HomeMy WebLinkAboutDAUPHINAIS MOSELEY FILING 1 DRAINAGE STUDYo
hlnter-Mountain
At-gineerinqLrd.
DRAINAGE STUDY
FOR
LION'S RIDGE SUBDIVIS]ON FILING NO. 5
TOWN OF VAIL
EAGLE COIJNTY, COLORADO
PREPAREII FOR:
DAUPHlNAI S-},IOSELEY CONSTRUCTI ON
FROJECT NUMBER V-8312E
APRIL 1990
Box No. 978 . Avon, Colorado81620' 94*5072Denver893-1531
1420 Vance Street . Lakewood, Colorado 80215' Phone: 232-0158
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I NTRODTJ(.]TION
This report addresses the storm flows and drainage crear,ed
by the Lion's Ridge No- 5 Subdivision, which is .l-ocabed in the
'fown ot' Vail. Uolorarlo - The site is bordered by Li:on s Rrdge Loop
Roarl to the nr:rth. by Interstate Highway 'l;) Lo the south, Solar
t-irest r-londr:miniums to the east. and Br:ffer {-reek Strodivisi-on to
the west,- it also addresses the e:{isting and ,leweloped sborm
flows ancl drainage patterne for the eniire orainage basin which
is borciered by Buffer Creek Road to the rvest, Interstate'/o tcr
the south, and Lion-s Ridge to the north and east, to the
drainage I j-ne which extends north from the Solar Cregt
Condominiums to the top ot Lions Ridse from Intergtate Highway
70 - ( See Figure l. )
EXISTING AND DEVELOPED CONDITTONS
The existing Bite is undevelopeci. The native vegetation
consists of oah brush, a6pen, mountaj.n brush and grasses igee
Figure ? and Tables l and 2), and drai-ns to the $te6t into the
Buffer Creei< Subdivision, then aeross Interstate '70 to Gore
Creek.
The proposed development consists of a new roadetay and 19
single-family lots. Several feet of fill will be placed on the
eite with construction of the new road. Development of the site
wlll increase the storm runoff from the slte and follow the
r
I e-.<ist j-ng clrainage F,artern to rjore 'Jreer.
I rjf tsi-te
I The otfsi:t:e area consists ct a portion Dt the Buffer [-lreei<
I Subciivi-si-on ancl portione ,rt t"he Lion.s Ridge No. 2 and :J tillngs.
I The nati','e vegetat j-r:n ot the unde'"reloped areas cnnsisb ot oak
I brush. aepen, mountain bruoh and grasses. The de,zeloped areae
I conelst ot ree itienttal Lot,s wi+.-h a minimum of ltJ.t)t)t") sqs3pe feet.
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I L]RI'IERIA
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The following reterence.s were used in the preparation of
! this report:
1 . PIat f or Lion I s Ridee flo - 5 Subclivision., 'll ovrn ot VaiI,
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Eagle County, Colorado.
I 2. TopograFhical map for Lion's Ri-dge No- 5 St-tbdivision.
I prepared by Inter-Mountain Engineering, Ltd-
I 3- Gore Creel< Flood Plain. Current t-londitiona. a component
I of the Compreheneive Plan, Town of Vail. Eagle Count:r', Colorado,
I prepared by Briscoe. Maphis, flurray. Lamont. Inc-. Management
I Consultants, in 1977.
I 4. Urban Hydrology for Small i^latersheds. IR 55' USDA Soil
I Coneervation Service. June 1986-
I 5. Handbooh of Hydraulics, Fifth Edition, King and Brater,
t McGraw-Hill Publiohing Co.
The storm flows generated by a 1o-year, Z4-hour and 1OO-
I year, Z4-hour frequency storn rdere analyzed. Flowe were computed
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uEing the methods outli-ned in SCS Tet-hnrcal Release No. 55' ,June
!966 Edibion-
SUBBASINS
(-lnqi fa
F',tr the purF,ose Lrt ca Lcttlating r.he siorm t lcl'rtE on and acrosg
the prcposed srte two sei,arate eubbasin 'tere detined- Subbasj,n I
Iies adjacent to the North Frontage Road ot Interst.ate Highway 7t.t
and inci-udeg lots 9. lii, 1l anct 12 oi the Bufter Ureek
Subdi.,rision. Flows sheet flow from the north to the F'rontage
Road ditch then to the e:<isting drainage Btructure across
Interstate Highway 70 to Gore Creek. Subbasin II includes most
of the proposed subdivision and an area north of Lion's Ridge
Loop to the top of the ridge- The subbasi:n j.s bisected by Lion's
Ridee loop which has a small roadside ditch on the north side of
the pavement. For the purpose of this design, hte assumed that
during the rnajor atorm event this ditch would flow fulI and not
i.ntereept any storm drainage. The f lor,ss sheet f low acrose the
road into the proposed subdivision and concentrate in a natural
drainage which exits on Meadow Drive in the Buffer Creek
Subdivision- It then flows through an existing culvert along
Meadow Drive or sheet flows on Meadow dri.ve to an inlet which
diverte the flow acrosa Interstate Highway 7O to Gore Creek.
Offsite
For the purpose of this study" offeite drainage was
considered to determine if the exieting drainage Btructurea were
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Iarge enough to rrarry the Ceve icFect t. iord lrom the enc rre
,Jrainage basrn to the cen+r,rar coliectl.cn lnirets on Meaciow L'rive.
then acrose Interstate Hiehwav 7(-) to Gore r,lreek. For the offei-te
drainage area, f ive separate subbasins were rleiined. Subbasin
III includes an area norlh ot Lion.s Ri.,lge Loop to the ridge.
then eouth rrt Lion-s Ridge Loop, and a portion ot Lot 21 ot the
Brrtf en rlreei< Subcliwi:-:i'rn. F.garn, tcr rhe purpose .Jt ilhis strrcii.r
we ae€llmed the small ditch norlt.h 'rt rhe pavement on Lion-s Ridge
Loop will not intercept the f lows ancl ',viLl sheet tlow across the
road anci concentrate in an existing drainage cn the south side ot
the road- It then flowe to Rictge Road in the Euft'er Creek
Subdivision and onto Meadow Drive to the existing central
colLection inlets- Subbasin IV li-ee to the west and adjacent to
Subbasin III, west to Buffer tlreek Road anci includes a portion ot
Lots 18 and 21. and Lots 19 and 2O of the Bufier Creek
Subdivision- During the major 6torm event, the area north of
Lion s Ridge Loop sheet flows to the road an,l foilow the north
side r:f the road to an inlet wi.th a Z4-inch Cl4P across Lion's
Ridge Loop at the intersect ion of Buffer r-lreeh Rc-aci - It then
follows Buffer Creek Road to Meadow drive and into the central
collection. The remaining gubbasin area also flowg to Buffer
Creek Road and to l,leadow Drive. By vislral inepecti-on it appears
that during the major storms. flows frorn this basin will sheet
flow across Buffer Creek Road and directly into Buffer Creek-
Subbasin V includes the developed Lota 13, 15 and a portion of
Lot 2L of the Buffer Creek Subdivieion. Subbasin VI i.ncludes the
developed Lote 15, 16, 17, and a portion of Lots 18 and 21 of the
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Buffer {lreek Subdi-visi.on. 'l'hese bas:ns sheet tlow ontrf Plea,lc.rw
Drive then into the central colleetion ini"et- Subbas Ln VII
congists ot Lots '7 and I of the Bufter t,lreeit Subtli-vi-sron and
sheet tlows to the di.tch on the north side or Ehe Front,-ege Road
then to the exi-stinEi drainagie structure across interstate Highway
70. (See Figure 5 for subbasin bounciaries- t
FLOWS
tr'lows for the exrsting and cieveloped couclrtions were
eomputed using the methods outl j.ned in SCS 'Iechnieal Release No-
55, June 1986 edition- The ot'fici.al zoning map for the Town of
Vail was utilised to determine the proiected densities ot the
undeveloped areas in this etudy. A conservative runoff curve
number (CN) of 87 was ueed for fLow calculations in the existing
and proposed developed areas with a B,zC hydrologic soil group-
This corresponds to the eugge.rted coefficient defined by the {JSDA
for flows calculated by the SCS method for resi-dential- distriets
with lot sizes of l,r8 acre or less. (See Tables 3 & 4. t
AII flows ."r ".]"rrlated fc,r the lu{j-year, Z4-hour storm
event. A summary of these flows is detailed below in the
followi"ng table:
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56
65
5S
87
87
67
oi
1u. t
1il- 1
13. 9
?3,I
14-3
14-3
6.4
6.4
0-9
o-9
1-5
1-5
1-3
t_3
Subbasin UN gl_lt-rt-t -rrr, 24-[a
t- . r;5
r..14
li. L1
E. ti3
0. 4,!
:J. IJE
rJ . i3(j
2-L7
o. B4
o.84
o. 38
0.38
2.46
I (P)
(D)
II (P) 6?
o.L
Pr3
(D)
IlI (P)
(t')
IV (P)
V (P I
(D)
VI (P)
(D)
inr ??
VII (P) 87
(Dl 87
(P = present conditions; D = developed eonditi-ons )
FiEure No. 5 depicts the eeparate drainage subbasins with
subbasin flows and accumul,ated subbasin tlows. The accumulated
present condition flow from the seven subbaeine tota] 7.32 ct-s
which diecharges through a Z4-inch CMP across Interstate Highway
7O and into Gore Creek.
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T|RAINAGE F.ACTLITIES
E:<ist i ng
Figure 6 depicts the existing anct propose,l rjrarn;ege
f aci-Iities and Table 5 tabul-ateo the p j.pe data anci maxrmum
n,=nnni iw rr.t'nl nt' rrer"h ninc The tnial e.<i nt.in.o tLow f rr:m the?qtr',f.rrvJ }/!F.e.
seven subbasins of '7 - 6? cf s is discharge in tiore (lreeh by a 24-
inch tlMP acrDBS Interstate i{ignway '70.
Prcposed
Figure 6 deFrct,s the p'roposed rirainage tacilitres to c'-r.rr'y
the 100-year, Z4-hrrup st')rm event. A drai.nage dicch musr be
constructed aLong the east sj.de ot Buffer Creek Road .Lo a
proposed 18-inch CMP (Pipe No- 10) near the southwest corner of
Subbasin IV which will discharge direct.Ly into Butfer Creeh- The
drainage ditches between existin€i pipes 1-Z and 2-3 mugb be
enlarged enoug:h to carry the flows from the proposed Lion-s Ridge
No. 5 subdivisi-on (subbasin I1) and subbasin III. The existing
l5-inch CMP (pipe no. l) will be replaced by an 18-inch CMP to
carry the flows for the developed conditions of subbasin I1- All
other drainage facilities are large enough to carry the lU0-year,
24-hour storm event for al-i developed conditions. The existing
Z4-inch CMPg (pipe nos - 6, 7 and 8 ) across Interetate Highway 7Ct
will camy a Qnax of 33. 25 and 36 cfs reepectiely. By di.verting
subbasin IV to Buffer Creel< the Qma:< for cleveloped conditions of
the entire basin wiII be 15.75 cfs.
The onsite runoff will flow to the drainage ditch afong the
propoaed Lion's Ridge Lane within the eubdivision- It will flow
to the west and concentrate at the existing natural draj.nage on
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the weet end of the proieet. A l5-inch CMP wil-l be installerl
across the driveways ot the proposed lrrts.
CC)NCLUSIONS
The improvement:5 for the proposeci subdivision will t:aLrse an
inere.ese in runoff within subbasin II. 'Ihe proposed Lot ,lesisn
wiII not alter the rlralnage basin botrndartes- AII the e:<isting
and i-ncreased runotf wilI be oiverted to the existing naturai-
drainage and the existing ,lrainage facilities wi:thin the Butfer
tlreek Subdivision-
Hi-storieally, the runoff from eubbasin IV drained into
Buffer Creek. By instaLLing an l8-inch CMP (PiPe no- 10) at the
low point of the subbasi-n the runoff will be diverted to its
natural origin -
With the exception of the existing 15-inch CMP (pipe no. 1)
which will be replaced by a lS-inch CMP, and by improving the
roadslde ditches on the north side of Meadow Drive, the exi.stlng
drainage facilities are adequate to earry the developed condition
runoff for the entire basin.
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ffi.ffirrrEr Attf'
vlfi;;'ff;l*"**- ffiInter-Mountain
::-:t l--::-iiia= A=-sineerincrLrd-
SUITE
'O!t,t20 VANCE STREET
LAt(Erooo, coLo. 80215
(303) 232-0!58
Lo*' l-19 ['o-s R,;:rz i-r.r.:5 l-e-p, "1a
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Arrqrt Goldins Acw
3c.. ate " l"' voo'Tan CtH
| - t/rc',vtrY IVIAP
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P.o.qu cr8
oero ltoTTIlFHAra
AV6[ Cq-O.8r82o
($31 9,10-5072
!t rlE tot
t4e0 vAtlcE gTEEr
LAKEltoo. clLo.80215
(30:1, ?3F0158Engineeringr.ta.
Inter-MountainROAt)
For.ct Lo.
t/ 83 /78
o.t. / By:
Strlat No.
/oTS ',') trt': e 't ci ru.zryc 6
€DITE T C(I-ORADO BIAT€
SOIL L-,.VEY AAP€N-CYPgttl
sFlcE oit JAttuaRY 4, 1909
AREA. PARTS OE EAEUE, OARFI€LO
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TASLE AI,...ACR€AG€ANO PNOPORT IO',IATE
lJodaio loai, I to l2 parc!nt rloparlhi lSor. .r lt lot.---------iKobr. tr lty cl.y 1o.., t to 6 p.rc.nt tlop.t----------ixobrr .a lty clry lot., 6 to l2 p.r<.nt .lop.r---------fKoDr. ri lty cl.y lor., LZ lo 25 p.rc.nt rtop.r--------:Kobar tllty clry loa,., <t..y, 3 to 26 g.rcant alopar----lL..vittvi I la lora, a to 25 D.rc.nl .1o9..-------------
llla I l.rlak. lot., !5 to 30 p.rc.ot tlo9.a--------------lftio. forr, lZ to 4t p.rc.ot rlopra--llli.|a lorn, 23 to 6t' grrc.ot rtog.i--llllircl. loar, 3 lo 30 parcant rtop.r----------llioan rtony loaa, I to 6 prrcant atopat----------------fioan rtony loar, 6 to L? p.ra.nl, alopar---------------!Io.n rtcny loa.r 12 to 23 p.r<.nt ttop.r--------------!ion.<f alna trndy 1o.., l? ro 23 p.r..ni rtop.r--------lilooad lih. arody 1o.., 2t to 50 p.ra.ot atop.r--------lliorval lol|rr t to 6 p.rcant itogar----------liorv.l lorr, 6 to 26 p.rc.nt slop.r----------illvrv.l lorr.r ZO to aO p.rcrnt tlop.r--lilorvrl-Trldal I cortrlar, !2 to 50 p.r<.nt rlopr.-------lltoyarrDn-Rock outrrop cor.t,lax, !6 to 60 parcahi aloptr!iuatal l"aa, I tc 6 prrcant rlopra----------ill$tr.l 1o.., 5 to la p.rc.nt rlot.r----------iEust.l lr.i, l? to Zg p.rc.nt iloprr--iRadrob lo.r, I to o p.rcrnt !lop.r----------iR..g.rt vir'y rtor,y rrn.ty to.i, 25 to 65 p.rcrnt ilop.tilihoy.ltcr-irrrv.l cont,l.x, 5 to l5 p.rc.ot rlogcr------lSt,.ie.ltrr'.ltorv.l cniFlex, l5 to :.5 ocrc.nl slopor-----!!n.rtl'.(. Eoba'lf t.hrly lo.r|, I to € garc...t rlot,r!-----
;5!utnLcL. r{1,!ly s.n,ry 1.i.., 6 tn !: D.rcrnt tlo9..----:lni(lri.rr ...1'l.ly r.r,'ly 1,.'., rZ to :5 F.,r(€ht 61.'t..r---:ri,..ulh.r. . nl,|.ly s.r.ty li.-, i5 t{ n:. t'prc!nt rlotrs---
::11.r lry !t.,ft..r. vary.hrr'n$ry l'!.||s, 'l t':5 l.errcnt
fO6 lTri.l.ll-gros^ato .odarrt.ly rtony a.ndy to|lrr, lZ tci 60 gaacaot r I oDra----------
t|)7 ilrrtccr, iolrl-ti.rg.l .orplox, I to 6 p.|.c.t|t rlop..---lO€ ltJ?rc<l-irr9.l corpl.x, 6 to l2 prrc.nt rlop.r---------1O9 lt,|.rc(r-fl.rg.l corel.x, 12 to 26 p.rc.ht alopaa--------llO ltrrrtcr-tl.i3r I .onplo:r, :5 to 65 p.rc.nl .lop.r--------tll lv.ndrror. cht||nary r.ody 1o.., 23 to 66 p.rc.nt rlop..!12 llSodhal I v.ry rtony lor., 6 to EO p.rc.nt tlop.l------l13 lXooilay lora, 3 to 30 paiaant slopaa----------
lla lVLo 1c.., I ta a taacant alcrar----------
8.. t.otnota al .na ct trll..
| :-T-]---T-----T--1- , ----:-----. '- I 'lllll:l
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ilpron cobbly lo.i. 3 to.25 p.rc.nt rtoprr-------------ilpron cobbly tori, 26 to 6t) o.rc.nt rtoo.r------------ttrr.erddy vary rtony to.., 23 to 66 p.ic.nt rlop.r----iltara lor||, 6 to 25 D.rcaftt rlooar----------llyrrr lorri, ?f' to 65 p.rcrnt rtop.r--!ly.r'r.ilty clry torn,6 to 26 D.r,c.nt rtop.r---------lly.rr .llty cl.y loa., e5 to 63 porcrht rtocrr--------iJarry lorn, la to 25 p.rcant rloDat--lJ.riy lori. e6 to 66-p.r.aot rtop.r----------
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(3031 23a-0150
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, arlra!.r o!.otaoo tt^rt rrtct o J^rJxr.r trat"- --. atll. aatat rti*trn'ir alr, t-lt d. ar.a, al'rala, a- a]trta ot-rlat, ae'trD
trla x.---tl x{a |ttr tlrtrE--c{rr.r..
r ,.tri r..r r||r. | &..(r i t rtaa a, a-;-r-
- l--- r--
-, rr-.r I t.tr. t ar.G.dy I Lrt.i tt ar. I t|.ria t at.a tt.rt. rO.rtr[i.a- r r...t [r.{r.a tC*..a..r.-l
Il',r ao' al. aa'___l| -i5'-'----; " i"-------i tltrl--i tt ad.a.--- att-----tt-.Irl
--- lr.a...t.---laat----- --.rtl--- ri.......---rxrt-----rr-.
--r tr.a...a.---$l|i----ttd.
lra.r-a.t I l.O-3.o1 ttt*..t I J.n-D.. I
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taoEaottala l!---------l|.ttr-----t(-.
ttlto, tr, ta, ?t----t c t-..--------l
rtl?a-..------------.1 a tr.{_---_-_-l
loa.r I Iaart.r----------l D tt..--------
tl
loa.r I t
c
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Id.r | |lr.trrt-tr---.t ! tb..----_---
a*r ..a...r', t I
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lt---------fiat!tr-i:--tl-r
i
rtlltao | --- lt.--------t||ttt-----tt-.
rtrta-trllt..a l|..r------i-tfi a|r-----t!-,
t!.aot --- tLe-------t||tat-----tt-,tttlttrtrtllrtrl4_.Olrt.,a t(.f-------tlata---_-t!_.
-'5rr.---------t a tr.--____---tllot., toa., lot , | |tlo.. I t-a tt ---------tl
rtl a tt _--__--_-t .--ttlIt
4.. t-t-a. .t .ia .r a.ar..
I-..ID..'.r....|||t.....-|l-.
rlltt.-- rt*-----.-D||*.---. t!-.
--- tl.a.rrt.---l|l rr.t. t!-.rtllilD-aollisa lLatrl.---lta-.a. lL-.
Itl
ttl
ti...--------t ---tl1i...-------.t ---
Titete Z
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P.o.aox 070
0st0 torrtl€t^la
AV6L CC-o.61820(s3l 9a$-5072
noro Inter-Mountain sulrE 101
14EO VANCE STFEET
LAKEIo@. CoLO.8o2i5
1303123:l-0r58Engineeringrta.
Pr"otact No.Y t'gtz Q
O.t. / ',ll
Shsat No.
Lor=I Lro*'r *l '=j.1tDz14 -S Pua)*A4€.
.*t-
-+I
I
---.i-
I
-----1.
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a3,;
'lO q,lro--rl< *,1cE tio-tiJ-1.ct'cJ 'itl,I
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5t
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ilgl
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iEtrr
.----r---
-1
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let
l,...._
{fEL'-
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r ri , i ri
Frauee 3
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P.0.B0x e7a
09to I0TT IN6|tAra ROAD
AVS|, CO-O.81E20
(:n3l s.F507e
surrE !01
taao v^fcE STEET
LAKEi000. co-o . ao2!5
(303, a32-0154
*i)'F,tae
tt!t. / 8y:
Shlrt tlo.
| | tar ] + .--L4t | - tY L rc>r.rc i<.:rqe_ -S DreA,*n,qc-
fioupa- +
IIII
t
:.I IIIIIITITIIIIIII
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4t
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Tablc 2-2a--&rnofr curvc numbcrr for urtu enast
I
t
Caver descriotion
Curre numberr for
hydrulogic soil gtoup-
Cover tlae end hydrologic condition
AYerzg€ percent
lmperbu rreet DA
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I
I
I
li
:l.
t
I
FUIIV da,el@ ulen otzos (oqqtztion cstablishtd)
Open spce (lrwru, parks, golf counes, cenet€riec,
.t4)t
Poc codition (grass cover < 5{l%) ..............
Frb condition Qrzss cover 5096 to ?5%).......,.,.
Crood ondition Grzss cover > 75%, . . . . . . . . . . . . . .
Iqervious rrers:
Paved parking lots, mofs. drive*ays, etr,
(erduding rightof-ray).
Streets end roads:
Peved; curts and stornr sewers (exeluding
riShtof-say). . . .
Ftved; open ditches (including right{f.way) ...,.,.
Cravel (induding right.of-$ey)
Dbt 0nduding rightof-way)
W€lErrr desert urban rreas:
Nabral dese!'t landscaping (penrious ararr onlyF...
Artificid desert hndrcaping 0mpen'ious weed
bqrier, deren shnb with l. to 2'inch slrld
or gevel Euldr and brcin borden).
