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<br />depths associated with this flooding were determined using Manning's "n" <br />equation. <br /> <br />Approximate lOa-year flood elevations for the Blue River (above Blue <br />River) were determined using inlet control charts and normal depth at <br />road crossings and normal-depth calculations for typical stream cross <br />sections. <br /> <br />A floodway was not computed for Meadow Creek because it is not <br />appropriate due to the wetland habitat of the area. In addition, the <br />floodway was computed for French Gulch by considering the entire <br />lOa-year peak discharge, <br /> <br />The Dillon Reservoir base flood elevation was determined to be <br />9,018.1 NGVD, and controls the flooding at the mouths of the Blue River <br />and Tenmile, Meadow, the Miners Creeks. <br /> <br />For each stream studied in detail, the boundaries of the 100- and <br />SOG-year floods, as applicable, have been delineated on topographic maps <br />at scales of 1:1,200 (Reference 34 and 35), 1:2,400 (Reference 36), <br />1:24,000 (Reference 37 and 38), and 1:4,800 (Reference 39) using flood <br />elevations determined at each cross section. <br /> <br />9,2 Second Revision <br /> <br />Blue River Middle Branch <br /> <br />This study was revised on August 9, 2001, to incorporate detailed <br />flood-hazard information along Blue River Middle Branch and Cucumber and <br />Illinois Gulches, and approximate flood-hazard information along Gold <br />Run Gulches and Blue River split-flow area around the vicinity of the <br />Town of Breckenridge, Colorado. <br /> <br />The hydrologic and hydraulic analyses for the restudy were performed <br />for FEMA by FIo Engineering Consultants, Inc., under Contract <br />No. EMW-92-C-3811. In July 1997, Flo Engineering Consultants, Inc., <br />submitted information contained in a report entitled IrDrainage Master <br />Plan for the Town of Breckenridge, Colorado, Drainage Report" <br />(Reference 40), <br /> <br />No final ceo meeting was held for this study. <br /> <br />Hydrologic analyses were carried out to establish peak <br />discharge-frequency relationships for the flood-hazard areas. Regional <br />frequency analyses were conducted to develop peak discharges for Blue <br />River Middle Branch and Cucumber Gulch, The purpose of these analyses <br />was to determine if the values from previous studies were still <br />representative of peak discharges in the Blue River basin in light of <br />flow data available since those studies were conducted. This <br />methodology was found to be more representative for lower return period <br />flows on the major tributaries of events dominated by snow melt, rather <br />than the HEC-l results obtained by modeling rainfall-runoff <br />characteristics, The u.s. Army Corps of Engineers (USACE) HEC-1 model <br />was used to develop peak discharges for Illinois Gulch. <br /> <br />Peak discharge-drainage area relationships for Blue River Middle Branch <br />and Cucumber and Illinois Gulches are shown in Table 1, "Summary of <br />Discharges." <br /> <br />37 <br />