HomeMy WebLinkAboutAPA2888FLOOD
PLAIN
INFORMATION
I
TALKEETNA RIVER -SUSITNA RIVER -CHULITNA RIVER
TALKEETNA,ALASKA
F
GB
1227
.U55
T3
1972
~OR THE MATANUSKA-SUSITNA BOROUGH BY THE DEPT.OF THf ARMY~
\SKA DISTRICT~CORPS OF ENGINEERS~ANCHORAGE~~A.
Alaska Resources
J U N E 19 7 2 Library &Information Services
Apr'orage,fUaska
CONTENTS
PREFACE
BACKGROUND INFORMATION
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Page J ~"9'0<..-
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Settlement
The Stream and Its Valley
Developments in the Flood Plain
FLOOD SITUATION
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5
Sources of Data and Records 5
Flood Season and Flood Characteristics 5
Factors Affecting Flooding and Their Impact 6
Obstructions to Floodflows 6
Flood Damage Reduction Measures 7
Other Factors and Their Impacts 8
Flood Warning and Forecasting 8
Flood Fighting and Emergency Evacuation Plans 9
Material Storage on the Flood Plain 9
PAST FLOODS
Summary of Historical Floods
Flood Records
Flood Descriptions
FUTURE FLOODS
Intermediate Regional Flood
.Standard Project Flood
Frequency
Hazards of Large Floods
Flooded Areas and Flood Damages
Obstructions
Velocities of Flow
Rates of Rise and Duration of Flooding
Photographs,Future Flood Heights
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GLOSSARY
ARLIS
Alaska Resources
.Ibrary &Information Services
!U1chorage,PUaska
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DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLA IN IN FORMATION
TALKEETNA
ALASKA
GENERAL MAP
JUNE 1972
PLATE
PREFACE
The portion of Talkeetna covered by this report is
subject to flooding from the Talkeetna,Susitna an d Chul itna
Rivers.The properties along these streams are p rimaril y
residential and commercial,and were severely damaged by the
flood of 1942.The open spaces in the flood plain which may
come under pressure for future development are extensive.
Although large floods have occurred in the past,studies indicat e
that even larger floods are possible~
This report has been prepared because a k now 1e d g e of
flood potential and flood hazards is important in land use planning
and for management decisions concerning flood plain utilizat ion.
It includes a history of flooding in Talkeetna and identifies those
areas t hat are subject to possible future floods.Special
emphasis is given to these floods through map s,photographs.
profiles,and c r 0 s s sections.The report does not provide
solutions to flood problems;however,it does furnish a suitable
basis for the adoption of land use controls to guide flood plai n
development and thereby prevent intensification 0 f loss and
damage.It will al so a id in the identification 0 f other flood
damage reduction techniques such as works to modify flooding
and adjustments,including flood proofing,w hi c h might be
embodied in an overall Flood Plain Management (FPM)program,
Other FPM program studies--those of environmental attributes
and the current and future land use role of the flood plain as
part of its surroundings --would also profit from this information.
i
At the request of the Matanuska-Susitna Boroughl and
endorsement 0 f the State of A1askal Department of Na tu ral
Resources l th i s report was prepared by the Alaska Distr ictl
Corps of Engineersl under continuing aut h 0 r it Y provided in
Section 206 of the 1960 Flood Control Actl as amended.
Assistance and cooperation of the Alaska Railroad l Fed eral
Aviation AgencYI Alakka Department of Highwaysl National
Weather Servicel Matantr'ska-Susitna Boroughl and privat e
citizensl in supplying useful data and photographs for the
preparation of this report are appreciated.
Additional copies of this report can be obtained from the
Matanuska-Susitna Borough.The Alaska Districtl Cor p s of
Engineers l upon requestl will provide technical assistanceto
planning age n c i e sin the interpretation and use of the data
presented as well as planning guidance and furtherassistance.
including the development of additional technical information.
ii
BACKGROUND INFORMATION
Settlement
Talkeetna#which is an Indian name meaning river of
plenty#was established early in the Twentieth Century just
below th e confluence of th e Susitna#Talkeetna,and Chulitna
Rivers.The village served a s a supply and trade center for
miners operating in the foothills of the Alaska Range and
Talkeetna Mountains.Reportedly#Talkeetna was originally
the site of a Tanaina Indian Village although there are presently
only two Indian families living in Talkeetna.
Talkeetna was the terminus of river boat traffic from
Cook Inlet up the Susitna River.It developed as a major camp
and distribution center wh en the railroad was built.The rail-
road station was established in 1915 and a Post Office in 1916.
During World War II man y 0 f the gold mines were shut
down as a result of war time wage and cost controls.After the
war,mining remained unprofitable#as it is today#and most of
the min e s remained c los e d.However#lenient homes tead
regulations brought many veterans into the area taking up some
of the population loss from unemployed miners.
Population fig u res for the unincorporated village of
Talkeetna are as follows:1920-70;1930-89;1939-136;1950-106;
1960-76;and 1970-182.
The Stream and Its Valley
The Talkeetna River and the Chulitna River a re major
tributaries of the Susitna River.Talkeetna River,with a total
drainage area of 2015 square miles,has its origin a t Talkeetna
Giacier in the Talkeetna Mountains.Fro:m thi s rugged terrain
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the river flows northwest 40 miles and then southwest 40 miles
to its junction with the Susitna River at the villlage of Talkeetna.
The are a s above Talkeetna,drained by the three rivers,
range from 350 to over 6,000 feet in elevation and all have
portions of their higher elevations glacier covered.Drainage
areas contributing to runoff at 10 cat ion s in or near the study
areas are shown in Table I.
TABLE I
DRAINAGE AREAS
(
Location
Talkeetna River at Mouth
Chulitna River at Mouth
Susitna River at Talkeetna
Susitna River Above Mouth
Of Chulitna River
River Length
Miles
80
80
200
200
Drainage Area
sq.mi.
2,015
2,630
1 1,035
6.390
The climate of the area is characterized by moderately warm
summers and cold winters with temperature extremes ranging
from p 1 us 91 degrees F.to 48 degrees below zero..Annual
precipitation averages 28.8 inches and annual snowfall 114 inches.
Rainfall is generally the heaviest in July.August and September
with monthly precipitation amounts about equal for the rest of the
year.
