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<br />above its confluence with Jimmy Camp Creek at the City of Fountain <br />(Reference 2). <br /> <br />2.4 Flood Protection Measures <br /> <br />The National Oceanic and Atmospheric Administration, in cooperation <br />with communities in El Paso County, has established a flash flood <br />warning system consisting of observers and automatic alarm systems <br />(Reference 3). <br /> <br />NO other flood plain management is in effect in Green Mountain <br />Falls. <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 equaled or exceeded once on the average during any <br />10-, SO-, 100-, or SOO-year period (recurrence interval) have been selected <br />as having special significance for flood plain management and for flood <br />insurance rates. These events, commonly termed the 10-, SO-, 100-, and <br />SOO-year floods, have a 10, 2, 1, and 0.2 percent chance, respectively, <br />of being equaled or exceeded during any year. Although the recurrence <br />interval represents the long term average period between floods of a <br />specific magnitude, rare floods could occur at short intervals or even <br />within the same year. The risk of eXperiencing a rare flood increases <br />when periods greater than 1 year are; considered. For example, the risk <br />of having a flood which equals or exCeeds the 100-year flood (1 percent <br />chance of annual exceedence) in any ~O-year period is approximately 40 <br />percent (4 in 10), and, for any 90-year period, the risk increases to <br />approximately 60 percent (6 in 10). 'The analyses reported herein reflect <br />flooding potentials based on conditions existing in the community at the <br />time of completion of this study. Maps and flood elevations will be <br />amended periodically to reflect futute changes. <br /> <br />3.1 Hydrologic Analyses <br /> <br />Hydrologic analyses were carri~d out to establish the peak discharge- <br />frequency relationships for eaCh flooding source studied in detail <br />affecting the community. <br /> <br />Flow rates for Fountain Creek were adopted from a COE hyd~ology <br />report of 1976 (Reference 4). <br /> <br />Peak discharge-drainage area r~lationships for Fountain Creek are <br />shown in Table 1. <br /> <br />6 <br />