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<br />Flooding problems within the City of Sal ida are aggravated by the <br />restriction of drainage channel s due to vegetation growth and <br />accumulated debris. <br /> <br />2.4 Flood Protection Measures <br /> <br />The City of Sal ida has no existing regulations or ordinances con- <br />cerning flood management or protection measures. There is very <br />little flood protection for the City of Salida. The main protection <br />from the South Arkansas River is from a bl uff on the north edge of <br />the river. This protects the City from more frequent floods. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />For flooding sources studied in detail in the community, standard hydro- <br />logic and hydraulic study methods were used to determine the flood <br />hazard data required for this study. Flood events of the magnitude which <br />are expected to be equalled or exceeded once on the average during any 10-, <br />50-, 100-, and 500-year floods, have a -ro,-2, I, and 0.2 percent chance, <br />respectiyely, of being equalled or exceeded during any year. Although the <br />recurrence interval represents the long term average peri od between fl oods <br />of a specific magnitude, rare floods could occur at short intervals or even <br />within the same year. The risk of experiencing a rare flood increases when <br />periods greater than 1 year are considered. For example, the risk of <br />having a flood which equal s or exceeds the IOO-year flood (1 percent chance <br />of annual occurrence) in any 50-year period is approximately 40 percent <br />(4 in 10), and, for any 90-year period, the risk increases to approximately <br />60 percent (6 in IO). The anal yses reported here refl ect fl oodi ng poten- <br />tials based on conditions existing in the county at the time of completion <br />of this study. Maps and flood elevations will be amended periodically to <br />reflect future changes. <br /> <br />3.1 Hydrologic Analyses <br /> <br />Hydrologic analyses were carried out to establish the peak discharge- <br />frequency relationships for floods of the selected recurrence inter- <br />vals for each stream studied in detail and to compare with results of <br />previous studies for the flooding sources studied here. <br /> <br />Peak discharges for the various recurrence interval s for the South <br />Arkansas River were taken from data prepared by CWCB for the Arkansas <br />River Basin at Salida, Colorado (Reference 1). <br /> <br />Streamflow data from 11 measuring stations located within the Upper <br />Arkansas River Basin was used in this analysis. This data is con- <br />tained in U.S. Geological Survey Water Supply Papers for the Arkansas <br />River Basin (Reference 3 and 4). <br /> <br />The peak fl ow figures for each frequency used in the hydraul ic <br />analysis of this study were estimated using a Regional Log-Pearson <br />Type III Analysis (including the 1957 data point). The 1957 peak <br /> <br />6 <br />