Sabrina Pit, Western Sydney UniversityYet again, large swathes of New South Wales are underwater. A week of solid rain has led to floods in the Mid-North Coast, Sydney and the Central Coast, with several areas being evacuated as I write.
As a resident of the NSW Far North Coast, which has had its share of devastating floods, many of the tense scenes on the news are sadly familiar.
Unless you have lived through it, it is hard to understand just how stressful a catastrophic flood can be in the moment of crisis. As research evidence shows, the long term impact on mental health can also be profound. And often it is the most disadvantaged populations that are hardest hit.
In many places, socio-economic disadvantage and flood risk go hand in hand.
In a study published last year, led by the University Centre for Rural Health in Lismore in close collaboration with the local community, colleagues and I looked at population data following Cyclone Debbie in 2017. We found people living in the Lismore town centre flood footprint experienced significantly higher levels of social vulnerability (when compared to the already highly vulnerable regional population). This study would not have been possible without the support of the Northern Rivers community who responded to the Community Recovery
after Flood survey, nor without the active support, enthusiasm and commitment of the Community Advisory Groups in Lismore and Murwillumbah and community organisations.
Notably, over 80% of people in the 2017 Lismore town centre flood-affected area were living in the lowest socio-economic neighbourhoods. The flood-affected areas of Murwillumbah and Lismore regions included 47% and 60% of residents in the most disadvantaged quintile neighbourhoods.
By examining data from the 45 and Up study, we also showed that participants living in the Lismore town centre flood footprint had significantly higher rates of smoking and alcohol consumption. They were also more likely to have pre-existing mental health conditions such as depression and anxiety, as well as poorer general health.
So even before disaster strikes, residents in flood-prone areas may be more likely to battle with financial and health issues. Our study showed disaster affected people also had the fewest resources to recover effectively. When floods arrive, the impact on mental health, in particular, can be acute.
A flood can be extremely stressful in the moment, as one rushes to protect people, property, pets and animals and worries about the damage that may follow. Can you imagine clinging to a rooftop in the rain in the middle of the night and waiting to be rescued?
The damage caused by floods causes enormous financial pain, and can lead to housing vulnerabilities and homelessness, especially for those without insurance — and research reveals a pattern of underinsurance in disadvantaged populations across Australia.
Even if you are lucky enough to have insurance, waiting to have your claim assessed and approved, then dealing with a shortage of tradies can take a real toll on your mental health. The waiting and the uncertainty can be especially hard.
Other flood research by colleagues and I, led by the University Centre for Rural Health, showed business owners whose homes and businesses had flooded were almost 6.5 times more likely to report depressive symptoms. Business owners with insurance disputes were four times more likely to report probable depression.
Flood affected business owners whose income didn’t return to normal within six months were also almost three times more likely to report symptoms of depression.
Lack of income can clearly cause stress for the individual, their family and their larger network. Small businesses play an important role in rural communities and employ a large number of people so the sustainability of local businesses is crucial.
We also found the higher the floodwater was in a person’s business, the more likely the person was to experience depressive symptoms.
People whose business had water above head height in their entire business were four times more likely to report depressive symptoms. Those who had water between knee and head height in their business were almost three times more likely to report probable depression. All this adds up to an increase in mental health issues that often follows a flood.
Six months after the flooding, business owners felt most supported by their local community such as volunteers and neighbours. However, those that felt their needs were not met by the state government and insurance companies were almost three times more likely to report symptoms of depression.
So, what can be done?
Firstly, we can boost preparedness. Risk and preparedness education may be especially needed for people who have recently moved to flood-prone regions. Many who have moved to regional areas recently may not be aware they live in a flood zone, or understand how fast waters can move and how high they can reach. Education is needed to raise awareness about the dangers. People may need help to prepare a flood plan and know when to leave.
Secondly, supporting people and local businesses after a disaster and assisting the local economy in its recovery could help reduce the mental health burden on people and the business community.
Thirdly, mental health services must be provided. A chaplaincy program was implemented in Lismore by the local government to assist business owners with emotional and psychological support after Cyclone Debbie and ensuing floods. This program was largely well received by business owners for having provided psychological support and raising mental health awareness.
However, the ongoing lack of mental health support remains an issue, especially in rural areas, and is exacerbated by disasters.
Fourthly, insurance disputes and rejection of insurance claims were among the strongest associations with likely depression in our research. We must find ways to improve the insurance process including making it more affordable, improving communication, by making claims easier and faster and boosting people’s understanding of what’s included and excluded from their policy.
No single organisation, government or department can solve these complex problems on their own. Strong partnerships between organisations are crucial and have been shown to work, as is direct and real-time support for flood-affected people.
