Iowa-like rain could swamp Lincoln

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By DEENA WINTER / Lincoln Journal Star

At first glance, Lincoln seems like a dry place; no big lakes or rivers running through town, no oceans lapping at its edge.

No Mississippi River to swallow the city.

Just innocuous Salt Creek meandering through town.

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A man makes his way under the overpass of 48th and Cornhusker Highway on June 11. (LJS File)

A man makes his way under the overpass of 48th and Cornhusker Highway on June 11. (LJS File)

But 11 creeks converge with Salt Creek in Lincoln, draining more than 1,000 square miles — all pointed like a gun at the heart of Lincoln. That’s why the city has battled more than 100 floods since 1900, 17 of them major, two of them catastrophic.

While the 10 dams and levees built in the Salt Creek watershed in the 1960s reduced flooding, Lincoln’s earthen berms can only handle up to a 50-year storm.

So Lincoln’s 19 square miles of low-lying areas could be under water if the city were hit with the kind of storms that have battered states to the east.

“We do have the potential to have some significant flooding in Lincoln,” said Nicole Fleck-Tooze of the public works department. “It’s not a matter of if it will happen, but when it will happen.”

Lincoln is protected by a 7-mile-long levee along Salt Creek that was initially designed to withstand 100-year storms.

But detailed floodplain mapping in the late 1970s led the feds to conclude they wouldn’t stand up to a 100-year storm, assuming all those streams peaked at the same time.

What’s a 100-year storm? About 5.5 inches of rain dumped within 24 hours, spread across about 100 square miles (Lincoln’s about 80).

Water has been on the brain a lot lately, with a spate of downpours, an eye on floods to the east and a federal report on global weather changes indicating extreme weather — including downpours — will become the norm in North America.

Fleck-Tooze’s department spends a lot of time and money trying to update flood plain maps, preserve flood storage areas and minimize risks for homes and businesses.

City Council members have recently questioned the cost of such work, but floods have a way of washing those concerns away and replacing them with questions about whether a community and feds did all they could. Monday-morning quarterbacking is common after a flood, but people aren’t as interested in the game plan before.

“Until you get a really major flood event … it’s hard for people to picture it in their mind,” Fleck-Tooze said.

So picture this: If Lincoln were to have a 100-year storm, portions of the University Place, East Campus, Russian Bottoms, Malone and Clinton neighborhoods would likely go under water.

Also, the area around Beal Slough — from 14th Street to 56th Street along Nebraska 2. And the area north of the stream called Dead Man’s Run from North 33rd to 48th streets would be “very vulnerable,” said Glenn Johnson of the Lower Platte South Natural Resources District, which is responsible for flood control in Lincoln.

“Lincoln’s vulnerable to flooding,” Johnson said. “We’re in a situation where if we had storms of the magnitude in Iowa and Wisconsin, we probably would’ve seen water going over the top of the reservoirs. They’re not designed for back-to-back days of six inches of rain.”

The great 1908 flood in Lincoln — which killed nine and left 1,000 homeless — is believed to have been a 100-year storm.

And when eastern Nebraska flooded in 1950, killing 14 people, that was considered more than a 50-year flood.

Some water began coming out of the banks of Stevens Creek in east Lincoln during recent storms. Heavy rains earlier this month caused localized flooding in Hickman and southeast Lancaster County. Dams were filled and operating through the emergency spillways.

The second week of downpours caused “pretty good flows” in Antelope Creek and the conduit at N Street was within 4 to 6 inches of filling, Johnson said. Once the conduit fills, the water would begin flooding into adjacent areas as it did during the Midwest flood of 1993.

And there’s a chink in Lincoln’s flood armor: The Salt Creek levee was built with dispersive clay, high in calcium, a mineral that erodes and dissolves when it comes into contact with water.

Holes started appearing in the levee in the 1970s. That clay, and the fact the levee wasn’t built high enough, led to its decertification as providing 100-year protection.

The NRD monitors the levee and when holes are found, they’re filled with non-dispersive clay. Fortunately, Johnson said, the holes generally work their way toward the channel, rather than the other direction.

There has been talk of raising the bridges across Salt Creek a couple of feet to improve flood protection, but the cost would be “astronomical,” Johnson said.

Fleck-Tooze said the city is looking at less-costly alternatives, such as upstream detention.

During big storms, NRD employees drive up and down levees in the dark, making sure there’s no seepage.

Johnson, who has worked for the NRD for 36 years, leads one of the teams that monitors levees. If it ever overtops, he’ll be making some unpleasant phone calls.

“Knock on wood,” he said, “I haven’t had to make that call yet.”

Reach Deena Winter at 473-2642 or dwinter@journalstar.com.