Originally published by Scimex.

Sydney has experienced another flooding event over the weekend with more wild weather expected todayThere are multiple evacuation warnings and orders in place affecting around 30,000 people. The Bureau of Meteorology says that localised heavy rainfall which may lead to flash flooding remains possible until later this evening over the Illawarra, Blue Mountains, Sydney Metropolitan, and parts of Hunter (including Central Coast) districts. Below Australian experts comment.

Organisation/s: Australian Science Media Centre

Funder: N/A

Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr Piet Filet is Convenor and founder of the Flood Community of Practice and Engagement Collaboration Specialist at the Australian Rivers Institute at Griffith University

“Reducing the flood impacts being experienced in the Sydney requires a long-term resilience building program with communities in flood prone catchments. The history of flood events not only reflects changing baselines in the frequency of extreme rainfall events, but also the need for key aspects of resilience building to be in place well in advance. Informed and engaged communities who live on floodplains need to be fully aware of what the risks and scenarios are for their locations well in advance of any flood events. Long term land use planning that minimises flood exposure is critical. Upstream catchment and nature-based measures that slow, store and reduce the flows of water are vital to reduce the height and extent of flood events downstream. Infrastructure in floodplains needs to have been built to withstand the impacts of fast flowing water and overcome the isolation of communities during floods. This multi strategy approach is being implemented in various parts of Australia and overseas and is a vital foundational approach for long term resilience needs of communities and their built and natural assets.”

Last updated: 05 Jul 2022 3:57pm

Declared conflicts of interest:

None declared.

Associate Professor Iftekhar Ahmed is from the School of Architecture and Built Environment at the University of Newcastle

“NSW is repeatedly being impacted by a recurring spate of floods. There is a lot of discussion on the linkage of these events to climate change. While much of the discussion points to the probable increasing frequency, magnitude and intensity of such hydrometeorological events, the unpredictability of climate change impacts, their transforming nature, and compound and cascading effects are less well understood.

For example, this year because of La Niña the rainfall has been extensive, which is compounding the effects of climate change. Such heavy rainfall at this time of the year is unseasonal and the effects of La Niña are expected to persist well into the winter season. A cycle of disaster after disaster induced by advancing climate change renders each cycle of lessons gained redundant, posing difficulty in translating the lessons when newly established knowledge thresholds are breached. 

These events are therefore a signal for preparedness and risk reduction at all levels – institutional and community, not only for the short term, but a long-term, anticipatory and systems approach. We will need to learn how to live with floods by building our resilience and adaptive capacity, and perhaps even explore new opportunities within the changing circumstances. “

Last updated: 04 Jul 2022 12:38pm

Declared conflicts of interest:

None declared.

Dr Ian Wright is from the School of Science at Western Sydney University

“Western Sydney is currently experiencing its fourth major flood event since March 2021. Western Sydney has spread onto flood-prone lands. Development has been approved despite the known risks of flooding. The NSW SES have continuously reminded us of how exposed many Western Sydney communities are to flooding emergencies.

Much of the flooding has been impacting vulnerable people. Many cannot afford insurance premiums for flooding. People are exhausted. Many have not recovered from previous flooding. Compounding stresses for flood-affected people include disruption from the covid pandemic, accelerating house prices and rising interest rates.

The NSW Government advocate raising the height of Warragamba Dam wall. This would then become a water supply dam that is also a flood mitigation dam.

The community are critical that Government has failed to adequately prepare for flooding emergencies. For example, the recently rebuilt Windsor bridge over the Hawkesbury River was completed in 2021, at a cost of $100 million. It has attracted criticism as it has now been closed from four floods in 18 months.

The SES remind us, that there was a giant flood in the Hawkesbury Valley in 1867 that, if repeated, would flood thousands of properties and probably cause major loss of life.”

Last updated: 04 Jul 2022 12:25pm

Declared conflicts of interest:

None declared.

Andrew Gissing is an emergency management researcher with Natural Hazards Research Australia and General Manager of Resilience at Risk Frontiers

“Flooding along the east coast so far this year has cost billions of dollars and tragically taken lives. Repetitive episodes of flooding imposes strain on communities and emergency services. Based on research by Risk Frontiers and the Bushfire and Natural Hazards Cooperative Research Centre we know that such consecutive events can hinder the recovery of communities as they are forced to continually pick up the pieces after each event. We can reduce flood risk by implementing risk mitigation strategies accompanied by land use planning which encourages development in low risk or flood free areas. 
Most lives lost in recent floods have been a result of people entering floodwater. It is vital that people follow the advice of emergency services not to enter floodwater. Floodwaters are difficult to judge and only a small error in judgement about their speed or depth can result in tragic consequences.”

