Black Hills Flood: The Dam Wasn't the Disaster

On the ninth of June, 1972, two creeks came off the eastern slope of the Black Hills about a dozen miles apart, in the same storm. Boxelder Creek ran the bigger flood and did almost no damage. Rapid Creek ran the smaller one and killed two hundred and thirty-seven people. Canyon Lake Dam failed that night, and for fifty years it has been the answer to what happened to Rapid City. The federal investigation that followed answers it differently. This is an engineer's look at the 1972 Black Hills flood: the storm that stalled over the eastern slope, the fifty-one square miles of uncontrolled drainage that produced almost all of the water, the reservoir that held a hundred and ninety-two acre-feet against a flood carrying thirteen thousand, and the decision Rapid City made afterward that most American cities did not. Chapters: 0:00 Intro 0:51 The Black Hills 1:55 The Dams 3:24 The Weather Charts 8:10 The Flood 13:51 The Timeline 16:11 Boxelder 17:21 The Aftermath 19:56 Rapid City's Response 20:51 Conclusions 21:14 Outro Sources: USGS Professional Paper 877, Schwarz, Hughes, Hansen, Petersen and Kelly, 1975, "The Black Hills-Rapid City Flood of June 9-10, 1972" Bureau of Reclamation, RCEM case histories Association of State Dam Safety Officials, Canyon Lake Dam case study GAO, CED-78-114 and related reporting on Public Law 92-367 Larimer, 1973, inundation mapping, Rapid City LIFE magazine, June 23, 1972, "Night of Terror on Dunbarton," by Dale Wittner Casualty figures follow PP877 and the American Red Cross. Some sources give 238. This episode exists because a viewer who studied at the South Dakota School of Mines wrote in about two classmates who lived through that night, and said he wished he had recorded them. If you were in Rapid City in 1972, or your family was, Rapid City Public Library and Pennington County hold oral history collections and are still accepting accounts. That record is worth more than anything in this video.