
be
computed
by
the
tandard
procedure.
Figure
howshatocal,verage-annualal-
uesof
he
rosion
ndexn
he
8
onterminous
Sta tesangeromesshan0
omorehan0 0.
Th e
erosion
ndexmeasureshecombined
effect
of
rainfall
ndts
ssociated
unoff.fheoil
nd
topography
were
xactly
heameverywhere,-
averageannual
oilo sse s
rom
lotsmaintained
incontinuous
allow
would
differndirectpropor-
tion
o
heerosion
ndex
values.However,
his
po-
tential
ifference
sartiallyffsetyifferences
in
soil,
topography,
vegetative
cover,
and
esidues.
On
ertile
oils
n
he
ighainfall
reas
f
he
Southern ta tes,
ood
egetaloverrotects
he
soilurfacehroughout
o s t
fhe
ear
nd
heavy
lantesiduesmayrovideexcellent
cover
also
uring
he
ormant
e a s o n .
n
heegions
whereheerosionndexsextremelyow,ainfall
is
seldom
adequateorestablishingannualmead-
owsand
hecover
providedby
othercropss
often
for
elatively
hort
eriods.enc e,erious
oil
erosion
azardsxist
n
semiaridegionsswell
as
n
humid.
F r e q u e n c y
i s t r ibut ion
The
soerodent
opsresent
2-year-average
annualvalues
of
Elor
the
delineated
areas.
How-
ever,bothhe
annual
andhemaximum-stormval-
uesat
aparticularocationvary
from
year
to
year.
Analysis
f
81tation
ainfallecords
howed
thathey
end
oollow
og-normal
requency
dis-
tributions
hat
are
usually
well
defined
bycontinu-
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PREDICTING
AINFALLROSION
LOSSES-A
GUIDE
O
ONSERVATIONPLANNING
us
ecords
from
0
o25
ears
49).
ables
f
probabilities
of annual andmaximum-
R
V a l u e s
o r
Tha w
Thetandard
ainfall
rosion
ndexstimates
rosive
orces
fhe
ainfall
ndtsirectly
runoff.nhePacificNorthwest,asmuch
s
0
ercent
fhe
rosion
n
he
teeplyolling
asbeenstimated
o
derive
rom
un-
ssociated
s ^ i t h
urface
hawsnd
nowmelt.
ypefrosion
s
otccountedor
y
he
rosionndex
ut
s
onsidered
ither
pre-
or
appreciable
nmuch
ofhe
Northwest
n
ortionsfhe
entral
Western
tates.
recipitationelationshipwouldotccount
peak
o s s e s
n
earlyprinigecause
a s
he
win-
rogresses,
heo il
ecomes
ncreasingly
more
as
he
o il
moisture
rofile
s
eing
illed.
storm
l
alues
t
he81
locations
re
resented
in
theappendix
(tables
17
and
18).
a n dn o w m e l t
the
urfacetructure
seing
rokenowny
repeated
reezing
nd
hawing,
nduddling
andurfaceealingreakinglace.dditional
researchfhe
rosion
r o c e s s e sndeansf
controlnder
heseonditions
s
rgentlyeeded.
In
he
eantime,
hearly
pring
rosion
y
runoff
rom
nowmelt,haw,
r
ightain
n
ro-
zen
o ilmay
e
ncluded
nhe
o il
o s s
computa-
tionsy
dding
ubfactor,g ,
oheocation's
erosion
ndex
obtain
R.
nvestigationsofimited
data
ndicatedhatnstimatef
g
may
e
b-
tainedyaking.5
imes
he
ocal
ecember-
through-March
recipitation,easured
snches
of
water.
F o r
example,
a
location
in
the
North-
M A U l
K A U A I
O A H U
MOLOKAI
FIGURE
2 . E s t i m a t e d
v e r a g e
n n u a l
al ueso f
he
a i n f a l l
ros ion
n d e x
n
a w a i i .
8/11/2019 AH 503 Wichmeier
14/67
NITED
TATE SEPAR T MEN TF
G R I C U L T U R E ,
A G R I C U L T U R E
A N D B O O K
U M B E R
37
hatas
n
rosion
ndex
f0
fig.
