The Big Thompson Flood of Nineteen Seventy-Six

The river you are crossing right now is the Big Thompson. It drains out of Rocky Mountain National Park and threads through a steep canyon in the foothills before reaching this flat stretch of the plains. On most days it runs gentle and clear. But on the evening of July thirty-first, nineteen seventy-six, the Big Thompson became one of the deadliest floods in Colorado history.

It was a Colorado centennial celebration weekend, and an estimated two thousand five hundred to three thousand five hundred people were in Big Thompson Canyon that night: campers, vacationers, families who had driven up from the Front Range to enjoy the narrow gorge and the river. What none of them knew was that a thunderstorm complex had stalled just below Estes Park and was dumping water at a catastrophic rate. In the span of four hours, roughly twelve to fourteen inches of rain fell over a small watershed. Seven and a half inches fell in a single hour, more than the canyon's bedrock and riverbed could channel or absorb.

The result was a wall of water up to twenty feet high that roared down through the canyon at tremendous speed. It swept away four hundred eighteen homes and fifty-two businesses. It shredded bridges and tore out sections of Highway Thirty-Four. Cars were carried downstream and crushed against canyon walls. People who tried to outrun the flood in their vehicles were killed. Those who climbed to higher ground survived. The Colorado State Patrol had a single warning phrase that became a lesson taught for decades afterward: if you are in a canyon and it is raining hard, climb to high ground. Do not wait for the water. Do not try to drive out.

One hundred forty-four people died that night. Five bodies were never found. President Gerald Ford declared Larimer County a federal disaster area. The flood rewrote flash flood warning protocols across the nation, accelerating the installation of automated rain gauges and warning sirens throughout Colorado's mountain canyons.

Memorials stand at the canyon today. The river has since flooded again, in twenty thirteen, though with far fewer casualties thanks to the warning systems born from this disaster. The Big Thompson looks peaceful from this highway crossing. That is part of what makes it worth remembering.