Why did this ice storm cause so many power outages in Austin?
Back in 2007, a big ice storm hit the city of Austin. Trees and power lines were coated in frozen precipitation, cutting power for around 35,000 customers, some of whom went days without electricity.
At the time, it was considered one of the worst local power outages in the city’s history. But even that storm doesn’t approach what happened this week.
In total, 265,000 customers — about half of all Austin Energy customers — lost power at some point during this week’s freeze. Around a quarter million people remained without power Friday, four days after the storm began. Austin Energy, the city’s publicly owned utility, has said it’s not even sure when electricity will be restored.
If there’s one question prompted by this power crisis, it is: Why? Why did so many people lose power?
The city’s utility says the answer is relatively simple and involves two key components: ice and trees. Austin happened to be the most populous area in the path of the storm. When ice from that storm hit the city’s celebrated urban tree canopy, outages were inevitable.
But that answer raises more questions about city policy around power line management, extreme weather preparedness and what might be done the next time a freeze descends.
At a press conference Thursday morning, Austin Energy General Manager Jackie Sargent called the freezing rain that converged on Central Texas this week a “historic” event.
“We are experiencing one of the most widespread ice storms to hit Austin and certainly one of the worst,” she said.
While it’s true that Austin rarely sees ice accumulation of the kind it just experienced, it’s not unheard of.
“Unfortunately, we don’t have a super complete archive of ice accumulations to work off of,” National Weather Service Meteorologist Keith White said. “From what I’ve been looking at, this kind of event only happens only once a decade give or take. … Probably less frequently than one a decade.”
White says that the 2007 storm — with reports of up to three quarters of an inch of ice cover — is the most similar storm we’ve had in recent history. Even the winter storm of 2021, which left much of the city without power due to a statewide grid failure, did not bring as much ice or cause as many local problems as this one.
But the fact that similar weather conditions in 2007 yielded different results means there’s something more than the weather at play in what happened this week.
Ironically, around the same year as that 2007 storm, city policy dictating tree trimming around power lines began to relax. The push came from property owners and neighborhood associations angered by what some described as Austin Energy’s propensity to “butcher” neighborhood trees.
According to the North Shoal Creek Neighborhood Association, the policy fight was sparked by the clearcutting of a stand of 200 trees on one block in Northwest Austin.
“Neighborhood residents sprang into action” a web post by the association reported. “As a result of the efforts by all, Austin Energy changed tree clearing policies to better preserve trees for the myriad benefits they provide.”
Michael Webber, a professor at UT Austin’s Department of Mechanical Engineering who served on the city’s Electric Utility Commission from 2008 to 2013, remembers “all sorts of battles over vegetation management” at the time.
“Very powerful people who are rich and are in the neighborhoods with the beautiful trees were complaining,” he said. “They didn't want their pretty trees in their yards touched by the city.”
The city enacted several changes. Until 2006, the city had cut back fast-growing tree branches up to 13 feet away from power lines, and slow-growing branches were pruned up to 9 feet back. After citizen pushback, Austin Energy allowed fast-growing trees to reach within 8 feet of the lines and slow-growing trees within 4 feet.
“I know that it triggers and elicits different emotions in different people, but at the end of the day, if we don’t trim the trees, we could find ourselves in a very precarious situation."Austin Energy COO Charles Dickerson in 2019
The city also became more sensitive to the wishes of property owners, allowing property owners to “refuse” tree-trimming plans and to hire their own arborists or suggest alternate solutions.
Austin Energy did not reply to an interview request over its tree-trimming policy.
“It created a whole heavy process to get [tree trimming] going,” Webber said.
Neighborhood groups educated each other on ways to reduce trimming in their parts of town.
“Remember, the crew that will actually be trimming the tree is probably not from Austin Energy but an outside contractor who wants to get done as fast as they can,” advises the Zilker Neighborhood Association. “They are not overly sensitive to pruning the minimum needed.”
By 2012, Austin Energy boasted that it was one of few utilities in the country that “attempts to meet with each property owner in advance of trimming” in its annual report.
But, according to city staff, city tree-trimming policy was also creating dangerous conditions around power lines.
In 2019, Austin Energy COO Charles Dickerson announced a reversal of tree-trimming policy.
“I know that it triggers and elicits different emotions in different people, but at the end of the day, if we don’t trim the trees, we could find ourselves in a very precarious situation,” he told a meeting of the Austin Energy Utility Oversight Committee.
