-------
Example 1. The Needle Branch Watershed
Worksheets III.l and III.2 (Needle Branch)
In this first example, for the Pacific Coast
provinces-low elevation, Dennis Harr (personal
communication, 1977) provided data from Needle
Branch of the Alsea Watershed in western Oregon.
The baseline LAI of 40 was reduced to an average of
1 for the first 3 years after silvicultural activity.
Rooting depth was average (4 feet) and an aspect
correction was made (effect assumed=l) for the
north facing watershed.
The first step in the procedure is to estimate the
baseline potential evapotranspiration.
For the pre-treatment condition [see worksheets
III.l and III.2 (Needle Branch)], the baseline
evapotranspiration by season (from fig. III. 10) is
shown in the summary below; the precipitation
data in the example were taken from the data base
record for the H. J. Andrews Experimental Forest.
It should be noted that the watershed has been
divided into one silvicultural prescription and one
silvicultural state both before (forested) and after
(clearcut) treatment.
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Precipitation
(item 10)
11.6 cm ( 6.5 in)
31.2 cm (12.3 in)
128.1 cm (50.4 in)
82.1 cm (24.4 in)
232.8 cm (91. 6 in)
Baseline ET
(item 11)
26 cm (10.2 in)
24 cm ( 9.5 in)
18 cm ( 7.1 in)
30.5 cm (12 in)
98.5 cm (38. 8 in)
For the pre-treatment (existing) condition, the
annual evapotranspiration loss is estimated at 98.5
cm or 38.8 inches. In this example the precipitation
is 91.6 inches, so the water potentially available for
streamflow is 52.8 inches.
For the post-activity conditions, the following es-
timates are presented:
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Baseline ET
(item 11)
(1)
26 cm
24 cm
18 cm
30.5 cm
98.5 cm
ET
modifier
(item 14)
(2)
0.55
0.54
0.28
0.27
Root
depth
modifier
(item 15)
(3)
1.0
1.0
1.0
1.0
Post-
silvicultural
activity ET
(col 1x2x3)
(4)
14.3 cm
13.0 cm
5.0 cm
8.2 cm
40.5 cm
The potential change in evapotranspiration is
98.5 cm minus 40.5 cm or 58.0 cm (22.8 inches) of
potential increase in flow. The observed change
averaged 19.8 inches for the 3-year study period.
The total potential flow for the post-activity period
is 52.8 baseline inches and 22.8 inches change or
75.6 inches total.
Example 2. The Coweeta Watershed
Worksheets III.l Am* III.2 (Coweeta)
For the Appalachian Mountains and Highlands,
Hewlett and Douglass (1968) reported on a
management demonstration on a 356-acre
watershed at Coweeta Hydrologic Laboratory near
Franklin, North Carolina. Of the 356 acres, 180
were clearcut, 92 were thinned, and the remainder
left uncut. The expected net change in evapotran-
spiration would be estimated in the following man-
ner.
Again, the watershed is considered fairly uniform
so only one silvicultural prescription has been
defined for all 356 acres. For the pre-treatment con-
dition, this also implies one silvicultural state —
forested. For the post-treatment condition, three
silvicultural states are implied — forested, thin-
ned, and clearcut.
For existing conditions, the baseline leaf area in-
dex for hardwoods at Coweeta is about 6 (Swift and
others 1975). The residual leaf area index on the
clearcut portion was 2, while that on the thinned
portion was 3 (Patric and Hewlett, personal com-
munication). The baseline evapotranspiration, as-
suming a leaf area index of 6 (latitude of 35°) and
using figure III.11, is shown in the summary below:
Season
(item 5)
Summer
Fall
Winter
Spring
Annual
Precipitation
(item 10)
27.0 cm (10.6 in)
23.3 cm ( 9.2 in)
75.2 cm (29.6 in)
60.5 cm (23.8 in)
186.0 cm (73. 2 in)
Baseline ET
(item 11)
39.1 cm (15.4 in)
20.1 cm ( 7.9 in)
8.9 cm ( 3.5 in)
13.0 cm ( 5.1 in)
81.1 cm (31.9in)
For the pre-treatment condition, the annual
evapotranspiration loss is estimated as 81.1 cm or
31.9 inches (item 17). The precipitation estimate
represents the average for the simulation years.
Therefore, if the estimated evapotranspiration is
31.9 inches and the precipitation is 73.2 inches, the
water potentially available for streamflow is 41.3
inches.
m.38
-------
WORKSHEET 1 1 I . 1
Water available for streamflo* for the existing condition In rainfall dominated regions
(1) Watershed name
(2) Hydrologlc region >L (3) Total prescription area (acres) 3S(o (4) Latitude 35
Season
name/
dates
(5)
y - y30
Winter
'V~ V
Spring
fl - s/(,
Summer
Silv
cultura prescription
Compartment
(6)
Un impacted
mpacted
ota
for se
Un Impacted
Impac
Tota
:ted
for se
Un i mpacted
Impacted
Tota
for se
Un impacted
Impacted
Si Ivicultural
state
(7)
FoKsttJ
ason
Forested
ason
Fot-«3t«d
ason
Fov-fffftfld
Total for season
(19) Annua ET
Area
Acres
(8)
3St>
3Sfe
3Sfe
351a
3S*t
3S"fe
9St>
Per-
cent
(9)
l.ooo
1 .000
(.000
1.000
1.000
1.000
(.000
1.000
Precipi-
tation
(cm)
(10)
A3. 3
S3.3
7s. a.
7S-.1,
40. sr
to.s"
a?.o
27.0
Basel ine
ET
(cm)
(11)
30.1
f.V
13.0
37.1
Basal
area
(ft2/ac)
(12)
Leaf
area
Index
(13)
Ł,
ta
le
If
ET
modifier
coef.
(14)
I.O
I.O
I.O
I.O
Root 1 ng
depth
modifier
coef.
(15)
I.O
I.O
I.O
1.0
Weighted
adjusted
ET
(cm)
(16)
ao. i
10.1
p.?
3.9
13.0
13.0
31.1
31.1
(cm)
Weighted
adjusted
seasonal
ET
(cm)
(17)
10. \
3.9
13.0
31.1
(20) Water available for annual streamflow (cm)
Water
aval lable
for sea-
sonal stream-
flow (cm)
(18)
3.2.
64.3
-------
WORKSHEET I I I . 2
Water available for streamflow for the proposed condition in rainfall dominated regions
(1) Watershed name
(2) Hydrologic region 3, (3) Total prescription area (acres) 35"4 (4) Latitude 3S
Season
name/
dates
(5)
fl-V»
Winter
lay V.
7i " «*
Spri ng
3/t'*/3\
Summer
fc/-%'
SI 1 vlcu 1 tura prescr ipt ion
Compartment SI Ivicultural
state
(6) (7)
Un impacted
Impacted
Total for se
Unlmpacted
Impacted
Total for se
Un impacted
Impacted
Total for se
Un imp acted
Impacted
IWiW
Cl«a«ui
TViimtd
ason
F»i-«tei
G«artufc
TVinnfcd
ason
rorest«ei
Cl«axiuŁ
TVmvte.^
ason
RiKstetl
Clcarmt.
"TVnA««fi
Total for season
Area
Acres
(8)
81
1*0
92.
3.Tfc
fl
IfO
90,
3Sfc
8-f
180
92.
3Sfc
?,oo
.feo
.TI
l.oo
.fc?
.J^
Rooting
depth
mod 1 f i er
coef.
(15)
(.0
(.0
1.0
1.0
1-0
1:0
1.0
1,0
1.0
I.O
1.0
I.O
Weighted
adjusted
ET
(cm)
(16)
V.Tt
8.A3
-------
For post-treatment conditions, the estimates
would be as follows:
(1) For the clearcut portion: leaf area index = 2;
root depth = average; no aspect adjustment.
[See worksheet in.2 (Coweeta).]
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Baseline ET
(item 11)
(fig 111.11)
(1)
39 cm
20 cm
9 cm
13 cm
81 cm
ET
modifier
(item 14)
(fig 111.16)
(2)
0.69
0.81
0.65
0.60
Root
modifier
(item 15)
(fig 111.19)
(3)
1.0
1.0
1.0
1.0
Post-
silvicultural
activity ET
(col 1x2x3)
(4)
26.9 cm
16.2 cm
5.8 cm
7.8 cm
56.7 cm
The pre-activity (baseline) annual evapotran-
spiration was 81 cm (31.9 in) for the watershed.
The weighted post-activity evapotranspiration is
estimated as 65.1 cm (25.6 in), and the change due
to the proposed silvicultural activity is 6.3 inches.
The water potentially available for flow following
the activity increases 6.3 inches from 41.3 to 47.6
inches.
The observed change in flow (Hewlett and
Douglass 1968) in the watershed studied was 6.2 in-
ches. It must be remembered that the leaf area es-
timates for the treated sites were based on the
recollections of the investigators. The estimates
were unbiased but arbitrary, and the prediction
may be better than can be generally expected of the
technique.
(2) For the thinned portion: leaf area index = 3;
root depth = average; no aspect correction.
[See worksheet III.2 (Coweeta).]
Example 3. The Grant Watershed
Worksheets III.l and III.2 (Grant)
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Baseline ET
(item 11)
(fig. 111.11)
(1)
39
20
9
13
81
ET
modifier
(item 14)
(fig. 111.16)
(2)
0.84
0.90
0.76
0.72
Root Post-
modifier silvicultural
(item 15) activity ET
(fig. 111.19) (col 1x2x3)
(3)
1.0
1.0
1.0
1.0
(4)
32.8cm
18.0cm
6.8cm
9.4cm
67.0cm
(3) For the managed but uncut portion: poten-
tial evapotranspiration is the same as the
baseline condition.
To estimate the net silvicultural impact on
evapotranspiration, the following procedure can be
applied for either annual or seasonal post-
silvicultural activity effect. It simply weights the
relative effect of each management condition as
shown in the table below:
For the Gulf and Atlantic region, John Hewlett,
University of Georgia, (personal communication)
has supplied data for Example 3. The basin is an
80-acre treated watershed where silvicultural ac-
tivities occur on the Georgia Piedmont, south of
Athens, in the Grant Memorial Forest. The
watershed is a pine-hardwood combination with an
initial leaf area index of 7 and an average rooting
depth of about 6 feet. It was clearcut, roller
chopped twice, and then planted — reducing the
leaf area index to 0.5. Again, a single silvicultural
prescription and one silvicultural state were
selected for the small uniform basin. The net
change in evapotranspiration was estimated in the
following manner [and transferred to worksheet
III.l (Grant)]:
(1) Assuming a baseline LAI of 7, the baseline
evapotranspiration by season (from fig.
ni.12) is tabulated as:
Unit
Clearcut
Thinned
Unmanaged
Acres
(item 8)
180
92
84
Area as
%of
total
(item 9)
50.6
25.8
23.6
Unit potential
evapo-
transpiration
56.7 cm
67.0cm
81.0cm
Weighted unit
evapo-
transpiration
(area % x ET)
28.7 cm
17.3 cm
19.1 cm
Total
356
100.0
65.1 cm
Season
(item 5)
Summer
Fall
Winter
Spring
Precipitation
(item 10)
41.2 cm (16.2 in)
30.2 cm (11. 9 in)
40.3 cm (15.9 in)
20.6 cm ( 8.1 in)
Baseline ET
(item 11)
32.1 cm (12.6 in)
24.9 cm ( 9.8 in)
11.4 cm ( 4.5 in)
23.7 cm ( 9.3 in)
Total
132.3 cm (52.1 in) 92.1 cm (36.2 in)
111.41
-------
WORKSHEET I I I . 1
Water available for streamflow for the existing condition In rainfall dominated regions
(I)
Watershed name 6t
Winter
Ml 1.1
7\- A*
Spring
*-%•
Sunnier
*-%
Silviculture prescription
Compartment
(6)
Un Impacted
Impacted
[otal for se
Un Imp acted
Impacted
total for se
Un 1 mpacted
Impacted
Total for se
Un Imp acted
Impacted
SI Ivlcultural
state
(7)
Fn-«ri*i
ason
FbwsUxl
ason
fijvciteJ
ason
MJI tf&tu
Total for season
Area
Acres
(8)
So
SO
16
80
So
So
ffo
80
Per-
cent
(9)
I.OOO
1 .000
1.000
1 .000
I.OOO
1.000
I.OOO
I.OOO
Prec 1 p 1 -
tat ion
(cm)
(10)
30. JL
30.4,
$0.3
.3
ao.fc
ao.t
fl.SL
-------
WORKSHEET II I .2
Water available for streamflow for the proposed condition In rainfall dominated regions
(1) Watershed name Gwurit 4J.
(2) Hydrologlc region 3 (3) Total prescription area (acres) SO (4) Latitude
Season
dates
(5)
V'/*>
Winter
•V-&
Spring
3/r%
Summer
X'S/3,
S i 1 v 1 cu 1 tura 1 prescr 1 pt 1 on
Compartment
(6)
Un impacted
Impacted
Total for se
Un Impacted
Impacted
Total for se
Un impacted
Impacted
Tota 1 for se
Un impacted
Impacted
Si Ivlcultural
state
(7)
Cl»a.«ut
ason
Clcueut
ason
Cl«a«u*
ason
"hw-ntfi
Tota 1 for season
Area
Acres
(6)
10
»o
80
JO
ac
So
80
SO
Per-
cent
(9)
1 ooo
1.000
I.Ooo
1 .000
1.000
t.ooo
I.OOO
1.000
Precipi-
tation
(cm)
(10)
3O. X
3o.i
-------
(2) For post-silvicultural activity conditions [see
worksheet HI.2 (Grant)], with a LAI = .5, the
estimates are tabulated as:
Season Baseline ET
(itemS) (item 11)
(fig 111.12)
ET Root Post-
modifier modifier silviculture!
(Item 14) (Item 15) activity ET
(fig 111.17) (figlll.20) (col 1x2x3)
Summer
Fall
Winter
Spring
Total
32.1 cm
24.9 cm
11.4 cm
23.7 cm
92.1 cm
.47
.47
.41
.34
1.0
1.0
1.0
1.0
15.1 cm
11.7 cm
4.7 cm
8.0 cm
39.5 cm
For the pre-treatment condition, the annual
evapotranspiration loss is estimated as 36.2 inches
(92.1 cm) from an average precipitation of 52.1 in-
ches (132.3 cm). The water potentially available for
streamflow is 15.9 inches (40.4 cm).
The potential change in flow based on changes in
evapotranspiration from 92.1 cm (existing con-
dition) to 39.5 cm (proposed condition) is 52.6 cm
(20.7 in). Hewlett estimated the observed change
at 11 inches by the paired watershed method. The
simulated water available for streamflow increased
from 15.9 to 36.6 inches.
m.44
-------
PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
IN STREAMFLOW (STREAMFLOW ESTIMATION)
(RAIN DOMINATED REGIONS)
APPALACHIAN MOUNTAINS AND HIGHLANDS (REGION 2)
GULF AND ATLANTIC COASTAL PLAIN AND PIEDMONT (REGION 3)
PACIFIC COAST REGIONS (PROVINCES 5, 6, 7)
Distributing the potential changes in streamflow
associated with various silvicultural activities is
more complex and contains more sources of error
than does estimating evapotranspiration and the
magnitude of change. Streamflow predictions not
only contain all the errors inherent in the
evapotranspiration predictions, but also those er-
rors inherent in maintaining a time-and-space-
variable soil water budget and in routing both
saturated and unsaturated flows to the channel
system. None of these factors involving routing
have been simulated in this effort. Therefore, all
calculations dealing with flow predictions deal with
estimating the water onsite that is potentially
available for streamflow.
The purpose of this procedure is to distribute the
expected change in flow, as estimated by the
preceding ET procedure, over some reasonable es-
timate of the baseline or pre-treatment flow
regime.
It has already been noted that the objective is to
estimate the streamflow change and not the ab-
solute value. Numerous simulations were made for
each watershed data set to determine the effect of
altering various watershed parameters and cover
conditions on potential streamflow. The complex-
ity of the data generated is significant because
simulations were made on five to six cover condi-
tions, three soil depths, two aspects, and several
latitudes (watersheds) for each region. To facilitate
presentation of the results, a least squares tech-
nique was used to fit the model wherein the change
in flow (AQ) that occurs is a function of the antece-
dent flow level (pre-silvicultural activity flow, Q;),
the reduction in leaf area index (CD), the aspect
(AS), the rooting or soil depth (RD).
The technique is not, however, a true regression,
and estimates of error are impossible since the data
base is simulated. The least squares model does
represent the relationship that existed between the
change in flow and the various levels of the other
parameters used in the simulations.
PROCEDURAL FLOW CHART
A flow chart for the suggested methodology of
calculating potential changes in streamflow as-
sociated with silvicultural practices is presented in
figure 111.21.
At the end of this section are three examples
which have been developed to demonstrate ap-
plication of the methodology; the worksheets for
each example (in.3 and III.4) are summaries of
calculations performed. A detailed description for
each step follows.
HYDROLOGIC REGION OR
PROVINCE
Decide which region or province most nearly ap-
proximates the hydrologic regime for the water-
shed of interest. Streamflow calculations are based
upon regional hydrologic relationships, and the
regional characterization is the same for this
procedure as it was for the ET procedure.
ANNUAL
HYDROGRAPH
AVAILABLE?
To distribute the expected changes in flow, it
must be known if a representative hydrograph is
available for the site. If not, the methodology
presented includes a flow duration curve represen-
HI.45
-------
( Hydrologic Region or Province j
Hydro-
graph
Available?
Spe-
cific Flow
Changes
Desired?
Yes
( Flow and Date of Interest
+
Sine Day
Regional 7-Day Flow
Duration Curve
Water Available for
Annual Streamflow-
Existing Condition
Adjustment Ratio
Existing Condition 7-Day
Flow Duration Curve
Leaf Area Index Reduction
Leaf Area Index Reduction
Aspect
Aspect
Relative Rooting Depth
Relative Rooting Depth
Change in Streamflow
Change in Streamflow
Proposed Condition 7-Day
Flow Duration Curve
Figure 111.21.—Flow chart of methodology for determining 7-day flow duration curve and change
in Streamflow for specific flow change for rainfall dominated regions.
m.46
-------
tative of each region over which changes in flow can
be distributed. If a site specific hydrograph is not
available, proceed to the block "Regional 7-Day
Flow Duration Curves." If a representative
hydrograph is available, proceed to the block
"Specific Flow Changes Desired?"
SPECIFIC
FLOW CHANGES
DESIRED?
If a site specific hydrograph is available, there
are two options. First, a determination of the ex-
pected change in flow for specific flow levels as a
function of the day or time of year when the flow
level might occur can be performed. This would ap-
ply when concerned with impacts on in-stream flow
needs or on temperature. Changes in specific flow
levels do not replace the procedure for distributing
annual changes; it is another analytical tool. In
most applications interest will be in distributing
the change in annual flow over the entire
hydrograph. (This constitutes a "no" answer.) In
this case, proceed to the section on "Existing Con-
dition 7-Day Flow Duration Curve" since a site
specific flow duration curve can be constructed
from the hydrograph. If estimates of changes in
specific flow levels only are desired, proceed to the
"Flow and Date of Interest" section.
REGIONAL 7-DAY FLOW
DURATION CURVE
20.
15
.
o>
o>
o
O
in
O
<
DC
UU
10
—
—
—
—
—
—
—
—
•
\
[••! \
\
\ ^
V
\v
Vj_- -
\
-••-^
ANNUAL FLOW E
Appalachian Moi
Eastern Coastal (
Pacific Coast
Easl
^••=H7vT
3Y INTEGRATION O
ntains & Highlands
3lain & Piedmont
fie Coast
ern Coastal Plain &
alachian Mountain I
s*=^
F11 POINTS
72.0 cm
75 1r.m
139.6cm
Piedmont
i Highlands
20 40 60 80
PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
Figure III.22.—Potential excess water available for streamflow, 7-day flow duration curve for the
Pacific Coast hydrologic provinces—Northwest (5), Continental/Maritime (6), and Central
Sierra (7); for Appalachian Mountains and Highlands hydrologic region (2); and for the Eastern
Coastal Plain and Piedmont hydrologic region (3).
100
m.47
-------
Figure III.22 represents distributions of water
potentially available for streamflow for each of the
regions presented as 7-day flow duration curves. As
such, they represent the average expected 7-day
flow distribution for the conditions under which the
simulations for each region were made. The major
problem with presenting a normalized flow dura-
tion curve is that the normal variation in climatic,
physiographic, and local basin characteristics
forces almost every annual distribution of flow to
be unique in both time and space. The assumption
made at this point is that a site specific curve is not
available. Therefore, select the duration curve for
the region and adjust it for site specific conditions.
WATER AVAILABLE FOR ANNUAL
STREAMFLOW—EXISTING CONDITION
The flow duration curves presented in figure
III.22 represent average distributions for the
watershed years simulated in each region. As such,
they represent the distribution of a specific volume
of water for each region and that volume may or
may not represent the expected flow from the site;
an adjustment is therefore necessary. The expected
flow from the site for either baseline or existing
condition has already been calculated in the
procedure for determining evapotranspiration.
Now the given flow duration curve (from fig. III.22)
must be scaled to reflect the expected flow. This
would not be necessary if a site specific flow dura-
tion curve were available.
ADJUSTMENT RATIO
The baseline potential flow duration curve for
the hydrologic region must be adjusted for the site
specific existing condition. This is done through
multiplication of selected points on the curve by
adjustment ratio. The adjustment ratio is defined
as the ratio of water available for annual
streamflow estimated by the ET procedure to the
total water available for streamflow represented by
the 7-day flow duration curve for the hydrologic
region (fig. III.22) expressed as:
where
AR
Qw
adjustment ratio
water available for annual streamflow
for the existing condition (from ET
calculation, Eq. ni.5)
QR = total water available for streamflow
represented by the regional 7-day flow
duration curve, (fig III.22)
For Coweeta, for example, the adjustment ratio
AR =
104.9
72.0
= 1.457
where:
104.9 cm
AR =
QR
(III.6)
water available for annual
streamflow for the existing condi-
tion
72.0 cm = total water available for
streamflow represented by the
regional 7-day flow duration curve
(from fig. 111.22).
Once the adjustment ratio is determined, a site
specific flow duration curve for the existing condi-
tion can be constructed.
EXISTING CONDITION 7-DAY
FLOW DURATION CURVE
If a site specific 7-day flow duration curve for the
existing condition is available, no adjustment is
necessary here. However, flow duration curves from
figure III.22 need to be adjusted in the following
manner. An acceptable number of points on the
regional 7-day flow duration curve (fig. in.22) must
be selected such that a new line can be fitted after
adjusting the points for site specific conditions.
(For example, 11 points at 10 percent intervals
such as from 0 to 100 percent may be chosen.) The
discharge (Qj^) for each point (i) chosen from the
regional 7-day flow duration curve is multiplied by
the adjustment ratio to give an adjusted flow level
(Qi). For example.
Qi=QR.XAR (III7)
where:
Qi = adjusted flow level
QR. = the discharge for each point (i) on the
regional 7-day flow duration curve
AR = adjustment ratio
III.48
-------
The existing condition 7-day flow duration curve
is the plot of adjusted flow levels (Qi) versus the
corresponding percent of time the flow is equaled or
exceeded.
See worksheets IE.3 (Needle Branch, Coweeta,
Grant) for detailed examples of determining the ex-
isting condition 7-day flow duration curve.
To this point, site specific estimates of the 7-day
flow duration curve for baseline or existing condi-
tions have been made. If a change in vegetal state is
proposed, the following sections describe the
procedures necessary to modify the existing flow
duration curve to reflect the impact of the vegeta-
tion change.
In order to calculate the change in streamflow
due to the change from existing to proposed condi-
tions, it is necessary to estimate the leaf area index
reduction, aspect, and relative rooting depth.
LEAF AREA INDEX
REDUCTION
where:
RD = relative rooting depth for watershed
RDW= rooting depth for watershed
RDA= average rooting depth for region
The average regional rooting depth has been dis-
cussed in a previous section.
CHANGE IN
STREAMFLOW
As noted earlier, the expected change in annual
flow is a reflection of changes in evapotranspiration
resulting from the average change in leaf area index
for the watershed. This section deals with the dis-
tribution of that change in flow over the annual dis-
tribution or the flow duration curve. This is done
using least square techniques.
AQ; = ho + biQ; + b2CD + b3AS + b4 RD (HI.9)
A representative value for the reduction of leaf
area index (LAI) in units of LAI due to vegetation
changes between existing and proposed conditions
must be supplied. Reduction in LAI is symbolized
as "CD." As indicated previously, basal area can
be used to estimate leaf area index.
ASPECT
A representative aspect for the watershed or
watershed subunit in coded form must be supplied.
The aspect code is as follows: North aspect = — 1,
south aspect = +1, east or west aspect = 0.
where:
AQ; = simulated potential change in water
available for streamflow
Qi = simulated potential water available for
streamflow under baseline or un-
disturbed conditions (cm/week)
CD = the reduction in leaf area index (in units
of LAI) from baseline
AS = dummy variable for aspect (—1 for north
slopes, +1 for south slopes, 0 for east or
west slopes)
RD = relative rooting depth
bj = least squares coefficient
The coefficients (tables III.3, HI.4, and HI.5) for
the regional least square models are as follow:
RELATIVE ROOTING DEPTH
Relative rooting depth (RD) for the region is sup-
plied. It is calculated as:
(m.8)
Table III.3.—Least square coefficients for equation III.9
for simulated potential change in water available for
streamflow for the Pacific Coast provinces
RD
Variable
Intercept
Qi
CD
AS
RD
Coefficient
bo
bi
bz
bs
b4
Estimated
coefficients
-0.05
-0.05
0.025
0.013
0.006
m.49
-------
Table 111.4.—Least square coefficients for equation 111.9
for simulated potential change in water available for
streamflow for the Appalachian Mountains and Highlands
Variable
Coefficient
Estimated
coefficients
Intercept
Qi
CD
AS
RD
bo
bi
b:
-0.03
-0.03
0.13
0.02
0.03
Table III.5.—Least square coefficients for equation III.9 for
simulated potential change in water avilable for streamflow
for the Coastal Plain/Piedmont
Variable
Coefficient
Estimated
coefficients
Intercept
Qi
CD
AS
RD
bo
-.19
-.12
.20
.01
.02
Addition of the potential change for streamflow
for interval i (AQ;) to the existing streamflow for
interval i (Q;) will yield the post-treatment
potential streamflow for interval i ( Q; + AQ;).
The average 7-day potential flow for the existing
condition can be estimated from the flow duration
curve using the equation:
N-l
Qaverage = [^(Qx + QN) + 2 Q;l X -LQQ-
L i=2 J N-l
(111.10)
10
or for N = 11 points:
r A" -,
Average = -5(Ql + Qn) + 2 Q. X .
i=2 J
10
The same applies to the post-treatment condition
flows (Qi+AQj).
Examples of calculations have been worked out
and presented in worksheets HL3 and IE.4. The
output from the calculations is an estimate of water
available for streamflow distributed over time.
The least squares method is one of two methods
for estimating increase in streamflow due to
silvicultural activity. The other method involves
computing the difference in water available for
streamflow between existing and proposed condi-
tions using evapotranspiration calculations; i.e.,
subtraction of item (20), worksheet ELI from item
(20), worksheet m.2 will accomplish this.
An estimate of the change in flow using the least
squares method can be made as follows. The
average 7-day flow for either pre- or post-treatment
condition can be estimated from the respective flow
duration curves using equation IIL9 or ni.10. The
average 7-day flow, when multiplied by 52, yields
the average annual flow. The same applies to the
post-treatment condition flows ( Q;+ AQ; ). The
difference in the two is also an estimate of the ex-
pected change in flow resulting from the proposed
activity; it will compare with, but not be the same
as, the estimates using the evapotranspiration
calculations.
PROPOSED CONDITION 7-DAY
FLOW DURATION CURVE
The proposed condition 7-day flow duration
curve is a plot of each adjusted flow level (Q; +
AQ;) versus percent of time that flow (Q;+ AQj) is
equaled or exceeded.
The primary purpose of this methodology is to
provide 7-day flow duration curves for conditions
before and after a proposed silvicultural activity.
At this point, sufficient instruction has been given
to enable construction of existing and proposed
flow duration curves. The next step, after plotting
the flow duration curves, would be to proceed to the
subsequent procedural chapters. However, if
changes in streamflow for a specific date or for a
specific flow level are required, the descriptions
that follow outline the procedure for their estima-
tion.
If an evaluation of the effect of time of year on
changes in various flow levels is not needed, the
analysis is now complete. If estimates of time
dependent changes are necessary, the analysis con-
tinues.
It should be noted that the procedure distributes
the impact of average vegetal changes over the
average watershed flow duration curve. The ET es-
timations made previously were not lumped but
were actually calculated by treatment and
prescription; they were then area weighted to ob-
tain the net annual change. This is not true of the
flow distribution procedure because it tends to
lump the various treatments and prescriptions into
a single watershed average, as the methodology is
strongest when applied in this manner. However,
the method is flexible; if separate evaluations of
each treatment or prescription are desired, they
can be determined and the relative effect of each
component can be evaluated in the same manner.
HI.50
-------
This depends on the objectives defined and the
resolution desired.
LEAF AREA
INDEX REDUCTION
FLOW AND DATE OF INTEREST
An estimate of the reduction in leaf area index is
required as defined for equation HI.9.
If an annual hydrograph for the existing condi-
tion is available and/or if changes in flow for
specific flow levels as functions of date of occur-
rence are desired, time dependent adjustments can
be made to reflect the effect of silvicultural activity
using the following least squares model:
AQi=b0+b1Qi+b2CD
+ CD + b3AS +b4RD + b5 Sine Day (in.ll)
With the exception of sine day, all variables are as
defined in equation III.9.
SINE DAY
In addition to fitting equation III. 9 for use in ad-
justing the potential flow duration curve, an ad-
ditional parameter was fitted for adjusting the an-
nual hydrograph. Hewlett and others (1977),
Hewlett and Hibbert (1967) and others have found
that the sine of the day (sine of the numerical day
in the year starting with December 21 as day 1,
January 1 as day 11 and so on) is useful in express-
ing the annual cycle of hydrologic processes.
Sine Day = sin f 360 X Day # | + 2 (m.l2)
I 365 J
Values of sine day for selected days may be found
in table III.6.
ASPECT
An estimate of aspect is required as defined in
equation in.9.
RELATIVE ROOTING DEPTH
An estimate of relative rooting depth is required
as defined in equation m.9.
CHANGE IN
STREAMFLOW
Equation III.11 is used to estimate the change in
streamflow caused by silvicultural activity for
specific levels or dates.
The estimated coefficients for equation HI. 11 by
regions may be found in tables III.7, ffl.8, or in.9.
Addition of the change in streamflow for a
hydrograph flow or date i (AQ;) to the hydrograph
streamflow value for flow or date i (Qj) gives
hydrograph streamflow value (Q;+ AQ;) for the
proposed condition at flow or date i.
Table 111.6.—Sine of day value (S) for use with flow prediction equation
111.11. Where S = sin (360 x day #/365) + 2
Day
1
7
14
21
28
Dec
1.66
1.76
1.88
2.00
2.12
Jan
2.17
2.27
2.39
2.49
2.59
Feb
2.65
2.72
2.80
2.87
2.92
Mar
2.94
2.98
2.99
3.00
2.99
Apr
2.99
2.97
2.93
2.88
2.82
May
2.77
2.70
2.61
2.52
2.41
Jun
2.36
2.26
2.15
2.03
1.90
Jul
1.84
1.74
1.62
1.51
1.43
Aug
1.37
1.29
1.21
1.14
1.09
Sep
1.06
1.03
1.01
1.00
1.01
Oct
1.01
1.04
1.08
1.13
1.20
Nov
1.23
1.30
1.39
1.49
1.60
m.5i
-------
Table III.?.—Least square coefficients for equation 111.11
for the Pacific Coast provinces-low elevation
Parameter
Intercept
QI
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
b>
bs
b«
b>
Estimated coefficient
value
0.21
-0.16
0.02
0.001
0.05
0.91
Table III.8.—Least square coefficients for equation 111.11
for the Appalachian Mountains and Highlands
Parameter
Intercept
Qi
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
bt
bi
b4
b.
Estimated coefficient
value
-0.08
0.01
0.13
0.04
0.02
1.17
Table III.9.—Least square coefficients for equation 111.11 for the
Coastal Plain/Piedmont
Parameter
Intercept
Qi
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
b2
bs
b4
be
Estimated coefficient
value
-0.19
0.13
0.20
0.01
0.02
-0.18
The equation (HI.11) allows the adjustment of
specific flow levels (Q;) as a function of the time of
occurrence. For example, the effect of treatment on
a 2 cm flow level in March would not necessarily be
the same as the effect of treatment on the same
flow level if it were to occur in August.
Examples: Determining Potential Changes In
Streamflow
An illustration of the calculations has been
worked out and is presented in worksheets III.3 and
III.4. The example uses the regional potential flow
duration curve and adjusts it for annual streamflow
estimated in the evapotranspiration calculation for
Needle Branch watershed previously presented (fig
m.22a).
Output from the calculations (wkshts. HI.3 and
ni.4) is an estimate of water available for annual
streamflow distributed over time. Both existing
and proposed condition levels are expressed as 7-
day average flow in cubic feet per second. These
values are then entered on the worksheets for sedi-
ment analysis presented in chapter VI.
Similar examples have been completed on
worksheets in.3 and III.4 for Coweeta (plotted on
fig. ni.22b) representing the Appalachian Moun-
tains and Highlands and for Grant Memorial
Forest (fig. in.22c) representing the Coastal Plain/
Piedmont.
The following summary compares the evapo-
transpiration method and the least squares method
to observed values for the three watersheds used in
the evapotranspiration estimation procedure.
Table 111.10.—A comparison (cm) of the evapotranspiration method and the least
squares method to measured values for the three watershed examples
Watershed
ET method
Streamflow increases-
Least squares method
Observed
Needle Branch
Coweeta
Grant WS#1
58.0
15.9
52.6
41.5
15.0
54.5
50.3'
15.82
28.03
'Harr, D., personal communication.
'Hewlett and Douglass (1968).
'Hewlett, J., University of Georgia, personal communication.
m.52
-------
WORKSHEET I I I .3
Flow duration curve for existing condition
rain dominated regions
(1) Watershed name
fJeeqle
(2) Hydrologic region
(3) Water available for annual streamflow existing condition (cm)
(4) Annual flow from duration curve for hydrologic region (cm) I3?.4>
(5) Adjustment ratio (3)/(4)
Point
number
i
(6)
/
z
3
4
5-
k>
7
t
9
10
//
Percent of
t i me f 1 ow
is equaled
or exceeded
(7)
0
10
ao
30
W
s-o
&o
10
80
JO
|00
Regional
flow
(cm/7 days)
(8)
is-.r
10
SO
4.0
/.3
/./s-
•75-
.50
.as-
.IS"
o
Existing
potential
flow Q;
(cm/7 days)
(9)
/4.?
7-7
V.8
/.?
/.3
/./
7
.5"
.a,
.1
0
Existing
potential
flow QJ
(cfs)
(10)
8.3
^
3.7
/./
.7
.&
.1
.3
.1
.06
0
Col. No. Notes
(1) Identification of watershed or watershed subunit.
(2) Descriptions of hydrologic regions and provinces are given in text.
(3) Item (20) of worksheet I I 1.1.
(4) From figure I I I.22.
(5) Item (3) T item (4).
(6) Number of each point taken from figure 111.22; or user supplied.
(7) X-axis of figure I I 1.22.
(8) From figure 111.22; or user supplied (unnecessary if col. (9) is user
supplied).
(9) Column (8) x item (5); or user supplied.
(10) Column (9) x area (acres) x 0.002363.
III. 53
-------
WORKSHEET II I.4
Flow duration curve for proposed condition
rain dominated regions—annual hydrograph unavailable
(1) Watershed name
(2) Hydrologic region
(4) Existing condition LAI
(5) Proposed condition LAI .
(7) Rooting depth modifier coefficient (RD) j (8) bp ".OS" (9)
(3) Watershed aspect code (AS)
(6) Change in LAI (CD) 3?
1
-.OS (10) b2 -035" (ID b3 -Ql3 (12) b4 .OO&>
Point
number
i
(13)
/
a.
3
4
s
(a
7
&
f
10
II
Percent of
time flow is
equaled or
exceeded
(14)
0
10
AC
30
to
So
60
70
So
10
JOO
Exi sti ng
potential
flow QJ
(15)
N.7
7.7
4.8
/.?
/.3
/.I
.7
.r
-i
.1
0
bQ
(16)
-.OS
-.of
-.OS"
-.oS"
-.OS"
-.OS"
-.OS"
-.oS"
-.OS"
-.05-
-.off
blOj
(17)
-.75-
-.3?
-.a«/
-.10
-.07
-.ot
-.o«*
-.03
-.01
-.01
o
b2CD
(18)
• ?7S-
.?7S"
.175"
MS"
975"
.975-
.975"
.975"
.975-
.9?r
.975-
b3AS
(19)
-.013
-.013
-.013
-.013
-.0)3
-.013
-.0)3
-.013
-.OI3
- OI3
-.O»3
b4RD
(20)
.006,
.004
.006
.006
.004,
.6
.004
.006
.006
006
.OO (a
Of
(cm)
(21)
.18
.54
.fc?
.83
.*(,
.«7
.Ł9
.90
.92.
.91
.93
Oi +AQj
(cm)
(22)
IS.)
S.I,
SS"
a.7
ia
a.o
,fc
/.
-------
WORKSHEET I I I .3
Flow duration curve for existing condition
rain dominated regions
(1) Watershed name
(2) Hydro logic region
(3) Water available for annual streamflow existing condition (cm)
(4) Annual flow from duration curve for hydrologic region (cm)
(5) Adjustment ratio (3)/(4) |.^S7
/QV.9
73.0
Point
number
i
(6)
/
I
3
4
s
1e
1
8
?
10
II
Percent of
time flow
is equaled
or exceeded
(7)
0
10
30
30
40
so
60
70
SO
70
|00
Regional
flow
(cm/7 days)
(8)
?.0
a.7
/.?
14
l^
.7
.r
-V
.3
.a,
o
Existing
potent! al
flow QJ
(cm/7 days)
(9)
13 J
3.?
*.*
1.0
/.*
/.o
•7
,6
.V
.3
O
Existing
potential
flow QJ
(cfs)
(10)
11.0
3.Z
M
/7
AS"
.?
.6,
.r
.3
.as^
o
Col. No. Notes
(1) Identification of watershed or watershed subunit.
(2) Descriptions of hydrologic regions and provinces are given in text.
(3) Item (20).of worksheet I I 1.1.
(4) From figure 11 1.22.
(5) Item (3) T item (4).
(6) Number of each point taken from figure 111.22; or user supplied.
(7) X-axis of figure I I 1.22.
(8) From figure 111.22; or user supplied (unnecessary if col. (9) is user
supplied).
(9) Column (8) x item (5); or user supplied.
(10) Column (9) x area (acres) x 0.002363.
m.55
-------
WORKSHEET I I I.4
! 1) Watershed name
Cotoceto.
Flow duration curve for proposed condition
rain dominated regions—annual hydrograph unavailable
(2) Hydrologic region
(5) Proposed condition LAI 3-
(3) Watershed aspect code (AS)_
(6) Change in LAI (CD) 3.8
0
(4) Existing condition LAI (p.Q _
(7) Rooting depth modifier coefficient (RD) J (8) bp '.03 (9) b i -.03 (10) b2 «J3 (11) 53
(12) b4
Point
number
i
(13)
/
JL
3
V
5
-------
WORKSHEET I I I .3
Flow duration curve for existing condition
rain dominated regions
(1) Watershed name
Grt
-------
WORKSHEET I I I .4
Flow duration curve for proposed condition
rain dominated regions—annual hydrograph unavailable
(1) Watershed name
(2) Hydrologic region
(3) Watershed aspect code (AS)_
(6) Change in LAI (CD) b.S"
(4) Existing condition LAI 7.O (5) Proposed condition LAI . "
(7) Rooting depth modifier coefficient (RD) / (8) bp -.1? (9) t>i -. |Cb (10) b2 .90 (11) 63 . 0 1 (12)
Point
number
i
(13)
1
X
3
V
Ł•
&
7
8
9
(0
II
Percent of
time flow is
equaled or
exceeded
(14)
0
10
ao
30
V°
so
t>0
70
KO
10
100
Existing
potential
flow Q-t
(15)
fc.7
J.O
.7
.6
.5"
.5"
.0
(16)
-.19
-.if
-.1?
-.19
-.19
-.19
-.19
-.19
-.19
-.19
-.1?
blQj
(17)
-.W
-.12.
-.0?
-.07
-.Ofe
-.0&
-.OS'
-.0
/.07
/.o?
AO*
/.09
l.ll
1.12.
1.13
9i + AQj
(cm)
(22)
7.0
40
/.*
1.7
l.t,
U
I.S
l.f
/.3
/.a.
/./
Ql + AQi
(cfs)
(23)
1.3
.V
• 3M
.31.
.30
.•So
.as
.a4>
.as-
.S3
.AI
ss
Item
Col.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)-
(12)
or
No. Notes
Identification of watershed or watershed subunit.
Descriptions of hydrologic regions and provinces gi
in the text.
Northern aspect = +1 , southern aspect = -1 , eastern
western aspect = 0.
Area weighted average for existing condition.
Area weighted average for proposed condition.
Item (4) - item (5).
Area weighted average.
From tables 1 1 1 .3 to 1 1 1 .5.
ven
or
Item or
Co I. No.
Notes
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
Column (6) of worksheet II
Column (7) of worksheet II
Column (9) of worksheet II
Item (8).
Item (9) x column (15) .
Item (10) x item (6).
Item (11 ) x item (3).
Item (12) x item (7).
Columns (16) + (17) + (18)
Column (15) + column (21 ).
Column (22) x area (ac) x
1 .3.
1.3.
1 .3.
+ (19) +
0.002363
(20),
for 7-day intervals.
-------
16-
14-
12-
i
•o
LL
UU
Ł 6-
r^ Post- treatment
^
20 40 60 80
PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
100
Figure lll.22a.—Pre- and post-silviculture! activity 7-day flow duration curve for Needle Branch.
m.59
-------
20 40 60 80
PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
100
Figure lll.22b.—Pro- and post-silvicuKural activity 7-day (low duration curve for Coweeta.
ni.eo
-------
0 20 40 60 80
PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
100
Figure lll.22c.—Pro- and post-sllviculUiral activity 7-day (low duration curve for Grant Memorial
Forest Watershed.
ni.ei
-------
PROCEDURAL DESCRIPTION: DETERMINING EVAPOTRANSPIRATION
AND WATER AVAILABLE FOR STREAMFLOW (ET ESTIMATION) (SNOW
DOMINATED REGIONS)
NEW ENGLAND/LAKE STATES (REGION 1)
ROCKY MOUNTAIN/INLAND INTERMOUNTAIN (REGION 4)
PACIFIC COAST REGION, HIGHER ELEVATION ZONES (PROVINCES 5, 6, 7)
The following methodology is presented as a
means of estimating evapotranspiration and poten-
tial streamflow for existing and proposed condi-
tions in snow dominated hydrologic regions.
In this handbook, the areas in which snow has a
significant hydrologic role are the New
England/Lake States hydrologic region (1), the
Rocky Mountain/Inland Intermountain hydrologic
region (4), and the higher elevation zones of the
Pacific Coast hydrologic provinces (5, 6, and 7).
These areas are shown in figure HI.9a. It is unfor-
tunate that for purposes of delineation the higher
and lower elevations of the Pacific Coast provinces
are separated, since hydrologically they are so
closely interlocked. In fact, the greatest area of
flood production in this province lies in the
elevational band where snowpacks can be melted
out by rainfall. Setting of the lower boundary of the
high elevation zone at 4,000 feet reduces this
problem somewhat.
Due to limited data from the snow dominated
regions and the necessity to conserve space, there
has been a great amount of "lumping" of regions
and regional response. However, differentiations
are made whenever possible.
REGIONAL DESCRIPTIONS
New England/Lake State Hydrologic Region (1)
This area actually comprises two separate
provinces: New England and Lake States. Wide
differences in wind and temperature subdivide the
region into two sections.
Snow in the northeastern section of the province
occurs in shallow packs, seldom over 3 feet in depth
on the level; it may reach much greater depths at
higher elevations. Subject to frequent incursions of
Arctic air from Canada and warm storms from the
Gulf Stream of the Atlantic Ocean, these snow-
packs frequently develop very heavy ice layers on
the surface. Spring rains on such packs yield a swift
return flow to streams, causing rapid rises in the
shallow rivers of the region. Continued rain melts
the relatively thin packs, adding to the flood. Ex-
tremely cold winters and cool summers limit tran-
spiration opportunities. Soils are frequently rocky
and water-holding capacities vary extensively. In
locations of glacial till where extensive ice cover
does not exist, the melting snows are absorbed into
the soil mantle.
In the Great Lakes portion of the region, ice
layering becomes less of a phenomenon, but early
spring melt and flooding become increasingly im-
portant. Snowpacks and snow become increasingly
wetter as one approaches the upper portion of the
Lower Peninsula and the Upper Peninsula of
Michigan. Snowfall and snowpacks are deeper and
drier than in much of New England. High water
absorptive capacity of the soils, lack of extensive
surface relief, and widespread bog (swamp)
development prevent extensive flood threats from
melting snow. High water tables generally provide
sufficient water to meet potential evapotranspira-
tion needs. While temperatures can become very
frigid from incursions of Arctic air, the lakes
provide an ameliorating influence.
Westward in Minnesota and Wisconsin, more
frigid temperatures are the rule. Snows frequently
are driven by high winds, and the dry snow is sub-
ject to much more redistribution than in other
areas. Snow distribution is of little importance in
the region except for this western edge.
Rocky Mountain/Inland Intermountain
Hydrologic Region (4)
This vast area covers parts or all of South
Dakota, Wyoming, Montana, Colorado, New Mex-
ico, Arizona, Utah, and Idaho. Most of the water
111.62
-------
for the region comes from snowpacks which ac-
cumulate in winter and melt in summer. In
general, winter temperatures are very cold, snows
are dry, and snowpacks have a thermal gradient.
That is, snow temperatures at the soil surface ap-
proach those of the soil itself (32°F or 0°C).
Temperatures from the soil to the snowpack sur-
face decrease, until at the air-snow interface they
reach air temperature, frequently —40°. However,
this region is far from homogenous and the climatic
differences affecting snowpack performance should
be recognized.
The entire region is subject to summer thunder-
storms which can cause disastrous flooding and as-
sist in recharging the soil water supply. The entire
area is usually subject to snow deposition as a
result of high winds and dry snow, except for two
major transition zones — (1) northern New Mexico,
southwestern Colorado, northern Arizona, and (2)
northern Idaho. These are transition zones between
the dry, low temperature snowpacks and continen-
tal frigid winter climate of the true Rocky Moun-
tain chain, and the warm climate, wet snowpacks
of the Pacific Coast. Dependent upon the direction
from which the storms and air masses come, the
snowpacks in these transition areas will be
representative of one of the other major provinces
all year; or they may resemble one province during
part of the year and resemble the other during
another part of the year.
In western Montana and in Wyoming plains and
rolling hills, there is enormous displacement and
redeposition of snow. This affects evapotranspira-
tion and tree growth since it removes the scanty
snow cover from vast areas and concentrates it in a
few locations. Obviously, this favors increased
plant growth and water use in these sites. Evapora-
tion (sublimation) loss from blowing snow is exten-
sive.
Snows in the Rocky Mountains of Wyoming and
Colorado and in the Wasatch Mountains are dry
and cold (the skiers' famed "powder snow"). Wind
redeposition is extensive in large, open areas. Par-
ticularly in Colorado, much of the mountain chain
lies in the Alpine Zone. Snowpacks mature and
melt in response to "ground heat" from below and
to warm air temperatures and increased solar
radiation in the spring. The thermal gradient in
such packs creates unstable snow layers; frequent
avalanching occurs from this cause and from
melting snow sliding over wind slab formations.
Since most melt occurs from the surface of the pack
downward, the pack largely wets up from the sur-
face. Most melt water goes directly into the soil.
Since the packs are "cold," first melt goes to
satisfying the thermal demand needed to bring the
snowpack to a thermal equilibrium (32°F or 0°C)
throughout the pack.
The shallow snows in northern Arizona fre-
quently are redeposited by wind. Because of the
lower latitude and higher insolation in winter,
however, midwinter melt is often sufficient to wet
the surface and prevent further movement.
Southwestern Colorado, northern Idaho, and the
Rocky Mountains of western Montana receive wet-
ter snows and even occasional rain. These cause
some limited ice layering in the snow in
southwestern Colorado.
Pacific Coast Hydrologic Provinces (5, 6, and 7)
This region begins in the San Bernardino Moun-
tains of southern California, continues northward
through the Sierra Nevada of California, the
Cascades of Washington and Oregon, and includes
the mountain ridges and peaks of western and
central Nevada. The same type of snowpacks occur
northward through British Columbia and into
southeastern Alaska, at least to Anchorage.
The maritime climate in the winter is warm and
wet. Summers vary depending upon the particular
portion of the province, but generally they are dry
with little or no summer precipitation. Summer
thunderstorm activity is extensive over the
southern Sierra Nevada, adding some water to that
area, largely in the relatively treeless alpine area.
The remainder of the Pacific Coast province, with
the exception of parts of Washington, receives little
summer precipitation.
Fall and winter precipitation is normally snow,
but extensive rainstorms sometimes occur up to
8,000 feet elevation in the Central Sierra (7).
Significant snow falls at elevations down to 4,000
feet, and, on rare occasions, significant amounts
fall to 2,000 feet. Rains remove snowpacks up to
6,000 feet elevation and infrequently remove
significant parts of the packs to over 7,000 feet.
Snowpack depth is extremely variable and has
been measured at maximum pack from 36 inches to
over 275 inches.
Snow redistribution normally does not occur due
to the wetness of the snow.
Snow metamorphism continues all winter as a
m.63
-------
result of the warm climate, and frequent ice lenses
occur throughout the packs, particularly on south,
open slopes. Temperatures normally remain at
32° F throughout the packs. When rain falls on
packs significantly lower than 32°F, serious
flooding can occur from rain and melt water flow-
ing over the frozen layer (Smith 1974).
Snowpack configuration of these warm, wet
snows typically consists of a mixture of heavy and
light density layers having different maturation
schedules and water-holding capacities. The con-
figurations vary dramatically by aspect and by
forest cover (Smith 1974, 1975).
Because of warm climate, frequent rains, and
melting snow, snowpacks in the subalpine are
usually wet and remain at thermal equilibrium
throughout the snow season. Frequent snowfalls
keep the albedo high (80-90) until spring melt out
is well under way, at which time albedo drops to
about 45 percent. Major winter melt is caused more
from absorption of solar radiation by the rocks,
trees and shrubs standing above the snow than
from direct solar radiation to the pack. These, in
turn, heat up and radiate sensible heat to the pack.
This creates the major melt until late season low
albedos of the snow increase radiation absorption
by the pack.
Because of the isothermal, wet condition of the
snow, forest cover change can be used to direct heat
into or away from the snow. Melt out date can be
moved forward or backward 2 weeks to 1 month by
increase or decrease of forest cover (Smith 1974,
1975).
While wind distribution plays little role in this
province, differential melt is substantial. The
greater amount of snow in forest openings on the
west-south walls were once thought to be the result
of distribution; it has since been found to be the
result of greater melt on the north and east side of
the opening (Smith 1974).
Forest interception has been found to have little
influence on snow placement under lodgepole; but
under red fir and other conical-shaped crowns, the
snow caught while the branches were extended
depresses the crowns, and snow is deposited near
the tree stem where it may differentially melt
(Smith 1974). This accounts for the previous
findings that only 65 percent of snow which fell in
the open was found in the forest. At one time it was
believed that much of this was lost to evaporation.
It has since been found that evaporation accounts
for less than 2 area-inches over such areas that
have half their area in forest and half in open.
LIMITATIONS AND PRECAUTIONS:
PROBLEMS ASSOCIATED
WITH HYDROLOGIC MODELING FOR
SNOW REGIONS
There are more problems associated with model-
ing the hydrologic responses of snow covered basins
than with modeling those subject to rainfall.
Snowfall redistributes the precipitation in time
and occasionally in space. Snow falling in the
Rocky Mountains is not reflected in the soil
moisture or streamflow until spring melt. In the
Pacific Coast province it may appear as soil
moisture or streamflow within a few days, or it may
not appear until spring. Due to lack of ice lenses,
melt or rain falling on snow in this region may enter
the soil under a forest growing on a south slope.
Removal of the forest may result in ice lens forma-
tion in the pack, and rain or melt may flow through
the snow to the stream and never reach the soil to
provide water for satisfaction of soil water deficit.
Soils are youthful and very porous, thus resulting
in rapid drainage of surplus water following
snowmelt. Since summers are usually long and
without precipitation, early snowmelt results in a
lengthening of the drought season.
PROCEDURAL FLOW CHART
Evapotranspiration for snow dominated regions
is estimated using precipitation and energy
relationships with subsequent adjustments made
for snow redistribution and vegetation cover den-
sity. The difference between precipitation and
evapotranspiration becomes water available for
streamflow if changes in soil moisture storage are
negligible.
The flow chart in figure III.23 outlines the
methodology procedure for estimation of potential
streamflow. Worksheets III.5 and in.6 have been
constructed to facilitate calculations.
Explanation of the flow chart follows.
HYDROLOGIC REGION OR PROVINCE
Based on the preceding discussion, select the
region which most closely characterizes the site.
HI.64
-------
CONDITION
The condition or point in time for which each
analysis is to be made must be specified. Condition
can represent baseline, existing (if different from
baseline) or proposed. The following discussion
centers on two conditions—existing and
proposed—primarily to evaluate impact of planned
activities; but the methodology is flexible and a
variety of conditions could be considered. The
methodology is looped so that procedural steps
return to this point after both evapotranspiration
and water available for streamflow have been
calculated for each condition.
ENERGY ASPECT
One of the first criteria for subdividing the
watershed or management unit is aspect. Energy so
strongly controls snow processes that the major
criterion for subdivision is the energy class for dif-
fering aspects.
Several aspect and elevation zones were com-
bined into three basic energy levels. The energy
aspects were defined as:
1. High energy-low elevation aspects (low, south
aspects)
2. Intermediate energy aspects
a. Low to mid-elevation north, east, and west
aspects
b. High elevation south aspects
3. Low energy-high elevation aspects (high
elevation north, east, and west aspects)
The significance of classifying by aspect is, of
course, in terms of energy available to melt snow
and to evapotranspire water. The elevation and
aspect of a site must be determined and placed in
one of the three energy aspects for use in further
analysis (item 4).
SILVICULTURAL PRESCRIPTION
For each condition, divide the energy aspect or
management unit into subunits based on
silvicultural prescription. The prescription should
be uniform for each subunit and may be uniform
for the entire energy aspect. By the same token, the
silvicultural prescription can be uniform (forested)
for one condition (existing) and varied (clearcut,
thinned) for another. Silvicultural prescription
designations allow flexibility to subdivide the
energy aspect into subunits based on significant
silvicultural or hydrological characteristics of
either the site or the prescriptions. This implies
subdivision based not only on silvicultural prac-
tice, but also on uniform soil depth and aspect.
SEASON
Evapotranspiration is calculated by season, and
seasonal dates can vary by region. In the modeling
effort, selection of seasonal dates for each region
and province was based on simulated
precipitation/streamflow relations. Basically, the
intent was to isolate the fall, the winter (period of
snowpack development and melt), and the growing
season. The season is entered in item (9).
In the Rocky Mountain/Inland Intermountain
region (4) and in the Continental/Maritime
province (6), seasonal evapotranspiration is
presented for three increments of time as follows:
Winter: Oct. 1—Feb. 28
Spring: March 1—June 30
Summer and fall: July 1—Sept. 30
In the Pacific Coast/Central Sierra province (7)
and in the Pacific Coast/Northwest province (5),
seasonal evapotranspiration is presented for four
increments of time:
Early winter: Oct. 1—Dec. 29
Late winter: Dec. 30—Mar. 28
Spring: Mar. 29—June 26
Summer and fall: June 27—Sept. 30
The New England/Lake States region (1) has
three seasons, varying slightly from the others:
Fall, early winter: Oct. 1—Jan. 31
Late winter, early spring: Feb. 1—Apr. 30
Growing season: May 1—Sept. 30
The procedure is looped so that evapotranspira-
tion and water available for streamflow are es-
timated by season within a silvicultural prescrip-
tion before the next prescription is considered.
m.65
-------
f Hydrologic Region or Province )
No
Condition
Energy Aspect
Season
Silvicultural State
Precipitation
J
Silvicultural Prescription }
Yes
No
Snow Retention Coefficient
from Figure 111.6
Yes
Snow
Redistri-
bution Likely?
Yes
No
Snow Retention Coefficient
from Appendix A
Adjusted
Precipitation
Evapotranspiration
m.66
-------
Cover Density
Evapotranspiration
Modifier Coefficient
Adjusted
Evapotranspiration
Water Available
for Annual Streamflow
All
Silvi-
cultural
States Considered?
All
Seasons
Considered?
Water Available for
Annual Streamflow
All
Silvi-
cultural
Prescriptions
Considered?
All
Energy
Aspects
Considered?
All
Conditions
Considered?
Figure 111.23.—Flow chart of methodology for determining water available for annual •treamflow, snow
dominated reglone.
m.67
-------
(1) Watershed name
(5) Vegetation type_
WORKSHEET
Water available for streamflow for the
(2) Hydrologic region
(6) Annual precipitation
Season
name/dates
(9)
Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
SI Ivicultural
state
(11)
Total for season
Area
Acres
(12)
%
(13)
Precipi-
tat I on
(in)
(14)
Snow
retention
coef .
(15)
Adjusted
snow
retention
coef.
(16)
Adjusted
precipi-
tation
(in)
(17)
Un impacted
Impacted
Total for season
Un impacted
Impacted
Tota 1 for season
Un impacted
Impacted
Total for season
Water
aval lable
for annual
streamflow
(In)
Un Impacted
Impacted
(30)
(31)
(32)
(33)
(34)
(35)
111.68
-------
Ill .5
existing condition in snow dominated regions
(3) Total watershed area (acres)
(7) Windward length of open area (tree heights)
(4) Dominant energy-aspect
(8) Tree height (feet)
ET
(In)
(16)
Basal
area
(ft2/ac)
(19)
Cover
density
%
(20)
1Cm
ET
mod I f I er
coef .
(22)
Adjusted
ET
(in)
(23)
Water available for streamflow (In)
(24)
(25)
(26)
(27)
(28)
(29)
m.69
-------
Notes for Worksheet I I 1.5
Item or
Co I. No. Notes
(1) Identification of watershed or watershed subunlt.
(2) Descriptions of hydrologic regions and provinces are given in
the text.
(3)-(8) User supplied.
(9) Seasons for each hydrologic region are described in the text.
(10) The unimpacted compartment includes areas not affected by
siIvicultural activity. The impacted compartment Includes areas
affected by siIvicultural activity. Impacted areas do not have
to be physically disturbed by the si IvicuItural activity. For
example, if an area is subject to snow redistribution due to a
si IvicuItural activity, it is an impacted area.
(11) Areas of similar hydrologic response as identified and
delineated by vegetation or si IvicuItural activity.
(12) User supplied.
(13) Column (12) T item (3).
(14) User suppIied.
(15) From figure I I I.6 or appendix A or user supplied.
(16) Snow retention coefficient adjustment for open areas:
.50
Poadj = 1 + ( Po~1)(~x~)
where:
Poadj = adjusted snow retention coefficient for open areas
(receiving areas)
P0 = snow retention coefficient for open areas
open area (in acres)
impacted area (in acres)
m.70
-------
Snow retention coefficient adjustment for forested source
areas (impacted forest areas):
, 1 - PoadJ X
r 1-X
where:
Pf = adjusted snow retention coefficient for areas affected by
snow redistribution (source areas)
open area (in acres)
A =
impacted area (in acres)
(17) Column (14) x column (16)
(18) From figures 111.24 to 111.40 or user supplied.
(19) User supplied (not required if % cover density is user
supplied)-
(20) From figures 111.41 to 11 I.45 or user supplied.
(21) (Column (20) -f Cdmax) x 100 where Cdmax is tne I cover density
required for complete hydro logic utilization. C^max is
determined by professional judgment at the site.
(22) From figures I I I.46 to I I 1.56.
(23) Column (18) x column (22).
(24)-(29) The quanitity [column (17)-column (23)] x column (13).
(30) Sum of column (24).
(31) Sum of column (25).
(32) Sum of column (26).
(33) Sum of column (27).
(34) Sum of column (28).
(35) Sum of column (29).
HI.71
-------
(1) Watershed name
(5) Vegetation type_
WORKSHEET
Water available for streamflow for the
(2) Hydro I ogle region
(6) Annual precipitation
Season
name/dates
(9)
Si Ivicultural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11)
Total for season
Area
Acres
(12)
*
(13)
Precipi-
tat I on
(In)
(14)
Snow
retention
coef .
(15)
Adjusted
snow
retention
coef.
(16)
Adjusted
precipi-
tation
(In)
(17)
Un impacted
Impacted
Tota 1 for season
Un Impacted
Impacted
Tota 1 for season
Un impacted
Impacted
Tota 1 for season
Water
aval I able
for annual
streamflow
(In)
Un Impacted
Impacted
(30)
(31 )
(32)
(33)
(34)
(55)
m.72
-------
I I 1.6
proposed condition in snow dominated regions
(3) Total watershed area (acres)
(7) Windward length of open area (tree heights)
(4) Dominant energy-aspect
(8) Tree height (feet)
ET
(in)
(18)
Basal
area
(ft2/ac)
(19)
Cover
density
%
(20)
*°?3W
ET
mod i f i er
coef .
(22)
Adjusted
ET
(In)
(23)
Water available for streamflow (in)
(24)
(25)
(26)
(27)
(28)
(29)
m.73
-------
Notes for Worksheet I I 1.6
Item or
Col. No. Notes
(1) Identification of watershed or watershed subunlt.
(2) Descriptions of hydrologic regions and provinces are given in
the text.
(3)-(8) User supplied.
(9) Seasons for each hydrologlc region are described In the text.
(10) The unImpacted compartment includes areas not affected by
si Ivicultural activity. The Impacted compartment Includes areas
affected by siIvlcultural activity. Impacted areas do not have
to be physically disturbed by the siIvlcultural activity. For
example, If an area Is subject to snow redistribution due to a
siIvlcultural activity, It Is an Impacted area.
(11) Areas of similar hydrologlc response as identified and
delineated by vegetation or siIvlcultural activity.
(12) User supplled.
(13) Column (12) T Item (3).
(14) User supplled.
(15) From figure I I I.6 or appendix A or user supplied.
(16) Snow retention coefficient adjustment for open areas:
.50
poadj = 1 + ( PO-IH—)
where:
poadj = adjusted snow retention coefficient for open areas
(receiving areas)
Po = snow retention coefficient for open areas
open area (in acres)
impacted area (in acres)
HI.74
-------
Snow retention coefficient adjustment for forested source
areas (impacted forest areas):
, 1- PpadJ X
T 1-X
where:
Pf = adjusted snow retention coefficient for areas affected by
snow redistribution (source areas)
open area (In acres)
impacted area (in acres)
(17) Column (14) x column (16)
(18) From figures I I 1.24 to 11 1.40 or user supplied.
(19) User supplied (not required if % cover density is user
supplied).
(20) From figures 111.41 to 11 1.45 or user supplied.
(21) (Column (20) 4 Cdmax) x 100 where Cdmax is the % cover density
required for complete hydro logic utilization. C(jmax is
determined by professional judgment at the site.
(22) From figures I I I.46 to 111.56.
(23) Column (18) x column (22).
(24)-(29) The quanitity [column (17)-column (23)] x column (13).
(30) Sum of column (24).
(31) Sum of column (25).
(32) Sum of column (26).
(33) Sum of column (27).
(34) Sum of column (28).
(35) Sum of column (29).
IE.75
-------
SILVICULTURAL
STATE
In order to assess the overall hydrologic effect of
silvicultural prescriptions on streamflow, each area
receiving different treatments is considered in-
dividually (items 10 and 11). The summation of
hydrologic effects in each treatment area yields an
overall effect for the prescription. Treatment areas
are delineated and grouped to reflect similar
hydrologic response. For example, large open areas
may be grouped, small open areas may be grouped,
forested areas may be grouped. Hydrologic
response is related to the type and quantity of
vegetation at a site as well as to physical factors
such as slope, soil texture, solar radiation, and
precipitation regime. In snow dominated regions,
cover density (Cd) and snow redistribution are
major criteria used for identification and delinea-
tion of silvicultural activity areas. Cover density
and snow redistribution are discussed later in this
section.
changed. If snow redistribution is not a factor, or if
openings are not present, precipitation need not be
adjusted and gross precipitation should be con-
sidered synonomous with "adjusted precipitation."
If openings are present, it must be considered if
snow redistribution is likely.
SNOW
REDISTRIBUTION
LIKELY?
As noted, precipitation characteristics in some
regions are such that the creation of openings can
significantly alter snow distribution, while in other
regions this is not the case. If openings are con-
sidered not to affect snow distribution (answer =
no) the precipitation estimate made above is con-
sidered to be the adjusted precipitation. If openings
can affect distribution then sizes must be
evaluated since this influences redistribution
characteristics.
PRECIPITATION
OPENING
>15H?
An estimate of precipitation by season (item 14)
must be supplied. It may vary by energy aspect.
Based on site measurements or extrapolation from
other data, the estimate may represent a long-term
mean or an extreme value, depending upon the ob-
jectives defined.
OPENINGS
PRESENT?
In some areas in which the major form of
precipitation is snowfall, the meteorological-
topographic relationship may not be significant,
but in other areas it is. In the Rocky Moun-
tain/Intermountain region, for example, snowfall is
the dominant form of precipitation and windblown
snow dominates the regime. In this area, when the
forest cover is removed through spatially dis-
tributed openings, snowfall distribution is
The aerodynamic change in roughness of the
vegetative surface modifies patterns of snow ac-
cumulation so that more snow may accumulate in
the cutover area and less in the uncut forest.
Objective methods for quantifying the univer-
sality of the effects of silvicultural activities on
snow redistribution through snowblowing are not
yet available; quantification of these effects must
be based on considerable judgment and experience
in a particular area.
Significant increases in snow accumulation near
the center of small forest openings—less than 15H
in diameter (H = height of surrounding trees) —
are substantially offset by decreases in snowpack
below the undisturbed forest so that total snow
storage on watersheds subjected cutting is not
changed. For openings less than 15H, determine
the redistribution coefficient directly from figure
in.6. When openings are large — greater than 15H
in diameter — however, total watershed snow
storage may be decreased through large sublima-
tion losses and transport of snow out of the basin
m.76
-------
(see fig. III.6 for approximate effect). Openings
greater than 15H in diameter or greater than 15H
in windward length produce a more complex snow
redistribution than smaller openings. A detailed
discussion of snow redistribution for openings
greater than 15H is presented in appendix in.A.
Depending upon the average size of the openings
in the silvicultural state, obtain a retention coef-
ficient from figure ffi.6, appendix in.A. or local
derivation, and proceed to determining the ad-
justed snow retention coefficient.
SNOW RETENTION COEFFICIENT
FROM FIGURE 111.6
For clearcuts less than 15H in diameter or in
windward length, the snow retention coefficient
(item 15) may be found on figure ELS. A represen-
tative average length or diameter can be applied to
a watershed with openings of varying diameters or
windward lengths. Alternately, if greater resolution
is required, the watershed can be subdivided so
that openings can be handled individually or in
groups.
Any large retention of snow as a result of forest
cutting can be an important factor in determining
the amount of runoff. For example, in the lodgepole
pine type in Colorado, this redistribution effect is
not greatly diminished 30 years after timber
harvest, in spite of regrowth of trees and associated
increase in forest cover density. It is thought that
changes in natural snow accumulation patterns
produced by timber harvest will persist until the
new crop of trees approaches the height of the
remaining undisturbed forest.
The significance of the snow retention coefficient
(p) lies in the opportunity that exists for both
decreasing the net water loss from the pack and for
altering the melt rate. As already noted, it can be
expected that the transpiration losses in the open-
ings will be decreased following cutting. By placing
a greater percentage of the total snowpack in these
openings and less in the residual forest, the ex-
posure of the net precipitation (in this case, snow)
to evapotranspirational processes can be reduced.
Because this snow is redistributed and because
cover conditions have been altered, a significantly
greater proportion of the pack is exposed to
sunlight, and differing melt rates can be expected.
In contrast, as the size of the opening increases
beyond 15H, the opportunity for increased ablation
losses and wind scour reduces the net precipitation
below pre-silvicultural activity levels. This effect is
significant since it represents a net loss in water in-
put to the system.
In old-growth subalpine forest, optimum
redistribution of snow occurs when the stand is (1)
harvested in small patches of less than 5H in
diameter; (2) the patch cuts are protected from
wind; and (3) the patches are interspersed at least 5
to 8H apart.
In regard to redistribution of a finite amount of
snow, in openings less than 15H there is a con-
tributing area for increases occurring in the open-
ings. The area of contribution is about equal to the
area of the opening; therefore, if the openings oc-
cupy more than 50 percent of the area, redistribu-
tion will be less efficient. In these situations P0,
would have to be adjusted to reflect the limiting
contributing area. If the area cut exceeds 50 per-
cent, the following adjustment in p0 can be used:
(IH.3)
X =
open area
total impacted area
It should be emphasized that the redistribution
theory does not require adjustment when timber is
harvested in small patches which occupy less than
50 percent of the watershed. In this case P0 = Poadj
since P0adj is used in the following equation. The
snow retention coefficient for the residual forest
stand (p f ) is calculated and weighted as follows:
= 1-PoadjX
(m
u
where:
pf = adjusted snow retention coefficient
for forested areas affected by snow
redistribution
poadj = adjusted snow retention coefficient
for open area (item 16)
The snow retention coefficient for the forested
impacted area is calculated under the assumption
that a silvicultural activity causes no net increase
or decrease of snow on the impacted area. Total im-
pacted area in snow dominated regions includes
areas affected by a silvicultural activity either
directly or indirectly. These effects may involve
snow redistribution and evapotranspiration.
SNOW RETENTION COEFFICIENT
FROM APPENDIX A
The procedure for calculation of snow retention
coefficients for openings larger than 15H in
diameter or windward length is found in appendix
III.A.
HI.77
-------
ADJUSTED PRECIPITATION
Adjusted seasonal precipitation (item 17) for a
silvicultural state is obtained by multiplying
seasonal precipitation (supplied by the user) by the
adjusted snow retention coefficient for that area. If
snow distribution is not significant for an activity
area, the snow retention coefficient is 1.0. The es-
timates of precipiation, corrected for treatment are
now used to estimate site specific evapotranspira-
tion.
EVAPOTRANSPIRATION
Analysis of several hundred station years of
records simulated by the Subalpine Water Balance
Model (Leaf and Brink 1973) has shown that
seasonal evapotranspiration (item 18) can be ex-
pressed as a function of seasonal precipitation. In
some areas the data base did not encompass
precipitation levels which would result in limiting
the evapotranspiration level, and for these regions
the potential effect has been estimated. Since
much of the area affected by snowpack develop-
ment is close to being arid, the baseline level of
evapotranspiration can be limited by insufficient
precipitation.
The evapotranspiration/precipitation relation-
ships developed for the Rocky Mountain/Inland
Intermountain hydrologic region (4) are plotted on
figures ffl.24 to HI.26. Unlike the presentation for
rain dominated regimes, the relationships are
presented as functions of seasonal precipitation by
energy aspect zones.
Similar relationships for the other hydrologic
regions follow:
Pacific Coast — Northwest (5) on figures m.27 to
HI.30
Continental/Maritime (6) provinces on figures
HI.31 to m.33
Central Sierra (7) on figures IH.34 to 111.37
New England/Lake States (1) on figures in.38 to
m.40.
It can be noted that simulated evapotranspira-
tion is strongly precipitation dependent at low
precipitation levels.
Consulting these figures (HI.24 to 111.40), it is
possible to estimate baseline evapotranspiration
for a given precipitation regime. The curves repre-
sent normalized averages based on simulations. If
more accurate baseline estimates of actual or
potential evapotranspiration can be supplied, these
may be more representative of a specific site. The
input required is an estimate of seasonal precipita-
tion from which evapotranspiration can be es-
timated.
One apparent discrepancy can be noted. A close
inspection of the curves reveals that, for those
seasons in which evapotranspiration is precipita-
tion dependent, the change in ET per unit change
in precipitation may be greater than 1. The curve
represents an integrated response and should not
be used to evaluate a change in seasonal precipita-
tion alone, as the curves represent dependence not
only on seasonal precipitation but on antecedent
precipitation as well.
In the Rocky Mountain/Inland Intermountain
hydrologic region, the October 1 through February
28 interval (figs. III.24 to III.26) is not precipitation
dependent since losses are essentially from in-
terception and evaporation from the snow surface.
These losses are aspect dependent, as shown in
figures in.24 to III.26. Evapotranspiration losses
during the March 1-June 30 interval vary with
precipitation below about 12 inches and also de-
pend on aspect. No aspect dependence was found
for evapotranspiration losses during the July 1-
September 30 interval, as shown in figure 111.26.
In the Continental/Maritime province (6), the
winter interval was found not to be precipitation
dependent, since losses are essentially from in-
terception and snow evaporation. These losses are
aspect dependent (figs. EI.31 to 111.33). Evapotran-
spiration losses during the March 1-June 30 inter-
val vary with precipitation below about 15 inches,
and also depend on aspect. No aspect dependence
was found for evapotranspiration losses during the
July 1-September 30 interval (fig. HI.33).
In the Central Sierra province (7), both the early
and late winter intervals were found not to be
precipitation dependent, since losses are essen-
tially from interception and evaporation from
snow. These losses are aspect dependent as in-
dicated by figures ni.34 to ni.37. Evapotranspira-
tion losses during the March 29-June 26 interval
(fig. ni.36) vary with precipitation below about 12
inches, and also depend on aspect. No aspect
dependence was found for evapotranspiration
m.78
-------
CO
CD
o
z" -
O _
h-
< -
Ł 5-
0.
CO .
Z 4-
<
rr
H 3-
0
Q.
< „
> 2-
UJ
1
__l
.<
I1-2-
^f
I
I
I
I
I
South
Aspect
East & West Aspects
North Aspect
I
I
I
CO
6 8 10 12
SEASONAL PRECIPITATION, inches
14
16
Figure 111.24.—Precipitation-evapotranspiration relationships for Rocky Mountain/Inland Inter-
moun»_
-------
CO
Q)
.C
o
z" ~
g ~
i—
DC _
— ^ —
Q. °
CO
Z 4 —
oc
HO ^H
O ^^
O
o_
> o —
LU
Z
co
'
/
/
'
^
\
**
X
/
f
1
ft 0 ' 2 ' 4
^,—
|
I
^^•^-^-^^-^^
1
All Aspects
1
6 ' 8 10 12 14 1(
w SEASONAL PRECIPITATION, inches
Figure 111.26.—Precipitation-evapotranspiration relationships (or Rocky Mountain/Inland Inter-
mountain hydrologic region (4), summer and fall season, by energy aspect.
CO
CD
ANSPIRATION, inc
o ^ cn c
1 1 1 1 1 1 1
5ONAL EVAPOTF
— N) C
1 1
55 c
CO
1
} 1
I
0 2
OC A
1
0 3
South
' 'f;>
East & Wes
North
1
0 4
Aspect
5t Aspects
Aspect
1
0 5
1
0 6C
SEASONAL PRECIPITATION, inches
Figure 111.27.—Precipitatlon-evapotranspiratlon relationships for the Northwest hydrologic
province (5), early winter season, by energy aspect.
m.so
-------
z" ~
o —
i 5:
to 4 —
Ł 3-
3ONAL EVAPOl
-A ro
1
< 1
1
1
1
South Aspect
East & We
North
1
st Aspects
Aspect
1
1
10
20 30 40
SEASONAL PRECIPITATION, inches
50
60
Figure 111.28.—Precipitation-evapotranapiration relationships for the Northwest hydrologic
province (5), late winter season, by energy aspect.
in
-------
0 20-
o
c
z"
0 10-
DC _
CL
CO —
1 5~
0
°- 3 —
>
HI
< 2~
Z
O
CO
L1J 1
.Ł'
/
I
,
X'' ^,'
/ ^ ^
/.r^r ^^
f^^^
I
^~ •" "
•
I
North Aspect
East & West Aspects
South
I
Aspect
I
I
468
SEASONAL PRECIPITATION, inches
10
12
Figure 111.30.—Precipitation-evapotranspiration relationships for the Northwest hydrologic
province (5), summer and fall season, by energy aspect.
CO IU —
03 _
O _
C
1 5-
|—
DC
CL 4-
CO ^
Z
0
CL
SEASONAL EV/
-» ro
1 1
(
J I
5 1
0 ' 1
Sout
East
Nort
5 ' 2
h Aspect
& West Aspec
n Aspect
0 2
ts
5 3C
SEASONAL PRECIPITATION, inches
Figure 111.31.—Precipitation-evapotranspiration relationships for the Continental/Maritime
hydrologic province (6), winter season, by energy aspect.
111.82
-------
0
o
c
Z
O
a. 4 —
co ~
<
O
Q.
UJ
Z
o
co
UJ
CO
2 —
—
—
—
—
/x
///"'
//
!/
1
^ -
X"
f
s*
X
<••
- ' —
,*••»
^
All So
Mid &
Highfs
^- •
nth & All Low
Elevations
High East, West Aspects
orth
10 15 20
SEASONAL PRECIPITATION, inches
25
30
Figure III.32.—Precipitalion-evapotranaplratlon relationships for the Continental/Maritime
hydrologic province (6), spring season, by energy aspect.
1 -
0 _
z" ~
O
i 5-
W 4 —
E 3-
O
Q.
ol 2-
_J
0
UJ
CO 1
C
x
/X
/
1
) 2
1
) ^
^ ^^"
1
i e
Ally
_^- —
^-^
1
f
\spects — All
•
1
J 1
Elevations
^— ^-^— ^— ^^— ^^
1
0 1
SEASONAL PRECIPITATION, inches
Figure 111.33.—Precipitatlon-evapotrarapiratlon relationships for the Continental/Maritime
hydrologic province (6), summer and fall seasons, by energy aspect.
EI.83
-------
CO
CD
.c
o
c
Z
g
<
tr
Q.
CO
<
cr
O
QL
<
LU
_l
<
O
CO
<
UJ
CO
b.u —
4.0 —
3.0 —
2.0 —
1.0 —
.8 —
.6 —
.5 —
(
) Ł
I
5 1
D 1
5 ' 2
South Aspect
East & West A
North Aspect
0 2
spects
I
5 30
SEASONAL PRECIPITATION, inches
Figure 111.34.—Precipitation-evapotranspiration relationships for the Central Sierra hydrologic
province (7), winter season, by energy aspect.
CO
0)
.c
o
c
o_
CO
<
DC
O
CL
<
HI
o
CO
<
111
CO
5 —
4 —
3 —
p _
1
I
I
1
1
South Aspect
East & West Aspects
North Aspect
1
1
0 10 20 30 40 50 6C
SEASONAL PRECIPITATION, inches
Figure 111.35.—Precipitation-evapotransplration relationships for the Central Sierra hydrologic
province (7), late winter season, by energy aspect.
m.84
-------
(0 1n
-------
1 5~
1 4-
!r 3-
a.
CO
z
DC 2
L EVAPOT
H 1-
CO
ft
, i
» I '
t 5 I
1
3 7 I
South Aspect
East & West f
North Aspect
3 9 1
Aspects
0 11 12
CO
SEASONAL PRECIPITATION, inches
Figure 111.38.—Precipitaiion-evapotranspiration relationships for the New England/Lake States
hydrologic region (1), fall-early winter season, by energy aspect.
(O
-------
in
05
u
c
Z
O
DC
Q.
CO
O
Q.
<
UJ
z
O
CO
<
m
CO
10 —
5-
4-
3
East & West
*'
/
Aspects ^
^"
• —
•^ ^ —
South Aspecl
North Aspect
10 15 20
SEASONAL PRECIPITATION, inches
25
30
Figure 111.40.—Precipitation-evapotranspiration relationships for the New England/Lake States
hydrologic region (1), growing season, by energy aspect.
losses during the June 27-September 30 interval
(fig. 111.37). However, due to the typically dry sum-
mer months, soil moisture deficits severely limit
evapotranspiration in the lower snow accumulation
areas to the south and at low elevations. The low
elevation curve of figure in. 34 reflects the low
evapotranspiration associated with high soil
moisture stresses. Where higher snowpacks and
later melt seasons provide more residual soil water,
evapotranspiration during the summer and fall is
markedly higher, as shown in the upper curve.
In the Northwest province, both the early and
late winter intervals were found not to be precipita-
tion dependent, and losses are essentially from in-
terception and evaporation from snow. These losses
vary with aspect as illustrated in figures 111.27 to
111.29. Evapotranspiration losses during the March
29-June 26 interval (fig. 111.29) vary with precipita-
tion below about 12 inches and also depend on
aspect. Aspect dependence was also found for
evapotranspiration losses during the June 27-
September 30 period (fig. 111.30) as well.
In the New England/Lake States hydrologic
region, the data base for simulations (fig. in.38 to
ni.40) did not provide data points for low annual
precipitation amounts. In addition, the
predominantly wet summers result in an
evapotranspiration rate that approaches the poten-
tial rate. Compared to western regions, elevation
was not considered a significant parameter af-
fecting evapotranspiration. Again, considering the
wet growing season, soil depth significantly af-
fecting evapotranspiration was not simulated, ex-
cept in extremely shallow and/or very coarse-
textured soils.
COVER
DENSITY
At this point an estimate of evapotranspiration
which assumes cover density is maximum (Cdmax)
has been obtained. However, maximum cover den-
sity may or may not be the case. If it is, the ET es-
timate is the same as the adjusted ET and the next
procedural step is the discussion on adjusted ET. If
the cover density is less than maximum, either
because of existing conditions or because of
proposed activities, an adjustment in ET must be
111.87
-------
made to allow for the cover density reduction. In
either case, it is advisable to review the description
of cover density to evaluate the site condition.
The estimates of baseline evapotranspiration
presented in figures EI.24 to m.40 represent es-
timates for the full cover density (complete
hydrologic utilization). To estimate the impact of a
proposed activity or to adjust baseline conditions
for past silvicultural activity or history that exists,
adjustments must be made to the evapotranspira-
tion values presented in figures III.24 to III.40.
COVER DENSITY
In terms of proposed silvicultural activities or
past history, the only significant site parameter
that is altered is cover density (item 20). Forest
cover density (Cd) is an index which theoretically
ranges from zero to less than one, it references the
capability of the stand or cover to integrate and
utilize the energy input to transpire water. Cover
density represents the efficiency of the three-
dimensional canopy system to respond to the
energy input. It varies according to crown closure,
vertical foliage distribution, species, season, and
stocking. It is significant in defining the energy
transmitted to the ground or the transmissivity
coefficient. The cover density and transmissivity
coefficient do not add up to one. Some estimates of
cover density and transmissivity are listed in table
HI.2.
Although evapotranspiration is a function of
cover density, a silvicultural management plan is
not expressed in terms of cover density, but
usually, in terms of some parameter such as basal
area. Before adjustments in evapotranspiration for
the proposed activity can be made, a pre- and post-
silvicultural activity cover density estimate must
be obtained.
Functions which relate basal areas to forest cover
density are plotted in figures HI.41 to ni.45. These
are generalized curves. Pre- and post-silvicultural
activity cover density estimates are needed as in-
put to the methodology. If no more accurate data
are available, then these figures (EI.41 to KI.45)
may be used as guides in determining the amount
of biomass or cover density removed using basal
area as an index to management. A note of caution:
inrTmTTTmTiTiT
100 200 300 4CO
BASAL AREA. ft.Vacre
Figure 111.41.—Basal area-cover density relationships for the
Rocky Mountains/Inland Intermountaln hydrologic region
(4)—spruce-fir, lodgepole pine, and ponderosa pine for
stem diameter > 4 inches dbh.
The curves represent species with a wide range of
stand conditions with respect to age and vigor.
The following steps are recommended for use of
figures HI.41 to ffl.45.
(1) Go to the appropriate basal area-cover den-
sity figure with an estimate of existing stand condi-
tion (basal area) and determine a cover density.
(2) Then evaluate the morphology of the stand
— is it at a point of complete hydrologic utilization
for the site? If so, then the cover density estimated
represents the maximum cover density (Cdmax) for
the site.
(3) If past history indicates that the site is not
fully occupied, then the cover density determined
(Cd) represents existing conditions only; at this
point, determine the maximum potential basal
area for the site in order to determine the max-
imum cover density (Cdmax).
HI.88
-------
iiini 11 ii HIM i mi minim iiiiiiiii n
0 100 200 300 400
BASAL AREA, ft.Vacre
Figure III.42.—Basal area-cover density relationships (or the
Continental/Maritime hydrologic province (6).
70 _
8 en""
cf =
1- nn
/ER DENS
i
Illlll
8 30 =
UJ
oc ~
P =
UJ «
z —
o
1
/
y
/
/
/
iniiiiii
10
/
Illllllll
0 2C
/
/
jgepole Pine
Illllllll
0 30
/
Illllllll
0 400
BASAL AREA, ft.Vacre
Figure 111.43.—Basal area-cover density relationships for the
Central Sierra hydrologic province (7).
(4) Once the basal area following the proposed
silvicultural activity is determined, return to the
figure a second or third time to obtain a post-
silvicultural activity cover density.
Baseline conditions or complete hydrologic
utilization is represented by maximum cover den-
sity (Cdmax). Subsequent figures presented in the
handbook to determine modifier coefficients for
impact adjustments use the ratio of Cd divided by
Cdmax-1° most applications, existing or pre-activity
density equals Cdmax, but since this is not always
the case, an intermediate analysis to define ex-
isting conditions may be required.
EVAPOTRANSPIRATION
MODIFIER COEFFICIENT
Where an estimate of pre- and post-silvicultural
activity cover density for a silvicultural state has
been obtained, the next step is to adjust the
regional baseline evapotranspiration, given in
figures 111.26 to 111.40. The pre-activity level is the
baseline level if past history has not altered the
fully forested condition or if the site is in a state of
complete hydrologic utilization.
For the Rocky Mountain/Inland Intermountain
region, figure III.46 shows modifier coefficients
(item 22) for differing levels of forest cover density
(Cd). The next step involves application of the coef-
ficients to evapotranspiration for each season to
quantify hydrologic impacts resulting from reduc-
tions in forest cover density.
Within the Continental/Maritime province,
figures ni.47 to 111.49 represent the modifier coef-
ficients which vary according to forest cover den-
sity. Again, equation HI.14 involves application of
EI.89
-------
70
100 200
BASAL AREA, ft.'/acre
300
400
100 200
BASAL AREA, ft.Vacre
300
400
Figure III.44.—Basal area-cover density relationships for the
Northwest hydrologic province (5).
Figure III.45.—Basal area-cover density relationships for the
New England/Lake States hydrologic region (1).
the coefficients to baseline evapotranspiration for
each of the three seasons to quantify hydrologic im-
pacts resulting from reductions in forest cover den-
sity. Two sets of relationships are given for middle
and high elevations (figs, ni.47 and IE.48) and
another for low elevations (fig. 111.49). The modifier
coefficients in figure III.49 are used to adjust
baseline evapotranspiration in areas of low
seasonal snowpack accumulation.
The modifier coefficients in figure El.49 also ap-
ply to montane watersheds in the Rocky Moun-
tain/Inland Intermountain hydrologic region (4).
These areas are generally outside the more produc-
tive and commercial subalpine forest zone.
In the Central Sierra province, simulations of
silvicultural activities were for a 50-percent reduc-
tion of the mature forest cover density (Cdmax) and
100-percent reduction. Modifier coefficients
derived from these simulations are plotted in
figures in.50 to HI.53. In this province, the modifier
coefficient for some seasons (primarily late winter)
can exceed 1.0 as the cover density is reduced. This
results from increased exposure of the snowpack,
resulting in increased sublimation and evapora-
tion. Two sets of relationships were derived.
Figures III.54 and III.55 should be used to modify
baseline evapotranspiration of figure 111.35 in high
snow accumulation areas; figures in.52 and in.53
are recommended for use in areas of moderate to
low snow accumulation for figure H[.35.
Modifier coefficients for the New England/Lake
State region (1) are presented in figure IE.56.
HI.90
-------
FOREST COVER DENSITY
Cdmax
Figure 111.46.—Evapotranspiration modifier coefficients for
forest cover density changes for the Rocky Moun-
tain/Inland Intermountain hydrologic region (4).
FOREST COVER DENSITY
Figure 111.48.—Evapotranspiration modifier coefficients for
forest cover density changes for the Continental/Maritime
hydrologic province (6) high and intermediate energy
aspects—winter season.
cdrnax/2
FOREST COVER DENSITY
Figure 111.47.—Evapotranspiration modifier coefficients for
forest cover density changes for the Continental/Maritime
hydrologic province (6) high and intermediate energy
aspects—spring, summer and fall seasons.
cdmax/2
FOREST COVER DENSITY
Figure 111.49.—Evapotranspiration modifier coefficients for
forest cover density changes for the Continental/Maritime
hydrologic province (6) low energy aspects—all seasons.
EI.91
-------
FOREST COVER DENSITY
Figure 111.50.—Evapotranspiration modifier coefficients for
forest cover density changes for the Central Sierra
hydrologic province (7) intermediate and low energy
aspects—early and late winter seasons.
0 ^dmax/2
FOREST COVER DENSITY
Figure 111.52.—Evapotranspiration modifier coefficients for
forest cover density changes for the Central Sierra
hydrologic province (7) high energy aspects—spring, sum-
mer and fall seasons.
ffi .8-
7
cdmax/2
FOREST COVER DENSITY
Figure 111.51.—Evapotranspiration modifier coefficients for
forest cover density changes for the Central Sierra
hydrologic province (7) intermediate and low energy
aspects—spring, summer and fall seasons.
FOREST COVER DENSITY
Figure III.53.—Evapotranspiration modifier coefficients for
forest cover density changes for the Central Sierra
hydrologic province (7) high energy aspects—early and late
winter seasons.
m.92
-------
cdmax/2
FOREST COVER DENSITY
Figure 111.54.—Evapotranspiration modifier coefficient* for
forest cover density changes for the Northwest hydrologic
province (5) all energy aspects—spring, summer, and fall
seasons.
I T I
0 °dma x/2
FOREST COVER DENSITY
Figure 111.55.—Evapotranspiration modifier coefficients for
forest cover density changes for the Northwest hydrologic
province (5) all energy aspects—early and late winter
seasons.
0.3
^dmax/2
FOREST COVER DENSITY
Figure 111.56.—Evapotranspiration modifier coefficients for
forest cover density changes for the New England/Lake
States hydrologic region (1) all energy aspects—all
seasons.
ADJUSTED EVAPOTRANSPIRATION
Adjusted seasonal evapotranspiration (item 23)
for the silvicultural state is obtained by multiply-
ing evapotranspiration (item 18) by its cor-
responding modifier coefficient (item 22).
WATER AVAILABLE FOR
STREAMFLOW
Multiplication of the treatment area (as a
decimal percentage of the watershed area, item 13)
times the difference between adjusted precipita-
tion and adjusted evapotranspiration (item 17-
item 23) is an estimate of area weighted contribu-
tion to total watershed flow that will be derived
from the treatment (or state) area by season and is
entered in one of the columns from 24-29. The
seasonal values for each hydrologic state should be
placed in Separate columns so that they can later
be summed and entered in columns 30-35, ap-
propriately.
111.93
-------
ALL
SILVICULTURAL
STATES
CONSIDERED?
At this point the contribution of flow from one
treatment area has been calculated and expressed
in inches of flow from the entire watershed for one
season. Only after all treatments for the prescrip-
tion and season are evaluated is a new season con-
sidered.
ALL
SEASONS
CONSIDERED?
Calculations of evapotranspiration and water
available for streamflow are performed for all
silvicultural states, seasons, within each prescrip-
tion.
A return to the silvicultural prescription step of
the flow chart and completion of the subsequent
steps until all evapotranspiration and water
available for streamflow for all treatments for a
prescription by season have been calculated is re-
quired.
Once the seasonal loop has been completed, an-
nual ET, by treatment, can be summed using the
following equation:
n
T^rri ^ "C^T* t^T^
d 1 A — Zj CjJjlj — € I T-J 1 1
,-=1 (in. H)
where:
ETA
.( ET
n n
ET; =
n =
annual evapotranspiration
evapotranspiration modifier coef-
ficients (by season) that vary with
forest cover density (item 22)
seasonal evapotranspiration (item
18)
number of seasons
WATER AVAILABLE
FOR ANNUAL STREAMFLOW
BY STATE
Since streamflow timing differs by silvicultural
treatment, water available for streamflow for the
entire year must be sorted by treatment. Water
available for streamflow for each treatment is
summed for each season yielding water available
for annual streamflow by season and treatment
(enter in col. 30-35). In the next section,
hydrographs will be constructed for each
silvicultural state. A composite hydrograph for the
entire watershed or watershed subunit will be ob-
tained by summing the silvicultural state
hydrographs.
ALL
SILVICULTURAL
PRESCRIPTIONS
CONSIDERED?
At this point, all calculations for the impacts of a
number of silvicultural states, by season, have been
completed for one prescription. If more than one
silvicultural prescription is recommended per
energy aspect or more energy aspects per condition,
the loop is repeated.
ALL
ENERGY
ASPECTS CONSIDERED?
Once all the calculations for each prescription
within an energy aspect have been considered, all
energy aspects within each condition need to be
evaluated.
To obtain an estimate of annual flow, for the con-
dition one first has to sum the contribution from
each state in the prescription using the following
equation:
35
QP= 2 QT (IE.15)
T = 30
where:
Qp =
Contribution (in area inches) to total
watershed flow, from the prescription.
QT = Flow from treatment area (items 30-35
from worksheets ni.5 or III.6 depending
on condition).
To estimate total watershed flow, the prescription
flows can be summed by adding the flows from the
various prescriptions together. If only one prescrip-
tion is defined, it represents the watershed flow.
ALL
CONDITIONS
CONSIDERED?
The flow chart is constructed so that water
available for annual streamflow is calculated for all
m.94
-------
energy aspects for one condition before the other
conditions are considered. The order in which
aspects and conditions are considered may be
changed to fit specific needs. Nonetheless, all con-
ditions (proposed, existing, etc.) and all energy
aspects (or watershed subunits) for the basin must
be dealt with in an orderly manner before
proceeding with hydrograph construction in the
section, "Procedural Description: Determining
Streamflow Timing and Volume Changes As-
sociated With Silvicultural Activities."
END
At this point the user has values of water
available for annual streamflow sorted by
silvicultural state, prescription, and energy aspect
and condition. The next step is construction of
desired hydrographs for the basin of interest.
Example: Determining ET And Water
Available For Annual Streamflow
(Snow Dominated Regions)
The following is an example of how to use the
methodology. Worksheets are not used but the
methodology steps are done in order to arrive at the
information needed for the worksheets. The exam-
ple is Hubbard Brook (New Hampshire),
watershed 3.
Step 1. Any watershed under consideration may
need to be delineated and divided into subunits by
aspect (item 4). Also needed in order to further
subdivide the watershed into homogeneous sub-
units are timber stand data, including the species;
basal area (item 19) or cover density (item 20);
history of cutting; and the proposed silvicultural
prescriptions (including the nature of the cut and
the size and spacing of openings if they will be
created).
Hubbard Brook watershed can be treated as hav-
ing one energy aspect with a southerly exposure.
The pre-silvicultural condition is fully forested (Cd
= Cdmax) an(l the example silvicultural prescription
is a reduction to Cd,= 0 (completely clearcut).
Step 2. Determine the average annual and
seasonal precipitation (item 14) that can be ex-
pected for the design year. This can be obtained
locally from published data, or from a
precipitation/elevation curve developed for the
area.
For Hubbard Brook the precipitation is 47.6 in-
ches per year, with 12.1 inches occurring between
October 1 and January 31, 13.0 inches occurring
between February 1 and April 30, and 22.5 inches
occurring between May 1 and September 30.
Given the information available to this point, it
is possible to estimate the potential baseline
evapotranspiration (item 18) which might occur on
the site in the following manner, using figure 111.38
(south aspect).
Season
(item 9)
10/1-1/31
2/1-4/30
5/1-9/30
Total
Precipitation
(item 14)
12.1
13.0
22.5
47.6
Baseline ET
(item 18)
2.45
2.65
16.70
21.80
Of the 47.6 inches of precipitation, approximately
21.8 inches will be used for evapotranspiration and
25.8 inches is water potentially available for
streamflow (item 30).
Step 3. After establishing baseline conditions,
changes due to the proposed silvicultural prescrip-
tion are determined. In this example, prescription
and state are one. First, evaluate the pattern and
nature of the cut; use the procedures given to ad-
just the precipitation input to reflect snow
redistribution if it can be expected to occur.
For Hubbard Brook, no adjustment is made for
redistribution. The comprehensive example
presented for the Rocky Mountain/Inland Inter-
mountain hydrologic region (4) presented subse-
quently in this handbook will illustrate the
procedure that should be used to quantify the im-
pacts of silvicultural activities on snow accumula-
tion and redistribution.
Step 4. When precipitation has been adjusted to
account for the proposed treatment, evapotran-
spiration must be adjusted to reflect the expected
change. This is done in the following manner using
input data above and figure 111.56 (assume Cd = 0
after harvest, Cd = Cdmax before harvest).
111.95
-------
Season
(item 9)
10/1-1/31
2/1-4/30
5/1-9/30
Total
Precipitation
(Item 14)
(given)
12.1
13.0
22.5
47.6
Baseline
ET
(Item 18)
(fig. 111.38)
2.45
2.65
16.7
21.8
ET Modifier
(item 22)
(fig. II 1. 56)
1.06
.88
.52
Post-activity
evapotran-
spiration
2.60
2.33
8.68
13.61
The expected post-activity evapotranspiration is
13.6 inches and the water available for
streamflow is 34.0 inches (47.6-13.6). The ex-
pected increase in flow, due to an evapotran-
spiration reduction, is 8.2 inches. The observed
change in flow (Hornbeck and Federer 1975)
averaged about 11.5 inches.
In the above example no adjustments were made
for snow redistribution. This, in turn, would adjust
post-silvicultural activity evapotranspiration rates
because precipitation would have been altered.
Also the basin silvicultural activity was not com-
plicated because the entire basin was treated uni-
formly in pre- and post-silvicultural activity condi-
tions. There was no need to adjust the response for
differing practices and aspects on the same
watershed. This will be covered in the complete ex-
ample for Horse Creek (ch. VIII). The methodology
presented in steps 1-4 is used to evaluate, for any
silvicultural activity, the water potentially made
available by the evapotranspiration reduction.
This water is then routed to the soil moisture and
streamflow components of the analysis (see next
section).
m.96
-------
PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
IN STREAMFLOW (STREAMFLOW ESTIMATION)
(SNOW DOMINATED REGIONS)
NEW ENGLAND/LAKE STATES (REGION 1)
ROCKY MOUNTAIN/INLAND INTERMOUNTAIN (REGION 4)
PACIFIC COAST REGION, HIGHER ELEVATION ZONES (PROVINCES 5, 6, 7)
Unlike the rain dominant regions, the hydrologic
regime in snow dominated regions allows water
potentially available for flow to be distributed in a
time dependent hydrograph or distribution graph.
In the snow dominated regions, a significant por-
tion of the annual flow does occur in a predictable
manner as the result of melting snow.
A significant impact on the hydrology of these
areas is modification of the rate of snowmelt
through forest manipulation which not only alters
the quantity of water, but the peak flow rates and
timing as well (Anderson and others 1976, Swanson
and others 1977). Therefore, in order to provide a
useful tool in evaluating the impacts of
silvicultural activities, it is necessary to provide a
means of distributing changes in potential flow and
a means for evaluating when changes would occur.
Of the two hydrologic regions (1 and 4) and three
hydrologic provinces (5, 6, and 7) that are snow
dominated, one is considered an exception. The
New England/Lake States hydrologic region (1),
because of its winter snowpack, had tcrbe included
in this group for modeling purposes. However, the
snowpack development in this region does not truly
dominate the hydrograph. The rainfall generated
portion of the hydrograph is also quite significant.
For this reason, the techniques for presenting the
effect of silvicultural activities on the water poten-
tially available for flow will be dealt with
separately at the end of this section in a manner
more closely related to rain dominated techniques.
HYDROLOGIC REGION OR PROVINCE
Define the hydrologic region characteristics of
the site. (This has already been done for the ET es-
timation.)
HYDROLOGIC
REGION 1?
Since snow does not dominate the hydrology of
the New England/Lake States region (1) to the ex-
tent it does in hydrologic region 4 and provinces 5,
6, and 7, streamflow procedures are different for
hydrologic region 1. For this region, flow duration
curves instead of hydrographs are developed. For
the rest of the flow chart for Region 1, review "New
England/Lake States (Region 1)" which is discus-
sed later in this section. For Region 4, and the
Pacific Coast hydrologic provinces 5, 6, and 7, con-
tinue with the procedure described immediately
below.
CONDITION
As with the ET calculations, perform the
analysis on each watershed condition.
PROCEDURAL FLOW CHART
The flow chart outlining the procedure for
streamflow estimation is given in figure 111.57 and
discussed below. Worksheets HI.7 and ni.8 have
been constructed to facilitate calculations.
ENERGY ASPECT
Watershed subdivision into energy aspect units
is the same as for the ET calculations.
m.97
-------
( Hydrologic Region or Province
Yes
New England/Lake States
Region 1
Baseline and Open Flow
Duration Curves
Cover Density Reduction j
Existing and Proposed
Flow Duration Curves
No
Condition
c
Energy Aspect
( Silvicultural Prescription )4
—K Silvicultural State )
1
/
/Open
No / Pres
1
Baseline
Distribution
Hydrograph
Interpolated
Distribution
Hydrograph
ings
Weighted Water Available
for Annual Streamflow
Silvicultural State
Hydrograph
Yes
Open
Distribution
Hydrograph
All
Silvi-
cultural
States Considered?
All
Silvi-
cultural
Prescriptions
Considered?
Figure 111.57.—Flow chart of methodology for calculation of composite hydrograph and 7-day flow duration
curve, snow dominated regions.
m.98
-------
SILVICULTURAL PRESCRIPTION
As with the ET calculations, the silvicultural
prescription for each energy aspect must be
defined. Each prescription can include one or more
silvicultural states or treatments.
SILVICULTURAL STATE
As defined, silvicultural state relates to the ac-
tual treatment or activity to be employed (i.e.,
thinning, clearing, etc.) or describes the vegetative
state in the absence of management.
The above items (condition, energy aspect,
silvicultural prescription, and silvicultural state)
define the watershed divisions which are used as
components to each analytical loop.
COVER
DENSITY
-------
WORKSHEET
Existing condition hydrograph
(1) Watershed name
Date
or
Interval
(3)
Distribution of water
Un impacted
%
(4)
Inches
(5)
cfs
(6)
%
(7)
Inches
(8)
cfs
(9)
Impacted
%
(10)
Inches
(11)
cfs
(12)
Item or
Co I . No.
(1)
(2)
(3)
(4),(7),
(10),(13),
(16),(19)
Notes
Identification of watershed or watershed subunit.
Descriptions of hydro I ogle regions and provinces are given In
text.
Supplied by user. Either date snowmelt begins or date of
peak snowmelt runoff.
Digitized excess water distribution (?) from tables 111.11 to
I I 1.22 for forested and open condition. Interpolate between
forested and open for other conditions.
m.ioo
-------
III.7
for snow dominated regions
(2) Hydro logic region
available for annual streamflow
Impacted (continued)
%
(13)
Inches
(14)
cfs
(15)
%
(16)
I nches
(17)
cfs
(18)
%
(19)
1 nches
(20)
cfs
(21)
Compos 1 te
hydrograph
cfs
(22)
(5),(8),
(11),(14),
(17),(20)
(6),(9),
(12),(15),
(18),(21)
(22)
Digitized excess water distribution (%) multiplied by water
available for annual streamflow gives flow In Inches.
To convert from area Inches to cfs, the area-Inch hydrograph
Is multIpI led by:
Total watershed area (In acres)
(12 in/ft) (1.98) (Number of days In Interval)
Sum of columns (6), (9), (12), (15), (18), and (21) gives the
composite hydrograph for the entire watershed in cfs.
III.101
-------
WORKSHEET
Proposed condition hydrograph
(1) Watershed name
Date
or
Interval
(3)
Distribution of water
Un Impacted
%
(4)
1 nches
(5)
cfs
(6)
%
(7)
1 nches
(8)
cfs
(9)
Impacted
*
(10)
1 nches
(11)
cfs
(12)
Item or
Col. No.
(1)
(2)
(3)
(4),(7),
(10),(13),
(16),(19)
Notes
Identification of watershed or watershed subunit.
Descriptions of hydrologlc regions and provinces are given in
text.
Supplied by user. Either date snowmelt begins or date of
peak snowmelt runoff.
Digitized excess water distribution (%) from tables 111.11 to
111.22 for forested and open condition. Interpolate between
forested and open for other conditions.
m.io2
-------
I I I .8
for snow dominated regions
(2) Hydrologic region
available for annual streamflow
Impacted (continued)
%
(13)
Inches
(14)
cfs
(15)
%
(16)
Inches
(17)
cfs
(18)
%
(19)
Inches
(20)
cfs
(21)
Compos 1 te
hydrograph
cfs
(22)
(5),(8),
(11),(14),
(17),(20)
(6),(9),
(12),(15),
(18),(21)
(22)
Digitized excess water distribution (?) multiplied by water
available for annual streamflow gives flow in inches.
To convert from area inches to cfs, the area-Inch hydrograph
is multiplled by:
Total watershed area (In acres)
(12 in/ft) (1.98) (Number of days in Interval T
Sum of columns (6), (9), (12), (15), (18), and (21) gives the
composite hydrograph for the entire watershed in cfs.
in.ios
-------
ID
Q.
W
UJ
a
x
UJ
-------
0)
0)
Q.
CO
CO
LU
O
X
LU
DC
UJ
I I I I I I I I I I
Figure 111.59.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
tain hydrologic region (4)—treated conditions, low energy aspects.
Figure 111.60.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
tain hydrologic region (4)—treated conditions, intermediate energy aspects.
ni.ios
-------
Figure 111.61.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
tain hydrologic region (4)—treated conditions, high energy aspects.
m.ioe
-------
Table 111.11.—Digitized excess water distribution for the Rocky
Mountain/Inland Intermountaln hydrologic region
(4)—low energy aspect.
Percentage In decimals of total annual flow which will occur
during 6-day flow intervals
6th day
interval 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0025
0.0100
0.200
0.0475
0.0725
0.0925
0.1050
0.1125
0.1150
0.1150
0.1125
0.0975
0.0550
0.0250
0.0125
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.00
0.0025
0.0100
0.0200
0.0325
0.0525
0.0950
.01425
0.1550
0.1550
0.1400
0.0800
0.0500
0.0325
0.0200
0.0100
0.0025
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Table 111.12.—Digitized excess water distribution for the Rocky
Mountain/Inland Intermountaln hydrologic region
(4)—Intermediate energy aspect.
Percentage In decimals of total annual flow which will occur
during 6-day flow Intervals
6th day
interval1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.0050
0.0150
0.0300
0.0450
0.0650
0.1000
0.1300
0.1375
0.1400
0.1350
0.1150
0.0600
0.0200
0.0025
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.0075
0.0200
0.0350
0.0550
0.0750
0.0950
0.1350
0.1550
0.1600
0.1300
0.0825
0.0325
0.0125
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1The intervals are fixed in time with respect to date of peak flow.
The peak data is user specified.
'The intervals are fixed in time with respect to date of peak flow.
The peak flow is user specified.
Continental/Maritime hydrologic province (6):
The baseline distribution graphs for the three
energy aspects within the province are plotted on
figure HJ.62. These represent the normalized
average from simulating many station years of
record. The same number of simulations were
made reducing the baseline cover density by 50
percent and then by 100 percent. Again, reduction
by 50 percent had little, if any, effect on changing
potential streamflow.
The relationships between potential flows for
fully forested and open conditions are presented in
figures in.63 to in.65 for each of the energy aspects.
Because of the relative consistency of the simulated
responses, the x or time axis has been dated. Again,
a timing shift of up to 6 weeks and a change in peak
flow rate can be noted.
The digitized excess water distributions
represented by figures DI.63 to EI.65 are presented
in tables HI. 14 to HI. 16 for each of the energy
aspects.
Central Sierras hydrologic province (7): Simula-
tions at a 50-percent reduction in the baseline cover
density did not indicate a significant change in
flow. Baseline distribution graphs of potential flow
for the three energy aspects are presented in figure
IE. 66. There are two peaks on low and intermediate
energy aspects. The potential flow distributions for
forested and open conditions are plotted by energy
aspects on figures m.67 to ITJ.69. Timing of peak
flow rate changed by as much as 6 weeks and the
rate itself by 3 percent.
m.io?
-------
Table 111.13.—Digitized excess water distribution for the Rocky
Mountain/Inland Intermountain hydrologic region
(4)—high energy aspect.
Percentage In decimals of total annual flow which will occur
during 6-day flow Intervals
6th day
interval1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.0050
0.0150
0.0250
0.0400
0.0600
0.0825
0.1050
0.1400
0.1575
0.1400
0.1050
0.0650
0.0375
0.0175
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0025
0.0075
0.0250
0.0425
0.0650
0.0825
0.1075
0.1475
0.1650
0.1450
0.1150
0.0625
0.0250
0.0075
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
The digitized excess water distributions for
baseline and open conditions by energy aspects are
presented in tables HI. 17 to 111.19.
Northwest hydrologic province (5): Distribution
graphs of excess water potentially available for flow
simulated for the Northwest hydrologic province
(5) are presented in figure 111.70 for the three
energy levels. The distribution graph for this
province is complex with several rainfall generated
peaks. The effect of simulating a 50-percent reduc-
tion in cover density was negligible. The fully
forested and completely open simulations are plot-
ted on figures IH.71 to ffl.73. Note the slight shift in
the snowmelt peak for the intermediate and low
energy zones (figs. EI.72 and 111.73).
Digitized excess water distributions
presented in tables IE.20 to HI.22.
are
'The intervals are fixed in time with respect to date of peak flow.
The peak data is user specified.
Excess water distribution values presented for
both the Northwest hydrologic province (5) and
Rocky MountainAnland Intermountain hydrologic
region (4) should be properly interpreted; they
have limitations. They are simulated distributions
and all the errors inherent in simulation apply (see
app. in.C for a detailed discussion). Because of the
predictability of the snowmelt generated portion of
the hydrograph, this portion of the distribution
table is most representative of what may be ex-
pected and when.
The rainfall generated portions of the distribu-
tion table are more speculative. Because of the
variability of rainfall patterns, these portions of the
hydrograph can be normalized only to the extent
Oct. 1
Aug. 18 Sept. 30
Figure 111.62.—Potential water excess distribution graphs for Continental/Maritime hydrologic
region (6)— baseline conditions, all energy aspects.
m.ios
-------
15
» 10
r i
•/!
I I
Baseline
5-
Oct. 1
6 days
May8
DATE
Aug. 18 Sept. 30
Figure 111.63.—Potential water excess distribution graphs for Continental/Maritime hydrologic
region (6)—treated conditions, low energy aspects.
Oct. 1
6 days
May8
DATE
Aug. 18 Sept. 30
Figure 111.64.—Potential water excess distribution graphs for Continental/Maritime hydrologic
region (6)—treated conditions, Intermediate energy aspects.
m.109
-------
-------
Table 111.14.—Digitized excess water distribution for the Con-
tinental/Maritime hydrologic province (6)—low energy
aspects.
Percentage In decimals of total annual flow which will occur
during 6-day flow Intervals
Table 111.15.—Digitized excess water distribution for the Con-
tinental/Maritime hydrologic province (6)—intermediate
energy aspects.
Percentage In decimals of total annual flow which will occur
during 6-day flow Intervals
Block
Oct. 1
Feb. 28
Apr. 11
Apr. 23
Jul. 18
Aug. 12
Aug. 18
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0061
0.0154
0.0267
0.0395
0.0541
0.0710
0.0922
0.0995
0.1019
0.0995
0.0922
0.0794
0.0669
0.0529
0.0352
0.0219
0.0133
0.0061
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0076
0.0047
0.0036
0.0031
0.0018
0.0010
0.0015
0.0026
0.0010
0.0021
0.0031
0.0026
0.0021
0.0026
0.0031
0.0026
0.0021
0.0010
0.0015
0.0008
0.0031
0.0036
0.0042
0.0026
0.0010
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0053
0.0125
0.0230
0.0356
0.0479
0.0645
0.0869
0.1093
0.1366
0.1237
Q.0946
'0.0634
0.0440
0.0212
0.0133
0.0069
0.0012
0.00
0.00
0.00
0.00
0.0006
0.0026
0.0047
0.0063
0.0070
0.0074
0.0079
0.0082
Block
Oct. 1
Feb. 28
Mar. 24
Apr. 5
Jul. 18
Sept. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.00
0.00
0.00
0.00
0.0008
0.0080
0.0184
0.0288
0.0437
0.0581
0.0706
0.0926
0.1115
0.1183
0.1183
0.1014
0.0733
0.0542
0.0372
0.0221
0.0120
0.0053
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0106
0.0068
0.0053
0.0046
0.0027
0.0015
0.0023
0.0038
0.0015
0.0030
0.0046
0.0038
0.0030
0.0038
0.0046
0.0038
0.0030
0.0015
0.0023
0.0011
0.0046
0.0053
0.0061
0.0039
0.0015
0.00
0.00
0.00
0.0008
0.0036
0.0077
0.0164
0.0284
0.0421
0.0605
0.0838
0.1014
0.1091
0.1070
0.0954
0.0694
0.0493
0.0344
0.0213
0.0125
0.0053
0.0016
0.00
0.00
0.00
0.00
0.00
0.00
0.0005
0.0030
0.0050
0.0070
0.0086
0.0096
0.0104
0.0109
ffl.111
-------
Table 111.16.—Digitized excess water distribution for the Con-
tinental/Maritime hydrologic province (6)—high energy
aspects.
Percentage in decimals of total annual flow which will occur
during 6-day flow intervals
Table 111.17.—Digitized excess water distribution for the
Central Sierra hydrologic province (7)—low energy aspects.
Percentage in decimals of total annual flow which will occur
during 6-day flow intervals
Block
Oct. 1
Mar. 12
Jul. 12
Aug. 18
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.0004
0.0061
0.0121
0.0194
0.0312
0.0497
0.0783
0.0892
0.1105
0.1247
0.1255
0.1134
0.0722
0.0521
0.0331
0.0223
0.0158
0.0101
0.0061
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0140
0.0090
0.0070
0.0060
0.0035
0.0020
0.0030
0.0050
0.0020
0.0040
0.0060
0.0050
0.0040
0.0050
0.0060
0.0050
0.0040
0.0020
0.0030
0.0015
0.0060
0.0070
0.0080
0.0050
0.0020
0.00
0.0004
0.0062
0.0175
0.0312
0.0578
0.0887
0.1058
0.1074
0.1016
0.0672
0.0494
0.0385
0.0333
0.0286
0.0229
0.0187
0.0154
0.0104
0.0062
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0020
0.0061
0.0085
0.0101
0.0114
0.0127
0.0138
Block
Oct. 6
Dec. 24
Feb. 28
Mar. 31
Jul. 6
Aug. 24
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.0004
0.0013
0.0034
0.0058
0.0071
0.0075
0.0071
0.0062
0.0044
0.0030
0.0026
0.0008
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0012
0.0032
0.0057
0.0081
0.0129
0.0201
0.0270
0.0363
0.0443
0.0561
0.0689
0.0762
0.0822
0.0862
0.0862
0.0810
0.0746
0.0621
0.0459
0.0294
0.0186
0.0113
0.0073
0.0040
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.0008
0.0025
0.0039
0.0062
0.0088
0.0102
0.0102
0.0098
0.0088
0.0071
0.0058
0.0043
0.0016
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0012
0.0024
0.0032
0.0057
0.0089
0.0146
0.0210
0.0295
0.0384
0.0505
0.0667
0.0792
0.0916
0.1033
0.1088
0.1081
0.0916
0.0537
0.0291
0.0113
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
m.ii2
-------
Table 111.18.—Digitized excess water distribution for the
Central Sierra hydrologic province (7)—intermediate energy
aspects.
Percentage In decimals of total annual flow which will occur
during 6-day flow Intervals
Table 111.19.—Digitized excess water distribution for the
Central Sierra hydrologic province (7)—high energy
aspects.
Percentage In decimals of total annual flow which will occur
during 6-day flow intervals
Block
Oct. 12
Dec. 12
Jan. 31
Mar. 31
Jul. 12
Aug. 12
Sept. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.0003
0.0005
0.0009
0.0024
0.0048
0.0048
0.0037
0.0025
0.0012
0.0006
0.0003
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0048
0.0125
0.0202
0.0278
0.0374
0.0471
0.0559
0.0663
0.0760
0.0860
0.0936
0.0948
0.0877
0.0743
0.0602
0.0463
0.0350
0.0254
0.0150
0.0069
0.0032
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Ctoarcut)
0.00
0.0004
0.0012
0.0033
0.0055
0.0076
0.0071
0.0063
0.0045
0.0025
0.0012
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0016
0.0028
0.0048
0.0069
0.0101
0.0130
0.0168
0.0208
0.0281
0.0355
0.0437
0.0511
0.0650
0.0818
0.0993
0.1148
0.1131
0.0868
0.0609
0.0453
0.0298
0.0175
0.0073
0.0016
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Block
Nov. 12
Dec. 6
Mar. 31
Apr. 6
Sep. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0020
0.0036
0.0053
0.0069
0.0098
0.0109
0.0133
0.0158
0.0186
0.0205
0.0238
0.0278
0.0323
0.0379
0.0451
0.0511
0.0591
0.0717
0.0950
0.0963
0.0865
0.0741
0.0579
0.0439
0.0350
0.0238
0.0170
0.0093
0.0040
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0020
0.0028
0.0040
0.0057
0.0069
0.0085
0.0093
0.0117
0.0134
0.0150
0.0166
0.0194
0.0215
0.0238
0.0266
0.0294
0.0338
0.0383
0.0443
0.0516
0.0641
0.0807
0.0975
0.1345
0.0758
0.0455
0.0366
0.0290
0.0202
0.0133
0.0089
0.0061
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
m.ii3
-------
01
o
CD
Q.
03
03
LU
O
X
LU
DC
111
z
Oct. 1
DATE
Sept. 30
Figure III.67.—Potential water excess distribution graphs for Central Sierra hydrologic region
(7)—treated conditions, low energy aspects.
Oct. 1
Sept.
DATE
Figure 111.68.—Potential water excess distribution graphs for Central Sierra hydrologic region
(7)—treated conditions, Intermediate energy aspects.
III.114
-------
Oct. 1
DATE
Sept. 30
Figure 111.69.—Potential water excess distribution graphs for Central Sierra hydrologic region
(7)—treated conditions, high energy aspects.
15
-------
15
o>
o
0>
a
CO
CO
LU
O
X
LU
EC
LU
I
10
Oct. 1
DATE
Sept. 30
Figure 111.71.—Potential water excess distribution graphs for the Northwest hydrologic region
(5)—treated conditions, low energy aspect.
15
05
2
0}
Q.
CO
CO
LU
O
X
LU
cr
LU
10
Baseline
Oct. 1
DATE
Sept. 30
Figure III.72.—Potential water excess distribution graphs for the Northwest hydrologic region
(5)—treated conditions, Intermediate energy aspect.
m.iie
-------
15-
10-
5-
\
> Baseline
Oct. l
Nov. 27
DATE
April 16 June 9 July 15
Sept. 30
Figure 111.73.—Potential water excess distribution graphs for the Northwest hydrologic region
(5)—treated conditions, high energy aspects.
that rainfall can be normalized. They do, however,
represent the nature of the change that may be ex-
pected. The limitations discussed in appendix IHC
apply most directly to these portions of the dis-
tribution table.
Digitized excess water distributions provide a
simplified means of estimating the potential
change in flow distribution which might occur fol-
lowing a proposed silvicultural activity. Using in-
puts developed from the evapotranspiration
calculations, an adjustment to the baseline condi-
tion for the proposed activity can be made in the
following manner for each watershed compartment
or energy aspect.
In region 4, the date of peak discharge from
snowmelt for baseline conditions must be specified.
Once the date for baseline has been established,
the date for the open situation also becomes es-
tablished. Interpolations of distribution graphs for
intermediate vegetal states are also dated.
BASELINE
DISTRIBUTION
HYDROGRAPH
Baseline distribution graphs for the appropriate
region can be selected from the previous discussion.
OPENINGS
PRESENT?
If cover density is less than maximum, it must be
determined if openings are present for the treat-
ment or state in question.
OPEN DISTRIBUTION
HYDROGRAPH
Distribution hydrographs for open conditions are
given by hydrologic region or province and aspect.
They can be found on the corresponding full
forested distribution hydrograph figures and tables
provided above.
m.117
-------
Table 111.20—Digitized excess water distribution for the
Northwest hydrologic province (5)—low energy aspects.
Percentage in decimals of total annual flow which will occur
during 6-day flow intervals
Table 111.21—Digitized excess water distribution for the
Northwest hydrologic province (5)—intermediate energy
aspects.
Percentage in decimals of total annual flow which will occur
during 6-day flow intervals
Block
Oct. 1
Nov. 27
Apr. 16
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0008
0.0020
0.0028
0.0032
0.0040
0.0048
0.0061
0.0085
0.0116
0.0153
0.0185
0.0204
0.0253
0.0401
0.0293
0.0200
0.0141
0.0104
0.0100
0.0116
0.0128
0.0153
0.0157
0.0149
0.0132
0.0120
0.0120
0.0136
0.0161
0.0192
0.0233
0.0277
0.0313
0.0325
0.0361
0.0382
0.0385
0.0385
0.0393
0.0393
0.0401
0.0397
0.0369
0.0337
0.0281
0.0208
0.0169
0.0121
0.0089
0.0065
0.0040
0.0028
0.0012
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0056
0.0064
0.0068
0.0076
0.0080
0.0092
0.0108
0.0120
0.0136
0.0153
0.0185
0.0204
0.0253
0.0401
0.0293
0.0200
0.0141
0.0104
0.0100
0.0116
0.0128
0.0153
0.0157
0.0149
0.0132
0.0120
0.0120
0.0136
0.0161
0.0192
0.0233
0.0277
0.0313
0.0359
0.0423
0.0470
0.0467
0.0447
0.0423
0.0411
0.0403
0.0395
0.0339
0.0255
0.0179
0.0092
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0020
0.0036
0.0048
Block
Oct. 1
Nov. 27
Apr. 16
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0004
0.0012
0.0020
0.0028
0.0040
0.0053
0.0065
0.0090
0.0119
0.0153
0.0198
0.0259
0.0354
0.0479
0.0437
0.0306
0.0214
0.0148
0.0139
0.0165
0.0206
0.0247
0.0243
0.0214
0.0198
0.0189
0.0206
0.0231
0.0272
0.0330
0.0330
0.0326
0.0322
0.0330
0.0330
0.0338
Q.0330
0.0322
0.0314
0.0296
0.0272
0.0247
0.0214
0.0165
0.0123
0.0070
0.0040
0.0012
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0044
0.0048
0.0057
0.0065
0.0073
0.0089
0.0105
0.0122
0.0147
0.0171
0.0198
0.0259
0.0354
0.0479
0.0437
0.0306
0.0214
0.0148
0.0139
0.0165
0.0206
0.0247
0.0243
0.0214
0.0198
0.0189
0.0206
0.0231
0.0272
0.0330
0.0330
0.0326
0.0322
0.0330
0.0354
0.0383
0.0392
0.0370
0.0334
0.0293
0.0183
0.0118
0.0065
0.0036
0.0024
0.0012
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0016
0.0024
0.0032
0.0040
0.0044
m.iis
-------
Table 111.22—Digitized excess water distribution for the
Northwest hydrologic province (5)—high energy aspects.
Percentage in decimals of total annual flow which will occur
during 6-day flow intervals
Block
Oct. 1
Nov. 27
Apr. 16
Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0004
0.0008
0.0012
0.0020
0.0032
0.0050
0.0066
0.0091
0.0127
0.0169
0.0231
0.0322
0.0425
0.0595
0.0540
0.0397
0.0264
0.0202
0.0174
0.0197
0.0314
0.0360
0.0325
0.0292
0.0264
0.0223
0.0210
0.0251
0.0371
0.0392
0.0359
0.0338
0.0322
0.0310
0.0306
0.0305
0.0277
0.0239
0.0206
0.0157
0.0107
0.0074
0.0044
0.0020
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0051
0.0053
0.0057
0.0065
0.0077
0.0100
0.0114
0.0158
0.0168
0.0237
0.0279
0.0322
0.0425
0.0595
0.0540
0.0397
0.0264
0.0202
0.0174
0.0197
0.0314
0.0360
0.0325
0.0292
0.0264
0.0223
0.0210
0.0251
0.0371
0.0392
0.0359
0.0338
0.0322
0.0310
0.0252
0.0199
0.0142
0.0096
0.0079
0.0063
0.0042
0.0038
0.0029
0.0021
0.0009
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0009
0.0017
0.0025
0.0033
0.0041
0.0047
0.0048
INTERPOLATED
DISTRIBUTION
HYDROGRAPH
Distribution hydrographs for partial cuts are in-
terpolated from full forested (complete hydrologic
utilization) and open distribution hydrographs.
Interpolation of distribution graphs is
straightforward and linear, although hydrologic
response to vegetation change is not linear. For any
partial reduction in Cd from Cdmax (baseline), the
interpolated distribution graph is obtained in the
following manner.
For each 6-day period, calculate the difference
between the baseline and open percentage of flow,
multiply the difference by the decimal percentage
of Cd change from Cdmax. Now add the product to
the baseline value to obtain the interpolated dis-
tribution (i.e., if Cdmaxis .40 and is reduced to .30,
this represents a 25-percent reduction in cover den-
sity). The intermediate distribution would be a
point 25 percent of the way between baseline and
open values.
WEIGHTED WATER AVAILABLE
FOR ANNUAL STREAMFLOW
Water potentially available for streamflow (P-
ET) has already been estimated for all conditions
and treatments in the preceding section on ET es-
timation. The objective now is to apportion that
annual flow using the appropriate distribution
graph.
SILVICULTURAL
STATE
HYDROGRAPH
Potential streamflow hydrographs for each
silvicultural treatment (items 6, 9, 12, 15, 18, 21)
are obtained by multiplication of the distribution
hydrograph value of each 6-day flow increment by
adjusted water available for annual streamflow
(items 30-35 worksheets III.5 or III.6). Area-inch
values (items 5, 8, 11,14,17, 20) are then converted
to cubic feet per second (cfs) using the following
formula:
m.119
-------
(cfs) =
(inches) (watershed area in acres)
(12 in/ft) (1.98) (number of days in interval)
(m.16)
ALL
SILVICULTURAL
STATES
CONSIDERED?
ALL
CONDITIONS
CONSIDERED?
The methodology is structured so the hydrograph
for one condition must be constructed before the
hydrograph for a second condition can be
calculated.
The following is the methodology appropriate for
region 1.
The hydrograph generated for each treatment
represents the weighted contribution to total
watershed flow. If the actual hydrograph from the
treatment (or prescription) is desired, the
hydrograph should be reverse weighted (multiplied
by watershed area/treatment or prescription area).
ALL
SILVICULTURAL
PRESCRIPTIONS
CONSIDERED?
At this point, a distribution of annual flow for
one prescription has been completed. All prescrip-
tions within an energy aspect must be completed
prior to looping an energy aspect.
NEW ENGLAND/LAKE
STATES
REGION (1)
The presentation of flow distribution is different
for the New England/Lake States hydrographic
region (1) than for the other snow dominant regions
and provinces because rainfall, as well as
snowmelt, plays a dominant role in the hydrologic
cycle there. For this reason, the output from the
simulations is presented in flow duration curves
rather than time dependent distribution graphs.
The reasoning for using one or the other is ex-
plained in appendix HLC.
ALL
ENERGY
ASPECTS
CONSIDERED?
BASELINE AND OPEN
FLOW DURATION CURVES
One energy aspect has been completed. To com-
plete analysis for one condition, repeat for all
energy aspects.
WATERSHED
HYDROGRAPH
Summation of the 6-day flow increments for each
silvicultural state or treatment hydrograph by
prescription and energy aspect yields the com-
posite hydrograph for the condition. Since all es-
timates of flow were area weighted, the hydrograph
values are additive.
As in the other regions and provinces discussed
here, simulations for a number of water years were
made under fully forested baseline conditions, un-
der a 50-percent reduction in cover density, under a
60- and 90-percent cover density, and under a fully
open condition. The baseline flow duration curves
for the New England/Lake States hydrographic
region are presented in figure 111.74. Peak flows
were simulated to be slightly greater on the low
energy (north) aspects due to a more concentrated
melt period. Simulations were not sensitive to any
aspect differences in potential low flows which
would come in both midwinter and late summer.
The procedure for modifying the flow duration
curve is a modification of the technique presented
III. 120
-------
for the rain dominant hydrologic regions (2, 3, 5, 6,
and 7). Baseline and open potential streamflow are
determined with techniques presented in the
streamflow analysis for rain dominated regions.
If the calculated potential baseline flow differs
from that presented in figures 111.75 to 111.77, replot
the flow duration curve. A number of points along
the flow duration curve should be read and the flow
(y axis) should be multiplied by the ratio of ex-
pected site specific baseline annual flow to annual
flow represented by flow duration curve. The new
flow (y) is then replotted at the same duration.
This will yield a new flow duration curve adjusted
for the difference in potential baseline flow during
the year of silvicultural activity and the normalized
year presented in this handbook.
The baseline flow procedure is repeated for open
conditions. Worksheet El. 3 of the section on rain
dominated regions is helpful for these calculations.
3.0
2.5
2.0
1.5
Q
-------
25 50 75
PERCENT OF TIME FLOW IS EXCEEDED
100
Figure
the
(D-
III.77.—Potential excess water flow duration curve for
New England/Lake States hydrologic region
treated conditions, high energy aspects.
melt) flows becomes more apparent. Interpolation
between calculated baseline and calculated open
flow duration curves will give the flow duration
curve for the silvicultural activity condition. This
is an arbitrary interpolation. Guidelines for inter-
polation are implied by figure El.77.
END
Watershed hydrographs or flow duration curves
for all conditions have now been calculated.
Example: Determining Streamflow Timing
And Volume Changes With
Silvicultural Activities, Excluding
"New England/Lake States
(Region 1)"
The following illustration presents a stepwise
procedure for application of the methodology for
Region 4 and Provinces 5, 6, and 7.
Directly following this procedural discussion are
examples of worksheets DI.7 and III.8. They are il-
lustrative of the data required for completing the
methodology.
Step 1. Using appropriate figures and
worksheets HI.5 and IE.6 as guides, calculate the
annual potential streamflow by silvicultural
state for both existing and proposed conditions.
Assume the area of the watershed is 100 acres.
Annual potential streamflows have been area
weighted. A typical result is shown below.
Existing condition
Silvicultural
activity
Forested impacted
Forested unimpacted
Clearcut
Partial cut
Excess
water
(in)
12
15
20
0
Watershed
area
represented
(%)
.200
.600
.200
0
Weighted
excess
water
(in)
2.4
9.0
4.0
0
Total flow
from watershed
Forested impacted
Forested unimpacted
Clearcut
Partial cut
Total flow
from watershed
15.4
Proposed condition
12
15
20
16
.250
.175
.450
.125
3.0
2.6
9.0
2.0
16.6
Step 2. This step applies to the Rocky Moun-
tain/Inland Intermountain hydrographic region
(4) only. The date on which the peak snowmelt
flow will occur must be known. Mark the
digitized excess water distribution graph
(baseline only). Peak flow rate is represented by
the largest flow percentage in the baseline
column of tables III.ll to HI.13. Once the date of
the expected peak has been established, dates of
the other components can also be established in
6-day increments.
Step 3. Select the appropriate digitized excess
water distribution from tables III.ll to III.22.
Enter baseline values for forested unimpacted
and forested impacted silvicultural activities in
worksheet III.7, columns (4) and (10). Repeat for
clearcut (open) values in column (10). Inter-
polate between open and baseline distributions
to obtain the partial cut digitized distribution.
Enter the partial cut distribution in column (16).
Repeat this procedure as necessary until existing
and proposed conditions are considered. If the
watershed has been divided into subunits based
on energy aspect, repeat the procedure for each
subunit.
Step 4. Multiply each silvicultural state dis-
tribution graph value by its corresponding an-
nual potential streamflow for that state. Enter
EI.122
-------
the products in the "inches" column for each
state.
Step 5. Convert "inches" into cubic feet per
second (cfs) using the formula —
(cfs) =
(inches) (watershed area in acres)
(12 in/ft) (1.98) (number of days in interval)
(in.16)
Step 6. For each interval on each worksheet add
(cfs) columns for all silvicultural states. Enter
the sums in column (19). The composite
hydrograph is given in column (19). If the
watershed has been divided into subunits, each
subunit composite hydrograph is weighted by
subunit percent of total watershed area. Existing
and proposed condition hydrographs are
calculated separately.
The preceding methodology assumes that the ef-
fect of increasing the amount of vegetation
removed is linear. This is not generally true since
only two points were simulated — no response and
full response; it is impossible to make an interpola-
tion other than linear. Any error due to this would
probably result in overestimating the impact of les- '
ser activities. This has a conservative effect on the
estimations.
m.123
-------
PROCEDURAL DESCRIPTION: DETERMINING SOIL MOISTURE CHANGES
AND INDIVIDUAL EVENT STORM RESPONSE
Earlier sections of this chapter have emphasized
changes in 6- and 7-day intervals for either
evapotranspiration, soil moisture, or water
available for flow. Responses to individual events
— primarily storm runoff — were not dealt with.
This section now addresses that issue.
The methodologies already developed assume
that water infiltrates into the undisturbed forest
floor, but there are exceptions. Two factors as-
sociated with stormflow production can be altered
by silvicultural activities: (1) The infiltration
characteristics of the surface, and (2) alteration by
disturbance of the storage capacity in the soil.
(Distribution and melt rate of winter snowpack can
also be affected by tree removal. Changes in both
the amount and melt rate of the pack can cause
either the infiltration rate or storage capacity of the
soil profile to be exceeded; this, in turn, causes
higher peak flow rates. This occurrence is not
treated as storm runoff, however, but was
previously treated as flow change.)
To address the first factor, most conventional
silvicultural practices, excluding site preparation,
do not significantly disturb the soil surface, except
for the access and decking systems. These systems
have the potential for changing slope hydrology in
that subsurface soil water is intercepted by road
cuts and routed over the surface along with the rain
falling directly on these surfaces. There is a poten-
tial for altering the timing and delivery route to the
channel of 10 to 15 percent of the precipitation. The
impact of this potential on the storm hydrograph
can be expected to be variable — the stormflow
peak and volume may or may not be increased by
water from the access system. This depends on how
the rerouted water enters the system. The net effect
can be to reduce or augment the peak, depending
upon normal basin response. However, consistent
with best management practices, if the access
system is properly designed, laid out, and drained,
then the intercepted water should be distributed
back over the basin surface and allowed to rein-
filtrate into the soil mantle (provided that storage
is available). This minimizes the impact on the
hydrograph.
To address the second factor, the most signifi-
cant impact that silvicultural practices can have
on stormflow is their effect on antecedent storage.
As will be shown in the discussions on soil moisture
deficits, as the intensity of cut increases, the deficit
or storage capacity at any point in time decreases.
With less storage capacity, more of the precipita-
tion appears as stormflow.
Much of the potential for non-point source pollu-
tion associated with silvicultural activities is as-
sociated with individual storm events. The impact
is not only as stream power as a function of volume
and peak flow rates, but also as the opportunity for
sediment delivery. Therefore, the hydrologist or
engineer usually needs to evaluate the expected
response to some "design" storm.
The general purpose of the hydrology section is to
present a methodology for estimating the
hydrologic impact of silvicultural activities, in-
cluding impacts on storm response. However, the
state-of-the-art in hydrology does not allow the
presentation of a regionalized, process-oriented
methodology for evaluating the impact, if any, of
site disturbance on the storm hydrograph.
Instead a qualitative evaluation will have to be
made based on how, when, and where the distur-
bance will be made, and how such disturbances
might affect the hill slope hydrology.
If the pathway water takes to the channel is not
altered by the silvicultural activity — and there is
little reason to believe it will be if best manage-
ment practices are followed — then the only other
impact which can occur will be a reflection of the
change in soil moisture storage capacities.
The problem of flood forecasting is twofold.
First, the impact silvicultural activities can have
on the soil water regime should be evaluated;
secondly, techniques for predicting stormflow
should be discussed. If the primary interest is in
the potential for change, then the soil water evalua-
tion discussed next will define those periods when
significant changes can occur. Subsequent develop-
ment will allow design storm selection.
Like the other procedures, the soil water
methodology varies by region, primarily because of
the nature of the model output. Once the moisture
status has been determined, the applications of the
stormflow prediction procedure would be similar,
although the relative weight of design criteria may
vary by region.
in. 124
-------
SOIL MOISTURE CHANGES
HUMID CLIMATES, (RAIN DOMINATED
REGIONS) PACIFIC COAST REGION,
LOW ELEVATION
(PROVINCES 5, 6, 7)
APPALACHIAN MOUNTAIN AND
HIGHLANDS (REGION 2)
GULF AND ATLANTIC COASTAL PLAIN
AND PIEDMONT
(REGION 3)
Dealing adequately with soil moisture depletion
rates and deficits is more difficult in a handbook
based on regions than is dealing with either
evapotranspiration or the potential streamflow.
Both evapotranspiration and streamflow follow
seasonal patterns, and they have predictable
regional relationships. Soil moisture follows the
same general pattern; however, soil moisture
deficits (or differences in deficits between sites of
pre- or post-silvicultural activity) can be
eliminated in a single storm event at any time
without any obvious reflection in evapotranspira-
tion or flow.
In this instance, the technique used to predict
the soil moisture distribution is by simulation;
other researchers have used different techniques.
Troendle (1970), Patric (1974), and others have
presented results of studies investigating baseline
and observed changes in soil moisture following
various cutting practices. Tichendorf (1969),
Helvey and others (1972), Kochenderfer and
Troendle (1971), and others have developed predic-
tion equations to estimate soil moisture as a func-
tion of descriptive parameters such as position on
slope, aspect, basal area, soil factors, and antece-
dent rainfall. These local techniques, if applicable,
may be better for defining a site specific baseline
soil moisture level than the normalized curve to be
presented. Like the expected flows, what is most
important is not necessarily the absolute value, but
the ability to adjust the soil moisture level ap-
propriately to evaluate the potential impact of a
proposed activity.
Seasonal deficits in soil moisture (or soil
moisture storage capacity) for a particular region
should be estimated from figures El.78, HI.79, or
111.80 directly. Then, for the proposed activity,
determine the modifier coefficient, by season, from
figure 111.81, 111.82, or HI.83.
Multiplying the modifier coefficient by the
baseline deficit will give the expected post-activity
level. The difference between the pre-activity and
post-activity deficit is the change that can be ex-
pected as a result of the activity. By the same
token, the pre-activity level for any past history
can be determined by adjusting the baseline curve
for present stand conditions. Figures 111.78 to 111.80
represent the average simulated soil moisture
deficit for the root zone in each of the regions.
Although figures III.78 to 111.80 have been
smoothed, the deficit at the end of the four seasons
has been plotted. It should be kept in mind,
however, that these represent average conditions
which could be modified or eliminated at any time
by a single storm event.
Modifier coefficients (figs. 111.81 to 111.83) are to
be applied to the baseline deficit extracted in order
to adjust for various levels of leaf area index. These
are representative curves and will give an index to
the change in antecedent moisture that can be ex-
pected as a result of the proposed activity.
Although the effect varies with storm size, soil
depth, and available storage capacity, antecedent
rainfall can eliminate the deficit at any time; dis-
cretion must be used in evaluating whether or not
conditions may be wetter or drier than "normal."
Adjustments in the baseline or existing soil
moisture deficit can also be made for differing
rooting or soil depth. The changes in evapotran-
spiration resulting from altering rooting depths
were almost a direct reflection of the changes in soil
moisture storage. Therefore, the deficits expressed
in figures in.78 to HI.80 can be adjusted for differ-
ing depth by multiplying the appropriate deficit by
the modifier coefficient expressed in figures 111.81
to m.83.
In the southern Appalachians, soils are deeper
(in excess of 6-8 feet) than in the rest of the region,
and the soil moisture distribution is more like that
of the Coastal Plain/Piedmont region. Therefore,
figure III.80 may be substituted for figure ni.79,
and figure m.83 for figure HI.82. This will allow an
estimate of the baseline distribution and post-
activity relationships for the generally deeper soils
in the southern Appalachians.
The simulations indicate (as did the observa-
tions reference) that aspect and, to some extent,
latitude did affect the soil water deficits. However,
the error associated with predicting them is such
that the site specific effect cannot be isolated.
Basically, simulated deficits appeared greater on
southerly aspects and in more southerly locations
than on northern aspects and locations.
m.125
-------
+10:
«. -5
O -1
ui -
O -15
cc
H -20
O =
w -30
-35:
-40 d
SPRING
SUMMER
FALL
WINTER
Figure 111.78.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the
Pacific Coast hydrologic provinces—Northwest (5), Continental/Maritime (6), and Central
Sierra (7).
WINTER
Figure 111.79.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the Appalachian
Mountain and Highlands hydrologic region (2).
u+10.
O
u_
LU
S °i
LU
CO
SPRING
SUMMER
FALL
WINTER
Figure 111.80.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the Eastern Coastal
Plain and Piedmont hydrologic region (3).
III.126
-------
1.2 —
•] "1
1.0 -
in
z '9
ai
r o
U_
LU
0
07
oc
UJ
"- e
D '"
O
5
DC
D
ft ,
0 ~
-J o
o -3
CO
2 —
/
.»"
/
/
/
/
/
/
f
/
/
/
.•* *
/
/
/
/
1'
•
4,..
•_
Summer
Fall
Winter & Sp
'ing
10
15 20 25
LEAF AREA INDEX
30
35
40
Figure 111.81 .—Seasonal soil moisture deficit modifier coefficients for the Pacific Coast hydrologic
provinces—Northwest (5), Continental/Maritime (6), and Central Sierra (7).
-] -\
9
H -8
HI
O 7
uZ
LL.
UJ
° R
0 '°
DC
HI
LL 5
5
0
2 4
0 ,_
c
x'
/y
)
/
/
/
/
r'
;
X
/
-
^/"
'
i
^^
— •
;
^ "^
Winter & Sp
Summer & 1
3
ing
:all
' 8
LEAF AREA INDEX
Figure 111.82.—Seasonal soil moisture deficit modifier coefficients tor the Appalachian Mountains
and Highlands hydrologic region (2).
m.127
-------
z
LLJ
g .7-
LL
LL
LLJ
O 6-
O
o:
HI
t -5-
Q
O
Summer
Winter & Fall
Spring
5
LEAF AREA INDEX
Figure 111.83.—Seasonal soil moisture deficit modifier coefficients for the Eastern Coastal Plains
and Piedmont hydrologic region (3).
SOIL MOISTURE CHANGES
(SNOWFALL DOMINATED REGIONS)
NEW ENGLAND/LAKE STATES (REGION 1)
ROCKY MOUNTAIN/INLAND INTER-
MOUNTAIN (REGION 4)
PACIFIC COAST, HIGHER ELEVATION
ZONES
(PROVINCES 5, 6, 7)
In the Rocky Mountain/Inland Intermountain
hydrologic region (4), baseline soil water require-
ments for conditions of full hydrologic utilization
are plotted in figure HI .84 for each of the three
seasons discussed. Baseline relationships plotted in
figure 111.84 represent recharge requirements for
moderate depth soils (which have 5.5 inches of
water holding capacity). For deeper soils (water
holding capacity greater than 10 inches), the
recharge requirements in figure 111.84 should be
multiplied by the following coefficients:
Table 111.23.—Soil moisture adjustment coefficients for the Rocky
Mountain/Inland Intermountain hydrologic region (4) by
aspect/elevation and season
Aspect
High north
Intermediate
Low south
Feb. 28
1.0
1.4
1.7
June 30
1.0
1.2
1.3
Sept. 30
1.0
1.2
1.4
Adjustment coefficients for soils having between
5.5 and 10 inches water holding capacity can be ap-
proximated by interpolation. To adjust the deficit
for deeper soils, multiply the deficit from figure
m.84 by the coefficient listed above (table HI.23)
(or the interpolated coefficient).
Figures ni.85 to in.87 depict the baseline as well
as the 50- to 100-percent reduction soil moisture
levels for the high north (ffl.85), low south (IH.86),
and intermediate (111.87) positions.
In the Continental/Maritime Province (6),
baseline soil water recharge requirements for condi-
tions of full hydrologic utilization are plotted in
figure 111.88.
III.128
-------
+1.00
High North
(Low Energy)
Low South
(High Energy)
-6.00
Oct. 1
Feb
June 30
Sept. 30
DATE
Figure III.84.—Baseline soil water requirement relationships for the Rocky Mountain/Inland Inter-
mountain region (moderate soil depth).
+1.00
-6.00
Oct. 1
Feb. 28
June 30
DATE
Sept. 30
Figure 111.85.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
Intermountain hydrologic region (4)—low energy aspects (high north).
m.i29
-------
+1.00
0.00
- -1.00-
H
LLJ
LU
gc
u
o
LU
GC
01
O
CC
<
O
W
DC
-2.00
-3.00 -
-4.00
-5.00 -
-6.00
Oct. 1
Feb. 28
DATE
June 30
Sept. 30
Figure 111.86.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
Intermountain hydrologic region (4)—high energy aspects (low south).
+1.00
-6.00
Oct. 1
Feb. 28
DATE
June 30
Sept. 30
Figure 111.87.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
Intermountain hydrologic region (4)—intermediate energy aspects.
m.iso
-------
+1.00
Low Energy
(High North)
High Energy
(Low South)
-6.00
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.88.—Baseline seasonal soil moisture recharge requirements for the Continental/
Maritime hydrologic province (6)—all energy aspects.
Changes in soil water status due to silvicultural
activities can be estimated from figures III.89 to
ni.91. Reductions of maximum forest cover density
(Cdmax) to Cdmax/2 by selection cutting will
not appreciably alter the baseline soil water
regime. However, recharge requirements should be
decreased uniformly between Cd = Cdmax /2, and Cd
= 0. Figures ffl.89 to 111.91 should be used for
moderate soils (approximately 3.5 and 5.5 inches
field capacity). For deeper soils (approximately 10
inches field capacity), recharge requirements
should be multiplied by the following coefficients:
Table 111.24.—Soil moisture adjustment coefficients for the
Continental/Maritime hydrologic province (6)
by aspect/elevation and season
Aspect
High north
Intermediate
Low south
Feb. 28
1.0
1.4
1.7
June 30
1.0
1.2
1.3
Sept. 1
1.0
1.2
1.4
Changes in soil water status due to silvicultural
activities can be estimated from figures 111.93 to
111.95. Reductions of maximum forest cover density
(Cdmax) to Qmax/2 by selection cutting did not
appreciably alter the baseline soil water regime.
However, recharge requirements should be
decreased uniformly between Cd = Cdmax/2, and Cd
= 0. Figures IH93 to 111.95 should be used for
moderate soils (approximately 5.5 inches field
capacity). For deeper soils (approximately 10 in-
ches field capacity), recharge requirements in
figures 111.93 to III. 95 should be multiplied by the
following coefficients:
Table 111.25.—Soil moisture adjustment coefficients for the
Central Sierra hydrologic province (7) by aspect/elevation and
season
Adjustment coefficients for soils having between
5.5 and 10 inches water holding capacity can be ap-
proximated by interpolation.
In the Central Sierra province (7), baseline soil
water recharge requirements for conditions of full
hydrologic utilization are plotted on figure 111.92.
Aspect
High north
Intermediate
Low south
March 29
1.1
1.4
1.0
June 27
1.0
1.2
1.7
Oct. 1
1.0
1.2
1.3
Dec. 30
1.0
1.2
1.4
Adjustment coefficients for soils having between
5.5 and 10 inches water holding capacity can be ap-
proximated by interpolation.
In the Northwest hydrologic province (5),
baseline soil water requirements for conditions of
m.131
-------
+1.00
W
o>
o
c
0.00
- -1.00—
z
LU
2
LU
DC
D
O
LU
-------
+1.00
-6.00
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.91.—Seasonal soil moisture recharge requirements for the Continental/Maritime
hydrologlc province (6)—high energy aspects.
+1.00
High North
(Low Energy)
Low South
(High Energy)
-6.00
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.92.—Baseline seasonal soil moisture recharge requirements for the Central Sierra
hydrologlc province (7)—all energy aspects.
m.133
-------
+1.00
-6.00
Oct. 1
Dec. 31
March 31
June 30
Sept. 30
Figure 111.93.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologic
province (7)—low energy aspects.
+1.00
-6.00
Oct. 1
Dec. 31
March 31
June 30
Sept. 30
Figure III.94.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologic
province (7)—intermediate energy aspects.
ni.i34
-------
+1.00
-6.00
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.95.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologlc
province (7)—high energy aspects.
full hydrologic utilization are plotted on figure
in.96. These curves are proposed for use in the
high-elevation coniferous forests where runoff is
derived primarily from melting snow.
Changes in soil water status due to silvicultural
activities can be estimated from figures in.97 to
in. 99. Reduction of maximum forest cover density
(Cdmax) to Cdmax/2 by selection cutting did not
appreciably alter the baseline soil water regime.
However, recharge requirements should be
decreased uniformly between Cd = Cdmax/2 and Cd
= 0. Figures in.97 to in.99 should be used for
moderate soils (approximately 5.5 inches field
capacity). For deeper soils (approximately 10 in-
ches field capacity), recharge requirements should
be multiplied by the following coefficients:
Table 111.26.—Soil moisture adjustment coefficients for the
Northwest hydrologlc province (5) by aspect/elevation and
season
Aspect
High north
Intermediate
Low south
March 29
1.0
1.0
1.0
June 27
1.6
1.8
1.8
Oct. 1
1.8
1.8
1.8
Dec. 30
1.0
1.0
1.0
For the New England/Lake States hydrologic
region (1), seasonal trends in soil moisture can be
shown by a nearly uniform temporal distribution of
precipitation during the summer periods. Figure
HI.100 shows the baseline site specific soil moisture
relations. Note that the maximum deficit occurs
during the middle of August and is less than 2 in-
ches. This relation generally will not change unless
very shallow and/or coarse textured soils are en-
countered.
Figures in. 101 to HI. 103 present the effects of
timber harvesting on soil moisture. No significant
differences were noted between the partial cut
(Cdmax/2) and the fully forested condition (Cdmax).
Reductions in forest cover density of over 50-
percent resulted in significant changes in the soil
moisture deficit which can be interpolated from
figures m.101 to m.103. ^
The soil moisture deficit patterns discussed were
simulated and represent potential deficits, not ex-
act numbers. The relative relationships between
cut and uncut seem reasonable and should give a
good index to the expected change.
m.135
-------
+1.00-
0.00-
0)
.c
o
~ -1.00—|
H
Z
LU
Lu -2.00-
DC
D
2 -3.00 —
DC
LU
I
o
LU
-4.00-
-5.00 —
-6.00.
Oct. 1
Dec. 31
High North
(Low Energy)
Low South
(High Energy)
March 31
DATE
June 30
Sept. 30
Figure 111.96.—Baseline seasonal soil moisture recharge requirements for the Northwest
hydrologic province (5)—all energy aspects.
+1.00-
0.00-
CO
CD
O
~- -1.00-
z
LU
Lu -2.00
DC
D
2 -3.00 -|
LU
O
< -4.00
I
O
LU
^ -5.00 H
-6.00.
Oct. 1
Open
dmx/2
(Baseline)
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.97.—Seasonal soil moisture recharge requirements for the Northwest hydrologic
province (5)—low energy aspects.
m.136
-------
+1.00-
« o.oo.
0)
o
"-1.00 —
I-
LU
w
gc
D
O
-2.00— •
-3.00 -I
LL.
LU
O
< -4.00
I
O
LJJ
1 -5.00 —
-6.00 •
09'
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.98.—Seasonal soil moisture recharge requirements for the Northwest hydrologic
province (5)—intermediate energy aspects.
+1.00
-6.00
V
Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.99.—Seasonal soil moisture recharge requirements for the Northwest hydrologic
province (5)—high energy aspects.
m.137
-------
+1.00-
0 00
CO
o>
o
-E -1.00-
01
^ 9 no
rr
O
UJ -3.00 —
DC
01
CD
5 -400-
O
01
1 -5.00-
^
Cdmx
Oct. 1 Dec
. 31 Marc
^^
h 31 Jun<
Open
Cdmx
5 30 Sept. 30
DATE
Figure 111.100.—Baseline seasonal soil moisture recharge requirements for the New
England/Lake States hydrologic region (1)—all energy aspects.
+1.00'
0.00—Open
- -1.00-
LU
^
LU
CC
-2.00-
o
oi -3.00—
cc
oi
-4.00-
I
O
01
-5.00—
-6.00-
•'dmx
Oct. 1
Open
'dmx
Dec. 31
March 31
DATE
June 30
Sept. 30
Figure 111.101.—Seasonal soil moisture recharge requirements for the New England/Lake states
hydrologic region (1)—low energy aspects.
III. 138
-------
+1.00
w 0.00 -
.c
o
^c
H- -1.00-
LU
I -2.00-
D
O
LU
DC -3.00-
LLJ
DC
O
OJ
DC
-4.00
-5.00 —
-6.00
'dmx
Oct. 1
Dec. 31
March 31
DATE
dmx
June 30
Sept. 30
Figure 111.102.—Seasonal soil moisture recharge requirements for the New England/Lake States
hydrologic region (1)—intermediate energy aspects.
+1.00
« 0.00~T Open
^
o
(-' -1.00-
u
-2.00-
O
-3.00 —
LU
O
< -4.00-
I
O
LU
CC
-5.00 '
'dmx
Oct. 1
Dec. 31
dmx
March 31
DATE
June 30
Sept. 30
Figure 111.103.—Seasonal soil moisture recharge requirements for the New England/Lake States
hydrologic region (1)—high energy aspects.
III. 139
-------
PREDICTING INDIVIDUAL STORM
RESPONSES
It is beyond the scope of this handbook to recom-
mend a stormflow prediction technique for specific
application. There are too many local techniques,
which may be far superior to any generalized ap-
proach, to warrant the presentation of a
generalized approach. It is recommended that the
technique best suited to a specific area be used. A
key criterion for selection, however, should be
whether or not the technique is sensitive to antece-
dent conditions. The whole basis for evaluating the
effect of silvicultural activities on stormflow is
through the changes which occur in antecedent
conditions. Any technique not sensitive to antece-
dent conditions would not reflect the impact of
silviculture.
All existing methodologies have significant
predictive errors, so the absolute magnitude of the
event will contain those errors regardless of the
method. However, a reasonable technique sensitive
to antecedent conditions should give an adequate
estimate of change.
One method, although regional in use, is the R
Index method (Hewlett and others 1977), shown to
work well in the East. Another method, not
process-oriented but sensitive to antecedent condi-
tions, is the SCS method (Soil Conservation Ser-
vice 1973). Chow (1974) lists several other methods,
while McCuen and others (1977) present an an-
notated bibliography of flood flow frequency
techniques.
The point to remember in the stormflow analysis
is that the change due to silviculture will equal or
be less than the change in the soil water balance.
Any time the balance for pre- and post-silvicultural
activity conditions is similar, so will be the ex-
pected response to individual events. By the same
token, response to precipitation events with greater
than a 1-year return period will become less af-
fected by treatment as the return period increases.
Most events capable of causing significant destruc-
tion will be unaffected or at least insignificantly so.
Following is a very brief discussion of the major
consideration in predicting individual storm re-
sponses and in selecting the design event.
Basis For Evaluating The Design Event
Dealing with individual events within the con-
text of this handbook is a twofold consideration.
First, there is the problem of quantifying the
magnitude or frequency of the event; and second,
estimating the expected change in that design
event due to silvicultural activities.
From the outset, it should be noted that there are
two levels of flood design; that is, one can design for
either major or minor projects. Major implies a risk
to human life. Minor implies no risk to life or limb.
From the standpoint of silvicultural activities,
design events are restricted to minor projects only.
There are two basic approaches for evaluating
the design event.
(1) An evaluation can be made of the probability
of equalling or exceeding a particular level of flow
or design flood. This can be done by performing a
flood frequency analysis on a historical flow record
for the site. This involves the ranking of various
levels of flow and the probability associated with
the probability of reoccurrence. Techniques for do-
ing this have been fairly well documented (Water
Resources Council 1967).
Two problems arise, however. First, one cannot
expect the historical record to be available and,
second, if it were available, handbooks or empirical
methodologies would not be available for determin-
ing the impact that silvicultural activities have on
a particular event.
The alternative approach is to determine the
hydrologic response expected from a design
precipitation or "input" event. This precipitation
input could be from rainfall, snowmelt, or rain on
snow. In doing this, the assumption is made that
the reoccurrence interval for rainfall is the same as
the flood event it produces. This is not necessarily
true, of course, because the design precipitation
event may produce a runoff event with a frequency
of occurrence less than or greater than the
precipitation event causing it. Larson and Reich
(1973) as well as others, however, found that the
relationship did average out for small watersheds
in Pennsylvania. They found that over the long-
term record the average difference in ranking
between return period for the precipitation event
and the return period for the resulting flow event
was zero. The variability in response to successive
events on the same basin is largely due to differing
antecedent conditions (Hewlett and others 1977) at
the time of the storm.
The latter approach, or design based on
precipitation, lends itself well to a stormflow
analysis consistent with this handbook. The soil
moisture distributions presented provide an es-
timate of antecedent conditions for both pre- and
post-silvicultural treatment conditions.
III. 140
-------
As noted, silvicultural activities require design-
ing for minor projects. Because of the relatively
small areas involved and the limited downstream
effect of silvicultural activities, the risks from in-
dividual events and the changes in them due to
silvicultural activities are usually associated with
the likelihood of a local, onsite failure (such as ex-
ceeding a culvert or bridge capacity, washing out
roads or drainage structures, exceeding channel
capacities, and other failures due to excessive on-
site water).
