HomeMy WebLinkAboutAPA25N
..--
N
CD
IJ')
M
ooo
IJ')
IJ')
r---
M
M
ALASKA POWER AUTHORI,TY
SUSITNA HYDROELECTRIC PROJECT
TASK 3 -HYDROLOGY
REGIONAL FLOOD STUDI ES
DECEMBER 1981
Prepared for:
ACRES AMERICAN INCORPORATED
1000 Liberty Bank Building
Ma.in at Court
Buffalo,New York 14202
Telephone (716)853-7525
Prepared by:
R&M CONSU L TANTS,INC.
P .0.Box 6087
5024 Cordova
Anchorage,Alaska 99503
Telephone:(907)279-0483
A,..............-8
Alaska.ources
Library &Informatlon Servlces
Anchorage,Alaska
Demeo,Inc.38-293
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
TASK 3 -HYDROLOGY
REGIONAL FLOOD STUDI ES
TABLE OF CONTENTS
Page
LIST OF TABLES iii
LIST OF FIGURES iv
1 -INTRODUCTION 1-1
2 -SUMMARY 2-1
3 -FLOOD FREQUENCY ANALYSIS 3-1
3.1 -Single Station Frequency Analysis 3-1
3.2 -Regionalization of Frequency Analyses 3-3
3.3 -Relative Standard Error of the Estimate for the
Index Method 3-8
3.4 -Comparison with Results of Previous Studies 3-9
4 -EVALUATION OF DESIGN FLOODS 4-1
5 -EVALUATION OF TYPICAL FLOOD HYDROGRAPHS
FOR SUSITNA RIVER AT GOLD CREEK 5-1
6 -FLOOD VOLUME DURATION FREQUENCY ANALYSIS 6-1
7 -REFERENCES 7-1
ARL
Al .a R ~rces
Library &Informatlon ServIces
Anchorage.Alaska
- i -
susi6/j2
TABLE OF CONTENTS (Cont'd)
ATTACHMENT A
ATTACHMENT B
ATTACHMENT C
ATTACHMENT 0
susi6/j3
Flood Frequency Curves for Annual
I nstantaneous Flood Peak Series,
Individual Stations
Flood Frequency Curves for Maximum
Annual October-May Mean,Individual
Stations
Comparison of Susitna Regional Flood
Peak Estimates with USGS Methods
Review of Flood Frequency Analysis,
Conducted by Dr.Robert F.Carlson,
University of Alaska,Fairbanks
-ii -
I ._
LIST OF TABLES
Number
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
5.1
5.2
6.1
susi6/j4
Title Page
Ratio of I nstantaneous Flood Peaks to Maximum
Mean Daily Flow for Specific Stations 3-10
Distribution Statistics for Annual Instantaneous
Peak and October-May Mean Daily Peak Flows 3-11
Mean Distribution Statistics for Annual
I nstantaneous Peak and October-May Maximum
Mean Daily Flows 3-12
Homogeneity Test,Annual Instantaneous Peaks 3-13
Homogeneity Test,October-May Instantaneous
Peaks 3-14
Regional Annual I nstantaneous Dimensionless
Flood Values 3-15
Regional October-May I nstantaneous Dimensionless
Flood Values 3-16
Physiographic and Climatic Parameters 3-17
Comparison of Regression Equations 3-18
Determination of Daily~lnstantaneous Peak Ratio,
Susitna River at Gold Creek 5-3
Tabulation and Statistics of Instantaneous
Peaks versus Peak Volumes,Susitna River
at Gold Creek 5-4
Highest Mean Discharge of Consecutive Days
from May through July,Susitna River at
Gold Creek 6-2
-iii -
LIST OF FIGURES
Number
3.1
3.2
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
6.1
susi6/j5
Title
Design Dimensionless Regional Frequency
Curvet Annual Instantaneous Flood Peaks
Design Dimensionless Regional Frequency
Curvet October-May Instantaneous Flood Peaks
Percent of Annual Maximum Floods,Susitna
River at Gold Creek
Dimensionless Hydrographs t May-July
Dimensionless Hydrographs t August-October
Seasonal Discharge Frequency Curves t
Susitna River at Gold Creek
Flood Volume Frequency Curvet May-July t
Susitna River at Gold Creek
Flood Volume Frequency Curvet August-
October t Susitna River at Gold Creek
Peak VS.Volume t May-July t Susitna River
at Gold Creek
Peak vs.Volume t August-October J Susitna
River at Gofd Creek
Typical Flood Hydrographs,May-July t Susitna
River at Gold Creek
Typical Flood Hydrographs t August-Octob~r t
Susitna River at Gold Creek
Volume-Duration Frequency Curves,May-July t
Susitna River at Gold Creek
-iv -
3-19
3-20
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
6-3
1 -INTRODUCTION
On January 1,1980,Acres American,Inc.,received notice to
proceed with the feasibility analysis of the Susitna Hydroelectric
Project.The analysis will consider the feasibility of constructing
one or possibly two dams along the upper Susitna River.The two
primary sites being considered are the Watana and the Devil
Canyon sites.
The objective of this study is to provide design flood peak
information for the design of the project and for assessing
pre-project flood conditions in the Susitna River reaches located
downstream and upstream from the proposed Watana and Devil
Canyon dam sites.Within this context,two types of floods were
studied:the largest annual floods and the largest annual floods
during ice conditions (October-May).Procedures were developed
to estimate the annual instantaneous peak and the October-May
instantaneous peak for selected frequencies of occurrence on
ungaged rivers within the upper Susitna River basin.Procedures
were also developed to estimate the error associated with estimates
made by the above mentioned procedures.Typical hydrographs
were developed indicating flood shape,peak,and volume for
selected frequencies of occurrence.Flow volume-duration
frequency curves were also developed for the May-July and
August-October periods on the Susitna River at Gold Creek.
susi6/k 1-1
2 -SUMMARY
This report describes the Susitna Regional Flood Peak Frequency
Analysis conducted by R&M Consultants,Inc.,for Acres American,
I nco Acres American,under contract with the State of Alaska,is
conducting a study concerning the feasibility of developing a
hydroelectric complex on the upper Susltna River.
The results of single station flood frequency analyses are
presented for 12 stations having annual instantaneous flood peak
data,and for 11 stations having maximum October-May mean daily
flow data.Four frequency distributions were'analyzed,from
which the Three Parameter Log Normal Distribution was selected.
SUbsequently,the October-May maximum mean daily flows for
selected frequencies of occurrence were converted to instantaneous
peaks.
By using the index method of regionalizing the data,procedures
were developed to estimate the annual instantaneous peak and the
October-May instantaneous peak for selected frequencies of
occurrence on ungaged rivers within the upper Susitna River
basin.Procedures were also developed to estimate the error
associ ated with estimates made by the above mentioned p raced u res.
The results of this analysis are then compared to those of previous
regional analyses.
Typical hydrographs for different frequency floods were developed
for the Susitna River'at Gold Creek.A flood volume-duration
analysis was also conducted for May-July flows recorded at Susitna
River at Gold Creek.
susi6/L 2-1
3 -FLOOD FREQUENCY ANALYSIS
The Susitna Regional Flood Frequency Analysis was conducted in
the following four steps;
a.Single station flood frequency analyses were conducted at
stations thought to be hydrologically similar to the upper
Susitna River basin.
b.The single station flood frequency analyses were regionalized.
c.An error analysis was conducted in order to estimate the
amount of error associated with flood peak estimates in
ungaged areas.
d.The results of this analysis were compared with 2 regional
analyses which have been conducted by the U.S.Geological
Survey.
Each of these steps is explained fully in the report that follows:
3.1 -Single Station Frequency Analysis
In order to select stream gaging stations that are hydrologically
similar to the upper Susitna River basin,factors such as mean
annual runoff volume,climate,and geology were examined for
rivers with USGS stream gaging stations in southcentral Alaska.
Of those stations identified,only those with 10 or more years of
record and greater than 150 square miles in size were utilized.
The basins finally selected were as follows:
Susitna River at Gold Creek
Susitna River near Denali
Maclaren River near Paxson
Susitna River near Cantwell
Chulitna River near Talkeetna
Talkeetna River near Talkeetna
Montana Creek near Montana
Skwentna River near Skwentna
Caribou Creek near Sutton
Matanuska River at Palmer
Tonsina River at Tonsina
Copper River near Chitina
The last four stations are not as good as the first eight,due to
their distance from the Susitna basin and their exposure to a
maritime climate.However,these differences were not sufficient to
warrant exclusion from the analysis.
susi6/m 3-1
Three types of floods were abstracted from the records:annual
instantaneous peak discharge,annual maximum mean daily
discharges,and annual maximum October~May mean daily
discharges.Both the annual instantaneous peak discharge and the
mean daily discharge data are available for each of the stations
selected,with the exception of Montana Creek.Montana Creek Is
a crest gage station with only annual instantaneous peak discharge
data available.
For each station with mean da!Iy discharge data,a ratio was
developed between the annual instantaneous peak discharge and
the annual maximum mean daily discharge (Table 3.1).Where an
occasional annual instantaneous peak discharge value was missing
from the station record,the ratio was used to predict the annual
instantaneous peak value.
A Fortran IV computer program (Condie et.al.,1977)was used to
fit the Gumbel I,Log Normal,Three Parameter Log Normal and
Log Pearson Type III distributions to both the annual
instantaneous flood peaks and the annual maximum October-May
mean daily discharges.The program ran ks the annual flood peaks
and fits the frequency curves by the method of maximum
Ii kelihood.When the maximum Ii kelihood methods have no true
solution,a moments fit is used.For the Log Pearson Type III
distribution,both the maximum likelihood and the moment fits are
calculated in the program.The ranked discharges are assigned
plotting positions by the Weibull formula:
T =(N +1)/ M
Where:
(3.1 )
T
N
M
=
=
=
return period in years
record length in years
the rank
Tables 3.2 and 3.3 Illustrate the degree of fit achieved by fitting
each of the distributions to both the annual instantaneous flood
peak series and the annual maximum October-May mean daily
discharge series.From the results shown in Table 3.3,the Three
Parameter Log Normal Distribution provides the best fit of the
data,although the Log Normal Distribution is also acceptable.The
Three Parameter Log Normal Distribution is adopted almost
exclusively throughout this study.At two stations in the annual
maximum October-May mean daily discharge series it was not
possible to fit the Three Parameter Log Normal Distribution to the
data.At these two stations,Susitna River at Cantwell and
Skwentna River near Skwentna,the Log Normal Distribution was
susi6/m 3-2
used.Plots of the flood frequency curves for each of the stations
and flood series are exhibited in Attachments A and B.
Since the computer program only considers recurrence intervals of
1.005,1.05,1.25,2,5,10,20,50,100,200 and 500 years,the
graphs of the annual instantaneous flood peak frequency curves
were extrapolated to the 10,000-year recurrence interval.
The annual maximum October-May mean daily discharge frequency
curves were converted to October-May instantaneous peak
discharge frequency curves using the ratios discussed earlier.
Thus,the remainder of this study only considers the annual
instantaneous flood peak frequencies and the October-May
instantaneous flood peak frequencies.
3.2 -RegionaHzation of Fr~An.aly...s..e.s.
Regionalization of the single-station frequency curves involves
developing regional relationships which can be used to calculate
design flood peaks within a "homogeneous flood region ll .
Theoretically,the flood response of all catchments within a
homogeneous flood region is the same.I n practice,however,the
term lIhomogeneousll implies that the response characteristics of the
individual basins are not significantly different and that these
differences,coupled with sampling errors associated with the
discharge measurement,yield errors in the regional relationships
which are within acceptable limits.The purpose of developing the
regional relationships is to apply them to ungaged drainage basins
as well as to gaged drainage basins for which discharge records
are too short to yield accurate results.
To determine if the stations selected were homogeneous with regard
to runoff,a standard Student's lit"test of homogeneity of the
Q20/Q 2 =Y 20 variables was used.For each flood series within the
region being analyzed,individual station Y 20 values were computed
(Tables 3.4 and·3.5)and were used to calculate the allowable
range in Y 20 by applying the following equation:
susi6/m 3-3
1 )]~
(m -1)
(3.2)
Where:
t m-l
m
=
=
=
=
=
ratio of 20-year return flood to the mean
annual flood for a single station
an average of the single station Y20 values
for a particular flood series
"t"statistic for m-!degrees of freedom at
the 95 percent confidence level
standard deviation of the individual stations
at the 20-year return period
number of stations in the region
As can be seen from Tables 3.4 and 3.5,all individual Y20 value
are within the limits of the 95%confidence level.Therefore,all of
the stations selected for use in the Susitna Regional Flood
Frequency Analysis are homogeneous with respect to both annual
instantaneous peak discharges and October-May instantaneous peak
discharges.
Once it was determined that all of the stations selected for use in
the analysis were homogeneous with respect to discharge,the
index method was used to regionalize the single-station data.The
index method consists of two parts (Dalrymple,1960).The first
involves the development of a regional dimensionless frequency
curve representing the ratio of the flood of any given frequency
to the mean annual flood.The second part requires the
development of regression equations for relating the mean annual
flood to the physiographic and climatic characteristics of the
drainage basins.By combining the mean annual flood with the
regional dimensionless frequency curve,a frequency curve for any
ungaged location within the region can be developed.
This method assumes that throughout large regions that are
considered to be homogeneous with respect to flood producing
characteristics,individual basins with widely varying drainage
areas will have frequency curves of equal shape and slope.Any
differences in the shape and slopes of the individual curves are
attributed to sampling error.
susi6/rn 3-4
To produce a regional curve from single station curves,Dalrymple
(1960)recommends that the dimensionless frequency curves for a
homogeneous region be evaluated as the median of the individual
frequency curves within the region.Since the weighted median
has also been found to be useful in this type of analysis (Acres
American,1977),the dimensionless discharges at the 1.005,1.05,
1.25,2,5,10,20,50,100,200 and 500-year recurrence intervals
were analyzed with regards to the mean,median and weighted
median at each recurrence interval (Tables 3.6 and 3.7).The
weighted median was determined by using the number of years of
record at a station as the weight for that station.The
dimensionless frequency curve was estimated from the median of
the 12 stations used in the analysis.The median value had a
better general fit than either the mean or the weighted median
values.The mean value at the 10,000-year return period was
abnormally high,while the weighted median values started
decreasing after the 100-year return period.
The confidence limits for each of the regional curves are based on
values computed at the 1.005,1.05,1.25,2,5,10,20,50,100,
200 and 500~year recurrence intervals from the standard deviation
of the single station curves about the regional curves,using the
following equations.
The standard deviation of single station curve values about the
regional curve is given by
ST =[~
em-I)
(3.3)
Where:
ST =
YT =
YT =
m =
standard deviation at T-year return period
value of median dimensionless regional curve
at T-year return period
value of dimensionless single station curve at
T-year return period
number of single station curves
The standard error of the median (or regional curve In this case)
as a proportion of the median is given by
susl6/m 3-5
s~5T (3.4):::)~YT ( m
Where:
SEM T =relative standard error 'median,i.e.
regional curve at T-yeal leriod.
The associated 95 percent confidence limits for
are derived from the standard error and the
statistic coefficients.
A stepwise mUltiple linear regression computer
al.,1977)was used to relate the mean annual
flow and the mean October-May instantaneous
physiographic and climatic characteristics of tl
The program performs a forward steppir
regression analysis and tests the "significancel'
those used in the equation and those remaini~
their II F"ratio at each step of the analysis.
of the estimate and the coefficient of determin<
for each step.The physiographic and climat
and their values for each of the stations
Table 3.8.
In order to test the effect of a log-transform OJ
H EC Multiple Linear Regression computer p
Non-transform and log-transform regressic
conducted on the mean annual instantaneous
mean October-May instantaneous peak flow.1
results obtained by HECls stepwise backward
results obtained in the initial analysis.The f
indicates that the log-transform analysis dil
statistics.Consequently,the non-transform r
were selected.
he regional curve
:orresponding lit II
~ogram (Dixon et.
)stantaneous pea k
pea k flow to the
drainage basins.
multiple linear
)f variables,both
to be used,by
1e standard error
on are determined
parameters used
:ire presented in
the flow data,the
gram was used.
analyses were
eak flow and the
~non-transformed
rogram duplicated
lowing information
not improve the
Jression equations
Standard Er >r
of Estimate (~95%Error
Mean Annual Flood
Non-Transform
Log-Transform
Oct-May Mean Flood
Non-Transform
Log-Transform
susi6/m
0.9994
0.9930
0.9709
0.9141
3-6
+1465
+2612
+3081
+4425
-3(1
-2~3
4%
14.5%
20%
50%
The equations that were finally selected,including the coefficient
of determination and the standard error of the estimate,are as
follows:
Mean Annual Instantaneous Flood Peak
QA -
R 2 =
S.E.E.=
7.06(D.A)+46.36(L)+697.14(G)
+200.15(MAP)-49.55(MAS)-2594
0.9994
1465
(3.5)
Mean October-May Instantaneous Flood Peak
R2
S.E.E.
=
=
=
1.56(D.A.)+143.35(L)-2894
0.9853
3081
(3.6)
Where:
Q A =
Qo-m =
D.A.=
L -
G =
MAP =
MAS =
Mean Annual Instantaneous Flood Peak,cfs.
Mean October-May Instantaneous Flood Peak,cfs.
Drainage Area,sq.mi.
Stream Length,mi.
Percent of Drainage Area Covered by Glaciers,%
Mean Annual Precipitation,in.
Mean Annual Snowfall,in.
Of the five pc;Jrameters selected for computing the mean annual
instantaneous flood peaks,drainage area explains over 98 percent
of the variation between the regional mean annual flood and those
of the individual stations.However,inclusion of the other four
basin and climatic parameters (main channel length,percent of
glacial area,mean annual precipitation,and mean annual snowfall)
significantly reduced the standard error of estimate for the mean
susi6/m
annual flood peak.Since the regional mean annual flood is the
basis from which all other recurrence intervals are estimated,the
four other parameters were included.
Similar logic applies to the selection of parameters for the mean
October-May instantaneous flood peak.Drainage area and main
channel length explain over 97 percent of the variation.However,
Inclusion of additional parameters did not significantly decrease the
standard error of estimate in this case,so only the above two
parametet"s were used.