)
verages
2nfrecipitation
etween e-
ndMarch1wouldhave
an
estimated
annual of.5 (1 2)
+
20 ,or
8.
This
type
of runoff
may
also
be
a
significant
factornhe
orthern
ier
of
Centralnd
astern
Sta tes.Wherexperiencendicates
his
o
e
he
c a s e ,
t
hould
e
ncluded
n
nd
lso
n
he
erosion
ndex istributionurves
s
llustrated
n
p a g e
27.
SOILRODIBIUTYA C T O RK)
Th e
eaning
f
heerm
soil
rodibility"
s
different
rom
hatof
he
ermsoil
ero-
he
ate
f
o ilrosion.
,n
he
oil
os s
maye
nfluenced
morey
and
lope,
haracteristics,
over,
nd
management
y
nherentroperties
f
heoil.
owever,
oils
rodemore
eadily
hanthers
ven
ll
theractors
re
he
a m e .
his iffer-
aused
yroperties
f
he
o il
tself,
s
e -
osheo il
rodibility.everal
arly
t-
were
made
o
determine
criteria
or
c i en-
lassifications
foilsccording
o
rodibility
,
8,28 ,
5 ),
ut
classifications
s e d
orerosion
were
only
elative
ankings.
Differences
nheatural
susceptibilities
of
oils
Definit ion
Theo il
rodibility
actor,
,
nhe
S LEs
aluexperimentally
etermined.
or
articular
soil,t
s
he
ate
of
o il
ossper
ero-
ndex
unit
asmeasuredon
"unit"
plot,which
as
e e n
arbitrarily
defined
s
ollows:
A
unit
plot
s
2 .6
t
ong,with
uniform
ength-
slopeof percent,ncontinuous
fallow,
illed
nddown
he
slope.
Continuous
fallow,
or
this
s
andhat
as
e e n
illed
and
kept
ree
egetation
ormorehan
ears.
uring
he
eriodof
so i l
oss
measurements,the
plot
splowed
laced
n
conventional
corn
seedbed
condition
pring
nd
s
illed
s
eededo
revent
vegetative
rowthnd
evereurface
rusting.
hen
allof
h e s e
conditionsare
met, , ,C,and
P
a c h
equal
.0 ,
and
equals
A/El.
The 2 .6
tength
and
percent teepnesswere
select ed
s
a s e
alues
or,
,nd
e c a u s e
they
re
heredominant
slope
engthnd
about
the
average
radient
nwhich
ast
erosion
mea-
to
rosion
re
ifficult
o
uantify
rom
ield
b-
servations.
ve n
soil
with
elatively
ow
erodi-
bilityactor
ay
howi gnsf
eriousrosion
whent
c c urs
n
ong
rteepl opesr
n
o -
calities
ithumerous
igh-intensityainstorms.
A o ilwith
high
natural
erodibility
factor, nhe
other
hand,
may
show
ittle
evidence
of
actual
ero-
s ionnder
gentle
ainfallwhen
t
c c urs n
hort
andgentle
lopes,
or
when
he e s t
possible
man-
agement
s
racticed.
he
f fects
ofainfalldiffer-
e n c e s ,lope,
over,
nd
anagementrec -
countedornhepredictionequation
by
hesym-
bols
R, , ,C,and
.
Therefore,
the
o ilerodibility
factor,
,
must
eevaluatedndependentlyof
he
effects
of
the
other
factors.
o f
actor
surements
n
henited tatesade e nmade.
Th e
designated
management
rovides
ondition
thatearlyliminates
f fects
fover,
manage-
ment,
andand
s e
esidual
and
hatc an
edupli-
cated
on
any
cropland.
Direct
easurementsf nell-replicated,
unitplots s
described
efiect
hecombined
f fects
of
allhe
oil
properties
hatsignificantly
nfluence
the a s ewith
which
articular o ilserodedy
rainfall
and
unoff
f
ot
protected.
owever,
s
an
average
valueor
given
soil,
and
direct
mea-
surement
f
heactorequires
o ilos s
measure-
m e n t sor
epresentative
ange
f
tormizes
and
ntecedento ilonditions.
