Uncontrolled Spillways

A stepped chute spillway in England. (Wikipedia)

“A controlled crest is one that includes gates which are used to control the flow; the uncontrolled crest is one unencumbered by gates”.^[1]

“Common to all uncontrolled spillways that are not integral with a concrete dam (i.e., located away from the dam on or through abutments, or on or through reservoir rim) is that existing topography must provide adequate space without excessive excavation. Also, the existing topography must allow appropriate orientation (alignment of the spillway between the reservoir and downstream river or stream) of the conveyance feature and terminal structure. Additionally, economics will come into play for all uncontrolled spillways”.^[2]