When big rains fall on land that was burned by wildfire, dangerous flash floods can come on strong and fast.
So as monsoon season approaches in northern Arizona, officials at Grand Canyon National Park are keeping a close eye on the 145,000-plus acres burned by last summer's Dragon Bravo Fire.
"It is still safe," said Joëlle Baird, a spokeswoman for the park. "However, with a post-fire landscape, it is susceptible to change."
Scientists studied the burned area and found that there's no increased flood risk to any permanent structures or overnight campgrounds, but there are some sections of hiking trail that are vulnerable.
Baird highlighted a 2-mile span of the North Kaibab trail from Supai Tunnel to the North Kaibab trailhead.
Park officials have a plan in place to keep people safe. Rain forecasts and a set of new streamgages will tell them when flood risk is getting high, triggering evacuations — especially at Bright Angel Campground and Phantom Ranch.
They also have a text alert system designed to reach backcountry travelers with satellite phones.
The warning system was built by a variety of experts from the National Park Service, the National Weather Service, the U.S. Geological Survey, and Coconino County Emergency Management.
Flash floods in areas scarred by wildfire can be massive and powerful. When rain hits a burned area, it can't soak into the soil. Instead, it quickly runs off the surface, picking up loose debris along its way. The floods are often a jumble of water, mud, plants, and rocks, moving through narrow areas at high speeds.
"If you have any kind of warning that this is coming," Baird said, "we would recommend people not delay and move to high ground immediately to seek safety. They are very rapid and very intense events."
The North Rim of the Grand Canyon is no stranger to floods. In 2021, there was a major flash flood in the Bright Angel Creek watershed. It didn't trigger evacuations, but similar rainfall totals could be more destructive now that they would be falling on a burned area. Flooding that year killed a rafter elsewhere in the canyon.
Baird said education will be a big part of keeping visitors safe this summer, and National Park staff will try to make hikers aware of safety risks. The North Rim has been reopening to visitors recently, and traffic is expected to pick up during the summer months.
This story was produced by the Mountain West News Bureau, a collaboration between KUNR, Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio, KJZZ in Arizona and NPR, with additional support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
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