A flash flood swept through the Grand Canyon on Saturday, killing at least two people. Such events are a vital part of the canyon’s ecosystem, but this one just happened to hit in the worst possible spot to cause damage, experts say.

At least one person is still missing after the flood, which may have been made more deadly because it swept through the scars left by wildfires on the Grand Canyon’s North Rim, above Bright Angel Canyon in Arizona.

The rains came from a typical monsoon storm; these storms rake across the Grand Canyon and the desert Southwest between June and September every year. “Flash floods are not a new thing for this canyon or for anywhere in the Grand Canyon region,” says Laura Crossey, a hydrologist at the University of New Mexico, who studies the canyon’s water.

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Deserts are prone to flash floods because there is little soil or vegetation to absorb downpours. The situation may be worse above Bright Angel Canyon, Crossey says: the region has burn scars from the 2025 Dragon Bravo and White Sage fires, and these can have an exacerbating effect. The scars hold debris for the water to carry down the canyon, and they also supply sediment and mud to the flow. That makes the water denser, meaning it can carry larger logs and boulders than clear water.

At almost any other place in the canyon, the flood wouldn’t have mattered. But this one swept through Bright Angel Canyon, the site of one of the few footpaths that lead up the Gran Canyon’s North Rim. Bright Angel Canyon also provides passage for the Transcanyon Waterline, which brings water from the North Rim to tourist sites on the South Rim.

On Monday park officials said that about 40 percent of the waterline was damaged or destroyed. Hotels and lodges on the South Rim were closed beginning at noon on August 31 because of extreme water restrictions.

Phantom Ranch, the only lodging below the rim of Grand Canyon, also sits at the base of Bright Angel Canyon, where it meets the Colorado River. According to the National Park Service, 62 people were airlifted out of the area in the midst of the rainstorms on August 29, and nearly all the footbridges that once crossed Bright Angel Creek have been washed away.

The rapids along the Colorado River in the Grand Canyon are created by similar floods and the debris they carry, says Jack Schmidt, director of the Center for Colorado River Studies at Utah State University. In fact, floods are how rivers carve canyons. On average, the Colorado River deepens the Grand Canyon by about the thickness of a piece of paper every year. But in reality, the carving occurs in fits and spurts, when floods carry huge boulders that gouge out streambeds and jam cobbles into the bedrock. This process chisels off new chunks of rock that will go on to do their own damage.

The Transcanyon Waterline has fallen victim before: in 1966, just a year after construction on the pipeline started, a so-called 1,000-year flood washed much of the infrastructure away.

“There’s a long history of this stuff happening,” Schmidt says. “It’s just that now, this time, it happened in the one tragic place where there is a permanent infrastructure and lots of people.”

It’s not yet clear how long it will take to repair the water supply to the South Rim. NPS is also in the midst of constructing a new water supply system to replace the Transcanyon Waterline infrastructure. Instead of pulling water from Roaring Springs high on the North Rim, the new project would pull water from Bright Angel Creek near the canyon bottom. Videos posted on social media showed the intakes for that new system as having been clogged with sediment and the bridges that held new pipes as having been washed away.

The new construction “obviously took a big a hit one way or another,” Crossey says, “but until they get into it and fully assess it, the loss is as yet unknowable.”

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