Selecting The Return Period For The Design
Event
Two factors need to be considered in selecting
the return period for the design event. The first is
the risk of failure that the planner is willing to ac-
cept during the life of the project. The second is the
expected life of the project or impact. The com-
bination of the acceptable risk of failure and ex-
pected life of the project combine to yield the
return period for the design storm. Techniques for
doing this are defined in Chow (1964), as well as in
most other hydrology textbooks.
Usually, the planner can accept a relatively high
risk of failure over a relatively short project life.
The result is that the concern is usually with the
magnitude of the annual, the 5-, or the 10-year
event. It must be remembered that the impacts of
silvicultural activities on a particular event are
really minimal in light of the variability between
individual events.
Silvicultural activities can significantly affect
frequent events of perhaps less than 1-year return
periods. They have minor, if any, effect on the an-
nual event and have an almost insignificant effect
on the 5- or 10-year event. Once the antecedent
conditions for pre- and post-silvicultural activity
conditions are equal, then the potential for a
significant response due to activity is eliminated.
This would be true whenever the soil moisture
modifier coefficients presented earlier are unity.
Selection Of Precipitation Input
Once the appropriate design event has been
selected, the precipitation input can be used from
onsite data by evaluating the return period; or, it
can be obtained from precipitation frequency
tables for the region (i.e., USWB 1961).
HI.141
-------
CONCLUSIONS
The impacts of silvicultural activities upon
potential streamflow can be evaluated using
procedures for either the snowpack or rainfall
regimes; both procedures will give an estimate of
the expected change in flow. The form of the out-
put varies depending upon the methodology used.
This discrepancy presents little problem, however,
since both the distribution graph and the flow
duration curve are acceptable, useful means of dis-
tributing and interpreting expected potential flow.
Estimates of potential flow (in area-inches) may
be converted to average daily discharge (in cubic
feet per second) and used in the total potential
sediment analysis (ch. VI). The estimate of dis-
charge represents the average discharge for the
period of time determined by the duration curve in-
terval or by the dated intervals. In either case, the
basic simulation interval upon which all distribu-
tions and duration curves are based is either a 6- or
7-day estimate.
Estimations of the potential impacts of a
proposed silvicultural activity upon potential
streamflow may be determined through use of the
procedures presented in this chapter. It is impor-
tant to combine such analysis with sound profes-
sional judgment and interpretation of the es-
timated impacts according to inherent errors and
local conditions. Combining analysis with profes-
sional interpretation should result in a reasonable
estimate of the potential impacts of management
alternatives consistent with the current state-of-
the-art in hydrology.
HI.142
-------
LITERATURE CITED
American Society of Civil Engineers. 1975.
Sedimentation engineering. Sediment. Comm.
Hydraul. Div. New York. 745 p.
Anderson, E. A. 1976. Snowpack energy balance
model: National Oceanographic and At-
mospheric Administration technical memoran-
dum. Natl. Weather Serv., NOAA. U.S. Dep.
Comm., Silver Spring, Md.
Anderson, H. W., M. D. Hoover, and K. G.
Reinhart. 1976. Forests and water: effects of
forest management on floods, sedimentation,
and water supply. USDA For. Serv. Gen. Tech.
Rep. PSW-18. 115 p. Pac. Southwest For. and
Range Exp. Stn., Berkeley, Calif.
Bailey, R. G. 1976. Ecoregions of the United States.
' USDA For. Serv., Ogden, Utah. 1 p.
Barr, A. J., J. H. Goodnight, J. P. Sail, and J. T.
Helwig. 1976. A user's guide to SAS 76. 329 p.
Sparks Press, Raleigh, N.C.
Bates, C.G., and A. J. Henry. 1928. Forest and
streamflow experiment at Wagon Wheel Gap,
Colorado. U.S. Monthly Weather Rev. Suppl. 30.
79 p.
Baumgartner, A. 1967. Energetic basis for differen-
tial vaporization from forest and agricultural
lands. In Forest hydrology, p. 381-389. W. E.
Sopper and H. W. Lull, eds. Pergamon Press,
N.Y.
Beasley, R. S. 1976. Contribution of subsurface
flow from the upper slopes of forested watersheds
to channel flow. Proc. Soil Sci. Soc. Am. 40:955-
957.
Bouchet, R. J. 1963. Climatic significance of actual
and potential evapotranspiration. Int. Assoc.
Sci. Hydrol. Publ. 62, p. 134-142.
Brown, G. W. 1973. Measuring transmitted global
radiation with fixed and moving sensors. Agric.
Meteorol. 11, p. 115-121.
Buckman, H. 0., and N. C. Brady. 1966. The
nature and properties of soils. 567 p. Macmillan
Co., N.Y.
Chow, V. T. 1964. Handbook of applied hydrology.
McGraw-Hill, N.Y.
Colman, E. A. 1953. Vegetation and watershed
management. 412 p. Ronald Press, N.Y.
Douglass, J.E. 1967. Effects of specie arrangement
of forests on evapotranspiration. In Forest
hydrology. W. E. Sopper and H. E. Lull, eds.
Pergamon Press, N.Y.
Douglass, J. E., and W. T. Swank. 1975. Effects of
management practices on water quality and
quantity: Coweeta hydrologic laboratory, North
Carolina. In Municipal watershed management
symposium proceedings. USDA For. Serv. Gen.
Tech. Rep. NE-13, p. 1-13. Northeast. For. Exp.
Stn.
Farnes, P. A. 1975. Preliminary report-suspended
sediment measurements in Montana. Soil
Conserv. Serv., Bozeman, Mont.
Federer, C.A. 1972. Solar radiation absorption by
leafless hardwood forests. Agric. Meteorol. (9): 3-
20.
Forrester, J. W. 1969. Industrial dynamics. 464 p.
M.I.T. Press, Mass. Inst. Tech., Cambridge,
Mass.
Frank, E. C., and R. Lee. 1966. Potential solar
beam irradiation on slopes. Tables for 30° to 50°
latitude. U.S. For. Serv. Res. Pap. RM-18,116 p.
Rocky Mt. For. and Range Exp. Stn., Fort Col-
lins, Colo.
Freeland, F. D. Jr. 1956. The effects of a complete
cutting of forest vegetation and subsequent an-
nual cutting off of regrowth upon some pedologic
and hydrologic characteristics of a watershed in
the southern Appalachians. Ph.D. thesis.
Michigan State Univ. 182 p.
Garstka, W. U., L. D. Love, B. C. Goodell, and F.
A. Bertie. 1958. Factors affecting snowmelt and
streamflow. U.S. Dep. Inter. Bur. Reclam. and
U.S. Dep. Agric. For. Serv. 189 p.
Gay, L. W., K. R. Knoerr, and M. 0. Braaten.
1971. Solar radiation variability on the floor of a
pine plantation. Agric. Meteorol. (8):39-50.
Godell, B. C. 1967. Watershed treatment effects on
evapotranspiration. In Forest hydrology. W. E.
Sopper and H. E. Lull, eds. p. 477-482.
Pergamon Press, N.Y.
HI.143
-------
Goldstein, R. A., and J. B. Mankin. 1972.
PROSPER: a model of atmosphere-soil-plant
water flow. p. 1176-1181. Proc. Summer Comput.
Simul. Conf., San Diego.
Goldstein, R. A., J. B. Mankin, andR. J. Luxmore.
1974. Documentation of PROSPER: a model of
atmosphere-soil-plant water flow. Environ. Sci.
Div. Publ. No. 579. Oak Ridge Natl. Lab., Tenn.
75 p.
Green, R. E., and I. C. Corey. 1971. Calculation of
hydraulic conductivity: a further evaluation of
some predictive methods. Proc. Soil Sci. Soc.
Am. 25:3-8.
Haeffner, A. D., C. F. Leaf, G. E. Brink, and D. E.
Sturges. 1974. Hydrologic model of
range/sagebrush lands. File Rep. USDA For.
Serv., Laramie, Wyo.
Hamon, W.R. 1961. Estimating potential
evapotranspiration. Am. Soc. Civ. Eng., J.
Hydraul. Div. 87(HY3):107-120.
Harr, R. D. 1976. Forest practices and streamflow
in western Oregon. USDA For. Serv. Gen. Tech.
Rep. PNW-49. 18 p. Pac. Northwest For. and
Range Exp. Stn., Portland, Oreg.
Helvey, J. D. 1971a. A summary of rainfall in-
terception by certain conifers of North America.
Proc. Int. Semin. Hydrol. Professors, Purdue
Univ., Ind. p. 103-113.
Helvey, J. D. 1971b. Predicting soil moisture in the
southern Appalachians. Thesis. Sch. For.
Resour., Univ. Ga., Athens. 79 p.
Helvey, J. D., J. D. Hewlett, and J. E. Douglass.
1972. Predicting soil moisture in the southern
Appalachians. Soil Sci. Soc. Am. Proc. 36:6:954-
959.
Hewlett, J.D., G.B. Cunningham, and C.A.Troen-
dle. 1977. Predicting stormflow and peak flow
from small basins in humid areas by the
R-index method. Water Res. BuU.13(2):351-374.
Hewlett, J. D., and J. E. Douglass. 1968. Blending
forest uses. USDA Agric. For. Serv. Res. Pap.
SE-37. 15 p. Southeast For. Exp. Stn.
Hewlett, J. D., and A. R. Hibbert. 1967. Factors af-
fecting the response of small watersheds to
precipitation in humid areas. In Forest
hydrology. W. E. Sopper and H. E. Lull, eds.
Pergamon Press, N.Y.
Hewlett, J. D., and C. A. Troendle. 1975. Non-
point and diffused water sources: a variable
source area problem. Proc. Am. Soc. Civ. Eng.
Symp., Irrig. and Drain. Div., Logan, Utah.
Hibbert, A. R. 1967. Forest treatment effects on
water yield. In Forest hydrology. W. E. Sopper
and H. E. Lull, eds. Pergamon Press, N.Y.
Hoover, M. D. 1971. Snow interception and
redistribution in the forest Proc. Int. Semin.
Hydrol. Professors, Purdue Univ., Ind. 3:114-122.
Hoover, M. D., and C. F. Leaf. 1967. Process and
significance of interception in Colorado sub-
alpine forest. In Forest hydrology. W. E. Sopper
and H. W. Lull, eds. 813 p. Pergamon Press,
N.Y.
Hornbeck, J. W., and C. A Federer. 1975. Effects of
management practices on water quality and
quantity: Hubbard Brook Experimental Forest,
New Hampshire. In Municipal watershed
management symposium proceedings. W. E.
Sopper and E. S. Corbett, eds. USDA For. Serv.
Gen. Tech. Rep. NE-13. p. 58-65. Northeast. For.
Exp. Stn.
Jones, E. B., and C. F. Leaf. 1975. Generalized
criteria for verification of water developed
through weather modification. Final Rep. to
Water Res. Tech., USDA Contract 14-31-0001-
9020. 154 p.
Kittredge, J. 1948. Forest influences. 394 p.
McGraw-Hill, N.Y.
Kittredge, J. 1953. Influences of forests on snow in
the ponderosa-sugar pine-fir zone of the central
Sierra Nevada. Hilgardia, Univ. Calif., Berkeley.
96 p.
Kochenderfer, J. N., and C. A Troendle. 1971. Soil
moisture under white pine and mixed hardwood
forest. (Abstr.) Trans. Am. Geophys. Union
52(4):201.
Lane, E. W. 1955. The importance of fluvia
geomorphology in hydraulic engineering. Proc.
Am. Soc. Civ. Eng., Vol. 81, Pap. No. 745.
Larson, C. L., and B. M. Reich. 1973. Relationship
of observed rainfall and runoff recurrence inter-
vals. In Floods and droughts, p. 34-43. E. F.
Schulz, V. A. Koelyer, and K. Mahmood, eds.
Proc. Second Int. Symp. Hydrol. Water Resour.
Publ., Fort Collins, Colo.
Leaf, C. F. 1970. Sediment yields from Colorado
snow zone. Proc. Am. Soc. Civ. Eng. J. Hydraul.
Div. Pap. 7005, 96(HYl):87-93.
III.144
-------
Leaf, C. F. 1974. A model for predicting erosion and
sediment yield from secondary forest road con-
struction. USDA For. Serv. Res. Note RM-274. 4
p. Rocky Mt. For. and Range Exp. Stn., Fort
Collins, Colo.
Leaf, C. F. 1975. Watershed management in the
Rocky Mountain subalpine zone: the status of
our knowledge. USDA For. Serv. Res. Pap. RM-
137. 31 p. Rocky Mt. For. and Range Exp. Stn.,
Fort Collins, Colo.
Leaf, C. F., and G. E. Brink. 1973a. Computer
simulation of snowmelt within a Colorado sub-
alpine watershed. USDA For. Serv. Res. Pap.
RM-99. 22 p. Rocky Mt. For. and Range Exp.
Stn., Fort Collins, Colo.
Leaf, C. F., and G. E. Brink. 1973b. Hydrologic
simulation model of Colorado subalpine forest.
USDA For. Serv. Res. Pap. RM-107. 23 p. Rocky
Mt. For. and Range Exp. Stn., Fort Collins,
Colo.
Leaf, C. F., and G. E. Brink. 1975. Land use
simulation model of the subalpine coniferous
forest zone. USDA For. Serv. Res. Pap. RM-135.
42 p. Rocky Mt. For. and Range Exp. Stn., Fort
Collins, Colo.
Lee. R. 1963. Evaluation of solar beam irradiation
as a climatic parameter of mountain watersheds.
Hydrol. Pap. No. 2. Colo. State Univ., Fort Col-
lins. 50 p.
Leopold, L. B., and W. Emmet. 1976. Bedload
measurements, East Fork River, Wyoming. (Un-
publ. Rep.)
Leopold, L. B., M. G. Wolman, and J. P. Miller.
1964. Fluvial processes in geomorphology. 522 p.
W. H. Freeman and Co., San Francisco.
Longwell, T. J., W. L. Parks and M. E. Springer.
1963. The moisture characteristics of Tennessee
soil. Tenn. Agric. Exp. Sta. Bull. 367. Knoxville,
Tenn. 46 p.
Lull, H. W., and I. C. Reigner. 1967. Radiation
measurements by various instruments in the
open and forest. U.S. For. Serv. Res. Pap. NE-
84. 21 p. Northeast For. Exp. Stn.
Luxmore, R. J., J. L. Stolzy, and J. T. Haldeman.
1976. Some sensitivity analyses of an hourly soil-
plant relations model. Environ. Sci. Div. Publ.
No. 847. Oak Ridge Natl. Lab., Tenn. 53 p.
McCuen, R. H., W. J. Rawls, G. T. Fisher, and R.
L. Powell. 1977. Flood flow frequency for un-
gaged watersheds: a literature evaluation. U.S.
Dep. Agric., Agric. Res. Serv. ARS-NE-86. 136 p.
McMinn, J. W., and J. D. Hewlett. 1975. First-year
water yield increase after forest cutting: an alter-
native model. J. For. 73:654-655.
Markovic, R. D. 1966. Statistical evaluation of
weather modification attainments. Hydrol. Pap.
No. 16. Colo. State Univ., Fort Collins. 44 p.
Megahan, W. F. 1974. Erosion over time on
severely disturbed granitic soils; a model. USDA
For. Serv. Res. Pap. INT-156. 14 p. Intermt. For.
and Range Exp. Stn., Ogden, Utah.
Megahan, W. F., and W. J. Kidd. 1972. Effects of
logging and logging roads on erosion and sedi-
ment deposition from steep terrain. J. For.
70:136-141.
Merriam, R. A. 1960. A note on the interception
loss equation. J. Geophys. Res. 65:3850-3851.
Miller, D. H. 1959. Transmission of insolation
through pine forest canopy as it affects the
melting of snow. Mitt Schweiz. Anst. forstl. Ver-
suchsw. 35:35-79.
Miller, D. L. 1964. Interception processes during
snowstorms. U.S. For. Serv. Res. Pap. PSW-18.
24 p. Pac. Southwest For. and Range Exp. Stn.,
Berkeley, Calif.
Miller, D. W., J. J. Geraghty, and R. S. Collins.
1962. Water atlas of the United States. Water
Inf. Cent., Inc. Port Washington, L.I., N.Y.
40 p.
Miller, E. E. and A. Klute. 1967. The dynamics of
soil water. Part I—mechanical forces. Agronomy
II. Amer. Soc. of Agronomy. Madison, Wise. p.
209-244.
Millington, R. J., and J. P. Quirk. 1959.
Permeability of porous media. Nature 183:387-
388.
Morton, F. I. 1971. Catchment evaporation and
potential evaporation further development of a
climatological relationship. J. Hydrol. 12:81-99.
Muller, R. A. 1971. Transmission components of
solar radiation in pine stands in relation to
climatic and stand variables. USDA For. Serv.
Res. Pap. PSW-71. 13 p. Pac. Southwest For.
and Range Exp. Stn., Berkeley, Calif.
III.145
-------
Northeastern Forest Experimental Station. 1975.
Municipal watershed management symposium
proceedings. USDA For. Serv. Gen. Tech. Rep.
NE-13. 196 p. Northeast For. Exp. Stn.
Patric, J. H. 1969. Changes in streamflow, duration
of flow, and water quality on two partially clear-
cut watersheds in West Virginia. (Abstr.) Trans.
Am. Geophys. Union 50(4) :144.
Patric, J. H. 1974. Soil-water relationships in uncut
and cut forests. In Notebook for logging road and
skid trail workshops. W. Va. Coop. Ext. Serv.
Patric, J. H. 1976. Article on hydrology. In
McGraw-Hill yearbook of science and
technology. McGraw-Hill, N.Y.
Penman, H. L. 1967. Evaporation from forests: a
comparison of theory and observation. In Forest
hydrology. W. E. Sopper and H. E. Lull, eds.
Pergamon Press, N.Y.
Peters, L. N., D. F. Grigal, J. W. Curlin, and W. J.
Selvidge. 1970. Walker Branch watershed pro-
ject: chemical, physical, and morphological
properties of the soils of the Walker Branch
watershed. ORNL-TM-2968 (Oak Ridge
National Laboratory, Tennessee). 96 p.
Reinhart, K. G. 1963. Effect on streamflow of four
forest practices in the mountains of West
Virginia. US For. Serv. Res. Pap. NE-1. 79 p.
Rosgen, D. L. 1975. Preliminary report —
procedures for quantifying sediment production
USDA For. Serv., Sandpoint, Idaho.
Rosgen, D. L. 1976. Channel processes. In
Guidelines for evaluating and controlling non-
point source pollution from silvicultural ac-
tivities. EPA-FS Interagency agreement EPA-
IAG-D6-0660, (review draft). U.S. Dep. Agric.
For. Serv. Watershed Sys. Dev. Unit, Fort Col-
lins, Colo.
Rosgen, D. L. 1977. Field procedures for quantify-
ing hydrologic impacts and sediment yields from
silvicultural activities — a workshop. USDA For.
Serv. Arapaho-Roosevelt Natl. For., Fort Col-
lins, Colo.
Satterlund, D. R. 1967. Forest types on potential
runoff. In Forest hydrology. W. E. Sopper and H.
E. Lull, eds. Pergamon Press, N.Y.
Satterlund, D. R., and H. F. Haupt. 1967. Snow
catch by conifer crowns. Water Resour. Res.
3(4): 1035-1039.
Shomaker, C. E. 1968. Solar radiation measure-
ments under a spruce and a birch canopy during
May and June. For. Sci. 14(l):31-38.
Simons, D. B., R. M. Li, and M. A. Stevens. 1975.
Development of models for predicting water and
sediment routing and yield from storms on small
watersheds. USDA For. Serv., Rocky Mt. For.
Range Exp. Stn. 130 p. Fort Collins, Colo.
Smith, J. L. 1974. Hydrology of warm snowpacks
and their effects upon water delivery — some
new concepts. In Advanced concepts and tech-
niques in the study of snow and ice resources.
Natl. Acad. Sci., Washington, D.C.
Smith, J. L. 1975. Water yield improvement of the
Pacific Southwest Forest and Range Experiment
Station and its usefulness to wildland resource
management. Proc. Lake Tahoe Res. Semin. IV.
Lake Tahoe Coord. Board and Lake Tahoe En-
viron. Educ. Consortium. South Lake Tahoe,
Calif.
Sohn, R. L., L. Becker, J. Estes, D. Simonett, and
W. H. Yeh. 1976. Analysis of information
systems for hydropower operations. Rep. to. Off.
Energy Programs, Natl. Aeronaut. Space Adm.,
Jet Propul. Lab., Calif. Inst. Technol.,
Pasadena. 161 p.
Soloman, R. M., P. F. Folliott, and J. R.
Thompson. 1976. Correlation between transmis-
sivity and basal area in Arizona ponderosa pine
forests. USDA For. Serv. Res. Note RM-318. 3 p.
Rocky Mt. For. and Range Exp. Stn., Fort Col-
lins, Colo.
Sopper, W. E., and H. W. Lull, eds. 1967. Forest
hydrology. Int. Symp. For. Hydrol. 813 p.
Pergamon Press, N.Y.
Swanson, R. H., and G. R. Hillman. 1977.
Predicting increased water yield after clearcut-
ting verified in west-central Alberta. Inf. Rep.
NOR-X-198. North. For. Res. Cent., Edmonton,
Alberta. 40 p.
Swift, L. W., W. T. Swank, J. B. Mankin, and
others. 1975. Simulation of evapotranspiration
and drainage from mature and clearcut
deciduous forests and young pine plantations.
Water Resour. Res. 2(5):667-673.
III. 146
-------
Tabler, R. D. 1975. Estimating the transport and
evaporation of blowing snow. Proc. Symp. Snow
Manage. Great Plains. Great Plains Agric.
Counc. Bismark, N.Dak.
Tajchman, S. J. 1971. Evapotranspiration and
energy balances of forest and field. Water
Resour. Res. 7:511-523.
Tichendorf, W. G. 1969. Tracing stormflow to vary-
ing source areas in a small, forested watershed in
the southeastern piedmont. Ph.D. Diss., Univ.
Ga., Athens, Univ. Microfilms, Ann Arbor,
Mich. 114 p.
Troendle, C. A. 1970. A comparison of soil-
moisture loss from forested and clearcut areas in
West Virginia. USDA For. Serv. Res. Note NE-
120. 8 p. Northeast For. Exp. Stn.
U.S. Army, Corps of Engineers. 1956. Snow
hydrology: summary. North Pac. Div., Portland,
Oreg. 437 p.
U.S. Army, Corps of Engineers. 1960. Runoff from
snowmelt. EM 1110-2-1406. 59 p.
U.S. Department of Agriculture, Agricultural
Research Service. 1975. Present and prospective
technology for predicting sediment yields and
sources. Proc. Sediment-Yield Workshop. U.S.
Dep. Agric. Sediment ARS-S-40. 285 p.
U.S. Department of Agriculture, Forest Service.
1975. Stream reach inventory and channel
stability evaluation. North. Reg., Missoula,
Mont. 26 p.
U.S. Department of Agriculture, Forest Service.
1976. Management alternatives for the Diamond
Creek Planning Unit, Caribou National Forest.
677-357/9. 224 p. U.S. Gov. Print. Off.,
Washington, D.C.
U.S. Department of Agriculture, Forest Service.
1977. Non-point water quality modeling in
wildland management: a state-of-the-art assess-
ment. Vol. II. Interagency Agreement No. EPA-
IAG-D5-0660. Environ. Protect. Agency, Athens,
Ga.
U.S. Department of Agriculture, Forest Service
and Environmental Protection Agency. 1976.
EPA—Forest Service phase I study. Produced
under U.S. Dep Agric. For. Serv.—Environ.
Protect. Agency Interagency Agreement EPA-
IAG-D5-0660.
U.S. Department of Agriculture, Soil Conservation
Service. 1972. Soil Conservation Service national
engineering handbook, section 4: hydrology. U.S.
Gov. Print. Off., Washington, D.C.
U.S. Department of Interior, Geological Survey.
1973. Water resource data for Colorado, 1969-
1973. Part I. U.S. Dep. Inter., Geol. Surv.,
Denver.
U.S. Weather Bureau. 1961. Rainfall frequency
atlas of the United States for durations from 30
minutes to 24 hours and return periods from 1 to
100 years. Tech. Rep. 40. 115 p.
Utah Water Research Laboratory. 1976. Erosion
control during highway construction — volume
II. Natl. Coop. Highway Res. Prog., Trans. Res.
Board, Nat. Res. Counc. Proj. 16-3, Utah State
Univ., Logan. 103 p.
Verry, E. S. 1976. Estimating water yield dif-
ferences between hardwood and pine forests.
USDA For. Serv. Res. Pap. NC-128. 12 p. North
Cent. For. and Range Exp. Stn., St. Paul, Minn.
Ve'zina, P. E. 1965. Solar radiation available below
thinned and unthinned balsam fir canopies.
Publ. No. 1105, 15 p. Can. Dep. For., Ottawa.
Water Resources Council. 1967. A uniform tech-
nique for determining flood-flow frequencies.
Bull. No. 15, Washington, D.C. 15 p.
Willen, D. W., C. A. Shumway, and J. E. Reid.
1971. Simulation of daily snow water equivalent
and melt. Proc. West. Snow Conf. 39:1-8. Bill-
ings, Mont.
Wischmeier, W. H., and D. D. Smith. 1965.
Predicting rainfall-erosion losses from cropland
east of the Rocky Mountains. U.S. Dep. Agric.,
Agric. Handb. No. 282. 48 p.
Zahner, R. 1967. Refinement in empirical functions
for realistic soil-moisture regimes under forest
cover. In Forest hydrology, p. 261-272. W. E.
Sopper and H. W. Lull, eds. Pergamon Press,
N.Y.
m.i47
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APPENDIX III.A: EFFECT OF LARGE OPENINGS ON EVAPORATION
AND TRANSPORT OF BLOWING SNOW
The technical basis for low snowpack retention in
large openings is derived from Tabler's ongoing
studies on the evaporation and transport of blowing
snow. Tabler surveyed snow accumulation patterns
in and around numerous large clearcuts in Wyom-
ing (Tabler 1975). His most recent results, in-
dicating seasonal snow accumulation patterns as-
sociated with large open areas (diameters > 15H)
(H = height of surrounding trees in feet) are shown
in figure III.A.I.1
Figure III.A. 1 shows a total of four zones that
must be analyzed to determine impacts from clear-
cutting large blocks:
Zone I —A 5 to 7H lee drift on the windward
margin
Zone II —A wind-exposed scour or fetch area
of indeterminate length
Zone HI —A IOH windward drift on the
leeward margin
Zone IV —A drift on the leeward margin whose
length is given by the equation:
LIy » 5H + 3Q/H
where:
Q = Total snow transport off the clearcut area
(D) in ft3 water equivalent/foot of width
normal to the prevailing wind
H = Height of surrounding trees
'Personal communication with Dr. Ronald D. Tabler, Rocky
Mountain Forest and Range Experiment Station, Laramie,
Wyoming.
Zone I
Wind
Zone II
8
Tabler has proposed equations for quantifying
seasonal snow accumulation in each of the four
zones. These equations are summarized in Table
m.A.i.
The terms in figure III.A. 1 and table HI.A.I are
defined as follows:
H = Height of surrounding trees
D = Clearcut diameter in feet (or width in
direction of wind)
Pa = Precipitation water equivalent in feet
a) = A coefficient which indexes the amount
of over winter snowpack ablation
(perhaps 0.2)
5 = Roughness (slash or regeneration height,
etc.) in feet
Q = Total snow transport off the clearcut area
(D) in ft3 water equivalent/ft of width
normal to the prevailing wind
The total water equivalent transport off the
clearcut block in ft3/ft can be computed by the
equation:
Q = 5000/U + 250 —a)| J0.87P;, - 0.26
H -i *•
+ (0.13P., - 0.155) a + (0.355 - 2P3/3)b
- P3c/3]
where: IOH
(EI.A.1)
a = 0.14
10,000
D-5H
b =0.14 10'000
D
10,000
U-5-7H-J
1
1
f Id — 1fiH --*-* -. . -I
8 -|
I
«-LIVa:5H + 3Q/H-t
Figure III.A.1.—General pattern of snow accumulation in large clearcut blocks (Tabler 1977).
m.148
-------
Table III.A.1.—Summary of equations for quantifying
snow accumulation In large clearcuts (D > 15H)
Zone
Parameter
Equation
Drift length
Max. snow aeptn
Precipitation retained
Precipitation relocated
Snowpack density
Effective length
Max. snow depth
Precipitation retained
Precipitation relocated
Snowpack density
Drift length
Max. snow depth
Precipitation retained
Precipitation relocated
L,= 5H
DMX| = 3.33P,
.Pi = (2/3) Pa
fl, = Pa/3
TSI ' '35
LM = D-15H
PII = 0.355
flu = O.SPa - 0.356 (assuming w = 0.2)
TSII = -35
LI,,* 10H
DMXIII * 0.3D MX|V= 0.35H
+ 0.20Hlog1Q
1
PHI* 0.07H+0.04Hlog10
flu, * Ps - 0.07H + 0.04Hlog10
UlH« )
fQ + pM
\8.1H2 /
Snowpack density
IV Total drift length
Max. snow depth
Location of max. depth
Deflation distance
(fig. III.A.2)
Snowpack density
Tsui * -40
L|V * 5H + 3Q/H
DMXIV" 1.18H + 0.65Hlog10
1 * 5H
d * 2H
TSIV* -45 '"•
/Q + PaLlv\
According to Tabler, there is, as yet, no accep-
table method for estimating the contribution of
Zone IE to the total snow transport Q. Reasonable
estimates for Q are obtained by assuming no net
contribution by Zone III (neither + nor —), leaving
a simplified version of equation HI.A.I:
Q * 5000 [(P:, - .356) (a - b) + (P:,/3) (b - c)]
Ignoring over-winter in-situ ablation (o> = 0.0)
and where terms are defined as above, if w were in-
cluded,
Q * 5000 [(P3 - wPs - .356) (a - b) + (1/3)
(b - c)]
Evaporation losses are computed from the equa-
tion:
Q,oss = P.^D - 1.53Q - 4.67P3H - 0.355D
+ 3.255H (III.A.2)
Equation III.A.2 can be changed in accordance
with the suggested revision of in.A.l, or (assuming
w = 0.0):
Qlos8~ P3(D - 10H) - Q - .355 (D - 15H)
- 10P3H/3 (m.A.3)
Figures III.A.2 through III.A.5 by Tabler
graphically show the effects of large clearcuts in
Wyoming. Undesirable impacts include not only
reduced snow accumulation, but also damage to
the residual forest from wind and excessive snow
accumulation in Zone IV.
HI.149
-------
5
H
g
Figure III.A.2.—Cinnabar Park, Medicine Bow National Forest
(elev. 9,600 ft). Origin of park la unknown, but may have
resulted from fire In young stand of lodgepole pine. A. Wind left
to right. Maximum width of park Is about 2,000 ft. B. Wind left
to right. Corridor or "snowglade" Is kept clear of trees by
snowdrift. C. Drift has maximum depth of about 35 ft.
-------
01
Figure III.A.3.—Snowglades forming downwind of clearcut
blocks on the Medicine Bow National Forest. This 45-acre
block was cut In 1967, with slash wlndrowed and burned in
1968. (Elev. = 10,000 ft; width parallel to wind—1,800 ft.) A.
Very little snow is retained on the clearcut—about 90% of
winter precipitation Is blown oft. B. Snowdrift Is 50 ft deep. C.
Damaged trees result In snow glade.
-------
.
Figure Ml.A.4.— Residual limber on downwind side of clearcut shown in fig. III.A.3. Late-lying
snowdrift keeps soil saturated throughout summer, making trees more vulnerable to windthrow.
A. Windfall was salvaged in 1974 in a strip 100 to 200 ft wide on downwind side of block. B.
Windfall between clearcut and glade accumulated since 1974 salvage. This view looks directly
into wind.
Figure III. A.5.—Windfall on lee side of 1972-73 clearcut. Wind is channeled into "corner" by forest
margin.
ffl.152
-------
APPENDIX III.B: HYDROLOGIC MODELING
PHILOSOPHY
Because of lack of sufficient data from ex-
perimental watersheds and the resulting inability
to characterize universal process response from the
experimental data available, process simulation
has been chosen as the basis for quantifying the
hydrologic impact. "Process" quickly became a
keyword in this effort and led to an important deci-
sion in the modeling effort — that physically based
process models were to be used wherever possible
rather than probalistic or stochastic models. Ex-
isting physically based mathematical models were
evaluated as part of an earlier Forest Service/EPA
contract EPA-600/3-77-078.
Mathematical modeling, or the objective
analysis of the information-feedback
characteristics of hydrologic systems, provides
criteria for estimating system hydrology, since
system structure, delay, and amplification are
taken into consideration. This modeling process re-
quires six basic steps as summarized by Jones and
Leaf (1975):
(1) Construction of a dynamic mathematical
model in which important interactions
between system components are defined.
(2) Programming and execution of the model
over a period of time on a digital computer.
(3) Comparison of model results against all per-
tinent available data. (The regional ap-
proach can be effectively used for model
validation.)
(4) Revision (tuning) of the model until it is ac-
ceptable as a representation of the actual
system.
(5) Alteration of certain model components in
order to represent changes in the real system.
(6) Repeat of step 3 to verify the "tuning" and/or
model alteration.
At each step in the above sequence, the previous
steps often need to be revised. The whole procedure
is not unlike the development of an aircraft or
automobile, where repeated design changes and
testing ultimately result in an operational
prototype.
However, all models are, in one way or another,
imperfect and simplified representations of reality;
there are limitations in the modeling approach. Ac-
curacy and validity of any model is not absolute
and has a meaning only relative to some prescribed
use. Consequently, subjective judgment is neces-
sary in selection, use and application; error is in-
herent in both the judgment made and the result
obtained. Errors in simulation may appear great,
but, given the present state-of-the-art, there is no
other way of quantifying a universal response
which can be interpolated to site specific applica-
tions.
Bear in mind that the danger in any quantitative
model-validation procedure is that it takes on an
"aura of authenticity" and may lead the inex-
perienced modeler to forget the underlying subjec-
tive assumptions. Primary confidence in modeling
must depend on: (1) how acceptable or plausible
the model is in describing natural processes, and
(2) the reasonable assumption that "if all the
necessary components are adequately described
and properly interrelated, the model system cannot
do other than behave as it should" (Forrester 1969).
Because much of the content of complex natural
system models is derived from nonquantitative
sources, the defense of such models ultimately
must rest in careful subjective evaluation of their
performance by experienced professionals who are
familiar with these systems.
In practice, the utility of a model lies in its
ability to precisely represent overall behavior of
natural systems and system response to changes in
one or more system components.
SELECTION OF THE MODELS USED
Several criteria were used in selecting ap-
propriate models.
An examination and evaluation were completed
on the structure of the models themselves, the
parameters used, and the means by which
parameters were estimated. Models that were
process-oriented were isolated; those that op-
timized parameter estimates to the point where
EI.153
-------
they no longer represented real-world inputs were
eliminated. In addition, those models having in-
herent feedback to the calibration phase which,
much like optimizing, detracted from true process
response were also eliminated. Adequate documen-
tation, referenced applications, and contact with
experienced users were relied upon heavily.
Selected models were process-oriented and did not
violate assumptions when in use. Finally, models
were selected according to the level of expertise, the
time frame, and the data base available.
After model selection, the second phase involved
testing and fitting the selected models to represen-
tative and experimental watersheds, evaluating
their range of applicability, and evaluating their
performance with respect to known responses.
The EPA/FS Phase I study (1976) reviewed
several models developed for forest hydrology.
They varied widely in terms of complexity and
scope, depending on their application. Most were
based on a practical engineering approach which
achieved a balance between theory, available data,
and operational objectives and constraints. The
successful application of each model depended to
some extent on empirical derivations of several
parameters and relationships, some of which were
unique to geographic areas.
Based on all the criteria and assumptions men-
tioned, two models were selected as the most
readily useful: The Subalpine Water Balance
Model (WATBAL) developed by Leaf and Brink
(1973b) and PROSPER (Goldstein and others
1974).
Other models may have been equally suited,
however, the two selected models best fit the re-
quirements of this handbook. It should be
emphasized that it was not an object of the selec-
tion process to promote any specific model.
GENERAL PRINCIPLES FOR APPLICATION
AND USE OF MODELS
Subalpine Water Balance Model Description
The Subalpine Water Balance Model (WAT-
BAL) was chosen because it had previously been
developed according to the above mentioned con-
cepts and because it was calibrated for the high-
elevation snowpack subalpine zones. This dynamic
hydrologic model was developed by the U.S. Forest
Service, and was specifically designed to simulate
the hydrologic impacts of watershed management
on snow pack (Leaf and Brink 1973b and 1975).
Figure III.B.l is a flow chart of the basic model.
Documentation for application of this model can be
found in appendix ni.C.
SET PHASE
INDICATOR TO
ACCUMULATION
PHASE
HO S
* <.
Figure III.B.1.—General flow chart of Subalpine Water
Balance Model (from Leaf and Brink 1973b). WATBAL model.
WATBAL models: (1) winter snow accumula-
tion, (2) the energy balance, (3) snowpack condi-
tion, and (4) resultant melt in time and space un-
der a variety of conditions. Combinations of aspect,
slope, elevation, and forest cover composition and
density are included. Much of the snowmelt por-
tion of the computer program was initially written
by the Watershed Systems Development Unit at
the Pacific Southwest Forest and Range Experi-
ment Station (Willen and others 1971). With this
snowmelt model, the probable effects of forest
cover manipulation have been simulated.
The model consists of three parts: (1) the deter-
mination of the form of precipitation (rain or
snow), (2) snowpack condition in terms of energy
level and free water requirements, and (3) the
melting process. Shortwave and longwave radia-
tion reaching the pack is estimated by means of a
transmissivity coefficient function, which depends
on the density and composition of the forest cover.
III. 154
-------
Radiation inputs are adjusted for slope and aspect.
Reflectivity of the snowpack is varied according to
precipitation, the energy balance, and time.
The snowpack is assumed to behave as a
dynamic heat reservoir; thus all elements in the
snowmelt portion of the model are expressed in
units of heat. The net external energy balance is
computed at the snow surface. Rain and snow are
converted from inches at the prevailing air
temperature to equivalent gram-calories. Each
precipitation event is added algebraically as a
caloric-heat event to develop the heat reservoir or
snowpack. Temperatures within the snowpack are
computed using unsteady heat flow theory. The
snowpack will yield melt water only when it has
reached a zero energy deficit (snowpack
temperature = 0°C) and its free water holding
capacity is satisfied. Snowmelt rates after the pack
is primed are governed primarily by the longwave
and shortwave energy balances at the snow surface.
Input Requirements For WATBAL
Data requirements for the Subalpine Water
Balance Model (WATBAL) are conventional. In-
formation, routinely available from such agencies
as the Soil Conservation Service, NASA, Forest
Service, Geological Survey, and National Weather
Service, is adequate for most applications. The
data requirements can be ranked in three
categories as follow:
1. Watershed characteristics
a. USGS topographic maps
b. USFS vegetation type maps
c. SCS soil survey data
2. Snowpack and snow cover extent
a. Conventional SCS snowcourse network
b. SCS SNOTEL network
c. NASA LANDSAT, etc.
3. Climatological data
a. Daily maximum and minimum
temperatures
b. Daily precipitation
The density of the available observation
networks will vary; however, as a rule of thumb, it
can be assumed that the snowcourse systems such
as SNOTEL will be adequate. Moreover, the den-
sity of the National Weather Service
Climatological Data network in the subalpine zone
also appears adequate for most purposes.
PROSPER Model
PROSPER is an atmosphere-soil-plant water
flow model that has been well documented (Golds-
tein and Manken 1972, Goldstein and others 1974)
and recently evaluated in the southern Ap-
palachians (Swift and others 1975). A schematic of
PROSPER is shown in figure m.B.2. The version
used has been operational on a daily basis, and a
description of the computational procedures for
each day follows (from Goldstein and others 1974):
(1) Precipitation for the day enters the system.
If there is no precipitation, the simulation
proceeds to step 2. Precipitation initially
enters the interception storage compartment
which has a maximum storage capacity as a
function of leaf area index. When the in-
terception compartment is full, any ad-
ditional precipitation becomes throughfall.
(2) If the intercept storage compartment does
not contain any water, i.e., if 60 = 0, then the
simulation proceeds to step 3.
If Bo > 0, then Fv(rx= 0) is calculated. Since
ra is the only resistance to evaporation of in-
tercepted water, rxis set to zero. If 9o>Fv(rx
= 0), then an amount of water equal to Fv(rx
= 0) is evaporated from the interception
storage compartment, Fw is set to zero, and
the simulation proceeds to step 3. If Fv(rx =
0) >9o then all of 9o is evaporated and an
amount of energy equal toLv9o (where Ly is
the latent heat of vaporization for water) is
subtracted from the total net radiation for
the day, RN. The adjusted value of RN will
be used instead of the total net radiation in
step 3.
(3) At this point, the simulation enters a loop to
calculate soil water transferred to the at-
mosphere by evapotranspiration and soil
water redistribution and drainage. In the
original implementation of PROSPER
(Goldstein and Mankin 1972a), the looping
structure was not incorporated into the com-
puter program. The saturated soil water con-
ductivities used in the original implementa-
tion were based on data for agricultural soils
(Miller and Klute 1967). For these values (on
the order of 1 cm/day) a single calculation of
soil water movement in a day using total
daily throughfall and solar radiation was
ni.155
-------
EVAPORATION
PRECIPITATION
EVAPOTRANSPIRATION
SURFACE 2
INTERCEPTION
STORAGE
EVAPOTRANSPIRATION SURFACE
ra+rx
THROUGHFALL
SURFACE 1
LATERAL FLOW
rs1
SOIL LAYER 1
-Wr
rrs1
rs12
SOIL LAYER 2
rrs2
rs23
rs,n-1,n
SOIL LAYER n
rp+rr1
VEGETATION
^ rr1+rr2
DRAINAGE
Figure III.B.2.—Schematic ol PROSPER (from Goldstein and others 1974).
m.i56
-------
adequate. However, saturated soil water con-
ductivities have been found to be two to
three orders of magnitude greater for forest
soils than for agricultural soils (Freeland
1956, Longwell and others 1963, Peters and
bthers 1969). For these high values of soil
water conductivity, single daily calculations
produce numerical instabilities. This neces-
sitates the inclusion of the loop structure
which makes N iterations in calculating the
daily water movement. The number of
passes through the loop, N, is dependent
upon throughfall, layer thickness, maximum
saturated soil water conductivity, and N for
the previous day.
(4) Upon entering the loop, soil water potentials,
conductivities and resistances are calculated
for the soil layers. One Nth of the daily
throughfall and net radiation are used to
calculate Fv [fx = gi(9x)] by the procedure
outlined in the previous section, unless Fx =
Fv [rx = gi(6 x )] has been set to zero in step
2, in which case the depletion of soil water by
evapotranspiration is zero. Also calculated
are 9X and Gj for all i. The volumetric soil
moisture content of each level, 9X , is read-
justed by 01 . If the moisture in any level ex-
ceeds saturation, the excess is removed by
lateral flow. The amount of water in the bot-
tom layer exceeding field capacity drains at a
rate equal to the hydraulic conductivity.
(5) If the program has not passed through the
loop N times at this point, the simulation
returns to step 3 and goes through the loop
again. If the simulation has gone through the
loop N times, then the daily total of
evapotranspiration, lateral flow from each
soil layer, and drainage are calculated by
summing the amounts calculated in each of
the N passes through the loop.
(6) The simulation proceeds to the next day and
returns to step 1.
Input Requirements For PROSPER
In general, daily precipitation, solar radiation,
temperature, vapor pressure, and average wind
speed are the climatic inputs. Vegetative inputs in-
clude the number of days from January 1 until the
vegetation is 50 percent leafed out and the number
of days from January 1 until 50 percent of the
leaves are off. An estimated, maximum (summer)
and minimum (winter), interception storage is also
needed, as are estimates of the leaf area index in
both summer and winter. Input requirements for
soil properties consist of moisture release curve
data for the upper two soil horizons (i.e., rooting
zone) and field capacity estimates for the other
three lower horizons. Also needed for input are the
saturated conductivity of the upper two horizons
and the moisture release-conductivity curves which
are generated internally using the techniques of
Millington and Quirk (1959) via the Green and
Corey (1971) program. Initial soil moisture con-
tents as well as field capacities for each of the five
layers are also needed.
Other parameters and coefficients are needed to
describe energy transfer rates and these were taken
from the PROSPER sensitivity analysis by Lux-
moore and others (1976) as there was little basis or
expertise for modifying them.
One constraint exists in the use of the PROSPER
model: The leaf area index-ET relationships were
developed for conditions that existed at Coweeta
Hydrologic Laboratory in North Carolina.
Although the universality of this function has not
been previously established, the model did perform
well when used elsewhere.
Model Output
By definition, neither PROSPER or WATBAL
are streamflow simulation models. PROSPER is
basically an evapotranspiration model with no sub-
surface routing components. WATBAL is a
snowmelt model and, like PROSPER, has no sub-
surface routing. Neither model is capable of
delivering water to a stream channel. The lateral
outflow and drainage simulated by these models
represents water which is on site and potentially
available for streamflow and may or may not repre-
sent routed streamflow.
The two models were each used for different
climatic regimes and there were differences in
modeling objectives and interpretation of each.
PROSPER was used primarily in humid, non-
snowpack areas; the rationale was to first simulate
evapotranspirational loss and then compare
seasonal and annual outflow with observed out-
flow. This comparison was usually acceptable.
Again the outflow simulated represented unrouted
water excess. However, the agreement between this
excess and observed streamflow improved as a
function of basin storage. Those shallow-soiled
basins with short resonance times or short "times
of concentration" had a fairly good correlation
between simulated excess water and observed flow.
III. 157
-------
Deep-soiled, slow responding watersheds like
Coweeta had poor correlations.
WATBAL was used primarily in regions where
significant snow packs develop, and where there
was need for a snowmelt routine. The same
problem of routing exists in WATBAL that exists
in PROSPER. However, the actual hydrograph
from the basins where WATBAL was used is
dominated by a seasonal snowpack and melt
runoff. This flow is more predictable, more con-
centrated, and the translation of melt to
streamflow is more direct. As a result, in those
hydrographs which are snowmelt-derived, there is
more direct correlation between simulated excess
water and actual streamflow. It was possible to pre-
sent this simulated flow as a time-serial
hydrograph. For those simulations that were rain-
fall driven, the timing of "simulated flows" was
distorted and delayed. It was unacceptable to pre-
sent these values as streamflow in any serial
presentation.
Since the magnitudes of simulated flow and
observed flow using PROSPER had similar fre-
quency distributions, the simulated outflow could
be presented in a frequency distribution (not time
dependent) as a representation of actual flow.
Again, both models adequately simulate the
evapotranspiration losses, and the simulated out-
flow is presented as water potentially available for
streamflow. No existing model actually simulates
an unbiased acceptable estimate of streamflow.
Existing models must be acceptable until better
models are developed.
In order to simulate treatment effect, after the
models were calibrated cover density parameters
affecting the intercepting and transpiring surfaces
were modified to estimate the response due to
treatment.
HI. 158
-------
APPENDIX III. C: CALIBRATION OF SUBALPINE
WATER BALANCE MODEL
The Subalpine Water Balance Model (Leaf and
Brink 1973b) was developed for, and has been suc-
cessfully applied to a number of representative
watersheds throughout the Rocky Mountain
region. For lack of a better tool, this model was also
used to simulate the snow pack hydrology of
representative watersheds in each hydrologic
region. This section illustrates application of the
model to a number of index watersheds.
INDEX WATERSHEDS
Each index watershed was divided into several
hydrologic subunits that vary according to slope,
elevation, aspect, and forest cover. The water
balance was simulated on each subunit; area-
weighted responses were computed and summed to
obtain the overall response for the entire basin.
Both time and spatial variations were thus taken
into account.
Daily temperature extremes in each of the sub-
units were estimated by extrapolating published
temperatures at nearby base stations, generally
cooperative stations operated by the National
Weather Service. Because reliable long-term radia-
tion data were not available for most areas,
shortwave radiation input to the model was
generated from potential solar beam radiation in-
put at the appropriate latitude, and then it was ad-
justed for the slope/aspect characteristics of each
subunit. These values were further adjusted by em-
pirically derived thermal factors to obtain an index
of incident shortwave radiation each day. Peak
seasonal snow accumulation was generally es-
timated from snow courses observed by the USDA
Soil Conservation Service.
Rocky Mountain/Intermountain Hydrologic
Region (4)
Mean annual water balances for representative
watersheds in the Rocky Mountain/Inland
hydrologic region (4) are summarized in table
IE.C.I. The Subalpine Water Balance Model was
calibrated and validated on each. The simulation
Table III.C.1.—Mean annual water balances (in Inches) for typical subalpine
watersheds in the Rocky Mountain/Inland Intermountain Region
Watershed
Seasonal
snowpack,
water
equivalent
Pre-
cipi-
tation
Evapo-
tran-
spira-
tion
Runoff
Colorado:
Soda Creek,
Routt NF
Fraser River,
Arapaho NF
Wolf Creek,
San Juan NF
Trinchera Creek,
SangredeCristo
Mountains
Wyoming:
South Tongue River
Bighorn NF
Montana:
W. Ford Stillwater
River, Custer NF
Idaho:
Diamond Creek,
Caribou NF
42.6
15.0
26.2
9.5
15.5
30.1
15.2
55.2
30.3
48.0
19.6
29.6
49.1
23.6
16.7
16.9
21.0
14.5
15.8
17.0
14.7
38.5
13.4
27.0
5.1
13.8
32.1
8.9
m.i59
-------
analysis for Wolf Creek, located in the San Juan
National Forest, Colorado is summarized below.
Leaf (1975) has previously summarized
hydrologic simulation analyses on Wolf Creek. The
watershed (fig. III.C.I) was divided into 11
hydrologic subunits that vary according to slope,
elevation, aspect, and forest cover (table III.C.2).
The water balance was simulated on each subunit;
area-weighted responses were computed and
summed to obtain the overall response for the en-
tire basin. Both time and spatial variations were
thus taken into account. Further division of forest
and open areas resulted in a total of 20 subunits
used for the simulation analysis (fig. III.C.2).
Daily temperature extremes in each of the sub-
units were estimated by extrapolating published
temperatures at Wolf Creek Pass IE, a cooperative
station operated by the National Weather Service.
Because reliable long-term radiation data were not
available in the Wolf Creek area, shortwave radia-
tion input to the model was generated from poten-
tial solar beam radiation at 38° N latitude and ad-
justed for the slope/aspect characteristics of each
subunit. These values were further adjusted by em-
pirically derived thermal factors to obtain an index
of incident shortwave radiation each day. Peak
snowpack accumulation on Wolf Creek was es-
timated from snowcourse transect data collected
by the USDA Soil Conservation Service and by
private contractors in the pilot project area. To in-
sure proper snowpack accumulation, the base sta-
tion daily precipitation was adjusted until the
specified water equivalent on each subunit was
reached to correct for errors in the spacially ex-
trapolated precipitation data.
Model Calibration
Eleven water years (1958-1968) were simulated
during calibration studies on Wolf Creek.
Published streamflow data during five subsequent
years (1969-1973) were then used to validate the
simulated output for the same period. This
analysis is shown in table III.C.3 on a monthly
residual volume basis to obtain a direct comparison
between potential excess water and the observed
snowmelt hydrograph. Streamflow data were ad-
justed to account for diversions from Wolf Creek
via the Treasure Pass Ditch (U.S. Dep. Inter.,
Geol. Surv. 1969-1973).
WOLF CREEK
12,000
11,000
9,000
SCALE - Mi.
Figure III.C.1.—Base map for Wolf Creek Watershed, San Juan National Forest, hydrologic subunits.
in. 160
-------
Table III.C.2.—Geographic description of the drainage basin, Wolf Creek watershed, Colorado (see figure III.C.1.).
Hydrologic Area
subunit
(sq. mi.)
Percent Sub-
of total unit
area code
Percent Percent Average Average Average Remarks
of of elevation aspect slope
division basin (ft) (%)
1 1.4
2 1.8
3 1.5
4 1.4
5 2.1
6 0.4
7 0.4
8 1.6
9 1.5
10 1.3
11 0.6
Total 14.0
10.3
12.6
11.0
9.8
14.8
2.6
3.1
11.2
10.8
9.5
4.3
100.0
1FW-0
10W-0
2FW-0
20W-0
3FW-121
30W-121
4FW-160
40 W- 160
5FW-192
50W-192
6FW-196
60W-196
7FW-9
70W-9
8FW-9
80W-9
9FW-45
10FW-45
11FW-76
110W-76
64.5
35.5
35.4
64.6
51.3
48.7
54.6
45.5
56.2
43.8
50.0
50.0
73.4
26.6
86.0
14.0
100.0
100.0
68.6
31.4
6.6
3.7
4.5
8.1
5.6
5.4
5.4
4.4
8.3
6.5
1.3
1.3
2.3
0.8
9.7
1.5
10.8
9.5
2.9
1.4
100.0
10,000
10,500
10,000
11,500
10,750
11,500
10,750
11,000
10,750
11,250
11,100
11,100
10,900
11,000
10,750
11,000
10,500
10,000
9,250
9,000
SE
SE
SE
SE
E
SE
S
SW
S
S
SW
SW
N
N
N
N
NW
NW
NW
W
40
40
30
40
20
40
20
45
35
40
30
20
15
15
10
10
20
15
45
50
Forest
Open
F
0
F
0
F
0
F
0
F
0
F
0
F
0
F
F
F
0
I F | FORESTED
ALPINE and OPEN
CLEAR CUT
SCALE - Mi.
Figure III.C.2.—Extent of forest cover on Wolf Creek Watershed.
m.161
-------
Table III.C.3.—Streamflow data (1969-1973) on a monthly residual volume basis, (inches) adjusted
to account for diversions from Wolf Creek.
Year
1969
1970
1971
1972
1973
May
0.08
0.05
0.04
0.19
0.02
June
0.25
0.32
0.33
0.17
0.56
July
0.07
0.07
0.03
0.00
0.36
Aug.
0
0
0
0
0.01
Total
0.40
0.44
0.40
0.36
0.95
Continental/Maritime Hydrologic Province (6)
In order to simulate the impacts of vegetative
manipulation in the Continental/Maritime
hydrologic province (6), an 8.1 square mile
watershed at the Corps of Engineers' Upper
Columbia Snow Lab (UCSL) was used as a study
area (U.S. Army 1956). The watershed is Skyland
Creek, a headwaters stream that supplies Bear
Creek, a tributary of the Middle fork of the
Flathead River in northwest Montana. Skyland
Creek is representative of most of the mountain
watersheds in Montana west of the Continental
Divide, with the possible exception of the Kootenai
drainage.
Skyland Creek watershed was divided for
analysis into seven subunits, with the objectives of
homogeneity with respect to slope, aspect, and
elevation, and proximity to a channel to reduce the
impact of routing (table ni.C.4). Several energy
slopes are represented. Skyland Creek is in an
elevation zone (5,000 to 7,500 ft.) that can be con-
sidered "high" in the northern Rockies. Low eleva-
tion zones (2,500 to 5,000 ft.) were also simulated.
Table III.C.4.—UCSL substation description
Sub
Unit
1
Area
(relative
to total)
percent
4
Slope Aspect
percent
40 W
Cover-
Type1 Density
percent
S-F 20
Eleva- General description
tion
x iooft
65-75 High steep breaklands;
10 25 NE S-F
21 20 NE LPP
11 25
15 45
31 30
Composite 100 30
(8.1 sq. mi.)
SW LPP
N LPP
LPP
30 SW
S-F
40
60
40
60
20
20
23% S-F 39
High energy
55-69 High moderate slope ridge;
Low Energy
49-58 Middle-high gentle slope
to stream;
Low energy
52-64 High ridge;
High energy
52-65 Middle-high steep ridge
to stream;
Very low energy
53-75 Middle to high moderate
slope
ridge to streamside;
Very high energy
59-69 High ridge;
Very high energy
49-75
'Vegetation types: LPP = Lodgepole pine; S-F = Spruce-fir
m.i62
-------
The technique will be outlined later in this report.
"Middle" elevation zones in this region are
probably not significantly different with respect to
commercial timber harvests; therefore, only two
zones were simulated.
Data for the calibration and validation phases
were derived from Snow Hydrology (U.S. Army
1956) and the associated logs. Water years (WY)
1947 through 1949 were used for calibration.
Calibration consisted of manipulation of several
parameters to enable the model to reproduce the
observed water balance and distribution of runoff
in the three years. Validation consisted of running
the calibrated model on three subsequent years
(WY 50-52) to compare the resulting output with
the observed hydrograph (table in.C.5).
Potential solar radiation was derived from Frank
and Lee (1966). Cover densities and vegetation
types were estimated from aerial photos and the
text (U.S. Army 1956). Potential evapotranspira-
tion by month was derived by Thornwaite's
method and modified by observed data. Soil
moisture holding capacities were developed from
comments in the text, and modified by energy-
elevation-vegetation observations. Transmis-
sivities (T) used are generally higher by .10 than
those suggested by the relationship T = .19 Cd^6
developed by Leaf and Brink (1973 b) in the central
Rockies. Transmissivity in the model controls the
incoming direct solar radiation to the snowpack
surface only. The model is very sensitive to T with
respect to the ripening of the snowpack. The higher
T's were necessary in the northern Rockies to make
the pack isothermal at an early date. Increases in
the corresponding cover densities (C d ) increases
the sublimation/evaporation losses beyond
reasonable limits. Note that C d used in the model
is highly subjective.
Reflectivity and melt thresholds were initially
set at suggested values valid in the central Rockies
and then were adjusted to help calibrate the model
for Skyland Creek.
Climatic data consisting of maximum and
minimum daily temperatures and daily precipita-
tion amounts for the base station at UCSL were
derived from laboratory logs for WY 47-52 and from
Climatological Data for Montana (Natl. Weather
Serv. 1953-1963) for WY 53-63. Some of the data for
the last 10 years were taken from stations at Sum-
mit, Montana, in which case the temperatures were
modified by monthly regression equations to the
base UCSL station, and precipitation was modified
by the long-term annual precipitation ratio
between the two stations.
Temperatures from the base station to the sub-
stations were modified by regression equations
derived from several onsite meteorological stations.
Snowpack data were derived from Snow
Hydrology for WY 47-49 and from Water Supply
Outlook in Montana (USDA Soil Conserv. Serv.
1950-1963). Peak dates correspond to reported peak
dates. Peak amounts, however, were adjusted to fit
the water balance on that date. They do, in fact,
approach the observed snow data in most cases.
The distribution of snow on each substation was by
regression of onsite and nearby snow sites with
elevation.
For the years when no observed discharge infor-
mation was available (WY 53-63), the peak water
Table III.C.5.—UCSL calibration and validation
Water year
Annual precipitation—
Ob*. Pred.
Annual runoff—
Obs. Pred.
Runoff efficiency—
Obs. Pred.
inrhes
47
48
49
Calibration
47-49
50
51
52
Validation
50-52
All years
47-52
46
45
37
43
53
56
35
48
46
46
45
37
43
52
56
35
48
46
30
34
22
29
24
42
27
31
30
29
29
22
27
36
36
23
32
30
— percent —
65 63
76
59
67
45
76
78
66
67
64
60
62
69
63
65
66
64
m.i63
-------
equivalent was adjusted to force the total
precipitation in the model to approximate the
observed precipitation.
The model simulated annual hydrographs with
accuracy during the six calibration-validation
years of WY 47-52 (table IH.C.5). Balances and
runoff efficiencies were excellent, while timing and
general distribution tended to be slightly higher
than observed. The average year technique for
analyzing response and changes due to treatments
tends to smooth annual deviations. However, the
deviations themselves will not affect the objectives
of this handbook. The model underestimated early
and late season runoff, which is probably due to the
lack of subsurface routing. This runoff is not very
significant with respect to the snowmelt portion of
the hydrograph.
The analysis for high elevations was by direct
evaluation of the subunits. For low elevations the
Skyland Creek watershed was assumed to be 2,000
feet lower.
All temperature intercepts were increased by
4°F. Although all vegetation might be assumed to
be ponderosa pine and lodgepole pine, forest cover
densities were not changed. The major adjustment
for elevation was the reduction of all peak water
equivalents to 1/3 the value used in the high eleva-
tion simulation. This adjustment is based on a
recommendation by Phil Fames, Montana State
Snow Survey Supervisor.1
UCSL Simulation Validity
The annual simulated precipitation, runoff, and
resulting runoff efficiencies are given in table
m.C.5. Water balance predictions are excellent
with the exception of WY 1948. Annual deviations
are not evident when the six years are averaged.
The model consistently underestimates early
and late season base flow which is observed in
several of the individual years and is evident still in
average year simulation. The volume of water in
those periods is very small with respect to the
snowmelt portion of the hydrograph. Peaks are
simulated slightly higher than those observed and
delayed to 6 to 12 days in several years. These
deviations are less but still evident in the average
year simulation.
Overall confidence in the UCSL simulations is
good. Evapotranspiration and soil moisture closely
'SCS, personnal communication, 1977.
match those observed onsite. Extended data (WY
53-63) is primarily from Summit, Montana. The
UCSL station is very similar to Summit. Little er-
ror is expected from using Summit data.
Less confidence can be placed on the low eleva-
tion modification. Although the changes are based
on process and observations, the elevation change
is much more complex than the modifications sug-
gest.
Central Sierra Hydrologic Province (7)
In order to simulate the impacts of vegetative
manipulation in the Central Sierra region, a 3.96
square mile watershed at the Corps of Engineers'
Central Sierra Snow Lab (CSSL) was used as a
study area (U.S. Army 1956). The watersheds in
north central California.
The Castle Creek watershed was divided for
analysis into seven hydrologic units, with the ob-
jectives of homogeneity with respect to slope,
aspect, elevation, and proximity to a channel to
reduce the impact of routing (table III.C.6).
Several energy slopes are represented. Castle Creek
is in an elevation zone (6,900-9,100 ft) that can be
considered "high" in the Sierras. Low elevation
zones (3,000-5,000 ft) and middle elevations (5,000-
7,000 ft) were simulated with the same watershed.
The technique will be outlined later in this section.
Data for the calibration and validation phases
were derived from Snow Hydrology (U.S. Army
1956) and the associated logs. Data supplied by Dr.
Jim Smith, (USDA For. Serv., Berkeley, Calif.),
were also used in the analyses. Water years 1947
through 1949, used for calibration, are discussed
here. Calibration consisted of manipulation of
several parameters to enable the model to
reproduce the observed water balance and distribu-
tion of runoff in the three years. Validation con-
sisted of running the calibrated model on two sub-
sequent years (WY 50-51) to compare the resulting
output with the observed hydrograph (table
in.C.7).
Potential solar radiation was derived from Frank
and Lee (1966). Cover densities and vegetation
types were estimated from aerial photos and text
(U.S. Army 1956). Potential evapotranspiration by
month was derived by Thornwaite's method and
modified by observed data. Soil moisture holding
capacities were developed from comments in the
text, and modified by energy-elevation-vegetation
m.164
-------
Table III.C.6.—CSSL substation description
Sub
Unit
Area
(relative
to total)
Slope Aspect
Cover— Eleva-
Type1 Density tion
General description
11
15
10
26
% % X 100 ft
45 SW Bare 0 79-91 High steep barren tallus;
Very high energy
15 SW S-F 15 74-79 Middle elevation gentle valleys
and hills;
High energy
25 E S-F 15 73-82 Middle elevation moderate slope;
Low Energy
15 SE S-F 25 72-82 Middle elevation gentle slope;
Moderate energy
20 N Bare 0 73-77 Middle elevation gentle slope
tallus;
Low energy
20 NE S-F 25 69-72 Middle elevation moderate
slope
Low energy
0 horiz. S-F 20 73 (river) Moderate meadows;
Moderate energy
30 25% bare 17 68-91
75% S-F
13
18
Composite 100
'Vegetation type: S-F = Spruce-fir
Table III.C.7.—CSSL calibration and validation
Water year
Annual precipitation—
Obs. Pred.
Annual runoff—
Obs. Pred.
47
48
49
Calibration
47-49
50
51
Validation
50-51
All years
47-51
48
63
52
54
69
81
75
62
48 30
64 44
51 33
54
69
81
75
62
36
54
70
62
46
33
44
35
37
49
62
56
45
Runoff efficiency—
Obs. Pred.
pert
63
70
63
65
79
85
82
72
69
70
68
69
71
77
74
71
m.165
-------
observations. Some transmissivities used are
somewhat higher than those suggested by the
relationship T = 0.19 Cdmax "06 developed by Leaf
and Brink (1973b) in the central Rockies. Trans-
missivity in the model controls the incoming
direct solar radiation to the snowpack surface only.
The model is very sensitive to T with respect to the
ripening of the snowpack. The higher T's were
necessary in the Sierras to make the pack isother-
mal at an early date.
Reflectivity and melt thresholds were initially
set at suggested values valid in the central Rockies
and subsequently adjusted in calibrating the model
to Castle Creek.
Climatic data consisting of maximum and
minimum daily temperatures and daily precipita-
tion amounts for the base station at CSSL were
derived from laboratory logs for WY 47-51, from
data furnished by Dr. Smith, and from
Climatological Data for California (Natl. Weather
Serv. 1951-1962) for WY 51-62. Some of the data for
the last 9 years were taken at Soda Springs,
California, in which case the temperatures were
modified by monthly regression equations to the
CSSL station, and precipitation was modified by
the long-term annual precipitation ratio between
the two stations.
Temperatures from the base station to the sub-
stations were modified by regression equations on
onsite meteorological stations.
Snowpack data were derived from Snow
Hydrology for WY 47-51. Peak dates correspond to
reported peak dates. Peak amounts, however, were
adjusted to fit the water balance on that date. They
approached the observed snow data observations in
most cases. The distribution of snow on each sub-
station was by regression of onsite and nearby snow
sites with elevation.
For the years when no observed discharge infor-
mation was available, (WY 51-56, WY 60-62) the
peak water equivalent was adjusted so that total
model precipitation approximated the observed
precipitation. Acceptable annual deviation of
predicted to observed precipitation was considered
at less than one inch.
The model simulated annual hydrographs during
the five calibration-validation years of WY 47-51
(table III.C.7). Balances and runoff efficiencies
were good, while timing and general distribution
tended to be slightly delayed. The average year
technique for analyzing response to changes due to
treatments tends to smooth annual deviations.
However, the deviations themselves did not affect
the objectives of this handbook.
The analysis for high elevations was by direct
evaluation of the subunits. For low and middle
elevations a similar watershed was assumed 4,000
and 2,000 feet lower, respectively, than Castle
Creek. The calibrated model was modified to ac-
comodate the lower elevations by changing two
basic parameters. Temperature intercepts were in-
creased by 8° F. and 4° F., respectively. The major
adjustment for elevation is the reduction of all peak
water equivalents to 0.67 and 0.20 of the value used
in the high elevation simulation. These adjust-
ments are based on snow wedge curves (U.S. Army
1956, plate 3-3).
CSSL Simulation Validity.
The validation and calibration years WY 1947
through 1951 water balances are in table III.C.7.
The hydrographs of the simulations for these five
years are compared with the observed hydrographs
on both annual and average bases to offer a level of
confidence.
On a year-by-year basis the model had a
tendency to underestimate early season runoff dur-
ing years when these events occur. The model
simulated these events with accuracy with respect
to timing, but underestimated the magnitudes. An-
nual peak flows were closely simulated in
magnitude; however, there was a consistent delay
in the model of perhaps one to six days. This delay
was considered to be insignificant since handbook
procedures were developed on a seasonal basis. The
model tended to be more responsive to inputs
yielding more abrupt changes in discharge than
those observed. This can be attributed to the lack
of subsurface routing of the model.
When all five years were averaged, most of the
annual deviations were not evident. Water
balances and efficiencies were within one inch (2
percent) of the average observed annual runoff.
Simulations of the snowmelt portion of the
hydrograph including the spring recession were ex-
cellent. Early season (October-November) yields
still were underestimated. The 19-inch average an-
nual evapotranspiration and the soil moisture
predicted were consistent with those reported in
the literature (U.S. Army 1956).
Based on these observations, the simulations of
response on Castle Creek are good, especially when
ni.166
-------
considered on an average basis. The annual
variability probably closely simulated the actual
system. Less confidence, however, can be placed on
a single year prediction. (Individual year predic-
tions are not the objectives of the model or its in-
tended use). When forest cover densities are
changed in the calibrated model to simulate
silvicultural activities, the resulting response
should follow the real system. Less confidence can
be placed on simulations where the elevations have
been assumed lower than Castle Creek. These
modifications were based on processes and
observed physical phenomena and were ex-
trapolated to reflect watershed conditions at some
distance to the south, and at lower elevations.
Alternate Simulations (CSSL)
The Castle Creek watershed as simulated had a
relatively low cover density (Camax = 17%) overall.
Two subunits were assumed to be void of signifi-
cant forest cover. The greatest cover on the remain-
ing five subunits was 25 percent. Therefore, in
order to simulate the greater changes in cover den-
sity on various energy slopes, the model calibrated
for the observed inventory was rerun with all sub-
units assumed to have an old-growth forest cover
density of 0.40, and again at Cdmax = .55. This
value of Cdmax represents a stocking of perhaps 150
square feet per acre. The corresponding values for
T were adjusted slightly upward from Lear's
relationship of T = f(Cd) consistent with the
adjustments made in calibration. The model with
this modified Cdmax was run with all the other
parameters consistent with the original simulation
to simulate old-growth commercial forest condi-
tions.
Northwest Hydrologic Province (5)
Vegetation manipulation impacts were
simulated for the higher elevation zones of the
coastal Pacific Northwest region using data from
the Willamette Basin Snow Lab (WBSL) (table
m.C.8). The specific watershed is Wolf Creek, a
2.07 square mile mountain headwaters stream in
the Willamette River system of west central Oregon
(U.S. Army 1956).
Wolf Creek is representative of the commercial
timberlands of the region at elevations that ac-
cumulate snow and produce a significant snowmelt
hydrograph. Simulations of the rain forests at lower
elevations in this province are discussed later. The
region is under a strong maritime influence. Runoff
is in response to both rain and snow, with rain oc-
curring throughout most of the year, except in late
summer.
The data base from the Corps of Engineers is in-
consistent (Table III.C.9). Reported runoff efficien-
cies ranged from 94 to 106 percent in the three years
Table III.C.8.—WBSL substation description
Sub
unit
Area Slope
(relative
to total)
Aspect Cover-
Type
Density
1 18
2 37
3 38
4 7
Composite 100
(2.07 sq. mi.)
20
20
35
0
24
NE
NE
SE
horiz.
S-F
S-F
S-F
S-F
60
60
55
10
55
Table III.C.9.—WBSL calibration and validation
Water year
Annual precipitation—
Obs. Pred.
Annual runoff—
Obs. Pred.
—Runoff efficiency—
Obs. Pred.
49
50
51
47-51
831
1111
1061
100
106
130
116
117
88
108
100
99
88
109
98
98
percent
1061
971
94'
99
83
84
84
84
'Model calibrated on runoff only. Precipitation data appears to be in error during calibration years.
m.i67
-------
of record. The precipitation amounts appear to be
in error—since they are 20-30 inches below the
long-term average. Therefore, calibration consisted
of comparing the annual hydrographs with the
observed hydrographs for WY 49-51. Precipitation
was not a calibration parameter in this case, reduc-
ing confidence in the water balance. However,
predicted evapotranspiration, soil moisture, and
annual runoff were close to the observed values.
Temperature coefficients were regressed when
possible against the few onsite stations. Due to the
nature of the hydrologic regimen, temperature
coefficients were then raised 3° to calibrate the
model.
The extended data base from WY 52-60 was
derived from Leaburg, Oregon — a nearby station
that receives considerably less precipitation and is
consistently 4-10° F. warmer. The variability at
WBSL was assumed to be represented by that at
Leaburg. Precipitation records were modified on an
annual basis, while maximum and minimum
temperatures were regressed individually on a
monthly basis.
The Wolf Creek watershed was divided into four
subunits (table III.C.8). Simulations were run on
12 years of climatic record.
WBSL Simulation Validity
Confidence in the WBSL simulation analysis is
less than at CSSL or UCSL for four reasons:
(1) The poor data base for precipitation during
the calibration years made it difficult to
completely verify the water balance.
(2) The maritime influence on snow accumula-
tion causes several different accumulation-
depletion events each year with almost con-
stant melt. This is difficult to simulate with
the Subalpine Water Balance Model in its
present configuration.
(3) Although the average year simulation during
the calibration period closely approximates
the observed hydrograph, the individual year
simulations are more variable in timing and
peaks than those observed. This response is
masked in the average year output.
(4) The lack of data for validation prohibited as-
sessment of the level of confidence on in-
dependent data not used in calibration.
In conclusion, the WBSL simulations reflect
regional water balances as reported in the
literature, but confidence is difficult to establish to
a degree due to lack of long-term small watershed
data at high elevations.
ni.168
-------
APPENDIX III.D: CALIBRATION AND VALIDATION SUMMARY
FOR SITES MODELED WITH PROSPER
Since PROSPER is primarily an evapotranspira-
tion model without a routing component, and
because the results were being reported in terms of
flow duration curves, not hydrographs, calibration
efforts were concentrated on simulating annual and
seasonal evapotranspiration and in reproducing the
observed distribution of flows. Therefore, timing
was not a critical design criteria in the calibration
scheme. The needs of this handbook dictated ac-
curacy in terms of the distribution of weekly flows.
There are calibration techniques the modeler can
employ to improve response, but use of these
methods depends on one's philosophy. In terms of
PROSPER there are essentially no calibration
variables, i.e., variables that do not have a physical
basis and/or that cannot be measured. If the user
wants the model to represent the physical system,
then the variable should not vary from one's best
estimate of them. This philosophy was followed in
the development of this chapter with two excep-
tions: Parameters were altered within the expected
range of their measured value, and in certain situa-
tions, the value of a parameter was altered from its
true value if such alteration could compensate for a
weakness in the model. In this respect, if storm
response was dampened excessively because of
routing deficiencies in the model, increases in con-
ductivity of the soil or decreases in its depth might
be made to compensate. These adjustments were
primarily made to the lower three soil horizons
since they did not directly affect the evapotran-
spiration draft and were, in a sense, dead storage.
A rigorous sensitivity analysis has been done by
Luxmoore and others (1976) on PROSPER. In
calibration, the water balance is adjusted primarily
by changing leaf on/leaf off dates, rooting depth,
interception storage, and leaf area index. No
changes were made in initial estimates of leaf area
index. Interception storage was adjusted to corres-
pond with estimates of interception loss using local
equations, and leaf on/leaf off dates were varied
over a two-week span. Very little was done to
calibrate PROSPER. Initial estimates of the
parameters were made.
The following is a description of the application
of PROSPER to various representatives and ex-
perimental watersheds by region.
THE APPALACHIAN HIGHLANDS AND
MOUNTAIN REGION (2)
Watersheds from four areas were used to repre-
sent the region. The Leading Ridge Watershed
Number 2 in central Pennsylvania, The Fernow
Forest Watershed Number 4 in northcentral West
Virginia, the Walker Branch Watershed near Oak
Ridge, Tennessee, and Coweeta Watershed
Number 18 near Franklin, North Carolina were
used.
Leading Ridge, Pennsylvania
Leading Ridge Watershed Number 2, operated
by Pennsylvania State University, is located in the
ridge and valley province in central Pennsylvania.
The vegetation on the 106-acre (43ha) watershed
consists of mixed hardwoods, primarily oak-
hickory, with little understory.
Initial parameter estimates and the necessary
data base were provided by James Lynch from the
watershed files at Pennsylvania State University.
The hydrologic characteristics of the dominant
soils were not available, and since the soil series at
Leading Ridge was the same as data available at
the Fernow Experimental Forest for their soils, the
model was run using Fernow soil hydrologic
parameters. Because evapotranspiration from the
initial calibration run was considered high, the
summer interception capacity was lowered from 0.3
cm to 0.25 cm to reduce the simulated evapotran-
spiration and match the interception loss with that
estimated using a local equation.
Four years of climatic data were provided, and
the first two years were used for calibration.
Calibration results were confounded because of
significant rain on snow events, i.e., runoff efficien-
cies greater than one. The remaining two years of
data used to test the calibration also had snowmelt
events. Since a significant snowpack generally does
not accumulate, and since available snowpack in-
formation was deemed unreliable, it was concluded
that using the snowpack model, rather than
PROSPER, would be unsuccessful. Further at-
tempts at calibration were deemed unnecessary.
m.169
-------
An October to September water year was chosen
and, with close examination of actual precipitation
versus observed streamflow, it can be noted that
there is a lag in annual response. Years of high
precipitation do not correspond with high levels of
flow and vice versa. For the data set as a whole, the
simulated streamflow comes within 0.8 percent of
the total observed flow. Average predicted
evapotranspiration during the 4-year period is 22.3
inches — this compares favorably with the poten-
tial evapotranspiration estimated at 22 to 24 in-
ches. Because of snowmelt runoff events, in-
dividual observed versus predicted hydrographs
ranged from good to poor. Since Hydrologic Region
2 has been characterized as an area where response
is not dominated by snowpack accumulation and
ablation, and given Leading Ridge's proximity to
the border between Hydrologic Regions 2 and 3, it
was felt that the simulation would more than ade-
quately represent the hydrologic response with
respect to the distribution of flows. A summary of
the simulation is represented in table III.D.l.
Table III.D.1—Calibration and validation summary for sites modeled by PROSPER
Water
Year
1961
1962
1963
1964
1964
1965
1968
1969
1966
1967
1968
1969
1970
1971
1966
1967
1968
1973
1974
1975
1971
1972
1972
1973
1974
#1
Actual
precip.
101.3
93.7
81.0
91.5
141.2
109.7
129.8
138.3
109.0
133.0
129.0
107.0
121.0
132.0
121.0
132.0
159.0
167.6
303.0
232.8
125.1
139.2
236.3
229.4
221.4
#2
Trans-
piration
39.2
30.1
33.1
29.3
34.2
33.3
33.4
40.4
61.1
68.9
65.9
63.2
60.0
73.1
57.6
57.5
56.4
52.1
45.1
47.9
30.4
25.2
53.1
50.2
50.3
#3
Inter-
ception
16.8
14.4
14.8
13.3
22.7
26.1
27.0
31.0
12.1
13.9
13.8
12.4
12.3
15.5
21.0
24.8
24.9
38.2
28.0
41.4
13.1
13.1
26.5
23.4
24.0
#4
Total
ET
65.2
53.5
57.1
51.0
64.4
67.1
67.2
78.9
78.9
88.6
85.3
81.0
78.0
94.7
83.2
86.9
85.8
94.0
80.0
92.8
53.2
46.7
87.3
81.7
82.3
Observed versus predicted response
#5 #6 #7 18 #9
Flow Changes in (Q + ASM) Actual Percent
Q soil moisture measured deviation
ASM OBSQ
Leading Ridge
41.6
41.8
29.0
43.5
Fernow
76.2
35.3
62.9
58.8
White Hall
25.1
37.5
40.6
25.5
37.2
37.1
Oxford
38.6
43.9
72.3
H.J. Andrews
82.8
251.0
162.1
Hubbard Brook
70.3
89.4
Coweeta
134.9
144.5
141.2
-5.4
-1.6
-5.1
-3.1
0.5
7.2
-0.3
0.7
5.5
6.5
2.7
0.6
6.0
0.5
-0.4
0.7
0.9
- 9.2
-24.0
-22.1
1.4
2.5
14.1
3.1
-2.3
36.2
40.2
24.9
40.4
76.7
42.5
62.6
59.5
30.6
44.0
43.3
26.1
43.2
37.6
38.2
44.6
73.2
73.6
227.0
140.0
71.7
91.9
149.0
147.6
138.9
44.0
41.4
22.1
33.0
56.4
35.3
51.6
60.8
26.8
36.0
37.7
31.9
33.1
41.1
13.4
15.2
46.8
72.9
213.0
151.2
66.7
104.5
135.8
150.3
135.9
-12.0
- 2.8
-12.7
+22.0
+26.0
+ 17.0
+ 17.6
+ 2.1
14.0
22.0
15.0
18.0
14.0
8.0
185.0
193.0
156.0
+ 1.0
+ 6.6
- 7.4
+ 7.5
-12.1
- 9.7
- 1.8
+ 2.2
ffl.170
-------
Fernow, West Virginia
The Fernow Experimental Watersheds are
operated by the U.S. Forest Service, Northeastern
Forest Experiment Station. Fernow Watershed
Number 4 was used. This 95-acre (38 ha), mixed
hardwood forest was chosen to represent the central
Appalachians, particularly the Allegheny Moun-
tains, and is located near Parsons, West Virginia.
The data set and initial parameter estimates
were provided from the files at the Fernow Ex-
perimental Forest by Northeastern Forest Experi-
ment Station. Numerous changes were made in the
parameter set before PROSPER was considered
calibrated on the watershed. However, most of
these changes entailed a sensitivity analysis to
become familiar with PROSPER. The final
parameter set differed from the initial one only in
that the first two soil layers (of five) were decreased
slightly in depth to enable PROSPER to execute
more efficiently. A slight adjustment was also
made in the distribution of roots between the two
upper horizons. The dates at which the canopy was
50 percent on and 50 percent off were increased and
decreased slightly to decrease ET and increase
early summer and fall storm response.
Four years of climatic data were available.
Calibration was done on the first two years of data.
The water year selected started May 1, and in-
dividual hydrograph simulation was considered
good, although, as was frequently the case, timing
was slightly offset to the right of the observed
hydrograph because of routing deficiencies. Annual
potential evapotranspiration, estimated by clas-
sical methods, ranged from 23 to 25 inches. Average
annual simulated evapotranspiration was 27.3 in-
ches. Thus, PROSPER slightly overestimated
evapotranspiration. A direct comparison between
observed and predicted flows is shown on table
m.D.l. Watershed Number 4 has a poor precipita-
tion runoff relationship, and we expected to
simulate more streamflow than was observed.
Leakage in Fernow Watershed ranges from 1 to 10
or more inches.
Walker Branch, Tennessee
The normal calibration and validation procedure
was unnecessary in this case since PROSPER was
developed and tested on Walker Branch. A
calibrated parameter and data set was provided by
Dale Huff at the Oak Ridge National Laboratories.
Walker Branch is located in eastern Tennessee,
and vegetation consists of mixed hardwoods,
primarily oak, hickory, and yellow poplar. A more
thorough description of the calibration and sen-
sitivity analyses can be found in the PROSPER
Documentation (Goldstein and others 1974).
Coweeta, North Carolina
The Coweeta Experimental Watersheds are
operated by the U.S. Forest Service and Coweeta
Hydrologic Laboratory. Watershed Number 18 was
used in this study. This watershed is
predominantly occupied by mixed hardwoods.
An initial parameter set was provided by Lloyd
Swift of the Coweeta Hydrologic Laboratory.
Calibration of PROSPER at this site proved to be
the most difficult calibration effort encountered,
due to some unique hydrologic features of the
watershed. The hydrologically active soil-regolith
varies from 30 to 100 feet. This gives a strong
baseflow component with a long resonance time.
However, the watershed also exhibits relatively
strong storm response during the dormant season.
Thus, the watershed is able to route water through
the system via several pathways. PROSPER is un-
able to simulate such a system, especially where it
is as strongly defined as at Coweeta. Numerous
changes were made in the initial parameter set in
order to achieve a parameter set which represented
an acceptable compromise between baseflow
simulation and storm response. Since the initial
parameter set produced outflow response which
was considerably more "flashy" than the actual,
soil depths were increased and soil conductivity
values were decreased in an effort to dampen storm
response.
Three years of climatic data were provided. One
year was used in model calibration. The water year
started May 1. Hydrograph simulation was con-
sidered fair; however, timing was offset to the right.
Simulated annual water balance was very good.
Mean total evapotranspiration was 33 inches. Con-
sidering this is a north-facing watershed, it com-
pared favorably with an average pan evaporation of
35 inches.
The 1973 water year was used as the base for the
simulation runs. This year had the most represen-
tative lower end of the resulting flow duration
curve. Since the effects of timber harvesting in this
HI.171
-------
area are most pronounced at low flow periods, the
1973 year was chosen as being the most represen-
tative.
The comparison of simulated or observed flow is
shown in table HI.D.I.
THE GULF AND ATLANTIC COASTAL
PLAIN/PIEDMONT REGION
This region was characterized by simulations
using data sets from two experimental watersheds:
The White Hall Watershed on the Georgia Pied-
mont near Athens, Georgia, and Oxford Watershed
Number 2 on the Gulf Coastal Plain near Oxford,
Mississippi.
White Hall, Georgia
White Hall is a small 60-acre experimental
watershed located on the Piedmont near Athens,
Georgia, and is operated by the University of
Georgia. Vegetation consists of mixed pine-
hardwoods typical of the revegetated cottonlands
common in the region. Initial parameter estimates
and the climatic data set were provided by Dr.
John D. Hewlett of the University of Georgia.
Only minor adjustments were made in the initial
parameter set. Initial estimates of soil depth were
cut in half to remove a considerable delay in storm
response. Saturated conductivity rates for the soil
profile were revised when more specific onsite infor-
mation became available to Dr. Hewlett.
Six years of data were provided. Calibration was
carried out on the first three years. Very little
calibration on the data set was needed once the
revised soils data were provided.
For convenience, May 1 was used as the start of
the water year because the date generally occurred
just after the seasonal peak and antecedent condi-
tions were similar from year to year. PROSPER
predicted 225 area inches of outflow for the 6-year
period; 207 area inches were observed, resulting in
an average error of 9 percent. Average estimated
evapotranspiration during the period was 33.2 in-
ches.1 Given this average and the total predicted
outflow (assuming some watershed or weir
leakage), the results can be considered very good.
The individual yearly values are shown in table
m.D.i.
The year starting May 1, 1971, was selected as
the basis for the simulation runs. This year most
closely resembled the average simulated flow dura-
tion curve. It was three inches above normal in
terms of total annual precipitation.
Oxford, Mississippi
The Oxford Experimental Watersheds are
located on the Coastal Plain in northern Missis-
sippi. They are operated by the U.S. Forest Ser-
vice, Forest Hydrology Laboratory, Southern
Forest Experiment Station. Watershed Number 2
was selected for use here. Watershed Number 2 is a
small, 4.6-acre pine-hardwood watershed. Initial
parameter estimates and data set were provided by
Mr. Stan Ursic at the Forest Hydrology
Laboratory.
The only deviation from the original parameter
given us was a slight adjustment in interception
capacities of the vegetation.
Three years of data were reduced to a form re-
quired by PROSPER. Normal evaluation of model
response cannot be made because a substantial
portion of basin outflow (approximately 10 inches
per year) is lost2 to deep seepage or does not appear
in the channel at the weir site; therefore, the
calibration goal was to simulate the estimated an-
nual evapotranspiration and to simulate the occur-
rence of the observed storm response in terms of
timing, not peaks. Relative to these goals the
results of calibration were very good. The estimate
of evapotranspiration losses had been derived
earlier from soil moisture studies. As expected, the
simulations overpredicted the storm response as
measured at the weir site. Calibration was carried
out on the first two years of the data set and a
validation made on the third year.
If the observed outflow is adjusted by the average
10 inches of seepage loss, then the predicted (shown
in table III.D.l) versus adjusted observed outflow
gives deviations of 1.4 percent, 9.8 percent, and 1.6
percent respectively for three years. Based on an
unpublished study by Ursic, annual evapotran-
spiration averages between 33 and 36 inches per
'Persona/ Communication, John D. Hewlett, University of
(! corgi a
2Personal Communication, Stan Ursic, Forest Hydrology
Laboratory.
III.172
-------
year. Annual evapotranspiration predicted by
PROSPER averages 33.6 inches.
The 1967 year was chosen as the base for the
simulation runs. It had the smallest deviations
from normal in total annual precipitation and total
annual runoff. It also had the most representative
simulated flow duration curve.
PACIFIC COAST HYDROLOGIC
PROVINCES — NORTHWEST (5),
CONTINENTAL MARITIME (6),
AND CENTRAL SIERRA (7)
LOW ELEVATION
Data sets for this region were readily available.
The H. J. Andrews Experimental Watersheds were
the only ones that had data sets conducive to run-
ning PROSPER. Watershed Number 2 was
selected.
Where available for the PROSPER simulations
on Hubbard Brook, the results of simulation,
although not used directly, are shown in table
ffl.D.l.
H. J. Andrews, Oregon
The H. J. Andrews Experimental Watersheds are
operated by the U.S. Forest Service, Pacific
Northwest Experiment Station. They are located
in the rain-predominant lower elevations of the
Willamette Basin in the Oregon Cascades. The
watershed used in this study was Number 2, a 149-
acre (60 ha) watershed supporting a heavy
Douglas-fir forest.
Information for initial parameter estimates and
climatic data was provided by Dr. Dennis Harr,
Pacific Northwest Forest and Range Experiment
Station. There were no changes from the initial
parameter set with the exception of adjusting the
interception losses. Three years of climatic data
were available.
Both hydrograph simulation and annual water
balance were very good. Timing was slightly offset
to the right. Average annual evapotranspiration as
computed by PROSPER was 47.3 inches, mostly
interception.
The 1975 water year was chosen as the basis for
the simulation runs. The 1973 water year was very
dry in comparison to long-term climatic records.
The 1974 water year was unusually wet.
In addition, PROSPER was calibrated to two
watersheds in the Lake States, New England
region. Marcell Watershed Number 2 near Grand
Rapids, Minnesota, and Hubbard Brook
Watershed Number 3 were used. The annual
balance for both was fairly good, but since a winter
snowpack is significant throughout the region,
PROSPER simulations distorted the dormant
season flows. A decision was made to base the
methodology for this region on the Leaf and Brink
(1973b) snowmelt model simulations. PROSPER
did well in estimating annual evapotranspiration
and streamflow, however. Only two years of records
were available for the PROSPER simulations on
Hubbard Brook. The results of simulation,
although not used directly, are shown in table
III.D.1.
m.173
-------
Chapter IV
SURFACE EROSION
this chapter was prepared by the following individuals:
Gordon E. Warrington
Coordinator
with major contributions from:
Kerry L. Knapp
Glen 0. Klock
George R. Foster
R. Scott Beasley
-------
CONTENTS
Page
INTRODUCTION IV.l
DISCUSSION: SURFACE SOIL LOSS IV.2
GENERAL CONCEPTS OF SURFACE SOIL LOSS IV.2
Detachment By Raindrop Impact IV.2
Detachment By Surface Runoff IV.3
Environmental Changes Created By Silvicultural Activities Which Affect
Surface Soil Loss Potential IV.3
PROCEDURAL CONCEPTS: ESTIMATING SURFACE SOIL LOSS IV.4
The Rainfall Factor, R IV.5
Energy-Intensity Values, El IV.5
Determining The Rainfall Factor IV.5
R Values For Thaw And Snowmelt IV.10
The Soil Erodibility Factor, K IV.10
Determining The Soil Erodibility Factor IV.11
The Topographic Factor For Slope Length And Gradient, LS IV.14
Slope Length Factor, A IV.14
Slope Gradient Factor, S IV.14
Determining The Topographic Factor IV.15
Irregular Slopes IV.15
The Vegetation-Management Factor, VM IV.21
Effects Of Canopy Cover, Type I W.21
Effects Of Mulch And Close Growing Vegetation, Type II IV.22
Residual Effects Of Land Use, Type in IV.23
Sediment Filter Strips IV.23
Determining The Vegetation-Management Factor IV.23
Seasonal Adjustments for VM IV.24
Estimated Soil Loss Per Unit Area IV.24
Converting MSLE To Metric IV.24
Erosion Response Units IV.29
Delineating Erosion Response Units TV.29
Summary IV.47
CONSIDERATIONS FOR REDUCING EROSION IV.47
APPLICATIONS, LIMITATIONS AND PRECAUTIONS: SURFACE SOIL
LOSS IV.49
DISCUSSION: SEDIMENT DELIVERY IV.52
GENERAL CONCEPTS OF SEDIMENT DELIVERY IV.52
Factors Influencing Sediment Delivery IV.52
Sediment Sources IV.52
Amount Of Sediment IV.52
Proximity Of Sediment Source IV.52
Transport Agents IV.52
Texture Of Eroded Material IV.52
rv.ii
-------
Deposition Areas IV.53
Watershed Topography IV.53
Sediment Delivery Model IV.53
PROCEDURAL CONCEPTS: ESTIMATING SEDIMENT DELIVERY ... IV.54
The Sediment Delivery Index IV.54
Evaluation Factors TV.54
Determining The Sediment Delivery Index IV.55
Estimating Sediment Delivery By Activity IV.60
CONSIDERATIONS FOR REDUCING SEDIMENT DELIVERY IV.60
APPLICATIONS, LIMITATIONS AND PRECAUTIONS: SEDIMENT
DELIVERY IV.62
THE PROCEDURE : IV.63
ESTIMATING SEDIMENT DELIVERY FROM SURFACE EROSION
SOURCES IV.63
LITERATURE CITED IV.64
APPENDIX IV.A: GULLY EROSION IV.67
APPENDIX IV.B: EROSION OVER TIME IV.68
APPENDIX IV.C: CONTROLLING DITCH EROSION IV.69
IV.iii
-------
LIST OF EQUATIONS
Equation
I V.I
IV.2.
Page
IV.3.
5
IV.8.
A = RKLSVM IV.4
IV.5
R= EL
100
E = 916 + 331 logioi IV.10
IV.4. K= (2.1 X 10-6) (12-Om) (M114) + 0.0325(8-2) + 0.025(P-3) .. IV.ll
_(KWMW + KdMd)
Mw + Md
IV.6. L = (A/72.6)m ..
IV.7.
IV.12
IV.14
s = (0.43 + 0.30s + 0.043s2) IV 14
6.613
0.43 +0.30s + 0.043s2
IV.9. LS = — • S
V 10,000 \
Aio,000+s2/
10,000
10,000 + s2
IV.9a. . -,„„„„,, 10!0(X)
IV. 10. Cinn = 0.169V - 0.356
IV.ll.
VM =
M
IV. 12. F = CRL
,1.49
IV.C.l. V = (— ) (R0.66) (go.5)
IV.15
IV.15
IV.17
IV.22
IV.55
IV.69
IV.iv
-------
LIST OF FIGURES
Number Page
IV. 1. —Flow chart of the procedural concepts involved in estimating sediment
delivery from surface erosion sources IV.6
IV.2. —Iso-erodent map illustrating average annual values of the rainfall
factor, R IV .8
IV.3. —Nomograph for determining the soil erodibility factor, K IV.13
FV.4. —Nomograph for determining the topographic factor, LS, on simple
slopes IV.16
IV.5. —Values of n for use with irregular slopes with appropriate values
of m IV.18
IV.6. —Values of n for use with irregular slopes where m = 0.6 IV.19
IV.7. —Generalized cross-section of outsloped road IV.20
IV.8. —Influence of vegetal canopy on effective El IV.22
IV.9. —Effect of plant residues or close-growing stems at the soil surface on the
VM factor IV.22
IV.10.—Effects of fine roots in topsoil on the VM factor IV.23
IV.ll.—Relationship between grass density and the VM factor IV.27
IV.12.—Relationship between forb density and the VM factor IV.28
IV.13.—The Horse Creek watershed boundary IV.30
IV.14.—Drainage net of the Horse Creek watershed IV.31
IV.15.—Individual hydrographic areas of the Horse Creek watershed IV.32
IV. 16.—Soil mapping unit boundaries for the Horse Creek watershed IV.33
IV.17.—Proposed transportation system (roads and log landings) for the Horse
Creek watershed IV.34
IV.18.—Proposed cutting units for the Horse Creek watershed IV.35
IV.19.—Composite map of all topographic and management treatments for the
Horse Creek watershed, hydrographic area 3 IV.36
IV.20.—Effect of individual parameters on the K factor when other parameters
are maintained at a low, moderate, or high influence on K IV.51
IV.21.—Potential sediment transport paths for different parts of a slope IV.53
IV.22.—Stiff diagram for estimating sediment delivery IV.56
IV.23.—Relationship between polygon area on stiff diagram and sediment
delivery index IV.57
IV.24.—Example of graphic sediment delivery model for road R3.1 IV.58
IV.C.l—Nomograph for Manning formula IV.70
IV.v
-------
LIST OF TABLES
Number Page
IV.1. —Example of data tabulation when using graphs for obtaining LS values
for irregular slopes IV.17
IV.2. —Velocities of falling waterdrops of different sizes falling from various
heights in still air IV.21
IV.3. —"VM" factor values for construction sites IV.24
IV.4. —"C" factors for permanent pasture, rangeland, idle land, and grazed
woodland IV.25
IV.5. —"C" factors for undisturbed woodland IV.25
IV.6. —"C" factors for mechanically prepared woodland sites IV.26
IV.7. —Values of organic matter, fine sand -f- silt, clay, structure, and
permeability used as constants when calculating K factor IV.50
IV.8. —Water availability values for given source area IV.59
IV.C.I.—Values for Manning's n and maximum permissible velocity of flow in
open channels IV.71
IV.C.2.—Hydraulic radius (R) and area (A) of symmetrical triangular
channels IV.73
IV.C.3.—Hydraulic radius (R) and area (A) of nonsymmetrical triangular
channels IV.74
IV.C.4.—Hydraulic radius (R) and area (A) of symmetrical trapezoidal
channels IV.75
IV.C.5.—Hydraulic radius (R) and area (A) of nonsymmetrical trapezoidal
channels IV.80
IV.vi
-------
LIST OF WORKSHEETS
Number Page
IV.1.—Soil characteristics IV. 37
IV.2.—Watershed erosion response unit management data IV. 38
IV.3.—Estimates of soil loss and delivered sediment IV. 41
IV.4.—Estimated VM factors IV.42
IV.5.—Estimated monthly change in VM factors IV. 43
IV.6.—Weighting of VM values for roads IV.44
IV.7.—Factors for sediment delivery index IV. 45
IV.8.—Estimated tons of sediment delivered to a channel IV. 46
IV.vii
-------
INTRODUCTION
Over the past 50 years, many attempts have been
made to identify soil and site characteristics that
can be used as parameters to quantify the amount
of accelerated soil erosion on agricultural and forest
lands. Most of the models that have been
developed are unique to the areas where they were
tested and may not be applicable to other loca-
tions. Models which estimate the movement of
eroded material through a forest environment to a
stream channel have not been extensively tested.
The most acceptable model that is used to es-
timate surface soil erosion on agricultural lands is
the Universal Soil Loss Equation (USLE)
developed by Wischmeier and Smith (1965). Since
this equation is not universally applicable to forest
environmental conditions, attempts have been
made to develop a Modified Soil Loss Equation
(MSLE). To adapt the USLE to forest conditions,
the cropping management factor (C) and the ero-
sion control practice factor (P) have been replaced
by a vegetation-management factor (VM) in the
MSLE. Although this approach for quantifying
surface soil loss on forest lands appears to be the
best method at this time, it has not been exten-
sively tested or validated on forest lands
throughout the United States.
The MSLE does not quantify the amount of
material that may come from gully erosion or soil
mass movement. A suggested method for
evaluating gully erosion is presented in appendix
IV.A.
The MSLE model is one of several tools to be
used when attempting to understand the effects of
different management practices on a given piece of
land. This erosion model provides only a long term
estimate or an index of the amount of soil loss from
a given site (Wischmeier 1976). It is only an es-
timate because: (1) A model, no matter how com-
plex, is a representation of reality and should never
be confused with reality (Bekey 1977), and (2)
planning creates a model of the future, and hence is
an estimate of something that has not yet occur-
red. However, th^s model can still be an effective
tool for guiding management decisions by testing
different approaches against an objective (such as
minimizing the amount of sediment that is
delivered to a stream) and evaluating the relative
magnitudes of the answers.
This chapter also presents a simple graphic
model for estimating the quantity of sheet and rill
eroded soil material delivered from the source area
to a stream channel. Although this model appears
feasible for application on all forest lands, it has
not been extensively tested. With additional field
testing and experience, the range and nature of this
model's sediment delivery factors will be modified.
Many of the techniques used to evaluate surface
erosion and sediment delivery are based on subjec-
tive evaluations of land characteristics. Persons
who have the responsibility for evaluating erosion
and sediment delivery need a general technical
background in soil science and hydrology, as well as
field experience in forest management. This
chapter presents charts, tables, and formulas that
are needed to use the MSLE and sediment delivery
index procedures. Examples are provided in both
this chapter and chapter VHI to illustrate a
systematic approach to quantifying surface soil
erosion on forest lands.
IV.l
-------
DISCUSSION: SURFACE SOIL LOSS
GENERAL CONCEPTS OF SURFACE SOIL
LOSS
Surface erosion is the wearing away of the land
surface by water, wind, ice, or other geological
agents. In this chapter, surface soil loss is dealt
with specifically as the mechanical detachment by
water of mineral soil particles and organic material
from the soil surface. Other forms of erosion such as
soil mass movement, piping, and gully are not
covered.
The energy for soil particle detachment by water
may be provided by rainfall impact and/or shear
from flowing water (e.g., runoff). The impact of
raindrops on an exposed soil surface breaks down
the surface structure and detaches soil particles
and individual aggregates from the soil. Unless the
soil surface is protected in some way by a low
vegetative canopy and a mineral or organic surface
mulch, this raindrop and runoff energy can detach
tremendous quantities of mineral and organic soil.
Detachment by raindrop impact removes soil
uniformly over a broad area of exposed soil. Such
soil loss may be almost imperceptible and is
usually referred to as sheet or rill erosion. Raindrop
splash enables thin, sheet flow to transport
detached particles a short distance to areas of more
concentrated water flow.
Detachment by overland flow usually occurs
with small concentrations of flowing water in rills.
Enough flow energy must be available so the
hydraulic forces exceed the soil's resistance to
detachment. Consequently, little soil detachment
by water flow will occur on areas with thin sheet
flow, near ridge tops, on very flat slopes, or where
surface runoff rates are low.
The separation of surface erosion into rill and
sheet components is conceptually useful. Sheet ero-
sion is a product of either raindrop impact or sheet
flow and is relatively uniform over the surface. This
distinction is important in determining the type of
control strategy that might be used (see "Chapter
II, Control Opportunities"). If it can be
demonstrated that rill erosion is the primary con-
tributor to the surface erosion total, then the con-
trol strategy would be directed toward dealing with
overland flow as an eroding agent. Such a strategy
would vary somewhat both in scope and in general
approach from one designed to deal with erosion
from raindrop impact or sheet flow.
Further discussion on surface erosion concepts
may be found in articles by Bennett (1934), Ben-
nett (1974), Cruse and Larson (1977), Ellison
(1947), Foster and Meyer (1975), Guy (1970),
Horton (1945), Meyer and others (1975 and 1976),
and Smith and Wischmeier (1962).
Detachment By Raindrop Impact
Three principal factors affect the amount of soil
detached by raindrop impact. The first factor is the
interception of rainfall by the overstory or tree
canopy. Dohrenwend (1977) reports that overstory
canopies are not likely to protect the forest floor
from the erosive impact of raindrops. In some cases
raindrop energy is amplified by the canopy when
the intercepted water falls as larger drops
(Chapman 1948, Trimble and Weitzman 1954).
The second factor is interception by the under-
story. The rainfall energy transmitted through the
overstory canopy may be intercepted by an under-
story canopy — of shrubs, herbs or grass — growing
near the surface. The amount of energy reduction,
if any, depends upon drop size and fall distance
(Dohrenwend 1977). In a natural forest the surface
is protected by a third factor, a mat of litter con-
sisting of leaves, needles, and other organic debris
accumulated from the overstory and understory
canopies. This litter mat absorbs a great deal of the
energy reaching the soil surface. If the depth of the
litter mat exceeds the penetration depth of the
raindrops, it is assumed that no mineral soil will be
detached (Simons and others 1975). The net effect
of the three layer screen — overstory canopy, un-
derstory canopy, and litter — can be a reduction of
rainfall impact energy to very near zero at the soil
surface.
The litter layer and organic material in contact
with the soil will contribute the greatest erosion
protection. Reduction of precipitation energy by
the overstory canopy is not generally considered to
be significant. The overstory plays a greater,
though less direct, role by replenishing the litter.
IV.2
-------
Detachment By Surface Runoff
Any surface runoff that may occur in the natural
forested environment generally moves over the soil
below the litter layer. The rate of energy expended
for this flow is low because water moves through lit-
ter at a lower velocity than it would over the sur-
face of bare ground. Consequently, the detachment
energy of the water flow and thus the quantity of
soil that is detached, both become very low where
good litter cover is present.
Where the litter layer is removed or the soil is
compacted, the infiltration rate is decreased. This
allows a given volume of rainfall to produce a
greater proportion of overland flow than would
otherwise occur, and more runoff energy is
available to be expended on the soil surface.
Environmental Changes Created By
Silvicultural Activities
Which Affect Surface Soil Loss Potential
In the natural forest environment, soil loss from
sheet and rill erosion is usually small. Only when
the natural environment is disturbed by logging,
road building, fires, or unusual activities, does soil
loss increase (Fredriksen 1972) and become a major
source of non-point pollution. The environmental
changes due to silvicultural activities that are dis-
cussed on the following pages often result in in-
creased soil loss due to destruction of the natural
protective soil cover, exposure and disturbance of
the soil surface, and/or increased runoff.
Reduction of the overstory canopy. — The
primary silvicultural activity is felling and logging.
Reduction of the overstory canopy decreases rain-
fall interception and may either cause an increase
or decrease in rainfall energy reaching the ground
surface, depending on the nature of the storm and
characteristics of the canopy. There is some indica-
tion that rainfall energy under hardwood canopies
may be greater than under conifer canopies (Swank
and others 1972, Trimble and Weitzman 1954). If
particular canopies intercept and coalesce water
droplets, then removal of these canopies could
result in lower rainfall energy at the ground sur-
face.
Removal or alteration of understory. —
Silvicultural activities often remove or seriously
alter the understory vegetation when the objective
is to eliminate vegetative competition to promote
the regrowth of timber. The result of brush removal
is a net reduction in the effectiveness of the under-
story to intercept precipitation. When this in-
terception value is lost, the rainfall energy moves
closer to the ground surface.
Disturbance of the litter layer. — The litter
layer, probably the most important factor in the
forest environment for absorbing rainfall energy, is
subject to damage by forest management ac-
tivities, such as logging. In cases where logs are
dragged repeatedly over the same area, the litter
layer may be destroyed and bare mineral soil ex-
posed. Where the litter layer is shallow, the amount
of exposed mineral soil may be great. Furthermore,
planting and site preparation, designed to favor the
establishment of trees, may involve destruction of
the protective litter layer. Burning for site prepara-
tion may consume the litter layer and expose
mineral soil, especially if the fuel is heavy and/or
the site is dry. Other activities, such as raking or
piling slash, also tend to destroy the litter layer and
expose large quantities of mineral soil. The overall
effects of these activities are elimination of protec-
tive material covering the mineral soil, and soil
compaction, which affects the infiltration and
erodibility properties of the soil surface.
Creation of bare soil areas. — In addition to
the possible changes within felling and logging
units, machine-construction of areas such as roads
(required to access and remove the timber) and
landings can expose extensive areas of mineral soil.
These constructed areas usually have few rainfall
intercepting surfaces above the soil and are fre-
quently the major source of erosion produced sedi-
ment.
Creation of channels. — Using heavy equip-
ment and skidding logs across the soil surface
creates ruts, gouges, or channels. When water is
collected and concentrated in these channels, flow
energy and erosion potential are greater than if an
equal amount of water were dispersed over the en-
tire slope area.
Creation of hydrophobic conditions from fire.
An extremely hot fire will consume essentially
all of the overstory foliage, understory vegetation,
and surface litter layer leaving the soil surface ex-
posed to the rainfall energy of future storms. If the
soil is coarse textured, it may become hydrophobic
following intense burning, i.e., shedding water as
runoff rather than allowing infiltration to occur. A
hydrophobic soil condition frequently occurs when
IV.3
-------
volatile organic compounds condense on cooler
subsurface soil particles during burning and,
thereby, leave a thin waxy surface that resists wet-
ting. Since soil non-wettability can increase surface
runoff, greater flow energies are available for soil
particle detachment and transport.
Creation of other situations. — Soil mineralogy
can promote non-wettability in some cases. For ex-
ample, soils with high amounts of volcanic ash
become hydrophobic if they become very dry. Soil
microorganisms often create barriers to water in-
filtration during dry periods. Although these
organisms, such as lichens, may protect the soil
against erosion, the additional runoff may con-
tribute to soil loss elsewhere on the slope.
PROCEDURAL CONCEPTS: ESTIMATING
SURFACE SOIL LOSS
This section discusses the concepts necessary for
estimating surface soil loss and for evaluating the
individual parameters involved. It is organized ac-
cording to a conceptual understanding of surface
soil loss and corresponds to the flow chart (fig.
IV.l).
An outline of the overall procedure for estimating
sediment delivery to a stream from surface erosion
sources is presented in "The Procedure" section of
this chapter. A detailed example for estimating
surface soil loss is provided in "Chapter VIII:
Procedural Examples." All concepts discussed here
are necessary for using the overall procedure.
Two different approaches are recognized by
agricultural and forest scientists for estimating sur-
face soil loss. The first of these is an empirical ap-
proach — predictive equations developed from
analyses of data. The second is the use of process
models — models developed through an analysis of
cause and effect relationships. Although process
models may ultimately be a more flexible tool
producing more accurate answers over a wider
range of conditions that can be obtained from em-
pirical models, they are still in the development
stage. In addition, process models often require
more data than are generally available. For these
reasons, process models are not recommended as
tools for predicting soil loss within the forest en-
vironment.
This chapter presents an empirical procedure
for estimating soil loss and adapts it to specific
silvicultural problems. The Universal Soil Loss
Equation (USLE), originally developed by
Wischmeier and Smith (1965) for use on midwest
agricultural soils, has been modified for use in
forest environments. The cropping management
(C) factor and the erosion control practice factor
(P) used in the USLE have been replaced by a
vegetation-management (VM) factor to form the
Modified Soil Loss Equation (MSLE). The follow-
ing discussion of MSLE and its various factors is
based on discussions in "Agricultural Handbook
282" (Wischmeier and Smith 1965) and "Upslope
Erosion Analysis" (Wischmeier 1972).
The modified soil loss model (MSLE) is:
A = R K L S VM (IV.l)
where:
A = the estimated average soil loss per unit
area in tons/acre for the time period
selected for R (usually 1 year.) It is not
intended to reflect climatic extremes of a
given year.
R = the rainfall factor, usually expressed in
units of the rainfall-erosivity index, El,
and evaluated from the iso-erodent map,
figure IV.2 (U.S. Department of
Agriculture, Soil Conservation Service
1977).
K = the soil-erodibility factor, is usually ex-
pressed in tons/acre/EI units for a specific
soil in cultivated continuous fallow tilled
up and down the slope.
L = the slope length factor is the ratio of soil
loss from the field slope length to that
from a 72.6-foot (22.1 m) length on the
same soil, gradient cover, and manage-
ment.
S = the slope gradient factor, is the ratio of
soil loss from a given field gradient to
that from a 9-percent slope with the same
soil, cover, and management.
VM = the vegetation-management factor, is the
ratio of soil loss from land managed un-
der specified conditions to that from the
fallow condition on which the factor K is
evaluated.
Numerical values for each of the factors have
been determined from research data. These values
may differ somewhat from one field or locality to
another; however, approximate numerical values
for any site may be estimated using figures and
tables present in this chapter or in the example in
chapter VIE.
IV.4
-------
The MSLE procedure can be used as a guide for
quantification of potential erosion of different land
management strategies only if the principle in-
teractions on which the equation is based are
thoroughly understood. Failure to understand the
equation and its background will lead to misuse
and/or invalid interpretation. Each MSLE factor is
discussed on the following pages to clarify the as-
sumptions of the model. If the assumptions do not
represent the actual processes in the forest environ-
ment, then predicted erosion values will not be the
same as actual erosion. The MSLE model may be
used to compare effects of different land uses on
soil loss if the assumptions used for evaluating each
factor in the MSLE do not change with changing
land uses.
The Rainfall Factor, R
Wischmeier and Smith (in press) reports that the
function of the rainfall factor, R, is to quantify the
interrelated erosive forces of rainfall and runoff
that are a direct and immediate consequence of
rainstorms. It reflects all erosive rains occurring
throughout the year in addition to annual maxima.
Since the rainfall factor, R, represents an
average annual value, the MSLE estimates average
annual soil loss. Soil loss estimates should not be
made for specific storms or specific time periods
without modifying the R factor to include a runoff
variable and using other MSLE values appropriate
for the specific events. Even then, soil loss es-
timates for specific events are subject to much
greater error than estimates of average annual soil
loss.
Energy-Intensity Values, El
Factor R is based on a rainfall energy-intensity,
El, parameter which is linearly proportional to soil
loss when all other factors are held constant
(Wischmeier 1972).
The iso-erodent map (fig. IV.2) presents average
annual El values for the contiguous United States.
The lines on the map join points with the same
erosion-index value (which implies equally erosive
average annual rainfall) and are called iso-erodent
lines. The value of R in erosion units per year along
each iso-erodent is the value of R in the erosion
equation.
The average and the maximum storm values at a
particular location will vary widely from year to
year. An analysis of rainfall records at 181 stations
indicated that maximum storm values tend to fol-
low log-normal frequency distributions that are
usually well defined by continuous records of from
20 to 25 years (Wischmeier and Smith in press).
El is an interaction term that reflects the com-
bination of raindrop splash erosion and runoff
detachment of soil particles from bare soil. The
sum of computed storm El values for a given time
period is a numerical measure of the erosivity of all
the rainfall within that period. The rainfall erosion
index at a particular location is the longtime-
average yearly total of the storm El values. The
storm El values reflect the interrelations of signifi-
cant rainstorm characteristics. Summing these
values to compute the erosion index adds the effect
of the frequency of erosive storms within the year.
Increases in rainfall energy due to driving winds
were not included in the rainfall factor
(Wischmeier and Smith 1958, 1965). Megahan
(1978) suggests that wind can increase rainstorm
erosion by as much as one order of magnitude
because the force vector of wind increases with the
sin of the slope angle. Therefore, on steep slopes
wind becomes an important factor.
Determining The Rainfall Factor
R is the number of erosion index units occurring
in an average year's rainfall for a site and may
either be computed or taken from a prepared map
(fig. IV.2).
It is defined as:
where:
R= EL
100
(IV.2)
E = the total kinetic energy in foot-tons/acre
inch of rain for each storm. For a storm to
be included, it must be greater than 0.5
inches (12.7mm) and be separated from
other storms by more than 6 hours.
I = the maximum 30-minute intensity in in-
ches/hour for the area, over the same
time period used for estimating soil loss.
The El value for any particular rainstorm can be
computed from recording rain gage data with the
help of a rainfall energy table published by
Wischmeier and Smith (1958).
IV.5
-------
LOCATION
R - INDEX MAP
% SILT & VERY FINE SAND
% SAND
% ORGANIC MATTER
SOIL STRUCTURE
SOIL PERMEABILITY
SLOPE LENGTH
SLOPE GRADIENT
' GROUND COVER %
SURFACE
L UNDERSTORY CANOPYl
TOPO MAP
'DELINEATED TO SHOWN
CUTTING BLOCKS
ROADS & LANDINGS
WATERSHED DIVIDES/
SOIL TYPE
.STREAMS
RAINFALL
FACTOR
SOIL ERODABILITY
FACTOR
SLOPE LENGTH
FACTOR
VEGETATIVE
MECHANICAL
FACTOR
AREA
ESTIMATED
POTENTIAL SOIL LOSS PER UNIT AREA
ESTIMATED SURFACE EROSION
SEDIMENT DELIVERED
TO STREAM
Figure IV. 1.—Flowchart of the procedural concepts involved in estimating
sediment delivery from surface erosion sources.
-------
/SOIL PERMEABILITY\
/ MAX 15 MIN STORM \
DISTANCE ACROSS
\ DISTURBANCE /
\ TO STREAM /
/%
%
\%
VERY FINE SAND)
SILT
CLAY
TRANSPORT
AGENT
% SOIL SURFACE
IN CONTACT WITH
VEGETATION OR
VEGETATIVE
RESIDUE
f SLOPE }I
\ SHAPE y y
SURFACE
ROUGHNESS;
TEXTURE OF
ERODED MATERIAL
DISTANCE FROM
LOWER EDGE
OF DISTURBANCE
TO STREAM
OPTIONAL
SITE FACTOR-
USER
SELECTED
SEDIMENT DELIVERY INDEX
PROCEDURAL STEP.
COMPUTATION OR
EVALUATION
Figure IV.1.—Flow chart of the procedural concepts involved in estimating sediment delivery from surface
erosion sources — continued.
-------
W.H. Wischrrteier, ARS, 1977
Figure IV.2.—Iso-erodent map illustrating average annual values of the rainfall factor, R.
IV.8
-------
Figure IV.2.—Iso-erodent map Illustrating average annual values of the rainfall factor, R — continued.
IV.9
-------
Research exploring the drop size and terminal
velocity of various storm events (Gunn and Kinzer
1949, Laws and Parsons 1943) led to derivation of
an equation for E in terms of the intensity of the
storm in foot-tons/acre inch as (Wischmeier and
Smith 1958):
E = 916 + 331 logioi (IV.3)
where:
E = storm kinetic energy in foot-tons/acre
inch
i = the intensity of the storm in inches/hour
An optional method of determining R requires
rain gage data from sites which have 30-minute
rainfall records available. Using equation IV.3 and
rainfall data, calculate the E value for each storm.
Using equation IV.2 and rainfall data, calculate R.
The more commonly used method for determin-
ing R is to take locational values of the rainfall fac-
tor, R, directly from the iso-erodent map (fig. IV.2)
(USDA, Soil Conservation Service 1977). The iso-
erodent map shows R values ranging from <20 to
550. The erosion index measures only the effect of
rainfall when separated from all other factors that
influence erosion. Points lying between the in-
dicated iso-erodents may be approximated by
linear interpolation.
If all soil and topography factors were exactly the
same everywhere, average annual soil losses from
plots maintained in continuous fallow, tilled up
and down the slope, would differ in direct propor-
tion to the erosion-index values. This potential dif-
ference is, however, partially offset by differences
in soil, topography, vegetal cover, and surface lit-
ter. On fertile soils in the high rainfall areas of the
United States, good vegetal cover protects the soil
surface throughout most of the year; heavy plant
residues, where present, provide excellent ground
cover during the dormant season. In the regions
where the erosion index is extremely low, good
ground cover is often limited to a relatively short
period of time. Natural soil erosion may occur both
in semiarid regions because of poor ground cover,
and in humid regions (with good ground cover) due
to high precipitation.
R Values For Thaw And Snowmelt
Wischmeier and Smith (in press) have observed
that, in the Pacific Northwest, up to 90 percent of
the erosion on the deep loess agricultural soils has
been associated with surface thaws and snowmelt
runoff. This type of erosion is not accounted for by
the rainfall erosion index, but it occurs frequently
both in the northwest and in portions of the central
western states. With this erosion, the linear
precipitation relationship would not account for
peak losses in early spring since as the winter
progresses, the soil becomes increasingly more
erodible. As the soil moisture profile is filled by
winter precipitation, the surface soil structure
breaks down by repeated freezing and thawing,
resulting in puddling, surface sealing and a reduc-
tion in infiltration. Additional research on the ero-
sion processes and means of erosion control during
snowmelt runoff is needed.
Until research designs a more acceptable method
of calculating erosion indices, Wischmeier and
Smith (in press) suggest that the early spring ero-
sion by runoff from snowmelt, thaw or light rain on
frozen soil may be used in the soil loss computa-
tions by adding a subfactor, Rg, to the erosion index
to obtain the R factor. Investigations with only
limited data indicate that the best estimate of Rs
may be obtained by taking 1.5 times the local,
December through March, precipitation, measured
as inches of water. For example, a location in the
northwest that has an erosion index of 20 (fig. IV.2)
and averages 12 inches (304.8mm) of precipitation
between December 1 and March 31 would have an
estimated average annual R factor of [1.5(12) + 20]
or 38.
Snowmelt runoff erosion may also be a signifi-
cant factor in the northcentral and eastern states,
particularly on loessal soils. Where experience in-
dicates that this type of runoff exists, it should be
included in factor R evaluation.
The Soil Erodibility Factor, K
The term "soil credibility" is distinctly different
from "soil erosion." The rate of soil erosion,
designated by A in the soil loss equation, may be
influenced more by land slope, rainstorm
characteristics, cover, and management than by
inherent properties of the soil. This difference in
soil erosion, due only to soil properties, is referred
to as soil credibility.
The physical properties of the soil, as they relate
to the inherent susceptibility of that soil to erode,
are discussed in soil science literature (Barnett and
Rogers 1966, Browning and others 1947, Lillard and
others 1941, Middleton and others 1932, Olsen and
Wischmeier 1963, Peele and others 1945,
Wischmeier and Mannering 1967). Wischmeier and
IV.10
-------
Mannering (1969) developed an empirical expres-
sion of soil erodibility as a function of 15 soil
properties and their interrelationships. Their equa-
tion, however, appeared to be too complex and
demanding for general use, and the soil erodibility
factor was later redefined in terms of five soil
properties.
Soil characteristics that influence soil erodibility
by water are: (1) those that affect the infiltration
rate, permeability, and total water-holding
capacity, and (2) those that resist the dispersion,
splashing, abrasion, and transporting forces of the
rainfall and runoff (Adams and others 1958). A
number of attempts have been made to determine
criteria for characterizing soils according to
erodibility (Lillard and others 1941, Middleton and
others 1932, Peele and others 1945, Smith and
Wischmeier 1962). Generally, however, soil clas-
sifications used for erosion prediction have been
largely subjective and have led only to relative
rankings.
The relative erosion hazard (erodibility) of dif-
ferent soils is difficult to judge from field observa-
tions. Even soils with a relatively low erodibility
factor may show signs of serious erosion under cer-
tain conditions, such as on long or steep slopes or in
localities having numerous high-intensity rain-
storms. A soil with a high natural erodibility factor,
on the other hand, may show little evidence of ac-
tual erosion under gentle rainfall when it occurs on
short and gentle slopes or when the best possible
management is practiced. The effects of rainfall,
length and degree of slope, and vegetative cover
management are accounted for in the MSLE equa-
tion by the symbols R, L, S, and VM. The soil-
erodibility factor, K, is evaluated independently of
the effects of the other factors and will vary
depending on the intrinsic properties of the soil.
Original values of the soil-erodibility factor, K,
in the MSLE were determined experimentally for
agricultural lands. A standard plot for determining
K experimentally is 72.6 feet (22.1m) long with a
uniform lengthwise slope of 9 percent, in con-
tinuous fallow, tilled up and down the slope. Con-
tinuous fallow, in this case, is land that has been
tilled and kept free of vegetation for a period of at
least 2 years or until prior crop residues have
decomposed. During the period of soil loss
measurements, the plot is plowed and placed in
conventional corn seedbed condition each spring
and is tilled as needed to prevent vegetal growth or
serious surface crusting. This provides a reproduci-
ble soil surface condition.
When all of these conditions are met, each of the
factors, L, S, and VM, has a value of 1.0 and K
equals A/EI, where A is the soil loss per unit area
(tons/yr) and El is the erosion index.
For a particular soil, K is the rate of erosion per
unit of erosion index from standard plots on that
soil. Conditions selected as unit values in the
USLE represent the predominant slope length and
the median gradient on which past erosion
measurements in the United States were made. It
is not known if a K factor determined in this man-
ner is completely appropriate for use on forest soils.
Until research clarifies this point, K will have to be
used on the basis of its original derivation.
Direct measurements of K on replicated stan-
dard plots reflect the combined effects of all the
variables that significantly influence the ease with
which a soil is eroded by rainfall and runoff. To
evaluate K for soils that do not usually occur on a
9-percent slope, soil loss data from plots that meet
all other specified conditions should be adjusted to
a 9-percent slope by means of the slope factor in the
Universal Soil Loss Equation (Wischmeier 1972).
Determining The Soil Erodibility Factor
Both the equation and nomograph (fig. IV.3)
(Wischmeier and others 1971) for determining K
values are discussed. The nomograph can be used
for all soils; however, the given equation is limited
as described below.
Soil erodibility equation. — Solution of the soil
erodibility equation is possible with data normally
available from standard soil profile descriptions
and routine laboratory analysis. The equation
should not be used with soils having more than 70
percent silt and very fine sand or with soils having
a low clay content because beyond 70 percent,
equation IV.4 no longer fits the nomograph curve.
The equation for soil erodibility is:
K = (2.1 X 10-6) (12-Om) (M1-14)
+ 0.0325(8-2) + 0.025(P-3)
(IV.4)
where:
K = soil erodibility factor used in the MSLE.
Om = percent organic matter; if organic matter
is >4%, use 4%.
M = particle size parameter: [percent silt
(100 - % clay)] where very fine sand
(0.05-0.1 mm) is included in the silt frac-
tion.
S = code for soil structure:
IV.ll
-------
Soil Structure Class
very fine granular
fine granular
medium or coarse granular
blocky, plately, or massive
MSLE
Code
1
2
3
4
= Code for Soil Conservation Service
permeability classes.
These are for the soil profile as a whole
(Wischmeier and others 1971), based on
estimated water flow in inches/hour
through saturated, undisturbed cores un-
der ' j-inch head of water (U.S. Depart-
ment of Agriculture, Soil Conservation
Service 1974):
Permeability class
MSLE
Permeability rates Code
in/hr
very slow
slow
slow to moderate
moderate
moderate to rapid
rapid
<0.06
0.06-0.2
0.2 -0.6
0.6 -2.0
2.0 -6.0
>6.0-20.0
6
5
4
3
2
1
General permeability classification guides and
discussion from the USDA Soil Survey Manual are
presented to help determine the appropriate
permeability classification. Soil permeability is
that quality of the soil that enables it to transmit
water or air. It can be measured quantitatively in
terms of rate of flow of water through a unit cross
section of saturated soil in unit time, under
specified temperature and hydraulic conditions.
Percolation under gravity with a '/2-inch head and
drainage through cores can be measured by a stan-
dard procedure involving presaturation of samples.
Rates of percolation are expressed in inches per
hour.
In the absence of precise measurements, soils
may be placed into relative permeability classes
through studies of structure, texture, porosity,
cracking, and other characteristics of the horizons
in the soil profile in relation to local use experience.
The observer must learn to evaluate the changes in
cracking and in aggregate stability with moisten-
ing. If predictions are to be made of the respon-
siveness of soils to drainage or irrigation, it may be
necessary to determine the permeability of each
horizon and the relationship of the soil horizons to
one another and to the soil profile as a whole. Com-
monly, however, the percolation rate of a soil is set
by that of the least permeable horizon in the solum
or in the immediate substratum.
The infiltration rate, or entrance of water into
surface horizons, or even into the whole solum, may
be rapid; yet permeability may be slow because of a
slowly permeable layer directly beneath the solum
that influences water movement within the solum
itself. The rate of infiltration and the permeability
of the plow layer may fluctuate widely from time to
time because of differences in soil management
practices, kinds of crops, and similar factors (U.S.
Department of Agriculture, Soil Survey Staff
1951).
Some guides for using the permeabililty codes
are: (1) fragipan soils fall into category 6; (2) soils
with surface permeability underlain by massive
clays or silty clays should be coded 5; (3) silty clay
or silty clay loam soils having a weak angular or
subangular blocky structure and moderate surface
permeability should be coded 4; (4) if the subsoil
structure remains moderate or strong, or texture is
coarser than silty clay loam, the code should be 3;
and (5) if the soil remains open, does not form sur-
face seals, and the profile does not restrict intake,
the code should be 1 or 2.
Soil credibility nomograph for factor K. —
Equation IV.4 is based on the nomograph with one
exception — the relationship for K changes when
the silt-very fine sand fraction exceeds 70 percent.
This change is not included in the equation, but is
incorporated into the nomograph (fig. IV.3).
Instructions for use of the nomograph are included
in the figure.
In certain situations, improved K values may be
obtained by using the following suggestions:
1. For claypans and fragipans, it may be
desirable to use separate credibility factors for
dry and wet seasons by using different
permeability ratings in the nomograph.
Permeabilities should be reduced in wet
seasons, but not for thunderstorms during the
dry season (Wischmeier and others 1971).
Weighted annual mean erodibility factors for
wet and dry seasons can be computed as fol-
lows:
R _(KWMW + KdMd)
Mw + Md
where:
K = weighted mean erodibility,
Kw = soil erodibility during wet season,
(IV.5)
IV. 12
-------
Figure IV.3.—Nomograph lor determining the soil credibility factor, K.
-------
Mw = number of wet months with erosive rain-
fall and/or snowmelt runoff,
Kd = soil credibility during dry season,
Md = number of dry months with erosive rain-
fall and/or snowmelt runoff,
2. Large surface material, such as gravel, is not
included in K value determinations, but
rather is a part of the vegetation-management
factor (VM) as it relates to mulch or ground
cover.
3. High clay subsoils containing iron and
aluminum oxides react differently than sur-
face soils containing those oxides (Roth and
others 1974). In this situation the nomograph
solution for K may not apply (Wischmeier
1976).
The Soil Conservation Service has determined K
factor values for some soils. Information about
these tables should be obtained from Soil Conser-
vation Service soil scientists who are familiar with
the soils in a given area.
The Topograhic Factor For Slope Length and
Gradient, LS
The rate of soil erosion by water is affected by
both slope length and slope gradient (percent
slope). The two effects are represented in the ero-
sion equation by L and S, respectively. In field ap-
plication of the equation, however, it is convenient
to consider the two as a single topographic factor,
LS, because of the interactions between the two
parameters.
Numerous plot studies (Wischmeier 1966) have
shown that soil loss in tons/unit area is propor-
tional to some power of slope length. Since the fac-
tor L is the ratio of soil loss from the slope length of
interest to that from a standard 72.6-foot(22.1m)
slope, the value of L may be expressed as:
L = (X 772.6)'
(IV.6)
where:
X = slope length in feet, and
m = 0.2 for slope gradients that are <1.0%
m = 0.3 for slope gradients >1.0 but<3.0%
m = 0.4 for slope gradients >3.0 but <5.0%
m = 0.5 for slope gradients that are >5.0%
m =0.6 for slope gradients over 12% with a
natural permeability code of 5 or 6 where
infiltration is very low, such as on con-
struction sites and roads (Wischmeier
and Smith in press).
The effect of slope length on soil loss is due
primarily to a greater accumulation of runoff on
longer slopes. Runoff velocity increases as water
volumes increase, and both detachment and tran-
sport capacity increase geometrically with in-
creased velocity (Wischmeier 1972).
The exponent m is significantly influenced by
the interaction of slope length and gradient, but it
may also be influenced by soil characteristics, type
of vegetation, and management practices.
Generally, increases in slope gradient, slope length,
or increases in runoff (due to reduced infiltration
caused by either soil type or vegetation-
management practices) create a need for a larger
slope length exponent (m) in equation IV.6 (Foster
and others 1977).
Slope Length Factor, X
Slope length is defined as the distance from the
point of origin of overland flow to: (1) the point
where the slope decreases to the extent that deposi-
tion begins; (2) the point where runoff enters a
well-defined channel that may be part of a
drainage network or a constructed channel such as
a terrace or diversion (Wischmeier and Smith
1965); or (3) the downslope boundary of a distur-
bance. A change in land use on a slope does not
change the effective slope length unless the runoff
from the upper slope is diverted off of the area in
some manner.
Slope Gradient Factor, S
A. W. Zingg (1940) concluded that soil loss varies
as the 1.4 power of percent slope. Musgrave (1947)
recommended use of the 1.35 power of percent
slope. Based on analyses of the data, Smith and
Wischmeier (1957) proposed the relationship:
= (0.43 + 0.30s + 0.043s2)
«
6.613
where:
s = slope gradient expressed as percent slope,
and
S = slope gradient factor.
IV.14
-------
The data adequately support this slope
relationship up to a 20 percent slope. Since the
equation is parabolic, slope relationships cannot be
extrapolated indefinitely beyond gradients of 20
percent and still obtain accurate estimates of soil
loss from the MSLE. However, the MSLE may be
used on slopes over 20 percent to compare the soil
loss effects of several different management ac-
tivities.
Determining The Topographic Factor
The LS factor is the expected ratio of soil loss/
unit area (tons/yr) on a slope as compared to a cor-
responding soil loss from the standard plot (9-
percent slope, 72.6 feet (22.1 m) long). For specific
combinations of slope length and slope gradient,
this ratio may be taken directly from a length-slope
nomograph (fig. IV.4). For example, a 10-percent
slope that is 360 feet (109.7 m) long would have an
LS ratio of 2.6.
Values of LS for slope gradients and lengths not
shown on the nomograph may be computed using
the following equation. A correction factor has been
added to equation IV .7 to avoid using sines of
angles.
LS
=(
\72.
/ 10,
\10,0
).43 + 0.30s + 0.043s2>
6.613 J
000+sV
(IV.8)
s = slope gradient in percent, and
m = an exponent based on slope gradient from
equation IV.6.
The use of equation IV.8 or figure IV.4 assumes
that the slopes are uniform from top to bottom.
Irregular Slopes
Slopes are usually convex or concave. Use of an
average gradient for the entire slope length sub-
stantially underestimates soil loss from the convex
slopes and overestimates the loss from concave
slopes (Foster and Wischmeier 1973). If equation
IV.8 or the nomograph (fig. IV. 4) is used on convex
slopes, the gradient of the steeper segment should
be used as the overall slope gradient for estimating
the LS factor. On a concave slope, where deposition
may occur on the lower end of the slope, the ap-
propriate length and gradient to use is the point
where the slope flattens enough for deposition to
occur.
In cases where the slope characteristics change
from top to bottom, averaging the slope
characteristics and applying one LS factor will not
accurately estimate soil loss. The calculations for
irregular slopes (Foster and Wischmeier 1973) are
recommended on areas where several slopes are
combined. This equation accounts for situations
where runoff comes from one slope segment and
flows to the next. However, if substantial sediment
deposition will occur due to a change in vegetative
cover or diversion of water, this procedure cannot
be used because it does not account for sediment
deposition.
Foster and Wischmeier's (1973) equation is
presented here, and an example of its use may be
found in chapter VIII.
LS
1
Xe
n
• 2
j-l
/„ xm + l
/ Vi
\(72.6)m
(72.6)'
10,000
10,000
(IV.9)
in which:
Xe =
j
*j =
XJ4 =
s =
m =
overall slope length in feet,
slope segment index,
the length in feet from the top to the
lower end of any segment j,
total slope length above segment j,
slope in percent,
an exponent based on slope gradient from
equation IV.6, and
slope factor °-43 + °'30s + °-043s2
6.613
for s2 segment j (Eq. IV.7)
Foster and Wischmeier (1973) developed an
alternative procedure for performing several steps
in the solution of equation IV.9 for irregular slopes.
The set of graphs (figs. IV.5 and IV.6) eliminates
the need for logarithms, a slide rule, or an
electronic calculator to raise the slope length values
to needed powers. These figures are a family of
curves for specific slopes ranging from 0.5 percent
to 140 percent. Each figure uses the appropriate
value for m as previously discussed.
IV.15
-------
9dO|S V
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ro-
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03
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s-
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8-
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SL 000 L 009 00* OOE OOZ 091 001 09 0* 0Ł 02 SI 01 9 * Ł 2
\9'L Z'U'tO LOB" 08' Oi 09 09' 9f Ot> 9E' OE' SZ' OZ' 81' 91' W 21' OL' 80' 90' SO' /
1 ! 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 /
\ f '0 = w J°i JoioB^ sn /
\ /
8-
2-
g-
b-
OJ
b-
g-
8-
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01*
8-
ro.
Oi
o"
C7l~
fe-
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co Ł-
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u
'9 8> 9> t1'* Z'fr 0> 8'Ł 9'Ł *'Ł Z'Ł 0'
% HJ9!pej6 edois
f x?
o °
CD C
QJ
to .^
s s
0. »-:
r-«- ^
°^ CO
Slope gradient %
1 2 .3 4 5 .6 .7 .8 9 1.
K
~o
-g
•° in
0
-S M
^
•S ^_
o
**—
"S 0
*-
o
•Ł
co
—i
^^
\
^
'?
-S
-s
-s
-o
.0
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. m
.0
-m
•^r
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-CM
-T-
. CO
•
-^
— CM
-S
\
\
\
LS factor for m = 0.2 \
/03 .04 .05 .06 .07 .08 .09 .10 .11 .12 .13.14.15 .20 N.
\^
N.
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° 1 2345 10 15 20 30 40 50 100 150 200 300 400 500 1000 15
I
_g
lO
-I
-8
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-I
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^
-8
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-C
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o Q.
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- CM
0
slope length (ft.)
Slope gradient %
G3 ^ C7I -1 -*%IO I
0 ° ° 8 88. :
- slope length (ft.) \
Figure IV.4.—Nomograph for determining the topographic
factor, LS, on simple slopes.
IV. 16
-------
The graphs (figs. IV.5 and IV.6) are based on the
following equation which is a portion of equation
IV.9.
M =
72.6
10.000
10,000+
(IV.9a)
where:
M = derived factor for simplifying calculation
of LS on irregular slopes,
S = slope steepness factor from equation IV. 7,
s = slope gradient in percent,
X = slope length in feet, and
m = an exponent based on slope gradient from
equation IV.6.
The symbol M is plotted on log-log graph paper
against values of slope length with curves for
specific slopes within the body of the graphs.
To illustrate the graphic procedure for obtaining
the LS factor for irregular slopes, a road with cut-
and-fill slopes (fig. IV.7) has been divided into seg-
ments representing the cut slope, the roadbed sur-
face, and the fill slope. It has been assumed that
sediment will not accumulate on the roadbed. The
first segment (cut slope) has a slope length of 4.8
feet (1.46 m) at 66.7 percent gradient, the second
segment (roadbed surface) has a slope length of 12
feet (3.66 m) at 0.5 percent gradient, and the third
segment (fill slope) has a slope length of 4.8 feet
(1.46 m) at 66.7 percent. The values are Xi = 4.8, X2
= 16.8, and X3 = 21.6 = Xe. Data for this procedure
are tabulated into table IV. 1.
For the first segment, enter figure IV.6 at 4.8 on
the horizontal axis, move upward to the curve for
70 percent slope (for greater accuracy, values
between can be interpolated) and read MZ = 29 on
the vertical scale. The upper end of this segment is
at zero length so Ma - Mi = 29.
For the second segment, use the graph for 0.5
percent slope entering the graph with lengths of
16.8 feet and 4.8 feet. For those, M2 = 1, MI = 0.25
and M2 - MI = 0.75. Repeat this procedure for seg-
ment 3.
The effective LS for any segment is obtained by
dividing (MS - MI) by the length of the segment as il-
lustrated. The overall LS value of 5.8 shown in the
last column was obtained by dividing the sum of
the (M2 - MI) by the total length (124.7/21.6 = 5.8).
The detail provided by the last two columns of the
tabulation may be helpful in designing effective
erosion control practices for each segment.
These values for LS, using this graphic ap-
proach, are not exactly the same as those
calculated from equation IV.9, as shown in chapter
VIII. This is due to errors inherent in using graphs.
Although these small errors exist, the numbers
determined with the graphs are sufficiently ac-
curate for general use.
Table IV.1.—Example of data tabulation when using graphs for obtaining LS value for irregular
Segment Slope
M2
Ml
Segment Segment
Length LS
(ft)
1
2
3
66.7
0.5
66.7
4.8
16.8
21.6
0.0
4.8
16.8
29
1
270
0.0
0.25
175
29
0.7
95
124.7
4.8
12.0
4.8
21.6
6.0
0.1
19.8
5.8
IV. 17
-------
1QOOO
1,000
.10
100
1,000
X = Slope Length (ft.)
Figure IV.5.—Values of n for use with irregular slopes (0.5 -100%) with appropriate values of m (0.2, 0.3, 0.4,
and 0.5).
IV. 18
-------
10,000
1,000
/t 100
10
"77
'////
rrn
10.000
10,000+S
1407, 27™ 60 50 40 35 3025
/ f / fi m t— y —7- > I / T—
t
7J-,
M//IA7/
/ 7
r/7r,
///
ZZ.
Z7
Z
2Z
77^
/
7ML
Mtt
2018
V/-A
LL
72
16 1 12
z
77777.
77/77
f / //
/ //
7777
~TT
10
100
X= Slope Length (ft)
Figure IV.6.—Values of M tor use with irregular slopes (10-140%) where m = 0.6.
Wi
7
1,000
IV.19
-------
Figure IV.7.—Generalized cross section of outsloped road.
IV.20
-------
The Vegetation-Management Factor, VM
The effects of vegetative cover and forest
silvicultural activities on soil detachment by rain-
fall and runoff are numerous and varied. Forest
residues from silvicultural activities may be
removed, left on the surface, incorporated near the
surface, plowed under, or burned. When left on the
surface, they may be chopped or they can remain
as left by the harvesting operation. Seedbeds may
be left rough with the capacity for surface storage
of rainfall and sediment, or they can be left
smooth. Different combinations of these variables
and possibly other conditions will have different ef-
fects on a soil's susceptibility to erosion. In addi-
tion, the effectiveness of residue management will
depend on the volume and distribution of remain-
ing residues. This in turn depends on rainfall dis-
tribution, on the soil fertility level, and on other
management decisions that affect the amount of
vegetative productivity on a given site.
The VM factor in the Modified Soil Loss Equa-
tion is the ratio of soil loss from land managed un-
der specified conditions to the corresponding loss
from tilled, continuously fallow conditions of a
standard plot. This factor measures the combined
effect of all the interrelated cover and management
variables discussed above.
Soil loss that would occur on a particular site if it
were in a continuous fallow condition is computed
by a product, R K L S, in the MSLE. Actual loss
from an area is usually much less than the com-
puted amount; just how much less depends on the
particular stage of growth and development of the
vegetal cover, and the condition of the soil surface
at the time when rain or snowmelt occurs.
The VM factor of the MSLE attempts to com-
bine vegetative cover and soil surface conditions
into one numerical factor. Use of the VM factor is
facilitated by separating it into three distinct kinds
of effects and evaluating each type as a subfactor:
Type I — effects of canopy cover, Type n — effects
of mulch or close growing vegetation in direct con-
tact with the soil surface, and Type El — residual
effects of land use (Wischmeier 1975).
Effects Of Canopy Cover, Type I
Leaves and branches that do not directly contact
the soil surface are effective only as canopy cover.
Canopies close to the surface have some influence
on the impact energy of falling raindrops.
Waterdrops falling from a canopy may have ap-
preciable force at the soil surface depending on
canopy height and drop size (Dohrenwend 1977).
Figure IV.8, taken from Wischmeier (1975) shows
canopy effects of water drops for different amounts
of canopy ground cover and canopy heights. If pos-
sible, increase in drop size because of canopy in-
terception is ignored, or is assumed to be offset by
the fact that some of the intercepted water moves
down the stems to the ground. The canopy factors
for various percentages of cover at heights of 0.5, 1,
2, and 4 m may be obtained directly from figure
IV.8. For a 60 percent canopy cover at a height of
1m, for example, the canopy factor is 0.58. This
means that the effective El with the canopy is only
58 percent of the actual El of the rainfall, and the
expected erosion would also be only 58 percent of
that predicted by the El obtained from the iso-
erodent map.
Table IV.2—Velocities (m/sec) of falling waterdrops of different sizes (mm)
falling from various heights (m) in still air
Median
drop diam.
2.00'
2.251
2.501
3.001
3.502
Drop fall height
0.5
2.89
2.93
2.96
3.00
3.04
1.0
3.83
3.91
3.98
4.09
4.19
2.0
4.92
5.07
5.19
5.37
5.55
3.0
5.55
5.74
5.89
6.14
6.37
4.0
5.91
6.14
6.34
6.68
6.98
6.0
6.30
6.63
6.92
7.37
7.79
20.03
6.58
7.02
7.41
8.06
8.63
1Laws J.O. 1941. Measurement of fall-velocity of water drops and rain drops. Transactions of the
American Geophysical Union 22:709-721. From Wischmeier 1975.
'Extrapolation of values given by Laws (1941).
'Values in the last column are considered terminal velocities.
IV.21
-------
Figure IV.8 is based on a medium drop size of 2.5
mm for both the rain and droplets formed on the
canopy. If the 3.35 mm droplets measured by
Chapman (1948) on a red pine plantation are as-
sumed to be characteristic for most tree canopies
(Trimble and Witzman 1954), figure IV.8 should be
modified. When modifying, subfactor values for
complete canopy cover can be computed from the
data in table IV. 2 below for a given diameter using
equation IV.10:
Cioo = 0.169V 0.356 (IV.10)
where:
Cioo = factor for canopy effect at 100 percent
ground cover, and
V = velocity, in meters/second, for a water
drop of a given diameter, falling a given
distance.
Values for less than complete canopy cover can
be found by drawing a line on figure IV.8, from the
point calculated for 100 percent cover to the upper
left corner where other lines are converging.
FACTOR FOR CANOPY EFFECT
8 6 g g I
^fe
*Av
• dr<
^
X
erac
jps
* ^ ^
N.
^
e fa
rom
s^
N
s
Ihe
can
"* **
^
V
ght
opy
~».
^
N
\
of
.^
^
XXN
\
^
X
\
""• .
s '
\
0.
im*
2m*
K
1m*
X
X
s
5m*
0 20 40 60 80 100
PERCENT GROUND COVER BY CANOPY
Effects Of Mulch And Close Growing Vegeta-
tion, Type II
A mulch on the soil surface is much more effec-
tive than an equivalent percentage of canopy cover.
There are two reasons for this: (1) raindrops in-
tercepted by the mulch have very little remaining
fall height to the ground, and their impact on the
soil surface is essentially eliminated; and (2) a
mulch that makes good contact with the ground
also reduces the velocity of runoff. This, in turn,
greatly reduces the runoffs potential to detach soil
material.
Effectiveness of type II cover can be expressed on
the basis of percent surface cover using the
relationship in figure IV.9 (Wischmeier 1975). If
FACTOR FOR MULCH AND
CLOSE GROWING VEGETATION
3 8 S g g I
\
\
\
\
\
N
\
X
s.
x
X
^^
^*s
^
Figure IV.8.—Influence of vegetal canopy on effective El, as-
suming bare soil beneath the canopy, and based on the
velocities of free-falling waterdrops 2.5 mm in diameter
(Wischmeier 1975).
PERCENT OF SOIL SURFACE COVERED BY MULCH
Figure IV.9—Effect of plant residues or close-growing stems
at the soil surface on the VM factor (does not Include sub-
surface root effects) (Wischmeler 1975).
the cover includes both canopy and surface mulch,
the canopy and mulch factors overlap and the
canopy factor can not be fully credited. Impact
energy of a raindrop striking the mulch is dis-
sipated at that point regardless of effects of canopy
interception on its fall energy. The mulch factor is
always taken at full value, and the canopy factor is
reduced so that it applies only to the percentage of
the soil surface not covered by mulch.
IV.22
-------
To illustrate this, assume a 30 percent mulch
cover combined with a 60 percent canopy at a
height of 1 m. From figure IV.9, the factor for
mulch cover effect is 0.47. Because of the 30 per-
cent mulch cover, the effective canopy cover is only
0.70 of the overall 60 percent cover, or 42 percent.
Entering figure IV.8 with a 42 percent canopy
cover, we obtain a factor of 0.70 for canopy effect.
The factor for this combination of canopy and
mulch cover is the product of the two subfactors
(0.47 times 0.70), which equals 0.33.
Residual Effects Of Land Use, Type III
This category includes residual effects of the
land use on soil structure, organic matter content,
and soil density; effects of site preparation or lack
of preparation on surface roughness and porosity;
roots and subsurface stems; biological effects; and
any other factors affected by land use.
Figure IV. 10 (Wischmeier 1975) was developed
for Type HI effects on undisturbed pasture, range,
forest, and idle land. The initial point (0.45) for the
curves is an estimate of the long-term effect of no
tillage and no vegetation. It was obtained from 10-
year soil loss records on a 12 percent slope of silt
loam soil that was not tilled after the first year but
was kept free of vegetation and traffic. The rate of
0 20 40 60 80 100
PERCENT OF BARE GROUND WITH FINE ROOTS
Figure IV.10.—Effects of fine roots in topsoil on the VM factor.
These values do not apply to cropland and construction
sites (Wischmeier 1975).
soil loss per unit of El declined annually until it
leveled off at about 45 percent of the rate for the
first 2 years of the study. The curvature and end-
points of the curves were based on comparisons of
soil losses from meadow with those from plots hav-
ing equivalent percentages of surface cover in the
form of applied straw mulch.
If an area has been cultivated or totally scalped
so that all of the fine roots from trees, grass, and
weeds are destroyed, then the Type HI effect as
described does not exist.
Sediment Filter Strips
Sediment filter strips are areas of residue or
other kinds of effective sediment traps. If surface
areas that are completely open (having minimal
amounts of residue and soil mixed with residue) are
separated from each other by small filter strips, a
factor of 0.5 should be included in the calculations
(Wischmeier 1972). If the open areas are not
separated by sediment filter strips, use a factor of
1.0 (see example in Chapter VIII).
Determining The Vegetation-Management
Factor
Use either previously published values or es-
timate the VM factor using Type I, n and El sub-
factors.
Previously published tables (tables IV.3, IV.4,
IV.5, and IV.6) and graphs (figs. IV.11 and IV.12)
are reproduced in this chapter with specific VM
values for use under some conditions. Table IV.3
applies only to construction sites (e.g., roads).
Tables from other literature are usually expressed
in terms of the C factor for the Universal Soil Loss
Equation. The C factor is considered appropriate
only if the forest situation and the situation
represented in the published tables have the fol-
lowing in common: the management practice
described in the table must have the same
characteristics as the one to be used, the vegetative
recovery rates must be the same, and all assump-
tions must be the same in practice as presented in
the tables. In addition there will be significant er-
rors if terminology used in the tables does not mean
exactly the same thing from one part of the country
to another.
Type I, II, and in values determined from figures
IV.8, IV.9, and IV. 10 are multiplied to obtain a VM
value for use in equation IV. 1. An example of this
procedure is given in chapter VIE.
This estimation procedure for VM does not
recognize the effects of time on fine root-density. It
is recognized that some changes in soil
characteristics which influence erodibility will oc-
cur due to various silvicultural activities. If these
soil changes are for a short time (only a few years),
IV.23
-------
Table IV.3.—VM factor values for construction sites
(Clyde et al. 1976 ).
Condition
1.
2.
3.
Bare soil conditions
freshly disked to 6-8 inches
after one rain
loose to 1 2 inches smooth
loose to 12 inches rough
compacted buldozer scraped up and down
same except root raked
compacted bulldozer scraped across slope
same except root raked across
rough irregular tracked all directions
seed and fertilize, fresh
same after six months
seed, fertilize, and 12 months chemical
not tilled algae crusted
tilled algae crusted
compacted fill
undisturbed except scraped
scarified only
sawdust 2 inches deep, disked in
Asphalt emulsion
1 ,250 gallons/acre
1,210 gallons/acre
605 gallons/acre
302 gallons/acre
151 gallons/acre
Dust binder
605 gallons/acre
1,210 gallons/acre
VM factor
1.00
0.89
0.90
0.80
1.30
1.20
1.20
0.90
0.90
0.64
0.54
0.38
0.01
0.02
1.24
0.66-1 .30
0.76-1.31
0.61
0.02
0.01-0.019
0.14-0.57
0.28-0.60
0.65-0.70
1.05
0.29-0.78
4. Other chemicals
1,0001 b fi ber glass roving with
60-150 gallons/ acre
Aquatain
Aerospray 70,10 percent cover
Curasol AE
Petroset SB
PVA
Terra-Tack
5. Seedlings
temporary, 0 to 60 days
temporary, after 60 days
permanent, 0 to 60 days
permanent, 2 to 12 months
permanent, after 12 months
6. Brush
7. Excelsior blanket with plastic net
0.01-0.05
0.68
0.94
0.30-0.48
0.40-0.66
0.71-0.90
0.66
0.40
0.05
0.40
0.05
0.01
0.35
0.04-0.10
they are accounted for by the VM factor. Long-
term changes in soil credibility, as a result of ac-
tivities changing soil structure and permeability,
should be evaluated by changing the K factor.
Adjustments for surface microrelief or roughness
and adjustments for different contouring practices
are also lacking from this presentation. More
research needs to be directed toward these ad-
ditional VM subfactors.
Seasonal Adjustments For VM
If necessary, the VM factor can be adjusted for
seasonal changes using equation IV. 11 to obtain an
average annual VM value.
= (VMgMg + VMdMd) dv.n)
Mg + Md
where:
VM = weighted mean vegetation-management
factor,
VM = VM factor for growing season,
M = number of growing season months with
erosive rainfall,
VM d= VM factor for dormant season,
Md= number of dormant months with erosive
rainfall and/or snowmelt runoff.
Estimated Soil Loss Per Unit Area
When all of the parameters of the MSLE (equa-
tion IV. 1) have been assigned the proper values,
the factors are multiplied to obtain an estimate of
soil loss for a specific unit area. The answer
generally will be expressed in tons/acre/year. If
other units of area and time are chosen for use in
the MSLE, they must be applied consistently
throughout the equation.
Converting MSLE To Metric1
The rainfall intensity-energy equation in the
metric system is: E = 210.3 + 89 logioi where E is
kinetic energy in metric-ton meters/hectare/cen-
timeter of rain, and i is rainfall intensity in cen-
timeter/hour. A logical counterpart to the English-
system El is the product: storm energy in metric-
ton meters/hectare times the maximum 30-minute
intensity in centimeter/hour. The magnitude of
this product would be 1.735 times that of the El as
defined in English units. The factor for direct con-
version of K to metric-tons/hectare/metric El units
is 0.2572.
'The equations used in this chapter usually require data to be
in the English system (inches, feet, Ibs., etc.) with the exception
of equation IV.10. Substitution of metric data without making
appropriate changes in equation coefficients will result in er-
roneous answers.
IV.24
-------
Table IV.4.—"C" factors for permanent pasture, rangeland, idle land, and grazed woodland1
(Soil Conservation Service 1977)
Vegetal canopy
Type and height Canopy
of raised canopy2 cover3
Type4
Cover that contacts the surface
Percent ground cover
No appreciable
canopy
Canopy of tall
weeds or short
brush
(0.5 m fall ht.)
Appreciable brush
or bushes
(2 m fall ht.)
Trees but no appre-
ciable low brush
(4 m fall ht.)
%
25
50
75
25
50
75
25
50
75
G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
0
.45
.45
.36
.36
.26
.26
.17
.17
.40
.40
.34
.34
.28
.28
.42
.42
.39
.39
.36
.36
20
.20
.24
.17
.20
.13
.16
.10
.12
.18
.22
.16
.19
.14
.17
.19
.23
.18
.21
.17
.20
40
.10
.15
.09
.13
.07
.11
.06
.09
.09
.14
.085
.13
.08
.12
.10
.14
.09
.14
.09
.13
60
.042
.090
.038
.082
.035
.075
.031
.067
.040
.085
.038
.081
.036
.077
.041
.087
.040
.085
.039
.083
80
.013
.043
.012
.041
.012
.039
.011
.038
.013
.042
.012
.041
.012
.040
.013
.042
.013
.042
.012
.041
95-100
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
1AII values shown assume (1) random distribution of mulch or vegetation, and (2) mulch of ap-
preciable depth where it exists. Idle land refers to land with undisturbed profiles for at least a period of
three consecutive years. Also to be used for burned forest land and forest land that has been harvested
less than 3 years ago.
2Average fall height of water drops from canopy to soil surface.
'Portion of total-area surface that would be hidden from view by canopy in a vertical projection (a
bird's-eye view).
4G: Cover at surface is grass, grasslike plants, decaying compacted duff, or litter at least 2 inches
deep. W: Cover at surface is mostly broadleaf herbaceous plants (as weeds with little lateral-root network
near the surface), and/or undecayed residue.
Table IV.5.—"C" factors for undisturbed woodland
(Soil Conservation Service 1977)
Effective canopy1
% of area
100-75
70-40
35-20
Forest litter2
% of area
100-90
85-75
70-40
"C"3
factor
.0001 -.001
.002-. 004
.003-.009
'When effective canopy is less than 20 percent, the area will be
considered as grassland or idle land for estimating soil loss.
Where woodlands are being harvested or grazed, use table IV.4.
2Forest litter is assumed to be at least 2 inches deep over the
percent ground surface area covered.
3The range in "C" values is due in part to the range in the per-
cent area covered. In addition, the percent of effective canopy and
its height has an effect. Low canopy is effective in reducing
raindrop impact and in lowering the "C" factor. High canopy, over
13 m, is not effective in reducing raindrop impact and will have no
effect on the "C" value.
IV.25
-------
Table IV.6.—"C" factors for mechanically prepared woodland sites
(U.S. Department of Agriculture Soil Cons. Serv. 1977.)
Percent of soil covered with residue
in contact with soil surface Soil Condition and Weed Cover"
Excellent Good
NCS WC5 NIC
None
A. Disked, raked or bedded1 2 .52 .20 .72
B. Burned3 .25 .10 .26
C. Drum chopped3 .16 .07 .17
1 0% Cover
A. Disked, raked or bedded1 2 .33 .15 .46
B. Burned3 .23 .10 .24
C. Drum chopped3 .15 .07 .16
20% Cover
A. Disked, raked or bedded1 2 .24 .12 .34
B. Burned3 .19 .10 .19
C. Drum choppd3 .12 .06 .12
40% Cover
A. Disked, raked or bedded1 2 .17 .11 .23
B. Burned3 .14 .09 .14
C. Drum chopped3 .09 .06 .09
60% Cover
A. Disked, raked or bedded1 2 .11 .08 .15
B. Burned3 .08 .06 .09
C. Drum chopped3 .06 .05 .06
80% Cover
A. Disked, raked or bedded1 2 .05 .04 .07
B. Burned3 .04 .04 .05
C. Drum chopped3 .03 .03 .03
1 Multiply A. values by following values to account for surface
roughness:
Very rough, major effect on runoff and sediment storage,
depressions greater than 6" 0 40
Moderate 0.65
Smooth, minor surface sediment storage,
depressions less than 2" 0 90
2The "C" values for A. are for the first year following treatment. For
A. type sites 1 to 4 years old, multiply "C" value by 0.7 to account for
aging. For sites 4 to 8 years old, use table IV. 4. For sites more than 8
years old, use table IV.5.
3The "C" values for B. and C. areas are for the first 3 years following
treatment. For sites treated 3 to 8 years ago, use table IV. 4. For sites
treated more than 8 years ago, use table IV.5.
'Soil condition and weed cover descriptors.
Excellent— Highly stable soil aggregates in topsoil with litter and
fine tree roots mixed in.
Good— Moderately stable soil aggregates in topsoil or highly stable
soil aggregates in subsoil (topsoil removed during raking), only traces
of litter mixed in.
