PHOENIX — The U.S. Army Corps of Engineers Los Angeles District, Arizona Department of Emergency and Military Affairs and Flood Control District of Maricopa County staff joined forces Sept. 9 to host an emergency exercise based on historic flooding in the state.
More than 100 representatives, including emergency responders and others with local, state and federal agencies participated in the exercise, according to Jake Van Tine, exercise planner with the LA District’s Emergency Management Branch.
“The scenario was based on a real-world event from 1993,” said Col. Julie Balten, LA District commander. “And, it’s not the first time we have joined forces with our Arizona National Guard teammates and state emergency managers on an extreme flood event with international implications.
“In August 2017, a flooding event in Nogales, Arizona, also was a complex mission with far-reaching responsibilities. Most recently, it was for the worldwide pandemic of COVID-19 and the FEMA alternate care facilities’ mission. It is so comforting to know that this relationship is in place and endures, no matter the challenge.”
The focal point of the recent joint exercise; however, was the Corps' Painted Rock Dam, located 120 miles southwest of Phoenix, a pivotal feature in the nearly 51,000-square-mile Gila River Watershed.
The purpose of the exercise was to evaluate flood response preparedness and communication across multiple agencies and how those agencies communicate the risks to the public. It also gave participants the opportunity to get to know each other before an emergency arises.
"The Painted Rock Dam exercise was a valuable opportunity to learn more about the dam, the facility response plans and the partners that we will be working with during an incident," said Maj. Gen. Kerry Muehlenbeck, adjutant general of the Arizona National Guard and director of the Department of Emergency and Military Affairs. "I am very pleased that the U.S. Army Corp of Engineers and our emergency management team took time to strengthen these relationships and prepare for emergency complexities to keep the residents of Arizona safe."
EXERCISE DAY 0-9 – JANUARY IN ARIZONA
The mock scenario began with news of a La Niña event influencing local weather – with 150 percent of normal precipitation – but no serious flooding or impoundment at Painted Rock Dam, which is normally a dry basin. However, over the course of nine days, the situation escalates.
The first alert from the Corps to downstream communities starts with the release of 500 cubic feet per second of water from the dam. By Day 5, the situation has escalated with the release of 10,000 cubic feet per second of water, exceeding the limit for most downstream structures, including low-water crossings and bridges.
By Day 7, the Bureau of Reclamation is unable to reduce its upstream discharges to mitigate the impacts to Yuma and Mexico from the dam, which is now releasing 22,500 cubic feet per second of water, in an attempt to avoid a spillway flow. By Day 9, the dam is releasing 50,000 cubic feet per second of water, doubling the real-world historic flows of 1993, and amplifying the needed response.
“The Painted Rock Dam exercise allowed us to personally get to know the state and county officials that we would be working with when we have a real emergency,” said David Kingston, chief of the LA District’s Emergency Management Branch. “It was also great that we had team members attending from the U.S. Army Corps of Engineers South Pacific Division, supporting the exercise. They were able to see and understand all of the nuances of operating this project.”
“It’s so important to address the tough questions when we have these opportunities,” Van Tine added. “Just like a championship team trains for the big game, so does the U.S. Army Corps of Engineers and its partners.”
The real-world peak outflow occurred on Feb. 27, 1993 at 25,600 cfs, water surface elevation didn't drop below the spillway crest until March 16. On July 7, the dam was still releasing 2,200 cfs.
NOTE: Thanks to Dena O'Dell for her editorial oversight and Robert DeDeaux for his visual story telling.