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The Big Thompson Flood: Colorado's Worst Natural Disaster

© B. J. Barton

Last week when I drove up the Big Thompson Canyon between Loveland and Estes Park, I stopped for a few minutes at one of the memorials to victims of the Big Thompson Flood. This memorial is for two police officers (Sgt. W. Hugh Purdy, Colorado State Patrolman and Michael Conley Estes Park Police Officer) who died while trying to save the lives of others on that truly awful night. The canyon is peaceful now, and many improvements to the road and to weather prediction capabilities have greatly reduced flash flood risks. Usually, I drive the canyon without thinking about it, but in July it is more likely to come to my mind, and then I remember it very well.

As with any event of such magnitude and emotional intensity, there are many conflicting "facts" and I have tried to choose those that appear most accurate. Some of it I remember from personal experience, though I was not in the canyon that night. (For my own account, see the article for July 22, 2003.) I have read that the probability of a flash flood like that one is only once in 300 years, or once in 10,000 years, and I don't know if either one is accurate, but here are the elements that came together to create Colorado's worst natural disaster.

The Terrain

The Big Thompson River has its beginning from snow fields on the eastern side of the Continental Divide in Rocky Mountain National Park. It's rivulets cascade down a spectacular array of 12,000 foot peaks into Forest Canyon and a beautiful little river winds through the meadows and wetlands of Morraine Park. Fed by other tributaries, it flows through the town of Estes Park onto Lake Estes, where it is controlled by Olympus Dam. Below the dam the river drops a little more than 2100 feet through the Big Thompson Canyon over 25 miles to the city of Loveland and on east to join the South Platte River. A north fork of the river curves around and enters the main stem at the small community of Drake, about half way down the canyon. Colorado Highway 34 also runs through the canyon. For two miles at the mouth of the canyon, the river and the road wind between the spectacular cliffs of the Narrows. Back in the days before the flood, the road ran right along the canyon floor next to the river.

The People