1000-year flood hits Colorado

by Cassady Craighill

September 13, 2013

Crossposted from Grist

By John Upton


Biblical hell has broken out in Colorado, where more than six inches of rain fell in 24 hours, contributing to flash floods that killed at least three people.

(Before you complain about our use of biblical, note thatits the word federal forecasters chose to describe the floodingin an official update on the National Weather Service website.)

Its insane right now, Ive lived in Colorado my whole life, and this is nothing that Ive ever, ever seen before, Andra Coberly, spokesperson for the YMCA in Boulder, where soggy residents were taking shelter, told NBC. Streets were turned into rivers and streams were turned into lakes.From the NBC report:

The torrential downpours that lashed parts of Colorado drove hundreds of people from their homes, shut down Boulder and the nearby university, and had police and fire responders scrambling all day as they worked to help stranded residents in what they described as a still-developing disaster.

The bad weather also hampered rescue efforts, making it impossible to get search and rescue helicopters into the air, officials said at a press conference on Thursday afternoon, and increasing the dangers for responders who tried to make their way into some of the most affected areas. About 6.8 inches of rain fell over the city in a 24-hour period, according to the National Weather Service.

Slatescience correspondent Phil Plaitreported from Boulderthatthe sheriff was asking people to stay inside and off the roads. His post describes the years of climatic pandemonium that culminated with this weeks deluge:

Weve been suffering a long drought in my hometown of Boulder, Colo., including unusually hot weather for the past few summers. The ground has been pretty hard, and weve had fires, which reduce the vegetation. Its been worrisome for some time, because we knew if it rained hard, we could be in trouble.

Were in trouble.


It started raining off and on a month or more ago, but then a couple of days ago, the skies opened up. Weve had more than an inch of rain in some places, and its had nowhere to go but down from the foothills of the Rockies. Boulder is now flooding; the Boulder Creek crested at 2.7 meters (8.8 feet) last night, well above its usual height.

Further afield, folks at theCooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison have been poring over satellite images and other data to try to make sense of the waterlogged chaos.Their startling conclusion: This event could be classified as a 500- to 1000-year event.

Meteorologist Jeff Mastersexplained in his Weather Underground blogthat a flow of extremely moist air from the southeast pushed up against the mountains, expanding and cooling as it climbed, forcing the moisture in it to fall as rain. He posted the following map,showing that rainfall on Wednesday and Thursday was not only heavy around Boulder the inundation was regional:

Click to embiggen.
Radar-estimated rainfall of six to eight inches on Wednesday and Thursday shown in dark red. (Click to embiggen.)

The Boulder area may not need to wait 1,000 years for another storm like this. Coloradans have been enduringwild swings in the weatherin just the last few years parched bydrought, ravaged byfire, blanketed byunseasonable snow,and now swamped with floods near-textbook examples of the climatic extremes that global warming is expected to wreak on the world.

Cassady Craighill

By Cassady Craighill

Cassady is a media officer for Greenpeace USA based on the East Coast. She covers climate change and energy, particularly how both issues relate to the Trump administration.

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