HomeMy WebLinkAboutSUS353EIDC 707 A STREET. ANCHORAGE. ALASKA. 99601 ; 11107) :ns..&23
GEOMORPHIC CHANGE I N THE
O~VIL CANYON TO TAL~rN A REACH
OF THE SUSITNA RIVER SJ.NCE 194 9
PRELIMINARY REPORT
ARCTIC ENVIRONME,'fTAL INFORMAnON AND DATA CENTER
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GEO!o\QRPIUC CHANG£ IN THE
DEVIL CANYON TO TALKEETNA REACH
OF THE SUSITNA RIVER SINCE 194 9
PRELIM!NARY REPORT
GEOMORPHIC CHANCE IN THE DEVIL CANYON TO ThLKEETNA REACH
Of THE SUSITNA RIVER SINCE 1949
PRELI!-trNARY REPORT
Pr epared by
Arct~c Envi r onmental
Informat1on and Data Center
Univ ersity of Alaska
7D7 A Street
An chorage , Alaska 99501
Submir.ted to :
Harza-Ebasco Susitna Joint Venture
711 H S~:reet.
Anch o rag e, Alask a 99501
f o r:
Alaska Power Authorit.y
334 West 5th Avenue, Second Floor
An chorage , Alaska 99501
Ma y 31 , 1984
.
'
Th1s repon: w a~· prt>;>a r ed by
Joseph C . LaBelle, Geomorpholog1st
TABL£ OF COJ\"l'£NTS
LIST OF FIGURES ••••••••••••••••••••••••••••••••••••••••••••••••••••••••• li
lln'IIODUCTION ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
METHODS •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2
RESULTS ••••••••••••••••••••••••••••••••••••••••••••••• , •••••••••••••••••• 3
CONCLUSIONS AND DISCUSSION ••••••••••••• , , , , •••••••••••••••••••••••••••••• 4
R£F£RENC£S •••••••••••••••••••••••••.•••• , •••••••••••••••••••••••••••••••• 6
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LIST OF FIGURES
Fiqure 1 . Compa rative geomorphology, 1949-51 to 1977-80, middle Susitna
River . Six plates: river miles 98-109, 109-119, 119-128,
128-138, 138-147, and 147-153 .
~igure 2 . Slough changes, middle Susitna River, since 1949 .
ii
INTRODUCTION
Analysi9 was undertaken of aerial photography of the Devil Canyon to
Tallceet.na reach, herein called the middle reach, of the Susitna River, t:aken
from 1949-51 and from 1977-80 . The purpose of the study was to determine
geomorphlc change in that reach of the river over the more than 30 years that
have elapsed since the earlier photography . It w;u; hoped that any noted
change in the river might be related to natural fish habitat transformation
over time, at least during the past 30 years. This would give an index of
habitat stabilit y in the natural system, and might give c~ues as to the
effects of the Susitna River Hydroelectric Project on future habitat
stability or change . Accordingly, the e .ntire middle reach of the river wa s
studied and mapped to show generalized geomorphic changes that have occurred ,
and the individual sloughs that have been identified by the Alaska Department
of Fish and Gam e (Friese, 1975) were analyzed more closely in order to
discern possible changes in slough type, which is an important clue to
habitat characte r istics . Three additional sloughs. here designated "X, Y,
and Z," were a l so included . These are shown in Klinger and Trihey (1984)
between sloughs 88 and SA (f'igu re 1). It should be noted that only
relatively large ~rphologic changes in river and slough character istics were
discernable at the scale of the photog r aphy used: detailed changes such as
water depth , riffle activity, beaver damming , etc., could not be
distinguished, nor could any direct indications be discerned as to the
suitability of the habitat s f or fish . This document reports preli:ninary
results showing the general di r ection of geomorphic changes of the river
r each and its sloughs . The final report will document results of ongoi ng
studies to resolve implication to fish ha~itat .
