|
<br />H14
<br />
<br />FLOODS OF 1965 IN 'THE UNITED STATES
<br />
<br />SOUTH PL.-liTrE RIVER BASI~, COL08.ADO, JCNr~ j 96.'1
<br />
<br />~< -
<br />1) I,)
<br />
<br />at riOO mb o'-er southern Xcyada. The Plum Creek basin was to the
<br />tOast. and slightly north of this low, the relati'-e pU::iitiolllllost \.'Ollducin>.
<br />to seyere weather distl:l'banc€s, This situation brourrht in cold air aloft
<br />which rednced the atmo,pheric stability to mOde!';;ely low lel"eb.
<br />The air cireulatioll about the J0"- produced some lifting'. This '\"as
<br />not. a prime factor in causing rain~ hut it was significant.
<br />The general upslope from P;lst to \\"c:,t of the High Plain:-, c:lllse(l
<br />a major uplift J.weaH~(,: the low-ll'n~l winds had an (:a~t('r].y, or llpslopl.'
<br />~'omp(J1)Pllt. The orographic elfect of ~Illall-scale f(.atlll'eS stwh a~ Hasp-
<br />berry :\Ioulltaill :111(1 n;I\\'~()ll Blltte c;wsed ~;hn\Yt'l' ,H,ti'.;iry 01'('1" these
<br />- ,
<br />peaks early in i he storm.
<br />Showers and thunderstorms started to de,'clop O\-er the area cast of
<br />the central Colorado mOllntains during the morning of ,June Hi. By
<br />eady afternoon the storms were locuted along ft 1l0l.th-sonth Ene
<br />roughly from Dellyer to Pueblo. The northern part of this line of
<br />storms almost t'uill('ioed ,,-ith rhe major axes of the Plum Creek and
<br />Chen)' Creek basins, a.. condition that. caused record-breaking Hooch;.
<br />The npper Ie,-el steering winds had olliy a slight westerly component:
<br />(herefol'e tIle thunderstorms "\yere nut carried away from the lllOtm~
<br />,.tiJls 'IS "eJlel"111,-ll'lpneJ1S j''1t rPln'lillO.J H,.<n' tlJo !:;rr1'-''''l'J'f'",',', '",J"e",-
<br />. -,'. b '" <... ~-...c.~._...,.......lt"...... C.I.\:.- 1.~....I."'U l < < ~'"'
<br />for more than an hour, Then the thunderstorms rnm-ed 81myly north-
<br />\\"cud along this north-south line. This direction was almost directly
<br />down East and. 'Vest Plum Creeks and Cherry Cn';:k:, thus the heH~-Y
<br />rainfall tended to follow and angment the peak flows.
<br />?lIore than 14 inches of rain fell near Palmer Lake and near Lark-
<br />'pur (pl. 1) in abont 4 hours, and o'-er 12 inches fell near Castle Hock
<br />in about the same time. ?lIost of this rain fell between 1400 and 1700"
<br />hours Jnne 16. By 1800 hours the westerly component of the npperJe,"el
<br />steering winds increased and mo\"ed the storm line eastward.
<br />
<br />traveled l\":.lS at a slight angle to the creeks and grner:llly dOWllS( ream.
<br />Rainfall amounts ranged up to 12. inches ill about'.:1 !lollr:'. along the
<br />Palmer Ridge southeast of Elbert (pl. 2), Higher intensi.ties for lesser
<br />a.mounts were recorded or ob5cn-e<1 nearby. The gage:3 mIles llorthwe,st
<br />of Eastom"ille canght 2.16 inches of rain between 1800 anti 1~00 hOilr',
<br />:"';.:23 inches fell in 45 minutes () miles snnth of Agate dUfmg the e....el1ing~
<br />2.75 iuehes fen in about 1;') minutes about ~2 mil"s l';l.st of Elbprt, and
<br />mo~t. of ;-t.,-\ illL'lH'~ felltwtwC'Pll 180n :lnd l!)On hnltl"S 1~ milC's n01'~henst
<br />of Kiowa. ~\ll t!JC':;c rainfalls equal or greatly ex('('('<1 tlw l()().yrar llltCll-
<br />~it1es fn:' the t.irne i111(-'YTnb gi\"pn.
