The White House action makes emergency federal funding available to support rescue crews working nonstop.
"This is ongoing," Edwards said Sunday of the record floods. "This is not over," even with the rains lessening as they move west and the sun appearing in some flooded areas.
The flooding submerged large parts of the region on Sunday, three days after water-swelled streams and rivers began rising.
Thousands were evacuated in Livingston Parish, near the capital Baton Rouge, the sheriff's department told local media.