Kelsey Munro Sydney Morning Herald 8 Dec 10;
Preserving Sydney's beaches against rising sea levels could cost more than $700 million over the next 50 years and would require the government to reverse its long-standing position regarding offshore sandmining, according to a study on climate change-induced beach erosion.
The report was commissioned by the Sydney Coastal Councils Group to investigate whether beach nourishment could stop Sydney's beaches from being washed away by the projected sea level rise of 10 centimetres a decade.
But the report also identifies a business case for beach nourishment, saying the economic benefits would outweigh the costs, compared with doing nothing.
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''At some point, which will come sooner for some beaches than others, Sydney beach sands will be depleted, and [offshore] sands in the shelf sand bodies could be used to nourish these beaches,'' said Professor Bruce Thom, the President of the Australian Coastal Society and an adviser to the coastal councils group.
Beach nourishment involves a floating dredge drawing up sand from deeper waters and depositing it in the shallower ''surf zone''. The action of the waves then pushes it onto the beach.
''It's a practice that has been used on the Gold Coast for many years,'' Professor Thom said. ''Different techniques, but the basic principle is the same: using sands from a local source, putting them into the surf zone, and [allowing] the waves to push sand on to beach.''
Many NSW coastal councils perform beach nourishment on a smaller scale but the sand must be sourced from lagoons or estuaries.
The report's author, Lex Nielsen from AECOM, determined that beach nourishment would need to be carried out in 10-year stages. The first and largest program would require 12 million cubic metres of sand at an estimated cost of $300 million to nourish all Sydney's beaches from Cronulla to Palm Beach.
Subsequent campaigns every decade would call for about 4 million cubic metres of sand at a cost of about $120 million an operation.
The report said sandmining off Cape Banks at Botany Bay would provide sufficient sand for the first stage of works but that the subsequent operations would have to source sand from elsewhere.
But a long-standing state government embargo on offshore marine sandmining would prohibit sand being mined at this scale off Cape Banks, a spokeswoman from the Department of the Environment, Climate Change and Water said.
Geoff Withycombe, from the coastal councils group, said the report identified a strong economic case for beach nourishment, based on detailed case studies of Narrabeen-Collaroy, Manly and Bate Bay in Sutherland.
Manly, as a tourist attraction and iconic Sydney beach, had the best economic case, with every dollar spent on sand nourishment yielding an economic benefit of $2.40.
''Of course, it's much harder to place a value of having the beach existing for future generations to enjoy, but that is the outcome we're aiming for,'' Mr Withycombe said.
