Thirty years ago on July 31, 1976, a massive flash flood roared through the Big Thompson Canyon in Colorado. In two hours, the Big Thompson Canyon flood killed 145 people (including six who were never found), destroyed 418 houses and damaged another 138, destroyed 152 businesses and caused more than $40 million in damages. For the story, go to the online presentation and/or the following website.
Here is another link dated 7/31/06 of videos regarding the flood.