As several rivers across Midwest and Great Plains are set to crest, a federal judge in Cape Girardeau, Mo., has given the US Army Corps of Engineers the green light to blast openings in a levee along the Mississippi River to ease the flood risk to cities and towns downstream.

The approach highlights a tool that hydrologists and environmental groups have advocated for years to reduce long-term flood risks: removing levees at strategic locations to allow floodwaters to spread into a river's flood plain.

It's a strategy being adopted elsewhere, notably in the Netherlands. Its advocates say it not only relieves stress on the remaining levees by lowering flood heights upstream and downstream, but it could also reduce the amount of soil and nutrients spring floods flush into the Gulf of Mexico. Researchers point to the nutrient runoff as the culprit behind a dead zone that builds each year off the Louisiana coast.

But the notion runs afoul of residents – including farmers who work the fertile flood plains – who see the levees as sentinels protecting their homes, farms, and businesses.

"The big challenge to doing this is the fact that these flood plains are privately owned. People have made significant investments, including generations of families' time, turning them into productive farms," says Jeffrey Opperman, an ecologist and a senior adviser to The Nature Conservancy, which is testing the concept along the Ouachita River, a Mississippi River tributary, in northern Louisiana.

Any successful approach, he says, must be "very consistent with private-property rights."

The Corps has yet to decide if it will go ahead with the plan. But its preparations for routing water onto the flood plain on the west bank of the Mississippi between Cairo, Ill., and New Madrid, Mo., highlights the challenges.

The Missouri plan

Spring snowmelt from record winter snows in the northern US are coursing down the Mississippi, while the storm system that devastated the South brought heavy rain to an already saturated Ohio Valley. This is feeding into the Ohio River, which meets the Mississippi at Cairo.

Ordinarily, during peak flows, the Ohio River – which also receives flow from the Tennessee River – sends roughly 10 times more water into the Mississippi River than the Mississippi above the junction provides. This year's snowmelt and storms have only added to that influx.

At the center of the debate is the Bird Point–New Madrid Floodway, a 130,000 acre patch of farmed river bottom designed as a flood-control tool. The floodway is one of three located along the lower Mississippi river. They were established after a Mississippi flood in 1927 killed nearly 250 people across 10 states, an acknowledgment that under severe conditions, levees alone were unlikely to keep floodwaters at manageable levels.

The floodway is flood-plain land bounded by two levees that form essentially a giant tub, with an open outlet at the southern end. Already, rising floodwaters near New Madrid have started to back into the tub from its "drain," according to residents.

When floodwaters rise too high, threatening to overtop levees protecting cities and towns upstream and downstream, the Mississippi River Commission has the authority to ask the corps to use explosives to open an inlet to the tub on its northernmost end. Floodwaters are forecast exceed levels reached during the 1927 flood and another devastating flood 10 years later.

The 130,000 acres that would be affected by the decision fall within Missouri, whose attorney general filed suit in federal court earlier this week as the Corps began to move barges into position to prepare and install the explosives. His counterparts from Illinois and Tennessee, with riverside cities threatened if floodwaters rise to the forecast levels, intervened on behalf of the Corps.

During a meeting Wednesday, the head of the Mississippi River Commission, Maj. Gen. Michael Walsh, told unhappy residents who live inside the floodway that the levee system at Birds Point has never seen the amount of pressure floodwaters are putting on it, according to local press reports of the meeting. Those conditions are forecast to linger for up to 10 days. The floodway is home to some 200 people.

The Corps is doing all it can along the tributaries feeding the Mississippi and Ohio Rivers to reduce the flows, Walsh said.

In a 12-page ruling, federal district court judge Stephen Limbaugh Jr., denied Missouri's plea for a temporary restraining order against the Corps, noting that "the Corps is committed to implementing the Plan 'only as absolutely essential to provide the authorized protection to all citizens.' Furthermore, this Court finds that no aspect of the Corps’ response to these historic floods suggests arbitrary or capricious decision-making is occurring."

Experiment on the Ouachita River

While the region holds its collective breath to see how the floodwaters behave, a project planned from the outset to control floods and restore the ecological health of the flood plain is underway along a stretch Ouachita River in northern Louisiana.

The project involves some 16,000 acres of land surrounded by a ring levee some 16 miles long and 30 feet high. Its potential for flood control became obvious in 1991, when record flooding on the Ouachita breached the levee and filled the man-made basin. Within 24 hours of the breach, river levels at Monroe, La., 20 miles downstream had dropped markedly, says Joseph McGowan, manager of the Upper Ouachita National Wildlife Refuge, which oversees the tract.

The US Fish and Wildlife Service bought the tract with financial help from the Nature Conservancy to reforest the area and incorporate it into the wildlife refuge. But after heavy rains periodically filled the basin, drowning many saplings, the FWS and TNC breached the levee in multiple places to restore more-natural flows.

Costs prevent the removal of the entire levee, and flood waters aren't like to wash it away – potentially complicating the task of returning the land to the mix of plant and animal life that existed prior to it becoming farmland in the 1960s, acknowledges John Carr, a biologist at the University of Louisiana at Monroe, one of several scientists undertaking a long-term monitoring program to track the tract's ecological health.

Still, the land will do what the Army Corps of Engineers hopes the Bird Point–New Madrid Floodway will do farther upriver. Says Dr. Carr: "It will hold a lot of water."