She toured Ingham, a cane-growing town north of Townsville, where she met emergency services workers and hosted a sausage sizzle.

Yesterday she visited a cane farm before flying back to the Victorian town of Whittlesea for a church service.

In Ingham residents are beginning the clean-up. But the situation remains dire in Queensland's gulf country, which is experiencing the highest river peaks in 35 years.

In Karumba, a remote fishing town in the state's north-west, residents have been asked to cut back on showers because the town had as little as three days' drinking water left after a water pipeline to nearby Normanton burst.

Some towns in the area have been without fresh food since early last month.

However, there is no shortage of beer. While the pub in nearby Burketown famously ran out of beer during floods a few years ago, alcohol deliveries are continuing to Normanton and Karumba by boat from the north.

The Purple Pub remained well stocked, said its licensee, Dorothy Prince. "[The alcohol] comes by barge around the top of Cape York."

Many in the gulf expect to be flood-bound for at least another month.

The floods have devastated the state's sugar industry, which was already struggling due to years of poor growing conditions, high costs and low returns.

The water has also damaged banana plantations, which were recovering from Cyclone Larry in 2006.

The price of Queensland bananas had risen to between $5 and $6 a kilogram at some markets.

Mark Panitz, the chief advocate of Growcom, a growers' organisation, said it was too early to calculate total losses, but farmers could expect "a few million dollars worth of damage".

About 7pc of the nation's fruit and vegetables are transported on semi-trailers to the southern states each week.

The produce route temporarily closed on Tuesday when the Bruce Highway was cut by flood waters.

The federal MP Bob Katter said funding was needed to flood-proof essential roads.

"With a little bit of money, maybe $150 million, we will never be caught in a situation where we can't get [produce] out again," Mr Katter said.