Last updated: 04 Jul 2022 12:12pm

Declared conflicts of interest:

None declared.

Dr Tom Mortlock is a Senior Analyst at Aon and Adjunct Fellow at Macquarie University

“Major flooding is impacting the Sydney basin again for the third time in two years. River flood levels on the Hawksbury and Nepean Rivers are still rising and at North Richmond, levels are comparable to the March flood already, at around 14 m. All major dams around Sydney catchments are at full capacity, and Warragamba Dam began spilling early morning on Sunday, at a rate comparable to the 2021 floods (240 GL / day). While we have dropped out of La Niña for now, there is a 50/50 chance of it reforming in the coming months. This, combined with a negative Indian Ocean Dipole, and anomalously warm sea surface temperatures off the Sydney coast, suggests a wetter than normal outlook for the coming season at least.


Last updated: 04 Jul 2022 12:11pm

Declared conflicts of interest:

None declared.

Kimberley Reid is an atmospheric scientist from the ARC Centre of Excellence for Climate Extremes at Monash University. Kimberly researches extreme rainfall and flooding over Australia.

“Warm, wet air from near the equator is feeding this East Coast Low and providing ample moisture for the Low to then dump over Sydney.

While climate change is enhancing extreme rainfall over other parts of the world, there currently is not a clear climate change signal over Eastern Australia. This is because there is also a lot of natural variability in East Australian rainfall (due to La Niña for example). However, our research of the March 2021 Sydney floods found that similar events over Sydney were likely to occur 80% more often by the end of the 21st Century.”

Last updated: 04 Jul 2022 12:10pm

Declared conflicts of interest:

None declared.

Dr Agus Santoso is a senior scientist at UNSW Climate Change Centre. He is also an adjunct science leader at CSIRO

“The flood risk over eastern Australia has remained high due to saturated soil and high dam levels through the back-to-back La Nina years since 2020.  Therefore, any weather systems that bring extreme rains could lead to flooding, despite La Nina being declared ‘over’ by the Bureau of Meteorology. 
In addition, a negative Indian Ocean Dipole (IOD) event is forming, and is forecasted to intensify into spring.  A negative IOD, marked by warming off northwestern Australia and over Indonesia, brings higher-than-normal rainfall across the southern parts of Australia, including NSW and Victoria.  
Moreover, there is about 60% probability that a La Nina may re-emerge in summer.   So, we should still be alert to the possibility of more flooding in the coming months.”

Last updated: 04 Jul 2022 12:08pm

Declared conflicts of interest:

None declared.

Dr Amy Peden is a Research Fellow in the School of Population Health at UNSW

“The Sydney floods have already turned deadly, with the drowning of a man in the Paramatta River. In addition, there have been hundreds of rescues with people who have driven into or walked into floodwaters. Drowning is the leading cause of death during times of flood, due to people entering floodwater either in vehicles or on foot. Floodwaters can hide hidden dangers including strong currents, submerged objects and damaged roads and bridges. It is absolutely vital that people heed emergency warnings and avoid entering floodwaters at all costs.”

Last updated: 04 Jul 2022 12:07pm

Declared conflicts of interest:

None declared.

Professor Jennifer McKay is Professor of Business Law at the University of South Australia

“Flooding occurs because people have invaded floodplains. We have huge legacy issues in Australia from ignorance and wilful blindness – see Governor Macquarie’s statement and details here: https://gallery.records.nsw.gov.au/index.php/galleries/50-years-at-state-records-nsw/1-4/

Legacy issues will require one form of response which may be buybacks and these have been tried in the past successfully. 
We need state laws or national laws to require flood susceptibility to be a part of the decision making process for urban settlements. Climate change and the enhanced risks that come with it must be considered, and this must apply the precautionary principle to not place residents and emergency service workers at risk in the more severe events that we can expect.
I think we need a national cabinet approach to this, guided by experts to set the standards. Otherwise, litigation will occur and also insurance will be impossible to attain and everyone will endure higher premiums. I did a PhD on this in 1983 and have several ideas to contribute. We at least need a royal commission.”

Last updated: 04 Jul 2022 12:04pm

Declared conflicts of interest:

None declared.