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<br />Previous Studies and Proiects <br /> <br />A report entitled "Floodplain Information Report, Lower South Arkansas River" dated April 1979 <br />was prepared for Chaffee County and the Colorado Water Conservation Board. The detailed <br />floodplain information within that report was adopted for use in the Salida Flood Insurance Study. <br /> <br />Community Response to the CWCB Desilmation and Approval Process <br /> <br />A letter from the ewCB was transmitted to the City of Salida regarding the Board's proposed <br />action for designation and approval of the Salida FlS. The City was receptive to the Board's <br />proposed actions, and sent an official letter requesting that the CWCB designate and approve the <br />floodplain information currently available to the conununity. A copy of the request letter is <br />included in the Appendix of this report. A meeting was held between the City Administrator and <br />ewCB staff to discuss hydrology issues, floodplain regulations, flood history, and the designation <br />and approval of the FlS this Hydrology Addendum. <br /> <br />ENGINEERING METHODS <br /> <br />HvdrolOlrlc Analvsis <br /> <br />Hydrology information used for the South Arkansas River floodplain delineation in Salida's FlS is <br />discussed in Section 3.1 of the PIS. The lOO-year peak flow for the South Arkansas River at its <br />confluence with the Arkansas River is reported to be 2,010 cfs, and the drainage area is 208 square <br />miles. The hydrology information for the Arkansas River mainstem was estimated by performing a <br />flood frequency analysis utilizing available gage data (recorded annual peak flows) on the Arkansas <br />River gage at Salida. The estimated lOO-year peak flow value for the Arkansas River mainstem at <br />Salida is 6,790 cfs. This value only applies to the reach of the river that is upstream of its <br />confluence with the South Arkansas River. Table I presents a summary of discharges for Salida. <br /> <br />Table 1 <br />Summary of Discharges <br /> <br /> <br />Arkansas River upstream of its confluence with <br />South Arkansas River <br />South Arkansas River at its confluence with the <br />Arkansas River <br />South Arkansas River at Coun Road 107 <br /> <br />1,218 <br /> <br />208 <br /> <br />2,010 <br /> <br />200 <br /> <br />1,980 <br /> <br />3 <br />