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What Makes a Catastrophic Flood? And Is Climate Change Causing More of Them?

What Makes a Catastrophic Flood? And Is Climate Change Causing More of Them?
With floods submerging expanses of the Midwest and government scientists warning that this spring could bring a historic flood season in the United States, it’s natural to ask why it is happening. What causes catastrophic flooding? And what is the role of climate change?

Each flood is its own phenomenon, tied to the specific circumstances in the area.

“Flooding is complex,” Deke Arndt, a climate scientist at the National Oceanic and Atmospheric Administration, said Thursday in a briefing on the potentially dire flood season.

“It has to do with precipitation falling to the ground,” Mr. Arndt said, “but also with the way that water is managed and the surface hydrology — how it flows across the land and is collected and runs off.”

The question of water management involves the building and maintenance of dams, levees, reservoirs and spillways. The “surface hydrology” part is about the landscape and how it affects the flow of water (for example, places rich in steep hills and valleys like Vermont can see severe destruction from intense rain events). And the development of housing, malls and other paved-over areas reduces the amount of open land that can absorb runoff.


Flooding in Hamburg, Iowa, this week.CreditCreditTim Gruber for The New York Times

 

Source:  Climate Forward, NY Times

By:  John Schwartz
March 22, 2019

LINK:  https://www.nytimes.com/2019/03/22/climate/what-causes-floods.html?em_pos=small&emc=edit_clim_20190327&nl=climate-fwd&nl_art=3&nlid=88090489c%3Dedit_clim_20190327&ref=headline&te=

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25 States Are at Risk of Serious Flooding This Spring, U.S. Forecast Says

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Flooding in Hamburg, Iowa, on Monday.CreditCreditTim Gruber for The New York Times

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Vast areas of the United States are at risk of flooding this spring, even as Nebraska and other Midwestern states are already reeling from record-breaking late-winter floods, federal scientists said on Thursday.

Nearly two-thirds of the lower 48 states will have an elevated risk of some flooding from now until May, and 25 states could experience “major or moderate flooding,” according to the National Oceanic and Atmospheric Administration.

“The flooding this year could be worse than anything we’ve seen in recent years, even worse than the historic floods of 1993 and 2011,” said Mary C. Erickson, deputy director of the National Weather Service, in a conference call with reporters. The major flooding this month in Nebraska, Minnesota, Iowa and elsewhere is “a preview of what we expect throughout the rest of the spring,” she said.

Some 13 million people could be exposed to major flooding, making this a “potentially unprecedented” flood season, said Edward Clark, director of NOAA’s National Water Center.

And much of the United States east of the Mississippi River, as well as parts of California and Nevada — in total, areas home to more than 200 million people — could see at least some flooding in the spring, the scientists said.

The projections were part of NOAA’s annual “Spring Outlook,” though the language of the 2019 report carried greater urgency than usual. That is not surprising, since the basins of the Upper Mississippi and the Red River of the North have already been hit with rain and snow this spring of up to twice normal levels.

“We’ve set over 30 records in Nebraska, Iowa and South Dakota” in the last week alone, said Kevin Low, a scientist with the National Weather Service’s Missouri River Basin Forecast Center. That flooding has devastated farmers and ranchers across the region, put communities like Hamburg, Iowa, underwater, and wiped out roads and bridges in others.

Gov. Pete Ricketts of Nebraska put a preliminary estimate of $1.4 billion in damages in his request for a federal disaster declaration, including $439 million in damages to public infrastructure and $85 million to homes and businesses.

Above-average rainfall that scientists expect for the spring, along with melting snow, would add to the flooding and extend it through the central and southern United States. NOAA identified the greatest risks for moderate to major flooding in the upper, middle and lower Mississippi River basins, the Red River of the North, the Great Lakes, and the eastern Missouri River, lower Ohio River, lower Cumberland River and Tennessee River basins.

The agency’s scientists also predicted that the chemical runoff from the rains would cause above-average hypoxia conditions — “dead zones” of water with low oxygen caused by nutrient pollution that can kill fish and other marine life — in the Gulf of Mexico and Chesapeake Bay.

