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<br /> <br />Redstone <br /> <br /> <br />~ Floodplain Information Report - Crystal River and Coal <br />Creek. Pitkin County, October 1979, by Wright Water Engineers, <br />Inc. for Pitkin County and the Colorado Water ~onservation Board. <br />The purpose of the report was fl. . . to provide information <br />relative to the occurrence of floods and to guide local officials <br />in the planning and regulation of the floodplain areas." <br /> <br />e <br /> <br />e <br /> <br />Crystal River, Colorado Hvdroloqv - Internal Office Report, <br />February 1979, by the Corps. This study used a regional analysis <br />of streamflow data collected at gaging stations within the basin <br />to develop the combined snowmelt and rainflood flow-frequency <br />relationships for Crystal River and its tributaries. <br /> <br />PURPOSE AND DESCRIPTION <br /> <br />The purpose of this analysis was to estimate the existing <br />level of flood protection provided by the Redstone levee system <br />and to scope potential levee improvements for increasing the <br />level of protection. <br /> <br />The study area extended from the county bridge leading into <br />town at the upstream end to the sewage treatment facility <br />downstream of Redstone, a distance of approximately 1 mile. The <br />present hydraulic conditions at Redstone were analyzed based on a <br />resurvey of critical cross sections by Pitkin County in early <br />1991. Although a detailed geotechnical evaluation of the <br />existing levee was not conducted, data from past studies and <br />reports (including some geotechnical evaluation) were included. <br />The analysis was conducted in four steps. The first step was to <br />identify pertinent available hydrologic data for the river system <br />(water surface profiles and velocity estimates). Second, the <br />hydrologic data were used to define hydraulic conditions by <br />comparison with FEMA requirements (3 feet minimum freeboard, <br />etc.). Third, existing bank and levee conditions were defined <br />along with an indication of likely locations for levee <br />modification and construction. Finally, data from similar <br />projects were used to develop an order-of-magnitude estimate of <br />quantities and costs to upgrade the Redstone levee system. <br /> <br />HYDROLOGY <br /> <br />The most recent hydrology from the 1988 FEMA study was used <br />as a basis for the hydraulic modeling in this study. Apparently, <br />hydrologic data used in the FEMA study were adopted from the 1979 <br />flood plain information report. The hydrology for the 1979 <br />report came from the 1979 Corps hydrology office report. Peak <br />flow values identified in the three reports and shown below were <br />used in this study. <br /> <br />2 <br />