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HEC-5C, A Simulation Model for System Formulation and Evaluation March 1974 Approved for Public Release. Distribution Unlimited. TP-41

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4. TITLE AND SUBTITLE HEC-5C, A Simulation Model for System Formulation and Evaluation

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6. AUTHOR(S) Bill S. Eichert

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) US Army Corps of Engineers Institute for Water Resources Hydrologic Engineering Center (HEC) 609 Second Street Davis, CA 95616-4687

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12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES Presented at the Hydrologic Engineering Center, Seminar on Analytical Methods in Planning, 26-28 March 1974, Davis, California. 14. ABSTRACT Overview of generalized computer model (HEC-5) for simulation operation of multipurpose reservoir system and evaluating economic consequences for flood control and hydropower purposes. 15. SUBJECT TERMS simulation, flood control, system analysis, computer modeling, hydropower, reservoir regulation, flood damage reduction, multipurpose reservoirs, water resources project 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON a. REPORT U

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HEC-5C, A Simulation Model for System Formulation and Evaluation

March 1974 US Army Corps of Engineers Institute for Water Resources Hydrologic Engineering Center 609 Second Street Davis, CA 95616 (530) 756-1104 (530) 756-8250 FAX www.hec.usace.army.mil TP-41

Papers in this series have resulted from technical activities of the Hydrologic Engineering Center. Versions of some of these have been published in technical journals or in conference proceedings. The purpose of this series is to make the information available for use in the Center's training program and for distribution with the Corps of Engineers. The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products.

HEC-5C, A SIMULATION MODEL^ FOR SYSTEM FORMULATION AND EVALUATION

by B i l l S. ~ i c h e r t ~

1. Need f o r Hydrologic and Economic Simulat ion Elodel

Because of the great expenditure o f funds requ i red t o const ruc t s t ruc tu res t o reduce f l ood ing i n a r i v e r basin, i t i s important t o make sure t h a t each p r o j e c t b u i l t i s j u s t i f i e d and i s more des i rab le than any o ther a l t e r n a t i v e . I n a complex r i v e r basin where numerous system components e x i s t o r are requ i red t o reduce f lood ing, the eva luat ion o f each a1 t e r n a t i v e requ i res a l a rge number o f ca l cu la t i ons . Un t i 1 r e c e n t l y a l l such evaluat ions had t o be done by r a t h e r crude techniques o r by labor ious manual procedures, al though a few simple computer models cou ld be used on p a r t s o f the study. For example, a study made 10 years ago, requ i red t h a t 10 f l o o d con t ro l rese rvo i r s be considered i n f i rming up the design o f a few new rese rvo i r s i n a f l o o d con t ro l system. She hydrology requ i red i n opera t ing the system ( a f t e r the h i s t o r i c a l f lows throughout the bas in were known) f o r several h i s t o r i c a l f loods requ i red th ree men working f u l l t ime f o r about 4 months a t a cos t o f about 825,000. I n s p i t e of the l a rge t inie and cost, many s i m p l i f y i n g assumptions had t o be made, no economic eva luat ion was made and no a l t e r n a t i v e so lu t i ons were i nves t iga ted because o f the inanpower, funds, and t ime l i m i t a t i o n s . The same job can be done today w i t h greater d e t a i l and accuracy w i t h a s imula t ion model such as HEC-SC w i t h l ess cos t and manpower and, i n add i t ion , each a l t e r n a t i v e can be studied w i t h a few hours o f work and a 420 cortiputer run which w i 11 show the average annual damages a t a1 1 damage centers and the ne t system f l o o d bene f i t s . The i n i t i a l work i n assembling the r e s e r v o i r data i n the requ i red computer format f o r t he system requ i res about one man-week o f work. The determinat ion of t he h i s t o r i c a l f lows f o r a l l major f loods o f record throughout the system i s the major task and has t o be done by e i t h e r manual o r computer techniques, bu t could be done w i t h about 3-man nionths o f e f f o r t f o r t h i s basin. The v e r i f i c a t i o n o f the nlodel on h i s t o r i c a l f l oods can be done i n a couple o f man ri~onths. Once the above tasks are cmlpleted, d e t a i l e d s imulat ions can be made e a s i l y and w i t h l i t t l e expense f o r numerous combinations o f reservoi r s , and o the r a1 te rna t i ves i n c l u d i n g nonstruc- t u r a l a1 te rna t i ves .

'presented a t The Hydrologl~ Englneerlng Center, Seinlnar on Analytical Methods i n Planning, 26-28 March 9974 a t Davjs, C a l i f o r n i a .

' ~ i 1 l 5 . Elcher t , D i rec to r , The Yydrologlc Engineerfng Center, 609 Second St reet , Su i te i , Davis, Cai i f o r n i a 95615.

2. Purpose o f Hater Resources Systenl Simulat ion Model - HEC-5C

This program was developed t o ass is t i n planning studies required f o r the evaluat ion o f proposed changes t o a system and t o ass i s t i n s i z i n g the system components for f l ood cont ro l and conservation require- wmts f o r each con~ponent reconended f o r the system. The program can be used i n studies made immediately a f te r a f lood t o ca lcu la te the prepro jec t condi t ions and t o show the e f fec ts of ex i s t i ng and/or proposed reservo i rs on f lows and damages i n the system. The program should a lso be useful i n se lec t ing the proper reservo i r releases throughout the system during f l ood emergencies i n order t o minimize f looding as much as possib le and y e t empty the system as qu ick ly as possible whi le maintaining the proper balance o f f l ood con t ro l storage among the reservoirs.