3.3 -Relative Standard Error of the Estimate for the Index Method
Equation (3.3)gives the standard deviation,ST'of the dimension-
less frequency curves about the regional curve.Equation (3.7)Is
then used to calculate the associated relative standard error of
estimate,SET'
SET
81'
(3.7)=
YT
Where;
YT =value of median dimensionless regional
curve for the i-year return period
SEM T in Equation (3.4)represents the standard error of estimate
of the median or regional curve.SET In Equation (3.7)
represents the standard error of the individual statiqn cu rves
about the regional curve.Note that S EM T =SET I (m )~.
In order to combine the errors SET associated with the application
of the index curve with the errors in the calculation of the mean
annual flood,Equation (3.8)is applied.An outline of the
derivation of this equation is presented in the report entitled
HRegional Flood Frequency Analysis"(Acres American,1977).
Where:
=+(3.B)
susi6/m
=composite relative standard error of estimate
of T-year event
=relative standard error of estimate associated
with the evaluation of the mean annual flood
3-8
Figures 3.1 and 3.2 present dimensionless flood frequency curves
which can be used in conjunction with Equations (3.5)and (3.6)
to predict the annual instantaneous and October-May instantaneous
flood peaks at specific recurrence intervals.The figures also
present curves for computing the associated composite 95 percent
confidence limits for the estimate.
3.4 -Comparison with Results of ere~ious Studies
Previous regional flood studies carried out in the Susitna River
basin and surrounding basins include:
(a)Lam ke,R.D .(1979)
Multiple regression equations for different recurrence
intervals were developed for two regions of the state.Area'
consists of most areas of Alaska with a maritime climate,
excluding the Aleutian Jslands and the Pacific Ocean side of
the Alaska Peninsula.Area I J consists of those parts of
Alaska with transitional,continental,and arctic climates,
together with the Aleutian I slands and the Pacific Ocean side
of the Alaskan Peninsula which have maritime climate.The
Susitna River basin is included in Area II.
(b)Freethey,G.W.and D.R.Scully (1980)
Multiple regression equations for different recurrence
intervals were developed using peak discharges from 50 Cook
Inlet gaging stations with 10 years or more of data.
No regional f~ood studies in the area have used the index method.
Table 3.9 lists the parameters used in the regression analyses and
compares the standard errors of estimate for the 2-,5-,10-,50-
and 100-year flood peaks.Values for the 100-year flood peaks
were not derived by either of the USGS studies.It is evident
from this table that the standard errors achieved in this study are
lower than those in the other studies.Fewer stations were used
in this study,but the stations were either within the transitional
climate region or were on its borders.The USGS studies used
gaging stations over much larger areas,with consequently larger
differences in climate.Attachment C presents a comparison
between the Susitna Regional Flood Peak estimates and estimates
using the two USGS methods.
susi6/m 3-9
TABLE 3.1
RATIO OF INSTANTANEOUS FLOOD PEAKS TO MAXIMUM MEAN
DAILY FLOW FOR SPECIFIC STATIONS
Station Name Location
Standard
Deviation
Number in
Sample
Susitna River at Gold Creek 1.060 0.036 31
Caribou Creek near Sutton 1.617 0.365 22
Matanuska River at Palmer 1.221 0.168 24
Susitna River near Denali 1.104 0.049 19
Maclaren River near Paxson 1.091 0.077 19
Susitna River near Cantwell 1.082 0.059 6
Chulitna River near Talkeetna 1.044 0.032 13
Talkeetna River near Talkeetna 1.219 0.102 16
Skwentna River near Skwentna 1.067 0.044 18
Tonsina River at Tonsina 1.031 0.036 28
Copper River near Chitina 1.043 0.061 23
1 Mean Ratio of Annual Instantaneous Flood Peak to Annual Maximum Mean
Daily Flow.
susi6/m 3-10
TAB L E 3.2
DISTRIBUTION STATISTICS FOK JU~NUAL INSTANTANEOUS PEAK
AJIDOCT-HAY MEAN Dt\ILY .PEAK FLOWS
)..AJt.J.XrrER t.()G It:Olt.u.,ltj.
$-:-"'f10lr0
:Cl""3(.!-
ll'f!,L~Ai:t:LDI'"A'l9!~£!.
CUHan I
a SlIM or HU.X
-~&["I1"'1~
esc
!~:_~.£)Jt-v.L
CU Sl:1'I0r K£,.I,H
-.Ilf.VIATlONS unrUHOf'"'....CK ...."ve.C\'.SlIY.OF nEAX
~lAn.\~~[~~!..4TIO:'t
~
LOC 'tAa$~riPl 111
(""C._I a)
51.,,"0'
~
......
O(·"lA.~IO:;
A\·C.CV.
I,.OC"~~Q~(lIu.h,,__,_ll,,-«.}jhc.od)
SUM or
!!!.VI<\tlOS'3
.......
Of:\'IAtl~
A~'~OUAL I~~,;:~N:rANEO~~Sco~:~~S r~~1s 0 ...,0
H20 or.a.thl>u C(.IIr.Sui c.~n 21 I 0.9))8
~.no'!l
4.22"
-22.90
-l::!.OJ
S.l6
1.14
~.O~M·1.8161
-0.04")}."'~4
·1?2a /i.n
-JCJ.)9·1.01·
-0.0305 2.~t~8·
-0.012.'").t-'Ol·
1 ~.01-
U.n-
·Ie.<a-
-l9.St
(,.\1.
7.11·
1>.)9
16.109
-19_0t
-19.S~
1.97
1.n
lS.S1
16.16
-20.11'
-11.98
~.)8
1.11
lI~O l'Wt ...,.usu 11..at r.ll~-Er 11 I 0.211);.66>1 10.0)4.JI ·').SlJO ).9110 ).46 '.11"-0.0121·:1.~9:.J·10.)9 I.OJ"1o.::J)U"ot:r ao,md..'>,h Too ~v Upper 1o...:14.ty I ..Too Leo.
1910 .s"'liil tn..R.nco Utl'••lt 20 I 1 ''!l':i IJ.)480 _".!JO lL~1 l-84H J.012S -]).:'j-11.:1 0.06J)-4,1l4}"1l.)'·-!I.'.i.),.)S.~6 -)•.8t 8.l'·140 Solution
.~9\1 ~I..C1s "on •.or.1'..."tlA 21 I 0.9061 1.44ilO -'\.16 I.U O.S'il9 1.6b81·-8.JS 6.:'''-0.]91S·1.M6>2).66 '.9]}.",B.9)·-a.lS-4.90 ICc 50l"liOCl
Af.C_f)t\.f'\L II I 0.))2\l.U4k -0.90-t.'6
,.U,"f'(n...It.0 ••TJoH.."'tlnJl I)1 1.11'0
ra1kl'«~n:-HI I 1.90)4 J1.1U9
10 I C.9lJl
~.51
3._0
1.''5
9.'5
1.'2-
-U.]/'
-lb.99
-S.('l
·20.29
-19.91
L'pper ••hnllh,~h t90 Low
L1pplr e;....n6.arj :.ri!O l.ov
U.S)
U.6S
IL2J
e.u-
JI.II!Jo
5.20'
].14
J.6S
6.21
J.,.
-J8.61
-U.6>'
),92
- l ..la
-'.'8
Uppec 1oWD4.ar7 b T~1,..)w
!.<lve ..lo'oln4ary 11 flAt I'll!':
H.N
13,8)
)9.01
40.Ots
H.t8
9.i~
5.21
'.2)·
6.01
3.0910
).11-
.s.4:-l8.~1"
-ZJ.)6
1.J:!
-O.~,.
-25.50'"
-9.15'·
-n.s~·
ll.90·
II.S9
14.0S
lC.::JG-
2].n
18.19-
12.n-
0.0)(,6-(,.lIB
O.J~12-f.8'>09·
O.O)~(,"S.9?98
-0.1I~1.:.166P
O.W61-'.801 J-
-0.0811 :.i1J]-
-?091l-4 0~')4'-
l.'4
6.2J
l.H
-l9.0J
rH•.)})1.}1
1."'.eo
-2).88·:;0.5&
-9.?S
-~~.n
0.0)0,·.2.'))1.
t .O~'!l8 '.1'.>99
0.9')61 1.;'081
1.D')'':)0.Ol~a
O.HlO 4.01')1
-lo2L"L~~'1
·0.14i1l.1.l811,8 loU 'lo.as-
3.J'I
s..u
9.S'·
e.16
IO.n
-l.St,
-)).81
- t .9~
-..1.))
-U,.9S~.38J4'
).lBO'
6.6'62--26.H
lIo.b!i6S--10.1':'
6.6lJl
28 I)0.6'WjI
11 I •.601'9
ne.S".,;~:\tn..20 II 1.01'8
ror.Chillna
..I TLnsin.
I'l.,nt ..n..Cc.
Sk\o"l:nlna R.
C<J;;pN R.
ellu ~II na ••
S>lsltn.l Ill.
.''o"sl./l.l I..
294]
19J:A.
n11
1"l1)
2080
~L{O
1'1i!1
OCT-MAY ~fEAN n.\1 LV PEAK FLOWS
1'20 S ...s'ena ~..,.;Cold C-.30 I 0.11l9~
(,.HI,1 -J6.6~-0.5291 !l.J4,~·'.~O.2.t1~~1l2~C..rlbvu Cc.nr.Sutton 2l 1 lolI..1
).1261 9.~,6.0.
12.90
-0.920&:).1100-1t./oJ 5.98 :1.0009·l.6ll5
O.Ol':"J·).U8'~
a.~6
n.B
-1.n·
.9.'~
l.IZ·
l.SI 24.1)
llpp_r ao"Rd.ry I.T_l.u'V
-9.l"1.16 le.l"·
Upp"r lo"'I'd...,I~TO(.Lov
-12.);8.2)
184')
2910
)W:Jlouskoi fl.
~u'"'tll"R.
.I.t p~I"l!.f"
b«n.lll
2'I 1.1691
16 I 1.)73'
6.11,H -16.1lol
S.)~Sl'"-lO.~J
6.'0
9.(19
-O.~ns('J.bHl!II.o -10_liD'"5.91
O.l~U ).6SStl -'J.\7.1.JO
·0.04/'9-1.b'!Ol
-0.09)"'").6"9
t9.2P
1~.(,,.
_10.10
-:0.81
6.95
6.56-
~O.1)
2'.98
-10.9'
~10.54
6.9'-
6.16
~~.H
21.'"
-1].1b
-u.S:;
6.1'6
II.n
1"912
19n
rt.clac-Enll.
S..sll....a.
L~I ~.1lJ1I
CJonr"'dJ to 1-0.0092
,.uu
3.10S2
0.'0..,.n.n
S.a8-
O.U:18 '.n61
-O.901.]-10.$9100-
O.Sl·IC.l~
~.))~t.58
_0.19)1·).IIS1"·38.S1"
flO SO...l.TIQ:oI
-6.)2 S.ll'".16
".00
-7.'3
lO.01
?))
,.'"
'4.V.·11.66
)Co ~~ll>tton
6.)1
l'U6 ::h"lttna R.Tal~r..llW 11 I O.~J6"3.'680 -Lib 1.93 -C.llB ).1061 0.J9"6.28 -0.1611·).]OSI·2'4.(,)O.'~6.lJ 24.4S ).)2 6.U'·11.11·2."1.6.
nIl Ta,..,.~ltu Ill.T..I).,c·ptn,)IS 1 0.1Io1:H ].).4"0.01·11.90 -0.2369 1.6C10-o H lLO}'".0.176"-~.60'12 ll./'b·0..56 H.~"22.&);.65 11.2)Upp"'r "'u",b:;y I.Too Lo...
292l!1 H",tuan.(t.0"
uo Skln'ftcna •.nf.SLw'I'ntu IS I _O.17'9V'1.1411 -0.12 9.0)-0.H1/'~.)2'''--o.ss-3.'6 NO SOL.:..'TIOIl H.68 l.lo 1.9S·)to Sol~:10'"
10110 TonlJna I...II T",n",',.,a "1_(,)01 U.2US -1.]1-JO.02 U.2~e'lo )_'9)~1 S.OL 9.98 ·0.06)2...l.6:))-21.2]-1.)6 1).'1 1'.)0 S.'9'2 9.n n.lI }.16 '.11·
ncqc"h .....~h In ,O(,I'Jo
eo..fftcltt'lt of .....vn ...n <II nat ...ral dna
~o"ff:«lttH of lo...et.:.sl:5 of n"("I"~d..l.I
co«~llelfht 01 .1.("""0:,.vf Ih......t .......l 101.ol (",or lht ....
coorUlcl«:tr or l...lto~l.or 11'>«n.l'"c.l1 1°1.0'ttlc dolt.
~od'hl.JlL 0:.~(·..r,..:...1 or I"'"nH ..r ..l 10110'th"t~allsro,..od d ..l ..
t(lot:ff 'c.hnt of kun"...tl of I"'..".ItoJe..)LOI"of th,tfallifor-e-<t doll.
"''''l.CV.-""'''''.Ie r:o,,(flclent of "'af"hllor:a lor all rcr ...ttl p.uloch ""c(lIUot"d
S 0'De·:J.at I an"-...:Q-QD/QO tOI'I.IS.1.5.)0 oIl1d 10 )luc r'l::uen 9.r 11ldll
H n D""'~JlLtl)C'I -~jQ·COI/S hI'1.25,1.S.10 .Ild 20 l'ftof U:H'rn p'l:rlodll
C(CUla.bll I
t,.."(l.()&I'lo ......t
)tllJl ...Cr.r ...1 PoIr;r_«lil.r ~c :.or.....1
I...·M 1..01 Pf'~rlOr"tYOIe III (_orn:::nl.)
LP-Hl LAi.fU.IQn Type 111 ~"U.h'''lL llk"lJho«I)
Ollj;rribolt JOG kit lirt in,..cho...n p"r.fI:::lC'tC'r
A Crt:.L~Cas.IIr.rlDn only
Upper bO\ltld.ry 1.roo Jo...-le,.tlua I ...tee th«•.alnlE\ld...of rl'tf'1..,......flood 0 ..record.
Lo""1'.<>\Ind:af7 11 too hllh -Ife:atcf than th•.---.lhU flood 0,"rc'Of~.
TheoreI1c..l Val .....
C"'_blf 1 I we:No~...l
C5·1.14 C51.-0.0
0;-5.'o;J.-l.O
..02-9.00.7.'6·LI'J"-b.n
lPL'o(O
C$U-O.O
ClJ..A-l.O
I ~.1I1.61-1.b49.Jl.0.0:2d:·2.'11M"·S.)Q ).~l--0.'}bB ]'OS~lli-1.10)1 )..101O.h)'J.OSlJ92J(If.CMel .....COppoH •.1110
.
es
n
esc
<Xl
es ....
o<U
w
I.....
N
Gumbel I
Coefficient of Skew
Coefficient of Kurtosis
Sum of Deviations
Hean Deviation
Log Normal
Coefficient of Skew
Coefficient of Kurtosis
Sum of Deviations
Mean Deviation
Three Parameter Log Normal
Coefficient of Skew
Coefficient of Kurtosis
Sum of Deviations
Xean Deviation
TABLe 3.3
MEAN DISTRIBUTION STATISTICS FOR ANNUAL INSTk~TANEOUS PEAK AND
OCT.-MAY MAXIMUM MEAN DAILY FLOWS
ANNUAL INSTANTANEOUS PEAKS OCT.-MAY MAXIMUM DAILY FLOWS
MEAN STANDARD COEFFICIENT OF MEAN STANDARD COEFFICIENT 0--DEVIATION VARIATION (%)DEVIATION VARIATION (%)
1.22 0.83 68 0.92 0.91 99
.5.86*3.34 57 5.46~\"3.20 .59
-17.64 15.7CJ 90 -2.86 8.43 29~
6.95 2.89 42 8.80 ~.17 36
0.42 0.92 219 0.23 0.48 209
4.85 2.29 47 3.73 0.87 23
-13.59 12.61 93 --I.27*5.45 429
6.91 2.95 43 7.21 2./0 37
-0.02*0.17'850 0.09*0.08 89
4.10 1.27 31 3.41 0.40 12
-13.34'"14.06'105 -4.45 6.32 1.42
5.n 2.26 :;8 6.79"/<2.52 37
Log Pearson Type III
(moments)
Sum 0:Deviatiofis
Mean Deviation
Log Pearson Type III
(maximum likelihood)
Sum of Deviations
Mean Deviation
-14.58
5.33
-18.09
5.09*
11.78
1.74
7.89
2.57
81
33
44
50
--2.53
7.22
-7.72
7.08
7.50
2.21
7.25
1.80
296
31
94
25
*Distribution best fitting a given parameter.
misc7/w1
TABLE 3.4
HOMOGENEITY TEST
ANNUAL INSTANTANEOUS PEAKS
Station
Susitna River at Gold Creek
Caribou Creek near Sutton
Matanus ka River at Palmer
Susitna River near Denali
Maclaren River near Paxson
Susitna River near Cantwell
Chulitna River near Tal keetna
Talkeetna River near Talkeetna
Montana Creek near Montana
Skwentna River near Skwentna
Tonsina River at Tonsina
Copper River near Chitina
Q 20 /Q 2 =y 20
1.83
1.82
1.49
1.81
2.02
1.68
1.47
2.33
1,.96
1.49
1.72
1.35
y 20 =1.748
5 20 =0.2776
Limits of 95%Confidence Interval
1.11 -2.39
The stations selected for use in the Susitna Regional Flood Peak
Frequency Analysis are homogenous with respect to the annual
instantaneous peaks at the 95%confidence level.
3-13
;c7/w2
TABLE 3.5
HOMOGENEITY TEST
OCTOBER -MAY INSTANTANEOUS PEAKS
station
Susitna River at Gold Creek
Caribou Creek near Sutton
Matanuska River at Palmer
Susitna River near Denali
Maclaren River near Paxson
Susitna River near Cantwell
Chulitna River near Tal keetna
Talkeetna River near Talkeetna
Skwentna River near Skwentna
Tonsina River at Tonsins
Copper River near·Chitina
020/02 =Y20
1.57
2.63
2.24
2.35
3.32
2.33
1.98
2.12
1.76
2.45
1.50
y 20 =2.205
5 20 =0.5175
Limits of 95%Confidence Interval
0.99 -3.41
The stations selected for use in the 5usitna Regional Flood
Frequency Analysis are homogenous with respect to the October -
May instantaneous peaks at the 95%confidence level.
