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<br />I
<br />
<br />,,. Objectives
<br />
<br />SliD-bas in to reclch the ",ost JownSlreJIIl1l I,,;rt of tliat S;JU-bdS i n. Tirr:~s
<br />of concentration w~r~ J~tenl1il\Cd oy olsses5ing udsin "Old chdnIl~l charac-
<br />ter; sties. Cor-cent rot i on to ;n* to the ch~nnel (over1 Jtld flow tir',~) "us
<br /><lel-en"ined od<;ed 1m ul;~t!r I>~si" char"ct"r 4n,! cldd"rl to dldon~l flow
<br />t ill:e d"te,'I.li fled frOl,l le~~tli and average velocity. f'lQw veloci I;J ",1$
<br />est i Inated f rO~l tYlli Cd 1 eli,!'''I!.' 1 sllape, cond it; on and ,,1 Q~l:, T j">e, of
<br />concentrdtion are tdbul dteJ for '-'JelL s'lb-OdS ill on T~blt: r'I-1.
<br />
<br />IV. HVDROLOGIC AN^lY$I~
<br />
<br />The purpose <Jf the hycrologic analysis h co odine the ~InQunt
<br />"rid tiHie dhtribution of the rJrloff n,'sultifJg frOin pr~cipitation which
<br />,'caches ~ SiJecific paint of interuSL Tile rreclp.tatlCH' r~noff '"a..Y be
<br />de r 1 ve~1 f rOlll ra] n fall or <; nOW''ie It, 0 I- bot h, dnd 'dJY re5lJ I t fro,,, J 1 on~ ,
<br />period of ~entl e rdi nfdll, at' a brief, intense tr,understorm. A st~-
<br />t 1st iCcll Jnalysfs uefl ,,~s the prohau i 1 ity th~t a certain ""Iount of ;;re-
<br />cipitat ion runoff may be expect~d "t 0 point of intere,t, on the
<br />Henl~e, of OIlcr every certain number of years.
<br />
<br />The result of the IlyJrol<.)~i~ a~ctlYSl'i I, d 11Jlloff Ilj~ro~rilpll f~r'
<br />~~cli sub-::'asin, for Cdc!r of the fow' dtsj~n ,turr., fl'~'lIJ~I"i~s. Th~
<br />hyd"o~rilf!h, rel ate all'0!l11~ of I-~"off to time. The pe"k lQO-yedr fre-
<br />quency runoff rate ("Peak Q") for ""ci! sub-bdS in is t~bul at"d on TJb1e
<br />J V-2, d~ is t i one to pe"k ("tp") .uld cd,e t illle ("tb")' r I "'e to peilk is
<br />the tillle re\jui red ~fter the storm be~i~, for the peak runuff rote to
<br />occur. Base ti"re represents tile til;le reyuir~d after Ule scorrn be~ills
<br />fDr the ru~off rate to reduce lo approxirr,ately 5% of its peak v"IIJ('.
<br />The base tilHe quant i ty Illay be used to '1I1ic~ly a;,;.,rux irr'dte the
<br />hydrogr~ph re1 ationsliip with tile 1'f!,IK floYI ,,~d t i",e to l1f!dk val "es_
<br />
<br />The hydrologic ddtd estilblishes the basic fdct5 upon which con-
<br />s ist~nt and orderly III anning IHay be base<l witlj rcgilrd to star"l
<br />drai~age. In teri;:s of overd 11 fl ooopl Ji n analysis, discharges ore
<br />defi net! for tile variOus bas i ns (f or eacli f;f the fOLlr des i gn st;or~,
<br />freljuencfes)ofthethreestudystrealilS,fortlrepur;JOSCofdefinillj
<br />the floud water surface eleviltio~s_
<br />
<br />Tile r1usk i Ilgu~: 'Ilethod of st red',; fl ow ''<.ill t i ng I-Ias el.l~ 1 oyed, to
<br />accu~nt for the alterat i011 i~ shape to tile <;trOOoll' flow hydrograph for
<br />fl LN tiF~e (and overbank stora~e), and 01 ';0 to cO'dbi Ile h.)-'(Jr-ograph<; of
<br />the variu'js sub-basins.
<br />
<br />Re~arding the urban drdi~age an<llysis, the d',jOllnt Gf rUlloff '"Idch
<br />i s ex~ected dt the variullS poi nts of interest through the ci ty alld
<br />environs is defi~ed for tile Initiol <lnd :,,~jor (5 yeal' "nd 100 year
<br />respect i ~e 1y) des i ~~ stor"IS. '
<br />
<br />B.
<br />
<br />~ethods
<br />
<br />For the urball ol'"llId~" d"d1;sh, the ,-atiorlol f(),.,IIuld 'idS IItiliZt<(j
<br />ta def.; ne runofr of a '"ore 10c"l i.e,j IIdt'lre, ba<;ed on th0 r~i"tJ1 I dot J
<br />deri ved fruj,1 tlie ilV~'UA and NWS recurds.
