Authorities warn of potentially life-threatening flash floods along the northern New South Wales coast stretching across a distance of more than 500 km.

Seeking to avoid a repeat of this disaster, state emergency services said
Seeking to avoid a repeat of this disaster, state emergency services said "additional people, vehicles, boats and helicopters" had been deployed to town of Lismore. (Reuters Archive)

Heavy rains have drenched Australia's east coast for the second time this month triggering evacuation orders for thousands of flood-weary residents as authorities warned the intense weather system will likely persist for the next 24 hours.

Several towns across northern New South Wales and southeast Queensland states were still battling to clear tonnes of debris after devastating floods early this month killed at least 21 people and swept away hundreds of farms, houses and livestock.

Multiple evacuation orders were issued for the town of Lismore on Tuesday, which was devastated last month when record-high 47 feet of floodwaters engulfed homes, swept away cars and stranded locals on the roofs of their homes.

Amid the rebuilding efforts, the Bureau of Meteorology on Tuesday warned of potentially life-threatening flash floods along the northern New South Wales coast stretching across a distance of more than 500 kms. There could be isolated rainfall of up to 12 inches in some regions over six hours, the weather bureau said.

The new low-pressure system could be less severe than the previous one but the already-sodden earth from weeks of relentless rains could result in a sudden rise in river levels.

La Nina weather pattern

Australia's east coast summer has been dominated by the La Nina weather pattern, typically associated with increased rainfall, for the second straight year with many rivers already near capacity before the latest drenching.

In the northern New South Wales town of Lismore, among the worst hit by record floods a month ago, residents in low-lying areas were ordered to evacuate late on Monday night.

"We are very much in the hands of the Gods today," Lismore mayor Steve Krieg told Channel Nine television on Tuesday. "If the expected rainfall comes in ... the river could rise quite dramatically."

Television footage showed residents grabbing sandbags from emergency services before fleeing their homes.

Krieg said the chances of another deluge within weeks while residents were rebuilding their lives "just really drains you emotionally and mentally."

In the state of Queensland, a man was found dead in his car in floodwaters on Monday, along with several dogs, despite police rescue attempts. A woman who was in the vehicle survived and was taken to a hospital to recover.

Amid criticism over slow relief, Prime Minister Scott Morrison, behind in polls in an election year, has declared the floods a national emergency and designated catastrophe zones in flood-stricken towns which will receive extra recovery funds.

Source: AFP