01-08-2025
Beach cusps on NSW far south coast mystify photographers and experts
An unusual geometric sand pattern spotted on a NSW far south coast beach is delighting locals and photographers alike.
The scallop-shaped sand formations stretch for hundreds of metres along Wallaga Beach, between Bermagui and Mystery Bay.
Local photographer David Rogers has seen similar patterns in bays further north, but was excited to see them "by chance" further south earlier this week.
"I'd seen this phenomenon before at a couple of places like Pearl Beach up in Sydney and Hyams Beach at Jervis Bay."
Mr Rogers first spotted the sand patterns from a nearby headland, before he used a drone to get a better look and noticed how the gentle waves shaped the shoreline.
"From above, it looks a lot more stunning than from on the ground," he said.
"I think it's just the repetitive nature and the formation of the cups.
The fascinating sand formation is not the only thing catching the eye of photographers in the area.
Terry and Kim Dixon managed to film migrating humpback whales three days in a row at nearby Tathra, at the regulated 100-metre distance.
Mr Rogers also spotted whales breaching on Wednesday near Kianniny Bay.
"We had a fantastic show for about half an hour," he said.
"That's nature for you."
Beach cusps have been well studied, but exactly why they occur remains something of a mystery.
Emeritus professor at the University of Sydney, Bruce Thom, has been studying the beaches of the NSW far south coast for more than 50 years.
Professor Thom said that for beach cusps to form, steady, low waves, also known as "incident waves" were required, along with medium to coarse sand, which stays in place after a swash.
"So those preconditions are operating, but that doesn't answer why they form in the first place," he said.
Along with Sydney and Jervis Bay, beach cusps have been previously documented at Shoal Bay in Port Stephens, Bengello Beach near Moruya, and McKenzies Beach south of Batemans Bay.
"They are being studied to death," Professor Thom said.
"All that adds to a rather complex scientific story that has fascinated beach scientists for well over 100 years."
A different type of sand movement is occurring at nearby Haywards Beach, which has resulted in damage to a well-known walking track.
The erosion was something Professor Thom was keeping an eye on, as he continued to study sand deposits on the far south coast.
"In 1974, the big storms came and wiped out a large section of the road, so it became a walking track," he said.
"In the 80s, we had a lot of sand come back from the near shore … but the more recent storms have started to reverse that trend.
"At Haywards, we're really seeing a dramatic switch back to erosion."
