\.S ��-I"- HYDRAULICS BRANCH
BUREAU OF RECLAMATION HYDRAULIC LABORATORt
OFFICE OFFICIAL FILE COPY ----· FILE COPY
fflN BORROWED RETURN PROMPTLY
CHERRY CREEK.DAM
AND RESERVOIR
CHERRY CREEK AND TRIBUTARIES COLORADO
REPORT OF MODEL STUDIES
• SPILLWAY AND STILLING 'BASIN I
MADE BY T HE HYDRAULIC LABORATORY
U.S. DEPARTMENT OF INTERIOR
BUREAU OF RECLAMATION DENVER,COLORADO
U.S. ENGINEER OFFICE DENVER, COLORADO
JULY 1944
•
September 11, 1944.
FOREWORD
The investigation and the report of model studies of the spill
way and the stilling basin tor Cherry Creek Dam and Reservoir,
Colorado, were conducted and compiled by the Hydraulic Laboratory,
Engineering and Geological Control and Research Division, Branch of
Design and Construction, Bureau of Reolanation, U. S. Department of
the Interior, Denver, Colorado.
These etudies were oonduoted as requested by the u. s. Engi
neer Department, Denver Dietriot Office, and by authority of a
direotiT• dated 19 February 1944, from the Office of the Chief of
Engineer,.
The conduct of the work wae under the general euperviaion of
J. E. Warnock. All operation, were direoted by Fred Looher and c.
V. Adkin1.
1
Figure
l 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19
LIST OF FIGURES
Location tnap ••••••••••••••••••••••••••••••••••••••• Original design •••••••••••••••••••••••••••••••••••• Original design A •••••••••••••••••••••••••••••••••• Alternate design •••••••••••••••••••••••••••••••••••
Alternate design A ••••••••••••••••••••••••••••••••• Alternate desi� B ••••••••••••••••••••••••••••••••• Alternate design A ••••••••••••••••••••••••••••••••• Alternate design B ••••••••••••••••••••••••••••••••• Al tern.ate desigri •••••.••••••••••••••••••••••••••••• Alternate design C ••••••••••••••••••••••••••••••••• Scour patterns ••••••••••••••••••••••••••••••••••••• Spillway discharge - Sta. 162+91.83 •••••••••••••••• Original design •••••••••••••••••••••••••••••••••••• Original design A •••••••••••••••••••••••••••••••••• Water surface profile - Alternate design C ••••••••• Second variation of alt.ernate design A ••••••••••••• Variation of alt.ernate design B •••••••••••••••••••• Water surface profile - Original design A •••••••••• Spillway tailwater curves ••••••••••••••••••••••••••
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Page No.
19 20 21 22 23 24 25 26 27
28 29 30 31 32 33 34 35 36 37
CONTENTS
Section
Foreword •••••••••••••••••.••••••••••••••.•••.•••••••••••.• Table of Contents ••••••••••••••••••••••••••••••••••••••••• List of Figures •••••••••••••••••••••••••••••••••••••••••••
I - INTRODUCTION AND SUMMARY
Intro duction
1. 2. 3. 4.
Summery
5.
6.
.Purpose and scope of model studies . . . . . . . . . . . . . . . Authority • • • • • • •... • •• •.••. • •..•.•••.•. •.•••• • • • . The definite project plan •••••••••••••••••••••••• General .......................................... .
Undesirable conditions and remedial :measures in the original design ••••••••••••••••••••••••••
Undesirable flow characteristics and remedial
Par;e No.
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l
2
2
3
4
measures in the alternate design •••••••••••••••• 5
7. 8. 9.
10. 11.
12.
13.
14.
15.
II - MODEL TESTS
Preliminary considerations ••••••••••••••••••••••••••• Initial tests of original design ••••••••••••••••••••• Revisions of o riginal design •••••••••• _ ••••••••••••••• Initial tests of the alternate design •••••••••••••••• Revisions of the alternate design •••••••••••••••••••• Tests leading to the final design •••••••••••••••••••• Final design • . • • . • • ..• • .... • • •...•• • • • .•.••••. • • .. • • .
II - RESULTS AND CONCLUSIONS
Analysis of the results •••••••••••••••••••••••••••••• Conclusions ••••••••••••••••••••••••••••••••••••••••••
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11
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UNITED STATES DEPARTMENT OF THE INTERIOR
BUREAU OF RECLAMATION
REfORT OF MODEL STUDIES 01" THE SPILLWAY AND STILLING BASIN FOR
CHERRY CREEK DAM AND RESERVOIR, COLORADO
I - INTRODUCTION A!"ID SUMMARY
Introduction
l. Purpose and scope of model studies
The purpose of the model studies of the spillway and stilling
basin, Cherry Creek De.m and Reservoir, Colorado, was to verify the
design and, by adjustment, develop a satisfactory hydraulic struc-
ture.
