Latest news with #NSWReconstructionAuthority
ABC News
3 days ago
- Science
- ABC News
Scientists look to Indigenous history to manage flood risk in Hawkesbury-Nepean Valley
Accounts of floods recorded in Aboriginal oral history centuries ago could provide vital clues to how climate change will affect flood risk in the future. Scientists working on a disaster adaptation plan for the Hawkesbury-Nepean Valley in Sydney's north-west are looking into the past to help predict the future. Stephen Yeo, senior flood risk specialist at the NSW Reconstruction Authority, said records at Windsor go back to the early days of European settlement. "On this river system, we have the longest record of floods in Australia from the early 1790s right up to the present," he said. "That's actually pretty short in geological time." The biggest flood recorded since European settlement was in June 1867. But there are early colonial accounts of Aboriginal elders describing an even bigger flood that happened eight years before the arrival of the First Fleet. "During that flood it apparently poured in torrents for seven nights and seven days," Dr Yeo said. He said this event changed what scientists know about the magnitude and frequency of flooding in the river system. "It suggests that the flood in 1780 was perhaps 2 or 3 metres higher than what we currently think is the record flood in 1867. "So that's actually really valuable information from that Aboriginal storytelling." Waterway scientist Daryl Lam is part of a team searching for traces of pre-settlement floods. "History is telling us what has happened before really can happen again, so if we can find evidence of big floods from the past, it gives us some understanding of what we can potentially see in climate change," he said. Samples of sediment have been collected from three locations high above the river bank. These samples will be taken back to a laboratory and analysed to pinpoint exactly when the sediment was deposited. Measurements taken at the site will allow researchers to calculate how high the floodwaters rose. "Here in the Hawkesbury-Nepean, we have gauge records that go beyond a hundred years," Dr Lam said. "If we take into account oral history, we might be able to push it out to 200 years or 500 if we are lucky. "With paleoflood reconstruction, we will be able to work out a longer timescale." Archaeologist Bec Chalker said evidence of Aboriginal occupation can be found in caves all along the river. "We find tools that are hidden up on crevices in the shelters, just like we would put our tools and kitchen utensils on a shelf at home." She said Indigenous knowledge built up over generations was proving to be a valuable resource. "We have a lot to learn, and I think people are more open to learning now." Climate change is adding to the flood risk with every degree of atmospheric warming increasing rainfall in the catchment by 8 per cent. Between 2020 and 2022, the area flooded six times. With 114,000 people now living on the flood plain, the NSW Reconstruction Authority is considering whether building levees and improving evacuation roads will help mitigate the risk. "Climate change is here, we have to factor it into today's decision-making," Dr Yeo said.
Sydney Morning Herald
3 days ago
- Climate
- Sydney Morning Herald
A megaflood devastated early Sydney. An even worse catastrophe is hidden in the city's ‘bathtub'
A thousand horses drowned. Gunshots blasted throughout the night to alert rescue boats to the locations of the stranded while floodwaters nearly 20 metres high swallowed even the homes on top of hills. The deluge that almost engulfed the entire western Sydney suburb of Windsor summoned torrents that ripped away buildings, bedsteads, tables, chairs, the bodies of pigs and a child seated upon a sack of flour. The Hawkesbury-Nepean flood of 1867 killed 20 people – including 12 from the same family – and left hundreds of survivors half-naked, starving and 'paralysed' with trauma, according to newspaper reports. It's the biggest flood ever recorded in Sydney and has acted for decades as the benchmark for emergency planners for just how catastrophic a flood can be. But there are tales of an even greater deluge. First Nations oral histories spoke of a flood so great in 1780 that even the few islands of high land in Windsor spared by the 1867 flood, which 2000 people used as refuge, went underwater. 