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based on conditions existing in the community at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analysis Hydrologic analyses were performed to establish the peak discharge-frequency relationships for floods of the selected recurrence intervals for each stream studied in detail in the county. The hydrologic analyses for the August 22, 2003, Matrix study of Colorado River and Eagle River were authorized by the CWCB and completed by Water Resource Consultants, LLC (WRC) (Reference 14). WRC completed their work on May 13, 2002, to update flood hydrology on the main stem of the Eagle River. Previous studies published by FEMA in May 1980 did not cover all the reaches of the Eagle River. A regression analysis of tributary area above 10,000 feet elevation was performed where gage data was lacking. Stream data taken at gages for the limited years of existence in the Eagle Basin was analyzed and natural flow frequency curves were developed. The peak flows determined for the 10-, 2-, 1-, and 0.2-percent-annual-chance floods were used to determine the flood profiles and the 100-year floodplain for this report. Table 1 lists the peak discharges for these floods on the Eagle and Colorado Rivers. There is not a long history of stream gage records on the Eagle River. The gage on the Eagle River with the longest period of record is located outside this study area. The Eagle River at Red Cliff gage is located upstream from this floodplain study area and has 73 years of record. The peak flood of record occurred in 1912. The Eagle River below Gypsum gage has the next longest period of record and has been in existence since 1947. This gage has a drainage basin of 944 sq. mi. The U.S. Geological Survey (USGS) gage records do not show a significant flood during this period of record. However, high flows occurred on the Eagle River in the years 1952, 1957, 1983, 1984, 1995, 1997, and 2003. There are five active USGS gages located on the main stem of the Eagle River and the portion of the Colorado River in this study area. Two other gages have existed in the past, but are no longer active, although records from the gages are useful in statistical gage analysis. The gages are listed in order from upstream to downstream. Eagle River USGS Gaging Stations Station No. Station Name Drainage Gage Period of Record Status Peak Area Elev. Discharge (sq.mi.) (feet) (cfs) 09063000 Eagle River at Red Cliff 70 8,654 191 1-1925, I 924-present Active 1,010 09064600 Eagle River near Minturn 186 8,078 I 990-present Active 1,810 09067005 Eagle River at Avon 395 7,410 1989-1999 Inactive 3,930 09067020 Eagle River WWTP at Avon 402 7,380 I 999-present Active 3,640 09067500 Eagle River at Eagle 629 6,560 1911-1924 Inactive 6,760 09070000 Eagle River below Gypsum 944 6,275 1947 -peresent Active 7,020 09070500 Colorado River near Dotsero 4,394 6,130 1941-present Active 22,200 17