Urtan district!:
Comcrcial Ntd businels.. . .
Industrid.......
R€3idertid districts by average lot size:
.tn ecre or tess tto*.rt housed- -. .. -. -. -...........
I U4 arre
: lB ecle
1ii2eclr.....,..
1ecre..........
2 arrel .........
-Dclrl@&tg ttttrln aw
Norty greded rnas (pewioru uees only,
rb veget tion)t . ,
ldla latd! (CN's a€ determined using cover t1ryer
d'nil-r to tbore in teble 2-&),
68
49
39
98
98
83
?6
72
63
96
89
8r
n
6ttl
6{
5t
t6
85
72
66
38
30
%n
t:2
?9 1669 7961 74
89
E4
80
9E
98g]
9l
E9
88
96
95
93
92
c7
86
854
.&,
9898
98 9889 9285 89c2 gl
n85
96
94
'91
r-1B;n9o
-89 EIg)
?9
a,
92
88
85
ao
7','2
m
6E
65
E6n
I
I
I
l.
i
9{9l
rAvq?8! rrnotr condition, rnd l. - 0-i6.tltc rrra*c pcrent ir:npcwinri rne shosr rrs urcd to dcvclop thr conpodte Clfr Oth:r rremptilu rn rr loltonr: Inrpcn*)ur rrcurt dirtctlt cmncct+{ lo thc drdnr|8? lyst m. irnpcrviol rnrr hrr.o r CN of $. nd pcrviur rr.a rf. srri.lerd Gquirrhnt to oDan
!q!! in Sood hydmlogic coditlorr. CN'r for othcr conbinrtiru of condtion! ntry b. comput d ndnt ftun 23 or Z.l.rCN! shorn_erc cquivrlent to dr6. of Futun. Conrporitc CN'r rnry bc conpurrd tor otLr coo&irutioil ol opcn rprcc corcr typo,
'Conpoitc.CN'r lor nrtunl dcrcn bndreping $out'd b. courpur.d idrf, tlgirn 2{ o" 24 b{.d 06 rh impJriod rrrl p.rsriri4r tCX
-.-9t) rnd th9- pnbur errr CN. The pcn'iour rnr CN'r lr ilumd rquiv-dont !o d.r.n rfrnb h poor hydrologic condiiion.rCoqqiu CNt to usa for thc &dgrr- of trrqonry rrrrunr durin6 jniffu nnd corrrtrucbn rhouli lc cinpua using tlprrr !3 or 2.{.br.d oo Uc dr&rc of dcvclopnont (imprniour rnr pcnrat4r, end ttn CNI for tb ne*ly 3rrded pcniour rrrlaP
t €IOVI-TR-55, Second Ed", Jurc 1986)
fnac€ s
2.6
I
t
I
t_Trblc Z-2d.-Runo(f currc numbcrr for arid rnd !.mhrid En3?l.ndrr
Covcr dcscriptbn
Cunc numben for
hydnlogic roil 3tup-
Oover t12e
Hydmloglc
conditiodr ar
I
t
t
I
I 75 E658 7841 6t
6rm51 8335n
n8572 8r68n
68
55
49
hor
Fdr
Good
t
I
Herbeccour-mixnrc of gnr* wecd* end
low-growiry brus\ eitb bruh th.
ntinor element.
Ork-erpen-mount in bnrlh mixtrrc of or& bnuh,
aspen, rnountein mehogenn bitter bnrsb maplc,
rnd other bnrh.
Phyott junipcr-pinf'on, juniper, or both;
gnss undentory.
h6
Frir
Cood
hor
Frir
C'ood
hor
F.b
Cood
Poor
Frir
Good
fl)aTL Ei6e 71
I
Sagebruh with 8!rs! undentory,
Derert rhrub-major phDts indude srltbush,
grearewood, cr,ecotebudr, bhakbnrh, bunrge,
pslo verde, mesquite, ard crctu!"
s"
80-
85
?9
63
48
89
s,
?r
E5
70
oo
88
E684i
1
66 r-r 7lsl54 sgt- tl
I
I
I
rAgent! ruroe conditioal sd L - o.lCS. For rrrg: in hunid r!Sbtq u!. t$t g.zc-
rlbor <-fllil _3nund cove (fttcr. grzrr. sd btrrtt onntorylfoir iill ro ?Iltt Srlrrr|d covlr.
Guxl: >1UI jrund covcr,
rCun'e nunrbcnr for gmup A lirve bccn drvetop.d only for deaet shnrb.
t
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1,.efCVl-TR-s5, Second Ed., June lS)
/aace 4
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TABLE 5
Plpe No.
.L
I (P)
2
?
4
5
6
I
9
10 (P)
P = Proposed
Length (ft)
59
59
r65
49
48.5
r31
7L
83
4t .5
30
65
Dlaneter (1n)
l5
18
l8
l8
18
18
24
24
24
24
18
Head (ft)
2.25
2.25
L7 .79
3.93
3.7 4
8.59
4. r8
2.65
3.70
2.4r
3.5
Q-.*(cfs)
7.5
9.0
11 .0
1l .0
L2.O
13.0
33.0
25.O
36
30
t2
Type
CMP
cuP
CMP
CMP
CMP
cuP
cuP
CMP
CMP
CMP
cuP
T
I
TABLE 5
PIPE DATA
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I APPENDTX
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L.
Saa+lczuF
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Wor&rhcct 2: Brurotleurvr numbcr end nrnofi
lroJrer Ltoru's Rtoe e !S-)g Dru?
rcrclon lr/rar, c- C O
ct*r. o-r@ D.e.log.d ,l
'l
I
t.
I
..t
t. lunof( cunrr ruobr r (Ct)
ttoll oer
end
hydrolojlc
group
(egpcadtr A)
Cotr s d.rcsl,pttoo
(corri !ypr, cf.rt!.ac, :ad
bydrologlc condlElor:
Frc.a! tlp.retour;
uraom.c!.d/co[o.c!.d l,lprnr!,out
erer reclo)
Prodct
ot
Cl r erre
,e,;1{! )-";-
'oorn: { g 7a
Oah -r\iD2^ , .+- tr.1 ra .\
itr: -t - -nr'- .-ond,/roS
<-t I ciert ! lq
'/> or-. 3,'l.I (z/.
Gr (rrrghrrd) - t::*p:"*e -t#. b/,( | ure clf r V/n
2. Runot!
lnqurncy
Setrtrlt,
lllolt, Q(Ure ?
oa .qr.
..aaaaaaaa.aa
P (20tqrr) ........o.......r.
|!d-Q{ rtBh rebk 2-lr ll3. 2-1,2-t rnd 2-{.)
tr
tr
lc
Stotr ll SBor! ,2 Ston 13
/oo
?.,4
o, t7
glSVt.TB.tq S.cood Ed- &ru. Uff)
RUNOFF FOR INCHES OF RAINFALL
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1{0TE: Runotf value determined by eguation q = (P-0'Z S)2
P+ 0.8 S
REFEREI{CE: ilational Engineering Handbook, Section l, HYOROLOGY
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
I 0.00 0.c0 0.01 0.02 0.03 c.04 0 .06
2 0.07 c. c9 0.L2 c. l4 0.1?c.20 o.2t 0.26 0.29 0. 33
3 0.37 0. 40 o.44 0.49 0.53 o.57 0.6 2 0.67 0. 71 0. 76
4 0. 8l c. 86 0.92 0.9?I.C2 i. 08 r.14 l. 19 I.25 1.3I
5 1.37 I .43 1.49 1.55 L.62 l. 68 L .14 l.8l I.87 1.94
6 2 .01 2 .07 2.l4 2.2L 2.28 2.35 2.42 2.49 2.56 2.63
7 2.70 2.78 2.85 2.92 3.0 0 3. 07 3.14 3.22 3.29 3. 3?
8 3.45 1.52 3.60 3.68 3.15 3. 83 3.91 3. 99 4.07 4.15
9 4.21 4.31 4.38 4.47 4.55 4.63 4.?l 4.79 4.87 4.95
10 5.03 5. L2 5.20 5.28 5.76 5.45 5.53 5.61 5.70 5.78
11 5.87 5.95 6.04 6.12 6.20 6.29 6.38 6.46 6.55 6.63
L2 6.72 6. 80 6.89 6.98 7.06 ?. 15 1 .24 7.12 ?.41 7. 5C
13 7.59 7.61 7.76 ?.89 7 .94 8. 03 8.11 8.20 8.29 8.38
l4 8 .47 8. 56 8.65 8. ?4 8.82 8.91 9.00 9.09 9 .18 9.27
15 9. 36 9.4 5 9. 14 9.63 9.t 2 9. 8l 9.90 9.99 lo.0€10.t8
16 LO.27 10.36 10.45 10.54 lo.6 3 10. ?2 10.81 10.90 11.00 I 1.09
t7 ll.l8 11.27 11. 36 I t.45 11.55 11.64 I I.73 I1.82 I 1.91 12.01
18 12.10 12. I9 12.28 12.38 L2.47 I 56 L2.65 T2.T5 L2.84 12.9t
l9 13.03 13.12 I3.2t 13. 30 13.{0 13.49 13.58 13.68 13.77 13.86
20 I3. 96 14.05 14.15 14.24 14.33 I4.43 L4.52 14.61 14.71 14. 8C
4l
tvfu!o
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-@o.oo7 (nL)o'Ee' 'r - -116ffi'I-?2r
Shrttos conccatreted flor
-@10. Arenjc reloel.ry. 9 (t!,Srrc 3-l) ........... Cclt
IU. lB .5EAT CorPutr 1. ...... nt
I
t,
It(
I
I
C6puc. v ....... Cclt
ll' rtd 19).......
Sue-aA$t N t
Worksheet 3: Time of concentration CIs) or b6vel time Cl1)
IroJ.cr /rur't 2,o& a' 5-:\,,r%e
ChecLrd
Gtrch oar: Ptar.nt Dav.loPcd
Glrch or: tc ta tbrouSh rsb.to
ft!S: Sp.c. lor o leay r. ttto ..gmotr prr tlo ltpa crl bc urod tor och
uortrhcrg.
taclodr r rPr achGlaclc, or darcrigtloo o! flou reglcntr '
-@!$, (Appllcrble to t ooJ,y)Se3*at lD
l. Sqrlecr dctcrtpBloo (.teblc 3-t)
2. Irul,q'r roughacr cocff., o (!.b1. 3-t) ..
3. Ifor bn3Gh' L (cotel L < 300 ft) ft
f . lrlort? 2{-|rr rrlahll, P2 .. . ..... . t'!
5. Ltrd.lop.' | .. ttlia
Coopqt. l! ...... br
Segcnt ID
7. Sortecc d.rcrlpBlo! (Dtvrd or rnprved ) .....
6. Elov l.otrh, L . lt
9. tlrtrtconrrc dope , I o r o o o r r e r r r . . . . . . . . . . . . frllt
Ch.nn 1 flod S.gr.nt ID
12. Cron .cstlon l flotrt tsc.' I oooorrooroooore Cc2
13. U.t!.d p.rlr!.r. p, . .. .. .. . . . . !t
tl. lydnullc rrdlu. t t'.i CotPut. ! ....o.. tGir
15. cb.!!.l rloge, r ............. ftlfc
16. . llrndaj'r rou3haer eocft., ! o oo oo r.. r o o r r r
r?. y - t.tg r13 rtl2
l!. tlor Ls8th, L . tt
Ilt. lr.ffiT Colput. tr ...... hr
20. llrtrrrhed ot rrb.s.r tc or tG (rdd ta ln rtrpr 6,
el$VI-TR-sS, Sccond Ed, Jutt U[6)
'a
D8
+l
oCIo
6
o6L:toa,
oIPa-
.10 -
.06 -
.04 -
| | | | | | | tt24610
Average veloclty, ftlsec
FlOrt &1.-Avcnfc rclociticr for crtimrtin3 brval aitn! for rhdlor conc.trttrt d llo?.
$2 (2fGVI.TR-55, Second Ed", June 1986)
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/\
?roJecr ( ro u's ?,t c-e- d{
/-Iaercton Vatc, CO
ct rc lr oo. {-fcr e]]DDrvc lop rd
l. Drcr:
Dsrtnag. ar.. .......i.. \.
Rumtl curvr nruber .... CX -
Ttr of colcaolraBt oo .. ta .
lelntall dktrtburlotr ttg. .
Poad and sraop ar:ar rprted
Ehroughout urccrrhad ....rr t
Fraquency
Bellfall, P (2i-hour)
Intctal ebo!,racgl,oo, Ir ..........
(Ucc ql tdEh r.b1e 4-l;)
CoEFrr. Ia/p ........
5qg^Wrlr tr
Checkrd
Drtr
Drco
d2 (rcrcr/640)
(Pro norkghccc 2)
hr (Froc sorkshccc 3)
(I, tA, II, TIt)
p.!c!o! of rn (- acr.! or ol2 covcred)
SBoE! rl scoro 9z Scor f3
/0 0
2,4
!a
yr
tn
l,zt t
1
.<?
, t7 |
4- a-a
I
I
I
,
i
II
2.
3.
5.
8.
9.
6. 0otc pcrk dtrchargc, q,' ..........e..... . cu/to' (Urc Tc aad lalp ntBh &trf,Utc t-21 3 lol
7. Ruaof!, a ..,........
(Fror rorkshccc 2).
Pood aod rre4 adJwtoclE lactor, F- ....(Urc pcrccne pond and Jr.op arre . P
rtBh trb1. 4-2. Facgor k 1.0 tor
zaro. pcrcanB pond and t-renp erca.)
Plek dtscherg.r qp . . . . . . . . . . . . . . . . . . . . . . .clr
(tlhcr q, - quArq?p)
PrGvf.TR.C5, S€cond Ed., Juac ts6)
/,0
Workshcct 4: Graphical Pesk DischarSc method
ryD"b
'oL
-rE-
, zc4
---lv
l,
-l
I. i
I
Chapter 4: Graphical Peak Discharge method
this chapter preserts the Graphical Peak Discharge
met}od for computing pedr discharge from rural and
urten areas. The Graphical method was developed
fton hydrograph analyses using TR.@ "Computer
Pmgram for hoject Forzlrlation -HydrologT" (SCS
1988). tte perk discharge equation used is
Qp = guAmQFp tEq. a'11
- Freak discharge (cfs);
- unit peak discharg€ (csm/in);
- drainsge area (mi4;
= runoff (in); and
=.pond and swamp adjustment factor.
The input requir€ments for the Graphical method are
. gs follows: (1) Tc 6r), (2) drainage area (mi4, 6)
sppropdate rainfall distribution (I, lA, II, or III), (4)
2,|-hour rainfall 0n), and (5) CN. If pond and swamp
:reas ane sprad tluoughout the watershed and are
not considered in the T" computation, an adjustment
for pond and swamp areas is also needed.
Peak dischargp computation
Fore seleeted rainfall frequency, the 24hour rainfdl
(P) is obtained &om appendix B or more detailed
local precipitation maps. CN and total runoff (Q) for
tlle watenhed are computed according to the
metlods outlined in chapter 2. The CN is used to
determine the initial abstraction 0J &om t:ble 4.1.
I.lP is then computed.
il the computed IrlP ratio is outside the nnge showrr
h exhibit 4 (eI,4tA, &II, and 4-IID for rhe rainfdl
distribution of inter"est, t}en the limiting value
sborild be used. If the ratio falls between the limiting
values, use linear intcrpolation. Figure 4l illustrates
tlte sensitivity of IrlP to CN and P.
Peek discharge per rquere mile per inch of nrnofi
(qJ is obained from exhibit &I, t-IA, &II, or &IIl
by using Tc (chapter 3), rainfall distribution tlpe, and
I./P ntio. Ttre pond and swamp adjustment factor is
obtained from table 4.2 (rounded to the nearest tabte
vdue). Use worksheet 4 in eppendix D to aid in
computing the peak discharge using the Gnphicd
Dethod
T
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where
Cp
9u
Ar!
e
Fp
rttrtutt
ll.t ll (tt. t..Lr
Flfurc &1.-Varirtion of I.1P for P ond C'!{.
Ir
0n)
Ir
0n)
Cunre
number
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40
4la
43
tt4
45
46
47
4E
49
50
5t
52
53
54
55
66
57
58
59
60
6l
68
63
6{
L'
66tl
6E
@
(2ICVI-TR-55, Second Ed., Jurc 1986)
3.000
2Ar8
L7@
2.651
25{5z&
2.W
2255
Lr61
LW
2.000
1gD
t.846Lnl
I.?TN
1.636
15?r
1509
1.4rl8
1390
L:rts
r.gEt%
t.r?t
r.1!5
Ltn
t.0g)
0.985
0.9{l
0499
0.857
0.E17
0.n8
0.7{0
0.?08
0.66',t
0.dp
0.597
0.564
0.582
0.500
0.{69
0.4it9
0.{10
038r
0.353
0346
0299
0n3
0247
0.92
0.198
0.1?4
0.151
0.128
0.105
0,083
0.062
0.oil
70
?l
72
78
74
76
76
at
78
79
80
8l
&
E3
84
85
E6
87
88
89
90
9l
92
$t
94
95
96n
98
Tablc &1.-I. valucs for nrnoff curve numbcrs
+l
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.,1.*-.,,_. -..,..:
€86I aunf "Pg Puoc€ 's9'uI-lA-0Iz)
Unit peak discharge (Qg), csm/in
coctooooootJ'r olo<)
I
I (-, 5 (tl orE - 9 P3CQ-r"
x
5
(D
&o
rt
oa
.D
Frla
ca
E('
r.l
t9
a
D
E
O
:l
I
c
5
Oi
@
=(D
0
{l
'oo
=oo
=.'
.e'r}
oJ
o
st81\o-: aDurl
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P
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--
or-
0g-
E-
Lrory'S ?>Oa oS
rl
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:
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Fo*rhcct e nurroll currG nrmrbcr rnd nuroll Sap^$Asta{ /
o.c. {- ?-?o
D.g.
,,DAEoJ.cc
Loc.lton
Clrch oar: Ptrrcs
l. lsnot? €urnr lllLr (ctr)
liotl aec
rod
$rologie
tlouP
(egpcndtr A)
Cor.s d.rcstpctoa
(corrr B7pr, !ru!lrl!, tad
Itdrolo8lc cotdirlo!;
FAc.ot tlp.avtour;
rconaccrd./ cooctcBrd lry.tv1orr!erq reclo)
Producg
ot
Cl r rme
3u, tJ'^'7 s
I tL) 6oct Lt' : , r, I
l/1s-s- {cL = r L-A
J.'^r : th,tla Lq <
6O1, - /*5 PQn - ttouhfa )"
t -l t Ilo rus l, - Co,- <c"J,,1.'i^
'fu,,, o"-. s, /e: ( -,1 /r/
Urc orly or C! ronrcr p.r lt!..tocelr r
t..:2 V
G! (rrr8hrrd) . ffi$ .@3-. 6?.1 _ or d[ .lr.. /0 /@
2. Runo!!
6CVl-:t8.54 Sccond Ed-.fur. lS)
Ston ll Scotl 12 Scon ft
/o 0
2, cl
d.z I
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CURVE
63
RUNOFF FOR INCHES OF RAINFALL
ll0TE: Runotl nlue determined by equation q = (P-0'2 S)2
P+ 0.8 S
REFERETICE: l{atimal.Engineering Handbook, Sectim f, HYDROL0GY
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
1 0.00 0.00 0.01 0.02 0.0 3 0.04 c.0 6 0.08
2 0.10 0. l3 0.15 o. r8a 0.2 r 0,24 o.2e 0.3 I 0.3 5 0. 39
3 0 .43 0.48 0.52 0.57 0.cl 0. 66 0 .71 0.76 0.8 I 0. 86
4 0.92 0.9?1.03 l. c9 1.I4 l. 20 L.26 L.32 1.38 I .45
5 I .51 L.57 1.64 l. 70 1.77 i. 84 1.90 1.97 2.04 2.ll
6 2.18 2.25 2.32 z. )9 2.C 6 2.53 2.6L 2.68 2.7 5 2.82
7 2. e0 2.98 3. o5 3.l3 3.20 3.28 3 .36 3.44 3.51 3.59
8 3.67 3.r5 3.83 3. 9l 3.99 4.O1 4.L5 4.23 4.31 4. 39
9 4.47 4.55 4.64 4.72 4.8 0 ll.88 4.91 5.0 5 5.I3 ,.22
t0 5.30 5. 38 5.47 5.55 5.C4 5.72 5.81 5.89 5.98 6.07
11 6.15 6.24 6.32 6.41 6.5 0 6. 58 6.67 6.7 6 6.84 6.93
L2 1.O2 7.lt 7 .20 7 .28 7 .37 7 .46 7 .55 7.64 7.7t 7.81
l3 7.90 7.9 9 8.08 8.17 8.26 8. 35 8.44 8.53 e.6 2 8.71
T4 I .80 8. 89 8.98 9.07 9. l6 9.25 9 .34 9.43 9.52 9.61
15 9.71 9. 80 89 9.98 lc.c7 10. 15 10.25 10.35 10.44 10.53
16 10.62 10.71 10.80 10.99 Ll.08 ll.l7 r 1.2?11.36 1r.45
t7 11.54 I 1.64 11. 73 11. 82 11.92 12.01 12.10 12. l9 L2.29 12. 38
18 L2.47 L2.57 12.66 L2.75 12.85 12.94 13.04 13.13 L?.22 Lt.32
19 13.41 13. 50 l.3. 60 I 2 69 13.79 I3. 88 13.97 14.0?14.16 14. 26
20 t4.35 14.45 L4.14 14.63 14.77 L4.62 14.92 15.0I l5.lt 15.20
43
S"e - B,rs tp Z
Worksheet 3: Time of concentration CI") or travel time (T1)
J-_
!ro5.c! Lr c zv s /<1 o G ei .--S
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|+
Iu' r. '53ftn
Ghrnncl flos
Capu!. f....... U
S.tnnr ID
Caput_. v ....... Cclt
,O&D.t.
Drt.
y'-?-qa
t-t c.rloa l /et <^ C O drrckrd
Gtrclr oor: ?rcrrat
Clrek or: lc ?a throu8h rab.nr
FttiS: Sprcr lor rr !.!t ar Rlo aaSnntr 9ar lloe ttP. ctd be urad for uch
rcrkrharg.
taeludr r up, tebrorclcr c daactlptloo ol flor raglcncr.
Shrct !1ou (Appllcrblr to T. ooly)Sr3rcac ID
l. Surtrcr dcrcrlptton (rrbla 3,.l)
2. tirnnlag'r roughacsr corft., a (erbtr 3-l) ..
