But he said the Mississippi at Vicksburg is challenging for southbound vessels, mostly barges carrying grain and other products from the nation's heartland.
Southbound tows must travel faster than the flow of the water for their rudders to steer effectively. At Vicksburg they must negotiate a 120-degree turn on the meandering Mississippi, then straighten up to pass under the railroad bridge and the Interstate 20 bridge.
The task is made more difficult by the Yazoo River, which empties into the Mississippi north of the bridges, increasing the speed of the current.
Herman Smith, superintendent of the Vicksburg Bridge Commission, said the railroad bridge is struck once or twice a year, usually during periods of high water.
During the river's historic 2011 flood, the span took five hits over two weeks. The river isn't in flood stage now, he said.
"There's a curve to the north of us, about three-quarters to a mile away from us. But it's the current," Herman Smith said.
The river's other most dangerous stretch is at St. Louis. There, six bridges cross the river over a distance of four mils, Smith said.
On Monday, 31 tugboats, barges and other vessels were parked waiting for the river to reopen, said Army Corps spokesman Kavanaugh Breazeale. The river was closed to traffic for 16 miles — eight miles north and eight miles south of Vicksburg.
Ann McCullough, spokeswoman for the American Waterways Operators, a trade association for the U.S. tugboat, towboat and barge industry, said the shutdown is concerning. But she couldn't estimate the daily economic impact.
"It's a significant matter when the nation's waterborne superhighway is disrupted for any reason," she said.
During the 2011 flood, officials said delays in loading a ship — because barges can't move on the river — can cost shipping companies from $20,000 to $40,000 a day. But the river is busier at some times than others, so it's difficult to gauge the current impact.