Fair— Highly unstable soil aggregates in topsoil or moderately
stable soil aggregates in subsoil, no litter mixed in.
Poor— No topsoil, highly erodible soil aggregates in subsoil, no lit-
ter mixed in.
5For each of the soil conditions, "C" factors are provided for no live
vegetation (NC column) and for 75% cover of grass and weeds hav-
ing about 0.5 meter fall height (WC column). For weed and grass
cover other than 0% and 75%, "C" values may be interpolated.
WC
.27
.10
.07
.20
.10
.07
.17
.10
.06
.14
.09
.06
.11
.07
.05
.06
.04
.03
Fair
NC
.85
.31
.20
.54
.26
.17
.40
.21
.14
.27
.15
.10
.18
.10
.07
.09
.05
.03
WC
.32
.12
.08
.24
.11
.08
.20
.11
.07
.17
.09
.06
.14
.08
.05
.08
.04
.03
Poor
NC
.94
.45
.29
.60
.36
.23
.44
.27
.18
.30
.17
.11
.20
.11
.07
.10
.06
.04
WC
.36
.17
.11
.26
.16
.10
.22
.14
.09
.19
.11
.07
.15
.08
.05
.09
.05
.04
IV.26
-------
55
to
0.50
0.40
0.30
o
(0
0.20-
0.10-
,0% Canopy of
Forbs and
- Weeds
,2556 Canopy of Forbs and
Weeds
s 50% Canopy of Forbs and
' Weeds
75% Canopy of Forbs and Weeds
10 20 30 40 50 60 70
Percent Ground Cover of Forbs
80 90 100
Figure IV.11—Relationship between grass density and the VM factor (Clyde and others 1976).
-------
0.50
0.40'
\
O 0.30
•*->
o
(0
\
> 0.20-
0.10-
-0% Canopy of Tall(0.5m)
Grass and Weeds
,25% Canopy of Tall Grass
and Weeds
, 50% Canopy of Tall Grass and
Weeds
75% Canopy of Tall(0.5m)Grass and
Weeds
10
20
30 40 50 60 70
Percent Ground Cover of Grass
80
100
Figure IV.12—Relationship between forb density and the VM factor (Clyde and others 1976).
-------
For practical purposes, it would be expedient to
redefine the unit-plot as having a length of 25
meters and a slope of 10 percent, to derive K on the
basis of those dimensions, and to recompute the
slope-effect chart. The translated values would be:
L =
LS =
Xo.5/5 where X is slope length in meters;
and S = (0.43 + 0.30s + 0.043s2)7.73
where, s = percent slope. Combining the
two,
. 00111s2 + 0.00776s + 0.0111).
(Wischmeier 1972).
Erosion Response Units
Potential sources of non-point pollution con-
stitute site specific problems within an individual
watershed. To estimate the magnitude of a specific
onsite soil loss and to identify the particular
drainageway where this erosion occurs, the
watershed must be divided into homogeneous
areas. Delineating erosion response units requires
identification of individual activities such as roads,
landings, cutting blocks, or skid trails, and the
relative contribution of each activity to potential
sediment yield.
Delineating Erosion Response Units
The following information needs to be shown on
a series of maps or overlays in order to identify and
delineate erosion response units:
1. Topographic information showing
hydrographic areas and channel network.
2. Soil and vegetative resource information used
for the quantification of surface erosion.
3. Project proposal showing the location of
roads, trails, landings, cutting units, etc.
The procedure for compiling these data is ex-
plained by steps:
Step 1. — Obtain a topographic map (fig. IV.13)
to show spatial relationships of the factors needed
in the quantification process. The amount of detail
desired and the amount that can be produced by
the analysis will depend upon the scale and ac-
curacy of the base map.
Step 2. — Extend the stream detail shown on
the topographic base (fig. IV. 14). Perennial
streams, and in some cases intermittent streams,
will be printed on the original topographic base;
however, this does not completely define the
stream channel network within that watershed. It
is important that the displayed stream network be
extended to include all intermittent channels that
are definable on the basis of the contour lines. Each
channel should be extended toward the watershed
divide from channels originally identified on the
base map. Field information, if available, should
be used to verify the final channel network.
Step 3. — Delineate individual hydrographic
areas (fig. IV.15). Draw the interior watershed
boundaries or hydrographic divides separating the
extended channel network that was identified in
step 2. At this point, a series of sub-watersheds or
hydrographic areas will have been delineated
within the watershed of interest.
Step 4. — Since soils information is required for
the evaluation of onsite erosion, soil mapping unit
boundaries should be drawn (fig. IV. 16). These soil
units may come from a standard soil survey, a soil
resource inventory, or a land systems inventory.
The soils may be grouped so that the delineated
map units represent soils that are homogenous with
respect to texture (percent sand, silt, clay), organic
matter, permeability, and structure. Vegetative
cover information, if available, should be mapped
to show the percent surface area occupied by
vegetation, mulch, rock, litter, and debris. Sedi-
ment delivery, as well as surface erosion, is greatly
influenced by these factors; having them mapped
prior to initiating quantification of erosion is
beneficial to the analysis.
For the purpose of bookkeeping, it is necessary to
number these erosion response units consecutively.
Begin near the mouth of the watershed with
number "1" and proceed clockwise toward the head
of the watershed and back around the mouth on the
opposite side.
Step 5. — Stratify the problem as it relates to
the proposed silvicultural activity by drawing
roads, cutting blocks, log landings, skid trails, and
other activities on an overlay for the topographic
base (fig. IV. 17). Placing this information on an
overlay will make the maps more readable and will
also facilitate making changes in a proposal
without destroying the entire topographic base.
Delineate the transportation system first, in-
cluding all existing and proposed roads, skid trails,
and aircraft landing areas. Then delineate the cut-
ting blocks as precisely as possible relative to the
topographic base (fig. IV. 18). Other items, such as
decking areas and log landings, should also be
shown on the topographic base whenever possible.
Once again, the detail that is shown will partially
determine the detail of the analysis.
IV.29
-------
Contour Interval = 40 feet
Figure IV.13.—The Horse Creek watershed boundary.
IV.30
-------
Contour Interval = 40 feet
Figure IV.14.—Drainage net of the Horse Creek watershed.
IV.31
-------
Contour Interval = 40 feet
Figure IV.15.—Individual hydrographic areas of the Horse Creek watershed.
IV.32
-------
Contour Interval = 40 feet
Figure IV.16.—Soil mapping unit boundaries for the Horse Creek watershed.
IV.33
-------
Contour Interval = 40 feet
Figure IV.17.—Proposed transportation system (roads and log landings) for the Horse Creek watershed
IV. 34
-------
1 mile = 5280 feet
Contour Interval = 40 feet
Figure IV.18.—Proposed cutting units for the Horse Creek watershed
IV.35
-------
Step 6. — All of the preceding information
should he incorporated onto a single map base or
preferably onto overlays using the previous map
scale (fig. IV. 19). The information in its overlaid
form should include the hydrographic areas, the
soil and vegetation resources, and the proposed ac-
tivities within each erosion response unit.
Step 7. — Further subdivisions of the proposed
activities are possible to identify specific sources
contributing eroded materials to the drainageway
via separate delivery routes within each
hydrographic area. The degree to which the
silvicultural activities are subdivided is important
to the final quantification process and may be
useful in ultimately applying controls to specific
parts of an area. The more detailed the subdivision
of activities the more complex the accounting
procedure and the more detailed the answer.
Step 8. — List the potential sediment source
areas on worksheets (IV.1-IV.8) by activity types
for each erosion response unit identified in step 4.
Hydrographic Area
Boundary
Figure IV.19.—Composite map of all topographic and management treatments for the Horse Creek
watershed, hydrographic area 3.
IV.36
-------
WORKSHEET I V.I
Soil characteristics for the
watershed
Soi 1 group
Top so i 1
1
Subsoi 1
Top so i 1
9
Subsoi 1
Top so i 1
•*,
Subsoi 1
E
+- —
c
CM
T3
ID E
W E
CD m
c o
-i- — •
C M- O
-O
I- 1_ «—
0) 0) •
Q. > O
_^J
Percent
"coarse silt'
0.062-0.05 mn
CM
o
0
+-
C O
Q) 1
o -t- in
1- — O
0 ._ .
DL in o
E
C CN
0 0
U 5-O
1_ (D •
-------
WORKSHEET IV.2
watershed erosion response unit management data for use in the MSLE and
sediment delivery index, hydrographic area
Erosion
response
un it
1 .
2.
5.
4.
5.
D.
7.
8.
9.
10.
1 1 .
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Slope
length of
disturbed
area (ft)
Slope
gradient of
disturbed
area (%)
Length of
road
section
(ft)
Average
width of
disturbance
(ft)
Area
(sq.ft.)
Area
(acres)
-------
2 of 3
WORKSHEET IV.2—continued
Area with surface residues
Percent
of total
area
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Percent
of surface
with mulch
Percent of
area with
fine roots
Open area
Percent
of total
area
Percent
of surface
with mulch
\
Percent of
area with
fine roots
Are open areas
separated by
f i Iter strips?
Percent of
tot a 1 area
with canopy
00
to
-------
3 of 3
WORKSHEET I V. 2—continued
Average
min imum
height of
canopy
(m)
1 .
2.
3.
4.
5.
6.
7.
8.
9.
10.
11 .
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Time for
recovery
(mo)
Average
dist. from
disturbance
to stream
channel (ft)
Overal I
slope shape
between
d i sturbance
and channel
Percent
ground
cover in
f i I ten
str ip
Surface
roughness
(qua I i -
tat i ve )
Texture of
eroded
mater ial
(% si It +
clay)
Percent
slope
between
disturbance
and channel
-------
WORKSHEET IV.3
Estimates of soil loss
for hydrographic area
and
delivered
of
sediment by erosion
response unit
watershed
Erosion response
un it
Soi 1
un it
R
K
LS
VM
Area
(acres)
Surface
soi 1 loss
(tons/yr )
SO,
Del i vered
sediment
(tons/yr)
-------
WORKSHEET IV.4
Estimated VM factors for si IvicuIturaI erosion response
watershed, hydrographic area
un its
Logging residue area
Erosion
response
unit
Fraction
of
total
area
Mulch
(duff &
residue)
Canopy
Roots
Sub
VM
Open area
Fraction
percent
of total
area
Mulch
(duff &
res idue)
Canopy
Roots
Fi Iter
str ip
Sub
VM
Total
VM
fe
-------
WORKSHEET IV.5
Example of estimated monthly change in VM factor following
construction for road cuts and fills in watershed,
hydrographic area
Month
Sep.l/
OctJ/
Nov.
DecJ/
Jan.?/
Feb.2/
?/
March-'
Apr! if/
Mayf/
June^/
July^/
Aug.
Percent cover and VM subfactors
Mulch
Percent
VM
Canopy
Percent 1 VM
Roots
Percent
VM
Monthly
VM
-' Begin seeding, enough rain is assumed to ensure seed germination.
21
- Snow cover with no erosive precipitation.
- Significant canopy effect developing.
4/
- Snowmelt runoff occurs, some protective vegetative cover lost during
winter.
- Significant root network developing from seeded grass.
IV.43
-------
WORKSHEET IV.6
Weighting of VM values for roads in
watershed, hydrographic area
Eros ion
response
un it
Cut or fill
Fract ion
of total VM
w i dth
Roadbed
Fract ion
of total VM
w i dth
Fi 1 1
Fract ion
of total VM
wi dth
Weighted
VM
IV.44
-------
WORKSHEET IV.7
Factors for sediment delivery index from erosion response units in
watershed, hydrographic area
Erosion
response
unit
Water
avai 1 abi 1 ity
Texture
of eroded
material
Percent
ground
cover
between
disturbance
and channel
Slope
shape
code
Distance
(edge of
disturbance
to channel )
(ft)
Surface
roughness
code
Slope
gradient
<»
Specific
site
factor
Percent
of total
area for •
polygon
SD|
fe
-------
WORKSHEET IV.8
Estimated tons of sediment delivered to a channel for each
hydrographic area and type of disturbance for watershed
Hydro-
graphic
area
Col umn
total
Distur-
bance
total
Percent
Cutting units
CC]
CC2
CC3
CC4
CC5
Land ings
LI
L2
L3
Roads
Rl
«2
"3
K4
"5
Total
tons/yr
Per-
cent
IV.46
-------
Summary
Once the data are accumulated, a specific es-
timate of surface soil loss can be made. To compute
an estimate of total soil loss for a unit area (one
acre), the MSLE must be applied to each activity
within the area. The unit area soil loss is multiplied
by the actual area that is disturbed by an activity
to obtain an estimate of surface soil loss per ac-
tivity. Soil loss for each activity is then added
together to obtain estimated total soil loss. This
overall procedure is further explained in "The
Procedure" section of this chapter.
CONSIDERATIONS FOR REDUCING
EROSION
Theoretically, it is possible to reduce soil loss by
making appropriate changes in any of the MSLE
factors. In actual practice, some factors are easier
to change than others. The following tabulation
describes the basic concepts underlying the
variable changes brought about by controls for sur-
face erosion. This conceptual presentation is to aid
in understanding controls and determining which
control practice to use. Details of specific control
practices may be found in "Chapter II: Control Op-
portunities."
IV.47
-------
MSLE
Factor
Preventive
Mitigative
R Where soils have high credibility factors, plan
silvicultural activities so that snowmelt rates are not
increased over natural conditions. Use management
techniques which will not create significant increases
in the amount of solar energy reaching the forest floor.
Reduce snowmelt runoff rates
by intercepting the solar energy
above the snow surface.
R
K
LS
Control over the rainfall portion of the R factor is not likely to occur because it is a
function of overall weather patterns.
Use management practices that do not reduce long-
term soil permeability, structure, or organic matter
content. For example, avoid soil compaction or crea-
tion of conditions that destroy organic matter.
Increase long-term organic mat-
tor ^r.K,fQi-it i'n Łne SOll by
vegetative
ter content in
promoting good
growth. This can lead to
desirable soil structure and
permeability. Obtaining
desirable soil texture changes
would be very difficult at best.
Usually slope length and slope gradient effects must be considered together because a
change in one also causes a change in the other.
L Control location and design of various types of con-
struction to avoid creating long cut and/or fill slopes,
large landings, and extensive activity areas.
Locate various types of diver-
sions, such as terraces, to reduce
the distance water can move
over land.
Control location and design of various types of construc-
tion and other activities on steep slopes.
Reduce steep slopes, created by
construction activities, by plac-
ing soil and rock at the base of a
cut slope and removing it from a
fill slope.
VM Control and design forest activities to minimize forest
floor destruction. Maintain adequate amounts of low un-
derstory canopy. This is important where surface resi-
dues are few or lacking. A high overstory canopy may ac-
celerate raindrop splash erosion from storms in areas
where the forest floor has been destroyed. An example
might be a campground with little or no surface residue
or understory canopy. Control the use and intensity of
fire on coarse-textured soils to prevent hydrophobic con-
ditions from developing.
Add mulch, or chemical
binders, establish vegetation, or
use other practices to change
VM so that acceptable levels of
soil loss are achieved. Use
various mechanical methods of
creating surface roughness or
small diversions, e.g., perform
final site preparation on the
contour rather than up and
down slope. Use wetting agents
to reduce or reverse hydrophobic
conditions enough to
significantly reduce soil loss
(Osborn and others 1964).
IV.48
-------
APPLICATIONS, LIMITATIONS AND PRECAUTIONS: SURFACE SOIL LOSS
The confidence limits on predictions by the
Universal Soil Loss Equation are the narrowest
(predictions are most accurate) for silt, silt loam,
and loam textures on uniform slopes of 5 to 12 per-
cent, and with slope lengths of less than 400 feet
(122m) (Wischmeier 1972). Beyond these limits,
significant extrapolation errors become more
likely. However, the MSLE appears to have suf-
ficient accuracy for comparing estimated soil loss
from different silvicultural management practices
on a given site over a wider range of forest en-
vironmental conditions. Predicting long-term (5- to
50-year) average soil loss for a given situation is
limited by lack of available data needed to
evaluate the individual terms rather than the
overall model. The prediction accuracy for forest
land may improve as research provides a more ac-
curate evaluation of the critical site factors over a
wider range of conditions within the forest environ-
ment.
Specific limitations of the MSLE are as follows:
1. The MSLE is empirical; it indexes the quan-
tity of soil loss under various forest condi-
tions and does not always show the factors in
correct relationships with actual erosion
processes. There are limitations due to the
use of empirical coefficients and fitted
curves.
2. The MSLE only estimates an amount of soil
loss, but does not deal with the probability or
chance of soil loss occurring.
3. The MSLE was developed to predict soil loss
on an average annual basis. Soil loss predic-
tions on a storm-by-storm basis often are er-
roneous because of the complicated interac-
tion between forces governing soil loss rates
that are not accounted for by the MSLE. On
any given site, these interactions may tend
to average out over long periods of time so
that their effect on long-term soil loss may be
minimal. The soil loss equation has been
rewritten in several attempts to develop
techniques to handle storm-by-storm losses
(Foster and others 1977, Williams 1975c,
Williams and LaSeur 1976). The accuracy
and reliability of such techniques is
questionable, and it is not recommended
that they be used for quantification.
4. It is assumed in the MSLE that the K factor
is a constant, average value throughout a
given analysis time period. However,
changes in surface particle size distribution
(texture) due to freeze-thaw or ongoing ero-
sion processes will affect the value of K.
Some of these effects, if they are short-term,
are provided for by the VM factor. Long-
term changes in the K factor due to soil com-
paction which occurs on roads, from equip-
ment operations, or by animal traffic needs
further study.
5. The LS factor has a low level of sensitivity to
potential errors in the estimation of slope
length because it is raised to a fractional
power. However, an error in slope gradient,
particularly on steep slopes, can result in a
large error in LS because of the parabolic
form of the equation.
6. The MSLE is most accurate for VM values
above 0.2. As VM approaches 0.01 and
below, the errors in the absolute estimate of
soil loss increase greatly; the smaller VM
becomes, the larger the potential absolute er-
ror.
7. The rainfall erosion index (R) measures only
the erosive force of rainfall and associated
runoff. The equation does not predict soil
loss that is due solely to thaw, snowmelt, or
wind.
8. Relationships of a given MSLE parameter to
soil loss are often appreciably influenced by
the levels of all other MSLE parameters
(Wischmeier 1976). Graphs in figure IV.20 il-
lustrate one example of this interrelationship
for the K factor. Table IV.7 shows values
used as constants in this example. Using
figure IV.20 and table IV.7 together it is
shown how changing one parameter, while
holding all others constant (either at high,
moderate, or low levels), affects erodibility,
the K factor. For example, Figure IV.20a il-
lustrates the effects upon the K factor when
organic matter is varied from 0 to 6 percent
and all other parameters are held constant.
When all other parameters are at low or
moderate levels, changes in organic matter
do not appreciably affect erodibility.
However, when all other parameters are held
IV.49
-------
Table IV.7.—Values of organic matter, fine sand + silt, clay,
structure, and permeability used as constants when
calculating K factor over a range of each parameter for low,
moderate, and high values of K.
Relative Level of K
% organic matter
% fine sand + silt
% clay
structure
permeability
Low
6
10
90
4
1
Moderate
3
35
65
3
3
High
0
70
30
1
6
at high levels, changes in organic matter do
have an appreciable influence on the K fac-
tor. There is a similar graph for each of the K
factor parameters showing the changes in K
due to a change in a parameter.
9. There are additional erosion processes not
accounted for in the MSLE that are impor-
tant in making accurate predictions of soil
loss. On steep slopes wind is an important
erosion factor and may increase rainstorm
erosion by up to one order of magnitude. Fall
freeze-thaw processes cause a change in the
median particle size of eroded material
(Megahan 1978).
10. No adjustments are made for timing of rain-
fall relative to vegetative growth periods. In-
tuitively, the amount of soil loss would be
different if most of the rainfall occurred dur-
ing a vegetative dormant season rather than
a growing period.
11. The MSLE does not separate runoff and
rainfall components of erosion. If this could
be done, the accuracy of estimated soil losses
might be improved in situations where one
factor is more important than the other.
12. There does not appear to be any acceptable
method to account for the influence of rock
and stone on the soil surface. A suggestion is
to view the rock or stone as a non-erodible
part of the surface; however, because of the
runoff from the surface of a rock, there might
be more soil loss than would occur without
any rock.
13. Coarse-textured soils that are exposed to an
intense fire may become hydrophobic, thus
promoting more surface runoff after a fire
than might have occurred under natural
vegetation. It is not known if adjusting the K
factor for a change in permeability will
provide a satisfactory estimate of this effect
on runoff-induced erosion.
14. The equation does not account for sediment
deposition that occurs in depressions within
a field, at the toe of a slope, along distur-
bance boundaries, or in terrace channels on a
slope (Wischmeier 1976).
15. Gully erosion cannot be accounted for by the
Modified Soil Loss Equation. (See appendix
IV.A). The use of the soil loss equation is
confined to sheet and rill erosion.
16. The relationships of factors influencing ero-
sion on soils that are high in organic matter,
that have developed from volcanic ash, or
that have permafrost are not well under-
stood. Use of the soil loss equation for these
soils may result in significant errors in the
amount of predicted soil loss.
17. The MSLE estimates average soil loss for 1
year only. Using MSLE for periods of over a
year is briefly discussed in appendix IV.B.
18. Accurate soil loss estimates from roads and
skid trails may not be obtained where they
intercept surface and subsurface runoff in
addition to precipitation. The MSLE does
not estimate soil loss by concentrated water
flow, such as in a road ditch. (See Appendix
IV.C: Controlling Ditch Erosion).
19. In forest areas with a dense overstory
canopy, there is a limit to map accuracy.
When a topographic map is prepared from
aerial photographs, the technician making
the map cannot see the actual ground sur-
face on the photograph — only the canopy
top. The map maker is usually not ac-
quainted with the area, but must still es-
timate the canopy height. Anything that
would cause some trees to grow taller than
others will cause errors in delineating con-
tour lines. For example, a small first-order
stream channel with its additional moisture
may cause trees to grow so that the tops are
level with tree tops on the drier interflueves
between channels, and thus be mapped as a
uniform ground surface.
IV.50
-------
"-
.7
.6
.5
.3
.2
.1
0
Moderate
1234567
PERCENT ORGANIC MATTER
cc
O
O
<
LL
.7
.6
.5
.4
.3
.2
10 20 30 40 50 60 70
PERCENT SILT AND FINE SAND
Figure IV.20a.—Effect of organic matter content on K factor
when other parameters are at low, moderate, or high
values.
Figure IV.20b.—Effect of silt and fine sand on K factor when Q-
other parameters are at low, .moderate, or high values. O
O
<
Figure I V.ZOc.—Effect of clay on K factor when other "- 3
parameters are at low, moderate, or high values.
Figure IV.20d.—Effect of soil structure on K factor when other
parameters are at low, moderate, or high values.
Figure IV.20e.—Effect of soil permeability on the K factor
when other parameters are at low, moderate, or high values.
.(
.6
.5
.4
.3
.2
.1
n
X
—~
N
— •»«
-/
N,
^-^
%>,
Si
w
X
^^
x
A?c
"*»,
>c(e
-»-^
pfe
•^ i j
Ir
• —
• — .
— . .
10 20 30 40 50 60 70 80 90
PERCENT CLAY
7
5
cc
O 4
U. -j
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)
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^*
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r-
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SOIL STRUCTURE FACTOR
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SOIL PERMEABILITY FACTOR
IV.51
-------
DISCUSSION: SEDIMENT DELIVERY
GENERAL CONCEPTS OF SEDIMENT
DELIVERY
To evaluate the effects of surface erosion on
water quality, it is necessary to estimate the
amount of eroded material that might be moved
from the eroding site into a receiving stream chan-
nel system. Unfortunately, the processes which
describe the delivery of eroded materials are less
well understood than those for erosion, and data for
sediment delivery are scarce.
Historically, the determination of the amount of
sediment that reached a stream channel revolved
around the concept of delivery ratios (Gottschalk
and Brune 1950, Maner 1958, Maner and Barnes
1953, Roehl 1962, Williams and Berndt 1972). A
delivery ratio is the volume of material delivered to
a point in the watershed, divided by the gross ero-
sion estimated for the slopes in the watershed
above that point. Values range from zero to one.
Apparently, a characteristic relationship of sedi-
ment yield to erosion does not exist. Many factors
influence a sediment delivery ratio; if these factors
are not uniform from one watershed to another, the
relationship between sediment yield and erosion
shows considerable variation (Renfro 1975).
Factors Influencing Sediment Delivery
Sediment delivery from a disturbed site to a
stream channel is influenced to varying degrees by
the following factors (Foster and Meyer 1977,
Megahan 1974, Renfro 1975). (There may be other
factors, not listed here, that are also important in
given situations.)
Sediment Sources
In terms of effects upon a sediment delivery in-
dex, there are at least three ways to describe sedi-
ment sources:
1. Type of disturbance — Materials originating
from logging areas, skid trails, landings, and
roads seem to have a range of delivery ratios
that are characteristic of each disturbance
type.
2. Type of erosion — Sheet, rill, gully, and soil
mass movement have one or more sediment
delivery parameters that are unique to that
particular form of erosion.
3. Mineralogy of the source area — Delivery
ratios are influenced by various physical
characteristics of sediment materials. Size,
shape, and density of individual particles and
their tendency to form stable aggregates are
usually reflected by their mineralogy. Wet-
tability of particles may be a function of
mineralogy or of unique biological systems
both of which influence the efficiency of sedi-
ment delivery.
Amount Of Sediment
When the amount of potential sediment exceeds
the runoff delivery capability, deposition occurs
and the amount of sediment delivered to a stream
channel is closely controlled by the amount of
runoff energy. If the amount of sediment is less
than the runoff delivery capability, then no deposi-
tion will occur between the disturbed area and a
stream channel.
Proximity Of Sediment Source
The distance that sediment must move and the
shape and surface area of the transport path all af-
fect the amount of material that may be lost from
the transport system.
Transport Agents
Surface runoff from rainfall and snowmelt is the
main agent for transporting eroded material. Sedi-
ment transport is dependent on the volume and
velocity of water as well as the character and
amount of material to be transported.
Texture Of Eroded Material
Individual particles of fine-textured material can
be moved easier than particles of coarse-textured
material because the finer the particle, the less
transport energy required. If a watershed is
dominated by fine-textured material, it is likely to
have more material delivered to a stream channel
by surface runoff than an equivalent situation with
IV.52
-------
coarse-textured material — assuming that soil ag-
gregates are not involved.
Deposition Areas
Microrelief that results in surface depressions or
other irregularities will deliver less sediment than a
smooth, flat surface. Decreases in slope gradient
also promote deposition of large size fractions of
transported material.
Watershed Topography
Size of the drainage area, overall shape of the
land surface, (concave to convex), slope gradient,
slope length, and stream channel density all affect
the sediment delivery ratio by varying amounts.
Sediment Delivery Model
From the previous discussion concerning factors
that influence sediment delivery over an area of
land, it can be seen that the amount of eroded
material deposited between a disturbed site and a
drainage channel is due to a variety of interacting
factors. To aid understanding overland sediment
transport, the process can be divided conceptually
into two parts.
The first requirement is a transporting agent
with sufficient energy to move the sediment. In this
case, surface runoff is the transporting agent. Its
energy is a function of the amount and velocity of
waterflow passing over a given area in a given time
period.
The second part deals with factors which tend to
stop or slow the movement of sediment and
waterflow over a slope. Microrelief, slope gradient,
slope length, slope shape, vegetation, and surface
residues all play a part in reducing the amount of
sediment that will actually reach a delivery point
(Neibling and Foster 1977, Zingg 1940).
The shape of the area over which sediment is
transported (fig. IV.21) also influences the amount
actually delivered to a drainage channel. In one
case, sediment entering delivery area A is funneled
so that a given amount passes over progressively
less surface during transit. This reduces the oppor-
tunities for deposition and also increases the energy
of the transporting agent, thus resulting in in-
creased sediment delivery efficiency. At the other
extreme, delivery area C spreads material and
water over progressively more area thus reducing
the transporting energy and increasing oppor-
tunities for in-transit deposition. Delivery area B
represents an intermediate situation between A
and C. A relative comparison of the three areas
would have A delivering more sediment than B,
which delivers more than C.
Figure IV.21.—Potential sediment transport paths (A,B, and
C) for different parts of a slope.
IV.53
-------
Any working sediment delivery model must have
clearly defined factors which represent the amount
of surface runoff available for transporting sedi-
ment, the length of the transport path, the gradient
of the path, the shape and changes in surface area
of the path, a measure of surface microrelief, and a
measure of ground cover. All of these factors should
have measurable parameters and be combined
together with the proper coefficients. To date, there
is no accurate way to estimate the amount of sur-
face runoff that might be available for sediment
delivery in the forest environment, the actual
shape and location of sediment delivery paths,
degree of surface roughness, or characteristics of
slope shape. An understanding of how to combine
these factors or what coefficients to use is not
known for most situations.
PROCEDURAL CONCEPTS:
ESTIMATING SEDIMENT DELIVERY
This section discusses the concepts necessary for
estimating sediment delivery and for evaluating
the individual parameters involved. It is organized
according to a conceptual perception of sediment
delivery and corresponds with the flow chart of
figure IV.l. An outline of the overall procedure for
estimating sediment delivery to a stream from sur-
face erosion sources is presented in "The
Procedure" section of this chapter. A detailed ex-
ample for using the procedure is provided in
"Chapter VIII: Procedural Examples." All con-
cepts discussed here are necessary for using the
overall procedure.
The Sediment Delivery Index
An index approach is recommended to help
bridge the gap between the need to estimate how
much sediment reaches a stream channel and the
lack of a working sediment delivery model to
provide such estimates. This approach provides a
relative evaluation of seven generally accepted en-
vironmental factors and one site specific factor that
are considered important in the sediment delivery
process. These eight factors are not necessarily the
only ones that may be needed in all situations. This
indexing procedure has not been validated by
research. Therefore, the computed quantities may
be different from measured quantities of sediment
delivered to a stream channel. Use of the index is
only an aid in evaluating the relative effects of dif-
ferent management practices on sediment delivery
from a given forest area.
Evaluation Factors
For this discussion, each of the following eight
factors is considered as though it acts in-
dependently of any other factor. In reality, these
factors interact with each other in complex ways.
1. Transport agent (e.g., water availability).
— Surface runoff from rainfall and snowmelt
is an important factor in the movement of
eroded material. It is estimated that overland
flow rates from sheet and rill erosion rarely ex-
ceed 1 cfs on agricultural land and generally
are less than 0.1 cfs on forest lands in the
United States.
2. Texture of eroded material. — Assuming
that aggregates do not form, individual parti-
cles of fine-textured soil material require less
energy for delivery than particles of coarse-
textured material. Sediment delivery efficien-
cies are higher on an area dominated by fine-
textured material than on an area dominated
by coarse-textured materials if the other fac-
tors influencing sediment delivery are equal.
3. Ground cover. — Ground cover (forest floor
litter, vegetation, and rocks) creates a tor-
tuous pathway for eroded particles to travel
which allows time for the eroded material to
settle from surface runoff water (Tollner and
others 1976). Protective ground cover may
also prevent raindrop impact energy from
creating increased flow turbulance which
would increase the carrying capacity of the
runoff flow.
4. Slope shape. — Concave slopes between the
source area and the stream channel promote
deposition of the larger size fraction of the
transported material (Neibling and Foster
1977). Convex slopes create more favorable
conditions for increasing the material carrying
capacity of the transporting agent. Slope
shape is a difficult factor to quantify, but it
seems to play an important role in sediment
delivery.
5. Slope gradient. — Slope gradient, along with
the volume of water available for sediment
delivery, provides the necessary energy to
deliver the eroded material. The efficiency of
IV.54
-------
the sediment delivery process increases with
increasing slope gradient.
6. Delivery distance. — Increasing the distance
from a sediment source to a stream channel or
diversion ditch increases the effect that other
factors have on the amount of sediment ac-
tually delivered. On the other hand, if a sedi-
ment source is very close to a stream channel,
the other factors affecting sediment delivery
have proportionally less opportunity to reduce
the amount of sediment delivered.
7. Surface roughness. — Roughness of the soil
surface affects sediment delivery similarly to
that of ground cover. Rougher surfaces create
more tortuous pathways for eroded particles
to pass over and more surface area for water
infiltration than smooth surfaces for a given
area (Meeuwig 1970).
8. Site specific factors. — In many parts of the
United States, unique forest environments
and/or soil factors influence the sediment
delivery efficiency. For example, soil non-
wettability (DeBano and Rice 1975),
mineralogy such as the Idaho batholith
described by Megahan (1974), biological ac-
tivity, or fire can change the sediment
delivery efficiency of some forest lands.
Within forested areas of the southeast United
States, microrelief adjacent to stream chan-
nels may cause concentrated water flows, thus
having a large effect on sediment delivery ef-
ficiency. Some soils have a greater tendency
than others to form stable aggregates, hence
reducing the sediment delivery efficiency.
Determining The Sediment Delivery Index
The stiff diagram shown in figure IV.22 uses vec-
tors to display the magnitude and scale of each ma-
jor factor identified as influencing sediment
delivery. The area of the polygon created by con-
necting the observed, anticipated, or measured
value for each factor is determined and related to
the total possible area (the polygon formed by con-
necting the outer limits of each vector) of the
graph. The percentage of area inside the polygon is
coupled to the delivery index through the use of
skewed probit transformations (Bliss 1935). Small
polygonal areas surrounding the midpoint indicate
a low probability of efficient sediment delivery, or,
in other words, a very low sediment delivery index.
Sediment delivery indexes will be low in most
forest ecosystems managed by the best forest prac-
tices. Polygons approaching the outer limits of the
stiff diagram indicate a high probability of efficient
sediment delivery. The fraction of the total stiff
diagram area formed by a given polygon is adjusted
using figure IV.23, to give the sediment delivery in-
dex.
The scale and magnitude of the vectors in figure
IV.22 have been defined as follows:
1. The magnitude of the transport agent is deter-
mined by the equation:
F = CRL (IV. 12)
where:
F = water availability,
ft- 2 !•>
C = 2.31 x 10"5 • • * (a conversion constant)
lil OCC
R = maximum anticipated precipitation and/
or snowmelt rate minus infiltration in
units of in/hr from local records, and
L = slope length in feet of the sediment source
area (perpendicular to contours).
Values of F for given values of R and L are in
table IV.8.
The maximum scale value in figure IV.22 is 0.1
cfs. If the flow is calculated to exceed 0.1 cfs,
use the scale factor of 0.1 for water availability.
This model assumes that the precipitation in-
put exceeds the site infiltration capacity caus-
ing overland flow conditions at the lower boun-
dary of the eroded material source area. If no
water is available then the sediment delivery in-
dex is zero (0.0).
2. Texture of eroded material is expressed as
percent of eroded material that is finer than
0.05 mm (silt size). A particle diameter less
than 0.05 mm was shown to be highly trans-
portable for sediment movement (Neibling
and Foster 1977). A scale factor of zero in-
dicates that the eroded material contains no
material less than 0.05 mm diameter, and a
factor of 100 percent indicates that all of the
eroded material is 0.05 mm or less in
diameter.
3. Ground cover that is in actual contact with
the soil surface, is expressed in percent cover
between 0 (bare soil surface) and 100 (mineral
soil surface completely covered). This factor is
scaled based on unpublished data by Diss-
meyer2 which relates relative ground cover
'Personal communication of unpublished material from G.
Dissmeyer, USDA Forest Service, State and Private Forestry,
Atlanta, Ga.
IV.55
-------
Percent Ground
Cover
Slope (
Shape
(
\
\
)
),„
V
^^
\
1
2
10 >
>^
fl
(
k-
\
10
\
\5
\
2
200,,
100 */
4
30
^
^
^
Texture of Available
Eroded Material Water
|
20
s
^
4
500 v*
*Ł•
Delivery Distance
feet
30
3
400
3000J
2000X
x
^
3—
N,"
P
/
•75
-50
•25
' /
SsJ
-3
_ n
• 1
n
- -
/
f
V
25
/
).02
Sc25
\
^
^
N
I
/
/
/
/^o.oso
50
\
.5C
s
X
/
).07
75
\
\
\
\
^
5
/
-
1C
-
N
in
Surface Slope
Roughness Gradien
0.10
0 Site
Specific
0
t
Figure IV.22—Stiff diagram for estimating sediment delivery.
density influence to overland water flow.
Slope shape is scaled in magnitude between 0
and 4, with 4 being a slope that is convex from
the boundary of the source area to the stream
channel. A scale factor of 0 describes a slope
concave from the boundary of the source area
to the stream channel, while a factor of 2
shows that one-half of the slope is concave
and the other half is convex or that the entire
slope is uniformly straight. A factor of 3 in-
dicates that a larger percentage of the slope is
convex in shape.
5. The slope gradient is the vertical elevation
difference between the lower boundary of the
source area and the stream channel divided
by the horizontal distance and expressed as a
percent between 0 and 100.
6. The distance factor is the login of the distance
in feet from the boundary of the source area to
a stream channel or ditch. Distances greater
than 10,000 feet (3,050 m) are considered in-
finite. The distance vector is marked using a
login scale so that distances are entered
directly onto the vector in figure IV.22.
IV.56
-------
1.0
0.9
OB
07
X
LLJ
Q
UJ
7
05
til
O
0.4
0.3
02
0.1
10 20 30 40 50 60 70
PERCENT AREA FROM STIFF DIAGRAM
Figure IV.23.—Relationship between polygon area on stiff
diagram and sediment delivery index.
80
90
100
7. The roughness factor is scaled in magnitude
between 0 and 4 with 0 being an extremely
smooth forest floor surface condition and 4 be-
ing a very rough surface. This is a subjective
evaluation of soil surface conditions.
8. The site specific factor influencing delivery
ratios is scaled between 0 and 100 and must be
assigned its effective magnitude by a user
familiar with the unique condition of the site.
Appropriate factor values are plotted on each
vector of the graphic sediment delivery model (fig.
IV.24). Lines are drawn to connect all plotted
points to form an enclosed, irregular polygon. If a
site specific factor is not used, draw a line directly
between plotted points on the slope gradient and
available water vectors. Determine the area inside
the polygon by: measuring with a planimeter, es-
timating with a dot grid, or calculating and sum-
ming the areas of the individual triangles. Deter-
mine the percent of the total graph area that is
IV.57
-------
Percent Ground
Cover
Texture of
Eroded Material
Available
Water
Slope
Shape
0.10
Site
Specific
Delivery Distance
feet
Surface
Roughness
100
Slope
Gradient
Figure IV.24.—Example of graphic sediment delivery model
lor road R3.1.
within the polygon. Using the S-shaped probit delivery index by using the percent area of the
curve in figure IV.23, determine the sediment polygon from figure IV.24.
IV.58
-------
Table IV.8.—Water availability values for given source area slope length (ft) and runoff (in/hr)1
3
bi
Surface
slope
length
10
20
30
40
50
75
100
150
200
250
300
350
400
450
500
1000
.025
.00006
.00012
.00017
.00023
.00029
.00043
.00058
.00087
.0012
.0014
.0017
.0020
.0023
.0026
.0029
.0058
.05
.00012
.00023
.00035
.00046
.00058
.00087
.0012
.0017
.0023
.0029
.0035
.0040
.0046
.0052
.0058
.012
0.75
.00017
.00035
.00052
.00069
.00087
.0013
.0017
.0026
.0035
.0043
.0052
.0061
.0069
.0078
.0087
.017
1.0
.00023
.00046
.00069
.00092
.0012
.0017
.0023
.0035
.0046
.0058
.0069
.0081
.0092
.010
.012
.023
Runoff
1.25
.00029
.00058
.00087
.0012
.0014
.0022
.0029
.0043
.0058
.0072
.0087
.010
.012
.013
.014
.029
1.5
.00035
.00069
.0010
.0014
.0017
.0026
.0035
.0052
.0069
.0087
.010
.012
.014
.016
.017
.035
1.75
.00040
.00081
.0012
.0016
.0020
.0030
.0040
.0061
.0081
.010
.012
.014
.016
.018
.020
.040
2.0
.00046
.00092
.0014
.0018
.0023
.0035
.0046
.0069
.0092
.012
.014
.016
.018
.021
.023
.046
2.25
.00052
.0010
.0016
.0021
.0026
.0039
.0052
.0078
.010
.013
.016
.018
.021
.023
.026
.052
2.5
.00058
.0012
.0017
.0023
.0029
.0043
.0058
.0087
.012
.014
.017
.020
.023
.026
.029
.058
2.75
.00064
.0013
.0019
.0025
.0032
.0048
.0064
.0095
.013
.016
.019
.022
.025
.029
.032
.064
3.0
.00069
.0014
.0021
.0028
.0035
.0052
.0069
.010
.014
.017
.021
.024
.028
.031
.035
.069
3.25
.00075
.0015
.0023
.0030
.0038
.0056
.0075
.011
.015
.019
.023
.026
.030
.034
.038
.075
3.5
.00081
.0016
.0024
.0032
.0040
.0061
.0081
.012
.016
.020
.024
.028
.032
.036
.040
.081
3.75
.00087
.0017
.0026
.0035
.0043
.0065
.0087
.013
.017
.022
.026
.030
.035
.039
.043
.087
4.0
.00092
.0018
.0028
.0037
.0046
.0069
.0092
.014
.018
.023
.028
.032
.037
.042
.046
.092
1The table values were obtained by the formula:
:= (2 31x10-* "2hr \(Rnnnff in/hr \ (slope length ft.)
V in sec./V /
-------
Estimating Sediment Delivery By Activity
Each land-disturbing activity should have an es-
timate of soil loss for the location where it occurs
and a delivery index based on site characteristics.
An estimate of the amount of sediment which
might reach a stream channel can be obtained by
multiplying the surface soil loss (tons/year) by the
sediment delivery index for each erosion response
unit.
All of the procedures used to arrive at an es-
timate of surface soil loss and sediment delivered to
a stream channel only provide a way to evaluate
alternative management practices. Only on-the-
ground monitoring can verify if the objectives have
been met by the management strategy.
CONSIDERATIONS FOR REDUCING
SEDIMENT DELIVERY
Theoretically it is possible to reduce sediment
delivered to a stream channel by making ap-
propriate changes in any of the index factors. In ac-
tual practice, some factors are easier to change
than others. The following tabulation describes the
basic concepts underlying each factor and the
changes brought about by controls for sediment
delivery. This conceptual presentation is to aid un-
derstanding of controls and determining which
control practice to use. Details of specific control
practices may be found in "Chapter II: Control Op-
portunities."
Sediment delivery
factors
Water
availability
Preventive
Mitigative
Control over the rainfall rate is not likely to occur because it is a function of overall
weather patterns.
Use management practices that maintain high in-
filtration rates. Avoid such things as soil compaction
which changes soil structure and permeability.
Control of soil moisture content by high consumptive
use promotes infiltration.
Increase infiltration rates
by breaking surface crusts,
and incorporating organic
matter or other soil
amendments to improve
aggregation of soil parti-
cles. Promote vegetative
growth for high consump-
tive water use and
desirable soil structure
development.
Where snowmelt is influential, use management prac-
tices which will not create significant increases in the
amount of solar energy reaching the snow pack.
Reduce snowmelt runoff
rates by increasing the in-
terception of solar energy
above the snow surface.
Texture of
eroded material
Soil texture is controlled by
mineralogy and weathering.
Maintain natural, stable soil aggregates which will act
as a coarse-textured material in response to sediment
delivery forces.
soil-forming factors that are generally related to
Use soil amendments
which promote floculation
and development of ag-
gregates.
IV.60
-------
Sediment delivery
factors
Preventive
Mitigative
Ground cover Control and design forest management activities to
minimize forest floor disturbance.
Add mulch, establish
vegetation, distribute
residues, or use other prac-
tices to create long tor-
tuous pathways for water
flow and sediment
delivery.
Slope shape Control location and design of various types of con-
struction and other activities that would create
adverse slope shapes.
Design concave slope seg-
ments for sediment
delivery control on con-
struction sites or with
other activities.
Slope gradient
Control location and design of various types of con-
struction activities to minimize the ci eation of steep
slopes.
Reduce slope gradients
created by construction
and other activities
wherever possible.
Delivery distance
Locate activities well away from stream channels to
maintain long delivery paths.
Relocate activity sites to
increase overall delivery
distance to a stream chan-
nel.
Surface roughness
Design activities to maintain natural surface
roughness. Avoid creating channels that shortcut
natural tortuous pathways.
Create ridges and depres-
sions on the surface to trap
sediment and increase
water infiltration.
Site specific
factors
This will depend upon the characteristics of the chosen site factor.
IV.61
-------
APPLICATIONS, LIMITATIONS AND PRECAUTIONS:
SEDIMENT DELIVERY
Very few attempts have been made to verify the
reliability of sediment delivery models due to the
difficulty of obtaining sufficient data for testing.
The following limitations attributed to this model
are not based on actual data but are deduced as be-
ing important. Future research may add to or
change ideas about these limitations.
1. Only sheet flow surface runoff is addressed
with the sediment delivery index. If chan-
neled flow develops, other approaches must
be used to describe sediment delivery.
2. The choice of factors used to describe sedi-
ment delivery is thought to apply in all cases;
however, these may vary with future research.
3. The scaling of each factor on the stiff diagram
is based on the best available information;
however, new research information will
probably show a need for some changes.
4. Many factors work together in various ways to
influence sediment delivery. These interac-
tions have not been studied extensively and
may not be expressed correctly by the model.
5. The model assumes that the only water used
to move the sediment is generated on the sedi-
ment delivery path. It does not consider the
potential for additional water from other
sources on the slope. Solution of this problem
depends on the development of a satisfactory
water routing model.
6. Individual sediment delivery routes have
various shapes and overall surface areas
which are not accounted for by the model.
7. Infiltration rates may be different on dis-
turbed areas than in sediment filter strips.
Only the infiltration rate for the disturbed site
is used.
8. Antecedent soil moisture conditions are not
incorporated into the model. If sediment
delivery is most likely to occur during certain
time periods with particular soil moisture
characteristics, then some adjustments could
be made in the infiltration rate.
IV.62
-------
THE PROCEDURE
ESTIMATING SEDIMENT DELIVERY
FROM SURFACE EROSION SOURCES
The following steps outline the overall procedure
for estimating sediment delivery to a stream from
surface erosion sources. Steps 1 through 11 repre-
sent the procedure for estimating surface soil loss,
and steps 12 through 15 represent the procedure for
estimating sediment delivery. A complete example
for using the procedure is provided in "Chapter
VIII: Procedural Examples." Most of the steps are
self explanatory; however, the specific concepts,
parameters and computations involved in the
procedure were discussed earlier in this chapter un-
der "Procedural Concepts: Estimating Soil Surface
Loss" and "Procedural Concepts: Estimating Sedi-
ment Delivery."
Step 1. — Identify the watershed of interest
and obtain the necessary materials
and information.
Step 2. — Delineate the drainage network in
as much detail as the topographic
base will allow.
Step 3. — Delineate the hydrographic divides
relative to the drainage network
identified in Step 2 above.
Step 4. — Delineate soil and vegetative
ground cover units based on ap-
propriate data.
Step 5. — Show the proposed land use ac-
tivity in detail, delineating cutting
units, roads, landings and skid
trails, etc.
Step 6. — Using overlays, incorporate all
map-related information onto a
single map base.
Step 7. — Show the direction of water flow for
each hydrographic source area.
Step 8. — Set up worksheets for estimating
potential sediment load (wkshts.
IV.l—IV.8).
Step 9. — List each source area that is
delineated, and number by erosion
response unit.
Step 10. —Working in individual hydro-
graphic areas, determine for each
erosion response unit the values for
the variables R, K, LS, and VM.
Step 11. — Using the values from step 10,
calculate the estimated surface soil
loss (tons/year).
Step 12. — Working by erosion response units,
determine for each treatment
source the sediment delivery index
(SDj).
Step 13. — Calculate the estimated tons per
year of sediment input to the
stream system by each erosion
response unit.
Step 14. — Arrange erosion response unit sedi-
ment values in matrix by treatment
type.
Step 15. — Evaluate results.
IV .63
-------
LITERATURE CITED
Adams, G. E., D. Kirkham, and W. H. Scholtes.
1958. Soil erodibility and other physical proper-
ties of some Iowa soils. J. Sci., Iowa State Coll.
32:485-540.
Barnett, A. P., and J. S. Rogers. 1966. Soil physical
properties related to runoff and erosion from ar-
tificial rainfall. Trans. Am. Soc. Agric. Eng.
9:123-125.
Bekey, G. A. 1977. Models and reality: Some reflec-
tions on the art and science of simulation.
Simulation 29(5):161-164.
Bennett, H. H. 1934. Dynamic action of rains in
relation to erosion in the humid region. Trans.
Am. Geophys. Union, Fifteenth meeting, p. 474-
488.
Bennett, J. P. 1974. Concepts of mathematical
modeling of sediment yield. Water Resour. Res.
10(3):485-492.
Bliss, C. 1.1935. The calculation of the dosage mor-
tality curve. Ann. Appl. Biol. 22(1):134-167.
Browning, G. M., C. L. Parish, and J. A. Glass.
1947. A method for determining the use and
limitation of rotation and conservation practices
in control of soil erosion in Iowa. J. Am. Soc.
Agron. 39:65-73.
Chapman, Gordon. 1948. Size of raindrops and
their striking force at the soil surface in a red
pine plantation. Trans. Am. Geophys. Union
29:664-670.
Clyde, Calvin F., C. Earl Israelsen, and Paul E.
Packer. 1976. Erosion control during highway
construction, Vol. II. Manual of erosion control
principles and practices. Utah Water Res. Lab.,
Utah State Univ., Logan.
Cruse, R. M., and W. E. Larson. 1977. Effect of soil
shear strength on soil detachment due to
raindrop impact. Soil Sci. Soc. of Am. J.
41(4) :777-781.
DeBano, L. F., and R. M. Rice. 1975. Water-
repellant soils: Their implications in forestry. J.
For. 71(4):222-223.
Dohrenwend, R. E. 1977. Raindrop erosion in the
forest. Res. Note No. 4, Mich. Technol. Univ.,
Ford For. Cent., Lanse, Mich. 49946. 19 p.
Ellison, W. D. 1947. Soil erosion studies — part I.
Agric. Eng. 28(4): 145-146.
Foster, G. R., and W. H. Wischmeier. 1973.
Evaluating irregular slopes for soil loss predic-
tion. ASAE, Pap. No. 73-227, Am. Soc. Agric.
Eng., St. Joseph, Mich.
Foster, G. R., L. D. Meyer, and C. A. Onstad. 1977.
A runoff erosivity factor and variable slope
length exponent for soil loss estimates. Trans.
Am. Soc. Agric. Eng. 20(4):683-687.
Foster, G. R., and L. D. Meyer. 1977. Soil erosion
and sedimentation by water — an overiew. In:
Proc. Natl. Symp. on Soil Erosion and Sedimen-
tation by Water. ASAE, publ. 4-77, Am. Soc.
Agric. Eng., St. Joseph, Mich. p. 1-13.
Fredrikson, R. L. 1972. Nutrient budget of a
Douglas-fir forest on an experimental watershed
in western Oregon. In: Proc. res. on coniferous
for. ecosyst, p. 115-131. J. F. Franklin, L. P.
Dempster, and R. H. Waring, eds. US/ffiP,
USDA, For. Serv., Pac. Northwest For. and
Range Exp. Stn., Portland, Ore.
Gottschalk, L. C., and G. M. Brune. 1950. Sedi-
ment design criteria for the Missouri Basin loess
hills. USDA Soil Conserv. Serv. Tech. Pap. No.
97.
Gunn, R., and G. D. Kinzer. 1949. The terminal
velocity of fall for water droplets. J. Meteorol.
6:243-248.
Horton, R. E. 1975. Erosional development of
streams and their drainage basins, hydrophysical
approach to quantitative morphology. Geol. Soc.
Am. Bull. 56:275-370.
Laws, J. 0. 1941. Measurement of fall-velocity of
water drops and rain drops. Trans., Am.
Geophys. Union 22:709-721.
Laws, J. 0., and D. A. Parsons. 1943. Relation of
raindrop size to intensity. Trans., Am. Geophys.
Union 24:452-460.
Lillard, J. H., H. T. Rogers, and J. Elson. 1941. Ef-
fects of slope, character of soil, rainfall, and crop-
ping treatments on erosion losses from dunmore
silt loam. Va. Agric. Exp. Stn. Tech. Bull. 72. 32
P-
IV.64
-------
Maner, S.B. 1958. Factors affecting sediment
delivery rates in the Red Hills physiographic
area. Trans. Am. Geophys. Union 39:669-675.
Maner, S.B. and L.H. Barnes. 1953. Suggested
criteria for estimating gross sheet erosion and
sediment delivery rates for the Blackland Prai-
ries problem area in soil conservation. U.S. Dep.
Agric., Soil Conserv. Serv., Western Gulf
Region, Fort Worth, Texas. Mimeograph.
Meeuwig, R. D. 1970. Infiltration and soil erosion
as influenced by vegetation and soil in northern
Utah. J. Range Manage. 23(3): 185-188.
Megahan, W. F. 1974. Erosion over time on
severely disturbed granitic soil: A model. USDA
For. Serv. Res. Pap. INT-156. 14 p. Intermt. For.
and Range Exp. Stn., Ogden, Utah.
Megahan, W. F. 1978. Erosion processes on steep
granitic roadfills in Central Idaho. Soil Sci. Soc.
Am. J. 42(2):350-357.
Meyer, L. D., G. R. Foster, and M. J. M. Romkens.
1975. Origin of eroded soil from upland slopes.
In: Present and Prospective Tech. for Predict.
Sediment Yields and Sour. U.S. Dep. Agric.,
Agric. Res. Serv. Rep. ARS-S-40:177-189.
Meyer, L. D., D. G. DeCoursey, and M. J. M.
Romkens. 1976. Soil erosion concepts and mis-
conceptions. Proc. Third Fed. Inter-agency
Sedimentation Conf.
Middleton, H. E., C. S. Slater, and H. G. Byers.
1932. Physical and chemical characteristics of
the soils from the erosion experiment stations.
U.S. Dep. Agric. Tech. Bull. 316. 51 p.
Musgrave, G. W. 1947. The quantitative evalua-
tion of factors in water erosion, a first approx-
imation. J. Soil and Water Conserv. 2:133-138.
Neibling, W. H., and G. R. Foster. 1977.
Estimating deposition and sediment yield from
overland flow processes. Proc. of Int. Symp. on
Urban Hydrol., Hydraul., and Sediment Contr.,
Univ. Kentucky, Lexington, Ky. p. 75-86.
Olson, T. C., and W. H. Wischmeier. 1963. Soil-
erodibility evaluations for soils on the runoff and
erosion stations. Soil Sci. Soc. Am. Proc. 27:590-
592.
Osborn, J. F., R. E. Pelishek, and J. S. Krammes.
1964. Soil wettability as a factor in erodibility.
Soil Sci. of Am. Proc. 28(2):294-295.
Peele, T. C., E. E. Latham, and 0. W. Beale. 1945.
Relation of the physical properties of different
soil types to erodibility. S. C. Agric. Exp. Stn.
Bull. 357.
Renfro, G. W. 1975. Use of erosion equations and
sediment delivery ratios for predicting sediment
yield. In: Proc. Sedimentation Yield Workshop,
Oxord, Miss. U.S. Dep. Agric., Agric. Res. Serv.
Rep. ARS-S-40.-33-45.
Roehl, J. W. 1962. Sediment source areas, delivery
ratios and influencing morphological factors. Int.
Assoc. Sci. Hydrol. Publ. No. 59.
Roth, C. B., D. W. Nelson, and M. J. M. Romkens.
1974. Prediction of subsoil erodibility using
chemical, mineralogical and physical
parameters. U.S. Environ. Protect. Agency Rep.
EPA-660/2-74-043. USGPO, Washington D.C
111 p.
Simons, D. B., R. M. Li, and M. A. Stevens 1975.
Development of models for predicting water and
sediment routing and yield from storms on small
watersheds. Colo. State Univ. Rep. CER 74-75-
DBS-RML-MAS24.
Smith, D. D., and W. H. Wischmeier. 1957. Factors
affecting sheet and rill erosion. Trans. Am.
Geophys. Union 38(6):889-896.
Smith, D. D., and W. H. Wischmeier. 1962. Rain-
fall erosion. Adv. Agron. 14:109-148.
Swank, W. T., N. B. Goebel, and J. D. Helvey.
1972. Interception loss in loblolly pine stands of
the South Carolina Piedmont. J. Soil and Water
Conserv. 27(4) :160-164.
Tollner, E. W., B. J. Barfield, C. T. Haan, and T.
Y. Kao. 1976. Suspended sediment filtration
capacity of simulated vegetation. Trans. Am.
Soc. Agric. Eng. 19(4):678-682.
Trimble, G. R., Jr., and S. Weitzman. 1954. Effect
of a hardwood forest canopy on rainfall inten-
sities. Trans. Am. Geophys. Union, 35(2); 226-
234.
U.S. Army Engineer School. 1973. Open channel
design, student pamphlet, U.S. Army Eng. Sch.,
Ft. Belvoir, Va. Stock No. E.004-C1-SP-003.
U.S. Department of Agriculture, Soil Conservation
Service 1977. Procedure for computing sheet and
rill erosion on project areas. U.S. Dep. Agric. Soil
Conserv. Serv., Tech. Release No. 41, (Rev. 2).
17 p.
IV.65
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U.S. Department of Agriculture, Soil Survey Staff.
1951. Soil survey manual. U.S. Dep. Agric.,
Agric. Handb. No. 18, U.S. Gov. Print. Off.,
Wash., D.C., 503 p.
Williams, J. R, H. D. Berndt. 1972. Sediment
yield computed with universal equation. J.
Hydraul. Div. Am. Soc. Civ. Eng.
98(HY12): 2087-2098.
Williams, J. R., and W. V. LaSeur. 1976. Water
yield model using SCS curve numbers. J.
Hydraul. Div. Am. Soc. Div. Eng.
102(HY9):1241-1253.
Wischmeier, W. H. 1972. Upslope erosion analysis.
In: Environmental impact on rivers, p 15-1 —
15-26. Colo. St. Univ., Fort Collins.
Wischmeier, W. H. 1975. Estimating the soil loss
equation's cover and management factor for un-
disturbed areas, p. 118-124. In: Present and
prospective technology for predicting sediment
yields and sources. Proc. Sediment-Yield
Workshop, U.S. Dep. Agric. Sediment Lab., Ox-
ford, Miss. Nov. 28-30, 1972. 285 p. MS, ARS-S-
40.
Wischmeier, W.H. 1976. Use and misuse of the
Universal Soil Loss Equation. J. Soil and Water
Conserv. 31:5-9.
Wischmeier, W. H., and D. D. Smith. 1958. Rain-
fall energy and its relation to soil loss. Trans.
Am. Geophys. Union 39(2):285-291.
Wischmeier, W. H., and D. D. Smith. 1965.
Predicting rainfall-erosion losses from cropland
east of the Rocky Mountains. U.S. Dep. Agric.,
Agric. Handb. 282, USGPO, Washington, D.C.
Wischmeier, W. H. and D. D. Smith. 1968. A un-
iversal soil-loss equation to guide conservation
farm planning. Trans. Int. Congr. Soil Sci. 1:418-
425.
Wischmeier, W. H., and J. V. Mannering. 1969.
Relation of soil properties to its erodibility. Soil
Sci. Soc. Am. Proc. 33:131-137.
Wischmeier, W. H., C. B. Johnson, and B. V.
Cross. 1971. A soil erodibility nomograph for
farmland and construction sites. J. Soil and
Water Conserv. 26:189-193.
Wischmeier, W. H., and D. D. Smith. Predicting
rainfall-erosion losses as a guide to conservation
planning. U.S. Dep. Agric. Sci. and Educ. Adm.,
Agric. Handb. 282, (rev.). [In press.]
Zingg, A. W. 1940. Degree and length of land slope
as it affects soil loss in runoff. Agric. Eng. 21:59-
64.
IV.66
-------
APPENDIX IV.A.:
GULLY EROSION
A gully is a channel created by concentrated but
intermittent flow of water, usually during and im-
mediately following heavy rains; however, con-
centration of snowmelt runoff may also be a factor.
Gullies are deep enough to interfere with, and
usually are not obliterated by, normal tillage or
silvicultural activities.
Quantitative estimates of soil loss and sediment
produced by gully erosion must be based on profes-
sional judgment about the overall erosional
processes in a particular location. Changes in the
geometry of a gully can provide an estimate of the
amount of material being eroded. Rates of
headward cutting, final average width, and depth
of each cycle of cutting can be used to compute the
volume of soil material removed from the gully.
The mass of soil material is calculated by multiply-
ing the volume by an appropriate bulk density fac-
tor for the particular soil.
Bulk density is usually expressed in grams per
cubic centimeter or pounds per cubic foot. Conver-
sion factors are:
g/cm3 = (0.016) (lb/ft3)
lb/ft3 = (62.43) (g/cm3)
An estimate of the proportion of eroded material
actually delivered to a stream channel may be
needed if the gully does not connect directly to a
stream system.
IV.67
-------
APPENDIX IV.B.:
EROSION OVER TIME
To predict long-term, onsite soil losses, changes
in the various parameters in the soil loss equation
must be estimated and redefined for each year. The
most important is the VM factor. The K factor
needs to be changed if management causes long-
term changes in soil characteristics to occur.
Future changes in VM and K factors become, at
best, an educated guess about what might happen
in any given year. Time trend analysis should be
based on both best condition and worst condition
parameters in order to show a range of possible out-
comes.
The part of the equation which is most likely to
change with time is the VM factor. The effects of
roughness and vegetation change with time either
as the surface roughness is broken down or as the
vegetation becomes healthier and covers more of
the surface. Estimates of VM changes must be
made relative to the time period of interest.
Fine materials in the surface soil tend to erode
away, leaving the heavier material, which is less
erosive to protect the surface (Clyde and others
1976, Megahan 1974, Wischmeier and Mannering
1969). Other long-term changes due to manage-
ment must also be evaluated.
IV.68
-------
APPENDIX IV.C.:
CONTROLLING DITCH EROSION
The simulation procedures in Chapter IV, "Sur-
face Erosion" do not consider road ditch erosion.
There is no technique to estimate the amount of
sediment delivered to the stream from road
ditches. Because some controls are designed to af-
fect road ditch erosion, the Manning formula (U.S.
Army Engineering School 1973) is used to estimate
the effect of various controls on road ditch stability
and water velocity. Manning's formula is:
V = (M9) (R0.66) (S0.6) (IV.C.l)
where:
V = velocity of flow in ft/sec,
R = hydraulic radius, =
cross-section area of the channel
wetted perimeter (ft)
(from tables IV.C.2 through IV.C.5)
S = slope of the channel in ft/ft, and
n = friction factor which depends on the
material comprising the channel from
Table IV.C.l
Manning formula limitations: (1) It will not
predict amounts of sediment delivered to the
stream from a road ditch. (2) The formula is based
on the amount of energy necessary to move parti-
cles of given size, and does not account for detach-
ment. Soils with strong structure are likely to be
more resistant than soils with weak structure. (3)
The maximum recommended velocity figures are
based on energy/particle size relationships.
An Example For Use Of The
Manning Formula
Problem — Determine whether the water
velocity for a given road ditch will
be below critical levels for erosion.
If velocities are too high, make and
evaluate changes.
Solution
1. Obtain hydraulic radius for channel. As-
sume that the road ditch is a symmetrical,
triangular channel 1.3 feet deep with
21/2:1 slopes. Check table IV.C.2 for
hydraulic radius which is 0.60 feet for
this size channel.
2. Obtain slope of channel. (Slope of the road
ditch is measured and found to be 0.003
feet per feet.)
3. Obtain roughness coefficient from table
IV.C.I.(The channel sides, in this case, are
sand and have a friction factor (n) of
0.020.)
4. Obtain maximum allowable velocity. (For
a sandy channel, the maximum velocity is
1-2 feet per second (table IV.C.l).)
5. Obtain V (velocity) for the specified chan-
nel by using the nomograph (fig. IV.C.l).
(Velocity for the specified ditch is 2.9 feet
per second.)
6. Compare the predicted velocity for the
specified ditch with the maximum recom-
mended velocity for sandy channels.
specified ditch
2.9 ft/sec
maximum velocity
1-2 ft/sec
If the specified ditch has too great a
velocity, it will erode. Therefore, controls
must be chosen that will reduce the water
velocity in the road ditch.
7. Water velocities in ditches can be reduced
by protecting the channel with vegetation,
rock, or by changing the channel shape.
(With vegetative protection, the friction
factor (n) becomes 0.030-0.050 and the
maximum recommended velocity becomes
3-4 feet per second.)
8. Obtain velocity for specified ditch with
vegetative protection by referring to the
nomograph (fig. IV.C.l). Velocity is 1.9
feet per second.
9. Compare the predicted velocity for the
specified ditch with the maximum recom-
mended velocity for vegetation protected
channels (average turf) with easily eroded
soil.
specified ditch
1.9 ft/sec
maximum velocity
3-4 ft/sec
10. If the specified ditch has a lower velocity
than the recommended maximum
velocities, it should be stable as long as the
vegetation remains intact.
IV.69
-------
f.3 .2
co
H-
o
o
Ll-
CC
LU
CL
LU
LU
LL
z
LU
n
LL,
O
I
CO
-.2
.10
1.09
-.08
-.07
r-06
..05
..04 ^
1-
no LU
-.03 LU
LL
'• Z
-.02 co
D
: °
QC
:.oi9 |
1 .008 <
1.007 g
..006 >
-.005
; 004 Q$?
" ^- ^x^^
• ^^^
<003
•
:.002
'
"
-.001
-.0009
- 0008
-.0007
-.0006
L.0005
i.0004
•..0003
EQUATION:
v_ 1.486 R2'3R1/2
-.3 n
-.4
-.5
_.6
:\^
..8
L.9
.1.0
-2
-3X-
•_
•
'-4
-5
:
-6
'
-7
-8
-9
-10
•
'
•
•
:20
CD
I]
O>
c
'c
H
^>
^
X
\.
\
\
\
<&^'
0>^
^
s^
^
^^ Z
^^ O
/s LU
\ W
\ , Ł
\ L- CL
N^^ ^
'^ LU
NZ
^
1—
|•^
EXAMPLE (SEE DASHED LINE) O
— I
GIVEN: R =0.6 LU
S = 0.003 >
n = 0.02
FIND: V
LINE FROM S VALUE TO n VALUE
INTERSECTS TURNING LINE, ESTAB -
LISHING TURNING POINT, LINE FROM
R VALUE THROUGH TURNING POINT
INTERSECTS VELOCITY SCALE AT
V = 2.9 FPS.
-50
• 40
-30
-20
**?*'
_W*/'
*f
-8
c
-7
r-
-6 Z
LU
i
LL
LU
-4 O
0
co
CO
•3 ^
: I
; O
-2 DC
1
_
1
-1.0
I- -9
''• .8
i .7
L .6
L •*
r.01
-.02
-.03
.04
^.05
:.oe
-.07
..08
-.09
i.10
-.2
-.3
Figure IV.C.1 Nomograph for Manning formula.
IV.70
-------
Table IV.C.1—Values for Manning's n and maximum permissible velocity of flow In open channels
Ditch lining
Manning's n
,fps'
1. Natural ec
a. Without
(1) Roc
(a) S
i
(b) Ji
(2) Soil:
TJ
0>
C
s
O)
O
Finegrained
»rth
t vegetation
k
mooth and
jnlform
igged & Irregul
s
>,
1
««
Gravel anc
soi
Sand and sandy
soils
o
io
Ł -j
0 -1
0
•o
t
a
2. o
55 -0
_i
_i
Highly Organic
ar
Unified
GW
GP
GM
GC
SW
SP
SM
SC
CL
ML
OL
CH
MH
OH
PT
USDA
Gravel
Gravel
Loamy
u
Gravelly Loam
Gravelly Clay
Sand
Sand
d
Loamy
QgnH
U
Sandy Loam
Clay Loam
Sandy Clay Loam
Silty Clay
Silt Loam
Very Fine Sand
Silt
Mucky Loam
Clay
Silty Clay
Mucky Clay
Peat
0.035 -
0.040-
0.022
C.023 -
0.023 -
0.022 -
0.024 -
0.020 -
0.022 -
0.020 -
0.021 -
0.023 -
0.022
0.023 -
0.022 -
0.022
0.023 -
0.022 -
0.022
0.040
0.045
0.024
0.026
0.025
0.020
0.026
0.024
0.024
0.023
0.023
0.025
0.024
0.024
0.024
0.023
0.024
0.024
0.025
20
15-18
6-7
7-8
3-5
2-4
5-7
1-2
1-2
2-3
2-3
3-4
2-3
3-4
2-3
2-3
3-5
2-3
2-3
'Maximum recommended velocities
IV.71
-------
Table IV.C.1—Continued
Ditch lining
Manning's n Vmax fps1
b. With vegetation
(1) Average turf
(a) Erosion resistant
soil 0.050 0.070 4 - 5
(b) Easily eroded soil 0.030 0.050 3 - 4
(2) Dense turf
(a) Erosion resistant
soil 0.070 0.090 6-8
(b) Easily eroded soil 0.040 - 0.050 5 - 6
(3) Clean bottom with
bushes on sides 0.050 0.080 4-5
(4) Channel with tree
stumps
(a) No sprouts 0.040 0.050 5 - 7
(b) With sprouts 0.060 0.080 6 - 8
(5) Dense weeds 0.080 0.120 5-6
(6) Dense brush 0.100 0.140 4-5
(7) Dense willows 0.150 0.200 8-9
2. Paved (Construction)
a. Concrete, w/all surfaces: Good Poor
(1) Trowel finish 0.012 0.014 20
(2) Float finish 0.013 0.015 20
(3) Formed, no finish 0.014 0.016 20
b. Concrete bottom, float
finished, w/sides of:
(1) Dressed stone in mortar 0.015 - 0.017 18-20
(2) Random stone in mortar 0.017 - 0.020 17 -19
(3) Dressed stone or smooth
concrete rubble (riprap) 0.020 0.025 15
(4) Rubble or random stone (riprap) 0.025 0.030 15
c. Gravel bottom, sides of:
(1) Formed concrete 0.017 - 0.020 10
(2) Random stone in mortar 0.020 - 0.023 8-10
(3) Random stone or rubble (riprap) 0.023 0.033 8-10
d. Brick 0.014 0.017 10
e. Asphalt 0.013 0.016 18-20
'Maximum recommended velocities
IV.72
-------
Table IV.C.2. Hydraulic radius (R) and area (A) of symmetrical triangular channels.
WP
-9-
d R = A/WP
1
Depth,
d
(leet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
3.5
4.0
Slope ratio
1:
A
0.25
0.36
0.49
0.64
0.81
1.00
1.21
1.44
1.69
1.96
2.25
2.56
2.89
3.24
3.61
4.00
6.25
9.00
12.25
16.00
1
R
0.18
0.21
0.25
0.28
0.32
0.35
0.39
0.42
0.46
0.50
0.53
0.57
0.60
0.64
0.67
0.71
0.88
1.06
1.24
1.41
W.
A
0.38
0.54
0.74
0.96
1.21
1.50
1.82
2.16
2.54
2.94
3.38
3.84
4.34
4.86
5.42
6.00
9.38
13.50
18.38
24.00
;:1
R
0.21
0.25
0.29
0.33
0.37
0.42
0.46
0.50
0.54
0.58
0.62
0.67
0.71
0.75
0.79
0.83
1.04
1.25
1.45
1.66
2
A
0.50
0.72
0.98
1.28
1.62
2.00
2.42
2.88
3.38
3.92
4.50
5.12
5.78
6.48
7.22
8.00
12.50
18.00
24.50
32.00
:1 2
-------
Table IV.C.3. Hydraulic radius (R) and area (A) of nonsymmetrical triangular channels.
WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
V
\
A
V^
X
'• 1
d
\
\
R
r
= A/WP
Slope ratio
1:1
A
0.50
0.72
0.98
1.28
1.62
2.00
2.42
2.88
3.38
3.92
4.50
5.12
5.78
6.48
7.22
8.00
8.82
9.68
10,58
11.52
12.50
13.52
14.58
15.68
16.82
18.00
-3:1
R
0.22
0.26
0.31
0.35
0.39
0.44
0.48
0.52
0.57
0.61
0.66
0.70
0.74
0.79
0.83
0.87
0.92
0.96
1.01
1.05
1.09
1.14
1.18
1.22
1.27
1.31
1V4:1
A
0.56
0.81
1.10
1.44
1.82
2.25
2.72
3.24
3.80
4.41
5.06
5.76
6.50
7.29
8.12
9.00
9.92
10.89
11.90
12.96
14.06
15.21
16.40
17.64
18.92
20.25
-3:1
R
0.23
0.27
0.32
0.36
0.41
0.45
0.50
0.54
0.59
0.63
0.68
0.73
0.77
0.82
0.86
0.91
0.95
1.00
1.04
1.09
1.13
1.18
1.22
1.27
1.31
1.36
2:1 -
A
0.63
0.90
1.23
1.60
2.03
2.50
3.03
3.60
4.23
4.90
5.63
6.40
7.23
8.10
9.03
10.00
11.03
12.10
13.23
14.40
15.63
16.90
18.23
19.60
21.03
22.50
3:1
R
0.23
0.28
0.32
0.37
0.42
0.46
0.51
0.56
0.60
0.65
0.69
0.74
0.79
0.83
0.88
0.93
0.97
1.02
.07
.11
.16
.20
.25
1.30
1.34
1.39
2'/*:1
A
0.69
0.99
1.35
1.76
2.23
2.75
3.33
3.96
4.65
5.39
6.19
7.04
7.95
8.91
9.93
11.00
12.13
13.31
14.55
15.84
17.19
18.59
20.05
21.56
23.13
24.75
-3:1
R
0.23
0.28
0.33
0.38
0.42
0.47
0.52
0.56
0.61
0.66
0.70
0.75
0.80
0.85
0.89
0.94
0.99
1.03
1.08
1.13
1.17
1.22
1.27
1.32
1.36
1.41
4:1-
A
0.88
1.26
1.72
2.24
2.84
3.50
4.24
5.04
5.92
6.86
7.88
8.96
10.12
11.34
12.64
14.00
15.44
16.94
18.52
21.16
21.87
23.66
25.52
27.44
29.44
31.50
3:1
R
0.24
0.29
0.34
0.38
0.43
0.48
0.53
0.58
0.63
0.67
0.72
0.77
0.82
0.86
0.91
0.96
1.00
1.06
1.10
1.15
1.20
1.25
1.30
1.35
1.39
1.44
5:1-
A
1.00
1.44
1.96
2.56
3.24
4.00
4.84
5.76
6.76
7.84
9.00
10.24
11.56
12.96
14.44
16.00
17.64
19.36
21.16
23.04
25.00
27.04
27.16
31.36
33.64
36.00
3:1
R
0.24
0.29
0.34
0.39
0.44
0.48
0.53
0.58
0.63
0.68
0.73
0.77
0.82
0.87
0.92
0.97
1.02
1.07
1.11
1.16
1.21
1.26
1.31
1.36
1.40
1.45
IV.74
-------
Table IV.C.4. Hydraulic radius (R) and area (A) of symmetrical trapezoidal channels
[2' bottom width].
WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
t
d
\
«-xd »U
A
- 2' —
-J
/
A =
WP =
R =
1
• xd2-*
2dV
•2d
1 + x2
+ 2
A/WP
Slope ratio
1:1
A
1.25
1.56
1.89
2.24
2.61
3.00
3.41
3.84
4.29
4.76
5.25
5.76
6.29
6.84
7.41
8.00
11.25
15.00
R
0.37
0.42
0.47
0.53
0.51
0.62
0.67
0.71
0.76
0.80
0.84
0.88
0.92
0.96
1.00
1.04
1.24
1.43
1'/2:1
A R
1.38 0.36
1.74 0.42
2.14 0.47
2.56 0.52
3.01 0.57
3.50 0.62
4.02 0.67
4.56 0.72
5.14 0.77
5.74 0.81
6.38 0.86
7.04 0.91
7.74 0.95
8.46 1.00
9.22 1.04
10.00 1.09
14.38 1.30
19.50 1.52
2:1
A
1.50
1.92
2.28
2.88
3.42
4.00
4.63
5.28
5.98
6.72
7.50
8.32
9.18
10.08
11.02
12.00
17.50
24.00
R
0.35
0.41
0.44
0.52
0.57
0.62
0.67
0.72
0.77
0.81
0.86
0.91
0.96
1.00
1.05
1.10
1.33
1.56
21/2
A
1.63
2.10
2.63
3.20
3.83
4.50
5.23
6.00
6.83
7.70
8.63
9.60
10.63
11.70
12.83
14.00
20.63
28.30
1
R
0.35
0.40
0.46
0.51
0.56
0.61
0.66
0.71
0.76
0.81
0.86
0.90
0.95
1.00
1.05
1.10
1.33
1.57
3:1
A
1.75
2.28
2.87
3.52
4.23
5.00
5.84
6.72
7.67
8.68
9.75
10.88
12.07
13.32
14.63
16.00
23.75
33.00
R
0.34
0.39
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.04
1.09
1.33
1.57
4:1
A
2.00
2.64
3.36
4.16
5.04
6.00
7.05
8.16
9.36
10.64
12.00
13.44
14.96
16.56
18.24
20.00
30.00
42.00
R
0.33
0.38
0.43
0.48
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.88
0.93
0.98
1.03
1.08
1.33
1.57
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5:
A
2.25
3.00
3.85
4.80
5.85
7.00
8.25
9.60
11.05
12.60
14.25
16.00
17.85
19.80
21.85
24.00
36.25
51.00
1
R
0.32
0.37
0.42
0.47
0.52
0.51
0.62
0.67
0.72
0.77
0.82
0.87
0.92
0.97
1.02
1.07
1.32
1.56
6:1
A R
2.50 0.31
3.36 0.36
4.34 0.41
5.44 0.46
6.66 0.51
8.00 0.56
9.47 0.62
11.04 0.67
12.74 0.72
14.50 0.77
16.50 0.81
18.56 0.86
20.74 0.91
23.04 0.96
25.46 1.01
28.00 1.06
42.50 1.31
60.00 1.56
7:
A
2.75
3.72
4.83
6.08
7.47
9.00
10.68
12.48
14.43
16.52
18.75
21.12
23.63
26.28
29.07
32.00
48.75
69.00
1
R
0.30
0.35
0.41
0.46
0.51
0.56
0.61
0.66
0.71
0.76
0.81
0.86
0.91
0.96
1.01
1.06
1.30
1.55
8
A
3.00
4.08
5.32
6.72
8.28
10.00
11.89
13.92
16.12
18.48
21.00
23.68
26.52
29.52
32.68
36.00
55.00
78.00
:1
R
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.30
1.55
9:
A
3.25
4.44
5.81
7.36
9.09
11.00
13.10
15.36
17.81
20.44
23.25
26.24
29.41
32.76
36.29
40.00
61.25
87.00
1
R
0.29
0.34
0.39
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.30
1.54
10
A
3.50
4.80
6.30
8.00
9.90
12.00
14.31
16.80
19.50
22.40
25.50
28.80
32.30
36.00
39.90
44.00
67.50
96.00
1
R
0.29
0.34
0.39
0.44
0.49
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.89
0.94
0.99
1.04
1.29
1.54
IV.75
-------
Table IV.C.4.—Continued
WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
1
A
2.25
2.76
3.29
3.84
4.41
5.00
5.61
6.24
6.89
7.56
8.25
8.96
9.69
10.44
11.21
12.00
16.25
21.00
t
d
4
1
R
0.41
0.48
0.55
0.61
0.67
0.73
0.79
0.84
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.24
1.47
1.68
"X
\
+-X
1 '/
A
2.38
2.94
3.54
4.16
4.82
5.50
6.22
6.96
7.74
8.54
9.38
10.24
11.14
12.06
13.02
14.00
19.38
25.50
\
d-J*
4:1
R
0.41
0.48
0.54
0.60
0.66
0.72
0.78
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.20
1.25
1.48
1.72
A
4'
2
A
2.50
3.12
3.78
4.48
5.22
6.00
6.82
7.68
8.58
9.52
10.50
11.52
12.58
13.68
14.82
16.00
22.50
30.00
V
jf x
— J *•
WP =
R =
Slope ratio
1 2V4:1
R A
/-
1
xd2
2d>
+ 4d
^ 1 + x
2 + 4
A/WP
R
0.40 2.63 0.39
0.47 3.30 0.46
0.53 4.03 0.52
0.59 4.80 0.53
0.65 5.63 0.64
0.71 6.50 0.69
0.76 7.43 0.75
0.82 8.40 0.80
0.87 9.43 0.86
0.93 10.50 0.91
0.98 11.63 0.96
1.03 12.80 1.01
1.08 14.03 1
1.14 15.30 1
1.19 16.63 1
1.24 18.00 1
1.48 25.63 1
1.72 34.50 1
.07
.12
.17
.22
.47
.71
3
A
2.75
3.48
4.27
5.12
6.03
7.00
8.03
9.12
10.27
11.48
12.75
14.08
15.47
16.92
18.43
20.00
28.75
39.00
1
R
0.39
0.45
0.50
0.57
0.62
0.68
0.73
0.79
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.20
1.45
1.70
4:
A
3.00
3.84
4.76
5.76
6.84
8.00
9.24
10.56
11.96
13.44
15.00
16.64
18.36
20.16
22.04
24.00
35.00
48.00
1
R
0.37
0.43
0.49
0.54
0.60
0.65
0.71
0.76
0.81
0.86
0.92
0.97
1.02
1.02
1.12
1.17
1.42
1.67
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5
A
3.25
4.20
5.25
6.40
7.65
9.00
10.45
12.00
13.65
15.40
17.25
19.20
21.25
23.40
25.65
28.00
41.25
57.00
1
R
0.36
0.42
0.47
0.53
0.58
0.64
0.69
0.74
0.79
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.40
1.65
6
A
3.50
4.56
5.74
7.04
8.46
10.00
11.66
13.44
15.34
17.36
19.50
21.76
24.14
26.64
29.26
32.00
47.50
66.00
1
R
0.35
0.40
0.46
0.51
0.56
0.62
0.67
0.72
0.77
0.83
0.88
0.93
0.98
1.03
1.08
1.14
1.38
1.64
7
A
3.75
4.92
6.23
7.68
9.27
11.00
12.87
14.88
17.03
19.32
21.75
24.32
27.03
29.88
32.87
36.00
53.75
75.00
1 8:1
R A
R
0.34 4.00 0.33
0.39 5.28 0.38
0.45 6.72 0.44
0.50 8.32 0.49
0.55 10.08 0.55
0.61 12.00 0.60
0.66 14.08 0.65
0.71 16.32 0.70
0.76 18.72 0.75
0.81 21 .28 0.80
0.86 24.00 0.85
0.91 26.88 0.90
0.96 29.92 0.95
1.01 33.12 1.00
1.06 36.48 1.05
1.12 40.00 1
1.37 60.00 1
1.63 84.00 1
.10
.35
.62
9
A
4.25
5.64
7.21
8.96
10.89
13.00
15.29
17.76
20.41
23.24
26.25
29.44
32.81
36.36
40.09
44.00
66.25
93.00
1
R
0.32
0.38
0.43
0.49
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.89
0.94
0.99
1.04
1.09
1.34
1.62
10
A
4.50
6.00
7.70
9.60
11.70
14.00
16.50
19.20
22.10
25.20
28.50
32.00
35.70
39.60
43.70
48.00
72.50
102.00
•1
R
0.32
0.37
0.43
0.48
0.53
0.58
0.63
0.68
0.73
0.78
0.83
0.89
0.94
0.99
1.04
1.09
1.34
1.61
IV.76
-------
Table IV.C.4. —Continued
WP
t
d
4
•xd
6'
A = xd2 + 6d
WP = 2d Vl +x2 + 6
R = A/WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
Slope ratio
1
A
3.25
3.96
4.69
5.44
6.21
7.00
7.81
8.64
9.49
10.36
11.25
12.16
13.09
14.04
15.01
16.00
21.25
27.00
1
R
0.44
0.51
0.59
0.66
0.73
0.79
0.86
0.92
0.98
1.04
1.10
1.16
1.22
1.27
1.32
1.37
1.61
1.86
1V4
A
3.38
4.14
4.94
5.76
6.62
7.50
8.42
9.36
10.34
11.34
12.38
13.44
14.54
15.66
16.82
18.00
24.38
31.50
1
R
0.43
0.51
0.58
0.65
0.72
0.78
0.85
0.91
0.97
1.03
1.08
1.14
1.20
1.25
1.30
1.36
1.61
1.87
2:
A
3.50
4.32
5.18
6.08
7.02
8.00
9.02
10.08
11.18
12.32
13.50
14.72
15.98
17.28
18.62
20.00
27.50
36.00
1
R
0.42
0.50
0.57
0.63
0.70
0.76
0.83
0.89
0.95
1.00
1.06
1.12
1.17
1.23
1.28
1.34
1.60
1.85
2V4
A
3.63
4.50
5.43
6.40
7.43
8.50
9.63
10.80
12.03
13.30
14.63
16.00
17.43
18.90
20.43
22.00
30.63
40.50
1
R
0.42
0.49
0.56
0.62
0.68
0.75
0.80
0.87
0.93
0.98
1.04
1.09
1.15
1.20
1.25
1.31
1.58
1.83
3
A
3.50
4.68
5.67
6.72
7.83
9.00
10.23
11.52
12.87
14.28
15.75
17.28
18.87
20.52
22.23
24.00
33.75
45.00
1
R
0.41
0.48
0.54
0.61
0.67
0.73
0.79
0.85
0.91
0.96
1.01
1.07
1.13
.18
.24
.29
.55
.80
4:1
A R
4.00 0.40
5.04 0.46
6.16 0.52
7.36 0.58
8.64 0.64
10.00 0.70
11.44 0.76
12.96 0.82
14.56 0.87
16.24 0.93
18.00 0.98
19.84 1.03
21.76 1.09
23.76 1.14
25.84 1.19
28.00 1.24
40.00 1.50
54.00 1.76
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5
A
4.25
5.90
6.65
8.00
9.45
11.00
12.65
14.40
16.25
18.20
20.25
22.40
24.45
27.00
29.45
32.00
46.25
63.00
1
R
0.38
0.45
0.51
0.56
0.62
0.68
0.73
0.79
0.85
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.47
1.72
6:1
A
4.50
5.76
7.14
8.64
10.26
12.00
13.86
15.84
17.94
20.16
22.50
24.96
27.54
30.24
33.06
36.00
52.50
72.00
R
0.37
0.43
0.49
0.55
0.61
0.66
0.72
0.77
0.82
0.87
0.92
0.98
1.03
1.08
1.14
1.19
1.45
1.70
7:
A
4.75
6.12
7.63
9.28
11.07
13.00
15.07
17.28
19.63
22.12
24.75
27.52
30.43
33.48
36.67
40.00
58.75
81.00
1
R
0.36
0.42
0.48
0.54
0.59
0.65
0.70
0.75
0.80
0.85
0.91
0.96
1.01
1.06
1.12
1.17
1.46
1.71
8:1
A
5.00
6.48
8.12
9.92
11.88
14.00
16.28
18.72
21.32
24.08
27.00
30.08
33.32
36.72
40.28
44.00
65.00
90.00
R
0.36
0.41
0.47
0.53
0.58
0.63
0.69
0.74
0.79
0.84
0.90
0.95
1.00
1.08
1.10
1.15
1.40
1.65
9
A
5.25
6.84
8.61
10.56
12.69
15.00
17.49
20.16
23.01
26.04
29.25
32.64
36.21
39.96
43.89
48.00
71.25
99.00
1
R
0.35
0.41
0.46
0.49
0.57
0.62
0.67
0.75
0.78
0.83
0.88
0.93
0.97
1.04
1.09
1.13
1.39
1.66
10:1
A R
5.50 0.34
7.20 0.40
9.10 0.45
11.20 0.51
13.50 0.55
16.00 0.61
18.70 0.67
21.60 0.72
24.70 0.77
28.00 0.82
31.50 0.87
35.20 0.92
39.10 0.97
43.20 1.02
47.50 1.07
52.00 1.12
77.50 1.38
108.00 1.65
IV.77
-------
Table IV.C.4.—Continued
WP
t
d
|
^ *7 >
\
«-x
\
d-frl«
A
I 8
~^/1
1
S X
J A xd2
WP 2di
+ 8d
/1 + X
2 + 8
R = A/WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
Slope ratio
1:1
A
4.25
5.16
6.09
7.04
8.01
9.00
10.01
11.04
12.09
13.16
14.25
15.36
16.49
17.64
18.81
20.00
26.25
33.00
R
0.45
0.53
0.61
0.69
0.76
0.83
0.90
0.97
1.04
1.10
1.16
1.23
1.29
1.35
1.41
1.46
1.76
2.00
1V4
A
4.38
5.34
6.34
7.36
8.42
9.50
10.62
11.76
12.94
14.14
15.38
16.64
17.44
19.26
20.63
22.00
29.38
37.50
1
R
0.45
0.53
0.60
0.68
0.75
0.82
0.89
0.95
1.02
1.08
1.14
1.21
1.27
1.33
1.40
1.45
1.72
1.99
2:
A
4.50
5.52
6.58
7.68
8.82
10.00
11.22
12.48
13.78
15.12
16.50
17.92
19.38
20.88
22.42
24.00
32.50
42,00
1
R
0.44
0.52
0.59
0.66
0.73
0.80
0.87
0.93
1.00
1.06
1.12
1.18
1.24
1.30
1.36
1.42
1.69
1.96
2Vz:1
A R
4.63 0.43
5.70 0.51
6.83 0.58
8.00 0.65
9.22 0.72
10.50 0.78
11.83 0.85
13.20 0.91
14.63 0.98
16.10 1.04
17.63 1.10
19.20 1.16
20.83 1 .22
22.50 1.27
24.23 1.33
26.00 1 .39
35.63 1.66
46.50 1 .93
3:1
A
4.75
5.88
7.07
8.32
9.63
11.00
12.43
13.92
15.97
17.08
18.75
20.48
22.27
29.12
26.03
28.00
38.75
51.00
R
0.43
0.50
0.57
0.64
0.70
0.77
0.83
0.89
0.95
1.01
1.07
1.13
1.19
1.24
1.30
1.36
1.63
1.89
4:1
A
5.00
6.24
7.56
8.96
10.44
12.00
13.64
15.36
17.16
19.04
21.00
23.04
25.16
27.36
29.64
32.00
45.00
60.00
R
0.41:
0.48.
0.55
0.61
0.68
0.74
0.80
0.86
0.92
0.97
1.03
1.09
1.14
1.20
1.25
1.31
1.57
1.83
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5:
A
5.25
6.00
8.05
9.60
11.25
13.00
14.85
16.80
•i8.85
21.00
23.25
25.60
28.25
30.60
33.25
36.00
57.25
69.00
1 6:1
R
0.40
0.47
0.53
0.59
0.65
0.71
0.77
0.83
0.88
0.92
1.00
1.05
1.11
1.16
1.22
1.28
1.54
1.80
A
5.50
6.96
8.54
10.24
12.06
14.00
16.06
18.24
20.54
22.96
25.50
28.16
30.94
33.84
36.86
40.00
57.50
78.00
R
0.39
0.44
0.52
0.58
0.64
0.70
0.75
0.81
0.86
0.91
0.97
1.03
1.08
1.13
1.18
1.24
1.50
1.77
7
A
5.75
7.32
9.03
10.88
12.87
15.00
17.27
19.68
22.23
24.92
27.75
30.72
33.85
37.08
40.47
44.00
63.75
87.00
:1
R
0.38
0.44
0.50
0.56
0.63
0.68
0.73
0.79
0.84
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.48
1.74
8:1
A R
6.00 0.37
7.68 0.43
9.52 0.49
11.20 0.54
13.68 0.61
16.00 0.66
18.48 0.72
21.12 0.77
23.92 0.83
26.88 0.88
30.00 0.93
33.28 0.98
36.72 1.04
40.32 1.08
44.08 1.14
48.00 1.19
70.00 1.45
96.00 1 .70
9:
A
6.25
8.04
10.01
12.16
14.49
17.00
16.96
22.56
25.61
28.84
32.25
35.84
39.61
43.56
47.69
52.00
76.25
105.00
R
0.36
0.43
0.48
0.54
0.60
0.65
0.71
0.76
0.81
0.86
0.92
0.97
1.02
1.07
1.12
1.18
1.43
1.70
10
A
6.50
8.40
10.50
12.80
15.30
18.00
20.90
24.00
27.30
30.80
34.50
38.40
42.50
46.80
51.30
56.00
82.50
114.00
1
R
0.36
0.42
0.48
0.53
0.59
0.64
0.69
0.74
0.79
0.84
0.90
0.96
1.01
1.06
1.11
1.16
1.42
1.69
IV.78
-------
Table IV.C.4.-Continued
WP
A = xd2 + 10d
WP = 2d V1 + x2 + 10
R = A/WP
Depth,
d
-------
Table IV.C.5. Hydraulic radius (R) and area (A) of nonsymmetrical trapezoidal channels
[2' bottom width].
\
I 1
WP
l\
y
%
A
Y ^
X
1
A = 1/2d2(x+y) + 2d
WP = d( Vl+y2 + Vl+x2) + 2
R = A/WP
Depth,
d
(feet)
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.2
2.4
2.6
2.8
3.0
3.5
4.0
Slope ratio
1:1
A
4.00
4.62
5.28
5.98
6.72
7.50
8.32
9.18
10.08
11.02
12.00
14.08
16.32
18.72
21.28
24.00
31.50
40.00
-3:1
R
1V2:1
A
0.61 4.25
0.66 4.92
0.70 5.64
0.75 6.40
0.80 7.21
0.85 8.06
0.89 8.96
0.94 9.90
0.99 10.89
1.03 11.92
1.07 13.00
1.17 15.29
1.26 17.76
1.35 20.41
1.43 23.24
1.52 26.25
1.76 34.57
1.97 44.00
-3:1
R
0.61
0.66
0.71
0.76
0.80
0.85
0.91
0.95
1.00
1.04
1.09
1.19
1.28
1.37
1.46
1.54
1.78
2.00
2:1 -
A
4.50
5.23
6.00
6.83
7.70
8.63
9.60
10.63
11.90
12.83
14.00
16.50
19.20
22.10
25.20
28.50
37.63
48.00
3:1
R
0.61
0.66
0.71
0.76
0.81
0.85
0.91
0.95
1.01
1.05
1.10
1.19
1.28
1.37
1.48
1.57
1.80
2.02
2Vz:1
A
4.75
5.53
6.36
7.25
8.19
9.19
10.24
11.35
12.51
13.73
15.00
17.71
20.64
23.79
27.16
30.75
40.70
52.00
-3:1
R
0.61
0.66
0.70
0.75
0.81
0.85
0.90
0.95
1.00
1.05
1.10
1.19
1.29
1.38
1.48
1.57
1.81
2.03
4:1
A
5.50
6.44
7.44
8.52
9.66
10.88
12.16
13.52
14.94
16.44
18.00
21.34
24.96
28.86
33.04
37.50
49.88
64.00
-3:1
R
0.59
0.64
0.68
0.73
0.79
0.84
0.90
0.94
0.98
1.03
1.09
1.19
1.28
1.38
1.48
1.57
1.81
2.04
5:1 -
A
6.00
7.04
8.16
9.36
10.64
12.00
13.44
14.96
16.56
18.24
20.00
23.76
27.84
32.24
36.76
42.00
56.01
72.00
3:1
R
0.58
0.63
0.68
0.74
0.79
0.84
0.88
0.93
0.98
1.03
1.08
1.18
1.27
1.37
1.48
1.57
1.81
2.04
IV.80
-------
Table IV.C.5. —Continued
WP
n
1
[\
y
A
^ „
u,
Depth,
d
(feet)
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.2
2.4
2.6
2.8
3.0
3.5
4.0
_^
*f
V
r x
J A = 1/2d2(x+y) + 4d
WP = d(/1+y2 + y 1+x2)
R = A/WP
+ 4
Slope ratio
1:1-
A
6.00
6.82
7.68
8.58
9.52
10.50
11.52
12.58
13.38
14.82
16.00
18.48
21.12
23.92
26.88
30.00
38.50
48.00
3:1
R
0.70
0.75
0.80
0.86
0.91
0.97
1.02
1.06
1.10
1.17
1.22
1.31
1.41
1.51
1.60
1.69
1.93
2.15
1 Vz:1
A
6.25
7.12
8.04
9.00
10.01
11.06
12.16
13.30
14.49
15.72
17.00
19.69
22.56
25.61
28.84
32.25
41.57
52.00
-3:1
R
0.69
0.75
0.80
0.86
0.91
0.97
1.02
1.07
1.12
1.17
1.22
1.32
1.42
1.51
1.61
1.71
1.94
2.17
2:1
A
6.50
7.43
8.40
9.43
10.59
11.63
12.80
14.03
15.50
16.63
18.00
20.90
24.00
27.30
30.80
34.50
44.63
56.00
-3:1
R
0.69
0.75
0.81
0.85
0.92
0.96
1.01
1.07
1.13
1.17
1.22
1.32
1.41
1.51
1.62
1.71
1.95
2.18
2V4:1
A
6.75
7.73
8.76
9.85
10.99
12.19
13.44
14.75
16.11
17.53
19.00
22.11
25.44
28.99
32.76
36.75
47.70
60.00
-3:1
R
0.68
0.74
0.79
0.85
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.31
1.41
1.51
1.61
1.71
1.95
2.18
4:1 -
A
7.50
8.64
9.84
11.12
12.46
13.88
15.36
16.92
18.54
20.24
22.00
25.74
29.76
34.06
38.64
43.50
56.88
72.00
3:1
R
0.66
0.72
0.78
0.81
0.88
0.93
0.98
1.04
1.08
1.13
1.18
1.29
1.38
1.49
1.59
1.68
1.93
2.16
5:1-
A
8.00
9.24
10.56
11.96
13.44
15.00
16.64
18.36
20.16
22.04
24.00
28.16
32.64
37.44
42.36
48.00
63.07
80.00
3:1
R
0.65
0.70
0.76
0.81
0.87
0.92
0.96
1.01
1.07
1.12
1.17
1.27
1.37
1.47
1.57
1.66
1.92
2.15
IV.81
-------
Chapter V
SOIL MASS MOVEMENT
this chapter was prepared by the following individuals:
Douglas Swanston
Frederick Swanson
with major contributions from:
David Rosgen
V.i
-------
CONTENTS
Page
INTRODUCTION V.I
DISCUSSION V.3
REVIEW OF RELEVANT WORK V.3
ASSUMPTIONS V.4
PRINCIPLES AND INTERPRETATIONS OF SOIL MASS
MOVEMENT PROCESSES V.5
Principle Soil Mass Movement Processes V.5
Slump-Earthflows V.6
Debris Avalanches-Debris Flows V.8
Soil Creep V.10
Debris Torrents V.14
Mechanics Of Movement V.15
Controlling And Contributing Factors V.17
CHARACTERIZING UNSTABLE SLOPES IN
FORESTED WATERSHEDS V.18
THE PROCEDURE V.22
ESTIMATING SOIL MASS MOVEMENT HAZARD AND
SEDIMENT DELIVERED TO CHANNELS V.22
PROCEDURAL DESCRIPTION V.22
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS V.46
CONCLUSIONS V.46
LITERATURE CITED V.47
V.ii
-------
LIST OF FIGURES
Number Page
V.I. —General flow chart of the soil mass movement procedure V.2
V.2. —Illustration of various types of soil mass movement processes V.6
V.3. —Slump and earthflow in deeply weathered sandstones and siltstones in
the Oregon Coast Ranges V.7
V.4. —Debris avalanche and debris torrent development on steep forested
watersheds in northwestern North America V.9
V.5. —An example of soil creep and slump-earthflow processes on forest lands in
northern California V.ll
V.6. —Deformation of inclinometer tubes at two sites in the southern Cascade
and Coast Ranges of Oregon V.13
V.7. —Simplified diagram of forces acting on a mass of soil on a slope V.16
V.8. —Detailed flow chart of the soil mass movement procedure V.24
V.9. —Dimensions of debris avalanche-debris flow failures for determining
potential volumes V.38
V.10.—Dimensions of slump-earthflow failures for determining potential
volumes V.38
V.ll.—Delivery potential of debris avalanche-debris flow material to closest
stream V.43
V.12.—Delivery potential of slump-earthflow material to closest stream V.44
V.iii
-------
LIST OF TABLES
Number Page
V.I.—Observations of movement rates of four active earthflows V.8
V.2.—Debris avalanche erosion in forest, clearcut, and roaded areas V.10
V.3.—Examples of measured rates of natural creep on forested slopes in the
Pacific Northwest V.12
V.4.—Characteristics of debris torrents with respect to debris avalanches and
land use status of initiations V.14
V.5.—Weighting factors for determination of natural hazard of debris avalanche-
debris flow failures V.26
V.6.—Weighting factors for determination of management-induced hazard of
debris avalanche-debris flow failures V.29
V.7.—Weighting factors for determination of natural hazard of slump-earthflow
failures V.32
V.8.—Weighting factors for determination of management-induced hazard of
slump-earthflow failures V.35
V.9.—Unit weight of typical soils in the natural state V.42
V.iv
-------
LIST OF WORKSHEETS
Number Page
V.I Debris avalanche-debris flow natural factor evaluation form V.28
V.2 Debris avalanche-debris flow management related factor evaluation
form V.30
V.3 Slump-earthflow natural factor evaluation form V.34
V.4 Slump-earthflow management related factor evaluation form V.36
V.5 Estimation of volume per failure V.39
V.6 Estimation of soil mass movement delivered to the stream channel. .. V.40
V.v
-------
INTRODUCTION
Accurate models and the data needed to predict
soil mass movement hazard and magnitude of
delivery to stream courses over broad areas are cur-
rently lacking. Existing techniques for site specific
stability analyses (based on the Mohr -Coulomb
Theory of Earth Failure) are quite accurate in as-
sessing the strength-stress relationships in a small
area. These techniques, however, require accurate
measurement of the engineering properties of the
soils involved and specific knowledge of the geology
and ground water hydrology at the site. Such data
are costly to obtain and vary greatly among sites,
even under the same geologic and climatic settings,
making this mechanistic approach impractical for
broad area hazard assessment.
A more practical approach is to combine:
1. A subjective evaluation of the relative
stability of an area using soils, geologic,
topographic, climatic, and vegetative in-
dicators obtained from aerial photos, maps,
and field observations.
2. A limited strength-stress analysis of the un-
stable sites using available or easily generated
field data.
3. Estimates of sediment delivery to streams
based on failure type, distance from the
stream channel, and certain site variables
such as slope gradient and slope irregularity.
This information can be integrated to provide a
measure of mass movement hazard and the level of
sediment contributed to adjacent stream channels.
Such an approach is developed in this chapter to
provide a uniform framework for slope stability as-
sessment and estimation of sediment delivery to
channels by soil mass movement. A flow chart of
this procedure is presented in figure V.I.
The primary objectives of the procedure are to
determine: (1) natural stability of the site, (2) the
sensitivity of the site to natural and man-induced
soil mass movement events (the hazard index of
soil mass movement generation or acceleration),
(3) the probable volume of material released by soil
mass movement, and (4) the amount of soil mass
movement material delivered to the nearest
drainageway.
Several common site and climatic factors which
vary greatly over a wide region are related to soil
mass movements. To provide for continuity over
multiple geographic areas, the major factors con-
trolling slope stability are summarized here by
dominant failure types and placed in a framework
of hazard index analysis.
If the user does not have experience in
delineating potential soil mass movement sites, ad-
ditional assistance will be required from specialists
in the allied fields of geology, geotechnical
engineering, and soil science. Users are strongly ad-
vised to seek assistance from these specialists
whenever possible.
This chapter examines two groups of erosion
processes: (1) rapid, shallow soil mass movements,
collectively termed "debris avalanches-debris
flows", but including a broad range of processes
such as debris slides and rapid mudflows (Varnes
1958); and (2) slow, deep-seated soil mass move-
ments, termed "slumps" and "earthflows" or col-
lectively "slump-earthflows." These mass move-
ment processes are described further in the section,
"Principals and Interpretations of Soil Mass Move-
ment Processes."
V.I
-------
SOIL MASS
MOVEMENT
BROAD DELINEATION OF POTENTIALLY
UNSTABLE TERRAIN
SLUMP-EARTHFLOW
SOIL MASS MOVEMENT TYPE
DEBRIS SLIDE-
DEBRIS AVALANCHE
HAZARD INDEX
HAZARD INDEX
QUANTITY OF SOIL
INVOLVED
DELIVERY OF INORGANIC
MATERIAL TO CLOSEST
STREAM (SLOPE POSITION)
PROCEDURAL STEP
COMPUTATION OB
EVALUATION
<3 > 'o-o
QUANTITY OF SOIL
INVOLVED
POTENTIAL
SEDIMENT DELIVERED TO
CHANNEL SYSTEM
DELIVERY OF INORGANIC
MATERIAL TO CLOSEST
STREAM (SLOPE
GRADIENT & SLOPE SHAPE)
Figure V.1.—General flow chart of the soil mass movement procedure.
V.2
-------
DISCUSSION
REVIEW OF RELEVANT WORK
Although quantitative assessment of all factors
contributing to mass movement is complex and dif-
ficult, a consistent analysis of the major con-
tributing factors can benefit the land manager,
whose activities may affect slope stability. Bur-
roughs and others (1976) discuss the effects of
geology and structure in northern California and
western Oregon on landslides generated by road
construction; Swanston and Swanson (1976)
describe the effects of geomorphology, climate, and
forest management activities on debris avalanche
and slump-earthflow activity in the western
Cascades; Greswel, and others (in press) have as-
sessed the effects of clearcut logging and road con-
struction on accelerated debris avalanche activity
during a single high intensity storm in the Oregon
Coast Range; Burroughs and Thomas (1977) have
analyzed the declining root strength in Douglas-fir,
after felling, as a factor in slope stability; and
Flaccus (1958), Hack and Goodlet (1969), and Wil-
liams and Guy (1973) discuss the effects of hur-
ricane and cloudburst triggered soil mass move-
ment in the eastern United States.
Some interesting and successful techniques also
have been developed for predicting unstable
ground and identifying controlling and con-
tributing factors. Pillsbury (1976), for example,
using a linear discriminant functions analysis, at-
tributed 90.5 percent of the debris avalanches in
clearcut areas of a northern California watershed to
the factors of slope percent and percent cover by
dominant and understory vegetation. Both of these
factors were determined by photogrammetric
techniques with no ground control. An additional
1.5 percent of debris avalanche occurrences was
determined by adding in the site factors of soil
weathering and percent quartz in bedrock. Using
photogrammetric procedures, Kojan, Foggin, and
Rice (1972) were able to predict 84.4 percent of the
debris slides following major storms in the Santa-
Ynez-San Rafael Mountains, California, based on
past landslide activity.
The factor of safety is commonly used as a quan-
titative expression of the hazard index of a soil
mass movement. In soil mechanics, it is customary
to express the balance of forces acting on a simple
slope as:
Factor of safety (F) =
Resistance of the soil to
failure (shear strength)
Forces promoting failure
(shear stress)
A safety factor of one (F=l) would indicate im-
minent failure. For broad land use planning pur-
poses, this technique is valid only for rapid, shallow
soil mass movements, such as debris avalanches
and debris flows. Quantitative models utilizing this
approach have been outlined in Swanson and
others (1973), Brown and Sheu (1975), Bell and
Swanston (1972), and Simons and Ward (1976).
The difficulty in determining some of the factors
(such as tensile strength of roots, location of the
failure surface, and water table position for various
storm intensities) has until recently, restricted the
use of such models to highly instrumented sites
where expensive investigations were warranted.
New data and techniques are being developed,
however, which are making these models more
practical as land management tools.
Swanston (1972, 1973) has employed a factor of
safety technique using a simplified infinite slope
model to predict slope stability hazard and stratify
lands according to management impact in
southeast Alaska. This technique uses slope
gradient as a prime hazard index. Bell and Keener
(1977) have developed a method of predicting
stable cut-slope heights based on the factor of
safety analysis of natural slopes. Burroughs and
Thomas (1977) have analyzed the effects of soil
shear strength, slope gradient, soil depth, ground
water rise, and root strength on stability hazard in
the central Coast Range of Oregon. Prellwitz (1977)
has made substantial progress in utilization of the
factor of safety approach without the need for ex-
pensive site investigation. The equations account
for buoyant density, fluctuating water tables, and
moisture density.
Soil mass movements can yield substantial sedi-
ment. Megahan (1972) and Megahan and Kidd
(1972a, 1972b) evaluated the effects of logging and
road construction on high erosion hazard land in
the Idaho Batholith. They report sediment yields
1.6 times greater from jammer logged sites than
from undisturbed areas (they did not differentiate
between surface erosion and soil mass movement).
Soil mass movements from logging roads in the
same area average 550 times greater than control
V.3
-------
areas. Swanston and Swanson (1976) report debris
avalanche erosion rates 2 to 4 times greater from
clearcuts and 25 to 344 times greater from roads
than from undisturbed sites in selected areas of the
Coast Range and Cascade Mountains of Oregon,
Washington, and British Columbia.
Prediction of sediment yield from individual soil
mass movement processes is not well documented.
Individual failure release volumes are available for
a few areas, but there is little information on how
much of the total volume initially reaches the
stream versus how much remains on the slope for
slow release over time. A summary of average
debris avalanche volume from six studies in the
Pacific Northwest reveals a broad range in average
volumes from area to area (Swanson and others
1977). For example, in the Mapleton Ranger
District of the Oregon Coast Range, an area of
steep, intricately dissected terrain with very shal-
low soil, average debris avalanche volume is less
than 100 yd3(76 m3), whereas steep areas of lower
drainage density and deeper soils have had debris
avalanches averaging more than 1,000 yd3(765 m3).
In the Mapleton area, Swanson and others (1977)
estimated that 65 percent of the material moved by
debris avalanches in forests entered streams.
Since sediment yield values for individual soil
mass movements are very limited, a series of con-
ceptual delivery curves were developed for this
handbook to approximate the sediment transport
potential of dominant soil mass movement
processes. These curves are presented as first ap-
proximations only, and it may be necessary to
develop specific delivery curves to more accurately
represent local conditions. Delivery relations are
needed to estimate sediment supply to streams
where it will be routed through the channel
network. The delivery curves in the analysis section
were developed from studies of recent failures in
the western Cascades and Coast Range of Oregon,
and were based on estimates of the percent of
material released during the initial failure that ac-
tually entered a stream. The site variables which
appeared particularly sensitive to the amount of
soil delivered to a drainageway were: slope gradient
and slope irregularity for debris avalanche-debris
flows, and slope position with respect to the closest
drainageway for slump-earthflows.1 Slump-
earthflow failures not adjacent to streams, are not
considered principal contributors to channel
loading in this analysis since their potential impact
on short-term sediment loading is negligible
and Swanson, unpublished data.
because of their low delivery efficiencies. Most of
the sediment from mid- and upper-slope failures of
this type remain on the slope following initial
failure and is delivered to the channel over ex-
tended periods, mainly by surface erosion and
creep.
ASSUMPTIONS
The procedures in this chapter are presented as a
guide for assessing the stability of natural slopes,
the potential impacts of silvicultural activities on
slope stability, and predicting sediment contribu-
tions to drainageways from soil mass movements.
In the absence of proven local techniques, these
procedures will provide the best available es-
timates of soil mass movement. The procedures are
not rigid. They are a frame of reference within
which local data and variables may be applied to
provide better estimates of relative soil stability
and contributions by soil mass movement to non-
point source pollution.
Because of the complex nature of processes and
variables and the need to present the procedures in
a format usable on an inter-regional basis, the fol-
lowing simplifying assumptions are necessary:
1. The determination of hazard index will be
based on the assumption of a maximum 10-
year return period, 24-hour rainfall
(precipitation intensity/duration) as a
potential storm event triggering mass move-
ment. If slides in a particular region occur
frequently, with storms less than a 10-year
return period, the hazard evaluation should
reflect this (i.e., a 10-year event is not neces-
sary for a high hazard index).
2. A three-part hazard index will be used. The
numerical ratings are subjective and depend
on what is considered to be acceptable for a
particular land management activity. For
purposes of this analysis:
a. "High hazard" means a greater than 66
percent chance for a soil mass movement
within the area evaluated for a 10-year
return period storm event.
b. "Medium hazard" means a greater than
33 and less than 66 percent chance for a
soil mass movement within the area
evaluated for a 10-year return period
storm event.
V.4
-------
c. "Low hazard" means a less than 33 per-
cent chance for a soil mass movement
within the area evaluated for a 10-year
return period storm event.
3. Large organic debris contributions to
drainageways, resulting from soil mass
movement are not considered in estimates of
sediment delivery. Although large quantities
of organic debris are incorporated in the total
volume of material released to the channel
by soil mass movement, much of it remains
in the channel near the point of entry.
4. Sediment delivery to the stream can be es-
timated from relationships between failure
type and slope gradient, slope position (point
of origin of failure), and morphology of the
surface.
5. Volume of sediment delivered to the channel
per unit area is a more realistic measure of
soil mass movement impact than is number
of events.
6. The instructions provided for quantifying
volumes can be readily applied by field
scientists.
7. Processes of soil mass movement described
at this broad planning level can be readily
identified and characterized regardless of
geographic location.
8. Only slump-earthflows and debris
avalanches-debris flows will be used to
evaluate direct, short-term contributions of
sediment to streams.
Each of these two categories have been iden-
tified and described on the basis of material
characteristics, failure geometry, and
mechanism of movement. These categories
are most affected by silvicultural activities
and have the greatest potential for short-
term water quality degradation.
9. Surface erosion of landslide material remain-
ing on the slope will be determined in
another section which deals with surface ero-
sion delivery to stream channels.
10. Debris torrents will not be evaluated
directly. It is assumed that when the hazard
is high for debris avalanches-debris flows, it
will also be high for debris torrents.
11. Sediment delivered to streams from erosion
caused by creep will not be directly
evaluated because of the close inter-
relationships of the variables involved in
both creep and slump-earthflow processes.
Sediment contributions from creep will be
indirectly assessed using the channel erosion
processes evaluated in "Chapter VI: Total
Potential Sediment".
PRINCIPLES AND INTERPRETATIONS
OF
SOIL MASS MOVEMENT PROCESSES
Silvicultural activities in mountainous regions,
particularly forest harvest and road construction,
can have a major impact on site erosion and can ac-
celerate transport of soil materials downslope by
soil mass movement. The resultant downstream
damage from aggradation and degradation of the
channel may cause bank erosion, disrupt aquatic
habitat, and produce undesirable changes in es-
tuarine configuration and habitat by siltation and
channel alterations. This is particularly true for
areas with steep slopes subject to high intensity
rain and/or rapid snowmelt.
Where heavy forest vegetation covers the slope,
the high infiltration capacity of the forest soils and
covering organic materials generally protect the
slopes from surface erosion. Under these condi-
tions, soil mass movement processes are generally
the dominant natural mechanisms of soil transport
from mountain slopes to stream channels. Only
where bare mineral soil is exposed by disturbance
of the vegetative and organic litter cover, either by
natural processes or silvicultural activities, does
surface erosion significantly contribute to this slope
transport process.
Principal Soil Mass Movement Processes
Downslope soil mass movements result primarily
from gravitational stress. It may take the form of:
(1) failure, both along planar and concave surfaces,
of finite masses of soil and forest debris which move
rapidly (debris avalanches-debris flows) or slowly
(slump-earthflows) (fig. V.2); (2) pure rheological
flow with minor mechanical shifting of mantle
materials (creep); and (3) rapid movement of
water-charged organic and inorganic matter down
stream channels (debris torrents).
Slope gradient, soil depth, soil water content,
and physical soil properties, such as cohesion and
coefficient of friction, control the mechanics and
rates of soil mass movement. Geological,
V.5
-------
weathered
bedrock,
soil, etc.
bedrock
Slump
Debris Avalanche
very rapid to
extremely rapid
Earthflow
Figure V.2.—Illustration of various types of soil mass move-
ment processes.
Debris Slide
very rapid
hydrological, and vegetative factors determine oc-
currence and relative importance of such processes
in a particular area.
Slump-Earthflows
Where creep displacement has exceeded the
shear strength of soil, discrete failure occurs and
slump-earthflow features are formed (Varnes
1958). Simple slumping takes place as a rotational
movement of a block of earth over a broadly con-
cave slip surface and involves little breakup of the
moving material. Where the moving material slips
downslope and is broken up and transported either
by a flowage mechanism or by gliding displacement
of a series of blocks, the movement is termed slow
earthflow (Varnes 1958) (fig. V.3). Geologic,
vegetative, and hydrologic factors have primary
control over slump-earthflow occurrence. Deep,
cohesive soils and clay-rich bedrock are especially
prone to slump-earthflow failure, particularly
where these materials are overlain by hard, compe-
tent rock (Wilson 1970, Swanson and James 1975).
Earthflow movement also appears to be sensitive to
long-term fluctuations in soil water content
(Wilson 1970, Swanston 1976).
V.6
-------
Figure V.3.—Slump and earthflow in deeply weathered sandstones and siltstones in the Oregon Coast
Ranges. The slump occurred almost instantaneously. The resulting earthflow, over a period of several
hours, dammed a perennial stream and produced the lake in the lower foreground.
Because earthflows are slowly moving, deep-
seated, poorly drained features, individual storms
probably have much less influence on their move-
ment than on the likelihood of occurrence of debris
avalanches-debris flows. Where planes of slump-
earthflow are more than several meters deep,
weight of vegetation and vertical root anchoring ef-
fects are insignificant.
Earthflows can move imperceptibly slowly to
more than 1 m/day in extreme cases. In parts of
northwest North America, many slump-earthflow
areas appear to be inactive (Colman 1973, Swanson
and James 1975). Where slump-earthflows are ac-
tive, rates of movements have been monitored
directly by repeated surveying of marked points
and inclinometers and by measuring deflection of
roadways and other inadvertent reference systems.
These methods have been used to estimate the
rates of earthflow movement shown in table V.I
(Swanston and Swanson 1976, Kelsey 1977).
The area of occurrence of slump-earthflows is
mainly determined by bedrock geology. For exam-
ple, in the Redwood Creek basin, northern Califor-
nia, Colman (1973) observed that of the 27.4 per-
cent of the drainage which is in slumps, earthflows,
and older or questionable soil mass movements, a
very high percentage of the unstable areas are
located in clay-rich and pervasively sheared
sedimentary rocks. Areas underlain by schists and
other more highly metamorphosed rock are much
less prone to deep-seated soil mass movement. The
area of occurrence of slump-earthflows in volcanic
V.7
-------
Table V.1.—Observations of movement rates of active earthflows in the western
Cascade Range, Oregon (Swanston and Swanson 1976) and Van Duzen River Basin,
northern California (Kelsey 1977)
Location
Landes Creek1
(Sec.21 T.22S, R.4E.)
Boone Creek1
(Sec.17T.17S, R.5E.)
Cougar Reservoir1
(Sec.29T.17S, R.5E.)
Lookout Creek1
(Sec.30T.15S, R.6E.)
Donaker Earthflow2
(Sec.10T.1N, R.3E.)
Chimney Rock Earthflow2
(Sec.30T.2N,R.4E.)
Halloween Earthflow2
(Sec.6T.1N,R.5E.)
'Swanston and Swanson 1976.
'Kelsey 1977.
Period of
record
years
15
2
2
1
1
1
3
Movement
rate
cm/yr
12
25
2.5
7
60
530
2,720
Method of
observation
Deflection of
road
Deflection of
road
Deflection of
road
Strain rhombus
Measurements across
active ground breaks
Resurvey of stake
line
Resurvey of stake
line
Resurvey of stake
line
terrains has also been closely linked to bedrock
(Swanston and Swanson 1976). There are
numerous examples of accelerated or reactivated
slump-earthflow movement after forest road con-
struction in the western United States (Wilson
1970). Undercutting the toes of earthflows and pil-
ing rock and soil debris on slump blocks are com-
mon practices which influence slump-earthflow
movement. Stability of such areas is also affected
by modification of drainage systems, particularly
where road drainage systems route additional
water into the slump-earthflow areas. These distur-
bances may increase movement rates from a few
millimeters per year to many centimeters. Once
such areas have been destabilized, they may con-
tinue to move at accelerated rates for several years.
Although the impact of deforestation alone on
slump-earthflow movement has not been
demonstrated quantitatively, evidence suggests
that it may be significant. In massive, deep-seated
failures, lateral and vertical anchoring by tree root
systems is negligible. Hydrologic impacts of
deforestation, however, appear to be important.
Reduced evapotranspiration will increase soil
moisture availability. This water is, therefore, free
to pass through the rooting zone to deeper levels of
the earthflow.
Debris Avalanches-Debris Flows
Debris avalanches-debris flows are rapid, shal-
low soil mass movements from hillslope areas. Here
the term "debris avalanche-debris flow" is used in
a general sense encompassing debris slides,
avalanches, and flows which have been dis-
tinguished by Varnes (1958) (fig. V. 4) and others
on the basis of increasing water content and type of
included material. From a land management
standpoint, there is little purpose to differentiating
among the types of shallow hillslope failures, since
the mechanics and the controlling and contributing
factors are the same. Areas prone to debris
avalanches-debris flows are typified by shallow,
noncohesive soils on steep slopes where subsurface
water may be concentrated by subtle topography
on bedrock or glacial till surfaces. Because debris
avalanches-debris flows are shallow failures, fac-
tors such as root strength, anchoring effects, and
the transfer of wind stress to the-jsoil mantle are
potentially important influence. Factors which in-
fluence antecedent soil moisture conditions and the
rate of water supply to the soil during snowmelt
and rainfall also have significant control over the
time and place of debris avalanches-debris flows.
The rate of occurrence of debris avalanches-
debris flows is controlled by the stability of the
V.8
-------
Figure V.4.—Debris avalanche and debris torrent development on steep forested watersheds In
northwestern North America, (a.) Debris avalanche developed in shallow cohesionleas soils on a steep,
forested slope In coastal Alaska, (b.) Debris torrent developed in a steep gully, probably caused by failure
of a natural debris dam above trees in foreground.
V.9
-------
landscape and the frequency of storm events severe
enough to trigger them. Therefore, the rates of ero-
sion by debris avalanches-debris flows will vary
from one geomorphic-climatic setting to another.
Table V.2 (Swanston and Swanson 1976) shows
that annual rates of debris avalanche erosion from
forested study sites in Oregon and Washington in
the United States, and British Columbia in
Canada, range from 11 to 72 m3/km2/yr. These es-
timates are based on surveys and measurements of
debris avalanche erosion during a particular time
period (15 to over 32 years) over a large area (12
km2 or larger).
An analysis of harvesting impacts in the western
United States (Swanston and Swanson 1976) (table
V.2) reveals that timber harvesting commonly
results in an acceleration of soil mass movement
activity by a factor of 2 to 4 times relative to
forested areas. In the four study areas listed in
table V.2, road-related debris avalanche erosion
was increased by factors ranging from 25 to 340
times the rate of debris avalanche erosion in
forested areas. The great variability in the impact
of roads reflects not only differences in the natural
stability of the landscape, but also, and more im-
portantly from an engineering standpoint, dif-
ferences in site location, design, and construction
of roads.
Soil Creep
Soil creep is defined as the slow, downslope
movement of soil mantle materials as the result of
long-term application of gravitational stress. The
mechanics of soil creep have been investigated ex-
perimentally and theoretically (Terzaghi 1953,
Goldstein and Ter-Stepanian 1957, Saito and
Uezawa 1961, Culling 1963, Haefeli 1965, Bjerrum
1967, Carson and Kirkby 1972). Movement is
quasi-viscous; it occurs under shear stresses suf-
ficient to produce permanent deformation, but too
small to result in discrete failure. Mobilization of
Table V.2.—Debris avalanche erosion in forest, clearcut, and roaded areas (Swanston and Swanson 1976)
Site
Period of
record
years
Area
percent
km2
Number
of
slides
Debris
avalanche
erosion
mVkmVyr
Rate of debris avalanche
erosion relative
to forested areas
Stequaleho Creek, Olympic Peninsula, Washington, U.S.A. (Fiksdal 1974):
Forest 84 79.0 9.3 25 71.8
Clearcut 6 18.0 4.4 0 0.0
Road 6 3.0 0.7 83 11,825.0
24.4
108
Alder Creek, Western Cascade Range, Oregon, U.S.A. (Morrison 1975):
Forest 25 70.5 12.3 7 45.3
Clearcut 15 26.0 4.5 18 117.1
Road 15 3.5 0.6 75 15,565.0
17.4
100
Selected drainages, Coast Mountains, S.W. British Columbia, Canada:1
Forest 32 83.9 246.1 29
Clearcut 32 9.5 26.4 18
Road 32 1.5 4.2 11
11.2
24.5
'282.5
276.7
58
H. J. Andrews Experimental Forest, western Cascade Range, Oregon, U.S.A.
(Swanson and Dyrness 1975):
Forest 25 77.5 49.8 31 35.9
Clearcut 25 19.3 12.4 30 132.2
Road 25 3.2 2.0 69 1,772.0
64.2
130
1.0
0.0
165.0
1.0
2.6
344.0
1.0
2.2
25.2
1.0
3.7
49.0
'Calculated from O'Loughlin (1972, and personal communication), assuming that area involving road construction in and
outside clearcuts is 16 percent of area clearcut. Colin L. O'Loughlin, is now at Forest Research Institute, New Zealand Forest
Service, Rangiora, New Zealand.
V.10
-------
the soil mass is primarily by deformation at grain
boundaries and within clay mineral structures.
Both interstitial and absorbed water appear to con-
tribute to creep movement by opening the struc-
ture within and between mineral grains, thereby
reducing friction within the soil mass. Creeping ter-
rain can be recognized by characteristic rolling,
hummocky topography with frequent sag ponds,
springs, and occasional benching due to local
rotational slumping. Local discrete failures, such
as debris avalanches and slump-earthflows, may be
present within the creeping mass (fig. V.5).
Natural creep rates monitored in different
geological materials in the western Cascade and
Coast Ranges of Oregon and northern California in-
dicate rates of movement between 7.1 and 15.2
mm/yr, with the average about 10 mm/yr
(Swanston and Swanson 1976) (table V.3). The
most rapid movement usually occurs at or near the
surface, although the significant displacement may
extend to variable depths associated with incipient
failure planes or zones of ground water movement.
Active creep depth varies greatly and largely de-
pends on parent material origin, degree and depth
of weathering, subsurface structure, and soil water
content. Most movement appears to take place
during rainy season maximum soil water levels (fig.
V.6 a), although creep may remain constant
throughout the year in areas where the water table
does not undergo significant seasonal fluctuation
(fig. V.6 b). This is consistent with Ter-
Stepanian's (1963) theoretical analysis which
shows that the downslope creep rate of an inclined
soil layer is exponentially related to piezometric
level in the slope.
There have been no direct measurements of the
impact of deforestation on creep rates in the forest
environment, mainly because of the long periods of
records needed both before and after a disturbance.
There are, however, a number of indications that
creep rates are accelerated by harvesting and road
construction.
In the United States, Wilson (1970) and others
have used inclinometers to monitor accelerated
creep following modification of slope angle, com-
paction of fill materials, and distribution of soil
mass at construction sites. The common occur-
rence of shallow soil mass movements in these dis-
turbed areas and open tension cracks in fills along
roadways suggests that similar features along forest
roads indicate significantly accelerated creep
movement.
On open slopes where deforestation is the prin-
cipal influence, impact on creep rates may be more
subtle, involving modifications of hydrology and
root strength. Where creep is a shallow
phenomenon (less than several meters), the loss of
Figure V.5.—An example of soil creep
and slump-earthflow processes on
forest lands in northern California.
The entire slope is undergoing creep
deformation, but note the discrete
failure (slump-earthflow) marked by
the steep headwall scarp at top
center and the many small slumps
and debris avalanches triggered by
surface springs and road construc-
tion.
V.ll
-------
Table V.3—Examples of measured rates of natural creep on forested slopes in the Pacific Northwest
(Swanston and Swanson 1976)
Location
Coyote Creek,
South Umpqua
River drainage,
Cascade Range
of Oregon,
SiteC-1
Blue River
drainage -
Lookout Creek,
H. J. Andrews Exp,
Forest,
Central Cascades
of Oregon,
Site A- 1
Blue River
drainage, IBP
Experimental
Watershed 10,
Site No. 4
Baker Creek
Coquille River
Coast Range,
Oregon
Site B-3
Bear Creek
Nestucca River
Coast Range,
Oregon
Site N-1
Data Parent material Depth of Maximum downslope Representative
source significant Creep rate creep profile
movement Surface Zone of
accelerated
movement
m mm/yr mm/yr
Swanston1 Little Butte
volcanic series;
deeply weathered, 7.3 13.97 10.9
clay-rich, andesitic
dacitic, volcani-
clastic rocks
Little Butte
Swanston1 volcanic series
5.6 7.9 7.1
Same as above
UPSLOPE DOWNSLOPE
I
P '
j
5 Ł
0-
Ul
a
-IO.O 0 IO.O
DEFLECTION (mm)
UPSLOPE DOWNSLOPE
I
I
/
I
-IO.O 0 IO.O
DEFLECTION (mm)
0
~Ł
15 i
UJ
o
SO
McCorison2 Little Butte
and Glenn volcanic series 0.5 9.0
SJmaflor?1 UPSLOPE °™"SWE
Swanston1 highly sheared 7.3 10.4 10.7
and altered clay-
rich argillite and
mudstone
Nestucca
Swanston1 formation
deeply weathered
pyroclastic rocks 15.2 14.9 11.7
and interbedded,
shaley siltstones
and claystones
i
I
•/ -
-IO.O 0 IO.O
DEFLECTION (mm)
JPSLOPE DOWNSLOPE
I
I
y -
\
-IO.O 0 IO.O
DEFLECTION (mm)
0 _
1
5 Ł
a.
Ul
o
10
0 „
E
5 f.
a.
LJ
a
10
1Douglas N. Swanston, unpublished data on file at Forestry Sciences Laboratory, USDA Forest Service, Pacific Northwest
Forest and Range Experiment Station, Corvallis, Oreg.
2F Michael McCorison and L. F Glenn, data on file at Forestry Sciences Laboratory, USDA Forest Service, Pacific Northwest
Forest and Range Experiment Station, Corvallis, Oreg.
V.12
-------
Table V.3—Examples of measured rates of natural creep on forested slopes in the Pacific Northwest (continued)
Redwood Creek
Coast Range
Northern California
Site3-B
Kerr Ranch
Swanston1 schist
sheared, deeply
weathered clayey
schist
UPSLOPE DOWNSLOPE
2.6
15.2
10.4
-10.0 o 10.0
DEFLECTION (mm)
0 „
10
Figure V.6.—Deformation of inclinometer tubes at
two sites in the southern Cascade and Coast
Ranges of Oregon (Swanston and Swanson
1976). (a ) Coyote Creek in the southern
Cascade Range showing seasonal variation in
movement rate as the result of changing soil
water levels. Note that the difference in readings
between spring and fall of each year (dry months)
is very small, (b) Baker Creek, Coquille River,
Oregon Coast Ranges, showing constant rate of
creep as a result of continual high water levels.
UPSLOPE
DOWNSLOPE
(b)
• SPRING
- D FALL
0
CL
LU
Q
5.0
UPSLOPE
2.5 0 2.5
DEFLECTION (mm)
5.0
DOWNSLOPE
(a)
• SPRING
DFALL
i i i
0
3 Ł
x
I-
„ Q.
9.0 5.0 0 5.0
DEFLECTION (mm)
9,0
V.13
-------
root strength caused by deforestation is likely to be
significant. Reduced evapotranspiration after
clearcutting (Gray 1970, Rothacher 1971) may
result in longer duration of the annual period of
creep activity and, thereby, increase the annual
creep rate.
Debris Torrents
Debris torrents involve the rapid movement of
water-charged soil, rock, and organic material
down steep stream channels. They typically occur
in steep, intermittent, and first- and second-order
channels. They are triggered during extreme dis-
charge by debris avalanches from adjacent hill-
slopes which enter a channel and move directly
downstream or by the breakup and mobilization of
debris accumulations in the channel (fig. V.4b).
The initial slurry of water and associated debris
commonly entrains large quantities of additional
inorganic and organic material from the streambed
and banks. Some torrents are triggered by debris
avalanches of less than 100 yd3 (76 m3), but
ultimately involve 1,000 yd3 (760 m3) of debris
entrained along the track of the torrent. As the tor-
rent moves downstream, hundreds of meters of
channel may be scoured to bedrock. When a torrent
loses momentum, there is deposition of a tangled
mass of large organic debris in a matrix of sediment
and fine organic material covering areas of up to
several hectares.
The main factors controlling the occurrence of
debris torrents are the quantity and stability of
debris in channels, steepness of channel, stability
of adjacent hillslopes, and peak discharge
characteristics of the channel. The concentration
and stability of debris in channels reflect the
history of stream flushing and the health and stage
of development of the surrounding timber stand
(Froehlich 1973). The stability of adjacent slopes
depends on factors described in previous sections.
The history of storm flows has a controlling in-
fluence over the stability of both soils on hillslopes
and debris in stream channels.
Although debris torrents pose significant en-
vironmental hazards in mountainous areas of
northwestern North America, they have received
little study (Fredriksen 1963, 1965; Morrison 1975;
Swanson and others 1976). Velocities of debris tor-
rents, estimated to be up to several tens of
meters/second, are known only from a few verbal
and written accounts. Torrents have been
systematically documented in only two small areas
of the Pacific Northwest, both in the western
Cascade Range of Oregon (Morrison 1975,
Swanston and Swanson 1976). In these studies,
rates of debris torrent occurrence were observed to
be 0.005 and 0.008 events/kmVyr for forested areas
(table V.4). Torrent tracks initiated in forest areas
ranged in length from 328 to 7,480 ft (100 to 2,280
m) and averaged 2,000 ft (610 m) of channel length.
Debris avalanches have played a dominant role in
triggering 83 percent of inventoried torrents
Table V.4—Characteristics of debris torrents with respect to debris avalanches1 and land use status of initiation in the
H. J. Andrews Experimental Forest1 and Alder Creek Drainage (Morrison 1975)
Site Area of Period of Debris torrents
watershed record triggered by
debris avalanches
Debris torrents
with no associated
debris avalanche
Rate of debris
Total torrent occurrence
relative to
forested areas
km2
number •
H. J. Andrews Experimental Forest, western Cascades, Oregon
Forest 49.8 25 9
Clearcut 12.4 25 5
Road 2.0 25 _17_
64.2 ~31~
Alder Creek drainage, western Cascade Range, Oregon
10
11
17
38
kmVyr
0.008
0.036
0.340
1.0
4.5
42.0
Forest
Clearcut
Road
12.3
4.5
0.6
17.4
90
15
15
5
2
6
13
1
1
-
2
6
3
6
15
0.005
0.044
0.667
1.0
8.8
133.4
'Frederick J. Swanson, unpublished data, on file at Forestry Sciences Laboratory, USDA Forest Service, Pacific
Northwest Forest and Range Experiment Station, Corvallis, Oreg.
V.14
-------
(Swanston and Swanson 1976). Mobilization of
stream debris not immediately related to debris
avalanches has been a minor factor in initiating
debris torrents in headwater streams.
Deforestation appears to dramatically accelerate
the occurrence of debris torrents by increasing the
frequency of debris avalanches. Although it has not
been demonstrated, it is also possible that in-
creased concentrations of unstable debris in chan-
nels during forest harvesting (Rothacher 1959,
Froehlich 1973, Swanson and others 1976) and pos-
sible increased peak discharges (Rothacher 1973,
Harr and others 1975) may accelerate the fre-
quency of debris torrents.
The impact of clearcutting and road construction
on frequency of debris torrents (events/kmVyr)
may be compared to debris torrent occurrence un-
der natural conditions. In the H. J. Andrews Ex-
perimental Forest and the Alder Creek study sites
in Oregon, timber harvesting appeared to increase
occurrence of debris torrents by 4.5 and 8.8 times;
and roads were responsible for increases of 42.5 and
133 times relative to forested areas.
Although the quantitative reliability of these es-
timates of harvesting impacts is limited by the
small number of events analyzed, there is clear
evidence of marked acceleration in the frequency of
debris avalanches-debris flows as a result of forest
harvesting and road building. The histories of
debris avalanches-debris flows in the two study
areas clearly indicate that increased debris torrent
occurrence is primarily a result of two conditions:
debris avalanches trigger most debris torrents
(table V.4) and the occurrence of debris
avalanches-debris flows is temporarily accelerated
by deforestation and road construction (table V.2).
Mechanics of Movement
Direct application of soil mechanics theory to
analysis of soil mass movement processes is dif-
ficult because of the heterogeneous nature of soil
materials, the extreme variability of soil water con-
ditions, and the related variations in stress-strain
relationships with time. However, the theory
provides a convenient framework for discussing the
general mechanism and the complex inter-
relationships of the various factors active in
development of soil mass movements on mountain
slopes.
In terms of factor of safety analysis, the stability
of soils on a slope can be expressed as a ratio
between shear strength, or resistance of the soil to
sliding, and the downslope pull of gravity or
gravitational stress. As long as shear strength ex-
ceeds the pull of gravity, the soil will remain in a
stable state (Terzaghi 1950, Zaruba and Mencl
1969).
It is important to remember that soil mass move-
ments result from changes in the soil shear
strength-gravitational stress relationship in the
vicinity of failure. This may involve a mechanical
readjustment among individual particles or a more
complex interaction between both internal and ex-
ternal factors acting on the slope.
Figure V.7 shows the geometrical relationship of
factors acting on a small portion of the soil mass.
Any increases in gravitational stress will increase
the tendency for the soil to move downslope.
Increases in gravitational stress result from in-
creasing inclination of the sliding surface or in-
creasing unit weight of the soil mass. Stress can
also be augmented by: (1) the presence of zones of
weaknesses in the soil or underlying bedrock
produced by bedding planes and fractures, (2) ap-
plication of wind stresses transferred to the soil
through the stems and root systems of trees, (3)
strain or deformation in the soil produced by
progressive creep, (4) frictional "drag" produced by
seepage pressure, (5) horizontal accelerations due
to earthquakes and blasting, and (6) removal of
downslope support by undercutting.
Shear strength is governed by a more complex in-
terrelationship between the soil and slope
characteristics. Two principal forces are active in
resisting downslope movement. These are: (1)
cohesion or the capacity of the soil particles to
adhere together, a soil property produced by
cementation, capillary tension, or weak electrical
bonding of organic colloids and clay particles; and
(2) the frictional resistance between individual par-
ticles and between the soil mass and the sliding
surface. Frictional resistance is controlled by the
angle of internal friction of the soil — the degree of
interlocking of individual grains — and the effec-
tive weight of the soil which includes both the
weight of the soil mass and any surface loading plus
the effect of slope gradient and excess soil water.
Pore water pressure — pressure produced by the
head of water in saturated soil and transferred to
the base of the soil through the pore water — acts
to reduce the frictional resistance of the soil by
reducing its effective weight. In effect, its action
causes the soil to "float" above the sliding surface.
V.15
-------
Figure V.7.—Simplified diagram of forces acting on a mass of soil on a slope (Swanston 1974a).
V.16
-------
Controlling And Contributing Factors
Particle size distribution or "texture" (which
governs cohesion), angle of internal friction, soil
moisture content, and angle of sliding surface are
the controlling factors in determining stability of a
steepland soil. For example, shallow coarse-grained
soils low in clay-size particles have little or no cohe-
sion, and frictional resistance determines the
strength of the soil mass. Frictional resistance is, in
turn, strongly dependent on the angle of internal
friction of the soil and pore water pressure. A low
angle of internal friction relative to slope angle or
high pore water pressure can reduce soil shear
strength to negligible values.
Slope angle is a major indicator of the stability of
low cohesion soils. Slopes at or above the angle of
internal friction of the soil indicate a highly un-
stable natural state.
Soils of moderate to high clay content exhibit
more complex behavior because resistance to
sliding is determined by both cohesion and fric-
tional resistance. These factors are controlled to a
large extent by clay mineralogy and soil moisture.
In a dry state, clayey soils have a high shear
strength with the internal angle of friction quite
high (>30°). Increasing water content mobilizes
the clay through absorption of water onto the clay
structure. The angle of internal friction is reduced
by the addition of water to the clay lattices (in ef-
fect reducing "intragranular" friction) and may ap-
proach zero in saturated conditions. In addition,
water between grains — interstitial water — may
open the structure of the soil mass. This permits a
"remolding" of the clay fraction, transforming it
into a slurry, which then lubricates the remaining
soil mass. Some clays are more susceptible to defor-
mation than others, making clay mineralogy an im-
portant consideration in areas characterized by
quasi-viscous flow deformation of "creep." Swell-
ing clays of the smectite group (montmorillenite)
are particularly unstable because of their tendency
to absorb large quantities of water and to ex-
perience alternate expansion and contraction dur-
ing periods of wetting and drying which may result
in progressive failure of a slope. Thus, clay-rich
soils have a high potential for failure given excess
soil moisture content. Under these conditions,
failures are not directly dependent on sliding sur-
face gradient as in cohesionless soils, but may
develop on slopes with gradients as low as 2° or 3°.
Parent material type has a major effect on the
particle size distribution, depth of weathering, and
relative cohesiveness of a steepland soil. It fre-
quently can be used as an indicator of relative
stability or potential stability problems. In humid
regions where chemical weathering predominates,
transformation of easily weathered primary
minerals to clays and clay-size particles may be ex-
tensive. Siltstones, clay stones, shales, nonsiliceous
sandstones, pyroclastics, and serpentine-rich rocks
are the most easily altered and are prime can-
didates for soil mass movement of the creep and
slump-earthflow types. Conversely, in arid or
semiarid regions, slopes underlain by these rocks
may remain stable for many years due to slow
chemical weathering processes and lack of enough
soil moisture to mobilize existing clay minerals. On
steep lands underlain by resistant rocks, especially
where mechanical weathering prevails, soils are
usually coarse and low in clay-size particles. Such
areas are more likely to develop soil mass move-
ments of the debris avalanche-debris flow type.
Parent material structure is a critical factor in
stability of many shallow soils. Highly jointed
bedrock slopes with principal joint planes parallel
to the slope provide little mechanical support to
the slope and create avenues for concentrated sub-
surface flow and active pore water pressure
development, as well as ready-made zones of
weakness and potential failure surfaces for the
overlying material. Sedimentary rocks with bed-
ding planes parallel to the slope, function in essen-
tially the same way, with the uppermost bedding
plane forming an impermeable boundary to sub-
surface water movement, a layer restricting the
penetration and development of tree roots, and a
potential failure surface.
Vegetation cover generally helps control the
amount of water reaching the soil and the amount
held as stored water against gravity, largely
through a combination of interception and
evapotranspiration. The direct effect of intercep-
tion on the soil water budget is probably not large,
especially in areas of high total rainfall or during
large storms, when most soil mass movements oc-
cur. Small storms, where interception is effective,
probably have little influence on total soil water
available for activating mass movements.
In areas of low rainfall, the effect of evapotran-
spiration is much more pronounced, but it is par-
ticularly dependent on region and rainfall. In areas
characterized by warm, dry summers, evapotran-
spiration significantly reduces the degree of satura-
tion resulting from the first storms of the fall
recharge period. This effect diminishes as soil
V.17
-------
water deficit is satisfied. Once the soil is recharged,
the effects of previous evapotranspirational losses
become negligible. Conversely, in areas of con-
tinuous high rainfall or those with an arid or
semiarid climate, evapotranspirational effects are
probably negligible. Depth of evapotranspirational
withdrawals is important also. Deep withdrawals
may require substantial recharge to satisfy the soil
water deficit, delaying or reducing the possibility of
saturated soil conditions necessary for major slide-
producing events. Shallow soils, however, recharge
rapidly, possibly becoming saturated and most un-
stable during the first major storm.
Root systems of trees and other vegetation may
increase shear strength in unstable soils by
anchoring through the soil mass into fractures in
bedrock, providing continuous long fiberous
binders within the soil mass, and tying the slope
together across zones of weakness or instability.
In shallow soils, all three effects may be impor-
tant. In deep soils, the anchoring effect of roots
becomes negligible, but the other parameters will
remain important. In some extremely steep areas
in western North America, root anchoring may be
the dominant factor in maintaining slope
equilibrium of an otherwise unstable area
(Swanston and Swanson 1976).
Snow cover increases soil unit weight by surface
loading and affects delivery of water to the soil by
retaining rainfall and delaying release of much
water. Delayed release of melt water, coupled with
unusually heavy storms during a midwinter or
early spring warming trend, has been identified as
the principal initiating factor in recent major
landslide activity on forest lands in central
Washington (Klock and Helvey 1976).
CHARACTERIZING UNSTABLE SLOPES
IN FORESTED WATERSHEDS
The following guidelines are designed to help
delineate the hazards of unstable slopes on forested
lands.
There are six environmental qualities that
should be carefully considered when judging
stability of natural slopes in terms of surface ero-
sion and soil mass movement. They are:
A. landform features
B. soil characteristics
C. bedrock lithology and structure
D. vegetative cover
E. hydrologic characteristics of site
F. climate
Each of these qualities encompasses a group of
factors which control stability conditions on the
slope and determine or identify the type of
processes and movements which are most likely to
occur.
Key factors identifying potentially unstable
slopes on any mountainous terrain include slope
gradient (a landform quality) and concentration of
precipitation (both intensity and duration). Soil
properties, including soil depth and such
diagnostic characteristics as texture, permeability,
angle of internal friction, and cohesion determine
the types of processes that will dominate and, to
some degree, determine the stable slope gradient
within a particular soil type. Bedrock structure, es-
pecially attitude of beds and degree of fracturing or
jointing, are important contributing factors con-
trolling local stability conditions. Many of these
factors are identifiable on the ground or in readily
available support documentation (climatological
records, etc.).
The following outline discusses the six en-
vironmental qualities important for judging
stability of natural slopes and the key factors as-
sociated with each.
A. Landform features
1. Landforms on which subject area occurs.
— A qualitative indicator of potentially un-
stable landform types. Obtainable from air
photos and topographic maps. For example,
alpine glaciated terrain characteristically ex-
hibits U-shaped valleys with extensive areas
of very steep slope. Fracturing parallel to the
slope is common, and soils, either of colluvial
or glacial origin, are usually shallow and
cohesionless. The underlying impermeable
surface may be either bedrock or compact
glacial till. Such terrain is frequently subject
to debris avalanche-debris flow processes.
Areas formed by continental glaciation
commonly exhibit rolling terrain consisting of
low hills and ridges composed of bedrock,
glacial till, and stratified drift separated by
areas of ground moraine and glacial outwash.
Glaciolacustrine deposits may be present
locally, consisting of thick deposits of silt and
clay which may be particularly subject to
slump-earthflow processes if disturbed.
V.18
-------
Fluvially formed landscapes underlain by
bedded sedimentary and meta-sedimentary
rocks may have slope steepness controlled by
jointing, fracturing, and faulting; by orienta-
tion of bedding; and by differential resistance
of alternating rock layers. Debris avalanche-
debris flow failures frequently occur in shal-
low colluvial soils along these structurally
controlled surfaces. Slump-earthflow failures
may occur in clay-rich or deeply weathered
units, in deeply weathered soils and colluvial
debris on the lower slopes, and in valley fills
adjacent to active stream channels.
Volcanic terrain consisting of units of easily
weathered volcaniclastic rocks and hard,
resistant flow rock commonly exhibit slump-
earthflow failures in deeply weathered
volcaniclastic materials. Such failures usually
occur just below a capping flow or just above
an underlying flow due to concentration of
ground water. Debris avalanche-debris flow
failures are common in shallow residual or col-
luvial soils developed on the resistant flow
rock units.
Because of the large variability in landform
processes and the modifying influence of
climatic conditions on weathering rates and
products, geologists with some knowledge of
the area should be consulted.
2. Slope configuration. — Shape of the slope in
the area of consideration. A qualitative in-
dicator of location and extent of most highly
unstable areas on a slope. Obtainable from air
photos and topographic maps. On both con-
cave and convex slopes, usually the steepest
portions have the greatest stability hazard.
Convex slopes may have oversteep gradients
in lower portions of the slope. Concave slopes
have oversteep gradients in their upper eleva-
tions.
3. Slope gradient. — A key factor controlling
soil stability in steep mountain watersheds.
Slope gradient may be quantified on the
ground or from topographic maps. It deter-
mines effectiveness of gravity acting to move a
soil mass downslope. For debris avalanche-
debris flow failures, this is a major indicator of
the natural soil mass movement hazard. For
slump-earthflow failures, this is not as im-
portant since, given the right conditions of soil
moisture content, soil texture, and clay
mineral content, failures can occur on slope
gradients as low as 2° or 3°. Slope gradient
also has a major effect on subsurface water
flow in terms of drainage rate and subsequent
susceptibility to temporary water table
buildup during high intensity storms.
B. Soil Characteristics
1. Present soil mass movement type and rate.
— Obtainable from air photos and field
checks. This is a qualitative indicator of size
and location of potential stability problems,
type of recent landsliding, and kinds of soil
mass movement processes operative on the
slope. These, in turn, suggest probable soil
depth and certain dominant soil
characteristics. For example, debris
avalanches-debris flows most frequently
develop in shallow, coarse-grained soils which
have a low clay content and low internal cohe-
sion. Soil creep, massive slumping, and large-
scale earthflows usually develop in deep,
cohesive soils high in clay content or in deeply
weathered pelitic sediments, serpentinite,
and volcanic ash and breccia.
2. Parent material. — A qualitative indicator
of probable shape of soil particles, bulk den-
sity (or weight), degree of cohesion or clay
mineral content, soil depth, permeability, and
presence or absence of impermeable layers in
the soil. These, in turn, suggest types of soil
mass movement processes operative within an
area. This information is obtainable from ex-
isting geologic and soil survey maps, by air
photo interpretation, and by field check.
Soils developed from colluvial or residual
materials and some tills and pumice soils
commonly possess little or no cohesion.
Failures in such soils are usually of the debris
avalanche-debris flow type.
Soils developed from weathered fine
grained sedimentary rocks (mudstones,
claystones, nonsiliceous sandstones, shales),
volcaniclastics, and glacio-lacustrine clays
and silts possess a high degree of cohesion and
characteristically develop failures of the
slump-earthflow type.
The mica content also has a major influence
on soil strength. Ten to twenty percent mica
will produce results similar to high clay con-
tent.
3. Occurrence of compacted, cemented, or
impermeable layer. — A qualitative in-
dicator of the depth of potentially unstable
soil and probable principal planes of failure
V.19
-------
on the slope. This information is obtainable
from borings, soil pits, and inspection of slope
failure scars in the field.
4. Evidence of concentrated subsurface
drainage (including evidence of seasonal
saturation). — A qualitative indicator of
local zones of periodic high soil moisture con-
tent including saturation and potentially ac-
tive pore water pressures during high rainfall
periods. These identify potential areas of
slope failure. This information is obtainable
by air photo interpretation and ground obser-
vation. Diagnostic features include broad
linear depressions perpendicular to slope con-
tour, representing old landslide sites and
areas of concentrated subsurface drainage,
and damp areas on the slope, representing
springs and areas of concentrated ground
water movement.
5. Diagnostic soil characteristics. — Key fac-
tors in determining dominant types of soil
mass movement process mechanics of motion
and probable maximum and minimum stable
slope gradients for a particular soil. This is
identifiable through field testing, sampling,
and laboratory analysis. Data on benchmark
soils also may be obtained from soil surveys
and engineering analyses for road construc-
tion in or adjacent to the proposed
silvicultural activity.
a. Soil depth. — Principal component of the
weight of the soil mass and an important
factor in determining soil strength and
gravitational stress acting on an unstable
soil.
b. Texture. — (Particle size distribution)
the relative proportions of sand (2.0 - 0.5
mm), silt (.05 - .002 mm), and clay (<.002
mm) in a soil. Texture, along with clay
mineral content, are important factors in
controlling cohesion, angle of internal fric-
tion, and hydraulic conductivity of an un-
stable soil.
c. Clay mineralogy. — An indicator of sen-
sitivity to deformation. Some clays are
more susceptible to deformation than
others, making clay mineralogy an impor-
tant consideration in areas where creep oc-
curs. "Swelling" clays of the smectite
group (montmorillonite) are particularly
unstable.
d. Angle of internal friction. — An in-
dicator of the internal frictional resistance
of a soil caused by intergranular friction
and interlocking of individual grains, an
important factor in determining soil shear
strength or resistance to gravitational
stress. The tangent of the angle of internal
friction times the weight of the soil con-
stitute a mathematical expression of fric-
tional resistance. For shallow, cohesionless
soils, a slope gradient at or above the angle
of internal friction is a good indicator of a
highly unstable site.
e. Cohesion. — The capacity of soil particles
to stick or adhere together. This is a dis-
tinct soil property produced by cementa-
tion, capillary tension, and weak electrical
bonding of organic colloids and clay parti-
cles. Cohesion is usually the direct result
of high (20 percent or greater) clay particle
content and is an important contributor to
shear strength of a fine grained soil.
C. Bedrock Lithology and Structure
1. Rock type. — A qualitative indicator of
overlying soil texture, clay mineral content,
and relative cohesiveness. It provides a
regional guide to probable areas of soil mass
movement problems and dominant processes.
For example, in the Cascades and Coast
Range of Oregon and Washington, areas un-
derlain by volcanic ash and breccias and silty
sandstone are particularly susceptible to
slump-earthflows. Where hard, resistant
volcanic flow rock is present, shallow planar
failures dominate. Slopes underlain by
granites and diorites are also more susceptible
to shallow planar failures, although where ex-
tensive chemical weathering has occurred,
such rocks may exhibit slump-earthflow
features. The slope stability characteristics of
a particular rock type or formation largely de-
pend on mineralogy, climate, and degree of
weathering, and must be determined for each
particular area.
2. Degree of weathering. — A qualitative in-
dicator of soil depth and type of soil mass
movement activities. In some rock types, it is
also an indicator of degree of clay mineral for-
mation.
3. Attitude of beds. — Quantifiable on the
ground, from geologic maps, and occasionally
V.20
-------
from air photos. This is an important con-
tributing factor to unstable slopes, especially
where attitude of bedding parallels or dips in
the same direction as the slope. Under these
conditions, the bedding planes form zones of
weakness along which slope failures can occur
due to high pore water pressures and
decreases in frictional resistance. Conversely,
bedding planes dipping into the slope fre-
quently produce natural buttresses and in-
crease slope stability. Care must be taken in
assessing the stabilizing influence of horizon-
tal or in-dipping bedding planes particularly
where well-developed jointing is present (see
no. 4).
4. Degree of jointing and fracturing. — Quan-
tifiable on the ground and occasionally from
geologic maps as dip and strike of faults, frac-
tures, and joint systems. Joints in particular
are important contributing factors to slope in-
stability, especially on slopes underlain by ig-
neous materials. Joints parallel to or dipping
in the same direction as the slope, create local
zones of weakness along which failures occur.
Jointing also provides avenues for deep
penetration of groundwater with subsequent
active pore water pressure development along
downslope dipping joint planes.
Valleys developed along high angle faults in
mountainous terrain may have exceptionally
steep slopes. Deep penetration of ground
water into uneroded fault and shear zones can
result in extensive weathering and alteration
of zone materials, resulting in generation of
slump-earthflow failures. Such zones can also
form barriers to ground water movement
causing redirection and concentration of
water into adjacent potentially unstable sites.
D. Vegetative Characteristics
1. Root distribution and degree of root
anchoring in the subsoil. — An indicator of
effectiveness of tree roots as a stabilizing fac-
tor in shallow steep slope soils. Quantifiable
on the ground by observing the degree of
penetration of roots through the soil and into
a more resistant substratum and by measur-
ing the biomass of the roots contained in a
potentially unstable soil. High biomass of
contained roots is an expression of the binding
capacity or "reinforcing" effect of roots to the
soil mass.
2. Vegetation type and distribution. — Cover
density, vegetation type, and stand age are
qualitative indicators of the history of soil
mass movement on a site and soil and ground
water conditions. This information is ob-
tainable by air photo interpretation and
ground checking.
E. Hydrologic Characteristics
1. Hydraulic conductivity. — A measure of
water movement in and through soil material.
This is quantifiable in the field and in the
laboratory using pumping tests and
permeameters. Low hydraulic conductivities
mean rapid storm generated saturation and a
high probability of active pore water pressure,
which produces highly unstable conditions in
steep slope soils.
2. Pore water pressure. — A measure of the
pressure produced by the head of water in a
saturated soil and transferred to the base of
the soil through the pore water. This is quan-
tifiable in the field through measurement of
free water surface level in the soil. Pore water
pressure is a key factor in failure of a steep
slope soil, and operates primarily by reducing
the weight component of soil shear strength.
F. Climate
1. Precipitation occurrence and distribution.
— A key factor in predicting regional soil
mass movement occurrences. Most soil mass
movements are triggered by soil saturation
and active pore water pressures produced by
rainfall of high intensity and long duration.
Isohyetal maps of rainfall occurrences and
distribution, constructed from data ob-
tainable from local monitoring stations or
from the Weather Bureau, can be used to pin-
point local areas of high rainfall concentra-
tion. It is advisable to develop a simple
relationship between rainfall intensity and
pore water pressure development for a par-
ticular soil type or area of interest so that
magnitude and return period of damaging
storms can be identified. This can be done
simply by locating a rain gage at the site or
using nearby rainfall data and correlating this
with piezometric data obtained from open-
ended tubes installed to the probable depths
of failure at the site. Each storm should be
monitored.
V.21
-------
THE PROCEDURE
ESTIMATING SOIL MASS MOVEMENT
HAZARD AND SEDIMENT
DELIVERED TO CHANNELS
This section delineates a procedure to be used on
potentially unstable areas to analyze the hazard of
soil mass movement associated with silvicultural
activities and to determine the potential volume
and delivery of inorganic material to the closest
drainageway. This is a broad level analysis
designed to determine where specific controls or
management treatment variations are required
because of possible water quality changes resulting
from soil mass movement. This procedure will not
substitute for site specific analysis of road design,
maintenance, and rehabilitation as may be re-
quired under current management procedures.
To assess soil mass movement hazards that
might deliver inorganic material to a stream
course, a basic qualitative evaluation is undertaken
based on the following information:
1. A delineation of hazard areas and dominant
soil mass movement types using aerial photo
and topographic map interpretation with
minimum ground reconnaissance.
2. An estimate of the likelihood of failure or
"sensitivity" of an area caused by both
natural and man-induced events, using sub-
jective analysis of controlling and con-
tributing factors within defined hazard areas.
3. An estimate of the volume of material
released by soil mass movements during
storm events with a 10-year return interval or
less.
