N.C. 12 is closed at Rodanthe on the Outer Banks where the storm cut an inlet in the barrier island. About 900 feet of road was washed away, cutting off Cape Hatteras and several Outer Banks towns from the rest of the state.
Several residents who had weathered the storm drove up to see the breach.
"This is absolutely crazy," said Anne Vroman, who lives part-time in Waves. "I've been here since 1974 and never seen anything like this. It's awful."
Water also washed over N.C. 12 between Hatteras and Frisco, at a place that was breached during Hurricane Isabelle in 2003, but the road remained intact.
Farther north, a 100-foot section of road has been undermined and is impassable near Duck, the DOT says.
Washouts of N.C. 12 have occurred in past hurricanes, some more extensive than others.
DOT crews are still assessing the roadway, said Marge Howell of the N.C. Joint Information Center.
Howell said a section on Ocracoke Island also is breached. "N.C. 12 is real spotty," she said.
Also, state workers have begun trying to restore ferry service along the coast in the wake of Irene. So far, no ferries were running late this morning.
The Department of Transportation reports electrical problems in Pamlico County at Cherry Branch on the Neuse River, site of some of the worst flooding.
The ferry division also reported no electricity at Stumpy Point, which serves as the emergency ferry route to Rodanthe on Hatteras Island.
A total of 228 roads are closed in the eastern part of the state, including N.C. 12. Here is a partial listing:
* N.C. 12 in the Outer Banks is closed due to flooding
* U.S. 301 is closed throughout Halifax County due to downed trees and power lines
* N.C. 561 is closed between Interstate 95 and U.S. 301 in Halifax County
* N.C. 903 is closed between Interstate and U.S. 301 in Halifax County
* U.S. 17 is closed near St. Francis Road near Windsor in Bertie County
* U.S. 13 is closed near Peanut Road near Snow Hill in Greene County
* U.S. 264 ALT is closed near Stephenson Street in Greene County
* U.S. 264 is closed in Beaufort County approaching Pitt County
* N.C. 11 is closed near Canady Road near Kinston in Lenoir County