Australian beaches could struggle to recover if a third La Niña weather event hits this year after many of the most popular stretches of sand suffered back-to-back weather events that stripped them of the sand.
As more extreme and intense weather events occur, protected beach areas will become more exposed, threatening coastal communities, experts warn.
Beaches can take months to recover after an erosion event.Credit:mitchell creek
Dr Mitchell Harley, Senior Lecturer at the University of NSW Water Research Laboratory, said Australian beaches are very dynamic and tend to fluctuate with the season. During storms, the beaches lose more sand, while in the warmer months the beaches tend to grow.
“We have been measuring Collaroy and Narrabeen beaches for 46 years and with those measurements there have been fluctuations over a large amount of space, up to 100 meters from one side to the other. The coast is breathing, but when we look at the long-term records, they have generally been stable recently,” he said.
“During big storms, like the ones we’ve seen in the last two years, what we see is that the waves wash the sand off the beaches. It doesn’t go away, it just moves into deeper water. The sand slowly returns to the beach during calm conditions.”
In the normal summer months, the waves move from a south or southeast direction. This usually means that the northern end of the beach gets narrower and the southern ends get larger.
But during La Niña events, they shift slightly counterclockwise and further east, leading to a higher risk of more beach erosion, particularly during the summer, and also to the ” beach rotation”, where the beach realigns itself to the prevailing current. direction of the wind.
As a general rule of thumb, every meter of shoreline sand takes five to 10 days to return to the beach, Harley said, and recovery can sometimes take months if beaches lose up to 40 meters of sand. But if there are back-to-back storm events, like the last two years with La Niña, beaches may have a hard time recovering and begin to threaten infrastructure.
“If we see more frequent events, we will see continued pressure on beachfront properties,” he said. “Everyone wants to live by the shoreline and there is always pressure to build more and more property along the shoreline, but it creates legacy issues that future generations will have to address, particularly around climate change and the tremendous threats it can cause. . To the coast.”
For example, wave sizes and sea levels will rise as the oceans continue to warm, causing further damage to beaches.
The coastline around Sydney is expected to experience between 20 centimeters and just over a meter of sea level rise over the next seven decades. This means that the state’s coastline can be expected to change significantly as climate change intensifies.
Meanwhile, tropical cyclones are likely to damage once-protected coastal areas as they move up the New South Wales coast.
“We haven’t seen that type of erosion in the past and this could create new erosion hotspots and that’s a big concern,” Harley said.
Harley is part of a team of investigators involved in a citizen science project that monitors beaches to gain a deeper understanding of how coastlines change over time.
Mark “Dippy” DePena, 67, has surfed the shores of Cronulla Beach since high school and said the shoreline has changed dramatically in the last 55 years.
“The sea does not forgive. It’s honestly very powerful,” she said. “We’ve had some weird weather, but this is the worst I’ve seen in Cronulla since 1974 and we’re really starting to worry,” she said. “They had to move the lifeguard tower, physically dismantle it, because it was starting to sink.”
DePena isn’t sure if his beloved Cronulla beach will be able to take much longer without mitigation measures, but he’s determined to do what he can to preserve the beach, or what’s left of it. Twelve years ago, he teamed up with fellow surfer and friend Andrew Pitt to develop the Bate Bay Sand Laying Committee with the intention of improving the dedicated surf reserve and safeguarding the coastline.
Mark “Dippy” DePena, 67, has surfed the shores of Cronulla Beach since high school and said he’s never seen the beach look so eroded.Credit:mitchell creek
“People want to live in the ocean, right? But these seas have actually stolen some of these front yards.”
Without adequate mitigation and adaptation efforts from government, councils and the community, ANU Associate Professor at the Fenner School for Environment and Society Dr Liz Hanna said there would be health impacts on people. . This includes displacement and loss of connection to the community.
“People will have to pay for their own coastal protection; some can afford it and some can’t,” he said. “Adaptation is complicated, containing the sea is terribly difficult.”
He suggested that, among other efforts, planned withdrawals should be considered before people are forced to be displaced. “We don’t really know how much time we have, but we can all agree that playing with your thumbs is not the right answer,” he said.
The NSW Government is working with local councils to plan for and respond to erosion, including monitoring permitted new development, ensuring environmental and community benefits remain, and providing funding for mitigation work.
The Department of Environment and Heritage also provides seven long-term offshore wave buoys and several ocean level recorders to measure changes.
Over the next 50 years, the Insurance Council of Australia has estimated that governments will need to invest at least $30 billion in coastal protection and adaptation projects.
“As these events increase in frequency and intensity, an increasing number of exposed properties in Australia will become uninhabitable,” a council spokesman said. “Insurance coverage is limited in these areas due to high and increasing risks, creating a protection gap.”
Charging
The council found in a report released last year that governments at all levels would need to invest at least $30 billion in large-scale coastal protection and adaptation projects over the next 50 years. the CSIRO Decadal Megatrends Reportpublished last week, found that 150 million people worldwide live on land that could be vulnerable to future sea level rise by 2050.
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