3-14
misc7/w6
TABLE 3.6
REGIONAL ANNUAL INSTANTANEOUS
DIMENSIONLESS FLOOD VALUES
Susitna Caribou Susitna Maclaren Susitna Chulitna Talkeetna Skwentna Tonsina Copper Montana
River Creek Matanuska River River River River River River River River Creek··
Return at Gold near River at near near near near near near at near near
Weighted
Period Creek Sutton Palmer Denali Paxson Cantwell Talkeetna Talkeetna Skwentna Tonsina Chitina Montana Mean Median Median---
1.005 0.50 0.45 0.45 0.81 0.79 0.49 0.76 0.62 0.66 0.53 0.76 0.17 0.58 0.52 0.58
1.050 0.58 0.55 0.57 0.83 0.81 0.59 0.80 0.66 0.72 0.61 0.81 0.34 0.66 0.64 0.76
1.25 0.75 0.73 0.77 0.88 0.86 0.76 0.88 0.77 0.84 0.77 0.89 0.63 0.79 0.77 0.86
2 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
5 1.36 '.'36 1.24 1.26 1.32 1.31 1.19 1.46 1.22 1.31 1.15 1.45
1.30 1.31 1.24
w
I 10 1.60 1.59 1.38 1.51 1.63 1.50 1.33 1.86 1.36 1.52 1.25 1.72 1.52 1.52
1.69......
lJ1 20 1.83 1.82 1.77 1.841.49 1.81 2.02 1.68 ).47 2.33 1.49 1.72 1.35 1.96 1.75
50 2.14 2.10 1.63 2.29 2.67 1.91 1.67 3.04 1.66 1.98 1.47 2.26 2.07 2.04 1.79
100 2.38 2.32 1.72 2.74 3.27 2.08 1.82 3.67 1.79 2.17 1.56 2.47 2.33 2.25 1.94
200 2.63 2.54 1.81 3.26 3.99 2.25 1.98·4.39 1.92 2.37 1.65 2.66 2.62 2.46 2.10
500 2.96 2.83 1.92 4.07 5.15 2.47 2.21 5.48 2.09 2.63 1.78 2.95 3.05 2.73 2.46
10,000 3.84 3.64 1.97 9.97 11.65 3.10 2.99 11.54 2.75 3.39 2.26 3.62 5.06·3.51 3.06
susi5/n 1
TABLE 3.8
PHYSIOGRAPHIC AND CLIMATIC PARAMETERS 1
Mean
Main Mean Area of Mean Minimum
Drainage Channel Stream Basin lakes 8<.Area of Area of Mean Annual Precipitation Annual January
Stalion Area Slope Length Elevation Ponds Forests Glaciers Precipitation Intensity Snowfall Temperature
Name Location (Sq.mi.)(ft./mi.)(mi.)(ft.)(%)(%)(%)(in.)(in.)(in.)(OF)
Susitna R.at Gold Creek 6,160 10.2 189.0 3420.0 1.0 7.0 5.0 29.0 2.0 200.0 -4.0
Caribou Cr.nr.Sutton 289 13.6 30.0 4190.0 0.0 10.0 0.0 28.0 1.5 80.0 2.0
Matanuska R.at Palmer 2,070 79.7 77.0 4000.0 0.0 14.0 12.0 35.0 1.5 80.0 4.0
Susitna R.nr.Denali 950 56.6 51.0 4510.0 1.0 1.0 25.0 60.0 2.0 400.0 -6.0
w
I Maclaren R.nr.Paxson 280 133.0 23.0 4520.0 1.0 0.0 19.0 55.0 1.5 400.0 -6.0f-'
-.J
Susitna R.nr.Cantwell 4,140 10.0 107.0 3560.0 2.0 5.0 7.0 32.0 1.5 200.0 -4.0
Chulitna R.nr.Talkeetna 2,570 23.0 87.0 3760.0 1.0 22.0 27.0 55.0 1.6 250.0 -5.0
Talkeetna R.nr.Talkeetna 2,006 35.0 90.3 3630.0 0.0 25.0 7.0 70.0 2.5 150.0 -2.0
Montana Cr.nr.Montana 164 114.0 25.0 1:930.0 3.0 54.0 0.0 40.0 2.2 90.0 0.0
Skwentna R.nr.Skwentna 2,250 30.6 98.0 2810.0 5.0 34.0 16.0 43.0 2.0 140.0 -5.0
Tonsina R.at Tonsina 420 71.0 46.0 3600.0 4.0 27.0 11.0 25.0 2.0 180.0 -2.0
Copper R.nr.Chitina 20,600 14.4 178.0 3620.0.3.0 22.0 17.0 37.0 2.0 120.0 -4.0
Values in this table are from the report entitled "Flood Characteristics of Alaska Streams"by lanake (1979).
TABLE 3.9
COMPARISON OF REGRESSION EQUATIONS
Study
Present
(a)
(b)
Homogenous
Flood Region
Susitna &
Neighboring
Stations
Area II
Cook Inlet
Number of
Hydrometric
Stations Used
12
163
163
132
26
50
Physiographic
Parameters
Utilized
D.A.,L,G,
MAP,MAS
D.A.,MAP,
LP,F,T
D.A.,LP,
MAP
Recurrence SE of
Interval Estimate
(Years)(Percent)
2 ±18
5 ±19
10 ±21
50 ±29
100 ±34
2 ±77
5 ±78
10 ±79
50 ±68
2 +56,-36
5 +51,-34
10 +52,-34
50 +61,-38
D.A.
L
G
MAP
MAS
LP
F
T
susi6/m
=drainage area,mi 2
=stream length,miles=percent of basin as glaciers=mean annual precipitation,inches=mean annual snowfall,inches=percent of area as lakes and ponds=percent of area forested
=mean minimum January temperature,of
3-18
.•.:.1::"[',_.
50 100 200 50020
......-1--1--.
10521.251.051.005
--1-.,,'-
0.3
--'11 111.(NOrr.E:'WI i111 II -m"f~II'li ill'~"-IF ·rf-·····:~I:.-.....:..'1-:1
I:·:['.:.•.·::...·.::·I.II·I·.:.~.
70.J+',I.THE fdEI~~'•f'li 9 L rjn~'·-I '..'..:.".:'~.=.:'11 :'~.:::::::~I .'.:.~:':.II I .k,'L-_I.IA:ri U w ,"~.:.::'-:.'1--..:.:..'-"..........-._--._...I..'.',":.:,IS UER ~R IIIf"\riD M ....I •..-".---..,.~'.._.I -HI,-
6.0 -,(......I j ±r !~7.i>6 (~J.!t I ~~-,q ~:~01#+:4f~126.f.ti~,'f-,-,,!->~.'~.
50·III '~'.I ..fl-'i rT -ttl'",I·c '·f·ill;,·I'::~·:·~:--_·-;,".:~~.::':'If"-,:::'----:.cr .I .1-wJ1=i E ;.:..+,.1":'.'"1J.'l l l ~l.LL·J.'·i:'lt rr 'T'...:.:~.'_i~\:-::r':_1,~.~::::--.I,'.~~:
- i I I:·:'r-·,_:.1 "I '.:'lil l·1.:'....;.'1',::-":~.=...?.Ii .:.'::'::::'='.--1:...-,
40 'jl ,i-"Q·M~tNMt'#11r\N.'"tt~'L -"'1''1 '.:...._-....:-::.:::--.:_...\,."":---'-1/:::\:.:::'.'...,1'1 I"g-obl de'l~''';'··IJ··l-·'·:",,:,:,,!.'-"'~:''::-:-~-;,:..:..--.":-.."..-....-n!I f40'r/,lW'!Nt.!n r~~'.~k rl .'I ;tiV ;...--.~--.--::.:~r ..:·.-1/·.''-:'r ::P, I Ii G P R~E NIl ro for:~'1'~I I S r~,-. .....·c__'..../,.-
30 _'!i -;,:,.;)'ft~~.1 "',I·t . _..:'i,.'~,~r::-...'.'','---~....--.
·MI P-~E/lltl i~Ju :~1 ~~I I 'I".I",:.,.\li II J I.:-::.-,:.::,.::.1----....:"~·v~::I ..:·=--1--l--H-H-tW11.:"C::::-.---..'.. . ..,.I .:'... .- .,-...,.'-.:--"._-_.-. " .,,,...-..,--
TIl I llIlf s:.-,t:.Illr>i·j I ' .-....I~n t"-..-_.,...,.-....1--'. I .------I I ... . . .F I'll--f-:-"~--.---.......-.-._.--_.I -----=-:..---:--::::~.:.·IT '1':"1 -'.-j~....,'[.....I--·lT-I<',..··_··--'III!-,.--.-_.._.','1+.-',.I.'.,.TI I I'-.--.17::--L ---- .I-PI •-----
, ,'r''1'II ,I ,,·'tl I ..I~"""'VF-''-l 11....._.
I-----H-+-..:l-UI UWlllll-W-U-l-l1WI1-I+11 wu'lllllllmi ~UL,um:r ~-..-::-.I~,...~:~=~~~,~1M
..'-I--'---
2.0 -t-tt+~.:='u:l.110
=Guui!
I
Z 0.7 ..,~0.6 .:~:''H~'-~-'~~__k'.,~1 T--I:·Il I ',T:-rTIiIIUlilT n"=~[[['III!·~"f·..+~.~i.il~'1·4::;-,l:-~~:'
oilt I--"". .~.L+I .I !~n :I'j i I I '.-.''...0 :I-r-.I .1-,---'['.r
t
!..d:':"·.-c-.C -......1+-,--,_.;;--I'. ...•..,~--. ....,-.1.1.. ._:-C=:"'!.;----1 i l j ,"
O 5
.',-.1.1 __--~...I I ,.-". .l'.:'-__:±FTI"'.'..-'.:::==~'.+1-.-1,,-:,".-::-:'[1 1 ..:-:~
•"I'IT......-r "1 ...)1.........'I J '-'-" .I'."-'II,I,,I .j ~'.'..I.'.'~~III'::,,::_~:;::,'~'I-.:',iT '.;---
r rII I I'I 1t I !--.•~I'..jLj.tc'".~:"••:c-::.i H-1,1 I··.•..:-~:-.~.":II 1---I-.I:.~,I I I U J ....'-jill'.jl ,I -.- . . . ,..Imljl~t'jm'r~...~I .•~:.·~..=:.'.I,I ..'<:C:~-~f-I~l~."~';jS
J
.[...,...'':':.~'~=1['..,.:.~:~:~..'~f~
..I . . ,-,-'..-.',-,.I...,I,I I I ''-,-----I I·--I I.)... ,
10,000
w>n::
::>
u --t-I ,1'11111 I 111:_=.':~CP)hRqsl .~._~II II '1--.'"CP1IF!~E~'I ,Ii~-..I"I -Jj ~I·...cQlii=b.':SlIT Ie '~~t~=~~~=II~~tJ;..
U1 1.0 " "I .:"..,I,~-t-I I (ONF 01 NC I ~. -'!~0.9 ';1
1
-'l I':.--:--::::1:
"
,I.::.:.::~r :C~_:,,'.:=,:,t·:··.iI:\.>
Q 0.8 ..".'.Ii .I ..\.•••::r '-'.C:I:
(f)j.-'.,II :::...-.:.:..R".'.......,.,I '1 ..:..-c __'1_1:11·1-,·111"1"1 j':',__:k::'-'"'"II .'.1...:.',:~'.::.--.-.I I'"~..t'.,:.-:.
W
I
f-'
W
RETURN PERIOD (YRS.)
R&M CONSUL.TANTS.INC.
Prepared for:
3.1.FIGURE
DESIGN DIMENSIONLESS REGIONAL FREQUENCY CURVE
ANNUAL INSTANTANEOUS FLOOD PEAKS
Prepared by:
..-u~~~
.•-.._+-
·1.1~~r.::'1'".:=lilt.•I:l.ll.LH 1iIIIIIllllllTl'!:~I.:-....
1.05
':::::I>I··lj·:·:·I~I:·11'---...~...---...
1.005
0.7 Ttth I',-_.-- .-1 .f1,'IT·:'..l :',1i4f1ffii +11,~'.:~.~.:,~'~'-~--~'·ll 1l1··'1M:l'','~~I ITr···:.::':ti=
0.6 ~-fttt I J~~~~-~:I~...:f:.:rH~:~'·::,l':'f-":+~'j·.:(p,>~,;·~~~k.:·.:~r~r:·~:~C,:·H~·~~';b
o.5 #~{).''-....'.v .-.}-I 'I'I "'..I:::.'t~III I .'.II':..::;:.:.:~,~.'~:l'',.:j:~-.II ~..:
1",'p~--':-:'1 1 ,'.11"-.\....:c ,,-:~':'.·t·".:.::~::.;:~~~l·jL~':~<'I-==;~~.:'+
I .:......:..·1:··'--:.'I,1 I ,I .:.:.(.:!I ~.I·
0.4 "I ..,.'--'1'1 'Ill'11 I-rm I ."...')I ..
0.3--+---<~-I-t-l•.f __:+.,.,1:ltll IH .J:~:I TIl II/J1:If ~rt ~tf~·
1.25 2 5 10 20 50 100 200 500
RETURN PERIOD (YRS.)
w>a::
:::)
u
(fl
(fl
W
-l
Zo
(flz
~1.0 ._L"
()0.9 ~I.~LLII0.8 ..~.'.-,..--'-'-..·'Pf#ttimtittr:Hmr~mmlliWJJttt-H+.LlJ 1III
_~I'_h-
W
I
f\.)
o
Prepared by:
DESIGN DIMENSIONLESS REGIONAL FREQUENCY CURVE
OCTOBER -MAY INSTANTANEOUS FLOOD PEAKS
Prepared for:
FIGURE·3.2 •
4 -EVALUATION OF DESIGN FLOODS
Using Figures 3.1 and 3.2,annual instantaneous flood peaks and
October-May instantaneous flood peaks call be predicted with a
minimum of additional data.The figures will prove useful in
assessing flood peaks at ungauged sites within the study area.
The figures should not be used for basins with drainage areas
smaller that 164 square miles,the smallest basin area included in
the study.Use of the equations and figures for these smaller
basins may result in unrealistic values.It is recommended that
the regression equations developed by Freethey and Scully (1980)
be used for determining flood peaks in these basins.Thei r
analysis included basins as smaH as one square mile,and the
equations have a smaller standard error than the regressiona
equations developed by Lamke (1979),as seen in Table 3.9.
It is necessary to have information concerning the drainage area,
the length of the main channel,the percent of the drainage area
covered by glaciers,the mean annual precipitation,and the mean
annual snowfall in order to predict the annual instantaneous flood
peaks on drainage basins ,in the upper Susitna River region.It is
also necessary to have information on drainage area and stream
length to predict October-May instantaneous flood peaks in the
upper Susitna region.When compiling this information,it is
important that the information come from the same source,or at
least represent the same precision,as the data used in the
regression analyses.
Thus,the drainage area should be computed from U.S.Geological
Survey topographic maps in the horizontal plane.Main channel
slope is taken as the average slope between points 10%and 85%of
the distance along the main stream from the lowest point of
interest to the basin divide.The percent of glacial area is the
total drainage area shown as glaciers on the topographic maps
divided by the basin drainage area,as measured by the grid-
sampling method or planimeters.The mean annual precipitation
and mean annual snowfall are determined from isohyetal maps
(NWS,1972 or Lamke,1979)using the grid sampling method.An
example of the use of the figures for determining instantaneous
flood peaks is given below.
Suppose it is desired to obtain the annual instantaneous flood peak
with a 50-year recurrence interval on an ungaged basin in the
upper Susitna River basin.The following drainage basin
characteristics were determined.
Area of Drainage Basin =164 sq.mi.
Stream Length =25.0 miles
Percent Area of Glaciers =0 percent
Mean Annual Precipitation =40 inches
Mean Annual Snowfall =90 inches
susi6/o 4-1
Using Equation (3.5),the mean annual instantaneous flood peak is
determined to be 3269 cfs.Using Figure 3.1,the ratio of the
50-year peak to the mean annual peak is 2.Q4.Thus,the fifty
year peak is
Qso ::2.04 (3,269 cfs)
QSO =6,670 cfs
The confidence limits on this estimate could be found in the same
manner by selecting the appropriate ratio from Figure 3.1.Thus
the 'upper and lower 95%confidence interval are:
Upper 9S%Confidence Interval
Q ::3.11 x 3269 =10,170 cfs
Lower 95%Confidence Interval
Q =1.01 x 3269 =3,300 cfs
susi6/0 4-2
5 -EVALUATION OF TYPICAL FLOOD HYDROGRAPHS FOR
SUSITNA RIVER AT GOLD CREEK
For the gaging station on the Susitna ,River at Gold Creek,typical
flood hydrographs were developed from several measured
hydrographs.The temporal distribution of annual maximum flood
peaks was first determined,and is presented in Figure 5.1.The
figure illustrates that the greatest frequency of floods (55%)
occurs in June and the second highest frequency of floods (26%)
occurs in August.
The five largest peak hydrographs were selected for two periods:
May-July (rain-and-snowmelt floods),and August-October (rainfall
floods).These were made dimensionless by dividing the flows by
the peak daily mean discharge,centered about the peak with
±15 days and plotted on the same graph.The mean hydrograph is
the arithmetic average of the five floods selected for each period.
The five dimensionless hydrographs and the corresponding mean
curve for each time period are depicted in Figures 5.2 and 5.3.
These figures illustrate that the mean curves are typical of the
general shape of the snowmelt and rainfall hydrographs,but that
there is considerable variation from year to year.
The seasonal discharge frequency curves depicted in Figure 5.4
were derived by assuming that all floods from May through July
are rain and snowmelt floods and that all floods from August
through October are rainfall floods with high-altitude snowmelt.
The seasonal daily peak discharges for each period are tabulated
in Table 5.1.The corresponding published annual instantaneous
peaks are listed in the respective seasonal period.The average
ratios between instantaneous peaks (Q I)and daily peaks (QD)for
the snowmelt and rainfall floods were calculated by averaging all
the ratios (Q t/QD)for corresponding instantaneous and daily
peaks.The calculated ratios (Q,/OD)are 1.063 for snowmelt
events and 1.052 for rainfall events.The missing instantaneous
peaks were then computed by mUltiplying the daily peak by the
appropriate COl/Q )ratio.Using the three parameter log-normal
frequency distrlbu~on and the instantaneous peaks from Table 5.1,
the frequency curves for the May-July and August-October periods
were computed.The annual instantaneous peak frequency curve is
included on Figure 5.4 for comparison.