<br />
<br />The quantity of rainf<lll whicl:evefitu<111Yl'eache';d:najor
<br />drainage channel is de~elldel1t upo~ tire durat ion Jnd intensity of the
<br />rai~fal 1, UPUll the qUilnt i ties of ,'ill n eVill-'orated or illlcr~oopted uy
<br />., ~get. t i <)11, L~pon the so i 1 i nf i ] t,' d l I on elld r ac l e r i s l j c, (wh i e II ~ re
<br />Jflecti'd tiy the 51 ope of the 1 Jn~) ~nd by the ~ol UII,e Gf 1oc<l1 l'urloH
<br />retai ned in de~ress fans.
<br />
<br />T he rat i Olld I f Orllll! 1.1 i 5 'J w C,,! XI\ "h'~"e;
<br />
<br />The Soi I COllservdt, io~ ~ervice (SCS) Ild<; "'arte exte~si'le studies
<br />a~d observJt ions on sturn' runuff frOlll di ffe-rent <lgricul,;urol 1a~d u,eo;
<br />oM <.Ii fferent sOll groups _ The SCS rUlluff COlllpUt<lt i un procedure a~
<br />l'1odHied by the Iluredu of Recl~",dtion "os used for edch subbil,ln (<;ee
<br />References3,24).
<br />
<br />Q ~ flml (cfs)
<br />C ~ cae! I]CI~I,t .It o"'tJ'I"', lJ! ,'.:nul t eXI'~LL~,i ir:l;:: on ,1!,'0;IIl!_
<br />01' ral,lta.11
<br />I ~ ra 1 nfd 11 i nlens i ly (i II/ln') (~,,~ i i 'JUI" : V -3)
<br />" " drJ i nau~ ~r€~ (,I(;"'''S)
<br />
<br />A ,;rnr" Jetcli led Jiscussion 'lid} b" fOl,,,,r 11\ ,L,ndctl.J ~I,~ill("','i 'I~
<br />tex,lJOoh (j.e., Ref,~,.encc 43).
<br />
<br />The nJlwff cU'IL~~Jt<ltion ~r<J~edu"e illv<Jlve,l defining the basin
<br />"cul've IM,bel'" (eN). nllS eN value curre~~oncs to a tabulation of
<br />rainfdll-runoff relationships of theSeS. Curv€ thl'dlJt'rselection is
<br />l'dS~d on sOIl ty~e, soi I perr.reabi 1 i tj (lTIoi stlJre illti I trat ion rate) r
<br /><;oil cover type and cond it ion J~d lo~d use. The SCS \IdS consu I teti in
<br />d~finin~ the eN values. T~e eN d~ter",i~ood for each of the st;b-basins
<br />is ,huwn on Tdb1~ J V-I, dS is the infi ltrcJt ion rote ut i 1i led_
<br />
<br />C. i'recivitJtion:,ndl,.si<;
<br />RJ info) I data froll' tlH! lI'IW~JA dm! LI,i' N~S (lor Ule Ci ty of
<br />!\UlltrOSC), <lS well cJS the rWM ,~tl"s (Rl1f~"~llc~ 1) "d, sCdti$lically
<br /><ill~lyz~u tu tlefille "~(lJrr~lI(e illterval I'rol>dtJilities and t.h~ r~s"lL'rl'
<br />rail\fall-fr~~LJr.ncy relJliorrship for IXlt.h th~ up~er bil,i'l arcds, ~'i "rll
<br />00; thc ri ty of Montro'i~. Th i '; rd illf"l! rel ,1t i 011 ,,'dS t'lCr. grad'IJt.e<l
<br />l!ct\iCerl the Ci ,y cf :~ontro,,, dnd tile '+I:,lr b~s i n aredS dccordilll! to I.I\"
<br />pr~<I".dlll~nt n,~i<lll,1l 1"'~(il,it"li"" l<<t,h'nl :;1,ml'l I" LI,c ~J()M MI<ls.
<br />'~e r2,~lt \s J r,ybnd "Iill: i'l~llrr'U,.~.~irr~ IJ\'iJlIA, r.',;~ JIl~ r:U;\A ,'i'I,",LII
<br />
<br />/11<;0 dff~ct.illg u,.; ~l~IJ-b~,;i" rdillf~ll-n,lI()ff r~l.ltion is ti,e >IIr.-
<br />h.js i ~ 's t i ,," . of conee III r" t i on ~ rh i 'i v" 1 ue rep res.:n t s tht' t i rrr" r.:'1<11 re<J
<br />flJr th~ I-'reClv'Lltlo~ ~'l1ic'l fnst f.~ll> ot tile U;!P~r ~xtr~','e or t~~
<br />
<br />~J7-
<br />
<br />-18-
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