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<br />A statistical analysis of gauging data was performed in accordance with Annual Flood <br />Frequency Analysis Using Bulletin 17B Guidelines1. This methodology utilizes <br />instantaneous peak flows and utilizes a Log Pearson Type III distribution to determine <br />flow values for recurrence intervals of 10, 50, 100, and 500 years (exceedance <br />probabilities of 0.10, 0.02, 0.01, and 0.002, respectively). <br /> <br />Peak gage records were obtained from the USGS on-line records available at <br />http://water.usgs.gov/co/nwis/sw. These are systematic records or records that were <br />actually measured. Historic records, Le., information gained from newspaper articles, <br />letters, personal recollections and other historical sources were not utilized in Log <br />Pearson Type III analysis of gage data. Generalized skew coefficients (G) as published <br />in Bulletin 17B were utilized. No attempt was made to determine a regionalized skew <br />coefficient, as USGS guidelines recommend a minimum of 40 gages with at least 25 <br />years of record each be used to develop skew coefficients. <br /> <br />DESCRIPTION OF DRAINAGE BASINS <br /> <br />The Eagle River basin covers 990 square miles or 57 percent of Eagle County, and 14 <br />square miles in Pitkin County. It drains in a northwesterly and westerly direction through <br />the center of Eagle County to Dotsero where it joins the Colorado River. The Colorado <br />River then flows 4.0 miles southwesterly to the Eagle-Garfield County line. <br /> <br />The lower Eagle River is separated from the Colorado River by Castle Peak on the north <br />and from the Fryingpan River Basin on the south by Red Table Mountain. The <br />topography is characterized by rolling hills and wide valley floors. Elevations vary from <br />6,120 feet at the mouth of the Eagle River to 11,785 feet on Red Table Mountain. <br /> <br />I Users Manual for Program PEAKFQ, Annual Flood Frequency Analysis Using Bulletin 17B <br />Guidelines, USGS, 30-Jan-1998. PEAKFQ performs statistical flood-frequency analyses of <br />annual-peak flows following procedures recommended in Bulletin 17B of the Interagency <br />Advisory Committee on Water Data (1982). PEAKFQ v. 4.0, USGS, Dec. 1,2000 was used for <br />all analyses. <br /> <br />3 <br /> <br />~ <br /> <br />Water Resource Consu I tants, LLC <br />.....l <br />