hydrolo6ic engineering center davis ca f/g 8/8 … · ad-a117 657 hydrolo6ic engineering center...
TRANSCRIPT
AD-A117 657 HYDROLO6IC ENGINEERING CENTER DAVIS CA F/G 8/8APPLICATION OF THE lEC-2 SPLIT FLOW OPTION.(J)APR 82 A E MONTALVO
UNCLASSIFIED HEC-TRAINING-18
1111 1A.0 MS
136
M=OCP RESOLUTION TEST CHART
U S Army Corps
The HydrolooltEnlimeoerng Conter
Application of
the HEC-2
Split Flow Option
!8
-- DTICELECTE
Traei,.g Document No. I JUL 3o-O
April 1902 3E
is 07 29 025
!1ne~pn~f~N
SECURITY CLASSIFICATION OF THIS PAGE (Who. Data Rnfereo
REPORT DOCUMENTATION PAGE BRE CMPTiNG FOR
I. REPORT NUMBER 0BFR OPE & R1
'F~ nI1I~flF 1APnne .L No.I iO NO . R9CIPIIENT'S CATALOG NUM BER
4. TITLE (And Subtitle) S. TYPE Of REPORT & PERIOD COVERED
Application of the HEC-2 Split Flow Option
S. PERFORMING ORG. REPORT NUMBER
7. AUTHOR(q) 6. CONTRACT OR GRANT NUMBER(*)
Alfredo E. Hontalvo
S. PERFORMING ORGANIZATION %AME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASU
US AM Corps of Engineers AREA & WORK UNIT NUMBERS
The Hydrologic Engineering Center609 Second Street, Davis, CA 95616
St. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE
Alpril 198213. NUMBER OF PAGES
14. MONITORING AGENCY NAME & AOGRESS(if different from Controfflne Office) IS. SECURITY CLASS. (of this report)
Unclassified
VS.. OECLASSIFICATION/DOWNGRADINGSCHEDULE
IS. DISTRIBUTION STATEMENT (of this Report!)
jDistribution of this publication is unlimited
17. DISTRIBUTION STATEMENT (of the abstract entered In Block" 20. If ffrent from Report)
IS. SUPPLEMENTARY NOTES
It. KEY WORDS (Continue on reverse olde If necessary and identify by block rumiber)
Digital Computer, Split Flows, HEC-2, Backwater, Open-Channel Hydraulics,Lateral Weir Overflows
20. ABSTRACT (Continue 5.reverse side If ndleaj and idbntfgb hr Nfoonmb
Training document designeZ to assis the user of computer program HEC-2split flow option and to acquaint them with its capabilities and limitations.Provide a detailed description of the HEC-2 split flow input requirements,output results, computation method and example applications.
DD I JAN78 1473 EDITION OF I Nov 6 SIs 0BSOLETE- - - SECURITY CLASSIFICATION OF THIS PAGE (Wi., bet m
TPAIMING KIOC!M3T NO. 18
APPLICATION OF TIM3 HUC-2 SPLIT PLOW OPTION
Alfrefo 3. Montalvo
A000sslon ForXNUS GRA&X
April 1982 DTIC TABUnannouncedZustifloation
Diatribut ioAvailability codes
Avail and/ow-Dust Speal
U. S. Army Corps of 3nginersWater Rebources Support Center
The Rydrologio Ungineer lag Center609 Second Street
Davis, California 95616
FORIOR
This training document was written to assist users of Conmter Program
HEC-2, Water Surface Prof iles, in the analysis of split flown. Financial
assistance for writing this document was provided by the Flood Plain M~anagement
Branch, Office of the Chief of Enqineers.
The author wishes to acknowledge contributions by Vernon R. Bonner and
Dill S. Richert to the material contained in this document and for their
reviews and coents.
b
TABL3 OF CONNS
FOR11DND
IN'TRODCTON1
Purpose and Scope 1
Program Documentation 1
530-2 SPLIT FLW OPTION 2
Capabilities 2Computat ion Procedure 4Program Limitations
530-2 SPLIT FLON INPUDECRIPTION 7
Split Flow Title Card 7Job Card Set 8Weir Reach Card Set 8Normal Depth Reach Card get 9Diversion Reach Card Set 9End split Flow 9Additional H30-2 Cards 10
GunumM~jODELING CONSIDEATouS 11
Split Flow Reach Longth Consideration 11
Hydrologic Considerations 1
R02RUUCU 19
Appendix I - 530-2 SPLIT FILOW INPUT AND OUTPUT DESCRIPTION
Appendix II - SPLIT FLOW EXAMPLE PROBLE
Appendix III - GRAPHICAL MET'HOD FOR SOLVING ISLAND DIVIDED FLOWS
APPLICATION 01 THIR WD-2 SPLIT FLOW OPTION
INTRCDUCMON
Purpose and Scope.
The purpose of this training document is to provide information on the
capabilities and limitations of the computer program RB3-2 Split Flow option.
This .ocument provides a detailed description of the input requirements, output
results, computational methods and example applications for the split flow
option. It is assumed that the user has a %nowledge of the basic H3C-2 input
requirem4nts. Information on 11C-2 input requirements is available in the
"HU-2 Wat~er Surface Profiles-Users Manual' (reference 1).
Program Documentation.
The split flow option was added to the REC-2 Computer Program by
Modification 55 which was imilemented April 1982. The primary documontation for
11C-2 is the January 1981 Users Manual which describes the program capabilities,
input reouirements, and output. To use the program, one would need a users
manual, as this document does not give details on many program features and
input formats. The users manual is available from the Rydrologic Engineering
Center.
... . .. .. ..V
1' .... . ... . . . .. ..... . .... ri .. . ... . .. ' , , . ..
HDC-2 SPLIT FLOW OPTION
Split flows are flows that leave the main river flow anO take completely
separate paths from the path taken by the main river flow. The split ftows may
return further downstream or may be completely lost. The REC-2 program assumes
that none of the split flows return and automatically reduces the discharges
downstream from the split flow location unless the user specifies wbere to
return the flow and what percent of it to return.
Capabilities.
The RE-2 split flow option has the followinq capabilities:
. Can solve up to 100 separate split flows simultaneously.
6 Up to 15 profiles may he solved in one execution.
e Three methods for determininq the split flows are availahle.