S eendividual
S t o r m oilosses
nder
A P P L Y I N GTHESOILLOSS
E Q U A T I O N . )
o
valuate
or
oils
hat
o
ot
usually
ccurn -percent
lope,o ilos s
ata
from
lotshatmeetall
he
other
specifiedondi-
tionsare
adjustedo
his
a s eby
.
Values
f
o r
pecific
oils
Representative
alues
of
or
o s t
f
he
o il
vailable
r e s e a r c h
information.
These tables are
types
and texture c lasses
c a n be obtained
from
tables
prepared
by
oil
cient is ts
sing
the latest
available
romhe
Regional
Technical
ervice
C e n -
tersr tatefficesfCS .aluesorhexact
8/11/2019 AH 503 Wichmeier
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PREDICTING
AINFALLROSION
OSSES-A
GUIDE
O
ONSERVATION
PLANNING
TABLE 1.
Computed
K values
for
soils on erosion
researchtations
Soil ou r c e
of
data
omputed
K
Dunkirkilt
oam
eneva,.Y.O.9
K e e n esiitoam
anesviile,hio48
S helby
oam
ethany,
Mo.41
L o d i
oam l
acksburg,
a.39
Fayette
ilt
oam
aCrosse,
Wis.
38
C e ci l
andylayoam
Watkinsville,
Ga.
36
Marshallil tloam
l
arinda,
owa
33
Ida
iltoam astaa,owa
33
M a n s i cclayloam
ays,
a n s .
32
Hagerstown
ilty
lay
oam tateollege,a..31
A u s t i nlay emple,
ex.
29
Mexico
il t
loam
cCredie,
Mo.28
Honeoyeilt
oam
Marcellus,
.Y.28
C e ci landyoam
l
emson,
.C.
28
Ontario
oam eneva,
.Y.
.2 7
C e ci lclayoam
atkinsville,
Ga.
26
B o s w e l lindandy
oam
yler,ex.
25
C e ci l
sandy
loam
atkinsville,
Ga.
23
Z a n e i s
inesandy
oam
ut
hrie,
kla.
22
T i f t o n
oamy
and
fton,
Ga.
10
Freeholdoamysand
arlboro,
.J.
08
B at hiaggy
il t
oam
with
urface
Arnot,
.Y.
05
s t o n e s
1>
n c h e semoved....
Albiagravelly
loam
eemerville,
.J.
03
*Evaluated from continuous fallow. All others were
computed
f r omowcropdata.
s o i l
onditions
tpecific
ite
ane
omputed
by
s e
f
he
o il
rodibility
nomograph
resented
in
he
nextsubsection.
Usuallyo ilype
ecomes
e s s
rodiblewith
decrease
niltraction,
egardlessf
whether
he
corresponding
ncrease
s
n
he
and
raction
r
the
layraction.
verall,rganic
matterontent
ranked
ext
o
article-sizedistribution
sanndi-
cator
f
rodibility.owever,
oi l 's
rodibility
isunction
ofomplexnteractionsfa
ubstan-
tial
umber
oftshysicalandhemical
roperties
and
ftenaries
within
tandardexture
l a s s .
Values
fetermined
or
3
ajor
o i l sn
which
rosionlotstudiesunder
naturalain
were
conducted
ince
930
re
isted
n
able
.
even
of
hesealues
re
rom
ontinuous
allow.
he
others
re
romrowcrops
averaging
0
lot-years
of
ecord
nd
rownnystems
orhich
he
cropping
ffect
adeenmeasurednthertud-
i e s .Othero i l s
n
which
aluable
rosion
tudies
haveeenonducted^ereot
ncluded
nhe
table
ecause
f
ncertainties
nvolved
n
djust-
mentsofhedata
or
effectsofcroppingand
man-
agement.
Direct
measurementf
herodibility
actor
s
both
ostly
nd
ime
onsuming
nd
as
een
feasible
onlyor
a
ew
majors o i l
ypes.
