After the flood

Biblical, unprecedented, catastrophic.  

The sheer scale and intensity of the natural disaster that swamped South-East Queensland and northern New South Wales were astonishing – but could the flooding have been predicted?

That is the question on many minds – from shaken homeowners who awoke to find their homes filling with floodwater, to authorities dealing with crippling repair bills and extensive rebuilding.

While Premier Annastacia Palaszczuk has blamed Queensland’s flood emergency on an "unpredictable rain bomb", it seems that the real culprit was more likely ‘rivers in the sky’. 

“Technically, there is no such thing as a rain bomb,” says University of the Sunshine Coast Meteorologist and Civil Engineer Dr Adrian McCallum.

He says the recent intense rainfall and subsequent catastrophic flooding was caused by a poorly understood phenomenon known as an ‘atmospheric river’.

“The so-called ‘rivers in the sky’ in the lower atmosphere can exist across the tropical and sub-tropical regions. 

“These rivers can transport high concentrations of water vapour inland, which as we saw, can result in record-breaking rain and catastrophic flooding when this low-level moisture-rich air is forced to rise, say by the Great Dividing Range.

“It is fascinating yet concerning stuff.

“This event was always going to be difficult to predict. What causes atmospheric rivers in Australia is still not exactly known and how they respond to climate change is not yet particularly understood.”

Dr Cook discusses the wisdom of building on the banks of a flood- prone river and lessons from the history of flooding in two recent articles in The Conversation.

As the extraordinary weather event continued its destructive path south this week, international leaders on climate change issued a grim warning that global warming was going to result in more natural disasters in Australia and around the world.

USC Professor David Schoeman, an author on the latest Intergovernmental Panel on Climate Change report released on 1 March, says to expect more of the same.

As the global climate warms, extreme weather events that rely on warm air will become more commonplace, says Professor Schoeman.

"Because of past inaction on climate change, planning for these events can no longer rely solely on cutting future emissions, we must also improve our planning and adapt to the impacts we know are coming.

These include not only more frequent intense-rainfall events, but also rising seas.

Working with nature to solve these problems will often be cheaper and work better than engineering “solutions” that depend on rubble and concrete.

"This is true for combating both floods and sea-level rise, among many other risks."

Is it fair to pin most of the blame on a changing climate?

Dr Schoeman says while climate change cannot be blamed for individual events, like the one we have just experienced, it does make such events more likely.

Human actions also change floods, according to Dr Margaret Cook.

“We need to think about our planning and ways that we can adapt our behaviour a little to try and mitigate these problems we've created,” Dr Cook says.

It is a sentiment supported by Dr McCallum who says the recent weather event is a reminder of our vulnerability and the need to more carefully consider where we approve construction and development.

“Because it's these times we realise perhaps we shouldn't be spreading into those areas where, traditionally, in these conditions, we can get large amounts of flood water.”

USC Lecturer in Environmental Engineering Dr Helen Fairweather says to manage flood risks in a changing climate, there is a need for climate-smart engineering to identify flood risks and mitigate future impacts.

There is much to unpack from this weather disaster and many lessons to be learned, according to Professor Claudia Baldwin, co-director of USC’s Sustainability Research Centre.

“We were warned that La Nina could produce a wetter season; it is difficult to predict exactly how and where it would happen.  But we do know which rivers are flood-prone, and flood mapping is widely available on Council websites.”

Professor Baldwin says governments, emergency responders, businesses and residents should learn from previous and current events.

 “The Queensland Flood Commission of Inquiry made many recommendations regarding flood modelling, river gauges, flood mapping, planning, and building controls.

“We have been asking for a report on how many of the recommendations have been implemented and how, and the status of those not implemented."