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<br />F'LOODS OF i 96'=:, IN THE UNITED STATES
<br />
<br />SOUTH PLATTE RIVEH UASrX, COLOR;\DO) JUNE 1965
<br />
<br />B13
<br />
<br />PLUM CREEK AND CHERRY CREEK BASINS
<br />
<br />Little or no r.lin fell in the Plum Creek basin on June 1-1- or 15, but
<br />+.76 inches had fallen at Castle Rock between ~Iay 21 and June 13.
<br />In the same period, 6.07 inches was recorded at Cherry Creek Dam
<br />and about 4 inches was recorded near Parker :11lt1 nE':1r Greenland.
<br />This antecedent moisture wet the soil and c:l.useu. a somewhat larg-el'
<br />and more rapid runoff from the- lat(-'l' h<:>H\-Y, int(,llse rain. IIowpn>r, the
<br />m;lgnitude and intensity of the rains on ,June IG would han~ (';1tl~('d
<br />de\"ftstat.ing floods \yithont [lny prin1ing of the soil.
<br />
<br />possibly as much as 15 inches in (") hour.:; ,1~ ~'nJl1n:ll"l.'Cl to the nrobable
<br />ll1aXim~lI11 of 22 inches. Thus, tht' H'l'.'" h(,i1\'Y ~'n(l inil'IlSl'. ~',linfall~
<br />were' f'xrrf'Hlply rare en~nt.s, but they might be exceeded sometime.
<br />
<br />RAINFALL ON JUNE 14-15
<br />
<br />1;)30 hours. This raiE {',.lllSed Huoding pl,irnaJ.iJy 11) thf~ BijOli Cr'eek
<br />basin.
<br />Very little rain fell in the Kiowa-Bijou area during the concentrated
<br />storm of June 16 O\'er the Plum and Cherry Creek basins.
<br />
<br />Ht>fl.YY, int(,ll:-f~ rains fen during t11l' ni~ht f)f .Tune 1.!-15 in the
<br />Lone Trpe Ctt'l>k, ('1'0\\' Cn>c>k, and Pa".!leC'. ('n"'C'k ba:-iins just. south
<br />of t11r Color;:do-\YYOlll!ng Statl' lim'. .\! f'llll' )()(':11 ions north of XUl111
<br />\\,ithin all area of [iO square mi]('~. rai1l.Lll1 r;lngpd from :l.;) to 7JJ
<br />illf'hi':', :u:d 1-~ lnchps fell at ~l. fifth Im'atill)t lll.';\)" rlH' ccnter of the are,l.
<br />The. l'e\.'onling: p;agc at :\nnn r('gi~,tL'n'd l.()(i ilWht':-) between 11 and lQ
<br />p.m, on .June 14. Amounts or ;).;j to 7.0 inche::;; ill'€', respectiyely, about
<br />twice the a-hOllr and (i-hour lOU-Yl:ar rainfalls. and the l-!--inch rainf:l.ll
<br />is about. four times the ~-+-hol!l' 100-Y0:\r rainfall.
<br />The larf!er fUl10lmts in the Pa"\Yllee Creek basin west and north or
<br />~terling ran::red from :1.0 to "L') inches: how(>ypr', oral rCDoi'ts of 1.05
<br />inches i-n ~o ~l1lilllltes and 1.+ illchps in :~o minutes inc1ic~ate the high
<br />inten~ity of tlH' rain. Thpse intellsitir-s are near thos~ for the 30-rninute
<br />2;")- year rainfall.
<br />
<br />RAINFALL ON JUNE 16
<br />
<br />KIOWA CREEK AND BIJOU CREEK BASINS
<br />
<br />Light rains fell oYer most. of the !\:iowa Creek and Bijou Creek
<br />basins on .June 14 and 15. Hyers and Deer Trail receiyed 2.74 and :2.G4
<br />inches, rpsppctlvely, Oll .Tune 15; about 1.45 inches fell in 1 hour at
<br />each locatIon. Bucket su;:yey reports SIlO..... :1- to 6. inches on June IG-
<br />at se\-en locations in East, ~liddle, and "Test Bijou Creek basins.
