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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />SECTIONTWO <br /> <br />FLOOD CURACTERISTICS <br /> <br />farther downstream, thus compounding problems. This floating debris commonly lodges against <br />bridge piers and bridge decks, reducing flow area or completely blocking the channel. The blockage <br />can produce severe increases in stage and flow velocity, often accompanied by bridge damage or <br />potentially complete failure. <br /> <br />Historically, ice effects have not been a problem on Cherry Creek. Ice jams, however, could occur <br />in the future although the chance of occurrence of such a phenomenon is quite remote. <br /> <br />2.3.2 Flood Damage Reduction Measures <br />The possibility of future flood damages in the upper Cherry Creek area has been somewhat reduced <br />by the construction of the 32 floodwater retarding structures within the upper portion of the <br />watershed. The effects of these floodwater retarding structures were taken into account in estimating <br />the flood discharges of different frequencies in the FEMA FrS. The Soil Conservation Service <br />completed construction of these structures in 1965 as part of an overall plan presented in two <br />watershed work plans. These plans were the "Franktown - Parker Tributaries of Cherry Creek <br />Watershed" and the "West Cherry Creek Watershed". These structures were designed for a rural <br />agricultural community with design floods having a 25-year recurrence interval. Dams such as these <br />can provide a false sense of security to the areas downstream. The small more frequent floods are <br />controlled making it appear that the area is not subject to flooding while the large rare floods are <br />little controlled and, during extreme events, dam failure may add to the flooding. <br /> <br />Large-scale flood control measures within the Watershed are deemed to be not feasible, floodplain <br />regulations can be an effective method for preventing future damages. To date, floodplain <br />regulations in Arapahoe and Douglas Counties conforms to requirements of the National Flood <br />Insurance Program (NFIP). Development within the existing regulatory floodplain requires a permit <br />from local jurisdictions that participate in the NFIP. <br /> <br />2-2 <br /> <br />