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Ihsi-,n F'ngineer•irtg Repof•1, C a.si: No.2(I05-04'-258 <br />Town of.4von'.s Recreationci/ [n-("ilurlnel L)iversioyt (RIC'D) ifi'cxter Righf rn thcr Eagle RIVEl' <br />The main feature rock at Baby Bob would have a flatter profile to form a hole. The hole <br />would form at all flows; however, above 200 cfs the downstream pool deepens to greater <br />than 3 feet. Depths of 3 feet and greater are generally considered adequate for rolling and <br />providing a reasonable recreational experience. Therefore, 200 cfs is the efficient flow <br />rate for the proposed Baby Bob structure because at that flow the depths of the pool are <br />the minimum necessary for a reasonable recreation experience. <br />The middle structure, Bob Jr., is located at an existing `natural' control section (Froude <br />Number = 1.0 naturally) in the channel. However, as with Baby Bob, the resulting <br />hydraulic jump is not sufficient to create a reasonable recreational experience. Placing a <br />pre-cast structure and excavating some bedrock would focus the hydraulic jump and <br />create the desired wave-hole type feature. The wave-hole feature created by this pre-cast <br />structure would begin to form at all flows, but beginning at 350 cfs, the downstream pool <br />deepens to greater than 3 feet. When the depths are greater than 3 feet, intermediate <br />freestyle kayakers would be able to Eskimo-roll their boats. Therefore, 350 cfs is the <br />efficient flow rate for the proposed Bob Jr. structure because at that flow the depths of the <br />pool are the minimum necessary for a reasonable recreation experience <br />The downstream structure, Bob Sr., relies on the large flows being constricted through <br />the bridge channelization and the expansion after the Bridge. A wave currently forms <br />here at greater than 3,500 cfs. Modifications to the channel are restricted from raising the <br />100-year Base Flood Elevations upstream of the structure. As designed, the pre-cast <br />structure to be placed at Bob Sr. is the maximum size that would not impact these Base <br />Flood Elevations. Under proposed conditions the flow becomes critical at 1,300 cfs (the <br />Froud Number = 1.0 at 1,300 cfs); however, the flow does not go through a super-critical <br />state. As shown in Table 3, while the Froude Number for Bob Sr. equals 1.0 at 1,300 cfs, <br />the flow does not go through a super critical state unless the Froude Number becomes <br />greater than 1.0 downstream of the structure. That occurs for the first time at a flow of <br />1,400 cfs. (See Table 3 showing the downstream Froude Number dropping to 0.7 at <br />1,300 cfs but increasing to 1.8 at 1,400 cfs.) Therefore, the modifications created by the <br />pre-cast structure would improve the existing wave to provide an advanced freestyle <br />recreation experience at flows as low as 1,400 cfs, which is the efficient flow rate far the <br />proposed Bob Sr. structure. <br />7 of 11 <br />M_: ??????1 <br />I V E R A <br />? ??•• •??? PO Bax ' l:; Gien??•ocd Sprine; Colora:lo ?{GrJ2 (97'.i) 9-1;; ') 'ihS':