<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 />
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