A report by actuarial consulting firm Finity concludes that Brisbane is likely to suffer future riverine flooding at higher levels than this year’s 4.5-metre peak.

It says six Brisbane River floods in the past 170 years have had a recorded peak higher than the 2011 floods, with the water height twice exceeding eight metres.

Finity Chairman Colin Brigstock and Principal Tim Andrews, who co-authored the report The challenge of insuring homes for flood, say history shows that the Brisbane River is prone to severe flooding, “and floods that are more severe than the 2011 floods appear to be likely at some stage”.

The report looks at the flood history of the Brisbane River and its correlation to La Nina weather patterns.

It found that since 1880, in the 16 years when flooding of two metres or greater has occurred, 36% of the floods occurred during a La Nina weather pattern, 54% during neutral weather patterns and only 9% during an El Nino pattern.

The current La Nina pattern has been described as being one of the strongest on record, with a Southern Oscillation Index (SOI) – a measure of sea surface temperatures that is indicative of a La Nina pattern – of 14. A figure of eight or above is described as a La Nina pattern.

The report also finds that flooding has occurred in four out of seven years where the SOI was 14 or higher. 

“There appears to be a strong statistical relationship between La Nina years and floods, with flooding being more likely when it’s a strong La Nina,” the report says.