1976 Big Thompson flood, Colorado: Thirty years later

In the early evening of Saturday, July 31, 1976, a large stationary thunderstorm released as much as 7.5 inches of rainfall in about an hour (about 12 inches in a few hours) in the middle reaches of the Big Thompson River Basin and to a lesser extent in parts of the Cache la Poudre River Basin (U.S. Geological Survey, 1979). In steep mountain terrain with thin or no soil, this large amount of rainfall in such a short period of time produced a flash flood that caught residents and tourists by surprise. The sudden flood that churned down the narrow Big Thompson Canyon scoured the river channel that night, caused over $35 million in damages (1977 dollars) to 418 homes and businesses, many mobile homes, 438 automobiles, numerous bridges, paved and unpaved roads, power and telephone lines, and many other structures. The tragedy claimed the lives of 144 people, including two law enforcement officers trying to evacuate people in danger, and there were 250 reported injuries (U.S. Geological Survey, 1979). Scores of other people narrowly escaped with their lives. More than 800 people were evacuated by helicopter the following morning.