Flood defences such as levees strengthen disaster resilience but can only offer so much protection, a Senate inquiry into climate risk’s impact on insurance premiums has heard.

“When it comes to levees, there are different standards of protection,” Suncorp scientific specialist Rhys Whitley told the inquiry on Friday.

“The levees are designed to protect at a particular flood height. While it is fine to put a levee in and, for the most part, they are a very effective means of protecting the community, and they will result in a discount or a reduction in premium ... not all levees are the same.”

Dr Whitley was responding to a question from the Senate select committee on why some communities have not seen changes to their premiums after levees were built.

“You can design a flood levee for a one-in-20-year event ... or a one-in-100-year event,” he said. “If you build a flood levee to a lower-standard protection, a weather event that is extreme enough will overwhelm those defences, so that’s one issue.

“The second issue is when these standards of protection are designed, they are typically based on historical information, which is limited ... we don’t have a continuous record for everywhere across Australia.

“When it comes to weather extremes, we can’t just rely on human observations. The weather system can produce events that are well beyond our experience, which is what we have seen with the east coast flooding of 2022.”

The committee held hearings over two days last week – in Ballina, NSW, on Thursday and in Brisbane the following day.

Suncorp and RACQ Insurance were the only two insurers that fronted the committee, which heard from community groups and councils frustrated at insurers’ pricing methods and post-disaster responses.

Asked about the role of climate on premiums, Dr Whitley said: “If we were to address the role of climate change, it would be small, less than inflation on average, probably less than a percent change year on year. We can’t ignore ... the role of natural climate variability.”

He says climate change will make weather extremes more frequent and more severe.

“How fast that change occurs is less clear because we’re dealing with the noise of the natural cycle, the natural oscillations in the climate ... So it’s very hard to say that this particular weather event will not have happened without climate change. When these weather events occur, it becomes evidence to us about how the risk profile is changing across Australia, so we must incorporate that information in the way we determine premiums, unfortunately.”