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<br />ma9nitude and the flood stages. <br />The flood peaks used in this study a.re c:ha.racteristic of rain- <br />fall-generated flood events with long flood durations. The esti- <br />ma.ted peak flood flows computed are listed in ~'able 1. <br /> <br />TABLE 1 <br /> <br />Flood Disch~rgE':~ <br /> <br />Beaver Creek at Brush <br /> <br />Flood Frequenq:y <br /> <br />Flood Discharge <br /> <br />10-Year <br />50-Year <br />100-Year <br />500-Year <br /> <br />12,4,00 cfs <br />37,000 cfs <br />55,000 cfs <br />119,600 cfs <br /> <br />The 100-year flood is one with a peak flow magnitude that has <br />a 1 percent chance of being equalled or exceeded in any given year <br />and a frequency of occurrence of about once in 100 years on the <br />long-term average. Similarly, the la-year, :;O-year and 500.'year <br />floods have a 10 percent, 2 percent and 0.2 percent chance of <br />being equalled or exceeded in any given year, and an average fre- <br />quency of occurrence of about once in the number of years indicated. <br />These flows have been estimated based on recorded flood oc- <br />currences in the high plains area of eastern Colorado, western <br />Kansas and southwestern Nebraska, and are typical of the Beaver <br />Creek drainage area. <br />Typically, the flood events will IT,ove into the Brush community <br />at a speed of 2 to 4 miles per hour. Flood peaks may last for a <br />duration of 2 to 10 hours while high flood st:ages may remain in <br />the area for periods of 20 to 30 hours. <br />The flat topography characteristic of this reach of Beaver <br />Creek tends to widen the flood plain area ane:. reduce the depths <br />and velocities of the flood flow as it passes through the area. <br />In the reach of Beaver Creek between the Burlington Northern rail- <br />road and Interstate 76, the average flow velocity in the main <br /> <br />-10- <br />