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The design of the in-stream structures is pertinent to this discussion and explains how the <br />same structure can provide navigable hydraulic features at lower levels and dynamic whitewater <br />features at higher levels while controlling and diverting the flow. <br />A plan view illustration of the U-structure is shown in Figure 2. This feature is used to <br />create a river wide "drop" and can be used to constrict lower flows to increase the velocity and <br />power of the water. By adjusting the gradient of the flow over the U-drop a wave or hydraulic <br />can be formed. The structure also features elevated wings that are positioned along both <br />riverbanks. These wings provide an eddy for easy recirculation to the wave. This structure is <br />also beneficial to the in-stream habitat. The gradient of the drop keeps a pool below the structure <br />scoured and creates a natural habitat for fish and aquatic life. <br />Figure 2. A top view of a 3-D computer model of a U-structure demonstrates its arched design. <br />This structure is very stable and will accommodate high volume/high velocity flows. The <br />structure features an arched shape laid in the plane defined by the riverbed with its footing sunk <br />into the riverbank, as shown in Figure 2, to beaz these loads. The azch is a classic support <br />structure that dates back to Roman civilization. This structure has two properties that make it <br />desitable for in-stream use. The first is that it is extremely strong and stable. This structure can <br />sustain very high and very imbalanced loads without becoming unstable. The second property <br />of arches that makes them desirable for in-stream use is that all stresses induced in the arch due <br />6� <br />