Laserfiche WebLink
<br /> <br /> <br /> <br />14 <br />Conveyance Systems <br />Conveyance systems are typically chutes or channels <br />that convey flow from the spillway crest structure to <br />the terminal structure. Conduits and tunnels are also <br />used for conveyance systems but are less common. <br />Chute conveyance systems are described in the <br />following subsections of this article. <br />Spillway Chutes or Channels <br />An open channel that conveys flows directly from the <br />crest into a stilling basin or downstream channel is <br />referred to as a chute conveyance system. Spillway <br />chutes are commonly located along one of the dam <br />abutments or through a saddle some distance from the <br />dam. A spillway chute is the most common conveyance <br />system, particularly on small dams. <br />Spillway chutes typically have a prismatic cross section. <br />The most common concrete chute design is a <br />rectangular channel; however, trapezoidal channels <br />are also common. Chutes can be converging or <br />diverging from the crest structure to the terminal <br />structure. Chutes can be lined with concrete, riprap, <br />Reno mattresses, articulated concrete blocks, etc., or <br />be unlined where acceptable foundation conditions <br />exist to resist unwanted erosion during operation. In <br />some instances, a chute can be partially unlined and <br />lined where only certain areas of the foundation need <br />to be protected. <br />The spillway chute can be smooth, rough, stepped, or <br />baffled. Stepped and baffled chutes can help dissipate <br />the energy of flood flows and can reduce the size of <br />the terminal structure or in certain circumstances <br />negate the need for a terminal structure. Spillway <br />chutes can be designed with a constant slope or with <br />vertical curves and variable slopes to match the dam <br />configuration, site constraints, and/or topography. <br />Typically, and preferably, spillway chutes are straight, <br />but in some cases, have horizontal bends where <br />complex flow conditions can occur and must be <br />considered as part of the design process. <br />Examples of a lined spillway chute are shown on <br />Figures 11 and 12. An example of an unlined spillway <br />chute is shown on Figure 13. <br /> <br />Figure 11: Lined Spillway Chute (Concrete) <br /> <br />Figure 12: Lined Spillway Chute (Articulated Concrete Blocks and <br />Riprap) <br />Figure 13: Unlined Spillway Chute