HomeMy WebLinkAboutAPA4113·.
To:
1.
SU:bjeot:P:roJeet,
This 11'/1:r~'J
Ccm:1ition
.~~..':t>~~
Denali
DensJ.:1
111575
1.11 575
1
2
5-~
below
for estimating
Freque~J(W
iil_~,?!~1t~_
5
10
25
lC'eak discha;.~e
~2 700v[i
1.9,200
;8,000
884,000
993;000
1,l4J,p OCJO
be full
begilJnillg ctf tJ.19 l!'Jfw.v I.,\\:;;!'!.!.&U
ot:conS'81"V'a-
flood u
load.
with bJIDdXells
glaciers
outlew,\'11111e
eOlldu~ive to lag
patt.erne is that,
has been so x'0Cent ths.t
to dev"ele<p an
U'!'he vegetat:tv'e
ooval'of:'~he '<~~"');.,;::l~
underllidn l/IJ J;:>ermai'1"(;tBt
tBGme
height,and
nt11S1,eg have .t..11e
causing ext:re.me:l;f 1<¥ng lag
20
are found &Too
detain l~fall G~
'I'he i'ol1O',;w.g disoharge reocrda \\'-ere availalfle for streams in tb.G
Susito.a River basin:
Susitna illver at Gold Creak
DJ.~ainage area-...6,l60 mi.1ss (U 6 S"Geological·Sur{e'~"
£igure t.ltis S .I&u..dy )
Per:tod of reoord",-F.llgusrt 1949--5eptembar 1962
MexirrIum pet>]{disat.lt.ll'ge.-.s80 ,600 oi's J JI.U1.e 15,1962
1{~15-a~volt1.1'l1e,Mr6«*feet-l,58.3,OC(),June 10""24 ,
1962
J.%2
of's,June 1962 (probabl;y~15t-h)
volume,ac~~f'eeJ~o'iJ dei.erminabl61 because
Qf pex-iods averaged discharges
Susitna Pd vel'r..ear Cantwell
Drainage area-4,l4O
Period of record.-.L~
i~
rJa.x::iJnum 15-day
7,
"
At Vee D8!.l",sita,it j~s
envisif>ood Devu CmIVcn
probable
September ~.";,J,.",,,"o
as
"
Analyses of'rec~ro€;.'\l
flood.WE!l."'e
tion amounts vrere no'~
avaj~able.A selection of
r flood-produoing Ertudy ..ia gl~lrt
for collection of within tt..e &'uSi"(;D2..
Hival"basin before final
It was believed to xm~sernt
site for conditior~~:
4
for Vee Dam-
P..fter exa.'Ilil1ir.g
·t:hat a xwpr<es<:m.,t:tai:.i ii'S
averaging
believed
net raim:"all
v~l~
2.94
cen:ter c'£
Ves wag
be ,8
540
21.-ho>.1I'unitgrat>h developed Devil Car~on blCQ'1C,;).!o
00 ooura.'I1Us t:J..,me was ·vemus an j"",tJ .Iff
eEl'
£a.<rtor 2,610 as on Plate 6.it.Cl..trVC was drawn tb..;rot~h
point pariillel Q'll."t'CUl¥~&a.s abrJ'im.-
porting data for time esi.!imat,~s be obtained
Of the 1961 event beoause of ()f rainfaLl data.The
~ot the net far t..lla al"ea 'be-I:i\veen Denali gage
UCl\YS to 70 hou..TtS..MSiu:u:i -ng 24 hom"s Y exo eSB.fl lag time
which falls on t.he .~urve as aX!ll.oal.JS factor
was computed ror this f'.l"e8..
48 9 lag time
the ooos·tructed curve.
B"J (judgment jl it wag U1V'Jk,,;'\'J\J,
lag times e An LLcal.JS
hoUl'S was
sentativa area
used to eliminate
above a.nd
obtain
ty 2
was
the McClaren
given f'or
UaJ'lel;na.factar •
•~u.J.""a was
aub-,
gave aJ)
tr..e entire w~·t~j";<:i}-;ed cH,7<JiJe:
in that study to estimate 'V--arlation in rainfall O\fer
basins of the watershed but the that Ii varls,tiol1 '>'''laS
discussoo.
No additional meteorological data which VlOuld change the Deiril Can';fOIl.
design storm e$timate1:'..ave been.acquired sinee making t.ha t study.It
was deoided:therefore;to use the Devil Canyon desig!l storm Yalues in
this study but to estimate a variation :L.~E.n.fbbasL'l storm fhi1(1ill1tS due to
topographic i~luence8.Such arl estimate is feasible because of tri8
looations of the damsi tea.Desig..'1.storm co:ndi tiooo postulat.e a strong
flow of moist air nOl"theastward -Cook Inlet over the Talkeetna
Mountains into the Susitna Rlver basill e Precipitation 'would 'be baa,,'Y
alOJ."lg the Talkeetna 1v"JCmntain Di\fide p about 5,0-00 to 6;Ov"O feet in eleva-
tion,but wou.ld decrease f1m,the lee aide (northeastward).Referring
to the drainage map,Plate 4,it v;ill be seen that of the pre'Cipi,ta-
tion along th.e lee side of the Talkeetna Mountains will cont:r1.bute 1;:,0
runoff'f:t'0111.tJle area.between Vee Damsite and Devil Canyon Damsi te •As
tile moist aiJ:'flow continues northeastward across tt..e mid pen of the
basin,it is believed precipitation would be less heavy t~Jan along the
lee side of the Talkeetna t~tains beoause of the lower elevation--
about 3$000 feet..Vee Da.m.site and the Tyone River drainage lie in this
6
area.
lif'Ung
12,l ooo
ilion ove:t~
Above Denali Dam
Intervening area fJ DenaJ.i
D9~to Vee Damsite
Vee DaroEite to Devil
OalJYOX1 site
Drainage a:rea
.,.(liiQ..tJ.~-m;i.:1ea 1
1 1 200
Average precipe
_~"'!.cp..§st .
