An entire outback town is being evacuated as floodwaters creep ever nearer, with river levels tipped to exceed major flood thresholds at the weekend.

About 450 people from the Northern Territory town of Daly River will be bussed to Darwin by Thursday afternoon to be housed in emergency accommodation.

Superintendent David Moore, the incident controller for the flood event, said on Wednesday an emergency declaration was in place.

Evacuations were a last resort but residents’ safety was the priority, he said.

“If you plan to self relocate now is the time to do it … while the roads are still open and passable,” he said.

Moore urged people not to drive through floodwaters and be wary of crocodiles and other wildlife in the rising water levels.

He could not say how many homes might be inundated but floodwaters were expected to pass the 14-metre level, which meant water and sewerage would be cut off in the town.

“We’re still looking at the modelling in relation to whether homes will be inundated,” Moore said.

Daly River community members had attended public meetings about the evacuation and buses were already on the way to take them to safety.

“Given the water levels are rising, this is something that has to happen immediately,” Moore said.

Under the emergency declaration, Moore has the power to evacuate people.

“No chances will be taken, so everyone will be evacuated,” he said.

Authorities would return residents to Daly River as soon as possible but the size of the flood meant that could be a week or even longer, Moore said.

Bureau of Meteorology NT manager Shanagh Gamble said a tropical low had brought rainfall totals of nearly 500 millimetres in the Daly River catchment, causing rivers to rise.

That had prompted a major flood warning for the town, where levels are expected to exceed major flood thresholds in coming days.

-AAP