The above purposes are accompl ished by s imulat ing the sequenti a1 operat ion o f various system components o f any conf igurat ion f o r short i n t e r v a l h i s t o r i c a l o r synthet ic f loods o r f o r long durat ion nonflood periods, o r f o r conlbina ti ons of the two. Specif i c a l l y the program may be used t o determine:

a. Flood con t ro l and conservation storage requirements o f each reservo i r i n the system.

b. The inf luence of a system of reservoirs, o r other structures on the spa t i a l and temporal d i s t r i b u t i o n o f runo f f i n a basin.

c. The evaluat ion o f operational c r i t e r i a f o r both f l ood con t ro l and conservation f o r a system of reservoirs.

d. The average annual f l ood damages, system costs, and excess f l ood bene f i t s over costs.

e . The deterr~i inat ion o f the system of ex i s t i ng and proposed reservoi r s o r o ther s t r uc tu ra l o r nonstructural a l t e rna t i ves t ha t r e s u l t s i n the maxirnuni ne t benef i t for f lood con t ro l f o r the system by making s imulat ion runs f o r selected a l t e rna t i ve systems.

3. Computer Requi rements

The program, w r i t t e n i n FORTRAN I V , was developed on a U N I V A C 1108 computer w i t h 64,UOO words o f storage. The U N I V A C version can simulate the operation o f 15 reservoirs, 25 cont ro l points, 5 diversions, and 9 power plants, using up t o 50 t ime periods i n each f lood o r nonflood event. Dimension l i m i t s have been increased f o r a CDC 7600 computer which al lows the s imulat ion o f 35 reservoirs, 75 cont ro l points, 11 diversions, and 9 power p lants f o r up t o 100 t ime periods f o r each runo f f event.

4. General Capabi l i t i e s o f Program

a. Configurat ion o f system - any system conf igurat ion may be used as long as dimension l i m i t s are not exceeded f o r number o f reservoirs, number o f control points, number o f diversions, etc.

(1) Reservoirs which have f lood cont ro l storage may be operated t o minimize f lood ing a t any number o f downstream cont ro l points.

( 2 ) R e s e r v ~ i r 5 w i t h conservation storage w i l l be operated f o r t h e i r own requirements ( p o ~ e r o r low f low) and can be operated f o r any nmber o f downstream cont ro l points.

(3 ) Reservoirs may be eas i l y deleted from the system.

( 4 ) Reservoirs i n systeni are kept i n balance ( i n the same degree o f t roub le) as rnuch as possible.

b. Outfls\irs can be speci f l e d f o r any number o f reservo i rs f o r any o r a l l t ime periods and program w i l l ad jus t o ther reservo i r releases as

.necessary; otherwise program w i 11 determine a1 l reservoi r releases.

c. Ef fec ts o f forecast e r ro rs can be evaluated by speci fy ing the number o f forecast periods and a corresponding contingency allowance ( i .e., e r r o r i n forecast ing).

d. Local f lows can be calculated from observed discharges and reservo i r releases ; system operation can be performed o r omitted a f t e r f lows are de ten~ l i ned.

e. The rnu l t i f l o o d opt ion may be used t o operate the system f o r a continuous per iod o f record ( f o r example, 5 events each containing 4 years o f monthly data may be used f o r a t o t a l o f 20 years). Also a mixture o f computational inter ivals may be used such as running a monthly operation f o r a few years (assuming no rou t ing i f desired) and then operating f o r d a i l y o r hour ly flows dur ing a major f l ood (w i t h de ta i led f lood rou t inq ) and then back t o a weekly o r monthly rou t ing i n te r va l , etc. An un l imi ted number o f events can be simulated i n t h i s manner.

f . Evaporation and a monthly va r i a t i on i n reservo i r operating leve ls can be considered i n the rout ings i f desired.

g. Volu~ninous output can be suppressed by requesting only a summary output. Detai led output f o r a few selected con t ro l po in ts can a lso be obtai ned.

h. Stream routing may be accomplished by the following methods:

(1) idodified Puls, Working RID , Muskingum, Straddle Stagger, and Ta tum.

( 2 ) Each routing method may be used several times for each reach.

(3) Actual releases that are routed by nonlinear (storage-outflow i s not a s t ra ight l ine) methods (Modified Puls or Working R I D ) use a l inear approximation fo r determining reservoir releases.

(4 ) Natural and cumulative local flows are calculated.

i . Reservoir routi ng i s based on:

(1 ) Accounting methods (release i s determf ned based on desired operation, storage i s equal to inflow less outflow plus previous storage).

(2) Surcharge routing - when desired release i s greater than physical out le t capacity, the arithmetical method, which i s a t r i a l and er ror method, i s used which will provide the same resul ts as the Modified Puls method.

( 3 ) Emergency releases - when desired release for current period plus channel capacity releases fo r future periods (up to l imit of fore- s ight specified) would cause reservoir t o exceed maximum flood storage i n current or future periods, a release i s made f o r the current period (up t o channel capacity or the out le t capacity) so that the reservoir does not exceed top of flood pool i n future period.

j. Multifloods

(1) Read and operate an unlimited number of floods fo r a reservoi r system.

(2) The ser ies of floods can each s t a r t a t different reservoir storages or f r o m same storages or can be continued using the storages from the previous flood.

( 3 ) Operate up t o 9 rat ios s f any or a l l floods read.

( 4 ) Long floods may be routed by d i v i d i n g the flood into flow events which are each less than the dimension limit of the time array. This may be done by manually set t ing i n several s e t s of flow data (with each less than the dimension l imi t ) or by allowing the computer to generate separate floods (when the data read exceeded the dimension 1 imi t ) . A nlinimum of a 10 period overlap between floods i s used t o preserve conti n u i ty.

