HomeMy WebLinkAboutAPA3491DAN BISHOP
~ Hydrologic Reconnaissance
of !he
Susi!na River Below
DevJ s Canyon
~nvironaid
October, 1974
Juneau
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J
March 18, 1975
Mr. J. V. House, Administrator
Alaska Power Administration
P. 0. Box 50
Juneau, Alaska 99802
Dear Mr. House:
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
NATIONAL MARINE FISHERIES SERVICE
P. 0. BOX 1668 -JUNEAU, ALASKA 99801
I am enclosing for your information the report "A Hydrologic
Reconnaissance of the Susitna River Below Devil•s Canyon,11
October 1974. The report was prepared by our consultant,
Dan Bishop of Environaid, Juneau, under Contract Number
03-4-208-302.
I understand that your office will reprint a limited number
of copies for your internal use and for information of others
involved in current studies of the potential Susitna River
hydroelectric project.
Sincerely,
tl ' --' r, fji3 . . -4+-fA:/ _,, !.:.~·-¢.£.:_
~-~ / (I ~ "-_, .~ ~)
Harry L'~· Rietze
Director, Alaska Region
I I
: ~nvironaid A Land-Wa!er Resource Consul!an! Group
__ j
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·._c:-J
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Mr. Harry L. Rietze
Director, Alaska Region
October 31, 1975
National Marine Fisheries Service
P .0. Box 1661
Juneau, AK 99802
Dear Mr . Rietze:
RR 4, BOX 4993
JUNEAU, ALASKA 99801
907 789-9305
The report, A Hydrologic Reconnaissance of the Susitna River Below
Devil Canyon, is submitted herewith to fulfill contract No. 03-4-208-302
which I made June 19, 1974, with the National Marine Fisheries Service
of NOAA.
Sincerely,
Daniel M. Bishop
I i
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TABLE OF CONTENTS
Scope and Objectives
A. Stream Temperatures
1. Estimates of surface water temperatures of
the Susitna, Chulitna and Talkeetna Rivers
2. Water temperature measurements, July, 1974
in Little Susitna, Susitna, Chulitna, and
Talkeetna Rivers, •• and related analysis of
Susitna heating •
. 3. Influence of suspended sediment on heating
of the Susitna.
4. Estimates of July heating conditions, nat-
ural and regulated flow conditions.
5. Mixed water temperature conditions below
Chulitna-Talkeetna confluence.
6. Summary.
B. Stream Velocity
1. Annual hydrograph patterns, present and
regulated flows.
2. Flow-duration curves for Susitna streams
and for regulated Susitna. Discussion of
late summer-fall low flows.
3.
4.
5.
6.
Distribution of flow velocities in cross-
sections.
Observations of surface velocities and of
related river perimeter particle size classes •
Regressions relating channel flow conditions
At Gold Creek to measured discharge.
Drop in stream velocity as related to
decrease in discharge per specific recurrence
interval.
7. Effect of loss of suspended sediment on velo-
cities of the Susitna.
8. Summary.
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c. Suspended Sediment
1. Suspended sediment rating curve for the
L ~-n:l
2. rrhe size class distribution of suspended
sediment.
D; Change in Middle Susitna River's Form
1. Background
2. River features seen on aerial photos and as
measured on the ground.
3. Extent of degradation likely with regulation.
4. Changes in channel form -width, depth, gradient,
meander length, sinuosity, width/depth ratio,
gradient with regulation.
5. Quantification of change in channel form.
6. Use of regressions, Figure 9, for predicting
form of regulated channels,
7. Influence of tributaries.
E, Springflows
1. Types of springflows recognized.
2. Possible effects of regulation of the Susitna on
Springflows.
APPENDIX
Instantaneous observations of river temperatures
during field visit, July, 1974.
Instantaneous observations of Susitna tributary water
temperatures during field visit, July, 1974.
Susitna River Reconnaissance, July, 1974 Thermograph
installation record.
Ph oios
-""'
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,,_)
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Figure 2:
Figure 3:
Figure 4:
Figure 5•
Figure 6a
Figure 71
Figure 8:
FIGURES ·IN TEXT
:_:: s ::.i ma ,~~ er: ?.r::-A11J.l
3usitna Rivers.
Measured temperatures of Susitna, Chulitna, Talkeetna
and Little Susitna Rivers.
Heating patterns with four water types.
Water temperature profiles for respective water types.
Annual hydrographs of four Susitna Rivers.
Annual hydrographs of the Susitna below Talkeetna.
Flow, duration curves for four Susitna Rivers.
Velocity distributions for three representative
discharge measurements of Susitna at Gold Creek.
Figure 9: Dependence of width, depth and velocity conditions of
the Susi tna River at Gold Creek to varied levels of
discharge.
Figure 10: Variation of Susitna suspended sediment concentration
with discharge.
Figure 11: Suspended sediment size classes found in selected
samples from Susitna River at Gold Creek.
Figure 12: Photo overlays showing river and shoreline features
of the Susitna River between river mile 90 and Devil's
Canyon.
TABLES IN TEXT
Table-1: Temperature differences between two stations on the
Table 2a
Table Ja
Table 4:
Table 5:
Table 6:
Little Susitna and between two stations on the Susitna
River.
Average width of the Susitna River as taken from 1962
photos and adjusted for average July flow conditions.
Matrix of factors summarizing the regulated stream
temperature regime in the Susitna River between Devil's
Canyon dam and Talkeetna •
Surface velocities measured at four stations about
75 ft. off the east bank.
Summary of photos of Susitna perimeter materialf and
of tributary streambed material~ suggesting maximum
flow velocities of the river or of respective tribu-
taries.
Widths, gradients, velocities, and shoreline types as
seen on Talkeetna Mtns. photography of the Susitna
River above Talkeetna.
Tab'le 7a Evaluations of likelihood of degradation action on
-"" the Susitna River, between Talkeetna and Davil' s
Canyon.
Table 8: Summary of springflows seen on the ground or identi-
fied on aerial photos.
PHOTOS USED WITHIN TEXT
Plate 1: Stream perimeter material on Susitna River at Gold
Creek.
~ Plate 2: Glacial till-slope along the R.R. at river mile 99!.
Plate 3: Terraced slope above Sherman.
Plate 4: Highly braided Susitna River below confluence of the
Chulitna and Talkeetna Rivers.
Plate 5: Susitna River valley viewed upstream from river mile
107.
Plate 6: Downstream view of Susitna River valley with Sherman
Creek in left foreground.
Plate 7: Metamorphic rocks (schists, shales, graywackes) are
common along the shoreline above Indian River.
Plate 8: Abandoned flood channel areas will rapidly vegetate
with cottonwood, alder and willow.
Plate 9: Springflow-fed secondary flood channels at river mile
104 3/4.
Plate 10: Flood channel at river mile 107! is fed by spring and
small tributary flows.
TABLES IN APPENDIX
Table A-1: Instantaneous observations of river temperatures
during field visit.
Table A-2: Instantaneous observations of Susitna tributary water
temperatures during field visit.
Table A-J: Thermograph installation record, July, 1974,
Plate A-1:
Plate A-2:
Plate A-3:
Plate A-4:
Plate A-5s
Plate A-6:
Plate A-7:
Plate A-8:
Plate A-9:
Plate A-10:
Plate A-11:
Plate A-12:
Plate A-13:
Plate A-14:
Plate A-15:
Plate A-16:
Plate A-17:
Plate A-18:
Plate A-19a
Plate A-20:
Plate A-21:
PHOTO APPENDIX
Perimeter of Susitna River at about Birch Creek,
river mile: 76-!.
Bedload deposited on beaver dam in flood channel
near Billion Slough, river mile: 82-i-.
Perimeter of Susitna River above Billion Slough,
river mile: 82i.
Perimeter of Susitna River below Chase, about river
mile: 90t.
Perimeter of Susitna River above tributary creek at
river mile1 92!.
Upstream view of river from river mile 92i.
Tributary entering Susitna River at river mile: 92i;
glacial boulders prominent.
Mouth of Lane Creek, river mile: 9~.
Perimeter material, Lane Cr., river mile: 96~.
Perimeter, Susitna River above Lane Cr., river mile:
96!.
Beaver-dammed, springfed (reported) pond-creek,
river mile: 98 J/4. ·.
Mouth of McKenzie Creek, river mile: 99 1/J. Bedload
deposit being trimmed off by the river.
McKenzie Creek, river mile: 99 1/3.
Active springflow erosion along banks of river
just above McKenzie Creek, river mile: 99i.
Susitna beach above McKenzie Creek, river mile: 99!.
Perimeter, Portage Creek, river mile: lOOi.
Perimeter, Susitna River at Curry, river mile& 103.
Streambed rubble in dry creekbed, Curry Creek,
river milea lOJ.
Susitna River above Curry Creek, river mile; lOJ
Perimeter, Susitna River below Indian River, river
mile: 121.
Indian River-Susitna River confluence; larger material
(foreground) is river deposited; smaller material
(middle) Indian River deposition. Indian River in
background.
Plate £-23: Portage River nchr mouth, looking upstream. river
mile: 130.,
Plate A-24: Portage River shoreline, looking downstream from i
mile above mouth •.
_cj Plate A-2.5: Portage River perimeter material on active bar near
the mouth.
j
-~~ A HYDROLOGIC RECONNAISSANCE OF THE SUSITNA RIVER BELOW DEVIL'S
CANYON DAMSITE ••• examining physical features that may be altered
As stated in the original proposal, this work was to provide
information on present and future (regulated) physical charact-
eristics of the Susitna River below Devil's Canyon. Available
information was to be gathered and selected field work done during
summer, 1974. T~e subsequent analysis was to concentrate on
features relating to the fishery resource habitat. Particular
attention was to be given to the Susitna River above Talkeetna
because this portion of the river is apt to be most changed and
it appears to have more available river-related information. The
work was to be a careful reconnaissance focusing the problem,
1
indicating the present state of knowledge, and reaching con-
elusions as to where problems or o,portunities may lin.
~pecific Objectives originally identified were:
A. Stream temperature
B. Stream velocity
C, Suspended sediment, and
D. Re-grading of the Susitna River profile.
To these I have added a brief discussion and review of springflows
in the river bottom as they may be influenced by regulation of the
river.
This work does not attempt to evaluate impacts on resources fron1
possible physical changes; rather it should lead to selection
of possible impacts that may be important in managing the river's
resources and need further investigation.
A. Stream Temperature
-Impoundment of the Susitna River will alter the temperature of
water discharged below Devil's Canyon dam. This change.will
reflect the heating and stratification characteristics of the
reservoir behind the dam as well as the design of turbine intake
facilities at the dam. These factors are not part of this work
though they will ultimately relate to downstream conditions.
The purpose of temperature work described in this report is to
assemble and display information known on the middle river's
present temperature regime and to project how this regime may
change below the dam.
2
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--.
1. Figure 1 shows estimates of the surface water temperatures
of the Susitna River at Gold Creek and of the Chulitna
Talkeetna "tributaries a~ their gaging stations,. This figure
represents a body of miscellaneous temperature measurements made
over a period of years (also included are daily temperature
measurements of the Susitna during the summer of 1957) and hence
are more limited in their use than continuously recorded temper-
atures.
ization.
Nevertheless, the data provide a meaningful character-
There is indication that the Susitna and particularly
the Talkeetna begin to warm earlier in the spring than the
Chulitna, evidently reflecting the smaller percent of glacial
headwaters. The Susitna at Gold Creek reaches considerably
higher surface water temperatures than the Chulitna and possibly
higher than the Talkeetna.
2. Surface water temperature measurements were made during
part of July on the Little Susitna (a clear water river), the
Susitna River at Gold Creek and at Sherman Creek, the Chulitna
River at the gaging station, and the Talkeetna River immediately
above the mouth.
These continuous records have been plotted from maximum and
minimum values in Figure 2. Diurnal patterns are evident in all
streams~particularly in the Chulitna and Little Susitna rivers.
The Talkeetna pair of thermographs recorded a pattern suggesting
the influence of springflows. This is possible at the site where
the recorders were installed but was not indicated by any
J
evidence of surface flow or clearer water next to the bank.
As ~gs suggested in Figure 1, the Susitna River re~ches h~gher
maximum daily t~mperatures than the Chulitna or the Talkee~na.
One objective of these measurements was to compare the heating
of a clearwater river (Little Susitna) with the Susitna. For
that reason two stations were used on each of these rivers.