Developments in the Flood Plain
The flood plain of t he Talkeetna River a t the village of
Talkeetna is wide and developed only on the south side at th e
mouth of the river.The only bridge in the study area is the
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Alaska Railroad Bridge which crosses just upstream from the
mouth of the Talkeetna River.
The flood plarn within-the village of Talkeetna is occupied
by residential an d commercial developments.The railroad,
highway,streets and utility 1 in e s,in addition to homes and
businesses,would be:subject to flooding.This flood plain is
only partially developed and f u t u redevelopment .·t s likely,
especi ally with the increase in tourist traffic because 0 f the
opening of the new Anchorage-Fairbanks highway.
3
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e
ALASKA RAILROAD BRIDGEILOOKING UPSTREAM FROM NORTH BANK OF TALKEETNA RIVER
FIGURE 1
FLOOD SITUATION
Sources of Data and Records
The U.S.Geological Survey has maintained stream gages
at the following locations upstream from Talkeetna for the period
indicated:
Location Period of Record
Susitna River at Gold Creek August 1949 to presen t
Chulitna River near Talkeetna February 1958 to presen t
Talkeetna River above Talkeetna June 1964 to presen t
The gag e location on the Talkeetna River is shown on the
general map.The 0 thers are not within the area covered by
this map.
To supplement the records of the gaging stations and those
of snow surveys,newspaper files,historical doc u men t sand
records were searched for information concerning past.floods ..
These records h a v e helped to develop a knowledge of floods
which have occurred on these rivers and have also shown that
the floods on the three rivers do not peak concurrently.
Maps prepared for this report were based on the U.S.
Geological Survey quadrangle sheet Talkeetna B-l.River cross
sections and structural data on the bridge and culverts were
obtained by field surveys performed by Alaska District,Corps
of Engineers,personnel.
Flood Season and Flood Charac teristics
Major floods h a v e occurred in the study area during the
spring,sum mer and fall seasons with the greatest recorded
flood occurring in September 1942.Floodflow stages can rise
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from normal flow to extreme flood peaks in a relatively short
period of time with high velocities in the main channels of the
rivers.
The flood of September 1942 resulted from a combination 0 f
48 hours 0 f heavy rains and melting snows which had recently
fallen in the mountains.In addition to floods caused by runoff,
Talkeetna is susceptible to floods caused by sudden releases of
water that have been impounded by ice jams.
Factors Affecting Flooding and Their Impact
Obstructions to Floodflows -Natural obstructions to flood-
flows include trees,brush and other vegetation growing along
the stream banks in flood plain areas.Man-made encroachments
on '0 r over the rivers,s u c has the railroad bridge,can also
create more ext~nsive flooding than would otherwise occur.
During floods,trees,brush and other vegetation growing in
flood plains impede floodflows,t h usc reating backwater and
increased flood heights.Trees and other debris may be washed
away and carried downstream to collect on the bridge or other
obstructions.As floodflows increase,masses of debris could
break loose and a wall of water and debris would surge down-
stream until another obstruction is encountered.Debris could
collect against the bridge until the load exceeds its structura.l
capacity and the bridge is destroyed.
In general,obstructions restrict floodflows and result in
overbank fl 0 w s and unpredictable are a s of flooding,possible
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destruction of bridges and culverts and an increased velo c ity
of flow immediately downstream.It is impossible to pred ict
the degree or location of the accumulation of debris;t her efo reo
for the purposes of th~s report,it was necessary to assume that
there would be no accumulation of debris at the bridge 0 r any
clogging of culvert openings in the development 0 f the flood
profiles.
Flood Damage Reduction Measures -In 1951 the Corps of
Engineers completed a n emergency bank protection proj ec t
at Talkeetna,Alaska,under Section 14 of the 1946 Flood Cont rol
Act.The project,located on the left bank of the Talkeetna River
below the A laska Railroad Bridge,consists of a brush and
timber fascine I,000 feet long which was constructed to arr est
erosion.Subsequent to construction of the emergency work,a
flood control project was authorized which called for a stone
revetment approximately 1,500 feet long downstream from th e
railroad bridge.In 1960 this authorized project was placed in
an inactive category as the emergencytitnbet fas,Cij):econstructed
in 1951 was performing satisfactorily.Recently,the river has
cut a small channel through the fascine structure and the village
is again threatened by erosion.A restudy by t he Corps of
Engineers of the authorized project to determine feasibility,
justification and local cooperation requirements under exis ting
conditions in the area will probably be undertaken in Fiscal Year
1973.
In an effort to control erosion and protect its bridge,the
Alaska Railroad,in 1949,made a channel change i mmediatel y
upstream from the bridge.This realignment cut off a
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meander of the river and allowed .the river to flow at hght angles
to the bridge.Figures 2 an d_.3 illustrate the before and after
conditions.
There are no existing Borough zoning ordinances,building
codes,0 r other regulatory measures specifically for the re-
duction of flood ·damage.The village of Tal k e e t n a is not
incorporated and therefore does not have any zoning powers.
This study has been requested so that it may be used as a basis
for the development 0 f Flood P 1 ad n Management planning
measures by the Matanuska-Susitna Borough.
Other Factors and Their Impact -The m aj 0 ri ty 0 f the
i nund ate dar e a at Talkeetna has been along the banks of
the Talkeetna River near its confluence with the Susitna River.
This is due largely to the compounded backwater influence
of the S usitna at high stages.When hi g h runoff from the
tributaries has occurred during these periods of high stages on
the Susitna,it has aggravated the flooding by increasing the
height and duration of the river's backwater effects.Flooding
and threats of flooding promote action by local officials in flood
warning and flood fighting activities.Due to the size and nature
of the village,the r e is no significant problem with floatable
materials being stored in the flood plain whhih might cause
additional damage.
(RFC)located in
Flood Warning and Forecasting -The
Service,Alaska River Forecast C en t e r
8·
National Weather
(
Anchorage,issues flood warnings for the Talkeetna area to radio
and television s tat ion s an d the 10 cal media for further
dissemination tor esidents of the area.In addition,the Center
maintains records 0 f daily river stages on the Susitna River at
Gold Creek,at the Alaska Railroad Bridge and at the Highway
Bridge a t Sunshine.The National Weather Service also issues
regular weather forecasts and hazardous weather warnings for
the area.
