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<br />Peak flows from snowmelt events typically occur from between mid-May and mid-July. <br />Peak events occurring after late July are almost always generated by rainfall events. <br />While localized rainfall events can produce peak flows higher than those calculated <br />utilizing snowmelt driven peak flows, these tend to be localized events that do not <br />produce peak flows on the main stem of the Eagle River. Thus, localized rainfall events <br />were excluded from analysis of peak flows on the main stem. Previous studies <br />consistently report that drainage basins from 10 to 20 square miles may produce higher <br />peak flows due to rainfall, but that for larger basins, snowmelt is the primary source of <br />peak flows. <br /> <br />Peak snowmelt runoff events are generated by runoff from snowmelt from higher <br />altitudes. Visual observations of snowmelt patterns, as well as data from NRCS Sno-tel <br />stations, suggests areas above approximately 10,000 feet in elevation are the primary <br />source of runoff during the peak streamflow season. This is further validated by a <br />statistical comparison of calculated peak runoff vs. drainage basin areas above and <br />below 10,000 feet. <br /> <br />PREVIOUS STUDIES <br /> <br />A number of previous studies have been performed over the past 25 years. Due to <br />limited gage data, most investigators resorted to areal comparisons of data, based on a <br />regression equation of Q = C · A (x), where Q is the flow at an ungaged location, C is a <br />coefficient that varies based on the recurrence interval, and A is tributary area in square <br />miles, and (x) is an exponent of 0.69 to 0.702. Table 2 shows the regression equations <br />reported by Gingery in the initial Flood Insurance Study hydrology report. <br /> <br />Tables 2 through 8 report peak flow values for various recurrence intervals as reported <br />in previously published studies. <br /> <br />6 <br /> <br />2 Hydrology Report, Flood Insurance Study, Eagle County, Gingery Associates, Inc., Aug. 9,1978 <br /> <br />~ <br /> <br />Water Resource Consultants, LLC <br />--i <br />