Differences between maximum temperatures and between minimum
temperatures for these respective pairs of stations are shown in
Table 1,
Table 1: Temperature differences between two stations on the
Little Susitna and between two stations on the
Susitna River,
Little Susitna River Susitna River
Date max lower sta pun lower sta max lower sta !min lower
-max upper sta -min up sta -max upper sta -min up
V-14 • 3 deg • F ------
-15 ·-• 6 .6 ----
-16 .4 .4 ----
-17 .o .2 • 5 --
-18 .5 • 5 .J o.o
-19 . J .o no maximum 1.2
-20 .2 .4 II II 1.2
-21 • 2 ,2 II " .9
-22 • 1 . 2 .9 1,0
-23 .2 .4 . 2 • 8
There is a distance of about 1.3 miles between the upper and
lower stations on the Little Susitna and six miles on the
Susitna River between Gold Creek and Sherman. Each of these
4
sta
sta
)
9 II L 3 5 9 ll
Fi9vre. 2: m~vYe.d Ternperdvres o-f 1/Jr-.e,e Svstt:JI'IC<-
RJvt!!.rr" ~11d or L I ft/1!!.. s U.f' rf-VJt:L Rt~e_.y,
_J
,-''I
__ _d
---"1
pairs of stations was located immediately below a USGS stream
measurements as shown in Table 1 and then to study the temperature
change in each of the respective sections of stream according to
the method developed by Edinger and Geyer (1965). The Little
Susitna proved to be unsuited to this analysis because the stream
was ~ubject to shading from streamside vegetation and was moving
so turbulently (gradient about 200 ft. in a mile) that much of
the heat being absorbed by the stream was probably by air-water
mixing.
Analysis of the measured six mile section of the Susitna River
proved interesting and instructive in terms of future change in
the temperature regime, Edinger and Geyer provide comprehensive
and rigorous theory to determine the rate at which a streamflow
changes temperature. This rate depends upon volume and area of
streamflow and upon meteorological features--dewpoint temperature,
wind velocity, and solar radiation. The work does not provide
for variation in albedo or re-radiation characteristics according
to differing water surface characteristics.
Between Gold Creek station (river mile 119) and Sherman (river
mile 113) the widths measured on the 1962 photographs are as
follows, and have also been reduced according to the regression
shown on Figure 8 of Section B. Average width is 559 ft, Stream
area is 559(5280)(6) = 17,?00,000ft.2 on 18 July.
5
River mile Width at 25,900 cfs estimated width at 17,)00 cfs
{18 July)
't I 1'"'\ J ,' ,, .p.;.. J~J -~+ .:_·"-';I Ov .1-". l. ..., •
118 415 " 395 '"
117 790 " 75) It
116 .8)5 .. 787 tl
115 615 It 586 "
114 480 " 457 'II
11) 410 It )91 "
Stream discharge during 18 July, the date selected for calculation,
was 17,)00 cfs or 1,494,720,000 ftJ/day.
From Edinger and Geyer the equation developed to solve for
predicted temperature at the lower end of a measured section is:
T1 = mixed water temperature, deg. F at beginning of
temperature section.
T2 = mixed water temperature, deg. F at end of measure-
ment section.
e -2,71828, base of Natural Logarithm
"
r2 = K • Area/ 62.4(disch., ftJ per day.
K = average ~urface heat exchange coef. in
BTU's7ft /day/deg. F, and depends on wind,
dewpoint temp., and T1 • a graphical approxi-
mation of K is provided by Edinger and Geyer,
and indicates a K = 85BTU/ft2/day/deg. F for
conditions on 7/18/74.
E = Equilibrium temperature toward whicn water temp-
erature is approaching.
E = Td f Hs/K, where Td = dewpoint temperature (46 deg. F
on 7/18/74)
Hs = gross solar radiation in
BTU's/ft2/day/deg. F
(1608 BTU/ft2/day/deg. F on 7/17/74}
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For the situation on the Susitna River, July 18th:
') ... /
•·. J...~'); and
E = 46 deg. + 1608/85 = 65 deg. F.
-.016 e =
Thus, the temperature. T2 , at the lower end of the.measured
section of the river= T1 (.985) + 65 deg. F-65(.985).
When the temperature at the beginning of the section is 56.5
(the maximum on 7/18/74) the temperature projected for six
miles downstream at Sherman= 56.5(.985) + 65-65{.985) =
56.6 deg. F.
This projected temperature compares with a measured value of
56.8 deg. F. The magnitude of error is sUfficiently small to
suggest that the methodology may be of use in evaluating present
and projected temperature conditions in the river between Devil•s
Canyon and the Talkeetna-Chulitna confluence.
3. Suspended sediment concentration in the Susitna may influence
the heating characteristic of the river. We explored this factor
through.library research at the University of Alaska at College
and also by measurements made in Juneau of heating in clear and
in silty water samples.
Stan Justice, graduate student with the University of Alaska's
Environmental Engineering Department reportsc
"Little is known about the effects of sediment
on temperature changes in water. Several pro-
fessionals at the University of Alaska were
questioned but none could say for certain what
the effects would be or provide any references.
7
"Water has a specific heat of 1.00 cal/gm/deg. C
and soil has a tpecific heat of 0.2 cal7grn/deg. C;
sedlme~~-laden water therefore has a lower specifi~
' ,• ',. .. 1 t . , ...... n~at ~nan aoes c.ear wa er even ~hougn SOll or
silt is about 1.6 times heaver than water. .
"For example, if a solution is one-tenth percent
suspended sediments, its specific heat would be:
C = (1.00 cal/grn/deg. C)(0.999) + (0.2 cal/gm/deg. C (~001.) = 0.9992 cal/~m/deg. c, and its d~nsity would
be1 e = (l.OOgrn/cmJ)(0.999) + (1.6gm/cmJ)(O.OOl) =
1.0006 grn/cm3. The calories reQ.uireg tQ heat a 6 cubic meter Qne degree are: (lmJ)(lO cmJjmJ)(~O cm3jm3)
(l.0006gm/cmJ)(0.9992cal/gm/deg.C = 0.9998"10 cal/deg.C
compared to 1.0000 calories required to heat a cubic
meter of distilled water. With identical heat input
conditions the temperature of silty Susitna water will
rise slightly faster (0.02%) than the temperature
ofclear water.
"The depth of short wave radiation penetration
will obviously be decreased by silty water. The
effect of this will be to increase heating at
the surface and decrease it at depth. The high
surface temperatures will cause an increase in
evaporation which removes heat by the formulaJ
Qe = 0.)4u(ew -ea)O, where u = wind velocity,
ew = vapor pressure for water and ea = vapor
pressure for air. (Delay 1966)
"Another effect of high surface temperatures is
to increase long wave radiation as described
by the classacal Stefan-Boltzmann6 equati~na 4 ¢r = 0.97KTw, where K =-1.71'10-kcal/m -k day an~ Tw = absolute temperature of water, 0 k (Parsons,
1971). This will also cause an incFeased loss
of heat with increase in surface water temperature.
"Albedo is the ratio of reflected short wave
radiation to incident short wave radiation.
For clear water it varies from 0.03 to o.o4
(Eagleson, 1970), but no data could be found
on the albedo of silty water. It can be assumed
that soil particles disrupting the water surface
will cause the albedo of silty water to be less
than that of clear water. But what is the effect
of silt below the surface? When looking at glacial
streams from the air, they appear grey-white
while clear streams are dark in colorr apparently
the particles reflect at least visible light and
8
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f--
probably some nonvisible light as well.
Pivovarov (197.3) writes that .. the effect of
w~~er transpa~ence on albedo may be consirt-
eraole" but he does n.y:; auantify :!l.i:::: state-
ment. ~
"Several people contacted suggested that the
sediment's color will have an effect upon
heat absorption and reflectance. Darker
sediment will absorb more than lighter sediment
but again there is no quanification.
"Short wave radiationis transmitted to and
heats the bottom of clear, shallow water
masses. Because this energy is re-rad-
iated out into the water, it has the same
effect on temperature as short wave radiation
entering shallow, silty water.
"Because heated surface water is Illixed with the
mass in a turbulent river like the Susitna, any
effects due to the decrease in light penetration
are apt to be eliminated. There should be rto
loss of heat due to.higher evaporation and long
wave radiation in silty river water. In a river
the primary factors affected by the sediment
load are lowering of specific heat and change of
albedo.
"Before heavy silt laden water sinks below
clear water in a reservoir, increased surface
heating and the change of albedo and specific
heat probably influence the temperature regime.
In the silt-free reservoir radiant energy is
absorbed in the first few meters, eliminating
the effects of surface heating. The clear
water surface has a higher.albedo and specific
heat, thus decreasing the heating rate.
"Extensive investigation of the sediment load•s
effect on solar heating is needed. Turbid water
samples should be .collected and examined for
specific heat, albedo. and light penetration.
Although more difficult, field investigation
should also be made of free flowing rivers ...
Measurements were made in Juneau during August, 1974 to explore
the heating of four kinds of fresh water held in 20 liter plastic
buckets and exposed to the sun. This work is summarized belowa
9
Kinds of waters
A = ?0,400 m·,l O·.f A·· T k t ·~h "d + _..._ _ ~ ,_ :tt..Ke .JJa~ e wa er w~:.. ev1 en v
! ... •
s·~ ~ l n ~L.rlg.
organic
TW = 20,300 ml of tap water from drilled well. Clear.
C = 20,600 m1 of Chulitna River water. Sample taken on
24 July at main hwy. bridge, near gaging station.
Based upon other sediment samples in records, this
water's sediment concentration is in the magnitude
of 1000 mg/1.
TA = 20,400 m1 of mixed waters from the Talkeetna and
Mendenhall Rivers. Rough estimate of sediment
concentration is 100 to 300 mg/1.
Containers:
White plastic garbage cans with 20 liter capacity.
Top diameter at water surfaces was 31.8 em., with a
surface area of 794 cm2 •
Measurements a
Temperature measurements were taken with a Yellow Springs
Electronic thermometer, reading to O.Ol°C. Measurements
were taken at 1, 3, 6, 10 and about 12 inches below the
water surfaces. The l-inch measurement depth represents
17.1% of.the volume; 3-inch = 23.1%; 6-inch = 29.3%t
10-inch = 23.1%; and 12-inch ::: 7.3%. These percentages
were used as weighting values to determing weighted aver-
age temperatures for the respective measurements.
Results:
Shown in Figures 3 and 4, summarize the respective heating
patterns.
Concl~siops pertinent to reconnaissance:
1. With ambient air temperatures above water temperatures,
the average water temperatures in containers of sedimented
water (Chulitna, Talkeetna) rose 17-20% faster than clear
10
-~
c ,_,
tap watera there was little difference in the average heating
of :~huli tna and ·r~l!ceetnB. w~ters. The organically :>taine':!.
water of Auke Lake may heat faster than tap water.
2. Rate of heat loss to the atmosphere at high temperatures
(above ambient air temperatures) was evidently lower for
clear tap water than for sedimented or organically stained
waters. I presume this was due to differing rates of back
radiation.
J. Sedimented water develops a much steeper temperature
profile with depth in a quiet container than clear water,
The more heavily sedimented water of the Chulitna stratified
much more strongly than the Talkeetna water.
4. Estimates will be made of July temperatures of the Susitna
River at Gold Creek and at river mile 91 near Chase for
conditions of natural and regulated flows, respectively.
These estimates will indicate the effect of changes in volume
of flow and channel heating characteristics on expected temp-
eratures. The effect of suspended sediment on water heating
is not included here. Assumptions used in these estimates
are as follows:
Bj.ver Disch!3.rge 1
Section of River
Devil•s Canyon to
Gold Creek
Gold Creek to
River mile 91
!J..J].reg. Jul~£ Flow
23,825 cfs
25,000
11
Reg. Jul:y Flow
1),648 cfs
14,800
River Areaa
(a) length:
Devil's Canyon to Gold Creak = 15 river miles ::: 79,200 .ft.
J/
Gold Creek to river mile 91 = 28 river miles = 146,840 ft.
:!,.!/ River mile 91 is near Chase and is about ten river
miles upriver from Talkeetna. This is the southernmost
river coverage of the Talkeetna air photography. The
Susitna flight does not reach this far north.
(l.J wtd~.
The regulated July discharges used for the two respective sections
of stream were as follows: Devil's Canyon to Gold Creek: 1.),648 cfs;
Gold Creek to river mile 91: 14,800. Adjusted widths were devel-
oped for these reduced flows in the following mannera
As discussed further in Section D, width of the regulated
Susitna at bankful flow is estimated at about .715 present
width at bankful flow. This reduction is based on a relation
relating stream width to the square root of discharges having
similar return intervals. This factor has also been applied to
the average widths, 565 and 49.3 ft. generated in Table 2, sug-
gesting that a ~ated flow of 25,000 cfs below Gold Creek will
have an average channel width of 404 ft. and a regulated flow
of 2.),825 cfs above Gold Creek will have an average width of
352 ft.
