Officials are planning to airlift supplies to Wilmington, a city of nearly 120,000 people, after still-rising floodwaters from Storm Florence cut if off from the rest of North Carolina.

At least 17 people have been killed, including a mother and three month old baby who died when a tree fell on their mobile home, as the tropical depression continues to move across the Carolinas.

Residents of Wilmington, the eighth largest city in North Carolina, spent hours on Sunday waiting outside stores and restaurants for basic necessities including clean water.

Police guarded the door of one shop, allowing only 10 people in at a time.

Authorities are planning to fly food and water into the coastal city, according to county commission chairman Woody White.

"Our roads are flooded," he said. "There is no access to Wilmington."

Radar imagery shows parts of Storm Florence extending across six states, with North and South Carolina at its centre.

Other states are in the storm's path, even though it has been downgraded from a hurricane.

"Not only are you going to see more impact across North Carolina but we're also anticipating you are about to see a lot of damage going through West Virginia, all the way up to Ohio as the system exits out," Brock Long, administrator of the Federal Emergency Management Agency (FEMA) said during an appearance on Fox News.

Residents near North Carolina's Lumber River were forced to step directly from their homes and into boats, as water surrounded them.

State officials also have environmental concerns to grapple with as regulators monitor the threat from large poultry and pig farms located in low lying areas.

The industrial-scale farms contain vast pits of animal waste that could pose a pollution threat if breached by floodwaters.

The flooding could become the worst in North Carolina's history and concerned officials have ordered tens of thousands of residents to evacuate.

It is unknown how many people have left the region or how many were able to flee in time.