Flood Fighting and Emergency Evacuation Plans -Although
there are no formal flood fighting or emergency evacuation plans
for the Talkeetna area,provisions for alerting area residents in
time 0 f emergency are accomplished by the Alaska Disaster
Office through th e Matanuska-Susitna Borough.T his office
maintains communication wi t h the National Weather Service
at its control center,establishing a "flood watch"during.the early
stages of flood threat.Residents along the river are warned by
radio and telephone 0 f approaching flood conditions and advised
to evacuate the area.Subsequent flood fighting,evacuation and
rescue activities are coordinated on a Borough-wide basis with
Borough officials.
Material Storage On The Flood Plain-As previously stated,
due tot h e size and nature of the community,there are no
significant quantities of floatable materials stored in the flood
plain at Talkeetna.I f they were present they could be carried
away by flood flows,causing serious damage to any structures
downstream.
9
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AERIAL VIEW OF TALKEETNA RIVER,LOOKING UPSTREAM,SHOWING
NATURAL CONDITIONS OF THE RIVER IN AUGUST,1949
FIGURE 2
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AERIAL VIEW OF TALKEETNA RIVER,AUGUST 1950,SHOiHNG THE CHANNEL CHANGE
CONSTRUCTED BY THE ALASKA.RAILROAD
FIGURE 3
VIEW OF FASCINE FROM UPSTREAM END AS IT APPEARED IN MAY,1951
FIGURE 4
FASCINE AS IT APPEARS TODAY
FIGURE 5
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PAST FLOODS
Summary of Historical Floods
Very little information is available concerning historical
floods at Talkeetna.Records indicate that an ice jam
occurred on the Susitna River at Gold Creek in 1919.bu t they
did not indicate whether or not Talkeetna was flooded.Floods
have also occurred in September 1942 and August of 1971.The
1942 flood is the highest of record and is the only one that cau sed
any significant damage.The 1971 flood had a peak which lasted
only a few hours and only flooded the lower.abandoned.part s
of the village.
Flood Re cords
Information on historical floods in the Talkeetna area was
obtained from the stream gaging stations maintained by the
U.S.Geological Survey a t a number of locations within the
Susitna Watershed near Talkeetna.Additional information on
past floods was obtained from interviews wit h residents along
the Talkeetna River.newspaper files and historical documents.
Flood Descriptions
The following are descriptions of the flood of record that
occurred at Talkeetna.Alaska in September 1942:
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EXCERPTS FROM THE ANCHORAGE TIMES,23 AND 26 SEPTEMBER 1942 (0)
WORST FLOODS FORCE RESIDENTS TO FLEE
Talkeetna
Under Water
Use Rowboats
Nagley Store,Trading
Post,DeVault Road-
House Are.Damaged
Returning travelers who knew Talkeet-
na "Before and after"today are re-
counting the ravages of Monday'S flood
when the Talkeetna,Chul itna and Big
Susitna rivers rose far above their
confining banks and partially inundated
Talkeetna village.
The river rise was estimated by sev-
eral as more than six feet,one cabin
on the Talkeetna river was torn away
and floated downstream to crack up
against a mass of debris,the DeVault
Roadhouse and the Talkeetna Trading
Post were flooded,the old pier and
boathouses on the Talkeetna are gone,
and the township itself is covered with
mud and glacier silt.
Stacks of stove wood,cut during the
summer for use this winter,were drift-
ed away,according to those returning
to Anchorage.
Women and children,sent hurriedly to
Sunshine Tuesday out of danger's way,
have been retu rned to the ir homes,it
was said.
Real danger,one Anchorage man reports,
was seen Monday might when the flood
waters reached within eight inches of
the dike.It was at that time,he said
today,that the entire town was threat-
ened for had the dike not held against
the great rush of water Talkeetna would
have been wiped ou t.
Travelers told too of the swollen
creeks,some of which widened to half a
mil e f rom the ir normal few yards.
Work crews,for which every available
able-bodied man was recruited,are still
working against odds to repair damaged
structures.:.:..=..::.:.----------
(a)Simulated from microfilm copy
14
Say River Rose
Six Feet To Flood
Homes and Stores
In one of the worst floods in memory
of sourdough residents,rowboats are
being used as a means of transportation
in Talkeetna,women and children have
been evacuated to safety,and the Big
Susitna,the Chul itna rampaging over
the ir banks.
The three great rivers,.swollen by
ij8 hours of heavy rains and new snows
running from the mountains after warm
winds,flooded their banks Monday and
sent a rush of water into homes,stores
and streets of the township.
While details of the damage were not
immediately available,an indication is
given by the report that between two
and three feet of water stood in the
H.W.Magley store which occupies one of
the hi ghes t spots in Talkeetna and
which,during the height of the flood,
was isolated as an island.
The Talkeetna Trading Post,operated
by Belle McDonald near the banks of the
Big Sus i tna,the DeVau It Roadhouse,
just across the road,and the Fairview
Inn were probably the most seriously
damaged,according to unofficial re-
ports.
Work crews were rushed to Talkeetna
to repair damaged structures weakened
by flood waters and Col,O.F.Ohlson
was there today supervising the work.
As flood water rose to an alarming
height Monday,women and children were
crowded on speeders and run to Sunshine
and housed in the section house.It is
bel ieved between 20 and 30 were sent to
temporary quarters to avoid mishap in
the flood area and to provide warm and
dry housing for the women and children.
No accidents have been reported in mea-
ger deta iIs brought to Anchorage.It
is bel ieved that stores and trading
posts had not as yet stocked their com-
plete winter suppl ies but that damage
by water to merchandise will amount to
a considerable loss.
FUTURE FLOODS
Floods of the same or larger magnitude as those that have
occurred in the past will occur in the future.Larger floods
have been experienced in the past on streams with simi lar
geographical and physiographical characteristics a s those
found in the study area.Similar combinations of rainfall and
runoff·which caused these floods could occur in the Talkeetna
area.Thereforel to determine the flooding potential of the
study area,it was necessary to consider storms and floods that
have occurred in regions of like topography,watershed cover
and physical characteristics.Discussion of the future floods
in this report is limited to those that have been designated as
the Intermediate Regional Flood and the Standard Pro jeet
Flood.The Standard Project Flood represents a reasonable
upper limit of expected flooding in the study area.The Inter-
mediate Regional Flood may reasonably bee xpected to occur
more frequently a 1 tho ugh it will not be as severe as the
infrequent Standard Project Flood.
