Helicopters fly over the Congaree River, swollen with floodwaters, near the Gervais Street bridge in West Columbia, S.C., on Sunday, Oct. 4, 2015. Hundreds were rescued from fast-moving floodwaters Sunday in South Carolina as days of driving rain hit a dangerous crescendo that buckled buildings and roads, closed a major East Coast interstate route and threatened the drinking water supply for the capital city.

Chuck Burton / AP

Helicopters fly over the Congaree River, swollen with floodwaters, near the Gervais Street bridge in West Columbia, S.C., on Sunday, Oct. 4, 2015. Hundreds were rescued from fast-moving floodwaters Sunday in South Carolina as days of driving rain hit a dangerous crescendo that buckled buildings and roads, closed a major East Coast interstate route and threatened the drinking water supply for the capital city.