Townsville flood maps reviewed as more homes go under

Townsville’s flood maps did not predict the inundation across riverside suburbs where new, ground-level homes were built.

Damaged furniture and appliances strewn in the flooded streets of Hermit Park as heavy rain continues to fall in Townsville. Picture: Lachie Millard

Townsville’s official flood maps did not predict the inundation across riverside suburbs where the city council approved swaths of new, ground-level homes and businesses in recent years.

The north Queensland city’s five-year-old maps will be redrawn following this week’s flood — the worst on record — in which hundreds of properties were inundated above their floorboards and up to 10,000 damaged across the region.

The maps, used to approve new developments, projecte­d that several low-lying suburbs, such as Idalia and Oon­oonba, would escap­e a one-in-100-year flood largely unscathed.

Townsville City Council’s spokeswoman said last night the model, which was based on expert modelling of different scenarios, was overwhelmed by an “unprecedented” monsoonal trough which is set to ease by tomorrow.

“The planning scheme require­s properties to be constructed above the 1 per cent AEP (one-in-100-year) flood level plus a freeboard allowance,” she said.

“The rainfall and flooding ­experienced in this event was ­unprecedented and significantly exceeded those levels.”

She said the modelling behind the maps included data collected during the city’s last major flood, the “Night of Noah” in 1998.

 

Michelle Nethery and David Sheppherd, whose flood-ravaged home in Idalia was built in 2005, said they were “never, ever” told that the neighbourhood was vulnera­ble to flooding.

“We had council maps for the zones,” Ms Nethery told The Aust­ralian, noting that a friend’s house that was predicted to go under escaped entirely. “They do it (develop low-lying land) everywhere. Half of the Gold Coast is built on swampland.”

Mr Sheppherd said the family had “never ever seen water in the street”, including after Cyclone Yasi struck in 2011.

Suburbs such as Idalia have been developed in recent years, with estates such as Fairfield offering new, ground-level houses based around shopping precincts.

Local Government Associa­tion of Queensland chief executive Greg Hallam said Towns­ville’s flood maps relied on “exhaustive modelling of every possible scenario”, looking at variable­s such as rainfall and artificia­l structures.

“We’re not God. We don’t have supreme knowledge. We only have the best science, the best knowledge we can have,” he said. “We now know with the (dam) gates fully open … what will flood and what won’t, so there will be a new set of flood maps prod­uced out of this event.”

Mr Hallam said Townsville’s maps were prepared using a “Monte Carlo” risk analysis, which models the likelihood of different outcomes in hard-to-predict situations, as recommen­d­ed in 2012 by experts attache­d to the Queensland Floods Commission of Inquiry.

Mr Hallam said home owners had no legal recourse to compensation if their neighbourhood was later revealed as a flood zone.

Premier Annastacia Palasz­czuk declined to comment on planning issues, saying she was focused on the recovery effort. She said more than 13,000 applic­ations had been made for disaster relief assistance, with $1.2 million paid out. The Insurance Council of Australia has processed 3500 claims worth $45m.

Scott Morrison yesterday extended the federal disaster recovery payment. Previously only available to homes that took a higher level of damage, the one-off payment of $1000 an adult and $400 a child now will be available to anyone whose home was inundated above the floorboards.