1. Weir flow assumption
2. Normal depth assumption
3. Rating curve assumption
0 All. or a percentaqe of the split flow can he returned.
* Option of either usinq the water surface or enerqy
elevation for comuting the split flows.
A Allows the use of ratinq curves for starting the backwater.
This capability is now a general HRU-2 capability and may
he used without having to use the split flow option.
2
he sntit flow optin is compatable with multiple profiles anA most of the
standard REC-2 options. The only options not available to the user, if the
split flow option is used, are encroachment methods 3, 4, 5, and 6.
There are many tvoes of split flows that occur in rivers. The following is
a list of the more commonly encountereA types of split flows.
. Split flows caused hv islands or hiqh ground.
" Split flow causA hy levee overtopping.
" Split flows caused by watershed divide overtopping.
" Split flow caused by diversion structures.
The H3C-2 split flow option is capable of analyzing all of the above split
flows, with the excention of the island or high ground type of split flews.
Appendix III has been provided in this document to assist the user that has a
split flow caused by islands or high ground. The solution procedure is the
classic dividPd flow analysis technique.
3
Computation Procedure.
The computation procedure used to salve the prohlem- of split flows is
basically a one dimensional steady state method of trial and error, as follows:
1. The program comnutes the water surface profile and adjusts the
discharges to reflect the assumee overflows. No overflows are assumed
to occur for the first iteration unless the user has specified overflow
values on JS cards.
FIGURE 1
2. "he location of each split flow reach (Fiquire 1) is defined in re~ation
to the model hy the upstream ane' Aownstream cross section numbers.
Based on the cross secion numhers, the water surface or energy
Plavatidns are eetermined from the water surface profile nerformed in
step one and are used to calculate the overflow.
3. The computed and assumed ovesrflnws for each salit flow reach ano their
cumulative values are compared. Tf the difference between Any of the
Values for computed anti assumed is greater than 2 percent, the proqram
makes a new assumption of nvprf~ows and repeats steins t throtiah 3 until
an acceptable tolerance is met or unti3l the Procyram has performed 20
iterations.
4
Proqram Limitations.
The following assumptions are implctt in the analytical exoressions used
in the RC-2 program and the split flow option:
1. Plow is steady because time dependent terms are not included.
2. Flow is gradually varied hecause a hydrostatic pressure distribution is
assumed in the energy equation.
3. Plow is one-dimensional because the total energy hea is the same for
all points at a cross section location.
4. Tbe river has a channel slope of no more than 10 nercent.
5. The split flows can be estimated hy the standard weir equation, the
normal depth equation, or a rating curve of outflow -vs- elevation.
6. Suhmorqence of the overflow weir by tailwater is Insiqnificant.
7. The weir flow is linearly integrated along the length of the weir based
on the upstream and downstream water surface or @nerqv elevations.
8. The normal depth conveyance is linearly integrated along the length of
the norma. depth cross section based on the upstream and downstream
water surface el .vations.
9. The direction of the main stream flow is at right angle to the split
flow.
10. Split flow is controlleA by either the water surface elevation or the
energy elevation.
i.. Plow boundaries are fixed. This is to say that the cross section an
weir qeometries An not erode or change with time.
S
12. Split flows that are not returned to the system are removed from the
entire model downstream from the split flov location. 3ecause HEC-2
does not take into account the variation of flow with time, the user
must be careful in using the RWU-2 split flow ootion in cases where the
s.plit flow. at an upstream location Aoes not have a constant effPct on
the peak discharqes further downstream. An explanation of this prohlem
and a solution strateqy is given in the section titled Rvdroloqic
Considerations.
LS
HFC-2 SPLIT FLOW INPUT DESCRIPTION
The solit flow intuit data must he entpre A as the first data of an HRC-2
run, with the excention of the ET) card (EnIT2 -roaram). The split flow Innut
data must always start with an SF card and end % th an EE card. Tho ER card
must he followed by the requ.ar HE.-2 inotit data cards.
The split flow input data uses the stanAa A HBC innut format, in which the
first field contains a two character car- -ir, and has six columns for
data while the next nine fields contair - each. The ahove format is
for numeric data. The format for title c~r ' columns for card identifier
and the remaininq seventy eiqht columns for aloha-numeric information.
The split flow data input varies from the standard HEC-2 format in that a
set of data cards is always preceded by a title card and the title card is
required. The order in which the cards are entered must he followed exactly for
each set or qroup of cards. The sets of cards need not he in any specific
order, but it is recommended that snlit flow reaches be entered in a downstream
lirection to make the output more readable. A detailed description of the split
flow data card inaut format is qiven in Appendix I. The followinq is a
description of the general card types.
Split Flow Title Card.
The SP card is a title card used to activate the split flow option. It is
a required card and must be the first input data card in the deck.
" I i I .... .... . Ill[FilLIII" 7
Job Card Set.
The job card set consists of the JC anA JP Lards. The job card set is
optional and is used to control the processing of the split flow data. A job
card set may be pladed anywhere in the siolit flow input data. The JC card is
the first card of the set and is used as a title card. The JP card is used to
set the level of printout, allowed error tolerance, maximum number of
iterations, use of either water surface or energy elevation, and percent of
split flow to return.
Weir Reach Card Set.
The weir reach set is composed of three types of cards. The first card of
the set is the TW card. The TW card is a title card and must be the first card
of the set. The second card is the WS card, which contains information dealing
with the number of points descrihinq the weir, weirflow coefficient, location of
the downstream and upstream limits of the weir in relation to section numhe.rs
and the section number where the flow returns. The third card of the set, the
WC card, describes the weir geometry by the use of station and elevation
coordinates. The coordinate Points must start at the downstream end and proceed
in an uostream direction.
Ih L.: . .. , . .. . ..... . .. . . . " " . .. . Il ill lll . . .. . . . . . .. . . . ... ... ... .. . ... .. " ' . ... I~l a " liel rl III - ] ll ... .. . " ' ' ' " ...
Normal Depth Reach CarA Set.
