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Preventing floods: what can we learn from Australia’s 'one-in-1000-year' event?

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analysis 040422The recent floods in Queensland and NSW have taken a heavy toll on Australia. However, amidst the losses, valuable lessons can be learned. MD HDI Global SE in Australia Stefan Feldmann, pictured, reflects on how we live with our changing environment.

In March 2022, a severe weather system combined with a La Niña season brought so much rain to the north-east of Australia that Brisbane, the state capital of Queensland, received 80% of its annual rainfall in just three days.

As rivers burst their banks, at least 15,000 houses were flooded, and the city's port had to be closed for safety reasons. It had been only a decade since the state was hit by similarly severe flooding in 2011.

As the unpredictable storm stretched south, the town of Lismore in northern NSW was overwhelmed by the floods. At times the local river reached water levels of over 14 metres, more than two metres higher than the previous peak in 1954.

With little warning, hundreds of people had to be evacuated, their lifelong belongings gone, many houses rendered unliveable.

Even further south, the floods caused damage and chaos in Sydney. Tragically, 22 people have died directly from the recent floods. The emotional toll for survivors is great and recovering from the loss of homes, businesses and personal possessions will take years.

A rise in unpredictable weather patterns

Australia’s recent experience is only one example. Many of the world’s people, often the poorest, live in regions that are susceptible to flooding.

Some of the world’s largest cities, like Jakarta in Indonesia or Lagos in Nigeria, can be inundated by rising water levels. With the increase in unpredictable weather patterns, many cities are improving their infrastructure.

However, as British scientists from the University of Nottingham argued in a report for academic magazine The Conversation: “Most of the focus remains on big engineering solutions like flood walls and embankments rather than a more holistic plan that would involve every level of society.”

Across the world, various strategies are being implemented for effective flood management. Flood levees, flood protection and defence structures as well as mobile flood barriers have provided effective flood management in many regions across European countries, such as Germany, the Netherlands, France and others.

Similar investments have also been made in communities in Australia. Among these is a temporary flood levee which saved the flood-prone town of Maryborough, 250km north of Brisbane, in the recent floods.

Effective flood management

The Maryborough levee consists of steel A-frames and is covered by plastic sheeting which is weighted down with a heavy-duty chain.

The model is the same that the Rockhampton City Council used in the 2017 floods to protect some parts of the city. The one in Maryborough, can be assembled by a team of 30-40 people within six hours. Although numerous houses and businesses were impacted when the flood peak reached 10.3-metres, Maryborough was able to save most of its central business district from being inundated with water in early 2022.

At the time, Fraser Coast Mayor George Seymour told ABC News that without the levee, which was commissioned in 2017, the whole CBD would have been under water.

"The state government provided funding for us to purchase it for flood protection," he said.

An example of coordinated flood mitigation, the Queensland government paid $4.8 million, while the Council provided $1.2 million for the levee – a worthwhile investment as prior floods in 2011, 2012 and 2013 caused nearly $43 million in damage.

Simple measures making a difference

Similar measures are available for homes and businesses as well.

Simple flood barriers or a floodgate on a door can be enough to save a house from major flooding, at least if there is one main access point. Another simple measure is to raise up the electrical switch gear so that no water can penetrate the switch.

Businesses can also consider temporary flood barriers that can be erected around essential equipment.

The decision on levees or even individual solutions for households or businesses, is a particularly complicated one, where costs, maintenance and aesthetics have to be taken into consideration.

In Lismore, for example, the CBD levee was constructed in 2005 after 30 years of debate that culminated in council deciding on a 1 in 10-year recurrence interval. The 2022 floods have clearly rendered this insufficient, along with any simple measures, where water levels rose to cover two-storey buildings in some areas.

Do whole towns need to be relocated?

There really isn’t a “one size fits all” solution to the issue, as flood expert Denis Simanovic from global reinsurance broker Gallagher Re explains.

“While levees and other structural mitigation measures work well to protect some locations, the physical nature of flooding in other locations means that their ability to reduce the risk is inefficient at best and a detriment to surrounding areas in a worst-case scenario.”

This, of course, raises the question if it would be more viable to relocate certain townships.

However, while Grantham in Queensland set a precedent for partially relocating highly flood-prone towns, Lismore is a much larger regional city with a population just short of 30,000, a significant percentage of which live with some flood risk.

“Voluntary purchases or moving the entire town would therefore be a very expensive mitigation option,” Mr Simanovic said.

While costly, current conditions suggest such measures may be necessary, unless an alternative mitigation approach is found.

In addition, much more care with future town planning for business and residential areas should be implemented also.

Larger scale flood mitigation

While larger scale dam projects have been proposed in Australia, not everyone is convinced this is the best approach to managing water security.

There are other larger scale mitigation methods though, that lead well beyond the focus on engineering. The British scientists from the University of Nottingham for instance point to so-called blue-green infrastructure in their research, which uses the planning system to integrate rivers, canals or wetlands (the blue) with trees, lawns, parks or forests.

“This can involve anything from small-scale ‘rain gardens’ that allow water to drain naturally through soil, through to much larger-scale artificial wetlands or ponds,” they write in their report for The Conversation.

China introduced so called “sponge cities” in 2013. The port city of Ningbo is one such example, where a 3km strip of brownfield was transformed into an eco-corridor and public park. This and other sponge cities, use nature to absorb, clean and distribute water, rather than using concrete to channel away rainwater.

The University of Nottingham scientists are concerned though, further measures and a more urgent approach is needed for flood mitigation to be effective in the future.

“As we have recently argued in our research, these cities must instead become truly ‘resilient societies’ – before it is too late.”

This shows how each town or city needs to assess its individual risk and respond to this risk with a solution that is most preferable to its needs.

More research is needed, however, to understand if this is viable for significant weather events happening in Australia.

Managing risks efficiently

Flood losses can without doubt be minimised with efficient prevention. A necessity, however, to start the process, is high-quality flood models.

“This is the single most important investment that a local government can make in understanding the underlying risk of flooding to their local community,” Mr Simanovic said.

“These will form the basis for deciding on future mitigation options.”

Those options will be critical for town planning and mitigating risks in future natural catastrophes.

Most insurers do have a natural catastrophe plan to manage their risk from major weather events, as Regional Claims Manager Australasia and ASEAN at HDI Global, David Lloyd, explains.

“From an insurance perspective, however, no matter how good that plan is, you can’t anticipate every eventuality,” he said.

“This is why the development of artificial intelligence, satellite imagery and GPS mapping to assess the extent of damage within hours of the event is critical to assisting insurers early and, of course, providing insurers with the ability to assist the insured more quickly thereby reducing damages and quantum.”

Logically, this is quite an investment, but it’s slowly become a “must have” for insurers, governments, organisations and local communities.

“Insurers need to see prudent investment to reduce exposure to flood events and subsequently insurance costs,” Mr Lloyd said. “The first step is to show the intent to mitigate, the second is funding and the third is implementation.”

While these all take time, with the frequency of these significant weather events, a coordinated societal approach and greater investment into flood mitigation will be critical for towns and cities at greatest risk over the next few years.

In the short term, communities have come together to support each other.

Relief payments have been made available by the government and 7000 defence personnel are working on the flood recovery nationally.

In the longer term, there is an opportunity to learn from these events and plan for the future. Together, we can do better, and insurance can play a role in helping organisations and governments do this.