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<br />INTRODUCTION <br /> <br />The purpose of this report is to provide a record of the <br />extent and magnitude of flooding on Lost Creek in Weld County, <br />Colorado, as a result of the failure of the Prospect Valley <br />Reservoir Dam at 9:00 a.m., Sunday morning, February 10, 1980. <br />The report is intended to document flow characteristics and damage <br />potentials from a flood produced by an actual dam failure. <br /> <br />LOST CREEK <br /> <br />Lost Creek is an intermittent right-bank tributary to the <br />South Platte River. The Lost Creek drainage basin encompasses <br />approximately 400 square miles, in Weld, Adams, and Arapahoe <br />Counties, above its confluence with the South Platte River. <br /> <br />The Location Map, Figure I, illustrates Lost Creek. Stream <br />flow in the creek and its tributaries is not continuous. At <br />several locations, below reservoirs or irrigation ditch crossings, <br />flow is generally not present. <br /> <br />Fifteen miles above its confluence with the South Platte <br />River and 2 miles west of Roggen, Colorado, Lost Creek crosses <br />beneath Interstate Highway 76 and the main line of the Burlington <br />Northern Railroad. The drainage area above this point is 94 <br />square miles. The streambed slope upstream of 1-76 is an average <br />of 13 feet per mile. <br /> <br />Lost Creek has several tributaries, such as South Lost Creek <br />and West Sand Creek, which drain the area east of Prospect Valley, <br />also known as Long Draw. Another, unnamed, tributary enters Lost <br />Creek on the west bank, approximately 10 miles upstream of 1-76. <br /> <br />FIG. I <br /> <br />I G"" I~ \\, vr.y jt. ~ ",:L,',}. 4~.. II I C..0, I L:' i <br />~-!'\r"A'\ .J\~~.' ;:.,.....L;;:J:C;Y~ t '0' I, ~._~_.:~ ! <br />-.....-.:-~'.Hra(P...f'II,.:, (;~, II \ r7~~Jl rj I < ;(~ /~I' - 8ttrnesville I! \ !- ','..~.';.---i <br />fi v-...____ !.erm.ers. I ., /:I I <br />f... ',', , '.~' ".~; ',' 1\. \' Gill (l,cl I .' ,,' <br />;;.'.~".---/H~-ve~~~\_L~~ ~~r It.? u ~ l~.',..~ I . ~ <br />bo-" ,.' '''" J"G?;-lo.ef! ~-.~ \ "II' \ ~hCK~O' <br />1/;- r-~-Ed~~:lr~: ~ Plq( /v- / N I ~c~~'. ' i\~*2-1;'~E'V( <br />-'"' \ '46r':~;y~::::; ~~'K~~ ' I~ .' v i ,;;c <br />[':'.\., l,aSal e p:--".-r;,-.s ,i I ~er".)ojardin R/VmS![)F.r\~. .--^.":, G,~,,-,~;~~h~:.:: <br />~~/~\"" N '~~~'>' \ '1-, %-4{~ t<L~CIT'~'1 -y ) . ""~:,) i <br />3P.p:-,,:. ' j i", 3 ;>;f 0.-" '-, .r--... '" "-- Canto 0 2 4 6' ).Qr.<h.r9+...,q, q,r,n~, <br />III /1.," . 1-1 _J:; I j -. ml. 'B:.)OU)', ~ <br />/.f Y/J'f'eck~a,??, ) #~ i \ r ~., I'-t ' <br />-;-I--y J7~;'crest lA:',:f:' f J ..$ I ~\ I [J ~"J';!-' r-...,~ ~~J1'" 't' ( '. 1 <br />1/Y~J!<i! VrI~1 ,ri\..r-'~:: ...,'-.. t7 ) <br />I\al V rr ~fr \b 0e( '\ ~ ;if II' ~r;~,~R,'vOI\: j. "'-.;.)1:/ <br />('"'<J ,~/'\ Millon v,.) ),( I W'""'~"'1 \ <br />,'-., ir:~v"'e"J R~ iLost Creek~s.~~1J~ yl~~: --/,... I" . <br />da ,48 5) I fit dJ "'# ,-,' 20mar /,r' ["""'II '\ <br />~ <' ~ ,. .,. J' ." <br />\ ./ \ _ ./"';... Crest r~ ~-=)l' :,'.: <br />~~ '~.<'"' ~J~)lKlugLake 1'\ ~a ': :l\~gg~,n B ~'" {)C'''..1I,l ~~ <br />~oi(, ,,77 ~" ~~! I (\ 7 Irr /,/f ~ ( <br />p ~ 6l,\ J~<, I IjL. ,'( I ~ .,-; f'''' 1...-.' <br />< ~ 'j \. :.. \ - ' '?, <br />. ,~,( ol' ~"~'P~~';f'(. Ke~:;~\l'; )TLorkd^-R~servoi? " <br />'. Apt.:r ) ~'..I I( '".s:- { ( " <br />s' ~ ~~ rospec,' 7e~?~-) \ - pros, ~ct~a"ey I ~ I'~} i <br />(Reservoir ~. ~.Pr L. '( ) J!\ II') : \~ .,' /.., 1 <br />rg '" ~f""'...J\ 1\\\'...".... .I.;,;;~><=) ; N' . I . . ~ <br /> <br />/ ,I{ / _1:'3);{ /i / \'7 \J reser'.ID;.' ! fiv' l:/ll.rv~)i \! 1..\\1,,\ I l I ._\ ( I ,r .,' ill $' <br />';~Lakg/~ . HI "r-I,,' '-'1.1\ ilr1\ii'l)~/,",Jg" II <br />~., 'rn Lake \ ~ \ / ~.) ". 1\1 ) }p' t'\"." " :;/ ~. ) <br />" . wr' ) I ~ I 1/ s \ ,,) \~ I V <5', I ~ <br />~~'~~~ D"~ \ f J I ( 1;,,/. ;/ (..1 IL.. ( <br />" ."{ A =<1 PIP /.,~ ( ~Il- / !S--,l <br />l~ '>'$-'l" (. ~ ' / r >$V~I/'il . <br />~ '"". '. ",' \ ::~ '\: . / ,~<!'.' '" /~ " <br />I~ ~~,~ "".~.. ~~( ~Il ~".I 7\ \ ; 11 / &1\ / r <br />I. , '19 ,.., ' co" OJi/.'/) I, I~ / :?j <br /> <br />\ ' <br />~.\ ~ <br /> <br />LOCATION MAP <br /> <br />1 <br />