Colorado’s “biblical” flood by the numbers

September 16, 2013

Shown is structural damage through Northern Colorado: Boulder, Longmont, Estes Park, Lyons, and Hwy 34 along the Big Thompson River. (Colorado National Guard)

The clean-up effort in the aftermath of the flood described as “biblical” by the National Weather Service is just beginning.  Today, the biggest civilian airlift operation is underway since Hurricane Katrina, searching for and seeking to rescue over 1,200 missing/stranded people in vast areas completely cutoff by floodwaters.

Here’s a collection of numbers which helps tell the story of this historic flood:

0.1 percent, the probability of such a rainstorm occurring in any given year in Boulder County (“Such values shouldn’t be taken as gospel—there are important caveats, including the hard-to-model behavior of the most extreme events—but they do suggest how truly noteworthy this week’s rains were,” writes Bob Henson, of the National Center for Atmospheric Research)

5 fatalities in Colorado from the flooding (source: Colorado Office of Emergency Management)


Shown is structural damage through Northern Colorado: Boulder, Longmont, Estes Park, Lyons, and Hwy 34 along the Big Thompson River. (Colorado National Guard)

9.08 inches of rain that fell between 6 p.m. mountain time Wednesday and Thursday in Boulder, shattering its highest previous 24-hour rainfall total (source: Bob Henson)

17.16 inches of rain in Boulder in the past week (source: Bob Henson)

21 helicopters in air today performing search and rescue in Colorado (source: NBC News)

Aerial views of flooding in Longmont Colorado via YouTube

30.12 inches of rain in Boulder this year, now it’s wettest year on record, with 3.5 months still to go. (source: Bob Henson)


(Dennis Adams-Smith/Climate Central)

Related: Flood-Ravaged Boulder, Colo., Sets Annual Rainfall Record (Climate Central)

60 hours Big Thompson River exceeded record flood stage

(National Weather Service)
(National Weather Service)

1,000  people (approximate) in Red Cross or independent shelters due to flooding (source Red Cross)

Colorado’s Big Thompson Canyon extreme flash flooding via YouTube

1,253 people reported missing (“approximate and changing throughout the day – local counties have most current numbers” says the Colorado Office of Emergency Management )

1,502  residential structures destroyed  (source: Colorado Office of Emergency Management)

Boulder Canyon Mudslide via YouTube

11,750 people evacuated (source: Colorado Office of Emergency Management)

17,494 damaged residential structures (source: Colorado Office of Emergency Management)

Video: Flood survivors recall disaster

Related: Historic flooding crushes records in Colorado and surrounding states | Massive flooding swamps Colorado Front Range, Boulder (PICTURES)

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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Jason Samenow · September 16, 2013