Authorities say storm surge driven by Hurricane Isaac is spilling over a levee in a thinly populated part of mostly rural Louisiana, south of New Orleans.
Plaquemines Parish spokesman Caitlin Campbell said water was running over an 18-mile (29-kilometer) stretch of the levee early Wednesday and some homes had been flooded.
Sheriff's deputies were going house-to-house looking for residents who'd remained after an evacuation order.
Campbell said streets in the area were still passable.
Parish President Billy Nungesser said a portion of the roof of his home on the parish's west bank had blown off. He describes wind-driven rain coming into his home as “like standing in a light socket with a fire hose turned on.''