By Kathy Finn
AMELIA, Louisiana (Reuters) - A day after Army engineers opened a key spillway to relieve flooding along the Mississippi River, residents of small Louisiana towns braced on Sunday for a surge of water that could leave thousands of homes and farms under as much as 20 feet of water.
The U.S. Army Corps of Engineers on Saturday opened two of the 125 floodgates at the Morganza Spillway 45 miles northwest of Baton Rouge, and expect to open two more on Sunday.
Opening the floodgates -- a move last taken in 1973 -- will channel water away from the Mississippi River and into the Atchafalaya River basin. That will take the floodwaters toward homes, farms, a wildlife refuge and a small oil refinery but avoid inundating New Orleans and Louisiana's capital Baton Rouge.
In Amelia, about 100 miles south of the spillway, crews worked around the clock to build earthworks and reinforce levees ahead of a torrent of water that is expected to reach the area on Monday or Tuesday.
"I hope they know what they are doing," said Hue Tran, watching the giant dump trucks from the Quik General food store, a short distance from the intercoastal waterway.
"I hope it will give us a little bit of peace but we're scared that the water will come over," said Tran, who has operated the store for 25 years.
Tran is prepared to evacuate if government officials give the word. Farther north, parts of St. Landry Parish already were under a mandatory evacuation order.
Weeks of heavy rains and runoff from an unusually snowy winter caused the Mississippi River to rise, flooding 3 million acres of farmland in Mississippi, Tennessee and Arkansas and evoking comparisons to historic floods in 1927 and 1937.
Louisiana towns in the path of the floodway like Krotz Springs, Butte LaRose and Morgan City are making similar plans for severe flooding that could be sustained for three weeks before the water works its way to the Gulf of Mexico.
FLOODWATERS COULD LINGER FOR WEEKS
About 2,500 people live in the spillway's flood path and 22,500 others, along with 11,000 buildings could be affected by backwater flooding -- the water pushed back into streams and tributaries that cannot flow normally into what will be an overwhelmed Atchafalaya River.
Some 3,000 square miles (7,770 sq km) of land could be inundated in up to 20 feet of water for several weeks. When flows peak around May 22, the spillway will carry about 125,000 cubic feet per second, about one quarter of its capacity.
Some 18,000 acres of cropland could be flooded as waters rise, hitting their crest in about a week and remaining high for several weeks.
Failing to open the spillway would have put New Orleans at risk of flooding that, according to computer models, would eclipse that seen during Hurricane Katrina in 2005. About 80 percent of the city was flooded by Katrina and some 1,500 people were killed.
In addition to threatening densely populated areas, lower Mississippi flooding was a risk for as many as eight refineries and at least one nuclear power plant alongside the river.
The refineries make up about 12 percent of the nation's capacity for making gasoline and other fuels.
The Corps said the gradual opening of the spillway's gates would prevent an immediate rush of water. Alon USA Energy was working on Sunday to build a levee around its 80,000 barrel-per-day refinery in Krotz Springs, which expects to be surrounded by water within 14 days of the spillway opening.
Exxon Mobil's 504,500 barrel per day refinery in Baton Rouge, the nation's second-largest, was not expected to cease operations but its Mississippi River dock was shut due to high water, a plant spokesman said.
(Additional reporting by Erwin Seba in Houston; Writing by Chris Baltimore; Editing by Bill Trott)