The normal deoth reach set Is composed of three types of cards. The first
card of the set is the TN card, which is a title card and must he the first card
of the set. The second card, the NS card, is similar to the WS card, with the
excpvtion that instead of havinq the wpirflow coefficient, it has the enerqy
slope and 'n' value. The third card, the NO card, is used to describe the
normal depth cross section aeometry by the use of station and elevation
coordinates, with the coordinates starting at the downstream end.
Diversion Reach Card Set.
The diversion reach set is composed of three types of cards. The first
card of the set is the TC card, which is a title card anA must he the first card
of the set. The seconA card, the CS card, contains information dealing with the
numher of Potnts Aescribinq the diversion retinq :urve, loaction of the
diversion in relation to section numhers, and the section numher were the
divertPd flow returns. The third card, the CR card, is used to Apccrithp the
ratinq curve tw the use of di.scharqe and elevation coordinates.
End Split Flow.
The EE card is requ4 red to terminate the split flow input Aata.
I.
Additional RBC-2 Cards.
Several additional input data cards have been added to the standard KBC-2
input to facilitate the use of the split flow option. The new cares are the JR,
JS, and RC cards.
The JR card is used to input a rating curve that is used to start the
backwater. The JR card follows the 31 card and is read when the JI card
variable STRT is greater than one. The STRT value in this case is useA to
indicate the number of rating curve values that will he reaO on the JR card.
The RC card is used to input a rating curve at any cross section, which
will be used instead of a calculated hackwater answer. It operates in the same
manner as an X5 card.
The JS card is used to specify the startina assumed split flow for each
reach defined in the split flow data sets. The JS card follows the J1 or JR
cards. It is an optional card and if omitted, the program assumes for its first
trial that no flow is being lost.
10
GENWRAL MODLIN( CONSIDERATIONS
The split flow option requires that the cross section numbers (Xl card)
continualIv increase in value from dwnstream to tiostream. Tt is rcoimmended
that station values in feet or miles measured along the main channel he used for
cross section numbers. This is imoortant because the RWf-2 proqram uses the
cross section numbers stecified on the split flow reaches to determine what
water surface or energy qrad. line elevations to ase in determininq the amount
of flow lost. Each split flow reach is located based on cross section numbers
at the downstream anti unstream ends of the reach. If the downstream and
upstream split flow locations do not match a cross section number, the program
will linearly interpolate between cross section numbers to determine the water
surfaces or energy qrade line elevations. A wise practice would be to start and
end the split flow reaches at cross section numbers that appear in the RSC-2
hydraulic model.
Split Flow Reach Lenqth Consideration.
The overf]ow reaches should be kept as short as possible. The longer the
split fl.ow reaches, the less accurate will be the split flows and backwater
answers. The split flow problem can be compared to the integration of a curve
by the Trapezoidal Rule, which is an approximate method of subdividing the curve
into a number of straciht line seqments and calculatinq the areas under each
straiqht line segment and then aAdinq lp the subareas to calculate the total
area under the curve. The smaller the straiqht line segments and the larger the
number of seqments, the more accurate will he the calculated area. The same
11
.4Ehi
I. I'.4
Ia
00q.'U
0
Iam
'U
2$ 'U0 -S a"
0 Z* ~I. *-.4 ~o '.4
-~ *
'I. I;- .4b4
m
I.4
-' I.4
00U
I
* w* * * * 0
* 13 0 0 48 N.4 .4 .4 .4 .4 0 0 2 0.4 .4 .4 .4 .4 .4 .4
W~I&A~~OZ IL
12
loqic applies to the calculation of the solit flows. The shorter the split flow
reaches and the additional cross sections defining them, the more accurate will
be the calculated outflows and water surface elevations.
The effect of subdividinq a split flow roach and adition of cross sections
can be seen in the following example. Figure 2 shows a profile olot of a stream
and a split flow reach which has a totW' reach lenqth of 1000 feet. The split
flow reach was modeled in four different ways. The first mod.l represented the
split flow reach as a single 1000 foot lonq reach. The second model divided the
split flow reach into two 500 foot reaches. The third Kadel divided the split
flow reach into four 250 foot reaches and the fourth moAel divided it into ten
100 foot reaches. Note that each reach has a cross section defininq it upstrem
and downstream. Additional cross sections must he used because the split flow
discharqes are calculated based on a linear interpolation of the upstream and
downstream cross section water surface or energy elevations. The effect of
diviAjnq up the split flow reach into shorter and shorter segments, is to
orolice answers which are more accurate. The results from these four moels are
presented on Ptaure 3, which shows plots of the flow in the main river -vs-
river distance. The results clearly show that the 1000 foot reach should be
diviAed into shorter reaches. The fourth model oroduced the most accurate
results, but it is a.so clear from the plotted results, that the second and
third models gave acceptable results.
The example also shows that the upstream portion of a uniform split flow
reach should he dividd into shorter s."nmnts than the downstream portion.
because a larqer provortion of the flow will he lost on the upper portion.
13
42
I I4 ~ ii4-5: a
I
Q.4S04m@W ~ -4--.
4-
I I
4-
4-EUiw
*
14 -4-.
Hy'roloqic Considerations.
A connon practice for hvyraulic analysis is to use the flood hydrograph
peak discharge values for the backwater calculations and ignore the fact that in
most cases the peaks of the hvdroqraphs do not occur at the same time. In many
cases the effect of this assumption on the calculateA water surface profile is
well within the accitracy for profile calculations. Most REC-2 models are
assembled in this manner. When it comes to a split flow analysis, the effect of
using the peak Aischaraes as steady flow shotu!d not be iqnored.
The HSC-2 split flow option, as a default, reduces all Aischarge values
downstream from a split flow reach hy the calculated split flow values. For
examnle, if 1000 cfs is lost at the headwaters of a stream, the program will
reduce all the discharges by 1000 cfs all the way downstream to the start of
model or to the section number where the user has specifte that it returns.
The only way to determine the validity of reAucina the Aischarqes in this manner
is to look at the entire hydrograph, to see how the loss from the split flow
effects the peak Oischarqes Aownstream. It may be that the peak discharge
further downstream will only he partially eFfected by the split flow loss. The
peak discharges downstream may be more Aeoendent on the timing of tributary and
local inflows.
