DENVER (KDVR) — Ten years ago, on Sept. 11, 2013, the Front Range experienced one of Colorado’s worst floods that covered 4,500 square miles — more than 10 times the size of Rocky Mountain National Park.

The rain started on Sept. 9 after a week of hot weather, just like September’s forecast this year. The heaviest rain began the evening of Sept. 11 and lasted for 30 hours. After that lighter rainfall continued until the 16th.

What happened

Larimer County Office of Emergency Management recorded a timeline of events.

By 7:30 p.m. on the 11th, rockslides began in Golden and flash flood warnings in Boulder County and some of Larimer County. By 10 p.m. flood sirens went off in Boulder and University of Colorado Boulder students were evacuated.

Toward the end of Sept. 11, flash flood warnings were issued for most of Larimer County and Highway 14 was closed by debris flows and rockslides in the Poudre Canyon.

By the morning of the 12th, multiple highways near Estes Park closed. Deputies evacuated Big Thompson Canyon and the part of Loveland in the Big Thompson River 100-year flood plain. The Rescue Authority went door-to-door to usher people out of these areas.

Multiple roads, highways and bridges were damaged and closed, ultimately cutting the city in half in less than 24 hours of heavy rain. By the 13th, the only way to Denver from the north was on U.S. 85 from Greeley.

A Colorado Parks and Wildlife hydrologist estimated that the Cache la Poudre River’s peak flow on Sept. 13 was about 11,000 cubic feet per second.

On Sept. 14 President Barack Obama declared a major disaster for Larimer, Boulder and El Paso counties to make federal recovery money more easily available.

Hundreds of people were evacuated on Sept. 14 and 16, and at the peak, there were almost 650 people unaccounted for.

By Sept. 19 that number had dropped, but there were still more than 100 unaccounted for people.

Total damage

According to the Larimer County Office of Emergency Management, for the week, Estes Park recorded 9.31 inches, Fort Collins had 5.3 inches and Buckhorn Mountain had 7.62 inches of rain. This is about half of Larimer County’s annual rainfall average of 16 inches.

When the flooding stopped, 19 inches of rain fell in Colorado. At least nine people were killed statewide and the damage cost estimate reached almost $4 billion.

More than 19,000 people were evacuated, 3,000 people had to be rescued, 26,000 homes were damaged or destroyed, 200 businesses were destroyed and 750 were damaged plus 485 miles of road were damaged or destroyed statewide along with 50 major bridges damaged.

Colorado’s 10 deadliest floods:

  1. Big Thompson Flood (1976): 144 deaths
  2. Great Pueblo Flood (1921): An estimated 120 deaths
  3. Dry Creek Flood (1904): 111 deaths
  4. Las Animas Flood (1905): 35 deaths
  5. Bear Creek Flood (1896): 27 deaths
  6. Flood of 1935: 27 deaths
  7. Flood of 1965: 21 deaths
  8. Flood of 1864: 15-20 deaths
  9. Flood of 1983: 10 deaths
  10. Flood of 2013: At least 9 deaths

All in all, this was Colorado’s 10th deadliest flood, but the damages were much worse than the deadliest flood in 1976 that killed 144 people in the Big Thompson Canyon area.

As of 2023, disaster costs in Larimer County reached over $100 million.