!. llos l.ngth, L (rotrl LSX0 ft) .......... ft
a. nro-tr 2A-hr nhfell, 12......... t!
5. Lnd rlop., r .. Itltz6't,'tr#Coc?ut. tt ...... bt
Shrlloc conceatretcd floo Scgccnt ID
7. Surtrcc d.!cs1pB1oo (prvrd or roprrrd) .....
8. filor lea8th, L ............ !r
9. llrlcc,ogrrc lLoge, a ........................ ttlll
t0. lvetrgc r.loclty. Y (!lnm 3-t) ........... tc-lt
12. Grou arctlonal flor rnr, l ....i.......... fe2
l!. tfetred p.rh.!rr, pj .......r... !r
lf. EydreuLic rrdtur, s'--! Ccputr a oo..... la
lt. cbrml rlopc, r .....1:.................... ftlfc
t6. - ltraolaj'r torghnerr corlf., o
l?. y - l.'9 r2lt rll2
!
-@
.@
al!. llos hajrh. L . lt
tlt. lG - 56frT cquc. lG ...... hr
2O. Irtrrrbed or rrbetc tc o! 13 (rdd ta ll .3.p. 6' ll' od 19) ....... tr
0lloVI-TR{6, S.cotd Ed.' JUP r$5)D8
{J
+,
o
CLo
6
ot!Ltor,go.P.!-
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.06 -
.04 -
.02 -t
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| | | | | | | | tlt?4610
Average veloclty, ftlsec
Flturr &'1.-.{vcnf vclociucr fo? ..tintrtin3 lnvcl tirnc for rhrllor concqtttibd nor.
€fOVI-TR-55, Second Ed.. June 1986)
I | | | tl
Workshcct 4: Graphicat Pesk Dbchars€ rnethod
,l!!o1.c! Lro a/ S l(r u G e- A S
1c- Co
Frequancy
l:tof:lI, P (2{-hour)
Iltclrl ebrcracBtor, It .................
(Urq Gt rrth hbl. 4-t:)
Corpucc l./p ........
vWe
Chrckrd
5ue'gAs/rv T
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tt
t!
,/7t!
2.
3.
6.
5.
7.
t.
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6. golr pcek dlschergr
(rhr r" aad r./p ,"htjiiii';8j"" '.".dla
t. D.B.:
Dntnrgr .r.l ....... jo. { . , OZ d2 (rcro/640)
loaof! curvr orrlbc .... d - 63 (trl trortrhoc 2)
ttrr of concrcGrtcloo .. ta . , Z 7 hr (lrot rrortrhtr r 3)
klatell dtrrrlbuElor Eyp. - -f- (I, tA, II, lll)
Pood asd sneop araer rnrudrhroughout rnlrrrhrd .:.... . € p.!c.o! of \ (- rcr.! or nl2 covcrcd)
PcaL dtrchergar {O . . . . . . . . . . . . . . . . . . . . .. .clr
(t|hrrr q, - qrAnQFr)
Scor-d ,l Scon f2 StoEE 13
/ou
2.4
o.+7
szol
^l,zl
t,3(
Burof!, q..........
(9roo mrkshrcr 2).
Pood eod reog edJuruclB feetor, p_ . . ..(Orc pcrcrar pord .nd *-p .r""- .P
rtch tebla 4-2. F.cEo! ir 1.0 for
aaro. parcrnt poad aod rnup trca.)
e[OVl.tRJq Srcod Ed.,Jq r$O
Chapter 4: Graphical Peak Discharge method
this chapter pes€nts the Graphical Peak Discharg€
mthod for computing peak discharge from nral and
urbsn ereas. lhe Gnphicai method was developed
from hydrograph anelyses using TR.20, ',Computer
Progran for hoject Formulatior-Ilydrology" (SCS
l!Hl). lbe peak discharge equation used is
q, - q{nQFp lgq' ell
- peak discharge (ds);
- unit peak discharge (csrn/in);
= drainage area (miz);
- nlroff (in); and
= pond and swamp adustment faclor.
lbe hput requirements for the Graphical met}od are
. er follows: (1) Tc Gr), (2) drainage area (mi4, €)
epropriete rainfall distribution (I, lA, II, or lll), (,1)
%-to,rr rahfdl 0n), and (5) CN. U pond and swamp
aelul ane spread throughout the watershed and are
aot coruidered in the Tc computation, an adustmant6r pond and swamp areas is dso needed.
Peah discharge computation
For e selected ninfdl frequency, the 2rt-hour rainfall(l) is obtained iom appendix B or more detailed
bcel precipitation megs. CN and total nnrofi (Q) fon
tie rpetershed are aomputed according to the
netlods outlined in cbapter 2. The CN is used to
&terraine &e initial abstnction 0J from table &1.IjP is t}en computed"
if the computed l"tr ratio is outside tlle range showr
h exhibit 4 ({.I, +IA, &II, and 4-III) for the rainfell
dirtribution of interest, then tlre limiting value
lhordd be used. If the ratio fdts between the linitirg
velueq use linear interpolation. Figure 41 illustrat€g
tle sensitivity of I./P to CN and p.
Pertc dischzrge per squere mile per inch of nlrotr
(qd ir obtained ftom exhibit 4.I, &IA, 4lI, or &lll
lf_uOtE T. (chapter 3), rainfall disrribution type, rnd
l./P ntio. The pond and sramp adjustment f".to. i.
obtained from table 4.2 (rcunded to the nearest table
vduel Us€ worksheet 4 in appendix D to aid in
cotputing the pedr dilch$ge using the Grephiol
aethod
l,
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t.
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rbere
qp
Qu
AE
Q
Fp
I.
0D)
Cune
number
I.
0n)
I
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I
lttrtuD
Lt.t ll (t l. l.Or.a
FlFr. 4.1.-Vrrirtton of I.1P for P and €T{.
I
I
ii
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40
41
42
43#
15
46
lil
{8
,19
50
5l
*,
59
64
oo
66
TI
58
50
60
6l
62
GS
64
66
66
at
68
@
@IOVI-TR-SS, Second E&, June 1986)
&000
28'8,
L7e
e65r
?-845
2.44
L
22-55
L16l
L@,
e0(x)
t.szz
I.8{5
\n4
1.704
LA6
1.5?l
t.500
1.148
l.&n
l.&ts
tztg
t,26
l.l?5
1.125\gn
1.080
0.985
0.9{l
0399
0a57
0au
0.7?8
0.7{0
o.?tB
0.6dt
0.632
0.59t
0.564
05@
0500
0.{@
0.4tl9
0.410
038r
035it
0326
0290
0g13
02A7
0.u,
0.1$
0.1?{
0.tst
0.128
0.105
0.083
0.0@
0.0il
70
7tn
73
?4
75
76n
78
?9
80
8l
u,
83
8l
85
86
s7
88
89
90
9l
92
s!
9{
95
96n
98
Tablc {-1.-I. valucr for runofr cun'e numbcrr
&l
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l,
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P
I
(tr otoo
(986I eunf '?g Puor€'t9-uJ,'lA{Ia
Unit peak discharge (9u), csm/in
E H 3', e gg
9?
@oooc)o
trtx
5
E
('D
?h(t
Fl
Gl(D
€c
eia
a
5
{tr
=
E.
o{
c
3o
o
'..loto
.D5
a+.'
-c,
0:
o
rt\o: rltt r
Gh-
oo-
b-
a
Worlshcct 2: Runofr curvc numbcr and runofr
?roJrct /ta+s Q'cor *3 Jt_-rre
Locetton l1z'r, C O Chrckcd D.t.
/=----Ctrcl. on : E!!SS-' Drvrlopod
t. Runolt curvr rlrbc ( Clf)
4.e at>F
Soll lrr
rod
hydrologlc
trollP
(epprodtr A)
Cov.! d.rctlpctor
(covrt Bypt, Erctclra!, ud
hydrologlc condlrlon;p.rc.ol loprtvtour;
unconnrccrd/cooo.clrd tcpcrvlous.r.r rrtlo)
Product
ol
Clf r erre
-n't2t,-n ';
Y-tc <- 1.., -r._ -1=
?.C-.\i9eF- 2J. t),.. - t t-
).J,'rL" -"c
.: ', /F ' (r la
Qo'c - ,\3 pP^ ^ 4a:) /4 -) '^
[:rt-''. -- !^o:. c4rct,/ro'^
Urc only oac G{ rourct pcr ll,ac.Tocals .
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cr (r.rshr.d) .Irorg:I# .'!r7=,
2. Runotf
Frrqurncy
8e1n!:11, P (26-hour)
&rnotf, a ...........(Ur P ead CU rl, rh ceblr 2-lr !tg. 2-1,or .qt. 2-3 rud 2-4.)
62.)
t
U& Clf -
tr
h
ta
-tzl
Scom 11 Scom 12 Stoo 13
/d,
/. /-1 'r
1 .'l ,''4 e
D2 €fGVt-TR65, Second Ed., Juno 1986)
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RUNOFF FOR INCHES OF RAINFALL
_ ( P-0.2 S)2
P+ 0.8 S
Section {, HYDR0L0GY
L-
I
_ll0TE: Runoff value deternined by equation Q
lrrr*rnar, larimat Engineering Handbok,
T
I
i
J-tr J
qr
r'r
d,tr )
Tr
r; I
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
I 0. 00 c.0t \0,.02 l: o.o:0.0 5 0.07
2 0.09 0.ll 0. l3 0. l6 1 0.le ', 0.22 0.25 0.2e o.12 0. 36
3 0.40 0.44 0.48 52 0.57 c.62 0.66 0. 7l 0.76 0.8t
4 0.86 0.92 0.97 l. 03 l.c8 i. t4 !.(U L.26 L.12 1.38
5 L.44 1.50 l. 56 1.63 1.69 l. 76 1..82 l.8e l.e5 2.,.)2
6 2 .09 2.l6 2.21 2.30 2. )7 2.44 2.rL 2.58 2.65 2-71
7 2"80 2.8-l 2.95 3. 02 3.tc 3.l?3.2t 3.33 3 .40 3. 48
8 3.56 3.63 3.7L 3.79 3.8 7 3. 95 4.0 3 4.lt 4.19 4.27
9 4.15 4.47 4. 5l 4.59 4 .67 4.75 4.8 3 4.92 5.00 5.08l05.17 5.25 5.11 5.42 5.50 5. 58 ,.67 5.7 5 5.84 5 -92
11 6.01 6.09 6.18 6.26 6 .35 6.43 6.52 6.61 6.69 6. 78
L2 6.87 6.95 7. 04 7.l3 t.22 7.30 7 .39 7.48 1.57 ?.65t37.74 7.83 7.92 8.01 8.IO 8.19 8.27 8.36 8.45 8 - 54l4E.63 8.72 8.8t 8.90 8.99 9.08 9. 1?9.26 9.35 9.44
15 9.5 3 9. 62 9.7l 9. 80 9.89 9. 99 10.08 10.17 10.26 10.35
16 10.44 10.53 1,0.62 10. 72 10.81 10.90 10.99 11.08 ll.t8 r1.27
T7 11 .36 I1.45 11. 54 I1.64 11.73 11.82 lt.9l 12.0 r 12. 10 12.19
18
t9
L2.28 12. 38 L2.47 12. 56 12.66 L2.75 L2.84 L2.94 13.03 l3.li?
L3.22 13.31 13.40 13. 50 13.59 13.68 13.78 13.87 13.97 14.06
20 14.15 L4.25 L4.14 t4.43 I4.53 14.62 14.t 2 14.81 l4.el 15. o0
42
ll
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.-r':.,!'.j'rir,.:.+i.
-tt - ;
,Worbhcct 3: Timc of conccntratlon Oc) or b?vel ttme Og)
tro3.sr L-'t.:'): . a:t:'L-j ,r>"ILr. 2 '1'? )
LcrG!,oo '/^'- ''\Cb.cl.d DrB.
Ctrclr oar: .!:::!t Drrrlosed
Qltclr or: ta ta chrouSh ruber.|
Fl!S: Spcr tor u rray .r GJo a.trctr 9er llor ctp. crl bt utrd tor reeh
sor'Lb..t.
lacludr . [p, acb.o.rlc, or {..crltclot of llou ..t!.tlta.
Sbert llan (AplUcrblr co t oaly)
l. Surfrcr d.rcrlptlo! (grbtr 3-t)
2. llraolcj'r rou3hlcrt coc!f., ! (!.b1. 3-l) ..
3. nog brgrh, L (86!.t L < 300 tE) ..........
a. $ro-t! 24-trr rrl.afrll, P2 ......... ls
5. trsd dopc, r .. CtlCc
Scarot tD
fB
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. .r - o.oo7 (nL)o'E'B--irEt-
'2'
thrtloe cotcestrrt.d flo?
-@
t0. Arrrr3c rcloc1ct, V (fl3ure 3-l) ..........r ltlt
tll. r. .55ftn c{Frr. Ir, ...... *
C.cpnt lt ...... bt
Setrlt lD
?. Sudrcl dorcriptloo (prvrd or rnprvrd) .. ...
t. Etdr LqtEh, L . tt
9. lhtrrcoonr llopc, I oo o r r o o r r o e o. .. . .. .. .. . ttltt
€hranrl flan Scjrnt lD
12. Grorr a.ctlou:, flo etrr, I orrrrorrrororoo lc2
ll. Irted p.rlr!.a, pa ..1........ l!
lf. Eydrrultc redtur, 3'.! Ciprr. !....... !t
fl
l!. tulnrl .lop., . ............. ltllt
16. .ltroaia3'r rou3hoor cort!., o
tr. y - l.a9 t2lt .llz
!
It. nor hrttb, L . lt
lt. ts.#
20. Irtrrrhed or lubrr.. lG oE lG (.ad tB ta .t.p. 6,
-@
i
I
I,t
I
Cflput. I ....... Cclt
Caps3. 13 ...... ht
il
f€o
.t4
b,D
,o4 l"
elGVl.ll{5. S.cod Ed.'&n tg8d)
.E
Dt
l'F- '
.10 -
.06 -
.04 -
(u
CLo
,n
o6g:o(,t-at.t,
a!-
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I I | | | | | tl24510
Average veloclty, ftlsec
Fl1ur: $I.-.lvrrar v.bcitl.. lor crtlmrtlnj tnvcl tirnr for rhdlor concrntntcd llor.
(21CVI-TR-i5, Second Eil, June 1986)
IatBlal abats.cBlor, Ir ,,.......(Urc Gt ntBh cabl. 6-l;)
Corpurc Ialp ........
6. Untc Acak dkcherge, q,. . . . . . . . . . . . . . , . . . . ctq/ir(Urc t aad I./p ntBh :xhlblB LL
3).21
?
2.
3.
0.
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I
PrlJ.cG Ltoars Qtoae 4? r"7-
Iacrlton l/f "- C O
/--._---.--Clrclr oart E:!:ac__Drvclopcd
l. Drta:
Dnlnegc arre ....... i.. \
&roolf curvr nrlbe r . . .. Cl
flr o! co0c.olr.Eloo .. t
blnlall dl.trtbosloo Irp.
tood aad stnop errer rgrred
Ehroughout rnCcrrhrd ......
--3.i a c.
, o3a d2 (rcrrc/640)
62 (?ro gorkrhrct 2)
ta
a
ra
ra
-
Praqucncy
Retnfall,
trL'bor'n I-7Tl.-l
:
Workslrcct 4: Graphical Pcsk lXlclrar3c mcthod
Chrckrd
Drc.
D.Ga
2-6^?
br (Pror rorkrhrcc
(1, ra, lr, ur)
parc.oc of A. (_ ectcr or d2 covcrcd)
7. Ruoo!!, a ..........(froc rorkshccc 2).
E. Pood aod sweop edJurtlcot facGor, l_ ....(Urc pcrcaor goud aad llrnrp ar.a . P
vlch cablc 4-2. p.ccor tr 1.0 lor
rcto. parccot good and rranp arca. )
9. Pcek, dbcharg.r qD . . . . . . . . . . . . . . . . . . . . . .
(I{hcrc {, - SotQPp)
P (2i-hour)
Stotr ll slotu tZ Sco6 ,3
/0 /c,
/,6 Z, tt
t!
tr
1[
/. zz;1 J 2>6
ltt t- o. 50
o o | ?oo'
O,oZlO.t1
o.zz - ll' cfr
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:
'l
BIGVI.TB-56, Second Ed., Jur lS6)D'
Chapter 4: Graphical Peak Discharge method
This drapter prcsents the Gnphical Peak Discharge
method for computing pe* discharge from nual and
urben erees, lhe Grzphical nretiod uras developed
&om hydrogrzph andyses using TR.20, ,,Computer
Program for hoject Fomurlation-Ilydrologr" (SCS
f98). Ite peak dbdnrge equation used is
qe - qnA6QFp 6gq. a-U
where
gp = pealc disclurge (ds}
9u = uit peak dgcharge (csnr/in);
An - drainage area (m!z;
Q - rurof (in) andF, = pond urd swarnp eqiustment factor,
The bput requirunents for tlre Graphical metlrod ar=
as followr: (l) T. (hrL (2) dni!8ge aree (Dd4, 6)
epprcpriate rainhll distribution ([, IA, II, or JII), (4)
Z*horrr rainfall 0n), end (5) CN. If pond and swamp
eners are spread tluoughout t}e watershed and are
not considered in the T" computation, an adustment
for pond and suranrp areas is also needed.
Peah discharge computation
For e selected ninfall frequency, the 26hour rainfall
(P) is obtained 6om appendix B or morc detailed
local precipitation nr+s. CN urd toal runotr (Q) for
the rraterched are computed according to the
metlo& outlined in chepter 2 Ttre CN is used to
detcmine the initial abstnction (IJ ftorn table 4-1.
I.lP is then comput€d.
if the computed Ir/P ratio is ouGide tlre range shown
in exhibit 4 (&I, 4LA,,4II, rnd &III) for tlre ninfdl
distribution of intercst" th€n ttre lirniting value
should be us€d. tf tlle rztio falls between the limiting
vdues, use line;r interpolation. Figur€ 4l illustra,t€s
the sensitivity of IrlP ro CN end p.
Ped< discherg€ per squane mile per inch of runofr(qj ir obtained from exhibit {-1, 4-lA, &II, or {.III
-bV
*ing Tc (chepter 3), rrinfrll distribution t1ae, end
I"/P ntio. Ilre pond end swemp rCj$tm€nt fector is
obteined from table 4-2 (rotrnded to the neerest ttble
vdue). Uc€ rorltshe€t 4 h appendix D to eid in
computing the peak diEcharge using the Graphicd
method
rtttu
Ll.t ll (tl. lr|.t
Flruc &1.-Verirtion of I./P for P end C!l.
Cunre
number
Trblc &1.-1. valucr for runofi cuve numben
Ir
6n)
&000
2Ar8
t0
|l
&
t3u
a5
{6
z7@
z65l
2.WLU
23,,81? 2.%548 Ll6l,19 LWt0 e00o5l tgn
70
?l
72
78
7r
,o
76n
?8
?9
60
8t
&2
83
8{
8rt
86
87
8{3
89
90
9t
v2
gil
9{
95
96
97
98
Ltn
l.(tso
0385
094r
0J99
65
66tI
68
60
I
I
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I
I
I
52 1.8{6 .5il Ln16{ r.?(x55 r.61656 t.trtr57 1.50958 l.{4850 139060 r3fr|6l tg's
.Jc.i*FLdfl'!Fl63 t.t756{ LYJ5
l'(2!OVI-TR-55, Second Ed., June 1986)
Ir
0n)
0.E5?
0-8t?
0.7t8
0.?{t
0.?ts
0.667
0.63e
0.597
056{
0.532
05m
0.{@
0.439
0.{10
0381
035i1
0346
0290
0n3
02a70w
0.t98
0.t?{
0.151
0.t2E
0.r05
0.o83
0.0@
0.(Xr
It€86I aunf r?g Puores'91'uJ,'l^{tz)
Unit peak discharge (Qu), csm/in
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,'l
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@ooooot\)oo
arS('tchI I8tlJr otoo
Ex
5I
tt(D
a
&(t
!!-l
GI(!
4tB
F
:l
cnou
.D
-l
19
=F
g
a
0
5
oo-
lrl r
3o
o
'ooto,|D t.'.t
ot
o
96\t\o..|.|
5-
c-
0o-
E.
tr
tn
t!
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' Workrhcct 2: Runof curtc numhr snd runoff
?ro3.cB /"lor^ts ?rOe * a3 ,r%.
r.c.rlon 14rC Co
Ctrclr oar: Prrseac .-*@\__
t. &Uott cuwr ruobrr (dl)
Sao-bosin V (Pev)
D.t.
I
I
I
..i
I
cil (rntghcrd) .4-Foducg -/1oi - 1/,4 ug clf -BoE.l .r.. Z.j , ?
-t
w
2. Runof!
Fs.qu.ocy
Retnlall,
Runott, Q(Urr P
or aqr.
P (2{-trqrr)
.rd C{ etBh c:llo 2-1, !18. 2-1,2-! erd 2-1.)
3o11 nec
aad
hydrolo3lc
8tou9
(eppcnd!,r A)
Covrr drrcrlgtloa
( covrr typr, craacsaaE, a[d
hydrologlc condtrloo;
t).tc.n! tap.retour;
rroconarcced/connrcard bprrvtouserlr reclo)
cn -ll A!aa
E acErrtrulor
Ptoduct
oCGlrtne(l
I
a
IeF
IF.
c
b
I
a\a
d
b
Te rton-A ot^'S
(2)r".o"'.:
(oL/c i'utc. t'i^
Do. i- - l: c?- - .2l46ya!'a'a.a
a.,...': 1 - ..-r'/' a C'-..t 1'e/-b 5. 1 €t!
