Severe flooding in Colorado smashes rainfall records

• September 17, 2013
flooding in Colorado

Colorado National Guardsmen respond to the disastrous flooding in Boulder. Creative Commons: The National Guard, 2013

In the United States, record-breaking flash flooding in Colorado sent a deluge of water through the canyons of the Rocky Mountains, killing at least eight and leaving hundreds stranded and unaccounted for.

In a weather event referred to as “biblical” by The National Weather Service, the Colorado city of Boulder saw 9.08 inches (23.06 cm) of rainfall in only 24 hours on September 12th — a new state record. The city’s three-day rainfall total reached 12.30 inches (31.24 cm) as of Thursday, which is more than half of the city’s average yearly rainfall.

The accumulation quickly turned roads into rivers, washed mud and debris through communities and created dangerous conditions for residents. Over 17,000 homes were either damaged or destroyed as a result of the rains.

Senator Mark Udall described the flooding as “liquid tornados” for the sudden danger and devastation it caused.

Over 600 people are still unaccounted for, and rescue efforts are searching rural Colorado towns for residents that were stranded when the flooding washed out roads.

The disaster has prompted the largest helicopter and aerial response mission in the US since Hurricane Katrina struck the Gulf Coast in 2005.

The 24-hour rainfall accumulation record set on September 12th is almost double the former record in Colorado, set in July 1919 at only 4.79 inches. This kind of rainfall is what meteorologists usually expect from tropical storms, not rainstorms in the nation’s heartland.

Given the unprecedented nature of this rainfall event, it is likely that climate change played a role in making it more extreme than it otherwise would have been. The intensity of this flood in Colorado is a 1 in 1,000 year event — it only has a 0.1% chance of occurring in any given year.

Extreme rainfall across the US in general has become more frequent due in part to climate change, according to the draft National Climate Assessment.

The city of Boulder is exceptionally vulnerable in such events because of its location at the mouth of a canyon and the presence of Boulder Creek, which runs through the city.

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About the Author

Emily is a graduate of St. Mary's College of Maryland with a B.A. in psychology. While in school, she spent her time leading environmental and social justice campaigns. She recently worked for the Chesapeake Climate Action Network as a grassroots organizer for a moratorium on natural gas fracking in Maryland.

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