Date: July 31, 1976
Significance: $35.5 million in damages; 144 dead
Holmes says: Flash floods are incredibly devastating. Scientifically, they are quite interesting. You have a tremendous amount of water that comes in a very short amount of time. Anytime you get in these mountainous areas, you have a potential for a flash flood. This case sticks in my mind because of the intensity of the [water] as it rushed from the Rocky Mountains into Big Thompson Canyon in Colorado. The rain started in the evening of July 31 and by the wee hours of August 1, you had 12 inches of rain in this narrow canyon. The water speeds were very high and people were just washed away. They didn't have an escape; it all happened very fast.