On Tuesday night, Isaac’s winds whipping and floodwaters high, a Braithwaite father and son kept watch over the minimal levee between eastern Plaquemines Parish and the Gulf of Mexico. As midnight hit, Jesse Shaffer Sr. and Jr. decided one would rest for an hour while the other sat on the levee, locally known as the “wall.” Then they would switch, hour by hour, charting the water’s rise. But at 12:10 a.m. Wednesday, relatives called to say the water already was rushing over the wall several miles south of their location.

On the northern end of Braithwaite, “it was coming up 6 inches every 10 minutes,” Shaffer Jr. said.

Water quickly flowed into lawns and down streets in eastern Plaquemines Parish. Then, it seeped into first floors. Residents who had remained in their homes soon climbed stairs with possessions in tow. As the water rose further, many climbed again, to attics and roofs.