To illustrate this problem, the following simple example is presented. As
shown on Figure 4, the Upper Main Stem has a split fow reach Just upstream from
the confluence with Tributary No 1. Fiqure 5 is a plot of the original
hydrographs for the Upper Main Stem, Tributary No 1, and their oombined
hydroqraphs on the Lower Main Stem. If flows that exceed 3000 cfa on the Upper
Main Stem are lost, then the modified hydroqraphs plotted on Flqure 6 occur.
15
Comparing the oriqinal hydrographs with the modified shows the peak discharge on
the Lower Main Stem reduced by 1000 cfs, veak flow on Tributary No 1 unaffected,
and the meak discharqe on the Lower Main Stem reduced by 500 cfs. The RU-2
split flow option woulA have reduced the Lower Main Stem peak lischarqe by 1000
efs and not by the correct amount of 500 cfs.
M
1+4 SPLIT FLOW REACH
*0
0
FIGURE 4
Consieration must also he qivon to the effect of storaqe routtnqs. The
effect of routinq a flooA wave is to reduce the peak eischarqe. Therefore a
peak discharqe further downstream hased on routinq will not he ro$uce, hv the
total amount that was lost upstroam.
16
FLOOD EYDiIAPEUSp,00! ITM psellf7000 PLIT FI.OV PMIN,
6000 - *-*UPflj NAZI 1711ALONI NAZI ME1 '
I6000
IIA 4000 /
* -- /.TT.o
1
I'1 8000/
1 000/
1000p
I
40 NAZ HISI
-4 -5 0A Z 8 10Till P12103
FIGURE 6FLOOD ITIEOC*APNS
SPLIT !L0V PIODLI!
a 000
h000-iPPIR NAZI SF11~ TIIUPTAET 10 1I ' LOVEU NAZI 521 /!
000/ \
0/
* /\I 8000/I
1 5000
1000 0
-4 -* 0 8 4 6 6 10
TIll szes0FIGURE .
17
The following procedure can be used to account for the hydroloqic aspects
of a split flow problem.
1. Make an Initial HDC-2 run which reduces the split flows all the way
downstream.
2. Alter the hydroloqtc model (R!C-1), at the split flow reach, to reflect
the lost flow and execute it again. Analyze the effect that the split
flows had on the peak discharges downstream from the split flow reach.
3. If the assumption of reducinq the lost flow is valid, then no further
analysis are needed. If the lost flow is only partially effective
downstream, then the lost flows should be returned further downstream.
This can be accomplished by modifying the HEC-2 discharqe cards to
reflect the expected reductions downstream from the split flow reach and
returning the split flows back into the model.
4. An HUC-2 run should he made and steps 2 and 3 repeated until an
acceptable solution is achieved.
This procedure is applicable for simple solit flow problems which
do not have more than three or four separate split flow reaches. For
the more complicated split flow problem, an unsteady state Uroqram
should he used. The D"OPzIR (Dynamic Wave Operational Model) program
developed by the National Weather Service (reference 8) is a one
dimension unsteady state program that can be used to solve the split
flow problem.
I Is
RFWERPMCrFS
1. OHEC-2, .ater qurface Profiles," T1.q1sr Manual, The Hvdroloqic
F.nqinerinq Conter, January 1.981.
2. ater Surface Profilpg,* THn Volume 6, The HydroInqic Fqnqineerinq
Center, Julv 1975.
3. "O)pnn Channel. Hydraulics," Vpn Te Chow, McGraw - 11ii! Book Cnmoany,
1959.
4. "SPILL, Spatially Varied Steadv Plow Analvsis,* Users Manual,
Moon-Yonq Ran, July 1.980.
5. *ExoprimentAl Investiqatton of Plow over Side W irs," Pl-Khashah and
Smith, V.H., Journal of the Hydraulics Division - ASCE, Vol. 102,No. HY9, Proc. Paper 12402, Sentemher, 1976.
6. "Spatially Varied Flow Over Side Weirs," Suhramanya, K. and Awasthy,
S.C.,Journal of the Hydraulics Division - ASCE, Vol. 98., No. HYI, Proc.Paper 8627, January, 1972.
7. "Effects of Channel Meanders on Flood Staqe in Valley," Smith, C.P.,
.Joumrnal of the Ryraics nivision - ASCE, Vol. 104, No. HYI, 1.978.
8. *National Weather Service OnerAtinnal Dynamic Wave Model,"Fread, D.L., National Weather Service, NOAA, April 1978.
19
APPENDIX I
SPLIT FLOW INPUT AND OUTPUT DATA DESCRIPTION
SLIT FLOW TITLE CARD
CARD SF - SPLIT FLOW CARD (REOUTRrT) IF SPLIT FLOW OPTION Is Tol sE rismD
The SF card- is useI to flaq the split flow option. Only one SF cardi canbe tisp.i. The SP care4 has to be the first card in an HWC-2 vleck.
Field Varijable Value Description
0 IA SF Cardi i'entification characters.
1-10 Aloha-numprir Title flata.
CA-RD JC -TITLE JOB CARD FOR SPLIT FLOW (OPTIONAL)
The JC nard is used to indicate that JP card follows. The JP card must
II foylow the JC card.
Field Variahle Value npscription
0 IA JC Ca?44 identification charactprs.I1-10 Alpnha-numpric Title data.
CARD JP - JOB PARAMETER CART
The JP card is used to set several job Parameters dealing with thesplit flow computations. The JC and JP cares are optional and can heplaced anywhere in the split flow data or completely left out. Theyshould be Placed normally after the SF cards.
Field Variable Value Description
0 IA JP Card identification characters.
1 ISFTR 0 Printout control of split flowcomputations will be held to a minim, m.
1 Trace each so]it flow iteration.
10 Trace both the split flow an- hackwater
iterations.
2 AEROR 0 The proqram will use a value of2 nercent allowed error for converqence.
+ The user may specify the allowed percenttolerance for convergence.
NAITER The maximum number of iterationsfor split flow to be executed per
profile (20 is the default value).
+ The user may specify the maximum
numher of iterations.
4 IUEG -1,0 The proqram will use the watersurface to determine the overflow.
I The proqram will use the energy gradeline to determine the overflow.
5 PERFR 0 One hundred percent of the overflowis to he returned at SNOFR (WS.4, NS.4,
and CS.4).
+ Percent of overflow to be returned atSNOFR (WS.4, NS.4, and CS.4).
