The Queensland government will launch a commission of inquiry into flooding that devastated the small towns of Grantham and Helidon in 2011, killing a dozen people.
The commission, to be run by former solicitor general Walter Sofronoff, will investigate the alleged role in the flood’s impact of a collapsed wall at a quarry owned by a Toowoomba business family.
The government also announced an independent review of whether works on a rail link in Brisbane’s north contributed to flash flooding that killed five people last Friday.
A report from consultant DHI found that a section of collapsed embankment at Grantham’s quarry was 260 metres long, not 55 metres as reported by an earlier floods inquiry.
Premier Annastacia Palaszczuk said the people of Grantham had suffered through “one of the most appalling natural disasters in Queensland’s modern history”.
As well as the 12 deaths, 50 families were “left with only the clothes they were wearing when a shattering wall of water swept through the town with little warning”, she said.
“They are determined that the deaths of their friends and neighbours and family members on that day will not be in vain.
“They deserve and require further closure. They want the truth to prevail.”
Palaszczuk said the inquiry, which would use independent hydrological modelling, would focus on whether the quarry breach caused or contributed to the flooding, whether it had a “material impact” on the damage, whether it had implications for the town’s evacuation, and on how the matters were initially investigated.
The quarry was owned by the Wagner family, which has grown wealthy from the cement business, but it has since been sold to Boral. Wagner’s director Denis Wagner has questioned the basis of the DHI report but said he welcomed any review of the original flood inquiry’s findings.
The inquiry will gather evidence from 11 May and conclude on 31 August.
The deputy premier, Jackie Trad, said the review of whether the Moreton Bay rail link contributed to the deadly flash floods in Brisbane’s north last Friday would run over the next 12 weeks. It would include analysis by the Snowy Mountain engineering corporation.
Five people lost their lives in three cars that were washed off the road by flash floods after record heavy rainfall around Caboolture.