F~rther, small r~ductions in width are then made based upon the
local channel form at Gold Creek (Figure 9) which suggests a
rate of reduction' in width proportional to discharge ( •11 ).
12 -
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Table 2: Average width of the Susitna River as taken from 1962
photos and adjusted for average July flow conditions.
-. I 't'iidt~ _..-:_:._-._,-er .. i
mile on 1962
location photos
91 520 ft.
92 560 ..
93 415 ..
94 615 II
95 675 ..
96 415 It
97 625 II
98 520 It
99 515 tt
100 630 ...
101 620 "
102 270 ..
103 370 It
104 590 II
105 470 "
106 830 ..
107 .. 610 .,.
108 600 II
109 720 ••
110 720 II
111 370 ..
112 730 ..
113 360 ..
114 415 II
115 790 ..
116 825 II
117 615 ..
118 480 "
119 410 ..
I . , • i-d .. .._, I' R • iLIQ,UC"' .:'l. .. ,,~n,_,n~~ . ,.,.p~
..( .... c) w >4 ,., ''* --'-.1. t """"" ... ~-'of .......
l_,,~-4+-h II"'"'-"""" '.,J.i.,
I .. AdJusted . '' ' wl.:::i:tns
Gold Creek to mile on 1962 Devil's Canyon
river mile 91 locatior photos to Gold Creek
404 ft. 120 420 ft. 417 ft.
543 .. 121 480 II 47?
403 " 122 620 " 6 )
624 II 123 800 It 793 "
685 " 124 630 ,, 634 ..
422 .. 125 415 .. 420 II
636 If 126 820 II 829 "
527 •• 127 520 II 526 If
523 " 128 420 " 425 If
639 II 129 520 " 526 II
629 .. 130 310 II 314 "
269 It 131 300 " 304 II
369 II 132 400 " 405 "
588 " 133 210 tl 213 "
469 ..
828 "
608 It Streamflows varied by very
considarable amounts during
598 II the sev.eral days of photo-
718 .. graphy ;Ysed. This was
account''d for. The average
718 II July discharges used werea
369 •• Devil's Canyon to Gold Creek:
23,825 cfs; Gold Creek to
728 It river mile 91: 25,000.
359 ••
414 II •'
788 tt
823 " ,,
613 II
479 "
409 •• '
565 ft. average width
lJ
49J ft. ave.
width
The 404 ft. width is reduced to 380 ft. for 14,800 cfs and the
ft. width is reduced to 123 ...
Estimates of widths are thusa
Devil's Canyon to
Gold Creek
Gold Creek to
River mile 91
un-reg. July flow
493 ft.
565 ft.
Resultant stream areas for the test sections:
reg, July flow
328 ft.
380 ft.
Devil's Canyon to
Gold Creek
un-reg. Julx flow reg. July flow
Gold Creek to
River mile 91
Eguilibrium Temperature Calculation:
:39,100,000 25,990,000
8J,400,000 56,100,000
E = dewpoint temperature 1 Gross solar r~d., BTU's per day
Gross solar radiation in BTU's/ft2/day-an average July value
was taken from the solar radiation tables for Palmer, Alaska,
published by the University of Alaska (Branton, et. al., 1972).
They indicate 390 Lys/day = 1440 BTU's/ft2/day.
Dewpoint temperature: The 7/18/74 condition where a dewpoint
of 46°F was used has also been taken here.
K, the heat exchange coefficient, gives the net rate at which
heat is lost or gained by a body of water for a unit temperature
difference. In these determinations 85 BTU's/ft 2/day/°F has
been used, assuming a wind speed of about 5 mph and an equilibrium
temperature of about 60°F. This value is derived from tabular
data in Edinger and Geyer (1965).
14
·-
)
--~
E, Eguilibrium Temperature, thus = 46°F f 1440/85 = 61°F.
a range of assumed values have been used (50-60°F) and are
tabulated with respective generated temperatures {T 2 ) for the
lower ends of the test sections.
The assumed values shown above have been used in the Edinger-
Geyer equation described in {2) above. These calculations are
not shown, but generate the following values:
Temp. T~ lEst. of T,.. water temp at lower
at uppe end unreg~l~ted regulated
Devil•s Canyon .50°F 0 .50.3 F 50.4°F
to Gold Creek 52 .52.2 .52.3
.54 .54.1 .54.3
.56 .56.1 .56.2
58 58.1 .58.1
60 6o.o 6o.o
Gold Creek 50 50.5 50.6
to river mile 91 52 52.5 52.5
54 54.3 54.4
.56 56.2 56.3
58 58.2 58.2
60 60,1 60.1
5. Water temperatures below the Susitna-Chulitna-Talkeetna
confluence can be estimated from respective river temperatures
above the confluence and their volumes of flow.
15
end
T = T ( Susitna flow } T (Chulitna flow)
mixed Susitna combined flow /Chulitna combined flow
Calculations have been made for combined temperatures on 15 June,
15 July, and 1 September, because these times appear to define
points in the temperature curve best.
a.
b.
Before regulations
June 15 , T _ 9 4(28,000) 1 B 0(22,200) 1 9 O{ l~1 10C} -• o),OOO r • 5),000 r • b),OOO
July 15: T 13 6(24,6.Q.O) I 8 7(26,400) Ill 0~0,600} -• 61, b'Oo • 61, 6oo r • 1, 6oo
S t 1 T = 9 6(§6,400} 1 6 l(~4,200} 1 8 6(1~,100) ep • · 1 • 8,000 r • 8,000 r • 8,000
After regulation: _y
= B. 8°c
=11. o6°c
= B.5°C
June 15: T - 9 5(1~,700) J 8 0(22,200} I 9 0(12,100) = 8 67oC -• 4 ,700 r • 48,700 r • 48,700 •
July 15: T = lJ.?(~i:~gg} I a.z<~f:~gg) I 11.o(~~~~gg} = 10,53°c
29,200) 16 (]4,500) 1 6(17,100) 40 Sept. l: T = 9.7(80,800 r •1 SO,BOO r a. 80,800 = 7.9 C
6. Summary: The preceeding work indicates that the Susitna
above Talkeetna will produce only small rates of temperature
change because it is such a large and fast-moving river. Loss
of suspended sediment will influence heating and cooling of the
river and its bottom as discussed. This influence, particularly
as it will relate to the river water, is thought to be small. lk
Alteration of the flow regime will not influence summer temperature ...JI!"
as much as might be expected because as summer discharge is
v r l!.."j v l d gJ -i:; ..-..., f..ll,rcd-Uf'" e_ Covf Cc.J (cd-, 0.., .f ~~ CA.. S S u ~ V ~"y
~,_,._,_J( c...IA~7L.f .._:...,_ 5.....,.,·,-h.,c... Q\~Jtr -i::~<4.r~O.rll..5',
16
>---
1-
---~
.d
decreased (favoring increased temperatures), the width/ depth
ratio is also decreased (reducing surface area and therefore
acting t.:> reduce heating). Increased late F'all and Winter
discharges, still with the reduced width/depth ratio, will
conversely favor reduced rates of cooling'. Release of colder
water below the dam will increase summer heating rate in the
river• conversely, warmer waters during winter will produce higher
water cooling rates.
In summarizing possible effects of river regulation on downstream
temperature conditions, the temperature of waters discharged
below the dam as well as the winter temperature regime have not
been included in this work, They were not considerations of the
original proposal. However, these two features will influence
some of the interactions which have been examined. To enhance
the usefulness of a summary, assumptions on released water
temperat.ures have been included in the matrix shown in Table :J.
In considering the effect of regulating the Susitna on water
temperatures downstream of the Chulitna-Talkeetna confluence, the
size of the regulated flow as compared to that of the tributary
rivers plays a key role, · Calculations shown in A-5 illustrate
this relationship. In this fashion, it can be shown that the
warmer winter flows of the regulated Susitna may dominate the
river for some distance downstream because the regulated winter
flows are much larger than those of the tributary rivers. Similarly,
the somewhat depressed temperatures of the regulated Susitna during
summer months will exert reduced influence on the downstream
_ temperatures because the regulated summer flows are reduced,
17
Table J: Matrix of factors summarizing the regulated stream
temperature regime in the Susitna River between Devil's
Canyon dam and Talkeetn~. The temneratures sho\vn for
T.'.~~ Su~_i +V'\.~ .; .... ~:nprl.l .. :1'+o1 ~/ '~'"''t.JY'-t"'·""a'Y'Y,-e.,.....f'":"'Yl ~1-~P G;~,..,, Y"P • __ _ ... _ ... ~ .. ,. ~·-< -~ ... -..1.._ ,j_,J ,._.._-, • "' .••• -'-L .,..,;, ~.. •• , • -...... a'" _
assumed.
Nov -May 1 May-15 June 15 June-15 Sept 15 Sept-1 Nov
Temperature
of stream-
flows re-
leased below
Devilts Can-
yon dam.
J4-40°F
(similar to
unreg regime~
40-55°F
(-2 to 6°F)
50-J6°F
(reduced rate
of change)
--L._ ----------~------------._------------------------------~-------------1
Summary of influences on the stream temperature regime ~
produced by other changes in the river following reg.
Change of
channel
width/
depth
ratio.
width/depth
reduction;
reduced
cooling
rate.
Change of increase in
streamflow~~ flow re-
discharged duce rate
with reg-of river
ulation of cooling
river.
Change of
suspended
sediment
concentra-
tion below
dam.
no
sediment
naturally
Expected Much incr.
temperature in cooling
conditions rate i~~ed.
in Susitna below dam
above due to 2-4°F
Talkeetna. increment
above freez;
more open
chan. thinner
ice; earlier
hl"IP!:~lr-11T\
width/depth
reduction;
reduced rate
of temp.
change.
relative
reduction
in flow
favors
stream
heating.
reduced sed-
iment con-
centration
means more
bottom heat-
ing; less
diurnal fluct.
transitional;
little change
in river temp.
warmer str.
margins; less
diurnal fluct.
width/depth
reduction;
reduced rate
of heating.
reduced flow
favor
heating.
reduced sedi-
ment; possibly
small reduction
in heating;
more bottom
heating; less
diurnal fluct.
cooler; 2-6°F
smaller
diurnal
fluctiation.
width/depth
reduction;
reduce rate
of cooling.
not much
change from
natural
flow. No
impact.
--"-··
.~
I --"-
k... ... reduced sedi-
ment; possibl r ~"'""
small reduc-
tion in sur-
face water
heating.
transitignal,
from 2-4 F
cooler at
15 §ept. to
2-4 F. warmer
1 Nov. delay
of ice
formation.
lLL
L_·
B. Stream Velocity
This s'9ction. is to describe and evalua.te Susitna River velocities
anj related streamflows under natural and regulated conditions,
respectively. Portions are also used in other sections, con-
versely, this section used information discussed further in
later sections. USGS records, both published and unpublished
(stream discharge measurement data) from their Anchorage sub-
district office have been used. Printout sheets received from
the u.s. Army Corps Engineers showing monthly regulated and un-
. regulated flows below Devil's Canyon dam were alsp used.
1. The annual hydrographs under present and tinder regulated
flow conditions are shown in Figure 5 for the Gold Creek station.
The annual hydrographs, natural and regulated for flows below
Talkeetna are shown in Figure 6.
These serve to describe the general flow regime, natural and
regulated. Change in hydrograph together with major alteration
of the total sediment flow downriver and changes in the pattern
of water temperatures released below the dam represent the
prime movers in altering the river regime below the dam.
From Figure 5 it is evident that the Susitna above the Chulitna
confluence will have a Fall-Winter regulated flow generally two
to five times the present normal pattern. To compensate for this
October through April increase in regulated flow, the high run-
off months, May through August will have .flows reduced by as
much as half {June).
19
I
r
i
3(),ooo
.eo .. ooo
OISCHA RG.C
-c:f.s-
lqooo
(sus lTNA ·-~~~.~-~~-:.~.: .. ~.·.~~-•. ~~~-~-~:9.~~ .... ·~ -"..... < ....,.,. .......
~·
,.··· ..
~tl' \
\
\~\+-SUS IT NA A'T GOI...P ct.
\~ · CHUL(TNA
SKWt:NTtdA
TALKEETI\IA
OC..I' NOV OEC JAN Fl:B MAR. APRJL MAY JUNe JULY AuG SEPT.
FfGUR.E 5 ! ANRUAL HYORObRA'PHS O'F FOUR.. SUS lTNA Rtt'E'RS
~ I ~ I 'JI I ..
60,000
s~~
"'400D
{)ISCHARG..&.
