As monstrous surf pummelled Sydney’s northern beaches and howling rain storms battered the city last weekend, Ian Turner and his hardy University of NSW
research team were in their element.
Six scientists sheltered from the tempest in the Collaroy Services Beach Club, getting what one colleague called a "prime viewing" spot as waves gouged
some 25 metres into the sand, leaving sharp vertical drops called scarps.
“It was unbelievable,” Turner, director of UNSW's Water Research Laboratory, recalled this week as he prepared for another weekend of wrath against the
coastline, this time unleashed by ex-tropical cyclone Uesi.
The researchers, though, were not your regular storm chasers. The university has operated a permanent monitoring site overlooking the famously erosive
sands of the Collaroy-Narrabeen beach strip since 2004.
It's where an "infinity pool" was dislodged during a powerful east coast low in 2016. That pool now forms part of the submerged temporary seawall aimed
at shoring up the sands during big wave events.
The east coast low in mid-2016 stirred up wild surf that slammed into Collaroy beach, dislodging a swimming pool and threatening to undermine buildings.CREDIT:PETER RAE
But Turner's recent outing had an additional purpose that could have long-term ramifications for how NSW, Australia and even elsewhere around the planet
identify beach erosion risks in a warming world, and prepare for their impacts.
Turner is part of a team working to create an early warning system that will notify coastal populations of the threat of significant erosion as much as
a week in advance. Partners include the Bureau of Meteorology, the state governments of NSW and Western Australia, and the United States Geological
Crucial to advancing the three-year project is data, and last week's storms provided both a wealth of information but also "heart palpitations" for the
scientists watching, Turner says.
The team's wave buoy was located directly offshore from that buried swimming pool. Despite being weighed down by a 100-kilogram anchor, the buoy was dragged
a couple of hundred metres offshore during last weekend's storm. It briefly stopped sending data to the satellite - something it is programmed to do
every quarter hour - but "then it popped back online, saying, 'hi, I'm fine and I'm recording'", Turner says. "Now we've got this fabulous direct comparison
[with inshore data] that we can use."
Coastal erosion at Collaroy-Narrabeen, as seen on Friday.CREDIT:NICK MOIR
The science of waves is both elegant and complex - which is why there are no early alerts for beach erosion but there are for riverine flooding or tsunami
For instance, the bureau collects data for waves in deep waters that have long been used by commercial and recreational shipping. As part of this project,
the agency has been developing and trialling methods to predict how these waves will behave when they reach the shore.
"One of the things that we're heavily focused on this year is evaluating how good - that is how reliable - that [forecasting] is," Turner says.\
Turner's UNSW colleague Mitchell Harley says an accurate warning system would need to anticipate many factors, such as the wave intensity, including the
length between waves, known as the wave period.
It would also need to forecast the height of the waves, including how they coincide with the tides.
The duration of the storm event that is generating the extra swell, and the direction the waves approach the beach all play roles in how much impact there
will be on the coast.
During last week's storm, waves reached 6.2 metres off Sydney but may only reach a maximum of 3.4 metres this weekend, Harley says. Unlike a week ago,
the waves won't be riding on a spring tide and that alone will trim heights by about 40 centimetres at the peak.
As bad as last weekend's battering was, it lasted about two days, shorter than the more destructive 2016 event which hammered the coast at Collaroy and
elsewhere along the coast for about a day longer. It was also more easterly (rather than coming in with the more northerly tack), which also curbed
the resulting erosion.
Principal research scientist at the bureau Diana Greenslade says her agency has developed a high-resolution wave model that provides improved forecasts
close to the shore. "The existing operational wave model provides model output at around 10 kilometre spatial resolution," she says. "This research
model provides output at around 250 metres resolution near the shore."
That finer detail will enable users to see clearly how waves will impact on the coastline in very specific locations, such expected conditions at the north
end of a beach compared with the south end.
Sea foam whipped up by the strong surf inundates properties along Collaroy on Sydney's northern beaches on Monday.CREDIT:NICK MOIR
The modelling capability is running in research mode at the moment, so is not operational. The model outputs will be assessed against near-shore wave buoy
measurements to further tune the performance of the model.
For the past century or longer, councils and home owners have built most of their infrastructure and houses in locations shielded by southerly headlands.
These tend to be vulnerable to storms coming in from elsewhere.
Over time, climate change will add to the challenges for coastal communities everywhere. Sea levels have been rising at 3 millimetres annually in recent
decades - something the warning system is designed to include.