Toachieve
a
etter
nderstandingfow
nd
owhatx-
tentachfariousropertiesofa
o il
ffectsts
erodibility,
nnterregional
tudy
as
nitiated
in961.hetudyncludedhes e
field-plot
rainfall
imulators
n
at
eastadozenStatesoob-
tain
omparativeata
n
umerous
o i l s ,
abora-
tory
eterminations
of
physical
andhemical
rop-
erties,
ndperation
f
dditional
allow
lots
under
atural
ain.
everal
mpirical
rodibility
equations
were
eported
3,
0),
A
o il
rodibility
nomograph
orarmland
nd
onstruction
i tes
(58)
rovidedoreenerallypplicablework-
ing
ool.pproximatealues
or
0
enchmark
s o i l s
n
awaii
are
istedn
table
2.
*See
ootnote
3,
p..
T AB L E
2.
Approximate
aluesofth esoil
erodibilityfactor,
K,
for
10
benchmarksoils
n iawaii
Order
S u b o r d e r Great
r ou p
S u b g r o u p
Family
Se r ie s
K
U lt is o ls Humults Tropohumults
Humoxic
ropohumults
Clayey,aolinitic,sohyperthermic
Waikane 0.10
O x i s o l s
Torrox Torrox
Typic
Torrox
Clayey,
aolinitic,sohyperthermic
Molokai
.24
O x i s o l s
Ustox
Eutrustox
Tropepticutrustox
clayey,
aolinitic,
sohyperthermic Wahiawa
.17
V e r t i s o l s U s t e r t s Chromusterts TypicChromusterts
Veryine,montmorillonitic,sohyperthermic
Lualualei
Kawaihae
.28
.32
A r i d i s o l s
Orthids
Camborthids Ustollic
amborthids
Medial,sohyperthermic
(Extremelystonyhase)
I n c e p t i s o l s Andepts
Dystrandepts
Hydric
ystrandepts
Thixotropic,
sothermic
Kukaiau
.17
I n c e p t i s o l s
Andepts Eutrandepts
Typicutrandepts Medial,sohyperthermic
Naolehu(Variant) .20
I n c e p t i s o l s Andepts
Eutrandepts
E n t icutrandepts
Medial,sohyperthermic
Pakini
.49
I n c e p t i s o l s
Andepts
Hydrandepts
Typic
ydrandepts
Thixotropic,sohyperthermic
Hilo
.10
I nc ep t iso ls
Tropepts
Ustropepts
Vertic
stropepts
Veryine,aolinitic,
sohyperthermic
Waipahu
.20
SOURCE;l-Swaify
and'
Dangler9).
8/11/2019 AH 503 Wichmeier
16/67
10
UNITEDTATESEPARTMENT
F
GRICULTURE,
AG RICULTURE
ANDBOOK
U M B E R37
Soilrodibi l i ty
Thesoil
oss
data
show
hatveryfine
sand
0 . 0 5 -
nn )
s
omparable
n
rodibility
o
silt-sized
ndhat
mechanical-analysis
ata
re
more
valuablewhen
xpressedyannter-
ernrhatdescribes
he
proportions
n
which
and,.silt,
nd
lay
ractions
re
combined
n
soil.
When
mechanical
analysis
dataased
n
tandard
S D A
lassificationre s e dor
he
n
igure3 ,
he
percentageof
very
fine
0.1-0.05mm)mustirst
e
ransferred
rom
sand
ractionohe
silt
raction.The
mechani-
a l
analysis
data
re
hen
effectivelydescribedy
article-size
arameter
M,
which
quals
percent
0.1-0.002
mm)
imesheuantity00-minus-
Where
he
ilt
ractiono es
otx-
0
ercent,
rodibility
aries
pproximately
s
he
.1 4
power
ofhis
parameter,
but
prediction
s
mproved
ydding
nformation
n
matter
ontent,
oiltructure,
nd
rofile
lass .
F or
oilscontaining
es s
han
0
percent
siltand
ine
and,
he
omograph
fig.
