Before the storm
It’s a catastrophe in anyone’s book, not least those of insurance companies anticipating the tens of thousands of claims likely to be lodged.
As the floods surged south in the days after Cyclone Debbie hit landfall near Bowen in north Queensland on March 28, a natural disaster was declared in five major centres in northern New South Wales.
— Fire & Rescue NSW (@FRNSW) April 4, 2017
Citing the chairman of the Insurance Council of Australia, the Australian Financial Review said “in insurance terms, a catastrophe means a disaster that causes a significant number of claims in a region” and for Cyclone Debbie that could be claims over $1 billion.
CSIRO’s Dr Chi-Hsiang Wang and colleagues have been researching the cost implications of extreme weather events but with a focus at the other end – predicting the likely cost before the storms.
Counting the cost of extreme events
Deloitte Access Economics last year delivered a report on building resilient infrastructure which estimated that, between 2002-03 and 2010-11, an annual average of more than $450 million was spent by Australian governments on restoring essential public infrastructure following extreme weather.
If it’s business-as-usual, the report said, $17 billion is expected to be spent on direct replacement costs of essential infrastructure due to natural disasters between 2015 and 2050.
These estimates don’t factor in the impacts of climate change.
In the case of Cyclone Debbie, the wind intensity exceeded the limitations of the building specifications.
“It’s not a surprise that we see considerable damage because the intensity is so high,” says Dr Wang.
Until now, a cyclone with the force of Debbie was considered a once in a 2,000 year event by Australian design standard for wind actions (AS/NZS 1170.2:2011). That may change.
“There’s a consensus among scientists, although not as strong as the consensus around rising global temperatures, that for some tropical cyclone basins around the world they are likely to see events of increased intensity,” he adds.
Dr Wang says the current practice for wind impact assessment of physical infrastructure uses only wind intensity (in terms of wind gust) to gauge the damage potential of windstorms.
“This ignores other threats brought upon by the accompanying rainfall and storm surge,” he says.
“With climate change that induces warmer sea surface temperature, rainfall from windstorms is expected to rise. To more accurately reflect a storm’s potential to cause destruction, we need a new windstorm intensity metric that takes into account the compound impacts of high wind, storm surge, and rainfall/hail.”
That notion of the multiplicity of hazards also follows through to calculating likely risks or impact to assets.
It is well recognised from historical events that interdependency exists among critical infrastructure such as energy, water supply, hospitals, transportation, and industry, which need to function cooperatively to produce and distribute a continuous flow of essential goods and services.
The recent experience in South Australia with last September’s Black System failure of the state’s electricity system is a case in point.
Risk assessments require a much more layered approach to predict the likely costs of damage.
Vietnam’s Da Nang serves as a case study
Dr Wang has worked with colleagues Dr Minh Nguyen and Mr Yong-Bing Khoo on assessing the predicted cost of cyclones in the Vietnamese city of Da Nang, one of the cities selected for the 100 Resilient Cities Rockefeller Foundation-funded project.
The city provided the historical damage data. Using that information and applying various scenarios of wind intensity to spatial information such as topography, terrain and shielding from the built environment, they established vulnerability models as well as hazard extent and intensity which showed which parts of the city would be weakest in a future cyclone event.
Da Nang served as a demonstration study of the Geographic Information Systems mapping tools based on CSIRO’s visual climate adaptation decision-making support platform, MetroEngines. This platform enables users to assess impact, costs and benefits of adaptation options for housing or infrastructure subjected to natural hazards.
“We’re able to establish a vulnerability curve – what percentage of buildings are likely to be damaged according to predicted wind speeds,” Dr Wang says.
“If there is more funding available, the intent is to conduct similar work in other wards of the city. We can make a damage assessment and illustrate adaptation options for the city as a whole to see what our research can look like and the city can use the outcomes for planning decisions.”
Those mitigating infrastructure decisions for extreme wind gust resistance might range from moving whole communities from high-risk areas, building stronger roof-to-wall connections, installing more resilient building envelopes, raising building standards for structural elements to resist more destructive forces. Similarly, decisions for coastal inundation mitigation might range from moving whole communities from low-lying areas, building sea walls, lifting building heights, creating floodwater retention and absorption capacities.
The Australian Context
Dr Wang says there is increasing interest globally in resilience building and anticipating future impacts of climate change on built environments.
But in Australia, there is room for improvement when it comes to building and infrastructure construction for cyclones and coastal inundation. MetroEngines, can be employed anywhere in Australia to assess natural hazard impact, costs and benefits of adaptation options for housing or infrastructure to assist future proofing for Australia.
There is particular need to address infrastructure issues also in light of predictions that Australia’s population is to double by 2075.
Dr Wang says they can now look at the projected climate, factor in the rate of frequency and intensity changes over time and the options into account.
“Government and regulatory bodies will need to consider the trade-off between higher infrastructure costs and the likely benefit of limiting damage,” Dr Wang says.
“Improving resilience of essential infrastructure has the potential to decrease the chance of disruption and generate significant benefits in terms of avoided disaster costs.”