Earthen levees on Missouri River at risk

Josh Funk in STL Today via the AP: Experts say several levees along the Missouri River, especially older ones in rural areas, are at risk of failing this summer as massive amounts of water continue to flow through the river system from upriver reservoirs, but chances of such failures in urban areas remain remote.

So far, most levees have held along the 811 miles the Missouri travels from the last dam at Gavins Point in South Dakota to its confluence with the Mississippi River near St. Louis. But engineers who have studied past floods say the earthen levees in rural areas are at greater risk. "Most of the levees are agricultural levees. They're not engineered. They're just dirt piled up," said David Rogers, an engineering professor at Missouri University of Science and Technology.

A few levees have failed, but most of the flooding thus far has covered more than 560,000 acres of mostly rural land. The water has forced some evacuations, but the extent of the damage may not be clear until it recedes. That's not expected to happen until the fall as the Army Corps of Engineers says it needs to continue releasing substantial amounts of water from upstream reservoirs inundated with heavy spring rains and melt from an above average Rocky Mountain snowpack.

...The corps predicts the Missouri River will remain 5 to 7 feet above flood stage in much of Nebraska and Iowa and may rise as high as 10 feet above flood stage in Missouri until at least mid-August.

The corps predicts that the river will eventually rise high enough to flow over some 18 to 70 levees, mostly in rural areas of southeast Nebraska, southwest Iowa and Missouri. Other levees will become saturated, and water can erode their foundations, seep underneath or find other flaws to exploit....

Water flows from the Missouri River over levee L-550, located north of Highway 136 in Atchison County, Mo., June 19. The local sponsor reported overtopping of the levee to the U.S. Army Corps of Engineers the morning of June 19. The levee is in the Federal Program (PL 84-99) and is operated and maintained by a non-federal sponsor. It was constructed by the Corps in the late 1940s. (U.S. Army Corps of Engineers photo by Carlos J. Lazo)