-c...fs-
3Q..Ot:~o
2Q.OOO
/0;000
NA11JRAL FLO\AJ..-....-.1
•. Rt:'-ULA:TED fl..O\V\ / ' ' : .. . ~ . . ,_ . : . ' . ...... -.................. ·····. .. . ...... . ····-·········-·· '
, ...... ... ..... .. .. -....... , ·' . .... · \ . . . . • • • . . • I .. . .
! . . . . . . .
OCT NOV DEC JAN FEB /'fAR· APRIL MAY JUNE. vULY Al.IG sen:
FIGIJ~E' : ANNUAL HYDRO~RAPII OF SUS ITNA BELOW IALl<EeTIYA
J... . l L __....i.. .
' !!';'
.l
Values of Figure 5 for the Susitna, and those used for Figure 6
~-re made with the assumptLJn of the Denali stora.ge dam also in
operation on the river. With this degree of regulation it appears
evident that water will often pass over the spillway from June
through August and probably into September as well, Construction
of the Watana-Vee dams would totally regulate the river eliminating
the spillage suggested in Figure 5. (From telephone conversation
on 8/8/74 with Mr. Gary Flightner, Hydrologist, u.s. Army Corps
Engineers).
2. Flow·duration curves for the Susitna family of rivers have
been developed and are shown in Figure 7. The duration curve for
the regulated Susitna at Gold Creek is also shown in Figure 7.
The ordinates of these curves were expressed in terms of percent
of average flow rather than in volume of flow, cfs. By doing
this, the curves are comparable in character.
The curves of natural flows suggest that the Susitna at Gold
Creek is somewhat less prone to higher flows than other Susitna
tributaries, The Talkeetna, by contrast, evidently experiences
larger peak flows more frequently.
The regulated Susitna is projected to maintain flows within
25% of average flow (9,843 cfs) about 80% of the time, These
average conditions do not, however, demonstrate conditions for
a particular year.
20
li1?
.·:iil
The monthly flows for August and September are particularly
examples inasmuch as this interval inclucles spa\ming
periods. The average Gold Creek flow for August is about 22,800
cfs; for September about 13,650 cfs. Regulated flows for
August and September will be about 16,260 and 12,130 cfs re-
spectively. In 1969 the August flow dropped to 8,879 cfs
and the September flow to 5,093 cfs. The former flow represented
about 39% of the present average for the month and the latter
22.3%. The Corps of Engineers' programmed estimate of what
average regulated flow would have been for August and September
of 1969 is approximately 6,224 cfs and 6,528 c.fs for the re-
spective months. The August regulated flow represents 38.3% of
average and the September flow 53.8%.
The record of unregulated flows at Gold Creek compared with the
projected regulated flows indicates the following occurrence
of flows. less than 9,000 cfs over the 24 years of record:
No, of years having monthly average( 9,000 cfs
August September ·
Unregulated flow 1 5
[Regulated flow 2 9·
It appears that regulation of flows will increase the occurrence
of low streamflow conditions during late summer periods. Further,
-ill· more comprehensive examination of size and frequency of late
summer low flows is warranted.
21
f:LOWS AS A '7o
OF
I~
?;. OF TIME fNO\CATED FLO\AJ.S E:QVALLED OR E.XC:.E~P~"D
i
\
i
\
\
\
\
\
\
\
\
\
\'.
\,_
\
\
\ •,
\~
60%
-......... ..
t=l"URE: 7 : FLOw DLiltATION C:\JR.\/ES 'F02. F"OlJ"R. SUS ITMA RlV~
-I"''
-f""-,
It __
~~-
, __
J. The distribution of flow velocities within three measurement
s~ctio-:1s <::::1ken on the Susitn:a ,,t Gold Creek are siH)Wn in the
isometric diagrams of Figure 8, These diagrams suggest the mag-
nitude and the distribution of velocities within narrower channel
reaches. The three discharges selected for examination represent
11 low • intermediate and high discharge conditions at the Gold
Creek station. Only the lowest dischargemeasurement indicates
any significant cross-sectional area with velocities suitable
for resident fish. While velocities at other river sections
"""'
above Talkeetna may not beas severe as the Gold Creek station,
i
I
I ·,":_)
the indication is that their velocities, too, are limiting to
resident fish.
4. Observation of surface velocity conditions were made at
four points along the Susitna River. River perimeter material
was photographed at nine locations and also suggests the high
range of. stream velocities to be expected.
Drift velocity was measured about 75 feet out from the river's
east bank. These measurements are summarized in Table 4 below:
Table 4:· Surface velocities measured at four stations about
75 feet of the east bank.
River mile Date Surface velocity Flow at Average flow vel-
location feet per second Gold Creek ocity at Gold Creek
76! 7/21/74 2.8 fps 20,)20 6.5 fps
82! t?/21/74 6.5 20,320 6.5
90t ?/20/74 5.1-5.7 19,900 6.4
109! ~/18/74 5.7-8.5 17,)00 5.9
22
Photographs of river perimeter material at nine locations on
t he r i v9r :1re s'1-:::n:a.riz2d in Table 4. Photos are inc luded in
the appendix materia l with the exception of the stream perimeter
at Gold Creek which is shown in Plate 1.
•
Plate 1
Stream perimeter material on Susitna River at Gold Creek.
2)
Table 5 Summary of photos of Susitna perimeter material,
Photo
Plate
Number
A-.l
A-2..
A-3
A-'(
A-5"
A-7
A-'
A-tD
A-13
A-1 5"
A-1(.
A-17
Pla..+e_ 1
. f\-zz.
A--:zo
A-z.q
and of tributary streambed material suggesting
maxirnum flow velocitie~ of the river or of resnective
tr lbiJ.t"]!' ies.
River
Mile
Location
96i
96~
99 1/3
99 1/3
119
12'1
121
13lt
Description
Stream
material
size range
Suggested
limit of flow
velocities *
Susitna near Birch 2-3 inches 8,2-8.8 fps
Creek.
Flood-flow depository 2-4 inches 8.2-10.5 fps
on beaver dam
Susitna above Billion 1-4 inches 5.2-10.5 fps
slough
Susitna near Chase
Susitna above tributary
Glacial till--derived
streambed rubble in
tributary
Lane Creek
2-6 inches
2-3 inches
12 t inches
8, 2-12 fps
6.9-8.8 fps
16.4 t fps
Susitna above Lane Cr. 3-4 inches 8.8-10.5 fps
McKenzie Creek
Susitna above McKenzie 3-5 inches 8.8-11.5 fps
Cr.
Portage Creek
Susitna near Curry 3-6 inches 8.8-12 fps
angular
Susitna at Gold Creek 6-12 inches 12•16.4 fps
angular
Indian River
Susitna below Indian R. 2-6 inches 8.2-12 fps
Portage River
* estimates of shearing velocities are adapted from Mamak, (1958).
24
The velocities suggested in Table 5 indicate the maximum range
of flow velocities fo~nd next to the stream bottom, In some
cases, however, the streambed also includes remnant material
that has seen little movement since the last glacial advance and
retreat. This is true in the tributary at river mile 92t
(Plate A-7, Photo Appendix). It is also true of the glacial
erratics seen in the Susitna channel between Chase and Lane Creek
(see Plate A-4, Photo Appendix).
The velocity and bedload observations provided here are very
limited. They appear, however, to provide a reasonable representa-
tion of conditions seen in the aerial photographs (above river
mile 91) and on the ground. There is little if any tendency of
the present unregulated Susitna to decrease in velocity between
Gold Creek and the Talkeetna-Chulitna confluence. The Susitna
above Gold Creek is somewhat faster than below Gold Creek.
5. River discharge-measurement information from the Gold Creek
station on the Susitna was used to develop regression curves
showing how average velocities, widths and depths at this site
vary with stream discharge. These curves; shown in Figure 9,
can be used with the annual hydrograph (Figure 5) to suggest the
range of channel conditions that presently occur during seasons
of the year. Used with the flow duration curves of Figure 7, an
appreciation can be developed for the percent of time specific
channel conditions are apt to occur. It is reasonable to expect
similar channel relations at numerous other of the more confined
25
. -
-.
~·.
11
9
8
7
11\\E
L. I"THM 4 2.3
2 X 3 CYCLIL.S ,_.o~.u: H4 u.S. I\. •
I<~UFF'EL a.. E8&E.R ca.
2 7 9 4 5 6 . 7 9 t -1 7 8 9 1
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-ll='~ _ --i~+--_ H-H:+H 4 Jjjl _ tl= _ -ltjl. !_·+l"'jjl
1
li. 1
-1--__ tr-0:-H+ .J.j l _. 1· _ ~-~ + ·11\t,., :~·~---~ .~-~m=r· -1-i-,#-#h: ~ . +l!·:· f·~'Li lit_·, ~~:iH _•_t I_· ;_ I+J f 1 ~1 ____ .j--i-(·ltil'! _ --1-!• ·L~ +I lJ ---!-J-i!'l i--tiiJJ.LH ,,:::, t I I I r I i ljj 11
I r fit' ' I l --. !_ i-l--i --!. : 1 n . I _11 1 . L ___ ' -]J Lr I !L I : -i-'-~u}:J iJJ, .::: , =t++ -++ H1 titr M Mrr,, i f Tnt rffi m! Ml1 ~,]~ --r-c-ntlHffi ® ~~ , H 1# lt ~~k ---, Iff+ ittf HHA !i , . H Hi 1t11 :1 iHt' ::,,
looo C..f.r 3 4 5 6 7 8 9 1.Cl ooo c:....f,. 2 3 4 5 6 7 8 9 1c:>o...ood c..Cs 2 3 5 6 7 s 9 l
-' 1/dlcJme c.f Sus•+na.. R,:~e.,-~IDINJ ,_-{: Gt:lld C,-~1<;..
FIGUR..E .!}: DEPENDANCE OF WIDTH. DEPTH, .AND VEI..OGtTY C.dl\lOJTIONS OF TNE :;> •
SVSIJNA AT ~t'.Jlll t:R.EFr Ttl VAQ/~Cl Li;?VJ::LS DF DHr.I-IAR..t:.l!!
channel situations between Talkeetna and Devil's Ca11yon. The
r::l~ tions~ips of Figuce 9 are not recorn...i.'":"lended for us~? in pr~viding
approximations of the relations between ~· width, y_, velocity and
regulated discharge. As discussed further in Section D, the river
under a regulated regime will form new channel relationships with
discharge. In particular, the width relation is apt to be much
altered; this in turn will be a factor in changing velocity
conditions.
6. Reduction of flows of specific recurrence interval will
affect velocity conditions. For example, if the two-year return
peak flow (Q2 } of the Susitna River at Gold Creek is reduced from
the present value of 49,300 cfs, to 25,000 cfs,1 what would be the
average velocity for the regulated Q2 ?
Applying the velocity curve of Figure 9 indicates an average of
10.5 fps for the natural Q2 , 49,300 cfs.; again, applying the
regression to the regulated Q2 of 25,000 indicates 7.2 fps. But
the channel will be altered by imposition of the regulated flow
regime.
Adaption of a relation developed by Leopold and Maddock (1953}
to this situation suggests that velocity will be altered according
to the 1/10 power of comparable (same return interval) discharges
for the two regimes.
1 This appears in Figure 7 to be a reasonable figure, but lacking
sufficient data is not the result of rigorous analysis,
26
Thus, bankful velocit~ for Q2 , natural
bankful velocity for Q2 , regulated
Bankful vt:lloc i ty for Q2 natural of
Gold Creek = 10.5 fps.
sr 1
t natural = g•1 , regulated
Susitna at
Hence, regulated bankful v.elocity = }.0.5(25,000)·~ {49 ,300)"
= 9.8 fps
which is 9. 8 -7. 2 = 2. 6 fps greater than the velocity pro.jected
ft>r 25,000 cfs under the present flow regime.
7. The effect of loss of suspended sediment on velocities of
the Susitna is also of interest. The hydrologist Schoklitsch is
-,, reported by Jarocki ( 1957) to have investigated this problem,
concludhlg
"that in the case of intensive sediment
transportation, water velocity determined
by means of empirical formulas should be
reduced 15-20 percent and· in the case of
big rivers (like the Danube or Rhine) even
to 30 percent."
Vanoni and Brooks (1957) have shown that
"muddy water has less resistance to flow
than clear water and that the muddier the
water (within reason) the less the resis-
tance.•
Their explanation is that
"sediment particles dampen turbulence,
hence the more particles of sediment,
the less turbulence; hence the less resis-
tance to flow."
