Spillways

Labyrinth weir spillways are commonly used to increase discharge capacity at existing dams.

(Image Source: Gannett Fleming)

“The basic purpose of the spillway is to provide a means of controlling the flow and providing conveyance from reservoir to tailwater for all flood discharges up to the spillway design flood (SDF). The spillway can be used to provide flood control regulation for floods either in combination with flood control sluices or outlet works, or in some cases, as the only flood control facility.^[1]

“One of the most common causes of dam failures is the inability to safely pass flood flows. Failures caused by hydrologic conditions can range from sudden failure, with complete breaching or collapse of the dam, to gradual failure, with progressive erosion and partial breaching”.^[2]

“Crest piers, abutments, and approach configurations of a variety of shapes and sizes have been used in conjunction with spillways… Not all of the designs have produced the intended results. Improper designs have led to cavitation damage, drastic reduction in the discharge capacity, unacceptable waves in the spillway chute, and harmonic surges in the spillway bays upstream from the gates. Maintaining the high efficiency of a spillway requires careful design of the spillway crest, the approach configuration, and the piers and abutments. For this reason, when design considerations require departure from established design data, model studies of the spillway system should be accomplished”.^[1]