(NewsNation) — More than 10,000 visitors have been evacuated from Yellowstone National Park in Southern Montana due to extreme flooding.

The flooding could constitute a “thousand-year event,” National Park Service officials said on a press call Tuesday evening. 

“These aren’t my words, but I’ve heard this is a thousand-year event,” Yellowstone Superintendent Cam Sholly said. “From what I understand, one of the highest cubic feet per second ratings for the Yellowstone River recorded in the ‘90s was at 31,000 CFS, and Sunday night we were at 51,000 CFS.” 

Sholly noted that despite the historic nature of the flooding, such events “seem to be happening more and more frequently.” 

A combination of heavy rain and mountain snowpack led to extreme flooding Monday that forced the park to close first its northern entrances, then all of the remaining entrances hours later. In just days, the flood may have forever altered the human footprint on the park’s terrain and the communities that have grown around it.

“The landscape literally and figuratively has changed dramatically in the last 36 hours,” said Bill Berg, a commissioner in nearby Park County. “A little bit ironic that this spectacular landscape was create by violent geologic and hydrologic events, and it’s just not very handy when it happens while we’re all here settled on it.”

Montana Gov. Greg Gianforte declared a statewide disaster as record floodwaters knocked out roads and bridges in Wyoming and Montana.

Road conditions are particularly dangerous, Sholly said, as the park approaches its peak tourism season. Flooding on Highway 89 across the Montana border cut off access to the town of Gardner, he said, and while access has since been restored, several thousand park visitors were stranded in Gardner along with residents at one point. 

Tuesday night, emergency crews were finally able to make at least one road passable for a strain of tourists to leave, but not all of them were able to evacuate. Mudslides and rocks falling are making all five entrances impassable near the national park. 

“Nobody’s seen anything like this. Not since 1918. And even then, the CFS levels of the river have never been higher. They’re even double, or even three times, as much as what they’ve been,” said Nolan Darr, a guide at Yellowstone Journeys.

The National Park Service released aerial footage showing the damage from the flood. On Monday, a home near the park was spotted being swept away by the rushing waters. The house floated for seven miles before hitting a bridge in Corwin Falls.

Some of the worst damage happened in the northern part of the park and Yellowstone’s gateway communities in southern Montana. National Park Service photos of northern Yellowstone showed a mudslide, washed-out bridges and roads undercut by churning floodwaters of the Gardner and Lamar rivers.

Yellowstone Teton Tours owner Darcy Lagana said, “It’s really intense in there. And our first focus as a community needs to be on how to make sure that everyone has what they need.”

The water toppled telephone poles, knocked over fences and carved deep fissures in the ground through a neighborhood of hundreds of houses. Electricity was restored by Tuesday, but there was still no running water in the affected neighborhood.

As of Tuesday, park officials said the entrances would not reopen until Wednesday at the earliest. Much of the road leading to the northern entry appeared to have been washed away in video taken by NPS helicopters.

Officials aren’t sure if the worst is over yet, but they do say that they’re in contact with tourists and campers who are still in the park. They’re prepared to do more helicopter rescues, if necessary. No deaths or injuries have been reported.

The park could remain closed as long as a week, and northern entrances may not reopen this summer, Sholly said.

Yellowstone tour guide Sean Jansen told NewsNation, “The northern two entrances will be closed undoubtedly for the rest of the season. If I had to bet my money on it, based on road conditions, — that’s going to take years if not longer to repair.”

The Associated Press and The Hill contributed to this story.