'J".. ..... ... ll rl l l IS f If .. .. .i - I l ' II : .. ... . .. .... ... .... . • .. ..... .." . .." "-1.....-. ..
CAPD TW - TITTA, CARn FOR NMIR LOICATION
The Tt% carev is required for Pach set of wetr outflow dAta set. TheTW care mu~st he fofllme hy a set of WS anAi WC car'is.
FiPeV VariAhle Value Description
0 IA TW Car'A ilentification characters.
1-10 Alpha-numerIc Title vAata.
1-3
CARD S - WEIR PARAMET,R DATA CARD
The WS card is required for each TW card used and must follow it.The WS card contains information dealinq with the number of points
describinq the weir, weir flow coefficient, location of the upstreamand downstream limits of the weir in relation to section numbers asused in the Xl cards, and the section number where the flow returns.
If the flow does not return, a value of -1 should he used. It isrequired that the section numbers used to set-up the backwatermodel increase from downstream to uostream. The same rule appliesfor supercritical models.
Field Variable Value Description
0 IA WS Care identification characters.
I NWPL + Number of coordinate points that describethe weir on the WC carA.
2 fSSNO 0,+ Downstream section number where thefirst weir coordinate apnlies.
3 USSNO 0'+ Upstream section number where theInst weir coordinate applies.
4 SNOFR 0,+ Section number where the lost weirflow returns.
-1 The weir flow (oes not return.
5 COFFL + Coefficient of Aischarqe for use in weir
flow equation.
6-10 Not used.
T 1-4
CARD WC - THE WEIR COORDINATE CARD
The WC card is used to input the weir coordinates. The weir coordinatesmust start at the downstream end and proceed upstream. The maximum number
of coordinates is 100.
Field Variable Value Description
0 IA W Card identification characters.
1,3,5, STA(I) + Station Value of weir coordinate.i7,9
2,4,6, ELOII) + Elevation value of weir coor6inate.8,10
1-5
CARD TN -TITLE CARD FOR NOIWAL DEPTH LOCATIO)N
The TN card is required for each set of normal ePth out!flow tAata set.
The TH card must be followed by a set of NS and NG cards.
Field Variable Valueb Descriotion
0 IA TN Card identification characters.
1-10 Alpha-numeric Title data.
CARD N4S - NORMAL~ I1'R PAR JP"T DATA CARD
The S card is similar to the WS carA with the oxceotinr that instead of
havinq the weir flow coefficient, it has the enerqv slope ani In' value.
Field Variable Value nescr iption
0 TA NS Card iMentificat.on characters.
1 NWPL + Number of coordinate points that describe the
normal Aenth flow cross section on the W, card
2 rS.qNO 0,+ rTlostream section number where the first
conordinate point on the NG card anplies.
3 USSNO 01+ Upstream section number where the last
coorAinate point on the MG card applies.
SOPR 0,+ Section number where the lost flow returns.
-! The lost flow does not return.
5 XNVND + The 'n' value to he used for normal depthcalculIat ion.
6 SOPNn + The enerqv sl.ope to he used for normal
Aeoth calculations.
7-10 Not used.
I-?
CAM Mr - TH GROUND COORDINATE CJR
The MG card is used to input the normal depth cross section coordinates.The coordinate must start at the downstream end and proceed u0stream.The maximum number of coordinates is 100.
?iold Var table Vau D.scr iption
0 IA NG Card ientification characters.
1,3,5, STA(!) + Station Value of cross section.7,9
2,4,6, FLO() + Elevation value, of cross section.8,10
1r-8
CARD TC - TITLE CAR) FOR RATING CURVE WCATION
The TC card is required for each set of ratinq curve outflow dataset. The TN card must be followed hy a set of CS and CR cards.
Field Variable Value Description
0 IA TC Card identification characters.
1-10 Aloha-numeric Title data.
CARD CS - RATIN(, CURVE PARAMETER DATA CARD
The CS card is sjm.1ar to the WS carA with the exception that thelocation (unstream anA downstream) is a noint location anO thereforethe value entereA for ,iSSO and DSSNO should normally he equal.
Field Variale Va'ue Description
0 IA CS Card identification characters.
I HWPL + Number of discharq. elevation pairs to heread from the CR cards to follow.
2 DSSNO 0,+ Downstream section number where theratinq curve aoplies.
3 ISSNO 0,+ Upstream section numher where theratinq curve applies.
4 SNOFR 01+ Section numer where the lost flow returns.
-1 The lost flow does not return.
5-10 Not Uses.
T-9
CARD CR RATING CURVE CAD
The CR card is used to input the rating curve of outflows. The
location of the rating curve has to he at a specific location on
the river. Therefore the location has to be specified at only one
point. The variables DSSNO and ISSWO should he set eaual. If theyare not, the program wil use the mean of the two locations.
The maximum nu*r of ratinq curve points is 100.
Field Variable Value Description
0 IA CR Card identification characters.
1,3,5, STA(I) + Discharqe values for ratinq curve.7,9
2,4,6, ELO(M) + Elevation values for ratinq curve.s,10
CARD EE - END OF SPLIT FLOW DATA CARD
The E card is required to terminate the reading of the split flow
data. The BE card should he in front of the first regular HEC-2card, such as the AC, C, or Ti cards.
Field Variable Value Descriction
0 IA BE Card identification characters.
1-10 Not used.
1
1-10
MOi'MIFICAIION TO J1 CAR"
The J1 card variahle STRT (Field 5) has $e.n altered so that the program
will accept a ratinq curve as a starting hackwatmr condition. The optionis activateA hv entering in field five (STRT variable) of the J1 card thenumber of discharqe elevation rating curve points. The rattnq curve isentereA after the Ji card using JR cards.
CART) JR - STARTING, RATING CURVE CARM
The JR cards are used to input a starting ratinq curve. A set can beplaced for each orofile beinq run. They must follow the J1 card andthe number of rating curve voints must he greater than two. It isrequireA that the number of ratinq curve points be entered on the Jicard, field five. A maximum of twenty discharqe elevation valuesis allowed. The proqram linearly interpolates between qiven ratinqcurve values and extrapolates for values outside the rating curve.
Field Variable Va!.ue Description
0 IA JR rard identification characters.
1,3,5, JI (I) + Discharqe values.