Intermediate Regional Flood
The Intermediate Regional Flood (IRF)is defined a s one
that will occur once in 100 years on the average,although it
could occur ina ny year.The peak flow 0 f t his flood was
developed from statistical analysis of streamflow and precipi-
tation records and basin runoff characteristics for the stream
under study.In determining the Intermediate Regional Flood
for the Talkeetna and Susitna Rivers,statistical studies were
made using the records of flood data from the U.S.Geological
Survey gaging stations throughout the v icinity of Talkee tna,
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Alaska.Peak flows thus developed for the Intermediate Regional
Floods at selected locations in th e study area are shown in
Table 2.
Standard Project Flood
The Standard Project Flood is defined as a major flood that
can bee xpected too ccur fro m a severe combination of
meteorological an d hydrological conditions that is consid ered
reasonably characteristic of the geographical area in which the
study area is located,excluding extremely rare c ombinati ons.
The Corps of Engineers,in cooperation with the NOAA Weather
Service,has made comprehensive studies a nd in ves tigations
based on the past records of experienced storms andfloods and
has developed generalized procedures for estimating the flood
potential of streams.Peak discharges for the Standard Pro ject
Flood at Talkeetna are shown in Table 2.Discharge hydrographs
for the Talkeetna SPF and the Susitna River SPF at Talkeetna
are shown on Plates 9 and 10,respectively.
TABLE 2
PEAK FLOWS FOR INTERMEDIATE REGIONAL
AND STANDARD PROJECT FLOODS
Drainage Intermediate Standard
Location Area Regional.Flood Project Flood
sq.mi.Discharge Discharge
cfs cfs
Susitna River
at Talkeetna 11,035 268,000 315,000
Talkeetna River
at mouth 2,015 97,000 121,000
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TABLE 3
FLOOD ELEVATIONS
Talkeetna River at Alaska Railroad Bridge
Flood Elevation (a)
Standard Project
Intermediate Regional
August 1971
(a)Feet.mean sea level
354.4
351.8
346.9
Frequency
A frequency curve of peak flows was constructed on the basis
of available information and computed flows 0 f floods u,p to
the magnitude of the Standard Project Flood.The frequency·curve
thus derived.which is available upon request.ref 1 e c t s the
judgment of the engineers who have studied the area an dar e
familiar with the region;however.it must be regarded as
approximate and should be use d with caution in connection
with any planning of flood plain use.Floods larger t han the
Standard Project Flood are possible but the combination of fac tors
necessary to produce such large floods would be extremely rare.
Hazards of Large Floods
The extent 0 f damage caused by any flood d e pen d s on
the topography of the area flooded.depth and duration of flooding.
velocity of flow.rat e 0 f r i s e,and developments in the flood
plain.An Intermediate Regional 0 r Standard Project Flood
on the Talkeetna and Susitna Rivers or on the Talkeetna River.
itself,will result in inundation of residential and c ommerc ial
areas in the village of Talkeetna.The sam eflood situation
on the Susitna River alone would result in only the lower end of
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the village.adjacent to the Susitna.being flooded ..Deep flood-
water.flowing at high velocity and carrying floating debris.will
create conditions hazardous to persons'and vehicles attempting
to cross flooded areas.In general•.floodwater 3 or more feet
deep and flowing at a velocity of 3 or more feet per second could
easily sweep an adult person off his feet.thus creating definite
danger of injury or drowning.
Flooded Areas and Flood Damages -The areas in the village
of Talkeetna t hat a re subject to flooding by the I nte rmediate
Regional and Standard Project Floods are shown on Plates 2 and
3.The actual limits of these overflow areas mayvary somewhat
from tho s e shown on the map s because the 50 foot contour
interval and scale 0 f the maps do not permit precise plotting
of the flooded area boundaries.As may be seen from these
plates.floodflows fro m the Susitna an d Talkeetna Rivers
cover essentially all 0 f the village.The highest stages of
flooding throughout the study area occur when the floodwaters
from the Talkeetna me e t with the high stages of the S usitna
River.Areas t hat will be flooded by the Intermediate Regional
or Standard Project Floods include com mer c i al an d res-
idential sections along with the associated roads and private
utilities.Considerable damage to these facilities would 0 ccur
during an Intermediate Regional Flood.The majority of homes
in Talkeetna would be damaged by this flood.Heavily laden flood
waters would deposit the i r silt load throughout the village
due to the lower velocities of overbank fl 0 w in t his ar ea.
Utilities and transportation facilities would be damaged in addi-
tion to an interruption of communications.Most of the water wells
are not completely sealed.therefore the flooding and subsequent
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pollution 0 f the wells would create a serious health hazard.
Both air fie 1d s would be damaged and their use limited.
Evacuation of people from the v illage would not be a major
problem though,due to the fact that highway access to Talkeetna
would not be affected.Fldodwaters will flow over the highway
and railroad just south 0 f Talkeetna,closing access in to the
community and disrupting rail traffic between Anchorage and
Fairbanks.
Damage would b e even more severe during a Standard
Project Flood due tot he wider extent and greater depths 0 f
flooding,higher velocity flow and longer duration of fl ooding.
Plates 4,5 and 6 show water surface profiles of the IRF and SPF.
Depth 0 f flow in t he channel can be estimated fro m these
illustrations.Typical crQss sections of the fl 0 0 d plain at
selected locations,together wit h t he water surface elevation
and extent of the IRF and SPF,are shown on plates 7 and 8.
Obstructions -During floods,debris colI e c tin g 0 n the
bridge and culverts could decrease their carrying capacity and
cause greater water de p t h s (backwater effect)upstream 0 f
these structures.Since the occurrence an d amount of debris
are indeterminate factors,only the physi cal characteristic of
the structure we reconsidered in preparing profiles 0 f the
Intermediate Regional and Standard Project Floods.S imila rly,
the map s 0 f flooded areas show the backwater effect of the
bridge but do not reflect the increased water surface elevation
that could he caused by debris collecting against the structure.
The b rid g e is high enough not to be inundated by floodflow s.