J er.-t ;/n' li.; 'i<e./tcz.: f q7, ;
0.t''o--t.',,
,t a- : - 2 6.t 4+ Ll
tlr1i4'/'?:E(B) Ve'?') L) ' z4qar
tt (+)( (3/8e) 132i)b"-\
,4.1 ; t-,. : ZBr4 qB /,4 /37
ftu';1
Te,ra <e s '7 tr'ti; : /8 c o
11 Y 37J.=4239 78 /o
oPe4 sqa ce
| 6 ,- r'--r;':T,.': lf.l /-ov.t n5, p":it:. {i-
5,'- <:-?.-'j^:))')
J! Urc only 6. c[ rourc. p.r lha.totalt -z3.q t ?0'7
Scoro ll Scotl f2 Scon 13
/a /Do
/,6 z,/
o, t3 D. 44
8rCVI-TR{A S.cond 84, Junc 1986)
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t,
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CURVE
71
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I
RUNOFF FOR INCHES OF RAINFALL
1{0TE: Runofl value determined by equation q = ( i-O'z S)2
0
P+ 0.8 S
REFERET{CE: llational Engineering Handbook, Section l, HYDROLOGY
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0 0.00
I 0.01 c.02 c. 03 05 0.0?o.l0 \0.13 o.l6 0.19 o.23
2 o.27 c.3t 35 0.40 rJ.44 ) o.+s 0.54 0 ;60 0.65 0.7c
3 0.76 c.82 0.88 0.94 I .00 1.07 1.ll t. I9 1.26 't 2?
4 I .40 1.46 I <2 I. 60 i AQ l. 75 1.82 1.89 1.97 2.04
5 2.12 2. t9 2. 27 2.35 2.43 2.50 ?.52 2.66 2.7 4 2.82
6 2 .90 2. 98 3. 06 3.14 3.21 l.3t 3.1?) .47 3.56 3.64
7 ).71 3.8t 3. 89 3.98 4. 06 4. L5 4.24 4.12 4.41 4.50
8 4.58 4 .67 4.76 4.84 4.93 5. 02 5.I I 5.20 5.28 ,.37
9 5.46 55 5. 64 5.7 ?,.82 5.91 6 .00 6;09 6. l8 6.27
10 6.36 6.45 6.54 6.6 ]6.7 2 6. 8t 6.90 7.00 ?.0 9 7.18
11 7 .27 7 .76 7 .45 7.55 't .64 'l 73 7 .e2 7.92 I .01 8. l0
I2 8.I9 8.29 8.38 8.4?8.5 7 8. 66 8.75 8.85 8.94 9. 0,
13 9. l3 t. tt 9.50 9. 60 9.69 9.79 9 .88 9.97
14 10.07 10. l6 LLI r ZO 1C.35 10.4 5 LC.54 IO.64 10.73 10.83 10. 92
15 1I.02 ll.ll ll 2L 11. 30 II 4\)i.:..49 ll.5e 11.6e lt.?8 11. 87
16 11.97 I2.06 12.I6 t2.25 12.3)12.45 L2.54 L2.64 t2.71 t2. 8t
t7 L2.93 13.02 I3. l.2 13.21 lt.3l t 3.41 13 5C I 3.6C I 3.69 13.79
18 13.89 13. 98 14. 08 14.18 14 .27 i rt. 3?L4.41 14.56 I4.66 14. 76
19 I4 I5 I4. 95 15. O5 15. t4 L5 .24 1r.34 15.q3 I R E2 15.63 15.7?
20 15082 15.92 I6.01 l6.ll I6.2I 16. 30 1.6.4{J 16.50 16.60 16.69
L-
5t
ll
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t0. Ante3e ecloclct, Y (flfirc 3-l) ........... ttlt
Itl. r. .53ftn c{put. I. ...... b
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l-
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S.lrat ID
l. Surlrcr d!.cslptloa ('rrblc !-l)
2. llrnnla3'r roughlcr cocff., I (ttbk 3-f) ..
t. Ilo l,cr€th, L (r6hl LS300 ft) .......... t3
a. lrc-tt 24{rr rrlalrtl, P2 ......... h
t. r'.d .top., r .. l.al tr
Cdput. lg ...... hs
Shrllor coaccntrrtcd floe Secsc ID
?. Surfrcc dcrcrtpcloo (prvad or uoprvrd ) .....
E. Elor l.otBhr L ............ lt
9. lletrrcourra .Iop., r ....................... t!/lt
Chrnncl flog S:3rnt lD
12. G:orr rcctt,onrl flor rnr, I o.rreeoroorro.r Cc2
t3. t S!.d gcrtrrrr, p, ........... tt
tl. lydrrult c ndlur, ;'.! Ccprtr r o...... ttr!
15. Ghron:l .lop., r ............. ttlft
15. .liraola3'r sou8h.... eoeff., o roroooorrrrorr
rr. r. l.$ tzli .ll2
!
tt. tlor Lrtth, I . tt
6. r..tr#F
lt.:8.#
-ta
t
ts^c r^l\
u d
t€O goo
d.0s-0,t0
s,b s,z
.o tl+1 ,o4 -l .;l
Co.pu3. V ....... CalJ
Caguc. ?t...... hr
T
I
I
20. Irtereh.d ot rubrnr tc or tr (rdd la lD .t.p. 6' ll, ..d lr) ....... tr
PIGVI-!B{5, S.cond E.t, Jun 1985)
'-l}.,€qb^ao:/4 T (?ta;
Worksheet 3: Time of concentration (Tc) or travel time O1)
lsoj.ct
.t -t G-Ltont;1tOGF'3 Drcr z- c'-? d
Chcct rd DrSa
Glrck oar: Prt..nG
Clrclr or: lc Ta chrouth rnbrrlr
ItrlzS 3 Sprcr tor .r rrot ra lco a.tmatr prr f1o BtP. cr! le urcd f or och
rorhrh.ag.
tacludr r ap, lcbrortlc, or d.rcrlplloa of flor rrtanB..
Sheet llos (Appltcrblr co T. ooly)+-B
!:.. t at)
/,).2 L/
3 00
niQ
,2.51+
-H
Dt
I
$
!,CIo
t
o6L5o
Eo+,s
',1,l
I
Average veloclty, ftlsec
Flnrrr &l'-'{vcrat. vclocltlcr for 6timrtln3 tnv.l t'nc for rhrltor conertnt d ltor.
45
g2
(2IOVI-TR"tO, Second Ed., June l9g{l)
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t
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t crtton (o r a Co
ctrclr onc: prcsrnr @D
Dnlnagc rrlt .......... \ ., 0 3 7 d,2 (rcrcr/640)
Ruaolf curvr m.robrr.... Cf,.
Itll of cocceolrelloo .. t .
Ratnfall dtttrlburlon ryp. - -)!l-
Poqd ead sraop arear rprrad
lhrouShouc gecarshcd ...... . 0 p.rclag oe \ L:Zecrcs or nl2 covcred)
- \'E (Qc-u):
ProJ.cr
Wo*sheet {: Graphical
Lront's Q,,>c-€ *3
Pca& Discharye mcthod ,aL^L'in
ry?glc s1s2 2-Q- /o
Orcckcd Drcc
l. lbce:
Frcquency
8:tnfall, P (2i-hour)
Scor[ tl Scoru 12 Storo 13
1o ,/o o
/,b ') //
O,r/) | o. fr7
0.3/
3o 0l S:a
o,t4 10.q
a/
,30 (Ero norkthrcc 2)
hr (Prol rukshact 3)
(r, IA, rr, ttl)
l
' cfr t,4tt I g,ez
Tn.rurt d,s'.lno-7* Z'/l c{s
fns,,,oru b. S> cfs 'f
F
ttr
z.
3.
6.
5.
6.
7.
l
Intclal abetraccloo, I. .......... tn(Osc ef t tch bbl. 4-l;)
Coopucc lalp ........
Untt pcak dkchargc, 1. .........
(Ure T. and I./P rdEh ;xhtbl,B 4- 2)
Ruooff, q..........
(froo norkshcec 2).
Pond aod rraop adJuGaaBB !:ctor, F- ....(Usc pcrccot pond and !n rp s,E.e . v
slch cablc 4-2. Facror tr 1.0 tor
zaro. p€tccnB pood aod sraog erca.)
PaaL dkcharg., qp . . . . . . . . . . . . . . . . . . . r . .
(l{hcrc A, . qu[QPp)
csdla
Itr
I
I
It
i
9.
€IOVI-TB€6, S€eond Ed, Junc 19B6)
D{
iJr'
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(986I aunf "pg Puoras ,gts.UJ-I,1{13;
Unit peak discharge (qu), csm/in
9t
(tl OrOo 3E g g grg gs
s
c.'
Ll
trtx
5
o
iF
&(l
!9
od(D
&c
F
ll
u2
(4t
IJ
|D
t
D-
0a
F
J5
=l.D
o
',., 6
o5o
56'.'
oJ
c|
i N-oto?
t
-----...........I
fi-
ll
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IIJI
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Chapter 4: Graphical Peak Discharge method
This dupter presents the Graphical Peak Discharye
metlod for computing peak discharge from nual and
ultan ar\eas. The Graphical metiod was developed
fron hydrcgraph analyses luing TR.2O ,.Coraputer
Program for hoject Formulatio*-llydrology" (SCS
l9&l). lte peak discharge equation used is
qp = quAnQFp Pq. eU
wbere
Qp - peak discharge (ds)
9u = unit peak discharge (c$n/in)
An = drainage a,rea (mi4
Q = runotr (in); andFn = pond and swamp adustnnent factor.
The input reguirements for the Graphical metlpd are
as follows: (f) T. 164, €) drainage area (mi4, €)
sppropriate rainfall distribution 0, tA, II, or III), (4)
24hour rainfall (in), and (5) CN. If pond and swamp
arreas are spread throughout the watershed and are
not cnnsidered in the T" cornputation, an adjustment
for pond and swamp areas is also needed. -
Peah discharge computation
For a select€d rainfdl frequency, the 24hour rainfdl
(P) is obtained fmm appendix B or more detailed
local precipitation maps. CN and total rwrofr (Q) for
the watershed are computed ar.,cording to the
methods outlined in dlapter 2. The CN is used to
determine tlre initial abstr"ction (IJ hom ta,ble lt.I.
I./P is then computed.
if the computed Ir/P retio is outside the nnge shown
in exhibit 4 (4-I, 4.IA,4II, and 4-IID for rhe rainfdl
distn'bution of interest, then the limiting vdue
Ebordd be used. lf tl|e ratio falls between the limiting
values, use linear interpolation. Figure 4-l illusttates
tlre sercitivity of l.tr to CN and p.
Peek discharge per squ.ne mile per inch of runof
(qd is obtained fuom €xhibit 4.I, 4-IA, 4-II, or 4.III
bV using T" (chapter 3), reinfatl distribution t1rye, end
Ir/P ntio. Ttre pond urd swernp adjustment fector is
obt ined from table {.2 (rounded to the nearcst table
vdue). Use worksheet 4 in appendix D to dd in
computing the peak discharye using tlre Gnphicd
method.
Curre
number
{0fla
43
tU
,t5
,t6
17
.18
{9
50
5l
52
53
6{
55
66
67
58
59
60
6l
62
63
6{
65
66
6?
68
69
t t t t t rt DLlit ll (rt, l.cr.t
Fljurc &1.-Vrrirtion of l./P for P end cl{.
0.85?
0-817
0.7t8
0.70
0.?ql
0.66?
0.dp
0597
0J64
05@
o.s{n
0.{69
0.,#B
0.{t0
0.381
0.35it
0Je6
029!)
0-??3
0247
0.8
0.198
0.t?a
0.t5r
0.r28
0.1(5
0.0&t
0.063
0.04r
Table {.1.-1. vducr for runoE cuwe numberr
Ir
0n)
Curve
nunber
Ir
6n)
&000
e8?8
L7@
2.65rzffiLU
2.W
22ti5
Lt67
LW
2000
r9?2,
t3t6
\n4
r.?0{
LA6
t57r
lJ09
l.{48
l39o
l.*ts
tztgt%
l.l?5
Lr25
r.o7l
l.m0
0.985
0.9{l
0t99
70
?ln
73
74
ID
?6
ta
?8
?9
8{)
EI
82
83u
85
86n
88
89
90
9l
g2
9:l
9{
95
96
97
98
€IGVI-TR€S, Second Ed-, June 1986)rl-l
Scze-8As.rd
I4
'
F
tI
r!
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lle
t
Fortdrcet 2: Rrmofi curre number and nurofi
FroJ.cB honC ,Qrreg*/ w Dle
t crBtor y'ar e Drra
Ctrclr onr: €AAtr.1 Drvrlopcd:_=/
l. Runof! c|tEll. rrobr r (CI)
2. Runof!
!icqurncy
Eelnfell, P (2{-hour)
&r9o^ll, _Q(Ut. P .nd Gl t'tth c.bl. 2-1, ttg. 2-1,or .qr. 2-t end 2-{.)
G[ (rnl8hcd) . .!gq.r eroducE .ffi - 5i,6 , urc of .
,t
a
I
@
Sotl oer
:td
hydrologie
tEouP
(eppcndlr A)
Ccrr dercrtpclol
(covrr typr, Brarloaag, .nd
hydrologtc condllLor;
Frc.nc tap.rvtour;
unconoaccrd/connec Brd loptrvtour
erce reclo)
ProducB
of
Cn r erre
{)qt- ,.+S .D2 r. - r2 ,Lt-.- t ' ,.
.Br,,t ) - C, '- z->n t -' o'n
ei'&.-''t'iy o '-' =,1". i.e./.
U'. only onr Cn losrcr pcr llne.tocalt.
Storl fl Scorl 12 Scon f3
1c, o
2V
Ae,
8IGVI.TR.55, Socond Ed., Junr 1986)
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CURVE
56
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It'4
r
r'L,.
RUNOFF FOR INCHES OF RAINFALL
_ (P-0.2 S)2
P+ 0.8 S
REFERETICE: tlationat Engineedng Handhok, Sectim {, HYDROLOGY
llOTE: Runoff rnlue deterrnined by equation Q
N 0.0 0.1 0.2 0.3 0.4 0.5 0.5 0.7 0.8 0.9
0
I 0 .00 0.00 0.01 0.0 t
2 o.o2 c.o3 0.05 0. c6 0.08 ,' o.lo 0.t2 0.l4 0. l7 0.l9
3 o.22 o .25 z-6 0. 31 0.34 0. 38 Q.42 o.45 o.49 0. 53
4 o.57 t/. OZ 0. 66 c. 70 0.?5 0. 79 0.8 9 0.9 4 0.99
5 l.04 1.09 I. l5 1.20 L.25 1.31 I .36 L.42 1.48 l. 54
6 I .60 I .66 L.72 l. 78 1. e4 l. 90 I .96 2.02 2.09 2.L5
7 2.22 2.28 2.t5 4I 2.48 z. ))2.62 2.68 2.75 2.82
8 2.89 2.96 3.03 3. 10 3. 1?3.25 7.32 3. 39 3.46 3.54
9 3.6t 3.68 3.76 3. 83 3. 9l l. 98 4.06 4. L3 4.2L 4.28
10 4.36 q.44 4. 51 4.59 +.67 4 .75 4.8 3 4.90 4. 98 5. 06
11 5.14 5.22 5. 30 5. 38 5.46 ,.54 5.6?5.70 5.78 5, 86
L2 5 .95 6.03 6. 1l 6.19 6.2'l 6.36 6.44 6.52 6 .60 6.69
13 6.77 6.85 6.94 7 .02 7.1I t.l9 7 .2?7.36 7.44 7.53
14 7.6I 7. 70 7.78 7.87 7.95 8.04 8.13 8.21 8.30 8.38
15 8.47 8. 56 8. 64 8.71 8.82 8. 90 8.99 9.08 9.16 e.25
16 9.34 9.41 9.52 9.60 9.69 9.78 9.8 7 9.96 l0 .04 10.13
L7 LO.22 tn 31 10. 40 10. {9 10.5I t0.67 10.?5 10.84 10. e3 t 1.02
18 tI.ll 1i .20 I I.29 11.38 t1.47 I1.56 11.65 I l.?4 11.8 3 It.e2
l9 12.01 12. t0 12. t9 12.28 t2 .17 12.46 t2 .55 L2.65 L2.7 4 12.83
20 L2.92 13.01 13.10 13. t9 13.28 Ll. ?7 L3.41 13. 56 13.6 5 13.?4
36
Sa9'Rtst'L' ll/'
Worksheet 3: Time of concentration (Is) or travel time (t1)
!t Duie D.B. {' 4'? o
Lc.cton /o' '- C 6
I'
I
I
l'
I'
I
I
I
I
I
I
I
I
I
I
I
I
T
I
I
t
Chcckcd
ctrch orr: @ Dcvclogcd
Cltcl. da: tc tt thtouSh rubrrrr
lults ! 3grcr tor .r rr[y rr tF ..$!cnt. P.r flon ttP. c8a bc urcd for rrch
. rorlrhrct.
toctld. r orp, rchcoellc ' or daacslPtlon of flou 'c8!'nlr'
Slrcct tlor (Appllcrblc co 1" oaly)SGtlGnr ID
l. Surfrcr dercalptlo! (.trble 3-l)
2. [rnulsS'r tou3hocsa cocff., o (!tbl. 3-l) ..
3. !1or l'.ngrh, L (rdtr1 L < 300 ts)
l. tr.o* 24+rs arlnfrll, P2 .........
5. Irnd rlopc, r
ft
1a
cUfr
hr
Ill. 1..56ffi
Chrnncl flog
-@Coaputr l! ......
Shallos conccrtrrtcd flos Scgucnt II)
7. Surfrcc datcslptloa (pevcd ot troPrvcd ) .....
E. tlog l.atth' L ............ lt
9. tlrtrrcourrr rlopr, | ....rrrrroo............. f!/tt
10. Avragc wloclty, V (flgurc 3-l) ........... ttls -@
12. Crolr rocttonll flor rrle, I rrorrrrreorrrrr ft2
13. tfctt.d g.al,!.t.r, pr......r.... fl
ll. Eydrrutlc rrdiur, r'.! corput. r ....... tl
PU
ll. Chrmct .lop., . ............. ftlft
15. .l|l.n{nt'r roughnerr coeff.r n r..r.oor......
r?. v - t.s t2l3 ,tlz
Cocput. Ia ...... *
Scgrcnt ID
Coaput. v ....... Ctlt
l!. l1or l.!tth, L . ft
re. 13 -#ColFrt. lt ...... ha
20. Lrt.r.h.d oa .ut s.. Tc or 1B (edd ta tn.t.P.6' llr rad 19) ....... hr
elOVl-TR-65, S€cotd Ed, Jttnc 156)
u'i?7
sf,o loo
,28 , /0
e.{-'t L''t
'0Ll+l ,ol
a
DA
.10 -
.05 -
.04 -
+,
oCIo
6
o6g
tou
o
{Ja!-
t
I
I
I
I
I
I
I
t
I
t
I
I
t
I
I
I
I
I
I
I
I
| | t I t,^t t,-t t2 4 !- ...tO
Average velocity, ftlsec
Fltr|r! &I.-lvctqr vclocitlcr for crtinrtlnf ttrvcl timc lor rh.tlor concfltrrt d flor.
(21GVI-TR-55, Second Ed.. June 1986)
2.
3.
4.
7.
D{
I I
I
I
I
I
tr
t
I
I
I
I
I
t
I
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I
t
I
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I
6. 0nic pcak dtrchtrgr, qo .........x cto/la(Urc t aad I./p ,acn &trtrr 4_b
Ruooft, a...........(9rot roorlshcec 2).
Pond and reeq adJuacoccc lecEor, F_ ....(Urc pcrccoc pood end t !r.ap araa . P
rlch gablc 4-2. Faccor i,t 1.0 lorzero pGrcen! pond eod suanp araa.)
9. Peak dl!ch.!g., {p ....... .cfc
(lJhrrr qn . qu\QFp)
€fOVI.TR{5, S€coDd Ed.' Jrnc fS6)
Pro1.cr (. ro ,r',
P (2t-hour)
Sua ^ats '+-',/r\l t I t
pcac.nc of { (- acr.! or ol2 covcrcd)
Storn Sl S co r-o 02 Storu il3
/c/ o
z,Lf
tq
yr
tn
,s7 |
r L?J
oo
,48
It.
Drrlnegc 8r!E .......... \ - , OZ d2 (ecrcr/640)
Rnooll cnrrc nrobrr .... q - f L (Fro rorkrhcer 2)
Ttr o! coocraGrectoo .. t" . ,2 t hr (lrol norkshcct 3)
Ralafall dkrrlburlon Eyp. - aT (t, IA, Il, tII)
Pond aod lrrop arcar rprtad
Ehroughout retershcd .:.... -
Ercquency
R:tnfall,
InlCtal aboBracc,loo, I. ..........(Urc 6l rdBh rable 4-l:)
5. Cocprte lalp ......
, Worksheet 4: Graphical Pca& Discharge method
Q,>zt !*b t%:ol.ct y'-4'?o
Chrckcd Drcc
------\,Ctrcle onr: ,@pt Dcvclopcd
l. D.ca:
A
I
I
T-
I
Ir
0n)
Curre
number
Ir
0n)
I
I
T
I
I
I
I
I
T
I
T
I
I
I
wtere
9p 'peak dischare€ (ds}
9u = unit peak discharge (csrn/in);An = drainage area (mB;
Q = runoff (in); andFo =.pond and swarnp adustment factor,
Tbe hput rcquirements for the Graphical method are
as follows: O) T. 1p1, (2) dninage ar€a (miq, (g)
sppropriate rainfall distribution (I, IA, II, or III), (4)
24hour minfall (in), and (5) CN. If pond and swamp
areatt are spread throughout t}e watershed and are
not considered in tbe Tc computation, an adjustment
for pond and swamp areas is-also needed. -
Peak discharge computation
For s selected rainfall frequency, the 24hotr rainfall
(P) is obtained from appendix B or more detailed
local precipitation maps. CN and total r.unoff (Q) for
the wstershed a^re computed according to t}e
rnetiods outlined in drapter 2. The CN b used to
determine the initial abstraction (lJ from table 41.
I./P is then computed.
if tlre computed l.tr ratio is outside the rznge shown
in exhibit 4 (eI, 4lA,4II, and 4III) for thoninfall
digFibution of interes! then the limiting value
sbould b€ used" If tle ratio filts between the limiting
vdues, use linear interpolation Figure &l illustrateJ
tlre sensitivity of lrt? to CN and p.
Peek discharge per square mile per inch of nrnofr
(qJ ir obtained hom e.rhibit +I, 4.IA, 4.II, or 4.III
lV_usinS T" (chapter 3), rainfall distribution t1Ae, and
I.P retio. The pond and snnmp aqiustnent iactor is
obtained hom table &2 (rounded to tjre nearest table
vdue), Us€ worksheet 4 in appendix D to Nid in
com-puting the pedr dbch:rgE using the Gnphicd
method
3.0(n
2AI€,
L7@,
e65l
L
2-&
2.W
2253
Lt61
LW
e000
t92,
1846
Ln1
L?04
LA6l5a
L50g
1.4{8
t39o
l.gB
r.gtgt%
l.l?5
1.125\tn
t.ut0
0.985
0.94r
0899
70
7l
72
fil
74
JD
?6n
78
?9
80
8t
&,
83u
85
86
g7
88
89
90
9l
92
9:'
9{
95
96
9?