<br />These amounts follO\wd hy only 48 hOl1rs rainfall of J to G inches in
<br />much of the Kio\Ya~Bijou area. The total precipitation and the high
<br />intensities oyer small areas produced extremely high rates of runoff"
<br />
<br />DESCRIPTION OF THE FLOODS
<br />
<br />The floods of .Tune 1~G5 in thc Sonth Platte Hinr basin occurred in
<br />Tour areas aIter olle or more storms Oil four COlls\-'{"utin>. .d;I~'S, .JtH:e
<br />1~17 Por>(,..,-ic Af c1x ct.-O'lm", \,.h"~.e drainao.c basins ~~re Pl'!!H'.!pal1y In
<br />.....L ..... -,-~,-,,_ "U", UL...... .... '-'''''.J . "'-". t--
<br />the mountains, from the South Platte Hiver at "\Yaterton, ,\"hich is
<br />npstream from Plum Creek~ to the Cache la Poudre Ri\'~r near Greeley,
<br />show that snowmelt runoff from the Hoeky :.\loulltalns ,\Y<lS a con-
<br />tributin{T but not significant, factor in the flood along the main stem
<br />0' . .. . ..,.
<br />of the South Platte Ri\.er. Also, the irref:,rular dlstrlOutlOn or tHe ne...'tvy,
<br />intense rainfall, (pIs. 1 and 2) was snch that some tribntarics con-
<br />tribnted little or no runoff to the flood,
<br />
<br />RAINFALL ON JUNE 17
<br />
<br />On the afternoon of *Jllue 17, thunderstorms de\"eloped south and
<br />east of DeIl\-er. The upper len~l steering winds were from the south-
<br />southwest. to southwest, and the westerly ('oml>ouent was greater than
<br />on the preceding day; therefore the rains were farther east. The oro-
<br />graphic effect of Palmer Hidge, the divide between the Arkansas Hi,'er
<br />and South Platte Ri,-er hasins, reinforced the nplift from the general
<br />east-west npslope tr:wersed by the prenliling sontheast winds. The cold
<br />~ow o\'er Nenlda had mo\'ed n'ry little during- the pre\"ious 24 hours;
<br />therefore, unstable atmospheric conditions were still present. The
<br />change in direction of the upper lc\'el steerin:,! winds between June 16
<br />and 17 was partly offset by the diffel'f"llrp; in ori.ent:Jtio!'!. beh':{~e!! Plum
<br />Creek and Bijou and Kiowa Creeks so that the direction the storms
<br />
<br />THE GREELEY-STERLING AREA
<br />
<br />Hea.vy, intense rains ulong a belt. about 30 luiIes wide and 100 miles
<br />long just south of the Colorado-"'yoming State line and from n~rth
<br />of Greeley to north of Sterling caused floods on ~nost left-bank trIbu-
<br />taries of the South Platte Hi,-er in the high plams:
<br />. Peak discharges were detet"mined nt one discontil~ued l!,t~ing station
<br />and at. fh-e miscellaneous sites in this area. The gagmg stat lOll on Lone
<br />Tree Creek near XUlln was operated during the 1951-57 water yea.rs,
<br />and the maximum discharge during this period was 775 efs in 1955,
<br />whereas the .Tune 14, 1~65, peak \\'"s5,810 cfs. ,
<br />A gu;ring station was operated on Crow Creek near.Ba.rnesvll.le fro:n
<br />J nly 1961 to September 1957. There was no flow at tIllS sIte durmg tIus
<br />period because all flo\\' is normally di,'erted or stored ?pstre"n: for
<br />irrigation, municipal supply, and stock water. .However, In June ~965,
<br />part of the flood flo\\' even bypassed the !I~ge sit~, and i~ overl~~d
<br />flow inundated farm inllds to the east. Tile peak near lSarnesvIlJe
<br />.J: 1 AAIV'>.J 'tAN\ l..~____ ~_ T_._':' 1~ " '~eal resident,
<br />oceurreu uetween v"'vv llIiu .1.VVV llVUL;) VU tJ UllC .1.0}. ...."'1. IV
<br />
|