Brisbane has been declared a natural disaster area, as soldiers and prisoners help repair damage caused by one of the biggest storms to hit the city in two decades.

About 30,000 properties across Brisbane, Redcliffe and the Gold Coast were without power on Monday afternoon after Sunday’s storm brought hail and wind gusts of up to 130km/h, unroofed homes and toppled power lines and trees.

Emergency authorities said up to 4,000 homes were damaged, with 300 homes “significantly damaged” and 30 deemed unliveable.

While most areas received 40mm to 60mm of rain, Ferny Hills, in the north-western suburbs of Brisbane received 80mm, 69mm of which fell in the space of 30 minutes on Sunday afternoon.

A 20-year-old man was killed when he was swept away by quickly rising water while photographing the storm in a drain with a 23-year-old friend at Chermside, in Brisbane’s northern suburbs.

Premier Anna Bligh compared the disaster to Cyclone Larry, which devastated north Queensland in 2006.

Acting Prime Minister Julia Gillard activated natural disaster relief and recovery arrangements, including the deployment of more than 100 chainsaw-equipped soldiers, and pledged to cover half of the state government’s clean-up costs.

“The public rightly expects all levels of government to work closely together in times of need so that the community can bounce back quickly,” Gillard said.

“The government’s thoughts are with the thousands of families that have been caught up in this disaster and most particularly with the family of the young man who tragically lost his life.”

Lord Mayor Campbell Newman said 1200 people, including emergency services personnel, Energex staff, Queensland police and the army, were working on the clean-up.

Police recruits and 20 low-level security prisoners were also involved in the effort, the state government said.

“Nothing like this has happened to the city for at least 10 years,” Newman said.

“Perhaps it goes back to 1985 with a very big storm back in those days.”

He said Energex had recorded 576 cases of toppled powerlines.

Some homes are expected to remain without power for another 48 hours.

The city council has warned residents in western Brisbane to boil their water or buy bottled water after a bird dropping-coated roof collapsed into a reservoir at The Gap – the worst-hit area of the city.

Transport services are expected to remain disrupted into Tuesday and traffic lights are out at many intersections.

Bligh said families severely affected by the storm were eligible for a cash assistance payment of up to $765 and individuals could claim $165.

“These are just the immediate cash payments for people who have literally got nothing, for people who need to buy food for their children or buy clothes,” she said.

Bligh said some people would not be able to return home for weeks.

Police patrols are being boosted to deter looters.

Bligh said up to 4000 insurance claims had already been made, but this would grow.

She also warned more storms were expected to hit south-east Queensland on Thursday.

Two Catholic schools badly damaged by the storms, St Andrew’s at Ferny Grove and St Peter Chanel at The Gap, will remain closed until at least Wednesday, school authorities say.