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5 Things You Should Know About Colorado's '1,000 Year Flood' (with Jaw-Dropping Photos)

Boulder may record more rainfall this past week than it usually gets in a year.

A condensate tank from an oil/gas well site floating in floodwaters in Weld County, Colorado.
Photo Credit: Carl Erickson


Colorado’s Front Range has been ravaged by heavy rain and flooding since last week, with 15 counties now impacted: Boulder, El Paso, Larimer, Adams, Arapahoe, Broomfield, Clear Creek, Denver, Fremont, Jefferson, Logan, Morgan, Pueblo, Washington, and Weld counties. Updates on the number of fatalities and missing is being updated but the latest reports are eight dead. More than 11,000 people have been evacuated and many thousands more are waiting for help.

Here’s what else you should know.

1. It’s really, really, big.

Rainfall totals across impacted counties vary, but there's been enough precipitation that the event is being called a 1,000-year flood. Andrew Freedman writes for Climate Connection that the “average yearly rainfall in Boulder is 20.68 inches.” A map of rainfall in the Denver Post shows that from Monday, September 9  to Sunday, September 15, over 15 inches of rain has fallen in the Boulder area. 

It’s possible that when all the numbers come in, that areas like Boulder will have more rain in a week than they usually record in a year.

2. History of flooding.

Cally Carswell wrote for High Country News that “the Front Range has always been flood prone.” She writes

According to the Boulder Area Sustainability Information Network (BASIN), when it comes to flooding, "the Boulder Creek drainage is considered among the most hazardous in the entire western United States." The city sits smack at the mouth of Boulder Canyon, and because its floodplain is so developed, the risks to human safety and property are especially high here.

Fort Collins experienced a devastating flood in 1997 that dumped 10 inches of rain in a matter of hours, killing five people and causing hundreds of millions of dollars in damages.

The rainfall and flooding has impacted more areas than Boulder and Fort Collins that are immediately downhill from the steep slopes of the Rockies. It’s believed that a 200-mile swath from north to south has been impacted, with flooding in communities in the flatlands east of the mountains, too. 

3. The hand of climate change?

While it is too soon to tell what role climate change may have played in this particular flooding event, it’s important to look at it in the context of global patterns. As Freedman writes for Climate Connection: 

An increase in the frequency and intensity of extreme precipitation events is expected to take place even though annual precipitation amounts are projected to decrease in the Southwest. Colorado sits right along the dividing line between the areas where average annual precipitation is expected to increase, and the region that is expected to become drier as a result of climate change. That may translate into more frequent, sharp swings between drought and flood, as has recently been the case. Last year, after all, was Colorado's second-driest on record, with the warmest spring and warmest summer on record, leading to an intense drought that is only just easing. 

4. It’s all connected.

The amount of precipitation isn’t the only climate change-related impact that should be considered; there are other contributing factors that may be making this massive flood event even more dangerous. Subhankar Banerjee writes for ClimateStoryTellers about the connection between climate change, forest health, wildfires, and floods:

In the last decade and a half Colorado (and its neighbor New Mexico) has gone through three major assaults—massive tree deaths, massive wildfires, and now massive floods—each in turn has been called “the worst natural disaster” the region has seen. Each in turn has also made the next one worse—millions of dead trees made the wildfires worse, and we are now learning that the wildfires are making the floods worse. 

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