<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 />
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<br />,'-., ir:~v"'e"J R~ iLost Creek~s.~~1J~ yl~~: --/,... I" .
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<br />~ <' ~ ,. .,. J' ."
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<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
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