Corps: More flood storage offers limited benefit

Friday, April 13, 2012
FILE - This June 29, 2011, file photo taken near the Iowa/Missouri state line shows Missouri River floodwaters mixed with sediment. The U.S. Army Corps of Engineers said Friday, April 13, 2012, that more flood storage space in the Missouri River's reservoirs would have reduced -- but not prevented -- last year's devastating floods. (AP Photo/The St. Joseph News-Press, Eric Keith)

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 it may not be enough. The report said officials may need to consider increasing the capacity of the Missouri River channel and reducing development in the flood plain.

"The reallocation of space in the reservoirs itself is not going to solve the problem," said Brig. Gen. John McMahon, commander of the corps' Northwestern Division.

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. Several other reports are expected to be completed before fall when the corps will develop next year's plan for managing the Missouri River.

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.

So far, the river appears to be in good shape heading into the 2012 flood season because of a relatively mild winter and dry spring. Officials have said that nearly all of the 16.3 million acre-feet of the planned storage space for floodwater remains free.

The corps predicts that runoff into the Missouri River this year should be about 94 percent of normal, although that could change.

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.

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Online:

Corps' latest Missouri River report: http://bit.ly/HDnC1V

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