Colorado Experience: Big Thompson Flood

Key Takeaways

• The 1976 Big Thompson flood killed 144 people and remains Colorado's deadliest flood, with waters peaking 20 feet above normal levels in just 15 minutes.
• Human modifications like straightening US Highway 34 and realigning the river at 27 points turned the canyon into a straight chute, worsening flood impacts.
• Despite a 1971 Army Corps of Engineers warning that catastrophic floods were likely every 6 years, residents declined flood insurance, believing they were safe above the river.
• The flood struck during Colorado's Centennial and U.S. Bicentennial celebrations, with 4,000 people in the canyon and no sirens or effective warnings reaching them.
• A stationary storm dumped up to 12 inches of rain in 6 hours over the canyon, while the nearest weather radar in Lyman was malfunctioning or misaligned.
• Survivor stories and lessons from 1976 directly helped save lives when the canyon flooded again in 2013, demonstrating the value of remembering past disasters.