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In the wake of the deadly flash floods in Texas on July 4, Texas leaders are betting on the life-saving potential of flood warning sirens.

"What can we do better looking forward? We need sirens," said Texas Lt. Gov. Dan Patrick in an 

 with NBC 5 in Dallas-Fort Worth. The floods killed at least 120 people.

Weather warning sirens are installed outside on tall poles, and make a loud wailing sound to warn people in the area when water levels rise, signaling an imminent flood. Some also broadcast spoken warnings and directions about how to get to safety. These types of sirens are widely used in the United States to warn people about tornadoes and tsunamis, but are much less common in areas that flood.

"If you had sirens blasting," Patrick said, "and if people had known 'if you hear a siren get to high ground,' maybe that would have saved some lives."

Patrick pledged the state would pay to have flood sirens installed in Kerr County, the epicenter of the recent flooding, "by next year."

There appears to be public support as well. A petition calling for flood warning sirens in Kerr County, 

, had garnered almost 40,000 signatures as of Thursday.

Emergency experts say such sirens can save lives in places like Kerr County, where many people go to vacation outdoors, and which is so prone to deadly flooding that the area is nicknamed Flash Flood Alley.

"Sirens are best for alerting people who are outside of a building," says Jeannette Sutton, an emergency warning researcher at the State University of New York at Albany, who has worked with both the Federal Emergency Management Agency and the National Weather Service.

Sirens are very loud, she says, and work well in rural areas where people are spread out. "[Sirens] are really going to get people who are camping along a river, which is a really good thing."

But sirens are just one piece of the puzzle, flood experts caution.

Sirens often aren't audible inside, so cell phone warnings, social media warnings, and television and radio alerts are still crucial. Ideally, people will receive multiple different kinds of warnings.

"We've gotta meet people where they're at," says Chad Berginnis, the executive director of the Association of State Floodplain Managers. "To have redundancy in your approach is a good thing."

Local leaders in Texas considered flood sirens in 2016

Nearly a decade ago, in 2016, Kerr County considered installing flood warning sirens, says former county commissioner Tom Moser.

The county ultimately didn't pursue them, because of opposition from residents. About 50 local residents attended a public meeting that year, to discuss a proposal for a new flood warning system, he says, "and there were people at that meeting that did not like the idea of sirens."

The main concern among residents was the potential for false alarms.

"Sirens going off in the night with a false indication, it would not be a good thing," Moser says. "So we took those out of the plan, just because so many people were objecting to sirens."

Indeed, false alarms are a disruptive and potentially dangerous problem with warning sirens, according to a 

 by the National Institute of Standards and Technology, a federal science agency.

One way to avoid false alarms is to make sure the siren is triggered reliably, the report notes. For flash flood sirens, that means installing river gauges throughout the area, so that water levels are monitored continuously and the sirens only go off only when dangerous flooding is occurring, says Berginnis.

Such gauges are an important part of any flood warning system, whether or not it includes sirens.

Kerr County tried to upgrade its river gauges in the decade before this month's catastrophic flood. The county sought about $1 million in funding for an updated river gauge system and better flood warnings in places where local roads cross rivers. But they were 

Sirens only work if people know what they mean

Sirens are only useful if people in the area know what to do when they hear the tone, emergency experts say.

"If they're just a noise that goes off, a lot of people won't know what they mean," explains Keri Stephens, a risk communication researcher at the University of Texas at Austin. "What the research really stresses is we actually need to teach the people that these warnings are meant for, what they mean."

That could mean public service announcements, drills in schools and workplaces and explanatory signs in the most vulnerable areas that direct people to high ground, she says. In places that already use sirens for other hazards, such as tornadoes, flood sirens might be less effective or require more public education.

Stephens says Japan offers a good example of such public education. The tsunami-prone nation has a system of warning sirens, and teaches school children about what to do if they hear one.

In a rural area that attracts tourists, such public education can be more difficult. People who are new to an area may not know what to do when they hear a flood warning siren for the first time. Some sirens can broadcast specific instructions, which can help. But they only work in some settings, and the words can be difficult to understand, says Sutton.

But even if people don't know their exact meaning, sirens can still be useful, Sutton argues. For example, tourists camping by a river that begins to flood during the night might not know exactly what to do if they're woken up by a siren. But "if it wakes people up at 3 in the morning so they're, like, 'Oh god, something must be happening!' and it makes them go look for information, then at least it gets them up and awake and moving," she says.

Other countries use sirens for flood warnings

It's unclear how many communities in the U.S. have flood warning sirens. But it is not a new idea in the Texas Hill Country, where the recent floods happened. The towns of 

, Texas, have had flood warning sirens for years. The town of Comfort, Texas, which is immediately downstream of hard-hit Kerrville, installed a flood warning siren 

 in 2019 after a pair of deadly flash floods.

Flood warning sirens are more widely used in other parts of the world. Switzerland has a 

, including in rural areas that may not have reliable cell service. And some alpine communities in the 

 as part of their early warning systems for flash floods, which have historically been 

. Many of those sirens run on power from solar panels, so they operate even if a flood knocks down power lines, as happened in Texas.

But sirens do not guarantee that people will get to safety. In Germany, 

 are used to warn residents about a wide variety of hazards, including floods. But catastrophic flash floods in 2021 still 

 in Germany and Belgium, even though many warning sirens went off. Germany 

 by upgrading warning systems across the country, to add river gauges and sirens capable of broadcasting specific directions for how to get to safety.

Sutton says installing flood sirens more widely in the U.S. comes with challenges.

"They're very expensive to purchase and then they're expensive to maintain," she says.

Most local communities cannot afford to pay for such a system on their own. And a Federal Emergency Management Agency (FEMA) program that was a major source of federal funding for such disaster infrastructure projects was 

Berginnis says not all flood-prone communities can afford, or need, sirens, but they all need robust plans for monitoring floodwaters and warning people when a flood is about to happen.

"I think the interesting thing about flood warning systems is everybody jumps to 'We need the most technologically advanced system,'" he says.

While sirens can help in some places, lower-tech solutions can also save lives, he stresses.

"In reality what you need is a good plan," Berginnis says. "You need a 

, and you need someone willing to stay up all night long to make sure the warnings are translated into action."

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Rebecca Hersher

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In the wake of the deadly flash floods in Texas, state leaders are exploring whether to install more flood warning sirens. Such sirens can save lives if they're part of a larger warning system.

How flood sirens could have saved lives in Texas

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