-- ( 5 ) Per iod o f record ana lys is may be made by analyz ing a s e r i e s

o f f l oods cons is t i ng o f monthly o r weekly data dur ing nonflood per iods and d a i l y o r m u l t i h o u r l y data dur ing f l o o d periods.

k. Ui vers i ons

(1) i l i vers ions can be made from any r e s e r v o i r o r c o n t r o l po in t . Only one d i ve rs ion from each con t ro l p o i n t o r r e s e r v o i r i s a1 lowed.

(2) Divers ions can be made t o any downstream con t ro l p o i n t o r r e s e r v o i r o r ou t o f the system.

( 3 ) u ivers ions may be routed using any l i n e a r method al lowed and nlul t i p 1 i ed by a constant represent ing the percent o f r e t u r n f low.

(4) Types o f d ivers ions

( a ) u ivers ions can be a func t i on of i n f l ows .

( b ) Divers ions can he func t ions o f r e s e r v o i r storages.

( c ) Divers ions can be constant.

( d ) Divers ions can be constant f o r c e r t a i n periods such as 50 c f s f o r January, 40 c f s f o r February, e t c .

(e ) Divers ions can be made f o r a l l excess water above the t o p of conservat ion pool up t o the d i ve rs ion p ipe capaci ty .

5. Reservoir Operat ional C r i t e r i a

a. Reservoirs are operated t o s a t i s f y cons t ra in ts a t i n d i v i d u a l rese rvo i r s , t o main ta in s p e c i f i e d f lows a t downstream con t ro l p o i n t s , and t o keep the system i n balance. Constra ints a t i n d i v i d u a l r e s e r v o i r s are as fo l l ows :

( 1 ) When the l e v e l o f a r e s e r v o i r i s between the top of conser- v a t i o n pool and the top o f f l o o d pool, releases are made t o attempt t o draw the r e s e r v o i r t o the top o f conservat ion pool w i thout exceeding the designated channel capaci ty a t t i le r e s e r v o i r o r a t downstream c o n t r o l p o i n t s f o r which the r e s e r v o i r i s being operated.

(2 ) lleleases are made equal t o o r g reater than the minimum des i red f lows when the r e s e r v o i r storage i s g reater than the top o f b u f f e r storage, and o r equal t o the requ i red f l o w i f between l e v e l one and the top o f b u f f e r pool . No re leases are made when the r e s e r v o i r i s below

level one (top of inactive pool ). Releases calculated fo r hydropower requiremnts wi 11 override minimum flows i f they are greater than the control 1 ing desired or required flows.

(3 ) Releases are made equal to or less than the designated channel capacity a t the reservoir unti 1 the top of flood pool i s exceeded, then a i l excess flood water i s dumped i f suff ic ient out le t capacity i s available. If insufficient capacity ex is t s , a surcharge routing i s made. Input options permit channel capacity releases (or greater) t o be made prior t o the time that the reservoir level reaches the tog of the flood pool i f forecasted inflows are excessive.

(4) The reservoir release i s never greater (or less ) than the previous period release plus (or minus) a percentage of the channel capacity a t the dam s i t e unless the reservoir i s i n surcharge operation.

b. Operational c r i t e r i a fo r specified downstream control points are as fol lows:

(1) Releases are not made (as long as flood storage remains) which wuld contribute t o flooding a t one or more specified downstream locations during a predetermined number of future periods except to sa t i s fy minimum flow and rate-sf-change of release c r i t e r i a . The number of future periods considered i s the lesser of the number of reservoir release routing coefficients or the number of local flow forecast perf sds .

(2) Releases are made, where possible, t o exactly maintain downstrean1 flews a t channel capcity ( fo r flood operation) or f o r minimum desired or required f l ows ( fo r conservation operation). I n making a release determination, local (intervening area) flows can be multiplied by a contingency allowance (greater than 1 for flood control and less than 1 f o r conservation) to account fo r uncertainty in fore- casting these flows.

c. Operational c r i t e r i a fo r keeping a reservoir system in balance are as follows:

( 1 ) Where two or more reservoirs are i n parallel operation above a comnon control point, the reservoir tha t i s a t the highest index level , assuming no releases for the current time period, will be operated f i r s t t o t r y t o increase the flows i n the downstream channel t o the target flew. Then the remaining reservoirs will be operated i n a pr ior i ty established by index levels to attempt to f i l l any remaining space i n the downstream channel without causing flooding during any of a specified number of future periods.

( 2 ) If one of two parallel reservoirs has one or more reservoirs upstreani whose storage should be considered in determining the pr ior i ty of releases from the two para1 le l reservoirs, then an equivalent index level i s deterniined for the tandem reservoiis based on the combined storage in the tandem reservoi r s .

( 3 ) If two reservoi rs are i n tandem (one above the o ther ) , the upstreain reservoir can be operated fo r control points between the two reservoirs. In addition, when the downstream reservoir i s being operated for control points, an attempt i s made to b r i n g the upper reservoir t o the same index level as the lower reservoir based on index levels a t the end of the previous time period.

6. Average Annual Flood Uamage Evaluation

Average annual damages (AAD) or damages for specific floods can be computed fo r u to 9 different categories for any or a l l control points (nonreservoirs ! using one or more rat ios fo r each of several his tor ical or synthetic floods. They will be computed for the following three conditions :

a . Natural or unregulated conditions.

b. Regulated conditions due to the reservoir system assumed.

c. Full regulation a t those reservoir s i t e s (uncontrolled local flows).

barnages calculated for base condi Lions (normally natural f l ows) usinq selected floods and ra t ios arc adjusted to average annual damages, computed by integrating the base conditions damage frequency curve or by using a predetermined average annual damage, The corresponding adjustment i s printed out to help verify the appropriateness of the floods and rat ios selected i n integrating the damage curve for base conditions. Uamages fo r modified conditions are based on the cumula- t i v e product of tlie damages associated with the modified peak flow for each flood ( fo r a certain damage center) times the probability interval assigned to each flood from the base condition integration. See figure 1 fo r an exanlple of the RAD integration. The damage fo r the uncontrolled local flows are also calculated in a similar manner to the modified conditions.