7,9
2,4,6, XJl(I) -#0+ Water surface elevation values.8,10
1-1
JS - CARD STARTING SPLIT FLOW ASSUMPTION CARD
The JS card is used to specify the startinq assumed lost discharges
for each reach defined in the split flow data set. ITf the JS cardis not entered for a profile, then the proqram assumes that the firsttrial assumed lost flow is zero for all the split flow reaches. TheJS card should follow thj JI card or the JR card if us.. A maximumof 100 values are allowed.
Field Variablo Value Description
0 TA JS Card ientification characters.
1 N + Numher of assumed lost discharges to read.
2 AW(4,1) + Assumed lost discharge for first reach.
3 ARW(4,2) + Assumed lost AiRcharqe for second reach.
ARLO(4,N) + Assumve lost Aischarge for lastreach.
Continue on in field one of additional JS cards up to ARLO(4,N).
-L1-12
J
CARD RC - RATING CURVE CARD
The RC card can he entered at any cross section and the program will
determine the water surface elevation based on the rating curve andnot on backwater computations. The RC card should he placed af ter theXl carA. A maximum of twenty discharge elevation values are allowed.The program linearly interpolates between given rating curve valuesand extrapolates for values outside the ratinq curve.
Field Variable Value Description
0 IA RC Card identification characters.
1 NRCP + Number of rating curve points beingread in.
2 PRC(l) + Discharge value.
3 XRC(l) -,0,+ Water surface elevation value.
4 ORC(2) + Discharqe value.
5 XPC(2) -,0,+ Water surface elevation value.
ARC(nRCP) + Last discharge value.
XRC.(NRrP) -,0,+ Last water surface elevation value.
Continue on in field one of additional RV cards up to ORC(NRCP) and
XRC (NRCP).
* -t3
REC-2 SPLIT F(q OPTION OUTPUT VARIABLES
Var iable Descr iption
ASQ The assumed split flow value used by the proqram to comptte thewater surface elevations.
0 COMP The computed split flow value based on the computed water surfaceelevation.
ERRAC The percent error between the assume di scharqe and comoutAdischarae.
TASQ The total assumed split flow for the entire REC-2 model.
TCn The total computed split flow for the entire HEC-2 model.
TABER Percent of error between the total assumed split flow and totalcomputed split flow.
NITER The number of iterations that the proqram has executed in computinqthe answer.
DSWS The computed downstream water surface elevation.
TISU The computed upstream water surface elevation.
DSSNO The downstream section number where the split flow reach heqins.
USSNO The upstream section number where the split flow reach ends.
TOTAL AREA The total cross sectional area for a normal depth overflowreach.
AVG VELOCITY The averaqe velocity of the normal depth overflow reach.
MAX DEPTH The maximum depth that occurs on the normal depth overflowsection.
AV DEPTH The average deoth of flow for the normal depth section base,on the total area divided hy the water surface topwidth.
TO? WIDTH The width of the normal depth overflow section.
TOP WIDTH The width of the overflow section based on the computedwater surface.
1-14
j APPENDIX II
SPLIT FLOW EXA-iPLE PROBLEM
EXAMPLE OF INPUT PREPERATION
The following problem is provided to illustrate the input preparation
required when using the split flow option. The input is shown on Figure 9 and
is described below. A comnlete HEC-2 computer oultnut listing for this example
is also provided.
A plan view of the levee system and floodway of the Red Fox River is shown
in Figure 7. A profile view of the stream bed, levees and overflow weir are
shown in Figure 8. As can he seen on the profile view, the right bank or south
levee is the critical levee for a split flow analysis. This is hecause it has
the overflow weir and is several feet lower than the north levee.
The starting water surface for this example will he based on a normal depth
calculation using a slope of .005 ft/ft. The weir coefficient for the levee
will. he 3.4 and for the overflow weir, 2.7. The weir coefficient for the
overflow weir is low to account for the s,1imerqence caused by the tailwater in
the floodwav.
The first card of the split flow innut data is the SF card. The split flow
reach in this example is dlivide into three shorter reaches. The first snlit
flow reach to be modeled is the most upstream reach which lies between sectionsI,3 and 4. The TW card follows the SF card and is used to identifv the reach.
The WS card follows the TW card and is used to specify the number of coordinatesKthat describe the levees qeometrv, location of the downstream and upstream
limits and the section number whepr the snlit flow returns. The split flw dopes
not return and a value of -1 is used to so indicate. Station and ePevation
coordinate data is enteree on the WC card to Aescrih the weir qeometrv. The
II-1
coordinate data start at saction 3 and proceeA upstream to section 4.
The same proceAure ,ised for the first upstream reach is used for the
overflow weir reach, which lies between sections 2 and 3, and for the downstream
levee reach which lies between section I and 2.
In this example prob em it was assumed that the weir equation was the more
amropriate to use for calculatinq the split flows. If a normal deoth or
diversion assumption had heen Preferrod, then thp only lifference in input would
have been that the normal depth or diversion snlit flow carAs woulA have been
used.
rx-I416-2
Ju
SET1M
(Z(
SET of
FIGUE 7 ~ar vie ofthe ed ox Rver Colrad
0*-
1- 1:
I c
:4 r.-4
_ 0i
co ,Q C
11-4
.- . . .-
to,0
I a -T
a. I
I I
T~ al04IL I.j
0; 1 LA
z cc
0
9
ODa41
eu f"M
.-*..4 1 N r 1 N
a~ 4L
. Lacc 00 ..
a4 U. q c in
** 0v 1:~
64 V - a c*~~~ ofow G A -
r4P 0A 1 8* 00.W
41 N C4 C4uk I%
-N C -A
C'-- ro o
"4 011-6
0 o ca Ccc auI cc cc 0004~ a
%Din ~ inee a
o cc a Oa Cac 0a C2 cca cc * -cc 0
zqoca 0044c; caoano0 acer-mco occaoI I4 1 m- an IvN NI N-I I -4 I
o N %
c; a c cc coo as n aa 0 cc coon a*o a O ccO Q..4n *0 cc *0 ace a0 C
Imn N 1 #-lot secv in-
a cc a cc a2 0 COO a 4n
C S V4rr4luVlu-I 9- ai -I cii4N'% cc
a ccc a ceCC cc Ce~ 0C% ocaM ace t" COCO cc Coen Coca
a * ccc a coa cc Ic r0 COcar-~. I* .- .n~ -0 %* m %* 4 I.
