Severe floods and heavy rainfall have swept through south-east Queensland and northern New South Wales in recent weeks, killing at least 17 people and damaging thousands of homes and businesses. Through it all, engineers have been critical to the emergency response.
Engineers are involved in the entire lifecycle of natural disaster management. Even before a flood hits, engineers have an important role to play in flood prevention. When floods do occur, they monitor dam levels and, in the aftermath, they assess infrastructure and help to improve the management of future flood planning.
The recent flooding was caused by a slow-moving low pressure trough situated off the coast, which led to abnormally high rainfall across south-east Queensland and coastal New South Wales.
By the start of March, Brisbane’s three-day rainfall record had been broken, with the city recording 677 mm of rain. More than 15,000 homes were flooded.
The Brisbane River peaked at 3.85 m. Although this was lower than the 4.46 m recorded in 2011, the catchment area was much larger this time around, meaning more rain fell across a wider area.
Multiple towns have been impacted, including Lismore, which recorded its worst ever flooding on record.
Food and fuel shortages, once the domain of COVID-19 lockdowns, were also caused by the severe flooding.
Disaster management
According to Engineers Australia Fellow and Chartered engineer Marie Gales FIEAust CPEng, engineers are central to disaster management.
“Flood engineers and dam engineers are managing an almost impossible situation … but at the same time, there [are] other engineers who are looking at infrastructure,” she told create.
“Then, in the immediate aftermath there’ll be structural engineers … checking the ferry terminals, checking the bridges.”
Gales, who is the President of Engineers Australia’s Queensland Division, noted the role of engineers does not stop once the immediate threat to lives and infrastructure has passed.
“Once the recovery is over, we then get into the rebuild phase,” she said. “That’s a real opportunity for design engineers and constructors to … build back better.”
Engineers Australia Honorary Fellow and Chartered engineer Dr John Macintosh HonFIEAust CPEng agreed that engineers are critical to the effective management of natural disasters.
“The most important role [for engineers] is understanding what the problem is, designing a solution to solve or manage the problem, and then … creating the end product,” he said.
“That’s the case for engineers across the board. They’re trained to … break problems down and solve them in a logical and substantiated manner. Flood investigations and flood management are exactly that.”
Macintosh’s background in water engineering places him in good stead to assess the situation in Queensland and New South Wales.
“I don’t think we’ve ever had a situation in the Brisbane River catchment where rain has fallen for so long without moving,” he said. “[Or where] a rainstorm could extend for so long at fairly high intensity, directly placed over the Brisbane catchment.”
According to Macintosh, the challenge for dam operators is balancing three key elements: increasing dam storage levels, reducing the impact of flooding downstream, and avoiding loss of life.
Learning from the past
The floods in greater Brisbane are an unwelcome reminder of the disasters of 2011 and 1974. However, certain developments were made after those events that have greatly assisted in 2022.
“One of the learnings from ’74 was [that some of] the people who died … were electrocuted after the event,” Gales said. “So we have electrical engineers extensively monitoring the situation.
“Another key learning from the 2011 flooding was replacing the ferry terminals as pontoons broke free and became like missiles in the river. The ferry terminal gangways now break free to let debris through.”
Macintosh said there had been three major administrative and technical developments that have improved flood management and community resilience.
First is the Brisbane River Catchment Flood Study, which provided hydraulic and hydrologic assessments of the catchment system for the first time.
“That study connected Brisbane River from the city up to [Wivenhoe] Dam in a good hydraulic model,” he said.
Such modelling enables engineers to predict the effect of releasing excess water on flood levels downstream.
Secondly, reporting on the capacity of Wivenhoe Dam has also been improved. Now, regular water supply capacity is differentiated from flood storage capacity.
This has made it considerably easier for engineers to understand the complete picture during a high rainfall event, Macintosh said.
“The other thing is that they have increased the flood storage capacity from what it was previously,” he added.
Such changes echo the principle of taking on board new information and “melding it into our methodologies” to avoid the past being repeated, he said.
Both engineers agreed that a key way to do this is to build resilience.
“Part of the new design [of the Brisbane River] was about being flood resilient, not flood proof,” said Gales.
Building resilience
Engineers Australia Fellow and Chartered engineer Professor Cheryl Desha FIEAust CPEng sees the value of preventative measures and planning.
“Planning well for a range of potential scenarios [is essential],” she said. “In preparing for them, we are also likely to be preparing for the unknowns.
“Risk management tells us that we’re dealing with some unknowns that we can’t imagine yet.”
Desha, an environmental engineer and Griffith University academic, has been at the forefront of initiatives to build Brisbane’s resilience as a city.
For example, she was instrumental in the design of Griffith University’s Engineering, Technology and Aviation building, also known as Building N79, which can be adapted for use in different disaster contexts.
The building features laboratories, workshops and learning spaces for students, but it can also double as an emergency response centre — as evidenced by its recent use by the Red Cross.
“Wherever we are practising as engineers, we must return to the assumptions that we make about what we do and question them for their validity in a climate change-impacted world,” Desha said.
“For me as an academic, it extends into revising the curriculum that we are responsible for and making sure our students are equipped with what they need to perform … because the rules are changing.”
Macintosh agrees.
“With climate change there’s uncertainty about what might happen in the future,” he said. “We’ve got to become more resilient.”
Join us this November at the Hydrology & Water Resources Symposium as we discuss current water issues, including the recent NSW and QLD floods, and explore innovations shaping the future of water engineering. Submit your abstract by Friday 20 May to be considered for inclusion on the program. Find out more at hwrs.com.au