The aftermath of the 2016 'superstorm' at Collaroy Beach. The aftermath of the 2016 'superstorm' at Collaroy Beach.

Coastal storms: national early warning system will help us better prepare for beach erosion and flooding

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Kay Harrison
Kay Harrison,

The world-first coastal hazard system reduces the risks associated with Australian coastal storms.

A new framework for a national early warning system (EWS) developed by UNSW engineers can forecast the beach erosion and flooding impacts of storms approaching Australia’s sandy coastlines.

The coastal hazard system predicts the severity of impacts every 100 metres alongshore and at identified ‘hotspots’ – considered vulnerable or housing valuable infrastructure – in near real time. It delivers rolling seven-day forecasts to local and regional coastal managers and emergency response agencies through a web portal.

The engineers detailed their system in a research paper published today in the international journal Coastal Engineering.

Changing storm patterns are emerging with climate change, affecting beachfront areas in diverse ways, says lead researcher Professor Ian Turner from UNSW’s Water Research Lab (WRL). Coastal hazards associated with significant weather events can extend over large regions yet vary greatly in local impact.

An EWS can provide the localised predictions coastal managers need to better prepare for emergencies and protect vulnerable coastal communities and property, he says.

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Beach erosion at Collaroy in the aftermath of the 2016 'superstorm' that struck Australia's east coast. Photo: UNSW Sydney

“Coastal storms pose a threat to livelihoods and assets along Australia’s coastlines: not just homes and buildings but roads, power and water utility corridors [and] sewerage lines,” says the coastal specialist.

“Our forecasting system enables us to anticipate the impacts of coming storms. It can tell us at a local level, will the beach become narrower or is it going to erode or indeed is it going to flood?”

Australia’s open ocean coastline is around 30,000 kilometres long; around a third of this shoreline is sandy. Approximately 50 per cent of Australians live within seven kilometres of the coast. The great majority of our urban and industrial infrastructure is located in coastal settings, where sandy beaches experience relatively high wave energy.

We’re accustomed to checking weather apps for hazardous heat, rain, wind, even surf, says Prof. Turner. “But while we've seen some pretty dramatic impacts of storms on the coast, to our knowledge, national forecasting agencies around the world don't have the capability to send out a coastal erosion warning when a storm is approaching.”

Coastal setting significantly influences storm hazards. While most existing coastal hazard EWSs forecast flooding risks, Australia’s narrow continental shelf means beach erosion poses a greater risk.
Prof. Ian Turner

New storm hazard matrix better informs our emergency response

The framework for national-scale coastal storm hazards early warning was developed in partnership with the Australian Bureau of Meteorology (BoM), NSW Department of Planning and Environment, WA Department of Transport, Northern Beaches Council, City of Mandurah, United States Geological Survey, the University of Western Australia (UWA) and UNSW Sydney. The research was funded by an Australian Research Council (ARC) linkage grant.

The EWS has been piloted in two geographically distinct regions since mid 2023 to facilitate future wide-scale deployment: on the east (Pacific Ocean) coast, ~450 km around Sydney, characterised by quartz sandy beaches; and on the west (Indian and Southern Oceans) coast, ~350 km around Perth characterised by a mix of sand beaches and limestone nearshore reefs. 

Hazards are categorised using a new Storm Hazard Matrix to help coastal managers identify appropriate management responses. The matrix considers the compound severity of their erosion (from minor beach narrowing to dune retreat) and flooding hazards. 

It draws on data from government partners on sea-floor mapping, nearshore waves and water-levels, and beach and dune features. The BoM also developed an experimental high-resolution wave modelling system that delivers seven-day wave forecasts for this project.

To evaluate the system’s accuracy, the research team has hindcast past storm events, such as the 2016 ‘superstorm’. The storm affected a 2000 km stretch of Australia’s east coast from Tasmania to the Queensland border, eroding 11.5 million cubic metres of sand, flooding towns and damaging infrastructure.

“Along many of the impacted beaches – for example Collaroy-Narrabeen here in Sydney – some areas of the beach experienced very dramatic damage and erosion, while nearby at the same beach the changes were much less dramatic,” Prof. Turner says. 

“Using our measurements of the changes that occurred along the NSW coastline in June 2016, we can retrospectively see how well we would have done in that storm and yes, we would have put a big red flag, where in fact, we memorably saw that swimming pool lying on the beach and homes being evacuated.”

Collaroy beach before and after the 2016 'superstorm'. Photo: Christopher Drummond

Beach erosion a bigger threat due to Australia’s narrow continental shelf

Coastal setting significantly influences storm hazards, Prof. Turner says. “While most existing coastal hazard EWSs forecast flooding risks, Australia’s narrow continental shelf means beach erosion poses a greater risk,” he says. 

Flooding predominantly occurs along coastlines dominated by storm surges (powerful ocean movements caused by wind and low pressure on the ocean’s surface). 

“In much of North America and large areas of Europe, the continental shelf is much wider, so most of the wave energy tends to dissipate before it gets to the coastline, but the water level gets higher.” 

However, the more densely populated and developed areas of Australian coastline – to the southeast and southwest – are less affected by storm surges, he says. “It's actually wave energy [from storms] hitting the coast that impacts and erodes our beaches and damages coastal infrastructure.”

Flooding is an issue for some West Australian coastal zones, says Associate Professor Jeff Hansen from UWA. “In WA, travelling south from the Perth metro area, the primary hazard transitions from erosion to inundation in Geographe Bay where the coastal profile is wide and shallow,” he says. 

Australia is a large continent with a really diverse coastline, Prof. Turner says. “By delivering timely information about approaching coastal storms, the new forecasting system we have developed with our partners can improve community preparedness and risk-reduction measures, to help reduce potential impacts to property, critical infrastructure and loss of life.”

The pilot Australian Beach Erosion and Coastal Flooding EWS can be viewed through the web portal.