6.0
Ine~~mental 21~,~hour aroounts were made.propor'tional to incremental €Ullounts .
of the Devil C:,u:lYon design storm.Listed telO'.v in design arrango.Irlent a.'t"e
adopted 8uohasL"1 design sto"fln "ITalues along w1 th excesses aomput,ed using
a daily :retention loss or 0.8 inch.
7
·0 "'"24 2.2 1.4 1,,7 0,,9
24 -4S 4.0 3.2 ,3,,1 2,,3
48 -72 ~o 8I"•
7,,8 5.4 6,,0 ;3,,6
Average over 4,l4O miles 1:/a ..A)
A 15-d€\Y at Denali gage 1913'400 QII:,-Qiavs
July 2l-August 4"19.-62.This \vas divided by l5
age dail,y disct.IBJ:~ge of 12,7&0 ora,which was used.as an e.VI"'<"NlP'A
base for design flood ccmputations of inflO\SI at Denali DEU'lls:Lte
The :reeorde4 15-day volume at Vee site,July 2l-August 4,1%2,was
3'2.\1:000 cf~aya.Subtraoting the volume recorded at Denali that
at Vee and dividL'rlg the reault by 15 ga.ve an a:verage daily disehal"g8 oi..'
9,7')0 era,which was used as an average 15-dey base flow ortginai~ing
fran the area between Denali Damaite and Vee Damsite.
~:LJ1§!si8B f~o;-Jd~.PAJJ:..~fl,m no~,.e~trtlc:~esL..Design ra1nfl~~runoff
tor -U1e area abo\fi~Denali Damaite and for the intervening area between
Denali Dam.aite and Vee Damsi te was compu.ted using res~et::tve
c1istl>ibu.tion gm';J;J.1B and the respec""ive exeesses previously "cabuls:t.e4.
F..eapectivebese flow V!9.S addE.oQ to each rainflood.total £lo.-Jd
computed at Denali Damaite was e.dded directly to the flOO"J
for t.he intervenir..;g area to Vee site without routirzg because of:t.he
short travel distance between Denali Damsite and the head of'JGhe pro-
posed Vee Hsasrvoir.'I'l:l9 l1ydrog:ra.ph ~n on Plate 1 haVing a peak
575,000
neal'
inspection indicates
aoos'the Susitna be.sin..It is
drc!.wn at Vee
total basin runcrLf £rom over 6,O~
ga.ge measures runoff the high ~'cV';;>i,)~'UJ..1D
area.'I1ti.s curve inJiies:tes a of 60,000 ef's for 4 g LW
square wiles,area above Vee Damsi te"
MaximUll1.15-day volumes recorded at sta-'(,ions wi thin the Suaitna Rivar
basin have been.plotted as on Plate 8 e A curve indicative of
,\l'olume at Vee Damsi te is controlled by a 15-dt:\'f V'olu;:r.e of 4l4,000 oore-
feet,June 4-18,1957,at Dena.li and a 15-day volume of 1,583:000 acre-
feet,June lO-24~1962$at 901d Creek.T1rl.s Cl'l,rve indioa.tes a 15.-.dS\Y
volume c;yf lpl80,OOO acre-feet for 4,140 wiles~
The l:3-year :l:e.oord of'streamflow a.t Gold Creek gage was used to est.imate
probable ~-,10-,9 25-year floods at Vee De:msite 8.B follows:A
Hal?isn t s frequel1cy cOl1r'.01tation was made using anlluaJ.max:i.mum pea.k dis-
oharges and all.l1ual 15-da;y volumes at the Gold Creek ga.ge~'I'h!3
5-,1.0-,and 25-;~lear vallloe at Gold given by these computations
were adJustet'l 6,160 sque.re miles to 4,9140 square miles IT.f the
area relatiol'...Bhip shawn by the slope of'the envelope o\U"Ves.A s~
of:these o~J?Utatior!.S follows.
<)
.c"V.
mean
5
10
25
o.
1.
49,023
;7,
66 180,
7/1 950
0.21
1.60
1/1044,700 I'In1',,>,,_'T'P;!'n',
Volume
Peak discharge
,._.JeW.M',,_,.
:>
1.02,
_{"{iO
993;00'0
1,141,000
The above 1'lood values at Vee Da1!lSit.e 'w'ere used to eonstroet the d1yer...
sian x-equire.i'nent hyd...-ographI3 Jj Plate :3.
I conanl"~~P.~~
Head i Flood Hydrology Section
Appr"Oved
H.S.Riesbol
Chief p I~dr'Olog>J Branon
10
i.
,
,
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I ..I ,!I !!-.--~--!.----0"-1 I :1 ---t----------'--'----
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'9 '1-~,~4 k $t l?$10 II
I :!i I t r I I •,.1 I::TfME·-DAYS Ir~.-·-.2.:.-._.---I-..-.---...!-l...-....'....--I--..-.-i----..--L-.-..-~----....-;......J_...:I
I .j i I r--..-.iiI ' ' IL~_.,..;,L_...-:._j __·_:_,_.~_±__....:...~1_.~_±_..~~.L ._l.~..__~_l._··~_~:...:...J.~_.J_··_L
R,))id'i
oR(\3':~~'se
DO'il..CANYON PflOJ[rDRAINAGE.f-ALASKA •
••,AREA MAP
n~IHtl 0.":t.~,:~'::'
",o .
x;:
sn.,..