ST. LOUIS • The flood of 2011 reached record levels in Caruthersville, Mo., on Wednesday as the Mississippi River topped the 46-foot mark set in 1937. And the water is still rising.

Forecasters expect a crest of 49.5 feet on Sunday — just a half-foot below the top of the flood wall that sits near the downtown business district.

But more than businesses would be damaged if floodwater came in. Caruthersville sits in a low-lying delta, so much of the town would be underwater, said Fire Chief Charlie Jones.

Volunteers and members of the Missouri National Guard have hastily constructed a secondary 3-foot-tall sandbag levee about 30 feet behind the flood wall, which officials hope would catch any spillover.

"This is our last-ditch effort to contain it from flooding the city," Jones said. "If the crest goes up, we will sandbag even higher."

The Mississippi has crested in most of hard-hit southeast Missouri, helped along by the Army Corps of Engineers' intentional breach Monday night of the Birds Point Levee just south of the confluence of the Ohio and Mississippi rivers. The breach caused river levels to drop 3 feet in Cairo, Ill., and elsewhere on the nearby Ohio, while flooding tens of thousands of acres of Missouri farmland.

But the breach seems to have had little impact in Caruthersville.

The community of 6,700 residents is still getting back on its feet after a wide twister tore through town on April 2, 2006. Among the buildings destroyed was the high school. For nearly six years, students met in trailers provided by the Federal Emergency Management Agency. They finally moved into their new $12 million school in February.

If the flood wall is topped and the sandbag levee doesn't hold, that new school probably would take in water, Jones said.

Flooding has already closed the Lady Luck Casino, and stored grain was destroyed when a levee surrounding a riverside grain terminal breached Monday. Many other businesses on the outskirts of town — outside the area protected by the wall — are wet.

Elsewhere, two southeast Missouri reservoirs operated by the Army Corps of Engineers, both near Poplar Bluff, Mo., were pouring over their emergency spillways.

The biggest concern was at Wappapello Lake. The force of the water was so great when the spill began Monday that a 400-foot section was ripped out of Highway T, leaving a gaping hole 30 to 50 feet deep in the state highway.

Stoddard County Emergency Management spokesman Dale Moreland said the water came up so fast that 10 families had to be rescued by boat. "They were surrounded by water pretty quickly and they had to get out," he said.

Andrew Jefferson, a park ranger at Wappapello Lake, said that contrary to rumors, the dam is not endangered. The water level crested at a record 400.04 feet on Tuesday and had dropped about a half-foot by Wednesday. Still, water was expected to continue spilling from the reservoir until May 12.

That water flows down the St. Francis River, worsening flooding. There have been no mandatory evacuations, but officials said many people have left on their own from nearby towns including Puxico, Dudley, Powe and Fisk.

Fisk, with only 349 residents, is protected by a levee that seems to be holding well, City Clerk Melody Fry said. The river is expected to crest Thursday, less than 3 feet short of the top of the levee.

"Several people have left," Fry said. "I think they got panicked. There were U-Haul trailers and trucks everywhere."

Clearwater Lake was expected to crest at 566.7 feet today, and spillage there was creating more flooding in towns along the Black River, including Poplar Bluff, where 1,000 people were evacuated for a few days last week because of overtopping of a levee.

Poplar Bluff police said the rise in the river this week did not cause any new evacuations, and the river level was starting to fall.