"The system would be underpinned by wave, tide and storm surge forecasts that are based around mean sea level, so any sea level change would be implicitly
included," Greenslade says.
Coastal erosion at Collaroy-Narrabeen after this week's storm left vertical drops known as scarps. CREDIT:NICK MOIR
Helpful for this weekend, the cyclonic remnant of Uesi will also move away from the NSW coast faster than earlier predicted and is not as intense as feared.
Still, one difference from a week ago will be longer wave periods - 15 seconds as compared with 12 seconds - meaning the waves can travel further up the
"They might lap at the edges of some beachfront properties at the two high tides," Harley says. "This is very unlikely to cause erosion or undermining
of these properties though."
Collaroy beach erosion after storm
After the Sydney area experienced its wettest weekend in more than 20 years, beach erosion and massive amounts of sea foam can be seen at Collaroy on the
Improved computer modelling is one area where the science is advancing. Arguably more crucial, though, are the gains in high-resolution satellite imaging
that can adjust predictions according to the ever-changing shape of the coastline. That's particularly true of the popular sandy beaches along southern
and eastern Australia.
Out west, the issues are slightly different. The Leeuwin Current flowing southwards along the Western Australian coastline can vary, dropping sea levels
by as much as 30 centimetres. Lots of offshore reefs also moderate wave behaviour.
Taylor hopes to have key erosion hotspots understood and modelled, first in Australia, over coming years with the potential to take the service international
in the longer term.
"What we need is the observations on the ground of the actual erosion that occurs during the storms that we monitor," he says. "So our effort over the
past 10 days has been making sure we quantify the impact of the event we had last weekend and are ready for the one this weekend, so that we can use
it for the modelling."
To assist that effort, researchers flew a laser scanner known as LIDAR between Sydney and the Central Coast, taking in places such as Macmasters Beach,
to get a regional perspective of the damage.
One reason eastern Australia ended 2019 in a severe drought was the absence of east coast lows last year or other big storms for a while. It also meant
beaches were full going into the recent storms. "It's been a relatively quiet period," Turner says, with "the sand buffer" wider than usual - at least
until a week ago.
Harley says places such as Stockton, in Newcastle, may be more at risk this weekend, even with a less intense event expected "because there is no protective
buffer from any increase in waves".
Cabins, a restaurant and other assets were all "teetering on the edge", forcing the local council to take steps to protect what's left of the shore, he
Vanessa Hill, a resident at Collaroy, says she would be keen to know in advance what was headed her way. “For people that don’t have a wall, they could
sand-bag ... it would help us prepare,” Hill says as waves crash into the seawall not far from her home on Friday.
Nearby resident Gary Silk was supportive too, saying that being forewarned could give homeowners time to put up protective structures in areas along the
beach identified as most vulnerable.
Silk's house was one of those to suffer considerable damage in 2016 and he has since led efforts to build a more permanent protective seawall. Still, “if
you just put a few sandbags down and that’s it, it’s not really going to be useful,” he says.
Mayor of the Northern Beaches Council Michael Regan welcomed efforts to develop erosion alerts.
"An early forecast tool would help us gain a better understanding of the amount of sand that would be removed - the level of erosion - at specific locations,"
Regan says. "This would assist in prioritising emergency response and communicating potential impacts to residents ahead of a forecast storm."
The council is as versed as any in the "wars of the seawalls". Residents who almost lost their homes in the 2016 storm have been battling ever since to
get approval for a permanent rocky revetment - or seawall - to ward off future erosion.
One delay has been securing funding, with the residents required to pay 80 per cent of the cost, while the council and the state government will chip in
10 per cent each.
Coastal engineer Angus Gordon has first-hand experience of the value of knowing how bad coastal erosion can get.
During the 2016 strike, Gordon was the first to warn authorities of the impending damage to gas, water and sewage pipes running under the dunes at Collaroy.
"I could smell gas all over the place, and the water pipes were also a problem," he says.
Gordon says the modelling that would go into preparing early warnings for erosion could also come in handy for the 50 councils up and down the coast required
to develop new coastal management programs following the passing of a new act in 2016 aimed at taking a more careful approach to what gets built near
That act created a Coastal Council of seven experts - including Gordon - tasked with giving independent advice on the programs.
Hints of the planning fits and starts in dealing with coastal erosion litter the NSW coast from Byron to Batemans Bay. Vacant plots at places such as Wamberal
or Collaroy now occupied by parks or parking lots - such as next to the Services Club - point to previous efforts by councils to buy up properties
doomed to end up in the surf.
"We need a total solution rather than piecemeal and emergency measures," Gordon says.