)
olves
he
O O
K
=2 .1
M'-'*
(10-')
( 1 2
~a )-f-3 . 2 5 ( b -2 ) +2 . 5 (e -3 )
(3 )
M
=
the
article-size
arameterdefined
bove,
a
=
percent
organic
matter,
b
=thesoil-structurecode
s ed
nsoilclassifica-
tion,
and
c=the
rofile-permeability
lass .
entersection
of
theselect ed
percent-silt
andper-
ines
omputeshe
alue f
M
n
he
orizontal
cale
fhe
omograph.
laynters
nto
he
omputation
s
00
he
percentages
of
sand
and
silt.)
Theata
ndicate
hange
nhe
elation
f
o
rodibility
when
he
ilt
andery
ine
sand
xceeds
about
7 0
percent.
This
change
was
eflected
ynflectionsnhe
ercent-
urves
that
oint
ut
a sotee ne-
y
umerical
equation.
Readers
who
would
ikemore
etailegarding
ata
nd
elationships
nderlyingheomo-
quationmayobtain
his
rom
ournal rti-
( 58 ,
60).
Nomograph
o l u t i o n
With
appropriate data, enter thecale at
he
N o m o g r a p h
leftnd
roceed
o
ointsepresentinghe
oil's
percentand0.10-2.0mm),ercent
rganicmat-
ter,tructureode,
nd
ermeabilitylass
s
l-
lustrated
y
he
otted
ine
nhe
omograph.
Th e
orizontalnd
ertical
oves
must
e
made
in
he
isted
e q u e n c e .
se
inear
nterpolations
between lottedi nes. he
structure
o de
and
per-
meabilitylas s esre
efinedn
he
omograph
forreference.
Manyagricultural
oilshave
oth
ine
granular
topsoilandmoderatepermeability. orh e s e oi ls,
Kmaye
eadrom
he
caleabeled'first
p-
proximationf ,"ndhe
ec ond
lock
f
he
graphsot
needed.
orall
ther
oi ls,
owever,
theroceduremust e
completedo
he o il
erodi-
bility calenhe
s e c o n d
halfofhe
graph.
The
echanicalnalysis,rganic
atter,
nd
structuredata
are
thosefor
the
topsoil.
o r
evalua-
tion
of
Kfor
desurfacedsubsoilhorizons,
hey
per-
tain
ohe
upper
n
ofhe
new o il
rofile.
he
permeabilitylass
she
rofileermeability.
C o a r s e
ragments
are
excludedwhen
determining
percentages
f
and,
ilt,
nd
lay.
f
substantial,
they
may
ave
ermanent
mulch
ffect
which
c a n
evaluated
rom
he
pper
urve
f
he
chartn
mulch
nd
anopy
f fectsp .9,
ig.
)
and
pplied
o
he
umber
btained
rom
he
nomograph
solution.
C o n f i d e n c eimits
In
estsagainstmeasured
K
values
anging
rom
0.03
o .69,
5
percent
ofthenomograph
solutions
differedromhe
measured values
yesshan
0. 02,
nd5
ercent
f
hem
y
es s
han
.04.
Limitedata
vailable
n97 1or
mechanically
exposed and subsoil
.horizonsndicated
bout
comparable
ccuracy
or
h e s e
onditions.ow-
ever,more
ecentdataaken
n
esurfaced
gh-
clay
ubsoils
howedhe
omograph
olution
o
lackhe
desired
ensitivity
o
differences
n
rodi-
bilitiesf
h e s eo ilorizons.
or
u choilshe
contentfreeronnd
luminum
xides
anks
next
oarticle-sizedistribution s
anndicator
of
erodibility
37),o m e
igh-clay
oils
orm
what
ha s
e e n
alled
rreversible
ggregates
n
he
surface
when
illed.
hes e
behave
ike
argerri-
maryparticles.
