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<br />6,7, B-1, B-2, 8, 9, 9a, C-l, C-2 and TC, all of <br />which drain into the Big Thompson River. Curve B <br />.pplies to subbasins 16 and 17 which drain into <br />the North Fork below Glen Haven, for which there <br />w.s a double peak with the hi9hest occurrin9 <br />last. Curve C applies to the rem.inin9 subb.sins <br />for which there were double pe.ks but with the <br />most severe one occurring first. <br /> <br />3. <br /> <br />CO,"" AR I SONS <br /> <br />The over.ll flood reconstructions <br />m.de using the 4-hour r.infall pattern in Figure <br />4 and the time distributions shown on Figure 5 <br />are considered reasonable. These reconstructed <br />peaks are su....rized in Table 1 along with the <br />USGS estimates. The timing of the reconstructed <br />pe.ks .long with the timings of the .ctual flood <br />pe.ks .s reported by eyewitnesses and by the USGS <br />.re listed on Table 2. Figure 7 illustr.tes . <br />graphic.l comparison of the magnitudes of the <br />flood pe.ks. The results of the study are <br />considered to be within acceptable limits for <br />this type of an.lysis. A comparison of the <br />m.gnitude of the flood peak estimates m.de by the <br />USGS .nd by the hydrograph reconstructions listed <br />in Table 1 shows that the three largest dif- <br />ferences occurred at subb.sins 5, 6 .nd 15, which <br />.re located within the storm centers. Field <br />observations of these three subbasins suggest <br />th.t the pe.ks estimated on the b.sis of slope- <br />.rea me.surements may have been affected by the <br />forming and bre.ching of debris b.rriers. <br /> <br />Depth-.re.-duration curves were <br />prepared by 10-minute interv.ls for the study <br />are.. These are shown in Figure 8. The 4-hour <br />maximum depth for 10 square miles is 10.0 inches. <br />This compares with 9.8 inches .s the maximum <br />4-hour depth for 10 square miles in the Rapi d <br />City storm of 9-10 June 1972. This comp.rison is <br />especially interesting in view of the meteoro- <br />logic.l similarity between the Big Thompson and <br />Rapid City storms which is discussed by Maddox <br />et al. (1977). Maximum 10-square nrlle rainfall <br />in previous notable Colorado storms of record <br />include: 11.7 inches (3 hours) in the Plum Creek <br />storm of 16 June 1965; 9.4 inches (4 hours) in <br />the Kiowa Creek storm of 17 June 1965; 20.6 <br />inches (6 hours) in the Colorado Springs storm <br />of 31 May 1935; and 10.4 inches (6 hours) in the <br />Pueblo storm of 3-4 June 1921. <br /> <br />Maddox et al. (1977) developed mass <br />curves for Glen Comfort and Glen Haven, Colorado, <br />for the 6-hour period from 0040 to 0630 GMT <br />1 August 1976 (1840 MDT 31 July to 0030 MDT <br />1 August 1976). Their mass curves were developed <br />using Limon, Colorado radar reflectivity data. <br />Copies of these curves bec.me available subse- <br />quent to prepar.t; on of the adopted percent.ge <br />mass curves 1n Figure 5. For comparison, the <br />Maddox et al. (1977) curves and the precipita- <br />tion mass curves used in this study for the Glen <br />Comfort .nd Glen Haven areas .re shown in Figure <br />9. A good comparison is refl ected in the shapes <br />of these m.ss curves but there is some difference <br /> <br />Table 1._: ~!ak. _~!s.ch.r~~s -,_~_~__~~~~~-~ .