This reduction in turbulence and resistance is evidently a result o+
· .. increase in viscosity and would be particularly evident in
27
streams with moderate to heavy loads of fine sediments. There
is probably so!:le reduction in turbulence in the Susitna during
summer months as a result of its present sediment load, and
conversely, some increase in turbulence of flow with the loss
of suspended sediment by regulation,
B. Summary: Regulation will produce major changes of the river
hydrograph above Talkeetna and very significant alteration of the
river hydrograph below the Chulitna-Talkeetna confluence.
Flow duration pattern will be much evened out by regulation.
However, regulation will evidently increase the occurence of low-
flow events during late summer. This relation should be examined
further.
Presently the river's velocities above Talkeetna appear too high
for resident fishes in the mainstream. Reduction of summer high
flows will reduce flow velocities more slowly than the rate
presently indicated by discharge measurements at Gold Creek.
Little improvement in habitat should be expected due to reduction
in velocity in the river. Some improvement in habitat may occur
in river reaches with large erratic boulders, dur to the possi-
bility of increased turbulence and enlarged eddies.
28
-
-
-
-
-
-
-
-
-
-
-
c. Suspended Sediment
1. A suspended sediment rating curve supplied to me by the
u.s. Army Corps Engineers has been converted from tons/day
to parts per million and is shown as Figure 10, This conversion
was made because fish are probably more interested in the quality
of the water than the rate the reservoir fills with sediment.
It can readily be seen from studying Figures Sand 10 together,.
that during six months of the year (November to May) the river
carries about S ppmor less suspended sediment while the river
in October carries around 25 ppm and in September and May around
150 ppm. These are generalized values but they suggest present
suspended sediment conditions in the river.
2. The size class distribution of suspended sediment in the
Susitna at Gold Creek is displayed in Figure 11. Chulitna and
Talkeetna suspended sediment size classes are also suggested by
values summari~ed and averaged.
It may assist the reader in studying these curves to recognize
that steepness of curve between two sediment size classes is in
proportion to the volume of material contained between those classes.
'~ A straight-line sloped curve would suggest equal distribution
of size classes• concavity suggests a preponderance of larger
particles; convex form suggests a majority of finer particles.
The iusitna load is fairly well distributed in size-classes.
except for the heavier flows that tend to produce larger pro-
29
AGURE Jo: VAR.lATIOU OP SVS rr"->A SUS'PfHVPe"P setHkl:Vl
COtvGe'I\JTP.I'"tt~ W IT't"t PI.JCHA R.c;.t; .' DATA
10 PP""'
TA""&-IV AT c:;;.C)LD CR..e"f:::l::. S"T'ATIOI\J.
(T\-4 r:!S!d C..V~\Jt!!s A,Z,.~ AOA?IE?"D p0t()M
su.speuoe-o se=-c>•t-tt::ot"'. ~AT1~"-cuave,-
PR.l>V&o•o TO M&' '8"( \). $'. AIZ.kV G,APs-
cct-.> &,tOE'S R. s)
..
' •• 1 -
fAn... topoe~ Ar
-
(
-
-
't--;·
-
-
-
-
-
-
-
.. ;j
portions of fine to medium sands, This increase in sands probably
~omes p3.rticularly from sedimants pick2d uo ""rom th(~ strea-:n
channel on higher flows.
While too much should not be ma~e of the Chulitna and Talkeetna
curves due to the averaging technique of summarizing, their
results are interesting. The Chulitna curve suggests rather even
I
distribution of sediment size classes with somewhat heavier pro-
portions of medium to coarse sands. The Talkeetna curve suggests
a somewhat low proportion of fine silts and clay with greater
amounts of larger silts and fine sands.
If the regulation of the Susitna produces deposition in the
Chulitna in and above its connuence with the Susitna (discussed
in Section D), the suspended sand fraction may be reduced.
The Susitna clay-size fraction is apt to pass through the reservoir
system. The Susitna values shown in Figure 10 suggest that 10-20 ~
of total May-October load as shown in Figure 9 may pass downstream
after regulation. I presume this has been investigated by or for
the Corps of Engineers. The data were not available to me.
D. Change in Middle Susitna River's Form •
1. The Susitna valley was a major route of ice-flow to the sea
15,000 years ago. Recession of the ice left many forms and -
deposits now seen in the valley, Between Talkeetna and Devil's
Canyon I saw occasional streamside banks of blue-glacial-till,
dense deposits (Plate 2) with a full range of particle sizes
30
-~:
-~tl
-I'< '-
-
--{;;';;:}
-lit:,;_
-
--' ~~J
I
I.
I
I
from much silt {and a little clay fraction ? ) t_o large boulders.
With these prominent bank deposits of t ill , large glacial boulders
are evident in the stream channels . (Plate A-4 , Photo Appendix)
increasing gradient and turbulence.
' . ~
·," r ~ ........ ,... -~
~t--~~'f.~.,~~~~~ ._.·~,·~ .. I -.~: ,•'; '-< • .>.?,;,~ .,. ;~ <~--4_ . " # :',_:., ....,_ ~j( ,_ :~~[~j
-~:::<~~ .···~-. 't:~:::-... "~' .~ .-.;;,;..-.. --~·,. i' ~-.:=~~~ .. ~~~
:. '~ ;-~.. -.....,. ~ • ~, .. 7!:,,..,:;·· -;. . -_-_,:~~~~~~
Plate 2 :. Glacial til:)..-slope along
the R.R. at river mile 99!.
,_
Abundant coarse-textured
{up to cobbles and pebbles)
deposits found along the
stream have also been labeled
glacial till material in
Soil Survey, Susitna Valley
Area~ Alaska, (Schoephorster
and Hinton, 197)). In the
streamside typing done for
this work I have grouped
these deposits in with. alluvial
deposits because I saw n~
difference--at least as these
deposits would influence the
stream,
The de-glacial and post glacial periods left terraces marking
_climatic stops along the river valley's road to the pr~sent
{see Wolman and Leopold, 1957). The land behind Sherman (Plate 3)
offers an example of terrace deposits. Other more recent 'terraces
are notable and have been indicated in the river map (Figure 12).
)1
The form and the behavior of the river is of course closely
tied to the character of its perim~ter lands. The valley 'above
Chase as far as Indi~n River is not part~cularly symmetrical.
The glacially scoured rock spur separating the lower Chulitna
from the Susitna is relatively low and not as active a bedload
)2
1
.I
1
I
r
producer as the east side of the river. Tributaries falling
steeply from the Talkeetna Mount::!.ins, for exampl9, Gold, Sherman.
Curry, .Portage, l'JlcKenzie Creeks carry heavy bedloadsJ not infre-
quently in torrent flows. The bedload material is large and
-generally angular in size as seen in the respective plates (see
Photo Appendix). Downstream from these steep tributaries a blue-
till-rich ~ector o.f the stream occurs from about Lane (river -. .
mile 97) to Chase (river mile 92)r than a transitional sector
between Chase and river mile 86 where the extensive alluvial
flood plains and terraces begin to dominate.
2. Features of the river as seen on the aerial photos and in
some locations as measured on the ground have been summarized
in Table 6.
The Susitna between Talkeetna and Devil's Canyon is generally
confined and is strongly braided only near the Chulitna confluence
(Plates.4, 5, & 6). It exhibits a moderately sinuous to braided
pattern and though it undoubtedly has the cross-over bars, riffles
and pools commonly found on alluvial rivers, these are not recog-
nizable on the aerial photographs because of the silt load.
Measurements of these features of stream form have not been made
for the Susitna. The photo widths shown in Table 6 are for the
main flow of the river. In some cases the existing river
channel includes areas that are covered by higher flows but not
by in-termediate or lower flows. The photo widths do not include
these areas where they occur.
JJ
Plate 4:
Highly braided
Susitn a River
"oelo•N c>Jnflue_:tce
o:f the Cb ul i cna.
and Talkeetna
Rivers·.
Plate 6 :
Downstream view
of Susitna River
valley with
Sherman Creek
in left f oreground.
Plate S:
Susitna River
valley viewed
upstream from
river mile 107 .
"
Table 6& Widths, gradients, velocities and shoreline types as
near
Chas
River
miles
above
mouth
76i
82i
90i
~ 91
92
•. ,, 93 belo
Lane
94
95
96
97
98
99
100
101
102
curry 103
104
105
106
... 107
108
109
109!
.seen on Talkeetna Mountains photography of the Susltna
above Talkeetna. Ph·otography made at several dates
dur-ir_g summert 1962. Widths fro:n air nhotos; grades
measured, July~l974, along water surfaces of east bank,
drift velocities off east bankr shore types as described
in D-2.
Flow -cfs Photo Flow -cfs Energy Surface Shore
on date of width·, on date of gradient velocity types*
photo--feet gradient, 75 ft.
graphy vel., obs. offshore
no photo. --20,)20 .0014 2.8 fps T-T
11 II --20,)20 .ooo8 6.5 T-T
•• " --19,900 .0022 p.l-5.7 T-T
)2,700 520 ft T-T .. 560 •• T-G
•• 415 " T-G
23,000 615 II T-G
" 675 .. T-G .. 415 It T-T .. 625 " R-R
,Jt 520 .. T-R
" 515 " R-T
" 630 .. R-R
" 620 .. T-R
25,900 270 f X T-R
" 370 ft. 18,820 .0003 --R-F .. 590 •• R-T
u 470 " R·T .. 830 .. R-T .. 610 .. R-T .. 6oo I R-T
•• 720 ft. R-T
II 17,300 .0020-.0023 5.8-8.5
( c·ontinued) '
)4
Sherm ar:
Gold C r.
Indian
Portag
River
R.
e
I
!
:
River·. Flow -cfs Photo Flow -cfs Energy surface miles on date of width, on date of gradient velocity
ab~~e 1 photogr~phy -feet gradient, 7 5 ft,
i 1 v-eL, obs, f " ' 1:10u ... h o_Is.nore
1
110 2.5,900 720 ft.
111 •• 370 ..
112 .. 730 ..
113 .. 360 .. .
114 " 41.5 tl
115 •• 790 ••
116 " 825 "
117 " 61.5 ..
118 .. 480 II
119 .. 410 " 17,200 .0019 8-10
120 •• 420 ••
121 II 480 u 17,200 .0011 --
122 " 620 tl
123 .. 800 ..
124 23,000 6)0 II
12.5 .. 415 "
126 " 820 tl
127 ,, 520 ..
128 " 420 "
129 " 520 ..
1)0 " 310 It about
131 .. JOO .. .OOJ
from
132 " 400 " APA
133 .. 210 .. Report
* First letter refers to right shore facing downstream,
Second letter refers to left shore.
•
35
Shore
types
T-R
R-T
R-T
F-F
T-R
T-R
T-T
T-T
R-T
R-F
T-T
F-R
T-R
T-R
G-T
G-T
A-T
A-F
A-R
G-T
R-R
R-R
R-R
R-R
I
..
...
-
~
"'" ]
-IL
--·---,-~
--::m.
-··~
Photo overlays have been made for features of the Susitna River
between Talkeetna and Devil's Canyon as shown on the Talkeetna
i'.Iounta.ins photo flight. These overlays have been joined in tu
flight lines and are shown as Figures 12 a, b, and c.
The classification and nomenclature used on these maps is as
follows a
Shoreline characteristics adjacent to rivera
R = bedrock, predominantly shale, schists, graywackes.
T = river-built terrace or flood-plain deposits.
Commonly includes coarse gravels and cobbles under
a variable thickness of silts and sands.
A = alluvium, colluvium, or coarse clean glacial till.
This material.was not deposited by rivex-action.
F = alluvial fans, commonly steep in stream gradient and
built of coarse materials.
G = compacted glacial till with boulders and fine
materials intermixed.
Channel and river characteristics:
bo = boulders in chahnel, generally indicating increase
in gradient and turbulence.
~ ~ = fast water, often standing waves.
• channel areas that the flows of the regulated
river will not commonly flood.
s = springflows into the river itself or into small
tributaries near to the river and in the valley
bottom.
Some of these terms·need·additional description as to asso-
ciated features:
)6
B. slopes to the river are often steep, yielding rotten
rock to the streambed; they do not yield springtlows
l . h . h . . . . ,.. ' j , 1 "1 ., . .... a~~~~ug. ~ne mea~1ng O! oerroc~ an~ I_ood pLaln or ~arraee
deposits often shows ponded areas.
T,A,F -springflows are often found where fans, terraces
or flood plain meets the mainstream or its flood channel.
G is associated with boulders in the channels of the tri-
butaries or the mainstream (see Plates A-4, A-7, Photo
Appendix); does not produce springflows, is a likely sedi-
ment source.
~~ -these flood channel areas will generally be abandoned
by the river when it is regulated. Such interpretations that
were made are in most cases fairly obvious on the photo-
graphs and, I think, are conservative (may underestimate)
in identifying the area o.f channel reduction.