The damage reduction due to the proposed system i s based on the difference between the AAD f o r the base conditions and the modified conditions. I f an existing reservoir system exis t s the damage reduction can be based on the difference between the base conditions and the modified conditions where the base conditions were determined from another simulation run (exi st inq reservoirs only).

A separate set of damage data can be used i f the modi f ied condi t ion damges do no t f o l l ow the base condi t ion discharge-damage curves as would be the case for a levee, channel improvement o r nonstructural a1 t e r n a t i ve such as f l ood proof i ng , r e l o c a t i on, purchase, f l ood p l a i n zoning, e tc .

7. iqul ti f l ood Select ion and Operatiow

The se lect ion o f the f loods used i n operating the system, i s o f garmount importance i n the deteminat ion o f the average annual damages. The f loods selected niust generate the peak f lows a t the damage centers ( p a r t i c u l a r l y the key ones) which repmsent the f u l l range s f the f low- frequency-damage re la t ionsh ip fo r base condi t ions as wel l as f o r modif ied condi t ions.

Even using a1 3 h i s t o r i c a l f loods o f record may introduce some bias i n the average annual damage if most h i s t o r i c a l f loods centered over a ce r t a i n p a r t o f the basin by chance and not over other areas. For instance one dam s i t e may have several severe h i s t o r i c a l f loods whi le another dam s i t e immediately adjacent t o t ha t area may, due t o chance, not have had any severe floods.

While i t i s possible i n the program, WEC-56, t o use only a s ing le f l ood and several r a t i o s o f t h a t f l ood i n computing average annual damages, t h i s procedure could introduce considerable b ias i n the resu l t s . It w u l d be f a r be t t e r t o use several h i s t o r i c a l f loods w i t h storm centering$ throughout the basin and t~ use several r a t i o s o f those f loods t o obta in flows a t the damage centers representing the f u l l range o f the flow-fmquency-daiiiar~e re la t ionsh ip f o r base condi t ions and f o r regulated condit ions. A good idea o f the adequacy o f the selected f loods and r a t i o s f o r reproducing base condit ions can be obtained by looking a t the cor rect ion f ac to r p r i n ted out a t each damage center f o r each damage category. This cor rect ion fac tor i s the r a t i o o f average annual damage computed by i nteqra t i ng the inpu t frequency-damage curve ( o r from inpu t on DA card) t o the average annual cianiage computed by assigning probahi l i ty i n te r va l s t o the system f lows computed by HEC-5C. When the cor rect ion f ac to r i s close t o 1.0, i t represents the base condi t ions very we l l , bu t may not represent the modif ied condi t ion i f on ly one o r two regulated f loods cause dantaqe. I t i s desirable t o have one f l ood t h a t does not cause darnages so t h a t the sma'llest f l ood w i t h damage doesn't receive too large a p r o b a b i l i t y i n t e r va l . I t i s a lso necessary t o have several modi f ied h i s t o r i c a l f loods produce dan~ages spread out over the modi f ied frequency curve s i nce the i n teg ra t i on o f the damage-frequency curve i s based on rectangular blocks f o r each f l ood using the p r o b a b i l i t i e s from the base condi t ion curve.

u Studies are c u r r e n t l y being made a t The Hydrologic Engineering Center

t o he lp e s t a b l i s h c r i t e r i a f o r the s e l e c t i o n of t he f loods and r a t i o s t o use.

8. Eva1 ua t i on o f A1 t e r n a t i v e Rese~vs i r Systems

I f t h i s computer program i s t o be used t o evaluate proposed reservo i r s , then the data cards should be assembled so t h a t a1 1 proposed rese rvo i r s a re included, even if some of them would serve as a1 te rna t i ves o f others. Contro l po in t s should be se lec ted and coded f o r a l l damage centers, c o n t r o l p o i n t s f o r r e s e r v o i r operat ion, and i n fo rma t ion po in t s . Once the e n t i r e system i s coded, a s i n g l e card can be used t o de le te rese rvo i r s fro111 t i le system f o r each a l t e r n a t i v e system selected. This card can be used t o d e l e t e ally r e s e r v o i r i n the system except f o r downstream tandem r e s e r v o i r s ( these rese rvo i r s can be deleted by removing the r e s e r v o i r cards). Flood damages f o r a s i n g l e f l o o d ( o r average annual f lood damages) can be evaluated a t any number of c o n t r o l po in ts . Reservoir costs can a l s o be evaluated by silowing how the costs vary w i t h r e s e r v o i r storage based on the top o f f lood c o n t r o l storage. I f costs and average annual f l o o d damdges a re ca lcu la ted , the ne t system f l o o d b e n e f i t s w i l l be p r i n t e d o u t f o r each a l t e r n a t i v e system operated. By c a r e f u l se lec t i on o f a l t e r n a t i v e systems, the system t h a t produces the maximum n e t f l o o d b e n e f i t s can be determined by a reasonable number o f separate computer runs.