8/11/2019 AH 503 Wichmeier
17/67
PREDICTING
A I N F A L LROSION
L O S S E S - A
U ID EOO N S E R V A T I O N
PLANNING
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8/11/2019 AH 503 Wichmeier
18/67
UNITE D
TATE S
E P A R T M E N T
F
G R I C U L T U R E ,
A G R I C U L T U R E
A N D B O O K
UMBER37
T O P O G R A P H I C
A C T O R
L S)
Bothhe
ength
nd
he
teepness
f
he
and
substantially
affect
he
ateof
soilerosion
by
hewo
ffects
ave
een
valuated
ep-
n
esearch
andare
epresented
n
he
soil
loss
quationy
nd
,espectively.
nield
applications,
owever,
onsidering
he
wos
single
opographicactor,
S,
s
more
onvenient.
S l o p e - E f f e c thart
L S
sheexpectedatio
of
soilos sperunit
area
ield
slope
o
hat
rom
72.6-ft
ength
of
-percent
slope
nder
therwise
dentical
his
atio
or
specified
combinations
of
lope
engthnd
niform
radientmay
e
irectly
rom
he
lope-effect
hartfig.
) .Enter n
he
horizontalaxis
with
he
fieldslope
move
vertically
o
he
appropriate
percent-
curve,
ndead
Sn
he
caleat
he
eft.
o r
xample,he
Sactor
or
00-ft
ength f
0-percent
lope
s
.4 .
h ose
who
refer
able
s eable
nd
nterpolate
etween
isted
Toompute
oil
os s
rom
l opeshatre
p-
onvex,
oncave,
romplex,hehart
S
valueseedo
e
adjusted
sndicatedn
he
S
a l u e s
orrregularl o p e s .igure
able
ssume
l opes
hat
ave
ssentially
radient.
he
hart
nd
able
were
e-
ived
by
the
equation
IS=X/72.6) * {65.4] s i n ' 8
+
4.56s in 6-j-0.065) (4)
where
X
=
slope
lengthin
feet;
6 =angleofslope;and
m=
0 .5
f
he
percentslopes
r
more,
.4 n
s l opesof .5
o
.5ercent,
.3
on
l opesof
o
3
percent,
and 0.2 on
uniform
gradients
of
less
than
percent.
The
asis
or
his
equations
given
n
hesub-
sectioniscussinghe
ndividualffects
f
lope
length
nd
teepness.
owever,
he
elationships
expressed
byheequation
were
derived
rom
data
obtainedn
ropland,nder
atural
ainfall,
n
s l opesangingrom
o
8
ercentn
teepness
andabout
0
to
0 0ftnength.
How
ar
beyond
these
anges
n
lopeharacteristics
he
elation-
ships
erived
romheataontinueo
ec c u -
ratea s
ot
e e n
etermined
yirect
oil
os s
measurements.
The a l ouse
egi on f
he
Northwestepresents
TABLE
3.
Values
of
the
topographic
factor,
LS,
forspecificcombinatiorisofslopelength
and
steepness^
Slope
e n g t h
( feet )
^ ^ l o ^ r
^ ^
^
^ ^ ^ ^ ^
^ ' ' ^ ^
0 .2 0.060 0.069 0. 07 5 0.080 0.086
0.092
0.099 0.105
.110
.114
.121 0.126
0.5
73
.083 .090
.096
.104 .110
.119
.126
13 2
13 714 5
.152
0. 8
86
.098 ,107 ,113 .123 .130
.141
.14915 6
16 2
17 1
.179
2 33 .163 .185
.201
.227 .248 .280 .30532 634 437 6
.402
3
90 .233 .264 .287
.325
.354 .400 .437
466
49 2
53 6 .573
4 .230
.303
.357
.400 .471
.528
.62\ .697
76 2
82 092 0 1.01
5
68
,379 ,464 .536 .656 .758 .928 1.07.20
.31
.52 1.69
6
.336
.476
,583
.673
.824
.952
1.17
1.35
.50
.65
.9 0
2.13
8 96
,701
.859
.992 1.21
1.41
1.72
1.98
,2 2.4 3
.81
3.4
10
85 .968 1.19 1.37 1.68 1.94 2.37 2.74
.0 6
.36
.8 7 4.33
12 0 3 1.28 1.56 1.80 2.21 2.55 3.13 3.61
.0 4
.4 2.11 5.71
14
1.15
1.62
1.99
2.30
2.81
3.25
3,98
4.59
.1 3
.6 2
.4 9
7.26
16
1.42 2.01
2.46
2.84 3.48
4.01
4.92
5.68.3 5
.9 5
.0 3
8.98
18
1.72 2.43 2.97 3.43 4.21 3.86 5.95 6.87
.6 8.41
.71
10.9
20 2.04 2.88 3.53 4. 08 5.00 5.77
7.07
8.16
.1 20. 01.5 12.9
^
is=
X/72.6) *
(65.41
s i n '
6-f 4.56in 0-\ -
0.065)
where
X=
s l o p e
e n g t h
n
f e e t ;
=0. 2o r
g r a d i e n t s
5
ercent,
.4
orercentl o p e s ,nd
.3or
3ercentre s s ) ;nd
=
numberfqual-lengthegmentsnto
whichheslopewas
divided.
