A blizzard battered North Dakota on Monday, threatening to create wind-whipped waves that could lash the patchwork levee system that has shielded much of Fargo from the swollen Red River.
Engineers scrambled to shore up the dikes in the hope of averting the latest potential disaster.
The winter storm was expected to bring up to a foot of snow and 30 mph winds that could weaken the levees with big waves. Officials acknowledged that no one knows whether the levees will withstand the punishment.
“The difficulty with an epic flood is nobody has been through it before,” city commissioner Tim Mahoney said. “You can't ask someone, ‘Hey, what's going to happen next?'“
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The Red River dropped to 38.96 feet Monday, nearly 2 feet below its peak but nearly 21 feet above flood stage. City officials have said they would breathe easier when the river falls to 36 or 37 feet or lower.
Authorities were not especially worried about the snowfall because flood levels will have dropped by the time it melts. But forecasters have warned all along that the river could still rise again. They believe the river could drop 2 more feet in the coming days before inching upward again.
Engineers are still worried that the levees could give way at any time, and they sent teams to vulnerable areas Monday to strengthen the system. National Guard members put sheets of plastic over the levees to shield them against waves.
Corps engineer Tim Bertschi said when water pressure gets strong enough, the sandbags can begin to shift, a weakness that surging water will quickly exploit.
Another potential problem is posed by large chunks of ice in the river's currents. When those chunks hit a levee, they can speed its erosion or punch holes in the plastic sheeting. Once water gets in, a levee becomes much more susceptible to failure.
Schools and many businesses were closed for a second week, meaning thousands of people are not drawing paychecks.
Flooding statewide was blamed for two deaths in what health officials said were apparent heart attacks brought on by exertion.