Fifty peak hydrographs were separated into the May-July and
August-October periods and plotted.The base flows were
estimated using standard techniques and subtracted from the
hydrographs.The volume of each flood was estimated by
ptanimetering the resulting hydrograph and tabulated in Table 5.2,
together with the corresponding instantaneous peak.The flood
volume frequency analysis for each period was conducted using the
three parameter log-normal frequency distribution.The
corresponding frequency curves with the 95%confidence levels are
illustrated in Figures 5.5 and 5.6.
susi6/p 5-1
A power curve regression analysis was used to determine the
correlation between the instantaneous peaks and the corresponding
volumes.The correlation proved to be significant,with correlation
coefficients of 0.794 and 0.825 for the May-July period and
August-October period,respectively.The statistics are tabulated
in Table 5.2 and illustrated graphically on Figures 5.7 and 5.8.
As the correlation is acceptable,it allows for the devel'opment of
the typical 100-,500-,and 10,000-year flood hydrographs
illustrated in Figures 5.9 and 5.10.These typical flood hydro-
graphs were produced by using the general shape of the mean
dimensionless hydrographs in Figures 5.2 and 5.3,and extrapo-
lating the peaks and volumes for the 500-and 10,OOO-year floods
from Figures 5.4, 5.5,and 5.6.The volumes beneath the flood
hydrographs are those determined in the frequency analysis.
The typical hydrographs discussed here are qualitative indicators
of flood hydrograph shapes.They should not be used for
rigorous analytical calculations t but are intended to supplement
them.
susi6/p 5-2
misc6/jl
TABLE 5.1
DETERMINATION OF DAILY INSTANTANEOUS PEAK RATIO
SUSITNA RIVER AT GOLD CREEK
May -July August -October
(Snowmelt Floods)(Rainfall Floods)
Instant-Instant-
Daily aneous Daily aneous
Peaks Peaks Ratio Peaks Peaks Ratio
Year (cfs) (cfs)QI/Q D (cfs)(cfs)QI/Q D
49 35,000 [38,700J
50 34,000 (37,300)1.097 27,600 [29,000]1
51 35,800 (37,400)1.044 31,800 [33,500]
52 43,300 (44,700)1.032 41,900 [44,100 ]
53 37,700 (38,400)1.065 28,100 [29,600]
54 30,100 [32,000]41,000 (42,400)1.034
55 39,000 [41,500]56,900 (58,100)1.021
56 51,500 (51,700)1.004 31,000 [32,600]
57 40,600 (42,200)1.039 26,600 [28,000]
58 28,000 (29,800]47,800 (49,600)1.038
59 39,600 [42,100 ]59,700 (62,300)1.044
60 39,300 [41,800]40,100 (41,900)1.045
61 54,000 (59,300)1.098 26,000 [27,400]
62 79,700 (80,600)1.011 31,000 [32,600]
63 49,000 (53,800)1.098 35,000 [36,800]
64 85,900 (90,700)1.056 21,600 [22,800]
65 39,900 (43,600)1.093 33,600 (35,400]
66 58,400 (63,600)1.089 33,500 [35,200]
67 50,000 (53,150]76,000 (80,200)1.055
68 39,700 (41,800)1.053 21,800 (22,900]
69 26,500 (28,400)1.072 16,800 [17,700]
70 30,800 [32,740]1 31,600 (33,400)1.057
71 66,300 [70,500]77,700 (87,400)1.125
72 70,700 (82,600)1.168 26,400 [27,800]
73 52,800 (54,100)1.025 30,500 [32,100]
74 33,600 (37,200)1.107 22,300 [23,500]
75 44,000 (47,300)1.075 .24,800 [26,100]
76 33,300 (35,700)1.072 32,000 [33,700]
77 52,600 (54,300)1.032 26,200 [27,600]
78 24,300 (25,000)1.029 20,800 (21,900]
79 39,300 (41,300)1.051 28,400 [29,900]
80 49,700 (52,000)1.046 31,100 [32,800]
QI!QO=X=1.063 QI /Q O=X=1.052
S.0.=.034 S.D.=.032
N=23 N=8
Notes:()Published instantaneous peaks
[ ] Instantaneous peaks computed by ratio.
5-3
misc6/j2
TABLE 5.2
TABULATION AND STATISTICS OF INSTANTANEOUS PEAKS
VERSUS PEAK VOLUMES
SUSITNA RIVER AT GOLD CREEK
Year
May -July
(Snowmelt Floods)
Instantaneous Peak
Peak,Q Volume,V
(cfs)P (ft3 x 10 9 )
August -October
(Rainfall Floods)
Instantaneous Peak
Peak,Q Volume,V
(cfs)P (1t3 x 10 9 )
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
STATISTICS
37,300
37,400
44,700
38,400
32,000
41,500
51,700
42,200
29,800
42,100
41,800
59,300
80,600
53,800
90,700
43,600
63,600
53,150
41,800
28,400
32,740
70,500
82,600
54,100
37,200
47,300
35,700
54,300
25,000
41,300
52,000
10.6
23.0
69.9
33.6
9.7
38.0
33.8
27.0
ND
28.4
18.4
30.8
63.7
26.7
83.4
35.6
30.8
19.9
32.2
11.8
16.1
50.1
82.8
36.8
23.9
28.0
18.8
45.9
12.9
12.6
NA
29,000
33,500
44,100
29,600
42,400
58,100
32,600
28,000
49,600
62,300
41,900
27,400
32,600
36,800
22,800
35,400
35,200
80,200
22,900
17,700
33,400
87,400
27,800
32,100
23 j 500
26,100
33,700
27,600
21,900
29,900
31,100
8.2
16.4
12.9
8.4
ND
19.0
ND
6.1
19.0
37.6
10.3
ND
ND
5.7
6.5
17.7
12.5
30.3
UPH
3.9
7.7
27.5
UPH
14.9
9.3
UPH
11.5
3.2
UPH
UPH
NA
40,090
18,214
Mean
Standard Deviation
Regression Equation
Correlation Coefficient
Sample Size
48,441 32.9 x 10 9
16,104 20.1 x 10 9
1.50
V :;:2820 Q p
r :;:0.794
n :;:29
13.7 x 10 9
9.0 x 10 9
1.33
V :::9840 Qp
r :::0.825
n :;:21
Notes:NO:;:No data
UPH :;:Undefined peak hydrograph
NA :;:Not available
5-4
I '
-----.-----.---,..---~---r--- .
.-----+------If---.-f--------~~..--.-\---,-~~~.-+I---f-----.\---
-_-'--.-1---.--1------'-~~..---------j-.----
__----I-__:.......j....__~_____l____---+--___+--,-f----->--.-.-1_--.-.\---1-------::.t~-=:-
10
0 ====:=i=====±=====±=====t==:=j:::::j=:===±=====:1:=====t=====t=====~=--.=--=---j---'-_--'--I -+-:---:--.:...--+__--+-.~-_.I--~---'-.L.--~--lf------j----l-----1--j-__~=-:-=
f---,-~---I-.,_'-__+---_!_----+---+-'.---
I :
-:...---'--I---,--1---~_l_~.,.......,.+-~+----+---+-:-----,--I----I-----j---._.-~:............~----+---+--+----,---f~---'~~--~--'-I--------\--~-_l_--+--:_._l_.---~
~--I----_l_--_+_--_+_-.--~-.-'1-"--;-----.-:---1--_._
60 .-.--1----I-.;........---.f---~I-,-f-~:C-c-':~:r.g./----~--=---I_----._-~=r---§_>--..1---_'_~
~-__l--_+----'-_I_-...;.~c+-----+-:..:_:_:_./:~::;:~.~.-j ..---~---;----1---.f----
----l-_...,...+~--r-.,.....;..-'-I-'-,--+--+-------'-.:~~~'rl·.-,---.----1---.....1 --'--.-1--_--+---
'===~=j===~=j::::=-...j..+--:'...;..~..:..-.....:.----II;=-.::"~..:--:--+-:~;.;.:·>.;.;:·:+:;.;.;,;·:'4::===.,---.·--+--.------.--+-....==-~~I-j·_~.-=--=--=-~t-:-.-=--:.-=--+---f---.-=--._-__-f
4 0 -.:....---L---I----!---I~-__l:;:;..:;:;..,:;.;.;:.;...~..+---~~-_+--__;_--+--~-__j
.._~~-!-----l--------I---~(:>+----f---i---~--'~--------.-f-,..__.___L--.-------
':-::----=t=-.--+--~-t----+---I,7::::~r-;-::u~::::~}I---'-.i-:-..--.-~_~~~~~=
---~--_+-----'---+---__t=''---'-.-+:;:.i~~~":-r·26-%I.---==L =~-;...-~.~~
-.-_-_-_-+-.-.....:......-+--~-11-.-=-'-_-.__-1'-_-,.,--.:_-+~\ttt~~-::¢'t+ti~=~·--~~~~
20 .~==~==~~~~~il~:~il~:~~:~-~
o
J F M A M J J A SON 0
u.o
(f)ooo
.J
LL
...J«::>zz«
MONTHS OF YEAR
SUSITNA RIVER AT GOLD CREEK
PERIOD OF RECORD -1950 -1980
R&M CONSULTANTS,INC.
PERCENT OF ANNUAL
MAXIMUM FLOODS
5-5
Prepared fa
FIGURE 5.1
--'--.--+-----~,I---....:.-~-+-.--.-'---~...-.__._'__.---..-F~.-:~_...__I~---=---~._--.,~---I-----_._'-'--I--~+-. --.
.-,-c-I--·--h--~f-------'_.-1-----~...~-._-'f----1·-----·--f·---._.--
.....:...-'--------.-j-----1----+---+.----+--.--+----r---'---'r---..---,--.----
1.0 _~_..:....'_=_==t=====tr:==j~=~:-,-.-±-!-!-'--1=-,-/~'-_--"~--j-'~:'.h -L---I-~~=t~-.-.-...:-.·-.--t···..-----1--,.......:...~-:....--I__----.~---_.~-..--f~----~--..-·~-'-_.1,'.\\_~_~..__j-.._---;. _
0.8
~~...:.......j___1_----.,.-.;..+..:-_:--+----:.....:......-Ii_...,-...:......;.+_~'P-i-~'.l".---1------l-L..--I-~.-,._+.-
\
DAYS TO PEAK DAYS AFTER PEAK
SUS ITNA RIVER AT GOLD CREEK
LEGEND
Date Peak Discharge
(c fs)
•••••••Mean Curve
June 23,1961 54,000
------June 15,1962 79,900--------_.June 7,1964 85,900
-----June 6,1966 58,400-------June 17,1972 70,700
R&/\/I CONSULTANTS,INC.
DIMENSIONLESS'HYDROGRAPHS
MAY -JULY
5-6
Prepared fO!
FIGURE 5.2
15
;i
105PEAK-5-10
=-J~:=--~-=-=-jI~~;~F--m~-,:-.-
1.0 -_.-t--H_--'-J-....----,--~I"\'-f---~-"l'..,.---.f--.._~__:...._~.__~_w+\'~_~-~I-I --,..-.__
-.--+-,-._.-.,---.-----:-.--11'-.•-a---'-'--~"----"----_.~.--....----j--..---I.-1--1---...'--.-----._.-",-'-'---f ---=..--.._;-
• '. I~-*. ,I I.'-f---.'-_.--o-;---t-,.:.....;-::".":!J~~..__._.",=t:~e~t:-:-i....-'.,"--_'_i_..__.~___I J .\\~-----;"--~'.t '~_
0.8 +-.'/.':1.tc~. ..i'.--,-I+-'..;...+......:......-;....,
:--,---.-1=:,.'"I.\ .7.,., ,_h'=:'~~'.:..:~I-\-............;.:-+-t-j +-..L...;~:.-.....,..-"-+"-'--,-
--....:....-~t--,--:-(.-J._-----;-~~\-~-:.-.-'--~~..-..•.._---.:...L~__\----_:'-""_111 +--...-_.--,eo . ...........p......-+------4+-1------1 .~._,._-'-<--}-..,....-...,.....~-_-I
..,·---I----r·--I---Il '1'1"-~_...--+.,--!-'-V l-~';"'"_"'".+-_--.-...L-_-..:
DAYS TO PEAK DAYS AFTER PEAK
SUSITNA RIVER AT GOLD CREEK
LEGEND
Date Peak Discharge
(cfs)
•••••••Mean Curve
Aug 26,1955 56,900
------Aug 3 ,1958 47,800--------Aug 24,1959 59,700
---------Aug 15,1967 76,000-----Aug 10,1971 77,700
R&M CONSULTANTS,INC.
Prepared fa
DIMENSIONLESS HYDROGRAPHS
AUG -OCT FIGURE 5.3
5-7
f,
.,,,.,.
I
l I
II I
,f
,.,
! '
/AG
,,
'I'I
II Iv
(/)
u:
u 50
(/)
-0 40oo
z 30
w
<.:>ex:
<3:
:t:
U 20(/)
0
,
:',.I
1·1.,
I :"t -l-H++...,-,
;....;
I '!
: I
!I IrI
i I I
2 5 10 20
,'.,
I ,
I
I
50 100 200 500
tl.+-...~-.....
I I
EXCEEOENCE INTERVAL -YEARS
SUSITNA RIVER AT GOLD CREEK
PERIOD OF RECORD -1950-1980
ANN·UAL SKEW IS 0.6830
MAY-JULY SKEW IS 1.130
AUG -OCT SKEW IS 1.134
Prevared by:Prepared fa:
~&M CONSUL.TANTS.INC.
SEASONAL DISCHARGE
FREQUENCY CURVES
5 8
IHI+H-:+-~:::.:~~:-~.:.,::~.;§'-:;::~:====~,~,:;;:;=~:l:.-=_=fr-l:!:l:::l~L :....~fr--~S.~--I,~'=~
200 III-I~I--II·:·I,I.I·~I,~1-li·II;I.I·~~:I:I'-lfl·lliilllllllllll'I'I~I-I~1'
";,'I ..,:,'Ii,,;.!,,/
-+--
I
I I
i ,
'-,'
-,=
/
,/---
'I I I,,",!"
:i I!~:'1 !;~I !I ~X
.~-_J~.-=1=
r~__- -
I-r '!I:~~:!!I
T1 !
II;i i!!I!I:Ii'i
::J,~
,..
,
I ;;,h-I ,,;I i "I,;,I ;I ',!,
:;i I :-',I ;'J ,:
I ,:I I :'.
I ,,I':!!!;;~I .
,,i II I i ,I
, I ;,;:II'I ,:. I ·i.i ;i;I ;!I I 1
I !!I J II I I I I i 111 I !iil !I!I i I I T
~L I :I ,,;I !1 i 1 !i !iI !;i i I I!
i I II i ,,]I i I !1 !i i !:i,;:!!I : I i T I I,
2 5 10 20 50 100 200 500'
Ij
20
90
eo
70
60
EXCEEDENCE INTERVAL -YEARS
SUSITNA RIVER AT GOLD CREEK
PE RIOD OF RECORD -29 yrs.
LEGEND
95 %CONFIDENCE LIMITS
VOLUME FREQUENCY CURVE
Prepared f(
R&M CCNSUCTANTS,ON:FLOOD VOLU::y~:~~ENCY CURVE _F_IG_U_R_E_5_._5\~~~(l
5-9
I
I ,
I I I,,
1 :V
I ,
.!
:'!I ,
j 1;
I!,I
,;'I
.;,
'\'I
, ' I:!I;
: I I,::'
, I \I '!'i
, i ;I
,!I.1;;.
: I ~i""I iI "
1
':-1-::'--lt-III-I-I-'I'I'i-'-I-I'li--I"lr;I"'I~rl"-I'I'I:--I-I"~~"'I"-II~"'1''::-j'I'-III-I"t=lrl"r11:I:I'i'I-I'I-
==+._-.._~._':"'"-.=--~-r 'j--F+=J:..t:-+_r-~+=~~:..==~.-.
.-,,'-f-,
200 ..c c ~..r -~=
,'i:iii i !i:
:~.r :I I 1 ~1 i 1
60
(J)50,
w ~
:::!':O')
3 Q 40
ox
>10
01-o IL 3
o --".-+-~
14.
--,,
• I •~
.~,I:,;
';,.
I"I'
I •~•• ;I
./I .I'
::.1 j ••'i;
:1.'I V I,.:........-r
,.'1./:/;'.';VI
,;.,:'/I 'j:i ,~I .:,.......:....+'-+-t--'-+-f-+--+i-t+l-t+'--l-'--+-T-+-++--t'+\-'I-h-~-'--i;::I ...."/.:;.' ,v ",;,~Ii,I .
500 '100 200
'I',"';:-/,.'I,/I',j,I 'ill r:I
,",I ' .,f---,''...:,.1+;Hi-+I+:71'v,U+:++-'H'~~~'.e./'*'-:-:~;1+:;.-+::+:+'-;+-'+-+-+-"';-+--H-l-1 +-+i-I-rlf-+...j.....-+H~:-;'-+---+'~
'_''_'~:.'!I,I::iii I I/,I !I i U'1,!::i i!i I I I I I hi i I I I
ii'riA"II/'Iii I,':':!i r Ii'!!i ,I
'---;-,:;iii i ;-:':-,-f£:-Ijt"'7i'7:+-1n;:;,,~,7i+'-l~17-:-1 :t4"!"""i:-;-:r.:~!'-:ir+i--+-t-t-h---:'-+";li+-:--f,-l;:~l-:-I-t-i-!-i---t--Hti-t-I +-'-,':--+--1
10L..-'-'-_......:..JL..:..L..J....j..W"'O"~...:....:..J....LJ.-'-'-.....:....J,-"-'-...l....'-.--t-'-'--'-'-..:...;..-'-t-'-'-L....:..+-~.1.--j-I-.:...:...J+..........-+-''--l..-+....:.........LLL.L.'-....l....l.......C........:..---L
2 5 10 20 50
E XCEEDENCE INTERVAL -YEARS
SUSITNA RIVER AT GOLD CREEK
PERIOD OF RECORD -21 yrs.
LEGEND
95 %CONFIDENCE ,LIMITS
VOLUME FREQUENCY CURVE
Prepared fa:
"~M CONSULTANTS,'NC~FLOOD VOLU::G ~:~~UENCY CURVE.:.....F.:.....:IG;",,;;;U...;.;R;,.::;E.....;5::;..;,.~61 ~~~I~
5-10
i':
.I;jI''
. i I t::1 ':
:::' ::;Ii:~::i:i i .:~I .-:1 V ~~I I ;I :;,+~;:.
