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<br />drainage area is less than 1 square mile, and areas protected from <br />the 100-year flood by levees. No base flood elevations or depths <br />are shown within this zone. <br /> <br />6.0 FLOOD INSURANCE RATE MAP <br /> <br />The Flood Insurance Rate Map is designed for flood insurance and <br />floodplain management applications. <br /> <br />For flood insurance applications, the map designates flood insurance <br />rate zones as described in Section 5.0 and, 1n the lOa-year floodplains <br />that were studied by detailed methods, shows selected ",hole-foot base <br />flood elevations. or a.verage depths. Insurance agents use the zones and <br />base flood elevations in conjunction with information on structures and <br />their contents to assign premium rates for flood insurance policies. <br /> <br />For floodplain management applications, the map shows by tints, screens, <br />and symbols, the 100- and 500-year floodplains, floodways, and the <br />locations of selected cross sections used in the hydraulic analyses and <br />floodway computations. <br /> <br />7.0 OTHER STUDIES <br /> <br />Previous studies for the Colorado River include the 1976 COE Flood <br />Hazard Information report (Reference 19) which was subsequently updated <br />in May 1980 and the December 1985 Flood Insurance Study for Mesa County, <br />Colorado (Reference 5). <br /> <br />A previous report on Indian Wash prepared by the COE (Reference 6), <br />which discussed damage from the 1958 flood and delineated the limits of <br />flooding, was used as a guide in delineating the sheetflow areas in this <br />study. <br /> <br />A later study on Indian Wash entitled Watershed Work. Plan. Indian Wash <br />Watershed. Mesa Count v was completed in 1961 by the Upper Grand Valley <br />Soil Conservation District (Reference 9). It included plans for flood <br />control structure IW-l. The plans were used for the hydrologic analyses <br />used in this study. <br /> <br />A Master Drainage Plan for Grand Junction was prepared in 1974 by <br />Nelson, Haley, Patterson and Quirk., now Arix Engineers (Reference 20). <br />The results of the hydrologic analysis of Indian Wash in that report <br />differ sLightly from the results of this study. The differences are <br />attributed to different study techniques and different assumptions <br />concerning the retarding effects of the Government Highline Canal. <br /> <br />A revision of the Mesa County Flood Insurance Study has been published <br />(Reference 21). The current study for the City of Grand Junction is in <br />agreement with the county study. <br /> <br />This study is authoritative <br />herein either supersede <br />determinations. <br /> <br />for the purposes of the NFIP; data resented <br />or are compatible with all previous <br /> <br />25 <br />