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That report was the source for the Parachute FIS, so the two reports are consistent. Additionally, information was obtained from a report titled "Hydro]ogy Report, Flood Insurance Studies in Mesa County", dated May 1989 {Reference 10). ]t was prepared by ].F. Sato & Associates, Inc a.~ part of their work under contract to FEMA in performing engineering for the 7/92 F]S' for Palisade, Grand Junction, Fruita and Mesa County. 2.0 STUllY AREA 2.1 Location Preliminary floodplain maps have been prepared by the U.S, Army Corps of Engineers for the Colorado River from Glenwood Springs to the upstream end of DeBeque Canyon as part of an ongoing Floodp]ain Information Report (Reference I I). The Corps of Engineers maps and the hydrologic analyses that preceded them are inconsistent with the City of Rifle FIS. Since the Corps of Engineers ,"vork is more CUlTcut, it was selected as being more valid for the Rifle area, There is no contlict between the Parachute FIS and the Corps of Engineers maps. The preliminary maps from the Corps of Engineers were used to delineate the floodplain from Rifle to DeBeque Canyon. The study reach of the Colorado River mainstem extends from Rifle dOI'o1lstream to the Utah. Colorado state line, A]though portions of the Colorado watershed arc locakd ill sever<ll other Colorado countics, the entire study reach lies in ~esa <JIld Garfield Counties in west-central Colorado. (see Figure]) 2.2 Study Reach The primary source ofhydro]ogy used in this study for the upstream portion of the study reach (between Rifle and the confluence with Plateau Creek, which is approximately 2.5 miles ups1ream of Cameo) is a 1985 Hydrology Report by the U.S. Army Corps of Engineers (Reference 7). The primary source of hydrologic information for the downstream portion of the study reach (between the confluence with Plateau Creek and the Utah state line) was the 1989 Sato Hydro]ogy Report prepared for the ] 992 FEMA studies of Mesa County and associated municipalities. The Hydro]ogy Report and the FIS' provide peak flow values for 50-year and ]OO-year floods for Palisade, Grand Junction, and Fruita and the adjoining areas of unincorporated Mesa County. 'ibe focus of this study on the Colorado River mainstem is from the Highway 13 bddge at Rifle, Colorado (approximately 93 miles upstream of the Utah stateline) downstream to the stateline, At the I.lpslrcam limit of the study the stream elevation is ~pproximately 5300 feet and at the do\'mstrcam limit of the study the stream elevation is approximately 4330 feet. The study reach contains four USGS gages. One is located upstream of DeBequc, one is upstream OfCanle0, one is at Palisade, and one is located upstream of the Utah state line. There is also a gage at Glenwood Springs, approximately 25 miles above the upstream study limit. Tributary gages are located on Plateau Creek near the confluence with the Colorado River and on the Gunnison Rivtlr at Whitcwater, Colorado, Information for the four gages "ithin the study reach. the gage at (Henwood Springs, and the gages on tributary streams is listed in Table I. The reports referenced above are avai]able at the office of the Culorado Water Conservation Board, at the Federal Emergency Management Agency (Region Vlll), at the U.S. Army Corps of Engineers (Sacramento District), at the Cities of Rifle and Grand Junction, at the Towns of PalaChat::. DeBcquc. P<lii:>ad.: a..,d f:ui:a. anc! ;;.t Me~a :;l:":d Ga.-field Cm.l,:lties, COt,bRADo' RIVER' (RIFLE TO' utAH) dAOEIO GAGE NAME 'RECORDYRS ' AREA (SQMl) LAT/LONG (LOCA'fIQW 09085100 GLENWOOO SPGS 29 6013 393338,]071759 (2M] E) 09093700 DEBEQUE (H Ml " 7370 392145,]080907 NE) 09095500 CAMEO (7 MI NE) 62 8050 391420,1081600 09]06150 PALISADE (.25 MI 5 8753 390555,1082116 S) 09163500 UTAlI STATE 44 17843 390745,1090136 LINE (1.5 M] U/S) TABLE 1 GAGE DATA , 3