Zion National Park is warning visitors to know before they go — because if they’re unfamiliar with the park’s monsoon season and flash flooding, it could cost them their lives.
“We have a lot of folks that are not familiar with monsoon season,” said Amanda Rowland, program manager at the park. “They’re not aware that thunderstorms can come out of nowhere — isolated, damaging winds and heavy rain that can be so isolated that maybe it’s happening in one canyon and you don’t even know that it’s happening when you’re two canyons away.”
She pointed to the Narrows, a popular hiking area where the towering walls block the view of the sky, so hikers cannot see clouds building overhead. And there’s little or no cell phone service in Zion, so hikers cannot receive weather alerts.
Although Utah is in the midst of an historic drought, it’s still monsoon season in Zion from mid-July into September. Sudden rain storms can result in flash floods without warning, increasing the water flow by more than 100 times in a matter of minutes. While flash floods typically occur in the late afternoon or early evening, they’ve also happened at every time of day — from the morning to the middle of the night — so no time should be considered safe.
Park staff is warning visitors to check the flash flood potential ratings provided by the National Weather Service. The risk in Zion is probable on Wednesday, and possible on Thursday. And, if bad weather threatens, visitors should not enter narrow canyons under any circumstances.
“Make sure you’re assessing the true risk of going into those areas,” Rowland said. In the event of a flash flood, park visitors are urged to get to higher ground, avoid driving in water and stay informed.
It’s not just Zion which is a flash flood risk. On Wednesday, flash floods are “expected” at Capitol Reef, Glen Canyon and Grand Staircase-Esclante and “probable” at Arches, Bryce Canyon, Canyonlands, Natural Bridges, Grand Gulch and San Rafael Swell, in addition to Zion. On Thursday, flash floods are “probable” at Bryce Canyon, Capitol Reef, Glen Canyon, Grand Staircase-Escalante and San Rafael Swell, and “possible” at Arches, Canyonlands, Natural Bridges, Grand Gulch and Zion.
This type of flash flood danger is not seen across the country, and out-of-state visitors are often completely unaware of it. A sudden cloudburst can dump an inch of rain in an area in an hour or less, and it doesn’t soak into even the most parched soil. It runs off through the slot canyons.
“It suddenly goes from no water and no waterfalls and, in 20 minutes, you have a lot of water coming down and around you, potentially taking out a road or taking out a trail that people are on. It’s incredibly dangerous,” Rowland said, adding, “It’s not just the water that’s being moved, but the amount of debris” — including “rocks the size of cars.”
(AP Photo/Rick Bowmer) A member of a search and rescue team wades in to Virgin River during a search Wednesday, Sept. 16, 2015, in Zion National Park, near Springdale, Utah. Seven hikers who entered a narrow desert canyon for a day of canyoneering became trapped and died when a flash flood filled the chasm with water.
And it can indeed be deadly. In 2015, seven park visitors — six Californians and one Nevadan — were killed when two-thirds of an inch of rain fell in an hour and a flash flood swept through Keyhole Canyon. The group had entered the canyon despite a “probable” flash flood warning that day.
Even native Utahns are not always informed, Rowland said.
“You never really know how much rain and how much water and debris is going to move,” Rowland. “So even if you’re familiar with what a flash flood is, being in that space and being in that moment, you can still be surprised.”
