This story was co-published with NBC News.

For several years, the U.S. military and federal and local officials knew that Offutt Air Force Base in Nebraska lay exposed to the threat of catastrophic flooding. But a key federal agency moved too slowly to approve plans to protect the base from last weekend's deluge, a top local official said.

The flooding submerged part of the runway and inundated dozens of buildings at one of the nation's most important air bases. The calamity likely will cost many times more to repair than it would have cost to prevent, said John Winkler, district general manager of the Papio-Missouri River Natural Resources District, the local government agency responsible for managing the section of the river nearest Offutt and Omaha.

The damage has crippled capabilities at an Air Force base considered essential to national security. Among its many roles, Offutt is home to the U.S. Strategic Command that oversees the Pentagon's nuclear strategic deterrence and global strike capabilities.

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The risks to Offutt, long known, were laid bare back in 2011 when floodwaters crept to within 50 feet of the runway.

But even as military officials in Washington and across the country increasingly realized that their defense infrastructure was vulnerable to the effects of climate change, the response to protect Offutt was agonizingly slow, Winkler said.

Crucially, construction never began to reinforce an earthwork levee system to protect the vital base from the Missouri River the next time it raged over its banks. Winkler said approval for the levee construction was complicated by myriad requirements from the Army Corps of Engineers that took six years to navigate.

Approval from the Corps finally came last year. The district approved construction bids earlier this year for work that will begin as soon as the floodwaters recede and the ground dries, probably in May or June.

Getting approval to raise the Missouri River levee that protects the Air Force base took six years and arrived too late. Construction is now expected to begin as soon as the floodwaters recede and the ground dries, likely May or June, a local official said. Credit: Tech. Sgt. Rachelle Blake/U.S. Air Force

Mike Glasch, deputy director of public affairs for the Army Corps of Engineers' Omaha District, said the Corps could not talk about the permitting process because of litigation involving the levee project.

Without the higher levees, Offutt lay vulnerable to the flooding that began late last week after an unusually intense cyclonic blizzard lashed the nation's midsection. Heavy rain hit thick snowpack upstream from Offutt, which lies near the confluence of the Platte and Missouri rivers, sending a wave of water over the existing levees.

The flooding submerged as much as a third of the base, closing down the runway and halting flight operations. "It's going to be a long recovery," the base commander, Col. Michael Manion, said Tuesday, speaking on video with floodwater still surrounding the buildings behind him.

It will be months before the base recovers fully and returns to normal operations, said Drew Nystrom, a base public affairs spokesman. Of the base's 10,000 personnel, the workspaces of about 3,000 are inaccessible. And while water no longer covers the runway, its return to operation is pending inspections, he said. Key components of the fighter operations have been dispersed to other bases, where they remain ready to deploy if necessary.

"Our ability to project air power has not diminished," Nystrom said.

2015 Report Called for Higher Levees

It's too soon for scientists to fully assess the role of climate change in the latest storm and flooding. After the 2011 flood, a National Oceanic and Atmospheric Administration study said the storm probably fell within the range of natural variability. But the science of attributing natural events to climate change has advanced since then, and this flood was worse—the most catastrophic in a half century, according to Nebraska Gov. Pete Ricketts.

"The devastating flooding at Offutt Air Force Base demonstrates once again how critical it is to understand the climate vulnerabilities of our installations," said John Conger, former assistant secretary of defense for energy, installations and environment under President Barack Obama and now director of the Center for Climate and Security, which studies the risks posed by climate change.

"This disaster illustrates the fact that each base has its own localized risks and that one size does not fit all," he said. "Our bases need to be building up resilience and readiness in the face of these risks."

A satellite image shows the river's flooding as it spread into Offutt Air Force Base on March 16. Credit: Joshua Stevens/NASA Earth Observatory

At Offutt, the risks exposed by the 2011 flood were formally recognized in 2015. A land use management plan—carried out by officials representing the base, the city of Omaha, the natural resources district and various cities and counties protected by the levee—warned that the levee needed to be built up, and cautioned that climate change might make matters worse.

Under the heading "Climate Adaptation," the report cited the 147 acres of wetlands on the base and the Platte and Missouri rivers just outside the fence, and said:

"During heavy rainfall, this area is prone to flooding, and flooding onto Offutt AFB may cause delays to missions and operations."

It went on: "Due to changes in the base flood elevation of the Missouri River, Federal Emergency Management Agency (FEMA) has identified the need to raise the levee between two inches to several feet for it to be capable of protecting the installation."

In particular, FEMA had ordered 19 miles of levees along the Missouri to be raised by 2 feet to protect Offutt and portions of Omaha, including one of the city's wastewater treatment facilities.

