Designing or Evaluating a Spillway?

ABSTRACT ONLY - While designing a spillway, an understanding of the conditions at the spillway chute and their impacts to conveyance and overall hydraulic behavior is required to provide an efficient, sustainable solution. Some commonly observed undesirable conditions at chutes include changing geometry, insufficient training walls, super elevated chute floor, changing roughness, potential for air entrainment and flow bulking, structural impedances including bridge crossings and piers, ball milling, and flow anomalies caused by improper gate operation. Other not-so-common conditions such as sudden increases in stream power, stagnation pressure, and cavitation can also impact a spillway’s hydraulic performance. Oftentimes well-defined relationships for these various chute conditions on spillway performance are not available, and therefore, their impacts are difficult to evaluate. Such conditions, when left unevaluated and unremedied, can result in a hydraulics-induced compromise of the chute that can ultimately lead to a failure of the spillway. This presentation will provide a perspective on such spillway chute conditions that are sometimes overlooked, but can adversely impact spillway performance. Actual spillway case studies will be used as examples. Recommendations for confirming spillway performance using CFD modeling will be discussed.