20
However,even without considering an accumulation of debris on
the structure,it still causes a substantial backwater effect.This
backwater causes a considerable portion of the area east of the
Alaska Railroad to be inundated by water during major floods
which approach the IRF in magnitude.With the exception of
The Federal Aviation Administration (FAA)facilities,there is,
at present,a minimum 0 f development in this area.Dama ge
to the FAA facilities would be relatively minor considering the
first floor elevations of these structures.Water will flow over
the railroad embankment and down into the village.The flood-
waters will also flow over the railroad and highway just south of
the viII age.Depths and quantity of flow cannot be accurately
determined,although both are anticipated to be minor.Overall
depths of flooding e as t 0 f the railroad line will range up to 6
feet with the deepest area adjacent to the railroad embankment
south of the FAA airfield.
Velocities of Flow -Water velocities during floods depend
largely on the size and shape of the cross sections,conditions
of t'h e stream and the bed slope,all of which varyondifferent
rivers and at different locations on the same river.During the
Intermediate Regional and Standard Project Flood s,average
velocities of main channel flow would range from 5 to 7 feet per
second 0 nth e Talkeetna River except at the railroad bridge
where they would range from 14 to 17 feet per second.W:tter
flowing abo v e 8 feet per second is capable of causing severe
erosion to streambanks and transporting large objects.Over-
bank flow in the Talkeetna area would average 1 to 2.5 feet per
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second.At these velocities,deposits of silt and other debris
can be expected.
Rates 0 f Rise an d Duration of Flooding -Floods on the
Talkeetna and Susitna Rivers generally h a v e a gradual rise
until the ground becomes saturated,then they expe rienc e a
constant,rapid rise of one to three days duration until the peak
is reached.Generally,the duration of the extremely high flows
does not exceed one or two days and then the flood waters drop
quickly.For the Intermediate Regional and Standard Proj ect
Floods,Table 4 g i v est he maximum rates of rise,height of
rise (f rom critical \\:;tage level to maximum floodflow level),
time of rise (time period corresponding to height of rise ),and
duration 0 f critical stage (period 0 f tim e flooding is above
critical stage level).
TABLE 4
RATES OF RISE AND DURATION
(Talkeetna River at Alaska Railroad Bridge)
Maximum Height Time Duration
FLOOD Rate of of of of
Rise Rise Rise Critical Stage
ft!hr ft hrs hrs
Intermediate Regional Flood .7 8.3 19 60
Standard Project Flood .8 10.9 26 82
Photographs,Future Flood Heights -The levels that the
Intermediate Regional and Standard Project Floods are expected
to reach a t various locations in the village of Talkeetna .are
indicated on the following photographs.
22
FUTURE FLOOD HEIGHTS AT THE ROADHOUSE ON THE MAIN STREET OF TALKEETNA
FIGURE 7
(
........._",...~•.-...:.~."p
FUTURE FLOOD HEIGHTS AT THE TALKEETNA MOTEL AND RESTAURANT
FIGURE 8
23
FUTURE FLOOD HEIGHTS AT THE B &K TRADING CO.-MAIN STREET,TALKEETNA.
U.S.POST OFFICE TO THE RIGHT
FIGURE 10
24
I
I
I
8~IS DNISnOH VV~~
~\T S~HDI8H aOO'M 8HillM -11 8HnDI~
GLOSSARY
Backwater.The resulting hi g h w ate r surface in a given
stream due to a downstream obstruction or high stages in an
intersecting stream.
Flood.An overflow of lands not normally covered by water
that are used or usable by man.Floods h a vet woe ss ential
characteristics:The inundation of land is temporary;and the
land is adjacent to and inundated by overflow from a river,
stream,ocean,lake,or other body of standing water.
Normally a "flood"is considered as any temporary rise in
streamflow or stage,but not the ponding of surface water,that
results in significant adverse effects in the vicinity.Adverse
effects may include damages from overflow 0 f 1 a nd areas,
temporary backwater effects in sewers and local drainage
channels,creation of unsanitary conditions or other unfavorable
situations by deposition of materials in stream channels during
flood recessions,rise of ground water coincident with increased
streamflow,and other problems.
Flood Crest.The maximum stage or elevation reached by
the waters of a flood at a given location.
Flood Peak.The maximum instantaneous discharge of a
flood at a given location.It usually occurs at or near the time
of the flood crest.
Flood Plain.The areas adjoining a river,stream,water-
course,ocean,lake,or other body of standing water that have
been or may be covered by floodwater.
26
Flood Profile.A graph showing the relationship of water
surface elevation to location,the latter generally expressed as
distance above mouth for a stream of water flowing in an open
channel.It is generally drawn to show surface elevation for the
crest of a specific flood,but may be prepared for conditions at
a given time or stage.
Flood Stage.The stage or elevation at w hie h overflow of
the natural banks 0 f a stream or body of water begins in the
reach or area in which the elevation is measured.
Head Loss.The effect of 0 b s t rue t ion s sue h as narrow
bridge openings 0 r buildings that limit the are:a througl!which
water must flow,raising the surface of the water upstream fr om
the obstruction.
Hydrograph.A graph showing flow values against time at
a given point,usually measured in cubic feet per second.The
area under the curve indicates total volume of flow.
Intermediate Regional Flood.A flood h a vi n g an average
frequency 0 f occurrence in the order of 0 nee in ID 0 years
although the flood may occur in any ye a.r .It i s bas e don
statistical analyses of streamflow records available for the
watershed and analyses of rainfall an d runoff characteristics
in the general region of the watershed.
Left Bank.The bank on the left side of a river,stream or
watercourse,looking downstream.
Right Bank.The bank on the right side of a river,stream,
or watercourse,looking downstream.
Standard Project Flood.The flood t hat may be expected
from the most severe combination 0 f meteorological and
27
hydrological conditions t hat a re considered reasonably char-
acteristic 0 f the geographical are a in w hi c h the drainage
basin is located,excluding extremely rare combinations.Peak
discharges for these floods are generally about 40-60 percent
of the Probable Maximum Floods for the same basihs.~As
used by the Corps of Engineers,Standard Project Floods are
intended as practicable expressions of the degree of protection
that should be sought in the design of flood control works,the
failure of which might be disastrous.
Underclearance Elevation.The lowest point of a bridge or
other structure over or across a river,stream,or wat ercourse
that limifs the opening through which water flo W.s.T his is
referred to as "low steel"in some regions.