9. Eva lua t ion o f Nonreservoi r A 1 t c r n a t i v e s

S t r u c t u r a l and nonst ruc tura l a1 t e r n a t i ves t o c e r t a i n rese rvo i r s can a l s o be evaluated i n the s y s t c ~ r ~ s imu la t i on w i t h o r w i thou t rese rvo i r s i n the system. The ex is tence o f a levee o r channel improvement can be r e f l e c t e d i n the r e s e r v o i r system opera t ion by changing the channel capac i ty i f appropr iate. A t the present t ime on l y one s e t o f r o u t i n g c r i t e r i a can be read f o r each reach and thus the na tu ra l and mod i f i ed rou t i ngs use the same c r i t e r i a . This l i m i t a t i o n requ i res t h a t when the r o u t i n g c r i t e r i a i s d i f f e r e n t between na tu ra l and modi f ied cond i t ions , the na tu ra l f lows rtiust be ca l cu la ted by a separate computer run and entered on cards f o r mod i f ied cond i t ions . Costs o f nonreservoi r a l t e r n a t i v e s can be st~own as func t ions o f the channel discharges. For a g iven design discharge an i n t e r p o l a t i o n i s made t o determine the c a p i t a l cos t app l i cab le t o the c o n t r o l p o i n t . The average annual f l o o d damages can be evaluated i n the same manner as f o r r e s e r v o i r a1 te rna t i ves . However, the zero dan~age p o i n t can be automat ica l l y changed t o the design discharge f o r mod i f i ed cond i t ions if a c o n t r o l p o i n t cos t card i s read. Two se ts of damage cards can be read as an a l t e r n a t i v e t o the above procedure, i n represent ing n a t u r a l and regu la ted cond i t ions , so t h a t t he e n t i r e damage curve can be changed f o r regu la ted cond i t ions .

Nonslructura l a1 te rna t i ves ( f lood proofing, f lood p l a i n zoning, e tc . ) can be handled i n the same manner as s t r u c t u r a l a l t e r n a t i v e s (usua l l y by us ing two sets of damage cards), however the nonst ruc tura l a1 t e r n a t i v e w i l l r e q u i r e d e f i n i n g the upper l i m i t of the f lood proof ing , zoning, etc. as a channel capaci ty o r design discharge.

10. Use o f HEC-5C i n Flood Control System Se lec t ion

As can be seen i n t a b l e 7 , q u i t e a few r e s e r v o i r systems have been s imulated using IiCC-5. liiost o f these systems have used the f l ood con t ro l vers ion which was released i n !.lay 1973, The vers ion which a l so inc ludes conservat ion operat ion (HEC-5C) has no t been o f f i c i a l l y released ye t , b u t i t has been used f o r f l o o d con t ro l s imula t ion and average annual damages have been ca lcu la ted f o r the Susquehanna, Red River o f t he North, and the Grand (6Jeosho) K i ver basins . Monthly conservat ion operat ion has been used on the Pajaro River, t he Red River o f the North, t he Hudson River Basin and several hypothet ica l systems. O f t he s tud ies conducted t o date by HEC using t h i s model , f i v e of them have been f o r p r e l in i inary p lann ing s tud ies and have been used f o r t he sole purpose o f determining the regu la ted f lows throughout the bas in f o r various h i s t o r i c a l and syn the t i c f loods. Each one o f these basins a l so had a HEC-1 r a i n f a l l r u n o f f data model developed i n order t o c a l c u l a t e t h e r u n o f f from syn the t i c f loods and t o use r a i n f a l l t o ge t a b e t t e r d i s t r i b u t i o n o f r u n o f f f o r h i s t o r i c a l f loods. The study o f t he 15 r e s e r v o i r system f o r the T r i n i t y R iver bias niade i n connection w i t h Design Meniorandunt s tudies fo r t he Tennessee Colony r e s e r v o i r i n order t o determine the f l o o d c o n t r o l storage i n t h a t downstream p r o j e c t (14 rese rvo i r s above i t ) and t o eva l - uate var ious a1 t e r n a t i ve plans o f channel improvements below the p ro jec t . The work on the e x i s t i n g f i v e r e s e r v o i r Merrimack bas in i s expected t o use HEC-5 i n a rea l - t ime operat ion mode using fo recas t ing rou t ines and automatic data c o l l e c t i o n by J u l y o f 1975.

The Susquehanna River Basin has 12 rese rvo i r s e x i s t i n g o r under construct ion, and another 22 p o t e n t i a l reservo i r s i t e s are being inves t iga ted along w i t h o the r s t r u c t u r a l and nonst ruc tura l a l t e r n a t i v e s i n a p re l im ina ry plannning study being conducted by the Bal t imore U i s t r i c t o f f i c e o f the Corps the Ht.C and a p r i v a t e consu l t ing f i r m Anderson-Nichols o f Iroston, l"lssachusetts. The dec is ion f o r s e l e c t i o n of' the desi red system w i l l make important use o f t h e average annual damage reduct ion and ne t b e n e f i t s o f the a l t e r n a t i v e systems which w i l l be p r i n t e d o u t fo r each a l t e r n a t i v e evaluated by WEC-SC.

11. E4odel Data Requirements and Output

The i n p u t data requirements f o r HEC-5C can be minimal f o r very p m l i m i n a r y p lanning s tud ies o r i t can be very d e t a i l e d f o r modeling e x i s t i n g systems. The minimum data requirements are as fo'11ows:

a. General Information (4 cards)

(1) Ti t le cards fo r Job (3 cards)

( 2 ) S i x miscellaneous items including the number of periods o f flow data, time interval of flows, e tc .

b. Reservoir Data ( 4 cards per reservoir)

( 1 ) Reservoir capacities for top of conservation and top of flood control elevations.

( 2 ) Oownstreanl control points for which reservoir i s operated

(3) Reservoir storage/outflow tables

c. Control Point (including reservoirs) Data (3 cards per control point)

(1 ) Identification number and t i t l e

( 2 ) Channel capacity

(3) Channel routing c r i t e r i a

d. Flow Uata

Inflow or local flow data for each control point for one or more historical or synthetic floods.

