Big Muddy digs in
Utilities spend millions as river bed drops.
Published Thursday, January 29, 2009
KANSAS CITY (AP) - The Missouri River is sinking.
And as engineers figure out why, the dropping river bed could eventually threaten billions of dollars in property development and the stability of levees and bridges. Itís already cost Missouriís largest city millions to ensure water for a half-million customers.
The problem is this: The Missouri River, in stretches from Rulo, Neb., to St. Louis, is losing elevation. Itís not affecting the amount of water in the channel, but the water is physically lower on the Earth because the river bottom is washing away.
Why itís happening has been a puzzle.
Because the water depth isnít really changing, the situation is nearly imperceptible to someone looking at the river from shore.
"Part of the whole problem is itís not visible," said John Grothaus, chief of the planning section for the U.S. Army Corps of Engineers in Kansas City, where the city has spent more than $4 million for pumps to reach lower river levels. "Itís not in the public eye, you canít see it on the river."
The cost for reversing the degradation - and whether thatís even possible - is still unknown. But the ultimate risk is to public infrastructure.
Scientists believe several spots - starting around the extreme southeastern Nebraska town of Rulo to the eastern Missouri community of Hermann - are experiencing some river degradation. But theyíre focused most on Kansas City because of the potential impact there.
When the river bed drops, it exposes more of the pylons holding up bridges. That decreases the support the foundation gets from being buried in the ground.
"You have to look if that were allowed to continue, what could be the problem that could occur," said Christina Ostrander, the corpsí project manager. "Right now you donít have a bridge that is in danger of failing, but if you were looking over the long haul, some kind of mitigation now could" be necessary.
Also at risk are levees, such as those separating the Missouri River from an estimated $20 billion in developments.
Federal data show that in the most problematic areas, the steam bed has dropped by about 12 feet over the last 50 years.
Since at least the 1920s there has been a gradual decline in the Missouri Riverís elevation, but the drop has been precipitous over the last decade.
Dredgers, the most frequent river travelers are sensitive about getting blamed for the degradation and are helping to fund an environmental impact study of their work.
Attorney David Shorr said the dredgers he represents see sediment filling the holes they dig within about a month. Shorr, who works in Jefferson City, said the corpsí river engineering projects are designed to cut down the river bottom.
"The corps is charged with the responsibility to create a navigation channel by Congress, they did that and did it well," Shorr said.
Itís unclear exactly why the Missouri River is sinking, though there are several possibilities:
● Less sediment.
● Natural processes. A river erodes land and gradually eases bends.
● Large floods that wash sand and soil out of the river.
● Commercial dredging.
● Human efforts to control the river. Levees and dikes also have confined the riverís natural flow.
The corps is betting that a preliminary study of the lower riverís degraded areas will bring more clarity.
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