Two different designs were submitted for tests. For the pur
pose of this report, the one shown on figure 2 will be designated
as the original design and the successive change will be designated
as original design A, fibure 3. The other design, as shown on fig
ure 4, is designated as the alternate design and the successive
changes as alternate design A, B, and C.
In order to expedite the testing and have a direct, visual com
parison between the designs, a la60 hydraulic model of each was con
structed in the laboratory. From the tests it was necessary to
establish for each of the designs the correct leng;th and the srepe
of crest and size of notch required to produce a predetermined head
dische.rge curve at the weir; to determine a suitable sh.ape for the
spillway chute; to design a satisfactory stilling basin for the an
ticipated variation in tailwater; and to determine the difference,
1
if any, in the scour immediately downstream from the stilling basins.
The tailwater elevations at the stilling be.sin, the nax imum
discharge, and the characteristics of the head-discharge curve were
established by the U. s. Engineer Office, Denver, Colorado.
2. Authority
This project was authorized by the Flood Control Act approved
August 18, 1941 (Public No. 228, 77th Congress, 1st Session), which
reads, in part, as follows,
•sEC. 3. That the following works of improvement for the benefit of navigation and the control of destructive floodwaters and ·other purposes are hereby adopted and authorized in the interest of national security and the stabilization of employment, and shall be prosecuted as speedily as may be consistent with budgetary requirements, under the direction of the Secretary of War and the supervision of the Chief of Engineers in accordance with the plans in the respective reports hereinafter designated and subject to the conditions set forth therein • • • • •"
• * * • * • • • * * • • • • "Missouri River Basin - The comprehensive plan for
the improvement of Cherry Creek and tributaries, Colorado, for flood control and other purposes in accordance with the recommendations of the Chief of Engineers in House Document Numbered 426, Seventy-sixth Congress, first session, is approved and there is hereby authorized $3,000,000 for the initiation and partial accomplishment of the project."
3. The definite project plan
The definite project plan (initial development) provides as
follows,
(a) Complete flood protection for the City of Denver by
the construction of a rolled-earth dam, including an outlet
control structure through the dam near the right abutmentJ an
2
a
..
overflow-spillway canal to pass the spillway-design flood from
the Cherry c·reek Basin into the Tollg�te Creek Basin and thence
through Sand Creek into the South Platte River at a location
downstream from Denver.
(b) The dam will be oonstruoted in such manner as to pro
vide for multiple-purpose developmen� (ultimate development),
making available to irrigation and other water-use interests
85,000 acre-feet of storage capacity.
(c) The definite projeot plan will inolude the oonatruo
tion of the dam to mltiple-purpose height, but it will include
only those features of the outlet oonduits and the spillway
necessary to acooJ1D11odate flood oontrol before irrigation or
other water uses are developed.
4. General
The propoaed multiple-purpose Cherry Creek Dam e.nd Reaervoir
is looated near the site of the existing Kenwood Dam on Cherry Creek
i� Arapahoe County (figure 1), at river mile 11.4 as measured from
the mouth of Cherry Creek at its junotion with the South Platte River
near the center of the business district of Denver. The Cherry Creek
drainage basin is approximately 57 miles in length and contains a
total of approximately 414 square miles. The area upstream from the
proposed Cherry Creek Dam oontains 386 square miles.
The proposed spillway and the stilling basin are located approx
imately 1.2 miles from the Cherry Creek Reservoir. The floodwaters
will flow from the reservoir via a canal to the spillway whioh will
3
drop the water to a canal discharging into Tollgate Creek. The flow
into Tollgate Creek will discharge into Sand Creek and reach the
Platte River at a point downstream from Denver.
Summary
6. Undesirable conditions and remedial measures in the original design
In the initial teats or the original design (figure 2), it was
discovered that the discharge capacity of both the notch and the
orest exceeded that in the design, thus indicating that this part
of the structure should be decreased in size.
The flow from the notoh spread laterally on the chute and
oaueed a high standing wave that overtopped the walls at the sides
of the ohute. The flow from the stilling basin oaused excessive
soour downstream. As a remedy for these conditions, the notch and
the spillway oapaoities 119re reduced. the training walls downstream
from the notch were raised and lengthened, and a sill and dentates
were placed in the pool.