Fouregments
would
roduce2,3,0,nd5
percent,espectively. egmentNo.
s lways t
the
op
fheslope.
Slope
toe
nfluenced
y
nteractions
withsoil
properties
andurfaceonditions,uthenteraction
ffects
have
not
beenquantified
y
esearch
data.
Neither
are
data
available
o
define
heimitson
he
equa-
tion's
applicability.
Thisquation
an
eerivedrom
he
ormerly
publishedquation
or
.
xpressing
heactors
a
unction f
he
ine
f
he
angleof
lopeather
thanheangent
s
moreccurate
ecause
ain-
drop-impact
orces
long
he
urface
nd
unoff
shear
tress
re
unctions
fheine. ubstituting
100
sin
or
percent
slope,
which
s
00
an ,does
not
ignificantly
ffect
he
nitial
tatistical
eriva-
tionr
hequation'solutions
or
lopes fess
than
20ercent.
utasslopes
ecome
steeper,
he
differenceetween
heine
nd
he
angente-
comes
ppreciable
ndrojections
ar
eyondhe
range
f
he lotata
ecome
moreealistic.
he
numeratorwasdividedyhe
constant
denomina-
tor
for
simplification.
8/11/2019 AH 503 Wichmeier
22/67
16 UN IT EDTATE S
E P A R T M E N T
FG R I C U L T U R E ,
A G R I C U L T U R E
A N D B O O KUMBER37
I r regular
S o i los ssalsoaffectedbytheshapeof slope.
ield
l opeseithersteepenoward
he
ower
convex
slope)
or
flatten
oward
he
owerend
lope) .se
f
he
verage
radient
o
igure
or
able
would
underestimate
o il
tothe
oot
of
a
convexslope
and
would
t
orconcave l opes.
rregular
l opes
a n
suallye ivided
ntoegmentshatave
niformradient,uthesegments
cannot
e
valuated
sndependent
l opeswhenunoff
fromone
segment
to
the
next.
However,here
wo
implifying
ssumptions
a n
eccepted,S
orrregular
l opesa ne
erivedyombininge l ec tedalues
he
lope-effecthart
nd
able
5 5 ) .
he
re
hat
1)he
hanges
n
radient
ot
sufficient
to
a u s e
pslope
deposition,and
)
he
rregularslope a n
edivided
nto
small
f
equal-length
egments
nu ch
man-
r
hatheradientwithin
ac h
egmentor
practical
purposes
c an be
considered
uniform.
After
ividing
heonvex,
oncave,rcomplex
nto
qual-lengthegmentssefinedar-
ier,
he
roceduressollows:
is t
he
egment
n
herder
n
which
hey
c c u r
nhe
beginning
at
he
upper
end.
Enter
he
slope-
chart
withhe
otal
slopeengthand
ead
S
ac h fheistedradients.
