n June of 1972, winds pushed moist air westward up the flanks of the Black Hills, forming severe thunderstorms. The huge thunderstorms remained over the mountains, where they dumped as much as 15 inches of rain in one afternoon and evening. This downpour unleashed a flash flood down Rapid Creek that was ten times larger than any previously recorded flood on the creek. The swirling flood- waters breached the dam at Canyon Lake,which increased the volume of the flood downstream through Rapid City. The floodwaters raced toward the center of the city. These floodwaters killed 238 peo- ple and destroyed more than 1,300 homes. They caused 160 million dollars in dam- age. Most of the damage occurred along the river channel, where many homes had been built too close to the creek, and in areas low enough to be flooded by this large volume of water.