A dam was a structure built to control the flow of water.
Ghum claimed that the Basks had violated the Co-existence Code by building a dam. (PROSE: The Oxaqua Incident)
The Eighth Doctor destroyed a fire elemental in Middletown by having some of the townspeople blow up the local dam. The resulting flood cooled and killed the elemental. (PROSE: The Burning)
In 1969, Rory Williams was caught and shot by Canton Delaware at Glen Canyon Dam. (TV: Day of the Moon)
In 1980, a military training site was built next to a dam in Caithness, Scotland. It was abandoned at some point before the dam was destroyed and thus flooded the area. (TV: Before the Flood) In 2119, an underwater mining facility known as the Drum stood in its place. The Twelfth Doctor and Clara Oswald visited the base and investigated a ghost invasion, caused by strange markings on the inside of an alien spaceship recovered from the water outside. (TV: Under the Lake)
In 2400, the Winston Dam was the only source of electrical power on Venus. (PROSE: The Secret of the Mountain)