Flood threat ongoing in Qld amid clean-up

The central Queensland town of Rockhampton is bracing itself for its worst flooding in more than 60 years as the clean-up after Cyclone Debbie continues across two states.

Forecasters warn the Fitzroy River will surge to a peak of 9.4m on Wednesday, an inundation not seen in the town since February 1954.

A temporary levee has been erected around Rockhampton Airport, which is due to close at noon on Monday as the waters threaten to swamp the runway.

More than 3000 homes and 1500 businesses in low-lying parts are expected to be affected by the flooding, as well as roads and railways.

Meanwhile, the gruelling clean-up has begun in Queensland's southeast and northern NSW, where at least five people are believed to have died as a result of flooding.

Three men and two women were killed in separate incidents on Friday and Saturday as the extent of the weather took many by surprise despite repeated warnings from authorities.

Logan mayor Luke Smith said on Sunday that almost 290 homes in the council area, south of Brisbane, could have been inundated by water.

Mr Smith said the unprecedented destruction meant the sky would be the limit when it came to estimating the damage bill.

Lismore mayor Isaac Smith said northern NSW looked like "a war zone", with an estimated 15,000 properties isolated by flooding.

Water levels in Lismore peaked within a metre of the 1974 record of 12.2m on Friday.

Prime Minister Malcolm Turnbull will on Monday speak to locals and survey the damage when he tours the flood-hit northern NSW towns of Lismore and Murwillumbah, before heading to across the border to Beenleigh in south-east Queensland.

He will be joined by NSW Premier Gladys Berejiklian in Murwillumbah.