2
~l£1'HODS
For comparison purposes, photographic oets of thP middle reach of the
Susitna River were gatl:ered for the extreme ends of the time period in
question. In each case it was necessary to use photography from more than
one y8ar in order to ~over the entire middle reach, since no one flight
included the whole reach. For the early part of the period, photography fro~
1949 to 1951, taken for the u .s . Geologica~ survey (USGS), wa s utilized . For
the late part of the period, photography from 1977 ~o 1980, taken for the
Bureau of Land Management (BLM), was used . Daily discharges from USGS
records for each photo set are shown in Figure 2 .
Since all photography was not taken at the same scale, manual al ~erna
tion in scale was done in o rder to bring all mapping to appr~ximately the
same scale of 1 :60 ,000 . This was done using a Lucy-graf, an opaque projector
with reducing and enlarging capabilities . Due to imprecision in the Lucy -
q raf , sliqht shifts may be noticed between corresponding parts of the river
in the map set (Figure 1). These have no serious effect in the portrayal of
geomorphic change .
Compa r isons of all identified side and upland sloughs for the two time
periods were accomplished us1ng the same set~ of photography, but also the
photomap sets of sloughs, depicted at various discharges, included in the
report by Klinger and Tr ihey (198 4).
RESULTS
Generalized changes in river mo·rpholoqy o ver the approx imately 35 years
since the original photography are shown ir the accompanying map set
3
1r1c;ure 1). Dunne; ti\at period, A number of old, vec;etated 1slands have
dlsappeared; numetous new gravel bars have appeared and there lS now a ~uch
larger total number of gravel bars1 many, old, barren gravel bars have now
become fuzther d~velcped and vegetated, and are no~ stabilized islan~s or
torraceSl and ti\ero appear to be many new gravel beaches on the upstream and
do~nstream ends of old islands.
Mo re detailed changes 1n the slcughs, including changes in slough types,
are indicated in rigure 2. It can be seen that some sloughs have cone 1nto
ex1stence s1nce 1949-51, some have changed character and/or type siqnifl-
clntly, and others have not yet chanc;ed enough to be not1ceable at this
scale. Notably, many sloughs have evol ved from s1de channels to side sloughs
or from side sloughs to upland slouqhs . In some few cases, the evolution has
progressed all ti\e way from a side slough to an upland slough. Specifically ,
seven sloughs changed from s1de channels to side sloughs (8, •z•, 13, 16, 21,
2lA, 22): two sloughs changed fr~ side sloughs to upland slough ("Y", 19);
and two changed froc s1de cho1nnels all the way to upland sloughs (1:!, 15).
One slough (8C) d1d not exist 1n 1949 and is now a side slough behind a newly
depos1ted gravel bar . Of tho sloughs studied , only Slough 11, which was
observed to be altered by ice jam E;ooding and e r osion processes in 1976 ,
evolved in the opposite direction, from an upland slough to a side slough .
CONCLUSIONS AND DISCUSSION
With the exception of Slough 11, which was c hanged by 1ce proce sses, all
sloughs that have changed type hGVO evolved to a perched condition; that is,
they ere now higher in elevotlon relative to the water sur face at a given
4
d1scharge. The perching o! the sloughs is appa r ently due to general r:~.ver
degradat1on over the 35-year per1od . As the r1ver has slowly eroded its bed,
water surface at any discharge has become lower 1n elevation relative to the
~u r rounding topography. It is interesting to note, however, that no sloughc
have changed type below Lane :reek, while 13 of the 24 studied sloughs above
Lane Creek have evolved to a new type . Of the sloughs that have not evolved
to another type, some degree of ?Crching is indicated at most of them by an
1ncr eased extent o f vegetat1on on the1r enclos1ng gravel bars or islands.
The evolutlon of many old, barren gravel bars to vegetated, and often
forested, islands and terraces is another indication o f long-term river
degradation. These iolando ond terraces ore no longer flooded dur:~.ng even
high normal summer stages, allowing a permanent vcgetat1on cove r to establish
itself. Th1s ind1cates that these islands and terraces are now also perched.
A great number of nev, barren gravel bars have appeared in the r1ver .