<br />~Iost of these amonnts feIllll 30 minutes to an hour between 1800 and
<br />
<br />RaInfall In the alHollnts and intensities that. occuJ'rcrt south of
<br />Denver in the Plum Creek basin on June 16 usually requires sonle
<br />
<br />12 inches and
<br />
<br />persiSlCl"lCe of sen::rrrl conditIo:n.s. There n1tlst be (1) largo:. fi.monnts
<br />of low-level moisture and a. strono- influx of this moisture to supply
<br />'"
<br />the rain-proflucing Inechanism ('ontinuonsly, (2) unstable atmospheric
<br />l'omlitions, particularly at. upper lc\'els, and C~) one or more Inech-
<br /><lllisms to lift the air. All of these conditions were present on June 16
<br />(U.S. "'eather Bureau, written commun., 1966).
<br />The air moyemen-t near the surface was one of the contributing
<br />factors. There were moderate ,,'incIs from the southea~t June 14-18
<br />Ll'ilJlrino. moist. ail' from the Gulf of :\Iexico, and surface de.wpoints
<br />~ h .
<br />""ere in the 10\\- (;O's and upper 50's (0 F), which are unusually high
<br />for raSh'I'Il Colorado. The influx of moisture was rapid, and the moist
<br />air ,,"as in a rather deep layer. The lo,y.leyel southeasterly flow was
<br />particularly strong on .June In; wind speeds of o"er 40 knots near
<br />2,000 feet ah()\'e the ground w("re reported l.\t Amarillo, Tex., and Dodge
<br />City, Kans. The surface wind at A\marillo began gusting during the
<br />aft;rnoon of ,Tune Hi. The low.le\"el flow had the characteristics of
<br />the low.le,'el jet in this region, but the relati,'ely high winds at the
<br />"round produced the unusual condition of a low.level jet in ~epth.
<br />A trough ",'er the "'estern Fnited States was retarded and mten.
<br />.:e"l ,,~d,_ ~^{\ n_1, f"...~lla..."..\ la't~Dl....t ',nm'oyirnntp-lv 18000 feet or
<br />t>IIlCll at ll1\:l.JVV 1l1V \.......~...~J .~.~A ,.. .'l'1.,-_n-' 0/ ~ !
<br />5,500 meters, By ~Tnnp, 16; a. quasi-st.'ltionary cold low had been created
<br />
<br />PRECIPITATION
<br />
<br />rN PERSPECTIVE
<br />
<br />The U.S. Weather Bureau (1961) has developed some relations
<br />between rainfall, intensity, and frequency. These relations are only
<br />general aud do not reflect the orographic effect of relatively isolated
<br />topographic features. The orographic effects of Dawson Butte and
<br />se,'eral other isolated features, especially those between Castle Rock
<br />and Palmer Lake, were quite pronounced during' the storm of .Tune Hi.
<br />Thus, a direct comparison het.ween the general relations and some
<br />of the observations of point rainfall could be misleading, Howen~r, if
<br />the possible anomalies are t'onsidered, tl~e comparison should provide
<br />some perspecti,'e for an e,'aluation of the rainfall that did occur.
<br />From the general relations, the 100-year f)-hour rainfall in the
<br />vicinity of Castle Rock is :1.2 inches, and the probable maximum 6.hour
<br />pl'cGipitation, for a. 10-squai'e-mile area~ is about 22 inches. The maxi-
<br />mUln obsen"ed 6-hour rainfall in Den,-er was ~.!)l inches in 1921.
<br />Rainfall oyer lO-square-mile. areas near Palmer Lake, Larkspur5
<br />alld Castle Rock and on the di,'ide between the .\rkallsas and South
<br />
<br />Platte Ri,-ers soulhea:sl oi Elbed, l.1\'eraged about. 10
<br />-1 hours This ::mount ,,"cuId he equ!ya!ent to ~.t. JeflJ:;t.
<br />
<br />:"....L........ ;.... 'J: .......
<br />111\."""':> ,H U' V"
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<br />333-527 0---69-3
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