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<br />e <br /> <br />e <br /> <br />e <br /> <br />FLOODPLAIN REPORT - Tyra Tract D and Sawmill Gulch, Breckenridge, Colorado <br /> <br />Existing Conditions Model-Upper Sawmill Gulch <br /> <br />In accordance with the direction of John Liou, a minimum of 14 cross-sections were deemed <br />sufficient to evaluate the floodplain upstream of the Tyra Tract D parcel according to FEMA <br />standards. Cross-sections were taken from the Town topographic mapping; they were not <br />surveyed (this was agreed-upon by FEMA and by the Town). Mannings "n" values of 0.080 and <br />0.120 were used for the channel and overbank areas, respectively. A flow rate of 248 cfs was <br />used throughout this upper reach. <br /> <br />The HEC model ran successfully and identified the limit of flooding without any significantly <br />unusual aspects. Table 2 presents the water surface profile data, while Plate 1 shows the <br />floodplain map in plan view. Plate I is the Town topography map, and uses the NAVD 1988. <br />The floodplain limits are accurate, but the elevations require an adjustment (subtract 5,91 feet) to <br />match the Tyra Tract D mapping. <br /> <br />Table 2 <br />Profile Data-Upper Sawmill Gulch <br /> <br />SECTION FLOW IN CFS WATER SURFACE ELEVATION <br />59.1 248 9742.4 <br />60 248 9753,0 <br />61 248 9762.5 <br />62 248 9771.8 <br />63 248 9775.5 <br />64 248 9777.6 <br />65 248 9784.2 <br />65.5 248 9796.2 <br />66 248 9809.6 <br />66.5 248 9820.1 <br />67 248 9839.2 <br />67.5 248 9850.7 <br />68 248 9861.3 <br /> <br />971-055.010 <br /> <br />Wright Water Enginee~, Inc. <br /> <br />Page 12 <br />