28
4.MINIMUM CONTOUR INTERVAL IS 50 FT.
PLATE 2
STANDARD
PROJECT
FLOOD
I.MAP BASED ON U.S.G.S.QUADRANGLE
SHEET TALKEETNA B-1.MINOR
ADDITIONS AND ADJUSTMENTS MADE
BY CORPS OF ENGINEERS.
FLOODED AREA MAP
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA
SCALE IN FEET
o 2000 4000
1~~~iiiil~~~~1
I"=2100'
3.AREAS OUTSIDE THE FLOOD PLAIN MAY
BE SUBJECT TO FLOODING FROM LOCAL
RUNOFF.
I T -3 J CROSS SECTION
LEGEND
2.LIMITS OF OVERFLOW SHOWN MAY VARY
FROM ACTUAL LOCATION ON GROUND AS
EXPLAINED IN THE REPORT.
OVERFLOW LI MITS
NOTES
-2S0""\.;-GROUND ELEVATION IN FEET
SEA LEVEL DATUM
• • •••LOCATION OF SUPPLEMENTAL
PROFILE
PREPARED BY THE
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
JUNE 1972
I···.·······:·:·:·:·.INTERMEDIATE:;:::::::::::::::;:;.STREAM REGIONAL
'::::::::::::::::::::~CHANNEL FLOOD:::::;:::::::;::::::_---
M+4 MILES ABOVE MOUTH
Cabin •
\....
I
tns
\
LEGEND
FLOOD PLAIN INFORMATION
STANDARD
PROJECT
FLOOD
LIMITS
AREA MAP
INTERMEDIATE
REGIONAL
FLOOD
NOTES
STREAM~CHANNEL
FLOODED
OVERFLOW
MAP BASED ON B.L.M.AERIAL PHOTO-
GRAPHS FLOWN AT 1500\IN 1971.
I.
APPROXIMATE SCALE IN FEET
o 200 400
IM!;;;;I I
TALKEETNA,ALASKA
3.AREAS OUTSIDE THE FLOOD PLAIN MAY
BE SUBJECT TO FLOODING FROM LOCAL
RUNOFF.
2.LIMITS OF OVERFLOW SHOWN MAY VARY
FROM ACTUAL LOCATION ON GROUND AS
EXPLAINED IN THE REPORT.
PREPARED BY THE
DEPARTMENT OF THE ARMY
ALASKA DISTRICT.CORPS OF ENGINEERS
ANCHORAGE.ALASKA
JUNE 1972
I
PLATE 3
380
,0
375
I I
. I
,;I'
370
,'
I~,'
+-+--+-L-1-....I I
:,I (/)
0,z
~
:-om
, I
I'
, I
LEGEND
- - - -STANDARD PROJECT FLOOD
- - -INTERMEDIATE REGIONAL FLOOD
• ••••AUGUST 1971 FLOOD
~STREAM BED
ALASKA
PROFILES
SECTIONCROSS
TALKEETNA RIVER
JUNE 1972
FLOOD PLAIN INFORMATION
TALKEETNA.
HIGH WATER
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
,'
':"1-
N
I
~
• I
16,00014,000
;I
•
12,000
I'
10,000
,
MOUTH
• I
-t-FEET ABOVE
8,000
I,
,,TALKEET,NA
I I
,,
i....!:
•
'f',.;, ,
o :
, i
,....
6,0001
, !
,;
'.I'"
I'
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I I
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4,000
'''''
..,.,
, I
I ;..-...l...-
I '
,'
,',
lei
0,
I I'.
2,000
, I
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•
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o
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340·
3~0
335
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z
Q
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PLATE 4
360 ;--,;!I;i I I I,i-I-~-:---ii--;'--;--j-!"7"-n-r~:-,
'-','I
1 I"'-r-Y~LLffi-UJlll I I I
oooa;;
ooo
I'--
DEPARTMENT OF THE ARMY
ALASKA DISTR ICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA
SUPPLEMENTAL HIGH WATER PROFILE
TALKEETNA RIVER OVERFLOW
DISTANCE IN FEE T
LEGEND
z
zo
t-
<!>
W
...J
W
~w
w
u..
Ei ~:tttF-=_--STANDARD PROJECT FLOOD "-~I+:.-+..-fl-!+--~t-LB?-I-+l-~.t I 'f-H-I--J I -
355 ~~I NTERMEDIATE REGIONAL FLOO .-.j-~l (-t--I--j'--¥.1,..Dt~T +++1=i ",'"[::r~GROUND LINE .:li t :t.L!,,~~:~~'i++j ""I .
f
-''lit~-'-mll-=!=~'~'-l--t-~_.~._--'t '""c'.+,'
-'.J ' ",LLL:+'1+"".~,'"t ,'"•T.!,..1-'",~"",' ,
(J)1:+NOTE:.J:J-L.c:tLL,Lf h H I...!·I~'+'t 1'::U1r.f:"H --.I ,-;i,:j'tf+t,+,'tttH=j-+~~-'--"'--
:;;1 -,__"L,+',r,,.J.'r TT">--"------V1;p-~"r "-+r '350~":'pFOR LOCATION OF TH,sf-lll:dJ:i~~~.J~:j:Wtt:i,'"l_;.:ck~lt+i.f":::q$~.L~-c'ROFILE SEE FLOODED _r-rW-ITi'r ~-r';.,-'......,----:-:l1'1"t'T:"or·i ..~'£":"-kr--:r-r I h 'T 1"*'1 -r..:;;..o.tt-L':AR--I :I ',-+-+-'-I~~-~_~, 'r";~:n,WH ,,-r-,,·.,r RO'"..:.o"r I
I ~_,_~~~AP Tj'1-..c.i--I-t-_~_I':__',:_._:~.'I ,-;.='.'L;1 ' "-,-r .D't--t-·rT
,f '-+','""-,'rr _""'_,'r,j;;i'oK,---',--"r,1..i -I 'f'--+,,1<',1 ,,~...',It.i::tlfq±tj-:nt±1-I:.2J-i r'J~~dfJ3-_~fl+c-t.tt±1-t~..~J:::_~'!'+-+-H-'1
Jirr
TTi li"l
!_.L':"-4+t-J~OOff._L-,..~-r-P.I-,l r-_~__f~-r~d '-r-t-l-rr:+TI':'imIT-.H -;;:-n~~:14-I-f-+--+-1---I-H+-H+++I I I -I.