Multiplyh e s ey
C h a ng e sn
o ilype
r
The
rocedure
or
rregularl opes
an
nclude
fhanges
no il
ype
within lope
length
55 ) .
heroductsofalueselected
rom
origure
and
able
o
evaluate S
or
irregular
l opesremultiplied
yhe
espective
aluesof beforesumming.
ollustrate,
s s u m e
the
alues
or
he
oils
n
he
hree
egments
f
heconvexslopenhe
preceding
example
were
. 27, .32 ,
and
. 3 7 ,
espectively.
he
average
L S
or
heslope
would eobtained sollows:
Slopes
the
orrresponding
actors
rom
able nddd
the
products
o
obtain
S
orhe
entire
slope. he
following
abulation
llustrates
herocedureor
a
400-ft
convex
slope
n
which
heupper
third a s
a
radient
of
ercent;
he
middle
hird,
0
er-
cent ;
and
he
ower
hird,5
percent:
Segmenf
Percent lope Table
Table
Product
1 5
1.07 0.19
0.203
2
10
2.74
.35
.959
3
15
5.12
.46
L S
2.355
=3.517
F or
he
concave
slope
of
he
a m e
ength,with
thesegment
gradients
n
everseorder,hevalues
inhe
hirdolumn
wouldeistedneverse
or-
der.
he
products
would
hen
e
. 9 7 3 ,
.959,and
0.492,
giving
u m
of2,42or S .
Resear ch
a s
ot
defined
ust
ow u c h
radi-
ent
changesneeded
nder
various
conditionsor
deposition
f
soilarticles
f
various
izes
o
e -
gin,
ut
depositional
areas
a ne
determined
y
observation.
henhe
lope
reaks
re
harp
enough
o
a u s e
deposition,herocedure a ne
u s e d
oestimate
S
or
slope
segments
aboveand
below
he
epositional
rea.
owever,t
willot
predict
he
otal
ediment
oved
rom
u ch
n
interruptedlopee c a u s e
t
oe sot
redict
he
amountofdeposition.
C o v e rA l o n ghe
Slope
Withinimits,
he
rocedure
ane
urther
x-
tendedoaccount
or
hanges
n
overalonghe
slopeength
ydding
olumnf
egment
values.However,
t
s
notapplicableorsituations
where
ractice
hange long
he
lopea u s e s
deposition. orexample,
grass
bufferstrip
cr oss
the
oot
of
slope
n
which
ubstantial
erosion
s
occurring
nduces
eposition.he
mount
f
his
deposition
s unction
f
ransport
elationships
(JO)
andannot
e
predictedytheSLE.
Segment
No .
Table
3
Table
4
K
Product
1
1.07
0.19 0.27
0.055
2 2.74
.35 .32
.307
3
5.12
.46
.37
KLS
.871
=
1.233
8/11/2019 AH 503 Wichmeier
23/67
PREDICTING
R A I N F A L L
R O S I O N L O S S E S - AGUIDE
O
O N S E R V A T I O N PLANNING
17
Equation
o r
Soil
D e t a c h m e n t
o n
This
rocedure
s
ounded
nn
quation
7 2 )
a n
e
applied
also
when
heslope
segments
eot
of
qual
ength.
o n c e p t s
nderlying
his
includethefollowing:
Sediment
oad
t
ocation
n
lope
so n -
ither
by
he
ransport
capacity
of
he
un-
ndainfall
r
y
he
mount
f
etached
aterial
vailableor
ransport.
henhe
of
detachedmaterial
xceedshe
ransport
deposition
c c ursandhe
sediment
oad
etermined
rimarily
y
he
ransport
apacity
heunoff
at
hatocation.
Where
pslope
de-
Successive
S e g m e n t s
o f
Slope
tachment
a s
ot
qualed
he
ransport
apacity,
sedimentoad
t
iven
ocation
s unctionof
erosion
characteristics
of
heupslopeareaand
a n
be
omputed
yheSLE.
o il
os srom iven
segment
of
heslope a nhen e
computed s
he
difference
between
he
sediment
oads
at
the
ower
and
upper
ends
of
thesegment.
Fosterand
Wischmeier
1 2)
resent
rocedure
forusinghisequationoevaluate Sorrregular
s lopesandoaccountforhe f fects
of
he o il
r
coverage
hanges
long
lope,oongs
he
changesdonot a u s edepositiono c c u r .
COVERND
MANAGEMENT
A C T O RC)
Coverand
management
f fects
ca
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