). In the past when the Susitna River has received less water
and/or sediment load, l.t has cut down to a new grade of balance
leaving terrace formations. In this section we will investigate
the extent to which a similar reaction will result from regulation ·
of the Susitna at Devil's Canyon.
When the unregulated river experiences reduction of total flows
of water and sediment, large peak flows still occur. When the
river adjusts to reduced flows by degrading, it is because the
load carrying ability of the river, particularly on higher flows,
is (a} greater than the load supplied to the river, and (b) the
velocities are sufficient allowing for the load being carried
to ~ move and scour out in-place streambed materials.
With regulation of the Susitna•s flows most of the suspended and
all of the bedload sediments carried by the river through Devil's
Canyon will be eliminated. But at the same time the·peak flows
J7
' \. I ~-', . '?-
RMIZ.~ .l/ £"~o· \ \
I I
I
-----~:
\
\
\ '
G
\
/
\
,.J,
I , '
I
--.-.4---
,A ---\ G
G A / J,
7-5 -'62
7-5-62
7-5-'b'L
7' 5 -E2
'-5 -'6Z
25~ 90u r:_-f5 TAK 8 183
A
r:
~
,C"">:, ')()() (_ I \ T \" f~k ~ 181
4>;" ' ••• \ IT j i
,1," •. ~ _I .·1 I \ , ;/ I J
,>'\ ~ ... I ;· ~
··/ ~ \ ~ j 1/..r-.,-o.,_~.. '0 ', + ) 82;-
1 I
r. /rr\:l T
' i,lf}· ~-
T \ \'T·\\'
I ;\\ I k 'if,~~~.~~y-. .,,1''
T I//
~ I / ___ ___, A "
~1 V/i 1,
~/j
T --.:V_; ol ,, ;~--
/i''f .V h
/fc! r1
\; 11
·~-----.,J-1,,:"_:)
ft?t<,,,j~ ~ R_
-~-~-.-/ I ~t F~t --~ J . \-~----~,
f"/\ '
I I //\
I _I .y / ' I : / t
'',, ~'" t:0_ .. ·. . I T ;
1: --~~~/-" J ,,
2 5. 90(_) L --{_J
( 7 __ , .~:~: ___ \1
\ \ ~ .. ,.L~'Y~ f!
\'-.J~\i \~~~I\ .'-..:!'~ ',
' I
i ;(I·
I J~'
I ~11io'1 -...j l.zo
~-~
~ \
0
f.l"\1010 i l
TAK 8 177
TAI-i-8 175
~~\ ~\
\ \ ·......-
\., s~ ~(15'"""\ I ~ \ ~t '-
\ \ II ' z,-,
00
c,CJ I '-._;I. , \ TAK 8 173
In~ . ~ , 11 \I ;_ ,
--. ~ ~ .. ··. ~--·.\ --~ .... ;~0 :') ~ \ ... ·. lr
I '~.:
:.t· "" 7'
.
'---,,
f:"" -'-~-:~~
l r -~·, :~':>· -I \;.
--··-..... ·· .. ···-..•... -. · ... -~ ····· ... ·-·~.
~l':'t.J(l'__ f2 b n "ur£. 11. "'--
.;_> .f '
e-;o
'02
{
-oo
0 c-:'t:..r
I I
I
I I
\(
\i,
\1
\ \,_
' t
1\' '; '"'+ 0::-., I ;
~,...ol ~-\><o'j If
/ \\
1
:1
<\'•
'1'-,.
'oo
I? ?',: f
~]'
-ooo
?;;}'
'I • .9
f?
C'~
~'11(
..9 ~
1'1t ~
<l-os
(
/ .-.
•J' r···\,
,:<~t'. I '.N\J \ 7-1-'6'2. .~· \ \~
32,700 c.-fs
~ ~G
G\" \I'
\ '
~~ _/\:_ .. ·._··.
n\ j < G 'l7 \ __ , - \
~ \ ;~ <-
~~\, ... ,~' ~<"' '\
'I\
~ ~ , , , 1-G2 "\ 'l-\ \ ~ '
, ~-G
3• 'f I
' ·,~ ' ""~"'" ': / ·-·
' ', ~ -""''· "'
,,
I
II ., (J \1 G
I ~ -rj ("'.~C
1-1 1 -~oi , . \/"+·u/r'.
;· ,'c~ T
~
T
'T
T -' -1-
'\ 1
1
::32,100 c...-f5.
commonly experienced below the dam are likely to be greatly
reduced. These two alterations act in opp~site directions with
regard to river channel degradation.
The character of relevant information on the Susitna River
relating to the degradation process is outlined below:
a) Flow; the two-year return period peak flow provides an
estimate of discharge conditions that exercise control over the.
channel form at bankful stage. The Susitna River at Gold Creek
presently indicates a Q2 of 49,000 cfs.; the Q2 of the river
under regulation will depend to a large degree on how the dam.
system is managed and on the future of the Watana and Vee dams.
l·have selected 2),000 cfs for use here. This value may be
high and thus tend to underestimate the regulating effect due
to flow. The naturally occurring unregulated peak flows of
greater return interval also are likely to bear on the river's
ability to scour and degrade in that such flows probably have
established the "floor" particle .size in many portions of the
river channel. It should be borne in mind when reviewing the
velocity diagrams shown earlier in Figure 8 that the 65,200
cfs flow shown is not much larger than the Q5 flow of 63,400
cfs. and that the former flow is capable of scouring particles
up to about 4-6 inches in diameter (as estimated from tabular
data provided in Mamak, 1958). Similarly, the Q25 of 88,100
cfs suggests scouring ability up to particle sizes of 6-8 inches
diameter.
38
b) Sediment load in the mainstream at Devil's Canyon is to
y •• ~.:.' _;.{'"'.· ·O'•'l~ ... dze '"'.o+ 1-:-.... ,.o··.··~.. r'o~c-ure-Qt~ -ns ~ d-d lo~d-,· n ·t-he -1'v -·•_:. -'" " <:: -. 1J v "-"· ,•t ... n . .::. .:> '-.;;,._,,p~r'.· ·~ cl. ::; ~ ui l. 2i.
have been made (see Section C) but I have not found bedload esti-
mates. It is probably reasonable to assume that bedload is
one to two times as large as sediment load (s. A. Schumm, 196)).
The bedload fans at mouths of large tributaries such as Portage
River, Indian River or smaller streams such as "Jack Long" Creek,
Gold Creek, Sherman Creek, etc., indicate large sediment loads
which under the present flow regime are rapidly entrained
by the mainstream. The size material delivered to the main-
stream ranges from boulders, cobbles, pebbles and gravel to
particles that are sandsize and smaller. It is evident on the
ground that some streams deliver a significant part of their
load to the river through periodic torrent flows. Some estimation
of particle size is provided in Table 5 and in the Plates of
_,
the Photo Appendix. However, I do not have a basis for assigning ~·
a bedload rate or for estimating the fractional percents of bed-
load provided through the river at Devil's Canyon versus bedload
supplied by downstream tributaries. I have assumed in the tenta-
tive conclusions drawn below that a major part of the middle
Susitna River's total sediment load will be eliminated by the
Devil's Canyon dam.
c) Only one location between Gold Creek and Portage River
appears to have the possibility of a rock floored stream bottom.
That site is at river mile 130 just below the mouth of Portage
39
l.-
lt-..
~ ..
Ri ver. Rock occurs commonly along this 11 mile stretch of the
river {Plat~ 7) but becom~s r.losely. confining on both sides of the
riv~r only at this point ups~ream.
Plate 7: Metamorphic rocks (schiste, sha~es, graywackes} are
common along the shoreline above Indian River.
Below Gold Creek only a rock margined reach at river mile 99 .5
below McKenzie Creek approaches such a condition. This reach ,
however, is about twice as wide as the river mile lJO site.
I have used the information above in what I think is a reasonable
and intuitive manner to rea~h some conclusions regarding possible
d egrad ation following regulation of the Susitna. More rigorous
conclus ions may be possible (see Gessler, 1971) but it is
evident that sufficient data is not available at this time .
40
Conclusions Regarding Degradation&
?3.hl!3 7 summarizes porti.')ns of the river b'=tv1e~n river mil'C'! 91
and Devil's Canyon that are likely to resist degrading action.
I have assumed that narrow river sections such as Gold Creek
have a sufficiently coarse and armored bottom to resist Q.egra-
dation. The re-supply of coarse bedload to reaches near sizeable
tributary bedload sources will act to resist degradation. The
' river at or above mile lJO may be protected by bedrock under
its channel. Other portions of the river, particularly in river
miles 92-96, may contain sufficient remnant glacial boulders
in the channel to armor the channel and prevent or limit down-
cutting. For several miles above the confluence of the Chulitna
with the Susitna·no downcutting will be likely because the
sediment load of the Chulitna will act to establish a local
base level ~ot included in Table 7 summary). Even in river
locations where some dovmcutting is apt to occur it may be limited
by formation of an armor coat during the degradation process.
Livesey {1963) reports of ''the experience downstream of Ft.
Randall dam where 15 ft. of degradation were expected, but
already after 3.5 ft. the bed became stable",
Degradation will begin upstream and and work down. The early
downcutting will occur more rapidly than later in the process
because the action is asymptotic in nature. The river may assume
a more atopped longitudinal profile than presently with downcut
areas limited to respective wider sections between reaches,
narrow, armored, or otherwise protected.
41
~
F'
L·,
-
'_-:J
L
4. Possible changes in channel form -width, depth, gradient,
meander length• sinuo~ity -can be generally evaluated using
principles of fluvial morphology. The pertinent assumptions
made regarding the Susitna River have largely been stated in.
{J) above. In .brief they arez (a) decrease in peak flows,
(b) a major but undefin'ed decrease in total sediment load
below Devil's Canyon but with heavy bedload sediment loads
still supplied by tributaries, (c) confining rock channels
exist above river mile 130 and to some degree at river mile
99.5.
Basic to studies of alluvial river form is the concept of a valley
and a river having features that are interrelated in cause and
effect. Usually a.river•s flowJsediment loads,and to varying
degrees its bedrock and geologic features, are causative,
independent variables. Stream width, depth, gradient, meander
pattern, and sinuosity are important dependent variables that
interact to flow and lo.ad and with each other to produce a
river and its valley.
Blench (1969) working from the Indian canal regime concepts
·developed essentially empirical formulae for estimating width
(b), depth (d), gradient (S), and meander length (M:1 ). Inde-
pendent variables he used are described functionally as followsc
Fn, bed ,factor, increases in proportion to a stream bottom's
ability to resist shearing action1 also increases
with the rate of bedload passing through a stream
channel.
F9 , side factor, increases in proportion to the ability of
' sides of a stream to resist erosion.
42
·.Table 7a Locations on air photography betwee.n river miles 90
and 130, where river channel will resist or limit
downcutting.
Stable points on Channel .River Miles Cause of Stability
near and above Chase 90-93 Till boulder zone will act
to armor the channel
vicinity Curry Creek 10)
vicinity Sherman Creek 11)
vicinity Gold Creek 119
vicinity Indian River 121
below Portage River 1)0
43
Rock on west shore opposed
by large and coarse bedloads
from Curry Creek which pro-
bably is subject to torrent
flows. ·
Sherman Cr. carries large,
coarse bedload to the river,
sometimes by torrent flow.
Fourth of July Cr. on west
shore also carries consid-
erable bedload volume, though
not as coarse. These loads
will provide resistance
to scour.
Similar to Curry Creek, though
no bedrock is evident.
Rock on east shore opposed
by bedload from Indian River
though this bedload is
dominantly gravel and hence
susceptible to scouring.
Combination of coarse
bedload from Portage River,
plus possible bedrock floor
will limit or prevent down-
cutting.
p;r·· -
-----;4A,
---~
Q, bankful flow,
kf meand~r slo-pe correction coef., accounting for the degr.ee of
haad lo33 that may oe asso-
ciated with a flow pattern,
straight, braided, meandering,
etc. {not used below).
Blench's formulae are particularly canal oriented and may not be
suitable for acourage determinations on rivers like the Susitna.
However, a useful table derived from his work (1969) is shown
below. I have indicated the likely changes in independent
variables due to dam construction as well as the resultant
changes predicted in channel form.
Independent
Variable
Fb -reduced
Fs -no change
Q -reduced
k undetermined
Dependent Variables
b d s·
Thus, using Blench's approach a decrease in channel width and
meander length and little change in river depth or gradient
conditions are predicted.
