Defence personnel have been called in to help evacuate people isolated during once-in-a-century flooding hitting a remote town in Western Australia’s Kimberley region.

Homes have been inundated in Fitzroy Crossing — home to about 1200 people — and the Great Northern Highway is cut in both directions as some residents are airlifted 400km to Broome by helicopter.

Weather conditions are making it difficult for aircraft to operate, and emergency services have warned evacuations could take time.

“DFES is bringing in more aircraft to bolster our evacuation and resupply efforts as some communities may be isolated for at least a week,” the Department of Fire and Emergency Services said in a statement.

The Fitzroy River level was still rising on Wednesday morning before a possible peak of 15.7 metres, smashing previous records for Fitzroy Crossing.

Federal Emergency Services Minister Murray Watt said the Albanese government approved a WA request for Australian Defence Force aircraft and personnel to help evacuate residents from Fitzroy Crossing and nearby areas.

Roads are cut across WA’s northern-most region. Photo: Facebook

Downstream at Noonkanbah, major flooding was also likely. The Fitzroy River there was at 12.15m and rising on Wednesday morning.

Travellers in Derby have been warned to leave the area and go to Broome.

The rain is coming from ex-tropical cyclone Ellie, which has dumped between 200mm and 600mm since Saturday and is predicted to deliver further widespread heavy falls into the week.

The weather system has been moving slowly towards the coast and is expected to dwell around Broome for the next 24 hours, lashing the region with strong winds and intense downpours.

The Bureau of Meteorology said heavy rainfall could lead to dangerous flash flooding as the storm delivered falls of up to 300mm within a 24-hour period.

The airport runway at Broome was closed due to the water levels after the town was hit with more than 120mm of rain between Tuesday morning and early Wednesday.

Prime Minister Anthony Albanese tweeted a message of support to flood victims across the country on Wednesday.

“My thoughts are with all those families dealing with floodwaters today – from the Kimberley to Menindee to the SA Riverlands,” Mr Albanese tweeted.

“We’re working with state and local governments to help in whatever way we can.”

The top end of Western Australia has gone under. Photo: Facebook

Meanwhile, major flooding continues in the western NSW town of Menindee, where the Darling River was holding steady at around 10.2m on Wednesday.

The bureau warned further rises to 10.7m were possible from Thursday, above the 1976 flood record of 10.47m.

“At present, 10 properties have been evacuated, while 20 other property owners have decided to shelter in place,” NSW SES incident controller Gavin Arnold said.

River levels are expected to remain above the major 9.7m flood level at Menindee through to mid-January and an evacuation order remains in place for properties expected to be impacted by flooding.

Remote rescues

Conservation workers had to be rescued after becoming stranded in remote areas of the Kimberley.

Four conservationists were waiting for help on Wednesday at a remote wildlife camp, with canoes at the ready in case they were forced to flee to higher ground.

The flooding has forced the evacuation of two sanctuaries run by the Australian Wildlife Conservancy.

Three people were choppered off the Charnley River-Artesian Range Wilderness Camp after the power and water systems went out.

Four others were airlifted from the Mornington Wilderness Camp on Wednesday.

Another four remained after floodwaters swamped most of the buildings at the site.

It’s hoped those still stuck there would be rescued later on Wednesday but much will depend on the weather generated by ex-tropical cyclone Ellie.

The four are safe and dry, sheltering in the highest of the structures that didn’t go under, says Aled Hoggett, the regional operations manager for AWC in the Kimberley.

“That’s where everybody has been sitting for the last couple of days. Everybody’s safe.

“They have been dry and sheltered but obviously it’s been a long and anxious wait for them. With the weather conditions the way they are, there’s been no certainty about our ability to evacuate them.”

The floodwaters rose to within 20 metres of the group’s safe haven.

“The houses are at the base of a ridge of rock. They’ve got canoes to the houses just in case they had to evacuate, and get up onto even higher ground. But fortunately the water only came so high and it has started to recede.”

He said the water rose very quickly after more than 350mm of rain was recorded at Diamond Gorge a few days ago.

“There’s been less rainfall over the last couple of days. Given that Mornington is quite high up in the catchment, these places that usually don’t flood they drain reasonably quickly.

“But given the nature of the cyclone and its projected track it may well come back over the area, and add significant additional rainfall.”

Flooding left workers stranded in the Mornington Wildlife Sanctuary in the central Kimberley region of Western Australia. Photo: AAP

Mr Hoggett says it will take some time to determine how the floods have impacted scientific work including an ongoing project to monitor a population of the endangered purple-crowned fairy-wren.

Four of the eight people caught up in the flooding at Mornington were from Monash University, and were there to carry out annual field work.

“They monitor the birds, including collecting samples for genetic analysis. At the moment we’re trying to make sure we rescue those samples and don’t lose the work they’ve already done this year,” Mr Hoggett says.

“But it will put a significant hole in that continuous data set. And in terms of science, continuous data sets are precious and we always try to avoid breaks in them.”

What’s guaranteed is Mornington will need a lot of clean-up work, with most buildings inundated including the office complex, communal facilities including the kitchen, pilots’ quarters, and accommodation buildings.