The Associated Press
JACKSON, Miss. — The Coast Guard reopened the swollen Mississippi River north of New Orleans on Tuesday, allowing cargo vessels on the nation’s busiest waterway to pass slowly, one at a time in the latest effort to reduce pressure from rising floodwaters.

A 15-mile stretch at Natchez, Miss., was closed entirely earlier in the day, blocking vessels heading toward the Gulf of Mexico and others trying to return north after dropping off their freight. Had the channel remained closed, it could’ve brought traffic to a standstill up and down the river, which moves about 500 million tons of cargo each year.

That sort of interruption could have cost the U.S. economy hundreds of millions of dollars for every day of idled barges carrying coal, timber, iron, steel and more than half of America’s grain exports.

Coast Guard officials said wakes generated by passing barge traffic could increase the strain on levees designed to hold back the river. Authorities were also concerned that barges could not operate safely in the flooded river, which has risen to the level of some docks and submerged others.

“We’re closely monitoring traffic along the river and all vessels must stay to the center of the river,” Coast Guard Cmdr. Mark Moland said.

In Vidalia, La., across the river from Natchez, Carla Jenkins was near tears as she watched the first tows and barge move north after the reopening. “The water from the wakes just keeps coming into our buildings. We’re going to have a lot more damage,” said Jenkins, who owns Vidalia Dock and Storage.

Moland said the Coast Guard tested wake impact before making the decision. The tests indicated sandbagging and other measures to protect most of the area could withstand the wakes if the vessels were ordered to move through the areas at the slowest possible speed.

It’s not clear how long barges would only be able to move one at a time through the section. The river is expected to stay high in some places for weeks.

The Coast Guard did not have comprehensive figures on how many vessels were immediately affected, but the agency stopped at least 19 near Natchez.

In past closures, the numbers have grown quickly. In 2008, the agency halted 59 ships within a day of shutting down a stretch of the river near New Orleans because of a barge and tanker collision.

Shipping companies had hoped for a swift reopening.

On a typical day, 600 barges move up and down the river, according to a spokesman for the Mississippi Valley Division of the Army Corps of Engineers.