When the model was tested under these conditions, the desired
flow characteristics were obtainedJ but there was considerable ob
jection to the standing wave formed in the area between the orest
and the side wall. To eliminate the standing wave the warped aide
walls were replaced by vertical walls which constrioted the open
i�g• between the longitudinal parts of the crest and the side walls
(figure 3). This submerged the standing wave and improved the flow
in the ohute. There 'W8l"8 no serious objections to the flow pattern
4
in this structure, and the arrantement of figure 3 we.s co�sidered
satisfactory from an hydraulic viewpoint.
6. Undesirable flow characteristics and remedial measures in the alternate design
The first tests with alternate desi�n A (figure 5) indicated
that in addition to decreasing the ca�city, either training walls
or some other device was required to keep the notch flow from spread
ing laterally and overtopping the side walls. The scour of riprap
along the side walls due to this overtopping is shown in figure 7D.
The discharge capacity of the structure was reduced by shortening
the crest length and varying the notch wid th unti 1 a predetermined
discharge curve similar to the one on figure 12 was obtained. Several
attempts.were made to stop the lateral spread of the notch flow. How
ever, as none of these was entirely satisfactory, the center notch was
eliminated and half sections of the original notch were placed at the
two ends of the crest (figure 8).
This arrangement caused a high standing wave in the center of
the chute which-gradually leveled until the flow had spread to the
width of the chute at the beginning of the stillins basin (figure 9).
There being little flow along the sides, low walls could be used
along most of the length of the chute (figure 15). Attempts to de
crease the height of the standing wave, such as using three notches,
bafflas, or a deflecting block were not successful, and in some cases.
they actually made flow conditions in the pool unstable. The design
as shown in figures 6 and 8 was considered satisfactory.
5
The suggestion was made that the height of standing wave might
be reduced by warping the side walls as shown in figures 9 and 10.
This did not improve the flow on the apron. However, the entrance
conditions to the notches were improved and there was considerable
improvement in the appearance of the structure.
This arrangement was selected as the final design. It was
superior to the original design A from both economic and hydraulic
viewpoints. The difference in energy dissipation in the stilling
basins of the two desie;ns is shown clearlJ• in figure 11.
II - MODEL TESTS
7. Preliminary considerations
A thorough study of the original design (figure 2) was Jlflde
in an attempt to anticipate its hydraulic performance before the
model was constructed. Conclusions, based upon previous field and
laboratory experience, were that the stilling basin was too short
for the existing entrance conditions. Following a computation of
the hydraulic characteristics through the spillway chute, the still
ing basin was lengthened 28 feet to obtain a desirable hydraulic
jump and sufficient energy dissipation in the pool. The crest cross
section was also developed in the laboratory from previous experi
mental data.
In the initial development, although the spillway and the still
ing basin will not be constructed, a canal from the reservoir to West
Tollgate Creek will be excavated to elevation 5598.00. In the
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ultinate development the canal will be deepened and widened. The
outlet channel below the stilling be.sin will be excavated to a slope
of 0.0015, be�inning at elevation 5567. It was planned that any
additional depth obtained would result from retrogression. Two tail
water elevation curves were submitted to the hydraulic laboratory,
representing conditions both before and after retrogression. The
outl$t channel in the model was built to represent conditions indi
cated to exist after retrogression and with a bottom width such that
the tailwa.ter in the model could be lowered to the required eleva
tions. Otherwise, the model of the original design was constructed
according to plan.
A sketch of the alternate design as submitted to the hydraulic
laboratory is shown on figure 4. The same design of stilling basin
and outlet channel was used in both models. The crest cross section
was developed from previous laboratory data and is shown on figure
9. A comprehensive study of the sketch and computation of the hy
draulic characteristics through the chute showed that other changes
could be made that would improve the hydraulic action of the chute
and also make it more economical. The over-all length of the chute
was reduced, and a new floor shape was developed. The bottom width
of the approach canal was reduced from 170 to 75 feet. The model
as it was first constructed is shown on figures 5 and 7A.
8. Initial tests of original design
The model was operated with flows of from 3,000 to.45,000 second-
feet (figure 13). There was a fairly even distribution of flow over
7
the lower part of the apron at all discharges. At the higher dis
charges, the water passing through the notch spread and climbed the
chute walls just above the stilling basin.
The entire head-discharge curve fell below that shown on figure
12, indicating surplus capacity. The flow over the sections of the
crest parallel to the longitudinal a.xis of the chute was considerably
less than that over the sections normal to the longitudinal axis.
