Beaches from Sydney to the Gold Coast which have been severely eroded by the recent storms and unusually high tides will recover – but it could take several years.
Professor Bill Boyd, from the School of Environmental Science and Management at Southern Cross University, said that by this time next year, beachgoers will have forgotten how badly damaged the beaches looked as the sand slowly returns to them.
Beaches are in a perpetual state of change, he said. It is normal for beaches to be eroded and build up sand once more.
“Beaches represent the dynamic nature of the ocean and the complex interplay of tides, currents and waves,” Professor Boyd said.
“In big storms, beach sand is washed away and deposited offshore on the continental shelf – many kilometres out to sea. When the sea is calm, that sand is gradually moved both slightly northwards by the prevailing inshore current and westwards, back onto our beaches.
“The sand – which originally came from more southern parts of Australia, like the sandstone-rich Sydney basin with its high quartz content – will eventually end up on the Moreton Bay islands and Fraser Island.
“This is an incremental process, with sand taking perhaps many thousands of years to travel slowly northwards up the coast.
“On the North Coast, beach erosion is normally an annual cycle. Typically, erosion happens in winter and beach building happens in summer, so we can usually expect to see the beaches rebuild after the winter.
“However, after a major storm and the kind of erosion we have seen recently, it may take several years for the beaches to recover back to their original shape. This can take even longer if we get major storms following each other.”
Professor Boyd said the long-term prognosis over the next centuries, however, was that our beaches will gradually lose sand. This will be due to several factors including increasing storminess and the continuing northwards drift of sand.
“There is nothing wrong with beaches eroding: that is normal. Beaches are there because of erosion,” he said.
“The big problem comes when people want to live near beaches and risk losing their houses. Our challenge is how to accommodate our desire to live by the beach and to balance the advantages with the risks.”
Professor Boyd said that the beach erosion was not of itself evidence of climate change, but simply part of the normal dynamics of beach formation.
PICTURE: Shelly Beach at Ballina is a classic example of beach erosion following last week’s wild weather.