.:,!I I I l .,.;",:",I/!!.::I '!l I:I;
~E±=~
=~-=:=
r.-"~F~,'-I.-:-fu8:3
.--I-----r--t---""..-,-+___+--__-i:=:;::
~::~
or--
-~_.
-------'
,
r-
=
-~.LL-..:....H;--,IL+-:+~'..;.'-i-'+-_~4'~'+I'~i~'-tl,'+~+-:;'-i-'+-~I'7"'..;''H:~"H7AT-If-+i -t-:-'f-';-';-'r,~I-f1'-:-'t;,r-;''4-'i'Ti'~~r:c..,'...;.1tr-t'..;.1T:'7':,'~~,::~o 1 ',!,,','',!I I'',i'Ii 'I;"',:"V,!1 'i",i,','I,'!'f',,,',
0,--,:__'-::'--E;:;'-;::':'':':-~;'';-_.:::-
_r~_'i ~t~~:~
_~.-'::--'"I-~~~--Jto:.==
.~~~.:_~~::~~-"':~1-----=t:-.:.:i:--=§t";f=
L-r ··r~~-~t=:..=_+
~-~"-+-~
1
eno
X
r<'l-'0-
---+--1-
"'::1-:-
::R=;:
r---+-----:.~
f---~;:t
i.I
',,:
-,=.=-
. 1 _~'---t~....
---l--.-.~t--------+-'-----j--,
,•,'''';''':-----+
.~-'f:"
,I/
'.,I
,'I.:1
"I
-==-=-:.!,.:::---'=L..r7:-1:::-:i..':-I-11:T:1.t+:.;.,:=.;---:=:"'~r-.l'IIl.-'!"','~:r"4'~-;-;~:'+'-::''~'F~~'~1-:.C',:c,:.'jH-'~'.:j'f!.;~:!:t'L.:':'1'f:::.J.'f-~':-i'_~i i'+1-:"+11
+:-+"-p,:+i'ttII:!r:111''';'1:t::1;i::':'-:it':-;-;::T''r'-;-':..:Ii::Ti';-c:t-:~:::2ht'",/t,:;:I I . " . I Ii;,I ,:;'_i ",I +!'!1+,.!.I I ~h':l
o .Ii',G 'I ".,"",I II!~:I:i:,II";;:ii'I!"""'i':I,'"","':,'!
----~-':---'-==f.':c--_.=-"7"~r.=;~~~
t:R
~:t-----4
>
W
~
::>
.-lo
>
ooo
...J
u..
10
,i
t EE--
~.I
1 '•+--.
~......::
(1000 cfs)
.-
SUSITNA RIVER AT GOLD CREEK
PERIOD_OF RECORD-29 YEARS
V =2820 0/50
r 2 :0.63
n :29
~&M CONSULTANTS,INC.
VOLUME VS.PEAK
MAY-JULY
5-11
Prepared fc
FIGURE 5.7
1=,,~
r------
'-~~~-~_:~='-+-
'+~
~_....t-----
:.
'-~'+-'
,.:'=t=..f='~-:L-=..E:';~I-=.::-:I;-'::==t:=.....-+-..:r.....-
::---~~.;.:.=--':!=:~i=
-.......~~.-.-.:;-
.~:.r-
--~I""
~.,.~.If-.-.
• I ,~".,I':~•~
',;,
.:~
",
/:,:
".!'/'.
~::e::::O:::;J.===t.-
,',
. I ;I I 'r ~\
I';',:1''l.'".!I f··:",":.
i j !I I I:I,:II ii!::I i I o'L I I !I I:I ~01 I ':,;:
;i /',i i Iii I '
1,;I,,,(
\I i I ::I II';i :
~
cf'
I , I
, r
.;I.f 11 !'j:
i i I I
I,il I"1.1·:i
;!;1!1::i!.'.!.
i ::I !,i:"
,,--;.';
,i;
I ii
i I"
':ii "ii:i:'·,:,iii'=,
"""-:-_'_1 ....~
t--
=
I,
I ,;,
!!'
"
-
,•1:,
I I :I I
I /',
i I i :1:1 "i'"
,i ,I i :,iGl :/!j
:!,i;i'Q
c 'i f I \.i i.~.:I!;Ii;
i I!,l,llill_.;=.-.-,,'=E
,...
';j I
;:
j I :;
, ,,
I I j
I I !.==
, I !i I : I i I
;,
.....
<J)
0
x
r<)......-
>
W
~
~
...J
0
>
Cl
0
0
...J
lL.0
=t:::::.-I::::
10 100
INSTANTANEOUS FLOOD PEAKS,Qp (1000 cfs)
1000
SUS I TNA RIVER AT GOLD CREEK
PERIOD OF RECORD -29 YEARS.
V ::9840 01.33
r 2 ::0.68
n ::21
R&M CONSULTANTS.INC.
VOLUME VS.PEAK
AU G.-OCT.
5-12
Prepared for
FIGURE 5.8
---'-...!.-j.......;...-......+·C-...l......+-.-I--·-,7-1-'--:--,--Ih---,-'l.~"----'l.+-~--'---H--..,.------~.~,+-~--'--+-I-~--
,I''I.
I 'i
i I
,I \l
I i
,I
I '
I !
i i,
i :I
I ,
I '
I i I
~;-,,r I I .,I
,/:II I ~1\;I I I
:+-t-I /I
:'....../, i ',/,I TJ.i-~
,/'Vi ,.....,I !, I
I-;~-+--I-l-+-";"'-i--J-l--l-+,-,,/-~~-=i""";:::'''';-.,.....j'''++.!..,-JI'-'-++-H~+j-+--++-H-+-+.j......;-:-+-"--I""";"++;~,,,,+-';"'::'---1:-t++-,rii~-1
8 0 ~"":""~I~I.w--:....:...W...L~i/~~--i..~:"";'-+---'---:-+:.J,-ih~'~:";"'+-:-t-t-~_!L.-\-\.,--t-t--!-----,.+.....~..;...t-'-...,...-i-~_;_!'""'"'"7__rl../:I!!/i i :/i !''\.:
,,:I
~L..C..-'--1----:._-I-+~..---:.~__r-;--+--+-;...+-'-!-+'-+...:....H-..;....H-r-,,-+..;...--++-_._-'-~·-..,...--+----i
I !
-to -5 PEAK 5 10 15
TIME -DAYS
SUSITNA RIVER AT GOLD CREEK
100,500,10000 yr.FLOOD VOLUMES
LEGEND
Flood Volume
ft~
Peak Discharge
(cfs )
-----100 yr
--500yr
---IO,OOOY
122.3 X 10 9
178.2 X 10 9
310.0 X /0 9
104,550
131,870
198,000
Prepared f
R&l\II CONSULTANTS.INC.
FLOOD HYDROGRAPHS
MAY -JULY
5-13
FIGURE 5.9 i
200
160
~--+----i----:----~---+-i----1---4----1----,
1 ==--=:..-i-l-__-l---------''---,-+-:-I.--+--"----;-+--~t---:---~----'-.----I--------4--+-----,--1~'--'-I-----r I _-:-__I~---'---__-I------'-_+-_.--!--t----4-
-:\
\.
,-.
,"\',
.,
"
§120
X
Cf)
\.L
U
I
W
(!)
0::
<t 80
I
U
Cf)
o
I '
!:
--"
,I
,I,
I '
II'
,-,
-7 ,
1 .-
1-'
/-1/,
1/.
,,',
-/'I
_/,
,--
. I
"\',
-,':
"
,"
,.~.
!:
'"I i
_...........:.'
, :~!
~...
•'"I.........
o
-15
;i I :
-to -5 PEAK
TIME-DAYS
5 10
,;
15
SUSITNA RIVER AT GOLD CREEK
LEGEND
----100 yr
--500 yr
---10,000 yr
Flood Volu me
ft :5
53.8 X 10 9
78_8 X 10 9
140.0 X 10 9
Pea k Discharge
( c f s )
90,140
119,430
185,000
PREPARED BY I
~~t::J ,,-,-~~6;M.J
R &M CON SULTANTS.INC.
FLOOD HYDROGRAPHS
AUG -OCT
5 14
PREPARED FOR
..:....:....::.FrIGUR~E5.10 Wi]
6 -FLOOD VOLUME-DURATION FREQUENCY ANALYSIS
To assist in designing temporary diversion structures and
determining reservoir filling sequences,a flood volume-duration
frequency analysis was conducted for May-July flows of the
Susitna River at Gold Creek.Table 6.1 is a computer tabulation
of May through July volume durations computed by the U.S.
Geological Survey.The mean discharge for the 3-,7-,15 ..and
30-day durations were utilized with the three parameter log-normal
frequency distribution to compute the volume-duration frequency
curves illustrated on Figure 6.1.
susi6/q 6-1
sUSITNA RIVER AT GOLD CREEK
HIGHEST MEAN DISCHARGE (CFS)OF CONSECUTIVE DAYS FROM MAY THROUGH JULY
VOLUME DURATIONS COMPUTED BY U.'S.GEOLOGICAL SURVEY
vfAR 1 3 7 15 10
1950 34000.0 23 32100.0 24 ?7000.0 ?~24'500.0 28 2?-700.n ?7
1951 3SAOO.0 27.32100.0 2S 291300.0 24 2c;?()0 ..0 27 1'?100.0 ~A
1952 43300.0 }3 42300.0 12 .19500.0 11 17000.0 9 :nooo.o 10
19~1 31700.0 21 31200.0 If'35S00.0 17 31000.0 19 ?7400.0 19
1954 10100.0 28 29S00.0 2R ?8AOO.0 2c;?6900.0 24 1'5700.0 22
1955 39000.0 20 3A700.0 16 3fl600.0 1~351)00.0'11'33800.0 R
19Sf:J 51500.0 9 49900.0 A 4fl$300.0 7 40100 ..0 4 34500.0 7
19'57 40600.0 14 39900.0 14 313400.0 IJ 3Sc;OO.0 13 32300.0 13
19513 32400.0 26 32100.0 26 28000.0 2f,?-AOOO.O 22 ?5A00.0 1'1
1(1)9 39600.0 lA 37200.0 19 30700.0 2?27100.0 ?3 26200.1)20
0'\1960 40000.0 15 36100.0 20 37.900.0 19 2f:Jlno.0 25 ?1100.0 2f,
I
N
1961 54000.0 6 52000.0 1 42100.0 9 lAAOO.O 10 301300.0 14
1962 79900.0 2 15200.0 ?64700.0 I'Sl?()O.O 2 43300.0 ?
19f:J)49000.0 11 46300.0 9 47.900.0 H 39?flO.0 7 14900.0 6
lCJtS4 AS900.0 1 81900.0 1 75000.0 1 tS1SOO.O 1 S0700.()1
1965 39900.0 16 37400.0 17 34100.0 lA 31100.0 18 30500.0 15
196f,58400.0 5 56600.0 5 49?-OO~0 .4 39~OO.O 5 31000.0 9
\C)67 soooo.o 10 46100.f)10 3A900.()I?1?t1()0.0 If>29QOO.O 16
19f:JA 397uO.0 11 38900.()15 3AI00.0 14 ]f:JSOI).O 11 37400.0 11
19/)9 26500.0 29 24400.0 29 20500.0 30 17700.0 30 1f:>700.0 30
1910 30800.02,1 30100.0 27 27100.0 77 2,)7no.0 ?f>23AOO.0 24
1971 66300.0 4 59000.0 4 48300.0 5 3R?OO.0 B 3')400.0 5
1972 70700.0 3 65600.0 3 51500.0/1 ]gROO.O 6 17300.0 4
1973 S2BOO.0 7 45300.0 11 40900.0 10 34tSOO.0 14 28600.0 lA
Ig74 33600.0 24 33200.0 2?12400.0 ?1 7.9'300.0 21)23200.()25·
1975 44000.0 12 42200.0 13 31100.0 15.33300.0 15 32300.0 12
1CJ7f>33300.0 25 12100.0 21 29~OO.0 21 2RAOO.O 21 245(10.0 23
1917 S2600.0 8 52200.0 f>48300.0 (,415()O.O 3 3HOOO.O 3
19713 24300.0 30 23AOO.O 30 23100.n ?9 2?f:JOO.O 29 21700.0 29
197C)39300.0 19 34800.0 21 32600.0 20 31700.0 17 ?9100.0 17
---
-=~-I"'::=
.+f-_.T 1-
,l~I.E
'F-
';0.-
r
-=:'J=.~-::._):1','_. -=I...1"1·,
-..-c::-I-\
_.~H~""f '>
.'-t~.=III '-F'=~~
~-----':'f
~-
-i+t +
H+i-7+--1i-t-t-+++HH++-+-:-+++++-H+++-l-t+++H+f+-+,+1'f-t+!-H-H-l-l-t--+-\-t'+'-H
,'0 __
!I
I I
,Ii
I !
100 .~
en 90u..:8 0 f±c+c ,,-+u 70'--:+
(f)
o 60 t:t".'
I I
:I
'I :1'1 .
~:::l-'•
.~
.j.
~"
ct=L:t=~
fi.':".'
, I
!I
~...
:.
:1
--;::t::::;:::-;::~
-
III
,.I,.
. I I I
.,;I'!I I !,
!j,;'I
50 100 200 500
++-rl-If-'-c+-H+H++-r--+-i-..,....;.---;---I--!;_._1-;\-,-,--'-Ii -1-+-1-,-_I-_'~I i .;...1 ,1...,.....,1--+-4
: I •.1:I ii'
il!I ,,1 iii:I
....,..-
20 1"
;IT
'I ..c(.
~,,,I I II:I
,I !;I i I i:I II
II I ;II I :i I
1 :!I l j II I !~1----:-
I':I'1 i I I I,,'I
f-..:r;I :;.II i i I !Ii',:
10 I
2 5 10 20
z
w 40
(,!)
0::
<t
~30u
(f)
Q
Z
<t
UJ
~
EXCEEDENCE INTERVAL -YEARS
SUSITNA RIVER AT GOLD CRE EK
PERIOD OF RECORD -1950 -1979
R&M CONSULTANTS.INC.
-VOLUME DURATION
FREQUENCY CURVES
MAY-JULY
6-3
Prepared fa
~FIGURE6.1 [ii
7 -REFERENCES
Acres American.1977.Regional Flood Frequency Analysis.
Prepared for the Canada New Brunswick Flood Damage
Reduction Program,Inland Water Directorate,Environment
Canada.
Condie,R.,Nix,G.A.,and Boone,L.G.1977.Flood Damage
Reduction Program Flood Frequency Analysis.Engineering
Hydrology Section,Water Planning and Management Branch,
I nland Water Directorate I Envi ronmental Canada,Ottawa.
Dalrymple.1960.Flood Frequency Analyses.
Survey.Water Supply Paper 1543-A.
U.S.Geological
Dixon,W.J.,
Jennrich,
P-Series.
BMDP-77.
Brown,M.B.,
R.I.1977.
University
Engelman,L.,Frane,
Biomedical Computer
of California Press,
J.W.,and
Programs,
Berkeley.
.....
Freethey,G.W.,and Scully,D.R.1980.Water Resources of the
Cook Inlet Basin,Alaska,U.S.Department of the Interior,
Geological Survey,Hydrological Investigations Atlas HA-620,
4 sheets.
Lamke,R.D.1979.Flood Characteristics of Alaskan Streams.
U.S.Department of the Interior,Geological Survey,Water
Resources Investigations 78-129,Anchorage,Alaska,61 p.
National Weather Service.1972.Mean Annual Precipitation
Inches:National Weather Service [Alaska),map .
susi6/r 7-1
susi6/u3
ATTACHMENT A
FLOOD FREQUENCY CURVES FOR ANNUAL
INSTANTANEOUS FLOOD PEAK SERIES,
INDIVIDUAL STATIONS
'I
Susitna R.at Gold Creek
THRFE f'ARAMFTI'R lO(j-NORMAL D1STRIRlJTION-WITH 95 PeT CL
PARAt~FTFRS t5TI~IATfl)RY MAXIMUM L1Kl!HOOD
IOFh----------------------------------------------------------------------------------------------------------------------------
9 ------------------------------------------------------------------.---------------------------------------------------------
B ---------------------------------------------------------~------------------------------------------------------------------
------------------------------------------------------------------------------_.._-----------------------------------------~
7 ----------------------------------------------------------~----------------------------------------------------.--~----~----b
I
I
I
I,1
r
I
I.11--..._
I
-~--------------
I.__.------
I
~---------------1
I
,---------~------------------1
I
I
I_·•M _
1
I
I
1
I
5
2
6
4
3
1 I I
5 ----------------------------------------------------------------------------------------------------------------------------Itt
tIl
4 ------------------------------------------------------------------------------------------------------------------.-.-.-----I I I I I J I tIl J I
I I J I I I I I J I I
3 1--------------------------------------------------------------------------.-------------------------~-----~-----------.-.---I I I I 1 I I I I I I
2 I------------I------------------I--------------------!-------------------!-~------~-t--------!---------J---~
I J I 1 I I 1------'I r I I I I I IIIIIIII
I 1 I I I IlOF5--------------------------------------------------------------------------------------I r I I T
q --------------------------------------------------------------------------.--R
7
X--~ASFRVEO DATAO--E5TIMATFn DATA*--95(CONFIDENrF LIMITS
•
Prepared for:
FIGURE:A.l
FREQUENCY CURVE
RIVER AT 'GOLD CREEK
ANNUAL FLOOD
SUSITNARSMCONSULTANTS,INC.
-
•
-
Susitna R.near Denali
THREE PAAAMETE~LOG-NORMAL DISTRIRUTIQN-WITH 95 prT (I
PARAMETERS ESTIMATED AY MAX1MUM IIKLIHOOD10E5-------------------------------------------------.--------------.-------------------------------------------------_-_,I ,I I t I I r , r
9 -------------------------------------------------------------------------------------------------------------._._I I I I I 'IIIIII I , I
8 -----------------------------------------------------------~-------------------------------------------------------.-------I I I [I I , I
I J I [I J I [
7 -------------------------------------------------------------------------~---------------------------------------------.-.I I I I I I T
I I I [I r I
6 -------------------------------------------------------------------------------------------------------------------------I I I I I I I J I I
, 1 I I J I I I I I I
I I I I I I I I I I
5 ------------------------------------------------------------------------------------------------------~-----------------I I ,I I I I I I
J I r [I I I I I
I I I I I I I
4 -----------------------------------------------------------------------------------------------------------I I r t I , [
I I ,I I I [
,I ,'!I [I I I J J I
1 I ,J I I 1
1 I ,I I I I
3 -------------------------------------------------------------------------------------------------------------------------I I I I I I
1 I I [I I
1 I [[I
I J ,[I
I I I r I 1r[I 1 I I
r I I I IX [
2 -----------------------------.-------------------------------------------------------J ,I I [r I
I ,I I I I I I
1 I I [I I I
I ,I r r I r I
I I I I J I r 1
I I !I I I I I I,J I I r I [
I [r [I I'r
I I I I I 1 [
[I I I I I r
I I I I [I I
I !I I ['J
I I [I I 1*I
[!I I I I !I I I I10E4--------------------------------------------------------------------"--------------------------------------------------------1.005 1.05 1.2~2.0 5.0 10.20.50.100.200.500.
