Communities may be cut off for up to a week as ex-tropical cyclone Ellie continues to dump heavy rain after crossing the Northern Territory coast more than a week ago.
Fitzroy River Lodge manager Kandula Herat said plans to evacuate guests and staff by helicopter had to be abandoned after the rising water swamped the landing pad.
"There was no place to land the chopper. The new bridge is pretty much washed away and the water is up to 15 metres," he told AAP on Tuesday.
"The river is overflowing and still rising."
Staff and authorities are now racing to find a boat big enough to cross the Fitzroy River's raging waters to evacuate the hotel's 15 guests.
"Another metre and a half and it's going to be inside the rooms. Every hour the situation is changing," he said.
"The swimming pool is gone, all under water. Cattle are floating everywhere. Pigs, kangaroos and wallabies, lots of dead animals."
Mr Herat said the lodge's guests and 18 staff were currently safe but cut off from the Great Northern Highway.
"It's all the people in the communities that need more help than us," he said.
An evacuation centre has been established at the nearby Fitzroy Crossing recreation centre with major flooding also expected to impact Willare, Noonkanbah, Mount Barnett and Christmas Creek on Tuesday and Wednesday.
The Bureau of Meteorology says the weather system is centred just north of Halls Creek and is expected to move slowly west over the next 24 to 36 hours and will be just east of Broome on Tuesday evening.
A vigorous monsoon flow wraps into the system which has dumped between 200 mm and 500 mm of rain since Saturday.
"Further widespread heavy falls are forecast for the next few days," the bureau said on Tuesday.
"River rises and areas of flooding are adversely affecting road conditions in the Fitzroy River catchment. Some roads may become impassable and some communities are now isolated."
Emergency WA said there was a possible threat to lives and homes due to river and stream levels rising quickly with fast flowing water.
Meanwhile, flood levels are holding steady at a western NSW town.
A flood peak of up to 10.7 metres had been tipped to hit Menindee on Monday, above the 1976 record of 10.46 metres.
But the bureau has since revised its forecast, declaring further rises to 10.7m are possible from and around Thursday.
Locals from 31 properties around Menindee were advised to evacuate before New Year's Eve, with residents from seven or eight heeding the warning.
Elevated river levels are expected to remain around the 10-metre mark for at least another fortnight as water continues to flow through the Darling River, the bureau said.
In other parts of the country, heatwave conditions have persisted over the past few days, with the worst of those in central WA, western Queensland and northeast South Australia.
Also in SA, the continued surge of water down the Murray has breached or inundated a string of agricultural levees including those at Mypolonga, Toora, Mobilong, Cowirra, Wall Flat, Long Island and Long Flat.
The State Emergency Service said more issues with levees could be expected as peak flows moved down the river.
The Murray is expected to peak at Waikerie and Morgan between now and January 7 and at Blanchetown, Swan Reach and Mannum between January 4 and 13.
In the Northern Territory, a severe weather warning for the Daly, Tiwi and Arnhem districts has been cancelled as damaging surf conditions ease.
A vigorous monsoon flow is continuing across the western Top End, but coastal wave heights are abating.
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