Supermarket shelves are bare in tropical cyclone-hit northern Australia, where widespread flooding has cut freight routes.

Residents in Broome are some of the hardest hit by road closures in Western Australia’s north-west, following Tropical Cyclone Zelia.

The system has been downgraded to a tropical low since it crossed the coast near Port Hedland on Friday but heavy rain is forecast to persist for days, further impacting isolated communities.

Roads have been cut across the region. They include the Great Northern Highway, which connects the north-west with WA’s south, meaning no fresh supplies can get through to many places, including Broome.

Broome Shire president Chris Mitchell said plans were being made for trucks to come in via South Australia and the Northern Territory.

“I believe the shelves are fairly bare,” he said.

“I am not sure how long the highway [to the south] will be closed but we can get stuff in from the territory and South Australia.”

However, the longer route through central Australia is expected to take more than a day.

The full extent of flood damage caused by Zelia is not expected to be known until water levels recede.

East Pilbara Shire president Anthony Middleton said it could be 10 days before local flood levels fell.

Road closures are a concern for East Pilbara Shire – which is Australia’s largest local government area and covers more area than Victoria and Tasmania combined. The shire has more than 3000 kilometres of unsealed roads.

The shire posted footage to Facebook on Sunday showing extensive damage to the road at the Coongan River crossing at Marble Bar.

Residents in the shire’s inland communities, including Marble Bar and Nullagine, are expected to be cut off for days.

Authorities are working hard to ensure the shire’s outer communities receive supplies amid “widespread” flooding.

“The wider shire, they are ones that are impacted. People can’t get in or out – that’s a concern for us,” Middleton said.

“Normally in a week to 10 days, we sort of know where we are sitting with the water receding, then it’s recovery and making sure our dirt roads are accessible for our communities.

“There’s just over 3000 kilometres of dirt road network. We have eight graders ready at any time, so we will prioritise them and go from there.”

Heavy rainfall inundated the region at the weekend. Coolenar Pool near Marble Bar, and fed by the De Grey River, peaked at nine metres – reportedly breaking a 25-year record.

Middleton said the latest flooding highlighted the need for road upgrades in his shire.

“It’s widespread flooding out here but this is not uncommon for us. This is the third time this year we’ve had roads cut off,” he said.

“This is another example of our road requiring upgrades.

“Trying to get supplies to communities in our area – that’s the challenge we face every time we have unprecedented rain.”

A flood “watch and act” warning is in place for the De Grey catchment, including the Marble Bar and Nullagine communities.

“You need to prepare for isolation as flooding is occurring,” it said.

“There is a possible threat to lives and homes due to dangerous, widespread flooding.”

One of the world’s largest iron ore hubs, Port Hedland, has reopened after being closed for days in preparation for Zelia’s arrival. Mining giants including BHP have reported no major damage to their sites.

Severe thunderstorms are forecast for WA’s southern interior and east of the Goldfields district on Monday.

-with AAP