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EXECUTIVE SUMMARY This report provides updated flood flows for the mainstem of the Eagle River from Minturn, Colorado to the Eagle-Garfield County Line. Flows are presented for the 10, 50, 100, and 500 year recurrence intervals (p = 0.10, 0.02, 0.01 and 0.002, respectively). The primary basis for the study is historical stream gauging data available at the time the report was prepared. Areal adjustments were made where gage data was lacking. Where calculated flow values did not vary by more than 10 percent from previously published Federal Emergency Management Agency (FEMA) Flood Insurance Study flow values, previously published values are reported. Due to the relative short duration of portions of the flow data, additional data in future years may allow the conclusions to be altered. The study was authorized by the Colorado Water Conservation Board and Eagle County Commissioners. The purpose of the study Was to update flood hydrology on the mainstem of the Eagle River as previous studies published by the FEMA in May of 1980 did not cover this reach of the Eagle River. This study was funded by the Colorado Water Conservation Board and was performed under contract between Eagle County and Water Resource Consultants, LLC, of Rifle, Colorado. Calculated flood flows for specific reaches of the main stem of the Eagle River are summarized in the Table 1 below. It is important to note that the flow value for the 100- year event in Minturn has increased significantly - from 2,800 cfs to 3,490 cfs for the 100 year runoff event. This is an increase of 25 percent. Although evaluating the Eagle River through the Town Minturn was not originally in the scope of work requested by CWCB and Eagle County, necessary efforts to produce reliable data henceforth included analysis of gages upstream from Minturn. Also, a gage on the Eagle River at Eagle was deemed unreliable, as regression analysis showed higher flow values at this location than further downstream at a gage with more than four times the length of record. An areal analysis was performed where gage data from mainstem gages or tributary gages was lacking. Observation has shown that areas above 10,000 feet in elevation are the primary source of snowmelt flooding potential. Correlations of areas above 10,000 feet to calculated peak runoff resulted in extremely good correlation coefficients of r2=0.97 to r2=0.98.