4. An estimate of the volume of sediment
released by soil mass movements which ac-
tually reach a water course based on slope
position, gradient, and shape and type of
movement.
Although soil mass movements are too infre-
quent for effective direct annual evaluation,
delivery volumes can be expressed on an average
annual basis for purposes of comparison between
pre- and post-silvicultural activity conditions.
A broad delineation of potentially unstable ter-
rain by slope characteristics and soil mass move-
ment types is an essential part of the hazard
analysis. A detailed flow chart (fig. V.8) shows the
sequence of analysis once the delineation of un-
stable terrain is accomplished.
The limits placed on variable ranges for high,
medium and low hazard indices are approxima-
tions based on the collective experience of practic-
ing professionals. The weighted values for hazard
indices are guides only, and they were determined
from consultation with practicing professionals as
well as a limited analysis of several unstable areas
in Colorado and western Oregon. However, they do
reflect the relative importance of the individual
factors and their effects on likelihood of failure by
the major soil mass movement types. These
weightings and the ranges of hazard index should
be adjusted to reflect the conditions prevalent
within a given area.
PROCEDURAL DESCRIPTION
The following information describes each step of
the procedural flow chart, fig V.8. Data from the
Horse Creek example are used to illustrate the fol-
lowing procedure. This complete example is
presented in "Chapter VIE: Procedural Example."
BROAD DELINEATION OF
POTENTIALLY UNSTABLE AREAS
Guidelines have been presented that provide a
qualitative characterization of'unstable or poten-
tially unstable slopes on forested lands. Using these
guidelines, evaluate the area of the proposed
silvicultural activity to ascertain the stability of
the site.
IDENTIFY AND MAP AREAS BY
SOIL MASS MOVEMENT TYPE
If the area is generally unstable or potentially
unstable, delineate the hazard areas and dominant
soil mass movement types (debris avalanches-
debris flows and slump-earthflows) using aerial
photos and topographic map interpretation. Poten-
tially unstable areas are those that may become
unstable due to the proposed silvicultural activity.
Unstable areas are those that have or presently are
undergoing a soil mass movement.
V.22
-------
CHARACTERIZE
SOIL MASS
MOVEMENT TYPE
Soil mass movements have been classified into
two major types: debris avalanches-debris flows
and slump-earthflows. Several site parameters and
management activities can be used to evaluate the
possibility of soil mass movement. Although both
movement types have similar factors that can be
used to evaluate the hazard of a failure, the relative
importance of these factors may be different
between the two movement types. In addition,
each kind of soil mass movement has some site or
management activity parameters that are specific
for that movement. Therefore, to evaluate the
hazard of a soil mass movement, each type must be
evaluated separately using the factors that have
been found to be significant in characterizing that
particular kind of failure.
DEBRIS AVALANCHE-
DEBRIS FLOW
Areas prone to debris avalanches-debris flows are
typified by shallow, noncohesive soils on steep
slopes where subsurface water may be concentrated
by subtle topography on bedrock or glacial till sur-
faces.
' NATURAL HAZARD SITE ^
CHARACTERISTICS
For debris avalanches-debris flows, the following
site characteristics have been found to be critical in
evaluating the potential hazard of a natural soil
mass movement: slope gradient, soil depth, subsur-
face drainage characteristics, soil texture, bedding
structure and orientation, surface slope configura-
tion, and precipitation input. This information can
be obtained from geologic and soils maps, pertinent
literature, field knowledge of local experts, etc. The
relative importance of each site characteristic is in-
dicated in table V.5 and worksheet V.I by the
weighting value assigned.
MANAGEMENT INDUCED
HAZARD CHARACTERISTICS
For debris avalanches-debris flows, the following
management activities have been found to be
critical in evaluating the potential hazard for in-
itiation or acceleration of a soil mass movement:
vegetative cover removal, roads and skidways, and
harvest systems. This information can be obtained
from past records of silvicultural activities or from
proposed silvicultural activity plans. The relative
importance of each management activity is in-
dicated in table V.6 and worksheet V.2 by the
weighting value assigned.
HAZARD INDEX
The hazard index analysis procedure places
weighted values on the factors affecting different
types of soil mass movement. A three-part hazard
index is used: high, medium, and low. The
numerical ratings are subjective and depend on
what is considered acceptable for a particular
silvicultural activity. Assumptions 1 and 2 in the
procedure detail and define a high, medium, and
low hazard.
The natural hazard index for debris avalanches-
debris flows is determined by summing the
weighted values from worksheet V.I and comparing
this value to the ranges of values for high, medium,
and low hazard indices. For example, if the sum of
the weighted values for the natural hazard index
(worksheet V.I) was 31, the hazard index would be
medium. The value 31 falls within the range of
values (21-44) for the medium hazard.
The relative hazard for debris avalanches-debris
flows caused by silvicultural activities is deter-
mined by summing the weighted values from
worksheet V.2. The overall hazard index caused by
natural plus existing or proposed silvicultural ac-
tivities is determined by adding the total weighted
value for the natural hazard. This overall weighted
value is compared with the range of values given for
a high, medium, or low hazard index. For example,
if the silvicultural activities resulted in a total
weighted value of 31, the overall weighted value of
both the natural (31) plus the silvicultural activity
(31) would be equal to 62 and the overall hazard in-
dex would be high.
V.23
-------
BROAD DELINEATION OF POTENTIALLY
UNSTABLE AREAS
c
IDENTIFY AND MAP AREAS BY
SOIL MASS MOVEMENT TYPE
CHA
/ Cf
DEBRIS AVALANCHE ^ /MOV
DEBRIS FLOW
,
,
HAZARD
INDEX
4
^
^
NATURAL HAZARD
SITE
CHARACTERISTICS
SLOPE GRADIENT
SOIL DEPTH
SUBSURFACE
DRAINAGE
CHARACTERISTICS
SOIL TEXTURE
BEDDING STRUCTURE
AND ORIENTATION
SURFACE SLOPE
CONFIGURATION
PRECIPITATION INPUT
' MANAGEMENT \
INDUCED HAZARD
CHARACTERISTICS
VEGETATIVE
COVER REMOVAL
ROADS AND SKIDWAYS
i HARVEST SYSTEMS /
RACTERIZE
DILMASS \
EMENTTYPE X ^
w
SLUMP-EARTHFLOW
NATURAL HAZARD \
SITE
CHARACTERISTICS
SLOPE GRADIENT
VEGETATIVE
INDICATORS
SUBSURFACE
DRAINAGE
CHARACTERISTICS
SOIL TEXTURE
BEDDING STRUCTURE
AND ORIENTATION
SURFACE SLOPE
CONFIGURATION
PRECIPITATION INPUT
' MANAGEMENT
INDUCED HAZARD
CHARACTERISTICS
VEGETATIVE
COVER REMOVAL
ROADS AND SKIDWA'l
i HARVEST SYSTEMS
\
rs
/
r+
i
HAZARD
INDEX
FOR THE TWO SOIL MASS MOVEMENTTYPES,
EVALUATE NATURAL VS. MAN INDUCED MASS MOVEMENT
SITE OF PROPOSED
SILVICULTURAL
ACTIVITY HISTORY
HISTORY
PAST
SILVICULTURAL
ACTIVITIES
SITE OF PAST
SILVICULTURAL
ACTIVITY
*
ESTIMATE TOTAL
AND AVERAGE
VOLUME PER SOIL
MASS MOVEMENT
/ VOLUME OF EACH FAILURE \
LENGTH
WIDTH
DEPTH
NUMBER OF FAILURES BY
MOVEMENT TYPE AND CAUSE
t 1
fe.
*
ESTIMATE TOTAL
AND AVERAGE
VOLUME PER SOIL
MASS MOVEMENT
1
V.24
-------
TOTAL
VOLUME RELEASED
BY SLOPE CLASS OR
POSITION CATEGORY
I
COMPUTE TOTAL WEIGHT
RELEASED PER SLOPE
CLASS OR CATEGORY
NUMBER OF SOIL MASS
MOVEMENTS BY SLOPE CLASS
, OR POSITION CATEGORY ,
ESTIMATED DRY UNIT WEIGHT
OF SOIL IN MASS MOVEMENT
TOTAL
VOLUME RELEASED
BY SLOPE CLASS OR
POSITION CATEGORY
COMPUTE TOTAL WEIGHT
RELEASED PER SLOPE
CLASS OR CATEGORY
ESTIMATE
DELIVERY
POTENTIAL
/SLOPE IRREGULARITY BY SLOPE \
\ CLASS OR POSITION CATEGORY /
fc
V
ESTIMATE
DELIVERY
POTENTIAL
ESTIMATE
TOTAL QUANTITY OF SOIL
DELIVERED PER SLOPE CLASS
OR POSITION CATEGORY
AND TOTAL AMOUNT
ESTIMATE
TOTAL QUANTITY OF SOIL
DELIVERED PER SLOPE CLASS
OR POSITION CATEGORY
AND TOTAL AMOUNT
I
ESTIMATE AN ACCELERATION
FACTOR TO ACCOUNT FOR THE
INCREASED DELIVERY
DUE TO THE SILVICULTURAL
ACTIVITY (MAN-INDUCED)
1
J
ESTIMATE INCREASED SOIL
DELIVERY DUE TO THE
PROPOSED SILVICULTURAL
ACTIVITY
Figure V.8.—Detailed flow chart of the soli mass movement procedure.
V.25
-------
Table V.5.—Weighting factors for determination of natural hazard of debris avalanche-debris flow failures
Factor
Slope gradient
Hazard index and range
High
>34°
Medium
29° -34°
Low
<29°
Weight
30
15
5
Soil depth
Subsurface drainage
characteristics
Soil texture
Bedding structure
and orientation
High
Shallow soils, <5ft
Medium
Moderately deep soils, 5-10 ft
Low
Deep soils, >10ft
High
High density, closely spaced incipient drainage depressions
Presence of bedrock or impervious material at shallow depth which
restricts vertical water movement and concentrates subsurface flow
Presence of permeable low density zones above the restricting layer
indicative of saturated flow parallel to the slope
Evidence of springs on the slope
Medium
Presence of incipient drainage depressions, but widely spaced
Presence of impervious material at shallow depths, but no low density
zones present
Springs are absent
Low
Incipient drainage depressions rare to absent
No shallow restricting layers present
No indications of near-surface flow
High
Unconsolidated, non-cohesive soils and colluvial debris including
sands and gravels, rock fragments, weathered granites, pumice and
noncompacted glacial tills with low silt content (<10%) and no clay
Medium
Unconsolidated, non-cohesive soils and colluvial debris with moderate
silt content (10-20%) and minor clay (<10%)
Low
Fine grained, cohesive soils with greater than 20% clay sized particles
or mica
High
Extensive jointing and fracturing parallel to the slope
Bedding planes parallel to the slope
Faulting or shearing parallel to the slope (the stability influence of bed-
ding planes horizontal or dipping into the slope is offset by extensive
parallel jointing and fracturing)
Medium
Bedding planes are horizontal or dipping into the slope with minor
jointing at angles less than the natural slope gradient
Minor surface fracturing — no faulting or shearing evident
Low
Bedding planes are horizontal or dipping into the slope
Jointing and fracturing is minor — no faulting or shearing evident
3
2
1
V.26
-------
Table V.5.—Weighting factors for determination of natural hazard of debris
avalanche-debris flow failures — continued
Factor
Hazard index and range
Weight
Surface slope
configuration
Precipitation input
High
Smooth, continuous slopes unbroken by benches or rock outcrops
Intermittent steep channels occur frequently with lateral spacing of 500
ft (152 m) or less
Perennial channels frequently deeply incised with steep walls of rock
or colluvial debris
Numerous breaks in canopy due to blow-downs — frequent linear or
tear-drop shaped even-age stands beginning at small scarps or
spoon-shaped depressions indicative of old debris avalanche-debris
flow activity
Medium
Smooth, continuous slopes broken by occasional benches and rock
outcrops
Intermittent, steep gradient channels occur less frequently with a
lateral spacing of 500-800 ft (152-244 m)
Infrequent evidence of blow-down or past landslide activity
Low
Slope broken by rock benches and outcrops intermittent, steep
gradient channels spaced 900 ft (275 m) or more apart
High
Area characterized by rainfall greater than 80 in/yr (203 cm/yr) dis-
tributed throughout the year or greater than 40 in/yr (102 cm/yr) dis-
tributed over a clearly definable rainy season
Locale is subjected to frequent high intensity storms capable of
generating saturated soil conditions on the slope leading to active
pore-water pressure development and high stream flow — area has a
high potential for mid-winter or early spring rainfall-on-snowpack
events
Storm intensities may exceed 6 in/24 hr at 10 yr recurrence intervals or
less
Medium
Area characterized by moderate rainfall of 20 to 40 in/yr (51 to 102
cm/yr)
Storms of moderate intensity and duration are common
High intensity storms are infrequent, but do occasionally occur
Moderate snowpack, but rain-on-snow events very rare
Storm intensities may exceed 6 in/24 hr (15 cm/24 hr) at recurrence in-
tervals greater than 10 yrs.
Low
Rainfall in area is low (less than 20 in/yr)
Storms infrequent and of low intensity
Stored water content in snowpack, when present, is low and only rarely
subject to rapid melting
12
V.27
-------
WORKSHEET V.1
Debris avalanche-debri? flow natural factor evaluation form
Index
High
vied ium
.ow
Slope
gradient
30
0
5
Soi 1
depth
3
(D
1
Subsurface
drainage
character i sties
G
2
1
Soi 1
texture
3
©
C
Bedd i nq
structure
and
or ientat ion
3
©
1
Slope
conf igurat ion
3
(P
1
Preci p i -
tat ion
input
12
©
3
to
oo
Factor summation table
Gross hazard index
High
Medium
Low
Factor ranae
Greater than 44
21 - 44
Less than 21
Natural
31
-------
Table V.6.—Weighting factors for determination of management-induced hazard of debris avalanche-debris
flow failures
Factor
Hazard index and range
Weight
Vegetation cover
removal
Roads and
skidways
Harvest systems
High 8
Total removal of cover — large clearcuts with openings continuous
downslope — such removal is sufficient to increase soil moisture levels
and reduce strength
Broadcast burning of slash
Medium 5
Cover partially removed with slope sections >34° left undisturbed —
clearcuts in small patches or strips less than 20 ac (8 ha) and discon-
tinuous on slopes
Low 2
Cover density altered through partial cutting — no clearcutting — no
broadcast burning of sites with >34° slope
High 20
High density (>15% of area in roads) on potentially unstable slopes
(>28°) — cut and fill construction
Roads and skidways located on steep, unstable portions of the slope
Uncontrolled fills with poor compaction produced by side-casting over
organic debris
Inadequate cross drainage (poor location; improper spacing and
maintenance, size too small'for 10 yr storm flow)
Lack of fill slope protection of drainage outlets
Concentrations of drainage water directed into identifiable unstable
areas
Medium
Mixed road types, both fully benched and cut-and-fill (balanced) —
moderate road density (8-15% of area)
Areas with slopes >34° or with identifiable landslide activity have been
avoided or fully benched
On potentially unstable slopes >29° skidways and cut-and-fill type
construction are limited
Ridgetop roads have large fills in saddles
Fills, where present, are constructed by sidecasting over organic
debris with little controlled compaction
Roads generally have adequate cross drains for normal runoff condi-
tions (number and location) but are undersized for the 10 yr storm flow
Fill slopes below culvert outfalls protected by rip-rap dissipation struc-
tures at potentially unstable sites
Major concentrations of water into identifiable unstable areas avoided
Low
Very few roads on slopes above 28° — low road density (less than 8%
of area) with roads on potentially unstable terrain (slopes between 29°
and 34°) predominantly of full bench type — most road locations or
construction limited to ridgetops with minimum fills in saddles and
lower slopes — adequate cross drains with major water courses
bridged and culverts designed for 10 yr storm flow or larger
High
Operation of tractor yarding, jammer yarding and other ground lead
systems on slopes >29° (53%)
Medium
No tractor logging — high lead with partial suspension on slopes >29°
(53%)
Low
Helicopter and balloon yarding — full suspension of logs by any
method — yarding by any method on slopes <29° (53%)
V.29
-------
WORKSHEET V.2
Debris avalanche-debris flow management
related factor evaluation form
1 ndex
High
Medium
_ow
Vegetation
cover remova 1
<Ł>
5
2
Roads and
skidways
<§)
8
2
Harvest
methods
2
0
Factor summation table
Gross hazard index
Range
Natural +
management
High
Medium
_ow
Greater than 44
21 - 44
Less than 21
V.30
-------
SLUMP-EARTH FLOW
HAZARD INDEX
Slump-earthflow prone areas are typified by
deep, cohesive soils and clay-rich bedrock overlying
hard, competent rock. Slump-earthflow soil mass
movement also appears to be sensitive to long-term
fluctuations.
NATURAL HAZARD SITE
CHARACTERISTICS
For slump-earthflows, the following site
characteristics have been found to be critical in
evaluating the potential hazard of a natural soil
mass movement: slope gradient, sub-surface
drainage characteristics, soil texture, surface slope
configuration, vegetative indicators, bedding struc-
ture and orientation, and precipitation input. This
information can be obtained from soils maps,
vegetative cover maps, pertinent literature, field
knowledge of local experts, etc. The relative impor-
tance of each site characteristic is indicated in
table V.7 and worksheet V.3 by the weighting value
assigned.
MANAGEMENT INDUCED
HAZARD CHARACTERISTICS
The hazard index analysis procedure places
weighted values on the factors affecting different
types of soil mass movement. A three-part hazard
index is used: high, medium, and low. The
numerical ratings are subjective and depend on
what is considered acceptable for a particular
silvicultural activity. Assumptions 1 and 2 in the
procedure detail and define a high, medium, and
low hazard.
The natural hazard index for slump-earthflows is
determined by summing the weighted values from
worksheet V.3 and comparing this value to the
ranges of values for high, medium, and low hazard
index. For example, if the sum of the weighted
values for the natural hazard index (wksht. V.3)
was 38, the hazard index would be medium. The
value 38 falls within the range of values (22-44) for
the medium hazard.
The relative hazard for slump-earthflows caused
by silvicultural activities is determined by sum-
ming the weighted values from worksheet V.4. The
overall hazard index resulting from natural plus ex-
isting or proposed silvicultural activities is deter-
mined by adding the total weighted value from
silvicultural activities to the total weighted value
for the natural hazard. This overall weighted value
is compared with the range of values given for a
high, medium, or low hazard index. For example, if
the silvicultural activities resulted in a total
weighted value of 8, the overall weighted value of
both the natural (38) plus the silvicultural activity
(8) would be equal to 46, and the overall hazard in-
dex would be high.
For slump-earthflows, the following manage-
ment activities have been found to be critical in
evaluating the potential hazard for initiation or ac-
celeration of a soil mass movement: vegetative
cover removal, roads and skidways, and harvest
systems. This information can be obtained from
past records of silvicultural activities or from
proposed silvicultural activity plans. The relative
importance of each management activity is in-
dicated in table V.8 and worksheet V.4 by the
weighting value assigned.
FOR THE TWO TYPES OF
SOIL MASS MOVEMENTS,
EVALUATE NATURAL VS. MAN-INDUCED
MASS MOVEMENT
Determine the quantity of material delivered to a
stream channel for each soil mass movement type
and evaluate any man-induced increase in mass
movement over that naturally occurring.
V.31
-------
Table V.7.—Weighting factors for determination of natural hazard of slump-earthflow failures
Factor
Hazard index and range
Weight
Slope gradient
Subsurface drainage
characteristics
Soil texture
Slope configuration
High 6
greater than 30° (58%)
Medium 4
15-30°(27%-58%)
Low 2
under 15° (27%)
High 6
Area exhibits abundant evidence of impaired groundwater movement
resulting in local zones of saturation within the soil mass — short, ir-
regular surface drainages which begin and end on the slope
Impaired drainage, indicated at the surface by numerous sag ponds
with standing water, springs and patches of wet ground
Impaired drainage involves more than 20% of the area
Medium 4
Some indications of impaired drainage, but generally involving less
than 10% of the area
Active springs are uncommon, infrequent, or contain no standing
water
Low 2
No evidence of impaired drainage
High 15
Predominantly fine grained cohesive soils derived from weathered
sedimentary rocks, volcanics, aeolian and alluvial silts and
glaciolacustrine silts and clays
Clay sized particle content generally greater than 20%
Clay minerals predominantly of the smectite group (montmorillonite),
exhibiting swelling characteristics upon wetting
Medium 10
Soils of variable texture including both fine and coarse grained compo-
nents in layers and lenses
The fine grained, cohesive component may contain a clay sized parti-
cle content greater than 20%, but clay minerals are predominantly of
the illite and kaolinite groups, exhibiting lower sensitivity to changes in
stress
Low 5
Soils of variable texture
Some clayey soils present but widely dispersed in small layers or
lenses
High 5
40% or more of the area is characterized by hummocky topography
consisting of rolling, bumpy ground, frequent benches and depres-
sions locally enclosing sag ponds
Tension cracks and headwall scarps indicating slumping are un-
vegetated and clearly visible
Slopes are irregular and may be slightly concave in the upper 1/2 and
convex in the lower 1/2 as a result of the downslope redistribution of
soil materials
Zones of active movement are abundant
Medium 2
5% to 40% of the area is characterized by hummocky topography
Occasional sag ponds occur, but slump depressions are generally dry
Headwall scarps are revegetated and no open tension cracks are visi-
ble
Active slump-earthflow features are absent
V.32
-------
Table V.7.—Weighting factors for determination of natrual hazard of slump-earthflow — continued
Factor
Hazard index and range
Weight
Vegetative
indicators
Precipitation
input
Low
Less than 5% of the area is characterized by hummocky topography
Old slump-earthflow features are absent or subdued by weathering
and erosion
No active slump earthflow features present, slopes are generally
smooth and continuous from ridge to valley floor
High
Phreatophytic (wet site) vegetation widespread
Tipped (jackstrawed) and split trees are common
Pistol-butted trees occur in areas of obvious hummocky topography
(note: pistol-butted trees should be used as indicators of active slump-
earthflow activity only in the presence of other indicators — pistol-
butting can also occur in areas of high snowfall and is often the result
of snow creep and glide)
Medium
Phreatophytic vegetation limited to occasional moist areas on the open
slope and within sag ponds
Tipped trees absent
Low
Phreatophytic vegetation absent
High
Area characterized by high rainfall of greater than 80 in/yr (203 cm/yr)
distributed throughout the year or greater than 40 in/yr (102 cm/yr)
distributed over a clearly definable rainy season
Locale is subjected to frequent high intensity, long duration storms
capable of generating continuing saturated conditions within the soil
mass leading to active pore water pressure development and mobiliza-
tion of the clay fraction
Area has a high potential for rain-on-snow events
Medium
Area characterized by moderate rainfall of 20 to 40 in/yr (51 cm/yr to
102 cm/yr)
Storms of moderate intensity and duration are common
Snowpack is moderate, but rain-on-snow events are rare
Low
Rainfall in the area is low (less than 20 in/yr) storms are infrequent and
of low intensity and duration
Stored water content in the snowpack, when present, is low throughout
the winter with no mid-winter or early spring releases due to
climatological events
1
0
18
10
V.33
-------
WORKSHEET V.3
SIump-earthflow natural factor evaluation form
1 ndex
High
Medium
Low
Slope
grad ient
©
4
2
Subsurface
drainage
characteristics
6
(Ł>
2
Soil
texture
15
©
5
Slope
conf igurat ion
©
2
1
Vegetat i ve
i nd icators
5
©
0
Preci p i tat ion
input
18
(To)
2
Factor summation table
Gross hazard index
High
Medium
Low
Range
Greater than 44
21 - 44
Less than 21
Natural
2,8
-------
Table V.8.—Weighting factors for determination of management induced hazard of slump-earthflow failures
Factor
Hazard index and range
Weight
Vegetation
cover removal
Roads and
skidways
Harvest systems
High 3
Total removal of cover or large clearcuts with openings continuous
downslope — such removal would be sufficient to increase soil
moisture levels and reduce root strength
Medium 2
Cover partially removed — clearcuts in small patches or strips less
than 20 acres (8 ha) is size and discontinuous downslope
Low 1
Cover density altered through partial cutting, no clearcutting evident
High 7
High density (>15% of area in roads) cut-and-fill type (balanced) con-
struction
Roads and skidways located or planned across identifiable unstable
ground
Roads crossing active or dormant slump-earthflow features
Massive fills or spoil piles on slump benches
Inadequate drainage creating concentrations of water at the surface
with diversion of surface drainage into unstable areas
Medium 4
Mixed road types, both fully benched and cut-and-fill (balanced) —
moderate road density (8-15% of area in roads), unstable areas
features avoided
Roads generally have adequate cross drains for normal runoff condi-
tions but are undersized for 10 yr storm flows
Diversions of concentrations of water into unstable sites avoided
Low 2
No roads present — if present, predominantly fully benched
Road density less than 8%
Most road location and construction on ridgetops or in alluvial valley
floors
Adequate cross drainage with dispersal rather than heavily con-
centrated surface flow
High 3
Operation of tractor yarding, jammer yarding or other ground lead
systems causing excessive ground disturbance
Medium 2
High lead yarding with partial suspension and skyline with partial
suspension
No tractor yarding
Low 1
Helicopter and balloon yarding
Full suspension of logs by any method
V.35
-------
WORKSHEET V.4
SIump-earthflow management
related factor evaluation form
Index
High
Medium
Low
Vegetation
cover remova 1
©
2
1
Roads and
skidways
7
4
-------
HISTORY OF PAST SILVICULTURAL
/ ACTIVITIES \
To estimate the man-induced increase in the
amount of soil delivered to a stream channel
caused by silvicultural activities, it is necessary to
compare soil mass movement in an area that has
not been subjected to silvicultural activities with
soil mass movement in an area that has been sub-
jected to silvicultural activities. It is essential that
the area selected for its previous silvicultural ac-
tivities be identical or very similar to the un-
disturbed area, not only in physical site conditions,
but also in proposed silvicultural activities. The
proposed site of the silvicultural activity may or
may not have existing soil mass movement which
could be measured and quantified. The other area
should have a history, if possible, of soil mass
movements from both natural and man-induced
causes.
VOLUME OF EACH FAILURE AND
NUMBER OF FAILURES BY
MOVEMENT TYPE & CAUSE
The site is inventoried using aerial photos and
possibly a limited field reconnaissance and a record
is made of each soil mass movement (the length,
width, and depth), (figs. V.9 and V.10). The cause
of each mass movement, either natural or in the
case of areas that have been subjected to past
silvicultural activity, man-induced, and the type of
mass movement are noted. The number of soil
mass movements by cause (natural vs. man-
induced) and type is computed.
SITE OF PROPOSED
SILVICULTURAL ACTIVITY
ESTIMATE TOTAL & AVERAGE
VOLUME PER SOIL MASS MOVEMENT
If the proposed silvicultural activity is to be con-
ducted in a previously undisturbed area, the in-
herent natural instability of the site can be es-
timated based upon existing failures or upon
failures occurring on a similarly undisturbed site.
SITE OF PAST SILVICULTURAL
ACTIVITY
Select an area adjacent to the proposed site of
the silvicultural activity, with similar site
characteristics and a history of similar silvicultural
activities. The inherent natural instability of the
area can be estimated based upon existing failures.
Failures caused or accelerated by the silvicultural
activity can also be measured.
The volume of individual soil mass movements
(V) is computed on worksheet V.5 by multiplying
the length (L), width (W), and depth (D) to obtain
cubic feet of soil moved. The total soil mass move-
ment by type (debris avalanche-debris flow and
slump-earthflow) is computed by summing the
volumes of the individual failures (wksht. V.5).
These values are summed and recorded on
worksheet V.6, step 1. The total number (N) of
failures by soil mass movement type is recorded on
worksheet V.6, step 2. The average volume per soil
mass movement (VA) by movement type is
computed by dividing the total volume (Vt) by the
number of failures (N) or VA = Vt/N and is recorded
on worksheet V.6, step 3. For example, if the total
volume (Vt) for debris avalanches-debris flows was
17,205 ft3 (487 m3) and the number of debris
avalanche-debris flow (N) was 5, the average
volume per debris avalanche-debris flow (VA) would
equal 3,441 ft3 (162 m3) or VA = 17,205 ft3/5 = 3,441
ft3.
V.37
-------
Figure V.9.—Dimensions of debris avalanche-debris flow failures for determining potential volumes. W
width; L = length; D = depth.
Figure V.10—Dimensions of slump-earthflow failures for determining potential volumes. W = width; L
length; D = depth.
V.38
-------
WORKSHEET V.5
Estimation of volume per failure
CO
ID
SI ide
Number
4erse
/
Wale
/
Z
3
V
S"
/
Debris avalanche-debr s flow
Natural
Creek
X
Ct-eek
X
Man-
induced
X
X
X
X
X
Length
(ft)
SĄ
so
u?
Ul
113
7s-
IIS
Width
(ft)
48
*1
^
17
19
53
19
Depth
(ft)
AS"
AS"
AST
AST
AS"
AS"
/.s
Vol ume
(ft3)
3,sra*
3,580
S-,031
3,0«G
3,041
3,a7X
3,3*0
Slump earthflow
Natural
Man-
induced
Length
(ft)
Width
(ft)
Depth
(ft)
Vo 1 ume
(ft3)
-------
WORKSHEET V.6
Estimation of soil mass movement delivered to the stream channel
(1) Watershed name
Male
Factor
(2)
Soi 1 mass movement type
Debris avalanche-
Debris flow
Natura 1
(3)
Man-induced
(4)
Slump flow
Natural
(5)
Man-inducec
(6)
1 Total volume (Vt) in ft
saso
17^05
2 Total number of failures (N)
3 Average volume per failure (VAMft
4 Number of failures per slope
cl ass
5 Number of failures per slope
position category
b1
d1
6 Total volume per slope class or
position category
(V) in ft5
V = VA x N
3^80
7 Unit weight of dry soil
material (Yd) (Ib/ft3)
V.40
-------
WORKSHEET V.6—continued
B Total weight per slope class
or position category (W)
in tons
~ 2,00(5
Wa
Wa'
Wb
Wbi
We
Wc,
wd,
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S = W x D
Da
Da-
Db
°b'
DC
DC-
Dd'
sa
Sa-
sb
sb-
t
Sdi
12 Total quantity of sediment delivered to
the stream channel in tons
3 Acceleration factor (f)
f = Tssilvicultural actlvlty/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed sllvi-
cultural activity (TS) In tons
Tssilvlcultural activity = TSnatural x f
/fc3
—
—
/
smooth
O.tl
—
—
/
lol
—
—
/
lol
CK
3
-------
NUMBER OF SOIL MASS MOVEMENTS
BY SLOPE CLASS OR
POSITION CATEGORY
The soil mass movement recorded previously by
type and cause must be differentiated by slope
class or category. Debris avalanches-debris flows
are differentiated by slope class which is based
upon slope steepness. There are three classes: a is
greater than 35° (70%), b is less than 35° (70%),
and greater than 28° (53%), and c is less than 28°
(53rc). Slump-earthflows are differentiated by
position on the slope. There are four position
categories: a' is adjacent to the stream, b' is the
lower 1/3 of the slope, c' is the middle 1/3 of the
slope, and d' is the upper 1/3 of the slope. This in-
formation is recorded on worksheet V.6, step 4 for
slope classes and step 5 for slope position
categories.
TOTAL VOLUME RELEASED BY
SLOPE CLASS OR POSITION CATEGORY
For both the proposed silvicultural activity area
and the area previously subjected to a silvicultural
activity, the total volume of soil mass movement
(Vt) by type and slope class (a,b,c) or position
category (a',b',c',d') is computed. The average
volume per failure (VA) is multiplied by the
number of failures in each slope class (a,b,c) or
position category (a',b',c',d') and recorded on
worksheet V.6, step 6. For example, if the average
volume per failure (VA) was equal to 3,441 ft3 (162
m3) and there were two debris avalanches-debris
flows in the 28° to 35° slope class (b), the total
volume for that soil mass movement type and slope
class (b) would equal 6,882 ft3 (324 m3) or 3,441 ft3
X 2 = 6,882 ft3.
sessed area for this determination if possible.
Otherwise, use the values for typical soils provided
in table V.9. For example, the soil was measured,
the dry unit weight was 99 lb/ft3 (1.57 g/cm3). The
dry unit weight of soil material is recorded on
worksheet V.6, step 7.
Table V.9—Unit weight of typical soils in the natural state
(Terzaghi 1953)
Unit weight
Description
Uniform sand, loose
Uniform sand, dense
Mixed-grained sand, loose
Mixed-grained sand, dense
Glacial till
V
lb/ft3
90
109
99
116
132
Td
g/cm3
1.43
1.75
1.59
1.86
2.12
= unit weight in dry state.
COMPUTE TOTAL WEIGHT RELEASED
PER SLOPE CLASS OR CATEGORY
Estimate the total weight of material (W)
released per slope class (a,b,c) or category
(a',b',c',d'). For the previously disturbed site (that
area subjected to a past silvicultural activity), dif-
ferentiate between natural and man-induced
failures. For example, if the dry unit weight was 99
lb/ft3 and the total volume released by debris
avalanche-debris flow with a slope class of 28° to
35° was 6,882 ft3, the total weight released for this
slope class would be 681,318 Ib or 6,882 ft3 X 99
lb/ft3 = 681,318 Ib. This is converted to tons by
dividing by 2,000 Ib/ton or 681,318 Ib divided by
2,000 Ib/ton = 341 tons (309 metric tons). These
values are recorded on worksheet V.6, step 8, by
slope class (a,b,c) or position category (a',b',c',d'),
type of mass movement, and for the previously dis-
turbed site, natural vs. man-induced failures.
ESTIMATED DRY UNIT
WEIGHT OF SOIL MASS MOVEMENT
SLOPE IRREGULARITY BY
SLOPE CLASS OR POSITION CATEGORY
Estimate the dry unit weight (7d) of the soil
materials included in the failures (V), expressed in
pounds/cubic foot. Use soil samples from the as
Estimate, by slope class (a,b,c) or position
category (a',b',c',d'), the gross irregularity of the
slope within the area of the proposed silvicultural
V.42
-------
activity and the area of the past silvicultural ac-
tivity. Two general classifications are used: smooth
and irregular. Smooth slopes generally have a uni-
form profile with a few major breaks or benches
which may serve to trap and collect soil mass
movement material. Incipient drainage depres-
sions and intermittent drainages have a constant
grade and lead directly to main drainage channels.
Irregular slopes generally have an uneven profile
with frequent benching or breaks, which tend to
trap and collect soil mass movement material. In-
cipient drainage depressions and intermittent
drainageways have an uneven grade with frequent
grade flattening and changes in direction. The clas-
sification is recorded on worksheet V.6, step 9.
ESTIMATE DELIVERY POTENTIAL
Determine the percentage of soil mass movement
material delivered (D) to the stream channel. An
estimated delivery relationship is presented in
figure V.ll, for debris avalanches-debris flows, and
is based upon the slope class (a,b,c) and ir-
regularity. An estimated delivery relationship is
presented in figure V.12 for slump-earthflows and
is based upon the slope position category
(a',b',c',d'). Delivery in percent, is recorded on
worksheet V.6, step 10. For example, the delivery
potential of a debris avalanche-debris flow on a
smooth 29° (55%) slope is 30%.
I I I
20 25 28 30
DEGREES
35
I
40
I
45
Figure V.11—Delivery potential of debris avalanche-debris flow material to closest stream.
V.43
-------
g
H
CO
LU
CL
O
_l
co
Ridgetop
d' upper 1/3 —
c' middle Vz —
b' lower 1/3 —i
a' Stream adjacent
slope
80 90 100
PERCENT DELIVERY
Figure V.12—Delivery potential of slump-earthflow material to closest stream.
ESTIMATE TOTAL QUANTITY OF SOIL
DELIVERED PER SLOPE CLASS OR POSITION
CATEGORY AND TOTAL AMOUNT
Determine the estimated quantity of soil mass
movement material delivered to the stream chan-
nel (S) for each slope class (a,b,c) or position
category (a',b',c',d'). For the area subjected to the
past silvicultural activity, separate by natural vs.
man-induced. The quantity of soil mass movement
material delivered to a stream (S) is computed by
multiplying the estimated total weight of released
soil material (W) by the delivery potential (D) ex-
pressed as a decimal percent. This should be done
for each slope class or position category. For exam-
ple, if the total weight of a released debris
avalanche-debris flow with a slope class of 28° to
35° class(6) was 341 tons, and the delivery poten-
tial was 30 percent, the amount of material
delivered to a stream channel would be 102 tons or
341 tons X 0.3 decimal percent. These values are
recorded in worksheet V.6, step 11. The total quan-
tity of soil mass movement material (TS) delivered
to the stream channel is computed by summing the
material delivered by each slope class (a,b,c) or
position category (a',b',c',d'). The total quantity
delivered is recorded on worksheet V.6, step 12. For
example, if the slope classes (a,b,c) for debris
avalanche-debris flow had the following values: Sa
= 171 tons, Sb = 102 tons, and Sc = 26 tons, the
total quantity of material delivered to the stream
channel by debris avalanche-debris flows would be
equal to 299 tons. If slump-earthflows were present
or possible, these values (a',b',c',d') would also be
summed and added to the debris avalanche-debris
flow value to get the quantity of total sediment
delivered to the stream (TS).
The computation provides an estimate of the
average total volume of material delivered to the
stream channel (TS) in the area of proposed
silvicultural activities under natural conditions
and can be used directly in "Chapter VI: Total
Potential Sediment."
V.44
-------
ESTIMATE AN ACCELERATION
FACTOR TO ACCOUNT FOR THE
INCREASED DELIVERY DUE TO
THE SILVICULTURAL ACTIVITY
(MAN-INDUCED)
Estimate the change in sediment delivery to the
stream channel on the previously disturbed area as
a result of all silvicultural activities by comparing
quantities and delivery rates for both natural and
man-induced failures. The acceleration factor (f) is
estimated by dividing the total quantity of soil
delivered to the stream channel due to silvicultural
activities (man-induced) (TS silvicultural activity)
by that due to natural causes (TS natural), record
on worksheet V.6, step 13. For example, if the
quantity of soil delivered due to silvicultural ac-
tivities was 299 tons and that delivered due to
natural cause was 101 tons, the acceleration factor
(f) would be 3.0. The acceleration factor is recorded
on worksheet V.6, step 13. Note total from both
natural and man-induced failures would be equal
to 299 tons (silvicultural activity) plus 101 tons
(natural) or 400 tons.
ESTIMATE INCREASED SOIL
DELIVERY DUE TO THE PROPOSED
SILVICULTURAL ACTIVITY
Estimate the increase in amount of soil mass
movement material that would be delivered from
the area being considered for the proposed
silvicultural activity. The total quantity of soil
mass movement material (TS) delivered to the
stream channel (natural conditions) is multiplied
by the acceleration factor (f) estimated from a site
previously subjected to similar silvicultural ac-
tivity, record on worksheet V.6, step 14. For exam-
ple, if the existing natural condition delivered a
total quantity of soil mass movement material to
the stream channel of 64 tons and the acceleration
factor estimated from a similar site subjected to a
similar silvicultural activity was 3.0, the estimated
potential soil mass movement material delivered to
the stream channel would be equal to 192 tons.
This completes the procedure for determining in-
creased soil delivery.
V.45
-------
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
Relating magnitude of management impact to
hazard index ranking has the shortcoming that
once a site is ranked as high hazard, alternate
management practices do not change the estimate
of management impact. Where data permit, quan-
tification of hazard index should be set up so that
management-caused changes in hazard index are
directly proportional to degree of accelerated ero-
sion. Such a system would permit realistic assess-
ment of various management alternatives on the
mass erosion rate. However, additional studies are
needed to quantify the impact of numerous
silvicultural activities.
CONCLUSIONS
This procedure is designed to quantify the poten-
tial volume of soil mass movement material that is
delivered to the closest drainageway as a result of a
proposed silvicultural activity. The analysis is con-
ducted on areas that have previously been
delineated as unstable. It should be reemphasized
that if the user does not have experience in
delineating unstable or potentially unstable areas,
additional assistance from qualified specialists
should be obtained.
V.46
-------
LITERATURE CITED
Bailey, R.G. 1971. Land hazards related to land-
use planning in Teton National Forest, Wyom-
ing. USDA For. Serv. Rep., Intermt. Reg., 131 p.
Bailey, R.G. 1974. Land-capacity classification of
the Lake Tahoe Basin, California-Nevada: A
guide for planning. USDA For. Serv., S. Lake
Tahoe, Calif. 32 p.
Bell, J.R. and Q.R. Keener. 1977. An investigation
of the feasibility of a cutbank slope design based
on the analysis of natural slopes. Rep. to USDA
For. Serv., Pac. Northwest For. and Range Exp.
Stn., Portland, Oreg. 113 p.
Bell, J.R. and D.N. Swanston. 1972. A broad
perspective to investigate the marked increases
in occurrence of debris avalanches and debris
torrents on recently clearcut slopes of igneous in-
trusive bodies in the Coastal Mountains of
northern California and southern Oregon. Report
on file with USDA For. Serv., Pac. Northwest
For. and Range Exp. Stn., Portland, Oreg. 20 p.
Bjerrum, L. 1967. Progressive failure in slopes of
overconsolidated plastic clay and clay shales. J.
Soil Mech. and Found. Eng. Div., ASCE., Vol.
93, p. 1-49.
Brown, C.B. and M.S. Sheu. 1975. Effects of
deforestation on slopes. J. Geotech. Eng. Div.
ASCE GTZ: 147-165.
Burroughs, E.R., G.R. Chalfant, and M.A. Town-
send. 1976. Slope stability in road construction.
USDIBur. Land Manage., Portland, Oreg. 102 p.
Burroughs, E.R. and B.R. Thomas. 1977. Declining
root strength in Douglas-fir after felling as a fac-
tor in slope stability. USDA For. Serv. Res.
Pap.INT-190. 27 p. Intermt. For. and Range
Exp. Stn., Ogden, Utah.
Carson, M.A. and J.J. Kirkby. 1972. Hillslope form
and process. Cambridge Press, London. 475 p.
Colman, S.M. 1973. The history of mass movement
processes in the Redwood Creek basin, Hum-
boldt County, Calif. M.S. thesis, University
Park, Penn. State Univ., 151 p.
Culling, W.E.H. 1963. Soil creep and the develop-
ment of hillside slopes. J. Geol., 71: 127-161.
Fiksdal, A.J. 1974. A landslide survey of the Ste-
qualeho Creek watershed. Supplement to Final
Report FRI-UW-7404, Fish. Res. Inst., Univ. of
Wash., Seattle, 8 p.
Flaccus, E. 1958. White Mountain landslides. Ap-
palachia. 32: 175-191.
Fredriksen, R.L. 1963. A case history of a mud and
rock slide on an experimental watershed. U.S.
For. Serv. Res. NotePNW-1, 4 p. Pac. Northwest
For. and Range Exp. Stn., Portland, Oreg.
Fredriksen, R.L. 1965. Christmas storm damage on
the H.J. Andrews Experimental Forest. U.S. For.
Serv. Res. Note PNW-29, 11 p. Pac. Northwest
For. and Range Exp. Stn., Portland, Oreg.
Froehlich, H.A. 1973. Natural and man-caused
slash in headwater streams. Loggers Handbk.,
Vol. 33, 8 p.
Greswell, S., D. Heller and D.N. Swanston. 1978.
(In press) Mass movement response to forest
management in the central Oregon Coast Range,
USDA For. Serv. Gen. Tech. Rep., Pac.
Northwest For. and Range Exp. Stn., Portland,
Oreg.
Goldstein, M. and G. Ter-Stepanian. 1957. The
long-term strength of clays and deep creep of
slopes. Proc. 4th Int. Conf. of Soil Mech. and
Found. Eng., 2: 311-314.
Gray, D. H. 1970. Effects of forest clearcutting on
the stability of natural slopes. Assoc. Eng. Geol.
Bull., 7:45-67.
Hack, J. T. and J. C. Goodlett. 1969. Geomor-
phology and forest ecology of a mountain region
in the central Appalachians. U.S. Geol. Surv.
Prof. Pap. 347. 66 p.
Haefeli, R. 1965. Creep and progressive failure in
snow, soil, rock and ice. 6th Int. Conf. on Soil
Mech. and Found. Eng., 3:134-148.
Harr, R. Dennis, Warren C. Harper, James T.
Krygier, and Frederic S. Hsieh. 1975. Changes in
storm hydrographs after roadbuilding and clear-
cutting in the Oregon Coast Range. Water
Resour. Res. ll(3):436-444.
V.47
-------
Kelsey, H. M. 1977. Landsliding, channel changes,
sediment yield, and land use in the Van Duzen
River Basin, North Coastal California, 1941-
1975. Ph.D. thesis, Univ. Calif. Santa Cruz.
370 p.
Klock, G. 0. and J. D. Helvey, 1976. Debris flows
following wildfire in north 'central Washington.
In Proc. Third Inter-Agency Sediment Conf.
Symp. 1, Sediment Yields and Sources. Water
Com. p. 91-98.
Kojan, E. P. 1973. Fox unit study area, Six Rivers
National Forest. Del Norte County, Calif. Report
on file, USDA For. Serv., Geotech and Mat. Eng.
Pleasant Hill, Calif. 50 p.
Kojan, E., G. T. Foggin, and R. M. Rice. 1972.
Prediction and analysis of debris slide incidence
by photogrammetry, Santa Ynez-San Rafael
Mountains, Calif., Proc. 24th Int. Geol. Cong.
Sect. 13, p. 124-131.
Megahan, W. F. 1972. Logging, erosion,
sedimentation-are they dirty words? J. For. 70:
403-407.
Megahan, W. F. and W. J. Kidd. 1972a. Effect of
logging roads on sediment production rates in the
Idaho Batholith. USDA For. Serv. Res. Pap.
INT-123. 14 p. Intermt. For. and Range Exp.
Sta., Ogden, Utah.
Megahan, W. F. and W. J. Kidd. 1972b. Effects of
logging and logging roads on erosion and sedi-
ment deposition from steep terrain. J. For.
70:136-141.
Morrison, P. H. 1975. Ecological and geo-
morphological consequences of mass movements
in the Alder Creek watershed and implications
for forest land management. B.A. thesis, Univ. of
Oreg., Eugene, 102 p.
O'Loughlin, C. L. 1972. An investigation of the
stability of the steepland forest soils in the Coast
Mountains, southwest British Columbia. Ph.D.
thesis, Univ. Vancouver, 147 p.
Pillsbury, N. H. 1976. A system for landslide
evaluation on igneous terrain. Ph.D. thesis, Colo.
State Univ., Fort Collins, 109 p.
Prellwitz, R. W. 1977. Simplified slope design for
low standard roads in mountainous areas. Report
on file, USDA For. Serv., Reg. 1, Missoula,
Mont. 20 p.
Rothacher, Jack. 1959. How much debris down the
drainage. Timberman. 60: 75-76.
Rothacher, Jack. 1971. Regimes of streamflow and
their modification by logging, In Forest land uses
and the stream environment. J. T. Krygier and
J. D. Hall, eds. Oreg. State Univ., Corvallis, p.
40-54.
Rothacher, Jack. 1973. Does harvest in west slope
Douglas-fir increase peak discharge in small
forest streams? USDA For. Serv. Res. Pap.
PNW-163, 13 p. Pac. Northwest For. and Range
Exp. Sta., Portland, Oreg.
Saito, M. and H. Uezawa. 1961. Failure of soil due
to creep. Proc. 5th Int. Conf. on Soil Mech. and
Found. Eng. 1: 315-318.
Simons, D. B. and T. J. Ward. 1976. Landslide
potential delineation. Report CER75-76DBS-
TJW23. Eng. Res. Cent., Colo. State Univ., Fort
Collins. 188 p.
Swanson, F.J., D. N. Swanston, C.T. Dryness, and
others. 1973. A conceptual model of soil mass
movement, surface soil erosion, and stream
channel erosion processes. US/Int. Bio. Program.
Conif. For. Biome, Univ. of Wash., Seattle.
Intern. Rep. 72. 19p.
Swanson, Frederick J. and Michael E. James. 1975.
Geology and geomorphology of the H. J. Andrews
Experimental Forest, western Cascades, Oregon.
USDA For. Serv. Res. Pap. PNW-188. 14 p. Pac.
Northwest For. and Range Exp. Sta., Portland,
Oreg.
Swanson, Frederick J., George W. Lienkaemper,
and James R. Sedell. 1976. History, physical ef-
fects, and management implications of large
organic debris in western Oregon streams. USDA
For. Serv. Gen. Tech. Rep. PNW-56. 15 p. Pac.
Northwest For. and Range Exp. Stn., Portland,
Oreg.
Swanson, Frederick J., M. M. Swanson, and C.
Woods. 1977. Inventory of mass erosion in the
Mapleton Ranger Dist. Siuslaw National Forest.
Unpub. Rep. on file, For. Sci. Lab., Pac.
Northwest For. and Range Exp. Stn., Corvallis,
Oreg. 61 p.
V.48
-------
Swanston, Douglas N. 1972. Results of mass ero-
sion hazard investigation. In: Geophysical
hazards investigation for the city and borough of
Juneau, Alaska. Summary Rep. Daniel, Mass,
Johnson, and Mendenhall Consult. Portland,
Oreg. 92 p.
Swanston, Douglas N. 1973. Judging landslide
potential in glaciated valleys of southeastern
Alaska. Explor.J.LI (4):214-217.
Swanston, Douglas N. 1974a. The forest ecosystem
of southeast Alaska. USDA For. Serv. Gen.
Tech. Rep. PNW-17. 22 p. Pac. Northwest For.
and Range Exp. Stn., Portland, Oreg.
Swanston, Douglas N. 1974b. Slope stability
problems associated with timber harvesting in
mountainous regions of the western United
States. USDA For. Ser. Gen. Tech. Rep. PNW-
21. 14 p. Pac. Northwest For. and Range Exp.
Stn., Portland, Oreg.
Swanston, Douglas N. 1976. Erosion processes and
control methods in North America. XVIIUFRO
World Cong. Proc. Div. I, p. 251-275.
Swanston, Douglas N. and Frederick J. Swanson.
1976. Timber harvesting, mass erosion and steep
land geomorphology in the Pacific Northwest. In
Geomorphology and engineering, p. 199-221.
Donald R. Coates, ed. Dowden, Hutchinson &
Ross, Inc. Stroudsburg, Pa.
Ter-Stepanian, G. 1963. On the long-term stability
of slopes. Norwegian Geotech. Inst., Publ. 52, p.
1-15.
Terzaghi, K. 1950. Mechanism of landslides In:
Application of geology for Engineering Practice.
Geo. Soc. Am. Berkey Vol. p. 83-123.
Terzaghi, K. 1953. Some miscellaneous notes on
creep. Proc. 3rd Int. Conf. Soil Mech. and
Found. Eng. 3:205-206.
Terzaghi, K. and R. B. Peck. 1960. Soil mechanics
in engineering practice. John Wiley and Sons,
Inc. N.Y. 566 p.
Varnes, D. J. 1958. Landslide types and processes.
In: Landslides and engineering practice. Eckel,
E.B., ed. Wash., D.C., Highway Res. Bd. Spec.
Publ. 29. p. 20-47.
Williams, G. P. and H. P. Guy. 1973. Erosional and
depositional aspects of hurricane Camille in
Virginia, 1969. U.S. Geol. Surv. Prof. Pap. 804.
80 p.
Wilson, S. D. 1970. Observational data on ground
movements related to slope stability. J. Soil
Mech. and Found. Eng. Div., Am. Soc. Civil
Eng. 96:1521-1544.
Zaruba, Q., and V. Mencl. 1969. Landslides and
their control. Elsevier Publishing Co., Inc., N.Y.
205 p.
V.49
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Chapter VI
TOTAL POTENTIAL SEDIMENT
this chapter was prepared by:
David L. Rosgen
with major contributions from:
Kerry L. Knapp
Walter F. Megahan
VLi
-------
CONTENTS
Page
INTRODUCTION VI. 1
DISCUSSION VI.3
STREAM CHANNEL MORPHOLOGY AND WATER QUALITY VI.3
Suspended Sediment VI.4
Interpretations Of Sediment Rating Curves VI.7
Time Series Analysis-Recovery VI.7
Turbidity VI.9
Bedload Determination VI.9
Evaluation Of Bedload Discharge Using Bedload Rating Curves VI.9
Effects Of Bedload Changes On Stream Channels And Sediment
Discharge VI.9
Effects Of Direct Channel Impacts On Bedload Sediment Discharge . VI.11
Effects Of Sediment Supply Changes And Stream Power Reductions On
Stream Channels VI.11
THE PROCEDURE VI.13
DETAILED ANALYSIS PROCEDURE VI.13
Suspended Sediment VI.17
Bedload Calculation VI.21
Total Sediment VI.26
LITERATURE CITED VI.31
APPENDIX VI.A: EXAMPLES OF CHANNEL STABILITY RATINGS .... VI.33
APPENDIX VLB: RELATIONSHIPS BETWEEN SEDIMENT RATING
CURVES AND CHANNEL STABILITY VI.39
APPENDIX VI.C: TIME SERIES ANALYSIS-RECOVERY PROCEDURE .. VI.43
VLii
-------
LIST OF EQUATIONS
Equation Page
VI. 1. log Y = b + n log Q VI. 17
VI.2. Spre= (Qpre) (C) (K) (T) VI.18
VI.3. Sp0it= (Qpo.,) (C) (K) (T) VI.18
VI.4. SMX= (CMX) (Qpre) (T) (K) VI.21
VI.5. logBs= b + nlogQ VI.22
VI.6. Bpre= (ibpre) (T) (K) VI.22
VI.7. Bpost= (ibpos() (T) (K) VI.26
VI.8. logi^a + blog,, VI.27
VI.9. log Q = 0.366 + 1.33 log A + 0.005 log S - 0.056 (log S)2 VI.30
VI.C.l. Y* = (b*e-Yt) (Q)
-------
LIST OF FIGURES
Number Pase
VI. 1. —Diagrammatic relationship of a stable channel balance VI.2
VI.2. —Relationships of sediment rate and size to supply rate and transport
capability VI.3
VI.3. —Sediment rating curves for streams in western Wyoming VI.5
VI.4. —Sediment rating curve for Needle Branch Creek, Oregon, 1964-1965
water year VI.6
VI.5. —Change in the sediment rating curve for the Eel River VI.7
VI.6. —Change in sediment rating curves of Needle Branch Creek VI.8
VI.7. —Bedload rating curve, central Idaho stream VI. 10
VI.8. —Relationship of bedload transport and stream power VI. 12
VI.9. —Procedural flow chart for estimating potential changes in total sedi-
ment discharge VI. 14
Vl.lOa.—Typical hydrograph VI.17
Vl.lOb.—Flow duration curve VI.17
VI.11. —Representative sediment sampling distribution VI.17
VI.12. —Sediment rating curve VI.17
VI.13. —Sediment rating curve for H.J. Andrews Stream 1 VI.19
VI.14. —Use of a constant maximum limit for sediment concentration compared
to sediment rating curve VI.21
VI. 15. —Relationship of sediment rating curves to stream channel stability
ratings, Region 1, USFS VI.22
VI.A.l. —Stream channels indicative of a stable channel due to resistant bed
and bank materials VI.33
VI.A.2. —Stream channels indicative of a stable channel due to resistant bed
and bank materials VI.33
VI.A.3.-VI.A.5.—Stream channels indicative of stable channel due to resistant
bed and bank materials VI.34
VI.A.6.-VI.A.8.—Highly unstable channels or channels having poor stability
ratings are generally associated with easily detached bank
and bed material where channel erosion is significant VI.35
VI.A.9. —Stability and associated sediment supply affected by organic
debris VI.36
VI.A.10.—Stability and associated sediment supply affected by organic
debris VI.36
VI.A.ll.—Changes in stability due to increases in sediment supply from road
crossings VI.37
VI.A.12.—Soil mass movement, due to debris avalanche processes, deliver exces-
sive amounts of sediment to the stream VI 37
VI.A.13.—Soil mass movement, due to slump-earthflow processes, deliver exces-
sive amounts of sediment to the stream VI.38
VLiv
-------
VI.B.l. —Relationship of sediment rating curves to stream channel stability
ratings, Region 1, USFS VI.39
VLB.2. —Relationship of channel stability ratings to sediment rating curves in
the Redwood Creek drainage VI.40
VI.B.3. —Relationship of channel stability ratings to sediment rating curves for
streams in the central Rocky Mountain region VI.41
VI.v
-------
LIST OF WORKSHEETS
Number Page
VI. 1.—Suspended sediment quantification VI.20
VI.2.—Bedload sediment quantification VI.23
VI.3.—Sediment prediction worksheet summary VI.24
VI.4.—Bedload transport-stream power relationship VT.28
VI.5.—Computations for step 21 VI.29
Vl.vi
-------
INTRODUCTION
One of the most significant and frequent water
quality changes resulting from silvicultural ac-
tivities is accelerated, inorganic sediment dis-
charge. Land and stream systems are constantly
adjusting to changes in the erosional rates of slopes
and the transport capabilities of the stream
systems draining those slopes. Silvicultural ac-
tivities can exponentially affect the rate of sedi-
ment discharge, depending upon the sensitivity of
the slopes and the affected stream reaches and the
degree and duration of impact.
It is difficult to predict absolute changes because
of the time-space variability inherent in stream
systems; however, several consistent analytical
relationships involving the prediction of sediment
supply and transport are available. These
relationships can be used to estimate relative
amounts of change in potential sediment discharge
resulting from proposed silvicultural activities.
VI.l
-------
_mm
.01 FINE
Feet per ml.
FLAT .
STEEP
STREAM SLOPE
to
• • • •
/0oNXt I v»V&0
• ^<^ • 4- • ,^^ -
3n~^L_ T \^^*^
OEGRAOATION
AGGRADATION
(Sediment Load) x (Sediment Size)
Cxr
(Stream Slope) x (Stream Discharge)
Figure VI.1.—Diagrammatic relationship of a stable channel balance (Lane 1955).
-------
DISCUSSION
In most cases, sediment objectives are stated in
terms of acceptable increases in suspended sedi-
ment based on state and federal laws and physical
site conditions. The analysis procedure estimates
the amount of potential change in suspended sedi-
ment discharge and bedload sediment discharge as
well as qualitative effects on channel stability.
Evaluation of potential sediment changes re-
quires use of analytical procedures to make a con-
sistent comparative analysis of baseline and ac-
celerated levels. The procedures outlined in this
handbook are not designed to predict absolute
values obtained for any given year. They do
however relate to the potential changes in the
physical processes, as affected by silvicultural ac-
tivities. The interpretation made from the results
of theses analyses requires a great deal of profes-
sional judgment.
STREAM CHANNEL MORPHOLOGY
AND WATER QUALITY
Streams are dynamic systems where configura-
tions are adjusted in response to eight interrelated
variables — width, depth, gradient, velocity,
roughness of bed and bank materials, discharge,
concentration of sediment, and size of sediment
debris (Leopold and others 1964). A change in one
or more of the eight noted variables produces
changes in channel processes with a net effect of
either aggradation or degradation. However, a
counteractive change occurs over time in the other
variables to prevent continued stream aggradation
or degradation (Shen 1976).
When a stream system is in a state of dynamic
equilibrium, the eroded material supplied to and
stored in the stream is balanced with the energy
available to transport the material. As changes af-
fect sediment supply and stream energy, the chan-
nel system undergoes a series of adjustments and is
in disequilibrium. Under wildland watershed con-
ditions, dynamic equilibrium is not a steady state
from year to year, and annual variations in scour or
deposition may occur. These channel adjustments
not only affect channel stability, but generally
result in significant changes in sediment discharge.
Lane (1955) diagrams a stability relationship
between sediment supply and stream energy (fig.
VI.1), indicating stream slope and discharge
(energy) are proportional to sediment load and
sediment size (supply). Process changes which af-
fect stream slope, stream discharge, sediment size
and concentration may create unstable conditions
which can result in stream channel aggradation
and/or degradation.
Shen and Li (1976) describe a relationship where
sediment discharge is a function of the supply rate
and transport capability of various sized particles
under a particular flow regime (fig. VI.2).
"Washload" is that portion of the suspended load
which is 0.0625 mm or smaller (silts and clays).
(FOR A PARTICULAR RIVER AND A
PARTICULAR FLOW CONDITION ONLY)
TOTAL
SEDIMENT
TRANSPORT
WASH
LOAD
dx
SEDIMENT SIZE (dx = 0.0625mm)
Figure VI.2.—Relationships of sediment rate and size to sup-
ply rate and transport capability (Shen and Li 1976).
Man-caused changes in channel process include
increased debris, constrictions due to road fill
encroachments, stream crossings, alterations in
streamflow amounts and timing through vegeta-
tion modifications, introduced sediment, and
direct channel alterations. These impacts affect
the rate and magnitude of channel adjustments
and may affect channel erosion through lateral
channel migration, change in bed form, and other
morphological changes. Such changes are
VI.3
-------
ultimately expressed as differences in sediment
concentration per unit discharge and as changes in
bedload transport.
The ability of streams to adjust to imposed
changes varies with the type of bed and bank
materials, the stability of the landform in which
the stream is incised, the amount and size of sedi-
ment in the channel, the hydraulic geometry of the
channel, and the runoff characteristics of the
watershed.
Stream channels reflect the current watershed
condition. The stability of natural channels varies
by geomorphic province and by reach within the
same watershed. The ability to interpret this
variance in stability is important when assessing
sediment discharge influenced by channel
processes. A stability evaluation provides a consis-
tent analytical comparison of stability between
stream reaches within a given region and is a
reproducible method of assessing channel
characteristics. Stability evaluations (Pfankuch
1975) examine primarily: (1) detachability of bank
and bed materials, (2) availability or supply of
sediment as a function of degree of entrenchment,
stored sediment, and landform adjacent to the
stream, (3) direct impacts on the channel, and (4)
energy forces available. Examples of streams with
various stability ratings are provided in appendix
VI. A.
Suspended Sediment
Suspended sediment is defined as that portion of
the total sediment load in transit under varying
flow regimes that is measured using depth-
integrated samplers (DH-48, DS-49, 59) as
described by Guy and Norman (1970). This
procedure, utilizing the equal transit rate method,
requires a continuous sample taken from the water
surface to within 3 inches of the stream bed. Sedi-
ment size generally includes sands or smaller, but a
specified size is not always predictable due to
changes in stream velocities.
Suspended sediment from stream channel ero-
sion is the major contributor to total annual sedi-
ment discharge in some streams draining forested
watersheds (Anderson 1975, Striffler 1963, Rosgen
1973, Flaxman 1975, and Piest and others 1975).
The sediment rating curve has been developed and
used for analyzing sediment discharge for the past
40 years. A sediment rating curve is derived from
values of measured suspended sediment, in mil-
ligrams/liter, correlated with stream discharge
(cfs). Sediment rating curves represent changes in
sediment supply and stream channel adjustments
associated with the accelerated sediment introduc-
tion.
Recent applications and interpretations of the
sediment rating curve approach have been used in
management applications (Flaxman 1975 and
Rosgen 1975a). This latter interpretation of the
sediment rating curve technique is presented for
use in this chapter. The sediment rating curve ap-
proach involves depth-integrated sampling for
suspended sediment over a wide range of climatic
situations and representative flows. Examples of
typical sediment rating curves are shown in figures
VI.3 and VI.4.
Most of the annual sediment discharge results
from streamflow that generally occurs less than 10
percent of the time. Since streamflow is the
primary variable associated with stream energy,
changes in flow amounts or timing directly in-
fluence sediment discharge. Although flows vary
from year to year, time-dependent plots generally
are not evaluated because long-term records are re-
quired. However, flow-dependent analysis can be
made based on representative flows monitored over
a water year (October 1 through September 30),
where variables affecting sediment concentrations
are determined concurrently with stream dis-
charge. Sampling "representative flows" involves
collection of suspended sediment during various
flow and seasonal conditions to detect any
variability in concentration for the same flow dur-
ing a water year. Significant variability can be
analyzed separately. Sampling intensity depends
on flow variation and anticipated supply changes.
Minimum sampling stratification for the develop-
ment of sediment rating curves is shown in step 3 of
the procedure.
If the representative flows cannot be sampled to
establish a sediment rating curve, continued
monitoring into the next water year may be re-
quired. The reliability of the procedure may be
reduced if representative flows, as defined, are not
sampled.
The many research efforts utilizing the sediment
rating curve approach are summarized in the
USFS-EPA "Non-Point Water Quality Modeling,
Wildland Management" (1977). Flaxman (1975)
used this approach to determine the amount of
channel erosion attributable to man's activities.
Applications by Fames (1975) were designed to
VI.4
-------
identify changes in sediment discharge as a result
of upstream changes in land use on selected
watersheds in Montana. The technique is presently
used as a portion of the analytical prediction
techniques for determining potential changes in
sediment due to timber harvest on some national
forests in Montana and Idaho (USDA Forest Ser-
vice 1975).
10000
100.0 200.0
STREAM DISCHARGE, (cfsj
Figure VI.3—Sediment rating curves for stream* In western Wyoming (Holstrom 1976).
VI.5
-------
onnn
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E,
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1 1 1
5
^ — 1
8 1
CO
Q
LU
Q
Z onn
Q.
CO
CO
100
1.0
t
•
/
•/
/
•
•
V
/
/•
•
•
/
/
•
•
•
/
•
/
/
•
t
•
•/
/
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4
A
-------
Interpretations Of Sediment Rating Curves
Shifts in the sediment rating curve reflect both
natural and man-induced changes that alter the
slope and intercept of the regression equation.
These shifts indicate the dynamic nature of stream
channels.
Examples of changes in sediment rating curves
have occurred following a major flood in 1964,
which shifted the sediment rating curve a full order
of magnitude on the Eel River in northern Califor-
nia (Flaxman 1975). Thus, an increase in stream
channel sediment supply that aggraded many river
reaches resulted in major channel adjustments and
associated increased sediment discharge (fig. VI.5).
10.000-
I.
1
g
n
S
Q
5
0.
(0
10-
100
/-
uobo ioOoo
STREAM DISCHARGE, (cfs)
100)000
Figure VI.5.—Change in the sediment rating curve for the Eel
River, Scotia, Calif., showing increases in sediment con-
centration per unit discharge when flood caused a change
in sediment deposition (Flaxman 1975).
For any given flow on the Eel River following the
flood, the sediment concentration was exponen-
tially higher. Suspended sediment discharge under
post flood condition is very sensitive to flow in-
creases. Flaxman (1975) cited similar results from
channel restoration measures applied to streams
where channel erosion was a predominant source of
the total annual suspended sediment discharge.
An analysis of the effects of clearcutting on sedi-
ment rating curves was recently conducted on the
Needle Branch drainage, near the Oregon coast
(Sundeen 1977). This analysis indicated a shift of
the regression constants of the sediment rating
curve following the first year of harvest (fig. VI.6).
Even though the highest flood peaks occurred
before harvest (due to the 1964 flood), the major
shift in the sediment rating curve occurred follow-
ing timber removal. The recovery of Needle Branch
has been fairly rapid; in the second year following
clearcutting, the sediment rating curve (1967-68)
returned nearer the pre-flood condition. Under the
post-flood condition, any further change in dura-
tion of bankful stage or in magnitude of peak flows
due to timber harvesting will produce exponen-
tially higher sediment discharge. These
relationships agree closely with those suggested by
Flaxman (1975).
The sediment rating curve technique has been
used to evaluate timber sale impacts in Montana
and Idaho (Rosgen 1975a). Changes in sediment
supply were linked to individual sources when a
surveillance monitoring program was initiated to
show these "shifts" in sediment rating curves. In
many instances, the major cause for the shifts and
change in stability was associated with sediment
supply increases by roads, debris slides and in-
creases in stream discharge. Stream channel im-
pacts can be evaluated through relationships
developed between measured sediment rating
curves and stream channel stability as explained in
appendix VLB.
Time Series Analysis-Recovery
Conceptually, it is desirable to predict not only
the magnitude and direction of change in sedi-
ment rating curves, but also the time required for
the sediment rating curve to return to its pre-
disturbance position. However, it is beyond the
state-of-the-art to actually predict a post-
silvicultural activity sediment rating curve.
Despite this, it is of value to qualitatively evaluate
recovery to help interpret analysis results.
A qualitative procedure for determining the
recovery potential of streams by morphological
descriptions was developed and used in northern
Idaho (Rosgen 1975c). It evaluates recovery poten-
tial based on depth of channel to bedrock, gradient,
material size, and channel stability ratings. The
recovery period is based on the type and dates of
impact from historical records on various streams,
differing channel materials, gradients, etc. Tested
quantitative techniques for determining recovery
periods and rates at which the sediment rating
VI.7
-------
1000.0
1.0
1.0 2.0 10.0
STREAM FLOW, (c.f.s.)
1000
Figure VI.6.—Change In sediment rating curvet for Needle Branch Creek, Oregon, showing the
shift in rating curves due to 1964 flood and silviculture! operations (Sundeen 1977).
VI.8
-------
curves return to pre-silvicultural activity condi-
tions have not been developed. A technique that
may have potential application is presented in ap-
pendix VI.C. Any recovery technique should be
developed locally, because great variation can be
expected in regional relationships of recovery
response.
Turbidity
Turbidity is an optical characteristic of water
quality, whereas suspended and bedload sediment
are related to the actual rate and weight of trans-
ported inorganic soil particles. It is often possible to
establish a correlation between turbidity and
suspended sediment concentration. A relationship
can be established using regression analysis based
on local data if the analysis is: (1) conducted on the
same stream reach under a wide range of flow con-
ditions, and (2) conducted so that the turbidity
sample is also depth integrated. If significant cor-
relations can be established between the two water
quality characteristics, one may be inferred from
the other. Turbidity will not be directly analyzed in
this chapter.
Bedload Determination
Bedload is inorganic soil particles of various sizes
which are transported in contact with or near the
streambed. Bedload transport becomes a predomi-
nant factor during major runoff events, where suf-
ficient energy is available to dislodge and transport
the larger sized particles generally armored in the
streambed or supplied to the stream from the chan-
nel sides and slopes. Studies of mountain streams
in northern Idaho have shown bedload to be less
than 5 percent of mean annual total sediment dis-
charge when measured concurrently with
suspended sediment on first to third order streams
(Rosgen 1974). Emmett (1975) determined that
bedload transport for gravel bed streams in the up-
per Salmon River area was approximately 1 to 10
percent of the suspended sediment load tran-
sported. However, evaluation of the basic processes
involved in bedload transport is valuable to deter-
mine the potential changes in stream channel
stability and in associated suspended sediment
concentrations.
Numerous empirical bedload transport equa-
tions are described in the EPA-USFS "Non-Point
Water Quality Modeling Wildland Management"
(1977). However, data for validation of natural
channels and for testing these bedload transport
equations are limited; therefore, it is difficult to
convert them to quantitative expressions of water
quality.
Evaluation Of Bedload Discharge
Using Bedload Rating Curves
The procedure presented in this chapter requires
bedload sampling concurrent with suspended sedi-
ment sampling. The method for establishment of
bedload rating curves is similar to the procedure for
developing suspended sediment rating curves.
Bedload is measured from the bed surface to 3 in-
ches above the bed using a pressure differential
type sampler (Helley and Smith 1971) during
representative flows in 1 water year. An example of
a bedload rating curve is shown in figure VI.7.
The calculations utilizing the bedload rating
curve procedure are designed to:
1. Predict a quantitative change in bedload sedi-
ment discharge by comparing changes in
amounts and seasonal distribution of excess
water;
2. Determine the relative contributions of
suspended and bedload sediment;
3. Provide data to develop local bedload-stream
power relationships to assess potential stream
channel changes and resulting changes in
bedload sediment discharge.
Effects Of Bedload Changes On Stream
Channels And Sediment Discharge
The potential impact on stream channels due to
introduced sediment and/or changes in stream
power is calculated using procedures similar to
those presented by Leopold and Emmett (1976).
This requires the development of regional or local
bedload stream power relationships expressed as a
function of the size of material being transported
(fig. VI.8). At high flows, transport rates become
directly proportional to stream power, as suggested
by Bagnold (1966). This is shown in figure VI.8,
where the ratio of transport rate (ib) to unit stream
power (w) is represented as ib/w = 100%. Stream
power, as used in the proposed method, is defined
as the unit weight of water (1,000 kg/m3) times the
discharge of water (m3) per meter width over the
total stream width (m) times the gradient of the
VI.9
-------
1.0-
5
c
o
LU
O
1-1
o
CO
Q
UJ —
Q
LU
CO
qSb=.042q,
r2 = 0.91
2.09
X
X
.01
.001
.1
1
T
1.0
STREAM FLOW, (cfs)
1
1
T
10
Figure VI.7.—Bedload rating curve, central Idaho stream (Megahan 1978).
VI. 10
-------
stream (m/m) (Leopold and Emmett 1976). The in-
tegration of cross-sectional area and velocities as-
sumes rectangular banks for the calculation. To
develop this relationship, it is necessary to measure
particle size of transported material, water surface
slope, stream discharge, and stream width.
The locally derived stream power-bedload trans-
port rate relationship should be calculated using
the same principles as in the regression
relationships of suspended sediment and bedload
transport to streamflow.
The objective is to estimate the potential for
stream channel scour and/or deposition caused by
direct impacts that change the stream power
variables (surface water slope and bankful width).
Introduced potential sediment volume and particle
size from soil mass movement are qualitatively
evaluated, based on the available stream power
and related sediment transport rates under bankful
discharge.
Effects Of Direct Channel Impacts On
Bedload Sediment Discharge
Effects of silvicultural activities on the stream
power variables and associated sediment transport
can be calculated. Activities that change local sur-
face water slope, discharge, and bankful stream
width can be affected by stream channel encroach-
ment of road fills, logging debris, and stream cross-
ings. Potential changes in bedload transport are
obtained through calculations involving
relationships similar to those depicted in figure
VI.8.
Field evaluations of channel alterations resulting
from certain silvicultural activities will provide in-
formation on changes in stream width and surface
water slope as measured above versus below chan-
nel impact areas. A change in stream power (as-
suming no change in sediment supply) would result
in a direct change in bedload discharge.
Effects Of Sediment Supply Changes And
Stream Power Reductions On Stream Channels
Channel effects caused by introduced sediment
from soil mass movement may be evaluated using
the bedload transport rate-stream power
relationship on the stream reach directly below the
source. A calculation involving bankful discharge,
bankful width and surface slope determines the in-
stantaneous maximum bedload transport rate.
Sediment deposition in the channel may result if
the potential delivered soil mass movement volume
and change in particle size exceeds the maximum
potential transport rate under a given stream
power.
A calculation involving bankful discharge is
needed if extrapolation of the bedload transport
rate-stream power relationship is needed above the
third order reach. Riggs (1976) presents a
procedure for determining bankful discharge. This
approach involves a relationship between stream
slope and velocity, eliminating the need to es-
timate a roughness coefficient to obtain velocity.
The bankful stage determination uses procedures
documented by Williams (1977), where a channel
configuration indicating a bankful stage is obser-
vable on the upper limit of the "active floodplain."
A reduction in stream power caused by a debris
dam would yield lower transport rates. Assuming
no reduction in sediment availability, the dif-
ferences in sediment yield may result in local
deposition or stream aggradation. The potential for
deposition or aggradation is evaluated in the
detailed procedures recommended in this chapter.
Until such benchmark references or long-term data
can be collected and analyzed, only qualitative
predictions of stream channel changes can be
made.
VI. 11
-------
CO
E
^)
UJ
cc
O
Q.
CO
z
<
cc
H
h-
z
UJ
Q
UJ
CO
' / /
III
I I I
10'1 1 10
UNIT STREAM POWER, a. , in kg/m-s
Figure VI.8.—Relationship of bedload transport and stream power for the East Fork River, Wyom-
ing (Leopold and Emmett 1976).
VI.12
-------
THE PROCEDURE
The analysis procedure for determining potential
changes in total sediment discharge is sequentially
diagrammed in the procedural flow chart, figure
VI.9. The following stepwise procedural description
and discussion correspond with the procedural flow
chart and provide directions for completing the
analysis. Worksheets provided for the analysis are
referenced where applicable. Table VI. 1 provides a
summary of all data input required to use the total
sediment discharge procedure.
The following assumptions are inherent in this
analysis procedure:
1. No distinction will be made between material
detached from the channel banks and that
previously deposited on the streambed and
channel bars which is available for redistribu-
tion under varying flow regimes.
2. Increases in stream discharge exponentially
increase suspended sediment and bedload
sediment. Statistical relationships can be
established for sediment rating curves.
3. Suspended sediment rating curves represent
the existing relationship between sediment
availability and stream discharge for a par-
ticular stream reach and watershed area.
Temporal and spatial distribution of sedi-
ment is not addressed in this procedure. For
the purpose of this analysis, temporal and
spatial distribution of sediment is assumed to
be constant.
4. The procedure is applicable to watershed
basins of third order size.
5. The size of material delivered to streams from
surface erosion is assumed to be silt and clay
(washload) or smaller than .0625 mm.
6. All of the introduced washload sediment is
transported through individual stream
reaches (i.e., no storage is calculated, and the
stream has sufficient energy to transport this
sediment size).
7. A relationship can be developed between sedi-
ment transport rate and stream power
through measurements of stream slope, dis-
charge, bedload transport rate, and particle
size (Dso = particle size for which 50 percent
of the sediment mixture is finer).
8. Water surface slope does not change with
water surface elevation (stage).
The prediction techniques presented in the
analysis section are not recommended to replace
local data or transport prediction capability, when
they are available. The analysis provides the basic
process relationships needed for evaluation until
local data become available. A monitoring program
to measure pre- and post-silvicultural activity sedi-
ment concentrations for the various flow regimes
would help verify the sediment discharge predic-
tions. Baseline channel geometry surveys should
also be conducted to determine changes in stream
aggradation or degradation, lateral migration, or
other channel adjustments.
It is important to notice that all the calculations
through step 20 are designed to relate quan-
titatively to the potential sediment discharge at
the third order reach. Step 21 is a qualitative in-
terpretation for various reaches in the subdrainage
as affected by stream channel response to in-
troduced sediment from soil mass movement, and
channel encroachments.
DETAILED ANALYSIS PROCEDURE
Step 1. Subdrainage and Stream Reach
Characterization
Procedure: Select a representative third order
stream reach where data collection is required.
Discussion: For quantitative evaluations (steps
1-20) this stream reach will be used. For qualitative
evaluation (step 21), individual first through third
order streams will be selected.
Step 2. Determination of Pre- and Post-
Silvicultural Activity Hydrographs or
Flow Duration Curves
Procedure: Obtain the output from the
hydrologic analysis for the selected third order
drainage as outlined in chapter El. Outputs re-
quired are:
a. Potential increase in total annual water
production;
b. Seasonal distribution of water (based on 6- or
7-day averages) (figs. Vl.lOa or Vl.lOb)
represented as either hydrographs or flow
duration curves for:
VI.13
-------
PROCEDURAL STEP
COMPUTATION OR
EVALUATION
DATA
INPUT
ANALYSIS
OUTPUT
PRE-SILV. ACT!
HYDROGRAPHS
OR FLOW DURATION CURVES
POST-SILV. ACT.
HYDROGRAPHS
OR FLOW DURATION CURVES
SEDIMENT RATING
CURVES AND
CHANNEL STABILITY
BEDLOAD
RATING CURVE
POST-SILV.
ACT. POTENTIAL
SUSPENDED
SEDIMENT
DISCHARGE
CONVERT
SUSPENDED
SEDIMENT LIMITS
IN mg/1 TO
TONS/YEAR
PRE-SILV.
ACT. POTENTIAL
SUSPENDED
SEDIMENT
DISCHARGE
PRE-SILV.
ACT. POTENTIAL
BEDLOAD
DISCHARGE
POST-SILV.
ACT. POTENTIAL
BEDLOAD
DISCHARGE
TOTAL PRE-SILV. ACT. POTENTIAL
SEDIMENT DISCHARGE
(BEDLOAD AND
SUSPENDED LOAD)
INCREASE IN TOTAL
POTENTIAL SEDIMENT DISCHARGE
POST-SILV. ACT. TOTAL POTENTIAL
SEDIMENT DISCHARGE
— ALL SOURCES
Figure VI.9-Procedural (low chart for estimating potential changes in total sediment discharge.
VI.14
-------
m
SUBDRAINAGEAND
STREAM REACH CHARACTERIZATION
MB]
INTRODUCED SEDIMEN
FROM
SOIL MASS MOVEMENT
TOTAL INTRODUCED
SEDIMENT FROM
SURFACE EROSION
CHANNEL GEOMETRY>
DATA FOR
THIRD ORDER STREAM;
fl9l
POST-SILV. ACT.
CHANNEL IMPACTS
JM.
TOTAL
COARSE-SIZE
SEDIMENT FROM
SOIL MASS
MOVEMENT
BEDLOAD SEDIMENT
TRANSPORT RATE
—STREAM POWER RELATIONSHIP
QUALITATIVE DETERMINATION
|OF CHANNEL CHANGE POTENTIAL
BASED ON
INTRODUCED SEDIMENT
FROM SOIL MASS MOVEMENT
AND CHANNEL IMPACTS
COMPARE POST-SILV. ACT. TOTAL POTENTIAL
SUSPENDED SEDIMENT TO SELECTED LIMITS
'Silvicultural Activity
Figure Vl.9—continued
VI. 15
-------
Table VI.1.—Summary of input required to use the total sediment discharge procedure.
Data requirements
1234567
Procedural steps
8 9 10 11 12 13 14 15 16 17 18 19 20 21
Aerial photography
and stream reach
selection
Pre-silvicultural activity
hydrographs
Post-silvicultural activity
hydrographs
Measured suspended
sediment (mg/l)
X X X X
Measured stream
discharge (cfs)
X X X X X X
Measured bedload sediment
(tons/day)
x x
Allowable maximum sediment
concentration (from water quality
objective) (mg/l)
Fine particle size from soil mass
movement source (ch. V) (tons)
Coarse particle size from soil mass
movement source (ch. V) (tons)
Measured width from measured
third order stream discharge (ft)
x x
Surface erosion (ch. IV) (tons)
Bankful stream width (ft)
Bankful surface water slope (ft/ft)
Bankful depth (ft)
Bankful discharge (cfs)
x
x
X
X
X
Measured depth from measured
third order stream discharge (ft)
Measured surface water slope from
measured third order stream
discharge (ft/ft)
x x
Predicted change in width with
post-silvicultural activity
Predicted change in surface water
slope with post-silvicultural
activity
(1) baseline condition (pre-silvicultural ac-
tivity)
(2) existing condition (pre-silvicultural ac-
tivity)
(3) proposed condition (post-silvicultural ac-
tivity).
Discussion: Distribution estimates of excess
water both before and after silvicultural activity
are required to determine changes in both
suspended sediment and bedload discharge. If a
particular short duration stormflow response is
responsible for the majority of the sediment dis-
charge in a particular reach, a shorter duration
(less than 7-day) analysis will increase the sen-
sitivity for flow related sediment transport calcula-
tions. Thus, the user may specify a local hydrologic
evaluation, which is more accurate than the
procedures recommended.
It may be necessary to determine the hydrologic
effect of various activities on the rising and reces-
sion limbs of the hydrograph. If a hysteresis effect
is prevalent, separate analyses may be made using
the relationships established in step 3.
VI.16
-------
100-
I
DC
50-
25-
100-
Ł
o
I
LL
5
LU
IT
CO
TIME
(SELECTED INCREMENTS)
Figure VI.10a—Typical hydrograph.
Pre-silvicultural activity
Post-silvicultural activity
50-
25-
5 50 1W)
PERCENT OF TIME a Q
IS EQUALED OR EXCEEDED
Figure VI.10b.—Flow duration curve.
Note: If silvicultural activity does not increase
flow, the calculations involving post-activity flow
related suspended and bedload increases would not
be needed for the evaluation.
Suspended Sediment
Step 3. Establish Sediment Rating Curves and
Determine Stream Channel Stability
Procedure: (a) Concurrently measure suspended
sediment, and associated stream discharge over
wide variations in flow conditions for a water year
(fig. VI.11). After the data have been collected a
regression analysis should be employed to calculate
coefficient of determination and the log trans-
formed regression equation of:
log Y = b + n log Q (VI.l)
where:
log Y = logarithm of suspended sediment con-
centration (mg/1)
b = constant representing intercept of the
regression line
n = constant representing slope of the
regression line
log Q = logarithm of stream discharge (cfs or
m3/sec)
The actual data points are plotted on log-log
paper with suspended sediment in mg/1 on the Y
axis and stream discharge in cfs on the X axis. Us-
ing this data, coefficients for a regression equation
of the form indicated in equation VI.l are
calculated. The regression line is then drawn on the
figure (fig VI.12).
•2 100-
O
i 50H
ill
DC
25-
SAMPLE
POINTS
I I I I I I I I I I I
TIME (MONTHS)
Figure VI.11.—Representative sediment sampling distribu-
tion.
LJJ
100-
Q
LU
w -
Q 0) 10-
LU
G
Z
LU
O.
W
D
1-
'I
I
1 10 100 100r
STREAMFLOW (cfs)
Figure VI.12.—Sediment rating curve.
VI.17
-------
(b) Calculate the coefficient of determination
(r2) for the relationship and identify variability
(such as hysteresis effect).
(c) Determine stream channel stability rating
for the reach being evaluated (Pfankuch 1975).
Discussion: Sampling should obtain sediment
concentration for representative flows, as well as
seasons where these concentrations expect to be
varied. Sampling as a minimum for representative
flow should reflect concentrations for the following
conditions:
1. Early and/or low elevation snowmelt runoff;
2. Early versus late season stormflow runoff;
3. Rising stage for both stormflow and snowmelt
runoff;
4. Recession stage for both stormflow and
snowmelt runoff;
5. Bankful stage on higher peaks;
6. High elevation releases and/or snowmelt
peaks;
7. Base flow;
8. Events which may affect the sediment rating
curve, such as rain on snow events, short
duration-high intensity storms, or long dura-
tion storms producing sustained high flows;
9. Disturbance factors influencing sediment
supply, such as debris jams, changes in chan-
nel stability (sampled concurrently above and
below to determine influence of stored sedi-
ment, etc.), road crossings or encroachments,
and large areas of subdrainage hydrologically
altered by vegetative modifications.
If significant differences in sediment concentra-
tion result from the rising versus falling limbs of
the hydrograph or earlier storm peaks, these
relationships should be kept separate and used in
the calculation of both pre- and post-silvicultural
activity streamflow effects to more accurately
portray existing conditions. A more detailed
hydrologic evaluation would increase the curve sen-
sitivity for these conditions. Separate regression
lines may be established and used for the ap-
propriate flows when calculating pre- and post-
silvicultural activity sediment discharge (steps 4
and 5) caused by increased flow only. This requires
additional data on water yield to reflect the poten-
tial runoff response to a particular activity on
various stormflow periods and rising versus falling
limbs of the hydrograph (fig. VI. 13) (Fredriksen
1977). The two sediment rating curves then can be
applied to those respective portions of the post-
silvicultural activity hydrograph (fig. VLlOa).
Step • 4. Calculate Pre-Silvicultural Activity
Potential Suspended Sediment
Discharge
Procedure: From the pre-silvicultural activity
hydrograph (baseline + existing condition, fig.
Vl.lOa) and the sediment rating curve (fig. VI. 12),
determine sediment concentration for each 7-day
average flow condition. Worksheet VI. 1 is provided
for this calculation. The formula used in worksheet
VI.l is:
Spre= (Qpre) (C) (K) (T) (VI.2)
where:
S = pre-silvicultural activity suspended sedi-
ment discharge (tons/yr)
C = concentration of suspended sediment
(mg/1)
Q = pre-silvicultural activity streamflow (cfs
or m3/sec)
K= conversion factor 0.0027 (.0864 if
streamflow is in mVsec) (Guy and
Norman 1970)
T = duration (days)
Calculation format is provided in worksheet
VI.l, columns 2 to 4. Summarized sediment dis-
charge increments (col. 4, wksht. VI.l) is trans-
ferred to worksheet VI.3, item A. To obtain values
of C, use the pre-silvicultural activity 6- or 7-day
average flow (fig. Vl.lOa); then utilizing figure
VI. 12, sediment rating curve, read vertically to the
regression line, then horizontally where the Y axis
indicates corresponding values of suspended sedi-
ment concentrations (C). This is done for each flow
value of pre-activity discharge given a specified (6-
or 7-day) duration. Worksheet VI.l provides an ac-
counting format for these calculations.
Step 5. Calculate Post-Silvicultural Activity
Potential Suspended Sediment
Discharge
Procedure: From the post-activity hydrograph or
post-activity flow duration curve (fig. VI. 10 a or b)
and the sediment rating curve (fig. VI. 12), deter-
mine the sediment concentration for each 7-day
average flow condition. Worksheet VI.l is provided
for this calculation. The formula that is used in
worksheet VI.l is the same as that in step 4, except
that post-activity values for flow are used.
Spost = (Qpost) (0 (T) (VI-3)
where:
S t = post-activity suspended sediment dis-
charge due to flow increase
VI.18
-------
•n
=r.<5'
5 c
§<
Q. Ik
» u
" 1
» j?
Si
< 3
I|
P'
3 O
i|
-------
WORKSHEET VI.1
Suspended sed imerit quant i f icat ion for
8
(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days
(b)
Number
of
days
pre-
si Ivi-
cultural
act i v i ty
(c)
Number
of
days
post-
si Ivi-
cu Itural
activity
(21
Pre-
si Ivi-
cultural
act i v i ty
flow
(cfs)
(3)
Sus-
pended
sediment
concen-
trat ion
(mg/l )
(4)
Total increment
suspended
sed iment
cols. (2) x (3)
x (1 .b) x .0027
(tons)
(5)
Post-
si Ivi-
cu Itural
activity
flow
(cfs)
(6)
Sus-
pended
sediment
concen-
trat ion
(mg/l)
(7)
Total increment
post-si Iv leu Itural
activity suspended
sediment
cols. (5) x (6) x
(l.c) x .0027
(tons)
(8)
Maximum
concentra-
tions from
selected
water qua 1 Ity
object I ve
(mg/l )
(9)
Maximum
sediment
discharge
cols. (2) x
(8) x (l.b)
x .0027
(tons)
(Totals are rounded to nearest tenth)
Total
Total
Total
tons/yr
Sumnary: Total pre-siIvicuItural activity suspended sediment discharge
TotaI post-si IvicuIturaI act ivity suspended sed iment d i scharge
Total maximum sediment discharge
-------
Qpost
c =
K =
T =
post-activity discharge (cfs)
concentration of suspended sediment
(mg/1)
conversion factor 0.0027 (.0864 if
streamflow is in mVsec) (Guy and
Norman 1970)
duration (days)
Summarize sediment discharge increments (col.
7, wksht. VI. 1) and transfer total to worksheet VI.3,
item B.
Discussion: The accuracy of this calculation is
highly dependent on the hydrologic evaluation and
on the observed variability in the sediment rating
curves. A variability range may be presented as an
option for tons/year of suspended sediment dis-
charge. However, for comparative purposes, pre-
activity values should be calculated similarly.
Step 6. Convert Suspended Sediment Limits in
mgA to tons/yr
Procedure: This calculation involves the same
procedure used in step 4, except the suspended
sediment concentrations (CMX) are derived from
various water quality objectives, expressed in mgA.
A conversion to comparable units in tons/year is
needed to compare potentials for prescribed con-
trols. Thus:
class lines using locally derived relationships (fig.
VI. 15). The major divisions above existing condi-
tions of channel stability should be used. A conver-
sion for pre-silvicultural activity flows from mg/1 to
tons provides an interpretation of the effects of in-
troduced sediment (in tons) on channel stability.
O)
E
LLJ
2
O
ill
CO
Q
HI
O
LU
Q.
CO
CO
100.0-
10.0-
1.0
\ \
10.0 100.0
STREAM DISCHARGE (cfs)
Figure VI.14—Use of a constant maximum limit for sediment
concentration compared to sediment rating curve.
where:
SMX= (CMX) (Qpre) (T) (K)
(VI.4)
SMX = maximurn suspended sediment discharge
(tons/yr)
CMX= selected maximum suspended sediment
concentrations (mgA)
K= conversion factor 0.0027 (.0864 (metric
tons) if streamflow is in m3/sec) (Guy and
Normal 1970)
T = duration (days)
Discussion: The pre-silvicultural activity sedi-
ment rating curve is used to compare analysis out-
put (tons/yr) to state standards which have al-
lowable departures for suspended sediment con-
centration increases. Concentration values for the
particular state standard are added to the existing
concentrations for each 6- or 7-day flow increment
(fig. VI.14).
If the water quality objective is to maintain
equilibrium or stability of a stream system, a
typical conversion would use stream channel
stability ratings versus sediment rating curves. Ex-
ceedance levels may be inferred from the stability
The calculation converts water quality objectives
in mgA to tons/year for comparative purposes only.
It does not set objectives, but only provides a basis
for comparison once water quality objectives are
set: This allows comparison of suspended sediment
discharge amount with these objections to deter-
mine when controls or mitigative measures may be
applied. Columns 8 and 9 in worksheet VI. 1 are
provided for this analysis.
Bedload Calculation
Step 7. Establish Bedload Rating Curve
Procedure: Measure bedload transport (Ib/sec or
kg/sec) using the Helley-Smith bedload sampler
concurrent with stream discharge (mVsec or cfs) for
representative flows.
The values of measured bedload transport in lb/
sec or tons/day are evaluated against stream dis-
charge in cfs in the log transformed regression
equation:
VI.21
-------
1000.0
u>
E 100.0
S 10.0
o
z
o
o
I-
LJJ
I .0
til
Figure VI.15.—Relationship of sedi-
ment rating curves to stream chan-
nel stability ratings, Region 1, USFS
(Rosgen 1975b).
DATA: 1972, 73, 74
IDAHO PANHANDLE N.F.
LO LO N.F.
CLEARWATER, N.F
(54) CHANNEL STABILITY RATING NUMBER
I
I
1.0 10.0 100.0
STREAM DISCHARGE, (cfs)
1000.0
log Bs = b + n log Q (VI.5)
where:
log Bs = logarithm of bedload transport (Ib/sec
or tons/day)
b = constant representing intercept of the
regression line
n = constant representing slope of the
regression line
log Q = logarithm of stream discharge (cfs)
Regression analysis should be used to obtain the
coefficient of determination (r2) and the regression
equation for the bedload rating curve.
Discussion: The same variables affecting the
sampling design and representative flow monitor-
ing apply to the bedload rating curves.
Step 8. Calculate Pre-Silvicultural Activity
Potential Bedload Discharge
Procedure: Using bedload rating curve (step 7)
and pre-activity excess water distribution (step 2)
for 6- or 7-day time intervals, calculate annual
bedload discharge using worksheet VI.2.
'= S^
(VI.6)
where:
Bpre = pre-silvicultural activity bedload dis-
charge (tons/year)
1bpre = measured bedload transport rate
(Ib/sec) for pre-activity excess water
T = duration (days)
K = constant to convert Ib/sec to tons/day
Discussion: The procedures used here are the
same as in step 4, with the exception that bedload
is used instead of suspended sediment. Enter the
total of the pre-silvicultural activity potential
hedload discharge as item E on worksheet VI.3.
Step 9. Calculate Total Pre-Silvicultural Activity
Potential Sediment Discharge (Bedload
and Suspended Load)
Add total pre-activity suspended sediment dis-
charge (tons/year) (step 4) and total bedload sedi-
ment discharge (step 8), and enter on worksheet
VI.3 as item K.
Step 10. Calculate Post-Silvicultural Activity
Potential Bedload Discharge
Use worksheet VI.2, columns 1, 5, 6, and 7.
Procedure: Compute rates using post-
silvicultural activity excess water (step 2) and
bedload rating curves (step 7) using equation:
VI.22
-------
WORKSHEET VI.2
Bedload sediment quantification for
(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days
(b)
Number
of
days
pre-
si Ivi-
cu 1 tura 1
act i v i ty
< (c)
Number
of
days
post-
si Ivi-
cu Itural
act i v i ty
(2)
Pre-
si 1 vicultural
act i v i ty f low
Ve
(cfs)
(3)
Bedload
transport
rate
'bpre
(tons/day)
(4)
Total pre-
sl 1 vlcu Itural
activity bed-
load discharge
cols. (3)"
x (1 .b)
n
°pre
(5)
Post-
si 1 v leu I tural
activity flow
Qpost
(cfs)
(6)
Bed 1 oad
transport
rate
'bpost
(tons/day)
(7)
Post-si 1 vicultural
activity bedload
discharge
cols. (6) x (1 .c)
"post
(Totals are rounded to nearest tenth)
Total
Total
tons/yr
Summary:
Total pre-si I vicu I tural activity bedload discharge
Total post-si I vicultural activity bedload discharge
VI.23
-------
WORKSHEET VI.3
Sediment prediction worksheet summary
Subdrainage name Date of ana|ysis.
Suspended Sediment Discharge
A. Pre-siIv[cultural activity total potential suspended sediment
discharge (total col. (4), wksht. VI.1) (tons/yr)
B. Post-si Ivicultural activity total potential suspended sediment
discharge (total col. (7), wksht. VI.1) (due to streamflow
increases) (tons/yr)
C. Maximum allowable potential suspended sediment discharge (total
col. (9), wksht. VI.1) (tons/yr)
D. Potential introduced sediment sources: (delivered)
1. Surface erosion (tons/yr)
2. Soil mass movement (coarse) (tons/yr)
3. Median particle size (mm) •
4. SoiI mass movement—
washload (silts and clays) (tons/yr)
Bed load Discharge (Due to increased streamflow)
E. Pre-siIvicuItural activity potential bedload discharge (tons/yr)
F. Post-si IvicuItural activity potential bedload discharge (due
to increased streamflow) (tons/yr)
Total Sediment and Stream Channel Changes
G. Sum of post-si Ivicultural activity suspended sediment + bedload
discharge (other than introduced sources) (tons/yr)
(sum B + F)
H. Sum of total introduced sediment (D)
= (D.I + D.2 + D.4) (tons/yr)
I. Total increases in potential suspended sediment discharge
1. (B + D.I + D.4) - (A) (tons/yr)
2. Comparison to selected suspended sediment limits
(1.1) - (C) (tons/yr)
VI.24
-------
WORKSHEET VI .3~conti nued
J. Changes in sediment transport and/or channel change potential
(from introduced sources and direct channel impacts)
1. Total post-si IvicuItural activity soil mass movement
sources (coarse size only) (tons/yr)
2. Total post-si IvicuItural soil mass movement sources (fine
or washload only) (tons/yr)
3. Particle size (median size of coarse portion) (mm)
4. Post-si IvicuItural activity bedload transport (F) (tons/yr)
Potential for change (check appropriate blank below)
Stream deposition
Stream scour
No change
K. Total pre-siIvicuItural activity potential sediment discharge
(bedload + suspended load) (tons/yr)
L. Total post-si IvicuItural activity potential sediment discharge
(all sources + bedload and suspended load) (tons/yr)
M. Potential increase in total sediment discharge due to proposed
activity (tons/yr)
(sum A + E)
(sum G + H)
(subtract L - K)
VI.25
-------
Bpost= (ibpJ(T)(K)
where:
Bpost = post-silvicultural activity bedload dis-
charge (tons/year)
'bpost = bedload transport rate (Ib/sec) for post-
activity excess water
T = duration (days)
K = constant to convert Ib/sec to tons/day
Discussion: The increase in bedload sediment
discharge is a function of increased streamflow
through vegetative alterations.
Total Sediment
Step 11. Obtain Introduced Sediment from Soil
Mass Movement
Obtain total potential sediment delivered by soil
mass movement processes in tons/year (ch. V). Add
to total sediment discharge, all sources, step 16.
Record on worksheet VI.3, lines D.2 and D.4.
Step 12. Obtain Total Coarse-Size Sediment from
Soil Mass Movement
Obtain total potential introduced coarse-sized
sediment delivered by soil mass movement
processes. Record on worksheet VI.3, lines D.2 and
J.I.
Procedure: Subtract the percentage of fines (silts
and clays) from total delivered sediment to obtain
the coarse fragment size (sands and larger) (Data
input for step 20).
Discussion: This indicates only the potential of
increased sediment available to a stream. Since
sediment routing is not attempted with these
procedures, it is not possible to determine the
amount of coarse-sized soil mass movement
material that would be available to the third order
drainageway over various periods. A certain
amount will go into temporary storage. A
qualitative evaluation in step 21 may provide ad-
ditional interpretations on stream channel impacts
due to the change in sediment supply from this
source.
Step 13. Determine Fine Size Volume from Soil
Mass Movement
Procedure: Calculate percent by volume of soil
mass movement material that is composed of the
fine soil fraction, .0625 mm or smaller — silts and
clays (washload). Compare output at step 16 —
post-activity total suspended sediment discharge
at the third order stream reach (step 15).
Step 14. Obtain Total Introduced Suspended
Sediment (tons/yr) from Surface Ero-
sion, Chapter IV
Procedure: Self-explanatory.
Discussion: Since the assumption is made that
the delivered sediment from surface erosion is
washload (silts and clays), then the total volume
delivered would be evaluated at the third order
reach. These data are used to compare introduced
sediment to selected limits (step 15).
Step 15. Compare Post-Silvicultural Activity
Total Potential Suspended Sediment
(in Tons) to Selected Limits
Procedure: Add total of suspended sediment in-
creases from:
1. Flow related increases (step 5)
2. Surface erosion source (step 14)
3. Soil mass movement, washload (step 13).
Subtract total of post-activity tons from al-
lowable maximum sediment discharge (S^jx)-
Discussion: Individual processes (surface ero-
sion, soil mass movement, and streamflow) can be
analyzed independent of each other to determine
respective contributions. In this manner, controls
which relate to specific processes may be properly
recommended where applicable (tables II.2 to 14,
ch. II).
Step 16. Post-Silvicultural Activity Total Poten-
tial Sediment Discharge—All Sources
Procedure: Total Sediment = 2 [output steps (5)
(10) (11) and (14)] Add total of sediment discharge
(in tons/yr) from:
1. Suspended sediment post-activity flow
related increases (step 5)
2. Bedload post-activity flow related increases
(step 10)
3. Soil mass movement volumes (step 11)
4. Surface erosion source (step 14).
Discussion: This calculation only evaluates
potential changes in sediment availability within a
third order watershed. It does not assume that all
eroded material is routed to the third order reach.
Step 17. Increase in Total Potential Sediment
Discharge From Silvicultural Activities
Procedure: Subtract total volume (tons/year) of
pre-activity sediment discharge (step 9) from total
post-activity sediment discharge (step 16).
VI.26
-------
Discussion: Although the data output represents
a combined total of all sources, individual con-
tributions may be evaluated where needed when
considering management controls or mitigative
measures.
Step 18. Collect Channel Geometry Data for Third
Order Stream
Procedure: Measure surface water slope (ft/ft) on
the stream reach where bedload data is collected.
Also measure stream width for the various flows as
measured in the establishment of the bedload
rating curve.
Discussion: This information is necessary to es-
tablish a sediment transport rate-stream power
relationship (step 20) for the third order watershed.
It is also required to obtain changes in sediment
transport rate on first to third order stream chan-
nels caused by activities which affect either surface
water slope or bankful stream width (step 19).
Step 19. Evaluate Post-Silvicultural Activity
Channel Impacts
Procedure: Determine post-activity changes in-
fluencing stream power calculations by surface
water slope or bankful stream width. Using post-
activity bankful width and/or surface water slope,
revised stream power calculations and resultant
revised bedload transport rates for impacted
stream reaches (step 20) may be obtained.
Discussion: Changes in stream width and/or sur-
face water slope can be obtained by field deter-
minations based on the results of similar activities
on stream reaches (i.e., upstream versus
downstream measured surface water slope as-
sociated with debris jams indicates relative change
anticipated with similar activities).
Step 20. Establish Bedload Sediment Transport
Rate-Stream Power Relationship for
Third Order Stream Reach
Procedure: Using width (step 2), water surface
slope and actual bedload transport data (step 7),
establish the relationship:
log ib = a + b logw (VI.8)
where:
log ib = logarithm of measured bedload transport
rate (Ib/sec/ft)
a = intercept of regression line
b =slope representing regression line
logo, = logarithm stream power (Ib/sec/ft)
stream power = (62.4 Ibs ft3 X surface water
slope (ft/ft) X stream dis-
charge (cfs)| -T- stream width
Use worksheet VI.4 for this calculation.
Determine the median sediment size in transport
from seiving the bedload sampler catch (Dso). If the
sizes in transport vary as stream power increases,
analyze data separately to develop various particle
size stream power requirements as shown in figure
VI.8 (Leopold and Emmett 1976).
Discussion: The purpose of this calculation is to
develop a local relationship of bedload transport
rate-stream power to predict potential stream
channel adjustments. If it is desired to complete
the same analysis on first and second order
streams, it will be necessary to obtain site specific
information for the respective reaches. This is re-
quired because a flow evaluation is not provided for
the first and second order streams.
The data required are:
1. Measure surface water slope (from riffle to
riffle).
2. Measure bankful stage width (using bankful
stage as described by Williams (1977)).
3. Measure bankful stage depth.
The reliability of the data will be reduced by ex-
trapolating bedload transport rate data to the first
and second order streams. Extrapolation is less
reliable because actual changes in bedload particle
size in transport and corresponding stream powers
are not measured. The processes affecting trans-
port rate, however, are the same; therefore, the
reduced reliability may be acceptable. If it is not
acceptable, measurement of the first and second
order reaches is recommended to more accurately
develop the bedload transport rate-stream power
relationships.
Step 21. Qualitative Determinations of Channel
Change Potential Based on Introduced
Sediment from Soil Mass Movement
and Channel Impacts (wksht. VI.5)
Procedure:
a. Determine change in surface water slope.
b. Determine change in bankful stream width.
c. Determine change in bankful stream depth.
d. Obtain volume of introduced sediment from
soil mass movement source (step 12).
VI.27
-------
WORKSHEET VI.4
Bed load transport-stream power relationship for
(1)
Water
surface
slope
S
(ft/ft)
(2)
Constant
(62.4)
K
(Ib/ft3)
(3)
Measured
stream
discharge
0
(cfs)
(4)
Stream
wi dth
W
(ft)
(5)
Stream
power
cols. (1) x (2) x (3)
col . (4)
(ft/lb/sec)
(6)
Measured
bed load
transport
rate
'b
(tons/day)
(7)
Convert bedloac
transport from
tons /day to
ft/lb/sec, [col .
(6) x 2,000]
486,400 x col. (4)
ib
(ft/lb/sec)
Complete the following analysis:
a. Plot value of stream power (u), column (5) on X-axis and values of bed load transport rate
Pb» column (7)], on double log graph paper.
b. Calculate regression equation and coefficient of determination (r^).
-------
WORKSHEET VI.5
Computations for step 21
(stream name)
Changes in bed load transport-stream power due to channel impacts
1. Potential changes in channel dimensions
a. Bankful stage width (Wpre) (wpost}
b. Bankful stage depth (Dpre) (
c. Water surface slope (Spre)
d. Bankful discharge
where: QBpre = °-366 + 1-33 log Apre + 0.05 log Spre - 0.056 (log Spre):
where: A = cross-sectional area (a) x (b)
S = water surface slope (c)
Calculate 33 '°9 Apost +0.05 log Spost
- 0.056 (log Sposf)2
2.a. Pre-siIvicuItural activity stream power calculation (wpre)
Spre 62*4 QBpre
u n.c) x (K) x (l7d)
pre
d.a)
2.b. Post-si IvicuItural activity stream power calculation
spost 62-4 QBpost
(l.c) x (K) x (l.d) _
post 55
fpost
(l .a)
3. Calculate post-si IvicuItural activity bedload transport rate at bankful
discharge, using post-si IvicuItural activity stream power
VI.29
-------
e. Determine median particle size (mm) of
delivered soil mass movement material.
f. Calculate bankful discharge on impacted
stream reach.
Procedure for determining bankful discharge:
(1) Determine upper limits of the active
floodplain (Williams 1977).
(2) Measure bankful stream width.
(3) Measure bankful stream depth.
(4) Calculate area (width X depth).
(5) Measure water surface slope.
(6) Solve for bankful discharge, Q in equa-
tion.
log Q = 0.366 + 1.33 log A + 0.005 log S
- 0.056 (log S)2
(Riggs 1976)
(VI.9)
where:
Q = discharge (cfs)
A = area (ft2)
S = water surface slope (dimensionless)
Extrapolate bedload transport rate-stream
power relationships established on third order
reach to the reach being evaluated.
h. Calculate maximum bedload transport rate
using bankful discharge stream power. Com-
pare to total introduced sediment from soil
mass movement source. If introduced sedi-
ment exceeds transport rate at bankful dis-
charge, sediment deposition may be expected
in the stream reach.
i. Calculate changes in sediment transport rate
caused by a reduction in surface water slope
from debris jams. If revised stream power
calculation creates a reduction in sediment
transport rate, sediment deposition in the
channel may be expected. This assumes there
is no reduction in sediment availability
within the watershed upstream of the reach
being evaluated.
Discussion: These qualitative evaluations in-
dicate relative potential for channel change,
namely deposition or stream channel aggradation
(longer than 1 year of influence). A numerical in-
dicator is used for this potential change. Long-term
monitoring is necessary to provide quantitative
prediction and time series recovery of stream chan-
nels in the interim. These calculations are recom-
mended when considering management controls
and/or mitigative measures.
VI.30
-------
LITERATURE CITED
Anderson, H. A. 1975. Relative contributions of
sediment from source areas and transport. Proc.
Sediment-Yield Workshop, Oxford, Miss. U.S.
Dep. Agric., Agric. Res. Serv. Rep. ARS-S-40.
285 p.
Bagnold, R. A. 1966. An approach to the sediment
transport problem from general physics. U.S.
Geol. Surv. Prof. Pap. No. 422-1. Washington,
D.C. 37 p.
Bernath, S. A. 1977. Co-variance analysis of the
channel stability/sediment rating curves. Un-
publ. Rep., U.S. Dep. Agric. For. Serv.,
Arapaho/Roosevelt Natl. For., Fort Collins, Colo.
Emmett, W. W. 1974. Sediment measurements in
the Sawtooth Range, Idaho. U.S. Geol. Surv.
personal communication.
Emmett, W. W. 1975. The channels and waters of
the upper Salmon River area, Idaho. U.S. Geol.
Surv. Prof. Pap. 70-A.
Fames, P. A. 1975. Preliminary report —
suspended sediment measurements in Montana.
U.S. Dep. Agric., Soil Conserv. Serv., Bozeman,
Mont.
Flaxman, E. M. 1975. The use of suspended sedi-
ment load measurements and equations for
evaluation of sediment yield in the west. Proc.
Sediment-Yield Workshop, Oxford, Miss. U.S.
Dep. Agric., Agric. Res. Serv. Rep. ARS-S-40.
285 p.
Fredriksen, R. 1977. Sediment data from H. J.
Andrews experimental watershed. U.S. Dep.
Agric. For. Serv., Pac. Northwest For. and Range
Exp. Stn., Corvallis, Oreg. Unpubl. data.
Guy, H., and V. Norman. 1970. Field methods for
measurements of fluvial sediment. Appl.
Hydraul., Book 3, Chapter 2. 59 p. U.S. Geol.
Surv.
Helley, E. J., and W. Smith. 1971. Development
and calibration of a pressure-difference bedload
sampler. U.S. Geol. Surv. Surv. Open-File Rep.
18 p.
Holstrom, T. 1976. Sediment rating curves for
western Wyoming. Unpubl. Rep. Utah State
Univ., Logan.
Lane, E. W. 1955. The importance of fluvial
morphology in hydraulic engineering. Proc. Am.
Soc. Civ. Eng. 8(745).
Laven, R. A. 1977. Sediment rating curves related
to channel stability. Unpubl. Rep. U.S. Dep.
Agric. For Serv., Six Rivers Natl. For., Eureka,
Calif.
Leaf, C. F. 1974. A model for predicting erosion and
sediment yield from secondary forest road con-
struction. U.S. Dep. Agric. For. Serv. Res. Note
RM-74. 4 p. Rocky Mt. For. and Range Exp.
Stn., Fort Collins, Colo.
Leopold, L. B., and W. Emmett. 1976. Bed load
measurements, East Fork River, Wyoming. Proc.
Natl. Acad. Sci. USA, Vol. 74, No. 7. p. 2644-
2648.
Leopold, L. B., M. G. Wolman, and J. P. Miller.
1964. Fluvial processes in geomorphology. 522 p.
W. H. Freeman and Co., San Francisco.
Megahan, W. F. 1974. Erosion over time on
severely disturbed granitic soils: a model. U.S.
Dep. Agric. For. Serv. Res. Pap. INT-156. 14 p.
Intermt. For. and Range Exp. Stn., Ogden,
Utah.
Megahan, W. F. 1978. Bedload transport rates.
Central Idaho Streams. U.S. Dep. Agric. For.
Serv., Intermt. For and Range Exp. Stn., Boise,
Idaho.
Pfankuch, D. J. 1975. Stream reach inventory and
channel stability evaluation. U.S. Dep. Agric.
For. Serv., Reg. 1, Missoula, Mont. 26 p.
Piest, R. F., J. M. Bradford, and R. G. Spomer.
1975. Mechanisms of erosion and sediment
movement from gullies. Proc. Sediment-Yield
Workshop, Oxford, Miss., U.S. Dep. Agric.,
Agric. Res. Serv. Rep. ARS-S-40. 285 p.
Platts, W. S., and W. F. Megahan. 1975. Time
trends in riverbed sediment composition in
salmon and steelhead spawning areas. South
Fork River, Idaho. In North Am. Wildl. Manage.
Inst., Washington, D.C. p. 229-239.
Riggs, H. C. 1976. A simplified slope-area method
for estimating flood discharge in natural chan-
nels. J. Res. U.S. Geol. Surv. Vol. 4. p. 285-291.
VI.31
-------
Rosgen, D. L. 1973. The use of color infra-red
photography for the determination of sediment
production, fluvial processes in sedimentation.
Proc. Hydrol. Symp. Natl. Res. Counc., Ed-
monton, Alberta, Can.
Rosgen, D. L. 1974. Bedload transport data. Un-
publ. U.S. Dep. Agric. For. Serv., Idaho Panhan-
dle Nat. For., Coeur d'Alene, Idaho.
Rosgen, D. L. 1975a. Preliminary report —
procedures for quantifying sediment production.
U.S. Dep. Agric. For. Serv., Sandpoint, Idaho.
Rosgen, D. L. 1975b. Suspended sediment data and
analysis 80 streams. 1972-1975 unpubl. data.
U.S. Dep. Agric. For. Serv., Idaho Panhandle
Nat. For., Coeur d'Alene, Idaho.
Rosgen, D. L. 1975c. Watershed response rating
system. Forest hydrology, part II. Reg. 1, U.S.
Dep. Agric. For. Serv., Missoula, Mont.
Rosgen, D. L. 1977a. Water quality data. Unpubl.
U.S. Dep. Agric. For. Serv., Arapaho/Roosevelt
Natl. For., Fort Collins, Colo.
Rosgen, D. L. 1977b. Validation of sediment rating
curves and channel stability analysis procedures.
Unpublished data for EPA contract #EPA-IAG-
D5-0660. U.S. Dep. Agric. For. Serv.-EPA.
Washington, D.C.
Shen. H. W. 1976. Some notes on alluvial channels.
Short course on the fluvial system, Colo. State
Univ., Fort Collins.
Shen, H. W., and R. M. Li. 1976. Water sediment
yield. Stochastic approaches to water response.
H. W. Shen, ed., Fort Collins, Colo.
Striffler, D. A. 1963. Suspended sediment con-
centrations in a Michigan trout stream as related
to watershed characteristics. Proc. Fed. Inter-
Agency Sediment Conf., U.S. Dep. Agric., Agric.
Res. Serv., Misc. Publ. No. 970. 933 p.
Sundeen, K. D. 1977. Estimating channel sediment
yields from a disturbed watershed. Unpubl. Rep.
U.S. Dep. Agric. For. Serv., Fort Collins, Colo.
U.S. Department of Agriculture, Forest Service.
1975. Forest hydrology, part II. Reg. 1, Missoula,
Mont.
U.S. Department of Agriculture, Forest Service.
1977. Non-point water quality modeling wildlife
management. A state-of-the-art assessment.
EPA-IAG-D5-0660. Washington, D.C.
Williams, G. P. 1977. Bankful discharge of rivers.
U.S. Geol. Surv., Open File Rep., Denver.
VI.32
-------
APPENDIX VI.A
EXAMPLES OF CHANNEL STABILITY
RATINGS
Figure VI.A. 1.—Stream channels in-
dicative of a stable channel due to
resistant bed and bank materials.
Figure VI.A.2,—Stream channels in-
dicative of a stable channel due to
resistant bed and bank materials.
VI.33
-------
Figures VI.A.3. - VI.A.5.—Stream
channels indicative of stable chan-
nel due to resistant bed and bank
materials.
VI.34
-------
,*"
Figures VI.A.6. - VI.A.8.—Highly un-
stable channels or channels having
poor stability ratings are generally
associated with easily detached
bank and bed material where chan-
nel erosion is significant.
VI.35
-------
Figure VI.A.9,—Stability and associated sediment supply af-
fected by organic debris which increase sediment storage
with resultant channel changes and bank erosion.
Figure VI.A.10.—Stability and associated sediment supply
affected by organic debris. Excessive deposition and as-
sociated increased sediment storage occurs with resultant
channel changes, bank erosion and other changes.
VI.36
-------
Figure VI.A.11.—Change* in stability
due to increases in sediment supply
from road crossing*. Such In-
troduced sediment sources can ex-
ceed the carrying capacity of the
stream.
Figure VI.A.12.—Soil mas* movement, due to debris avalanche processes, deliver excessive
amounts of sediment to the stream. This will often change the stream stability and associated
supply-energy relationship.
VI.37
-------
Figure VI,A.13.—Soil ma*» movement, due to slump-earthflow processes,
deliver excessive amounts of sediment to the stream. This will often change
the stream stability and associated supply-energy relationships.
VI.38
-------
APPENDIX VLB
RELATIONSHIPS BETWEEN SEDIMENT RATING CURVES AND CHANNEL STABILITY
To provide a link between the morphological
characteristics of stream channels, as determined
by the channel stability rating procedure
(Pfankuch 1975), and sediment rating curves,
regression analyses were made on over 80 streams
in northern and central Idaho and northwestern
Montana involving sediment rating curves and
channel stability ratings. The relationship is shown
in figure VI.B.l (Rosgen 1975b). Correlation coef-
ficients (R2) were 0.94 for the "good and excellent"
(38 to 76), 0.91 for the "fair channel stability" (77
to 114), and 0.94 for the "poor or unstable" chan-
nels (115 to 132). A covariance analysis was con-
ducted (Bernath 1977) indicating highly significant
correlations when comparing stability ratings for
various populations. The F values were highly
significant at the 0.01 level.
Since then, work conducted in California has
shown widespread application of this technique
where 27 streams with sediment rating curves were
evaluated using the same stability procedures (fig.
VI.B.2). Concentrations for the same flows are con-
siderably higher in the California streams, but the
stability evaluation provides a comparison of the
different regression constants and stability ratings
within a given locale using the same procedures
(Laven 1977). Similar relationships are indicated
in figure VI.B.3 where sediment rating curves were
related to stability ratings in Colorado (Rosgen
1977b).
Additional validation of this procedure has been
conducted in Wyoming, Oregon, New Mexico,
North Carolina, New Hampshire, Vermont, and
Virginia; tentative results indicate that this
procedure applies to many areas other than where
it was developed (Rosgen 1977a). This success is
due to the application of the procedures (process
related) rather than extrapolation of actual curves
or regression equations from region to region. The
use of this procedure demands the development of
1000.0
100.0
o
s
LU
O
o
O
I-
LU
LU
CO
10.0
DATA: 1972, 73, 74
IDAHO PANHANDLE N.F
LO LO N.F.
CLEARWATER, N.F.
(54) CHANNEL STABILITY RATING NUMBER
I
I
1.0 10.0 100.0
STREAM DISCHARGE, (cfs)
1000.0
Figure VI.B.L—Relationship of sediment rating curves to stream channel stability
ratings, Region 1, USFS (Rosgen 1975b).
VI.39
-------
1,000,000-
100,000—
^3>
z
o
r; 10000—
DC
I-
z
LU
o
z
o
o
uooo—
h-
z
LU
Q
LU
Q
LU
Q
Z
LU
Q.
C/)
D
100—
10-
Numerical
Stability
Ratings
01
I I I
1.0 10 100
STREAM DISCHARGE, (CSM)
1,000
10,000
Figure VI.B.2.—Relationship of channel stability ratings to sediment rating curves in the Redwood Creek
drainage, California (Laven 1977).
VI.40
-------
1000.0
i 1 JTJIfflo i i
STREAM DISCHARGE, (cfs)
I I I 11
567 89100.0
Figure VI.B.3.—Relationship of channel stability ratings to sediment rating curves for streams in the central
Rocky Mountain region. (Rosgen 1977a).
VI.41
-------
local curves based on actual sediment rating curve
data. Once this step has been completed, informa-
tion can be obtained from many miles of stream
reach upstream or adjacent to where sediment data
have been collected. Thus, the channel stability
procedure, if used in a consistent comparative
analysis over a wide range of stream types, can be
used to infer the regression constants of the sedi-
ment rating curves. This would not be as accurate
as actual measurements on 100 percent of the
stream reaches being evaluated in a subdrainage;
however, time and financial constraints might
justify this approach once local validation has been
accomplished. Potential shifts in stability as a
result of direct sediment introduction may be infer-
red through the use of channel stability — sedi-
ment rating curve relationships in a given locale.
The "stability threshold" of streams can be in-
terpreted as the lines between the major stability
classes as shown in figure VI.B.l. This interpreta-
tion would be used where either actual or proposed
potential sediment discharge, as calculated, could
be compared to that sediment discharge using the
maximum concentrations for the stability class and
pre-activity seasonal distribution of excess water.
These are based on measured data in the develop-
ment of these relationships. If potential introduced
sediment is anticipated during periods of lower
flow, a comparison may be made, utilizing less
than bankful stage discharge. If the increased sup-
ply is higher than the maximum sediment dis-
charge for that flow condition, a stability change or
associated shift in sediment rating curve may
occur.
VI.42
-------
APPENDIX VI.C
TIME SERIES ANALYSIS-RECOVERY PROCEDURE
It is often desirable to determine the duration of
sediment impacts in a stream system. Little work
is available which sets time series recovery for sedi-
ment rating curves, although observations indicate
relative rates of recovery which vary considerably
between streams. It is not possible to predict this
recovery at this time; however, a procedure can be
applied once channel morphological data are col-
lected and pre- and post-sediment rating curves are
measured.
Time recovery for streams using the sediment
rating curve approach may be shown as:
A. Pre-silvicultural activity sediment rating
curve or baseline characterization
relationship.
log Y = b + n log Q (VI.l)
where:
log Y = logarithm of pre-silvicultural activity
suspended sediment concentration
(mg/1)
b = pre-silvicultural activity regression
constant expressing intercept of the
regression line
log Q = logarithm of pre-silvicultural activity
instantaneous stream discharge in
cubic feet per second
n = pre-silvicultural activity regression ex-
ponent expressing slope of the regres-
sion line
B. Post-silvicultural activity relationship ex-
pressing the time series recovery.
Y* = (b*e-Yt) (Q) <•>•»-«) (VI.C.l)
where:
Yt* = post-silvicultural activity sediment con-
centration (mg/1) for a specified time fol-
lowing activity
b = post-silvicultural activity regression con-
stant expressing intercept of the regres-
sion line
e = base of natural logarithms
-Y = negative exponent expressing
relationship of recovery of intercept
Q = post-silvicultural activity instantaneous
stream discharge (ft3 per section)
n* = post-silvicultural activity regression ex-
ponent expressing slope of the regression
line
-z = negative exponent expressing recovery
relationship of slope
t = time (years) since initial disturbance
The relationships can be used to determine the
rate of decline of the sediment rating curve follow-
ing disturbance. Data requirements include the
availability of measured pre- and post-silvicultural
activity rating curves on streams to calculated
values of Yt and zt for similar stream systems for
various years.
Models which determine potential "time-
trends" in erosion and sedimentation are published
and have been used in the central and northern
Rocky Mountains (Megahan 1974 and Leaf 1974).
Sediment reduction resulting from roads was
primarily addressed where vegetative recovery
greatly reduced delivery to a stream.
Before this stream channel-time recovery ap-
proach can be applied, stream morphological data
will be needed prior to and following treatments of
various streams to determine what variables are
responsible for the shift in the sediment rating
curve. Before adjusted values of Yt and zt are
available, qualitative broad interpretations of
recovery are presently all that can be applied.
VI.43
-------
Chapter VII
TEMPERATURE
this chapter was prepared by the following individuals:
John B. Currier
with major contributions from:
Dallas Hughes
vn.i
-------
CONTENTS
Page
INTRODUCTION VE.l
THE PROCEDURE VH.2
SOURCES OF ENERGY INFLUX CONTRIBUTING TO INCREASED
WATER TEMPERATURE VH.2
Net Radiation, NR VU.2
Advective Energy Flux, Ad VH.2
Conductive Energy Exchange Between Streambed Material And Water, Cd . VII.2
Evaporation And Condensation, E VH.3
Convective Energy Exchange, Cv VII.3
BROWN'S MODEL: ESTIMATING MAXIMUM POTENTIAL
TEMPERATURE INCREASE VE.3
PROCEDURAL DESCRIPTION VLL3
Determination Of Incident Heat Load, H VIf.3
Determination Of Discharge, Q VEL14
Determination Of Exposed Surface Area Of Flowing Water, A VII. 14
Determination Of Maximum Potential Daily Temperature Increase, AT . VII.16
Evaluation Of Downstream Temperature Increases VII.18
Total Increase In Water Temperature VII.18
Reduction In Water Temperature Due To Groundwater Inflow VII.18
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS VH.20
LITERATURE CITED VH.21
APPENDIX VH.A: VALIDATION OF BROWN'S MODEL VH.22
APPENDIX VII.B: STREAMSIDE SHADING VH.24
TOPOGRAPHIC SHADING VH.24
VEGETATIVE SHADING VH.24
APPENDIX VII.C: WATERSIDE AREAS VH.27
COMMERCIAL TIMBER VDL27
STRIP WIDTH Vn.27
APPENDIX VH.D: GENERAL RELATIONSHIPS BETWEEN LIGHT
INTENSITY OR TRANSMISSION OF SOLAR RADIATION
AND VEGETATIVE COVER VE.29
VH.ii
-------
LIST OF EQUATIONS
Equation Page
VII.l AH = NR±Ad±Cd±E±Cv VII.2
\7TT rt T"\ rfl i TA rp
Vll.^ ATfl = Uili+Uzlz vn 2
VH-3 AT = — 0.000267 VJJ.3
VII.3a A adjustedH adjusted
AT = —' 0.000267 VII.16
Q
VII.4 measured average stream width
sine | azimuth stream azimuth sun |
VIJ.5 height vegetation
tangent solar angle
VH.6 H adjusted = [% WH] + [%B (1.00-C) H] VII.14
VII.7a Atotal=LW VII.15
VII.7b Ashadebrush = LW(% stream shaded by brush only) • VII.15
VII.7c Apresentiyexp0sed= (Atotai_ Agj,adebrush)
(% transmission through existing vegetation) VII.16
VII.7d Aadjusted = Atotai — A exposed pre-silvicultural activity VII.16
VII 8 D T -I- TO T
Trj=_M_M — VH.18
VH.9 DGTG+DTTT
TD — Vn.19
VJJ.iii
-------
LIST OF FIGURES
Number Page
VII.l Flow diagram showing the sequence of steps and data required for
evaluating the maximum potential daily temperature increase in °F. VII.4
VII.2 Solar ephemeris for 35° N latitude VII.6
VH.3 Solar ephemeris for 40° N latitude VII.7
VII.4 Solar ephemeris for 45° N latitude VII.8
VII.5 Solar ephemeris for 50° N latitude VII.9
VII.6 Use of a solar ephemeris VII.10
VII.7 Hourly values (BTU/ft2-min) for net solar radiation above water sur-
faces on clear days between latitudes 30° N and 50° N for several solar
paths VII.13
VII.8 Determination of net hourly solar radiation using noon angle of 72° . VII. 13
VII.9 Correction factor for the heat-sink effect of bedrock streambeds VII. 14
VII. 10 Transmission of solar radiation as a function of stem density and crown
closure VII. 17
VII.l 1 Components of the mixing formula for evaluating the downstream im-
pact of increased water temperature caused by silvicultural activities
upstream VII.18
VII.12 Components of the mixing formula for evaluating the impact of ground
water temperature and inflow on reducing temperature increases due
to silvicultural activities upstream VII. 19
Vn.B.l Low-growing shrubs and brush adjacent to water a course may provide
adequate shade, while taller vegetation is necessary further from the
stream VH.25
VII.B.2 Position of the sun in relation to the riparian vegetation determines the
time and extent of vegetative shading VII.25
VII .B .3 Orientation of the sun with the stream determines the length of shadows
necessary to completely shade the water surface VII.26
VII.C.l The relation between waterside area width and angular canopy density VII.27
VII.C.2 The relation between angular canopy density (ACD) and heat blocked
(AH) Vn.28
VII.D.1 Transmission of solar radiation as a function of stem density and crown
closure VH.30
VH.iv
-------
LIST OF TABLES
Number Page
VII.l Variation of solar angle and azimuth with time of day VII.5
VII.2 Computation of stream's effective width (EW) and vegetative shadow
length (S) based upon stream azimuth, solar azimuth, and solar angle VII.12
VTI.A.l Summation of validation test using data from Fernow Experimental
Watershed, Parsons, West Virginia VII.22
VII.D.l Effects of stand density removal on light intensity VII.29
VII.D.2 Effects of tree spacing on light intensities VII.29
VII.D.3 Percent light intensity through small- and large-crown trees VII.29
VII.D.4 Percent light intensity through eastern conifers VII.29
VII.D.5 Percent light intensity through conifer plantations VII.29
VII.D.6 Stand basal area and equivalent solar loading beneath the canopy .. VII.29
vn.v
-------
INTRODUCTION
The temperature of small headwater streams of
forested areas is an important determinant of
overall water quality. Temperature acts not only to
control the metabolic rates and functions of
aquatic biota but also serves to maintain com-
munity structure. Change in temperature affects
species composition. Microorganisms at the base of
the food chain may be directly affected which even-
tually will affect all higher organisms in the food
pyramid.
Water temperature changes may be either
beneficial or detrimental. A moderate temperature
increase in streams that are cooler than optimum
could increase productivity and have a beneficial
effect on the aquatic environment. However
streams having temperatures that approach
critical threshold limits during the summer months
may exceed these limits and have a detrimental ef-
fect on aquatic organisms. In addition, winter
stream temperatures may be decreased by canopy
removal. Exposure of the water surfaces could
result in greater convectional heat loss from the
water to the atmosphere.
Increased stream temperature affects fish pop-
ulations in several ways, many of which are
detrimental. High temperature kills fish directly,
decreases the dissolved oxygen (DO) concentra-
tion, increases the susceptibility of fish to disease
by increasing bacteriological activity, affects
availability of food, and alters feeding activities of
fish. Increased stream temperatures indirectly
alter community composition by providing a
habitat favorable to warm water species.
There are numerous publications that relate the
impacts of timber harvesting to stream
temperature and subsequent effects on fish popula-
tions (Eschner and Larmoyeux 1963, Brown and
others 1971). Their studies show that removal of
shading vegetation as a result of harvesting can in-
crease stream temperatures because of increased
exposure to solar radiation. The magnitude of the
impact is a function of the amount of critical
canopy removed, duration of exposure, streambed
material, area exposed, stream discharge, initial
water temperature, and groundwater influx (Stone
1973). Cloud cover is not considered since max-
imum potential daily temperature increase is being
evaluated.
VH.l
-------
THE PROCEDURE
SOURCES OF ENERGY INFLUX
CONTRIBUTING TO
INCREASED WATER TEMPERATURE
Removal of stream side vegetation that provides
shade to the water surface can cause significant
stream temperature increases. Several sources of
energy influx interact and contribute to the net
change in temperature of a stream. This
relationship may be expressed in the following
energy budget equation (Brown 1969 and Lee
1977):
= NR±Ad±Cd±E±C,
(VH.l)
where:
AH = energy manifested by a change in water
temperature,
NR = net radiation (incoming-outgoing all
wave radiation),
Ad = advective energy exchange due to
precipitation, ground water, or tributary
flows,
Cd = conductive energy exchange between
streambed material and water,
E = evaporation and condensation, and
Cv = convective energy exchange at water sur-
face, atmosphere interface.
Net Radiation, NR
Brown (1969, 1972) has shown that 95 percent of
the energy influx of small, completely exposed
streams can be accounted for by net radiation. Net
solar radiation is defined as the algebraic sum of in-
cident and reflected sun and sky shortwave radia-
tion, incident and reflected atmospheric longwave
radiation, and longwave radiation emitted by the
water body. It is the principal energy influx con-
trolling the maximum temperature increase in ex-
posed streams. Solar radiation itself is not control-
lable, but the amount of water surface exposed can
be controlled. Shading by vegetation limits the
amount of solar radiation received by the water
course (Reifsnyder and Lull 1965).
Advective Energy Flux, Aa
Advective energy flux is the transmission of heat
by horizontal currents through a fluid such as the
atmosphere or water. In specific situations these
significantly modify temperature increases; for ex-
ample, advective inputs by groundwater normally
decrease maximum summer temperatures.
Groundwater temperatures generally approach the
average annual air temperature, and so are
generally cooler than surface water during the sum-
mer months. The magnitude of this reduction will
depend upon the temperature difference between
the surface and the groundwater, and upon the
volume of groundwater entering the stream as com-
pared to the volume of streamflow in the surface
water.
Advective inputs by tributaries may either in-
crease or decrease maximum receiving stream
temperature depending upon whether the tributary
stream contains warmer or cooler water. Like
groundwater, the magnitude of the change in water
temperature of a receiving stream will be deter-
mined by the temperature and volume of the
tributary flow compared to the temperature and
volume of the receiving stream. Temperature
changes associated with ground water or tributary
flows can be expressed mathematically by a simple
proportion:
D2T
22
(vn.2)
Di + D2
where:
ATa = change in water temperature, receiving
stream,
Di = discharge, receiving stream,
Ti = temperature, receiving stream,
D2 = discharge, tributary stream, and
T2 = temperature, tributary stream.
Conductive Energy Exchange Between
Streambed Material And Water, Cd
In a conductive energy exchange heat is trans-
ferred through matter by kinetic energy (energy of
motion) from particle to particle. Stream
VH.2
-------
temperatures will vary with streambed composi-
tion. Generally, bedrock streambeds will act as
heat sinks with resulting conductive losses of
energy from the water body to the rock (Brown
1972). Gravel, sand, and fine materials comprising
streambeds have interparticulate voids that
minimize conductive heat losses. The color of the
rock also influences the magnitude of the conduc-
tive heat loss. Darker rock will absorb more energy
than lighter rock.
Evaporation And Condensation, E
Evaporation is the principal process by which
heat is lost from the water surface. It occurs
whenever the saturation vapor pressure of the
water is greater than the ambient vapor pressure.
This happens during the summer when the water is
cooler than the air and, in particular, during the
midday period. Heat loss from the water via
evaporation is only a fraction of the radiant energy
influx and does not significantly alter the max-
imum temperature increases in most small streams
where silvicultural activities are conducted.
However, as the water temperature increases to
equilibrium, evaporation increases and heat loss
from the water due to evaporation may exceed the
heat influx from net radiation.
of a section of stream channel to direct solar radia-
tion using the energy budget approach. Field
measurements showed that net thermal radiation
accounted for over 95 percent of the energy influx
to exposed water courses (Brown 1969). (Validation
of Brown's model is discussed in appendix VILA.)
The energy term in the initial model was simplified
based upon the assumption that net solar radiation
is the only source of energy to an exposed stream.
The simplified model is:
AH
AT = — 0.000267
Q
(vn.3)
where:
AT =
maximum potential daily
temperature increases expected
from exposing a section of stream to
direct solar radiation, in degrees
Fahrenheit.
surface area in square feet of stream
exposed to direct solar radiation,
discharge of the stream, in ftVsec
incident heat load (net solar
radiation) received by the exposed
water surface in BTU/ft2—min, and
0.000267 = constant required for unit conver-
sion converts flow from ft3/sec to
Ib/min.
A =
Q
H
Convective Energy Exchange, Cv
PROCEDURAL DESCRIPTION
Convective energy exchange occurs whenever
there is a temperature gradient between the water
mass and air mass. The energy exchange may be
positive or negative depending upon whether the
air is warmer or cooler than the water. During
critical periods of maximum water temperature,
the air mass will usually be warmer than the water
and will reinforce the radiant energy influx to in-
crease water temperature.
Brown's procedure for determining the max-
imum potential daily temperature increase in
terms of incident heat load (H), discharge (Q), and
exposed surface area of flowing water (A) follows.
These descriptive paragraphs correspond with the
procedural flow chart organization in figure VII. 1.
Determination Of Incident Heat Load, H
BROWN'S MODEL: ESTIMATING
MAXIMUM POTENTIAL
TEMPERATURE INCREASE
Brown (1970, 1972) developed a model for
predicting the maximum potential daily change in
temperature resulting from the complete exposure
The incident heat load (net solar radiation), H,
received by a water surface is determined by (1) the
maximum solar angle of the sun; (2) the length of
time a given volume of water will be exposed to
solar radiation; (3) the amount of bedrock in the
stream; and (4) the amount of vegetative and
topographic shading of the water surface. The fol-
lowing steps are involved in computing the incident
heat load.
VH.3
-------
LATITUDE SITE
SELECTION OF SOLAR EPHEMERIS
LENGTH OF STREAM EXPOSED
AVERAGE WIDTH FLOWING WATER
IN EXPOSED STREAM SECTION
CRITICAL TIME OF YEAR
-MONTH AND DAY
TOTAL SURFACE
AREA OF FLOWING WATER
DETERMINATION
OF SOLAR ANGLE
AND AZIMUTH
PERCENT FLOWING WATER SURFACE
SHADED BY BRUSH
c
HEIGHT OF ADJACENT VEGETATION
ORIENTATION OF STREAM
FLOWING WATER SURFACE AREA
SHADED BY BRUSH
DETERMINATION OF EFFECTIVE STREAM
WIDTH AND SHADOW LENGTH
OF ADJACENT VEGETATION
TRANSMISSION SOLAR RADIATION
THROUGH EXISTING VEGETATION
MAXIMUM SOLAR ANGLE
SURFACE AREA FLOWING WATER
EXPOSED TO SOLAR RADIATION
C
PERCENT SLOPE OF
ADJACENT TOPOGRAPHY
EVALUATE TOPOGRAPHIC SHADING
TOTAL SURFACE AREA
FLOWING WATER EXPOSED
BY REMOVAL OF ALL
SHADING VEGETATION
INCIDENT HEAT LOAD
NET SOLAR RADIATION)
PERCENTSTREAMBED
COMPRISED OF BEDROCK
ADJUSTED NET SOLAR RADIATION
FOR BEDROCK STREAMBEDS
C
DISCHARGE
4<
-4
L.
C
PROCEDURAL STEP
COMPUTATION OB
EVALUATION
A fe. ANALYSIS
^ W OUTPUT
MAXIMUM POTENTIAL DAILY TEMPERATURE INCREASE
Figure VII.1. Flow diagram showing the sequence of steps and data required for evaluating the maximum
potential daily temperature Increase in degrees Fahrenheit.
VII.4
-------
LATITUDE SITE
The latitude of the site must be known. Exact
latitudinal location to the nearest minute or second
is not required, as the difference in net radiation
over two to three degrees of latitude is not signifi-
cant for this analysis procedure.
SELECTION OF SOLAR EPHEMERIS
A solar ephemeris is defined as a table or figure
that gives the sun's location, angle and azimuth,
for each day. Four solar emphemerides are
provided (figs. VII.2 VII.5), representing four
latitudes — 35° N, 40° N, 45° N, and 50° N. Select
one solar ephemeris most appropriate for the
latitude of the site of the silvicultural activity. For
example, if the latitude of the site is 40- Vz ° N, the
solar ephemeris for 40° N would be utilized.
c
CRITICAL TIME OF YEAR —
MONTH AND DAY
Select the time of year when stream temperature
increases are critical. This normally occurs during
the summer months when the stream is lowest and
heat influx is greatest.
Using the previous example, locate the declina-
tion in the solar ephemeris for 40° N latitude (fig.
VII.3) that corresponds to the date when maximum
water temperature increase is anticipated. If the
critical period is the second week in July, the
declination would be +21-l/2°. Interpolate between
given declination lines for dates other than those
given. For the declination of the second week in
July, interpolate between declinations +23°27' and
+20° (June 22 and July 24, respectively).
DETERMINATION OF SOLAR
ANGLE AND AZIMUTH
the stream depends on the solar angle and
azimuth. As the solar angle increases, more radiant
energy reaches the water surface and there is a
reduction of reflected radiation. Brown (1970)
developed curves for net incoming (shortwave and
diffuse) solar radiation (BTU/ft2-min) based upon
solar angle and reflectivity. He determined that
heat might be added to a stream by incoming
longwave radiation; however, back radiation from
the water was about the same magnitude.
Therefore, the net change in stream heat from
longwave radiation is assumed to be zero. Solar
angle and azimuth, of course, depend upon season,
time of day, and latitude.
Continuing with the same example, with a
declination +21-1/2°, determine the azimuth and
solar angle for various times during the day from
the solar ephemeris (fig. VII.6) and record the
values as shown in table VII. 1. Azimuth readings
are found along the outside of the circle (fig. VII.6)
and are given for every 10 degrees. Solar angle (i.e.,
degrees above the horizon) is indicated by the con-
centric circles. The time is indicated above the
+23°27' declination line and is given in hours, solar
time.
Table VI 1.1.—Variation of solar angle and azimuth with time of
day1
Daylight savings
time
12:30
1:00 (solar noon)
1:30
2:10 (oriented with stream)
2:30
2:45
3:10
angle
70
72
70
68
65
60
55
Solar
azimuth
155
180
205
225
235
240
245
Maximum radiation will occur during the mid-
day hours on clear days. The heat load received by
1See "Chapter VIII: Procedural Examples" for worksheets cor-
responding to data appearing in this chapter's tables and figures.
To determine the solar angle and azimuth that
would occur at 12:30 p.m. daylight savings time:
follow along the +21- Vz° declination line that is in-
terpolated between the +20° and +23°27' line.
Locate the point that is equal distance between the
11:00 a.m. (12:00 a.m. daylight savings time) and
noon (1:00 p.m. daylight savings time) time inter-
val. This point represents 12:30 daylight savings
time.
VII.5
-------
35° N.
350
NORTH
30
NW
40
NE
120
SW
220
SE
210
150
200
SOUTH '70
160
Decli-
nation Approx. dates
+ 23° 27' Tune 22
+ 20° May 21. July 24
+ 15° May 1, Aug. 12
+ 10° Apr. 16, Aug. 28
+ 5° Apr. 3. Sept. 10
0' Mar. 21, Sept. 23
- 5° Mar. 8. Oct. 6
-10° I.'eb. 23, Oct. 20
-15° Feb. 9, Nov. 3
-20' Jan. 21, Nov. 22
-23'27' Dec. 22
Figure VII.2.—Solar ephemerk for 35° N latitude.
vn.e
-------
40° N.
a50 NORTH |0
340. —~r 5
330
NW
210
200
190 SdUTH 170
Decli-
nation Approx. dates
+23° 27' Tune 22
+ 20° May 21, July 24
+ 15° May 1, Aug. 12
+10° Apr. 16, Aug. 28
+ 5" Apr. 3, Sept. 10
0° Mar. 21, Sept. 23
— 5" Mar. 8, Oct. 6
-10° Feb. 23, Oct. 20
—15° Feb. 9, Nov. 3
—20' Tan. 21, Nov. 22
-23' 27' Dec. 22
Figure VII.3.—Solar ephemeris for 40° N latitude.
vn.?
-------
45° N.
340
350
NORTH
20
330
30
NW
320
40
NE
50
60
230
SW
/
220
\
140
130
SE
210
150
200
190 SOUTH 170
160
Decli-
nation
+ 23' 27'
r .W
H5-
+ 10*
+ 5"
0°
- 5°
-10*
-15°
—20°
—23° 27'
Approx. dates
June 22
lay 21. Tuly J4
May 1, AUJJ. U
Apr. 16, Aug. 28
Apr. 3, Sept. 10
Mar. 21, Sept. 23
Mar. 8, Oct. 6
Feb. 23, Oct. 20
Feb. 9, Nov. 3
Tan. 21, Nov. 22
Dec. 22
Figure VII.4.—Solar •prwiMfi* for 45° N latitude.
vn.s
-------
50" N.
340
350
NORTH
20
330
30
NW
310
320
\
NC
300
sw
210
150
200
190 SOUTH 170
160
Decli-
nation
4 23* 27'
•r .!<)"
-MS"
4-10*
4- 5"
0°
— 5°
-10'
-15°
—20°
—23' 27'
Apprux. dates
June 22
May 21, July J4
M.iy 1, Aug. 1.!
Apr. 16, Aug. 28
Apr. j, Sept. 10
Mar. 21, Sept. 23
Mar. 8, Oct. 6
Feb. 23, Oct. 20
Feb. 9, Nov. 3
Jan. 21, Nov. 22
Dec. 22
Figure VII.5.—Solar ephemerb for 50° N latitude.
VH.9
-------
40° N.
350 NORTH
340^ r-~f~~
20
30
14 July
14 July
Decli-
nation
+ 23' 27'
+ 20°
+ 15°
+ 10°
+ 5°
0"
— 10°
-15°
—20"
-23* 27'
Approx. dates
Tune 22
May 21. July 24
May 1, Aug. 12
Apr. 16, Aug. 28
Apr. 3, Sept. 10
Mar. 21, Sept. 23
Mar. 8, Oct. 6
Feb. 23, Oct. 20
Feb. 9, Nov. 3
Jan. 21, Nov. 22
Dec. 22
Figure VII.6.—Use of the solar ephemeris given the following illustrative data: latitude of 40-1/2° N, second
week in July, and 12:30 p.m. daylight savings time.
VII.10
-------
The solar angle is determined by noting where
the point established above (12:30 p.m. with a
declination of +21-Va0) occurs in respect to the
solar angle lines present on figure VII.6. The solar
angle lines are represented as concentric circles and
range from 90° at the center to 0° at the periphery.
The point established above falls on the 70° line;
therefore, the solar angle is equal to 70°.
The solar azimuth is determined by noting where
the point established above occurs in respect to the
solar azimuth lines that radiate out from the center
of the circle. The point falls midway between the
150° and 160° lines; therefore, the solar azimuth
equals 155°.
More points should be selected about the midday
period when solar radiation is at the greatest inten-
sity as opposed to the early morning and/or late
afternoon when solar radiation is less.
HEIGHT OF ADJACENT VEGETATION
ORIENTATION OF STREAM
The height of vegetation adjacent to the stream
effects the shading of the stream. Taller vegetation
casts longer shadows and so can be further from the
stream and still provide shade. The orientation of
the stream azimuth in respect to the sun also deter-
mines the length of shadow. For a more detailed
discussion of these relationships, refer to appendix
VH.B.
DETERMINATION OF STREAM
EFFECTIVE WIDTH AND SHADOW LENGTH
OF ADJACENT VEGETATION
Evaluate the orientation of the sun (i.e., solar
angle and azimuth determined previously, table
VII.l), with the stream and determine what vegeta-
tion exists that shades the stream. To do this, com-
pare stream effective width with shadow length.
Determine the maximum solar angle (i.e., max-
imum radiation influx to stream) that will occur
when the stream is exposed due to the silvicultural
activity.
Assuming a stream azimuth of 225° and a height
of 70 feet for vegetation adjacent to the stream, the
following numerical computations illustrate how
stream effective width and shadow length can be
evaluated.
The direction the shadows fall across the stream
will determine effective width of the stream (for a
discussion of effective width, see appendix VII.B,
"Streamside Shading").
Effective width is computed using the following
formula:
EW =
measured average stream width
sine I azimuth stream azimuth sun
(VH.4)
The azimuth of the particular stream used for
this illustration is 225°. This value (EW) varies
depending on the time of day. For example, at
12:30 p.m. (table VII.1), EW would be equal to:
EW =
1.5 ft
sine I 225° - 155°
= 1.6 ft
The absolute value of azimuth of the stream less
azimuth of the sun must be less than a 90° angle.
Should the difference exceed 90°, subtract this ab-
solute value from 180° to obtain the correct acute
angle. The sine is then taken of this computed
acute angle.
Shadow length (S) is computed using the for-
mula:
S =
height vegetation
tangent solar angle
(VH.5)
For example, at 12:30 p.m., S would be equal to:
S =
70 ft
= 25.5 ft
tangent (70°)
Note, the only periods of the day that should be
considered are those times when existing vegeta-
tion that will be eliminated by the silvicultural
operation effectively shades the stream; i.e., when
the shadow length extends onto some portion of the
stream.
In the illustration used previously, the existing
trees scheduled to be cut do provide shade to the
stream. The only time of the day when the existing
trees do not shade the stream occurs about 2:10
p.m. when the stream's effective width is infinity
vn.n
-------
Table VII.2.—Computation of stream's effective width (EW) and
vegetative shadow length (S) based upon stream azimuth,
solar azimuth, and solar angle
Daylight savings
time
12:30
1:00
1:30
2:10
2:30
2:45
3:10
Solar
angle
70
72
70
68
65
60
55
azimuth
(°)
155
180
205
225
235
240
245
Effective width
(EW = 1.5/sine
225-Solar azimuth)
(ft)
1.6
2.1
4.4
(infinity)
8.6
5.8
4.4
Shadow length
(S=70/tangent
Solar angle)
(ft)
25.4
22.7
25.5
28.2
32.6
40.4
49.0
(sun is oriented with the stream) and the shadow
length is only 28.2 feet (table VII.2). Therefore,
removal of this vegetation would result in exposure
of the water surface to increased solar radiation.
The proposed silvicultural operation would have
the maximum impact on water temperature at 1:00
p.m. (solar noon) when the solar angle and radia-
tion are greatest and when existing vegetation
presently providing shade is removed. Therefore,
the maximum solar angle would be 72°.
not possible due to the angle of the sun and
relatively gentle topographic relief.
PERCENT SLOPE OF
ADJACENT TOPOGRAPHY
The percent slope of the adjacent topography
must be measured or estimated.
EVALUATE
TOPOGRAPHIC
SHADING
Topographic shading should be evaluated to
determine if the water course would be shaded by
topographic features. For topographic shading to
be present, the percent slope of the ground must
exceed the percent slope of the solar angle (i.e.,
tangent solar angle).
If the slope of the topography adjacent to the
stream is 30 percent and table VH.2 gives the solar
angle as 72° or 308 percent, topographic shading is
INCIDENT HEAT LOAD
(NET SOLAR RADIATION)
Given a specific site, the rate of incoming radia-
tion is constantly changing. To determine the ap-
proximate heat load for the model, the length of
time a given volume of water will be exposed to
direct solar radiation also must be determined.
Travel time of the stream can be found by measur-
ing any of the following: average stream velocity
using a current meter (ft/sec); empirical
relationships using channel slope data; and/or dye
tracing. The net solar radiation must be averaged
for the time that the water will be exposed. This is
accomplished by identifying or interpolating the
appropriate midday solar angle curve and locating
on the time axis the period of day that the stream
will be exposed (fig. VTJ.7).
The radiation value occurring at the midpoint of
the proposed period can normally be used as the
average net radiation value. However, when the
travel time is several hours and the exposed period
goes from midmorning to early afternoon (for ex-
ample, 9 a.m. to 1 p.m.), it may be necessary to
consider the change in slope of the curve and to
select a net radiation value more representative for
the period rather than the midpoint. However, it
should be noted that this model is for stream
reaches less than 2,000 feet in length; travel time
will normally not exceed 2 hours and generally will
be less than 1 hour, thereby eliminating the need to
determine an average net radiation value.
VII.12
-------
Estimate the incident heat load for the site (fig.
VII.7). Continuing with the previous example:
1. Use the maximum solar angle determined
previously (72°).
2. In figure VII.8, interpolate between the 70°
and 80° curve to obtain the 72° values.
3. Determine the critical time period (1:00 p.m.
in this example).
Find the average H value. Travel time
through the exposed section of stream channel
is only 0.3 hour; therefore, it is not necessary
to find an average H value. From figure VII.8,
with a 72° midday angle, the H value for 1:00
p.m. is approximately 4.7 BTU/ft2-min; if we
had used the solar ephemeris for 45° N
latitude, the H value would have been 4.5
BTU/ft2-min. Figure VII.8 illustrates the
procedure used to obtain H in this example.
c
I
m
5 —
Figure VII.7.—Hourly values (BTU/ft2-
min) for net solar radiation above
water surfaces on clear days
between latitudes 30° N and 50° N
for several solar paths (Brown 1970).
5
Q 4
CC
§
o
Solar Angle
(At Solar Noon)
12 1 2 3
TIME of DAY
(Daylight Savings Time)
1
Solar Angle
(At Solar Noon)
55-
m
-4.7
Q
<
DC
8
UJ
3 —
Figure VII.8.—Determination of net
hourly solar radiation using noon
angle of 72°. H Is 4.7 BTU/ft2-mln.
2 —
8 9 10 11
12 1 2 3
TIME of DAY
(Daylight Savings Time)
vn.i3
-------
PERCENT STREAMBED
COMPRISED OF
BEDROCK
The percentage of streambed comprised of
bedrock must be measured or estimated.
ADJUSTED NET SOLAR
RADIATION FOR
BEDROCK STREAMBEDS
Bedrock in the streambed acts as a heat sink,
and conductive loss of energy from the water to the
rock may occur. Brown (1972) recorded a 20-
percent reduction of the incident heat load in a
streambed entirely composed of bedrock. Assum-
ing a linear relationship for lesser exposure of
bedrock, use figure VII.9 to adjust H when bedrock
is exposed in the streambed.
H adjusted = [% WH] + [%B (1.00-C) H] (VII.6)
100
90-
80-
70-
O
2 60-
O
HI
10 50-
UJ40-
DC
111
Q- 30-
20-
10-
0.05 0.10 0.15
CORRECTION FACTOR
0.20
where:
W = percent streambed without bedrock1
(e.g., 0.10),
H = unadjusted heat load (e.g., 4.7 BTU/ft2-
min with a solar ephemeris for 40° N
latitude),
B = percent streambed with rock1 (e.g., 0.90),
and
C = correction factor1 (e.g., 0.18).
C is obtained from figure VTI.9. In the example,
bedrock comprises 90 percent of the streambed;
therefore H should be reduced by 18 percent.
Hadjusted = 0.10(4.7) + 0.90 (1.00 - 0.18) 4.7 = 3.94
Determination Of Discharge, Q
C
DISCHARGE
Figure VII.9.—Correction factor for the heat-sink effect of
bedrock streambeds.
Discharge, that takes place during the critical
summer period following silvicultural activities,
when maximum water temperature may be an-
ticipated, represents the flowing portion of the
stream. This value should reflect any changes in
discharge quantity and timing due to the
silvicultural operation. "Chapter III: Hydrology"
presents a discussion of a procedure and
methodology for deriving these values. Discharge
should be measured during the critical summer
period prior to the proposed silvicultural activity.
Any adjustments in discharge due to the
silvicultural activity can then be made on this
previously measured value.
Determination Of Exposed Surface Area
Of Flowing Water, A
The exposed surface area of a stream is that por-
tion of the flowing water affected by the
silvicultural operation. Large pools with little or no
flow do not significantly influence temperature in-
crease of the flowing water. Brown (1972) found no
temperature gradient in small pools in the direc-
tion of flow and only a small (0.2° C) gradient in
large pools. The lack of complete mixing in the
1AU percent values used in equation VII.6 should be in
decimal form.
vn.i4
-------
pools limits the transfer of heat (i.e., absorbed solar
radiation) from the stagnant water in the pool to
the flowing water. If the total surface area of pools
is considered in determining stream surface area
exposed, the predicted potential temperature in-
crease will be inaccurate; and if more than one pool
is present in the reach, the magnitude of error is in-
creased even more. Dye can be used, if necessary,
to determine the surface area of a pool that should
be used in predicting temperature change.
Furthermore, the surface area of flowing water
exposed by removal of vegetation must be adjusted
to account for the surface exposure prior to the
removal of the vegetation. Riparian vegetation and
timber do not normally shade a stream so com-
pletely as to preclude the transmission of all solar
radiation to the water surface. For example, a
western coniferous stand with 400 square feet of
basal area/acre may allow 5 to 15 percent of the
solar radiation to penetrate (Reifsnyder and Lull
1965).
The following steps are involved in computing
the exposed surface area, A.
LENGTH OF STREAM EXPOSED
AVERAGE WIDTH FLOWING WATER
IN EXPOSED STREAM SECTION
The length of stream that will be exposed by the
silvicultural activity is measured or estimated. The
average width of flowing water in this exposed sec-
tion of stream is measured or estimated during the
time of year when stream temperature is critical.
Accuracy of these measurements or estimates is
critical as the accuracy of the analysis is dependent
upon this information (see app. VILA, "Validation
of Brown's Model").
Atotal = LW
= 530 ft X 1.5 ft
= 795 ft2
(VH.Va)
PERCENT FLOWING WATER SURFACE
SHADED BY BRUSH
The percent shade provided by riparian brush
and shrubs is estimated by field observation.
Again, this estimate should be made during the
time of year when stream temperature is critical.
For the example discussed here, it was estimated
that 15 percent of the flowing water surface was
shaded.
FLOWING WATER SURFACE
AREA SHADED BY BRUSH
The combination of shade provided by brush and
tree canopy will generally prevent most of the net
solar radiation from reaching the water surface.
The surface area shaded by brush is therefore
determined.
In this example, with 15 percent of the flowing
water shaded during the critical period, surface
area shaded by brush would be estimated at 120
square feet.
^ shade brush
LW (% stream
shaded by brush only)
= 530 ft X 1.5 ft X 15%
= 120 ft2
(Vll.Vb)
TOTAL SURFACE AREA
OF FLOWING WATER
TRANSMISSION SOLAR
RADIATION THROUGH
EXISTING VEGETATION
The length of stream exposed, multiplied by the
average width of flowing water, gives surface area.
For example, a stream with a length of 530 feet
and an average width of flowing water of 1.5 feet
has a total surface area of flowing water of 795
square feet.
The solar radiation passing through the existing
crown canopy must be measured or estimated.
Refer to appendix VII.B for a discussion of how this
might be measured and appendix VII .D for tabular
displays of the relationship between stand density
and transmission of solar radiation.
