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<br />The steel girder truss bridge which was in place from 1936 - 1976 <br />was never damaged or threatened by flood water. The 1965 flood <br />did not reach the bottom of the bridge and the house northweat of <br />the bridge was not flooded, <br /> <br />I <br />I <br />I <br />I <br />I <br />j <br /> <br />CIlAPTERV <br />HYDROLOGIC ANALYSIS <br /> <br />Flood Characteristics <br /> <br />Water has never overtopped the abandoned railroad embankment along <br />the weat bank of Running Creek. However, the railroad embankment <br />was eroded during the 1935 flood from reference line stations 51+00 <br />to 65+00, <br /> <br />Flood flow. on Running Creek occur primarily during the May through <br />AU!lustperiod. Historical accounts indicate that floods are cau.ed by cloud- <br />bur.t type thunderstorms which produce heavy rainfall a~unt. over relatively <br />stn.!lll areas. Floods are characteri~ed by rapid rises, large peak flows, <br />short durations, and comparatively low volumes of total runoff. A typical <br />flood event would pass through the study area and recede within six to eight <br />hours after the initid rise. <br /> <br />Water flowed in the .hallow cutoff channel between reference line <br />station. 35+00 and 50+00 during the 1935 flood, <br /> <br />Method. of Analysi. <br /> <br />TI,e hydrologic analysis was performed to e.tabli.h the 10- and tOO-year <br />frequency flood di"char~es in the study reach. Thi. analysis is based on <br />existing basin conditions which are n~t expected to change .ignificantly in <br />the future. <br /> <br />Four independent ~ethod" were used to predict expected flood magnitudes <br />(0. Runnin~ Creek. Each method has its st.ength. and weakne..es in it. appli- <br />cation to the Running Creek drainage ba.in. n,.,r"sultsofeachroethodwere <br />compared and ftnal discharge. were selected after the "valuation of the reli- <br />ability of each method. A brief deseripti.on of e.ch method (allow.: <br /> <br />1. U.S. Gcological Sllrvey Regional Analy.is-The Regional Analysi ai. <br />pubLi.hed inU.S, Geological Survey Water Supply Paper No. 1680. Hi.ba.ed <br />on extensive statistical analysi. of actual floods which bave occur.cd in the <br />South Platte basin. for flood predictions, the ~verall South Platte basin la <br />divldedintoreglons..ith.imilathydrologiccharacteristics. Thcregi.on <br />>:hi"hen"OlIlp<I.se.RunningC.cekalsoincludestl'eKiow.,CnekandCherryCr"ek <br /> <br />-20- <br /> <br />-24- <br />