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<br />SECTION II <br /> <br />I NTROOUCTI,ON <br /> <br />Several floodplain delineation studies have been performed for the South <br />Platte River over the past years. The most recent floodplain studies in the <br />Littleton area were the 1978 Flood Insurance Study and the 1983 Centennial <br />Downs Study. <br /> <br />2) Obtain hydraulic mapping for the subject area showing 1983 topogra- <br />phy, which would be consistent with the mapping of the Urban Drainage <br />and Flood Control District. <br /> <br />Attention to the reach of the South Platte River in the vicinity of Bowles <br />Avenue occurred as a resul t of an urban renewal project at South Santa Fe <br />Drive and Bowles Avenue to be built by the Writer Corporation. This attention <br />resulted in questions being raised about the reliability of the 1978 Flood In- <br />surance Study. Review of the 1978 study indicated that: <br /> <br />3) Determine the floodplain and floodway for the subject area using cur- <br />rent mapping, bridge and channel characteristics for comparison with <br />the FEMA 1978 floodplain mapping, using the former one-percent flood <br />for 1978, and the up-to-date one-percent flood flow. <br /> <br />1) The hydraul ic water surface flood profi le appeared inconsistent with <br />known channel conditions; and <br /> <br />4) Prepare floodplain and floodway maps using conditions with Crestline <br />Bridge removed, and with modest channel cleanup at the Bowles Avenue <br />Bridge. <br /> <br />2) The 12,000 cfs flood discharge used in the 1978 study was higher than <br />the adopted one percent (100-year) flood discharge of the Urban <br />Drainage Flood Control District (UDFOC). <br /> <br />5) Evaluate the added impact of having the USACE channel constructed up <br />to a point immediately downstream of West Crestline Avenue. <br /> <br />The floodplain regulatory matter resulted in a problem <br />newal project schedule and feasibility was questioned. <br />to wait until the USACE channelization was constructed. <br /> <br />in that the urban re- <br />The project might have <br /> <br />Review of the regulatory floodplain and floodway, however, indicated that the <br />1978 Federal Insurance Study was not applicable. <br /> <br />The objectives of the WWE 1984 Study were: <br /> <br />1) Determine the latest and most appropriate regulatory flood magnitude <br />for the South platte River at Bowles Avenue. This was for the one- <br />percent flood. <br />