This story was updated to add more detail about the author’s research funding, collaborative partners and affiliation. It is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. You can read the rest of the stories here.
We’re often warned to avoid mosquito bites after major flooding events. With more water around, there are likely to be more mosquitoes.
As flood waters recede around Townsville and clean-up efforts continue, the local population will be faced with this prospect over the coming weeks.
But whether a greater number of mosquitoes is likely to lead to an outbreak of mosquito-borne disease is tricky to predict. It depends on a number of factors, including the fate of other wildlife following a disaster of this kind.
Mosquitoes lay their eggs in and around water bodies. In the initial stages, baby mosquitoes (or “wrigglers”) need the water to complete their development. During the warmer months, it doesn’t take much longer than a week before they are grown and fly off looking for blood.
So the more water, the more mosquito eggs are laid, and the more mosquitoes end up buzzing about.
But outbreaks of disease carried by mosquitoes are dependent on more than just their presence. Mosquitoes rarely emerge from wetlands infected with pathogens. They typically need to pick them up from biting local wildlife, such as birds or mammals, before they can spread disease to people.
Historically, major inland flooding events have triggered significant outbreaks of mosquito-borne disease in Australia. These outbreaks have included epidemics of the potentially fatal Murray Valley encephalitis virus. In recent decades, Ross River virus has more commonly been the culprit.
A focal point of the current floods is the Ross River, which runs through Townsville. The Ross River virus was first identified from mosquitoes collected along this waterway. The disease it causes, known as Ross River fever, is diagnosed in around 5,000 Australians every year. The disease isn’t fatal but it can be seriously debilitating.
In recent years, major outbreaks of Ross River virus have occurred throughout the country. Above average rainfall is likely a driving factor as it boosts both the abundance and diversity of local mosquitoes.
Flooding across Victoria over the 2016-2017 summer produced exceptional increases in mosquitoes and resulted in the state’s largest outbreak of Ross River virus. There were almost 1,700 cases of Ross River virus disease reported there in 2017 compared to an average of around 300 cases annually over the previous 20 years.
Explainer: what is Ross River virus?
Despite plagues of mosquitoes taking advantage of flood waters, outbreaks of disease don’t always follow.
Flooding resulting from hurricanes in North America has been associated with increased mosquito populations. After Hurricane Katrina hit Louisiana and Mississippi in 2005, there was no evidence of increased mosquito-borne disease. The impact of wind and rain is likely to have adversely impacted local mosquitoes and wildlife, subsequently reducing disease outbreak risk.
Australian studies suggest there’s not always an association between flooding and Ross River virus outbreaks. Outbreaks can be triggered by flooding, but this is not always the case. Where and when the flooding occurs probably plays a major role in determining the likelihood of an outbreak.
The difficulty in predicting outbreaks of Ross River virus disease is that there can be complex biological, environmental and climatic drivers at work. Conditions may be conducive for large mosquito populations, but if the extreme weather events have displaced (or decimated) local wildlife populations, there may be a decreased chance of outbreak.
This may be why historically significant outbreaks of mosquito-borne disease have occurred in inland regions. Water can persist in these regions for longer than coastal areas. This provides opportunities not only for multiple mosquito generations, but also for increasing populations of water birds. These birds can be important carriers of pathogens such as the Murray Valley encephalitis virus.
In coastal regions like Townsville, where the main concern would be Ross River virus, flood waters may displace the wildlife that carry the virus, such as kangaroos and wallabies. For that reason, the flood waters may actually reduce the initial risk of outbreak.
There is still much to learn about the ecology of wildlife and their role in driving outbreaks of disease. And with a fear of more frequent and severe extreme weather events in the future, it’s an important area of research.
Although it remains difficult to predict the likelihood of a disease outbreak, there are steps that can be taken to avoid mosquito bites. This will be useful even if just to reduce the nuisance of sustaining bites.
Cover up with long-sleeved shirts and long pants for a physical barrier against mosquito bites and use topical insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Be sure to apply an even coat on all exposed areas of skin for the longest lasting protection.
The devastating Townsville floods have receded but the clean up is being complicated by the appearance of a serious bacterial infection known as melioidosis. One person has died from melioidosis and nine others have been diagnosed with the disease over the past week.
The bacteria that causes the disease, Burkholderia pseudomallei, is a hardy bug that lives around 30cm deep in clay soil. Events that disturb the soil, such as heavy rains and floods, bring B. pseudomallei to the surface, where it can enter the body through through a small break in the skin (that a person may not even be aware of), or by other means.
Melioidosis may cause an ulcer at that site, and from there, spread to multiple sites in the body via the bloodstream. Alternatively, the bacterium can be inhaled, after which it travels to the lungs, and again may spread via the bloodstream. Less commonly, it’s ingested.