More rainfall in the Midwest is a predictable consequence of climate change, according to the most recent National Climate Assessment, which was produced last year by 13 federal agencies. A warmer atmosphere can hold more moisture, which comes down as precipitation.

The current flooding in the Missouri River basin and beyond has been caused in part by heavy rains, but has been further complicated by other factors, like frozen ground that kept water from being absorbed.

Andrew Dessler, a professor of atmospheric sciences at Texas A&M University, said that understanding the role of climate change in weather events like the Nebraska floods required applying the tools of a growing field known as attribution science. “Without doing the analysis, you don’t know what role climate change played,” he said. “Certainly, floods happened before climate change.”

However, he added, heavier rainfall events are among the most common conditions associated with climate change. Humans have loaded so much planet-warming carbon dioxide into the atmosphere that “the starting assumption has to be that climate change is affecting everything” to some extent, he said.

“The real question isn’t, ‘Is climate change playing a role?’” Dr. Dessler said. “It’s, ‘How big a role is climate change playing, and what is the role?’”

The National Weather Service describes moderate flooding as involving some inundation of structures and roads near streams, with some evacuations; major flooding involves extensive inundation of structures and roads and significant evacuations.

By comparing this year’s potential flooding to the seasons of 1993 and 2011, Ms. Erickson was citing some of the worst weather disasters the United States has faced since the Great Mississippi Flood of 1927.

The 1993 flood in the Midwest killed 50 people and caused $15 billion in damages; a reporter for The New York Times called it “a watery rampage by nature like no other.

In the 2011 floods, the Army Corps of Engineers took the extraordinary measure of blowing up 11,000 feet of Mississippi River levee to let water flow into the Birds Point floodway in Missouri, saving the little Illinois town of Cairo but inundating more than 100,000 acres of farmland and homes.

For more news on climate and the environment, follow @NYTClimate on Twitter.

LINK:  https://www.nytimes.com/2019/03/21/climate/climate-change-flooding.html?em_pos=small&emc=edit_clim_20190327&nl=climate-fwd&nl_art=2&nlid=88090489c%3Dedit_clim_20190327&ref=headline&te=1

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The Fight to Tame a Swelling River With Dams That May Be Outmatched by Climate Change

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The Gavins Point Dam in South Dakota was at the heart of a difficult decision during recent flooding along the Missouri River.CreditCreditJenn Ackerman and Tim Gruber for The New York Times

Along the Missouri, John Remus controls a network of dams that dictates the fate of millions. ‘It was not designed to handle this.’

The Gavins Point Dam in South Dakota was at the heart of a difficult decision during recent flooding along the Missouri River.CreditCreditJenn Ackerman and Tim Gruber for The New York Times

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There were no good choices for John Remus, yet he had to choose.

Should he try to hold back the surging Missouri River but risk destroying a major dam, potentially releasing a 45-foot wall of water? Or should he relieve the pressure by opening the spillway, purposely adding to the flooding of towns, homes and farmland for hundreds of miles.

Flood damage in Hamburg, Iowa.CreditJenn Ackerman and Tim Gruber for The New York Times
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Flood damage in Hamburg, Iowa.CreditJenn Ackerman and Tim Gruber for The New York Times
Steve and Roxanne Adkins trying to save belongings from their flooded home near Hamburg on Monday.CreditJenn Ackerman and Tim Gruber for The New York Times

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Steve and Roxanne Adkins trying to save belongings from their flooded home near Hamburg on Monday.CreditJenn Ackerman and Tim Gruber for The New York Times

Mr. Remus controls an extraordinary machine — the dams built decades ago to tame a river system that drains parts of 10 states and two Canadian provinces. But it was designed for a different era, a time before climate change and the extreme weather it can bring.

“It’s human nature to think we are masters of our environment, the lords of creation,” said Mr. Remus, who works for the United States Army Corps of Engineers. But there are limits, he said. And the storm last week that caused him so much trouble was beyond what his network of dams can control.

“It was not designed to handle this,” he said.

The storm, the “bomb cyclone” that struck the upper Midwest, dumped its rain onto frozen soil, which acted less like dirt and more like concrete. Instead of being absorbed, water from the rain and melted snow raced straight into the Missouri River and its tributaries.