The depth over the crest varied from a minimum of approximately 2.6
feet at the notch to a maximum of approximately 9 feet at the chute
walls for a discharge of 45,000 second-feet. This condition was due
partly to the drawdown in the water surface through the notch and
partly because the flow of the approaching water was not normal to
the axis of the crest. The efficiency of the longitudinal sections
was reduced thereby.
An imperfect hydraulic jump formed in the stilling pool. The
jet of water from the apron was diving under the tailwater and flow
ing along the bottom. Consequently, there was insufficient energy
dissipation and considerable scour immediately downstream from the
pool.
A very high standing wave was formed in the side channels just
below the crest. The choking action accompanying the wave gave an
impression of insufficient channel capacity for the water passing
over the crest.
9. Revisions of original design
Several changes were sugr,ested in attempting to improve the
8
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•
hydraulic performance of the structure (figure 3). Since the exten
sions of the downstream ends of the crest serve as training walls,
it was thought that by raising and lengthening them the tendency of
water to olimb the chute walls could be eliminated. These walls were
extended 20.5 feet down the apron and sloped from the crest elevation
at the notch to a height of 6. 25 feet at a point 105 feet below the
notch. This reduced the lateral flow and minimized the tendency of
the water to climb the chute walls. The flow pattern on the apron
was also improved.
As a means of raising the head-discharge curve, the crest seo
tions were moved toward the center of the chute to obtain a notoh
bottom width of 12 feet (figure 3). The sections of crest parallel
to the longitudinal axis of the chute were shortened 10 feet. Thia
moved the sections normal to the longitudinal axis downstream 10
feet. The resulting head-discharge curve agreed favorably with the
required curve. The desired discharge curve having been obtained,
the depression in the approach floor was filled with no change in
the discharge curve.
A row of dentates and an end sill were built in the stilling
basin to break up the jet flowing along the bottom (figures 3 and
13). A good hydraulic jump was created, thus dissipating consider
able energy. Scouring was materially reduced; but the scour pattern
(figure llA) shows that the section immediately below the basin re
qu ires riprapping. The scour pattern was obtained by replacing the
riprap with fine sand and operating the model with the maximum
9
discharge of 46,000 second-feet until the channel had stabilized.
This required one hour and fifteen minutes.
The belief was expressed that considerable saving could be
effected by making the vertical walls of the stilling basin the same
height as the chute walls, the additional height required to be se
cured by slope paving from the tops of the basin walls on a 2al
slope. With this arrangement large vortices were formed below and at
the sides of the stilling basin. The result was poor energy dissi
pation and consequently deep scour below and to the sides of the
stilling basin. No further consideration was given to this type of
design, and the original vertical walls were replaced. The model
was considered to indicate satisfactory hydraulic performance except
for the high standing wave in the side channels below the crest.
The lOal slope at the upper end of the chute floor was extended
up through the side channels to the foot of the crest sections lying
normal to the longitudinal axis of the chute, to alleviate the high
standing wave. As this change was of little value, the level floor
was replaced.
The warped walls of the chute were replaced by straight, vertical
walls set in such positions that they constricted the side channels
(figures 3 and 14). This change resulted in submergence of the stand
ing wave. A smoother and a more even distribution of flow along the
apron was also obtained. It could be seen that the chute walls would
have to be raised considerably to provide sufficient freeboard. Fig
ure 18 is a water-surface profile along the chute walls for a
10
'
discharie of 46,000 second-feet. Due to the diffioulty and the cost
of constructing this design in the field, it was considered best to
abandon it in favor of the alternate design shown on figure.9.
10. Initial tests of the alternate design
The model of the so-called alternate design was not constructed
according to the original sketch of figure 4 but according to the
revised laboratory design of figuJO 5. The first tests with the de
sign on figure 5 showed that at all flows the discharge from the
center notch spread laterally until it impinged on the walls and de
flected down the chute {figure 7). At the higher discharges, the
lateral component of velocity was sufficient to carry the flow over
the walls, thus resulting in scour of the adjoining riprap. Thia is
evident from a close inspection of figure 7.
It was also found that the head-discharge curve was consider
ably lower than that anticipated in the design. This indicated that
the area over the notch passed more water than was originally
assumed. As a result, it was necessary to decrease gradually the
crest length until the desired conditions were obtained. This was
accomplished by moving the side walls toward the center and alter
ing the approach channel to satisfy the new requirements. The shape,
the curvature, and the location of the crest remained unchanged.
