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<br />0J29J5 <br /> <br /> <br />y Drrection of Flow <br /> <br />-.*'-~' <br /> <br /> <br />Figure 3. A section view of the apex oftheU-structure. <br /> <br />Figure 3 shows a section view of the apex ofthe arch. This Figure shows that the arch is <br />sunk into the riverbed such that the crest of the structure, which is the highest point on the <br />upstream side, is even with the existing riverbed. Setting the structure even with the existing <br />riverbed has two effects. First it ensures that the unconstricted river level is no higher than the <br />existing river level and secondly it ensures that there are no dynamic fluid forces on the structure <br />due to current flow. Sinking the arch in the riverbed also supports the structure laterally and <br />prevents torsion on the structure. <br /> <br />A base rock, also shown in Figure 3, is shown at the downstream end of the structure. <br />The base rock is sunk into the cobble and is keyed into the rock that forms the structure in order <br />to reinforce the structure and to protect the structure from erosion caused by eddy currents. <br /> <br />These structures are designed such that the river is usable at a variety of water levels. <br />Figure 4 shows a profile view of the V-structure looking upstream. This view highlights the <br />versatile design of these structures. The low flow channel can be designed to provide deep <br />passage and a usable hydraulic feature during typical low flows. During the mid-range flows the <br />low flow channel and part of the high flow would be submerged. During run-offthe high flow <br />chmmel would create a larger, more usable hydraulic feature (a hydraulic jump or wave train), <br />and at extreme flood the river will overflow the shoulders of the structure. The downstream side <br />of these shoulders are stepped to provide seating during normal flows and to prevent the <br />fomlation of dangerous hydraulics during extreme flooding. <br /> <br />-8- <br />