In a recent Defense Department survey that highlighted the security risks climate change poses to more than 3,500 military installations, non-storm surge flooding ranked third on the list of most-reported severe climate-related events. Credit: Tech. Sgt. Rachelle Blake/U.S. Air Force

Officials responsible for flood preparedness at and around Offutt moved to address the risks, taking preliminary steps such as environmental assessments for raising the levee, but the process moved slowly.

"We didn't have our head in the sand," said Winkler, the manager of the local natural resources district.

"There is no arguing with the science. We could see the dramatic changes in the weather we were experiencing," he said. "We knew we had to react, and we are in the process of preparing for the new future."

But the levee improvements didn't come in time for this month's flood.

'A Window into the Future'

Military experts say climate-related disasters—such as the flooding of the Missouri River, wildfires that have interrupted military training across the country and punishing heat that is sickening thousands of military personnel a year—must be taken into account as part of training and missions.

"For the Department of Defense, the takeaway from this event has to be what lessons have been learned," said retired Army Lt. Col. Frank Galgano, an associate professor in the Department of Geography and the Environment at Villanova University.

"You can't say it was an act of God and hope it doesn't happen again. You have to look at the frequency of these events and plan for the future."

The flooding surrounded fuel tanks at Offutt Air Force Base and tipped over one, which military officials said was empty and had been decommissioned. Credit: 55th Wing Command

The flooding should be seen as a "window into the future," when the potential loss of strategic bases like Offutt and the Norfork Naval Station in Virginia to flooding would have consequences for the nation's military preparedness, he said.

"If this pattern persists, it may signal a larger problem," Galgano said.

As the floodwaters pushed onto Offutt over the weekend, Air Force personnel worked round-the-clock to shore up facilities, including the base headquarters building and its maintenance facility. They put in place 235,000 sandbags and 460 flood barriers, but ultimately had to surrender.

"It was a lost cause," a base spokeswoman, Tech. Sgt. Rachelle Blake, told the Omaha World-Herald. "We gave up."

Outside the gates of Offutt, flooding prompted evacuations in at least 23 of the state's counties, according to Nebraska Emergency Management Agency officials.

Across 14 states bordering the Missouri and Mississippi rivers, more than 10 million people were under flood warnings at one point.

New Military Building Standards for Floodplains

This is the second time in six months that an Air Force base has sustained ruinous damage from a natural disaster. Hurricane Michael ripped apart Tyndall Air Force Base in Florida last October, causing so much damage that its long-term recovery is in question.

The disaster at Offutt amplifies national concerns that flooding poses significant threats to military installations. Last year, federal legislation requiring flood mitigation on military bases was signed into law.

With the risks posed by sea level rise and extreme weather increasing, new constructions rules were added for increasing the elevation of buildings in the 100-year floodplain. Credit: 55th Wing Command

The John S. McCain National Defense Authorization Act, signed by President Donald Trump, directed the Department of Defense to assess which facilities are located in flood-prone areas and require those facilities to create plans to mitigate the risk.

At a minimum, new buildings that are not mission-critical must be built 2 feet above the 100-year floodplain and new mission-critical facilities must be 3 feet above it.

Even before that directive, officials at Offutt were looking to the future.

A $1.3 billion STRATCOM headquarters that opened on the base earlier this year was built on higher land and wasn't directly affected by the flooding. The building's design, including being surrounded by a barrier to reduce flood risk, also recognized the urgency to prepare for climate-related natural disasters.

Planning for a Changing Future

In 2018, the Defense Department released a survey that highlighted the security risks climate change posed to more than 3,500 military installations. Non-storm surge flooding ranked third on the list of most-reported severe climate-related events.

A Pentagon report released to Congress earlier this year warned that climate change threatened key bases. "The effects of a changing climate are a national security issue with potential impacts to Department of Defense missions, operational plans, and installations," the report said.

However, in a table in the report listing the risks faced by each of dozens of bases, Offutt did not report intermittent flooding as a risk. Critics in Congress said the report was inadequate.

Meanwhile, in its formal national security outlook released in December 2017, the Trump administration did not mention the risks of climate change.

As the floodwater starts to recede, Offutt Air Force Base will be dealing with the debris that washed in, as well as the damage flooding has caused inside buildings and to hangars, equipment and base infrastructure. Credit: 55th Wing Command

At Offutt, the focus now is on assessing the flood's damage and ensuring the base is more prepared for the next big storm.

Winkler said there is no question the $22.7 million fortification of the levees would have saved Offutt from much of the damage that likely will cost far more.

"Should we have built it faster? Yes," Winkler said. "But that's easy to say now."



Read more on the military and climate change in the ICN series Dangers Without Borders: Military Readiness in a Warming World