~ome of these, such as the gravel bar enclosing Slough SC, did not exist at
all in 1949 and have fo~ed as a result of deposition o r emergence . Soge
other sloughs, which have evolved trom side channels to side sloughs, did so
not o nly because o= perching bue also becou>Se of deposieion and !un:her
g r owth of the enclos:~.ng gravel bars .
£me r gence of gravel bars to an e x posed condition could bt> a result of
the above-ncted long-terl!l river degradation. lis the water level recedes to a
lower elevation, preex1.st1ng g ravel bars emerge above the water surface .
However , there appears to be a much greater number of exposed gravel Jars in
the middle reach of the Suu tna IU•ter now than th9re was in 1949-51 and many
old bars ~re now much l~rqcr in Sl%e. If lonq-term river degradaeion were
the only e x planat:Lon, one might eKpec t the general number of barren gravel
bars to •emain relatively constant as new bars emerged and old, exposed bars
5
became perched and vegetated. The great increase in the number and sizes of
barren gravel bars see=s to hint at aggradat-on ~n the r~ver.
It is specul a~ed that there may have been a short-term period of river
aggradauon suporiJ:Iposed upon the long-terrn process of river degradation
dunng the last 35 years. Studies are now in progress to det.enane the
uming and rate of changes that led ~o the appea.cance ot the gravel ba rs.
Photograph'l at inte~1als throughout the 35-year period is be1ng ~~alyzed to
try to detertnne the process that initiated the ac;g radat:ion phase. The
results of these studios and discussion of the implications o! geomorph1c
change on fish habitat:& will appear in the final report of this study.
6
Friese, Nancy V., 1975. Preauthor~zat~on assessment of anadromous fish
populaeions of the ueper Sus1ena River watershed in the vicinitv of the
proposed Devil Canyon Hydroelectr~c Pro)ect. Alaska Department of Fish
and Game, Division of Commercial Fisheries, Anchoraqe, AK. 108 pp.
Klinger, Shar on , and Woody Trihey, 1984. Oraft report, May . Response of
aquatic habitat surface areas to mainstem dischar~e in the Talkeetna to
Dev~l Canyon reach of the Susitna River, Alaska. Report prepared by
E. Woody Trihey and Associates for the Har~a-Ebasco Susitna Joint
venture . 11 pages plus appendices.
• Vegetalion
0 S lough
0 Sto ugh
sc S ide Channel
ss Side Slough
us Upland Slough
...
River Mile ,.
ss
Wo\btm
1949-1951
1977-1980
us
.----------F i gure 1 ----------,
COMPARATIVE GEOMORPHOLOGY
19 49-51 to 1977-80
M iddle Susltna River
River Mile 98·109
1 of 6
Appro> !mate Scale 1:60.000
1 Inch " .9 Miles
• Vegetation
CD Slough
0 Slough
sc Side Channel
ss Side Slough
us Upland Slough
... River Mile
us
1949·1951
1977·1980
...---------F igure 1---------,
COMPARATIVE GEOMORPHOLOGY
1949·51 t o 19n.ao
Middle Susltna Ri ver
River Mile 109·11 9
2 oiS
Approximate Scale 1:60.000
1 Inch = .9 Miles
• Vegetation
0 Slough
0 Slough
sc Side Channel
ss Si de Slough
us Upland Slough
... Ri ver Mile
sc 1949·1951
ss
1977·1980
ss
.----------Figure 1----------,
COMPARATIVE GEOMORPHOLOGY
1949-51 to 1977-80
M iddle Susltna River
River Mile 119·128
3 of 6
Approxi mate Scale 1:60,000
1 Inch = .9 M iles
ss
ss
• Vegetation
0 Slough
0 Sloug~
sc Side Channel
ss Side Slough
us Upland Slough
... Ri11e r M ile
1949·1951
ss
1977·1980
ss
.----------F i gure 1----------,
COMPARATIVE GEOMORPHOLOGY
1949·51 to 1977·80
Middle Susltna River
River Mile 128·138
sc
Approximate Scale t:60,000
1 Inch = .9 Miles
• V8jjelallon
0 Slough
0 Slough
sc Side Channel
ss Side Slough
us Upland Slough
... River Mile
us
1949·1951
A
1977·1980
[
Flgure 1
MPARATIVE GEOMORPHOLOGY
1949·51 to 1977-80
Middl e S u sltna River
River M ile 138·1 47
5 ol6
Approxi mate Scal e 1:60 ,000
1 Inch "' .9 Miles
• Vegetation
0 Slough
0 Slough
sc Side Channel
ss Soda Slough
us Upland Sloug h
... River Mile
1949·1951
\
1977·1980
\
\
\
\
.----------Figure 1---------,
COMPARAT IVE GEOMORPHOLOGY
1949·51 t o 1977·80
M id d le S us l tna River
River M ile 147·153
6 of 6
\
Appro•imate Scale 1:60,000
1 Inch = .9 Miles
Figure 2 . Slough Change , ~Iiddle Susitna River, Stnce 1949
TYPE Comparative
Slough 1949-51 1984 • Phot.oqraphy Slough Changes Not.ed
l ss ss 7/3/51 No appazent changes in slough,
6/19/77 but bar at slough mouth has
become vegetat.ed .