11. Revisions of the alternate design
To reduce the lateral flow and thus eliminate the undesirable
flow over the chute walls, two schemes were tried. In the first
one, training walls of various heights were placed at each side of
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the notch and extended approximately 120 feet downstream. The walls
produced the desired results at low flow, but at higher discharges
the radial flow from the crest was deflected by-the training walls
to the chute walls where it fonned a high fin and intermittently
splashed over onto the riprapped banks.
The second attempt was more successful. It consisted of rais
ing the apron to within five feet of the top of the crest and extend
ing the notch through the apron as shown on figure 16. This produced
a fairly even distribution of flow across the lower part of the apron
at all discharges. However, there was still a tendency for same of
the water passing through the notch to spread laterally and climb the
walls near the stilling basin. The apron could have been raised
still more and the notch extended to the stilling pool, thus elimi
nating the side-wall fin entirely. However, in the initial develop
ment of the project, the canal from the reservoir will be excavated
to elevation 5598.00. With part of the apron at this elevation or
higher, a considerable portion of the structure would have to be
built on backfill. As there was considerable objection to this fea
ture, the original apron was replaced and no further tests were made
in that direction.
12. Tests leading to the final design
From the results of the previous tests, it appeared that the
design could be made workable if the notch was div ided and half sec
tions placed at the ends of the crest with the channel wall forming
one side of each notch. Accordingly, the center opening was plugged,
12
'
and new notohes were cut at eaoh end of the crest. Their combined
area was slightly more than that of the original oenter notoh. The
tests with this arrangement revealed that at low disoharges there
was a pronounced concentration of flow in the center of the apron
which continued into the stilling basin. As the discharge increased,
a standing wave formed in the center of the apron just below the
crest and spread gradually as it approached the pool. When the dis
charge reached the maximum of 45, 000 second-feet, the lateral dis
plaoement of the flow from the standing wa.v.e approximately equalled
the chute width as it reaohed the end of the apron. The result was
a sheet of water of uniform depth as it entered the stilling basin.
This phenomenon produced a very satisfactory hydraulio jump, with
the result that there was little movement of the erodible material
downstream from the stilling basin. There was very little depth of
flow along the ohute walls except in the immediate vicinity of the
notch·. This was a distinct.advantage as it was now possible to use
walls of considerably less height than in any of the previous de
signs.
It was suggested that three notohes, one at eaoh end of the
crest and one in the oenter, be tested in an attempt to reduce the
height of the standing wave and obtain a better distribution of the
flow on the apron at low discharges. With this arrangement a stand
ing wave of the same height as before was fonned on each side of the
oenter line, in the area between adjacent notches. As these waves
spread on the apron, part of the flow returned to the center line of
13
the struature to form another standing wave and the remainder traveled
to the side of the structure and overtopped the walls. With some
experimenting and adjusting of the size and the an�les of the notches,
satisfactory flow conditions could have been obtained. However, it
was obvious that in order to accomplish this the center notch would
have to be considerably smaller than the side notches. The possibi
lity of clogging by debris caused abandonment of the plan.
At this time it as suggested that there might be an improvement
in the flow pattern if the notches were moved away from the channel
walls. The sections between the notches and the channel walls would
form buttresses, thus affecting favorably the economy of the design.
The notches were moved 10 feet toward the center line (figure 17).
The standing wave was not affected materially, but another fin of
water was formed between the notches and the chute walls which ex
tended well above the top of the wall. The scheme was abandoned,
and the notches were returned to their former positions.
At this point the alternate design, with notches at the ends of
the crests, was accepted as the final design, and the laboratory
proceeded to make refinements to improve the appearance and to curve
the chute walls to conform more nearly to the flow pattern (figure 6).
13. Final design
In the arrangement shown on figure 6, the ourvature of the chute
walls was easedr the entrances to the notches were streamlined, and
the transition above the crest consisted of plane surfaces. This
change did not affect the flow pattern (figure 8} or the head-discharge
14
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curve. Therefore, the design was considered satisfactory. However,
two more attempts were ma.de to reduce the height of the standing
wave. In the first trial, four rows of half-elliptical baffles were
placed on the apron, extending from the foot of the crest to a point
75 feet downstream. Two rows were placed in line with the inside
faces of the notches and the others were placed parallel to them and
10 feet nearer the oenter line of the structure. The major axes of
the baffles 119re placed in the direction of flow through the notches,
and companion rows were spaced such that the openings were staggered.
This scheme accomplished the purpose to some extent, wt the improve
ment was not sufficient to warrant their use.
