A day after US army engineers opened a key spillway to relieve flooding along the Mississippi River, residents of small Louisiana towns are braced for a surge of water that could leave thousands of homes and farms under as much as six metres (20 feet) of water.
Four of the 125 floodgates at the Morganza Spillway 72kms (45 miles) northwest of Baton Rouge have been opened since yesterday.
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 towns like Amelia, about 160kms (100 miles) south of the spillway, crews worked around the clock to build earthworks and reinforce levees ahead of a torrent of water expected to reach the area tomorrow or Tuesday.
Weeks of heavy rains and runoff from an unusually snowy winter caused the Mississippi River to rise, flooding three 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 last for three weeks before the water works its way to the Gulf of Mexico.
About 2,000 people were ordered to evacuate from St Landry Parish, just south of Krotz Springs.
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.