Additional input inforn~ation useful for planning studies:

a. Average Annual Uamage Data (a n~inimum of 4 cards per damage center)

Peak d i scharge-damage-frequencies tables

b. Lost Data ( 1 card per control point)

(1 ) Keservoir capital costs vs storage

( i Control point capital costs vs channel discharge and (3) Capital recovery factor

(4 ) Annual operati on and inai n tenance costs

The output available from the program includes

a. Listing of input data

b. Results of system operat ion arranqed by downstreani sequence o f c o n t r o l po in ts .

c. Results o f system opera t ion arranged by sequence o f t ime per iods

d. Sumrrlas-y o f f l o o d i f i g f o r system

e. Summary o f reservoi r re1 eases and con t ro l p o i n t f lows by pe r iod

f . Summary o f conservat ion operat ion if monthly r o u t i n g was made

g. Sunmary o f maxinluril ff ows, storages, etc., f o r each f l o o d event

h. Sumary of ~:iaximuin and i~rinimurn data f o r a l l f loods

i. Sumnjary o f average annual damages

j. Sumn~ary o f system costs (annual and c a p i t a l ) and ne t bene f i t s . Exan~ples o f some o f the summaries are shown as f i gu res 2-12.

12. Stra tegy f o r Se lec t ion s f A l t e r n a t i v e Systems

For systems w i t h on ly a few poss ib le components the s t ra tegy f o r determining the best a l t e r n a t i v e s can he q u i t e simple s ince each poss ib le a l t e r n a t i v e can be evaluated. For systems w i t h a l a rge number o f poss ib le a1 te rna t i ves , the s t ra tegy can be d i f f i c u l t t o predetermine and the best a v a i l a b l e procedure t o f o l l o w may be t o simply s e l e c t a l t e r n a t i v e s t o be evaluated one a t a t ime f o l l o w i n g a c a r e f u l review o f in format ion obta ined from previous runs.

Cer ta in econon~ic c r i t e r i a must be observed f o r the f i n a l system selected. The incremental cos t o f t he new components o f the proposed system i~rust be 'less than the damage reduct ion accomplished by t h e new components. I n add i t i on , each p r o j e c t must be j u s t i f i e d on the bas is o f the l a s t increment added, That i s t o say, t he cos t o f each p r o j e c t must be l ess than the d i f f e r e n c e between the average annual damages o f the proposed system w i t h and wi thout t h a t p r o j e c t .

A c e r t a i n m i nir~,urn performance c r i t e r i a i s a1 so necessary. This phi losophy says t h a t i f a c e r t a i n l e v e l o f p ro tec t i on can no t be provided by tire system then it would be b e t t e r n o t t o b u i l d any s t ruc tu res than t o g i v e the p u b l i c a sense o f f a l s e secu r i t y .

With the above ideas i n mind i t seenis necessary t o f i r s t determine a n~inirnum system t h a t w i 11 prov ide an acceptable l e v e l o f p ro tec t i on . Next see i f var ious a l t e r n a t i v e s can be used t o ge t a l a r g e r value o f the maximum n e t bene f i t s . When the nlaximum n e t b e n e f i t s appears t o be obta ined (and i t i s p o s i t i v e ) then each p r o j e c t should be deleted i n

turn t o see i f that project prevented more damages than i t cost to build. The process of maximizing the net benefits by selecting a1 ternatives and evaluating using HEC-SC, a t present, can only be based on good engineering judgment. After a few studies are completed using t h i s new tool , perhaps more defini te guidance wi 11 be available.

13. Future Use of Model fo r Multipurpose Systems

The current version of the program does have capabi l i t ies for m u 1 t i - purpose operation of reservoir systems, b u t does not have multipurpose economic evaluation routines. While the program can operate for low flows a t one or more downstream points, for flood control operation and for i ndi vi dual tiydropower requi rements , the conservation capabi l i t i e s have not been tested on a suff ic ient number of systems to provide the necessary confidence . When a few more sys tems have been successful ly operated for conservation and flood control together, that confidence wi 11 be obtained.

The major additions necessary for the future are i n the area of hydropower systems, multipurpose benefit evaluation and extensive testing.

14. Conclusions

I t appears tha t the IiEC-5C simulation model should be a useful tool - fo r planners to evaluate the e f fec ts of water resource projects and

nonstructural alternatives in most r iver basins because i t can accurately, quickly, and inexpensively simulate the hydrologic and economic responses of the systen~. While much of the detailed analysis of hydrology, reservoir regulations, and economics can be accomplished by the model, considerable engineering ingenuity wi 11 be required t o insure that the proper data i s used i n the nlodel, that the model i s giving valid resu l t s , and that the proper sequence of alternatives are evaluated i n order to determine the best plan for the reduction of damages in a basin.

I t also seems probable that the model will be useful for simulatinq niultipurpose reservoir operation. In this connection considerable work will be required to develop economic and social parameters to allow multipurpose evaluation of the system alternatives similar to flood control.

Considerable experience and research w i 11 be required to develop procedures, techniques and/or optimization subroutines which will enable the prograin to be used i n the most e f f ic ien t manner i n the selection of the best n~ultipurpose al ternat ives for the basin.

