Among all disasters, dam collapses are, fortunately, relatively scarce. Let me sum up those I know about (in Europe, where I live): Cwmrwyn, Wales, 1889, 25 dead. Bila Desna, Austria-Hungary, 1916 (then), 110 dead. Saas Fee, Switzerland, 1960, 14 dead (in fact, a landslide on an unfinished dam building site). And the most famous, Vaiont, Italy, 1967, one thousand-and-something dead. There an extreme amount of water raised by a landslide splashed over the dam, that in fact remained standing. Maybe it would be useful to search for the folklore around those places... I know, a bit tedious.