Authorities urged residents to flee more Australian towns on Tuesday as swollen rivers carried deadly floodwaters deeper into another state and worsened a natural disaster the government says may be its costliest ever.

Victoria state is the latest region afflicted in a weeks-long flooding crisis that has left 30 people dead and caused once-a-century floods in many areas.

The Victoria city of Horsham resembled a lake after the Wimmera River overflowed its banks on Tuesday and bisected the community before starting to recede in the afternoon. About 500 homes in the city of 14,000 people were surrounded by water.

Officials sent three emergency alerts overnight to residents in the path of the high water.

“At 5 a.m. they were out on the megaphone just yelling ‘evacuate’,” West Horsham resident Brett Insall said, but he stayed at his home. “I’m not too worried about it. It’s only water.”

State Emergency Service Incident Controller Stephen Warren said the water would slowly recede through the day. “We may even be able to get the (Western) highway open late in the day and actually have some access later tonight,” Mr. Warren told reporters.

Across north-central Victoria state, more than 3,500 people have evacuated their homes, with 51 towns and 1,500 properties already affected by rising waters.

The Wimmera River towns of Dimboola and Warracknabeal faced inundation over the coming 24 hours, Victoria officials said.

An evacuation warning was issued to residents of Kerang, who face isolation for at least three days when the Loddon River peaks. Emergency officials said any resident unable to cope without electricity, water, sewer and telephone connections should leave their homes.

Floodwaters have already left 1,000 households in Victoria’s northwest without power, and thousands more homes are under threat of cuts as substations and low-lying power lines are submerged.

Energy supplier Powercor was building earthen barriers around the substation in Kerang, in a floodplain expected to be inundated by two meters of water.

Prime Minister Julia Gillard announced the formation of a business task force to assist with rebuilding devastated infrastructure in Queensland. She said a day earlier that the floods that ravaged Queensland could be the country’s most expensive natural disaster ever.

Most of the 30 people who died in Queensland were killed a flash flood that hit towns west of the state capital, Brisbane. The state’s flooding inundated 30,000 homes and businesses and left 12 people missing.

The price tag from the relentless floods was already at $5 billion before muddy brown waters swamped Brisbane last week.

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