Preparing for worst-case flood

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A catastrophic levee breach on the Missouri River could force mass evacuations of nearly half of the people living in Council Bluffs.

Eppley Airfield in Omaha could find itself under 10 feet of water.

And the Gallup campus on the Nebraska side of the river could become an island.

As waters rise, city officials in Omaha and Council Bluffs hope for the best while preparing for the worst. For the worst to occur, it would take a mountain of “what if” developments: destruction of the levees, and rainfall of biblical proportions over the cities and to the north. But time to plan is one luxury that city officials have during this summer of forced floods.

Unlike the devastating Iowa floods of 2008, no one is getting taken by surprise. That year, torrential rains fell on already saturated soil and swelled tributaries, topped levees and devastated huge portions of Cedar Rapids and Iowa City.

“They had only slight warning — two days — there was going to be a problem. I don't think anyone knew how bad the problem was going to be,” said Elwynn Taylor, a climatologist with the Iowa State University Extension Office.

Officials in Omaha and Council Bluffs have known for weeks about the coming floodwaters systemically being released from dams in Montana and the Dakotas. They have had time to prepare.

Council Bluffs is developing evacuation plans for nearly 30,000 people, while Omaha has ordered 28 industrial water pumps to help keep low-lying areas along the river dry. On both sides of the Missouri, officials are focusing laser-like attention on the levees, ready to jump if one shows any signs of weakness.

In the event of a large-scale levee breach, Council Bluffs and the city of Carter Lake would get hit hardest. Carter Lake would literally become a lake, as would the region known as Lake Manawa.

Downtown Omaha, which is built on higher elevation, would remain largely dry, according to flooding estimates released by the Army Corps of Engineers. The bulk of flooding in Omaha would be confined to areas along the riverfront, notably Eppley Airfield and some parts toward the southern end of Offutt Air Force Base.

Omaha businesses along the riverfront could experience some flooding, but likely less than catastrophic. Both ConAgra Foods, with its riverside campus, and Union Pacific, which has a dispatch center along the river, expect no major problems — even in the event of a levee breach. Both, though, are closely monitoring the river's rise.

“We have a number of contingency plans in place. It's better to be prepared,” said Dave Jackson, a ConAgra spokesman.

The news is even better for sports and music fans.

The Qwest Center Omaha and the new baseball stadium, TD Ameritrade Park, likely would escape a levee breach unscathed. The two were built on ground high enough that the flooding would be contained to the parking lots, said Terry Atkins, a civil engineer with Lamp Rynearson & Associates, the engineering company that worked on both projects. The structures also are protected by pumps.

The worst news would be for travelers and businesses on both sides of the river that rely on Omaha's airport to bring in goods and business executives.

Eppley Airfield is one of the city's most threatened — and valued — pieces of infrastructure. The airport contributes an estimated $745 million a year to the local economy, and a shutdown of weeks or months could hit the region's economy hard.

The airport faces two risks: a potential levee breach and elevated groundwater levels.

If the levee breaks, much of the airport could be under water.

A key current threat is water that bubbles up from underground that could, under worst-case scenarios, cover the airport's runways and overrun parts of the terminal — though airport officials have pumps to clear pooling water.

Levee failures top the list of potential concerns for Omaha and Council Bluffs. The 1950s-era levees are being put to a high-risk test. They will be under stress much of the summer, as federal officials release water from swollen dams upstream.

The water level on the Missouri is expected to hit a peak of about 36 feet and hold at a high level for two months or more, putting unrelenting pressure on the 42-foot-high levees.

The longer the flooding lasts, the riskier it becomes.

“It's just common sense. The longer you have pressure on anything, the more stress you have,” said Marty Grate, environmental services manager with Omaha's Public Works Department.

Levees aside, another big fear is rain.

Heavy and unseasonable rainfall in Montana and the Dakotas could put devastating pressure on upstream dams and swell the Missouri even higher. Soils in the upstream states are as saturated as a wet sponge, and any additional rainfall will come south, said climatologist Taylor.

“Everything that falls upstream is coming down,” he said.

Heavy rains in Omaha and Council Bluffs also could cause problems, especially if Omaha is forced at some point to shut down floodgates used to drain rainwater from the city into the Missouri River.

Most of the floodgates remain open but may have to be closed at some point, Grate said.

The threat of rain comes with a lot of “what ifs,” including how much, how long it rains and where it falls. If more than 10 inches is dumped near the river downtown over the span of a day, the area could flood; but such rains are “unlikely,” and the city would quickly deploy its pumps, Grate said.

The city has hired an engineering firm to run several computer models on what could happen if there were a sudden downpour on the city and the floodgates were closed.

It is part of Omaha Mayor Jim Suttle's effort to stay “ahead of Murphy's law.”

“This is uncharted water — no pun intended,” Suttle said.

The model also will show exactly what low-lying areas will need help in the event of a massive rainstorm, allowing the city to deploy water pumps to vulnerable areas. (The city has purchased or leased an additional 28 water pumps to the four it currently owns. Each can handle about 6,000 gallons a minute.)

One early model shows the Magellan tank farm along the road to the airport — the huge white tanks that hold gas — vulnerable to pooling water in the event of a 2-inch rainstorm, Grate said. Another shows ConAgra vulnerable to pooling water, he said.

Though the cities are planning for the worst, officials in both Omaha and Council Bluffs said they have high hopes the levees will hold and the crisis will end without any “what ifs” becoming reality.

The evacuation plan to move 30,000 people out of Council Bluffs might never be used, but it's best to have a plan in case entire neighborhoods have to be evacuated and emergency centers need to be established, said Art Hill, a city spokesman.

Bluffs officials are putting the finishing touches on how the public would be notified of a levee breach, and how the elderly and the infirm would be transported.

The planning is all-consuming and can be fine-tuned throughout the coming months as the Missouri River hovers at flood stage, spawning a tense summer for Omaha and Council Bluffs.

“This is a disaster of a magnitude they haven't prepared for in the past in Council Bluffs,” said U.S. Rep. Steve King of Iowa. “They've done all the planning they can and planned for an orderly evacuation in the event that something goes wrong.”

World-Herald staff writer Juan Perez Jr. contributed to this report.

Contact the writer:

402-444-1309, robynn.tysver@owh.com

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View the fast-moving floodwaters near Blair, Neb., shot by World-Herald Videographer Kyle Benecke. On Friday, it was a newly-planted cornfield, by Saturday morning the Missouri River had taken over.

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This is the first time Lake McConaughy's morning glory emergency spillway flushes water out of Nebraska's largest reservoir in its 70-year history. The spillway released about 2,000 cubic feet per second Thursday.

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