A Year's Worth of Rain in Eight Days: Boulder, CO's 1,000-Year Flood

When the rain started on Monday evening on September 9, 2013, people in Boulder, Colorado were relieved. The state had been experiencing some late-summer heat flashes and drought in the days leading up to the flood. Boulder County, which lies at the base of the foothills of the Rocky Mountains, faced eight days of torrential rainfall which claimed eight lives and caused over $3 billion in damages in what was characterized as a 1,000-year flood. While Boulder’s picturesque location makes it a popular destination for those looking to enjoy all that nature has to offer, it also lies in a natural flood plain which complicated water diversion and relief efforts in the wake of this natural disaster.

As a middle-schooler, it was pretty great to have school cancelled for a few days, but as reports of the disaster began coming in—roads were destroyed, power lines were felled, and houses washed down bloated rivers—it became clear that Boulder’s citizens and government were unprepared for the disaster that was unfolding. By early Wednesday morning, rain was falling at three-quarters of an inch every half hour; Boulder Creek began flowing at 3,401 cubic feet per second, when its normal flow in September had been measured at 54 cfs. With the massive amount of rainfall coming in from multiple directions, emergency responders found themselves paralyzed by the deluge. Many roads began to collapse due to the water in the ground below; massive sinkholes that formed swallowed cars whole and prevented first responders from reaching vulnerable residents in the mountains.

Erosion of a mountain road.

Likewise, when the mountainsides began to crumble and mudslides shut down the remaining roads into the mountains, many people became trapped in their homes and those who had already evacuated had no way back. The area proved susceptible to mudslides because of the 2010 Fourmile Fire, where almost all of the tree coverage in the area burned down, leaving the ground fallow and more prone to soil erosion.

A house in Jamestown, which was ripped off of its foundation by flood waters.

When the rains finally stopped eight days later, Boulder had received over 17 inches of water, with 9.08 inches happening in a 24-hour period. The National Weather Service classified this level of flooding as “biblical,” which makes sense considering the yearly average precipitation in Boulder hovers around 18 inches. President Obama declared the flood as a national emergency, and enlisted the Federal Emergency Management Agency (FEMA), for which 7,600 Boulder residents applied for help.
The floods ended up affecting more than just Boulder County; the damages to property and infrastructure across the Front Range were immense, with tracts of crops being submerged and destroyed, crude oil tankers that spilled into the South Platte River. All in all, 19,000 homes were destroyed, 50 highway bridges were damaged or destroyed, and the human environment faced additional incalculable ecological impacts with waste, sewage, and ancillary effects of the flood. 

The Boulder flood has become a shared memory for many residents in Boulder, many of whom now drive on those repaired roads into the small, mountainous towns of Lyons, Jamestown, and Ward—most of which were washed away and are only now being rebuilt. Radio stations in the area constantly play The Lumineers’ hit song, “Ophelia,” which references the disasters of the flood. However, only time will tell how the residents of Boulder will handle future flash floods and whether the collective memory of the 2013 flood will help direct emergency response and prevention efforts.

Before and After Aerial Photos of Boulder.

Outside of Boulder High School, which borders Boulder Creek.

References

NOAA’s Earth Systems Research Laboratory: Annual Precipitation for Boulder, CO. “https://www.esrl.noaa.gov/psd/boulder/Boulder.mm.precip.html.”

Aguilar, John and Charlie Brennan. “Eight Days, 1,000-year Rain, 100-year Flood.”
21 Sept. 2013. https://www.dailycamera.com/2013/09/21/eight-days-1000-year-rain-100-year-flood/

Hamilton, Lawrence. “The Protective Role of Mountain Forests.” GeoJournal.
https://www.jstor.org/stable/41145532?seq=1#metadata_info_tab_contents Vol. 27, No. 1, Mountain Environments (May 1992), pp. 13-22.

Samenow, Jason. The Washington Post. “Colorado’s “biblical” flood by the numbers.” Sept 16, 2013. https://www.washingtonpost.com/news/capital-weathergang/wp/2013/09/16/colorados-biblical-flood-by-the-numbers/