Collaroy residents decry seawall as communities brace for erosion

Every time a storm lashes Collaroy beach, residents worry it will be washed away.

This northern beaches coast – sufficiently famous to be included in the Beach Boys’ 1963 hit Surfin’ USA – is perhaps one of the state’s most studied coastal erosion sites. But with a La Nina event set to bring heavy rains, thunderstorms and strong swells this summer, it’s not just Collaroy Beach likely to see erosion.

The coastal strip was pummelled during a massive storm in 2016 that damaged homes and pulled a swimming pool into the ocean, costing homeowners and local government almost $25 million to fix. Another two big storms further eroded the sand dune in July 2020.

Since then, residents, council and the state government have been working to protect the properties and beach from storm surges, including building a seven-metre-tall concrete wall. Once completed, at least three-quarters of the wall will be covered by sand.

Northern beaches community attending a rally to protest against the building of a seawall from Collaroy.Credit: Steven Siewert

The project stretches 1.3 kilometres from Collaroy to South Narrabeen, encompassing 49 private properties dotted with 11 public land areas, which include a car park and a surf club.

And the works have become the topic of local controversy, with some residents worried that the seawall will cause more harm than good and sand directly in front of the wall could be washed away in the next storm.

President of the northern beaches branch of the Surfrider Foundation, Brendan Donohue, organised a protest on Saturday to encourage council to invest in alternative measures to protect the beach, including a nourishment plan that would artificially replace the sand. The local community group has been protesting against a seawall for almost 30 years.

“Protective works are a far preferable measure to a vertical seawall,” he said. “The community is not happy.”

Northern Beaches Council said there had been comprehensive community consultation about the council’s coastal zone management plan for Collaroy Beach.

Senior lecturer at the UNSW Water Research Laboratory Mitchell Harley said many of the erosion issues that Collaroy faced stem from poor planning almost 100 years ago. Many other coastal communities face similar legacy issues, with councils in desperate need of greater support to address contentious issues, he said.

President of the Northern Beaches branch of the Surfrider Foundation, and Collaroy resident, Brendan Donohue .Credit: Brook Mitchell

“There are a number of these places up and down the coast, and we are trying to solve issues that were put in place hundreds of years ago. The lesson from that is with climate change and sea level rises, there is an increase in pressures on the coasts,” he said.

“We will see more and more of these issues come up, and so the important thing is that we don’t create additional legacy issues by poor planning decisions that we make today.”

The La Nina weather pattern declared this week will add further pressure on many coastal communities, with cooler temperatures, rain and storm events likely to worsen erosion.

The construction of the new Collaroy seawall.Credit: Brook Mitchell

Dr Harley and his colleagues have been measuring the erosion on Collaroy for 45 years, and found it was usually worse during La Nina. The team will be monitoring the beach through newly installed instruments to observe how weather systems impacted on beaches and seawalls.

“Normally we get waves coming from the south or south-east. During La Niña events, they shift slightly anti-clockwise, so they are more easterly,” Dr Harley said.

This means there’s a higher risk of more erosion on the beach, particularly over the coming summer, and also “beach rotation” – where the beach realigns itself to the prevailing wind direction, he said. This typically means the northern end of the beach gets narrower and the southern ends get larger.

The scene after the storm damaged properties at Collaroy in 2016. Credit: Peter Rae

A report by the Insurance Council of Australia, released this month, estimates the Australian government will need to invest $30 billion in large scale coastal protection and adaptation projects over the next 50 years.

The projected figure represents just 1.2 per cent of the average yearly infrastructure spending by all local, state and federal governments. The report noted insurance cover for “actions of the sea” are generally not available and are further constrained due to the increasing risks from climate change.

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