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<br />separately for snowmelt events, as well as for rainfall events. The <br />owmel~ events, <br />i. e.. I the combl.ne oc <br />a given discharge for snowmelt and rainfall events was very close to <br />the probability of occurrence equal to or exceeding that discharge <br />for the snowmelt event alone. The discharge-drainage area relation- <br />ships developed for the 10-, 50-, 100-, and SOO-year recurrence- <br />interval discharges for the snowmelt events provided a correlation <br />coefficient of approximately 97 percent. A detailed description of <br />this methodology is provided in a hydrology report prepared by the <br />study contractor (Reference 6). <br /> <br /> <br />" <br />... <br /> <br />The discharges for French Gulch were taken from the Breckenridge <br />Flood Plain Information report (Reference 8). <br /> <br />Peak discharge-drainage area relationships for streams studied in <br />detail are shown in Table 1. <br /> <br />3.2 Hydraulic Analyses <br /> <br />Analyses of the hydraulic characteristics of streams in the county <br />were carried out to provide estimates of the elevations of floods of <br />the selected recurrence intervals. along each stream studied in the <br />county. <br /> <br />Water~surface elevations of floods of the selected recurrence inter- <br />vals for all detailed studies Were computed through use of the u.s. <br />Army Corps of Engineers HEC-2 step-backwater computer program <br />(Reference 11). <br /> <br />Cross sections for the backwater computations and flood plain <br />delineation for Blue River were obtained from topographic maps <br />(Reference 12) and field surveys (Reference 13). Cross sections on <br />Willow Creek were taken from field surveys and topographic maps <br />"(RErf.~r"ence 14) . Straight Creek cross sections were taken from field <br />surveysancJ. topograplUCi"maps (Refe:rericesHJ:S and 16). " TerunH.e Creek <br />cross sections were obtained from field surveys and topographic maps <br />(Reference 17). Cross sections on West Tenmile Creek were taken <br />from field surveys and topographic maps (Reference 18). Digitized <br />cross sections were used for analyzing the Snake River. These <br />sections were taken from field surveys and topographic maps (Refer- <br />ence 19). Cross sections on Soda Creek were taken from field sur- <br />veys and topographic maps (Reference 20). Cross sections on Meadow <br />Creek were obtained by field surveys. <br /> <br />- <br /> <br />Bridges, dams, and culverts on all the streams were measured to <br />obtain elevation data and structural geometry. <br /> <br />Locations of selected cross sections used in the hydraulic analyses <br />are shown on the Flood Profiles (Exhibit 1). For stream segments <br />for which a floodway is computed (Section 4.2), selected cross sec- <br />tion locations are also shown On the Flood Boundary and Floodway Map <br />(Exhibit 2). <br /> <br />10 <br />