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<br />flood plain problems. <br /> <br />DR~f1 <br /> <br />In comparing flood levels between this and the FEMA study, the <br />first difference is at the entrance to the storm drain. The <br />development at Sawmill Creek Condominiums has resulted in lowering <br />the flood elevation by several feet. upstream at cross section <br />8.0, the current study is within one foot of the FEMA level. At <br />this location the current study is based on the Town topographic <br />mapping. At cross section 8.1, the current study is two feet lower <br />than FEMA. No FEMA cross-section is located at this point. Cross <br />section 8.1 is based on surveys performed for this study. At cross <br />section 10.0, a new cross section was surveyed for this study to <br />compare with the FEMA cross section. The surveyed cross section <br />has a minimum channel elevation of 9637.1, and a low point in the <br />overbanks of 9635.6 (this is one of the perched channel locations <br />released to earlier in the report). On the other hand, the FEMA <br />cross section minimum elevation is 9640.0 and the cross section has <br />a flat channel bed at 155 feet. Referring to the Town topographic <br />mapping, the minimum channel elevation is 9632.0. This cross <br />section is a good example of the inaccuracies encountered on <br />Sawmill Creek. <br /> <br />Between cross section 11.0 and 13.0, the FEMA study does not <br />reflect the development and channel relocation that has occurred <br />since the study was conducted. <br /> <br />upstream of Four O'Clock Road, the FEMA cross sections were used <br />for this study to the upstream limits of the FEMA study. <br />Therefore, the two studies coincide in this area. <br /> <br />In general, the flood plain has been defined as being v~ry wide on <br />Sawmill Creek. Therefore, in spite of the FEMA study's possible <br />inaccuracies, it appears to have kept development out of the areas <br />prone to flood damage. It is recommended that prior to any future <br />development adjacent to Sawmill Gulch that the developer perform <br />a detailed study of the flooding potential on his property based <br />on actual surveyed cross sections. In addition, the potential for <br />flooding from flows breaking out upstream and affecting the <br />property should also be considered. <br /> <br />Illinois Gulch <br /> <br />Existing flooding problems on Illinois Gulch are created by two <br />factors, inadequate culverts and a poorly defined channel. The <br />area with the highest potential for damage is at the Columbine Road <br />crossing. Due to an inadequate culvert, the flow will break out <br />at this location and flood the Bell Tower Mall. A portion of the <br />flow may travel as far as the intersection of Park Avenue and <br />Columbine Road. The flow could flow to Main Street and possibly <br />cause further damage. Further upstream at the Broken Lance Drive <br />crossing, the culvert is inadequate and the flow overtops the <br /> <br />39 <br />