Melioidosis can cause a variety of symptoms, but often presents as a non-specific flu-like illness with fever, headache, cough, shortness of breath, disorientation, and pain in the stomach, muscles or joints.
People with underlying conditions that impair their immune system – such as diabetes, chronic kidney or lung disease, and alcohol use disorder – are more likely to become sick from the infection.
The majority of healthy people infected by melioidosis won’t have any symptoms, but just because you’re healthy, doesn’t mean you’re immune: around 20% of people who become acutely ill with melioidosis have no identifiable risk factors.
People typically become sick between one and 21 days after being infected. But in a minority of cases, this incubation period can be much longer, with one case occurring after 62 years.
While most people who are sick with melioidosis will have an acute illness, lasting a short time, a small number can have a grumbling infection persisting for months.
One of the most common manifestations of melioidosis is infection of the lungs (pneumonia), which can occur either via infection through the skin, or inhalation of B. pseudomallei.
The challenges in treating this organism, though, arise from its ability to form large pockets of pus (abscesses) in virtually any part of the body. Abscesses can be harder to treat with antibiotics alone and may also require drainage by a surgeon or radiologist.
Thankfully, a number of antibiotics can kill B. pseudomallei. Those recovering from the infection will need to take antibiotics for at least three months to cure it completely.
If you think you might have melioidosis, seek medical attention immediately. A prompt clinical assessment will determine the level of care you need, and allow antibiotic therapy to be started in a timely manner.
Your blood and any obviously infected body fluids (sputum, pus, and so on) will also be tested for B. pseudomallei or other pathogens that may be causing the illness.
While cleaning up after these floods, make sure you wear gloves and boots to minimise the risk of infection through breaks in the skin. This especially applies to people at highest risk of developing melioidosis, namely those with diabetes, alcohol use disorder, chronic kidney disease, and lung disease.
Many parts of Queensland have been declared disaster zones and thousands of residents evacuated due to a 1-in-100-year flood. Townsville is at the epicentre of the “unprecedented” monsoonal downpour that brought more than a year’s worth of rain in just a few days, and the emergency is far from over with yet more torrential rain expected.
Such monumental disruption calls for emergency work to safeguard crucial infrastructure such as bridges, dams, motorways, railways, power substations, power lines and telecommunications cables. In turn, that requires accurate, timely mapping of flood waters.
For the first time in Australia, our research team has been monitoring the floods closely using a new technique involving European satellites, which allows us to “see” beneath the cloud cover and map developments on the ground.
Given that the flooding currently covers a 700km stretch of coast from Cairns to Mackay, it would take days to piece together the big picture of the flood using airborne mapping. What’s more, conventional optical imaging satellites are easily “blinded” by cloud cover.
But a radar satellite can fly over the entire state in a matter of
seconds, and an accurate and comprehensive flood map can be produced in less than an hour.
Our new method uses an imaging technology called “synthetic aperture radar” (SAR), which can observe the ground day or night, through cloud cover or smoke. By combining and comparing SAR images, we can determine the progress of an unfolding disaster such as a flood.
In simple terms, if an area is not flooded on the first image but is inundated on the second image, the resulting discrepancy between the two images can help to reveal the flood’s extent and identify the advancing flood front.
To automate this process and make it more accurate, we use two pairs of images: a “pre-event pair” taken before the flood, and a “co-event pair” made up of one image before the flood, and another later image during the flooding.
The European satellites have been operated strategically to collect images globally once every 12 days, making it possible for us to test this new technique in Townsville as soon as flooding occurs.
To monitor the current floods in Townsville, we took the pre-event images on January 6 and January 18, 2019. The co-event pair was collected on January 18 and January 30. These sets of images were then used to generate the accurate and detailed flood map shown below.
The image comparisons can all be done algorithmically, without a human having to scrutinise the images themselves. Then we can just look out for image pairs with significant discrepancies, and then concentrate our attention on those.
Our technique potentially avoids the need to monitor floods from airborne reconnaissance planes – a dangerous or even impossible task amid heavy rains, strong wind, thick cloud and lightning.
This timely flood intelligence from satellites can be used to switch off critical infrastructure such as power substations before flood water reaches them.
Any Lismore local will tell you that flooding is a fact of life in the Northern Rivers. In the floods of 1954 and 1974, the Wilsons River rose to a record 12.17 metres. This time around, the river peaked at 11.59m, breaching the flood levee built in 2005 for the first time.
So what are the conditions that caused those historic floods? And are they any different to the conditions of 2017?
Like the current flood, cyclonic rains also caused the 1954 and 1974 events. But unlike those past events, both of which were preceded by prolonged wet weather, almost all of the extreme rainfall from ex-Tropical Cyclone Debbie fell within 24 hours.