In the second trial, a triangular blook 12 feet high was placed
on the center line of the apron with the apex against the crest to
deflect the flow from the crest into that from the notches. Thia
reduced the height of the standing wave considerably. Howaver, the
resulting flow into the stilling basin did not produce a stable jump.
So the plan was abandoned.
It was suggested that an improvement in the flow pattern could
be obtained by warping the walls from a point in the canal to some
point downstream from the crest. The model was revised as shown on
figure 9. There was no improvement in the flow pattern on the apron
(figure 10). However, the entrance conditions to the notches were
improved to the extent that their bottom widths were reduced from 10
to 9 feet.
This structure presented a more pleasing appearance than the
15
previous arrangement, and it was selected as the final design. The
head-discharge curve is shown on figure 12. The resulting soour
pattern, after an equivalent prototype flow of 45, 000 seoond-teet
tor 1.26 hours in the model, is .shown on figure 13A. The scour test
was not continued for a greater period of time because the channel
bed in the model had stabilized.
III - RESULTS AND CONCLUSIONS
14 • .Analysis of the results
The hydraulic performance of ori@;i.na1 design A was satisfactory.
However, from an economic viewpoint it did not compare favorably
with the final design. The depth of water on the chute at the walls
of the first design was considerably deeper than that at the walls
of the final design, necessitating higher walls over a greater length
(figures 16 and 18).
Original design A also required a greater length of crest than
was necessary on the final design, due to the unfavorable entrance.
In the longitudinal section of the crest the water flowed diagonally
to the crest axis, causing an appreciable reduction in the coeffi
cient of discharge. In addition, the downstream portion suffered a
reduction in head due to a drawdown in water surface in the area be
tween the crests which also contributed toward reducing the over-all
coefficient. The width of the notch required to pass 10,000 second
feet at elevation 6623.00 was much less for original design A than·
for the final design. Thia was due to more favorable approach con-
16
t
ditions above the notch, more slope in the downstream apron, and the
fact that critical flow occurred downstream from the notch. In the
final design the control section of the notch was at the upstream
edge of the crest and cri tica.l flow oc_curred before the water reached
the apron.
With both designs, a suitable hydraulic jump was formed in the
stilling basins and visual observations did not indicate any differ
ence in performance. However, a scour test revealed that original
design A 1coured much more severely near the pool walls than did the
final design (figure 11). This might have been caused by the converg
ing chute walls of the original design which concentrated the flow and
reduced the effective width of. the pool at maximum discharge.
At the early stages of retrogression in the downstream channel
leading into Tollgate Creek, the water surfaoe will be thirty to
forty feet above the stilling-pool walls at maximum discharge. Thia
condition will not produce any unfavorable conditions at the struc
tur, if sufficient bank protection is provided against wave aotion in
the vicinity of the structure. Aa retrogression progresses and the
tailwater approaches the top of the stilling basin walls, a vortex
will form on each side of the pool and there will be considerable
return flow into the stilling basin. The velocity of this return flow
is sufficient to cause scour and sloughing of the banks. If this ia
to be prevented, protection must be provided for velocities of approx
imately 12 feet per second.
17
15. Conclusions
(a) The stilling pool for the final design. as shown on figure
9. is satisfactory for discharges up to 45.000 second-feet in combi
nation with the corresponding tailwater elevations as shown on figure
19.
(b) The final design (figure 9) is superior to that shown on
figure 6. from an aesthetic viewpoint. There is no appreciable dif
ference in their hydraulic properties.
(c) For the final design. the bottom velocitiea downatream from
the pool are less conducive to scour than those of the original de
sign A. Any decrease in the channel area immediately downstream from
the pool will have a tendency to increase the scour.
(d) The variation in the alternate design. as shown on figure
16. could be ma.de workable. It was not considered practical tor
structural reasons.
(e) The three-notch arrangement could have been made satisfac
tory. and the height of the standing wave could have been reduoedJ
but the narrowness of the center notch would have presented a clogging
hazard.
