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<br />The flood profiles presented in this study are based on flow through <br />unobstructed hydraulic structures such as bridges, dikes, dams and levees. <br />Therefore theresu1ts should be considered valid only if these structures <br />do not fail and remain unobstructed. A detailed description of the <br />hydrauliC analysis is included in the Technical Addendum. <br /> <br />INTERPRETATION AND USE OF REPORT DATA <br /> <br />Flood Frequency and Discharge <br />The 10-, 50-, 100-, andSOO-year floods were used as the flood frequencies <br />forthisfloodplainana1ysis, Thus, the data developed in this report will <br />be compdt1ble not only for regulation purposes, andK.B.I041designations <br />but also for Federal Emergency Management Agency flood insurance rate <br />studies. Data prepared in this study will be used 1n the Federal Flood <br />Insurance Study. <br /> <br />These various flood events have an averageoccuranceofonce 1n the number <br />of years as indicated, For example, the 100-year flood occurs, on the <br />average, once in a 100yearperiod,and has a one percent chance of being <br />equaled or exceeded in any given year. <br />The particular uses for the various flood events in addition to those <br />stated above areas follows: <br /> <br />10-year and 50-year flood events Information regarding these more <br />frequent floods is especially useful for future engineering studies and <br />land use planning purposes related to minor road systems, minorchanne1 <br />improvements, the location of parks and recreational facilities, agri- <br />cultural lands, and appurtenant structures. For structures and uses of <br />this type on the smaller tributar1es and in areas where the high riSk of <br />structural fallure is economically feasible and the hazard to life and <br />property i s none~i stent, the use of the more frequent floods as des1gn <br />criter1amaybeconsidered, <br />100-year flood event nThI' 100-year flood event may also be used for <br />engineering design purposes where a lower risk of failure than th<:,lO- or <br />50-year flood is desired. However, the most fmportant use of the lOO-year <br />flood event 11es in f1oodplaindesigOdtion and land use regulation as set <br />forth in the state stat~tes. "a,e State of Colorado con~~dl'r~ t\'\1' loo-year <br />frequency flood as the flood event to be used in designing and protecting <br />structures and dwellings fur hurnanoccupatlon. Therefore, all f100dpla1n <br />regulations are based upon the100-yearflood, Also, the area whiCh would <br />be inundated by the 100-year flood may be delineat<:,li as an area of state <br />interest as set forth in H.B. 1041 d the state's land use bill. <br /> <br />SOO~year fl ood e~ent __ The SOD-year fl ood event is useful 1n making the <br />pUblic aware that floods larger than the 100-year flood can and do occur. <br />Just because a person 1 s 1 i vi ng above the 100~year f1 ood boundary does not <br />mean that he , s completely sa fe frOfll f1 Qod i ng. The 5GG-ycar fl.::od c~'c;:t <br />can a1so be used for regulating high risk developments with thf' floodplain <br />such as nucl ear power plants, or the storage or manufacture of to~1c or <br />e~ p1 osi VI' material s. <br />Table 5-1 lists the discharge and water sudace elpvat10ns for the 10-, <br />50-,100- and500.year flood events at selected reference points, forthI' <br />reach of Arkansas River from MinneQua Dam to appro~imately Colorado Highway <br />115 (Appendi~ n. Table 5-11 11sts the discharges and water surface <br /> <br />21 <br /> <br />22 <br />