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12

Technical Paper Series TP-1 Use of Interrelated Records to Simulate Streamflow TP-2 Optimization Techniques for Hydrologic

Engineering TP-3 Methods of Determination of Safe Yield and

Compensation Water from Storage Reservoirs TP-4 Functional Evaluation of a Water Resources System TP-5 Streamflow Synthesis for Ungaged Rivers TP-6 Simulation of Daily Streamflow TP-7 Pilot Study for Storage Requirements for Low Flow

Augmentation TP-8 Worth of Streamflow Data for Project Design - A

Pilot Study TP-9 Economic Evaluation of Reservoir System

Accomplishments TP-10 Hydrologic Simulation in Water-Yield Analysis TP-11 Survey of Programs for Water Surface Profiles TP-12 Hypothetical Flood Computation for a Stream

System TP-13 Maximum Utilization of Scarce Data in Hydrologic

Design TP-14 Techniques for Evaluating Long-Tem Reservoir

Yields TP-15 Hydrostatistics - Principles of Application TP-16 A Hydrologic Water Resource System Modeling

Techniques TP-17 Hydrologic Engineering Techniques for Regional

Water Resources Planning TP-18 Estimating Monthly Streamflows Within a Region TP-19 Suspended Sediment Discharge in Streams TP-20 Computer Determination of Flow Through Bridges TP-21 An Approach to Reservoir Temperature Analysis TP-22 A Finite Difference Methods of Analyzing Liquid

Flow in Variably Saturated Porous Media TP-23 Uses of Simulation in River Basin Planning TP-24 Hydroelectric Power Analysis in Reservoir Systems TP-25 Status of Water Resource System Analysis TP-26 System Relationships for Panama Canal Water

Supply TP-27 System Analysis of the Panama Canal Water

Supply TP-28 Digital Simulation of an Existing Water Resources

System TP-29 Computer Application in Continuing Education TP-30 Drought Severity and Water Supply Dependability TP-31 Development of System Operation Rules for an

Existing System by Simulation TP-32 Alternative Approaches to Water Resources System

Simulation TP-33 System Simulation of Integrated Use of

Hydroelectric and Thermal Power Generation TP-34 Optimizing flood Control Allocation for a

Multipurpose Reservoir TP-35 Computer Models for Rainfall-Runoff and River

Hydraulic Analysis TP-36 Evaluation of Drought Effects at Lake Atitlan TP-37 Downstream Effects of the Levee Overtopping at

Wilkes-Barre, PA, During Tropical Storm Agnes TP-38 Water Quality Evaluation of Aquatic Systems

TP-39 A Method for Analyzing Effects of Dam Failures in Design Studies

TP-40 Storm Drainage and Urban Region Flood Control Planning

TP-41 HEC-5C, A Simulation Model for System Formulation and Evaluation

TP-42 Optimal Sizing of Urban Flood Control Systems TP-43 Hydrologic and Economic Simulation of Flood

Control Aspects of Water Resources Systems TP-44 Sizing Flood Control Reservoir Systems by System

Analysis TP-45 Techniques for Real-Time Operation of Flood

Control Reservoirs in the Merrimack River Basin TP-46 Spatial Data Analysis of Nonstructural Measures TP-47 Comprehensive Flood Plain Studies Using Spatial

Data Management Techniques TP-48 Direct Runoff Hydrograph Parameters Versus

Urbanization TP-49 Experience of HEC in Disseminating Information

on Hydrological Models TP-50 Effects of Dam Removal: An Approach to

Sedimentation TP-51 Design of Flood Control Improvements by Systems

Analysis: A Case Study TP-52 Potential Use of Digital Computer Ground Water

Models TP-53 Development of Generalized Free Surface Flow

Models Using Finite Element Techniques TP-54 Adjustment of Peak Discharge Rates for

Urbanization TP-55 The Development and Servicing of Spatial Data

Management Techniques in the Corps of Engineers TP-56 Experiences of the Hydrologic Engineering Center

in Maintaining Widely Used Hydrologic and Water Resource Computer Models

TP-57 Flood Damage Assessments Using Spatial Data Management Techniques

TP-58 A Model for Evaluating Runoff-Quality in Metropolitan Master Planning

TP-59 Testing of Several Runoff Models on an Urban Watershed

TP-60 Operational Simulation of a Reservoir System with Pumped Storage

TP-61 Technical Factors in Small Hydropower Planning TP-62 Flood Hydrograph and Peak Flow Frequency

Analysis TP-63 HEC Contribution to Reservoir System Operation TP-64 Determining Peak-Discharge Frequencies in an

Urbanizing Watershed: A Case Study TP-65 Feasibility Analysis in Small Hydropower Planning TP-66 Reservoir Storage Determination by Computer

Simulation of Flood Control and Conservation Systems

TP-67 Hydrologic Land Use Classification Using LANDSAT

TP-68 Interactive Nonstructural Flood-Control Planning TP-69 Critical Water Surface by Minimum Specific

Energy Using the Parabolic Method

TP-70 Corps of Engineers Experience with Automatic Calibration of a Precipitation-Runoff Model

TP-71 Determination of Land Use from Satellite Imagery for Input to Hydrologic Models

TP-72 Application of the Finite Element Method to Vertically Stratified Hydrodynamic Flow and Water Quality

TP-73 Flood Mitigation Planning Using HEC-SAM TP-74 Hydrographs by Single Linear Reservoir Model TP-75 HEC Activities in Reservoir Analysis TP-76 Institutional Support of Water Resource Models TP-77 Investigation of Soil Conservation Service Urban

Hydrology Techniques TP-78 Potential for Increasing the Output of Existing

Hydroelectric Plants TP-79 Potential Energy and Capacity Gains from Flood

Control Storage Reallocation at Existing U.S. Hydropower Reservoirs

TP-80 Use of Non-Sequential Techniques in the Analysis of Power Potential at Storage Projects

TP-81 Data Management Systems of Water Resources Planning

TP-82 The New HEC-1 Flood Hydrograph Package TP-83 River and Reservoir Systems Water Quality