More interesting still is the fact that we are not currently experiencing La Niña conditions, which have historically formed the backdrop to severe flooding in eastern Australia.
The 1954 flood was preceded by an east coast low from February 9-11, followed by a decaying tropical cyclone from February 19-22. Thirty people were killed as flood records were set in Lismore, Kyogle, Casino, Nimbin and Murwillumbah. Some places received more than 1,000mm of rain in 14 days.
In 1974, former Tropical Cyclone Zoe unleashed torrential rain over Lismore, Wyrallah and Coraki. From March 10-13, some stations received almost 1,000mm in just four days. One analysis described the flood as a once-in-70-year event.
This time around, the remains of Tropical Cyclone Debbie delivered extreme rainfall to northern NSW towns including Murwillumbah, Chinderah and Lismore, despite having crossed the coast several days earlier and more than 1,200km to the north. Floods as far apart as Rockhampton in central Queensland and northern New Zealand show the storm’s colossal area of influence.
During the event, 20 rainfall stations in Queensland and 11 sites in NSW recorded their wettest March day on record. Mullumbimby, in the Brunswick River catchment, received a staggering 925mm during March – over half the annual average in a single month – causing major flooding in the region.
The heaviest rainfall in the Wilsons River catchment was at Terania Creek, which received 627mm over March 30-31, 99% of it in the 24 hours from 3am on March 30. Lismore recorded 324.8mm of rain in the 18 hours to 3am on March 31, its wettest March day in more than 100 years. A little further out of town, floodwaters submerged the gauge at Lismore Airport, so unfortunately we do not have reliable figures for that site.
The main difference between the current flooding and the 1954 and 1974 floods is that the previous events both occurred against a background of sustained La Niña conditions. These tend to deliver above-average tropical cyclone activity and high rainfall totals, which increase flood risk.
During the early 1970s, Australia experienced the longest period of La Niña conditions in the instrumental record. This unleashed phenomenal deluges across virtually the entire country. By the end of 1973, many catchments were already saturated as the wet season started early, culminating in the wettest January in Australia’s rainfall records.
In 1974 the Indian Ocean was also unusually warm (what meteorologists call a “negative Indian Ocean Dipole (IOD) phase”), further enhancing rainfall in the region. When negative IOD events coincide with La Niña conditions in the tropical Pacific, the warm sea temperatures reinforce one another, resulting in more evaporation and increased rainfall. This double whammy resulted in the exceptionally wet conditions experienced across the country during 1974.
In January 1974, the Northern Territory, Queensland and Australia as a whole recorded their wettest month on record, while South Australia and New South Wales recorded their second-wettest January on record. Torrential monsoon rains in the gulf country of Queensland transformed the normally dry interior into vast inland seas, flooding all the way to Lake Eyre in the arid zone of South Australia.
In contrast, Tropical Cyclone Debbie formed under neutral conditions, rather than during a La Niña. In fact, the Bureau of Meteorology is currently on El Niño watch, meaning that there is double the normal risk of an El Niño event bringing low rainfall and high temperatures to Australia by mid-2017.
So, unlike the 1950s and 1970s, the current flooding happened despite the absence of conditions that have driven major flooding in the past. It seems extraordinary that such a damaging cyclone could develop under these circumstances, and deliver such high rainfall over such a short time. This suggests that other factors may be at play.
A rapidly warming climate means that storms are now occurring in a “super-charged” atmosphere. As temperatures increase, so does the water-holding capacity of the lower atmosphere. The oceans are also warming, especially at the surface, driving up evaporation rates. Global average surface temperature has already risen by about 1℃ above pre-industrial levels, leading to an increase of 7% in the amount of water vapour in the atmosphere.
Of course, it is hard to determine the exact impact of climate change on individual storms. However, climate scientists are confident about the overall trends.
Australia’s land and oceans have warmed by 1℃ since 1910, with much of this warming occurring since 1970. This influences the background conditions under which both extremes of the rainfall cycle will operate as the planet continues to warm. We have high confidence that the warming trend will increase the intensity of extreme rainfall experienced in eastern Australia, including southeast Queensland and northern NSW.
While it will take more time to determine the exact factors that led to the extreme flooding witnessed in March 2017, we cannot rule out the role of climate change as a possible contributing factor.
CSIRO’s latest climate change projections predict that in a hotter climate we will experience intense dry spells interspersed with periods of increasingly extreme rainfall over much of Australia. Tropical cyclones are projected to be less frequent but more intense on average.
That potentially means longer and more severe droughts, followed by deluges capable of washing away houses, roads and crops. Tropical Cyclone Debbie’s formation after the exceptionally hot summer of 2016-2017 may well be a perfect case in point, and an ominous sign of things to come.