RECUn~ENCE INTERVAL IN VrARS
X--OBSERVED OATh
O--FSTIMATED DATA
*--95(CONFIDEN(E LI~ITS
R&M CONSULTANTS.INC.
ANNUAL FLOOD FREQUENCY CURVE
SUSITNA RIVER NEAR DENALI
FIGURE:A.2
Prepared for:
[ii]
~claren R.near Paxson
I
I-------
I
I
I
I
I
I
-------------------------------------------------------------------9 ------------------------------------------------------------------------A
7
6 --------------------------------~---------------------I r 1 -;X--X-----------------!J_I I
5 .__________________________---x__IX I I·I --------------
I ------------------------------I I I4...__•__~1 __~__X :::~;:~I'I ----1------------------------------
r r I ,-----------------------------------------------------.--.---••--I I 1 II1'I I I -----------------------3 r,I,I'I J I I , I
r I:---------~--------------------~-----------------------.----.---------------I 1 I IrrIIII---------.-------------,I . I I1Ir'I I'I r I I I
2 ~!.-!._____I I'I I I II I I I
I --------------------------------------~----------------.-----------I J IIII-------------------~I 'I I'I I I I I
1 1 I J I I I I I I I I
I I ::J I'I J I I I I
lDF3------------------------------_I I I II I I r I
I 00 5 1 5 ---------------.-----I I I I•.0 I 25 2----------------------------------X--ORSERVFD DATA •nECURRENCE INTERVA~nIN YEARS 5.0'10.-----i~:-------;~:---i~~:-2~~:---;~~:
O--ESTIMATED DATA
*--95(CONFIDENrF.LIMItS'
THRFF PARAMFTER LOG-NORMAL.DJSTRI~UTJ'N-WITH 95 PCT CL
PARM1F.TFRS ESTIMATED RY "'AX'~'LJ~l L!KLlHOOD
lOFS------------------------------------------------------------.---------------------------------------------------------------
9 --------------------------.-------------------------------------------------------------------------------------------------
8 ---------------------------------------------------------------------------------'-------------------------------------------I J , .t I·I I I I I Il:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::~
r I ,I I I I I
5 -------------------------------------------------------------------------------------------------~-------------------I I 1 1 I'I I I1I,I ,I I I I I
4 -------------------;-----------------------------------------------------------------------.--------------------r ,1 ,I 1-.I I I
1 I I I I,I I I
3 ----------------------------------------------------------------------------------------------------------I I I
I 1 I
I I I I 1 I I
2 -~------------------------------------------------------i-----------------------~------~---------r 1 I J I 1 1rI,,I I
I I 1 I I:IrI,I I I
I 1 1 I I I
1 I 1 I I
lOF4-----------------------~-----------~--------------------------------------------
I I I 'I
R&"'!I ,CONSULTANTS,I!'\lC.
ANNUAL FLOOD FREQUENCY CURVE
MACLAREN RIVER NEAR PAXSON
FIGURE:A.3
Prepared for:
•
Susitna R.near Cantwell
LI)(.-t:OR~'AL DI~T~ln'}TIO(J-~IJTH 'l~PCT CLlQCS----------------------------------------------------------------------------------------------------------------------------~-----------~-------------------------------------------------------------------------------------------~--------------------
I-----------------
I
I
I
I
I
I
I
I
~-------------------------------------------------------------------------I
--------------------------------"-----------------------------------------------------------------
I
I._-------------.---------------------._-----------._----------------------------.--------------------------------------
()
~-
'7
6
l.
:,:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::---
4 ----------------------------------------------------------~-------------
?
I r I I
I I (-[
I I I I
I I 1 I I
2 -----------------------------------------------------~-----------------------.----------------------------------------------
I I'I
[I [
[ I I
I I I
1 r-I
I I I I I III I I IlQ(3--------------------------------------------------------------------------------------------------------------.-------------1.onS 1.05 1,15 1,0 ~,n 1",1(1.<;n.1'11;.200.500.
RF.CU?QEIICE 1~ITF.QIJI\L ll~YEARS -
X--OflSERVEI)OIlT/\
O--ESTIMIITED DATA
.--9S(CONFIDE/icr Ll'-IIT'>
R&M CONSULTANTS,INC.
ANNUAL
SUSITNA
FLOOD FREQUENCY CURVE
RIVER NEAR CANTWELL
FIGURE:A.4
Prepared for:
m
-
-
•
-
-
-
I
I-_._---------
I
I-----------------------[ I 1 I
I , I I
I I , I
J ~j--------i---------i~---------
I
X--OR~FRVED DATA
0--r5TIMAT~D DATA
*--95'CONFIDFNCF LIMITS
-----------------------~--------------------------------------------
3
5 r I I
.1 I ,
1 I T
4 ------------------------------------------.--------I,
I X ..*I I
x-~----j--------j---------j-----j--------------
I I J I I
J J I I I
I I I I I
~i~----X ~-----!l !1 !1 _
~.,I I I I J I I
,I J I'I I
I I I I I t I
I I I I I I I
J J [I I 1 I
I I J I I I I
.I I I I'r I
?----------------------------------------------------------------------------------------------------------------------------I I I I I I I
I I J I J r I
I I I I I I I
I I I I I 1 I
I I I I I 1 I
I I I I [r I
,I I I 1 r I
I [I r I I I
I [I I'J I,I [I I , I
I I I I I I I
I ,I I I I II I
I I I I I 1 I
1 I 1 ,I I I I 1 I tIOF4----------------------------------------------------------------------------------------------------------------------------1.005 1.05 1.2~2.0 5.0 10.20.50.100.200.500.
RfCURRENCF INTfRVAL IN YEARS
Chulitna R.near Talkeetna
THR,f.PARAMtTFR LOG-NOR'1Al DI5TR'AUTl~N-WTTH 95 PeT nPARM'tTERS E5TIr~ATff)flY MAXIMl)t.I I IKL 'HOODIOF5------------------------------------------------------------------------------------------------------------r 1 1 I I I I I
9 -----------------------------------------------------.---------------------------------------------------~------------------I 'I IIII,
A --------------------------------------------------------------------------------------------------I I I XI
I I I
7 ------------------------------------------------------------------------------------------I I
[1
6 -~---------------------------------------------------------------------------------I
I
Preoared
~&M CONSULTANTS.INC.
ANNUAL FLOOD FREQUENCY CURVE
CHULITNA RIVER NEAR TALKEETNA
FIGURE:A.S
Prepared for:
•
J
I
I
~
I
-I---------I
X--Of\5FRVFD DATA
O--ESTtMATFf)nATAA--~5ICON~tDFN(F LIMITS
Talkeetna R.near Talkeetna
THRFF.PARAMFTFR LO(,-"IORMAI.nI5TRIAUTI,1N-I..JlTJ~95 PeT n
PARAMETEQ5 fSTIMATFn AY MAXtHUM IIKl!HOOf)10Fb----------------------------------------------------------------------------------------------------------------------------
q ----------------------------------------------------------------------------------------------------------------------------
B --------------------------------------------------------~-------------------------------------------------------------------I I T 1 .I I 1 I I t I
7 -------------------------------------------------------------------------------------------------_
b -----------------------------------------------------------~----------------------------------------------------------------.I.I I I I t I I I
5 ----------------------------------------------------------------------------------------------------------------------------,J T I I r I I
I J I J I I I
4 .--------.-------------------------------------------------------------~----------------------------------_-------------I I 1 ,I .-I [
I I T [, I I I
3 ------------------------------------------------------------------------:--------------------------.---------------) I I r r"'I I,,I I I J IrII,I I I
2 ---------------------------------------------------~------------------------------------------------------, .I I I I
I I rrII r
I I I 1 I I I
I J I I 'I Ir1IIIII10F5--------------------------------------------------------------------------------------------------------------I r T I I 1 I
9 ---------------------------------------------------------------------------------------
B ------------------------------------------------------------------------------------
7 ---------------------------------------------------------------------------------I I I t I X I I
b -------------------------------------------------------------------------------x---------------------------------------I I r I I 1 I I 1
5 ------------------------------------------------------------------------------------------------------I I I I I I I
4 -------------------------------------------------------------------------------------~-~-~---~tIl 1 I I .
J I I I I r I I3--------------------------------------------------X--------------------------------------------------, I 'I I I I I
I r r I I I I
I I r I I I t
I I I I I I,I
2 --------------------------------------------------------------------------------------------------I I I I I r I I I
I I I I I I I I I IIl---i_~I I 1 I I I I I
I I t I I I I I 1 I I I
I I I r !I I I 1 I I I
1 I r 1 . I I I I I I IIOF4----------------------------------------------------------------------------------------------------------------------------1.005 1.05 1.25 2.0 5.0 10.20.50.100.200.500.
RECURRENCE INTERVAL IN yEARS
R&M CONSULTANTS,INC.
ANNUAL FLOOD FREQUENCY CURVE
TALKEETNA RIVER NEAR TALKEETNA
FIGURE:A.6
Prepared for:
•
-~-----------------------------1
-------------------------------~-----------I,
I
:.s-t'
I
I
----------------~----I
I
I
I
I---------.._---.-.---
I
I
I
---------.~----------------------------------------------------.-.-------I
I
I,
I
I---~-------------------~4 ~-_
[
-----------x-----~-------------------------------------------------------------------------------------------------
')
I,
I
3 ------------------------------------------------rr
1
4 -------------------------------------it ..---
2
9
H
7
6 -~---------f-------
I
Trr
T I
1 T
IOF31----------~----------------
·------i-------------------!---------~-----!_____________________________I I I I
4 ---------------~--------------------------------------====~==~=~~=~=~====:i::==:!_
3 /--_____________I I IT "
--------------------~-----i---------j-----j------1-------
?-z---------------------------!J I II!--7--------------------i-------------------~----------~------------------!-----!------!-------
:I I 1 I f II I I I.
r [I I ' I II,I I I I I I lit ,
IOF2-!!___"I I.I ,1.005 1.05 1.2~---------------------------------------------!I I
X--ORSERVFD DATA RFCURRENCE INTfRV~LO'N YEARS 5.0 10.20.50:---ioo:-zoO:---SOO:
O--fSTIMATF.D DATAIt--95(CONFIDEN(F LIMITS
Montana Cr.near Muntana
T'IRFf PAf~AMfTFR LO(,-NORf'AL DISTRIRlJTI1N-WTTH 95 peT CL
PARM'FTERS ESTIMATED RY MAXIMlJM L1KLlHOOn
10~4:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::~:::::::::::::::~======
r I ,I I ~------~~..
7 ----------------------------------------------------------------------------b
R&M CONSULTANTS,INC.
ANNUAL FLOOD FREQUENCY CURVE
MONTANA CREEK NEAR MONTANA
FIGURE:A.7
Prepared for:
•
T
I
lO--
L---
3
Skwentna R.near Skwe"tna
THRFF PAPAMFTFR l('lC,-NORMAI.Dt5TR!PIJT!~~I-WfTH q')peT rl
PARA'·IFTEtlS E~Trr~ATrn FlY MAXIMUM IIKLIHOOD10F5----------------------------------------------------------------------------------------------------------------------------I I ITt I I I I T I
9 ---------------------------------------------------------~------------------------------------------------------------------I I I I I !I ..-"'""l I
1 I I I I I I ~I I
R ------------------------------------------------------------~------------------------------------------------I I I I
I I I J
7 ------------------------------------------------------------------------------------------------------I t I I I [I I
I I I I I I 1 I I
b ------------------------------------------------------------------------------------------------------I I I I I I I
I I I I I 1 I
I 1 I I X I I
5 -----------------------------------------------------------------------------------X------------------------------------I ,T I I I 0 I I J [r J I I [~I J I I
4 ~~------------------~--------------------!__________I ~I~~~--_+:--~-~-=-~.=-=--=-~-=-=-~.-:-:-~-~-~-~~
I I I I
I I I I T
I I I I I
J I J I 1
t I X I x I I I--X----------------------------------------------------------------------------t I I
I I t 1
I I I I
I I I I
I I [I
[I I I.
I 1 I I I J I----------.-P---------------------------------------------------~_[I I I I I I I , I
I r I 1 I I I I I I
I I 1 1 I I I I I I
I I [1 I I I J I I
I I 1 I I I 1 I I [
I I I I I I T [ I I
r I I I I I I I I,I
I I I I I I I r I 1
J I I I I I I I I I
I I I 1 I I I I I I
I I I I I I I I I I
I I I 'I I I'I ,J
I I I I I lIt I ·1
I 1 I t I I I I [ I I10F4------------------------------------------------------------------------------------------------------------------.---------1.005 1.05 1.7.')2.0 5.0 10.20.50.100.200.500.
RfCURPENCf INTERVAL IN YEARS
X--OA5FRVFD DATA
O--ESTIMATFO OATA*--95(CONFIDENCF LIMITS
PreDared by:
R&M CDNSULTANTS.INC.
ANNUAL FLOOD FREQUENCY CURVE
SKWENTNA RIVER NEAR SKWENTNA
FIGURE:A.8
Prepared for:
•
Caribou Cr.near Sutton
THRFE PAR AM FTFR LOG-NORMAL DiS TRI RlIT!ON-W I TH 95 PCT Cl
PARAMFTF.QS FSTiMAHrl RY MAX1MUM L1KLlHOOnlOFS----------------------------------------------------------------------------------------------------------------------------
9 ----------------------------------------------------------------------------------------------------------------------------
A ----------------------------------------------------------~-----------------------------------------------__----------------
7 ----------------------------------------------------------------------------------------------------------------------------
6 ----------------------------------------------------------------------------------------------------------------------------
I
I
I
I
._--------------------~--------------------------------I
1
I{
2
:3
b r
:i=====:::::::~::::::::::::::::======::======-------------
I
._----------------~-------------------------I
I
._------~-----------------------------------I
I._------------------------------------------I
Ir
2 ----------------------------------------------------------------------------------------------------------------------I
Ir
I
I
J I I I I I
10F4----------------------------------------------~--------------------------------------------I I I I I I
9 ----------------------------------------------------------------------------------
8 ----------------------------------------------------------------------------7
PreDared by:
R&M CONSUI.TANTS,INC.
ANNUAL FLOOD FREQUENCY CURVE
CARIBOU CREEK NEAR SUTTON
FIGURE:A.9
Prepared for:
iU
X--QBSFRVFO DATA
O--FST1~ATFn DATA
*--95(CONFIDENCE LIMITS
Macanuska R.ac Palmer
THRFF J"lARAMFTFR LOG-NORMAL DISTRIPIJTI:JN-WITH <'IS peT n
PARAMETERS eSTIMATED RY MAXI~llJM I !KL!HOOO10F.5----------------------------------------------------------------------------------------------------------------------------J J I I I I I I I ,I
Q ----------------------------------------------------------------------------------------------------------------------------I J I I I J I I I J
I TIl I I 1 I I I
R -----------------------------------------------------------------------------------------------------.----------------------I I I J I I I I
I I I I I I I I
7 --------------------------------------------------------------------------------------------------------------------------I I I I I I I
I I I I I I I
6 -------------------------------------------------------------------------------------~------------------------------------r 'r T I I [T I I Ir[1 1 I I I 1 I I I
I r I I I I I I I I
5 -------------------------~---------------------------------------------------------------------------------------------1,J J T I I I I I
1 I J J I I I
,I r I I I I I
4 --------------------------------------------------------------------------.---------------x---------------------------I I J r I I 1 r
I J XI T I I Ir1II I I I
1 I I 1
J r I I I I
I I J J l'I J
3 -------------------------------------------------.------------'-------------------------------------------I r I [I I J
I I I I I I
J I I I'I I
r I I I I I I
I I I I I I t
I I I I I I [
--------I 1 I I I I
~--------------------------~-----~-----------------------------------------~I I I I 1 I 1
I I I I 1 J I
I I I I I r I
I I I I I I I
I I I I I I I
I I I I I I I
J I I I I I [
I I _I I I I I
I I I I!I I
I I I I I J I
I 1 I I 1 J [
I I 1 I I 1 I
I [I 1 I I I10F4~------------~----------------~--------------------:--------~-!!~_!!~-!-!
1.005 1.0'i 1.2'i 2.0 S.O 10.20.SO.100.200.500.RECuRRENcr INTERVAL IN yEARS
R&M CONSULTANTS,INC.
ANNUAL FLOOD FREQUENCY CURVE
MATANUSKA RIVER AT PALMER
FIGURE:A.10
Prepared for:
liffil
I
I
[
1----1---0-------o 1 I----0--------------------
X--ORSERVF~DATA
n--ESTJ~~TF.n DATA
---q5(CONFIDfNCE Ll~ITS
--------------------------------._--------------------.---.------------..----------------------------------~---~---------------~---.---------------
5
3
6 --------------------------------~-----------------------
2
4 ---------------------------~
-------------.-------.--------------------.-------.--.-------~~-------------_._---------------------------------._--.-.-.---I I I [!I I I I I I I
5 ------------------------------------------------------------------------------.---------------------------------------------I I I [r I I I I T I
I I I J I I I I I I J
4 ---------------------.-------------------------------------------------~----------------------------------------------------I ,I r I [I I I I I I
J J r J I I I I I I I
3 ------------------------------------------------------------------------------------------------------------------.---------I I [I I I I IIr_..J I I I I I
I I I I I I I I I I I
2 --------------------------------------------------------------.--------••-.---------------------------------------.---.-----J ' J I I [I
1 I I I [I
[I I I I I
[I J J[r I 1
J J I I I I IIOF4------------------------·-----------------------------------------.-----------------------------I I ,I I I
9 ----------------------------------------------------------------------------~-~---~-B
7
-~...[
~-~----------------._---------------------J [III I~~-~-i----------i------~-i---------i---~-i------i------j
------~~-------.-------------------------------------------------------------J I I I r [I I
I I [I r I J 1
--------------------------~----------.------------------------------------------.---------Iii I I I 1 r I
[i J r [I ( I [
I :[I I [I 1 [
I : I r J I J ,I
-----.-----------------------------------.--.-------------------------~-----------------------------~----------------------I I I J I I [
[I I I J J IrIIJI I I
I 1 [I [ I I
I I I I J [IrII[I 1 J J I I I [
10F3----------------------------------------------·----------------------------------------------------~------------------------1.005 1.05 1.2,2.0 5.0 10.20.50.100.200.500.
