On Sunday, the city authorities were forced to open the gates at the Ross River dam to release water, after it had swollen to double its size following a week of record rainfall.
Australia's tropical north experiences heavy rains during the monsoon season at this time of the year, but the recent downpour has surged far above normal levels.
Rainfall in the Townsville area wasn't as bad as feared overnight.
Thousands of people in northeast Australia should expect "unprecedented flooding", authorities have warned, after relentless downpours forced a dam to be fully opened on Sunday.
Around 400 Townsville residents have sought shelter at nearby Lavarak military barracks and the Red Cross is also assisting with the response and recovery effort.
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Emergency services tackled thousands of calls from people overnight around the city of Townsville, where evacuation centers were filling up.
"Remember to keep an eye out for your neighbours affected by flood where it is safe to do so and call emergency services if you need help", Queensland Police said.
Schools in Townsville remained closed on Monday along with the city's airport.
But that was before dam releases were doubled in anticipation of more rain, sending nearly 2000 cubic metres of water per second charging out of the Ross River Dam.
"We've just seen the wettest week on record in Townsville with more than 1000mm of rain falling - and it's not over yet". This setting will release approximately 1900 cubic metres of water per second out of the dam.
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The Australian media cited the officials as saying that "dangerous and high velocity flows" had been spotted along the Ross River.
About 10,000 people have already lost power since Friday - and more power outages due to public safety concerns are likely.
A severe weather warning was issued at 4.54am Monday for damaging, locally destructive winds and more heavy rainfall for Townsville, Herbert and the Lower Burdekin.
"Small boats worked through the night to evacuate members of the community", said local commander Brigadier Scott Winter. Queensland Premier Annastacia Palaszczuk has warned Townsville residents that flooding has not yet reached its peak as torrential rain continues.
While the flood risk will continue for the rest of the week, forecasters say an end to the disaster is in sight. Grocery store chain Woolworths said it was sending in food supplies by barge, while supermarket chain Coles was flying stocks into Cairns and trucking them to Townsville.
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"It is basically not just a one in 20-year event, it is a one in 100-year event", she told reporters Saturday. But the current conditions in the Townsville area are rare.