C a raine emcee co a c ccc
CC CC a a cc a cOc a ccInc ccc c cc a r-ac 0COc
a; az, cc C rZA89n caCC;~c o4ccecac art n *u-40 r- air- 0 -4r4 cm f Q M
%D gn in
0coon cca0 an eeOC cc acm0 COCaul aol COCO coc aCoca CC) Caln Coco
ao a 40c cinema acc a442 C Q COCOa
0 t-%Iu-4f% %oin$-i~o %Dc"M Nin 4wfnu4
0
a a a '0cc a a ccc a COCO a cc0 0cc 0cccaa 0 00M s ccc ccc0 0 a a aCaO a ac a40 oaa a aa
comaW % cu-m anaa f"~eO in 040 4 ii- - -N lN-M MN4
cc Coco aeo a coca 0 ccac a ccao 0 40985 99to P4 C acu-4 a8S 0 0 0fq~ c a -ICcam" 4 caca or4 -a av f"Mcca
'04 0 DIn in qr44leec 0c c000 cc a acoc a OCO0cc
~~~ vtin u-oa rim C~sr
11-7
O,
00 -OO00 a
C; 0 (% c C '0
f eqm OMIfl
CA Z 0, gn 00 -caoo04V4m
r4 C4 0C4*'
o~r 0%0 O%-4No C r4 9l-C N-4
M8 m * muI
I4 ~ ~ ge .c0E400 10 -00
N 00 U -W *00 Na sf 000
muzl n ~ %Din0%otE-4 r4 % -4
C!u- 149-
O-~o 00 0f- 4 C C
0~ .o in *e i a eab~4 49 Ifl;l 4% a C; 0
a,0 t* - i 0 *1 %D -%00 O - *tn r. w0N-0
C 0 0 r~
'C40 ane ca tn 510 v~P4 I a~fto 14 6 1 4
4 4 s 4 o
~ 0[,.-40 aC
0 0-4 0
u-- 8 Mq 4t I M fn Zip m
0 0
C3 a 0
o 0 40
en) C4U
E-4 E-4 Ch
o=t 0n 0o f- 0
cim E4P 0C.- 0% inin M 00~U'0% a
~C N~qCr4 r4 P-4
0 ~~~ 0 *0e4 0%
Q 0% L.40 94 ~0 0%CO 4 P
0 0 0
N N- o
ONNM'.0.c 4. m
C40 4 oer M
C;Co
SUM)
da Oc Co 0. E
o ~ *a
thoomi 1c; V 1;
Ni II~ tI 0
N- xD~r %n N
04
cc
'-4
a
CA0
S -4
0~ 64 0rIP4~~' a j
owaoa z "I
0 0 04
qe -4lIn - N fn 1~c000
ania
O-W *00 Or- -0
r. z 0 UN O *44r-0
94 .00;C C 4~ 4;09 14 0
a- 4 C" a..- V40
*o V4 r- N~0 0- NP4 C4 1cN
0 ; U!0 00 4
E-40 .00 In-c *Oe 0 *encen Er ca. % 0 V$
O 0 0.p4- C4. C 9
e~~01)I 000 04 00
C40 U2 W*Q0 W~
(44 So In .0 4 0 .0r
44 InIZD4 ~ ~ 1 14 It.4 nC;tri40-
No ONf * 0 O*4 a in.".V!C01InaEO ca 0 a
GON IS 0 -0 .
9 09
o o 0o o 0
wq 2E2 %0Mtn C49 r4
o4 00 0
goo
V~% a% 00 0 A
04o *d n WZC4 ZooNLf C4o.r
Co 21-4 ~ L O %0Lfl 0 oCo~~a 0. .. q 0
g 00 0
en 0r Co vo
.0koL
.00 9' ,
OM % U
*6~O Ch 0%C 0 '
W 00
W tow H 0%0
104 ~ ~ q Co C
2 ~ ~ - C04 20440 -4
~ . 0
1. %0.
oc ~ '4A A00 Cm4. O N%
0 cl> x t
11-a%
'-4
'41
a0 C
1-1-
0 ry 0
NOl
oo W.
co E-o ;
* r 0 ~ 0
aco14 £4 0
P7~ pa
a11-1
E-4 E-
0 0 00
,4 NIA p. 4 NM '-40t
00 ~ 0 * DO0n 0-3 .- 0
94xa. 9 *0; fn rO
. . N . 0.w110 C;0r 0 4 .
I.~N 0
N 4-014p%000 m4 .00W4 IflO4 %am
C o f 0u "E- Z4 *NO E-4 .A-4 E- C 0I
bd tn *or .- 4 In* 0E-4C
N0 oc 0 inc, c 0 0
0t29E N4r
0n 0 1 04~ t~wo
gu * 4 E* m
v-4 %D V N PMO A cc 0 0 0 0 0N M N.q .0 m . 0
mlmaA1 r-I inoq 0%0
io 0> ~ 2 4
0 l Bata69 0..4 r-f ino OcWco 69P4~ 0, CA6C4 r0c owo q.
C. 4 f" *C4 I o"04 4gSmj I h o
ca 9 d 0 4 0 0-4 a m 411 (nI4 EM f.0 ME.9 0 X m01 0~~jDIt f"hO 40 rf 0 0 D
0t N* qv * q. - *W*N0. r*uI* f" 04 f
0011411-14
4
04 C0
o Lo 0on to 0
o
on 00 N
N* 0. 03.en D f C4 toN to 4
00.090 en90 3:4
c" N 00 C
W W CD
0 0 (A2
MR 8
MQ
%IO*0 0 0
94 4
pato nr-
.- 4w *r 4 0?C4 00
04-E- 0PN 4 -
0 oiu;a C;00 4C;9
*nC-0 *N .0r-
Ho0 0 Go.qw .0r
11 0 .gnCDq
.-4
0h 40 Vn0
%0 U) CO 0 1N1
m in c *%, -w q
do O*40 G h-
a r ov; 0I.- Ot-49 C40w C4 2r
N04 m %DWI q Nen ent"C en
In %DJ - fWmu V CO 04 OO0 fCAk mo~w NwO% LAUino wOO%
m. r-im -i ur- N V
v-4- 4r- va m-4 W CO 0 -040~ r. o MV 0ONf
0:v4c enq~ w D r-(~ w N04cc
Ln tnr4 n r- 0 V oMO IL O t-r-- 4t o4I
.CO . d r . ~ q . . .