l_1 ~~;;;.r,,~_~_-'-_~'..ll~.r-R-I-·t-~f--i--t--L'I',----+-.-----_._--1-,I~~:.:;::x',f oJ,","-.i..,,,"'T'.L 'r J,:',I"""._.'",-"
345 e:::rr,.,_L _._llit:..,'_I,lfl-,-c-1xt ',,-r+->---I--'--+-H---
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, , I IU_IJ'I -I,_+-'t$f$l''IIi-!---ll·--nIr 1 I I I,~'iTn --',-'.-,,,t:H---_"-l,C+-""L--:1+':~-~~+-,,,..,1<,"
r +-'N.+
J
'I -,=r +--t-j-'{.:)::)=T~-+'w "340 r+Nr:'t ,r '+Tit-'"-J-Ll"::,.l-fttf::1~-;=:'-_f---t---H--....-
, .J 'Prm 1 rrr H .:'f -I 1 -I -n-..l_H-f', :I +-f-4--..', I ' ",-n°r-........,!i'I'f r+-+-_--l-l-..l ..i~,',,'Ii,,-.H T-1-',-,---+-
I c..'II r-d-~.!~/f I -.L ;-+t-·H-'I','.I~fm-j-'i-r·~--"--~:~e-H-11:>--:J:!fr "'",,'r +-..I~J.,'r.±,+i+-I--+_+-.-F~~-'+1--~~trT':'-'.j-H--t ...--+!-+-1-~~~~~.g
[1 .,']l',,[.I'I "",,-1+t-+JJ ,+'+0,_~~,++''].'I-r-'-,.."I ,1",.J"Iii
.,"-D i--i--.'--+I It ."'335 ini-!,'I'-r-+f+i:-1-LLw_u l _'L t ,i 1-:--I ~T tt+-l +0 +"__~~._" I I ,-i'1-1--,----!.1--1'I'-1-lJ-+--o 0 ------.J...'"I j---11-;\-+-+1 ,--,--,~_Ilo00.l-l-I.-I(.[:o 0 ._.~0 00
0
_0 0 0
(\J r<>-0v .({)
JUNE 1972-----------,0'ATe c.
DISTANCE IN FEET
EAST OF ALASKA R.R.BETWEEN TALKEETNA RIVER a F.A.A.
LEGEND
Standard Project Flood
intermediate Regional Flood
August 1971 Flood• 0 •••
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA
SELECTED CROSS SECTIONS
TALKEETNA RIVER
JUNE 1972
NOTE:
Sections token looking downstream.
Additional sections not shown but
available at District Office.
ooo
lD
••~
ooo
~
ooo
~
ooo
r0
I
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ooo
340,,,,,,'
o
360.__.._?_~~~~_.~~~~~:~~==~~~.-~__'~
355 '==:=:.:-i-..-.......J.-.__,I ,
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:~__'~
.'';-1 ..~'_~'-~~='--L--0--345 I '±-~~--,~-,-'-f----+-,.~,-;....:.-=:-:-==---~=---:;=-.,-=-'=:=----
-~------
""',,..:--.-..._------1355·""!"'!""FF-l-J.L '~~.;-+-·.....;..·1 -..:...-------c-.--,-_:._~r--:--+,I ,,~,,-+-.._;---:",I-r-rT:t4 'r-;:.L'".-=--:_J::"
,350·.I ,1 I'W....;..-i-----.J...+..-t-.,...,·...:.........J-.--!--i-i ~'T I't+tt+-~__~-'-:-:8~-~~
.-;-:-::r';
=;~~~~~~~~S::8±~I-~-i~-It'~-!B '-'p"'--
+--....,....;...,,~
__..I I
320 ,,,
o .0 0 0
000 0
00 m 0 -
~~~~
DISTANCE IN FEET
ALASKA RAILROAD BRIDGE
:E
;:)...«o
..I
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I.&J
..I
«
I.&J
(/)...
I.&J
U.I
LL
Z
z
Q
~>I.&J
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l.IJ
PLATE 7
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA
SELECTED CROSS SECTIONS
TALKEETNA a SUSITNA RIVERS
JUNE 1972
N,OTE=
Sections token looking downstream.
Additional sections not shown but
available at District Office.
LEGEND
___Standard ProjeetFlood
- --Intermecllat.Regional Flood
•••••AUCJust 1971 Flood
DISTANCE IN FEET
SUSITNA RIVER AT TALKEETNA
355,II:',1+._'-=i:--Lh--l ~I I I -:j=-f '.--H:-=t:f:+-~j:f=-Il =f:l:fHt·..=-11'~~t~:,._.U.:_~<~_I~+tt~'=!,-~~.---'_'_-..-_::'-=.+_,-~::-+:'__._350~•.LL IT,-,','rl ,j;'!f},I-:-l,:tt,-rtttL,It-J [j:±)±tJ:_,-ct Jitl-,.,..--,1 " ,-,.'f -'j --'r'I~~'--,,,I.-.ri '''1'h +1----'f",1
".••I ~j'-'ii - -d·1 '"-!:~tl1~-r.----..'-I.
345 ~i,:f - ---::-'---."=----:::"--,,'!l:-~__-".:'-=1-n j -":'--"-l"
1 .~-.''ql --. - -,,-"-',.j-"-j '!
340 I'll r I ."-,11-~------:--i 1'---.:\'f~~1l.'e'r ,,,'-;-'-',:-:.--",---'-1-'
lliill ·I ....-I'=-,-"- - -.,:IIII'1-1 ---.'-_..."---;-i I I 1 ,--i,,~.:-l---,,-11 i3351----t-+--t 1-
, i .I I .", ',J t!-"I I-!, I ~I I I,I I 'I I I :.-iii I.I --:--t 11'1-11 I,,II r , 'I I ,:I'I I "'I'f 11 I 'I "I ILIlIIr1 'I.·I r .;..I I ..t330jtIII,It,.'I II ,I ,I I t III I I,[I"I I 1.11..;:I I,I:1I I,I,
4000 5000 6000 7000
DISTANCE IN FEET
TALKEETNA RIVER 1500'ABOVE ALASKA R.R.BRIDGE
z
Q
~~
LIJ
.J
W
345 ~....-:-n rr-:-:-,! . :"".,I',!,r.-;-1 I .,.'II!I I I :r"llli
;::::. . . ::,'~,: :I :i ~,i:ii',~i ,'::~II 'I !I I',!i I -I .:I:- ,- - ,,
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11~[I!i I:til::I
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,"."..•:'I !!" ' :~:I I I I I!