Modeling Capability TP-84 Generalized Real-Time Flood Control System

Model TP-85 Operation Policy Analysis: Sam Rayburn

Reservoir TP-86 Training the Practitioner: The Hydrologic

Engineering Center Program TP-87 Documentation Needs for Water Resources Models TP-88 Reservoir System Regulation for Water Quality

Control TP-89 A Software System to Aid in Making Real-Time

Water Control Decisions TP-90 Calibration, Verification and Application of a Two-

Dimensional Flow Model TP-91 HEC Software Development and Support TP-92 Hydrologic Engineering Center Planning Models TP-93 Flood Routing Through a Flat, Complex Flood

Plain Using a One-Dimensional Unsteady Flow Computer Program

TP-94 Dredged-Material Disposal Management Model TP-95 Infiltration and Soil Moisture Redistribution in

HEC-1 TP-96 The Hydrologic Engineering Center Experience in

Nonstructural Planning TP-97 Prediction of the Effects of a Flood Control Project

on a Meandering Stream TP-98 Evolution in Computer Programs Causes Evolution

in Training Needs: The Hydrologic Engineering Center Experience

TP-99 Reservoir System Analysis for Water Quality TP-100 Probable Maximum Flood Estimation - Eastern

United States TP-101 Use of Computer Program HEC-5 for Water Supply

Analysis TP-102 Role of Calibration in the Application of HEC-6 TP-103 Engineering and Economic Considerations in

Formulating TP-104 Modeling Water Resources Systems for Water

Quality

TP-105 Use of a Two-Dimensional Flow Model to Quantify Aquatic Habitat

TP-106 Flood-Runoff Forecasting with HEC-1F TP-107 Dredged-Material Disposal System Capacity

Expansion TP-108 Role of Small Computers in Two-Dimensional

Flow Modeling TP-109 One-Dimensional Model for Mud Flows TP-110 Subdivision Froude Number TP-111 HEC-5Q: System Water Quality Modeling TP-112 New Developments in HEC Programs for Flood

Control TP-113 Modeling and Managing Water Resource Systems

for Water Quality TP-114 Accuracy of Computer Water Surface Profiles -

Executive Summary TP-115 Application of Spatial-Data Management

Techniques in Corps Planning TP-116 The HEC's Activities in Watershed Modeling TP-117 HEC-1 and HEC-2 Applications on the

Microcomputer TP-118 Real-Time Snow Simulation Model for the

Monongahela River Basin TP-119 Multi-Purpose, Multi-Reservoir Simulation on a PC TP-120 Technology Transfer of Corps' Hydrologic Models TP-121 Development, Calibration and Application of

Runoff Forecasting Models for the Allegheny River Basin

TP-122 The Estimation of Rainfall for Flood Forecasting Using Radar and Rain Gage Data

TP-123 Developing and Managing a Comprehensive Reservoir Analysis Model

TP-124 Review of U.S. Army corps of Engineering Involvement With Alluvial Fan Flooding Problems

TP-125 An Integrated Software Package for Flood Damage Analysis

TP-126 The Value and Depreciation of Existing Facilities: The Case of Reservoirs

TP-127 Floodplain-Management Plan Enumeration TP-128 Two-Dimensional Floodplain Modeling TP-129 Status and New Capabilities of Computer Program

HEC-6: "Scour and Deposition in Rivers and Reservoirs"

TP-130 Estimating Sediment Delivery and Yield on Alluvial Fans

TP-131 Hydrologic Aspects of Flood Warning - Preparedness Programs

TP-132 Twenty-five Years of Developing, Distributing, and Supporting Hydrologic Engineering Computer Programs

TP-133 Predicting Deposition Patterns in Small Basins TP-134 Annual Extreme Lake Elevations by Total

Probability Theorem TP-135 A Muskingum-Cunge Channel Flow Routing

Method for Drainage Networks TP-136 Prescriptive Reservoir System Analysis Model -

Missouri River System Application TP-137 A Generalized Simulation Model for Reservoir

System Analysis TP-138 The HEC NexGen Software Development Project TP-139 Issues for Applications Developers TP-140 HEC-2 Water Surface Profiles Program TP-141 HEC Models for Urban Hydrologic Analysis

TP-142 Systems Analysis Applications at the Hydrologic Engineering Center

TP-143 Runoff Prediction Uncertainty for Ungauged Agricultural Watersheds

TP-144 Review of GIS Applications in Hydrologic Modeling

TP-145 Application of Rainfall-Runoff Simulation for Flood Forecasting

TP-146 Application of the HEC Prescriptive Reservoir Model in the Columbia River Systems

TP-147 HEC River Analysis System (HEC-RAS) TP-148 HEC-6: Reservoir Sediment Control Applications TP-149 The Hydrologic Modeling System (HEC-HMS):

Design and Development Issues TP-150 The HEC Hydrologic Modeling System TP-151 Bridge Hydraulic Analysis with HEC-RAS TP-152 Use of Land Surface Erosion Techniques with

Stream Channel Sediment Models

TP-153 Risk-Based Analysis for Corps Flood Project Studies - A Status Report

TP-154 Modeling Water-Resource Systems for Water Quality Management

TP-155 Runoff simulation Using Radar Rainfall Data TP-156 Status of HEC Next Generation Software

Development TP-157 Unsteady Flow Model for Forecasting Missouri and

Mississippi Rivers TP-158 Corps Water Management System (CWMS) TP-159 Some History and Hydrology of the Panama Canal TP-160 Application of Risk-Based Analysis to Planning

Reservoir and Levee Flood Damage Reduction Systems

TP-161 Corps Water Management System - Capabilities and Implementation Status