When Lake Dunstan was created when a dam was built for a hydro scheme, most of the town of Cromwell was lost. There are a few old buildings remaining. We went for a 'tiki tour' around a bit of Central Otago - starting in Cromwell.
The local electric company did the same thing near here. They flooded small towns mostly blacitizens lived there, And now we have a big lake. The water runs over a dam and gives electricity.