A "large-scale" report into waterlogged South-East Queensland's dams is expected by the end of the year, six years after it was commissioned, the state government says.
Water Minister Glenn Butcher told ABC Radio Brisbane this week that an "extensive" study into the dams had been underway since 2016, with Somerset Dam the priority for any recommended works.
The update on flood mitigation strategies and water storage capacity came after former premier Campbell Newman warned that any delays meant Brisbane businesses and residents were not protected from future flood events.
Mr Butcher said the Palaszczuk government made a decision to continue with a dam safety and improvement program for Somerset, Wivenhoe and North Pine dams when it took office.
"We need to identify what we need to do about the safety works, but can we at the same time raise [dam walls on] Somerset or Wivenhoe or both?"
Somerset Dam was the priority because it was the oldest, the Minister said.
"Geotechnical work is being done, big-scale physical hydrological models have been tested, and I will get that report delivered to me in 12 months but hopefully by the end of the year.
"It's extensive work, it's large-scale work on a dam that's aged."
A pre-feasibility study commissioned by Mr Newman in 2014 recommended three projects that could flood-proof Brisbane and Ipswich:
- raising Wivenhoe Dam's wall by between 1.5 and 4 metres
- building a new dam at Linville on the Upper Brisbane River
- building another dam on Lower Warrill Creek near Willowbank
Mr Butcher said the current government had ruled out the Warrill Creek option "in the early stages", and added that while a dam at Linville had "potential", it would not have made a difference to the recent floods.
He said the priority was to look at raising the walls of Somerset and Wivenhoe dams and "if we can't do that, we'll look at Linville".
The government had completed improvement works on the Cooloolabin, Ewen Maddock, Sideling Creek, Wappa and Leslie Harrison dams, Mr Butcher said.
"[Then] once we get through Somerset, we will know what to do on Wivenhoe because they work as one dam.
"We need upgrades done by 2035."
Need to account for all waterways
But Mr Newman said government inaction meant businesses and residents were once again facing ruin from a flood disaster.
"We've seen in this flood event ... a river flood event which was less than 2011, but we've also seen flooding in creek catchments which was far worse, so there's been overall a larger impact," he said.
"One of the things looking at river flooding in Brisbane, yes, Wivenhoe and Somerset dams provide protections upstream on the Brisbane and Stanley river systems, but you've got a whole lot of other water courses that flow in below the dam — for example, the Bremer River and Lockyer Creek.
According to reports handed to Mr Newman more than seven years ago, raising the Wivenhoe Dam wall would reduce the number of flooded properties by 8,150 in an event similar to that of January 2011.
But he admitted that project could have taken up to 10 years to build and might not have been completed in time to alleviate the impact of the recent floods.
Another plan has been considered
Mr Newman's government also assessed an alternative plan put forward by late accountant John Hodgkinson, Gold Coast retiree Trevor Herse and grazier Ron McMah.
The trio believed connecting Borumba Dam near Imbil to Wivenhoe and Somerset could protect Brisbane, Ipswich and Gympie from floods.
The Bligh government had also considered the idea as an alternative to the failed Traveston Dam project but rejected it.
In the plan, water could be pumped from Wivenhoe to Borumba, allowing it to drop considerably and improve its capacity to hold back water from the lower catchments.
Somerset would be reduced to the level of its drinking water compartment as well, allowing both dams to hold about 3 million megalitres in a flood.
The project, however, failed to gain traction.
Meanwhile, Seqwater said this week it had stopped releasing water from Wivenhoe Dam — a response to the heavy falls in the dam catchment area during the last week of February — and its flood operation centre had been stood down.
The organisation said the dam would continue to receive water from upstream that may require low-flow operational releases.