VII.15
-------
SURFACE AREA FLOWING
WATER EXPOSED TO
SOLAR RADIATION
Using surface area exposed under current
vegetative canopy cover, correct for transmission of
light thr-ough the existing stand that has a percent
crown closure. Whenever possible, use only angular
canopy density values (see "Angular Canopy Den-
sity" in app. VII.C). If only vertical crown closure
values are available, estimate percent transmission
of solar radiation. Values for these estimates may
be obtained from Technical Bulletin 1334, pages
72-76 (Reifsnyder and Lull 1965). Assuming a
crown closure of 65 percent, figure VII. 10 shows
that approximately 8 percent of the solar radiation
will be transmitted through the canopy and reach
the stream.
"presently exposed ~~ '"total ^shadebrush/
(% transmission through existing
vegetation) (VII. 7c)
= (795 ft2 - 120 ft2) X 8%
= 54 ft2
The flowing water, therefore, has approximately
54 square feet exposed to solar radiation.
Assuming that all vegetation is removed, the ex-
posed surface area of flowing water would be 741
square feet in the example. If some of the current
vegetative cover were to remain, the surface area
shaded by the remaining vegetative cover would
also be subtracted from Atota] .
Determination of Maximum Potential
Daily Temperature Increase, AT
Determine the maximum potential daily
temperature increase in degrees Fahrenheit using
H, Q, and A values as derived through the previous
steps. Compute the maximum potential change in
daily temperature assuming all riparian vegetation
is removed using Brown's model:
AT = 0.000267
Q
(vn.3)
where:
AT =
A =
Q =
H =
maximum potential daily temperature
increase in degrees Fahrenheit
adjusted surface area
mean discharge that will occur within the
exposed reach during critical period fol-
lowing silvicultural operation
adjusted heat load BTU/ft2-min
TOTAL SURFACE AREA
FLOWING WATER EXPOSED
BY REMOVAL OF ALL SHADING VEGETATION
The surface area required is the additional sur-
face area of flowing water that would be exposed
due to the silvicultural activity. The total surface
area of flowing water cannot be used because part
of the stream (in the example, 54 ft2) is exposed un-
der the existing pre-silvicultural activity vegetative
conditions.
Equation VH3 becomes:
AT =
adjusted
Q
0.000267 (VII.3a)
(The use of subscripts indicates that the variables
in Brown's original model, equation VII.3, have
been refined in this handbook.)
In the example:
Aadjusted = 741 ft2
Hadjusted = 3.94 BTU/ft2-min
Q = 0.4 cfs
"adjusted "total
~ "exposed pre-silvicultural activity (VH.7d)
= 795 ft2 - 54 ft2
= 741 ft2
so that:
AT = 741 ft2 X 3.94 BTU/ft2 - min
0.4 cfs
0.000267 = 1.9° F
VII. 16
-------
100
90
80
0 10
CROWN CLOSURE, percent
20 30 40 50
60
70
-------
Evaluation Of Downstream
Temperature Increases
To evaluate downstream impacts of increased
water temperatures caused by silvicultural ac-
tivity, a mixing formula is used (fig. VH.11):
Tn =
(VII.8)
where:
T
I)
DM
TM
D-
= temperature downstream after the
treated stream enters the main stream,
= discharge main stream,
= temperature main stream above the
treated tributary,
= discharge stream draining treated area,
T-r = temperature stream below treated area
equals temperature above plus computed
temperature increase (i.e., Brown's
model) or (TA + AT) = TT ,
TA = temperature stream above treated
area (measured in field), and
AT = temperature increase computed
using Brown's model.
The mixing ratio formula merely weights the resul-
tant temperature (TD) by discharge. (It should be
noted that small streams with large temperature
increases will be diluted if the stream flows into a
larger water course.)
Site Proposed
Silvicultural Operation
T
D
Figure VII.11.—Components of the mixing formula for
evaluating the downstream impact of increased water
temperature caused by silvicultural activities upstream.
Please note, there are two factors to consider
when estimating the total downstream
temperature increase due to upstream silvicultural
activities. First, the total increase in water
temperature caused by the operation itself must be
determined (i.e., Brown's model). Second, the
reduction of water temperature due to groundwater
inflow must be determined. These factors must be
estimated, and these estimates are generally sub-
ject to considerable error.
Total Increase In Water Temperature
Water temperature increases due to silvicultural
activities have already been discussed. These in-
creases will not normally be reduced by subsequent
passage through undisturbed stands if the distance
is short. The air temperature over a stream during
the critical summer period is usually warmer than
the water, even in undisturbed areas; furthermore,
the net radiation input will continue to be positive.
Therefore, it will generally be impossible for the
water temperature to be reduced by convective,
evaporative, or radiative energy loss to the at-
mosphere.
It follows that up to some limit, known as the
equilibrium temperature, successive silvicultural
activities on one stream will have a compounding
effect on water temperature increases: water
temperature increases due to downstream ac-
tivities will be added onto increases caused by up-
stream operations. This compounding effect may
be eliminated or minimized, however, if the travel
time between activities is of such duration as to
preclude arrival of water from an upstream activity
to a lower activity before evening when cooler air
temperatures and back radiation can lower the
water temperatures, or when there are inflows of
cooler groundwater of sufficient magnitude to
dilute warmer surface water.
Reduction In Water Temperature Due To
Groundwater Inflow
Groundwater is cooler than summer surface
water, and it can reduce water temperature in-
creases caused by silvicultural operations. Since
groundwater temperature is fairly constant for
wide areas, well and/or spring water temperatures
can be used as a measure of groundwater
temperature. A rough rule to be applied, if neces-
sary, is that the groundwater temperature is ap-
proximately equal to the average annual air
temperature.
VII. 18
-------
Groundwater discharge can be measured in the
field. Increasing discharge downstream can be as-
sumed to be groundwater inflow only if there are no
inflowing tributary streams and if there has been
no recent precipitation event which might still be
entering the stream as quick flow rather than base
flow.
In trying to estimate groundwater discharges on
small streams, the error of measurement is likely to
be high and the potential for groundwater cooling
the stream is quite large. This combination can
lead to significant error in predicting temperature
change below an exposed reach.
Once groundwater temperature and inflow have
been measured, or estimated, the mixing ratio for-
mula can be used to evaluate its impact on reduc-
ing temperature increases caused by silvicultural
operations upstream. Groundwater that becomes
surface flow is subject to radiation and convection
heat influxes resulting in temperature increases.
The formula is the same mixing ratio as the one
previously presented in equations V.2. and V.8.
Tn =
DGTG+DTTT
(VH.9)
Figure VII.12.—Components of the mixing formula for
evaluating the impact of ground water temperature and in-
flow on reducing temperature increases due to silvicultural
activities upstream.
These variables are represented on figure YE. 12
where:
TD = temperature downstream at some point
of interest, degrees Fahrenheit,
DG = discharge of the groundwater, cfs; it is
equal to the discharge at the point of in-
terest less the discharge immediately
below the silvicultural operation,
TG = temperature groundwater, degrees
Fahrenheit,
DT = discharge immediately below the
silvicultural operation, cfs, and
TT = stream temperature below the
silvicultural operation which is equal to
the temperature above plus computed
temperature increase or TA + AT = TT ,
and where:
TA = temperature stream above the treated
area (measured in field), and
AT = temperature increase computed using
Brown's model.
Temperature Above
Cut
Site Proposed
Silvicultural
Operation
(Cut)
DT TT Discharge
and Temperature
Below Cut
TA + increase
Discharge and
Temperature Groundwater
At Some Point of Interest
VH.19
-------
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
1. Application of the model should be limited to
stream sections of less than 2,000 feet in length.
Beyond this distance, evaporative and convec-
tive energy losses, assumed to be negligible in
the simplified model, become important sources
of dissipation.
2. Accurate measurement of data is critical.
a. It is essential to measure the average width
of flowing water when stream temperature is
critical (i.e., during the summer months).
Streambed or water surface width should not
be used for computing average width of flow-
ing water if any exposed rocks, gravel bars,
or pools are present in the cross section; to do
so would result in computed maximum
temperatures in excess of actual values.
b. Discharge should be measured whenever
possible and should represent the mean dis-
charge through the exposed reach of stream.
If there will be no increase in discharge dur-
ing the critical summer period following the
silvicultural activity, the discharge
measured before the activity may be used.
However, if the silvicultural activity will
result in increased discharges during the
summer, all calculations must be based
upon the post-silvicultural activity dis-
charge. ("Chapter HI: Hydrology" can be
used to estimate the discharge during the
critical summer period.)
c. Shading, both vegetative and topographic,
must be determined as accurately as possi-
ble. Angular canopy density measurements
should be taken to estimate vegetative
shading. All shading is important. Under-
story noncommercial trees, brush, and low
shrubs may be more significant for shading
purposes than commercial timber. Assuming
the stream is completely shaded at all times
is probably erroneous and will result in es-
timated temperature increases far above ac-
tual increases.
d. The proportion of the exposed streambed
composed of bedrock must be estimated in
order to account accurately for the heat sink.
3. Small streams with braided flows require more
accurate field measurements of stream width
than larger, single channel streams.
4. The capacity of a stream for absorbing heat is
limited. As stream temperature approaches air
temperature, equilibrium will be reached.
5. The model does not consider inflowing cool
ground water. Such a consideration could
significantly reduce the maximum temperature
increase predicted by the model. If inflowing
ground water could alter the temperature in-
crease, its impact can be evaluated by using a
mixing formula (eq. VII.9).
VE.20
-------
LITERATURE CITED
Brazier, Jon R., and George W. Brown. 1973. Buffer
strips for stream temperature control. Res. Pap.
15. For. Res. Lab. Sch. For., Oreg. State Univ.,
Corvallis. 9 p.
Brown, George W. 1969. Predicting temperatures of
small streams. Water Resour. Res. 5(l):68-75.
Brown, George W. 1970. Predicting the effect of
clearcutting on stream temperature. J. Soil and
Water Conserv. 25:11-13.
Brown, George W. 1971. Water temperature in
small streams as influenced by environmental
factors and logging. Proc. Symp. For. Land Uses
and Stream Environ. [Oreg. State Univ., Oct.
19-21, 1970] p. 175-181.
Brown, George W. 1972. An improved temperature
prediction model for small streams. Water
Resour. Res. Inst. WRRI-16. Oreg. State Univ.,
Corvallis. 20 p.
Brown, George W., and James T. Krygier. 1970. Ef-
fects of clear-cutting on stream temperature.
Water Resour. Res. 6(4):1133-1139.
Brown, George W., G. W. Swank and Jack
Rothacher. 1971. Water temperature in the
Steamboat drainage. USDA For. Serv. Res. Pap.
PNW-119. Pac. Northwest For. and Range Exp.
Stn., Portland, Oreg.
Eschner, Arthur R., and Jack Larmoyeux. 1963.
Logging and trout: Four experimental forest
practices and their effect on water quality. Prog. -
Fish Cult. April 1963. p. 59-67.
Hughes, Dallas R. 1976. Personal communication.
Reg. Hydrologist, USDA, For. Serv., Pac.
Northwest Reg., Portland, Oreg.
Lanty, Richard L. 1971. Guidelines for stream
protection in logging operations. Res. Div. Rep.
Oreg. State Game Comm. Portland, Oreg.
Lee, Richard. [In preparation.] Forest
Microclimatology. Columbia Univ. Press.
Meehan, W. R., W. A. Farr, D. M. Bishop, and J.
H. Patric. 1969. Some effects of clearcutting on
salmon habitat of two southeast Alaska streams.
USDA For. Serv. Res. Pap. PNW-82. Pac.
Northwest For. and Range Exp. Stn., Portland,
Oreg.
Reifsnyder and Lull. 1965. Radiant energy in rela-
tion to forests. USDA For. Serv. Tech. Bull.
1334. Ill p.
Smithsonian Institute. 1968. Smithsonian
meteorological tables. 6th ed. Smithson. Misc.
Collect. Vol. 114. Smithson. Inst. Press, Wash.
D.C. 527 p.
Stone, Earl. 1973. The impact of timber harvesting
on soils and water. President's Advis. Panel on
Timber and Environ. Rep. Senate Hearings, p.
427-467.
Swift, Lloyd W., and James B. Messer. 1971.
Forest cuttings raise temperatures of small
streams in the southern Appalachians. J. Soil
and Water Conserv. (May-June 1971.)
U.S. Department of Agriculture, Forest Service.
[n.d.1 Water temperature control. Pac. North-
west Reg., Portland, Oreg. GPO 797-425. p. 27.
VH.21
-------
APPENDIX VILA:
VALIDATION OF BROWN'S MODEL
Brown developed and verified his model in the
West, and utilization by western forest hydrologists
has had good results.
To determine its national applicability, a very
limited validation of the model was conducted in
the East using two treated, clear-cut watersheds
(Watersheds 3 and 7) and a control (Watershed 4)
on the Fernow Experimental Watershed, Parsons,
West Virginia.
The field data collected from Watersheds 3 and 7
consisted of the length and width of the exposed
stream reach following treatment, discharge, and
percent bedrock in streambed. In addition, the ac-
tual water temperature was recorded so that the es-
timated water temperature increase, computed us-
ing Brown's model, could be compared with the ac-
tual increase. Water temperature of the control
watershed was also measured and was used to ap-
proximate the water temperature of the treated
watersheds before treatment.
Using Brown's model, initial estimations of the
water temperature increases following treatment
were +6° F to +10° F higher than the actual
measured values. It was determined that the
average stream width, not the average width of
flowing water, was measured. When the average
width of flowing water was measured Brown's
model estimated within +1° F to +3° F of the ac-
tual water temperature increase, table VE.A.l. No
data were available to estimate the amount of
streamside vegetative shading and, therefore, the
estimated values would tend to be high.
Table VILA.1.—Summation of validation test using data (°F)
from
Fernow Experimental Watershed, Parsons, West Virginia
Watershed/
treatment
3/clearcut
7/clearcut
4/control
Estimated
temperature
using
procedure
presented
°F
64
63
—
Measured
temperature
°F
63
60
58
Difference
+ 1
+3
—
This validation not only indicates that Brown's
model is applicable for use in the East, but also
reaffirms the importance of obtaining accurate
field measurements. The model is only as accurate
as the data that are used.
Actual computations for the two treated
watersheds follow:
Watershed 3, Clearcut
L = 2,336 ft
W = 1.35 ft (average width flowing water)
[Initial width used was 3.30 ft but this was the
average width of the stream.]
A = LW = 2,336 ft X 1.35 ft = 3,154 ft2
Latitude = 39°
Maximum water temperature occurs on
August 28
Maximum Solar Angle = 60° on August 28
Bedrock = 20% Correction Factor = 0.95
H = 4BTU/ft2-min
H adjusted = H X Bedrock Correction Factor
= 4 BTU/ft2 X 0.95
= 3.8 BTU/ft2-min
Q = 0.53 ft3/s
AT _ A Hadjusted 0.000267
Q
= 3,154ft2 (3.8 BTU/ft2 - min) 0.000267
0.53 ft3/s
= 6° F
Water temperature = 58° F for Control
Watershed 4 (not cut)
Control temperature + AT = Estimated water
temperature of
clearcut
58° F + 6° F = 64° F
Estimated temperature = 64° F1
Measured temperature = 63° F for Watershed 3
'No information on shading brush; therefore estimated in-
crease may be high.
VII.22
-------
Watershed 7, Clearcut
L = 2,380ft
W = 1.80 ft (average width flowing water)
[Initial width used was 2.60 ft, but this was the
average width of the stream.]
A = LW = 2,380 ft = 2,380 ft (1.80 ft)
= 4,284 ft2
Latitude = 39°
Maximum water temperature occurs on
August 28.
Maximum Solar Angle = 60° on August 28
Bedrock = 25% Correction Factor = 0.95
H = 4BTU/ft2-min
H adjusted = H(Bedrock Correction Factor)
= 4 (0.95) = 3.8 BTU/ft2-min
Q = 0.83 ftVs
A Hadjusted 0.000267
Q
4,284ft2 (3.8 BTU/ft2 - min) 0_000267
0.83 ftVs
= 5° F
Water temperature = 58° F for Control
Watershed 4 (not cut)
Control temperature + AT = Estimated water
temperature of
clearcut
58° F + 5° F = 63° F
Estimated temperature = 63° F2
Measured temperature = 60° F for Watershed 7
Wo information of shading brush; therefore, estimated in-
crease may be high.
VH.23
-------
APPENDIX VII.B:
STREAMSIDE SHADING
Research conducted throughout the country has
demonstrated that removal of commercial and
noncommercial streamside vegetation will result in
increased water temperatures due to increased ex-
posure of the water surface to direct radiation. Us-
ing Brown's model, the magnitude of the
temperature increase varies with the proportion of
stream exposed.
Maximum increases are associated with clear-
cutting in the streamside area. The increases
reported range from a few degrees to 28° F,
depending upon the area and discharge of the
streams affected (Eschner and Larmoyeux 1963,
Meehan and others 1969, Brown and Krygier 1970,
Brown 1971, and Swift and Messer 1971). Water
temperature can be maintained, however, if there
is adequate shading of the water surface during
periods of maximum solar radiation. Shading may
be topographic, vegetative, or a combination of
both.
TOPOGRAPHIC SHADING
Shading by topographic features includes not
only the major land forms, but also the minor
changes in relief associated with streambanks. The
potential for topographic shading is determined
partly by orientation of the stream with the sun,
and partly by latitudinal location.
Orientation of topographic features in relation to
stream and sun is crucial. Streams oriented east-
west may be shaded in the morning by topographic
features to the south. North-south oriented streams
may be shaded in the morning by topographic
features situated to the east, and to the west in the
afternoon.
Latitudinal position of the stream influences the
extent to which topography or surrounding vegeta-
tion may be effective because latitude determines
solar angle. The path of the sun varies during the
year from 23- Ą1° N latitude (June 21) to 23-V^0 S
latitude (December 22). When the solar angle is
vertical, directly overhead, there is no possibility
for topographic shading; as the angle decreases
from the vertical, the probability and effectiveness
of topographic shading are increased.
VEGETATIVE SHADING
Vegetative shading normally will be the domi-
nant onsite factor controlling the amount of solar
radiation directly striking the water surface.
Shading is not limited to dominant and codomi-
nant tree species, but encompasses all vegetation
to include brush, shrubs, and other low-growing
species.
1. The effectiveness of the shade created will vary
with vegetation type. The effect of type includes
not only species differences but also age class.
The proportion of tree bole in a live crown in-
fluences the extent of shade provided. Mature
coniferous stands, with much of the lower bole
free of limbs, may offer only partial shade;
whereas younger stands, with most of the bole in
live crown, will provide adequate shade for
small headwater streams.
2. The density or spacing of vegetation also deter-
mines the amount of radiation the water
receives. In poorly stocked stands with low den-
sity and crown closure, the trees may be so
widely spaced as to preclude effective shading of
the water course.
3. For a stream of a given width, the height of
vegetation necessary to effectively shade a water
course will vary with the distance from the
stream and the solar angle and orientation.
There is a direct relationship between distance
from the stream and height of vegetation neces-
sary to provide adequate shade (fig. VII.B.I).
4. For a stream of a given width, there is also a
relationship between solar angle and height of
vegetation needed to provide stream shading.
When the solar angle is perpendicular to the
stream surface (i.e., directly overhead), the only
shading is that from vegetation overhanging the
water; the height of riparian vegetation becomes
irrelevant (fig. VH.B.2).
5. Orientation of the sun with respect to the stream
determines the "effective" width of the stream
versus the actual stream width. Effective width
is the length of shadow required to reach com-
pletely across the stream. The actual width
would equal the effective width only when the
sun was oriented at right angles to the stream
VH.24
-------
Figure VII.B.1.—Low growing shrubs and brush adjacent to a water course may provide adequate shade,
while taller vegetation is necessary further from the stream.
Figure VII.B.2.—Position of the sun in relation to the
riparian vegetation determines the time and extent of
vegetative shading.
VH.25
-------
(e.g., due east of a north-south flowing stream,
fig. VII.B.3). At all other times the effective
width would be greater than the actual stream
width and would reach a maximum value (in-
finity) when the sun was directly above the
stream.
Figure VII.B.3.—Orientation of the sun with the stream determines the length of shadows necessary to com-
pletely shade the water surface.
VII.26
-------
APPENDIX VII.C:
WATERSIDE AREAS
Designation of waterside areas by land managers
can be used to prevent or minimize water
temperature increases. It is not feasible to establish
general standards for waterside areas; however,
Brazier and Brown (1973) have evaluated some of
the factors that determine the effectiveness of such
areas.
COMMERCIAL TIMBER VOLUME
Commercial timber volume is not a significant
parameter for determining shading of the stream
by the vegetation in the waterside area. Due to the
relatively narrow width of the headwater (1st, 2nd,
and 3rd order) streams, the effectiveness of the
shade produced by noncommercial tree species,
shrubs and low growing vegetation can be as great
as that produced by commercial species. In addi-
tion, there is a great variability between volume
(board feet) and crown closure (density) which is
manifested in the spacing and number of trees per
unit of area. A few large trees with a large commer-
cial volume may have little protective capability
because of wide spacing, or because crowns may be
too high or sparse to shade the streams. Many pole-
sized trees with a smaller commercial volume may
effectively shade the stream due to their close spac-
ing and dense canopy.
STRIP WIDTH
In the past, land managers have arbitrarily
designated waterside areas according to such fac-
tors as width (which has ranged from less than 50
feet to several hundred feet), topography, or per-
cent slope. Strip width alone is not an important
factor in determining effectiveness of the vegeta-
tion in shading the stream. Strip width is critical
for stream protection only as it is related to canopy
density, canopy height and stream width (fig.
VII.C.l).
Canopy densities of less than about 15 percent
angular canopy density (ACD) do not provide suf-
ficient shade for a measurable reduction in heat
load. Above this value, however, there should be a
100^
I
s.
80—
~ -i
in
I 60-
o
O 40-
3
O)
< 20-
T
I
40
I
T
60
I
20 40 60 80
Waterside Area (feet)
I
100
Figure VII.C.L—The relation between waterside area width
and angular canopy density (Brazier and Brown 1973)
VII. 27
-------
direct relationship between heat reduction and
angular canopy density until the canopy ap-
proaches 100 percent ACD. As the density ap-
proaches 100 percent, additional increments in
density should block less radiation than the
previous increment. Therefore, with greater canopy
density, the relationship between the amount of
heat blocked and the angular canopy density
should approach some maximum value at a level
less than complete blockage of all incidental radia-
tion (fig. Vn.C.2).
When the angular canopy density is not known or
cannot be measured, stream shading may be es-
timated using a clinometer or abney level to iden-
tify those crowns which contribute shade to the
stream. Vertical crown closure values can be used
to obtain a rough estimate of stream shading, but it
should be noted that angular canopy density and
vertical crown closure are normally significantly
different. The importance of obtaining accurate
measurements of stream shading cannot be
overemphasized; it is the basis for establishing ef-
fective waterside area widths to protect the stream
from excessive temperature increases.
c
i 3
m
o
o
CD
|
I I I I I I I I I I
10 100
Angular Canopy Density, %
Figure VII.C.2.—The relation between angular canopy density
(ACD) and heat blocked (AH) (Brazier and Brown 1973).
VH.28
-------
APPENDIX VII.D:
GENERAL RELATIONSHIPS BETWEEN LIGHT INTENSITY OR
TRANSMISSION OF SOLAR RADIATION AND VEGETATIVE COVER
Table VII.D.1.—Effects of stand density removal on light
Intensity (%) (USDA For. Serv.)
Percent
Quantity Fully stocked
removed stand removed
Stem density
Canopy closure
Basal area
0
25
50
'75
0
25
50
75
0
25
50
75
Light intensity
8
14
26
'55
4
6
16
43
10
15
27
52
Table VII.D.4.—Percent light Intensity through eastern conifers
(Reifsnyder and Lull 1965)
Basal area Light intensity
Species (ftVac)
White pine, balsam fir 209
White pine, white spruce, balsam fir 171
White pine, red pine 103
White, red, jack pine, white spruce,
balsam fir 103
7
9
27
25
Table VII.D.5.—Percent light intensity through conifer
plantations (Reifsnyder and Lull 1965)
Spacing
Light in open
'Example: Removing 75 percent of the stems would increase
the light intensity from 8 percent to 55 percent.
2X2
4X4
6X6
8X8
15.9
36.0
46.6
55.4
Table VII.D.2.—Effects of tree spacing (ft) on light
intensities (%) (USDA, For. Serv.)
Spacing
(«)
4X4
6X6
7X7
9X9
Trees
(number/ac)
2,721
'1,210
889
538
Light Intensity
15
'16
36
60
Table VII.D.6.—Stand basal area (ft2/a) and equivalent solar
loading (BTU/ft2-min) beneath the canopy
(Hughes 1976, personal communication)
'Example: By removing slightly less than half the trees (538)
from a 6 X 6 foot spacing (1,210) increases the light intensity from
16 percent to 60 percent.
Table VII.D.3.—Percent light Intensity through small-1 and
large-2 crown trees (Reifsnyder and Lull 1965)
Stem density
(in/ac)
200
700
1,200
1,900
3,700
Basal area
(ft/ac)
20
60
100
180
400
Percent of small-crowned trees
0-33 34-67 68-100
Percent light Intensity
87
57
34
13
7
90
70
50
30
10
94
78
63
43
12
Solar load ing
% of open
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Total stand basal area
Dense crown1 Moderate crown2
255
200
160
135
120
105
90
80
70
60
55
45
35
30
25
20
10
5
0
400
305
245
210
180
160
140
120
105
90
80
70
55
45
35
30
20
10
0
'Small—western white pine, western larch, and Douglas-fir.
2Large—grand fir, western hemlock, and western red cedar.
'Dense crown includes normally stocked stands of western
hemlock, western redcedar, Sitka spruce, Pacific silver fir, and un-
even aged mixed stands. Also overstocked hardwood stands.
2Moderate crown includes even aged Douglas-fir stands, and
normally stocked red alder or black cottonwood.
VH.29
-------
100
0 10
CROWN CLOSURE, percent
20 30 40 50
60
POINTS FROM PUBLISHED STUDIES
O IN WHICH CROWN CLOSURE WAS
REPORTED OR COULD BE ESTIMATED
POINTS FROM STUDIES IN WHICH
STEM DENSITY WAS REPORTED OR
COULD BE ESTIMATED.
CROWN CLOSURE
(UPPER SCALE)
STEM DENSITY
(LOWER SCALE)
0 1000 2000 3000 4000 5000 6000 7000
STEM DENSITY, inches per acre
Figure VII.D.1. Transmission of solar radiation as a function of stem density and crown
closure (Reifsnyder and Lull 1965).
VH.30
-------
Chapter VIII
PROCEDURAL EXAMPLES
this chapter has been prepared by the coordinators
for chapters III-VII
vrn.i
-------
CONTENTS
Page
INTRODUCTION Vffi.1
PROCEDURAL EXAMPLE FOR GRITS CREEK—A RAIN DOMINATED
HYDROLOGIC REGION VIE.2
DESCRIPTION OF AREA AND PROPOSED SILVICULTURAL ACTIVITY VIII.2
Water Quality Objectives VIII.2
DATA BASE VIII.5
HYDROLOGY ANALYSIS VDI.5
Water Available For Streamflow—Existing Conditions VIE.5
Water Available For Streamflow—After Proposed
Silvicultural Activity VIE.13
Flow Duration Curve Development—Existing Conditions VIII.13
Flow Duration Curve Development—After Proposed
Silvicultural Activity Vffl.14
SURFACE EROSION ANALYSIS VIE.16
Erosion Response Unit Delineation VIII. 16
Using the Modified Soil Loss Equation (MSLE) VIII.22
Rainfall Factor VIII.22
Soil Erodibility Factor VIII.22
Length-Slope Factor VIII.22
Vegetation-Management Factor Vin.24
Surface Area Of Response Unit VIII.25
Sediment Delivery VIII.25
Differences Between Management Alternatives VIE.26
TOTAL POTENTIAL SEDIMENT ANALYSIS VHI.26
Suspended Sediment Calculation VIE.26
Bedload Calculation VIII.30
Total Potential Sediment Calculation VIII.30
Channel Impacts VIE.31
TEMPERATURE ANALYSIS VEI.31
Lower Reach VIE.31
Computing H, Adjusted Incident Heat Load VIE.31
Computing Q, Stream Discharge VIE.34
Computing A, Adjusted Surface Area VEI.34
Middle Reach VIE.35
Computing H, Adjusted Incident Heat Load VIE.35
Computing Q, Stream Discharge VIE.35
Computing A, Adjusted Surface Area VIE.35
Upper Reach VIE.36
Computing H, Adjusted Incident Heat Load VIE.36
Computing Q, Stream Discharge VIE.36
Computing A, Adjusted Surface Area VIII.36
vm.ii
-------
Page
The Mixing Ratio Formula VIII.37
ANALYSIS REVIEW VIII.38
Worksheets For Grits Creek, Alternatives A and B Vffl.41
PROCEDURAL EXAMPLE FOR HORSE CREEK—A SNOW DOMINATED
HYDROLOGIC REGION VIII.72
DESCRIPTION OF AREA AND PROPOSED SILVICULTURAL ACTIVITY. VIII.72
Water Quality Objectives VHI.72
DATA BASE Vffl.72
HYDROLOGY ANALYSIS VHI.72
Water Available For Streamflow—Existing Conditions VHI.72
Water Available For Streamflow—After Proposed
Silvicultural Activity VEI.81
Streamflow Discharge And Timing—Existing Conditions VIII.82
Streamflow Discharge And Timing—After Proposed
Silvicultural Activity VEI.83
SURFACE EROSION ANALYSIS VHI.83
Erosion Response Unit Delineation VIII.83
Using The Modified Soil Loss Equation (MSLE) Vffl.85
Rainfall Factor VHI.85
Soil Erodibility Factor VHI.85
Length-Slope Factor VHI.86
Vegetation-Management Factor VIII.87
Surface Area Of Response Unit Vm.88
Sediment Delivery VEI.89
SOIL MASS MOVEMENT ANALYSIS VHI.91
TOTAL POTENTIAL SEDIMENT ANALYSIS VHI.91
Suspended Sediment Calculation VIII.91
Bedload Calculation VHI.95
Total Potential Sediment Calculation VHI.95
Channel Impacts VEI.97
TEMPERATURE ANALYSIS VIII.100
Computing H, Adjusted Incident Heat Load VIII.100
Computing Q, Stream Discharge VIII.102
Computing A, Adjusted Surface Area VIII.102
The Mixing Ratio Formula VIII.102
ANALYSIS REVIEW VIII.103
Interpretation Of The Analysis Outputs VIII.103
Comparing Analysis Outputs To Water Quality Objectives VIII. 104
Control Opportunities For Soil Mass Movement VIII. 104
Control Opportunities For Surface Erosion VIII. 105
Control Opportunities For Temperature VIII. 105
Revised Silvicultural Plan VIII.108
Worksheets For Horse Creek, Proposed And Revised Plans VIII. 109
LITERATURE CITED VEI.160
Vffl.iii
-------
LIST OF FIGURES
Number Page
Vm.l. —Timber compartments for Grits Creek watershed VIE.3
Vm.2. —Road constructed for Alternative B, Grits Creek watershed Vffl.4
VIII.3. —Annual flow duration curves for existing and alternative A or B
conditions, Grits Creek watershed VIE.15
VItI.4. —Drainage net, Grits Creek watershed VIII.17
Vin.5. —Hydrographic areas, Grits Creek watershed VIE.18
VIII.6. —Soil groups, Grits Creek watershed Vffl.19
Vm.7. —Silvicultural treatments, Grits creek watershed VIE.20
VIII.8. —Enlargement of example hydrographic area showing individual ero-
sion response units VIE.21
VIE.9. —Stiff diagram for alternative A CC3.1, Grits Creek watershed VIE.27
VIII.IO.—Sediment rating curve, Grits Creek watershed VIE.28
VIII.ll.—Channel stability threshold limits in relationship to the sediment
rating curve, Grits Creek watershed VIE.29
VIII.12.—Water temperature evaluation, Grits Creek watershed VIE.32
VIII. 13.—Pre- and post-silvicultural activities annual hydrograph, Horse Creek
watershed VIE.84
VEI.14.—Stiff diagram for CC3.1 of proposed plan, Horse Creek watershed .. VIE.90
VEI.15.—Horse Creek drainage showing potential areas of mass movement... VIE.93
VIII.16.—Sediment rating curve, Horse Creek watershed VIE.94
VEI.17.—Bedload rating curve, Horse Creek watershed VIII.96
VIII.18.—Bedload transport-stream power relationship, Horse Creek
Watershed VIE.99
Vin.iv
-------
LIST OF TABLES
Number Page
VIII.l.—A summary of information required for the analysis procedures, Grits
Creek watershed Vni.6
VHI.2.—Summary of quantitative outputs for Alternative A, Grits Creek
watershed VHI.39
Vin.3.—Summary of quantitative outputs for Alternative B, Grits Creek
watershed VHI.40
VIII.4.—A summary of information required for the analysis procedures, Horse
Creek watershed VEI.73
Vin.5.—Summary of quantitative outputs for proposed plan, Horse Creek
watershed VEI.92
Vin.6.—Summary of quantitative outputs for revised plan, Horse Creek
watershed VHI.107
vm.v
-------
INTRODUCTION
This chapter provides examples of silvicultural
activities on two hypothetical watersheds—one in a
rain dominated hydrologic region (Grits Creek) and
one in a snow dominated region (Horse Creek). It
demonstrates the procedural analyses that would
be conducted to evaluate the potential non-point
source pollution associated with each example.
Where such potential non-point source pollution
would exceed established water quality objectives,
the procedure for considering control opportunities,
thereby revising the original silvicultural plan, is
explained.
All figures, tables, and worksheets mentioned
within this chapter are referenced according to
their original chapter number. Only figures unique
to chapter VIE have been given "VIE" numbers.
VEI.l
-------
PROCEDURAL EXAMPLE FOR GRITS CREEK—A RAIN DOMINATED
HYDROLOGIC REGION
DESCRIPTION OF AREA AND
PROPOSED SILVICULTURAL ACTIVITY
Foresters from the Appalachian Hardwood
Products Company1 inventoried a 356-acre tract of
hardwoods (fig. VIII. 1) owned by the company in
the southern Appalachians. The watershed is at a
latitude of 35°N. The baseline leaf area index
(LAI) is 6. Dominant aspect is southwest, and the
average rooting depth for the watershed is 4 feet.
The tract was divided into timber compartments
A, B, and C (fig. VIII.1) based upon stand composi-
tion; management prescriptions were proposed for
each. A description of each timber compartment
and the prescribed management options follows.
Compartment A is an 84-acre stand along the
ridgetop of the watershed. It is composed of low
quality northern red oak and a dense laurel-
rhododendron understory. Trees are short and
branchy because of repeated ice damage, and the
growth potential is low in these steep, rocky, shal-
low soils. Because of high recreation use and the
poor site condition for timber production, the com-
pany forester recommended that no silvicultural
activity be conducted.
Poor oak-hickory stands are present on the lower
slopes in compartment B, producing little timber;
but soils are deep, well watered, and capable of
timber production. The proposed residual leaf area
index is estimated to be 2. The forester recom-
mended that the 180-acre timber stand be
regenerated by clearcutting all woody vegetation
after harvesting mechantable timber.
Compartment C, 92 acres, contains a 40-year-old
stand of excellent yellow poplar mixed with over-
mature remnants of other cove hardwoods. It was
originally estimated that the yellow poplar would
be from 85 to 120 feet high at age 50, but the growth
rate of the overcrowded stand has slowed during
lThis is intended to be a fictitious company name; any
similarity to an actual company is entirely coincidental.
the last 7 years. A thinning has been recommended
by the company forester to increase growing space
for crop trees. Additional cuts will be required at
20-year intervals. The proposed residual leaf area
index is estimated to be 3. Compartment C would
be reevaluated for a possible clearcut in 40 years, in
accordance with the company's policy of even-aged
management. Then the site would be regenerated
to yellow poplar or other desirable species.
Based upon these management prescriptions,
engineering and harvesting system analyses were
made. Two alternatives were developed for analysis
using the basic steps outlined in "Chapter II:
Control Opportunities," Appendix n.A, example
two. The significant resource impacts were "bare
soil" and "compaction." Based on a knowledge of
the site and professional judgment, the following
control opportunities were selected.
1. Prescribe yarding and skidding layout.
2. Revegetate treated areas promptly, as local
conditions dictate.
The two engineering and harvesting alternatives
were based on different yarding systems, road loca-
tions, and revegetation prescription. Alternative A
was based on tractor yarding with road locations
shown in figure VIE.2. Alternative B was based on
cable yarding systems and required an additional
road (fig. Vffl.2) to achieve reasonable yarding dis-
tances. Revegetation of all roads, including run-
ning surfaces, was planned in Alternative B. Both
alternatives were analyzed and the results com-
pared to water quality objectives.
Water Quality Objectives
Water quality objectives were established for the
Grits Creek area by the Regional Planning Com-
mission in conjunction with State 208 planners.
The established objectives required that channel
stability be maintained, that total potential sedi-
ment discharge be limited to 25.5 tons/yr and that
water temperature increases be no greater than
3° F.
VIH.2
-------
1 mile
Figure VIII.1.—Timber compartments (or Grlto Creek watershed.
vm.3
-------
Road for Alternative B
1 mile
Figure VIII.2.—Road constructed for Alternative B, Grits Creek watershed.
vra.4
-------
DATA BASE
The collected data are presented in table Vffl. 1
and worksheets IV.l, IV.2, V.I, and VII.2.
(Proposed and revised worksheets are located at
the end of section "Procedural Example for Grits
Creek—. . .") Soils were mapped by the Soil
Conservation Service. All data presented are re-
quired, unless otherwise specified, for a complete
water resource evaluation of Grits Creek, the major
drainage in the tract. The complete evaluation re-
quires analyses within the following categories
(numbers for the corresponding chapters in this
handbook appear in parentheses):
Hydrology (HI)
Surface Erosion (IV)
Total Potential Sediment (VI)
Temperature (VH)
HYDROLOGY ANALYSIS
The hydrology analysis serves as a guide to es-
timate change in potential streamflow associated
with silvicultural activities in rainfall dominated
regions. The methodology and procedures
presented in this document are only guidelines to
complement professional judgment for a particular
situation.
Water Available For Streamflow—
Existing Conditions
Step 1. — The first step in the hydrologic evalua-
tion of Grits Creek is to estimate the water
available for streamflow under existing conditions
using worksheet ELI. The necessary procedures are
outlined below. (Numbers in parentheses refer to
items or columns on the worksheet.)
(1) Watershed name. — Grits Creek may be
treated as a single watershed unit for hydrologic
evaluation (see "Chapter HI: Hydrology").
(2) Hydrologic region. — Grits Creek is
located in hydrologic region 2, Appalachian Moun-
tains and Highlands. The region is also described
in chapter HI.
(3) Total watershed area. — Drainage size is
356 acres.
(4) Latitude. — The latitude of Grits Creek is
35°N. This is necessary input since evapotranspira-
tion was found to be a partial function of latitude in
region 2.
(5) Season. — The seasons for rainfall
dominated regions are: fall (September, October,
November); winter (December, January,
February); spring (March, April, May); and sum-
mer (June, July, August).
(6) Compartment. — The entire watershed is
considered to be unimpacted under existing condi-
tions (i.e., no areas affected by previous
silvicultural activities).
(7) Silvicultural state. — Watershed areas are
grouped into zones of similar hydrologic response
as identified by silvicultural or vegetational state.
For Grits Creek, the only silvicultural state is
"forested." There is a single silvicultural prescrip-
tion for the existing condition consisting of a single
silvicultural state — forested.
(8) Area, acres. — The silvicultural zone is
"forested," and this forested area is 356 acres.
(9) Area, %. — This refers to the percentage of
the prescription area in each silvicultural state. In
this case, the forested area is 100 percent (1.00 as a
decimal percent) of the prescription area.
(10) Precipitation. — Enter estimates of
seasonal precipitation to the nearest 0.1 cm. For
Grits Creek, precipitation averaged 23.3, 75.2, 60.5,
and 27.0 cm for fall, winter, spring, and summer,
respectively. Analysis requires precipitation and
evapotranspiration to be entered in centimeters.
(11) Baseline ET. — Baseline evapotranspira-
tion (ET) for a latitude of 35°N is taken from figure
III. 11. Respective values for fall, winter,
spring, and summer are 20.1, 8.9, 13.0, and 39.1
cm.
(12) Basal area. — Since the leaf area index is
known, basal area is not needed.
(13) Leaf area index. — The leaf area index has
been estimated as 6 for Grits Creek. Leaf area in-
dex does not change with seasons since leaf fall is
taken into account when ET estimates are deter-
mined.
(14) ET modifier coefficient. — Evapotran-
spiration modifier coefficients, as functions of leaf
area index and season, are obtained from figure
ffi.16. For undisturbed forested areas, the ET
modifier coefficent is 1.0 for all seasons.
(15) Rooting depth modifier coefficient. —
Rooting depth modifier coefficients are taken from
figure in. 19 for an average soil depth. In this exam-
ple, all rooting depth modifier coefficients are
equal to 1.0.
vm.5
-------
Table VI I 1.1.—A summary of information required for the analysis procedures. Grits Creek watershed
Description of the
information
required
n format i on
requirements
by chapter!/
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology
Flow — hydrograph or flow
duration curve
Bankful
Basef low
Representative flows to be used to
establish suspended and bed load
rating curves
Width stream
Bankful
Baseflow (average width flowing
water)
Depth stream (bankful)
Water surface slope
Suspended sediment for representative
f lows
Bed load sediment for representative
flows
Channel stability rating
Orientation stream — azimuth
Low flow period (date)
Percent streambed in bedrock
Bedrock adjustment factor
Length reach exposed
Travel time through reach
0
X,P
X
X
X
X
X
X
X
X,P
X
X
X
X
p
X
X
N/fl
Uow«*- KacK . O.Sefe ; Middle. »-€ack •. o.Scfe -} (Lpptr beack ; 0.1 cfe
Ra.w« 3znt .10
0
N//I
Uowev reack : S.O ft ^ Middle veack '• 3.S ft. j u.ppcv rftitU. : 2.0 ft
N/fl
M/fl
Fujuve. ~3SL • I0
M//I
Faiv-
35°
Last coe«k of flugust
15%
Figure int.? J 0.15
Lower r«ick : 3,ooo ft 3 middle v«ack : 1,900 ft • u^per Knack •. l^ooo tt
Lower v-eaek : feSmiKi j wiicUf*. KacK ; so wiin ; Uf pev- >-eaok •• AS wm
- P - Data provided in this handbook
0 - Optional data, not required for analysis
X - Usei—provided data
-------
Table VI11.1.--continued
Description of the
Information
requ I red
Information
requ 1 rements
by chapter
III
IV
V
VI
VII
Information for watershed
Information on hydrology — continued
Normalized hydrographs
of potential excess water
Normalized flow duration curves
Date of peak snowmelt discharge
Map of drainage net
Presence of springs or seeps
Change stream geometry
Water surface slope
Bankful width
Bankful depth
P
P
0
X
X
X
X
X
X
X
X
X
M/fl
Rgure.Jt.a.a,
w/fl
Figure. 3fflL.f
M/fl
N/fl
N/fl
M/fl
Information on climate
Precipitation
Form
Annual average
Seasonal distribution
Storm intensity and frequency
Extreme event
1 yr, 15-minute storm intensity
Drop size
Precipitation — ET relationship
Wind direction
X
X
X
P
X
0
0
0
X
0
X
X
Rain
ISC..O cm
7/1 i »/30 •• 33.3awt • u/ 1, »/AS , IS.SLc*. ', 3/t i. %, • <#.Sc«\ ; '/ -fe %, • 3?.oc^
N/fl
3.5 m/hr
M/fl
tt/fl
N/fl
-------
Table VIII .1.—continued
Description of the
information
required
1 nf ormat ion
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on climate — continued
Snow retention coefficient
Date snowmelt begins
Maximum snowmelt rate
Radiation
Solar ephemeris
Heat influx
Iso-erodent map for "R" factor
X,P
0
0
p
p
p
M/fl
N/A
N/fl
Fi<,u.teJZlE.i
Ffguv-e3lL7
figure. IHE.lj 3oo
Information on vegetation
Species
Height
Overstory
Understory
Riparian vegetation
Presence phreatophytes
Crown closure (%)
Cover density
Leaf area index (pre)
Basal area
Basal area — Crimv relationship
Ground cover
X
X
p
X
0
p
X
X
X
X
X
X
X
X
X
X
SotttWv ovd Cove tardtoood
80%
10 ft 4* 60#
aft 4 |a.tt
N/fl
Uoiuer >-e«c.K: J«% werslovy ,5°% iuiy , SS% anJevstery j
uppev >-eack: SO&wrsUy , so% u«dt«tvy
M/ft
C,
N//I
N/fl
Wo-ks^^t JC-l
3
t—I
(-H
00
-------
Table VI I I .1.— continued
Description of the
information
required
Percent transmission solar radiation
through canopy
Percent stream shaded by brush
Base line ET
ET modifier coefficient
Rooting depth
Rooting depth modifier coefficient
Information
requirements
by chapter
1 1 1
IV
V I VI
VI 1
Information for watershed
Information on vegetation — continued
X,P
P
X
P
X,P
X
Tobi«s 301.0.1 *TJ3nL.o.tJfi3Ure3ar.o.i;ioui»- reacU. 57. p--« ,'S7. post j vn'iJJIc. Katk : 5% ore. ,
lo?o post j upp€r 1-eo.tk •' S % prt. , la% past
Lowev v«ack : 3-S % j widdk, wact.:^o% -} «fy«v- «ack <*>Ł%
Rgare. 3E- »
Fi9u.ve.3IL Ife
Average
Figav<. HL \9
Information on soils and geology
Depth soi 1
Percent sand (0.1-2.0 mm)
Percent silt and very fine sand
Percent clay
Percent organic matter
Soi 1 texture
Soi 1 structure
Permeab i 1 i ty/ 1 n f i 1 trat i on
Presence of hardpan
Nomograph for "K" factor
Baseline soil-water relationships
Soil -water modifier coefficients
Jointing and bedding planes
X
X,P
P
X
X
X
X
X
X
X
X
P
X
X
X
X
X
Worksheet JE.l
Wov-lcsWei; 35C.1
Wovksln-ett OZ.-l
WorlcsWi HL.l
U)8»-lcsl»€€t m . 1
UJwIcskee"!: T3C . i
tOahlcsli€€"t 15T-1
llUovlts^ 3L .1 a«d tuo^slicet 3E .?
Wo
F,-^^. IE. 3
N/fl
W/fl
M/A
-------
Table VI I 1.1.—continued
Description of the
i nf ormat ion
required
Information
requ i rements
by chapter
1 1
IV
V
VI
VI 1
Information for watershed
Information on soils and geology — continued
Soi 1 s map
Previous mass movements
Number
Location
Unit weight dry soil
Del i very potential
Percent silt and clay delivered
Median size coarse material
0
X
X
X
X
X
X
F
X
X
B^urelSniL.fi
M/fl
M/fl
M/fl
N/fl
M/fl
N/ A
N/A
Information on topography
Map (hydrologlc region)
Latitude
Size watershed
Elevation
Aspect
Slope
Length
Gradient
Dissection
Shape/ Irregu larity
Nomograph for "LS" factor
X
X
X
X
X
X
X
X
X
p
X
X
X
X
X
X
X
X
(Z.S&S map, fiau^TTTr.*/ s hydwiosic v^gioK A.
35°
356 acres
Ranges WA 3750 ib WO ft
SoJkiaest
East 53% -y w
-------
Table VII I .1.—continued
Description of the
i n format i on
requ ired
nformation
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on topography — continued
Surface roughness
X
fYlo
-------
Table VII I .1.—continued
Description of the
Information
required
Information
requirements
by chapter
1 1 1
IV 1 V
VI
VI 1
Information for watershed
Information on si 1 vlcu Itural activity — continued
Transportation system
Area disturbed
Location
Cut slopes (location and slope)
Fill slopes (location and slope)
Cut and fill vs. ful 1 bench
Ins lope vs. outs lope
Surface
Width
Gradient
Surfacing (amount and kind)
Road density
Harvesting system
Landings
Location
Size
Gradient
Ground cover
Time for vegetative recovery of
disturbed surfaces
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Figuve. uniL . i -lcsli«<,t or. a.
Figure. 3ZflL. 2. o*d tuifrtstaei H .1*
tofrUe^tlT.a.jlttatk'affft-aoft • slope • I7<# - /€.
U ft tr J3ft
0% fe 1%
Bore, eairtk.
N/A
TvticW yawlin^
' VJ
Rauire. "OTTT . 2- avid to«4slve«t 31 . 2. -} along wxuls
\jOo4cskeet UC.2- ; vat-iclok
WovUheel JE.a j v/ariotJt
Wov4cstieetl!r. X
M/fl
-------
(16) Weighted adjusted ET. — The weighted
adjusted ET is calculated by multiplying baseline
ET [col. (11)], ET modifier coefficient [col. (14)],
rooting depth modifer coefficient [col. (15)], and
area as a decimal percent [col. (9)]. Weighted ad-
justed ET values for fall, winter, spring, and sum-
mer are calculated as 20.1, 8.9, 13.0, and 39.1 cm,
respectively.
(17) Weighted adjusted seasonal ET. — The
sum of weighted adjusted ET values [col. (16)] for a
season equals the weighted adjusted evapotran-
spiration for that season. Values are in centimeters
rounded off to one decimal place.
Weighted adjusted seasonal ET
Season
Fall
Winter
Spring
Summer
20.1cm
8.9cm
13.0 cm
39.1cm
(18) Water available for seasonal streamflow.
— The difference between weighted adjusted
seasonal ET [col. (17)] and seasonal precipitation
[col. (10)] is the water potentially available for
seasonal streamflow. For Grits Creek, fall, winter,
summer, and spring potential streamflows were
3.2, 66.3, 47.5, and -12.1 cm, respectively.
(19) Annual ET. — The sum of adjusted
seasonal ET values [col. (17)] is annual ET. This is
81.1 cm for Grits Creek.
(20) Water available for annual streamflow.
— The sum of water available for seasonal
streamflow values [col. (18)] is the water available
for annual streamflow. This is 104.9 cm for Grits
Creek.
Water Available For Streamflow—After
Proposed Silvicultural Activity
Step 2. — The second step in the hydrologic
evaluation of Grits Creek is to estimate the water
available for streamflow if the proposed
silvicultural activity is implemented. The neces-
sary steps in worksheet ffi.2 are detailed below.
(Numbers in parentheses refer to items or columns
in the worksheet.) Since the acreage cut does not
change for the two management alternatives, the
analysis is the same.
(l)-(5). — Same as worksheet ELI.
(6) Compartment. — For the proposed condi-
tion of Grits Creek, there are two compartments:
impacted and unimpacted. The impacted com-
partment includes those areas affected directly or
indirectly by the proposed silvicultural activities,
while the unimpacted compartment includes areas
unaffected by the proposed silvicultural activities.
(7) Silvicultural state. — Watershed areas are
grouped into zones of similar hydrologic responses
as identified by silvicultural or vegetational state.
For the proposed condition of Grits Creek, the un-
impacted compartment has one silvicultural
state—forested. For the impacted zone, there are
two—clearcut and thinned. As with the existing
condition, there is one silvicultural prescription.
However, this prescription consists of three
silvicultural states — forested, clearcut, and
thinned.
(8) Area, acres. — For the proposed condition,
the silvicultural states are forested, clearcut, and
thinned with respective areas of 84, 180, and 92
acres.
(9) Area, %. — The area of each silvicultural
state in column (8) is divided by item (3), total
watershed area, and rounded off to the third
decimal place. In this example, decimal percentage
for forested, clearcut, and thinned zones and are
0.236, 0.506, and 0.258, respectively.
(10) Precipitation. — Seasonal precipitation to
the nearest 0.1 cm is entered by the user. For Grits
Creek, mean seasonal precipitation was 23.3, 75.2,
60.5, and 27.0 cm for fall, winter, spring, and sum-
mer, respectively.
(11) Baseline ET. — Baseline ET is the same for
each silvicultural state within a season. The values
taken from figure HI. 11 for a latitude of 35°N are
20.1, 8.9, 13.0, and 39.1 cm for fall, winter, spring,
and summer seasons, respectively.
(12) Basal area. — Since the leaf area index
(LAI) has been estimated, basal area data are un-
necessary.
(13) Leaf area index. — Leaf area index (LAI)
values have been estimated by a professional
forester as 2 and 3 for clearcut and thinned areas,
respectively.
(14) ET modifier coefficient. — Evapotrans-
piration modifier coefficients, as functions of leaf
area index and season, are obtained from figure
in.16. In this example, the modifier coefficients
are:
Season
Fall
Winter
Spring
Summer
Forested
1.00
1.00
1.00
1.00
Clearcut
0.81
0.65
0.60
0.69
Thinned
0.90
0.76
0.72
0.84
VIII.13
-------
(15) Rooting depth modifier coefficient. —
Rooting depth modifier coefficients are taken from
figure ni.19 for an average soil depth. Here, all
rooting depth modifier coefficients are equal to 1.0.
(16) Weighted adjusted ET. — Multiplication
of baseline ET, ET modifier coefficient, rooting
depth modifier coefficient, and area as a decimal
percent yields adjusted ET values as follows:
Season Forested Clearcut Thinned
Fall 4.74cm 8.23cm 4.67cm
Winter 2.10cm 2.93cm 1.75cm
Spring 3.07cm 3.95cm 2.41cm
Summer 9.23cm 13.65cm 8.47cm
(17) Weighted adjusted seasonal ET. — Sum-
mation of adjusted ET values by activity yields
weighted adjusted seasonal ET for the watershed.
Fall, winter, spring, and summer values are 17.6,
6.8, 9.4, and 31.4 cm, respectively.
(18) Water available for seasonal streamflow.
— The difference between weighted adjusted
seasonal ET and seasonal precipitation is water
available for seasonal streamflow. The respective
values are 5.7, 68.4, 51.1, and -4.4 cm for fall,
winter, spring, and summer, respectively.
(19) Annual ET. — The sum of weighted ad-
justed seasonal ET values [col.(17)] is annual ET.
This is 65.2 cm.
(20) Water available for annual streamflow.
— The sum of column (18), seasonal streamflow, is
equal to water available for annual streamflow.
This is 120.8 cm.
Flow Duration Curve Development—Existing
Conditions
Step 3. — The third step in the hydrologic
evaluation is to estimate the flow duration curve
for the existing condition. The necessary steps out-
lined in worksheet III.3 are detailed below.
(Numbers in parentheses refer to the items or
columns on the worksheet.)
(1), (2). — Same as worksheet III.l.
(3) Water available for annual streamflow —
existing condition. — This value has been
calculated in worksheet III.l, item (20), to be 104.9
cm.
(4) Annual flow from duration curve for
hydrologic region. — Figure III.22 gives the an-
nual flow for watersheds in hydrologic region 2 as
72.0 cm using 11 points to calculate the area
beneath the curve.
(5) Adjustment ratio. — Estimated water
available for annual streamflow divided by flow,
represented by the flow duration curve, equals the
adjustment ratio. The adjustment ratio is rounded
to the third decimal place and used to correct the
given flow duration curve to equal the expected
yield. For Grits Creek, it is:
104.9
72.0
= 1.457
(6) Point number. — This is the numerical
order of points used to define the flow duration
curve.
(7) Percent of time flow is equaled or ex-
ceeded. — These values are read at equidistant in-
tervals along the X-axis of figure III.22. The inter-
val is a function of the number of desired points
[i.e., if 11 points are used, the interval is 100/(11-
1)].
(8) Regional flow. — These are the Y-axis
values of figure III.22 corresponding to the X-axis
values in column (7). This column is not necessary
if a flow duration curve for the existing condition is
available.
(9) Existing potential flow. — Regional flow
[col. (8)] is multiplied by the adjustment ratio
[item (5)] to give the existing potential streamflow.
If a flow duration curve for the existing condition is
available, no correction is necessary. Column (9) is
plotted versus column (2) to yield the flow duration
curve for the existing condition (fig. VIII.3).
(10) Existing potential flow (cfs). — Conver-
sion of cm/7 days to cubic feet per second (cfs) is
accomplished by multiplying column (7) x area
(acres) x 0.002363 for 7-day intervals.
Flow Duration Curve Development-
After Proposed Silvicultural Activity
Step 4. — The final step in the hydrologic
evaluation of Grits Creek is to estimate the 7-day
flow duration curve for conditions after the
proposed silvicultural activity has been conducted.
The necessary steps outlined in worksheet III.4 are
detailed as follows. (Numbers in parentheses refer
to the items or columns on the worksheet.)
(1), (2). — Same as worksheet UI.2.
(3) Watershed aspect code. — The dominant
aspect of Grits Creek is southwest. Hydrologic
characteristics dictate that, for the purposes of flow
duration curve calculation, an aspect of west be as-
signed a code of zero for the watershed (this
eliminates the aspect adjustment).
(4) Existing condition LAI. — Existing LAI
has already been given as 6.
VIII.14
-------
I
i—'
01
Alternative A or B
20 30 40 50 60 70 80
PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
90
100
Figure VIII.3.—Annual How duration curves for existing and alternative A or B conditions, Grits Creek watershed.
-------
(5) Proposed condition LAI. — Proposed con-
dition leaf area index is an area weighted index for
the silvicultural states which for this example are
forested, clearcut, and thinned areas. Leaf area in-
dex values are from worksheet III.2, column (13).
The weighted post-activity index can be
calculated as:
weighted forest + weighted clearcut
+ weighted thinned
= weighted average
or
(6 X 0.236) + (2 X 0.506) + (3 X 0.258) = 3.2
(6) Change in LAI. — The difference between
existing and proposed condition leaf area indices
yields the change in leaf area index. In this case, it
is 6 - 3.2 = 2.8.
(7) Rooting depth modifier coefficient. — For
Grits Creek, the rooting depth modifier coefficient
is 1.
(8)-(12). — The least squares equation coef-
ficients for the example are found in table in.4.
(13)-(15). — Same as columns (6), (7), (9), and
(10) of worksheet III.3, respectively.
(16) b0 . — This is item (8) found in table III.4.
(17) biQj. — Item (9) X column (15).
(18) b2CD. — Item (10) X item (6).
(19) bsAS. — Item (11) X item (3).
(20) b4RD. — Item (12) X item (7).
(21) AQj. — Sum of columns (16), (17), (18),
(19), and (20).
(22) Qi + AQj. — Column (15) + column (21).
(23) Q; + AQi (cfs). — Column (22) x area
(acreas) x 0.002363 for 7-day intervals. This is the
predicted flow duration curve for the proposed
silvicultural activity when plotted against column
(14) (fig. VII.3).
SURFACE EROSION ANALYSIS
The quantity of surface eroded material
delivered to stream channels from sites disturbed
by the proposed silvicultural activities is estimated
in two stages. First, the quantity of material that
may be made available from a disturbed site is es-
timated using the Modified Soil Loss Equation
(MSLE). Second, a sediment delivery index
(SD i ) is estimated. When this is applied to the es-
timated quantity of surface eroded material
available, an estimate of the quantity of material
that may enter a stream channel is obtained.
Erosion Response Unit Delineation
Topographic maps (figs. VIII.4 to VIII.7) have
been prepared for the Grits Creek watershed, fol-
lowing steps 1 through 7 as discussed in chapter IV.
These maps show the drainage net, hydrographic
areas, soil groups, and silvicultural activities. Road
locations for management alternatives A and B are
shown in figure VIII. 1. An enlarged map of
hydrographic area 13 (fig. VIII.8) shows the com-
posite of cutting units, roads, stream channels, and
soil groups used for the soil erosion and sediment
delivery example problem.
Steps 1-7. — Prepare topographic maps (ch. IV).
Step 8. — Set up worksheets for estimating
potential sediment load from surface erosion.
Worksheets IV.1 and IV.2, have been prepared
with field data for Grits Creek management alter-
native A. Individual soils in the Grits Creek
watershed have been grouped where there exist
similar texture, organic matter, structure, and
permeability characteristics. Worksheet IV.1 shows
the three soil groups used for surface erosion
evaluation. Data on worksheet IV.l should not
change when different management alternatives
are evaluated for the watershed.
Worksheet IV.2 displays various types of data
needed for evaluating the effects of management
alternative A for Grits Creek watershed,
hydrographic area 13. Individual erosion response
units are identified and listed. A different erosion
response unit is created for each change in manage-
ment activity, each design change for a given ac-
tivity (e.g., a road change from a cut-and-fill design
to a complete fill for a stream crossing), or each
change in environmental parameters affecting ero-
sion (e.g., an change in soil characteristics).
Worksheet IV.3 is a summary of the values used
in the MSLE and sediment delivery index for ero-
sion response units in hydrographic area 13 of the
Grits Creek watershed. The values for both
management alternatives are obtained using the
steps and discussions which follow. Only values for
'alternative A are used to illustrate methods for
solving the equations, however, values for alter-
native B are similarly determined.
Step 9. — List each erosion source area and
number by erosion response unit.
For the Grits Creek watershed, the response
units have been coded as follows. The treatment
types are selection cuts (SC), clearcuts (CC), and
VHI.16
-------
1 mile
Figure VIII.4.—Drainage n«t, GrIU Creek watershed.
VIII. 17
-------
~—Si ;_1.; -•!';.,--jT^sg?
1 mile
Figure VIII.5.—Hydrographlc areas, Grito Creek watershed.
VIII.18
-------
1 mile
Figure VIII.6.—Soil groups, Grits Creek watershed.
VIII.19
-------
[ ] Clearcut
Selective Cut
1 mile
Figure VIII.7.—Silviculture! treatments, Grits Creek watershed.
vm.2o
-------
Uncut UC13.1' CC132
UC = Uncut
CC = Clearcut
SC = Selective cut
R =Road
Figure VIII.8.—Enlargement of example hydrographlc area showing Individual erosion response unMs.
vin.2i
-------
roads (R). There are no landings, because logs will
be yarded to various locations along the side of the
road and onto the road surface. The example
hydrographic area is number 13. The disturbance
types are numbered (e.g., clearcut CC13.1, clearcut
CC13.2) to identify them in the following evalua-
tions for soil loss and sediment delivery.
Using The Modified Soil Loss Equation (MSLE)
Step 10. — Working with each erosion response
unit individually, determine for each source area
(silvicultural activities and roads) the values to be
used for each of the following variables:
R — Rainfall factor
K — Soil erodibility factor
LS — Length-slope factor
VM — Vegetation-management factor
Area — Surface area of response unit
Values for these factors are entered on worksheet
IV.3 using the following procedures.
Rainfall Factor
For the Grits Creek area, R = 300 (fig. IV.2.)
This R value is the same over the entire Grits Creek
area and will be used for all erosion response units
and both management alternatives.
Soil Erodibility Factor
The K value can be estimated using the
nomograph in figure IV.3, or by using equation
IV.4. The data for soil group 2 needed to compute
the K value using equation IV.4 are found on
worksheet IV. 1. K must be determined for both
topsoil and subsoil. For disturbances which enter
the subsoil, such as roads, the subsoil value of K
must be used.
Application of the equation to determine the K
factor is shown in the following example for topsoil
in soil group 2. Because of inflections in the family
of curves on the nomograph (fig. IV.3) for percent
sand, the equation cannot be used when silt plus
very fine sand exceeds 70 percent.
K = (2.1 X 10-6) (12-Om) M1-14
+ 0.0325 (S-2) + 0.025 (P-3) (IV.4)
where:
Om = % organic matter
M = (% silt + % very fine sand) (100 - % clay)
S = structure code
P = permeability code
Substituting values for topsoil (soil group 2) from
worksheet IV. 1 into equation IV.4:
K = (2.1 X 10-6) (12-4) [40 (100-20)]1-14
+ 0.0325 (2-2) + 0.025 (2-3)
K = 0.14
Length-Slope Factor
The length-slope factor, LS, is a combination
factor which incorporates the slope gradient and
the length of the eroding surface into a single fac-
tor. The LS factor must be estimated for each ero-
sion response unit.
Two methods may be used to estimate the LS
factor on straight slopes. One is to use equation
IV.8 to derive the estimated LS value. The second
method utilizes a nomograph (fig. IV.4) to estimate
the LS value.
The cutting units (SC13.1, SC13.2, CC13.1, and
CC13.2) are each different in regard to slope
gradient and length. Therefore, LS for each cutting
unit must be evaluated separately. Using equation
IV.8 and data from worksheet IV.2, the LS value
for CC13.1 is calculated as follows for.slope length X
= 132 feet and slope gradient s = 12 percent.
T e _ / x Y A>-43 + °-30s + 0.043s2\
AJO — I 1 I 1
\72.6y \ 6.613 /
10,000
10,000 + s2,
(IV.8)
where:
X = slope length, in feet
s = slope gradient, in percent
m = an exponent based on slope gradient from
equation IV.6
Using data from worksheet IV.2:
LS =
72.6
°'5 /0.43 + 0.30(12) + 0.043(12)2
6.613
10,000
LS = 2.05
/ 10,000 \
\10,000 + (12)2/
VHI.22
-------
Similar calculations are made for erosion response
units SC13.1, SC13.2, and CC13.2.
To compute the length-slope value for the road
sections (R13.1, R13.2, and R13.3), the equation for
irregular slopes is used in this example. An alter-
native method using graphs (figs. IV.5 and IV.6) is
discussed in chapter IV. The LS equation for roads
is:
LS
72.6
(IV.9)
The number of calculations can be reduced by
simplifying equation IV.9 to:
LS
1
(IV.9.1)
= entire length of a slope, in feet
= length of slope to lower edge of j^h seg-
ment, in feet
= slope segment
= slope gradient, in percent
= dimensionless slope steepness factor for
segment j defined by
S. = (0.043s2 + 0.30s. + 0.43)76.613
m = an exponent based on slope gradient
n = total number of slope segments
For the road R13.1, using values in worksheet
IV.2 and assuming that no sediment is deposited on
the road surface, the computations are as follow:
Slope segment 1 (cut)
A, =3.5 feet
A i -i = 0.0 feet (there are no preceding slope seg-
ments, hence length is 0.0 ft)
s = 1707r
m = 0.6 (for slopes on construction sites; see
eq. IV.6)
S, =
0.043s2 + 0.30s + 0.43
6.613
substituting for s:
c 0.043(170)2 + 0.30(170) + 0.43
&i =
6.613
Substituting S, A, and m values for j = l into equa-
tion IV.9.1 to the right side of the summation sign
gives:
196
(3.5)1-6 - (0)
1.6'
10,000
(72.6)
0.6
10,000 + (170)2/
= 28.59
Slope segment 2 (roadbed)
A2 = 3.5 + 12.0 = 15.5 feet
A2_i = 3.5 feet
s = 1%
m = 0.6 (for slopes on construction sites)
S2 =
0.043s2 + 0.30s + 0.43
6.613
substituting for s:
0.043(1)2 + 0.30(1) + 0.43
S2 — — = 0.117
6.613
Substituting S, A, and m values for j=2 into equa-
tion IV.9.1 to the right side of the summation sign
gives:
0.117
= 0.65
'(15.5) L6 - (3.5) l*
v (72.6) °-6
10,000
-I-
Slope segment 3 (fill)
A3 = 3.5 + 12.0 + 4.5 = 20.0 feet
A3_t = 3.5 + 12.0 = 15.5 feet
s = 100%
m = 0.6 (for slopes on construction sites)
0.043s2 + 0.30s + 0.43
6.613
substituting for s:
0.043(100)2 + 0.30(100) + 0.43
= - =
6.613
VIII.23
-------
Substituting S, X, and m values for j=3 into equa-
tion IV.9.1 to the right of the summation sign gives:
gives:
69.6
/(20.0)16 - (15.5)u
(72.6)
10,000
10,000 4- (100)2
= 107.54
Solving the entire equation IV.9.1, using the
calculated values where:
X = 3.5 + 12.0 + 4.5 = 20 feet
then:
LS =
1
(slope seg. 1 + slope seg. 2
+ slope seg. 3)
= — (28.59 + 0.65 + 107.54)
20
= 6.84
A similar LS calculation is made for road R13.5.
Road R13.2, however, is a fill across a stream chan-
nel and becomes two problems, each with two seg-
ments. Each segment starts at the middle of the
road surface, and the second segment includes one
of the fill slopes. An average LS value from both
halves of the road is used as the final LS value
(1.81) to be entered on worksheet IV.3.
Vegetation-Management Factor
The vegetation-management factor (VM) is used
to evaluate effects of cover and land management
practices on surface erosion over the entire slope
length used for the LS factor. VM factors are deter-
mined for all cutting units and roads.
(1) Cutting units. — Worksheet IV.2 has the
field data used for calculating a VM factor for the
clearcut units (CC13.1 and CC13.2) and the selec-
tive cut units (SC13.1 and SC13.2). Example
calculations are shown for clearcut CC13.1. The
cutting unit is divided into two areas based on the
presence or absence of logging residues. A ground
cover of slash and other surface residues covers 55
percent of the unit (wksht. IV.2). The remaining 45
percent is scattered with open areas of bare soil and
soil duff mixtures averaging 15 feet in diameter.2
"^Information about the amount of residue is often expressed in
tons per acre. Maxwell and Ward (1976) have published photos
and tables for parts of Oregon and Washington which relate
visual appearance of a site with the volume of residue and
amount of ground cover.
In the 55 percent of the area (CC13.1) covered by
slash and other surface residues, fine tree roots are
uniformly distributed over 99 percent of the area.
In the 45 percent of clearcut area CC13.1 that is
open, fine tree roots are uniformly distributed over
80 percent of the open area. All of the overstory and
understory canopy has been removed.
Using worksheet IV.4, first, enter percent area as
0.55 and 0.45 for area covered by residues and open
area, respectively. Separate calculations are made
for the logging residue areas and open areas.
Second, the logging slash represents the mulch
and close growing vegetation. Because slash varies
in density, assume that small openings a few inches
in diameter exist over 40 percent of the surface.
from figure IV. 9, the 60 percent cover provides a
mulch factor of 0.25. The 45 percent of CC13.1 that
is open is assumed to have 45 percent of the surface
protected by widely scattered slash. Using figure
IV.9, a mulch factor of 0.35 is found for this situa-
tion.
Third, zero canopy cover gives a canopy factor of
1.0 for both areas (fig. IV.8).
Fourth, evaluate the role of fine roots that are
remaining in the soil. The slash area has fine roots
uniformly distributed over 99 percent of its surface
area and figure IV. 10 shows a corresponding fine
root factor of 0.10. The open area has fine roots un-
iformly distributed over 80 percent of its area;
figure IV.10 gives a corresponding value of 0.12.
Fifth, determine if the open areas are connected
with each other such that water can flow downslope
from one to another (ch. IV). In this example, the
open areas are isolated from each other by bands of
logging residue, requiring the use of a sediment
filter strip factor of 0.5 (see "Sediment Filter
Strips" section of "Chapter IV: Surface Erosion").
If these sediment filter strips did not exist, a factor
of 1.0 would be used.
Sixth, using worksheet IV.4, multiply the VM
subfactors for logging residue (0.55) (0.25) (1.0)
(0.10) = 0.0138. Similarly for the open area: (0.45)
(0.35) (0.12) (0.5) = 0.0095. The overall VM factor
for CC13.1 is the sum of the two factors: (0.0138) +
(0.0095) = 0.023.
Similar calculations are made for CC.13.2,
SC13.1, and SC13.2. Values are shown on
worksheet IV.4.
(2) Landings. — No landings are planned for
Grits Creek.
VIII.24
-------
(3) Roads. — The VM factor must represent two
conditions on the road areas: (1) the road running
surface, and (2) the cut-and-fill banks that are
needed (fig. IV.7).
The average width of disturbed surface for road
R.13.1 is 1.8 + 12.0 + 3.1 = 16.9 ft
Running surface 12-° ft = 0.7101 = fraction of
16.9 ft total width
Cut slope 1-8 ft = 0.1065 = fraction of total
16.9 ft
width
Fill slope
3-1 ft = 0.1834 = fraction of total
16.9 ft width
The weighted VM factor for the road R13.1 is
calculated and shown on worksheet IV.6. Similar
calculations have been made for roads R13.1 and
R13.5.
Surface Area Of Response Unit
Total surface area within each treatment
unit—clearcuts, selective cuts, and roads—is given
in worksheet IV.2 and is entered on worksheet IV.3.
All other MSLE factors are also entered into
worksheet IV.3. Total potential onsite soil loss is
computed by multiplying all the MSLE factors on
worksheet IV.3.
The infiltration rate used in determining the R
factor is the maximum rate at which water could
enter a soil. In actual situations, the water entry
rate will usually be somewhat lower than the in-
filtration rate and can be based on the soil
permeability with consideration for effects of
various management practices.
Using data from worksheet IV.2 and footnotes
from worksheet IV.7, the calculations for CC13.1
are:
F = (2.31 X 10-5 ft2 hr ) (2.5 in/hr - 2.0 in/hr)
\ m sec/
(132 ft + 0 ft)
F = 0.0015 ftVsec
2. Texture of eroded material is based on the
amount of very fine sand, silt, and clay shown
on worksheet IV. 1. For this case, it has been
assumed that one-half of the clay will form
stable aggregates, with the remaining clay in-
fluencing the sediment delivery index. For soil
group 3 topsoil, the following calculations
were made:
texture of
eroded material
+ % silt
Sediment Delivery
Step 12. — The computed potential sediment is
delivered to the closest stream channel using a
sediment delivery index (SDj). Worksheet IV. 7 is
used to organize the data for each erosion response
unit for each factor shown on the stiff diagram (fig.
vm.9).
1. Water availability for sediment delivery is
calculated using equation IV.12 for each ero-
sion response unit:
F = CRL
(IV.12)
where:
F =
R =
L =
available water (ftVsec)
[1 year, 15 minute storm (in/hr)] - [soil
infiltration rate (in/hr)]
[slope length distance of disturbance (ft)]
+ [slope length from disturbance to
stream (ft)]
C = 231 X 10-B
ft2 hr
in sec
+ % very fine sand
= f + 26 + 19
= 57
3. Ground cover is the percentage of the soil sur-
face with vegetative residues and stems in
direct contact with the soil. The ground cover
on the area between a disturbance and a
stream channel is determined from field
observations and used for the sediment
delivery index. For CC13.1, 53 percent is
shown on worksheet IV.2 for ground cover.
4. Slope shape is a subjective evaluation of
shapes between convex and concave. From
worksheet IV.2, for CC13.1 the slope shape is
concave.
5. Distance is the slope length from the edge of a
disturbance to a stream channel. For CC13.1
(wksht. IV.2) the distance is 0.0, because the
disturbance extends to the channel.
VIII.25
-------
6. Surface roughness is a subjective evaluation
of soil surface microrelief ranging from
smooth to moderately rough. Worksheet IV.2
shows a moderate surface roughness for
CC13.1.
7. Slope gradient is the percent slope between
the lower boundary of the disturbed area and
the stream channel. Worksheet IV.2 shows a
gradient of 12 percent for the disturbed area.
8. Site specific is an optional factor that was not
used in this example. See chapter IV for more
discussion of this factor.
The tabulated factors for CC13.1 (wksht IV.7)
are plotted on the appropriate vectors of the stiff
diagram (fig. VIII.9) as discussed in chapter IV.
Use any one of several methods to determine the
area bounded by the irregular polygon that is
created when points on the stiff diagram are joined.
The area of the polygon for this example is 107.9
square units. The stiff diagram has 784 square
units. The percentage of the total area enclosed by
the polygon is:
/107.9
\ 784
(100) = 13.8%
Entering the X-axis of the probit curve (fig.
IV.23) with 13.8 results in a sediment delivery in-
dex (SDX) of 0.02. This is the estimated fraction of
eroded material that could be delivered from this
disturbance to the stream channel.
Step 13. — Find the estimated quantity of sedi-
ment (tons/yr) delivered to a stream channel by
multiplying surface soil loss by the sediment
delivery index (wksht. IV.3) for each erosion
response unit.
Step 14. — Using worksheet IV.8, tabulate quan-
tities of delivered sediment (tons/yr) for each
hydrographic area by the erosion source. When
completed, this table provides a summary of sur-
face erosion sources and estimated quantities of
sediment production from each hydrographic area.
Step 15. — Totals and percentages are shown on
worksheets IV.8. The total quantity of delivered
material is entered on table Vin.2.
Differences Between Management Alternatives
A second set of worksheets IV.2 to IV.8 show data
and results of calculations for Grits Creek alter-
native B. Specific differences between alternatives
A and B can be seen by comparing values in the
two sets of worksheets. For example, alternative B
results in more of the total surface area covered
with residues and mulch and more fine roots. The
results of these effects are shown on worksheet IV.3
as the VM factor. For alternative A, CC13.1, VM =
0.023 as compared to VM = 0.003 for alternative B,
CC13.1. The lower VM for alternative B indicates
that vegetative materials on the ground are more
effective in reducing erosion than they are in alter-
native A. There are similar differences in the VM
factor for other cutting units and roads. The net ef-
fect is a total of 34.2 tons/yr for alternative A and
6.7 tons/yr for alternative B (wksht. IV.8).
TOTAL POTENTIAL SEDIMENT ANALYSIS
The following steps are diagrammatically shown
in figure IV.9.
Step 1. —The stream reach characterization will
be obtained on the lower reaches of the third-order
stream channel on main Grits Creek.
Step 2. — See figure VIII.3, flow duration curve
for Grits Creek.
Suspended Sediment Calculation
Step 3. — Establish suspended sediment rating
curve.
a. Obtain sediment rating curve from the
measured depth integrated suspended sedi-
ment sampling and concurrent stream dis-
charge measurements. A plot of these figures
is shown in figure VIII. 10.
b. log Y = 0.61 + 0.96 log Q
r2 = 0.98
c. Channel stability rating: fair. The analysis
outlined by Pfankuch (1975) was used to ob-
tain this value. A correlation between the
various ranges in stream channel stability and
sediment rating curves as explained in appen-
dix VLB was obtained for the Grits Creek
watershed. Figure Vni.ll indicates the chan-
nel stability threshold limit which is the up-
per limit for a fair rating.
VHI.26
-------
Percent Ground
Cover
Texture of
Eroded Material
100-
Available
Water
Slope
Shape
0.10
Site
Specific
Delivery Distance
feet
Surface
Roughness
Slope
Gradient
Figure VIII.9.—Stiff diagram for alternative A CC3.1, Grits Creek watershed.
VIII.27
-------
SUSPENDED SEDIMENT (mg/l)
° -^ N) CO
-» N> CO Jx C71 O OO
_i roco^ui o oooo o oo
'
/
7
\
/
0^
>
^
>•
•
/
/
m/
s O1
• ./ *
/
/ y
^
/.
y
'
/
•
/
'
i&f/
^yv
f^r s
/
/•
'.
s
ent R<
itinc
3C
ur\
te
0.1
0.2 0.3 0.4 0.5
1 2345 10
STREAM DISCHARGE (cfs)
20 30 40 50
100
Figure VIII.10.—Sediment rating curve, Grit* Creek watershed.
VIH.28
-------
300
200
100
SUSPENDED SEDIMENT (mg/
—i ro co j> en
_*> ro co J> en o OOOO
/
'
/
C
/
/
h?
/
s
in
/
/
T,
n(
/
y
^
3l
•
Stability
"Poor"
Stability
s
'
/ •
/
/
m/
s O-
Thres
^"Fa
' Stab
•/ «!
*
*
hole
/
7
ir"
iiity/
Li
'
X
ni
/
.
'
tm
/
Ł
/
p^
/
»
/
(
'
^
/
~y
/
\dt?'S~
rV/
&Y
/
/*
'•
~— Sedim
s
ent R<
atinc
3C
ur\
^e
0.1
0.2 0.3 0.4 0.5
1 2345 10
STREAM DISCHARGE (cfs)
20 30 40 50
100
Figure VIII.11.—Channel •lability threshold limit* In relationship to the eedlment rating curve, Qrlte Creek
watershed.
VIII.29
-------
Step 4. — Calculate pre-silvicultural activity
potential suspended sediment discharge.
a. Using worksheet VI. 1, columns (1) through
(4). Use sediment rating curve (fig. VIII.10)
for concentration values in column 3.
b. Record the total of 11.6 tons/yr on worksheet
VI.3, line A.
Step 5. — Calculate post-silvicultural activity
potential suspended sediment discharge (due to
streamflow increases).
a. Using worksheet VI.1, columns (1), (5), (6),
and (7).
b. Record the total of 19.6 tons/yr due only to
flow increase on worksheet VI.3, line B.
Step 6. — Convert selected limits (mg/1) into
units compatible with the analysis (tons/yr).
Maximum limits were set using the stream chan-
nel stability-sediment rating curve relationship for
the watershed. Since the channel stability rating
was fair, the threshold limit between the fair and
poor stability classes was used (fig. VIII.ll). For ex-
ample, using 20 cfs, a value of 70 mgA from the poor
curve and 190 mg/1 from the channel stability
threshold limit curve are obtained, resulting in a
120 mgA increase. The concentrations from the
threshold line between fair and poor were used in
worksheet IV. 1, column (8). Using columns (2), (8),
and (9) of worksheet VI.1, a total of 25.5 tons/yr is
obtained and recorded on worksheet VI.3, line C.
Bedload Calculation
Step 7. — Bedload measurements were taken,
but because of the heavily armored channel, no
bedload was caught in a Helley-Smith sampler.
Bedload rates appear to be negligible except in the
event of a flood.
Step 8. — Not applicable because no bedload
material was caught in sampler.
Step 9. — Calculate pre-silvicultural activity
potential sediment discharge (suspended and
bedload).
a. From step 4, (suspended sediment) = 11.6
tons/yr.
b. Record on worksheet VI.3, line K.
Step 10. — Not applicable—no bedload
material.
Total Potential Sediment Calculation
Step 11. — The proposed activity contributed no
sediment from soil mass movement processes.
Step 12. — Not applicable—no bedload
material.
Step 13. — Not applicable—no bedload
material.
Step 14. — Determine total delivered tons of
suspended sediment from surface erosion.
a. Surface erosion source fc 34.2 tons/yr
b. Record on worksheet VI.3, line D.I.
Step 15. — Compare total potential post-
silvicultural activity suspended sediment (mg/1) to
selected limits (tons/yr). On worksheet VI.3:
Add totals of:
Surface erosion (line D.I) 34.2 tons/yr
Total post-silvicultural activity
suspended sediment discharge due
to flow related increases
(line B) 19.6 tons/yr
Soil mass movement (washload)
(line D.4) 0.0 tons/vr
Total 53.8 tons/yr
Subtract the total pre-silvicultural
activity suspended sediment discharge
(line A) from the previously
determined figure 11.6 tons/yr
The remainder is the total increase in
potential suspended sediment
discharge (line I.I) 42.2 tons/yr
Subtract the maximum allowable increase in
suspended sediment discharge (line C)
from the total increase in potential
suspended sediment discharge (line I.I)
25.5 tons/vr
The remainder is the net change (this
may be either a positive or negative
number) +16.7 tons/yr
Step 16. — Total potential post-silvicultural ac-
tivity sediment discharge—all sources:
Summation of steps 5, 10, 11, and 14.
a. Post-silvicultural activity suspended sedi-
ment (flow
related increases)
(step 5, wksht. VI.3, line B) = 19.6 tons/yr
b. Bedload—not applicable.
VIII.30
-------
c. Soil mass movement volume
—not applicable.
d. Surface erosion (step 11,
wksht. VI.3, line D.I = 34.2 tons/yr
Total 53.8 tons/yr
Record on line L, worksheet VI.3.
Step 17. — Total potential sediment discharge
increase resulting from silvicultural activity:
a. Subtract total potential pre-silvicultural ac-
tivity sediment discharge (step 9) from total
potential post-silvicultural activity sediment
discharge (step 16)
Total post-worksheet IV.3,
line L 53.8 tons/yr
Total pre-worksheet VI.3,
line K 11.6 tons/yr
Total potential sediment
increase 42.2 tons/yr
b. Record on worksheet VI.3, line M.
The total potential sediment increase is also
recorded in table VIII.2 for management alter-
native A and table Vin.3 for management alter-
native B.
Channel Impacts
Step 18. — Not applicable to Grits Creek
because direct channel impacts from debris, width
constrictions, or gradient changes are not an-
ticipated with the proposed action.
Step 19. — Not applicable.
Step 20. — Not applicable.
Step 21. — Not applicable.
TEMPERATURE ANALYSIS
Grits Creek was segmented into four reaches for
temperature evaluation purposes (wksht. VII.2 and
fig. VIII.12). This was necessary because of the
variety of silvicultural activities—partial and
clearcut—and length of stream involved—more
than 1 mile from headwater to mouth. The first
reach consists of an open meadow, 600 feet long,
with no vegetative shade. The trees to be cut near
the mouth are distant enough from the stream that
they provide no shade. Therefore, the proposed
silvicultural activity will not directly impact water
temperature near the mouth. The partial cut area
is approximately 3,800 feet along the center portion
of the watershed. Since the evaluation procedure is
valid for reaches up to 2,000 feet, this section of
stream was divided into two reaches—a lower reach
2,000 feet long, and a middle reach of 1,800 feet.
The headwater portion of the stream is in a clear-
cut; the upper reach is 1,000 feet long.
Following is the evaluation for each stream reach
and an integration of the individual reaches to ar-
rive at an estimated maximum daily potential
temperature increase at the mouth. The analysis is
the same for both management alternatives since
the exposure to the stream has not changed.
Lower Reach
Computing H, Adjusted Incident Heat Load
Step 1. — Determine H (i.e., incident heat load)
based upon latitude of site, critical time of year
(month and day), and orientation of stream.
Step 1.1. — Select the solar ephemeris that most
closely approaches the latitude of the site, 35°N
(fig. VII.2).
Step 1.2. — Locate the declination in the solar
ephemeris (fig. VII.2) that corresponds to the date
when maximum water temperature increase is an-
ticipated: last week August; therefore, a declina-
tion of +10°.
Step 1.3. — Once the declination, +10°, is
known, determine the azimuth and solar angle for
various times during the day from the solar
ephemeris (fig. VII.2) and record the values in
worksheet VII. 1. Azimuth readings are found along
the outside of the circle and are given for every 10°.
Solar angle (i.e., degrees above the horizon) is in-
dicated by the concentric circles and ranges from
0° at the outermost circle to 90° at the center of the
circle. The time is indicated above the +23°27'
declination line and is given in hours, solar time.
Note that the time of day shown on worksheet VH.l
is given as daylight savings time (DST).
Step 1.4. — Evaluate the orientation of the sun
(i.e., azimuth and angle determined in step 1.3
above) with the stream, and determine what
vegetative shading effectively shades the stream.
To do this, compare stream effective width with
shadow length. Determine the maximum solar
angle (i.e., maximum radiation influx to stream)
VIII.31
-------
WATER TEMPERATURE PRIOR
TO SILVICULTURAL ACTIVITY 63°F
GROUND WATER TEMPERATURE 48°F
o
CD
DC Ł
o
CD .2
D
AT = 5.1°F
Qy = 0.2 cfs
Ty = 63
5.1°F = 68.1°F
= 68.1°F
.
O *i
.
— p oo
" "
QM = 0.3 cfs (of this 0.05 cfs is groundwater)
TM = (0.05 cfs) (48° F) + (0.25 cfs) (68.7° F)
(0.05 cfs) + (0.25 cfs)
= 65.3°F
TM=65.3°F
"5
f
-------
that will occur when the stream is exposed follow-
ing the silvicultural activity. Height of the existing
vegetation immediately adjacent to the stream is
80 feet.
Step 1.4.1. — The direction the shadows fall
across the stream will determine effective width of
the stream.
Effective width is computed using the following
formula:
measured average stream width
K\V =
sine
azimuth stream
azimuth sun |
(VII.4)
Azimuth of the particular stream is 35°. For ex-
ample, at 12 p.m. (wksht. VII. 1) EW would be
equal to:
KVV =
4 ft
sine I 35° - 148°
= 4.4 ft
The absolute value of azimuth of the stream sub-
tracted from the azimuth of the sun must be less
than a 90°-angle. Should the difference exceed 90°,
subtract this absolute value from 180° to obtain the
correct acute angle. Then the sine is taken of this
computed acute angle.
Step 1.4.2.
the formula:
S =
Shadow length is computed using
height vegetation
tangent solar angle
(VII.5)
For example, at 12 noon, S would be equal to:
S = 80 ft/tangent 62° = 42.5 ft
Summary of steps 1.4.1 and 1.4.2: The existing
trees that are scheduled to be cut provide shade to
the streams. The only time when trees might not
shade the stream is 2:15 p.m., when the stream's
effective width is infinity (sun is oriented with the
stream) and the shadow length is only 46.2 feet.
Therefore, removal of the vegetation would result
in exposure of the water surface to increased solar
radiation.
The proposed silvicultural activity would have
the maximum impact on water temperature at 1
p.m. (solar noon) when the solar angle (65°) and
radiation are greatest.
Step 1.5. — Topographic shading should be
evaluated to determine if the water course would be
shaded by topographic features. For topographic
shading, the percent slope of the ground must ex-
ceed the percent slope of the solar angle, (i.e.,
tangent of the solar angle). In this case,
side slope east = 53%
side slope west = 50%
Solar angle expressed as percent for:
8a.m. DST
9 a.m.
1 p.m.
5p.m.
6 p.m.
32%
58%
214%
58%
32%
Therefore, topographic shading is possible before
9 a.m. and after 5 p.m. There is no topographic
shading the rest of the day.
Step 1.6. — Calculate the incident heat load for
the site. This is obtained from reading the values
shown on figure VII.7. The following is done to read
values from this figure:
Step 1.6.1. — Select the correct curve (shown in
fig. VII.7) obtained from the correct solar
ephemeris (fig. VII.2): in this example, 35°N
latitude, given a declination of +10° results in a
solar angle of 65°. Note that the midday value will
always have an orientation, i.e., azimuth, of due
south.
Step 1.6.2. — In figure VII.7, interpolate
between the 70° and 60° curves to obtain the 65°
value.
Step 1.6.3. — Determine the critical period,
which in step 1.4 was found to be 1 p.m. DST.
Step 1.6.4. — Find the average H value. In this
example, the travel time through the reach is es-
timated to be 1 hour, so it is not necessary to find
an average value. From figure VII.7, with a 65°
midday angle, the H value for 1 p.m. is approx-
imately 4.3 BTU/ft2-min.
Step 1.7. — Because bedrock acts as a heat sink,
reducing the heat load absorbed by the water, the
H value must be corrected for this heat loss.
C is obtained from figure VII.9. In the example,
bedrock comprises 75 percent of the streambed;
therefore, H should be reduced by 15 percent.
VIII.33
-------
Hadjusted = t% WH1 + t%B d-00 - C) H] (VII.6)
where for Grits Creek:
W = percent streambed without bedrock
= 25%
H = unadjusted heat load = 4.3 BTU/ft2 - min
B = percent streambed with rock = 75%
C = correction factor from figure VII.9 = 0.15
Therefore,
H = [0.25 X 4.3 BTU/ft2-min]
adjusted + [Q ?5(1 00 _ Q 15) x 4 3 BTU/ft2
— min]
Hadjusted = 3.82 BTU/ft2-min
Computing Q, Stream Discharge
Step 2. — Determine stream discharge following
the proposed silvicultural activity during the
critical summer low-flow period when maximum
temperatures are anticipated. In this example, a
pre-activity baseflow measurement during the
critical summer period was taken. Discharge dur-
ing the critical period was 0.5 cfs.
Computing A, Adjusted Surface Area
Step 3. — Determine the adjusted surface area of
flowing water exposed by the proposed
silvicultural activity.
Step 3.1. — Total surface area of flowing water
Va, = LW (VH.7a)
where:
L = length of reach exposed
W = width of flowing water
A,,,ta| = 2,000ft X5ft
= 10,000 ft2
Step 3.2. — Total surface area shaded by brush
Ashade brush =LW (9? shaded by brush only) (VII.7b)
= 2,000 ft X 5 ft X 25%
= 2,500 ft2
Step 3.3. — Surface area exposed under current
vegetative canopy cover: correct for transmission of
light through the existing stand that has a 90-
percent overstory crown closure and a 50-percent
understory crown closure. Since only vertical crown
closure values are available, estimate the percent-
age transmission of solar radiation through the
canopy. In using figure VII.D.l for crown closures
greater than 70 percent, assume a 5-percent trans-
mission of solar radiation.
"presently exposed ~~ '•"total shade brush'
X % transmission through
existing vegetation (VII.7c)
= (10,000 ft2 - 2,500 ft2) X 5%
= 375 ft2
Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion is removed is:
"adjusted = "total ~~ A presently exposed
= 10,000 ft2 - 375 ft2
= 9,625 ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if all vegetation is
removed from lower reach. Solve equation VII.3a.
AT
A H
adjusted adjusted
Q
X 0.000267 (VII.3a)
Aadjusted = 9,625 ft2
Had]Us»ed =3.82 BTU/ft2- min
Q = 0.5 cfs
= 19.6°F
AT = (9'625
BTU/ft.2-min)
0.5 cfs
The proposed silvicultural activity will only
result in a partial cut of the overstory, leaving a
vertical crown closure of 50 percent. The under-
story will not be cut; however, some loss is to be ex-
pected during removal of the overstory. Understory
vertical crown closure remaining after the
silvicultural activity is expected to be 45 percent. It
is estimated that the percent transmission of solar
radiation through the canopy will be 15 percent.
The brush shading the stream will remain.
Therefore,
A total = 2,000ft X 5ft
= 10,000ft2
Ashade brush = 2,000 ft X 5 ft X 25%
= 2,500ft2
= (10,000ft2 - 2,500 ft2) X 85%
= 6,375ft2
^ shade remaining
canopies
'adjusted
= A — (A
total v presently exposed
~*~ " shade brush
remaining canopies
= 10,000 ft2 - (375 ft2 + 2,500 ft2
h 6,375 ft2)
= 750ft2
VIII. 34
-------
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VII.3a.
AT =
"adjusted " adjusted
Q
X 0.000267
(VII.3a)
Aadjusted = 750 ft2
Halted = 3.82BTU/ft2-min
Q = 0.5 cfs
AT =
(750 ft2) (3.82 BTU/ft2-min)
0.5 cfs
X 0.000267
= 1.5°F
Middle Reach
Computing H, Adjusted Incident Heat Load
Step 1. — The only difference between the lower
reach and the middle reach, when estimating H, is
that the average width of flowing water is reduced
from 5 feet to 3.5 feet. Thus, the effective stream
width values would change, but the final H ad-
justed value would remain unchanged—3.82
BTU/ft2-min.
Step 3.2. — Total surface area shaded by brush
(VE.7b)
A u _, = LW (% stream shaded by
shade brush , , .
brush only)
= 1,800 ft X 3.5 ft X 40%
= 2,520ft2
Step 3.3. — Surface area exposed under current
vegetative canopy cover: correct for transmission of
light through the existing stand that has a 90-
percent overstory crown closure and a 55-percent
understory crown closure. Since only vertical crown
closure values are available, estimate the percen-
tage of solar radiation through the canopy. Again it
is estimated that only 5-percent transmission of
solar radiation is allowed through the canopies (fig.
VH.D.1)
A presently exposed = (Atotal ~~ Ashade brush / '° trans-
mission through existing
vegetation (VTI.7c)
= (6,300 ft2 - 2,520 ft2) X 5%
= 189ft2
Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion is removed is:
= "total ~ A presently exposed
= 6,300 ft2 - 189 ft2
= 6,111ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if all vegetation is
removed from middle reach. Solve equation VII.3a
^adjusted
Computing Q, Stream Discharge
Step 2. — A pre-silvicultural activity baseflow
measurement during the critical summer period
was taken for this reach. Discharge during the
critical period was 0.3 cfs.
Computing A, Adjusted Surface Area
Step 3. — Determine the adjusted surface area of
flowing water exposed by the proposed
silvicultural activity.
Step 3.1. — Total surface area of flowing water
total
= LW
= 1,800 ft X 3.5 ft
= 6,300ft2
(VII.7a)
AT =
^adjusted *~* adjusted
Q
X 0.000267
(VII.3a)
Aadjusted = 6,111ft2
H adjusted = 3.82BTU/ft'-min
Q = 0.3 cfs
AT =
(6,111 ft2) (3.82 BTU/ft2-min)
0.3 cfs
X 0.000267
= 29.7°F
The proposed silvicultural activity will only
result in a partial cut of the overstory, leaving a
crown closure of 50 percent. The understory will
not be cut; however, some loss is expected during
removal of the overstory. Understory vertical crown
closure is expected to be 50 percent. It is estimated
VIII.35
-------
that the percent transmission of solar radiation
though the canopy will be 10 percent. The brush
shading the stream will remain.
Therefore,
Atotal
As
hade brush
canop.es
'adjusted
= 1, 800 ft X 3.5 ft
= 6,300ft2
= 1,800 ft X 3.5 ft X 40%
= 2,520ft2
= (6,300 ft - 2,520 ft) X 90%
— Atotal ( "presently exposed
' Asna(je brush
' "shade remaining canopies/
= 6,300 ft2-(189 ft2
+ 2,520 ft2+ 2,402 ft2)
= 189ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VII. 3a.
AT =
^adjusted **adjusted
X 0.00027
(VH.3a)
"adjusted ~ 189 ft
Hadjusted = 3.82BTU/ft2-min
Q = 0.3 cfs
(189 ft2) (3.82 BTU/ft2-min)
= 0.6°F
0.3 cfs
Upper Reach
Computing H, Adjusted Incident Heat Load
Step 1. — The only difference between the lower
and middle reaches and the upper reach, when es-
timating H, is that the average width of flowing
water is reduced to 2.5 feet. Because of this, the ef-
fective stream width values would change, but the
final H adjusted value would remain un-
changed—3.82 BTU/ft2-min.
Computing Q, Stream Discharge
Step 2. — A pre-silvicultural activity baseflow
measurement was taken for this reach during the
critical summer period, resulting in a value of 0.2
cfs.
Computing A, Adjusted Surface Area
Step 3. — Determine the adjusted surface area of
flowing water exposed by the proposed
silvicultural activity.
Step 3.1. — Total surface area of flowing water
Atotal = LW (VII.7a)
= 1,000 ft X 3.0 ft
= 3,000ft2
Step 3.2. — Total surface area shaded by brush
Ashade brush = LW (% stream shade by brush only)
= 1,000 ft X 3.0 ft X 65% (VH.Tb)
= 1,950ft2
Step 3.3. — Surface area exposed under current
vegetative canopy cover; correct for transmission of
light through the existing stand that has an 80-
percent overstory crown closure and a 60-percent
understory crown closure. Since only vertical crown
closure values are available, estimate the percent-
age of solar radiation through the canopy. It is es-
timated that only 5-percent transmission of solar
radiation is allowed through the canopies (fig.
VII.D.1).
A presently exposed = (Atotal ~ "shade brush ) % trans-
mission through existing vegetation
= (3,000 ft2-1,950 ft2) X 5%
= 53ft2
Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion is removed is:
A adjusted = Atotal ~ A presently exposed
= 3,000 ft2 - 53 ft2
= 2,947 ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if all vegetation is
removed from the upper reach. Solve equation
VH.Sa.
AT =
A T-f
"adjusted n adjusted
Q
X 0.000267
(VH.Sa)
Aadjusted = 2,947ft2
Hadjusted = 3.82BTU/ft2-min
Q = 0.2 cfs
AT =
(2,947 ft2) (3.82 BTU/ft2-min)
0.2 cfs
X 0.000267
= 15.0°F
VHI.36
-------
The proposed silvicultural activity will be a com-
mercial clearcut resulting in the complete removal
of the overstory and understory canopies. The
dense laurel and rhododendron brush along the
stream will not be removed.
Therefore,
Atotal = 1,000 ft X 3 ft
= 3,000ft2
Ashade brush = 1,000 ft X 3 ft X 65%
= 1,950ft2
Atotal ~ (A presently exposed
+ A shade brush )
= 3,000ft2 - (53ft2 + 1,950ft2)
= 997ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VII.3a.
"adjusted
A H
• .uljuMed ** adjusted
- - -
Q
.__
X 0.000267 (VII.3a)
Aadjusted = 997ft2
Hadju,«ed = 3.82BTU/ft2-min
Q = 0.2 cfs
(997 ft2) (3.82 BTU/ft2-min)
AT = - - - x 0.000267
0.2 cfs
= 5.2°F
The Mixing Ratio Formula
The lower reach of Grits Creek is to be partially
cut, with a potential temperature increase of 1.5°F.
The middle reach will also be partially cut, with a
potential temperature increase of 0.6°F. The upper
reach is to be clearcut, with a potential
temperature increase of 5.1°F.
An estimate of the integrated impact on the
water temperature is necessary so that a com-
parison can be made with the water quality objec-
tive—allowing a maximum temperature increase of
3°F.
A mixing ratio formula will be used to estimate
the downstream temperature impacts. The water
temperature before the silvicultural activity was
63°F, and the groundwater temperature measured
at a spring was 48°F.
For the upper reach, the estimated water
temperature increase, 5.1°F, is added to the pre-
silvicultural activity water temperature 63°F, to
estimate the temperature of the water as it leaves
the proposed clearcut area, 5.1°F + 63°F = 68.1°F.
The water temperature entering the middle
reach will be 68.1°F. The estimated water
temperature increase in the middle reach is 0.6°F.
However, the two values should not be added to get
an estimate of the water temperature leaving the
middle reach because groundwater influxes within
this reach will mitigate the water temperature in-
crease caused by the proposed silvicultural ac-
tivity. The following mixing ratio formula should
be used:
Tn =
(VH.9)
where:
TD = temperature downstream where the mid-
dle and lower reaches are separated
DG = discharge of groundwater, 0.05 cfs
D = discharge immediately below partial cut,
0.30 cfs
TG = temperature groundwater, 48°F
TT = stream temperature below silvicultural
activity which is equal to the
temperature above plus computed
temperature increase, 68.7°F
T_ — T -I- AT
T — I AI L\ i
TA = temperature streams above treated (par-
tial cut) area, 68.1°F
AT = temperature increase, 0.6°F
Therefore,
(0.05 cfs) (48°F) + (0.25 cfs) (68.7°F)
D (0.05 cfs) + (0.25 cfs)
= 65.3°F
The water temperature entering the lower reach
will be 65.3°F. The estimated water temperature
increase in the lower reach is 1.5°F. Again, the two
values should not be added as explained above.
The following mixing ratio formula should be used:
DGT(; + DTTT
TI> = D +D— (vn.9)
where:
TD = temperature downstream where lower
reach ends
DG = discharge of groundwater, 0.05 cfs
DT = discharge immediately below partial cut,
0.50 cfs
TG = temperature of groundwater, 48°F
Vin.37
-------
TT = stream temperature below silvicultural
activity which is equal to the
temperature above plus computed
temperature increase, 66.8°F
TT = TA + AT
TA = temperature stream above treated (par-
tial cut) area, 65.3°F
AT = temperature increase, 1.5°F
Therefore,
(0.05 cfs) (48°F) + (0.45 cfs) (66.8°F)
° (0.05 cfs) + (0.45 cfs)
= 64.9°F
The estimated overall water temperature in-
crease at the mouth would be 1.9°F (64.9°F - 63°F
= 1.9°F). This value is entered in the tables Vffl.2
and VIII.3 for both management alternatives.
ANALYSIS REVIEW
The estimated outputs are summarized in tables
VHI.2 and VIII.3 for Grits Creek alternatives A and
B, respectively. These estimates must be compared
to the water quality objectives to determine if one
or both of the alternatives are acceptable.
In determining acceptability of the alternatives,
accuracy of the estimations must be considered.
The two major sources of variation affecting ac-
curacy of outputs are: (1) models, which by their
very nature, cannot completely represent all fac-
tors affecting the estimated output, and (2) quality
of input data — there is a decrease in the accuracy
of the estimated output as the quality of the input
data decreases. Establishing an acceptable level of
accuracy for the estimated outputs is left to the
professional judgment of a user who understands
the strengths and weaknesses of the models and
data sets used.
The computed outputs for total potential sedi-
ment from all sources and the potential
temperature changes are compared to the water
quality objective at the mouth of the watershed.
The water quality objective for Grits Creek was to
maintain channel stability, limit total potential
sediment discharge to 25.5 tons/yr, and limit the
maximum temperature increase to 3°F. The post-
silvicultural activity total suspended sediment dis-
charge from all sources was 26.3 tons/yr for alter-
native B and 53.8 tons/yr for alternative A (tables
VIII.2 and VHI.3). Although alternative B resulted
in 0.8 tons/yr in excess of the allowable maximum,
it was judged to be within the accuracy range for
the data and models used. Since both alternatives
were consistent with temperature objectives, the
mix of controls in alternative B was considered ac-
ceptable from a water quality standpoint.
Vin.38
-------
Table VIII.2
Summary of quantitative outputs for: Pffo-nflJU/fc fl (yl-'its
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soi 1 Mass
Movement :
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Output description
Water ava liable for
streamf low
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration
curve
Surface soi I loss
Sediment del i vered
Hazard index
Weight of sediment
Acceleration factor
Sediment discharge
due to flow
change
Total suspended sed
from a I I sources
to stream channel
Coarse >0.062 mm
Fine <0.062 mm
Total
Bed load
Suspended
Total
iment discharge
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
activlty
/0O cm
^^^_
/3./C»r,
A/.fl.
A/./)
$Łflf..-3
/M.
M.fl.
\^
\
CNo*.
0.0-W/Yr
It. t> ha/fi-
ll, (o W/yr
(U Uu/yr
\
""\^
Post-
activity
/ao.ffdn
/S.?cw
/3./crv»
A/-/).
W.fl.
fi3.3DL.3
3300 -U»/yr
3il (Ylass ^
^N
dO -fen^/r
/f.t-Us/yr
/?.t ^ns//r
sayW/xv
fQ.SL^HS/yr
AS'F
Chapter
reference
(worksheets)
JL/,2t2
JUJjUC.a
31,3^.*
HT.SjJT.V
jm.3
or.*
o>/ei«€iCtj
^^
"\^
1ZH.3 ];«e E
2T.3 CneF
XL. 3 ltn« A
2E.3 line 6
3Zt. 3 line 1C
TILS IW G.
3C.3 n«e A
hW Z.I +A
30Iv5 Ut W
anr.^
VHI.39
-------
Table VI11.3
Summary of quantitative outputs for: fllternoenVC BJGvt'fc
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soil Mass
Movement :
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Output description
Water aval lable for
streamf low
annua
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration curve
Surface soi 1 loss
Sediment delivered
Hazard index
Weight of sediment
to stream channel
Coarse >0.062 mm
Fine <0.062 mm
Total
Acceleration factor
Sediment discharge
due to flow
change
Bed load
Suspended
Total
Total suspended sediment d scharge
from al 1 sources
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
activity
lotf cm
^\^_
/3.I cwt
A). A.
/U.fl
•ftjian:..*
w.fl.
N.fl.
\^
\
(Mo Ł.',(
0.0 4wtf/yf
//.fe kvu/yv
l/.t -fenj/yr
luWyr
\^
^\_
Post-
activity
fto.Łc»i
/s.?c»n
/3.1cm
N.fl.
M.fl.
XfanL.3
wo WKV
6.7 Jwts/^v
•^
Dloss IHsver
"**•
0.0 4ms/yr
/JltU^r
1WW/JV
36.3 ^Hi/yr
«7^«^r
/.SflF
Chapter
reference
(worksheets)
jc.i.JC.a.
ac.ijU.^
at 3^.^
xs/H-f
JSC.3
3JT.?
ieni:)
^\
3L.3 line *
tt.-8 lm«F
3lC..3lii%. A
5L.3hVitfi
3ZL.3 l|n«K
JBT^ f.^, A.
3E.3 'Ate A
IlM *.l* «
3ZL.3 U« m
3ff!.a-
vin.40
-------
Worksheets for Grits Creek
alternatives A and B
Worksheets are presented in numerical order with all III.1-III.4
alternative A, followed by III. 1-III.4 alternative B; IV.1-IV.8 alternative
A, followed by IV.1-IV.8 alternative B, etc.
VIII.41
-------
WORKSHEET I I I.1
Water available for streamflow for the existing condition in rainfall dominated regions
(1) Watershed name GnTs Creek.
(2) Hydrologic region
(3) Total watershed area (acres) oS(o (4) Latitude 3S
Season
name/
dates
(5)
Fal I
I ' '/3,
Winter
iv-y
vi fyt
Spring
r,-%
Summer
(,/ 8/
/ - /S|
Si 1 vicu 1 tural prescription
Compartment
(6)
Un impacted
Impacted
Total for se
Un impacted
Impacted
Si Ivicultural
state
(7)
Forested
ason
roi"Ł8TW
Total for season
Un impacted
Impacted
Fbr«4«
-------
Item or
Col. No. Notes
(1) Identification ot watershed or watershed subunit.
(2) Descriptions of hydrologic regions and provinces are given in text.
(3),(4) Supplied by user.
(5) Seasons for rainfall dominated regions are fall (September, October,
November), winter (December, January, February), spring (March,
April, May), and summer (June, July, August).
(6) The unimpacted compartment includes areas not affected by the
si Iv[cultural prescription. The impacted compartment includes areas
affected by the si IvicuItural prescription.
(7) Areas of similar hydrologic response as identified and delineated by
vegetation or si IvicuItural state.
(8) Supplied by user.
(9) Column (8) 4 item (3).
(10) Measured or estimated by the user.
(11) From figures 111.10 to 111.12; or user supplied.
(12) Supplied by user. Unnecessary if leaf area index is known.
(13) From figures 111.13 and 111.14; or user supplied.
(14) From figures 111.15 to 111.17.
(15) From figures 111.18 to I I 1.20.
(16) Calculated as (11) x (14) x (15) x (9); or user supplied.
(17) Seasonal sum of column (16).
(18) Column (10) - column (17).
(19) Sum of column (17).
(20) Sum of column (18).
-------
WORKSHEET I I I.2
Water available for streamflow for the proposed condition in rainfall dominated regions
(1) Watershed name GrviTs
(2) Hydrologic region
(3) Total watershed area (acres) 3S"fe (4) Latitude 35"
Season
name/
dates
(5)
Fal 1
fl-%
Winter
'*f-&
Spri ng
%-y*
Summer
tf-%1
Si I vicu Itural prescription
Compartment
(6)
Un Impacted
Impacted
Total for se
Un impacted
Impacted
Si Ivicultural
state
(7)
Posited
Clearcut
Th'mnfia
ason
Fovcsttd
Clear-cu;
Thinne*
t
Total for season
Un impacted
Impacted
PbresW
Clearwt
TKmneJ
Total for season
Impacted
Rvested
^QarCAi
Thinner
Total for season
Area
Acres
(8)
*4
180
93,
35fc
84
ISO
?3L
3S
-------
Item or
Col. No. Notes
(1) Identification of watershed or watershed subunit.
(2) Descriptions of hydrologic regions and provinces are given in text.
(3),(4) Supplied by user.
(5) Seasons for rainfall dominated regions are fall (September, October,
November), winter (December, January, February), spring (March,
April, May), and summer (June, July, August).
(6) The unimpacted compartment includes areas not affected by the
siIvicultural prescription. The impacted compartment includes areas
affected by the siIvicultural prescription.
(7) Areas of similar hydrologic response as identified and delineated by
vegetation or siIvicultural state.
^ (8) Supplied by user.
j^ (9) Column (8) T item (3).
01
(10) Measured or estimated by the user.
(11) From figures 111.10 to I I 1.12; or user supplied.
(12) Supplied by user. Unnecessary if leaf area index is known.
(13) From figures I I 1.13 and 111.14; or user supplied.
(14) From figures III.15 to 111.17.
(15) From figures 111.18 to I I 1.20.
(16) Calculated as (11) x (14) x (15) x (9); or user supplied.
(17) Seasonal sum of column (16).
(18) Column (10) - column (17).
(19) Sum of column (17).
(20) Sum of column (18).
-------
WORKSHEET I I I.3
Flow duration curve for existing condition
rain dominated regions
(1 ) Watershed name
rifs Creek
(2) Hydrologic region
(3) Water available for annual streamflow existing condition (cm)_
(4) Annual flow from duration curve for hydrologic region (cm)
(5) Adjustment ratio (3)/(4) /VS7
7A.O
Point
number
i
(6)
/
X
3
1
S
(*
7
8
9
10
//
Percent of
time flow
is equaled
or exceeded
(7)
0
10
50
30
-------
WORKSHEET I I I.4
Flow duration curve for proposed condition
rain dominated regions—annual hydrograph unavailable
(1) Watershed name Gn-ils C>r€e\C.
(4) Existing condition LAI (e. 0
(2) Hydrologic region
(5) Proposed condition LAI
3.2,
(3) Watershed aspect code (AS)_
(6) Change in LAI (CD) 3-8
(7) Rooting depth modifier coefficient (RD) / (8) bp -.03 (9) bj ".Q3 (10) b? -/3 (11) b^ -03- (12) 64,
.03
Point
number
i
(13)
1
2
3
*
5"
4,
7
8
9
10
II
Percent of
time flow is
equaled or
exceeded
(14)
O
10
20
30
*o
so
feo
70
80
JO
10V
Existing
potential
flow Qj
(15)
13.1
a?
J.S
9.O
/.8
(.0
.7
.fe
.Ą
.3
0
bQ
(16)
-.03
-.03
-.03
- .03
- 03
-.03
-.03
-.03
-.03
-.03
-.03
bl
.34,
.36
.34,
.34,
.3fe
.34.
.3fc
b3AS
(19)
0
0
0
0
0
0
0
0
0
0
0
b4RD
(20)
.03
.03
.03
.03
.03
.03
03
.03
.03
.03
.03
AQi
(cm)
(21)
-.03
.A4
AB
.30
.31
.33
.3+
.3*
•3T
.3S
.36
-------
WORKSHEET IV.1
Soil characteristics for the 6-rjTS
watershed
Soi 1 group
Top so i 1
1
Subsoi 1
Top so i 1
0
Subsoi 1
Topsoi 1
•*
Subsoi 1
E
-t- '-
c
CD O
U TJ 1
l_ C 0
CD ro •
CL U) CM
10
S"S"
-0
I- L. —
CD Q> •
CL > O
17
1(0
IS
17
1?
17
f. _ i
+- E
— to
in o
-t- 0) O
c in 1
O
I?
H
ax
13
A(o
as
E
-t-
C CM
CD O
O >-O
U (D •
d> — O
CL O V
as-
/sr
10
10
asr
^0
Percent
organic
matter
V.o
1,0
-------
1 of 3
G-vVts Creek
WORKSHEET IV.2
watershed erosion response unit management data
sediment delivery index, hydrographic area 13 ,
for use in the
g/jgrnalive.
MSLE and
Erosion
response
unit
1. SC 13.1
2. 5C.I3.A
3. CCI3-/
4. J,on dip*.
= 43,560
/toad CA.O&&ZA a.
-into a channel..
It U>
fytom the. nut oft the. fioad bzcauAe. Aedune.nt jj>
-------
2 of 3
WORKSHEET IV.2—continued
Area with surface residues
Percent
of total
area
1. MO
2. 15"
3. SS
4. (oO
5.
6. 0
1. 0
8. fcO
9.
10. &0
11. 0
12. Ł0
13.
14. O
15. O
16. foO
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Percent
of surface
with mulch
85
8S-
4>0
6,0
O
0
ss-
85-
0
86T
0
O
85-
Percent of
area with ,,.
f ine roots —'
?Y
n
9?
<*9
0
0
so
50
O
SO
O
0
SO
Open area
Percent
of total
area
60
55-
^5"
Ą0
loo
IOO
-------
WORKSHEET I V.2—cont inued
3 of 3
Average
mi n imum
height of
canopy
(m)
i. a.
2. X
^) -n.—
4. _
5.
6. a.
7. —
e. a.
9.
10. JL
11 . -
12. 2.
13.
14. 2.
15.
16. 0.
17.
is. a.
19. -
20. a.
21 .
22. —
23. -
24. —
25.
Time for
recovery
(mo )
4
UMKMOUW
•
Average
d i st . from
disturbance
to stream
channel (ft)
O
o
O
o
/38
O
193
O
193
Overal 1
slope shape
between
d i sturbance
and channel
COMCAVC
COMCAUE
QONCAVE
COWCAVE
COMCAVE
STRftl&HT
COMCAl/fiT
STfcBI&HT
COMCAVE:
Percent
ground
cover in
f i Iter
strip
88
84>
?4
90
S?
0
SCo
0
94
Surface
roughness
(qual i-
tat i ve )
MODERATE-
MOOERflTE-
moDERATe
moDER-ATE
DlOOtefiTE
smooTH
(HODERftTe
smoorH
MOOEKATC
Texture of
eroded g,
mater i al — ^
(? silt +
clay)
y?
S7
S7
SO
39
38
SO
SO
SO
Percent
slope
between
disturbance
and channel
8
Ifo
la.
AO
8
IOO
Ib
100
/a.
<
-1 It hat
been aAAum&d that k o& thu c.la.ij lejncu.yu> on-b-tim cu> btabtt aggie.gateA and tkat the, H.ut ofa the. clay pŁu6
*and and biXjt &nteA the. Ae.dime.nt de.ti.veAy
-------
WORKSHEET IV.3
Estimates of soil loss and delivered sediment by erosion response unit
for hydrographic area /3 of Grits C.4>
^o.o
/./
3107
SD,
O.OA.
0-OX
o.oa.
o.o
o.oi
o.H
0.01
Del i vered
sed iment
(tons/yr)
O.OST
0.37
0.07
o.o
0.90
o.a,
3. a.
f—H
B
- SC - Section cut
CC - Cl&aAcut
R - Road
-1 T - Top* o^l
S -
•21
of, two LS vaJLuu, one.
eac/i
a
tke. n.oad, Atasuting out tkn cn.nt&i tine, and including
-------
WORKSHEET IV.4
Estimated VM factors for siIvicuIturaI erosion response units
Gr i"ts Creek watershed, hydrographic area /3
Ol
CO
Logging residue arLea
Erosion
response
unit
SCI3.I
SCI3.-3.
CCI3. 1
CCI3.^
Mil CUT
BED
FILL
RI3.2. FILL
BED
FILL.
RI3.ST CUT
BED
FILL
Fraction
of
total
area
o.Mo
0.^
O.SS"
o.fco
0.0
o.o
o.feo
ofeo
o.o
O.fcO
o.o
0.0
o.fco
Mulch
(duff &
residue)
o./o
O.IO
0.25-
o.Ar
-
—
0.10
O.IO
—
O.IO
—
-
O.IO
Canopy
0.98^
0.98
1.0
1.0
—
—
0.88
O.SS
-
O.S8
—
-
1.0
Roots
O.IO
O.IO
OJO
O.|0
-
—
o.ai
o.ai
—
0.31
-
—
o.ai
Sub
VM
.003?
.00
J.o
0.3G
1.0
1.0
O.VI
— Canopy e^ecti onŁi/ appty to open OHHOA without neAJ-due. and
— Example. caJLcvJLoJUioYi- F/iom woikAhe.et IV.2, &5% 0(j the. iuAiJace. kaA match, ieav-Lng 151 without tnuUl-ch. If, the. canopy
-ci unibointy dii,t>iibute.d oueA 451 0|S Ae. ioiaŁ nAea, the.n oniy 151 0(j tke cflwopy can coueA iKe atea wtifcocrf mutch.
TVieAetfo/i.e: (0.15) (0.45) (WO) - 71 o coveAtd bij the. canopy. Thit, neAuttA in a
l/M - 0.9S.
—'. EnteA on uioiki>he.et IV. 3.
— VM fjOti load* il> &ol a iecoveAe.d condition.
-------
WORKSHEET IV.6
Weighting of VM values for roads in
C»-ee< watershed, hydrographic area
13
Erosion
response
unit
KI3.I
RI3.2.
RI3.S
Cut or fill
Fraction
of total VM
width
(OJ065) (0.88)
(0.0118} (o-3fe)
^ ^
(O.|b%) (|.0)
-» »• —
Roadbed
Fract ion
of total VM
wi dth
+ (0.7 ioi) CIA)
+ Co.7i^ (10]
+ Co.s^n) (\.o)
\
Fi 1 1
Fract ion
of total VM
wi dth
+ (o.|g3
-------
WORKSHEET IV.7
Factors for sediment delivery index from erosion response units in
&TUS Creek watershed, hydrographic area /3
Erosion
response
unit
SCI3.I
SCI3.2.
CCJ3.I
«ai
RI3-I
RI3.1
R.I3.S
Water (.
aval 1 abi 1 ity
o. ooa.
a/
O.003
iy
O.oolS
o.o
JJ
o.oia
o.ool J
o.oifc"^
Texture
of eroded
mater i al
47
57
*7
so
38
38
SO
Percent
ground
cover
between
disturbance
and channel
47
U,
53
47
47
O
53
Slope
shape
code
a*
3.S
2.S-
«
3.S"
3.0
3.S-
Distance
(edge of
disturbance
to channel )
(ft)
1
1
1
1
138
«*
l?3
Surface
roughness
code
i
I
i
i
Z
1
*•
Slope
gradient
($)
*
l\o
,Z
30
?
loo
^
Specific
site
factor
—
—
—
—
—
—
—
Percent
of total
area for
po 1 ygon
/a.a
J3./
13.1
—
1.0
30.9
8. 2,
^/
SD|
o.oi
o.oo.
o.oa.
i/
o.o
0.01
o./V
o.oj
Cn
Cn
I/ Majtimum J5 min. annual ttoim oŁ 2.5 -in/hA.
~2/ InfrMxation note, ofi 2.0 in/hi (baAnd on t>o-UL peAmiabillty].
TJ ln(,iJUnaŁion note, of, 3.0 -Ln/kn. ibaJ>e.d on &oiŁ
~4/ Infiltration note, of, 0.1 In/kn (boAe.d on t>oJJL
T/ EnieA on woAfeifieet IV. 3.
~6/ Wfeen uw-te/t avcMabi&ity -Us Z«AO, fke.n the. Ae.dime.nt deZtueAi/ -index -u zeAo.
-------
WORKSHEET IV.8
Estimated tons of sediment delivered to a channel for each
hydrographic area and type of disturbance for Gfjfo Creek watershed,
Al+«t>n«cfl\/e, A
Hydro-
graphic
area
/
3,
3
4
5-
(o
7
8
?
10
II
U
/3
/
-------
1 of 3
Gnrijs Cve&k
WORKSHEET IV. 2
watershed erosion response unit management data for use in
sediment delivery index, hydrographic area 13
the MSLE
. S
and
Erosion
response
unit
1. SCI3J
2. SCI3.2.
3. CC.I3J
4- CCI3.2.
5. R 13.)
5. CUT
7. BED
8- PILL
9. Rj3.au
10. FILL
11. 6ED
12. FILL
13. R|3.3
14. CUT
15. BED
16. FILL
17. RI3.4J/
18. FILL
19. BED
20. FILL
21. RJ3.S
22. ClCT
23. BEP
24. FILL
25.
Slope
length of
disturbed
area (ft)
IU
384.
133.
H8<4
3.5-
ia.o
4.5T
a.o
13.0
5.0
H.O
11.0
5.0
a.s-
ia.o
fe.o
8.0
ia.o
10.0
Slope
gradient of
disturbed
area (%)
9
It
is.
10
no
1.0
loo
IOO
0
JOQ
170
a.
JOO
loo
o
100
J*0
J
IOO
Length of
road
section
(ft)
543
a4
543
*6
6/4,
Average
width of
d isturbance
(ft)
Ife.Y
U
14.O
3.1
18.0
L<4
13.0
3.6,
IL.4,
a.o
//.o
3.fc
/*.o
l.g
ia.o
y.i
23.0
3.9
la.o
7J
Area
(sq.ft.)
Area
(acres)
6.1
5-7
/.4
4.V
fl.Al
O-Ol
o.al
0.0 1
0.33
K
en
—
-1 1
200
43,560
4ecXion
between
a b&uiam.
-into a cha.nn Ae.paSLate.d
thu fi&>t o^ the. fioad foecmtie
-------
2 of 3
WORKSHEET I V.2~cont i nued
Area with surface residues
Percent
of total
area
1. HO
2. HS
3. 60
4. 65
5.
6. 0
7. 60
8. /OO
9.
10. (00
11 . 4,0
12. (GO
13.
14. 0
15. feO
16. /t>0
17.
18. 100
19. fco
20. loo
21.
22. 0
23. feo
24. |oo
25.
Percent
of surface
with mulch—/
100
|OO
loo
95-
O
8S
85"
85-
8S-
8Ł-
0
SS
85"
85"
85"
85-
0
85"
85-
Percent of
area with
fine roots
99
W
??
??
0
40
(00
loo
60
/OO
o
4o
loo
loo
Ł>0
loo
o
fco
|OO
Open area
Percent
of total
area
GO
S5-
^0
35"
100
40
0
0
40
0
100
40
0
0
40
0
too
40
0
Percent
of surface
with mu 1 ch
80
75-
8ST
SO
0
0
0
0
0
o
o
0
Percent of
area with
fine roots
11
11
11
11
O
60
IOO
100
60
loo
0
60
100
IOO
60
/OO
0
60
|OO
Are open areas
separated by
f i Iter strips?
yes
ves
YŁS
yes
wo
wo
wo
MO
NO
MO
WO
WO
Percent of
total area
with canopy
4S"
4S-
0
a
AST
0
as
as"
o
AS"
ar
0
as*
as
0
AS
0
0
0
en
00
— Not appreciable to scalped a/iaa4 unŁtŁ uegstation
-------
WORKSHEET I V.2—cont i nued
3 of 3
Average
mi n imum
height of
canopy
(m)
1- Ł
2- 4.
3.
4.
5.
6- 2,
8. 2_
9.
10. 2,
1 1 .
12. fl.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Time for
recovery
(mo )
J
UMKNOWfJ
i
Average
dist. from
disturbance
to stream
channel (ft)
0
o
o
o
138
O
11 3
Overal 1
slope shape
between
disturbance
and channel
CONC/WE
COMCflvE
CoWCflVF
GONJCflVE
COM CAVE
STRfil&HT
CDNCRVE
Percent
ground
cover in
f i Iter
strip
fe7
Llo
S3
sn
47
O
S3
Surface
roughness
(qual i-
tat i ve)
mODERflTE-
mODERflTE
MODECOTF
MOOERflTE-
mooeRftTG"
smooTH
MOD CRATE
Texture of
eroded gi
material —
(? silt +
clay)
47
S7
57
50
3?
3S
s-o
Percent
slope
between
disturbance
and channel
8
1C,
ia.
ao
?
(00
IX
Ol
CO
-1 It ha*
b on-b-Ltt t
-band and A
-------
WORKSHEET IV.3
Estimates of soil loss and delivered sediment by erosion response unit
for hydrographic area / 3 of G-rftS Cr€€JC watershed
II
Erosion response
un it
SCJ3.I
seis.a
ŁC/3./
CC/3.JL
A/3.1
RI3.il
R (3. 5
RM
R.13.5*
Soil
unit-7
Tl
T3
T3
T&
SI
SI
S3
S3
S3
R
3oo
300
3oo
3oo
300
3oo
Sot)
3oo
300
K
0.0?
o./S
0.1*
O.H
O.a7
o.^
S.o
IS.«
0.08
aa.o
0.3)
7s.o
SD|
o.oa.
o.ox
O.OSL
0-0
o.oi
o-if
O.O/
OJ4»
O.OI
Del i vered
sed iment
(tons/yr)
O.OSL
0.13
o.oi
o
O.Ko
o.o|
o.aa
O.OS"
0.75-
SC -
CC -
R - Road
- T -
S -
Co*
a &JUL
two LS vainer, one. faoti each koJLfa oŁ the. fiocid, Atasuting at the. c.e,nt&i tino, and
-------
WORKSHEET IV.4
Estimated VM factors for si IvlcuItural erosion response units
Grits Creek. watershed, hydrographic area 13
Logging residue area
trosion
response
unit
SC.I3.I
SCI3.1
CC13.I
CCI3.X
ftlll^CttT
BED
FILL
RI3.3. FILL
BED
FILL
RI3.3 CUT
ge&
Pia
Ris.
o.?<|
l.o
l.o
0.87
0./8
—
—
1.0
-
O.S7
O.I?
—
—
1.0
—
0.87
0.1*
—
Roots
O.I
O.I
0.1
O.I
—
—
—
—
0.18
—
-
—
-
—
o.lt
-
—
—
—
F i 1 ter
strip
o.ff
o-s-
o.S
Q.S-
l.o
l.o
—
—
l.o
—
l.o
10
—
—
l.o
—
l.o
1.0
—
Sub
VM
.0034
.003?
.00)8
.001.1
.0870
.O7i
0.0
0.0
.012,
0.0
D.J70
0.070-
0.0
0.0
0.011
0.0
O.J70
q.oli
o.o
TotaT
VM
.00 IX
.00^8
.0030
.oasq
.870
.083
.010
.010
.083
.010
,«70
.083
.010
.0)0
.083
.0)0
.870
.0*3
.010
_/_/ Canopy t^tctA only apply to ope.n ouuuu, without ie4.cdue and
y Example. c.alc.uZation: fn.om vioi.kAhe.it. IV. 2, &0% of, the. Aun.^a.c.e. in the. open ane.a hM malah, le.avj.ng 20% without mulch.
T-i the. canopy u> wUfioimly dit,tfbibute.d o\ieA 45% o& the. total oAea, the.n only 20% 0)j the. canopy can coueA the. a/ie.a
uiithout muZch. Thejit&oie.: (0.20} (0.45) {100} 9% o<( the. aneA without mulch, that -LA coveAe.d by the. canopy. ThiA
X-UultA In a. l/M 0.95.
_3/ EnteA on (aolkAhe.et IV.3.
4/ VU do>i loadA iA ^01 a le.coveA.e.d condition.
vra.8i
-------
WORKSHEET IV.6
Weighting of VM values for roads in
G-t-its Creek. watershed, hydrographic area
13.
Erosion
response
un it
RI3.I
Ria-a.
ft is. a
M».4
*<3.s-
Cut or fill
Fraction
of total VM
wi dth
il.lOfes) (0.810}
0.0778^ (fl.Olo }
0J&O (0.87o^
a.ldOO^ (0.0/oS
fo.iiotf^ ro.^^o^
Roadbed
Fraction
of total VM
wi dth
+(o.7lo(Ho.o*3}
+(o.iMi$(o.o8$
+ ffl.fcUhf)(0.0«3^
•^(o.fe647^?o)o83^
+ (o.Jrai-fi (o.o«3l
^
Fi 1 1
Fraction
of total VM
wi dth
* (o.im) (0.0 10)
+ (0.aW> (o.oi
-------
WORKSHEET IV.7
Factors for sediment delivery index from erosion response units In
CtCfeX watershed, hydrographic area i3
Eros 1 on
response
unit
SCI3.I
S
lit
40
S
loo
Ife
loo
i&
Specific
site
factor
—
—
—
—
-
—
—
—
—
Percent
of total
area for
po 1 ygon
111
ia.7
U.I
—
5.1
30.9
(,./
2^.3
s-.t
^
O.OJL
o.ox
o.oa.
0.0^
o.oi
O.It
o.oi
o.ffc
O.OI
CO
!/ Maxtmura J5 min. annuat &toxm oŁ 2.5 -tn/fi*.
?/ In(5^tt(tt<.ow ^ui^e 0|5 2.0 -Ln/kn. (fatued on
I/ In^ittMLtion lati o$ 3.0 -In/hi ibtu,e.d on &OJJL peMne.ab-iM.ti/].
?/ IniJiWwLtion /urte otf 0.1 ^n/fiA (boied on i>o*Jl ph.e.et IV. 3.
6/ When uiateA avaitab-i&ity -u zato, then the. ie.dime.nt deJti.veJiy -lnde.x. -it, z&to.
-------
WORKSHEET IV.8
Estimated tons of sediment delivered to a channel for each
hydrographic area and type of disturbance for (art-its
a I rev-noil ue, 8
watershed,
Hydro-
graphic
area
/
a.
3
1
5
fo
7
8
9
10
II
la.
(3
H
ir
Me
17
Col umn
total
Di stur-
bance
total
^ercent
Cutting units
SC,
o.ol
o.o/
0.01
0.0
0.02.
0.0
0.0|
0.0|
O.O?
SC2
0.01
0.01
0.13
o.o
0.0
o.o
0.15
0.47.
3.3
CC]
o.ol
o.ol
o.ol
0-0)
o.oo.
0.01
o.ol
o.ol
0.01
o.ol
0.0|
o.o
O.Ol
0.0
o.ol
o.o
O.ol
o./J-
CC2
o.oi
o.ol
o.ol
o.ol
0.0|
0.01
O.Ol
o.o
0.0
o.o
0.07
CC3
o.o
0.0
0.2.0.
3.3
Roads
"1
o.a.
0.03
O.I
o.a
O.k>
0.°3
o.a
0.°3
0.03
0.03
0.03
o.ol
o.a.
O.I
0.1
O.I
O.I
3.0?
«2
O.I
0.01
O.OI
O.I
o.oi
O.ol
0.0|
O.ol
0.01
0.1
0.01
O.ol
o.ol
O.Ol
0.0|
o.va
«3
O.ol
O.I
O.ol
o.o|
0.1
O.I
0.4
0.03
o.l
o.a
O.I
O.I
0.1
—
l.llo
K4
O.I
o.oi
O.I
o.ol
o.o/
O.ol
o.l
0.05"
O.oS'
-
-
o.
-------
WORKSHEET VI.1
Suspended sediment quantification for Grits Creek.
Time
(a)
ith hydro-
raphs use
ate; with
low dura-
ion curves
use % of
365 days
1
5
10
2.0
30
40
SO
t*o
10
80
?0
100
(\ )
i ncremen
(b)
Number
of
days
pre-
s i 1 vi-
cu 1 tura 1
act i vi ty
3.C,
(8.1
3C..5-
73.0
tol.s
I-&.0
isa.s-
aif.o
ass.0
a'fa.o
3.J8.0
36S.0
h
(c)
Number
of
days
post-
si I v i-
cu 1 tura 1
act i vi ty
3.fc
(8.1
36. S"
73.0
/0?.S"
;
-------
WORKSHEET VI.3
Sediment prediction worksheet summary
Subdrainage name Gr\ts Or€ek fflhWtflue /Q Date of analysis_
Suspended Sediment Discharge
A. Pre-siIvicuItural activity total potential suspended sediment
discharge (total col. (4), wksht. VI.1) (tons/yr)
B. Post-si IvicuItural activity total potential suspended sediment
discharge (total col. (7), wksht. VI.1) (due to streamflow .
increases) (tons/yr) \l'(e
C. Maximum allowable potential suspended sediment discharge (total
col. (9), wksht. VI.1) (tons/yr)
D. Potential introduced sediment sources: (delivered)
1. Surface erosion (tons/yr) 3i.**
2. Soil mass movement (coarse) (tons/yr) 0
3. Median particle size (mm) ""
4. SoiI mass movement—
washload (silts and clays) (tons/yr)
Bed Ioad Discharge (Due to increased streamflow)
E. Pre-siIvicuItural activity potential bedload discharge (tons/yr)
F. Post-si IvicuItural activity potential bedload discharge (due
to increased streamflow) (tons/yr)
Total Sediment and Stream Channel Changes
G. Sum of post-si IvicuItural activity suspended sediment + bedload
discharge (other than introduced sources) (tons/yr) \7-\e
(sum B + F)
H. Sum of total introduced sediment (D)
= (D.I + D.2 + D.4) (tons/yr)
I. Total increases in potential suspended sediment discharge
1. (B + D.1 + D.4) - (A) (tons/yr)
2. Comparison to selected suspended sediment limits
(1.1 ) - (C) (tons/yr) +
Vffl.66
-------
WORKSHEET VI .3—continued
J. Changes in sediment transport and/or channel change potential
(from introduced sources and direct channel impacts)
1. Total post-si IvicuItural activity soil mass movement
sources (coarse size only) (tons/yr) 0
2. Total post-si IvicuItural soil mass movement sources (fine
or wash load only) (tons/yr) Q
3. Particle size (median size of coarse portion) (mm)
4. Post-si I vicu Itural activity bedload transport (F) (tons/yr) Q
Potential for change (check appropriate blank below)
Stream deposition _
Stream scour _
No change y
K. Total pre-si I vicu Itural activity potential sediment discharge
(bedload + suspended load) (tons/yr)
(sum A + E)
L. Total post-si I vicu Itural activity potential sediment discharge
(all sources + bedload and suspended load) (tons/yr) S3.
(sum G + H)
M. Potential increase in total sediment discharge due to proposed
activity (tons/yr)
(subtract L - K)
V1II.67
-------
WORKSHEET VI .3
Sediment prediction worksheet summary
Subdrainage name &HJS Creek fkrhoW B) Date of analysis
Suspended Sediment Discharge
A. Pre-si I vicu Itural activity total potential suspended sediment
discharge (total col. (4), wksht. VI. 1) (tons/yr) \\-(a
B. Post-si IvicuItural activity total potential suspended sediment
discharge (total col
increases) (tons/yr)
discharge (total col. (7), wksht. VI.1) (due to streamflow ~ ..
C. Maximum allowable potential suspended sediment discharge (total
col. (9), wksht. VI.1) (tons/yr)
D. Potential introduced sediment sources: (delivered)
1. Surface erosion (tons/yr) P.7
2. Soil mass movement (coarse) (tons/yr) 0
3. Median particle size (mm) *""
4. SoiI mass movement—
washload (silts and clays) (tons/yr)
Bed load Discharge (Due to increased streamflow)
E. Pre-siIvicuItural activity potential bedload discharge (tons/yr) 0
F. Post-si IvicuIturaI activity potential bedload discharge (due
to increased streamflow) (tons/yr) 0
Total Sediment and Stream Channel Changes
G. Sum of post -si I vicu Itural activity suspended sediment + bedload
discharge (other than introduced sources) (tons/yr) //•
(sum B + F)
H. Sum of total introduced sediment (D)
= (D.I + D.2 + D.4) (tons/yr) 6. /
I. Total increases in potential suspended sediment discharge
1. (B + D.1 + D.4) - (A) (tons/yr) /
-------
WORKSHEET VI .3~cont i nued
J. Changes in sediment transport and/or channel change potential
(from introduced sources and direct channel impacts)
1. Total post-si IvicuItural activity soil mass movement
sources (coarse size only) (tons/yr) 0
2. Total post-si IvicuItural soil mass movement sources (fine >.
or wash load only) (tons/yr) 0
3. Particle size (median size of coarse portion) (mm)
4. Post-si I vicu Itural activity bedload transport (F) (tons/yr) 0 _
Potential for change (check appropriate blank below)
Stream deposition _
Stream scour _
No change \r
K. Total pre-si I vicu Itural activity potential sediment discharge
(bedload + suspended load) (tons/yr) \\,(o
(sum A + E)
L. Total post-si I vicu I tura I activity potential sediment discharge
(all sources + bedload and suspended load) (tons/yr) «6.3
(sum G + H)
N. Potential increase in total sediment discharge due to proposed
activity (tons/yr)
(subtract L - K)
VIH.69
-------
WORKSHEET VI1.1
Variation of solar azimuth and angle with time of day
Time of day
(Daylight savings time)
/a -'30
/ : 00 Solav noovi
1:30
_ . _ On«v\4e
-------
WORKSHEET VI I.2
Evaluation of downstream temperature impacts
Stream reach
appefc
MIDDLE
LOWER
Aad justed
«*•
?97
/g?
7S-Q
Had justed
*Tu/ft*-win
3.JSL
3,SX
3.S2,
Q
Surface
c4s
o.z
O.diS
O.Vs-
Subsurface
C^5
0.05
o.os
Ail/
°F
s.x
0.6
is
T2/
•F
68.1
65.3
6f?
= Aadjusted * Hadjusted x 0.000267 where Q is surface flow only.
2/ Q
— T from mixing ratio equation.
-------
PROCEDURAL EXAMPLE FOR HORSE CREEK—A SNOW DOMINATED
HYDROLOGIC REGION
DESCRIPTION OF AREA AND PROPOSED
SILVICULTURAL ACTIVITY
The Timber Management Assistant on the
Glacier Ranger District, Rocky National Forest3,
prepared a 5-year timber management plan for the
district. After cruising the Horse Creek drainage,
he determined that a sale of 600,000 board feet of
lodgepole pine was warranted based upon the stand
condition and timber market.
The sale has been designed as a group of 24 small
clearcut blocks of approximately 12.5 acres each.
The blocks have been designated in the field with
orange marking paint. Engineering has flagged the
center lines of the roads that will need to be con-
structed and has surveyed the actual location, col-
lecting sufficient data to design the roads to forest
standards. See figures IV. 17 and IV. 18 for the road
locations and layout of proposed clearcut blocks.
Resource specialists have been asked to review
the proposed sale and to evaluate potential im-
pacts. Information from a general soil survey of the
area is available.
Water Quality Objectives
The established water quality objectives re-
quired that suspended sediment discharge be
limited to 38.6 tons/yr and that water temperature
increases be no greater than 1.5°F for the Horse
Creek drainage.
3This is intended to be a fictitious forest; any similarity to an
actual forest is entirely coincidental.
DATA BASE
Necessary data have been obtained from
resource specialists in timber, soils, hydrology, and
engineering.
The collected data are presented in table VIII.4.
A complete water resource evaluation includes
analyses in the following categories (numbers for
the corresponding chapters in this handbook ap-
pear in parentheses):
Hydrology (III)
Surface Erosion (IV)
Soil Mass Movement (V)
Total Potential Sediment (VI)
Temperature (VII)
HYDROLOGY ANALYSIS
Horse Creek is situated in hydrologic region 4, a
snow dominated region. The procedure presented
in "Chapter III: Hydrology" for the snow
dominated regions (including wkshts. III.5, III.6,
in.7, and in.8, proposed and revised worksheets
are located at the end of section "Procedural Ex-
ample For Horse Creek—. . .") is applied to es-
timate potential volume and timing of the
streamflow under the present conditions and under
the conditions that would exist if the proposed
silvicultural activity is implemented. Necessary
data for conducting this evaluation is presented in
table Vin.4.
Water Available For Streamflow—
Existing Conditions
Step 1. — The first step in the hydrologic evalua-
tion of Horse Creek is to estimate the water
available for streamflow under the existing condi-
tions. The following details the necessary steps out-
lined in worksheet m.5. (Numbers in parentheses
refer to items or columns on the worksheet.)
VIII.72
-------
Table VI I 1.4.—A summary of information required for the analysis procedures. Horse Creek watershed
Description of the
information
required
Information
requirements
by chapter.!/
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology
Flow — hydrograph or flow
duration curve
Bankful
Basef low
Representative flows to be used to
establish suspended and bed load
rating curves
Width stream
Bankful
Basef low (average width flowing
water)
Depth stream (bankful)
Water surface slope
Suspended sediment for representative
flows
Bed load sediment for representative
flows
Channel stability rating
Orientation stream — azimuth
Low f 1 ow per i od ( date )
Percent streambed in bedrock
Bedrock adjustment factor
Length reach exposed
Travel time through reach
0
X,P
X
X
X
X
X
X
X
X,P
X
X
X
X
p
X
X
0.73 c-fe
-------
Table VII I .4-. —continued
Description of the
i n format I on
required
nformation
requirements
by chapter
1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology — continued
Normalized hydrographs
of potential excess water
Normalized flow duration curves
Date of peak snowmelt discharge
Map of drainage net
Presence of springs or seeps
Change stream geometry
Water surface slope
Bankful width
Bankful depth
P
P
0
X
X
X
X
X
X
X
X
X
Fiqu»e H.fcl a"d ^le HE. 13
N/fl
June 11th
Figuve tt.ll awd Agu.e. H./ST
/es
O.Oa.50 -ft/ft
a.s- ft
0.8&
Information on climate
Precipitation
Form
Annual average
Seasonal distribution
Storm Intensity and frequency
Extreme event
1 yr, 15-minute storm Intensity
Drop size
Precipitation — ET relationship
Wind direction
X
X
X
P
X
0
0
0
X
0
X
X
Snow 3 maximum snowpaclc does mi exceed AO " water eiju.ii/a/eKt
3
-------
Table VI I I .1-.—continued
Description of the
information
required
Information
requirements
by chapter
I I I
IV
V
VI
VI I
Information for watershed
Information on climate — continued
Snow retention coefficient
Date snowmelt begins
Maximum snowmelt rate
Radiation
Solar ephemeris
Heat influx
Iso-erodent map for "R" factor
X,P
0
0
p
p
p
Fi3u»e UL.to
N/fl
N/fl
Figute 3HL .3
Rau*c. 3Z3L.7
Rgure. JT.l
Information on vegetation
Species
Height
Over story
Understory
Riparian vegetation
Presence phreatophytes
Crown closure (?)
Cover density
Leaf area index (pre)
Basal area
Basal area — C^ relationship
Ground cover
X
X
p
X
0
p
X
X
X
X
X
X
X
X
X
X
Uod^epJe ^>me.
10 K
N/fl
N/fl
N/fl
65%
33%
N/fl
3.00 ft yacre.
Figur*. ISL.'H
Worksheai: "Or. &
-------
Table VIII .4-.—continued
Description of the
i nf ormat i on
requ i red
nformat on
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on vegetation — continued
Percent transmission solar radiation
through canopy
Percent stream shaded by brush
Basel ine ET
ET modifier coefficient
Rooting depth
Rooting depth modifier coefficient
Depth soi 1
Percent sand (0.1-2.0 mm)
Percent silt and very fine sand
Percent clay
Percent organic matter
Soi 1 texture
Soi 1 structure
Permeabi 1 ity/lnf i Itration
Presence of hardpan
Nomograph for "K" factor
Baseline soi 1 -water relationships
Soil -water modifier coefficients
Jointing and bedding planes
X,P
P
X
P
X,P
X
Figure IE. O.I ->8%
is7o
R9uY«s Jt.ae.; Winoy frufe «t a«al«s I«SS thai^ -fke MakiMj slope;
j«'mfe tmtty C(mc«iiH>niŁt% u)o»«y-. ° Q
I
O5
-------
Table VIII .4-.—continued
Description of the
information
required
Information
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on soils and geology — continued
Soi Is map
Previous mass movements
Number
Location
Unit weight dry soi 1
De 1 i very potent i a 1
Percent silt and clay delivered
Median size coarse material
0
X
X
X
X
X
X
p
X
X
F,3u»-e. IS- -Ik
W*rU*t 3T.S
Fiftixre.3ZIIL.'S-
Fi3tt»e:2IIL.IS"
?0 Its/ft3
Rgu»«. IT."
34%
|0 Mm
Information on topography
Map (hydrologic region)
Latitude
Size watershed
Elevation
Aspect
Slope
Length
Gradient
Dissection
Shape/ 1 rregu 1 ar i ty
Nomograph for "LS" factor
X
X
X
X
X
X
X
X
X
p
X
X
X
X
X
X
X
X
USG-S map } figure H. 1 ; Hydrolo^c M^jioK V
-------
Table VIII .4-.— continued
Description of the
Information
required
Information
requirements
by chapter
III IV
V
VI
VI 1
Information for watershed
Information on topography — continued
Surface roughness
X
Moderak ^ SModfk
Information on the si 1 vlcu Itural activity
Past history
Harvesting
Fires
Other disturbances
Proposed harvest
Location units
Size cuts
Leaf area index removed
Cover density removed
Basal area removed
Cover density overstory remaining
Cover density understory remaining
Average minimum canopy height
Slash and duff~l itter
Cover percent
Height
Percent bare soi 1
X
X
X
X
X
X
X
X
X
0
0
0
X
X
X
X
X
0
X
X
N/fl
w/fl
W/fl
Rflu»«. 3E.I8, worksta«t nr.a,
Rqur«, J3T. 1? j 3OO acres -t- /I acres «f roads
N/fl
100 Ł
100%
tioAsslneek 3ST-1
Worksk^et JC.l,
O.S'w
W//I
Wor^€6-t ISC.il
3ft
Workskcet H.iL
oo
-------
Table VI I I .1-.--continued
Description of the
information
required
1 n format ion
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on si 1 vicultural activity — continued
Transportation system
Area disturbed
Locat i on
Cut slopes (location and slope)
Fill slopes (location and slope)
Cut and fill vs. ful 1 bench
Ins lope vs. outs lope
Surface
Width
Gradient
Surfacing (amount and kind)
Road density
Harvesting system
Landings
Location
Size
Gradient
Ground cover
Time for vegetative recovery of
disturbed surfaces
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Worksheet HL-SL j ll.Saeres
Figure 31.17
WoAst^tUI.a. • levgik W& j slope 66.7%
UJorU*€t 2T. a ; |««3-tk W & ; sfe^ 4>-7%
Ga±/fil|
Wo^staet J3T- 3. j oiofeleflxz.
/a.W
tUorkslwwi 3&. A j 0.0
Wov-lcsk^et JEE.2. ; bore
4.% = (J/.S acws iroads/Vtr aftr*s ^-^J
Twusk)V- skidam^
Figure 33C.I7
VOorU>cet IT-iL
Warkslieet IE. 1.
Worlcslice-t 3JT. It
1 year
-------
(1) Watershed name. — Horse Creek can be
evaluated as a single hydrologic unit. Division of
the basin into hydrologic subunits based upon
energy aspect or silvicultural zone is, therefore, un-
necessary.
(2) Hydrologic region. — Horse Creek is"within
hydrologic region 4. Hydrologic regions are
described in chapter HI.
(3) Total watershed area. — There is one
silvicultural prescription for the existing condition
with an area of 600 acres.
(4) Dominant aspect. — The most represen-
tative aspect for Horse Creek is southwest.
(5) Vegetation type. — Lodgepole pine is the
most hydrologically significant vegetation type.
(6) Annual precipitation. — Annual precipita-
tion averages 34.3 inches.
(7) Windward length of open area. — There
are no clearcuts on Horse Creek; the watershed is
undisturbed.
(8) Tree height. — Average tree height is 70
feet.
(9) Season. — There are three hydrologic sons
in region 4: winter (October, November, December,
January, February); spring (March, April, May,
June); and summer and fall (July, August,
September).
(10) Compartment. — Since the area is un-
disturbed, with no previous silvicultural activity,
there are no impacted areas.
(11) Silvicultural state. — Watershed areas are
grouped into zones of similar hydrologic response
as identified and delineated by silvicultural or
vegetational state. For Horse Creek, the only
silvicultural state is "forested."
(12) Area, acres. — Horse Creek is undisturbed.
There are no meadows or roads within the basin;
the watershed is completely forested. Therefore,
unimpacted forested area equals the silvicultural
prescription area, which is the total watershed area
of 600 acres.
(13) Area, %. — This refers to the percentage of
watershed area in each silvicultural state. In this
case, the unimpacted forested area is 100 percent
(1.00 as a decimal percent) of the total watershed
area.
(14) Precipitation. — Precipitation averaged
16.1, 12.1, and 6.1 inches for winter, spring, and
summer and fall seasons, respectively.
(15) Snow retention coefficient. — Since there
are no clearcuts or other open areas within the
watershed, snow redistribution is not a factor.
(16) Adjusted snow retention coefficient. —
Since snow redistribution is not a factor, there is no
adjustment.
(17) Adjusted precipitation. — (No adjust-
ments to the precipitation estimates are neces-
sary.)
(18) ET. — Baseline evapotranspiration (ET) is
obtained from figures III.24 to IE.26. For Horse
Creek, baseline ET is 2.1, 7.6, and 9.2 inches,
respectively, for winter, spring, and summer and
fall.
(19) Basal area. — The basal area for the
forested zone is 200 ft2/ac.
(20) Cover density, %. — For a basal area of 200
ft2/ac, figure ni.41 gives a cover density of 33 per-
cent.
(21) Cover density, %Cdmax. — In the case of
Horse Creek, a cover density of 33 percent was
judged sufficient for full hydrologic utilization.
Therefore, it is considered to beCdmax, so the
percentage is 100.
(22) ET modifier coefficient. — The modifier
coefficient is 1 for all seasons since the cover den-
sity is atCdmax.
(23) Adjusted ET. — (No adjustments are
necessary.) Values for Horse Creek are 2.1, 7.6, and
9.2 inches for winter, spring, and summer and fall,
respectively.
(24), (25), (26), (27), (28), (29) Water available
for streamflow. — The following formula is used
to calculate water available for seasonal streamflow
by silvicultural state:
Q = A (P-ET) (in.15)
where:
Q = water available for seasonal streamflow
for a silvicultural activity
A = silvicultural activity area as a decimal
percent of the total prescription area [col.
(13)]
P = adjusted precipitation inches [col. (17)]
ET = adjusted ET inches [col. (23)]
(30), (31), (32), (33), (34), (35) Water available
for annual streamflow. — The sum of water
available for streamflow by season represents an-
nual streamflow. For Horse Creek, the unimpacted
forested zone generates 14.0 + 4.5 + (-3.1) = 15.4
inches of water available for annual streamflow.
(Negative values imply storage depletion.)
VIII.80
-------
Water Available For Streamflow—After
Proposed Silvicultural Activity
Step 2. — The second step in the hydrologic
evaluation of Horse Creek is to estimate the water
available for streamflow if the proposed
silvicultural activity is implemented. The following
details the necessary steps outlined in worksheet
III.6. (Numbers in parentheses refer to the items
or columns in the worksheet.)
(1), (2), (3), (4), (5), (6). — Same as worksheet
III.5.
(7) Windward length of open area. — All roads
and clearcuts on Horse Cree.k are treated as single
clearcuts with a windward length of 6 tree heights
and a total area of 311.5 acres (11.5 acres in roads).
(8), (9). — Same as worksheet HI.5.
(10) Compartment. — For the proposed condi-
tion of Horse Creek, there will be two compart-
ments: impacted and unimpacted. The impacted
compartment includes those areas affected
(directly or indirectly) by the proposed silvicultural
activities, while the unimpacted compartment in-
cludes areas unaffected by the proposed
silvicultural activities.
(11) Silvicultural state. — For the proposed
condition, Horse Creek will have one silvicultural
state for the unimpacted compartment (forested)
and two for the impacted compartment (forested
and clearcut). The set of silvicultural states com-
prises the single silvicultural prescription for the
proposed condition.
(12) Area, acres. — The 135 acres in the
northeast corner of the watershed will not be im-
pacted by the proposed silvicultural activity. The
remaining 465 acres in the watershed will be
directly or indirectly impacted by the proposed
silvicultural activity. Trees will be completely
removed from 311.5 acres, consisting of 300 acres
clearcut and 11.5 acres in roads. The remaining
153.5 impacted acres will not be harvested, but will
be affected by snow redistribution. For the pur-
poses of calculation, clearcuts and roads are clas-
sified as clearcut (impacted), while the un-
harvested area affected by snow redistribution is
classified as forested (impacted).
(13) Area, %. — Column (12) is divided by item
(3) giving decimal percent areas of 0.225, 0.256, and
0.519 for forested (unimpacted), forested (im-
pacted), and clearcut (impacted) areas, respec-
tively.
(14) Precipitation. — This corresponds to
column (14) of worksheet HI.5.
(15) Snow retention coefficient. — From figure
III.6 the snow retention coefficient for a clearcut 6H
in windward length is 1.3. The snow retention coef-
ficient for the forest (unimpacted) remains 1.0,
while that for the forested (impacted) area is not
defined by figure III.6.
(16) Adjusted snow retention coefficient. —
For the forested (unimpacted) area, it is assumed
that there is no net change in precipitation from
snow redistribution. The adjusted snow retention
coefficient for the clearcut area is determined by
weighting the snow retention coefficient as follows:
p ,.=
'oadj
0.50
X
(in.3)
where:
dj= adjusted snow retention coefficient for
the clearcut area
= snow retention coefficient from figure
III.6 = 1.3
y _ clearcut area (including roads)
total impacted area
This is the percent of impacted area to be
clearcut. Substituting values:
X =
311.5 ac
(311.5 ac + 153.5 ac)
Substituting values for Horse Creek:
I" 0.50
P<,aHj= 1 + (1-3-1) 311.57(311.5 + 153.t
= 1.22
The adjusted snow retention coefficient for the
forested area in the impacted compartment is
calculated using the following formula:
Pt =
1- X
(111.13)
where:
Pf =
Poadi~
adjusted snow retention coefficient for
the impacted forested area
adjusted snow retention coefficient for
the clearcut = 1.22
_ clearcut area (including roads)
total impacted area
VIII.81
-------
This is the percent of impacted area to be clearcut.
Substituting values:
y = 311.5 ac
(311.5 ac + 153.5 ac)
Substituting values for Horse Creek:
1 - [(1.22) ((311.5)7(311.5 + 153.5)) ]
1 - [311.57(311.5 + 153.5)]
Pf =
= 0.55
(17) Adjusted precipitation. — Multiplying the
precipitation value in column (14) by the adjusted
snow retention coefficient in column (16) gives ad-
justed precipitation. For example, the adjusted
precipitation for the clearcut area of Horse Creek is
16.1 X 1.22 = 19.6 inches.
(18) ET. — Same instruction as worksheet III.5.
(19) Basal area. — For forested areas, the basal
area greater than 4 in dbh is 200 ft2/ac, while the
clearcut basal area greater than 4 inches dbh is
zero. These data are needed to estimate cover den-
sity, if cover density is not supplied by the user.
(20) Cover density. — For a basal area of 200
ftVac, figure in.41 gives a cover density of 33 per-
cent. For a basal area of zero, the cover density is
zero.
(21) Cover density,%Cdmax. — A cover density of
33 percent has been judged sufficient for full
hydrologic utilization and has been assigned the
value of Cdmax. Division of cover density percent in
column (17) by Cdmax gives %Cdmaxwhen multiplied
by 100.
(22) ET modifier coefficient. — The %Cdmaxcan
be entered into figure III. 46 to obtain the ET
modifier coefficient. For a %Cdmax of 100, figure
IE.46 gives ET modifier coefficients of 1.0 for all
seasons. For a %Cdmax of zero, the ET mdifier
coefficients from figure 111.46 are 0.60, 107, and 0.55
for winter, spring, and summer and fall, respec-
tively.
(23) Adjusted ET. — Multiplying ET in column
(18) by the ET modifier coefficient in column (22)
yields the adjusted ET.
(24), (25), (26), (27), (28), (29) Water available
for streamflow. — Multiplication of the treatment
area (as a decimal percentage of the watershed
area, item 13) times the difference between ad-
justed precipitation and adjusted evapotranspira-
tion (item 17- item 23) is an estimate of area
weighted contribution to total watershed flow that
will be derived from the treatment (or state) area
by season and is entered in one of the columns from
24-29.
For example, for the clearcut in winter:
Q = 0.519(19.6-1.3) = 9.5 inches
(30), (31), (32), (33), (34), (35) Water available
for annual streamflow. — The summation of
seasonal streamflows is an estimate of the water
available for annual streamflow. Horse Creek
values are 3.5, 1.1, and 13.5 inches for the (unim-
pacted) forested, (impacted) forested, and clearcut
areas, respectively.
