More than 20 people are missing and dozens have been evacuated after flash flooding swept through parts of the Grand Canyon National Park.

Saturday’s “significant flash flood” in Bright Angel Canyon and the Phantom Ranch area swept large boulders, metal structures and other debris into the Colorado River.

The US National Park Service has appealed to the public for information on more than 20 people who may be missing or unaccounted for since Saturday’s flood.

By Sunday morning, 62 people had been evacuated from Phantom Ranch and the lower North Kaibab Trail, with more evacuations planned.

Torrents of water wiped out footbridges over Bright Angel Creek and significantly altered the landscape, widening the creek bed and creating what appeared to be a new river rapid.

As the park service tries to account for all of those in the area, it has asked anyone with details about people hiking or camping there to get in touch.

It said it was working with the Arizona Department of Public Safety to continue evacuations on Sunday.

“This is a reminder of what a dynamic and active landscape Grand Canyon is,” said Jack Schmidt, director of the Centre for Colorado River Studies at Utah State University.

Popular tourist spots including the Bright Angel Campground, Phantom Ranch and parts of the North Kaibab trail remained closed on Sunday while park officials surveyed the damage, the park said. Rafting trips on the Colorado River also have been halted.

More than 60 people were evacuated from Phantom Ranch, which has a historic canteen and dorms, and is a common spot for rafters to get off and on the river. More evacuations were planned Sunday, the park said.

More rain and thunderstorms were possible for the area into Monday.

-AAP