Yellowstone River floods in the US once every 500 years

The devastating flood that occurred along the Yellowstone River in the United States this week constitutes a once-in-500-year event, according to a press release from the US Geological Survey (USGS).

Unprecedented rains and rapid snow melt in recent days have caused rivers in parts of Montana, Wyoming and Idaho to overflow, swallowing bridges and sweeping away entire stretches of roads.

More than 10,000 visitors to Yellowstone National Park were forced to leave. All park entrances are expected to remain closed until at least Monday (20).

“In two streams, Yellowstone River in Corwin Springs and Yellowstone River in Livingston, the peak flow was greater than 0.2% inundation (or 1 in 500 years),” USGS hydrologist Katherine Chase said in the statement.

Further downstream, “the Yellowstone River in Billings was between 1% (or one in 100 years) and 0.2% (1 in 500 years) flooding,” according to the note, which pointed out that the flow data is “currently being reported” as ‘provisional’ until follow-up analyzes of the transmission channel and data are completed.”

However, Chase noted that, “while these floods are often referred to as greater (or rarer than) a one-in-500-year event, there is the same probability that they could occur in any year.”

USGS frequencies are calculated from historical data for Yellowstone River locations.

Such as CNN reported this week, scientists have shown that climate change is affecting how often extreme weather events occur, and the trend is expected to continue as the planet continues to warm.

Over a three-day period last week, Yellowstone National Park received about two to three times the typical rainfall for the entire month of June, and this month’s rainfall was already over 400% of the average in northwest Wyoming and in southern Montana, according to the National Weather Service.

Yellowstone’s South Side to Reopen

All five entrances to Yellowstone Park remained closed Friday, while flood recovery and repair efforts are underway in preparation for the park’s reopening, according to a statement from the park’s superintendent’s office.

According to the statement, the National Park Service does not yet have an estimated reopening date for the entire complex — nor an idea of ​​the total repair costs. The text outlines an extensive list of needed road and infrastructure repairs in each section of the park to reopen.

“We’ve made tremendous progress in a very short period of time, but we have a long way to go,” Superintendent Cam Sholly said in the statement. “All emergency and life safety objectives within the park were achieved or stabilized within the first 96 hours of the flood event, with no major injuries or death.”

The park service announced on Saturday (18) that the southern circuit will reopen to the public on Wednesday (22).

Current conditions of Yellowstone’s North Entrance Road through the Gardner Canyon between Gardiner, Montana, and Mammoth Hot Springs.

We will continue to communicate about this hazardous situation as more information is available. More info: https://t.co/mymnqGvcVB pic.twitter.com/S5ysi4wf8a

— Yellowstone National Park (@YellowstoneNPS) June 13, 2022

“At 8:00 am on Wednesday, Yellowstone National Park will begin allowing visitors to access the southern circuit,” the note reads.

“The south loop is accessed from east (Cody), west (West Yellowstone) and south (Grand Teton/Jackson). Accessible areas include Madison, Old Faithful, Grant Village, Lake Village, Canyon Village and Norris.”

Remote areas accessible from roads open to the public will be available for daytime use only. Night use of trails in the south will be allowed on July 1st.

While the northern circuit is closed, “park staff has engaged more than 1,000 business owners, partners, commercial operators and residents of surrounding communities to determine how to manage summer visits,” the park service said.

To ensure that the southern circuit is not overloaded with visitors and to balance visitor access demand, the park will institute an interim visitor access plan.

“The interim plan, known as the Alternating License Plate System (ALPS), was suggested as a solution by gateway communities during a massive public engagement with the park last week,” the statement reads.

Montana Governor Greg Gianforte has taken an optimistic tone about flood recovery and reconstruction by encouraging continued tourism to Big Sky State. The “best days are ahead of us,” he told reporters on Friday.

“We are open. You have to come,” Gianforte said of Yellowstone Park. “The vitality of our communities depends on it. We are open for business and we want you to come.”

Officials previously said the northern section of the park will likely remain closed for the remainder of the season.

Judson Jones, Haley Brink and Hannah Sarisohn of CNN contributed to this report.