Last weekend, monsoon rains sent a flash flood rushing through the Grand Canyon. The massive surge of roiling brown water carried trees, rocks and debris into the Colorado River, leaving at least two people dead and damaging bridges and plumbing.
The flood was a sudden, dramatic event for one of the nation’s most-visited national parks. But in many ways, it wasn’t entirely unprecedented.
“It is unusual, but it is usual to have unusual events somewhere in Grand Canyon National Park almost every year,” said Laura Crossey, a professor in earth and planetary sciences at the University of New Mexico. “There's dozens and dozens and dozens of side canyons. Depending on where the storm cells hit, different canyons flash at different times and in different years.”
Crossey has been studying the Grand Canyon’s geology and hydrology since the late 1990s and installed the popular “Trail of Time” geology exhibit on the South Rim.
Floods happen throughout the canyon fairly often. It stretches across 277 miles and includes many side canyons, which spider out from the main channel of the Colorado River. The amount of rain that caused the recent flood, Crossey said, probably wasn’t particularly extraordinary.
The place where those rains fell, though, is what makes Saturday’s flooding so unique.
The heavy monsoon rains fell on the burn scar left behind by the 2025 Dragon Bravo Fire, which scorched nearly 150,000 acres.
Wildfires leave the land ashy and dead, and unable to soak up water. Where spongy soil and healthy plants might have once soaked up heavy rains and held the water in place, wildfires leave dead trees and ashy, lifeless soil that water flows across quickly.
Then, making matters worse, rushing water can pick up burned, dead logs and branches that lack roots to hold them in place, adding density and debris to the surging floodwaters.
Adding to that, the floodwaters pushed through a portion of the canyon with an abnormally large amount of human-built infrastructure. Bright Angel Canyon was home to a campground, a number of bridges and a water pipeline. When the floods hit, it was also home to temporary housing for construction workers.
Pieces of that manmade infrastructure ended up in the floodwaters.
“That's not normally what you get in a flood in Grand Canyon,” Crossey said. “You normally have trees, maybe rocks and mud and sand and so forth. But you don't usually have pieces of bridge.”
The floodwaters severely damaged the only water pipeline serving the national park. Officials said about 40% of the pipeline is damaged, forcing a pause on tourist stays at lodges and hotels inside the park and emergency water restrictions for year-round residents.
At the bottom of the canyon, much of the mudslide and the debris it carried ended up in the path of the Colorado River. The river carved the canyon over millions of years and is now one of the world’s most famous destinations for whitewater rafting.
Crossey said the flooding may have dammed a portion of the Colorado River, forcing its waters to slightly reroute, but probably did not completely block them.
Experienced rafters say similar floods and slides are a natural part of the river’s evolution through the Grand Canyon.
“Every few years, I feel like there's a monsoon storm that changes something down there,” said Ben Reeder, a senior trip leader at Colorado River and Trail Expeditions, a rafting outfitter based in Salt Lake City. “You always have to be on your toes. You always have to be looking ahead, and you can't expect it to ever be the same whenever you go down.”
Reeder, who also serves on groups that set management policies for the Colorado River and Grand Canyon, has spent most of the past 18 years guiding trips there.
He has seen big monsoon rains — and the resulting floods — from his boat.
“It is raw power,” Reeder said. “The kind of rain that hurts. It was so wild just to feel so insignificant in this place. Then you're seeing waterfalls pouring off the rim 1,000 feet, falling down basically to the river, and knowing that you can't pull over to the side.”
Reeder said floods make the Grand Canyon a dynamic ecosystem, and he has had to adapt and relearn routes through its changing course after major mudslides.
When he was first starting out as a raft guide in the area, it took Reeder years to learn how to navigate Dubendorff Rapids. Then, in August 2024, when mud, rocks and debris surged through Galloway Canyon into the rapid, the course of the river was altered and Reeder had to change his approach to navigating its whitewater.
“It felt like I finally nailed my run and had it super dialed,” he said. “And then it totally changed. You have to scout the rapid and it took me a few tries to kind of perfect it.”
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Grand Canyon National Park staff and partner agencies continue to assess damage from last week’s deadly flash flood. The park is now expanding its temporary closures. -
Those in the Grand Canyon on Aug. 29 knew the risks, but this storm packed an extra punch, washing out key footbridges and doing more damage to infrastructure than previous decades of turbulent water. -
The Aug. 29 flooding damaged the Transcanyon pipeline that supplies water to the national park. As a result, the highest level of water restrictions are now in effect in the park. -
Deadly flooding at the Grand Canyon is damaging the area's economy, with a washed-out pipeline severing the South Rim's water supply and shutting down lodging at the popular tourist vista for an indefinite period. -
A system of text alerts may have helped evacuate people from harm's way during the recent deadly flooding along the Colorado River in Grand Canyon.