Streamflow Discharge And Timing — Existing
Conditions
Step 3. — The third step in the hydrologic
evaluation of Horse Creek is to estimate the dis-
charge and timing of the existing condition. The
following details the necessary steps outlined in
worksheet El.7. (Numbers in parentheses refer to
the items or columns in the worksheet.)
(1), (2). — Same as worksheet III.5 and III.6.
(3) Date or interval. — Based on previous
knowledge of the area, peak discharge for Horse
Creek occurs June 19. Six-day intervals centered
around this date are listed in column (3).
(4) Forested (unimpacted),%. — Values from
the forested column of table III. 13 are entered into
column (4) with a peak discharge of 0.1575 percent
occurring on June 19.
(5) Forested (unimpacted), inches. — Forested,
(unimpacted), percent [col. (4)] is multiplied by
potential streamflow for the existing condition
from the forested (unimpacted) zone [item (30),
wksht III.5] which is 15.4 inches.
(6) Forested (unimpacted), cfs. — Each value
in column (5) forested (unimpacted) in inches, is
multiplied by the following factor:
total watershed area (ac)
(12 in/ft) (1.98) (number of days in interval)
For example, on May 26, 0.92 inches is converted to
cfs as follows:
cfs = (600) (Q-92> = 3.87 cfs
(12) (1.98) (6)
(7) - (21). — Not applicable to the existing con-
dition of Horse Creek.
VIE .82
-------
(22) Composite hydrograph. — The sum of
columns (6), (9), (12), (15), (18), and (21) gives the
composite hydrograph in digital form. A plot of
column (3) versus column (22) yields the existing
condition hydrograph (fig. VIII.13).
Streamflow Discharge And Timing — After
Proposed
Silvicultural Activity
Step 4. — The final step in the hydrologic
evaluation of Horse Creek is to estimate the dis-
charge and timing of the streamflow if the proposed
silvicultural activity is implemented. The following
details the necessary steps outlined in worksheet
in.8. (Numbers in parentheses refer to the items or
columns on the worksheet.)
(1), (2). — Same as worksheet HI.5, IH.6, and
m.7.
(3) Date or interval. — The date of peak
snowmelt discharge for Horse Creek is June 19, the
peak discharge date for the forested (unimpacted)
zone. Six-day intervals are labeled accordingly.
(4) Forested (unimpacted), %. — Same in-
structions as worksheet DI.7.
(5) Forested (unimpacted), inches. — Column
(4) is multiplied by potential streamflow for the
proposed condition from the forested (unimpacted)
zone [item (25), wksht. IE.6]. For Horse Creek this
value is 3.5 inches.
(6) Forested (unimpacted), cfs. — Each value
in column (5), is multiplied by the following factor:
total watershed area (ac)
112 in/ft) (1.98) (number of days in interval)
total watershed area (ac)
(12 in/ft) (1.98) (number of days in interval)
600
= 4.209
(12) (1.98) (6)
(7), (8), (9). — Not applicable for the Horse
Creek example.
(10) Forested (impacted),%. — These values are
taken from the forested column in table III. 13.
(11) Forested (impacted), inches. — Column
(10) is multiplied by potential streamflow for the
proposed condition from the forested (impacted)
zone [item (32), wksht. 131.6]. For Horse Creek this
value is 1.1 inches.
(12) Forested (impacted), cfs. — Conversion of
inches to cfs involves multiplication of each value
in column (11) by:
600
= 4.209
(12) (1.98) (6)
(13) Clearcut (impacted),%. — Percent poten-
tial streamflow distribution for open areas is taken
from the open column of table III. 15. Note that
peak discharge from clearcut areas occurs before
peak discharge from forested areas.
(14) Clearcut (impacted), niches. — Column
(13) is multiplied by potential streamflow for the
proposed condition from the open (impacted) zone
[item (33), wksht. HI.6] . For Horse Creek this value
is 13.5 inches.
(15) Clearcut (impacted), cfs. — Convert inches
to cfs by multiplying values in column (14) by the
factor:
_ total watershed area (ac) _
(12 in/ft) (1.98) (number of days in interval)
= 4 209
(12) (1.98) (6)
(16) - (21). — Not applicable for the Horse Creek
example.
(22) Composite hydrograph. — The sum of
columns (6), (9), (12), (15), (18), and (21) for each
interval gives the composite hydrograph for the en-
tire Horse Creek watershed (in cfs) (fig. VIII. 13).
SURFACE EROSION ANALYSIS
The quantity of surface eroded material
delivered to stream channels from sites disturbed
by the proposed silvicultural activities is estimated
in two stages. First, the quantity of material that
may be made available from a disturbed site is es-
timated using the Modified Soil Loss Equation
(MSLE). Second, a sediment delivery index
( SDj ) is estimated. When this is applied to the
estimated quantity of available surface eroded
material, an estimate of the quantity of material
that may enter a stream channel is obtained.
Erosion Response Unit Delineation
Steps 1-7. — A method for preparing the maps
(or overlays) for these steps is discussed in chapter
IV. Figures IV. 14 to IV.19 show the results of these
steps for the drainage net, hydrographic areas, soil
VIII .83
-------
12
11
10
9
8
7
6
5
4
3
2
1
0 •
Existing Condition Flow
Proposed Condition Flow
LU
O
ir
<
I
o
CO
Q
MARCH
APRIL
MAY JUNE
MONTH
JULY
AUGUST
Figure VIII.13.-Pre- and post-sllviculiural activities annual hydrograph, Horse Creek watershed.
VIII. 84
-------
groups, location of cutting units, roads, and
landings.
Step 8. — Set up worksheets for estimating
potential sediment load from surface erosion.
Worksheets IV.1 and IV.2 show field data for ero-
sion response units by hydrographic area and type
of disturbance. Individual soils in the Horse Creek
watershed have been grouped according to similar
texture, organic matter, structure, and perme-
ability characteristics. Worksheet IV.l shows the
three soil groups used for surface erosion evalua-
tion. Data on worksheet IV.l should not change
when different management proposals are
evaluated for the watershed.
Worksheet IV.2 displays various types of data
needed for evaluating the effects of the proposed
management of Horse Creek watershed,
hydrographic area 3 (fig. IV. 15). Individual erosion
response units are identified and listed. A different
erosion response unit is created for each change in
management activity, each design change for a
given activity (e.g., road change from a cut-and-fill
design to a complete fill for a stream crossing), or
each change in environmental parameters affecting
erosion (e.g., a change in soil characteristics).
Worksheet IV.3 is a summary of the values used
in the MSLE and sediment index for erosion
response units in hydrographic area 3 of the Horse
Creek watershed. The values for both management
proposals are obtained using the steps and discus-
sions which follow. Only values for the proposed
plan are used to illustrate methods for solving the
equations; however, values for the revised plan are
similarly determined
Step 9. — List each erosion source area and
number by erosion response unit.
For the Horse Creek watershed, the response
units have been coded as follows. The treatment
types are clear cuts (CC), landings (L), and roads
(R). The example hydrographic area is number 3.
Disturbance types are numbered sequentially (e.g.,
clearcut CC3.1, clearcut CC3.2, etc), to identify
them in the following evaluations for soil loss and
sediment delivery.
Using The Modified Soil Loss Equation (MSLE)
Step 10. — For each erosion response unit and
source area (silvicultural activities and roads),
determine the values to be used for each of the fol-
lowing variables:
R Rainfall factor
K Soil credibility factor
LS Length-slope factor
VM Vegetation-management factor
Area Surface area of response unit
Values for these factors are entered on worksheet
IV.3 using the following procedures.
Rainfall Factor
This value is obtained from figure IV.2. For the
Horse Creek area, R = 45. This R value is the same
over the entire Horse Creek area and will be used
for all erosion response units.
Soil Erodibility Factor
The K value can be estimated using the
nomograph in figure IV.3, or by using equation
IV.4. The data for soil group 2 needed to compute
the K value using equation IV.4 are found on
worksheet IV.l. K must be determined for both
topsoil and subsoil. For disturbances which enter
the subsoil, such as roads, the subsoil value of K
must be used.
Application of the equation to determine the K
factor is shown in the following example for soil
group 2 topsoil. This example is also plotted on the
nomograph (fig. IV.3) for the subsoil. Because of in-
flections in the family of curves on the nomograph
(fig. IV.3) for percent sand, the equation cannot be
used when silt plus very fine sand exceed 70 per-
cent.
K = (2.1 X 10-6) (12-Om) M1-14
+ 0.0325 (S-2) + 0.025 (P-3) (IV.4)
where:
Om = % organic matter
M = (% silt + % very fine sand) (100-% clay)
S = structure code
P = permeability code
Substituting values for topsoil (soil group 2) from
worksheet IV.l into equation IV.4:
K = (2.1 X 10-6) (12-4) [40 (100-10)]1-14
+ 0.0325 (4-2) + 0.025 (4-3)
K = 0.28
The K value of the subsoil (0.30) may be deter-
mined from either the nomograph or equation.
VIII.85
-------
Length-Slope Factor
The length-slope factor, LS, is a combination
factor which incorporates the slope gradient and
the length of the eroding surface into a single fac-
tor. The LS factor must be estimated for each ero-
sion response unit.
Two methods may be used to estimate the LS
factor on straight slopes. One method is to use
equation IV.8 to derive the estimated LS value.
The second method utilizes a nomograph (fig. IV.4)
to estimate the LS value.
The cutting units (CC3.1 and CC3.2) are each
different in regard to slope gradient and length.
Therefore, LS for each clearcut unit must be
evaluated separately. Using equation IV.8 and data
from worksheet IV.2, the LS value for CC3.1 is
calculated as follows for slope length A = 100 feet
and slope gradient s = 38 percent.
LS =
72.6
10,000
10,000+s2
0.43 + 0.30s + 0.043s2 \
6.613
(IV.8)
where:
X = slope length, in feet
s = slope gradient, in percent
m = an exponent based on slope gradient from
equation IV.6
Using data from worksheet IV.2:
LS =
100_V5/0.43 + 0.30(38) + 0.043(38)2
72.6,
6.613
10,000
10,000+(38)2
LS = 11.5
A similar calculation is performed for clearcut
CC3.2 and landing L3.1. All values are tabulated in
worksheet IV.3.
Road R3.1 is outsloped with a typical cross sec-
tion shown in figure IV.7. Road R3.2 is assumed to
be fill, over culverts. Average dimensions will be
the same as for R3.1 with the cutbank changed to a
fill slope.
To compute the length-slope value for the road
sections (R3.1, R3.2,) the equation for irregular
slopes is used in this example. An alternative
method using graphs (figs. IV.5 and IV.6) is discus-
sed in chapter IV.
Q \m + l
bJAJ-l
72.6'
(IV.9)
The number of calculations can be reduced by
simplifying equation IV.9 to:
m + l _ \m + l
LS = I_ .
10,000
10,000 + s2
72.6
(IV.9.1)
where:
Xe
entire length of a slope, in feet
Xj = length of slope to lower edge of j
segment, in feet
j = slope segment
Sj = slope gradient, in percent
Sj = dimensionless slope steepness factor for
segment j defined by:
(0.043s2 + 0.30Sj + 0.43)76.613
m = an exponent based on slope gradient
n = total number of slope segments
For the road R3.1, using values in worksheet IV.2
and assuming that no sediment is deposited on the
road surface, the computations are as follows:
Slope segment 1 (cut)
Xi = 4.8 ft
^1-1 = 0.0 ft (there are no preceding slope seg-
ments, hence length is 0.0 ft)
s = 66.7%
m = 0.6 (for slopes on construction; see eq.
IV.6)
0.043s2 + 0.30s + 0.43
S, =
substituting for s:
6.613
c 0.043(66.7)2 + 0.30(66.7) + 0.43 Q0
oi — = 6i
6.613
Substituting values of S, X, and m for j = l into
equation IV.9.1 to the right of the summation sign
gives:
Vin.86
-------
10,000
10,000 + (66.7)2
= 20.83
Slope segment 2 (roadbed)
*2 = 4.8 + 12.0 = 16.8 ft
X2-i = slope length = 4.8 ft
s = 0.5%
m = 0.6 (for slopes on construction sites)
S2 =
0.043s2 + 0.30s + 0.43
6.613
substituting for s:
0.043(0.5)2 + 0.30(0.5) + 0.43
S-, =
6.613
= 0.09
Substituting S, X, and m values for j=2 into equa-
tion IV.9.1 to the right side of the summation sign
gives:
Solving the entire equation IV.9.1, using the
calculated values
where:
Xe = 4.8 + 12.0 + 4.8 =21.6 ft
then: -,
LS = ~~r~ (slope seg. 1 + slope seg. 2
pe seg. 3)
(20.83 + 0.54 + 76.53)
+ slope seg. 3)
1
21.6
= 4.53
A similar LS calculation is made for road R3.2.
Road R3.2 is a fill, over culverts across a stream
channel, however, and it becomes two problems,
each with two slope segments. Each segment starts
at the middle of the road surface, and the second
segment includes one of the fill slopes. An average
value (4.3) for the LS factor using the two LS
values just determined by splitting the road in half
is entered on worksheet IV.3.
0.09
= 0.54
(16.8) L6- (4.8)
1.6
(72.6)
0.6
10,000
10,000 + 0.52
Slope segment 3 (fill)
*3 = 4.8 + 12.0 + 4.8 = 21.6 ft
X3.i = slope length = 16.8 ft
s = 66.7%
m = 0.6 (for slopes on construction sites)
0.043s2 + 0.30s + 0.43
S, =
substituting for s:
6.613
0.043(66.7)2 + 0.30(66.7) + 0.43
S:i = = 32
6.613
Substituting S, X, and m values for j=3 into equa-
tion IV.9.1 to the right side of the summation sign
gives:
32
A21.6)1-6 - (16.8)L
,0.6
10,000
(72.6)
10,000 + (66.7)2
= 76.53
Vegetation-Management Factor
The vegetation-management factor (VM) is used
to evaluate effects of cover and land management
practices on surface erosion over the entire slope
length used for the LS factor. Values for VM are
determined for all cutting units, roads, and
landings.
(1) Cutting units. — Worksheet IV.2 has the
field data used for calculating a VM factor for
clearcut units CC3.1 and CCS.2. Example calcula-
tions are shown for clearcut CC3.1. The cutting
unit is divided into two areas based on presence or
absence of logging residues. A ground cover of slash
and other surface residues covers 65 percent of the
unit (wksht. IV.2). The remaining 35 percent is
scattered in open areas of soil averaging 10 feet in
diameter.4 In both areas, fine tree roots are un-
iformly distributed over 90 percent of the clearcut
block. All of the overstory and understory canopy
has been removed.
Using worksheet IV.4, first enter percent area as
0.65 and 0.35 for area covered by residues and open
^Information about the amount of residue is often expressed in
tons per acre. Maxwell and Ward (1976) have published photos
and tables for parts of Oregon and Washington which relate
visual appearance of a site with the volume of residue and
amount of ground cover.
vm.87
-------
area, respectively. Separate calculations are made
for the logging residue and open areas.
Second, the logging slash represents the mulch
and close growing vegetation. Because slash varies
in density, assume that small openings a few inches
in diameter exist over 10 percent of the surface.
From figure IV.9, the 90-percent cover provides a
mulch factor of 0.08. The 35 percent of CC3.1 that
is open is assumed to have 10 percent of the surface
protected by widely scattered slash. Using figure
IV.9, a mulch factor of 0.78 is found for this situa-
tion.
Third, zero canopy cover gives a canopy factor of
1.0 for both areas (fig. IV.8).
Fourth, evaluate the role of fine roots that are
remaining in the soil. Since they are uniformly dis-
tributed over 90 percent of the entire clearcut area,
the value, 0.10, from figure IV. 10 can be used for
both logging residue and bare areas.
Fifth, determine if the open areas are connected
with each other, such that water can flow
downslope from one to another (ch. IV). In this ex-
ample, the open areas are isolated from each other
by bands of logging residue, requiring the use of a
sediment filter strip factor of 0.5 (see "Sediment
Filter Strips" section of chapter IV). If sediment
filter strips did not exist, a factor of 1.0 would be
used.
Sixth, using worksheet IV.4, multiply the VM
subfactors for logging residue (0.65) (0.08) (1.0)
(0.10) = 0.005. Likewise, the subfactors for bare
area are: (0.35) (0.78) (1.0) (0.1) (0.5) = 0.014. The
overall VM factor is the sum of the VM subfactors:
(0.005) + (0.014) = 0.019.
Clearcut CC3.2 will have 60-percent logging
residue cover and 40-percent bare, with bare areas
averaging 10 feet in diameter. Fine roots will be un-
iformly distributed over 85 percent of both areas.
There will not be any canopy. Bare areas will have
filter strips between them. The assumptions about
residue density are the same as for CC3.1. Values
are shown on worksheet IV.4.
(2) Landings. — Landing L3.1 is assumed to
represent a surface described in table IV.3 as
"freshly disked after one rain," with a VM factor of
0.89.
(3) Roads. — The VM factor must represent two
conditions on the road areas: (1) the road running
surface, and (2) the cut-and-fill banks that are
needed (fig. IV.7).
The following assumptions have been made for
road erosion response units R3.1 and R3.2.
a. All cut-and-fill slopes will be seeded and fer-
tilized within 10 days after completion of the
road section.
b. Vegetation will be fully established within 1
year.
During the first year, the VM factor will be
changing constantly from bare soil to a vegetated
surface on the cut-and-fill slopes. To account for
this change, VM is estimated monthly; total those
months with erosive rainfall or runoff, and then
divide by the total number of erosion months to ob-
tain an average VM value for those time periods
with potential for erosive rainfall and/or snowmelt
runoff (wksht. IV .5). Use the method described for
clearcuts to estimate VM for the site by month.
The VM factor will be effected initially by the
ground cover (fig. IV.9). As the vegetation matures,
canopy and fine roots will also influence the VM
factor.
Summing the VM values from worksheet IV.5
and dividing by 8 months (3.36/8 = 0.42) gives a
VM value of 0.42 to use for the first year following
construction with cut-and-fill slopes.
The VM for the roadbed (1.24) for R3.1 is ob-
tained from table IV.3 for compacted fill without
surfacing.
Total width for
exposed surface = 2.9 ft + 12 ft + 2.9 ft
= 17.8 ft
Running surface = 12'° ft = 0.6742
17.8 ft
= fraction of total width
Each cut or fill = 2.9ft
slope 17.8 ft
= 0.1629
= fraction of total width
The weighted VM factor for Rl.l and R1.2 is
calculated from data on worksheet IV.2 and shown
on worksheet IV .6.
Surface Area Of Response Unit
Total surface area within each treatment
unit—clearcuts, landings, and roads—is given in
worksheet IV.2 and is entered onto worksheet IV.3.
All other MSLE factors are also entered onto
worksheet IV.3. Total potential onsite soil loss is
computed by multiplying all factors on worksheet
IV.3.
VIII.88
-------
Sediment Delivery
Step 12. — The computed potential surface soil
loss is delivered to the closest stream channel using
the sediment delivery index (SDj ). Worksheet
IV.7 is used to organize the data for each erosion
response unit, for each factor shown on the stiff
diagram (fig. IV.22).
1. Water availability for sediment delivery is
calculated using equation IV. 12 for each ero-
sion response unit.
F = CRL (IV. 12)
where:
F = available water (ftVsec)
R = [1 yr, 15 min storm (in/hr)] - [soil in-
filtration rate (in/hr)]
L = [slope length distance of disturbance (ft)]
+ [slope length from disturbance to
stream (ft)]
f f 2 Li
C = 2.31 X 10-5 : —
in sec
The infiltration rate, used in determining the R
factor, is the maximum rate at which water could
enter a soil. In actual situations, the water entry
rate will usually be somewhat lower than the in-
filtration rate and can be based on the soil
permeability, with consideration for effects of
various management practices.
Using data from worksheet IV.2 and footnotes
from worksheet IV.7, the calculations are:
F = (2.31 X 10-5
ft2 hr
(1.75 in/hr
in sec
- 0.26 in/hr) (100 ft + 15 ft)
= (2.31 X 10-5) (1.49) (115)
= 0.004 ftVsec
2. Texture of eroded material is based on the
amount of very fine sand, silt, and clay shown
on worksheet IV. 1. For this case, it has been
assumed that half of the clay will form stable
aggregates with the remainder influencing the
sediment delivery index. For soil group 2 top-
soil, the following calculations were made:
texture of
clay
2
+ % very fine sand
10
eroded material =
- + % silt
2
45
-+ (15) + (25)
3. Ground cover is the percentage of the soil sur-
face with vegetative residues and stems in
direct contact with the soil. The ground cover
on the area between a disturbance and a
stream channel is determined from field
observations and used for the sediment
delivery index. For CC3.1, 90 percent is shown
on worksheet IV.2 for ground cover.
4. Slope shape is a subjective evaluation of
shapes between convex and concave. From
worksheet IV.2 for CC3.1 the slope shape is
straight.
5. Distance is the slope length from the edge of a
disturbance to a stream channel. For CC3.1
(wksht. IV.2), the distance is 15 feet.
6. Surface roughness is a subjective evaluation
of soil surface microrelief ranging from
smooth to moderately rough. Worksheet IV.2
shows a moderate surface roughness for
CC3.1.
7. Slope gradient is the percent slope between
the lower boundary of the disturbed area and
the stream channel. Worksheet IV.2 shows a
gradient of 38 percent for the disturbed area.
8. Site specific is an optional factor that was not
used in this example. See chapter IV for more
discussion of this factor.
The tabulated factors for CC3.1 (wksht. IV.7) are
plotted on the appropriate vectors of a stiff
diagram (fig. VIII.14) as discussed in chapter IV.
Use one of the several methods to determine the
area bounded by the irregular polygon that is
created when points on the stiff diagram are joined.
The area of the polygon for this example is 94.94
square units. The stiff diagram has 784 square
units. The percentage of the total area enclosed by
the polygon is:
f94-94") (100) = 12.1%
V 784 / \ /
Entering the X-axis of the probit curve (fig.
IV.23) with 12.1 results in a sediment delivery in-
dex (SD j ) or 0.02. This is the estimated fraction of
eroded material that could be delivered from the
disturbance to the stream channel.
Step 13. — Find the estimated quantity of sedi-
ment (tons/yr) delivered to a stream channel by
multiplying surface soil loss by the sediment
delivery index (wksht. IV.3) for each erosion
response unit.
VHI.89
-------
Percent Ground
Cover
Texture of
Eroded Material
100-
Available
Water
Slope
Shape
0.10
100 Site
Specific
Delivery Distance
feet
Surface
Roughness
Slope
Gradient
Figure VIII.14.—Stiff diagram for CC3.1 proposed plan, Horse Creek watershed.
vni.9o
-------
Step 14. — Using worksheet IV.8, tabulate quan-
tities of delivered sediment (tons/yr) for each
hydrographic area by the erosion source. When
completed, this table provides a summary of sur-
face erosion sources and estimated quantities of
sediment production from each hydrographic area.
Step 15. — Totals and percentages are shown on
worksheet IV.8. The total quantity of delivered
material is shown in table VIE. 5.
SOIL MASS MOVEMENT ANALYSIS
A step-by-step description, using the Horse
Creek data, was presented in "Chapter V: Soil
Mass Movement." The following discussion sum-
marizes the results of that detailed description.
Evaluation of the existing soil mass movement
hazard (fig. VIII.15) in the Horse Creek drainage is
based upon seven natural site factors using table
V.5 and worksheet V.I. Based upon the informa-
tion collected and presented in the beginning of the
example, the natural soil mass movement hazard
index is medium, with a factor summation of 31.
The value 31 falls within the medium hazard range
(21-44).
The proposed silvicultural activity will result in
an increased soil mass movement hazard.
Worksheet V.2 is completed based upon the
proposed silvicultural activity. The information re-
quired to complete this worksheet is presented in
table Vin.4. The three silvicultural activity factors
total 31. Adding the existing natural hazard value
of 31 to the silvicultural activity hazard value of 31
gives the total value for the post-silvicultural ac-
tivity: 62. This value falls within the high hazard
range (greater than 44).
There is evidence of one soil mass movement in
Horse Creek watershed approximately 20 years ago
on a smooth 67 percent (34°) slope. The dimensions
of the failure are 84 feet long, 28 feet wide, and 1.5
feet deep. The bulk density was found to be 90
lbs/ft3 (1.43g/cm3).
To evaluate the potential impact of the proposed
silvicultural activity on soil mass movement, Horse
Creek must be compared to an adjacent watershed,
Mule Creek. Mule Creek, which had a silvicultural
activity similar to that proposed for Horse Creek,
was investigated to ascertain the actual impacts
that followed a silvicultural activity. Mule Creek
watershed is considerably larger than Horse
Creek—3,900 acres vs. 600 acres (1,620 ha vs. 243
ha)—however, both watersheds have similar site
characteristics—soils, geology, precipitation,
vegetation, etc. Prior to the silvicultural activity in
Mule Creek, there had been only one soil mass
movement (debris avalanche-debris flow), approx-
imately 25 years ago, on a smooth 84 percent (40°)
slope-length 115 feet, width 19 feet, depth 1.5 feet
and bulk density 99 lbs/ft3. During the 4 years since
the silvicultural activity, five debris avalanche-
debris flows have occurred:
1. Smooth 73 percent (36°) slope—length 80
feet, width 24 feet, and depth 1.5 feet.
2. Smooth 73 percent (36°) slope—length 129
feet, width 26 feet, and depth 1.5 feet.
3. Smooth 55 percent (29°) slope—length 121
feet, width 17 feet, and depth 1.5 feet.
4. Smooth 55 percent (29°) slope—length 113
feet, width 18 feet, and depth 1.5 feet.
5. Smooth 40 percent (22°) slope—length 95
feet, width 23 feet, and depth 1.5 feet.
Using the procedure outlined in chapter V and
figure V.8, worksheets V.I, V.2, V.5, and V.6 were
completed. Based upon these computations, it was
determined that 192 tons of soil mass movement
material could potentially be delivered to Horse
Creek due to the proposed silvicultural activity.
This total is shown on table VIII.5.
TOTAL POTENTIAL SEDIMENT
ANALYSIS
Step 1. — The stream reach characterization will
be obtained on the lower 1/4 mile of the third-order
stream channel on Horse Creek.
Step 2. — See figure VIII.13 pre- and post-
silvicultural activity hydrographs.
Suspended Sediment Calculation
Step 3. — Establish suspended sediment rating
curve.
a. Data were obtained from depth integrated
suspended sediment sampling and concurrent
stream discharge measurements taken over a
period of 1 year. Samples were taken during
representative flows and are plotted in figure
VIII.16.
VIII.91
-------
Table VI I 1.5
Summary of quantitative outputs for:
sJSssk
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Sol 1 Mass
Movement:
Chapter V
Total
Potential
Sed iment :
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Output descr
Water aval I able for
streamf low
pt ion
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration
curve
Surface soi I loss
Sediment delivered
Hazard index
Weight of sediment
Acceleration factor
Sediment discharge
due to f low
change
to stream channel
Coarse >0.062 mm
Fine <0.062 mm
Total
Bed load
Suspended
Total
Total suspended sediment discharge
from a I I sources
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
acti vity
IS.t in
"^\_
/o.a ofs
3~une IS"
M.fl.
W.fl.
N.fl.
31
M.fl.
M.A.
M.fl.
^\^
/.«/ -K>ns/yr
7,1 W^r
&S* lw/xr
7.3. S" W/yr
511-9 Us/yr
1.7 af
Chapter
reference
(worksheets)
oiL.Sjjir.6
2Ls,:n[.t
nr.7,ar.«
01.7,11.?
3E-3
JE.?
3:,/;$r.2.
Ik
&.(*
3C.3 ime e
*nr s lint F
St. 3 /live 0
It-3 '"« &
1&3 /.M K
31,3 W G-
3Zt.3 U« fl
U«X.UA
2t.2 li'»cW
nzzr.^
vra.92
-------
llllim Road
Clearcut
Debris Slide
Figure VIII.15.—Horse Creek draihage showing potential areas of mass movement.
VIII P3
-------
100.0
1.0 10.0
STREAM DISCHARGE, (cfs)
100.0
Figure VIII.1B.—Sediment rating curve, Horse Creek watershed.
Vin.94
-------
b. log Y = 0.31 + 0.64 log Q
r2 = 0.95: coefficient of determination. See
figure Vm.16 for plot of data.
c. The channel stability rating procedure by
Pfankuch (1975) was used to obtain a fair
rating.
Step 4. — Calculate pre-silvicultural activity
potential suspended sediment discharge. See figure
VIII.13 for pre- and post-silvicultural activity
hydrographs. Use data from worksheet VI.1.
a. Use worksheet VI.1, columns (1), (2), (3), and
(4).
b. Record the total of 7.1 tons/yr on worksheet
VI.3, line A.
Step 5. — Calculate post-silvicultural activity
potential suspended sediment discharge (due to
streamflow increase).
A Use worksheet VI. 1, columns (1), (5), (6), and
(7).
b. Record the total of 8.8 tons/yr on worksheet
VI.3, line B.
Note that there is a 24-percent increase in sedi-
ment discharge due only to flow increase.
Step 6. — Convert water quality objective from
state water quality standards (mg/1) into units
compatible with the analysis (tons/yr).
a. Maximum allowable limits as set by state
water quality standards for suspended solids
is a 30 mg/1 increase above existing condi-
tions.
b. Use columns (8) and (9) on worksheet VI. 1 to
calculate maximum allowable, sediment dis-
charge.
c. Record the total of 38.6 tons/yr on worksheet
VI.3, line C.
Bedload Calculation
Step 7. — Establish bedload rating curve.
a. Data points for bedload transport (tons/day)
are plotted against stream discharge (cfs),
figure VIII. 17. Data are shown from worksheet
VI.2.
b. log Y = -3,43 + 2.18 log X
r2 = 0.99: coefficient of determination
Step 8. — Calculate pre-silvicultural activity
bedload discharge.
a. Use columns (1), (2), (3), and (4) on
worksheet VI.2.
b. Record the total of 1.4 tons/yr on worksheet
VI.3, line E.
Step 9. — Calculate pre-silvicultural activity
sediment discharge (suspended and bedload).
a. From step 4, obtain 7.1 tons/yr (suspended
sediment) and from step 8, 1.4 tons/yr
(bedload sediment) and add for a total of 8.5
tons/yr.
b. Record this total on worksheet VI.3, line K.
Step 10. — Calculate post-silvicultural activity
bedload sediment discharge.
a. Use columns (1), (6), (7), and (8) on
worksheet VI.2.
b. Record the total of 1.9 tons/yr on worksheet
VI.3, line F.
Total Potential Sediment Calculation
Step 11. — Obtain total potential sediment
delivered by soil mass movement. Sum the con-
tributions of the coarse size (wksht. VI.3, line D.3)
and fine size material (wksht. VI.3, line D.4) to ob-
tain the total soil mass movement contributions
which equal 192 tons/yr.
Step 12. — Obtain total potential coarse size
sediment delivered by soil mass movement.
a. 24 percent (table IV. 1) of delivered soil con-
sists of coarse silts, silt, and clay sizes (only
half of the total clay is included in this
category) [wksht. IV.l (soil 2—topsoil)]; thus
76 percent of the delivered soil is coarse
material (including the remaining half of the
clay, as stable aggregates); therefore, 0.76 X
192 tons = 146 tons/yr of coarse material
delivered to streams.
b. Enter this value (146 tons/yr) on worksheet
VI.3, lines D.2 and J.I.
c. Median size of coarse portion = 10 mm;
record on worksheet VI.3, lines D.3 and J.3.
Step 13. — Determine washload volume
delivered from soil mass movement.
a. 24 percent of total delivered volume is
washload (tons/yr), therefore,
total volume soil mass
movement = 192 tons/yr
VIII.95
-------
•(
-^
«j
"S f\A
c
O 03
H op_
DC -02
O
Q.
(/)
Z01-
^v
02
r—
< °05-
Q 003
LU
DO
002
.001 <
/
/
/
/
J
7
i
/
>
t
j
'
L
t
i
0
m ~
1
gv = -G
r2 = 0.
.43 H
99
,2.
18
L
3?
)
X
1.0
10.0
100.0
STREAM DISCHARGE, (cfs)
Figure VIII.17.—Bed load rating curve, Horse Creek watershed.
Vffl.96
-------
total coarse size soil mass
movement = 146 tons/yr
total washload (fine) size = 46 tons/yr
b. Record this total (46 tons/yr) on worksheet
VI.3, lines D.4 and J.2.
Step 14. — Determine total delivered tons of
suspended sediment from surface erosion.
a. The total of 17.7 tons/yr is obtained from
worksheet IV.8.
b. Record this value on worksheet VI.3, line D.I.
Step 15. — Compare total potential post-
silvicultural activity suspended sediment (mg/1) to
selected limits (tons/yr). On worksheet VI.3:
Add totals of: tons/yr
Surface erosion (line D.I) 17.7 tons/yr
Total post-silvicultural activity
suspended sediment discharge
(line B) 8.8 tons/yr
Soil mass movement (washload)
(line D.4) 46.0 tons/yr
Total 72.5 tons/yr
Subtract the total pre-silvicultural
activity suspended sediment discharge
(line A) from the previously
determined figure 7.1 tons/yr
The remainder is the total increase in
potential suspended sediment
discharge (line I.I) 65.4 tons/yr
Subtract the maximum allowable suspended
sediment discharge (line C) from the
total increase in potential suspended
sediment dischrge (line I.I) 38.6 tons/yr
The remainder is the net change (this
may be either a positive or negative
number) (line 1.2) +26.8 tons/yr
Step 16. — Total potential post-silvicultural ac-
tivity sediment discharge—all sources.
a. Summation: from steps 5, 10, 11,
and 14. tons/yr
1. Post-silvicultural activity sediment
flow related increases (step 5,
wksht. VI.3, line B) 8.8
2. Post-silvicultural activity bedload
load, flow related increases
(step 10, wksht. VI.3, line F) 1.9
3. Soil mass movement volumes
(step 11, wksht. VI.3,
line D.2 plus D.4) 192.0
4. Surface erosion source (step 14,
wksht. VI.3, line D.I)
Total
b. Record on worksheet VI.3, line L.
17.7
220.4
Step 17. — Increase in total potential sediment
discharge resulting from silvicultural activity.
a. Subtract total pre-silvicultural activity sedi-
ment discharge (step 9) from total post-
silvicultural activity sediment discharge (step
16).
tons/yr
1. Total post-silvicultural activity
(wksht. VI.3, line L) 220.4
2. Total pre-silvicultural activity
(wksht. VI.3, line K) 8.5
3. Total potential sediment increase . 211.9
b. Record this total increase of 211.9 tons/yr on
worksheet VI.3, line M.
Channel Impacts
Step 18. — Channel geometry.
a. Collect channel geometry data for third-order
stream being impacted. Record on worksheet
VI.5.
1. Water surface slope, measured 0.005 ft/ft
2. Bankful stream width 4.8 ft
3. Bankful stream depth 0.8 ft
b. Channel geometry for the first-order stream
being impacted. Record on worksheet VI.5.
1. Water surface slope 0.029 ft/ft
2. Bankful stream width 1.0 ft
3. Bankful stream depth 0.6 ft
Step 19. — Evaluate post-silvicultural activity
channel impacts. Determine post-silvicultural ac-
tivity changes that impact the channel, which
would influence stream power calculations by
altering water surface slope and/or bankful stream
width. The debris-slide on the stream reach being
evaluated will change the water surface slope from
0.029 to 0.250 with an increase in bankful width
from 1.0 feet to 1.5 feet.
Step 20. — Establish bedload transport rate-
stream power relationship for third-order reach or
closest adjacent drainageway that has measured
data.
Vffi.97
-------
Water surface slope
(K) Constant
Use worksheet VI.4
VIH.18).
= 0.005
= 62.41b/ft3
for calculations
(see fig.
Step 21. — Make a qualitative determination of
channel change potential based on introduced sedi-
ment from soil mass movement and channel im-
pacts: Soil mass movement source (coarse size) 146
tons/yr (wksht. VI.3, line J.I). The debris-slide
delivery to the first-order stream is instantaneous.
a. To determine channel response on the
delivered material, the following calculations
are made:
1. Stream power under bankful discharge for
first-order reach (wksht. VI.5,
line 2A) 1.32 ft/lb/sec
2. Maximum sediment transport under max-
imum stream power at bankful discharge
(fig. VIII. 18) 0.0018 ft/lb/sec
Based on this calculation, the introduced coarse
(0.08 tons/day) size (10mm) soil mass movement
material of 142 tons exceeds the transport
capability of the stream under bankful stream
power (0.08 tons/day). Since bankful discharge has
a relatively short duration, the 0.08 tons/day trans-
port would be decreased as discharge, and resul-
tant stream power is reduced over time. The ex-
pected channel response would be local deposition
of sediment (dominant particle size of 10 mm) on
the streambed. This would adjust local slope and
the width-depth ratio of the channel (based on
similar channel response due to debris-slide im-
pacts on similar channels adjacent to Horse Creek).
b. To determine the change in steam power and
bankful discharge for Horse Creek at the first-
order reach, the following calculations are
made:
A = (width 1.0 ft) (depth 0.6 ft)
= 0.60 ft2
S = 0.029
log Q = 0.366 + 1.33 log 0.60 + 0.05 log 0.029
-0.056 (log 0.029)2
Q = 0.73 cfs (pre-silvicultural activity)
c. Changes in transport rate due to changes in
stream power from:
1. Reduced surface water slope
2. Increased width
3. Reduced depth
4. Reduced bankful discharge
Using worksheet VI.5:
Post-silvicultural activity width 1.5 ft
Post-silvicultural activity depth 0.2 ft
Post-silvicultural activity slope 0.0250
Post-silvicultural activity (Qb)
discharge 0.28 cfs
Post-silvicultural activity stream
power (w) 0.29 ft/lb/sec
Post-silvicultural activity bedload
transport rate (fig. Vffl.18) 2.6 X 10~6
ft/lb/sec
This value (2.6 X 10~6 ft/lb/sec) is
converted to tons/day/ft of width by
multiplying by 86,400 sec/day and dividing
by 2,000 Ib/ton 0.001 tons/day/ft
This value (0.001 tons/day/ft) is converted to
tons/day by multiplying by 1.5 feet (bankful width
of stream).
Thus, a reduction in bedload sediment trans-
port from 0.08 tons/day to 0.002 tons/day would
indicate an increase in sediment storage in the
channel; until such time, recovery would return
to pre-silvicultural activity rates. This would
reduce the channel stability rating, and by the
imbalance in sediment supply—stream energy,
disequilibrium conditions would be expected
(this is evaluating the coarse fragment portion of
soil mass movement sediment supply only).
e. Difference.
Maximum instantaneous, pre-silvicultural
activity transport at bankful
(Qepre) 0.08 tons/day
Maximum instantaneous, post-silvicultural
activity transport at bankful
(Q Bpost) 0.002 tons/day
A difference of 0.078 tons/day
VHI.98
-------
u
0>
w
0)
LU
cn
O
CL
CO
z
Z
HI
2
Q
UJ
CO
g
Q
UJ
CO
.01
.005
.001
.0005
.0001
.00005
.00001
J.
Measured Values
Extrapolated Values
.01
.05 .1 .5 1.0
STREAM POWER (CU) (ft./lbs./sec.)
5. 10.0
Figure VIII.18.—Bedtoad transport-stream power relationship, Horse Creek watershed.
Vin.99
-------
TEMPERATURE ANALYSIS
Several of the proposed cutting blocks are close
to streams; removal of the trees would expose the
streams to increased solar radiation. The ad-
ditional radiation would result in an increase in the
maximum daily water temperature.
The maximum increase in the daily water
temperature must be evaluated to determine if the
water quality objectives for the stream will be met.
The proposed clearcut in hydrographic area 29 was
selected to illustrate the procedure to estimate the
maximum potential daily temperature increase.
All cutting blocks that could impact water
temperature would be evaluated similarly.
Computing H, Adjusted Incident Heat Load
Step 1. — Determine H (i.e., incident heat load)
based upon latitude of site, critical time of year
(month and day), and orientation of stream.
Step 1.1. — Select the solar ephemeris that most
closely approaches the latitude of the site, 40
1/2°N.
Step 1.2. — Locate the declination in the solar
ephemeris (fig. VH.3) that corresponds to the date
when maximum water temperature increase is an-
ticipated: second week in July; therefore, use a
declination of +21 1/2°.
Step 1.3. — Once the declination, +21 1/2°, is
known, determine the azimuth and solar angle for
various times during the day from the solar
ephemeris (see fig. VUG) and record the values in
worksheet Vn.l. Azimuth readings are found along
the outside of the circle and are given for every 10°.
Solar angle (i.e., degrees above the horizon) is in-
dicated by the concentric circles and ranges from
0° at the outermost circle to 90° at the center of the
circle. The time is indicated above the +23°27'
declination line and is given in hours, solar time.
To determine the solar azimuth and angle that
would occur at 12:30 p.m. daylight savings time
(DST):
Step 1.3.1. — Follow along the +211/2° declina-
tion line that is interpolated between the+20° and
+ 23°27' line. Locate the point that is equal dis-
tance between the 11 a.m. (12 noon DST) and noon
(1 p.m. DST) time interval. This point represents
the 12:30 p.m. DST.
Step 1.3.2. — The solar angle is determined by
noting where the point established above (12:30
p.m. with a declination of +21 1/2°) occurs in
respect to the solar angle lines present .on the
figure. The solar angle lines are represented as con-
centric circles and range from 90° at the center to
0° at the periphery. The point established above
falls on the 70° line; therefore, the solar angle is
equal to 70°.
Step 1.3.3. — The solar azimuth is determined
by noting where the point established in step 1.3.1
occurs in respect to the solar azimuth lines that
radiate out from the center of the circle. The point
falls midway between the 150° and 160° lines;
therefore, the solar angle equals 155°.
More points should be selected about the midday
period, when solar radiation is at the greatest in-
tensity.
Step 1.4. — Evaluate the orientation of the sun
(i.e., azimuth and angle determined from step 1.3
above) with the stream, and determine what
vegetation effectively shades the stream. To do
this, compare stream effective width with shadow
length. Determine the maximum solar angle (i.e.,
maximum radiation influx to stream) that will oc-
cur when the stream is exposed following the
silvicultural activity. Height of the existing vegeta-
tion immediately adjacent to the stream is 70 feet.
Step 1.4.1. — The direction the shadows fall
across the stream will determine effective width of
the stream. Effective width is computed using the
following formula:
measured average stream width
EW =
sine | azimuth stream azimuth sun |
(VII.4)
The azimuth of the particular stream used for
this example is 225°. Effective width varies
depending on the time of day. For example, at
12:30 (wksht. VII.l) EW would be equal to:
1.5ft
= 1.6 ft
EW =
sine! 225° - 155°
The absolute value of the azimuth of the stream
subtracted from the azimuth of the sun must be
less than a 90° angle. Should the difference exceed
90°, subtract this absolute value from 180° to ob-
tain the correct acute angle. The sine is then taken
of this computed acute angle.
vm.ioo
-------
Step 1.4.2. — Shadow length is computed using
the formula:
S =
height vegetation
tangent solar angle
(VII.5)
For example, at 12:30, S would be equal to:
S = 70 ft/tangent 70° = 25.5 ft
Note, the only periods of the day that should be
considered are those when existing vegetation that
will be eliminated by the silvicultural activity ef-
fectively shades the stream (i.e., when the shadow
length extends onto some portion of the stream).
Those periods of the day when the stream is not ef-
fectively shaded by the existing vegetation will not
have an increase in net radiation if the vegetation is
removed by the silvicultural activity. Also, there
may be periods of the day when the stream is effec-
tively shaded by existing vegetation that will not
be removed by the silvicultural activity; therefore,
the proposed silvicultural activity will have no im-
pact on water temperature.
Summary of steps 1.4.1 and 1.4.2: The existing
trees that are scheduled to be cut provide shade to
the stream. The only time when the trees do not
shade the stream is about 2:10 p.m., when the
stream's effective width is infinity (sun is oriented
with the stream) and the shadow length is only 28.1
feet. Therefore, removal of this vegetation would
result in exposure of the water surface to increased
solar radiation.
The proposed silvicultural activity would have
the maximum impact on water temperature at 1
p.m. (solar noon) when the solar angle and radia-
tion are greatest.
Step 1.5. — Topographic shading should be
evaluated to determine if the water course would be
shaded by topographic features. For topographic
shading, the percent slope of the ground must ex-
ceed the percent slope of the solar angle (i.e.,
tangent of the solar angle). In the present example,
the
side slope = 30%
solar angle = 72° or 308%
Thus, topographic shading is not possible due to
the angle of the sun and relatively gentle
topographic relief.
Step 1.6. — Calculate the incident heat load for
the site. This is obtained from reading the values
shown in figure VII.7. To read these values, apply
the following:
1. Select the correct curve (shown in fig. VII.7)
obtained from the correct solar ephemeris (fig.
VII.3): in this example, 40°N latitude, given a
declination of +21 1/2°: 72°. (Note that the
midday value will always have an orientation,
i.e., azimuth, of due south.)
2. In figure VII.8, interpolate between the 70°
and 80° curve to obtain the 72° values.
3. Determine the critical time period, which in
step 1.4 was found to be 1 p.m.
4. Find the average H value. In this example, the
travel time through the reach is only 0.3
hours, so it is not necessary to find an average
H value. From figure VII.8, with a 72° midday
angle, the H value for 1 p.m. is approximately
4.7 BTU/ft2-min. (Note: If the solar
ephemeris had been used for 45°N latitude,
the H value would have be approximately 4.8
BTU/ft2—min. If the solar ephemeris had
been used for 35°N latitude, the H value
would have been 4.5 BTU/ft2-min). Figure
Vn.8 illustrates the procedure used to obtain
H.
Step 1.7. — Because bedrock acts as a heat sink,
reducing the heat load absorbed by the water, the
H value must be corrected to reflect this heat loss.
Hadjusted = WH +[B(1.00-C)H] (VII.6)
where for Horse Creek:
W = percent streambed without bedrock =
10%
H = unadjusted heat load = 4.7 BTU/ft2-min
with a solar ephemeris for 40°N latitude
(step 3.6)
B = percent streambed with rock = 90%
C = correction factor = 18% (see explanation
for C directly below)
(Note: All percent values used in eq. III.6 are in
decimal form.)
Now, C is obtained from figure VII.9. In the ex-
ample, bedrock comprises 90 percent of the
streambed; therefore, H should be reduced by 18 i
percent.
Thus,
Hadjusted =[0.1X4.7]
+ [0.9 X (1.00 - 0.18) X 4.7]
= 3.94 BTU/ft2-min
vm.ioi
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Computing Q, Stream Discharge
Step 2. — Determine stream discharge following
the proposed silvicultural activity during the
critical summer low-flow period when maximum
temeratures are anticipated. A pre-activity
baseflow measurement during the critical summer
period was taken. Discharge during the critical
period was 0.4 cfs.
Computing A, Adjusted Surface Area
Step 3. — Determine the adjusted surface area of
flowing water exposed by the proposed
silvicultural activity.
Step 3.1. — Total surface area of flowing water
Atotai=LW (Vll.Va)
where:
L = length of exposed reach
W = width of flowing water
A ( = 530 ft X 1.5 ft
total
= 795 ft2
Step 3.2. — Total surface area shaded by brush
Ashade brush = LW(% stream shaded by brush only)
(VH.Tb)
= 530 ft X 1.5 ft X 0.15
= 120 ft2
Step 3.3. — Surface area exposed under current
vegetative canopy cover; correct for transmission of
light through the existing stand that has a 65 per-
cent crown closure. Since only vertical crown
closure values are available, estimate the percen-
tage transmission of solar radiation through the
overstory canopy. Values for these estimates may
be obtained from figure VII.D.l. A crown closure of
65 percent permits about 8 percent transmission of
solar radiation.
A presently exposed ~ (Atotal - "shade brush I
X % transmission through existing
vegetation (VH.7c)
= (795ft2- 120 ft2 X 0.08)
= 54ft2
Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion is removed is
•"•adjusted Atotal ~~ A presently exposed
= 795 ft2 - 54 ft2
= 741 ft2
Step 4. — Estimate AT, maximum potential
daily temperature increase in °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VH.Sa
Aadjusted "adjusted
Q
AT =
X 0.000267 (VII.3a)
A = 741 ft2
H = 3.94 BTU/ft2-min
Q = 0.4 cfs
(741 ft2) (3.94 BTU/ft2 - min)
AT =
0.4 cfs
X 0.000267
= 1.9 °F
(VH.7d)
The Mixing Ratio Formula
The following example is provided to illustrate
the use of the mixing ratio formula for evaluating
downstream water temperature impacts. The
water temperature increase associated with the
proposed clearcut in hydrographic area 29 has
previously been evaluated, and a maximum poten-
tial daily temperature increase of 1.9°F was es-
timated. With similar evaluations made for
proposed clearcuts in hydrographic areas 27 and 28,
an estimate of the water temperature of the main
stream draining this area can now be obtained.
The data and results of the individual water
temperature evaluations are recorded on worksheet
VII.2. The pre-silvicultural activity stream water
temperature is 55°F. The sequence of steps to ob-
tain an estimate of the water temperature of the
main stream draining this area follows.
Hydrographic area 27 stream reach. — The es-
timated maximum potential daily stream
temperature increase (2.5°F) is added to the pre-
silvicultural activity stream temperature (55°F) to
obtain an estimate of the water temperature
(57.5°F) below the proposed clearcut draining this
hydrographic area.
Hydrographic area 28 stream reach. — The es-
timated maximum potential daily stream
temperature increase (2.1°F) is added to the pre-
silvicultural activity stream temperature (55°F) to
obtain an estimate of the water temperature
(57.1°F) below the proposed clearcut draining this
hydrographic area.
Vm.102
-------
To estimate the water temperature below the
confluence of the streams draining hydrographic
areas 27 and 28, the mixing ratio formula may be
used.
where:
TD = temperature downstream after the
tributary (hydrographic area 28) enters
the main stream (hydrographic area 27)
DM = discharge main stream = 0.4 cfs
TM = temperature main stream above
tributary = 57.5°F
DT = discharge stream draining treated area =
0.3 cfs
TT = temperature stream below treated area
equals temperature above plus computed
temperature increase (i.e., Brown's
model) or
TT = TA + AT = 55°F + 2.1°F
= 57.1°F
TA = temperature stream
above treated area
= 55°F
AT = temperature increase
computed using
Brown's model = 2.1°F
Therefore,
„ (0.4 cfs) (57.5°F) + (0.3 cfs)(57.1°F)
1 n = -
(0.4 cfs) + (0.3 cfs)
= 57.3°F
The main stream below the confluence will have
a water temperature of 57.3°F.
Hydrographic area 29 stream reach. — The es-
timated maximum potential daily stream temper-
ture increase (1.9°F) is added to the pre-
silvicultural activity stream temperature (55°F) to
obtain an estimate of the water temperature
(56.9°F) below the proposed clearcut draining this
hydrographic area.
To estimate the water temperture below the con-
fluence of the main stream and the stream draining
hydrographic area 29, the mixing ratio formula
may be used.
Tn =
DMTM + DTT
(VII.8)
where,
TD = temperature downstream after the
tributary (hydrographic area 29) enters
the main stream
DM = discharge main stream = 0.7 cfs
TM = temperature main stream above
tributary = 57.3 °F
DT = discharge stream draining treated area =
0.4 cfs
TT = temperature stream below treated area
equals temperature above plus computed
temperature increase (i.e., Brown's
model)
TT = TA + AT = 55°F + 1.9°F
= 56.9°F
TA = temperature stream
above treated area
= 55°F
AT = temperature increase
computed using Brown's
model = 1.9°F
Therefore,
= (0.7 cfs) (57.3°F) + (0.4 cfs) (56.9°F)
D (0.7 cfs) + (0.4 cfs)
= 57.2°F
The main stream below the confluence will have
a water temperature of 57.2°F or a maximum daily
temperature increase of 2.2°F. This same
procedure is used to evaluate other tributary
streams further downstream.
Groundwater influence has previously been
demonstrated in the Grits Creek example.
ANALYSIS REVIEW
Interpretation Of The Analysis Outputs
The proposed silvicultural plan has been
evaluated in the preceding discussion and es-
timated values from various outputs are shown in
table VEI.5. These outputs are compared to
previously determined water quality objectives.
When considering whether these objectives have
been met or not, it is important to consider the
reliability of the computed values as previously dis-
cussed in the analysis review for Grits Creek. A
review of the data reliability and the computed
outputs for Horse Creek indicates the possibility
VIII.103
-------
that the water quality objectives will not be met;
therefore, a revised silvicultural plan that includes
a different mix of controls should be prepared and
evaluated.
Comparing Analysis Outputs To
Water Quality Objectives
Two potential non-point source pollutants must
be controlled—total potential sediment and water
temperature. Evaluation of the individual compo-
nents of the estimated total potential sediment
value (216 tons), clearly indicates the major con-
tribution of potential sediment is from soil mass
movement (192 tons). The surface erosion (17.7
tons) and increased flow (6.3 tons) contributions,
although significant, are an order of magnitude less
than the soil mass movement. Therefore, first
priority is to evaluate control opportunities for
minimizing the soil mass movement non-point
source. The second priority is to consider control
opportunities for the surface erosion component.
The sediment contribution from increased
streamflows cannot be significantly altered without
major reductions in amount of area harvested or
changes in the cutting pattern. Since the proposed
silvicultural plan has an optimum layout of cutting
units, and their contribution to increased flow was
small, no further consideration of flow-related con-
trols is necessary.
Since existing stream temperatures (55°F) are
suitable for the fishery resource and the area is un-
disturbed, mitigative controls before the activity
are unnecessary; only preventive controls need be
considered.
Following is a discussion of the procedures ap-
plied to select a different mix of controls that could
be implemented to meet the water quality objec-
tives—first for total potential sediment and then
for temperature. These procedures are discussed in
chapter II, appendix A, "Example Three: Selecting
Controls When Plans Do Not Meet Water Quality
Objectives." After identifying control oppor-
tunities, the favorable and adverse impacts of the
controls, along with possible interactions, are
evaluated before finally selecting control oppor-
tunities to be used.
Control Opportunities For Soil Mass Movement
Since it is very difficult to apply effective
mitigative controls after a large soil mass move-
ment occurs, only preventive control opportunities
will be evaluated. Table E.2 of "Chapter E:
Control Opportunities" presents the potential
resource impacts and control opportunities.
Soil mass movement initiation or acceleration in
the Horse Creek watershed may be caused by road
construction, due to large fill sections, and loss of
root strength, due to vegetative removal. Based
upon this assessment of the causes of soil mass
movement, controls for slope configuration changes
and vegetative changes are reviewed in table II.2,
and preventive controls are identified.
Once the possible preventive control oppor-
tunities have been identified, table II.3 is used to
determine which variables that influence soil mass
movement are affected by the various control op-
portunities. That portion of table II.3 dealing with
slope configuration and vegetative change is ex-
amined. From the possible control opportunities
for slope configuration change, it is apparent that
some controls influence several variables and
would, therefore, be more effective in controlling
soil mass movement than controls that influence
only one. The following preventive control oppor-
tunities affect the principal variables influencing
soil mass movement:
1. Bench cut and compact fill
2. Full bench section
3. Reduce logging road density
4. Road and landing location
5. Slope rounding or reduction in slope cut
Possible preventive controls for vegetative change
are:
1. Cutting block design
2. Maintain ground cover
From this list of possible control opportunities,
the proposed silvicultural activity was modified for
soil mass movement by:
a. Elimination of cutting block 14 on the un-
stable area. The volume of timber not
removed in this unit has been obtained
elsewhere by making slight changes to enlarge
other cutting units on stable terrain.
b. Removal of the road and landings in
hydrographic areas 26 and 27 that served cut-
ting block 14. '
By incorporating these controls, the soil mass
movement hazard index will be reduced from high
to moderate. Worksheet V.2 is completed based
upon the above preventive controls. The new
silvicultural activity factor total is 7. Combining
this with the natural total of 31 gives the new total
Vm.104
-------
value for the modified silvicultural activity of 38,
which falls within the medium hazard range (21-
44) for soil mass movement.
Control Opportunities For Surface Erosion
By reviewing worksheet IV.8, the maps (figs.
FV.14 to IV. 18), and using professional judgment,
the following resource impacts and conditions were
noted:
Problem No. 1: Some landings were located
close to a stream, allowing
direct delivery of eroded
material.
Problem No. 2: Because there was no road sur-
facing included in the proposed
silvicultural plan, erosion
resulted from bare road sur-
face.
Control opportunities for Problem No. 1, road
and landing location, are discussed under resource
impacts for soil compaction, bare soil, excess
water, and water concentration. Bare soil and com-
paction are directly related to the number of
landings and miles of road in the proposed
silvicultural activity area. Since the initial plan
has incorporated the minimum number of landings
and miles of roads, controls listed here are not as
applicable as controls for excess water and water
concentration. Using sections B and C of the
"Control Opportunities" chapter, the following ap-
plicable controls were selected:
Excess water
1. Cutting block design
2. Waterside area
3. Revegetate treated areas
Water concentration
1. Reduce road grades
2. Road and landing location
3. Waterside areas
The cutting block designs have been carefully
chosen, and there is little opportunity to make
significant changes. The proposed silvicultural
plan already contains provisions for revegetating
treated areas. The remaining control, waterside
areas, is discussed below.
Under "water concentration," the control oppor-
tunity "reduce road grades" is not practical, since
the road locations are determined by minimum
grades to reach benches and suitable cutting
blocks. Considering the control opportunity "road
and landing location," it was determined that there
were opportunities to make some slight modifica-
tions in landing locations by moving them back
from stream channels. At the same time, the con-
trol opportunity "waterside areas" (leaving some
area to act as a sediment filter strip) was also
utilized to reduce the amount of sediment
delivered to a channel.
Using the same calculation procedures outlined
in chapter IV and in the example for the proposed
silvicultural plan, a new analysis was made using
revised values for the different landing locations
(wkshts. IV.2 to IV.4 and IV.6 to IV.8).
By moving a landing a short distance away from
a stream channel, three factors affecting sediment
delivery are changed (compare wksht. IV.7 for both
plans—proposed and revised). First, the distance
from the edge of the disturbance to the stream
channel is increased, creating more area for sedi-
ment deposition; second, the amount of ground
cover between the disturbance and channel in-
creases; third, the surface roughness increases
slightly. The net result is a change in the sediment
delivery index from 0.11 under proposed manage-
ment, to 0.01 in the modified plan. This would
reduce the amount of eroded material that might
be delivered to a stream by 91 percent for each
landing next to a stream. The total from all
landings has been reduced from 0.9 tons/yr to 0.03
tons/yr (wksht. IV.8 for both plans).
Control opportunities for Problem No. 2, "no
road surfacing," are found in section B under bare
soil, with "protection of road bare surface areas
with non-living material" being the most practical.
A decision was made to use 6 inches of crushed
gravel on all roadbeds. The same procedures out-
lined under roads should be applied to the
proposed silvicultural plan, except that the VM
factor has now been changed for the running sur-
face from 1.24 (wksht. IV.6, proposed) to 0.005
(wksht. IV.6, revised). The weighted VM factor for
the road is now 0.17, which compares with a value
of 0.91 for the proposed plan. A summary on
worksheets IV.8 (for both plans) shows that the
total for all roads has now been reduced from 8.1
tons/yr to 1.3 tons/yr, or an 84 percent reduction.
Control Opportunities For Temperature
To meet the temperature water quality objec-
tive, the maximum potential daily temperature in-
crease must be reduced by applying preventive
controls. Table II.2 of "Chapter II: Control Oppor-
tunities" presents potential resource impacts and
vm.io5
-------
control opportunities to be evaluated. Water
temperature increases resulting from silvicultural
activities are caused by removal of vegetation that
shades the stream. Therefore, controls for stream
shading are reviewed in table n.2.
Three preventive control opportunities are
presented that could be used to meet the water
quality objectives:
1. Cutting block design
2. Directional felling
3. Waterside area
Directional felling away from the stream is
already specified in the proposed silvicultural plan
and so is not an alternative. Both cutting block
design and waterside areas are viable control op-
portunities.
Cutting block design. — Using the basic
procedure presented in "Chapter VII:
Temperature," compute the maximum length of
stream channel that could be exposed with a resul-
tant maximum potential daily temperature in-
crease of 1.5°F.
From the previous evaluations: The stream reach
length that would be exposed if the proposed
silvicultural activity was implemented was 530
feet. Maximum potential daily temperature in-
crease would be 1.9°F. The water quality objective
limits the maximum potential daily temperature
increase to 1.5°F (temperature objective). A direct
relationship can be established to estimate the
reach of stream that could be exposed (length ob-
jective)/
L
where:
AT = potential daily temperature increase
Tobj = allowable daily temperature increase
L = potential exposed stream length
Lobj = allowable exposed stream length
L,,
1.5°F
1.9°F
X 530ft = 418ft
By modifying the proposed cutting block design
so that no more than 418 feet of the stream is ex-
posed, the water quality objective will be met.
Waterside areas. — Using the basic procedure
presented in "Chapter VII: Temperature," com-
pute the minimum crown closure that is required to
prevent a maximum potential daily temperature
increase greater than 1.5°F.
From the previous evaluation:
Atotai = 795 ft2
Ashade brush = 120 ft2
Hadjusted = 3.94 BTU/ft2-min
Q = 0.4 cfs
Estimate the maximum A adjusted value that
would result in a AT value of 1.5°F, water quality
objective.
'A adjusted'' " adjusted )
AT =
1.5°F =
Q
X 0.000267
X 0.000267
0.4 cfs
Rearranging the equation gives:
A = (1.5"F)(0.4cfB) = ,?of 2
^adjusted (3 Q4 BTU/ft2_min) (0.000267)
-"•adjusted "total •" presently exposed
Rearranging the equation gives:
"presently exposed ~ "total ~~ " adjusted
= 795ft2 - 570 ft2 =225 ft2
presently exposed ~ ^ total ~ shade brush ' X PerC6nt
transmission through existing
vegetation
Rearranging the equation gives:
percent
transmission
through
existing
vegetation = Apresently exposed /(Atotal _ A shade brush )
225 ft2
795 ft2 - 120 ft2
= 0.34
From figure VH.D.l, 34 percent transmission cor-
responds to a crown close of 35 percent. A reduction
in the amount of vegetation removed from the
streamside zone so that 35 percent crown closure
existed after the silvicultural activity would meet
the water quality objectives for temperature.
The forest manager, after reviewing both viable
control opportunities and discussing the alter-
natives with other resource specialists, selected the
waterside area control. Using this control, only
mature overstory trees were removed, leaving a
productive understory for other uses.
VIH.106
-------
Table VI I 1.6
Summary of quantitative outputs for: Rgviseg ?W. tioVSg. Creek
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soil Mass
Movement:
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
_ine
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Output descr ption
Water aval 1 ab 1 e for
streamf low
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration
curve
Surface soi 1 loss
Sediment del i vered
Hazard index
Weight of sediment
to stream channel
Coarse >0.062 mm
Fine <0.062 mm
Total
Acceleration factor
Sediment discharge
due to f low
change
Total suspended sec
from a 1 1 sources
Bed load
Suspended
Total
iment discharge
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
act i vity
IS.n< e
TIL. -3 line F
3ZL.3 lw« A
JDL.3 li«i< B
XL. 3 KM k:
S(. 3 )i»« 8
JZt.3 I.'IK fl
lirx LI* A
3ZT.3lrt»eM
JZZT.2,
vm.io7
-------
Revised Silvicultural Plan
Based on these possible control opportunities, a
revised silvicultural plan was prepared that con-
sisted of the following changes:
1. Leave vegetation on the unstable area in
hydrographic area 26, eliminating cutting
block CC14.
2. Increase slightly all other cutting units to ac-
commodate loss of timber from cutting block
CC14.
3. Eliminate road and landings to serve cutting
block CC14.
4. Move some landings further away from
streams.
5. Use 6 inches of crushed rock on all road sur-
faces.
6. Use waterside areas with a crown closure of 35
percent to shade streams.
The summary of computed outputs for the
revised silvicultural plan with these controls is
shown on table Vin.6.
The next step is to assess the possible adverse
impacts of these controls. With the removal of
more timber on other cutting units, it is expected
that the surface erosion figures would increase;
however, the changes were insignificant on all but
hydrographic areas 14 and 16. These two areas
show an increase of 0.2 tons/yr of delivered sedi-
ment (wksht. IV. 8 for both proposed and revised
plans).
For this hypothetical example, the net effect of
these controls has been a reduction in all non-point
source pollutant outputs (table VIII.6). The soil
mass movement hazard index was reduced from 61
to 39. The anticipated impacts of the introduced
material on the first-order drainage has been
eliminated. The delivered sediment from surface
erosion sources has been reduced from 17.7 to 9.8
tons/yr. The transport efficiency of the stream
channel will be maintained and is capable of
handling the available sediment without major
channel adjustments and stability change. Con-
sidering the water quality objectives, limiting
suspended sediment discharge to 38.6 tons/yr and
allowing a maximum water temperature increase of
1.5°F, the revised silvicultural plan is determined
to be acceptable from a water quality standpoint.
Vm.108
-------
Worksheets for Horse Creek,
proposed and revised plans
Worksheets are presented in numerical order with all III.1-III.4
proposed followed by III.1-III.4 revised, IV.1-IV.8 proposed followed
by IV.1-IV.8 revised, etc.
vm.io9
-------
(1) Watershed name Horse.
Creek
(5) Vegetation type L.Q,
WORKSHEET
Water available for streamflow for the
(2) Hydro logic region T
(6) Annual precipitation 3^.3
Season
name/dates
(9)
WINTER
"/ - V*
Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11 )
Forested
Tota I for season
Area
Acres
(12)
4,00
too
%
(13)
l.ooo
l,ooo
Precipi-
tation
(in)
(14)
/Ł.!
/G.I
Snow
retention
coef .
(15)
1.0
Adjusted
snow
retention
coef.
(16)
1.0
Adjusted
precipi-
tation
(in)
(17)
/fe./
SPRING-
3/ ' Vao
Un impacted
Impacted
Forested
Total for season
too
Ł00
l.ooo
1.000
/a.i
/a.)
1.0
l.o
/a.l
SUMMER
a«
-------
III.5
existing condition In snow dominated regions
(3) Total watershed area (acres)
(4) Dominant energy-aspect
(7) Windward length of open area (tree heights) O
(8) Tree height (feet) JO
ET
(In)
(18)
a.)
Basal
area
(ft2/ac)
(19)
400
Cover
density
(20)
33
pCdmax
(21)
100
ET
modifier
coef .
(22)
1.0
Adjusted
ET
(In)
(23)
4.1
Water available for streamflow (In)
(24)
l
-------
Notes for Worksheet 111.5
Item or
Col. No. Notes
(1) Identification of watershed or watershed subunlt.
(2) Descriptions of hydrologlc regions and provinces are given In
the text.
(3)-(8) User supplied.
(9) Seasons for each hydrologlc region are described In the text.
(10) The unlmpacted compartment Includes areas not affected by
siIvlcultural activity. The Impacted compartment Includes areas
affected by siIvlcultural activity. Impacted areas do not have
to be physically disturbed by the si IvlcuItural activity. For
example, If an area Is subject to snow redistribution due to a
siIvlcultural activity. It Is an Impacted area.
(11) Areas of similar hydrologlc response as Identified and
delineated by vegetation or si IvlcuItural activity.
(12) User supplled.
(13) Column (12) * item (3).
(14) User supplled.
(15) From figure I I I.6 or appendix A or user supplied.
(16) Snow retention coefficient adjustment for open areas:
.50
Poadj 1 + < PO-I)(~jp
where:
poadj adjusted snow retention coefficient for open areas
(receiving areas)
po snow retention coefficient for open areas
open area (In acres)
Impacted area (in acres)
vm.ii2
-------
Snow retention coefficient adjustment for forested source
areas (impacted forest areas):
p 1- PoadJ X
f 1-X
where:
Pf = adjusted snow retention coefficient for areas affected by
snow redistribution (source areas)
open area (In acres)
Impacted area (In acres)
(17) Column (14) x column (16)
(18) From figures I I I.24 to I I I.40 or user supplied.
(19) User supplied (not required if % cover density Is user
supplled).
(20) From figures 111.41 to I I I.45 or user supplied.
(21) (Column (20) T C,jmax> * 10° where Cdmax is tne % cover density
required for complete hydro logic utilization. C(jmax 's
determined by professional judgment at the site.
(22) From figures I I I.46 to I I I.56.
(23) Column (18) x column (22).
(24)-(29) The quanitity [column (17)-column (23)] x column (13).
(30) Sum of column (24).
(31) Sum of column (25).
(32) Sum of column (26).
(33) Sum of column (27).
(34) Sum of column (28).
(35) Sum of column (29).
vin.m
-------
(1) Watershed name
Creek.
(5) Vegetation type LoOagbolg. Pine
WORKSHEET
Water available for streamflow for the
(2) Hydrologic region T
(6) Annual precipitation 3#3 /flC/HS
Season
name/dates
(9)
WINTER
tf- &
Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11)
FowjsteJ j
F«west«d
Clearoct
Total for season
Area
Acres
(12)
(3S-.0
153-5-
311 .5
(,00. 0
%
(13)
.aar
.a»«,
.51?
l.ooo
Precipi-
tation
(in)
(14)
llc.l
IU
/fe.l
/t..l
Snow
retention
coef .
(15)
1.00
—
1.3
Adjusted
snow
retention
coef.
(16)
1.00
.55"
I.1X
Adjusted
precipi-
tation
(In)
(17)
(U
*.^
l?.6,
SPRING-
3/ k/
T( /30
Un impacted
Impacted
Festal
Rji-estei
Cteafcui
Tota I for season
/3S.O
I53.5"
311.5"
too.o
.aas"
.ssfc
.519
1.000
U./
U.I
ia./
ya.i
1.00
_
A3
1.00
.55-
/.ax
/a./
fe.7
(4.8
summER
and
FflLL
V, - >/30
Un impacted
Impacted
Forested
Forested
Clea.irc.ut
Total for season
I35.O
153. ff
311.5
iOO.O
•aas"
.asfe
.si?
1.000
6.)
ti
fe.i
fe.i
/.o
1.0
1.0
L_ '-°
/.o
/.o
tl
kl
4.1
Un impacted
Impacted
Total for season
Water
aval I able
for annual
streamflow
(in)
Un impacted
Impacted
F«w«ted (30)
(31 )
Forested (32)
Cleavaeb (33)
(34)
(35)
Vffl.114
-------
III.6
proposed condition In snow dominated regions
(3) Total watershed area (acres) (oOO
(4) Dominant energy-aspect
(7) Windward length of open area (tree heights)
(8) Tree height (feet) 70
ET
(in)
(18)
4.1
3.1
S.I
Basal
area
(ft2/ac)
(19)
AOO
100
0
Cover
density
(20)
33
33
O
'^dmax
(21)
100
loo
o
ET
modi f ler
coef .
(22)
1.00
1.00
.to
Adjusted
ET
(In)
(23)
3.1
4.1
1.3
Water available for streamflow (In)
(24)
3.2<
(25)
(26)
1-7
(27)
7.5
(28)
(29)
7.4,
4.1
7.t>
a oo
200
0
33
33
O
100
IOD
0
1.00
l.oo
1.07
7. la
6 1
8.1
/.O
0.2,
3.S"
9,2,
y A,
7.2.
3.0O
800
O
33
33
0
100
(00
0
/.oo
/.oo
.55"
9.1
9. 1
5.1
-0.7
-0.8
o.r
(3.5-
Vffl.115
-------
Notes for Worksheet I I I.6
Item or
Co I . No. Notes
(1) Identification of watershed or watershed subunit.
(2) Descriptions of hydrologic regions and provinces are given in
the text.
(3)-(8) User supplled.
(9) Seasons for each hydrologic region are described in the text.
(10) The unimpacted compartment includes areas not affected by
siIvicultural activity. The impacted compartment includes areas
affected by siIvicultural activity. Impacted areas do not have
to be physically disturbed by the si IvicuItural activity. For
example, if an area is subject to snow redistribution due to a
siIvicuItural activity, it is an impacted area.
(11) Areas of similar hydrologic response as identified and
delineated by vegetation or si IvicuItural activity.
(12) User supplied.
(13) Column (12) T item (3).
(14) User supplied.
(15) From figure I I I.6 or appendix A or user supplied.
(16) Snow retention coefficient adjustment for open areas:
.50
Poadj 1 + ( P0-' )(~)
where:
Poadj adjusted snow retention coefficient for open areas
(receiving areas)
Po snow retention coefficient for open areas
open area (in acres)
impacted area (In acres)
VIII.116
-------
Snow retention coefficient adjustment for forested source
areas (Impacted forest areas):
p 1- PoadJ X
f 1-X
where:
Pf adjusted snow retention coefficient for areas affected by
snow redistribution (source areas)
open area (In acres)
Impacted area (In acres)
(17) Column (14) x column (16)
(18) From figures I I I.24 to 11 I.40 or user supplled.
(19) User supplied (not required if % cover density Is user
supplled).
(20) From figures 111.41 to I I I.45 or user supplied.
(21) (Column (20) T C(jmax) x 100 where Cdmax is the % cover density
required for complete hydro I ogle utilization. C(jnax is
determined by professional judgment at the site.
(22) From figures I I 1.46 to I I 1.56.
(23) Column (18) x column (22).
(24)-(29) The quanitity [column (17)-column (23)3 * column (13).
(30) Sum of column (24).
(31) Sum of column (25).
(32) Sum of column (26).
(33) Sum of column (27).
(34) Sum of column (28).
(35) Sum of column (29).
vm.ii7
-------
WORKSHEET
Existing condition hydrograph
( 1 ) Watershed name UorSK.
Date
or
interval
(3)
APRIL 2
14
ao
3fc
MflY OL
8
14
30
3fc
JUNE 1
7
13
1?
ZS
JltLV /
7
13
1?
SLS
31
Distribution of water
Un impacted
Forested
%
(4)
.OOOO
.OOOO
.0000
.0000
.0050
.0150
.0550
.0.sa
?.09
/0.83
?.o?
6.82-
-------
111.7
for snow dominated regions
(2) Hydrologlc region 4
available for annual streamflow
Impacted (continued)
%
(13)
Inches
(14)
cfs
(15)
%
(16)
Inches
(17)
cfs
(18)
%
(19)
Inches
(20)
cfs
(21)
Compos 1 te
hydrograph
cfs
(22)
.00
.00
.00
.00
.3*
.77
1*4-
Ml
3.87
S.3S-
&.S2,
?.o?
10.13
9.0?
4-8X
-------
WORKSHEET
Proposed condition hydrograph
(1) Watershed name HotSt
Date
or
Interval
(3)
flPRIU 8
1*
30
at
Mfl/ a
8
14
ao
2k
TUNE /
7
13
I?
as
JU.LV /
7
13
19
25
31
Distribution of water
Un 1 mpacted
Forested
%
(4)
.0000
.0000
.OOOO
.0000
.0050
.0/50
.oaso
.0
-------
II I .8
for snow dominated regions
(2) Hydro I ogle region '
available for annual streamflow
Impacted (continued)
Clearoit
%
(13)
.0000
.ocas'
.0075"
.•oaso
.ofas
.ofcs-o
.083&
.1075"
• UTS'
.(IcSO
.l
-------
to
to
WORKSHEET IV.1
Soil characteristics for the r/OrSC
watershed
Soi 1 group
Topsoi 1
i
Subsoi 1
Topsoi 1
Subsoi 1
Topsoi 1
3
Subsoi 1
|
-i- •—
c
0 0
U -0 1
l_ C O
0 (0 •
CL in CM
10
AO
so
10
(>S
70
c
(D E
ui E
0 in
C 0
•i— • — •
c: M- o
(D 1
O >^O
L. 1_ ^
Q) O
10
30
as-
ao
iff
(s-
— i
-1- E
— in
en o
•
+- 0 O
c to i
0 1- CN
(J (D >Ł>
U O 0
0) U •
a. = o
\Z
9
4
3
a
?
E
CM
o
o
-f— •
C O
0) 1
(j +- in
1_ — O
Q — .
a. in o
30
^
IS
15-
10
5"
e
^
^_
C CM
Q) O
O >-O
1_ (D «
Q) — O
CL U V
10
as-
10
35
/O
/o
+- u
c: — i_
0 c 0
u ro +-
t- D)+-
0 1_ ID
Q- O E
7.0
1.0
1.0
l.o
V.o
3-0
Soi 1
structure
MSLE
code
3
4
L ..
V
Ą
a
3
Descrip-
ti ve
TO coarse
G-MwaLflR
PRlsmwrJc
8LOCKY
BiocKy
FlME*
&RRUULAR.
COARSE"
Soi 1
permeabi 1 ity
MSLE
code
5"
5"
-------
1 of 3
Creek
WORKSHEET IV.2
watershed erosion response unit management data for use
sediment delivery index, hydrographic area 3 « propost
in
the MSLE
plarx
and
Erosion
response
un it
1 . CC 3.1
2. CC3-3L
5. L3, I
4. R3J
5. CU.T
5. aeo
7. FILL
a. R3.a -*/
9. C.U.T
10. BED
11- FIUU
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
S lope
length of
d isturbed
area (ft)
IOO
ISO
kS
fc.7
Length of
road
section
(ft)
680
30
Average
width of
di sturbance
(ft)
410
J7.8
a.^
/a.o
a. 9
/7.g
a.9
/a.o
2.?
Area
(sq.ft.)
JJ
Area
(acres)
8.0
(o
O.33
0.31
o.oi
to
CO
nj
= 43,560
noad &
-------
WORKSHEET I V. 2—continued
2 of 3
3/
Area with surface residues — '
Percent
of total
area
1. 6S-
2. (,o
3. 0
4.
5. (00
6. o
1 . IOO
8.
9. \OO
10. o
11. 100
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Percent
of surface
with mulch
70
10
—
70
—
70
70
—
70
Percent of JU
area with
fine roots
?0
ffS"
—
so
—
so
50
—
so
3/
Open area — '
Percent
of total
area
3S-
VO
/OO
O
/OO
O
0
IOO
o
Percent
of surface
with mulch
10
10
UMKWOWAJ
— .
O
—
• —
O
l_ —
Percent of JU
area with
f i ne roots
?o
ffS
UMKNOtuAj
—
0
—
—
O
—
Are open areas
separated by
f i Iter strips?
yes
yes
NO
NO
NO
Percent of
total area
with canopy
O
O
o
?o
o
?0
?o
0
?o
— Not
e.nd o& ^6t6-t i/eot
to i>c.al.pe.d
the.
until ve.QntaŁion
-------
WORKSHEET I V .2—cont i nued
3 of 3
Average
min imum
height of
canopy
(m)
1 . —
o _
3. —
4.
5.
6.
7.
o.s-
—
o.s
8.
9.
o.s
10. —
T1
0.5-
12.
T3.
14.
T5.
16.
T7.
18.
19.
20.
2
.
22.
23.
24.
25.
Time for
recovery
(mo)
UNkwowM
U.NKWOUJW
U.WK.NJOWN
I YEAR
1 YEAR
Average
dist. from
disturbance
to stream
channel (ft)
IS"
IS
O
IOO
o
Overal 1
slope shape
between
di sturbance
and channel
STRfll&HT
STRfllG-HT
STRfll&HT
STRflKJHT
STRfilGriT
Percent
ground
cover in
f i Iter
str ip
90
JJm. cu> stable. aggie.gat&A and that the.
band and bJUUL e.nt&i the. Ae.dune.nt deAiveAy
tke. day pint, v&iy
-------
WORKSHEET IV. 3
Estimates of soil loss and delivered sediment by erosion response unit
for hydrographic area 3 _ of Horse Cteefc, _ watershed
p . Jl
Erosion response
un it
CC3.I
CC3.2,
U3.I
K3.I
R3.a
Sol 1
un it
ra.
Ta.
Til
S3.
SSL
R
^5-
^ŁT
45-
fS"
4sr
K
o.w
o.as
o.as
0.30
0.30
LS
//.*/
7-4,
o.v.o
0.3
0.3
0.01
Surface
soi 1 loss
(tons/yr )
23.0
15.0
/.S"
18-0
0.6
SO,
o.oa
0.0 a.
0,11
o.o/
o.aa.
Del i vered
sediment
(tons/yr)
0-S
0.3
0.2.
0.2.
O./
to
O5
- CC -
L - Landing
R - Road
- T -
S - Sub&oU.
a {Wi
oft two LS
, onu {on &ac.h kal& o& the. fioad, Atat&ing at the. canteA Line, and i.ncŁu.ding
-------
WORKSHEET IV.4
Estimated VM factors for si IvicuItural erosion response units
Crgefc. watershed, hydrographic area 3 .
Lodging residue area
irosion
response
un it
CC3.I
ccs.a.
Fraction
of
total
area
0.4,5
o.feo
Mulch
(duff &
residue)
O.08
O.08
Canopy
l.o
1.0
Roots
o.io
o.ll
Sub
VM
o.oos
O-OOS"
Open area
Fraction
percent
of total
area
0-3ST
o.yo
Mu 1 ch
(duff &
residue)
0.7*
0.7S
Canopy
l.o
1.0
Roots
O.IO
0.11
Filter
strip
0.5"
0.5-
Sub
VM
o.o/he.&t IV. 3.
-------
WORKSHEET IV.5
Example of estimated monthly change in VM factor following
construction for road cuts and fills in H0>"SC Cree-k> watershed,
hydrographic area 3.
Month
Sep.l/
OctJ/
Nov.
Dec.2/
Jan.^/
FebJ/
March^/
April*/
Mayf/
June^/
Julyl/
AU2j_
Percent cover and VM subfactors
Mulch
Percent
0
8
ao
—
—
—
—
10
as
so
&0
70
VM
/.oo
0.80
o.s?
0.78
0.5T0
o.3a
0.31S
O.I?
Canopy
Percent | VM
0
la
a a.
—
—
—
—
10
ao
70
g3
90
/.oo
O.S8
0.^0
o.?o
o.sa
O.MI
0.30
o.as
Roots
Percent
ao
^yo
50
VM
0.3S
oa7
o.:u
Month 1 y
VM
1.00
0.70
o.V7
—
—
—
—
0.70
o.V/
0-OS
o.oa
O.Oj
-/ Begin seeding, enough rain is assumed to ensure seed germination.
2/
- Snow cover with no erosive precipitation.
- Significant canopy effect developing.
47
- Snowmelt runoff occurs, some protective vegetative cover lost during
winter.
- Significant root network developing from seeded grass.
VIII. 128
-------
WORKSHEET IV.6
Weighting of VM values for roads in
Ho»*SC, Creek watershed, hydrographic area
Erosion
response
unit
A 3.1
R3.A
Cut or fill
Fraction
of total VM
width
(o./«9) (o.«a;
(o.y&a?; (0-W
Roadbed
Fraction
of total VM
wi dth
+ (o.fc7v*X i.a.
-------
WORKSHEET IV.7
Factors for sediment delivery index from erosion response units in
watershed, hydrographic area 3.
Eros i on
response
unit
CC3.I
ccs.a.
L3.I
fi.3.1
boo
<\ «J . ot^
Water jj
aval labi 1 ity
JJ
o.oo4
O.OOfe
0.003
0.004
o.ooH *
Texture
of eroded
material
^5"
45"
45-
MS
48
Percent
ground
cover
between
disturbance
and channel
?o
i.
fit (faaieti on
— ' Maximum )5 mtn. annual
-' In^^ttfuution >mte. o
-------
WORKSHEET IV.8
Estimated tons of sediment delivered to a channel for each
hydrographic area and type of disturbance for Hovsg. Creelc
watershed
pi-onoseo ryianrtaewe/iJ
Hydro-
graphic
area
/
a
3
1
s
(o
7
3
9
10
II
i a.
I3
if
IS
ik
17
1?
1?
ao
^
a?
a.8
a?
30
SI
32.
Col umn
total
Distur-
bance
total
Percent
Cutting units
CC,
0.0
0.3
o.s
0.0
0.3
—
o.o
O.I
o.a
0.2.
o.o
o.l
—
0.3
0.0
0.3
o.o
o.o
0.0
0.3
0.0
0.0
0.0
0.3
o.o
o.o
o.a
3.1
CC2
0.0
o.a
0.3
o./
o.a
0.3
o.o
Q.I
0.3
o.s
0.3
0.3
o.o
O.I
o.o
2.7
CC3
0.3
0.3
O.I
O.I
o.s-
/.3
CC4
o.a
0.3
0.3
oA
/.a
CC5
0.1
0-1
8.7
M?. 2.
Landings
LI
0.0
O.I
o.a
o.o
o.o
aa
o.o
0.0
o.o
o.o
0.0
O.I
O.I
o.o
o.o
o.o
o.a
o.?
1-2
o.o
o.o
o.o
o.o
o.o
0.0
13
0.0
o.o
o.o
0.0
o.?
S.I
Roads
"1
o.o
O.I
o.a
0.0
o.o
0.0
0.0
o.l
O.I
o.a
0.0
O.I
o.a
o.a
0-0
0.0
o.o
O.o
o.l
O.I
o.a.
o.o
o.a
o.a
o.o
o.o
o.s
2.3
R2
o.o
o.l
o.l
o.o
o.l
0.0
O.I
O.I
o.l
o.a
0.3
O.I
O.I
0.3
0.3
0.3
0.0
o.a
o./
O.I
0.0
o.o
o.a
3.3
*3
0.1
O.I
O.I
O.I
O.I
o.l
04
0.3
0.3
0.3
O.I
0.2
0.2
0.1
Q.I
*.l
R4
Q.I
O.I
O.I
O.I
O.I
O.I
o.l
0.1
0.8
R5
O.I
o.l
8.1
-------
1 of 3
Horse Creek
WORKSHEET IV.2
watershed erosion response unit management data for use
sediment delivery index, hydrographic area 3,
in the MSLE and
Eros ion
response
unit
1. caa.J
2. CC3.a
3. L3. /
4. R3./
5. CUT
6. BEb
7. PILL
8. R3-A JJ
9. FILL
10. flED
11. PILL
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Slope
length of
disturbed
area (ft)
Maa
80
48
-------
2 of 3
WORKSHEET I V.2—-centinued
Area with surface residues—'
Percent
of total
area
1 . 6>S
2. fcO
3. 0
4.
5. 100
6. 0
7. IOO
8.
9. IOO
10. o
11. IOO
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Percent
of surface
with mu Ich
90
90
—
70
—
7O
70
—
70
Percent of
area with ,
fine roots -u
?0
85"
—
so
—
SO
so
—
5-0
Open area — /
Percent
of total
area
3S
i the end ofa tke fi-Lut yeaA fio-ttoMcng
A /
— Not appLicabie to bcatped asiecu> u.ntU. vegetation AJ.
— S-tx -inc.hu 0){ c/MAhed gftave-t, 3/4 -inch on moJUL&i -in i>-ize, placed on Banning
-------
WORKSHEET IV.2—continued
3 of 3
Average
minimum
height of
canopy
(m)
1 — ••
2. —
3. —
4.
5. O.S
6. —
7. o.S
8.
9. O.S
10. _
11. O.S
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
T i me for
recovery
(mo)
UMKNOtuU
UNKNOWN
UMtCNOU)M
1 veflR.
1 Y5AH
Average
d i st . from
disturbance
to stream
channel (ft)
IS
IS"
a.o
100
0
Over a 1 1
slope shape
between
disturbance
and channel
STRAIGHT
STRAt&HT
STRfllG-MT
STR.A1G-HT
STRRI6HT
Percent
ground
cover in
f i Iter
str ip
90
90
90
ff9
0
Surface
roughness
(qual i-
tat i ve )
rnoDeR.«TE
m«DER«Te
W^>l>fR.ATe
moaeeATe
SMOOTH
Texture of
eroded Ł/
mater ial —
(% si It +
clay)
4S
«/Ł•
«*s-
US
W
Percent
slope
between
disturbance
and channel
38
30
5"
30
47
a
— It hcu> been /UAumud that k o& the. cZ&y
and &-Ltt e.nteA the, -Ae.dJjme.nt
on-A^te. cu>
&y&te.m.
agg^ingcutu and that the. tut oft the. c.tay
-------
WORKSHEET IV.3
Estimates of soil loss and delivered sediment by erosion response unit
for hydrographic area 3 of Morse Cr€ek watershed
Erosion response
unit -I/
CC 3.1
CC 3.2
L.3.1
R3.\
R3.^
Soili|
unit^
T2,
T 2.
T 2.
s a.
s a.
R
45
45"
US
HZ
4S
K
o.as
o.as
o.as
0-30
0.30
LS
114
<>., one
a
eac/i
load, *>tcviŁing at thu ce.nteA Line, and Including
-------
WORKSHEET IV.4
Estimated VM factors for siIvicuIturaI erosion response units
MorSS Creak watershed, hydrographic area .3
Logging residue area
Erosion
response
un it
CC3.I
CCS. 3.
f\3. 1 CttT
BED
FILL
R3.SI FILL
BED
FILL
Fract ion
of
total
area
O.foS
O.(o0
Mulch
(duff &
residue)
O.08
O.O8
Canopy
l.o
l.o
Roots
OJO
o.//
Sub
VM
0.005-
0.005"
Open area
Fraction
percent
of total
area
0.3S-
O.MO
l.oo
l.oo
Mulch
(duff &
residue)
0.78
0.7S
O.OOS2'
O.ooS--^
Canopy
l.o
1.0
l.o
l.o
Roots
o-io
o.//
Filter
strip
o.s
0.5-
Sub
VM
o.o/
-------
WORKSHEET IV.6
Weighting of VM values for roads in
tiorge Creek watershed, hydrographic area
Erosion
response
un it
KS.I
R3.3.
Cut or fill
Fraction
of total VM
wi dth
(
Roadbed
Fraction
of total VM
wi dth
+ (o.feo) (o.oos^
+ /0-*o> fa<»S\
\ J ^I«TT-M^
Fi 1 1
Fraction
of total VM
width
+ (o.ao) fo.te)
•f fo.ao^ (o<<4-i\
Weighted
VM
= 0,17
= 0. /7
VHI.137
-------
WORKSHEET IV.7
Factors for sediment delivery index from erosion response units in
nOrSŁ Creek. watershed, hydrographic area 3 .
Erosion
response
unit
CC3.I
ccs.a.
L3.|
R 3.1
R3.2.
Water
aval labi I i ty
_ay
O.OO
-------
WORKSHEET IV.8
Estimated tons of sediment delivered to a channel for each
hydrographlc area and type of disturbance for Horse, Creek watershedj
Hydro-
graphic
area
/
a.
3
1
0.04
0.0
O.o3
0.01
o.oa
0.0
0.0
0.03
o.is
R3
o.oa
O.oi
o.oa
o.oa
0.01
o.oi
0.03
0.01
o.o
0.03
o.oa
0.03
0.03
o.oa.
0.03
0.3S
R4
0.01
0.01
0.01
o.oa.
0.01
o.oi
i/
0.01
O.W
«5
o.oa.
0.01
/.30
0.3 ll /3.X
Total
tons/yr
o.o
/.o?
o.%
o.oa.
0.11
o.o &o>i mtu,t, uiaAtLng.
T/ Landing vio&ian leAponte. u.nitt> uLuru-naJtid by c.ontnat!> {,on maA& waiting.
bj Road eA.o64.on tuponAe. urMt, eliminated by c.onŁnot!> ^01 ma&i
VIII.139
-------
WORKSHEET V.1
Debris avalanche-debris flow natural factor evaluation form
I ndex
High
^ed i urn
.ow
Slope
grad lent
30
©
5
Soi I
depth
3
©
1
Subsurface
dra i naae
character i st ics
©
2
1
Soi 1
texture
3
@
0
Bedd inq
structure
and
or ientat ion
3
©
1
Slope
conf iqurat ion
3
©
1
Precipi-
tation
input
12
©
3
Factor summation table
Gross hazard index
High
Medium
Low
Factor ranqe
Greater than 44
21 - 44
Less than 21
Natural
31
-------
WORKSHEET V.2
Debris avalanche-debris flow management
related factor evaluation form
Index
High
Medium
-OW
Vegetation
cover remova 1
©
5
2
Roads and
skidways
(§)
8
2
Harvest
methods
@
2
0
Factor summation table
Gross hazard index
High
^ledi urn
Low
Range
Greater than 44
21 - 44
Less than 21
Natural +
management
31431 = 6^
vni.i4i
-------
WORKSHEET V.5
Estimation of volume per failure
S 1 i de
Number
Worse
/
/Hole
/
i
3
i
S~
I
Debris avalanche-debris flow
Natural
Creek
X
Oeek
X
Man-
induced
X
X
X
X
X
Length
(ft)
w
80
U9
Ul
It3
;s-
//s
Width
(ft)
<2S
*1
a&
/7
/*
53
/?
Depth
(ft)
AS"
AS"
AS"
AS-
AS"
A5-
AS
Vol ume
(ft3)
3,5-3.8
3,8SO
^031
3,08(o
3,0*11
3,a7?
3,3^0
Slump earthflow
Natura 1
Man-
induced
Length
(ft)
Width
(ft)
Depth
(ft)
Vol ume
(ft3)
-------
This page intentionally left blank.
VHI.143
-------
WORKSHEET V.6
Estimation of soil mass movement delivered to the stream channel
(1 ) Watershed name
Mal
Factor
(2)
Soil mass movement type
Debris avalanche-
Debris flow
Natural
(3)
Man-induced
(4)
S 1 ump f low
Natura
(5)
Man-inducec
(6)
1 Total volume (Vt) in ft
3480
2 Total number of failures (N)
3 Average volume per failure (VAMft )
4 Number of failures per slope
class
5 Number of failures per slope
position category
Total volume per slope class or
position category
(V) in ft3
V = VA x N
Va'
3^0
vc'
V
Unit weight of dry soil
material (Yd) (Ib/ft3)
VIH.144
-------
WORKSHEET V.6—cent inued
8 Total weight per slope class
or position category (W)
in tons
2,060
wa
WB,
Wb
wb.
We
wc-
Wdi
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S W x D
Da
Da'
Db
°b'
DC
DC'
Dd'
sa
SB-
Sb
V
sc
Sc'
Sd'
12 Total quantity of sediment delivered to
the stream channel in tons
13 Acceleration factor (f)
f TSs! Ivicultural actlvity/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed sllvi-
cultural activity (TS) in tons
TSsi Ivicultural activity = Tsnatural x f
/t3
—
—
/
smootK
O.tl
—
—
/
lol
—
—
/
|0|
W
3
-------
WORKSHEET V.6
Estimation of soi I mass movement del ivered to the stream channel
(1) Watershed name Horse
H
Factor
(2)
Soi 1 mass movement type
Debris avalanche-
Debris flow
Natural Man-induced
(3) (4)
Slump flow
Natural Man-lnducec
(5) (6)
1 Total volume (V-f) in ft
2 Total number of failures (N)
3 Average volume per failure (VAMft )
ssas
4 Number of failures per slope
class
5 Number of failures per slope
position category
a1
6 Total volume per slope class or
position category
(V) in ft'
V VA x N
va'
V
7 Unit weight of dry soil
material (Y(j> (Ib/ft3)
?o
VHI.146
-------
WORKSHEET V.6--continued
B Total weight per slope class
or position category (W)
in tons
w = V x Yd
2,000
wa
W3'
Wb
wb,
We
WC'
Wdi
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S = W x D
Da
Da'
Db
Db'
DC
DC'
Dd'
Sa
V
Sb
Sb,
Sc
sc.
sd-
12 Total quantity of sediment delivered to
the stream channel in tons
13 Acceleration factor (f)
f = TSsilvlcultural actl vlty/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed silvi-
cultural activity (TS) in tons
T^si | vicu Itural activity = ^natural x *
—
(5?
/
sr»tooTn
—
o.4o
—
/
—
64
—
/
Li
^^
—
^^
—
—
^^
—
FVOKH Mule
Cr««lc
^.0
/?!
—
—
—
—
— .
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
VIII.147
-------
WORKSHEET V.2
Debris avalanche-debris flow management
related factor evaluation form
Index
High
vied ium
_ow
Vegetation
cover removal
8
5
©
Roads and
skidways
20
8
-------
WORKSHEET V I.I
ffte onJ Post fi>v P~p»s«d av>J Rwised S/wcuW»r»l Ha,sJ
(1 )
Time increment
(a)
ith hydro-
graphs use
ate; with
flow dura-
ion curves
use % of
365 days
flPR 8
14
w
Xo
MAY a
?
/
(0
(o
(,
V
^y
(a
^0
(o
6>
(2)
Pre-
si Ivl-
cu 1 tural
activity
flow
(cfs)
0.00
0.34
0.?7
1.1,4
3.frl
3.87
5.3S-
6.8a
J.o?
10. AS
7.0?
6.81
Y.«l
3.44
1.14
0.34
0.00
<3)
Sus-
pended
sed i ment
concen-
trat ion
(mg/l)
—
1.0
9.0
a. 8
3.7
f.8
5.9
6.?
8.3
8.?
8.3
4,9
5.1
3.6>
3.1
/.o
—
(4)
Total increment
suspended
sedi ment
cols. (2) x (3)
x U.b) x .0027
(tons)
0.01
0.03
0.0?
o. /t>
0.3O
0.51
0.7fc
/.«
/.v*
/.a.2.
OK
0.35
0./
1.0
O.S"
-
(7)
Total Increment
post-si Ivlcultural
activity suspended
sed iment
cols. (5) x (6) x
(l.c) x .0027
(tons)
—
MEGLI
0.01
0.04>
O.IS
0.32,
0.4?
0.77
/.sa.
/.t.7
/.so
/.as
0.70-
0.33
0./S"
O.OS"
0.02,
0.01
NESLI
—
(8)
Max i mum
concentra-
tions from
selected
water qual Ity
objective
(mg/l)
—
-
—
—
31.0
3JI.O
33.8
33.7
34.8
35.9
34,?
38.3
38.9
3S.3
3C.7
3S.I
33.4
33.2.
31. 0
—
(9)
Max i mum
sediment
discharge
cols. (2) x
(8) x U.b)
x .0027
(tons)
—
—
-
—
0.11
O.SO
0.87
1.13
3.18
3.11
4.08
S.(,4
4.^
Ł.bi
1.0S
3.39
/.33
0.60
0.17
(Totals are rounded to nearest tenth)
Total
Total 8.8
tons/yr
Summary: Total pre-slIvicultural activity suspended sediment discharge = TJ
Total post-si Ivicultural activity suspended sediment discharge = g.g
Total maximum sediment discharge =
Total 38.(o
tons/yr
-------
WORKSHEET VI.2
Vl
O
Bedload sediment quantification for Horse Creek
(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days
APR 8
It
20
afc
MAY 1
8
H
AO
at
TUIO /
7
13
1?
zs
JU.L /
7
13
1?
AS
31
(b)
Number
of
days
pre-
si Ivl-
cu 1 tura 1
activity
6.
Ł>
fe
fc
&
k
4,
6 J
lo
C.
k
Ł»
(«
&
G.
k
6
&
fe
6
(c)
Number
of
days
post-
si IvI-
cu 1 tural
act 1 v ity
6,
(.
1.
b
lo
b
(a
6
Ł>
6>
6>
t
C?
t.
&
6
6
k
fc
6p
(2)
Pre-
si Ivicultural
activity flow
Ve
(cfs)
0.00
0.3«/
0.97
/.fcV
S.H
3.87
5:35-
fe.sa,
?.o?
laas
9.o?
fc.?a,
V.ai
3M4
1-lH
0.3
-------
This page intentionally left blank.
VIII.151
-------
WORKSHEET VI .3
Sediment prediction worksheet summary
Subdrainage name tiorSfc CfCfek _ Date of analysis W Af /O
~ '
PlttH
Suspended Sediment Discharge
A. Pre-si I vicu Itural activity total potential suspended sediment
discharge (total col. (4), wksht. VI. 1) (tons/yr) 7. 1
B. Post-si IvicuItural activity total potential suspended sediment
discharge (total col. (7), wksht. VI.1) (due to streamfJow
increases) (tons/yr) O-o
C. Maximum allowable potential suspended sediment discharge (total
col. (9), wksht. VI.1) (tons/yr) 3o.fe
D. Potential introduced sediment sources: (delivered)
1. Surface erosion (tons/yr) /7-7
2. Soil mass movement (coarse) (tons/yr)
3. Median particle size (mm) /O
4. SoiI mass movement—
washload (silts and clays) (tons/yr)
Bed Ioad Discharge (Due to increased streamflow)
E. Pre-siIvicuItural activity potential bedload discharge (tons/yr) AT
F. Post-si IvicuItural activity potential bedload discharge (due
to increased streamflow) (tons/yr)
Total Sediment and Stream Channel Changes
G. Sum of post-si IvicuItural activity suspended sediment + bedload .. n
discharge (other than introduced sources) (tons/yr) |Q- /
(sum B + F)
H. Sum of total introduced sediment (D)
= (D.1 + D.2 + D.4) (tons/yr) tflQff. 7
I. Total increases in potential suspended sediment discharge
1. (B + D.1 + D.4) - (A) (tons/yr)
2. Comparison to selected suspended sediment limits
(1.1) - (C) (tons/yr) +
VIII.152
-------
WORKSHEET VI .3~continued
J. Changes in sediment transport and/or channel change potential
(from introduced sources and direct channel impacts)
1. Total post-si IvicuItural activity soil mass movement ,,
sources (coarse size only) (tons/yr) I\\Ł
2. Total post-si IvicuItural soil mass movement sources (fine .
or wash load only) (tons/yr) TV?
3. Particle size (median size of coarse portion) (mm) \Q
4. Post-si IvicuItural activity bedload transport (F) (tons/yr) /./
Potential for change (check appropriate blank below)
Stream deposition ^^
Stream scour
No change
K. Total pre-siIvicuItural activity potential sediment discharge Q
(bedload + suspended load) (tons/yr) Q.5"
(sum A + E)
L. Total post-si IvicuItural activity potential sediment discharge .
(all sources + bedload and suspended load) (tons/yr) g?30-T
(sum G + H)
M. Potential increase in total sediment discharge due to proposed -.• Q
activity (tons/yr) c*.\\-7
(subtract L - K)
Vm.153
-------
WORKSHEET VI.4
Bed load transport-stream power relationship for Worse CreelfC. FVocoSBa Plavy
(1)
Water
surface
slope
S *
(ft/ft*
O.oaso
O.oos^
o.ooso
o.ooso
o.ooso
0.0050
o.ooso
(2)
Constant
(62.4)
K
(Ib/ft3)
W-f
43. «
«.*
62.*
W.f
63.V
«.»
(3)
Measured
stream
discharge
0
(cfs)
\o.s
3.0
7.0
5.0
-------
WORKSHEET VI .5
Computations for step 21 (jerse
(stream name)
osed SilrfeuHujraJG P
Changes in bed load transport-stream power due to channel impacts
1. Potential changes in channel dimensions
a. Bankful stage width (Wpre) 10 (wpost) /-^
b. Bankful stage depth (Dpre) O.b (Dpost} d.&
c. Water surface slope (Spre) O.Qfl? (Spost) O.OUSO
d. Bankful discharge (Qepre* ^-^3 ^Bpost* °-^
where: Qspre = 0.366 +1.33 log Apre + 0.05 log Spre - 0.056 (log Spre);
where: A = cross-sectional area (a) x (b) 0-v)
S = water surface slope (c) 0.0'Xf
Calculate Qepost Us'n9 post-si IvicuItural A and S
^Bpost = 0.366 + 1.33 log Apos+ +0.05 log Spost
- 0.056 (log Spost)2
2.a. Pre-siIvicuItural activity stream power calculation
Spre 62.4 QBpre
,„ (l.c) x (K) x (l.d) .
;?::, o-°)
2.b. Post-si IvicuItural activity stream power calculation
spost 62-4 PBpost
0)
f = ^-L^.—=_~—-—^-i^- = \.v«*y\v«-ij\.u.*.*j ^ *
Wpost 7T7\
(i .a)
3. Calculate post-si IvicuItural activity bedload transport rate at bankful
discharge, using post-si IvicuItural activity stream power
VHI.155
-------
WORKSHEET VI.3
Sediment prediction worksheet summary
Subdrainage name Worse CWlcYfouis&J SlluieJWl P\a\n\ Date of analysis
~
Suspended Sediment Discharge
A. Pre-siIvicuItural activity total potential suspended sediment
discharge (total col. (4), wksht. VI.1) (tons/yr) /.|
B. Post-si IvicuItural activity total potential suspended sediment
discharge (total col. (7), wksht. VI.1) (due to streamflow
increases) (tons/yr)
C. Maximum allowable potential suspended sediment discharge (total
col. (9), wksht. VI.1) (tons/yr)
D. Potential introduced sediment sources: (delivered)
1. Surface erosion (tons/yr) /.o
2. Soil mass movement (coarse) (tons/yr) 0
3. Median particle size (mm) ~~
4. SoiI mass movement—
washload (silts and clays) (tons/yr) 0
Bedload Discharge (Due to increased streamflow)
E. Pre-siIvicuttura I activity potential bedload discharge (tons/yr) /
-------
WORKSHEET V I . 3—cont i nued
J. Changes in sediment transport antj/cr channel change potential
(from introduced sources and direct channel impacts)
1. Total post-si IvicuItural activity soil mass movement
sources (coarse size only) (tons/yr) 0
2. Total post-si IvicuItural soil mass movement sources (fine
or wash load only) (tons/yr) 0
3. Particle size (median size of coarse portion) (mm) •—
4. Post-si I vicu Itural activity bedload transport (F) (tons/yr) /.7
Potential for change (check appropriate blank below)
Stream deposition _
Stream scour _
No change V
K. Total pre-si I vicu Itural activity potential sediment discharge
(bedload + suspended load) (tons/yr)
(sum A + E)
L. Total post-si I vicu Itural activity potential sediment discharge
(all sources + bedload and suspended load) (tons/yr) o/O.b
(sum G + H)
M. Potential increase in total sediment discharge due to proposed
activity (tons/yr) _J_L_ _
(subtract L - K)
Vin.157
-------
WORKSHEET V I I . 1
Variation of solar azimuth and angle with time of day
Time of day
(Daylight savings time)
?:00
10. '00
fl :00
II :30
U:00
ISU30
/ ;00
/ :30
a^oo
3US
,5:30
3 :00
Solar
angl e
30
43
54
S?
62.
45-
65
4s-
6 a.
60
SS
S^
^3
30
Shadow!/
length (S)
(ft)
/3ft 6
SS.8
s&l
5o.O
^.S"
37.3
37.3
37.3
-------
Ol
co
WORKSHEET VI 1.2
Evaluation of downstream temperature Impacts
/.
S.
3.
V-
5.
6.
7
S.
Stream reach
flrea. 47
Area. S18
fBelou cimflucne«)
Area. Ł9
/W 30
f6a|ou confiuetwa)
^adjusted
*«•
?so
565"
741
^adjusted
8T(A./<'4'--»>,\»,
«/.3l
tf/X
aw
c
Surface
c4s
O.^f
0.3
O.^f
Subsurface
0(5
—
—
—
All/
°F
S.S
Q.\
IJ
&
•F
57.5"
S7.3
^.9
S-?. fl.
\J Łj _ Aadjusted x Hadjusted x 0.000267 where Q is surface flow only.
2/ °
- T from mixing ratio equation.
-------
LITERATURE CITED
Maxwell, W. G., and F. R. Ward. 1976a. Photo ponderosa pine type; ponderosa pine and as-
series for quantifying forest residues in the: sociated species type; lodgepole pine type USDA
coastal Douglas-fir-hemlock type; coastal For. Serv. Gen Tech. Rep. PNW-52.
Douglas-fir-hardwood type. USDA For. Serv.
Gen. Tech. Rep. PNW-51. ™ , , « T
Pfankuch, D. J. 1975. Stream reach inventory and
Maxwell, W. G., and F. R. Ward. 1976b. Photo channel stability evaluation. USDA For. Serv.,
series for quantifying forest residues in the: Reg. 1, Missoula, Mont. 26 p.
VIII.160
-------
Chapter IX
DISSOLVED OXYGEN AND ORGANIC
MATTER
this chapter was prepared by the following individuals:
Stanley L. Ponce
John B. Currier
-------
CONTENTS
Page
INTRODUCTION IX.l
DISCUSSION IX.2
OXYGEN SOLUBILITY IN FRESH WATER IX.2
IMPORTANCE OF DISSOLVED OXYGEN TO FISH IX.2
THE OXYGEN BALANCE IN A STREAM IX.4
DISSOLVED OXYGEN AND LOGGING IX.8
Water Temperature Increases IX.8
Logging Debris IX.8
PREDICTING DISSOLVED OXYGEN DEFICITS,
THE DO SAG METHOD IX.ll
Predicting Components Of The DO Sag Method IX.13
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS IX.14
CONCLUSIONS IX.15
LITERATURE CITED IX.16
IX.ii
-------
LIST OF EQUATIONS
Number Page
IX.l. S*(P)=S760-p IX.2
DC.2. P= 29.92 / exp (E/25,000) IX.2
IX.3. S(T) = 14.56 - 0.38163T + 0.0066366T2 - 0.0005227T3 IX.2
IX.4. ADOm = DOm(i)-DOm(o) IX.4
Bt.5. D0m(i) = D0m(o) IX.4
DC.6. Substrate + 02 °rganism » C02 + H20 + energy + other byproducts IX.5
IX.7. dD
-Ł- = -K2D IX.12
IX.8. dL
-7- = -KiL IX.12
at
DC.9. dL dD
~ dT = ~dt~ IX'12
IX.10. dD
-^- = KiL IX.12
IX.11. D = KiLa [exp (_Kjt) - exp (-K2t)] + Da exp (-K2t) IX.12
K2—Ki
IX.12. Ki
Dc = — La exp (-Kitc) IX.12
IX.13. K! K2 f Da (K2-Ki)"| TV
tc= -_ T. In — 1- ^T IX.13
c K2-Ki Li L KlLa J
IX-14- K2(T) = 1.016(T-20) [181.6 E - 1657 S + 20.87] IX.13
IX.15, E = (S) (u) (g) IX.13
DC-16- Kim = 0.796 [1.126(T-ao)K1(ao)l; 2° < T < 15° C ix.13
K'17- K1(T) = 1.000 [1.047(T-20)K1(2o)]; 15° < T < 32° C IX.13
DC 18 (T-20)
K1(T)= 1.728 [0.985 K1(20)); 32° < T < 40° C IX.13
K.19. La(T)=La(20)[1.0 + 0.0033(T-20)];20
-------
LIST OF FIGURES
Number Page
IX. 1.—Relationship between temperature, pressure (elevation), and dissolved
oxygen IX.3
IX.2.—Hypothetical section of stream channel to be considered in the dissolved
oxygen mass balance IX.5
IX.3.—Sources and sinks of dissolved oxygen in a mountain stream under
natural conditions (after Ponce 1974b) IX.6
IX.4.—The biochemical oxygen demand process in a mountain stream (after
Ponce 1974b) IX.7
IX.5.—Surface dissolved oxygen levels (mean and range) taken twice weekly in
the clearcut watershed (Needle Branch) and control watershed (Flynn
Creek) during the year of timber harvest (1966) IX.10
IX.6.—Intragravel dissolved oxygen levels in the clearcut watershed (Needle
Branch) from December 1965 to May 1966 (before logging) IX.11
IX.7.—The dissolved oxygen sag IX.12
IX.iv
-------
LIST OF TABLES
Number Page
IX.1.—Mean cumulative BOD in milligrams of (Vg (dry weight) by Douglas-fir
needles and twigs, western hemlock needles, and red alder leaves in
stream water at 20° C (Ponce 1974a) IX.9
IX.2.—Mean cumulative BOD in milligrams of (Vg (dry weight) by Douglas-fir,
western hemlock, and red alder leaves under conditions of temperature
fluctuation (Ponce 1974a) IX.9
IX.3.—K1(2o) and La (2o) values for selected tree species and materials IX.13
IX.v
-------
INTRODUCTION
The dissolved oxygen (DO) concentration in
small, forest streams strongly influences the
character and productivity of the aquatic
ecosystem. Fish and other aquatic organisms need
dissolved oxygen to survive, grow, and develop.
Silvicultural activities may influence the dis-
solved oxygen concentration of a stream draining a
logged area. If timber harvesting exposes the
stream to direct solar radiation, the water
temperature will increase, as discussed in chapter
VII, resulting in a decrease in the saturation con-
centration of DO in the water. In addition, if large
quantities of organic debris are allowed to enter
and remain in the stream channel over an extended
period, they may contribute to decreased DO levels
by: (1) forming debris ponds, which enhance
heating of water and reduce the reaeration rate; (2)
releasing dissolved materials, such as sugars,
nutrients, and phenolics, which are readily ox-
idized by microorganisms; and (3) forming a
benthic mat that can inhibit the flow of DO into
the intragravel water.
It is not possible to accurately predict the impact
of silvicultural activities on the DO concentration
of forest streams. The physicochemical properties of
oxygen solubility, the pool and riffle nature of
mountain streams, and the non-point source pollu-
tants affecting DO concentration make such
prediction very difficult. However, several
mathematical models have been proposed for use
with forest streams. In general, these models are
merely extensions of methods developed for quies-
cent waters, such as rivers and lakes, and most
have met with only limited success. One notable
exception is a model by Berry (1975) specifically
developed to predict the impact of logging debris
on dissolved oxygen content in small forest
streams. This model can be used to predict DO
concentrations in the surface water of a stream
where DO content has a critical bearing on a
resource management decision. However, if only a
rough estimate of the DO concentration in the sur-
face water is required, the Streeter and Phelps
(1925) DO sag method may be used. Little work has
been done concerning oxygen dynamics in the in-
tragravel /one of a stream. As a result, there are no
models available to predict DO changes in the
streambed gravels following logging.
Although accurate prediction may not be possi-
ble, a clear understanding of oxygen dynamics in a
stream is essential to identify silvicultural ac-
tivities that will adversely affect the DO concentra-
tion in a small forest stream. As a result, informa-
tion on oxygen solubility, the dissolved oxygen
balance, dissolved oxygen and logging, and land
use practices to protect and maintain the oxygen
concentration in a forest stream is explained prior
to discussion of the Streeter-Phelps model. Evalua-
tion of the impacts of silvicultural activities on DO
concentrations is essential in identifying potential
impacts on the fishery resource of a DO reduction
caused by timber harvesting.
IX. 1
-------
DISCUSSION
OXYGEN SOLUBILITY IN FRESH WATER
Although free oxygen is abundant in the at-
mosphere (20.9 percent by weight), it is relatively
insoluble in water. The saturation concentration
varies between 14.6 mg/l (ppm)1 at 32° F (0° C) to
7.6 mg/1 at 86° F (30° C) under 29.92 inches of Mer-
cury (760 mm) atmospheric pressure. In fresh
water, oxygen solubility, or saturation concentra-
tion, is determined by atmospheric pressure and
the temperature of water. Figure IX.1 illustrates
the relationship between temperature, pressure
(elevation), and concentration of dissolved oxygen.
Atmospheric pressure. — The effect of pressure
is described by Henry's law, which states that the
solubility of a gas in a liquid is directly propor-
tional to the pressure of the gas above the liquid. As
the atmospheric pressure (partial pressure of ox-
ygen) increases, there is a proportional increase in
the water's capacity to hold oxygen. The pressure
effect can be calculated by equation IX. 1:
„ Qp-p
~ & 760-p
(IX.l)
where:
S*p) = the oxygen solubility in mg/l at at-
mospheric pressure P in inches (mm) of
mercury,
S = the oxygen solubility at 29.92 inches (760
mm) of mercury, and
p = the pressure (inches or mm) of saturated
water vapor at the temperature of the
water (American Public Health Associa-
tion, Inc. 1971).
At elevations below 3,000 feet (900 m) m.s.l. and
temperatures below 77° F (25° C), p can be con-
sidered negligible. If the elevation (E in feet) is
known, an approximate value of P can be
calculated by:
P = 29.92 / exp (E/25,000) (IX.2.)
'In fresh water (total dissolved solids <7,000 mg/l) 1 mg/l =
I ppm (Hem 1970). As a result, the English unit of concentra-
tion will not be given throughout the balance of this chapter
since it is equivalent to the mg/l of concentration.
Water temperature. — The solubility of oxygen
in water is inversely proportional to water
temperature. This is important because some
silvicultural activities expose the stream to direct
solar radiation, resulting in an increase in the
stream water temperature (chapter VII). As the
water temperature increases, its capacity to hold
oxygen decreases. The temperature effect can be
calculated by:
S(T) = 14.56 - 0.38163T + 0.0066366T2
- 0.00005227T3
(IX.3)
where:
S(T) = the solubility of oxygen (mg/l) in water of
a given temperature, and
T = the temperature in °C.
IMPORTANCE OF DISSOLVED
OXYGEN TO FISH
Adequate levels of DO in the surface and in-
tragravel water are essential for survival offish. An
"adequate level" of DO is a vague term and varies
with the species and age of the fish, prior ac-
climatization, temperature of the water, and con-
centration of other substances in the water (McKee
and Wolf 1963). However, fishery biologists often
use the following "rule of thumb" for minimum DO
concentrations for freshwater biota: 5 mg/l for
warm water species, declining to a lower limit of 4
mg/l for short periods, provided that the water
quality is favorable in all other respects; and no less
than 6 mg/l, or 7 mg/l during spawning times, for
cold water species.
Fish often are exposed to DO concentrations well
below 5 mg/l for prolonged periods. DO concentra-
tions between 5 and 2.5 mgA are generally con-
sidered sublethal to fish. Under such conditions,
fish experience an oxygen stress, and if the ex-
posure is extended, their activity, growth, and
reproduction may be reduced.
Several responses to oxygen deficiencies by fish
within the surface water and by fish eggs and
embryos in the intragravel water have been
reported. Shellford and Allee (1913) studied the
avoidance reaction of 16 species of fish to different
IX.2
-------
ELEVATION IN THOUSANDS OF FEET
10" 12° 14° 16°
TEMPERATURE,°C
Figure IX.1.—Relationship between temperature, pressure (elevation), and dissolved oxygen.
concentrations of oxygen. They reported a definite
effort by all the fish to avoid water substantially
deficient in oxygen. Jones (1952) ran a similar ex-
periment with stickleback, minnows, and trout fry.
At temperatures near 68° F (20° C), all three
species reacted violently and retreated rapidly
when they swam into water containing 0.5 to 1.0
mg/1 of DO. At a concentration of 3.5 mg/1, the
reaction was again one of rejection but much
slower. Whitmore and others (1960) conducted
avoidance tests with juvenile chinook and coho
salmon, large mouth bass, and bluegill. They found
all four species markedly avoided water containing
less than 4.5 mg/1 of DO; some coho avoided con-
centrations of 6 mg/1.
Davison and others (1959), studying dissolved
oxygen requirements of cold water fishes, reported
that at a temperature of 64° F (18° C), young coho
salmon survived for 30 days at a DO level of 2.0
mg/1. During this period the fish ate little and lost
weight. At a higher DO level, near 3.0 mg/1, the fish
ate more food and gained weight. However, this
gain was much less than that of similar fish in
IX.3
-------
oxygen-saturated water. Herrmann and others
(1962) further examined the influence of oxygen
concentration on growth and food consumption of
juvenile coho salmon. They found that at 68° F
(20° C), both growth and food consumption over a
prolonged period declined gradually as the oxygen
level dropped from 8.3 to about 5.5 mg/1. The
decline of each was rapid as the oxygen level
dropped from about 5 to 1.8 mg/1, and fish often
died at DO levels below 1.0 mg/1. The fish ate very
little and lost weight at oxygen levels at or below 2
mg/1.
These studies indicate that fish attempt to avoid
areas significantly deficient in oxygen, and that
when fish are exposed to such water for a prolonged
period, their growth and food consumption rates
decrease.
The value of high oxygen levels in the intragravel
water is often overlooked. However, it is critical for
Pacific Coast salmonoids, as well as other sport and
commercial fish that spawn in small forest streams.
The salmonoid species deposit their eggs 10 to 12
inches (25 to 30 cm) deep into the stream gravels.
The eggs hatch, and the embryos develop for ap-
proximately 3 months before the fry emerge into
the surface water (Lantz 1971). Continuously high
oxygen levels during embryo development are very
important. If oxygen becomes deficient, the per-
cent egg survival, rate of embryo development, and
quality of fish produced may decrease significantly.
Shumway and others (1964) examined the in-
fluence of oxygen concentration and water move-
ment on the growth of steelhead trout and coho
salmon embryos. In their experiment, embryos
raised from fertilization to hatching were exposed
to different concentrations of DO ranging from 2.5
to 11.5 mg/1 and water velocities ranging from 2 to
138 in/hr (3 to 350 cm/hr) under a near constant
temperature of 50° F (10° C). They found that fry
produced from embryos raised at oxygen levels of
less than 4.0 mg/1 hatched later and were smaller at
hatching than fry from embryos raised at oxygen
levels near saturation. They also reported that
reduced water velocities affected the fry in much
the same manner as reduced oxygen levels,
although the effect was not as pronounced.
Garside (1966) conducted a similar experiment
which examined the effects of oxygen and
temperature on brook and rainbow trout embryo
development. The embryos of each species were ex-
posed to oxygen concentrations of 2.5, 3.5, and
10 mg/1 at each of four temperatures — 36° F (2.5°
C), 41° F (5.0° C), 45° F (7.5° C), and 50° F (10° C)
— from the time of fertilization to late develop-
ment. The development rate slowed and the
hatching period increased for both species of fish as
temperature levels increased and oxygen levels
declined.
THE OXYGEN BALANCE IN A STREAM
The oxygen concentration in a stream is deter-
mined by the addition and depletion of dissolved
oxygen by biological and physical processes. Under
undisturbed conditions, a forest stream is in a state
of oxygen balance. Aquatic animals and decom-
position agents continuously withdraw free oxygen
while, at the same time, oxygen is supplied inter-
mittently by green plants during daylight, and con-
tinuously by direct absorption from the at-
mosphere.
The oxygen system within a stream may be
described using the mass balance approach. The
change in mass of DO (ADOm) within a fixed
volume of stream is equated to the inputs (DO m(i))
minus the outputs (D0m(o)) of oxygen and may be
expressed as:
ADOm = DO
'm(i) •
DO
m(o)
(IX.4)
If an oxygen balance exists, there will be no net
change in the oxygen mass within the volume, and
the equation may be reduced to:
D0m(i) = DO
m(o)
(K.5)
The oxygen balance of a section of mountain
stream (fig. IX.2) under undisturbed conditions is
illustrated diagrammatically in figure IX.3. The
size of the arrows between components indicates
the magnitude of oxygen transfer.
A mountain stream is replenished with oxygen
from three sources: the direct absorption at its sur-
face, the photosynthetic process of green aquatic
plants, and, to a minor extent, the influent ground
water.
Surface water is supplied with oxygen primarily
by direct absorption (reaeration) from the at-
mosphere. The reaeration rate is a function of the
DO concentration at the surface, while the disper-
sion of oxygen thoughout the water is controlled by
simple molecular diffusion and mass transfer. In
IX.4
-------
Stream Bank
Stream. Bank
Figure IX.2.—Hypothetical section of stream channel to be
considered in the dissolved oxygen mass balance.
general, the rate of reaeration in a still water body,
such as a pond or lake, is relatively slow. However,
forest streams often have steep gradients that
result in turbulence, which produces vertical and
horizontal mixing as well as oxygen entrainment,
all of which greatly increase the reaeration rate.
During daylight, plankton and algae that are
often present in quiet pools photosynthesize and
produce free oxygen as a byproduct. In large, low
gradient streams or lakes, photosynthesis may
serve as a major source of oxygen; however, in small
forest streams, it is generally only a very minor
source of oxygen (Camp 1965).
The intragravel water is supplied with oxygen
primarily by mass transfer and diffusion from the
overlying surface water. The rate of this transfer
and diffusion is relatively slow, because the mixing
agents present in the surface water are inhibited in
the intragravel water. Water velocity through the
intragravel layer is much lower than the surface
layer: 1 to 2 in/hr (2 to 5 cm/ hr) compared to 20 to
60 in/sec (50 to 150 cm/sec) (Narver 1971).
A second, and generally very minor, input of ox-
ygen into the intragravel water is oxygen carried in
by influent ground water (Vaux 1968). Sheridan
(1962) found that oxygen input by ground water in
pink salmon streams in southeast Alaska was very
small. He concluded that the major intragravel ox-
ygen source was direct diffusion from the surface
layer.
The predominant dissolved oxygen sink in an un-
polluted mountain stream, both in the surface and
intragravel water, is biochemical oxygen demand
(BOD). DO will be lost to a lesser extent to respira-
tion by larger aquatic life and plants, to the at-
mosphere by direct diffusion — if the stream is in a
state of oxygen supersaturation — and to effluent
ground water flow.
Biochemical oxygen demand imposes the
greatest drain on a stream's DO supply. The BOD
process in a mountain stream is illustrated
diagrammatically in figure IX.4. The decomposi-
tion agents (decomposers) may be separated into
two classes: dispersed and attached organisms.
Dispersed organisms flow freely within the stream;
attached organisms remain stationary, attached to
rocks and other fixed objects. Both exert an oxygen
demand. In a small forest stream, where the
gradient is high and the flow turbulent, dispersed
organisms generally predominate. In streams
where the gradient is low and there are a number of
quiescent pools, attached organisms may exert a
significant demand. In general, the decomposers
are comprised primarily of bacteria, protozoa,
fungi, and, to a lesser extent, larger aquatic life
(insects and fish).
The substrate, or food source, is composed of
suspended material (finely divided plant material),
dissolved material (nutrients and simple sugars
leached from plant material), and benthic deposits
(organic material that has settled to the stream
bottom).
Once the material is ingested, the assimilative
process is one of wet oxidation within the decom-
posers. This process may be expressed by the fol-
lowing reaction:
Substrate + 02
» C02 + H2O
(IX.6)
+ energy + other byproducts
In this process, the decomposers utilize oxygen to
break down the substrate to produce carbon diox-
ide, water, energy for growth and reproduction, and
other byproducts.
Larger aquatic life impose another sink on a
stream's dissolved oxygen supply (fig. DC.3).
Although a mountain stream may appear to be
relatively free of larger aquatic life, it generally
supports a multitude of organisms, such as snails,
DC.5
-------
Dissolved Oxygen in
Inflow Stream Water
S
Atmospheric
Oxygen
I I
Sub-Saturation
Green Plant
Photosynthesis
Super-Saturation
Dissolved Oxygen
in Outflow Water
Dissolved Oxygen
in Outflow Water
Dissolved Oxygen
in Inflow
Intragravel Water
Dissolved Oxygen
in Outflow
Intragravel Water
!u
Aquatic
Animal
Respiration
I
Dissolved Oxygen in
Intragravel Water
Influ
uent
;
I
i
Effluent
Dissolved Oxygen
in Ground Water
Biochemical
Oxygen Demand
1
JL
Green Plant
Respiration
Figure IX.3.—Sources and sinks of dissolved oxygen in a mountain stream under undisturbed conditions
(Ponce 1974b).
IX.6
-------
Agents of Decomposition
Dispersed
Organisms
Attached
Organisms
Oxygen
Supply
Energy for
Organisms
Organic
Substrate
^
«•
-M
Suspended
Material
Dissolved
Material
Benthic
Deposits
Oxidative Assimilation
Carbon
Dioxide
Water
^m
Other
Byproducts
Substrate + O? organism ».CO2 + H2O + energy + other byproducts
Figure IX.4.—The biochemical oxygen demand process in a mountain stream (Ponce 1974b).
IX.7
-------
insect nymphs, crayfish, and fish. All these
organisms require oxygen. The rate of oxygen
removal by these organisms is a function of the
species present and their environment.
The oxygen balance is an important water
quality concept. Alteration of any of the sources or
sinks will result in a new oxygen equilibrium con-
centration and may have a pronounced effect on
the aquatic life present.
DISSOLVED OXYGEN AND LOGGING
Timber harvesting can have a substantial im-
pact on the DO balance in upland streams, par-
ticularly if logging debris are allowed to enter and
remain in the stream channel. Timber harvesting
may affect dissolved oxygen concentrations in
small forest streams in several ways.
Water Temperature Increases
Logging may alter the temperature regime in a
small stream (chapter VII). Brown and Krygier
(1970) evaluated the effect of two different methods
of clearcutting on stream temperature in Oregon's
Coastal Range. They found that the maximum
temperature increased from 57° to 85° F (13.9° to
29.4° C) on the completely clearcut watershed 1
year after cutting. In terms of oxygen decrease, due
only to temperature fluctuation, the saturation
concentration of oxygen would have dropped 28
percent (from 10.3 to 7.4 mg/1). Temperature levels
in the stream draining the watershed, which was
patchcut with vegetation buffer strips left along the
channel, showed no significant change in stream
temperature due to timber harvesting, and main-
tained DO levels near those of the control stream.
Similar trends have been observed in the Ap-
palachian highlands. Eschner and Larmoyeux
(1963) report that, prior to treatment, there was lit-
tle difference between water temperatures of the
control watershed and the watershed to be entirely
clearcut. However, the first year following cutting,
the maximum water temperature measured on the
clearcut watershed was 75° F (23° C), 20° F (11°
C) greater than the maximum recorded on the con-
trol stream. In terms of DO solubility in the
stream, the saturation concentration would have
dropped 19 percent (9.0 to 7.3 mg/1).
Logging Debris
Slash is a byproduct of logging. It is composed of
limbs, branches, needles, and leaves of trees. This
debris, along with forest floor material, may ac-
cumulate in the stream channel, particularly if log
yarding across the channel is permitted. Once this
organic material enters the channel, it may
adversely affect the DO concentration in several
ways: (1) by exerting a high BOD, (2) by restricting
flow and reducing reaeration, and (3) by accen-
tuating water temperature increases.
The oxygen demand (BOD) by plant matter has
been well documented. Plant materials contain
simple sugars and other nutrients that are readily
leached in water (Currier 1974, Ponce 1974b).
Microorganisms consume these leached con-
stituents and, in turn, exert a demand on the
stream's oxygen supply. This demand for oxygen
may continue for a relatively long period.
Chase and Ferullo (1957) studied the effect of
autumn leaf fall on the oxygen concentration in
lakes and streams in the eastern United States.
After 1 year, maple leaves demanded about 750 mg
of O^/g of initial dry weight, while oak leaves and
pine needles required about 125 mg of 02/g of in-
itial dry weight. The oxygen uptake was relatively
rapid: by day 100 maple had achieved about 70 per-
cent, and oak and pine 55 percent, of the demand
exerted in 1 year.
Slack and Feltz (1968) examined the effect of leaf
fall on quality changes in a small Virginia stream.
They reported no significant change in oxygen con-
sumption as the leaf fall rate increased from 0 to
0.05 Ib/ft2/day (0 to 2 g/m2/day). As the rate in-
creased from 0.05 to 0.28 Ib/ft2/day (2 to 12 g/m2/-
day), however, there was a corresponding drop in
DO from 8 mg/1 to less than 1 mgA. Upon natural
flushing of the stream by a storm, the DO
responded by climbing to near saturation con-
centration (11 mg/1).
Ponce (1974a) determined the BOD of Douglas-
fir needles and twigs, western hemlock needles, and
red alder leaves in stream water. The oxygen de-
mand by these materials was measured for 90 days
at 68° F (20° C) and for 5 days under the condition
of temperature fluctuation similar to patterns
observed in clearcut watersheds of the Oregon
Coastal Range. Selected results of Ponce's work are
presented in tables IX.l and IX.2. It is apparent
that this material exerts a substantial oxygen de-
mand: 101, 178, and 273 mg of O^g for Douglas-fir,
IX.8
-------
Table IX.1.—Mean1 cumulative BOD in milligrams of Oz/g (dry weight) by Douglas-fir needles and twigs, western
hemlock needles, and red alder leaves in stream water at 20° C (Ponce 1974a)
Vegetation
type
Douglas-firneedles
Western hemlock needles
Red alder leaves
Douglas-fir twigs
5
63
32
79
25
10
76
88
124
47
Days
20
97
130
169
75
45
"Wn
J2/Q
99
169
239
100
60
96
176
260
—
90
101
178
273
—
'The mean of four replications for each species
Table IX.2.—Mean1 cumulative BOD in milligrams of 02/g (dry weight) by Douglas-fir, western hemlock, and red alder
leaves under conditions of temperature fluctuation (Ponce 1974a)
Vegetation
type
Douglas-fir needles
Western hemlock needles
Red alder leaves
1
46
24
72
2
62
55
131
Days
3
.... 4 r\ i
124
81
124
4
175
92
207
5
190
97
237
1The mean of three replications for each species.
western hemlock, and red alder leaves, respec-
tively, over 90 days; and 100 mg of O^g for
Douglas-fir twigs over 45 days at 20° C. This de-
mand is exerted relatively rapidly with 96, 73, and
62 percent of the 90-day demand achieved in 20
days for Douglas-fir, western hemlock, and red
alder leaves, respectively. When the temperature
fluctuated, the oxygen demand increased by a fac-
tor of 3 for each leaf type over the 5-day test period.
The toxicity of the leachate extracted from each
of these vegetative species was determined on gup-
pies and steelhead trout fry. The concentration of
leachate needed to produce toxic effects was so
high that oxygen depletion probably would be
responsible for death long before the leachate ef-
fect would.
Hall and Lantz (1969) reported the effects of log-
ging on habitat of coho salmon and cutthroat trout
in coastal streams of Oregon. Two small
watersheds were studied, one completely clearcut,
the other patchcut with buffer strips. They were
compared with a third watershed that served as a
control. Felling on the clearcut watershed began in
the spring. Timber was felled along the stream, and
logs were yarded uphill by cable across the stream
to landings. This resulted in the accumulation of
considerable quantity of debris in the channel,
which restricted flow and formed pools. The large
material remained in the channel throughout the
summer. In early fall, the channel was cleared of
the large material to permit free flow.
DO concentration was substantially reduced in
surface and intragravel waters of the clearcut
watershed (figs. IX.5 and IX.6). The DO reduction
was noted first in the intragravel water, after felling
began along the stream. A layer of debris on the
gravel and ponding of the surface water caused a
substantial decrease in the rate of oxygen transfer
from the surface to the intragravel water. This
decrease, coupled with an oxygen demand by the
decomposing debris, caused a rapid decline in DO
in the intragravel water. DO concentrations in the
surface water from late spring through most of the
summer were too low to support salmon and trout
in one-third of the streams available to the
salmonoids; juvenile coho salmon placed in live-
boxes there survived less than 40 minutes. The
lowest oxygen concentration reported, 0.6 mg/1,
was observed in a pool resulting from a dam com-
posed of debris. During this period, oxygen con-
centration of the control stream and the stream
IX.9
-------
11-
10-
9-
O —
7 -
6 -
5 -
4 -
3 -
2 -
1 _
n
iFC ' '
*x 4 /
M T *' *V'
i-4-4- ?
May
i i i i i i i i
Ł
/
-
-
-
-
_
-
_
i
E
z "-
Uj 10-
^ 7 -
Q 4-
LU 3 -
> 2-
-J 1 -
° °
IFC
H i J
\ / .
-i ~\ i
i i
WEIR 305
CO
0 11-
10-
q
8 -
7 -
6 -
5 -
4 -
3 -
2 -
1 -
0
1 ' '
FC
L }
T\ i
Nxl /
I
1
WEIR 305
1 1 i '..
y_
r T/" -
- ^•
^ /
X /
rt
i
0 WEIR 305
i i f 1 1 1 1
-
-
, T T T/I
/X>*N>^ 1 « ~
T"~~r~ ~*
-
_
August
_
iii i
610 915183
11-
10-
9-
8-
7-
6-
5-
4-
3 —
2-
* __
I i i i i i iiir
IFC Z
T T
f '"-•"- -9
' ' ^^^" " 1^ '
^~\<'' I ""
->- -
-L -
_
September _
_
1 I i i i i i i
11-
10-
9-
8-
7-
6-
5
4-
3 —
2-
1 —
'I'l',
T T T
J~ T '"K^>
I J_
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» ^
^-~~,
-
-
-
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-
.
-
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October
ill i
0 WEIR 305 610 915 1830
DISTANCE UPSTREAM FROM WEIR (meters)
Figure IX.5.—Surface dissolved oxygen levels (mean and range) taken twice weekly in the clearcut
watershed (Needle Branch) and control watershed (Flynn Creek) during the year of timber harvest
(1966). Sampling on Needle Branch occurred at 500 feet (152 m) in the area accessible to salmon and
6,004 feet (1,830 m) (upper edge of clearcut). Samples from Flynn Creek were taken only at the weir (Hall
and Lantz 1969).
draining the patchcut watershed remained at near
saturation levels. Upon removal of large debris
from the channel and establishment of free-flowing
conditions, the DO concentration rapidly returned
to near pre-logging conditions in the surface water.
Intragravel oxygen concentrations, however,
remained about 3.0 mg/1 lower than the pre-logging
concentrations for the next 2 years, and continued
to decline over the next 4 years to levels less than
2.0 mg/1 at several locations.
Although a portion of the intragravel DO decline
was attributed to long-term BOD by organic mat-
ter that intruded the gravel, it was concluded the
major cause for the prolonged reduction was
IX. 10
-------
restriction of water flow through the gravel due to
sedimentation in the gravel bed. Garvin (1974)
found that, in the absence of sedimentation, log-
ging debris intrusion into streambeds resulted in a
large, but short-term, reduction of DO concentra-
tion in the gravel. Within 6 months, DO levels
returned to almost normal.
During this period, winter freshets provide the
streams the energy to flush the material through
the system. However, if the material is deposited
between early spring and late summer, serious ox-
ygen deficit is much more likely. During this
period, the streams are generally at low flow and do
not have sufficient energy to transport the debris.
It is apparent that logging debris may be respon-
sible for severe oxygen deficits within small forest
streams. However, it should be noted that the pol-
lution impact of this material, particularly the
finely divided debris, depends not only on the
amount that enters the stream, but also the season
it enters the stream. Debris deposited in an Oregon
Coastal Range stream between early fall and late
winter generally caused only minor oxygen deficit.
PREDICTING DISSOLVED OXYGEN
DEFICITS, THE DO SAG METHOD
Berry (1975) developed a working computer
model to predict the impact of logging debris on
dissolved oxygen concentrations in small forest
streams. Since this model appears to yield reliable
results, it can be used to predict DO concentration
12-
O)
E, ~
Z 8-
LU
O _
X
0 6-
Q
HI —
d 4-
CO
CO _
Q
2-
o
I \
i
I
[
1
1 c
1 1
100 44(
D 4
.
:
7!
5 6
[
-
0(
) 6
*
r-
I
3
r
• Mean 1 1965-66
Range J (N=9)
O Mean 1 1966-67
Range / (N=13)
I I
D 775 SURFACE
SAMPLING STATIONS
Figure IX.6.—Intragravel dissolved oxygen levels in the clearcut watershed (Needle Branch) from
December 1965 to May 1966 (before logging). (All standpipes in Needle Branch were removed during
logging; the six for which data are shown were replaced in their previous locations). Surface dissolved
oxygen levels are shown for comparison (Hall and Lantz 1969).
IX. 11
-------
for resource management decisions. However, if
only a coarse estimate of the oxygen deficiency is
required, it may be obtained by using the DO sag
method developed by Streeter and Phelps (1925).
The numerous limitations associated with this
method that greatly affect the accuracy of the
prediction will be noted later.
The DO sag concept is illustrated in figure DC.7.
It is assumed that the rate change in oxygen deficit
is governed by two independent reactions which oc-
cur simultaneously: reaeration and biochemical ox-
ygen demand (depletion). Each of these processes,
in turn, may be described by a differential equa-
tion.
Q.
g 10
0
2
O
U-
20
1 1 ' I" I
DISSOLVED
OXYGEN SAG •
/I I .I I I I I I
20
10 1
10
TIME, days
Figure IX.7—The dissolved oxygen sag.
In the reaeratation equation, it is assumed that
rate of oxygen absorption by the water is propor-
tional to the oxygen deficit in the water. This rela-
tion may be expressed as:
ar=
(DC.7)
where:
D = the oxygen deficit in mg/1
t = time in days, and
K2 = is the reaeration constant (base e) in
units of I/day.
In the depletion equation, it is assumed that the
rate of biochemical oxygen demand (BOD) due to
biochemical oxidation is proportional to the
amount of BOD present. This may be expressed as:
- KT
dt ~ ~KlL
(IX.8)
where:
L = the BOD concentration in mg of (Vg,
Ki = the BOD rate coefficient (base e) in units
of I/day, and
t = is as previously defined.
Equation IX.8 also may be expressed in terms of
oxygen deficit, D. Since BOD concentration is
measured in terms of the quantity of oxygen con-
sumed, it follows that the rate change in BOD is
equal to the rate of oxygen depletion. The rate of
oxygen depletion may be expressed as the rate
change in oxygen deficit:
dt
dD
dt
(IX.9)
Substituting equation IX.8 in IX.9 yields equation
IX.10:
dD
dt
= K,L
(IX.10)
Equations IX.7 and DC. 10 may be combined and
solved for D, which enables the calculation of ox-
ygen deficit at any given time, resulting in equation
IX. 11:
D = ?L- [exp (-K,t) - exp (-K2t)]
K2-Ki
+ Da exp (-K2t)
(IX.ll)
where:
La and Da are, respectively, the initial BOD con-
centration and initial oxygen saturation deficit in
units of milligrams of Oz/1 at time (t) equal to 0,
exp is the base of natural logarithms, and the
remaining terms are as previously defined. Equa-
tion DC. 11 is commonly referred to as the Streeter-
Phelps equation, and may be used to predict any
point on the dissolved oxygen sag curve (fig. DC.7).
Of particular interest is the point of maximum
deficit, Dc (mg of O2/1) — the lowest point in the
DO sag curve — and the time it occurs, tc (days).
The point of maximum deficit may be calculated
by equation IX. 12 developed by Fair (1939):
Ki
Dc = ~La exp (-
(DC.12)
DC. 12
-------
The critical time, tc, is obtained from equation
IX. 13 developed by Fair (1939):
Ki
tc-K,-Ki
ln
Da(K2-
(K2-Ki)"|
KiLa J
(IX.13)
All terms in equations IX. 12 and IX.13 are as
previously defined.
Predicting Components Of The DO Sag Method
Although the DO sag method appears to be sim-
ple to apply, it is difficult to obtain reliable results
because of the lack of accurate values for Ki, Kz,
and La. Berry (1975) suggests the following equa-
tions to predict these components.
The reaeration rate constant. — The reaera-
tion rate constant can be predicted with equation
IX.14 developed by Holtje (1971):
fT—201
K2(T) = 1.016 [181.6 E
- 1657 S + 20.87]
(IX.14)
where:
K2(T)= the reaeration rate constant (I/day) at the
water temperature T (°C),
E = energy of dissipation (ftVsec3 or mVsec3),
and
S = the average channel slope (ft/ft or m/m).
The energy of dissipation can be calculated by:
E = (S)(U)(g) (IX.15)
where:
U = the average velocity (ft/sec or m/sec), and
g = the gravitational acceleration constant
(32.2 ft/sec2 or 980 cm/sec2).
The leachate BOD rate constant. — The
leachate BOD rate constant, KI(T) (liter/day), can
be determined by the set of equations developed by
Zanoni (1967):
K1(T) = 0.796 [1.126(T-20)K1(20)];
2° < T < 15° C
K1(T) = 1.000 [1.047(T-20)K1(20)];
15°
-------
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
The applications of the DO sag method have
been discussed earlier. However, the method has
several important limiting factors. The oxygen sag
method does not account for the following:
1. The continuous redistribution of both the
BOD and oxygen by the effect of longitudinal
dispersion.
2. Changes in channel configuration that alter
the characteristics of surface turbulence and
the reaeration rate, K2.
3. Diurnal variation in oxygen content and water
temperature.
4. The variation of Ki over time.
5. The removal of oxygen from the water by dif-
fusion into the intragravel layer.
6. The addition of BOD below the point of
reference.
7. The effect of suspended and dissolved sub-
stances on the rate of diffusion of oxygen from
the surface into the main body of the stream.
8. Nitrogenous BOD (the method assumes
nitrogenous BOD does not occur).
9. Ponding.
IX. 14
-------
CONCLUSIONS
Changes in dissolved oxygen concentration in
streams resulting from silvicultural activities
usually can be linked to changes in stream
temperature and introduced organic debris.
Control practices and abatement goals that meet
temperature and sediment standards will also
minimize the reduction of dissolved oxygen.
Introduced organic matter may contribute ad-
ditional stress on dissolved oxygen concentration
beyond that produced by increased water
temperature. Primarily, the magnitude of the im-
pact of organic matter on dissolved oxygen in-
creases with:
1. The amount and type of organic debris enter-
ing the stream either directly or indirectly
through runoff;
2. The extent to which the debris dams the
stream course and produces pools, thus
facilitating heating and reduction of reaera-
tion; and
3. The length of time the debris remains in the
stream water.
Steep slopes near the stream channel increase
the probability of debris washoff, and a decrease in
the stream channel gradient reduces the rate of
reaeration.
Introduction of solid organic debris during
silvicultural activities can be minimized or
eliminated. Finer organic particles normally will
enter a stream along with the surface eroded
materials. For organic material to enter the stream
via surface erosion in sufficient quantity to
adversely affect the aquatic ecosystem, the quan-
tity of eroded soils would have to be so large that it
would present a problem in itself, overshadowing
any deterioration of water quality due to the
organic matter component.
Large debris can be prevented from entering the
stream by felling trees away from the stream, by
avoiding the stream in all skidding operations,
and/or by leaving an adequate streamside zone.
Froehlich (1976) found accelerated debris loading
through logging to be most strongly related to the
timber felling process. Conventional felling
resulted in a fivefold increase in organic loading,
whereas directional felling only doubled the load.
Streamside zones provided a debris barrier that
limited or totally prevented the loading increase,
with effectiveness in restricting organic loading
varying with width of the area.
Large debris deposited in a stream during a
silvicultural activity normally should be removed
as soon as possible. However, some large debris
within a watercourse can provide stable and
diverse habitats for biota. Removal of debris that
have been in position for any extended period and
have trapped considerable sediment normally
should not be undertaken until the full impact (loss
of habitat, increased turbidity, realignment of
stream, etc.) is evaluated. A general policy for
removal of all debris in a stream is unreasonable
and could result in damage to water quality and
aquatic habitat (Triska and Sedell 1977).
IX.15
-------
LITERATURE CITED
American Public Health Association, Inc. 1971.
Standard methods for examination of water and
waste water. 13th ed. Washington, D. C. 874 p.
Berry, J. D. 1975. Modeling the impact of logging
debris on the dissolved oxygen balance of small
mountain streams. M.S. thesis. Oreg. State
Univ., Corvallis.
Brown, G.W., and J. T. Krygier. 1970. Effects of
clear-cutting on stream temperature. Water
Resour. Res. 6(4):1133-1139.
Camp, T. R. 1965. Field estimates of oxygen
balance parameters. Proc. Am. Soc. Civ. Eng.
91(SA5):1.
Chase, E. S., and A. F. Ferullo. 1957. Oxygen de-
mand exerted by leaves stored under water. J.
New Eng. Water Works Assoc. 71:307-312.
Davison, R. C., W. P. Breese, C. E. Warren, P
Doudoroff. 1959. Experiments on the dissolved
oxygen requirements of cold water fishes. Sewage
and industrial wastes. 31:950-966.
Eschner, A. R., and J. Larmoyeux. 1963. Logging
and trout: Four experimental forest practices
and their effect on water quality. Prog. Fish Cult.
25:59-67.
Fair, G. M. 1939. The dissolved oxygen sag — an
analysis. Sewage Works J. 11:445-461.
Froehlich, H. A. 1976. Accumulation of large debris
in forest streams before and after logging. For.
Eng. Dep., Oreg. State Univ., Corvallis. 10 p.
Garside, E. T. 1966. Effects of oxygen in relation to
temperature on the development of embryos of
brook trout and rainbow trout. J. Fish, Res.
Board Can. 23:1121-1134.
Garvin, W. F. 1974. The intrusion of logging debris
into artificial gravel streambeds. Water Resour.
Res. Inst., Oreg. State Univ., Corvallis. WRRI-
27.
Hall, J. D., and R. L. Lantz. 1969. Effects of log-
ging on habitat of coho salmon and cutthroat
trout in coastal streams. In Symp. salmon and
trout in streams. T. G. Northcote, ed. Univ. B.
C., Vancouver, p. 355-375.
Hem, J. D. 1970. Study and interpretation of the
chemical characteristics of natural water. U.S.
Geol. Surv. Water Supply Pap. 1473. 363 p.
Herrmann, R. B., C. E. Warren, and P. Doudoroff.
1962. Influence of oxygen concentration on the
growth of juvenile coho salmon. Trans. Am. Fish.
Soc. 89:17-26.
Holtje, R. K. 1971. Reaeration in small mountain
stream. Ph.D. diss. Oreg. State Univ., Corvallis.
146 p.
Jones, J. R. E. 1952. The reactions offish to water
of low oxygen concentration. J. Exp. Biol.
29:403-415.
Lantz, R. L. 1971. Guidelines for stream protection
in logging operations. Oreg. State Game Comm.,
Portland. 29 p.
McKee, J. E., and H. W. Wolf. 1963. Water quality
criteria. Calif. State Water Resour. Control
Board, Resour. Agency Calif., Sacramento. 548
P-
Narver, D. W. 1971. Effects of logging debris on fish
production. In Proc. symp. for. land uses and
stream environ. J. T. Krygier and J. D. Hall, eds.
Oreg. State Univ., Corvallis. p. 100-111.
Ponce, S. L. 1974a. The biochemical oxygen de-
mand of Douglas-fir needles and twigs, western
hemlock needles, and red alder leaves in stream
water. M.S. thesis. Oreg. State Univ., Corvallis.
141 p.
Ponce, S. L. 1974b. The biochemical oxygen de-
mand of finely divided logging debris in stream
water. Water Resour. Res. 10(5):983-988.
Shellford, V. E., and W. C. Allee. 1913. The reac-
tions of fishes to gradients of dissolved at-
mospheric gases. J. Exp. Zool. 14:207-266.
Sheridan, W. L. 1962. Waterflow through a salmon
spawning riffle in Southeastern Alaska. U.S.
Fish and Wildl. Serv., Spec. Sci. Rep., Fish. No.
407, 20 p.
Shumway, D. L., C. E. Warren, and P. Doudoroff.
1964. Influence of oxygen concentrations and
water movement on the growth of steelhead trout
and coho salmon embryos. Trans. Am. Fish. Soc.
93:342-356.
IX.16
-------
Slack, K., and H. R. Feltz. 1968. Tree leaf control
on low flow water quality in a small Virginia
stream. Environ. Sci. and Tech. 2(2):126-131.
Streeter, H. W., and E. B. Phelps. 1925. A study of
the pollution and natural purification of the Ohio
River. Publ. Health Bull. 146. U.S. Public
Health Serv. U.S. Dep. Health, Educ., and
Welfare, Washington, D. C. 75 p.
Swanston, F, and T. Dyrness. 1973. Stability and
steepland. J. For. 71(5):264-269. [Illus.]
Triska, F., and J. Sedell. 1977. Accumulation and
processing of fine organic debris. Dep. Fish, and
Wildl., Oreg. State Univ., Corvallis. 13 p.
Vaux, W. G. 1968. Interchange of stream and in-
tragravel water in a salmon spawning riffle. U.S.
Fish, and Wildl. Serv. Spec. Sci. Rep., Fish. No.
405. 11 p.
Whitmore, C. M., C. E. Warren, and P. Doudoroff.
1960. Avoidance reactions of salmonoid and
centrarchid fishes to low oxygen concentrations.
Trans. Am. Fish. Soc. 89:17-26.
Zanoni, A. E. 1967. Waste water deoxygenation at
different temperatures. Water Res. 1:543-566.
IX. 17
-------
Chapter X
NUTRIENTS
this chapter was prepared by the following individuals:
John B. Currier
Coordinator
with major contributions from:
Arthur P. O'Hayre
X.i
-------
CONTENTS
Page
INTRODUCTION X.I
DISCUSSION X.2
SOLUBLE COMPONENT EVALUATION X.2
The Loehr Study X.2
The Hubbard Brook Study X.3
INSOLUBLE COMPONENT EVALUATION X.4
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS X.7
CONCLUSIONS X.7
LITERATURE CITED X.8
APPENDIX X.A: DETAILED DISCUSSION OF THE
NUTRIENT CYCLE X.12
INPUT TO THE NUTRIENT CYCLE X.12
Atmosphere X.12
Atmospheric Nitrogen X.12
Atmospheric Phosphorus X.12
Soil and Rock X.15
Nitrogen Inputs From Soil And Rock X.15
Phosphorus Inputs From Soil And Rock X.15
Forest Fertilization X.15
THE INTRACYCLE PROCESS X.15
Intracycle Nitrogen X.15
Mineralization X.15
Nitrification X.16
Intracycle Phosphorus X.18
Organic Phosphorus X.18
Inorganic Phosphorus X.18
OUTPUTS FROM THE NUTRIENT CYCLE X.19
Dissolved Materials X.19
Removal Of Vegetation X.19
Nitrogen Outflux X.19
Pathways Of Nitrogen Removal X.19
Nitrification And Mineralization X.20
Phosphorus Outflux X.20
APPENDIX X.B: EIGHTEEN STUDIES OF NUTRIENT
RELEASES FOLLOWING SILVICULTURAL ACTIVITIES X.21
X.ii
-------
LIST OF FIGURES
Number Page
X.I. —Range of total N and P concentrations found in various non-point
sources X.2
X.2. —Summary of studies undertaken to quantify nitrogen release following
silvicultural activities X.3
X.3. —Percent nitrogen (N) in surface foot of soil X.5
X.4. —Percent phosphorus (P205) in surface foot of soil X.6
X.A.I.—Biochemical cycle for nitrogen in a forest X.13
X.A.2.—Nitrogen (NH+4N-N and NOs-N) in precipitation X.14
X.A.3.—Simplified nitrogen cycle showing N utilized in the nitrate (NO :0 and
ammonium (NHt) forms and acid and base relations associated with
the various processes X.16
X.A.4.—Flow model of nitrogen cycling in an oak-hickory forest at Coweeta Ex-
perimental Forest, North Carolina X.17
X.A.5.—General estimate of the relative proportion of phosphorus present in
each component of the geochemical, biochemical, and biogeochemical
cycles of loblolly pine plantation ecosystem X.18
X.iii
-------
LIST OF STUDIES
Number Page
X.I. —Hubbard Brook Experimental Forest, New Hampshire X.22
X.2. —Hubbard Brook Experimental Forest, New Hampshire X.23
X.3. —White Mountain National Forest, New Hampshire X.24
X.4. —White Mountain National Forest, Upper Mill Brook, New Hampshire X.25
X.5. —Leading Ridge Watershed 2, Pennsylvania State University X.26
X.6. —Fernow Experimental Forest, West Virginia X.27
X.7. —Coweeta Hydrologic Laboratory, North Carolina X.28
X.8. —USAEC's Savannah River Plant, Aiken, South Carolina X.29
X.9. —Grant Memorial Forest, Georgia X.30
X.10.—H.J. Andrews Experimental Forest, Eugene, Oregon X.31
X.11.—Bull Run Watershed, Portland, Oregon X.32
X.12.—South Umpqua Experimental Forest, 50 Kilometers ESE Rosberg,
Oregon X.33
X.13.—Alsea Basin, Oregon Coast Range X.34
X.14.—Bitterroot National Forest, Montana X.35
X.15.—Priest River Experimental Forest, Idaho X.36
X.16.—Marcell Experimental Forest, Minnesota X.37
X.17.— West Central Alberta, Canada X.38
X.18.—Dennis Creek, Okanagan Valley, British Columbia X.39
X.iv
-------
INTRODUCTION
Much concern has been expressed over nutrient
additions to streams following silvicultural ac-
tivities. Of the nutrients, nitrogen and phosphorus
generally have the greatest impact upon water
quality. Introduction of nitrogen and phosphorus to
forest streams may result in enrichment of the
receiving waters (i.e., eutrophication), as these two
chemicals are normally limiting factors in the
production of aquatic vegetation. Accelerated ad-
ditions of nutrients to streams following
silvicultural activities may result in accelerated
eutrophication and adversely affect stream water
quality. In other cases, however, enrichment of
streams may be beneficial, particularly in streams
relatively devoid of dissolved nutrients in their
natural state.
Streams may show symptoms of overenrich-
ment; however, there is usually minimal oppor-
tunity for a buildup of these nutrients in the stream
system because of the continual transport of water
and the normally brief period of increased nutrient
influx to the stream. Other nutrients rarely cause
water quality problems. This discussion, therefore,
is limited to nitrogen and phosphorus. (For ad-
ditional information on the nutrient cycle, see ap-
pendix X.A.)
Research conducted throughout the United
States and Canada has found that nutrient outflux
following silvicultural activity usually does not
result in any measurable deterioration of water
quality. The most notable exception is the Hub-
bard Brook experimental watershed in New
Hampshire. This was, however, an extreme ex-
perimental treatment and not a normal
silvicultural activity. Based upon existing research,
it can be concluded that nutrient release associated
with silvicultural activities may occur; but
resulting concentrations of nitrogen and
phosphorus will normally not be great enough to
adversely affect the water quality of the receiving
forest streams.
Quantification of nitrogen and phosphorus influx
into a watercourse, given a specific site and
proposed silvicultural activity, is not possible at
this time. There are no available models capable of
accurately predicting the total nutrient addition to
streams due to silvicultural activities. The soluble
component of the nutrient outflux can be examined
presently only through a comparison of those
nutrients contributed by silvicultural activities
with those nutrients contributed by other land
management practices. The insoluble component
can be estimated with cautious use of one available
model.
X.I
-------
DISCUSSION
SOLUBLE COMPONENT EVALUATION
The Loehr Study
Numerous studies have been made of the
relationship between streamflow and chemical load
in the stream. The dilution theory principle (an
average relationship between dissolved chemical
load and stream discharge) is now widely accepted.
A number of models have been proposed to
describe the dilution theory (Carson and Kirkby
1962, Hendrickson and Krueger 1964, Toler 1965,
Hem 1970, Hall 1971, Betson and McMaster 1975).
However, this theory assumes both a relatively con-
stant source of dissolved nutrients and a constant
rate of release by weathering, independent of the
volume of water passing through the soil. These
models, therefore, are not suitable for evaluating
nutrient outflux due to silvicultural activity
because release is variable, depending upon vegeta-
tion uptake and microbiological processes.
In lieu of an adequate model, an evaluation of
the relative impacts of non-point source nutrient
pollution from silvicultural activities and other
land uses has been published by Loehr (1974) and
is presented here. Loehr compared available infor-
mation on characteristics and relative magnitudes
of certain non-point sources entering surface waters
and commented on the feasibility of controlling
these sources. Concentrations of organic and in-
organic compounds representative of the range that
could be anticipated from various non-point
sources were compared. Loehr's results are dis-
played in figure X.I and indicate that concentra-
tions of nitrogen and phosphorus lost from forest
lands approximate those found in precipitation.
