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1949_H03l1Vyralnfalloverameltlngsno",paekeaused flooding on the South Platte River from mld-May to late June from Littleton, Colorado to North Platte, Nebraska. Considerable dam- age ..liS Ineurred by homes. farm buildings, and crops along thet reach 01 the river. 1957 _ Int03nse local rlllns over the Sand CrGek basin cllus03d flooding on the South Platte River for a distance do..n- strellm from Send Creek. High rurlll damages ..ere Incurred In some 10<;1Itlons. 1965 - Heavy to of the South PllItte River the South PllItte River. the northern sections of torrential rainfall over large portions basin created extensive flooding elong 1973 _ Sno..melt runoff from the lo..er mountain area of the South Platte River basin began lIbout the middle 01 ~pril. Rainfall, amounting to as mueh as 6 Inches, ..hlch "'liS the major causative factor of the flooding In the South Platte River basin, began on 5 May. Shllrp Increases In flo.. as a result of the reln- hili runoff WOr03 recorded at all gaging statIons along the South PllItte River from LIttleton to the Colorado-Nebraska State line. Th03 rlllnfall runoff WlIS augmented by mountain snowmelt runoff which was also Increasing during this period. The result ..as general flQOdlng throughout the South Platte River basin; flood- Ing was cher~terlzad by high, sharp hydrograph pa3ks from the raInfall runoff followed by 1I slo.. recession because of the con- tinuIng mountain snowmelt runoff. 6Ilnkfull discharges were exper- ienced along portions of the main stem of tho South Platt03 River for most of the month of May end on Into June. High water mark dat~ from thIs flood In Weld County 15 contained in table 7. The Flooded Are~s, plates 3 through 22, show the area flooded by this I100d. Heavy rainfall occurred OVer portions of the South Platte River basin on the 14th and 15th of June. ~s the storm system moved south..~rd, torren- tllll ralnfell centered principally over the Plum Creek ",~tershed on 16 June and on the Bljou Creek watershed on 17 June. Storm rainfall of th03 period extended over some 3,000 square miles of the South Platte River basin, Including the Plum Creek. Cherry Cree+<', end Sand end TOil Gate Creek watersheds In thc Denver region, ~nd the Bljou Creek, Klow~ Creek, Commanehe Creek. Badger Creek. and Beaver Creek ..atersheds to the east. FI~lng occurrod On the South Platte River from Plum Creek downstream to North Plath. Ncbras+<'.. as a result of thl ~ rainfall. 1969 Heavy rains during this period started on the ..ft&rovv~ of 4 ~ay and continued with only Int~r~ltt~nt hrA~ks until a May. The storm covered an are.. along and near the eastern slopes of the MOuntains and extended into portions of the high plalns. The heaviest amounts were centered 25 mIles southwest of Denver and extended In .. band along the foothills north",ard to near Estes Park. The weather station at Morrison reported a total storm rainfall of 11.27 Inches and a maximum dally amount ot 5.71 Inches. Gllneral flooding reslilted along the South Pllltte River. Future Floods Floods of the same or larger magnitude as those that have occurred couid occur in the future, To determine tho flood hezarc posed by the South Piette RIver In Weld County, the la-year, 50. year, laO-year. and 5ll0-year tIOO<ls..erean"lyzed. Th......y"iludes of these future floodS are pr03SenTed In this report In ~bte 8 and 1n the form of water surf~ce prof lies, stllQc-dlscherqe curves, flood wIdth delIneations, end the relationship of these futuro floods to the flood of May-June 1973. " Frequency The 500.year flood Is not the larqest flood that can occur but the probabIlity of larger I100ds Is remote. As can he saen trom the gaging recordS lor the South Platte Ri~~r. discharQ9s "