'There was a big flood before European settlement, in which the Aboriginal peoples climbed the tallest trees, but were still swept away,' said Dr Stephen Yeo, a flood risk specialist at the NSW Reconstruction Authority. Based on these anecdotes, Yeo believes the 1780 flood could have been two to three metres higher than the 1867 disaster, reaching 22.3 metres at Windsor. If verified, adding the deluge to the flood record would have profound effects on what we know about disaster risk. Based on current knowledge, for example, the 1867 flood has a one-in-500 chance of happening each year. Add in the 1780 flood and that chance jumps to one-in-200. 'Perhaps that 1867 flood actually can happen more frequently. And if the same happened again today, it would be much more catastrophic because there's so much more development in western Sydney on that vast floodplain,' Yeo said. Today a disaster on that scale would force the evacuation of 114,000 people, damage or destroy 19,000 homes, and inflict $7.5 billion in damage, according to the Reconstruction Authority. At least 2200 homes and other buildings were damaged in the 2022 Hawkesbury-Nepean flood. Verifying the 1780 flood would also raise '1-in-100-year flood' levels expected in the Hawkesbury-Nepean, which are events that have a 1 per cent chance of happening each year. These are the flood levels used to decide the height of floors for properties built in flood-prone areas. At Windsor, if the 1780 flood was indeed two metres higher than that of 1867, it would increase the expected 1-in-100-year flood level by 1.3 metres, to 18.6 metres. These estimates are crucial for emergency planning. The Hawkesbury-Nepean Valley is one of the highest-risk flood zones because it's built like a 'bathtub', with five major tributaries gushing in and narrow sandstone gorge choke points that cause floodwater to back up and rise rapidly. That's why archaeologists and river experts have hitched a ride on State Emergency Service boats to a sandy riverbank on the Nepean, about 45 minutes up into the Blue Mountains National Park from Penrith. Here the Reconstruction Authority is leading a 'paleoflood' research project, which refers to the study of past or ancient floods, to see if it can confirm stories of the 1780 flood by analysing sediment. Geomorphologist Tim Cohen, with an akubra hat and a passion for dirt, is in a square-hewn hole dug into a hill about 30 metres above the river. There are layers of dark chocolate soil and light caramel sands, with the paler layers a mark of powerful past floods that carried heavy sand high up onto land. 'Here you see a really perfect layer cake stratigraphy. So you see muds, sands, muds, sands. And the sands represent the big floods,' Cohen, an associate professor at the University of Wollongong, said. 'This could represent a flood that's 30 metres deep,' he said, gesturing to a thick sandy stripe. 'That's an extraordinary rain event. But I guess the question is, 'How extraordinary is it? How often does it happen?' ' To answer that question, Cohen and colleague Dr Daryl Lam from Water Technology are capitalising on an extraordinary quirk of physics: grains of sand keep a record of when they last saw sunlight. 'Every grain of sand is like a rechargeable battery,' Cohen said. 'When it's buried, it receives the radioactive decay of surrounding minerals, and that's the charge. And what releases the charge is sunlight.' Cohen hammers stainless-steel tubes into the sediment to collect cylinders of sand without exposing them to sunlight. Each end of the tubes is quickly covered in foil. From here, the samples go to a red-light lab, where scientists scour the sand with corrosive baths of hydrochloric acid, hydrogen peroxide and hydrofluoric acid to remove skerricks of dirt, bugs, charcoal and tree roots. What's left is pure quartz. A laser is fired at each grain, which simulates the sun and triggers the release of the radioactive 'charge' as a tiny flash of electrons measured by a photomultiplier. Back at the dig site, Cohen measures the amount of radioactive uranium, thorium and potassium in the dirt, and the level of cosmic radiation hitting the ground from space, to establish how much 'charge' the grains were receiving during their time underground. Knowing the amount of natural radiation the grains of quartz were exposed to, and how much 'charge' they released in the lab, allows the researchers to calculate how long ago the sand was buried. 'That's what we're after; when we date the time of deposition, that tells us about the time of the flood,' Cohen said. Radiocarbon dating can go back 50,000 years; this method can go back a million. Loading A flood so big it brought sediment this high would be 'nuts' but is theoretically possible, said Cohen. As flooding turns deadlier under climate change, looking back at past disasters can help us understand when and why deadly floods may strike. 'The longer your record, the better your capacity to predict the likelihood of rare extreme events,' Cohen said.