-18
,
R 68 W
T3S
T 4 S
TSS
T 6 S
T 8 S
N
R 67 W
D
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T 9 S
)
I
/ I
T 10 S
DOUGLAS COUNTY-·-- ELPAs·o couNfY �
T II S
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DAMS COUNTY
,fRAPAHOE ·. COUNTY
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FIGURE. R 63 W
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CHERRY CREEK_
AND TRIBUTARIES
LOCATION MAP
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C H E R R Y C R EEK D A M
S P I L L W � Y - U L T I M A T E D E V E L O P M E N T
N EA T L I N ES O F W A TE R P A S S A G E S A L T E R N A TE D E S I G N
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C H E R R Y C R E E K D A M
S P I L L W A Y - U L T I M A T E D E V E L O P M E N T
N E A T L I N E S O F W A T E R P A S S A GES A L TE R N A T E D E S I G N A
P L A N
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/ - - Origin o f p a r a b ol a / Y = 0. 0059984 X l. ?O
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ft : _ �O __ [ rigin of Parabola Sta. t 64+47. t8' 1"'02: I - , : - / � Y=-0.0059984 X 1· 7o El. 5598.0 f
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C H E R R Y C R EEK D A M
SPI L L W A Y - U L TI M A T E D E VEL O P M E N T N EA T L I NES O F WA TER PA S S A G ES
A L TE R NA TE D E S I G N 8 S E C T I O N A - A
A · ---.-� ..J A
""'1 G> C ;o l"1
11'
FIGURE 7
A. Model arrangement B. Discharge 10 , 000 C.F. S.
'· C. Dis chfil'ge 25 , 000 C. F. S. D. Discharge 45 , 000 C.F. s.
ALTERNATE DESIGN A
A. Model arrangement.
c.. Dis charge 25 , 000 C.F .. S •
FIGURE 8
B .. Discharge 10 , 000 C.F. S.
D. Discharge 45 , 000 C .F. S.
.ALTERNATE �SIGN B
-.---r-�- -'-=--:..:.--t ... 4•-4 7'20"
0 0 <o a,
lj Worp rtefrf;ii
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P L A N
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· · ·: y •0. 0?
9984 x 1.10 Sto. 164 + 71.00
S E C T I O N A - A
C H E R R Y C REEK A N D TRI B U TA R I ES - C O L O R A D O
C H E R R Y C R E E K D A M
S P I L L W A Y - U L T I M A T E D E V E L O P M E N T
N E A T L I NES O F WA TER PA S S A G ES
A L T E R N A T E D E S I G N C
[FI N A L D E S I G N]
LJ·i / 25' �-!
0 0 .,;
.. :I' D E N TA TE D E TA I L
LJ-10,67t�_i
0 0 "'
_j
S I L L D E TA I L
;; ' -Top of crest
+Y
, · · - El. 5 623.0 - X O + X
,,., :t - y
El .5598.o- ·, • \
R, 10.25' r,50•-41 ·
:- - - - - -- - 2 7. oo'-- -- -----...!6. oo' k -
TA B LE O F COORDINATES FOR O G EE SEC T I O N X I N FEET J 1 /V FEET
0.000 0.000 +0. 1 1 5 +o. 1 65
0.230 0. 3 1 0 0.344 0.439 0.459 0.539 , 0.574 0.633 0.689 0. 7 1 2 0.9 1 8 0. 844 1 . 1 5 0 0. 950 1 .607 1 . 1 02 2.066 1 . 1 85 2.527 1 . 2 1 3 3.2 1 4 1 . 2 1 0 3 . 9 1 0 1 . / 60 4.590 1 .036 5 .740 0. 735 6 .890 + 0.299 8.040 - 0.2 76 9. / 80 0.9 1 8
1 0.340 1 . 676 1 1 .480 2.526 1 7.230 8.380
+22.960 - 1 6. 740
FIGURE 10
A. Model arrangement B. Discharge 10 , 000 C.F. S.
c. Di scharge 25 , 000 C.F. s •. D. Dis charge 45 , 000 C.F . S •
.ALTERNATE DESIGN C
FIGURE 11
A. Scour after flow 45 , 000 C .. F. S. Original Design A.
B. Scour after flow 45 , 000 C . F. S. Alternate Design C .
SCOUR PATTERNS.
5640
en -z
5630 0
I-ct
w _J w .... �
.1, ..... w u ',, ct
a:: I/
5620
0:: I w ., ct /
I/
I
56 1 0 I
I -,
j .I
0 1 0
-
---� ----� -_Lo,.--
i-..... _i,.,,,o' -
C H E R RY CREEK AND TR IBUTARIES - COLO R A DO CHER R Y CREEK D A M
SPI L L WA '( D I SCHA RGE - STA. l62 t 91. 83
ULT I M A TE DE:VELOPMENT F I NA L DES IGN
20 30 40
D I S C HARGE - T H O U SANDS C. F. S. 50
.,, GI C
;D r, "'
FIGURE 13
A. Model arrangement
B. Discharge 45 , 000 C.F. S.
ORIGIN.AL DESIGN
FIGURE 14
A. Model arrangement
B. Flow conditions with discharge of 45 , 000 C.F. S.
ORIGINAL DESIGN A
µ End of canal
5638. 00 I-
... / . 5632. 24 - -I ,
w w lJ...
