Rising floodwaters on the Mississippi River have led the U.S. Coast Guard to close the river to shipping at the Natchez Port. As AP reported:

The swollen Mississippi River has been closed to shipping at Natchez, Miss., shutting the major artery for moving grain from farmland in the Midwest to the Gulf of Mexico for export.

The U.S. Coast Guard closed the river Monday at the Natchez port because barges on the water could put pressure on the levees. It’s not clear how long the closure will last, but any interruption can create a backlog of shipping barges and slow commerce.

The Mississippi River is expected to crest Saturday in Natchez at 63 feet, down a half-foot than earlier predictions, but almost five feet above a record set in 1937.

About 70 miles upriver, areas around Vicksburg have seen some of the worst flooding. More than 4,200 people are displaced by flooding in Mississippi.

Along the banks of the Mississippi engineers, volunteers and even inmates have joined patrols to monitor levees and alert authorities to possible leaks. As the Associated Press explained:

All along the Mississippi, a small army of engineers, deputies and even inmates is keeping round-the-clock watch at the many floodwalls and earthen levees holding the water back. They are looking for any droplets that seep through the barriers and any cracks that threaten to turn small leaks into big problems. The work is hot and sometimes tedious, but without it, the flooding could get much worse.

Although the job requires 24-hour vigilance, Reynold Minsky, president of a north Louisiana levee district, said there are some places in his mostly rural district of forest and farmland where he will not ask anyone to go after sundown.

“Unless we’ve got a serious situation that we know we’ve found before dark, we don’t ask these people to go into these wooded areas because of the snakes and the alligators,” Minsky said while taking a break from helicopter tours of the levees. “That’s inhumane.”

Minsky’s 5th Louisiana Levee District is plagued these days by “sand boils,” places where river water has found a way through earthen levees and bubbled up on the dry side like an artesian well. He insists they are no reason for alarm. If the water is clear, as it has been so far, that means the levee is not eroding. Stopping the boil involves ringing it with sandbags.

Many residents are preparing for the prospect of flooding damaging their homes and communities, as Melissa Bell reported:

The Mississippi River has slowly overtaken land in Missouri, Illinois, Kentucky, Tennessee, Arkansas and Louisiana. About 100 homes were damaged or destroyed after a levee was blown up in Missouri. Near Baton Rouge and New Orleans, areas of town have been evacuated, even though spillways were opened to divert the water from most heavily populated neighborhoods.

In Butte LaRose, the Associated Press interviewed Chalmers and Chandler Wheat, two brothers who thought their house would be all right so long as the water level didn’t exceed 2 feet.

“If the water gets higher, we’re pretty much ...” Chalmers Wheat told the Associated Press, before his brother chimed in: “Screwed.”

If that is the case, for the Wheat brothers and hundreds more like them, The Post’s Ed O’Keefe explains that there are some protections for them after the flooding:

“More than half of the U.S. population now lives in coastal watershed counties or floodplain areas, according to the Federal Emergency Management Agency.

More from The Washington Post

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Politics: Obama gives commencement speech in flood-ravaged Memphis

Video: Residents warned to leave Cajun county as floodwaters rise