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<br />FLOODPLAIN REPORT - Tyra Tract D and Sawmill Gulch, Breckenridge, Colorado <br />.ltl.AFT) <br /> <br />of the report, a location map based on the U. S. Geological Survey (USGS) quadrangle). <br />Sawmill Gulch is a drainageway with significant watershed area. The gulch originates above <br />timberline west of the town, and then flows easterly and northerly until it discharges into the <br />Blue River in the central portion of Breckenridge. Four 0' Clock Road is a significant point of <br />demarcation for Sawmill Gulch. Downstream of Four O'Clock Road, Sawmill Gulch is under <br />study by the Federal Emergency Management Agency (FEMA) in conjunction with the Town of <br />Breckenridge. The FEMA contractor, Foothills Engineering Company (FEe) of Denver, <br />Colorado, is in the process of preparing a revised study for Sawmill Gulch from its confluence <br />with the Blue River to Four O'Clock Road. The changes reflect new hydrology and updated <br />topography that have occurred since the adoption of the effective 1979 FEMA Flood Insurance <br />Study (FIS), <br /> <br />For this report, Four O'Clock Road is the downstream study limit. The upstream limit is at the <br /> <br /> <br />current Town boundary, about one mile upstream of Four O'Clock Road. Two study reaches are <br /> <br />contained within the study limits: Tyra Tract D, which extends for about 400 feet upstream of <br /> <br />Four O'Clock Road, and upper Sawmill Gulch, which extends an additional 4,800 feet to the <br /> <br /> <br />southwest. <br /> <br />GENERAL FLOODPLAIN CONSIDERATIONS <br /> <br />Sawmill Gulch is a FEMA-designated floodplain. The currently effective FEMA study was <br />issued in 1979 and covers Sawmill Gulch from its confluence with the Blue River to about 1,000 <br />feet south of Four 0' Clock Road. The 1979 study is being revised to reflect new hydrology and <br />updated topography. In 1979 the FEMA floodplain was based upon a 100-year peak flow of 120 <br />cubic feet per second (cfs), but more recent estimates place the 100-year peak at 248 cfs, slightly <br />more than double the 1979 value. Physical changes have also taken place to Sawmill Gulch: <br />there are clear signs of surface disturbance within the floodplain limits on the south side of Four <br />O'Clock Road. Finally, recent mapping efforts suggest that changes, datum shifts, or lack of <br />details render the 1979 floodplain mapping as suspect. <br /> <br />971-055,010 <br /> <br />Wright Water Engineers. Inc. <br /> <br />Page 2 <br />