z 5 6 1 8 .00 (/) z 0 -<( 5 5 98 00 > w
I I
__J w � w (.) 5 5-78 .00 <( Li.. a:: => (/)
a:: 5 5 5 8.00 w I-<(
3:
5 5 3 8. 00 '
5 5 1 8. 00 ,.., ,.., � � ai ai + +
N ,.., 1.0 1.0
t:> -+-(/)
,_ { I I
- -c;
' I'\
\
\ \ \ I'\: , '
I\ f'-\ 1"-..... --
n i l /wav b -Jttom - -
I"")
� -m + s:r 1.0
a a C H E RRY CREEK AND TRI BUTA RIES - C O LO RA D O cri
C H ER R Y CREEK D AM I()
WATER SURFA CE PROFILE ALONG WALL � I OF SPILLWAY- DISCHARGE 45,000 C.F.5.
..... , ...... :-.... - .7' r-.. " ' ..... I'-.:
F E E T
ULTI M A TE D E VELOPMEN T ALTER/I/ATE DESIGN C
F I N A L DES IGN
' ...... �
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...... � �
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... I\. ,,.._ I\.
"11..
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m ai + + U") 1.0 1.0 1.0
�
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2 1 gj � l a -+- l
a C.f) •
co 'a l� o, l t--.. c:: <.o ·- -c:: I o c:: ;-
·- C/) g, cn1 ..-r-I
I
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� I 0 1 c:: ·u; I -2 1 0, � I � I 15 1 -g l Lu ,
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t--1.0
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-
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>-
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-
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1 : U1
FIGURE l6
. A. Mo del arrangement �.. Discharge 10·, 000 C.F . S •
C. Discharge 25 , 000 C.F .• S. D .. Discharge 45 , 000 c.F. S.
SECOND VARIATION OF .ALTERNATE DESIGN A.
FIGURE 17
A. Model arrangement
B.. Discharge 45 . 000 C.F. S.
VARIATION OF ALTERNATE DESIGN B.
� -
5 6 3 8.00 ,,
I-w w LL
z 5 6 1 8 .00 -(/) z 0 -I- 5 5 9 8.00 <[ > w _j w w
5 5 78 .0 0 (.) <[ LL a:: ::> (/)
a:: 5 5 5 8.00 w I-<[
;: 5 5 3 8 .00
5 5 1 8 .0 0 0 0 0 r<') (0
<i .... (/)
�End o f cana l I I I I I I I I I I I I I I -
;:.£ ,. 5 6 3 2.42
I .....
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\
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: ··-
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r-,...
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ct .... <I)
i I I
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I
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I I I I
a >--.._ C H E R R Y C R E E K A N D T R I B U T A R I E S - C O L O R A D O -q f - --
C H E R R Y C R E E K D A M -- (X) t >--.._ -.- :1 --U L T I M A T E D E V E L O P M E N T - CX) --
WA TER S U R FA C E PRO FI L E A L ONG WA L L O F -.- � T --
-'- o r >-->--S P I LL WA Y - D I S C H A R G E 45,000 C. F. S. -f- ...... 1
O R I G I N A L D ES I G N A Cf) -,_ I 1
>---I
• ':: T --(/) -
I I 0 -i--.... c: I "°t
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EL. 5558.20--.i..l --"\. \. C: --
'-.\ '0\1.E I --,, (l) I(/) ---en I
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� (0 U) ,:, ct ct <i. ("'I
F E E T .... I- .... <I) CJ) <I)
• o,
•
5600
5 5 90
55 8 0
1-1.J.1 W 5 5 7 0 lL
I z
� 5 5 6 0 lJ.I
5 5 5 0
/ 5 5 4 0
I
5 5 3 0
0
S. A. M. 2-5-44
F I G U R E 1 9
•
.--v--B e fore retrogression, V
i..--
/ /
V w
V <{
/ V
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A fter retrogress� � -�
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V
10 20 30 40
D I S C H A R G E I N THOUSAN DS OF S ECON D - F E E T
CH ER RY. C R EEK, COLO .
C H E R R Y C R E E K D A M
U L T I M A T E D E V E L O P M E N T S PI L LWA Y TA I L WA TER
CU R V ES FOR STA TIO N 1 7 1 + 90
�
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50
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