The Age
3 days ago
- Climate
- The Age
A megaflood devastated early Sydney. An even worse catastrophe is hidden in the city's ‘bathtub'
A thousand horses drowned. Gunshots blasted throughout the night to alert rescue boats to the locations of the stranded while floodwaters nearly 20 metres high swallowed even the homes on top of hills. The deluge that almost engulfed the entire western Sydney suburb of Windsor summoned torrents that ripped away buildings, bedsteads, tables, chairs, the bodies of pigs and a child seated upon a sack of flour. The Hawkesbury-Nepean flood of 1867 killed 20 people – including 12 from the same family – and left hundreds of survivors half-naked, starving and 'paralysed' with trauma, according to newspaper reports. It's the biggest flood ever recorded in Sydney and has acted for decades as the benchmark for emergency planners for just how catastrophic a flood can be. But there are tales of an even greater deluge. First Nations oral histories spoke of a flood so great in 1780 that even the few islands of high land in Windsor spared by the 1867 flood, which 2000 people used as refuge, went underwater. 'There was a big flood before European settlement, in which the Aboriginal peoples climbed the tallest trees, but were still swept away,' said Dr Stephen Yeo, a flood risk specialist at the NSW Reconstruction Authority. Based on these anecdotes, Yeo believes the 1780 flood could have been two to three metres higher than the 1867 disaster, reaching 22.3 metres at Windsor. If verified, adding the deluge to the flood record would have profound effects on what we know about disaster risk. Based on current knowledge, for example, the 1867 flood has a one-in-500 chance of happening each year. Add in the 1780 flood and that chance jumps to one-in-200. 'Perhaps that 1867 flood actually can happen more frequently. And if the same happened again today, it would be much more catastrophic because there's so much more development in western Sydney on that vast floodplain,' Yeo said. Today a disaster on that scale would force the evacuation of 114,000 people, damage or destroy 19,000 homes, and inflict $7.5 billion in damage, according to the Reconstruction Authority. At least 2200 homes and other buildings were damaged in the 2022 Hawkesbury-Nepean flood. Verifying the 1780 flood would also raise '1-in-100-year flood' levels expected in the Hawkesbury-Nepean, which are events that have a 1 per cent chance of happening each year. These are the flood levels used to decide the height of floors for properties built in flood-prone areas. At Windsor, if the 1780 flood was indeed two metres higher than that of 1867, it would increase the expected 1-in-100-year flood level by 1.3 metres, to 18.6 metres. These estimates are crucial for emergency planning. The Hawkesbury-Nepean Valley is one of the highest-risk flood zones because it's built like a 'bathtub', with five major tributaries gushing in and narrow sandstone gorge choke points that cause floodwater to back up and rise rapidly. That's why archaeologists and river experts have hitched a ride on State Emergency Service boats to a sandy riverbank on the Nepean, about 45 minutes up into the Blue Mountains National Park from Penrith. Here the Reconstruction Authority is leading a 'paleoflood' research project, which refers to the study of past or ancient floods, to see if it can confirm stories of the 1780 flood by analysing sediment. Geomorphologist Tim Cohen, with an akubra hat and a passion for dirt, is in a square-hewn hole dug into a hill about 30 metres above the river. There are layers of dark chocolate soil and light caramel sands, with the paler layers a mark of powerful past floods that carried heavy sand high up onto land. 'Here you see a really perfect layer cake stratigraphy. So you see muds, sands, muds, sands. And the sands represent the big floods,' Cohen, an associate professor at the University of Wollongong, said. 'This could represent a flood that's 30 metres deep,' he said, gesturing to a thick sandy stripe. 'That's an extraordinary rain event. But I guess the question is, 'How extraordinary is it? How often does it happen?' ' To answer that question, Cohen and colleague Dr Daryl Lam from Water Technology are capitalising on an extraordinary quirk of physics: grains of sand keep a record of when they last saw sunlight. 'Every grain of sand is like a rechargeable battery,' Cohen said. 'When it's buried, it receives the radioactive decay of surrounding minerals, and that's the charge. And what releases the charge is sunlight.' Cohen hammers stainless-steel tubes into the sediment to collect cylinders of sand without exposing them to sunlight. Each end of the tubes is quickly covered in foil. From here, the samples go to a red-light lab, where scientists scour the sand with corrosive baths of hydrochloric acid, hydrogen peroxide and hydrofluoric acid to remove skerricks of dirt, bugs, charcoal and tree roots. What's left is pure quartz. A laser is fired at each grain, which simulates the sun and triggers the release of the radioactive 'charge' as a tiny flash of electrons measured by a photomultiplier. Back at the dig site, Cohen measures the amount of radioactive uranium, thorium and potassium in the dirt, and the level of cosmic radiation hitting the ground from space, to establish how much 'charge' the grains were receiving during their time underground. Knowing the amount of natural radiation the grains of quartz were exposed to, and how much 'charge' they released in the lab, allows the researchers to calculate how long ago the sand was buried. 'That's what we're after; when we date the time of deposition, that tells us about the time of the flood,' Cohen said. Radiocarbon dating can go back 50,000 years; this method can go back a million. Loading A flood so big it brought sediment this high would be 'nuts' but is theoretically possible, said Cohen. As flooding turns deadlier under climate change, looking back at past disasters can help us understand when and why deadly floods may strike. 'The longer your record, the better your capacity to predict the likelihood of rare extreme events,' Cohen said.