RECuRRENCE INTERVAL IN yEARS
Tonsina R.at Tonsin3
THAFE PARAMFTFR LOG-NnR~Al DISTRIRUTlnN-WITH 95 peT Cl
PARAMETERS ESTIMATED RY MAXIMUM l.IKLIHOODIOF5----------------------------------------------------------------------------------------------------------------------------
9 ------------------------.--------------------------------------------------------------------.------------------------------
R ------------------------------------------.---------------------------------------------------------------------------------r I I J ;J I I I I I I
7 ----------------.------------------------------------------------------~-----------------------------------------~----------6
PreDared by:
F=lS,M,CONSULTANTS.INC.
ANNUAL FLOOD FREQUENCY CURVE
TONSINA RIVER AT TONSINA
FIGURE:A.ll
Prepared for:
•
Cl)ppL:r I~.n\~;(r Chllna
r 1/r'r f P ~il ~•.[1 En L 0',-'1';~"~L ()I <,1 ~I ['IJ T [~':-1.11 1 II ')',r r'-I
r ~R AI \~rF fl S (S T I {\~TE ~II Y '"X ("'.1'"LI ~L r II 0 0 ~
lnr~----------------------------------------------------------------------------------------------------------------------------f)~~_
:.===================================:=======::=====:=::::::====:::=====::==::::::::::=:::::=::::::::::::::::::=::::=:::::::::
~-----------------------------------------------------------------------'--------------------------------------------------.--
I.
[
J,
I
1
~-------------------------~------------
~
:>
I(.(-~
,~------------I--~~~:::~:::::~:
r
[
I
I
[
I 1 I I I [I
10~j------------------------------------------------------------------------_
,--------------~--------------------------------------------------------------------------------------------------~-j
I
(
(
J
1.(J J I I r I I I [
lrc'--------------~-------------------------------------------------------------------------------------------------------------1.005 .1.05 1.·~5 2.fl ~.I\1n.?".-no FH!.200.500.
fl f.C I !fir.~'J (<.]I:If r>V 1\LIN Y r ~R S
x--()nSERVED DI\TII
O--ESTIMATED OIlTII
• - -Q S (CON FlO f:NC F LI ;1 ITS
Prepared for:
R&M CONSULTANTS.INC.
ANNUAL FLOOD FREQUENCY CURVE
COPPER RIVER NEAR CHITINA
FIGURE:A.12 •
susi6/u4
ATTACHMENT B
FLOOD FREQUENCY CURVES FOR
MAXIMUM ANNUAL OCTOBER-MAY MEAN,
INDIVIDUAL STATION
Susitna R.at Gold Creek
T 'If'r c ,,~r>'I.'[TF f'Lor.-II 0 II :1f.l.~I ~,T "I .>II r r r:'I -\ I 1 fI ~'.i'(r (I
P A q ~'~F r F D ~F sri '·lld (D "y ..,x ,',,,.,L I r,r"()..,r,
1~r ~----------------------------------------------------------------------------------------------------------------------------
I I ,I 1 I I
~----------------------------------------------------------------------------------------------------------------------------
sn£'.1 '1'1.?on.-,">n.
I
r
r
I
r
t
1
11'15.'")
-----------------~--------------------
?
---------------------------------------------.--------------------------------------------
r --------------------------------------------------------------~------
'>------------------------------------------------------------------------------------
I, I
I
~-------------------------------------------------------
r
I
(-------------------------------------------------------
[I I I !I 1 J
I I 1 I I "I I[r f ';I [r
[1 I '1 !I 1 1
I I I ',;I I
[I r I I I I I
1 1 I I {{I 'I
[I I I I!I I
I 1 (I 1 I [ 1
I I I I I I I I
I r r I I 1 (I
I l'I [I I I
I I)'1 I I I
[",1 ('I I I I J I
l~r~--------x-------------------------------------------------------------------------------------------------------------.------ , •[)()S , •n S 1 • '5 .'•Gnr("~1,0 I:C r ['"-';V I,L I;J Y r ,r;5
X--()U~ERVED DArn
n--~STIHATED DATA
.--')',((OflF[I'>FI'U L,"pr,
PreDared by:
R&M CONSULTANTS.INC.
OCT-MAY FLOOD FREQUENCY CURVE
SUSITNA RIVER AT GOLD CREEK
FIGURE :B.1
Prepared for:
i[j]
Susitna R.n~~r nenali
T<j I!(r PA fI MI r:T U,lOr,-fJQ II 'H l f)I S r n 1 PU T r OI!-\.![T H ')~r>eTC l
P ~q HI U ~fI ~EST [II A T[D fl y rq XI r~IJ '1 l.f r l [>I n 0 f)
ln r S----------------------------------------------------------------------------------------------------------------------------~---------------------------------------------------------------------------------------------------------------~------------
~----------------------------------------------------------------------------------------------------------------------------
~::=:==::::=::=:::::::::=::=:=::::::::::==:===:::~:=::::::::::::::::::::::::==:::::::::::::::::::::::::::::::::::::::::::::::
~-------------------------------------------------------------------------------------------------------------
I
~-----------------------------------------------------------I I
I l·
r
I
1
J
------------------------------------------------~-----------------------------------------------~
~----------------------------------------------------------------------------------------------------------------------
I
S -------------------------------------------------------------------------------------------------------------1--------------
I,
I
?----------------------------------------------------------------------------------~----------------
!l -----------------------------------------------------
r
J
I
1
I I I IIn:~~~~~~~~~~~~:=~~~=::=====~=======~=:========~~~=~=~=~=i==~~~~~~=======----!---
I
I
I
I
I
1 I I 1 1 I I I I J
1IlF~----------------~---------------------------------------------------~-------------------------------------.-----------------1,(l[1S 1.05 1.2S 2.0 5.n·-In.2(1.sn.10n.200.500.
rUIJflllHlr [PJT r flV.4l [tJ YE1\RS .
x--nRSFRVED nA'~
n--E~TI~ATED DATA
.--~S(CONF[OE~(F ll·'[TS
Prepared for:
R&.M CONSULTANT.5.I.NC.
OCT-MAY FLOOD FREQUENCY CURVE
SUSITNA RIVER NEAR DENALI
FIGURE :B.2 •
-----------------------------------------------------------------------------------------------_._--------------------------
Maclaren R.n2ar Pox50n
Tlj~rr PAPJ\lIfTER lOG-rlQIl,"AL,nl~T"IIlIITr()I!-~'IlI!')';reT (I
r II 11 ~II r T r 11 S E srI :\II T ~0 1!Y II II XII:WI LI r.l r II (\I)n
'nr~------------------------------------------------------------------------------:---------------------------------------------~
----------------------------------------------------------------------------------------------------~-------._--------------
--------------------------------------------------------~---------------~-----~---~~----------------------...-------------
7
I~---:~----------------------------_
';
I~I XJIIX1 I I
"'\'1 .I..._.1 1 : 1 1 1
________,-:-::---'__-I.1 1 1 1 1 17~~~u----n----n nn nn _1 1 1 1 1 I·
:i i::::::::::::::::::i::::::::::::::::::::i:::::::::::::::::::i::::::~:~~l~~~~~~~~l~~~~~~~~~j~~~~~1~~~~~~1~~~~~~:
~
7 .------------------------------------------------------------------------------------
6
)---------------------------------------------------------------------------
\-------------------------------------------------------------------------------------------------------------
1 I r I J
I I I I .(
r I 1 1 I
I I r I J 1
'0F~------------------------------------------------------------------------------------------o
4 _...-- - - - - -----------~- - - _...- - ---'-- - - - - - - - - - - - - - - - - - - - - -...- - - - - - -"':'"- - - - - - - --[-- - -...- - - - --:--...- - - - - --.,..- - - - - _...- - - - - - - -...- - - - - - - - - - -...- - -
------------_..._----------------------------------------------------------~--------------------------------------------------.I'
J
?-----------------------------_._---------------------------------------------------------------------------------------------I
1
[
I I r 1 I I I 1 I I I'OE?----------------------------------------------------------------------------------------------------------------------------1.00S .1.05 1.<:5 2.0 5.n 1".20.<1.1nn.200.SOO.
I'H IJ 11 J~F II (E I 'I T r ~V 1\l p:Y r .\II S
X--O"SEIlVE 0 '~I\1/\
0--EST I 11"TED 01\T1\
•--?5 ( COIH IDE ~l ((LI '11 r s
~
Prepared for:
FIGURE:B.3
FREQUENCY CURVE
RIVER NEAR PAXSON
OCT-MAY FLOOD
MACLARENR&M CONSULTANTS.·INC.
Prepared by:
SusJtna R.nenr Cantwell
L0r.-r:OrWAL DI~TPJrl'JTIOlj-\Jlr'l 'J r ,oCT CL
10~~----------------------------------------------------------------------------------------------------------------------------~6 ~-_
-------------------------------------------'-------------------------------------------
-----------------------------------------~-~---~------------------------------------------
------------------------------------------------------,'------------------------------------------
-----------------------------------------------~--------------------------------------------------------7--~----------
J
'1
o
J
I
r
I
I
r1')r ~_.- r
A -----------------------------------------------------------------------------------------
I
I
I
1
------------------------------------------------------------------------------------------~---------~-----------------------
?
r
[
I
I
I I 1 [I r I J [I·I
1 I I I I I r r I I I10[3--------------------------------------------------------------------------------------------------------------0-------------1.(1(15 l o ns 1.n ?n S.r\I".?0.c.(\.1'11".200.500.
r.~C U'll'f I JeEl"r r l)'/1\L [I~Y(1\R 5
x--nf1SERVEll DIITA
O--ESTIMATED 011111
---95(CONFIDFtlU U'lJT-;
Prepared for:Prepared by:
R&M CONSULTANTS,INC.
OCT~MAY FLOOD FREQUENCY CURVE
SUSITNA RIVER NEAR CANTWELL
FIGURE:B.4 iffil
. I
~
:'
':>
'l
I
I
J ~_
10EG------------~x
I
~-----.------------------------------.-----------------~-------
,----------------------------------------------------------------------------------------------------~---_._-----------------
~--------------------------------------------.------------------------------------------_._---~-------------~----------------
~----------------------------------------------------------------------------
6 ------------------------------------------------------------------------------------------------
)-----------------------------------------------------------------------------------------
:i~~~~~~~~~~~~~~~~~~~~~~~~~~~~=~~=~===~=~====~=~~=~~~==~======~===~=i~~~=~==~==t=~~=~~=~~~===~~=~==~=~~===~=~=~=~~~~~=~
Chulitna \(.ncar Talk~ct"a
r H r.r F f'A ~r,'.,~T [R L 'I :,-t I 'J ~.\'""I ~T ~I "I)TIC'J -~I 1 II ')S ! (I
r ~q A-.,ET r 0 S EST J lolA TED fl Y I!~~H'IJ I'LI ~L J III)(\('l'lrS----------------------------------------------------------------------------------------------------------------------------o ~~---.•-~_
,i~_
1
I
[
1·
~-----------~-------------------------------------------------------------------------------------------------------------t---r r
I I
I I
I I
1 I
I I 1 I J I I [I I I
10 r S-------------------------------------------------------------------------------------------------------------~-------.------1.005 1.05 1./5 <.0 ,.1 ,.1.;>"."~.110.200.50(1.
P J:CU Jl q I't;C(I 'I I r Jl V .\L IIJ YF.1\P ~
X--O'lHilVFD DATA
O--ESIIMATED DATA
• --9 5 ((0 tlf IDE UCF L PI!T <;
Preoared
~&M CONSULTANTS,INC.
OCT-MAY FLOOD FREQUENCY CURVE
CHULITNA RIVER NEAR TALKEETNA
FIGURE:B.5
Prepared for:
•
Talkpctna R.near Y~Jkeetna
[lInl:PAPA!,'rTF.R L'Jr,-~/lJll"'AI.n[~TRI~IJfl(J'!-\:ITIl (J',P(T (I.
I'..,II J\..'E IE n ~r:5 T I :1 I.r r 0 1\Y :.;AX I 11 UfA II ~l J II C 0 lJ
10r~--------------------------------------------------------------------------
1 ----------------------------------------------------------------------
---------------------------------------------------------------------------------------------------------------------------
r
I
I
I I r r I I
~------------.----------------------~-----------------
--------~--~-------~--------------------------------------------
I------------------------------------------------------------------------------------------
I
------------------~-------------------------------------------------------------------------------------------------)I I I I I I [IrIIIrI I I !-----------------------------------------------------------------------------~----------------------------I I I I I I I I I
I [J [r I r I I
r I I [I I I I I
1 I 1 r I r [ [I------------------------------------------------------------------------------------------------------------------------2
I
Ir
[
[
J I
lr)F I,~------------I------------------:----
p
~
r
I r 1 [r I I
~-~-------------------------------------------------------------------------------------------------r I I r r 1 r
t I !J I I
[
I
I
[
r [[1 J I I r I I I
I I I 1 1 I I I [ I I
l~F~----------------------------------------------------------------------------------------------------------------------------1 •n (l ~1 •()5 1 •?5 ;>•(l ~•n 1 ()•2 (l •'.fl •1 nr.200.500.
~rCI"<PFfJrf jr:T~IIVl\l III YFARS
X--O'1QRVEO DATA
(l--EST!MAIF.O DATA
.--<)~(COIHIDENCE L1·llf~.
Prepared for:
~&M CONSUL.TANTS,INC.
OCT-MAY FLOOD FREQUENCY CURVE
TALKEETNA RIVER NEAR TALKEETNA
FIGURE:B.6 •
Skwentnil R.ne.n Skwentna
1 "',-'·(\II/Ifll.OJ~Tlllnl)T[O'·J-~.'lT;1 ':lS rrl (I.
1 ,'I r,- - -...-...- -................_.....__......-...- - - - - - - - - - - - - - - - - - -.._...__........__....._.......-....- -...- -...- - -.........- -......-...- - - - ---...- - - - - - - - - - - - - - - -..- - - - -..
"--------------------------------------------------------------------------------------------------------_..------------------
--zt~~~~~~~~~~~~~~~~.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~~:~~~~~i~~~~~~~~~~~~~~~~~~~~')
t ----------------------------------------------------------------------------------~------
J
1,
7 ------------------------.------------------------------------------------------------------------------------------------
~-------------------------~--------------------------------------------------------------------------------------------------
I
I
I
I
i --------------------------------------------~-------------------------------------------------------------------------------I
I
I
I
[
I l [[I I I 1 . I I Ilnr'-----------------------------------------------------------------------------------------------------'.ons l.OS 1.2~".0 s.n 1:1.?'1.~r.100.200.sao.rr (I'f)"f 1I cr J r ITF R ",\l ItJ Yr"R ~
x--O~~ERvED OAr~
'1--f~TI"ATED OAT A
•--<)S (COil F IDE t.Cf L I 'I 1 r c:.
R&M CONSULTANTS.INC,
OCT-MAY FLOOD FREQUENCY CURVE
SKWENTNA RIVER NEAR SKWENTNA
FIGURE:B.7
Prepared for:
•
Caribou Cr.ne~r S~tton
1 ,"'"r ,~n ,\"r T r R L 0 Ii -'lor:/,;:d.0'~J !/I "'IT J f)':-!,,f T II r;~I'(T 'I
r.,I''':Ir r r R <,f S T I ;lItT r D "y 'I t.X r ,"J ',I I.(>:[I II ()nr,1.·'-'-----------_
':-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------~-------------------------------------------~--
-------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
---------------------------~--~--------------------------------------------------------------------
I J I 1 I I I I'
J J ,I I I J r I
-----------------------------------------------------------------------------~-------------------.-----._-
I I I I 'I'I I I I
I I 1 (1 J I I I
I I 1 I l.I I I I
I I I I (r I I I
x
'X--O~~ERVED n~T~
r - -r S T1 ;,~T(n n AT II
.--')'((OrHID(tI(E ll'IIT<;
----------------------------------------------------------------------------------------------------------------------------
r.
,.------------------------------------------------------------._-------------------------------------------------------------------------------------------------------------------------------
"I _
I
I
(
r
I J
1 '\r '- -I-----------1---------
------------------------------------------------------------------
I,
I
-----------------------------------------------------------------------------
r
I
I
I
I r (I r r I ((I • I
I I I I I I I J I I 111'r1 •_
1.,["\,;1.1)5 1.?~'~.r.,5.n 1'1..1'1.<:,1,1["\'1,200.500.
/-E (UII "F(:(r 1:/1 r 'l V ,;l "J YI A II S
R&M CONSULTANTS.INC.
OCT-MAY FLOOD FREQUENCY CURVE
CARIBOU CREEK NEAR SUTTON
FIGURE:B.8
Prepared for:
liciJ
L
6
2
~
r.-------------------------
7 ----------------------------------------------------I
Matanuska R.at Pa]~cr
T II nr r:p n n....'f TE P lOG -Ji 0 n I-I Al ~I ~r n J n I)r I ,,~-l.'I r II ()~F CT n
r n "/I Hf TE nS E srI 11 /I TEO It Y t;\X It"J'~L I '<'l I II r r,f)1nrS---------------------------------------------------------------------------------------------------------------------.------
9 ----------------------------------------------------------------------------------------------------------------------------
f -------------------------------------------------------~-----------------------------------------------_
I I I I'1 I I 1 J I I
7 ------------------------------------------------------------------------------.---------------------------------------------
6 ------------------------------------------------------------------------------.----------------------------------------------J I I J I I I I I I I----------------------------------------------------------------------------------------------------------------------------
I I I I I I I I I I
I I I I I ,,'I l r I I
L ------------------------------------------------------------------------------------I I I I
I I I I
)---------------------------------~---------------------------------------I I I I
I I I 1
1 I 1 I
/----------------------------------------------------------------------------------------------• J I I I
I I I I
I I J I
I I I (
I 1 J I
l I I I
10f~---------------------------------------------------------------------I I I Io _
I I I I------------------------------------------------------------
I I I J I I I'-----------------------------------------------------
I 'I I f----------------------------------------------------------------------------
J I 'I I I I I I
-----~------~-----------_:_------~-_:_------_:_-------_:_---_:_----_:_----_:I I .
