Members of the 3rd brigade used 15 boats, each holding six people at a time, to move people to safety as major flood warnings were issued for the Ross River in northern Queensland.
Residents were also urged to stay out of the water due to crocodile and snake sightings around the city.
The Bureau of Meteorology said “dangerous and high velocity flows” of around 1,900 cubic metres of water per second would be released from the Ross River dam from Sunday night into Monday morning.
“Unprecedented areas of flooding will occur in Townsville,” the bureau said in a statement warning of risk to life and property. “Expect access routes to be cut. Conditions will change rapidly and continuously.”
Forecasters estimated 450mm of rain would fall in the dam catchment area over a 24 hour period.
The dam had reached almost 250 per cent capacity by the early hours of Monday morning.
Townsville City Council issued a flood map and urged residents in more than 20 suburbs to “move away from riverbanks and get to higher ground".
“Residents still in their homes in these suburbs should move to the highest ground in their dwelling,” it added.
Footage showed torrents of water being released from the dam before it was closed to the public on Sunday evening.
The 3rd brigade said defence members were “working as hard and as quickly as they can to meet the need” for evacuation in the Idalia and Oonooonba areas of Townsville.
“Those seeking evacuation should take minimal personal items as the size of the boats will not allow for baggag,” it said in a statement.
“Pets will be evacuated but need to be on a lead or otherwise suitable contained.”
Townsville airport said it had cancelled all flights after 6pm on Sunday due to safety concerns.
The city was already suffering from once-in-a-century flooding after days of monsoon rains lashed the region, with an estimated 500 homes under water by Sunday.
Meteorologist Adam Blazak said: “Normally a monsoonal burst might last a few days, but this one’s been going on over a week now and is set to continue for a few more days as well.”
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