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Health, Science, Environment

'Slow-motion tsunami' headed down the Missouri River

This article first appeared in the St. Louis Beacon, June 3, 2011 - Some call it a slow Big Muddy tsunami. Others speak of "historic levels" of water releases from the river's giant reservoirs. And a few fear a "man-made natural disaster" if heavy rains add sudden strength to those historic discharges.

Whatever the surge of muddy floodwater that the Missouri River eventually ends up delivering into the Mississippi River at St. Louis, the next few weeks promise to bring plenty of drama -- and hopes for dry weather.

The Lower Missouri crests, anticipated later this month, will result from record snowfalls in the Rocky Mountains and rain in the upper Great Plains -- both of which are part of the 2,341-mile-long Missouri River's massive watershed, which drains 530,000 square miles.

As the snow melts into tributaries that drain into the Big Muddy, the Army Corps of Engineers is usually able to retain much of that water in a series of six giant reservoirs in the Upper Missouri and release the water in a way that prevents major ups and downs.

But as those reservoirs are filled nearly to capacity, the Missouri River Basin Water Management Division announced that it would be forced to release water at near-record levels starting this week and perhaps peaking in mid-June.

Because water takes about a week to get from the southernmost reservoir to the St. Louis region, the expected high water would not hit this area until late June -- and the potential for flooding, according to the National Weather Service, will depend partly on how much rain falls in the meantime and how high the swollen Mississippi is when its sister river delivers its surge of water from the Northwest.

"It truly may be a tsunami that comes rolling through the Missouri river valley," warned U.S. Rep. Blaine Luetkemeyer, R-St. Elizabeth, whose district includes much of the Big Muddy's floodplain in central and eastern Missouri.

While such a river surge would be much slower and more predictable than post-earthquake ocean waves, Luetkemeyer told the Beacon on Thursday that he had called the commander of the Corps' Northwestern Division, Brig. Gen. John McMahon, to discuss what might be done to mute the impact in Missouri.

Corps officials say they are doing everything possible to regulate the river discharges, but the reservoir spigots had to be opened  this week to prevent severe damage to the dams. Jody Farhat, who runs the Missouri River Basin's water management division, said Thursday that the reservoirs are expected to release a record 150,000 cubic feet a second (cfs) from five of its reservoirs by mid-June. The average release in June usually ranges from 70,000 to 90,000 cfs.

"It's a historic event based on historic inflows to the Missouri River system," said Col. Robert Ruch, who commands the Corps' Omaha district. He said the May inflow was the second-highest total recorded since 1898, exceeded only in 1952. Across the basin, Ruch said the Corps already has supplied 12 million sandbags and a dozen large pumps to help minimize flood damage in cities such as Pierre, S.D., and Sioux City, Iowa.

Col. Anthony J. Hofmann, who heads the Corps' Kansas City district, told government officials late Thursday that "preparation continues for a flood event on the Lower Missouri," with discussions with state and local officials, as well as amassing more than 2 million sandbags and other supplies to help with the anticipated flooding.

Heavy Rain in June Would Worsen Flooding

While it is difficult to predict the exact outcome of the reservoir discharges on the Missouri as it nears St. Louis, all sides agree that heavy rains would complicate the situation.

"The Corps has a plan worked out to try to keep the flooding to a minimum, but if we get heavy rain, all bets are off," Luetkemeyer said.

His concerns are shared by state officials. On Thursday, Missouri Gov. Jay Nixon, a Democrat, warned at a press conference in St. Joseph -- where the river may crest as high as 15 feet above flood stage -- that "Missourians will be facing imminent flooding along the Missouri River and additional rainfall and snowmelt in the watershed will only worsen the situation."

St. Joseph's representative in Congress, Rep. Sam Graves, R-Tarkio, who represents much of northwest Missouri, said this week that "the volume [of water] set to come downstream right now will amount to a man-made natural disaster. I want to find out if there is any extra capacity that can be used upstream."

Graves said he wants the Corps to take a second look at all their options. "The answer is not simply to release more water and create larger floods downstream," he said in a statement. "The impact on farmers and landowners all along the Missouri is going to be tremendous if they carry out this plan."

National Weather Service hydrologists in the St. Louis area said this week that it is a bit too early to predict the level of water in the Missouri River as it nears the Mississippi confluence. In general, they say, a dry June would limit floodwaters, but heavy rains could produce moderate to severe flooding. The discharges from the reservoirs upstream are likely to raise Missouri levels by 3 to 4 feet this summer, officials said, with higher crests possible if there is heavy rain.

The Missouri River Basin page of the National Weather Service's River Forecast Center shows the current and predicted river stage levels all along the river until it merges into the Mississippi River above St. Louis.

The struggle over managing Missouri River levels has been going on for decades, even before the big upstream dams and reservoirs were built a half century ago. The Corps, with varying instructions from Congress, has sought to respond to often conflicting demands of ecology, recreation, commerce and flood control on the river.

The Corps was sharply criticized for the way it managed those reservoir releases during the Flood of 1993 -- when high water on both the Missouri and the Upper Mississippi rivers converged with devastating consequences in the St. Louis region. Since then, levees along the Missouri River in the region have been strengthened, meaning that it would take a massive flood to overtop them.

"They are looking at possible Missouri River flood levels approaching the 1995 and 1993 floods -- depending partly on how many levees up north are holding," Luetkemeyer told the Beacon. Depending on how many levees are topped along the Upper Missouri, he said, "we could get to levels in the Lower Missouri that we've seen only a few times in our history. Hopefully, that won't happen."

One cautionary approach that may be taken by the Corps and Ameren -- which operates big hydroelectric dams on Big Muddy tributaries in central Missouri -- is to lower levels in some of those reservoirs now so that they could hold back more water later.

"Right now, for instance, they are allowing as much water as they can out of the Bagnell Dam and the Truman Dam," which control water levels at the Lake of the Ozarks and the Truman Reservoir, Luetkemeyer said. The goals are "to draw them down now as much as they can, so that the water from the Osage River in central Missouri does not add to the problem from there to St. Louis."

Such downstream tactics may be needed later this month because the Corps has only limited options on its near-capacity reservoirs upstream. Those reservoir releases will continue for many weeks, Corps officials say, as the snow melt is just beginning in the Rockies.

"All this planning could be blown apart if we get another stretch of heavy rain here in Missouri" and in nearby states. "In the last several years, June has been the wettest month of the summer," Luetkemeyer said.

"We're contacting all of the county and city officials along the river in my district and of course state officials are also working on the problem. We need to get the word out so people along the river can prepare for what's going to happen."

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