~1~e!. D_oo_~ of J,uly 3~. ,19?6 <br /> <br /> Publi!hed <br />~ubbujn l;~:lie,.~I!':~ .1.. 19/61 RecoMtrUChd Oifferern::e <br />Ident1fi- ,,~ Pe.~ Afii pule Pialc--- lpercentl <br />cation!! mil ftl!! ftJ/s/m'Z mil ftJi! 1t3/5/m,2 <br /> ._____.___._u_____' -----------. .___.____._._~H___ <br />1 Dr,. GulCh nea,-Estn Park 2.00 3,210 1,605 LOS 3,120 1,815 ." <br />" O"yGulch-tontributingbelo.osite2 2.94 2,272 '" <br />3 Dry Gulch at Estes Part 6.12 4,460 '" 4.99 4,445 891 <br />.. SiteJtosite4 2.84 2,875 I,Oll <br />, Big TIIOlllpson Rher below (stes Park '" 1,130 1.83 5,143 '" .J< <br />, DigTIIOIIpsonRhfr tributlry Ilelow 1.31 8,100 6,350 1.35 5,400 4,000 .3B <br /> lDVIE!landlleigllts 2.68 1,300 2,124 <br />. DigTII~sonRiVfr,siteltllGhnCllIlIfort <br />, Dal't Gulch atGlenCDIIlfort 1.00 1,210 1,21u 1.00 3,900 3,900 ." <br />) MoelsOr"",atGlenC(lm(lrt 3.31 6,910 2,Ose 3.11 5,970 1,801 ." <br />B.' DigTIIOIIps(lnRiYer, Tribs. frOol'hft, 1.94 1,830 2,490 <br /> GhnColllfort to lon9 Gulch <br />B-1 Dig ThOlllps(lnRhtr, tribs. frOol'right, 1.60 2,920 1,825 <br /> GhnColllfort to lon9 Gulch <br />8 RahbitGlllchnnrGrlke 3.'1 3,540 1,038 3.42 4,000 t,ll0 .13 <br />, LongGlllch nurOrakt 1.99 5,500 2,16011 1.98 5.100 2,879 ., <br />9+9.... Long Gulch plus tributlry 2.31 6,300 2,6S8 <br />C. I +C- ~ R_inin9 contribllrion btlOOl long Gulch l.05 1,110 1,085 <br />10 8igTh~sonllhtrlboveOrake '" 28,200 26.55 31,560 1,189 '11 <br />II North Fort Dig TlltJI'IIIIsonlliver at Ghn lIaven 18,5 888 0.81 80' '" ., <br />11 Fo~ CrHk It Ghn Haven 7.t8 1,300 1.35 1,090 801 .n <br />13 Devils GulCh nur Gltn Haven 0.91 2,810 3,088 0.96 2,510 2,605 .10 <br />" \o'estCrHk nurGltnHavln n.1 2,320 3_14 2,160 '88 ., <br />" North FOrk Dig Thl;llllJlsonlli,"r, intervening 1.I3 2,010 I,ll'} <br /> lItes 13 to 15 <br />" NoYthForkBi9ThOfllpsonlllvertrlbutlry 9,610 1,001 1.34 '.225 3,153 .S6 <br /> nurGlenHaven l.lB <br />EO NortllForkBi9Thl;llllJlsonlllver, tribs. f,~ 2,524 <br /> rigllt, sitesl5tol1 1.05 2,650 <br />El North ~ ork 8i 9 Th(llllpson IIi ver, tribs. f,~ <br /> left, siteslStol1 l.15 I,no 1,061 <br />" BlaCk CreK near Ghn Hlven 3.11 1,190 '" 1,88 2/1,320 701 .1B <br />11 MilllrForknearGlenHavln 13.9 2,060 3.03 "2,150 710 -, <br />, North ~ork 81g ThOll9S0n Ill.,tr, tribs.close 0.58 '" '" <br /> botlawsittl1 <br />18 North ~ork 8ig ThOll9S0n River tributary 2,;1l 1.24 112,840 2,290 .11 <br /> nelrOrakt 1.26 ],240 <br />18>101 5ubblsin 18 plus contr1butingar4l1 Idjlunt 2.06 3,1l4 I ,80~ <br /> on the east <br />19 North ~ol"!o; 8ig Tho-.pSM Rht~ abOve Or'~e 80.2 8,110 1~.6S 11,890 lJ4 .,' <br />eo,. North ~ort 8igTh~son River It Drlke ~!I9,5(0) 16.6~ ll,360 '" ," <br />20 Bi9 ThOlllJ"on River below Oral::e 216-)0,100 43.20 ]~,02Ll 811 .16 <br />11 ~i9 ThOlllJl$on River at Mouth of Clnyon JOS lI,2DO 43.l0 31,640 15, '1 <br />" LittleThllllpsonlllvrrneitrhtesPark ,.71 1,940 2.14 2,OUU 730 '3 <br /> <br />11 TMse ~ubasins Identified by nulllber~ only Ire the 115G'i Sltt5 lGrolier, H II.. 19761. .IT of the ~"oha:;ins are ~hown '" tile <br />oHin outline 'IIIp (fi\Pol~e II, . <br />lICGlllJlutrdforpetkCOl"I)lrlsononly-fIOWlnc1udedlnsubblsinl7forfloodreconst",ctlOn. <br />11 COIIIJIuted for pea. cOlllJlarison only. S"bIH'" t8+~ us'" f(l" flOOd reconst"'ctlon. _ ,) <br />!I EstlOlltrd by "'ille~ from ".ge chart for tnlS study. The pul>1islled fl9\lre in U.~. Geolo"icll ~urvey (1971) H 11,7 LV ft 'S. <br /> <br />140 <br />