Luke Thomas and Air Force Tech Sgt. Vanessa Vidaurre at a flooded portion of Offutt Air Force Base. In March, historic flooding included breaches of two levees protecting the base from the Missouri River.

NORTH SIOUX CITY, S.D. — Three historic floods on the Missouri River — 1993, 2011 and 2019 — have made it clear that something needs to change if flood risks are going to be reduced on the lower half of the river.

Not enough changed after 1993 and 2011, as this year’s flooding made abundantly clear.

So the affected states — Nebraska, Iowa, Kansas and Missouri — are joining with the U.S. Army Corps of Engineers to undertake a multiyear study of options to reduce flooding on the lower Missouri.

Brig. Gen. D. Peter Helmlinger, commander of the Northwestern Division of the corps, cited the study as part of the path forward during Wednesday’s U.S. Senate field hearing on Missouri River management. Sen. Mike Rounds, R-S.D., hosted the hearing.

“We need to do something different from just rebuilding the systems we have now,” Helmlinger testified at the hearing. “What that something looks like, I can’t speak to the details.”

Already the corps has spent more than $1 billion repairing levees along the river, and that’s with about two-thirds of known projects accounted for.

The Missouri River is home to North America’s largest reservoir system, six massive dams on the upper river. Below those dams is an extensive network of levees and other structures that work to constrain the river.

But as this year’s historic flooding proved, none of that was any match for nature. Most of the rain and snow fell below the flood-control dams, and such a glut of flooding poured into the Missouri River basin that 350 miles of levees were damaged, Helmlinger said.

“(The flood) demonstrated that we have insufficient capacity to carry water safely through the lower basin,” Helmlinger told Rounds and the approximately 50 people gathered for the hearing in City Hall at North Sioux City.

The four affected states are in the midst of agreeing to the jointly funded study, which will likely take a couple of years to complete, Helmlinger said.

Some solutions are more feasible than others, but the list of options includes higher levees, a wider flood plain (moving levees farther out), additional dams and fewer chokepoints, Helmlinger said.

Other options that have been discussed at the local level include moving homes and businesses out of harm’s way.

Already, the states have begun working with the corps on a study of chokepoints, those obstructions along the river that cause water to back up. Typically these are bridges and related infrastructure.

Highway 2 in Iowa has been one such chokepoint, and Iowa has expedited its replacement after this year’s flood. At a cost of about $34 million, that bridge is being replaced with one that is wider and provides more room for water to flow under it.

Similar chokepoints exist farther downstream, including the old Plattsmouth bridge.

Higher levees will cost more money, and if the plan produces that as a solution, those long-term improvements won’t slow down existing repairs, Helmlinger said.

Giving the river more room to roam by moving levees farther away from the water is controversial because it means buying up farmland. Helmlinger said purchasing land for any levee setbacks would be done with willing buyers.

“We’d want to work with willing individuals who are ready to sell land to improve the flood plain, and we know there would be individuals against that,” Helmlinger said.

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Dams aren’t high on the list of probable solutions, Helmlinger said, for two reasons. First, they’re costly, and second, most of the good dam sites already have been taken. If dams were built, they would be along tributaries, not the main stem of the Missouri.

Public input will be part of the process, Helmlinger said in response to a question from Rounds.

“It seems to me if I were a landowner or lived along the river, I’d be concerned … I’d lose some of my property based on new recommendations,” Rounds said.

Rounds pushed for two issues that he believes will help.

First, Rounds said the installation of a system of 600 snow-water sensors in the plains along the Missouri River is overdue. The system, which measures the water content of snow, is needed so that the corps can more accurately estimate spring runoff. The sensors have been on the drawing board for some time, but have been delayed by lack of funding. Those delays have driven home the need to tie funding to projects so that the money can’t be spent elsewhere, Rounds said.

John Remus, chief of water management for the Missouri River Basin/Omaha District of the corps, told Rounds that the first phase of that system is getting underway and as soon as sensors are installed, the corps will begin drawing data from them. That means this winter the corps will begin getting data — albeit a limited amount — on the amount of water bound up in Plains snowpack.

Second, Rounds said he’d like to see the corps match water releases from the dams to long-term cycles of dry and wet years — in other words, the corps should have been releasing more water earlier this year and more than normal through the winter given that the region in the midst of a years-long wetter than normal cycle.

“(The corps) does too much based on an average,” Rounds said. “It appears to me that you could have bigger tools if you make the assumption we’re in a wet cycle.”

Helmlinger and Remus said it’s not possible to make annual decisions based on years-long weather patterns. However, the corps can make adjustments based on short-term forecasts such as an expectation of a wet spring or summer.

Historic wet years can be followed by historic droughts — that was the case in 2011 and 2012, when the Missouri River basin swung wildly between extreme runoff and extreme drought, Remus pointed out.

Release too much water during a wet year and you might not have enough water in the reservoirs to release downstream in dry years — even though that water is needed for downstream operation of such things as nuclear- and coal-powered electric plants, municipal water supplies and barge travel.

Corps officials told Rounds that changing the river’s management based on trends would require a change in the Master Manual, the guidebook to the river. That’s politically divisive and takes years because of competing interests on the river.

Rounds himself said after the hearing that he didn’t think the Master Manual would be reopened, despite pressure from some riverside property owners to do so.

”Not at this point,” he said.

This report includes material from the Associated Press.