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Back to spillwaysSpillways & Outlets - Overflow spillways

Water flowing over spillway

Water flowing over spillway of
Booth Wood concrete gravity
dam in Yorkshire, England

An overflow spillway is most often constructed as part of a gravity dam or a buttress dam. The spillway section is lower than the other sections of the dam allowing water to flow over its top and down its front face.

Water cascading down the overflow spillway of Caban Coch Dam

Water cascading down the
overflow spillway of Caban
Coch Dam in Mid-Wales

Sometimes, the whole of the dam acts as an overflow spillway.

Curved downstream face of Caban Coch Dam spillway

Curved downstream face of
Caban Coch Dam spillway

A close up of the spillway when it is dry shows that the top and downstream face are curved to control the flow of water over it.