Rebuilding for flood resilience

Back in January 2011, deadly flash flooding in Queensland’s Lockyer Valley claimed 14 lives and completely destroyed 29 houses in the town of Grantham. Nearly every home in the entire town was structurally damaged in the flood.

Four months later, the Queensland Reconstruction Authority and Lockyer Valley Regional Council announced a bold plan to rebuild virtually the entire town on higher ground. The first residents had moved into their new homes, located on a nearby hill, by Christmas of that year.

It probably seemed like an extreme step at the time. But as we reflect on the devastation caused by two back-to-back years of severe summer flooding on Australia’s east coast, it’s hard not to wonder if Grantham was onto something.

The ABC has reported that more than 3,000 flood-affected homes in NSW are currently considered uninhabitable and 1,200 people are in emergency accommodation in the Northern Rivers region. Within the region, the town of Lismore has become emblematic of the destruction the floods have caused. Lismore’s mayor, Steve Krieg, has flagged that the council has had ‘preliminary’ discussions about following in Grantham’s footsteps and relocating some residents to higher ground.

In Queensland, tens of thousands of properties have been reported impacted by recent flooding, and 13 lives lost. The Queensland state government last week announced $771 million in funding to aid recovery for residents and businesses affected by this year’s floods.

Even as I write these words, the Bureau of Meterology is continuing to issue flood warnings for parts of New South Wales.

And this all comes only a year after another major flooding event in NSW in early 2021. Scientists have warned that floods are becoming more likely in Australia due to ongoing climate change.

So, where do we go from here? Can science help us rebuild more flood-resilient homes and communities?

What exactly is flood resilience?

‘Flood resilience is firstly the ability to resist and withstand floods, but also the inherent capability of the community to recover,’ says Andrew Gissing, general manager for the resilience program at Risk Frontiers, a company specialising in natural hazard risk and catastrophe modelling and solutions.

Adrian Turner, CEO of the Minderoo Foundation’s Fire and Flood Resilience Initiative, agrees.

‘At the highest level, it’s about being able to absorb the flood and being able to recover quickly from it,’ he says.

For Turner, flood resilience is a function of the community itself as much as the surrounding natural and built environments.

‘It’s the social fabric of that community, it’s the strong leadership in the community,’ he says. ‘It’s the diverse economy in the community to be able to bounce back from the flood.’

How can science help?

Gissing says that flood resilience requires a multi-faceted approach, integrating factors including mitigation, resilient building design, warning systems, land use planning, landscape management and emergency planning.

Tracking, modelling and predicting floods is complicated business. There are many different types of flood, including riverine, estuarial and urban, which are affected by different parameters. As climate change marches on, predicting flood behaviour gets even trickier.

‘We tend to build models based on past behaviour and ground-truth those models in past outcomes,’ Turner explains.

But with the level of unprecedented extreme climate events we’ve been seeing, those models can ‘break down’ and struggle to make accurate predictions, he says.

Despite this, Turner is optimistic about the promise of new space-based surveillance systems and datasets to overcome these challenges.

At the household level, rebuilding with materials that can better withstand flood damage is one strategy to shore up flood resilience. For example, tiles and solid timber can stand up to floodwaters better than carpets and particle board, Gissing says.

Turner says we should think about moving electrical and HVAC systems above the floodline in rebuilt houses, as well as including rooms above the floodline that are accessible to the outside, and ensuring that any structures below the floodline are built watertight.

Iftekhar Ahmed, an associate professor in construction management and disaster resilience at the University of Newcastle, suggests we might be able to learn from flood resilience strategies used by communities in other parts of the world.

‘If you go back to the traditional architecture in many parts of Asia, you see that [buildings] are raised above water – they have these stilts,’ he adds.

The stilts are traditionally made of timber or bamboo, but concrete posts are an even more durable option for raising buildings above the water line.

Building houses on stilts rather than a flat foundation can also help mitigate ‘settling’, or sinking into the ground, following a flood. Having the house supported at multiple points allows for differential settling, which is easier to fix by digging and filling in where needed.

However, Ahmed says that retrofitting existing structures to be more flood-proof is too expensive and difficult to be practical in many cases. That’s where broader mitigation strategies around the landscape and location come into play.

Gissing points out that buy-back or relocation schemes, as occurred in Grantham, can be expensive, and so recommends they be focused in areas with the greatest risk of loss of life in floods.

However, Turner thinks it’s an option that should be discussed more.

‘I do think we have to have a serious conversation as a country about relocating homes and even communities away from flood zones,’ he says.

Ahmed suggests that actually allowing floodplains to return to wetlands while moving residential areas to higher ground could be a win-win.

While that idea may or may not catch on, it’s clear that the surrounding natural environment can be just as important as building materials to reduce the damage caused by floods. Turner gives the example of maintaining and restoring estuaries.

‘We’ve allowed the wrong sorts of vegetation to grow in a lot of our estuaries that don’t absorb water the right way, and we tend to let debris accumulate in estuaries as well,’ he says.

Making improved flood resilience a reality

‘I think the technology substantially exists [and] we know what needs to be done from a building point of view,’ says Turner.

‘The thing that’s holding us back, I don’t think is the science or technology. I think it’s the economics.’

Both Gissing and Turner highlight the figure, from a 2015 Productivity Commission report, that Australia currently spends 97 per cent of disaster funding on recovery and only three per cent on preparation and mitigation.

‘It’s upside-down,’ says Turner. ‘There’s a whole lot more we could be doing ahead of time.’

Everyone has a role to play, from the federal to state and local governments as well as individual households.

For example, one thing nearly all households can do is develop a flood preparedness plan, so we’re not caught out when disaster strikes.

Turner says the insurance industry also holds levers to support flood resilience strategies – for example, through offering discounts on insurance premiums if policy-holders take steps to flood-proof their homes.

Governments can contribute through better data-sharing about disaster events and by implementing building codes and other incentives to promote flood-resilient communities and landscapes.

Ahmed points to new regulations introduced following Hurricane Katrina in the US, which required buildings to be raised above the ‘base flood level’ – in some cases, up to three or four metres above the ground.

Unfortunately, getting such large-scale changes off the ground doesn’t necessarily mesh well with current election cycles.

‘It takes strong political leadership to take a longer-term view,’ says Turner. But it needs to be done.

‘If we have a system that’s only focused on response and recovery, then we never get off the treadmill,’ he says. ‘The best time to deal with resilience is when there isn’t a crisis.’

Turner also reckons there’s more that the research community can do to reach government and the broader community.

‘It’s no good if insights are sitting in a research paper,’ he says. ‘They have to be translated into a new building material or informing how infrastructure can be built back to withstand future events.

‘Sometimes incredible research gets stuck in the lab versus having a clear pathway out to have impact.’

And speaking of communication, there’s one particular phrase he’d like to see disappear from our vocabulary: the ‘one in 100-year’ fire or flood event.

‘People understand that as not a one per cent risk, they understand it as, well, now I’ve got 99 years until the next one,’ he says.

‘I mean, we’ve had two unprecedented natural disasters in three years. We’ve got to stop calling these events “one in 100-year”.’