The Black Hills Flood of 1972, also known as the Rapid City Flood, was the most detrimental flood in South Dakota history, and one of the deadliest floods in U.S. history. The flood took place on June 9–10, 1972 in the Black Hills of Western South Dakota. 15 inches (380 mm) of rain in a small area over the Black Hills caused Rapid Creek and other waterways to overflow.
The flood caused a tremendous amount of damage. Flood waters displaced large rocks, trees, trailers, and vehicles, and carried homes away. In Rapid City the flood resulted in the deaths of "238 including 5 missing," 14 of the deaths were trained professionals. The flood resulted in over 3,000 people being injured. A total of 1,335 homes were ruined, and 2,820 homes were damaged. More than 200 businesses were ruined, and around 5,000 cars were demolished. The damage in Rapid City totaled $66 million in 1972 dollar value. As for Keystone, "eight people were killed and much of the town was washed away." The damage in Keystone totaled around $1.5 million. The total cost of the 1972 Black Hills flood totaled $165 million, including infrastructure and utilities. The total amount of rain the Black Hills received was "800,000 acre feet" equal to "1 billion metric tons of water".
The National Weather Service Office (NWS) in Rapid City in 1972 was taking hourly surface observations, issuing local storm warnings and providing local forecasts to the media. The personnel in Rapid City were not properly trained to make forecasts or use the technologies available to them. They lacked access to vital weather information to warn the area citizens. More details