This flood was caused by an upstream dam failure. Nearly 9 of every 10 presidential disaster declarations result from natural phenomena in which flooding was a major component. A wall of water 19 feet high roared down the Big Thompson Canyon where many people were camping. 140 people perished and millions of dollars of property were lost. Flash floods usually result from intense storms dropping large amounts of rain within a brief period.
Flash floods occur with little or no warning and can reach full peak in only a few minutes.
The force of six inches of swiftly moving water can knock people off their feet. The best protection during a flood is to leave the area and go to shelter on higher ground. Flash flood waters move at very fast speeds and can roll boulders, tear out trees, destroy buildings, and obliterate bridges. Walls of water can reach heights of 10 to 20 feet and generally are accompanied by a deadly cargo of debris. The best response to any signs of flash flooding is to move immediately and quickly to higher ground.