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passage and a usable hydraulic feature during typical low flows. During the mid -range flows <br />the low flow channel and part of the high flow channel would be submerged. During run- <br />off the high flow channel would create a larger, more usable hydraulic feature (a hydraulic <br />jump or wave train), and at extreme flood the river will overflow the shoulders of the <br />structure. The downstream side of these shoulders are stepped to provide seating during <br />normal flows and to prevent the formation of dangerous hydraulics during extreme flooding. <br />0%,crllow Channel <br />Fligh 'low Clianncl <br />Law Flow Channel <br />Figure 9. The upstream view of the U- structure shows how it is designed to accommodate <br />varying flow levels. <br />Low Flow <br />The low flow chute is designed to create depth and a defined riffle channel at <br />lower flows. This chute provides boat passage for numerous craft at lower <br />flows. Past experience has shown that depth of flow, capacity, and control <br />of the flows are well defined, at lower flows, by this channel. Figure 10, <br />shown below, is an example of a low flow channel with flow in it. <br />26 <br />