OMAHA, Neb. — More flood storage space in the Missouri River's reservoirs would have reduced — but not prevented — last year's devastating floods, the U.S. Army Corps of Engineers said Friday.
The corps said in a newly released report that there still would have been widespread flooding damage last year because of the massive volume of water that moved through the river.
It also noted that any increase in the amount of flood storage space in the reservoirs would reduce the economic benefits the river offers through barge traffic, recreation and hydropower. In fact, all the other uses of the river besides flood control require more water be held in reservoirs, not less.
But increasing flood storage space in reservoirs is just one option to reduce flood risk, and corps officials said it may not be enough.
"It's going to require a significant effort and investment over time if we're going to reduce risk," said Brig. Gen. John McMahon, commander of the corps' Northwestern Division.
Reducing the flood risk along the Missouri River over the long run might require changing the way communities and states think about development in the flood plain and widening the levee system to allow for more room in the channel, McMahon said.
Some of the same measures were recommended after past floods, McMahon said, but weren't done because they are costly and require significant political will.
"The 2011 event reminds us of what we learned just a couple decades ago after the 1993 flood," McMahon said.
Last year, flooding caused at least $630 million of damage to flood-control structures along the 2,341-mile-long river, and hundreds of thousands of acres of farmland were damaged along the river, which flows from Montana through North Dakota, South Dakota, Nebraska, Kansas, Iowa and Missouri.
Friday's report is part of the analysis being done to determine whether the corps needs to increase the 16.3 million acre-feet of space that is normally cleared out each spring for flood control purposes.
The report is designed to spur debate, not make a recommendation. Several other reports are expected to be completed before fall when the corps will develop next year's plan for managing the Missouri River.
Within hours of its release, the corps' report was being criticized. Iowa Rep. Steve King said it was flawed because it didn't consider how economic development and life along the river could be helped by better flood control.
"We must provide protection to those who live and work in the Missouri River basin so that life there can continue and redevelopment can take place," King said. "We cannot do that, however, with incomplete reporting from the corps."
Last year, heavy May rains in the Northern Plains combined with above-average snowpack caused the flooding, which began in June and continued into the fall in many places. In a normal year, 24.8 million acre-feet of water flows through the river. Last year, the record amount of runoff that moved through the Missouri River reached 61 million acre-feet, which is significantly higher than any other year since 1880.
The corps said there may be limited benefit to clearing out enough storage space each year to handle an amount of water equivalent to the 2011 flood because it was so unusual.
A report from outside experts released in December said the corps did the best it could in dealing with last year's record flooding, but the panel recommended several changes that could prevent a disastrous repeat.
The corps has been working to implement some of those recommendations, including updating the hydrologic studies it uses. But the corps says many of the suggestions require either detailed study or additional funding, so they can't be implemented right away.
So far, the Missouri River appears to be in good shape heading into the 2012 flood season thanks to a relatively mild winter and dry spring. Officials have said that nearly all of the planned storage space for floodwater remains free. The corps also predicts that runoff into the river this year should be about 94 percent of normal, although that could change.
Starting Monday, the corps plans to hold a series of public meetings in seven cities along the river to discuss this year's forecast and listen to any comments about the way it plans to manage the reservoirs.
Corps' latest Missouri River report: http://bit.ly/HDnC1V