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<br />.. 5
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<br />Appendix I
<br />
<br />
<br />:rilE; ad,j.ustll)ent. fa,etorsused ai'e the, sam;'; q.s. ;re,eQ!1l1llep.de\i by, the Wi3atller.
<br />!lurE;<iu.' ,.:Thi','bar.r.~er.c~r1"eqHons are based. on;the.ri'laj;iqn.of .the. in-
<br />trow 'qarfier. wher~, ,~he;.'.~SiP!,qr,t,:i.ve storm centersaetu~llY:..9ccJ)rred and., .
<br />th~ {riflo" ba,ir~"F:bf .Pl.TIPl}:Ca,non Watershed. Since the largest-of .the
<br />three :s.1:;orms)lsed;, MaY..30;~3,1',],9i35" Cherry Cr<=:ek:,cer;,:toqr, wl.J,sonly,1.J, ,'.
<br />6-\wiir.s.to'rm;".,it .was.cons;id,er,,,,d,that the averag<;'l6.-hour and l~-hour, :i, ,.,
<br />prEi,cip:i.tatiqn..relatJ,onllhi"ps.hO\l],d. be, adjusted, This adj ustm<ent. ,was,,:
<br />apiiJ.i~d.\ottiei2';,hourRteCiptt~tiop oilly and, was made byapplying'i"
<br />the. ratio of the 6;,ho\lr to ,the, 12.,..hour m?x:j.mum:. possib.leprecipitati.ow.:
<br />values taken fromdepth-area duration curves for small areas in the
<br />Peeos River Basin. These curves'.,(ere qbtained from the Weather Bureau,
<br />Hydrometeorologica1 Seetioll 19 October .1951. A 12-hour storm maSs .
<br />curve was drawn byp10tting~he:average 6~h6urpreeipitation and the
<br />adjusted 12-hour precipitat.ion as shown On P1a,t:e 1. This mass eurve
<br />gave 30-minute precipitation inerementsduring the maximum 6-hour period
<br />generally in aecordancewI1::h..pci'eentag8" dis.tiibutlon' shown on plate 11
<br />of Civil Works Engineer.puiletin 52-8.
<br />
<br />3-05. The ru.ll~ff .from the selected storm rainfall was determined
<br />. . '-,
<br />considering an itiit~al loss of 1.70 inches and a minimum infiltration
<br />rate of 0.40 inch per hour. The spillway. design flood was computed by
<br />applying the indicated !CUlloff fFom the 1'laximu.'Il possible storm to the
<br />adopted 30 minute unit hy<;lrograph. Thi!' .resulted in a flood hydro-
<br />graph with a peak disehargeof 6,500.cubiq feet per s'econd and a volume
<br />of 1,161 aere-feet which is equivalent t,o 19.1 inches, of runoff from
<br />the 1.14 square miles of.~ra:inage area:; . .
<br />
<br />'-<. ' ,,:.." .
<br />. .' . . .
<br />,,\ ',...' . ....
<br />IV - RESERVOIR STORAGE CAPACITIES
<br />
<br />...', ,:4-Ql~" ~~a ,and .capaci:ty~ Area and capactty eury<;'lS .,for the,..
<br />r~s"l~:vs)ir,,<),re.sl?:q~m on. p),l.J,te,,~ of the project.re'p.ort~:.:'J:oPo-
<br />graphic maps . used.J.n. the.,derivation of these curves wef.'e.:p:(ler;ared,
<br />(rom .:the topographic surYElY Of ;the area made during Ju1yan<;l August
<br />:+951.. This ml.J"p.hjJ.s a contour ,interv&l of,S :feet and a. ,sca,le of c. ...,
<br />1 inc,r" 'equiils5Gfeet, ._ These maps: were?-djusted toa<;:count, ,for ex""..'
<br />ca va 'hon. of . embankment" material from the.reseryoi, area, . The . area'
<br />eurve was determined by.pianimetering each 5-foot eontour and p10t-
<br />1;ingthe cOmputed points. The, point" >Tere. then. conn"cted l:lY a smooth
<br />Ollrv:e~ . ,The.. area ,at ..eachfoot of elevation was then .seleeted fromth€...
<br />~~~;V~,~nd. ~he;end~~rea 'm~thod was used to compute theoar;acityeurve.
<br />At ,thespi11way ere!'t,. elevation 6211, the total storage cap!\c,:ityof..
<br />the.r.eservpi~.w~)UJ.d .~~ 406.,acre~feet at maJ<;imum.water. sl)rface, e1eya-,'.
<br />tiOll 62),8,2., .561I.J,ere-!e2t, and .at top of dam; .elevation6223.5.,6n,.'
<br />ac;r~.7fe~t.. .
<br />
<br />. '4~6~. . Re~ ~ivoir S tor age and ef:t ects . -The required. flood - ..
<br />con:t:pL~tora,!?;e ,11iJ.sbase,dO!l trye.. standard pr,oj 89t floqd,.deye10ped
<br />from a. vQlume,standPQint "IS .d:i.scussed in, paragraph 3-01. The a110- . ,
<br />cated Hood coritrol stor'dge of 361 al1r~-t;eet,w9u1d control the standarg
<br />project flood to spillway crest (elevation 6211.0) with the outflow
<br />limited to the ungated sluice and the sediment reserve of 45-acre-feet
<br />assumed depleted. The outflow of the sluice at spillway erest is 103
<br />cubic feet per second. A1thou~h the standard project flood used for
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