1976 Big Thompson flood, Colorado — Thirty years later

Fact Sheet 2006-3095
By:  and 



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. 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. Scores of other people narrowly escaped with their lives. More than 800 people were evacuated by helicopter the following morning. This fact sheet presents a summary of the hydrologic conditions of the 1976 flood, describes some of the advances in U.S. Geological Survey (USGS) flood science as a consequence of this disaster, and provides a reminder that extreme floods like the 1976 Big Thompson flood have occurred in other locations in Colorado in the past and will occur again.

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Publication type Report
Publication Subtype USGS Numbered Series
Title 1976 Big Thompson flood, Colorado — Thirty years later
Series title Fact Sheet
Series number 2006-3095
DOI 10.3133/fs20063095
Edition Version 1.0
Year Published 2006
Language English
Publisher U.S. Geological Survey
Contributing office(s) U.S. Geological Survey
Description 5 p.
Public Comments See also poster GIP 35
Time Range Start 1976-07-31
Time Range End 1976-07-31
Country United States
State Colorado
Other Geospatial Big Thompson River Basin
Google Analytic Metrics Metrics page
Additional publication details