View from inside one of Zion's canyons (not where the hikers descended) (Ada Be/Flickr)

Officials at Zion National Park are reevaluating their permit system after a flash flood took the lives of seven hikers earlier this month.

The group of hikers had reserved a backcountry permit—required for all canyons that require ropes and harnesses—and was canyoneering in Keyhole Canyon on Sept. 14 when a flood engulfed the canyon.

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Rangers had issued the permit earlier that morning in accordance with current permit regulations.

As is, canyoneering is only restricted when flash flood warnings are issued by the National Weather Service, but not when floods are “probable.” When an official warning is posted, rangers stop issuing permits and close off potentially-affected canyons. Meanwhile, those who obtained permits earlier in the day may be completely unaware of the change.

That appears to be what happened on Sept. 14. The NWS had originally predicted the flood potential to be “moderate,” or—as the rangers say—“probable.”

However, at 2:22 p.m. the NWS issued a flash flood warning. The hikers were out of cellphone range and already rappelling into the canyon, unaware of the heightened risk. Between 4:30 p.m. and 5:30 p.m., the flood rushed through the slot canyon.

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Rangers are now conducting an “after-action review” to see what, if anything, they could have done differently. They are also reassessing how they gather information from the NWS and how they supply that information to visitors.

Although the park posts weather conditions and updates on permits and social media, visitors often play the largest role in determining whether or not the canyons are safe.