John Remus operates the six dams built years ago to manage the Missouri River.CreditJenn Ackerman and Tim Gruber for The New York Times

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John Remus operates the six dams built years ago to manage the Missouri River.CreditJenn Ackerman and Tim Gruber for The New York Times

Devastating flooding hit Missouri, Iowa, Kansas and Nebraska. Near Omaha, one-third of Offutt Air Force Base was inundated, including a runway. One Missouri River tributary, the Little Sioux River, rose almost 16 feet in one day.

And early last Thursday, the Niobrara River smashed through the nearly century-old Spencer Dam while pushing huge chunks of ice downriver. By the end of the day, the Niobrara and other tributaries had filled the reservoir behind the Gavins Point Dam, near Yankton, South Dakota, and Mr. Remus faced his decision.

Gavins Point is relatively small, not designed to hold back that kind of inflow. But losing the dam would be catastrophic.

The Gavins Point Dam, where Mr. Remus opened the floodgates to avoid damaging the structure. CreditJenn Ackerman and Tim Gruber for The New York Times

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The Gavins Point Dam, where Mr. Remus opened the floodgates to avoid damaging the structure. CreditJenn Ackerman and Tim Gruber for The New York Times

To save Gavins Point, he ordered its spillways opened. At its peak, 100,000 cubic feet of water per second, the same as Niagara Falls, poured into a river already surging toward record heights.

“We filled up our bucket, and the spigot kept running,” Mr. Remus said. The results of last week’s storm are still evident: As of Wednesday, at least three people had been killed and there were emergency declarations in four states.

Few people hold sway over as much water as Mr. Remus, the chief of the Army Corps’ Missouri River Basin Water Management Division. He operates six massive dams that help shape and define a river stretching more than 2,000 miles through the American heartland.

His decisions affect the lives of countless communities and ecosystems — the cities, factories and power plants that draw water from the river; the endangered species that nest on its sandbars; the farmers who cultivate its floodplains.

Often, their interests conflict. “You’re not going to make them happy,” he said, “but you can provide them with an explanation.”

An imposingly large man with a neat mustache, Mr. Remus, 59, grew up in Western Nebraska and speaks deliberately. In his tidy, windowless office in Omaha, the main feature is a tabletop map of roughly half the United States. Over the course of several interviews, he discussed his work and said the Corps had not looked at climate change from a planning perspective.

“Scientists say that, in the Missouri Basin, we’ll be spending more time at each end of the spectrum — longer and more severe floods, longer and more severe droughts,” Mr. Remus said. And this year, he had “nothing but bad options.”

A 2012 report on climate change in the Missouri River Basin, commissioned by the Bureau of Reclamation (the Corps’ western equivalent) predicted by the middle of this century a roughly 6 percent average annual increase in upper-basin runoff and a bit more than a 10 percent increase in the lower river.

The Missouri Basin had more runoff from rain and snow last year than all but two years since record-keeping began in 1898. “Is that normal variation?” he asked, or “are we working our way to a new normal?”

“Something’s changing, what that is exactly. …” he said, trailing off.

Flooding near Bartlett, Iowa, last year. This past week, levees like the one to the right breached.CreditJenn Ackerman and Tim Gruber for The New York Times

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Flooding near Bartlett, Iowa, last year. This past week, levees like the one to the right breached.CreditJenn Ackerman and Tim Gruber for The New York Times

Mr. Remus’s stewardship of the river is guided by a 432-page document, the Master Manual, which lays out the eight congressionally authorized purposes he must balance. They are flood control, river navigation, hydroelectric power, irrigation, water supply, water quality, recreation (such as fishing or boating), and the preservation of endangered species.

One problem with that: The Master Manual does not explicitly tell Mr. Remus which is more important. Thus the eight purposes exist in a near constant state of tension.

“You can’t say that you serve all of them equally,” Mr. Remus said. The word he clings to is “balance.” But when extreme flooding looms, he said, “the balance goes away.”

Then, all that matters is flood control.

