The water is waist-deep in parts of eastern New Orleans.
More than eight inches of rain has fallen in the flood-prone city, forcing the Army Corps of Engineers to close a gate on a suburban canal where the waters threatened to top the walls.
Mayor Ray Nagin shut City Hall early Oct. 22 and schools also closed.
People are being asked to stay indoors until the flood potential subsides.
The flooding is occurring in parts of eastern New Orleans, damaged by Hurricane Katrina.
Officials say all the city's pumps are working properly.