98
I
Chapter 4: Graphical Peak Discharge method
This chapter pr€s€nts the Graphical Peak Discharge
netlod for computing peak discharge ftom rr:ral and
r5bu areas. lhe Graphical method was developed
fron hydrograph ar:alyses using TR-20, ,,Crcmputer
&ograrr for hojec Forrulrtion{lydroloeiy" (SCS
l9B3I the peak dfudarge equation used is
g = q'drnQF tEq. 4-U
Curve
number
40.lla
4il
tU
45
{6
47
48
49
50
5l
52
53
5,1
oo
66
67
58
59
60
6l
62
63
6{
65
66
67
68
69
(21GVI-TR65, Second Ed., June 1986)
tttrtlltt
Ltit ll (t l. txr.a
Fljun {-1.-Vrrbtion of l.1P for P rnd Cl|.
085?
0-El7
0.Tt8
0.7{)
0.703
0.6dt
0.692
0.59?
0-564
0.5@
0.500
0.469
0.439
0.410
oitSl
0.31t3
03al
0*299
0.2?:t
0.247
0.u,
0.198
0.1?,t
0.151
0.r28
0.r0i0.8
0.062
0.(xl
Table &1.-I. values for runofr cunc numbers
&1
9tt
I
I
I
I
t
I
oo
€86I aunf l'pg Puor€ 'gg'uJ'I^{ra
Un'it peak discharge (9r), csm/inE H g a ge
trlx
5
(!
ao
0a(D
€c
o-
u
at
-E(!
rt
=D'
o.t
tc
ca
=.D
o
C'r'oo
=cl.$o
'+a.ou
o3
.|
$truqir\.,\o.; ||
t.
I
I
I
t
T
I
I
I
I
t
I
?
T
I
t
t
I
I
I
I
I
I
I
I
I
I
I
I
I
T
I
I
t
I
-sz16^8/lnSza-n E
lroJ.ct
Worblrcct 2: Bunoficurrc number and runoi
srDlU-
Chrchrd
l*- q,DrBl
DrB.
Ctrclr oar: Prrra! .Etryg_)\=
l. Runolf currrr ruqbrr (el)
€roc-c-+5-
Sol! oen
:nd
hydrolo3lc
tlouP
(eppcndk A)
€orr drrcrtpetot
(cota! !tpa, craelrat, eld
h'drologlc condt clor;
9.tc.oB tlp.rvtoq;.r'coalrccrd/connrcBrd tlpalrlourtro recto)
Producf
oldrene
&a iPd c.t{
.?1 . m,,rc,
'2:,t- -/.
OAE - As pe, t\ - ,r7oa., .r.ai .'\
$-.rs I - Co). 4.orq, t ist,\
e.\ I &a i,4 ,1
Ls oe-a- s,f<i'
.!/
-
U". only oe Clf rourcc pcr llac.
G! (rcl8hcrd) ffirylF -?-3{{1r('a /4'7
2. Runof!
Prrqurncy .................. F
Relntell, P (Z4{rour) t!
Ruaotlr_Q ta(ur P end Gt rteh cebl 2-lr ai;:-i:i. -or .qr. 2-l end 2-{.)
b{, Ll u.. 6r -lz51
Scon ll,Scon 12 Scon lt
/ao
z, r/
E. LL
efOVI.TR.tq S.otrd Ea, Jrurr 1986)
I
I
t
I
I
I
I
I
I
I
I
t
I
T
I
t
I
I
I
I
I
RUNOFF FOR INCHES OF RATNFALL
N0TE: Runolf valuedetennined byequation q = (P-0.2S)2
p+ 0.8 S
REFEREIICE: t{ational Engineering Handbook, Section l, HYDR0LOGY
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
1 0.00 0. 00 0.01 u.trt 0.03 0.05 0.06 c.09 o-ll
z 0.t4 l6 0.19 0.211 0.2 6 0.30 0.34 0.3e 4.42 0.46
2 0.51 o.55 0. 60 0.65 0.70 0. 75 0.8t 0. 86 0.9 ?0.97
4 I . UJ t. c9 l. l5 I.2t | .27 l. 33 1.39 1.46 1.52 l. 5e
5 1.65 1.72 1.79 l. 86 1.93 z. 00 2.07 2. Ltl 2.21 2 -2e
6 2 .35 2.4)2.50 2. 57 2.65 2.7 2 2.80 2.87 2.95 3.03
7 3.10 3. l8 3.26 3.34 3.42 3. 50 3.58 3.56 3.7 4 1- 82
8 3 .90.3.98 4.06 4. L4 4.22 4.30 4.39 4.47 4.55 +.64
9 4.72 4. 80 4.89 4.91 5.C6 5. t4 5.23 5. 3l 5.qo 5-48l05.57 5.65 5.74 5.83 5.91 6. 00 6.0e 6.1?c.26 6- 351l6.44 6.52 6I 6. ?0 6.7 9 6. 88 6 .96 7.0 5 7.14 7 -27t27 .32 7.4L 7.50 7.59 7.6I 7 .7f 7.86 7.95 8.04 8- 13l38.22 8.31 8. 40 8.49 8.58 e.67 8.76 8.85 e.94 9-O?l4 e.13 9.22 3l 9.40 9.4 9 58 9.68 9.77 9.86 9.95
15 10.04 r0.14 1O.23 10.32 10.41 r0.51 10.60 10.69 10.78 0.88
16 10.97 I 1.06 ll. t6 r1.25 1I.34 1I.44 11.53 11.62 11..?2 11.81
L7 11 .90 12.00 12. 09 12. t8 L2.2e 12.37 L2.41 12.56 12.65 l2 -75
18 L2.84 12.94 13.03 13.I2 L3.22 I3. 3l I3.41 13. 50 13.60 13.69l913.79 13. 88 13. 98 14. 0?14. l7 14.26 I4.35 L+.45 L4.54 14.64
20 L4.73 14.83 14.93 15.02 I5. l2 15.2t 15.31 15.4C 15.50 15. 59
45
I
I
a
I
I
I'
I
I
t
l'.
1..
t
I
I
I
t
li
I
I
t
t
I
l,
Il(
I
I
fr.
Colput. It ......
fc
1a
ct|tc
hr -@
-@
Workshect 3: Time of concentration (ts) or travel time (T1)
troJ.ct C/ONJ ZtgcF {S ryElb-
, / ..- /-\trcrclon ,/A,( L u chccked
Clscla oaa: tc ta chrou8h rubrrar
FflS s Sgrcr lor .t !.!t r. !r.o ..gEca!r P.r f 1ou ttPc era bc urcd for uch
roslthcag.
Iacludr r t Pr acbclatlc ' ot darellPlloo ol flou rcg;ocncr.
Sihcct llos (Appllcrblc to t" ool!)Scglcnt ID
l. Surfrcr dascrt ptloo (.trblc 3-l)
2. tlrnnlng'e roughacra eocff., s (trbl. 3-l) ..
t. llw lcngrh, L (BdBrl LS 300 fs) ..........
t[. l\ro-yt 24-hr reLafall, PZ .........
5. Lnd .lopc, I
Ctteh oor: Prc3ca! ,@ffi=-\
6. rG.t#.#
Shatlos coaccnlretad flor Scgaent ID
?. Sorfrcc dllcslpt1oo (prved or unPrvcd ) .....
t. lla lcatth, L ............ tt
9. Trtrrcourra rlopc, 3 ro.oo.orrr............. ft/tt
10. lvrregc v.loclty, v (!t8urc 3-l) ........... tt'[s
u. r. - 36fun Cooput! l. .. . ... hr
Chrnncl flos Srgrcnc ID
11. Grorr acctton l flor rrcr, r o..roor.ooororr Ct2
t3. l|cttcd parlnlcr, Er ....................... fL
ll. Eyrtrrullc rrdlur, t'.-1 Colputr r ....... fc
tI
t5. Cterncl rlopc, r ............. fclfs
16. .lbnotng'r roughnrtr cocff., o rrrrrroorrorro
rr. v - r.es '1l3 .l/2
le. tr.#Corprra TG ...... ha
20. tlrrrrrhcd or rubrro ?c or ts (.dd tt ln rtrpr 5,
Corpute v ....... ftlr,
SIGVI-TR.I5, Second Ed., Jum l$5)
D.ta
lrrla
F 7
:s ",,4" o
,28 t0
/o,1 /. J
,oll+l ,ot
.m[f
D8
I
I
I
I
I
I
I
I
I
I
I
I
I
t
I
I
I
I
I
I
I
I
oclo
6
o
UIL:toa,Lc,{J,t-
.10 -
.06 -
.04 -
| | | | | t,t I t tr II 2 4 5' 10. 20
Average ve1ocl ty, ftlsec
Flgrr & 1.-Avcra;c vclociticr for clrtflrtint tEvGl tirnc for shr||or concmtrrtcd nor,
(21OVI-TR-55, Second Ed", June 1986)
I
I
I
t
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Drelnage sre. .......i.. \. ,O -L o(2 (rer$/640)
Rnnof! curvr nuober .... q - 6 { (Fro gorkrhccc 2)
tloa of concsols.tloo .. T. . , ? 7 hr (lrol erorkrhr.E
R:l,afall dlrtrlbucloa rypo - fu (I, t/|, II; III)
Po[d and suaap ar:as lgrrad
trhroughoqt rncershtd .:. ... -
3)
pcrcaoB of L ( .crr!os slz covcred)
2.
3.
8rcquency......
Ralnfall, P (2t-hour)
SEoEr! ,t Scoro tZ StorE t3
/d cl
2,4
l,[
,t
t!
/,oYl
'4f
q0 06.
7.
8.
6. lntBlal abscraclion, Ia ..........
(Use et FfEh Eable 4-l:)
5. Coopucc talp ........
Untc peak dlschergc, qu ..........(Uae T" eod I./p r.fch :rhlbft 4-_)
Runof!, a ...........
(Froo norkshecr 2).
Pood aud sralp edJurto:B! fectoa, p_ ....(Urc pcrcent pond and $raop erle . P
rtch c.blc 4-2. !.cBor tr 1.0 forrero pcrcenB pond and rralp erca.)
9. Prak dttchargcr rl, ...... .c!r
(tfhcrc qO . quAsQFp)
cru/1n
1o o ,zL
z'oa
l*
I
PIOVI.TR{S, S€cond Ed, Jum f9$)
Sc/8'8rr /,- fu
Iforkshcct 4: Graphical Peak Ilischarye method
/'ProJGct Lr"^LE'(,Oa€{{ tt Dth"o.c, {^d- z o
locrcton U+t t Lct Checkcd Drcc
Clrclc ooc: Prcrcn!
t. Drc.:
I
I
T
I
l,
l.
t.
I
T
I
I
wb€re
Qp
Qu
An
a
Ir
tu)
Ir
0n)
I
I
li
I
I
t
The input requiremenrs for the Graphical method are
ss follows: (l) Tc ftr), (2) drainage area (mi4, G)
appropriate rainfall distribution (I, [A, II, or III), (4)
.24hour Binfdt (in), and (5) CN. If pond and swa,mp
anea,s arc spread throughout the watershed and are
uot consjdered in the T. computation, en adiustrnent
for pond aad $rEnp areas is-also needed.
Peah discharge computation
For a selected rainfdl frequency, lhe Z4hour rainfall
(P) is obtained from appendix B or more detailed
local precipitation maps. CN and total nrnoff (Q) for
tle wetenhed are computed according to t$e
methods outlined h chapter 2, The CN is used to
deternine the initial abstrzction (IJ fum table 41.
I./P is then computed"
if tlte computed I./P ratio is outside tl|e range shownh exhibir 4 (+I, sIA, sII, and 4-IID for rhtrainfall
distribution of intercst, tllen tlre limiting velue
cbould b€ rxed. If the ratio falls between the liniting
vdues, use linear interpolation. Figure 41 illustratei
tlrc sensitivity of I"lP to CN and p.
Peek discharge p€r square mile per inch of runoE
(qd ir obained from erhibir +I, 4-IA 4.II, or 4-IlI
!y_*ing Tc (chepter 3), rainfatl distribution tlpe, urd
I1P retio. The pond end swemp adjustment iector is
obtained Aom uble 1.2 (rormded to tlre neerest Eblevducl Use norksheet 4 in eppendix D to .id in
coutpulinS thc pedr rxing the Grrphicat
acthod-
40
,u
4tlI
44
45
46
17
IE
t9
50
5l
5:t
8t
54
55
56
TI
58
59o
6l
6ea
0l
66
68
CT
6Ec
3.000
LS.IS
L?@,
a65r
Lffi
2.44
L3,d,8
2255
LI6I
LW
2.0(n
ts2,
r.846
Ln4
l.?:04
l.616
l.57l
1.509
l.{48
t.gx]
t.cBtzn
tl26
l.r?5
l.ti5\tn
1.080
oss
ogal
0t99
70
.L
72
73
74
?5
?6
tan
?9
80
8t
&
83
EI
85
86tl
88
89
90
9ln
93
9{
95
96n
96
I
li
t
T
]T
Ed., Junc tg86)
Chapter 4: Graphical Peak Discharge method
This clrapter prcsents tle Graphical Peak Discharge
metlpd for compuring pealr discharge &om nual and
urtan areas. Ttre Graphical method was deveioped
ftom hydrograph anaiyses using TR-20, ,,Computer
hogran for hoject Formulation-llydrology,'- (SCS
198i1). Tbe peak discharge equarion used is
qp = qoA'QFp 6Eq. a.U
- peak discharge (ds);
- tmit pedr discharge (csr:/in);
= drainage area (mi4;
= runotr (h); and
= pond and srramp adjustment factor.
ttlrtlllt
Llrt ll (tlt t..rr,
Fljurc &1.-Varirtion of l./! for P rnd C]{.
Cune
number
0.857
0al?
o7t8
o74{t
0.?(ts
0.66'/
0.68
0.597
0.56{
0"5@
0.5(n
0.4a
0.4:p
0.410
OJEI
03sl
o.&tr
0:9!t
0213
02470E
0.r98
0.t?{
0.15r
0.t8
0.1(F
Q.083
0.0e10r|l
Tablc &1.-1. valucr for runof currc numbers
€rGVI-TR.SS, Sccond +l
It(986I aunr "pg Puot€ '9S'UI'I.\{tz)
Uni t peak d ischarge (Qu ) , csm/i n
E E H e:gg
l.,'
T
I
I
t.
I
oooo
Gi
'.
5
a
6(t
GI(t
Ec
i
u)
a2
-tt
|D
l|
E
0
rl
o3
3o
o
'c|o5oot.'
.!|
o5
o
+tqi5st\o,^|D
t
I
I
I
I
I
I
t
I
I
I
t
I
J
I
t
on-
. Og-
E-
1DCE I
t-J
r.loP.d ,I
i
I
I
:
I
I
II
I
I
I
t
I
I
I
I
I
I
t
t
t
I
I
I
I
I
I
t
Sua^B15z,t-, -;T
Wcfohcct 2: Runotl cuwc numbcr and runofi
koJrct
l. Luao! f curvr nnber (Cil)
2. Runof!
''.-\ . ./ ,'n -W2o2. D... 4/<//O
ChrcLed Dtsr
Qf (rnrghccd) . .:::l t:::i. .8 . 54, ,/ uro clf .st' 6,./
-;
f?1
lrequcncy .. ...... ..... ,s
8elnfell, P (20-hogr) t!
Ruaolt, q ........... lo(Ur P ead Ctr stch crbt 2-lr !ii:-i:i. --
or .qt. 2-3 rad 2-t. )
t9o{L aer
end
hydrologtc
tao|lP
(eppcadlr A)
Co,vtr dr:crtgcloa
(covrr typr, !!ar!E nt, ead
hydrologlc condlElo!;
p.tcaaE tap.rvtoot;
uncomgclrd/coanreBrd l,!pa!l'tou!.r.t rrB10)
Producr
oldrene
Ur. onlt olr CU rourcc Acr ltnc.localr.
Scoru lt Scon 12 Sto 13
/d o
2.4
,t3
8[GVI-TR.54 Sccond Ed, Juno l$ID
I
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I
t
t
T
I
I
I
I
I
I
t
t
t
I
1{0TE: Runoff value detemined by equatim Q
RUNOFF FOR INCHES OF RAINFALL
_ (P-0.2 S)2
P+ 0.8 S
ll
I
ii
I
tl
rl.l
|l
REFEREilCE: ilational Engineaing Handhok, Sction 1, HYDR0LOGY
CURVE
59
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
1 0.00 0. 00 0.0 r 0.0 t 0.02 0.
2 0.05 0.0?0. 08 0. l1 0. l3 0.l5 0.13 0.21 0.24 0.27
3 0.30 0. 34 0.3?0.41 0.45 0.49 o.5 3 0.58 0.62 0. 67
4 0.71 0.76 0.81 0.86 0. 91 0. 96 l.0I 1.0?t.l2 1.18
5 1.23 L.29 t. 35 t.4l L.47 1.53 I.59 1.6 5 l.7l l. 77
6 I .84 1.90 1.97 2.03 2. l0 2. Lf 2.21 2.30 2.3r 2. 44
7 2.5L 1e 58 2.65 2.72 2.79 2.86 2.93 3.00 3.08 3.15
8 4.22 3.30 3.31 ?.45 t.52 3.60 t.67 3.75 3.82 3.90
9 3. 98 4.05 4.l3 4.21 4.29 4.31 4.45 4.53 4.60 4. 6e
r0 4.76 4.84 4.92 5.01 5.C9 5.l7 5.25 5.t3 5.4t 5.49
l1 5 .58 5.66 5.74 5. AZ 5 .91 5.99 6.07 6.l6 6.24 6.t3
t2 6.41 6. 50 6.58 6.66 6.7 5 6.83 6.92 ?.01 ? .0e 7. 18
13 7 .26 7.t5 7.4t 7.52 7.61 7.69 7.78 7.87 7.95 I
14 8.13 8.22 8. 30 8. 39 8.4 8 8.57 8.66 8.7 4 8.8 3 8. 92
15 9.01 9. t0 9. t9 9.28 9.36 9.45 9.54 9.63 9.72 9. 81
16 9 .90 9.99 10.08 10.17 10.26 10.35 10.44 10.53 10.62 10. ?l
l7 10 .80 r0.89 10.98 11.07 1!.l6 11.25 11.35 I 1.44 11.53 I 1.62
18 ll.7l 11.80 11. 89 t1.98 12.C8 I2.17 L2.26 L2.t5 12.44 L2.53
19 L2.6!t2.72 12.81 12. 90 13.C0 t3.09 t3.18 Lt.21 13.36 13.46
20 13.55 13.64 t3.74 13.83 13.92 14.01 t4.ll 14.20 L4.29 14. 39
39
I
I
I
l'
l
Saa -,9 ls,','l r+r-
Worksheet 3: Time of concentration Ctg) or travel time (Ti)
I,oni" Q,o ce fg ,,LL ^r,
y'-4 -7 olsoJ.cr
Lcatloo
Fllli: Specr for rt lray.a tro r.SEGott P.r flou !t9. cra br ulcd for och
rorbhcat.
toctudr r np, rchclrltct ot &acrlPBtoo of llou n3lcn!r'
Sihrct tlor (Appllcrble co t. ooly)Segrcnt ID
t. Surfrcr d.tcalpttoo (.trbk 3-l)
2. lt nnl,!8'. routh!.!. cocft., o ( erbt'c a-f) ..
3. Ilor bn8th, L (86..1 LS 3O0 ft) .......... l!
a. ti o-tr 20-hr rrlofrll, P2 ......... 1o
5. Lnd .lopc, r .. trl la
Ch.cl.d
-
llrl.
I
t
t
t
I
t
I
I
I
I
I
I
6't.-t#
l?. e . t.rg {/t .trz
-w
Strllos coaccatrrtcd floe Scgreat lD
7. Sqrftcc dclcslpcloo (prvrd or unPeved) .....
t. Eld l.otth, L ............ ft
9. ltrrtrrcoutr rlope, | . r . r r r o o o o r . . . . . . . . . ... . lBllt
10. Ayrtega roloclty, V (figurc 3-l) ........... Cclt
Irt. l. .55ft1
Ghrnncl tlor
12. Ctorr rcctlonrl flou rro, I oorooooooorrooo k2
13. L!t.d p.sl-c.r, p,........... ft
ll. Ey&rullc rrdts., r'-i C6prt. r....... fB
15. Ghraoot .lop., | .....]:.................... f!/fB
15. .llraalnj'r rorghaer corff., a rrooorrorr...r
Co6pu3. tt ...... hr
Cooputa Tt ... ...
Scgrrnc ID
Cooputr v ....... tclt
-@
Il(
I
I
It. Ilor l.nlth, L . lt
?19. lr .IffiT Cmputr tG ...... hr
20. lt !.t.h.d ot .ub.r.r tc or lG (rdd ta ln .3.P. 6, tl, md 19) ..".... hr
@IOVI.TB{6, Sccoad Ed"' Jtlrrc lS)
l/n,. ac
uP UP
300 4oa
,/O '32
5 )l
, oLl+l ,o I
g
Ild
o
CLo
ai
oa^L
=o(,Lru+ra-
l,
I
I
I
l,
I
I
I
I
t
I
I
.to
:
.06 -
.04 -
.02 -I
'l
t
I
I
I
t
I
I
t
| | I | | | | | | | r/L 2 4:6 10
Average velocl ty, ft,/sec
F[un l.l.-.{vcn3: vclocitlcr for Grtimiainf tt|vcl tinc for rhdlor com.ntnt d llor.
efOVl-TR-s5, Secoad Ed., June l98ti)
I
I
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I
t
I
t
I
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I
Worksheet 4: Graphical Pea& Discharge mcthod
BtDe4e D.!. r/u/?orr-_
Chcckcd D.E.
l. D.ca:
Drelnege .,r.r .......... \ - ,O I d.2 (rcrar/640)
Rrnolf curve mrb.r .... q - 59 (lra rrorkrhmr, 2)
tLlr o! coocaorreEloa .. t . ,5 I hr (!rot norkshecc 3)
-narufaii <itrcrrbqcron Eyp.- . 7 (r, tA, rr, rrt)
Potd eod straop arrar rprced
Ehroughout secarrhrd ...... -
2.
3.
Frequency
Ralntall,P (2i-hour)
Storq fl Stom 12 5l0r! ,3
/o0
311
,56
230|'
, t3 l'
yl
to
la6.