For millenniums, the Missouri was a wide, sinuous river. Passage was treacherous and steamboats frequently sank in the shallows. The river flooded in the spring, and you could walk across it in the fall.

After the devastating dust bowl years of the 1930s and a series of severe floods in the early 1940s, Congress decided to do something. It was the era of big dams. Across America, landscapes were being rearranged to suit human needs.

Over time, the broad, shallow river was transformed into a deep, narrower channel more conducive to the river shipping business, in the process creating new land along the banks.

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The Missouri River in 1934, wide and meanderingCreditU.S. Army Corps of Engineers

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The river in 1946, narrowed by dikesCreditU.S. Army Corps of Engineers

Levees were built near the new channel to prevent flooding and farmers were offered the new land at low cost. According to the Corps, 522,000 acres of floodplain and river habitat were converted to farmland or otherwise lost.

While farmland in some places was being created, elsewhere it was being submerged behind immense dams and their vast new reservoirs. Some 350,000 acres of that land belonged to Native Americans.

Faith Spotted Eagle said she remembers when her childhood village was permanently covered by one of the Missouri River reservoirs.CreditJenn Ackerman and Tim Gruber for The New York Times

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Faith Spotted Eagle said she remembers when her childhood village was permanently covered by one of the Missouri River reservoirs.CreditJenn Ackerman and Tim Gruber for The New York Times

Faith Spotted Eagle, a 70-year-old tribal elder and activist from the Yankton Sioux Reservation in South Dakota, said she remembers as a child having to leave her family’s home in the village of White Swan, now beneath 140 feet of water at the bottom of Lake Francis Case, a reservoir created by the Fort Randall Dam.

The Yankton never consented to their land being submerged. In 2002 the tribe was paid $23 million for the 2,851 acres that were affected in the 1950s, and is still fighting for compensation for hundreds of additional acres it says have since been eroded away.

“It’s all loss, loss, loss,” she said.

Erosion caused by floods on the Yankton Reservation in South Dakota.CreditJenn Ackerman and Tim Gruber for The New York Times

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Erosion caused by floods on the Yankton Reservation in South Dakota.CreditJenn Ackerman and Tim Gruber for The New York Times

For the federal government, though, it was worth it.

Downtown Kansas City and Omaha have not flooded since the dams went in. Cheap hydroelectric power is abundant. With the river in check, the economy grew.

Early last Thursday, floodwaters near Bartlett, Iowa, overtopped a levee north of David Lueth’s house. The Sheriff ordered an evacuation.

Mr. Lueth, 61 years old, disregarded the order.

Instead, he rushed to move 1,000 bushels of soybeans stored in a bin beside his house. If the beans got wet, they would rot.

The sky was blue and trumpeter swans flew overhead, a beautiful day, he said. But Mr. Lueth was near tears. Water from the Bartlett breach was rolling his way. At the prospect of leaving his home and farm, he said: “I was physically sick this morning. Threw up twice.”

David Lueth near his farm in Percival, Iowa, in September. Behind him is ruined corn. CreditJenn Ackerman and Tim Gruber for The New York Times

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David Lueth near his farm in Percival, Iowa, in September. Behind him is ruined corn. CreditJenn Ackerman and Tim Gruber for The New York Times

It reminded him vividly of what happened eight years ago, in the great flood of 2011. Then, another nearby levee was almost completely destroyed. It cost him his life savings, $100,000, to restore his land.

To Mr. Remus, 2011’s destructive flood represented a rare opportunity to rethink the Missouri River levee system to accommodate more floodwater. The easiest way to do that would be to move levees away from the river, making the flood plain bigger.

He took his argument to the local board that oversaw the destroyed levee. Faced with the costs of rebuilding their levee practically from scratch, he reasoned, they might be willing to move it back.

Leo Ettleman, 64, was at those meetings and said he remembers saying, “John, we can’t afford it,” to which he says Mr. Remus replied: “Can you afford floods?” (Mr. Remus said he didn’t recall the conversation.)

Mr. Remus’s effort largely failed. The levee was set back some, but not nearly as much as the Corps had proposed.

