Dozens of rural Australian communities were sandbagging their properties Sunday as they nervously watched four river systems rising from heavy rains upstream.

More than 3,500 people have evacuated their homes in north-central Victoria state, where some towns are predicting the worst floods in 100 years.

"In some of our river systems, we are seeing unprecedented stream rises," said State Emergency Service operations director Trevor White, saying the flood event was one of Victoria's biggest since records began.

Neil Pankhurst, mayor of the Murray River port of Echuca, said the town's levee was designed to withstand a one-in-100-year flood, which is dangerously close to what is expected late on Sunday night.

"The levee is designed to contain a flood of the level we're expecting and we believe it will hold," Pankhurst said.

He said some low-lying properties were likely to be isolated by floodwaters but most homes would not have water above floor level, he said.

People were watching warily after witnessing the devastation floods have wreaked in Queensland state.

Three weeks of flooding in the northeastern state left a vast territory underwater and caused 28 deaths, most of them from a flash flood that hit towns west of Brisbane on Monday. Fourteen people are still missing.

In Grantham, 70 percent of the town remained cordoned off while searchers looked for bodies.

"People I hope will understand the pressure that the police are working under in these sorts of circumstances and be patient," Queensland state Premier Anna Bligh said. "They are working as hard as they can to be in a position to allow people back into Grantham as quickly as possible."

The wall of water that swept through the town left dozens of smashed cars wedged in trees or bogged in fields, tilted houses off foundations and piled up muddied belongings in the streets.

In nearby Murphys Creek, a church service at the local pub was held for survivors to grieve and remember their lost friends and family.

"Words really cannot express what the people of the Lockyer Valley are feeling at the moment," local parliament representative Scott Buchholz said after the service. They "are emotionally fragile yet display a bravery that is remarkable."

Flooding has also spread from Queensland into New South Wales, where nearly 7,000 people are reliant on airdrops of food and other supplies after being isolated by floodwaters.