2 ss 55 7/3/51 No apparent c ha ng es in slough,
6/19/77 but more veget.at.ion has
developed on out.er part.
of enclosing gravel bar .
1-.'hiskers ss ss 7/3/51 No apparent changes .
6/19/77
3i\ us us 7/3/51 No apparent. changes .
6/19/77
38 ss ss 7/3/51 No apparent. changes .
6/19/77
4 us us 7/3/51 No apparent changes .
6/19/77
5 us us 7/3/51 No apparent changet .
6/19/77
6 us us 7/3/51 No apparent. changes
6/19/77
61\ us us 7/3/51 No apparent. changea .
6/19/77
7 55 8/14/49 Slough not. discernable on photos .
6/19.'77
8 sc 55 8/14/49 I n 1949 che enclostng gravel , 6/19/77 bars were much smaller,
8/1/80 lowe r, mostly awash , and
com:~letely unvegetated . The
"slough• was a std• channel.
In 1977-80 t.he bars are
larger, higher, and better
defined, with much veget:ation
from g rasses up to htgh brush
and small trees .
Figure 2 . (cont inued)
Slough
eo
ec
as
l!nn=ed
X
Unnamed
'i
Unnamed
z
SA
9
98
TYPE
19~9 -51 1984 •
us us
Old SS
not
exist
ss ss
us us
ss us
sc ss
ss ss
ss ss
us us
Comparative
Photography
8/14/49
8/1/90
8/14/49
8/1/90
8/14/4 9
8/1/80
8/14/49
8/1/80
8/14/49
8/1/80
8/14/49
8/1/80
8/14 /49
8/11 /80
8/10/49
8/11/80
8/10/49
8/11/80
Slough Chang e s Noted
No apparent changes .
In 1949 t here was no enc~?sing
g ravel bar and the slough did
not e x1 st. In 1980 the
enclosing gravel bar is small
and lightly vegetated in 1ts
center , up to small brush .
No apparent changes .
No apparent changes .
Enclosing g r avel island did
not e1:ist in 1949; only s mal ~.
partly eme r gent, unvegetated
bars existed . In 1980 the
enclos1ng gravel 1sland is
larger , high , and completely
vegetated up through strands
of trees .
In 1949 exlSted as s1des
channe l behind heavily
forested island. In 1980
slough exists in lowe r part
of channel only, with berm in
uppe r part . Shore ward of
slough, ba r s that were bare
and a wa sh in 1949 are no w
higher and fully vegetated .
No apparent changes.
No apparent changes in slough,
but bars on west end of
enclosing island have become
vegetated .
No apparent changes .