Dickerson said the city would begin cutting fast-growing tree limbs up to 15 feet away from power lines and slow-growing trees up to 10 feet away.
“If we don't trim with this level of prudence, we can wind up with more outages and possibly fires,” he said.
But over the last four years and despite increased funding for tree trimming in 2021, the city has not caught up on its backlog of lines that need to be trimmed to the new standard.
“The City Council ... had restricted the trimming on the trees down to an unsustainable manner,” Austin Energy’s Elton Richards said in a press conference Thursday night. “It's probably going to take another three years to get the whole city back on a normal cycle.”
Richards said city contractors have been concentrating increased trimming in areas with the greatest wildfire danger (typically West Austin) and the greatest number of outages.
With the storm, it's easy to forget that last month was one of Austin's warmest Januarys on record, much of it characterized by early-summer-like days of hot sun and no precipitation.
That heat was just another in a string of weather anomalies going back for years, including a drought and heatwave in 2022 and another devastating (though not as icy) arctic blast in 2021.
Tree experts say that recent history likely amplified the devastation wrought by this week’s storm, leaving dead or weakened branches more vulnerable to the weight of the ice.
“The effects of this on the forests will be seen for years. With all these torn branches, it's going to be points of entry for decaying fungus, which over the years will cause rotten trees, leaving them more prone to fail, down the road, through events like windstorms.”Karl Flocke, Texas A&M Forest Service.
“There are definitely trees that have had stress and accumulative damage,” said Camille Wiseman, a forester with the Texas A&M Forest Service. “These sorts of stressors accumulate over time.”
When weakened trees get covered with ice, the results can be dramatic.
“Just a little bit of additional ice, an additional 10th of an inch or so will put hundreds and hundreds of additional stress on a tree,” White, from the National Weather Service, said, “especially a lot of our oaks, like we have in this area.”
That could explain why trees, even those that have never been pruned or touched by a human hand, were so severely damaged by this storm.
It also means that this year’s storm will leave even more broken trees to confront whatever extreme weather event may come next.
“The effects of this on the forests will be seen for years,” said Karl Flocke, another forester with the Texas A&M Forest Service. “With all these torn branches, it's going to be points of entry for decaying fungus, which over the years will cause rotten trees, leaving them more prone to fail, down the road, through events like windstorms.”
What’s to be done
While work crews struggle to bring power back to those still affected, Austinites are already wondering how such a disaster can be avoided in the future.
By Austin Energy’s own admission, it was caught off guard by the severity and impact of the storm.
The utility has been criticized for waiting too long to call in help from neighboring utilities. Austin Mayor Kirk Watson has also said local officials need to improve emergency communication and outreach.
Austin Energy has said it will do an after-action report on the storm.
When it comes to how to better prepare for the next freeze, the most obvious answer may be to improve or increase city tree trimming to make up the backlog left through years of inadequate policy. That's something Austin Energy says it will consider.
But even Richards, who has long promoted more aggressive tree trimming, says that would not have saved the city from major outages.
“I'm telling you guys, this isn't a [vegetation] management issue,” he told reporters Thursday evening. “Even outside the 15 feet [zone] above where we cut to standard, the ice that was on those branches caved on top of” transmission lines.
“This truly is an act of God, there’s no other way of saying it,” he told KUT earlier that day while surveying a downed tree. “You take a 40-foot tree that’s coming down. There’s no vegetation management in the world that would prevent that.”
That might leave some to wonder whether there is a better solution.
In the aftermath of the devastating wildfire caused by power lines touching trees in California, PG&E, the state’s big transmission company, began the costly process of burying power lines.
Now, in the aftermath of the storm emergency here, it’s no surprise that some are suggesting the same thing, to the apparent chagrin of Austin Energy’s Jackie Sargent.
“It's very expensive to retrofit a system and go back and bury power lines,” she said when asked about it Thursday. “Very expensive. Billions of dollars.”
But others think burying lines might make sense.
Webber said he believes it could even end up saving money in the long run.
During an interview, both Webber and I received alerts that our local school districts would be closed for the fourth day in a row because of the ice storm and power outages.
“Closing schools or [closing] economic activity four days in a row is really expensive and very disruptive,” he said. “We tend not to price the costs of disruption or lack of reliability into our analysis.”