By Janelle Miles, ABC
Erosion has left metres-high escarpments at Surfers Paradise. Photo: ABC/Mark Davies
Waves as high as "three or four-storey buildings", whipped up by ex-Tropical Cyclone Alfred, have gouged millions of cubic metres of sand from about 500 kilometres of coastline between Coffs Harbour in New South Wales and Queensland's Sunshine Coast.
Ex-Cyclone Alfred has caused beach erosion so extreme, it's left escarpments up to six metres high in some dunes, including on iconic Gold Coast tourist stretches.
University of Newcastle coastal erosion expert Michael Kinsela said the outcome of the cyclone's wrath - bringing with it sustained waves up to 15 metres high - should not be seen as all bad news for Australia's east coast tourist spots.
"No doubt the erosion is severe and the pictures are very dramatic, but what I'm seeing is pictures of eroded beaches and dunes, not pictures of roads falling into the sea and sea walls failing," Dr Kinsela said. "In that sense, it's a very positive outcome and something that coastal managers plan for.
"It's actually a good outcome in such an extreme situation."
Dr Kinsela praised Australia's coastal management, particularly on the Gold Coast, for maintaining beaches and dunes that protect waterfront infrastructure from the severity of a rare cyclone venturing so far south - the first to cross Queensland's southeast coast in more than half a century.
"The way they manage sand on Gold Coast beaches is through a sand-pumping system that moves sand from south of the Tweed in NSW," he said.
"There's been a multi-decade method now to ensure there's plenty of sand on Gold Coast beaches. The buffer of sand that was there is intentional and has pretty much protected all of the Gold Coast waterfront infrastructure.
"The sea wall runs in front of the road along the Gold Coast waterfront as well, so they haven't had waves attacking the road.
"The beaches have been damaged, but that's preferable to the roads and buildings being damaged."
Coast erosion at Tweed Heads as Cyclone Alfred loomed closer. Photo: ABC
Complex questions for recovery
Dr Kinsela said the question of how long it would take beaches to recover was "complex" and would depend on issues like the weather in coming weeks.
Rare giant waves coming from the east, generated by ex-Tropical Cyclone Alfred, pounded east coast beaches, robbing them of sand in the days leading up to landfall, but Mother Nature will eventually send the sand back to the coastline, once swells return to normal.
"This is a significant event," he said. "It'll take weeks to months to have what people might call 'nice' beaches again, but the beaches will be there and waves will start returning the sand next week.
"There's a lot of active sand management on the Gold Coast. There'll probably be some remediation works to speed things up too.
"We could have more storms and more erosion. What we hope is that we just have a run of really steady and constructive swells now and the sand just gets put back quickly."
Coastal managers and researchers used drones and laser scanners to map Australia's beach topography in detail, before ex-Tropical Cyclone Alfred. That will be repeated in the wake of the storm to measure the impact.
Dr Kinsela said it was too early to say exactly how much sand Cyclone Alfred had taken from east coast beaches, but it would be in the "millions of cubic metres".
Until the measurements come in, he said it was also unclear where the cyclone rated in terms of historical beach erosion events in Australia, but it was unlikely it would top the erosion seen in NSW in 1974 or the Gold Coast's worst beach erosion in 1967.
"It is when we experience a series or cluster of very extreme storms in just months that the worst erosion impacts and slowest recovery times, occur," Dr Kinsela said.
"One extreme storm on its own can be damaging, sure, but if the beaches and dunes are healthy before such a storm, the impacts… are hopefully limited or at least not too severe."
- ABC
