USACE working with Zion National Park to keep visitors safe

U.S. Army Corps of Engineers Sacramento District working with Zion on flood warning system to keep visitors safe

Published April 27, 2020
Updated: April 27, 2020

Looking over a map of Zion National Park (clockwise from left) park ranger Tim Knauss, Sacramento District's Darrin Rummel and Corrie Stetzel, Zion Park Ranger Annette Werderich, and Sacramento District's Lori Schultz, work together to determine strategic locations for placement of stream and rain gauges.


A color-coded Flash Flood Potential warning system is seen inside the visitor’s center of Zion National Park.


Sacramento District's Darrin Rummel, Corrie Stetzel and Lori Schultz look over a 3D model of Zion and its many canyons in order to get a sense of how the tributaries feed into the Virgin River.

Imagine an adventurous day of hiking deep into one of Utah’s rugged slot Canyons. Sure it’s a bit cloudy, but rain isn’t forecast in the area for another two hours. What you don’t know, is that it’s already pouring a couple miles upstream with water levels rising fast. And all that water is headed your way.

The scenario above is one Zion National Park is all too familiar with, and record numbers of visitors means keeping hikers safe has become more challenging than ever. Since cloudburst storms can rapidly flood desert slot canyons, it can be difficult, if not impossible, to provide flash flood warnings to hikers in a timely manner.

Zion is determined to change that, and is actively seeking help from the U.S. Army Corps of Engineers Sacramento District with solutions to ensure park visitors can have the safest experience possible while hiking the slot canyons.

“On behalf of Zion, the Utah Department of Emergency Management approached the Corps to ask whether there is some type of flood warning system that Zion could use in conjunction with the slot canyons,” said Sacramento District’s Corrie Stetzel, lead planner on the Zion National Park Flood Risk Warning Support project. 

“Initially, UDEM wanted to know if there was a way to install some kind of warning system at the entrances to slot canyons that would work similar to  traffic lights,” said Stetzel. Such a warning system would come complete  with red, yellow and green lights. Sort of a Hiking Slot Canyons for Dummies version of a warning system – a solution Zion park rangers immediately found cringe-worthy.

“Given that roughly ninety percent of the park is designated wilderness, such a system feels inherently at odds with the Park Service mission of preserving wild and untamed resources,” said Darin Rummel, Sacramento District’s environmental manager for the project.

An idea-sharing meeting between the Corps, park personnel, Washington County and the United States Geological Survey in early March helped reveal that the park service really wanted to improve the consistency of risk messaging with park partners, outfitters (businesses that lead visitors on hikes into the canyons) and weather forecasters, thus boosting the chances of keeping visitors safe.

“We’re making great strides in this area,” said Daniel Fagergren, Zion’s Chief Park Ranger. “We’re sharing our weather reports, providing real-time updates with partners. A lot of the outfitters have agreed to not sell or rent if flooding is possible or probable, which is a great step in the right direction.”

While Zion currently uses a color-coded Flash Flood Potential system inside the visitor’s center, many visitors simply do not see it, especially if they bypass the center or are accessing the slot canyons with an outfitter. The park’s current system is a four-color rating system, with yellow representing the safest end of the spectrum and red indicating the highest danger. Zion has also used a warning system that sends messages to those using Twitter, and the National Weather Service pushes flood warning notifications to cell phones. But there is often no reception available for those who are already deep within the canyons.

“Some of the things we’re not able to achieve yet are the structural-based, technology-based issues to reach people. I think the best way to do it would be to provide something like an Amber Alert, a flooding alert to individual phones, but the technology isn’t in place in the canyons to allow for that,” said Fagergren.

“The thing is, even if you were able to put a system in place that solves one canyon, like The Narrows, or part of The Narrows, it doesn’t cover the 600 other canyons,” said Fagergren.

Due to the continually increasing popularity of Zion over the years, the need for risk-messaging has become much more urgent. According to park attendance figures, the park hosted approximately 500,000  visitors annually in 1960. By 2019, visits to the park topped 4,400,000, and permits for canyoneering day trips had risen to more than 38,000.

“As of 1961, Zion had experienced only one major casualty event related to canyoneering, but as visitation has soared the dangers have increased,” said Stetzel.

In 1961, four teenaged Boy Scouts and a Scout master were killed by a flash flood as they hiked in The Narrows slot canyon. In 2015 a group of seven individuals perished in Keyhole Canyon. The fear is that with so many visitors in the canyons at once, the probability for a mass casualty event is increasing.

“The Narrows is particularly popular and is the area most at risk for a mass casualty event should heavy rains catch people off-guard,” said Rummel. “The Narrows has literally thousands of visitors hiking back into the canyon every day. If you were to have a major weather event occur and no warning system in place…” he shrugs with a shake of his head, as if to say, not good.

A separate but related project between Zion and the Corps may also help with the goal of visitor safety. Sacramento District’s Lori Schultz is working on a hydrologic model of Zion that could ultimately help with the technical accuracy of predicting flash floods in the slot canyons.

“Right now, predicting the weather and water flow into the canyons is a bit of an art form,” said Stetzel. “We are working to remove the guesswork.”

In conjunction with the hydrologic model, the Corps and Zion discussed installation of a system of rain and stream gauges that could improve modeling and forecasting and help further reduce guess work. 

“If we get the rain and stream gauges put in and are able to collect better data, we could have a whole new project in a couple of years to improve the model based on that new data,” said Stetzel.

Silver Jackets Interagency Projects focus on bringing together State, Federal and local partners needed to work together during a flood response. In order to participate, the Corps seeks “in-kind” commitments from each partner agency. In Utah, the Silver Jackets state team lead is the Utah Division of Emergency Management.

Under this arrangement the Corps can’t pay for, or implement, a warning system for Zion National Park, but the Corps role is to use its extensive expertise during a 12-18 month timeframe to aid Zion in the process of determining the best options.

“The idea behind the Silver Jackets interagency work is that it allows you to get to know the people you’re working with before a disaster,” said Project Manager Melissa Weymiller. “We don’t want the first time we work with an agency to be during a major flood. So these smaller, 12-18 month projects allow us to build a partnership, to start relying on each other, to share resources and data.”

Zion continues to prioritize the safety of guests, balancing that with the goal of minimizing the effect on the park’s wilderness. As the Corps seeks to help find best solutions, further risk communication meetings have been held with gear outfitters in the community. The Corps project team recently coordinated with a researcher at Dixie State University, Utah, to develop a software program that delivers flash flood warnings to the park’s shuttle buses. Further, the researcher’s monitoring equipment was adapted to track water surface elevations at The Narrows.

“Part of our risk-messaging focus is helping visitors make good decisions for themselves. A green light doesn’t automatically make the canyon safe if the visitor is unprepared for the journey. Good risk-communication educates the visitor about risk and teaches them how to properly evaluate that risk for themselves,” said Rummel.