Schumm, (19?1) working from a different perspective and with
a differing set of independent-dependent variables, provides a
similar summary of effects. His independent factors are g,
stream discharge (average or ban~f'ul); and gs, the bed material
load. Dependents are channel width, b, depth, d, n , meander
44
length, .§., gradient; J:, channel sinuosity, and f, the width/
depth •• ra ... ~o. The Susitna situation h·3 summa.r izes as below:
+ + p+~ Q ---b-, d-, -s-, F-. ' Qs ' -,
suggesting narrower channel, shorter meander length, greater
sinuosity, reduced b/d ratio. The reduced b/d ratio further·
indicates that depth will remain constant or increase. Increase
in sinuosity suggests that gradient will decrease.
5. The analysis of (4) above, is useful in indicating direction
of change. Schumm further points to additional work he indicates
will provide quantification for b, d, s, , P, F, (see Schumm
1971). This basis for quantification is built around .f!!, percent
silts and clays in the perimeter forming the stream channel, and ~~
gm, mean annual discharge. In the case of the Susitna, Qm is
a meaningless variable because mean annual discharge will remain
essentia.lly unchanged and thus does not provide· a description of
the effect of regulation of flow. N is probably not a meaningful
variable either because the percent silts and clays is apt to
be consistently very low.
The most useful quantitative relationships in the case of the
Susi tna appear to be those developed by Leopold and illaddock (195J),
whose regressions relate mean annual or bankful discharges to
width, depth, and velocity at respective stations along rivers.
Their work, as well as that done by others, shows very general
agreement that stream width for a given return-interval frequency
45
-~~
···~
of flow is proportional to the {discharge) 5 found at a location
pro purt ional
to about (discharge)·4 , and mean velocity to about (discharge)·1 •
While strictly speaking this work does not include a basis for
the comparison to be made for a situation as may occur on the
Susitna, it appears sufficiently broad in application to warrant
use.
width:
depths
at the present Q? (assumed bankful condition) of 49,)00
c.fs, width at Gold Creek is shown in the regression of
Figure 8 at about 435 ft. For the regulated Q2 flow
assumed at 25,000 cfs, width would bee
4 35fij§:3ggj:; = )10ft.
(depth = x-sectional area ;.. width) At present Q2 , depth
at Gold Creek= 11ft.; depth at regulated Q2 , 25,000.
-11(25,000J"! = 8 4 ft - ( 49,)00 • • •.
velocity, At present Q2 mean velocity is about 10.5 fps.
Velocity at regulated Q2 :
_ 10.5f25,0001·~ = 9 8 fps -. 49,)00 • • •
A comparison of present versus projected widths at 25.000 cfs
suggests 125 ft. reduction, a very large change. Referring
again to Figure 8, it is evident that the new depth for Q2 of
25,000 cfs is virtually the same as that presently shown for this
discharge. This is because Susitna depths at Gold Creek actually
vary as the .36 power of discharge at that station, a very
similar relation to the (.4) power found along the run of
46
rivers. The large reductions projected for width, while depth
• -1:' -· 1 " ..L.. • .. rema1ns .~.au·_y cons~.ant, ar9 co'!'lsl.s"tant w~th the predicti::>ns
provided from Schumm in (4) above.
Mean velocity for the regulated Q2 is indicated to drop from
10.5 fps to 9.8 fps when compared with the existing Q2 , but
will be significantly higher than the original 25,000 cfs velocity
of 7. 2 fps.
The projections made above look fairly reasonable, though the
width reduction appears somewhat greater than 'I would expect.
In using the Leopold-Maddock relationships to project channel
conditions in the regulated Susitna from present knowledge of
channel and flow, we are projecting from one flow regime to a
new and different one, but with unchanged channel material.
The new regime will have greatly reduced peak flows; conversely
more sustained and somewhat larger lower flows. The above
projections of width, depth and velocity were made with the
assumption that this change in regime will not greatly alter
the nature of channels in unchanged bed materials.
6. Width, depth and velocity in a specific narrow type cross-
section are related logarithmically to discharge in Figure 9.
These curves represent present conditions.
The depth curve also provides, I believe, a reasonable estimate
of variation in mean depth with change in regulated discharge
at Gold Creek.
47
/ifl7-
_,. ..
-~
-~
_,
The slope of the depth curve can be used as a reasonable basis
for drawing curves to estimate depth at other stream sections
of generally similar form. To do this a discharge measurement
is necessary at the point in question. This measurement provides
a coordinate position for the depth curve to pass through,
I do not recommend use of the width or velocity curves for pre-
diction of regulated channel conditions. The w/d value is lik~ly
to reduce; at the same time velocity relation in such reaches will
also change.
7. Tributary streams will influence and be influenced by changes
in the Susitna.
a. The Chulitna River, quite evidently, carries a large bed
and suspended load to its confluence with the Susitna. From the
general braided appearance of the Chulitna at its mouth ~
the extension of that condition several miles up the Susitna,
it appears that this portion of the two rivers has a sediment
transporting regime that could readily become depositional.
The loss of the Susitna•s peak flows, particularly during the
sediment-loaded summer months, will significantly reduce velocity
conditions at the confluence of the two rivers reducing both
bed and suspended load-carrying abilities.
This action will favor deposition and related flooding in the
flats of the Chulitna above its confluence. Deposition will
begin at the mouth and work upstream. It will occur at a faster
48
rate than the downcutting mentioned earlier, and will be limited
upstream by the incised canyon of the Chulitna.
The form of the Susitna river for some distance upstream from
the Chulitna may be influenced by deposition. A backwater
reaction may act to prevent any downcutting in the river near
the Chulitna, and may in fact produce deposition in that sector.
While the Talkeetna does not carry the sediment load of the
Chulitna, it too may be influenced by regulation of the Susitna.
The reaction would be particularly in response to the Chulitna's
deposition of sediments acting to backwater the Talkeetna.
Again, I expect the occurrence of floods on the Talkeetna ~o be
somewhat stimulated (see also, u.s. Army Corps Engineers, 1972).
b. Portage River carries a significant bedload as shown by the
fan at its mouth. Some further movement into the river of this
fan may occur, but it will be limited because the river is narrow
here. Since I do not expect significant downcutting in this
portion of the river, similar resultant downcutting action on
the Portage River bottom will be more a function of the effective
lowering of the Susitna•s water surface during high flows. This
·~,
changed relation between mainstream and tributary peak flow IJ!"-
condition will favor some downcutting adjustment at the mouths
of tributaries. In the case of Portage River the bedload material
at the mouth is very coarse and will make this process very slow.
49
c. Indian River is more apt than Portage River to experience
downcutting at its mouth because it ha.s·a gravel bottom near
the mouth. Again, this action will resul-c particularly from
relative lowering of the Susitna during peak flows. Downcutting
action will stimulate an increase in bedload rate which will again
stabilize at a later time.
d. Smaller tributaries such as Gold Creek, Sherman Creek,
Fourth of July Creek, etc. will also be somewhat stimulated to
cut down near their mouths and to produce an increase in bedlo~d
rate which will diminish as a new equilibrium is approached,
e. Tributaries fed by springs or ponded areas will downcut
but at much slower rates. Differences produced in peak flow
conditions as a result of regulating the Susitna will not develop
to as large an extent here because springs are highly regulated
in flow condition.
However, the type of.e.rosive action seen in Plate A-14 {Photo
Appendix) will continue at least to clean the spring source
beds of finer material and to this extent some degrading action
may be seen. Particularly pertinent work has been done on this
problem by Clayton {1966 ?); who provides a basis for calculating
size of particle moved by upwelling springflows. In some cases
he shows that springs are capable of putting cobble-size particles
into motion; the critical factor is piezometric gradient, (the
water head which the spring outflow is capable of developing).
50
In summary I did not find ~prings in or near the Susitna Valley
that appe~:re d to have flows of high piezometric head.; fo.r that
reason I do not expect particles much larger than sand to be
in motion in spring beds except very near their juncture with
the mainstream where high gradients can develop and thus signi-
ficant downcutting occur.
This downcutting face will move toward the spring source but at
an increasingly slow rate.
8. Flood channels and flood plains will be abandoned and
vegetated after regulation of the river. Approximations of these
areas are shown on the overlays of Figure 12. Based on the
frequent evidence of seedlings and older ne~growth on such areas,
(Plate 8) rapid vegetation may be expected. Species will be
primarily cottonwood, alder and willow. The margins of spring-
flow channels such as one shown in Plates 9 and 10 will be
more narrowly confined with vegetation.
51
Plate 8r
Abandoned flood
channel areas will
rapidly vegetate
with cottonwood,
alder and willow.
..
I
I
1-
I
I
Plate 10: Flood Channel
at river mile 107 ~ is fed
by spring and small tribu-
tary flows,
..
51 a
Plate 9: Springflow-fed
secon1ary ~:ood chann~ls at
r iver mile . 104 J/4.
E. Springflows
C" • • • 0p~1~gs occurrlng 1n or near the valley bottom probably ~ome
~ostly from unconfined aquifers suggesting that only low
pressures are available.
1. Three kinds of springs were identified in the middle Susitnaa
a) Discharges from the perimeter of beds of steep tributaries
or from their fan deposits adjacent to the rivera these
flows are fairly constant in volume; water temperatures
are conditioned by stream temperatures depending upon
the distance of tra~el within the aquifer.
b) Discharges fed by the river upstreama these are apt
to be close to (downstream from) a significant drop in
river gradient. They will, of course, occur thro·ugh
alluvial deposits.
It should be borne in mind that head loss of flow in
..
the river will always be much less than flow through an
aquifer, th'us limiting th·e springflow that may be expected.
Volume of flow from such springs will depend directly
upon the water level of the river upstream. Again,
water temperature will be conditioned by distance of
travel through the aquifer.
\2 ..
-,-
L
.-;·
c) Discharges dominantly from and through alluvium leading ..,,
to the valley bottom, water source(s) not primarily
from adjacent stream flows: Such ground-water flows
are apt to be the aost constant in di~cbarg~ ana in
52
temperature. They may, however, fluctuate in volume
as the vallAJ groun1-watA~ level changes. If, for axqmple,
a drop in the Susitna produces a general lowering of
valley bottom water-table, then the ground-water flow
feeding the spring will not enter surface flow. This
. fluctuation will occur unless and to the extent that a
channel is sealed and therefore a local water table is
perched.
This type breakdown has been used in Table 8, which summarizes
the springflows either seen on the ground or tentatively identi-
fied on the aerial photography.
2. Considering possible effects of regulation of the Susitna
on springflow conditions, the river level has been pointed out
earlier and observed last summer by ADF & G field crews as
capable of influencing volume of spring flow discharges, By
consulting Figure 6, as well as pertinent features of Section D,
the summary shown below was constructed to indicate the direction
of influence of river regulation on valley ground-water level
and hence on the depth and surface discharge of springflows.
Month
October
January
Mid-April
June
September
Influence of river regulation on valley ground-
water level (compared with existing relationship)
begin to increase groundwater levels
river regulation has greatest elevating effect
on ground-water table.
end of elevating effect on water table; beginning
of depressing effect.
greatest depressing effect on ground-water table
smaller potential influence on water-tablea however,
September evidently can be a drought month under
a regulated regime indicating very significant
depressing effect on dry years.
It is reasonable to conclude that during the months of October
through March springflows may be enhanced in the river valley
bottom: during the months rtlay through mid-Septem"t>er these spring-
flows may be depressed. The degree, the variability, and the
years-timespan of these changes will require further work to
establish.
.54
fllf'.·
Table 8: Summary of springflows seen on the ground or identi-
fied on aerial photos.
Location
t 2-90-90 J/4
R-9li
R-92~
R-95t
L-96i
R-96!
L-97t
L-99 1/J
R-101-}
L-lOJt
L-104 J/4
L-105t
L-108!--i
L-109
L-111~
L-lllt
L-11.3
R-114t
L-117 J/4
R-llBt
L-119
L-119;
R-119 J/4
R-120t
L-122t
L-124!
Type (a)
(b)
(c)
c
a
c
c
a,c
a
a
a
a
a
a,c
a,c
a
a,c
a,c
b,c
a
c
c
c
a
c
a
c
a
c
Temperature
Observations
17.1°C
11.4
8.1
16.0
7.5
6.0
Other Observations
discharges into river
into small slough, an
old channel
into small flood channels
from Curry Cr., discharges
into river.
sizeable springflows into
flood channels
from lake-fed stream;
sizeable spring-channel flows.
into side channel near river
sizeable springflows into .
flood channels.
into short flood channel
discharges into river.
into flood channel
from Gold Cr., discharges
into river.
into small side channel
ponded area -abandoned channels
ponded area -abandoned channels
into flood channel
~see text for description of springflow types identified.
