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FLOOD LEVEL CALCULATIONS <br />2/3 <br />V _ 1.49 S1lz (Ai <br />n; P,. <br />V; = Water velocity in channel (fps) <br />Ai = Channel cross sectional area (ft) <br />P; = Channel cross sectional wet perimeter (ft) <br />S = Channel slope (percent grade) <br />ni = Manning's number (gravel lined channel) <br />Event A, (ft) P, (ft) n; V, (fps) S Volume (cfs) <br />10 year 24 475.00 182.80 0.02 16.05 1.3% 7.626.05 <br />10 year 24 hour event volumetric flow rate = 7,600 cfs <br />Cross-sectional area and perimeter determined from 10 Year Cross Section Detail. <br />Approximate water surface level = 5360' <br />The water level is based on the known flow of 7,600 cfs (10 yr/24 hr event) at that point <br />in the river. This river flow data comes from the Delta County Flood Insurance Study <br />dated August 1991. The drainage area considered in that study was the north fork of the <br />Gunnison River north of Hotchkiss, CO. Manning's equation was used to determine the <br />height of water necessary to pass that known flow at that point on the river.