:: : :,.:":::I ; ;~i~II,I I II ,1 l'I'I
-~...':"I'...I 'I I .I r j I , ',-H'H i I-330'-~---;---"--4 ",+,,t·...,-'.--1 .........-l-..~• 1 , " ."."":"I I ,,',L ~I I 'I 'I I !",
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1
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lIJ 325 "."f··.....""". ,I ':-1 .~LL'I:I I,:ill - , ,'.e-t-+-~--+---L-l---l----l-l--l-~-l--I-4---l--+---l--
>..."iLl",,·,1 II.'1·[1 I "I""It -11-1 I'I -m'""11LIJ~:::-,::.~:i:I ,:,1 :I :-i'.+d +,t ":Iii ;~i r .-:I t---:II --t:-T,.-,"---f r
.J i :' :.::'::,!1 ~,!:[::I I li H'-'I!-,'"I -- :It·:,"'I.t"
<[".-..: :,.....:. :I Ii I II :,I ::I,I,I l"I II II :-l ',"I!'I ;I .----i URI--
lIJ l'" "I""'t'I'.",I I I I,rill I:,l .,I,. ..,;,!!I,I I j 1 "J I I I Lf l I:11 J I,LLI(I)320 _.-----------.-.....,....,..,~.--l-l--'-'-_•..L..--.-_.~,.J.--I..!--L.-__;"'"l _'L...l-+----L+" - -"..
...~0 0 0 0 000 000 0
000 0 000 0 0 0 0
~0 0 0 0 000 0 0 0 0
LL.N 1'0 V ICl \.0 I'-00 (1)0 -N
Z
PLATE 8
-===t===..-
-==t=:~
-~
;::-;-..::t=i=
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___-1..-1-_
--1-.....-...-~
--i:r'::'-.::-=C
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-==t+_:-..:-
=~
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=:.:;-=....:..:.t==
~t:E'::__._1 !':....__.::::j.:;_•._.L:..,
-'
~~~
\;.~=~
=
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T-~'::""?""'"
r-T.:j.:r-
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....,..,...,.
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20
40
en
~
u
z
ooo
L&J 605 'i~:;:-~.,:-.~
<I:_"=--__•.:r:u
(J)
o
--:.......-=-~~16 18 20
0 0 2 4 6 8 10
TIME IN DAYS
12
--~=
14
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA.
TALKEETNA RIVER AT TALKEETNA
STANDARD PROJECT FLOOD
HYDROGRAPH
JUNE 1972
PLATE 9
'---"-----'-'
300
~------=--+~~-~---...-,~~::;j:;:tS-ttr;~;::--:-~.=._~-~--~-~.~=~~---:----;::;.PEAK:315.00Q.Ct!..F·~·I-1--'-+.,=:1'-EJ~Lb::::::!=t,:':_~:._.:---~·~~g~~~fl~:~~:~~~~;~1j-~ili~~s
----:1:=1--.-_-,--=_=r _~
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p~~~::'11 '--,--,
250
C/)
Lt.:o 200
0
0
o~
z
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CJ="'-T'"0
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100
w 150
(!)
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Ci
50
'..!....:'
--L...l...:i
~
';';~i:t:;::l
r::J.!.~':'~I.+.r
"=
16
.~-
-+-
18 20
00 2 4 6 8 10
TIME IN DAYS
12 14
DEPARTMENT OF THE ARMY
ALASKA DISTRICT,CORPS OF ENGINEERS
ANCHORAGE,ALASKA
FLOOD PLAIN INFORMATION
TALKEETNA,ALASKA
SUSITNA RIVER AT TALKEETNA
STANDARD PROJECT FLOOD
HYDROGRAPH
JUNE 1972
PLATE 10
0::UJ>0::o::<{UJZ>C-.J0::::)<{IZUluo::UJUJ~>.J-<{o::
~<(
Zt::en
:Jen
."r-ooc
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:D-
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same flood
with development
and
encroachmen(f:;.
natural stream
flooded
.t
natural
stream
bank-full
BUILDING
in the
FLOOD PLAIN
can make
FLOODS
WIDER
and
DEEPER
TOOLS of FLOOD PLAIN MANAGEMENT for the reduction of Fiood Damage and Human Suffering
~~~.Q)~~-,//~~~~~~~,,/~Vv--";~--..."~------"...~.~_.-----~.A:::~-4 __~~~----fii~.
I ~/
tl ~/f:-\.I -\.(\"\~@~~_//~~/Q g-~
.,.-........09 /"g"'"/~~//.,.~~v~~l;;p~"rz:v
///~(j 110
'........'/---~
MEASURES TO REDUCE VULNERABILlT'
TO FLOODS provide ~or a future with more freedon
from flood damage,often at minor cost and with little
adverse effect on the environment . . . . . .
REGULATIONS -ZONING,BUILDING
CODES,URBAN RENEWAL,SUBDIVISION
FLOOD PROOFING •RELOCATIONS
OTHER
MEASURES
aid the Flood Pla;n
occupant in coping
w;th floods . . .
Warning a
Emergency
Plans
Tax
Adjustments
Flood
Insurance
CHANNE~"--'-~
ENLARGEMENT
DAMsa
RESERVOIRS
MEASURES TO MODIFY FLOODS
are often required to alleviate existing problems and
sometimes to forestall future problems . • .
~
C!:Ta:
~0 .#
,/l)Towers /*II 0 ~
Ii If ~~It /1 Gravel ~~
•fIX.-~Pit ~~
9
FLOOD PATTERNS
FOR
TALKEETNA,ALASKA
LEGEND
apprOXimate limits
of overflow
I NORMAL STREAM
'NTERMEOlATE
REG'ONAL FLOOD (tRFl
STANDARD PROJEC1'
FLOOD (SPF)
PROFILES in the
Flood Pla;n Information Reporf
show elevations of
these floods
for the entire study area
..".-
ARLIS
Alaska Resources
Library &lnforU1rlUO n ;prvl.ces
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