L= left side of river looking downstream; R = right side.
55
CITATIONS
Blench, T., Mobile-bed Fluviolog*, Edmonton, Alberta, Canada:
The Univ. Alberta Press, 19 9. 168 pp.
Branton, c. I., R. H. Shaw and L. D. Allen,
Radiation'', Uniy, Alaska Tech, Bull.
"Solar and Net
No. .3., June, 1972.
Clayton, L., s. J. Tuthill and w. B. Bickley, Effects of Ground-
~ater Seepage on the Regimen of an Alaskan Stream, senior
author from Univ. North Dakota, others from Muskingum
College, New Concord, Ohio1 found in my notes from Hydro-
logy Abstracts, date not available.
Delay, w. H., and J. Seaders, "Predicting Temperatures in
Rivers and Reservoirs", Proceedings of ASCE, SAL, Feb.
1966. pp. 115-1.3.3.
Edinger, J. E. and J. C. Geyer, "Heat Exchange in the Environment"
Cooling Water Studies for Edison Electric Inst., R.P. 49
third printing, John Hopkins Univ., June 1971.
Gessler, J., River Mechanics, Vol. I, Ft. Collins, Colorado:
H. w. Shen, Box 6o6Ft. Collins, Co., 1971. pp. 8-1
thru 8-24.
Jarocki, w., A Study of Sediment, Wydawnictwo filorskie: Gydnia,
1957. OTS Pub.-g0-2127.3: 196.3.
Leopold, L. B. and T. Maddock, Jr., "Hydraulic Geometry of Stream
Channels and Some Physiographic Implications .. ; U1 s. Geol.
Survey, Prof. Paper 252. 57 p.
Livesey, R. H.,. Channel Armoring Below Fort Randall Dam":
Federal Interagency Sedimentation Conference, Jackson,
Miss.
Mamak, w., River Regulation, Arkady, Warszawa, Poland, l958r
translated reprint of "Regulacja rzek i potokow". 125 pp.
Parsons, R. M.p "Temperature Prediction in Stratified Water":
Mathematical Model-Users Manual, Environmental Protection
Agency, l25 pp. • ·
Pivovarov, A. A., Thermal Conditions in Freezi~ Lakes and
Rivers, New York• John Wiley and Sons. 1.3 pp.
Schoephorster, D. R •. and R. H. Hinton, Soil Survey: Susitna, u.s.n.A., Soil Conservation Service in cooperation with
University of Alaska, ·
Schumm, s. A., A Tantative Classification of Alluvi~-River
Channelst u.s. Geol. Survey Circ., 1963. ~77 pp.
Yalley Area Alaska, 71 pp.
--~...--~' "Fluvial Geomorphology: Historical Perspective••
R~ver Mechanic~ Vol. I, Chapter 4, P. o. Box 606, Ft. Collins,
Colorado: H, w. Shen, 1971. pp. 4-1 thru 4-JO.
--~...--~' "Fluvial Geomorphology: Channel Adjustment and
R1.ver Metamorphosis" River Mechanics, Vol. I, Chapter 5,
P. 0. Box 606, St. Collins,.Colorado: H, W. Shen. 1971.
pp. 5-l thru 5-22,
. u.s. Army Corps of Engineers, Flood Plain Information, Talkeetna
River, Susitna River, Chu!itha Rlver: De'pt. of the Army,
Alaska District, Corps Engineers, Anchorage, Alaska, June,
1972.
Vanoni, v. A. and N. H. Brooks, "Laboratory Studies of the
Roughness and Suspended Load of Alluvial Streams .. ,
California Inst, Tech. Sedimentation Lab. Re~ort, E-68,. 'Pasadena,
California, 121 pp.
Wolman, M. G,, and L. B. Leopold, 'River Flood Plains: Some
Observations on their Formation": u. s. Geol. Survey
Prof. Paper 282-C.
Table A~l: Instantaneous Observations of River Temperatures
During Field Visit
;:)at; e -Time
7-13-74-1745
7-13-74-1845
7-25-74-1820
7-14-74-1010
7-24-74-1230
7-14-74-1100
7-24-74-1340
7-15-74-1750
7-25-74-2030
7-14-74-21)0
7-21-74-1000
7-23-74-2035
7-2)-74-12)0
7-17-74-1230
7-2)-74-0900
7-17-74-0830 .
7-2)-74-1515
7;...16-74-1415
7-17-74-1615
7-23-74-1530
7-18-74-1040
7-19-74-1015
7-19-74-1045
7-19-74-1130
7-19-74-1545
7-20-74-1100
Water ~smp3rature
Chulitna-River Mile 99i
" ' ..
tt II
"
tt
99
99
Little Susitna at Gaging Station
II u 11 It II
Little Susitna @ Edgerton Park
Road Bridge .. •• II
Little Su.sitna@ Main Hwy. Br. .. .. .. .. It
Talkeetna River near R.R. bridge .. tt ..
•• II II ••
Susitna R. @ Portage River
" " " Indian River
" " It II II
" 11 " Gold Creek .. tt II II
" 11 " Sherman
" II II tl
II II tl II
Susitna-river mile 109!
" (Curry) 11 lOJ
" (Portage Cr) 1 00~
" (McKenzie Cr) 99 1/J
It
II
" (Lane Cr) river mile 96t
" (above Chase) ·" 93
5.9°C
6.0°
6. 8°
6.2°
8.3o
6.4°
8.9°
9.1
10.8°
11.6°
9.4°
10.8°
10.8°
1).2°
9.5°
11.3°
11.4°
lJO
14.2°
11.4°
12.4°
1).4°
14.5°
14.4°
14.4°
12.5°
Table A-2: Instantaneous Observations of Susitna Tributary
• ... 1 Water Temperatures During Field Visit
.J Date-Time River-Mile Trib. Name? Water Temp.
-·l
_j 7-23-74 10:20 lJll Portage River 8,5°C
-, 7-2J-74 l)aOO 127i "Jack Long" Creek 10.1°
J 7-17-74 12:30 121 Indian River 11.5°
7-16-74 19s00 119 Gold Creek 10,8°
_j 7-16-74 14al5. 113 Sherman Creek 11.0°
7-17-74 16tl5 113 Sherman Creek 12.0°
,---n
6.0° 7-16-74 14al5 113 Spring flow into R.
7-17-74 16a)O 11) .. II . II 8.6°
''"1 7-17·7/.t-18:30 llli ,, II II ?.5o
7-17-74 18al5 lllt Clearwater flow in 16° -from small
-, flood channel lake-fed Cr.
7-.18-74 10:40 109~ Spring flow along R. 8,1°· (shows algal:.
growth)
~ 7-1.8-74 11 :)0 lOBi Spring entering lower11 4o
'''1 end flood channel •
7-18-74 14:00 108 Clear water flood 17.1°
channel c1
12.4° 7-18-74 14:)0 107
7-19-74 10tl5 lOJi Curry Cr. 10.1°
(intermittent)
7-19-74 10a45 lOOJ.. . 4 Portage Cr • 11.5°
'1 7-19-74 12a00 99i McKenzie Cr. (spring 10.0° flows also
.~
98 J/4 7-19-74 12:45 Un-named (reported il.6 '", springfall)
.. d 7-19-74 15a45 96t Lane Creek 9.1° Springs just
upriver.
'o.,
92! 10,4° 7-20-74 llaOO Un-named
_.j
l
~ • k ~ -
Table A-J: 'Phermograph Installation Record, July 1974
Tape #r s tat ion I
--
12911 1 su~d
Go
11916 I Susi
Sh
12925 I Susi
Sh
12933 I Litt
Upp
12930 ILitt
Up})
12931 ILit
low
12924 I "
12949 IChul
12954 IChul
12959 !Talk
RiVH
12957
tna @
ld Creek
tna @
erman
tna @
erman
J.e Susi tna
cr statior
le Susi tna
ar statior
lA Susitna
c;r station
..
i tna River
itna River
.
eatna
r'
.,
--
Installation Total
Date-Water Recorded Time Error ·
Time Temp. Temp.
17/July 11.2°C 12.2°C All times
at 8:30 1 hr slow
16/July 13.°C 13.9°C Gain li" hr
at 14:15 in 7 days
16 July 13°C 13.3°C All times
at 14:20 1 hr/10 min
slow
17 July 6.2°C 6.7°C Gain 40 min
@ lOslO in 10 days
14 July 6.2°C 7.2°C li hrs slow
@ lOslO in 10 days
14 July 6.4°C 7.2°C 5 1/3 hrs
@•10::30 fast in
ten days
" 6.4°c 7.5°C Ji hrs
slow in
ten days
13 July 6.o0 c 6.7°C 6 hrs
@ 18:45 fast
13 July 5.9°C 6.7°C bad
@ 17a40 record
14 July 11.6°c 12.1°C 3! hrs
@ 2la40 fast
14 July 11.6°C 12.9°C 6! hrs
@ 2lr40 fast
'
Removal
Date-Recorded Water ~ecorded
Time Date-Time Temp, Temp.
23 July 23 July 11,4°c 11.1°C
at 15al~ at 14aOC
23 July 23 July 11.4°c 11.7°C
at 15z3C at 17 s3C
23 July 23 July 11.4°c 11.1°C
at 15z 3< at 16aJC
24 July 24 July: 8.3°C 7 .8°C
at 12t3C at 14:0C
24 July 24 July 8,3°C 8.6°c
at 12a3C at 13:0C
24 Jul~ 24 July 8.9°C 8,6°c
at 13 a ~c at 2laOC
.. 24 July 8.9°C 9.2°C
at 16a3C
25 July 25 July 6,8°c 6.7°C
at 18a3! at 24&0(
25 July 17 July 6,8°C 3.6°c
at 18a2C at ?tOO
23 July 23 July 10. 8°c 10.3°C
at 20s3~ at 2la 3C
" 24 July 10,8°C 11.1°c
@ 2&00
I~
r
r
I
PUtts A-1: Per1met~r of !.>ua1 tnca R. at ubout treh
cr. ,1'1 ver m1le '76t.
\
Pla te A•l : Bftdload depoa1ted on
beaver dam in flood chAnnel nr .
Billion Slough, rlv~r mile 82i.
Plate A-3: ?er1~t~r of Suattna R.
nr. ,1 111on lough• river mile B2t•
Plate A1'4: ·~r1metf!r of uualtnn
abou~ r1v~r mile 90i•
-
• 'below ;haat~,
•
Jlt-te. A-5: f f!r1me t~ r of :Just tmll
~. obove tr1b. or. at r. m1~02t
Plate A-6t p!!t~ ... !'lm vt.-w of ~~v~r t'"~om rl v~r t:1!le
~2·J
I
I
Plate A-7: Tributary
entering Suaitna R.at
river mile 921 . Glacial
boulders prominent.
Pate A-8: Mouth of Lane
Cr ., river mile 96t.
Plate A-9:. Perimeter
material , Lane Cr.,
river m1ie 9St/
Plate·A-10: Perimeter, sus1tna R.,
above; Lane Cr. ,river mile 96i
?let~ A-11: Beaver-dammed, apr1ngfed(reported.1 pond-creek, river mile 98 3/4.
Plate A•l2: Mouth ot McKenzie cr., riv~r mile
99 1/3~ Bedload being rapidl7 trimmed otf·b7
the river.
I
I
Plate A-13: McKenzie Cr., river mile 99 1/S.
Plate A-14: Active~apr1ngflow erosion along
banks of river just above McKenz1e·cr., river
~~9~
Plate A•l5: Sumtna beach above Mckenzie Cr.,
river mile 99i.
Plate A•l 6: Perimeter ,
Jortege Cr. ,riveT-mile 100~
Plate A•l7: Perimeter , SusS. tne R., at Cultt'y ,
river mile 103 .
Plate A•l8: Streambed rubble 1n dry creekbed ,
Cu:rry Cr • , r 1 v e r m1 ie 103 .
..
•
'
Plate A-19: Sus1tna • above Curry
· Cr~, river mile 103.
Plate -20: r1met~r, sue1tna R.
·below nd1an • , r1 Vf'-r m1le 121.
I
I Plate A-21: Indian R. -Sus1tna R. confluenoe; larser met'l ,
(foreground) la river deposited; amsller mnt'l(middle)
.Indian R. deposition. Indian R. in background.
~late A-22: Indian R. pn~1-
m~te~ gravel .at mouth.
Plate A-23a Portag~ R. near mouth, looking upat~eaa,
river mlle 130.
•
I
I
•
•
I
I
Ple t~ A-24: Porte ge R . ahore }.lne
looking downstreem fro m t mile
abov., mouth.
Plate A~25: Portage B. perimeter material on acti ve
bar near mouth •.