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<br />2.4 Flood Protection Measures <br /> <br />Other reservoirs in the Blue River basin above Breckenridge <br />provide only incidential flood protection (Reference 1). <br /> <br />The recent changes that have been made in the Blue River channel <br />through part of Breckenridge will significantly reduce flood <br />potential in the town. The improvements were made with the <br />intention of containing a 100-year flood. During a 100-year <br />flood event, much of the flow, which previously would have <br />spilled over the banks, will now be confined to the channel, <br />particularly in the areas from the northern corporate limits <br />to approximately 400 feet downstream of Watson Road; from <br />approximately 600 feet downstream of Lincoln Avenue to the <br />Washington Avenue footbridge; and, in the area of the Four <br />Seasons shopping center. <br /> <br />There is no flood plain management in the Town of Breckenridge. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />For the flooding sources studied in detail in the community, standard <br />hydrologic and hydraulic study methods were used to determine the flood <br />hazard data required for this study. Flood events of a magnitude which <br />are expected to be equalled or exceeded ~ on the average during any <br />10-, 50-, 100-, or 500-year period (recurrence interval) have been <br />selected as having special significance for flood plain management and <br />for flood insurance premium rates_ These events, commonly termed the <br />10-, 50-, 100-, and 500-year floods, have a 10, 2, 1, and 0.2 percent <br />chance, respectively, of being equalled or exceeded during any year. <br />Although the recurrence interval represents the long term average <br />period between floods of a specific magnitude, rare floods could occur <br />at short intervals or even within the same year. The risk of experiencing <br />a rare flood increases when periods greater than 1 year are considered. <br />For example, the risk of having a flood which equals or exceeds the <br />100-year flood (1 percent chance of annual occurrence) in any 50-year <br />period is approximately 40 percent (4 in 10), and, for any 90-year <br />period, the risk increases to approximately 60 percent (6 in 10). The <br />analyses reported here reflect flooding potentials based on conditions <br />existing in the community at the time of completion of this study. <br />Maps and flood elevations will be amended periodically to reflect <br />future changes. <br /> <br />5 <br />