The Guardian
12-06-2025
- Climate
- The Guardian
‘Too frightened to pick things up': NSW flood-affected residents return home to find snakes and spiders have moved in
Some New South Wales residents returning home after last month's record-breaking floods are finding mud isn't the only thing waiting to greet them. Thousands of mid-north coast residents left their homes in May after flooding inundated dwellings and washed away livestock. Some are only just returning weeks after the floods – and about 120 households remain in emergency accommodation, according to the NSW Reconstruction Authority. After evacuating their home on 16 May, Julie Botfield and her children returned to their Clybucca rental home on 2 June to find many unwanted house guests which had slithered their way on to the property after the area surrounding their home flooded. 'In total till today we had 39 snakes, all varieties, very large to babies. I had two snake catchers come to the property to relocate them, this also assisted with the cleanup as I was too frightened of picking things up or entering the shed,' Botfield told Guardian Australia on Wednesday. Her house was also covered with huge numbers of spiders. Dave Owens, the former NSW police deputy commissioner who has been appointed Hunter and mid-north coast recovery coordinator, said it's not uncommon for animals to take refuge in people's homes after floods – just like humans, the animals are looking for somewhere safe and dry. 'So when people return to their homes, it's not just flood waters and mud they have to contend with – in some cases snakes, spiders and other animals,' Owens said. 'If you find animals, particularly snakes or spiders, residents are urged to be careful and contact an expert to help safely remove them – the same goes for any cows or livestock they may find on their properties.' The owner and director of snake education company Reptile Solutions, Stuart Johnson, said many of the instances of snakes entering homes have occurred in lower-lying areas, such as around the Clybucca and surrounding parts of the Maclean. He said some animals had washed into people's homes during the floods. Sign up for Guardian Australia's breaking news email 'A lot of those animals naturally refuge in things like underneath vegetation, foliage, hollow logs and things, which is a lot of the stuff that gets picked up and dragged along with the flood and deposited so it gathers up along fences and inside of buildings.' He suggests mid-north coast residents who encounter snakes or spiders while cleaning up should avoid them – and call in professionals. 'The major cause for snake bites and spider bites is through direct contact, where people try to directly capture or harm the animal,' Johnson said. 'So be vigilant and seek the appropriate assistance through trained and qualified individuals to assist in safely handling and removing the animals.'
ABC News
08-06-2025
- Climate
- ABC News
Snakes, spiders and mould confront residents after NSW Mid North Coast floods
Mud and mould are not the only issues facing those returning to their homes after major flooding on the New South Wales Mid North Coast. Clybucca resident Julie Botfield was evacuated by boat with two of her children and their dogs during the height of the flooding in late May. She said she was shocked by what she discovered at the rural property when she returned to inspect it a week and a half later. "The snakes and spiders were an issue in me getting back in there," Ms Botfield said. "There were 30 snakes down in the shed alone … I wasn't expecting that many. Ms Botfield, a single mother, was assisted by Brenden Kendall, who lives near Kempsey and helps people needing snakes relocated. "I saw a few baby snakes up and down the driveway just walking up to the property, some were still hiding in the shed," Mr Kendall said. "Once we got up to the shed, we ended up with a total of 30 snakes caught. Ms Botfield, who rents the property, said she also had it treated for pests as the walls were covered in spiders. "I had a pest man come [after the flood] … he said it was the worst property he has ever treated." NSW Reconstruction Authority Recovery coordinator Dave Owens said it was not uncommon for animals to take refuge in uninhabited properties after floods. "The animals are looking for somewhere safe and obviously residents are vacated," he said. "So, when people go back in, it's not just the floodwater and mud on the ground, it's snakes, it's spiders, it's other creatures, so you need to be careful." Ms Botfield said the time it took before she was able to return and access the property meant that mould had also spread. "The storms and rain keep coming." Mr Owens said mould was a significant issue after a flood, and airing out impacted homes as soon as possible was vital. "Open all doors and windows to let in fresh air and sunlight … reduce humidity by limiting humidifiers, indoor plants and unflued gas heaters," Mr Owens said. "To clean mould off surfaces, use detergent or diluted vinegar, four parts vinegar to one part water. "For stubborn mould, you can use a diluted bleach solution but never mix vinegar and bleach." A household cleaning expert has also recommended oil of cloves for cleaning mould. North Coast Public Health Unit's environmental health officer David Basso said mould spores could cause health problems for people who were sensitive or allergic to them. "The health effects from mould exposure can be a runny or blocked nose, irritation of the eyes and skin and difficulty breathing, particularly [in] people with asthma." He said removing mould would be more challenging during winter. "When we have adverse weather, it's difficult to maintain that proper airflow through your home," he said. Mr Owens said about 700 residential properties across the region were still deemed uninhabitable and the focus was on getting displaced families back home. "It could be as simple as they've had water over the floor, and we need to get a sparkie [electrician] in to check it's safe and then they can move back in," he said. "We have about 150 households in emergency accommodation. "A lot of people have gone to family and friends, couch surfing is a term that's been used." Ms Botfield is currently staying with family and said she was prepared for a long road ahead. "I've had Disaster Relief Australia out to help and they have been great … they even found another two snakes," she said. "I want to show my kids we are strong and resilient, we've got this."