5.
6.
7.
8.
Inlrl,al ebrBracElot, Ir ..........
(Usc Gl rrtEh rable 4-t:)
Coopuc! Ia/p ..................
Ucl,r pcak dkchargc, qo .........y(Usc t aad I./p rdBh ;xhtbtB t--lt I
Runoff, a...........(Froo rorkshcec 2).
Poad aod rr:op adJurtocat facGor, ?- ....(Usc pcrccor poad aod ssirEp arla . P
rtBh r.bl. 4-2. gecBor k 1.0 lorlero p€rcant gond and sranp erca.)
PeaL, dl,rchargG, ep ......
(tfhcrr qO . qo{QPp)
cro/1o
to
' cfr ,3 O,.
€IGVI.TB€6, Sccond Ed., Jum l9&DD{
I,
I
T,
wbetrg
qp
Qu
AtD
e
FP
t
l.
I
I
I
I
I
I
I
Ir
6n)
Currre
number
Ir
Cn)
3.000
agrS
z7@
a65tzffiL&
214828
Lra
LW
2.000
1qD
r.8{6
Ln4
LTIN
l.636
t5?r
1.50!t
1.448
r.390
t.3!ts
l2?9
t.26
l.t?ti
t.xls
Lgn
1.Gil'
0.985
0.9{r
08srt
70
7l
72
?3
74
75
76n
ftl
?9
80
8l
e,
&lu
E5
E6
c7
8{1
89
90
9l
92
93
94
95
96
9?
98
40
4l
4t2
4846
16
47
48
49
60
5l
52
5it
5{
55
66
67
58
59
60
6l
6A
63
6{
65
66
TI
68
69
I
I
I
I
I
I
i
I
I
I
Chapter 4: Graphical Peak Discharge method
This cbapter presents the Graphicd Peak Discharge
method for computing pesk discharye from rural and
urtan areas. The Graphical method was developed
qun hydroqph analyses using TR-20, ,.Computer
Progran for hojec Forzrulation-Ilydrologyd (SCS
1S). lte peat Os*arge equation r:sed is
Qp - guArnQFp tEq. 4-U
- fpak discharge (cfs);
= rurit peak discharg€ (csn/in}
= draina8e area (mi4;
= runotr (in); and
- pond and svamp adustment factor.
lte input r€quirements for the Graphical method are
es follows: (l) Tc ftr), (2) drainage area (mi4, €)
rppropri.te rainfall distribution (I, IA, II, or III), (4)
2&bou ninfdl (in), and (5) CN. If pond and swamp
rrautarc spread t}roughout the watershed and arre
not considered in the T. computation, an adjustment
for pond and swamp areas is also needed.
Peak discharge computation
For e selected ninfall frequency, the 2Ahour rainfall
(P) is obtained from appendix B or more detailed
hcal precipitation maps. CN and totd nurotr (e) for
ttre watcnhed are computed according to the
metbods outlined in chapter 2. The CN is used to
deternrlne the initial abstraction 0J from uble 4.1.
I./P is then computed"
if the computed I.1P ratio is outside the range shown
h exhibit 4 (&I,4IA,4II, and 4.IID for thtrahfall
dismution of interest" then tlle limiting value
lhould be used. If tbe ratio falls between the limiting
vdue3, use linear interpolation, Figure 4l i ustrateJ
tJte sensitivity of I"/P to CN and p.
Pesk discharge p€r square rnile per inch of nurof
(grJ is obteined from e.rhibit .|.I, 4.IA, 4-II, oll-III
-bl_*tng Tc (chapter 3), rainfall distribution t1pe, and
I./P ntio lte pond and swamp adjustment iactor is
obteined from table 4-2 (rounded to the nesr€t t3ble
vduel Ure worksheet 4 in rppendix D to eid in
com-puting the peak disch$ge using the Graphicd
method
(2fOVI-TR-55, S€cond Ed., &nc 1986)
lttrt!ttt
Ltit ll (tt. !.cla
Flturr {.1.-Yrriatlon of I.{P for P end CN.
0.857
081?
0.n8
0.7&
0.?Gt
0.66.t
0.6n
0.597
0.56{
0.5@
0.500
0.469
0.€9
0.{10
o38r
0.353
03!6
02sg
0.273
0247
0.u,
0.198
0.17{
0.151
0.ua
0.105
0.0&t
0.062
0.ur
Teblc &1.-I. ralues for runofi cure numben
+t
9?
I:
T
or C'roo
I
I
(986I aunf "Pg Puoras '9g'uI-IA{IZ)
Unit peak discharge (Qu), csm/in
@ooo
(.)S('lqls = 3 8t coooooo
t'
t
I
I
I
I
r,x
5I
a
ID!t
=g
o(t
rt
GI(D
=
aia
u
!t.!
{E
=tr
ELo
ig
c
=o
o
'oo:'oot
a+.'
.4,
ot
o
\*
\o.i rrltt
I
I
I
I
I
I
t
T
P
a:
E-
I
I"
3uB-$4st,u EI
I
I
I
l
I
I
I
t
I
I
t
Fortsh:ct 2: Brurof? ctuyG nutnhr and nuroll
EL-"e,r'<e-
Chrcltcd
an l'J'?Q
D.ra
l. lunof I curvt ruohr (Ct)
rl
I
!
/t'Ctrck onr: Pr.a.ac /Drvdoprd
Soll nar
ead
hydrologlc
tloup
(eppendlr A)
Covtr docrtptlon
( covrr !ypr, !raaEaa!!, .!d
bydrolog!,c condlrloo;
p.tcanc tlprrvtour;
unconaccctd/connrc Brd tlpan lou!.r.. serlo)
Paoduc!
ol
Cl : erle
?ai< -,4.: 5 Q z' . .1" J'r." ?.' -'
b/-..': - - ^r', <')/^1'-'52.
| '=n-2.^ ' 2a
/o' ): '''- --'-le-,
Utc only onr Gf gonrcc pcr ltna.locals .
T
,l
t
I
I
t
I
I
t
,l.t>rl
Gr (rnlshred) . g!!,!_t@! .?;- 73,L z urc Gr -w
2. Runof!
!icqucncy
Retntall, ? (l0-hoqr) ..":""""""'
&rao-tf , _Q(Ur P ead ef etrh ceblr 2-1, iii:-i:i,o! .qt. 2-t rrd 2-a.)
tr
tl
lo
Ston ll Slon ,2 Scon 13
//o
2,1
a,s I
elGVI.TB"t6, Sccod Ed., Jnnc 1986)
I'
I
T
I
I
t
t
t
I
I
I
I
t
III
I
;tI
I
I
;t
RUNOFF FOR INCHES OF RAINFALL
I{OTE: Runoff value determined by equation q = ( P- 0'2 S )
2
p+ 0.8 S
REFERET{CE: tlational Engineering fiandbook, Sectim {, HYDROLOGY
CURVE
73
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0 0.00 0.01
I 0.02 c. 03 05 c. 07 0.lc 0. l3 0. l6 0.20 0.24 0.28
2 0.32 0.37 0. 4l 0. 46 (;.;0.57 0.62 0.6 8 0.74 0. 8c
3 0.86 0. 92 u. v6 1.05 1.ll i.l8 L.Z)I.32 1.39 1.46
4 I.53 I.60 1.67 I.75 l. e2 i. 90 I.97 2.05 2. L2 2.24
5 2 .2a 2.36 2.44 2.5?2 .6C 2.68 2.f 6 2.84 2.92 3.01
6 3 .09 3. 1?3.25 1.34 1.4 2 3. 5l 3.59 3.68 ?.7 6 3.85
7 3..93 4.02 4. tl 4. l9 4.2e 4.31 4.46 4.54 c.63 4.72
8 4. 8l 4 .90 4.99 q no 5.17 ).1)5.34 5.41 5.52 5.61
9 5.70 5.80 5.89 5.98 6.c7 6. 16 6.21 6. ?4 e.qt 6.52
10 o.6?6. 7l 6.80 6. 89 6.9I 7.08 7 .11 7.26 7 .35 7.45
t1 7 .54 7.6J .,73 7 .82 ,.tl e.0r 8.10 8.19 e.29 8.38
L2 8.48 8.57 8. 66 8. ?6 8.€5 8.95 9.0 4 9.13 9.21 9.32
13 9.42 9. 5l 9.61 9. 70 9.8C 9. 89 10.08 t0.18 t0.27
14 10.37 I0.46 1c. 56 1c.65 i0.?5 \c. 84 I0.94 11.04 ll 13 f 1.2:2
15 11 .32 I 1.42 lt.5I lt 6l 1t.71 1i. 80 11 .90 I1 .9e 12.09 12.19
16 12.28 t2.38 L2.41 L2 .51 12.C7 12.76 12.86 12.96 l2 nF 13.15
T7 r3.25 13.34 13.44 13.54 I3.63 l2 ?1 13.83 L}.92 14.02 14. l2
18 t4.21 14.31 I4. 4l 14. 50 14.6C i4.70 14.?9 14.89 I.r.99 15.0e
19 I5.18 15.28 15.38 L5.47 15.57 15.67 L5.77 15.86 l5 .96 16.06
20 16.16 16.25 I6.35 16.45 16.55 Ir,.64 l6 . ?rr 1,6. 8 4 16.94 17.03
5J
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I
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,rfu"
Chrckrd
Clrclr orr: ,t.r.{@
Cltelr onr: tc lc ghrouSh .ub.rQ'
fiytls: Sprcr for r. lrot rr tuo a.tmotr prr tlor ltF cra bc urcd lor "chEtk h.at.
tncludr a !aP' lchaElBtcr or daacrlPtloo of flor reglcnrr'
Slrcct floo (Appl,lcablc to t" ooly)S.8!cnt ID
l. Ssrfece dcrcrlpiloo (crblc 3-l)
2. llrnnttS'r roughncla cocft., o (trbl. 3-t) ..
3. llou lcn8rh, L (rdlrl L < 300 l!)
4. tno-t! 24-trr rrl,ofel.l, P2 .........
5. Ilnd llopc, t
Cooputr TB ......
Scgocnt ID
?. Surfecc drlcrlpBloo (Pevcd or uapeved ) .....
E. Elon lcnt3h, L .........;.... . ft
9. tlrtorcourc llope, r ........................ !r/ft
10. Averegc wloclty, V (flgurc 3-l) ........... lclt
Ill. ?. .53ftn cooPut. It ...... ha
Chrnncl tloc Scgrcnt ID
t2. Ctou rcctloo.l flor trer, I reer;ooorrrrorr Cc2
13. l|c!!.d p.rlc!.r, p, . .... .... .. f t
ll. Eydrrullc trdlua, a . j corPu!. I .o..... fipr
15. Graacl .lop., . ............. ltltB
16. . lleuoLn3'r roughoer coaff .t o .. o oo o... r..rr
17. v - t.lg r1l3 .r/z
It. llou lca3th, L ............ tt
I19. t3 .5ffiT Colpuc. tG ...... hr
20. lt t.rrh.d or rubrro tc os tr (rdd ta 18 .c.P. 6' ll' .!d t9) ..r....
elGVl-TR65, Second Ed., June 1986)
fr
1!
Ctl tt
h!-@n!
0.007 (nL)-'-c' 't - -I]E5.'..TFE2 t
Shrllos conccacretcd flos
-@
Coputt Y ....... C.clt
SuB^8*stJ T
IVorksheet 3: Time of concenhation Ct6) or tnvel time Crl)
/,,,^,.. 1,;,^^'3{Psolact \ ,'r '/ \) "\ " i' € !- \)D.t.
Ibt.
utr uP
2 ?c ,J, 'J )
ll
, oL l+l .ol
E
D8
|uao
6
o
UIg
=o(,
3.{,{Ja!-
I
I
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I
I
I
I
I
I
t
I
I
I
I
I
I
I
I
I
I
I
,l
.10 -
.06 -
.04 -
t24610
Average veloclty, ftlsec
Fltun 3.1.-.&cnC vclociticc for cttimstint tnvd tim. for rhdlor concc|rtrrt d flor.
(2lOVl-TR-i5, Second Ed., June 1986)
ttl
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I
Wor{sheet 4: Graphical Peak Dlschargl method
'i--t, 'l to
Clrrckrd
S.r9^$d5,rry @
b.. q-J'?0
Drca
plrcrnB of L ( acrar or ct2 eovcred)
SEorr ,l ScorE rz Slot-o f3
/o6
2U
yr
tn
11q
.5,/l
a,t/
efGvI.TR{q Second Ed., Jrrae l$6)
4.
5.
IotCtal abe!rac!,1on, I.
(Use Gl Elch bblc 4-t:)
Coopuce lelp ........
6. Untc peak dlrchergr, q.. . . . . . . . . . . r. . . . . . . cct/l,o(Uec t aad I./p t tth ;xhlbrt a-Ll
Ctrclc ocr: P!.r.nc Drvcloocd
I. Drca!
Dr:lnagc .rar ..........
Rsnoff curvc mnbcr ....
Frcquency
Ratnfall,P (2i-hour)
7. Runoff, q ..........
(8roo rorkshecg 2).
8. Pond aad sraop adJurrenE facBor, F- ....(Urc perceor pond ead $raap rrra . P
vtBh cable 4-2. Factor ls 1.0 tor
zaro. perccnt pond aod rratp :rca.)
9. Pca&, dkchargr. .lp ......
(utrcrc qO - 9'r\QFp)
ntt' 'J' cl' (ecrcs/640)
--2- 2 (Ero norkehacs 2)
Itna of cooc.rlt.ltoc .. Tc - ,{J hr (Froc rorkrhcac 3)
Relnfall dltBrltuBtoo typ. - 1> (t, IA, Il, II!)
Poad and sraop ereer rgrted(hroughouc saE:rrhad
\
cil
2.
3.
' efr
D{
I
I
l,
I
I
I
T
I
I
I
I Ir
0n)
Ir
(in)
I
I
I
I
I
I
I
ii
I
T
I
wteFe
Qp - peak discharge (ds);
Qu = unit pealt disciurge (csm/rn);
Am = drainage area (miz);
Q = nrnoff (in); andFo = pond and swamp adustment factor.
The input requir€ments for the Graphical method are
. es follows: O) T. (hr), (2) drainage area (mi4, €)
rpprcpriate rainfall distribution (I, IA, II, or III), ({)
24hour mhfall (in), snd (5) CN. If pond and swamp
{rcas:rre spread throughout the watershed and are
Dot considered in the T. computation, an adjustment
for pond and swamp areas is also needed. -
Peak discharge computation
For a s€lected ninfall ftequency, the 24-hour rainfall
(P) is obtained frorn appendix B or more detailed
local pr€cipitation maps. CN and total nrnoff (Q) for
tlp watershed are computed according to the
netltods outlined in drapter 2. the CN is used to
detetmine the initial ebstraction (IJ from table 4-1.
I"t? is then computed"
if the computed lntr ratio is outside. tlre range shown
h €xhibit 4 (+I, &lA,4II, and 4-III) for tlre rainfall
distribution of interest, then the limiting vdue
.hould be used. If tbe ratio falls between the limiting
values, use linear intcrpolation. Figrre 4.1 illustrates
the sensitivity of I"r? to CN end p.
Peelc discharge p€r square mile per inch of nrnoE
(qJ i,s obkined from exhibit +I, 4tA, {.II, or 4.III
by trsing Tc (chapter 3), rainfdl distribution t1pe, and
IJ? ratio. The pond and sramp adjustment factor is
obtained hom table {.2 (rounded to tlre nearest table
vdue). Use worlsheet { h rppendix D to aid in
computing the peak dbctnrge using the Graphicd
nethod
3.000
2A|.8
L7d2
e65r
2545
2.U
2.48
22fi
LI6I
eo82
2000
t.c2,
la46
Lfu
1.flX
1.636
t.571
r.tql
1.448
1.390
l.&t3
tn9
t.26
Lr?5
t.lzti
Ltn
t.(tso
0.985
0.94r
0"699
?0
7l
72
?3
74
75
76n
7E
?9
80
6la
83
84
85
86
c7
88s
90
9l
92
git
94
95
96n
96
Chapter 4: Graphical Peak Discharge method
Tbis drapter pr€sents the Graphical Peak Discharge
metlod for computing pe:k discharge ftom nrral and
urtan areas. fire Graphical method was developed
ftom hydrograph analyses rrsing TR-20, "Computer
Prograrn for hoject Forurulation-llydmlogy" (SCS
l9B3). Tbe peak discherg'e equation used is
qp = quAnQFp teq.a-u
,|{)
,tI
42
.a
tA
45
46
47
,a
49
50
5r
62
53
5{
oo
56
57
58
59
60
6le
63
64
65
66
el
€8I
(2lCVl-TR-55, Second Ed., June 1986)
t t t l t lt D
tt.t ll (t t. l.<r.a
Flnrc &1.-Vrriatton of I./P for P rnd C'I{,
Currye
nulber
0a57
08r7
0.7t8
o.7&
0.7G
0.66't
0.dp
0.597
0.564
0.582
0.500
0.4dt
0.4:F
0.{10
0.381
0.3|3
0346
0290
0zt3
02t7
0.u,
0.198
0.1?{
0.151
0.r28
0.105
0.083
0.064
0.ul
Tablc {.1.-1. valuct for runofr currc numbers
+l
It(986I aunf "pg puoJas '-o9'uI'IA{IZ)
Unit peak discharge (Qu), csm/in
I
I
T
l.
I
T
I
I
I
.l
@ooooor\! ul 5 (t orI I 3 88
t5,
5
o
r?
rl
GIo
e
Fta
a2
x
l|
!9)F
!!
r.t
=03
3o
o
'.tIo.$o'
..
.q, l--
ot
o
*fru.3S\oraT
I
T
T
T
I
I
I
II
I
53
,
tr
ta
h
I
I
I
I
T
t
I
t
I
I
I
I
t
I
Ij
I
t
I
T
t
,/ /'1Pro1.ct CidrlS Z,DGE* -S
t/Lc.clon y'a r:- t-"
l. Runolf cunre ruubar (C!t)
Wor&rhcct 2: Rrurofi currc numhr and nurof?
E -J,-/AQ
Ghrckrd
I
,I
I
I
i
:
I
G[ (rntShrrd) . tour eroduct. JSZ -
<t,O
2. turnof!
Ur Clf -t-s3t
Sqg-D+:rtrt F-l
r,.c.y''l'?e
*a.'-
Ctrctr onr: ''- Prrrcac @pcloged
ttotl ner
:od
hydrologtc
t!oqP
(:ppcadlr A)
Conr dccrtgctoa
(corrr typr, cr!.c!.uc, .!d
hydrologle condlrlon;
D.lcaoB ttp.rylout;
unconnccBad/connrclcd tlp.frt oq!errr racto)
(..r.t
trux
Product
of
CI r erre
OFa,- : .a '. .<- /ij cea .'.>-- t.J- - , -
Ar/3'1 --2 - a2,'1,'')^
Urc onty oar Gl rorcc por ltcr.toc.lr -
3tom lt Ston 12 Ston f3
/tc)
z. q
,0{
8ICVI.TR-54 Sccond Ed, Junr l!f,6)
I
t
lr
l.
t
t
I
I
t
t
I
taxhre b grven in appendix A for determining the
lliQ r'l'qeifcation for disturbed soils.
CorE ttTe
Trbl€ 2-2 address€s most cover t1pes, srch as
vegdation, bare soil, afrd imperviorx surfaces. Th€re
rre e nunrber'of methods for determining cover tJry€.
the mct common are field reconnaissance, aerial
gbotographs, and land use map8.
a.
Tnatncnt
Mnnl is a cover type modifier (used only in
t ble 2-2b) to describe tlle management of cultivated
{ri,ntltural lands. It includes mechanical ptzctices,
och as contouring and terracing, and management
Fecdcq such as crop totstions and reduced or no
flrya
Ilydrologic condition
Huil.mloob conditimt indicates t}e efrects of mver
trttre and treatment on infiltntion and runofr and is
le'nerallv estimated ftom density of plant and residue
6ue" on sample areas' 6ood hydrologic condition
indicates that the soil rxually has a low nrnofr
Dotential for that specific hydrologic soil group' cover
iile. and treatrnertt. Some factors to consider in
,iii-ating the efrect of cover on infillration and
nrnofi are (a) canopy or density of lawrs' ctlps' or
other vegetative areas; (b) amount of year'rcund
cover; (cI amount of grass or closeseeded legumes in
tltstions; (d) pereent of residue cover; and (e) degree
of surface roughness.
Tablc 2-I.-Runofi &pth for sclcctcd CNr and rainfall amountsr
Rrmotr depth for curve number of-
lLhf.ll {} 15 50 53 55 98959065
t
I
I
I
I
itnhts
I
t.0 0.00 0.00 0.00 0.mt2 .00 .m .00 .(}Lt .00 .m .m .c)1.6 .m .00 .00 .mll .00 .(n .00 .002A, J .6 .m .00 .^<.vz25- ' .00 .m .(2 '"-.$
. ' &0 .00 .@, .09 .19
35 .@, .08 .6 35{0 .06 .18 33 53- 15 .r4 J9 50 ,74att 2A .a .69 S
60 5() "S l.l4 lJc?.0 a4 121 1.68 LUZ&0 125 r.74 225 Ln9.0 l.?t 2E e88 3.4910.0 2.a e80 &56 18It.o z.?a 3.5i! 4fi 5.00t2.0 8.s 1.19 5.00 5.?9l3r) ro {.89 6.76 6.61tro 4.65 6.62 455 7.u.
tfo 531 6.36 7.C6 Ae)
0.00 0.00' 0.00 0.03 0.08 0.r7 0J2 0.56 0.79
.$ .(n .(B -91 .15 g .46 .74 39
.00 .v2 .06 .13 2A 39 .61 .92 r.l8
.01 .(E .ll 20 g 52 .76 l.tl lsE
.G .G) .l? a .u .65 98 129 158
.06 .14 21 38 56 .80 1.00 1.48 Ln
.t? 30 .46 .65 39 1.18 r53 l'96 2n
33 5r .?l .96 t25 1.59 1.98 L45 Ln
-sil .75 t.ol 130 1.64 2.t2 L45 2.94 3n
.?6 r.0:l lJ3 l.6r LU 2.46 Lgz 3'41 3'n
r3o 1.65 a(x z{5 2.89 &87 &E8 4.4i1 {.?6
13:t ut' ?sl 828 &78 Un 4t5 5.rl t?6
160 &10 &68 {.15 1.69 5% 582 6.41 6.?6
xct 3J9 {.46 6.fi 5.63 621 6.8r ?.{0 ?.76 \
dlo 1.72 53it t.96 6.5? 7.18 7.79 8.40 8.76
{.90 i56 612, 648 7.52 E.16 8.78 9.{0 9.?6
nT2 6{3 ?.r3 731 8.48 9.13 9.n 1039 10.?6
6.56 7.n &05 8.?6 9.45 10.11 10.?6 u39 11.76
7.4i2 82! 85 9.?l 10.42 ll.l0 lt.?6 ut39 ra?6
E3o 9.U 9.9r 10.6"t lt.ttg rz08 l2?5 13.39 t&?6
9.19 ro.fi l0a5 ll.61 1237 l&fi l&?{ l1J9 l{-76
I
t
lit
I
,l
rtrroohtr rho nl[a dlovn to obtrh nurf &lrhr for CN'r or ninfrlt urur mt rlloun'
(2IGVI-TB-55, Second Ed., Jrure 1985)24
)\/I
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I
l'
l.
