The November 2022 Floods
- Briefing Note 473
After this year’s record-breaking rain and flooding, flooding has once again engulfed widespread parts of south-eastern Australia. Several towns in Victoria have experienced flash flooding, whilst country towns in western New South Wales (NSW) have been evacuated due to major flooding. Forbes is expected to exceed its highest flood level on record. Meanwhile, South Australia has experienced severe weather causing widespread power outages.
New South Wales
In NSW, the entire central west is on high alert. The Bureau of Meteorology (The Bureau) has issued 8 major flood warnings, affecting 25 towns. On Monday, multiple towns, including Forbes, recorded more than 100 mm of precipitation in under 24 hours, which fell on already saturated catchments.
Forbes is experiencing its second major flood in a fortnight. The Lachlan River at Forbes is anticipated to reach 10.8 m, peaking on Thursday and reaching levels similar to the 1952 flood. The flooding started on Tuesday and is expected to continue through to the weekend. Around 500 to 600 homes and businesses are predicted to be inundated. The recent downpour of rain has caused the Wyangala Dam to spill at record levels, with 230,000 megalitres being released a day and greatly exacerbating river water flow.
The nearby small town of Eugowra, a population of 800 residents, had water reached roof height on Monday. The torrential rain reportedly doubled the height of Mandagery Creek that passes through the centre of Eugowra. There are reports of destroyed roads and infrastructure, upturned cars and caravans, homes washed away, and structures knocked over due to the extremely strong flow of water. It is important to note that many residents are uninsured as premiums grew up to $40,000 a year due to the high flood risk with the town in a designated floodplain.
Further along the Lachlan River another nearby town of Parkes is isolated as all major roads are inundated and Nanami, Cowra, Cottons Weir, Jemalong Weir, Condobolin, Euabalong, and Hillston have flooded. At Cowra, the Lachlan River peaked at 14.3 m, and could reach 14.6 m.
The Macquarie River is also experiencing major flooding. Bathurst recorded its wettest 24-hr period in 25 years with 86.4 mm. The river peaked at 6.64 m and roads have been severely damaged, but there have been no reports of homes being inundated so far. Major flooding was observed in downstream towns of Dubbo and Narromine while the flood peak is projected to reach Warren by the end of the week.
Prolonged flooding is occurring further North along the Peel and Namoi Rivers. Major flooding has occurred at Gunnedah and is expected to occur at Gunnedah and Wee Waa before the end of the week. Elsewhere, The Tumut, Murrumbidgee, Murray, Edward, Culgoa, Birrie, Bokhara, Narran, Barwon, Darling, Belubula, Mandagery rivers also all have major flood warnings.
As of Tuesday, the State Emergency Services (SES) had performed 222 flood rescues and received 909 requests for help. To assist with the disaster response, around 100 Australian Defence personnel have been deployed, and volunteers are arriving from New Zealand. There are also 14 aircrafts dedicated to supporting and rescuing residents and another four assisting with logistics and transport. On Monday, about 150 people were rescued from roofs in Eugowra and nearby Molong.
These events have extended the count to 70 local government areas that are now subject to natural disaster declarations.
Victoria
Torrential rain has caused flash flooding across Victoria. As of Tuesday, the SES has received 550 calls for assistance, including 318 for flooding assistance.
The Mornington Peninsula has been the worst affected region, where homes have been inundated and roads blocked and damaged. Further flash flooding warnings were issued to residents at Mount Martha, Mornington, Hastings, and Dromana as well as in the north-west of Ballarat, Beaufort and Lexton.
There have been several reports of landslides, damaged roads and infrastructure from flash flooding, and at Inverleigh flood waters caused a freight train to derail.
Major flood warnings have been issued along the Murray and Edward Rivers. Recent heavy rainfall, coupled with the persistent rainfall over the last several weeks and dam releases, have led to major flooding at Wakool Junction, Torrumbarry, Barham, Echuca and Moama. Additionally, major flooding warnings have been issued for Boundary Bend, Euston, Mildura, Wentworth Stevens Weir, Yarrawonga and Tocumwal. Flood levels at Wakool Junction are greater than the previous record from 1975, despite the peak not being expected until the weekend.
South Australia
Although South Australia (SA) was not impacted by widespread flooding, severe thunderstorms across the state have caused widespread power outages. There were a total of 420,000 reported lightning strikes over SA on Saturday. Power outages affected more than 163,000 homes and businesses in SA. Wind gusts of up to 106 kph were recorded at Adelaide Airport, with strong winds also recorded at Sellicks Hill, Kuitpo and Noarlunga. Small hail in the range of 2-3 cm were reported in the Port Lincoln area, damaging crops.
Heavy rain from these severe storms did result in localised flash flooding at Port Lincoln. Several roads were inundated, and businesses along the main road, Liverpool Street, were flooded due to saturated drainage systems in the city.
Climate Drivers
The climate drivers leading to this event are akin to the October 2022 Victoria floods [Evans (2022)]. The combination of a negative ENSO event (La Nina), a negative Indian Ocean Dipole (IOD) event and a positive phase of the Southern Annular Mode promote unusual convergence of moist air in the south-eastern Australian region. Unfortunately, eastern Australian rainfall events might not be quite over yet as The Bureau recently updated its climate outlook for Australia with La Niña likely to extend to Jan-Mar 2023. However, the negative IOD is likely to decline by mid-December [The Bureau (2022)].
References
Evans et. al. (2022). “The October 2022 Victorian Floods”. Risk Frontiers. https://riskfrontiers.com/insights/victorian-floods-october-2022/
The Bureau. “Climate outlooks—weeks, months and seasons”. The Bureau. http://www.bom.gov.au/climate/outlooks/#/overview/influences 10/11/2022
About the author/s
Jacob Evans
Jacob has been involved in the development of our FloodAUS, CyclAUS and QuakeAUS Cat-Loss models. He specialises in data science and mathematics.
Jacob received his PhD in Condensed Matter Physics from Macquarie University. Jacob’s interests include data science, numerical modelling, physics and mathematics.
Joining Risk Frontiers in 2017, Jacob has worked across a range of projects from model development and climate risk management to resilience and portfolio modelling.
Notably, Jacob has employed techniques such as machine learning and statistical analysis to understand the vulnerability of risk across Risk Frontiers catastrophe suite, as well as applying machine learning algorithms for flood, cyclone and earthquake models. He also works on hazard and loss modelling.
Maxime Marin
Maxime’s interests focus on physical oceanography and climate sciences. He holds a PhD in Quantitative Marine Science from the University of Tasmania. During his PhD, Maxime investigated global characteristics, changes and drivers of marine heatwaves, to improve our knowledge of these ocean extreme weather events.