Overton, Mo. Scientists, government officials and environmentalists agree that a two-decade-long project to restore Missouri River habitat helped reduce flooding last month. They just don't know how much.
Although the Missouri River had flooded since the U.S. Army Corps of Engineers began the project - working with state and federal conservation departments in Iowa, Kansas, Missouri and Nebraska - it wasn't until recently that the project was big enough to do much to control flooding.
Last month, a series of storms dumped a half-foot of rain in some parts of Nebraska, Kansas and Iowa over several days, flooding tributaries and pushing the Missouri River to flood stage. The conservation project areas and levee breaks in western Missouri allowed floodwaters to spread out on the river's flood plain, creating longer but lower crests downriver.
"Did it make a significant difference overall? Probably not. Did it make localized differences? Absolutely," said Mike George, the corps' project manager.
The conservation project aims to fix some of the changes made to maintain navigation on the river. The project includes eliminating and moving some levees to open up shoreline for wetlands, river-bottom hardwood forests and prairies and widening the river's channel by cutting chutes and notches into the riverbank to create shallow, slow-moving water for fish.
After last month's storms, conservation officials in each of the states bordering the lower Missouri River reported at least some flooding in the conservation project areas. But exactly how much of the land flooded and how that affected flooding elsewhere is still unknown.
Corps hydrologist Mike Chapman said there is preliminary evidence that the project reduces flooding, but it will take computer modeling to determine how much water went into conservation project areas and how that affects conditions downstream.
"The only way of knowing for sure is with a computer model. Anything beyond that is speculation," he said. "It's correct to say, though, that there is some benefit, but to quantify that without a model study is a stretch."
Chapman, the corps' river engineering and restoration section chief, said the project's biggest effect on flooding was likely from efforts to widen the river's channel, which allows the water to spread out rather than pile up.
Washington University geochemist Bob Criss, who studies river floods, said disasters were prevented in many areas. He said a measuring station at Glasgow - about 225 miles from where the river pours into the Mississippi River north of St. Louis - recorded flows at the same levels as the Great Flood of 1993. But just 30 miles downstream, he said, there was a lot less water.
"We lost several hundred thousand cubic feet of water," Criss said. "This is like the average flow of the Mississippi River at St. Louis disappeared at that part of the river."
He noted that the water also seemed to move more slowly than in the past, helping reduce flooding and lowering the peak.
'Heck of a lot of water'
David Galat, an ecologist with the University of Missouri-Columbia, said while it makes sense that permitting floods in uninhabited areas reduces severity in areas protected by levees, he believes the zeal to justify conservation efforts has led some to push that benefit more conclusively.
"It's a lot harder to really prove it. There's a heck of a lot of water out there and you would have to flood a lot of land," said Galat, who specializes in large river ecology.
Congress first authorized the habitat restoration program in 1986 to help offset decades of river management practices in the lower Missouri River basin that rounded off sweeping bends and deepened channels to aid boat traffic at the expense of wildlife.
In its most recent annual report on the habitat project's progress, the corps predicted the entire habitat project will cost more than $2.6 billion.
The U.S. Fish and Wildlife Service estimates that 500,000 acres of river habitat were lost by straightening sweeping curves to help navigation. The habitat mitigation project is allowed to turn 166,000 acres of shoreline into wildlife areas in the lower Missouri basin. So far, about 47,000 acres have been set aside for the project.
"We put the river in a strait jacket, and now, we're just starting to loosen the controls on it," said Gene Zuerlein, a fisheries biologist for the Nebraska Game and Parks Commission.