I I
I r J I I I I I
I~I I I I I J I 1,'1~------------------------------------------------------------------------------------------------------------
I I I I J I J I I J
V I I I I I r 11 I I
I I I I I I I r I I I
I I I I I!I \ I I I
I f I I I I 1 I I I
I I'I I I.1 1 1 I I (
'nt~--------------------------------------------------~---------~_
i.nos 1.0S 1.25 2.r 'i.r ..1n.'0.<'1.11"1["\.?OO.500.
pql/nprllcr 1'I,r~V~L II~YF.,'~S
.
x--orSEnVEO OATA
O--ESTIMATEO OATA
'--?5(CONFlOEJlCE U'·lITS
R&N1 CONSULTANTS,INC.
OCT-MAY FLOOD FREQUENCY CURVE
MATANUSKA RIVER AT PALMER
FIGURE:B.9
Prepared for:
iID
.....-
t,------------------------------------------------------------------------------------------------------
[
I
I------------------------------
I
I
J
I
I
1---------------------------------------------------------------------
I
I
~-----------------------------------------------------------------------------------------------*--------
1 I 1 I ,I I I 1 1
~-----------------------------------------------------------------------------------------------------------------
I
I1;,~--------
.--------------------------------------~-------------------------I
Ir
1
J I
'Il!""'----II---------1------------------
t l~_
1 ------------------------------------------------------------------~--------------------------------------
~
Tonsina R.at TonRinB
1"r;c,-r 1\r 1\''iF ,E r.lor,-rJO R '·1 ft l 0 1ST <l I 1'1)T [ 0 Ii -I I I T I I 'F,r (T (I
r ~"~:'C(~R<;EST I r·,.\1 E()'l Y n 1\):[:.1[fI'l I ~l I ""()0
1 '~~:::::::::::=::=:=::=::::::::::::::::::::::=:::::::=::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::~:::::::o ~_
----------------------------------------------------------~------------------------_._--------------------------------------
I
J
I
I
.--I
I J I I I I I j I I II~r?--------------------------------------------------_
1.nn~1.05 1.2~~.O ~.n In.2n.~1.10n.200.SOD.
rUlIHrFI:CF Ir;Trf?\lJlL [II vr.~~s
x--nnSfRVED OI\TA
r--ESTIMATED DATA
.--'l'j(COlI,lOftier ll'lITS
Prepared for:PreDared by:
R&M CONSULTANTS,INC.
OCT-MAY FLOOD FREQUENCY CURVE
TONSINA RIVER AT TONSINA
FIGURE:B.10 •
Copper R.near Chitna
THRFF PARIlMFTFR LOG-NORMAL nrSTPlf'lJTI:1N-WITH 9'i pn n
P~RA""FTERS EST '~AHn nY MAX IMIJM I.IKL 'HOOf)IOF6------------------------------------------------------.---------------------------------------------------------------------,IT·r I I ,I 1 1 I
q ----------------------------------------------------------------------------------------------------------------------------,I ,I I I I l', I
I I ,I I I I 1 I I I
R ----------------------------------------------------------------------------------------------------------------------------r I ,I I I I I I I I
I I I I 1 1 I I I I I
7 ----------------------------------------------------------------------------------------------------------------------------1 I I I I I I lIT Irr[I I I I I 1 r (
b ----------------------------------------------------------------------------------------------------------------------------[(,J I I I I 1 I J
,[I I I I I I I J IrI,I I I I I I J J
5 ----------------------------------------------------------------------------------------------------------------------------,,r J 'I I I 'I
I I r I I I I I 'I
I I I I I [[I I l
4 -----------------------------------------------------.---------------------------------------------------------------------I I I I I I I I r',r J I I I I I I
1 ,,J I I J ,•Irr,I I I I J 1 I
I [,I I I I I J 1
,I [I I r I I 1 I
3 ------------------------------------------------------------------------------------------------------'J r I I J I'I [I I I Ir,,J I 1---"
I r 1 ,I I .---II,,,I
,I ,,1 I
1 ,,,l~~I
2 i------------,--------------------------------------------------------,~---A-?--:------------r --i------j------I
I ,I I I J ,I
,J I I I'II
T ,I I .)(,,I
1 ,I I ,J I I rr[I 1 I I I [ I
r r I I I I I , I,,I I I I I (
I ,I I I J I
I I I I I I I
I I I I', I
I I I I"I,I 1 I J I , I
,1 1 I I I I I r ,IIOE5----------------------------------------------------------------------------------------------------------------------------1.005 1.05 1.2';2.0 5.0 10.20.50.100.200.500.
RFCIJRRENCE INTFRVAL IN YEARS .
X--~A5fRVED n~T~
0--F5TIMAT~D D~T~*--95(CONFIDfNCF LIMITS
Prepared by:
R&M CON5UL.TANTS.INC.
OCT-MAY FLOOD FREQUENCY CURVE
COPPER RIVER NEAR CHITINA
FIGURE :
Prepared for:
B.n iffil
misc7/w8
ATTACHMENT C:
COMPARISON OF SUSITNA REGIONAL FLOOD PEAK
ESTIMATES WITH USGS METHODS
Single1 USGS 2 USGS 3
Susitna Area II Cook Inlet
Return Station Regional Regional Regional
Period Estimate Estimate Estimate Estimate
Station Location (Yrs.)(CFS) (CFS)(CFS)(CFS)
Susitna River at Gold Creek 1.25 37,100 37,700
48,700
2 49,500 49,000 59,200 43,800
5 67,000 64,200 73,000 53,400
10 79,000 74,500 83,400 55,300
50 106,000 100,000 104,000 71,600
100 118,000 110,000 115,000
Caribou Creek near Sutton 1.25 3,310 1,910 2,510
2 4,500 2,480 3,620 2,670
5 6,120 3,240 5,130 3,680
10 7,170 3,760 6,280 4,200
50 9,480 5,050 8,810 6,210
100 10,500 5,570 10,500
Matanuska River at Palmer 1.25 19,700 20,800 20,400
2 25,500 27,000 25,700 24,000
5 31,800 35,400 32,500 30,500
10 35,200 41,000 37,400 32,800
50 41,600 55,100 47,300 44,600
100 43,900 60,700 53,300
Susitna River at Denali 1.25 14,000 12,400 15,900
2 15,900 16,100 21,700 18,100
5 20,200 21,100 30,000 23,600
10 24,100 24,500 36,500 25,700
50 36,600 32,800 50,900 35,600
100 43,600 36,200 59,700
rnisc7/w9
ATTACHMENT C (Continued)
Single1 USGS 2 USGS 3
Susitna Area If Cook Inlet
Return Station Regional Regional Regional
Period Estimate Estimate Estimate Estimate
Station location (Yrs.)(CFS)(CFS)(CFS)(CFS)
Maclaren River near Paxson 1.25 4,450 3,760 4,880
2 5,150 4,880 7,180 4,960
5 6,800 6,390 10,600 6,790
10 8,420 7,420 13,300 7,660
50 13,700 9,960 19,800 11,200
100 16,800 11,000 24,000
Susitna River near Cantwell 1.25 24,600 25,400 34,000
2 32,300 33,000 42,500 29,800
5 42,200 43,200 53,600 36,900
10 48,400 50,100 61,900 38,400
50 61,700 67,200 78,700 50,400
100 67,100 74,200 88,500
Chulitna River near Talkeetna 1.25 33,100 28,500 28,200
2 37,800 37,000 36,200 42,600
5 45,100 48,500 47,100 53,400
10 50,400 56,300 55,300 56,400
50 63,100 75,500 72,600 75,200
100 69,000 83,300 82,700
Tal keetna River near Tal keetna 1.25 20,300 20,900 30,000
2 26,300 27,200 38,500 56,600
5 38,500 35,600 50,100 71,400
10 49,100 41,400 58,900 76,300
50 80,100 55,500 77,400 103,000
100 96,700 61,200 88,300
misc7/w10
ATTACHMENT C (Continued)
Station Location
Montana Creek near Montana
Skwentna River near Skwentna
Tonsina River at Tonsina
Copper River at Chitna
Return
Period
(Yrs.)
1.25
2
5
10
50
100
1.25
2
5
10
50
100
1.25
2
5
10
50
100
1.25
2
5
10
50
100
Single1
Station
Estimate
(CFS)
2,040
3,230
4,670
5,540
7,290
7,990
26,800
32,000
38,900
43,400
53,200
57,300
3,540
4,600
6,040
6,990
9,090
9,980
146,000
164,000
189,000
206,000
242,000
257,000
Susitna
Regional
Estimate
(CFS)
2,520
3,270
4,280
4,970
6,670
7,350
23,600
30,700
40,200
46,600
62,500
69,000
4,820
6,250
8,190
9,510
12,800
14,100
127,000
164,000
215,000
250,000
335,000
370,000
USGS 2
Area II
Regional
Estimate
(CFS)
1,130
1,700
2,500
3,100
4,490
5,470
15,700
20,400
26,500
31,100
40,400
46,200
2,130
3,040
4,260
5,160
7,130
8,490
146,000
165,000
191,000
210,000
246,000
265,000
USGS 3
Cook Inlet
Regional
Estimate
(CFS)
1,580
2,220
2,540
3,770
19,400
24,600
25,800
34,300
1
2
3
Based on three parameter log normal distribution and shown to three significant figures
Lamke j R.n.(1979)Flood Characteristics of Alaskan Streams,USGS,Water Resources
Investigation,78-129
Freethey G.W.and n.R.Scully (1980)Water Resources of the Cook Inlet Basin,Alaska,
USGS,Hydrological Investigations Atlas HA-620
susi6/u5
ATTACHMENT D
REVIEW OF FLOOD FREQUENCY ANALYSIS,
CONDUCTED BY DR.ROBERT F.CARLSON,
UNIVERSITY OF ALASKA,FAIRBANKS
..
..
-
..
-
-
-
~nstitute of Water Resources
UNIVERSITY OF ALASKA
FAIRBANKS.ALASKA 9970 \
MEMORANDUM REPORT
81-22
To:
From:
Date:
John Lawrence,Acres American Inc.
Steve Bredthauer,R&M Consultants,Inc.
Robert F.carlSo~
June 11,1981
Subject:Susitna Hydroelectric Project
This report is in response to John D.Lawrence1s letter of April 3,1981,
asking me to review the regional flood analysis conducted'by R&M Con-
sultants.The review is 'meant to include:
a)Validity of gaging stations selected for the regional analysis
and their representation of the hydrologic region analyzed.
b)Adequacy and limitations of the analysis in development of
regression expressions and the assumed 3-parameter log nor-
mal distribution.
c)Validity of the shape,peak,and volume of the design flood
hydrographs as developed.
dl Discussion of review findings with Acres and R&M.
The review is based on three reports which have been transmitted from
R&M to Acres:
a)Two letters from James Aldrich to Ian Hutchinson,Re:Susitna
J:::,
Regiona1 Flood Peak Analysis,Project No.052305,dated
October 27,and December 22,1980.
PLLASE,REPLY 8Y AIRMAIL
UNIVERSITY OF ALASKA
b)A letter from Brent Drage to Ian Hutchison,Re:Susitna Regional
Flood Analysis,Subtask 3.05,dated March 9,1981.
The time and budget constrain~s of the review contract did not permit me
to conduct an independent computation and verification of the values contained
in the report.Therefore,the review is based on the material as presented
by R&M.Nevertheless,several key values could be checked by comparison
with published information.
'i Part (a).Validity of selected gaging stations.
The stations selected for regional analysis represent the transitional-
continental climate zone of the Susitna basin.The Susitna basin's
outstanding geographic characteristic is the combination of drainage
from the south side of the Alaska range,the north side of the Tal-
keenta mountains and the large flat boggy sub-basin north of Lake Louise.
It is doubtful whether any other basin faithfully represents this type
of hydrologic region.Of the twelve stations chosen for the regional
analysis,the Susitna's hydrologic regime is best represented by:
1.Susitna at Gold Creek.
2.Susitna near Denali.
3.Maclaren near Paxson.
4.Susitna near Cantwell.
5.Chulitna near Talkeetna.
6.Skewnta near Skewnta.
7.Montana near Montana.
-=:.
8.Talkeetna-near Talkeetna.
-2-
PLEASE REPLY BY AIRMAIL
UNIVERSITY OF ALASKA
stations that are not as closely representative'are:
~1.Matanuska at Palmer.
2.Tonsina at Tonsina.
3.Copper near Chitina.
4.Caribou near Sutton.
The second group has been selected primarily on the basis of station
distance from the Susitna basin and a different exposure to the coastal
maritime climate.r do not feel the differences are great enough to
warrant their exclusion from the regional analysis.
Part (b).Adequacy of the regression expressions and the assumed
3-parameter log normal distribution.
The assumed 3-parameter log normal distribution:Given the'very
sparse data base of the Susitna area streamflow records in combination
with the great variability of extreme values,an attempt should be made
to model or fit the sample data with a theoretical distribution of simple
construction and few parameters.The analysis indicates that either
the log-normal (LN)or the three-parameter log-normal (3PLN)distri-
butions are nearly equally satisfactory.The 3PLN distribution has the
advantage of further adjusting for the skew by inserting a lower trunca-
tion limit.I feel that,in view of the slight difference in pre-
dictability between the two distributions,the LN ;s preferred because
of its simplicity.The analysis is not greatly compromised by using a
3PLN distribution,but the small reduction of the total deviation does
&:.
-3-
PLEASE REPLY BY AIRMAIL
UNIVERSITY OF ALASKA
not seem to warrant the additional complexity.-An inspection of rough
frequency plots shows a good agreement between the fitted distribution
and the sample points for both the LN and the 3PLN distributions.In
summary,my preference for a frequency distribution would be the LN,but
I do not see any great disadvantage in using the 3PLN.
The regression analysis:The regression analysis which attempts to pre-
dict the mean annual peak flow from watershed parameters has been carried
out in a standard manner.A standard step-wise regression program has
been used with up to twelve watershed parameters.Of the twelve,five
':parameters (drainage area,stream length,glacier area,mean annual
precipitation,and mean annual snowfall)were shown to be statistically
significant predictors of the mean annual instantaneous peak flow.Of
these five,only the first three are directly related to.basin parameters.
The last two are estimated values and must be calculated from nearby
gages or yet other basin parameters.Of the first three,the stream
length and glacier area are potentially strongly related to drainage
area.Larger areas are expected to be longer and,in the Susitna area,
they should be strongly related to higher elevation?and glaciers.
Therefore,since drainage area is the most obvious predictor and far
outweighs the others,it should be retained as the only independent
predictor.The same reasoning holds-for predicting the mean October-May
peak flow.
There is one aspec!of the regression analysis which is puzzling.The
usual reason for an analysis of mean annual flood versus drainage
-4-
PLEASE REPLY BY A
-
UNIVERSITY OF ALASKA
basin characteristics is to allow a regional es~imation equation to be
developed.Yet I can find no evidence of the completion of this equation
or of its intended use.When using the 3PLN frequency model,three
values of the sample must somehow be estimated (the mean,standard
deviation,and skewness of the sample)or the three parameters of the
distribution must be calculated (in this case the truncation level,the
mean of the logs,and the standard deviation of the logs).I can find
no estimates of the other two and only the Susitna at Gold Creek ;s used
in the third memorandum.
My recommendation would be to estimate the mean annual flood (or May-.,
October flood)from the drainage area and to use a pooled regional stan-
dard deviation.and skewness to complete the description of the regional
curve.The great sparseness of the data base must be constantly kept in
mind and the most variable parameters pooled whenever possible.
~'In summary,unless some use is made of the regression exercise,which is
not apparent in the three memorandums,I would not recommend its inclusion
in the final report.
Part (c).Validity of the shape,peak,and volume of the design flood
bydrograph.
The first step,a dimensionless comparison of the five largest hydro-
graphs,seems to be straightforward and correct.I think the mean curve
should be smoothed ~ut.a bit more,perhaps with a moving average method.
-5-
PLEASE REPLY BY AIRMAIL
UNIVERSITY OF ALASKA
The time base (which determines the volume)is not clear.Also,whether
the base flow was removed from the peak prior to the plot is not clearly
indicated.I was not furnished with Enclosure 3 (the fifty peak hydro-
graphs),so it is difficult for me to make an accurate assessment.
/
V
Although a flood peak versus volume relationship was established in
Figure 7 of Memorandum 3,it is not clear whether the flood volumes were
estimated from this graph or established independently through a separate
frequency analysis.I assume a separate analysis has been made and the
peaks and volumes,say for a 50-year return period,are matched to form
the hydorgraph.That seems to be a logical procedure,but the volume
under the stated flood·peak hydrograph should equal the corresponding
estimated flood volume.There is no clear indication that this comparison
has been made.
In summary,the flood peak-volume analysis has been carried out in a
satisfactory way,but the several points mentioned above should be
cleared up for the final report.
Part Cd).Discussion of review findinqs with Acres and R&M.
I had preliminary discussions with Brent Drage and Tim Renschler of R&M
Consultants about the analysis.My comments were essentially the same
as those I have presented here.In late May,I had a meeting with Steve
Bredthauer of R&M £onsultants during which we discussed the three memorandum
reports in some detail.Again,the substance of my remarks has been
presented here.
-6-
PLEASE REPLY BY AIRMAIL
UNIVERSITY OF ALASKA
Part (e).Some additional items for discussion.
The instantaneous-daily flow ratio analysis seems to be logical and
consistent.An average value of 1.1 for all stations would seem to
be appropriate.The mean daily values should be used for the frequency
analysis since they are stable and available in every case.Then the
calculated ratio should be used when required.
A comparison of the predicted values of mean daily floods for the 100-
year return period from four sources compares reasonably well.The
values are:
Lamke's U.S.G.S.Report l20~OOO cfs
U.S.Corp's Interim Feasibility Report 110,000 cfs
R&M1s Lognormal Estimate 112,625 cfs
R&M's 3-Parameter Lognormal 117,782 cfs
These values are reasonably close,given the general vagueness which
is a part of every flood frequency analysis.One can be fairly sure
that the flood frequency analysis has been carried out correctly.
Part (f).Concluding remarks.
This memorandum report completes my review of the Susitna flood frequency
report.r hope the comments will be useful for understanding the appli-
cation of the frequency analysis and for preparation of this final
~.
report.I will be willing to assist in any additional analysis which may
be required or to answer questions about my comments.
-7-
PLEASE RE