Flooding near David Lueth’s property in September.CreditJenn Ackerman and Tim Gruber for The New York Times

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Flooding near David Lueth’s property in September.CreditJenn Ackerman and Tim Gruber for The New York Times

Today the whole episode stands as a case study in how difficult it can be for Mr. Remus to balance everyone’s needs. The levee’s rebuilding was followed by years of litigation in which the Corps was accused of prioritizing wildlife at the expense of flood control.

The plaintiffs alleged that Mr. Remus’s predecessor would have prevented flooding if she had not favored the threatened and endangered species. Last March, a federal judge agreed and found the government liable for flood damage dating back to 2007.

Listed as threatened since 1986, piping plovers nest above the waterline on sandbars. The puffy, migratory beach dwellers once were plentiful, but as the river changed, the birds became scarce.

And last year along the Missouri, the plovers were a clear loser. Mr. Remus had to release floodwaters building behind the dams just as mating pairs of plovers were tending their eggs near the water’s edge.

On a humid morning last summer, Jessica Archer took five “Area Closed” signs from a small boat and threw them clattering onto the sand. A no-nonsense 26-year-old from a small Iowa town, she was part of a team of Army Corps biologists counting plovers as well as endangered interior least terns.

When a fellow biologist picked up two signs instead of one, Ms. Archer snapped at her — “put one down,” she said — but she wasn’t upset about the signs. She was frustrated that they probably wouldn’t be able to save two plover nests they had just discovered.

Jessica Archer, a biologist, at Walnut Woods State Park in Des Moines. Last summer she worked for the Army Corps of Engineers on a survey of endangered piping plovers.CreditJenn Ackerman and Tim Gruber for The New York Times

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Jessica Archer, a biologist, at Walnut Woods State Park in Des Moines. Last summer she worked for the Army Corps of Engineers on a survey of endangered piping plovers.CreditJenn Ackerman and Tim Gruber for The New York Times

She had good reason to think that. Mr. Remus was, in fact, opening the floodgates upriver.

“It’s a bad year for the birds,” he had said in an interview just a few days earlier.

Last year was the third-wettest year in the Missouri Basin since record-keeping began in 1898.

Mr. Remus said that both he and his predecessor (who declined to be interviewed) managed the river strictly according to the Master Manual, their bible of river management.

But last year, something had to give. In 2018, only 27 percent of plover and tern nests survived.

Birds on the Missouri River in Pierre, S.D.CreditJenn Ackerman and Tim Gruber for The New York Times

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Birds on the Missouri River in Pierre, S.D.CreditJenn Ackerman and Tim Gruber for The New York Times

This past Friday, Mr. Lueth was melancholy as he lingered in his home. It was, he said, “like leaving your child at the I.C.U.”

By Monday, the sadness had turned to anger. Why should he, his neighbors, and the towns of Bartlett and Hamburg, be the ones flooded?

He was certain Mr. Remus could have done more. What about people upstream, “Why don’t they take the damage?” he said. If the Gavins Point Dam wasn’t helping, let it fail.

Weather like this, storms that exceed the system’s ability to manage flooding, is clearly a problem. “Whether it’s global warming, or a tilt in the earth. …” Mr. Lueth said, leaving his thought unfinished. “It’s time to change, now.”

If the government wants his land for a spillway or a new dam, he said, they can have it. Just pay him fair market value, $8,000 to $9,000 an acre.

On Monday, Mr. Lueth was helping a friend move some farming equipment to higher ground when they paused, he said, to watch hundreds of deer race across a flooded field, chased from the woods by high water. On Tuesday, Mr. Lueth lost his home.

A flooded road near Hamburg, Iowa.CreditJenn Ackerman and Tim Gruber for The New York Times

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A flooded road near Hamburg, Iowa.CreditJenn Ackerman and Tim Gruber for The New York Times

For more news on climate and the environment, follow @NYTClimate on Twitter.

LINK:  https://www.nytimes.com/2019/03/21/climate/missouri-river-flooding-dams-climate.html?em_pos=small&emc=edit_clim_20190327&nl=climate-fwd&nl_art=1&nlid=88090489c%3Dedit_clim_20190327&ref=headline&te=1

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