Figure 2 . (continued)
Slough
9A
10
11
12
13
14
15
TYPE
194 9 -51 1984 •
ss ss
us us
us ss
sc us
sc ss
us us
sc us
Comparative
Photography
8/14/49
8/11/80
8/14/49
8/11/80
8/14/49
8/11/80
8/14/49
8/11/80
8/14/49
8 /11/80
8/14/49
8/11/80
8/10/49
B/11,'80
Slough Changes Noted
No apparent changes in slough,
but channel appea r s wider
n.ow and the morpholoqy of the
enclosing island ha s slightly
changed.
No apparent ch~~ges .
In 194 9 existed only as a
short upland slough at edge
of terrace . In 1976, a
bre~~up 1ce )am occurred that
flooded the terrace and e r oded
the present slough , cutting off
the terrace to an 1sland.
In 1949 ent1re channel was
flooded and appeared as a
s1dc channel . In 1980 only the
lower part of the channe l is
normally wetted, as an upland
slough.
In 1949 enclosing gravel bar
was less developed and
mostly awash; slough appears
as side channel . In 1980 the
enclosing gravel bar is
better developed and higher,
enclosing a side slough .
No apparent changes .
I n 1949 channel wa s com-
pletely flooded and appeared
as side channel . In 1980 only
the lower part of the channel
is normally wetted, as an up -
land slough.
Figur e 2 . (continued)
Slouqh
16
17
18
19
20
21
TYPE
19·''3-5_1 _1984 .
sc ss
us us
C<Y.:Iparative
Photoqraphy
8/10/49
8/11/80
8/10/49
8/11/80
(Not identifiable)
ss
ss
sc ' ss
us
ss
ss
8 /10/49
8/11/80
8 /10/49
8/11/80
8/10/49
8/ll/80
Slough Changes NoteU
In 1949 , enclos1ng gravel
ba r was less develop~.
mostly awash: slough appeared
as s1de channel . In 1980, the
enclosing grave l bar is better
developed and higher, enclosing
a s1de slough.
No apparent changes.
In 1949, slough occupied
channel beh1nd gravel bar
that is partly awash . In
19~0. slcuqh is lower part
of channel behind vegetated
bar.
In 1949 slough was behind
par t ially vegetated 1sland .
In 1990, island is heavily
fo r ested .
In 1949, channel below fir st
enclosing island was open
(no gravel berm) , making
entire !owe r section of
slough a side channel. In
1980, a high gravel bar has
formed in the channel, mak1ng
a high be rm and causing t he
l ower section of slough to
be a side slough. Behind the
upper island, the channel 1s
a s1de slough 1n both years .
Figure 2 . (continued)
Slough
21A
22
TYPE
1949-S-1-1984 •
sc l:.S
sc ss
Colllj)a r ative
Photography
8/10/4 9
8/11/80
8/10/49
8 /11/80
Definitions (Klinger and Trihey , 1984 )
Slough Changes Noted
I n 194 9 channel was totally
flooded and appe~ed as a side
channel . In 1980 enclosing 1sland
a ppear s better developed and higher
a nd slough is side slough .
In 1949 channel was totally
flooded and appeared as a side
channel . In 1980 enclosing
island appears higher and
slough is a s i de slough .
SC -Si.de Channel . These contain turb1d , glac1al waters, the same as found
in the ma1nstem. These channels convey less than ten percent of the total
flow .
SS -Side Slough . These contain clear water . Local surface runoff and
upwelling are the primary water sources that supply clear wate r to the side
sloughs . Side sloughs have non -veget.ated upper thah•egs that are overtopped
during per1ods of mode r ate to high ma1nstem discha r ge . Once overtopped, side
sloughs are considered side channels .
iJS -Upland Slough . These con~ain 'lear water a nd depend upon upwelling
and/or local runoff as thei r clear ~ate ~ sources . Upland sloughs possess
vegetated upper thalwegs that ate s3ldom over topped by mainstem discharge .
• 1984 Type classificat1on from Klinge r and Trihey , 1984 .
PHOTOGRAPHY
August 10, 1949
August 14 , 1 Cl49
July 3, 1951
June 1g, 1977
August 1 , 1980
August 11, 1980
DlSCHARCE (c f s)
29 ,900
28,600
18,200
4 1,000
31,100
22 ,600