Additional data to support Loehr's findings are
presented in figure X.2, and appendix X.B. Loehr's
findings have been confirmed by all the data with
the exception of the data from the Hubbard Brook
experiment.
3 .0
10.0
5.0
_
o>
E
z" 1.0
o
INCENTRA1
0
en
O
0 0.1
0.05
0.01
—
—
= Q
~ N
Ic a?
on i- a
_ u
a
- N
I I I I I
Ditation .
.•
U
— 0
— a
|
N
i C
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~ P
ED
•
.).
p
J
4)
u
«*-
(fl
N
P
™ t\
\
1
s
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\;
V
\
N
k
8
«•—
3 i— i
-
p
^
4
j>
^
I04r
H
N
P
103
100
™
N |
N
D°
L ||
a. n
§•- -D O O
c— "° S * *
— c -I n _« Ł «Ł
•| Hll §iS
k.o> i_ w t_ i- (Oca
-tt OQ 30 S
-------
X
O)
O
Ul
o
8
10.0
5.0
2.0
1.0
0.5
0.2
0.1
0.05
0.02
0.01
w iS
0 Ł
u_ "-
22
*j O O O
w'Swo'iicSiotoSi'S o
>25Q.Z«Z75>2 "-
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-------
This study represents the application of an ex-
treme treatment and not a normal silvicultural ac-
tivity. Its results have been verified by other
studies, although the magnitude of the changes in
nutrient release has not been as great in other
studies. The conditions under which the Hubbard
Brook study was conducted show that significant
water quality degradation is possible if (1) all
vegetation is killed, (2) revegetation is prevented
by application of herbicides, and (3) the soils are
coarse textured, with a low cation exchange
capacity. These conditions do not normally exist
under prevalent land management practices.
Silvicultural activities are presently constrained so
that devegetation of a complete watershed is not
generally a viable land management option. In ad-
dition, the application of herbicides to prevent
revegetation is contrary to normal forestry opera-
tions. Finally, many forest soils have a greater
capacity to fix nitrogen and phosphorus, or
otherwise prevent the loss of nutrients from a site.
INSOLUBLE COMPONENT EVALUATION
Nitrogen in the soil is primarily organically
bound and is not readily transported in solution.
Nitrate and ammonium ions are available and can
be transported in solution in the soil water and
eventually reach a watercourse. The nitrate ion
(NO 3) is the principal dissolved nitrogen form lost
from the forest ecosystem; the ammonium ion
(NHt) is ordinarily strongly adsorbed to exchange
surfaces and is not readily lost. However, these
available forms of nitrogen — NO 3 and NHIj —
make up only a small proportion of the total
nitrogen present in soil.
Phosphorus in soil may be present in the organic
or inorganic form. The soluble inorganic forms
derived from chemical weathering or decomposi-
tion of organic matter are readily immobilized in
the soil and are not easily leached from it. The
primary mode of transport for organic forms of both
nitrogen and phosphorus is surface erosion.
Outflux of insoluble, precipitated or adsorbed,
organic nitrogen and total phosphorus can be es-
timated in a manner proposed by Midwest
Research Institute in their report to EPA (McElroy
and others 1976). As proposed by Midwest,
"loading" functions for organic nitrogen and total
phosphorus can be estimated based upon the "sedi-
ment loading" function derived from a modified
version of the Universal Soil Loss Equation.
Concentrations of total nitrogen and phosphorus in
the surface foot of soil can be obtained from ex-
isting general maps (figs. X.3 and X.4), from
regional or local Soil Conservation Service data, or
by actual measurement. The Midwest model in-
cludes an enrichment ratio that is based upon the
soil texture and organic matter content. The
general loading function is:
where:
Y =
a =
S =
c =
Y = aSCr
total loading (organic and adsorbed
nitrogen or total phosphorus) from sur-
face erosion, Ibs/ac/yr (kg/ha/yr),
dimensional constant (20 for English
units or 10 metric units),
sediment loading from surface erosion,
tons/ac/yr (MT/ha/yr),
total (organic nitrogen or total
phosphorus) concentration in surface foot
of soil, g/lOOg,
enrichment ratio, nitrogen values
generally range from 2 to 5, and
phosphorus values range from 1 to 3, with
an average value of 1.5. The enrichment
ratio is the concentration of nitrogen or
phosphorus in the eroded material
divided by its concentration in the soil
proper (Massey and others 1953,
Stoltenberg and White 1953).
X.4
-------
01
NITROGEN
Percent N
Highly Diverse
Insufficient Data
Figure X.3.—Percent nitrogen (N) in surface foot of soil (after Parker 1946).
-------
><
\
PHOSPHORIC ACID
Percent ?2O5
0.0-0.04
[ JO. 05 -0.09
0.10-0.19
0.20-0.30
Figure X.4.—Percent phosphorus (PzOs) in surface foot of soil (after Parker 1946).
-------
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
The insoluble component model represents the adequately tested in forested situations and should
current state-of-the-art; however, it has not been be used with caution.
CONCLUSIONS
Reinhart (1973), Loehr (1974), Patric and Smith time because the concentrations and yields of
(1975), and Sopper (1975) evaluated available constituents are comparable to those of
studies and concluded that normal silvicultural precipitation. These two non-point sources,
operations do not raise nitrogen and phosphorus forest runoff and range land runoff, may
concentrations above public health standards for generally be considered as background sources
drinking water. Loehr (1974) concluded: unless current practices or available data
Control of forest land runoff and range land change drastically.
runoff does not appear to be necessary at this
X.7
-------
LITERATURE CITED
Alexander, M. 1967. Introduction to soil
microbiology. 472 p. John Wiley & Sons, Inc.,
New York.
Aubertin, G. M., and J. H. Patric. 1972. Quality
water from clearcut forest land? North. Logger
and Timber Process., March 1972. p. 14-15, 22-
23.
Aubertin, G. M. and J. H. Patric. 1974. Water
quality after clearcutting a small watershed in
West Virginia. J. Environ. Qual. 3(3):243-249.
Bateridge, T. 1974. Effects of clearcutting on water
discharge and nutrient loss, Bitterroot National
Forest, Montana. M.S. Thesis. Off. Water
Resour. Res., Univ. Montana, Missoula. p. 36,
38, 42-46.
Betson, R. P., and W. M. McMaster. 1975. Non-
point source mineral water quality model. J.
Water Pollut. Control Fed. 47(10):2461-2473.
Bormann, F. H., and G. E. Likens. 1967. Nutrient
cycling. Sci. 155(3761):424-429.
Bormann, F. H., and G. E. Likens. 1970. The
nutrient cycles of an ecosystem. Sci. Am.
223(4):92-101.
Brown, G. W., A. R. Gahler, and R. B. Marston.
1973. Nutrient losses after clear-cut logging and
slash burning in the Oregon coast range. Water
Resour. Res. 9(5): 1450-1453.
Carson, M. A., and M. J. Kirkby. 1972. Hillslope
form and process. 475 p. Cambridge Univ. Press,
London.
Coffee, R. C., and W. V. Bartholomew. 1964. Some
aspects of ammonia sorption by soil surfaces.
Soil Sci. Soc. Am. 28(4):485-490.
Colman, E. A. 1953. Vegetation and watershed
management. 412 p. Ronald Press Co., New
York.
Corbett, E. S., J. A. Lynch, and W. E. Sopper.
1975. Forest-management practices as related to
nutrient leaching and water quality. In
Conference on non-point sources of water pollu-
tion proceedings. Va. Water Resour. Res. Center;
Va. Polytech. Inst. and State Univ. [Blacksburg,
Va., May 1, 2, 1975.] p. 157-173.
Cramer, 0. P., ed. 1974. Environmental effects of
forest residues management in the Pacific
Northwest — a state-of-knowledge compendium.
USDA For. Serv. Gen. Tech. Rep. PNW-24, 34 p.
Pac. Northwest For. and Range Exp. Stn.,
Portland, Oreg.
Cravens, J. H. 1974. Personal communication. Reg.
For., USDA For. Serv., East. Reg., Milwaukee,
Wis.
DeBell, D. S., and C. W. Ralson. 1970. Release of
nitrogen by burning light forest fuels. Soil Sci.
Soc. Am. 34(6):936-938.
DeByle, N. V., and P. E. Packer. 1972. Plant
nutrient and soil losses in overland flow from
burned forest clearcuts. Natl. Symp. Watersheds
Trans, p. 296-307.
Dochinger, L. S., and T. A. Seliga. 1976.
Proceedings of the first international symposium
on acid precipitation on the forest ecosystem.
USDA For. Serv. Gen. Tech. Rep. NE-23,1074 p.
Northeast. For. Exp. Stn., Broomall, Pa.
Douglass, J. E., and W. T. Swank. 1975. Effects of
management practices on water quality and
quantity: Coweeta Hydrologic Laboratory,
North Carolina. USDA Gen. Tech. Rep. NE-13,
p. 1, 10, 13. Northeast Exp. Stn., Broomall, Pa.
Feth, J. H. 1966. Nitrogen compounds in natural
water — a review. Water Resour. Rev. 2(l):41-58.
Fredriksen, R. L. 1971. Comparative water quality
— natural and disturbed streams. In Forest land
uses and stream environment symposium
proceedings. For. Ext., Oreg. State Univ. [Cor-
vallis, Oreg., October 1970.] p. 125-137.
Fredriksen, R. L. 1977. Personal communication.
Res. Soil Sci., For. Sci. Lab., Corvallis, Oreg.
Fredriksen, R. L., D. G. Moore, and L. A. Norris.
1975. Impact of timber harvest, fertilization, and
herbicide treatment on stream water quality in
the Douglas-fir regions. Proc. 4th North Am. For.
Soils Conf., Laval Univ., Quebec City, Can. p.
283-313.
X.8
-------
Greenwood, D. J. 1962. Measurement of microbial
metabolism in soil. In The ecology of soil
bacteria. T.R.G. and D. Parkinson, eds. p. 138-
157. Univ. Toronto Press, Can.
Grier, C. C. 1975. Wildfire effects on nutrient dis-
tribution and leaching in a coniferous ecosystem.
Can. J. For. Res. 5(4):599-607.
Hall, F. R. 1971. Dissolved solids — discharge
relationships, 2 applications to field data. Water
Resour. Res. 6(3):591-601.
Hem, J. D. 1970. Study and interpretation of the
chemical characteristics of natural water. 2nd
ed. U.S. Geol. Surv. Water Supply Pap. 1473.
363 p.
Hendriksen, G. E., and R. A. Krueger. 1964.
Geochemistry of natural waters of the Blue Grass
Region, Kentucky. U.S. Geol. Surv. Water Sup-
ply Pap. 1700. 136 p.
Hetherington, E. D. 1976. Dennis Creek: A look at
water quality following logging in the Okanagan
Basin. Environ. Can. For. Serv. p. 1-28.
Hewlett, J. D. 1977. Personal communication.
Prof. For. Hydrol., Sch. For. Resour., Univ. Ga.,
Athens.
Hobbie, J. E., and G. E. Likens. 1973. Output of
phosphorus, dissolved organic carbon, and fine
particulate carbon from Hubbard Brook
watersheds. Limnol. and Oceanogr. 18(5): 734-
742.
Hornbeck, J. W., G. E. Likens, R. S. Pierce, and F.
H. Bormann. 1973. Stripcutting as a means of
protecting site and streamflow quality when
clearcutting northern hardwoods. 4th North Am.
For. Soils Conf., Quebec, Can. p. 209-225.
Johnsen, D. R. 1953. A laboratory study of the
decomposition of vegetable debris in relation to
the formation of raw humus. Plant and Soil
4:345-369.
Jorgenson, J. R., C. G. Wells, and L. Metz. 1975.
The nutrient cycle: Key to continuous forest
production. J. For., July. p. 400-403.
Junge, C. E. 1958. The distribution of ammonia
and nitrate in rain water over the United States.
Trans. Am. Geophys. Union 39(2) :241-248.
Keeney, D. R. 1973. The nitrogen cycle in
sediment-water systems. J. Environ. Qual.
2(l):15-29.
Kormondy, E. J. 1976. Concepts of ecology.
Prentice-Hall, Inc., Englewood Cliffs, N.J.
Kramer, J. R., S. E. Herbes, and H. E. Allen, eds.
1972. Phosphorus: Analysis of water, biomass,
and sediment. In Nutrients in natural waters, p.
51-101. Wiley-Intersci., John Wiley & Sons, Inc.,
New York.
Lewis, W. M., Jr. 1974. Effects of fire on nutrient
movement in a South Carolina pine forest. Ecol.
55:1120-1127.
Likens, G. E. 1976. Acid precipitation. Chem. and
Eng. News 54(48):29-44.
Likens, G. E., F. H. Bormann, N. M. Johnson, and
others. 1970. Effects of forest cutting and her-
bicide treatment on nutrient budgets in the Hub-
bard Brook watershed ecosystem. Ecol. Monogr.
40(l):23-47.
Likens, G. E., F. H. Bormann, J. S. Eaton, and
others. 1976. Hydrogen ion input to the Hubbard
Brook Experimental Forest, New Hampshire,
during the last decade. In Proceedings first inter-
national symposium on acid precipitation and
the forest ecosystem. USDA Serv. Gen. Tech.
Rep. NE-23, p. 293. Northeast. Exp. Stn.,
Bloomall, Pa.
Loehr, R. C. 1974. Characteristics and comparative
magnitude of non-point sources. J. Water Pollut.
Control Fed. 46(8): 1849-1872.
Lutz, H. J., and R. F. Chandler, Jr. 1961. Forest
soils. 514 p. John Wiley and Sons, Inc., New
York and London.
McCarty, P. L., chairman. 1970. Chemistry of
nitrogen and phosphorus in water. J. Am.
Waterworks Assoc. 62:127-140.
McElroy, A. D., S. Y., Chiu, J. W. Nebgon, and
others. 1976. Loading for assessment of water
pollution from non-point sources. U.S. Environ.
Prot. Agency. Off. Res. and Dev., Washington,
D.C. p. 267-268.
Massey, H. F., M. L. Jackson, and 0. E. Hays.
1953. Fertility erosion on two Wisconsin soils.
Agron. J. 45(11):543-547.
X.9
-------
Mikola, P. 1960. Comparative experiment on
decomposition rates of forest litter in Southern
and Northern Finland. Oikos 11:161-166.
Mitchell, J. E., J. B. Waide, and R. L. Todd. 1975.
A preliminary compartment model of the
nitrogen cycle in a deciduous forest ecosystem. In
Mineral cycling in Southeastern ecosystems.
Howell, F. F., J. B. Gentry, and M. H. Smith,
eds. AEG Symp. Series (CONF-740513).
Moore, D. G., and L. A. Norris. 1974. Soil processes
and introduced chemicals. USDA For. Serv.
Gen. Tech. Rep. PNW-24, 33 p. Pac. Northwest.
For. and Range Exp. Stn., Portland, Oreg.
National Academy of Sciences and National
Academy of Engineering. 1972. Water quality
criteria 1972. U.S. Environ. Prot. Agency,
Washington, B.C. p. 594.
Parker, F. W., J. R. Adams, K. G. Clark, and
others. 1946. Fertilizer and lime in the United
States — resources, production marketing and
use. U.S. Dep. Agric. Misc. Publ. 586. 96 p.
Patric, J. H., and D. W. Smith. 1975. Forest
management and nutrient cycling in eastern
hardwoods. USDA For. Serv. Res. Pap. NE-324,
12 p. Northeast. For. Exp. Stn., Bloomall, Pa.
Patric, J. H., and G. M. Aubertin. 1976. Response
of a headwater stream to diameter-limit timber
harvesting. Unpubl. manuscr. on file at USDA
For. Serv., Northeast. For. Exp. Stn., Bloomall,
Pa. 15 p.
Pierce, R. S., C. W. Martin, C. C. Reeves, and
others. 1972. Nutrient losses from clearcuttings
in New Hampshire. In National symposium
watersheds in transition. Am. Water Resour. As-
soc. Proc. Ser. 14. p. 285-295.
Reinhart, K. G. 1973. Timber harvest clearcutting
and nutrients in the Northeastern United States.
USDA For. Serv. Res. Note NE-170. 5 p.
Northeast For. Exp. Stn., Bloomall, Pa.
Reuss, J. 0. 1976. Chemical and biological
relationships relevant to the effect of acid rain-
fall on the soil-plant system. In Proceedings of
the first international symposium on acid
precipitation and the forest ecosystem. USDA
For. Serv. Gen. Tech. Rep. NE-23, 293 p.
Northeast For. Exp. Stn., Bloomall, Pa.
Reuss, J. 0., and R. L. Smith. 1965. Chemical reac-
tions of nitrites in acid soils. Soil Sci. Soc. Proc.
p. 267-270.
Robinson, E., and R. C. Robbins. 1970. Gaseous
nitrogen compound pollutants from urban and
natural sources. J. Air Pollut. Control Assoc.
20(5): 303-306.
Rothacher, J., C. T. Dryness, and R. L. Fredriksen.
1967. Hydrologic and related characteristics of
three small watersheds in the Oregon cascades.
U.S. For. Serv. PNW-unnumbered. Pac.
Northwest. For. and Range Exp. Stn., Portland,
Oreg. 54 p.
Singh T., and Y. P. Kalra. 1975. Changes in
chemical composition of natural waters resulting
from progressive clearcutting of forest catch-
ments in West Central Alberta, Canada. Int. As-
soc. Sci. Hydrol. Symp. Proc. Publ. 117. p. 435-
449. [Tokyo, Japan. December 1970.]
Smith, W. H., F. H. Bormann, and G. E. Likens.
1968. Response of chemoautotrophic nitrifiers to
forest cutting. Soil Sci. 106(6):471-473.
Snyder, G. G., H. F. Haupt, and G. H. Belt, Jr.
1975. Clearcutting and burning slash alter
quality of stream water in Northern Idaho.
USDA For. Serv. Res. Pap. INT-168, 34 p.
Intermt. For. and Range Exp. Stn., Ogden,
Utah.
Sopper, W. E. 1975. Effects of timber harvesting
and related management practices on water
quality in forested watersheds. J. Environ. Qual.
4(l):24-29.
Stewart, W. D. P. 1975. Nitrogen fixation by free-
living micro-organisms. Int. Bio. Programme 6.
471 p. Cambridge Univ. Press, Eng.
Stoltonberg, N. W., and J. L. White. 1953. Selec-
tive loss of plant nutrients by erosion. Soil Sci.
Soc. Proc. 17(4):406-410.
Stone, E. 1973. The impact of timber harvesting on
soils and water. Appendix M. In Report of the
President's Advisory Panel on timber and the en-
vironment. April. U.S. Gov. Prin. Off. 197310-
505-287. p. 445-467.
Stuart, G., and D. Dunshie. 1976. Effects of timber
harvest on water chemistry. Hydol. Pap. USDA
For. Serv. East. Reg. 34 p.
X.10
-------
Stumm, W., and J. J. Morgan. 1970. Aquatic
chemistry. 583 p. Wiley-Interscience: New York,
London, Sydney, Toronto.
Swank, W. T., and J. E. Douglass. 1975. Nutrient
flux in undisturbed and manipulated forest
ecosystems in the Southern Appalachian Moun-
tains. Int. Assoc. Sci. Hydrol. Symp. Proc., Publ.
117. p. 445-456. [Tokyo, Japan. December 1970.]
Switzer, G. L., and L. E. Nelson. 1972. Nutrient ac-
cumulations and cycling in loblolly pine, Pinus
taeda, plantation ecosystems: The first twenty
years. Soil Sci. Soc. Am. Proc. 36(1):143-147.
Tabatabai, M. A., and J. M. Laflen. 1976. Nutrient
content of precipitation over Iowa. In
Proceedings of the first international symposium
on acid precipitation and the forest ecosystem.
USDA For. Serv. Gen. Tech. Rep. NE-23, p. 293.
Northeast. For. and Range Exp. Stn., Bloomall,
Pa.
Tisdale, S. L., and W. L. Nelson. 1966. Soil fertility
and fertilizers, p. 194-243. Macmillan Co., New
York.
Toler, L. G. 1965. Relation between chemical
quality and water discharge of Spring Creek,
Southwestern Georgia. U.S. Geol. Surv. Prof.
Pap. 525-C. p. C209-C213.
U.S. Senate Hearings Subcommittee on Public
Lands. 1971. "Clear-cutting" practices on
national timberlands. First session on manage-
ment practices on the public lands, p. 1057-1064.
Verry, E. S. 1972. Effect of an aspen clearcutting
on water yield and quality in Northern Min-
nesota. In National symposium on watersheds.
Trans. Am. Water Resour. Assoc. Proc., Ser. 14.
p. 276-284.
Waide, J. B., and W. T. Swank. 1975. Nutrient
recycling and the stability of ecosystems:
Implications for forest management in the
Southeastern United States. Proc. Natl. Conv.
Soc. Am. For. [Washington, D.C. Sept. 28-Oct.
2, 1975.] p. 404-424.
Weber, D. F., and P. L. Gainey. 1962. Relative sen-
sitivity of nitrifying organisms to hydrogen ions
in soils and in solutions. Soil Sci. 94(3):138-145.
X.ll
-------
APPENDIX X.A:
DETAILED DISCUSSION OF THE NUTRIENT CYCLE
The forest nutrient cycle is generally segmented
into three compartments — input, intracycle, and
output. The action and interaction of the major
compartments of the process are depicted in figure
X.A.I. Placing the nutrient cycle in such a format
forces the investigator to consider the processes and
variables that are likely to be impacted by
silvicultural activities and the effect that these
changes will have on soil and water chemistry.
INPUT TO THE NUTRIENT CYCLE
Nutrient inputs to a forest ecosystem come prin-
cipally from (1) the atmosphere, (2) the soil and
underlying bedrock, and (3) depositions by floods
on alluvial terraces. Alluvial deposition is not a
dominant nutrient input factor for many of the
forested areas. Man enters the cycle with fertilizer
additions.
Atmosphere
Atmospheric inputs account for most of the
nutrients entering the cycle, usually during a
precipitation event, in the form of dissolved gases,
aerosols, and solid particulate matter.
Nonprecipitation events, commonly referred to as
dry fall, also contribute solid particulate matter;
and in some areas, aerosols are carried by prevail-
ing winds and storm tracts from cities, industrial
centers, and agricultural lands, then deposited on
the forest without benefit of a precipitation event
(U.S. Senate Hearings 1971, Jorgensen and others
1975). Deposition of dry fall and aerosols may oc-
casionally be extensive during initiation of a
precipitation event, when these materials are
"washed" from the atmosphere. In any event,
precipitation falling on a forested area is not
chemically pure water but may contain many
chemical compounds, ranging from beneficial
nutrients (such as nitrogen) to deleterious acid
compounds (U.S. Senate Hearings 1971). An exten-
sive coverage of the addition of acidic materials to
the forest ecosystem can be found in the
"Proceedings of the First International Symposium
on Acid Precipitation and the Forest Ecosystem"
(Dochinger and Seliga 1976).
Atmospheric Nitrogen
Precipitation contains significant quantities of
numerous substances including nitrogen; one of the
primary sources of nitrogen input to the forest
ecosystem is through the atmosphere (fig. X.A.I).
Nitrogen occurs in the gaseous form — principally
as N2, NO, N02 and NHs, and in aerosols — as
NH^ and NOs. However, the gaseous nitrogen
form N2 is considered inert and cannot be directly
utilized by most organisms. Biological fixation by
microorganisms during the intracycle process
(discussed in detail in "The Intracycle Process")
converts free nitrogen to the ammonia form which
is then utilized in biological functions.
The compounds named are naturally produced;
however, increasingly large concentrations of them
are the result of industrial activities, vehicle ex-
hausts, and agricultural operations (Feth 1966,
Robinson and Robbins 1970). Transport of
relatively large quantities of nitrogenous com-
pounds from various concentrated pollutant
sources by prevailing winds or storms has resulted
in the deposition of large amounts of these
materials (Likens and others 1976). Such deposi-
tion occurs not only as dissolved and particulate
matter in precipitation, but it also occurs during
nonprecipitation periods as dry fall and aerosol
deposition. Junge (1958) reported a nationwide sur-
vey of ammonium and nitrate in rainwater over the
United States. The study indicated that concentra-
tions of NH^ and NO 3 varied markedly. Nitrogen
input values have been estimated for the United
States and are presented in figure X.A.2. It should
be noted that the values are based on regional
averages and specific sites can differ markedly
from the regional values due to local conditions.
Electrochemical and photochemical fixation,
lightning, and radiation convert a limited amount
of elemental nitrogen to available inorganic forms.
Atmospheric Phosphorus
Precipitation may also be a source of phosphorus
input into the system, but the quantities involved
can generally be assumed to be minor in com-
parison to those from the weathering of soil and
rock (Tabatabai and Laflen 1976).
X.12
-------
Atmospheric Inputs
Water
Transport
t
I
I
Volatilization
I
I
Dry Fall Interception Interception Loss | Evaporation
t
Evapotranspiration
Precipitation
Vegetation
Harvesting
00
^ Chemical
Transport
Overland
Flow
I
1
1
t
I
i
i
III !
j Foliar Drip Decomposition
fj| Fixation
Impervious Area
or Bare Soil
Litter & Organic
Layer
1 1 I 1
Percolation
t H t
' T '
Subsurface Flov
i Lead
t
Streamflow
(Exchange/
Transport)
V
Soil Water _
ling 1
Leaching
i
! Ne
i i FyphsinnA
1 Processes ^
'Weathering ^
w Minerals. *.
Soil
Micro-
organisms
A i
Mineralization
i
j Immobilize
1
i
1
1
1
1
UpU
1
ition |
1
1
1
Mineral Soil,
Weathering
Bedrock
ike
4.
i Goundwater Flow
Ground water
^-Weathering i
Figure X.A.1—Biochemical cycle for nitrogen in a forest.
-------
.5 kg/ha/yr
.5 kg/ha/yr
2.0 kg/ha/yr
1.0 kg/ha/yr
1.0 kg/ha/yr 1.5 kg/ha/yr 2.0 kg/ha/yr 2.5 kg/ha/yr
1.5 kg/ha/yr
1.0 kg/ha/yr
1.0 kg/ha/yr
1.0 kg/ha/yr
1.5 kg/ha/yr
Figure X.A.2.—Nitrogen (NH+4 and NO;,) in precipitation.
-------
Soil and Rock
Forest Fertilization
Chemical decomposition and physical weather-
ing of the soil and bedrock continually release
nutrients to the ecosystem. Soil and bedrock are
the principal sources of metallic cations,
phosphorus, and trace metals.
Soil. — Weathering and decomposition of the
solum and regolith add significant amounts of
nutrients to the forest and the intracycle processes.
Weathering and decomposition occur much more
rapidly within the upper soil horizons (i.e., rooting
zone) where plants, animals, bacteria, and soil
fungi all contribute to decomposition of the soil and
secondary minerals, and where the physical
processes, particularly freezing and thawing, ac-
celerate the weathering of the soil and rock (Lutz
and Chandler 1961).
Bedrock. — Geologic weathering and decom-
position of bedrock are not primary sources of
nutrient input to the forest ecosystem over a short
period (i.e., timber rotation age), in that nutrients
released from rock do not normally enter the forest
ecosystem directly through the intracycle
processes, but are removed from the system via
deep ground water. An exception occurs when the
root zone penetrates to bedrock.
Nitrogen Inputs From Soil and Rock
Geologic formations do not have large amounts
of nitrogen present, so nitrogen inputs to the forest
ecosystem from geologic weathering and chemical
decomposition are insignificant, especially when
compared with nitrogen inputs from the at-
mosphere.
Introduction of nitrogen and phosphorus to the
forests by fertilization can be a potentially signifi-
cant input source. However, at the present time
forest fertilization has not been extensively under-
taken and has been limited to the Pacific
Northwest and to the Southeast. Fertilization is
the only major nitrogen input source that the forest
land manager can control. A more complete
evaluation of its use and potential water quality
degradation is presented in "Chapter XI:
Introduced Chemicals."
The introduction of phosphorus to the forest by
fertilization may also be a significant input in some
locations but, as mentioned previously, forest fer-
tilization is not being applied to large acreages
nationally. See "Chapter XI: Introduced
Chemicals," for a more complex discussion.
THE INTRACYCLE PROCESS
Intracycle processes (fig. X.A.1) are numerous
and varied. Nutrients entering the ecosystem in
available form are utilized by vegetation and
animals and become unavailable (i.e., they become
stored nutrients). The transfer rate of nutrients
between living organisms (vegetation and animal),
forest floor, and mineral soil is dependent upon the
nutrient's chemical and physical characteristics
and physiological function (Jorgensen and others
1975).
Intracycle Nitrogen
Phosphorus Inputs From Soil and Rock
Phosphorus input to the forest ecosystem comes
almost exclusively from chemical decomposition of
rocks. Phosphorus is estimated to rank eleventh
among elements in igneous rocks. It occurs in all
known minerals as phosphates (McCarty 1970).
Apatites, the principal minerals containing
phosphorus, are found in almost all igneous and
sedimentary rocks. Phosphorus in soil can be
classed generally as organic or inorganic.
Phosphorus is found predominantly in the mineral
fraction in combination with a heavy metal, iron,
aluminum, or magnesium (McElroy and others
1976).
Mineralization
Mineralization, or ammonification, is ac-
complished by heterotrophic bacteria, ac-
tinomycetes, and fungi. These ammonifying
microorganisms1 metabolize organic nitrogen —
lTwo general groups of organisms fix nitrogen — symbiotic
nitrogen fixers and free-living nitrogen fixers. Symbiotic
organisms are associated with legumes, and several tree species,
notably alder. The quantity of nitrogen fixed by symbiotic
organisms exceeds that fixed by free-living nitrogen fixers by a
factor of 100. Symbiotic nitrogen fixers are restricted to the ter-
restrial environment, whereas free-living nitrogen fixers are
found in both terrestrial and aquatic environments.
Azotobacter. Clostridium, and blue-green algae are the primary
free-living nitrogen fixers (Stewart 1975, Weber and Gainey
1962, Kormondy 1976).
X.15
-------
amino acids, urea, uric acids and peptone (usually
in the form of an amine group, ~NH.2) — to an in-
organic form, ammonium. Excess ammonium
produced by the organisms is released; some of this
nitrogen is lost from the soil to the atmosphere as
gaseous ammonia, NHa (Kormondy 1976).
Mineralization is the principal nitrogen process
conducted by microorganisms in highly acidic soils.
DeByle and Packer (1972) reported that nitrifica-
tion rates were barely detectable in acid soils under
a coniferous stand. They concluded that am-
monium was probably the principal form of
available nitrogen present and that because of its
high solubility could easily be lost in deep seepage
or overland flow.
However, most of the nitrogen remains within
the forest ecosystem, being utilized by soil
microorganisms or vegetation, becoming adsorbed
on clay and organic colloids (through cation ex-
change), and by remaining in solution in the soil
water (Bormann and Likens 1967).
Nitrification
Nitrification (fig. X.A.3) is the biological conver-
sion of organic or inorganic nitrogen compounds
from a reduced to a more oxidized state, NOs.
Although nitrification usually applies to
autotrophic oxidation of ammonia or nitrate ions,
numerous heterotrophs, including bacteria, algae,
and fungi are known to oxidize organic nitrogen to
nitrite or nitrate. It is generally acknowledged that
the rate of nitrogen oxidation by heterotrophs is
negligible compared to that by autotrophs.
Autotrophic nitrifying bacteria are confined largely
to Nitrosomonas (oxidation of NH^ to NO 2) and
Nitrobacter (oxidation of NO 2 to NOlj); however,
five other genera have also been shown to oxidize
nitrogenous compounds. Adequate oxygen must be
present for nitrification to occur. Nitrification has
been detected in aquatic systems with approx-
imately 0.3 ppm dissolved oxygen (Greenwood
1962).
For most soils, nitrification depends very much
on pH. It usually decreases greatly at a pH below
6.0 and becomes negligible at a pH of 5.0 (Alex-
ander 1967). The Hubbard Brook study, where
nitrification rates were increased in an acid soil
(pH 4) following a complete clearcut, is a par-
ticularly notable exception to the norm. It was
hypothesized by the investigators that the in-
creased nitrification rate was caused by a little
known species of nitrifying bacteria adapted to
more acid conditions (Likens and others 1970).
Nitrate and nitrite, end products of the nitrifica-
tion process, are the principal components of
nitrogen outflux from the forest ecosystem. (This
process is discussed in more detail under "Outputs
From the Nutrient Cycle — Nitrogen Outflux" in
this appendix.)
Plant
NH2
R-C—R -*-
ASSIMILATION
NH3 -•-
Organic Nitrogen
NO3+H2O
NH4r
•2H+ ^NH4++2O2
DENITRIFICATION
- N03-
2H
Soil
NH2
_C_
H
R ORGANIC
NITROGEN
MINERALIZATION
OH-
2H+
NH4++2O2
N03-
NITRIFICATION
H+*N03~+H20
Figure X.A.3.—Simplified nitrogen cycle showing N utilized in the nitrate (NO3) and ammonium (NHt)
forms and showing acid and base relations associated with the various processes (after Reuss 1976).
X.16
-------
The intracycle nitrogen processes have been in-
tensively investigated at the Coweeta Experimen-
tal Forest, North Carolina. A relatively un-
disturbed oak-hickory stand was selected, and a
flow model of the nitrogen cycle for this forest was
prepared. An estimate of the nitrogen pools,
vegetation increments of nitrogen, and transfer
rates among the various compartments was made
and is illustrated in figure X.A.4. The model
shows that most of the nitrogen in the undisturbed
forest is contained in large storage pools that turn
over slowly. Over 80 percent of the total nitrogen in
this forest ecosystem is bound within soil organic
matter, with about 11 percent in total vegetation, 3
percent in litter, 4 percent in microbial biomass,
and 2 percent in free soil (Mitchell and others 1975,
and Waide and Swank 1976).
X1
Reproductives
2.738
Figure X.A.4—Flow model of nitrogen cycling In an oak-hickory forest at Coweeta Experimental Forest,
North Carolina. Values Inside boxes represent standing crops of nitrogen (kg N/ha); values inside dotted
lines are vegetation Increments (kg N/ha/yr); numbers on arrows represent nitrogen transfers among
compartments (kg N/ha/yr). This diagram shows nitrogen transfer associated with nitrogen uptake by
plants and return to litter-soil pools (after Waide and Swank 1976).
X.17
-------
Although the values presented in the flow model
are valid only for the specific site studied, the flow
model itself has general applicability to all forest
types. Detailed analyses, similar to the one under-
taken in this study, are necessary to quantify the
actual amounts and rates of nitrogen in the cycle,
but are not feasible except in a research environ-
ment. Forest managers could utilize the results of
such studies to evaluate the potential impacts of
changing the nitrogen cycle.
Intracycle Phosphorus
that may make up the dissolved organic
phosphorus fraction of waters draining a forested
ecosystem (Stumm and Morgan 1970). It has been
estimated that about 40 to 50 percent of the organic
soil phosphorus consists of nucleic acids, inositol
phosphate and phospholipids; the remainder is
largely unidentified. It is known that decomposi-
tion of organic matter results in the mineralization
of organic phosphorus and the release of inorganic
phosphate. Actual chemical reactions involved are
not fully known.
Phosphorus intracycle processes (figure X.A.5)
are neither fully understood nor quantified.
Research to date has been limited in scope to
general processes and to site factors that influence
them. Phosphorus occurs as both inorganic and
organic compounds.
Geochemical
5%
Figure X.A.5—General estimate of the relative proportion of
phosphorus present in each component of the
geochemical, biochemical, and blogeochemlcal cycles of
loblolly pine plantation ecosystem, 20th year (after SwKzer
and Nelson 1972).
Organic Phosphorus
Organic phosphorus compounds found in forest
soils and water are products of biochemical reac-
tions. Almost no information is available to iden-
tify specific compounds or groups of compounds
Inorganic Phosphorus
Inorganic phosphorus compounds occur as con-
densed phosphates and orthophosphates.
Condensed phosphates are generally manmade
compounds but some are also generated by all liv-
ing organisms. These latter compounds are un-
stable in water, where they are slowly hydrolyzed to
the orthophosphate form (McCarty 1970).
Inorganic phosphate compounds generally react
with metallic cations and clays present in soil to
form complexes. Phosphate materials held by the
soil may be loosely adsorbed and remain available
to plants or may be firmly fixed and unavailable.
Acidic mineral soils generally contain ap-
preciable quantities of adsorbed aluminum and
smaller but significant amounts of iron and
manganese. These ions combine with phosphates
to form insoluble compounds that may be
precipitated from soil solution or adsorbed on the
surface of iron and aluminum oxides or on clay par-
ticles. The more acidic soils contain more adsorbed
aluminum and iron; therefore, the products of
phosphorus fixation are largely complex
phosphates of iron and aluminum.
Another mechanism whereby phosphorus is fixed
in the soil is the reaction of phosphates with silica
clays. Phosphorus and polyphosphates are ad-
sorbed onto clay minerals by chemical bonding of
the anion to positively charged edges of the clays
and by substitution of phosphates for silicate in the
clay structure. In general, high phosphate adsorp-
tion by clays occurs at lower pH values (Stumm
and Morgan 1970); in most soils phosphorus
availability is at a maximum in the pH range 5.5 to
7.0 and decreases as the pH drops below 5.5
(Tisdale and Nelson 1966).
X.18
-------
OUTPUTS FROM THE NUTRIENT CYCLE
Nutrients are naturally lost from the forest
ecosystem in the form of dissolved or particulate
matter in moving water or colluvium or both,
through removal of the vegetation, through the dif-
fusion or transport of gases or particulate matter by
wind, and by fire or by animal activity. Gaseous ex-
change from the soil and vegetation to the at-
mosphere has not been extensively studied, but it
does not appear that this would account for ap-
preciable nutrient loss.
surface. Soil water loss (i.e., evapotranspiration) is
reduced, which increases soil moisture. Nutrients
made available in the soluble form during the
decomposition processes may exceed nutrient up-
take capacity of the vegetation remaining on the
site. Excess available nutrients then become lost
from the forest ecosystem in surface and ground
water flows to streams and deep seepage (Cramer
1974).
Nitrogen Outflux
Dissolved Materials
Nutrients are lost from the system in overland
flow, subsurface flow and ground water. Numerous
studies have shown that overland flow rarely occurs
within an undisturbed forest (Colman 1953); and
even following silvicultural activities, overland
flow does not normally contribute significantly to
watershed discharge.
The chemical content of subsurface flow and
ground water depends on both biochemical and
geochemical cycles. Thus the chemical composi-
tion will vary regionally and seasonally depending
on variations in rates of decomposition of organic
matter and immobilization by microorganisms,
differences in weathering and exchange processes,
and changes in concentration brought about by
vegetative uptake. Nutrients carried in the water
draining a forest ultimately enter the streams and
determine the chemical character of the receiving
stream.
Removal Of Vegetation
Timber harvesting results in the loss of nutrients
from the forest ecosystem. The proportion of
nutrients in the vegetation lost from the forest is
determined by the utilization that is made of the
tree, being maximized when the entire tree (bole,
limbs, foliage, and roots) is utilized and minimized
when only the bole is removed from the site. The
removal of overstory vegetation results in ac-
celerated decomposition of organic matter on and
in the forest floor due to an increase in soil
temperature and moisture content. Increased soil
temperatures are caused by removal of the shading
trees, which allows direct solar heating of the soil
Pathways Of Nitrogen Removal
Nitrogen is lost from a forest ecosystem by
volatilization, removal of the biomass through
harvesting, and by leaching to surface and subsur-
face flows.
Volatilization. — Generally, volatilization
losses are extremely limited due to the nature of
the forest environment. However, large volatiliza-
tion losses of nitrogen occur when forest and log-
ging residue are burned. Wildfire and prescribed
burning of slash result in loss of organic nitrogen in
the vegetation (DeBell and Ralston 1970). Grier
(1975) reported that a wildfire on the Entiat Ex-
perimental Forest, Washington, caused a reduction
of 97 percent of the nitrogen in the forest floor and
two-thirds of the nitrogen in the Ai horizon of the
mineral soil. Ash from fires may be carried by the
wind or by surface erosion into a watercourse.
Losses via volatilization were discussed in
"Nitrification and Mineralization."
Removal of the biomass. — Nitrogen as-
similated by vegetation and utilized in biomass
production is lost from the site when the vegetation
is harvested and physically removed from the site.
Surface and subsurface flow. — Nitrogen loss
from a site in the surface water or soil water has
direct and immediate impact on the quality of
water draining a forested area. Nitrogen may be in
solution (principally as NO 3) or transported by the
water adsorbed to suspend particles (principally as
NHt and organic compounds). The intracycle
processes — mineralization and nitrification —
that have as their end products nitrate and am-
monium, will be discussed in the next section.
Nitrogen losses associated with surface erosion
(i.e., adsorbed nitrogen) may be estimated using
the insoluble component model previously
presented.
X.19
-------
Nitrification And Mineralization
The acid-base relations associated with nitrifica-
tion and mineralization are shown in figure X.A.3.
Acidity of the system remains unchanged as long as
plant uptake of nitrogen equals the rate of
mineralization of nitrogen and neither NH1 nor
NOs accumulates in the soil.
When mineralization occurs followed by
nitrification, an excess of hydrogen ions (H+) is
released, which may replace cations on the ex-
change sites. If plant uptake of nitrate does not
take place, both nitrate ions and metallic cations
are subject to leaching by subsurface flow. Bor-
mann and Likens (1970) found that excess
hydrogen ions may be released from exchange sites
and go into solution in soil water, and are thereby
lost from the forest ecosystem. The result is an in-
creased outflux potential of nutrients from
deforested watersheds that have increased
nitrification rates. They reported that increased
concentrations of calcium, magnesium, sodium,
and potassium in water draining a clearcut oc-
curred almost simultaneously with increased
nitrate concentration.
Nitrate, an end product of nitrification reactions
of the intercycle stage, is the principal component
of nitrogen outflux from the forest ecosystem.
Increased biological nitrification may result from
silvicultural activities that reduce the vegetative
cover, thus resulting in increased soil temperatures
and moisture.
Accelerated nitrogen losses following some
silvicultural activities have generally been at-
tributed to changes in the forest floor environment
conducive to nitrifying bacteria and to a reduction
in assimilation due to the reduced vegetative cover.
Microbial populations in the forest floor
generally increase following a timber harvest that
exposes the soil to increased radiation, which
results in warmer soil temperatures. Little decom-
position takes place during the period when the soil
is frozen or covered with snow. Thus, temperature
of the growing season appears to be the decisive
factor (Johnsen 1953, and Mikola 1960). The poten-
tial increase in nitrification rates is greater in the
northern climates, where thick humus layers ac-
cumulate on the mineral soils and temperatures of
shaded soils remain low most of the year (Stone
1973).
Soil moisture also influences the growth of
microbial populations: removal of the overstory
vegetation reduces interception and transpiration
losses which results in increased soil moisture.
Saturated soils, however, may retard microbial
growth and thus reduce nitrification rates.
If nitrification and plant uptake of ammonium
ions are less than the rate of mineralization, am-
monium accumulates in the soil (fig. X.A.3). Am-
monium ions are adsorbed on cation exchange sites
and are not readily leached. Clay soils and soils
with high cation exchange capacities hold am-
monium ions most efficiently. Leaching of NH^ oc-
curs in soils with higher pH and lower cation ex-
change capacity (Coffee and Bartholomew 1964).
Denitrification. — Denitrification, the
biochemical reduction of nitrate and/or nitrite, is
one possible route whereby nitrogen may be lost
from the forest ecosystem — microorganisms may
reduce the nitrate and/or nitrite forms of nitrogen
to gaseous nitrogen, and in some cases these forms
are reduced to ammonia. Denitrification will occur
in any microbial microenvironment that is essen-
tially anaerobic. The microorganisms utilize the
nitrogen oxides as a source of oxygen in the
presence of glucose and phosphate. The rate of
denitrification is partially controlled by pH.
Denitrifying microorganisms are active in soils that
range in pH from 5.8 to 9.2 (with an optimal value
between pH 7.0 and 8.2).
Many commercial forest lands have soil pH
values below 5.8 and are normally aerobic;
therefore denitrification is severely limited, if
detectable at all (Lutz and Chandler 1961, and
Keeney 1973).
Phosphorus Outflux
Phosphorus is lost from the forest ecosystem in
surface and subsurface water, and in vegetation
removed from the site during silvicultural ac-
tivities. Water quality is affected only by
phosphorus lost from the site and entering the
stream. Phosphorus loss via water transport in-
cludes not only the phosphorus dissolved in water,
but also that adsorbed to suspended solids.
Generally, the greatest loss of phosphorus from a
forest will occur as insoluble phosphorus complexes
adsorbed on the clay-sized materials that are
transported by surface flow. Research investiga-
tions (app. X.B.) have generally not reported
significant increases in phosphorus concentrations
in the receiving streams following silvicultural ac-
tivities. It would appear that increases in available
phosphorus due to silvicultural activities are nor-
mally utilized or fixed, and only a small fraction is
transported from the site to a watercourse in the
absence of excessive erosion.
X.20
-------
APPENDIX X.B:
EIGHTEEN STUDIES OF NUTRIENT RELEASES FOLLOWING
SILVICULTURAL ACTIVITIES
The results of research investigations into
nutrient release of nitrogen and phosphorus follow-
ing silvicultural activities are summarized and
presented in figure X.2. A more thorough presenta-
tion of the results of these investigations is
presented in the following 18 studies.
The Hubbard Brook study initiated concern
regarding nutrient release following clearcutting
and is presented first (study X.B.I.). It should be
noted that the treatment was extreme. The
NOa-N and NHt-N concentrations were greater
in the precipitation than in the streams draining
the control watersheds.
Concentrations of nitrogen and phosphorus in
the control watersheds may be used as estimates of
baseline water quality for the various geographic
areas studied. It should be realized, however, that
there may be considerable variation between adja-
cent watersheds as well as between geographic
areas.
X.21
-------
Study X.B.I
Hubbard Brook Experimental Forest,
New Hampshire
Silvicultural Watershed 2 had all trees and brush cut (but left in place)
treatment: during November and December 1965, and herbicides were
applied during the following three summers to inhibit
regrowth. Watersheds 4 and 6 were undisturbed and were
used as controls.
Vegetation: Northern hardwoods — beech, birch, and maple.
Drainage: Treated, Watershed 2, 39 ac (15.6 ha).
Control, Watershed 4, 90 ac (36 ha).
Control, Watershed 6, 33 ac (13.2 ha).
Sampling: October 1965-September 1968.
Results:
Study and NOs-N NHJ-N Total dissolved P
year Mean annual Mean annual Maximum Mean annual
mg/l
Watershed 2
1965-66
1966-67
1967-68
Watershed 4
1965-66
1966-67
Watershed 6
1965-66
1966-67
1967-68
Precipitation
1 965-66
1966-67
1967-68
0.21
8.67
11.94
0.19
0.20
0.19
0.16
0.29
0.32
0.34
0.35
0.11
0.05
0.04
0.09
0.05
0.09
0.04
0.02
0.16
0.14
0.17
...
... —
0.0026 0.00156
... ...
...
... —
... ...
0.00118
... ...
... ...
_.
Sources: Likens and others 1970; Hobble and Likens 1973.
X.22
-------
Study X.B.2
Hubbard Brook Experimental Forest,
New Hampshire
Silvicultural Progressive strip cutting. A 90 ac (36 ha) watershed was
treatment: divided into 49 east-west strips, each 82 ft (25 m) wide.
Every third strip was clearcut in October 1970. The remain-
ing strips are cut at 2-year intervals.
Vegetation: Uneven-aged northern hardwoods — beech, birch, and
maple.
Drainage: Treated, Watershed 4, 90 ac (36 ha).
Sampling: January 1968-September 1972.
Results:
NO3-N
Average concentration
Date
November 1970
December 1970
January 1971
February 1971
March 1971
April 1971
May 1971
June 1971
July 1971
August 1971
September 1971
October 1971
Estimated
(if untreated)
mg/l
0.43
0.50
0.61
0.6B
0.70
0.86
0.52
0.16
0.11
0.04
0.02
0.02
Actual
0.56
0.70
0.74
0.79
0.88
1.24
0.77
0.25
0.25
0.34
0.43
1.15
Date
November 1971
December 1971
January 1972
February 1972
March 1972
April 1972
May 1972
June 1972
July 1972
August 1972
September 1972
NO~3-N
Average concentration
Estimated
(if untreated)
mg/l
0.11
0.13
0.38
0.36
0.61
0.72
0.61
0.09
0.07
0.11
0.02
Actual
1.54
1.76
1.72
1.44
2.08
1.90
1.72
0.72
0.56
0.63
0.47
1No noticeable change in NH1 concentration between treated and control watersheds.
Source: Hornbeck and others 1973.
X.23
-------
Silvicultural
treatment:
Church Pond:
Conner Brook:
Davis Brook:
D.O.C. Creek:
Gale River:
Greeley Brook:
HB 101:
Stony Brook:
Vegetation:
Study X.B.3
White Mountain National Forest,
New Hampshire
Timber sales conducted on the White Mountain National
Forest. All areas were clearcut; more than 75 percent of the
timber was cut. Adjacent undisturbed watersheds were also
monitored.
Clearcut in summer 1969, 329 ac (133 ha); 10 ac (4 ha);
watershed monitored.
Clearcut in May 1969-Dec. 1969, 282 ac (114 ha); three 20
ac (8 ha) watersheds were monitored.
Clearcut Sept. 1969-Sep 1970, 160 ac (65 ha); three
watersheds were monitored — 2.5 ac (1 ha), 7 ac (3 ha), 10
ac (4 ha).
Clearcut July 1970, 126 ac (55 ha); two 20 ac (8 ha)
watersheds were monitored.
Clearcut Dec. 1968-Aug. 1970, 297 ac (120 ha); three
watersheds were monitored — two 10 ac (4 ha) and one 5 ac
(2 ha).
Clearcut initially 1960 and again 1967, 371 ac (150 ha);
three watersheds were monitored — 35 ac (14 ha), 10 ac (4
ha) and 5 ac (2 ha).
Clearcut Nov. 1970, 30 ac (12 ha); 25 ac (10 ha) watershed
monitored.
Clearcut Nov. 1968-May 1970, 160 ac (65 ha); 10 ac (4 ha)
watershed monitored.
Northern hardwoods (beech, birch, and maple) were pre-
sent on all areas except Greeley Brook which had
predominantly red spruce.
Drainage:
Sampling:
Results:
Watershed
Church Pond
Control
Clearcut
Conner Brook
Control
Davis Brook
Control
Clearcut
D.O.C. Creek
Control
Clearcut
See "Silvicultural
Biweekly
NO3-N
Max
mg/l -
0.95
1.60
0.40
0.09
5.26
1.22
3.54
analysis
Mean
0.81
1.40
0.20
0.02
3.84
0.52
1.90
treatment," above.
from April-November
Watershed
Gale River
Control
Clearcut
Greeley Brook
Control
Clearcut
Stony Brook
Control
Clearcut
1971.
Max
0.50
6.39
0.79
1.85
0.81
3.73
NOa-N
Mean
--mg/l
0.20
4.47
0.54
1.31
0.18
1.99
Source: Pierce and others 1972.
X.24
-------
Study X.B.4
White Mountain National Forest,
Upper Mill Brook, New Hampshire
Silvicultural Harvesting operations were conducted on the Upper Mill
treatment: Brook sale area from December 1971-February 1973
Watershed
No.
1
2
3
4
5
6
8
9
C
Date
Jan.-Feb. 1972
Feb.-Mar. 1972
Dec. 1971-Jan. 1972
Dec. 1971-Jan. 1972
June-Sept. 1972
Sept. 1972-Feb.1973
Treatment and
drainage area
Thinning (10-20 ac)
Thinning (10-20 ac)
Clearcut( 10-20 ac)
Clearcut (20-30 ac)
Clearcut with buffer
(10-20 ac)
Clearcut (10-20 ac)
Control (30-40 ac)
Control (20-30 ac)
Control (620 ac)
Vegetation:
Drainage:
Sampling:
Northern hardwoods.
See "Silvicultural treatment," above.
1972-1974, 10 to 12 samples per year were collected. This
number of samples was based on previous data evaluations.
Results
Watershed and
treatment
1 and 2— thinnings
3— Clearcut
4— clearcut
5— clearcut/buffer
6— clearcut
8 and 9— controls
C— control (upstream)
NOa-N
Mean
0.45
0.79
0.96
0.39
0.23
0.23
0.27
NO3-N
Max
2.10
2.55
2.48
1.51
1.35
1.21
1.02
Total N
Mean
0.92
1.32
1.50
0.94
0.81
0.71
0.67
Total N
Max
mn/l --------
2.50
3.55
3.40
2.92
4.10
2.88
4.20
POs3
Mean
0.02
0.03
0.02
0.02
0.02
0.02
0.01
PO43
Max
0.11
0.13
0.09
0.09
0.16
0.12
0.04
Source: Stuart and Dunshie 1976.
X.25
-------
Study X.B.5
Leading Ridge Watershed 2,
Pennsylvania State University
Silvi cultural
treatment:
Vegetation:
Drainage:
Sampling:
Forty-six percent of the watershed was successively clear-
cut and herbicided. The sequence of operation was (1)
winter of 1966-67—21.3 ac (9 ha) of the lower watershed
were clearcut; (2) summers of 1967, 1968, and 1969 —
stumps were treated with herbicide to control stump
sprouting; (3) winter of 1971-72 — 2.70 ac (1.0 ha) of the
middle watershed were clearcut; and (4) both clearcuts
treated with herbicide in June 1974.
Uneven-aged oak, hickory, and maple.
Treatment, Leading Ridge Watershed (LR) 2,106 ac (42 ha)
with 48.3 ac clearcut.
Control, Leading Ridge Watershed 1, 303 ac (121 ha).
Control, Leading Ridge Watershed 3, 257 ac (100 ha).
Weekly sampling for nutrient concentrations in streamflow
began in 1972.
Results:
Date
Control
LR-1
Treatment
LR-2
NOa-N
mn/l
Control
LR-3
Oct. 1972-Sept. 1973
Oct. 1973-May 1974
June1974-Dec. 1974
June-Aug. (ave max)
Sept.-Dec. (ave max)
Sept.-Dec. (max measured)
Clearcutting had no apparent effect
0.02 0.10 0.01
0.04 2.08 0.08
0.4
5.0
8.4
Source: Corbett and others 1975.
X.26
-------
Study X.B.6
Fernow Experimental Forest,
West Virginia
Silvicultural Watershed 3 was clearcut 1969. Watershed 4 was un-
treatment: disturbed and used as a control. Watershed 2 was subjected
to a diameter-limit cut in August 1972.
Vegetation: Mixed deciduous — oaks, maples, yellow poplar, black
cherry and beech.
Drainage: Watershed 3, 84 ac (34 ha).
Watershed 4, 94 ac (38 ha).
Watershed 2, 38 ac (15 ha).
Sampling: Weekly sampling, May 1970-April 1971, Watersheds 3
and 4.
Weekly sampling, Aug. 1972-Sept. 1974, Watershed 2.
Results:
Watershed
Watershed 4
1970 growing season
1970-71 dormant season
Watershed 3
1970 growing season
1970-71 dormant season
Watershed 2
Growing season
Pre-silvicultural activity
Post-silvicultural activity
Dormant season
Pre-silvlcultural activity
Post-sllvicultural activity
NOa-N NHJ-N
Mean Max Mean
0.32 — 0.48
0.10 — 0.13
0.1 B 0.59 0.35
0.49 1.42 0.14
0.2
0.6
Values unchanged
Values unchanged
PO43
Ave
0.04
0.02
0.07
0.04
Sources: Aubertin and Patric 1972; Aubertin and Patric 1974; Patric and Aubertin 1976.
X.27
-------
Study X.B.7
Coweeta Hydrologic Laboratory,
North Carolina
Silvicultural treatment:
Watershed
No.
1
2
6
14
13
18
17
21
28
32
37
34
Vegetation:
Drainage:
Sampling:
All trees and shrubs cut 1956-57, no products removed;
white pine planted 1957, 40 ac (16.2 ha).
Control, mixed mature hardwoods, 30 ac (12.1 ha).
Cut 1958 and products removed; lime added, fertilized, and
grassed in 1959; refertilized 1965; herbicided 1966 and 67,
22 ac (8.9 ha).
Control, mixed mature hardwoods, 151 ac (61.1 ha).
All trees and shrubs cut 1936, recut 1962; no products
removed, 40 ac (16.2 ha).
Control, mixed mature hardwoods, 31 ac (12.5 ha).
All trees and shrubs cut 1942; recut annually through 1955,
no products removed; white pine planted in 1956, 33 ac
(13.4 ha).
Control, mixed mature hardwoods, 60 ac (24.3 ha).
All trees and shrubs cut on 190 ac (77 ha); cove hardwoods
thinned on 96 ac (39 ha); no cutting on 69 ac (28 ha);
products removed 356 ac (144.1 ha).
Control, mixed mature hardwoods, 102 ac (41.3 ha).
All trees and shrubs cut in 1963; no products removed, 108
ac (43.7 ha).
Control mixed mature hardwoods 81 ac (32.8 ha).
See "Silvicultural treatment," above.
See "Silvicultural treatment," above.
May 1972-April 1973.
Results:
Watershed1
1
2
6
14
13
18
17
21
28
32
37
34
NOa-N
Mean
0.029
0.004
0.619
0.004
0.044
0.003
0.154
0.003
0.094
0.003
0.149
0.002
Max
0.077
0.017
1.230
0.024
0.084
0.014
0.249
0.016
0.208
0.015
0.246
0.019
NHJ-N
Mean
rng/| -
0.003
0.002
0.004
0.004
0.003
0.004
0.004
0.004
0.003
0.003
0.004
0.003
Max
0.020
0.020
0.010
0.031
0.014
0.022
0.012
0.024
0.017
0.013
0.038
0.024
PO
Mean
0.006
0.006
0.007
0.005
0.004
0.005
0.012
0.004
0.004
0.004
0.006
0.006
43-P
Max
0.022
0.020
0.030
0.017
0.013
0.018
0.336
0.029
0.020
0.013
0.095
0.019
'Watersheds listed below are alternated treated and controlled (1—treated, 2—control) for com-
parison. Refer to "Silvicultural treatment" for details.
Sources: Douglass and Swank 1975; Swank and Douglass 1975.
X.28
-------
Study X.B.8
USAEC's Savannah River Plant,
Aiken, South Carolina
Silvicultural Prescribed burn of surface litter.
treatment:
Vegetation: Loblolly pine.
Drainage: Approximately 450 ac (180 ha).
Sampling: Ground water samples were taken at control and burned
areas 5 weeks after burn.
Results: Ground water.
Sample NOs-N PO33-P
area Mean Std Mean Std
error error
mg/l
Burned 0.007 0.0005 0.0047 0.0012
Control 0.006 0.0009 0.0040 0.0010
Source: Lewis 1974.
X.29
-------
Study X.B.9
Grant Memorial Forest,
Georgia
Silvicultural 77 ac were clearcut beginning in October 1974. Harvesting
treatment: and site preparation (roller chopping) was completed in
December 1975. The site was planted in January 1976. An
adjacent untreated watershed was monitored as a control.
Vegetation: Old field Loblolly pine.
Sampling: December 1973-January 1977 (approximately 200 weekly
samples).
Results: (Mean cone, of all samples)
Watershed
NOa-N
mg/l
Total P
Treated
Calibration, Dec. 1973-Oct. 1974
Harvest and site prep., Nov. 1974-Dec. 1975
Following planting, Jan. 1976- Jan. 1977
Control
Calibration, Dec. 1973-Oct 1974
Nov. 1974-Dec. 1975
Jan. 1976-Jan. 1977
0.058
0.029
0.028
0.149
0.113
0.108
0.210
0.190
'0.476
0.216
0.230
'0.582
'Particularly high values of phosphorus occurred during September-October 1976. Although unex-
plained, it is important to note that both the treated and the control watersheds exhibited high values dur-
ing this period.
Source: Hewlett 1977.
X.30
-------
Silvicultural
treatment:
Vegetation:
Drainage:
Study X.B.10
H. J. Andrews Experimental Forest,
Eugene, Oregon
Patchcut using high-lead yarding; with 25 percent of the
area cut, plus an additional 6 percent in roads. Clearcut en-
tire drainage, but no roads were present. Harvesting opera-
tions were begun in the fall of 1962 and were completed in
1966. Both areas were broadcast burned following yarding.
A third drainage was undisturbed and served as a control.
Old-growth Douglas fir.
Patchcut, 237 ac (96 ha).
Clearcut, 149 ac (60 ha).
Control, 250 ac (101 ha).
Sampling:
Results:
Date and
treatment
1966 (H)<
1967 (B)
1968 (R)
1971 (R)
1972 (R)
119 samples were collected, usually during storm runoff,
during the period April 1965-July 1968.
N<
Mean
annual
0.020
0.050
0.200
0.046
0.023
Clearcut
Instan-
taneous
max
0.050
0.066 0.110
0.600 0.001
0.065
0.056
PO4a
Mean
annual
0.024
0.039
0.036
0.034
'-P
Instan-
taneous
max
0.066
0.121
0.050
0.045
Measurement
Maximum
12-day mean
Maximum and mean maximum taken during a 12-day period
after broadcast burning in 1967
NOs-N NHJ-N PO43-P
Clearcut Control Clearcut Control Clearcut Control
mg/l
0.60
0.43
0.01
7.60
1.19
0.001
0.13
0.05
0.05
Patchcut
Dissolved solids concentration Increased as a result of harvesting. The effect lasted for 6 years and
was no longer statistically different from the pre-sllvlcultural activity In 1968.
NOl-N
Instan-
Control
PO^'-P
Instan-
Date and
treatment
1966 (U)
1967 (U)
1968 (U)
1971 (U)
1972 (U)
Mean
annual
0.010
0.003
0.001
0.0003
0.0015
taneous
max NHJ-N
mn/l
... ...
0.003
<0.001
—
—
Mean
annual
0.026
0.016
—
0.032
0.016
taneous
max
...
—
—
—
—
'H = harvested, B = burned, R = revegetating, and U = undisturbed.
Source: Fredriksen 1971; Fredriksen 1977; Fredriksen and others 1975; Rothacher and others 1967.
X.31
-------
Silvicultural
treatment:
Vegetation:
Drainage:
Sampling:
Study X.B.ll
Bull Run Watershed,
Portland, Oregon
Clearcut on 25 percent of watersheds — the slash on one
was burned and left to decompose on the other. On the
burned watershed, harvesting was done the summer of 1969
and the slash was burned in the fall of 1970. On the un-
burned watershed, two seasons (1971 and 1972) were re-
quired to completely fell the units; harvesting was com-
pleted summer of 1973. The untreated watershed served as
a control.
Old-growth Douglas fir.
Fox Creek: Clearcut and burned, 145 ac (59 ha).
Clearcut and not burned, 175 ac (71 ha).
Control, 625 ac (253 ha).
Sampling began April 1970. Proportional samples taken
over 3-week intervals throughout each year.
Results:
Clearcut
Year and
treatment
1970 (H)1
1971 (B)
1972 (R)
1973 (R)
1974 (R)
1975 (R)
1976 (R)
Dissolved
NOs-N
Mean
annual
0.012
0.027
0.046
0.034
0.045
0.023
—
Max
0.019
0.079
0.056
0.057
0.064
0.034
0.033
NHt-N
Mean
annual
0.003
0.005
0.001
0.001
—
—
—
Max
0.020
0.100
0.022
0.090
—
...
—
organic N
Mean
annual
it
- - mg/i
0.037
0.036
0.040
0.036
0.043
0.043
—
Max
0.058
0.049
0.062
0.058
0.133
0.075
0.051
Total
phosphorus
Mean
annual
0.035
0.027
0.014
0.028
0.011
0.016
—
Max
0.065
0.055
0.030
0.100
0.093
0.032
0.025
Clearcut—Not Burned
1970 (U)
1971 (F)
1972 (F)
1973 (H)
1974 (R)
1975 (R)
1976 (R)
1970 (U)
1971 (U)
1972 (U)
1973 (U)
1974 (U)
1975 (U)
1976 (U)
0.002
0.004
0.014
0.022
0.080
0.093
—
0.006
0.003
0.005
0.013
0.002
0.002
—
0.014
0.017
0.030
0.042
0.115
0.114
0.066
0.027
0.020
0.040
0.056
0.053
0.028
0.040
0.002
0.005
0.001
0.003
—
—
...
0.005
0.004
0.002
0.002
—
—
—
0.005
0.089
0.010
0.036
—
—
—
Control
0.013
0.078
0.018
0.007
—
...
—
0.036
0.038
0.029
0.032
0.032
0.044
—
0.045
0.043
0.036
0.038
0.034
0.050
—
0.078
0.096
0.046
0.042
0.082
0.076
0.066
0.063
0.064
0.070
0.062
0.081
0.068
0.065
0.028
0.032
0.013
0.021
0.011
0.020
—
0.040
0.032
0.014
0.024
0.013
0.015
—
0.070
0.055
0.045
0.030
0.062
0.046
0.030
0.065
0.070
0.080
0.100
0.090
0.033
0.031
'H = harvested; B = burned; F = felled; R = revegetating, and U = undisturbed
Source: Fredriksen 1977.
X.32
-------
Study X.B.12
South Umpqua Experimental Forest,
50 kilometers ESE of Rosberg, Oregon
Silvicultural Shelterwood harvest — 50 percent of the area removed;
treatment: small clearcut — 30 percent of the area in 20 small clearcuts
from 0.6 - 1.4 ha (3.1 ac); complete clearcut — all trees
removed. Logging residue on watersheds was piled and
burned. Roads were constructed June-September 1970 and
harvesting done June-September 1971.
Vegetation: Mixed conifer.
Drainage: Coyote Creek: Shelterwood, 171 ac (69 ha).
Complete clearcut, 123 ac (50 ha).
Small clearcut, 169 ac (68 ha).
Control, 120 ac (49 ha).
Sampling: Sampling began October 1, 1969. Proportional samples
taken over 3-week intervals throughout each year.
Results:
Shelterwood
Disolved
NOs-N
Year and
treatment
1970
1971
1972
1973
1974
1975
(U)<
(RC)
(H)
(R)
(R)
(R)
mean
annual
IT
0.001
0.002
0.004
0.003
0.001
0.004
max
ig/l
0.005
0.016
0.012
0.033
0.017
0.019
NH4-N
mean
annual
mg/l
0.002
0.002
0.003
0.005
max
0.027
0.010
0.009
0.015
organic N
mean
annual
mg/l
0.077
0.048
0.075
0.039
0.051
0.067
max
0.165
0.126
0.114
0.060
0.155
0.151
Total-P
mean
annual
0.032
0.052
0.043
0.048
0.030
0.038
max
mg/l
0.080
0.090
0.095
0.115
0.076
0.069
Ortho-P
mean
annual
0.015
0.020
0.026
0.014
0.015
0.016
max
mg/l
0.030
0.033
0.070
0.090
0.021
0.021
Complete Clearcut
1970
1971
1972
1973
1974
1975
(U)
(U)
(H)
(R)
(R)
(R)
0.001
0.005
0.002
0.126
0.242
0.275
0.009
0.018
0.007
0.178
0.365
0.510
0.001
0.002
0.003
0.018
0.020
0.010
0.008
0.043
0.093
0.064
0.080
0.084
0.104
0.123
0.142
0.132
0.178
0.252
0.176
0.161
0.048
0.086
0.062
0.100
0.068
0.091
0.150
0.133
0.140
0.205
0.130
0.148
0.048
0.051
0.054
0.064
0.054
0.060
0.100
0.115
0.062
0.112
0.082
0.092
Small Clearcut
1970
1971
1972
1973
1974
1975
1970
1971
1972
1973
1974
1975
(F)
(RC)
(H)
(R)
(R)
(R)
(U)
(U)
(U)
(U)
(U)
(U)
0.003
0.055
0.004
0.026
0.007
0.019
0.001
0.005
0.003
0.002
0.004
0.004
0.022
0.177
0.031
0.120
0.087
0.059
0.004
0.025
0.005
0.034
0.022
0.034
0.003
0.001
0.001
0.009
0.001
0.003
0.002
0.014
0.031
0.004
0.005
0.034
0.006
0.012
0.006
0.061
0.105
0.073
0.081
0.056
0.070
0.084
Control
0.105
0.058
0.078
0.124
0.072
0.089
0.149
0.142
0.120
0.142
0.138
0.121
0.185
0.133
0.095
0.057
0.132
0.137
0.034
0.032
0.035
0.038
0.023
0.034
0.036
0.060
0.045
0.053
0.036
0.049
0.090
0.049
0.070
0.090
0.058
0.077
0.118
0.200
0.080
0.110
0.069
0.071
0.016
0.013
0.031
0.011
0.011
0.011
0.025
0.029
0.039
0.025
0.024
0.024
0.038
0.026
0.045
0.021
0.018
0.022
0.060
0.114
0.045
0.045
0.033
0.026
1U-undisturbed, F-fertilized, H-harvest, RC-road construction R-revegetating
Source: Fredriksen 1977.
X.33
-------
Silvi cultural
treatment:
Vegetation:
Drainage:
Sampling:
Results:
Study X.B.13
Alsea Basin, Oregon Coast Range
Needle Branch was completely clearcut beginning in
March 1966; logging slash was burned (very hot fire) in Oc-
tober 1966. Deer Creek was 25 percent clearcut in three log-
ging units. Only one unit in Deer Creek was burned (light
burn). Flynn Creek remained untreated and served as the
control.
Douglas fir and alder. Alder was predominant species on
Flynn Creek (68%) and Deer Creek (68%). Douglas fir
predominated on Needle Branch (80%).
Needle Branch, 175 ac (70.68 ha).
Deer Creek, 750 ac (303.32 ha).
Flynn Creek, 500 ac (203.14 ha).
2 years before and 2 years after logging.
Watershed
and treatment
Needle Branch
Clearcut
Deer Creek1
Patchcut
Flynn Creek1
Control
Water
year
1965
1966
1967
1968
1965
1966
1967
1968
1965
1966
1967
1968
NOa
Max
observed
0.20
0.70
2.10
1.65
3.17
2.10
2.70
2.40
3.19
2.18
2.70
2.20
U
Yearly
mean
mg/i -
0.12
0.19
0.44
0.43
1.12
0.98
1.21
1.12
1.21
1.16
1.18
1.18
Total phosphate P
Min
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
Max
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
1Migh nitrate-N values probably due to alder.
Source: Brown and others 1973.
X.34
-------
Silvicultural
treatment:
Vegetation:
Drainage:
Study X.B.14
Bitterroot National Forest,
Montana
Three watersheds were clearcut and three paired
watersheds were used as controls. Lodgepole Creek was 97
percent clearcut, most of it in 1969 and 1970. Mink Creek
was 83 percent clearcut in 1968 and dozer piled in 1971. The
lower 46 percent of Little Mink Creek was clearcut in 1963,
dozer piled in 1971, burned in 1972, and planted in 1973.
Mixed coniferous, ponderosa pine, Douglas fir, lodgepole
pine, Engelmann spruce, and subalpine fir.
1. Lodgepole Creek, treatment, 497 ac (201 ha).
1. Spruce Creek, control, 467 ac (189 ha).
2. Mink Creek, treatment, 614 ac (249 ha).
2. Springer Creek, control, 866 ac (350 ha).
3. Little Mink Creek, treatment, 103 ac (41 ha).
3. Little Mink Creek, control, 152 ac (61 ha).
Sampling:
Results:
Watershed
1. Lodgepole Creek
1. Spruce Creek
2. Mink Creek
One year from October
NOa-N
Mean annual
mg/l
0.19
0.11
0.17
1,
2.
3.
3.
1972-September
Watershed
Springer Creek
Little Mink Creek
Little Mink Creek
30, 1973.
NO3-N
Mean annual
mg/l
0.13
0.40
0.17
Source: Bateridge 1974.
X.35
-------
Study X.B.I5
Priest River Experimental Forest,
Idaho
Silvicultural Three watersheds were treated. Benton Creek was clearcut
treatment: in 1969, with a waterside area remaining along stream, and
broadcast burned in 1970. Ida Creek was clearcut in 1970.
with waterside area, and the slash was windrowed and
burned. Canyon Creek was also clearcut with a waterside
area, and broadcast burned.
Vegetation: Mixed conifers, western white pine, western red cedar,
Douglas fir, and western larch.
Drainage: Not defined.
Sampling: Benton Creek, September 1970 to June 1972.
Ida Creek, October 1970 to June 1972.
Sampling was done above and below the silvicultural operation.
Results:
Watershed
Benton
Control
Treatment
Ida
Control
Treatment
-NO:
Mean
0.20
0.18
0.14
0.16
i
-------
Study X.B.16
Marcell Experimental Forest,
Minnesota
Silvicultural 62.5 ac of aspen uplands were clearcut between December
treatment: 1970 and January 1972.
Vegetation: Aspen/birch and black spruce (bog).
Drainage: Treatment, 84 ac (34 ha).
Control, 130 ac (52 ha).
Sampling: Pre-silvicultural activity samples (9) were taken in the
spring, summer and fall. Post-silvicultural activity sampl-
ing (26 samples) was concentrated during high flows.
Results:
Sampling
Organic -N
Std
Mean error
Mean
NH4 -N
Std
error
NCh N
Std
Mean error
mg/l
Mean
Total -N
Std
error
Mean
Total P0«
Std
error
Silvicultural-
activity
Pre-
Post-
Control
Pre-
Post-
0.93
0.80
0.92
0.85
0.19
0.07
0.16
0.07
0.35
0.55
0.25
0.41
0.10
0.11
0.03
0.06
0.31
0.16
0.30
0.12
0.12
0.06
0.10
0.01
1.69
1.50
1.48
1.39
0.18
0.13
0.14
0.07
0.15
0.17
0.13
0.12
0.03
0.03
0.01
0.02
Source: Verry 1972.
X.37
-------
Study X.B. 17
West Central Alberta,
Canada
Silvicultural Clearcutting progressively over 13 forest watersheds located
treatment: in 3 working circles (management units).
Vegetation: Lodgepole pine, white spruce, and aspen.
Drainage: Ranged in size from 1,725 to 5,914 acres (700 to 2,400 ha).
Sampling: Summer 1974, 117 samples during spring snowmelt and 104
samples during summer recession period.
Results:
Marlboro Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
Berland Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
McLeod Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
Source: Singh and Kalra 1975.
Nl
Mean
0.52
0.22
0.68
0.18
0.39
0.10
0.34
0.09
0.48
0.20
0.48
0.22
n;
Std
error
0.07
0.03
0.09
0.02
0.05
0.01
0.06
0.02
0.03
0.03
0.03
0.03
N
Mean
• m(
0.04
0.006
0.02
0.006
0.011
0.004
0.047
0.028
0.010
0.008
0.016
0.005
03
Std
error
-./i
3'1
0.02
0.0002
0.01
0.001
0.003
0.001
0.009
0.004
0.002
0.002
0.003
0.001
PO.
Mean
0.011
0.007
0.012
0.008
0.010
0.005
0.008
0.004
0.012
0.006
0.009
0.005
•3-P
Std
error
0.001
0.001
0.001
0.001
0.001
0.003
0.0005
0.0001
0.001
0.0003
0.001
0.0005
X.38
-------
Study X.B.18
Dennis Creek, Okanagan Valley,
British Columbia
Silvicultural Clear-cutting 383 ac (155 ha) representing about 25 percent
treatment: of the drainage area.
Vegetation: Engelmann spruce-subalpine fir.
Drainage: Dennis Creek treatment, 2,370 ac (960 ha).
James Creek control, 2,000 ac (810 ha).
Sampling: Sampling was done at two sites each above and below the
silvicultural operation and on an adjacent undisturbed
watershed.
Results:
Total
Kjeldahl nitrogen
Min Mean Max
Below cut
Sitel
Site 2
Above cut
Site 1
Site 2
Control
Sitel
Site 2
Source: Hetherington
0.090
0.090
0.095
0.095
0.100
0.100
1976.
0.189
0.242
0.166
0.191
0.308
0.328
0.351
0.596
0.346
0.418
0.448
0.467
Min
0.002
0.002
0.002
0.002
0.002
0.002
NO3-N
Mean
mg/l
0.003
0.028
0.004
0.010
0.015
0.029
Total phosphorus
Max Min Mean Max
0.010 0.005
0.368
0.013 0.002
0.050
0.040 0.014
0.124
0.015 0.038
0.010 0.031
0.028 0.056
X.39
-------
Chapter XI
INTRODUCED CHEMICALS
this chapter was prepared by the following individuals:
Duane G. Moore
John B. Currier
with major contributions from:
Logan A. Norris
Xl.i
-------
CONTENTS
Page
INTRODUCTION XI.l
DISCUSSION XI.2
MAGNITUDE AND SCOPE OF CHEMICAL USE XI.2
Pesticides XI.2
Fertilizers XI.4
Patterns Of Chemical Use XI.4
Insecticides XI.4
Herbicides XI.5
Fungicides XI.5
Rodenticides XI.5
Fertilizers XI.5
CONCEPTS OF HAZARD AND CHEMICAL ACTION XI.5
CHEMICAL BEHAVIOR OF PESTICIDES XI.6
Initial Distribution of Spray Materials XI.7
Movement, Persistence, And Disposition of Pesticides XI.8
Distribution In Air XI.8
Distribution In Vegetation XI.8
Distribution On The Forest Floor And In Soil XI.9
Distribution In Surface Waters XI. 12
Entry Of Pesticides Into The Aquatic Environment XL 12
Movement To Streams From The Air XI. 12
Movement To Streams From Vegetation XI.13
Movement To Streams From The Forest Floor And Soil XI. 13
Summary Of Pesticide Entry Into The Aquatic Environment XL 16
Behavior In The Aquatic Environment XI. 16
Volatilization XL 16
Adsorption XL 16
Degradation XL 17
Downstream Movement XL 17
CHEMICAL BEHAVIOR OF FERTILIZERS XI.18
Initial Distribution In Air, Vegetation And Forest Floor XI.18
Entry Of Fertilizers Into The Aquatic Environment XI.18
Summary of Fertilizer Entry Into The Aquatic Environment XL22
Behavior In The Aquatic Environment XI.23
CONCLUSIONS XI.24
LITERATURE CITED XI.25
APPENDIX A: WATER QUALITY DATA—PESTICIDE CHEMICALS .. . XI.31
APPENDIX B: WATER QUALITY DATA—FERTILIZER CHEMICALS .. XI.43
APPENDIX C: REFERENCE SOURCES FOR PESTICIDE CHEMICALS XI.51
Xl.ii
-------
LIST OF FIGURES
Number Page
XI. 1. —The interaction of chemicals with the environment XI. 6
XI.2. —The distribution and disposition of chemicals in the environment.. XI.7
XI.3. —Lateral movement of spray particles XI.7
XI.4. —Recovery of 2,4-D, amitrole, 2,4,5-T and picloram from red alder
forest floor material XI.10
XI.5. —Chemical adsorption in soil is an equilibrium reaction XI. 10
XI.6. —Persistence of individual pesticides in soils XI. 11
XI.7. —Precipitation and herbicide runoff patterns at the Beacon Rock Study
Area XI. 14
XI.8. —Relative mobility of pesticides leached in columns of soil XI. 15
XI.9. —The degradation of 2,4-D in a bacterially active water culture XI. 17
XI. 10. —Coyote Creek watersheds, South Umpqua Experimental Forest, Um-
pquaNational Forest, Oregon XI. 19
XI.11. —Fertilization of a 68-ha watershed XI.21
XI.A.l. —Cascade Creek Treatment Unit XI.31
XI.A.2. —Eddyville Treatment Unit XI.32
XI.A.3. —West Myrtle Treatment Unit XI.32
XI.A.4. —Camp Creek Spray Unit XI.33
XI.A.5. —Keeney-Clark Meadow Spray Units XI.33
XI.A.6. —Wildcat Creek Spray Unit XI.34
XI.A.7. —Farmer Creek Treatment Watershed XI.35
XI.A.8. —Precipitation, stream discharge, and concentrations of tryclopyr in
stream water following application of 3.36 kg/ha by helicopter to a
small watershed in southwest Oregon in May 1974 XI.37
XI.A.9. —Boyer Ranch, southwest Oregon. Small 7-ha hill-pasture spray unit
treated with Tordon 212 XI.38
XI.A.10.—Discharge of herbicide in streamflow from small 7-ha hill-pasture
watershed, Boyer Ranch, southwest Oregon XI. 39
XI.A. 11.—Concentration of endrin in streamflow after aerial seeding with
endrin-coated Douglas-fir seed XI.40
XI.A.12.—Water yield and bromacil release from watershed 2, Hubbard Brook
Experimental Forest, West Thornton, N.H XI.41
XI.A.13.—Atrazine concentration in streamflow during and for SVz months after
herbicide treatment XL42
XLiii
-------
LIST OF TABLES
Number Page
XI.1. —Pesticide use in forests, July 1, 1975, to September 30, 1976 XI.2
XI.2. —Reported pesticides used for silviculture in the United States XI.3
XI.3. —Residues of herbicide in forage grass XI.8
XI.4. —Effect of slope, rate of application and movement over untreated sod
on the concentration of picloram in runoff water XI. 13
XI.5. —Concentration of fertilizer nitrogen in selected water samples XI.20
XI.6. —Nitrogen lost from treated watershed 2 and untreated watershed 4
during the first 9 weeks XI.20
XI.7. —Nitrogen lost from treated watershed 2 and untreated watershed 4
during the first year XI.21
XI.A.l. —Cascade Creek Unit, Alsea Basin, western Oregon XI.31
XI.A.2. —Eddyville Unit, Yaquina Basin, western Oregon XI.32
XI.A.3. —Concentration of 2,4-D in West Myrtle Creek, Malheur National
Forest, eastern Oregon XI.32
XI.A.4. —Camp Creek Spray Unit, Malheur National Forest, eastern Oregon XI.33
XI.A.5. —Concentration of 2,4-D in streams in Keeney-Clark Meadow, eastern
Oregon XI.33
XI.A.6. —Concentration of Amitrole-T in Wildcat Creek, Coast Range, western
Oregon XI.34
XI.A.7. —Concentration of amitrole in stream water, loss or dilution with
downstream movement. Amitrole-T applied to 105 ha at 2.24 kg/ha XI.35
XI.A.8. —Concentration of dicamba in Farmer Creek XI.36
XI. A.9. —Concentrations of 2,4-D and picloram in drainage waters from a 7-ha
hill-pasture watershed in southwest Oregon XI.38
XI.A.10.—Total DDT content of stream water flowing from sprayed area before
treatment and for 3 years after treatment XI.39
XI.A.11.—Concentration of herbicides in water samples, as determined by odor
tests XI.40
XI.A.12.—Concentrations of 2,4-D and 2,4,5-T herbicide in water samples from
Monroe Canyon, San Dimas Experimental Forest, northeast of
Glendora, California XI.41
XI.B.l. —Stream water quality following forest fertilization, fall 1975:
Hoodsport-Quileene Ranger Districts Olympic National Forest,
Washington XI.43
XI.B.2. —Stream water quality following forest fertilization, spring 1975:
Hoodsport-Quileene Ranger Districts, Olympic National Forest,
Washington XI.44
XLiv
-------
LIST OF TABLES (Continued)
Number Page
XI.B.3. —Stream water quality following a wildfire and fertilization with
reseeding for erosion control, 1971: Entiat Experimental Forest,
central Washington XI.45
XI.B.4. —Stream water quality following forest fertilization, 1970: Mitkof
Island, southeast Alaska XI.46
XI.B.5. —Stream water quality following forest fertilization of two small
watersheds, 1970 and 1971: Siuslaw River Basin, western Oregon XI.46
XI.B.6. —Stream water quality following fertilization of forested watersheds on
the Olympic Peninsula, spring 1970: Quileene Ranger District,
Olympic National Forest, Washington XI.47
XI.B.7. —Stream water quality after fertilization of a small forested watershed
on the west slopes of the Cascade Mountains, 1970: Oregon XI.47
XI.B.8. —Stream water quality after fertilization following wildfire in north
central Washington, 1970: Chelan, Washington XL48
XI.B.9. —Stream water quality following forest fertilization, spring 1976:
Quileene Ranger District, Olympic National Forest, Washington . XI. 48
XI.B.10.—Stream water quality and quantity of flow following fertilization of a
forested watershed, 1971: Fernow Experimental Forest, West
Virginia XI.49
XI.B.ll.—Stream water quality following fertilization of a gaged experimental
watershed, spring 1970: South Umpqua Experimental Forest,
Oregon XI.49
XI.B.12.—The impact of forest fertilization on stream water quality in the
Douglas-fir region—a summary of monitoring studies in Alaska,
Idaho, Oregon, and Washington XI.50
XI.v
-------
INTRODUCTION
Chemicals have played an important role in the
success story of modern American agriculture.
These same management tools — fertilizers, insec-
ticides, herbicides, fungicides, rodenticides,
avicides, piscicides, etc. — are equally important
in meeting the rapidly growing demand for forest
products. Their magnitude, intensity, and pattern
of use is vastly different in forestry, and these
chemicals provide an economically feasible means
of controlling insects and disease and increasing
timber production. However, their widespread use
cannot proceed without adequate consideration of
the potential impacts upon environmental quality.
The forest land manager has a responsibility to
protect the environment from contamination and
thus must be aware of the potential hazards in-
volved with each silvicultural practice that uses
chemicals.
Chemicals introduced into a watershed as part of
a silvicultural activity represent a potential non-
point source of pollution for forest streams.
Research findings and a long history of use have es-
tablished that most forest chemicals offer
minimum potential for degradation of the aquatic
environment when they are used properly (Norris
and Moore 1976). This chapter discusses the types
of fertilizers and pesticides used, the magnitude
and scope of chemical use, the behavior of
chemicals in the forest environment, and the
mechanisms by which chemicals may reach forest
streams. This information forms the basis for un-
derstanding the non-point source pollution
processes that result from chemicals used in
silvicultural activities and for selecting effective
controls. There is insufficient data to permit us to
quantify control effectiveness.
XI. 1
-------
DISCUSSION
MAGNITUDE AND SCOPE OF CHEMICAL
USE
Newton and Norgren (1977) have categorized the
chemicals used in forest management into three
general groups based upon the broad objectives of
their use. One group is herbicides which are used
when forest productivity is to be focused on
selected species. Herbicides do not influence the
basic productivity of the forest ecosystem, but are
used to channel that productivity into selected
timber species that have special value. The second
group of chemicals, including insecticides and
rodenticides, is used to reduce losses of important
tree species. The specific targets of these chemicals
are insect and animal pests that are capable of
damaging or destroying commercially desirable
tree species. Fungicides used to control diseases in
existing stands are also included in this group. The
behavior of these two major groups is discussed
together as "pesticides" in this publication. The
third group of chemicals includes only fertilizers.
Chemicals in this category are used to increase
growth rates of commercial tree species by raising
the overall productivity of forest ecosystems. Fer-
tilizer chemicals also are used as fire retardants
and will be included in this group rather than dis-
cussed separately. A wide variety of other
chemicals are used in forestry for insect and disease
control in nurseries, for soil stabilization, for dust
control, for road surfacing, and various other pur-
poses. However, these latter chemical uses are
limited in scope and will not be discussed in this
publication.
The potential impact of introduced chemicals
upon forest water quality depends largely on the
chemical and its pattern of use. In intensive
agriculture, chemicals may be applied one or more
times during a crop cycle. Crop cycles are short;
thus, regular and repeated applications are a com-
mon practice. By contrast, most forest land will not
be treated with chemicals at any time during a crop
cycle. Lands that are treated seldom receive more
than one treatment in a crop cycle. (Crop cycles
range from 20 to more than 100 years.) A large
number of chemical compounds are registered for
use in agriculture, while in forestry less than 15
principal pesticides are used. Forestry practices ac-
count for only slightly more than 1 percent of the
total pesticide use and less than 1 percent of the
total fertilizer consumption in the United States.
Pesticides
Pesticide use on forest lands between July 1,
1975, and September 30, 1976, is summarized in
table XI. 1. The figures represent both pesticides
used by the Forest Service and pesticides used on
projects involving Federal assistance provided by
the Forest Service (USDA 1977). In general, these
figures underestimate the total use in forestry
because they do not include pesticide use by other
Federal land management agencies or by various
State and private groups. In addition, data
presented for insecticide use have been modified by
deducting the figures for one large project con-
ducted to control defoliation caused by the Eastern
spruce budworm. This single insect control project
accounted for 85 percent of the total figure for
Table XI.1.—Pesticide use in forests, July 1, 1975, to September 30, 1976'
Pesticide used
Acres treated
Percent
Pounds used2
Percent
Herbicide
Insecticide
Fungicide
Rodenticide
Piscicide
Bird repellent
235,551
326,148
34,109
22,599
481
714
38
53
5
4
0
0
563,517
'192,175
143,431
6,053
833
289
62
21
16
1
0
0
'Reporting period is 15 months, FY 1976 and Transition Quarter (USDA 1977).
'Reported as pounds of active ingredients.
3Data presented do not include 3,501,950 acres treated with 2,663,208 pounds of insecticide
chemicals to control defoliation caused by the Eastern spruce budworm. These data were omitted in
order to provide a closer approximation of the annual pesticide use pattern.
XI.2
-------
treated land area and 75 percent of the total figure
for applied pesticide chemicals during the 15-
month period covered by the report. Large control
projects of this magnitude (3,501,950 ac) do not oc-
cur on an annual basis; therefore, the data were
modified as described in order to provide a closer
approximation of the annual pesticide use pattern.
Most insecticides applied to forests in the United
States are applied to Forest Service and adjacent
lands through Federal cooperative insect control
projects for which the Forest Service has respon-
sibility. Thus, the figures presented in table XI. 1
provide a fairly close estimate of the total annual
use of insecticides. Herbicide use projects are car-
ried out independently by the various forest land
management groups, and the figures presented
reflect a considerable underestimate of total her-
bicide use. It is apparent, however, that herbicide
use is considerably greater than insecticide use in
terms of the amount of chemical applied,, and
probably exceeds insecticide use in terms of total
area treated annually (with the exception of large
insect control projects).
To further illustrate the scope of pesticide use in
forests, a list of individual pesticide compounds or
combinations is presented in table XI.2. The land
area treated with each pesticide provides an indica-
tion of its importance in forest land management.
Data presented were obtained from the Fiscal Year
(FY)-1976 and Transition Quarter Pesticide-Use
Report (USDA 1977) and essentially represent an-
nual usage. The total number of pesticide
chemicals or combinations is quite large, but the
major applications employ only a few. Seven her-
bicide chemicals account for 95 percent of the total
herbicide use.
These figures indicate that approximately 0.2
percent of the commercial forest land in the United
States is treated with pesticides in any given year
(0.8 percent in FY-1976 including the large Eastern
spruce budworm spray program). Therefore, in-
teraction between pesticides and water quality is
not an extensive problem. In those areas treated
with pesticides, however, the interaction, although
localized, can be intense.
Table XI.2—Reported pesticides used for silviculture in the United States, July 1, 1975, to September 30, 1976.1
Herbicides
Acres treated
Herbicides
Acres treated
Insecticides
Acres treated
2,4-D
2,4,5-T
2,4-D & Picloram
Picloram
2,4-D & 2,4,5-T
MSMA
2,4-D & 2,4-DP
Simazine
Simazine and Atrazine
Atrazine
Diphenamid
Mineral Spirits
Dalapon
2,4,5-TP (Silvex)
Dicamba
2,4-D & Dicamba
79,713
40,155
36,662
29,891
12,797
7,624
6,073
5,424
3,000
2,440
1,673
1,219
1,215
1,198
981
950
Cacodylic Acid
Methyl Bromide
Dacthal
Amitrol
Trichlorobenzoic Acid
Trifluralin
Ureabor
Ammonium Sulfamote
Pentachlorophenol
Bromacil
Prometryne
Glyphosate
688
605
473
412
354
227
200
194
190
166
156
146
Carbaryl
Lindane
Trichlorfon
Malathion
DDT
Acephate
Dibrom
Difluron
Mirex
Bacillus Thuringiensis
Crotoxyphos
Dimethoate
Azinphos Methyl
Methomyl
Dursban
Pyrethrins
274,036
65,076
258,705
50,488
36,875
25,900
3,000
21,800
1,674
2950
900
851
681
450
368
300
'Compiled from U.S. Forest Service Pesticide Use Reports, the amounts include chemicials used by the Forest Service
and chemicals used on projects involving Federal assistance by the Forest Service (USDA 1977). Actual total amounts are
considerably greater.
2Does not include amounts used to control Eastern spruce budworm.
3DDT and Carbaryl were used for plague control.
XI.3
-------
Fertilizers
Fertilizers are applied annually to only a small
portion of commercial forest lands. Levels of
management on most forest lands have not yet
reached the intensity where fertility would severely
limit economic yields; however, several major
forest industrial corporations and public agencies
have been using forest fertilization as a standard
management practice for a little over 10 years. Fer-
tilization operations are restricted to the Pacific
Northwest, where nitrogen deficiencies are com-
monly encountered, and to the Southeast, where
phosphorous deficiencies often limit tree growth
and reduce survival of young stands.
Fertilization of forest stands in the Pacific
Northwest was initiated in 1965 when one in-
dustrial corporation aerially fertilized 1,500 acres of
Douglas-fir with urea. Between 1965 and 1975, ap-
proximately 750,000 acres of Douglas-fir were fer-
tilized in western Oregon and Washington (Moore
1975b, Norris and Moore 1976). Annual fertiliza-
tion increased rapidly up to 1973 when 160,000
acres were treated in 1 year. The practice then
dropped drastically as the energy crisis caused a
shortage of fertilizer and also raised the price of
nitrogen use to nearly double the cost per acre. Fer-
tilization practice is increasing again now in the
Pacific Northwest, but has not yet reached the
earlier peak of annual fertilizer application.
The first forest fertilization project in the
Southeast was conducted in 1963 on 630 acres
(Groman 1972). The scope of operations in the
Southeast has not approached that of the
Northwest, but by 1971 approximately 110,000
acres had received chemical fertilizers. When a
moderate, but steady, increase in the practice was
assumed, a gross estimate of total fertilized acreage
through 1975 was 350,000 acres.
Investigations conducted in the hardwood stands
of the Northeast indicate that nitrogen deficiencies
appear to be limiting growth, and the application
of potassium has effectively stimulated growth on
old fields that are being reforested. However, ad-
ditional field research is needed before forest fer-
tilization will be used in that region (Beaton 1973,
Mader 1973d, Weetman and Hill 1973).
Fertilizers, like pesticides, are applied to a very
small proportion of the total commercial forest
land each year, and applications to any given site
occur infrequently. Through 1975, the total acreage
fertilized was only 0.2 percent of the commercial
forest land in the United States, and the forested
area fertilized in any one year did not exceed
250,000 acres. However, a much larger total acreage
of commercial timber stands is considered poten-
tially amenable to fertilization. The use of this
practice to increase the volume of wood fiber
produced per unit area, and over a shorter period of
time, can be expected to increase.
Patterns Of Chemical Use
Insecticides
At present, there are very few insecticides
registered for use on forest lands. Insect damage
problems in recent years have been handled as
special projects, where approval for a particular
chemical or formulation is usually granted by
regulatory agencies on a case-by-case basis. An en-
vironmental impact statement must be prepared
for each project and is used as the basis for ap-
proval or denial of the proposed chemical control
program.
The chlorinated hydrocarbon insecticides are not
usually selected for use in forestry when alternate
chemicals are available. The application of DDT in
Idaho, Oregon, and Washington for control of the
Douglas-fir tussock moth in 1974 was an exception.
Insecticides more likely to be used in forestry are
various organophosphate and carbamate com-
pounds. Nonresidual biological control agents are
also being used. Recent research has developed
suspensions of insect disease cultures that are quite
specific for the target insects. Virus cultures have
been used in several projects with considerable suc-
cess and low impact on nontarget terrestrial and
aquatic insects. This material is now registered for
use in the control of Douglas-fir tussock moth.
Applications of insecticides to forest areas are
almost exclusively made by aerial spraying. Large
or contiguous areas may be treated in a single pro-
ject to control an outbreak of defoliating insects on
commercially valuable timber. Regional projects
may include a large part of an entire river drainage
basin. Thus, in any one year, a large percentage of
the total amount of a given insecticide applied to
forests in the United States may be applied in only
one region. Several to many years will normally
elapse before an application of any magnitude is
made again in the same region. While the potential
for impact of insecticides on water quality and the
aquatic community may be relatively widespread
on a regional basis, it is still infrequent in occur-
rence.
XI.4
-------
Herbicides
Herbicidal chemicals are used for a wide variety
of purposes in silvicultural activities including fuel
break management; vegetation control on
powerline, road, and railroad rights-of-way; con-
version of hardwood brush to conifers; release of es-
tablished conifers from hardwood brush competi-
tion; thinning; cull tree removal in established
stands; and control of noxious weeds. The most
commonly used chemicals are the phenoxy her-
bicides (2,4-D,2,4,5-T, and Silvex), picloram, and
triazines (atrazine and simazine), and the organic
arsenicals (MSMA and Cacodylic acid).
Herbicides are applied by a variety of means —
aerial (rotary or fixed-wing aircraft), low pressure-
high volume ground spray equipment, mist
blowers, stem injection devices — and in a variety
of forms — pellets, granules, and undiluted con-
centrates. Treatment areas are typically small (5 to
200 ac) and widely scattered. Large contiguous
blocks are seldom treated. The annual extent of
herbicide use remains reasonably constant on a
regional basis; therefore, the opportunity for in-
teraction between herbicides and streams occurs
regularly, but is of limited scope in any one
drainage system. Use of herbicides on any given
site is usually limited to one or, at most, two ap-
plications.
Fertilizers
Forest fertilization is carried out in the Pacific
Northwest by aerial application. Present opera-
tions are conducted almost exclusively with
helicopters (Moore 1975b). In the Southeast and on
Southern pine lands, ground equipment is used to
fertilize young stands and aerial equipment makes
application on older stands. Soils in Florida, the
Flatwoods, and Atlantic Coastal Plain subregions
are deficient in phosphorus and fertilizer is applied
to them at time of planting or soon thereafter.
Older stands respond to nitrogen or to nitrogen plus
phosphate, if the stand is on a phosphorous
deficient site (Bengston 1970).
Fertilizers may be applied to relatively large con-
tiguous areas, but a more typical practice is to fer-
tilize smaller management units in a patchwork
fashion. Treated areas are usually some distance
from users of potable or irrigation waters. The in-
frequency of application coupled with application
to undisturbed forest soils and vegetation tends to
minimize the potential for impact on water quality.
Buffer strips can be maintained along major
streams, but it is not possible to avoid all of the
smaller headwater streams. Thus, some forest
streams in a fertilized watershed will normally con-
tain detectable amounts of chemical immediately
after application.
Fungicides
Fungicidal chemicals receive intensive use in
forest nurseries, but are seldom used in
silvicultural activities. Nursery use is more com-
parable to agricultural use than to forestry use and
is not included in this discussion. Fungicide treat-
ments to stumps and roots for control of root and
butt rots affect only small and isolated areas and
provide little, if any, opportunity for impact on
water quality.
Rodenticides
Rodenticide use has decreased sharply in recent
years. The small quantities used in forestry and the
methods of applying them to the ground indicate
that any effects on water quality are not likely to be
detectable.
CONCEPTS OF HAZARD
AND CHEMICAL ACTION
Pesticides used in forest management are
selected because of their known effects on specific
targets. The hazard involved in their use is the risk
of adverse effects on nontarget organisms. Two fac-
tors determine the degree of hazard: (1) the toxicity
of the chemical and (2) the likelihood that non-
target organisms will be exposed to a toxic dose.
Toxicity alone does not make a chemical hazar-
dous. The hazard comes from exposure to toxic
doses of that chemical. Even the most toxic
chemicals pose no hazard if organisms are not ex-
posed to them. Therefore, an adequate assessment
of the hazard involved in the use of any chemical
requires that both the likelihood of exposure and
the toxicity of the chemical be considered (Norris
1971).
Chemical action is the direct effect of a chemical
on an organism. Chemical action on any organism
XI.5
-------
requires exposure and, furthermore, requires suf-
ficient quantity of chemical present at the site of
action, in an active form and for a sufficient period
of time, to produce a toxic effect. There are two
kinds of toxicity: acute and chronic. Acute toxicity
is the fairly rapid response of organisms to one, or a
few, relatively large doses of chemical administered
over a short period of time. Chronic toxicity is the
slow or delayed response of organisms that occurs
after repeated or continuous exposure to small
doses of chemical extending over a relatively long
period of time. There are various gradations
between these two extremes. The kind of response
(acute or chronic) observed in nontarget organisms
depends on the magnitude of the dose, the duration
of exposure, and the behavior of the chemical.
Toxicity. — A consideration of the principles of
toxicity or a review of the toxicity characteristics of
silvicultural chemicals is beyond the scope of this
chapter. Newton and Norgren (1977) provide an ex-
cellent summary of this topic. Reference sources for
the more frequently used silvicultural chemicals
are given in appendix XI.C.
Potential for exposure. — The potential for ex-
posure of nontarget organisms is determined by the
initial distribution of the chemical and its subse-
quent movement, persistence, and disposition in
the environment. When a chemical is applied to a
forested watershed, there is an interaction between
the properties of the chemical and the properties of
the environment. These interactions follow the
basic laws of physics, chemistry, and biology and
define chemical behavior (fig. XI.l). The resulting
quantities of a chemical found in different parts of
the environment at varying times after application
determine the duration and magnitude of exposure
of different organisms to the chemical. The overall
impact of chemicals on both target and nontarget
organisms and the selective action of chemicals de-
pend on this exposure.
CHEMICAL BEHAVIOR OF PESTICIDES
The behavior of a chemical consists of its move-
ment, persistence, and disposition in the environ-
ment. Such behavior determines how much
chemical is in what part of the environment for
what period of time and in what form. The initial
distribution of a silvicultural chemical and its sub-
sequent behavior in the terrestrial environment
determines its potential role as a non-point source
pollutant. Its behavior in the aquatic environment
and its inherent toxicity determine its importance.
LAWS OF
BEHAVIOR
POTENTIAL
OF
EXPOSURE
Of OMHOttHŁKT
Figure XI.L—The Interaction of chemteata with th« environment (Morris 1971).
XI.6
-------
CHEMICAL APPLIED
Direct
Application
Fallout
Washout
•- s&t-Leochma,,*4^^^ AW-saW
WATER-—Decay, exudation-pLANTS—Decay, exudation—» SOIL
I Absorption ' ' Absorption '
Surface runoff, sheet erosion, leaching
Figure XI.2.—The distribution and disposition of chemicals in the environment (Foy and Bingham 1969).
Initial Distribution Of Spray Materials
Aerially applied chemicals are distributed in-
itially among four major components of the forest
environment: air, vegetation, the forest floor, and
surface waters (fig. XI.2). The amount of chemical
entering each portion of the environment is deter-
mined by the chemical and equipment used and
the environmental conditions that prevail at the
time of spraying (Norris and Moore 1971).
Some spray material is dispersed by the wind as
fine droplets called "drift." The degree of lateral
movement of spray drift depends on droplet size,
height of release, and wind velocity (fig. XI.3)
(Reimer and others 1966). Additional amounts of
chemical may remain in the air due to volatiliza-
tion of spray materials while falling through the
air. Most of the pesticide chemical not lost through
drift or volatilization is intercepted by vegetation
or the forest floor. Some small amount of pesticide
may fall directly on surface waters.
5 M.P.H WIND *•
Figure XI.3.—Lateral movement of spray particles of various
diameters falling at terminal velocity in an 8 km/hr cross-
wind (5 mph = 8 km/hr; 1 ft = 0.3048 m) (Reimer and others
1966).
XI.7
-------
Movement, Persistence, And Disposition
Of Pesticides
The movement of pesticides includes movement
within a given compartment of the environment
(leaching in the soil profile) or movement from one
compartment to another (washing pesticide
residues from leaf surfaces to the forest floor by
precipitation). Persistence is the tendency of
pesticides to remain in an unaltered form. The dis-
position of pesticides concerns the various physical,
chemical, and biological pathways taken by
chemicals in becoming biologically harmless
products. These aspects of chemical behavior will
be discussed for each environmental compartment.
Distribution In Air
Losses of herbicides and insecticides to the air
may be appreciable, but there is little quantitative
data. During one test in western Oregon, for exam-
ple, from 20 percent to 75 percent of a herbicide ap-
plication did not reach the ground, but these
results were confounded by the presence of nearby
overstory vegetation1. Use of helicopters in place of
fixed-wing aircraft and the introduction of
improved drift control nozzles and spray additives
have greatly reduced the amount of chemical
reaching sites outside the target zone.
More recent work has used spray interception
disks. Norris and others (1976b) reported 85 per-
cent recovery of picloram and 70 percent recovery
of 2,4-D when using the spray interception disks in
a southern Oregon brush field that had been
sprayed by helicopter. On four powerline rights-of-
way in Oregon and Washington treated by
helicopter with 2,4-D and picloram, interception
disks recovered 71 percent of the 2,4-D and 90 per-
cent of the picloram.
Several things can happen to that portion of
chemical that becomes dispersed in the air. Fine
droplets (drift) or vapors (volatiles) can be moved
to other locations where they settle to the earth.
Droplets and vapors can also be washed out with
rain, absorbed or taken up by plants and other
organisms, or adsorbed on various surfaces.
Another possible fate for many pesticides is
^Newton, M., LA. Norris, and J. Zauitkouski. Unpublished
data on file Sch. For.. Oregon State Univ., Corvallis.
photodegradation (Moilanen and others 1975).
With the exception of direct application or the
deposition of spray drift, the air is not an important
source of chemicals that later enter the aquatic en-
vironment.
Distribution In Vegetation
The amount of pesticide intercepted by vegeta-
tion depends on the rate of application, the nature
and density of the vegetation, and the physical
characteristics of the spray material. Chemicals in-
tercepted by vegetation may be volatilized into the
atmosphere, washed off by rain, or adsorbed on the
leaf surface. There is limited absorption and very
little translocation of many pesticides intercepted
by foliage. Through the action of rain, much of the
unabsorbed pesticide will be washed from the sur-
face of the leaf. Pesticide remaining on the leaf sur-
face and any pesticide not translocated to other
plant parts will enter the environment of the forest
floor during leaf fall.
Pesticides retained by the plant may be excreted
back into the environment through the roots or
they may end up in some plant storage tissue to be
released at a later time. Through metabolic ac-
tivity, plants may degrade a pesticide to non-
biologically active substances.
Studies of herbicides show that the highest con-
centrations of residue occur in foliage shortly after
application (see1 table XI.3) (Morton and others
Table XI.3.—Residues of herbicide1 In forage grass
Tim* after
treatment
(Weeks)
0
1
2
4
8
16
52
2,4-D1
100
60
50
30
6
1
—
Herbicide rae
2,4,5-T*
100
60
30
15
6
2
—
Mue
Picloram9
135
—
32
—
24
16
3
'Rate of application equals 1.12 kg/ha.
2Data from figure 4 In Morton and others 1967.
'Data from table 5 in Qetzendaner and others 1969.
XI.8
-------
1967, Getzendaner and others 1969). A combina-
tion of factors causes the residue concentrations to
decrease rapidly with time. Growth, dilution,
weather, and metabolism of the herbicide by the
plant are particularly important.
Weathering is very important in reducing residue
levels of carbaryl on foliage. Wells (1966) reported
that rain in excess of 1.8 inches (45 mm) falling 12
to 24 hours after spraying reduced initial residue
levels of carbaryl on oak foliage from 190 ppm to
about 15 ppm 3 days later. Degradation of carbaryl
residues on plants is less important, but plants ab-
sorb only small amounts (Union Carbide 1968).
Formulation also influences persistence of residues
on foliage (Fairchild 1970). Carbaryl applied in an
80 percent wettable powder formulation had a half-
life (the time required by an organism to eliminate,
by biological or chemical processes, half the quan-
tity of a substance taken in) of 3 to 4 days, while
carbaryl applied in a Sevin-4-oil formulation was
found to have a half-life of 8 to 10 days on range
grasses. Typical initial residue levels on forest
foliage ranged from 30 to 100 ppm immediately
after treatment. These residues decreased to 5 to 20
ppm after 2 or 3 weeks (Back 1971).
Dylox (trichlorfon) insecticide is relatively non-
persistent; only small amounts remain on treated
foliage beyond 1 week after application. Residue
levels of 0.33 to 3.3 ppm trichlorfon on leaves, 0.42
to 1.1 ppm on twigs, and 1.5 ppm on forest litter 26
days after application were reported by Wilcox
(1971). Residues were still detectable after 106
days, even though residues declined most rapidly
over the first 7 days following spraying (Devine and
Wilcox 1972). Weiss and others (1973) reported
that Dylox residues dropped sharply within a few
days after spraying, and that after 60 days, 15 per-
cent of the initial level remained on leaves, 5 per-
cent on the forest floor, and less than 1 percent in
the soil.
Orthene, also an organophosphate insecticide, is
readily degraded by plants. It has an observed half-
life of from 5 to 10 days (Chevron 1973). This insec-
ticide adheres to or is absorbed by leaf surfaces and
washing of field-treated vegetation will remove no
more than 5 percent of the residue present.
Translocation from treated leaves to other parts of
the plant is only very slight. Orthene is not persis-
tent on forest vegetation because of its short half-
life (Devine 1975). Following field applications at
V4-, %, and IVfc-lb active ingredient/acre, residues
on leaves and in forest floor material declined to
nondetectable levels in 1 to 2 months.
Distribution On The Forest Floor And In Soil
The forest floor is a major receptor of aerially ap-
plied spray materials. Pesticides on the forest floor
may be volatilized and reenter the air, adsorbed on
soil mineral or organic matter, leached through the
soil profile by water, absorbed by plants, or
degraded by chemical or biological means.
Volatilization of chemicals from the soil surface
may be responsible for the redistribution of fairly
large amounts of some pesticides such as DDT and
perhaps some phenoxy ester herbicides.
The length of time chemicals persist in the forest
floor and soil bears strongly on the probability they
will contaminate the aquatic environment.
Pesticide degradation is usually biological, but
chemical degradation is important in the loss of
amitrole and the organophosphate insecticides
(Hance 1967, Kaufman and others 1968, Norris
1970).
The common brush control herbicides (2,4-D,
amitrole, 2,4,5-T, and picloram) are all degraded in
the forest floor although their rates of degradation
vary considerably (fig. XI.4). In red alder (Alnus
rubra) forest floor material, 80 percent of the
amitrole and 94 percent of the 2,4-D were degraded
in 35 days, but 120 days were required to degrade
87 percent of the 2,4,5-T. Picloram degradation was
slow, 35 percent in 180 days (Norris 1970).
Adsorption and leaching are processes which
work in opposition to one another. Adsorbed
molecules are not available for leaching, but ad-
sorption is not permanent. The amount of pesticide
that is adsorbed is in equilibrium with the amount
of pesticide in the soil solution. As the concentra-
tion of pesticide in the soil solution decreases, more
pesticide will be released from adsorption sites (fig.
XI.5). Thus, adsorption provides only temporary
storage, and the soil is, in effect, a reservoir of the
chemical that will eventually be released. Leaching
is a slow process, capable of moving pesticides only
short distances (Harris 1967, 1969). Herbicides are
generally more mobile in soil than insecticides, but
mobility is relative, and even the movement of her-
bicides is usually measured in terms only of inches
or a few feet.
Most of the chemicals applied to the forest,
regardless of method of application, eventually
reach the forest floor and soil compartments.
Chemical behavior in this part of a forest
watershed is particularly important because it
determines whether these introduced chemicals
will be immobilized, degraded, or transported to
XI.9
-------
LEGEND
Q 2,4-D
• Picloram
EJ 2,4,5-T
• Amitrole
20
40
80 100
TIME .days
120 140 160 180
Figure XI.4.—Recovery of 2,4-D, amitrole, 2,4,5-T, and picloram from red alder forest floor material
(Norris 1970).
CHEMICAL+ADSORBENT ^1
^T CHEMICAL : ADSORBENT
Figure XI.5.—Chemical adsorption in soil is an equilibrium reaction.
the aquatic environment. The forest floor and soil
make up a very active biological system that
provides a number of processes by which pesticides
can be destroyed, thus preventing their accumula-
tion or redistribution. Each pesticide material,
however, has its own chemical and physical proper-
ties that give it some degree of stability against
degradation. Kearney and others (1969) have
grouped the pesticides into major chemical classes
and summarized their persistence in soil (fig.
XI.6). Only the organochlorine insecticides have
persistence times expressed in years. Persistence in
the soil of all the other classes or groups of
pesticides is measured in weeks or months. The
length of each bar in figure XI.6. indicates the time
required for 70 to 100 percent degradation of the
particular pesticide when it was applied at normal
rates. Data used to construct the graphs were ob-
tained from studies conducted in agricultural soils,
but the same pesticides used in forestry should
have the same relative stability in forest soils.
Some pesticides that are degraded by soil microbial
activity persist for a shorter period of time in forest
soils.
XI. 10
-------
Organochlorine insecticides
•••
Chlordane
DDT
BHC, Dieldrin
Heptachlor, Aldrin, Metabolites
Phosphate insecticides
Diazinon
0123456
Years
Malathion, Parathion
J I I I
468
Weeks
10 12
Urea, triazine, and picloram herbicides Benzoic acid and amide herbicides
Propazine, Picloram
•••
Simazine
Atrazine, Monuron
IH
Diuron
Linuron, Fenuron
[Prometryne
i i i i
2,3,6-TBA
••
Bensulide
•1
Diphenamide
CDAA, Dicamba
I I 1
I
4 6 8 10
Months
12
0 ? 4 6 8 10 12 14 16 18
Months
Phenoxy, toluidine, and nitrile herbicides Carbamate and aliphatic acid herbicides
2,4,5-T
•
Dichlobenil
••
MCPA
2345
Months
Dalapon, CIPC
CDEC
468
Weeks
10 12
Figure XI.6.—Persistence of individual pesticides in soils (Kearney and others 1969).
XI.11
-------
Carbamate and organophosphate pesticides are
relatively nonpersistent in the forest floor and soil.
When Sevin-4-oil was applied at 1 pound car-
baryl/acre to control the gypsy moth, pesticide
residues in the soil were still detectable 64 days
later, but were below the level of detection (0.2
ppm) 128 days after spraying (Wilcox 1972).
Dylox (trichlorfon) breaks down rapidly in the
soil. In studies carried out in New York (Judd and
others 1972), trichlorfon was not detected in any
forest soil or lake mud samples after 4 days. Wilcox
(1971), in another New York study, reported that
after 14 days no residues were detected in soil.
Malathion applied to soil persisted for 2 days in one
study and 8 days in another (Pimentel 1971).
Devine (1975) found that residues of Orthene in soil
dissipated in 3 days. Studies conducted by
Chevron Chemical Company (1973) on the per-
sistence of Orthene in nine soils types indicated a
half-life of 0.5 to 6 days when treated at 1 ppm.
Distribution In Surface Waters
Degradation of environmental quality in the
forest is often first recognized by changes in stream
quality. Stream contamination is a most important
expression of environmental contamination in the
forest because water is not only the habitat for
many biological communities, but also a critical
commodity to downstream users. Pesticides may
enter streams by several pathways and forest
managers can greatly influence the amount of
chemical which enters streams near treated areas.
Entry Of Pesticides Into
The Aquatic Environment
Any amount of pesticide that has not been
degraded, adsorbed, volatilized, or taken up by
plants is available to move into the aquatic en-
vironment.
Movement To Streams From The Air
That portion of the introduced chemical which is
not lost as drift or intercepted by vegetation or the
forest floor will fall directly on surface waters. This
route of entry offers the greatest potential for short-
term, but high-level, contamination of streams by
pesticides in the forest environment. Stream con-
tamination by herbicide residues from forest spray
operations in Oregon has been intensively studied
(Norris 1967, Norris and Moore 1971, Norris and
Moore 1976, Norris and others 1976a, Norris and
others 1976b, Norris and others 1977). Herbicide
residues were found for short periods in all streams
that flow through or by treated areas.
Although stream monitoring has been carried out
in conjunction with numerous field applications of
herbicides over a period of more than 10 years,
measured residues of the phenoxy herbicides have
never exceeded 0.1 mg/1 in western Oregon.
Concentrations of amitrole to 0.4 mg/1 were found
in one stream immediately below a spray unit in
the Coast Range of Oregon (Norris and others
1966). Examples illustrating several important
points about minimizing residues in streams are
presented in appendix XI.A.
For a given rate of application, the concentration
of herbicides in streams depends on the surface
area of the stream in relation to its volume. The
total amount of herbicide entering a stream varies
with the length of the stream which receives the
spray materials and with the location of the spray
unit boundaries with respect to the stream. The
highest concentrations of herbicide are found in
streams originating in or flowing directly through
spray units. In contrast, lowest concentrations are
found in streams which are totally excluded from
the spray area.
Surface water contamination caused by direct
application of DDT was measured during and after
forest spraying in eastern Oregon. The maximum
DDT concentration (0.28 ng/\) was a sample taken
a few hours after spraying. Most samples contained
less than 0.01 »g/l DDT (Tarrant and others 1972).
Endrin has also been found in forest streams fol-
lowing direct aerial seeding with endrin-coated
Douglas-fir seed. The maximum concentration of
0.070 Mg/1 occurred immediately after seeding and
decreased rapidly to below detection level (0.001
Mg/1) within 5 hours (Moore and others 1974). At a
second site in the same study, the maximum con-
centration of endrin found in a slower moving
stream was 0.013 ng/l. However, residue concentra-
tions decreased slowly and did not reach the detec-
tion limit of 0.001 jtg/1 until 10 days after seeding.
During insecticide application, some spray does
reach small inconspicuous streams and small
bodies of water such as shallow ponds or puddles
even though direct application to larger bodies of
water is avoided. Triclorfbn has been found in
small amounts in water samples collected im-
mediately after spraying, but the concentration
dropped below detectable limits 4 days after spray-
XI.12
-------
ing (Judd and others 1972). In an outdoor pond
trichlorfon had a half-life of 0.3 days (Chemagro
1971).
The movement of spray drift from treatment
areas to surface waters is also an important source
of pesticides in the aquatic environment, especially
when large contiguous areas are sprayed. The
amount of spray drift which occurs is influenced by
the carrier, the size of the droplets, and the height
of release. Wind speed, temperature inversions,
relative humidity, and temperature are en-
vironmental factors which influence the droplet's
size, rate of evaporation, speed of vertical descent,
and, therefore, the extent of its lateral movement
(Hass and Bouse 1968).
Movement To Streams From Vegetation
Only small amounts of pesticides will enter the
aquatic environment from the washing action of
rain on the vegetation that overhangs stream
courses and from leaves falling into the water.
Residues on buffer strip vegetation will normally be
restricted to small amounts of chemical moved
laterally as spray drift during application and
volatile material brought down by precipitation.
Some pesticide chemicals are excreted from plant
roots, but the quantities are very small and only
the roots in the stream or hydrosoil would add
chemicals to the water. How much chemical enters
the stream in this way has not been studied.
Movement To Streams From The Forest Floor
And Soil
Two competing reactions, leaching or infiltration
and surface runoff, are the ways by which
chemicals are moved from spray areas to streams.
Factors favoring infiltration will decrease the
amount of surface runoff and with it the overland
flow of introduced chemicals. The amount of
chemical actually entering a stream due to surface
runoff will depend on:
1. Distance from treated area to the nearest
stream,
2. Infiltration properties of the soil or surface
organic layer,
3. Rate of surface flow, and
4. Adsorptive characteristics of surface
materials.
Conditions that retard the rate of surface runoff
will minimize the immediate level of stream con-
tamination. The long-term stream load of pesticide
will be reduced as well, since a longer residence
time in the soil provides greater opportunity for ad-
sorption and degradation.
Runoff from agricultural lands and discharge
from manufacturing plants are the principal
sources of water pollution by pesticides (Nicholson
1967). Barnett and others (1967) maximized the
probability of runoff by applying artificial rain (2.5
inAr) to recently tilled agricultural land and found
38 percent of the 2,4-D isooctyl ester in washoff
(sediment plus water), but only 5 percent of the
2,4-D amine salt. In another study, only small
amounts of 2,4,5-T and picloram moved from com-
pacted sod or recently plowed fallow clay loam soil
following artificial rainfall of 0.5 inch in 1 hour
(Trichell and others 1968). Movement of con-
taminated water over untreated soils significantly
reduced the concentration of herbicide in the runoff
(table XI.4).
Table XI.4.—Effect of slope, rate of application, and movement over untreated sod
on the concentration of picloram In runoff water12
Rat*
(Ib/ac)
2
1
2
1
Slope
(percent)
Percent
8
8
3
3
Portion of plot
treated
Upper half
Entire
Upper half
Entire
Picloram In runoff
water3
ppm
2.1
3.8
1.3
2.0
Applied
picloram
runoff
Percent
1.6
5.5
0.9
2.8
'Data from Trichell, and others 1968.
'Picloram applied as potassium salt In water .88 Ibs/ac (400 g/ac).
•Simulated rainfall was 0.5 ip/hr, 24 hours after herbicide application.
XI.13
-------
BEACON ROCK STUDY AREA
w
a;
"§1.0-
0
30-
.020-
a.
10-
0
RAINFALL PATTERN
r
r-.
L
in
I Ifll I
ni k
'4 ' i'UI 'U U 1 ' 1 i
I
P a?
:• i
'•:
10 20 30
SEPT.
50 CONCENTRATION OF HERBICIDE IN RUNOFF WATER
)7 HO A_r>
51 U*.*"
|n 38 ^
.-jtl | Sampling Date
'* ^ r
= •;
10
1 PR
20 30 10 20 30 10 20 30
OCT. NOV. DEC.
Figure XI.7.—Precipitation and herbicide runoff patterns at the Beacon Rock Study area. A total of 6 and 1.5
Ibs/ac of 2,4-D and picloram, respectively, was applied in two treatments (July and August 1967). Her-
bicide residues were measured in ponded drainage water from the treated area (Morris 1969).
In areas where runoff is likely to occur, pesticide
washoff will be greatest during the first storms after
the pesticide is applied. The greatest potential for
pesticide movement exists when significant
amounts of precipitation occur shortly after ap-
plication. On a powerline right-of-way in
southwestern Washington, the highest concentra-
tions of the herbicides 2,4-D and picloram in runoff
water were associated with the first significant
storm following the herbicides' application (fig.
XI.7). The concentrations of herbicides declined
with time despite subsequent storms of even
greater intensity (Norris 1969). Mobilization of
chemicals in transitory stream channels by the ex-
panding stream system described by Hewlett and
Hibbert (1967) is believed to account for the im-
mediate flush of chemical observed with the first
significant storms. Norris and others (1976a,
1976b) found the total discharge of picloram and
trichlopyr from two watersheds was approximately
equal to the amount of chemical applied to an
ephemeral stream channel.
There is ample evidence to show that phenoxy
and amitrole herbicides are not lost in runoff dur-
ing intense fall precipitation from lands treated
with herbicides in the spring in western Oregon
(Norris 1968). Favorable conditions and ample
time for degradation of the herbicides under these
circumstances reduce the chance that they will be
mobilized in ephemeral stream channels.
In order to determine to what extent trichlorfon
might move with surface runoff, Chemagro (1971)
sprayed this insecticide on sloping plots of three
soil types at 20 pounds active ingredient/acre.
Simulated rainfall was then applied once weekly
XI.14
-------
for 5 weeks. After the 5-week period, total residue
in runoff water from a silt loam soil was 2.86 per-
cent of the total applied. Losses from a sandy loam
were 0.65 percent, and from a high organic silt
loam, 0.35 percent.
Pesticides leach into the soil profile and subse-
quently are transported to streams by subsurface
drainage; this is another possible route to stream
contamination. Leaching, however, is a relatively
slow process in highly organic forest soils; only sm-
all amounts of chemical move through short dis-
tances. Harris (1967, 1969) has determined the
relative mobility of pesticides in soil columns
leached with water (fig.XI.8). Herbicides in general
are more mobile in soil than pesticides, but this
mobility is only relative. Even the herbicides move
only short distances in the soil under normal condi-
tions (Scifres and others 1969, Wiese and Davis
1964).
Orthene is not tightly bound by soil particles and
is, therefore, susceptible to leaching. However, it
does not persist long enough to allow any signifi-
cant movement, either by leaching or surface
runoff (Chevron 1973). This compound also
degrades rapidly in water. In the laboratory,
Orthene showed a half-life in water of 46 days, but,
in the field, degradation is accelerated by
breakdown in aquatic vegetation and soil
microorganisms in bottom mud; measurable
residues were gone in 1 to 9 days (Chevron 1973,
1975; Devine 1975).
Boschetti (1966) reported carbaryl residues of 1
to 3 parts per billion (ppb) in streams in or near
areas treated for gypsy moth control in the
Northeast. In a later study (Devine 1971), carbaryl
residue in ponds and streams ranged from non-
detectable to 50 ppb during an 8-day period follow-
ing spraying. Residues in pond mud ranged from
nondetectable to 620 ppb.
DDT is very low in water solubility (1.2 ng/\) and
is extremely resistant to movement in soil
(Bowman and others 1960, Guenzi and Beard 1967,
Reikerk and Gessel 1968). Any appreciable move-
ment of DDT through soils by leaching must,
therefore, be the result of movement of colloidal
particles of the free or adsorbed pesticide. The
likelihood of large amounts of the chemical enter-
ing the aquatic system seems remote when move-
ment of chemicals by leaching can be measured in
inches and the distance between spray units and
streams may be hundreds of feet.
Figure XI.8.—Relative mobility of
pesticides leached in columns of soil
(Harris 1967, 1969).
Phenoxy and Picloram
Herbicides
Misc. Herbicides
Phenylurea, Triazine, and
Other Herbicides
Cipc and Toluidine Herbicides
| Thionazin
Diazinon
Disulfoton and Phorato
I Chlorinated Hydrocarbon Insecticides
least mobile
o.is
RELATIVE MOBILITY
0.15 1.0
most mobile
XI.15
-------
Summary Of Pesticide Entry Into The Aquatic
Environment
To summarize, most chemicals enter the aquatic
environment through either direct application or
drift of spray materials to the water surface. The
forest manager has considerable control over these.
Research has demonstrated that direct application
of spray materials to water surfaces can be
minimized by excluding streams from treatment
areas. Careful selection of spray equipment,
chemical formulations, and conditions of applica-
tion will minimize the potential for drift.
Mobilization of residues in ephemeral stream
channels during the first significant storms follow-
ing chemical application is the second most impor-
tant source of chemical residues in forest streams.
Pesticide residues moving overland with surface
runoff during intense precipitation is the third
most important way by which chemicals may enter
the aquatic system. The phenoxy herbicides,
amitrole, and the carbamate and pyrethrum insec-
ticides degrade rapidly so they are available for
overland transport to streams for only short
periods. Picloram may persist for more than one
season, but its tendency to leach into the soil
profile reduces its chances of moving by surface
runoff into streams. DDT and similar compounds
are resistant to degradation and leaching,
therefore, they are exposed to overland transport
for extended periods of time. However, the
chlorinated hydrocarbon insecticides are no longer
selected for use in forestry when alternate
chemicals are available. Overland flow of water on
forested watersheds is relatively uncommon, and
pollution of streams from this source will be limited
to areas where rates of infiltration are considerably
less than normal rates of precipitation. The stream
contamination that does occur will be reduced
when the contaminated water moves over the un-
treated buffer strips. Leaching is not a significant
process in the entry of forest chemicals into
streams. Specific Controls are listed under "Aerial
Drift and Application of Chemicals," and "All
Resource Impacts" in Section B of Chapter H:
Control Opportunities.
Behavior In The Aquatic Environment
How an aquatic organism responds to a chemical
will depend on the duration and magnitude of the
exposure and the interaction of the organism with
other stresses in its environment. How a chemical
behaves in the aquatic environment will determine
both duration and magnitude of the exposure.
Chemicals may be lost from the aquatic environ-
ment through volatilization; adsorption in stream
sediments; absorption by aquatic biota; degrada-
tion by chemical, biological, or photochemical
means; or dilution with downstream movement
(fig. XI.2).
Volatilization
The amount of pesticide lost from water by
volatilization varies with both the properties of the
chemical and the environmental conditions. The
chlorinated hydrocarbon insecticides (like DDT)
are of very low solubility in water and tend to col-
lect at water surfaces in films where they may be
subject to co-distillation. Water suspensions con-
taining 5 ng/[ DDT have been reported to lose 30
percent of the insecticide in 20 hours at 79° F
(26° C) (Bowman and others 1964). Fuel oil carriers
may concentrate oil soluble pesticides at water sur-
faces (Cope 1966).
Adsorption
In turbulent streams chemicals will be quickly
dispersed throughout the water allowing maximum
interaction with various adsorbing surfaces (Cope
and Park 1957). Reductions in pesticide concentra-
tions in water by adsorption depend on the rate, ex-
tent, and strength of adsorption, and the mixing
characteristics of the stream (which will govern the
opportunity for interaction within the stream bot-
tom). Researchers have given these factors only
limited attention. Clay and fine silt are effective in
adsorbing and reducing the activity of DDT and
other chlorinated hydrocarbon insecticides in river
water (Ferguson and others 1966, Fredeen and
others 1953). Bottom sediments from bodies of
water treated with various phenoxy herbicides fre-
quently contain residues which may indicate ad-
sorption (Bailey and others 1970, Smith and Ison
1967). Aly and Faust (1965) reported that the
amounts of 2,4-D adsorbed on suspended clays in
water were small. Considerable research is needed
to clarify the importance of adsorption in reducing
pesticide concentrations in water.
XI.16
-------
Degradation
There are conflicting reports on the persistence
of pesticides in streams. In one study, 2,4-D esters
were hydrolyzed to free acid in 9 days in lake water,
but 2,4-D acid persisted up to 120 days (Aly and
Faust 1964). In another study, only 40 percent
degradation of 2,4-D in water was observed in 6
months, during which excellent conditions for
biological activity were present (Schwartz 1967). A
considerable decrease in degradation of 2,4-D was
observed in bacterially active natural river waters
that had reduced levels of dissolved oxygen (fig
XI.9).
Robson (1968) reported that the persistence of
2,4-D in fresh water was decreased from 9 weeks to
1 week when small quantities of soil previously
treated with phenoxy herbicides were added. Rapid
degradation of 2,4-D occurred in water samples col-
lected from areas with a history of repeated 2,4-D
applications (Goerlitz and Lamar 1967). Many sur-
face waters may lack suitable conditions for
biological degradation of herbicides or they may
not contain populations of microbes adapted to use
of the phenoxy herbicides as substrates (Hemmet
and Faust 1969).
Degradation of certain chemicals is pH depen-
dent. Amitrole resists degradation in activated
sludge cultures, distilled water, or sewage held at
room temperatures for various periods of time
(Ludzak and Mandia 1967). Carbaryl rapidly
degrades in sea water, but it will persist for longer
periods in the more acid conditions found in forest
streams (Aly and El-Dib 1971, Karinen and others
1967). The rapid hydrolysis of malathion in water is
also pH dependent (Guerrant and others 1970), 50
percent decomposition occurred in 26 days at pH
6.0 and in 2.5 hours at pH 10.0.
In studies conducted as a part of gypsy moth
suppression in the Northeast, carbaryl persistence
in the aquatic environment was found to be brief.
Romine and Russian (1971) suggest that an initial
level of 1 mg/1 will be completely gone in 1 to 2
days. In an earlier study, water residues of 30 jug/1
dropped to 1-5 Mg/1 in 1 day (USDA 1964).
Carbaryl, the phenoxy herbicides, amitrole, and
picloram are all susceptible to photodegradation
(Crosby and Li 1969, Karinen and others 1967).
The importance of this reaction in the natural en-
vironment is questionable, however, because most
streams are shaded and there is limited penetration
of the water by ultraviolet radiation.
Downstream Movement
Downstream movement of chemicals and the
resulting dilution due to natural stream mixing and
the addition of uncontaminated water from side
streams is one of the most important mechanisms
by which the concentration of pesticides in streams
is reduced near treatment areas. Although the
hazard of exposure is not eliminated until the
residues are completely degraded to nontoxic com-
pounds, dilution as the result of downstream move-
ment can reduce the concentrations of pesticides in
streams to levels that do not represent a hazard to
nontarget organisms. DDT residues were carried
downstream in well defined blocks and did not per-
sist for long periods at sampling stations located
.0
o.
Q
4
CM"
Q WARM - AEROBIC
° COLD - DEOXYGENATED
• COLD - AEROBIC
20
40 60
TIME, (days)
80
100
Figure XI.S.'—The degradation of 2,4-D In a bacterlally active water culture (DeMarco and others 1967).
XI. 17
-------
along an 85-mile stretch of the Yellowstone River
following spray operations in Montana (Cope
1961). Marked reductions in concentrations of
amitrole and the phenoxy herbicides were observed
in water due to downstream movement (Marston
and others 1968, Norris and others 1966).
CHEMICAL BEHAVIOR OF FERTILIZERS
Initial Distribution In Air, Vegetation, And
Forest Floor
Many concepts concerning the initial distribu-
tion of pesticides apply also to fertilizers, but there
are some important exceptions. The rate at which
nitrogen fertilizer is applied varies with site and
timber type but is usually 150 or 200 pounds of urea
nitrogen/acre. Phosphorus is applied at rates
between 80 and 100 pounds P206/acre in the
southeast. In contrast with pesticides, where
significant quantities may remain in the at-
mosphere, essentially all of the fertilizer applied
reaches the intended target. However, because of
the higher rates of application, it is necessary to
make at least two flights over the unit and a uni-
form rate of application over an entire unit is dif-
ficult to obtain (Strand 1970).
The introduction of large, specially coated urea
granules (forest grade) has eliminated the drift
problems that were experienced when standard
agricultural urea was used. Drift problems still ex-
ist, however, when standard agricultural urea (45%
N) is used, or when experimental liquid formula-
tions of nitrogen are substituted for the forest
granules. Should liquid fertilizer formulations
come into commercial use, their initial distribution
in the environment will be subject to the same fac-
tors controlling distribution of aerially applied
pesticides.
Because very little granular fertilizer is in-
tercepted by a dry forest canopy, the forest floor is
the major receptor. The initial distribution of
aerially applied fertilizers is thus restricted to the
forest floor and to exposed surface waters within
the treated areas.
Urea fertilizer is highly water soluble and readily
moved into the forest floor and soil by any ap-
preciable amount of precipitation. Under normal
conditions, urea is rapidly hydrolyzed (4-7 days) to
the ammonium ion by the enzyme urease. When
moisture is limited, however, urea granules may be
slowly hydrolyzed on the forest floor, resulting in a
marked increase in surface pH and a loss of am-
monia nitrogen by volatilization. In a laboratory
study, Watkins and others (1972) measured losses
of ammonia nitrogen ranging from 6 percent to 46
percent of the urea nitrogen applied to forest floor
and soil depending on the nature of the surface,
surface pH, and rate of airflow across the surface.
Although some applied nitrogen is undoubtedly
lost by volatilization in the field, it is generally con-
ceded that such losses are small. Time of applica-
tion is important, and forest fertilization projects
are usually conducted during the spring or fall
months to take advantage of precipitation. Urea
nitrogen is quickly distributed throughout the liv-
ing complex, becomes a part of the nutrient
budget, and is cycled within the ecosystem.
CO(NH2)2 [solid] H2°»CO (NH2)2 [solution]
CO (NH2)2 + 2H20 urease > (NH4)2 C03
(NH4)2C03 —H2°' C°2 » 2 NH4HC03
Entry Of Fertilizers Into The
Aquatic Environment
Fertilizer chemicals may enter the aquatic en-
vironment by one of several routes. Direct applica-
tion of chemicals to exposed surface water is the
most important way. This can be minimized by
carefully marking and avoiding larger streams dur-
ing applications, but it is usually impractical to
avoid small headwater streams, which frequently
are intermittent and difficult to see from the air.
Exposed surface water may absorb ammonia
nitrogen that has volatized from the forest floor
into the air. It is doubtful, however, that this source
adds significant amounts to the streams.
Overland flow, or surface runoff, is a major
source of nutrients in streams draining nonforested
areas, but it is not an important route for fertilizers
from treated forest watersheds to enter streams
since surface runoff rarely occurs. Subsurface
drainage is another possible way soluble forms of
nitrogen enter into streams. Forest soils are excel-
lent filters for most plant nutrients because of their
high exchange capacities and dense root systems
which can absorb and recycle nutrients (Moore
1970). However, measurable levels of ammonium-,
XI. 18
-------
nitrate-, urea-, and organic-nitrogen have been
found in several streams that were monitored for
water quality in western Oregon and Washington.
There is an enormous amount of literature con-
cerning the effects of farm fertilization on water
quality, but only a few papers concerning the ef-
fects of forest fertilization. Soileau's (1969) exten-
sive bibliography (701 entries) on effects of fer-
tilizers on water quality contains no references on
effects of forest fertilization.
Several forest fertilization projects have been
monitored recently and examples of the data ob-
tained are presented in appendix XI.B. Data from
one study conducted in the Pacific Northwest are
discussed below to illustrate the magnitude and
pattern of nutrient loss to streams. Measures that
may be used to minimize the potential for stream
contamination are also indicated.
Moore (1971) measured the amounts and forms
of nitrogen entering streams during and following
aerial application of 200 Ibs/ac of nitrogen (as urea)
to an experimental watershed in southwestern
Oregon in March 1970 (fig XL 10). Data obtained
during the first 15 weeks after application are sum-
marized in table XI.5. Urea concentrations in-
creased slowly and reached a maximum of 1.39
mg/1 urea-N 48 hours after application started.
Ammonium-N increased slightly above pre-
treatment level, but never reached 0.10 mg/1.
Nitrate-N began to increase slowly the second day,
reached 0.168 mg/1 in 72 hours, and was 0.140 mg/1
at the end of 2 weeks. Nitrite-N was not detected
and wouldn't be expected to occur in well aerated
streams.
All urea losses of applied nitrogen occurred dur-
ing the first 3 weeks. Losses in the form of
ammonium-N, even though small, continued for 6
weeks. During the first 9 weeks after application,
net loss of applied nitrogen amounted to only 1.81
kilograms from watershed 2 (table XI.6).
COYOTE CREEK WATERSHEDS
SOUTH UMPQUA EXPERIMENTAL FOREST
0-125 0-25 0-375
MILES
0-5
PROPOSED ROADS
TO S. UMPQUA RIVER
EXISTING ROAD
20 SMALL 2-3 A
CLEARCUTS
TOTALING 52 A
NORTH
Figure XI.10.—Coyote Creek watersheds, South Umpqua Experimental Forest, Umpqua National Forest,
Oreg. (Moore 1971).
XL 19
-------
Table XI.5.—Concentration of fertilizer nitrogen In selected water samples
collected at watershed 2, South Umpqua Experimental Forest, following
application of 200 pounds urea-N/ac (Moore 1971)
Date
Time
Urea-N
NHaN'
NOs-N
Total
3/25
3/26
3/27
3/28
4/1
4/8
4/15
4/22
5/6
5/27
6/17
7/8
0800
0815
1230
2025
0805
1640
2005
0805
—
—
—
—
—
—
—
—
.007
.437
.237
.171
1.389
.606
.488
.075
.007
.028
0
0
0
—
—
—
mi
IT'!
.001
.016
.012
.034
.048
.036
.029
.036
.016
.015
.010
.010
.013
0
0
0
n/l
.002
.040
.069
.067
.107
.150
.168
.117
.091
.140
.030
.021
.022
.004
.002
.006
.010
.493
.318
.272
1.544
.792
.685
.228
.185
.183
.040
.031
.035
.004
.002
.006
'Includes both ionized (NH4+) and un-ionized (NHs) ammonia-nitrogen
Table XI.6.—Nitrogen lost from treated watershed 2 and untreated watershed 4,
South Umpqua Experimental Forest, during the first 9 weeks after application
of 224 kilograms urea-N/ha (Moore 1971)
Unit
Urea-N
NHa-N
NOa-N
Total
Kilnnrnms N
Watershed 2
Watershed 4
Net loss
Percent of total loss
0.65
0.02
0.63
34.75
0.28
0.06
0.22
12.25
1.01
0.05
0.96
53.00
1.94
0.13
1.81
100.00
Low streamflow caused by limited precipitation
throughout the summer and fall months resulted in
essentially no loss of applied nitrogen during the
next 24 weeks. Storm activity in November
brought the soil moisture level back to maximum
storage capacity. In December the nitrate-N con-
centration in samples for the fertilized watershed
reached a second peak of 0.177 mg/1 (fig. XI.ll).
Both streamflow and nitrate-N levels remained
high throughout December and January, resulting
in the loss of an additional 23.8 kg applied nitrogen.
This second peak accounted for 92 percent of the
total amount of fertilizer nitrogen which was lost
during the first year.
Total net loss of applied nitrogen from the fer-
tilized watershed (68 ha) during the first year
amounted to 25.85 kg, or 0.38 kg of nitrogen/ha
(table XL 7). Over the same period the total
amount of soluble inorganic nitrogen lost from the
control watershed (49 ha) was 2.15 kg, or 0.04 kg
nitrogen/ha. Data for soluble organic nitrogen,
total phosphorus, silica, and exchangeable cation
content of the stream samples, including sodium,
potassium, calcium, magnesium, iron, manganese,
and aluminum, indicate that there was no ap-
parent effect of nitrogen fertilization on loss of
native soil nitrogen or other plant nutrients: Move-
ment may have occurred in the soil profile, but
there was no measurable change in stream water
quality.
Initial losses of applied nitrogen were largely
caused by direct application of urea fertilizer to the
drainage channel. These losses were measured first
as an increase in urea-nitrogen and then as a small
increase in ammonium-nitrogen, the latter as a
result of hydrolysis of urea applied to open water.
The nitrate-nitrogen entering the stream shortly
after application was probably leached from the
soil immediately adjacent to the stream channel.
XI.20
-------
25 29 2 6 10
MARCH — APRIL 1970
TIME AFTER APPLICATION
0. 2-1
1.5-,
1.0-
mg/l
0.5
0.0
— - UREA -N
,', NO, - N
l\
\ \ NH3 - N
1 i
I i
I s
/ \
mg/l
0. 1-
14
0. 0 LJT
MAR MAY JUL SEP NOV JAN MAR
1970 1971
Figure Xl.11.—Fertilization of a 68-ha watershed with 224 kg urea-nitrogen/ha in March 1970. A. Immediate
effect on water quality; B. Effect on nitrate-nitrogen concentration in streamflow for 1 year following fer-
tilization (Fredriksen and others 1975).
During the first 9 weeks after application, approx-
imately half of the applied nitrogen was lost
through direct application and half entered the
stream as nitrate-nitrogen. However, all of the ap-
plied nitrogen lost during this 9-week period
amounted to only 7 percent of the total loss that oc-
curred over the first year.
High streamflow coupled with the second peak in
nitrate-nitrogen levels during the winter storm
period accounted for 92 percent of the total loss. In
February and March 1971, streamflow remained
high, but most of the mobile nitrogen had already
been lost, and nitrate-nitrogen concentrations had
returned to near normal.
Similar data have been obtained in each of the
monitoring studies that have been conducted in the
Douglas-fir region and elsewhere. The length of the
monitoring period has varied from a few weeks fol-
lowing treatment to 6 or 7 months, and in a few
studies monitoring continued for at least a full
year. Sampling usually continued until the forms
of nitrogen being measured decreased to near
pre-treatment levels. Increases in the concentra-
tion of urea-N are almost entirely caused by direct
application to surface waters, and the peak con-
centration reached is directly proportional to the
amount of open surface water in the treated unit.
Peak concentrations above 5.0 mg/l are in every
case associated with projects where no buffer strips
were left along the main streams; or where fertilizer
application was carried out early in the spring,
when the drainage system was greatly expanded by
spring runoff of snowmelt. Even when buffer strips
of 30 to 90 m are left along main streams and
tributaries, some direct application to water sur-
faces still will occur because of a relatively dense
network of small feeder tributaries that are only a
foot or two wide and cannot be identified from the
air.
Peak concentrations of urea-N do not persist for
more than a few hours. Concentrations
characteristically reach a peak each day that fer-
tilizer is being applied and then drop rapidly back
toward pre-treatment levels. Within 3 to 5 days
after application is completed, levels of urea-N in
the stream have returned to pre-treatment con-
centrations.
Table XI.7.—Nitrogen lost from treated watershed 2 and untreated watershed 4,
South Umpqua Experimental Forest, during the first year after application
of 224 kilograms urea-N/ha (Moore 1971)
Unit
Urea-N
NHa-N
NOa-N
Total
... Kl
Watershed 2
Watershed 4
Net loss
Percent of total loss
0.65
0.02
0.63
2.44
0.28
0.06
0.22
0.86
27.09
2.07
25.02
96.70
28.03
2.15
25.88
100.00
XI.21
-------
Ammonium-N levels also increase as a result of
direct application of urea-N to open water. Urea is
readily hydrolyzed to ammonium-N in the aquatic
system. Urea applied to the forest floor and soil will
not reach the stream since it hydrolyzes rapidly to
ammonium carbonate and is held on cation ex-
change sites in the soil and forest floor like any
other salt. Concentrations of ammonium-N in the
stream are rapidly reduced through uptake by
aquatic organisms and by adsorption on stream
sediments. Levels in the streams sampled exceeded
1.00 mg/1 only when direct application of urea to
the stream was noted. Peak concentrations are nor-
mally 0.10 mg/1 or less and do not persist for more
than a few hours, but levels of ammonium-N re-
main slightly above pre-treatment level for up to 3
and 4 weeks.
projects, where direct application to the open sur-
face waters has been avoided or minimized by buf-
fer strips along the main streams and tributaries,
measured amounts of applied nitrogen entering the
stream are less than 0.5 percent.
Increased phosphorous concentrations following
application of phosphate fertilizers have not been
reported. Phosphorus added to forest soils is readily
utilized by forest organisms or is rapidly converted
to nonsoluble forms. Powers and others (1975) have
stated that most forest soils have the capacity to tie
up, in nonmobile form, many times the quantity of
phosphate that foresters are likely to apply. There
have been no reports of significant increases in
phosphorous concentration in streams following
fertilizer application.
The peak concentration of nitrate-N in stream
samples usually occurs from 2 to 4 days after fer-
tilization. Magnitude of the peak concentration de-
pends on whether buffer strips are left along the
main stream channels, the width of the waterside
area, and the density of small feeder and tributary
streams in the drainage system of the fertilized
area. Peak concentrations of nitrate-N are
generally below 1.0 mg/1, but higher levels have
been measured in a few studies. Concentrations
usually decrease rapidly after the peak is reached,
but remain above pre-treatment level for 6 to 8
weeks. In monitoring studies where sampling has
continued through the first winter following fer-
tilization, additional peaks in the concentration of
nitrate-N have been measured. These peaks
usually coincide with the more intense winter
storms, and the concentration drops sharply
between storms. Maximum concentrations
measured are still low and tend to decrease with
each successive storm.
Losses of applied nitrogen are usually very small
because the maximum concentrations are generally
low, and streamflow decreases rapidly with the
onset of the growing season. Following spring ap-
plication, about half of the applied nitrogen enter-
ing the stream during the first 30 days is from
direct application and is measured as urea-N and
ammonium-N; the other half enters as nitrate-N.
All subsequent losses of applied nitrogen to the
stream enter as nitrate-N. During early fertiliza-
tion projects, where buffer strips were either inade-
quate or not used, estimated total loss was between
2 and 3 percent of the applied nitrogen. In later
Summary Of Fertilizer Entry Into The Aquatic
Environment
The most important mechanism of fertilizer
entry into the aquatic environment is direct ap-
plication to open surface waters. Numerous studies
(appendix B) have shown that the amount of ap-
plied nutrients entering streams has resulted in
minimal increases in the instream concentrations
of nitrogen and phosphorus. When direct applica-
tion of fertilizer to streams can be reduced or
prevented by use of adequate buffer strips and
marking of water courses, the potential impact on
stream quality can be minimized.
Transport of mobile forms of nitrogen (nitrate-
N) to streams by subsurface drainage from the
riparian zone during dormant season storms is the
second most important mechanism by which fer-
tilizer nitrogen may enter the aquatic system.
Again, the use of adequate buffer strips will reduce
the potential impact on water quality. Nitrogen
that does enter the stream is rapidly decreased
through utilization by biological communities in
the stream. Concentrations are further reduced by
dilution with downstream movement. Studies con-
ducted to date indicate that forest fertilization will
not result in degradation of water quality to the
detriment of other resources. With only one excep-
tion, none of the studies have recorded nitrogen
concentrations that approach the Public Health
Service maximum permissible levels for drinking
water (Moore 1971, Hornbeck and Pierce 1973,
Moore 1975b, Sopper 1975, Norris and Moore 1976,
Newton and Norgren 1977).
XI.22
-------
Behavior In The Aquatic Environment
Forest fertilizers properly applied to an entire
watershed undoubtedly will change the nutrient
balance among soil, vegetation, animal life, and
water in the forest ecosystem, but should pose little
or no threat to water quality (Cole and Gessel
1965). Fertilizers applied directly into streams,
however, do represent a potential problem, and the
total impact of the introduced chemicals will de-
pend on their behavior in the aquatic environment.
When urea nitrogen is introduced into small
streams of forested watersheds, either from wildlife
activity or through aerial application of fertilizers,
it disappears rapidly and only traces can normally
be detected in undisturbed ecosystems. Urea is
hydrolyzed to ammonium nitrogen by urease en-
zyme adsorbed on suspended solids and bottom
sediments. Ammonium nitrogen may remain in
solution or be adsorbed by suspended organic and
inorganic colloids and bottom sediments. All forms
of nitrogen are diluted by downstream movement
caused by natural stream mixing and increased
flow volume from side streams and ground water.
Dissolved inorganic and organic nitrogen may also
be removed by aquatic organisms to such an extent
that they are undetectable at a downstream sam-
pling point (Thut and Haydu 1971).
Phosphorus is not considered a mobile element
in the soil system. Even those forms of phosphorus
that are readily available for plant uptake are not
subject to leaching to any significant extent.
Phosphate fertilizer applied to a forest watershed
would not be expected to enter the stream system
except by direct application. Since most headwater
streams in relatively undisturbed forest watersheds
contain only low concentrations of phosphorus, the
small amounts of phosphorus added during a nor-
mal fertilization program would be rapidly utilized
by the biological community in the stream. Many
of the streams in forested areas of the Douglas-fir
region are nutrient deficient, and it has been sug-
gested that forest fertilization may have a
beneficial effect on forest stream productivity
(Thut and Haydu 1971).
The fate of nitrogen applied to cultivated crops
has been studied extensively (Allison 1966), but
only limited data are available on the nitrogen cy-
cle in temperate forests (Cole and others 1967,
Weetman 1961). The output of nitrogen in drainage
from actively growing forest stands appears to
nearly balance inputs in precipitation (Cooper
1969). Since stream enrichment resulting from
forest fertilization is apparently small and of short
duration, it can be assumed that any deleterious ef-
fects that do occur will not persist. However, the ef-
fect of small additions at upstream sites on ac-
cumulation of nutrients in downstream impound-
ments must be considered.
XI.23
-------
CONCLUSIONS
The amount of a particular chemical that enters
a stream will vary depending on many of the fac-
tors discussed in this chapter. Each of the compo-
nents of the forest environment indicated in figure
XI.2 can be designated as a compartment in a
systems diagram or conceptual model and the
various processes responsible for transformation or
movement of chemicals within or between com-
partments identified. With an adequate data base
for any given site and a thorough knowledge of the
controlling processes, one could then predict the
extent of non-point source pollution that would be
expected as the result of using a silvicultural prac-
tice that includes the application of a pesticide or
fertilizer chemical. Although much is known about
the behavior of chemicals in the environment, we
still lack a precise mathematical model that will
meet this objective. Therefore, the major routes of
entry of chemicals into forest streams have been
identified, and the processes which are involved
within each environmental compartment are iden-
tified and discussed primarily from a conceptual
and qualitative basis. This framework should
provide a logical basis for understanding the
mechanisms and processes which may result in
non-point source contamination of stream water in
a qualitative way even though quantitative es-
timates are not yet possible.
Based on research experience, history of use, con-
sideration of the manner in which most chemical
application operations are conducted, and an
analysis of the chemical and physical properties
which influence the behavior of chemicals in the
environment, it is estimated that the following con-
centrations of various chemicals may be en-
countered in the aquatic environment near treat-
ment areas.
Herbicides. — A strong background of research
experience permits prediction with confidence that
concentrations of 2,4-D, picloram, 2,4,5-T, and
amitrole exceeding 0.05 mg/1 will seldom be en-
countered in streams adjacent to carefully control-
led forest spray operations. Concentrations ex-
ceeding 1 mg/1 have never been observed and are
not expected to occur. The chronic entry of these
herbicides into streams for long periods after ap-
plication does not occur.
Insecticides. — Concentrations of carbamate in-
secticides exceeding 0.1 mg/1 will rarely be found in
forest streams. Carbamate and pyrethrum insec-
ticides do not persist in the environment and they
offer little opportunity for movement to streams.
The organophosphorous insecticide, malathion, is
rapidly degraded in soil and water and enters water
only by stream channel interception and limited
streamside surface runoff. Ultra-low-volume aerial
applications will rarely produce more than 0.5 mg/1
malathion in streams.
Fertilizers. — There is still only a limited
history of field use and research experience con-
cerning the behavior and fate of fertilizer nitrogen
introduced into the aquatic environment as a result
of forest fertilization. Available data suggest,
however, that concentrations of the various forms
of nitrogen found in streams adjacent to treated
units are well below accepted standards for public
water supplies. The impact of these introduced
chemicals on various elements of the ecosystem
must be investigated.
Direct application to surface waters is the major
source of aerially applied forest chemicals in the
aquatic environment. Drift is another important
pollution source with pesticides, but not with fer-
tilizer. Careful selection of chemicals, carriers, and
equipment and control of the manner in which the
project is conducted can materially reduce both the
direct application and the drift of chemicals to
streams. Specific control opportunities were
described in Chapter II. Volatilization, adsorption,
degradation, and downstream movement of
residues will minimize the exposure time of aquatic
organisms to chemicals which do enter the aquatic
environment.
The forest manager has no control over the in-
herent toxicity of a selected chemical, but the
hazards of chemical use to nontarget organisms can
be minimized by limiting their exposure to
biologically insignificant doses. Research ex-
perience and history of use have established that
important forest chemicals offer minimum poten-
tial for pollution of the aquatic environment when
they are used properly. The key to proper use is an
understanding of the ways which chemicals can
enter streams and an appreciation of the factors
which influence the degree to which these
mechanisms operate.
XI.24
-------
LITERATURE CITED
Allison, F. E. 1966. The fate of nitrogen applied to
soils. Adv. Agron. 18:219-258.
Aly, 0. M., and M. A. El-Dib. 1971. Studies of the
persistence of some carbamate insects in the
aquatic environment. In Fate of organic
pesticides in the aquatic environment. R. F.
Gould, ed. Adv. Chem. 111:211-243. Am. Chem.
Soc., Washington, D.C.
Aly, 0. M., and S. D. Faust. 1964. Studies on the
fate of 2,4-D and ester derivatives in natural sur-
face waters. J. Agric. Food Chem. 12:541-546.
Aly, 0. M., and S. D. Faust. 1965. Removal of 2,4-
dichlorophenoxyacetic acid derivatives from
natural waters. J. Am. Waterworks Assoc.
57:221-230.
Aubertin, G. M., D. W. Smith, and J. H. Patric.
1973. Quantity and quality of streamflow after
urea fertilization on a forested watershed: First-
year results. In Forest fertilization symposium
proceedings. USDA For. Serv. Gen. Tech. Rep.
NE-3, p. 88-100. Northeast. For. Exp. Stn., Up-
per Darby, Pa.
Back, R. C. 1971. Memo summarizing Sevin
residues on forest foliage. Union Carbide Corp.
Bailey, G. W., A. D. Thurston, Jr., J. D. Pope, Jr.,
and D. R. Cochrane. 1970. The degradation
kinetics of an ester of silvex and the persistence
of silvex in water and sediment. Weed Sci.
18:413-419.
Barnett, A. P., E. W. Hauser, A. W. White, and
J. H. Holladay. 1967. Loss of 2,4-D in wash-off
from cultivated fallow land. Weeds 15:133-137.
Beaton, J. D. 1973. Fertilizer methods and applica-
tions to forestry practice. In Forest fertilization
symposium proceedings. USDA For. Serv. Gen.
Tech. Rep. NE-3, p. 55-71. Northeast. For. Exp.
Stn., Upper Darby, Pa.
Bengston, G. W. 1970. Potential increases in wood
production through fertilization of forest land in
the South. In Nutritional problems and practices
on forest land symp. Coll. For. Resour., Univ.
Wash., Seattle. Mimeo, unnumbered pages.
Boschetti, N. M. 1966. Sevin residues in water and
top soil following its use on a watershed area. In
Report on the surveillance program conducted in
connection with an application of carbaryl
(Sevin) for the control of gypsy moth on Cape
Cod, Massachussetts. Commonw. Mass. Pestic.
Board Publ. 547, p. 52-62.
Bowman, M. C., F. Acree, and M. K. Corbett.
1960. Insecticide solubility: solubility of carbon-
14 DDT in water. J. Agric. Food Chem. 8:406-
408.
Bowman, M. C., F. Acree, C. S. Lofgren, and M.
Beroza. 1964. Chlorinated insecticides: Fate in
aqueous suspensions containing mosquito larvae.
Science 146:1480-1481.
Burrough, E. R., Jr., and H. A. Froehlich. 1972. Ef-
fects of forest fertilization on water quality in two
small Oregon watersheds. U.S. Dep. Inter., Bur.
Land Manage., Tech. Note 159, 8 p.
Chemagro Corporation. 1971. Synopsis of the ef-
fects of Dylox on the environment. In The effects
of Dylox on the environment. Vol. 1. 20 p.
Chemagro Corp., Res. and Dev. Dep., Kansas
City, Mo., May 3. Unpubl.
Chevron Chemical Corporation. 1973. The impact
of Orthene on the environment. 39 p. Chevron
Chem. Co., Richmond, Calif. January. Unpubl.
Chevron Chemical Corporation. 1975. Orthene, a
new concept in insect control. Chevron Chem.
Co., Proj. No. 75238-13-RI Oct. 1975. 19 p.
Cole, D. W., and S. P. Gessell. 1965. Movement of
elements through a forest soil as influenced by
tree removal and fertilizer additions. In Forest
soil relationships in North America, p. 95-104.
Oreg. State Univ. Press, Corvallis.
Cole, D. W., S. P. Gessell, and S. F. Dice. 1967.
