From his office in Nebraska City, Dan Mauk can hear the pile drivers across the Missouri River, pounding steel beams into bedrock for a set of bridges in the Iowa flood plain.
It’s been music to his ears.
Last year, historic flooding shattered roads and levees across the region. The many closures disrupted lives, made travel more dangerous and dealt a blow to the regional economy.
Interstate 29 in Iowa and bridges in Nebraska and Iowa were closed multiple times from mid-March until early October. Nebraska City, a town of 7,100, was cut off from I-29 and neighboring communities in Iowa for a total of 124 days after Iowa Highway 2 flooded shut.
“It was pretty rough last year,” Mauk said. “We’re crossing our fingers for this year.”
That pounding that Mauk is hearing?
It’s a $34 million investment in reducing the likelihood that Highway 2 floods shut. The Iowa Department of Transportation is building a set of bridges over a low spot in the Missouri River flood plain. Road work being done elsewhere in the Missouri River Valley is elevating flood-prone sections of I-29 and reinforcing the shoulders of Interstate 680.
Despite these improvements, the system remains vulnerable:
- Some levees remain fractured, some haven’t been restored to their full height and even those that are fully rebuilt remain weak and vulnerable to erosion until a thick grass covering takes hold.
- Some highways in the flood plain still have low spots. Highway 2 on the Iowa side and U.S. 34 on the Nebraska side are among those with low spots vulnerable to ponding water.
“We’re aware there may be problems, and we’re monitoring everything,” Scott Suhr, transportation planner for District 4, said of concerns on the Iowa side. “At this time, there’s not a risk. We hope it stays that way.”
Last year was the second time in 10 years that historic flooding in the Missouri River Valley shut down Interstate 29 as well as travel between Nebraska and Iowa across the Missouri River. The previous year was 2011.
In 2011, the Iowa Department of Roads rebuilt I-29 and I-680 back to normal, but after 2019, the department decided to shore up the weakest links, Suhr said.
“We thought the flood would never happen again,” Suhr said of 2011. “Until obviously, 2019 happened.”
Austin Yates, the District 4 traffic operations engineer in Council Bluffs, provided the following update on the roads system in Iowa:
I-29 near Honey Creek
Damaged levees allowed floodwater to pool in a low spot in this area. The highway was shut down four times from March 14 to Oct. 7, for a total of 100 days, Yates said. To eliminate the low spot, the Iowa Transportation Department elevated about a mile of northbound I-29 an average of 14 inches, he said.
The southbound lanes weren’t elevated, he said. If the area floods, the agency plans to close the southbound lanes and route traffic head-to-head on northbound I-29.
The Interstate runs across the Missouri River Valley, so it is directly in the path of strong currents during flooding. After the March 2019 flood, the Department of Transportation decided to armor the sides of the Interstate to reduce the threat of erosion.
I-680 was closed three times last year for a total of 38 days from March 14 to Sept. 27. The Department of Transportation began placing Flexamat, concrete matting, on the shoulders of I-680 after the first round of flooding but had to stop when the river rose again.
Flexamat is used in coastal areas, and it proved itself on I-680 in the subsequent rounds of flooding, Yates said. I-680 was able to reopen in 2019 without the complete reconstruction required in 2011. Flexamat has also been placed along the interchange of I-680 and I-29.
I-680 also has several culverts that will allow floodwater to pass on downstream.
I-29 in north Council Bluffs
About 1,000 feet of I-29 in north Council Bluffs, between the 25th and 16th Street exits, has been vulnerable to flooding. It was covered with water for only a few days last year, but that was enough to cause problems in Council Bluffs because Interstate traffic was routed through a residential neighborhood.
Both northbound and southbound lanes were raised, in some areas as much as 28 inches, Yates said. If a closure is necessary this year, this improvement allows the department to route traffic onto 16th Street, an arterial road that can better accommodate heavy traffic.
The most vulnerable area on this highway that crosses the Missouri River is a low spot on the Nebraska side. The Nebraska Department of Transportation isn’t expecting Highway 34 to flood, said Jeni Campana, a spokeswoman. “But it’s an area we’re watching.”
Highway 2 bridges
Because of an unusual design, going into 2019, the levee protecting an elevated Highway 2 roadbed on the Iowa side jutted into the Missouri River Valley in a horseshoe fashion. This created a pinch point, or narrowing of the river valley, and was blamed for worsening flooding by backing up water from Highway 2 upstream to the Platte River.
The roadbed has been removed and is being replaced by bridges across the flood plain. (With the roadbed gone, the levee could be straightened, which eliminated the horseshoe pinch point). As a result, floodwater will be able to flow downstream under the bridge instead of backing up behind an obstruction. Traffic is already moving on the eastbound bridge. The westbound bridge is expected to open in June.
SW Iowa interchanges
Three interchanges are still closed in southwest Iowa: the Bartlett, McPaul/Thurman and Percival exits. Those closures are due to heavy damage to county roads, not problems with I-29, Yates said. The traveling public is not as affected by these closures as are the communities along the Interstate. That’s because gas stations and restaurants weren’t right at the interchanges before the flood.
The state will reopen the interchanges when the county roads are repaired. Until then, exiting traffic would have nowhere to go, so the ramps are being kept closed.