Historic Missouri River bridges resist wider flood corridor
Bridges at Brownville, Plattsmouth described as pinch points
NEBRASKA CITY – U.S. Army Corps of Engineers experts gathered at Nebraska City Wednesday to explain a developing resilience study for the Missouri River downstream of Sioux City, Iowa, and how pinch points at River Country bridges might be eliminated.
The historic truss bridge at Brownville was closed for 216 days during the catastrophic flooding of 2019 and corps engineers said they are working with transportation departments in both Nebraska and Missouri to see how the 87-year-old structure might fit into plans for flood control in the future.
The study offers eight alternatives, including recommitting to Pick-Sloan legislation of 1944 to make sure there are 3,000 feet between levee systems. Hydraulic Engineer Paul Boyd explained that width of the flood corridor would grow to 5,000 feet before the river reaches St. Louis.
Boyd: “This increased conveyance alternative was looking to get that at minimum. In a lot of places it was already 3,000 feet wide, in some places it was 2,000 feet wide, so we would only have to widen it a 1,000. The Plattsmouth bridge is a major constriction point. It’s only 1,100 feet wide. So the conveyance width there is roughly a third of what the idea was.”
The corps expects recommendations from the Nemaha County/Atchison County spin-off study later this year.
Iowa used overflow bridges to remove the Nebraska City pinch point at the Highway 2 bridge and similar construction may be needed if the Brownville bridge is to stay open. Farmers say raising the level of Highway 136 will not solve flooding risks because floods in 2011 and 2019 washed the road out.