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To check Worrall's assumption of snowmelt peak flows, the months in which annual peaks have been recorded were summarized, and strip charts from USGS gaging stations were examined. The snowmelt assumption was found to be valid. Because the Worrall study was completed in early 198 I, it did not use the most current Water Resources Council guidelines (Reference 4). In addition, floodflows in the years 1981, 1982, and 1983 after the study was completed were significantly high. For instance, the June 27, 1983, peak flow of 618 cfs on the Fraser River at Winter Park is the second highest flow of record. To determine whether these changed conditions would affect the results significantly, data from one of the eight USGS gaging stations were analyzed using flow data through 1983 and Bulletin 17B procedures. A decrease of approximately 5 percent from the IOO-year peak flow of679 cfs was used by Worrall; using Bulletin 17Band the extended database results in a flow value of 648 cfs. The Worrall regressions were used for this study for the following reasons: although the Worrall study was completed before the Water Resources Council published Bulletin 17B, the differences are not considered significant enough to materially affect the results of the study; adding the diversion flows to the USGS gage records is a conservative assumption; the Worrall discharge values agree well with other studies in the Fraser River basin; and the Worrall flow estimates have been widely used by developers. Peak discharges for the approximate Fraser River study in the vicinity of Granby were computed by a multiple regression analysis using data from six gages. This method correlates actual annual peak flood data ofthe tributary basins to the USGS Granby station. (Reference 5) Peak discharges for the approximate Tenmile Creek study in the vicinity of Granby were computed by a composite frequency-discharge curve. The composite curve was based on both rainfall and snowmelt frequency-discharge cureves. The rainfall frequency curve wa based on the Soil Conservation Service (SCS) method with a 6-hour storm event. (Reference 5) Peak discharge-drainage area relationships for streams studied by detailed methods are shown in Table 2. 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of flooding from the sources studied were performed to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the Flood Insurance Rate Map (FIRM) represent rounded whole-foot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data tables in the FIS report. Flood elevations shown on the FIRM are primarily intended for flood insurance rating purposes. For construction and/or floodplain management purposes, users are cautioned to use the flood elevation data presented in this FIS in conjunction with the data shown on the FIRM. Water-surface elevations (WSELs) of floods of the selected recurrence intervals were computed through use of the USACE's HEC-2 step-backwater computer program (Reference 6). Cross sections for the backwater analyses were obtained from several sources. For the Fraser River and Vasquez Creek reaches previously studied by Worrall, the cross-section data were used without modification (Reference 1). F or the reach of the Fraser River through Beaver Village, cross sections from a developer's study were used in the upper 8