Design Engineering Report: Avon Exhibit 1

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De,sign En?,riYtc:del•ir? l2c:J?oF•t, C}ca,se tVcz20113-E 6i'-25.5 Totirn qf,=ivc7r7's R«reationu/ !rr-(."{iannc( L1iversiort (RUCf)1 kt a€cr tttght ltr the Eugle River Any potential increase in flow velocities would be locally dissipated as a result of the hydraulic jumps which are created. Reach wide sediment transport and fluvial geomorphology would be unaffected by the project because of the armored cobble boulder bed and exposed bedrock that has created a stable channel. No change in configuration of the downstream riffle is anticipated because of the existing stable channel. No changes to channel form downstream of the project area are expected. The environmental effects of the proposed RICD flow could prove beneficial to the future ecology, riparian zone and fluvial geomorphic processes by maintaining flows. The proposed RICD may help to maintain a resemblance to the pre-development hydrograph that all riparian ecological processes have evolved upon. IX. Hydraulic Analysis There are three proposed recreation enhancement structures within the reach. Each of the three structures is located at what is known as a"control section," in which flows pass through a"critical" state. In the CWCB's 2003 Technical Criteria, the CWCB defined control as: "A section across the stream where a manmade structure causes the flow to pass through critical depth when flow changes from sub-critical to super-critical. " Each of the three structures enhances a hydraulic jump for recreation; this hydraulic jump happens at a section across the river where flows pass from a sub-critical state to a super- critical state. The proposed structures "control" the flow to create the desired hydraulic jump. The "critical" state of flow is measured by a Froude Number. When a Froude Number is greater than 1.0 the flow is super-critical, when less than 1.0 the flow is sub- critical, and when equal to 1.0 the flow is considered critical. Table 3 shows the Froude Numbers for the three structures. For each structure, these Froude Numbers were calculated at three sections: at the structure, upstream of the structure, and three feet downstream of the structure, to reveal the control section and the hydraulic jump. This table includes the hydraulic parameters of depth, velocity and Froude Numbers for each of the three sections for each structure (based on 1 dimensional hydraulic modeling with mixed flow regime). The upstream structure, Baby Bob, is located at an existing `natural' control section (Froude Number = 1.0 naturally) in the channel. However, the resulting hydraulic jump is not organized well enough to provide the recreational experience sought. Therefore, the control section would be reworked at the average existing grade with large boulders to reform into a small hole. The natural boulders would not be grouted in the channel and some shifting is expected; however the boulders would be sized to and keyed into the bed so they would be stable and would not overturn in a 100-year flood scenario. 6 of 11 t j ? ? .Itrnc _'OfJf I oefr?? POBon_'I'±CIem?ocd5prinp;Celtn:?dt:SIGC?(?t70)?iJ7415trR