I
I
t
I
I
I
I
I
I
I
I
I
I
I
t
I
S,€^gA:t,v .A
Iforlshect 3: Time of concentration (Is) or travel time (T1)
I /^ JJ_ _
t!oj.c! Lr,'azJ '{.rDG€ -S
t.o.rrton ;/o' '- '- I Ch.ckcd llrt.
[OT!S ! 3prcr lor .r trty aa 3to ..gs!!a P.s tlor tyPG cra bc urcd fot ereh
. rcrlrhc.t.
Iocludr . !.Pr 3chcE tle. or dercrlgtloo of flor rcglcntr'
Sihrct llou (ApPllcrblc co T. oaly)Scgocot ID
l. Surfrcr dGtctipclo! (trblc 3-l)
2. u.nntq'. tougloco cocff., o (ttblc 3-l) ..
3. lloo l-n8th, L (totel L ( 300 ft)
i[. tgo-yr 2{-hr rrtafell, P2 .........
5. lrnd llopc, r
fr
1o
trl ft
b36. 1,.?#$#
l?. v - l.{e r:/3 .t/2
Cosput. tr .......G{1
Sh.lloe cooccotntcd flor Scgncnt ID
?. Surtrca dclcrlpBloa (prvrd or unptvrd ) .....
6. Fla l.oath, L . fc
9. grtcscou:rc rlope, 3 rrrorrorrorr........... tlllt
10. Avrregc rclocltt, v (fl$rc 3-t) ........... ttl.
Irl. t. .36ftn co8put. Ie ...... tr
Chenncl tlor Scgncnt ID
12. Ctor rccBlonrl f!,or rne, I rrrrrrroooorooe Crz
13. g.t!.d g.sl-!.a, p, ........... ft
l{. Bydrrullc ndtrr, t'-i c6ps3. ! ....... fB
?Y
15. Cbraml .log., . ............. ftlft
16. .llraala3'r rou3hn.r. cocft.r o rrorooorrr....
.[,;!
tt. llor La3rh, L . ft
tr. rr -#
20. ta.t.r.h.d or lubrr.. tc or lt (rdd ta h 3c.Pt 6'
Corputr Y ....... Ctl.
CocFrS. lG ...... hr
ef0Vl-fR-s1 Second Ed"' June 1986)
H
a
D€
I
I
I
I
I
I
I
I
I
I
I
I
I
t
I
I
I
I
I
I
I
,l:
.10 -
.06 -
.04 -
+,rb
oILo
cl
oU'Ltoi,Lo.a,a-
| | -ta | | | | | | t It2-46lo20
Average veloclty, ftlsec
Flpn &l.-.{vcnfe vclociticr for crtimrtin3 tnvcl tirne for shrltor co||ccntrtt d fl,or.
(2IOVI-TR.55, Second Ed-, June 1986)
5.
6.
7.
E.
9.
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Workshect 4: Graphical Peah Discharge mcthod
Pro1.cr L,un,s Q:a,€ *{rvu*
t
!/,/^-\LcrBlon :/ .L'(- - J Clrrckcd
---f--Ctrclr oot: Prc!.nB Dcvrloocd
l. Drce:
Dretnegc arla ...... .. .. \.
Ruaoft curvc nrobcr . ... Cf,.
ttr of cooc.olrait oo .. tc .
Ratlfall, dtrcrlboclon tygc -
Pood .nd lraop arcar rgreadghroqghout rraccrshed
Frcqucncy
Ratafall,
.ed q d2 (rcrcr/640)
'== r (Pro tlort,thrcg 2)
, Z"? hr (?rol sorkshacc 3)T J.t/- (I, lA, lI, III)
2.
3.P (Zt-hour)
p.rccn! of A" (- acrcs or c12 covcrcd)
SEor[ el Slom tZ Scon 03
/o o
z-. +
tn
yr
tn
'ttJ
IotBlal abalracBtou, I. ..........
(Usc C$ irlth hble 4,-l:)
CoEpuBc lalp ........
Untt pcdc dkchargc, q. . . . . . . . . . . ,,r. . . . .(Uac T. aod I./P rdth ;rhtbtt 4-L)
Ruoolf, q ...........
(8roo workshccc 2).
Pond aud rveap adJurtocuG f.cEor, F- ....(0rc perceor pond and !*ratrp aree . Y
utBh rabla tb-2. Factor ls 1.0 lor
z€ro pctccnt pond .nd sraap erca.)
Pcak dlscharg., qp ......
(Thcrc q, . quAJFp)
32d
,05-l'
' ct.,OG
cro/la
to
:
'l
BIGVI.TR"66, Second Ed., Junc 19g6)
Sqa'Bksttr Gn
o.c, y'-'! -7't
DrE.
D{
I
I
l,
l.
t
I
I
Ir
0!r)
Ir
0n)
I
I
I
I
t
I
I
I
I
I
T
li
I
I
I
rhelr
g - peak aischarg€ (ds}qr - urdt peak discharge (csrn/in}Aa - dretnage area (mi4;
Q - nurofr (in)r and
Fp - pond and swamp adjustment factor.
Tbq gp"t requirements for t}e Graphical method are
rs follorru: O) T. 161, (2) drainage aiea (nrfl), (g)
lpfoedate rainfall distnlbution (I, IA, tI, c lltl, tO2l.furr rsinfall (in), and (5) CN. If pond and o*,.rp'
argalr arte spread thmughout the watershed and ari
not corcjdered in the Tc computation, an adjtrstment
tor poad and ssamp areas is also needed"
Peah discharge computation
For r celect€d rainfall frequency, t}e 24-hour rainfall
(P) is obtained from appendix Ii or morc detailed
local precipitation rmps. CN and total nrnofi (Q) for
the vatershed ar.e computed according to the
T€thds outlined in drapter 2. The CN is used to
detxririne the initid abstnction (I.) from bble 41.I/P is then computed.
pt\
-clmputed Ir/P ratio is outside tlre rznge shownb e*ibit 4 (4-1, +llt" 4II, and &lII) for the-rainfail
distribution of intercsl t}en tlre limiting value
sbrdd be used. lf tbe ratio falls between the limiting
vdues, use linear interpolation Figure 4l iltustrates-
tne sensitivity of I"r? to CN and p.
Peak dischrrge per squane mile per inch of nrnof(qd ia obuined from exhibit +I, 4-IA, 4.lI, or {.Ilt
.by-*q Tc (chapter 3), tzinfall disei[ution type, anaItf? ntio. Tbe pond and swamp a4iustment iector is
obteined lrom table {.2 (rounded to tlre neerest tablevduel Use wor.lsheet 4 in :ppendix D to rid in
conpulins the peek discharge using the Gnphical
Dethod
&000
2.918
z?@
z65l
LW
2.4A4
2348
2255
z161
z0lJz
4000
r.9?9,
r.846
I.TIl
1.704
1.636
t.5?l
1.500
t.{48
1.390
r.cB
t.ztg
t.26
1.175
Llzi\tn
1.080
0.985
0.941
0499
70
7t
72
7B
74
75
76n
?8
?9
80
8l
&,
t3
8r
85
&t
cl
EE
89
90
9l
c2
98
9{
95
96n
98
Chapter 4: Graphical Peak Discharge method
1$is drapter prcsents the Graphical peak Discharce
uethod for computing peak discharge ftom nrrat ird
tlrbrn ereas. the Graphical method was develooed
fron hydrogrzph aralyses using TR.20, ,.Complter
ryFlg for hoject Forzurlation-Ilydrology; (SCSlS). 1le pesk discharg,e equation rised is--
Qp 'QriAa1QFp tEq.4-U
@IGVI-TR.55, Second Ed, June 1986)
IIt,tult
t trt n (D, ti.,|.r
Fllurr &1.-Yrrlrtion of l./p for p lrd CN.
Curre
number
40
4l
42
,a
&
,15
{6
47
{8
49
60
5l
62
68
5{
55
56
57
58
59
6{'
6l
68
63u
65
66
el
6E
@
0.E57
0tl7
0.?78
0.70
(l.7IB
0.6frt
0.$a
0597
0564
0.532
0.5q)
0.{69
0.439
0.{t0
038r
035!t
0Jat
0299
0.ct!
0247
0.u2
0.t98
0.t?{
0.151
0.128
ot05
0.088
0.0G2
0.oil
Tablc ,t-I.-I. valucr for nrnofi curve numbcrs
+l
T
I
I
l'
I
I
T
I
I
It(986I aunf "pg Puor€ 'gg-UI'l/\{Ia
Unit peak discharge (9r), csm/inl,
oooor\r (, 5 !4 Or
= I t 8t
,
5
Er!
a
GI
|D
€B
F
Ia
u)
!t
|D
-lE,
D'
cL
t
:l
0
-{s
I(D
o
C'r'c)ota.5@
-l-n, u
o
=
fl
$fr.r
YOst\o,: .i
Gfi -
I
I
I
I
t
I
I
t
P
I
Oo-
5-
,,1 .,- - =
S r,r8-BlJ ru {
Lt O /\t J
lforlshcct 2: Runofi curvc numbcr and nurof?
Drc orr.4-r'^ ?p
DrC.
Clrelr onr:
l. Eunof? cunrr nnbrr (6f)
't
:rl
t
!.
I
'i
ISotl nar
ead
hydrologle
trouP
(epgcndlr A)
Covrr dercrlpct on
(covcr Bypr, !r!ag!art!, aod
bydrologlc condl r.1oo:
p.rcanc ttp.rtout;
uncourccrd/cocn.clad tapcrvtoureru racto)
Ptoducg
ot
Gl : eru
Q- <" u- - ,
Urc only one C[ rourcc A.r ttn..locals.
cr (rnrshrrd) ffiff 1'h3 . 32 _ usr ct -r.. o,q
-;
@
2. Runolf
Fiequcncy rr
Selnttll, P (2i-hour) tr
&rnofl,_Q .!............ 10(Ur ? ead ef rtBh rebrr 2-1, iii:-i:i. -oa .q.. 2-! ud 2-t.)
Storo ll Scon 12 Scoo f3
/o o
2, I
€IGVI.TB-$6, Sccond Ed., Junc 1986)
l
I
I
I
I
II
I
I
I
I
I
II
IIi
:1
,l
,l
t
RUNOFF FOR INCHES OF RAINFALL
NOTE: Runoff value determined by equation q = (P-0'2 S)2
p+ 0.8 S
REFEREIICE: flationat Engineering Handbook, Section 4, HyDROLOGY
N 0.0 0.1 o.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0 00 0.cl v.uz 0.05 0.0 9 c. l3 l?
I 0.22 0.2a 0.34 c.40 0.4 7 c.54 0.6 !0.6I 0.?5 0.83
2 0.el 0.99 t. o7 t. l5 \r.23-l.3t I .40 1.48 1.5 7 1.65
3 i .74 I.83 l. e2 2.0l ?.10 2. 19 2.22 2 .37 2.46 2.55
4 2.64 2.7 3 2.82 2.92 t at l. 10 3.20 3.2e 3.38 3.48
5 3.57 -2.66 3. 76 3.85 J.9)4. 04 4.14 4.23 4.33 4.41
6 4.52 4.62 4.7L 4. 8l 4.9C 5.10 5.19 5.29 5.39
7 5.48 5.58 5.68 5.77 |. q7 5. 97 6.06 6. t6 6 .26 6. 36
g
9
6.45 6.55 6.65 6.75 6.84 6. 94 7 .0q 7.t4 7.2t f.33
7 .43 7.53 1.63 7.12 7 .82 7.e2 8.02 8.L2 8 .21 8. 3l
10 8.41 8. 51 8.6l 8.71 d.tsu 8.90 9.00 9.lc 9.20 9.3C
11 9.39 9.49 9.59 Y. OY 9.7 9 9.89 9.99 10.o8 lc. t8 t0.2e
t2 10.38 10.4e 10.5e 1C.68 10.78 I c.87 10.97 11.07 lr.t7 r 1.2?
l3 1I .37 II.47 11. 57 I l. 67 1l 7o 11.86 11.96 LIoUE 12.16 12 .26
14 I2.36 12.46 lz. f o 12. 56 t2.75 12.85 12.95 13.05 13.15 13. ?5
15 1r.35 13.4 5 13.55 13.65 t1 75 I 84 i.3 .94 14.04 14.14 L4.?4
16 1i.34 Lq.44 L4.54 I {. 64 L4 .1tl L4.84 L4.94 15.0 4 15. l4 t5.21
L7 15.33 I5.43 15.53 15.63 15,73 I5.83 I5.91 16.03 l6 t3 L6.23
l8 16.33 t6.43 16.53 16.63 I6.7 3 16. 82 I6.92 t7 .o2 t?.12 L7.22
19 L7 .t2 Ll .42 L7 .52 L7 .62 17.72 17.82 L1 .92 18.02 l8 L2 t8 .22
20 I e.32 18.42 t8.52 I8. 62 18.?l Ir.8l I8.91 19.01 t9.tl 19.21
67
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Worksheet 3: Time of concentration (1") or havel time (I1)
S,e -}astN q
D.c. ,/- /-?o
Drt.
Ltc,.,,s /2,,> le<,,> .J?A-<rt--'-'u:ePlojact i-'t'u '\t a /<\;-' 't '- - Dt-:
t/,,, r:\OreekcdLcftlon t/ u _ \_ iJLC|tloo
Glrclr oor : -tr!tj'b{G;D
Ctrclr oc: tc tt throuSh rubrru
mts: Sprcr lor .a r.oy .r tro a.tmolr prr flor ttP' cro bc urrd lor och
. rorlrharc.
tacludr I up, rcbrorllcr ot d.acrlPlioo oa flou rrglrntl'
-@.,1!$, (Appllcrblc co 1" only)S.tacnB lD
l. Surfrcc d..crlpilon (.trblc 3-l)
2. thnnlng'r toughacr eorft., a (trble 3-l) ..
3. llog 1.n8th, L (rot.l L < 300 tt) ..........
l. flro-7r 2{-hr rrlofell, ?2 .........
5. Lnd.lopcr t
1o
C.lf,r
hr6.r,."#+#
te. tr.#
-m
Slrrlloc coocaorr.tcd floe Sctlcng ID
1. $rrfrcc d.!c!1P31oo (prvrd or uoprvcd ) .....
Coaput. tt ......
E. FIor lca3th' L ............
9. lbcrrcoutrr rlopr, | .ooroooorerr
10. Avrrrgc vrloclty, V (!18urc 3-l) ...........
u. rr -#Cooput. It ......
Ghenncl tlos Scglcnc ID
fc
C.lCc
Cclt
ha '7/o'i1
12. Croaa .cctlona! flot tro, I roe.roo..rrrr.r tr2
13. tfGtlcd p.rtct.a, p" ........... ft
ta. E drrullc ndtur, t'-J CotPut. r .......ru
lt. Cbraa:l .lop.. . ............. fcllB
16. . llennlnj'r rou3hnrrr cocl!., n .. o r r.. o r o o. oo
lr. v - t.lr t3l3 .tlz cooputr y .......
It. Flou hn3ch, L ............
Corput. tt ......
fB
Cc-l t
fr
h!
20. gr3.s.h.d or .ut r.r tc or tB (.dd tB ln 33.P. 6' ll' rnd 19) ....... hr
elGVI.'lB-54 Second Ed.' June 1986)
a
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a,I
.P
c,Cl'o
ta
orat-
=o(,go
.aJ
a!-
.10 -
.06 -
.04 -
.02 -
.005 I | | | | | | | tt124610
Average veloclty, ftlsec
Flpn 3,'1.-.{vcrq: vclocilicr for Grtirnrtint tnvcl lime for rhrllor comcntnLd llor,
I | | | ttt
(21&VI.TR-55, Second Ed., June 1986)
\ ne ^8AS t rv p,I
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Worksheet 4: Graphical Pcsk Discharsc mcthod
//1pro1ecr Lrct^lS 2',DCe *S-
ry Dql-n
t ll ' . ," .rlocrcton i/+l l , i- u Chcckrd
D.ta
DrB.
l. Drca:
Dr.llt|g. tr.r .....,.d.. \.
Rsaotf curvr nnbrr . . .. Cll .
tl!! of coac.ota.lLo[ .. tc .
Ralafell dktrlbutlon Eyp. -
Poad aod sreop trcar rprud
Bhroughouc raccrshcd ...... .
' oo / d2 (rcro/640)
E i (trq rorlrhrcq 2)
V hr (?ror rcrkgh.r 3)
-
2.
3.
Ercqucncy
R:lnfall, P (2i-hour)
latelal abrlracEloo, Ir ..........
(Urc Gl sfth B.blc 4,-l:)
Coupucc Ia/P........ ..........
Poad and ts.!p .djulrq.tc fteGor, l_ ....(Urc pcrccot pood end $ralp araa . P
rlch 8.b1. tl-2. FacBor lt 1.0 lor
zero pcaccnt pond and srrop erca.)
Pealc dtgcherg.! qp ...... .c!r
(Thcrr {, - q,r[QFp)
p.rcloB of A, (-.cr.! or nt2 covcrcd)
Scon ,[SBorl! rZ storl! ,3
/o)
.') 'J
t!
rE
ta
,?aa
,13
80
l.zz I
t.
'8.
9.,8a
elOlrI.TR.56, Second Ed., Junc lgBB)
-,/-l o
Clrclc om: /prrsrrr. F;;;
6. 0ctc pcat dttchergr, q. ..........r....... crdta(Urc T" ead I"/p r'lBh &htbt B 4-h
D.
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Chapter 4: Graphical Peak Discharge method
This chapter presents the Graphical Peak Discharge
metJrod for computing peak disctrarge from nrral elrd
urtan areas. ltre Gnphical method was developed
fron hydrogrzph analyses using TR.Z0, ,.Computer
Proqry for hoject Formularion-llydrology,'' (SCS
l9B3I Tbe pe* aisctsrge eqr:ation us€d is
Tb9 input requirements for the Graphical method ar€rs follows: (f) Tc ftr), (? drainage area (mr?, (B)
lpptDpriate rainfall distntution 0, IA, II, or III), (4)
24-bour rainfalt (in} end (S) CN. If pond and ,*"rrrp
treas aFe spred tluoughout the uatenhed and are
not considered in the T. computation, an adjustment
ror pond atd suramp areas is dso needed.
Peah discharge computation
For a seleced rainfall ftequency, tlre 24-hour rainfall .
(P) is obtained from appendix B or morc detailed
local precipitation maps. CN and total runof (Q) for
tlre watersh€d are comput€d according to the
methods outlined in chapter Z. The CN is used to
deterrnrine the initial abstraction (lJ from tabte 41.IjP is ttren mmputed.
if t}e computed I"/P ratio is outside tlre range shown
in exhibit 4 (eI, eIA,4II, and &IID for ttrininfan
distribution of interest, t}en the lirniting value
chould be used. lf the ratio falls betwe€n the limiting
vdues, use linear interpolation Figure +l illustratBi'
&e sensitivity of Ir/P to CN and p.
Peek disch:rge per squrre mile per inch of nrnotr(qrt i! obtaitled from exhibit +I, {-IA" 4II, or &IIt
lf_uSnq Tc (chapter 3), rainfall distriburion t1rye, and
Irt? ntio. The pond and slpamp eqiustment iactor is
obEined bom table +2 (rounded to the neerest tablevduel Us€ uorksheet 4 in appendix D to 8id in
conpuling tbe peak dirhargi'rrsing t}e Graphicat
l!€thod
9p - Qu&nQFp tEq. a.U
- lreak discharge (ds);
- unit peak discharg€ (csn/in);
= dminage area (mi4;
= runoff (in) and
= pond and swamp adustment factor,
ltrrtlllt
br.t n (t). t|.t a
Flpr: &1.-Vrriation of L/P for P and C?{.
Curye
number
Ir
0n)
L
tu)
Ed., June 1986)
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t
T
40{l
42
43
tt4
45
46
47
4E
49
60
5l
62
63
51
56
56
TI
5E
59
6{'
6l
62
63
6{
et
66
6'
6E
69
ma
7i2
?:t
74
75
76n
78
?!)
80
8l
&
83
84
85
86
a7
88
89
90
9r
c2
git
9{
95
96n
98
&0(n
z.EE
z7e,
aetr
2.W
2-1/A
2.W
22fi
LITIzw
2.000
t.w2,
1.846
\n1
l.7It4
1.636
L5n
1.509
t.t4E
LSn
laB
t-??t
t.%
Lr?5
t.r4i
LUNl.m
0.985
0.9{r
0f99
0.657
0817
0.n8
0.7{0
0.flB
0.6{it
0.frE
0.597
0.564
0.5:P
0.500
0.{69
0.4i8
0.410
0381
0.353
0326
0299
0.n3
0247
0.n,
0.r98
0.1?,r
0.r51
0.r2E
0.105
0.083
0.06c
0.0{l
Table ,l-1.-1. valuer for nrnoff cunc numbcn
€IOVI-TR-SS, Second +l
9?(986I aunf "pg puor€'9S-uI'IA{IZ)
Unit peak d ischarge (9u), cstn/in
H HE
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@{(tI
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'oo5oot.'
.ll
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+f
Y'Dqt\o--6t/|l
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Wclrshcct 2: Rrurof? curvc numbcr and runof?
,-l^!roj.c! -'J" I <': 'i'i : S rgf-iJ
tocecton \/z '- ( )
crr.t. o*@{
l. l,unof! curvr urobcr (Ctrf)
:,
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D.ta
Drcr
Soll aec
eod
hydrologlc
troqP
(eppcndlr A)
CoY.a dalcstpctoa
(corc cypc, Brarcaa!!, atd
bydrol,oglc condlBlo!;
Frcanc t oprrvtour;,.nconcoc!ad/coanac!.d Lopcnrlour:rca ragl,o)
EJ actatElrz
Produc!
ot6 r rrce
Qe:,.2- -' i
1 ,1.- -z I .{ -
U* only oar Gl coqrcr pcr ltnc.lotak .