CO-4M( e-4(r'P4 r-4( C 4 C4 4
bcM mr0 00 0 00CCC O cU-x c 4 qrin in 4 4 A N Pui %~a %0
'-4
0z * ***
4
o.-,o~~ 0vI coo00Ct . . . . . . . 19 S *S
0'-4 a 0~ooc 000 000n r!04~V- N'% (4% ~
1-1- C- -(4 0-4 N 4 N N r4
0-4 00 0 000 00000 -4u4e InAorUccC)00
1*4 43A C-4 C; 4 4;4c* ;**
Q44V O* 0O 0
43~430 c0o0 000 coo
ra
4W UtC C ; ; C 4 3 C.
4~
:.;' VW 00 0000 0
41 . 4 L
4r 0004a 000 000 c0043WVO 1 00 0300 0,00
* 4340~. a 3 1. 00 0 0 0
U40 C4 We
43 W ~-4aco Mo c1o1cse
r-44
000O 000 000
000 000co 000
000vo 000 -00
A ac~E; 0.-i- 1.r-.- 01c0 0:C,.-40-4 0-4""e r4NN4 Onfn W~C wC t m
000. U: t U~j
.0;r: ;c ; C; C. FO. a.00004 00 0I-
Ni-l-I i-I042 z 10- -
00M M1qr 0.0 400
NWO~~iL ONV WUKr NflN0001-4 r-40 N .WU "10. Z4N CaN Ra00 0 a
r'011 0-41
00-4 0 V4 r cowcoo000000000
cm OM 0f'1. 00o00
M i-N 'INc NM f" * 0
0x0co 000 000 c0oo 22222
1-4 000000 000 000UO UOC
C4 11-17 490
APPENDIX III
GRAPHICAL METHOD FOR SOLVING ISLAND DIVIDED FLOWS
ISLAND SPLIT FLOW
Where an island or other obstruction in the river separates flow into
two or more channels over a substantial length (several cross sections),
the quantity of water passing on each side of the island must be determined
since total energy loss, past the island, must be the same for both sides.
The example in fig. III.1 illustrates how to solve the divided flow
problem graphically. The total discharge is proportioned between the north
and south channels, arbitrarily. The water surface elevation for the total
flow is determined for river mile 10.0, and a water surface profile is
calculated for each assumed discharge through the north channel and through
the south channel. The resulting potential water surface elevations at river
mile 10.8 are plotted in fig. 111.2. A "total" discharge curve is obtained
at river mile 10.8 by sumuing north and south channel discharges for comnon
water surface elevations. This total flow curve intersects the total river
discharge, 5000 cfs, at elevation 104.32, thereby defining the upstream
water surface elevation. By intersecting the north and south channel curves
at elevation 104.32, their respective discharges can be read from the figure.
111-1
00
'.4
-0 z -4 r-4 r-4 r-4 4
* 0-4 31A.10 0 0
-4 V4 Sal.0 -I I
00 151 " 8;4
2 n 100000
A0 6 -
'-V44
to4(lU .2 -PA 0
0a in 0 . & I0 0 1.i C4.4 L
cc a H 114 0 "
4 . C w 0 co
w0 CO
FA w 1 . 4 0 8- -40 0 N L 0
'A4 0. cocoa
0-o~ 00001.4 8 0 %D N-4,0
too 1. 0 4 ;C.10 1e "4-1r4 4P
P4 004J0 V-4-4
U *4 0
0004
w 00000
Flq. 111-i Example problem for $ubcritlcal islandtype flow computations
111-2
106
105__ _ _ _ _
R,
103
102___ __ __ _ -L
2 3 5Dicag In 10-F
Fi.112Gahcliteplto o iie
flwpsoniln
2111-
Uinr1 aM Anf adSECURITY CLASSIFICATION OF THIS PAGE (Mhen Data Entered')
REPORT DOCUMENTATION PAGE BE AD ISTOUCTIONS, BEFORE COMPLETIN¢G FORK'
I. REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPIENT'$ CATALOG NUMBER
Traningn nri imen 0.4. TITLE (end Subtitle) S. TYPE OF REPORT & PERIOD COVERED
Application of the HEC-2 Split Flow Option
S. PERFORMING ORG. REPORT NUMBER
7. AUTHOR(a) I. CONTRACT OR GRANT NUMBER(s)
Alfredo E. Montalvo
S. PERFORMING ORGANIZATION NAME AND ADDRESS I0. PROGRAM ELEMENT. PROJECT. TASK
US Army Corps of Engineers AREA & WORK UNIT NUMBERS
The Hydrologic Engineering Center609 Second Street, Davis, CA 95616
It. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE
April 1982IS. NUMBER OF PAGES
14. MONITORING AGENCY NAME & ADDRESS(IU different from Controlling Office) IS. SECURITY CLASS. (of this repot)
Unclassified
Iea. ECL ASSIFI CATION/ DOWNGRADINGSCHEDULE
16. DISTRIBUTION STATEMENT (of thle Report)
Distribution of this publication is unlimited
17. DISTRIBUTION STATEMENT (of Ihe abstract entered In Block 20, It different from Report)
IS. SUPPLEMENTARY NOTES
II. KEY WORDS (Continue on reverse aide it necessary and identify by block number)
Digital Computer, Split Flows, HEC-2, Backwater, Open-Channel Hydraulics,Lateral Weir Overflows
20. ABSTRACT lContinuen rovee aide It neeeeay and Identify by blo k ntuber)Training document designed to assist thie user of computer program HEC-2
split flow option and to acquaint them with its capabilities and limitations.Provide a detailed description of the HEC-2 split flow input requirements,output results, computation method and example applications.
FORM ]I
DD , JAN7 1473 EDITION OF I NOVSS IS OBSOLETE
SECURITY CLASSIFICATION OF THIS PAGE (When Date etereo