Sydney - Australia's east coast received its biggest downpours in decades Thursday, confounding efforts to clean up after weekend storms that tore off roofs, downed trees and left thousands of homes without power.

Brisbane, the Queensland state capital, was again in the eye of the storm, with rainfall of up to 250 millimetres prompting thousands of householders to call emergency services for help.

Crews were out in boats, paddling along flooded highways and taking stranded motorists aboard.

One woman drowned after her car was swept off a highway. A bridge in Ipswich, near Brisbane, was washed away.

"It was like watching one of those movies with Indiana Jones in front of the big wall of water trying to save his life," Ipswich Mayor Paul Pisasale said. "The walls of water just pushed out the front of shops, smashed doors."

The biggest storm cell in 30 years swept Sunday over Brisbane, turning night into day and bringing down trees and power lines and damaging hundreds of homes. The Defence Force was called in to help rescue efforts, and some areas were declared disaster zones.

Local official Steve Jones said with so many roads turned to rivers, it was too early to estimate the damage bill. "Our biggest problem is that we can't see the problem," he said. "Once the water subsides we will know more."

RACQ Insurance chief executive Bradley Heath put the bill of the weekend damage at "hundreds of millions of dollars."