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Duration and Rate 0/ Rise Floods in tne Boulder Creek Basin are produGed by Intense rainfallduringthunder,torms. Typically, tne floods occur inthe springl)nd ea.-lysurMler ",hen snowmelt runof/ is highest. Usually sovo.-aldaysofmoderate.-alnfaIICO'"1binewlththesno"",elt.-unoffto ~turatc tho valleys and fill the streams. Then, ",hen an intense rainstorm accurs, flooding is produced. However, intonse rainstarms, often refor.-ed to as cloud bursts, can by themselves produce flooding. The pnlg.-ess of a storm and flooding Is illustratod by reports of the 1938 flood whiCh occurred On South Boulde.- Crook and Boulder Creek below the mouth of South Boulder Creek. A heavy .-ain- storm which started upst.-eam of Eldorado Springs about 4:00 p.m. extended dawn to Eldorado Springs by 6:30 p.m. and continued for abaut 7 hours. Recards from tho gage near Eldarada Springs shawed 90 cubic feet per second or near base flow at 7:00 P.m., 970 c.f.s. at 8:00 p.m. and the peak of 7,.390c.l.s. at 10:00 p.m. The peak discharge held for nearly I hour and then graduillly diminiShad toa dischargeaf I,020c.t.s. which was recorded 9 hours after the peak. Theflood- waters were reported to have reached the ~uth of Sauth Boulccr Creek oy 10:50 p.m. Assuming that these floodwaters correspond to the aischarges which passed Eldorado Springs between 3:00 A 9:00 p.m. ratharthiln tathepeakdischargewhjcht>eganat 10:00 p.m. the "veragotr3vei rate of thefiood woyld be5miles per hoyr. After ontering the flatter ~ulder Creek channel, the flood slowed down to an J"erage tr<lvcl rate of about I.Smiles per hou.-. It isnaredthat the flood occurrOd at nignt whilo neavy rll;ns wercstill 131ling<lnd when conditions were nat favarable for evacuation ar flood fighting. Stroarnflowincrcdsedfromnor-mal stag<ltapeakflooding in:lhaurs bYr stayed within 1hl' stredmbanks forat>out the first I 1/2 hours. 29M<ly-2June 1894 Heavy rains fell over themountainsextendir>g from the Colorada - .'yomi ng Corder southward into tile Reout> I ican and Ar~"nsas river basins. Rainfail a"er the Boulder and South Boulder Creek basins wJS particularly Mcavy. Rainfall recards fo.-a 96 hour period ending at 3,00 a.m. an 2 June 1894 shaw that the mountain drainage areare<;eivedfrom4.St06 inchesofpre<;ipitation. Rainfal11lmOynts aver the high plains gradually decreased from west to east varying trom 5 Inches at Boulder ta I)ppraxlmatoly 2.5 inches at the mouth of 8ouldorCroek. ThemauntainrainfaIICC<rlblnedwiththesnowrneltrun- ott to produce the greatest flood known at Boulder, whiCh came roaring down the v"lley during the night ot 30 May 1694. wilaings, bridges, andevan long sections of roads and railroads were w..shed away. Altnoughdamages wereextensi"e, a dollar amount was notostimatod at that time. I ~2 June 1914 Rains in the mauntains comtdned with runoff from an oxceptlanallyheavysnowp"ckproducod,whatnewspaperaccounfscalled, "thewors.t flood On aouldor Creek followTng the 1894 flood". Boulder's wator supply s"stem and the Bouldor County farm "'era severly ~amaged. Numerous r~lOS and briogos in the mountains were also damaged or J"stroyed. 2-7 June 1921 Little Is known of this flood oxcopt thdt iJproJuCi>d ttm higl"'stPBilkdischnrgeeverrecordedatthoOradel,lgage. Adischa.-ge of 2,~(}O c. t .5. was rocorded on "Juno. Ral nfa II tota led 3.36 i n<;hes aT JGWlder througn " po~loa of 2~7 Juno. fiood Descriptions Jre provlaed to illustratetno flood potential . 3~la Juna 1923 Th is storm centered over j-t,,, high P Idi "s o~sr of the " "