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<br />. <br /> <br /> <br />, ~IO:-"'>.~ <br />;,,!-i";"I''''::>~ <br />~~f>;,~:::.:.~;~}. <br />.. .... ......"::'!\ ~ <br />~, '<'. "'. ~ ,,;:, 0 <br />? '} '~. <br />.....: . <br />~.,,~~... <br />"~:}~;~f~; <br /> <br />....... <br /> <br />. <br /> <br />United States Department of the Interior <br /> <br />GEOLOGICAL SUHVI';Y <br />Denver Fl'<.h'\'al Cent.pr <br />})tmver. (;ohlr.tdo H()~:?;, <br /> <br />IN IItWI.Y Ht:n~lt '1'0; <br /> <br />Water Resources Division <br />Colorado District <br /> <br />May 8, 1974 <br /> <br />. <br /> <br />Memorandum <br /> <br />. <br /> <br />To: <br /> <br />The Record <br /> <br />From: J. F. McCain, WRD, Lakewood, Colorado <br /> <br />Subject: OPERATIONS -- lOa-year peak discharge at Wellington, Colorado <br /> <br />. <br /> <br />. <br /> <br />On April 28, 1974 I talked with Don Bressler of Colorado Water Conserva-' <br />tion Board about the 100-year peak discharge at Wellington, Colorado, <br />Don requested the U.S. Geological Survey estimate the lOa-year peak <br />discharge based on the best analysis that could be completed with exi~t- <br />ing data. That' same day Ted Hurr and I made a field inspection of the <br />Wellington area. The following paragraphs contain a descriptio~ of my <br />analysis and conclusions. George Leavesley offered cow~ents and made <br />independent computations for the unit-graph method. <br /> <br />Boxelder Creek: <br /> <br />. <br /> <br />The drainage area of Boxelder Creek upstream from Colorado Hi8hw2,y No. l <br />is 131 square miles. The laO-year 'peak discharge for the site .-.'",s <br />computed by three methods as described below. <br /> <br />. <br /> <br />1) USGS WSP 1680: The basin is shown in Regian B, hydrologic ar2a <br />7. From figure 7, p. 9 the mean-annual flood is 200 cfs. l'rom fi8'lre 2, <br />p. 4, the ratio of the 100-year to the 2.33-year flood is o.pproximat,-,ly <br />10.3. Therefore, calculated using this procedure the lCO-year peak <br />discharge equals 2060 cfs. <br /> <br />. <br /> <br />2) Station Data in Area: Estimates of the lOa-year flood for <br />seven stations in similar type terrain as Boxelder Creek were made using <br />available flood data through 1972. Based on this technique the IOO-year <br />flood is 3500 cfs. <br /> <br />. <br /> <br />. <br />