9@t O
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cr (nc!8hcrd) . ffis$ss' -'r'! -
/,i
2. Runot!
lraqucncy
btnlell, P (24-hour)
Runotf, q...........
(Ur. P .nd cil ntrh teble 2-1, fig. i-i.or .qr. 2-t end 2-0.)
Urc Gf -GT
Scon fl Sconr 12 Stotl 13
/o o
Z4
,37
enVIjtR.56, Sccond Ed., Jnnc 1986)
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CU RVE
67
tb
It
':
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,II
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RUNOFF FOR INCHES OF RAINFALL
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II
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tloTE: Runoff value determined bv eouation g = (P-0'2 S)2' P+0.8S
REFERENCE: National Engineering Handbook, Section {, HYDROLOGY
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
1 0 .00 0.00 0l 0.02 0.c3 0.05 0.07 0.0 9 0.12 0.l(
2 0.l7 c.2l o.24 0.z8 a .32 0. 36 0.40 o.44 0 .49 0. 54
3 0.59 0.64 0.69 o,7 4 n in 0.85 0.9?1.03 1.09
4 t.l5 l.2t 1.27 l. 34 1.40 i. 4?1.53 1.60 1.67 1.74
5 1.80 1.8?1. 95 2.02 2.Ce Z. 16 2.23 2.31 2.38 2 .46,
5 2.53 2 .61 2.o6 2.7 6 2.84 2.92 2.99 3.07 3. 15 3.23
7 3.31 3.39 3.47 3.55 3.6 3 l.7t 3. ?9 3.88 3.96 4.04
I 4.L2 4.2L 4.29 4 .37 4.46 4.54 4.63 4. 7l 4.80 4.88
9 4.97 5.05 5. l4 5.2?5. 31 5.40 5.4 8 5.51 5.66 5.75
l0 5.83 5.92 6.0l 6.lo 6.18 6.27 6.36 6.45 6.54 6.62
11 6.12 6. 8l 6. 90 6.98 7.C7 7.16 7.2t 7.34 7 .4)7.52
T2 ? .61 ?.71 t.80 7.89 ?.9 E 8. 07 8.16 a.25 e.34 8. 43
13 8.53 8. 62 8.71 8. 80 8.89 e. 98 9.0I 9.1?9.26 9.J5
L4 9.45 9.54 9.63 9.12 e.e2 9. 9l t0.c0 10.09 10.t9 10.2e
15 10.3?1C.47 1c. 56 10.65 I0.?5 I 0.84 l0 .94 ll.0?11.t2 Lt.22
16 I I.31 I 1.40 1I. 50 11.59 11.69 11.78 t1.87 1I.97 12.06 12. t6
t7 L2.25 12.35 12.44 t2.54 12.63 12.7 7 L2 82 l2 .91 t3.01 13.10
18 13.20 13.29 13. 39 13.48 13.58 13.6?L3.77 t3.8?13.96 14.06
19 I4.15 14.25 L4.34 L4.44 L4.53 1q.63 L4.7 2 14.82 14.92 15.01
20 l5.lt 15.20 15.30 15.39 L5 .49 15.59 15.68 15.78 15.8 7 15.97
47
Iij_
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mlts ! Sgrcr lor rt lray la tuo ..t!Gotl prr tlor BtP. c'o bc urcd fot elch
rcrkahact.
tacludr r orp, rcheortlcr os drrcltptlon of flou 3'8ECn!r '
-@!$, (Appl!.crblc co l. only) Scgocnt ID
l. Sur-frcc dcscrlptloo (i.bl. 3.l)
2. ltrnnJ'ag'e roughnc$ coc!t., o (t.bl. 3-l) ..
3. Flos length, L (lotrl LS 300 tl) .......... fr
{. trroTr 24-hr rdafell, P2......... 10
5. lrad .lopr' t .. trllt
Ctrclc our: tt.::DGD
Ct rclc onc: T]- Tr lhrou8h rubrnr
6.?r-w
lt. e - t.tg ,]/3 .l/2
.ECorput. lt ...... br
Shrllog conccntratcd flor Sagp.nc ID
7. Ssrfrce dclcrlPBloa (prvtd or uaprvcd ) .....
8. Etor lcotth' L ............ lt
9. uetcrcourrc rlopc, I or.roor..rro........... !t/fl
10. Avctrge vcloclGy, Y (fl8ure 3-l) ........... tclc
tll. t. -33ftn colPura I. ...... *
Chenncl florr SG8!Gn! tD
t2. Ctolr rccttonel flou rru, l rorroreroorrrrr ttl
t3. gcrlcd p.rlo.tar, p. ........... f!
la. Btdrrullc rrdtur, r'.-! CoEPut. t ......r fttv
15. Chrancl .lope' . ............. ftlfc
16. . ltenntng'r roughncrr cocff., a .rorrr.rrrr.ro
-t4
re. tr -51fu
c put. Y ....... Cclt
Cooput. tG ...... hr
20. grrrtrhcd or rubrrrl Tc or tG (rdd ta 1n 3c.P. 6. ll' rnd t9) ....... hr
efGVI-Tn-5S, Sccond Ed.' Junc 1986)
1 L e ^9 Lstr"t E
Worksheet 3: Tirne of concentration CIs) or haYel time CI1)
' ''.- *"+Pso1.ct Ltotr 3' ltDC€ .:*Du'!e ArrM,'
t./Lcrcton '/^' ,_ '.- ') Cheekrd
-
Drl.
E
D8
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oCIo
ai
o6L
=o(,
Lc,
o-
.10 -
.06 -
.04 -
.005 | | | t | | t)t I t1246'10
Average veloclty, ftlsec
Fltun 3-I.-.{vcng: velocitics for rrtimrtinf tnvcl timc for shellow concmtntcd tlor.
ttl
(ZI0-VI.TR-55. Second Ed.. June 1986)
2.
3.
4.
7.
8.
9.
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' Sae-84J "'tT
" Workshcet 4: Graphical Peak Discharye method
ProJGcr Lro ni': 2t C Z+- I -9 rttZU
Gtrrcked
rg D*o t<'' j' 2 )
DrE.
l. Deca:
Dralnegr .r€. .......... \ .
Ruaoft curvr nnbrr .... Cn.
lln of coEcaolaaclol .. Ta -
Ratnfall dlttrlbuElon rtp. ,.
Pood aad sreop ercar rgrtedghroughouC rnccrshcd ....r. I
,OO Z-a.2 (rcrcr/640)
67, (?ro sorkrhcct, 2)
' 'o hr (Prol rorkrhrcc 3).-- (r, Il, tr, trr)
ceo/1o
ltr
pclccoB of A, (_ acrar or u12 covcred)
Frcquency
lalnfall, P (2{-hour)
Scora Sl s to ro lrz Stor[ ,3
/a o
-) /;
1o
yr
1tr
,qgslIntclal abclracBlon, Ia .......
(Usc 6l ertBh reble Gl:)
Coopucc la,/p ........
6. Oolc pcak dl.schergc, q.. ..... ......l-....(Use T. ead I./p dBh ;xhtblt q-21
Ruoof!, a...........(froo rorlrshccc 2).
Pond and svalp adJurtoc[! facBor, F_ ....(Usc pcrccnt pood and $raap arca . P
ulch cabl,c 4-2. Faccor k 1.0 lor
zero. p€rccot poad aad sraop area.)
Peak dtscherg.r qp ......
(tJtrcrc qO - e,rA.QFn)
,4/
6oo
,3zl
' cfa ,38
@IGVI.TR.56, Second Ed.' Juao l$6)DI
I
t
Chapter 4: Graphical Peak Discharge method
This chaptcr pr€sents the Graphical Peak Discharge
method for omputing pe8k discharge from rural and
urtan areas. lte Graphiel method wes devetoped
from bydrograph analyses ruing TR.20, "Computer
Prcgram for hoject Formulation-Ilydrology" (SCS
1983). lte peak discharge equation used is
qp 'quAEQFp [Eq.4-l]
where
gp - peak disclurge (ds);
qu - unit peak dirchargp (csrdin)
Arn - dreinagB area (mi4;
Q = nrnofr Cur); and
Fp = pond and sramp adustment factor.
The input reguiremgnts for the Graphical met}od are
. es follows: (f) Tc ftr), (2) drainage area (miz), (8)
appopriate rainfall distribution (I, IA, II, or III), (4)
24hour rainfdl 0n), and (5) CN. If pond and swamp
arean ane spread thmughout the watershed and ar.e
oot considered in the T" computation, an adjustment
for pond and swamp areas is dso needed.
Peak discharge computation
For a relected rainfall frequency, the Z-hour rainfall
(P) is obtained from appendix B ormore detailed
local precipitation maps. CN and total nrnofi (Q) for
t}re watershed are computed according to the
methods outlined in chapter 2. The CN is used to
determine the initial abstraction (IJ from t3,ble 4.1.
I/P is then compute4
if the computed I./P ratio is outside the rznge shown
in erhibit 4 (+I, ,LlA, +lI, and 4-lll) for the rainfdl
distribution of ints€st tllen the limiting vdue
should be used. If the ratio falls between the limiting
values, use linear interpolation. Figure 4.1 illustrates
the sensitivity of Ir/P to CN end P.
Peak discharge per squane mile per inch of rrurofr
(qd is obtained from exhibit 4.I, 4-IA, 4II, or 4-III
by uing T" (chapter 3), rainfall distribution tlpe, and
l./P ntio. The pond and swamp adjustment factor is
obteined Fom table 4-2 (rounded to tlre nearest table
vdue). Use worksheet { in appendix D to aid in
computing the peak using the Graphical
met}od
I
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0n)
Cunre Lnurnber Cn)
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ttrrtlllt
Ll.t ll (tl. lraa
Fldre l-1,-Vrrirfmn of l./P for P ud Cll.
Cune
number
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I
I
&
{t
1t2{la
45
46
17
48
49
50
5l
52
59
5{
55
66
5?
58
59
60
6l
6A
63
6{
65
66
6?
68
60
&000
?AE
zTd\
2651
23tS
L14,'
z.ga
2.8
LI6I
2.o&,
Lmotg,
It46
Ln4
L?IX
L536
r5n
L509
1.4r8
1J90
13:B
tgtr
t92tt
l.l?5
t.125
Ltn
l.tBo
0.s5
0.9{l
0-E99
0.857
0817
0.7?8
0.7{0
0.7(E
0.66'/
0.6u
0.597
0.56{
0.532
0500
0.,163
0.{i}9
0.4r0
0381
035:l
0346
0299
0nB
0247
0.w
0.r98
0.1?4
0.r51
0.128
0.!05
0.083
0.0@
0.041
70
7l
72
73
74
?5
76n
?8
?9
g)
8r
&
83
8r
85
E6
cl
88
89
90
9rn
93
9{
95
96
9?
98
t
Tablc &1.-1. nlucc for runofi cuuc numbcrs
(2IGVI-TR-55, Second Ed-, June 1986)+t
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Unit peak discharge (9u), csm/inH se
9?
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lo*rhcct 2: Rnnotlcur'! numhr and nurofi SuB -g+s/N V7'-
lc.cton tJ+r .- f- C)
ryD.la
Qrrckrd
Drcr ',' ' n- I I
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'/.-'--><'--\C,ltch oar: r?rurag-litlvrlopcd j
l. luaolf cunrt rubrr (6|)
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bydrolo3te
Sroup
(:pprtrdlr A)
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Lydrolog!.c condt!,loa;
t rca6t tlp.rtour;
|[conn cf.d/coacrcBcd tsp.!?lou!.r.. F rlo)
ProducE
ot6l r enr
".<q: --)r '' )
t.:/fl l: r.z a'j e -- =
-V
-
Ur. ottlt on C[ ronrcr grt llnr.
cr (crrShrd) .ffis -/'r'.=l .rBra /,3
2. &rnof!
toEelr .
A'-O / Urc Cf, -,GV,
lrrgurncy . . . . . . . ,, . . . . . . . . F
lelntell, P (26tour) tl
lumft, _Q tD(ur. p .rd cr vtr,h cebtr 2-t, iii:-i:i. --
or .qr. 2-t ead 2-{. )
AbVI.TR.56 thcond E4 Junr llllD
Ston ll Scotl f2 Scoa 13
/ad
Z-,-f
/.zc
RUNOFF FOR INCHES OF RAINFALL
(P-0.2S)2
P+ 0.8 S
REFEREI{CE: l{ational Engineering Handbook, Section {, HYDR0LOGY
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ll0TE: Runotf value determined by equation Q =
CURVE
87
N 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0 c.00 0.cl L.02 0.05 0.0 9 c.l3 0.t?
1 0.22 0.28 0. 34 c. q0 0.47 c. 54 0.61 0.68 c.75 0.83
2 0,91 0.99 l.I5 'r ,1 l. 3I 1.40 1.48 1.5?1.65
3 i .74 1.83 Lo-rZ 2.01 2.10 2. Le 2.22 2.37 2.46 2.55
4 2.64 2.7t 2.82 2.92 3.CI i. l0 3.20 3.29 3.38 3.48
5 3.57 ).7 6 3. S5 3.95 4.04 4.14 4.23 4.31 4 .4?
6 4.52 4.62 4.71 4. 8l 4.9C 5.10 5. le ,.29 5.)9
7 5 .48 5.58 5.68 5.17 r 07 5. 9?6.06 6.l6 6.26 6. 36
8 6.45 6.55 6. 65 6.75 6. e4 6. 94 7.0.+7.14 7.23 7.33
9 7 .43 7.53 7. 63 't.72 7.e2 7.92 8.02 8.T2 I .21 8. 3l
10 8.41 o <t 8.6I 8.71 8.80 e.90 9.0f.r 9.lc 9 .20 9. 3C
11 9.39 9 .49 9.59 9. 69 9.?9 9.89 9.99 10. o8 lc.I8 10.2e
L2 10.38 10.4e 10.58 1C.68 I0.?3 I 'J. 87 10.97 I1.0?I I.I7 I I.27
l3 1r .37 11.47 1t. 57 I t. 6?II.?O 11.86 r1.96 12.06 12.16 12 .26
14 12.36 12.46 L2.56 12. 66 12.?5 r2.85 12.9'13.0 5 t3.r5 Lt.25
15 13.35 I3.4 5 L3. r,I3. 65 I3.?5 r 3.84 13.94 14.04 l(I4 14.?tl
16 I {.34 I (.44 I4. 54 l(.64 t4.?4 I4. 84 14.94 15.04 15.14 t5.2?
L7 15.33 15. 43 15.53 I5.63 15.?3 I5. 83 15.9 3 16.0 3 l6 L3 L6.23
18 33I6 16.43 16.53 16.61 16.71 I6.82 t6.92 l?.02 l?.12 L7.22
19 I7.32 L7 .42 l?.52 17.62 17.72 17. 82 l?.92 18.02 I8 L2 L8.22
20 18.32 18.42 18.52 18.62 18.?l I b. 8t 1.8 .9 1 19.01 19.11 19.21
67
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Worksheet 3: Time of concentration Cts) or travel time Cl1)
tr l 'tko Drt.
Chrckrd
-
Drt.
,t t>-4
Ctrch oorf Prrlrne-' DrvrloPcd
crr.r. *.i-:] t.-trroultr ruberrr
2 a - O'007 (nL)0'6s. .r - -ll-dl5--6-FE2 |
Strrllog concrltrrtcd flos
m.t!:l: Specr lot r. !.ot rr tso r.t!Gq!t P.r lloe ttD' crq br ured for .|cb
. srlrb..t.
tacludr a crPt acb.tatte, or derctl'ptton ol llor rclpcntl'
Sbcct llos (Appllcrblc to t- oaly)Segrac ID
l. 3grfrec dclcr1pc1on (trblr 3-l)
2. tlrmlog'r roughlase coc!f., I (srblr 3.l)..
!. !1or, lcngth, L (!ot.l tS 3OO ll) .......... ft
l. lrro-yr 2{-hr rrlsfell,, 12 ......... 1a
5. lrnd rlopc, r .. tr.ltl-
Coqut. 1g...... br
Scgcnt ID
7. Surlecr &rcrlptloo (prvrd or uaPrvrd ) .....
8. Eloo 1ea3th, L ............
9. Hrtorcorrrr rlope, a ............
10. lvrrrgc vrlocitt, f (ftjurr 3.l) ...........
Iu. r. '53ft1
6emc1 f 1or
12. ftor .GcBloorl flor erre, I ooo.rroo.rr-ro Cx2
1,3. lhttrd pcrlr!.s, pr........... !3
ll. lydrultc rrdlur, r-- f Cqst. r ....... ttPI
l!. Cbeonel .lop., . ............. ftltB
t6. . lhanlaj'r !os8ho.r corft., !.rrrrrorer....
l?. r-t.qg'lj.rl2
l!. llor lmjth, L ............ lc
ttt. lB . ffi6T Caprlc. tt ...... hr
20. tLt.r.h.d ot erbrro tc or t! (.dd tG b rcrpl 6'
efSVI-lB{6, Sccod Ed' &m 1I5)
Crput. It ......
-E
-tI
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I,eol
Ir
trltr
ttlt
br
Scpcnr lD
Capo3. V ....... Cll''
ll, ead 19) ....... br
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AGVI.TR{6, Srcod Ed., Jun rS6)
Worksltcct 4: Graphical Pcsk Dfuchar3l mcthod
lFoj.cr ( tons Qt DG €- ,---S:ll-Dz/k
.f - -)Lc.rton |/ttc-. t-'J Cbrckrd
Ctrclr oor : {_Pr"""!rr_rylgrd/
l. Drcs:
\ Dot-g. .rcr .......... \ . ,'JC L- d2 (rcro/640)
tnoo!! curn nllber .... q - O a .(lrl rorbhecc 2)
tt'r o! coic.qrr.Bror .. t .
=T
hr (tra norkrh.c 3)
iatllaii dtrErrbuclor Byg.= .
=r'
(t, IA, tI, tll)
Posd atd :saqp arcar lprrad
rhroughout mtarrhrd ....-- ' , p.rc.aB ol rn (- .cr.! or ct2 covered)
Frcqucncy
8:tolall, P (Zitour)
Ittctal ebrcraccloc, Ir ..........
(Urc Gl rrlth c.bl. 4,-l;)
colpuca la/p . . . . . . . . . . . . . . . . . | . . . . . . . . ..
7. Rurott, a ........... :......(9roc rlorkrhaec 2).
6. Pood end rrnlp edJurcnrc! fecEor, F- ....(0tc prrecot goad ead tr:ap .raa . Y
rtch ctbh 4-2. Frccor tr l.O lora.ro pa-rclnr, poad end sreag erre.)
9' ?cel' dtrchergQr {p . . . . . . . . . . . . . . . ,. . . . . . .
(lllnrr q, . e.,flafr)
'ct.
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6. Untc Acak d&chergr, q.' . . . . . . . . . . , . . . . . . . cro./t q
(Urc t rod I./p ntBh &drrbtc L-h
Chapter 4: Graphical Peak Discharge method
Ilis chapter presents the Graphical Peak Discharge
method for eomputing pesk discharg€ from ntal and
utaa areas. Tbe Graphical method was developed
lon hydrogaph uralyses using TR.20, ,.ftmputer
lryryn for hoject Formulation-tlydmloeiy,'- (SCS
1983). lte peak discharg€ equation used is
qp = quAnQFp [Eq. 4-r]
where
qp - peak discharge (cfs);
9u - unit peak dischargt (csnr/in);
Attr = drainage area (miz);
Q = nrnoff (in); and
Fo = pond and sramp adjustment factor.
Tbe input requirements for the Graphical method are
. rs follows: (1) Tc Or), (0 drainage area (mi4, (g)
lppropriate rainfail distn"bution (I, lA, II, or III), (4)
24boru rainfdl (in), and (S) CN. If pond and srramp
arss aFe spread thrcughout the watershed and are
not considered in the T" computation, an adjustment
for pond and swamp areas is also needed.
Peah discharge computation
Fora seleCed rainfdl frequency, the 2rthour rainfall
(P) is obtained from appendix B or morc detailed
local preeipitation maps. CN and total nmotr (Q) for
tle watcrshed are computed according to the
methods outlined in chapter 2. fire CN is used to
deterzrine the initial abstrzction 0J fum table &1.IjP is tien computed"
if the computed I./P ratio is outside the range shownh exhibit 4 (+I, &IA,4II, and 4-III) for thtrainfall
distribution of interes! tien t}re limiting value
lhdrld b€ used. If ttre ratio falls between t}e limiting
vdues, use linear interpolation. Figure 4l illustrateJ
tlle sensitivity of I"t? to CN and F.
Perk dischrrge p€r square mile per inch of nrnoff
(qd is obtained from exhibit 4I, 4.IA, 4.II, or 4-III
_bf_usinS Tc (chapter 3), rainfall distribution t1rye, andI.P:atio. The pond and sramp a4iustment i""tor is
obteined bom table 4.2 (rounded to the nearest table
velue). Us€ nor&sheet 4 in appendix D to 8id in
cotrputing the pedr dbcharye rrsing the Graphical
netbod
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Fl3n 1.1.-Varirtion of l./P for P and Cl{.
Cune
number
Ir
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40
,tla
43u
{5
,16
47
{8
{9
50
5t
6i2
5g
54
oo
66
67
58
59
60
6t
62
63
64
65
56
61
68
69
70
tt
72
?3
74
IJ
?6
al
?8
?9
80
8lp,
83
84
as)
86n
88
89
90
9l
92
93
94
95
96
97
98
&000
aaTtl
z7@
z65t
2At5LU
2.W
2255
Lr61
e0{P
4000
t.E2
l846
Ln4
l.?04
L686
1.571
1.509
1.44E
1390
t.&t3
tzt9
tc26
l.r?5
l.lzi
\gn
l.0g)
o96tt
o94t
0899
0.85?
0.8r7
0.n8
0.740
O.?IB
0.667
0.en
0.597
0.564
0.582
0.500
0.{@
0.{39
0.410
0381
0.353
0.326
0299
o.gig
0247
0.@,
0.198
0.t?4
0.151
or28
ot(E
0.083
0.@
0.fir
1986)
T
€lOn-TR-ss, Second Ed., June
I
Tablc {.1.-I. valucs for runoff cutre numbcn
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r\l (, 5 (Jt Ol
= I t -t @
o(rr oroo I
-1
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'floao
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=
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