Dr Kiem said the speculation of a 40-year flood cycle had “some credibility” after he found the five-year target periods had an “abnormally higher number of floods” than other periods.

“We have about 125 years in our study period and we had four five-year target periods where based on the speculation you would expect higher floods,” he said.

“Those four five-year periods make up only 16 per cent of the record but they actually contain about 80 per cent of the major floods in south-east Queensland.

“The next serious widespread flooding in south-east Queensland is expected in 2050-54 if this holds true."

He said sea surface temperature fluctuations and pressure changes in the north and south Pacific Ocean, called interdecadal Pacific Oscillation (IPO), happened in 20- to 40-year cycles and were possibly linked to the major flooding events.

“There has been a lot of work in the last decade linking IPO with rainfall and flood variability and drought variability in Australia,” he said.

“When the IPO is in its negative phase, that is when you get a gathering of warm sea surface temperatures off the east of Queensland,” he said.

“Warmer sea surface temperatures mean evaporation is increased and when you have increased evaporation off the ocean there is more water in the atmosphere ... so it rains more often and when it does rain there is more water in the atmosphere to fall.

“When those negative phases occur, they line with periods where we see really frequent floods.”

Dr Kiem said there was “no trend” of recent flooding events being any worse than the floods a hundred years ago.

While the examination was limited in terms of a statistical analysis, typically at least 30 samples are required for an analysis, Dr Kiem said the assumption that flooding was random seemed “unlikely to be valid”.

"If you look at all of the record, when you are in one of these IPO negative phases, the chance of a flood occurring is 12 to 13 times more likely ... if you are in that phase,” he said.

He said the possible cyclical nature of flooding was “totally at odds” with the ways we estimate and deal with flood risk.

“From an engineering point of view, the underlying assumption that underpins all engineering design is that the chance of a flood occurring is random and the chance is the same from one year to the next or one decade to the next,” he said.

“We assume floods are independent and identically distributed ... it underpins all engineering but what we are finding here is that assumption is flawed because the chance of a flood from year to year is not the same."