Distribution and cycling of nitrogen,
phosphorus, potassium, and calcium in a second-
growth Douglas-fir ecosystem. Symp. Primary
Prod, and Miner. Cycling in Nat. Ecosyst., Univ.
Maine Press, Orono.
Cooper, C. F. 1969. Nutrient output from managed
forests. In Eutrophication: Causes, conse-
quences, correctives, p. 446-463. Natl, p. 197-232
Acad. Sci., Washington, D.C.
Cope, 0. B. 1961. Effects of DDT spraying for
spruce budworm on fish in the Yellowstone River
system. Am. Fish. Soc. Trans. 90:239-251.
XI.25
-------
Cope, 0. B. 1966. Contamination of the fresh water
ecosystem by pesticides. In Pesticides in the en-
vironment and their effects on wildlife. J. Appl.
Ecol. 3(Suppl.):33-44.
Cope, 0. B., and D. C. Park. 1957. Effects of forest
insect spraying on trout and aquatic insects in
some Montana streams. U.S. Dep. Agric. For.
Serv. Prog. Rep. 1956.
Crosby, D. G., and Ming-Yu Li. 1969. Herbicide
photodecomposition. In Degradation of her-
bicides, p. 321-364. Marcel Dekker, New York.
DeMarco, J., J. M. Symons, and G. G. Robect.
1967. Behavior of synthetic organics in stratified
impoundments. J. Am. Waterworks Assoc.
59:965-976.
Devine, J. M. 1971. Determination of Sevin (1-
naphthyl N-methylcarbamate) residues in
water, mud, leaves, and leaf litter. Lake Ont.
Environ. Lab. Rep. No. 106 (Nov. 8), 11 p. State
Univ. Coll., Oswego, N.Y. Unpubl.
Devine, J. M. 1975. Persistence of Orthene residues
in the forest and aquatic environment. In En-
vironmental impact study of aerially applied
Orthene (0, S-dimethylacetylphosphor-
amidothioate) on a forest and aquatic ecosystem.
Lake Ont. Environ. Lab. Rep. No. 174, p. 48-82.
State Univ. Coll., Oswego, N.Y.
Devine, J. M., and H. H. Wilcox m. 1972. Per-
sistence of Dylox residues in a forest and lake en-
vironment. Appl. For. Res. Inst. Rep. No. 10:21-
36. N.Y. State Coll.
Douglass, J. E., D. R. Cochrane, G. W. Bailey, and
others. 1969. Low herbicide concentration found
in streamflow after a grass cover is killed. U.S.
Dep. Agric. For. Serv. Res. Note SE-108, 3 p.
Southeast. For. Exp. Stn., Asheville, N.C.
Fairchild, H. E. 1970. Significant information on
use of Sevin-4-Oil for insect control. Union Car-
bide Corp. Undated folder of text and various
reports.
Ferguson, D. E., J. L. Ludke, J. P. Wood, and J. W.
Prather. 1966. The effects of mud on the bioac-
tivity of pesticides on fishes. J. Miss. Acad. Sci.
11:219-228.
Foy, C. L., and S. W. Bingham. 1969. Some
research approaches toward minimizing her-
bicidal residues in the environment. Residue
Rev. 29:105-135.
Fredeen, F. J. H., A. P. Arnason, and B. Berke.
1953. Adsorption of DDT on suspended solids in
the river water and its role in Blackfly, Simulium
arcticum, control. Nature 171:700-701.
Fredriksen, R. L., D. G. Moore, and L. A. Norris.
1975. The impact of timber harvest, fertilization,
and herbicide treatment on stream water quality
in western Oregon and Washington. In Forest
soils and forest land management. B. Bernier
and C. H. Winget, eds. Proc. 4th North Am. For.
Soils Conf., p. 283-313. Laval Univ. Press,
Quebec.
Getzendaner, M. E., J. L. Herman, and B. van
Giessen. 1969. Residues of 4-amino-3,5,6-
trichloropicolinic acid in grass from applications
of Tordon herbicides. J. Agric. Food Chem.
17:1251-1256.
Goerlitz, D. F., and W. L. Lamar. 1967. Determina-
tion of phenoxy acid herbicides in water by
electron capture and microcoulometric gas
chromatography. U.S. Geol. Surv., Water Sup-
ply Pap. 1817-C, 21 p.
Groman, W. A. 1972. Forest fertilization: A state-
of-the-art review and description of environmen-
tal effects. EPA-R2-72-016, 57 p. Pac. Northwest
Water Lab., Natl. Environ. Res. Center, En-
viron. Prot. Agency, Corvallis, Oreg.
Guenzi, W. D., and W. E. Beard. 1967. Movement
and persistence of DDT and lindane in soil
columns. Soil Sci. Soc. Am. Proc. 31:644-647.
Guerrant, G. 0., L. E. Fetzer, Jr., and J. W. Miles.
1970. Pesticide residues in Hale County, Texas,
before and after ultra-low volume application of
malathion. Pestic. Monit. J. 4(1):14-20.
Hance, R. J. 1967. Decomposition of herbicides in
the soil by non-biological chemical processes. J.
Sci. Food Agric. 18:544-547.
Harris, C. I. 1967. Movements of herbicides in soil.
Weeds 15:214-216.
Harris, C. I. 1969. Movement of pesticides in soil.
J. Agric. Food Chem. 17:80-82.
Hass, R. H., and L. F. Bouse. 1968. Possibilities for
controlling drift with thickened sprays. Prog.
Rep. No. 2605. Tex. Agric. Exp. Stn., College
Station.
Helvey, J. D., A. R. Tiedemann, and W. B. Fowler.
1974. Some climatic and hydrologic effects of
XI.26
-------
wildfire in Washington state. In Proc. annu. tall
timbers fire ecol. conf., Oct. 16-17. p. 201-222.
Portland, Oreg.
Hemmett, R. V., Jr., and S. D. Faust. 1969.
Biodegradation kinetics of 2,4-
dichlorophenoxyacetic acid by aquatic
microorganisms. Residue Rev. 29:191-207.
Hewlett, J. D., and A. H. Hibbert. 1967. Factors af-
fecting the response of small watersheds to
precipitation in humid areas. In Forest
hydrology, p. 275-290. W. E. Sopper and H. W.
Lull, eds. Pergamon Press, New York.
Hornbeck, J. W., and R. S. Pierce. 1973. Potential
impact of forest fertilization on stream flow sym-
posium proceedings. In Forest Fertilization.
USDA For. Serv. Gen. Tech. Rep. NE-3, p. 79-
87. Northeast. For. Exp. Stn., Upper Darby, Pa.
Judd, J. H., T. G. Coffey, and H. H. Wilcox IE.
1972. Impact of Dylox on the aquatic environ-
ment. Appl. For. Res. Inst., N.Y. State Coll. For.
Rep. No. 10:59-77.
Karinen, J. F., J. G. Lamberton, N. E. Stewart,
and L. C. Terriere. 1967. Persistence of carbaryl
in the marine environment, chemical and
biological stability in aquarium systems. J.
Agric. Food Chem. 15:148-156.
Kaufman, D. D., J. R. Plimmer, P. C. Kearney,
and others. 1968. Chemical versus microbial
decomposition of amitrole in soil. Weed Sci.
16:266-272.
Kearney, P. C., E. A. Woolson, J. R. Plimmer, and
A. R. Isensee. 1969. Decontamination of
pesticides in soils. Residue Rev. 29:137,149.
Klock, G. O. 1971. Streamflow nitrogen loss follow-
ing forest erosion control fertilization. USDA
For. Serv. Res. Note PNW-169, 9 p. Pac.
Northwest. For. and Range Exp. Stn., Portland,
Oreg.
Krammes, J.S., and D.B. Willets. 1964. Effect of
2,4-D and 2,4,5-T on water quality after a spray-
ing treatment. USDA For. Serv. Res. Note PSW-
52, 4 p. Pac. Southwest. For. and Range Exp.
Stn., Berkeley, Calif.
Ludzack, F.J., and J.W. Mandia. 1967. Behavior of
3-amino-l,2,4-triazole in surface water and
sewage treatment. 16th Ind. Waste Conf., Eng.
Ext. Ser. 109., p. 540-554. Purdue Univ.,
Lafayette, Ind.
Mader, D.L. 1973. Fertilizer needs and treatment
responses for wood fiber production: Field assess-
ment. In Forest fertilization symposium
proceedings. USDA For. Serv. Gen. Tech. Rep.
NE-3, p. 140-154. Northeast. For. Exp. Stn., Up-
per Darby, Pa.
Malucg, K.W., C.F. Powers, and D.F. Krawczyk.
1972. Effects of aerial forest fertilization with
urea pellets on nitrogen levels in a mountain
stream. Northwest Sci. 46(l):52-58.
Marston, R.B., D.W. Schultz, T. Shiroyama, and
L.V. Snyder. 1968. Amitrole concentrations in
creek waters downstream from an aerially
sprayed watershed sub-basin. Pestic. Monit. J.
2:123-128.
Meehan, W.R., F.B. Lotspeich, and E.W. Mueller.
1975. Effects of forest fertilization in two
southeast Alaska streams. J. Environ. Qual.
4(l):50-53.
Moilanen, K.W., D.G. Crosby, C.J. Soderquist,
and A.S. Wong. 1975. Dynamic aspects of
pesticide photodecomposition. In Environmental
dynamics of pesticides, p. 45-60. R. Haque and
V.H. Freed, eds. Plenum Press, New York.
Moore, D.G. 1970. Nitrogen in the environment —
a critical look. In Nutritional problems and prac-
tices on forest land. Symp. sponsored by Coll.
For. Resour., Univ. Wash., Seattle. Mimeo, un-
numbered pages.
Moore, D.G. 1971. Fertilization and water quality.
In 1971 annual meeting western reforestation
coordinating committee proceedings, p. 28-31.
West. For. and Conserv. Assoc., Portland, Oreg.
Moore, D.G., J.D. Hall, and W.L. Hug. 1974.
Endrin in forest streams after aerial seeding with
endrin-coated Douglas-fir seed. USDA For. Serv.
Res. Note PNW-219, 14 p. Pac. Northwest For.
and Range Exp. Stn., Portland, Oreg.
Moore, D.G. 1975a. Effects of forest fertilization
with urea on water quality — Quileene Ranger
District, Washington. USDA For. Serv. Res.
Note PNW-241, 9 p. Pac. Northwest For. and
Range Exp. Stn., Portland, Oreg.
Moore, D.G. 1975b. Impact of forest fertilization on
water quality in the Douglas-fir region — a sum-
mary of monitoring studies. In 1974 national con-
vention of the society of American foresters, New
York, proceedings, p. 209-219.
XI.27
-------
Moore, D.G. 1977. Personal communication. Soil
Sci., USDA For. Serv., Pac. Northwest For. and
Range Exp. Stn., Corvallis, Oreg.
Moore, D.G., J.D. Hall, and W.L. Hug. 1974.
Endrin in forest streams after aerial seeding with
endrin-coated Douglas-fir seed. USDA For. Serv.
Res. Note PNW-219, 14 p. Pac. Northwest For.
and Range Exp. Stn., Portland, Oreg.
Morton, H.L., E.D. Robinson, and R.E. Meyer.
1967. Persistence of 2,4-D, 2,4,5-T and dicamba
in range and forage grasses. Weeds 15:268-271.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. EPA-
910/9-77-036. 224 p.
Nicholson, H.P. 1967. Pesticide pollution control.
Science 158:871-876.
Norris, L.A. 1967. Chemical brush control and her-
bicide residues in the forest environment. In Her-
bicides and vegetation management, p. 103-123.
Oreg. State Univ. Press, Corvallis.
Norris, L.A. 1968. Stream contamination by her-
bicides after fall rains on forest land. Res. Prog.
Rep., p. 33-34. West. Soc. Weed Sci.
Norris, L.A. 1969. Herbicide runoff from forest
lands sprayed in summer. Res. Prog. Rep., p. 24-
26. West. Soc. Weed Sci.
Norris, L.A. 1970. Degradation of herbicides in the
forest floor. In Tree growth and forest soils, p.
397-411. Oreg. State Univ. Press, Corvallis.
Norris, L.A. 1971. Chemical brush control, assess-
ing the hazards. J. For. 69(10):715-720.
Norris, L.A., and M.L. Montgomery. 1975.
Dicamba residues in streams after forest spray-
ing. Bull. Environ. Contain, and Toxic. 13(1):1-
8.
Norris, L.A., and M.L. Montgomery, and E.R.
Johnson. 1977. The persistence of 2,4,5-T in a
Pacific Northwest Forest. Weed Sci. 25:417-422.
Norris, L.A., M.L. Montgomery, and G.D. Savelle.
1976a. Behavior of triclopyr in soil and
streamwater on a small watershed, southwest
Oregon. In Abstracts, 1976 annual meeting.
Abstr. No. 82, p. 36. Weed Sci. Soc. Am., Feb. 3-
5. Denver.
Norris, L.A., M.L. Montgomery, and L.E. Warren.
1976b. Leaching and persistence of picloram and
2,4-D on a small watershed in southwest Oregon.
In Abstracts, 1976 annual meeting. Abstr. No.
81, p. 35-36. Weed Sci. Soc. Am., Feb. 3-5.
Denver.
Norris, L.A., and D.G. Moore. 1971. The entry and
fate of forest chemicals in streams. In Forest land
uses and stream envirionment symposium
proceedings, p. 138-158. J.T. Krygier and J.D.
Hall, eds. Oreg. State Univ., Corvallis.
Norris, L.A., and D.G. Moore. 1976. Forests and
rangelands as sources of chemical pollutants. In
Non-point sources of water pollution. Sem. Publ.
SEMIN WR 021-76, p. 17-35. Water Resour. Res.
Inst., Oreg. State Univ., Corvallis.
Norris, L.A., M. Newton, and J. Zavitkovski. 1966.
Stream contamination with amitrole following
brush control operations with amitrole-T. Res.
Prog. Rep., p. 20-23. West. Weed Control Conf.
Norris, L.A., M. Newton, and J. Zavitkovski. 1967.
Stream contamination with amitrole from forest
spray operations. Res. Prog. Rep., p. 33-35. West.
Weed Control Conf.
Pierce, R.S. 1969. Forest transpiration reduction by
clearcutting and chemical treatment. Proc.
Northeast Weed Control Conf. 23:344-349.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
and Technol., Washington, D.C. 220 p.
Powers, R.F., K. Isik, and P.J. Zinke. 1975. Adding
phosphorus to forest soils: Storage capacity and
possible risks. Bull. Environ. Contam. and
Toxic. 14:257-264.
Reigner, I.C., W.E. Sopper, and R.R. Johnson.
1968. Will the use of 2,4,5-T to control stream-
side vegetation contaminate public water sup-
plies? J. For. 66:914-918.
Reimer, C.A., B.C. Byrd, and J.H. Davidson.
1966. An improved helicopter system for the
aerial application of sprays containing tordon-
101 mixture participated with Norbak. Down to
Earth 22(1) :3-6.
Reikerk, H., and S.P. Gessel. 1968. The movement
of DDT in forest soil solutions. Soil Sci. Soc. Am.
Proc. 32:595-596.
XI.28
-------
Robson, T.O. 1968. Some studies of the persistence
of 2,4-D in natural surface waters. In Ninth
British weed control conference proceedings, p.
404-408.
Romine, R.R., and R.A. Bussian. 1971. The
degradation of carbaryl after surface application
to a farm pond. Union Carbide Proj. Rep.
111A13. 5 p. Unpubl.
Schwartz, H.G., Jr. 1967. Microbial degradation of
pesticides in aqueous solutions. J. Water Pollut.
Control Fed. 39:1701-1714.
Scifres, C., O.C. Burnside, and M.K. McCarty.
1969. Movement and persistence of picloram in
pasture soils of Nebraska. Weed Sci. 17:486-488.
Smith, G.E., and D.G. Ison. 1967. Investigation of
effects of large-scale applications of 2,4-D on
aquatic fauna and water quality. Pestic. Monit.
J.
Soileau, J.N. 1969. Effects of fertilizers on water
quality. 107 p. Term. Val. Auth., Muscle Shoals,
Ala.
Sopper, W.E. 1975. Effects of timber harvesting
and related management practices on water
quality in forested watersheds. J. Environ. Qual.
4(l):24-29.
Stephens, R. 1975a. Effects of forest fertilization in
small streams in the Olympic National Forest,
spring 1975. Unpubl. For. Serv. Rep. 43 p. Olym-
pia, Wash.
Stephens, R. 1975b. Effects of forest fertilization in
small streams on the Olympic National Forest,
fall 1975. Unpubl. For. Serv. Rep. 40 p. Olympia,
Wash.
Stephens, R. 1976. Effects of forest fertilization in
small streams in the Olympic National Forest,
Quileene Ranger District, spring. Unpubl. For.
Serv. Rep. 36 p. Olympia, Wash.
Tarrant, R.F., D.G. Moore, W.B. Bollen, and B.R.
Loper. 1972. DDT residues in forest floor and soil
after aerial spraying, Oregon, 1965-1968. Pestic.
Monit. J. 6(l):65-72.
Thut, R.N., and E.P. Haydu. 1971. Effects of forest
chemicals on aquatic life. In Forest and land uses
and stream environment symposium
proceedings. J.T. Krygier and J.D. Hall, eds.
Oreg. State Univ., Corvallis.
Tiedemann, A.R. 1973. Stream chemistry following
a forest fire and urea fertilization in north central
Washington. USD A For. Serv. Res. Note PNW-
203, 20 p. Pac. Northwest. For. and Range Exp.
Stn., Portland, Oreg.
Tiedemann, A.R., and G.O. Klock. 1973. First-year
vegetation after fire reseeding and fertilization
on the Entiat Experimental Forest. USDA For.
Serv. Res. Note PNW-195, 23 p. Pac. Northwest.
For. and Range Exp. Stn., Portland, Oreg.
Trichell, D.W., H.L. Morton, and M.B. Merkle.
1968. Loss of herbicides in runoff water. Weed
Sci. 16:447-449.
Union Carbide Corporation. 1968. Technical infor-
mation on Sevin carbaryl insecticide. Union Car-
bide Corp. 10G-0449A Bookl. 56 p.
U.S. Department of Agriculture. 1964. The effects
of the 1964 gypsy moth treatment program in
Pennsylvania and New Jersey on the total en-
vironment. USDA Agric. Res. Serv.,
Moorestown, N.J. Unpubl.
U.S. Department of Agriculture. 1977. U.S. Forest
Service pesticide use report for FY1976 and tran-
sition quarter. 19 p. Mimeo.
Watkins, S.H., R.F. Strand, D.S. DeBell, and J.
Esch, Jr. 1972. Factors influencing ammonia
losses from urea applied to northwestern forest
soils. Soil Sci. Soc. Am. Proc. 36(2):354-357.
Weetman, G.F. 1961. The nitrogen cycle in
temperate forest stands. Woodland Res. Index,
Pulp Pap. Res. Inst. Can. No. 126, 28 p.
Weetman, G.F., and S.B. Hill. 1973. General en-
vironmental and biological concerns in relation
to forest fertilization. In Forest fertilization sym-
posium proceedings. USDA For. Serv. Gen.
Tech. Rep. NE-3, p. 19-35. Northeast For. Exp.
Stn., Upper Darby, Pa.
Weiss, C., T. Nakatsugawa, J.B. Simeone, and J.
Brezner. 1973. Gas chromatographic analysis of
spray residues in a forest environment after
aerial spraying of Dylox. In Environmental im-
pact and efficacy of Dylox used for gypsy moth
suppression in New York state, p. 15-25. Appl.
For. Res. Inst., N.Y. State Coll. For., Syracuse,
N.Y.
Wells, L.F., Jr. 1966. Disappearance of carbaryl
(Sevin) from oak foliage in plots aerially sprayed
XI.29
-------
for control of gypsy moth on Cape Cod, Mas- Wilcox, H.H. III. 1971. The effects of Dylox on a
sachusetts, in 1965. In Report of the surveillance forest ecosystem. Lake Ont. Environ. Lab., Prog.
program conducted in connection with an ap- Rep. State Univ. Coll.. Oswego, N.Y.
plication of carbaryl (Sevin) for the control of
gypsy moth on Cape Cod, Massachusetts. Com-
monw. Mass. Pestic. Board Publ. 547, p. 12-17. Wilcf>x- H-H . ™- 1972 Environmental impact
study <>t aerially applied Sevm-4-Oil on a forest
Wiese, A.F., and R.G. Davis. 1964. Herbicide and aquatic ecosystem. Lake Ont. Environ.
movement in soil with various amounts of water. Lab.. Prog. Rep. (Dec. 7), 55 p. State Univ. Coll.,
Weeds 12:101-103. Oswego, N.Y.
XL 30
-------
APPENDIX XI.A
WATER QUALITY DATA — PESTICIDE CHEMICALS
Table XI.A.1.—Cascade Creek Unit, Alsea Basin, western Oregon (Morris 1967)
Sample points1
Sample point 4
Sample point 5
Hours after
spraying
2,4,5-T
Hours after
spraying
2,4,5-T
Hours after
spraying
2,4,5-T
M9/I
0.05
0.62
1.28
2.0
4.0
5.2
9.8
24.7
48.2
274.8
0
16
7
4
4
4
4
2
1
1
0.17
1.33
2.2
3.9
5.4
1
2
1
1
0
0.27
1.40
2.0
3.9
lost
3
3
0
'Entire watershed feeding the sampled stream was sprayed.
2Herbicide was detected for 16 weeks at sample point 3.
Figure XI.A.1.—Cascade Creek Treatment Unit. (26 ha (2%)
of a 1400-ha watershed was treated with 2.24 kg/ha 2,4,5-T.
Large streams not included in treatment area.) (Morris
1967).
I mile
XI.31
-------
Table XI.A.2.—Eddyville Unit, Yaquina Basin, western Oregon' (Morris 1967)
Sample point 12
Sample point 13
Sample point 14
Hours after
spraying
2,4-D
Hours after
spraying
2,4-D
Hours after
spraying
2,4-D
M9/I
0.83
1.83
2.8
Z53.5
33
13
13
9
1.33
2.3
3.3
4.3
253.6
62
71
58
44
25
1.38
2.3
3.3
4.3
Z53.6
30
44
25
23
11
1Rate of application was 2.5 to 3.36 kg/ha.
2No further residues detected although sampling continued for 10 months.
Figure XI.A.2—Eddyville Treatment Unit. (20 ha (10%) of a
287 ha watershed was treated with 2,4-D (LVE) at rates
ranging from 2.5 to 3.36 kg/ha. Sampled streams flowed
from or through treatment area.) (Morris 1967).
Table XI.A.3.—Concentration of 2,4-D in West Myrtle Creek,
Malheur National Forest, eastern Oregon' (Morris 1967)
Sample point 1
Sample point 22
Hours after
spraying
2,4-D
Hours after
spraying
2,4-D
1.7
3.7
4.7
6.0
7.0
8.0
9.0
13.9
26.9
37.9
78.0
80.8
168.0
132
61
85
10
26
75
59
51
3
9
8
1
0
2.0
3.9
5.0
6.2
7.2
8.2
9.2
14.1
17.0
38.0
77.8
81.0
104.8
168.0
0
0
0
2
7
8
13
14
7
6
9
9
3
1
'Rate of application was 2.24 kg/ha.
2Sampling point 2 is 1.6 km downstream from point 1
North
I mile
Figure XI.A.3.—West Myrtle Treatment Unit (240 ha treated
in one block. Live streams Included In the treatment area.)
(Morris 1967).
XI.32
-------
Table XI.A.4.—Camp Creek Spray Unit,
Malheur National Forest, eastern
Oregon1 (Morris 1967)
Hours after
spraying
2,4-D
0.1
2.0
5.4
8.8
84.5
168.0
o
25
1
1
3
0
1Rate of application was 2.24 kg/ha.
North
Figure XI.A.4.—Camp Creek Spray Unit. (121 ha treated with
2.24 kg/ha 2,4-D (low volatile esters). Spray boundaries ad-
jacent to, but did not include, live streams.) (Morris 1967).
Table XI.A.5.—Concentration of 2,4-D in streams in Keeney-
Clark Meadow eastern Oregon1
(Norris 1967)
Hours after
spraying
2,4-D
Hours after
spraying
1Rate of application was 2.24 kg/ha.
2,4-D
0.7
2.5
3.1
3.6
4.1
6.1
8.1
9.6
840
48
128
106
106
121
176
138
14.3
37.8
56.4
100.1
103.6
289.9
297.0
113
91
76
115
95
5
7
pelat
Figure XI.A.5.— Keeney-Clark Meadow Spray Units. (89 ha
treated with 2.24 kg/ha 2,4-D. Flat, marshy area with many
small live streams and other sites with standing water.)
(Norris 1967).
XI.33
-------
Table XI.A.6.—Concentration of Amitrole-T in Wildcat Creek,
Coast Range, western Oregon1
(Morris and others 1966)
Sample point 2
Sample point 3
Hours after
spraying
Amitrole-T
Hours after
spraying
Amitrole-T
0.05
0.39
0.74
1.13
1.43
1.73
2.1
3.3
4.8
5.8
7.1
8.1
9.5
10.4
15.3
26.1
30.1
46.1
71.5
1
30
35
37
17
16
19
21
12
8
5
4
3
2
1
7
4
2
0
0.05
0.33
0.67
1.07
1.38
1.60
2.0
2.8
4.2
5.2
6.9
8.0
10.3
15.2
20.5
26.0
45.7
69.4
0
0
9
90
110
40
35
24
14
7
5
5
3
2
25
8
3
0
'Rate of application was 2.24 kg/ha.
I mile
© *» Sampling Point
Stream
Watershed Boundary
Figure XI.A.6.—Wildcat Creek Spray Unit. (28 ha treated with
2.24 kg/ha amitrole-T. Spray units include live streams.)
(Norris and others 1966).
XI.34
-------
Table XI.A.7.—Concentration of amitrole in stream water,
loss or dilution with downstream movement.
Amitrole-T applied to 105 ha at 2.24 kg/ha1
(Morris and others 1967)
Hours after
spraying
hours
0.1
0.5
1
2
3
4
5
6
8
10
12
14
24
35
48
72
Amitrole concentration on
sampling point
1
1
5
7
45
24
8
10
9
3
2
1
1
1
1
0
0
2
0
0
2
42
15
18
5
5
3
2
1
1
2
0
0
0
3
iin/l
M9'1
0
0
0
0
0
4
6
6
12
2
2
2
1
1
0
0
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
'Study was conducted in Coast Range of Oregon. Sampling
point 1 was located just below boundary of sprayed unit; point 2
was 3.2 km downstream from point 1; point 3 was 0.48 km below
point 2; and point 4 was 1.49 km below point 2. No detectable
quantity of amitrole was found between 3 and 150 days after treat-
ment.
Watershed Boundary
(Area =244 hectares )
Treatment Boundary
(Area =67 hectares )
Figure XI.A.7.—Farmer Creek Treatment Watershed. (67 ha of a 244 ha
watershed sprayed by helicopter with 1.12 kg dicamba and 2.24 kg 2,4-D
per ha. Sampling point 1 is about 1.3 km from edge of treated unit) (see
table XI.A.8) (Morris and Montgomery 1975)
XI.35
-------
Table XI.A.8.—Concentration of dicamba in Farmer Creek' (Morris and Montgomery 1975)
Sampling date
6/05/71
6/07/71
6/08/71
6/09/71
Hours after
application
hours
(prespray)
0.3
0.6
1.0
1.2
1.7
2.1
2.5
2.7
3.3
3.8
4.3
4.8
5.2
6.2
6.8
7.8
8.8
10.2
13.1
22.8
30.1
37.5
50.2
Dicamba
M9/I
0
0
0
0
0
0
1
0
0
3
12
16
28
37
33
30
27
24
16
11
6
2
0
0
Sampling
date
6/10/71
6/11/71
6/13/71
6/16/71
6/18/1
6/21/71
6/30/71
7/08/71
7/09/71
8/11/71
8/20/71
8/25/71
9/01/71
9/02/71
9/07/71
9/29/71
10/19/71
11/17/71
11/29/71
12/22/71
5/18/72
6/08/72
6/30/72
7/28/72
Dicamba
/ug/i
2
4
9
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
'Coastal Oregon; 67 ha treated with 1.12 kg/ha dicamba and 2.24 kg/ha 2,4-D.
XI.36
-------
STREAM DISCHARGE AND PRECIPITATION
Figure XI.A.8—Precipitation,
stream discharge, and con-
centrations of tryclopyr In
stream water following ap-
plication of 3.36 kg/ha by
helicopter to a small
watershed In southwest
Oregon In May 1974 (Morris
and others 1976b).
A. First 20 hours after ap-
plication.
B. First significant storm ac-
tivity, channel flushing.
E
o
<
cc
.a
a.
a.
O)
DC
LU
LU
CO
LU
cc
80
40
No Rain
No Stream Discharge
i i i i i i i i i i i i i i i i i i r
Triclopyr in Water
i i i i i i
4 8 12 16
TIME AFTER APPLICATION, (hours)
20
Is
I 2
z"
< 1
CC
Q.
Q.
'16
O)
12
co 4
LU
CC
0
B
STREAM DISCHARGE AND PRECIPITATION
Rain
Stream
Discharge
120
o Malfunction
Triclopyr in Water
i i i i i i i i i
28 30 1
OCTOBER
o—o Concentration
f|f Discharge
I
5 7 9 11
NOVEMBER
DATE
13 15 17
XI.37
-------
Table XI.A.9.—Concentrations of 2,4-D and plcloram In
drainage waters from a 7-ha hill-pasture
watershed in southwest Oregon1 (Norrls and others 1976a)
Date
9/18/69
10/09/69
10/13/69
10/21/69
11/14/69
11/24/69
12/01/69
12/09/69
12/19/69
12/24/69
1/01/70
1/24/70
Rain
7.9
3.0
5.0
—
0.1
2.0
6.8
9.9
4.6
18.6
2,4-D
/
0
22
0
3
0
0
0
0
0
0
0
0
Picloram
,n/l
110
43
64
39
0
0
0
0
0
12
1
0
'Rate of application—2.3 kg picloram and 4.6 kg 2,4-D in 93.5
I/ha applied as Tordon 212 by helicopter.
WATERSHED, SAMPLING STATIONS AND RATE OF APPLICATION
LEGEND
"S"Weir
• Interception Disc
O Cluster
Intermittent Stream
0 30 60 90 I2O 150 180 BO 240 270
SCALE, METERS
Figure XI.A.9.—Boyw Ranch, MuthwMt Oregon. Small 7-ha hlll-pattura
•pray unit treated with Tordon 212 (Norrls and others 1976a).
XI.38
-------
Table XI.A.10.—Total DDT content of stream water flowing
from sprayed area — before treatment and for 3 years
after treatment1 (Tarrant and others 1972)
Date
Days
after
spraying
Total DDT residues In
Rattlesnake Creek
East Fork
West Fork
5/24/65
6/19/65
6/23/65
7/14/65
8/26/65
11/17/65
6/07/66
7/19/66
11/09/66
7/04/67
11/07/67
7/16/68
11/12/68
-30
- 4
1
21
64
147
349
391
505
742
869
1,131
1,251
<
ND
.104
.031
.028
.014
.010
ND
ND
.032
.010
ND
.277
.022
.015
ND
ND
ND
.010
'Area sprayed with DDT at rate of 0.84 kg/ha.
'Blank = levels of DDT isomers and metabolites less than 0.01
mg/l but greater than 0.002 mg/l.
ND = not detected
HERBICIDE DISCHARGE
Area in Stream
Discharged Channel
Total Applied Total % % of Total
^ 2,4-D 29800 g 6g 0.02 0.21
^ Picloram 14900g 43g 0.29 0.2I
V)
§>20
uT
o
X
HERBICIDE DISC
D 01 6
—
-
"l
I
fwrt 777\
!
W(
1
1
1
HI Picloram -
—
i OCTOBER 1 ^^JOVEMBER^
•3-ld 11-201 I2I-3B •-! • 12-301
SAMPLING PERIOD
Figure XI.A.10.—Discharge of herbicide In streamflow from small 7-ha hill-pasture watershed,
Boyer Ranch, southwest Oregon. Treatment was with Tordon 212 at 2.3 kg picloram and 4.6 kg
2,4-D per hectare (Norrls and others 1976a).
Note: All of the herbicide discharged with streamflow is accounted for by the quantity applied to
the stream channel and adjacent banks. (The question mark for the period December 21 through
31 reflects equipment malfunction resulting in no measure of stream discharge.)
XI.39
-------
Table XI.A.11 .—Concentration of herbicides in water samples,
as determined by odor tests1 (Reigner and others 1968)
Herbicide and time
of sample
Pennsylvania New Jersey
streams streams
M9/I
2,4,5-T butory ethanol ester:
Immediately after spraying 40
4 hours later 20
Next 9 samples2 ND3
After first large storm 10
2,4,5-T emulsifiable acid:
Immediately after spraying 40
4 hours later 10
Next 9 samples2 ND
After first large storm 20
All downstream samples
(both herbicides) ND
40
20
ND
ND
20
ND
ND
ND
ND
'Test panel used procedure approved by American Society for
Testing and Materials.
2Samples taken daily for first week; twice a week for next 2
weeks.
3ND = no detectable odor.
Figure XI.A.11.—Concentration of
endrin in streamflow after aerial
seeding with endrin-coated
Douglas-fir seed. Needle Branch
Watershed—seed treated with 1.0%
endrin and sown at 0.84 kg/ha;
Watershed 1, H.J. Andrews Ex-
perimental Forest—seed treated at
0.5% endrin and sown at 0.56 kg/ha
(Moore and others 1974).
NEEDLE BRANCH
18 December 1967-12 January 1968
I
if
UJ —
cc
100
200 300 400
HOURS AFTER SEEDING
500
O.OSf—
WATERSHED NO. 1
30 October 1967
MEAN STREAMFLOW
0.049 m'/s
2 3
HOURS AFTER SEEDING
J
5
XI.40
-------
Table XI.A.12.—Concentrations of 2,4-D and 2,4,5-T herbicide In water samples from
Monroe Canyon, San Dlmas Experimental Forest, northeast of Glendora, California
(Krammes and Wlllets 1964)1
Date
Site
Weir
Surface
WelM
Well 2
May 10/61
May 22/61
June 5/61
July 24/61
July 31/61
Aug. 28/61
Sept. 25/61
Oct. 30/61
Jan. 29/62
Feb. 26/62
June 20/63
0.00
.00
.05
.05
.00
.00
.00
.00
.00
.00
.00
PI
—
0.09
.03
.00
.00
.00
.00
—
—
—
—
0.01
.00
.00
.00
.04
.00
...
—
—
—
0.01
.00
.00
.01
.00
.00
—
—
—
'The riparian zone and intermediate slopes of a 354-ha watershed were hand sprayed several times
with a mixture of equal parts of 2,4-D and 2,4,5-T in diesel oil. Care was taken to avoid any direct con-
tamination of the stream. A total of 1701 of herbicide was applied on May 10,1961, but actual rates of ap-
plication are not known. Maintenance spraying was carried out again in June, 1963, also followed by
hand spraying at later dates. Stream contamination was below the safe limit of 1 ppm. No traces of diesel
oil were found. Riparian zone vegetation was handsprayed during the week following the May 22, 1961
sampling and just before the June 20, 1963 sampling.
2.0
1.5
CLEARCUT WATERSHED
i.o-
.5-
STREAMFLOW -
AREA INCHES/DAY
BROMACIL
PPM
J J ' A ' S ' 0 N D I JFMAM J ' J ' A ' S '
1966 1967
Figure XI.A.12.—Water yield and bromacll release from
watershed 2, Hubbard Brook Experimental Forest, West
Thornton, New Hampshire (Pierce 1969).
Note: Watershed 2 (15.8 ha) was clearcut of all timber and
woody vegetation in late fall and early winter of 1965. In June
1966, bromacll was broadcast sprayed by helicopter at a rate
of 28 kg/ha. Persistent sprouts were sprayed with 2,4,5-T in
the summer of 1967. About 20 percent of the bromacil left the
watershed through the stream in Vk years. The concentration
of 2,4,5-T in the stream was less than 1 mg/l for the entire
period following application.
XI.41
-------
cr
a.
in
CD
ce
LlJ
0.
(Ł
2
g
i-
<
Q
z
o
o
UJ
in
10 15 20
MAY
15 20
JUNE
15 20
JULY
10 IS
AUGUST
20 25
Figure XI.A.13.—Atrazine concentration in streamflow during and for 31/z months after herbicide treatment
(Douglas and others 1969).
Note: A 9-ha watershed was treated May 3-6,1966, with 3.9 kg atrazine and 0.95 I technical paraquat per hec-
tare, including the water course. Surviving vegetation was sprayed again on July 5-11 with a mixture of 3.36
kg 2,4-D (isobutyl esters) and 5 kg atrazine per hectare, but a 3-m buffer strip was left unsprayed on both
sides of the stream. Atrazine content in water samples from the stream is graphed above. Paraquat was
detected in only 5 of more than 35 samples, and maximum concentration measured was 19 /jg/l. After the se-
cond spraying, 2,4-D was never detected in the stream and the concentration of atrazine did not increase,
even during storms.
XI.42
-------
APPENDIX XL B
WATER QUALITY DATA — FERTILIZER CHEMICALS
Table XI.B.1.—Stream water quality following forest fertilization, fall 1975:
Hoodsport-Quileene Ranger Districts, Olympic National Forest, Washington (Stephens 1975b)
Treatment: Urea pellets were applied to several thousand acres of second growth Douglas-fir. As a general rule,
stream buffer strips of 100 ft (30 m) were left along tributary streams which were flowing greater than
0.5 ft3/sec (14 I/sec). 300 ft (91 m) wide buffer strips were left along main streams.
Site
Rate of Date of Treatment
application application area
Ib-N/ac kg-N/ha
Range concentrations
Urea-N NH3-N NOs-N
McDonald Creek
Pre-treatment
Post-treatment
Jimmycomelately
Pre-treatment
Post-treatment
Gold Creek
200 224 Oct.-Nov. 75
ac ha
316 128
-mg/l-
0.01-0.02 0 0.03-0.05
0.32-0.01 0-0.18 0.03-2.85
200 224 Oct.-Nov.75 48 20
200 224 Oct.-Nov. 75 229 93
0-0.05
0-0.07 0.03-0.13
Pre-treatment
Post-treatment
Elbo Creek
Pre-treatment
Post-treatment
Mile & V2 Creek
Pre-treatment
Post-treatment
Fulton Creek
Pre-treatment
Post-treatment
Waketickeh Creek
Pre-treatment
Post-treatment
0
0-0.31
200 224 Oct.- Nov. 75 33 13
0
0-0.28
200 224 Oct.-Nov. 75 169 68
0-0.02
0-0.22
200 224 Oct.-Nov.75 592 240
0
0-0.13
200 224 Oct.-Nov. 75 1432 580
0-0.01
0-0.84
0
0-0.22
0
0-0.10
0
0-0.02
0
0-0.10
0
0-0.55
0.02-0.05
0.02-0.18
0.01-0.02
0-0.07
0.06-0.07
0-0.92
0.01-0.02
0.01-0.09
0-0.02
0-0.40
XI.43
-------
Table XI.B.2.—Stream water quality following forest fertilization, spring 1975:
Hoodsport-Quileene Ranger Districts, Olympic National Forest, Washington (Stephens 1975a)
Treatment: Urea pellets were applied by helicopter to several thousand acres of second growth Douglas-fir. As
a general rule, stream buffer strips 200 ft (60 m) wide were left along streams which were flowing
greater than 0.5 ftVsec (14 I/sec).
Site
Rate of Date of Treatment
application application area
Ib-N/ac kg-N/ha
Range
concentration
NCh-N
Mile & 1/2 Creek
Pre-treatment
Post-treatment
Trap per Creek
Pre-treatment
Post-treatment
Salmon Creek
Pre-treatment
Post-treatment
Eddy Creek
Pre-treatment
Post-treatment
Jackson-Mar pie
Pre-treatment
Post-treatment
Turner Creek
Pre-treatment
Post-treatment
200 224
Apr. 75
ac ha
292 118
200 224 Apr. 75 200 81
200 224 Apr. 75 112 45
200 224 Apr. 75 240 97
200 224 Apr. 75 460 186
200 224 Apr. 75 286 116
mg/|
0.01-0.03
0-0.18
-0.03
0.01-0.54
0
0.03-0.65
0
0-0.72
0-0.01
0-0.50
0-0.04
0-0.25
XI .44
-------
Table XI.B.3.—Stream water quality following a wildfire and fertilization with reseeding for erosion control, 1971:
Entiat Experimental Forest, central Washington (Klock 1971; Tiedemann and Klock 1973;
and Helvey and others 1974)
Treatment: Following a wildfire in August 1971, three watersheds were monitored for water quality. Fox Creek
was used as a control, Burns Creek was fertilized with ammonium sulfate and McCree Creek was
fertilized with urea. An unburned watershed, Lake Creek was also monitored as an undisturbed con-
trol.
Site
Fox Creek
Rate of
application
Ib-N/ac kg-N/ha
Control
Dates of
appli-
cation
Percent of
total
applied
no application
Treatment
area
ac ha
1,169 473
Peak concentrations
Urea-N NCh-N NH4-N
mg/l •
Pre-treatment
Post-treatment
McCree Creek
1970
1971
10.035
N.D.
N.D.2
N.D.
N.D.
N.D.
48
urea
54
10/30/70
11/05/70
11/08/70
7.5
24.3
68.2
1,270
513
Pre-treatment
Post-treatment
Burns Creek
Pre-treatment
Post-treatment
Lake Creek
1970
1971
51 57
(NH4)2SO4
1970
1971
Control
1972
10/30/70
11/09/70
13.6
86.4
N.D.
0.616
1,394 564
N.D.
0
no application
N.D.
0.210
N.D.
0.068
0.065
N.D.
<0.02
N.D.
0
'Attributed to wildlife activity
2N.D.—Not detected, concentration below detection limit of equipment.
XI.45
-------
Table XI.B.4.—Stream water quality following forest fertilization, 1970:
Mitkof Island, southeast Alaska (Meehan and others 1975)
Treatment: Two areas of cutover land were fertilized
Site Rate of Date of
application application
Ib N/ac kg N/ha
Falls Creek
Control
1970
1971
Treated 190 210 May 70
1970
1971
Three Lakes
Control
1970
1971
Treated 190 210 May 70
1970
1971
N.D. = Not Detected
in May 1970 by helicopter with
Treatment Urea-N
area
—
N.D.
N.D.
—
N.D.
N.D.
—
N.D.
N.D.
—
N.D.
N.D.
urea pellets.
NOa-N
iiiy/i
0.23
0.24
1.26
1.66
0.20
0.18
2.36
0.30
NHs-N
0.23
0.11
1.28
0.11
0.10
0.12
0.14
0.08
Table XI.B.5.—Stream water quality following forest fertilization of two small watersheds, 1970 and 1971:
Sluslaw River Basin, western Oregon (Burrough and Froehlich 1972)
Treatment: Two watersheds, Nelson Creek and Dollar Creek, were fertilized by helicopter with urea pellets.
There were no buffer strips established along watercourses within the treated area. Untreated adja-
cent watersheds were also monitored as a control.
Site:
Rate of Date of Treatment Peak Concentration
application appli- area Urea-N
Ib-N/ac kg-N/ha cation
NHa-N
NOa-N
ac ha mg/l
Nelson Creek
treated
untreated
Dollar Creek
treated
untreated
200 224 Apr. 70 94
8.6
0.20
200 224 Apr. 71 85
44.4
<0.02
0.32
0.33
0.49
0.15
7.6
4.3
0.13
0.16
XI.46
-------
Table XI.B.6.—Stream water quality following fertilization of forested watershed on the Olympic Peninsula,
spring 1970: Quileene Ranger District, Olympic National Forest, Washington (Moore 1975b)
Treatment: Two watersheds, Jimmycomelately and Trapper Creek, were fertilized by helicopter with urea. Pel-
letlzed or large granule forest grade urea was unavailable so agricultural grade was used. Drift of the
fertilizer was noted. The stream was flagged and fertilizer was not applied within 200 ft (60 m) of the
stream.
Site:
Jimmycomelately
Pre-treatment
Post-treatment
Trapper
Pre-treatment
Post-treatment
Rate of Date of Treatment Peak Concentration
application appli- area Urea-N
Ib-N/ac kg-N/ha cation
200 224 Apr. 70 120 49
0
0.71
200 224 Apr. 70 158 64
0.013
0.71
Ntft-N
<0.004
0.04
<0.004
0.01
N03-N
0.002
0.042
0.055
0.121
Table XI.B.7.—Stream water quality after fertilization of a small forested watershed on the west slopes
of the Cascade Mountains, 1970: Oregon (Malueg and others 1972)
Treatment: A watershed was fertilized by helicopter with urea pellets. No effort was made to prevent the direct
application of urea into the water courses.
Site:
Rate of Date of Treatment
application appli- area
Ib-N/ac kg-N/ha cation
Cencentrations
NH4-N
NO2-N
NOa-N
Crabtree Creek
Pre-treatment
Post-treatment
200
224
May 70
ac
569
ha
230
mg/l
<0.01
<0.08
<0.01
<0.01
<0.01
<0.25
XI.47
-------
Table XI.B.8.—Stream water quality after fertilization following wildfire in north-central Washington, 1970:
Chelan, Washington (Tiedemann 1973)
Treatment: Urea fertilization following wildfire. Falls Creek was
Grade Creek was unburned and unfertilized.
Site:
Falls Creek
Pre-treatment
Post-treatment
Camas Creek
Grade Creek
fertilized, Camas Creek was not fertilized, and
Rate of Date of Treatment
application appli- area
Ib-N/ac kg-N/ha cation
ac
70 78 Oct. 70 6,180
1,680
6,920
ha
2,500
680
2,800
Peak Concentrations
Urea-N
0.330
0.029
0.006
1 0.450
NHa-N
0.011
0.011
0.001
0.011
NOa-N
0.016
0.310
0.042
0.016
'Attributed to animal activity.
Table XI.B.9.— Stream water quality following forest fertilization, spring 1976: Quileene Ranger District,
Olympic National Forest, Wash. (Stephens 1976)
Treatment: Urea pellets were applied to 800 ac of second-growth Douglas-fir. As a general rule, stream buffer
strips 100 ft (30 m) wide were left along tributary streams which were flowing greater than 0.5 ftVsec
(14 I/sec); 300 ft (91 m) wide buffer strips were left along main streams.
Site:
Townsend Creek
Pre-treatment
Post-treatment
Big Quileene
River
Pre-treatment
Post-treatment
Rate of Date of Treatment Range Concentrations
application appli- area NHa
Ib-N/ac kg-N/ha cation
200 224 Apr. 76 102 41
0
0-0.11
200 224 Apr. 76 800 324
0-0.03
0-0.05
NOa
0-0.05
0-0.008
0-0.06
0-0.09
Urea
0-0.02
0-0.75
0-0.01
0-0.04
XI.48
-------
Table XI.B.10.—Stream water quality and quantity of flow following fertilization of a forested watershed, 1971:
Fernow Experimental Forest, W.Va. (Aubertin and others 1973)
Treatment: Hardwood sprouts and seedlings were fertilized by helicopter with urea. No attempt was made to
avoid a small perennial stream.
Site:
Rate of Date of Treatment Concentration
application appli- area NH4-N NOs-N
Treated
1970-1971
1971-1972
Control
1970-1971
1971-1972
Ib-N/ac kg-N/ha cation max ave max
230 258 May 71 74 30
0.8 0.23 19.8
0.19
-« — - -.- ... ...
0.19
0.20
ave
0.76
0.10
0.10
0.21
Table Xl.8.11.—Stream water quality following fertilization of a gaged experimental watershed,
spring 1970: South Umpqua Experimental Forest, Oreg. (Moore 1971)
Treatment: Watershed 2 was fertilized in March 1970 by helicopter. Urea, prill formulation, was applied and
there was no attempt made to leave an untreated buffer zone along the stream. Watershed 4 was un-
treated and served as a control.
Site:
Watershed 2
Watershed 4
Rate of Date of
application appli-
Ib-N/ac kg-N/ha cation
200 224 Mar. 70
Treatment
area
ac ha
169 68
120 49
Concentrations
Urea-N NHa-N
1.39 0.048
0.006 0.005
NOs-N
0.177
0.002
XI.49
-------
Table XI.B.12.—The impact of forest fertilization on stream water quality in the Douglas-fir region—
a summary of monitoring studies in Alaska, Idaho, Oregon, and Washington (Moore 1975a, 1977)
Treatment: Aerial application of urea.
Site: Rate of Date of
application appli-
|b-N/ac ka-N/ha cation
Burns Creek1
Canyon Creek
Coyote Creek
Crabtree Creek
Dollar Creek
Elochoman Creek
Fairchilds Creek
Falls Creek
Jackson Creek
Jimmycomelately Creek
McCree Creek
Mica Creek
Mill Creek
Nelson Creek
Newaukum Creek
Pat Creek
Quartz Creek
Roaring Creek
Row Creek
Skookumchuck Creek
Spenser Creek
Tahuya Creek
Thrash Creek2
Three Lakes Creek
Trapper Creek
Trout Creek
Turner Creek
Waddel Creek
Wish bone Creek
50
200
200
200
200
200
200
190
150
200
50
200
200
200
150
200
200
200
150
150
200
200
200
190
200
200
200
200
200
Treatment
area
56
224
224
224
224
224
224
213
168
224
56
224
224
224
168
224
224
224
168
168
224
224
224
213
224
224
224
224
224
Nov1970
Nov1969
Mar 1970
May 1969
Apr 1971
Nov1969
Apr 1972
May 1970
May 1969
Apr 1970
Oct1970
Sep1972
Dec 1969
Apr 1970
Sep 1971
Apr 1972
May 1972
Mar 1972
Oct1972
Sep 1969
Nov 1972
Oct1972
May 1974
May 1970
Apr 1970
Mar 1968
Mar 1972
Dec 1969
May 1972
ac
1390
3325
170
570
85
735
475
650
235
120
1265
115
565
95
6085
600
125
660
6500
470
7680
4005
300
170
160
1600
870
1480
115
ha
562
1346
68
230
34
297
192
263
95
49
513
47
228
38
2463
243
51
267
2630
191
3108
1620
121
69
64
648
352
600
46
Urea-N
Pre- Post-
treatment
Peak Concentration
NHs-N NOs-N
Pre- Post-
treatment
Pre- Post
treatment
my /i
0
0.005
0.006
—
0.016
0.073
0.008
nd
0.007
0.002
0
0
0.02
0.016
0.009
0.003
0.004
0.007
0.006
0
0.019
0.01
—
nd
0.008
0.10
0.004
0.01
0
0
15.20
1.39
24.00
44.40
19.10
23.40
nd
0.09
0.71
0.62
0.30
0.68
8.60
0.26
3.26
1.75
0.76
0.13
2.63
0.37
27.20
—
nd
0.70
14.00
4.36
2.48
0.30
0
nd
0.005
0
0.030
nd
0.009
0.020
0.004
0
0
0
0
0.010
0
0.007
0
0.004
0.005
0.004
0.041
0
nd
0.015
0
0.12
0
0
0
0
nd
0.048
0.080
0.490
nd
0.280
1.28
0.044
0.040
0
0
0.12
0.32
0.008
0.079
trace
0.040
0.022
0.026
0.123
1.40
0.06
0.13
0.010
0.700
0.046
0.340
0
0
0.005
0.002
0
0.060
nd
0.030
0.015
0.065
0.005
0
0.15
0.02
0.290
0.011
0.061
0.120
0.017
0.004
0.005
0.005
0.01
nd
0.003
0.034
0.03
0.032
0.02
0.12
0.068
0.80
0.177
0.25
0.13
4.00
0.828
1.67
0.116
0.042
0.210
0.28
1.32
2.10
0.438
0.388
0.70
0.210
0.044
0.085
0.005
1.83
1.88
2.36
0.121
0.160
0.243
0.99
0.28
1(NH4)Z SO4 applied
"NhUNOa applied
nd = no data available or not determined
XI.50
-------
APPENDIX XI.C:
REFERENCE SOURCES FOR PESTICIDE CHEMICALS
Common name:
Chemical name:
Other names:
Registered use:
2,4-D
2,4-dichlorophenoxyacetic
acid
Stauffer, Esteron, Amine,
Dacamine
Control method for herbaceous
and woody plants on cropland,
forest, and rangeland, in
orchards, on fallow land, and
in pastures.
References
Bjorklund, N.-E., and K. Erne. 1966. Toxicological
studies of phenoxyacetic herbicides in animals.
Acta Vet. Scand. 7:364-390.
Gratkowski, H.J. 1961. Toxicity of herbicides on
three northwestern conifers. U.S. Rep. Agric.
For. Serv., Pac. Northwest For. and Range Exp.
Stn., Stn. Pap. 42. 24 p. Portland, Oreg.
House, W.B., L.H. Goodson, H.M. Gadberry, and
K.W. Docktur. 1967. Assessment of ecological ef-
fects of extensive or repeated use of herbicides.
Final rep. Midwest Res. Inst. Proj. 3103-B. Adv.
Res. Proj. Agency ARPA order No. 1086. Dep.
Defense Contract No. DAHC 15-68-C-0119.
369 p.
Innes, J.R.M., B.M. Ulland, M.G. Valeric, L.
Petrucelli, L. Fishbein, E.R. Hart, A.J. Pallota,
R.R. Bates, H.L. Falk, J.J. Gart, M. Klein, I.
Mitchell, and J. Peters. 1969. Bioassay of
pesticides and industrial chemicals for
tumorigenicity in mice: a preliminary note. J.
Natl. Cancer Inst. 42:1101-1114.
Johnson, J.E. 1971. The public health implications
of widespread use of the phenoxy herbicides and
picloram. Bioscience 21:899-905.
Lawrence, J.N. 1964. Aquatic herbicide data. U.S.
Dep. Agric., Agric. Handb. 231.
Leonard, O.A. (Ed.) 1961. Tables on reaction of
woody plants to herbicides. West. Weed Control
Conf. Res. Prog. Rep., p. 27-37.
Leonard, O.A., and W.A. Harvey. 1965. Chemical
control of woody plants. Calif. Agric. Exp. Stn.,
Davis, Calif., Bull. 812. 26 p.
Mrak, E. 1969. Report of the Secretary's Commis-
sion on pesticides and their relationship to en-
vironmental health. U.S. Dep. Health, Educ.
and Welfare. December.
Newman, A.S., and J.R. Thompson. 1950. Decom-
position of 2,4-dichlorophenoxyacetic acid in soil
and liquid media. Soil Sci. Soc. Am. Proc.
14:160-164.
Norris, L.A., and D.G. Moore. 1971. The entry and
fate of forest chemicals in streams. In Forest
Land Uses and Stream Environment Sym^
posium Proc., p. 138-158. J.T. Krygier and J.D.
Hall, eds. Sch. For. and Dep. Fish, and Wildl.,
Oreg. State Univ., Corvallis.
Oregon Extension Service. 1977. Oregon weed con-
trol handbook. 158 p. Oreg. State Univ., Coop.
Ext. Serv., Corvallis.
Palmer, J.S., and R.D. Radeleff. 1964. The tox-
icological effects of certain fungicides and her-
bicides on sheep and cattle. Ann. N. Y. Acad. Sci.
111:729-736.
Romancier, R.M. 1965. 2,4-D, 2,4,5-T, and related
chemicals for woody plant control in the
southeastern United States. Ga. For. Res.
Counc. Rep. No. 16, 46 p.
Rose, V.K., and T.A. Hymas. 1954. Summary of
toxicological information on 2,4-D and 2,4,5-T
type herbicides and an evaluation of the hazards
to livestock associated with their use. Am. J. Vet.
Res. 15:622-629.
Rudolf, P.O., and R.F. Watt. 1956. Chemical con-
trol of brush and trees in the Lake States. U.S.
Dep. Agric, For. Serv. Lake States For. Exp.
Stn., Stn. Pap. No. 41. 58 p. St. Paul, Minn.
XI.51
-------
Tucker, R.K., and D.G. Crabtree. 1970. Handbook
of toxicity of pesticides to wildlife. U.S. Dep.
Inter., Bur. Sport Fish, and Wildl., Res. Publ.
84.
U.S. Department of Agriculture, Forest Service,
1978. Vegetation management with herbicides.
Final environ, impact statement. Pac Northwest
Reg. USDA-FS-R6-FES (Adm) 75-18 (Rev.).
Mar. 6,1978. 330 p. plus append. Portland, Oreg.
Verrett, J. 1970. Testimony before the United
States Senate Committee on Commerce. Sub-
Comm. on Energy, Water, Nat. Resour. and En-
viron. Apr. 15, 1970. Ser. 91-60, p. 190-203.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. 430 p. Champaign, 111.
Hughes, J.S., and J.T. Davis. 1963. Variations in
toxicity to bluegill sunfish of phenoxy herbicides.
Weeds 11:50-53.
Martin, H. (ed.) 1971. Pesticide Manual: Basic In-
formation on the Chemicals used as Active Com-
ponents of Pesticides. 2nd ed. British Crop
Protect. Counc. p. 169.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Office
Sci. Technol. U.S. Govt. Printing Off., Wash.,
D.C. 220 p.
U.S. Department of Agriculture, Forest Service.
1978. Vegetation management with herbicides.
Final environ impact statement. Pac. Northwest
Reg. USDA-FS-R6-FES (Adm) 75-18 (Rev.).
March 6, 1978, Portland, Oreg. 330 p. plus ap-
pend.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Sci. Soc. Am., 3rd ed. 430
p. Champaign, 111.
Common name:
Chemical name:
Other Names:
Registered Use:
Dichlorprop, 2,4-DP
2-(2,4-dichlorophenoxy)
propionic acid
Weedone 2,4-DP, Weedone
170, Envert 170
Brush control on non-
agricultural lands
References
Amchem Products, Inc. 1972. Toxicity summary
for Weedone Brush-Killer-170. Data sheet.
Ambler, Pa.
Anderson, K.J., E.G. Leighty, and M.T.
Takahashi. 1972. Evaluations of herbicides for
possible mutagenic properties. J. Agric. Food
Chem. 20(3):649-656.
Burger, K., C. MacRae, and M. Alexander. 1962.
Decomposition of phenoxyalkyl carboxylic acids.
Soil Sci. Soc. Am. Proc. 26(3):243-246.
Hiltibran, R.C. 1967. Effects of some herbicides on
fertilized fish eggs and fry. Trans. Am. Fish. Soc.
96(4):414-416.
Hirsch, P., and M. Alexander. 1960. Microbial
decomposition of halogenated propionic and
acetic acids. Can. J. Microbiol. 6:241-249.
Hughes, J.S., and J.T. Davis. 1962. Toxicity of
selected herbicides to bluegill sunfish. Proc.
Louisiana Acad. Sci. 25:86-93.
Common name:
Chemical name:
Other names:
Registered use:
2,4,5-T
(2,4,5-Trichlorophenoxy)
acetic acid
Esteron 245—PGBE ester;
Ded-weed—Isooctylester;
Brush/killer Lo Vol 4T—
Isooctylester; Dinoxol—
Butoxyethanol ester.
2,4,5-T is registered for control
of woody and herbaceous
plants; especially for brush
control, selective conifer
release, and control of woody
plants in rangeland and
pastures.
References
Advisory Committee on 2,4,5-T. 1971. Report of the
Advisory Committee on 2,4,5-T to the Ad-
ministrator of the Environmental Protection
Agency. Submitted May 7, 1971.
Abesson, N.B., W.E. Yates, and S.E. Wilce. 1970.
Key to safe and effective aerial application: con-
trolling spray atomization. Agrichem. Age
13(12): 10,12,13,16,17.
XI.52
-------
Allen, J.R., J.P. Van Miller, and D.H. Norback.
1975. Tissue distribution, excretion, and
biological effects of [14 ] tetrachlorodibenzo-p-
dioxin in rates. Food Cosmet. Toxicol. 13:501-
505.
Allen, J.R., D.A. Barsotti, and J.P. Van Miller.
1977. Reproductive dysfunction in non-human
primates exposed to dioxins. Presented at 16th
Annu. Meet., Soc. Toxicol., Toronto, 1977.
Abstract in.
Anderson, K.J., E.G. Leighty, and M.T.
Takahashi. 1972. Evaluations of herbicides for
possible mutagenic properties. J. Agric. Food
Chem. 20(3):649-656.
Arend, J.L., and E.I. Roe. 1961. Releasing conifers
in the Lake States with chemicals. U.S. Dep.
Agric., Agric. Handb. 185. 22 p.
Bache, C.A., D.D. Hardie, R.F. Holland, and D.J.
Lisk. 1964. Absence of phenoxy acid herbicide
residues in the milk of dairy cows at high feeding
levels. J. Dairy Sci. 47:298-299.
Crosby, D.G., and A.S. Wong. 1977. Environmen-
tal degradation of 2,3,7,8,-tetrachlorodibenzo-p-
dioxin (TCDD). Science 195:1337-1338.
Drill, V.A., and T. Hiratzka. 1953. Toxicity of 2,4-
D and 2,4,5-T acid: a report on their acute and
chronic toxicity in dogs. Arch. Indust. Hyg.
Occup. Med. 7:61-67.
Gratkowski, H. 1961. Use of herbicides on forest
lands in southwestern Oregon. U.S. Dep. Agric.
For. Serv. Pac. Northwest For. and Range Exp.
Stn., Res. Note 217. 18 p. Portland, Oreg.
Gratkowski, H., and R.E. Stewart. 1973. Aerial
spray adjuvants for herbicidal drift control.
USDA For. Serv. Gen. Tech. Rep. PNW-3. 18 p.
(illus.) Pac. Northwest For. and Range Exp.
Stn., Portland, Oreg.
House, W.B., L.H. Goodson, H.M. Gadberry, and
K.W. Docktur. 1967. Assessment of ecological ef-
fects of extensive or repeated use of herbicides.
Final Rep., Midwest Res. Inst. Proj. 3103-B.
Adv. Res. Proj. Agency ARPA Order No. 1086.,
Dep. Defense Contract No. DAHC 15-68-C-0119.
369 p.
Hughes, J.S., and J.T. Davis. 1963. Variations in
toxicity to bluegill sunfish of phenoxy herbicides.
Weeds 11:50-53.
Lines, J.R.M., B.M. Ulland, M.G. Valeric, and
others. 1969. Bioassay of pesticides and in-
dustrial chemicals for tumorigenicity in mice: a
preliminary note. J. Natl. Cancer Inst. 42:1101-
1114.
Johnson, J.E. 1971. The public health implications
of widespread use of the phenoxy herbicides and
picloram. Bioscience 21:899-905.
Kenega, E.E. 1974. 2,4,5-T and derivatives: tox-
icity and stability in the aquatic environment.
Down to Earth 30(3): 19-25.
Leonard, O.A., and W.A. Harvey. 1965. Chemical
control of woody plants. Calif. Agric. Exp. Stn.
Bull. 812. 26 p. Davis, Calif.
Mahle, N.H., H.S. Higgins, and M.E. Getzen-
daner. 1977. Search for the presence of 2,3,7,8-
tetrachlorodibenzo-p-dioxin in bovine milk.
Bull. Environ. Contam. Toxicol. 18(2): 123-130.
Mrak, E.M. 1969. Report of the Secretary's Com-
mission on pesticides and their relationship to
environmental health. U.S. Dep. Health, Educ.
and Welfare. U.S. Gov. Print. Off., Washington,
D.C. 677 p.
Norris, L.A., M.L. Montgomery, and E.R.
Johnson. 1977. The persistence of 2,4,5-T in a
Pacific Northwest forest. Weed Sci. 25(5):417-
422.
Norris, L.A., and D.G. Moore. 1971. The entry and
fate of forest chemicals in streams, p. 138-158. In
Forest land uses and stream environment.
Krygier, T.J., and J.D. Hall, eds., Symp. Proc.,
Oreg. State Univ., Corvallis.
Palmer, J.S., and R.D. Radeleff. 1964. The tox-
icological effects of certain fungicides and her-
bicides on sheep and cattle. Ann. N.Y. Acad. Sci.
111:729-736.
Rowe, V.K., and T.A. Hymas. 1954. Summary of
toxicological information on 2,4-D and 2,4,5-T
type herbicides and an evaluation of the hazards
to livestock associated with their use. J. Am. Vet.
Res. 15:622-629.
Shadoff, L.A., R.A. Hummel, L. Lamparski, and
J.H. Davidson. 1977. A search for 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) in an en-
vironment exposed annually to 2,4,5-
trichlorophenoxyacetic acid ester (2,4,5-T) her-
bicides. Bull. Environ. Contam. Toxicol.
18(4):478-485.
U.S. Department of Agriculture, Forest Service.
1978. Vegetation management with herbicides.
final environ, impact statement, Pac. Northwest
Reg. USDA-FS-R6-FES (Adm)75-18(Revised).
March 6, 1978, Portland, Oreg. 330 p. plus
append.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. 430 p. Champaign, 111.
XI.53
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Common name:
Chemical name:
Other names:
Registered use:
Atrazine
2-chloro-4-ethylamino-6-
isopropylamino-s-triazine
AAtrex 80 W
Selective control of broadleaf
and grassy weeds in conifer
reforestation where it serves to
increase seedling survival ap-
preciably; also used in forest
and Christmas tree planta-
tions of Douglas-fir, grand fir,
noble fir, white fir, lodgepole
pine, ponderosa pine, and
Scotch pine.
References
Alabaster, J.S. 1969. Survival of fish in 164 her-
bicides, insecticides, fungicides, wetting agents
and miscellaneous substances. Int. Pestic. Contr.
l(2):29-35.
Anderson, W.P. 1977. Weed science principles, p.
244-247. West Publ. Co.: St. Paul, N.Y., Boston,
Los Angeles, San Francisco.
Bickford, M.L., and R.K. Hermann. 1967. Her-
bicide aids survival of Douglas-fir seedlings
planted on dry sites in Oregon; root wrapping has
little effect. Tree Planters' Notes 18(4):l-4.
Butler, P.A. 1963. Commercial fisheries investiga-
tions. In Pesticide wildlife studies. U.S. Fish and
Wildlife Serv. Circ. 167, p. 11-24.
Esser, H.O., G. Dupuis, E. Ebert, G.J. Marco, and
C. Vogel. 1975. S-Triazines. Vol. 1, p. 129-208. In
Herbicides—chemistry, degradation, and mode
of action. 2nd ed., [revised and expanded] P.C.
Kearney, and D.D. Kaufman, eds., Marcel Dek-
ker, N.Y.
Federal Water Pollution Control Administration.
1968. Water quality criteria. Rep. Natl. Tech.
Adv. Comm. to the Seer. Inter. Fed. Water Pol-
lut. Contr. Admin., U.S. Dep. Inter. 234 p.
Gratkowski, H. 1975. Silvicultural use of herbicides
in Pacific Northwest forests. USD A For. Serv.
Gen. Tech. Rep. PNW-37. 44 p. Pac. Northwest
For. and Range Exp. Stn., Portland, Oreg.
Jones, R.O. 1965. Tolerance of the fry of common
warm-water fishes to some chemicals employed
in fish culture. Proc. 16th Annu. Conf.
Southeast. Assoc. Game Fish Comm., 1962. p.
436-445.
Kearney, P.C. 1970. Summary and conclusion, p.
391-399. In Residue Reviews, Vol. 32. Single
pesticide volume: the triazine herbicides.
Springer-Verlag: N.Y., Heidelberg, Berlin.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. U.S.
Environ. Protect. Agency Rep. No. EPA-910/9-
77-036. 224 p. EPA Reg. X, Seattle, Wash.
Palmer, J.S., and R.D. Radeleff. 1969. The toxicity
of some organic herbicides to cattle, sheep and
chickens. U.S. Dep. Agric., Agric. Res. Serv.
Prod. Rep. No. 106. 26 p.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
Technol., Washington, D.C. 220 p.
St. John, L.E., D.G. Wagner, andD.J. Lish. 1964.
Fate of atrazine, kuron, silvex, and 2,4,5-T in the
dairy cow. J. Dairy Sci. 47(11):1267-1270.
Tucker, R.K. and D.G. Crabtree. 1970. Handbook
of toxicity of pesticides to wildlife. U.S. Dep.
Inter., Fish and Wildl. Serv., Bur. Sport Fish.
and Wildl. Resour. Publ. No. 84. 131 p.
Walker, C.R. 1964. Simazine and other s-triazine
compounds as aquatic herbicides in the fish
habitat. Weeds 12(2):134.139.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. p. 29-35. Champaign, 111.
Common name:
Chemical name:
Other names:
Registered use:
Carbaryl
1-Naphthyl N-methyl
carbamate
Sevin, Sevin 4-Oil
Suppression of various insect
outbreaks including the gypsy
moth, cankerworm, saddled
prominent and tent caterpil-
lar, and the spruce bud worm
(eastern and western).
References
Anderson, E. J. 1964. The effects of Sevin on honey
bees. Gleanings Bee Cult. 92(6) :358-364.
Boschetti, N.M. 1966. Sevin residues in water and
top soil following its use on a watershed area. p.
52-62. In Report of the surveillance program con-
ducted in connection with an application of car-
baryl (Sevin) for the control of gypsy moth on
XI.54
-------
Cape Cod, Massachusetts. Mass. Pestic. Board,
Publ. 547. 75 p.
Fairchild, H.E. 1970. Significant information on
use of Sevin-4-Oil for insect control. Union Car-
bide Corp. [Undated folder of text and various
reports.]
Felley, D.R. 1970. The effect of Sevin as a
watershed pollutant. Ph.D. diss., SUNY Coll.
Environ. For., Syracuse Univ., N.Y. 97 p.
Karinen, J.F., J.G. Lamberton, N.E. Stewart, and
L.C. Terriere. 1967. Persistence of carbaryl in the
marine estuarine environment. Chemical and
biological stability in aquarium systems. J.
Agric. Food Chem. 15(1): 148-156.
Macek, K.J., and W.A. McAllister. 1970. Insec-
ticide susceptibility of some common fish family
representatives. Trans. Am. Fish. Soc. 99:20-27.
Metcalf, R.L., W.P. Flint, and C.L. Metcalf. 1962.
Destructive and useful insects. 1087 p. McGraw
Hill, N.Y.
Muncy, R.J., and A.D. Oliver. 1963. Toxicityoften
insecticides to the red crayfish, Procambarus
clarki (Girard). Trans. Am. Fish. Soc. 92:428-
431.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. U.S.
Environ. Protect. Agency Rep. No. EPA 910/9-
77-036. 224 p. EPA Reg. X, Seattle, Wash.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci
Technol., Washington, D.C. 220 p.
Sanders, H.O., and O.B. Cope. 1966. Toxicities of
several pesticides to two species of cladocerans.
Trans. Am. Fish. Soc. 95:165-169.
Sanders, H.O., and O.B. Cope. 1968. The relative
toxicities of several pesticides to naiads of three
species of stoneflies. Limnol. and Oceanogr.
13:112-117.
Stewart, N.E., R.E. Millemann, and W.P. Breese.
1967. Acute toxicity of the insecticide Sevin and
its hydrolytic product 1-naphthol to some marine
organisms. Trans. Am. Fish. Soc. 96:25-30.
Thomson, W.T. 1977. Agricultural chemicals book
I: insecticides. Thomson Publ., Fresno, Calif.
Tucker, R.K., and D.G. Crabtree. 1970. Handbook
of toxicity of pesticides to wildlife. U.S. Dep.
Inter. Fish and Wildl. Serv., Bur. Sport Fish.
and Wildl. Res. Publ. No. 84. 131 p.
Union Carbide Corporation. 1968. Technical infor-
mation on Sevin carbaryl insecticide. Union Car-
bide Corp. ICG-0449A Bookl. 56 p.
Union Carbide Corporation. 1970. Facts on Sevin
carbaryl insecticide. Union Carbide Corp. Publ.
F-43382. 28 p.
U.S. Department of Agriculture, Forest Service.
1977. Final environmental statement,
cooperative spruce budworm suppression pro-
ject—Maine.
Weiden, M.H.J., andH.H. Moorefield. 1964. Insec-
ticidal activity of the commercial and ex-
perimental carbamates. World Review. Pest
Contr. 3:102-107.
Common name:
Chemical name:
Other names:
Registered use:
Chlorpyrifos
0,0-diethyl-0-(3,5,6-trichloro-
2-pyridyl) phosphorothioate
Dursban, DOWCO 179,
LORSBAN
Insect control.
References
Dow Chemical, U.S.A. 1974. Dursban insecticide
technical information. Brochure. 14 p.
Evans, E.S., J.H. Nelson, N.E. Pennington, and
W.W. Young. 1975. Lavicidal effectiveness of a
controlled-release formulation of chlorphyrifos in
a woodland pool habitat. Mosquito News
35(3):343-350.
McMartin, K.D. 1977. Control of cattle lice with a
low volume pour-on formulation of chlorpyrifos.
Down to Earth 33(1): 18-19.
Oberheu, J.C., R.O. Soule, and M.A. Wolf. 1970.
The correlation of cholinesterase levels in test
animals and exposure levels resulting from ther-
mal fog and aerial spray applications of Dursban
insecticide. Down to Earth 26(1):1216.
Thomson, W.T. 1977. Agricultural chemicals book
I: insecticides. 236 p. Thomson Publ., Fresno,
Calif.
Walker, A.I. 1975. Field tests of Dursban M insec-
ticide against gypsy moth larvae. Down to Earth
31(1)26-28.
Walsted, J.D., and J.C. Nord. 1975. Applied
aspects of pales weevil control. Down to Earth
XI.55
-------
Common name:
Chemical name:
Other names:
Registered use:
Dalapon
2,2-dichloropropionic acid
Dowpon, Dowpon C, Dowpon
M
A moderately specific grass
herbicide commonly used as a
pre-plant treatment on conifer
planting sites.
References
Alabaster, J.S. 1969. Survival of fish in 164 her-
bicides, insecticides, fungicides, wetting agents
and miscellaneous substances. Int. Pest Control
ll(2):29-35.
Bohmont, B.L. 1967. Toxicity of herbicides to
livestock, fish, honey bees and wildlife. Proc.
West. Weed Contr. Conf. 21:25-27.
Cope, O.B. 1965. Sport fisheries investigations.
p.51-63. In Effects of pesticides on fish and
wildlife, 1964 research findings of the Fish and
Wildlife Service. U.S. Fish and Wildl. Serv. Circ.
226.
Frank, P.A., R.J. Demint, and R.D. Comes. 1970.
Herbicides in irrigation water following canal-
bank treatment for weed control. Weed Sci.
18:687-692.
Holstun, J.R., and J.W.E. Loomis. 1956. Leaching
and decomposition of sodium 2,2-
dichloropropionate in several Iowa soils. Weeds
4:202-207.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. U.S.
Environ. Protect. Agency, Rep. No. EPA 910/9-
77-036. 224 p. EPA Reg. X, Seattle, Wash.
Surber, E. W., and Q.H. Pickering. 1962. Acute tox-
icity of endothal, diquat, hyamine, dalapon, and
silvex to fish. U.S. Dep. Inter., Fish and Wildl.
Serv., Prog. Fish-Cult. 24:161-171.
Warren, L.E. 1964. The fate of dalapon in the soil.
Pap. presented at the Wash. State Weed Conf.,
Yakima. Nov. 2-3, 1964.
Warren, L.E. 1967. Residues of herbicides and im-
pact on uses by livestock, p. 227-242. In Sym-
posium proceedings, herbicides and vegetation
management in forests, ranges, and non-crop
lands. Oreg. State Univ., Corvallis.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. 430 p. Champaign, 111.
Common name:
Chemical name:
Other names:
Registered use:
Dicamba
3,6-dichloro-o-anisic acid; also
2-methoxy-3,6-dichloroben-
zoic acid
Banvel, Banvel Brush Killer,
Banvel 5G Granules
Brush control on non-
croplands, including forest
lands.
References
Andus, L.J. 1964. The physiology and biochemistry
of herbicides, p. 104-206. Acad. Press.
Boppart, E.A. 1966. Chemical leaching and bioas-
say of Banvel D granules. Biol. Res. Sect., Her-
bic. Rep. 47-H-66. Velsicol Chem. Corp.
Cain, P.S. 1966. An investigation of the herbicidal
activity of 2-methoxy-3,6-dichlorobenzoic acid.
Ph.D. diss., Agron. Dep., Univ. 111., Urbana.
131 p.
Friesen, H.A. 1965. The movement and persistence
of dicamba in soil. Weeds 13:30-33.
Harris, C.I. 1963. Movement of dicamba and
diphenamid in soils. Weeds 12:112-115.
Markland, F.E. 1968. Evaluation of encapsulated
granules of Banvel D for leaching characteristics.
Velsicol Chem. Corp. Biol. Res. Sec., Herbic.
Rep. 31-H-68.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. U.S.
Environ. Prot. Agency Rep. No. EPA 910/9-77-
036. 224 p. EPA Reg. X, Seattle, Wash.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
Technol., Washington, D.C. 220 p.
Velsicol Chemical Corporation. 1971. Banvel
federal label registrations. Velsicol Chem. Corp.
Bull. 07-001-501. 15 p.
Velsicol Chemical Corporation. 1971. Banvel her-
bicides for brush and broadleaf weed control.
Velsicol Chem. Corp., unnumbered pamphlet.
Velsicol Chemical Corporation. 1971. Banvel her-
bicides general bulletin. Velsicol Chem. Corp.
Bull. 07-151-501. 4 p.
Weber, J.B., and J.A. Best. 1971. Activity and
movement of 13 soil-applied herbicides as in-
fluenced by soil reaction. South. Weed Sci. Soc.
Proc. 24:403-413.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. p. 139-141. Champaign, 111.
XI.56
-------
Common name:
Chemical name:
Other names:
Registered use:
Diflubenzuron
N(((4-Chorophenyl)
amino)carbonyl)-2,6-di
fluorobenzam ide
Dimilin, Difluron, TH-6040
Control of the gypsy moth; also
used in aquatic ecosystems.
References
Schoeltger, R.A. 1976. Annual progress report, fish-
pesticide research laboratory. U.S. Dep. Inter.,
Fish and Wildl. Serv., Columbia, Mo.
Thompson-Hayward Chemical Company. 1977.
Environmental safety and interactions of
Dimilin. [Typed Rep.] 31 p.
Thomson, W.T. 1977. Agricultural chemicals book
I: insecticides, acaricides and oricides. 236 p.
Thomson Publ., Fresno, Calif.
Common name:
Chemical name:
Other names:
Registered use:
Ethylene Dibromide
1-2 dibromoethane
EDP, Fumo-gas, E-D-Bee,
Bromo-fume, Soil-Fume, Dow-
fume, Urifume
Forest insecticide against
Douglas-fir beetle, Jeffrey pine
beetle, mountain pine beetle,
roundheaded pin beetle,
spruce beetle, California
flatheaded bores, Monterey
pine ips, fir engraver beetle,
and western pine beetle.
References
Henderson, C. 1966. Special report, pesticide sur-
veillance program, Teton bark beetle. Cont. Proj.
Div. Fish Serv., U.S. Dep. Inter., Bur. Sport Fish
and Wildl., Fort Collins, Colo.
Hoyle, H.R. 1951. Hazard to men engaged in spray-
ing spruce trees with an ethylene dibromide
emulsion. T3.5-6-8. Biochem. Res. Lab. Rep.
Dow Chem. Co., Denver. [Unpubl. Rep.]
Pillmore, R.E. 1966. Letter to Chief, Sect, of
Chem., Physiol., and Pestic-Wildl. Stud., U.S.
Dep. Inter., Fish and Wildl. Serv. [June 6,1966.]
Rowe, V.K., H.C. Spencer, D.D. McCallister, and
others. 1952. Toxicity of ethylene dibromide
determined on experimental animals. Arch. Ind.
Hyg. and Occup. Med. 6:158-173.
Tracy, R.H. 1970. Letter to Reg. For., U.S. Dep.
Agric., For. Serv. [Nov. 10, 1970.]
U.S. Department of Health, Education, and
Welfare. 1963. Studies on the effect of forest in-
sect control with ethylene dibromide on water
quality. PR-9, USPHS, HEW, Denver.
White, V.L. 1972. Letter to Stanley I. Undi, U.S.
Dep. Agric., For. Serv. from Great Lakes Chem.
Corp. [Feb. 21, 1972.]
Common name:
Chemical name:
Other names:
Registered use:
Fenitrothion
0,0-dimethyl-0-(3 methyl-4-
nitrophenyl) phosphorthioate;
also 0,0-dimethyl 0-(4-nitro-
m-tolyl) phosphorothioate (1)
Sumithion, Sumitomo
Control of hepidoptera,
diptera, orthoptera,
hemiptera, and coleoptera in
field crops and on fruits and
vegetables; forest protection
through control of Japanese
pine sawyer, pine caterpillar,
hemlocklooper, spruce
budworm, bark beetle, and
weevil; control of insects af-
fecting public health such as
mosquitos, flies, bedbugs, and
cockroaches; and control of
locust and grasshopper.
References
Associate Committee of Scientific Criteria for En-
vironmental Quality. 1975. Fenitrothion: the ef-
fects of its use on environmental quality and its
chemistry. Natl. Res. Counc. Can. NRCC No.
14104. 162 p.
Benes, V., and R. Sram. 1969. Mutagenic activity
of some pesticides in Drosophila melanogaster.
Ind. Med. 38:50-52.
Hazelton Laboratory. 1974. Toxicology studies,
part III. Three-generation study in rats. In Tox-
icology studies of Sumithion. Sumitomo Chem.
Co. Ltd., Osaka, Japan.
XI.57
-------
Industrial Bio-Test Laboratories. 1972.
Teratogenic study with Sumithion in albino rab-
bits. Ind. Bio-Test Labs. [Unpubl. rep.]
Industrial Bio-Test Laboratories. 1974. Ninety-day
subacute one year and two year oral feeding
study with Sumithion in beagle dogs. Ind. Bio-
Test Labs. [Unpubl. rep.]
Kadota, T. 1974. Two year chronic feeding toxicity
of Sumithion on rats. Sumitomo Chem. Co. f Un-
publ. rep.] Osaka, Japan.
Kadota, T., and J. Miyamoto. 1975. Acute toxicity
of Sumithion lOO^r w/v EC in mice and rats.
[Unpubl.]
Miyamoto, J. 1972. Toxicological studies with
Sumithion, acute/rats, mice. Sumitomo Chem.
Co., [Unpubl. rep.] Osaka, Japan.
Miyamoto, J. 1974. Decomposition and leaching of
Sumithion in four different soils under
laboratory conditions. Sumitomo Chem. Co.,
[Unpublished rep.] Osaka, Japan.
Miyamoto, J. 1974. Stability in water. Sumitomo
Chem. Co., [Unpubl. rep.] Osaka, Japan.
Namba, N., T. Twamoto, and T. Saboh. 1966. Oral
toxicity and metabolism of Sumithion on cattle,
sheep and pigs. Hokkaido Natl. Agric. Exp. Stn.
Res. Bull. 89:82.
Sumitomo Chemical Company. 1972. Toxicology
studies, part IV: delayed neuroloxicity of
Sumithion. Osaka, Japan.
Sumitomo Chemical Company. 1975. Sumithion
technical manual. Osaka, Japan.
Yasuno, M., S. Hirakoso, M. Sasa, and M. Uchida.
1965. Inactivation of some organophosphorous
insecticides by bacteria in polluted water.
Japanese J. Exp. Med. 35:545-563.
Zitko, V., and T.D. Cunningham. 1974.
Fenitrothion derivative and isomers: hydrolysis,
adsorption and biodegradation. Fish. Res. Board
of Can. Tech. Rep. No. 458.
Common name:
Chemical name:
Registered use:
Malathion
(0,0-dimethyl dithiophospate
of diethylmercaptosuccinate)
Control of a number of forest
insects including defoliators
and sucking insects of conifers
and hardwoods.
References
Eaton, J.G. 1970. Chronic malathion toxicity to the
bluegill, Lepomis macrochirus Rafinesque.
Water Res. 4:673.
Environmental Protection Agency. 1975. Initial
scientific and minieconomic review of malathion.
EPA 540/1-75-005. Off. Pestic. Programs. 251 p.
Golz, H.H. 1959. Controlled human exposures to
malathion aerosols. Am. Med. Assoc. Arch. Ind.
Health 191516-523.
Konrad, J.G., C. Chesters, and D.E. Armstrong.
1969. Soil degradation of malathion, a
phosphorodithioate insecticide. Soil Sci. Soc.
Am. Proc. 33(2):259-262.
Macek, K.J., and W.A. McAllister. 1970. Insec-
ticide susceptibility of some common fish family
representatives. Trans. Am. Fish. Soc. 99:20-27.
Matsumura, Fumio. 1975. Toxicology of insec-
ticides. Plenum Press. N.Y.
Mount, D.I., and C.E. Stephen. 1967. A method for
estimating acceptable toxicant limits for fish —
malathion and butoxyethanol ester of 2,4-D.
Trans. Am. Fish. Soc. 96:185-193.
Muncy, R.J., and A.D. Oliver. 1963. Toxicity often
insecticides to the red crayfish, Procambarus
clarki (Girord). Trans. Am. Fish. Soc. 92:428-
431.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. EPA
910/9-77-036. 224 p.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci
Technol., Washington, B.C. 220 p.
Rider, J.A. 1958. Studies on the effects of EPN and
malathion in combination on blood
cholinesterose of man. Prep. Natl. Agric. Chem.
Assoc. 5 p.
Roberts, J.E. and others. 1962. Presistence of insec-
ticides in soil and their effects on cotton in
Georgia. Abstr. Rev. Appl. Ent., Vol. 50, Ser. A,
Part II. 567 p.
Sanders, H.O. 1970. Toxicities of some herbicides
to six species of freshwater crustaceans. J. Water
Pollut. Contr. Fed. 42:1544-1550.
Sanders, H.O., and O.B. Cope. 1966. Toxicities of
several pesticides to two species of cladocerans.
Trans. Am. Fish. Soc. 95:165-169.
Sanders, H.O., and O.B. Cope. 1968. Toxicity of
several pesticides to naiads of three species of
stoneflies. Limnol. and Oceanog. 13:112-117.
XI.58
-------
Walter, W.W., and B.J. Stojanovic. 1973.
Microbial vs. chemical degradation of malathion
in soil. J. Environ. Qual. 2(2):229-232.
Common name:
Chemical name:
Other names:
Registered use:
MSMA
Monosodium methane ar-
sonate or Monosodium acid
methan arsonate
Silvisar 550 Tree Killer,
Vichem 120 Arsonate
Silvicide, Glowon Tree Killer
For post-emergent weed con-
trol and as a silvicide for con-
trol of undersirable conifers
and big leaf maple.
References
Bollen, W. B., L. A. Norris, and K. L. Stowers.
1974. Effect of cacodylic acid and MSMA on
microbes in forest floor and soil. Weed Sci.
22:557-562.
Dickens, R., and A. E. Hiltbold. 1967. Movement
and persistence of methanearsonates in soil.
Weeds 15:299-304.
Duble, R. L., E. C. Hold, and G. G. McBee. 1969.
Translocation and breakdown of DSMA in
coastal bermuda grass. J. Agric. Food Chem.
17:1247-1250.
Ehman, P. J. 1965. The effect of arsenical buildup
in the soil on subsequent growth and residue con-
tent of crops. Southern Weed Control Conf. Proc.
18:685-687.
Frost, D. V. 1970. Tolerances for arsenic and
selenium: A psychodynamic problem. World
Rev. of Pest Contr. Spring 1970, 9(l):6-27.
Johnson, L. R., and A. E. Hiltbold. 1969. Arsenic
content of soil and crops following use of
methane arsonate herbicides. Soil Sci. Soc. Am.
Proc. 33:279-282.
Morton, H. L., J. O. Moffett, and R. H. Mac-
Donald. 1972. Toxicity of herbicides to newly
emerged honey bees. Environ. Entomol.
1(1): 102-104.
Mrak, E. M. 1969. Report of the Secretary's Com-
mission on pesticides and their relationship to
environmental health. U.S. Dept. Health, Educ.
and Welfare. U.S. Gov. Print. Off., Wash, D.C.
677 p.
Newton, M., and H. A. Holt. 1968. Hatchet-
injection of phenoxys, picloram, and arsenicals
for control of some hardwoods and conifers. Proc.
Western Soc. Weed Sci. 22:20-21.
Newton, M., and L. A. Norris. 1976. Evaluating
short- and long-term effects of herbicides on non-
target forest and range biota. Symposium on
Biological Evaluation of Environmental Impact,
Counc. for Environ. Qual. Annu. Meet. Ecol.
Soc. Am. and AIBS. New Orleans. [Published
also in Down to Earth 32(3): 18-26].
Norris, L. A. 1974. The behavior and impact of
organic arsenical herbicides in the forest: Final
report on cooperative studies. USD A Forest Ser-
vice, Pac. Northwest For. and Range Exp. Stn.
98 p.
Wagner, S. L., and P. H. Weswig. 1974. Arsenic in
blood and urine of forest workers as indices of ex-
posure to cacodylic acid. Arch. Environ. Health
28(2):77-79.
Woolson, E. A. (Ed.). 1975. Arsenical Pesticides.
ACS Symposium Series 7, Am. Chem. Soc.,
Washington, D.C. 176 p.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
1971. Correlation between available soil arsenic,
estimated by 6 methods, and response of corn
(Zea Mays L.). Soil Sci. Soc. Am. proc.
35(1):101-105.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
1971. The chemistry and phytotoxicity of arsenic
in soils. I. Contaminated field soils. Soil Sci. Soc.
Am. Proc. 35:938-943.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
1973. The chemistry and phytotoxity of arsenic
in soils. II. Effects of time and phosphorus. Soil
Sci. Soc. Am. Proc. 37:254-259.
Common name:
Chemical name:
Registered use:
Orthene (acephate)
(O,S,Dimethyl acetylphos-
phoramidothioate)
Control of gypsy moth.
XI.59
-------
References
Bossor, J., and T. F. O'Connor. 1975. Impact on
aquatic ecosystem. In Environmental impact
study of aerially applied orthene (0,S-
dimethylacetyl-phosphoramidothiote) on a
forest and aquatic system. Rep. No. 174, p. 29-
47. Lake Ont. Environ. Lab., State Univ. Coll.,
Oswego, N.Y.
Chevron Chemical Corporation. 1972. Technical
information experimental data sheet. October. 2
p. Chevron Chem. Co.
Chevron Chemical Corporation. 1976. Technical
information experimental data sheet. February.
4 p. Chevron Chem. Co.
Schoeltger, R. A. 1976. Annual progress report
1975-76. Fish-Pestic. Res. Lab., U.S. Dep. Inter.,
Fish and Wildl. Serv., Columbia, Mo.
Thomson, W. T. 1975. Agricultural chemicals.
Thomson Publ., Indianapolis.
Witherspoon, B., Jr. 1977. Letter to Superv., Spec.
Prod. Dev., Chevron Chem. Co.
Common name:
Chemical name:
Other names:
Registered use:
Picloram
4-amino-3,5,6-trichloro-
picolinic acid
Tordon, ATCP
Control of annual and deep
rooted perennial weeds in non-
cropland.
References
Beatty, S. 1962. Results of dietary feeding studies
of 4-amino-3,5,6-trichloropicolinic acid in rats.
Biochem. Res. Lab., Unpubl. Rep. 35. 12-38212-
2. Nov. 15. Dow Chem. Co., Midland, Mich.
Buttery, R. F., T. R. Plumb, and N. D. Meyers.
1972. Picloram — background information state-
ment. 43 p.
(ioring, C. A. I., C. R. Youngson, and J. W.
Hamaker. 1965. Tordon herbicide . . . disap-
pearance from soils. Down to Earth 20:3-5.
Green, C. R. 1970. Effect of picloram and phenoxy
herbicides in small chaparral watersheds. West.
Soc. Weed Sci., Res. Prog. Rep., Sacramento,
Calif, p. 24-25.
Grover, R. 1967. Studies on the degradation of 4-
amino-3,5,6-trichloropicolinic acid in soil. Weed
Res. 7:61-67.
Hamaker, J. W., H. H. Johnston, T. R. Martin,
and C. T. Redemann. 1963. A picolinic acid
derivative: A plant growth regulator. Science
141:363.
Hardy, J. L. 1966. Effect of Tordon herbicides on
aquatic chain organisms. Down to Earth 22:11-
13.
Jackson, J. B. 1965. Toxicological studies on a new
herbicide in sheep and cattle. Am J. Vet. Res.
27:821.
Kenaga, E. E. 1969. Tordon herbicides — evalua-
tion of safety to fish and birds. Down to Earth
25:5-9.
Lynn, G. E. 1965. A review of toxicological infor-
mation on Tordon herbicides. Down to Earth
20:6-8.
McCollister, D. D., and M. L. Lang. 1969. Tox-
icology of picloram and safety evaluation of
Tordon herbicides. Down to Earth 25:5-10.
Norris, L. A. 1968. Degradation of herbicides in the
forest floor. In Tree growth and forest soils. C. T.,
Youngberg, and C. B. Darey, eds., Proc. 3rd
North Am. For. Soils Conf., Oreg. State Univ.
Press, Corvallis.
Olson, K. 1963. Toxicological properties of Tordon
22K (M-2477). Dow Chem. Co., Biochem. Res.
Lab., Midland, Mich. Toxicol. Ref. 2 MO-2477-
1.
Thompson, D. J., J. L. Emerson, R. J. Strenring,
and others. 1972. Teratology and post-noted
studies on 4-amino-3,5,6-trichloropicolinic acid
(picloram) in the rat. Food Cosmet. Toxicol.
10:797-803.
Tucker, R. H., and D. G. Crabtree. 1970. Hand-
book of toxicity of pesticides to wildlife. Bur.
Sport Fish and Wildl., Fish and Wildl. Serv.,
U.S. Dep. Inter. Res. Publ. No. 84 [Natl. Tech.
Info. Serv. No. PB 198 815].
U. S. Department of Agriculture. 1969. The tox-
icity of some organic herbicides to cattle, sheep
and chickens. Prod. Res. Rep. No. 106:22.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. p. 302-306. Champaign, HI.
Youngson, C. R., and R. W. Meikle. 1972. Residues
of picloram acquired by a mosquitofish, Gam-
busia sp., from treated water. Dow Chem. Co.,
Walnut Creek, Calif. Rep. GH-1210.
XI.60
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Common name: Silvex-fenoprop
Chemical name: 2-(2,4,5-trichlorophenoxy)
propionic acid
Other names: Kuron, Weedone
Registered use: Control of woody plants, trees,
and shrubs; specific brush con-
trol in forest site preparation
and release; aquatic herbicide.
References
Anderson, W.P. 1977. Weed science principles, p.
220-228. West Publ. Co.: St. Paul, N.Y., Boston,
Los Angeles, San Francisco.
Bond, C.E., R.H. Lewis, and J.L. Fryer. 1960. Tox-
icity of various herbicidal materials to fishes.
Robert A. Taft Sanit. Eng. Center, Tech. Rep.
W60-3:96-101.
Environmental Protection Agency. 1974. Herbicide
report: chemistry and analysis, environmental
effects, agricultural and other applied uses. Sci.
Adv. Board. 195 p.
Hughes, J.S., and J.T. Davis. 1964. Effects of
selected herbicides on bluegill sunfish. Proc.
Southeast Assoc. Game Fish Comm. 18:480-482.
Kearney, P.C., and D.D. Kaufman. 1971. Her-
bicides—chemistry, degradation and mode of ac-
tion. Vol. 1, p. 1-101. Marcel Dekker. N.Y.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. EPA
910/9-77-036.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
and Technol., Washington, B.C. 220 p.
Sanders, Herman O. 1970. Toxicities of some her-
bicides to six species of freshwater crustaceans.
J. Water Pollut. Contr. Fed. 42:1544-1550.
Surber, E.W., and Q.H. Pickering. 1962. Acute tox-
icity of endothal, diquat, hyamine, dalapon, and
silvex to fish. Prog. Fish. Cult. 24:164-171.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. Champaign, 111.
Common name:
Chemical name:
Simazine
(2-chloro-4,6 bis(ethylcunino)-
s-triazine)
Other names: Princep SOW
Registered use: Weed control in Christmas
tree plantations.
References
Anderson, W.P. 1977. Weed science principles, p.
244-247. West Publ. Co.: St. Paul, N.Y., Boston,
Los Angeles, San Francisco.
Bond, C.B., R.H. Lewis, and J.L. Fryer. 1959. Tox-
icity of various herbicidal materials to fishes. In
Biological problems in water pollution. Trans.
1959 Sem., p. 96-101. U.S. Dep. Health, Educ.,
and Welfare.
Bond, C.B., R.H. Lewis, and J.L. Fryer. 1960. Tox-
icity of various herbicidal materials to fishes.
Robert A. Taft Sanit. Eng. Center Tech. Rep.
W60-3:96-101.
Burnside, B.C., E.L. Schmidt, and R. Behrens.
1961. Bissipation of simazine from the soils.
Weeds 9(3)477-484.
Cope, O.B. 1964. Sport fishery investigations. In
The effects of pesticides on fish and wildlife. U.S.
Bep. Inter., Circ. 226, p. 51-63.
Geigy Agricultural Chemicals. 1970. Princep her-
bicide. Geigy Chem. Corp. Tech. Bull., 8 p.
Ardsley, N.Y.
Jordan, L.S., W.J. Farmer, J.R. Goodin, and B.E.
Bay. 1970. Nonbiological detoxication of the s-
triazine herbicides. Residue Rev. 32:267-286.
Kearney, P.C., and B.B. Kaufman. 1971. Her-
bicides—chemistry, degradation and mode of ac-
tion. Vol. 1, p. 129-191. Marcel Bekker, N.Y. and
Basel.
Klingman, G.C. 1961. Weed control: as a science.
421 p. John Wiley & Sons, N.Y.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. EPA
910/9-77-036.
Pimentel, B. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
and Technol., Washington, B.C.
Ragab, M.T.H., and J.P. McCollum. 1961.
Begradation of C14-labeled simazine by plants
and soil microorganisms. Weeds 9(l):72-84.
H.O. Sanders. 1970. Toxicities of some herbicides
to six species of freshwater crustaceans. J. Water
Pollut. Contr. Fed. 42:1544-1550.
Talbert, R.B., and O.K. Fletchall. 1964. Inactiva-
tion of simazine and atrazine in the field. Weeds
12:33-37.
XI.61
-------
Walker, C.R. 1964. Simazine and other s-triazine
compounds as aquatic herbicides in fish
habitats. Weeds 12(2)134-139.
Water Quality Criteria. 1968. Report of the
Technical Advisory Committee to the Secretary
of the Interior. U.S. Dep. Inter., Fed. Water Pol-
lut. Contr. Admin.
Weed Science Society of America. 1974. Herbicide
handbook of the Weed Science Society of
America. 3rd ed. p. 29-35. Champaign, 111.
Wellborn, T.L., Jr. 1969. The toxicity of nine
therapeutic and herbicidal compounds to striped
bass. Prog. Fish. Cult. 31:27-32.
Common name:
Chemical name:
Other names:
Registered use:
Trichlorfon
Dimethyl-(2,2,2-trichloro-l-
hydroxy-ethyl) phosphorate
Dylox
Control of the gypsy moth lar-
vae on forest land shade trees.
References
Borough, H.W., N.M. Randolph, and H.G. Wim-
bish. 1965. Imidan and trichlorfon residues on
coastal Bermuda grass. Tex. Agric. Exp. Stn.
Prog. Rep. PR-2385.
Jensen, L.D., and A.R. Gaufin. 1966. Acute and
long-term effects on organic insecticides on two
species of stonefly naiads. J. Water Pollut.
Control Fed. 38:1273-1286.
Matton, P., and O.N. LeHam. 1969. Effect of
organophosphate Dylox on rainbow trout larvae.
Can. Fish. Res. Board 26:2193-2200.
Newton, M., and J.A. Norgren. 1977. Silvicultural
chemicals and protection of water quality. EPA
910/9-77-036.
Pickering, Q.H., C. Henderson, and A.E. Lemke.
1962. The toxicity of organic phosphate insec-
ticides to different species of warm water fishes.
Trans. Am. Fish. Soc. 91:175-184.
Pimentel, D. 1971. Ecological effects of pesticides
on non-target species. Exec. Off. Pres., Off. Sci.
and Technol., Washington, B.C.
Sanders, H.W., and O.B. Cope. 1966. Toxicities of
several pesticides to two species of cladocerans.
Trans. Am. Fish. Soc. 95:165-169.
Schafer, E.W. 1972. The acute oral toxicity of 369
pesticidal, pharmaceutical and other chemicals
to wild birds. Toxicol. and Appl. Pharmacol.
21:315-330.
Wilcox, H.N. 1971. The effects of Bylox on a forest
ecosystem. Lake Ont. Environ. Lab. Prog. Rep.,
State Univ. Coll., Oswego, N.Y.
XI.62
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GLOSSARY
Below is a glossary of terms appearing in the text
of this handbook. Those terms drawn from specific
sources have been cited with a code in parentheses
following the definition. Such citations are listed
under "Sources" at the end of the Glossary (e.g.,
DOT stands for "Dictionary of Geological Terms").
Those terms with no citations have had a definition
prepared for use in this handbook. Words not listed
in the glossary can be found in standard sources.
Access road: Any road used to gain access to an
area for the purpose of carrying out some form of
management. These roads may be a temporary
or permanent part of the transportation system.
Active flood plain: See Bankful stage.
Activity: Work processes conducted to produce,
enhance, or maintain outputs or to achieve
management and environmental quality objec-
tives.
Acute toxicity: Brief and severe physical and/or
psychological disturbances resulting from a
single dose or exposure to a toxic or poisonous
substance.
Advected energy [fluxes]: The process of energy
transport by the atmosphere or water bodies
from one location to another due to circulation of
these bodies.
Aeration potential: (See Oxygen saturation level.)
Aerial drift: The movement of pesticide droplets or
particles by wind and air currents from the target
area to an area not intended to be treated.
(PAST)
Aerial skidding: The process of hauling logs by
sliding them off the ground along a cable. (SAF)
Aggradation: The raising of the surface of
streambeds, floodplains, and the bottoms of
other water bodies by the accretion of material
eroded and transported from other areas. It is the
opposite of degradation.
Aggraded stream: A stream that has built up its
grade or slope by deposition of sediment. (DGT)
Ammonification: The biochemical process whereby
ammoniacal nitrogen is released from nitrogen-
containing organic compounds. (SSSA)
Ammonifying microorganisms: Microorganisms
that are responsible for ammonification of
nitrogen-containing organic material. (See Am-
monification.)
Angle of internal friction (coefficient of friction):
The angle at which the driving forces in a soil
mass due to gravity are equal and opposite to the
resisting forces due to friction; a measure of soil
strength due to interlocking of individual soil
particles.
Angular canopy density (ACD): A measure of the
canopy density along the path of incoming solar
radiation. It is measured using a gridded mirror
tilted at an angle so that a person looking down
on the mirror views the surrounding vegetative
canopy in the same perspective as the incoming
solar radiation. The number of grids covered by
the canopy can be measured and converted to a
percent canopy cover.
Animal skidding: The use of animals such as mules
or horses to slide loads along the ground.
Antecedent moisture: The degree of wetness of a
soil at the beginning of a runoff or storm period,
expressed as an index or as the total volume of
water stored in the soil. (WPG)
Antecedent rainfall: The rainfall or precipitation
occurring during some period prior to the event
of interest. This expression is intended to express
watershed wetness. (VTC)
Aquatic environment: An environment in which all
conditions, circumstances, and influences sur-
rounding and affecting the development of an
organism or groups of organisms pertain to
water. (WPG)
xn.i
-------
Area-inches: A measure of volume. One inch of
depth over the entire surface of a delineated
piece of land.
Armor: (1) To apply rock, mulch, or vegetation to
damaged areas to serve as protective covering.
(2) To use rock, concrete, asphalt, gravel, riprap,
gabions, or equivalent for protection of a ditch,
channel, or low water crossing. (3) Any natural-
occurring quality, characteristic, situation or
thing that serves as a protective covering.
Aspect: The compass direction that the slope of the
land faces toward (e.g., north, northwest, south),
(WPG)
Balanced road construction: Cut-and-fill road
design; material cut on the uphill side of a road is
placed in fills on the downhill side.
Balloon logging: A system which employs balloons
to transport timber from the stump to a collec-
tion point.
Bankful discharge: Discharge at a river cross sec-
tion which just fills the channel to the tops of the
bank, marking the condition of incipiant
flooding.
Bankful stage: Water surface elevation of the ac-
tive floodplain.
Bankful width: The width of the effective area of
flow across a stream channel when flowing at
bankful discharge.
Bare soil: Mineral soil without vegetative ground
cover, rock, or litter on the soil surface.
Basal area: The area of the cross-section of a tree
stem near its base, generally at breast height and
inclusive of bark. Stand basal area is generally
expressed as the total basal area per unit area.
(SAF)
Baseline condition: Hydrologic state of a watershed
where complete hydrologic utilization is
achieved. (See Complete hydrologic utilization)
Bedding: A silvicultural process where soil is
placed in long ridges approximately 6 inches high
and 6 feet at the base to elevate tree roots above a
high water table or to concentrate soil nutrients
where they can be readily utilized.
Bedding planes: Planar or nearly planar surfaces
that visibly separate each successive layer of
stratified rock.
Bedload: Material moving on or near the stream
bed by rolling, sliding and sometimes making
brief excursions into the flow a few diameters
above the bed. It is not synonymous with dis-
charge of bed material.
Bedrock sink: Term used to denote when bottom
bedrock is functioning as a heat sink within a
flowing stream. (See Energy sink)
Bench: A working level or step in a cut which is
made in several layers. A small terrace or com-
paratively level platform breaking the continuity
of a slope. (DOT)
Best Management Practices (BMP): A practice or
combination of practices that are determined (by
a state or designated area-wide planning agency)
through problem assessment, examination of
alternative practices, and appropriate public
participation to be the most effective, prac-
ticable (including technological, economic, and
institutional considerations) means of
preventing or reducing the amount of pollution
generated by non-point sources to a level com-
patible with water quality goals.
Biochemical oxygen demand (BOD): The amount
of dissolved oxygen, generally expressed in parts
per million, required by organisms for the
aerobic biochemical decomposition of organic
matter present in water. (WWU)
BMP: (See Best Management Practices.)
BOD: (See Biochemical oxygen demand.)
Braided stream: A stream flowing in several
dividing and reuniting channels resembling the
strands of a braid, the cause of the division being
the obstruction by sediment deposited by the
stream.
Broadcast burn: Allowing a controlled fire to burn
over a designated area within well-defined boun-
daries for reduction of fuel hazard, as a
silvicultural treatment or both. (SAF)
Bucking: To cut tree length logs into shorter
lengths.
Buffer strip: (See Waterside area.)
Cable logging: Cable systems are designed to yard
logs from the felling site by a machine equipped
with multiple winches. Cable logging is highly ef-
ficient for logging steep rough ground on which
XH.2
-------
tractors cannot operate. Cable systems could be
classified as either high lead, skyline, or balloon.
(CEAP)
Cable yarding: Operation of hauling logs to a col-
lection point using a cable system. (See cable
logging.)
Caloric deficit: The energy (calories) needed to
bring a snowpack temperature up to an isother-
mal temperature of 0° C.
Canopy: The more or less continuous cover of
branches and foliage formed collectively by the
crowns of adjacent trees and other woody growth.
(SAF)
Carbamate: A synthetic organic pesticide which
contains carbon, hydrogen, nitrogen, and sulfur,
and belongs to a group of chemicals which are
salts or esters of carbonic acid. Carbamates may
be fungicides, herbicides, or insecticides. Exam-
ples: aldicarb, carbaryl, carbofuran, and
methomyl.
Cation exchange: The exchange of cations held by
soil particles with other cations that are in the
water solution surrounding the soil particles.
Cation exchange capacity (CEC): The sum total of
exchangeable cations that a soil can absorb. Ex-
pressed in milliequivalents per 100 grams of soil
or per gram of soil (or of other exchangers such as
clay). (SCS, SSSA)
Channel bars: An alluvial deposit or bank of sand,
gravel, or other material at the mouth of a
stream or at any point in the stream itself which
causes an obstruction to flow. (NIA)
Channel gradient change: A change in channel
slope which can alter energy relationships that
can, in turn, cause streambank and channel ero-
sion or aggradation.
Channel interception: That portion of precipitation
that falls directly into the channel or into open
water channel extensions.
Channel stability: The relationship of sediment
supply and stream energy available in a channel
system. As changes occur in either supply or
energy, the channel stability is affected and the
channel tends to adjust its boundaries to accom-
modate the change, i.e., when the supply exceeds
the carrying capacity (aggradation occurs) or the
energy exceeds supply (degradation occurs).
Channel stability rating: A numerical rating of
channel stability using Pfankuch's (1972)
procedures which account for hydraulic forces,
resistance of channel to flow forces, and the
capacity of the stream to adjust and recover from
changes in flow and/or sediment load.
Chemical-biological balance: Biological balance
relating to the relationship of the earth's
chemicals to plant and animal life
(biogeochemical). (WPG)
Chip and spread: Converting wood to chips and
scattering the resultant material. (SAF)
Chlorinated hydrocarbon: A synthetic organic
pesticide that contains chlorine, carbon, and
hydrogen; they are generally very persistent
(compared to carbamates or organophosphates).
Examples: DDT, endrin, lindane. Same as
Organochlorine.
Chronic toxicity: Physical and/or psychological
disturbances resulting from repeated doses or ex-
posure of a poisonous or toxic substance over a
period of time.
Claypan: A dense, compact layer in the subsoil
having a much higher clay content than the
overlying material, from which it is separated by
a sharply defined boundary. (SSSA)
Clay stone: An indurated clay having the texture
and composition, but lacking the fire lamination
or platyness of shale.
Clearcutting: The harvesting in one cut of all trees
on an area for the purpose of creating a new,
even-aged stand. The area harvested may be a
patch, stand, or strip large enough to be mapped
or recorded as a separate age class.
Cohesion: The bonding of soil particles by thin
water films, generally resulting in an increase in
shear strength up to some minimum moisture
content.
Cohesive soils: Soils that have relatively high shear
strength when moist.
Colluvial debris (colluvium): A general term ap-
plied to loose and incoherent deposits, usually at
the foot of a slope or cliff and brought there
chiefly by gravity. Talus and cliff debris are in-
cluded in such deposits. (DOT)
XH.3
-------
Compaction: The packing together of soil particles
by instantaneous forces exerted at the soil sur-
face resulting in an increase in soil density
through a decrease in pore space.
Complete hydrologic utilization: Exists when the
vegetation onsite is capable of utilizing water
and energy at the maximum rate for the species
and site.
Condition: Refers to a hydrologic state of a
watershed, i.e., baseline, existing or proposed.
Cover density: An index which references the
capability of the stand or cover to integrate and
utilize the energy input to transpire water. It
varies according to crown closure, vertical foliage
distribution, species, season, and stocking.
Creep: (See Soil creep.)
Cribbing: A structure which can be made of metal,
treated timber, or precast reinforced concrete,
generally not watertight, used to contain un-
stable earth masses either above or below a road
surface.
Critical temperature threshold: The temperature
at which physiological effects on fish begin to be
produced. The temperature threshold is an in-
dicator of other water constituents such as dis-
solved oxygen.
Crop tree: Any tree forming or destined to form a
part of the forest crop. Usually a tree selected in
a young stand or plantation to be carried through
to maturity. (SAF)
Cross drainage: A means, generally a culvert, of
moving water from the uphill side of a road to the
downhill side.
Crown closure: The percent of vegetation crown
compared to open area as determined from an
aerial photograph.
Cut-and-fill: Fill — the material added to reach
the formation level. Cut — the excavation
formed when the material is removed.
Cut banks: The concave wall of a meandering
stream that is maintained as a steep or overhang-
ing cliff by the impinging of water at its base.
(See also Cut slope.) (DOT)
Cut slope: On sloping land, exposed banks above a
road created by excavation during road construc-
tion.
Cutting block: Cutting area or felling area. An area
on which trees have been, are being, or are to be
cut. (SAF)
Cutting plan: Part of the silvicultural plan that
describes the method of cutting (clearcut,
seedtree, etc.).
Debris avalanche: Rapid, shallow mass movement
on a hillslope involving soil, rock, and organic
matter; less fluid in behavior than debris flow.
Debris dam: A dam in a channel resulting from the
collection of tree limbs, logs, and other obstruc-
tions.
Debris flow: Rapid, shallow mass movement on a
hillslope involving soil, rock, and organic matter;
more fluid behavior than debris avalanche.
Debris in channel: Those obstructions in a stream
channel as a result of silvicultural activities or
natural events.
Debris jam: See Debris dam.
Debris slide: The slow-to-rapid downward move-
ment of predominantly unconsolidated and in-
coherent earth and debris in which the mass does
not show backward rotation but slides or rolls
forward, forming an irregular hummocky deposit
which may resemble morainal topography.
(DOT)
Debris torrent: Rapid, turbulent movement of soil,
alluvium, and organic matter down a stream
channel.
Defoliant: A herbicide which causes the leaves of a
plant to drop off.
Degradation: The general lowering of the surface of
the land or stream by erosive processes, by the
removal of material through erosion and trans-
portation by flowing water. (DOT)
Denitrification: The biochemical reduction of
nitrate and/or nitrite to molecular nitrogen or an
oxide of nitrogen. Under some conditions, it
results in a loss of nitrogen from the forest
ecosystem.
Deposition: The mechanical or chemical processes
through which sediments accumulate in a resting
place.
Desiccant: A material used to draw moisture from
or dry up a plant, plant part, or insect. Desic-
cants are used primarily for pre-harvest drying of
XE.4
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actively growing plant tissues when seed or other
plant parts are developed but only partially
mature; or for drying of plants which normally do
not shed their leaves, such as rice, corn, small
grains, and cereals.
Detection limit: The level at which, with current
technology, a water quality component can be
detected with certainty.
Directional felling: Cutting trees so that they will
fall in a predetermined direction for purposes
such as increased logging efficiency, minimizing
stand damage, and reduction in pollution im-
pacts.
Ditch check: A small dam or structure in a road
ditch to slow water velocity.
Ditch drain: Means of moving concentrated water
from an inside road ditch to an outside area.
Drag(s): A frame, usually iron, for roughly leveling
a relatively loose or soft surface. (SAP)
Dry fall: Deposition of solid particles from the at-
mosphere during nonprecipitation events.
Dry ravel: Downslope movement of sediment parti-
cles or small rock on steeper slopes without flow-
ing water.
Duff: The matted, partly decomposed organic sur-
face layer of forested soils. (SOIL)
Earthflow: Slow (rates of centimeters to meters per
year), deep-seated (failure plain commonly 5-15
meters below surface) mass movement. (AGI)
Effective stream width: Length of shadow required
to reach from one bank to the other; thereby ef-
fectively shading the stream.
Effective weight: Dry weight of soil minus the ef-
fect of buoyancy in the zone of saturation. (AGI)
Electrochemical exchange: Chemical action
employing a current of electricity (lightning) to
cause or to sustain a chemical reaction. (DMM)
Endline: To winch in without the use of block or
pulleys to change the direction of pull.
Energy aspect: Refers to a combination of elevation
and three aspect classes — (1) north, (2) south,
and (3) east and west — used in determining
energy inputs for generating snowmelt and
evapotranspiration estimates.
Energy balance: An accounting of all energy inputs
and outputs within some defined system.
Energy sink: A place where energy can be stored or
absorbed for use at some other time or place.
Enrichment ratio: The concentration of nitrogen or
phosphorus in the eroded material divided by its
concentration in the soil proper. (PNE)
Erosion—The wearing away of the land surface by
running water, wind, ice, or other geological
agents, including such processes as gravitational
creep. Detachment and movement of soil or rock
by water, wind, ice, or gravity. (SSSA)
The following terms are used to describe different
types of water erosion:
Accelerated erosion—Erosion much more rapid
than normal, natural, geological erosion,
primarily as a result of the influence of the ac-
tivities of man or, in some cases, of animals.
(SSSA)
Channel erosion: Erosion in which material is
removed by water flowing in well-defined
channels: erosion caused by channel flow.
Gully erosion: The erosion process whereby water
accumulates in narrow channels and, over
short periods, removes the soil from from this
narrow area to considerable depths ranging
from 1 or 2 feet to as much as 75 to 100 feet.
(SSSA)
Rill erosion: An erosion process in which
numerous small channels of only a few inches
in depth are formed; occurs mainly on recently
cultivated soils. (SSSA)
Sheet erosion. The removal of a fairly uniform
layer of soil from the land surface by runoff
water. (SSSA)
Splash erosion: The spattering of small soil par-
ticles caused by the impact of raindrops on
very wet soils. (SSSA)
Erosion hazard: The possibility of soil loss due to
erosion processes.
Erosion response unit: A delineated homogenous
area that will respond uniformly to forces which
cause surface erosion.
ET: (See Evapotranspiration.)
XH.5
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Evapotranspiration (ET): The loss of water from a
given area by both evaporation from soil and
open water surfaces, and by transpiration from
plants.
Excess water: Increases in available water resulting
from evapotranspiration reduction from canopy
removal. Excess water can also be caused by
reduced infiltration rates into bare or compacted
soil.
Exchange surface: Surface of soil particles that ex-
hibit enhanced chemical activity, exchanging
absorbed ions with ions present in the soil water.
Exfiltration: Water flowing from soil mantle back
onto the soil surface from saturated soils due to
bedrock constrictions, concentration in draws,
excessive precipitation, etc.
Existing condition: The current hydrologic state of
the watershed. It may be thought of as, but is not
necessarily the same as a fully forested
watershed with the trees capable of maximum
evapotranspiration (ET) for the energy and
water available.
Factor of safety: A measure of the stability of a soil
or rock mass, ratio of material strength retarding
motion to applied stress tending to cause motion.
Fault: Surface or zone of rock fracture along which
there has been displacement. (AGI)
Felling: The act of cutting down a standing tree.
(SAF)
Fertilization: The act of applying fertilizer.
Fertilizer: Any organic or inorganic material of
natural or synthetic origin which is added to a
soil to supply one or more elements essential to
the growth of plants. (SSSA)
Field capacity index: The moisture content in the
soil at one-tenth bar of soil-water pressure.
Fill slope: Man-made slope below a roadbed
resulting from road construction where ad-
ditional material is added to build up all or part
of the road surface.
Filter strip: (See Waterside areas.)
Fireline: A term for any cleared strip used in fire
control. More specifically, that portion of a con-
trol line from which flammable materials have
been removed by scraping or digging down to the
mineral soil. (SAF)
Flow duration curve: A graphical presentation of
the percent of time streamflow equals or exceeds
various levels of flow.
Fly logs: Logs carried completely off the ground
during yarding.
Foliar drip: Loss of nitrogen from trees and under-
story to litter and organic layer on forest floor.
Ford: An unbridged stream crossing.
Forest cover density: An index representing the ef-
ficiency of a three-dimensional canopy system to
respond to energy input.
Fracture: Any break in rock, whether or not dis-
placement is involved.
Fragipan: A natural soil horizon with higher bulk
density than the overlying horizons, seemingly
cemented when dry but having a moderate to
weak brittleness when wet. The layer is low in
organic matter, mottled, slowly or very slowly
permeable to water, and may show occasional or
frequent bleached cracks which define polygons.
Free water: The water (liquid state) being held
within a snowpack. This free water is generally
considered to be less than 6 percent by volume
for free-draining snow.
Free water surface: The surface of water bodies
(i.e., streams, lakes, ponds, etc.).
Frictional resistance: Mechanical resistance to the
relative motion of contiguous bodies or of a body
and a medium.
Fuel break: A wide strip with a low amount of fuel
in a brush or wooded area to serve as a line of fire
defense and usually covered with grass to provide
soil cover. (WPG)
Fuel management: The management and
manipulation of fuels (vegetation) so as to lower
fire hazard.
Fuel management plan: Part of the silvicultural
plan that describes the type of fuel management
to be used.
Full bench road: (See Full bench section.)
Full bench section: To construct a roadbed entirely
on natural ground. Generally used on cross slopes
55 percent or greater.
xn.e
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Fungicide: An agent, such as a spray or dust, used
for destroying fungi. (RHD)
Gabion: A specially designed basket or corrosion
resistant wire boxes used to hold rock and other
coarse aggregate. These wire boxes may be
locked together to form sea walls, revetments,
deflectors, and other structures. (WWU)
Glacio-lacustrine clays: Fine clay-size particles
deposited in glacial lakes. Usually clay size but
not clay minerals.
Gravitational stress: Acceleration of a mass due to
gravity.
Ground cover: Any material (i.e., rock, litter,
vegetation) which is attached to or lying on the
soil surface.
Ground-lead cable yarding systems: A method of
powered cable logging in which a main line is led
out to the logs through a lead block fastened
close to the ground level. Generally operated by a
double-drum power unit carrying the main and
haul-back lines. (SAF)
Gunite: (See Shotcrete.)
Hand pulpwooding: The procedure of driving
trucks through the woods to felling sites and
hand-loading wood cut primarily for manufac-
turing into wood pulp.
Hardpan: A hardened or cemented soil horizon or
layer. The soil material may be cemented by iron
oxide, silica, calcium carbonate, or other sub-
stances. The hardness does not change ap-
preciably with changes in soil moisture content.
Harvesting: (See Timber harvesting.)
Hazard index: Indicates the intensity of analysis
that may be necessary to adequately evaluate
soil mass movement potential.
Headwall scarp: Steep (generally 50°) slope at the
upslope end of a mass movement landform
produced by the downslope movement of
material away from the face. (AGI)
Heat flux: The quantity of heat transported during
a given time period through a unit area that is
perpendicular to the flow direction.
Heat sink: (See Energy sink.)
Helicopter logging: A system for hauling timber
from stump to a collection point that employs a
helicopter as the means of transportation.
(CEAP)
Herbicide: A substance used to inhibit or destroy
plant growth. If its effectiveness is restricted to a
specific plant or type of plant, it is known as a
selective herbicide. If its effectiveness covers a
broad range of plants, it is considered to be a
non-selective herbicide. (WPG)
Heterotrophic bacteria: Bacteria requiring com-
plex organic compounds of nitrogen and carbon
for metabolic synthesis.
High-lead logging: A method for transporting logs
from the stumps to a collecting point by using a
power cable, passing through a block fastened
high off the ground, to lift the front end of the
logs clear of the ground while dragging them.
(CEAP, SAF)
High-lead yarding: The initial hauling to a col-
lecting point in a high-lead logging system. (See
High-lead logging.)
Hummocky topography: Irregular landscape of
benches and depressions, indicative of mass
movement activity.
Humus layer: The well-decomposed, more or less
stable, part of the organic matter in mineral soil.
(SOIL)
Hydrographic area: A small sub watershed of a first
order watershed.
Hydrologic province: A subunit of a hydrologic
region. Provinces are divided based on major
climatic and hydrologic differences. (See
Hydrologic regions.)
Hydrologic regimes: The climatic, lithologic,
topographic, vegetation factors, and the tem-
poral distribution of seasonally variable factors
which determine the extent of stability between
a stream and its drainage basin.
Hydrologic regions: Regions that have been
delineated based upon major climatic and
hydrologic differences.
Hydrologic utilization: The use of soil-water for
biological growth and maintenance. Complete
hydrologic utilization is equivalent to potential
evapotranspiration.
Hydrolyzation: A chemical decomposition in which
a compound undergoes a reaction with water
resulting in new compounds or ions.
XII.7
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Ignition pattern: Distribution of many individual
fires over an area simultaneously or in quick suc-
cession. (KPD)
Impacted areas: Uncut and cut areas of the
watershed which are affected by a silvicultural
prescription.
Immobilization: The chemical or physical binding
of ions and compounds such that they are not
chemically active or capable of going into solu-
tion.
Impaired drainage: Where subsurface water move-
ment is obstructed by a relatively impermeable
material, as at the failure plane of an earthflow.
(AGI)
Incident heat load: The source of heat influx that
causes water temperature to increase.
Incipient drainage depression: Linear depression
orientated downslope that may carry surface
runoff only during infrequent storms, commonly
the site of debris avalanche-debris flow.
Incremental precipitation: The amount of
precipitation falling over some specified interval
of time.
Infiltration rate: A soil characteristic determining
or describing the maximum rate at which water
can enter the soil under specified conditions, in-
cluding the presence of an excess of water.
(SSSA)
Inorganic phosphorus: Phosphorus compounds
that do not include carbon. Ionic forms are
readily soluble in water.
Insecticide: A pesticide used to control insects.
Inside road ditch: A channel located adjacent to a
road at the foot of the cut bank designed to con-
centrate water and reduce erosion on the road.
Insloped road: A road sloped (at 1 to 2 percent)
toward the cut bank to facilitate the drainage of
water off of the road surface.
Insoluble component: That portion of the nutrients
entering a stream as relatively insoluble com-
pounds or ions via surface flow either adsorbed to
soil particles or as suspended solids.
Integral arch: An arch attached to the skidding
machine to provide lift to the loading end of the
log, and to improve the ease of backing up on
rough steep terrain.
Interception loss: That portion of precipitation
that is caught and retained on vegetation, litter
layer or structures and subsequently evaporated
without reaching the ground. (GOM)
Intracycle: A cycle (i.e., nutrient cycle) within the
ecosystem. The forest nutrient cycle is generally
segmented into three compartments: inputs, in-
tracycle, and outputs.
Intracycle process: Biochemical processes taking
place within an intracycle. (See Intracycle.)
Intragravel water: Water within the pore spaces of
stream bottom gravel material.
Isothermal snowpack: A snowpack that has the
same temperature throughout its vertical profile.
Jackpot burn: (See Spot burn.)
"Jack-strawed" trees: Patch of trees tipped in dif-
ferent directions, commonly indicative of mass
movement activity. (AGI)
Jammer: A light weight 2-drum winch with a
wooden spar, generally mounted on a vehicle
which is used for both skidding and loading.
(SAP)
Joint: Surface of actual or potential fracture or
parting in a rock, without displacement.
Landslide: Sudden downslope movement of earth
and rock.
Land system inventory: A seven level land inven-
tory system which uses selected differentiating
characteristics of soils, natural vegetation, and
geology for identifying and delineating compo-
nent parts of a landscape. The maps and as-
sociated legends produced at a given inventory
level provide data for use at selected levels of
land management.
Latent heat exchange: Energy given off or absorbed
in a process (evaporation/condensation).
Leaf area index: Ratio of leaf surface area to pro-
jected ground surface area.
Leave strip: (See Waterside area.)
Limiting nutrient: An essential nutrient which is
not available to timber in adequate amounts to
insure normal growth (i.e., nitrogen, phosphorus,
and potassium).
Linear depression: Incipient drainage depression.
XH.8
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Litter interception: That component of precipita-
tion that is intercepted by the litter layer and
eventually evaporated back to the atmosphere.
Litter layer: The surface layer of the forest floor
consisting of freshly fallen leaves, needles, twigs,
stems, bark, and fruits. (SAP)
Logging plan: Part of the silvicultural plan that in-
cludes a planimetric map which depicts the type
of logging system, landings, and road plan to be
used.
Log landing: Any place where round timber is as-
sembled for further transport, commonly with a
change of transport method. (SAP)
Lop and scatter: To chop branches, tops, and
small trees after felling and then spread the
resulting materials more or less evenly over the
ground without burning. (SAP)
Lopping: Cutting off one or more branches of a
tree, whether standing, felled, or fallen. (SAP)
Machine pile (and burn): Slash which is put in
piles by machinery to subsequently be burned.
Manning's equation: An empirical formula used to
calculate the velocity of flow based on channel
roughness, the hydraulic radius, and the slope of
the energy gradient line.
Mass failure: (See Mass wasting.)
Mass movement: Unit movement of a portion of
the land surface as in creep, landslide, or slip.
Mass wasting: A general term for a variety of
processes by which large masses of earth
materials are moved by gravity either slowly or
quickly from one place to another.
Masticate: Chewing or grinding wood into small
pieces.
Mechanized logging operations: The use of self-
propelled ground equipment to fall and bunch
and/or limb and buck or top a tree.
Melt threshold temperature: An index temperature
relating to when the snowpack will begin to melt.
Microrelief: Small-scale, local differences in
topography that are only a few feet in diameter
and have elevational differences of a few inches
to 6 feet. (SSSA)
Mineral soil: A soil consisting predominantly of,
and having its properties determined
predominantly by, mineral matter. Usually con-
tains less than 20 percent organic matter, but
may contain an organic surface layer up to 30 cm
thick. (SSSA)
Mineralization: The release of mineral matter from
organic matter as a result of microbial decom-
position.
Mitigative controls: The physical, chemical, or
vegetative measures applied to ameliorate ex-
isting problems.
Modified Soil Loss Equation (MSLE): The Univer-
sal Soil Loss Equation (USLE) as it has been
revised for application to forest conditions.
Mohr-Coulomb Theory of earth failure: States that
failure in a material occurs if the shear stress on
any plane equals the shear strength of the
material. (AGI)
Montmorillonite: (See Smectite.)
Mudflow: Rapidly flowing mass of predominantly
fine-grained earth materials possessing a high
degree of fluidity during movement.
Mulch: (1) Any material such as straw, sawdust,
leaves, etc., that is spread upon the surface of the
soil to protect the soil and plant roots from ef-
fects of raindrops, soil crusting, freezing,
evaporation, etc. (SSSA) (2) Any loose covering
on the surface on the soil, whether natural, —
like litter, or deliberately applied like straw,
grass, or foliage, or artificial material such as cel-
lophane. Used to conserve moisture, check weed
growth, and protect from climate. (SAP)
Natural event: Event that takes place according to
the laws of nature — inherent — not induced or
changed by man's activities.
Nitrification: Biological oxidation of ammonium to
nitrate or a biologically induced increase in the
oxidation state of nitrogen.
Nitrogen fixation: Biological conversion of elemen-
tal nitrogen (N2) to organic combinations or to
forms utilizable in biological processes. (SSSA)
Nitrosomonas: A soil bacteria that obtains energy
for growth by oxidizing ammonia to nitrites.
Non-cohesive soil: Soil with a relatively low shear
strength.
XE.9
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Non-point sources: For silviculture, sources from
which the pollutants discharged are: (1) induced
by natural processes, including precipitation,
seepage, percolation, and runoff; (2) not
traceable to any discrete or identifiable facility;
and (3) are better controlled through the utiliza-
tion of Best Management Practices, including
process and planning techniques. (EPA) Non-
point sources as used in this document includes
natural pollution sources not directly or in-
direclty caused by man.
Normalized hydrograph: Representative
hydrograph expressed as the percentage of an-
nual flow which can or will occur during any 6-
day interval.
Nutrient availability: The state in which nutrients
must be to be available to plants.
Onsite: The specific area on which an event, occur-
rence, or activity has taken or will take place.
Onsite chemical balance changes: Silvicultural ac-
tivity can result in release of chemicals which, in
turn, may leach or wash into streams, thereby af-
fecting nutrient and Biochemical Oxygen De-
mand (BOD) levels in water.
Open water: (See Free water surface.)
Organic phosphate: Phosphorus compounds that
include carbon. They are not generally found as
water soluble ions.
Organophosphate: A synthetic organic pesticide
which contains carbon, hydrogen, and
phosphorous. It acts by inhibiting a blood
chemical called "Cholinesterase." As a rule,
organophosphates are less persistent than the
chlorinated hydrocarbon family. Examples:
malathion and parathion.
Outslope construction: Used in construction to
spread both the material and the potential flow
of water out over a very large front with a subse-
quent low energy per unit for transport.
Overland flow (sheet flow): Runoff water which
flows over the ground surface as a thin layer and
does not infiltrate prior to reaching a stream, as
opposed to the channelized (concentrated) runoff
which occurs in rills and gullies. (WPG)
Overload stream: An aggraded stream, one with an
excess of sediment supply as evidenced in a
braided stream.
Overstory: That portion of trees in a forest forming
the uppermost canopy layer.
Oxygen saturation levels: The maximum amount
of oxygen that theoretically can be dissolved
within water for the given temperature and
elevation.
Patch cut: A modification of clearcutting. A 40- to
200-acre area cut as single settings, separated for
a long as practicable, preferably until the
regeneration is adequately shading the forest
floor. (SAF)
Permeability class: An arbitrary classification of
soil permeability into classes (i.e., very slow,
slow, slow to moderate, moderate, etc.) Used in
determining the soil erodibility factor (K) of the
Modified Soil Loss Equation.
Pesticide: A chemical substance, compound, or
other agent used to control, destroy, or prevent
damage by a pest.
Phreatophyte: A plant that habitually obtains its
water supply from the zone of saturation, either
directly or through the capillary fringe. (DMM)
Piezometric surface: An imaginary surface
representing the static head of groundwater and
defined by the level to which water will rise in a
well.
Piping (soil piping): Subsurface erosion that causes
the formation of tunnel-like cavities.
"Pistol-butted" trees: Trees with a "J" shaped
base with the stem displaced downslope, due to
mass movement, snow creep, and other
processes.
Planar failures: Shallow soil mass movement with
a nearly flat plane of failure.
Plant growth regulator: A substance or organism
that increases, decreases, or in some way changes
the normal growth or reproduction of a plant.
Plow layer: A surface soil layer that has been mixed
by human activities to an extent that the original
properties of the soil have been modified.
Point bars: Sediment deposited on the inside of a
growing meander loop. (DGT)
Pollution:. The manmade or man-induced altera-
tion of the chemical, physical, biological and
XII.10
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radiological integrity of water. (Section 502, PI
95-217 clean Water Act)
Pool areas: A body of water or portion of a stream
that is deep and quiet relative to the main cur-
rent. (NIA)
Pore space: The volume of the various pores in a
soil. The space not occupied by solid particles.
Pore water pressure: The stress transmitted
through the fluid that fills the voids between par-
ticles of a soil or rock mass.
Prescribed fire (prescribed burn): Skillful applica-
tion of fire to natural fuels under conditions of
weather, fuel moisture, soil moisture, etc., that
will allow confinement of the fire to a predeter-
mined area and at the same time will produce
the intensity of heat and rate of spread to ac-
complish certain planned benefits. (KPD)
Prescribed underburning: Skillful application of
fire used to reduce fuels under stands following
logging to reduce fuels created by some cultural
treatments; to kill unwanted trees and shrubs
and/or reduce fuels from leaf and needle fall; and
to control certain tree diseases. It is successful
only with fire-resistant tree species and low to
moderate fuel loadings.
Preventive controls: Those controls that apply to
the pre-implementation, planning phase of a
silvicultural activity.
Probit: a statistical unit of measurement of
probability based on deviations from the means
of a normal frequency distribution.
Proctor curves: Curves resulting from the standard
Proctor compaction test showing the variation of
optimum soil-water content related to maximum
density. (EM)
Proposed condition: The hydrologic state of a
watershed following a proposed silvicultural ac-
tivity. It is synonymous with the "post-
silvicultural" activity condition.
Procedural controls: Those controls that are con-
cerned with administrative actions of a
silvicultural activity.
Raindrop splash erosion: (See Erosion.)
Reaeration: The replenishment of deficit oxygen
concentration in water.
Reflectivity: The fraction of radiation that is
reflected back to the sky by the snowpack. A
term used in energy budget modeling.
Release: Freeing a tree, or group of trees, from more
immediate competition by cutting, or otherwise
eliminating, growth that is overtopping or closely
surrounding them. (SAP).
Residual soil: Soil developed in situ from underly-
ing parent material.
Resource impacts: Change to the resource that
alters natural processes.
Restricted drainage: Where subsurface water
movement is obstructed by a relatively
impermeable material, as at the failure plane of
an earthflow.
Retaining structure: Structure which retains or
restrains an oversteepened slope.
Rheological flow: A more or less viscous liquid flow
of solid material.
Riffle: A shallow rapids in an open stream where
the water surface is broken into waves by
obstructions wholly or partly submerged. (NIA)
Ripping: (See Soil ripping.)
Riprap: A foundation or sustaining wall of stones
put together without order on an embankment
slope or water course to prevent erosion.
Rodenticide: A pesticide used to control rodents.
Rolling chopper: A cylindrical roller or water-filled
drum equipped with several full-length cutting
blades. Its purpose is to crush and cut brush and
slash into small lengths.
Rolling dip: (1) To conform a road to the landscape
by following the natural grade changes. (2) Used
when constructing a road on nearly level terrain
to provide for drainage by making small changes
in grade.
Rotational failure: Mass movement with concave
failure plane.
Sag pond: Poorly drained depression formed by
rotational mass movement.
Salvage cut: The harvesting of trees that are dead,
dying, or deteriorating (e.g., because overmature
or materially damaged by fire, wind, insects, or
xn.n
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other injurious agents) before the timber
becomes worthless.
Saturated hydraulic conductivity: A measure of
the rate of water traversing a unit area of soil in
unit time per unit hydraulic gradient with the
soil in a saturated condition.
Scalping: Paring off low and surface vegetation
together with most of its roots to expose a
vegetation-free soil surface, generally
preparatory to sowing or planting. (CEAP)
Scarification: Loosening the topsoil or breaking up
the forest floor to expose mineral soil.
Scour: Removal of loose material by running water,
from the wetted portion of a stream channel.
Sediment: (1) Particles derived from rocks or
biological materials that have been transported
by a fluid. (2) Solid material (sludges) suspended
in or settled from water.
Sediment delivery index: An estimated fraction
of the total potential soil loss from a disturbed
site that may be moved over land and
deposited in a stream channel.
Sediment delivery ratio: The volume of sediment
material actually delivered to a point in a
watershed divided by the total amount of
material available for delivery.
Sediment discharge (yield): The average quan-
tity of sediment, mass or volume, but usually
mass, passing a section in a unit time. The
term may be qualified as, for example,
suspended-sediment discharge, bedload dis-
charge, or total sediment discharge.
Sediment rating curve: A graphical representa-
tion of the existing relationship between sedi-
ment concentration in mg/1 and stream dis-
charge in cfs.
Sediment supply: The amount of inorganic sedi-
ment made available in the channel for
transport as either suspended or bedload sedi-
ment. Sources of sediment include contribu-
tions from surface erosion and soil mass move-
ment, and that derived from the channel itself.
Sediment transport: Term used to discuss the
movement of sediment within a stream chan-
nel system.
Sediment trap: Usually a small depression to
capture sediment coming from on-going con-
struction. A temporary measure to trap sedi-
ment.
Suspended sediment: In the process by which
running water transports material, smaller
particles are lifted far from the bottom and are
sustained for long periods before being dis-
tributed through the whole body of the cur-
rent. This constitutes the suspended load or
that component called suspended sediment.
(DGT)
Seed tree cutting: Removing trees in a mature
stand so as to effect permanent openings of their
canopies. This provides conditions for securing
regeneration from the seed of trees retained for
that purpose.
Selection cutting: A method of logging which
removes trees from all size classes in an uneven-
aged stand to maintain proper stocking as incre-
ments of trees move from younger to older
classes.
Serpentine: A mineral of the serpentine group,
such as antigorite and chrysotile. These minerals
are prone to mass erosion. (DGT)
Shale: Fine-grained indurated detrital sedimen-
tary rock formed by consolidation of clay, silt, or
mud, and characterized by finely stratified
structure.
Shear strength: The internal resistance of a body to
shear stress.
Shear stress: That component of stress which acts
tangential to a plane through any given point on
a body.
Sheet flow: Surface runoff which flows over the
ground in a thin layer as contrasted with runoff
that is concentrated in rills and gullies.
Shelterwood cutting: A method of harvest cutting
involving two or three separate cuttings. The last
cutting removes the shelterwood after adequate
regeneration, encouraged by prior cuttings, has
become established.
Shotcrete (also known as gunite): A mixture of ce-
ment, sand, or crushed slag and water sprayed
over exposed soil on hillslopes to protect against
surface erosion.
xn.i2
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Siltstone: Indurated silt having the texture and
composition, but lacking the fine lamination of
shale.
Silviculture: The science and art of cultivating
forest crops, based on a knowledge of silvics,
which is the study of the life history and general
characteristics of forest trees and stands with
particular reference to locality factors, as a basis
for the practice of silviculture (SAF).
Silvicultural activity: Activity associated with
the care and cultivation of forest trees. It in-
cludes harvesting, regeneration systems, ac-
cess systems, and various cultural practices
(site preparation and timber stand improve-
ment) that are appropriate to various manage-
ment objectives.
Silvicultural plan: A plan outlining a proposed
silvicultural activity, which should include
methods of cutting, felling, yarding, fuel
management, site preparation, miscellaneous
cultural activities, and road and access system
plans.
Silvicultural state: The status of the vegetation
complex on units of land to which a
silvicultural prescription has been applied. A
silvicultural system or treatment actually ap-
plied to a unit or a description of the
vegetative cover on all or a part of the unit.
The state may be described as clear cut,
thinned, forested, open, etc.
Silvicultural prescription: The management
alternatives applied to a watershed or
watershed subunit. The delineation of a
watershed into a single unit or series of sub-
units to which the prescription is to be applied,
is based on uniformity of soil depth, vegeta-
tion, precipitation, aspect, and other unique
site factors. A uniform practice over the entire
unit or several practices resulting in more than
one silvicultural state per silvicultural
prescription; i.e., the prescription may consist
of patch cutting, thinning, and leaving part of
the area uncut. The silvicultural prescription
includes for each unit that part of the
silvicultural plan that affects the evapotran-
spiration status of the vegetation.
Simulation: A technique for analyzing complex
inter-relationships among variables based upon
known or assumed influence of one variable on
another. Often referred to as modeling, simula-
tion provides a means of estimating and compar-
ing the effects that a change in one or more of the
variables will have on the other variables.
Site preparation: Preparing a site for the regenera-
tion or planting of trees.
Site preparation plan: Part of the silvicultural plan
that describes site preparation techniques to be
used.
Site productivity: The present capability of a site
for producing a specified plant or sequence of
plants under a defined set of management prac-
tices.
Skidding (timber transport): A term for hauling
loads by sliding from stump to roadside. The
timber may slide more or less wholly along the
ground (ground skidding) with its forward end
supported (high lead skidding) or wholly off the
ground — sliding along a cable — during its
main transit (aerial skidding). (SAF)
Skid road (skid trail): Any path, more or less
prepared, over which logs are dragged. (SAF)
Skyline cable system: A cable logging system
which employs a heavy cable stretched between
two supports upon which traverses a carriage to
support at least the leading end of the log. (SAF)
Skyline logging: A method for transporting logs
from stumps to collecting points that uses a
heavy cable stretched between high points (such
as in tall trees braced with guy lines) to function
as an overhead track for a load carrying carriage.
Logs are lifted up by cables or other similar
devices, and powered cables are used to move the
load back and forth along the main cable.
(CEAP)
Slope configuration change: Alteration of the land
slope, such as occurs in roadbuilding when cuts
and fills are constructed.
Slope gradient: The amount of inclination from
horizontal of a piece of land. Gradient is expres-
sed in degrees or percent (tangent of the slope
angle which is the amount of rise divided by the
horizontal distance).
Slump: A slip resulting from the downward and
backward rotation of a soil block or group of
blocks with small lateral displacement. Closely
XII.13
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related to earthflow in terms of their occurrence
and genetic process. (DGT)
Smectite clay: Group of expanding lattice clay
minerals. (AGI).
Snowpack ripening: The process of coarse crystal
formation with an increase of the liquid phase
within the snowpack. (VTC)
Snow redistribution: The change in the distribu-
tion of snow attributable to land management
activities (i.e., increasing deposition in openings
within forested areas).
Snow retention coefficient: A coefficient used in as-
sessing snowpack redistribution associated with
timber harvesting. The coefficient is the ratio of
expected accumulation divided by the baseline
or pre-harvest accumulation.
Soil creep: Slow, gradual, more or less continuous
permanent deformation of soil under
gravitational body stress.
Soil mass movement: Movement of soil material en
masse under gravitational body stress.
Soil resource inventory: Term used by U.S. Forest
Service for the systematic examination of soils in
the field and laboratory, including descriptions,
classifications, and mapping of soils and
management interpretations according to their
productivity and behavior under use. (See Soil
survey.)
Soil ripping: Act of breaking up hard gravel, soft
rock, tearing out stumps and boulders.
Soil survey: The systematic examination, descrip-
tion, classification, and mapping of soils in an
area. Soil surveys are classified according to the
kind and intensity of field examination. (SSSA)
Soil texture: The relative proportions of the various
soil separates [sand, silt, and clay] in a soil as
described by the classes of soil texture. (SCS,
SSSA)
Solar ephemeris: A table showing the positions of
the sun on a number of dates in a regular se-
quence. (RHD)
Solar loading: The flux of solar energy reaching the
forest floor or water body of interest.
Soluble component: That portion of the nutrients
that enters a stream as soluble ions via surface or
subsurface flow.
Spot burn (jackpot): A method of burning where
scattered concentrations of slash or other fuels
are reduced by burning in place under fuel
moisture and weather conditions which maintain
low flame lengths and fire intensities.
Stability threshold: The maximum change that a
stream reach can withstand and still maintain
it's morphological characteristics due to either
sediment supply and/or stream energy changes
where channel adjustments will be initiated to
accommodate these changes over time.
Stage felling: To fell timber and remove it in stages
so as to reduce breakage, normally small timber
first.
Stations (engineering): A unit of measure
equivalent to 100 horizontal linear feet.
Stiff diagram: A method of plotting several
variables using vectors on a graph, so that the
combined effects of the variables are shown as an
irregular polygon with a particular area.
Stream aeration: The process of air being mixed
with and re-entering the stream water. This
process can be observed visually as white or
foaming water.
Stream channel encroachment: Encroachment oc-
curs when bankful discharge width of a stream is
reduced due to direct alterations such as bridges,
roadfills, culverts, organic debris, etc.
Stream equilibrium: The balance of the
availability of sediment supply based on the
erosional rates of adjacent slopes, the stream
system, and the energy available to transport
this erosional debris in such a manner that the
morphological characteristics of the stream
channel are maintained.
Stream gradient: (See Water surface slope.)
Stream order: A method of numbering streams as
part of a drainage basin network. The smallest
unbranched mapped tributary is called first
order, the stream receiving the tributary is called
second order, and so on.
Stream power: Numerical expression of stream
energy utilized in determining bedload transport
rate which is the product of water surface slope,
stream discharge, and a unit force factor of 62.4
Ibs/ft3-width of stream.
xn.i4
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Stream productivity: The amount of living matter
actually produced within the stream under in-
vestigation.
Stream shading changes: Changes that occur when
trees and/or understory vegetation that con-
tribute to the shading of water in streams are
removed.
Streamside areas: (See Waterside area.)
Streamside management zone: (See Waterside
area.)
Strip cutting: Removal of the crop in strips in one
or more operations, generally for encouraging
regeneration. (SAP)
Stripping: Clearing or removing ground cover.
Structure index: An index of soil structure
(granular, blockly, massive, etc.) used in deter-
mining the credibility (K) factor of the Universal
or Modified Soil Loss Equation.
Subsurface flow: That part of the runoff that per-
colates through the soil mantle primarily under
the influence of gravity before emerging as
streamflow.
Surface erosion: (See Erosion).
Swelling clays: Expanding lattice clays which in-
crease in volume when water moves into the
crystal structure and decrease in volume when
water is removed.
Swing operation: Moving logs to a landing from a
distant deck to which they have been yarded.
(CLS)
Symbiosis: The living together of two different
organisms with a resulting mutual benefit. A
common example includes the association of
rhizomes with legumes. The resulting nitrogen
fixation is sometimes called symbiotic nitrogen
fixation. (See Nitrogen fixation).
Temporary road: A timber access road which is
closed to traffic between timber needs. When
closed the road is barriered, scarified, and
reseeded to grass and forbs.
Tension cracks: Fissures in the earth formed by dif-
ferential displacement between two blocks of
earth caused by tensional stresses.
Terracing: Use of terraces (raised levels with sloped
front or sides) in site preparation.
Thermal pollution: Disruption of the aquatic en-
vironment or other beneficial use due to heating
of a stream or other water body.
Throughfall: The part of rainfall that reaches the
ground directly through the vegetative canopy,
as drip from leaves, twigs, and stems. (VTC)
Timber harvesting: A general term for the removal
of physically mature trees in contrast to cuttings
that remove immature trees. (SAF)
Timber stand improvement: A loose term compris-
ing all intermediate cuttings made to improve
the composition, constitution, condition, and in-
crement of a timber stand. (SAF)
Topographic shading: Shading of streams, water
bodies, or other areas of interest by topographic
features positioned between the sun and area of
interest, thereby eliminating direct solar radia-
tion.
Toxicity: Quality, relative degree, or specific
degree of being toxic or poisonous to an
organism; the ability of a substance or chemical
to produce injury. (RHD)
Tractor logging: Any system of logging in which a
tractor furnished the motive power, whether by
direct hauling or by skidding. (SAF)
Tractor skidding: Hauling logs by sliding using a
tractor as the motive power. (SAF)
Translational movement: Downslope movement of
a mass of soil and/or rock on a surface roughly
parallel to the general ground surface.
Translocation of chemicals: The movement of a
chemical within a plant or animal after it has
entered by some path.
Transmissivity of solar radiation: Ability of solar
radiation to pass through the forest canopy to the
forest floor, snow pack surface or water surface.
Transport capability: In general terms, the integra-
tion of several variables which influence the
ability of the stream to transport the sediment
made available. The variables include velocity,
gradient, bed roughness, existing sediment load,
and particle size of material being transported.
Transportation plan: A plan that coordinates the
transportation system for relatively large areas
delineated by very limiting topographic features,
economic centers, and legislative constraints. It
XH.15
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provides the interface for the logging road system
and the public road system.
Transportation system: The transportation
network including all existing and planned
roads, skid trails, bridges, airfields, and other
transport facilities wholly or partly within or ad-
jacent to the watershed area for silvicultural ac-
tivities. (WPG)
Trash rack: A screen of parallel bars or mesh
placed across a stream or turbine intake to in-
tercept floating debris. (DMM)
Treated seed: Seeds that are chemically treated
with a pesticide or fertilizer.
Understory: The woody species growing under a
more or less continuous cover of branches and
foliage formed collectively by the upper portions
of adjacent woody growth. (WPG)
Uneven-aged stands: Stands with trees that differ
markedly in age.
Unimpacted areas: Those unharvested zones of a
watershed which are unaffected by a silvicultural
prescription.
Universal Soil Loss Equation: An equation used for
evaluating potential soil loss in specific situa-
tions. A = RKLSPC wherein A = average an-
nual soil loss in tons/acre/year, R = rainfall fac-
tor, K = soil erodibility factor, L = length of
slope, S = slope gradient, P = conservation prac-
tice factor, and C = cropping and management
factor. (WPG)
Variable source area: The portion of the watershed
that actively contributes to runoff. These areas
are dynamic and vary with antecedent soil
moisture, storm size and duration.
Vegetative change: Changes which include the
removal of vegetative ground cover, canopy
cover, or a change in vegetative type.
Vegetative cover: The vegetation that is effective in
protecting the ground surface. May be composed
of overstory and understory vegetation.
Vegetative ground cover: The effective vegetation
and organic matter that is protecting the soil;
this cover includes litter.
Vegetative shading: Shading of streams, water
bodies, or other areas of interest by vegetation
positioned between the sun and area of interest
thereby reducing the direct solar radiation strik-
ing a surface.
Volatilization: The evaporation or changing of a
substance from liquid to vapor. (SOIL)
Volcanic flow rock: Extrusive igneous rock —
generally the result of a lava flow.
Volcaniclastic: Fragmental rock of volcanic origin;
may be a lava flow breccis, ash flow breccia, air
fall ash, mud flow (lahar) breccia, or other
material.
Washload: That portion of the suspended load
which is 0.062 mm or smaller (silts and clays).
Washoff: The flushing of chemicals deposited as
dryfall or introduced chemicals from the foliage
during precipitation events.
Water balance: A measure of continuity of flow of
water. It is an accounting of all the inputs and
outputs of the hydrologic system. (VTC)
Water bar: A ridge or mound made across a road or
cleared strip to divert water to one side. (CEAP)
Water concentration: The condition that results
when water is intercepted and allowed to con-
verge instead of infiltrating into the soil or
spreading naturally.
Water quality objective: A quantified statement
that defines the quality of the water resource for
a specific stream or stream segment. It is related
to the uses of the water resources and may be in
terms of existing water quality standards or other
quantifiable conditions relating to water quality
such as degree of channel aggradation or
degradation.
Water quality standard: Quantitative or
qualitative criteria for chemical, physical, and
biological characteristics that are established for
the purpose of providing water that is suitable for
specific uses.
Water resource goal: A broad but concise state-
ment of the desired state or condition for the
water resource.
Water surface slope: The slope or gradient of the
stream energy grade line. For open channels, it is
measured as the slope of the water surface and is
frequently considered parallel to the stream bed.
XH.16
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Waterside area: Land area of varying size and
shape immediately adjacent to stream courses or
to water bodies on which the type and/or inten-
sity of land use is tempered to meet defined
water resource goals. Terms such as streamside
management zone, aquatic habitat zone, water
influence zone, floodplain, buffer strip, and leave
or filter strip are often used when referring to
management direction for waterside areas.
Water yield: The runoff from a watershed, in-
cluding ground water outflow. Water yield is the
precipitation less the evapotranspiration losses
and change in storage.
Water yield increases: Increases in water yield
resulting from reduction in other components of
the hydrologic balance — primarily evapotran-
spiration.
Weak link: A reference to the channel reach that is
the most unstable either from an increase in
streamflow and/or increase in sediment supply.
Many such weak links are in a disequilibrium
condition.
Winching: To hoist or pull with as if with a winch.
Windbreak: A planting of trees, shrubs, or other
vegetation, usually perpendicular or nearly so to
the principal wind direction, to protect soil,
crops, homesteads, roads, etc., against the ef-
fects of winds such as wind erosion and the
drifting of soil and snow. (SSSA)
Yarding: The operation of the initial hauling of
timber from stump to a collecting point. Pulling
logs from the tree stump to the skid way, landing,
or (in rare cases) the mill.
XII.17
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SOURCES
KEY TO PUBLISHED SOURCES
AGI: Gary, M,, R. McAfee, Jr., and C.L. Wolf,
eds. Glossary of geology. Am. Geol. Inst.
CEAP: U.S. Department of Agriculture, Forest
Service. 1978 Silvicultural activities and
non-point pollution abatement: A cost-
effectiveness analysis procedure.
Prepared under Interagency No. EPA-
IAG-D6-0660 with the Environ. Prot.
Agency, Athens, Ga.
CLS: Studier, D. D., and V. W. Binkley. 1974.
Cable logging systems. U.S. Dep. Agric.,
For. Serv.
DGT: American Geological Institute. 1962. Dic-
tionary of geological terms. Doubleday,
Garden City, N.J.
DMM: Thrush, P. W., ed. 1968. A dictionary of
mining, mineral and related terms. U. S.
Dep. Inter.
EM: U.S. Department of the Interior, Bureau of
Reclamation. Earth manual, 2nd ed.
U.S. Gov. Print. Off., Washington, D.C.
EPA: U.S. Environmental Protection Agency.
Federal Register Vol 41, No 119, Friday
June 18, 1976 page 24710 - Preamble to
parts 124 and 125, Application of Permit
Program to Silvicultural Activities.
COM: Huschke, R. E., ed. 1959. Glossary of
meteorology. Am. Meteorol. Soc.,
Boston, Mass.
KPD: Davis, K. P. 1959. Forest fire: control and
use. McGraw-Hill, New York.
NIA: U.S. Fish and Wildlife Service, Office of
Biological Services. 1976. Nomenclature
of instream assessments. West. Water
Allocation, Washington, D.C.
PAST: Stimmann, M. W. 1977. Pesticide applica-
tion and safety training. Div. Agric. Sci.,
Univ. Calif.
PNE: Stottenberg, N. L., and J. L. White. 1953.
Selective loss plant nutrients by erosion.
Proc. Soil Sci. Am. 17:406-410.
RHD: Stein, J., ed. 1973. The Random House dic-
tionary of the English language. Random
House, New York.
SAF: Ford-Robertson, F. C., ed. 1971. Ter-
minology of forest science, technology,
practice and products. Soc. Am. For.,
Washington, D.C.
SCS: Soil Conservation Society of America.
1976. Resource conservation glossary.
2nd ed.
SOIL: U.S. Department of Agriculture. 1957. The
yearbook of agriculture 1957. House Doc.
No. 30, Washington, D.C.
SSSA: Soil Science Society of America. 1975.
Glossary of soil science terms. Madison,
Wis.
VTC: Chow, V. T., ed. 1964. Handbook of applied
hydrology. A compendium of water-
resources technology. McGraw-Hill, New
York.
WPG: Schwarz, C. F., E. C. Thor, and G. H.
Eisner. 1976. Wildland planning glos-
sary. U.S. Dep. Agric., For. Serv. Gen.
Tech. Rep. PSW-13. Pac. Southweat
For. and Range Exp. Stn., Berkeley,
Calif.
WWU: Veatch, J. 0., and C. R. Humphreys. 1966.
Water and water use terminology.
Thomas Printing and Publishing Co.,
Ltd., Kaukauna, Wis.
XH.18
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/8-80-Q12
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
An Approach to Water Resources Evaluation of Non-point
SiIvicultural Sources (A Procedural Handbook)
5. REPORT DATE
August 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Forest Service
U.S. Department of Agriculture
Washington DC 20250
10. PROGRAM ELEMENT NO.
A28B1A
11. CONTRACT/GRANT NO.
EPA-IAG-D6-0660
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory—Athens GA
Office of Research and Development
U.S. Environmental Protection Agency
Athens GA 30605
13. TYPE OF REPORT AND PERIOD COVERED
Final . 12/76-12/79
14. SPONSORING AGENCY CODE
EPA/600/01
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This handbook provides an analysis methodology that can be used to describe and
evaluate changes to the water resource resulting from non-point si 1vicultural activi-
ties. It covers only the pollutant generation and transport processes and does not
consider the economic, social, and political aspects of pollution control.
This state-of-the-art approach for analysis and prediction of pollution from non
point siIvicultural activities is a rational estimation procedure that is most useful
in making comparative analyses of management alternatives. These comparisons are used
in selecting preventive and mitigative controls and require site-specific data for the
analysi s.
This handbook also provides quantitative techniques for estimating potential
changes in streamflow, surface erosion, soil mass movement, total potential sediment
discharge, and temperature. Qualitative discussions of the impacts of siIvicultural
activities on dissolved oxygen, organic matter, nutrients, and introduced chemicals
are included.
A control section provides a list of control practices that haye been used ef-
fectively and a methodology for selecting mixtures of these controls for the preven-
tion and mitigation of water resource impacts. Such mixtures are the technical basis
for formulating Best Management Practices.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COS AT I Field/Group
Non-point pollution
SiIviculture
Pollution control
Water pol1ution
68D
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS /ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
861
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
XI I.19
f, U.S GOVERNMENT PRINTING OFFICE- 1980-657-165/0081
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